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UBC Theses and Dissertations

Studies on the ultrastructure of desmids and its relation to their taxonomy Gerrath, Joseph Fredrick 1968

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STUDIES ON THE ULTRASTRUCTURE  OF DESMIDS  AND ITS RELATION TO THEIR TAXONOMY by JOSEPH  FREDRICK  GERRATH  B.A., U n i v e r s i t y o f B r i t i s h Columbia, 1959 B.Sc»  (Hon.), U n i v e r s i t y o f B r i t i s h Columbia, I963  M.Scr, U n i v e r s i t y o f B r i t i s h Columbia, I 9 6 5  A THESIS SUBMITTED  IN PARTIAL FULFILMENT OF  THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY i n the Department of Botany  We a c c e p t t h i s t h e s i s as conforming t o the r e q u i r e d standard  THE UNIVERSITY OF BRITISH COLUMBIA June, 1968  In p r e s e n t i n g  for  this  thesis  in partial  an a d v a n c e d d e g r e e a t t h e U n i v e r s i t y o f B r i t i s h  that  the L i b r a r y  Study.  thesis  shall  I further  make i t f r e e l y  agree that  f o r s c h o l a r l y p u r p o s e s may  publication  of this  w i t h o u t my w r i t t e n  available  permission  thesis  June  27,  gain  shall  that  n o t be  permission.  The U n i v e r s i t y o f B r i t i s h V a n c o u v e r 8, Canada Date  copying of  It i s understood  for financial  Botany  1968  Columbia  I agree  f o r r e f e r e n c e and  f o r extensive  J.  Department o f  Columbia,  this  be g r a n t e d b y t h e Head o f my  D e p a r t m e n t o r by h ils r e p r e s e n t a t i v e s .  or  f u l f i l m e n t of the requirements  F.  Gerrath  copying  allowed  i  Abstract. The  c e l l w a l l was s t u d i e d i n 13 s p e c i e s i n 10 genera  of the Desmidiaceae i n order t o determine whether u l t r a s t r u c t u r a l d i f f e r e n c e s e x i s t among the three  subfamilies  of the Desmidiaceae: Penieae. C l o s t e r i e a e , and Cosmarieae. The  c e l l w a l l o f the Penieae comprises two d i s t i n c t l a y e r s ,  an i n n e r l a y e r of c e l l u l o s e m i c r o f i b r i l s and an outer electron-dense at  layer.  The s e m i c e l l w a l l s do n o t o v e r l a p  the isthmus r e g i o n and the l a c k of pores i n the w a l l i s  confirmed. without join.  The c e l l w a l l o f the C l o s t e r i e a e i s one-layered  pores and the s e m i c e l l w a l l s o v e r l a p where they The c e l l w a l l of the Cosmarieae i s one-layered  pores through which a p e c t i c f i b r i l l a r sheath The  with  i s secreted.  s e m i c e l l w a l l s o v e r l a p a t the isthmus. In the u n i c e l l u l a r Cosmarieae an i n i t i a l w a l l l a c k i n g  pores i s present d u r i n g e l o n g a t i o n of the new s e m i c e l l following c e l l d i v i s i o n . a f t e r formation  This i n i t i a l wall i s discarded  o f the mature c e l l w a l l c o n t a i n i n g  In the f i l a m e n t o u s  pores.  Cosmarieae both i n i t i a l and mature  w a l l s a r e formed before s e m i c e l l e l o n g a t i o n o c c u r s .  cell In the  c o l o n i a l desmid, Cosmocladium saxonicum, the connecting st ra nd s between c e l l s comprise s e v e r a l f i b r i l l a r  subunit  strands each a s s o c i a t e d w i t h one of a group of pores near the isthmus of the c e l l . Cytoplasmic  microtubules  a r e present  immediately  below the plasma membrane i n the isthmus r e g i o n of c e l l s  ii f i x e d with glutaraldehyde.  These microtubules are o r i e n t e d  p e r p e n d i c u l a r to the c e l l a x i s . of  Spondylosium nulchrum was  A s i n g l e c e l l a t metaphase  examined.  Evidence  f o r the  e x i s t e n c e of l o c a l i z e d centromeres i n the chromosomes of t h i s species i s presented.  Bundles of s p i n d l e microtubules  a t t a c h to the metaphase chromosomes a t l o c a l i z e d r e g i o n s and not a t any other p a r t of the chromosome. The r a r e l y c o l l e c t e d s p e c i e s Pleurotaenium (Wolle) B r u n e i  spinulosum  (Cosmarieae) has a c e l l w a l l w i t h the same  f i n e s t r u c t u r e as i n the genus Penium ( P e n i e a e ) .  The  t r a n s f e r of t h i s s p e c i e s to the genus Penium as Penium spinulosum  (Wolle) comb. nov.  i s t h e r e f o r e proposed.  Table of Contents Abstract L i s t of Tables L i s t of Figures Acknowledgment  i i i . i iv v xiv  Introduction  1  Terminology  3  M a t e r i a l and Methods  .4  Results Penieae Penium margarltaceum  9  Penium s p l r o s t r l o l a t u m  22  Penium spinulosum  30  Closterleae Closterlum llneatum  41  Cosmarieae Pleurotaenlum nodosum Trlploceras v e r t l c l l l a t u m  47 ... 6 l  Bambuslna b r e b i s s o n l l  76  Desmldlum s w a r t z l l  88  Desmldlum c y l l n d r l c u m  90  Hyalotheca d l s s l l l e n s  101  Sphaerozosma laeve  I l l  Spondyloslum pulchrum  117  Cosmocladium saxonlcum  135  Discussion  147  Bibliography  160  List  Table  of  I.  Tables  Sources  of  Cultures  of Desmidiaceae Page•  Studied. 6  V  L i s t of Figures Fig.  1  Diagram o f c e l l of Cosmarlum (Cosmarieae) showing overlap  of semicell w a l l s ,  p. 8  Fig.  2  Diagram o f c e l l o f C l o s t e r l u m  Fig.  3  Diagram of c e l l o f Penium (Penieae).  Fig.  4  Diagram o f pore apparatus o f the Cosmarieae. p . 8  Fig.  5  L i v i n g c e l l o f Penium margar1taceum.  p; 13  Fig.  6  Penium margarltaceum.  Apex o f c e l l .  p . 13  Fig.  7  Penium margarltaceum.  Isthmus r e g i o n o f c e l l . p . 13  Fig.  8  Penium margarltaceum.  Longitudinal  c e l l wall. Fig.  9  Penium margar1taceum.  section of  Oblique t a n g e n t i a l  section  p i 15  10 Penium margar1taceum. through isthmus r e g i o n ,  Fig.  p; 8  P? 15  through c e l l w a l l , Fig.  11 Penium margar1tac eum.  Longitudinal  section  p . 1? Oblique s e c t i o n through  c e l l w a l l and cytoplasm a t isthmus r e g i o n , Fig.  Transverse s e c t i o n o f  12 Penium margarltaceum. through a p y r e n o i d .  Fig.  13 Penium margarltaceum.  14 Penium margar1taceum.  15 Penium margarltaceum.  cell  Transverse s e c t i o n o f p . 19  Longitudinal  section  through p a r t o f an elongated mitochondrion, Fig.  p* 17  p; 17  c e l l showing a x i a l c h l o r o p l a s t . Fig.  p. 8  (Closterieae).  p. 19  Transverse s e c t i o n o f  c e l l showing dictyosomes and mitochondrion,  p . 21  vi P i g . 16  L i v i n g c e l l of Penium s p i r o s t r i o l a t u m .  F i g . 1 7 Penium s p i r o s t r i o l a t u m . of c e l l w a l l , F i g . 18  Longitudinal  section  Longitudinal  section  pi 2 5  Penium s p i r o s t r i o l a t u m .  through c e l l w a l l a t isthmus. F i g . 1 9 Penium s p i r o s t r i o l a t u m .  P> 2 5  Oblique  s e c t i o n through c e l l w a l l , F i g . 2 0 Penium s p i r o s t r i o l a t u m .  tangential  pi 2 ?  Tangential  through o u t e r c e l l w a l l l a y e r , Fig. 2 1  p. 2 5  Penium s p i r o s t r i o l a t u m .  p. 2 7  Tangential  through inner c e l l w a l l l a y e r , F i g . 2 2 Penium s p i r o s t r i o l a t u m .  section  section  pi2 9  Tangential  section  through outer c e l l w a l l l a y e r a t isthmus, F i g . 2 3 Penium splnulosum. l a t e r a l margins, F i g . 2k  Penium splnulosum. l a t e r a l margins.  F i g . 2 5 Penium splnulosum.  L i v i n g c e l l with s t r a i g h t ptL i v i n g c e l l with undulating  p*«T  3^  Longitudinal  s e c t i o n of  c e l l w a l l through one o f the s p i n e s , F i g . 2 6 Penium splnulosum.  Tangential  inner c e l l w a l l l a y e r . F i g . 2 7 Penium splnulosum.  F i g . 28  Longitudinal pi' 36  Penium splnulosum.  Tangential  pi 3 8  section  p. 3 ^ through  Pi 3 °  through c e l l apex,  c e l l wall,  pi 2 9  section  section  through  vii Pig.  29  Penium splnulosum.  L o n g i t u d i n a l s e c t i o n of p." 4-0  c e l l w a l l a t isthmus r e g i o n , Fig.  3 0 Penium splnulosum.  Transverse s e c t i o n of c e l l p. 4-0  showing a x i a l c h l o r o p l a s t . Fig.  31  L i v i n g c e l l of Closterlum llneatum.  Fig.  32  Closterlum llneatum. through c e l l w a l l .  Fig.  33  Longitudinal section pY 4 4  Closterlum llneatum.  Longitudinal section PT 4 4  through apex of c e l l . F i g . 34- Closterlum llneatum.  Longitudinal section P» 4-6  through isthmus r e g i o n . Fig.  35  Closterlum llneatum.  Tangential  through c e l l w a l l r i d g e s . Fig. 36 37  P i 4-6  p*? 5 2  Methyl v i o l e t stained c e l l of P. nodosum,  F i g . 3 8 Pleurotaenlum /nodosum.  Pleurotaenlum nodosum. c e l l wall,  p? 5 2  Oblique s e c t i o n through  p i 5k  F i g . 4-0 Pleurotaenlum nodosum.  Longitudinal section  through c e l l w a l l and pore apparatus, F i g . 4-1  p. 5 2  Longitudinal section  of c e l l w a l l through a pore, Pig* 39  section  L i v i n g c e l l s In l i g h t microscope of Pleurotaenlum nodosum,  Fig.  p^' 4-4-  Pleurotaenlum nodosum.  p i 54-  Tangential s e c t i o n of  c e l l w a l l showing l a y e r s of m i c r o f i b r i l s , F i g . 4-2 Pleurotaenlum nodosum.  p. 5 6  Longitudinal section  through isthmus region of c e l l ,  p i 56  viii F i g . 43  Pleurotaenlum nodosum.  Section of pyrenoid. p i 58  F i g . 44  Pleurotaenium nodosum.  Transverse s e c t i o n of  isthmus microtubules, F i g . 45  pv 58  Pleurotaenlum nodosum.  Transversa s e c t i o n of pv 60  c e l l through c h l o r o p l a s t s . F i g . 46  Pleurotaenlum nodosum.  Longitudinal section  of isthmus microtubules,  p. 60  F i g . 47  L i v i n g c e l l of T r l p l o c e r a s v e r t l c i l i a t u r n ,  F i g . 48  Trlploceras v e r t l c i l l a t u m . methyl v i o l e t ,  F i g . 49  p. 65  C e l l stained w i t h  p. 65  Trlploceras v e r t l c i l l a t u m . through protuberance.  Longitudinal section  p» 65  F i g . 50  Trlploceras v e r t l c i l l a t u m .  Cross s e c t i o n of pore. p.67  F i g . 51  Trlploceras v e r t l c i l l a t u m .  Cross s e c t i o n of  s o l i d cap i n the pore bulb. F i g . 52  Trlploceras verticiliaturn. of c e l l w a l l through a pore.  F i g . 53  Trlploceras v e r t l c i l l a t u m .  p« 67 Longitudinal section p. 69 Longitudinal section  through Isthmus region of d i v i d i n g c e l l , F i g . 54  F i g . 55  Trlploceras v e r t l c i l l a t u m .  Section showing  mitochondria  p. 71  and vacuoles,  Trlploceras v e r t l c i l l a t u m . dictyosome.  F i g . 56  p; 69  Section showing a  p i 71  Trlploceras v e r t l c i l l a t u m . of c e l l through a pyrenoid.  Transverse s e c t i o n p. 73  ix Pig.  57  Trlploceras vertIclllaturn.  Transverse s e c t i o n  of c e l l through protuberances, Fig.  58  Trlploceras vertIclllaturn. isthmus microtubules.  Fig.  59  60  Section showing the  j>i 75  T r l p l o c e r a s vertic111aturn. semicell i n divided c e l l .  Pig.  p. 73  T r l p l o c e r a s vertic111aturn.  I n i t i a l w a l l of new p. 75 Section of new  s e m i c e l l w a l l i n c e l l w i t h half-elongated semicell.  new  pv 75  Fig.  61  Bambuslna b r e b l s s o n i l . L i v i n g c e l l s .  Fig.  62  Bambuslna b r e b l s s o n i l . Filament stained w i t h methyl v i o l e t to show narrow sheath,  Fig.  63 64  p. 79  Bambuslna b r e b l s s o n i l . L o n g i t u d i n a l s e c t i o n through l a t e r a l margin of c e l l apex.  Fig.  P*. 79  p. 79  Bambuslna b r e b l s s o n i l . L o n g i t u d i n a l s e c t i o n of cell.  P? 81  F i g . 65  Bambuslna b r e b l s s o n i l . Lobe of c h l o r o p l a s t . P'» 83  F i g . 66  Bambuslna b r e b l s s o n i l . Pyrenoid.  Fig.  Bambuslna b r e b l s s o n i l . L o n g i t u d i n a l s e c t i o n  67  of d i v i d i n g c e l l , F i g . 68  p. 83  p?° 85  Bambuslna b r e b l s s o n i l . L o n g i t u d i n a l s e c t i o n through the f o l d region of the d i v i s i o n septum, p. 87  F i g . 69  Bambuslna b r e b l s s o n i l . L o n g i t u d i n a l s e c t i o n through u n f o l d i n g w a l l s of elongating s e m i c e l l s .  Fig.  70  L i v i n g c e l l s of Desmldlum s w a r t z i l .  Fig.  71  Desmldlum s w a r t z i l . violet.  P'S 92 4  p. 92  C e l l s stained w i t h methyl  p.87  X  F i g , 72 F i g . 73  Desmldlum s w a r t z l l .  A p i c a l view of c e l l stained  w i t h methyl v i o l e t .  P.  Desmldlum s w a r t z l l .  Longitudinal section  92 p. 92  through c e l l a t isthmus. F i g . ?4  Desmldlum s w a r t z l l .  L o n g i t u d i n a l s e c t i o n of  two c e l l s joined a t a p i c a l pads. F i g . 75  Desmldlum s w a r t z l l . a p i c a l pad.  P* 94  L o n g i t u d i n a l s e c t i o n of  p'. 94 ;  F i g . 76: ;desmldlum;swartzll. Transverse s e c t i o n of c e l l . T  F i g . 77  Desmldlum s w a r t z l l . sheath,  Section through pores and  p? 96  F i g . 78  Desmldlum c y l l n d r l c u m .  Living ceills.  Fig# 79  Desmldlum c y l l n d r l c u m .  Sheath stained w i t h  methyl v i o l e t , F i g . 80  p.96  P. 98  p." 98  Desmldlum c y l l n d r l c u m .  Surface view of c e l l s  stained w i t h methyl v i o l e t showing pores,  p i 98  F i g . 81  Desmldlum c y l l n d r l c u m .  Section of c e l l w a l l . p . 98  F i g . 82  Desmldlum c y l l n d r l c u m .  Longitudinal section  through c e l l apex,  100  F i g . 83  Desmldlum c y l l n d r l c u m .  Section through isthmus, p i 1 0 0  F i g . 84  Desmldlum c y l l n d r l c u m .  Longitudinal section  through d i v i s i o n septum,  pi? 100  F i g . 85  Hyalotheca d i s s l l l e n s .  Living c e l l s ,  F i g . 86  Hyalotheca d i s s l l l e n s .  Sheath stained w i t h  methyl v i o l e t ,  p. 104  p. 104  xi F i g . 87  Hyalotheca d l s s l l l e n s .  Longitudinal section  through l a t e r a l margin of c e l l apex. Fig.  88  Hyalotheca d l s s l l l e n s .  p.  Hyalotheca d l s s l l l e n s .  106  Narrow c o n n e c t i o n P«  between a d j a c e n t a p i c a l w a l l s . F i g . 90  Hyalotheca d l s s l l l e n s . Pv  w a l l s a t isthmus. F i g . 91  106  Overlapping s e m i c e l l 106  Hyalotheca d l s s l l l e n s .  S e c t i o n through two  pores and a d j a c e n t sheath, F i g . 92  Hyalotheca d l s s l l l e n s .  pv  108  Tangential section  through c e l l w a l l and a d j a c e n t sheath, F i g . 93  Hyalotheca d l s s l l l e n s . of  F i g . 94  P*.  sheath p r i s m s .  p.  p:  110 Tangential section  110  F i g . 95  Sphaerozosma l a e v e .  Living c e l l s ,  p,  114  F i g . 96  Sphaerozosma l a e v e .  Two l i v i n g c e l l s .  P»  F i g * 97  Sphaerozosma l a e v e .  Sheath s t a i n e d w i t h  methyl v i o l e t . F i g . 98  Pv  Sphaerozosma l a e v e .  Sphaerozosma l a e v e .  L o n g i t u d i n a l s e c t i o n of p>  Longitudinal section  through a p i c a l protuberance, F i g . 100 Sphaerozosma l a e v e .  114  114  c e l l through nucleus and protuberance. F i g . 99  108  Longitudinal section  Hyalotheca d l s s l l l e n s . through sheath,  1 0 l | f  Enlarged a p i c a l r i n g  s e p a r a t i n g two c e l l s . F i g . 89  .«„  pv  116  Microtubules,  p.  116  114  xii Pig.  101  Sphaerozosma laeve.  Fig.  102  L i v i n g c e l l s of Spongyloslum pulchrum.  Fig.  103  Spondyloslum pulchrum. methyl v i o l e t .  Fig.  104  Section of c e l l w a l l .  p.ll6  pv 122  Sheath stained w i t h  p f 122  Spondyloslum pulchrum. in polarized l i g h t .  C e l l s photographed  p? 122  Fig.  105  Spondyloslum pulchrum.  A p i c a l view of c e l l . p. 122  Fig.  106  Spondyloslum pulchrum.  S e c t i o n of c e l l w a l l  through two pores. Fig.  107  Spondyloslum pulchrum. through a p i c a l pad.  Fig.  108  109  Longitudinal section  p.* 126  Spondyloslum pulchrum. through sheath.  Fig.  p. 124  Tangential s e c t i o n  p.' 126  Spondyloslum pulchrum.  Tangential s e c t i o n  through s e v e r a l pore bulbs. Fig.  110  Spondyloslum pulchrum.  p'. 128 ;  Tangential s e c t i o n  through c e l l w a l l and sheath c o l l a r s . Fig.  Ill  Spondyloslum pulchrum.  Section of metaphase  spindle showing chromosomes. Fig.  112  Spondyloslum pulchrum.  113  Spondyloslum pulchrum.  p. 130  Section of same  metaphase s p i n d l e as F i g . 111. Fig.  p. 128  p. 130  Transverse s e c t i o n  through centromere of metaphase chromosome, p. 132 Fig.  114  Spondyloslum pulchrum.  Enlarged p a r t of F i g . 111. j  Spindle microtubules near mitochondria,  p. 134  xiii F i g . 115  Spondyloslum pulchrum. Nucleolar m a t e r i a l near s p i n d l e p o l e ,  134  pv  P«' 138  F i g . 116  L i v i n g c e l l s of Cosmocladlum saxonlcum.  F i g . 117  Cosmocladlum saxonlcum. Feathery s t r u c t u r e s i n methyl v i o l e t stained sheath.  P«  138  F i g . 118  Cosmocladlum saxonlcum. S e c t i o n of c e l l w a l l . p?l40  F i g . 119  Cosmocladlum saxonlcum. A p i c a l view of c e l l . p. 140  F i g . 120  Cosmocladlum saxonlcum. connecting s t r a n d .  F i g . 121  Oblique s e c t i o n through 140  Cosmocladlum saxonlcum. S e c t i o n through Isthmus pore group, p.* 140 5  F i g . 122  Cosmocladlum saxonlcum. Low m a g n i f i c a t i o n micrograph of c e l l s ,  F i g . 123  Cosmocladlum saxonlcum. Enlarged view of a strand subunit.  F i g . 124  pv* 142  vV 144  Cosmocladlum saxonlcum.  Longitudinal section  through isthmus r e g i o n showing microtubules. F i g . 125  Cosmocladlum saxonlcum. Enlarged view of nucleus and pyrenoid i n F i g . 122.  F i g . 126  Cosmocladlum saxonlcum. of isthmus microtubules.  pv 146  Longitudinal section p.' 146  PT144  xlv Acknowledgment T h i s i n v e s t i g a t i o n was begun a t Queen Mary C o l l e g e , U n i v e r s i t y of London, and supported by a Commonwealth Scholarship  provided  by the B r i t i s h C o u n c i l .  The author  wishes t o express h i s g r a t i t u d e to Dr. M. B. E. Godward of Queen Mary C o l l e g e  f o r providing laboratory  to Dr. E . G. Jordan f o r suggestions concerning  facilities, electron  microscope techniques and to Mr. L. S h e l l s of C a r l Z e i s s L t d . f o r i n s t r u c t i o n i n the o p e r a t i o n  of the Z e i s s  e l e c t r o n microscope. T h i s study was completed a t the U n i v e r s i t y of B r i t i s h Columbia under the d i r e c t i o n of Dr. J . R. S t e i n . was supported by two N a t i o n a l Research C o u n c i l  The work  Scholarships  to the author and by N a t i o n a l Research C o u n c i l Grant No. A1035 to Dr. S t e i n . facilities  Dr. T. B i s a l p u t r a provided  f o r specimen p r e p a r a t i o n and permitted  of h i s Z e i s s e l e c t r o n microscope.  laboratory the use  The author expresses  thanks t o Dr. S t e i n , Dr. B i s a l p u t r a , Dr. R. F. Scagel and Dr. K. Cole f o r c r i t i c a l r e a d i n g  of t h i s manuscript.  1  Introduction. Desmids a r e members of the green a l g a l order Zygnematales  i n which s e x u a l r e p r o d u c t i o n occurs by  c o n j u g a t i o n of n o n - f l a g e l l a t e d gametes.  The  Zygnematales  comprise a t l e a s t t h r e e w e l l - d e f i n e d f a m i l i e s : the Zygnemataceae, or Sp irogyra-Zygnema group of f i l a m e n t o u s a l g a e ; the Mesotaeniaceae, or saccoderm desmids; and the Desmidiaceae, or placoderm desmids. Gonatozygaceae,  A f o u r t h f a m i l y , the  i s sometimes segregated from the  Mesotaeniaceae. The f a m i l i e s Desmidiaceae and Mesotaeniaceae are d i s t i n g u i s h e d on the b a s i s of w a l l s t r u c t u r e .  In the  Desmidiaceae the c e l l w a l l i s composed of two symmetrical h a l v e s which g e n e r a l l y o v e r l a p a t a c o n s t r i c t e d The w a l l i s u s u a l l y ornamented s t r i a t i o n s , and may  w i t h knobs,  region.  s p i n e s or  have pores through which a sheath of  pectic material i s secreted.  The Mesotaeniaceae have  u n c o n s t r i c t e d c e l l s w i t h the w a l l not composed of two h a l v e s , u s u a l l y unornamented, and l a c k i n g p o r e s . On the b a s i s of l i g h t microscope i n v e s t i g a t i o n s of the  c e l l w a l l three s u b f a m i l i e s of the Desmidiaceae have  been r e c o g n i z e d ( K r i e g e r 1 9 3 7 ) •  The Penieae, w i t h one  genus, Penium, have elongated, s t r a i g h t c y l i n d r i c a l There may but  cells.  be a s l i g h t c o n s t r i c t i o n a t the c e n t r a l r e g i o n  not as pronounced  as i n c e r t a i n other Desmidiaceae.  The c e l l w a l l i s sometimes composed of s e v e r a l s e c t i o n s and the p o s i t i o n where c e l l d i v i s i o n w i l l occur cannot be  2 predicted  (Lutkemuller 1 9 0 2 ) .  The  Closterieae, with  one  genus, C l o s t e r i u m ,  have elongated c e l l s narrowed a t both ends  and  or curved.  u s u a l l y lunate  c o n s t r i c t i o n and  There i s no  central  the w a l l i s a l s o o f t e n composed of  several sections.  The  occur i s v a r i a b l e but  p o s i t i o n where c e l l d i v i s i o n i s predictable  since i t i s indicated  by a w a l l t h i c k e n i n g d e v e l o p i n g b e f o r e c e l l The  will  division.  t h i r d group, the Cosmarieae, or Cosmarium-type  desmids, i n c l u d e s  the m a j o r i t y  l i s t s 30 genera i n t h i s group.  of desmids. The  Bourrelly  c e l l of the  (1966)  Cosmarieae  i s u s u a l l y c o n s t r i c t e d a t a c e n t r a l r e g i o n where c e l l division The  occurs. taxonomy of the Desmidiaceae i s based on  made w i t h the l i g h t microscope 1908,  1912;  West, West and  Kossinskaya i 9 6 0 ) . the c e l l w a l l are  The  1923;  s i z e , shape and  Krieger  but  1905  1937;  ornamentation of  important c r i t e r i a f o r g e n e r i c  s p e c i f i c separation and  West 1904,  (West and  Carter  studies  other c h a r a c t e r s  such as  zygote morphology are a l s o employed.  The  and chloroplast  introduction  of the e l e c t r o n microscope to b i o l o g i c a l  investigations  has  information  presented a method f o r o b t a i n i n g new  the s t r u c t u r e of the desmid c e l l .  Several  electron  microscope s t u d i e s on desmids have^been p u b l i s h e d  but most  d e a l w i t h the genera M i c r a s t e r i a s . Cosmarium. and (Brandham and and  Godward 1965;  R o u i l l e r 1957;  Chardard 1964,  Drawert and  on  1965;  Metzner-Kiister  Closterium Chardard  I96I;  Drawert  3 and Mix I 9 6 l a - h , 1962a-c, 1954;  Mix 1 9 6 6 ,  1968;  1963;  Kamiya 1 9 6 1 , 1 9 6 2 ;  Waddington 1 9 6 2 ) .  Leyon  The o b j e c t i v e s of  the p r e s e n t i n v e s t i g a t i o n were to survey the u l t r a s t r u c t u r e of s e v e r a l genera of the Desmidiaceae and t o determine whether u l t r a s t r u c t u r a l d i f f e r e n c e s e x i s t among the subfamilies.  S p e c i a l emphasis  i s given  three  to the f i n e  s t r u c t u r e o f the c e l l w a l l but o b s e r v a t i o n s  are a l s o  p r e s e n t e d on the cytoplasm of the c e l l s of s e v e r a l  species.  Terminology.' A number of s p e c i a l i z e d terms a r e employed study of desmids.  Some of the f r e q u e n t l y used terms are  d e f i n e d here and i l l u s t r a t e d  i n F i g . 1-4.  The c e l l of a  Cos mar i um-1ype desmid comprises two h a l v e s , which a r e i d e n t i c a l or m i r r o r overlap  i n the  images.  or s e m i c e l l s ,  The s e m i c e l l  a t a c o n s t r i c t e d r e g i o n c a l l e d the isthmus  The two ends of the c e l l are the a p i c e s .  walls (Fig. 1).  The Penieae and  C l o s t e r i e a e are s i m i l a r i n s t r u c t u r e but some s p e c i e s  have  c e n t r a l s e c t i o n s c a l l e d g i r d l e bands i n s e r t e d between the semicells  (Fig. 2, 3 ) .  Pores a r e p r e s e n t i n the c e l l w a l l s Desmidiaceae. derived  The terms d e s c r i b i n g pore s t r u c t u r e are  from e a r l y work w i t h the l i g h t  (Lutkemuller  of most of the  microscope  1 9 0 2 ) and are r e t a i n e d by e l e c t r o n  microscopists  (Chardard and R o u i l l e r 1 9 5 7 ; Drawert and Metzner-Kiister The term pore apparatus i s used to d e s c r i b e complex which comprises three d i s t i n c t p a r t s  I96I).  the whole pore (Fig. 4 ) .  4 The h o l e i n the c e l l w a l l i s the pore or pore (German: Porenfaden).  filament  On the i n s i d e of the c e l l w a l l the  pore b u l b (German: Porenzwiebel) i s s i t u a t e d under the pore;  On the o u t s i d e of the w a l l there i s a s t r u c t u r e  which i s c a l l e d the sheath c o l l a r i n the p r e s e n t investigation  (German: Porenknopfchen)•  The sheath i s  composed of i n d i v i d u a l p a r t s , sheath prisms (German; Gallertprismen),  each a s s o c i a t e d w i t h one pore a p p a r a t u s .  M a t e r i a l and Methods; C l o n a l u n i a l g a l c u l t u r e s of the desmids shown i n Table I were e s t a b l i s h e d from c o l l e c t i o n s made by the author.  The c o l l e c t i o n s i t e and i s o l a t i o n date are a l s o  i n d i c a t e d i n Table I.' A c u l t u r e of Penium margarltaceum (LB 6 0 0 ) was obtained from the Indiana U n i v e r s i t y c u l t u r e collection  (Starr 1 9 6 4 ) .  medium was used.  A modified soil-water culture  Approximately 0 ; 5 cc each of s o i l and  h o r t i c u l t u r a l peat were p l a c e d i n a t e s t tube w i t h 20 ml distilled  water and the tube was a u t o c l a v e d f o r 4 5 - 6 0  minutes.  C u l t u r e s were grown a t 20°C under a 16 h r / 8 hr  l i g h t dark c y c l e w i t h i l l u m i n a t i o n a t 2 0 0 - 2 5 0  ft.-c.  (2100-2600 l u x ) ; Sheath and pore s t r u c t u r e were s t u d i e d w i t h the l i g h t microscope by s t a i n i n g l i v i n g c e l l s w i t h 1% methyl v i o l e t , and s t a i n i n g w i t h 0 . 1 $ ruthenium r e d i n d i c a t e d the presence of p e c t i c substances.  C h l o r - z i n c - i o d i n e and IKI-  H^SOjj, were used t o t e s t f o r the presence of c e l l u l o s e i n  5 the c e l l w a l l .  Methylene blue and Congo r e d were a l s o  used t o s t a i n the sheath. For study w i t h the e l e c t r o n microscope  c e l l s were  f i x e d a t 20°C f o r one hour w i t h 1% osmic a c i d or w i t h 2 - 5 $ g l u t a r a l d e h y d e f o l l o w e d by p o s t f i x a t i o n f o r one hour w i t h 1% osmic a c i d .  1  or c a c o d y l a t e b u f f e r  Phosphate b u f f e r  ( 0 . 1 5 M, pH  7.2)  ( 0 . 1 M, pH 7»0 and 5 v 8 ) were used.  The f i x a t i o n s used a r e noted w i t h -each  micrograph.  Dehydration i n an ethanol-propylene oxide s e r i e s was f o l l o w e d by embedding i n Maraglas. were s e l e c t e d by examining compound microscope.  C e l l s t o be s e c t i o n e d  the b l o c k w i t h low power of a  Small p i e c e s of the b l o c k were c u t  out w i t h a coping saw and mounted f o r s e c t i o n i n g on a P o r t e r Blum MT-1  microtome.  S e c t i o n s were c u t w i t h a g l a s s  or diamond k n i f e and p i c k e d up on formvar-coated  grids.  The s e c t i o n s were s t a i n e d 3 0 - 6 0 minutes w i t h u r a n y l a c e t a t e ( s a t u r a t e d s o l u t i o n i n 7 0 $ methanol) and 5 - 7 minutes w i t h lead c i t r a t e H i t a c h i HU-11  (Reynolds I 9 6 3 ) i  Micrographs were taken w i t h  and Z e i s s EM-9A e l e c t r o n  microscopes.'  6 TABLE SOURCES  OF CULTURES  I  OF DESMIDIACEAE Isolation Date  Species Penieae  STUDIED Source*  22/6/64  Mike L. (Haney)  9/7/64  P l a c i d L. (Haney)  26/8/65  Loon L. (Haney)  Pleurotaenium nodosum  11/8/64  P l a c i d L. (Haney)  Trlploceras  22/7/63  Mike L. (Haney)  Penium  spirostriolatum  Penium spinulosum Closterieae Closterium llneatum Cosmarieae  Cosmarieae  (unicellular)  vertlcillatum  ( c o l o n i a l and f i l a m e n t o u s ) 3/7/67  L o s t L. (Coquitlam)  26/8/65  Gwendoline L. (Haney)  26/8/65  P l a c i d L. (Haney)  Desmldlum c y l l n d r i c u m  I6/6/67  Pond 30 mi. south Kenora, O n t a r i o  Hyalotheca d l s s i l i e n s  12/6/67  Pond 30 mi. south Kenora, O n t a r i o  Sphaerozosma l a e v e  7/8/63  Dead Dog C r . (north of F t . S t . James)  Spondylosium  26/8/65  P l a c i d L. (Haney)  Bambusina  brebissonii  Cosmocladium Desmidium  *  saxonicum  swartzll  pulchrum  Name i n parentheses i n d i c a t e s Columbia.  n e a r e s t town i n B r i t i s h  7 Fig.  1  Diagram of c e l l of Cosmarium o v e r l a p of s e m i c e l l w a l l s a = cell i  Fig.  2  (Cosmarieae) showing  (arrow),  apex,  = isthmus.  Diagram of c e l l of C l o s t e r i u m  (Closterieae).  g ss g i r d l e band.  Fig.  3  Diagram of c e l l of Penium  (Penieae).  g = g i r d l e band.  Fig.  4  Diagram of pore apparatus of the Cosmarieae. w = cell  wall,  pm = plasma membrane, pb = pore b u l b , sc = sheath c o l l a r , s = sheath.  9 Results. Subfamily The  Penieae  Penieae are d i s t i n g u i s h e d by s t r a i g h t c y l i n d r i c a l  c e l l s with l i t t l e i n the c e l l w a l l  or no  isthmus c o n s t r i c t i o n and  (Fig. 3 K  no  pores  In some s p e c i e s e l o n g a t i o n  i n s e r t i o n of c y l i n d r i c a l c e l l w a l l p i e c e s o c c u r s . of c y t o k i n e s i s i s v a r i a b l e .  Two  The  by site  or f o u r a x i a l c h l o r o p l a s t s  and  a p i c a l vacuoles containing  The  nucleus i s s i t u a t e d a t the middle of the c e l l between  the c h l o r o p l a s t s . Penium de  The  s e v e r a l g r a n u l e s are  subfamily  contains  only one  present.  genus  Brebisson.  Penium margaritaceum (Ehrenberg) de Penium margaritaceum has  Brebisson  elongate c y l i n d r i c a l  measuring 1 3 0 - 2 1 5 u long by 16-20  jm wide.  The  cell  wall  comprises s e v e r a l s e c t i o n s marked o f f by t r a n s v e r s e (Fig.  5)«  The  outer  surface  covered w i t h s m a l l g r a n u l e s .  lines  of the w a l l appears rough The  and  iodine-H^SOij, c e l l u l o s e  t e s t g i v e s a p o s i t i v e r e a c t i o n f o r the cell  cells  inner p a r t of  the  wall. E l e c t r o n micrographs of the c e l l w a l l show t h a t i t  comprises two  d i s t i n c t layers  i s c a . 300 mu  t h i c k and  ( F i g . 6-8).  The  c o n s i s t s of a loose network of  randomly o r i e n t e d c e l l u l o s e m i c r o f i b r i l s 4 - 5 (Fig.  9,  11)..  The  outer w a l l l a y e r i s more  extending out from the  inner l a y e r  mu  thick  electron-dense,  inner w a l l l a y e r c a . 600 mu  ( F i g . 8)  10 and  a l s o extending down i n t o the inner w a l l l a y e r ( F i g . 8 , 9)»  The  m i c r o f i b r i l s o f the outer  l a y e r a r e a l s o 4 - 5 mp. t h i c k .  Tangential  s e c t i o n s through the outer w a l l l a y e r show a  perforated  s t r u c t u r e w i t h holes  (Fig.  9).  Each hole  1 0 0 - 1 5 0 mu i n diameter  i s surrounded by a r e g i o n of lower  e l e c t r o n d e n s i t y than the remainder of the outer w a l l l a y e r . The  l a r g e r electron-dense  areas seen i n t a n g e n t i a l s e c t i o n s  correspond t o t h i c k e r areas seen i n l o n g i t u d i n a l s e c t i o n s and  t o the g r a n u l e s seen on the c e l l w a l l w i t h the l i g h t  microscope ( F i g . 5» 6> 9 ) .  The p e r f o r a t i o n s  i n the outer  w a l l do n o t extend through the inner w a l l l a y e r . The  c e l l w a l l s do n o t overlap a t the isthmus as i n  the Cosmarieae ( F i g , 7 . 1 0 ) . continuous a c r o s s  The inner w a l l l a y e r i s  the isthmus and the outer w a l l l a y e r has  a furrovr a t the isthmus r e g i o n  (Fig. 1 0 ) .  Immediately  below the plasma membrane i n the isthmus r e g i o n there a r e m i c r o t u b u l e s approximately 20 mu i n diameter o r i e n t e d perpendicular The  t o the l o n g i t u d i n a l a x i s of the c e l l  (Fig. 11).  m i c r o t u b u l e s and the m i c r o f i b r i l s of the inner w a l l  l a y e r do n o t have the same o r i e n t a t i o n . The  a x i a l c h l o r o p l a s t s have s e v e r a l narrow  r a d i a t i n g from a c e n t r a l row of pyrenoids The  t h y l a k o i d s a r e arranged i n stacks  and  of i n d e f i n i t e l e n g t h  dense g l o b u l e s  (Fig. 1 2 ) .  lobes  (Fig. 12. 1 3 ) .  of v a r i a b l e  thickness  Many s p h e r i c a l e l e c t r o n -  caf' 150 mu i n diameter a r e present  among the  bands of t h y l a k o i d s , u s u a l l y i n u n i s e r i a t e rows ( F i g . 1 2 ) .  11  Some of the bands of t h y l a k o i d s and  traverse  the c h l o r o p l a s t  others terminate near the middle of the c h l o r o p l a s t  (Fig. 13). The granular  l a r g e , elongate pyrenoids have an electron-dense  matrix surrounded by a sheath of s t a r c h  (Fig. 12).  Chloroplast  the s t a r c h g r a i n s .  t h y l a k o i d s pass through gaps between  They e i t h e r t r a v e r s e  b l i n d l y w i t h i n the m a t r i x . membranes i n the pyrenoid the  separation  grains  the pyrenoid  The s e p a r a t i o n  of the t h y l a k o i d  i s c a . 13 mp, about the same as  i n the r e s t of the c h l o r o p l a s t .  M i t o c h o n d r i a a r e g e n e r a l l y very elongated w i t h up  or end  to 15 V- and width c a . 0.6 u (Fug.  length  1 4 ) . They a r e found  c l o s e to the c h l o r o p l a s t , u s u a l l y occupying a pocket between c h l o r o p l a s t lobes  ( F i g . 1 5 ) • Dictyosomes a r e a l s o s i t u a t e d  i n the v i c i n i t y of the c h l o r o p l a s t lobes  (Fig. 15).  Dictyosomes comprise 7-8 f l a t c i s t e r n a e about 30 mu t h i c k by 2 u long and the dictyosome v e s i c l e s a r e c a . 100 mu i n diameter.  Mnay ribosomes c a . 15 mu i n s i z e a r e s c a t t e r e d  i n the cytoplasm ( F i g . 1 5 ) .  The l a r g e nucleus (12 u x 7 u)  i s a t the isthmus r e g i o n and c o n t a i n s  a central  nucleolus  w i t h s e v e r a l l e s s e l e c t r o n - d e n s e channels i n i t ( F i g . 7 ) .  Penium  Fig.  5  margaritaceum  Living c e l l  of P. margar1taceum.  x930»  Arrows mark boundaries of g i r d l e band.  Fig.  6  Micrograph 4124.  Apex of c e l l .  Arrows i n d i c a t e  t h i c k e r p a r t s o f outer w a l l t h a t appear as g r a n u l e s i n the l i g h t microscope.  x5400.  F i x a t i o n : k% g l u t a r a l d e h y d e . P o s t f i x a t i o n : 1% osmic B u f f e r : c a c o d y l a t e - pH  Fig.  7  Micrograph 4108. nucleus  acid. 7.0.  Isthmus r e g i o n of c e l l .  (n) i s a t the isthmus r e g i o n .  Arrow  i n d i c a t e s isthmus furrow i n the outer c e l l layer.  x5100.  F i x a t i o n as i n F i g . 6 .  The  wall  14  Penium margarltaceum  Fig.  8  Micrograph 4503. wall.  L o n g i t u d i n a l s e c t i o n of c e l l  The outer w a l l l a y e r (o) i s embedded i n  the i n n e r w a l l l a y e r (1). x48000. e = embedded p a r t of outer w a l l l a y e r . F i x a t i o n : 4$  glutaraldehyde.  P o s t f I x a t i o n : 1% osmic a c i d . Buffers cacodylate  Fig.  9  Micrograph 4125*  - pH 7.0.  Oblique t a n g e n t i a l s e c t i o n through  c e l l w a l l showing i n n e r w a l l l a y e r (1), outer layer  (o) and r e g i o n of o v e r l a p  i n d i c a t e thickened  (e).  areas corresponding  v i s i b l e w i t h the l i g h t microscope. F i x a t i o n as i n F i g . 8.  wall  Arrows t o granules  xl6500.  16  Penium margar i tac eum  Fig.  10  Micrograph  4102.  L o n g i t u d i n a l s e c t i o n through  isthmus r e g i o n showing furrow outer w a l l l a y e r .  (arrow) i n the  x20000.  F i x a t i o n : k% g l u t a r a l d e h y d e . P o s t f i x a t l o n : 1% osmic a c i d . 7»0.  B u f f e r : c a c o d y l a t e - pH  Fig.  11  Micrograph  4092.  Oblique s e c t i o n through  cell  w a l l and cytoplasm a t isthmus r e g i o n showing c y t o p l a s m i c microtubules  (arrows).  x42000.  F i x a t i o n as i n F i g . 10.  Fig.  12  Micrograph  4507.  Transverse  s e c t i o n of  cell  through a p y r e n o i d showing s t a r c h g r a i n s (s) around p y r e n o i d , grana mitochondrion  i n c h l o r o p l a s t (g),  (m), dictyosome (d) and o s m i o p h i l i c  g l o b u l e s i n c h l o r o p l a s t (arrow). F i x a t i o n as i n F i g . 1 0 .  xl8300.  17  18  Penium  F i g . 13  margaritaceum  Micrograph 4-4-95.  Transverse s e c t i o n of c e l l  showing a x i a l c h l o r o p l a s t , mitochondria and dictyosome  (d).  (m)  x6300.  F i x a t i o n : k% g l u t a r a l d e h y d e . P o s t f i x a t i o n : 1% osmic a c i d . B u f f e r : c a c o d y l a t e - pH  F i g . 14-  Micrograph 4-104-.  7.0.  Longitudinal  section  p a r t of an elongated mitochondrion. F i x a t i o n as i n F i g . 1 3 .  through  xl5500.  19  20  Penium margarltaceum  F i g . 15  Micrograph  4520.  Transverse  section  of  showing dictyosomes (d) and mitochondrion situated  between lobes of the c h l o r o p l a s t  X26500. F i x a t i o n : 4$ Postfixation: Buffer:  glutaraldehyde. 1% osmic a c i d .  c a c o d y l a t e - pH  7.0.  cell (m) (ch).  21  22 Penium s p i r o s t r i o l a t u m Barker  C e l l s of Penium s p i r o s t r i o l a t u m measure 14-5-250 u long by 3 0 - 3 5 u wide. c e l l w a l l and  the  Longitudinal  s t r i a t i o n s on  the  thicker c e l l s differentiate this  from Penium margaritaceum ( F i g . 16).  The  species  elongate  c h l o r o p l a s t s are a x i a l w i t h a c e n t r a l row  of p y r e n o i d s .  E l e c t r o n micrographs of the c e l l w a l l of Penium s p i r o s t r i o l a t u m are Two  s i m i l a r to those of P.  d e f i n i t e w a l l l a y e r s are p r e s e n t , an  l a y e r 4-00-600 mu thick  ( F i g . 17,  t h i c k and 18).  The  an outer one  margaritaceum.  inner  about 1000  defined. thick.  The  granules and  surrounded by a r e g i o n  100  mu wide ( F i g . 20)v  do not The  (Fig. 19,  20)  i n diameter w i t h a space  extend through the  The  holes  of lower e l e c t r o n d e n s i t y  The  perforations  i n the  inner w a l l layer  mu  wide ( F i g ; 21).  ( F i g . 17,  p a r a l l e l m i c r o f i b r i l s are p r e s e n t but of a d j a c e n t bands i s random.  Bands of the  ca.  outer l a y e r  i n n e r w a l l l a y e r i s composed of a network of  m i c r o f i b r i l s 6-8  mu  the outer l a y e r  between c e n t r e s of the h o l e s .  are  sharply  f i b r i l s are approximately 10  by h o l e s 100-180 mu  of about 300 mu  the  appears more  w i t h the outer margin  In t a n g e n t i a l s e c t i o n  is perforated  mp.  outer l a y e r i s denser than  c o r r e s p o n d i n g l a y e r i n P. margaritaceum and g r a n u l a r than f i b r i l l a r ,  fibrillar  4--10  orientation  19).  The  outer c e l l w a l l l a y e r a t the  has a d e f i n i t e furrow ( F i g . 16, noticeable  18) which i s e s p e c i a l l y  i n t a n g e n t i a l s e c t i o n ( F i g . 22).  w a l l l a y e r i s continuous a c r o s s  the  semicells  ( F i g . 18).  l a y e r that i s overlapping continuous a c r o s s  the  The  the  isthmus.  The  inner  isthmus, o f t e n w i t h  a d i f f e r e n c e i n t h i c k n e s s between the the two  isthmus r e g i o n  inner w a l l l a y e r of  p a r t of the outer  wall  inner w a l l l a y e r i s a l s o  24  Penium s p i r o s t r i o l a t u m  Fig.  16  L i v i n g c e l l showing isthmus furrow  ( f ) and  boundaries of g i r d l e bands (arrows),  Fig.  17  Micrograph 2 0 5 4 .  x500.  L o n g i t u d i n a l s e c t i o n of  w a l l showing i n n e r l a y e r  ( i ) , outer l a y e r  and r e g i o n of o v e r l a p ( e ) .  cell (o)  xl2600.  Fixation: 2.5$ glutaraldehyde.  Fig.  18  P o s t f i x a t i o n : 1% osmic  acid.  B u f f e r : phosphate  - pH  7»2.  Micrograph 2 0 5 8 .  Longitudinal section  through  c e l l w a l l a t isthmus, i n d i c a t e d by the furrow ( f ) i n the outer w a l l  (o). ( i = inner wall)  F i x a t i o n as i n F i g . 1 7 .  x40500.  Penium s p i r o s t r i o l a t u m  P i g . 19  Micrograph 2110.  Oblique t a n g e n t i a l  section  through c e l l w a l l showing inner w a l l  ( i ) and  areas where the outer w a l l l a y e r i s embedded i n the  inner layer  F i x a t i o n : 2.5$  xl6500.  (e).  glutaraldehyde.  P o s t f i x a t i o n : 1% osmic a c i d . B u f f e r : phosphate - pH  Fig.  20  Micrograph 204-9.  7.2.  Tangential  outer c e l l w a l l l a y e r showing  s e c t i o n through perforations  surrounded by narrow areas of lower e l e c t r o n density  than the remainder of the w a l l .  F i x a t i o n as  in Fig.  19.  X51500.  Penium s p i r o s t r i o l a t u m  F i g ; 21  Micrograph 2 0 5 2 .  Tangential  inner c e l l w a l l l a y e r .  Arrows i n d i c a t e bands  of p a r a l l e l m i c r o f i b r i l s . Fixations  2.5$  s e c t i o n through  x52500.  glutaraldehyde.  P o s t f i x a t i o n : 1% osmic a c i d . B u f f e r : phosphate - pH  F i g . 22  Micrograph 2 3 0 7 .  7.2.  Tangential  s e c t i o n through  o u t e r c e l l w a l l l a y e r a t isthmus r e g i o n .  The  furrow ( f ) i n the outer w a l l l a y e r a t the isthmus i s shown.  XI3500.  F i x a t i o n as i n F i g . 2 1 .  29  30 Penium spinulosum (=Pleurotaenium  (Wolle) comb. nov. spinulosum  (Wolle) B r u n e i )  Although B r u n e i ( 1 9 4 9 ) p l a c e d t h i s s p e c i e s i n Pleurotaenium  (Cosmarieae)  the p r e s e n t study  indicates  t h a t i t belongs i n the genus Penium ( P e n i e a e ) .  C e l l s of  Penium spinulosum measure approximately 4 0 0 u l o n g , 5 ° u wide a t the s e m i c e l l base and 42 u wide a t the apex.  The  o u t l i n e of the l a t e r a l s e m i c e l l w a l l may be s t r a i g h t (Fig.  2 3 ) or u n d u l a t i n g ( F i g . 24) i n c e l l s of the same clone  w i t h the l a t t e r more common.  There i s a d e f i n i t e  c o n s t r i c t i o n a t the isthmus.  P. spinulosum d i f f e r s  all  from  other Pleurotaenium and Penium s p e c i e s by having spines  4 - 8 u l o n g c o v e r i n g the e n t i r e c e l l w a l l except f o r the apex (Fig.  2 3 , 2 4 ) . The s p i n e s near the apex a r e u s u a l l y  s l i g h t l y l o n g e r and s t o u t e r .  Methyl v i o l e t s t a i n s the  s p i n e s but ruthenium r e d does n o t , although a w a l l l a y e r below the s p i n e s s t a i n s w i t h ruthenium r e d i n d i c a t i n g the presence o f p e c t i c m a t e r i a l . and f i e l d  Some c e l l s from both c u l t u r e s  c o l l e c t i o n s have a c y l i n d r i c a l g i r d l e  section  i n t e r p o s e d between the two s e m i c e l l s , a c h a r a c t e r i s t i c of the Penieae. In  e l e c t r o n micrographs  the c e l l w a l l comprises two  d e f i n i t e l a y e r s s i m i l a r to those of the two Penium s p e c i e s already described ( F i g . 2 5 , 2 7 ) .  A coarse f i b r i l l a r  network makes up the i n n e r l a y e r which i s 7 5 0 - 9 0 0 mu t h i c k .  31 In o b l i q u e s e c t i o n s t h i s f i b r i l l a r network i s especiallyclear thick.  10 mu  ( F i g . 26).' The m i c r o f i b r i l s a r e approximately  There i s no d e f i n i t e p a t t e r n i n the o r i e n t a t i o n of  the m i c r o f i b r i l s but bands of 4-8 p a r a l l e l are seen i n some areas  ( F i g . 26).  microfibrils  The outer w a l l l a y e r i s  very dense and appears g r a n u l a r i n s e c t i o n s .  It i s partly  embedded i n the i n n e r l a y e r and appears l e s s dense i n the overlapping area  ( F i g . 25» 2 8 ) .  The t h i c k n e s s of the outer  w a l l l a y e r i s 5 0 0 - 1 0 0 0 mu on the l a t e r a l c e l l w a l l and s l i g h t l y more a t the a p i c e s  (Fig. 2 7 ) .  The spines on  the c e l l a r e p r o j e c t i o n s o f the outer w a l l 8-9 ;u long (Fig;  25 )•''  They a r e i n c l i n e d toward the apex.  In t a n g e n t i a l  s e c t i o n s the spine bases are dense areas about 1 u i n diameter ( F i g ; 2 8 ) . base t o j o i n a d j a c e n t  Thick r i b s r a d i a t e from each spine spine bases.  The i n t e r v e n i n g spaces  are c r i s s - c r o s s e d w i t h s m a l l e r p a r t i t i o n s producing i r r e g u l a r reticulum ( F i g . 28). the c e l l w a l l .  an  No pores are present i n  F i n e n e e d l e - l i k e p r o j e c t i o n s about 500 mu  long extend outward from the s m a l l e r p a r t i t i o n s of the outer w a l l l a y e r ( F i g . 2 7 ) and i n c r o s s s e c t i o n s appear as s o l i d dots The  ( F i g . 28).  s e m i c e l l w a l l s do not o v e r l a p a t the isthmus  r e g i o n as they do i n Pleurotaenium nodosum ( F i g . 4 2 ) . There i s a furrow i n the outer w a l l l a y e r a t the isthmus but the inner w a l l l a y e r i s continuous (Fig.  29).  a c r o s s the isthmus  In some i n s t a n c e s there i s a conspicuous  32 difference the  i n thickness  two s e m i c e l l s .  between the inner w a l l l a y e r s of  F i g . 29 shows an example where one  i n n e r w a l l l a y e r i s ca.'' 6 6 0 mu t h i c k and the other i s c a . 920 mu t h i c k , r e f l e c t i n g a d i f f e r e n c e two  i n age between the  semicells. Cross s e c t i o n s  is axial  of the c e l l r e v e a l t h a t the c h l o r o p l a s t  ( F i g . 3 0 ) . However, the pyrenoids a r e not i n an  a x i a l row but s c a t t e r e d randomly ( F i g . 2 4 ) .  The  are arranged i n t o d e f i n i t e grana ( F i g . 3 0 ) .  The remainder  thylakoids  of the cytoplasm i s f i l l e d w i t h many s m a l l vacuoles ( F i g . 27,  30).  33  Penium spinulosum  Pig.  23  L i v i n g c e l l w i t h almost s t r a i g h t l a t e r a l Arrow i n d i c a t e s p o s i t i o n of isthmus.  Fig.  2k  L i v i n g c e l l with undulating same clone as c e l l  (py).  F i g . 25  Arrow i n d i c a t e s  Note s c a t t e r e d p y r e n o i d s  xkkO.  Micrograph 1113. through one ow  x440.  l a t e r a l margins from  in Fig. 23.  p o s i t i o n of isthmus.  margins.  L o n g i t u d i n a l s e c t i o n of c e l l  of the s p i n e s .  F i x a t i o n : 1% osmic a c i d . B u f f e r : phosphate - pH  (iw = inner w a l l l a y e r ,  x21500.  = outer w a l l l a y e r ) .  7.2.  wall  34  35  Penium splnulosum  Pig.  26  Micrograph 0 8 6 0 .  Tangential  inner c e l l w a l l l a y e r .  s e c t i o n through  Arrows i n d i c a t e a band  of s i x p a r a l l e l m i c r o f i b r i l s .  x47500.  F i x a t i o n : 1% osmic a c i d .  F i g . 27  7»2.  B u f f e r : phosphate  - pH  Micrograph 1 2 0 0 .  L o n g i t u d i n a l s e c t i o n through  c e l l apex.  Needle-like  projections  p r e s e n t on the outer w a l l F i x a t i o n as i n F i g . 2 6 .  (o).  (arrow) are  x3850.  36  37  Penium spinulosum  F i g . 28  Micrograph 1222.  Tangential section  through  c e l l w a l l . Large p a r t i t i o n s connect the spine bases  (arrows) and s m a l l e r p a r t i t i o n s form a  reticulum layer  i n the outer l a y e r .  (iw) i s f i b r i l l a r .  F i x a t i o n : 1% osmic Buffer:  x5300.  acid.  phosphate - pH  The inner  7.2.  wall  38  39  Penium spinulosum  Ijrig.  29  Micrograph 0 8 6 8 .  Longitudinal  c e l l w a l l a t isthmus r e g i o n . p r e s e n t i n the outer w a l l .  section A furrow  The  through (f) i s  inner w a l l of  the s e m i c e l l on the r i g h t i s t h i c k e r than t h a t the l e f t .  X15000.  F i x a t i o n : 1% osmic  Fig.  30  acid. 7.2.  B u f f e r : phosphate  - pH  Micrograph 1 0 6 0 .  Transverse s e c t i o n of c e l l  showing a x i a l c h l o r o p l a s t c o n t a i n i n g x4250.  F i x a t i o n as i n F i g . 2 9 .  grana ( g ) .  on  4  0  41 Subfamily T h i s subfamily  Closterieae  eontains  one genus,  Closterium  N l t z s c h , c h a r a c t e r i z e d by lunate c e l l s w i t h no isthmus constriction species . ' 1  (Figv 2 ,  )v  Pores a r e r e p o r t e d  i n some  I n t e r c a l a t e d g i r d l e s e c t i o n s e x i s t i n some  1  s p e c i e s and the d i v i s i o n s i t e i s more r e g u l a r than i n the Penieae, o c c u r r i n g a t a s p e c i a l i z e d l i n e on the c e l l (German: R i n g f u r c h e , K r i e g e r 1 9 3 7 ) which develops each d i v i s i o n .  before  The nucleus i s a t the isthmus r e g i o n and  there a r e u s u a l l y two c h l o r o p l a s t s . reported  wall  A p i c a l vacuoles  t o c o n t a i n gypsum c r y s t a l s a r e p r e s e n t .  Closterium  lineatum  Closterium  Ehrenberg  lineatum  has narrow, elongate curved  cells  measuring 4 5 0 - 5 0 0 u long by 28-30 u wide a t the isthmus and 10-12  u wide a t the apex ( F i g . 3 1 ) .  Several  faint  l o n g i t u d i n a l l i n e s a r e g e n e r a l l y v i s i b l e on the c e l l i n the l i g h t microscope.  wall  The c h l o r o p l a s t s a r e a x i a l w i t h  a c e n t r a l row of p y r e n o i d s .  Only the c e l l w a l l was s t u d i e d  w i t h the e l e c t r o n microscope. The with l i t t l e the  c e l l w a l l appears g r a n u l a r  i n e l e c t r o n micrographs  i n d i c a t i o n o f f i b r i l l a r nature  ( F i g . 3 2 ) . At  isthmus r e g i o n the w a l l i s 600-800 mu t h i c k i n c r e a s i n g  to 1 2 0 0 - 2 0 0 0 mu t h i c k a t the apexv  A diagonal  suture  line  42 marks the o v e r l a p of the s e m i c e l l w a l l s a t the (Fig.  34).  isthmus  The outer boundary of the w a l l i s l i m i t e d  by  two dense l i n e s , the i n n e r one approximately 10 mu  thick  and the outer one s l i g h t l y t h i n n e r ( F i g . 32, 33 )•  Low  r i d g e s extending out c a . 300 mu correspond t o the l i n e s v i s i b l e on the c e l l w a l l i n the l i g h t microscope. r i d g e s a r e most conspicuous i n t a n g e n t i a l s e c t i o n but are a l s o seen i n l o n g i t u d i n a l s e c t i o n s  These ( F i g . 35)  ( F i g . 34).  Although pores are r e p o r t e d t o be p r e s e n t i n t h i s species  ( K r i e g e r 1937) no s t r u c t u r e s c o r r e s p o n d i n g  pore apparatus of the Cosmarieae i n e l e c t r o n micrographs.  to the  ( F i g . 4) c o u l d be found  At the c e l l apex there are l e s s  electon-dense channels i n the w a l l which c o u l d serve as areas through which m a t e r i a l i s s e c r e t e d ( F i g . 33)•  These  channels are about 100 mu wide and pass outward through the w a l l from an i n n e r l a y e r density. was  (200 mu t h i c k ) of low  electron  No c o n n e c t i o n w i t h the o u t s i d e of the c e l l  found but s e r i a l s e c t i o n s of the a r e a were not o b t a i n e d .  F u r t h e r work i s necessary to v e r i f y the presence or of  wall  a connection.  absence  43  Closterlum lineatum  Fig;  31  L i v i n g c e l l of C l o s t e r i u m l i n e a t u m . of  the nucleus  (n) and  The  the a p i c a l vacuole  position (v)  is indicated. x200.  Fig.  32  Micrograph c e l l wall.  1247.  Longitudinal section  Arrow i n d i c a t e s two  through  electron-dense  l i n e s a t outer boundary of the w a l l .  xl2500.  F i x a t i o n : 1% osmic a c i d . B u f f e r : phosphate - pH  Fig.  33  Micrograph 276O.  7«2.  Longitudinal section  through  apex of c e l l showing p o s s i b l e channels f o r the passage of m a t e r i a l through the c e l l : w a l l X14000.  F i x a t i o n as i n F i g . 3 2 .  (arrows).  45  Closterlum  Fig.  34  lineatum  Micrograph 6 9 - 9 .  L o n g i t u d i n a l s e c t i o n through  isthmus r e g i o n showing overlap (arrows) and a r i d g e  of s e m i c e l l w a l l s  ( r ) on the c e l l w a l l .  X12500. F i x a t i o n : 1% osmic a c i d . B u f f e r : phosphate - pH  Fig.  35  Micrograph 2 7 4 4 . c e l l wall ridges  7.2.  Tangential (r).  F i x a t i o n as i n F i g . 3 4 .  s e c t i o n through  xl9200.  46  47 Subfamily  Cosmarieae  T h i s l a r g e s u b f a m i l y c o n t a i n s genera t h a t have a conspicuous c o n s t r i c t e d semicells  (Fig. 1).  isthmus r e g i o n c o n n e c t i n g the  The c e l l w a l l c o n t a i n s pores and a  p e c t i c sheath i s p r e s e n t i n most s p e c i e s . s i t e i s always a t the isthmus. f i l a m e n t o u s or u n i t e d i n globose  The  Species may  be  division unicellular,  colonies.  Genus Pleurotaenium,Nageli  T h i s u n i c e l l u l a r genus has s t r a i g h t , elongate cylindrical cells. may  The t r u n c a t e a p i c e s may  have a r i n g of s m a l l knobs.  be naked or  A l a r g e vacuole c o n t a i n i n g  s e v e r a l gypsum c r y s t a l s i s p r e s e n t a t each apex. c h l o r o p l a s t s may  The  be p a r i e t a l bands or a x i a l bands.  Pleurotaenium nodosum ( B a i l e y ) L u n d e l l  C e l l s of Pleurotaenium nodosum measure 2 5 0 - 3 5 0  u  l o n g by 45-48 u wide a t the s e m i c e l l base and 2 0 - 2 3 u wide a t the apex ( F i g . 3 6 ) . '  Four r i n g s of i n f l a t i o n s are  p r e s e n t on each s e m i c e l l and a r i n g of s h o r t c o n i c a l knobs i s p r e s e n t a t the apex ( F i g . 3 6 ) v Methyl v i o l e t  staining  r e v e a l s pores over the whole c e l l w a l l which are not arranged i n a r e g u l a r p a t t e r n ( F i g . 3 7 ) .  Knobs of sheath  48 m a t e r i a l are s t a i n e d a t the o u t s i d e which have d i v i d e d and wall layer i s discarded  of each p o r e .  In c e l l s  completely d i f f e r e n t i a t e d an from the o u t s i d e  initial (Fig. 36).  of the c e l l  T h i s l a y e r i s thought to be a primary w a l l t h a t i s present only d u r i n g  the e l o n g a t i o n  cytokinesisV  The  of the new  c h l o r o p l a s t s are p a r i e t a l bands and  s p h e r i c a l vacuole i s p r e s e n t i n the  semicell following  a t each apex.  a  The nucleus i s  isthmus r e g i o n between the c h l o r o p l a s t s of the  two  semicells. 1-1.5  In e l e c t r o n micrographs the c e l l w a l l measures u t h i c k and  comprises many t h i n l a y e r s of c e l l u l o s e  m i c r o f i b r i l s approximately 10 mu wide ( F i g . 3 8 ,  40).  The  f i b r i l l a r nature of the w a l l i s c l e a r l y seen i n o b l i q u e sections  (Fig. 39,  41);  M i c r o f i b r i l s of s u c c e s s i v e  layers  are o r i e n t e d a t an angle of 3 0 - 7 0 ° to each other but i s no The  there  c o n s i s t e n t angle d i f f e r e n c e throughout the w a l l .  c e l l w a l l does not comprise two  the Penieae;  ;  d i s t i n c t l a y e r s as i n  A narrow electron-dense  l i m i t of the w a l l  ( F i g . 3 8 . ' 40)'.  l a y e r marks the  outer  At the isthmus r e g i o n  both s e m i c e l l w a l l s g r a d u a l l y become t h i n n e r and  overlap  ( F i g . 42)tf The  pores are c y l i n d r i c a l holes t i n the c e l l  w i t h a lumen ca". 100  mu  i n diameter ( F i g . 3 8 ,  39,  A t h i n dense l a y e r marks the margin of the pore and microfibrils  wall 40). the  of the w a l l surround t h i s l a y e r ( F i g . 4 0 ,  41).  49 W i t h i n the pore lumen there i s a t h i n p e r i p h e r a l l a y e r of m a t e r i a l continuous w i t h the e x t e r n a l sheath c o l l a r and the i n t e r n a l pore b u l b ( F i g . 3 8 , 4 0 ) . of the pore lumen appears  empty.  The c e n t r a l a r e a  The pore b u l b has a  c a p - l i k e s t r u c t u r e under the pore surrounded by a network of f i b r i l l a r m a t e r i a l ( F i g . 3 9 , 4 0 ) .  The plasma membrane  i s withdrawn i n the r e g i o n of the pore b u l b to form a h e m i s p h e r i c a l pocket. funnel-shaped  The sheath c o l l a r  s t r u c t u r e extending out c a . 300 mu from the  c e l l w a l l and measuring (Fig. 3 8 ) .  i s generally a  about  700 mu a t i t s widest p o i n t  A l o o s e mass o f f i b r i l s extends from the sheath  c o l l a r a f u r t h e r 1 0 0 0 mu.  A t h i n sheath l a y e r i s p r e s e n t  c l o s e to the c e l l w a l l between the pores  (Fig. 4 0 ) .  As many as 12 c h l o r o p l a s t bands a r e p r e s e n t i n t r a n s v e r s e s e c t i o n s of the c e l l are arranged  (Fig. 45).  The t h y l a k o i d s  i n conspicuous grana and s m a l l s p h e r i c a l  e l e c t r o n - d e n s e b o d i e s a r e p r e s e n t i n rows i n the stroma. There a r e numerous s m a l l pyrenoids surrounded by s t a r c h sheath  (Fig. 43).  S e v e r a l t h y l a k o i d s enter the dense  p y r e n o i d m a t r i x through gaps between the s t a r c h g r a i n s and many completely t r a v e r s e the p y r e n o i d matrix.' Much o f the cytoplasm i s occupied by s m a l l v a c u o l e s , some appearing empty and others f i l l e d w i t h f i b r i l l a r material (Fig. 4 4 ) .  M i t o c h o n d r i a a r e numerous i n the  c e n t r a l p a r t of each s e m i c e l l and c l o s e t o the c h l o r o p l a s t s  (Fig. the  4-5).  Large dictyosomes  chloroplasts  (Fig.  isthmus and c o n t a i n s Immediately there the cell the  1  4-5).  The n u c l e u s  p l a s m a membrane  are microtubules  15-20  isthmus  These  is  the  occur  near  situated  (Fig.  i n the  mu i n d i a m e t e r  isthmus p e r p e n d i c u l a r to 4-6).  u long also  a central nucleolus  below the  ( F i g . 4-4-,  2-3  at  4-2).  isthmus going  longitudinal axis  region  around of  the  microtubules are r e s t r i c t e d  r e g i o n and do n o t  occur  elsewhere  the  i n the  to  cell.  51 Pleurotaenium nodosum  Fig.  36  L i v i n g c e l l s i n l i g h t microscope showing  the  isthmus c o n s t r i c t i o n (c) and a p i c a l knob ( k ) . Lower c e l l  i s d i s c a r d i n g an i n i t i a l w a l l  from a r e c e n t l y formed s e m i c e l l .  Fig.  37  Methyl v i o l e t s t a i n e d c e l l  (arrow)  xi|45.  i n surface  view.  The pores and sheath c o l l a r s have s t a i n e d (arrow).  Fig.  38  x620.  Micrograph 1900.  L o n g i t u d i n a l s e c t i o n of c e l l  w a l l through a pore showing pore bulb (pb), sheath collar  ( s c ) , plasma membrane (pm), outer margin of  c e l l wall  (o) and t h i n l a y e r of sheath above the  c e l l wall  (s). X26500.  F i x a t i o n : 5$ g l u t a r a l d e h y d e ; P o s t f i x a t i o n : 1% osmic a c i d . B u f f e r : phosphate - pH  7;2.  53  Pleurotaenium nodosum  F i g * 39  Micrograph 1 8 3 8 . wall;  Oblique s e c t i o n through  cell  Arrow i n d i c a t e s dense margin of a pore;  The pore bulb (pb) c o n t a i n s a network of microfibrils.  x26500.  F i x a t i o n : 5% g l u t a r a l d e h y d e . P o s t f i x a t i o n : 1% osmic  F i g . 40  acid. 7.2.  B u f f e r : phosphate  - pH  Micrograph 1 9 0 6 .  Longitudinal  section  through  c e l l w a l l and inner p a r t of pore apparatus.  The  dense boundary of the pore i s i n d i c a t e d by an arrow.  A cap-like structure  the pore the w a l l .  i s s i t u a t e d under  (c) and the sheath (s) i s p r e s e n t above X26500.  F i x a t i o n as i n F i g . 3 9 .  55  Pleurotaenium  F i g , 41  nodosum  Micrograph  4666.  T a n g e n t i a l s e c t i o n through  c e l l w a l l showing l a y e r s of p a r a l l e l Arrow i n d i c a t e s dense margin of pore. Fixations 2.5$  microfibrils. x57000.  glutaraldehyde.  P o s t f i x a t i o n : 1% osmic a c i d . B u f f e r : phosphate - pH  F i g ; 42  Micrograph  1830.  7.2.  L o n g i t u d i n a l s e c t i o n through  isthmus r e g i o n of c e l l s s h o w i n g o v e r l a p of s e m i c e l l s (arrow),  l a r g e nucleus  (n) and n u c l e o l u s  X3500. F i x a t i o n : 5$  glutaraldehyde.  P o s t f i x a t i o n : 1% osmic a c i d . B u f f e r : phosphate - pH  7«2.  (nu).  57 Pleurotaenium nodosum  F i g . 43  Micrograph 1821. pyrenoid ( t ) and  S e c t i o n of p y r e n o i d .  The  matrix i s t r a v e r s e d by s e v e r a l surrounded by s t a r c h g r a i n s  F i x a t i o n : 5%  (s).  thylakoids xl6500.  glutaraldehyde.  P o s t f i x a t i o n ; 1% osmic a c i d . B u f f e r : phosphate - pH  F i g . 44  Micrograph 1862.  7*2.  Transverse s e c t i o n of isthmus  m i c r o t u b u l e s (arrow) below the plasma membrane (pm). x47500.  Vacuole (v) c o n t a i n s  fibrillar  F i x a t i o n as i n F i g . 4 3 . ' -  material.  58  59  Pleurotaenlum nodosum  F i g . 45  Micrograph 1828.  Transverse s e c t i o n of  through s e v e r a l c h l o r o p l a s t s c o n t a i n i n g (g) and  osmiophilic globules  M i t o c h o n d r i a (m) and  grana  (arrow).  a dictyosome (d) are  p r e s e n t c l o s e to the c h l o r o p l a s t s . F i x a t i o n : 5%  cell  also  xl5500.  glutaraldehyde.  P o s t f i x a t i o n : 1% osmic a c i d . B u f f e r : phosphate - pH  Fig.  46  Micrograph 1 8 1 6 .  Longitudinal  microtubules ( t ) . F i x a t i o n as  7.2.  in Fig.  x71000. 45.  s e c t i o n of  isthmus  61  Genus T r i p l o c e r a s  Bailey  T h i s genus of u n i c e l l u l a r desmids has elongate c e l l s w i t h s e v e r a l r i n g s of protuberances and 2 - 4 - f u r c a t e a p i c e s (Fig.  4-7).  The nucleus i s a t the isthmus and the  two  c h l o r o p l a s t s are a x i a l w i t h a c e n t r a l row of p y r e n o i d s .  Triploceras verticlllaturn Bailey  C e l l s of T r l p l o c e r a s v e r t i c i l l a t u m measure 3 4 0 - 4 0 0 u long by 4 0 - 4 5 M wide.  The protuberances are  flat-topped  near the base of the s e m i c e l l but they become i n c l i n e d and pointed  near the apex ( F i g . 4 7 ) .  Methyl v i o l e t s t a i n s a  s m a l l knob of sheath around each pore  (Fig. 4 8 ) .  The f i n e s t r u c t u r e of the c e l l w a l l i s s i m i l a r to t h a t of Pleurotaenium nodosum.  The w a l l i s 800-1300  mu  t h i c k and comprises many t h i n l a y e r s of m i c r o f i b r i l s . The c e l l w a l l a t a protuberance i s s l i g h t l y (Fig.  49).  thicker  A t h i n e l e c t r o n - d e n s e l i n e marks the outer  boundary of the c e l l w a l l and-, there  i s another narrow l i n e  c a . 20 mu beyond the w a l l which i s continuous w i t h the sheath m a t e r i a l a t the pores ( F i g . 5 2 ) . overlap  The s e m i c e l l  walls  a t the isthmus as i n Pleurotaenlum nodosum. Pores i n the c e l l w a l l are about 200 mu i n diameter  and are s i m i l a r to those of P. nodosum ( F i g . 50,  52).  Below the pore a c a p - l i k e s t r u c t u r e occupies p a r t of the pore bulb ( F i g . 51,  52)  w i t h a few m i c r o f i b r i l s occupying  62 the r e s t of the pore bulb  ( F i g . 51)•  W i t h i n the pore lumen  a l a y e r of sheath m a t e r i a l i s present around the edge of the pore  (Fig. 52).  The  sheath extends  outward from  pore up to 1000 mu and c o n s i s t s of many f i n e  the  microfibrils.  The c h l o r o p l a s t i s a x i a l w i t h about seven lobes t h a t r a d i a t e from a c e n t r a l area c o n t a i n i n g the pyrenoids ( F i g . 56,  57).  Each major lobe u s u a l l y b i f u r c a t e s .  are arranged  The t h y l a k o i d s  i n t o d e f i n i t e grana w i t h a v a r i a b l e number of  t h y l a k o i d s i n each stack ( F i g . 5 5 ) •  Pyrenoid s t r u c t u r e i s  s i m i l a r to t h a t of the pyrenoids of Pleurotaenium nodosum. C e n t r a l l e s s dense areas are present i n some pyrenoids (Fig. 5 6 ) .  E l e c t r o n - d e n s e g l o b u l e s about 150  mu  i n diameter  are common i n the c h l o r o p l a s t stroma and are o f t e n arranged i n groups ( F i g . 5 7 ) . M i t o c h o n d r i a and dictyosomes c h l o r o p l a s t lobes ( F i g . 5 5 ) •  a r e u s u a l l y near  the  Mitochondria are elongate  and narrow, about 300 mu wide and up to 10 u long ( F i g . 5 4 ) . Dictyosomes are 2-3  U long and have 6-12  cisternae (Fig. 55)•*»  Vacuoles occupy a l a r g e p a r t of the cytoplasm between the c h l o r o p l a s t l o b e s .  Some appear empty and  f i l l e d w i t h a l o o s e g r a n u l a r substance, or a whorled  arrangement of m i c r o f i b r i l s  Large v e s i c l e s about 600 mu wide w i t h an c e n t r a l r e g i o n surrounded  others are  scattered m i c r o f i b r i l s ( F i g . 51»  55).  electron-dense  by a l e s s dense p e r i p h e r y are  present near the c h l o r o p l a s t lobes ( F i g . 5 4 ) .  The  r e t i c u l u m i s r e p r e s e n t e d by a few elongated v e s i c l e s  endoplasmic (Fig. 55).  63 A s e c t i o n of a c e l l  i n which c e l l d i v i s i o n i s complete  and where e l o n g a t i o n of the young s e m i c e l l s has s t a r t e d i s shown i n F i g . 53* at  The parent s e m i c e l l w a l l s a r e separated  the isthmus and the new s e m i c e l l w a l l s a r e s t i l l  thin.  The d i v i s i o n septum i s c a . 500 mu t h i c k and comprises  two  l a y e r s which can be d i s t i n g u i s h e d near the outer margin (Fig.  53, 59). Between the newly developed  c e l l w a l l and the plasma  membrane there a r e i r r e g u l a r membranous and f i l a m e n t o u s s t r u c t u r e s , some f l a t t e n e d a g a i n s t the i n n e r s u r f a c e of the c e l l wall (Fig. 59)• connected  In p l a c e s the membranes a r e s t i l l  w i t h the plasma membrane ( F i g . 6 0 ) .  Large  vacuoles  i n the cytoplasm c o n t a i n m i c r o f i b r i l s and membranes s i m i l a r to  those o u t s i d e the cytoplasm  (Fig. 5 9 ) .  s i m i l a r i n s i z e t o the dictyosome near the d i v i s i o n w a l l ( F i g . 5 9 ) . at  the isthmus  Small vacuoles  v e s i c l e s a r e numerous The microtubules present  i n i n t e r p h a s e c e l l s a r e a l s o present i n  d i v i d e d c e l l s but only a l o n g the plasma membrane a d j a c e n t to the o l d s e m i c e l l w a l l ( F i g . 5 8 ) . Fig.  60 shows the c e l l w a l l of a young s e m i c e l l that  has elongated t o approximately h a l f of the mature s i z e .  The  w a l l i s c a . 2 0 0 mu t h i c k and i s uniform and f i b r i l l a r w i t h no evidence of p o r e s .  The outer s u r f a c e of the young w a l l  i s covered w i t h a t h i n l a y e r of electron-dense m a t e r i a l (Fig.  6 0 ) and many vacuoles a r e seen coming out of the  cytoplasm  (Fig. 6 0 ) .  64  T r l p l o c e r a s ver t i c 111a turn  F i g . 4-7  L i v i n g c e l l of T. v e r t i c i l l a t u m . isthmus c o n s t r i c t i o n .  F i g . 48  x280.  C e l l s t a i n e d w i t h methyl v i o l e t showing s t a i n e d pores  F i g . 49  Arrow i n d i c a t e s  x540.  (arrow).  Micrograph 2 9 7 5 . protuberance.  Two  Longitudinal section  through  pore bulbs (b) are p r e s e n t a t  the base of the protuberance. F i x a t i o n : k% g l u t a r a l d e h y d e . P o s t f i x a t l o n : 1% osmic B u f f e r : c a c o d y l a t e - pH  acid. 7.0.  xl7000.  ®  66  Trlploceras  F i g . 50  vertlcillatum  Micrograph 2 9 1 4 .  Cross s e c t i o n of pore  near i n t e r n a l s u r f a c e of c e l l w a l l  (p)  (w).  x52000.  F i x a t i o n : h% g l u t a r a l d e h y d e . P o s t f i x a t i o n : 1% osmic B u f f e r : c a c o d y l a t e - pH  F i g . 51  Micrograph 2 9 1 5 .  acid. 7»0»  Cross s e c t i o n of s o l i d  (arrow) i n the pore b u l b . microfibrils  A network of  ( f ) surrounds the cap.  x550°0»  A vacuole (v) near the pore b u l b c o n t a i n s fibrillar  material.  F i x a t i o n as i n F i g . 5 0 .  cap  68  Triploceras vertlcillatum  Fig.  52  Micrograph 2 6 1 8 . wall  (w)  L o n g i t u d i n a l s e c t i o n of  through a pore.  A c a p - l i k e plug  (arrow) i s s i t u a t e d under the pore and material  sheath  (s) i s coming out of the pore.  F i x a t i o n : k%  cell  xl7000.  glutaraldehyde.  P o s t f i x a t i o n : 1% osmic a c i d . B u f f e r : cacodylate  Fig.  53  Micrograph 2 9 7 4 .  - pH  7»0.  L o n g i t u d i n a l s e c t i o n through  isthmus r e g i o n of d i v i d i n g c e l l .  The  division  septum (s) i s s p l i t t i n g a t the margin  (arrow),  n = nucleus.  x5100.  F i x a t i o n as i n F i g .  52.  Trlploceras  F i g . 54  vertlcillatum  Micrograph  54-8.  (m), vacuoles  S e c t i o n showing mitochondria  (v)  t  electron-dense globules (gl)  and vacuole w i t h dense i n t e r i o r  (arrow).  x7800.  F i x a t i o n : 1% osmic a c i d . B u f f e r s phosphate - pH  F i g . 55  Micrograph  4471.  mitochondrion reticulum  (m)  7.2.  S e c t i o n showing dictyosome p  vacuole  ( v ) , endoplasmic  (er) and c h l o r o p l a s t granum ( g ) .  x40000. F i x a t i o n : 4$ glutaraldehyde. P o s t f i x a t i o n : 1% osmic a c i d . ' B u f f e r : c a c o d y l a t e - pH  7.0.  (d),  71  72  T r l p l o c e r a s vertlc111aturn  Fig.  56  Micrograph  4-515•  Transverse  through a p y r e n o i d .  s e c t i o n of c e l l  The pyrenoid has a c e n t r a l  l e s s electron-dense r e g i o n and i s surrounded starch grains ( s ) .  by  x3700.  F i x a t i o n : 4$ glutaraldehyde. P o s t f i x a t i o n : 1% osmic a c i d . B u f f e r : c a c o d y l a t e - pH 7 « 0 .  Fig.  57  Micrograph  4-518.  p a s s i n g through ring of  Transverse  s e c t i o n of c e l l  s e v e r a l protuberances  ( r ) . Each protuberance  of one  c o n t a i n s one lobe  the c h l o r o p l a s t ( c h ) . E l e c t r o n - d e n s e  (g) a r e p r e s e n t i n the stroma. F i x a t i o n as i n F i g . 5 6 .  x3700.  globules  74  Triploceras  Fig.  58  verticiliaturn  Micrograph 2976. microtubules  S e c t i o n showing isthmus  (arrow) below plasma membrane  (pm).  X95000. Fixation:4$  glutaraldehyde.  P o s t f i x a t i o n : 1% osmic a c i d . B u f f e r : cacodylate  F i g . 59  Micrograph 2 9 8 3 .  7.0.  - pH  Initial  i n d i v i d e d c e l l . The  semicell  d i v i s i o n septum i s s p l i t t i n g  a t the margin (arrow). fibrillar  w a l l of new  m a t e r i a l and  Vacuoles (v) c o n t a i n i n g dictyosome v e s i c l e s (d)  are present near the new  wall.  Membranous  b o d i e s (x) are present between w a l l and membrane. F i x a t i o n as  F i g . 60  plasma  x!3500. in Fig.  Micrograph 3425.  58.  S e c t i o n of new  c e l l w i t h h a l f - e l o n g a t e d new  semicell wall in  semicell.  w a l l ( i ) has a t h i n electron-dense  The  l a y e r (a) on i t s  outer s u r f a c e .  Vacuoles (v) are coming out  the cytoplasm.  xl3000.  F i x a t i o n as i n F i g .  58.  initial  of  75  76 Genus BambusIna K u t z i n g  T h i s f i l a m e n t o u s desmid genus i s d i s t i n g u i s h e d  from  all  o t h e r s except Desmidium by the f o r m a t i o n of f o l d s i n  the  division wall  (Fig. 61).  I t d i f f e r s from Desmidium by  having l o n g i t u d i n a l s t r i a t i o n s on the c e l l w a l l near the apex.  The c h l o r o p l a s t s are s t e l l a t e  i n a p i c a l view w i t h  one c e n t r a l p y r e n o i d .  BambusIna b r e b i s s o n l l K u t z i n g  C e l l s of Bambusina b r e b i s s o n i i measure 25 u l o n g , 22 u wide a t the isthmus and 15 M wide a t the apex ( F i g . 61). Near the isthmus two i n f l a t i o n s are p r e s e n t on o p p o s i t e s i d e of the c e l l w i t h a shallow isthmus groove between them ( F i g . 61). (Fig.  sheath surrounds the f i l a m e n t  62). In  200  A narrow  e l e c t r o n micrographs the l a t r e r a l c e l l w a l l Is c a .  mu t h i c k except f o r a t h i c k e n e d r i d g e  8 p. from the apex ( F i g . 6 7 ) .  (500 m)x) about  The a p i c a l w a l l i s c a . 150  mn  t h i c k and adheres to the a p i c a l w a l l of the a d j a c e n t c e l l (Fig.  6 4 ) . The l a t e r a l margin of the a p i c a l w a l l i s  thickened and p r o t r u d e s s l i g h t l y  (Fig. 63).  Pores a r e p r e s e n t i n both a p i c a l and l a t e r a l walls  (Fig. 67).  cell  Pore diameter i s c a . 100 mu and the  l a t e r a l pores near the isthmus t r a v e l o b l i q u e l y through the c e l l wall  (Fig. 67).  The pore b u l b c o n t a i n s a network of  77 fibrils  and there  i s a low sheath c o l l a r from which  m i c r o f i b r i l s extend 1 . 5 - 2 . 0 u from the w a l l  (Fig. 6 7 ) .  C h l o r o p l a s t s t r u c t u r e i s s i m i l a r t o that of T r i p l o c e r a s w i t h grana of v a r i a b l e s i z e ( F i g . 6 4 , 6 6 ) . granules a r e present  and pyrenoid  Osmiophilic  structure i s i d e n t i c a l  w i t h t h a t o f other desmids ( F i g . 6 5 ) • Mitochondria 1 u long and 0 . 5 P- wide and dictyosomes c a . 1 u long c l o s e t o the c h l o r o p l a s t ( F i g . 6 4 ) .  Endoplasmic  about occur  reticulum  and  many v a c u o l e s a r e present  i n the cytoplasm ( F i g . 6 4 ) .  The  nucleus i s c e n t r a l l y l o c a t e d and has a l a r g e s p h e r i c a l  nucleolus. Micrographs of c e l l s i n stages f o l l o w i n g c y t o k i n e s i s were o b t a i n e d .  A f t e r c y t o k i n e s i s a f o l d develops i n the  new w a l l which g i v e s the d i v i s i o n septum an H-shaped form (Fig  67)•  A l a y e r of l e s s e l e c t r o n dense m a t e r i a l  occupying the c e n t e r  of the f o l d and extending out t o the  l a t e r a l margin of the c e l l primary w a l l  (Fig. 6 8 ) .  i s i n t e r p r e t e d as the i n i t i a l or  The secondary or mature w a l l i s  l a i d down under t h i s i n i t i a l w a l l .  In l a t e r stages the  f o l d e d w a l l separates as the i n i t i a l w a l l i s t o r n a p a r t by the e l o n g a t i o n  o f the new s e m i c e l l ( F i g . 6 9 ) .  The area  between the f o l d s remains i n c o n t a c t as the a p i c a l w a l l s of the mature s e m i c e l l s .  In the mature w a l l the p o s i t i o n  of the f o l d remains as a s l i g h t d e p r e s s i o n  ( F i g . 6 4 ) and  the outer  corner  of the d i v i s i o n septum i s i d e n t i f i e d as the  thickened  r i d g e on the w a l l mentioned e a r l i e r  (Fig. 6 7 ) .  78  BambusIna b r e b l s s o n i i  Fig.  61  Living cells,  one w i t h f o l d e d d i v i s i o n w a l l ( f ) .  Isthmus (1) Is I n d i c a t e d  Fig.  62  63  xl^OO.  Filament s t a i n e d w i t h methyl v i o l e t to show narrow sheath ( s ) .  Fig.  in c e l l at l e f t .  Micrograph 4619»  x750.  L o n g i t u d i n a l s e c t i o n through  l a t e r a l margin of c e l l apex showing r i d g e i n w a l l a t apex ( a r ) . F i x a t i o n : k%  glutaraldehyde.  P o s t f i x a t i o n : 1% osmic a c i d . B u f f e r : cacodylate  - pH  7«0.  xl6000.  thickened  79  80 Bambusina b r e b i s s o n i l  F i g . 64  Micrograph 4 6 0 2 . showing dictyosome  L o n g i t u d i n a l s e c t i o n of c e l l ( d ) , endoplasmic  c h l o r o p l a s t grana  ( g ) , nucleus  and mitochondrion  (m).  X7100.  F i x a t i o n : 4$ g l u t a r a l d e h y d e . P o s t f i x a t i o n : 1% osmic B u f f e r : c a c o d y l a t e - pH  acid. 7.0.  reticulum (er),  (n), p y r e n o i d  (p)  81  82  Bambusina b r e b i s s o n i i  F i g * 65  Micrograph 3896.  Lobe of c h l o r o p l a s t showing  grana (g) and  dense g l o b u l e s  F i x a t i o n : k%  glutaraldehyde.  x51000.  (arrow).  P o s t f i x a t i o n : 1% osmic a c i d . B u f f e r : cacodylate  Fig.  66  Micrograph 3897 • thylakoids X51000.  ( t ) and  - pH  7.0.  Pyrenoid t r a v e r s e d surrounded by  F i x a t i o n as  in Fig.  65.  by  chloroplast  starch grains  (s).  84  Bambusina  Fig.  67  breblssonll  Micrograph 3 9 0 0 .  Longitudinal  section  c e l l w i t h H-shaped d i v i s i o n septum.  of d i v i d i n g  L a t e r a l pores  (1) and a p i c a l pores (a) are p r e s e n t i n the c e l l wall.  A,B,C,D i n d i c a t e p o i n t s on the w a l l  correspond to p o i n t s on the d i v i s i o n septum in  Fig; 68;  x6000.  F i x a t i o n : k% g l u t a r a l d e h y d e . Postfixation: Buffer:  1% osmic a c i d .  c a c o d y l a t e - pH 7 . 0 .  that  85  86  Bambusina b r e b i s s o n i i  Fig,  68  Micrograph  3892,  L o n g i t u d i n a l s e c t i o n through  the f o l d r e g i o n of the d i v i s i o n septum.  A,B,C,D  i n d i c a t e p o i n t s on the septum corresponding p o i n t s on the mature c e l l 67.  to  wall indicated i n F i g .  The i n i t i a l w a l l (iw) i s the l e s s dense  middle l a y e r .  A pore (p) i s d e v e l o p i n g  mature w a l l of the septum.  i n the  xl8000.  F i x a t i o n : Wfo g l u t a r a l d e h y d e . P o s t f i x a t i o n : 1% osmic a c i d . B u f f e r : cacodylate  Fig.  69  Micrograph 4 6 1 6 .  - pH 7.0.  L o n g i t u d i n a l s e c t i o n through  u n f o l d i n g w a l l s of e l o n g a t i n g s e m i c e l l s The i n i t i a l w a l l (iw) and mature w a l l in density.  xl8500.  F i x a t i o n as i n F i g . 6 8 .  (arrow).  (mw)  differ  87  88 Genus Desmidium  A.  C. Agardh  T h i s f i l a m e n t o u s genus has ( P i g . 70)  broader than long  and  c e l l s which are  which are not  w i t h l o n g i t u d i n a l l i n e s a t the apex as Replicate  w a l l s are  usually-  ornamented  i n Bambusina.  formed a f t e r c e l l d i v i s i o n .  Desmidium s w a r t z i i A.C.  Agardh  C e l l s of Desmidium s w a r t z i i measure 15  u long  by  (Fig.  72).  4-0 u wide and  are  The  j o i n e d together a t three a p i c a l protuberances  c e l l s are  or pads and  t r i a n g u l a r i n cross  section  the c e l l s are arranged so t h a t the  appears t w i s t e d  (Fig. 70).  filament  A narrow sheath and  rows of pores are demonstrated by methyl v i o l e t (Fig.  71t  72).  The  several staining  isthmus i s conspicuous only a t A large,  5-6-lobed  c h l o r o p l a s t i s p r e s e n t i n each s e m i c e l l  (Fig. 72).  angles of the c e l l  (Fig. 70).  nucleus i s i n the middle of the c e l l between  the  The  the  chloroplasts. In e l e c t r o n micrographs the w a l l s t r u c t u r e with that described  f o r Pleurotaenium nodosum and  verticillatum.  w a l l i s 2 5 0 - 3 0 0 mu  The  t h i c k and  of many l a y e r s of m i c r o f i b r i l s ( F i g . 7 3 ) . the  semicell walls The  overlap  (Fig.  At the  Triploceras composed isthmus  73).  pores i n the l a t e r a l w a l l are c a . 100  diameter near the pore bulb and  is identical  mu  in  s l i g h t l y wider toward  the  o u t s i d e of the w a l l ( P i g . 7 7 ) • network of m i c r o f i b r i l s and about 200 mu  The pore bulb c o n t a i n s a  the sheath c o l l a r extends  from the w a l l ( P i g . 7 7 ) .  composed of f i b r i l s  The  sheath i s  extending out from the sheath  up to 4 u from the c e l l w a l l ( F i g . 7 6 ) .  collar  Pores are a l s o  p r e s e n t i n the a p i c a l w a l l and have the same s t r u c t u r e as the l a t e r a l pores  (Fig. 74).  The  c e l l s i s f i l l e d with f i b r i l l a r i d e n t i c a l to the l a t e r a l sheath  space between a d j a c e n t  m a t e r i a l which appears ( F i g . 74,  75).  The w a l l s of a d j a c e n t c e l l s are c l o s e l y pressed together a t the a p i c a l pads which are protuberances  flattened  of the a p i c a l w a l l ( F i g . 7 4 ,  75).  A thin  l a y e r of e l e c t r o n - d e n s e m a t e r i a l i s p r e s e n t between the pads and pores are present i n the w a l l of the a p i c a l (Fig.  pad  75). One  l a r g e , lobed, a x i a l c h l o r o p l a s t i s present i n  each s e m i c e l l ( F i g . 7 6 ) .  U s u a l l y two  go i n t o each angle of the c e l l . p r e s e n t i n the c h l o r o p l a s t .  c h l o r o p l a s t lobes  S e v e r a l pyrenoids  C h l o r o p l a s t and  are  pyrenoid  s t r u c t u r e i s i d e n t i c a l w i t h t h a t of desmids a l r e a d y described  (e.g. Bambusina).  M i t o c h o n d r i a 1-4  u long and dictyosomes c a . 1.5  long occur c l o s e to the c h l o r o p l a s t lobes  (Fig. 74).  u  90 Desmidium c y l i n d r i c u m G r e v i l l e  C e l l s of Desmidium c y l i n d r i c u m a r e approximately c y l i n d r i c a l but have l a t e r a l i n f l a t i o n s near the isthmus (Fig.  78).  C e l l s measure 22 u long by 4-0 u wide.  c e l l s a r e j o i n e d a t the f l a t t e n e d a p i c e s . 10-15  Adjacent  A broad sheath  u wide surrounds the f i l a m e n t and s t r i a t i o n s can be  seen i n the sheath i n c e l l s s t a i n e d w i t h methyl v i o l e t (Fig.  79).  revealed  S e v e r a l rows of pores on each s e m i c e l l a r e  by s t a i n i n g ( F i g . 8 0 ) .  The c h l o r o p l a s t i s  s t e l l a t e with four to s i x lobes. In e l e c t r o n micrographs the w a l l of D. c y l i n d r i c u m has  e s s e n t i a l l y the same s t r u c t u r e as t h a t of D. s w a r t z i i .  The  l a t e r a l w a l l i s c a . 2 0 0 mu t h i c k ( F i g . 81) and the  a p i c a l w a l l i s c a . 100 mu t h i c k ( F i g . 8 2 ) . The  overlapping  of the s e m i c e l l w a l l s a t the isthmus i s shown i n F i g . 8 3 . The  l a t e r a l edge of the a p i c a l w a l l i s thickened  outside  o f the w a l l a t the apex there  i s a loose  and on the fibrillar  l a y e r which i s i n t e r p r e t e d as the remnant of the i n i t i a l w a l l formed a f t e r c e l l d i v i s i o n  ( F i g . 8 2 ) . R e p l i c a t e or  f o l d e d w a l l s a r e formed f o l l o w i n g c y t o k i n e s i s  ( F i g . 84-) as  i n Bambusina w i t h subsequent u n f o l d i n g when the new s e m i c e l l expands. Pores 1 5 0 - 2 0 0 mu wide a r e present  and t h e i r  structure  i s i d e n t i c a l t o those o f D." s w a r t z i i ( F i g . 8 1 ) . The sheath i s f i b r i l l a r w i t h many m i c r o f i b r i l s coming from the sheath collar.  91  Desmidium s w a r t z i i  Fig.  Fig.  70  71  L i v i n g c e l l s i n l i g h t microscope showing  the  isthmus grooves  x910.  72  (a).  C e l l s s t a i n e d w i t h methyl v i o l e t to show pores (arrow).  Fig.  ( i ) and a p i c a l pad  xl250.  A p i c a l view of c e l l s t a i n e d w i t h methyl v i o l e t showing narrow sheath (s) and a x i a l (ch).  Fig.  73  x920.  Micrograph 24-82. cell  chloroplast  L o n g i t u d i n a l s e c t i o n through  showing o v e r l a p of s e m i c e l l w a l l s a t isthmus  ( i ) , pore i n w a l l (p) and sheath ( s ) . Note thickened r i d g e on w a l l  (arrow).  Fixation: 2.5$ glutaraldehyde. P o s t f i x a t i o n : 1% osmic  acid.  B u f f e r : phosphate - pH  7.2.  xl5000.  92  93  Desmidium  Fig.  74  swartzii  Micrograph 2 3 2 3 . two c e l l s  Longitudinal  section  j o i n e d a t a p i c a l pads (arrows). x 3 5 0 0 .  a = pores i n a p i c a l  wall.  d = dictyosomes between c h l o r o p l a s t Fixation: 2.5$ Postfixation: Buffer:  Fig.  75  through  glutaraldehyde. 1% osmic  phosphate - pH  Micrograph 2481. a p i c a l pad.  lobes.  acid. 7.2.  Longitudinal  section  through  A pore (a) i s p r e s e n t i n the w a l l  of the pad and i s s i m i l a r to the l a t e r a l pore ( 1 ) . xl9000.  F i x a t i o n as i n F i g . 74.  94  95  Desmidium s w a r t z i i  Pig.  76  Micrograph 4-348.  Transverse s e c t i o n of  showing a x i a l c h l o r o p l a s t w i t h pyrenoids i n the l o b e s . sheath  (s).  The c e l l  i s surrounded  by  cell (arrow) fibrillar  x3500.  Fixation: 2.5$ glutaraldehyde. P o s t f i x a t i o n : 1$ osmic a c i d . B u f f e r : phosphate - pH  Fig.  77  Micrograph 4-353. sheath (sc)  (s),  7.2.  S e c t i o n through pores  Pore bulb (b) and sheath  are l a b e l l e d .  x29000.  F i x a t i o n as i n F i g . 7 6 .  and  collar  97 Desmidium c y l i n d r i c u m  F i g . 78  L i v i n g c e l l s i n l i g h t microscope. p o s i t i o n of isthmus. visible  Fig;  79  Arrows i n d i c a t e  Note sheath boundaries  i n unstained c e l l s .  x450.  Sheath s t a i n e d w i t h methyl v i o l e t .  Sheath  s t r i a t i o n s are v i s i b l e c l o s e to the c e l l s (arrow).  Fig.  Fig.  80  81  x760.  S u r f a c e view of c e l l s s t a i n e d w i t h methyl violet  showing rows of pores (arrow) i n c e l l  wall.  x!250.  Micrograph 2 3 0 3 . pore apparatus.  S e c t i o n of c e l l w a l l x20000.  b = pore b u l b , sc = sheath c o l l a r ; s = sheath. Fixation: 2.5$ glutaraldehyde. P o s t f i x a t i o n : 1% osmic a c i d . B u f f e r : phosphate  - pH  7.2.  (w) and  s  99 Desmidium  F i g . 82  cylindricum  Micrograph 2 3 0 4 . cell  L o n g i t u d i n a l s e c t i o n through  apex showing pore i n a p i c a l w a l l  remnant of i n i t i a l w a l l Fixation: 2.5$  (arrow).  (a)  and  x20000.  glutaraldehyde.  P o s t f i x a t i o n : 1% osmic a c i d . 7.2.  B u f f e r : phosphate - pH  F i g . 83  Micrograph 2 2 8 7 .  S e c t i o n showing overlap  s e m i c e l l w a l l s a t the F i x a t i o n as i n F i g .  F i g . 84  Micrograph 4 6 5 7 .  isthmus (arrows).  of xl6500.  82.  L o n g i t u d i n a l s e c t i o n through  d i v i s i o n septum showing f o l d e d mature w a l l s separated  by  F i x a t i o n as  i n i t i a l wall in Fig.  82.  (1).  xl6500.  (mw)  100  101 Genus Hyalotheca  Ehrenberg  T h i s f i l a m e n t o u s genus has c e l l s which are c y l i n d r i c a l with l i t t l e (Fig.  85).  Two  or no isthmus  constriction  a x i a l c h l o r o p l a s t s are p r e s e n t i n each  c e l l around a c e n t r a l n u c l e u s .  Hyalotheca d i s s i l i e n s  ( J . E. Smith) de B r e b i s s o n  C e l l s of Hyalotheca d i s s i l i e n s measure 12-14 by 23-24 u wide and are surrounded 15  u wide ( F i g . 8 5 ) . "  by a broad  sheath c a .  Ruthenium red and methyl v i o l e t  s t a i n the sheath w i t h sheath s t r i a t i o n s c l e a r l y u s i n g the l a t t e r s t a i n In ca.  250 mu  (Fig.  87).  visible  the l a t e r a l c e l l w a l l i s  the a p i c a l w a l l i s c a . 200 nru t h i c k  At the margin of the apex a r i n g of dense  f i b r i l l a r m a t e r i a l extends from the a d j a c e n t c e l l  out to meet a s i m i l a r  ( F i g . 87)•  measures about 800 mu wide and section  both  (Fig. 86).  e l e c t r o n micrographs t h i c k and  u long  (Fig. 88).  ring  This a p i c a l r i n g  i s somewhat t r i a n g u l a r i n  A dense l a y e r ca.' 50 mu  thick i s  s i t u a t e d between the a p i c a l r i n g s of a d j a c e n t  cells.  The a p i c a l w a l l s of a d j a c e n t c e l l s are separated by a space 1 0 0 - 2 0 0  mu wide w i t h narrow c r o s s connections  v i s i b l e i n some s e c t i o n s (Fig-; 8 9 ) . o v e r l a p a t the isthmus  (Fig. 90).  The  semicell walls  102 Pores 1 0 0 - 1 5 0 mu i n diameter are p r e s e n t i n both a p i c a l and l a t e r a l w a l l s (Fig; microfibrils  1  87).  A network of  i s s i t u a t e d under the pore and the sheath  c o l l a r extends c a ; 2 0 0 mu from the c e l l w a l l  ( F i g . 91).'  In c r o s s s e c t i o n the sheath c o l l a r i s about 6 0 0 mu i n diameter  (Fig; 9 2 ) .  Pores a r e p r e s e n t v e r y c l o s e t o the  isthmus o v e r l a p (Fig;' 9 0 ) .  The sheath i s composed o f  l o n g m i c r o f i b r i l s c a . 10 mu wide extending from the sheath collar  (Fig. 9 3 ) .  In the outer p a r t of the sheath the  m i c r o f i b r i l s become b e a d - l i k e and the boundary  fibrils  of each sheath p r i s m a l s o have t h i s appearance  (Fig. 9 3 ) .  T a n g e n t i a l s e c t i o n s through the sheath show the conspicuous i n d i v i d u a l sheath prisms  ( F i g . 9^)-.  103  Hyalotheca d i s s i l i e n s  F i g . 85  L i v i n g c e l l s i n l i g h t microscope. of the isthmus  F i g . 86  Sheath  ( i ) i s not conspicuous.  position x850.  (s) s t a i n e d w i t h methyl v i o l e t to show  sheath s t r l a t i o n s .  F i g . 87  The  Micrograph 2280.  x850.  Longitudinal section  through  l a t e r a l margin of c e l l apex showing a p i c a l r i n g (r) j o i n i n g the c e l l s .  Lateral  (a) pores are p r e s e n t .  xl6000.  F i x a t i o n : 2.5$ glutaraldehyde. Postfixation:  1% osmic a c i d .  B u f f e r : phosphate - pH  7.2.  (1)  and  apical  104  105  Hyalotheca  F i g . 88  dlsslllens  Micrograph  2277.  Enlarged a p i c a l r i n g  s e p a r a t i n g two c e l l s .  (ar)  A dense connecting  layer  (c) i s p r e s e n t between the two p a r t s of the r i n g . x51000. Fixation: 2.5$ Postfixation:  glutaraldehyde. 1% osmic a c i d .  B u f f e r : phosphate - pH  F i g . 89  Micrograph  2268.  7*2.  Narrow connection  between a d j a c e n t a p i c a l w a l l s .  (arrow)  X54-500.  F i x a t i o n as i n F i g . 8 8 .  F i g . 90  Micrograph isthmus xl6500.  2135•  Overlapping s e m i c e l l w a l l s a t  (arrows) w i t h two a d j a c e n t p o r e s . F i x a t i o n as i n F i g . 8 8 .  106  Hyalotheca  Fig.  91  dissiliens  Micrograph 2259*-  S e c t i o n through two  and a d j a c e n t sheath ( s ) .  pores  x50500.  b = pore b u l b , sc = sheath  collar.  Fixation: 2.5$ glutaraldehyde. P o s t f i x a t i o n : 1% osmic  F i g . 92  acid. 7.2.  B u f f e r : phosphate  - pH  Micrograph 3 9 1 9 .  Tangential section  c e l l w a l l and a d j a c e n t sheath. sheath c o l l a r  (p) and  (sc) are c u t i n c r o s s s e c t i o n .  X4-2700. F i x a t i o n : k% g l u t a r a l d e h y d e . P o s t f i x a t i o n : 1% osmic Buffer:  Pores  through  c a c o d y l a t e - pH  acid. 5»8.  108  S  Hyalotheca  Fig.  93  dissiliens  Micrograph  2146.  sheath prisms (arrow)  Longitudinal section  (sp).  Fibrils  2.5$  Postfixation:  xl7000.  glutaraldehyde. 1%  osmic  B u f f e r : p h o s p h a t e - pH  F i g . 94  become b e a d - l i k e  i n o u t e r p a r t of s h e a t h .  Fixation:  of  Micrograph 3918.  acid. 7.2.  Tangential section  through  sheath showing i n d i v i d u a l sheath prisms ( s p ) . xl4000. F i x a t i o n : 4$ g l u t a r a l d e h y d e . P o s t f i x a t i o n : 1% osmic a c i d . B u f f e r : c a c o d y l a t e - pH  5»8.  111 Genus Sphaerozosma Corda emend. B o u r r e l l y  The d i s t i n g u i s h i n g c h a r a c t e r of t h i s f i l a m e n t o u s genus as d e f i n e d by B o u r r e l l y  (1964-) i s the presence of  a s y m m e t r i c a l l y arranged protuberances on the c e l l a p i c e s (Fig.  96).  There are two c h l o r o p l a s t s i n each c e l l  each  w i t h one l a r g e p y r e n o i d .  Sphaerozosma laeve (Nordstedt) Thomasson  C e l l s of Sphaerozosma laeve measure 14—16 by 20-25 p. wide w i t h a broad sheath 12-15 95»  97 )•  staining  u long  u thick (Fig.  Sheath s t r i a t i o n s are r e v e a l e d by methyl ( F i g . 97)•  violet  The a p i c a l protuberances are about  4- p. l o n g and arranged so t h a t they extend on o p p o s i t e s i d e s of the a d j a c e n t s e m i c e l l In thick of  e l e c t r o n micrographs  ( F i g . 101).  (Fig. 96). the c e l l w a l l i s c a . 200  The a p i c a l protuberances are e x t e n s i o n s  the c e l l w a l l 3-4- u l o n g and 1 u wide ( F i g . 9 8 ) .  The  c e n t e r of the protuberance c o n t a i n s a narrow space (Fig.  99).  mp.  The o v e r l a p of s e m i c e l l w a l l s a t the  i s shown i n F i g . 9 8 .  isthmus  M i c r o t u b u l e s are p r e s e n t under the  plasma membrane a t the isthmus  ( F i g . 100).'  The a p i c a l w a l l s of a d j a c e n t c e l l s are not i n c o n t a c t but are separated by c a . 0.5 material of  (Fig;' 98).  u of s h e a t h - l i k e  Between the c e l l s  1  i s a dense l a y e r  m a t e r i a l continuous w i t h the sheath surrounding  a p i c a l protuberance extends  ( F i g . 98).  the  T h i s sheath m a t e r i a l  a l o n g the l a t e r a l c e l l w a l l , probably s e r v i n g to  keep the c e l l s of the f i l a m e n t together as the a p i c a l protuberances  do not c o n t a c t the a d j a c e n t c e l l  Pores cav 150 c e l l w a l l ( F i g . 101)•  m  u  ( F i g . 99)  i n diameter are p r e s e n t i n the The pore b u l b c o n t a i n s a c a p - l i k e  s t r u c t u r e s i m i l a r t o t h a t of T r i p l o c e r a s v e r t l c i l l a t u m . The  sheath c o l l a r extends  200-250  sheath f i b r i l s a t t a c h to i t ( F i g .  mp. from the w a l l and  101).  113  Sphaerozosma l a e v e  Fig,  95  L i v i n g c e l l s w i t h arrow i n d i c a t i n g of deep isthmus c o n s t r i c t i o n .  Fig,  96  97  98  (arrows).  x800.  Sheath s t a i n e d w i t h methyl v i o l e t to show sheath striations  Fig.  x800.  Two l i v i n g c e l l s separated from f i l a m e n t t o show a p i c a l protuberances  Fig.  position  (s).  xl600.  Micrograph I633.  L o n g i t u d i n a l s e c t i o n of c e l l  through nucleus (n) and a p i c a l protuberance ( a ) . The c e l l c o n t a i n s many s t a r c h g r a i n s ( s ) . F i x a t i o n : 1% osmic B u f f e r : phosphate  acid. - pH 7«2.  x5250.  Sphaerozosma laeve  F i g . 99  Micrograph 1 5 2 4 .  Longitudinal section  a p i c a l protuberance.  through  A c e n t r a l channel i s p r e s e n t  (arrow) i n the protuberance.  A sheath of dense  m a t e r i a l (s) surrounds the protuberance. F i x a t i o n : 1% osmic B u f f e r : phosphate  F i g ; 100 Micrograph 1 6 3 7 .  xl8000.  acid. - pH  7.2.  M i c r o t u b u l e s (arrow) below  plasma membrane (pm) a t isthmus r e g i o n .  x25500.  F i x a t i o n as i n F i g . 9 9 .  F i g . 101  Micrograph 1647.  S e c t i o n of c e l l w a l l  through a pore apparatus F i x a t i o n as i n F i g . 9 9 .  (arrow).  (w)  xl8000.  116  Genus Spondyloslum  11?  de B r e b i s s o n  C e l l s of Spondyloslum  have a deep isthmus c o n s t r i c t i o n  and are u n i t e d a t t h e i r a p i c e s i n t o f i l a m e n t s  ( F i g . 102).,  T h i s genus i s d i s t i n g u i s h e d from Sphaerozosma by the l a c k of a p i c a l protuberances, from Bambusina and Desmidium by the l a c k of a f o l d e d d i v i s i o n septum, and from  Hyalotheca  by the presence of c e l l s w i t h a deep isthmus c o n s t r i c t i o n .  Spondyloslum  pulchrum  C e l l s measuring  ( B a i l e y ) Archer  40 u long, 75-80 u wide, and 25 M  t h i c k w i t h a narrow isthmus apical projections sheath extends  (27 u) are j o i n e d a t s l i g h t  into filaments  (Fig. 102).  A broad  from the l a t e r a l w a l l c a . 40 u and  sheath  s t r i a t i o n s are conspicuous w i t h methyl v i o l e t s t a i n i n g (Fig.  103).  material  The ruthenium r e d t e s t f o r p e c t i c sheath  i s p o s i t i v e w i t h the i n n e r p a r t of the sheath  s t a i n i n g more d e e p l y . ^SO^  and  The c e l l w a l l s t a i n s w i t h  iodine-  shows a marked b i r e f r i n g e n c e w i t h p o l a r i z e d  l i g h t i n d i c a t i n g i t s c e l l u l o s i c nature  ( F i g . 104).  Two  p a r i e t a l c h l o r o p l a s t s are p r e s e n t i n each s e m i c e l l ( F i g . 1 0 5 ) . In e l e c t r o n micrographs t h i c k and comprises (Fig.  106).'  the c e l l w a l l i s c a . 400  many t h i n l a y e r s of m i c r o f i b r i l s  The a p i c a l p r o j e c t i o n s l i e c l o s e together  w i t h an e l e c t r o n - d e n s e substance  occupying the  space  mu  118 between the c e l l s  ( F i g . 107).  As i n a l l Cosmarieae  the  s e m i c e l l w a l l s o v e r l a p a t the isthmus. Pores a r e numerous i n the c e l l w a l l , having a diameter of c a ; 100 mu i n the i n n e r p a r t and s l i g h t l y wider i n the outer p a r t of the w a l l  ( F i g . 106).  In  t a n g e n t i a l s e c t i o n s the c i r c u l a r pore i s surrounded by an e l e c t r o n - d e n s e a r e a c a . 25 mu t h i c k  ( F i g . 110).  The pore  bulb i s composed of a network of f i b r i l l a r m a t e r i a l .  In  c r o s s s e c t i o n s through the pore b u l b the i n n e r a r e a of microfibrils is radial  i s circular  (Fig." 109).  i n arrangement  and the outer a r e a  As i n other Cosmarieae  the pore b u l b  l i e s i n a pocket between the w a l l and the c y t o p l a s m i c membrane ( F i g . 106). The sheath c o l l a r extends outward 300  from the pore c a .  mu and i s c a . 500 mu i n diameter a t i t s widest p o i n t  ( F i g . 106).-  In s e c t i o n s cut through the pore apparatus  j u s t o u t s i d e the c e l l w a l l the sheath c o l l a r appears as an a n n u l a r r i n g c a . 180 mu t h i c k ( F i g . 110).  In the c e n t r a l  lumen of the pore c o l l a r t h e r e i s a mass of f i b r i l l a r m a t e r i a l t h a t can be f o l l o w e d i n t o the pore lumen i n other sections  ( F i g . HO).  1  In s e c t i o n s through the sheath c o l l a r  f u r t h e r from the c e l l w a l l the c e n t r a l lumen of the c o l l a r d i s a p p e a r s (Fig;  1  110).  The c o l l a r then appears as a  u n i f o r m l y g r a n u l a r c i r c u l a r a r e a w i t h the m i c r o f i b r i l s the  sheath r a d i a t i n g from the margin.  Sections passing  of  119 above the sheath c o l l a r c u t through the m i c r o f i b r i l s  of  the sheath which are shown i n l o n g i t u d i n a l s e c t i o n i n Fig.' 106i'  These m i c r o f i b r i l s  form a compact bundle i n  c r o s s s e c t i o n s near the sheath c o l l a r but g r a d u a l l y d i v e r g e as they go out i n t o the sheath ( F i g . 108).  The  boundaries  of a d j a c e n t sheath prisms are not v i s i b l e c l o s e t o the w a l l but can be d i s t i n g u i s h e d i n the outer p a r t of the sheath (Fig.  108). Pores are a l s o p r e s e n t i n the a p i c a l  where the c e l l s j o i n same diameter  (Fig.* 1 0 7 ) .  wall  region  These pores are of the  (ca. 100 mp) as the l a t e r a l p o r e s .  However  5  s i n c e the space between the c e l l s i s f i l l e d w i t h an e l e c t r o n dense substance, there i s no sheath c o l l a r and the pore ends blindly  a t the outer edge of the c e l l w a l l  ( F i g . 107).  The c h l o r o p l a s t s have conspicuous grana and many t h y l a k o i d s t r a v e r s e the p y r e n o i d ground other Cosmarieaev  substance as i n  A s t a r c h sheath surrounds the pyrenoid  and s e v e r a l o s m i o p h i l i c g l o b u l e s are p r e s e n t among the stroma lamellae.' dictyosomes  The s t r u c t u r e of m i t o c h o n d r i a and  corresponds to t h a t of other desmids and  o r g a n e l l e s are c l o s e to the c h l o r o p l a s t s .  Vacuoles  both occupy  a l a r g e p a r t of the c e l l . A metaphase c e l l of Spondylosium sectioned.  pulchrum  The chromosome number of t h i s c e l l  approximately 11;  was  was  The chromosomes shown i n F i g . I l l , 112  120 are t r a n s v e r s e l y s e c t i o n e d and the microtubules of the s p i n d l e g e n e r a l l y l i e i n the plane of the s e c t i o n s .  The  s p i n d l e microtubules do n o t converge a t the p o l e s but pass between many mitochondria t h a t occupy the p o l a r r e g i o n (Fig. I l l ,  114).  In some s e c t i o n s mitochondria occur among  the s p i n d l e microtubules c l o s e t o the metaphase p l a t e ( F i g . 112)v 111,  Many s m a l l v a c u o l e s a r e present i n the s p i n d l e ( F i g ; 112).  Chromosomal microtubules a t t a c h t o the  chromosomes a t l o c a l i z e d centromeres ( F i g . 113 )•  The  m i c r o t u b u l e s a t t a c h to electron-dense p l a t e s on each chromatid  ( F i g . 113)•  Although a continuous s e r i e s of  s e c t i o n s c o u l d not be obtained only one r e g i o n of microtubule attachment i s seen on each chromosome.  Non-  chromosomal microtubules pass between the chromosomes ( F i g . 113 )•  No n u c l e o l a r m a t e r i a l i s p r e s e n t around the  chromosomes but there i s a s m a l l amount near one p o l e of the s p i n d l e ( F i g . 1 1 5 ) .  Spondylosium pulchrum  F i g . 102  Living cells (a).  j o i n e d a t a p i c a l protuberances  The d e e p l y c o n s t r i c t e d isthmus r e g i o n (  c o n t a i n s a conspicuous n u c l e u s ( n ) .  F i g . 103  Sheath s t a i n e d w i t h methyl v i o l e t to show sheath s t r i a t i o n s ( s ) .  F i g . 104-  F i g . 105  x560.  x64-0.  C e l l s photographed i n p o l a r i z e d l i g h t . walls birefringent.  x560.  A p i c a l view of c e l l .  Two  are p r e s e n t .  x6l0.  chloroplasts  Cell  (ch)  123 Spondylosium  Pig.  106  pulchrum  Micrograph 5 2 - 1 7 .  S e c t i o n of c e l l w a l l  through two pores and a d j a c e n t sheath microfibrils  ( f ) . x43600.  b = pore b u l b ; sc = sheath c o l l a r . Fixations 2.5$ glutaraldehyde. P o s t f i x a t i o n : 1% osmic a c i d . B u f f e r : phosphate - pH  1  7.2.  (w)  124  125 Spondyloslum pulchrum  F i g . 107  Micrograph 5 3 - 2 2 .  L o n g i t u d i n a l s e c t i o n through  a p i c a l pad showing dense m a t e r i a l between c e l l s (arrow).  A pore i s p r e s e n t i n the w a l l of the  a p i c a l protuberance ( a ) . F i x a t i o n : 2.$%  x9750»  glutaraldehyde.  P o s t f i x a t i o n : 1% osmic a c i d . B u f f e r : phosphate - pH  Fig.  108  Micrograph 53-24. sheath showing X17000.  7.2.  T a n g e n t i a l s e c t i o n through  i n d i v i d u a l sheath prisms ( s ) .  F i x a t i o n as i n F i g . 1 0 7 .  12?  Spondylosium  F i g . 109  pulchrum  Micrograph 52-14.  Tangential section  s e v e r a l pore bulbs ( b ) .  Circularly  m i c r o f i b r i l s are surrounded  through  arranged  by r a d i a l l y  x34000.  arranged m i c r o f i b r i l s .  Fixation: 2.5$ glutaraldehyde. P o s t f i x a t i o n : 1% osmic a c i d . B u f f e r : phosphate - pH  F i g . 110  Micrograph 5 2 - 1 1 . c e l l wall  7.2.  Tangential section  through  (w) and a d j a c e n t sheath c o l l a r s ( s c ) .  Pores are surrounded by an e l e c t r o n - d e n s e a r e a (arrow).  xl5000.  F i x a t i o n as i n F i g . 1 0 9 .  128  129 Spondylosium pulchrum  P i g . I l l Micrograph  326?.  S e c t i o n of metaphase s p i n d l e  showing chromosomes (ch) and s p i n d l e microtubules  ( t ) . Mitochondria  (m)  concentrated a t the s p i n d l e p o l e .  are xl6300.  F i x a t i o n : k% glutaraldehyde . 1  P o s t f i x a t i o n : 1% osmic a c i d . B u f f e r : c a c o d y l a t e - pH  F i g . 112  Micrograph  3018.  7«0.  S e c t i o n of same metaphase  s p i n d l e as F i g . 111.  Note mitochondria  s i t u a t e d c l o s e to the chromosomes ( c h ) . X16500.  F i x a t i o n as i n F i g .  111.  (m)  130  131  Spondyloslum pulchrum  F i g . 113  Micrograph  3392.  Transverse s e c t i o n  through  centromere r e g i o n of metaphase chromosome. Chromosomal microtubules  (arrows, top and  bottom) a t t a c h to chromosome. microtubules attaching.  Non-chromosomal  (net) pass by chromosome x83000.  F i x a t i o n : h% g l u t a r a l d e h y d e . P o s t f i x a t i o n : 1% osmic a c i d . B u f f e r : c a c o d y l a t e - pH ? . 0 .  without  132  133  Spondylosium pulchrum  P i g . 114  Micrograph  3268.  Enlarged p a r t of P i g .  S p i n d l e microtubules  (arrow) e n t e r the r e g i o n  a t the s p i n d l e p o l e c o n t a i n i n g (m).  111.  mitochondria  X51000.  F i x a t i o n : h%  glutaraldehyde.  P o s t f i x a t i o n : 1% osmic a c i d . B u f f e r : c a c o d y l a t e - pH  Fig.  115  Micrograph  3313*  7.0.  N u c l e o l a r m a t e r i a l (arrow)  near s p i n d l e p o l e .  x60000.  F i x a t i o n as i n F i g .  114.  135 Genus Cosmocladlum de Brebisson  The d i s t i n g u i s h i n g features of t h i s c o l o n i a l genus are the connectingstrands which j o i n the c e l l s ( F i g . 116). Globose c o l o n i e s of two to many Cosmarium-like c e l l s are formed• Cosmocladlum saxonlcum de Bary  C e l l s of Cosmocladlum^saxonlcum 22-24 ;u wide ( F i g . 116).  are 28-32 u long by  The strands u n i t i n g the c e l l s  a r i s e from c l u s t e r s of pores near the isthmus ( F i g .  119)•  These strands do not s t a i n w i t h ruthenium r e d , methyl v i o l e t , congo red or methylene b l u e .  There are  12-15  pores i n each isthmus c l u s t e r and two pore c l u s t e r s per s e m i c e l l ( F i g . 119)•  The sheath surrounds the colony and  s t a i n s w i t h ruthenium red and methyl v i o l e t .  Feathery  s t r u c t u r e s are v i s i b l e using the l a t t e r s t a i n ( F i g .  117).  There i s one c h l o r o p l a s t with one pyrenoid i n each s e m i c e l l . The c e l l w a l l i n e l e c t r o n micrographs Is 100-150 mu t h i c k ( F i g . 118).  I t does not r e a d i l y s t a i n w i t h u r a n y l  acetate and lead c i t r a t e , often w i t h only the outer p a r t being s t a i n e d .  The overlap of s e m i c e l l w a l l s a t the isthmus  i s shown i n F i g . 124.  Pores ca. 200 mu wide are present  and have a s t r u c t u r e s i m i l a r to those of other members of the subfamily. There i s no well-developed sheath c o l l a r  136 and, although f a n - l i k e s t r u c t u r e s are v i s i b l e i n stained c o l o n i e s i n the l i g h t microscope,  only s c a t t e r e d m i c r o f i b r i l s  are v i s i b l e i n the sheath i n e l e c t r o n micrographs ( F i g . 122). Strands connecting the c e l l s of a colony c o n s i s t of s e v e r a l subunits ( F i g . 120) each of which i s associated w i t h one of the pores of the isthmus c l u s t e r ( F i g . 122). The base of each strand subunit, about 180 mu i n diameter, i s i n s e r t e d i n t o a pore of the isthmus region ( F i g . 123). The strand subunits expand, becoming d e f i n i t e l y f i b r i l l a r toward the middle ( F i g . 123) and overlapping the subunits t  which a r i s e from the other c e l l of the p a i r .  The subunits  d i v i d e as they leave the pore w i t h the two p a r t s going i n d i f f e r e n t d i r e c t i o n s ( F i g . 121).  M i c r o f i b r i l s attached to  the plasma membrane come out i n t o the pore bulb ( F i g . 121). The c h l o r o p l a s t has s e v e r a l lobes extending from a l a r g e c e n t r a l pyrenoid ( F i g . 122).  The pyrenoid matrix i s  traversed by many t h y l a k o i d s and the c h l o r o p l a s t contains obvious grana ( F i g . 125). Large vacuoles occupy much of the c e l l ( F i g . 122). Mitochondria and dictyosomes 1-3 u long are present c l o s e to the c h l o r o p l a s t ( F i g . 122).  The nucleus l i e s i n the  isthmus r e g i o n and has a c e n t r a l s p h e r i c a l nucleolus ( F i g . 125).  Microtubules below the plasma membrane perpendicular  to the c e l l a x i s are present a t the isthmus ( F i g . 124, 126).  137 Cosmocladium saxonioum  Fig.  116  Living  cells  joining  Fig.  117  the  showing c o n n e c t i n g cells  of  the  colony.  S t a i n i n g w i t h methyl v i o l e t structures from the  (arrow)  cell  (c).  strands  i n the xl500.  x4l0.  reveals  sheath  (arrows)  that  feathery radiate  139 Cosmocladium  Fig.  118  saxonicum  Micrograph 2468.  S e c t i o n of c e l l w a l l (w).  X20000.  F i x a t i o n : 2.5$  glutaraldehyde.  P o s t f i x a t i o n : 1% osmic a c i d . B u f f e r : phosphate - pH 7 » 2 .  Fig,  119  A p i c a l view of c e l l s t a i n e d w i t h methyl v i o l e t to  Fig,  120  show isthmus pore group  Micrograph 2382. connecting subunits  (arrow),  x2200.  Oblique s e c t i o n through  s t r a n d showing s e v e r a l strand  (su).  x23000.  F i x a t i o n as i n F i g . 118.  Fig.  121  Micrograph 2467. group.  S e c t i o n through isthmus pore  Note b i f u r c a t i o n of s t r a n d u n i t as i t  l e a v e s pore (arrow).  x20000.  F i x a t i o n as i n F i g . 118.  1  4  0  141  Cosmocladlum saxonicum  Fig.  122  Micrograph  2399.  Low  m a g n i f i c a t i o n micrograph  of c e l l s showing s t r a n d subunit (su) i n longitudinal section. d =  x6400.  dictyosome.  m = mitochondrion, n s= n u c l e u s , v = vacuole. s = sheath w i t h s c a t t e r e d  microfibrils.  Fixations 2 . 5 $ glutaraldehyde. P o s t f i x a t i o n : 1% osmic a c i d . B u f f e r s phosphate - pH  7.2.  143 Cosmocladium  F i g . 123  saxonicum  Micrograph 2396.  Enlarged view of strand  subunit i n F i g . 122.  The subunit i s dense and  s o l i d as i t passes through the pore i n the w a l l (w) but becomes f i b r i l l a r middle o f the s t r a n d .  (arrow) near the  Note f i n e  microfibrils  near the plasma membrane i n the pore bulb ( b ) . x24000. F i x a t i o n : 2.5$ glutaraldehyde. P o s t f i x a t i o n : 1$ osmic a c i d . B u f f e r : phosphate - pH 7.2.  F i g . 124  Micrograph 2 4 3 8 .  L o n g i t u d i n a l s e c t i o n through  isthmus r e g i o n showing the o v e r l a p of the semicell walls  ( l a r g e arrows) and the isthmus  m i c r o t u b u l e s ( s m a l l arrows) under the plasma membrane (pm).  x72000.  F i x a t i o n as i n F i g . 1 2 3 .  144  Cosmocladlum  F i g . 125  saxonlcum  Micrograph 24-03. F i g . 122.  Enlarged view of p a r t of  The nucleus (n) has a c e n t r a l  n u c l e o l u s (nu) and the a d j a c e n t p y r e n o i d has a conspicuous sheath of s t a r c h ( s ) . X13000. d = dictyosome. g = grana. m = mitochondrion. F i x a t i o n : 2.5$ g l u t a r a l d e h y d e . P o s t f i x a t i o n : 1% osmic  F i g . 126  acid. 7.2.  B u f f e r : phosphate  - pH  Micrograph 24-75•  L o n g i t u d i n a l s e c t i o n of  isthmus m i c r o t u b u l e s .  X72000.  F i x a t i o n as i n F i g . 125.  146  147  Discussion. The  c e l l w a l l of the Desmidiaceae was  be two-layered on the b a s i s of i t s s t a i n i n g using l i g h t microscopy (Lutkemiiller  considered to reactions The Desmidiaceae  1 9 0 2 ) .  were subdivided i n t o three s u b f a m i l i e s : the Penieae, w i t h unconstricted  c e l l s l a c k i n g pores and a regular s i t e of  c y t o k i n e s i s ; the C l o s t e r i e a e , w i t h unconstricted  cells  l a c k i n g pores and w i t h a regular s i t e of c y t o k i n e s i s ;  and  the Cosmarieae, with c o n s t r i c t e d c e l l s w i t h pores present and a constant s i t e of c y t o k i n e s i s . By means of e l e c t r o n microscopy Chardard and R o u i l l e r ( 1 9 5 7 )  and Drawert and Metzner-Kuster ( I 9 6 I ) showed only  one l a y e r i n the w a l l of the Cosmarieae. confirms t h e i r observations.  The present study  With the exception of Penium  (Pleurotaenlum) spinulosum. which w i l l be discussed l a t e r , a l l Cosmarieae i n v e s t i g a t e d have the c e l l w a l l composed of s e v e r a l t h i n l a y e r s of oriented m i c r o f i b r i l s .  The  d i f f e r e n c e i n the angle of .orientation of the m i c r o f i b r i l s is rarely  9 0 ° ,  but more often  6 0 - 7 0 ° .  The s t a i n i n g of  the  w a l l w i t h ruthenium red supports the view that p e c t i c substances are present among the c e l l u l o s e m i c r o f i b r i l s of the w a l l (Drawert and Metzner-Kuster I 9 6 I ) .  The  cellulosic  nature of the w a l l i s shown by s t a i n i n g w i t h c h l o r - z i n c iodine and The  iodine-HgSO^ reagents (Lutkemuller  1 9 0 2 ) .  c e l l w a l l of Closterlum lineatum (subfamily  Closterieae)  i s s i m i l a r to that of the Cosmarieae.  The  148 wall  i s not two-layered  (1902) d e s c r i b e d  Lutkemuller  Closterlum species, staining HgSOj^.  dense as  reactions Chardard  report  only  using  i n C l . acerosum.  (I96I),  electron-  chromic a c i d observed  layer  Drawert  treated  wall  two d i s t i n c t  micrographs.  In the  parallel  to the  the m i c r o f i b r i l s a r e  oriented.  is difficult  Just three  (1957)  (Chardard I 9 6 5 ) .  i n electron  and i n t h e o u t e r  Closterieae  and i o d i n e -  A narrow  the m i c r o f i b r i l s a r e o r i e n t e d  transversely It  using  of C l . monlllferum.  of microfibrils  axis  based! on  o f t h e c e l l w a l l was i n t e r p r e t e d  differentiation"  and M e t z n e r - K i i s t e r  cell  i n several  (1965) and Chardard and R o u i l l e r  "a s u p e r f i c i a l  inner layer  microscopists.  layers  chlor-zinc-iodine  on t h e o u t s i d e  preparations  two w a l l  including C l . lineatum.  one l a y e r  layer  layers  as r e p o r t e d by l i g h t  to characterize  on t h e b a s i s species.  of electron  However,  the  subfamily  microscope  the f o l l o w i n g  study of  tentative  s t a t e m e n t s c a n be made: a)  The C l o s t e r i e a e  a two l a y e r e d overlap  the  The C l o s t e r i e a e  differ  of pores: i n the c e l l w a l l  bands  (sections  central  of wall  region  the Cosmarieae  and i n h a v i n g  b e t w e e n t h e two s e m i c e l l b)  lack  c e l l wall  resemble  a definite  i n lacking l i n e of  walls. from the Cosmarieae  and the f o r m a t i o n  of  l n the girdle  t h a t a r e formed by e l o n g a t i o n  of the c e l l )  i n several  species.  of  149  The f i n e s t r u c t u r e of the c e l l w a l l of the subfamily Penieae d i f f e r s sharply from that of the C l o s t e r i e a e and Cosmarieae.  The presence of two d i s t i n c t l a y e r s i n the  c e l l w a l l of Penium contrasts w i t h the uniform w a l l i n the other two s u b f a m i l i e s .  The l a c k of s t r u c t u r e s corresponding  to the pore apparatus of the Cosmarieae as w e l l as the l a c k of a sheath are a l s o d i s t i n g u i s h i n g features of the Penium cell wall.  Chardard  (1964)  sheath i n P. margar1taceum.  reports the presence of a He used ruthenium red as an  e l e c t r o n s t a i n a f t e r osmic a c i d f i x a t i o n and considered the stained outer w a l l l a y e r t o be the sheath.  He a l s o  s t a t e s that t h i s outer l a y e r may be l a c k i n g and that i t s appearance depends on the p h y s i o l o g i c a l s t a t e of the c e l l . The  outer w a l l l a y e r was found i n a l l c e l l s sectioned In  t h i s study and could be d i s t i n g u i s h e d I n the l i g h t microscope i n c e l l s from e i t h e r young o r o l d c u l t u r e s .  Mix  (I968)  studied w a l l s t r u c t u r e i n P. margaritaceum. P. s p i r o s t r i o l a t u m and P. c y l l n d r u s and observed two c e l l w a l l l a y e r s i n each. The outer l a y e r i s i n t e r p r e t e d as p a r t of the c e l l w a l l i n the present study because of i t s greater density compared w i t h the sheath m a t e r i a l of the Cosmarieae and because i t s f i b r i l l a r s t r u c t u r e reaches down i n t o the inner w a l l l a y e r . The  chemical nature of the two w a l l l a y e r s was not  investigated.  The r e s u l t s of Chardard  (1964)  i n d i c a t e the  presence of p e c t i c substances i n the outer l a y e r based on i t s s t a i n i n g w i t h ruthenium r e d .  The inner l a y e r s t a i n s  150 w i t h the standard c e l l u l o s e r e a g e n t s , c h l o r - z i n c - i o d i n e and iodine-HgSOjj, (Liitkemuller  1902).  Pleurotaenlum splnulosum was correctly.' Docldlum  T h i s r a r e s p e c i e s was  (Wolle 1881) but was  (194-9)  Pleurotaenlum by B r u n e i  c l e a r l y not  classified  o r i g i n a l l y p l a c e d In  t r a n s f e r r e d to the genus because  i t resembled  other  members of the genus and because pores were r e p o r t e d t o be present.  S e v e r a l p o i n t s of evidence e x i s t f o r removing  t h i s s p e c i e s from Pleurotaenlum and p l a c i n g i t i n the genus Penium.  The d i f f e r e n c e between the f i n e s t r u c t u r e of the  w a l l of P I . splnulosum and t h a t of o t h e r Cosmarieae a l r e a d y been I n d i c a t e d .  has  The c e l l w a l l of P I . splnulosum i s  i d e n t i c a l i n s t r u c t u r e w i t h those of Penium s p i r o s t r i o l a t u m and P. margaritaceum.  The l a c k of o v e r l a p p i n g w a l l s a t the  isthmus and the absence  of pores i n the c e l l w a l l f u r t h e r  support the view t h a t P I . splnulosum should be to are  the genus Penium.  transferred  The c h l o r o p l a s t s of P I . splnulosum  s t e l l a t e and a x i a l w h i l e those of other Pleurotaenlum  s p e c i e s are almost always p a r i e t a l bands.  A  new  d e s c r i p t i o n of the s p e c i e s Pleurotaenlum splnulosum B r u n e i i s n e c e s s a r y and t h i s s p e c i e s should now Penium splnulosum  be  (Wolle) called  (Wolle) comb. nov.  The u l t r a s t r u c t u r e of the pore apparatus of the Cosmarieae  has been determined by Drawert and Mix  and Chardard and R o u l l l e r  (1957)•  (1961a)  The pore diameter i s  130-180 mu f o r M l c r a s t e r l a s r o t a t a (Drawert and Mix 1961a)  151  and approximately 140 mu f o r M. p a p l l l l f e r a (Chardard and R o u l l l e r 1 9 5 7 ) • The present study confirms the general observations and measurements of these authors but there i s some v a r i a b i l i t y i n s t r u c t u r e among the genera.  The  pore bulb i s described by Drawert and Mix ( 1 9 6 1 a ) as resembling the plug of a wash b a s i n f i t t i n g i n t o the pore opening,  ;  A s i m i l a r s t r u c t u r e i s observed i n  Pleurotaenlum nodosum and T r l p l o c e r a s v e r t l c i l l a t u m where a cap-shaped s t r u c t u r e covers the pore opening.  In other  species s t u d i e d such a s o l i d s t r u c t u r e i s not seen,  A  loose f i b r i l l a r mass w i t h a zonatlon i n t o c i r c u l a r l y arranged and r a d i a l l y a r r a n g e d . m i c r o f i b r i l s i s present i n these species (e.g. Hyalotheca d i s s l l l e n s ,  Spondyloslum  pulchrum). Sheath s t r u c t u r e i n the Cosmarieae i s v a r i a b l e w i t h some species having l i t t l e sheath (e.g. T r l p l o c e r a s v e r t l c i l latum. Pleurotaenlum nodosum) and others having a broad sheath (e.g. Spondyloslum pulchrum).  The sheath i s always  composed of I n d i v i d u a l p a r t s , each s i t u a t e d over one of the pores.  Drawert and Metzner-Kuster ( 1 9 6 1 )  demonstrated  the i n d i v i d u a l sheath prisms of Hyalotheca d i s s l l l e n s i n oblique s e c t i o n s through the sheath.  The boundaries of  the i n d i v i d u a l sheath prisms are seen i n some of the desmids i n the present study (e.g. Hyalotheca d i s s l l l e n s . Spondyloslum  pulchrum)•  The nature of the connecting strands of Cosmocladium  Is n o t c e r t a i n . " L u t k e m u l l e r 1902)  The e a r l i e r a u t h o r s concluded t h a t the  a s p e c i a l group of pores Heimans  (1935)»  connecting  on e i t h e r  studying  study used the  and S c h r o d e r and c o n f i r m s saxonlcumsconnectlng pores.  following  strands  the  species  strand formation occurs  may be a b l e  as L u t k e m u l l e r  a different  connecting  i n C.  Isthmus  group with  subunits.  method  of  strands  of  investigated.  s t r a n d s may a r i s e  i m a g i n e how t h e a d d i t i o n a l c o n n e c t i n g  going  walls  cell division.  such strand  b u t w i t h o n l y two p a i r s o f p o r e g r o u p s  to  the  i n C . subramosum.  connecting  appear  that  one s t r a n d s u b u n i t  C o s m o c l a d i u m a r e f o r m e d r e m a i n s t o be  strand units  from  u s e d b y Heimans i s recommended  The p r o b l e m o f how t h e  or four p a i r s of  1902,  isthmus.  initial  J o i n w i t h the  s t r a n d c o m p r i s i n g 12-15 of  the  t h e i r conclusion that  In o r d e r t o d e t e r m i n e whether  parts  of  same s p e c i e s  Each pore c o n t r i b u t e s  entire  A restudy  side  s t r a n d s were f o r m e d f r o m t h e  The p r e s e n t  the  strands arose  C . subramosum. s t a t e d  d i s c a r d e d b y young s e m i c e l l s  of  ( S c h r & d e r 1900,  split  in different  outside  direction.  it  Three  f r o m one  is difficult  strands a r i s e .  t o p r o d u c e more t h a n one s t r a n d .  c o n c l u s i o n c a n n o t b e made f r o m t h e r e s u l t s  A  of  to The  the pore w i t h the The same p o r e  cell  two  group  definite  the  present  study. C e l l d i v i s i o n i n the growth o f an a n n u l a r septum  Cosmarieae (Krieger  involves  1937).  The  the  inward  septum  153 is  attached  the  two o l d s e m i c e l l s .  young is  to a c y l i n d r i c a l w a l l  semicells  reached.  represent the  the  is  (I966)  is  is  that  that  the  is  formed.  found i n M l e r a s t e r l a s showed  separates  semicell  semicell  t h i n and l a c k s  i n i t i a l wall  mature c e l l w a l l  wall  mature  half elongated  v e r t l c i l l a t u m the w a l l  that  In the u n i c e l l u l a r Cosmarieae  expand u n t i l t h e  In the  section  of  pores  later  morphology  Trlploceras and must  discarded  A similar thin  sp;  after  initial  (Waddingtdn 1 9 6 2 ) .  i n i t i a l walls  M i c r o f i b r i l s are also  initial of  the  w a l l of  visible  i n the p r e s e n t  In the initial into  wall  single  cells  new s e m i c e l l w a l l s  of  micrographs obtained initial  the  filament  is different  early  process  H-piece  stages  in this  c e l l wall  not  were  would  Is  group.  i n the  formed.  This  mitosis  before  electron  Although  formed a f t e r  of  In  l a i d down  following  an  disintegrate  i n c e l l d i v i s i o n were  may o c c u r  is  formation  The f o r m a t i o n  t h e new s e m i c e l l b e g i n s .  of  process  the  the d i s c a r d i n g of  cell division.  d i v i s i o n septum i s  cylindrical  this  Cosmarieae  Desmldlum and Bambusina the elongation  of  o c c u r o r the  after  of  study.  filamentous cannot  The  at  i n u n i c e l l u l a r Cosmarieae has  b e e n s t u d i e d and no m i c r o g r a p h s obtained  i n sections  Trlploceras vert1ciliaturn.  mature c e l l w a l l  Mix  o f Tetmemorus and  P l e u r o t a e n l u m a r e composed o f m i c r o f i b r i l s o r i e n t e d random.  the  not  way. and  i n i t i a l wall  An the  persists  154  as the l e s s electron-dense l a y e r between the mature c e l l w a l l s which are l a i d down on both s i d e s .  The p o s i t i o n of  pores i n the mature w a l l i s i n d i c a t e d by l e s s dense areas but i t i s not c l e a r how the l o c a t i o n i s determined.  When  the new s e m i c e l l s elongate the w a l l s separate a t the outer edge of the d i v i s i o n septum and g r a d u a l l y the w a l l unfolds to form the mature s e m i c e l l shape.  Pieces of the I n i t i a l  w a l l remain attached to the outside of the mature c e l l wall.  The two new s e m i c e l l s remain i n contact i n the  area i n t e r n a l to the c e l l w a l l f o l d . c e l l elongation  This d e s c r i p t i o n of  i n BambusIna b r e b l s s o n l l d i f f e r s s l i g h t l y  from that given by H a u p t f l e i s c h  (1888) from l i g h t microscope  observations and repeated without a l t e r a t i o n i n Krieger (1937).  H a u p t f l e i s c h shows the separation of the folded  parts of the w a l l before the l a t e r a l edge separates whereas i n the present study the reverse was found to occur. The s t r u c t u r e of the mature s e m i c e l l i n Bambusina can be r e l a t e d to the s t r u c t u r e of the unexpanded s e m i c e l l . The two l a t e r a l c e l l w a l l sections near the apex i n mature s e m i c e l l s correspond to the folded part of the d i v i s i o n w a l l w i t h the edge of the f o l d marked by a s l i g h t depression i n the mature w a l l .  The two narrower sections near the  isthmus represent the d i v i s i o n w a l l outside the f o l d and the l a t e r a l part of the new s e m i c e l l w a l l i n P i g . 6 7 with the thickening i n the mature w a l l marking the 9 0 ° angle between the two s e c t i o n s .  155 Chloroplast ultrastructure uniform. was  The p r e s e n c e  of grana  i n desmid  (196ld,  r e p o r t e d b y D r a w e r t a n d Mix  rotata  and b y  i n the Desmidiaceae  (1964, 1965)  Chardard  chloroplasts  f)  for  for  Micrasterlas  Cosmarium l u n d e l l l l .  C l o s t e r l u m a c e r o s u m and P e n i u m m a r g a r i t a c e u m . been found  in a l l  investigation. singly  a constant  of  chloroplast  Desmidiaceae  c a n be  a central the  time  1961,  is  the  1962,  and s e v e r a l  thylakoids  matrix but  is  of  the  subfamilies  No c o r r e l a t i o n of  the  same i n a l l d e s m i d s  Leyon  1962a,  (e.g. area  with  The  matrix  glutaraldehyde-  pass  through  the there  pyrenoid through which  This area  chloroplast  studied  Chardard  T r l p l o c e r a s F i g . 56)  i n the  pass.  of a s i n g l e  1954).  thylakoids  surrounded by the  in a l l pyrenoids  thylakoids  studied.  ( D r a w e r t and Mix  l e s s dense  invagination  globules  made.  I n some s p e c i e s  many d f  one  to  g r a n u l a r and e l e c t r o n - d e n s e  matrix.  present  osmiophlllc  the desmids  structure  Kamiya  osmium f i x a t i o n  is  of  ultrastructure  the p r e s e n t  appears  of  i n the  Grana have  packed groups between the  feature  Pyrenoid  1964, I965t  studied  The p r e s e n c e  or i n c l o s e l y  is  up t o  species  is  is not  an  stroma i n t o  the  matrix.  i s not  It  c e l l nor i n a l l  pyrenoid found  cells  of  species. Mitochondria  elongated internal  i n the desmids  or Y-shaped structure  studied  ( D r a w e r t and Mix  is uniform.  may be  l96lh)  but  short, the  The m i t o c h o n d r i a o f  156 Mlerasterlas  rotata  1961h) a n d  Mix  measure  P b y 0.4  5-35  the elongated  desmids  h a v e m i t o c h o n d r i a up t o 15 u l o n g . that  well  observed  present  study  Drawert and Mix observed  (osmic a c i d f i x a t i o n )  since  i s present  This  i s probably  a well defined  i n some c e l l s  to the c h l o r o p l a s t  desmids w i t h a x i a l  the r e s u l t  structure  i n the  of poor  o u t e r m i t o c h o n d r i a l membrane  of Trlploceras vertlcillatum  with glutaraldehyde-osmic close  a n d t h e same  i n t h e m i t o c h o n d r i a o f most s p e c i e s  study.  fixation  the  l n the present  t h e o u t e r membrane o f t h e m i t o c h o n d r i o n i s n o t  preserved is  u (Drawert and  acid.  fixed  Mitochondria are located  lobes.  In cross  chloroplasts  sections  ( e . g . Penium.  m i t o c h o n d r i a l i e i n the grooves  of  Trlploceras)  between the  chloroplast  lobes• Dictyosomes chloroplast. found rotata  a r e found c l o s e  Desmid d i c t y o s o m e s  in plants,  u i n Cosmarlum l u n d e l l i i  study  dictyosomes  u i n M. d e n t l c u l a t a  1-3  1965).  u long.  number o f c i s t e r n a e  make up t h e d i c t y o s o m e  dictyosome  are present  vesicles  Cytoplasmic plants  by L e d b e t t e r  been observed  i n many o t h e r s  In the present  A variable • and s m a l l  a t b o t h ends o f t h e s t a c k .  m i c r o t u b u l e s were and P o r t e r  largest  i n C l o s t e r l u m acerosum and c a .  (Chardard  are usually  of the  P i n Mlerasterlas  196lg), 1.6-3.6  1963). 1-3 p  to the lobes  a r e among t h e  m e a s u r i n g up t o 5*5  (Drawert and Mix  (Drawert and Mix  2  also  first  seen  (I96I) a n d have  (Miihlethaler  i n vascular subsequently  1967).  The  Isthmus m i c r o t u b u l e s  (23-2?  size  near the  Desmidiaceae properties  p l a s m a membrane i n v a s c u l a r are  seen  i n osmium-fixed  mitotic  apindle  size  the  to  the  mu) and f i x a t i o n  microtubules not  of  of  correspond to  those  plants.  The m i c r o t u b u l e s  Spondylosium pulchrum are  isthmus  observed  These  in glutaraldehyde-fixed  cells.  cells of  function  cellulose This  i n the  similar  microtubules  the  f o r m a t i o n and o r i e n t a t i o n o f  i s based  the  c e l l wall  on t h e  In the  are  c e l l w a l l of  m i c r o f i b r i l s are not  oriented  i n the  the  microtubules.  The m i c r o t u b u l e s  at  the  isthmus r e g i o n  i n elongating  cells  isthmus.  microtubules  other  the  Penium margaritaceum,  constricted  isthmus,  orientation  i s not  microfibrils. not  involved  and a r e n o t isthmus  also  the  Therefore,  the  present In  such  is  However,  no are  which does n o t have  that of  in c e l l wall deposition  constriction.  only  the  i n the  with c e l l s  a  whose cell  isthmus m i c r o t u b u l e s  only associated  in  isthmus r e g i o n  has m i c r o t u b u l e s  same a s  the  same d i r e c t i o n  formation  a r e a s away f r o m t h e  1967).  Desmidiaceae  are  occurring at  present.  that  semicells.  one w o u l d e x p e c t t h a t c e l l w a l l  than those at  the  oriented  the  as  thought  (Muhlethaler  observation  and m i c r o f i b r i l s o f t e n  same d i r e c t i o n .  in  microtubules.  m i c r o f i b r i l s of  conclusion  but  the  M i c r o t u b u l e s n e a r t h e p l a s m a membrane a r e to  in  wall are  probably  Desmidiaceae  containing  the  158 The chromosomes o f t h e d e s m i d s a r e r e p o r t e d a s having d i f f u s e based  or non-localized  on t h e p a r a l l e l s e p a r a t i o n  anaphase.  In the r e l a t e d  centromeres  of chromatids  t h a t some S p l r o g y r a s p e c i e s  with localized  centromeres  and o t h e r s  at  o r chromosomes w i t h d i f f u s e  Sirogonlum,  which i s s i m i l a r  r e p o r t e d t o have p o l y c e n t r i c  have  have  chromosomes  chromosomes  polycentic  centromeres.  to Spirogyra, chromosomes  is  also  (Hoshaw a n d  1967). The c e n t r o m e r e  two d e n s e  bands  and b u n d l e s  i n e l e c t r o n micrographs  or p l a t e s on each s i d e  of spindle microtubules  (Godward 1 9 6 5 ) . the  i960)  f a m i l y Z y g n e m a t a c e a e Godward  (195*0 r e p o r t s  Waer  (King  o f t h e chromosome  attach  to these  I n chromosomes w i t h d i f f u s e  spindle microtubules  a l o n g t h e chromosome  attach  singly  (Godward 1 9 6 5 ) .  comprises  plates  centromere  a t many  points  A t metaphase  Closterlum ehrenbergll  the absence o f bundles  microtubules  t o t h e chromosome was i n t e r p r e t e d  as the  evidence  attaching  f o r the existence  chromosomes o f t h i s  of diffuse  species  in  showing  at several  points  I n t h e metaphase bundles  spindle microtubules o n t h e chromosome chromosomes  of spindle microtubules  in  (Brandham a n d Godward  Unpublished micrographs e x i s t  singly  spindle  centromeres  Godward I 9 6 6 ) . Mlerasterlas  of  in  of  1965.  metaphase  attaching  (Godward  I965).  o f Spondyloslum pulchrum  attach  a t one r e g i o n on  159 the  chromosome  attachment of  (Fig.  region  higher plant  is  a localized  attach  chromosomes  Desmidiaceae  material  is  staining  substance  reported  Godward and J o r d a n  1965)  same a s  that  to of  Thus the  the  S.  this centromere  Since  other points  on  no the  p u l c h r u m must have  and Z y g n e m a t a c e a e t h e  to p e r s i s t  around the  1965)*  during mitosis  chromosomes  in Closterium ehrenbergil  substance persistence  is of  present  as a dark  (King  I960, of  (Brandham and Godward this  around the  study  no  chromosomes.  the n u c l e o l a r m a t e r i a l around  chromosomes d u r i n g m i t o s i s be a c o n s t a n t  nucleolar  In e l e c t r o n m i c r o g r a p h s  and i n S p o n d y l o s i u m p u l c h r u m o f  nucleolar  of  of  centromere.  In the  metaphase  the  and a n i m a l chromosomes.  spindle microtubules chromosome t h e  The s t r u c t u r e  113)•  phenomenon.  i n desmids does n o t appear  the to  Bibliography. B o u r r e l l y , P.  1964  Une nouvelle coupure generique dans  l a f a m i l l e des Desmldlees: l e genre T e l l l n g l a . Rev. A l g o l . , n.s., 2 B o u r r e l l y , P.  1966  Vertes.  J  187-191•  Les Algues d»Eau Douce. I . Les Algues  P a r i s , N. Boubee & Gie. 1965  Brandham, P. and Godward, M.B.E.  U l t r a s t r u c t u r e of  the nucleus of the green a l g a Closterlum e h r e n b e r g l l . J . Roy. Micr. Soc. 84: 499-507. Brunei, J . 1949  The rediscovery of the desmid Pleurotaenlum  splnulosum. w i t h d e s c r i p t i o n of a new v a r i e t y from Madagascar. Chardard, R.  1964  C o n t r i b . I n s t . Bot. Montreal 64: 3-19. Etude de 1 ' u l t r a s t r u c t u r e de deux algues  Zygophycees: Mesotaenlum oaldarlorum e t Penium margaritaceum. Chardard, R. I 9 6 5  Rev. C y t o l . B i o l . Veget. 2£: 77-93.  Nouvelles observations s u r  1 * i n f r a s t r u c t u r e de deux Algues Desmldlees: Cosmarlum l u n d e l l l l e t Closterlum acerosum.  Rev.  C y t o l . B i o l . Vege't. 28: 15-30. Chardard, R and R o u i l l e r , C.  1957  t r o l s Algues Desmldlees. ellectronlque.  L u l t r a s t r u c t u r e de f  Etude au microscope  Rev. C y t o l . B i o l . Veget. 18: I 5 3 - I 7 8 .  Drawert, H. and Metzner-Kuster, I . I96I  L i c h t - und  elektronenmikroskopische Untersuchungen an Desmidiaceen.  I . Zellwand- und G a l l e r t s t r u k t u r e n  b e l e l n i g e n A r t e n . P l a n t a $6: 213-228.  161 Drawert, H. and Mix, M.  1961a L i c h t - und elektronen-  mikroskopische Untersuchungen an Desmidiaceen. I I . H u l l g a l l e r t e und Schleimbildung b e i M l c r o a s t e r l a s . Pleurotaenlum und Hyalotheca. Drawert, H. and Mix, M.  P l a n t a ^ 6 : 237-261.  1961b L i c h t - und elektronen-  mikroskopische Untersuchungen an Desmidiaceen. I I I . Der Nucleolus im Interphasenkern von Mlerasterlas rotata. Drawert, H. and Mix, M.  F l o r a 150: 185-190.  1961c L i c h t - und elektronen-  mikroskopische Untersuchungen an Desmidiaceen. IV. B e i t r a g e z u r elektronenmikroskopischen S t r u k t u r des Interphasenkernes von M l e r a s t e r l a s r o t a t a . Z. N a t u r f o r s c h . 16b: 5 4 6 - 5 5 1 . Drawert, H. and Mix, M.  I96ld  L i c h t - und elektronen-  mikroskopische Untersuchungen an Desmidiaceen. V. Uber d i e V a r i a b i l i t ' a t der C h l o r o p l a s t e n s t r u k t u r bei Mlerasterlas rotata. Drawert, H.' and Mix, M.  I96le  P l a n t a jj>6: 6 4 8 - 6 6 5 . Der E i n f l u s s von  A n t i b i o t i k a auf d i e l i c h t m i k r o s k o p l s c h e und elektronenmikroskopische S t r u k t u r von M l e r a s t e r l a s . Ber. deutsch. b o t . Ges. 2*t  s  Drawert, H. and Mix, M.  I96lf  (^6)-(47).  L i c h t - und elektronen-  mikroskopische Untersuchungen an Desmidiaceen. VI. Der E i n f l u s s von A n t i b i o t i k a auf d i e Chloroplastenstruktur b e i Mlerasterlas r o t a t a. Planta  51-70.  Drawert, Hv and Mix, M.  I96lg  L i c h t - und elektronen-  mikroskopische Untersuchungen an Desmidiaceen. V I I . Der Golgi-Apparat von M l c r a s t e r i a s r o t a t a nach P i x i e r u n g mit Kaliumpermanganat und Mikroskopie 16: 207-212.  Osmiumtetroxyd. Drawert, H. and Mix, M.  196lh  L i c h t - und elektronen-  mikroskopische Untersuchungen an 5-Desmidiaceen. V I I I . Die Chondriosomen von M l c r a s t e r i a s r o t a t a . F l o r a l g l : 4-87-508. Drawert, H. and Mix, M.  1962a  L i c h t - und elektronen-  mikroskopische Untersuchungen an Desmidiaceen. IX. Die S t r u k t u r der Pyrenoide von M l c r a s t e r i a s rotata.  P l a n t a $8: 50-74-.  Drawert, H. and Mix, Mi 1962b  Zur Frage der I d e n t i t a t  von Karyoiden und Golgi-Apparat b e i den Conjugaten. Naturwissenschaften 4j£: 353-354-. Drawert, H. and Mix, M.  1962c  L i c h t - und elektronen-  mikroskopische Untersuchungen an Desmidiaceen. X. B e i t r a g e zur Kenntnls der "Hautung" von Desmidiaceen.  Arch. M i k r o b l o l . 4£: 96-109.  Drawert, Hi and Mix, M.  I963  L i c h t - und elektronen-  mikroskopische Untersuchungen an Desmidiaceen. X I . Die S t r u k t u r von Nucleolus und Golgi-Apparat b e l M l c r a s t e r i a s d e n t l c u l a t a Breb. P o r t u g a l i a e Acta B i o l i , Ser. A, 2  s  17-28.  Godward,  M.B.E.  1954  polycentric  The d i f f u s e  chromosomes  centromere o r  i n Splrogyra.  Ann. B o t . ,  n . s . , 18: 143-156. Godward,  M.B.E.  special CL. Godward,  I965  Problems o f n u c l e a r d i v i s i o n  reference  Duddington,  M.B.E.  ed.,  I966  to the a l g a e . ed. , Viewpoints !  Chlorophyceae.  with  I n J . D . 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Zur F e i n s t r u k t u r  der Zellwande und M i k r o f i b r i l l e n e i n i g e r Desmidiaceen von Cosmarlum-Typ. Mix, M.  I968  Arch. M i k r o b i o l . ^5_: 116-133.  Zur F e i n s t r u k t u r der Zellwande i n der  Gattung Penium (Desmidiaceae).  Ber. deutsch. b o t .  Ges. 80: 715-721. Muhlethaler, K.  I967  U l t r a s t r u c t u r e and formation of  plant c e l l walls. Reynolds, E.S. I 9 6 3  Ann. Rev. P l a n t P h y s i o l . Ij8: 1-24.  The use of lead c i t r a t e a t high pH  as an electron-opaque s t a i n i n e l e c t r o n microscopy.  J . C e l l B i o l . 12: 208-212. 1900  Schroder, B. Ber.  Cosmocladlum saxonlcum de Bary.  deutsch. b o t . Ges. 18: 15-23. 1902  Schroder, B.  Untersuchungen uber G a l l e r t b i l d u n g e n  der Algen. Verh. naturhlst.-med. Ver. Heidelberg  1'. 139 S t a r r , H.C.  1964  The c u l t u r e c o l l e c t i o n of algae a t  Indiana U n i v e r s i t y . Waddington, C H .  1962  Development.  Am. J . Bot. $ U 1013-1044.  New Patterns i n Genetics and  New York, Columbia Univ. Press.  West, W. and West, G.S.  1904  A Monograph of the B r i t i s h  Desmidiaceae. V o l . I . London, Ray S o c i e t y . West, W. and West, G.S.  I905  Desmidiaceae. V o l . 2. West, W. and West, G.S.  London, Ray S o c i e t y .  1908 A Monograph of the B r i t i s h  Desmidiaceae. V o l . 3» West, W. and Wes;t, G.S.  A Monograph of the B r i t i s h  1912  Desmidiaceae. V o l . 4.  London, Ray S o c i e t y . A Monograph of the B r i t i s h London, Ray S o c i e t y .  West, W;, West, G.S., and Carter, N.  1923  the B r i t i s h Desmidiaceae. V o l . 5*  A Monograph of London, Ray  Society. Wolle, F. Bot.  1881 American freshwater algae. B u l l . Torrey Club 8: 1-4.  

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