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Morphological, physiological and cytological studies of alfalfa (medicago) Holliday, Elisabeth Mary 1932

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MORPHOLOGICAL, PHYSIOLOGICAL M3) CYTOLOGICA1 STUDIES OF ALFALFA (HEDIOAGQ) PART I THE MORPHOLOGY OP THE ALFALFA RHIZOME AI© ITS ANATOMY Iff COHPARISOI WITH THE AERIAL STEM AND THE ROOT. PART I I SOME FACTORS AFFECTIHG THE GEOTROPIC RESPONSE OF THE ALFALFA RHIZOME. PART I I I CYTOLOGICAL STUDIES OF ALFALFA WITH REFERENCE TO CHROMOSOME NUMBERS AND HID IVIDUA1IT Y. "by E l i s a b e t h Mary H o l l i d a y A Thesis submitted f o r the Degree o f MASTER OF ARTS I n the DEPAETHEN2? OF BOTANY The U n i v e r s i t y o f B r i t i s h Columbia APSIL, 1932. AJ V 59a«- author wishe-.s to tak© t h i s opportunity of' aolmswle&glng hey -frery sineere gratitude to. I f e A» H* Sat&Mnsaa for sagge-stiaisa and eritioisais.j 'to Bsv -<J* G-* Mo© f o r asaiBtanee- i n sele.&tion of material sack to those who made tmttlngs *md helped i a .field work« SABLE OF COHgEETTS PAGE The Morphology of the A l f a l f a Rhizome and i t s Anatomy i n Comparison with the A e r i a l Stem and i the Root — . . 1 Explanation of Plates • 1 & I I Literature Cited • I - VI Some facto r s ai'fectizig the Geo t r o p i c Response of the A l f a l f a Rhizome — — — 18 Lit e r a t u r e Cited — >- • — — I - V Cytolo g i c a l Studies of A l f a l f a with Reference t o Chromosome Ilumber and I n d i v i d u a l i t y • SI Explanation of Plates . I - IV Lit e r a t u r e Cited — — • • j & II P l a t e u . — — — I - v ! 1 WE MORPHOLOGY OF THE ALFALFA RHIZQME MJ) ITS AHAiEOMY IB COMPARISON WISH  SHE AERIAL STEM AMD TEE R005. HISTORY Off ALFALFA A b r i e f review of the h i s t o r i e s of various species of a l f a l f a s as outlined by several authors (10, SS, £4, 27) indicates that many have t h e i r o r i g i n In the temperate regions of A s i a . From these l o c a l i t i e s the c u l t i v a t i o n of a l f a l f a was e a r l y introduced into Southern European countries. I t has not, however» been ascertained with certainty, whether a l f a l f a i s indigenous to America, as i t i s known to have been brought by the Spaniards to Mexico, spreading from there throughout the United States and Canada* Amongst the various types described are some wild rhizome forming plants. Such are associated with hardiness, as they thrive s uccessfully under conditions including moist and dry climates, and s o i l s ranging from s t i f f heavy clays to almost pure sand. The plants under i n v e s t i g a t i o n i n t h i s paper represent a cross between the variegated a l f a l f a Medicago media or "Grimm" and the yellow flowered f a l c a t a or "Donn." There are several v a r i e t i e s of the species media believed to r e s u l t from a cross between Medicago s a t i v a and Medicago f aleata, of which the Grimm i s one. It occurs where the d i s t r i b u t i o n of M« s a t i v a and i£. f a l c a t a overlap throughout Russia and Central A s i a , She Donn, a very hardy species,, i s widespread throughout Southern S u s s i a s S i b e r i a and Central Asia, t h r i v i n g i n l o c a l i t i e s of severe drought and co l d s i m i l a r to the American 1« W. p r a i r i e s * Shese two species d i f f e r considerably i n form of growth. She stems of the Grimm are erect and us u a l l y no rhizomes are produced, but c e r t a i n plants are on record as having t h i s character. She Donn, on the other hand, has short semi-erect stems i n a thick matted growths with rhizomes sprouting about two inches below the surface of the ground,, and breaking through to the surface at varying distances from the c e n t r a l axis, thus increasing considerably i t s circumference. She Donn parents were brought from S» Dakota to the Uni v e r s i t y of B. Go and planted alongside the Grimm and Ontario Variegated varieties., Prof. Bcving, knowing the almost complete s t e r i l i t y of the Donn, attempted i n 1917 to obtain crosses by allowing the Grimm, growing alongside of i t , to blossom simultaneously, thus assuring i t s f e r t i l i z a t i o n . Out of the two hundred and f i f t y plants produced from seed gathered from these Donn plants, s i x showed unmistakable hybrid characters intermediate between those of the two parents. • She F 1 hybrids as described by Dr. Moe (19) were 3 i n t e r m e d i a t e i n form o f growth between the Donn and Grimm p a r e n t s , She stems, approximately the l e n g t h o f those o f the Grimm hut more procumbent, and the p r o d u c t i o n o f underground rhizomes a t t h e i r bases s i m i l a r to those o f the Donn, pr o v i d e evidence of t h e i r h y b r i d n a t u r e . GROSS MORPHOLOGY Off TEE RHIZOME The a b i l i t y t o produce rhizomes i s a v e r y d e s i r a b l e q u a l i t y o f these h y b r i d s , She advantages a r e s e v e r a l . The r e s u l t i n g i n c r e a s e I n c i r c u m f e r e n c e g i v e s an e x c e l l e n t ground c o v e r i n g , a f a v o r a b l e f a c t o r as f i e l d s o f e r e c t a l f a l f a are prone to become patchy. I n c o l d c l i m a t e s when the r e s t i n g buds are beneath the e a r t h d u r i n g extreme weather ample p r o t e c t i o n i s a f f o r d e d and c o n t i n u e d growth a s s u r e d . I t has been demonstrated t h a t , so l o n g as the t i p s a re below ground, no i n j u r y from f r o s t r e s u l t s . In d r y c l i m a t e s the rhizome seems to a c t as a water storage organ, due to i t s somewhat f l e s h y nature when young, and a l s o t o i t s p r o t e c t i o n from e x c e s s i v e e v a p o r a t i o n . Such f a c t s a re e x p l a n a t o r y of the wide range o f t o l e r a n c e of rhizome b e a r i n g p l a n t s . I t has been noted, furthermore, t h a t , i n d r y r e g i o n s the rhizome s p r o u t s i n the s p r i n g , s t o r i n g water d u r i n g the hot summer months, w h i l s t i n c o l d e r c l i m a t e s growth commences i n the autumn, the rhizome remaining as a bud or shoot of a few inches i n l e n g t h u n t i l the growing season o f s p r i n g . ' As d e f i n e d by Asa Gray the rhizome, i s a "stem o f r o o t - l i k e appearance, p r o s t r a t e on or under the ground, from which r o o t l e t s may be sent o f f , the apes progressively sending up herbaceous stems or flowering s t a l k s and often leaves*" Oakley (S3), i n a study of the rooting stems of timothy* considers the true rhizome i£ an underground stem which roots at the nodes and produces stems or leaves progressively* More recently some discussion of the a p p l i c a t i o n of the term rhizome i s expressed by Holms (12). He considers the term rhizome should be r e s t r i c t e d to subterranean stems, representing the primary axis and developed d i r e c t l y from the primary stem t i p . They are d i f f i c u l t to d i s t i n g u i s h from stolons (subterranean a x i l l a r y shoots}. He considers the so-called rhizome of the G-ramineae and Cyperaceae as stolons, whilst Oakley (23) considers the stolon as a prostrate stem above ground.. I t i s evident that, as more attention i s paid to d e t a i l , several types of rooting stems can be described* and as no d e f i n i t e agreement as to terms seems to have been reached* the term "rhizome" seems most acceptable f o r the present. Some experiments performed by Oliver (24) on plants producing rooting rhizomes, reveal the f a c t that the rhizome-forming growth of most plants has i t s o r i g i n i n the a x i l s of the seed leaves. He discovered that the parts of the stem previously occupied by the cotyledons are drawn two or three inches into the s o i l , the only explanation offered, being that the- main root must contract considerably. An examination of the U. B« 0. plants indicates that D rhizome buds commence growth l a t e i n the summer—August or September. They originate at or above the crown on that portion of the stem drawn underground and continue a l a t e r a l extension f o r several inches u n t i l l a t e i n Bovember (Plate 1), During t h i s period the rhizome i s a white shoot e x h i b i t i n g d e f i n i t e stem c h a r a c t e r i s t i c s by the d i v i s i o n into nodes and at these, the growth of large clasping s t i p u l e s i n the a x i l s of whioh are dormant buds (Plate S, P i g . 1 ) . These develop l a t e r into branches, (Plate 2, F i g . 2 ) , In November the rhizome t i p s ascend to the surface of the ground almost at r i g h t angles, She exposed s t i p u l e s and rhizome turn a reddish purple and a few green leaves are developed immediately. At t h i s time also , the underground portions of the rhizome adjacent to the stem begin to produce an external cork l a y e r , Throughout the remainder of the winter there i s l i t t l e further growth, the t i p s with green leaves remaining just above the ground surface* When the growing season again commences, several changes take place. The main rhizome axis elongates further, the portion pushed above ground resembling an a e r i a l stem. On the other hand, the underground portion develops a cork l a y e r and increases i n diameter, thus bearing considerable resemblance to the r o o t . The dormant buds frequently develop into l a t e r a l branches which extend into a e r i a l shoots bearing leaves. Prom below the s t i p u l e s slender root t i p s emerge, developing l a t e r into r o o t l e t s and roots of normal s i z e . 2?ig» 3, -Plate 2 shows an enlarged r h i some of r o o t - l i k e appearance, with the r o o t l e t s hearing nodules c h a r a c t e r i s t i c of a l f a l f a . Similar r o o t l e t s appear on the roots In three •vertical rows ax more or les s equidistant Intervals. A l l ro o t l e t s appear to emerge to the surface through l e n t i e e l s (Plate 2, Fi g * 4)« With these external changes i n morphology questions n a t u r a l l y a r i s e as to the in t e r n a l anatomy. What resemblance does the young rhizome bear to the a e r i a l stem? What changes take place as the two types of stem are evolved? With an external r o o t - l i k e appearance, i s there a change to a root structure i n t e r n a l l y ? Therefore an in v e s t i g a t i o n comparing the anatomy of the a e r i a l stem, root and rhizome would seem pertinent, MATERIAL AED METHODS Mater i a l i l l u s t r a t i n g various stages of development was k i l l e d and fi x e d i n B. C, F i x i n g Solution, The usual method of c l e a r i n g i n z y l o l proved unsatisfactory as the greater portion of the material was woody* and the roots and rhizomes f i l l e d with starch, rendering sectioning very d i f f i c u l t . However, by using butyl alcohol f o r a cle a r i n g agent (37) and longer periods of p a r a f f i n i n f i l t r a t i o n , such were overcome to a great extent. Sections 1 5 -25^ i n thickness were cut with a rotary microtome and stained with Haidenhaim's haematoxylin and i r o n alum with counterstain of l i g h t green i n clove o i l . Some very s a t i s f a c t o r y sections were cut with a s l i d i n g microtome hut had the disadvantage of not being i n s e r i a l order. Camera luci d a diagrams on plates at the end of the t e s t i l l u s t r a t e various points* Since the object of the paper i s a comparison of the anatomy of the rhizome with that of the a e r i a l stem and the root, the l a t t e r two should receive primary consideration to form a f a m i l i a r basis. THE AERIAL STEM - (BLASE 8. FIG. 1). The a e r i a l stem of a l f a l f a , i s t y p i c a l of an herbaceous dicotyledon, somewhat four-angled, internodally a continuous undlssected siphonostele, nodally l e a f and branch gaps extending from the p i t h to the cortex. The epidermis consists of a single layer of c e l l s , a s l i g h t l y thickened c u t i c l e modifying i t s outer periphery. Stomata at i r r e g u l a r intervals appear to function without- the a i d of l e n t i c e l s . The cortex, several c e l l s i n thickness, i s abundantly supplied with chloroplasts aggregated around each c e l l periphery. Groups of f i b r e s with thickened walls are situated above the phloem caps. At each of the four stem angles these groups are increased i n number, apparently affording greater support. Phloem i s found In caps, each subtending a protoxylem t i p * which adjoins the p i t h i n a point. The secondary xylem constitutes the major portion of the cylinder* As the a e r i a l stem i s annual, there are no annual rings i n the xylem region. Tracheae with a wide lumen are f a i r l y numerous. In l o n g i t u d i n a l section, s p i r a l p i t t e d and r e t i c u l a t e vessels are evident and traeheids bearing simple p i t s 0  TEE ROOT PLATES (4 AMD 5. ) The structure of the root i s t y p i c a l l y dicotyledonous, a r a d i a l t r i a r c h protostele i n primary growth, the positions of xylem and phloem of secondary t i s s u e s , being, as i s usually the eese, fundamentally the same as that found. In the stem.. The primary protoxylem p e r s i s t s but becomes intermingled with'metosylem. There are three primary aggregate storage rays, but there are several rays of secondary growth considerably Increasing the number of xylem strands. In l o n g i t u d i n a l section the branching of the f i b r e s separating the ray into sections i s very evident. Such a type of ray i s considered by J e f f r e y (15) as aggregate. The outer surface of the root i s protected by an impervious cork layer several c e l l s In thickness. Groups of f i b r e s of varying numbers are situated at i r r e g u l a r i n t e r v a l s throughout the cortex* appearing long and tapering i n lo n g i t u d i n a l section with no wall markings. .Both storage rays and cortex become f i l l e d with stored starch grains. Secondary xylem consists of r e t i c u l a t e vessels only, interspersed with selerenehymous f i b r e s , AS the root i s perennial, annual xylem rings are evident. Root branches appear to arise on one of the primary rays, which subtend a protoxylem t i p , the vascular system being derived from primary xylem flanking either side of the 9 ray» Small r o o t l e t s as mentioned before occurring i n three v e r t i c a l rows^appear also to originate on the three primary raye vrhich are subtended by l e n t i c e l s (Plate 6). The xylem of the r o o t l e t consists of short s p i r a l l y thickened elements interspersed with numerous parenchyma c e l l s * TEE RHIZOME In early strges of growth the anatomy of the rhizome i s very s i m i l a r to that of the a e r i a l stem, with the. exception of a thinner c u t i c l e and the absence of c o r t i c a l chloroplasis (Plate Z, F i g * 2)» After secondary xylem growth has commenced a phellogen towards the inner layers of cortex becomes active, cutting o f f a. thick layer of cork c e l l s (Plate 7 V 8)* At about the same time the I n t e r f a s i c u l a r cambium becomes active giving r i s e to storage rays which penetrate the vascular c y l i n d e r . The f i n a l stages of a c t i v i t y are the sloughing of the peripheral cortex and epidermis, and complete penetration of the rays to the p i t h r e s u l t i n g i n separate bundles. With increase of the xylem cylinder the r e l a t i v e mass of p i t h i s very much reduced. Breach gaps are formed i n the usual manner extending from p i t h to cortex at the nodes. Adventitious r o o t l e t s , s i m i l a r to those found on the roots, a r i s e at the nodes below branch buds (Plate 10). 'J'hey also appear to arise on a storage ray subtended by a l e n t i e e l (Plates 11, IE). '5!he thickened portion of the plant drawn undergrounds the apex giving r i s e to a e r i a l stems, the base terminating i n 10 the crown from which the roots a r i s e , and the interspaces between these points giving r i s e to rhisomes, i s stem t i s s u e . It i s modified by both a thick cork layer s i m i l a r to the root, and storage ray c e l l s . A large p i t h remains from which branch gaps extend to the cortex giv i n g r i s e to rhizomes {Plate 13). In connection with a l l underground structures there appears just inside the cork phellogen a peculiar stimulation of cork-like c e l l s to enclose groups of f i b r e s (Plate 13, F i g , 1) • From an examination of l o n g i t u d i n a l sections i t appears that the whole group of f i b r e s i s surrounded by these c e l l s (Plate 14, F i g . 2). Continued growth seems to force the f i b r e s through the cork layer to tne surface (Plate 14, Pig, 3., Plate 13, Fig s , 2, 3), Frequently a single group seems to be pushed through with no r e l a t i o n to any other group (Plate 14, Fig« 3), It was noted, however, that there seems to be an intimate r e l a t i o n with two groups to form an indentation on the surface when some cork c e i l s are sloughed (Plate 14, F i g , 1)„ SJJ J ^ S I O J L i t t l e comment concerning the a e r i a l stem i s necessary. I t may be considered as i*e presentative of the higher forms of dicotyledons i n the possession of an annular stem with a small amount only of secondary growth. She siphonostelic vascular system would also place i t amongst these (14). Ch a r a c t e r i s t i c also of such a type i s the 11 confinement of cambium a c t i v i t i e s to the f a s i c u l a r region. Groups of f i b r e s above the phloem caps are described i n the Purslane (7) situated immediately within the endodermis, and are considered as c o n s t i t u t i n g a part of the p e r i c y c l e . The anatomy of the root i s t y p i c a l of an herbaceous dicotyledon, i t s vascular system being more primitive than the stem. Certain features studied by Le Clerg (18) are s i m i l a r , but he studied the vascular structure only. There seem to be some features with respect to secondary root branches which do not correspond with reported cases. Artschwager (3) found that the number of r o o t l e t s i s frequently of the same number as the number of protoxylem points. This f a c t i s well i l l u s t r a t e d . The general opinion Is that r o o t l e t s a r i s e i n or immediately within the p e r i c y c l e opposite pro to xylem tips.. A l f a l f a r o o t l e t s a r i s e on a primary ray, which i s considered by Jeffrey and Bailey (4, 5„ 15) as subtending protoxylem. This point was, however, d i f f i c u l t to determine d e f i n i t e l y as the protoxylem seems to intermingle with the metaxylem. Je f f r e y makes the following statement, "Since the secondary roots d e f i n i t e l y take t h e i r o r i g i n from the same clusters of protoxylem which are subtended by aggregate rays i n the secondary wood, It follows that the secondary roots are correlated with aggregate rays p r e c i s e l y as the traces of the l e a f are embedded i n s i m i l a r modifications of the r a d i a l parenchyma i n the case of the stem." However he also states, "The young root appears as a l o c a l development of c e l l s on the c e n t r a l cylinder of the main root opposite protoxylem, r r and furthermore, n23ie fibrov&seular supply of the root makes i t s e x i t from the stele or fibre-vascular c y l i n d e r vri.th.out causing any gap or interruption* ! f Eames (9) states that the r o o t l e t arises opposite the xylem rays v.?lien more than two of these are present- P r i e s t l e y (25) also considers that meristeiaatic a c t i v i t y i s induced i n the pericycle c e l l s , u s u a l ly opposite the xylene As roots are described with the primary and secondary xylem a l t e r n a t i n g . I t may be concluded that such i s the case f o r a l f a l f a . Secondary xyleia appears to provide the vascular system f o r the developing l a t e r a l root* It seems evident also that the o r i g i n of the l a t e r a l roots i s not i n the p e r i c y c l e as stated by Eases and P r i e s t l e y (8, 25)* With regard to the p o s i t i o n of the l s n t i c e l s 9 Wetmore (32) reports that they occur i n pairs one on either side of each r o o t l e t * On the contrary i t appears that the ray giving r i s e to a r o o t l e t i s subtended by a l e n t i c e l , the r o o t l e t f i n a l l y emerging through i t . I t i s , however, commonly agreed (8, 32} that the l e n t i c e l i s formed opposite one or more multIserlate rays. As the r o o t l e t arises i n one of these, one of Its natural paths of emergence would be through the l e n t i c e l . Shore Is the p o s s i b i l i t y that emergence might be above or below the l e n t i c e l , but material was i n s u f f i c i e n t to decide such a point. The rhizome, as a modified subterranean stem, i s common to several monocotyledons such a«3 Cyperaceae and IS Gramineae (33,54) and to a number of dicotyledons, Holms (11) reports a large number of plants producing root shoota, from l i s t s compiled by early i n v e s t i g a t o r s . As most of these were herbarium specimens, i t may be concluded that the underground stem resembling a root, as investigated here, i s probably more common than the so-called l a t e r a l roots bearing shoots. Recently Arber (B) presents the following statement, "That shoot? and roots s u p e r f i c i a l l y d i s s i m i l a r as they are, yet have a fundamental correspondence i s revealed by the f a c t that shoots can give r i s e to roots, and that roots though more ra r e l y , may produce shoot buds." Eames (8) describes Agrimonia as having an annual a e r i a l a tern end rhizome woody, with d i s t i n c t modifications f o r storage, showing t r a i - a i t i o n a l stages between the two extreme typos. The structure of the rhizome i s considered as a highly advanced modification of dicotyledon herbs due to the production of mult-Iseriate storage rays penetrating the xylem cylinder from a functional Inter-fasieuJLar cambium (£9, 31). Considerable discussion over the enlargement ef the storage ray has l e d to d i f f e r e n t theories- J e f f r e y (20) Is quoted as considering the increase i n parenchyma i s due to the transformation of xylem elements into such, but Sirmot (£8) contradicts t h i s view s t a t i n g that h i s examples ore from underground stems and rhizomes where decrease In cambial a c t i v i t y i s supplemented by widening of the medullary rays or by an increase i n the development of secondary parenchymatous 14 t5nsu.es between bundles » Recently Alexandrov (1) has noted that the oldest xylem vessels of Cannabis s a t i v a petioles are re g u l a r l y d e l i g n i f i e d and replaced by p r o l i f e r a t i n g parenchyma* .He believes t h i s may occur normally to a great-extent. She i n i t i a l growth of the storage rays commences some time a f t e r secondary wood i s produced, a f a c t i n accordance with £innot*-s -view (28). That the storage rays appear i n the f a l l soon becoming f i l l e d with stored starch v e r i f i e s the general conclusion that the rhizome i s primarily a storage organ* Adventitious r o o t l e t s s i m i l a r to those found on the roots o r i g i n a t i n g on storage rays ore produced. Their o r i g i n appears to be i n accordance with reported cases. Several authors (5, 35} have noted that the adventitious root arises i n the medullary ray i n connection with the primary vascular system B thus being of the same o r i g i n as the branch and l e a f . Others, however, i n working on out tings, conclude that the roo t l e t s arleo i n the pericycle (6, V s 30)» Relations to the l e n t i e e l s are s i m i l a r to those on the root and therefore also d i f f e r from reported examples. The p o s i t i o n of the adventitious r o o t l e t In r e l a t i o n to tho node also presents varying opinions. A l f a l f a r o o t l e t s a r i s e below or immediately adjacent to the branchy i f more than one i s present. Jeffrey (14) states that roots are often, but not invariably, related to the bases of leaves. Howe (13) ' 15 find s that the root i n i t i a l of the f i r s t adventitious root at the node i s derived from the c e l l Immediately below the l e a f initial« Oakley (23) also shows timothy r o o t l e t s appearing below the node, Wilson (35) 0 however- f i n d s that adventitious roots a r i s e In the a x i l s of branch buds and he considers they are produced from aborted branch or l e a f buds 8 I t :1s commonly agreed.that they are always preduced at the node. The p o s i t i o n of the cork phellogen i n stems may be i n one of three places, a r i s i n g i n the exoderrais, perioycle, or i n an intermediato position i n the cortex (26), Wien the phellogen occurs i n the inner tissues, i t arises w i t h i n a secondary endodermis. sloughing of the cortex following as the food supply cut o f f . The phellogen. of the a l f a l f a arises i n the inner cortex, the outer layers sloughing off* The c o r t i c a l c e l l s imderneath continue growth so that a cortex i s b u i l t iin beneath the cork (35)» A consideration of the incorporation of f i b r e s Into the cork layer finds no explanation as to tho cause or use. The meristematic a c t i v i t y may be explained as the c e l l s immediately beneath the cork continue to st3.1nula.te growth (35 )* The only reference which might be applicable to such structures i s an abstract. (20) reporting s t r u c t u r a l features such ac growth ruptures of cork or b a r k which may serve to f a c i l i t a t e t r a n s p i r a t i o n r:nd gas exchanges These are not to . be regarded'a,1? true lent-icels. I f the reference i s to structures somewhat si m i l a r to those on the alfalfa„ the 3L^ ' dissimilar5.ty to a . l e n t i c e l and the persistence o f the cork layer precludes the p o s s i b i l i t y of the idea of gas exchange, unless there i s a terminal'opening i n the..layer*- I t i s suggested that there might be one by the figures i n Plate 14, F i g s . 1, 2, also Plate 15, F i g * 2* Further investigations on the structures ©rs - n$e«asary before anything d e f i n i t e can be. agreed upon,-J. Y . jglg§A§g; ' ... (1) Eli© gross morphology .of the yo\mg-rhizome i n d i c a t e s that i t i s a true stem wh i l s t the older. rhizome e x t e r n a l l y resembles a root g i v i n g r i s e to shoots* (B) She a e r i a l stem i s t y p i c a l of an herbaceous dicotyledon* (S) The root i s triar«ii.» the primary storage, rays .giving r i s e to r o o t l e t s , the vascular systems ef which seam connected with the secondary xylem flanking the. r&yv (4) • S&e rhizome- I s i n a l l , stages -a stem structure,: having a persistent pith*. (5) . 'Certain •features of the old rhizome resemble the roots,. Such are the. development of a thick cork l a y e r , the production of rootlets„ development of annular rings i n the vascular system, .also the 'development of numerous • mult.Issrlate storage rays*. (6} Adventitious r o o t l e t s , a r i s e at nodes below branch buds, opposite storage rays*-, fheir. vascular system Is 'Connected with the primary xylem* (7) Eootlets on both the root ana the rhizome appear to emerge through l e n t i c e l a * Alersandrov, W. G., — n l s S i g n i f i c a t i o n a Reversible or I r r e v e r s i b l e Process?" Zeitsehr. Wiss. B i o l . Abt. E. Planta. 7: 040-346. 1929. Arber, Agnes — "Root and Shoot i n the Angiosperms. A Study of Morphological Categories•" Hew Phyt. 29: — 1930. Artschwager, E., — "Studies on the Potato Tuber." Jour. Agric. Res. 27: 809-835. 1924. Bailey, I. \% 9 — "The Evolutionary History of the F o l i a r Ray i n the Wood of Dicotyledons and i t s Phylogenetic Signi f i c a n c e . " Ann, Bot, 26: 647-661.. 1912. and Sinnot, E. W., — "Investigations on the Phylogeny of the Angiosperms." Bot. Gaz. 58: 36-60. 1914. Carlson, M. E., — "Origin of Adventitious Roots of Golems-" Bot. Gaz. 87: 119-127. 1927. (7) Conrad, M. and 2iramermann, P. \ 7 . , — "She Origi n of Adventitious Hoots i n Cuttings of Portulaca oleraeea, L." Boyee Shomp• Inst« 3: 337-546. 1931, {8} Eames, A. Jo, — "On the Origi n of the Herbaceous Type i n the Angiosperms. 1 1 Ann. Bot, 25: 215-224. 1911* (9) and McDaniels, — "Introduction to Plant Anatomy," • HcGraw H i l l Bk. Oo. 9 Hew York. 1925. (10) Hansen, I» E., — "fhe Wild A l f a l f a s of S i b e r i a with a Perspective View of the A l f a l f a s of the World." V. S. D. A., B. P. I. Bui. 150. 1909. (11) Holms, Theo., "On the Development of Buds upon Boots and Leaves*" Ann* Bot. 39: 867-881, 1925. (12) , — "fhe Application of the ferm Bhizome*" Ehodora, 31: 6-17* 1929, Abstract by S. 3?» Blake* 211 (ISJ Eoue, Mo 3>», ' — "Origin of Leaf and Adventitious and Secondary Soots of Ceratopteris t h a l i e troldes«" Sot- Gaz. 92: 326 -029„ 1931. ( 1 4 ) J e f f r e y , E. C , — "Ehe Pteropsida*" Bot. Gasu 5 0 : 4 0 1 - 4 1 4 . 1 9 1 0 -(3 .5) , — "She Anatomy of Woody Plants." Univ. of Chicago Press. 1 9 1 7 . (16) b and 2orrey, B. E., — "Physiological and Morphological Correlations i n Herbaceous Anglosperms." Bot. Gas. 7 1 : 1-32. 1921. • ( 1 7 ) Exidelka, W. P., —> "Botannical Study of Peppermint* 1 1 Sesmos, 5 1 : 1 3 9 - 1 7 6 . 1926,, Abstract. (18) LeClurg, E. L., and Burr e l l , L. V.'., — "Vascular Structure and Plugging of A l f a l f a Boots." C o l . Exp* Station Bui, 3 3 9 : 1928* ( 1 9 ) Moe, G. G«, — " A l f a l f a Stadies." 1 9 2 9 . (20) Muhldorf, A. —- "Anatomy and Physiology of Le n t i c e l s , e s p e c i a l l y of Gymnosperms and Acaeeae•" Bui. J?GC. Stunts Cernauti ( 1 & 2 ) , 3 2 6 - 3 2 9 . 1 9 2 7 . M (21) Oakley, R . A . and Garver,S,, — "two Types of P r o l i f e r a t i o n i n A l f a l f a . " U* S. D. A., B. P« I* Oir. 115. 1913. (22) t — "ifedieago f a l e a t a , a Yellow .flowered . A l f a l f a . " • IJ. So B» A*.». Bui* 428* 191?.-(23) and Morgan. W*.-E„-t "Seetlng Stems i a Timothy*51 Jour.* Agr* Res* 21: 1.75-178.. 2919, , (PA) Oliver, G. ¥;#.r *~ "Some, lew A l f a l f a V a r i e t i e s f o r Pasture'," U* S. I). A,, B« P,' X, Bui* 2 5 8 . . .1913.,. ( 2 5 ) P r i e s t l e y , and P e a r s a l l , — " G r o w t h Studies*" Attn* Bot» 36 : 247*848. 1 9 2 2 ( 2 6 ) , and Woffenden, 3i« M . , «~ "Causal factors i n .Cork Jormation." Hew Phyt. 21: 252-268., 1922. (27) Seofield, 0.- S.# — "B.otannMal 'History and C l a s s i f i c a t i o n of A l f a l f a , " tT, S. D« A* B» P» 1. Buio 131. 1908, (28) Sinnot, E. Wo and Bailey, I * w»» — "The Origin and Dispersal of Herbaceous Angiosperms." Ann* Bot. 28: 5 4 2 - 6 0 0 * 1914. {29} Sinnot, B. W., (30) Taylor, G {31} Thompson, W-» P*> '(38) Wetmore, B» H« (33} W i l l e , J?*, ( 3 4 ) ( 3 5 ) VJilson, 0 . L i — "The Significance of the f o l i a r Bay i n the Evolution of Herbaceous Anglosperms." Ann. Bot. 36: 523-633. 1922. — "She O r i g i n of Adventitious Growths i n Acanthus montanus •" i'rans. and Proc. Bot. Soc. Edin. 29: 291-296. 1926. -» "On the Origin of the Multiseriate Kay of the Dicotyledons." Ann. Boto 25: 1005-1014. 1911. — "Organization and Significance of Lentieels i n Dicotyledons." Bot. Gaz. 82: 71-88 and 113-131. 1926. — "Anatomlseh-physiologische Untorsu©hurigen am Gramineenrhizom." Beiaft« Bofcam Centrabl. 3 3 : 1-70. 1917. — "Beitrage zur Anatomie des Cyperaee aerhiz oms. I b i d . 43: 267-309. 1926. — "Adventitious Soots and Shoots i n an Introduced Weed." B u l l . Sorrey Bot. Club, 54: 34-38. VI Wilson, 0. 2., — "Studies on the Anatomy of A l f a l f a . " Eans, Univ. S c i . B u l l * 7: 291~ 299, 191S, Z i r k l e , C., "She Use o f If* Butyl Alcohol i n Dehydrating Woody tissues f o r P a r a f f i n Embedding." Science. 71: 103-104. 1950 „ EXPLAHATIQig Off PLAICES Diagram of rhizome prG3.uei.ng a l f a l f a plant to i l l u s t r a t e o r i g i n of rhizomes, f s l l ) , ffig.» 1 -- Young rhizome as a white shoot, (x 1). H g c 2 ~- Rhizome branches from nodal buds. Ascending t i p developing green leaves, (x 1)* EhliJbL ^ l d rhizome thickened, l a t e r a l shoots and r o o t l e t s developing below them. ,{x 1).& g i g , 4: Root i l l u s t r a t i n g one v e r t i c a l row of l e n t i o e l s from which emerge r o o t l e t s , (x 1)• g i g . 1 Transverse section of a e r i a l a l f a l f a stem, (x 120). 2Pig.» ..,£_.— Transverse section of rhizome as i n Plate 2, £lg. 1, (x 12Q). Transverse section of root, showing primary tissues and some secondary growth, (x 120)* Transverse section of older root, (x 180). Transverse section showing vascular tissue connecting r o o t l e t and the c e n t r a l axis, {x 120). Transverse section of rhizome showing inception of cork and storage rays, (x 120). I I • Plate vTII — transverse section of rhisome—further development of cork and ray c e l l s , (x 120). " IK — transverse section of rhisome—vascular tissue to root trace developing below a l e n t i c e l e fx 120). " I. — Longitudinal section, r o o t l e t branching from rhizome below developing bude fx 120)« " XI — Transverse s e c t i o n — r o o t l e t emerging through l e n t i c e l . (x 120). " 211 ~~ Sraneverse section of small r o o t l e t from rhizome» (x 120)„ " Z I I I — Eransverse section of underground main axis showing branch gap f o r rhizome« (x 100}* " £17 g i g . 1 — Transverse section--bundles of f i b r e s surrounded by cork cells» (x 120). F i g . 2 Same near surface, (x 120). g i g . 3 — " emerging to surface * (x 120). « J I J ..... gjg. 1 — -Transverse section—two groups of f i b r e s forming indentation on root, •{x 120). gig* 2 — Longitudinal s e c t i o n — - f i b r e s surrounded by cork c e l l s below cork layer* fx 120)« gi g . 3 Longitudinal s e c t i o n — f i b r e s rupturing cork l a y e r and protuding from the surface. fx 120). P L A T E I P L A T E K P L A T E H . P L A T E A U P L A T O T PLATED ( -TEX P L A T E H P L A T EX PLATED. 18 SOHE FAQTORS AFFECTIHG THE GEOTRQPIG RESPONSE OF THE ALFALFA RHIZOME A c o n s i d e r a t i o n o f the e v i d e n t d e s i r a b l e c h a r a c t e r i s t i c s o f rhizome p r o d u c i n g a l f a l f a as d e s c r i b e d i n P a r t I , supports the i d e a t h a t an i d e a l a l f a l f a p l a n t might be e v o l v e d by c a r e f u l breeding,, The h y b r i d s developed a t U. B. G. seemed to i n c l u d e the i d e a l , and B r . Moe c o n t i n u e d t h i s experiment. She Fg g e n e r a t i o n showed a s e g r e g a t i o n was t a k i n g p l a c e , which i n the Fg g e n e r a t i o n was v e r y e v i d e n t by the appearance o f dwarf forms and unusual types. Both the I?2 and Fg g e n e r a t i o n s showed the rhizome c h a r a c t e r i n v a r y i n g degrees. A f t e r t a k i n g c e r t a i n p l a n t s to I t h a c a , Sew York, wide disparagements appeared. She Fg g e n e r a t i o n showed about 25$ o f the p l a n t s d e v e l o p i n g rhizomes, the Fg from 14»35$, and most F^ from 5-15$, a g r a d u a l l y d e c r e a s i n g number. However, i t must be ta k e n i n t o a ccount t h a t the p l a n t s there as compared to Vancouver were much younger and the degree o f growth seems to be determined t o a c e r t a i n extent by age. The unknown g e n e t i c c o n s t i t u t i o n o f the Grimm a l s o p r e s e n t s b r e e d i n g d i f f i c u l t i e s . I n p r a c t i c a l l y no case a t It h a c a , d i d a progeny show 50$ o f the p l a n t s producing rhizomes, w h i l e a t Vancouver i t i s apparent t h a t the c h a r a c t e r f o r rhizomes Is 19 dominant s as over 50$ of the Eg produced rhizomes. Br. Moe (15) then concluded, " I t would therefore seem that environment plays an important part i n the expression of t h i s character, and that at t h i s time i t would be unwise to submit an hypothesis as to the mode of inheritance." With the above idea i n mind, some experiments on d i f f e r e n t types of plants were attempted with the hope that some clue might a r i s e regarding the factors causing the growth of rhizomes. I t was decided to use cuttings from c e r t a i n plants of the W& generation. Accordingly types recorded as producing numerous rhizomes, an intermediate number, and few or no rhizomes were chosen. About one hundred cuttings were made from each and planted i n f l a t s i n the greenhouse i n November, 1930. At Intervals during the winter, the plants were examined f o r rhizome development and i t was noted that several developed rhizomes i n the period from Movember to April<> Some very contradictory r e s u l t s were obtained though,in A p r i l , 1931 when i t was decided to sel e c t a recorded non-rhizome and a numerous rhizomed plant to compare the respective numbers having produced rhizomes. Only h a l f the plants from the rhizome plant showed any development, which i n any case was very small, as shoots of -J-" - •§•" only had developed. On the other hand, those from the non-rhizome d plant showed a few with rhizomes 1" - 2" i n length and nearly a l l showed evidence of some development. I t should be noted, however, that t h i s p a r t i c u l a r stock plant recorded 2 0 as non-rhizome producing had a more vigorous top growth than almost any other plants. In May 1931, the cuttings of c e r t a i n plants from the greenhouse were transplanted to the f i e l d . At that time, t h e cuttings from eaeh plant were divided into two groups, those having some evidence of rhizome development and those without. These were kept separate and planted at opposite ends of the rows. The average length of rhizome was also noted, The accompanying table shows that with the exception of one B133 £28 there i s a decided tendency f o r a l l to produce rhizomes, and no constancy seems apparent i n the r a t i o s of rhizome to non-rhizomed cuttings of the three group whose parent plants d i f f e r as to rhizome characters. There does appear, however, to be some constancy as to the type of rhizome formed, which as w i l l be demonstrated l a t e r , i s very s i g n i f i c a n t . The majority of rhizome-forming plants had developed rhizomes 1" - 6" i n length, whilst the non-rhizomed plants had only buds or shoots of about i n length. The intermediate types, being somewhat variable i n any case, show varying degrees both as to number and general character. I t might here be noted that at t h i s stage of immature development the only evidence of rhizomes was us u a l l y a shoot of -k" i n length or l e s s , which might extend l a t e r a l l y as a rhizome or might extend immediately into an a e r i a l shoot. Thus these observations should not be taken as s i g n i f y i n g the evidence of rhizome production, but rather the i m p o s s i b i l i t y Table to show the percentages of cuttings showing evidence of rhizome development at the time of transplanting. May, 1951, BOW PLAIT HO. TYPE $ WITH RHIZOMES AT. LEHGTH OF RHIZOME 50 R.43P.31 long rhizomes 1-3" 51&52 R.54P.25 ti- 32,8$ 1-3" 53&54 B.SOP.19 ll 21.6$ 1-3" 55&56 R.133P.27 non**' rhizome 17*G$ buds & shoots -g-" 57&58 . •.. . « • 0 . 0$ • • • » . 59&6G R.1G4P.30 !? 35.2% »! 61&62 E«104P»40 • -ft 13.6$ ••!? 6S&64. R.102P.8 interm0 26.1$ 1-3" 65&66 E.111P.-80 12 e 5$ buds & shoots -|-n 67&68 R.136P.34 n 23.8$ 1-3" 69&70 R.141P.16 w 44.3$ and shoots -|-" Si-of correct determination t i l l a more mature stage i s reached. Experiments on the plants set out i n the f i e l d consisted of subjecting the plants to physical treatments, These included c u t t i n g o f f the tops of the plants at two-week in t e r v a l s during the summer and e a r l y f a l l , cutting others once and twice during the summer, exposing the portion of the stem g i v i n g r i s e to rhizomes and h i l l i n g the same portion up with s o i l * Where numbers permitted two plants of each row, which were of s i m i l a r genetic o r i g i n , both of those having already produced rhizomes, and those not having done so when transplanted, were included i n eaeh experiment. The plants were examined at the end of August to note the amount and character of rhizome development. The most s t r i k i n g observation was that plants having t h e i r tops cut every two weeks, with one or two exceptions, showed no sign of rhigomes. Concerning those on which rhizomes had developed when set out, i t may be concluded that instead, of continuing to extend, h o r i z o n t a l l y , the rhizome t i p ascended to the surface producing leaves and a e r i a l stems, which had i n turn been cut o f f . Since, during the i n t e r v a l from May to August, the plants were not examined, d i r e c t observations were not made of these stages. Plants with tops cut once or twice show a few buds along the stem. Uo very apparent difference was noticeable between those with the bases exposed and those well bedded, except perhaps that those exposed were fewer i n number. The long rhizomed plants had rhizomes 1" - 3" 21a Sable to show type of rhizome and stem i n the f i e l d i n August, 1931. ROW "BLAST HO. TYPE LENGTH OF RHIZOME RELATIVE HOS. OP RHIZOME TYPE OP A E R I A L STEM 50 R.43P.31 long rhizomes 1-3" numerous at r t . s spreading 51&52 fi.-54P.H5 n 1-3" w Tl . 5S&54 E.60P.19 n 1-3" several 45° tendency to spread 55&56 R.133P.27 non-rhizome buds So shoots i j " few erect 67&S8 R.135P„£8 SI buds . ..at : n 59&60 R.104P.30 u erect & tendency to spread 61&62 E.104P.40 r> •• n •it 63&64 R.102P.8 interm. buds & shoots - ••it- erect 5C&66 R.111P.20 « 1-2" several 45° 67&68 R.136P.34 1-2" several at r t . a t! . 69&7G E.141P.16 1-2" several 45° erect & tendency to spread 22 i n length, while those of the intermediate and non-rhizome groups had only buds or shoots about i n length* In view of t h i s l a s t statement i t should again be pointed out that very short shoots do not serve to provide d e f i n i t e evidence f o r rhizome production. At the end of March 1952, when the plants had been growing i n the f i e l d f o r almost a year, an examination was again made. As pointed out i n Part I the rapid development of the rhizome taxes place i n the autumn, and again a f t e r a dormant period i n the winter l a t e r a l branches begin to develops Therefore at thi s time It was possible to ascertain d e f i n i t e l y which plants had produced rhizomes and which had not. She most s i g n i f i c a n t observation was that those plants which had t h e i r tops cut every two weeks i n the previous summer were very small, with s t i l l no top development, and no rhizomes were produced on any plants. The three d i f f e r e n t groups of plants were c l e a r l y recognizable. Those producing numerous rhizomes had. a large number of well developed rhizomes, those intermediate forms had fewer numbers and les s spread i n circumference and those not producing rhizomes had ei t h e r none or very few. The cut t i n g of the tops once or twice seemed not to in t e r f e r e with normal production In any way. There was, however, considerable difference between the length of rhizomes produced on plants with th e i r bases exposed and those well protected. Those well Eable to show type of rhizome development i n March„ 1932 e . ROW ' MiM$ so;* 2YPS REI&OHE C H A R J . C 2 1 R . &m mmm* £0 . 3k43P%31. long rhizomes w e l l developed 51&52 : ;R«;MB^25: . •tt 5S&54 ; ;&6QP*l9."' • -i* '.•fewer . 555=56 no-a~ : rhizome very few 57&S8 R*433P*2S, - » hone.'. : 59&60 it very few 61&62 R*104P*40 •ft'" -6S&64 ; R>aO.SP,28' .,, i n term;*,' in t e r n . 65&66 R*111P*20 few 67&G8 R»13SP»34 El. well . , -> • developed 69&70 •' R,>141P«16* If ' :• • • S3 protected had numerous, long rhizomes whilst those exposed, seemed to have e i t h e r short rhizomes or ones which did not spread out l a t e r a l l y , V/ith regard to the non-rhizome plants, i t was noted that i n general, a smaller portion of the main axis had been drawn into the s o i l by the roots as compared to the two to three inches normally drawn i n by rhizome-forming plants., Those plants which were well bedded up had a thicker growth and greater spread i n circumference, There were, however, no long rhizomes. The shoots placed underground seemed to extend l a t e r a l l y f o r from one to two inches and then turn upwards. There were fewer shoots produced than normally, as the stem axis o r i g i n a l l y drawn underground was shorter, GREEHHOPSE EKPERIMEBTS J?or the purpose of demonstrating, i f possible, some ef f e c t s of temperature s o i l and moisture,, experiments were conducted i n the greenhouse. In May 1931, at the same time that plants were transplanted to the f i e l d , some were transplanted to pots f o r these experiments, A rhizome-forming plant R54P27 was divided into two groups of cuttings, those already having produced rhizomes and those without, A t y p i c a l non-rhizome plant R117P30 with no rhizomes was also chosen. Two series were set up, one kept outside the greenhouse and one i n s i d e . Conditions of moist, dry, humus, a c i d of PH about 5 and a l k a l i PE 7.9,soils were prepared. Due to d i f f i c u l t y i n maintaining a d e f i n i t e PH both tended to revert to a neutral condition a f t e r a period of time. An examination of the greenhouse plants at the end of August showed that E.542,27 had produced rhizomes or buds i n nearly every case i n s i d e , Those grown In humus and kept very moist had the best development, Those kept dry and i n s o i l o r i g i n a l l y a l k a l i n e showed the l e a s t rhizome growth. The non-rhizome plant Bell7P,30 developed no rhizomes i n dry, acid or a l k a l i n e conditions * but a few i n the humus« Of those grown outside, no rhizomes were produced on the plants i n an o r i g i n a l l y acid s o i l . A l l others seemed to have pra-ctically the same c h a r a c t e r i s t i c s as those ins i d e , A s i m i l a r examination at the end of March j, 1932, v e r i f i e d the r e s u l t s obtained i n August, The growth of the rhizomes on the plants outside was not noticeably d i f f e r e n t from those inside* The rhizomes developed i n s o i l o r i g i n a l l y acid seemed smaller and those i n humus had the best-development, DI8QUSSI0I Before discussing any p a r t i c u l a r points a discussion of geotropism i n general i s pertinent, Geotropism has received the attention of a number o f workers, but up to the present time l i t t l e i s r e a l l y understood concerning the stimulus i n plants» The roots and stems have opposite responses and are resp e c t i v e l y considered, as p o s i t i v e l y and negatively geotroplo* Occasional examples of a reversal or absence of response seem evident. Into this category f a l l the rhizomes of the a l f a l f a s stem-like In structure (Part I) but with no geotropic response f o r some time. Several fa c t o r s which seem to have an influence i n modifying geotropic response have been demonstrated* These include a c i d i t y , moisture, sugar and amino acid content (22) and possibly, that hormones as the actual formative substances of d i f f e r e n t organs are important (10, 18)« Since i t Is probable that there are several factors i n combination, e l u c i d a t i o n of the problem Is d i f f i c u l t . The view that a c i d i t y seems e f f e c t i v e In a p o s i t i v e response i s concluded by Schley (21) and several others (14 8 25, 26) 0 Small considers that the accumulation of carbondioxide In underground tissues i s responsible f o r a r e l a t i v e l y increased a c i d i t y . This idea, however, i s subject to c e r t a i n c r i t i c i s m s due to the lack of experimental evidence e Changes i n permeability of the c o l l s are recognized as taking place (23, 24) and such would r e s u l t from changes i n acidity,. Moisture changes seem to r e s u l t i n an increased turgor of c e l l s In c e r t a i n regions thus causing a curvature (17, 21}. From h i s t o l o g i c a l evidence I t Is usually considered that the c o r t i c a l c e l l s are the ones so affected r e s u l t i n g i n a difference i n the r e l a t i v e sizes of such areas, causing stre t c h i n g and curvature at c e r t a i n -points* Loeb has accomplished more than any other investigator b y his experiments on Bryophyllum calycinum (IS). Ee concludes that 26 the stimulus i s c a r r i e d by a l i q u i d containing the various materials required for growth such as sugars, amino acids and hormones, This l i q u i d would n a t u r a l l y flow on the lower side of a h o r i z o n t a l l y placed shoot. She lower cortex therefore Increases i n turgor and a curve upward Is the r e s u l t . He demonstrates (10) that sterns s p l i t l o n g i t u d i n a l l y show no curvature i f the cortex Is placed above. Also a shoot with i n c i s i o n s a l t e r n a t e l y on e i t h e r side give a negative response, So attempt to carry out metabolism teste was made, p a r t i c u l a r l y as r e s u l t s so f a r obtained have not been d e f i n i t e l y conclusive.* Certain anatomical and morphological characters are suggestive however. The young shoot i s f l e s h y with a r e l a t i v e l y small amount of vascular system. This condition p e r s i s t s during a rapid growing period i n the f a l l , during which there i s no evidence of starch being stored. At the time when starch Is beginning to be stored i n tho developing storage ray c e l l s , reducing the number of the available water containing c e l l s , the rhizome ceases to elongate and the t i p gives a negative response to gravity. This evidence would demonstrate that when metabolic changes take place, there i s a change i n response to gravity* I t has been pointed out by Waight (35) dealing with f e r n fronds negatively geotropic before u n r o l l i n g , t h a t maximum gx-owth i s associated with minimum presentation tine*. Tho response there appears to be Inhibited u n t i l the growing period in over. The p o s i t i o n of the rhizome bud appears to have 27 considerable influence* O l i v e r (17) found that c e r t a i n a l f a l f a plants probably by contraction of the roots, drew a portion of the main stem axis underground. In Part I i t was demonstrated that there Is a portion of the stem underground. Oakley (IS) emphasizes the importance of a low set crown i n the Grimm, thus protecting new shoots and underground buds, Ho work has been attempted on the d i r e c t evidence or nature of contractions i n a l f a l f a plants. Investigators on c o n t r a c t i l e roots (28, 34, 35) have concluded they function for the purpose of drawing bulbs and corms into the ground and the same may be concluded here, That, since roots and shoots are d i f f e r e n t i n function and s i m i l a r l y i n protoplasmic properties and geotropic response, i s the view of both Bose and Small ( 1 B 27). This being the case, some i n h i b i t i o n of the stimulus or response o r d i n a r i l y produced must be present. It is agreed that the area responsive to a stimulus i s the growing t i p (2, 11, 29). The rhizome, an underground stem, the mechanical-pressure of the s o i l may have some e f f e c t . I t i s believed to influence the primary and secondary orientation of roots downward (8, 9 ) . FIELD EXPERIMENTS The most outstanding observation i s the f a c t that plants weakened by frequent cutting do not produce rhizomes. Garver (5) performed some experiments along this l i n e and found smaller root systems and general weakened condition. 28 Loeb { 1 1 } s t a t e s w i t h r e g a r d t o dormant buds t h a t , "growth, depends on the a v a i l a b i l i t y of c e r t a i n m a t e r i a l , and i n h i b i t i o n t o the n o n - a v a i l a b i l i t y o f s u c h , " C e r t a i n p l a n t s had a l r e a d y d e v e l o p e d rh izomes when s e t o u t . On f r e q u e n t c u t t i n g s t h e n , these must have responded t o a n e g a t i v e s t i m u l u s , S p a l d i n g (33) e x p r e s s e s the v iew t h a t i n j u r y such as the c u t t i n g o f the t o p s o f the main s tem causes an I r r i t a t i o n r e s u l t i n g In g r e a t e r c u r v a t u r e of the s h o o t s , She i d e a i s a l s o p r e s e n t e d t h a t the shoots o b t a i n a g r e a t e r food s u p p l y accompanied by changes i n metabo l i sm and r e s u l t i n g i n c u r v a t u r e . In c o n n e c t i o n w i t h t h i s o b s e r v a t i o n Loeb (13} shows t h a t i f the main a x i s of a p l a n t i s removed, the l a t e r a l b ranches r e c e i v e a g r e a t e r s u p p l y o f subs tances and a r e s u l t i n g i n i n c r e a s e d c u r v a t u r e . Exposure o f the p o r t i o n o f stem drawn underground to the a i r r e s u l t s i n a n e g a t i v e response o f the rh izomes more q u i c k l y than s i m i l a r rh i zomes remain ing underground . Two f a c t o r s may be s i g n i f i c a n t . F i r s t the i n h i b i t i n g e f f e c t o f the m e c h a n i c a l p r e s s u r e of the s o i l i s removed, and s e c o n d l y stems are p o s i t i v e l y h e l i o t r o p i c and are exposed to l i g h t by t h i s e x p e r i m e n t . T h i s l a t t e r v iew would e x p l a i n the f a c t t h a t no p o s i t i v e r e s p o n s e i s o b t a i n e d u n t i l the growing t i p has reached the s u r f a c e o f the s o i l . GREENHOUSE EXPERIMENTS Temperature seems to have some e f f e c t on rh izome p r o d u c t i o n , as a few whicomes were produced d u r i n g the w i n t e r 29 i n the greenhouse when t h e y would n o t n o r m a l l y have been p r o d u c e d . I t does n o t , however, seem t o have any e f f e c t on the g rowing r h i z o m e , except t h a t t h e r e i s not a l o n g i n a c t i v e p e r i o d b e f o r e l e a v e s a re produced on the t i p s , such as f o r those grown o u t d o o r s . C e r t a i n p o i n t s on the d i f f e r e n t c o n d i t i o n s seem s u g g e s t i v e a l t h o u g h i n s u f f i c i e n t d a t a was o b t a i n e d to make d e f i n i t e c o n c l u s i o n s . I t has been found t h a t a l f a l f a i s not so t o l e r a n t o f an a c i d medium as o f a s l i g h t l y a l k a l i n e one (6, 7), P l a n t s i n the fo rmer env ironment seemed t o have s m a l l e r r h i z o m e s . The b e s t growth was noted on those i n humus and k e p t m o i s t . T h i s i n d i c a t e s t h a t rh izome p r o d u c t i o n i s f a v o r e d by g e n e r a l good c o n d i t i o n , a f a c t o r a l s o e v i d e n t i n those p l a n t s weakened by c o n t i n u a l c u t t i n g . I t may be t h a t humus s o i l gave s i m i l a r wate r c o n d i t i o n s on both s i d e s o f the rh izome c o n s e q u e n t l y s i m i l a r deve lopment . T h i s might a p p l y a l s o t o p l a n t s watered f r e q u e n t l y . m swmmi t i l from observations made i t seems that the a b i l i t y to produce rhizomes i s inherent i n c e r t a i n plants* ( 2 ) Certain factors such as general vigor of growth evidently influence the production of shoots. (3) I t has been shown that a portion of the main stem of c e r t a i n plants i s drawn undergrounds, and t h i s provides the conditions conducive to normal rhizome growth. I MTERATI3RE CITED (1) Bose, F. G. (2) (3) Eaton, S. 7., ( 4 ) Galloway, B. L«, (5) Garver, So, (6) Haas, A* R. 0 = , (7) J o f f e , J . S., — " L i f e Movements i n Plants*" Trans». Bos e. Res. Inst* Calcutta* &*. 1919. — "Researches on the Growth of Plants.." Mature, 105 s, 648-651* 1920, "Geotroplsm." Bot. Gaz. 77: 257-238. 1924. *»« "Two fypes of P r o l i f e r a t i o n i n • A l f a l f a * " U. S. B. A., B... P. I. C i r . 115o 1913* — " A l f a l f a Root Studies." U. Si B. A., Bui. 1087. 1922. — "Ef f e c t of Reaction of Solution on Growth of A l f a l f a . . " Bot. Gaz. 83: 207-211. 1927. — "The Influence of S o i l Reaction on Growth of A l f a l f a . " S o i l Science, 10: 301-307. 1920. Abstract. (8) Holman, M« 9 (9) . (10) Iioeb, (11) , (12) , (13) . ,, (14) Lynn, M, J«, (15) Mos, G . G . , I I ~- "Orientation of Secondary Roots*" Am, Journ, B o t , 3: 274-318, 1916. — " O r i e n t a t i o n o f P r imary T e r r e s t r i a l Roots,," I b i d , 407*414, 1916, "On the Association and Possible Identity of Boot forming and Gootropio. Substances or Hormones i n . Bryophyllum ealyeinuiiu" Science ' 4 4 ; 210-211*- ' 1916« «» "A Q u a n t i t a t I Y O Method of Ascertaining the Mechanism o f Growth and o f I n h i b i t i o n o f Dormant Buds," Science 4 5 : 436-437-.. 1917 , *—» "'fhe Chemical Basis of Regeneration and G e o t r o p i s m . " Science 46: 115-118 . 1918. — "Regeneration," MeGraw H i l l Blc* Co. 9 Hew York. 1924. — "The R e v e r s a l o f Geo t r o p i c Response in the Stem." lew P h y t . 20 : 116-123*. 1921. — " A l f a l f a Studies." 1929-(16) O a k l e y , B* A., (17) O l i v e r , G. W*, (10) P h i l l i p s , E. G,„ (19) Reed, 32.-, (20) Ricome, M« H*» (21) Schley, E. 0., (22) , (25) S m a l l , J . , (24) , I I I ~~ "Medicago f a l c a t a , a Yellow Flowered A l f a l f a * " U. S.. Do -<:.*, B u i . 428, 1917* — "Some lie?; A l f a l f a V a r i e t i e s f o r Pastures*" 19 IS, — "GeotropiGQ." Bot, Gaz. 65: 168-178. 1920. — "Hypothesis of Formative Stuffs as applied to Bryophvllum c s l y c i m u n . " Bet. Gas. 70: 113~14E,- 1923, —• "L* o r i e n t a l ion des ranoau:-: dans r respaee* n Compt, Rend. Acad- Scl., Paris-, 171: 754-735. 1921. • '• — "Geotropic Stimulation." Bot.;. Gas * 56: 480-489. 1913. — "Presentation and Gecreaetion." Bot. Gaz. 70: 69-81* 1920. — "Geotropism and the Weber Feehner law." yum.- Bot. 31: 813-314 —"Changes of E l e c t r i c a l Conductivity under Geotropic Stimulation." J . P r o c . Roy, Soc. London B: 349-36 1918. (25) Small, J . , . ~- "A Theory of Geotropism, with, some Experiments on- the Chemical Reversal of Geotropic Response i n Stem and Boots'" Hew. Phyt* 19 s 49-63* 1920, (26) .. ,» — "Preliminary Bote on a Hydrion D i f f e r e n t i a t i o n Theory of Eeliotr o p l s h u " .Ibid f 276-276* 1920,. {'27) i and Eea, — "Du tho RoYersaX of Geotrople Curvature In the Stem*" l h l d ; 9 208-2.09*= 1920 = (28) Smith, F» If*,. ~ e "The Corm and Contractile Roots of Brodlaea lactea.*'" Am* Journ„ Bot, 17: 316-927* 1930, (29) Snow, R., — "The Conduction of Geotropio E x c i t a t i o n i n Roots:**. •Ann* Sot. 37: 43-53*. 1923* (30) [„ — "Conduction of Tropic E x c i t a t i o n * " Ami. Bote 38: 153-174. 1924. ( 3 1 ) Southworth^ w#, — " A Study on the Influence of Root System In Promoting Hardiness i n A l f a l f a * " Sc:.c Agr. 1: 5-9, 1921, (32) , — " A l f a l f a Hybridisation," Soi. Agr. 2: 257-264, 1921-22. (33) Spalding , ?. M*. (34) Thoday s D,, (35) (36) Waight, 5". M* 0„, f nfhe Traumatropie Curvature i n Hoots.« Ann. Bot. 8: 423-451. 1894. "She Contractile Boots o f Oxalis incarnata." Inn. Bot*. 40: 571-584. 1926» "The Mechanism of Root Contraction." Plant Phys, 6: 721-725* 1931. "On the Presentation Time and Latent Time f o r Reaction to Gravity In Fronds of Acplenium bulbiferum." Ann. Bot.. 37: 55-61* 1923. 31 CYiEOLQGICAL STUDIES OF ALFALFA WISH REFERENCE  TO CHROMOSOME NUMBER AMD IIO)I¥IPUALIgY H 2RQDUC TION Comparatively l i t t l e work has been attempted on the chromosome numbers of Medicago, but, as indicated i n Part I, hybrids are very numerous and of a considerably d i v e r s i f i e d character. I f the theory that chromosomes are the bearers of hereditary characters i s to be accepted, then the hybrids may d i f f e r i n number of chromosomes from t h e i r parents, p a r t i c u l a r l y i f the l a t t e r have not the same chromosome numbers or at l e a s t some differences i n c h a r a c t e r i s t i c s should be apparent, A study of the chromosome numbers and characters comparing the two parent species, Bonn and Grimm and th e i r s i s hybrids o r i g i n a l l y obtained a t U. B. C , opens an in t e r e s t i n g f i e l d of work along t h i s l i n e . Shis stady forms only a very preliminary introduction to the f i e l d , as there was only s u f f i c i e n t time to provide some comparison with the recent work of Fryer (1) who worked on a considerable number of species and hybrids of the genus Medicago. Amongst h i s plants were the Medicago f a l c a t a or Bonn and M. media, the "Grimm" Pers, His re s u l t s are shown In the following table, quoting also the numbers found by Karpechenko. ss Uryer Earpeehenko 2x x H. f a l e a t a (Strains I, II) 32 16 " (Strain III) 16 n media— Grimm, Pers. 32 _ Ghlmpu (2) gives numbers fo r other species as 16 and 32. MATERIA! AlTD METHODS Cuttings from the Donn, Grimm and each of the s i x hybrids were grown i n pots i n the greenhouse. Root t i p s were taken from these during the middle of the day and f i x e d i n B. C. F i x i n g Solution. P a r a f f i n sections were cut from 4.5-5/<^in thickness and stained, with Haidenhaim's haeniatoxylin and mordant of i r o n alum. Ho buds were available with young d i v i d i n g spore mother c e l l s of the anther, thus only mitotic d i v i s i o n s could be observed. With the aid of a Bauseh and Laumb microscope f i t t e d with a f l e & r i t e lens and hyperplane eyepiece x 15, camera lu e i d a drawings with a magnification of 2500 diameters were obtained. CHROMOSOME BOMBER AJTD INDIVIDUALITY Ho very d e f i n i t e conclusions can be drawn from the small amount of work attempted, but some very good figures were obtained which give some clue as to probable d i p l o i d numbers i n mitosis and also to some i n d i v i d u a l i t y i n shape. The chromosomes are extremely minute, rendering determination o f the e n t i r e t y of each chromosome somewhat d i f f i c u l t at the magnification obtainable. ss SHIMS The chromosomes of t h i s s p e c i e s seem to assume v e r y c h a r a c t e r i s t i c shapes a t the metaphase c e n t r a l p l a t e ( P l a t e I, J i g s . 2, 3) s u g g e s t i n g t h a t a t t h i s stage they are double. She number o f double chromosomes appears to be 8. I n the prophase, however, there appear t o be 16, but i n the anaphase o n l y 8 are d i s c e r n i b l e , T h i s would demonstrate t h a t s p l i t - t i n g o f somatic chromosomes occurs i n the prophase, the h a l v e s coming i n t o c l o s e a s s o c i a t i o n w i t h each other a g a i n a t the metaphase and s e p a r a t i n g on the s p i n d l e fibres» Such b e i n g the case, the d i p l o i d number would be 8» In the prophase, curved f a l c a t e rods o f v a r y i n g s i s e s are e v i d e n t . A t the metaphase the p a i r s are shortened and t h i c k e n e d w i t h s e v e r a l v e r y d e f i n i t e almost heart-shaped p a i r s . I n the anaphase some elongate and become curved a g a i n w h i l s t o t h e r s seem to remain d e f i n i t e l y Y-shaped, I n P l a t e I, F i g . 5 chromosome (a) appears to be double w i t h s p i n d l e attachments. DOBI The Donn, a c l o s e l y r e l a t e d s p e c i e s to the Grimm ( P a r t I ) , appears to have s i m i l a r c h a r a c t e r i s t i c s to the extent of number and apparent s p l i t t i n g o f the somatic chromosome i n the prophase. P l a t e I, P i g . 7 chromosome (b) i n d i c a t e s a chromosome s p l i t t i n g , p r o v i d i n g some evidence f o r the p o s s i b i l i t y o f p r o p h a s i c s p l i t t i n g . In the same f i g u r e chromosome (a) i s s i m i l a r to one i n the Grimm. Curved and s t r a i g h t r o o t s a re a l s o c h a r a c t e r i s t i c a t d i f f e r e n t s t a g e s . BIBB,IS VARIETIES Compared to the tv/c p a r e n t s p e c i e s t h e r e seems to be a d e f i n i t e i n c r e a s e , sometimes a d o u b l i n g o f chromosome numbers , e v i d e n t i n the h y b r i d s s t u d i e d . From the f i g u r e s o b t a i n e d i t a l s o appears t h a t the s p l i t t i n g o f chromosomes takes p l a c e i n the p r o p h a s e . Curved U-shaped chromosomes and s t r a i g h t rods a r e the forms I n the prophase* No good metaphase s t a g e s were f o u n d , but the e a r l y anaphase ( P l a t e I I , F i g . 7} shows c u r v e d rode drawing away f rom the c e n t r a l p l a t e . L a t e i n the anaphase as the p o l e s a r e r e a c h e d , the r o d s seem to s t r a i g h t e n out p r i o r to f o r m i n g the t e l o p h a s e mass . C h a r a c t e r i s t i c i n d i v i d u a l i t y was apparent In the p a i r o f l a g g i n g chromosomes i n e v e r y l a t e anaphase s tage observed ( P l a t e I I , F i g s . 8, 9 ) . HYBRID 156 The prophase f i g u r e s a re s i m i l a r t o o t h e r h y b r i d f i g u r e s w i t h c u r v e d and s t r a i g h t rods* Metaphase f i g u r e s seemed to c o n s i s t o f s t r a i g h t s h o r t e n e d rods w h i l e the anaphase showed the same c h a r a c t e r i s t i c o f c u r v e d r o d s drawing away f rom the c e n t r a l p l a t e as E-56. L a t e anaphase- s t a g e s a l s o e x h i b i t a p a i r o f l a g g i n g chromosomes/ HYBRID 7 Fewer f i g u r e s were o b t a i n e d f o r vgiis one so t h a t c h a r a c t e r i s t i c s tages were not n o t e d . A t the metaphase o f each m the p a i r s seem to v a r y i n s i z e and shape . Ho d e f i n i t e l a g g i n g was noticed» HYBRID 190 Metaphase chromosomes v a r y i n s i s e and shape and are f r e q u e n t l y p a i r e d ( P l a t e I f , P i g , 4 } * I t would appear t h a t the number i s 12, HYBRID. 68-The c h a r a c t e r i s t i c s seemed s i m i l a r to a l l p r e v i o u s ones s t u d l e d c However, a p a i r o f c r o s s e d chromosomes seemed t o o c c u r q u i t e f r e q u e n t l y * HYBRID 71 Y e r y few f i g u r e s were o b t a i n e d but such as were found I n d i c a t e t h a t the 2K number appears t o be 12 o r d i n a r i l y but some c e l l s show 8 o n l y , t h a t i s they r e v e r t t o the number o f the p a r e n t s . nscussioE The Grimm and Donn p a r e n t s o f the a l f a l f a h y b r i d s deve loped a t the IF. B. C. have t h e d i p l o i d number 8 . S e v e r a l o f the h y b r i d s have the number 16 , two have 12 u s u a l l y , and one o f the l a t t e r , H y b r i d 71, shows c e l l s which r e v e r t t o the number o f the p a r e n t s , namely 8 . F r y e r (1) i n h i s i n v e s t i g a t i o n s on Medicago chromosome numbers came to the c o n c l u s i o n t h a t the d i p l o i d numbers o f the Donn and Grimm were 16 and 52 r e s p e c t i v e l y , and those o f the c r o s s e s o f s e v e r a l o ther s p e c i e s were 52. Prom c y t o l o g l e a l ev idence o b t a i n e d i n the i n v e s t i g a t i o n , however, 36 some q u e s t i o n a r i s e s as to the i n t e r p r e t a t i o n o f m i t o t i c f i g u r e s , p a r t i c u l a r l y o f the p r o p h a s e . H i s i l l u s t r a t i o n s appear t y p i c a l o f the prophase i n shape , form and number to those i n t h i s d e s c r i p t i o n . The o b s e r v a t i o n o f metaphase and anaphase f i g u r e s , which he does not show, r e v e a l the f a c t t h a t i n no case a re t h e r e more than h a l f the number o f chromosomes found i n the p r o p h a s e . For t h i s r e a s o n i t seems t h a t the more p r o b a b l e e x p l a n a t i o n would be to c o n s i d e r t h a t the s p l i t t i n g o f the chromosomes takes p l a c e In the prophase or t e l o p h a s e r a t h e r t h a n a t the metaphase. The t ime f o r chromosome s p l i t t i n g i n m i t o s i s has been r e c o r d e d In v a r i o u s ways . The most genera l , c o n c e p t i o n i s t h a t i t o c c u r s i n the metaphase, but some are o f the o p i n i o n t h a t i t o c c u r s much e a r l i e r i n e i t h e r the t e l o p h a s e or p r o p h a s e c Sharp (6) conc ludes t h a t i t o c c u r s i n the prophase r a t h e r than t e l o p h a s e and W i l s o n (11) a l s o suppor t s the Idea o f p r o p h a s i c s p l i t t i n g . Sharp (7) quotes the views o f s e v e r a l a u t h o r s . Some b e l i e v e t h a t t r u e s p l i t t i n g takes p l a c e i n the prophase but Is n o t e v i d e n t t i l l the anaphase, as the chromosomes i n c o n t r a c t i n g p r i o r to the metaphase, b r i n g the h a l v e s i n t o so c l o s e a c o n n e c t i o n w i t h each o t h e r t h a t no d i v i s i o n I s v i s i b l e . . Others observe t h a t In a few cases the p a i r e d chromosome groups are e v i d e n t i n the prophase* Prom d a t a o b t a i n e d i t seems v e r y e v i d e n t t h a t s p l i t t i n g i n t o d e f i n i t e h a l v e s takes p l a c e i n the prophase and t h a t these h a l v e s come t o g e t h e r a g a i n i n the metaphase as~ the chromosomes c o n t r a c t . 37 T h i s v iew seems the o n l y e x p l a n a t i o n o f o therwise s e e a i n g l y e o n t r a d i c t o r y numbers. That some o f these apparent prophase f i g u r e s might be p o l a r v iews o f o t h e r s t a g e s was checked w i t h r e g a r d t o t h e i r r e s p e c t i v e p o s i t i o n s . I t was found t h a t the m a j o r i t y were i n the p i t h o f the growing p o i n t . i n l o n g i t u d i n a l s e c t i o n s * Thus i t seeras a r e a s o n a b l e c o n c l u s i o n t h a t those a r e t r u e prophase f i g u r e s and n o t p o l a r v iews* With r e g a r d to the cons tancy o f chromosome numbers i n c l o s e l y a l l i e d , s p e c i e s * c o n s i d e r a b l e work has been u n d e r t a k e n by Jtutz ( 3 e 4} i n d e a l i n g w i t h Oenothera mutants* In v iew o f the f a c t t h a t the chromosome numbers o f some h y b r i d s may be l e s s than 16, some c o n s i d e r a t i o n o f her c o n c l u s i o n s e re i n t e r e s t i n g * She c o n c l u d e d t h a t 14-chromosome forms were c o n s t a n t and 15-chromosome forms i n c o n s t a n t * Forme h a v i n g t w i c e 14 are more l i k e l y t o be cons tan t t h a n those w i t h more than 14 but fewer than £8 chromosomes «• I n c o n s t a n c y o f numbers Is brought about by v a r i o u s methods, such as f a i l u r e to s p l i t l o n g i t u d i n a l l y , s p l i t t i n g o f chromosomes i n t o f ragments , o r i n t e r c h a n g e o f segments d u r i n g the sp i reme t h r e a d s t a g e . C o n s i d e r a t i o n o f these does not come i n t o the c a t e g o r y o f t h i s s t u d y but suggests the p o s s i b i l i t y o f s l i g h t d i f f e r e n c e s i n number,, p a r t i c u l a r l y as c e r t a i n h y b r i d s seem to degenerate i n o l d e r g e n e r a t i o n s ( P a r t I I } . In two eases the chromosome number appears to be 12 w i t h o c c a s i o n a l c e l l s l i i H y b r i d 71 h a v i n g 8 chromosomes l i k e the 38 p a r e n t s o Any a t tempt to i d e n t i f y p a r t i c u l a r chromosomes, due to the r e l a t i v e l y s m a l l number o f f i g u r e s o b t a i n e d to d a t e , cannot be o f much s i g n i f i c a n c e • Many workers have been s u c c e s s f u l i n p r o v i n g the i d e n t i t y o f i n d i v i d u a l chromosomes o f g i v e n species« However, I t i s demonstrated tha t t h e r e a re c e r t a i n r e c o g n i z a b l e d i f f e r e n c e s i n s i z e and shape end a d e f i n i t e s i m i l a r i t y i n bo th number and shape o f the c l o s e l y a l l i e d a l f a l f a s p e c i e s * Shapes i n c l u d e d are s t r a i g h t , c u r v e d , U-shaped f o r m s , t r i a n g u l a r and double forms w i t h s p i n d l e f i b r e a t tachments• T a y l o r ( 8 , 9 , 10) has devoted c o n s i d e r a b l e a t t e n t i o n t o c o n s t r i c t i o n s o f chromosomes and methods o f at tachment to the s p i n d l e f i b r e s * Ho s a t e l l i t e s were n o t e d but F r y e r (1) r e p o r t s them i n s e v e r a l cases and T a y l o r i n d e s c r i b i n g the chromosomes o f G a s t e r i a , r e p o r t s hooked forms which are s i m i l a r i n appearance to many o f the a l f a l f a hooked chromosomes. Such he c o n s i d e r s as h a v i n g s u b - t e r m i n a l s p i n d l e at tachments and many p o s s e s s s a t e l l i t e s , thus s u g g e s t i n g t h a t under h i g h e r m a g n i f i c a t i o n s a t e l l i t e s might be observed i n the forms s t u d i e d . He p o i n t s ou t , however, t h a t d i f f e r e n t f i x i n g s o l u t i o n s have v a r i o u s e f f e c t s on c o n s t r i c t i o n s , r e n d e r i n g any d e f i n i t e c o n c l u s i o n r e g a r d i n g these as a matter o f c o n j e c t u r e s 59 (1) i l i e d i p l o i d somatic* chromosome numbers o f the Bonn , Grimm and s i s rhizome* p r o d u c i n g h y b r i d s r e s u l t i n g f rom a c r o s s between these two ,a re summed up i n the f o l l o w i n g t a b l e . 2x Grimm ~ 8 Bonn ~ .8 H y b r i d -5-6 - 16 11 3.86 « 16 ° 7 - 16 n 190 - p r o b a b l y 12. " 68 - 1 6 n 71 - p r o b a b l y 12 or 8* (2) I t seems apparent t h a t the s p l i t t i n g - o f the chromosomes t a k e s p l a c e i n the prophase s t a g e , the h a l v e s coming t o g e t h e r a g a i n a t the metaphase t o form a double chromosome• (2-) I n the anaphase the h a l v e s a g a i n s e p a r a t e , assuming hooked and U-shapes w i t h p r o b a b l y a s u b - t e r m i n a l s p i n d l e a t t a c h m e n t . (4) Hooked XT-shapes and s t r a i g h t r o d s a r e p r e s e n t i n a l l s p e c i e s s t u d i e d * (5) I n d i v i d u a l i t y I n shape i s d i s c e r n i b l e to a c e r t a i n e x t e n t i n : 4 0 fa3 Donn and Grimm doub le chromosomes w i t h s p i n d l e f i b r e a t tachments and shaped rods* (b) H y b r i d s 56 and 156 w i t h a p a i r o f l a g g i n g chromosomes I n the anaphase «. 1 C D F r y e r , I . , (g-J Ghin\pu s M, Y,, (3) Blitz., A*. ( 4 ) (5) Sharp , L . I . , (6) m — " G y t o l o g i e a l S t u d i e s In M e d i c a r e , M s l i l o t u s and T r i g o n e l l a . . " C a n . J o u r n r P.es. 3 . 1930-«« " C o n t r i b u t i o n a l 1 e t u d e c a r y o l o g u e du genre M e d i e a g o , " Cor.pt. p.end, A c a d , S e i * P a r i s , 1 8 7 : 245-247,-: X928 e — '^Oenothera Mutants w i t h D i m i n u t i v e 'Chromosomes." Am. Journ, . B o t e 3 : 502-526. 1916. ~» "15 and 16 Chromosome Oenothera M u t a n t s , " Am, Journ* Bot* 4 : -5g-3.il* 19.17. • ^Somatic Chromosomes In. f l c i a , * " - L a C e l l u l e , 29: 297-228* 1913.. — "Somat ic Chromosomes i n f r a d e s o a n . t l a . " Am* Journ„ Bot,. 7: 341-355, 1920. ~- "An I n t r o d u c t i o n to C y t o l o g y . " McGraw K i l l Blr. Co . P l ew Y o r k . 1926. 22 " C y t o l o g i c a l S t u d i e s on G a s t e r i a I . Chromosome Shape and I n d i v i d u a l i t y . " Am. J o u r n . B o t . 1 1 : 51-59» 1924. , ? 0 j - t o l o g i c a l S t u d i e s on G a s t e r i a I I . An, J o i m u B o t . 12 : 219-223. 1925 . "Chromosome C o n s t r i c t i o n s as D i s t i n g u i s h i n g C h a r a c t e r i s t i c s i n P l a n t s o" An* J o u m . B o t . 1 2 : 238-244. 1925* "She C e l l i n Development and H e r e d i t y * " E e H i l l a n Co.,, Hew Y o r k . 1925„ I SggSAlMIQff 02? PM?gSS ' . A l l m a g n i f i c a t i o n s a re x £500 P l a t e I , F i g . 1 — Grimm, prophase o r e a r l v anaphase, showing 1 6 chromosomes, s e v e r a l i n p a i r s . Fj^ g_e_j3 «*» Grimm, metaphase, doub le chromosomes on c e n t r a l p l a te , . |lg: 6__g ~- Grimm, metaphase, 8 doub le chromosomes. Fig*__4 —- Grimm, e a r l y anaphase, 8 chromosomes, drawing away f r o m c e n t r a l p l a t e * Fig. . . 5 — Grimm, anaphase., showing one double chromosome {a} w i t h s p i n d l e f i b r e a t tachments , 8 chromosomes moving to each pole.* F i g * 6 - D m a , p rophase , showing 16 chromosomes wj.th s e v e r a l I n p a i r s . F i g . , 7 Bonn, p rophase , showing double chromosome (a) w i t h s p i n d l e f i b r e at tachments and (b) chromosome s p l i t t i n g . F i g * t 8 ~~ Bonn, p r o p h a s e , showing 16 chromosomes, some w i t h rounded- p r o t r u b e r a n c e s a t ends* F i g . 9 —- Bonn, l a t e prophase o r e a r l y metaphase, 16 chromosomes. P l a t e I I , Fig. 1 — Bonn, metaphase, showing 8 double chromosomes. XI P l a t e I I , ffig. 2 =- Donn, anaphase, showing 8 chromosomes moving to eaeh p o l e . f i g . 3 — B>56, p rophase , showing 32 chromosomes, s e v e r a l i n p a i r s . F i g . 4 — B>56, p rophase , showing 2 8 chromosomes, s e v e r a l i n p a i r s . F i g . 5 — E - 5 6 , prophase , showing p a i r s o f chromosomes, *"**' e a r l y anaphase*: H^65, e a r l y anaphase, hooked chromosomes on s p i n d l e f ib res , , . Pig#, 8 —' B>D6, l a t e anaphase , w i t h p a i r o f l a g g i n g chromosomes, F i g . 9 — &-|6 : , l a t e anaphase , w i t h p a i r o f l a g g i n g chromosomes, P l a t e I l l y . P i g , 1 —'• H ^ B 6 , p rophase , w i t h p a i r s .of . chromosomes,. FI-M.L,^. Ik$±l§,<>' p rophase , w i t h 3 2 chromosomes, s e v e r a l i n p a i r s e HM^SL "** 5^S§.? metaphase, p a i r s a t c e n t r a l p l a t e . P i g . 4 ~- H^X56, metaphase* P i g a 5 — H-156, e a r l y anaphase, hooked forms on s p i n d l e f i b r e s . . P i g . 6 -*~ H-156, anaphase, showing 16 chromosomes moving to each p o l e . I l l P l a t e I I I , F i g * 7 — H-156, l a t e anaphase, showing p a i r o f l a g g i n g chromosomes, F i g , 8 — B>7, p rophase , 52 chromosomes, s e v e r a l i n p a i r s . F i g , S ™- H^?, metaphase, p a i r s at c e n t r a l p l a t e , P l a t e I ? , F i g , _ l — H-7, metaphase. F i g , ; 2 —- E-% e a r l y anaphase, tf-ehaped chromosomes on spindle f i b r e s , FIg>_3 B>7» anaphase, 16 chromosomes moving to - each pole* Flg;^_4 —• H^ 7» l a t e anaphase,. 15 chromosomes a t po le , . F i g , 5 — H~19Q A metaphase, some paired, Fig^..6 H-lffO* metaphase, some chromosomes paired. F i g , 7 — B-190, l a t e anaphase, 12 chromosomes moving to each pole* F i g . 8 H-68 s prophase, showing 32 chromosomes. F i g * 9 —» E - 6 8 s metaphase, P l a t e Fig« 1 — £-68, l a t e metaphase, shov/ing several paired ehromosomeSo F i g . 2 '— H-68, anaphase, showing 16 chromosomes moving to p o l o s and hooked chromosomes on s p i n d l e f i b r e s . F i g ^ 3 £-71, anaphase, showing 8 chromosomes moving to central plate* F i g , , 4 — E - 7 1 , l a t e anaphase, showing Q chromosomes moving to central plate. 11 P l a t e Yy. P i g * . 5 — E~TLt l a t e metaphase, showing some p a i r s . l?lg»- & «*- B>71»' anaphase, showing 11 chromosomes moving 'to p o l e s and hooked shapes on s p i n d l e f i b r e s * P L A T E I . PLATE PLATED. 

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