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Some aspects of the association between Rhabdogloeum pseudotsugae Sydow and Rhabdocline pseudotsugae… Parker, Arthur Kneeland 1951

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SOME ASPECTS OF THE ASSOCIATION BETWEEN RHABDOGLOEUM PSEUDOTSUGAE SYDOW AND RHABDOCLINE PSEUDOTSUGAE SYDOW by ARTHUR KNEELAND PARKER A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF ARTS i n the Department of B i o l o g y and Botany We accept t h i s t h e s i s as conforming t o the standard r e q u i r e d from candidates f o r the degree of MASTER OF Members of the Department of THE UNIVERSITY OF BRITISH COLUMBIA A p r i l , 1951 Sj l*s-( AS SOME ASPECTS OF THE ASSOCIATION BETWEEN RHABDOGLOEUM  PSEUDOTSUGAE SIDOW AND RHABDOCLINE PSEUDOTSUGAE SYDOW by Arthur Kneeland Parker ABSTRACT Rhabdogloeum pseudotsugae Sydow has been suspected of being the imperfect stage of Rhabdocline pseudotsugae Sydow s i n c e t h e i r o r i g i n a l d e s c r i p t i o n by Sydow i n 1 9 2 2 . Because Rhabdogloeum has been r e p o r t e d so seldom i n North America, and never i n Europe, t h i s p o s s i b i l i t y has been con s i d e r e d s l i g h t by most i n v e s t i g a t o r s . I n v e s t i g a t i o n of the problem of Rhabdocline pseudotsugae i n B r i t i s h Columbia r e v e a l e d s e v e r a l new aspects of the a s s o c i a t i o n between the two l e a f - c a s t d i s e a s e s . I n s p e c t i o n of Rhabdocline and Rhabdogloeum c o l l e c t i o n s from the i n t e r i o r o f B r i t i s h Columbia i n d i c a t e d t h a t the a s s o c i a t i o n of Rhabdogloeum pseudotsugae and Rhabdocline  pseudotsugae i s more p r e v a l e n t than was f o r m e r l y b e l i e v e d . C o l l e c t i o n s from the c o a s t , and on Vancouver I s l a n d i n p a r t i c u l a r , i n d i c a t e d t h a t the a s s o c i a t i o n i s probably l e s s p r e v a l e n t t h e r e than i n the i n t e r i o r . In r e l a t i o n to the frequent and widespread occurrence of Rhabdocline through-out the Douglas f i r range however, Rhabdogloeum i s seldom found. I f Rhabdogloeum pseudotsugae i s the i m p e r f e c t stage of Rhabdocline pseudotsugae, then i t appears t h a t f r e q u e n t l y the Rhabdogloeum stage and o c c a s i o n a l l y the Rhabdocline stage i s completely suppressed, as both stages have been found d i s s o c i a t e d from each other. Frequent o b s e r v a t i o n of a group of tagged Rhabdocline-i n f e c t e d t r e e s on Vancouver I s l a n d over a p e r i o d ,of two years d i d not r e v e a l the presence o f a Rhabdogloeum stage. T i s s u e c u l t u r e s of l e s i o n s from these tagged t r e e s , how-ever, r e s u l t e d i n the growth of a fungus q u i t e s i m i l a r i n appearance to t h a t produced i n t i s s u e c u l t u r e s by l e s i o n s t y p i c a l of those produced by Rhabdogloeum pseudotsugae. T h i s supports the view t h a t Rhabdogloeum pseudotsugae i s the imperfect stage of Rhabdocline pseudotsugae. Obser-v a t i o n of these t r e e s i n d i c a t e d t h a t Rhabdocline pseu-dotsugae i s capable o f v e g e t a t i n g two years b e f o r e pro-ducing a p o t h e c i a . Apparently i t i s a l s o capable o f v e g e t a t i n g more than two years or of i n f e c t i n g l e a v e s other than those of the c u r r e n t y e a r . ACKNOWLEDGEMEN TS The author wishes to express h i s a p p r e c i a t i o n t o Dr. F. Dickson, P r o f e s s o r , and Dr. D. C. Buckland, A s s o c i a t e P r o f e s s o r , of the Department o f B i o l o g y and Botany, ..University of B r i t i s h Columbia, f o r t h e i r a d v i c e and en-couragement d u r i n g t h i s i n v e s t i g a t i o n . G r a t e f u l acknowledgement i s due Dr. R. E. F o s t e r , O f f i c e r - i n - C h a r g e , and s t a f f o f the Dominion La b o r a t o r y of F o r e s t Pathology i n V i c t o r i a f o r r e n d e r i n g every pos-s i b l e a s s i s t a n c e throughout-the i n v e s t i g a t i o n , and to Dr. L. S. G i l l and Dr. T. ¥. C h i l d s o f the D i v i s i o n of Fo r e s t Pathology, United S t a t e s Department of A g r i c u l t u r e , f o r p l a c i n g c e r t a i n herbarium c o l l e c t i o n s at the author's d i s p o s a l . The b i b l i o g r a p h y ^ o f t h i s t h e s i s i s i n the form r e q u i r e d f o r p u b l i c a t i o n i n Phytopathology, the o f f i c i a l organ o f The American P h y t o p a t h o l o g i c a l S o c i e t y . TABLE OF CONTENTS Page INTRODUCTION 1 METHODS .. ^  2 OBSERVATIONS 4 Study of herbarium specimens 4 Study of fresh material 5 •EXPERIMENTS AND RESULTS 6 Tissue cultures 6 Growth rates •••• 10 Fruiting in culture 12 Inoculations 13 DISCUSSION 15 SUMMARY • • 18 BIBLIOGRAPHY - 19 LIST OF FIGURES Le s i o n s of Rhabdocline pseudotsugae on two-y e a r - o l d l e a v e s o f Douglas f i r * Photomicrograph of a c r o s s - s e c t i o n of a Dougla f i r l e a f with an a c e r v u l u s of Rhabdogloeum  pseudotsugae on the upper s u r f a c e and an apothecium of Rhabdocline pseudotsugae on the lower s u r f a c e . X approx. 40 T i s s u e c u l t u r e s o f l e s i o n s t y p i c a l o f those caused b y Rhabdogloeum pseudotsugae on malt ,agar at the end of e i g h t weeks ( l e f t ) and f i v e weeks* ( r i g h t ) . The agar has* turned an o l i v e -green c o l o u r i n the e i g h t week o l d c u l t u r e and has remained unchanged 1 i n the* f i v e week o l d c u l t u r e . M y c e l i a l growth at room temperature, from a l e s i o n t y p i c a l "of those caused by' Rhabdogloeum  pseudotsugae on malt agar a t the end of f o u r weeks, tzjy "~ *• ' ' M y c e l i a l growth a t ro'om temperature from a l e s i o n t y p i c a l of those caused by Rhabdocline  pseudotsugae oh" malt" agar at" the 'end of f o u r weeks. X 2/3 -Photomicrograph of m i c r o c o n i d i a and macroconid i a from a- t i s s u e c u l t u r e - of a ie'sion t y p i c a l o f those caused by Rhabdocline pseudotsugae. X approx. IO5O ' " " '- " '• A camera-luci'da" drawing-of spore's o c c u r r i n g i n t i s s u e c u l t u r e s of l e s i o n s t y p i c a l of those caused by Rhabdocline pseudotsugae. X approx. IO65 A photomicrograph of m i c r o c o n i d i o p h o r e s from a t i s s u e c u l t u r e of a l e s i o n t y p i c a l of those caused by Rhabdocline pseudotsugae. X approx. 1050 A camera-lucida drawing of m i c r o c o n i d i o p h o r e s from t i s s u e c u l t u r e s of l e s i o n s t y p i c a l of tho caused by Rhabdocline pseudotsugae. X approx. 1050 F i g u r e 10 A photomicrograph of macroconidiophores from a t i s s u e c u l t u r e of a l e s i o n t y p i c a l of those caused by Rhabdocline pseudotsugae» X approx. 1050 F i g u r e 11 A camera-lucida drawing of macroconidiophores from t i s s u e c u l t u r e s of l e s i o n s t y p i c a l of those caused by Rhabdocline pseudotsugae* X approx. 1050 LIST OF TABLES Table I L i s t o f Rhabdogloeum pseudotsugae c o l l e c t i o n s i n B r i t i s h Columbia with average spore s i z e s o btained from each, and a r e c o r d of those c o l l e c t i o n s showing an a s s o c i a t i o n with Rhabdocline pseudotsugae. SOME ASPECTS OF THE ASSOCIATION BETWEEN RHABDOGLOEUM PSEUDOTSUGAE SYDOW AND RHABDOCLINE PSEUDOTSUGAE SYDOW INTRODUCTION The problem of Rhabdocline pseudotsugae Sydow, the fungus organism c a u s i n g a needle c a s t d i s e a s e o f Douglas f i r , i s becoming of i n c r e a s i n g importance i n North America ( 9 , 11 , 2 2 , 2 9 , 3 2 ) . T h i s i s a t t r i b u t e d to the i n c r e a s i n g demand f o r second-growth Douglas f i r f o r timber and f o r Christmas t r e e s t o c k . C o n s i d e r a b l e concern has been shown i n Europe s i n c e the i n t r o d u c t i o n o f the d i s e a s e i n t o S c o t -land from North America about 1913 (33) and i t s i n t r o -d u c t i o n i n t o Germany from S c o t l a n d about 1926 ( 2 ) . Rhab-dogloeum pseudotsugae Sydow has been found a s s o c i a t e d w i t h Rhabdocline pseudotsugae i n North America o n l y r a r e l y and has never been reported from Europe (2 , 8 , 2 8 ) . Both pathogens were named and d e s c r i b e d by Sydow i n 1922 ( 2 6 ) , Rhabdocline pseudotsugae being p l a c e d i n the Ascomycetes, P h a c i d a l e s and Rhabdogloeum pseudotsugae i n the Fungi I m p e r f e c t i , M e l a n c o n i a l e s . He suggested at the time t h a t Rhabdogloeum pseudotsugae was the imp e r f e c t stage of Rhabdocline pseudotsugae. In 1926 Wilson and Wilson (33) r e p o r t e d t h a t , i n America, c o n i d i a of Rhabdocline pseudot~ sugae developed on the upper s u r f a c e of l e a v e s d u r i n g J u l y . In r e f e r r i n g t o t h i s statement by Wilson and Wilson, Van V l o t e n (28) p o i n t e d out t h a t an a s s o c i a t i o n o f imperfect w i t h p e r f e c t f r u i t i n g bodies d i d not c o n s t i t u t e p roof o f t h e i r r e l a t i o n s h i p . In 1945 E l l i s and G i l l (13) named and d e s c r i b e d a new s p e c i e s of Rhabdogloeum, R. hypophyllum, a s s o c i a t e d with Rhabdocline pseudotsugae i n the southwestern United S t a t e s . Rhabdogloeum hypophyllum d i f f e r s from R. pseudotsugae i n having c o n s i d e r a b l y s m a l l e r c o n i d i a , l o n g e r c o n i d i o p h o r e s and t h i c k e r u n d e r l y i n g hyphal l a y e r s , from which the conidiophores a r i s e . Rhabdogloeum pseudotsugae has been r e p o r t e d so i n -f r e q u e n t l y i n North America t h a t the p o s s i b i l i t y o f i t being the imperfect stage of Rhabdocline pseudotsugae has been c o n s i d e r e d s l i g h t by most i n v e s t i g a t o r s ( 2 ) . Because of the i n c r e a s i n g importance of Rhabdocline  pseudotsugae i n t h i s country the Dominion L a b o r a t o r y of F o r e s t Pathology, V i c t o r i a , B r i t i s h Columbia, assigned the author to i n v e s t i g a t e the d i s e a s e . T h i s t h e s i s c o n s t i t u t e s a r e p o r t on a p o r t i o n of the i n v e s t i g a t i o n and prese n t s some of the r e s u l t s o f s t u d i e s aimed a t . c l a r i f y i n g the a s s o c i a t i o n between Rhabdocline pseudotsugae and Rhabdog-loeum pseudotsugae. METHODS A l l herbarium specimens of the two f u n g i d e p o s i t e d with the Dominion Laboratory of Fores t Pathology, V i c t o r i a , 3 B r i t i s h C o l u m b i a were e x a m i n e d . E x a m i n a t i o n s were made a l s o o f p o r t i o n s o f a l l c o l l e c t i o n s o f t h e s e f u n g i d e p o s i t e d w i t h t h e U n i t e d S t a t e s D epartment o f A g r i c u l t u r e , D i v i s i o n o f F o r e s t P a t h o l o g y , A l b u q u e r q u e , New M e x i c o , and some o f t h o s e d e p o s i t e d w i t h t h e U n i t e d S t a t e s D epartment o f A g r i -c u l t u r e , D i v i s i o n o f F o r e s t P a t h o l o g y , P o r t l a n d , O r e g o n . F r e e h a n d s e c t i o n s were made o f l e s i o n s on most o f t h e s e s p e c i m e n s . The s e c t i o n s were mounted i n 5 p e r c e n t p o t a s -s i u m h y d r o x i d e and measurements made w i t h a F i l a r m i c r o -m e t e r . E a c h s p o r e s i z e r e c o r d e d r e p r e s e n t s t h e a v e r a g e measurement o f f i f t y o r more s p o r e s . A l l m a t e r i a l f o r c u l t u r i n g was o b t a i n e d f r o m t a g g e d t r e e s i n t h e B r i t i s h C o l u m b i a F o r e s t E x p e r i m e n t a l S t a t i o n a t C o w ichan L a k e on V a n c o u v e r I s l a n d . One t r e e was i n f e c t e d w i t h Rhabdogloeum p s e u d o t s u g a e and t h e r e m a i n i n g t r e e s , o n e - h a l f m i l e d i s t a n t were i n f e c t e d w i t h R h a b d o c l i n e  p s e u d o t s u g a e . The t r e e s have been examined p e r i o d i c a l l y by t h e a u t h o r s i n c e May, 1949. I n m a k i n g t i s s u e c u l t u r e s o f l e s i o n s whole l e a v e s were d i p p e d i n 95 p e r c e n t a l c o h o l , s u r f a c e s t e r i l i z e d i n 1:1000 m e r c u r i c c h l o r i d e f o r two m i n u t e s and washed i n t h r e e s e p a r a t e d i s h e s o f s t e r i l e w a t e r . The l e s i o n s were t h e n c u t o u t , p l a n t e d on D i f c o m a l t a g a r and k e p t a t room t e m p e r -a t u r e (60 - 8 0 ° F ) . I n March 1950, u s i n g a method d e s c r i b e d b y G r i f f i t h (14)» two hundred c u t t i n g s of the pr e v i o u s year's growth of Douglas f i r t r e e s were made f o r use i n i n o c u l a t i o n ex-periments. The c u t t i n g s were from the tagged t r e e s having n e c r o t i c l e s i o n s t y p i c a l of Rhabdocline pseudotsugae on two-year-old and o l d e r needles ( F i g . 1). OBSERVATIONS  Study of Herbarium Specimens There were twenty-eight d i f f e r e n t l o c a l i t i e s through-out the Douglas f i r range i n B r i t i s h Columbia represented by herbarium c o l l e c t i o n s . Examination r e v e a l e d Rhabdogloeum  pseudotsugae t o be present i n nine w i d e l y s c a t t e r e d l o c a l i t -i e s a t the time the c o l l e c t i o n s were made (Table I ) . At Cranbrook i n s p e c t i o n o f 206 t r e e s on a one-tenth acre p l o t of Christmas t r e e stock i n J u l y , 1950 y i e l d e d t h i r t e e n t r e e s i n f e c t e d with R. pseudotsugae. I n t e n s i v e s c o u t i n g i n the Cowichan Lake F o r e s t Experimental S t a t i o n has y i e l d e d o n l y one i n f e c t e d t r e e w i t h the pathogen (30). C o l l e c t i o n s made from the other areas do not i n d i c a t e a systematic search f o r the pathogen. An a s s o c i a t i o n of Rhabdogloeum pseudotsugae w i t h Rhabdocline pseudotsugae ( F i g . 2) was noted i n c o l l e c t i o n s i from f i v e of the nine l o c a l i t i e s . In the Lemoh Creek area a t r e e was found with an i n f e c t i o n of Rhabdogloeum unas-s o c i a t e d with Rhabdocline, whereas other t r e e s a few yards away.had on l y a Rhabdocline i n f e c t i o n . In the Sooke area a l s o a t r e e was found i n f e c t e d with o n l y Rhabdogloeum and f u r t h e r i n s p e c t i o n s made i n J u l y , 1949 and May, 1950 s t i l l r e v e a l e d no Rhabdocline i n f e c t i o n . The remaining two c o l l e c t i o n s i n f e c t e d with Rhabdogloeum but showing no e v i -dence of Rhabdocline, one from Langford, the other from Kamloops, were made e a r l y i n May, too e a r l y i n the year f o r an a s s o c i a t i o n t o be e v i d e n t . A c e r v u l i of Rhabdogloeum were found on needles two-years o l d and o l d e r i n the c o l l e c t i o n s from Sooke and Kamloops and on needles one-year-old and o l d e r on the r e -mainder. The spore measurements obtained from the c o l l e c t i o n s and t a b u l a t e d i n Table I , d i d not vary a p p r e c i a b l y from one another or from those d e s c r i b e d by Sydow (26). Study o f Fresh M a t e r i a l In May of 1949 and i n May, 1950 a l l Douglas f i r t r e e s w i t h i n a 132 f o o t (two chain) r a d i u s of the tagged Rhab-d o c l i n e - i n f e c t e d t r e e s f a i l e d to show any s i g n o f Rhab-dogloeum. No s i g n o f Rhabdogloeum was found on f r e s h m a t e r i a l c o l l e c t e d from the tagged t r e e s i n t h i s a r e a over a p e r i o d o f twenty-two months. C o l l e c t i o n s r e p r e s e n t -ed every month of the year except A p r i l . The t h r e e separate crops o f Rhabdocline' a p o t h e c i a observed d u r i n g 6 t h i s p e r i o d occurred o n l y on two-year-rold, and o l d e r n e e d l e s . A l l but a very few l e a v e s with l e s i o n s were c a s t by the end of August each y e a r . As the d i s e a s e was not severe d u r i n g the observed p e r i o d , not a l l the l e a v e s of any one year on a branch were i n f e c t e d . New a p o t h e c i a appeared each year on some of these p r e v i o u s l y u n i n f e c t e d two-year-old, and o l d e r n e e d l e s . Signs o f d i s e a s e appeared on one-year-old, and o l d e r l e a v e s of the tagged Rhabdogloeum-infected t r e e . G h l o r o t i c l e s i o n s appeared i n the p e r i o d September - January and were the f i r s t i n d i c a t i o n s o f new i n f e c t i o n . A c e r v u l i o c -curre d on the upper s u r f a c e o f l e a v e s and a p o t h e c i a o f Rhabdocline pseudotsugae o c c a s i o n a l l y appeared d i r e c t l y below the a c e r v u l i on the lower s u r f a c e o f the l e a v e s . EXPERIMENTS AND RESULTS Ti s s u e C u l t u r e s Over the two-year p e r i o d s i x s e t s o f t i s s u e c u l t u r e s were made of the l e s i o n s on tagged t r e e s . Each set was made d u r i n g a d i f f e r e n t l a t e f a l l and wint e r month. Of the 163 t i s s u e c u l t u r e s obtained from f o u r R h a b d o c l i n e - i n f e c t e d t r e e s , f o r t y - f i v e per cent r e s u l t e d i n macroscopic growth s i m i l a r t o t h a t obtained from a polysporous c u l t u r e o f Rhabdogloeum pseudotsugae ( F i g s . 4» 5)t t h i r t y per cent produced no growth and the remaining t w e n t y - f i v e per cent 7 produced a number of d i f f e r e n t organisms. . Seventy-four per cent of the t h i r t y - o n e c u l t u r e s made from l e s i o n s o c c u r r i n g on the Rhabdogloeum-infected t r e e r e s u l t e d i n growth s i m i l a r to the polysporous i s o l a t e , t e n per cent produced no growth and s i x t e e n per cent produced a number o f d i f f e r e n t organ-isms. _ M y c e l i a l growth from these t i s s u e c u l t u r e s appeared on the agar i n from one to s i x weeks.. Subsequent growth, which was white and i r r e g u l a r i n p a t t e r n , reached a d i a -meter of about 10 mm. w i t h i n two to t h r e e .weeks. A f t e r t h r e e t o f o u r weeks of v i s i b l e growth a yellow-green c o l o u r appeared a t the centre of the mats and extended over most of the mat w i t h i n s i x to e i g h t weeks. L i g h t - g r e y and l i g h t -brown patches of mycelium were o f t e n i n t e r s p e r s e d with the yellow-green. The malt agar under the mats turned an o l i v e - g r e e n to a dark-brown c o l o u r i n about two months ( F i g . 3). M i c r o c o n i d i a and macroconidia were produced i n both t i s s u e c u l t u r e s and polysporous c u l t u r e ( F i g . 6, 7 ) . M i c r o c o n i d i a from the t h r e e sources were pa l e green t o h y a l i n e and oblong t o o v a l . M i c r o c o n i d i a from f i v e t i s s u e c u l t u r e s o f the Rhabdogloeum-infected t r e e measured 3.1 - 5.5u x 1*5 - 2.4^.(mean 2.1 x 4.^j. Ten spores from each of f o u r t i s s u e c u l t u r e s and twenty from the remaining t i s s u e c u l t u r e were measured. M i c r o c o n i d i a from f o u r 8 t i s s u e c u l t u r e s of R h a b d o c l i n e - i n f e c t e d t r e e s measured 2.1 - U.3px 1.2 - 2.3u(mean 1.7 x 3»3ji)* Ten spores from each o f two t i s s u e c u l t u r e s and twenty from the remainder were measured. Macroconidia from s i x t i s s u e c u l t u r e s o f the Rhabdogloeum-infected t r e e measured 8.3 - 14.3^. x 3.4 - 5.8ja(mean 4 .7 x 11 .4^i). Ten spores from each t i s s u e c u l t u r e were measured. Ma c r o c o n i d i a from f o u r t i s s u e c u l -t u r e s o f R h a b d o c l i n e - i n f e c t e d t r e e s measured 9 . 1 - 13.7p-x 3»3 - 5.4u(mean 4 .3 x 1 0 . 5 u ) . Ten spores from each o f two t i s s u e c u l t u r e s and twenty from the remainder were measured. Chi-square v a l u e s of the means of these spore measurements were computed. A value o f 0.26 was obtained f o r the len g t h s and 0.11 f o r the widths of m i c r o c o n i d i a . The p r o b a b i l i t y of o b t a i n i n g g r e a t e r Chi-square v a l u e s f o r these dimensions were between 0 .6 and 0 .7 f o r the l e n g t h s and between 0 .7 and 0 .8 f o r the widths. A Chi-square value of 0.07 was obtained f o r l e n g t h s and 0 .05 f o r the widths of macroconidia. The p r o b a b i l i t y o f o b t a i n i n g g r e a t e r Chi-square values f o r these dimensions were be-tween 0.7 and 0 . 8 f o r the l e n g t h s and between 0 .8 and 0 . 9 f o r the widths. To have n i n e t y - f i v e per cent c o n f i d e n c e , a Chi-square value of 3*84 would have t o be obtained w i t h the mean valu e s o f the spore measurements, from the d i f -f e r e n t t i s s u e c u l t u r e s , t o i n d i c a t e a s i g n i f i c a n t d i f f e r e n c e . M i c r o c o n i d i a from the polysporous c u l t u r e measured 3.8 - 6.2^i x 1.7 - 3.2p. (mean 2.3 x 5.Op.). M a c r o c o n i d i a from t h i s c u l t u r e measured 10.5 - l6.0p. x 3.8 - 6.5^(mean 5.2 x 13.6^i). These spore s i z e s were based on the measure-ment of twenty spores of each t y p e . M a c r o c o n i d i a from a l l c u l t u r e s were s i m i l a r i n shape to those o c c u r r i n g i n n a t u r e . When produced i n abundance they o c c u r r e d as o l i v e - g r e e n masses which o f t e n covered a c o n s i d e r a b l e p o r t i o n o f the m y c e l i a l mat. ' M a c r o c o n i d i a were one or t w o - c e l l e d and were g e n e r a l l y l i g h t - g r e e n i n c o l o u r although o c c a s i o n a l l y h y a l i n e . Germination on malt agar took p l a c e at room temperature w i t h i n about twenty-f o u r hours. Both one and t w o - c e l l e d spores germinated. In some of the o l d e r c u l t u r e s one c e l l o f the septate spores became dark-w a l l e d . A s i m i l a r c o n d i t i o n was noted by Wilson and Wilson (33) i n mature ascospores of Rhabdocline pseudotsugae. M i c r o c o n i d i o p h o r e s appeared s i m i l a r i n shape to those producing m a c r o c o n i d i a - ( F i g . 8, 9» 10, 1 1 ) , and measured 8.0 - 40.Op. i n l e n g t h by 2.0 - 3«2p. i n width (mean 2.6 x 12. 5 j i ) • Macroconidiophores measured 8.5 - 39.5u i n l e n g t h by 2 - 3.2p: i n width (mean 2.6 x 12.Op;). These c o n i d i o - -phore s i z e s were based on the measurement of t e n m i c r o -c o n i d i o p h o r e s and ten macroconidiophores.• Subsequent s i n g l e spore i s o l a t i o n s of macroconidia produced i n c u l t u r e from the t h r e e sources gave s i m i l a r 10 results.. Repeated attempts t o germinate and grow m i c r o -c o n i d i a f a i l e d . _ • . In January 1950, t h i r t y - s i x l e a v e s were taken from f o u r tagged R h a b d o c l i n e - i n f e c t e d t r e e s f o r t i s s u e c u l t u r e purposes. Only those l e a v e s with a l e s i o n s i m i l a r i n ap-pearance t o one o c c u r r i n g on an adjacent l e a f were taken. The p o s i t i o n s of the c o n t r o l l e a v e s were marked and ob-s e r v a t i o n s were made t o see i f t h e r e was any i n d i c a t i o n o f Rhabdogloeum pseudotsugae, i n the l a t t e r p a r t o f March and May and i n the f i r s t week of August. At the time o f obser-v a t i o n i n August, f o u r t e e n o f the l e a v e s had been cast... No evidence of Rhabdogloeum pseudotsugae was observed on the remaining n e e d l e s . T h i r t y - o n e per cent o f the t i s s u e c u l t u r e s made from these l e a v e s produced growth s i m i l a r t o t h a t d e s c r i b e d above; t h i r t y - s i x per cent f a i l e d t o produce growth of any k i n d and the remaining t h i r t y - t h r e e per cent gave r i s e t o a number o f d i f f e r e n t organisms. During the months of January, February, March and May, le a v e s from tagged t r e e s having n e c r o t i c l e s i o n s t y p i c a l of those caused by Rhabdocline pseudotsugae were p l a c e d i n moist chambers and i n s p e c t e d p e r i o d i c a l l y . No evidence of Rhabdogloeum or a p o t h e c i a of Rhabdocline appeared. Growth Rates A comparison o f growth r a t e s was made of i s o l a t e s 11 from a needle l e s i o n on a R h a b d o c l i n e - i n f e c t e d t r e e ( i s o l a t e d August 1950) , a needle l e s i o n from a Rhabdogloeum-i n f e c t e d t r e e ( i s o l a t e d August 1950) and a polysporous c u l t u r e of Rhabdogloeum pseudotsugae ( i s o l a t e d September 1949)• The i s o l a t e s were grown on t h r e e per cent D i f c o malt agar a t room temperature f o r f o u r weeks. S e c t i o n s were then cut from the edge of the c u l t u r e u s i n g a s t e r i l e 4 mm. cork borer and were t r a n s f e r r e d t o f r e s h p l a t e s con-t a i n i n g t h r e e per cent D i f c o malt agar. The p l a t e s were then d i v i d e d and p l a c e d i n s i x constant temperature chambers with temperatures r a n g i n g from 5 t o 30°C. Growth was • measured weekly f o r e i g h t weeks. A f t e r f i v e weeks the growth r a t e i n a l l chambers d e c l i n e d c o n s i d e r a b l y . A l l t h r e e i s o l a t e s grew best a t 15°G and those at 30°C f a i l e d t o grow. At 15°C the t i s s u e c u l t u r e s o r i g i n a t i n g from the Rhabdogloeum-infected t r e e a t t a i n e d a maximum diameter of 4 . 1 cm., the polysporous c u l t u r e of Rhabdogloeum pseudot-sugae 3«2 cm. and the i s o l a t e o r i g i n a t i n g from the Rhab-d o c l i n e - i n f ected t r e e 2.9 cm. These i s o l a t e s were grown a l s o at 15°C f o r e i g h t weeks on prune, corn-meal, dextrose and potatoe-dextrose a g a r s . The media, i n the order of g r e a t e s t growth a t t a i n e d by the t h r e e i s o l a t e s were: potatoe-dextrose, d e x t r o s e , malt, prune and corn-meal. The growth r a t e s o f the t h r e e i s o l a t e s decreased a f t e r the f i f t h week on a l l media. 12 The t i s s u e c u l t u r e from the Rhabdogloeum-infected t r e e showed more growth on a l l media than d i d the remaining two i s o l a t e s which grew at approximately equal r a t e s . The growth of a t i s s u e c u l t u r e made from a Rhabdog-loeum-inf ected l e a f was observed on separate p l a t e s con-t a i n i n g three per cent D i f c o malt agar a d j u s t e d t o v a r i o u s pH v a l u e s . The organism was grown i n P e t r i d i s h e s a t 15°C and measurements of growth were made weekly f o r e i g h t weeks. A Beckman pH meter was used to o b t a i n the r e a d i n g s . The average diameter-growth of the organism i n c r e a s e d w i t h i n c r e a s i n g pH up to 7.7» and d e c l i n e d s h a r p l y a t the next h i g h e s t pH, which was 8 . 3 . There was o n l y a s l i g h t i n c r e a s e i n growth between the t h r e e c u l t u r e s whose pH readings were 4.15» 5.45? and 6 . 0 0 . F r u i t i n g i n C u l t u r e M o d i f i c a t i o n s of the methods d e s c r i b e d by Gwynne-Vaughan and Barnes (15)» and Zentmyer et a l (35)» t o o b t a i n p e r f e c t f r u i t i n g bodies i n c u l t u r e were t r i e d , u s i n g i s o l a t e s from l e a f l e s i o n s of R h a b d o c l i n e - i n f e c t e d t r e e s and the Rhabdogloeum-infected t r e e . The experiments were s t a r t e d i n November. Claussen's medium was prepared and poured i n t o P e t r i d i s h e s as d e s c r i b e d by Gwynne-Vaughan and Barnes. E i g h t of these poured p l a t e s were then inocur-l a t e d with i s o l a t e s from the R h a b d o c l i n e - i n f e c t e d t r e e 13 and eight were inoculated with the isolate from the Rhabdogloeum-infected tree. From each of those groups of inoculated plates, four were placed in the greenhouse, two outdoors and the remaining two were l e f t at room temperature. No evidence of perfect f r u i t i n g bodies was" noted within three months. Douglas f i r leaves were sterilized using propylene oxide after the method described by Zentmyer. The s t e r i -lized leaves were placed in test tubes and Petri dishes containing warm liqui d , two per cent Bacto-agar which held the leaves firmly in position on hardening. Fourteen test tubes and fourteen plates *were then inoculated with isolates from the Rhabdocline-infected trees and an equal number of tubes and plates were inoculated with isolates from the Rhabdogloeum-infected tree. Eight plates from each group were placed outdoors, four were placed in a greenhouse and the remaining two were l e f t at room temper-ature. The test tubes were dispersed in a similar manner. No evidence of perfect fruiting bodies was noted within three months. Inoculations Early in August 1950, eighty of the cuttings des-cribed on page 4 were inoculated with a spore suspension made from tissue cultures obtained from Rhabdocline-14 i n f e c t e d t r e e s and f o r t y were i n o c u l a t e d w i t h a spore suspension made from t i s s u e c u l t u r e s o b t a i n e d from Rhab-dogloeum-infected t r e e s . Spores were suspended i n a s t e r i l e f i v e per cent g l y c e r i n e s o l u t i o n and were sprayed on the c u t t i n g s w i t h an atomizer. T h i r t y c u t t i n g s sprayed with a f i v e per cent g l y c e r i n e i n water s o l u t i o n were used as a c o n t r o l . The c u t t i n g s were p l a c e d i n a moist chamber f o r s i x t y hours a f t e r i n o c u l a t i o n s were completed and were then removed t o a greenhouse. Most of the buds on the c u t t i n g s f a i l e d t o open and i n no case was growth o f the c u r r e n t year v i g o r o u s . The c u t t i n g s were i n s p e c t e d i n October, 1950 and were found t o have c h l o r o t i c l e s i o n s on the p r e v i o u s year's growth s i m i l a r t o those o c c u r r i n g on t r e e s n a t u r a l l y i n f e c t e d by Rhabdocline pseudotsugae at t h a t time o f y e a r . F i f t y - f o u r per cent o f both s e t s of c u t t i n g s i n o c u l a t e d w i t h spores from t i s s u e c u l t u r e sources and s i x t y - n i n e per cent of t h e c u t t i n g s used i n the c o n t r o l had l e s i o n s . Subsequent t i s s u e c u l t u r e s from the t h r e e groups of c u t t i n g s produced c u l t u r e s s i m i l a r t o those obtained from Rhabdogloeum and Rhab-d o c l i n e - i n f e c t e d t r e e s . 15 DISCUSSION I n s p e c t i o n of herbarium c o l l e c t i o n s from the i n t e r i o r o f B r i t i s h Columbia i n d i c a t e d t h a t the as--s o c i a t i o n o f Rhabdogloeum and Rhabdocline i s more p r e v a l e n t than was f o r m e r l y b e l i e v e d . C o l l e c t i o n s from the c o a s t , and on Vancouver I s l a n d i n p a r t i c u l a r , i n d i c a t e d t h a t the a s s o c i a t i o n i s p r o b a b l y l e s s p r e v a l e n t t h e r e than i n the i n t e r i o r . . In r e l a t i o n t o the fr e q u e n t and widespread o c -currence o f Rhabdocline throughout the Douglas f i r range . however, Rhabdogloeum i s seldom found. The c o l l e c t i o n s from Sooke and Lemon Creek i n d i c a t e d t h a t Rhabdogloeum does occur u n a s s o c i a t e d with Rhabdocline. I f Rhabdogloeum  pseudotsugae i s the i m p e r f e c t stage of Rhabdocline pseu-dotsugae , i t i s apparent t h a t , f r e q u e n t l y , the Rhabdogloeum stage i s completely suppressed and t h a t , o c c a s i o n a l l y , the Rhabdocline stage i s suppressed. In S c o t l a n d , Wilson (34) o c c a s i o n a l l y found one-year-o l d l e a v e s on Douglas f i r showing no s i g n of Rhabdocline i n f e c t i o n w h i l e those of the p r e v i o u s year were d i s e a s e d . He s t a t e d t h a t " e i t h e r the i n f e c t e d needles have remained on t h e t r e e f o r two years or they have become i n f e c t e d d u r i n g t h e i r second y e a r , but both these c o n d i t i o n s appear abnormal". Boyce (2) has suggested t h a t the d i s e a s e i s capable of v e g e t a t i n g f o r n e a r l y two y e a r s . Observations made d u r i n g the past two years i n an area where o n l y the (1) That p o r t i o n o f B. C. east o f the Cascade Mountains. •16 two-year-old and older leaves bore apothecia i n early sum-mer favour Boyce's suggestion. The appearance of Rhab-doc l i n e - l i k e lesions on cuttings used as a control f o r inoculation experiments supplies further evidence f o r t h i s suggestion. The time of the appearance of these ch l o r o t i c lesions on the one-year-old leaves of the cuttings coin-cides with the time of t h e i r appearance on the one-year-old leaves of trees nat u r a l l y infected with Rhabdocline  pseudotsugae. As the cuttings were kept i n a greenhouse away from sources of i n f e c t i o n i t i s very u n l i k e l y that they became infected a f t e r c o l l e c t i o n . As i n the same year, apothecia of Rhabdocline appeared on the two-year-old and older leaves of na t u r a l l y infected trees, the fungus must either be capable of vegetating f o r two or more years, or ..it i s able to vegetate for. only two years and of i n f e c t i n g leaves of both current and previous years. Rhabdogloeum pseudotsugae, occurring on one-year-old and older needles, would appear capable of eithe r vegetat-ing one or more years or of i n f e c t i n g leaves of both current and previous years. The tissue cultures from Rhabdocline-infected trees were sim i l a r i n nearly a l l respects tested to those from Rhabdogloeum-infected trees. While the average growth rate of the tissue culture from the Rhabdogloeum-infected tree was greater than that of the ti s s u e culture from the 17 R h a b d o c l i n e - i n f e c t e d t r e e , the type o f growth and the s i z e and shape of spores occurring- i n a l l c u l t u r e s would i n -d i c a t e t h a t they were the same organism, Chi-square v a l u e s of average spore measurements i n d i c a t e d t h a t t h e r e was no s i g n i f i c a n t d i f f e r e n c e i n s i z e between the spores from t i s s u e c u l t u r e s of the Rhabdogloeum-infected t r e e and ~ those from t i s s u e c u l t u r e s of the R h a b d o c l i n e - i n f a c t e d t r e e . A f a i r comparison o f growth r a t e between the . polysporous c u l t u r e and the t i s s u e c u l t u r e s cannot be made because of the d i f f e r e n c e i n time between i s o l a t i o n s and d i f f e r e n c e i n the type of inoculum used. I s f i n a l p roof t h a t Rhabdogloeum pseudotsugae i s the i m p e r f e c t stage o f Rhabdocline pseudotsugae awaits re s u l t s . - o f s u c -c e s s f u l i n o c u l a t i o n experiments, a new s e r i e s has been des i g n e d . M i c r o c o n i d i a have not been found a s s o c i a t e d i n . n a t u r e w i t h Rhabdocline pseudotsugae. Rhabdogloeum pseudotsugae, o r Rhabdogloeum hypophyllum, nor d i d E l l i s and G i l l (13) r e p o r t f i n d i n g them i n c u l t u r e s of Rhabdogloeum hypophyl-lum. In accordance w i t h the f i n d i n g s o f Drayton (10), t h e i r presence i n c u l t u r e s of Rhabdogloeum pseudotsugae would probably i n d i c a t e the occurrence of a p e r f e c t stage i n the l i f e - c y c l e of t h i s organism. 18 SUMMARY I n s p e c t i o n o f c o l l e c t i o n s o f Rhabdocline pseudotsugae and Rhabdogloeum pseudotsugae r e v e a l e d the two organisms t o be a s s o c i a t e d on Douglas f i r i n the i n t e r i o r and c o a s t a l r e g i o n s o f B r i t i s h Columbia. The a s s o c i a t i o n appeared t o be more common i n the i n t e r i o r than on the c o a s t . In r e l a t i o n t o the frequent and widespread occurrence o f Rhabdocline, Rhabdogloeum i s seldom found. Rhabdogloeum  pseudotsugae appeared t o be capable of o c c u r r i n g unas-s o c i a t e d w i t h Rhabdocline pseudotsugae. O b s e r v a t i o n o f Rhabdocline pseudotsugae on Vancouver I s l a n d i n d i c a t e d i t s c a p a b i l i t y o f v e g e t a t i n g two y e a r s b e f o r e producing a p o t h e c i a . I t i s a l s o capable of e i t h e r v e g e t a t i n g more than two years o r of i n f e c t i n g l e a v e s o t h e r than those o f the c u r r e n t y e a r . T i s s u e c u l t u r e s of l e s i o n s on Rhabdocline pseudot-sugae - i n f e c t e d t r e e s t h a t o c c u r r e d on two-year-old and o l d e r l e a v e s , produced c u l t u r e s o f a fungus q u i t e s i m i l a r i n appearance t o t h a t obtained from a polysporous c u l t u r e and "tissue c u l t u r e s of l e s i o n s s i m i l a r i n appearance t o those caused by Rhabdogloeum pseudotsugae. T h i s supports the view t h a t the imperfect stage of Rhabdocline pseudot-sugae i s Rhabdogloeum pseudotsugae. 19 BIBLIOGRAPHY 1. Anonymous. Two leaf-east diseases of Douglas f i r . Forestry Commission, London, England. Leaflet No. 18, 1946. 2. Boyce, J.S. Forest Pathology. McGraw-Hill. 600 pp. 1948. 3. .......... Pacific Northwest conifers and their diseases in Great Britain. The Timberman 2£: 170, 172,. 174, 176; 1926. 4* •• Check l i s t of disease of economic plants i n the United States. U. S. Dept. of Agric. Bull. 1366: 88. 1926. 5. Observations on forest pathology i n Great Britain and Denmark. Phytopath. 17_: 1-18. 1927. 6. Brown, A.B. Observations on leaf f a l l i n the Douglas f i r when infected with Rhabdocline pseudot-sugae Syd. Ann. Appl. B i o l . 12: 745-754. 1930. 7. Day, W.R. A leaf-cast of the Douglas f i r due to Rhabdocline pseudotsugae Syd. Quart. Journ. Forestry 21: 193-199. 1927. 8. Dearness, J. New and noteworthy fungi. V. Mycologia 20: 235-246. 1928. 9. Dickerman, M.B. Christmas tree shipments drop twenty-four per cent; Northern Rocky Mountain Forest and Range Expt. Sta. Bull. 59. 1948. 20 10. Drayton, F.L. The sexual mechanism of Sclerotinia Gladioli. Mycologia 26: 46-72. 1934. 11. Ehrlich, J. Recently active leaf diseases of woody plants in Idaho. U. S. Dept Agr. Plant Dis. Rptr. 26: 391-393. 1942. 12. E l l i s , D.E. Conifer diseases hitherto unreported from the Southwest. U. S. Dept. Agr. Plant Dis. Rptr. 23: 341. 1939. 13. E l l i s , D.E., and L. S. G i l l . A new Rhabdogloeum associated with Rhabdocline pseudotsugae in the Southwest. Mycologia XL' 326-332. 1945. 14. G r i f f i t h , B.G. Effect of indolbutyric acid, i n -doleacetic acid, and alpha napthalene-acetic acid on rooting of cuttings of Douglas f i r and Sitka spruce. Journ. Forestry _3J$: 496-501. 1940. 15. Gwynne-Vaughan, H.C.I., and B. Barnes. The structure and development of the fungi. The Macmillan Co. New York. (Univ. Press, Cambridge, England.) 1927. 16. Henry, A., and M. G. Flood The Douglas f i r . Proc. Royal Irish Acad. 25.: 67-92. 1920. 17 Die Douglasiennadelschutte und die Moglich-keit ihrer Bekampfung. Deut. Dendrol. Gesell. Mitt. 4Jt' 294-304. 1932. 21 18 Zur Biologie der Douglasiennadelschiitte. Ztschr. F. Forstw. u. Jagdw. 6/j.: 68O-693. 1932. 19. Liese, J. Die Douglasienrassen und ihre Anfalligkeit gegeniiber der Douglasiennadelschiitte (Rhabdocline pseudotsugae). Deut. Dendrol. Gesell. Mitt. 259-264. 1936. 20. Newton, Wm., and C. J. Lines. The rooting of Cypress and Rose cuttings as influenced by Arasan, Fermate, and Spergon, and each fungicide in combination with naphthalene acetic acid. Scientific Agriculture 28: 574-576. 1948. 21. Peace, T. R. The variation of Douglas f i r in i t s native habitat (Pseudotsugae t a x i f o l i a B r i t . syn. P. douglasii Carr.) Forestry 22: 45-61. 1948. 22. Roe, A. L. What caused "Blight" on Christmas trees in the Northern Rockies in 1947. Northern Rocky Mountain Forest and Range Expt. Sta. Research Note 65. 1948. 23. Rohde, T. Das Vordringen der Rhabdocline-Schutte in Deutschland. Forstarchiv 8: 247-249. 1932. 24 Die Folgen des Rhabdocline-Befalls in deutschen Douglasienbestanden. Forstarchiv 8: 317-326. 1932. 22 25. Sowder, A.M. Christmas trees - the industry. U. S. Dept. Agr. Yearbook of Agriculture. 1949. 26. Sydow, H. Ein Beitrag zur Kenntnis der P i l f l o r a Nordamerikas, insbesondere der Nordwestlichen Staaten. Ann. Mycol. 20: 17S-218. 1922. 27 . Tubeuf, C.von. Rhabdocline-Erkrankung an der Doug-' lasie und ihre Bekampfung. Ztschr. f. Pflanzenkrank. 4_2: 417-426. 1932. 2 8 . Van Vloten, H. Rhabdocline Pseudotsugae Sydow, oorzaak eener ziekte van Douglasspar. (German resume.) Proefschrift, Landbouwho-ogeschool te Waganingen. 168 pp. 1932. 29; Wagener, W.W., T. W. Childs, and J.W. Kimmey. Notes on some foliage diseases of forest trees on the'Pacific slope. U. S. Dept. Agr. Plant Dis. Rptr. 195-197. 1949 . 3 0 . Waldie, R.A. A study of Rhabdocline Pseudotsugae Sydow and an a l l i e d imperfect form Rhab-dogloeum pseudotsugae Sydow in Southwestern British Columbia. A thesis submitted for the Degree of Bachelor of Arts. University of British Columbia. 1945. 31. Weir, J.R. A needle blight of Douglas f i r . Jour. Agr. Res. 10: 99-103 . 1917 . 23 . 32 . Wellner, C A . and A. L. Roe. Management p r a c t i c e s for Christmas t r e e p r o d u c t i o n . Northern Rocky Mountain F o r e s t and Range Expt. S t a . Paper 9 . 1947. 33 . W i l s o n , M., and Mary J . F. Wils o n . Rhabdocline pseudotsugae Syd.: A new d i s e a s e o f the Douglas f i r i n S c o t l a n d . Roy. Sc o t . Arbor. Soc. Trans. *£: 3 7 - 4 0 . 1926. 34 . W i l s o n , M. D e f o l i a t i o n o f the Douglas f i r . Garden C h r o n i c l e 81: 323-324. 1927. 35 . Zentmyer, G.A., W.C. Snyder, and H.N. Hansen. Use of n a t u r a l media f o r i n d u c i n g s p o r u l a t -i o n i n f u n g i . Phytopathology 40: 971 . 1950. TABLE I LIST OF RHABDOGLOEUM PSEUDOTSUGAE COLLECTIONS IN BRITISH COLUMBIA WITH AVERAGE SPORE SIZES OBTAINED FROM EACH, AND A RECORD OF THOSE COLLECTIONS SHOWING AN ASSOCIATION WITH RHABDOCLINE PSEUDOTSUGAE L o c a l i t y o f C o l l e c t i o n s Date o f C o l l e c t i o n Occurrence of Rhabdocline i n A s s o c i a t i o n w i t h Rhabdogloeum Average C o n i d i a l (1) Measurements u VANCOUVER ISLAND Lake Cowichan May 6,1944 Present 5.3 X 16.7 Sooke Absent 4.9 X 14.5 Langford Absent 5.4 X 15.1 INTERIOR Spences B r i d g e June 23,1949 Present 6.6 X 14.4 Kamloops May 5,1950 Absent 5.7 X 15.6 W i n f i e l d May 16,1950 Present 5.8 X 14.3 Lemon Creek June 5,1950 Absent 6.3 X 16.4 Cranbrook J u l y 6,1950. Present 6.3 X 15.3 Invemere J u l y 7,1950 Present 6.1 X 15.4 (1) The spore s i z e s r e c o r d e d by Sydow i n the o r i g i n a l d e s c r i p t i o n o f Rhabdogloeum pseudotsugae were 15-21u x 4-5u. The spore s i z e s recorded by E l l i s and G i l l f o r Rhabdogloeum hypophyllum were 2.2-3.7u x 6 . 7 - l l . l u . F i g u r e 1. L e s i o n s of Rhabdocline pseudotsugae on two-year-old l e a v e s of Douglas f i r 7L t Figure 2 . Photomicrograph of a cross-section of a Douglas f i r leaf with an acervulus of Rhabdogloeum pseudotsugae on the upper surface and an apothecium of Rhabdocline  pseudotsugae on the lower surface, X approx. 40 Figure 3. Tissue cultures of lesions typical of those caused by Rhabdogloeum pseudotsugae on malt agar at the end of eight weeks (left) and five weeks (right). The agar has turned an olive-green colour in the eight week old culture and has remained unchanged in the five week old culture. Figure 4. Mycelial growth at room temperature from a lesion typical of those caused by Rhabdogloeum pseudotsugae on malt agar at the end of four weeks. X 2/3 Figure 5. Mycelial growth at room temperature from a lesion typical of those caused by Rhabdocline pseudotsugae on malt agar at the end of four weeks. X 2/3 F i g u r e 6 . Photomicrograph of m i c r o c o n i d i a and macroconidia from a t i s s u e c u l t u r e of a l e s i o n t y p i c a l of those caused by Rhab-d o c l i n e pseudotsugae. X approx. 1050 F i g u r e 7» A camera-lucida drawing of spores o c c u r r i n g i n t i s s u e c u l t u r e s of l e s i o n s t y p i c a l of those caused by Rhabdocline pseudotsugae. X approx. 1065 3 o F i g u r e 8 . A photomicrograph of m i c r o c o n i d i o p h o r e s from a t i s s u e c u l t u r e of a l e s i o n t y p i c a l of those caused 'by Rhabdocline pseudotsugae. X approx. 1050 F i g u r e 9« A camera-lucida drawing o f m i c r o c o n i d i o p h o r e s from t i s s u e c u l t u r e s of l e s i o n s t y p i c a l of those caused by "Rhabdocline pseudotsugae. X approx. 1050 Figure 10. A photomicrograph of macroconidiophores from a tissue culture of a lesion typical of those caused by Rhabdocline pseudot-sugae . X approx. 1050 Figure 11. A camera-lucida drawing of macroconidio-phores from tissue cultures of lesions typical of those caused by Rhabdocline  pseudotsugae. X approx. 1050 

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