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A study of certain fungi associated with dwarf mistletoe infections and their relation to the moisture… Baranyay, Joseph Alexander 1961

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A STUDY OF CERTAIN FUNGI ASSOCIATED WITH DWARF MISTLETOE INFECTIONS AND THEIR RELATION TO THE MOISTURE CONTENT OF WESTERN HEMLOCK by JOSEPH ALEXANDER BARANYAY Fo r e s t Engineer,.Sopron U n i v e r s i t y , Hungary, 1944 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF M.A. i n the Department of B i o l o g y and Botany e accept t h i s t h e s i s as conforming to the r e q u i r e d standard. THE UNIVERSITY OF BRITISH COLUMBIA December, 1961 In presenting t h i s t h e s i s i n p a r t i a l f u l f i l m e n t o f the requirements f o r an advanced degree a t the U n i v e r s i t y of B r i t i s h Columbia, I agree t h a t the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r reference and study. I f u r t h e r agree that permission f o r e xtensive copying of t h i s t h e s i s f o r s c h o l a r l y purposes may be granted by the Head of my Department o r by h i s r e p r e s e n t a t i v e s . I t i s understood t h a t copying or p u b l i c a t i o n of t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l not be allowed without my w r i t t e n permission. Department The U n i v e r s i t y of B r i t i s h Columbia, Vancouver 8, Canada. - i i -ABSTRACT Studies on the seasonal changes i n the moisture content of western hemlock Tsuga h e t e r o p h y l l a (Raf.) Sargent, demonstrated two moisture minima, one i n the s p r i n g and one i n the f a l l , and two maxima, one i n the s p r i n g and the second i n the w i n t e r . S i g n i f i c a n t d i f f e r e n c e s were noted f o r both bark and wood moistures between good and poor s i t e s , between seasons of the year and f o r the i n t e r a c t i o n between s i t e and seasons o f the y e a r . The r e l a t i v e t u r g i d i t y of bark from the good s i t e was below the 80 per cent l e v e l f o r 95 days through an e n t i r e y e a r . On the poor s i t e i t remained under t h i s c r i t i c a l value f o r 123 days of the 8 months o b s e r v a t i o n p e r i o d . Dwarf m i s t l e t o e d i d not appear to a f f e c t the water economy of the p o r t i o n of branches t h a t had not been invaded by the endophytic system. However the p a r a s i t e produced moisture s t r e s s i n the bark a t the c e n t r a l area of i n f e c t i o n s . An i n v e s t i g a t i o n of the f u n g i that were a s s o c i a t e d w i t h cankered areas o f dwarf m i s t l e t o e i n f e c t i o n s r e v e a l e d the occurrence of twelve d i f f e r e n t species of f u n g i . Nine of these were Ascomycetes and three were Fungi Imperfect!. There were two undescribed species, and one s p e c i e s , M y t i l i d i o n decipiens K a r s t . had not been reported p r e v i o u s l y f o r N 0 r t h America. P r e l i m i n a r y t e s t s of the p a r a s i t i s m of seven species i n d i c a t e d t h a t one, a member of the Fungi Imperfect!, was m i l d l y p a r a s i t i c . - i i i -ACKNOWLEDGMENTS The author wishes to express h i s acknowledgment to Dr. J.E. B i e r o f the Department of B i o l o g y and Botany, U n i v e r s i t y of B r i t i s h Columbia, f o r h i s t e c h n i c a l guidance, a s s i s t a n c e and encouragement throughout the study and to Dr. R. Bandoni who has been most h e l p f u l w i t h h i s guidance i n the m y c o l o g i c a l aspects o f the work. Sincere thanks are extended to members of the F o r e s t Entomology and Pathology Laboratory, Calgary, who a s s i s t e d i n v a r i o u s ways. Dr. G.P. Thomas, o f f i c e r - i n - c h a r g e , and Dr. J.C. Hopkins have been most h e l p f u l w i t h t h e i r guidance i n the p r e p a r a t i o n of the manuscript and Dr. R.F. Shepherd f o r h i s guidance i n the s t a t i s t i c a l a n a l y s i s o f the data. The h e l p of a l l others who a s s i s t e d i n the various phases of the work i s g r a t e f u l l y acknowledged. - iv -TABLE OF CONTENTS Page ABSTRACT I . INTRODUCTION 1 I I . LITERATURE REVIEW Water R e l a t i o n s h i p s o f Hemlock 2 Dwarf M i s t l e t o e on Western Hemlock 5 Fungi on Western Hemlock 13 I I I . METHODS OF INVESTIGATION Host Moisture Determinations 14 C u l t u r a l S t u d i e s . . . 19 I n o c u l a t i o n Methods .............................. 20 IV. RESULTS OF INVESTIGATION Seasonal Changes of Moisture Content i n Western Hemlock 21 E f f e c t o f S i t e on Moisture Content o f Western Hemlock 25 E f f e c t o f Dwarf M i s t l e t o e on the Water Economy of I n f e c t e d Western Hemlock Branches ............. 25 In v a s i o n by Fungi of Dwarf M i s t l e t o e I n f e c t i o n s i n Western Hemlock 30 Pathogenecity o f Fungi I s o l a t e d from Dwarf M i s t l e t o e I n f e c t e d Branches of Western Hemlock ... 48 V. DISCUSSION 50 VI. CONCLUSIONS 52 VI I . LITERATURE CITED 55 V I I I . ILLUSTRATIONS F i g u r e .1. Ripe dwarf m i s t l e t o e f r u i t s , x 8 6 2. Dwarf m i s t l e t o e seed. Approx. x 100 ........ 7 3. Dwarf m i s t l e t o e seed a t the moment of e j e c t i o n 8 - V -Page ILLUSTRATIONS (Continued) Figure 4. Endophytic system of dwarf mistletoe, x 25 10 5. . Witches broom on western hemlock caused by dwarf mistletoe. x .§ 11 6. Taking bark samples with cork borer 17 7. P r e c i s i o n balance for weighing samples i n moisture determinations 17 8. Saturation of samples . 18 9. Samples for moisture determination i n drying oven 18 10. Taking wood samples 19 11. R e l a t i v e t u r g i d i t i e s of western hemlock bark and wood, dry-weight moisture per cent of bark, d a i l y p r e c i p i t a t i o n , and d a i l y a i r temperatures, Un i v e r s i t y Campus Forest, Vancouver, B.C 23 12. Rela t i v e t u r g i d i t i e s of western hemlock bark and wood, d a i l y p r e c i p i t a t i o n , and d a i l y a i r temperatures, U n i v e r s i t y Research Forest, near Haney, B.C 24 13. Moisture content determination for dwarf mistletoe i n f e c t e d western hemlock branches 29 14. Branch canker on western hemlock, showing the margin of the canker and the cup-like dead bark, x J 33 15. Longitudinal section of branch canker showing r e s i n i n f i l t r a t i o n , x | 33 16. Cross s e c t i o n of a swelling, showing the canker (without bark) and the advanced stage of heartwood i n f e c t i o n , x 1 33 17. Apothecium of Dasyscypha a g a s s i z i i showing the yellow hymenium, and the margin with white excipular h a i r s , x 25 33 - v i -Page ILLUSTRATIONS (Continued) F i g u r e 18. Apothecium of D u r a n d i e l l a tsugae. x 350 ........... 37 19. A c l u s t e r o f apothecia of Helotium columbianum i n d i f f e r e n t stages o f development, x 450 ., 37 20. D. tsugae. a. A s c i w i t h ascospores and paraphyses. b. Ascospores 38 21. D. a g a s s i z i i . M a l t agar c u l t u r e , s i x weeks o l d 39 22. D. tsugae. Freehand s e c t i o n of the apothecium, showing the arrangement o f a s c i , epithecium, t i s s u e of the hypothecium, b l a c k excipulum, and the c o l l a r on the l e f t s i d e . Approx. x 50 39 23. D. tsugae. M a l t agar c u l t u r e , s i x weeks o l d 39 24. D. tsugae. Sickle-shaped c o n i d i a . x 800 39 25. H. columbianum. a. A s c i w i t h ascospores and paraphyses. b. Ascospores 42 26. H. columbianum. Freehand s e c t i o n of the apothecium, showing the arrangement of a s c i , subhymenium, t i s s u e of the hyptheclum, and the somewhat darker excipulum. x 150 43 27. H. columbianum. M a l t agar c u l t u r e , s i x weeks o l d 43 28. Lophium mytilinum. Malt agar c u l t u r e , s i x weeks o l d ......................................... 43 29. L. mytilinum. Hyphae w i t h bulbous s w e l l i n g s , x 800 43 30. Epicoccum sp. M a l t agar c u l t u r e , s i x weeks o l d 47 31. Epicoccum sp. Hyphae with c o n i d i a . x 550 ........ 47 32. P e s t a l o t i a sp. Malt agar c u l t u r e , s i x weeks o l d 47 - v i i -Page ILLUSTRATIONS (Continued) Figure 33. P e s t a l o t i a sp. Conidiospores with appendage, x 1000 47 34. Results of inoculations of western hemlock branches with P e s t a l o t i a sp 49 IX. TABLES Table I. Analyses of variance for " s i t e " and "seasons" i n r e l a t i o n to observed r e l a t i v e t u r g i d i t i e s .... 26 X. APPENDICES Appendix A. F l o r o - e c o l o g i c a l d e s c r i p t i o n of areas sampled i n an i n v e s t i g a t i o n of Arceuthobium  campilopodum G i l l f. tsugensis on western hemlock. Appendix B. Map of area sampled at the U n i v e r s i t y Research Forest. Appendix C. Relative t u r g i d i t y values of bark and wood, sampled i n good and poor s i t e s at two-week i n t e r v a l s . - 1 -INTRODUCTION Western hemlock, Tsuga h e t e r o p h y i l a (Raf.) Sargent Is some-times adversely a f f e c t e d by dwarf m i s t l e t o e , Arceuthobium campylopodum G i l l forma t s u g e n s i s . S e r i o u s l y a f f e c t e d trees produce hypertrophies, mostly on branches but sometimes on stems, i n the form of s w e l l i n g s , witches' brooms and b u r l s . C h a r a c t e r i s t i c o f many of these hyper-t r o p h i e s i s a c e n t r a l l y l o c a t e d canker o f fungus o r i g i n t h a t i n v o l v e s mostly the bark but sometimes the u n d e r l y i n g wood. C e r t a i n of these cankers g i r d l e and k i l l the m i s t l e t o e i n f e c t e d branches. The reason f o r the formation of cankers on branches and stems that are i n f e c t e d by dwarf m i s t l e t o e i s not known, whether they r e s u l t d i r e c t l y from the a c t i v i t i e s o f dwarf m i s t l e t o e or from the a c t i v i t i e s o f secondary pathogens. I t has been demonstrated w i t h some bark i n h a b i t i n g pathogens, and w i t h some ho s t s , t h a t the amount of moisture that obtains i n the bark a t d i f f e r e n t seasons of the year can have a pronounced e f f e c t upon the a b i l i t y of pathogens to s u c c e s s f u l l y c o l o n i z e t h e i r h o s t . ( B i e r 1959). An i n v e s t i g a t i o n was made of r e p r e s e n t a t i v e stands of western hemlock that were i n f e c t e d by dwarf m i s t l e t o e and which e x h i b i t e d t y p i c a l cankers to determine, ( l ) the e f f e c t o f dwarf m i s t l e t o e i n f e c t i o n on the water economy of western hemlock, (2) the r e l a t i o n s h i p between the water economy and the incidence o f secondary pathogens i n m i s t l e t o e i n f e c t i o n s . - 2 -Both of the investigations were ca r r i e d out at selected points i n the Campus Forest of the U n i v e r s i t y of B r i t i s h Columbia at Vancouver, and i n the U n i v e r s i t y Research Forest near Haney, B.C. The laboratory phases of the work were done at the U n i v e r s i t y of B r i t i s h Columbia Department of Biology and Botany, i n Vancouver. LITERATURE REVIEW Water Relationships of Hemlock A l l changes i n tree growth are influenced by the acceleration or retardation of p h y s i o l o g i c a l processes, which i n turn are influenced by environmental f a c t o r s , one of the most important of these i s water. In most environments tree growth i s l i m i t e d by the available water supply more than by any other factor with the possible exception of temperature. According to Kozlowski 1958, i n many c l i m a t i c zones water acts as a l i m i t i n g f a c t o r . Only r a r e l y are s o i l moisture supplies at optimal l e v e l s during the growing season and i n most of the world tremendous losses i n growth r e s u l t each year because of s o i l moisture d e f i c i t s . I t i s true that the growth of trees i s conditioned by complex environments and that water i s only one factor i n t h i s environ-ment, but the component factors are i n t e r r e l a t e d and i n t e r a c t i n g i n t h e i r e f f e c t s ( B i l l i n g s 1952, Kozlowski 1955). - 3 -P r a c t i c a l l y a l l of the water absorbed by roots i s subsequently t r a n s p i r e d through the stomata of l e a v e s . I n d a y l i g h t hours the r a t e o f water l o s s exceeds the ra t e o f water uptake i n most p l a n t s . This causes an i n t e r n a l water d e f i c i t . I t i s not u n t i l the l a t e hours of the day that a b s o r p t i o n exceeds t r a n s p i r a t i o n , a t which time the water d e f i c i t i s c o r r e c t e d . The development of i n t e r n a l water d e f i c i t s seems to occur d a i l y i n most tre e s during the growing season (Subramanian and Saraswathi - Devi, 1959). I n a d d i t i o n to d i u r n a l v a r i a t i o n s i n the water content of t r e e s there i s also a seasonal v a r i a t i o n . The l a t t e r r e s u l t s from the maturation of t i s s u e s and seasonal d i f f e r e n c e s i n the r a t e s o f absorption and t r a n s p i r a t i o n . E a r l y s t u d i e s on the seasonal changes i n moisture content were made by H a r t i g (1868), who found t h a t the t o t a l water content o f coniferous t r e e s was l e a s t i n the summer and greatest i n the w i n t e r . Geleznow (1876) noted a drop i n the moisture content of hard-woods i n R u s s i a i n the summer months, although the change from winter to summer i n Pinus s y l v e s t r i s L i n n , noted by him was only minimal. Gibbs (1930-1958) has made d e t a i l e d i n v e s t i g a t i o n s on the seasonal changes i n the moisture content of some Canadian f o r e s t t r e e s . According to him the p a t t e r n o f seasonal water change i s t h a t the wood and bark u s u a l l y a t t a i n a maximum moisture content i n the s p r i n g , a f t e r which i t decreases i n the summer and e a r l y f a l l , the minimum moisture l e v e l being reached at the end of the growing season. He found t h a t moisture l e v e l s i n creased f o r a short p e r i o d f o l l o w i n g the c e s s a t i o n _ 4 -of growth, but t h a t during the winter the moisture content again d e c l i n e d . According to Gibbs there are t h e r e f o r e two maxima of moisture content i n s p r i n g and f a l l and two minima i n l a t e summer and w i n t e r . Gibbs i n v e s t i g a t e d the water r e l a t i o n s o f eastern hemlock (Tsuga canadensis Carr.) f o r a p e r i o d of seven years. He s t u d i e d the heartwood and sapwood of b u t t s , middles, and t o p s . Considerable v a r i a t i o n occurred among i n d i v i d u a l t r e e s , but a l l e x h i b i t e d a s i m i l a r seasonal p a t t e r n of sapwood moisture content which was not r e f l e c t e d i n the heartwood. The sapwood showed a very marked water l o s s In w i n t e r , a summer maximum i n June and J u l y and a low water content at the end of the summer and a steady increase from September to November or December. Wet and dry patches occurred i n the heartwood of hemlock. The wet patches were f u l l of water and the dry contained l i t t l e more water than was r e q u i r e d to saturate the c e l l w a l l . Gibbs work a p p l i e d to eastern hemlock and no i n v e s t i g a t i o n s of t h i s type have been reported f o r western hemlock, Tsuga h e t e r o p h y l l a (Raf.) Sargent. - 5 -Dwarf M i s t l e t o e on Western Hemlock Dwarf m i s t l e t o e , Arceuthobium campylopodum G i l l forma ts u g e n s i s , i s an important pathogen of western hemlock. I t i s one of e i g h t species of the genus Arceuthobium, f i v e o c c u r r i n g i n North America but only one o f which i s known to i n f e c t western hemlock. The western hemlock dwarf m i s t l e t o e stem i s segmented, about 4 to 5 inches l o n g . The s c a l e - l i k e leaves and stems c o n t a i n very l i t t l e c h l o r o p h y l l w i t h which to c a r r y out photosynthesis (Freeland 1943). The p l a n t t h e r e f o r e depends upon the host not only f o r water, but a l s o f o r the greater parts o f i t s requirement f o r elaborated food. S e v e r a l c o n f l i c t i n g views have been expressed on the extent of the p a r a s i t i s m of m i s t l e t o e . I t seems t h a t the r e l a t i o n -s h i p may be one of t o t a l p a r a s i t i s m under c e r t a i n c o n d i t i o n s and one o f semiparasitism under o t h e r s . I f a e r i a l p l a n t s are developed the r e l a t i o n s h i p i s probably s e m i p a r a s i t i c because the a e r i a l p l a n t c a r r i e s out some photosynthesis. The c o l o r o f the a e r i a l p l a n t v a r i e s from purplish-brown, y e l l o w i s h - g r e e n to green. Male and female p l a n t s may be produced on the same t r e e but on separate i n f e c t i o n s (Buckland and Marples 1952). Fl o w e r i n g time extends from s p r i n g u n t i l f a l l but most fl o w e r s are formed i n August and September. According to G i l l (1954) A. campylopodum may produce s e v e r a l f l o w e r crops on one shoot. The l o n g e v i t y of shoots has not y e t been - 6 -s t u d i e d i n d e t a i l . The only e x t e r n a l t r a c e of dead p l a n t s are basal cups that are embedded i n the bark of the host. The f r u i t i f l e s h y , o v a l i n shape and contains a s i n g l e seed. I t i s attached to the shoot by a p e d i c e l ( F i g . 1). F i g . 1. Ripe dwarf m i s t l e t o e f r u i t s . X 8 The! proximal end of the seed coat c o n s i s t s of t h i c k - w a l l e d c e l l s that are arranged i n a dome-like formation, which on d r y i n g appears as a dark brown cup. The d i s t a l end of the seed coat has a broad t a i l t hat contains v i s c i n ( F i g . 2 ) . F i g . 2. Dwarf m i s t l e t o e seed. Approx. X 100 The v i s c i n absorbs water at maturity, l e a d i n g to an increase i n i n t e r n a l pressure. An a b s c i s s i o n l a y e r develops between the t i p of the p e d i c e l and the base of the f r u i t . As soon as the f r u i t separates from the p e d i c e l , because of i n t e r n a l p r e s s u r e s , the seed i s e j e c t e d i n t o the a i r ( F i g . 3 ) . When the f r u i t i s r i p e the p e d i c e l i s elongated and recurved so t h a t the t a i l of the seed p o i n t s downward ( G i l l 1935). The I n t e r n a l f o r c e i s s u f f i c i e n t to p r o p e l the seed f o r a d i s t a n c e o f 30 f e e t . - 8 -F i g . 3. Dwarf m i s t l e t o e seed a t the moment of e j e c t i o n . Apart from t h i s there i s l i t t l e o f a c t u a l knowledge o f how dwarf m i s t l e t o e seeds are disseminated. The seed c a r r i e s a s m a l l amount of v i s c i n , which has an important r o l e i n the attachment of the seed to the s u b t r a t e . When the seed reaches the sub t r a t e the v i s c i n c e l l s are moist. R a i n or dew may g r e a t l y expand these c e l l s which serve as the water r e s e r v o i r s o f the germinating seeds. The d r y i n g out of the v i s c i n mass al s o has an important r e s u l t , the a x i s of the seed i s s l i g h t l y s h i f t e d i n such a way as to aim the r a d i c u l a r apex o b l i q u e l y towards the substrate ( K u i j t 1960). - 9 -Needles o f the host are the primary i n t e r c e p t o r s of seeds as Roth observed on ponderosa pine (1959). The numerous and w i d e l y spreading needles o f f e r a t a r g e t of great area and because of t h e i r i n d i v i d u a l f l e x i b i l i t y they are i d e a l l y s u i t e d to seed i n t e r c e p t i o n . The t r a n s f e r o f the seeds from the needles to the s u s c e p t i b l e stem becomes necessary. The v i s c i n c a r r i e d by the seed absorbs water, becomes s l i p p e r y and the seeds begin to s l i d e along the needles. Seeds lodge mostly at the base of the needle which are f a v o u r i t e places of entry i n t o the host. The seeds are e x p e l l e d i n the f a l l of the year, and germination i s u s u a l l y delayed u n t i l the f o l l o w i n g s p r i n g , but may occur immediately ( K u i j t 1955). L i g h t and water are e s s e n t i a l c o n d i t i o n s f o r germination. The s e e d l i n g grows toward the surface o f the host branch u n t i l i t s t i p reaches the base of a needle. Here an h a u s t o r i a l d i s c i s formed, the sharp edges of which remain meristematic ( K u i j t 1960). The p e n e t r a t i o n of the epidermis and co r t e x i s not c l e a r l y understood. The endophytic system of dwarf m i s t l e t o e s c o n s i s t o f a c o r t i c a l and a s i n k e r system according to t h e i r p o s i t i o n , d i r e c t i o n of growth, form and i n t e r n a l s t r u c t u r e . The c o r t i c a l system c o n s i s t s o f l o n g i t u d i n a l strands s i t u a t e d near the phloem area of the host branch ( K u i j t 1960). The l o n g i t u d i n a l strands grow i n both d i r e c t i o n s , towards the t i p and base ( K u i j t 1955). The s i n k e r system a r i s e s from the c o r t i c a l strands and can be t r a c e d i n the phloem, cambium, and xylem ( F i g . 4 ) . According to G i l l (1935) the s i n k e r s are unable to penetrate the wood, but they are embedded by the y e a r l y growth. This - 10 -hypothesis has been challenged r e c e n t l y by K u i j t (1960) who b e l i e v e s that s i n k e r s cannot become p a s s i v e l y embedded u n t i l they have pene-t r a t e d the cambium and have a c t u a l l y anchored themselves i n mature xylem. I f p e n e t r a t i o n can proceed to t h i s extent some c e n t r i p e t a l expansion may take place i n t o the wood. F i g . 4. Endophytic system o f dwarf m i s t l e t o e . X 25 a. C o r t i c a l strand b. S i n k e r s There are two known d i s t r i b u t i o n p a t t e r n s o f endophytic systems, l o c a l i z e d and d i f f u s e (Cohen 1954, K u i j t 1960). I n the l o c a l i z e d p a t t e r n a f u s i f o r m s w e l l i n g i s produced, w i t h a e r i a l p l a n t s on the margin of the advancing i n f e c t i o n , and the m i s t l e t o e i s no longer r e p r o d u c t i v e l y a c t i v e i n the c e n t r a l n e c r o t i c area ( K u i j t 1960). - 11 -The d i f f u s e p a t t e r n i s a s s o c i a t e d with a type of brooming which v a r i e s according to the host and species of dwarf m i s t l e t o e . On western hemlock the growth of title endophytic system lags behind t h a t o f the shoot apices o f the host ( K u i j t 1960). This produces a v e r y s w o l l e n main branch and a l s o secondary branches t h a t are u s u a l l y s w o l l e n a t the base. The r e s u l t i n g brooms are compact ( F i g . 5) and bear s c a t t e r e d a e r i a l p l a n t s , u s u a l l y at the t i p s o f s w e l l i n g s . F i g . 5. Witches broom on western hemlock caused by dwarf m i s t l e t o e . X 3: - 12 -Trunk i n f e c t i o n s of western hemlock r e s u l t i n hy p e r t r o p h i e s , such as b u r l s , but do not cause brooms. Two types o f trunk b u r l s are known, the f i r s t r e s u l t i n g from d i r e c t i n f e c t i o n and the second at the base of i n f e c t e d branches ( K o r s t i a n and Long, 1922). K o r s t i a n and Long (1922), Rankin (1929), P e r r y (1923), K u i j t (1955, 1960) and P i e r c e (1960) s t a t e that the s w e l l i n g s are centres where abnormal amounts of food m a t e r i a l s are s t o r e d . The a p p r o p r i a t i o n of food by the p a r a s i t e r e s u l t s i n an unbalanced r e l a t i o n between the crown and the root system of the host, the gradual r e d u c t i o n of the root system and a s s i m i l a t o r y l e a f surfaces o f the host causes a f a l l i n g of the annual increment and lower v i t a l i t y (Weir 1918). Old witches brooms may be s e v e r a l hundreds of pounds i n weight, and because of t h i s the supporting branches are sometimes t h i c k e r than the main stem ( K o r s t i a n and Long, 1922) . The weight of the brooms i s o f t e n g r e a t l y i ncreased by the accumulation of dead needles and snow or other forms of water. Consequently they are r e a d i l y broken o f f by winds. The r e s u l t a n t open wounds o f f e r e x c e l l e n t entry p o i n t s f o r f u n g i and the d r i e d f a l l e n brooms increase the f i r e hazard (Boyce 1948). According to Wellwood (1956) stem s w e l l i n g s occur only i n l o c a l i z e d areas but have a marked e f f e c t on the p r o p e r t i e s o f the s u r -rounding wood, causing abnormal g r a i n and spongy or p i t c h soaked wood. The bark of b u r l s d i e s soon, causing open wounds. There i s l i t t l e doubt t h a t dwarf m i s t l e t o e reduces the q u a l i t y and q u a n t i t y of merchantable timber. Lumber production from a t r e e can be reduced by 30-50 per cent. - 13 -The witches brooms cause heavier than normal limbs and r e s u l t i n g large knots that are extremely hard and dense (Korstian and Long, 1922 and G i l l , 1957). Growth i s eccentric and i n heavily i n f e c t e d trees the s p e c i f i c gravity of the wood i s less than i n healthy trees. T h i s r e s u l t s i n lowered strength and lowered pulp y i e l d s (Wellwood 1956). It i s not known whether dwarf mistletoe k i l l s western hemlock d i r e c t l y . The l i f e c ycle, anatomy and. morphology of dwarf mistletoe i s reasonably w e l l known. As a primary parasite i t may weaken i t s host p h y s i o l o g i c a l l y . However l i t t l e i s known of the influence of the p a r a s i t e on the water economy of the host, and of possible e f f e c t s on s u s c e p t i b i l i t y of the host to pathogenic fungi. Fungi on Western Hemlock Most of the research on the fungi that are associated with western hemlock has dealt with those that cause decay. A l l e n (1902) mentioned that Fomes p i n i (Thore) Lloyd, Polyporus s c h w e i n i t z i i Fr. and Echjnodontium tinctorium E. and E. occurred on western hemlock. Weir and Hubert (1918) reported that E. tinctorium was responsible for most of the decay i n western hemlock i n northern Idaho. According to Foster and Foster (1951) the most important decay fungi that attack western hemlock i n B r i t i s h Columbia are Fomes p i n i c o l a (Sw.) Ske., P o r i a  subacida (Pk.) Sacc., Fomes annosus (Fr.) Cke., A r m j l l a r i a mellea Vahl. ex Fr., Stereum abietinum Pers. a Fomes p i n i (Thore) Lloyd, Polyporus  sulphureus B u l l , ex F r . , P o r i a tsugina (Murr.) Sacc. and T r o f f . , and - 14 -Echinodontium tinctorium E. and E. The r e l a t i v e importance of these fungi varies with l o c a t i o n , E. tinctorium does not occur i n western hemlock on the Queen Charlotte Islands but 60 per cent of the loss through decay i n t h i s species i n the Big Bend region of B r i t i s h Columbia i s a t t r i b u t e d to t h i s fungus (Foster and Craig, 1950). Hepting and Kimmey 1949, reported that mistletoed knots and burls were the most important l o c i for i n f e c t i o n by decay fungi i n western hemlock. Englerth 1942, observed that Fomes h a r t i g i i A l l e s c h . and Fomes applanatus (Pers.) G i l l . , were the most common species i n f e c t i n g western hemlock through cankers of o l d mistletoe b u r l s . In the absence of mistletoe these two fungi were r a r e l y found i n western hemlock. In the trees dissected 18.3 per cent of the i n f e c t i o n s occurred through eit h e r mistletoed limbs or b u r l s . These i n f e c t i o n s caused 30.9 per cent of the t o t a l rot volume. - 15 -METHODS OF INVESTIGATION Host Moisture Determinations Western hemlocks were sampled at two l o c a l i t i e s : i n the Univ e r s i t y Campus Forest at Vancouver and i n the U n i v e r s i t y Research Forest near Haney. The trees sampled on the Campus Forest were growing i n a good s i t e , those on the Research Forest were growing i n a poor s i t e . F l o r o - e c o l o g i c a l s i t e descriptions of the sample areas are given i n Appendix "A". A map of the sampling area on the Research Forest i s presented as Appendix "B". A t o t a l of 122 branches were cut at two-week i n t e r v a l s i n the period February 21, 1959 to February 10, 1960 from trees on the Campus Forest. Seventy-two branches were cut at two-week i n t e r v a l s on the Research Forest i n the period June 16, 1959 to February 11, 1960. A l l of the branches were cut between 10:00 and 11:00 A.M. to standardize the e f f e c t s of d i u r n a l f l u c t u a t i o n s i n moisture content. The surface of each cut was sealed with shellac to prevent water l o s s . The branches were c a r r i e d to the laboratory f o r water content determinations. A cork borer was used to take bark samples ( F i g . 6). Disks of bark were taken from the upper and lower sides of the branches at the proximal and d i s t a l end of dwarf mistletoe i n f e c t i o n s . These samples were weighed immediately ( f r e s h weight)(Fig. 7) and were transferred to d i s t i l l e d water f o r 24 hours ( F i g . 8). - 16 -Following t h i s they were surface dr i e d on f i l t e r paper and reweighed (saturated weight). They were then oven dri e d at 100°C. for 24 hours ( F i g . 9) and reweighed (dry weight of the saturated sample). Using these data an average value for r e l a t i v e t u r g i d i t y was c a l c u l a t e d f o r each branch according to Wetherley (1949) as follows: Relative t u r g i d i t y = f r e s n weight - dry weight of saturated sample x 100 saturated weight - dry weight of saturated sample _ weight of water i n a sample x 100 weight of water required to saturate the same sample Samples of wood ( F i g . 10) were taken i n a s i m i l a r manner as f o r the bark samples, and r e l a t i v e t u r g i d i t y values were obtained f o r each branch. C u l t u r a l Studies Dwarf mistletoe infected branches with cankers were c o l -l e c t e d i n the Campus Forest and i n the Research Forest between May 1959 and March 1960. C u l t u r i n g of inf e c t e d material was c a r r i e d out i n the following way. The surface of the bark at the advanced margin of the cankers was s t e r i l i z e d with alcohol, and af t e r the removal of outer bark a small piece of inner bark was removed with a s t e r i l e s c a l p e l and placed on malt agar. F i g . 7. P r e c i s i o n balance f o r weighing samples i n moisture determinations. - 18 -F i g . 8. Saturation of samples. F i g . 9. Samples f o r moisture determination i n drying oven. - 19 -Fig. 10. Taking wood samples. - 20 -The f r u i t i n g bodies o f f u n g i , found on or at the c l o s e v i c i n i t y of cankers, were washed w e l l i n running tap water, then i n d i s t i l l e d water. A f t e r d r y i n g , p a r t o f the hymenial l a y e r was removed, broken up and p l a c e d on malt agar. About 4 square mm. was t r a n s f e r r e d from the edge of the colony to a f r e s h commercial malt agar p l a t e . Cultures were kept at room tem-perature which ranged around 25°C. A l l c u l t u r e s were grown i n the l i g h t . I n o c u l a t i o n Methods I n o c u l a t i o n s were made to t e s t the p a r a s i t i s m of seven of the f u n g i t h a t were found c o l o n i z i n g dwarf m i s t l e t o e i n f e c t i o n s . The f u n g i to be l i s t e d were s e l e c t e d on the f o l l o w i n g bases: a. p a r a s i t i s m of the genus already demonstrated, b. data on p a r a s i t i s m o f the genus l a c k i n g , c. f u n g i a s s o c i a t e d w i t h cankered t i s s u e s . Using these c r i t e r i a the f u n g i t e s t e d were Dasyscypha a g a s s i z i i Berk, and C u r t . , C a l i c i o p s i s sp., D u r a n d i e l l a tsugae sp. nov., Helotium  columbianum sp. nov., Lophium mytilinum (Pers.) F r i e s , Epicoccum sp. and P e s t a l o t i a sp. E i g h t s t i c k s , twelve inches l o n g , were cut from h e a l t h y branches o f western hemlock. The surfaces of the cut ends .were se a l e d with a t h i n l a y e r o f p a r a f f i n to prevent the s t i c k s from f a s t dehydration. Four of the s t i c k s measured 8-10 mm. i n diameter and had r e l a t i v e l y t h i n bark, - 21 -the remaining f o u r measured 20-30 mm. i n diameter and had r e l a t i v e l y -t h i c k bark. Two wounds, one to be used f o r i n o c u l a t i o n and the other to serve as a c o n t r o l , were made on each s t i c k by burning an area o f healthy-bark w i t h a hot copper bar. The diameter o f each wound was about 5 mm. Agar plugs o f about the same s i z e , c o n s i s t i n g o f a c t i v e l y growing mycelium o f one o f the s e l e c t e d species were placed i n the wounds. To keep the inoculum moist d u r i n g a two-week p e r i o d moist cotton was placed above and below the wounds and covered w i t h Saran Wrap. Both the c o n t r o l s and i n o c u l a t i o n s were t r e a t e d i n the same way. The i n o c u l a t e d branches were put i n t o a p l a s t i c bag, to maintain humidity, and the bag was placed i n t o a 10°C. chamber. This low temperature served to r e t a r d c a l l u s formation and at the same time to create a favourable c o n d i t i o n f o r the fungus to grow. The Saran Wrap and cotton were removed a f t e r two weeks and the s t i c k s were l e f t to incubate i n the chamber f o r another f o u r weeks. RESULTS OF INVESTIGATION Seasonal Changes o f Moisture Content i n Western Hemlock The r e s u l t s o f the i n v e s t i g a t i o n s i n t o the water content o f western hemlock are presented i n F i g s . 11 and 12. The s p r i n g minimum occurred i n April-May. The r i s e to the s p r i n g maximum which occurred at the end o f June, was sudden and was f o l l o w e d by a gradual decrease to the summer minimum. The summer minimum was extended to e a r l y f a l l on the good s i t e , but on the poor s i t e i t reached i t s lowest - 22 -p o i n t i n the second h a l f of August. The r e f i l l i n g of hemlock was gradual l e a d i n g to a w i n t e r maximum, a f t e r which the moisture l o s s was v e r y marked. The w i n t e r maximum appears to be f u n c t i o n of temperature. I n the Campus F o r e s t , where the cl i m a t e i s m i l d e r , the highest moisture content was measured at the end of January. I n the Research F o r e s t the h i g h e s t w inter moisture was measured on the 19th of November. A sudden drop of moisture was observed l a t e r , which appeared to be r e l a t e d to the decrease i n temperature. From the 24th of November u n t i l the 26th of January the temperature was e i t h e r c l o s e to or below the f r e e z i n g p o i n t , and the d a i l y maximum and minimum were c l o s e together. The d r i e s t p o i n t was reached at the end of a two-week c o l d p e r i o d and an increase i n moisture c o i n c i d e d w i t h a r i s e i n temperature. The same e f f e c t obtained at the Campus F o r e s t on two occasions, November 18 and January 30 to February 13, when the drop i n moisture content of bark c o i n c i d e d w i t h low temperatures. The.amount of d a i l y p r e c i p i t a t i o n d i d not appear to a f f e c t the bark moisture contents to the same extent as temperature. The moisture content of hemlock wood was more h i g h l y v a r i a b l e than f o r hemlock bark, although seasonal v a r i a t i o n s f o r wood s i m i l a r to those f o r bark were observed, p a r t i c u l a r l y f o r the Research F o r e s t . I n the present i n v e s t i g a t i o n i t seems that the changes i n the moisture content of wood were f o l l o w e d about two weeks l a t e r by s i m i l a r changes i n the bark. The amount of water expressed on a dry weight b a s i s can be compared w i t h the r e l a t i v e t u r g i d i t y ( F i g . 11). Relative turgidites of western hemlock bark (solid line) and wood ( long dash two short), dry-weight moisture percent of bark (short dash ),daily precipitation, and daily air temperatures, University Campus Vancouver B.C. Poor Site Daily Precip. Inch. MAX Daily Air temp.F° M , N -Fig. 12. Relative turgidities of western hemlock bark (solid line) and wood ( long dash two short), daily precipitation and air temperatures, University Research Forest,near Haney B.C. - 25 -E f f e c t o f S i t e on Moisture Content of Western Hemlock An i n v e s t i g a t i o n was made of the e f f e c t of s i t e on the moisture content o f western hemlock branches and analyses of variance were used to evaluate c e r t a i n of the data. In t h i s procedure the main f a c t o r s , s i t e , and seasonal changes were analysed, f i r s t alone and then i n com-b i n a t i o n s w i t h each other. Data on the r e l a t i v e t u r g i d i t i e s o f bark and wood are presented i n Table I . The r e s u l t s show s i g n i f i c a n t d i f f e r e n c e s f o r both bark and wood between s i t e s and seasons of the year, and a l s o an i n t e r a c t i o n between s i t e and seasons of the year. Seasonal changes were more pronounced i n the poor s i t e than i n the good s i t e . This i s i l l u s t r a t e d i n F i g s . 11 and 12. In the good s i t e the r e l a t i v e t u r g i d i t y of bark remained below 80 per cent f o r 95 days d u r i n g the year. I n the poor s i t e i t remained below 80 per cent f o r 123 days of the eight-month o b s e r v a t i o n p e r i o d f o r t h i s s i t e . E f f e c t of Dwarf M i s t l e t o e on the Water Economy of I n f e c t e d Western Hemlock Branches. Studies were c a r r i e d out of the i n f l u e n c e of m i s t l e t o e i n f e c t i o n s on the r e l a t i v e t u r g i d i t i e s o f invaded and uninvaded p o r t i o n s of i n f e c t e d branches. The r e l a t i v e t u r g i d i t i e s o f branches w i t h a e r i a l p l a n t s were compared w i t h those f o r branches without a e r i a l p l a n t s . The t u r g i d i t i e s of samples taken from below i n f e c t i o n s were compared w i t h those from above. - 26 -TABLE I. ANALYSES OF VARIANCE FOR "SITE" AND "SEASONS" IN RELATION TO OBSERVED RELATIVE TURGIDITIES 1 Source of v a r i a t i o n Sum of squares Degrees of freedom Mean square Variance r a t i o B a r k S i t e 2,130.843 1 2,130.843 110.9742 Seasonal changes 1,955.480 17 115.028 5.991 2 S i t e x Seasonal changes 4,086.323 17 240.372 12.519 2 Residual 4,377.886 228 19.201 T o t a l 12,550.532 263 W o o d S i t e 2,428.367 1 2,428.367 45.538 2 Seasonal changes 3,468.864 16 216.804 4.066 2 S i t e x Seasonal changes 8,300.891 16 , 518.806 9.729 2 Residual 12,158.337 228 53.326 T o t a l 26,356.459 261 1 Based on rough data shown i n Appendix "C". 2 S i g n i f i c a n t d i f f e r e n c e at 1 per cent l e v e l . - 27 -No s i g n i f i c a n t d i f f e r e n c e s were found e i t h e r between samples with or without a e r i a l p l a n t s , or between samples taken from branches above and below the i n f e c t i o n s . Dwarf m i s t l e t o e d i d not appear to a f f e c t the water economy of those p o r t i o n s o f branches t h a t had not been invaded by the endophytic system. The r e l a t i v e t u r g i d i t i e s o f bark were measured f o r two m i s t l e -toe i n f e c t e d branches, an approximately e i g h t - y e a r - o l d and a f i f t e e n -y e a r - o l d i n f e c t i o n , to detect i f p o s s i b l e moisture content d i f f e r e n c e s i n the bark w i t h i n the swollen p o r t i o n of each branch . The samples were taken from a l l f o u r surfaces of the i n f e c t i o n s . The r e s u l t s are presented i n F i g . 13. The moisture content o f the bark was highest at both t i p s of the s w e l l i n g s ( F i g . 13, b and d) except i n the upper surfaces where maximum moistures obtained at the centres ( c ) . On a l l surfaces of the s w e l l i n g s , except the upper s u r f a c e , the moisture content was lowest i n the middle of the i n f e c t e d area ( F i g . 13, c ) , the o l d e s t i n f e c t e d p o r t i o n of the s w e l l i n g . The i n d i c a t e d moisture patterns of the s w e l l i n g s s t u d i e d , f o l l o w the e a r l i e r observations o f G i l l (1935) and K u i j t (1960) who p o i n t out that the bark i n the c e n t r a l p o r t i o n of dwarf m i s t l e t o e s w e l l i n g s are c h a r a c t e r i s t i c a l l y n e c r o t i c . S i m i l a r p a t t e r n s were found on both the young and o l d branch i n f e c t i o n although the t u r g i d i t y values were d i f f e r e n t . On the y o u n g . i n f e c t i o n only one bark sample produced a r e l a t i v e t u r g i d i t y lower than 80 per cent. The o l d i n f e c t i o n y i e l d e d The approximate age o f i n f e c t i o n was obtained by the determination of length o f s i n k e r s . The annual r i n g s o f wood surrounding the s i n k e r s were counted. - 28 -three areas w i t h values lower than 80 per cent. According to B i e r ' s f i n d i n g s (1959) these r e s u l t s I n d i c a t e t h a t branches w i t h o l d e r i n f e c t i o n s would be more predisposed to fungus i n f e c t i o n s than branches w i t h young i n f e c t i o n s . The l i m i t e d amount of experimentations p o s s i b l e i n t h i s aspect of the study d i d not permit a s u i t a b l e e x p l a n a t i o n of the h i g h r e l a t i v e t u r g i d i t y values measured f o r the " l e f t s i d e " of the o l d e r i n f e c t i o n . F u r t h e r work on the moisture c o n d i t i o n s of the bark of m i s t l e t o e i n f e c t e d branches should perhaps i n c l u d e a c o n s i d e r a t i o n of anatomical d i f f e r e n c e s that may o b t a i n i n the bark. An experiment u s i n g dyes was set up to compare the p a t t e r n of sap f l o w i n h e a l t h y and i n i n f e c t e d branches. A f l a s k c o n t a i n i n g a d i l u t e s o l u t i o n of s a f r a n i n was connected to the cut surface of a severed branch and was l e f t i n p o s i t i o n f o r 48 hours. Three i n f e c t e d and un-i n f e c t e d branches were t r e a t e d i n t h i s way. This experiment i n d i c a t e d t h a t dwarf m i s t l e t o e s i n k e r s do not i n f l u e n c e the f l o w of sap w i t h i n branches. - 29 -lower side upper side left side right side left side right side lower side upper side Fig. 13. EIGHT Y E A R OLD branch infection F I F T E E N Y E A R OLD branch infection 80 70 Moisture content determination for dwarf mistletoe infected western hemlock branches. The samples were taken from four sides of the infections at a, b,c,d,e. Solid line upper, short dash line lower, long and one short dash line left side, long and two short dash line right side bark. - 30 -Invasion of Fungi of Dwarf M i s t l e t o e I n f e c t i o n s i n Western Hemlock An i n v e s t i g a t i o n of the f u n g i t h a t are a s s o c i a t e d w i t h dwarf m i s t l e t o e i n f e c t i o n s was c a r r i e d out over a 10-month p e r i o d from May, 1959 to March, 1960. The m a t e r i a l was c o l l e c t e d i n the U n i v e r s i t y Campus Forest i n Vancouver, and at the U n i v e r s i t y Research F o r e s t i n Haney. I n searching f o r f u n g i on t r e e s i n f e c t e d by dwarf m i s t l e t o e , p a r t i c u l a r a t t e n t i o n was p a i d to the cankered p o r t i o n s o f s w e l l i n g s . S e v e r a l views have been expressed on the o r i g i n of the cankers r e l a t e d to m i s t l e t o e i n f e c t i o n s . K o r s t i a n and Long (1922) s t a t e d t h a t o l d e r s w e l l i n g s may e v e n t u a l l y become n e c r o t i c , and that n e c r o t i c areas are o f t e n accompanied by r e s i n flow. ' According to K u i j t (1955) " r e s i n cankers" are u s u a l l y i n d i c a t i v e of l a r g e areas of r e s i n i n f i l t r a t e d sapwood, the i n f i l t r a t i o n process c o n t i n u i n g u n t i l the f i b r o v a s c u l a r system becomes clogged w i t h r e s i n and the limb i s k i l l e d . The progress o f n e c r o s i s due to the a c t i v i t y of dwarf m i s t l e t o e alone i s u s u a l l y very slow. On the other hand n e c r o t i c areas may serve as seats of i n f e c t i o n f o r bark and wood i n h a b i t i n g f u n g i ( G i l l 1935). I n older stems, where there i s an accumulation of s i n k e r s w i t h i n a r e l a t i v e l y s m a l l area, the s i n k e r s may become so numerous as to push the cambium as i d e . When t h i s occurs cankers may be formed (Cohen 1954). The type of canker observed i n t h i s study occurred t y p i c a l l y on both young and o l d branches. The bark of the branch s p l i t s at the advanced margin of the canker and the dead bark forms a r o o f - l i k e - 31 -s t r u c t u r e above the cankered area ( F i g . 14). The dead bark remains adherent w h i l e the branch i s a l i v e and absorbs and r e t a i n s moisture w e l l . I t t h e r e f o r e forms favourable m i c r o c l i m a t i c c o n d i t i o n s f o r the germination of spores and f o r m y c e l i a l growth. In l o n g i t u d i n a l s e c t i o n cankers u s u a l l y show l a r g e areas of resin-soaked sapwood ( F i g . 15). The sapwood i s u s u a l l y s t a i n e d by d i f f e r e n t f u n g i . Sometimes the u n d e r l y i n g heartwood i s decayed. Since the most advanced stages of decay were always at or near the canker, i t was assumed th a t the f u n g i had entered at t h i s p o i n t ( F i g . 16). Cultures were made from the decayed wood and two species were i d e n t i f i e d as Polyporus adustus ( W i l l d . ) F r . and Trametes v a r i i f o r m i s (Pk.) Pk. A f u r t h e r purpose o f the study was to i d e n t i f y the agents d i r e c t l y r e s p o n s i b l e f o r the formation of cankers, and subsequently r e s p o n s i b l e f o r b r i n g i n g about c o n d i t i o n s favourable f o r the i n v a s i o n of s t a i n and decay f u n g i . 1. Dasyscypha a g a s s i z i i Berk, and Curt. ( F i g s . 17 and 21). The f i r s t apothecium was found i n June 1959. The hymenial l a y e r c o n s i s t e d o nly o f paraphyses u n t i l December and the f i r s t r i p e ascospores were observed i n February. The apothecia were found s c a t t e r e d or s i n g l y , u s u a l l y on the t h i c k dead bark of cankers. The s i z e o f the f r u i t i n g body was somewhat s m a l l e r than given i n the l i t e r a t u r e . An i n t e r e s t i n g f e a t u r e i s t h a t the f r u i t i n g bodies are most abundant and gregarious on dead tr e e s and branches. D. a g a s s i z i i i s e i t h e r s a p r o p h y t i c or weakly p a r a s i t i c , and - 32 -according to Bingham and E r l i c h (1943) i t was found heretofore only on two l i v i n g hosts, Pinus strobus L. infected with the b l i s t e r rust canker, and on weakened Abies balsamea XL.) M i l l . Since no account concerning the culture of this fungus was found i n the l i t e r a t u r e , experiments dealing with c u l t u r a l c h a r a c t e r i s t i c s were c a r r i e d out and showed colonies on malt agar grow slowly, attaining a diameter of 7.5 cm. i n s i x weeks at room temperature. The advancing margin i s s l i g h t l y i r r e g u l a r . The slow spreading mycelium i s at f i r s t white, fine cottony, dense, l a t e r zonate, l i g h t pinkish-buff, to ochreous buff. The reverse i s brownish, ranging from b l a c k i s h at the center of the colony to brown and then to pale yellow at the edges. The mycelium consists of long, s l i g h t l y flexous, septate, branched narrow hyphae, 1.5 - 4.0 u^ i n diameter. Occasionally the hyphae are broader with bulbous swellings up to 7.0 u^ wide. Conidia were not produced within the eight week period. Specimens are deposited i n the herbarium of the Uni v e r s i t y of B r i t i s h Columbia. 2. C a l i c i o p s i s sp. This fungus was found i n association with a canker on both dwarf mistletoe infected branches and on non-infected branches. On the non-infected branches a small, 5-10 mm. long, more or less oval type of canker was formed which d i f f e r e d from the type of canker previously described and found on swellings caused by dwarf mistletoe. I f the same C a l i c i o p s i s species causes both types of cankers, then the difference i n appearance of the canker from the above mentioned, i s possibly due to the d i f f e r e n t anatomical structure of bark tissue on the swelling. - 33 -PLATE I. F i g u r e s 14-17 - 34 -This C a l i c i o p s i s sp. d i f f e r s from C a l i c i o p s i s pseudotsugae F r i t z p . i n the r e l a t i v e s i z e s o f a s c i and ascospores. The spermagonia th a t are found i n a s s o c i a t i o n w i t h the ascocarps o f C. pinea Peck, and C. pseudotsugae were l a c k i n g i n the fungus on western hemlock. The ascocarps o f t h i s fungus were a s s o c i a t e d w i t h the cankered p o r t i o n s o f dwarf m i s t l e t o e s w e l l i n g s . They u s u a l l y formed on the bark bordering the c a l l u s a t the t i p s of cankers, but sometimes occurred on dead bark. They were sometimes gregarious but most commonly they occurred s i n g l y i n a l i n e along the s p l i t of a canker. Specimens are deposited i n the Herbarium of U.B.C. 3. Copnodium spongiosum B a r r . F r u i t i n g bodies of t h i s fungus were c o l l e c t e d i n January, 1960. Because of i t s known saprophytic nature c u l t u r e s were not attempted from l i v i n g host t i s s u e s . The f r u i t i n g bodies corresponded w i t h the d e s c r i p t i o n s given by Barr (1955). 4. D u r a n d i e l l a tsugae sp. nov. ( F i g s . 18, 20, 22, 23 and 24). This fungus f r u i t s on dwarf m i s t l e t o e cankers, sometimes i n the c a v i t i e s l e f t by f a l l e n dwarf m i s t l e t o e p l a n t s . A p o t h e c i i s erumpentibus, g r e g a r i i s v e l d i s p e r s i s , c a e s p i t o s i s ad 12 congregatis (communis 2 - 4 ) , r a r o s o l i t a r i i s , versus basim l e v i t e r a t t e n u a t i s , c o l l a r e sub corymbos apotheciarum, o r b i c u l a r i b u s , u n d u l a t i s v e l , d i s t o r t i s , 0.8 - 1.0 mm. diam., 0.8 - 1.4 mm. a l t i s , a t r i s , g l a b r i s , c o r n e l s , c a r t i l a g i n e i s i n humido; hymenio convexo v e l plane, a t r i s i n s i c c o , cinereus i n humido, marginatej hypothecio plectenchymato, a s c i s c y l i n d r a c e o - c l a v a t i s , s t i p i t a t i s , o c t o s p o r i s (70-) 80 - 90 (-100) x (6-) - 35 -8 - 8.5yu; asc o s p o r i s h y a l i n i s , f u s i f o r m i b u s , 2 - 8 s e p t a t i s (16-) 19 - 23 (-27) x 2.0 - 3.5 yu; paraphysibus h y a l i n i s , f i l i f o r m i b u s , s e p t a t i s , simplicibus,~ 1.0 - 1.5'yu diam., ad apicem i n c r a s s a t i s a g g l u t i n a t i s que, epithecium fuscum formantibus. Apothecia erumpent, gregarious to s c a t t e r e d , c a e s p i t o s e , w i t h up to about twelve i n a c l u s t e r , u s u a l l y 2 - 4 together, r a r e l y s i n g l e ; w i t h a s t r o m a - l i k e main stem, s l i g h t l y narrowed below, forming a p e c u l i a r c o l l a r beneath the c l u s t e r o f apothecia; apothecia c i r c u l a r to undulate-or somewhat d i s t o r t e d by crowding, 0.8 - 1.0 mm. i n diam. 0.8 - 1.4 mm. i n h e i g h t , b l a c k , glabrous, hard, horny, becoming c a r t i l a g -inous when moist; hymenium convex to plane, b l a c k when dry, becoming gray when moist, more f l e s h y than the.excipulum, margin r a i s e d ; t i s s u e o f the hypothecium plectenchymatous, composed of interwoven, ascending brownish to n e a r l y h y a l i n e hyphae 1.5 - 2 JU i n diameter, c u r v i n g toward the o u t s i d e where the w a l l s are darker, forming a r i n d - l i k e excipulum; subhymenium d i f f e r e n t i a t e d as a y e l l o w i s h , more compact zone, a s c i c y l i n d r i c c l a v a t e , t a p e r i n g below to a short s t a l k , e i g h t spored, (70-) 80 - 90 (-100) x (6-) 8 - 9.5 yu; ascospores h y a l i n e , f u s i f o r m , pointed or obtuse, s t r a i g h t , sometimes s l i g h t l y curved, i r r e g u l a r l y arranged, two to e i g h t c e l l e d (16-) 19 - 23 (-27) x 2 - 3.5yu; paraphyses h y a l i n e , f i l i f o r m , septate, simple, 1.0 - 1.5yu i n diam., the t i p s s l i g h t l y swollen to about 2.0 - 2.5 JU, and embedded i n a brownish, gelatinous m a t r i x , forming an epithecium. Only one asexual f r u i t i n g body was found. I t was erumpent, s l i g h t l y compressed, and tapered towards the base. The c o n i d i a were - 36 -h y a l i n e , elongated, e i t h e r s i c k l e - s h a p e d to sigmoid or almost s t r a i g h t w i t h s h a r p l y p o i n t e d ends. They v a r i e d i n length from 34 to 73 jx but were c o n s i s t e n t l y 2.5 JU t h i c k . There was no d e f i n i t e s e p t a t i o n but gu t t u l e s were common. Because of* the general lack of asexual f r u i t i n g bodies i t was impossible to e s t a b l i s h t h e i r connection with the ascocarps and to observe t h e i r s t r u c t u r e i n any d e t a i l . Cultures from ascospores d i d not y i e l d c o n i d i a . On the basis o f Groves* d e s c r i p t i o n s (1954) and the p r o x i m i t y "to ascocarps of the one asexual f r u i t i n g body noted, the two are b e l i e v e d to be r e l a t e d . The c o l o n i e s obtained from ascospores grew very s l o w l y , a t t a i n i n g a diameter o f 1.7 - 2.0 cm. i n s i x weeks. The margin was bayed, and the mycelium was white at f i r s t , becoming brownish-yellow and f i n a l l y brown w i t h a white margin. The fungus produced a p e c u l i a r reddish-brown pigment i n c u l t u r e that exceeded the l i m i t of the mycelium and formed a r i n g around the colony. The reverse was also zonate, the d i s c o l o r a t i o n being darkest where the a e r i a l mycelium was white. The a e r i a l mycelium was more or l e s s mounded and furrowed and aggregated i n t o e rect t u f t s . The hyphae were g u t t u l a t e , narrow (1.0 - 2.0 ji i n diam.), c o n s t r i c t e d at wi d e l y spaced septa, u s u a l l y branched a t r i g h t angles, forming r o p e - l i k e aggregates t h a t were tapered and very pointed towards the end. C o n i d i a l f r u i t i n g bodies were not produced w i t h i n the e i g h t week p e r i o d , although d r o p l i k e b l a c k i s h l i q u i d appeared on the surface o f m y c e l i a l t u f t s . Apothecia were c o l l e c t e d between December 1959 and February 1960 i n the U n i v e r s i t y Research F o r e s t near Haney. The type specimen: No. J.A.B. 15, was c o l l e c t e d i n Haney on February 25, 1960, and i s deposited i n the myc o l o g i c a l herbarium a t U.B.C. - 37 -PLATE I I . F i g u r e s 18-19 PLATE I I F i g . 18. Apothecium of Durandiella tsugae. x 350 F i g . 19. A cluster of apothecia of Helotium columbianum i n different stages of development, x 450 - 38 -PLATE I I I . F i g u r e 20 PLATE I I I F i g . 20. D. tsugae. Drawings made with aid of a camera lu c i d a . a. A s c i , ascospores and paraphyses. b. Ascospores. ® - 39 -PLATE IV. F i g u r e s 21 PLATE IV F i g . 21. D. a g a s s i z i i . Malt agar culture, s i x weeks old. F i g . 22. D. tsugae. Freehand section of the apothecium, showing the arrangement of a s c i , epithecium, tissue of the hypthecium, black excipulum, and the c o l l a r on the l e f t side. — Appr. x 50 F i g . 23. D. tsugae. Malt agar culture, s i x weeks old. F i g . 24. D. tsugae. Sickle-shaped conidia. x 800 - 40 -5. Helotium columbianum sp. nov. ( F i g s . 19, 25, 26 and 27). F r u i t i n g bodies of t h i s fungus were observed i n the deep s l i t s o f dwarf m i s t l e t o e cankers, a r i s i n g from a t h i c k , white m y c e l i a l mat. A p o t h e c i i s ascendis ex s u b i c u l o albo, c o l o r i s aurantiorum, g r e g a r i i s v e l d i s p e r s i s , c e s p i t o s i s ad 8 - 10 congregates (communis 2 - 4 ) , r a r e s o l i t a r i i s , 0.8 - 2.0 mm. diam., o r b i c u l a r ! b u s , s t i p i t e b r e v i , versus basim a t t e n u a t i s , 0.5 - 1.0 mm. a l t i s , a l b i d i s v e l p a l l i d e f l a v i s , aliquantum p u l v e r u l e n t l s , d u r i s , carnoso i n humido; hymenio piano v e l convexo, marginato; hypothecio plectenchymato; a s c i s c y l i n d r a c e o c l a v a t i s , s t i p i t a t i s , o c t o s p o r i s 50 - 65 x 4.5 - 6.0 jx] ascosporis h y a l i n i s 5.0 - 8.0 x 1.5 - 2.5 ja, e l l i p t i c i s v e l o v a t i s , oblique u n i s e r i a t i s v e l d i s e r i a t i s i n s u p e r i o r ! parte a s c i , g r a n u l a t i s v e l g u t t a t i s ; paraphysibus f i l i f o r m i b u s , s e p t a t i s , s i m p l i c i b u s , quandoque ramosis, 1.5 - 2.5 JX diam.., ad apicem i n c r a s s a t i s . Apothecia u s u a l l y on a white cottony subiculum, orange, gregarious or s o l i t a r y , caespitose, w i t h up to 8 - 10 i n a c l u s t e r — u s u a l l y 2 - 4 — , r a r e l y s i n g l e , 0.8 - 2.0 mm. i n diameter, c i r c u l a r , s h o r t s t i p i t a t e ; s t i p e s l i g h t l y narrowed below, 0.5 - 1.0 mm. l o n g , g r a d u a l l y expanding i n t o the c l u s t e r of apothecia above, the c o l o r of s t i p e i s w h i t i s h - y e l l o w , somewhat p u l v e r u l e n t ; the whole f r u i t i n g body hard when dry, becoming f l e s h y when moist; hymenium orange, plane or convex, at f i r s t w i t h a t h i c k , r a i s e d i n f o l d e d margin, which l a t e r may disappear or curve outward; t i s s u e o f the hypothecium plectenchymatous; the h y a l i n e hyphae forming a darker excipulum toward the o u t s i d e ; subhymenium d i f f e r e n t i a t e d as a more compact zone, a s c i c y l l n d r i c c l a v a t e , - 41 -t a p e r i n g below to a globose b a s a l c e l l , eight spores, 50 - 65 x 4.5 -6.0 ja.) ascospores 5.0 - 8.0 x 1.5 - 2.5 yu, h y a l i n e , e l l i p t i c a l or o v a l , simple, contents granular or g u t t u l a t e , o b l i q u e l y u n i s e r i a t e to i r r e g u l a r l y b i s e r i a t e i n the upper p a r t of ascus; paraphyses h y a l i n e , f i l i f o r m , septate, simple, sometimes branched at the lower p a r t , r e a c h i n g a diameter of 1.5 - 2.5 yu, swollen a p i c a l l y . The type specimen: No. J.A.B. 14, was c o l l e c t e d i n Haney on February 11, 1960, and i s deposited i n the m y c o l o g i c a l herbarium of U.B.C. I n the" c u l t u r e s obtained from ascospores the c o l o n i e s grew very s l o w l y , a t t a i n i n g a diameter of 2.0 cm. i n 4 weeks, the margin was s l i g h t l y bayed and t h i n , the mycelium white and farinaceous w i t h f i n e l o o s e l y s c a t t e r e d mycelium, the reverse was creamish-white. The hyphae were h y a l i n e and s e p t a t e , 1 - 4 u^ i n diam., g u t t u l a t e , forming r o p e - l i k e s t r ands. C o n i d i a were not produced w i t h i n eight weeks. Immature ascocarps were f i r s t noted i n November 1959. Mature ascospores were f i r s t noted i n February 1960. A r i s i n g from t h e same type of subiculum, sometimes i n p r o x i m i t y to an ascocarp, were long, s t i p i t a t e sporocarps with p i l e u s - l i k e heads and producing c o n i d i a . The c o n i d i o -phores were u s u a l l y simple, more or l e s s Acremonium-like, and produced a s i n g l e s p h e r i c a l conidium. Attempts to c u l t u r e the fungus on a v a r i e t y of agar media f a i l e d , thus preventing the demonstration of a connection between the c o n i d i a l form and Helotium columbianum. 6. Lophium mytilinum (Pers.) F r i e s . ( F i g s . 28 and 29). H y s t e r o t h e c i a of t h i s fungus were found on the t h i c k dead bark of dwarf m i s t l e t o e s w e l l i n g s , u s u a l l y c l o s e to the cankers. The same fungus i s known to occur on other coniferous t r e e s o f North America and Europe. The fungus on - 42 -PLATE V. Figure 25 PLATE V Fi g . 2 5 . H. columbianum. Drawings made with aid of a camera lucida. a. A s c i , ascospores and paraphyses. b. Ascospores. - 43 -PLATE VI. F i g u r e s 26-29 PLATE VI F i g . 26. H. columbianum. Freehand section of the apothecium, showing the arrangement of a s c i , subhymenium, tissue of the hypothecium, and the somewhat darker excipulum. x 150 F i g . 27. H. columbianum. Malt agar culture s i x weeks old. F i g . 28. Lophium mytilinum. Malt agar culture, s i x weeks old. F i g . 29. L. mytilinum. Hyphae with bulbous swellings, x 800 - 44 -western hemlock compared c l o s e l y w i t h the d e s c r i p t i o n s given by Bisby (1932, 1952). H y s t e r o t h e c i a were c o l l e c t e d i n the p e r i o d December 1959 - February 1960 near Haney. Specimens are deposited i n the herbarium of U. B.C. The c o l o n i e s obtained from ascospore c u l t u r e s grew s l o w l y , a t t a i n i n g a diameter of 4.0 cm. i n s i x weeks. The margin was s l i g h t l y bayed and l i g h t e r i n c o l o r than i n the centre p a r t . The a e r i a l mycelium was l i g h t brown, mounded at the center, and v e l v e t y . The immersed hyphae were brownish-black. The reverse was b l a c k . The a e r i a l mycelium was composed of pale brown to brown, septate, branched, rough-walled hyphae, 2.0 - 2.5 JX i n diameter. The immersed hyphae were darker i n c o l o r , had bulbous s w e l l i n g s and s h o r t l a t e r a l branches with s w o l l e n ends. These swollen t i p s are b e l i e v e d to be the f i r s t stage i n the formation of conidiophores and c o n i d i a . Conidia were not produced w i t h i n the e i g h t weeks that the c u l t u r e s were grown. 7. M y t i l i d i o n d e c i p i e n s K a r s t . H y s t e r o t h e c i a of t h i s fungus were found on the bark of dwarf m i s t l e t o e s w e l l i n g s , sometimes i n a s s o c i a t i o n w i t h Lophium mytilinum. They were o c c a s i o n a l l y found on dead adherent western hemlock needles. L. mytilinum was not found on dead needles. H y s t e r o t h e c i a of M. decipiens were noted e a r l y i n December 1959 and c o l l e c t i o n s were made u n t i l the end of February 1960. I t s occurrence on western hemlock at Haney i s b e l i e v e d to be the f i r s t North American record o f t h i s fungus. The fungus has been v a r i o u s l y described by E l l i s and Everhart (1892), Rabenhorst (1896), Saccardo (1883), and Lohman (1939). The - 46 -t h i s t u f t was somewhat dimpled, p a l e y e l l o w at f i r s t becoming orange at the center and greyish-orange towards the margin l a t e r , s l i g h t l y zonate, w i t h frequent s m a l l pale y e l l o w and dark orange f l e c k s and o c c a s i o n a l pale r a d i a l s t r i p s t h a t broaden towards the margin. The reverse was deep orange-yellow with a 3 - 5 mm. i n wide d i f f u s i o n band of the same c o l o u r . The hyphae were septate and t h i n - w a l l e d w i t h bulbous t h i c k e n i n g s . There were c r y s t a l l i n e pigments along many hyphae, g i v i n g them a rough appearance. The c r y s t a l s are i n s o l u b l e i n water but d i s s o l v e i n "&% KOH. The hyphae were y e l l o w , g u t t u l a t e , r a r e l y branching, and 2 - 4 yu i n diameter. Conidia produced w i t h i n s i x weeks, were globose to subglobose (12-) 17 - 22 (-28) yu, brownish at the beginning becoming b l a c k , t e r m i n a l on e i t h e r hyphal t i p s or on short l a t e r a l branches. The outer w a l l s o f immature c o n i d i a were e c h i n u l a t e , and broken up i n t o l a r g e i r r e g u l a r fragments. The mature c o n i d i a were 4 - 8 c e l l e d , separated by r a d i a l l y arranged septa. The spores were formed i n crowded c l u s t e r s . 12. P e s t a l o t i a sp. ( F i g s . 32 and 33). This fungus was obtained only i n c u l t u r e . The c o l o n i e s grew very f a s t covering the p l a t e w i t h i n three weeks. The margin was f a i r l y even w i t h r a i s e d a e r i a l mycelium forming a dense p i t t e d t u f t about 1.0 - 1.5 mm. t h i c k t h a t was white at f i r s t , becoming l i g h t g r a y i s h l a t e r . There was no d i s c o l o r a t i o n on the reverse, except f o r b l a c k patches, due to the a c e r v u l i . . The hyphae were h y a l i n e , g u t t u l a t e , r a r e l y branched, v a r i e d from 4.5 to 7.0 yu i n diam., and u s u a l l y c r y s t a l l i n e . C o n i d i a were produced w i t h i n s i x weeks i n submerged b l a c k a c e r v u l i t h a t were formed i n clumps v a r y i n g i n s i z e from 1.0 to 4.0 mm. PLATE V I I F i g . 30. Epicoccum sp. M a l t agar c u l t u r e s i x weeks o l d . F i g . 31. Epicoccum sp. Hyphae w i t h c o n i d i a . x 550 F i g . 32. P e s t a l o t i a sp. M a l t agar c u l t u r e , s i x weeks o l d . F i g . 33. P e s t a l o t i a sp. Conidiospores w i t h appendage, x 1000 - 4 7 -PLATE VII. Figures 30-33 - 48 -The w a l l s o f the a c e r v u l i were composed of dense hyphal webs from which r a d i a l l y arranged, h y a l i n e , conidiophores arose. The c o n i d i a were e l l i p t i c a l and 4 - c e l l e d , the two c e n t r a l c e l l s being brown at f i r s t and brownish-black l a t e r . There were one or more g u t t u l e s . The end c e l l s were h y a l i n e , the b a s a l c e l l w i t h a long 35 - 45 yu conidiophore and the a p i c a l c e l l with a branched b r i s t l e - l i k e appendage. The number of branches v a r i e d from 2 to 5, u s u a l l y 3. The spores were c o n s t r i c t e d at the septa, e s p e c i a l l y a t the end c e l l s . The conidiospores measured (14-) 18 - 23 (-25) x 5.0 - 7.0 yu. The length of appendages was 10 - 21^u. The exuded c o n i d i a formed a shiny black drop on the surface of the a e r i a l mycelium. Pathogenecity of Fungi I s o l a t e d from Dwarf M i s t l e t o e I n f e c t e d Branches of Western Hemlock., Four weeks f o l l o w i n g t h e i r i n o c u l a t i o n i n t o wounded branches Dasyscypha a g a s s i z i i , Epicoccum sp., and P e s t a l o z i a sp. had formed heavy surface m y c e l i a l growth, but a f t e r a f u r t h e r e i g h t weeks only P e s t a l o t i a sp. was d i s c e r n a b l y a c t i v e . F i v e of the seven i n o c u l a t i o n s of t h i s fungus r e s u l t e d i n w e l l defined bark necroses ( F i g . 34). On r e i s o l a t i o n from the i n f e c t e d bark the fungus was i d e n t i c a l i n c u l t u r e to t h a t used i n the i n o c u l a t i o n . Three of the i n o c u l a t i o n s of C a l i c i o p s i s sp. r e s u l t e d i n s l i g h t d i s c o l o r a t i o n s of the bark of the t e s t s t i c k s . Since the fungus could not be r e i s o l a t e d from the bark, t h i s alone was not considered d e f i n i t e enough to prove i t s p a r a s i t i s m . The l a c k of time necessary f o r f u r t h e r i n v e s t i g a t i o n s precluded f u r t h e r t e s t i n g of t h i s fungus. - 49 -F i g . 34. R e s u l t s o f i n o c u l a t i o n s of western hemlock branches w i t h P e s t a l o t i a sp. Upper wounds c o n t r o l s , lower wounds i n o c u l a t i o n s . - 50 -DISCUSSION The r e l a t i v e t u r g i d i t y method of c a l c u l a t i n g the moisture content of samples of western hemlock bark and wood was used i n preference to other p o s s i b l e methods. The use of t h i s method allows the e l i m i n a t i o n of t i s s u e d e n s i t y as a v a r i a b l e , e.g., t h i n t i s s u e s can h o l d more water at s a t u r a t i o n than dense t i s s u e s . The expression of moisture as a percentage o f the dry weights of bark and wood was not used, since a decrease i n the water/dry weight r a t i o can be caused by e i t h e r a decrease of water or a r i s e of dry weight. R e l a t i v e t u r g i d i t y expresses the amount of moisture t h a t i s i n the bark as a percentage of the amount of moisture t h a t i s h e l d at s a t u r a t i o n p o i n t . This method appeared to be eminently more s u i t a b l e than the dry-weight method. I n the present study of western hemlock there was a w e l l defined seasonal v a r i a t i o n i n moisture content f o r both bark and wood. Gibbs (1939) working with eastern hemlock, found a w e l l defined seasonal v a r i a t i o n f o r the sapwood but a l e s s w e l l defined v a r i a t i o n f o r the heartwood. The methods employed by Gibbs i n v o l v e d the s e p a r a t i o n of sapwood and heartwood w h i l e i n the present study, e n t i r e branch cross s e c t i o n s were sampled. The d i f f e r e n t techniques employed may e x p l a i n the discrepancy. I n general, r e s u l t s obtained f o r eastern hemlock by Gibbs and f o r western hemlock i n t h i s study were s i m i l a r . There appeared to be two " s t r e s s " periods i n the moisture regime of western hemlock, i n the e a r l y s p r i n g and l a t e summer. The e a r l y - 51 -s p r i n g s t r e s s period, was the most s e r i o u s , the r e l a t i v e t u r g i d i t i e s of bark and wood were much l e s s than 80 per cent. B i e r (1959) found that correspondingly low bark moistures were necessary i n western hemlock, w i l l o w , and poplar f o r the r a p i d development of d i f f e r e n t canker d i s e a s e s , and that when moisture l e v e l s rose about 80 per cent cankers became i n -a c t i v e . The seasonal changes of bark and wood moisture could perhaps i n f l u e n c e the establishment of canker causing f u n g i on dwarf m i s t l e t o e i n f e c t e d branches. The q u a l i t y of western hemlock s i t e s seems to have a s i g n i f i c a n t e f f e c t on the moisture regime of western hemlock. In the good s i t e the l a t e summer moisture s t r e s s p e r i o d d i d not c o i n c i d e w i t h the dry p e r i o d of the summer. The moisture contents of t r e e s i n t h i s s i t e showed l e s s f l u c t u -a t i o n than i n poor s i t e , probably because of the b e t t e r water h o l d i n g c a p a c i t y of the s o i l and the deeper root systems of t r e e s i n good s i t e s . Most, of the roots of trees i n t h i s s i t e were l o c a t e d i n the "A" and "B2" l a y e r s , at a depth of about 36 inches. (See Appendix "A"). Most of the roots of trees i n the poor s i t e were found i n the AQ l a y e r , which was 16 inches or l e s s deep. The A Q l a y e r c o n s i s t e d mostly of decaying wood that d r i e d out q u i c k l y during the summer. Th i s c o n d i t i o n was r e f l e c t e d i n a sudden drop of moisture i n the t r e e s growing i n the poor s i t e . The moisture contents of trees remained below 80 per cent longer i n the poor s i t e than i n the good s i t e during the p e r i o d of experimentation. At the outset of the study i t was b e l i e v e d that dwarf m i s t l e t o e c o n t r i b u t e to a s e r i o u s moisture l o s s from i n f e c t e d branches, because of t r a n s p i r a t i o n by the a e r i a l p l a n t s , and that the gr e a t e s t moisture s t r e s s - 52 -would occur at and d i s t a l to the i n f e c t e d areas of branches. I f t h i s was found to be the case, I t could e x p l a i n i n p a r t the h i g h m o r t a l i t y of the t i p s of branches i n f e c t e d by dwarf m i s t l e t o e . However the present study f a i l e d to demonstrate these r e l a t i o n s h i p s , except to show t h a t bark moisture i s lowest at the c e n t r a l p o r t i o n of dwarf m i s t l e t o e s w e l l i n g s , and sometimes drops below 80 per cent. A p o s s i b l e e x p l a n a t i o n f o r the high frequency of-branch t i p m o r t a l i t y i s the g i r d l i n g a c t i o n of f u n g i that have become e s t a b l i s h e d i n dwarf m i s t l e t o e i n f e c t e d areas, s i n c e i t i s known ( B i e r 1959) t h a t canker f u n g i are most a c t i v e i n host m a t e r i a l t h a t i s under moisture s t r e s s . CONCLUSIONS Resu l t s o f t h i s study p o i n t to the f o l l o w i n g conclusions: (1) R e l a t i v e t u r g i d i t y measurements of western hemlock bark and wood r e s u l t e d i n , two moisture minima, one i n the e a r l y s p r i n g and.one i n the f a l l , and two maxima, one i n the l a t e s p r i n g and the second i n the w i n t e r . (2) S i g n i f i c a n t d i f f e r e n c e s were noted f o r both bark and wood moistures between good and poor s i t e s , between seasons of the year and f o r the i n t e r a c t i o n between s i t e and seasons of the y e a r . Moisture contents were higher and f l u c t u a t e d l e s s i n the good s i t e than i n poor s i t e . The summer drought d i d not c o i n c i d e w i t h the summer minimum i n the good s i t e but d i d r e s u l t i n an immediate drop of moisture content i n the poor s i t e . The winter maximum seemed to be a f u n c t i o n of a i r - 53 -temperature s i n c e i n the m i l d c l i m a t e of the good s i t e i t reached i t s peak i n February. I n the c o l d e r poor s i t e the w i n t e r maximum occurred i n the middle of November. The d i f f e r e n c e i n time at which the peaks occurred i n the two s i t e s was probably caused by a i r temperature d i f -ferences between these s i t e s . (3) The r e l a t i v e t u r g i d i t y of bark i n the good s i t e was below the eighty per cent l e v e l f o r 95 days through an e n t i r e y e a r . I n the poor s i t e i t remained under t h i s c r i t i c a l value f o r 123 days o f the e i g h t months' observation p e r i o d f o r t h i s s i t e . (4) Dwarf m i s t l e t o e d i d not appear t o a f f e c t the water l e v e l of the p o r t i o n of branches t h a t had not been invaded by the endophytic system. However the p a r a s i t e produced moisture s t r e s s i n the bark at the c e n t r a l areas of i n f e c t i o n s . (5) There was a canker a s s o c i a t e d w i t h dwarf m i s t l e t o e I n f e c t i o n s . Although the o r i g i n of these cankers was not determined, t h e i r occurrence was c l e a r l y r e l a t e d to the dwarf m i s t l e t o e i n f e c t i o n . The almost u b i q u i -tous occurrence of Ascomycetes and Fungi Imperfect! on n e c r o t i c areas of dwarf m i s t l e t o e i n f e c t i o n s i n d i c a t e s the formation of s p e c i a l c o n d i t i o n s i n the bark at these p o i n t s . (6) An i n v e s t i g a t i o n of the f u n g i that were a s s o c i a t e d w i t h cankered areas of dwarf m i s t l e t o e i n f e c t i o n s r e v e a l e d the occurrence of' twelve d i f f e r e n t species of f u n g i . Nine of these were Ascomycetes and three were Fungi I m p e r f e c t i . There were two undescribed s p e c i e s , D u r a n d i e l l a  tsugae and Helotium columbianum, and one, M y t i l i d i o n decipiens K a r s t . , had not been reported p r e v i o u s l y f o r North America. - 54 -(7) P r e l i m i n a r y t e s t s of the p a r a s i t i s m of seven species i n d i c a t e d t h a t only P e s t a l o t i a sp. was m i l d l y p a r a s i t i c . - 55 -LITERATURE CITED The western hemlock. U.S. Dept. Agr., Bur. F o r . B u l l . , 33:1-55. 1902. Species of sooty molds from western North America. Canadian J o u r n a l of Botany, 33:497-514. 1955. 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General i n t r o d u c t i o n . Water contents o f c e r t a i n Canadian t r e e s . Canadian J o u r n a l of Research C, 17:460-482. 1939. . Patterns i n the seasonal water content of t r e e s . I n : K.V. Thimann: The physiology of f o r e s t t r e e s , 3:43-69. 1957. G i l l , L.S. Arceuthobium i n the U n i t e d S t a t e s . Transactions of the Connecticut Academy of A r t s and Sciences, 32:111-245. 1935. . Dwarf m i s t l e t o e of lodgepole pine. U.S. F o r e s t Serv. F o r e s t P e s t L e a f l e t , 18:1-7. 1957. . Dwarf m i s t l e t o e of ponderosa pine i n the Southwest U.S.D.A., Rocky Mt. F o r . and Rg. Exp. S t a . , S t a . Pap. 14. 1954. Groves, J.W. The genus D u r a n d i e l l a . Canadian J o u r n a l o f Botany, 32:116-144. 1954. H a r t i g , R. Ueber die V e r t h e i l u n g der organischen Substanz, des Wassers und Luftraumes i n den Baumen und ueber d ie Ursache der Wasserbewegung i n t r a n s p i r i e r e n d e n P f l a n z e n . Untersuch. f o r s t b o t . I n s t . Munchen, 2:1-112. 1868. Hepting, G.H, and J.W. Kimmey. Heart r o t . Year Book of A g r i c u l t u r e , 462-465. 1949. K o r s t i a n , C.G. and W.H. Long. The western y e l l o w pine m i s t l e t o e . U.S.D.A. B u l l e t i n 1112. 1922. The growth a c t i o n , and i n t e r a c t i o n o f s o i l and other f a c t o r s . J o u r n a l of F o r e s t r y , 53:508-512. 1955. Water r e l a t i o n s and growth of t r e e s . J o u r n a l of F o r e s t r y , 56:498-502. 1958. Dwarf m i s t l e t o e s . B o t a n i c a l Review, 21:569-628. 1955. Mor p h o l o g i c a l aspects o f p a r a s i t i s m i n the dwarf m i s t l e t o e s (Arceuthobium). U n i v e r s i t y of C a l i f o r n i a P u b l i c a t i o n s i n Botany, 30:337-436. U n i v e r s i t y of C a l i f o r n i a Press Berkeley and Los Angeles 1960. Kozlow s k i , T.T. K u i j t , J . Lohman, M.L. Karsten's type specimens of Hysteriaceae i n c o n i f e r s . Mycologia, 31:354-365. 1939. - 58 -P e r r y , W.J. P i e r c e , W.R. Rabenhorst, G.L. Raiikin, H.W. Roth, L.F. Can m i s t l e t o e be e r a d i c a t e d by pruning? J o u r n a l o f F o r e s t r y , 20:627-628. 1922. Dwarf m i s t l e t o e and i t s e f f e c t upon the l a r c h and Douglas f i r of western Montana. School o f F o r e s t r y , Montana State U n i v e r s i t y , M i s s o u l a , Montana, B u l l e t i n No. 10. 1960. Kryptogamen f l o r a von Deutschland, O e s t e r r e i c h und der Schweiz. Die P i l z e , 13:1210. 1896. Manual of tree d i s e a s e s . The M a c M i l l a n Co., New York, 54-55, 163, 214. 1929. N a t u r a l emplacement o f dwarf m i s t l e t o e seed on ponderosa pine. F o r e s t Science, 5:365-369. 1959. Saccardo, P.A. S y l l o g e fungorum; Pata V I I . 1883. Subramanian, D. and L. Saraswathi-Devi.- Water i s d e f i c i e n t . 9:313-342. I n : J.G. H o r s f a l l and A.E. Diamond: P l a n t pathology, V o l . 1. Acad. Press, New York and London. 1959. Weatherley, P.E. Weir, J.R. Studies i n the water r e l a t i o n s o f the co t t o n p l a n t . I . The f i e l d measurement of water d e f i c i t s i n l e a v e s . New P h y t o l o g i s t , 49:81-97. 1950. E f f e c t s o f m i s t l e t o e on young c o n i f e r s . J o u r n a l o f A g r i c u l t u r a l Research, 12:715-718. 1918. Weir, J.R. and E.E. Hubert. A study of h e a r t - r o t i n western hemlock. U.S. Dept. Agr., B u l l . , 722:1-37. 1918. Wellwood, R.W. Some e f f e c t o f dwarf m i s t l e t o e on western hemlock. F o r e s t r y C h r o n i c l e , 32:282-296. 1956. - 1 -APPENDIX "A" FLOED-ECOLOGICAL DESCRIPTION OF AREAS SAMPLED IN AN INVESTIGATION OF ARCEUTHOBIDM CAMPILOPODUM GILL F. TSTJGENSIS ON WESTERN HEMLOCK. 1. U n i v e r s i t y Campus F o r e s t , Vancouver, B.C. Vegetation: A. Trees. Tsuga h e t e r o p h y l l a (Raf.) Sargent has e x c e l l e n t development i n a l l canopies. Thuja p l i c a t a Donn. has a v a r i a b l e occurrence t h a t i s u s u a l l y confined to the lower canopies. Prunus emarginata (Dougl.) D. D i e t r . , occurs only i n the lower canopies. Alnus r u b r a Bong, as a s h o r t - l i v e d species l o s e s dominance to coniferous s p e c i e s . B. Lesser v e g e t a t i o n . The shrub l a y e r i s discontinuous, represented by Rubus s p e c t a b i l i s Pursh., Sambucus rubens Michx. and G-aultheria s h a l l o n Pursh. The herb l a y e r not y e t developed because o f the f u l l canopy c l o s u r e . U s u a l l y present are Polystichum munitum ( K a u l f . ) P r e s l . , Athyrium f i l i x  femina (L.) Roth and D r y o p t e r i s a u s t r i a c a (Jacq.) Woyner. Dominant among the mosses are Mnium punctatum Hedw. and Plagiothecium undulatum (Hedw.) Bruch & Schimp. Topography and s o i l : The area i s f l a t , e l e v a t i o n 300 f e e t . S o i l i s c o ncretionary reddish-brown, the whole p r o f i l e i s w e l l drained, parent m a t e r i a l g l a c i a l out-wash. S i t e index f o r hemlock i s : 160. S o i l p r o f i l e : A 0 - 5 " Dark grey mottled brown, f r i a b l e ' , granular humus l a y e r , densely penetrated by r o o t s . B2 6 - 36" Reddish-brown mottled by r e d . B l o t c h y s t r u c t u r e loamy sand, f r i a b l e , evenly penetrated by r o o t s . Charcoal i n the upper p a r t . C 37" + Greyish-brown cemented loamy sand (hard pan). - 2 -2. U n i v e r s i t y Research F o r e s t , near Haney, B.C. V e g e t a t i o n : A t the Haney s i t e skunk cabbage (L y s i c h i t u m americanum Hu l t e n & S t . John) a s s o c i a t i o n was formed on the lower wet p a r t o f the area and Polystichum on the d r i e r upper l o c a t i o n (see Appendix "B"). L y s i c h i t u m a s s o c i a t i o n : A. Trees. No trees i n t h i s a s s o c i a t i o n . B. Lesser v e g e t a t i o n . The shrub l a y e r i s represented by G a u l t h e r i a s h a l l p n , on decaying wood. I n the herb l a y e r L y s i c h i t u m  americanum i s dominant, other species present are A n g e l i c a spp., Sphagnum spp. and among the mosses Mnium punctatum. Polystichum a s s o c i a t i o n : A. Trees. Tsuga h e t e r o p h y l l a occurs i n a l l canopies but i n reduced v i g o r . Thuja p l i c a t a u s u a l l y confined to the lower canopies. Pseudotsuga m e n z i e s i i (Mirb.) Franco; the major species i n the surrounding young stand. B. Lesser v e g e t a t i o n . The shrub l a y e r i s not completely developed and i s dominated by Acer c i r c i n a t u m Pursh., Rubus s p e c t a b i l i s , G-aultheria s h a l l o n mainly on decaying wood and Vaccinium alascaense. The herb l a y e r i s l e s s w e l l developed, Polystichum muniturn i s the only species present. Mosses are represented by Plagiotheclum undulatum. Topography and s o i l : The topography v a r i e s from f l a t to gently s l o p i n g . E l e v a t i o n 1,300 f e e t . S o i l i n the L y s i c h i t u m a s s o c i a t i o n i s black muck at l e a s t 2 f e e t deep. Water l e v e l i s over the s o i l s u r f a c e . In the Polystichum a s s o c i a t i o n the s o i l developed under good drainage c o n d i t i o n s . The present higher water t a b l e had a l a t e r o r i g i n a f t e r the p r o f i l e was formed. A s m a l l creek was l a t e r c l o s e d by f a l l e n t r e e s . This r a i s e d the water t a b l e and - 3 -slowed the drainage. (Appendix "B"). S i t e index f o r hemlock i s : 70. S o i l p r o f i l e : A Q 16" - 0" M o s t l y decaying wood, densely penetrated by hemlock r o o t s . A_2 0" - 2" Brownish-grey i n f i l t r a t e d by organic matter. This coarse sandy l a y e r i s s t r o n g l y i n f l u e n c e d by the h i g h water t a b l e , which i s j u s t at i t s lower boundary. Charcoal about t h i c k between A Q and A2. B 3 U + Coarse sandy brown l a y e r apparently s t r u c t u r e l e s s . Parent m a t e r i a l i s g l a c i a l t i l l , stones are quartz d i o r i t e . The t r e e s sampled formed a s m a l l l o g g i n g r e s i d u a l group. Surrounding area was c l e a r cut i n 1958 because of heavy dwarf m i s t l e t o e i n f e c t i o n . - 1 -APPENDIX "B" MAP OF AREA SAMPLED AT THE UNIVERSITY RESEARCH FOREST. O l d h e m l o c k s t a n d - 1 -APPENDIX "C" RELATIVE TURGIDITY VALUES OF BARK AND WOOD, SAMPLED IN GOOD AND POOR SITES AT TWO-WEEK INTERVALS Bark Branches Branches Date of Sampling r II I l l IV Average I II III IV Average Good S i t e Poor S i t e June 16 88 88 79 94 87.2 74 81 82 91 82.0 30 90 94 88 79 87.8 75 74 76 , - 75.0 J u l y 14 93 83 ^89 85 87.5 75 74 77 78 76.0 28 81 87 86 91 86.3 91 82 86 83 85.5 Aug. 11 90 . 85 87 88 87.5 79 93 81 - 84.3 25 84 88 80 90 85.5 73 80 81 76 77.5 Sept. 22 84 86 84 80 83.5 90 80 75 82 81.8 Oct. 6 83 81 86 75 81.3 88 85 83 82 84.5 20 83 84 89 81 84.2 88 86 83 - 85.7 Nov. 3 82 - 90 84 80 84.0 - 80 83 78 80.3 19 90 81 84 82 84.2 82 82 83 78 81.3 Dec. 3 94 - 93 85 90.7 79 75 76 77 76.8 17 89 93 83 87 88.0 73 75 72 75 73.8 31 92 88 81 - 80 85.3 88 - 86 74 82.7 Jan. 14 89 88 82 81 85.0 70 65 62 68 66.3 28 98 87 85 93 90.8 89 83 77 80 82.3 Feb. 11 76 - 70 72 72.7 , 84 78 84 81 81.8 Average - 85.4 - 79.9 Each measurement i s the average of two, one taken above and the other below i n f e c t i o n ; previous t e s t showed no s i g n i f i c a n t difference between samples above and below i n f e c t i o n . .Wood Branches Branches Date of Sampling I II III IV Average I I I I I I IV Average Good S i t e Poor S i t e June 16 80 68 70 78 74.0 53 60 65 56 58.5 30 63 67 70 75 68.8 63 73 72 56 66.0 J u l y 14 82 63 80 73 74.5 70 73 69 66 69.5 28 54 73 76 68 67.8 67 66 74 67 68.5 Aug. 11 89 81 72 79 80.3 56 63 51 58 57.0 25 84 73 76 70 75.8 59 60 52 64 58.8 Sept. 22 78 76 64 74 73.0 67 77 66 58 67.0 Oct. 6 60 69 73 60 65.5 78 68 83 76 76.3 20 78 81 78 75 78.0 76 77 65 - 72.7 Nov. 3 74 73 79 70 74.0 - 72 68 84 74.6 19 78 64 76 73 72.8 85 72 78 66 75.3 Dec. 3 67 - 77 74 72.7 76 81 73 86 79.0 17 87 82 82 79 82.5 80 61 68 76 71.3 31 83 85 82 77 81.8 68 92 72 73 76.3 Jan. 14 84 89 87 91 87.8 66 72 75 70 70.8 28 99 82 86 90 89.3 72 - 89 83 81.3 Feb. 11 77 - 73 71 73.7 69 73 70 85 74.3 Average 76.0 70.4 Each measurement i s the average of two, one taken above and the other below i n f e c t i o n ; previous test showed no s i g n i f i c a n t difference between samples above and below i n f e c t i o n . Publications 19^8. Baranyay, J.A. The role of blue beech, Carpinus betulus. i n Hungarian sil v i c u l t u r e . Erdogazdasag. Budapest. 195^. Tompa, K. and Baranyay, J.A. Silviculture - a textbook f o r forest technicians. Mezogasdasagi Kiado. Budapest. 1956. Baranyay, J.A. Maintenance and improvement of young spruce stands i n the Middle Mountains Region, Hungary. Az Erdo 5(11):433-U8U. 1956. Jablanczy, A., Baranyay, J.A. and Henzel, J*.. A selectively managed farm forest. Technical University (Sopron), For. Faculty, Publ. 1. 1957. Tompa, K. jet. al.. Handbook of forestry. Hungary Dept. Agr., Publ. Budapest. (A compilation by Tompa of seven contributions to a general text on forestry, of which Baranyay contributed Chap. 2. "The forest and i t s environment". Chap. 3. "Forest ecology". Chap. 5. "Silviculture", and Chap. 11. "Conservation and aesthetic values".) i960. Baranyay, J.A. and Bourchier, R.J. Province of Alberta, Forest Disease Survey; In Ann. Rept; of the Forest Insect and Disease Survey. Can. Dept. For., For. Ent. and Path. Branch. Ottawa. 

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