Lecture II — 29 — Occurrence of Mycorrhizae 



DouGALL, 1927, had cited the same species from Idaho) ; and Klecka 

 and VuKOLOv (1935) who Ust A. alba as ectotrophic. 



Pseudotsuga is not popular with mycorrhizal students : but one of 

 the four species has been investigated at aU for mycorrhizae and this 

 species only in a cursory way. In its native haunts it was described as 

 both ecto- and endo-trophic by McDougall (1927) in Utah, and as 

 having an endophyte in Canada by Lewis (1924) ; while Laing 

 (1923) insists that this species does not form mycorrhizae readily. 

 Klecka (1935) and Dominik (1937) find the species mycorrhizal in 

 Europe while Birch (1937) records its fungi in New Zealand. Tsuga 

 has received passing attention : five species are noted as mycorrhizal, 

 of which one species, T. heterophylla is said by Laing to have semi- 

 ectotrophic mycorrhizae the hyphae being found only between the 

 cortical cells, and there is no mantle. 



Twelve of the 39 species of Picea are cited as mycorrhizal and one 

 of them, P. Abies, the Norway spruce, has been studied in detail by 

 several investigators, especially Melin (1925). Using Melin's cul- 

 ture methods, Modess (1939) synthesized various Hymenomycetes 

 with seedlings of P. Abies, a study further reported in 1941 when he 

 Usted 8 species of Hymenomycetes and one Gasteromycete that formed 

 mycorrhizae with this spruce. Melin's methods were likewise used 

 by Fries (1942) in synthesizing monospore mycelia of Scleroderma 

 aurantiiim with spruce whereby mycorrhizae were formed but not as 

 abundantly as with pine. Also in Sweden, Lindquist (1939) did his 

 work on spruce and wrote philosophically on the physiology of myco- 

 trophism; and Rom ell (1938) reports on his trenching experiments 

 with spruce, and their bearing on the problems of mycotrophy. In 

 another cultural study, Bjorkman (1940) reports on the ecology 

 of the mycorrhizae of this spruce, while Thomas (1941) presents a 

 plot study of young spruce plantations in the Rhine Valley. Besides 

 the Norway spruce studied in Europe, various other spruces have been 

 studied or noted in America and Japan. 



Larix shares with Picea the attention accorded by Melin. Five 

 species of Larix are recorded as mycorrhizal by various authors ; and 

 more recently How (1942) has made a monographic study of the 

 mycorrhizal relations of L. decidua. Colla (1931) records Hypho- 

 lonia fasciculare with the same species of larch; and Thomas (1941) 

 notes larch plantations in the Rhine Valley. Pseudolarix is recorded 

 onlyby Noell (1910). 



Finally, in the Coniferales, we come to Pinus, the most studied 

 genus of Gymnosperms. Thirty-seven species and varieties of Pinus 

 are recorded mycorrhizal but of these only four have been studied 

 in detail, namely, Strobus, sylvestris, pinaster and montana. 



