MYCORRHIZAL FORMATION 303 



luteus, for example, occurs constantly on the litter under Finns 

 montana. Elsewhere in Europe it has been found under P. mon- 

 tana, P. austriaca, and P. sylvestris and is presumed to be respon- 

 sible for mycorrhizae. Similarly Boletus elegans occurs under 

 Larix and is supposed to be restricted to larches. Noack (1889) 

 observed that Geaster fimbriatus, G. fornicatus, and Cortinarius 

 calisteus form mycorrhizae on pine, and Tricholoma terreus on 

 spruce. Masui (1926) observed Cantharellus floccosits as the 

 mycorrhizal associate on Abies firma in Japan. Aielin (1925) 

 regarded Boletus luteus, B. gramriatus, B. variegatus, and B. badius 

 as responsible for the production of "Knollenmykorrhiza" on 

 Finns sylvestris in Sweden. His "Gabelmykorrhiza" on pine, 

 fungal components of which he identified as Mycelium radicis 

 sylvestris f$, and M. radicis sylvestris y, have features resembling 

 the mycelia of species of Tricholoma and Cortinarius, respec- 

 tively. 



Certain hypogean Ascomycetes, including Elaphomyces gran- 

 ulatus, Terfezia leonis, and Tuber sp., form mycorrhizae on hard- 

 woods. The evidence that species of Penicillium can produce 

 mycorrhizae appears to be unconvincing. 



The mycorrhizal associates in liverworts and in many herba- 

 ceous seed plants are Pythium-like or Phytophthora-like in aspect. 



A Rhizoctonia type of fungus is the common endophyte of 

 orchids. Organisms of similar appearance have been isolated from 

 the roots of wheat, corn, barley, potatoes, tobacco, carrots, and 

 other flowering plants. 



Peyronel has attributed the cause of confusion in the identity 

 of the fungal constituent of mycorrhiza to the coincidental inva- 

 sion of the roots by two distinct fungi, one a Phycomycete, the 

 other a Rhizoctonia-like species. The Phycomycete produces 

 vesicles and arbuscles that may eventually be digested by the 

 host cells, and it is overgrown by the second species. In 1924 

 Peyronel published a list of species, distributed among 37 families, 

 that possessed this dual type of invasion [Rayner (1927)]. It 

 may be inferred from his observations that the presence of two 

 mycorrhizal associates in one and the same host root occurs widely 

 among seed plants. 



Several endophvtes of orchids have been specifically identified 

 by Bernard. From Cattleya and Cypripedium he isolated Rhi- 



