AUTOBASIDIOMYCETES 



451 



In the case of the potato, it forms a membranous layer inclos- 

 ing the stem for several inches above the surface of the ground. 

 This layer is composed of rather loosely interwoven hyphae, and 

 on account of this character it is difficult to say if the plant is 

 properly placed under the genus Corticium, or whether it might 

 not with equal propriety be considered a species of Hypochnus. 

 The basidia are short, cylindrical, or oblong, and apparently many 



Fig. 222. Corticium vagum var. Solani 

 a, young hyphae ; &, cells from growth in tufts ; c, basidia and spores 



may be produced from a single parent hypha, each basidium being 

 cut off from the hypha by a septum placed in the manner charac- 

 teristic of the branching mycelium. The basidia bear four sterig- 

 mata and spores, although commonly only two may be observed 

 at one time. The spores, according to Rolfs, are somewhat ellip- 

 tical or irregular in outline, frequently obovate and nearly hyaline, 

 9-15 X 6—13 fi. Spore germination proceeds in ordinary nutri- 

 ent media, and as a rule a septum is formed in the germ tube 

 shortly after it emerges from the spore, the proximal portion of 

 the germ tube being somewhat less in diameter. When produced 



