434 



COMPARATIVE MORPHOLOGY OF FUNGI 



Brachybasidium is very interesting from the viewpoint of comparative 

 morphology; for there can be no doubt that this thick-walled probasidium 

 affords protection and makes it possible for the basidium to await favor- 

 able conditions for germination. In this sense, it is comparable to the 

 sclerobasidia of the Phragmobasidiomycetes. The chiastobasidial Auto- 

 basidiomycetes have attained the same degree of development in this 

 family as the stichobasidial Phragmobasidiomycetes in the Septobasidia- 

 ceae, and the lepto-forms of the Uredinales. 



Corticiaceae. — This family includes the simplest forms of the Poly- 

 porales; they show beginnings of the various directions of development 

 and form thereby, as is shown in the scheme on page 430, the key to the 



Fig. 276. — Brachybasidium Pinangae. Section of zeugite sorus with three germinating 



zeugites. ( X 390; after Gaumann, 1922.) 



whole order. Their representatives are mostly saprophytes on earth, 

 wood or dead parts of plants. Their basidia are generally four, more 

 seldom two, or six to eight spored. Usually their spores are hyaline and 

 smooth, rarely, as in Hypochnus (Tomentella), rough and brown or yellow. 

 According to the structure of their fructifications, they may be divided 

 into three intergrading stages of development. The forms of the 

 lowest stage, as Tulasnella of the Tulasnelaceae, Helicobasidium of the 

 Auriculariales and Sebacina of the Tremellales, spread out on the sub- 

 strate in an arachnoid covering; the basidia rise, like free conidiophores, 

 at unequal heights on the same hyphae, singly or in candelabra (Fig. 265, 

 1) ; thus there are formed no, or only diffuse, fructifications and hymenia. 

 In the second stage, the hyphae intertwine to homogeneous, leathery or 



