418 COMPARATIVE MORPHOLOGY OF FUNGI 



In most forms the mature basidiospores are uninucleate. In some the 

 nucleus divides immediately after it enters the spore, so that the spore is 

 early binucleate (Fig. 265, 14). The fact that this early division regularly 

 appears in the four-spored chiastobasidia, especially in the higher families, 

 e.g., Lycoperdaceae, Nidulariaceae and the Sclerodermataceae, leads to 

 the assumption that there may be a question here of a third division of the 

 primary basidial nucleus which has been delayed and transferred to the 

 spore. In other cases, the reasons seem to be of a more local sort and 

 e.g., to lie in ratio of nucleus to cytoplasm as sometimes divisions begin 

 without being successfully completed. Finally, in still other cases, it is, 

 perhaps, only a question of premature germination. 



The basidiospores, especially in the colored spored forms, often 

 germinate only under definite and narrowly limited conditions (Cool, 

 1922) ; if these are not fulfilled, no germination takes place. If one con- 

 siders that the number of fructifications remains approximately constant 

 and that the same mycelia, as they are often perennial, may produce for 

 years a large number of fructifications, one may have an approximate idea 

 of how seldom in nature these conditions can be realized, and what an 

 enormous amount of material is squandered, since from several billion 

 spores only one succeeds to the formation of a fructification. In the 

 lower, thin-walled forms, germination chiefly follows (with some even 

 regularly) with a secondary spore or sprout mycelium which only later 

 develops to a true mycelium. These forms were grouped together by 

 Patouillard (1900) into a class, the Heterobasidiae, since the basidia are 

 often indefinite in form. In the higher forms with thick-walled spores, 

 they develop directly to mycelia; as the basidia are more stable in form, 

 they comprise a class, the Homobasidiae. These mycelia, whether they 

 proceed from the sprout cells or directly from the basidiospores are usually 

 the uninucleate primary mycelia which we discussed earlier. We have, 

 thus, completed a survey of the life cycle of the Basidiomycetes and now 

 present schematically the different possibilities of this life cycle. Here 

 the Uredinales and Ustilaginales, which will be discussed in detail later, 

 are excluded. 



As an example of the first type a heterothallic form, Coprinus fimeta- 

 rius, whose life cycle is as follows may be cited: 



+ Basidiospores 



r 



Uninucleate + imperfect form} Binucleate ± imperfect form 



^Uninucleate --mycelium 



r 



— Uninucleate— imperfect form 



C R 



Uninucleate + mycelium ^ --^Binucleate + myceliunAFructification-*Basidia 



— Basidiospores 



Diagram XXV. 



