12 



CLASS BASIDIOMYCETEAE: SUBCLASS 

 TELIOSPOREAE 



Introduction 



IN CONTRAST to the Condition in the CUass Ascomyceteae the ultimate 

 reproductive spores in the Basidiomyceteae are produced externally 

 upon usually terminal cells within which caryogamy and subsequent 

 meiosis produce successively a diploid and then four haploid nuclei. In the 

 Ascomyceteae the haploid nuclei formed as a result of the meiotic divi- 

 sions of the diploid nucleus become the centers of ascospores formed 

 within the ascus. The difference is apparently that in the one class the 

 spores are produced internally but in the other externally. In reahty even 

 in the latter case distinct spore walls are sometimes produced around the 

 spores within the pocket-like outgrowths from the main cell so that the 

 basidiospore is an internally produced spore surrounded by and usually 

 adhering to the wall of the projecting pocket from the basidium. 



(Fig. 119.) 



The basidiospores or sporidia throughout the class are universally 

 unicellular when first formed and usually uninucleate (except in the more 

 unusual cases where two nuclei enter the spore from the basidium). In 

 many species the nucleus divides within the spore before the latter is set 

 free. In Dacrymyces and some other genera the basidiospore becomes 

 transversely septate into several cells at or shortly after maturity. In 

 color the spores in this class vary from hyaline (the majority of species) 

 to pink or to yellow-brown, brown, purple-brown, and black. 



Typically in the Ascomyceteae there are various means by which the 

 ascospores are expelled from the ascus, thus providing for their distribu- 

 tion. Similarly in most of the Basidiomyceteae where the spores are 

 produced in the open air there is a special provision for the discharge of 

 these spores from their points of attachment. The spores are usually dis- 

 charged with considerable violence, usually all four spores being dis- 

 charged successively at intervals of several seconds to several minutes, 



366 



