THE TIIALLOPIIYTA 



293 



of a much-branched mycelium extending throughout the sub- 

 stratum, and a definite fruiting body which is developed at the 

 surface. Each group displays a rather specialized method of 

 spore formation. 



The Ascomycetes are distinguished by their production of 

 spore sacs or asci (singular, ascus) in each of which are borne 

 eight spores, the ascospores (Fig. 168). A group of asci are 



Fig. 168. — Spore production in an ascomycete. Portion of the hymenium, 

 or fruiting surface, of Peziza, showing the asci, each with eight ascospores. 

 Among the asci are slender, sterile hairs, or paraphyses, and two young asci. 



generally embedded in a mass of sterile hj^phae and partially or 

 completely surrounded by a protective envelope of compact 

 mycelium. Such a fruiting body is known as an ascocarp. In 

 many cases, this ascocarp has been found to originate as the 

 result of a sexual union deep in the mycelium, the whole process 

 bearing a considerable resemblance to that found among the red 

 algae. The ascomycetes include an immense variety of types, 

 only a few of which can be mentioned here. 



1. Pezizales or Cup Fungi (Fig. 169). — Throughout this order 

 the ascocarp is a broad disc, cup, or funnel, and the name Dis- 



