CHAPTER XXVI. 



ASCOMYCETES. 



The Fungi belonging to the Ascomycetes, the first sub-class of the 

 septate section, are very various in habit. Many are parasites, 

 often on leaves and stems of Flowering Plants : for instance the 



Mildews, such as Sphaerotheca. Others 

 are saprophytes, such as the small and 

 prevalent Moulds, Aspergillus and Pent- 

 cillium. Others again form large fruiting 

 bodies, such as those of Peziza, or the 

 edible Truffle (Tuber), or the Morel (Mor- 

 chella). Some are parasitic on animals, as 

 in the case of Cordyceps, which invades 

 caterpillars and the larvae of Cock- 

 roaches. The Ascomycetes are thus not 

 only a large but very varied group of 

 Fungi. 



Their characteristic feature is a club- 

 shaped or oval body, the Ascus, within 

 which Ascospores usually to the number 

 s ' 1 of eight are contained (Fig. 316). Such 

 asci may occasionally be produced singly 

 FlG - 316. j n very simple forms, such as Sphaero- 



MoreMA/orcL/S^s^SaPalascL theca ; but they are commonly associated 

 SsluTT^o.) wSiSKESS together in large numbers, in fruit-bodies 



of various form. In many cases the 

 development of the asci has been found to follow on the formation 

 of sexual organs, of which the female is an oogonium, sometimes with 

 a receptive trichogyne, as in the Red Seaweeds. The ascospores may 

 therefore be held to be of the nature of post-sexual tetraspores formed 



418 



