CHAPTER XXVIII. 



a 



EU-MYCETES. (a) ASCOMYCETES. 



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

 septate Eu-mycetes, are very various in habit. Many are parasites, 

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

 dews, such as Sphaerotheca. Others are sap- 

 rophytes, such as the small and prevalent 

 Moulds, Aspergillus and Penicillium. 

 Others again form large fruiting bodies, 

 such as those of Peziza, or the edible 

 Truffle (Tuber), or the Morel (Morchella}. 

 Some are parasitic on animals, as in the 

 case of Cordyceps, which invades cater- 

 pillars and the larvae of Cockroaches. 

 The Ascomycetes are thus not only a 

 large but a very varied group of Fungi. 



Their characteristic feature is a club- 

 shaped or oval body, the Ascus, within 

 which Asco-spores usually to the number 

 of eight are contained (Fig. 362). Such 

 asci may occasionally be produced singly 

 in very simple forms, such as Sphaero- 

 theca ; but they are commonly associated 

 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 a carpogonium, sometimes with a receptive trichogyne, as in the 

 Red Seaweeds. The ascospores may therefore be held to be of the 

 nature of post-sexual carpospores. In other cases the sexual organs 



429 



FIG. 362. 



the 



Portion of the hymenium of 

 Morel (Morchella esculent a). a = ax i. 

 p = paraph yses. sh = sub-hymenial 

 tissue. ( x 240.) (After Strasburger.) 



