CHAPTER XXVIII. 



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. 



Portion of the hymenium of the 

 Morel (Morchella esculenta). a = asci. 

 =paraphyses. sA=sub-hymenial 

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



