CHAPTER XXVIII. 



EU-MYCETES.— (a) ASCOMYCETES. 



The Fungi belonging to the Ascomycetes, tlie 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 

 TrufHe {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. 



PortioD of the hymeiiium of tlie 

 Morel [Morchella esculenia). fl = asci. 

 ^^paraphyses. s^^sub-hymeniai 



tissue. {X240.) {.\fter Strasburger.} 



