EU-MYCETES. (a) ASCOMYCETES 



435 



either case the result at ripeness is that the fruit appears as a dry 

 spherical sac, filled with ascospores set free by the disappearance of 

 the ascus-walls, and of the nutritive tissues that embedded them. On 

 germination the ascospores form a new mycelium. (Fig. 367, 2, 3, 4.) 



In Aspergillus both the antheridial and carpogonial cells are multinucleate, 

 and it appears that sometimes a normal sexual fusion takes place. But in 

 others the antheridium degenerates, and sexual fusion is replaced by a fusion 

 of ascogonial nuclei in pairs. Thus Asper- 

 gillus illustrates that degradation of 

 sexuality, evidence of which is common 

 among the Fungi. 



The type of life-history seen in these 

 simple Mildews and Moulds is common 

 for other Ascomycetes, though it may be 

 worked out with greater complication. 

 But in many of them the sexual organs 

 are so degraded that they, or their 



a 



A B 



FIG. 368. 



A, a sclerotium of Peziza, which has germinated and given rise to numerous 

 trumpet-shaped discs. B, section through such a sclerotium (sc), and the Peziza 

 disc (d) to which it has given rise, b = stalk. a=asci. Magnified and slightly dia- 

 grammatic. (From Marshall Ward.) 



equivalents, if present, have hitherto escaped observation. There is normally 

 an alternation of generations, the critical points of which are the sexual 

 fusion in the carpogonium, and the reduction which precedes the formation 

 of the ascospores. The stage of the ascogenous hyphae, which intervenes 

 between these events may be regarded as a diploid sporophyte. The rest is 

 held to be the haploid gametophyte, which is liable to indefinite repetition by 

 means of conidia. The fruit-body is then a composite structure, consisting 

 essentially of the ascogenous hyphae, constituting the sporophyte, which is 

 enveloped in a covering derived from the mycelial gametophyte. The nearest 

 analogies are with the fruiting bodies of the Red Seaweeds. 



Both the mycelial and the fruiting stages of Ascomycetous Fungi 

 are subject to modifications according to habit and circumstance, 

 and either may attain large size. The mycelium may, by repeated 



