240 



PEZIZA 



inner surface of the cup. These form a palisade-like layer (the 

 hymenium, h.) composed of numerous elongated sporangia or 

 asci (Fig. 127, A, a-f), interspersed with the slender hair-like 

 ends of barren hyphse (p.). Each ascus contains eight ellipsoidal 

 ascospores (e, /), which are liberated when mature through a 

 terminal aperture on contact with moist air. Mere breathing 

 on a ripe fruit-body may often cause the liberation of a cloud 

 of spores. 



FIG. 127. Peziza vesiculosa. B, Section of half an'apothecium (diagram- 

 matic), and A, Small part of the hymenium enlarged, showing asci 

 in progressive stages of development (-/). h., hymenium ; p., barren 

 hyphae of same ; s., small-celled subhymenium. (After Goebel.) 



The ascus is typical of the Ascomycetes as a whole, and 

 constitutes one of the chief characteristics. For, by contrast 

 with the Basidiomycetes (cf. p. 245), the spores are produced 

 within the mother-cell, whilst in contradistinction to the Phyco- 

 mycetes they are nearly always only eight in number, though some- 

 times fewer (e.g. two or four, as in the Truffle), or more numerous 

 (sixteen or thirty-two). In many cases the asci, as in Peziza, 

 are grouped together in compact and often large fruit-bodies, 

 the hymenium either covering a great part of the exposed surface 

 (as in the Morel, Morchella, Fig. 126, D, and Geoglossum, Fig. 

 126, B) or being completely enveloped within sterile hyphae ; 



