ASCOMYCETES 131 



Geopyxis catinus (Peziza catinus), the terminal cell of the ascogenous 

 hypha (like the hook cell of Pyronema confluens) is uninucleate, the sub- 

 terminal is binucleate (Fig. 80) . This subterminal cell grows out laterally 

 and develops to an ascus (Guillermond, 1905a). 



Somewhat further removed is the Plicaria (Galactinia) type, (Maire, 

 1905) which includes Plicaria succosa (Galactinia succosa) and Acetabula 

 leucomelas (Peziza leucomelas). In these, the ends of the ascogenous 

 hyphae include a series of cells with a dicaryon each, the terminal cell of 

 which develops to an ascus by the fusion of its nuclei. This type, how- 

 ever, in spite of its morphological picture, which is entirely at variance 

 with the Pyronema type (as also the systematic relationships of all these 

 forms would allow us to suppose), does not seem to be fundamentally 

 different. As an anomaly in Pustularia vesiculosa (Peziza vesiculosa), the 

 ascogenous hyphae may form a hook of the Pyronema type, whose crook 

 cell, instead of developing to an ascus by repeated division of its dicaryon, 

 grows into an elongate hypha whose terminal cell proceeds to the forma- 

 tion of an ascus according to the Plicaria type. 



Still further removed from the hook type, is a fourth which has not 

 yet been investigated cytologically. In it the cells of the ascogenous 

 hypha, as in the Plicaria type, apparently each contain a dicaryon. A 

 large number of them, however, develop asci (in contrast to the Plicaria 

 type) so that the asci lie behind each other, as in a chain, and then divide. 

 Possibly this type is the most primitive of the four, as it has only been 

 definitely ascertained in the lower Plectascales. It has been named by 

 Dangeard (1907) the rectascous type in contrast to the curvascous type 

 of Pyronema. 



In a fifth type, finally, no true ascogenous hyphae are formed, but 

 asci develop from a cell complex which arise directly from the fertilized 

 cells of the ascogonium. We will discuss this type more fully in the 

 Laboulbeniales. 



The further development of the asci, as far as is known, is the same 

 in all Ascomycetes. The primary ascus nucleus, which has arisen from 

 the fusion of the dicaryon, undergoes three steps in division with meiosis, 

 whereupon the eight daughter nuclei cut out eight ascospores from the 

 cytoplasm of the ascus by free cell formation. The cytoplasm remaining 

 behind is called epiplasm; in addition to the nourishment of the ascospores 

 growing in it, it provides for the formation of the sculpturing of the spore 

 walls. In certain forms, the number of divisions may be limited to two or 

 rise to sixteen, whereupon in the first case the number of nuclei is reduced 

 to four, in the second rises to many thousand (64,936). In case the asco- 

 spores are thick walled, they possess a typical terminal germ pore or a 

 meridional slit; in the latter case the two halves of the ascospore wall 

 separate in germination like the cover of a box. According to the 

 Anglo-Saxon school (especially represented by Harper and Gwynne- 



