SECT. I 



387 



a 



like, firm, pseudo-parenchymatous bodies, which germinate under certain 

 conditions (Fig. 107). In the fructifications the hyphae are also nearly 

 always aggregated into a more or less compact tissue (Fig. 106). 



The distinction between the two main groups is apparent in their 

 reproductive organs. 



1. The Ascomycetes in their typical forms possess sexual organs. 

 The oogonia, Avhich here go by the name of ascogonia or, as in the 

 Red Algae, of carpogonia, show profound differences in the genera 

 which have as yet been accurately inves- 

 tigated and the same may be said of the 



male organs. In all cases, however, the 

 fertilised carpogonium does not become a 

 resting oospore, but, while in connection 

 with the maternal plant (gametophyte), 

 develops into an asexual generation (sporo- 

 phyte). In this process hyphse bud out 

 from the carpogonium, and their ultimate 

 branches terminate in the asci which are 

 sporangia of a specialised type. 



The ASCUS ( 60 ), which is so character- 

 istic of the whole group, originates from a 

 tubular cell ; this to start with contains 

 two nuclei which fuse, and the resulting 

 nucleus by repeated division gives rise to 

 eight nuclei. By a process of free cell- 

 formation the spores become limited by 

 cell-walls in the way shown in Fig. 96 

 (Figs. 327, 334). In contrast to the forma- 

 tion of spores in the sporangia of Phyco- 

 mycetes the cytoplasm of the ascus is not 

 completely used up in the formation of 

 the ascospores. The spores usually form a longitudinal row, and 

 are ultimately ejected from the ruptured apex of the ascus by the 

 swelling of the remaining cytoplasm. In the great majority of the 

 Ascomycetes the number of ascospores in the ascus is eight. 



In the majority of Ascomycetes the asci, which originate from the 

 carpogonium, are associated in special fructifications ; vegetative 

 filaments of the mycelium take part in the formation of these. 



Sexual organs are not at present known in all the groups of 

 Ascomycetes. In certain orders they are entirely wanting, perhaps 

 as a result of reduction, so that the asci in these cases spring directly 

 from the mycelium. 



2. The Basidiomycetes no longer possess sexual organs ; only in 

 the Uredineae or Rust-fungi are structures found which can be 

 regarded as persisting male organs, and cells which appear to 

 correspond to the carpogonia of Ascomycetes (cf. p. 406). Asci are 



FIG. 327. Portion of the hyim-iimni 

 of Morchella esculentu. a, Asci ; 

 p, paraphyses ; sh, Milihynu-iiial 

 tissue, (x 240.) 



