GROUP I. THALLOPHYTA : FUNGI. 



293 



are brought by means of water into contact with the projecting 

 trichogyne. One of them adheres to the trichogyne ; the cell-walls 

 are absorbed at the point of contact, and the protoplasm of the 

 spermatium enters the trichogyne, with the result that the 

 ascogonium developes into an ascocarp. 



It is probable that, in consequence of sexual degeneration, the 

 sexual organs are f unctionless in the majority of those Ascomycetes 

 in which both kinds of them are present. 



The Ascocarp. In those Ascomycetes in which there is an 

 archicarp, the ascocarp is developed directly or indirectly from 

 that organ : when no archicarp is present, the ascocarp is developed 

 directly from the mycelium. 



The simplest form of ascocarp is found in Ereinascus (Fig. 171). 

 After the sexual process has taken 

 place, a large spherical cell is formed 

 at the point of junction of the two 

 sexual organs. This cell is an ascus, 

 and produces within it eight ascospores. 

 Here the whole ascocarp consists of a 

 single naked ascus. 



The ascocarp of some of the Ery- 

 sipheae (e.g. Sphserotheca) is but little 

 more complex than that of Eremascus. 

 Here likewise the archicarp gives rise 

 directly to a single ascus ; but an in- 

 vestment is formed round the develop- 

 ing ascus by the growth round it of 

 hyphae from the adjacent mycelium, 

 which cohere to form a layer of paren- 

 chymatous tissue. 



In the majority of forms the development of the ascocarp is 

 indirect. The archicarp gives rise to a greater or smaller number 

 of filaments, branched or unbranched, the ascogenous hyphce 

 (which closely correspond to the ooblastema-filaments of the 

 Rhodophycese, see p. 273), from which the asci are formed as 

 branches, and which together form a compound sporophore. The 

 asci are developed close together, forming a hymenial layer or 

 group, and may or may not be enclosed, either completely or 

 partially, by an investment formed from the surrounding myce- 

 lium. In the latter case, vegetative hyphae grow in among the 

 ascogenous hyphae and terminate in a number of sterile filaments, 



PIG. 172. Sexual reproduc- 

 tion in Pyronema confluent : e 

 archicarp with trichogyne () 

 which has fused with the 

 pollinodium a. ( x 300 : after 

 Kihlman.) 



