298 



PART III. THE CLASSIFICATION OF PLANTS. 



sexual organs are f unctionless in the majority of those Ascomycetes 

 in which both kinds of them are present. In some forms sexual 

 degeneration has proceeded so far that no male organ is developed 

 (e.g. Chaetomium, Melanospora) ; in others there is not only no male 

 organ, but the female organ is either rudimentary, being re- 

 presented only by a structure known as Woronin's hyphae (e.g. 

 Xylaria), or cannot be detected at all (e.g. Claviceps, Pleospora). 

 The Reproductive Organs of the Sporophyte. The sporophyte is 



PIG. 207. Sexual reproduction in 

 Pijronema, confluens : c archicarp with 

 trichogyne (t) which has fused with the 

 pollinodium a. (x300: after Kihlman.) 



FIG. 208. Section of the homoiomerous 

 thallus of Collema(a Lichen) : a the ascogo- 

 nium; t the trichogyne; Ji the hypba; n the 

 algal filaments (Nostoc). (x350: after Stahl). 



a fructification termed the ascocarp, which (assuming its sexual 

 origin, p. 279) corresponds to the cystocarp of the Rhodophyceae. 

 In those Ascomycetes in which there is an archicarp, the ascocarp 

 is developed directly or indirectly from that organ, either as the 

 result of fertilisation, or parthenogenetically, in those forms 

 respectively in which a sexual process does or does not take place. 

 When no archicarp is present, or when it exists in only a rudi- 

 mentary form (Woronin's hypha), the ascocarp is developed 

 directly from the mycelium. 



The simplest form of ascocarp is found in Eremascus (Fig. 206). 

 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 Podosphsera (one of the Erysipheae) is but little 

 more complex than that of Eremascus. Here likewise the archi- 

 carp gives rise directly to a single ascus ; but an investment is 



