624 LECTURE XXII. 



which more or less resemble those of Pyronema, but there is 

 at present no evidence that a sexual process takes place 

 between them. On the contrary, there is reason to believe 

 that these Ascomycetes, though morphologically sexual, are 

 not physiologically sexual. Still the ascogonium gives rise to 

 asci and ascospores, but the ascospores must be regarded as 

 being parthenogenetically produced. They are, then, not 

 actually sexually produced spores, but they are homologous 

 with them. In other forms (Chaetomium, Melanospora) only 

 one organ, the ascogonium has been found ; it seems that the 

 pollinodium has here disappeared. In these cases also the 

 ascogonium produces asci and ascospores, and it is clear that 

 these ascospores must be parthenogenetically developed. In 

 others again (Xylaria), even the ascogonium is rudimentary 

 (Woronin's hypha), and, finally, in others (Claviceps, Cordiceps, 

 Pleospora) no trace even of an ascogonium can be found. But 

 even in these cases asci and ascospores are produced, the asci 

 springing from the vegetative mycelium. It is here a case, 

 not of parthenogenesis, but of complete apogamy ; the sexual 

 production of spores is replaced by an altogether asexual 

 process ; but the mode of development of the spores resembles 

 that of the sexually produced spores of the sexual forms. 



In the remaining groups of the Fungi, the Uredineae and 

 the Basidiomycetes, no sexual process has been observed. In 

 the Uredineae, spermatia, like those of the Ascomycetes, are 

 commonly produced, but no female organ has been discovered. 

 However, the Uredineae produce fructifications, termed cecidia, 

 which somewhat resemble those of the Ascomycetes, but the 

 spores (aecidiospores) are developed, not in asci, but by ab- 

 striction. It may be that we have in the aecidium a fructifica- 

 tion which, though apparently produced independently of a 

 female organ, corresponds to that of the Ascomycetes which 

 is produced from the ascogonium in consequence of fertilisa- 

 tion ; we know, in fact, that this is true of the fructification of 

 the asexual Ascomycetes. But when we come to the fructifi- 

 cation of the Basidiomycetes, such a correspondence cannot be 

 traced. No kind of sexual organ has been discovered in the 

 Basidiomycetes, in spite of the most careful and complete 



