tn] 



PLECTASCALES 



67 



In G. candidus (fig. 27 d) the antheridium and oogonium already differ 

 in form at the time of their union, and, in the majority of cases, appear to 



Fig. 2j. Gymnoascus Reesii Baran.; a. surface view of conjugating cells; 

 b. the same in longitudinal section; c. a later stage, septate oogonium 

 giving rise t" hyphae ; Gymnoascus candidus Eidam; 



(/. surface view of conjugating cells; e. same in longitudinal section; 

 all after Dale. Ctenomyces serratus Eidam; /'. surface view of con- 

 jugating cells, X400; after Eidam. 



arise from different hyphae. As in G. Reesii the antheridium is straight, 

 but the oogonium elongates before fusion and grows spirally around it till 

 the apices meet and fuse (fig. 27 e). Afterwards the oogonium undergoes 

 septation and gives rise to ascogenous hyphae. The sheath of protective 

 hyphae is very scanty, represented by a few thin-walled filaments. 



Amauroascus verrucosus forms sexual organs which, in their early stages, 

 closely resemble those of G. Reesii. Two similar multinucleate hyphae 

 grow up, and later one of them, the oogonium, enlarges considerably; it 

 branches without septation, and gives rise to ascogenous hyphae which are 

 cut off by transverse walls. Our knowledge of development in this species 

 is due to Dangeard, who has not observed fusion between the sexual 

 cells. 



In Ctenomyces serratus (fig. 27/"), which occurs saprophytically on 

 1 athers, organs quite similar to those of G. candidus have been described 

 by Eidam, and more recently by Dangeard. The}- are multinucleate, and 

 the oogonium is long and elaborately coiled and ultimately becomes seg- 

 mented. In this species, as in the others he has studied, Dangeard regards 

 the central hypha not as an antheridium, but as a nutritive structure which 

 he terms a trophogone. He denies the passage of its contents into the 

 female organ. 



5— 2 



