66 



PLECTOMYCETES 



[CH. 



igio WAGER, H. and PENISTON, A. Cytological Observations on the Yeast Plant. Ann. 



Bot. xxiv, p. 45. 

 191 1 GuiLLlERMOND, A. Les Progres de la Cytologic des Champignons. Prog. Rei Bot. 



iv, pp. 433 and 468, et seq. 

 191 1 Nadson, C. A. and Konokotine, A. G. Guilliermondia, un nouveau genre de la 



faraille des Saccharomycetes a copulation he"terogamique. Bull, du Jard. Imp. de 



St Petersbourg, xi, p. 117. 



1913 Marchand, H. La conjugaison des spores chez les levures. Rev. Gen. de Bot. xxv, 

 p. 207. 



1914 BAYLISS, W. M. The Nature of Enzyme Action. Monographs on Biochemistry. 

 Longmans, Green & Co., London (and see literature cited). 



Gymnoascaceae 



The Gymnoascaceae differ from the Endomycetaceae in that their asci 

 are borne on a sporophytic mycelium which originates from the female 



organ after the fertilization stage. 

 These ascogenous hyphae are sur- 

 rounded by a loose weft of protec- 

 tive filaments which bear spines or 

 variously coiled or hooked branches 

 (fig. 26). The asci are ovoid or pyii- 

 form, and each contains eight spores. 

 The species of Gymnoascus occur 

 in various habitats, on dung, bees' 

 nests, dead grass, etc. 



In G. Reesii, according to Dale, 

 two branches grow up from the 

 same hypha, one on each side of 

 a septum, and become twisted 

 around one another. These are the 

 antheridium and oogonium; their 

 free ends swell into club-shaped 

 heads which lie in close contact and 

 each becomes delimited by a transverse septum. The walls between them 

 break down, and the contents of the antheridium pass over into the 

 oogonium (fig. 27 a, b). Both cells are at first uninucleate, but later coeno- 

 cytic, and, though the history of the nuclei has not been traced, it seems 

 almost certain that fusion must sooner or later occur. 



Up to this point the sexual cells are usually quite similar in form, but 

 now the antheridium grows larger and more spherical, remaining almost 

 straight, while the oogonium puts out a prolongation which winds around 

 it, undergoes septation and soon branches to give rise to ascogenous 

 hyphae (fig. 27 c). 



Fi 



26. Gymnoascus sp.; a. ascocarp, x 26; 

 b. ascus and free ascospores, x 1040. 



