352 FUNGI 



resting- spore or the single gamete, as the case may be, produces a 

 mycelial germ-tube, as a sporid does. 



When the resting-spores germinate in nutritive fluids, as the ex- 

 periments of Brefeld show, the product is, according to the species, either 

 directly a mycele which bears spores, or an abundant yeast-like out- 

 growth from the promycele. In cases where the resting-spores failed to 

 germinate, they were permitted to do so in water, and the sporids so 

 formed, on being introduced into a nutritive fluid, gave rise to myceles 

 bearing acrospores, resembling, as the case might be, either the gametes 

 or the sporids. 



Accessory acrospores resembling the sporids are borne on branches 

 of the mycele of certain species of Entyloma before the production of 

 resting-spores. The branches of the mycele which bear them protrude 

 through the stomates and epiderm of the host. They probably give 

 rise to new myceles, as the spends" do. The same thing occurs in 

 Tuburcinia Trientalis (Berk.), only here the accessory spores differ in 

 form from the promycelial sporids. They produce in this case un- 

 doubtedly each a mycele which bears resting-spores. 



Brefeld regards the conjugation of the gametes as a merely vege- 

 tative process, and in no way analogous to any sexual act. De Bary 

 ('Comp. Morph.,' p. 182) subjects Brefeld's arguments to destructive 

 criticism, while stating Brefeld's case in the fairest terms. While the 

 student is referred to the source quoted for the details, it may be shortly 

 stated that de Bary's arguments are broadly based on the regularity 

 with which conjugation occurs, and on the fact that it takes place 

 equally regularly in pairs, under the normal conditions of germination 

 in water. He shows, besides, conclusively how the process differs from 

 the well-known vegetative anastomosing of hyphae, c. 



De Bary regards the higher forms of Ustilagineae, such as the coil- 

 forming. Urocystis, Sorosporium, and Tuburcinia, and Sphacelotheca 

 with its well-developed stroma, as connected through the simpler forms 

 (e.g. Entyloma) with Protomyces. Both produce (in the one case acro- 

 genous, in the other endogenous) conjugating cells of equal value. The 

 next indicated ally is Cladochytrium, the spores of which are zoospores 

 (a matter not affecting the homology), but these fail to conjugate so far 

 as is known. At all events the nearest ally appears to be, in the present 

 state of our knowledge, that group of Chytridiaceae to which Cladochy- 

 trium belongs, through Entyloma and Protomyces. 



The peculiarity is to be noted that in Protomyces and the Ustila- 

 gineae the act of conjugation takes place at a stage of the life-history 

 which bears no homology with the sexual states of other Phyco- 

 mycetes. 





