U ST IL AGIN ALES 611 



with the general experience that in these, the hereditary fixed characters 

 are again set free. 



In the Ustilaginaceae which in many respects, e.g., in regard to para- 

 sitism in intercellular spaces, are more pronouncedly parasitic than the 

 Uredinales but can also be saprophytic, one can explain on biological 

 grounds the vegetative germination of the promycelium more simply 

 than in Puccinia Malvacearum. In contrast to the Uredinales, on the 

 germination of the smut spores there follows a longer saprophytic portion 

 of existence (indicated by the sprout mycelium) which has so markedly 

 characterized the majority of the species here considered that at this 

 stage of development, only sprout mycelium is known. Thus, it is not 

 surprising that this sprouting has displaced the formation of the now 

 biologically superfluous basidiospores and proceeds directly from 

 promycelium. 



Thus we have in the Ustilaginaceae a last member of a phylogenetic 

 series which includes Platygloea and Septobasidium in the Auriculariales, 

 Tremella and Sirobasidium in the Tremellales and Kordyana and Exoba- 

 sidium in the Cantharellales, where the basidiospores germinate chiefly 

 or regularly by sprout mycelia. This would have the effect that not 

 only the basidiospores, which in part remain on the basidium, develop to 

 sprout mycelia but that the sprout mycelium, without this circuit, arises 

 directly from the basidial cells. Here, apparently, we have the same 

 phenomena which we were able to pursue step by step in the Endomycet- 

 aceae-Saccharomycetaceae series of the Ascomycetes where the asci no 

 longer proceed to ascospore formation but germinate directly to 

 sprout mycelia. 



In the Saccharomycetes, the asci, because of their direct development 

 to sprout mycelia, lost their characters of sporophores (sporangia) and 

 became vegetative structures. In the Ustilaginaceae the basidia, by the 

 elimination of basidiospore formation and vegetative germination, lost 

 successively their characters as basidia; the division into four in the pro- 

 mycelium, having become senseless in the absence of spore formation, 

 has disappeared and the germ tube which arises from the smut spores 

 proceeds directly to the formation of sprout mycelium. It is perhaps no 

 accident that the form most marked in this direction, Ustilago longissima, 

 inhabits a waterplant, whereby the extreme development of the pellicle 

 sprout mycelium may be explained as a biological adaptation. U. 

 longissima, U. bromivora, etc., would be considered end forms in which the 

 gonotocont has lost its typical form and was replaced by a purely vege- 

 tative germination. Pro-Ustilago, Hemi-U stilago and Eu-Ustilago are 

 therefore not a phylogenetically conditioned, ascending series but a 

 biologically conditioned, descending series with constantly increasing 

 intensity of adaptation which begins with Eu-Ustilago and in Pro-Ustilago 

 disappears with complete obliteration of morphological characteristics. 



