SUMMARY OF SUBCLASSES TELIOSPOREAE AND HETEROBASIDIAE 457 



cytology and taxonomy of these genera were studied by Rogers (1932, 

 1933). (Fig. 152 A, B.) 



From the two foregoing genera Ceratobasidium is distinguished by the 

 stout "epibasidia," elongate cornute or flexuous, continuous with the 

 "hypobasidium" (rarely a cross septum). The spore fruit is arid or waxy. 

 Six or more species. By the usual absence of septa cutting off the "epi- 

 basidia" and their cornute shape they approach on the one hand Dac- 

 rymyces [in C. sterigmaticum (Bourd.) Rogers, in which only two such 

 horns are produced, while the remaining species with their four "epi- 

 basidia" approach Pellicularia in the Thelephoraceae (Eubasidiae). 

 From the latter they differ by the germination by repetition, of the 

 basidiospores. (Fig. 152 C.) 



Summary of Subclasses Teliosporeae and Heterobasidiae 



A comparison of these subclasses demonstrates more or less basic 

 similarities throughout, in basidium production. Between the Auri- 

 culariales, Uredinales, and Ustilaginales there are such basidial similari- 

 ties that they are often placed together in one group. On the other hand 

 the tendency for the septation of the basidium in the Tremellales to be 

 oblique instead of vertical is taken by some mycologists who have studied 

 these groups intensively to indicate gradation from one to the other. 

 Rogers (1934) suggested that the septa at the base of the "epibasidia" of 

 Tidasnella may be accounted for by displacement upward of the vertical 

 septa of the basidium of Tremella. The peculiar tuning-fork type of 

 basidium of Dacrymyces could be considered a derivation from the 

 Tidasnella type by the loss of their cross septa entirely and the reduction 

 of the "epibasidia" to two (as actually does occur in Ceratobasidium 

 sterigmaticum) . 



The question of the phylogeny of these groups is treated more fully 

 in Chapter 17, but the following suggestions may well be made here: 



Studies by Juel (1898), Neuhoff (1924), Martin (1931), and Rogers 

 (1934) have led the latter to an interpretation of the relationships in the 

 class somewhat different from that of the author. He holds in common 

 with some of the others mentioned, that the primitive basidium con- 

 sisted of two parts, the basal hypobasidium, binucleate at first, within 

 which the nuclear union occurs, and one or more outgrowths, the epi- 

 basidia. Into the latter the nuclei pass from the hypobasidium. Meiotic 

 division may occur either in the latter or in the epibasidium, if there be 

 but one. Each epibasidium produces a true sterigma which bears a 

 basidiospore. The genus Tulasnella is considered by Rogers to represent a 

 primitive form. In the ovoid or pyriform hypobasidium of this genus the 

 fusion nucleus divides into usually four nuclei. One of these passes out 

 into each of the four (sometimes fewer) stout epibasidia which usually 

 become separated from the now almost empty hypobasidium by a basal 



