SUBCLASS TELIOSPOREAE 379 



and consists of primary (monocaryon) and secondary (dicaryon) phases. In 

 the latter certain cells enlarge and their two nuclei unite to form a diploid 

 nucleus. This cell is a teliospore. It usually has a thick, colored wall and 

 serves as a resting spore. With the proper environmental conditions this 

 teliospore germinates by sending out a thin-walled straight or curved, four- 

 celled or one-celled hypha, the promycelium, within which the zygote nucleus 

 divides meiotically to form four (or, by further mitotic division, more) 

 nuclei. Usually four sporidia are formed on the promycelium and into each 

 of these a single nucleus enters. These sporidia are shot off with violence 

 or (in the Family Ustilaginaceae) fall off, and give rise to the primary type 

 of mycelium or by union of two sporidia of suitable sexual compatibility the 

 secondary type of mycelium arises. The teliospores are formed within or 

 upon the host tissues in so-called sori. Various secondary types of (asexual) 

 reproduction are produced. 



Heterobasidiae: mostly saprophytic, but in many cases parasitic upon various 

 types of Bryophyta or Vascular Plants. Mycelium septate, mostly falling 

 into two phases, the monocaryotic and dicaryotic. From the latter are pro- 

 duced the spore fruits characteristic of the subclass. The basidia are usually 

 produced in a hymenium, i.e., they stand side by side like a palisade, but 

 may be more scattered. They arise as enlarged binucleate cells whose nuclei 

 fuse. Only rarely does the basidium become dark-colored and thick-walled. 

 Usually the formation of the basidiospores takes place without much delay. 

 The basidia may be one-celled and forking (Dacrymycetales), transversely 

 four-celled (Auriculariales), longitudinally four-celled (Tremellales), or one- 

 celled with four enlarged epibasidia bearing the basidiospores (Tulasnellales) . 

 Spore fruits are more often gelatinous when wet, or waxy. The basidiospores 

 often germinate by budding at many points in water. Possibly Sporoboloniyces 

 was derived from this subclass. 



Eubasidiae: Mostly saprophytic but some species parasitic. Very often living 

 in the wood of living or dead trees. Basidia one-celled, without epibasidia 

 but bearing usually four long or short sterigmata, each bearing a single 

 basidiospore which usually germinates by a germ tube, even when fallen 

 into water. Basidia produced with some exceptions in definite hymenial 

 layers which may be exposed to the air before the spores become mature 

 (the "Hymenomycetes"), or enclosed in the spore fruit until after the spores 

 are completely mature (the "Gasteromycetes"). In this subclass are found 

 the largest spore fruits of the whole Phylum Carpomyceteae (Higher Fungi). 



Subclass Teliosporeae 



The subclass Teliosporeae corresponds to Dietel's limits of subclass 

 Hemibasidii in the second edition of Engler and Prantl's Die Natiirlichen 

 Pflanzenfamilien (1928). These fungi have been sometimes called the 

 Brand Fungi. Usually the two orders Uredinales and Ustilaginales have 

 been considered to be more or less closely related. They were placed close 

 together by Fries (1832) as Ordo IV* Hypodermii,i and by Plowright 

 (1889) and by most of the later botanists. Bennett and Murray (1899) 



1 It should be noted that Fries did not believe that these were true fungi but that 

 the spores arose by the transformation of the tissues of the host plant and were not 

 used for the propagation of the rust or smut. 



