Cytology of the Teliospores, Basidia, and Basidiospores of Sphenospora kevorkianii Linder

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Abstract
A cytomorphological study of the telia of S. kevorkianii, a parasite on leaves of the orchid Epidendrum, reveals a type of development similar to that already described for Puccinia, except that the septum of the telio-spore is vertical instead of transverse. Nuclear fusion occurs in the teliospore. Paraphyses originate from the same cells as do the teliospores; they are typically binucleate. Teliospores germinate to produce basidia without requiring a resting period. Two successive nuclear divisions take place in the basidium and the septa are laid down in irregular order. In most cases the basidia are 3-celled, with one cell binucleate and the other 2 uninucleate, but a number of variations from this type are described. Occasionally a nucleus appears to be cut in two by a developing septum of the basidium. Mature basidia produce from 1-4 basidiospores, most often 3. The majority of spores are uninucleate, but those arising from binucleate basidial cells are binucleate. There is some evidence that the binucleate spores are heterocaryotic. This developmental study indicates that the taxonomic treatment of the genus Sphenospora by Dietel is probably the most acceptable at the present time. It is suggested that the genus be retained for the present in the tribe Ravenelieae of the Pucciniaceae.

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