Three Noteworthy Species of Disperis (Orchidaceae) Unrecorded for East Africa

Abstract

In a genus such as Disperis which comprises mostly small species having flowers of a complicated structure, and which in addition are easily overlooked in their wooded habitats, it is to be expected that new or unrecorded species remain to be discovered. Moreover, without close study, many of the species resemble each other to such an extent that it is easy for one to pass new taxa over in the field as ones already known. A remarkable instance of this close resemblance has recently come to light in South Tanzania. Mr. R. C. Wingfield discovered what appeared to be a single species of Disperis in a cypress plantation above Mbeya, Tanzania, flowering in April and early May, which did not match any of those mentioned in my account of the East African species (Verdcourt in Summerhayes, Fl. Trop. East Africa, Orchidaceae (part I): 216-230, figs. 39-41 (1968)). He also asked the Rev. Dr. Leedal to look out for more material; both dried and spirit material together with detailed notes were sent to Kew and certainly proved not to belong to any species I had dealt with. A careful study of this material revealed that two different plants were involved, outwardly appearing identical but with very different lips. These differences appeared as though they could have been caused by portions becoming detached with age, so yet more material was requested in bud to confirm or otherwise if this took place. The additional material only served to confirm that two taxa grew together, and a more detailed investigation revealed subtle correlated characters in the positions of the pockets on the lower sepals. The species with the more complicated lip surprisingly proved to be identical with a South African species known from Cape Province and also from the Drakensberg Mountains in Natal; the other with a much simpler lip appears to be a locally derived mutant which I am reluctantly describing as a new species.