Abstract
As has been repeatedly emphasized elsewhere, species in section Pilifer Volk are often very difficult to distinguish (Perold 1990b, 1990c). This is nowhere better illustrated than in the case of R duthieae Volk Perold and R. sarcosa Volk Perold. both initially described as new species, which are now regarded by me as synonyms of R. albovestita Volk. Comparisons are drawn between the thallus dimensions, dorsal cell pillars, spore ornamention and other characters, in support of the above conclusion. An updated distribution map and a list of the specimens examined are added, because several new collections have been made since the original publications.
Highlights
As has been repeatedly emphasized elsewhere, species in section Pilifer Volk are often very difficult to distinguish (Perold 1990b, 1990c). This is nowhere better illustrated than in the case of R duthieae Volk & Perold and R. sarcosa Volk & Perold. both initially described as new species, which are regarded by me as synonyms of R. albovestita Volk
Comparisons are drawn between the thallus dimensions, dorsal cell pillars, spore ornamention and other characters, in support of the above conclusion
It has previously been shown that thallus morphology can vary considerably within a species and that the environment plays an important part in determining thallus colour, width and thickness (Pandê 1924; Abeywickrama 1945)
Summary
Subsequent gatherings, Volk 81-273, 81-274 trom Aberdeen in the central Cape, were tentatively named R. albovestita, but after further study, Volk became convinced that this was yet another new species, later to be named R. duthieae, in litt. [5.5.83 (PRE)]. 1 had informed him of the close similarity between the two species in the spore ornamentation on both faces, as seen on SEM micrographs (Figures 1 & 2). R. sarcosa was regarded (Volk & Perold 1986) as being distinct, on account of the white margin of the thallus (Figure 3A), its mostly inconspicuous scales that do not project above the thallus margins, the dorsal cell pillars which have inflated basal and smaller terminal cells and the spore ornamentation with deep-set, ringed areolae. Micrographs of more mature spores of R. sarcosa specimens, Volk 81-274b (Figure 5A, C, D, F) and 81-292b (Figure 5B, E), clearly have similar proximal faces and their distal faces, especially of Volk 81-274b (Figure 5C, D), when compared with young spores of Smook 4036 (Figure 2C, D), have much in common, and toward the centre, the ornamentation appears to be in two different levels; my LM photograph of R. sarcosa (Volk & Perold 1986: Figure 2.7) has eight areolae across the diameter on the distal face, as in R. albovestita
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