Studies in the genus Riccia (Marchantiales) from southern Africa. 17. Three new species in section Pilifer: R. elongata, R. ampullacea and R. trachyglossum

Species in section Pilifer Volk (1983) are often very difficult to identify (Perold 1990b). Most of them require close examination of the dorsal cell pillars in reasonably fresh collections, as these cells can seldom be reconstituted in long dried material. The three species, R elongata. R ampullacea and R trachyglossum, here described as new, have been maintained in cultures for lengthy periods, during which their dorsal cells were studied. The spore ornamentation was also quite useful in separating these species. R elongata is known from eastern Transvaal, R. ampullacea from the Witteberg Mountains of the eastern Cape Province and the Drakensberg Mountains of Lesotho and Natal, and R. trachyglossum is so far known only from (he highlands of Lesotho. Spesies in seksie Pilifer Volk (1983) is dikwels baie moeilik om te identifiseer (Perold 1990b). Die meeste vereis deeglike ondersoek van die dorsale selpilare in redelik die omvorming

R. elongata has been named for, and can be recognized by its longish, narrow, frequently simple branches, with the sides tightly inflexed when dry, and by large, wavy, white scales. It is rather similar in habit to R. simii Perold (1990a) (= R. albomarginata auct. non Bisch. sensu Sim) (Volk pers. com m .), but differs from it by its scales being less prominent, and less closely imbricate, by its lower dorsal pillars, spore ornamentation and distribution.
The shiny, round, bulging cells in the dorsal pillars are a character shared by a few other members in section Pilifer Volk, e.g. R. concava Bisch. (Perold 1989), R. jurjuracea Perold (1990b) and R. trachyglossum Perold (1990b), but these species frequently develop purple colouration on exposure to the sun and differ from R. elongata in habit, spore ornamentation and distribution.
R. elongata is rare and is so far known only from a few localities in eastern Transvaal at altitudes of ± 1 600-2 000 m above sea level, with summer rainfall of 8 0 0 -1 000 mm p.a. It has been found growing on dry slopes in association with grasses and Exormotheca sp., on a rock 'island' in a lake, (Elandsmeer) and at a seepage area at the edge of weathered rock outcrops, in association with R. volkii S. Arnell, R. natalensis Sim, and R. sorocarpa Bisch. (Figure 4). It is highly probable that S.M. Perold 303 and Volk 84-644, both from Moorriver, Natal, also belong to R. elongata, but these gatherings are sterile and cannot be placed here with certainty.
Due to the collapse of many dorsal cells, especially in the proximal part of the thallus, the dorsal face has a rather roughened or scurfy appearance. For this reason, the specific epithet, trachyglossum has been chosen. It is derived from a Greek phrase, meaning 'rough tongue'; the word is treated as a noun in apposition to the generic name, and therefore has a neuter ending, even though the name Riccia is feminine.
R. trachyglossum is distinguished from other species in section Pilifer, which have globose to bulging dorsal cells, by its somewhat smaller size, rather low hyaline scales and raised, tumid margins toward the apex. The spores are generally incompletely reticulate on both faces. It is so far known only from Lesotho, at altitudes ± 2 5 0 0 -3 000 m above sea level, where it grows on soil banks in bogs, together with other Riccia spp.: R. stricta (Lindenb.) Perold, R. crystallina L. emend. Raddi, R. sorocarpa Bisch. and with Cyperaceae spp.