Studies in the genus Riccia ( Marchantiales ) from southern Africa . 19 . Two new species : R . pulveracea , section Pilifer and R . bicolorata , section Riccia , group ‘ Squamatae ’

R. pulveracea, specimens of which were collected by Duthie and tentatively referred to R concava by her. is described here, following the recent collection of fresh material. This species is distinguished from other members of section Pilifer (Volk 1983) by low. generally two-celled, free-standing dorsal cell pillars, which when dry, appear powdery, hence the specific


INTRODUCTION
Several specimens of ihe Riccia species, here described as R pulveracea, were collected al Bloemfontein by Duthie, more than 50 years ago.She provisionally referred them to R. concava Bisch.ex Krauss, but. as mentioned in a previous paper (Perold 1989c), Duthie and Garside never published anything on R. concava.Moreover, the specimens do not form pari of the main Riccia collection at BOL, where the packets arc mounted on herbarium sheets.Instead, they are stored in boxes, 125 x 100 x 30 mm, mounted wilh glue on loose pieces of cardboard and annotated by Duthie in pencil.On examination, the dorsal cells could not be revived and measured, as was to be expected, bin spores were collected and repeatedly photographed wilh SEM.Only with the collection, cultivation and study of fresh gatherings and by comparison ol their spore ornamentation (fortunately quite a useful character in this particular instance) could the old Duthie specimens be identified and referred to the new species.R. pulveracea.R. bicolorata, the other species new ly described in this paper, can be recognized by bi colon red scales, their hyaline margins heavily encrusted with calcium deposits, which also cover the unistratose cells on the dorsal surface of the thiil 1 i.It is rarely collected in the north-western, southern and central Cape Province and is rather similar to R pottsiana Sim (1926).but larger, and the scales are not so regularly arranged.
The proximal spore face is quite coarsely granular and rather similar to that of R. sorocarpa Bisch.Occasionally the distal face has 3 -5 short radiating ridges.This may * (= epithelium) added by SMP, in accordance with Volk 1983.have prompted Duthie, who collected specimens of this species near Bloemfontein more than 50 years ago, to refer them to R. concava.Frequently the latter also has radiating ridges, but the proximal spore face has numerous areolae and is hardly granular; the dorsal cell pillars on the thallus are taller, and the generally larger thalli often acquire a mauve tinge on exposure to intense sunlight.Its distribu tion is also different (Perold 1989c).R. furfuracea Perold (1990b) also has rather low dorsal cell pillars and is somewhat similar to R. pulveracea, but here the spore ornamentation is far less granular on the proximal face and the distal face is usually marked with a central cross.
R. bicolorata can be distinguished from other members of section Riccia, group 'Squamatae' (Na-Thalang 1980), by the appressed, bicoloured scales for which it has been named, by the dark broken line along the thallus margins, formed by the adherent purple bases of the scales, and by   4), where it grows on alkaline soil, sometimes in association with R. alboporosa, R. albomata and with R. pulveracea.

FIGURE 5 .
FIGURE 5.-Riccia bicolorata.Morphology and anatomy.A, thallus wet; B, thallus dry; C, dark margin of thallus and projecting scales seen from above; D, dorsal cells and air pores from above; E, transverse section through dorsal epithelium and some assimilation cells; F, transverse section through branch.G, scale.A-G, Smook 6990a.Scale bars on A, B, F = 1 mm; D, E = 50 /xm; C, G = 100 /xm.
Romanowski for developing and printing the micrographs; to the artist, Ms J. Kimpton and to Mrs J. Mulvenna for typing the manuscript.Sincere gratitude is expressed to Dr E.O.Campbell, Massey University, New Zealand, and Prof. Dr S. Jovet-Ast, Muséum National de'Histoire Naturelle, Paris, for refereeing this paper.
© FIGURE 7.-Riccia bicolorata.Spores.A, proximal face; B, proximal face, side view; C, F, distal face; D, distal face, side view; E, ridges and areolae toward margin.A -F , Smook 6990a.A -E , SEM micrographs; F, LM photograph.Scale bars on A-E = 50 /xm; diameter of spore on F = ± 85 /xm.its habit, as described above.It is somewhat similar to R .argenteolimbala Volk & Perold, but the latter has a more compact thallus, triangular pores and apolar spores; R. albolimbata S. Arnell and R. albom ata Volk & Perold are larger plants with wavy scales (Volk et al. 1988); R. montana Perold (1989a) has ligulate branches, and R. alboporosa Perold (1989a) has a spongy appearance.R. pottsiana is another species which bears some similarity to R. bicolorata, but it is smaller and its dark red scales are more regularly arranged.Messrs E.G.H. Oliver, P. Herman and J. van Rooy for kindly collecting specimens.Sincere thanks to Mrs A. REFERENCES R. bicolorata is known from a few collections in north western, central, southern and eastern Cape (Figure