Studies in the Marchantiales ( Hepaticae ) from southern Africa . 7 . The genus Cryptomitrium ( Aytoniaceae ) and C . oreades sp . nov

As far as is known, the rare genus Cryptomitrium is reported here for the first time lor the whole continent ot Africa with the description of a new species, C. oreades, from the mountain Kingdom of Lesotho in southern Africa. The specimen, attributed to the genus Reboulia from southern Africa, was misidentified.

Thalloid.smallish to medium-sized, margins purple, thin, medianly thicker and rather Hat to slightly concave, green, in kxise patches; at seepage, on soil overlying rocky outcrops.Branches simple or rarely once pseudodichotomously furcate; thickened over midrib, thinning toward scalloped or irregularly erenate margins, laterally striate from above; apex slightly notched, dorsally not grooved along midline.Dorsal epidermis hyaline, cell walls thickened, especially at the corners, but not bulging, some cells containing an oil body; air pores simple, small, slightly raised, surrounded by 3 concentric rings of cells without radial thickening of Ihe walls and leading below into topmost layer of individual empty air chambers, in 2 or 3(4) storeys, bounding walls unistratose, chlorophyllose; storage tissue with angular cells, not restricted to keel; rhizoids of both kinds, smooth as well as pegged.Scales dark red or reddish pink, in 2 forwardly directed ventral rows, not imbricate, roughly triangular to transver sely rectangular, with I or 2(3) filiform appendages.Autoicous.Antheridia in groups, sunken into dorsal tissue along midline and opening into projecting, conical papil lae above.Carpocephalum single, raised on stalk with one rhizoidal furrow, lacking air chambers and arising dorsally at apical notch of thallus or ventrally along margin, head disciform-round, with 1 or 2 layers of air chambers, separated from one another by unistratose cell plates and opening above via compound air pores; 3-6 capsules borne below, protruding between membranous lips of in volucres; capsular wall apically bistratose, inner cells with thickening bands, remainder of wall unistratose, cells thinwalled.Spores triangular-globular, winged, distal face with ± reticulate ornamentation, or thick sinuate ridges; proximal face with high, thin, conspicuous triradiate mark, each facet with incomplete areolae.Elaters long, tapering, bispiral.
TYPE.-Lesotho: 1 km from New Oxbow Lodge on road to Mokhotlong, ± ]/ i km from bridge to the left, along Tiholohatsi River, at interface between basalt rock slope and grassy fringe, under large boulder in wet seepage area on soil, in alpine hcath-grassland, alt.± 2 9(X) m, April 1994, Perold & Duckett 3228 (PRE, holo.).dry; in loose patches, simple or once pseudodichotomously furcate.Branches mostly up to 12 x 3-5(-6) mm, (450-)600-800 (im thick over midrib, laterally thinning out into wings, apex slightly notched, purple filiform tips of scale appendages reflexed over edge; margins thin, acute; flanks sloping very obliquely upward and outward; ventral face medianly rounded, on either side of midrib with a row of apically directed, ± triangular to transversely rectangular, purple or reddish scales (Figure IB).

DISCUSSION
This species is characterized by a disciform-round car pocephalum, borne on an erect, uni-furrowed stalk which arises ventrally at the margin and emerges laterally to the thallus in close proximity to the dorsally situated an theridial group.Worldwide only two other species have been described in this genus; firstly C. tenerum from North America (Alameda, California, Washington and Mexico) as well as from Costa Rica, Guatemala, Chile and Argentina, and secondly C. himalayense (Kashyap 1915) from India (Mehra & Sokhi 1977).Cryptomitrium oreades differs from the other two species mainly by the lateral position of its stalk; in C. tenerum and C. hima layense the stalk is dorsally situated near the apex of the thallus; their thalli are also thinner and more delicate than those of our species.The genus Cryptomitrium is clas sified in the family Aytoniaceae and in the subfamily Reboulioideae Grolle, together with Asterella, Mannia and Reboulia.The genus Reboulia does not occur in southern Africa (Perold 1994);Amelfs (1963) only record of it from Rustenburg Kloof, Collins 775C, is a specimen of Asterella wilmsii and was clearly misidentified.So far, C. oreades is known from only two localities in Lesotho (Figure 3), growing at high altitude in association with the moss Gymnostomum aeruginosum J.E. Sm.
The specific epithet, oreades, is derived from the Greek word 'oread', meaning 'mountain nymph' and was chosen because of the mountainous location of this species.
FIGURE 1.-Cryptomitrium oreades.Morphology and anatomy of thallus.A, dorsal face of thallus with carpocephalum on stalk emerging at side of thallus; B, ventral face of thallus; C, carpocephalum seen from below; D, ventral scale; E, transverse section of stalk; F, transverse section of thallus; G, air pore and surrounding cells seen from above; H, transverse section of air pore and dorsal cells; I, thin, unistratose portion of wall; J, bistratose apical portion of capsule wall with thickenings, from above; K, transverse section of bistratose portion of capsule wall.A-C, E, F, I-K, Van Rooy 305/; D, G, H, Perold & Duckett 3228.Scale bars: A-C, F, 1 mm; D, 500 pm; E, 250 pm; G-K, 50 pm.