Studies in the genus Riccia ( Marchantiales ) from southern Africa . 4 . Three endemic species

Three endemic species of the group 'Ciliatae' (subgenus Riccia sectio Riccia) are dealt with. The description of R. natalensis Sim is emended, as Sim's original description (1926) was sketchy and Arnell (1963) had no fresh material to examine, which resulted in some inaccurate observations: R. microciliata Volk & Perold is a diminutive new species w'ith conspicuous, arched marginal and occasionally dorsal cilia, whereas R. mammifera Volk & Per­ old. another new species, has enlarged cells (or short cilia) along the thallus margins.


1.
Riccia natalensis Sim in Transactions of the Royal Society of South Africa 15: 9 (1926); Arnell: 18 (1963).R. natalensis is described in detail, as Sim's origi nal description was very brief and Arnell had no fresh material to examine, which led to some inaccu rate observations.Thallus monoicous, perennial, bright green, in more or less complete rosettes (Figure 1A), in greg arious patches or scattered, medium-sized to large, furcate, sometimes bifurcate, branches moderately divergent, often only one branch well developed, ligulate or obovate, wider towards apex, up to 12 x 4 mm.4-8 times broader than thick, terminal seg ments 3-5 mm long; apex shortly emarginate.upper surface deeply furrowed apically, more proximallv slightly concave to almost flat as groove widens and becomes shallow (Figure IB); margins raised, tumid, subacute to rounded, slightly attenuate, forming a short wing with numerous cilia (Figure ID), flanks sloping up and outwards, pale brown to violet with age; ventral surface slightly rounded, green, when dry. pale green dorsallv, only apex and distal sides partly inflexed, with cilia erect and con spicuous.Cilia crowded at apex and younger distal margins, becoming sparser and more distant proximally, never present over sporangia, triangular, 160-300 (^100) |im long.30-50 ^m wide or base, of ten bulging on one side, gradually narrowing to blunt or subacute tip, straight or slightly curved (Fig ure IE), hyaline, surface finely granulate (Figures ID. 2D), when dry. somewhat flattened, slightly twisted, with one or both margins inflexed, giving walls and apex a partly thickened appearance (Fig ure IE), similar to cilia of R. trichocarpa (see Volk 1983: Table II).Anatomy o f thallus: cells of dorsal epithelium in one layer, hyaline, broadly globular or mammillate (Figures 1C. 2C).but sometimes upper wall collapsed and cells cup-like; air-pores triangular or 4-sided: in section (Figure 1G).assimilation tissue (chlorenchvma) almost A the thickness of thallus.cells isodiametric or shortly rectangular, in vertical or sloping columns of 6-8 (-10) cells, enclosing 4-6sided air-canals 20-40 |im wide; storage tissue nearly \ the thickness of thallus.cells rounded, irregularly arranged, up to 50 ^im wide; rhizoids both smooth and tuberculate.about 20 um wide.Scales small, about 300 x 160 |.im (Figures IF. 2B) hyaline, not persistent, cells isodiametric.thin-walled.Antheridia numerous in distal part of groove, hyaline ostioles projecting about 1 (X) j.im.Archegonia scattered along median part of lobes, necks purple.Sporangia 2-8 per lobe, bulging dorsallv.overlying epithelium sometimes blotched with purple, with 100-200 spores.Spores (95-) 110-115 um in diameter, triangular-globular, polar, straw-coloured, pellucid: with broad undulating wing up to 10 ^m wide, mar gin smooth or finely crenulate.at marginal angles incised or with a pore (Figure 3F): distal face convex to slightly flattened, reticulate with 6-9 rounded or angular areolae across diameter (Figures  1J).R. natalensis is easily recognized by the conspicu ous marginal cilia, the broad, thin thallus and by the bright green dorsal colour.It is a relatively scarce species and infrequently collected; it is endemic to the south-eastern Transvaal, eastern Orange Free State and northern and central Natal (Figure 4), and has not been found in the drier, western parts of southern Africa.It appears to be hydrophytic as it grows on damp, loam-rich soil, sometimes on black turf, near seepages, and on streambanks and is often associated with R. stricta (Trev.)Duthie and species of Anthoceros, Selaginella, Eragrostis and Crassula.Soil pH 5,1 and 6,0.R. natalensis is placed in the 'Ciliatae'-group (sec tion Riccia).together with the other ciliated species found in southern Africa: R. crozalsii Lev., R. trichocarpa Howe (= R. canescens Steph.) and the two new spp.R. microciliata and R. mammifera.Sim (1926) described the epithelium of the thallus as 'about 2 layers of larger, much laxer cells', but there is only one layer of cells present.He also states that 'all along the outer portion of the thallus surface rise pellucid, single-celled mamillae numerous and irregular, giving an appearance of white scales to the thallus when it is dry.'The 'mamillae' clearly refer to the cilia along the margins.Arnell (1963) remarks that the epidermal cells were destroyed in the type specimen w hen he examined it and he could not con firm Sim's observation that these cells are mammillate in the lateral portion of the thallus.In his key to the Riccia species, Arnell places R. natalensis in the group without cilia (!) at the thallus margin, and in cludes it with those species where the dorsal epithe lium consists of free cell pillars, R. albomarginata Bisch.and R. concava Bisch.(section Pilifer Volk 1983).He seems, therefore, to have misinterpreted Sim's reference to 'mamillae' and took it to apply to the epithelial cells.Furthermore he describes the ci lia as smooth, whereas they are granulate.Both Ar
Under adverse conditions small perennating bul bils, w'hich enable the plant to survive, are formed from the apices of the thalli.
This rare species has been collected only twice.It grows on the banks of small streams, in the north western and central Transvaal, on temporarily wet, clayev soil, shaded durine part of the dav.(Figure 4).Originally it was suspected that R. mammifera and R. coronata Sim might be synonymous.The type and only specimen of R. coronata (Sim 8730, from Mooi River, Natal) has been lost.Arnell (1963) mista kenly described the Duthie 5004 (BOL) specimen of R. alatospora (see Volk & Perold 1985) as R. coro nata.According to Sim's diagnosis R. coronata, has 'scales fairly large, horizontal when moist', and the row of long white mammillate cells (cilia) would probably be up to about 450 jim long, judging by the dimensions of the thallus in Sim's drawing and those given in the text.R. mammifera, on the other hand, has small inconspicuous, evanescent scales, and the marginal cells are only up to 150 jim long; other par ticulars in Sim's description are too meagre.R. mammifera has therefore been described as a new species and is distinguished from other ciliate south ern African species by the broad thallus, by the short wide, non-canaliculate cilia, and by the spore orna mentation on the distal face, consisting of mostly hexagonal areolae with raised tubercles at the nodes.R. mammifera with enlarged cells (or short cilia) along the thallus margins has here been treated as a member of the 'Ciliatae' group.
Pande & Udar (1958) reported small cilia, 100-150 (Lim long at the margins and on the surface of the thallus in R. melanospora Kash., a character also present in R. atromarginata Lev., but rarely encoun tered, and certainly not previously seen in a south ern African species.
tae' group, by being much smaller and by its arched, deeply channelled, striate cilia; R. trichocarpa Howe (= R. canescens Steph., Jovet-Ast (1983)) is about twice as large, and has long, straight, pointed cilia; R. crozalsii Lev. is confined to the wetter regions of the south-western Cape and is also larger, with a more delicate texture and granulate cilia; R. natalen sis is 10-12 mm long and about 4-8 times broader than high, with wide triangular cilia and R. mammifera sp.nov.has enlarged marginal cells up to 150 [im long.