New taxa, combinations and records of Pteridophyta from southern and central Africa

Four new taxa of ferns are described and illustrated from southern Africa:  Ophioglossum convexum J.E. Burrows, Mohria caffrorum (L.) Desv. var. ferruginea J.E. & S.M. Burrows,  Marsilea farinosa Launert subsp. arrecta J.E. Burrows and Asplenium sebungweense J.E. Burrows. The combination of Grammitis rigescens (Bory ex Willd.) J.E. Burrows is made. Ophioglossum thomasii Clausen,  O. rube Hum Welw. ex A. Braun.  Vinana ensiformis Swartz and Asplenium buettneri Hieron. ex Brause are new records for Zimbabwe, while Hymenophyllum splendidum V.d. Bosch and  Asplenium uhligii Hieron. are new records for Malawi and Zimbabwe. Actiniopteris semiflabellata Pichi-Sermolli is recorded from Namibia and Thelypteris oppositiformis (C. Chr.) Ching is recorded from the Transvaal.

Within all the populations seen of O. convexum there are large numbers of plants that do not bear fertile spikes. These plants all have the lamina appressed flat on the ground although those plants that carry a fertile spike appear to have a petiole that raises the lamina 2 -3 mm above the ground, with the lamina typically held at ± 30° from the horizontal.

O.
convexum is closely related to O. rubellum Welw. ex A. Braun (Figure 2)  O. convexum is also similar to O. nudicaule L. f. (Figure  3). O. nudicaule sens, strict, is, in the author's opinion, confined to the Cape Province and has up to five leaves per plant, each leaf being concave when viewed from above, with the whole lamina somewhat deflexed. Like most species o f O phioglossum , O. convexum does not appear to be closely linked to climate or altitude, occurring in the Transvaal in montane grassland at altitudes of between 1 200 and 1 900 metres, but in warmer climates and at lower altitudes north of the Limpopo River ( Figure   4). Proliferating roots as found in this species are not unusual in the genus, although they are seldom documented (Chen & Chiang 1972). Due to its proliferous roots the species tends to form colonies o f several square metres.  Rhizome erect to procumbent, 5 -8 mm in diameter, with closely packed, tufted, erect fronds. Rhizome scales rusty brown, linear-lanceolate, attenuate, entire, concolorous, 2 -6 mm long. Stipe 4 0 -1 2 0 mm long, brown basally, stramineous distally when dry, variously set with dark, reddish brown, subulate, entire scales, 0 ,5 -2 mm long, and scattered scales near the base similar to those on the rhizome, becoming subglabrous with age. Lamina 1 2 0 -3 0 0 x 3 0 -6 0 mm, narrowly elliptic to narrowly oblanceolate, with the basal pinnae decrescent, 3-pinnatifid. Pinnae ± 25 x 16 mm, ovate to triangular, bluntly acute. Pinnules oblong, obtuse, deeply pinnatifid into rounded lobes, margins widely and shallowly serratecrenate, involute, glabrous above, with occasional, minute subulate scales below, both surfaces with scattered, opaque, linear, gland-like projections ± 0,1 mm long. Rachis and secondary rachises sulcate above, densely set with dark, reddish brown, subulate scales similar to those on the stipe, almost obscuring the rachis when young. Sori submarginal, partly covered by the involute margins ( Figure 5B).

O phioglossum rubellum Welw. ex A. Braun in
M. caffrorum var. ferruginea is separated from var. caffrorum by its thick mat of dark, reddish brown scales that clothe the rachis when young and by the glabrous to subglabrous lamina which, in old pressed fronds, turns a metallic grey. In addition, it appears to be restricted to wet situations along the margins of mountain streams and around springs, whereas var. caffrorum is also found on drier soils and in the shelter of boulder bases, rock cracks, as well as in scrub on the forest ecotone. Like M. hirsuta J.P. Roux, it appears to be restricted to high altitudes of between 1 700 and 2 300 m ( Figure 6). Differs from subsp. farinosa (Launert 1968(Launert , 1983 in that the pedicels are longer and arise from both the base o f the stipe and the axils o f the stipe, and the sporocarps are held at ± 180° to the pedicels. (Figure 7B).

A ctiniopteris sem iflabellata Pichi-Sermolli in
A plant of this fern was first collected by M. Muller o f the Windhoek Herbarium in the Naukluft Mountains in 1979 and determined as A. radiata (Swartz) Link. Upon closer examination, it became apparent that the collection was A. sem iflabellata, based upon the homomorphic fronds (although the fertile fronds are somewhat larger than the sterile fronds), the two types of rhizome scales (one concolorous, the other with a dark central stripe) and. most characteristically, the dried fronds which are only slightly inclined to one side, whereas in the other three African species the fan o f the dried frond is bent at 90 or more from the vertical.
A. semiflabellata has. up to now, only been recorded as far south as Tanzania, Burundi and Zaire, extending northwards to north Africa and south Asia. This find in such an isolated situation, therefore, represents an interesting and puzzling extension for the species, although the arid habitat of the Naukluft Mountains is very similar to that in which it occurs throughout much o f its range. Rhizome creeping, ± 5 mm in diameter, with fronds spaced 4 -1 0 mm apart, sometimes appearing tufted. Rhizome scales 2 , 5 -4 mm long, dark brown, linearlanceolate, clathrate, subentire, with a long hair-tip. Stipe up to 260 mm long, as long or longer than the lamina, castaneous to almost black, lightly set with dark brown, clathrate, linear-lanceolate scales up to 2 mm long, glabrescent. Lamina 1 5 0 -2 5 0 x 100-140 mm, ovatetriangular in outline, 2-pinnate to deeply 3-pinnatifid, with the basal pair of pinnae longer than those above. Pinnae ovate to triangular. Pinnules obcuneate to oblanceolate. 4 -1 4 mm broad, becoming deeply pinnatifid proximally, apical margins deeply and irregularly serrate and incised, dark green, glabrous above, paler below and glabrous dis mally with scattered black, hair-like scales up to 1 mm long near the pinnule bases and along the secondary rachises, venation flabellate, prominent on both surfaces. Rachis black proximally, becoming matt-green distally, set with scattered, blackish scales and hairs. Sori numerous, linear, set along the veins; indusium linear, entire, 3 -9 x 0,2 mm ( Figure 7A).

Pichi-Sermolli (1983) has clearly shown that, in terms
A. sebungweense is closely allied to A. aethiopicum but is distinguished from the latter by the ovate-triangular frond, the relatively longer stipe and the thinner and more widely creeping rhizome. It occurs at altitudes of between 850 and 1 120 m, in hot and dry, deciduous woodland where it finds a degree o f protection in deep ravines in the sandstone mantle that covers much of north-western Zimbabwe (Figure 4). A. aethiopicum is not found in this area and the two species are not known to overlap. A. sebungweense is remarkably constant morphologically compared to the highly variable A. aethiopicum.