Ceropegia arenarioides M.G.Gilbert

Goyder, D. J., Gilbert, M. G. & Venter, H. J. T. (2020). Apocynaceae (part 2). In: M. A. García (ed.), Flora Zambesiaca, Vol. 7(3). Royal Botanic Gardens, Kew.

Diagnosis

Closely related to C. nilotica but easily separated by the shape and colouration of the corolla lobes which are longer (c.21 mm vs. 4–14(20) mm in C. nilotica), coming to a narrowly acute to attenuate point (vs. bluntly acute to rounded or even impressed) and with the lower half pure white below a uniformly purplish brown tip (vs. transversely banded: dark at the base, then with a relatively narrow band of near white, followed by another dark band and a clear bottle green or brown tip); also similar in the overall shape and colouration to C. arenaria from which it differs by the narrowly acute to attenuate corolla apex, inconspicuously shortly white pilose (vs. a distinctly clavate corolla apex with conspicuous purplish clavate hairs in C. arenaria).

Type

Zimbabwe, W, Insiza, 5 mi N of Filabusi, 1200 m, 18.ii.1971, Wild 7821 (K001400222 holotype).

Morphology Stem

Stems twining, semisucculent, glabrous

Morphology Leaves

Leaves somewhat succulent; petiole c.8 mm long, glabrous; leaf blade ovate, to 42 × 18 mm, margin serrulate/denticulate, both surfaces glabrous

Morphology Reproductive morphology Inflorescences

Inflorescence extra-axillary, peduncle to 30 mm long, cyme racemelike, with rachis to 23 mm long, few-flowered, flowers opening in succession

Morphology Reproductive morphology Flowers Pedicel

Pedicel c.6 mm long, glabrous

Morphology Reproductive morphology Flowers Calyx

Sepals subulate to linear-lanceolate, c.4.5 × 1.1 mm, glabrous

Morphology General Buds

Bud with flat sinuses and long beak

Morphology Reproductive morphology Flowers Corolla

Corolla 49–55 mm long, slightly curved; tube 28–34 mm long, basal chamber double, lower ovoid, 8–8.5 × 3.8–5.5 mm wide, then abruptly expanded into a second subglobose inflation 4.2–6.2 mm diam., gradually narrowed at apex, limb cylindrical, 2.4–3.1 mm wide, widening abruptly to 10–13 mm at mouth, exterior pale cream uniformly covered with purple spots, glabrous; sinuses rounded, spreading and gaping; lobes triangular-attenuate, c.21 mm long, plicate, apices converging to form a narrowly conical cage, apex bluntly acute to acuminate, abaxially glabrous, margin shortly pilose, adaxially white for more than half length, tip dark purplish brown, uniformly sparsely stiffly hairy

Morphology Reproductive morphology Flowers Corona

Corona subsessile, 3.5–4 mm high, 2.5–3 mm diam.; outer lobes each forming a shallow pouch, entire, glabrous; inner lobes erect, converging over gynostegium, linear, c.3 mm long, apices obtuse, glabrous

Morphology Reproductive morphology Flowers Pollinia

Pollinia yellow

Morphology Reproductive morphology Seeds

Follicles and seed not recorded.

Distribution

Caprivi, Botswana, Zambia, Zimbabwe, Mozambique. Also in Namibia

Ecology

Among bushes, including Acacia tortilis and Colophospermum mopane, and piles of twigs on reddish ground and hard brown loam; 300–1200 m.

Conservation

Probably LC. Fairly widely distributed and probably under recorded because of confusion with C. nilotica.

Note

A number of collections that have hitherto been included within Ceropegianilotica differ very clearly in the form and colouring of their corolla lobes which have more in common with the South African species C. arenaria R.A Dyer. They resemble C. nilotica quite closely in vegetative morphology but differ by the longer corolla lobes which extend into a slender, acuminately tapered beak

Recognition

In C. nilotica and C. arenarioides the lobe margins are uniformly shortly pilose. Bruyns 8549 (BOL) has the same distinctive corolla but has filiform leaves and fusiform roots. The status of this form deserves further investigation. Ceropegia arenaria has a similarly coloured corolla but differs most obviously by the largely creeping stems with often reduced leaves and by the corolla lobes with linear to slightly spathulate tips which converge slightly at the base to form a narrowly clavate beak with vibratile purplish clavate marginal hairs contrasting strongly with the much shorter erect hairs below the beak The other difference is in the colour pattern of the corolla lobes: in C. nilotica there are three or four transverse bands of colour, a basal blackish green or brown zone, a middle white band, sometimes quite narrow but always present, and a coloured apex, often similar to the basal area but then with a clearly delineated green or brown apex whereas in this species there are only two zones, a large, white basal zone taking up c. 2/3 of the lobe and the purplish brown tip nilotica there are three or four transverse bands of colour, a basal blackish green or brown zone, a middle white band, sometimes quite narrow but always present, and a coloured apex, often similar to the basal area but then with a clearly delineated green or brown apex whereas in this species there are only two zones, a large, white basal zone taking up c. 2/3 of the lobe and the purplish brown tip In C. nilotica the shorter lobes converge abruptly to form a broadly acute to rounded or even impressed apex