Ceropegia stylesii Heiduk, 2023

Heiduk, Annemarie, 2023, Ceropegia stylesii (Apocynaceae-Asclepiadoideae) - a novel species with rotate flowers from Ngome, South Africa, Phytotaxa 579 (2), pp. 117-124 : 118

Ceropegia stylesii Heiduk , sp. nov. ( Figs. 1 and 2 )

Type: — SOUTH AFRICA. KwaZulu-Natal province, Ngome , 975 m, 04 February 2021, D.G.A. Styles & A. Heiduk 5870 (holotype: NU0092554 !) .

Diagnosis: — Ceropegia stylesii is vegetatively very similar to C. gerrardii . The flowers, however, apart from being considerably smaller (diameter ca. 6 mm vs.> 20 mm in C. gerrardii ), are distinct from C. gerrardii with ascending corolla lobe tips (vs. radially spreading to reflexed in C. gerrardii ) which are densely pilose to tomentose (vs. puberulent in C. gerrardii ). The staminal corona lobes of C. stylesii are adpressed to the stamen and the style-head with their tips covering the style-head (vs. erect, exceeding the style-head and protruding as a bundle from the flower centre in C. gerrardii ).

Description: —Plants perennial, erect herbs. Rootstock composed of fleshy, fusiform roots. Stems annual, green, rigid, hirsute to hispid, single or two from rootstock, 250–400 mm tall, 25–35 mm in diameter, internodes 13–24 mm, often branched at some internodes starting from second internode. Leaves porrect to spreading, shortly petiolate; petiole channelled above, hirsute, 1.2–1.8 mm; lamina ovate, 17–30 × 11–20 mm, with 3–5 lateral nerves, base cordate, apex acute to obtuse, green, scabrid to hirsute above and below, margin entire, undulate, hirsute to hispid. Inflorescence axillary, at upper internodes, uniflorous, semi-pendulous; bracts narrowly triangular, 3.2–3.6 × 0.5 mm, densely hirsute to hispid; pedicel hirsute to hispid, green, sometimes reddish-brown speckled, slender, curved, 14–16 × 0.5 mm. Sepals narrowly lanceolate, acute, radially spreading and protruding from underneath the flower base, hirsute with densely pilose margins, 5.5–6.2 × 1.5 mm, slightly reflexed, green with sparse reddish-brown speckles. Flowers superficially resembling miniature versions of C. gerrardii flowers, with faint sweet scent. Corolla rotate, non-tubular, ca. 6.0 mm in length and diameter. Corolla lobe bases glabrous, waxy in appearance, creamish-white inside, greenish-white and dark purple speckled outside, basally fused and forming an annulus surrounding the base of the gynostegial column, then free but forming an inflated, apically slightly constricted basket-like structure around the gynostegium, margins fringed with unicellular, clavate, vibratile, ca. 1.0 mm long purple trichomes. Corolla lobe tips free, porrect, 3.7–5.0 mm long, radially spreading from basket-like corolla base, replicate, folded back longitudinally forming a raised median ridge, concave below, underside light purple or greenish and purple speckled, scatteredly puberulent, upper surface convex, deeply dark purple to almost black, velvety in appearance, densely pilose to villose, margins with longer stiffer trichomes 0.5 mm in length. Gynostegium shortly stipitate. Gynostegial corona of staminal and interstaminal parts, 2.5–3.0 mm in diam., ca. 3.5 mm in height, forming a nectar cup underneath each guide rail; interstaminal corona lobes erect, 0.7 × 0.6 mm, each divided into two short lobules, greenish-purple at base, dark purple at tips, with white ca. 0.2 mm long trichomes; staminal corona lobes adpressed to stamen and style-head, covering the latter with tips overlapping (or rarely connivent), 1.5 × 0.5 mm, tips slightly asymmetrically bilobed, whitish-purple with dark purple spots, glabrous. Pollinarium: pollinia ovoid, ca. 310 × 230 µm, yellow, insertion crest ca. 150 × 50 µm; caudicles ca. 50 µm long; corpusculum oblong, 215 × 75 µm, brown. Follicles paired, narrowly fusiform, ca. 70 × 5.0 mm, glabrous. Seeds ovate, brown with lighter brown margin, coma white.

Figures

FIGURE 1. Ceropegia stylesii from Ngome, KwaZulu-Natal, South Africa. A, Habit of a plant in habitat. B, Stem with flower and bud. C, Habitat on a steep and rocky slope at the type locality. Scale bar in B: 0.5 mm. Photographs: David Styles.

FIGURE 2. Morphological details of Ceropegia stylesii flowers. A, Flower of C. stylesii in comparison to a C. gerrardii flower (right). Note the staminal corona lobes protruding much from the C. gerrardii flower (white arrow). B, Side view of a C. stylesii flower in situ. C, Gynostegium and corona. D, Gynostegium and corona in top view. E, Longitudinal section through a flower. F, Pollinarium. Scale bars: 5 mm (A), 2 mm (B), 1 mm (E), 0.5 mm (C, D), 0.2 mm (F). Photographs: David Styles (A, B) and Annemarie Heiduk (C–F).