Oxalis fenestrata Dreyer, Roets & Oberl., 2014

Roets, F., Oberlander, K. C. & Dreyer, L. L., 2014, New relatives of Oxalis pes-caprae (Oxalidaceae) from South Africa, Blumea 59 (2), pp. 131-138 : 135-136

2. Oxalis fenestrata Dreyer, Roets & Oberl. , sp. nov. — Fig. 3

Type. Dreyer, Roets & Oberlander MO1527 b ( STEU), cultivated from Dreyer, Roets & Oberlander MO1527 a, originally from South Africa, Northern Cape, Richtersveld Conservancy, Tierhoek camping site, 2816 DD, June 2012, flowering .

Geophyte with thick succulent stem, up to 40 cm tall, bright apple green, nearly entirely glabrous. Bulb up to 30 cm deep, large, ovoid, 2–7.5 cm long, with numerous, dark brown, rumpled and splitting tunics with prominent veins. Rhizome white, up to 25 cm long, glabrous, with large (c. 5 mm long) semi-amplexicaul, light brown, membranous, alternating scales. Arial stem well-developed, thick and succulent, distinctly tapering towards the tip, often branching, bright apple green, glabrous. Leaves alternate along stem or loosely apically congested in groups of 3–5, often on short side stems, glabrous; leaf base semi-amplexicaul, winged below articulation with petiole; petioles slender, up to 9 cm long, glabrous; leaflets 3, obcordate to broadly obcordate, adaxially glabrous, abaxially glabrous to very sparsely hairy on veins and base, margin glabrous to very sparsely hairy, petiolules prominent, 1–1.5 mm, region below apical incision usually with distinct, variously shaped white to pale green and translucent patch. Peduncles 1–6 flowered, longer than the petioles. Bracts 2–8, erect, up to 1.5 mm long, glabrous to sparsely hairy, usually with prominent calli. Pedicels slender, 20 mm long, pendulous in bud and in fruit. Sepals 5, lanceolate, acute, without calli, glabrous to very sparsely glandular-pilose, up to 9 × 5 mm. Corolla c. 20 mm long, with broad funnel-shaped yellow tube. Petals 5, claw yellow, ± half the length of the petal, lobes white. Stamens 10, in 3 whorls; 2 whorls per plant, lower whorl c. 3 mm long, middle whorl c. 5.5 mm long, longest whorl c. 9 mm long; filaments sparsely hairy, with mostly simple hairs and a few glandular hairs towards the base, with prominent blunt teeth on longest whorl; anthers oval, yellow. Ovary narrowly ovoid, 4–5 mm long, 5-loculed, glabrous, 5–6 ovules per locule; styles 5, separate, hairy with both simple and glandular hairs, reciprocally herkogamous with two stamen whorls, short-whorled styles curving outwards between filaments, mid- and long-whorled styles erect. Stigmas green, fimbriate. Fruit capsule slightly longer than sepals. Seed endospermous.

Diagnostic characters — Tall geophyte with thick, branched, succulent, bright apple green stems. Leaflets usually with prominent clear white markings just below the apical incision. The few-flowered inflorescences produce large, white flowers, with pedicels that are often distinctly darker in colour than the peduncle. It is closely related to other branched, umbellate species, such as O. knuthiana , O. petricola and O. rubricallosa and grows in fairly similar habitats. It can immediately be distinguished from these species by the combination of translucent white patches on the leaflets, thick stems, white corollas and ecallose sepals. This species flowers from August to September. The specimens collected near Kubus (Drijhout 2916) seem to lack the white to pale green and translucent patch at the apical incision.

Distribution — Only known from southern slopes in the western end of the Richtersveld Conservancy, Northern Cape, where it grows in shady crevices between granite boulders and in rock fields.

Additional specimens examined. SOUTH AFRICA, Northern Cape, Richtersveld Conservancy, Tierhoek camping site,2816 DD , June 2012,sterile, Dreyer, Roets & Oberlander MO1527 a ( NBG, STEU); Northern Cape, Richtersveld Conservancy, 1.4 km north-west of Tierhoek campsite, June 2012,sterile; Dreyer, Roets & Oberlander MO1532 ( NBG, STEU) ; Northern Cape Province, Richtersveld Conservancy, Vanderster Mountain,near Kubus ,2816BD, June 1980, flowering, Drijhout 2916 ( NBG) South Africa .

Figures

Fig. 3 a. Typical habitat of Oxalis fenestrata in the Richtersveld Conservancy; b. Oxalis fenestrata habit; c. flower; d. leaves; e. peduncles with prominently callose bracts (arrows); f. bulb (Drijhout 2916, NBG); g. excavated plants showing thick and fleshy, tapering, apple green stems. — Scale bars = 1 cm. — Fig. b & d provided by P.C.V. van Wyk.