Xysmalobium undulatum (L.) W.T.Aiton

Apocynaceae (part 2), David Goyder, Timothy Harris, Siro Masinde, Ulrich Meve, Johan Venter. Flora of Tropical East Africa, 2012

Morphology General Habit

Robust perennial herb with thick, carrot-like, tuberous rootstock.

Morphology Stem

Stems erect, one to several, (0.2–)0.5–1.5 m tall, unbranched, renewed annually, stout at least at the base, sparsely to densely pubescent with spreading white hairs, the base of the stem often glabrescent

Morphology Leaves

Leaves with petiole 1–5(–10) mm; lamina very variable in shape, linear or linear-lanceolate to ovate or ovate-lanceolate, 7.5–19(–27) cm × 0.5–8.5(–12) cm, apex acute or acuminate, base cordate, somewhat hastate, truncate or broadly rounded, margins crispate, undulate or smooth, often slightly revolute, tips of lateral veins anastomosing to form a wavy submarginal vein, with sparse to dense spreading white hairs, particularly on principal veins and near margins

Morphology Reproductive morphology Inflorescences

Inflorescences umbelliform, 12–26-flowered, densely pubescent.

Morphology Reproductive morphology Inflorescences Peduncles

Peduncles arising laterally from the upper nodes, robust, 12–45(–90) mm long, up to 3 mm thick.

Morphology Reproductive morphology Inflorescences Bracts

Bracts linear, 3–4(–11) mm long.

Morphology Reproductive morphology Flowers Pedicel

Pedicels slender, (8–)14–18 mm

Morphology Reproductive morphology Flowers Calyx

Sepals ovate to lanceolate, 4–8(–11) × 1–2.5 mm, about half as long to as long as the corolla, apex acute or attenuate, pubescent

Morphology Reproductive morphology Flowers Corolla

Corolla cream or greenish white, often tinged with brown or pink outside, divided almost to the base; lobes spreading, ovate, 5–10 × 2.5–6 mm, lower 2/3 glabrous, somewhat concave, upper 1/3 variably pubescent, usually lanate but occasionally glabrous or subglabrous, the apex acute, recurved

Morphology Reproductive morphology Flowers Corona

Corona very fleshy, ± tetrahedral in shape and attached by one of the apices to the base of the gynostegium, or stalk narrow for most of its length and widening abruptly to the ± triangular outer face, the outer face 2–4 × 2–3.5 mm

Morphology Reproductive morphology Flowers Gynostegium

Gynostegium raised on a distinct stalk formed from the anther filaments; stalk 1–3(–4) mm long, usually only partially obscured by the corona lobes but lobes occasionally overlapping base of anthers when gynostegial stalk short

Morphology Reproductive morphology Flowers Androecium Stamens Anthers

Anther wings jutting out abruptly from column, anthers 2–3 mm tall, appendages membranous, ovate or ± circular, 1–2 mm, rounded or acute.

Morphology Reproductive morphology Flowers Pollinia

Pollinia slender pear-shaped to short club-shaped, 0.75–1.5 mm long, attached by the tip to the translator arm; translator arms narrowly winged in upper part, 0.5–1 mm long; corpusculum dark brown, ovoid, 0.5 × 0.25 mm

Morphology Reproductive morphology Flowers Gynoecium Style

Stylar head ± level with top of anthers, obscured by the anther appendages

Morphology Reproductive morphology Fruits

Fruit a single follicle, 5–8 cm long, 1.5–2.5 cm wide, somewhat inflated or not, lanceolate or ovate in outline with an obtuse or attenuate apex, the entire surface covered with soft hairy prickles

Figures

Fig 109, p 451

Ecology

Fairly common on road or stream banks and in seasonally waterlogged depressions, occasionally in montane grassland; 1000–2400 m

Note

This species is very variable, with distinctive local forms. One such variant occurs around Lake Victoria and has shorter corolla lobes and a less stipitate gynostegium than typical material, and linear-lanceolate leaves. Another small-flowered form is found in the Southern Highlands of Tanzania and the Nyika Plateau of neighbouring Malawi, but the leaves in this variant are much broader.

Distribution

Flora districts: U2 U4 K3 K4 K6 T1 T2 T4 T6 T7 T8 Range: Ethiopia, Angola, Zambia, Malawi, Zimbabwe and South Africa

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.

Type

“ApocynumAfric. lapathi folio” in Commelin, Hort. Med. Amstelae. Pl. Rar. Exot.: 16, t.16 (1706), iconotype designated by Wijnands in Bot. Commelins: 48 (1983).

Morphology General Habit

Robust perennial herb with thick, carrot-like, tuberous rootstock

Morphology Stem

Stems 1 to several, (0.2)0.5– 1.5 m tall, erect, unbranched, renewed annually, stout at least at the base, sparsely to densely pubescent with soft, spreading white hairs, the base of the stem often glabrescent

Morphology Leaves

Leaves shortly petiolate; petiole 1–5(10) mm; lamina 7.5–19(27) × 0.5–8.5(12) cm, very variable in shape, linear or linear-lanceolate to ovate or ovate-lanceolate, apex acute or acuminate, base cordate, somewhat hastate, truncate or broadly rounded, margins crispate, undulate or smooth, often slightly revolute, lateral veins ± parallel, spreading to near 90° to the midrib but ascending slightly near the base, tips of lateral veins anastomosing to form a wavy, submarginal vein, indumentum a sparse to dense covering of spreading white hairs, particulartly on principle veins and near margins

Morphology Reproductive morphology Inflorescences

Inflorescences umbelliform, 12–26-flowered, densely pubescent, peduncles arising laterally from the upper nodes, robust, 12–45(90) mm long, up to 3 mm thick

Morphology Reproductive morphology Flowers Pedicel

Pedicels slender, (8)14–18 mm

Morphology Reproductive morphology Flowers Calyx

Sepals 4–8(11) mm long, 1–2.5 mm wide, about half as long to as long as the corolla, ovate to lanceolate, apex acute or attenuate, pubescent

Morphology Reproductive morphology Flowers Corolla

Corolla cream or greenish white, often tinged with brown or pink outside, divided almost to the base; lobes 5–10 mm long, 2.5–6 mm wide, ovate, lower 2/3 glabrous, somewhat concave, upper 1/3 variably pubescent, usually lanate but occasionally glabrous or subglabrous, spreading, the apex acute, recurved

Morphology Reproductive morphology Flowers Corona

Corona very fleshy, ± tetrahedral in shape and attached by one of the apices to the base of the gynostegium, or stalk narrow for most of its length and widening abruptly to the ± triangular outer face, the outer face 2–4 mm wide, 2–3.5 mm high

Morphology Reproductive morphology Flowers Gynostegium

Gynostegium raised on a distinct stalk formed from the anther filaments; stalk 1–3(4) mm long, usually only partially obscured by the corona lobes but lobes occasionally overlapping base of anthers when gynostegial stalk short; anther wings jutting out abruptly from column, the anthers 2–3 mm tall

Morphology Reproductive morphology Flowers Pollinia

Pollinia 0.75–1.5 mm long, variable in shape from slender pear-shaped to short club-shaped, attached by the tip to the translator arm; translator arms narrowly winged in upper part, 0.5–1 mm long; corpusculum dark brown, ovoid, 0.5 mm long, 0.25 mm wide

Morphology Reproductive morphology Flowers Gynoecium Style

Stylar head apex ± level with top of anthers

Morphology Reproductive morphology Fruits

Fruit a single follicle, somewhat inflated or not, lanceolate or ovate in outline with an obtuse or attenuate apex, the entire surface covered with soft hairy prickles.

Distribution

Zambia, Zimbabwe, Mozambique, Malawi. Widespread across eastern and southern Africa from Ethiopia to South Africa.

Ecology

Fairly common on road or stream banks and in dambos, occasionally in montane grassland; 1000–2400 m.

Note

A very variable species with distinctive local forms. A small-flowered variant with particularly broad leaves is found on the Nyika Plateau and the neighbouring Southern Highlands of Tanzania. Material from Namuli in northern Mozambique is also of this form.