Thunbergia holstii Lindau

Acanthaceae (part 1), Kaj Vollesen, Flora of Tropical East Africa, 2008

Morphology General Habit

Erect shrub or subshrub to 1.5(–2) m tall; young branches quadrangular, with greyish to brownish bark, narrowly winged with the wings excurrent at the nodes as pseudo-stipular spines up to 2 mm long, glabrous but for thin lines of hairs at youngest nodes, with dense tufts of brownish hairs in axils.

Morphology Leaves

Leaves with petiole 1–4 mm long, glabrous or with a few hairs; lamina ovate to elliptic or broadly so, largest 1.5–8 × 0.7–3(–3.8) cm, apex acuminate to rounded, base cuneate to rounded (rarely attenuate), margin entire but usually strongly undulate, glabrous or hairy along midrib beneath.

Morphology Reproductive morphology Flowers

Flowers solitary; pedicels 0.5–3 cm long, glabrous, near base sometimes held in a fold created by the basal convolutions of the leaf-margin; bracteoles pale green, ovate to elliptic or broadly so, (1.2–)1.7–3.5 × (0.5–)0.8–2(–2.3) cm, acute to obtuse, glabrous.

Morphology Reproductive morphology Flowers Calyx

Calyx rim 1–2(–4) mm high, segments to 1 cm long, always some over 3 mm, glandular.

Morphology Reproductive morphology Flowers Corolla

Corolla limb and upper part of tube purple to dark purple or dark blue, lower part of tube tube whitish, throat yellow; tube (2.5–)3–4.5 cm long; lobes 1–2.5 cm long.

Morphology Reproductive morphology Flowers Androecium Stamens Filaments

Filaments 10–12 and 12–14 mm long, with scattered glands at base and apically or along whole length; anthers 4–5 mm long.

Morphology Reproductive morphology Fruits

Capsule 2.5–3.2 × 1–1.2 cm, glabrous.

Morphology Reproductive morphology Seeds

Seed dark brown, ± 8 mm in diameter.

Figures

Fig. 6.

Ecology

Acacia and Acacia-Commiphora bushland, often on rocky hills, coastal bushland; near sea level to 1700 m

Note

I have not seen any wild specimens from either Zanzibar or the Tanzania coast opposite Zanzibar, but it is certainly widely grown as an ornamental. The two Kirk collections labelled “Zanzibar” and “Mainland” are almost certainly from cultivated plants. It is also widely grown in the rest of tropical Africa as well as in India and SE Asia.

Distribution

Range: Somalia Flora districts: K4 K6 K7 T1 T2 T3 T4 T5 T6 Range: Kenya. Range: Somalia Range: Tanzania.

Extinction risk predictions for the world's flowering plants to support their conservation (2024). Bachman, S.P., Brown, M.J.M., Leão, T.C.C., Lughadha, E.N., Walker, B.E. https://nph.onlinelibrary.wiley.com/doi/full/10.1111/nph.19592

Conservation

Predicted extinction risk: not threatened. Confidence: confident

Flora Zambesiaca Acanthaceae (part 2) by Iain Darbyshire, Kaj Vollesen and Ensermu Kelbessa

Morphology General Habit

Shrub to 1.5 m tall; cystoliths absent.

Morphology Leaves

Leaves ovate to elliptic with undulate margin, to 8 cm long, apex acuminate to rounded, base cuneate to rounded.

Morphology Reproductive morphology Flowers

Flowers solitary in leaf axils; each flower clasped by 2 large pale green ovate to elliptic bracteoles to 3.5 cm long.

Morphology Reproductive morphology Flowers Calyx

Calyx with numerous linear segments to 1 cm long.

Morphology Reproductive morphology Flowers Corolla

Corolla purple to dark purple or dark blue, tube to 4.5 cm long, lobes subequal, spreading, to 2.5 × 2.5 cm.

Morphology Reproductive morphology Flowers Androecium Stamens

Stamens 4, included in throat, anthers bithecous, thecae at base with a boss, covered with short stiff glossy setose hairs.

Distribution

Native of East Africa. Widely cultivated throughout the tropics.