Ayenia crotonoides Christenh. & Byng

Sterculiaceae, Martin Cheek & Laurence Dorr; Nesogordonia, Laurence Dorr, Lisa Barnett. Flora of Tropical East Africa. 2007

Type

Type: Tanzania, Lushoto District: Usambara, Gombelo, Holst 2159a (B†, holo.; K!, iso.)

Morphology General Habit

Shrub or small tree, 1.5–5(–8) m tall; branches drooping

Morphology Leaves

Leaves oblong, ellipticoblong or broadly linear-oblong, 6–14(–28) cm long, 2–7(–12.5) cm wide (occasionally exceptionally large leaves are collected), apex acuminate to longapiculate, margin entire to subundulate, base cuneate or rounded to truncate, glabrous above except for a few minute stellate hairs on the midrib, glabrous below except for scattered minute (almost scale-like) stellate hairs on the midvein and other large veins, palmately 3(–5)-nerved from the base, pinnately nerved above, domatia consisting of simple and fasciculate hairs and a small flap of tissue in the axils of the veins below, foliar nectary at the base of the midrib below, sometimes indistinct, multiaperturate; chartaceous; petiole 1–9 (16) cm long, ± pulvinate apically, sparsely stellate-pubescent, constricted and slightly contorted at the base when dry; stipules subulate, 5–7 mm long

Morphology Reproductive morphology Inflorescences

Inflorescences pendulous, axillary cymes, 4–7 cm long; peduncle 2–3.5(–7) cm long; pedicels 0.4–1.5 cm long, articulated above the middle; peduncle and pedicels stellate-pubescent or sub-glabrous, both expanding in fruit

Morphology General Buds

Floral buds narrowly turbinate, ± 2 mm long, with a stipe ± 1 mm long, densely stellate-pubescent or sub-glabrous

Morphology Reproductive morphology Flowers Calyx

Sepals broadly lanceolate, 2.5–4 mm long, 1–1.3 mm wide, stellate-pubescent or sub-glabrous outside, always pubescent within.

Morphology Reproductive morphology Flowers Corolla

Petals white turning pink or pale yellow, 6–8 mm long, the claw ± 1.5 mm long, geniculate, tapering or more abruptly constricted, the hood and recurved wings 1.7–2 mm wide, the dorsal appendage (lamina) ± fusiform, 3–5.5 mm long, glabrous

Morphology Reproductive morphology Flowers Androecium Stamens

Staminal tube ± 1 mm long, anthers sessile, 0.5–0.8 mm long; staminodes minute

Morphology Reproductive morphology Flowers Gynoecium Ovary

Ovary turbinate, ± 1 mm long, ± 0.7 mm in diameter, distinctly papillate or warty; style 1–2 mm long, stigmatic surface 5-lobed. Capsules slightly ellipsoid, 1.6–2.3 cm long, 1.8–2.3 cm wide (excluding spines), surface of fruit with scattered stellate hairs or glabrous, spines widely-spaced, stout, straight or slightly unciform, (1–)2–4 mm long, dehiscing lonculicidally, then incompletely septicidally from the apex; seed narrowly elliptic, ± 12–15 mm long, ± 4–7 mm in diameter, glabrous, greyish-brown (sometimes glaucous), raphe conspicuous.

Ecology

Moist forest, especially riverine habitats; 10–400 m

Conservation

Although this species appears to be fairly common in terms of numbers of specimen sites (± 20), its range is rather restricted and its habitat significantly threatened, accordingly it is here assessed as near threatened, provisionally.

Note

The type of B. fruticosa has glabrous flower buds. When there were very few collections of Byttneria from the East African coast, specimens with stellate-pubescent flower buds were separated out as a new species that was never published. The material is otherwise remarkably uniform and no character or combination of characters has been discovered that correlates with this minor pubescence variation. Plotting the distribution of a score of specimens of both forms confirms that there is no geographical separation either. Indeed, careful examination of the glabrous form often reveals the presence of at least a few stellate hairs. It therefore seems unlikely that we have anything but a single, somewhat variable species along the coast. While this treatment was in press, Luke (pers. comm.) sent new records extending the geographical range to T 6 ( Luke & Luke 4463 from Selous Game Reserve, Stiegler’s Gorge), and extending the altitudinal range: the lowermost record given above being based on Luke & Robertson 2335 (Mwena River, Kwale District) and the higher on Pakia & Luke 1534a (E Usambaras near Sigi HQ). One collection ( Luke & Robertson 2706) has conspicuous galls on the under surface of the leaf blade.

Distribution

Flora districts: K7 T3 T6 Range: Endemic