1. Thyrsanthella difformis (Walter) Pichon, Bull. Mus. Natl. Hist. Nat., sér. 2. 20: 192. 1948.
[E F]
Climbing dogbane
Echites difformis Walter, Fl. Carol., 98. 1788; Forsteronia difformis (Walter) A. de Candolle; Trachelospermum difforme (Walter) A. Gray
Stems glabrous or very sparsely pubescent when young. Leaves: petiole 1–10(–15) mm, glabrous; blade elliptic to obovate-elliptic or occasionally linear-lanceolate or suborbiculate, 2.7–6(–12) × 0.4–3.5(–7) cm, membranous, base acute to rounded or obtuse, apex acuminate or apiculate, surfaces sparsely pubescent or glabrous. Peduncles 2.5–5 cm, sparsely pubescent or glabrous. Pedicels 4–8 mm, minutely pubescent or glabrous. Flowers: calyx lobes ovate-lanceolate, 3–4 mm, pubescent or glabrous; corolla glabrous or very sparsely eglandular-pubescent abaxially, eglandular-pubescent adaxially, tube 2.5–3.5 × 1–1.5 mm, throat 2.5–3.5 × 2–3 mm, lobes spreading or reflexed, obliquely obovate, 3–4 × 2–3 mm. Follicles 10–23 × 0.1–0.3 cm. Seeds 8–11 × 1.5–2 mm.
Flowering spring; fruiting spring–fall. Bottomlands, swamps, moist upland forests and woodlands; 0–400 m; Ala., Ark., Del., Fla., Ga., Ill., Ind., Ky., La., Md., Miss., Mo., N.C., Okla., S.C., Tenn., Tex., Va.
The leaves of Thyrsanthella difformis can exhibit a remarkable variability in width, even on branches of the same plant, most notably in young sprouts of the forest floor.
