1. Trianthema portulacastrum L. (sea purslane, horse purslane)

Pl. 202 e, f; Map 809

Plants perennial herbs (sometimes woody at the base farther south), succulent, with a short taproot. Stems 15–100 cm long, highly branched from the base, ascending to spreading, glabrous or sparsely pubescent in longitudinal lines. Leaves opposite, with the two leaves at each node unequal in size, petiolate. Stipules fused to the petioles and appearing as narrow wings of tissue at the petiole base, the petioles thus appearing to wrap around the nodes. Leaf blades 1–4 cm long, obovate to broadly elliptic or nearly circular, flattened but thick, rounded or abruptly narrowed at each end, usually with a short point at the tip, glabrous or sparsely hairy. Flowers solitary or in small clusters in the leaf axils, deeply perigynous, each with a pair of minute bracts that are fused to the calyx, often hidden by and sometimes fused with the expanded petiole bases. Calyx 5-lobed, the lobes 2.0–2.5 mm long, arched inward over the flower top, green on the outer surface, tinged pink or purple on the inner surface. Petals absent. Stamens 5–10, the filaments fused to the calyx tube. Pistil 1 per flower, the ovary superior but sometimes appearing nearly inferior in fruit, consisting of 1 carpel, with 1 locule (sometimes incompletely 2-locular), the placentation parietal. Style 1(2), the stigma 1(2). Ovules 3–9. Fruits capsules, 3.5–4.5 mm long, cylindrical, with the margin extended into a pair of irregular wings at the tip, circumscissilely dehiscent by a ring at the middle, the uppermost 1 or 2 seeds usually dispersed with the cap, the other 2 or 3 seeds dispersing from the capsule base. Seeds 1.6–2.0 mm wide, somewhat flattened, broadly kidney-shaped (the embryo appearing curved or coiled), with a small aril, the surface wrinkled, reddish brown to black. 2n=26, 36. May–October.

Introduced, uncommon in western Missouri (apparently native to Africa and Australia; introduced and weedy in the New World tropics; in the U.S. from Florida to California north to New Jersey, Oklahoma, and Missouri). Railroads and open, disturbed areas.

Although the leaves of this species are prepared as a vegetable in some parts of Africa and Asia, they are also widely used medicinally (ranging from cathartic to abortifacient) and are reputedly poisonous to livestock (Bogle, 1970).