Metastelma monense Britton, Bot. Porto Rico 6: 97. 1925.
Synonym: Cynanchum monense (Britton) Alain
Herbaceous vine, twining, evergreen or partially deciduous during the flowering period, much branched, attaining 5 m in length, with abundant milky latex. Stems green, slender, cylindrical, glabrous, 1 mm or less in diameter. Leaves opposite or clustered on short axillary branches; blades 7-16 × 1.5-3 mm, oblanceolate, oblong or obovate, coriaceous, glabrous, the apex obtuse, rounded, or truncate and apiculate, the base obtuse or attenuate, the margins entire, revolute, slightly ciliate; upper surface dull, with the midvein sunken and whitish, without glands at the union with the petiole; lower surface pale green, with a prominent midvein, the secondary venation slightly conspicuous; petioles light green or yellowish, compressed and sulcate, 1.5-2 mm long; stipules interpetiolar, triangular, ca. 0.4 mm long. Flowers few, fragrant, arranged in sessile cymes; pedicels 1-1.5 mm long. Calyx crateriform, green, the sepals ovate, ca. 1 mm long, papillose or glabrous outside; corolla white, ca. 2.5 mm long, the lobes ovate-lanceolate, free to the base, the inner surface densely short-pubescent from the middle to the distal portion, strigulose in the central basal portion; corona white, with lanceolate segments, fleshy, almost as long as the lobes of the corolla; gynostegium sessile. Follicles fusiform, ca. 2.5 cm long, glabrous.
Phenology: Collected in flower from December to May.
Status: Endemic to Puerto Rico.
Selected Specimens Examined: Acevedo-Rdgz., P. 4273.
Distribution: Locally common on Mona Island and recently discovered by Franklin Axelrod (Uprrp) in the Guánica Forest.
Public forest: Guánica and Mona.