Platycarpum

  • Authority

    Rogers, George K. 1984. Gleasonia, Henriquezia, and Platycarpum (Rubiaceae). Fl. Neotrop. Monogr. 39: 1-135. (Published by NYBG Press)

  • Family

    Rubiaceae

  • Scientific Name

    Platycarpum

  • Type

    Type species. Platycarpum orinocense Humboldt and Bonpland.

  • Synonyms

    Platycarpium Roem. & Schult.

  • Description

    Genus Description - Shrubs to large trees, usually with gnarled appearance. Stipules arranged with single lobe between each pair of petioles (rubiaceous), valvate, caducous, deltoid to oblong or lanceolate, rounded to acuminate at apex, adaxially densely antrorse-pubescent. Leaves decussate or in whorls of 3 or 4, clustered at ends of branches; lamina usually elliptic to oblanceolate, highly variable at apex and base, usually revolute at margins; petiole usually bearing abaxially at base 1 (rarely to 5) variously shaped gland(s). Inflorescence a complex terminal cyme, highly variable in size and density, consisting of determinate central axis bearing dichasial branches; bracts near base resembling foliage leaves, more distal bracts and bracteoles linear or subulate. Hypanthium broadly obconic, densely pubescent; calyx lobes (4-)5 (-6), usually 4-12 mm long, usually oblong to lanceolate, externally densely pubescent, internally pale-sericeous; corolla usually 1-2 cm long, usually funnelform, zygomorphic, externally white to rose-colored, densely pale-hirsute, internally with red markings, usually yellow-bearded and with pilose ring at base of tube, otherwise usually glabrous; corolla lobes generally ovate to oblong, rounded to acute at apex, often apiculate; filaments inserted near base of tube, with the 2 flanking beard most basal, bent such that all anthers dehisce toward beard; anthers narrowly elliptic, usually apiculate. Capsule 2-6 cm long, about as wide as long, 0.5-2.0 cm thick, usually emarginate at both ends. Seeds 2 per locule, collateral, elliptic or D-shaped, thin (ca. 1 mm thick), with marginal wing, papillose.

  • Discussion

    Distribution and Ecology: Especially common in the Guayana Highland, region of the Río Orinoco near the Venezuela-Colombia border, and region of the upper Rio Negro in Brazil and Venezuela. The range extends to western Guyana (Platycarpum eglandulosum), the upper Río Vaupés in central Colombia (P. schultesii), the state of Acre at the extreme west of Brazil (P. acreanum), and the Rio Madeira on the southern side of the Amazon River in the state of Para, Brazil.