Mecranium virgatum (Sw.) Triana

  • Family

    Melastomataceae (Magnoliophyta)

  • Scientific Name

    Mecranium virgatum (Sw.) Triana

  • Primary Citation

    Trans. Linn. Soc. London 28: 140. 1871

  • Basionym

    Melastoma virgata Sw.

  • Description

    Description Author and Date: James D. Skean, Jr., January 2011, based on Skean, J. D., Jr. 1993. Monograph of Mecranium (Melastomataceae-Miconieae). Syst. Bot. Monogr. 39: 1-116.

    Type: JAMAICA. Mountain woods, without specific locality, fl, without date [1785 or 1786], Swartz s.n. (lectotype: designated by Skean, 1993, S!; isolectotypes: BR! S!).

    Description: Shrub or small tree to ca 7 m tall. Twigs slightly to moderately 4-angled, 2-3 mm in diameter, smooth, essentially glabrous, but youngest buds and nodal ridges often with a few unbranched to irregularly branched and matted multicellular hairs; internodes 0.9-3.8 cm long. Leaf blade 6-18.3 cm long, 1.7-5.5 cm wide, ovate to elliptic, coriaceous, often plicate if plant in full sun; apex acuminate; base cuneate or slightly decurrent, less commonly acute; very obscurely serrate in distal ca 3/4 to nearly entire, flat or slightly revolute, especially near base; venation usually suprabasal, with 1 pair of conspicuous secondary veins joining midvein 1-11 mm above lamina base, and 1 pair of inconspicuous, intramarginal secondary veins; adaxial surface with midvein and largest pair of secondary veins flat or slightly impressed, the intramarginal secondary veins and tertiary veins flat or not visible; abaxial surface with midvein and largest pair of secondary veins raised, the intramarginal secondary veins and tertiary veins flat or very slightly raised, the quaternary and higher order veins often slightly raised, the surface essentially glabrous, but with some scattered minute, glandular hairs; marsupiform domatia and persistent axillary hair tufts absent from abaxial surface at junction of midvein and largest pair of secondary veins. Petiole 7-29 mm long, glabrous. Inflorescences borne ± exclusively on leafless nodes below leaves and on old wood, 1.4-5.5 cm long, 0.5-4.6 cm wide, 1-2 branched; peduncle 3-17 mm long. Hypanthium 2.8-4.4 mm long, 1.5-2.9 mm wide, narrowly obconical, base prolonged into a "pedicel" 0.3-1.1 mm long, very sparsely pubescent with minute glandular hairs, the portion free from ovary 0.4-2.3 mm long; portion of calyx bearing external teeth 0.3-0.7 mm long. Calyx teeth ca 0.2 mm long, 0.2 mm wide. Calyptra present in bud, dome-like, with a caducous apiculum to ca 0.1 mm long. Petals 2.9-5.2 mm long, 2.7-5.8 mm wide, obovate, slightly cupped adaxially, white, reflexed; apex rounded, emarginate. Stamens white; filament narrowly ovate, 3-5.7 mm long, 0.3-0.6 mm wide; anther narrowly obovate, 2.2-3.4 mm long, 0.4-0.5 mm wide, the anther sacs 1.1-1.8 mm long, opening by a gaping foramen, septum torn. Ovary inferior, ca 2.7-3.2 mm long, 1.4-2.3 mm wide, the apical appendage 0.8-1.3 mm high; style 5.8-9.9 mm long, 0.4-0.6 mm wide, white, straight or often strongly curved; stigma 0.4-0.7 mm wide. Berries 7-9 mm long, 5-7 mm wide, purple-black, glabrous or with a few minute glandular hairs; seeds 0.5-0.7 mm long, 0.3-0.4 mm wide. Fig. 50.

    Habitat and Distribution: Jamaica: hardwood forests on limestone and low-elevation cloud forests in the eastern half of the island; 60-1370 m. (Fig. 51).

    Phenology: Flowering from late January through April and producing mature fruits May through August.

    Taxonomy and Systematics: Mecranium virgatum is a distinctive, essentially glabrous species with comparatively large white flowers borne more or less exclusively on leafless nodes and old wood below the leaves. Only one collection examined (Adams 7914; UCWI) had some flowers borne in the axils of leaves. The hypanthium bases and fruit bases of this species are unique in the genus because they are prolonged like pedicels (Fig. 50G-H.). The other species of Mecranium have rounded hypanthium bases. This is the only species of Mecranium that has been analyzed chemically (Gibbs 1974). George R. Proctor collected specimens for studies of antitumor agents, but no significant activity was reported (Proctor, pers. comm.). Proctor (1972) reported that this species had white berries. The mature fruits that I have examined have all been purple-black, like those of other species in the genus.

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