Mecranium birimosum (Naudin) Triana
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Family
Melastomataceae (Magnoliophyta)
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Scientific Name
Mecranium birimosum (Naudin) Triana
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Primary Citation
Trans. Linn. Soc. London 28: 140. 1871
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Basionym
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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: [HISPANIOLA] "SAINT DOMINGUE": Hamlet T [Haiti, Massif de la Selle], fl, without date [1788-1791], Beavois s.n. (holotype: P!, photos: NY! F!, fragment of holotype: F!).
Description: Shrub or small tree to 2.5 m tall, perhaps larger. 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 1-2.6 (-9.7) cm long. Leaf blade 4.4-8.7 cm long, 1.7-3.2 cm wide, narrowly ovate or elliptic, less commonly obovate, very coriaceous, leaves of stump sprouts and sucker-shoots to 14 cm long and 6 cm wide; apex acuminate, less commonly acute or rounded; base cuneate or slightly decurrent; margin obscurely serrate in distal ca 3/4, but usually appearing entire because slightly revolute; venation slightly suprabasal, usually with 1 pair of conspicuous secondary veins joining midvein 1-3 (-5) 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 slightly impressed; 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 flat or very slightly raised, the surface essentially glabrous, but with some scattered minute, glandular hairs; marsupiform domatia present on abaxial surface in axils at junction of midvein and largest pair of secondary veins, persistent axillary hair tufts absent. Petiole 6-15 (-19) mm long, glabrous. Inflorescences borne in leaf axils and on leafless nodes below leaves, 3.3-7.9 cm long, 2-2.3 cm wide, 1-3 branched; peduncle 14-31 mm long. Hypanthium broadly obconical or subglobose, 1.6-2.6 mm long, 1.8-2.4 mm wide, very sparsely pubescent with minute glandular hairs, the portion free from ovary 0.4-0.7 mm long; portion of calyx bearing external teeth 0.3-0.6 mm long, and with additional narrowly triangular internal projections 0.2-0.7 mm long, 0.1-0.3 mm wide. Calyx teeth ca 0.2 mm long, 0.2 mm wide. Calyptra present in bud, dome-like, with a caducous apiculum 0.1-0.3 mm long. Petals 2.1-2.5 mm long, 1.3-2.0 mm wide, obovate, slightly cupped adaxially, white, spreading; apex rounded, emarginate. Stamens white; filament narrowly ovate or elliptic, 1.7-2.2 mm long, 0.4-0.6 mm wide; anther narrowly obovate, 1.7-2.2 mm long, 0.5-0.7 mm wide, opening by 2 pore-like slits that extend laterally across apex and down adaxial surface of anther sacs, septum between anther sacs intact, the anther sacs 0.3-0.6 mm long. Ovary inferior, 1.5-1.8 mm long, 1.2-1.8 mm wide, the apical appendage 0.4-1.4 mm high; style 2.3-4.1 mm long, 0.3-0.4 mm wide, white, straight or slightly curved; stigma 0.4-0.6 mm wide. Berries ca 5 mm in diameter, purple-black, sparsely pubescent with minute glandular hairs; seeds ca 0.8 mm long, 0.4 mm wide. Fig. 20.
Habitat and Distribution: Hispaniola: endemic to "rak bwa," i.e., low elevation hardwood forests on limestone, and broad-leaved cloud forests in the Massif de la Selle and Massif de la Hotte of Haiti; 1050-1800 m. (Fig. 21).
Phenology: Flowering and fruiting sporadically from July to March.
Taxonomy and Systematics: Mecranium birimosum is a species with white petals and anthers that open by two slits. It has the autapomorphy of an additional whorl of 4 narrowly triangular calyx projections, which are internal to and opposite the internal calyx lobes (see Fig. 20I). The leaves of M. birimosum have marsupiform mite domatia at the two major vein intersections on the abaxial leaf surface (Fig. 20D), and were found (in Skean 2031) to contain immature scavenger mites (Oribatulidae). In sterile condition, M. birimosum is most likely to be confused with M. multiflorum (Figs. 15B, 34), a species of sympatric occurrence in the Massif de la Selle. The latter has smaller flowers and less coriaceous leaves with revolute margins at their bases. Figure 22 compares the leaf bases of M. birimosum and M. multiflorum. In M. birimosum the leaf bases are more cuneate and are not revolute. Note that the distance between conspicuous tertiary veins is shorter in M. birimosum. Marsupiform mite domatia, present in M. birimosum, are lacking in M. multiflorum, and in their place are often located poorly developed tufts of caducous hairs. Today the species is probably very rare in the Massif de la Selle. I was able to locate but a single plant in the muddy, eroded mountains at Furcy, near Port-au-Prince. This area is now essentially devoid of any native forest. Specimens of M. birimosum from the Massif de la Hotte, with elliptic or obovate leaves and more rounded apices, were described by Urban & Ekman (1927) as M. torbecianum, after Torbec, a nearby settlement. Occasionally similar obovate leaves are found on plants of M. birimosum in the Massif de la Selle. Both obovate and ovate-leaved specimens are now known from the Massif de la Hotte in the region of Morne Formon. In my opinion the two existing obovate-leaved collections (Ekman H5294, Ekman H10689) were taken from the crowns of rather large plants, as indicated by Ekman when he described the plant from which Ekman H10689 was taken as a "medium-sized tree." While in the field I have observed similar leaf variation within other species of the genus (e.g., M. alpestre, M. puberulum, M. tricostatum). Often the crown leaves of large individuals are more obovate than those found on smaller specimens. Mecranium birimosum probably was named for its mode of anther dehiscence.
- Sorry, no descriptions available for this record.
