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The families of flowering plants

L. Watson and M.J. Dallwitz

Memecylaceae DC.

~ Melastomataceae.

Including Mouririaceae G. Gardner

Habit and leaf form. Trees and shrubs. Mesophytic. Leaves opposite; petiolate; simple. Lamina entire; lanceolate, or oblong, or ovate; pinnately veined (with a single midrib); cross-venulate. Leaves exstipulate. Lamina margins entire, or serrate (?). Leaf development not ‘graminaceous’.

Leaf anatomy. Stomata paracytic (at least in Memecylon). Lamina without secretory cavities. The mesophyll with sclerenchymatous idioblasts, or without sclerenchymatous idioblasts; containing crystals. The crystals druses and solitary-prismatic (often with styloids).

Axial (stem, wood) anatomy. Young stems cylindrical, or oval in section. Secretory cavities absent. Cork cambium present; initially deep-seated, or initially superficial. Nodes unilacunar. Primary vascular tissues in a cylinder, without separate bundles; often bicollateral. Internal phloem present. Cortical bundles absent (always? — 2 genera listed by Metacalfe and Chalk 1950). Medullary bundles absent (at least from the 2 genera listed by Metacalfe and Chalk 1950). Secondary thickening developing from a conventional cambial ring, or anomalous. The anomalous secondary thickening from a single cambial ring. Primary medullary rays wide, or mixed wide and narrow, or narrow.

The wood diffuse porous. The vessel end-walls simple. The axial xylem commonly with fibre tracheids. The parenchyma paratracheal (only, mostly?), or apotracheal and paratracheal (sometimes?). ‘Included’ phloem often present (foraminate type). The wood not storied.

Reproductive type, pollination. Plants hermaphrodite (mostly), or androdioecious (Lijndenia). Pollination entomophilous.

Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’. The ultimate inflorescence units cymose. Inflorescences axillary. Flowers regular to somewhat irregular. The floral irregularity involving the androecium. Flowers 4 merous, or 5 merous; cyclic. Free hypanthium present (tubular or campanulate above the ovary).

Perianth with distinct calyx and corolla; 8–10; 2 whorled; isomerous. Calyx 4, or 5; 1 whorled; gamosepalous; regular; valvate, or open in bud. Corolla 4, or 5; 1 whorled; polypetalous; contorted; regular.

Androecium 4–5, or 8, or 10. Androecial members free of the perianth; all equal, or markedly unequal; free of one another; 1 whorled, or 2 whorled. Androecium exclusively of fertile stamens, or including staminodes. Stamens 4–5, or 8, or 10; isomerous with the perianth, or diplostemonous. Anthers versatile; dehiscing via pores (apically), or dehiscing via short slits, or dehiscing via longitudinal slits; bilocular; initially tetrasporangiate (bisporangiate when mature); appendaged (from the connective, which has a dorsal, concave gland). Endothecium developing fibrous thickenings. Microsporogenesis simultaneous. Tapetum glandular. Pollen grains aperturate; 3 aperturate, or 6 aperturate; colporate, or colpate and colporate (cf. Melastomaceae); 3-celled.

Gynoecium (3–)4–5(–14) carpelled. The pistil 1–5 celled. Gynoecium syncarpous; eu-syncarpous; inferior. Ovary 1(–5) locular. Styles 1; apical. Stigmas 1. Placentation when unilocular, free central; when multilocular, axile to basal. Ovules in the single cavity when unilocular, 3–10; when multilocular, 2–3 per locule; ascending; collateral (in the locules, or whorled when unilocular); anatropous; bitegmic; crassinucellate. Outer integument contributing to the micropyle. Embryo-sac development Polygonum-type. Endosperm formation nuclear.

Fruit fleshy; indehiscent; a berry; 1–5 seeded. Seeds non-endospermic. Embryo well differentiated (large). Cotyledons 2 (equal). Embryo chlorophyllous (1/2).

Seedling. Germination cryptocotylar.

Physiology, phytochemistry. Cyanogenic, or not cyanogenic. Iridoids not detected. Saponins/sapogenins absent. Aluminium accumulation demonstrated (very commonly).

Geography, cytology. Tropical. Pantropical.

Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Myrtiflorae; Myrtales. Cronquist’s Subclass Rosidae; Myrtales. APG III core angiosperms; core eudicot; Superorder Rosanae; malvid. APG IV Order Myrtales (as a synonym of Melastomataceae).

Species 430. Genera 7; Klaineastrum (= Warneckea), Lijndenia, Memecylon, Mouriri, Pternandra, Spathandra, Votomita, Warneckea.

General remarks. Description corrected by S.S. Renner (1992). Differing from Melastomataceae sensu stricto in the pinnate leaf venation, stems cylindrical or oval in section, versatile anthers with fibrous endothecium, ovary with free central placentation and few-seeded fruits; also (relying on limited sampling) paracytic foliar stomata, and seedlings with cryptocotylar germination.

Illustrations. • Mouriri arborea, as Mouriria: Hook. Ic. Pl. 5–6 (1842–3). • Memecylon capitellatum: Trimen, Ill. Fl. Ceylon (1894). • Memecylon aberrans, M. humbertii and M. urschii: Fl. de Madagasc. (1951). • Memecylon sphaerocarpum, as M. tinctorium: Wight, Ill. Indian Bot. 1 (1840).

We advise against extracting comparative information from the descriptions. This is much more easily achieved using the DELTA data files or the interactive key, which allows access to the character list, illustrations, full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting or lacking specified attributes, distributions of character states within any set of taxa, geographical distribution, genera included in each family, and classifications (Dahlgren; Dahlgren, Clifford, and Yeo; Cronquist; APG). See also Guidelines for using data taken from Web publications.

Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 1992 onwards. The families of flowering plants: descriptions, illustrations, identification, and information retrieval. Version: 5th March 2018.’.