The families of flowering plants

DELTA home

L. Watson and M. J. Dallwitz

Melastomataceae Juss.

Excluding Memecylaceae.

Habit and leaf form. Herbs, or shrubs, or trees, or lianas; non-laticiferous. Self supporting, or epiphytic, or climbing; the climbers usually root climbers. Hydrophytic, helophytic, and mesophytic; when hydrophytic, rooted. Leaves whorled (rarely), or opposite (and decussate, one of each pair in some tribes commonly larger than the other, the smaller then sometimes withering early); sometimes somewhat turgescent; petiolate; simple. Lamina entire; lanceolate, or oblong, or ovate; palmately veined and parallel-veined (no dominant midrib, the several strong veins diverging at the base, converging at the apex); cross-venulate. Leaves exstipulate. Lamina margins entire, or serrate. Leaf development not ‘graminaceous’. Domatia occurring in the family (seen in about 10 genera); manifested as pits, or pockets.

General anatomy. Plants with ‘crystal sand’, or without ‘crystal sand’.

Leaf anatomy. The leaf lamina dorsiventral, or centric. Mucilaginous epidermis present, or absent. Stomata mainly confined to one surface (abaxial), or on both surfaces; anomocytic to anisocytic, or diacytic (often mixed). Hairs of numerous kinds present (in the family); eglandular and glandular; mostly multicellular, or unicellular (less commonly). Multicellular hairs multiseriate; branched, or simple. Complex hairs usually present; peltate, or stellate, or clavate, or capitate (often shaggy). Lamina without secretory cavities. The mesophyll with sclerenchymatous idioblasts (commonly), or without sclerenchymatous idioblasts; containing crystals. The crystals druses (mostly), or raphides (occasionally). Main veins vertically transcurrent, or embedded. Minor leaf veins without phloem transfer cells (Heterocentron, Medinilla, Tibouchina).

Axial (stem, wood) anatomy. Young stems often tetragonal. The cortex containing cristarque cells (Osbeckieae), or without cristarque cells. Secretory cavities absent (but secretory cells with undetermined contents common). Cork cambium present; initially deep-seated, or initially superficial. Nodes unilacunar. Primary vascular tissues in a cylinder, without separate bundles; bicollateral. Internal phloem seemingly universally present. Cortical bundles present (often), or absent. Medullary bundles present (often, often with central xylem), or absent (the family exhibiting medullary and/or cortical bundles in all combinations). Secondary thickening absent (?), or developing from a conventional cambial ring, or anomalous. The anomalous secondary thickening from a single cambial ring. Primary medullary rays narrow.

The wood diffuse porous. The vessels usually in numerous small radial multiples, and commonly with irregular clusters, occasionally tangential. The vessel end-walls exclusively simple. The vessels with vestured pits, or without vestured pits; without spiral thickening. The axial xylem without fibre tracheids (usually), or with fibre tracheids (some Astronioideae); with libriform fibres, or without libriform fibres; including septate fibres, or without septate fibres. The parenchyma paratracheal (only, in most genera), or apotracheal and paratracheal. ‘Included’ phloem present (some Astronioideae), or absent. The wood not storied.

Reproductive type, pollination. Plants hermaphrodite, or androdioecious (some Astronieae). Floral nectaries present (in about a dozen genera), or absent. Nectar secretion from the perianth, or from the androecium. Pollination entomophilous, or ornithophilous, or cheiropterophilous.

Inflorescence, floral, fruit and seed morphology. Flowers solitary (rarely), or aggregated in ‘inflorescences’. The ultimate inflorescence units cymose. Inflorescences in great variety, usually panicled or contracted cymes. Flowers often bracteolate (the bracteoles often brightly coloured); calyptrate, or not calyptrate; regular, or somewhat irregular. The floral irregularity involving the androecium. Flowers 3–5(–7) merous; cyclic. Free hypanthium present (tubular or campanulate).

Perianth with distinct calyx and corolla; 8–10(–14); 2 whorled; isomerous. Calyx 4, or 5(–7); 1 whorled; gamosepalous (the lobes variously a mere rim on the hypanthium, sometimes united and forming a calyptra); entire, or lobulate, or blunt-lobed, or toothed; regular; calyptrate, or not calyptrate; imbricate, or valvate, or contorted, or open in bud. Corolla 4, or 5(–7); 1 whorled; usually polypetalous; contorted; regular.

Androecium 4–5, or 8, or 10(–96) (usually twice C). Androecial members free of the perianth; all equal, or markedly unequal (often with the filaments twisted, bringing all the anthers to one side of the flower); free of one another; 1 whorled (standing so even when ‘both whorls’ present), or 2 whorled. Androecium exclusively of fertile stamens (often dimorphic), or including staminodes. Staminodes 4, or 5 (often alternating with the fertile members); in the same series as the fertile stamens. Stamens 4–5, or 8, or 10(–96); isomerous with the perianth to diplostemonous to polystemonous; inflexed in bud; filantherous (often geniculate at the base of the connective). Anthers basifixed; non-versatile; usually dehiscing via pores (apically, with one, two or rarely four pores per anther), or dehiscing via short slits, or dehiscing via longitudinal slits; initially tetrasporangiate; often appendaged (basally, from an extension of the connective or with dorsal connective spurs), or unappendaged. Endothecium not developing fibrous thickenings (thin and non-fibrous or even ephemeral). Anther epidermis persistent. Microsporogenesis simultaneous. The initial microspore tetrads tetrahedral, or isobilateral, or decussate. Anther wall initially with one middle layer, or initially with more than one middle layer (up to 7). Tapetum glandular. Pollen grains aperturate; (2–)3(–6) aperturate; colporate, or colpate and colporate (typically tricolporate, with three alternating poreless furrows (‘pseudocolpi’); 2-celled (Tobe and Raven 1984), or 3-celled (see Brewbaker).

Gynoecium (3–)4–5(–14) carpelled. The pistil 1 celled, or (3–)4–5(–14) celled. Gynoecium syncarpous; eu-syncarpous; superior to inferior (the hypanthium variously quite free, or adhering to the ovary completely or only by its longitudinal nerves). Ovary (3–)4–5(–14) locular, or 1 locular (locule number usually equalling G, but sometimes unilocular through partitions failing to develop). Epigynous disk absent. Gynoecium stylate. Styles 1; apical. Stigmas 1; wet type; papillate; Group III type. Placentation when unilocular, median parietal; usually axile. Ovules (2–)6–50 per locule (usually ‘many’); anatropous (usually), or orthotropous (Rhexia); bitegmic; crassinucellate. Outer integument contributing to the micropyle (in addition to the inner one). Embryo-sac development Polygonum-type. Polar nuclei fusing prior to fertilization. Antipodal cells formed; 3; not proliferating; ephemeral. Synergids hooked. Hypostase present. Endosperm formation nuclear. Embryogeny onagrad, or solanad.

Fruit fleshy, or non-fleshy; dehiscent, or indehiscent; a capsule, or a berry. Capsules loculicidal. Fruit 20–100 seeded (i.e. ‘many seeded’). Seeds non-endospermic; small. Embryo well differentiated (but minute). Cotyledons 2 (often unequal). Embryo achlorophyllous (1/1). Micropyle zigzag.

Seedling. Germination phanerocotylar.

Physiology, phytochemistry. Anatomy non-C4 type (Melastoma). Cyanogenic, or not cyanogenic. Cynogenic constituents phenylalanine-derived (?). Alkaloids usually absent. Iridoids not detected. Saponins/sapogenins absent. Proanthocyanidins present, or absent; when present, cyanidin and delphinidin. Flavonols present, or absent; kaempferol, or kaempferol and quercetin, or quercetin and myricetin. Ellagic acid present (5 genera, 5 species). Aluminium accumulation demonstrated (very commonly).

Geography, cytology. Sub-tropical to tropical. Pantropical and subtropical. X = 7–18 (or more).

Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Myrtiflorae; Myrtales. Cronquist’s Subclass Rosidae; Myrtales. APG 3 core angiosperms; core eudicot; Superorder Rosanae; malvid; Order Myrtales.

Species about 4400. Genera about 180; Acanthella, Aciotis, Acisanthera, Adelobotrys, Allomaieta, Allomorpheia, Allomorphia, Amphiblemma, Amphorocalyx, Anaectocalyx, Anerincleistus, Antherotoma, Appendicularia, Arthrostemma, Ascistanthera, Astrocalyx, Astronia, Astronidium, Axinaea, Barthea, Beccarianthus, Behuria, Bellucia, Benevidesia, Bertolonia, Bisglaziovia, Blakea, Blastus, Boerlagea, Boyania, Brachyotum, Bredia, Brittenia, Bucquetia, Cailliella, Calvoa, Calycogonium, Cambessedesia, Campimia, Carionia, Castratella, Catanthera, Catocoryne, Centradenia, Centradeniastrum, Centronia, Chaetolepis, Chaetostoma, Chalybea, Charianthus, Cincinnobotrys, Clidemia, Comolia, Comoliopsis, Conostegia, Creochiton, Cyanandrium, Cyphostyla, Cyphotheca, Dalenia, Desmoscelis, Dicellandra, Dichaetanthera, Dinophora, Dionycha, Dionychastrum, Diplarpea, Diplectria, Dissochaeta, Dissotis, Dolichoura, Driessenia, Enaulophyton, Eriocnema, Ernestia, Feliciadamia, Fordiophyton, Fritzschia, Graffenriedia, Gravesia, Guyonia, Henriettea, Henriettella, Heterocentron, Heterotis, Heterotrichum, Huberia, Huilaea, Hypenanthe, Kendrickia, Kerriothyrsus, Killipia, Kirkbridea, Lavoisiera, Leandra, Lithobium, Llewelynia, Loreya, Loricalepis, Macairea, Macrocentrum, Macrolenes, Maguireanthus, Maieta, Mallophyton, Marcetia, Mecranium, Medinilla, Melastoma, Melastomastrum, Meriania, Merianthera, Miconia, Microlepis, Microlicia, Mommsenia, Monochaetum, Monolena, Myriaspora, Myrmidone, Neblinanthera, Necramium, Neodriessenia, Nepsera, Nerophila, Ochthephilus, Ochthocharis, Omphalopus, Opisthocentra, Oritrephes, Osbeckia, Ossaea, Otanthera, Oxyspora, Pachyanthus, Pachycentria, Pachyloma, Phaiantha, Phyllagathis, Pilocosta, Plagiopetalum, Pleiochiton, Plethiandra, Pogonanthera, Poikilogyne, Poilannammia, Poteranthera, Preussiella, Pseudodissochaeta, Pseudosbeckia, Pterogastra, Pterolepis, Pyramia, Rhexia, Rhyncanthera, Rousseauxia, Salpinga, Sandemania, Sarcopyramis, Schwackaea, Scorpiothyrsus, Siphanthera, Sonerila, Sporoxeia, Stenodon, Stussenia, Svitramia, Tateanthus, Tayloriophyton, Tessmannianthus, Tetrazygia, Tibouchina, Tibouchinopsis, Tigridiopalma, Tococa, Topobea, Trembleya, Triolema, Tristemma, Tryssophyton, Tylanthera, Vietsenia.

General remarks. Description corrected by S.S. Renner (1992).

Illustrations. • Technical details: Spennera (= Aciotis), Huberia, Kibessia, Melastoma, Naudinia, Osbeckia, Pyramea, Tulasnea. • Technical details: Dissotis (Thonner). • Centradenia inaequilateralis: Bot. Reg. 29 (20), 1843. • Marcetia excoriata: Bot. Reg. 29 (31), 1843. • Osbeckia chinensis: Bot. Reg. 542, 1821. • Osbeckia nepalensis var. albiflora: as Osbeckia nepalensis, Bot. Reg. 1475 (1831). • Osbeckia stellata: Bot. Reg. 674, 1822. • Tibouchina granulosa: Bot. Reg. 671, 1822. • Tibouchina heteromalla: Bot. Reg. 644, 1822. • Leaf hairs of Centradenia, Medinilla, Pyramia, Sphaerogyne, Tibouchina: Solereder, 1908).

The descriptions are offered for casual browsing only. We strongly advise against extracting comparative information from them. This is much more easily achieved using 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).

Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 1992 onwards. The families of flowering plants: descriptions, illustrations, identification, and information retrieval. Version: 16th May 2016.’.