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The families of flowering plants

L. Watson and M.J. Dallwitz

Humiriaceae Juss.

Alternatively Houmiriaceae Juss.

Habit and leaf form. Trees, or shrubs. Leaves persistent; alternate; spiral, or distichous; leathery; petiolate; non-sheathing; aromatic (often, with ‘balsamic’ juice), or without marked odour; simple. Lamina entire; pinnately veined; cross-venulate. Leaves stipulate, or exstipulate. Stipules when present, caducous (tiny). Lamina margins entire, or crenate, or serrate.

Leaf anatomy. The leaf lamina dorsiventral. Stomata present; anomocytic, or paracytic. Hairs present (but scarce), or absent. Complex hairs absent. Lamina without secretory cavities. The mesophyll with sclerenchymatous idioblasts, or without sclerenchymatous idioblasts; containing crystals. The crystals druses, or solitary-prismatic.

Axial (stem, wood) anatomy. Secretory cavities absent. Cork cambium present; initially superficial. Primary vascular tissues in a cylinder, without separate bundles; collateral. Internal phloem absent. Cortical bundles absent. Medullary bundles absent. Secondary thickening developing from a conventional cambial ring. Primary medullary rays mixed wide and narrow.

The wood diffuse porous. The vessels medium; almost exclusively solitary. The vessel end-walls oblique; scalariform. The vessels without vestured pits; without spiral thickening. The axial xylem with tracheids; without vasicentric tracheids; with fibre tracheids; without septate fibres. The fibres without spiral thickening. The parenchyma apotracheal and paratracheal. ‘Included’ phloem absent. The wood not storied.

Reproductive type, pollination. Unisexual flowers absent. Plants hermaphrodite.

Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; in panicles. The ultimate inflorescence units cymose. Inflorescences terminal (rarely), or axillary; axillary or rarely terminal thyrses. Flowers regular to somewhat irregular. Free hypanthium absent. Hypogynous disk present; intrastaminal; of separate members, or annular (cupular).

Perianth with distinct calyx and corolla; 10; 2 whorled; isomerous. Calyx 5 (but the lobes of the two outer members sometimes suppressed); 1 whorled; gamosepalous (usually connate below into a thickened tube or cup); three or five blunt-lobed; cupuliform, or tubular; persistent; imbricate. Corolla 5; 1 whorled; polypetalous (the petals usually 3–5 nerved, thick); imbricate, or contorted; persistent, or deciduous.

Androecium 10–30, or 40–100 (Vantanea). Androecial members branched (fascicled, with trunk bundles, or with clusters and singles); free of the perianth; coherent (the filaments connate for much of their length into a tube); 1–4 whorled, or 5 whorled (one to several series). The androecial bundles when present, alternating with the corolla members. Androecium exclusively of fertile stamens, or including staminodes. Stamens 10–100 (to ‘many’); diplostemonous to polystemonous; sometimes in 5 antesepalous clusters of three, and 5 antepetalous singles. Anthers dorsifixed to basifixed, or adnate (to the base of the fleshy connective); versatile; dehiscing via longitudinal slits; bilocular (the locules often well separated), or four locular; bisporangiate, or tetrasporangiate; conspicuously appendaged. The anther appendages apical (the connective expanded and prolonged). Pollen shed as single grains. Pollen grains aperturate; 3(–4) aperturate; porate (rarely), or colporate.

Gynoecium (4–)5(–7) carpelled. Carpels reduced in number relative to the perianth to isomerous with the perianth to increased in number relative to the perianth. The pistil (4–)5(–7) celled. Gynoecium syncarpous; synstylovarious to eu-syncarpous; superior. Ovary (4–)5(–7) locular; sessile. Gynoecium stylate. Styles 1; apical. Stigmas 1; (4–)5(–7) lobed (or entire). Placentation axile to apical. Ovules 1–2 per locule; pendulous; epitropous (the micropyle directed upwards and outwards); with ventral raphe; when paired, superposed; anatropous; bitegmic; crassinucellate. Endothelium differentiated. Endosperm formation probably nuclear.

Fruit fleshy (with more or less fleshy exocarp); indehiscent; a drupe (the endocarp woody, sometimes with resin cavities, then buoyant for distribution by water); usually 1 seeded, or 2 seeded (germinating by valves or opercula). Seeds copiously endospermic. Endosperm oily. Cotyledons 2 (?). Embryo slightly curved, or straight.

Physiology, phytochemistry. Ellagic acid present.

Geography, cytology. Paleotropical and Neotropical. Tropical. Tropical America, and one species in tropical West Africa. X = 12.

Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Rutiflorae; Geraniales. Cronquist’s Subclass Rosidae; Linales. APG III core angiosperms; core eudicot; Superorder Rosanae; fabid. APG IV Order Malpighiales.

Species 50. Genera 8; Duckesia, Endopleura, Hylocarpa, Humiria (Houmiria), Humiriastrum, Sacoglottis, Schistostemon, Vantanea.

General remarks. See Cuatrecasas 1961.

Illustrations. • Humiria balsamifera, H. floribunda and Sacoglottis cuspidata: technical details (Fl. Bras. 12, 1872). • Humiria balsamifera var. floribunda: Martius, Nova Gen. et Spec. Pl. Brasiliensium 2 (1826). • Sacoglottis amazonica: Hook. Ic. Pl. 26 (1897). • Le Maout and Decaisne: Humiria crassifolium.

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: 15th April 2018.’.