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The families of flowering plants

L. Watson and M.J. Dallwitz

Peraceae (Baill.) Benth. ex Klotsch

~ Euphorbiaceae.

Habit and leaf form. Trees, or shrubs (with stellate hairs or scales, simple hairs, or glabrous); non-laticiferous, without coloured juice. Leaves alternate (usually), or opposite (very rarely); shortly petiolate; non-sheathing; simple. Lamina entire; pinnately veined; cross-venulate. Leaves stipulate to exstipulate (the stipules minute or obsolete). Lamina margins entire.

General anatomy. Plants without laticifers.

Leaf anatomy. Mucilaginous epidermis present. Lamina without secretory cavities.

Axial (stem, wood) anatomy. Secretory cavities absent. Internal phloem absent. Cortical bundles absent. Medullary bundles absent. Secondary thickening developing from a conventional cambial ring.

The parenchyma abundant, apotracheal. ‘Included’ phloem absent.

Reproductive type, pollination. Fertile flowers functionally male and functionally female, or functionally male, or functionally female. Plants monoecious, or dioecious. Gynoecium of male flowers pistillodial, or vestigial, or absent.

Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; in heads. Inflorescences 3–4 flowered, involucrate, unisexual or bisexual capitula; with involucral bracts (1–2 small, free outer bracts, and two larger, variously connate, spathaceous inner bracts); more or less spatheate (by the inner bracts). Flowers cyclic. Free hypanthium absent. Hypogynous disk absent.

Perianth sepaline (sometimes, in male flowers), or absent (from female flowers, and sometimes from male flowers); of male flowers, when preent, 4–6; 1 whorled. Calyx of male flowers, when present, 4–6; 1 whorled; gamosepalous; entire to lobulate, or blunt-lobed, or toothed; cupuliform; valvate.

Androecium in male flowers, 2–5. Androecial members free of the perianth; coherent; 1 adelphous (united below into a column). Androecium exclusively of fertile stamens. Stamens 2–5; reduced in number relative to the adjacent perianth to isomerous with the perianth (when the perianth present); erect in bud. Anthers dehiscing via longitudinal slits; extrorse, or latrorse.

Gynoecium 3 carpelled. The pistil 3 celled. Gynoecium syncarpous; synstylovarious to eu-syncarpous; superior. Ovary 3 locular. Gynoecium shortly stylate, or non-stylate. Styles 1; apical. Stigmas 1, or 3; entire or 3 lobed; when entire peltate. Placentation apical. Ovules 1 per locule; pendulous; arillate (the seed carunculate).

Fruit somewhat fleshy, or non-fleshy; tardily dehiscent; a capsule (drupiform, with woody endocarp and fleshy or spongy mesocarp, the smooth epicarp wrinkled when dry). Capsules with the valves splitting along the midline but not springing back elastically, usually remaining attached basally to the pedicel, the slender central column splitting longitudinally into three. Seeds endospermic (the endosperm fleshy); black and shiny and with a tracheoidal exotegumen, atypical of Euphorbiaceae sensu lato. Cotyledons 2 (broad, flat). Embryo straight. Testa smooth (shining).

Geography, cytology. Neotropical. Tropical. Mexico to tropical South America, West Indies.

Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Malviflorae; Euphorbiales. Cronquist’s Subclass Rosidae (by inference); Euphorbiales. APG III core angiosperms; core eudicot; Superorder Rosanae; fabid. APG IV Order Malpighiales.

Species about 40. Genera 1; only genus, Pera.

General remarks. Recent inclusion of other Euphorbiaceae-Peroideae (Chaetocarpus, Clutia, Pogonophora and Trigonopleura) in this family may be justifiable, but is not yet accounted for here.

Illustrations. • Pera glabrata: Fl. Brasiliensis II (1895).

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.’.