Family Stylocerataceae

Stylocerataceae Baill.

~ Buxaceae

Habit and leaf form. Glabrous trees. Leaves evergreen; alternate; leathery; non-sheathing; simple. Lamina entire; pinnately veined to palmately veined (subtriplinerved basally, the nerves incised above and prominent below). Leaves exstipulate. Lamina margins entire.

Leaf anatomy. Stomata present; cyclocytic.

Lamina dorsiventral.

Stem anatomy. Cortical bundles absent. Medullary bundles absent. Internal phloem absent. Secondary thickening developing from a conventional cambial ring. ‘Included’ phloem absent. Xylem without tracheids; with fibre tracheids. Vessel end-walls scalariform (commonly with more than thirty bars). Wood parenchyma apotracheal.

Reproductive type, pollination. Fertile flowers functionally male, or functionally female, or functionally male and functionally female. Plants monoecious, or dioecious. Female flowers without staminodes (at least, not mentioned). Gynoecium of male flowers absent.

Inflorescence, floral, fruit and seed morphology. Flowers solitary (female flowers, sometimes), or aggregated in ‘inflorescences’. Inflorescences axillary; short, spicate, unisexual or when monoecious sometimes bisexual. Flowers bracteate (each male flower subtended by a small triangular bract, the female flowers several-bracteate).

Perianth sepaline (in female flowers), or absent (in male flowers, with are reduced to stamens). Calyx of female flowers 3–5 (scarcely distinguishable from the bracts); polysepalous; much imbricate.

Androecium of male flowers 6–30. Androecial members borne on the lower part of the bract; free of one another. Androecium exclusively of fertile stamens. Stamens 6–30 (crowded); very shortly filantherous, or with sessile anthers. Anthers introrse (thick); bilocular. Pollen grains aperturate; 3 aperturate, or 12–20 aperturate (polyforate); colporate, or foraminate.

Gynoecium 2–3 carpelled. Carpels reduced in number relative to the perianth to isomerous with the perianth. The pistil 4 celled, or 6 celled (the 2–3 primary locules each being bilocellate, via complete secondary longitudinal septa). Gynoecium syncarpous; synovarious (usually), or synstylovarious; superior. Ovary morphologically 2–3 locular. Locules secondarily divided by ‘false septa’. Gynoecium stylate. Styles 2–3 (persistent); free (usually), or partially joined (below, rarely). Stigmas 2–3 (these long, decurrent, ventrally grooved, apically recurved). Placentation apical, or axile to apical (?). Ovules 1 per locule (per locellus), or 2 per locule (per primary locule); pendulous; anatropous.

Fruit more or less fleshy; indehiscent; a drupe (crowned by the persistent, often widely separated styles). Seeds copiously endospermic (the endosperm fleshy).

Geography, cytology. Neotropical. Tropical. West tropical South America.

Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Rosiflorae; Buxales. Cronquist’s Subclass Rosidae; Euphorbiales. APG 3 core angiosperms; peripheral eudicot; Superorder Buxanae; Order Buxales (as a synonym of Buxaceae).

Species 3. Genera 1; only genus, Styloceras.