The families of flowering plants

L. Watson and M.J. Dallwitz

Stylocerataceae Baill.

~ Buxaceae.

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

Leaf anatomy. The leaf lamina dorsiventral. Stomata present; cyclocytic.

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

The vessel end-walls scalariform (commonly with more than thirty bars). The axial xylem without tracheids; with fibre tracheids. The parenchyma apotracheal. ‘Included’ phloem absent.

Reproductive type, pollination. Plants monoecious, or dioecious. Female flowers without staminodes (at least, these not mentioned in descriptions seen). 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); with sessile anthers (more or less, or subsessile). 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 (i.e., 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.

General remarks. Cf. Buxaceae (q.v.), but differing in the naked male flowers with usually numerous, more or less sessile anthers borne on a solitary bract, female flowers in which the loculi of the ovary are completely divided by secondary longitudinal septa (Pachysandra being an exception in Buxaceae), and (in so far as limited sampling can be relied upon) wood lacking tracheids and fibre tracheids.

Illustrations. • Styloceras kunthianum: Bonpland & Humboldt, ‘Nova genera et species plantarum’ 7 (1825). • Styloceras laurifolium: Bonpland & Humboldt, ‘Nova genera et species plantarum’ 7 (1825).

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: 13th March 2017.’.