Trigonostemon

Family Euphorbiaceae. Order Euphorbiales.

Small trees to shrubs. Buttresses absent. Spines absent. Stilt roots absent. Bark gray; not peeling in strips. Exudate absent. Terminal buds not enclosed by leaves.

Complex hairs absent. Stinging hairs absent. Mature twig indumentum present, or absent; sparse.

Leaves opposite, or spiral; not scale-like; simple; of different sorts on a single twig, or all of the same type; not modified into spines; coriaceous; not gland-dotted; symmetric at the base; not dissected; smooth margined, or with small to large teeth on margin. Epidermis waxy, or not waxy. Venation pinnate. Secondary veins open; prominent to not prominent, but visible. Smallest veins prominent to not visible; net like to ladder like. Intramarginal vein absent. Stalk of blade less than a quarter the length of the blade to more than half the length of the blade; not winged; attached to base of leaf blade; swollen; swollen at both ends. Stipules present; free from one another; laterally placed; not encircling the twig; scale-like; not fringed; small; not persistent. Domatia absent. Basal glands absent. Hairs on mature leaf present, or absent; dense, or sparse.

Inflorescences present; terminal, or axillary, or on the trunk or branches; the flowers from a single point on the stem, or on an unbranched axis, or on a branched axis; specialized inflorescence units absent; numerous and persistent inflorescence bracts absent. Flowers at least some flowers unisexual; with male and female flowers on the same plant; stalked; about 0.5 cm long or across; round; with male or female parts not raised on a column. Hypanthium absent. Disk present. Perianth present; with distinct calyx and corolla whorls, or with all whorls looking like sepals. Sepals 5; free; persistent in fruit; not growing any further after flowering, or growing slightly after flowering. Epicalyx absent. Petals present, or absent (female flowers); 5; free; not fleshy; deciduous; not stalked; deeply cut in two, or entire. Stamens 3-5; filaments present; joined; free of the perianth; of different sizes; anisomerous, or isomerous. Anthers 2 loculed; attached by the base; not awned; dehiscing by long slits. Ovary superior. Carpels joined; 3. Locules 3. Styles free; 3. Stigmas 2 lobed; not distinctive. Fruit capsular; non-fleshy; not multiple; splitting; not enclosed in, or sitting on, fleshy perianth parts; wingless. Seeds 3 per fruit; less than 5 mm to about 1 cm long; wingless; uniform in cross-section; aril absent; endospermic.

Petioles long; leaves usually with often distantly placed teeth; variable genus. Taxon images: trigonos.gif


Cite this publication as: Jarvie, J.K. and Ermayanti (1996 onwards). `Tree Genera of Borneo - Descriptions and Illustrations' URL http://django.harvard.edu/users/jjarvie/Borneo.htm/.
Dallwitz (1980) and Dallwitz, Paine and Zurcher (1993) should also be cited.