Alstonia

Family Apocynaceae. Order Gentianales.

Emergent trees to small trees. Buttresses present, or absent; tall. Spines absent. Stilt roots present, or absent. Bark white, cream, brown, black; not peeling in strips. Slash cream, yellow. Vertical stripes in the inner bark or wood absent. Odor absent. Exudate present; white; flowing; not blackening on exposure to air. Terminal buds enclosed by leaves, or not enclosed by leaves.

Complex hairs absent. Stinging hairs absent. Mature twig indumentum absent.

Leaves whorled; 3-10 per whorl; not scale-like; simple; all of the same type; not modified into spines; coriaceous; not gland-dotted; symmetric at the base; not dissected; smooth margined. Epidermis not waxy. Venation pinnate. Secondary veins open, or closed; prominent, or not prominent, but visible. Smallest veins not prominent, but visible, or not visible; net like. Intramarginal vein present. Stalk of blade less than a quarter the length of the blade; not winged; attached to base of leaf blade; not swollen. Stipules absent. Domatia absent. Basal glands absent. Hairs on mature leaf present, or absent; dense.

Inflorescences present; terminal; on an unbranched axis, or on a branched axis; specialized inflorescence units absent; numerous and persistent inflorescence bracts absent. Flowers bisexual; stalked; about 0.5 cm long or across, or to about 3 cm long or across; round; with male or female parts not raised on a column. Hypanthium absent. Disk present, or absent; the stamens outside the disk. Perianth present; with distinct calyx and corolla whorls. Sepals 5; partially joined; not persistent in fruit; not growing any further after flowering. Epicalyx absent. Petals present; 5; all joined; not fleshy; deciduous; not stalked; entire. Stamens 5; filaments present; free of each other; joined to the perianth; all equal in size; isomerous; opposite the sepals (when isomerous). Anthers 2 loculed; attached by the base; not awned; dehiscing by long slits. Ovary superior. Carpels partially joined, by base, or partially joined, by styles; 2. Locules 1. Styles solitary. Stigmas 1 lobed; distinctive; head shaped. Fruit follicular; non-fleshy; not multiple; splitting; not enclosed in, or sitting on, fleshy perianth parts; wingless. Seeds 100 per fruit (many); barely visible; wingless; uniform in cross-section; aril absent; endospermic.

Copius white latex from slash; large trees with pale bark and large buttresses; leaves in whorls of 3-8; fruit long slender follicles. Taxon images: genalsto.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.