Trigonobalanus

Family Fagaceae. Order Fagales.

Large trees to small trees. Buttresses present, or absent; tall, or short. Spines absent. Stilt roots present, or absent. Bark gray; not peeling in strips. Slash cream, gray. Vertical stripes in the inner bark or wood present. Odor absent. Exudate absent. Terminal buds not enclosed by leaves.

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

Leaves whorled; 3 per whorl; not scale-like; simple; all of the same type; not modified into spines; coriaceous to leathery; not gland-dotted; symmetric at the base; not dissected; smooth margined, or wavy margined, or with small to large teeth on margin (if wavy or toothed, in the upper part of the blade only). Epidermis waxy, or not waxy. Venation pinnate. Secondary veins open; prominent, or not prominent, but visible. Smallest veins not prominent, but visible, or not visible; net like to ladder like. Intramarginal vein present, or absent. Stalk of blade less than a quarter the length of the blade; not winged; attached to base of leaf blade; not swollen, or swollen; swollen at one end. Stipules present; joined; 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; sparse.

Inflorescences present; terminal, or axillary; on an unbranched axis; specialized inflorescence units absent; numerous and persistent inflorescence bracts present at the bottom of the inflorescence. Flowers at least some flowers unisexual; with male and female flowers on the same plant; not stalked; with the parts barely visible to the eye, or about 0.5 cm long or across; round; with male or female parts not raised on a column. Hypanthium absent. Disk absent. Perianth present; with distinct calyx and corolla whorls. Sepals 6; partially joined; not persistent in fruit; not growing any further after flowering. Epicalyx absent. Petals absent. Stamens 6; filaments present; free of each other; free of 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 joined; 3. Locules 3. Styles solitary, or free; 3. Stigmas 1-3 lobed (1 or 3); distinctive; head shaped. Fruit a nut; non-fleshy; not multiple; not splitting; not enclosed in, or sitting on, fleshy perianth parts; wingless. Seeds 1 per fruit; less than 5 mm to about 1 cm long; wingless; uniform in cross-section; aril absent; non-endospermic.

Usually with several coppice like stems; leaves in whorls of three; stipules joined; cupule opens with 3-7 3-sided nuts. Taxon images: trigonob.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.