Pterospermum

Family Sterculiaceae. Order Malvales.

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

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

Leaves spiral; not scale-like; simple; all of the same type; not modified into spines; coriaceous; not gland-dotted; very asymmetric at the base (base); not dissected; smooth margined. Epidermis not waxy. Venation pinnate, or trinerved, or palmate. Secondary veins open; prominent, or not prominent, but visible. Smallest veins prominent, or not prominent, but visible; ladder like (spaced). Intramarginal vein absent. Stalk of blade a quarter to one half the length of the blade to more than half the length of the blade; not winged; attached to surface of leaf blade, attached to base of leaf blade; not swollen. Stipules present; free from one another; laterally placed; not encircling the twig; scale-like; not fringed; large, or small; not persistent. Domatia absent. Basal glands absent. Hairs on mature leaf present; dense, or sparse.

Inflorescences present; axillary; the flowers from a single point on the stem; specialized inflorescence units absent; numerous and persistent inflorescence bracts absent. Flowers bisexual; stalked; to about 3 cm long or across, or to about 10 cm long or across; round; with male or female parts raised on a column; with male and female parts raised on a stalk. Hypanthium absent. Disk absent. Perianth present; with distinct calyx and corolla whorls. Sepals 5; free, or partially joined; not persistent in fruit; not growing any further after flowering. Epicalyx absent. Petals present; 5; free; not fleshy; deciduous; not stalked; entire. Stamens 15; filaments present; joined; free of the perianth; all equal in size; triplostemonous. Anthers 2 loculed; attached along the side; not awned; dehiscing by long slits. Ovary superior. Carpels joined; 5. Locules 5. Styles solitary. Stigmas 1 lobed; not distinctive. Fruit capsular; non-fleshy; not multiple; splitting; not enclosed in, or sitting on, fleshy perianth parts; wingless. Seeds 100 per fruit (many); less than 5 mm, or about 1 cm long; winged; uniform in cross-section; aril absent; endospermic.

Leaf undersurface hairy; flowers generally showy. Taxon images: genptero.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.