Family Gonystylaceae

Gonystylaceae Van Tiegh

~ Thymelaeaceae

Habit and leaf form. Trees. Leaves alternate; leathery; petiolate; non-sheathing; gland-dotted (commonly pellucid-punctate), or not gland-dotted; simple. Lamina entire; pinnately veined (with numerous nerves). Leaves exstipulate. Lamina margins entire.

Leaf anatomy. Mucilaginous epidermis present. Stomata present; mainly confined to one surface (abaxial); cyclocytic. Hairs present; eglandular; unicellular.

Lamina dorsiventral; with secretory cavities. The mesophyll containing calcium oxalate crystals. The mesophyll crystals druses.

Stem anatomy. Cork cambium present; initially superficial. Primary vascular tissue centrifugal. Internal phloem absent. Secondary thickening developing from a conventional cambial ring (with no intraxylary phloem, by contrast with Thymelaeaceae sensu stricto). ‘Included’ phloem absent. Xylem with tracheids. Vessel end-walls simple. Vessels with vestured pits. Primary medullary rays narrow (mostly uniseriate). Wood parenchyma apotracheal to paratracheal (intermediate).

Reproductive type, pollination. Plants hermaphrodite.

Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; in panicles. The ultimate inflorescence unit cymose. Inflorescences terminal. Flowers regular. Free hypanthium present. Hypogynous disk absent.

Perianth with distinct calyx and corolla (unless the ‘corolla’ of Hutchinson, Cronquist et al. is interpreted as an extrastaminal disk, as by Airy Shaw 1973); 12–45; anisomerous. Calyx 5; 1 whorled; polysepalous, or gamosepalous (?); five blunt-lobed; regular; imbricate. Corolla 7–40; polypetalous (the petals 7–40, linear or deltoid, sometimes divided almost to the base, inserted on the hypanthium). Petals deeply bifid, or entire.

Androecium (8–)30–100 (usually ‘many’). Androecial members free of the perianth; free of one another. Androecium exclusively of fertile stamens. Stamens (8–)30–100 (usually ‘many’); polystemonous; filantherous. Anthers basifixed; non-versatile; dehiscing via longitudinal slits. Pollen grains aperturate; 4–11 aperturate (?); (oligo-) foraminate.

Gynoecium 3–5 carpelled. Carpels reduced in number relative to the perianth to isomerous with the perianth. The pistil 3–5 celled. Gynoecium syncarpous; eu-syncarpous; superior. Ovary 3–5 locular. Gynoecium stylate. Styles 1; apical; much longer than the ovary (threadlike, bent). Stigmas 1; small. Placentation apical. Ovules 1 per locule; pendulous; arillate.

Fruit non-fleshy (thick walled, becoming woody); tardily dehiscent; a capsule. Capsules loculicidal. Fruit 1–3 seeded. Seeds non-endospermic; large. Embryo straight.

Geography, cytology. Paleotropical. Tropical. Malaysia.

Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Malviflorae; Thymelaeales. Cronquist’s Subclass Rosidae; Myrtales. APG 3 core angiosperms; core eudicot; Superorder Rosanae; malvid; Order Malvales (as a synonym of Thymelaeaceae).

Species 30. Genera 1; (?)only genus, Gonystylus.

Economic uses, etc. Timber tree — ramin.