Family Dipentodontaceae

Dipentodontaceae Merr.

Habit and leaf form. Small trees, or shrubs. Leaves deciduous; alternate; petiolate; non-sheathing; simple. Lamina entire; ovate; pinnately veined; cross-venulate. Leaves stipulate. Stipules intrapetiolar; caducous (lanceolate). Lamina margins dentate (denticulate).

Leaf anatomy. Stomata present; anomocytic.

Stem anatomy. Secondary thickening developing from a conventional cambial ring. Vessel end-walls oblique; scalariform (with many cross bars). Wood parenchyma absent.

Reproductive type, pollination. Plants hermaphrodite.

Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; in umbels. Inflorescences axillary; long pedunculate, globose, 25–30 flowered umbels, the pedicels jointed in the middle; initially with involucral bracts (the involucre of 4–5 small, deciduous members); more or less pseudanthial. Flowers small; regular; 5–7 merous; cyclic; tetracyclic. Free hypanthium absent. Hypogynous disk present; extrastaminal; of separate members (5–7 glands, opposite the corolla members — alternatively interpretable as staminodes).

Perianth with distinct calyx and corolla; 10–14; 2 whorled; isomerous. Calyx 5–7; 1 whorled; gamosepalous (the linear, pubescent sepals shortly united at the base). Calyx lobes markedly longer than the tube. Calyx persistent; valvate. Corolla 5–7; 1 whorled; polypetalous, or gamopetalous (? — the petals linear, indistinguishable from the sepals or slightly narrower); valvate; regular; persistent.

Androecium 5–7, or 10–14 (if the nectaries are interpreted as staminodes). Androecial members free of the perianth; free of one another; 1 whorled, or 2 whorled (if taken to include the nectary glands). Androecium exclusively of fertile stamens, or including staminodes (if the nectary glands are seen as staminodal). Staminodes 5–7; in the same series as the fertile stamens, or internal to the fertile stamens (antepetalous). Stamens 5–7 (persistent); isomerous with the perianth; oppositisepalous; erect in bud. Anthers dehiscing via longitudinal slits; tetrasporangiate. Pollen shed as single grains. Pollen grains aperturate; 3 aperturate; colporate (colporoidate).

Gynoecium 3 carpelled. Carpels reduced in number relative to the perianth. The pistil 1 celled, or 3 celled (at the base). Gynoecium syncarpous; eu-syncarpous; superior. Ovary 1 locular (though with partial partitions at the base). Gynoecium stylate. Styles 1; attenuate from the ovary; apical. Stigmas 1; small, capitate. Placentation free central. Ovules in the single cavity 6 (borne atop the columnar, free central placenta); ascending.

Fruit non-fleshy; tardily dehiscent; a capsule (tomentose); 1 seeded (small, oblong, with a persistent style, surrounded by the persistent calyx, corolla and androecium).

Geography, cytology. Paleotropical. Sub-tropical, or tropical. Northeast India, southern China and Burma.

Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Violiflorae; Violales. Cronquist’s Subclass Rosidae; Santalales. APG 3 core angiosperms; core eudicot; Superorder Rosanae; malvid; Order Huertiales.

Species 1. Genera 1; only genus, Dipentodon.