Family Didymelaceae

Didymelaceae Leandri

~ Buxaceae

Habit and leaf form. Trees. Leaves evergreen; alternate; leathery (or chartaceous, drying yellowish green); non-sheathing; simple. Lamina entire; pinnately veined; cross-venulate. Leaves exstipulate. Lamina margins entire.

Leaf anatomy. Stomata present; cyclocytic.

The mesophyll with sclerencymatous idioblasts.

Stem anatomy. Xylem with tracheids; with vessels. Vessel end-walls scalariform. Wood parenchyma replaced by lignified cells.

Reproductive type, pollination. Plants dioecious.

Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; in spikes (female), or in panicles (short, male). Inflorescences axillary (or supra-axillary); shortly panuculate (male), or simply spicate with thickened rachis (female). Free hypanthium absent. Hypogynous disk absent.

Perianth sepaline, or absent (the male flowers subtended by 0–2 scales, the female by 0–4, interpretable as bracts or sepals); if so interpreted, 1–4. Calyx if so interpreted, 1–2 (male), or 1–4 (female).

Androecium in male flowers, 2. Androecial members coherent (very shortly connate); 1 adelphous; 1 whorled. Androecium exclusively of fertile stamens. Stamens 2; very shortly filantherous (the short filaments connate, according to Cronquist), or with sessile anthers (according to Airy Shaw). Anthers cuneate, dehiscing via longitudinal slits; extrorse. Pollen shed as single grains. Pollen grains aperturate; 3 aperturate; colporate (but the colpi peculiarly 2-orate).

Gynoecium at least ostensibly 1 carpelled. The pistil 1 celled. Gynoecium seemingly monomerous (i.e. with no evidence of pseudomonomery); seemingly of one carpel; superior. Carpel non-stylate, or stylate; having a large, oblique, decurrent stigma with a median groove, sometimes recurved at the tip; 1 ovuled. Ovules pendulous; epitropous; hemianatropous; bitegmic (the integuments prolonged into an elongate collar).

Fruit fleshy (large). The fruiting carpel indehiscent; drupaceous (with a lateral groove). Fruit 1 seeded. Seeds non-endospermic. Embryo well differentiated. Cotyledons 2 (these thick).

Geography, cytology. Paleotropical. Tropical. Madagascar.

Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Malviflorae (or Rosiflorae?); Euphorbiales (or Buxales?). Cronquist’s Subclass Hamamelidae; Didymales. APG 3 core angiosperms; peripheral eudicot, or core eudicot (?); Superorder Buxanae, or Superorder Rosanae (?); Order unassigned to Order (as a synonym of what?).

Species 2. Genera 1; only genus, Didemeles.

Description inadequate for reliable classification.