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The families of flowering plants

L. Watson and M.J. Dallwitz

Didymelaceae Leandri

~ Buxaceae.

Habit and leaf form. Trees. Leaves persistent; 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 sclerenchymatous idioblasts.

Axial (stem, wood) anatomy. The vessel end-walls scalariform. The axial xylem with tracheids. The 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 III core angiosperms; peripheral eudicot, or core eudicot (?); Superorder Buxanae, or Superorder Rosanae (?). APG IV Order unassigned (as a synonym of Buxaceae).

Species 3. Genera 1; only genus, Didymeles.

General remarks. This description is inadequate for reliable classification; but it differs from that of Buxaceae (q.v.) in 12 characters representing leaf anatomy, androecium, gynoecium, and details of the ovule and seed.

Illustrations. • Didymeles madagascariensis: • Didymeles madagascariensis: Petit-Thuars, Hist. Veg. dans les iles aust. d'Afrique (1804). • Didymeles madagascariensis, as D. excelsa: Grandidier, Madagascar Botanique 3 (1890).

We advise against extracting comparative information from the descriptions. This is much more easily achieved using the DELTA data files or the interactive key, which allows access to the character list, illustrations, full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting or lacking specified attributes, distributions of character states within any set of taxa, geographical distribution, genera included in each family, and classifications (Dahlgren; Dahlgren, Clifford, and Yeo; Cronquist; APG). See also Guidelines for using data taken from Web publications.

Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 1992 onwards. The families of flowering plants: descriptions, illustrations, identification, and information retrieval. Version: 5th March 2018.’.