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The families of flowering plants

L. Watson and M. J. Dallwitz

Buxaceae Dum.

Including Columellaceae Dulac (p.p.), Haptanthaceae, Pachysandraceae J.G. Agardh; excluding Didymelaceae, Stylocerataceae.

Habit and leaf form. Shrubs (mostly), or trees, or herbs. Leaves evergreen; alternate, or opposite; leathery; petiolate; non-sheathing; simple; epulvinate. Lamina entire; pinnately veined; cross-venulate. Leaves exstipulate. Lamina margins entire, or dentate; flat, or revolute. Leaf development not ‘graminaceous’.

Leaf anatomy. The leaf lamina dorsiventral. Stomata mainly confined to one surface (abaxial); cyclocytic. Hairs present (thick walled); eglandular; unicellular, or multicellular. Unicellular hairs simple. Multicellular hairs uniseriate; simple. Complex hairs absent. The mesophyll containing crystals. The crystals druses and solitary-prismatic (and sand). Minor leaf veins without phloem transfer cells (Buxus).

Axial (stem, wood) anatomy. Cork cambium present; initially superficial (Buxus). Nodes unilacunar. Primary vascular tissues in a cylinder, without separate bundles; collateral. Internal phloem absent. Cortical bundles present (commonly), or absent. Medullary bundles absent. Secondary thickening developing from a conventional cambial ring. Primary medullary rays narrow. The axial xylem with vessels, or without vessels (the bordered pits sometimes small and rather indistinct).

The wood ring porous, or semi-ring porous, or diffuse porous (?). The vessels small (or very small); exclusively solitary. The vessel end-walls more or less exclusively scalariform (often with numerous bars). The vessels without vestured pits; with spiral thickening, or without spiral thickening. The axial xylem with tracheids; without septate fibres. The fibres with spiral thickening, or without spiral thickening. The parenchyma apotracheal (typically as isolated cells). ‘Included’ phloem absent. The wood not storied.

Reproductive type, pollination. Fertile flowers functionally male, or functionally female. Plants monoecious (nearly always), or dioecious, or polygamodioecious (rarely with some perfect flowers).

Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’ (mostly), or solitary (female flowers, sometimes); in racemes, or in spikes, or in heads; bracteate; small; regular; cyclic. Free hypanthium absent. Hypogynous disk absent.

Perianth with distinct calyx and corolla (but the inner members not petaloid), or sepaline (usually described as consisting of sepals or of tepals, but reasons for the preference are not obvious); 4, or 6 (the tepals small, decussate or imbricate); free; usually 2 whorled (usually 2+2 in male flowers, 3+3 in female flowers); isomerous; sepaloid; similar in the two whorls; green.

Androecium 4, or 6. Androecial members free of the perianth; free of one another; 1 whorled, or 2 whorled (?). Androecium exclusively of fertile stamens. Stamens 4, or 6; opposite the tepals, or (Notobuxus) with two opposite the outer tepals and four in two pairs opposite the inner tepals; filantherous (the filaments often broad or thick). Anthers slightly dorsifixed, or basifixed; non-versatile; dehiscing via longitudinal slits; conspicuously introrse; tetrasporangiate. Endothecium developing fibrous thickenings. Anther epidermis persistent. Microsporogenesis simultaneous. The initial microspore tetrads tetrahedral, or isobilateral. Anther wall initially with one middle layer, or initially with more than one middle layer. Tapetum glandular. Pollen grains aperturate; 3–20 aperturate (to ‘many’); colpate, or colporate, or foraminate (tricol(por)oidate or polyforaminate); 2-celled.

Gynoecium 3 carpelled. Carpels isomerous with the perianth, or increased in number relative to the perianth. The pistil 3 celled, or 6 celled (Pachysandra). Gynoecium syncarpous; synovarious; superior. Ovary 3 locular. Locules secondarily divided by ‘false septa’ (Pachysandra), or without ‘false septa’. Gynoecium stylate. Styles 3; free; apical. Stigmas dry type; papillate; Group II type. Placentation axile to apical. Ovules 2 per locule (but the primary locules divided into uniovulate locelli in Pachysandra); pendulous; apotropous; with dorsal raphe; arillate (the fruit usually carunculate), or non-arillate; anatropous; bitegmic; crassinucellate. Outer integument contributing to the micropyle. Embryo-sac development Polygonum-type. Polar nuclei fusing prior to fertilization. Antipodal cells formed; initially 3; proliferating (sometimes, a little), or not proliferating. Synergids pear-shaped (with filiform apparatus). Endosperm formation cellular, or nuclear. Embryogeny onagrad.

Fruit fleshy, or non-fleshy; dehiscent, or indehiscent; a capsule, or a drupe. Capsules when fruit capsular, loculicidal. Fruit elastically dehiscent (often), or passively dehiscent (?). Seeds copiously endospermic. Endosperm oily. Embryo well differentiated. Cotyledons 2. Embryo achlorophyllous (1/2); straight. Testa smooth; black (shiny).

Seedling. Germination phanerocotylar.

Physiology, phytochemistry. Sugars transported as oligosaccharides + sucrose, or as sugar alcohols + oligosaccharides + sucrose (in Buxus sempervirens). Not cyanogenic. Alkaloids present (usually), or absent. Arbutin absent. Iridoids not detected. Saponins/sapogenins absent. Proanthocyanidins present, or absent. Flavonols present; kaempferol and quercetin. Ellagic acid absent (3 genera).

Geography, cytology. Holarctic, Paleotropical, and Neotropical. Temperate to tropical. Scattered, tropical and temperate. X = 10, 14.

Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Rosiflorae; Buxales. Cronquist’s Subclass Rosidae; Euphorbiales. APG 3 core angiosperms; peripheral eudicot; Superorder Buxanae; Order Buxales.

Species 100. Genera 5; Buxus, Haptanthus, Notobuxus, Pachysandra, Sarcococca.

Economic uses, etc. Supplies ornamentals, and hard, finegrained wood from Buxus (boxwood). Formerly used by wood-engravers for preparing ‘woodcuts’ for printing.

Quotations

Get thee all into the box-tree
(‘Twelfth Night’, ii., 5)

He was like to behold
The box-tree, or the aspis dead and cold
(Chaucer, ‘The Knight’s Tale’. Aspis = aspic(?) = savoury jelly based on meat or fish stock, re. its colour and coldness compared with that of a snake (asp))

Illustrations. • Technical details: Buxus. • Technical details: Pachysandra. • Buxus sempervirens (B. Ent., 1831).


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: 19th October 2016. delta-intkey.com’.

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