The families of flowering plants.
IncludingColumellaceae Dulac (p.p.), Pachysandraceae J.G. AgardhExcluding 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. Leaves without a persistent basal meristem.
Leaf anatomy. Lamina dorsiventral. Minor leaf veins without phloem transfer cells (Buxus).
Stem anatomy. Cork cambium present; initially superficial (Buxus). Nodes unilacunar. Cortical bundles present (commonly), or absent. Medullary bundles absent. Internal phloem absent. Secondary thickening developing from a conventional cambial ring. ‘Included’ phloem absent. Xylem with tracheids; without fibre tracheids; with vessels. Vessel end-walls scalariform. Vessels without vestured pits. Wood parenchyma apotracheal.
Reproductive type, pollination. Fertile flowersfunctionally male, or functionally female. Unisexual flowers present. 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.
Perianthwith 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. Stamens4, 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. Ovary3 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).
Physiology, biochemistry. Not cyanogenic. Alkaloids present (usually), or absent. Iridoids not detected. Proanthocyanidins present, or absent. Flavonols present; kaempferol and quercetin. Ellagic acid absent (3 genera). Arbutin absent. Saponins/sapogenins absent. Sugars transported as oligosaccharides + sucrose, or as sugar alcohols + oligosaccharides + sucrose (in Buxus sempervirens).
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 4; Buxus, 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.