Brassicaceae Burnett

Scientific Description

Common name. Mustard Family.

Habit and leaf form. Herbs (mostly), or shrubs (rarely), or lianas (rarely). ‘Normal’ plants (mostly), or switch-plants (e.g. Caulanthus, and sometimes spiny, e.g Vella). Leaves well developed, or much reduced (occasionally). Plants non-succulent (mainly), or succulent (a few, e.g. Cakile). Annual, biennial, and perennial; plants with a basal concentration of leaves, or with neither basal nor terminal concentrations of leaves. Self supporting (usually), or climbing (rarely). When shrubby, often pachycaul. Hydrophytic, helophytic, mesophytic, and xerophytic; when hydrophytic, rooted. Leaves of hydrophytes submerged and emergent. Heterophyllous, or not heterophyllous. Leaves minute to very large; alternate; spiral (usually), or distichous (rarely); fleshy (occasionally), or ‘herbaceous’ (mostly); petiolate, or subsessile, or sessile; sheathing to non-sheathing; foetid (sometimes), or without marked odour; simple (usually), or compound (rarely); epulvinate; when compound, pinnate (with articulated leaflets). Leaf blades when simple, dissected to entire; when simple-dissected, pinnatifid, or runcinate; one-veined (rarely), or pinnately veined; cross-venulate. Leaves without stipules. Leaf blade margins entire, or serrate, or dentate. Leaves without a persistent basal meristem. Leaf anatomy. Hairs present, or absent. Branched hairs present, or absent. Stem anatomy. Nodes unilacunar, or tri-lacunar, or multilacunar. Secondary thickening absent, or developing from a conventional cambial ring, or anomalous (?— given the occasional presence of cortical and/or medullary bundles); usually from a single cambial ring.

Reproductive type, pollination. Fertile flowers hermaphrodite. Unisexual flowers absent. Plants hermaphrodite. Floral nectaries present (nearly always), or absent. Nectar secretion from the perianth (from the sepals), or from the disk, or from the androecium. Anemophilous (rarely, e.g. Pringlea), or entomophilous (nearly always).

Inflorescence and flower features. Flowers aggregated in ‘inflorescences’ (usually), or solitary (rarely); in corymbs (usually), or in racemes. The terminal inflorescence unit racemose. Inflorescences terminal, or axillary, or leaf-opposed (e.g. Coronopus); not pseudanthial (usually), or pseudanthial (occasionally, more or less). Flowers ebracteate (usually), or bracteate; ebracteolate; minute to medium-sized; fragrant, or odourless; more or less regular (usually), or somewhat irregular. The floral asymmetry (when noticeable) involving the perianth (the outer petals of pseudanthia sometimes radiate and larger). Flowers 2 merous; cyclic; tetracyclic to pentacyclic, or polycyclic (normally six, fewer when C and A cycles lacking). Floral receptacle nearly always with neither androphore nor gynophore (by contrast with Capparaceae — the long, slender gynophore of Stanleyeae being exceptional). Free hypanthium absent. Hypogynous disk present (often), or absent; of separate members, or annular (the glands sometimes confluent). Perianth with distinct calyx and corolla, or sepaline (the corolla occasionally lacking); 8 (usually), or 4; characteristically 3 -whorled (K 2+2, C4, calyx decussate with the outer pair median, the petals diagonal), or 2 -whorled (occasionally, when C lacking); anisomerous (i.e. K in two whorls of 2, C in one whorl of 4). Calyx 4; always theoretically 2 -whorled (and usually more or less obviously so in bud); polysepalous; decussate; regular; sometimes dimorphic, with the lateral (inner) members often basally saccate for nectar storage; persistent, or not persistent. Corolla 4 (diagonal); 1 -whorled; polypetalous; imbricate, or contorted; regular (usually); white, or yellow, or orange, or purple, or blue. Petals clawed (nearly always), or sessile (e.g. Cuphonotus, Geococcus). Androecium 6 (usually), or 2, or 4, or 8–16 (rarely). Androecial members branched (commonly, in that the inner whorl of 4 is derived from only 2 primordia), or unbranched; free of the perianth; markedly unequal (commonly, the outer pair shorter), or all equal; free of one another, or coherent (the inner four sometimes basally connate in pairs); 2 -whorled (mostly 2+4), or 1 -whorled. Androecium exclusively of fertile stamens. Stamens 6 (usually), or 2, or 4, or 8–16 (rarely); tetradynamous (nearly always), or not didynamous, not tetradynamous (when the outer pair lacking); oppositisepalous. Filaments appendiculate, or not appendiculate. Anthers basifixed; non-versatile; dehiscing via longitudinal slits; introrse; unilocular to bilocular; tetrasporangiate; variously appendaged, or unappendaged. Pollen shed as single grains. Gynoecium 2 carpelled. The pistil 1 celled, or 2 celled. Gynoecium syncarpous; eu-syncarpous; superior. Ovary unilocular, or plurilocular; ‘falsely’ 2 locular (usually), or 1 locular. Locules secondarily divided by ‘false septa’ (nearly always, interpreting the replum as a ‘false septum’, as evidenced by the longitudinally split parietal placentation), or without ‘false septa’. Gynoecium transverse. Ovary sessile (usually), or stipitate (rarely, then cf. Capparaceae). Gynoecium non-stylate, or non-stylate to stylate. Styles 1 (more or less reduced); attenuate from the ovary, or from a depression at the top of the ovary; apical. Stigmas 1–2; when two or bilobed, commissural (nearly always), or dorsal to the carpels (Moricandia, Matthiola); 1 - lobed, or 2 - lobed; more or less capitate; dry type; papillate; Group II type. Placentation parietal (but peculiarly so, the two placentas each usually longitudinally divided by the frame of a thin septum, the ‘replum’, separating the locules). Ovules (1–)3–50 per locule (i.e. usually several to ‘many’ per placenta, each of the two placentas usually having two uniseriate rows separated by the replum); commonly pendulous, or horizontal; with ventral raphe; non-arillate; anatropous.

Fruit and seed features. Fruit subterranean (Geococcus), or aerial; non-fleshy; dehiscent (usually), or indehiscent (Cakile, Raphanus, Coronopus, etc.), or a schizocarp (rarely, e.g. sometimes in Coronopus), or lomentaceous (or partially so). Mericarps when schizocarpic, 2. Fruit a silicula to a siliqua (with variations on this theme, sometimes partly or entirely lomentaceous), or capsular-indehiscent (when neither dehiscent nor lomentaceous). Capsules usually valvular (the valves falling or spreading upwards to reveal the replum). Seeds scantily endospermic, or non-endospermic; mucous, or not mucous; small to medium sized; winged, or wingless. Embryo well differentiated. Cotyledons 2; flat, or folded; when flat, accumbent, or incumbent; when folded, conduplicate, or spirolobous, or diplecolobous. Embryo chlorophyllous (32/52); bent (folded, the cotyledons against the radicle). Seedling. Germination phanerocotylar, or cryptocotylar.

Physiology, biochemistry. Mustard-oils present. Aluminium accumulation not found. Photosynthetic pathway: C₃ (almost exclusively), or C₃-C₄ intermediate.

Special features. Replum present and complete (usually), or incomplete or absent.

Geography, cytology, number of species. World distribution: cosmopolitan, concentrated in the North temperate and Mediterranean. X = 5–12(+). 3200 species.

Economic uses, etc. Important food crops from Brassica (cabbage, cauliflower, broccoli, kohlrabi, turnips, Brussels sprouts); Raphanus (radish); Rorippa (watercress); condiments from Brassica (mustard), Armoracia (horse-radish); ornamentals from about 50 genera, e.g. Matthiola, Hesperis, Cheiranthus, Lunaria, Iberis, Alyssum, Arabis.