Habit and leaf form. Herbs. Annual. Leaves basal and cauline. Plants with a basal concentration of leaves, or with neither basal nor terminal concentrations of leaves. Stem internodes solid. To 0.02–0.3 m high. Mesophytic, or xerophytic. Leaves medium-sized; alternate; spiral; ‘herbaceous’; sessile; non-sheathing; foetid, or without marked odour; simple; epulvinate. Leaf blades dissected to entire; one-veined, 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; glandular hairs absent; complex hairs absent. Branched hairs present (these bifid). Extra-floral nectaries absent.
Reproductive type, pollination. Fertile flowers hermaphrodite. Unisexual flowers absent. Plants hermaphrodite.
Inflorescence and flower features. Flowers aggregated in ‘inflorescences’; in racemes (dense or elongating), or in corymbs (elongating). The terminal inflorescence unit racemose. Flowers pedicellate; ebracteate; ebracteolate; small; regular; 2 merous; cyclic. Floral receptacle with neither androphore nor gynophore. Free hypanthium absent. Hypogynous disk present; of separate members. Perianth with distinct calyx and corolla; 8; 3 -whorled (K 2+2, C 4). Calyx present; 4; 2 -whorled; polysepalous; spreading; decussate; regular. Corolla present; 4; 1 -whorled; alternating with the calyx; polypetalous; imbricate, or contorted; regular; white, or cream, or yellow. Petals clawed. Androecial members definite in number. Androecium 6. Androecial members branched (in that the inner whorl of 4 is derived from only 2 primordia); free of the perianth; markedly unequal; free of one another; 2 -whorled (2+4). Androecium exclusively of fertile stamens. Stamens 6; tetradynamous; all more or less similar in shape; hypogynous, on receptacle. Filaments not appendiculate. Anthers basifixed; non-versatile; dehiscing via longitudinal slits; introrse; unilocular to bilocular; tetrasporangiate; unappendaged. Pollen shed as single grains. Gynoecium 2 carpelled. The pistil 2 celled. Gynoecium syncarpous; eu-syncarpous; superior. Ovary plurilocular; 2 locular. Locules secondarily divided by ‘false septa’. Gynoecium transverse. Ovary sessile. Gynoecium stylate. Styles 1; apical. Stigmas 1, or 2; 1 - lobed (flat or capitate); capitate. Placentation parietal. Ovules 3–10 per locule; with ventral raphe; non-arillate; anatropous.
Fruit and seed features. Fruit 4–13 mm long; non-fleshy; dehiscent; a silicula. Capsules valvular. Fruit 2 celled; 6–20 seeded. Seeds 3–10 per locule. Seeds scantily endospermic, or non-endospermic; mucous; small to medium sized. Embryo well differentiated. Cotyledons 2; accumbent to incumbent. Embryo bent (folded, the cotyledons against the radicle).
Physiology, biochemistry. Mustard-oils present.
Special features. Fruit body with no clear differentiation into valve and beak regions. Replum present and complete; narrow. Fruit bilaterally compressed; compressed at right angles to the septum. The inner (lateral) pair of sepals not noticeably saccate. Petals not peculiarly elongated as in Stenopetalum. Valves of the fruit slightly winged, or keeled. Fruit apically notched to not apically notched.
Etymology. From the Greek for "phlegm" and "seed"; the seeds emit a mucus when soaked.