Habit and leaf form. Herbs. Annual. Leaves basal and cauline. Stem internodes solid. To 0.2–0.4 m high. Mesophytic and xerophytic. Leaves small to medium-sized; alternate; spiral; ‘herbaceous’; petiolate to sessile; sheathing to non-sheathing; foetid, or without marked odour; simple; epulvinate. Leaf blades dissected; coarsely pinnatifid (to remotely dentate); one-veined, or pinnately veined; cross-venulate. Leaves without stipules. Leaf blade margins remotely dentate (to coarsely pinnatisect). Leaves without a persistent basal meristem. Leaf anatomy. Hairs present; glandular hairs absent; complex hairs absent. Branched hairs present. 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, or in corymbs. The terminal inflorescence unit racemose. Flowers pedicellate (erect to spreading); ebracteate; ebracteolate; minute to 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; decussate; regular. Corolla present; 4; 1 -whorled; alternating with the calyx; polypetalous; imbricate, or contorted; regular; white, or pink, or blue (or lavender). 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; attenuate from the ovary; apical. Stigmas 1 (or 2); 1 - lobed (depressed-capitate); more or less capitate. Placentation parietal. Ovules (1–)3–50 per locule; with ventral raphe; non-arillate; anatropous.
Fruit and seed features. Fruit 4–26 mm long; non-fleshy; dehiscent; a siliqua (fusiform). Capsules valvular. Fruit 2 celled; 6–18(–24) seeded. Seeds 3–9 per locule (rarely 12). Seed rows per locule 2. Seeds scantily endospermic, or non-endospermic; mucous; oblong to obovate; small to medium sized; wingless. Embryo well differentiated. Cotyledons 2; incumbent. Embryo bent.
Physiology, biochemistry. Mustard-oils present.
Special features. Fruit body with no clear differentiation into valve and beak regions. Replum present and complete; broad. Fruit terete. The inner (lateral) pair of sepals saccate basally for nectar storage. Petals not peculiarly elongated as in Stenopetalum. Siliquae fusiform (and hairy, by contrast with Pachymitus). Valves of the fruit neither winged nor keeled; conspicuously longitudinally veined; longitudinally 1 veined.
Additional comments. The differences between Harmsiodoxa and Pachymitus seem dubious. Hewson's (1982) key depends on supposed differences in petal colour and siliqua form, of which the former represents a discrepancy with the descriptions.
Etymology. Hermann August Theodor Harms (1870–1942), professor of botany at the Prussian Academy of Science and the Greek for "credit, honour, glory".