Eruca Mill.

Scientific Description

Family Brassicaceae.

Habit and leaf form. Herbs. Annual. Leaves cauline. Stem internodes solid. To 0.1–0.8 m high. Mesophytic. Leaves small to medium-sized; alternate; spiral; ‘herbaceous’; petiolate to sessile (upper leaves may be sessile); non-sheathing; foetid; simple, or compound; epulvinate; when compound, pinnate. Leaf blades when simple, dissected to entire; lyrate pinnatifid; pinnately veined; cross-venulate. Leaves without stipules. Leaf blade margins dentate. Leaves without a persistent basal meristem. Leaf anatomy. Hairs present (pilose or sparsely hispid), or absent; complex hairs absent. Branched hairs absent. 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. Inflorescences terminal. Flowers pedicellate; ebracteate; ebracteolate; small to medium-sized; regular; 2 merous; cyclic. Floral receptacle with neither androphore nor gynophore. Free hypanthium absent. Hypogynous disk present; of separate members. Nectariferous glands 4. Perianth with distinct calyx and corolla; 8; 3 -whorled (K 2+2, C 4). Calyx present; 4; 2 -whorled; polysepalous; more or less erect; decussate; regular. Sepals inner pair somewhat saccate. Corolla present; 4; 1 -whorled; alternating with the calyx; polypetalous; imbricate, or contorted; regular; with contrasting markings (with dark veins); white, or yellow (pale). Petals long; 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 (2 outer, 4 inner); tetradynamous; all more or less similar in shape; hypogynous, on receptacle, outer stamens lateral. Filaments not appendiculate. Anthers basifixed; non-versatile; dehiscing via longitudinal slits; introrse; unilocular to bilocular; tetrasporangiate; appendaged, or 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); commissural; 2 - lobed; capitate. Placentation parietal. Ovules (1–)3–50 per locule; with ventral raphe; non-arillate; anatropous.

Fruit and seed features. Fruit 10–40 mm long; non-fleshy; dehiscent; a siliqua. Capsules valvular. Fruit 2 celled; 20–100 seeded (‘many’). Seeds 10–50 per locule (‘many’). Seed rows per locule 2. Seeds scantily endospermic, or non-endospermic; not mucous; small to medium sized; wingless (spherical or ovoid). Embryo well differentiated. Cotyledons 2; folded; conduplicate. Embryo bent.

Physiology, biochemistry. Mustard-oils present.

Special features. Fruit body distinctly differentiated into valve and beak regions. Beak seedless. Replum present and complete. Fruit bilaterally compressed to terete; somewhat compressed parallel with the septum. The inner (lateral) pair of sepals somewhat saccate basally for nectar storage, or not noticeably saccate. Petals not peculiarly elongated as in Stenopetalum. Nectariferous glands lateral and median. Valves of the fruit neither winged nor keeled; conspicuously longitudinally veined; longitudinally 1 veined.

Etymology. Origin of name is uncertain; Eruca is a Latin name for E. sativa and some linguists believe that it derived from uro (I burn), from the hot taste of the seeds.