Geococcus Harv.

Scientific Description

Family Brassicaceae.

Habit and leaf form. Herbs. Annual. Leaves basal and cauline. Plants with a basal concentration of leaves. Stem internodes solid. To 0.1 m high (prostrate). Mesophytic, or xerophytic. Leaves small to medium-sized; alternate; spiral; ‘herbaceous’; petiolate; sheathing to non-sheathing; foetid, or without marked odour; simple; epulvinate. Leaf blades dissected; pinnatifid; pinnately veined; cross-venulate. Leaves without stipules. Leaf blade margins entire, or dentate. 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. Inflorescences few-flowered, appearing basal due to the reduced main axis. Flowers pedicellate; ebracteate; ebracteolate; minute; 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. Petals sessile. 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 (the outer pair shorter); 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 non-stylate, or stylate. Styles 1; apical. Stigmas 1; 1 - lobed (depressed-capitate); capitate. Placentation parietal. Ovules (1–)3–50 per locule; with ventral raphe; non-arillate; anatropous.

Fruit and seed features. Fruit subterranean; 3–15 mm long; non-fleshy; dehiscent; a silicula, or a siliqua. Capsules valvular. Fruit 2 celled; few. Seed rows per locule 2. Seeds scantily endospermic, or non-endospermic; mucous; small to medium sized; wingless (oblong to obovate). 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 bilaterally compressed. 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 (medians ‘obsolete’), or lateral only. Valves of the fruit neither winged nor keeled; conspicuously longitudinally veined; longitudinally 1 veined.

Etymology. From the Greek for "earth" and "kernel, berry"; refers to the hard seed pods turned down so as to embed themselves in the earth.