Habit and leaf form. Weak, straggling coastal shrubs (to 150 cm high). Plants succulent. Young stems tetragonal. Stem internodes solid. Xerophytic. Leaves small; opposite; fleshy; subsessile to sessile; strong-scented; simple. Leaf blades entire; flat, or solid (flat above, convex below); semi-terete, or solid/angular; linear, or oblong, or obovate; obovate (obovoid). Leaves with stipules (AKC), or without stipules (L). Stipules if present, caducous (minute). Leaf blade margins entire. Vegetative buds not scaly. Leaf anatomy. Hairs absent. Extra-floral nectaries absent. Stem anatomy. Secondary thickening absent, or developing from a conventional cambial ring.
Reproductive type, pollination. Fertile flowers functionally male, or functionally female, or functionally male and functionally female. Unisexual flowers present. Plants monoecious, or dioecious. The unisexual flowers when monoecious, not conspicuously in separate aggregates. Male flowers with pistillodes, or without pistillodes.
Inflorescence and flower features. Flowers aggregated in ‘inflorescences’. The terminal inflorescence unit racemose. Inflorescences terminal (male flowers), or axillary (male and female flowers); conical, strobiloid spikes with flowers in four ranks. Sometimes with one fertile male flower between two female flowers at the apex of branchlet, or with only one axillary female flower and an apical fertile male flower or single male and female flowers on the same short leafy shoot. Flowers sessile; bracteate (young male flowers subtended by 2 concave bracts with membranous margins. The bracts cochleariform and imbricate in male inflorescences, smaller and partially incorporated in the fleshy female spikes); bracteolate (male flowers with 2 united bracteoles forming a campanulate structure); small; somewhat irregular to very irregular (i.e, in male flowers, where ‘symmetry’ is applicable); male flowers zygomorphic. The floral asymmetry of male flowers involving the perianth. Flowers when male, 4 merous; when male, cyclic. Free hypanthium absent. Hypogynous disk absent. Perianth with distinct calyx and corolla (in male flowers), or absent (in female flowers, where the lower bracts are united); when present, i.e in male flowers, 2 -whorled. Calyx present (male flowers), or absent (female flowers); 1 -whorled; gamosepalous; blunt-lobed; cupuliform, or campanulate; bilabiate. Corolla present (male flowers), or absent (female flowers); when present, 4; when present, 1 -whorled; polypetalous, or gamopetalous (the claws more or less united); regular. Petals clawed. Fertile stamens present, or absent (from female flowers). Androecial members definite in number. Androecium of male flowers 4. Androecial sequence not determinable. Androecial members free of the perianth; all equal; free of one another; 1 -whorled. Androecium exclusively of fertile stamens. Stamens 4; all more or less similar in shape; isomerous with the perianth; oppositisepalous (at least, alternating with the corolla). Anthers dorsifixed; versatile; dehiscing via longitudinal slits; introrse; tetrasporangiate; appendaged. The anther appendages apical (via extension of the connective by ca. 2 mm). Fertile gynoecium present, or absent (from male flowers). Gynoecium 2 carpelled (but secondarily partitioned from each carpel midrib). The pistil 4 celled. Gynoecium syncarpous; synstylovarious to eu-syncarpous; superior (but the 8–10 gynoecia of adjoining flowers coherent, and adherent to the bract bases). Ovary plurilocular; 2 locular (but secondarily partitioned). Locules secondarily divided by ‘false septa’. Ovary sessile. Gynoecium non-stylate. Stigmas 1, or 2. Placentation basal. Ovules 1 per locule; funicled; ascending; anatropous.
Fruit and seed features. Fruit fleshy; indehiscent; a drupe. The drupes with separable pyrenes (four). Fruit 4 celled. Gynoecia of adjoining flowers combining to form a multiple fruit. The multiple fruits coalescing. Fruit 4 seeded. Seeds non-endospermic. Embryo well differentiated. Cotyledons 2. Embryo straight.
Physiology, biochemistry. Mustard-oils present.
Geography, cytology, number of species. Paleotropical, Neotropical, and Australian. World distribution: Pacific, West Indies, north coastal South America, central America to Florida, New Guinea, Queensland. 2 species.
Etymology. Batis is the Greek word for samphire, which is a name used for plants growing on saline flats.