Tetragonia L.

Scientific Description

Common name. Spinach. Family Aizoaceae.

Habit and leaf form. (Sub-) shrubs, herbs, and herbaceous climbers. Plants succulent. Annual, or perennial. Leaves cauline. Young stems cylindrical. Stem internodes solid. Self supporting, or climbing; some scrambling (or sprawling). Mesophytic, or xerophytic. Leaves alternate; spiral; leathery and fleshy; petiolate; non-sheathing; simple. Leaf blades entire; flat; pinnately veined; cross-venulate. Leaves without stipules. Leaf blade margins entire. Leaf anatomy. Extra-floral nectaries absent.

Reproductive type, pollination. Fertile flowers hermaphrodite, or hermaphrodite and functionally male, or hermaphrodite, functionally male, and functionally female. Unisexual flowers present, or absent. Plants hermaphrodite, or andromonoecious (terminal flowers sometimes male), or polygamomonoecious.

Inflorescence and flower features. Flowers solitary, or aggregated in ‘inflorescences’; in cymes, or in racemes, or in spikes, or in fascicles. The terminal inflorescence unit cymose. Inflorescences axillary; few-flowered or racemiform cymes. Flowers pedicellate, or sessile; ebracteate; ebracteolate; small; regular; 3–5 merous. Free hypanthium present; incorporating calyx and stamens; usually angled, winged or horned. Perianth sepaline (though somewhat petaloid, being coloured within); 4–5; 1 -whorled; joined; persistent; accrescent. Calyx present (the perianth being so interpreted); 4–5; 1 -whorled; gamosepalous (the calyx tube continuous with and textured like the hypanthium); blunt-lobed; induplicate valvate; regular; fleshy (at least when young, coloured within); persistent; accrescent. Corolla absent. Androecial members definite in number, or indefinite in number. Androecium 4–100 (to ‘many’). Androecial members branched (i.e. ‘fasciculate’), or unbranched. Androecial sequence determinable, or not determinable. Androecial members adnate (near the top of the tube); all equal; free of one another, or coherent (sometimes fasciculate); 1 - adelphous, or 2–5 - adelphous. The androecial groups when fasciculate, opposite the petals. Androecium exclusively of fertile stamens. Stamens 4–100 (4–many); all more or less similar in shape; reduced in number relative to the adjacent perianth to polystemonous; alternisepalous (or scattered or clustered). Anthers dehiscing via longitudinal slits. Gynoecium (1–)3–8 carpelled. The pistil 1 celled, or 2–10 celled. Carpels reduced in number relative to the perianth, or isomerous with the perianth, or increased in number relative to the perianth. Gynoecium syncarpous; synovarious; partly inferior, or inferior. Ovary unilocular, or plurilocular; 1 locular, or 2–10 locular. Gynoecium stylate. Styles 2–10; free. Stigmas 2–10. Placentation axile, or apical. Ovules in the single cavity 1; 1 per locule; shortly funicled; pendulous; with dorsal raphe; hemianatropous.

Fruit and seed features. Fruit fleshy to non-fleshy; indehiscent; a drupe (sometimes winged or spiny, crowned by the accrescent calyx); 1 seeded (or several). Seeds endospermic. Embryo curved.

Geography, cytology, number of species. World distribution: mostly southern hemisphere. 50–60 species.

Economic uses, etc. Tetragonia expansa furnishes table greens — ‘New Zealand spinach’.

Etymology. From the Greek for "four" and "corner, angle"; refers to the shape of the fruit of some species.