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The families of flowering plants

L. Watson and M.J. Dallwitz

Tetragoniaceae Link.

~ Aizoaceae.

Habit and leaf form. Sub- shrubs and herbs. Plants succulent; green and photosynthesizing. Self supporting, or climbing; some scrambling. Mesophytic, or xerophytic. Leaves alternate; spiral; leathery; petiolate; non-sheathing; simple. Lamina entire; pinnately veined; cross-venulate. Leaves exstipulate. Lamina margins entire.

Leaf anatomy. Stomata present; anomocytic. Minor leaf veins without phloem transfer cells (Tetragonia).

Reproductive type, pollination. Plants hermaphrodite, or monoecious, or polygamomonoecious (?).

Inflorescence, floral, fruit and seed morphology. Flowers solitary, or aggregated in ‘inflorescences’; when aggregated in cymes and in racemes. The ultimate inflorescence units cymose. Inflorescences not scapiflorous; few flowered, or racemiform cymes. Flowers small; regular; 3–5 merous. Free hypanthium present (continuous with and textured like the calyx).

Perianth sepaline (but coloured inside); 3–5(–7); joined; 1 whorled; persistent; accrescent. Calyx (the perianth being so interpreted) 3–5(–7); 1 whorled; gamosepalous; regular; fleshy (at least when young, coloured within); persistent; accrescent; induplicate valvate.

Androecium 1–100 (to ‘many’). Androecial members branched, or unbranched; adnate (to the perianth tube); free of one another, or coherent (sometimes fasciculate); 1 adelphous, or 2–5 adelphous (?). Androecium exclusively of fertile stamens. Stamens 1–35; reduced in number relative to the adjacent perianth to polystemonous; oppositisepalous (or at least, the staminal groups antesepalous). Anthers dehiscing via longitudinal slits; bilocular.

Gynoecium (1–)3–8(–10) carpelled. Carpels isomerous with the perianth, or reduced in number relative to the perianth, or increased in number relative to the perianth. The pistil 1–10 celled. Gynoecium syncarpous; synovarious; partly inferior, or inferior. Ovary (1–)3–8(–10) locular. Styles (1–)3–8(–10); free. Placentation axile, or apical. Ovules 1 per locule; shortly funicled; pendulous; with dorsal raphe; hemianatropous.

Fruit fleshy to non-fleshy; indehiscent; a drupe, or a drupe and a samara (sometimes winged, horned or spiny, crowned by the accrescent perianth). Seeds endospermic. Embryo achlorophyllous (1/1); curved.

Physiology, phytochemistry. C3 and CAM. C3 physiology recorded directly in Tetragonia reduplicata. CAM recorded directly in Tetragonia reduplicata. Plants accumulating free oxalates. Sieve-tube plastids P-type; type III (a).

Geography, cytology. Mostly Southern hemisphere.

Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Caryophylliflorae; Caryophyllales. Cronquist’s Subclass Caryophyllidae; Caryophyllales. APG III core angiosperms; core eudicot; Superorder Caryophyllanae. APG IV Order Caryophyllales (as a synonym of Aizoaceae).

Species 60. Genera 2; Tetragonia, Tribulocarpus.

General remarks. Evidently close to Aizoaceae (q.v.), with these compiled descriptions differing only in ovule, fruit and seed details (with betalains perhaps reflecting limited sampling).

Economic uses, etc. Tetragonia expansa is used as table greens (New Zealand spinach).

Illustrations. • Le Maout and Decaisne: Tetragonia. • Tetragonia tetragonoides: habit (photo). • Tetragonia tetragonoides: flowers (photo).

We advise against extracting comparative information from the descriptions. This is much more easily achieved using the DELTA data files or the interactive key, which allows access to the character list, illustrations, full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting or lacking specified attributes, distributions of character states within any set of taxa, geographical distribution, genera included in each family, and classifications (Dahlgren; Dahlgren, Clifford, and Yeo; Cronquist; APG). See also Guidelines for using data taken from Web publications.

Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 1992 onwards. The families of flowering plants: descriptions, illustrations, identification, and information retrieval. Version: 15th April 2018.’.