~ Chenopodiaceae, Amaranthaceae
Habit and leaf form. Herbs. Plants succulent. Annual. Leaves alternate; fleshy; simple; exstipulate.
Stem anatomy. Internal phloem absent. Secondary thickening developing from a conventional cambial ring (with ‘normal stem anatomy’). ‘Included’ phloem absent. Xylem with libriform fibres. Sieve-tube plastids P-type; type III (a).
Reproductive type, pollination. Plants monoecious.
Inflorescence, floral, fruit and seed morphology. Flowers solitary (female flowers), or aggregated in ‘inflorescences’ (male flowers). Inflorescences of male flowers in strobilate, terminal spikes, the female flowers solitary in the 4–5 uppermost leaf axils.
Perianth sepaline (male flowers), or absent (female flowers); of male flowers, 4; 1 whorled. Calyx (in the male flowers only) 4; 1 whorled; polysepalous (membranous).
Androecium 4. Androecial members free of the perianth; free of one another; 1 whorled. Androecium exclusively of fertile stamens. Stamens 4; isomerous with the perianth; alternisepalous; filantherous (the filaments long, filiform). Anthers versatile. Pollen shed as single grains. Pollen grains aperturate; 6 aperturate; foraminate (the apertures operculate).
Gynoecium 3 carpelled. Carpels reduced in number relative to the perianth. The pistil 1 celled. Gynoecium syncarpous; synstylovarious; superior. Ovary 1 locular. Styles 1; apical. Stigmas 3 (finally exserted). Placentation basal. Ovules in the single cavity 1; campylotropous (?).
Fruit fleshy. Gynoecia of adjoining flowers combining to form a multiple fruit (the aggregate enclosed in the swollen stem apex, forming a berrylike structure).
Geography, cytology. Antarctic. Temperate. Patagonia.
Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Caryophylliflorae; Caryophyllales. Cronquist’s Subclass Caryophyllidae; Caryophyllales. APG 3 core angiosperms; core eudicot; Superorder Caryophyllanae; Order Caryophyllales (as a synonym of Amaranthaceae).
Species 1. Genera 1; only genus, Halophytum.