Oxalidaceae R.Br.

Perennial, rarely annual, herbs, sometimes succulent (not in Australia), often with fleshy rhizomes, bulbs, corms or tubers, rarely bulbils present, or shrubs, small trees, or sometimes vines (not in Australia); juice acrid because of soluble calcium oxalate accumulation. Leaves alternate and spiral, herbaceous species often forming a basal rosette, digitate or pinnate (paripinnate in Biophytum, the terminal leaflet is reduced to a bristle or mucro), trifoliolate or rarely unifoliolate, often with prominent pulvini; petiole usually well-developed, sometimes expanded into a blade-like phyllodium, or woody and persistent; stipules present or absent; leaflets entire; leaflets often exhibiting sleep movements, with the leaflets folded at night, sometimes sensitive to touch. Inflorescence often cymose (sometimes umbel-like), or sometimes reduced to a single flower, axillary; bracts and bracteoles usually present. Flowers actinomorphic, hypogynous, bisexual, usually heterostylous (distylous or tristylous), or rarely plants androdioecious (not in Australia), rarely some cleistogamous and apetalous (not in Australia). Sepals 5, free, quincuncially overlapping, persistent in fruit. Petals 5, free or slightly connate, usually convolute or seldom imbricate, contorted, base clawed, sometimes with multicellular glandular hairs. Stamens usually 10 in two whorls, filaments connate basally, outer filaments shorter than inner, or sometimes 5 without anthers (not in Australia); anthers extrorse; dithecal, tetrasporangiate, dehiscing by longitudinal slits. Nectary disc absent, but often the outer filaments thickened and producing nectar at base, or nectary-gland borne at base of outer petals. Gynoecium of 5 connate carpels. Ovary superior, 5-locular; styles usually 5, free; stigmas usually capitate or punctate. Ovules (1–) 2–8 (–10) per locule; placentation axile or rarely parietal. Fruit a loculicidal capsule (Biophytum- sometimes splitting to base into 5 spreading valves, not in Australia; Dapania-not in Australia; Oxalis), or a 5-ribbed berry (Averrhoa; Sarcotheca-not in Australia). Seeds 1–10 per locule, with fleshy endosperm; arils usually present (absent in Averrhoa bilimbi and Sarcotheca, not in Australia); in those species with capsules, the elastic, translucent arilliform epidermis turns inside out, explosively ejecting the seeds from the capsule.

The fruit of Averrhoa carambola (Star Fruit) is edible, and is sometimes used as a bleaching agent (Cocucci 2008). Many species of Oxalis are cultivated as ornamentals for their showy flowers and foliage (e.g., see Spencer 2002). The tubers of Oxalis tuberosa (Oca), a crop from Andean civilisations, are locally important as an alternative to potatoes.