~ Oxalidaceae p.p.
Habit and leaf form. Small trees, or shrubs, or lianas; non-laticiferous and without coloured juice. Self supporting, or climbing. Leaves alternate; petiolate; non-sheathing; compound; pulvinate; (impari) pinnate, or unifoliolate, or ternate. Lamina pinnately veined. Leaves exstipulate. Lamina margins entire.
Leaf anatomy. Stomata present; paracytic.
Stem anatomy. Vessel end-walls simple. Sieve-tube plastids P-type.
Reproductive type, pollination. Plants hermaphrodite (mostly), or androdioecious (Dapania); when hermaphrodite, heterostylous (heterodistylous).
Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; in cymes, or in racemes, or in panicles. The ultimate inflorescence unit cymose, or racemose. Inflorescences axillary or ramiflorous racemes or panicled cymes, the pedicels articulated. Flowers small; regular; 5 merous; cyclic; pentacyclic. Free hypanthium absent. Hypogynous disk absent.
Perianth with distinct calyx and corolla; 10; 2 whorled; isomerous. Calyx 5; 1 whorled; gamosepalous (shortly connate basally), or polysepalous. Calyx lobes when gamosepalous, markedly shorter than the tube. Calyx regular; imbricate. Corolla 5; 1 whorled; polypetalous (but sometimes loosely connivent in the middle, above the claws); contorted, or with open aestivation; regular. Petals clawed.
Androecium 10. Androecial members free of the perianth; markedly unequal; coherent (shortly connate basally); 1 adelphous; 2 whorled (5+5). Androecium exclusively of fertile stamens, or including staminodes. Staminodes when present, 5; internal to the fertile stamens (the members of the inner whorl, lacking anthers). Stamens 5, or 10; isomerous with the perianth, or diplostemonous; alternisepalous; opposite the corolla members, or both alternating with and opposite the corolla members. Anthers dorsifixed; dehiscing via longitudinal slits; introrse. Endothecium developing fibrous thickenings. Microsporogenesis simultaneous. Anther wall initially with more than one middle layer. Tapetum glandular. Pollen grains aperturate; 3 aperturate; colporate (colporoidate).
Gynoecium 5 carpelled. Carpels isomerous with the perianth. The pistil 5 celled. Gynoecium syncarpous; synovarious; superior. Ovary 5 locular (somewhat 5-lobed). Gynoecium stylate. Styles 5; free; from a depression at the top of the ovary; apical. Stigmas 5; capitate (at least in Averrhoa). Placentation axile. Ovules 1–6 per locule; pendulous; superposed; non-arillate; anatropous, or hemianatropous and anatropous; bitegmic; crassinucellate. Outer integument contributing to the micropyle. Endothelium differentiated. Embryo-sac development Polygonum-type. Antipodal cells formed; 3; not proliferating; ephemeral. Synergids pear-shaped. Hypostase absent. Endosperm formation nuclear. Embryogeny asterad.
Fruit fleshy; dehiscent (Dapania), or indehiscent (mostly); in Dapania, a capsule, or a berry (usually). Capsules in Dapania, widely loculicidal. Fruit usually several seeded. Seeds endospermic. Endosperm more or less ruminate, or not ruminate (Dapania); oily (fleshy). Embryo well differentiated. Cotyledons 2. Embryo chlorophyllous (1/2); straight. Testa hard, smooth or transversly rugose.
Physiology, biochemistry. Not cyanogenic. Proanthocyanidins present; cyanidin. Flavonols absent. Ellagic acid absent (Averrhoa). Sugars transported as sucrose (in Averrhoa). Anatomy non-C4 type (Averrhoa).
Geography, cytology. Paleotropical, or Paleotropical and Neotropical (?). Tropical. Madagascar, Western Malaysia, tropical South America.
Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Rutiflorae; Geraniales. Cronquist’s Subclass Rosidae; Geraniales. APG (1998) Eudicot; core Eudicot; Rosid; Eurosid I. APG 3 (2009) Order: Oxalidales.
Species 16. Genera 3; Averrhoa, Dapania, Sarcotheca.
Economic uses, etc. Edible fruit from A. carambola (star-fruit, five-corner).