The families of flowering plants

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L. Watson and M. J. Dallwitz

Averrhoaceae Hutch.

~ 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.

Axial (stem, wood) anatomy. Primary vascular tissues in a cylinder, without separate bundles to comprising a ring of bundles (the pericycle bounded by a ring of sclerenchyma); collateral. Secondary thickening developing from a conventional cambial ring.

The wood diffuse porous. The vessel end-walls simple. The vessels with spiral thickening, or without spiral thickening. The axial xylem with libriform fibres; including septate fibres. The fibres without spiral thickening.

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 units 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 (being 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, phytochemistry. Anatomy non-C4 type (Averrhoa). Sugars transported as sucrose (in Averrhoa). Not cyanogenic. Proanthocyanidins present; cyanidin. Flavonols absent. Ellagic acid absent (Averrhoa). Sieve-tube plastids P-type.

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 3 core angiosperms; core eudicot; Superorder Rosanae; fabid; Order Oxalidales (as a synonym of Oxalidaceae).

Species 16. Genera 3; Averrhoa, Dapania, Sarcotheca.

General remarks. Descriptions compiled for this package have Averrhoaceae differing from the closely related Oxalidaceae sensu stricto (q.v.) in habit, staminodes when present internal to the fertile stamens, colporate pollen, non-arillate and crassinucellate ovules, and the often fleshy fruits.

Economic uses, etc. Edible fruit from A. carambola (star-fruit, five-corner).

Illustrations. • Technical details: Averrhoa (Hutchinson). • Averrhoa bilimbi, A. carambola and Connaropsis monophylla: Nat. planzenfam. 3 (1896).

This description is offered for casual browsing only. We strongly advise against extracting comparative information from it. This is much more easily achieved using 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).

Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 1992 onwards. The families of flowering plants: descriptions, illustrations, identification, and information retrieval. Version: 9th March 2015.’.