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The families of flowering plants

L. Watson and M.J. Dallwitz

Peridiscaceae Kuhlm.

Excluding Medusandraceae.

Habit and leaf form. Trees. Leaves large; alternate; leathery; petiolate; non-sheathing; simple. Lamina entire; pinnately veined (above, though trinerved at the base, with a large pit in the axil of each of the basal laterals beneath); cross-venulate. Leaves stipulate. Stipules intrapetiolar; free of one another; caducous. Lamina margins entire.

Leaf anatomy. Stomata present; anomocytic.

Axial (stem, wood) anatomy. Internal phloem absent. Cortical bundles absent. Medullary bundles absent. Secondary thickening developing from a conventional cambial ring. Primary medullary rays mixed wide and narrow.

The vessel end-walls oblique; scalariform. The axial xylem with fibre tracheids; without libriform fibres; including septate fibres, or without septate fibres. The parenchyma apotracheal (diffuse). ‘Included’ phloem absent.

Reproductive type, pollination. Plants hermaphrodite.

Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; in racemes, or in fascicles. Inflorescences axillary; axillary fascicles or clusters of small racemes. Flowers bracteolate (the bracteoles large, persistent); small; regular. Free hypanthium absent. Hypogynous disk present; intrastaminal (the stamens seated on or around it); cupulate or annular (multilobate).

Perianth sepaline (apetalous); 4–7; 1 whorled. Calyx 4–7 (hairy); 1 whorled; polysepalous; regular; imbricate (Cronquist), or valvate (Hutchinson).

Androecium 30–100 (‘many’). Androecial members branched, or unbranched (?); maturing centrifugally (?); free of the perianth; free of one another, or coherent; when cohering, rather irregularly connate towards the base. Androecium exclusively of fertile stamens. Stamens 30–100 (‘many’); polystemonous. Anthers dehiscing via longitudinal slits; introrse; unilocular (and small). Pollen shed as single grains. Pollen grains aperturate; 3 aperturate; colporate.

Gynoecium 3 carpelled, or 4 carpelled. Carpels reduced in number relative to the perianth to isomerous with the perianth. The pistil 1 celled. Gynoecium syncarpous; synovarious; superior, or partly inferior (half sunken into the disk in Peridiscus). Ovary 1 locular. Gynoecium stylate. Styles 3, or 4; free; short. Stigmas 3, or 4. Placentation apical. Ovules in the single cavity 6–8; pendulous.

Fruit fleshy; indehiscent; a drupe. The drupes with one stone. Fruit 1 seeded. Seeds abundantly endospermic (the endosperm horny, according to Cronquist), or non-endospermic (according to Hutchinson and Airy Shaw). Embryo small well differentiated. Cotyledons 2. Embryo curved.

Geography, cytology. Neotropical. Tropical. Tropical South America.

Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Violiflorae (or Malviflorae?); Violales (or Urticales?). Cronquist’s Subclass Dilleniidae; Violales. APG III core angiosperms; core eudicot; unplaced at Superordinal level. APG IV Order Saxifragales.

Species 2, or 7. Genera 2, or 3; Peridiscus, Whittonia (and cf. Soyauxia).

General remarks. Not reliably classifiable, given the shortage of data and conflicting statements in the descriptions seen. See comments under Flacourtiaceae.

Illustrations. • Peridiscus lucidus: Hook. Ic. Pl. 25 (1896). • Peridiscus lucidus: Hutchinson.

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: 5th March 2018.’.