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The families of flowering plants.                                                                                                                                                                

Peridiscaceae Kuhlm.

                        

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ExcludingMedusandraceae

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. Leavesstipulate. Stipules intrapetiolar; free of one another; caducous. Lamina margins entire.

Leaf anatomy. Stomata present; anomocytic.

Stem anatomy. Cortical bundles absent. Medullary bundles absent. Internal phloem absent. Secondary thickening developing from a conventional cambial ring. ‘Included’ phloem absent. Xylem with fibre tracheids (sometimes septate); without libriform fibres. Vessel end-walls oblique; scalariform. Primary medullary rays mixed wide and narrow. Wood parenchyma apotracheal (diffuse).

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).

Perianthsepaline (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 well differentiated (small). 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 3 core angiosperms; core eudicot; unplaced at Superordinal level; Order Saxifragales.

Species 2. Genera 2; Peridiscus, Whittonia.

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

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