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The families of flowering plants

L. Watson and M.J. Dallwitz

Medusandraceae Brenan

~ Peridiscaceae.

Habit and leaf form. Trees; with coloured juice (yellow, throughout the plant including the xylem). Leaves deciduous; alternate; petiolate; non-sheathing; ostensibly simple, or compound (on the evidence of complex vascularization and a pulvinus at the distal end of the petiole); reasonably interpreted as unifoliolate. Leaflets pulvinate. Lamina entire; ovate, or obovate; pinnately veined; cross-venulate; attenuate to the base, or cuneate at the base. Leaves stipulate. Stipules small, very caducous. Lamina margins distantly, slightly crenate to serrate.

Leaf anatomy. Stomata present; anomocytic. Hairs present (of an unusual, thick-based type, abaxially). Lamina with secretory cavities (associated with the veins). Secretory cavities containing yellow juice.

Axial (stem, wood) anatomy. Secondary thickening developing from a conventional cambial ring, or anomalous.

The vessel end-walls oblique; scalariform. The parenchyma paratracheal (and diffuse).

Reproductive type, pollination. Plants hermaphrodite.

Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; in racemes. The ultimate inflorescence units racemose. Inflorescences axillary; paired or solitary, dense, pendent, catkinlike racemes. Flowers bracteate (the bracts tiny, caducous); small; regular; pentacyclic. Free hypanthium absent. Hypogynous disk absent.

Perianth with distinct calyx and corolla; 10; 2 whorled; isomerous. Calyx 5; 1 whorled; polysepalous, or gamosepalous (then basally connate); regular; persistent; more or less accrescent; open in bud. Corolla 5; 1 whorled; polypetalous (the petals small); imbricate; regular.

Androecium 10. Androecial members free of the perianth; markedly unequal; free of one another; 1 whorled, or 2 whorled (?). Androecium including staminodes. Staminodes 5; non-petaloid (oppositisepalous, elongate and much exceeding the petals, serpentine and very densely pubescent above the base, tipped by vestigial anthers). Stamens 5; isomerous with the perianth; alternisepalous; opposite the corolla members; erect in bud. Anthers dehiscing by longitudinal valves (the outer, abaxial loculi by an outwardly recurved valve, the inner adaxial locules by inwardly recurved valves); latrorse; four locular; tetrasporangiate. Pollen shed as single grains. Pollen grains aperturate; 3 aperturate; colporate.

Gynoecium 3(–4) carpelled. Carpels reduced in number relative to the perianth. The pistil 1 celled. Gynoecium syncarpous; synovarious; superior. Ovary 1 locular; sessile. Gynoecium stylate. Styles 3(–4); free (short); apical; shorter than the ovary (remote, conical divergent). Stigmas 3(–4); small. Placentation apical (but very peculiar, there being a slender placental column extending from the base of the ovary to its top, to which the ovules are attached). Ovules in the single cavity 6(–8); pendulous (from the top of the placental column); epitropous; anatropous.

Fruit leathery, non-fleshy; dehiscent; a capsule (subtended by the reflexed, accrescent calyx). Capsules three valvular. Fruit 1 seeded. Seeds copiously endospermic. Endosperm slightly ruminate. Seeds large. Embryo well differentiated (small, near the edge of the endosperm). Cotyledons 2. Embryo straight.

Seedling. Germination cryptocotylar.

Geography, cytology. Paleotropical. Tropical. West tropical Africa.

Taxonomy. Subclass Dicotyledonae; Tenuinucelli (?). Dahlgren’s Superorder Corniflorae (?); Cornales (?). Cronquist’s Subclass Rosidae; Santalales. APG III core angiosperms; core eudicot; unplaced at Superordinal level. APG IV Order Saxifragales (as a synonym of Peridiscaceae).

Species 1. Genera 1; only genus, Medusandra (M. richardsiana).

General remarks. These compiled descriptions show Medusandra (tropical Africa) differing from Peridiscaceae (q.v., tropical South America) in about twenty conspicuous floral, fruit and seed characters, as well as in the coloured juice and published observations on leaf and wood anatomy.

Illustrations. • Medusandra richardsiana (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: 15th April 2018.’.