The families of flowering plants


L. Watson and M. J. Dallwitz

Medusagynaceae Engl. & Gilg

~ Ochnaceae.

Habit and leaf form. Small trees, or shrubs; not resinous. Leaves opposite; leathery; petiolate; simple. Lamina entire. Leaves exstipulate. Lamina margins shallowly crenate.

Leaf anatomy. The leaf lamina dorsiventral. Stomata present; mainly confined to one surface (abaxial); anomocytic. Adaxial hypodermis present (mucilaginous). Lamina without secretory cavities (but with mucilage cells). The mesophyll containing mucilage cells; without sclerenchymatous idioblasts; containing crystals (around the midrib and main vascular bundles). The crystals druses.

Axial (stem, wood) anatomy. The cortex without cristarque cells. Secretory cavities absent. Cork cambium present; initially superficial (subepidermally). Nodes multilacunar. Primary vascular tissues in a cylinder, without separate bundles to comprising a ring of bundles; collateral. Internal phloem absent. Cortical bundles present. Medullary bundles absent. Secondary thickening developing from a conventional cambial ring, or anomalous (?).

The wood diffuse porous. The vessels small; mostly solitary. The vessel end-walls simple. The vessels without vestured pits; without spiral thickening. The secondary phloem stratified into hard (fibrous) and soft (parenchymatous) zones. ‘Included’ phloem absent.

Reproductive type, pollination. Plants andromonoecious.

Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; in panicles. The ultimate inflorescence units cymose. Inflorescences terminal; small, lax, opposite-flowered, terminal mixed panicles. Flowers small; malodorous; regular. Free hypanthium absent.

Perianth with distinct calyx and corolla; 10; 2 whorled; isomerous. Calyx 5; 1 whorled; gamosepalous (connate basally). Calyx lobes markedly longer than the tube. Calyx regular; not persistent (deciduous, according to Hutchinson and Airy Shaw, though persistent according to Cronquist); imbricate. Corolla 5; 1 whorled; polypetalous; imbricate; regular; white, or red, or pink (white, becoming rose); deciduous.

Androecium 50–100 (‘many’). Androecial members free of the perianth; free of one another. Androecium exclusively of fertile stamens. Stamens 50–100 (‘many’); polystemonous; filantherous (the very slender filaments shorter than the petals, subpersistent). Anthers small, basifixed; dehiscing via longitudinal slits; bilocular (the pollen sacs often set at different heights). Pollen shed as single grains. Pollen grains aperturate; (2–)3(–4) aperturate; porate.

Gynoecium 17–25 carpelled. Carpels increased in number relative to the perianth. The pistil 17–25 celled. Gynoecium syncarpous; synovarious, or synstylovarious; superior. Ovary 17–25 locular (with as many external grooves). Gynoecium multi- stylate. Styles 17–25; free; apical to lateral (in a subapical ring, on the shoulders of the carpels — fancifully medusoid in appearance); shorter than the ovary (stout). Stigmas 17–25; capitate. Placentation axile. Ovules 2 per locule; funicled; pendulous (the lower), or horizontal (the upper); superposed; bitegmic; tenuinucellate.

Fruit non-fleshy; dehiscent and a schizocarp. Mericarps if viewed as such, 17–25; ultimately comprising follicles. Fruit if interpreted as a syncarp, a capsule. Capsules initially septicidal (from below, the carpels separating but remaining attached distally, the dehisced capsule becoming umbrella-shaped and the separated carpels ultimately dehiscing ventrally). Seeds winged.

Physiology, phytochemistry. Aluminium accumulation not found.

Geography, cytology. Paleotropical. Tropical. Seychelles.

Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Theiflorae; Theales. Cronquist’s Subclass Dilleniidae; Theales. APG 3 core angiosperms; core eudicot; Superorder Rosanae; fabid; Order Malpighiales (as a synonym of Ochnaceae?).

Species 1. Genera 1; only genus, Medusagyna.

General remarks. Fay et al. (1996) postulated relationship with Ochnaceae and Quiinaceae, on evidence of rbcL sequencing. The morphological description compiled here differs from that of Ochnaceae (q.v.) in the opposite, exstipulate leaves, andromonoecism, and gynoecium and fruit characters, as well as in leaf anatomical, stem anatomical and pollen morphological characters relying on limited sampling. However, contributions by Dickison (1990a and b) have yet to be accounted for.

Illustrations. • Technical details: Medusagyne (Hutchinson). • Medusagyne oppositifolia: Hook. Ic. Pl. 13 (1877).

