Family Curtisiaceae

Curtisiaceae (Harms) Takht.

~ Cornaceae

Habit and leaf form. Trees. Leaves opposite; leathery (shining above, rusty-tomentose below); simple. Lamina entire. Leaves exstipulate. Lamina margins coarsely dentate.

Leaf anatomy. Stomata present; anomocytic.

Lamina dorsiventral.

Stem anatomy. Internal phloem absent. Secondary thickening developing from a conventional cambial ring. ‘Included’ phloem absent. Vessel end-walls scalariform. Vessels without vestured pits. Wood parenchyma apotracheal.

Reproductive type, pollination. Fertile flowers hermaphrodite. Plants hermaphrodite.

Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; in panicles. The ultimate inflorescence unit cymose. Inflorescences terminal; many-flowered, dichotomous, tomentose thyrses. Flowers minute; regular.

Perianth with distinct calyx and corolla; 8; 2 whorled; isomerous. Calyx 4; 1 whorled; gamosepalous; funnel-shaped (turbinate); valvate. Corolla 4; 1 whorled; polypetalous; valvate.

Androecium 4. Androecial members free of the perianth; free of one another; 1 whorled. Androecium exclusively of fertile stamens. Stamens 4; isomerous with the perianth; oppositisepalous; alternating with the corolla members. Anthers introrse; tetrasporangiate. Pollen grains aperturate; 3 aperturate; colporate.

Gynoecium 4 carpelled. Carpels isomerous with the perianth. The pistil 4 celled. Gynoecium syncarpous; synstylovarious, or eu-syncarpous; inferior. Ovary 4 locular. Epigynous disk present (densely barbate). Gynoecium stylate. Styles 1; apical; short, subconical, glabrous. Stigmas 1, or 4; if regarded as single, 4 lobed. Placentation apical. Ovules 1 per locule; pendulous; epitropous (the micropyle turned outwards); with ventral raphe; anatropous; unitegmic; crassinucellate. Endosperm formation cellular.

Fruit fleshy; indehiscent; a drupe (small, subglobular). The drupes with one stone (4-locular). Fruit 4 seeded. Seeds copiously endospermic. Endosperm oily. Embryo well differentiated. Cotyledons 2. Embryo straight.

Physiology, biochemistry. Not cyanogenic. Iridoids detected; ‘Route I’ type (+seco).

Geography, cytology. Cape. Temperate, or sub-tropical. South Africa.

Taxonomy. Subclass Dicotyledonae; Tenuinucelli (?). Dahlgren’s Superorder Corniflorae; Cornales. Cronquist’s Subclass Rosidae; Cornales. APG 3 core angiosperms; core eudicot; Superorder Asteranae; Order Cornales.

Species 1. Genera 1; only genus, Curtisia.

This family exemplifies the well known difficulties in distributing certain Dicot families between Dahlgren’s Araliiflorae and Corniflorae. It is equally hard to assign them with confidence to the higher level groupings Crassinucelli and Tenuinucelli. This is interesting, given that the latter evidently represent a major divergence in the Dicot line of descent (cf.Young and Watson 1970, Chase et al. 1993).