Tall, glabrous, dioecious, perenuial herbs. Leaves alternate, exstipulate, imparipinnate. Flowers in axillary or terminal racemes bearing clusters intermixed with simple leaves. Male flowers: calyx divided into 3-4(-5) unequal lobes; petals absent; stamens 8-12(-25), filaments short, anthers two-celled, membranous, dehiscing longitudinally. Female flowers: calyx 3-8-Iobed; petals absent; gynoecium inferior, 3-4(-5)-carpellary, syncarpous, with 3-4(-5) parietal placentae, ovules many; styles 3-4(-5), free, deeply bifid; stigmas equal to the number of the placentae and opposite the lobes of calyx. Fruit a pedicelled, narrowly oblong, pendulous, 3-4(-5)-ribbed, coriaceous capsule, opening at the top between the styles. Seeds numerous, minute, exalbuminous.
A family of a single genus with only 2 species, distributed over S.E. Europe, W. Asia and N. America. Represented by only 1 species in W. Pakistan. Previously 3 genera were included in this family, namely Datisca, Tetrameles and Octomeles, but in most recent treatments the last 2 genera are separated from Datiscaceae and included in Tetramelaceae. The plants now included in Datiscaceae are exclusively perennial tall herbs with imparipin¬nate glabrous leaves, whereas those included in Tetramelaceae are always large trees, often buttressed, with simple leaves which are lepidote-mealy, hairy or tomentose below. The Datiscaceae is placed near Begoniaceae, Cactaceae and Haloragidaceae by some authors.
Acknowledgements: We are grateful to the United States Department of Agriculture for financing this research under P.L. 480. Thanks are also due to Messrs B.L. Burtt, I.C. Hedge and Miss J. Lamond of the Royal Botanic Garden, Edinburgh for critically going through this manuscript and making useful suggestions.
