YASIN J. NASIR
Botany Department, Gordon College, Rawalpindi.
Monoecious trees or shrubs. Leaves alternate, pinnately nerved, deciduous. Flowers small, bracteate; the male in catkins; the female in erect spikes or strobili. Male flowers: Perianth of 2-4 tepals. Stamens 2-4. Female flowers: Perianth absent. Gynoecium bicarpellary, syncarpous; ovary bilocular, each locule with one pendulous ovule; styles 2, free. Fruit a small compressed nut, often surrounded by the fused bract and bracteoles.
A family of 2 genera and c. 95 species distributed in the temperate and arctic regions of N. and S. America, Europe and Asia. Represented here by both the genera.
Acknowledgements: We are grateful to the U.S. 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 going through the manuscript and giving valuable suggestions.