Stewart Herbarium, Gordon College, Rawalpindi.
Monoecious trees or shrubs. Leaves alternate, simple, doubly serrate, prominently nerved, stipulate. Flowers precocious. Male flowers in catkins, solitary in the axil of bract; bracteoles 2, adnate to the bract; stamens 4-8. Female flowers 2-4, in short bud-like spikes, bracteolate; perianth small with irregular lobes, adnate to the ovary; carpels 2. united; ovary inferior with 1 pendulous ovule in each locule; styles 2, red. Fruit a nut, ovoid or sub-globose, surrounded by an involucre. Seed non-endospermic.
A genus with 15 species; temperate N. America, C. & SE. Europe to E. Asia. The family is sometimes included in the Cupuliferae along with the Carpinaceae, from which it differs in the ovoid buds which are obtuse, leaves with fewer veins, male flowers bracteolate and fewer female flowers.
Acknowledgements: We are grateful to the United States Department of Agriculture for financing this research under P. L. 480. Thanks are also due to Mr. B. L. Burtt of the Royal Botanic Garden, Edinburgh, for his helpful suggestions.