Stewart Herbarium, Gordon College, Rawalpindi.
Monoecious trees. Leaves alternate, rarely opposite, imparipinnate, exstipu¬late, deciduous; bract solitary; bracteoles usually 2. Perianth of 3-5 tepals. Male catkins lateral, many flowered; stamens 3-40. Female flowers few to many, in terminal racemes or spikes; perianth inferior, enclosed in a cupule; carpels 2, syncarpous; ovary inferior, unilocular with 1 erect ovule; style short, with 2 stigmas. Fruit a drupe or a nut. Seed solitary, non-endospermic.
A family of 7 genera and 50 species; N. temperate to subtropical; S. America and eastward to India, W. Pakistan and Indo-China; widely cultivated. Represented in W. Pakistan by 2 genera and 2 species.
Acknowledgements: We are grateful to the United States Department of Agriculure for financing this research under P.L. 480. Thanks are also due to Mr. B.L. Butt of the Royal Botanic Garden, Edinburgh, for his valuable suggestions.