This section is from the book "Handbook Of Hardy Trees, Shrubs, And Herbaceous Plants", by W. Botting Hemsley. Also available from Amazon: Handbook of hardy trees, shrubs, and herbaceous plants.
This differs from the last genus in having the male catkins usually in threes, each flower with 8 or fewer stamens, and the epicarp or husk splits into 4 regular valves, with a smooth en-docarp or shell. The species are all North American. Kapva is an ancient name of the Walnut. These handsome trees are almost unknown in England, and rarely quoted in our nursery catalogues, probably on account of their not being very hardy.
G. olivaeformis, Pecan-nut, is an elegant slender tree, and the only species bearing really palatable nuts, which are imported in small quantities. They are smooth, 4-ribbed and olive-shaped. G. alba is the Shell-bark Hickory, valuable for its timber and Hickory nuts. G. glabra, syn. porcina, is the Pig-nut or Broom Hickory. G. amara is called Bitter Nut or Swamp Hickory, and C. tomentosa is the Mocker Nut or White-heart Hickory. The tough young wood and the highly coloured older timber of some of the species is in great request.
Pterocarya Caucasica and Japonica are rare trees in cultivation. They are distinguished by their female flowers being in catkins, and the fruits furnished with two lateral wings. Ph. fraxinifolia is another name of the Caucasian species. Fortuncea Chinensis is a shrub or tree from Northern China with smooth sharply serrated leaflets, and the female flowers in dense bracteolate cones or spikes. The fruit is small, 2-winged and concealed beneath the rigid scales or bracteoles.