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.
Deciduous trees, very near the Hornbeams in foliage, but having the female flowers in terminal drooping catkins, each enclosed in an inflated membranous involucre, which enlarges and closes over the fruit. The mature female catkins strongly resemble those of the Hop, giving the tree a very singular and pretty appearance. There are three or four species, natives of Europe, Asia, and North America. Ostrya is the ancient Latin name of O. vulgaris.
O. Virginica, a similar tree, bears the names Iron-wood and Lever-wood in North America.