This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol1", by Nathaniel Lord Britton, Addison Brown. Also available from Amazon: An Illustrated Flora of the Northern United States, Canada and the British Possessions. 3 Volume Set..
Shrubs or small trees, with broad thin serrulate or incised leaves. Staminate aments sessile at the ends of twigs of the previous season, expanding much before the leaves, the flowers solitary in the axil of each bract, of about 4 stamens and 2 bractlets; filaments 2-cleft or 2-divided, each fork bearing an anther-sac, which is villous at the summit. Calyx none. Pistillate flowers from scaly buds, clustered at the ends of short branches of the season, each in the axil of a bract, consisting of an incompletely 2-celled ovary adnate to a calyx, a short style and 2 slender stigmas; bractlets 2, enlarged in fruit, forming a leaf-like involucre to the nut, remaining nearly distinct or united into a tubular beak. Nut ovoid or oblong, sometimes compressed, large, bony. [Name Greek, from the helmet-like involucre.]
Species 7, in the northern hemisphere. Besides the following, another occurs in California. Type species: Coryhts Avellana L.
Involucre of 2 broad laciniate bractlets; leaves serrulate.
Involucral bractlets united, prolonged into a tubular bristly beak.
Corylus awericana Walt. Fl. Car. 236. 1788.
A shrub, 3°-8° tall, the young shoots russet-brown, densely hispid-pubescent with pinkish hairs, the twigs becoming glabrous. Leaves ovate or broadly oval, acute or acuminate at the apex, serrulate all around, cordate or obtuse at the base, glabrous or nearly so above, finely tomentose beneath, 3'-6' long, 2'-4 1/2' wide; petioles 2"-4" long; staminate aments mostly solitary, 3-4' long; involucre of the nut compressed, composed of the 2 nearly distinct finely pubescent leaf-like bractlets, which are lacinate on their margins, commonly broader than high and exceeding the nut; nut compressed, light brown, striate, 1/2' high.
In thickets, Maine and Ontario to Saskatchewan, Florida and Kansas. March-April. Nuts ripe July-Aug.
Corylus rostrata Ait. Hort. Kew. 3: 364. 1789.
A shrub, similar to the preceding species, but the foliage usually less pubescent. Leaves ovate or narrowly oval, acuminate at the apex, cordate or obtuse at the base, incised-serrate and serrulate, glabrous, or with some scattered appressed hairs above, sparingly pubescent at least on the veins beneath, 2 1/2-4' long, 1'-2 1/2' wide; petioles 2"-4" long; involucral bractlets bristly hairy, united to the summit and prolonged into a tubular beak about twice the length of the nut, laciniate at the summit; nut ovoid, scarcely compressed, striate, 5"-7" high.