This section is from the book "Wayside And Woodland Blossoms", by Edward Step. Also available from Amazon: Wayside And Woodland Blossoms: A Guide To British Wild-Flowers.
The Hazel is one of the most look-ahead kind of trees, for almost before this year's nuts have all dropped off, or been picked off, she puts out the tiny, cylindric grey bodies that continue to lengthen all the winter and by February have become loose and open. Then it can be seen that these catkins consist of male flowers, for the yellow stamens are evident, and soon every breeze shakes out a little cloud of yellow pollen. Looked at analytically, the catkin is seen to be made up of a large number of scaly bracts, of which one large and two small go to a flower, and these are so arranged as to form a pent-house roof over the eight stamens. The female flowers are altogether different. They each consist of a two-celled ovary, with two slender, crimson styles, and enclosed in a kind of calyx, three-parted. Two of these flowers are then associated in a bud-like involucre, situated at the end of a twig. In spring, before the leaves appear, these open and the crimson stigmas are put forth to catch a little of the flying pollen. By September one cell of the ovary has developed into a hard shell containing one large seed (kernel) and clasped by a large raggedly-cut hood - the developed involucre.
When the tips of the nutshells become brown-tinged, then appear boys, squirrels, dormice and nuthatches, and by their combined industry the tree or bush is soon despoiled of its load.
Corylus avellana. - Cupuliferae. All the many varieties of Filberts, Kentish-Cobs, Spanish-nuts, and Barcelona-nuts are but varieties of Coryhis avellana.
The name is from the Greek, Korus, a helmet, from the form of the involucre.