I know of no other tree that produces its fruit in this way, nor do I know what special benefit to the plant arises from this arrangement. Towards the solution of this problem it may be suggested that as it produces no petals the shrub has energy to form abundant pollen, some of which will certainly be wind-wafted on to the spreading stigmas if there are no leaves in the way. Hence the advantage to wind-fertilized flowers of blossoming before the leaves appear. As the two kinds of flowers in the Hazel often do not come to maturity simultaneously, the advantages of cross-fertilization are thus secured. Moreover, the tufted stigmas secure the fertilization of some of their number.
Fertilization acts as a stimulus.
The male catkins have performed their function and have dropped off, so nourishment flows towards the female one. In order, however, that the fruit may not ripen too soon and so fall to the ground and rot before the winter's frosts, it must not develop thus early in spring. The food is, therefore, thus employed in producing a branch below the nascent bunch of nuts. The Hazel is found in Northern Africa, in Central and Northern Asia, and throughout Europe south of 63 degree N. latitude, having very much the same range as the Beech. It reaches an altitude of about 3,800 feet in the Alps, and 1,600 feet in the north of Britain.