The Wych Elm is a native of our country, and is also very common, but it occurs principally in the woods of the North. It is very similar in general appearance to the last species, which it also resembles in having several barely distinguishable varieties; but it generally attains a much greater girth, and does not throw off such an abundance of suckers from its roots. Its twigs are downy; and the leaves, which are larger than those of _U. campestris_, are irregularly doubly serrate, with hairs on the prominent ribs of the under side, and are arranged in two straight rows, one on each side of the twig. The flowers are very similar to those of the Common Elm; and the fruit is a broad oblong or almost round samara, with the seed in the _centre_. Both species are pollinated by the wind; and, as is the case with wind-pollinated flowers generally, the stamens protrude well out of the flower, and produce abundance of pollen. [Illustration: THE OAK IN FLOWER.] Four of our forest trees belong to the order _Cupuliferæ_; these are the Oak, Beech, Hornbeam and Hazel. The first of them--the Oak (_Quercus Robur_)--is easily recognised in the winter by its deeply-furrowed, corky bark, its zigzag, spreading branches, and the clusters of oval buds at the tips of the twigs. In summer it may be known at once by the oval, sinuate leaves with blunt lobes. The flowers of the Oak appear with the leaves in April or May; they are imperfect, but both male and female blossoms appear on the same tree. The former are in slender, drooping, interrupted catkins; and each flower has ten stamens. The latter are in clusters of a few only, and each separate flower is enclosed in a cupule of overlapping scales. The ovary has three cells, and contains six ovules; but, as a rule, only one ovule of each flower is fertilised. Sometimes, however, two, three, or more of the ovules become fertilised, thus producing an acorn which will give rise to as many separate seedling trees. At times we meet with an Oak nearly every acorn of which contains two or more ovules. This tree is remarkable for the number of insects which feed on its leaves, and also for the number of different species of gall-flies which produce galls on its leaves and stems. Two well-marked varieties occur: one--_pedunculata_--with sessile leaves and long flower stalks; and the other--_sessiliflora_--with stalked leaves and short flower-stalks. [Illustration: THE BEECH IN FRUIT.]