Two species of Elm are common in our woods and hedgerows. The small-leaved or Common Elm (Ulmus campestris), and the Wych Elm (U. montana). Both are distinguished by their thick, furrowed, corky bark; and their rough oval-cordate leaves with unequal sides. They are often placed in the same order (Urticaceæ) as the well-known Stinging Nettles, but some authorities form a distinct order for these two species alone, under the name of Ulmaceæ.
The Common Elm is not indigenous, but was introduced into our country by the Romans. It is, however, one of our commonest trees, and is especially abundant in the South. The midrib of the leaf is covered below with irritating, glandular hairs, somewhat resembling those of nettles in structure and function; and the stipules are deciduous, falling early in the season. The flowers are perfect, appearing before the leaves in March and April, and are in small, dense clusters, principally on the topmost branches. Each flower has a little, bell-shaped, persistent perianth; a superior ovary with two styles; and four or five stamens with black anthers. The fruits are very thin oval samaras with the seeds above the centre, but they seldom ripen in our country. They are produced in such abundance that the ground is often almost completely covered with them when they fall. Botanists recognise several varieties of this species, but these differ so slightly from one another that they are barely distinguishable. The Common Elm throws off a large number of suckers from its roots, often producing a dense undergrowth round its bole.
The Elm in Flower.
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.
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.
The Beech in Fruit.