Читать книгу Studies of Trees - Jacob Joshua Levison - Страница 31

Distinguishing characters: The tree can be told at a glance by its general branching habit. The limbs arch out into a wide-spreading fan or vase-like crown which loses itself in numerous fine drooping branchlets. See Fig. 37.

Fig. 37.—American Elm.

Leaf: The leaves are simple, alternate, and from 2 to 5 inches long.

Fig. 38.—English Elm in Winter.

Form and size: It is a tall tree with a trunk that divides a short distance above ground. Its general contour, together with the numerous branches that interlace its massive crown, give the elm an interesting and stately appearance which is unequaled by any other tree.

Fig. 39.—Lombardy Poplar.

Range: Eastern North America.

Soil and location: The elm prefers a deep, rich and moist soil, but will adapt itself even to the poor soil of the city street.

Enemies: The leopard moth, a wood-boring insect, and the elm leaf beetle, a leaf-eating insect, are the two most important enemies of the tree. Their ravages are very extensive.

Value for planting: The tree has a character of its own which cannot be duplicated for avenue or lawn planting.

Commercial value: The wood is strong and tough and therefore has a special value for cooperage, agricultural implements, carriages, and shipbuilding.

Other characters: The buds are small, brown, and smooth, while those of the European elms are covered with down. The small side twigs come out at almost right angles to the larger terminal twigs, which is not the case in other species of elm.

Fig. 40.—Leaf of Carolina Poplar.

Other common names: White elm.

Comparisons: The English elm (Ulmus campestris) is also a tall, dignified tree commonly seen under cultivation in America, but may be told from the American species by the difference in their general contour. The branches of the English species spread out but do not arch like those of the American elm, and the bark of the English elm is darker and coarser, Fig. 38. Little tufts of dead twigs along the main branches and trunk of the tree are characteristic of the English elm and will frequently help to distinguish it from the American elm.

The Camperdown elm may be recognized readily by its dwarf size and its low drooping umbrella-shaped crown.