📔 Studies of Trees in Winter

The birch does not lose its pendulous grace in mere limp dejection, like most of the weeping varieties of trees that gardeners love to propagate, but it holds its head high and the slender branches droop down,—a striking contrast to the weeping willow and other lachrymose specimens of horticultural art.

There are two distinct plans of branching in trees. When the main trunk extends upward to the tip, as it does in the larch and other conical trees, it is said to be excurrent, and when the main stem divides into many more or less equal divisions, as we find it in the American elm and other spreading trees, it is said to be deliquescent,—the latter form is the most common one among our deciduous trees.

The inner structure of these dicotyledonous trunks is seen when we examine the cross section cut of a felled tree. In the centre is the heartwood, the durable wood of commercial value, the cells of which are hard and dry; next it the soft sapwood, the living part of the tree containing cells filled with sap; then the cambium layer, the zone of growing cells, and outside of this the bark.

In young trees there is a conspicuous central portion of pith which remains after the tree matures, as long as the heartwood is sound. The lines radiating from the centre to the circumference are called medullary or pith rays and form the “silver grain” of the wood.