Cornell Nature-Study Leaflets / Being a selection, with revision, from the teachers' leaflets, home nature-study lessons, junior naturalist monthlies and other publications from the College of Agriculture, Cornell University, Ithaca, N.Y., 1896-1904

by New York State College of Agriculture

Fig. 232. Shoot of the common white pine, one-third natural size.

It will be interesting to find out something about the leaves of our common evergreens. Let us look at some of them.

The White Pine.

In [Fig. 232] is shown a white pine branch. Notice that the leaves are borne in bunches or clusters of five. Each bunch of leaves is produced in the axil (or angle) of a minute scale-like body, but this scale can best be seen and studied on the very young growth. It has been worn away or broken from the older growth by the wind and the rain and the other forces of nature.

Fig. 233. Cone of white pine. It has shed its seeds. Half natural size.

Another strange fact should be well observed. The leaves of the maples and other deciduous trees are borne only on the present season's growth; but this is not the case in the pines, and kindred trees. If we trace back the growth of the past two or three years, we may find that there are as many leaves on the wood that is two years old as there are on the last season's growth; and in many cases we can find leaves on the part of the branch that is three years old. This means that the pine leaves or needles are two and sometimes three years old when they fall. The [Fig. 232] shows the falling of the leaves from the different years' growth. The part of the branch between the tip and A is the last season's growth; between A and B it is two years old; the part between B and C is three years old. The part that grew four seasons ago—beyond C—has no leaves.

The different seasons' growth is indicated not by distinct "rings" as in the case of deciduous trees, but by the branching. Each whorl of branches about a limb represents the end of a season's growth. A young pine tree, or the younger limbs of an old tree, shows this character very plainly.

Do the leaves of the pines and of the other evergreen trees fall at the end of the growing season, as the leaves of most of the deciduous trees do? Or do they gradually become lifeless and fall at any season, from the force of the wind and other natural forces? Tie a large sheet of cloth in the top of some evergreen tree, in such a way as to form a receptacle to catch the leaves. Do you catch leaves in winter as well as in summer? Do you find leaves on the snow?

As there are several different kinds of pines, we must picture carefully in our minds the foliage of the white pine, for it is different from that of any others. The leaves are soft and very slender, and from three to four inches long. The base of each cluster of leaves is at first surrounded by a small sheath. A scar is left when the leaves drop and these scars can often be seen on parts of the branches that are eight or ten years old. Do the leaves of other kinds of trees make a scar when they fall?