Ontario Teachers' Manuals: Nature Study

by Ontario. Department of Education

TREES

A study of the pines of the locality may be commenced in November, after the deciduous trees have lost their leaves and have entered their quiescent winter period. This is the time when the evergreens stand out prominently on the landscape, in sharp contrast with the other trees that have been stripped of their broad leaves and now look bare and lifeless. If no pines are to be found in the vicinity, cedar or hemlock may be substituted. The lessons should, as far as possible, be observational. The pupils should be encouraged to make observations for themselves out of school. At least one lesson should be conducted out-of-doors, a suitable pine tree having been selected beforehand for the purpose. The following method will serve as a guide in the outdoor study of any species of tree:

THE WHITE PINE

Have the pupils observe the shape and height of the tree from a distance and trace the outline with the finger. Compare the shape of this tree with others near by of the same species and then with members of other species. Have the pupils describe in what particulars the shapes differ in different trees. They will come to realize that the difference in shape results from differences in length, direction, and arrangement of branches. They may notice that other evergreens resemble the pine in that the stems are all straight and extend as a gradually tapering shaft from the bottom to the top, that all have a more or less conical shape, and that the branches grow straight out from the main stem and not slanting off as in the case of the maples and elms.

Coming close to the tree, the pupils may first examine the trunk. By using a string or tape-line, they may find out how big it is around and the length of the diameter. Tell them how big some evergreens are (the giant trees of the Pacific Coast are sometimes over forty feet around). Have them notice where the trunk is largest, and let them find out why a tree needs to be so strong at the ground. Heavy wind puts a great strain on it just at this point. Illustrate by driving a long slat or lath into the ground firmly: then catching it by the top, push it over, and it will break off just at the ground. If a little pine tree could be taken up, the pupils would be interested in seeing what long, strong, fibrous roots the pine has.

Let them examine the bark of the trunk and describe its colour and roughness. The fissures in the bark, which are caused by the enlarging of the tree through the formation of new wood under the bark, are deeper at the bottom of the tree than at the top—the tree being younger and the bark thinner, the nearer to the top we go. How old is the very top, down to the first whorl of branches? How old is the stem between the first and second whorls? Between the third and fourth? Let the pupils find out in this way the age of a little pine that is regular and unbroken. The whorls of branches near the ground are usually small and dead in young trees and in old trees have completely disappeared. Relate the size of the trunk to its age, and also relate the size and length of the branches to their age. Where are the youngest branches and how old are they? What branches are oldest? Notice how the branch is noticeably larger just where it joins the trunk, as this is the point of greatest strain. Are the branches the same length on all sides of the trunk? If not, find one where branches are shorter on one side than on the other and try to discover the cause. Usually, if other trees are near enough to shade a certain tree, the branches are shorter and smaller on the shaded side.

Let the pupils look up into the tree from beneath and then go a little distance away and look at it. They will notice how bare the branches are on the inside, and the teacher will probably have to explain why this is so. They will discover that the leaves are nearly all out toward the ends of the branches. The leaves get light there while the centre of the tree top is shaded, and the great question that every tree must try to solve is how to get most light for its leaves. The pupils will now see an additional reason why the lower limbs should be longer than the upper ones. The greater length of the lower limbs brings the leaves out into the sunlight.

Why this tree is called an evergreen may now be considered. Why it retains its leaves all winter is a problem for more advanced classes, but if the question is asked, the teacher may get over the difficulty by explaining to the class that the leaves are so small and yet so hardy that wind and frost and snow do not injure them.

The pupils may each bring a small branch of twig back to the school-room, if the white pine is growing commonly about, otherwise the teacher may provide himself with a branch upon which to base another observation lesson in the class-room.

If the tree has cones on it, an effort should be made to get a few, as they will also be considered in a subsequent class-room lesson. If the cones have not yet opened when they are picked, so much the better, as they will soon open in a warm room, and the pupils will be able to examine the seeds and notice how they whirl through the air in falling. If possible, let the pupils have an opportunity of seeing pine trees growing in the woods as well as in the open.