. Bulletin. Forests and forestry -- United States. THE END OF THE STRUGGLE. 61 without the means of overtopping one another. When the end of the period of principal height growth is reached the trees are interfering with each other very little, and the struggle for life begins again in a differ- ent way. As the principal height growth ceases, and the tops no longer shoot up rapidly above the side branches, the crowns lose their pointed shape and become com- paratively fiat. (See figs. 57, 58.) The chief reason why trees stop growing in height is that they are not able to keep the up[)er parts
. Bulletin. Forests and forestry -- United States. THE END OF THE STRUGGLE. 61 without the means of overtopping one another. When the end of the period of principal height growth is reached the trees are interfering with each other very little, and the struggle for life begins again in a differ- ent way. As the principal height growth ceases, and the tops no longer shoot up rapidly above the side branches, the crowns lose their pointed shape and become com- paratively fiat. (See figs. 57, 58.) The chief reason why trees stop growing in height is that they are not able to keep the up[)er parts of their crowns properly supplied with water above a certain dis- tance from the ground. This distance varies in different kinds of trees, and with the health and vigor of the tree in each species, but there is a limit in every case above which the water does not reach. The power of the pumping machinery, more than any other quality, determines the height of the Fig. 59.—Diagram to show why a sharply conical crown receives more light than a flat one. THE E^'D GF THE STRUGGLE. Now that the tree can no longer expand at the top, it must either suffer a great loss in the number of its leaves or be able to spread at the sides; for it is clear that not nearly so many leaves can be exposed to the light in the flattened crown as in the pointed one, just as a pointed roof has more surface than a flat one. (See fig. 59.) It is just at this time, too, that the trees begin to bear seed most abundantly, and it is of the greatest importance to eac'h tree that its digestive appa-. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original United States. Division of Forestry. Washington : G. P. O.
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