No two plants or parts of plants are identically exposed to the conditions in which they live. The large branches in Fig. [1] probably had more room and a better exposure to light than the smaller ones. Probably no two of the leaves in Fig. [2] are equally exposed to light, or enjoy identical advantages in relation to the food that they receive from the tree.
Fig. 3.—A Battle for Life.
Examine any tree to determine under what advantages or disadvantages any of the limbs may live. Examine similarly the different plants in a garden row (Fig. [3]); or the different bushes in a thicket; or the different trees in a wood.
The plant meets its conditions by succumbing to them (that is, by dying), or by adapting itself to them.
The tree meets the cold by ceasing its active growth, hardening its tissues, dropping its leaves. Many herbaceous or soft-stemmed plants meet the cold by dying to the ground and withdrawing all life into the root parts. Some plants meet the cold by dying outright and providing abundance of seeds to perpetuate the kind next season.
Fig. 4.—The Reach for Light of a Tree on the Edge of a Wood.
Plants adapt themselves to light by growing toward it (Fig. [4]); or by hanging their leaves in such position that they catch the light; or, in less sunny places, by expanding their leaf surface, or by greatly lengthening their stems so as to overtop their fellows, as do trees and vines.
The adaptations of plants will afford a fertile field of study as we proceed.