§ 220. Along with some unfamiliar facts, I have here set down facts which are so familiar as to seem scarcely worth noting. It is because these facts have become meaningless to perceptions deadened by infinite repetitions of them, that it is needful here to point out their meanings. Not alone for its intrinsic importance has the unlikeness between the attached ends and the free ends been traced among plants of all degrees of integration. Nor is it simply because of the significance they have in themselves, that instances have been given of those varieties of symmetry and asymmetry which the free ends of plants equally display: be they plants of the first, second, third, or any higher order. Neither has the only other purpose been that of showing how, in the radial symmetry of some vegetal aggregates and the single bilateral symmetry of others, there are traceable the same ultimate principles as in the spherical symmetry and triple bilateral symmetry of certain minute plants first described. But the main object has been to present, under their simplest aspects, those general laws of morphological differentiation which are fulfilled by the component parts of each plant. If organic form is determined by the distribution of forces, and the approach in every case towards an equilibrium of inner actions with outer actions; then this relation between forms and forces must hold alike in the organism as a whole in its proximate units, and in its units of lower orders. Formulas which express the shapes of entire plants in terms of surrounding conditions, must be formulas which also express the shapes of their several parts in terms of surrounding conditions. If, therefore, we find that a plant as a whole is radially symmetrical or bilaterally symmetrical or asymmetrical, according as the incident forces affect it equally on all sides of an axis, or affect it equally only on the opposite sides of one plane, or affect it equally in no two directions; then, we may expect that, in like manner, each member of a plant will display radial symmetry where environing influences are alike along many radii, bilateral symmetry where there is bilateralness of environing influences, and unsymmetry or asymmetry where there is partial or entire departure from a balance of surrounding actions. To show that this expectation is borne out by the facts, will be the object of the following four chapters. Let us begin with the largest parts into which plants are divisible; and proceed to the successively smaller parts. CHAPTER VIII. THE SHAPES OF BRANCHES.