Line in Organic Forms
Look at any of the systems of line in the organic structures of nature: the radiating ribs of the scallop shell, or the spiral of many other varieties; the set of the feathers upon the expanded wing of a bird; the radiation of the sun's rays; the flowing line of the wave movement; the lines of structure in flowers and leaves; the scales of a fish; the scales of a pine-cone or an artichoke. We feel that any of these combinations of lines are harmonious and beautiful, and we know that they are essential to the character and structure. They are organic lines, in short. They mean life and growth. In principle they are radiating and recurring lines; in each form they repeat each other in varying degrees of direction and declension of curve. No two lines are alike, yet there is no contradiction and no unnecessary line, and variety is combined with unity. Each affords a perfect instance of harmonious composition of line, and gives us definite principles upon which to work (see illustration, p. [140]).
These systems of line in organic nature have been adopted and adapted by art, and are found throughout the historical forms of ornament which, as we have good reason to believe, were often derived from mechanical structures, illustrating the same principles; which, again, the logic of geometry enforces in drawing on plane surfaces.
All organic structures teach us the same lesson of relation and recurrence of line. The bones of all vertebrate animals, from fish to man, illustrate the constant repetition in different degrees of the same character and direction of line. The vertebral column itself is an instance, and the recurring spring of the ribs from it, like the branches from the stem of a tree, further expressed in the ramification of the jointed bones of the limbs and extremities. The principle may be followed out in the structure of the muscles in their radiating fibres, which the delicate contours and flowing lines of the surface of the body only combine in a greater degree of subtlety (see illustration, p. [142]).
Look at the anatomy of any tree, as it is disclosed to us in its wintry leaflessness, a beautiful composition of line rather than of form (see illustration, p. [143]).