es, it is more beautiful,
because varied by the freedom of the separate branches. I believe it has
been ascertained that, in all trees, the angle at which, in their
leaves, the lateral ribs are set on their central rib is approximately
the same at which the branches leave the great stem; and thus each
section of the tree would present a kind of magnified view of its own
leaf, were it not for the interfering force of gravity on the masses of
foliage. This force in proportion to their age, and the lateral
leverage upon them, bears them downwards at the extremities, so that, as
before noticed, the lower the bough grows on the stem, the more it
droops (Fig. 17, p. 67); besides this, nearly all beautiful trees have a
tendency to divide into two or more principal masses, which give a
prettier and more complicated symmetry than if one stem ran all the way
up the center. Fig. 41 may thus be considered the simplest type of tree
radiation, as opposed to leaf radiation. In this figure, however, all
secondary ramification is unrepresented, for the sake of simplicity; but
if we take one half of such a tree, and merely give two secondary
branches to each main branch (as represented in the general branch
structure shown at _b_, Fig. 18, p. 68), we shall have the form Fig. 42.
This I consider the perfect general type of tree structure; and it is
curiously connected with certain forms of Greek, Byzantine, and Gothic
ornamentation, into the discussion of which, however, we must not enter
here. It will be observed, that both in Figs. 41 and 42 all the branches
so spring from the main stem as very nearly to suggest their united
radiation from the root R. This is by no means universally the case; but
if the branches do not bend towards a point in the root, they at least
converge to some point or other. In the examples in Fig. 43, the
mathematical center of curvature, _a_, is thus, in one case, on the
ground, at some distance from the root, and in the other, near the top
of the tree. Half, only, of each tree is given, for the sake of
clearness: Fig. 44 gives both sides of another example, in which the
origins of curvature are below the root. As the positions of such points
may be varied without end, and as the arrangement of the lines is also
farther complicated by the fact of the boughs springing for the most
part in a spiral order round the tree, and at proportionate distances,
the systems of curvature which regulate the form of vegetation a