Why the lower branches of a tree bend downward
Branch geometry lettered a-b-c-d and f-n-m, showing how a limb turns down and a shoot dries
A page of red-chalk branch studies with lettered diagrams explaining tree ramification. Leonardo notes that the lower branches, once they have formed the angle at which they separate from the trunk, bend downward so as not to crowd the branches above them on the same trunk and to take in more nourishing air. A first lettered figure (e, b, c, d, a) shows how branch a c, having made the side a c of angle b a c, bends down into c d, so that the small branch c dries up as useless. A second figure (o, n, m, f) states the rule that the master branch always runs below, as branch f n m demonstrates.
On this page
Lower branches bend down to avoid crowding and gather air
Once the lower branches have generated the angle of their separation from the trunk, they always bend downward so as not to close in against the branches that succeed them above on the same trunk, and so as better to take the air that nourishes them.
Diagram a-b-c-d: the branch bends and the useless shoot dries
As the angle b a c shows, the branch a c, after it has made the side a c of the angle, bends downward into c d, and the little branch c dries up through being useless.
Diagram f-n-m: the master branch runs below
The master branch always goes below, as the branch f n m shows, which does not run by way of f.