Botanical Sketches and Drawings

ON THE GROWTH OF BRANCHES AND THE NATURE OF LEAVES

The branch of the leaf Leonardo often uses "branch of the leaf" to refer to the petiole or the small twig supporting the foliage is always directed toward the sky, and never toward the earth.

The growth of the branches of trees is of two kinds: either the branches are opposite to one another, or they are arranged in a spiral.

THE LAW OF THE SUN AND MOON

All the leaves which are on the side of the tree that is turned toward the north are larger than those on the south side. This happens because the leaves on the north side have more moisture, and the sun does not dry them out as much as those on the south side.

The sap flows more abundantly where the sun's heat is less intense.

The thickness of a branch is always equal to the sum of the thicknesses of all the branches that spring from it. This is a famous observation now known as "Leonardo's Rule" for tree branching.

If you take a plant and turn it upside down, the leaves will immediately turn themselves back toward the sky. This is because the leaf always seeks the light and the air, which are its nourishment.

Note: Observe the way the elm tree distributes its weight.

OBSERVATIONS ON THE BARK

The bark of the tree on the side toward the south is much more cracked and dry than on the side toward the north. The sun burns the skin of the tree.

| Orientation | Leaf Size | Bark Condition | | :--- | :--- | :--- | | **North** | Larger | Smooth and moist | | **South** | Smaller | Cracked and dry |

The center of the pith The soft, spongy central tissue in a stem of a branch is never in the middle of its thickness, but is always closer to the side that faces the south than to the side that faces the north.