Botany
Botany for Painters & Elements of Landscape
All the branches of a tree at every stage of its height when put together are equal in thickness to the trunk below them.
— Leonardo da Vinci, §394
Overview
Leonardo's botanical writings represent a complete theory of landscape painting — not a botanical treatise in the scientific sense, but a painter's guide to understanding and representing trees, leaves, and foliage with precision. These chapters, primarily from the late manuscript MS. G (c. 1510–1515), lay down rules for branch structure, leaf arrangement, and the effects of light on vegetation.
The observations move from the structural (how branches relate to the trunk in thickness) through the directional (how branches grow toward light) to the optical (how light and shade play across leaves and canopies).
The Structure of Trees
§393–396 — Classification and proportion
393. TREES.
Small, lofty, straggling, thick, that is as to foliage, dark, light, russet, branched at the top; some directed towards the eye, some downwards; with white stems; this transparent in the air, that not; some standing close together, some scattered.
394. All the branches of a tree at every stage of its height when put together are equal in thickness to the trunk below them.
All the branches of a water course at every stage of its course, if they are of equal rapidity, are equal to the body of the main stream.
Note how he immediately connects trees to rivers — the branching pattern is the same in both. Leonardo always sees the universal principle behind the particular phenomenon. Fractal geometry wouldn't be formally described for another 450 years, but Leonardo was already looking at it. -D
The Direction of Growth
§404 — How leaves seek light and dew
404. The tips of the boughs of plants and trees, unless they are borne down by the weight of their fruits, turn towards the sky as much as possible.
The upper side of their leaves is turned towards the sky that it may receive the nourishment of the dew which falls at night.
The sun gives spirit and life to plants and the earth nourishes them with moisture. With regard to this I made the experiment of leaving only one small root on a gourd and this I kept nourished with water, and the gourd brought to perfection all the fruits it could produce, which were about 60 gourds of the long kind, and I set my mind diligently to consider this vitality and perceived that the dews of night were what supplied it abundantly with moisture through the insertion of its large leaves and gave nourishment to the plant and its offspring.
MS. G
Leonardo the experimental botanist — he grew a gourd from a single root, keeping it alive with water only, and counted 60 fruits. Then he deduced that dew on the leaves was the secret nutrient source. This is controlled experimentation, documented with precision, in 1510. -D
The Painter's Instruction
§402 — Why these rules matter
402. Wherefore, O Painter! you, who do not know these laws! in order to escape the blame of those who understand them, it will be well that you should represent every thing from nature, and not despise such study as those do who work only for money.
This is Leonardo in his sixties, writing with the accumulated authority of a lifetime of looking. The rule about branch thickness — that all branches at any level equal the trunk below — has been confirmed by modern dendrology. He figured it out by observation alone. -D