All trees seen against the sun are dark towards the middle and this shadow will be of the shape of the tree when apart from others.
The shadows cast by trees on which the sun shines are as dark as those of the middle of the tree.
The shadow cast by a tree is never less than the mass of the tree but becomes taller in proportion as the spot on which it falls, slopes towards the centre of the world.
The shadow will be densest in the middle of the tree when the tree has the fewest branches.
[Footnote: The three diagrams which accompany this text are placed, in the original, before lines 7-11. At the spots marked B Leonardo wrote Albero (tree). At A is the word Sole (sun), at C Monte (mountain) at D piano (plain) and at E cima (summit).]
Every branch participates of the central shadow of every other branch and consequently [of that] of the whole tree.
The form of any shadow from a branch or tree is circumscribed by the light which falls from the side whence the light comes; and this illumination gives the shape of the shadow, and this may be of the distance of a mile from the side where the sun is.
If it happens that a cloud should anywhere overshadow some part of a hill the [shadow of the] trees there will change less than in the plains; for these trees on the hills have their branches thicker, because they grow less high each year than in the plains. Therefore as these branches are dark by nature and being so full of shade, the shadow of the clouds cannot darken them any more; but the open spaces between the trees, which have no strong shadow change very much in tone and particularly those which vary from green; that is ploughed lands or fallen mountains or barren lands or rocks. Where the trees are against the atmosphere they appear all the same colour—if indeed they are not very close together or very thickly covered with leaves like the fir and similar trees. When you see the trees from the side from which the sun lights them, you will see them almost all of the same tone, and the shadows in them will be hidden by the leaves in the light, which come between your eye and those shadows.
TREES AT A SHORT DISTANCE.
[Footnote 29: The heading alberi vicini (trees at a short distance) is in the original manuscript written in the margin.] When the trees are situated between the sun and the eye, beyond the shadow which spreads from their centre, the green of their leaves will be seen transparent; but this transparency will be broken in many places by the leaves and boughs in shadow which will come between you and them, or, in their upper portions, they will be accompanied by many lights reflected from the leaves.
Taken from The Notebooks of Leonardo da Vinci edited by Jean Paul Richter, 1880.