Two Trees in Sunlight and Light on Rounded Foliage
Diagrams of two trees lit by the sun and of a plant under the lit hemisphere of the sky
Two pen diagrams anchor this leaf. The first proves that an eye (c) sees two trees (b and d) lit by the sun (a) with unequal proportions of light to shadow, the tree nearer the sun's rays reading as darker, so that tree d shows only shadow while tree b appears half-lit and half-shaded. A brief chapter reminds the painter that shadow-darkness varies with the density of a tree's branching, and a final chapter, illustrated by a semicircular hemisphere enclosing a small tree (labelled a, b, c, d, o, p, n), argues that the parts of a plant farthest from the earth wear the least dark shadows.
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Two trees lit by the sun seen with unequal light and shade
Letting the eye be c, which sees two plants b and d lit by the sun a, Leonardo argues the eye will not see the same proportion of light to shadow in one tree as in the other: the tree nearer the concourse of solar rays reaching the eye reads as darker. Thus of tree d the eye c sees only shadow, while it sees tree b half-lit and half-shadowed.
A reminder that shadow varies with the density of branches
Leonardo reminds the painter that within one same species of plant the darkness of the shadows varies as much as the rarity or density of the branchings varies. Denser branching yields deeper, more varied shadow.
Parts of a plant farthest from the earth are least shadowed
Under the universal light, the part of a plant more remote from the earth shows itself clothed in shadows of less darkness. With the plant a b set under the illuminated hemisphere n b c, the lower part sees the earth p c and only a little of the sky, while the higher part in the concavity a sees more of the lit hemisphere.