Quotation from: The Notebooks of Leonardo Da Vinci

Written by: Leonardo da Vinci

438.

OF TREES THAT ARE LIGHTED BY THE SUN AND BY THE ATMOSPHERE.

In trees that are illuminated [both] by the sun and the atmosphere
and that have leaves of a dark colour, one side will be illuminated
by the atmosphere [only] and in consequence of this light will tend
to blueness, while on the other side they will be illuminated by the
atmosphere and the sun; and the side which the eye sees illuminated
by the sun will reflect light.