The Da Vinci Notebooks at sacred-texts.com
If the light comes from m and the eye is at n the eye will see the colour of the leaves a b all affected by the colour of m --that is of the atmosphere; and b c will be seen from the under side as transparent, with a beautiful green colour verging on yellow.
If m is the luminous body lighting up the leaf s all the eyes that see the under side of this leaf will see it of a beautiful light green, being transparent.
In very many cases the positions of the leaves will be without shadow [or in full light], and their under side will be transparent and the right side lustrous [reflecting light].