EXPOSURE TO LIGHT 243 
Fic. 228. — Geranium growing near a window, toward which it is bending 
and thereby bringing the leaves in a better position in reference to light. 
three kinds of tissues. First, there are the conductive tissues 
which bring the water and mineral salts to the leaf and carry 
away the manufactured foods. Second, there is the protective 
tissue consisting of epidermis which protects the delicate tissues 
within the leaf against drying, intense light, the entrance of 
destructive organisms, and to some extent gives rigidity to the 
