THE LEAF 30 
The weight of the leaf causes it to tend to bend downward, 
with the result that there is a tendency for the upper portion 
cy 
Beeneeanee 
ne Cuenteale 
Vero ov aee® 
Bees eOcareraes 
Ore eG), 

Fig. 26. Cross section of a midrib and adjoining portion of thin part of the 
blade of cocoa leaf (Evrythroxylon coca) 
e, epidermis ; ¢, collenchyma; p, parenchyma; ph, phloém; x, xylem. (x 66) 
\\ 
WA WS 

Fie. 27. Termination of veins in a leaf (Hibiscus), as seen in a section cut 
parallel with the epidermis. (x 425) 
to be stretched and the lower portion compressed. The collen- 
chyma occurs, therefore, in those parts of the midrib in which 
there is the greatest need for strengthening material. 
