LEAVES 



151 



in such a manner that it is possible for the leaf to manu- 

 facture the food for the growing plant. 



Parts of a Typical Leaf. The point of attachment of the 

 leaf to the stem is the pulvinus. The tissues at this point 

 are modified for the purpose of separating the leaf from the 



FIG. 88. Petioles. Figures showing the comparative length of petioles of 

 different leaves. 



stem and healing the wound caused by such separation. 

 Stipules are leaflike expansions of the petiole. In red clover, 

 pea, and rose they are very characteristic; many leaves have 

 no stipules. The stemlike part of the leaf is the petiole; the 

 broad expanded part of the leaf is the blade; the part of the 



