56 PLANT BIOLOGY 



c. Make a drawing, natural size, by tracing the out- 

 line of the leaf -stalk and blade. Draw carefully 

 the principal veins and a few of their branches, 

 being careful to show their relative size and their 

 connections. Label leaf -stalk, blade, main veins, 

 network of veins. 



2. (Optional.) Examine a compound leaf, e.g. rose, clover, 

 locust, pea, horse-chestnut. Notice that the blade is 

 divided into three or more parts known as leaflets, 

 which are attached either to the end of the leaf- 

 stalk or on either side of the mid-vein of the com- 

 pound leaf. 



a. In what respect, therefore, does the blade of a com- 

 pound leaf differ from the blade of a simple leaf ? 



6. Compare the arrangement of the leaflets in a leaf like 

 the rose, locust, or pea with that in the Virginia 

 creeper or horse-chestnut. Which leaves have the 

 leaflets arranged like the bones in the palm of the 

 hand (palmately compound), and which have the 

 leaflets arranged along the side of the mid- vein as in 

 a feather (pinnately compound, from Latin, pinna = 

 feather) ? 



c. At the base of the leaf -stalk of the rose, clover, or pea leaf, 

 notice two leaf-like objects (small in the case of the 

 rose). These are known as stipules. Stipules are also 

 found as a part of many simple leaves. How do 

 stipules differ from the other parts of leaves ? (See 

 Fig. 19.) 



B* Gross structure of leaves. Secure thick leaves such as 

 sedum, tulip, hyacinth, or onion. 



1. Peel off from .the upper and lower surface a thin 



membrane known as the epidermis. Hold the 



epidermis between yourself and the light. Tell 



what you have done and state two characteristics 



. of epidermis. 



