66 THE NATURE AND WORK OF PLANTS 



The entire leaf, as well as that of the body of 

 the seed-plant, is covered with a thin sheet of cells, 

 the epidermis. The epidermis may be peeled off in 

 whitish strips by using a needle, or point of a sharp 

 knife. 



60. Leaves with both surfaces alike. — The leaves 

 examined in the preceding paragraph are held in a 

 horizontal position on the stems. Examine leaves 

 that are held in an upright position or nearly so, like 

 those of the narcissus, iris, or lily. The nerves will 

 not be so apparent, and both surfaces present nearly 

 the same appearance and would show about the 

 same arrangement of the cells. 



61. Compound leaves. — Examine the leaves of 

 the locust, pea, bean, or sumach. The three principal 

 parts may be found, but the lamina appears to be 

 branched or cut up into a number of smaller leafiets, 

 each with its own stalk by which it is fastened to 

 the midrib or r^hachis of the leaf. The number of 

 leaflets in the bean is three (see also § 217). Deter- 

 mine the number in the locust, pea, and other speci- 

 mens you may find. The compound leaf is capable 

 of doing more work than the simple forms showing 

 the same extent of lamina. 



