AGRICULTURAL BOTANY 139 



veinlets joining the parallel veins. For this venation 

 examine the leaves of grass, corn, and the lily. Nearly 

 all endogenous plants have parallel-veined leaves, hence 



A B 



FIG. 64. Venation of Leaves. 

 A , netted-veined ; B, C, parallel-veined. 



the leaf venation forms a ready though not a certain 

 means of distinguishing these two great classes of plants. 



Forms of Leaves. - Figures illustrating and naming 

 the forms of leaves, their margins, bases, and apexes, 

 are in the Appendix. 



Structure of the Leaf Blade. If a cross section of 

 a leaf is examined under a high power microscope, the 

 leaf will be found to be made up of cells of various 

 forms. On both surfaces of the leaf will be seen a thin 

 skin that covers the whole. This colorless skin, the 

 epidermis, serves as a protection to the cells under- 

 neath. It is easily removed from some fleshy or soft 

 leaves, like those of the houseleek. Children often 

 suck the leaves of the live-forever, and thus loosen the 

 epidermis. 



Just under the epidermis, on the upper side of the leaf, 



