20 WALL'S MANUAL 



ment, in this manner : plant seeds in a box of soil, 

 with straw or moss spread over it, and narrow strips 

 of wood placed over all, so that the contents of the 

 box will not fall out when inverted ; turn the open 

 side downward over a mirror or a bright surface of 

 tin, so that the light will reach the soil only from below, 

 and the seeds will germinate, the stem will descend 

 toward the light, whilst the roots will ascend into the 

 dark soil above it. 



Functions of the Stem. These are : first, to convey 

 the sap from the roots to the leaves, where it is prepared 

 for the nutrition of the plant, and thence to carry it 

 to the various parts to be nourished by it ; second, to 

 sustain the leaves, flowers, and fruits, so as to expose 

 them properly to the action of air and light. 



THE LEAF. 



The leaf combines, in an eminent degree, the useful 

 and the beautiful. The almost countless shapes, 

 from the straight and slender blade of grass to the 

 deeply lobed oak leaf, and the broad palm, present to 

 the eye a wonderful variety of nature's handiwork. 

 The green color, the most pleasant to the eye, seems 

 to have been provided by a wise Providence to soften 

 the bright glare of a summer's sun, and thus pro- 

 mote the comfort of His creatures. To the plant itself 

 the leaf boars the most important relation. It is the 

 breathing organ of the plant its lungs, as also the 

 digestive organ its stomach. 



Functions of the Leaf. When the pap of the plant 

 ascends from the root to the leaf, it carries with it in 

 solution a portion of the material necessary for the 

 nourishment of the growing plant, but this food is 



