PLANTS FROM THE SEED. 



73 



121. The root and the stem grow not only in opposite directions, 

 hut in a different mode. The little stem, pre-existing in the seed, 

 grows throughout its whole length, (but most in its upper part,) 

 so that a radicle of perhaps less than a line in length may become a 

 stemlet two or three inches long. It is by this elongation that the 

 seed-leaves are raised out of the soil, so as to expand in the light 

 and air. Meanwhile a root begins to be formed at the other end of 

 the radicle; and this lengthens by continued cell-multiplication mainly 

 at its lower extremity, the parts once formed scarcely if at all elon- 

 gating afterwards ; but the growth takes place continuously at the tip 

 alone. The primary stem, bearing the pair of seed-leaves, soon 

 completes its development, and ceases to lengthen. Then, if not 

 before, the plumule (Fig. 106, c) begins its growth and develops 

 into a second stemlet on the summit of 



the first, bearing its pair of leaves. It 

 lengthens in the manner its predeces- 

 sor did, and carries up the second pair 

 of leaves to some distance above the 

 first ; then from between them springs 

 a third joint of stem, crowned with its 

 pair of leaves (Fig. 107) ; and so on, 

 building up the whole herb or tree by 

 this succession of similar growths or 

 joints of stem. The root, on the other 

 hand, grows on in a downward direc- 

 tion continuously, is not composed of a 

 series of joints, and bears no leaves or 

 other organs. 



122. The youngest seedling is there- 

 fore provided with all the organs of 

 vegetation that the full-grown plant 

 possesses ; and even the embryo in 

 the seed is already a miniature vege- 

 table. It has a stem, from the lower 

 end of which it strikes root in ger- 

 mination ; it has leaves, and it has or 



soon forms a bud, which develops into new joints of stem bearing 

 additional leaves, while beneath it sends its root deeper and deeper 



FIG. 107. A seedling Maple which has developed two additional joints of stem, each with 

 their pair of leaves. 



7 



