OF THE EMBRYO AND SEEDLING. 11 



may afterward be compared. The first growth is seen in the 

 elongation of the radicle or caulicle, and its assumption, as far as 

 possible, of a vertical position, and the production of a root from 

 the naked end. As it emerges from the seed in consequence of 

 this elongation, the root-end of the caulicle points downward into 

 the soil, the caulicle bending, if need be, to assume this position ; 

 and the nascent root, partaking of this disposition, grows in a 

 downward direction. Hence the root has been called the Descend- 

 ing Axis of the plant. While this avoids, the opposite or budding 

 end (as it may be termed) seeks the light, and when free takes 

 an upward direction. The result of this, and of the elongation 

 of the caulicle, is to carry the budding end out of the soil and 

 into the air, where the growing cotyledons unfold or expand and 

 become the first leaves, or Seed-leaves. This initial stem and its 

 continuation therefore constitutes the Ascending Axis. If the 

 budding end happen to lie pointing downward and the root-end 

 upward in the ground when germination begins, both will curve 

 quite round, as they grow, to assume their appropriate directions. 

 If obstacles intervene, each will take as nearly as possible its 

 wonted direction, through an instinctive tendency and action, 

 which insures that each part of the plant shall be developed in 

 its fit medium, the root in the dark and moist earth, the stem 

 and leaves in the light and air. 



22. The plantlet, thus established, has now all the essential 

 Organs of Vegetation, as they are called, 



i. e. root, stem, and leaves. Its subse- 

 quent development, so far as vegetation 

 (apart from proper reproduction) is con- 

 cerned, consists in the addition of more 

 of these, until the whole herb, shrub, or 

 tree is built up. 



23. In Maples (as in the Morning Glory, 

 Fig. 16, and many others) the embryo in 

 the seed, and until after the full develop- 

 ment of its cotyledons or seed-leaves, 

 shows no rudiments of the subsequent 

 growth. The embryo grows into the plant- 

 let wholly by the appropriation of prepared 

 nourishing matter which was provided by 



the mother-plant and stored in the seed, in the case of the 

 Maple, wholly in the embryo itself, mainly in its cotyledons. 



FIG. 9. Maple embryo developed into plantlet of one phytomer, and producing 

 rudiments of the second: the lower portion covered with root-hairs is the root; the 

 naked portion above is the caulicle. 



