508 PHANEROGAMS, 



contained in the seed ; in most Conifers, on the contrary, this portion becomes 

 greatly elongated, making a sharp bend in an upward direction, pierces the soil, 

 and draws the cotyledons with it. As soon as these are exposed to light, the 

 hypocotyledonary portion straightens itself, the whorl of cotyledons expand, and, 

 having become green while still underground, act as the first foliage-leaves of 



Fig. ^^d.—Pztius Pittea ; /longitudinal section through the middle of the seed, jv the micropylar end; //conuiiencement 

 of germination, emergence of the root ; /// completion of germination, after the endosperm lias been absorbed (the seed 

 lay at too small a distance below the surface, and was therefore raised up by the cotyledons when the stem began to grow) ; 

 A shows the ruptured testa s, B the endosperm e, one half of the testa having been removed, C longitudinal section of the 

 endosperm and embryo, D transverse section at the commencement of germination; c the cotyledons, ru the primary root, 

 X the embryo-sac pushed out by it (ruptured in B), he hypocotyledonary portion of the axis, w' secondary roots, r red mem- 

 brane within the hard testa. 



the seedling, the apex of its axis having in the meantime formed a bud with 

 new leaves (Fig. 346). 



Mode of Growth and External Differentiation. The terminal bud of the stem 

 of the seedling grows more rapidly, though frequently interrupted, than the lateral 

 shoots which arise subsequently. The primary stem is thus a direct prolongation of 

 the axis of the embryo; it never ends in a flower, but grows indefinitely at the 



