12 



GROWTH OF THE PLANT FROM THE SEED. [^LESSON 3. 



they were so gorged and, as it were, misshapen, that they became 



quite unfitted to perform the office of 

 foliage. This office is accordingly first 

 performed by the succeeding pair of 

 leaves, those of the plumule (Fig. 17, 

 18), which is put into rapid growth by 

 the abundant nourishment contained in 

 the large and thick seed-leaves. The 

 latter, having fulfilled this office, soon 

 wither and fall away. 



29. This is carried a step farther in 

 the Pea (Fig. 19, 20), a near relative 

 of the Bean, 

 and in the" 

 Oak (Fig. 

 21, 22), a 

 near relative 

 of the Beech. 

 The differ- 

 ence in these 

 and many 

 other similar 

 cases is this. 



The cotyledons, which make up nearly 



the whole bulk of the seed are exces- 

 sively thickened, so as to become nearly 



hemispherical in shape. They have lost 



all likeness to leaves, and all power of 



ever fulfilling the office of leaves. Ac- 

 cordingly in germination they remain 



unchanged within the husk or coats of 



the seed, never growing themselves, but 



supplying abundant nourishment to the 



plumule (the bud for the forming stem) 



between them. This pushes forth from 



the seed, shoots upward, and gives rise 



FIG. 16. A Bean : the embryo, from which seed-coats have been removed : the small 

 stem is seen above, bent down upon the edge of the thick cotyledons. 17. The same in early 

 germination ; the plumule growing from between the two seed-leaves. 18. The germination 

 more advanced, the two leaves of the plumule unfolded, and raised on a short joint of stem. 



FIG. 19. A Pea : the embryo, with the seed-coats taken off. 20. A Pea in germination. 



