PLANTS FROM THE SEED. 



75 



m 



the 



illustrations of the kind. The ample store of nourishment in such 



cases enables the germinating plantlet to grow with remarkable 



vigor, and to develop the strong plumule 



with its leaves before the seed-leaves 



have expanded, or the root has obtained 



much foothold in the soil. In these 



instances the cotyledons are so much 



thickened that, . 



although they 



turn greenish 

 light, 



they only im- 

 perfectly as- 

 sume the ap- 

 I pearance and 

 perform the( 

 functions of or- 

 dinary leaves ; 

 and the earli- 

 est real foliage 

 consists of the 

 leaves of the 

 plumule. Such 

 cotyledons 

 serve chiefly 

 as depositories 

 of nourishment 

 for the germi- 

 nating plant. 



124. Still more strongly marked cases of this kind are presented 

 by the Pea (Fig. 118, 119), the Chestnut and Horsechestnut, the 

 Oak (Fig. 120, 121), &c. Here the cotyledons are excessively 

 thickened, so as to lose all likeness to leaves and all power of ful- 

 filling the office of foliage. Accordingly they remain unchanged 

 witliin the seed-coats, supplying abundant nourishment to the 



FIG. 112. A Beech-nut, cut across. 113. Beginning germination of the Beech, showing 

 the plumule growing before the cotyledons have opened or the root has scarcely formed. 

 114. The same, a little later, with the second joint lengthened. 



FIG. 115. The embryo (the whole kernel) of the Bean. 116. Same early in germination ; 

 the thick cotyledons expanding and showing the plumule. 117. Same, more advanced in 

 germination ; the plumule developed into a joint of stem bearing a pair of leaves. 



