LKSSON 3.] GROWTH OF Tilt: PLANT FROM THIC SKED. 



i;< 



to tlio first leaves that a|)p(':ir. In most cases of the sort, the railitle, 

 or short original stemlet of the embryo be- 

 low the cotyledons (which is plainly shown 

 in the Pea, Fig. li)), lengthens very little, 

 or not at all ; and so the cotyledons remain 

 under ground, if the seed was covered by 

 the soil, as every one knows to be the case 

 with Peas. In these (Fig. 20), as also in 

 the Oak (Fig. 22), the leaves of the first 

 one or two joints are imperfect, and mere 

 small scales ; but genuine leaves immedi- 

 ately follow. The Ilorsechestnut and Buck- 

 eye (Fig. 23, 24) furnish another instance 

 of the same sort. These trees are nearly 

 iclated to the ]\laple ; but wlnle the seed- 

 h'avcs of the Maple show themselves to 

 be leaves, even in the seed (as we have 

 already seen), and when they germinate 

 fulfil the olhce of ordinary leaves, those 

 of the Buckeye and of the Ilorsechestnut 

 (Fig. 23), would never be suspected to be 

 the same organs. Yet they are so, only 

 in another shape, — exceedingly thickened 

 by the accumulation of a great quantity 

 of starch and other nourishing matter in 

 their substance ; and besides, their contigu- 

 ous faces stick together more or less firmly, 

 so that they never open. But the stalks 

 of these seed-leaves grow, and, as they 

 lengthen, push the radicle and the plumule 22 



out of the seed, when the former develops downwardly the roct. the 

 l;it!<T iii)\v;ir(]ly tin- Irnty sti-m and all it bears (Fig. 24). 



30. l)('|)Osit of Food OUlsidc of the Embryo. Very often ih" nourish- 

 ment provided for the seedling phintlet is laid up, not in the embryo 

 itself, but around it. A good instance to begin with is furnished by 

 the common Morning-GU)ry, or Convolvulus. The embryo, taken 

 out of the seed and straightened, is shown in Fig. 2r>. It consists 

 of a short stemlet and of a j)air of very thin and delicate green 

 leaves, having jio stock of nourishment in them lor sustaining the 



FIG. 21. An acorn divided Icnglliwi 



2 



riic germinating Oak. 



