THE EMBRYO. 333 



630. When the embryo, instead of being arrested in its growth 

 in the seed while yet minute and rudimentary, developes so far as 

 to exhibit its component organs, and form its cotyledons into evi- 

 dent, but usually more or less thickened leaves (as in the Almond, 

 Fig. 457, 458, the Bean, the Maple, Fig. 105, &c.), it absorbs the 

 nutritive matter of the nucleus immediately in the course of its 

 growth ; either completely, as in the examples just adduced, or par- 

 tially, so as to leave a thin albumen (as in Polygala, the Bladder- 

 nut, &c.). In such exalluminous seeds (viz. those entirely desti- 

 tute of albumen), the requisite store of nourishment, whether of 

 farinaceous, mucilaginous, or oily matter, or frequently of all these 

 kinds combined (as in flax-seed, the walnut, the almond, &c.), 

 is lodged in the embryo, chiefly in the cotyledons, instead of being 

 accumulated around it. Here the embryo occupies the whole cav- 

 ity, or forms the whole kernel of the seed, and is directly invested 

 by the integuments (Fig. 454, 1047) ; while in albuminous seeds, 

 the albumen is interposed between them, at least on one side 

 (Fig. 463, 559), and more commonly on all sides (Fig. 451, 452). 



631. The Embryo, being an initial plantlet or new individual, is of 

 course the most important part of the seed ; and to its production, 

 protection, and support, all the other parts of the fruit and flower 

 are subservient. It becomes a plant by the mere development of 

 its parts : it therefore possesses, in a rudimentary or undeveloped 

 state, all the essential organs of vegetation, namely, a root, stem, and 

 leaves, as has already been explained (113, 118, Fig. 105-107). 

 In numerous cases, as in the Maple, the Linden (Fig. 626), and the 

 Convolvulus (Fig. 927), &c., these several parts are perfectly 

 distinguishable in the seed; and the seed- 

 leaves are already foliaceous : sometimes 



they are large, but thickened by the nourish- 

 ing matter they contain, as in the Almond 

 (Fig. 457), and the Oak (Fig. 1047). Fre- 

 quently, however, we only observe an oblong 

 body, cleft or barely two-lobed at one end, 



T-- Aft 1 , i. 457 458 



as in rig. 454 ; but in germination the undi- 

 vided extremity elongates into a root, the two lobes at the opposite 

 end disclose their real nature by expanding into leaves, and the 

 stem rises between them. 



FIG. 457. Embryo (the whole kernel) of the Almond. 453. The same, with one of the co- 

 tyledons removed, showing the plumule, a. 



