324 



THE SKKD. 



tion, and support all the other parts of the fruit and flower are sub- 

 servient. 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. Its 

 general structure and development have already been explained in 

 considerable detail (118 - 130). 



636. In albuminous seeds it is naturally the smaller and its parts 

 the legs developed in proportion to the amount of albumen, and the 



several organs are 

 developed or even 

 formed in germina- 

 tion. In exalbumi- 

 nous seeds', where 

 the embryo con- 

 stitutes the whole 

 kernel, its several 

 parts are ordina- 

 rily conspicuous, 

 although they are 

 often more or less disguised by thickening; as the cotyledons in 

 the Almond (Fig. 108) and Cherry (Fig. Ill), and especially in 

 the Pea (Fig. 118), the Acorn (Fig. 120), the Horsechestnut (Fig. 

 630), and the like. 



637. The parts of the embryo, as already illus- 

 trated (120) are the Radicle, the Cotyledons, and 

 the Plumide. The radicle is the axis, or rudimen- 

 tary stem, — the first internode of the axis (121, 

 157), from the lower extremity of which the root 

 is produced, while the other bears the cotjdedons, 

 i. e. the leaves of the first node ; and the plumule 

 is the bud which crowns the summit of the radicle. 



G38. Owing to the mode of its formation (580), the radicle of the 



FIG. 610. Vertical section of the seed of a Peony, showing a small embryo near the base of 

 the copious albumen. 611. The embryo, detached, and. more magnified. 



FIG. 612. Section of a seed of Barberry, with a straight embryo in the axis of the albu- 

 men. 613. Its embryo, detached. 



FIG. 614. Section of a Potato-seed, showing the embryo coiled in the albumen. 615. Its 

 embryo, detached. 



FIG 616. Section of the seed of Mirabilis or Four-o'clock, showing the embryo coiled round 

 the outside of the albumen. 617. Its embryo, detached, and partly spread out. 



FIG 618. Embryo of the Pumpkin, with its short radicle and large and flat cotyledons, 

 seen flatwise. 619. A vertical section of the same, viewed edgewise. 



