324 



TIIK SEKD. 



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 vegeiation, 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 less 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 Ilorsechestnut (Fig. 

 630), and the like. 



G37. The parts of the embryo, as already illus- 

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

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

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

 157), from the lower extremity of which lhe root 

 is produced, while the other bears the cotyledons, 

 i. c. the leaves of the iirst node ; and the plumule 6is m 



is lhe bud which crowns the summit of the radicle. 



G38. Owing to the mode of its formation (-380), the radicle of the 



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

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



FIG C12. Section of a seed of Barberry, with a straight embryo in the axis of tho albu- 

 men G13. 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. G17. Its embryo, detached, and partly spread out. 



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

 seen flatwise. 610. A vertical section of the same, viewed edgewise. 



