288 



DICOTYLEDONOUS EMBRYO. 



and /, root), the cotyledons are applied by their faces, and the 

 radicle (figs. 516, 517 r) is folded on their edges, so as to be lateral, 

 while the cotyledons, c, are decumbent (accumbo, I lie at the side). In 

 Notorhizece (varov, back), the cotyledons (fig. 518 c) are applied to each 



other by their faces, and the radicle r, is folded on their back, so as 

 to be dorsal, and the cotyledons are incumbent (ineumbo, I lie upon or 

 on the back). In Orihoploceoe (otfog, straight, and SS-AO'KO?, a plait), the 

 cotyledons are conduplicate (fig. 513, 1, 2, c), while the radicle, r, is 

 dorsal, and enclosed between their folds. In other divisions, the radicle 

 is folded in a spiral manner (fig. 515), and the cotyledons follow the 

 same course. In the Dodder (fig. 502), the embryo appears as an 

 axis without divisions, having several turns of the spiral on different 

 planes. 



602. The seed sometimes is composed of the embryo and integu- 

 ments alone, the former being either straight or folded in various ways, 

 as already shown. In other cases there is an addition of perisperm or 

 nutritive matter, in greater or less quantity, according to the state of 

 development which the embryo attains (figs. 492, 493, 494). When 

 the embryo is surrounded by the perisperm on all sides except its 

 radicular extremity (fig. 494), it becomes internal or intrarius (infra, 

 within); when lying outside the perisperm, and only coming into con- 

 tact with it at certain points, it is external or extrarius (extra, without). 

 When the embryo follows the direction of the axis of the seed, it is 

 axile or axial, and it may be either external, so as to come into contact 

 with the perisperm only by its cotyledonary apex (fig. 519), or internal 

 (figs. 492, 493, 494). In the latter case, the radicular extremity may, 

 as in some Coniferae, become incorporated with the perisperm appa- 

 rently by means of a thickened suspensor. When the embryo is not 

 in the direction of the axis, it becomes abaxile or abaxial (fig. 520 e); 



Fig. 516. Embryo of a Pea, cut transversely. Upper half separated to show the fleshy accum- 

 bent cotyledons, c. r, Radicle applied laterally. 



Fig. 517. Embryo of Isatis tinctoria. c, Accumbent cotyledons, r, Radicle. 1. Embryo 

 entire. 2. Transverse section of the embryo. 



Fig. 518. Embryo of Cheiranthus Cheiri, Wallflower, c, Incumbent cotyledons, r, Radicle. 

 L Embryo entire. 2. Transverse section of the embryo. 



