340 



DICOTYLEDONOUS EMBKTO. 



equitant (fig. 222 m, p. Ill) and semi-equitant (fig. 222 n, p. Ill) 

 vernation. 



The radicle may be either straight or curved, and, in particular 

 instances, it gives a marked character to the seed. Thus, divisions 

 of the order Cruciferse are founded on the relative position and folding 

 of the radicle and cotyledons. In the division Pleurorhizm (TXeuga, 

 side, and g/^a, root), the cotyledons are applied by their faces, and 

 the radicle (figs. 612, 613 r) is folded on their edges, so as to be 

 lateral, whUe the cotyledons, c, are accumbent (accumbo, I lie at the 



Pig. 612. 



Fig. 613. 



side). In Notorhimm (viZrog, the back) the cotyledons (fig. 614'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 (incumbo, 

 I lie upon, or on the back). In Orthoplocece (og^og, straight, and 

 'jtXoKTi, a plait) the cotyledons are conduplicate (fig. 609, 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. 611), 

 and the cotyledons follow the same course. In the Dodder (fig. 598) 

 the embryo appears as an axis without divisions, having several turns 

 of the spiral on different planes. 



The seed sometimes is composed of the embryo and integuments 

 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. 588, 589, 590). When 

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

 radicular extremity (fig. 590, p. 332), it becomes internal or intrarius 

 (intra, within) ; when lying outside the perisperm, and only coming 

 into contact with it at certain points, it is external or extrarius (extra, 



Fig. 612. Embryo of a Pea, cut transversely. Upper half separated to show the fleshy 

 aecumhent cotyledons, c. r, Radicle applied laterally. Fig. 613. Embryo of Isatis tinctoria. 

 c, Accumbent cotyledons, r, Radicle. 1, Embryo entire. 2, Transverse section of the 

 embryo. Fig. 614. Embryo of Cheiranthus Cheiri, Wallflower, d, Incumbent cotylcdons_ 

 r. Radicle. 1, Embryo entire. 2, Transverse section of the embryo. 



