342 



POSITION AND FOEM OF THE EMBRYO. 



tached to the pericarp, pe, by the funiculus, /. The chalaza and 

 hUum are confounded together at ch, the micropyle being at the 

 opposite end. The integuments of the seed, t, cover the embryo with 



its perisperm, ps ; the coty- 

 ledons, c, point to the Mlum 

 and chalaza ; while the 

 radicle, r, points to the 

 micropyle, and the embryo 

 is thus reversed or inverted. 

 Again, in an anatropal seed 

 (figs. 589, 590, p. 332), 

 where the micropyle is close 

 to the hHum, and the 

 Kg- 619. Kg. 620. chalaza at the opposite 



extremity, the embryo is erect or homotropal (S/ioiog, like, and 

 Tgs'jnii, I turn), the radicle or base of the embryo being directed to 

 the base of the seed. In some anatropal ovules, as in Castor oU 

 (fig. 579, p. 329), the exostome is thickened or carunculate, c, and 

 the endostome does not correspond exactly to it, so that 

 the radicle, e r, of the embryo is directed to a point a 

 little removed from the exostome. In curved or campy- 

 lotropal seeds (fig. 455, p. 255) the embryo is folded so 

 that its radicular and cotyledonary extremities are ap- 

 proximated, and it becomes amphitropal (a//-f>i, around, 

 r^B'?rcii, I turn). In this instance the seed may be 

 exalbuminous, and the embryo may be folded on itself 

 (fig. 620), or albuminous, the embryo surrounding more 

 or less completely the perisperm, and being peripherical 

 (fig. 618). In fig. 620 the seed of Erysimum cheiran- 

 thoides is shown, with the chalaza, ch, and the hUum, h, 

 nearly confounded together, the micropyle, m, the embryo 

 occupying the entire seed, with the radicle, r, folded on the cotyledons, 

 c, which enclose the plumide, fl'. Thus, by determining the position 

 of the hilum, chalaza, and micropyle, the direction of the embryo may 

 be known. 



According to the mode in which the seed is attached to the 



Fig. 619. Orthotropal seed of Sterculia Balanglias^ cut longitudinally, -with the portion 

 of the pericarp, pc, to which it is attached. /, Funiculus, ch, Chalaza and hilum con- 

 founded together, i. Integuments of the seed, or spermoderm. ps, Perisperm, the sum- 

 mit of which only is seen, c. One of the cotyledons. The other cotyledon has been re- 

 moved to show the gemmule, g. r. Radicle which is directed to the foramen at the apex 

 of the seed. The embryo is antitropal or inverted. Fig. 620. Campylotropal seed of 

 Erysimum cheiranthoides, cut longitudinally, m, Micropyle. ch, Chalaza not far removed 

 from the hilum, h. t, Testa or episperm, mi. Inner covering of the seed or endopleura. 

 r, Radicle, c, Cotyledons, g, Gemmule. The embryo is curved or amphitropal Fig. 

 621. Vertical section of the carpel of Triglochin Barrelieri. p, Pericarp crowned by the 

 sessile stigma, s. g, Seed. /, Funiculus, r. Raphe, c, Chalaza. 



Fig. 621. 



