The Elements of Botany, For Beginners and For Schools

by Asa Gray

Fig. 425. Seed of Bitter Cress, Barbarea, cut across to show the accumbent cotyledons. 426. Embryo of same, whole.

Incumbent, or with the plane of the cotyledons brought up in the opposite direction, so that the back of one of them lies against the radicle, as shown in Fig. [427, 428].

Fig. 427. Seed of a Sisymbrium, cut across to show the incumbent cotyledons. 428. Embryo of the same, detached whole.

391. As to the situation of the embryo with respect to the albumen of the seed, when this is present in any quantity, the embryo may be Axile, that is occupying the axis or centre, either for most of its length, as in Violet (Fig. [429]), Barberry (Fig. [48]), and Pine (Fig. [56]); and in these it is straight. But it may be variously curved or coiled in the albumen, as in Helianthemum (Fig. [430]), in a Potato-seed (Fig. [50]), or Onion-seed (Fig. [60]), and Linden (Fig. [414]); or it may be coiled around the outside of the albumen, partly or into a circle, as in Chickweed (Fig. [431, 432]) and in Mirabilis (Fig. [52]). The latter mode prevails in Campylotropous seeds. In the cereal grains, such as Indian Corn (Fig. [67]) and Rice (Fig. [430^a]), and in all other Grasses, the embryo is straight and applied to the outside of the abundant albumen.

Fig. 429. Section of seed of Violet; anatropous with straight axile embryo in the albumen. 430. Section of seed of Rock Rose, Helianthemum Canadense; orthotropous, with curved embryo in the albumen. 430^a. Section of a grain of Rice, lengthwise, showing the embryo outside the albumen, which forms the principal bulk.