764 



LECTURE XLII. 



because it has been already absorbed again by the cotyledons of the embryo before 

 and during the ripening of the seed. In consequence of this the cotyledons in. such 

 seeds grow so large that they completely fill up the whole of the very considerable 

 space within the seed-coats, whereas the plumule and radicle of the embryo form 

 but minute appendages. 



In what has been said however I have been anticipating the developmental 

 processes which occur after the fertilisation itself: some points have yet to be 

 mentioned concerning the origin of the embryo from the oosphere. As occurs even 

 in the Selaginellse, and to a much greater extent in the Gymnosperms, so also in the 

 Angiosperms there is developed from the fertilised oosphere not only the embryo 



Fig. ^^i,.— Ricinus commiciiis, I the ripe endosperinic 

 seed in longitudinal section. // the seedling of the cotyledons 

 which are still in the endosperm— compare .4 and B. s testa, 

 e endosperm, c cotyledon, he hypocotyl, lu primary root, tv' 

 secondary roots, x the caruncle, an appendage characteristic 

 of Euphorbiacese. 



FIG. 445-— Bean H'icia Faba), A the exalbumi- 

 nous seed after removal of one of the cotyledons ; the 

 other is still present c. -w radicle, kn plumule of the 

 embryo ; j testa. S germinating seed ; j- testa, / its 

 ruptured lobes, ti hilum. st petiole of one of the 

 cotyledons, k curvature of the epicotyl z'; Ac the very 

 short hypocotyl ; h primary root ; if .f its apex ; iit bud 

 in the axil of one of the cotyledons. 



proper, but a support or pro-embryo, by means of which the embryo is connected with 

 the membrane of the embryo-sac. The young embryo hence appears generally as a 

 sphere on a stalk which may be long or short ; for the fertilised oosphere grows in 

 the first place more or less in length, forming a tube which becomes segmented by 

 transverse walls, and finally, the true embryo arises from the most anterior of these 

 cells, which then breaks up by divisions in three directions situated at right angles to 

 one another, into octants, and as it grows up becomes further divided in the pericline 

 and anticline directions. These processes will be suflliciently clear from Fig. 446 

 I-IV. It is not before the spherical body is transformed into a small-celled mass 

 of tissue that the inception of the first leaves and primary root begins. All that 



