EMBRYOLOGY OF DICOTYLEDONS 



369 



in water, and gentle pressure applied by tapping the cover- 

 glass. 



. More advanced stages can be obtained in the same way from 

 progressively older seeds. These show rather longer suspensors 



FIG. 216. Embryology of the Shepherd's Purse (Capsella bursa-pastoris). 

 The successive stages are numbered I-IX. In VII and VIII only the 

 embryo and a small part of the adjacent suspensor are shown. IX is 

 a longitudinal section of a mature seed, showing the coiled embryo. 

 b., basal cell; Co., cotyledons ; e., embryo ; p., plumule ; r., radicle ; 

 S., suspensor. 



and an increasing number of divisions in the enlarging embryonal 

 cell (Fig. 216, IV-VI). The latter soon segments into octants, 

 by three walls at right-angles to one another (III, IV), and sub- 

 sequently dermatogen, periblem, and plerome are successively 

 delimited by walls parallel to the surface (V, VI). Mean- 

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