J 



FIG. 89. Capsella Bursa-pastoris. A, first division of terminal (embryo) cell; B, quad- 

 rant stage ; (7, octant stage ; Z>, differentiation of dermatogen ; E, differentiation 

 of periblem and plerome (latter shaded) ; F, completion of periblem of root ; G- y 

 beginning of differentiation of dermatogen of root-tip (indicated by mitotic figure) ; 

 H, later stage, showing plerome, periblem, dermatogen, and one layer of root-cap 

 (plerome and dermatogen shaded); 7, two layers in root-cap (the plerome and 

 portion of dermatogen derived from hypophysis shaded) ; J, young embryo sur- 

 rounded by endosperm ; walls of ovary also shown ; x 400. 



197 



