Fie. 89. — Capsella Bursa-pastoris. A, first division of terminal (embryo) cell ; 2?, quad- 

 rant stage; C, octant stage; /^differentiation of dermatogen ; E, differentiation 

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

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

 //, 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 



