TIG. 82. Sagittaria variabilis. Development of embryo. A, proembryo of three cells; 

 a, basal cell (in all figures) ; J, middle cell (dividing) ; c, terminal cell from which 

 the cotyledon is derived; #y, synergid; B, same stage, but terminal cell dividing; 

 <?, middle cell (b) has divided,"* being the cell from whose derivatives the stem-tip 

 arises, and terminal cell (c) dividing; Z>, both cells derived from b are dividing; 

 , terminal cell has given rise to four cells (c), and the region derived from the 

 middle cell (b) has developed further ; /", showing further development of the 

 middle cell region (5), while the terminal cell region has made no further progress ; 

 (r, dermatogen differentiated in the terminal cell region (c), and the middle region 

 (b) further developed ; H, differentiation of dermatogen beyond the terminal region 

 (c), the middle region (b) showing the differentiation between hypocotyl (A) and 

 region producing stem-tip ; /, more advanced stage, showing same regions as in H, 



and the plerome and periblem 

 x 260. After SCHAFFKBR.*' 

 189 



i^^ivu. /i vsuuvi.u.g oLcui-Li^/j A^ iijui c aci>aiiv;cJ. otiigc^ nui 



but the dermatogen of the root-tip not yet formed, and 

 undifterentiated. A-F, x 400 ; G, x 260 ; H, x 400 ; /, 



