3o8 



ECOLOG Y. 



symmetrical that plants suited by their long habit of growing at 

 certain depths of water, or in soil of a certain moisture content, 

 are readily drawn into zones parallel with the shore line. 



Fig. 258. 

 Sagittaria variabilis. 



Several zones can be readily made out in this region; two of 

 them at least do not show in the picture since they are sub- 

 merged. 



475. Submerged zones in the foreground. — If we treat of the 



