ZONAL DISTRIBUTION OF PLANTS. 



401 



slope where this photograph was taken is so 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 



Fig. 494- 

 Sagittaria variabilis. 



into zones parallel with the shore line. Several zones can be 

 readily made out in this region; two of them at least do not show 

 in the picture since they are submerged. 



714. If we treat of the two submerged zones, the first one is 

 in the rear of the point from where the photograph was taken, 

 and consists of extensive areas of chara in four to five meters of 



