THE HYDROPHYTE SOCIETIES 



127 



existence. Some plants float in the water and have no direct 

 connection with the soil; others are rooted to the soil but float 

 in the water (water lilies). Some are rooted in the mud but 

 extend far; above the water (cat-tails) ; some grow in wet soil; 

 still others grow in dry soil and are easily killed by too much 



FIG. 83. Zone formation of vegetation dependent upon depth of water. 



water. These facts enable us to group plants into societies de- 

 pendent upon their water requirements. (Figs. 83 and 84.) 



The Hydrophyte societies are made up of those plants which 

 live in the water or in very wet swampy soils. Ponds and lakes 

 in which the water varies in depth frequently show many of 

 these societies to an advantage ; the floating plants in the moder- 

 ately deep water, the cat-tails near the margin and the willows 

 on the margin. Eice is one of the few hydrophytes which is of 

 great agricultural importance. 



