28 BROOKLYN BOTANIC GARDEN MEMOIRS 



place by Dr. R. L. Dickinson on that day. He shows the relative size of 

 the body of water in 1918, by indicating the position of it in the center of 

 the pool. Such changes cannot fail to affect the speed of establishment and 

 the composition of the vegetation. 



Figure 6. Open stage of kettlehole. Center with Eleocharis obtusa. The white- 

 flowered plant toward the margin is Eupatorium perfoliatuni. Note shore lines of seasonal 

 fluctuations of water level. 



In those where water is fugitive or lacking at the surface, the following 

 is presented after a study of many kettleholes in all stages of development. 



LOW kettleholes: open stage. 



Low kettleholes without woody vegetation are still occasionally to be 

 seen, but in all those examined there was standing water a few inches deep 

 in early June, but practical dryness by midsummer. 



In such kettleholes there are usually well marked zones of vegetation 

 dominated by some characteristic plant, or assemblage of them, and in the 

 one illustrated (Figs. 6 and 7) all the lowest and therefore wettest part of 

 itwas covered hy Eleocharis obtusa. This small sedge is succeeded, towards 



