32 BROOKLYN BOTANIC GARDEN MEMOIRS 



Where this is pronounced the kettlehole may be found dotted with bushes, 

 while in those just emerging from the purely herbaceous state, the few 

 bushes found appear to be putting up a losing fight. 



The permanent appearance of even a few bushes seems, in the kettle- 

 holes that have been examined, always to be associated with a lack of 

 standing water, except perhaps in the early spring after the melting of 

 snow. Whether the silting in of material from the banks is the true ex- 

 planation of the disappearance of standing water or not, it is certainly true 

 that in those kettleholes where water is fugitive or beneath the ground level, 

 certain definite changes occur, followed by an encroachment of woody 

 vegetation. The accompanying photograph shows a kettlehole in just 

 this stage. A little water was found in it in June, none after. (See 

 Figures 8 and 9.) 



Its banks are very steep and the assumption that silted material has 

 raised the floor of it enough so that shrubs will not smother from excess 

 water, seems reasonable. It may also be that fires, which would scarcely 

 affect herbaceous vegetation, would destroy pioneer shrubs in such places, 

 thus greatly retarding the transition from an open kettlehole to a partially 

 wooded one. 



That there is always an orderly progression from open kettleholes to 

 those about to be described, in which woody plants get a firm foothold, is 

 probably not true. Some have been found where the process is arrested, 

 due to unusually wet seasons or perhaps to fire, and one finds only dead 

 shrubs, and a partial recrudescence of the purely herbaceous vegetation. 

 But that this progression is going on, that bushes, and finally the dense 

 wooded thickets of the climax type are ultimately developed, seems to be 

 demonstrated. 



The vegetation of a kettlehole of this developing type, where woody 

 plants seem for the first time to have a firm foothold, is of interest, in view 

 of the final stages to which it appears to point with rather definite directness. 

 As the photograph (Fig. 8) shows the center is dotted with dead clumps 

 of Scirpus cyperinus, with here and there, in the higher places on the floor, 

 a live one. Detailed studies of the remaining herbaceous vegetation in 

 such kettleholes resulted in the following list of plants. The dominant 

 species is given first, and in order of frequency, the others: 



Triadenum virginicum 



Gratiola aurea 



Slum cicutaefolium 



Lycopus rubellus 



Onoclea sensibilis 



