NOTES AND COMMENT 



Professor Ernst Bessey's interesting account of the angiospermous 

 areas known as "hammocks" within the pinelands of southern Florida 

 (Plant World, 14:268-277) recalls a theory of their origin which I formed 

 the last time I traversed this region, which was in coming north from a 

 cruise among the Florida Keys with Dr. Howe in the spring of 1909, on a 

 train of the Florida East Coast Railroad. We had been talking about 

 mangroves and their function as land-builders, a subject which has inter- 

 ested us on many occasions, and as the train swung away from the coast, 

 crossing the "prairies" toward the pineland margin south of Home- 

 stead, we remarked on the gradual substitution of mangrove clumps by 

 mixed mangrove and other hardwood shrubs and trees, the mangroves 

 extending to about the limit of saline influence. I formed the impres- 

 sion at that time of the possible parallelism of these hardwood islands in 

 the wide marshy stretches with the hammocks in the pinelands. An 

 elevation of the land of no more than two or three meters would so drain 

 it as to make the wet ground habitable by upland plants after the salin- 

 ity had been reduced by leaching, and during this doubtless gradual ele- 

 vation and leaching, the islands would provide a suitable nidus for the 

 establishment of more hardwood trees and shrubs and the various other 

 elements which go to make up the hammock association, while the pines 

 would be free to spread over the wider prairie areas. The upland 

 areas now occupied by pinelands and hammocks have doubtless been 

 elevated to their present position within a relatively recent geologic 

 time. Former studies of the hammocks with Professor Rolfs had brought 

 me to Professor Bessey's conclusion that the subsoil has little or nothing 

 to do with the striking floral differentiation of hammock and pineland, 

 it being the aeolian or coral-rock bottom of all south Florida, so far as 

 we could ascertain, and I then suspected an ancient origin. Professor 

 Bessey's paper has brought the topic again to mind and I present the 

 above theory as a contribution to the discussion. Will Professor 

 Bessey print such evidence as he has of the increase in size of the ham- 

 mocks? I know that some are said to cover more ground than they 

 formerly did, but my visits to the region have been of such short duration 

 that I could not satisfy myself of the truth of the proposition. 



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