OSMOTIC CONCENTRATION OF SAP. 2O5 



The water here was not abnormally saline. One sample 

 taken near the stilt roots of the collection of RJnzophora made 

 January 22 gave A = 2.05, P = 24.7. Another sample taken 

 near the pneumatophores of Avicennia gave A = 1.96, P = 



23-5- 



These determinations are in excellent agreement with those 

 given by Garry ('15) for sea water from southern localities. 

 Among his maximum values are A = 1.90-1.93 for Pacific 

 Grove, Cal., A = 2.04 for Beaufort, N. C., and A = 2.24 for 

 Naples. 



Back of the swamp which fringes a small bay with water too 

 deep for the growth of either of the species, is a considerable 

 area of almost sterile mud flat. Here the soil solution must 

 become highly concentrated by evaporation from the superficial 

 soil layers of the water left by occasional tidal overflow. We 

 had no means of measuring this, but a sample of water from a 

 slight depression, possibly diluted by a recent shower, gave when 

 frozen A = 5.77, P = 68.9. The mangroves occur only on the 

 edges of these mud flats. Practically the only other species found 

 here are the succulent-leaved halophytes, Balis maritima and 

 Sesuvium Portulacastrum. 



The determinations from subtropical Florida were based on 

 plants growing on the mainland shore of Biscayne Bay at Miami 

 and Cocoanut Grove and on the Everglades or Front Prairie, 

 as some term it, south of Florida City. 



A single sample of Biscayne water taken near the shore at 

 Cocoanut Grove gave A = 1.45, P=I74. This determination is 

 distinctly lower than those cited for the seacoast localities, and 

 more nearly comparable with the A = 1.09 for Kiel Harbor, 

 A = 1.30 for the open Baltic sea, or A = 1.66 as determined in 

 the Kattegat by Dakin and cited by Garry (loc. cit.}. 



The dwarfed mangroves growing on the Everglades near 

 Florida City are in a practically non-saline substratum. A 

 sample of water from a ditch froze at -.009, a value in good 

 agreement with that for bog and pond water as studied by Living- 

 ston ('04) and Transeau ('16). 



Scott ('16) classifies water with a depression of 0.03 as 

 fresh. 



