J. ARTHUR HARRIS AND JOHN V. LAWRENCE. 



The reader will have noticed three salient results in these 

 constants. First, the concentrations in Avicennia are distinctly 

 higher than in Rhizophora. Second, that the Florida collections 

 give distinctly lower constants than do those made in Jamaica. 

 Third, that there is a distinct reduction in the osmotic concen- 

 tration as the Florida plants leave the shores of the bay and 

 penetrate into the non-saline substratum of the Everglades region. 



C. Laguncularia racemosa Gaertn. f. 



At Port Henderson, Laguncularia racemosa occurs both in 

 the swamp and on the relatively sterile mud flats. 

 In the swamp the trees gave: 



Jan. 22, A 2.07, P = 24.9 



Jan. 22, A == 2.05, P == 24.6 



Mar. 26, A == 2.13, P ---- 25.6 



Mar. 30, A == 2.14, P ---- 25.7 



Average, A = 2.10, P --- 25.20 

 On the relatively sterile mud flats the concentrations were: 



Jan. 20, A = 2.90, P ---- 34.8 

 Jan. 25, A == 2.90, P == 34.7 

 Mar. 26, A == 2.79, P = 33.5 

 Mar. 30, A == 2.69, P -= 32.3 

 April 2, A :: 2.75, P == 33.1 



Average, A == 2.81, P ---- 33.68 



While it was not possible to assert that the osmotic concentra- 

 tion of the leaf sap of Avicennia was significantly higher when 

 growing on the sterile mud flats, there can be no reasonable 

 question of the relative values of the constants in the case of 

 Laguncularia. The five individual values from the flats are 

 without exception higher than the four available from the swamp. 



Two large trees of L. racemosa on the mainland shore of Bis- 

 cayne Bay gave : 



Miami, Feb. 17, A = 2.11, P = 25.3 



Cocoanut Grove, Feb. 26. A = 2.24, P = 26.9 



Young trees about i| m. high gave: 



Miami, Feb. 24, A = 1.81, P = 21.7 



Cocoanut Grove, Feb. 26, A = 1.73, P = 20.8 



