2O6 J. ARTHUR HARRIS AND JOHN V. LAWRENCE. 



III. PRESENTATION OF CONSTANTS. 

 A. Avicennia nitida Jacq. 



The leaves of trees of Avicennia nitida from the Port Henderson 

 swamp proper gave: 



Jan. 20, A = 4.26, P = 51.1 

 Jan. 22, A = 3.29, P = 39.4 

 Jan. 22, A = 3.56, P = 42.7 

 Mar. 26, A = 3.47, P = 41.5 

 Mar. 30, A = 3.60, P = 43.2 

 April 2, A = 3.84, P = 4.6.0 



Average, A = 3.67, P = 43.98 



Plants from the edges of the sterile mud flats gave the following 

 values : 



Jan. 20, A = 3.67, P = 43.9 

 Jan. 25, A = 4.55, P = 54.4 

 Mar. 26, A = 3.90, P = 46.7 

 April 2, A = 4.29. P ---- 51.3 



Average, A = 4.10, P = 49.08 



Thus on the southern coast of Jamaica Avicennia nitida is 

 characterized by leaf sap showing a concentration of about 45 to 

 50 atmospheres. In view of the considerable variation in the 

 individual determinations it is impossible to assert that the con- 

 centration in the plants growing on the edge of the sterile mud 

 flats is significantly higher than that of those occurring in the 

 swamp proper. 



For the most part, the leaves taken were fully mature, but on 

 Jan. 2oth, it was possible to secure some new-growth leaves in the 

 collection from the mud flats. These gave A = 3.56, P = 42.6 

 as compared with A = 3.67, P = 43.9 for the old leaves. Thus 

 the old and the young organs show about the same concentration 



* 



of tissue fluids. 



Two collections of the leaves of seedlings, about 1-2 dm. in 

 height, growing in mud or shallow water in the rather dense shade 

 of the trees gave: 



Jan. 20, A = 4.47, P = 53.5 

 Jan. 22, A = 4.02, P = 48.1 



