672 BOWMAN— THE RED MANGROVE. 



concentration of 88.5 per cent, dilution of salt and fresh water. 

 An explanation of these phenomena seems to be offered in the ex- 

 periments of Haas on the hydrogen ion concentration and the be- 

 havior of sea water on the addition of alkali. 



8. The relations of tannic acid and dextrose in the hypocotyl, as 

 deduced from the experiments, show that there is no definite de- 

 crease in the quantity of tannin with a corresponding increase in the 

 amount of dextrose as growth of the seedling progresses. The rela- 

 tion is constant and in plants of successively large growth a ratio 

 exists between the two substances approximating % to i per unit 

 increase. A series of tests for the enzyme, tannase, showed this 

 enzyme to be absent, thus tending to confirm the view that the 

 tannin in the hypocotyl is not a reserve food. 



10. It is set forth that the red mangrove is facultative in its 

 growth, regarding salinity of water and inshore and offshore situa- 

 tions, as shown in a comparative study and measurements of leaf 

 sections. 



10. It is set forth that the red mangrove is facultative in its 

 physiologic relations to fresh and salt water, but that it needs salt 

 water for its optimum development and that there is a correlation 

 between the height and abundance of trees and the salinity of the 

 water in which they grow. By experimental methods it was de- 

 termined that the condition of the trees and their distribution in 

 estuaries depends on the presence of top and bottom layers of fresh 

 and salt water moving in opposite directions. 



11. Finally, by means of data secured from various sources it 

 is shown that the red mangrove may be regarded as a plant of 

 economic importance, not only as a source of tannic acid and char- 

 coal, but also as a ballast-retaining plant in tropical coastal engi- 

 neering work. 



