PHYSIOLOGY OF THE RED MANGROVE. 641 



Haas, strong sodium hydroxide solution (2.4813 N) was added to 

 sea water in small amounts and titrated by means of the gas chain 

 and the results given in a curve (p. 517) and in explanation of this 

 curve, the investigator says : " The titration curve shows that on 

 adding alkali to sea water the hydroxy! ion concentration at first 

 rises rapidly and then very slowly until the magnesium hydrate has 

 all been precipitated. After this further additions of alkali cause 

 a more rapid rise in the concentration of the hydroxyl ion, but this 

 rise is soon checked by the precipitation of calcium hydroxide. 

 After the calcium hydroxide is all precipitated further addition 

 of alkali will cause a corresponding increase in the concentration of 

 the hydroxyl ion." 



While we are not in this paper concerned primarily with the con- 

 centration of the hydroxyl ion, the formation of the successive 

 precipitations proves very interesting and it is phenomena of this 

 sort \^hich very likely cause the transpiration of the seedlings to 

 go on more actively in dilutions over 35 per cent, salt water when 

 planted in New Jersey soil and also to accelerate the transpiration 

 when planted in Tortugas shell sand in concentration less than 35 

 per cent, salt water. This latter group of results may be logically 

 explained by the hypothesis that with the atmospheric humidity and 

 temperature conditions the same, the transpiration would be ac- 

 celerated in the less highly concentrated solution, according to the 

 general law of transpiration, since the relatively pure calcium car- 

 bonate composition of the shell sand is less soluble than the more 

 complex New Jersey soil. It is also less finely comminuted than 

 the latter soil and as Reed^^^ has shown in the transpiration of 

 wheat seedlings that calcium carbonate added in small amounts to 

 water cultures or soil cultures has an accelerating effect, then also 

 the dilution of the sea water being less than 35 per cent, there are 

 smaller amounts of salt in it, so that on the whole the behavior in 

 regard to transpiration of these cultures is normal for the condi- 

 tions. 



The acceleration, however, of the rate of transpiration of cul- 

 tures in New Jersey soil and concentrations over 35 per cent, salt 



110 Reed, H. S., " The Efifect of Certain Chemical Agents upon the Tran- 

 spiration and Growth of Wheat Seedlings," Bot. Gaz., Vol. XLIX., 1910, p. 81. 



