124 *" A. H. Graves, 



Haven Harbor, and not often even in a 105 per cent strength 

 solution of this. 



This would lead one to conclude a priori that the water of New 

 Haven Harbor does not contain as much salts as the 3 per cent quantity 

 of NaCl of the above experiment, and certainly not as much as 

 the 3.5 per cent of ordinary ocean water. 



On next ascertaining the percentage of salts contained in the 

 water of New Haven Harbor (procured, as in the first experiment, 

 from Savin Rock, near the entrance to the Harbor, at high tide), 

 I found by evaporation that the proportion was about 2.8 per cent, 

 as would be expected from the a priori conclusion. This amount, 

 therefore, explains why Ruppia plasmolyzed in a 3 per cent salt 

 solution, but did not plasmotyze in the water of New Haven Harbor. 



The sea water used, although purposely obtained at the entrance 

 to the harbor and at high tide, is, therefore, quite brackish. The 

 fact that Long Island Sound is considerably shut off from the ocean 

 and also has several large rivers emptying into it, probably 

 accounts for this. Very probably a similar percentage of salts 

 prevails all along the Connecticut coast. 



It is possible that the sea water used in Ganong's experiments 

 had a greater content of salt. If so, his results with Atriplex and 

 Hordeum mean somewhat more than the comparison in the table 

 indicates. 



An interesting point which should not be overlooked, since it 

 shows how delicately adjusted these plants are, comes to light in the 

 sometimes slight plasmolysis of Ruppia in the 105 per cent solution. 

 A little calculation shows that this is about identical in strength with 

 the 3 per cent salt solution, at which plasmolysis occurs very slowly. 

 It is perfectly clear, then, that Ruppia is adapted to life in water 

 containing a solution of sodium chloride and other salts ; that this 

 solution does not equal in strength that of the ocean in general and 

 hence may be termed brackish ; and furthermore, that Ruppia could 

 not live in such ocean water ; that this adaptation of the plant is 

 brought about through an ability to resist plasmolysis by maintain- 

 ing in some way a higher osmotic tension than prevails in submerged 

 fresh water plants, probably by the presence of an equalizing salt 

 solution in the cells themselves. 



