190 



Pub. Puget Sound Biol. Sta. 



Vol. 2, No. 45 



l^lant. That this diffusion does not occur in normal sea water but is caused 

 by a change in permeability of the cells to chlorides brought about by the 

 fresh water is shown by the fact that the amount of chlorides in undi- 

 luted sea water is not increased by the presence of the kelps, but remains 

 exactly the same as in normal sea water, viz. 16.949 grams per liter. As 

 is to be expected, the preceding data shows that the amount of salts lost 

 increases with decreased salt concentration of the water. Undoubtedly 

 there is a very exact relation between the salinity of the water and the 

 outward diffusion of salts from plants, but variations in size of the plants 

 used preclude its determination here. 



Having shown that a loss of salts is one reason for the lowering of 

 the osmotic pressure of Nereocystis as the salinity of the water decreases, 

 it remained to be determined whether an abnormal intake of water oc- 

 curred at the same time which would so dilute the cell sap as to be a 

 factor in changing its pressure. It was thought that as the larger pro- 

 portions of fresh water had caused correspondingly greater losses of salts 

 from the plants, so also the more dilute concentrations of sea water might 

 be shown to cause the greater intake of water. The method followed was 

 to cut the bulbs from plants of as nearly the same" size as possible, being 

 careful to include enough of the stipe s.o that the cut would come below 

 the hollow part of the stipe, then to wipe these bulbs as dry as possible 

 with a soft cloth and weigh them carefully. One was then placed in 

 normal sea water, a second in an equal volume containing 10% fresh 

 water, a third in 20%, a fourth in 40%, and so on up to entirely fresh 

 water. After remaining in the various dilutions for 24 hours, the bulbs 

 were wiped dry in exactly the same way as before, then carefully weighed. 

 An increase in weight of those in diluted sea water above that occurring 

 in those in water of normal concentration indicates the absorption of 



Table 4. Shoxving the relation betzeeen the salinity of the water and the 

 increase in weight of Nereocystis bulbs left in it for 24 hours 



