128 BOTANICAL GAZETTE [AUGUST 



It is noteworthy that the Ca and K, which are added to inhibit 

 the toxic effect of NaCl, are themselves poisonous at the concentra- 

 tion at which they are here employed. 



These antagonistic effects of Ca and K toward a pure NaCl solu- 

 tion were illustrated still more strikingly in experiments on the egg 

 of Fundulus. The newly fertilized eggs of this fish develop equally 

 well in sea water and in distilled water, but die in a pure m/2 NaCl 

 solution without forming an embryo. If, however, a small but defi- 

 nite amount of a salt with a bivalent kation, even of such poisonous 

 salts as BaCl 2 , ZnSO 4 , and Pb(CH 3 -COO) 2 , is added, the eggs will 

 produce embryos. From these and similar observations LOEB was 

 led to formulate his conception of the necessity of physiologically 

 balanced salt solutions, in which are inhibited or counteracted the 

 toxic effects which each constituent would have if it alone were 

 present in the solution. 



The blood, the sea water, and to a large extent RINGER'S solution, 

 are such physiologically balanced salt solutions. The observations 

 of HERBST, as well as those of RINGER, are easily explained on this 

 basis. The fact that the elimination of any one constituent from 

 the sea water makes the solution unfit to sustain life does not prove 

 that the eliminated substance is needed by the animal for any purpose 

 other than to counteract the poisonous action of some other constit- 

 uent of the solution. 



Botanists have not thus far made use of these conclusions, for the 

 obvious reason that facts similar to those mentioned above have not 

 been observed in plants. I have recently made a number of experi- 

 ments which show that there exist in plants phenomena similar to 

 those observed by LOEB on Fundulus and other marine animals. 



The species of marine plants chosen for investigation may be 

 divided into two groups: 



Group i comprises plants which can live a long time in distilled 

 water. It includes the following: BLUE-GREEN ALGAE, Lyngbya 

 aestuarii; GREEN ALGAE, Enteromorpha Hopkirkii; FLOWERING 

 PLANTS, Ruppia maritima. 



Group 2 is composed of plants which quickly die in distilled 

 water. It includes the following: GREEN ALGAE, Enteromorpha 

 intestinalis; BROWN ALGAE, Ectocarpus confervoides ; RED ALGAE, 



