Duggar — Relation of Marine Algae to Salt Solutions. 485 



these plants. It is not desirable to discuss in detail the mat- 

 ter of the magnesium-calcium relationship at this time, but a 

 brief comparison of the effects of some common salts on 

 phanerogams may be included. The following table from 

 Kearney and Cameron shows the limits of concentration per- 

 mitting roots of white lupine to retain their vitality for 

 twenty-four hours. 



Of these same substances, however, the concentrations 

 which absolutely prevent growth arrange themselves in a 

 different manner, thus : — 



In my own studies, the arrangement of , the salts according 

 to their killing action remains practically the same as 

 that where the line of health is indicated, as is cleary shown 

 in the following table. 



This variation in the resistance of marine algae to nutrient 

 salts added to sea water is not proportional to the relative 

 amounts of these salts already present in sea water. This 

 may readily be seen by a glance at the composition of sea 

 water in the vicinity of Naples. An early analysis by Roth* 



♦ Roth, — Chem., Geol. I. p. 524. 



