144 University of California Publications in Agricultural Sciences [Vol. 3 



duplicate cultures containing one salt in varying concentrations in 

 each, or one salt constant and varying concentrations of a second salt. 

 In some instances both salts varied but only in concentration, the 

 same ratios being maintained. These are few. The number of con- 

 centrations reported vary from three to fourteen in a series, depend- 

 ing upon the salt used. Before two salts were taken together, the 

 effects of each separately upon the plants were determined. Usually 

 this meant only the establishment of the toxic limits of the salts em- 

 ployed when used in the nutrient solution. Several series of this kind 

 are not reported here, as no analytical work was done upon them. 



Calcium and magnesium salts were used to a large extent because 

 of the fact that their kations can be determined with less experi- 

 mental error than most other nutrient salts where the small amounts 

 of material dealt with here are considered ; also it was of interest 

 to determine whether or not there is a lime-magnesia ratio for plants 

 grown under carefully controlled conditions. Copper, zinc, iron, and 

 mercury salts were used because of the fact that their toxic and antag- 

 onistic effects have not been previously determined as regards absorp- 

 tion. Potassium chloride was the only monovalent salt used. 



A longer growing period than has usually been employed was con- 

 sidered important. McGrOwan, 23 in conducting experiments in pure 

 solutions of sodium, potassium and calcium chlorides, found growth 

 better in the first two at the end of six days, but far superior in a 

 solution of calcium chloride in twenty-five days. In a qualitative way 

 the same relationships were observed in the present investigation. It 

 seems reasonable to assume that the results obtained in six weeks with 

 plants are more nearly representative of the true effect of various 

 solutions than those obtained in two or three day periods or even in 

 three week periods. But it is not assumed that the results herein 

 reported are the same as those which might be obtained were the 

 plants grown to maturity. It is hoped that more data may be pre- 

 sented shortly on this point. 



In the following section, in which the experimental results are 

 given, the time factor and the basic nutrient solutions are constants. 



Experimental Data 



All analyses are reported as percentages of the dry weights of the 

 plants. To make the results obtained as clear as possible, graphs and 

 photographs have been used throughout as well as the tables giving 

 the actual percentage composition of the plants. 



25Bot. Gaz., vol. 45 (1908), p. 45. 



