126 



M. M. McCooL 



METHOD 



Analyzed salts of high quality were used in all experiments. The 

 normal (equivalent) solution was made the basis of comparison. A normal 

 solution of a monovalent salt contains one gram molecule in a liter 



of solution; while a normal solution of 

 a bivalent salt contains one half gram 

 molecule in a liter. In general, stock 

 solutions of N/1 were made and the 

 desired concentrations were subse- 

 quently prepared by dilution. In 

 some of the experiments wheat seed- 

 lings were used, in others Canada field 

 peas. The seeds were treated for 

 fifteen minutes with a solution of 

 formaldehyde containing one part of 

 the toxic agent in six hundred parts 

 of v/ater. Following this treatment 

 the seeds were left in running water 

 for twenty-four hours and were then 

 allowed to germinate between filter 

 papers over sphagnum or peat moss 

 saturated 'with, water. In this way 

 entirely satisfactory seedlings were 

 obtained. 



The seedlings, after having been 

 washed with distilled water, were 

 transferred to the culture solutions 

 when the radicles 

 inches in lengih. 

 development there 

 branching of the 

 of as nearh" uniform size as possible were chosen for the cultures. 



All glassware used in the experiments was carefully washed with the 

 chromic-acid cleaning mixture and then rinsed with tap water and distilled 

 water. Ordinary glass tumblers were used as culture vessels. Prehminary 

 experiments were made in order to determine whether or not there is 

 any appreciable difference in the growth of plants in distilled water and 



Fig. 1. — Showing method of making cul- 

 tures. The black paper shell has been 

 removed in order to expose the roots 



were about two 



At this stage of 



was no lateral 



roots. Seedhngs 



