1912] 



A. R. Rose 



431 



TABLE 2. 



Normal" Growth in 0.06 per cent. Ca{NOi)z Solution 



Date of Planting, 1911 



April I . , 

 April 24. 

 May 5 . . 



Rate of Growth per Plant in Millimeters 



ist Day 



22 

 14 

 15 



4th Day 



6th Day 



20 



17 



8 



11 



II 

 8 



Average per Day 

 for First Six Days 



17.8 

 12.7 

 12.3 



The individual plants in the several beakers showed no such 

 Variation among themselves, except occasionally ; when one or two 

 lagged behind the others, they were discarded as defective samples. 

 This shows that factors besides the Solutions used play an impor- 

 tant part and that it is therefore desirable to have all comparisons 

 o£ the effects on root growth made on plants grown in the same 

 period of time. If there must be comparisons between plants grown 

 at different times, there should be in each group control tests with 

 Solutions of the same chemicals and of the same dilution. In any 

 one period, the growths are quite comparable, as is shown by the 

 data for the following eight tests. 



TABLE 3. 



Data Showing Comparatively Uniform Rates of Growth in Various Nutrient 



Media During Given Periods 



