411] 



E. 8. Johnston 



213 



sidered, the values obtained being expressed as averages per 

 plant, for each of the four-week periods. The temperature 

 conditions, the evaporating power of the air and the intensi- 

 ty of radiation were recorded for each of the two exposures, 

 but these are left out of the present consideration. 



The results obtained from these three plant measurements 

 are shown in the accompanying table, wherein all the values 

 are expressed in terms of the corresponding value for the 

 period ending May 22. In this table the dates of beginning 

 and ending of the several culture periods are shown in the first 

 two columns. Each value given in the table represents an 

 average growth-rate representing a single plant, for a time 

 period of 28 days. 



EXPERIMENTAL DATA 



The different kinds of growth-rates are seen to vary inde- 

 pendently, from period to period, but two of the growth 



Data not obtained because of insect injury to plants. 



