Variation and Correlation in Timothy. 



453 



standard deviation was higher in 1905 than in either of the two succeeding 

 years, in which it was practically the same. 



Place variation in height. — The frequency polygon for height (Fig. 142) 

 shows a greater range of variation in 1907 than in the two preceding 



Fig. 142. Place variation in height. Heavy lines the curves 

 for the different years; dotted lines the summation 

 curves. 



years. In 1906 and 1907 there was a shifting of the population toward 

 the higher values. The empirical modes were at 40, 42, and 45 in 1906, 

 at 32, 39, and 41 in 1907, while in 1905 there were but two modes — at 

 36 and 40. Reference to the table of constants (Table V) shows the 



