128 ILLINOIS STATE ACADEMY OF SCIENCE 



The seedlings are arranged and numbered according to 

 their size on the first day, that is, on the day they were 

 placed in the constant temperature case and six days after 

 planting. Following the method given in the articles cited, 

 these 75 seedlings are arranged in five groups, or quintiles, 

 according to their size on the first day. In order to avoid 

 having seedlings of the same size fall in two different quin- 

 tiles, the number of plants in the quintiles varies. Thus, 

 Quintile I contains the 15 smallest seedlings on each day 

 of measurement. Quintile II contains the 16 next larger; 

 Quintile III, the 17 next larger; Quintile IV, the 12 next; 

 and Quintile V, the 15 largest ones. The number of seed- 

 lings in the respective quintiles was maintained during 

 the growth period. In but two cases, after the initial dis- 

 tribution, did two seedlings fall on the separating line of 

 contiguous quintiles. In these cases one of the seedlings 

 was arbitrarily placed in the next highest quintile. The 

 quintile distribution for each successive day for seedlings 

 starting in the several quintiles is given in Tables 50 to 

 54. These tables give the total number of distributions, 

 excluding those of the first day, when, of course, all distri- 

 butions were in the particular quintile to which the seed- 

 lings were originally assigned, and also the mean quintile 

 position for each day. A study of the tables shows that by 

 the sixth day only 3 of the 15 seedlings which started in 

 Quintile I are still in this quintile and by the tenth day only 

 2 remain. Three of the 15 reach Quintile V by the ninth 

 day. Out of the total of 165 distributions only 42, or 25.5% 

 are in Quintile I. The mean quintile position for these 

 seedlings changes from 1 on the initial day to 3 on the 

 eleventh and twelfth days. This final mean quintile posi- 

 tion is above the general mean, which owing to the differ- 

 ence in the number of seedlings in the several quintiles is 

 2.95. Only 18.8 ^r of the total number of distributions for 

 seedlings starting in Quintile II fall in this quintile. For 

 Quintile III the per cent is 20.9; for Quintile IV, it is 25; 

 and for Quintile V, 25.5. The mean quintile position for 

 seedlings starting in Quintile V drops from 5 on the first 

 day to 2.87 on the ninth day. The curves for the mean 

 quintile positions on the successive days are plotted in Plate 

 V. As is to be expected where the variation can be in either 



