19 



but no account was taken of them unless the difference in 

 level was at least 2mm ; in some exceptional cases it was as 

 much as 18mm. That no such correlation exists in these 

 seedlings is shown by a comparison of the root, shoot, and 

 plant weights of an abnormal seedling with the corres- 

 ponding average weights of the group to which it belongs. 

 Such a comparison shows that the weights of the seedling 

 are sometimes above and sometimes below the average 

 weights. 



7. Quintile Distributions. 



An article by Pearl and Surface (14) on "Growth and 

 Variation in Maize" states, on page 120, "There is, then, a 

 marked tendency for the plants which were relatively small 

 at the beginning of the season to have remained, on the 

 average, relatively small throughout most of the season." 

 Or, to quote further (page 170), "Extreme variants at the 

 beginning of the season tend strongly, on the whole, to re- 

 main extreme variants during the whole season." This 

 tendency is said to be due to the effect of internal rather 

 than to external stimuli. 



Reed, (15) in studying growth and variability in Helian- 

 thus, follows the method of argument of Pearl and Surface 

 and concludes that, "Plants which started in a given quar- 

 tile showed a well-marked tendency to remain in that quar- 

 tile during the entire grand period of growth. Plants which 

 were small at maturity were generally small from the be- 

 ginning, those which were large at maturity had a well- 

 marked superiority from the start." He, too, thinks plants 

 show this tendency because of inherent factors. 



In order to determine whether the seedlings used in the 

 present experiments revealed similar traits the data for all 

 seedlings which were grown in water and which were 

 placed in the 25 C temperature case on the sixth day after 

 placing them to germinate, were collected. A group of 

 75 seedlings containing individuals from seeds of all den- 

 sities and sizes was thus obtained. The heights of these 

 seedlings on each successive day and the density and size 

 of the seeds from which each grew are given in * Table 49. 



*It has been found necessary in the publication of these experiments to omit 

 Tables 1-17, 21-36, 40-49. These tables can be found in the original thesis at the 

 Library of the University of Illinois. 



