100 Pearl and Surface. 



time to time so that the number of plants completing the season was 

 slightly less than sixty in each case (cf. tables 25 to 27). 



The growth of the plant was recorded by measuring the total 

 height. In order to do this it was necessary to have a base to measure 

 from which would not shift with the growth of the plant or would not 

 be altered by the cultivation. To do this a small stake, one inch square 

 and fifteen inches long, was driven into the ground near each plant to 

 be measured. These stakes were driven down until the tops were 

 nearly level with the ground. This formed a solid base from which all 

 measurements were taken. 



The measurements were made with a meter stick to which a 

 sliding arm, about eight inches in length, was attached. The measure- 

 ments were recorded to the nearest millimeter. 



From the nature of a young corn plant it is somewhat difficult 

 to obtain a good character for measuring its height. After some expe- 

 rimenting it was decided to use the height to the tip of the tallest leaf 

 when this was stretched up. This is by no means an ideal character. 

 In the first place we are measuring the combined growth of two things 

 viz., the leaf and the stalk internodes. The second difficult}' lies in 

 the fact that as each new leaf unfolds there comes a time when it 

 exceeds in height the preceding leaf. This means that one is measuring 

 the height, first to the tip of one leaf and then to the tip of another. 

 These difficulties did not prove to be as serious as was at first expected. 

 They are undoubtedly responsible for certain irregularities in the 

 measurements. These will lie discussed more in detail when we come 

 to deal with the data. 



It is realized that in certain respects the present data are unsatis- 

 factory. A better measure of the growth would have been the total 

 weight of the plant. Obviously, however, it is impossible to obtain such 

 data at fre(iuent intervals on the same plant. For the object we had 

 in view, no better measure of growth suggested itself at the time these 

 measurements were taken. 



In addition to the observations on leaf height noted above, 

 measurements of the tassel height were also taken as soon as the 

 tassels appeared. The tassel forms an excellent character for measuring 

 growth but it appears too late in the development of the plant to be 

 of much use. During the latter part of the season both the leaf height 

 and the tassel height of each plant were measured. The measurements 

 are dealt with separately in everj' case. 



