Or. E. Briggs, P. Kidd, and C. West 



209 



In the case of the results cited above Kreusler states that the seed 

 was selected with care. The weight of the seed seems to have varied, 

 for example, from -35 to • U) i*m. in the year 1877. He gives no idea as 

 to the coefficient of variation of the samples of seeds nor does he give the 

 coefficient of variation of the dry-weight of the plants for each harvest, 

 but merely the mean value. One cannot therefore say what is the probable 

 error of the figures given for Unit Leaf Rate. Again, the number of 

 plants taken at each harvest seems to have been determined rather by 

 labour involved than by accuracy of results desired. This is perfectly 

 natural when the magnitude of the work is considered. In the case of 



Temp. 



6 8 10 



Weeks from Sowing. 



U.L.R. 



1 2 



— — ■ — Sunshine. 



Fig. 6. Badischer Friih— Mais 1878. 



the earlier harvests about 100 plants were used; this number was reduced 

 to about 40 in the later harvests. The number used, for the determina- 

 tion of leaf-area was usually one-half the number harvested. 



In order to obtain an idea of the order of probable error to be ex- 

 pected, 40 plants were gathered this year by the authors from an 

 ordinary crop of maize. These gave a mean dry-weight of 6-38 gms. with 

 a probable error of -25 ±. 



In Fig. 3 the Unit Leaf Rate curves for five different varieties of maize 

 grown at the same time under similar conditions are presented. The 

 fluctuations in these curves for the first eight weeks show a good agree- 



