NILSSON'S DISCOVERY 61 



reason to doubt their validity was at hand, and moreover, the 

 evidence was only scanty and widely scattered, without 

 affording sufficient material of facts for a thorough criticism. 

 The results of the English breeders were hardly accessible at 

 that time, and so the Svalof experiments had to begin by 

 following the German principle. Summing up the princi- 

 pal features, we may state that it commenced with the choice 

 of a certain number of ears, and cultivated their progeny as a 

 mixed family, in which, year after year, the best heads were 

 chosen in adequate number for the continuance of the race. 



The experiment station at Svalof has accepted the prin- 

 ciple that the selection cultures must be made on the sams 

 soil and under the same conditions as the ordinary field cul- 

 tures. Especially, the distances at which the seeds were 

 sown from each other had to be the same, this being a point 

 which had often been dealt with in another way, since by a 

 somewhat larger relative distance, the treatment and the 

 final distinguishing of the single plants is notably facilitated. 

 This principle has been found to be reliable, and has been 

 kept unchanged through all the periods of experimentation, 

 which have supplanted almost all others. 



Moreover, the methods of testing and comparing have 

 been largely improved. Instead of the personal apprecia- 

 tion of the qualities of the ears, accurate measurements have 

 been adopted. An elaborate book-keeping required the 

 statement of a large number of qualities by short indica- 

 tions, and figures came to be preferred to descriptions. The 

 length of the ears was given, their form indicated by width 

 and breadth, and by the place where both reached their max- 

 imum value. The density could be measured by the num- 

 ber of nodes and spikelets, and in the latter, the number of 

 single kernels could be noted. Other valuable qualities 

 required separate tools and instruments, and even the degree 

 of brittleness had to be expressed by figures. 



