64 AMERICAN BREEDERS' ASSOCIATION. 



nated and do originate one from another by mutation. Several such 

 methods have already been devised and their value is becoming daily 

 more appreciated. One of the earliest of these isolation methods was 

 that used by Vilmorin in the improvement of the sugar beet. It is 

 known as " Vilmorin's Isolation Principle," and consisted as applied 

 to beet culture, in the growing of the offspring of individual seed 

 plants in parallel rows one row from each parent and the use of 

 a portion of each row in determining the percentage of sugar of the 

 particular hereditary line to which that row belonged. Seed plants 

 for the next year's crop were then selected from the rows showing the 

 best performance record, i. e., the highest sugar content associated 

 with other desirable qualities. Johannsen has demonstrated that this 

 method is fundamental in the improvement of beans by selection, 

 since what appeared to be a homogeneous variety possessing only 

 fluctuating variations was found capable of being at once separated 

 into a number of distinct hereditary lines each with its own charac- 

 teristic size, form, and weight of seed, width of hull, etc. The ear- 

 Etest is essentially the same method applied to the breeding of 

 

 The centgener method," designed by Mr. Hays for use in grain- 

 ding experiments at the Minnesota State Experiment Station, is 

 one of the best and most complete isolation methods yet devised, and 

 the splendid results in the immediate discovery of several wheats of 

 surpassing merit have brought the method into deserved prominence. 

 To still another agricultural genius is due the credit of having 

 worked out an isolation method in the breeding of economic seed crops, 

 and of having achieved noteworthy results quite independently of the 

 mutation theory, but his method like those already mentioned owes its 

 preeminent success to its accord with that theory. This man is Dr. 

 Hjalmar Nilsson, Director of the Swedish Agricultural Station at 

 Svalof. Dr. Mlsson has doubtless had from the first a clearer con- 

 ception than had any one else, of the true constitution of the economic 

 crops, for within a year after he was made Director of the Svalof Sta- 

 tion in 1890, he had recognized the composite character of the several 

 named horticultural and agricultural varieties, and had decided that 

 the elementary species is the unit with which the economic breeder 

 must deal. Up to that time the work of the Swedish Station had 

 consisted largely in the testing of named varieties, each variety being 

 accepted as a horticultural unit; but, upon the adoption of the n<>w 

 point of view, the director and his corps of assistants set to work to 

 separate the elementary forms making up the several varieties, and 

 to study and tabulate their characteristic differences. They found that 

 every elementary species has its own normal mean condition of its 

 several morphological and physiological features including all those 

 characters which determine the success or the failure of an economic 

 crop. In the fifteen years during which this discovery has formed the 

 basis of operations at Svalof, that station has become famous for its 

 achievements, despite the fact that all of its publications have been 





