INTRODUCTION 293 



Line Selection and Progeny Test. Turning now to the second of the 

 four general methods, we find that the progeny test of individual plants 

 was first used by Le Couteur and Shirreff. But it was Louis de Vilmorin 

 who first gave special attention to the value of the progeny test (1856) 

 and, contemporaneously with Hallet, practised the selection of single 

 plants, i.e., of pure lines in wheat, oats and barley, followed by separate 

 tests of their progeny. This method was first used in America by Willet 

 M. Hays who began the improvement of small grains at the Minnesota 

 Experiment Station in 1888. Convinced by the results of extensive 

 variety tests that systematic breeding would be required in order to 

 secure a marked increase in yield of first class wheat, Hays devised the 

 centgener method of grain breeding, which, briefly, consists of planting 

 about 100 seeds from each selected plant in trial plots; the more promising 

 centgeners being selected for testing on a larger scale. Hays' work re- 

 sulted in the isolation in 1892 of two plants whose progeny within a 

 decade were grown on thousands of acres. Although many new strains 

 were secured, the rigid tests of several consecutive years in which the 

 most promising strains were compared with each other and with the best 

 commercial varieties, resulted in securing but few really superior varieties.. 

 However, these made possible an increased production of wheat through- 

 out the northern states and in Canada. 



The Swedish Seed Association was organized in 1886 and established 

 an experiment station at Svalof. During the first 5 or 6 years only 

 mass selection was practised, but soon after Hjalmar Nilsson became 

 director in 1891 the "Vilmorin Method" was introduced. At Svalof 

 it came to be known as the "System of Pedigree" or "Separate Culture." 

 Nilsson was led to adopt this system as the method for originating 

 new varieties by the accidental discovery that the only wheat plots 

 that were entirely uniform were grown from single plant selections. The 

 new varieties produced at Svalof are now grown throughout the agricul- 

 tural portion of Sweden. This station is also engaged in the systematic 

 improvement of peas, clovers, grasses and potatoes. All this work is 

 based on mass and line selection followed by field tests and distribution. 



The first application of the pure-line conception to a naturally cross- 

 fertilized plant was made by Shull and by East working independently 

 with corn. By guarding and self-pollinating individual plants for suc- 

 cessive generations, a number of morphologically distinct strains were 

 isolated, thus proving that the original population was a mixture of 

 biotypes. These same methods, however, had been employed for a 

 number of years by Webber, Hartley, and probably others in working 

 with corn, cotton, and other naturally cross-fertilized plants. In recent 

 years the plant-row test has been used for the improvement of old 

 strains or production of new ones. In Germany, von Lochow in 1894 



