INTRODUCTION 293 
Line Selection and Progeny Test.—Turning now to the second of the 
four general methods, we find that the progeny lest 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, z.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 
Digitized by Microsoft® 
