SELECTION 



339 



seed from the selected rows is sown in small multiplying plots. At the 

 Maine Station these plots are 1-2000 acre in area and usually in duplicate 

 (see Fig. 141). These plots are subjected to still further selection and 

 only the best retained. The next step is to sow each selected pure line 

 in one or more field plots. At Maine 1-40 acre plots are used and each 

 line is tested in duplicate or quadruplicate plots for several years and 

 only those that are superior in some respects at least to commercial 

 varieties are retained. At the Ohio Experiment Station according to 

 Williams, "In following the pure line method of selection, decided dif- 

 ferences in winter resistance, stiffness of straw, yield of grain and bread- 



FIG. 141. Planting board used in pure line work with small grains at the Maine Exper- 

 iment Station. It provides a plot Hooo acre in area with the plants nearly as close together 

 as when sown in the field. (After Surface and Zinn, Maine A. E. S.) 



making qualities have been found in the progeny of individual heads 

 selected from ordinary varieties of wheat." In Fig. 138 are shown two 

 very distinct pure lines of Gypsy wheat as they appeared in 1907. In 

 Figs. 139 and 140 the same pure line appears as grown in 1909 and 1915 

 respectively. This selection, has been introduced under the name of 

 Gladden. 



Ineffectiveness of Continued Selection Within Pure Lines. Con- 

 vinced of their failure to make any progress as a result of continued 

 selection within pure lines, some experiment stations have abandoned 

 this line of work. Hutcheson has reported on the results of 13 years 

 of continuous selection in six pure lines that were isolated by Hays 

 in 1901. These pure lines represent five of the sub-species of common 

 wheat, Triticum vulgare. In brief the method consisted of selecting each 

 year the best 100 grains from each of five or more best plants in each line. 

 This seed was planted at regular distances in centgener plots the following 

 year, each centgener representing a single plant selection. Hutcheson 



