PLANT BREEDING 179 
When thoroughly dry, the product of each plant is weighed, 
and only a few of the heaviest groups of heads are kept for seed. 
2. The second year about a hundred of the seeds of each 
mother plant are planted in a group (bundred-group or cent- 
gener). To each such group is given a special designating 
number. Heads of several of the best plants in each hundred- 
group are reserved for seed. The total produced by each 
hundred-group is weighed. This enables the experimenter to 
estimate the comparative value of the mother plants. 
3, The third year the process of the second year is repeated. 
+. The fourth year the same process is repeated. 
5. The fifth year the most promising varieties are planted 
in small fields in the ordinary way. Those varieties which yield 
abundantly in the field and turn out well in the milling tests 
which are applied to the harvested grain, are distributed among 
farmers for seed wheat. 
A. new variety can soon be introduced over an immense 
territory. It is estimated that in fifteen years from the time 
of planting one seed its descendants might be made to cover 
more than 5,000,000 acres of wheat fields. 
Wheat breeding is still making such rapid progress that at 
present it is not possible to say how much the quality and 
quantity of our wheat crop may yet be improved by the in- 
troduction of better varieties. The total number of acres in 
the United States differs considerably from year to year. It 
seems likely, as a rule, to exceed 45,000,000.1 The average 
yield ranges between 10 and 15 bushels per acre, although it is 
possible, with the most improved seed on the best soils, to raise 
more than 40 bushels per acre.? Choice of the best seed would 
undoubtedly increase the average yield 5 or more bushels 
per acre. It is easy to see how important a gain this would be 
if it were calculated in terms of the current price of wheat. 
1See Carleton, “The Future Wheat Supply of the United States,” 
Science, August 5, 1910. 
2See Hopkins, Svil Fertility and Permanent Agriculture. Ginn and 
Company, Boston. 
