2 BULLETIN 1354, U. S. DEPARTMENT OF AGRICULTURE 
Charles White, designated U. S. Selection No. 201, in 1916. Mass 
selection was begun at the same time, to provide a standard for 
measuring progress and in the hope of establishing a variety of 
economic value for the locality. In selecting within self -fertilized 
lines, the better plants of a line, the better lines of a strain of related 
lines, and the better strains of No. 201 were chosen in general. The 
basis of selection was the production of sound grain per plant, con- 
sideration being given also to maturity, general plant proportions, 
and freedom from extreme abnormalities. Data showing the effects 
of mass selection through six generations and the productiveness of 
crosses made following four generations of selection within self- 
fertilized lines have been published (6). 2 The present bulletin, a 
second progress report, presents the data obtained in 1922 and 1923. 
These include (1) a comparison of the productiveness of successive 
generations of self -fertilized lines of corn, (2) a comparison of crosses 
between these lines, and (3) data on the yields of crosses between 
lines after six generations of self-fertilization, the yields of analogous 
crosses following four generations of self-fertilization having been 
presented previously (6) . 
THE COMPARISON OF SUCCESSIVE GENERATIONS 
The number of generations of self-fertilization to practice before 
comparing crosses between lines of corn has been a subject of dis- 
cussion among corn breeders. The comparison of the productive- 
ness of successive generations of self-fertilized lines and their crosses 
was made in the hope that it might give some information on this 
question. 
GROWING SEED FOR COMPARISON 
In order to compare the different generations fairly it was necessary 
to have seed of each that was of the same age and that had been 
grown under identical conditions. The remnants of the breeding 
ears had been saved each season. Seed from some of these remnants, 
together with seed from the 1921 breeding ears, was planted in indi- 
vidual rows at the Arlington Experiment Farm, Rosslyn. Va., in 1921. 
Some of the plants representing each selected line were self-pollinated, 
and others were crossed with other selected lines. In making cross- 
pollinations a mixture of pollen from two to five plants was used to 
obtain a better representation of the staminate parent. 
METHOD OF COMPARISON 
The productiveness of the different lines and crosses was compared 
in cooperation with the Tennessee Agricultural Experiment Station 
at Knoxville, Tenn.. in 1922. The successive generations of one 
strain were compared in a unit consisting of a number of rows 90 
hills long. The individual plats consisted of single rows of 10 hills 
with 2 plants per hill, making 20 plants per plat, facts permitting. 
The comparisons of crosses between strains were made in a similar 
manner. The plan of planting one of these units, that in which 
the crosses between the 3-1- and 5-1- strains were compared, is 
shown in Table 1, as an example. The index numbers used to indi- 
cate the location of the different crosses in this table correspond to 
those in column 1 of Table 2. 
The serial numbers (italic) in parentheses refer to "Literature cited," at the end of this bulletin, 
