50 
BULLETIN 1489, U. S. DEPARTMENT- OF AGRICULTURE 
esting to note the high average yields of these crosses, the real im- 
portance attaches to those crosses that yield most. Thus, in these 
data, 5 crosses yielded more than TO bushels per acre, the highest 
yield being 74.1 bushels, or 35.5 per cent more than Hogue. 
Selection within selfed lines as a basis for corn improvement has 
been under trial at the Minnesota station for a number of years. 
The results of some of these experiments recently have been sum- 
marized by Hayes (30, p. 351) as follows : 
In 1924, of a total of 21 double crosses tested, 3 yielded less than the higher 
yielding commercial variety. One double cross exceeded the better commercial 
variety by 30 per cent. The 7 double crosses in which dent inbred strains 
were used yielded 13 per cent more on the average than the better variety, while 
12 flint-dent crosses average 9 per cent more than the better variety. Of 2 
flint double crosses one gave a low yield and the other yielded rather well. 
The results in 1925 were similar and certainly indicate that double crosses in 
which desirable appearing selfed lines are used may be expected to yield more 
than the present standard varieties. 
The experiments at the Minnesota station also have included lim- 
ited experiments with synthetic varieties through the F 2 generation. 
The results of these are given in Table 9. 
Table 9. — Yields of the F 2 generation of synthetic varieties and of the commer- 
cial parent varieties at University Farm, St. Paul, Minn., in 1925 
[After Hayes (30, p. 352)] 
Selfed lines 
used in 
Acre yields 
Designation 
synthetic 
variety 
Bushels 
Increase 
above (+) 
Num- 
ber of 
years 
selfed 
Num- 
ber of 
lines 
or decrease 
below (— ) 
parent 
variety 
(per cent) 
Minnesota No. 13: 
51.3 
I 45.3 
44.8 
i 47.5 
51.9 
} CO. 5 
40.3 
43.3 
43.9 
40.1 
Synthetic 
1 1 
5 
3 
1 
-11.7 
Rustler: 
Commercial 
Synthetic 
f 1 
J 2 
1 3 
I 4 
2 
7 
5 
3 
+6.0 
Northwestern Dent: 
{ I 
2 
8 
+16.6 
King Phillip: 
3 
11 
+7.4 
Longfellow: 
3 
8 
-8.7 
It should be emphasized that these data give the results of pre- 
liminary experiments to determine the possibilities in this method of 
utilizing selection within self -fertilized lines, not the yields of strains 
of known productiveness. In view of this fact the results are 
extremely promising. 
The Delta Prolific variety of corn, originated by the Bureau of 
Plant Industry, has been among the higher yielding varieties in a 
number of varietal experiments in eastern Arkansas and in some 
