34 BULLETIN 1489, IT. S. DEPARTMENT OP AGRICULTURE 
Two varieties, A and B, are grown in alternate rows in a small 
field sufficiently isolated from other corn to prevent mixing. If 
variety B is to be the pollen parent the first year, the tassels are 
pulled' from all of the A plants as they appear and before they 
have shed any pollen. The silks on the A plants then are pollinated 
by pollen from the B plants, and the ears represent the cross A X B, 
giving the pistillate (female) parent (A) first. As none of the A 
plants shed pollen, the ears of B are pure, and seed may be selected 
from them to maintain this variety. Either of two plans may be 
followed the second year. If enough hybrid seed for two years was 
produced the first year, only a small plat of A need be grown in 
order to maintain a stock of this variety. This plan should be 
followed unless it is known that the reciprocal crosses of the varie- 
ties, in this case A X B and B X A, are equal in productiveness. If 
they are equal, A and B may be planted in alternate rows again the 
second year, but this time the B plants are to be detasseled. Seed 
of the cross B X A and pure seed of A then will be obtained. The 
work of the third year will be like that of the first year in either 
event, and seed of both parents and the cross may be obtained 
conveniently. 
The tassels may be pulled easily just when they are emerging 
from the " boot," as the upper whorl of leaves that incloses the 
tassel frequently is called. The early morning is the best time for 
this work, as tassels can be pulled more easily and plants may be de- 
tasseled then that otherwise might shed pollen later in the day. 
During the peak of the tasseling period the crossing plat should be 
gone over each day, whereas every other day is often enough at the 
beginning and toward the end of the tasseling jDeriocl. 
PLACE OF VARIETAL HYBRIDS 
There are certain specific conditions under which a larger propor- 
tion of high-yielding first-generation crosses possibly may be ex- 
pected than that indicated by the experiments referred to. Crosses 
between early flint and dent varieties have given promising results 
for growing under short-season conditions. Similarly, crosses be- 
tween single-eared and prolific varieties have shown possibilities 
for use in the southern edge of the Corn Belt. Even so, the crosses 
must be tested individually over a series of years and on different 
soils before the profitable ones can be known. Moreover, even if a 
cross, between Reid and Learning for example, were shown to be 
high } 7 ielding, this evidence would apply only to the cross between 
the specific strains that were used as parents. Crosses between other 
strains of these varieties might produce inferior yields. 
Growing F 1 crosses between varieties of corn has possibilities as 
a means of obtaining increased yields. It also is somewhat com- 
plicated and can be utilized only after specific crosses have been 
shown to be profitable experimentally. The method does not seem 
to offer the promise that crosses between selfed lines do under most 
conditions and probably has little place as a method of increasing 
corn yields. On the other hand, it may be of much importance under 
special conditions when it is desired to combine in the F x hybrid the 
dominant traits from each of two varieties. 
