40 BULLETIN 1489, U. S. DEPARTMENT OP AGRICULTURE 
silks within it. One of the best aids in preventing stray pollination is 
to apply an abundance of pollen of the desired kind. Very little 
pollen is needed to pollinate all of the silks on a shoot. Using 
plenty, however, reduces the likelihood of stray pollen grains func- 
tioning even if they reach the silks. 
Another method of controlled pollination that has been found 
highly efficient under some conditions has been described (36). 
With this method the shedding tassel is cut off and bagged with the 
ear shoot at the time the latter is cut back. The stem of the tassel is 
inserted in a small bottle of water attached to the stalk below the 
ear. Under favorable conditions the tassel will continue to shed 
pollen for two or. three days, the silks thus being pollinated as they 
emerge. 
SELECTION 
Selection is just as essential when working with selfed lines as 
in open-fertilized material. Indeed, it is more essential. The pur- 
pose of selfing is to fix what is selected. Fixation is relatively slow 
and may never be accomplished in open-fertilized corn. Characters 
become fixed relatively soon under self-fertilization and then are no 
longer modified. It obviously is important, therefore, that many of 
the unfavorable characters be eliminated as quickly as possible. 
Selection should begin with the plants furnishing the foundation 
stock and should be continued at each step where there is oppor- 
tunity. This means that only the best kernels on the ears from the 
best plants in the best individual rows of one season should be used 
for the next season's breeding stock. 
Selection for general kernel type should be practiced among the 
ears rather than among the kernels of the individual ears. The most 
careful selection among the kernels is warranted, however, when 
kernel characters such as endosperm texture, composition, or color 
are involved. Thus, selecting the white kernels from a selfed ear 
segregating for kernels with yellow and white endosperms will fix 
this character immediately. Selection of the deepest yellow kernels, 
on the other hand, will increase materially the proportion of homo- 
zygous, yellow ears in the progeny. Defective kernels already have 
been illustrated (pi. 5, C and D) and discussed briefly in connection 
with heritable characters. Some kernels are so defective that they 
would be eliminated by failing to germinate even if planted. Other 
defects. are not so marked, and, if not eliminated by conscious selec- 
tion, may become fixed as undesirable characters in otherwise excel- 
lent lines. 
Plant selection among and within selfed lines may be considered 
for convenience from two points of view, (1) eliminating the worst 
and (2) retaining the best. The first condition that confronts the 
breeder working with selfed lines of corn is the large number of 
abnormal plant types that occur. Albino, virescent, and pale-green 
seedlings are noted, as well as seedlings that are malformed in one 
way or another. Thus, in one breeding experiment, of the 2,750 
progenies from ears self -fertilized for the first time, 532 (14 per 
cent) segregated for some form of seedling chlorophyll abnormality 
(37). In another experiment 1,872 progenies were grown from seed 
selfed for the first time and representing 468 different stocks of 
