38 BULLETIN 1489, U. S. DEPARTMENT OF AGRICULTURE 
HAND POLLINATING 
In order to control pollination definitely, whether in selfing or 
crossing, it is necessary to pollinate by hand. Briefly, hand polli- 
nating consists (1) in protecting the silks from any pollen until 
enough silks have emerged; (2) in collecting and applying uncon- 
taminated pollen from the selected plant; and (3) in again protect- 
ing the silks from any stray or foreign pollen. Paper bags are 
used for protecting the silks before and after pollinating and for 
collecting the pollen that is used. This operation is relatively simple, 
although the large numbers of pollinations that must be made require 
much time and attention in the aggregate. 
Normally, most corn plants begin to shed pollen a day or more 
before their silks appear. The ear shoots usually emerge from between 
the leaf sheath and culm at one or more nodes at about the time of 
tasseling (pi. 9), and two or more days elapse in general between 
the first appearance of the ear shoot and the emergence of the earliest 
silks from the enveloping husks. 
Pollen usually is shed first from the anthers toward the tip of 
the central spike of the tassel (pi. 2, A). Shedding then proceeds 
downward along the central and lateral spikes. The same tassel 
may continue to shed pollen for a week or more, although there is 
much variation in the duration of shedding, depending upon the 
strain of corn and the condition of the weather. Pollen is shed 
most abundantly during the two or three hours in the morning after 
the dew has dried off. Shedding continues during the day, however, 
and there may be secondary peaks of more active shedding following 
showers or even after periods of cloudiness. 
There is some question as to the length of time pollen will remain 
viable. Practically, it is safe to assume that pollen will not be viable 
on the day after it was shed. Contact with moisture will cause pollen 
to burst and lose its viability. After some experience, poor pollen 
usually can be distinguished from good by the way it looks when 
poured from the bag. 
There are many exceptions to these general conditions. In some 
strains the silks will emerge from the ear shoots before the latter 
appear. Other strains will silk before shedding pollen. Moreover, 
the entire blossoming process is affected markedly by the climatic 
conditions. Not only may the rate of the process be modified, but 
the entire order may be reversed. The best ways to meet the various 
unusual conditions that occur during hand pollinating are details that 
can be learned only by experience. The present description is limited 
to what occurs normally under the conditions in most parts of the 
United States. 
Although any well-made bag of suitable size may be used for 
bagging the ear shoots before pollination, small bags made of a heavy 
glassine or a vegetable parchment paper are more convenient. These 
are transparent enough so that the emergence of the silks may be seen 
without removing the bag, saving time and eliminating one chance 
of contamination with stray pollen. Many corn breeders are using 
a bag 2y 2 by 6 inches made of triple-strength glassine paper with 
a safety folded bottom and glued with waterproof glue. Others 
prefer a larger bag made of parchment. Whatever the size, the 
