llen grains need to breathe quite as much as a red squirrel needs
to breathe. Therefore they must not be placed in glass or metal or
tightly sealed. Further, the pollen grains need to be kept cool in order
to avoid attacks from the greatest enemy of all organic life, the
microbes or the lower fungi. Probably we may keep pollen for a longer
time than it could ordinarily be kept, if it is placed in cold storage,
but practically I have tried the experiment on only one occasion. Last
year I wished to cross the chinkapin with the white oak. The white oak
blossoms more than a month in advance of the chinkapin in Connecticut,
and the question was how we could keep the white oak pollen. Some of it
was placed in paper boxes in cold storage; some in paper boxes in the
cellar in a dry place. Pollen which had been kept in the cellar and
pollen which had been kept in cold storage were about equally viable. It
is quite remarkable to know that pollen can be kept for more than a
month under any circumstances. Hybridization occurred in my chinkapins
from this white oak pollen. Sometimes, where the flowering time of such
trees is far apart, it is important to know how we may secure pollen of
one kind for the female flowers of the other. Two methods are possible.
In the first place, we may secure pollen from the northern or southern
range of a species for application upon pistillate flowers at the other
end of the range of that species. Another way is to collect branches
carrying male flowers before the flowers have developed, place them in
the ice house or in a dark, cold room without light until the proper
time for forcing the flowers, and if these branches are then placed in
water, the water changed frequently as when we are keeping flowers
carefully, the catkins or other male flowers will develop pollen
satisfactorily a long time after their natural time of furnishing
pollen, when they are brought out into the light. In protecting
pistillate flowers from the pollen of their own trees, with the nut tree
group where pollen is wind-borne rather than insect borne, I find that
the better way is to cover the pistillate flowers with paper bags, the
thinner the better, the kind that we get at the grocery store. It is
best to pull off the undeveloped male flowers if they happen to be on
the same branch with the female flowers, and then place the bags over
the female flowers at about the time when they blossom, in advance of
pollination of the ma