Nature Bulletin No. 80 August 24, 1946
Forest Preserve District of Cook County
Clayton F. Smith, President
Roberts Mann, Superintendent of Conservation
mid-August until early frost, people are "pollen-conscious" --
particularly those who suffer with hay fever. Millions of flowers are in
bloom, including the ragweeds which are heavy producers of pollen.
Hay fever is an "allergy" or protein sensitivity to this pollen, carried
scores or even hundreds of miles by the wind, which sticks to the thin
moist membranes of the eyes, nose, throat and lungs.
Most plants, including trees, have flowers. The stamens of a flower are
covered with fine yellow grains called pollen. If there is to be
fertilization, these grains must be transferred to the pistil in which the
seeds are formed. Some plants, such as peas and beans, are self-
fertilized but most kinds are cross-fertilized: the pollen being carried
from one plant to another by wind or on the bodies of insects attracted
to them by the nectar in the flowers. Under a microscope the pollen
grains of one species are distinctively different from those of another in
size, shape, markings and color.
Curiously, the tiny fragile pollen grains from trees are more durable
than any other part of the tree if they fall upon the surface of a swamp
or bog and accumulate under water. Scientists, examining the pollen
grains found in deep peat bogs, from bottom to top, read there the story
of the changes in climate and vegetation that occurred during and since
the Ice Age.
When the last glacier melted away, some 50,000 years ago, large blocks
of ice broke off and were left behind. These melted to form lakes and
potholes. The decaying remains of aquatic plants slowly filled many of
the potholes to form peat bogs.
As the glacier retreated, vegetation followed it, advancing across the
vast tundra or barren lands that stretched from its front almost to the
Ohio River. The pollen grains in these peat bogs show that the first
trees were firs and spruces, in forests that persisted for centuries. Then
came the pines and tamarack; after them the birches, linden and elms;
and then the oaks, maples and hickories. That is the story as told by the
pollen grains in peat bogs.
The earth changes. Things disappear. So will your hay fever.
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Update: June 2012