Nature Bulletin No. 80   August 24, 1946
Forest Preserve District of Cook County
Clayton F. Smith, President
Roberts Mann, Superintendent of Conservation

****:POLLEN

From 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.