BARREN AND EDMONSON COUNTIES.



  The largest trees are oaks, about fifteen inches in diameter
three feet from the ground. I saw scarcely a willow or a maple
of any kind. The soil is a stiff limestone, considerably impreg-
nated with iron, making it of a red color, and not highly pro-
ductive of ordinary cereals. The surface is very uneven, being
full of sinkholes, formed by the falling in of the cavernous
passages which form a network under this whole district. The
celebrated Mammoth Cave is only one of the hundreds of cav-
erns of this remarkable region. Not in the trees only, but
also in the herbaceous flora, was the limited number of spe-
cies noticeable. It is well understood that the aborigines of
this country were accustomed to burn over the surface of the
prairies; but for what purpose it does not seem to be perfectly
understood. There may have been several considerations
which led them to this quite universal custom. It has been
said that they thus destroyed the old culms of grass, and
cleared the way for the springing of the tender shoots in the
spring. They may also have had in view the destruction of
hurtful insects, as the grasshoppers, by destroying their eggs.
or of noxious serpents, which must have been destroyed in
immense numbers by the annual fires on the prairies. Another
reason may have had consideration; the tall dead grass would
be liable to be fired by accident at any time, and thus human
life and many villages be endangered in the night, or in times
of high winds, with no means of escape: but if at a certain
time, when all are on the lookout, the firing should take place,
there would be no danger to life or property.
  This habit of firing the prairies must have exerted a wide
influence on the character and distribution of plants in the
parts of our country where prairies existed. Certain plants
could not survive the fires. The annuals must have been
greatly diminished by the custom. Those which were peren-
nials under ground, would suffer less than any other class of
plants. The fire swept off everything above the surface-
seeds not covered by the soil, young plants of trees; but the
well-protected living roots of herbaceous perennials, with the
nourishment of another crop of shoots stored away safely be-
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