Page:Popular Science Monthly Volume 85.djvu/358

354 the aid of fire. All forests of it bear the marks of frequent ground fires, which in some places come nearly every year. At the present time, of course, most of the fires are of human origin, but those set by lightning in prehistoric times could spread over much larger areas than they do now, on account of the absence of clearings, roads, and other

 (Finus serotina) August, 1913.

artificial barriers, so that the frequency of fire at any one spot may not be much greater now than it was originally. A fire every year during the lifetime of the tree would be likely to prevent its reproduction, but in any area that escapes burning for a few years once in fifty years or so there is opportunity for a new crop of trees.

If fire were withheld too long the oaks and other hardwoods which grow in the long-leaf pine regions would take possession of the ground and gradually crowd the pine out, for its seedlings do not thrive in shade. Proofs of this can be seen in many places in the coastal plain, where fire is barred by the topography, as on bluffs bordering swamps, or by water, as on islands and narrow-necked peninsulas. Such places, in which the soil must have been originally much the same as in the neighboring pine forests, are nearly always occupied by what is known as "hammock" vegetation, consisting mostly of hardwood trees, which make a rather dense shade and cover the ground with humus.