changed conditions.

In western North America the closing stages of the Paleozoic were
marked by important oscillations. The Great Basin, which had long
been a mediterranean sea, was converted into land over western
Utah and eastern Nevada, while the waves of the Pacific rolled
across California and western Nevada.

The absence of tuffs and lavas among the Carboniferous strata of
North America shows that here volcanic action was singularly
wanting during the entire period. Even the Appalachian deformation
was not accompanied by any volcanic outbursts.

LIFE OF THE CARBONIFEROUS

PLANTS. The gloomy forests and dense undergrowths of the
Carboniferous jungles would appear unfamiliar to us could we see
them as they grew, and even a botanist would find many of their
forms perplexing and hard to classify. None of our modern trees
would meet the eye. Plants with conspicuous flowers of fragrance
and beauty were yet to come. Even mosses and grasses were still
absent.

Tree ferns lifted their crowns of feathery fronds high in air on
trunks of woody tissue; and lowly herbaceous ferns, some belonging
to existing families, carpeted the ground. Many of the fernlike
forms, however, have distinct affinities with the cycads, of which
they may be the ancestors, and some bear seeds and must be classed
as gymnosperms.