As these
conditions advance in the Permian period, the forests wither and
shrink. Of the extraordinarily mixed vegetation which we found in
the Coal-forests some few types are fitted to meet the severe
conditions. The seed-bearing trees, the thin, needle-leafed
trees, the trees with stronger texture of the wood, are slowly
singled out by the deepening cold. The golden age of Cryptogams
is over. The age of the Cycad and the Conifers is opening.
Survivors of the old order linger in the warmer valleys, as one
may see to-day tree-ferns lingering in nooks of southern regions
while an Antarctic wind is whistling on the hills above them; but
over the broad earth the luscious pasturage of the Coal-forest
has changed into what is comparatively a cold desert. We must
not, of course, imagine too abrupt a change. The earth had been
by no means all swamp in the Carboniferous age. The new types
were even then developing in the cooler and drier localities. But
their hour has come, and there is great devastation among the
lower plant population of the earth.
It follows at once that there would be, on land, an equal
devastation and a similar selection in the animal world.
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