k at these interesting inhabitants of the Middle Ages of the
earth, before they pass away or are driven, in shrunken regiments, into
the shelter of the narrowing tropics.

The principal change in the aspect of the earth, as the cold, arid
plains and slopes of the Triassic slowly yield the moist and warm
ow-lying lands of the Jurassic, to consists in the character of the
vegetation. It is wholly intermediate in its forms between that of the
primitive forests and that of the modern world. The great Cryptogams of
the Carboniferous world--the giant Club-mosses and their kindred--have
been slain by the long period of cold and drought. Smaller Horsetails
(sometimes of a great size, but generally of the modern type) and
Club-mosses remain, but are not a conspicuous feature in the landscape.
On the other hand, there is as yet--apart from the Conifers--no trace of
the familiar trees and flowers and grasses of the later world. The vast
majority of the plants are of the cycad type. These--now confined to
tropical and subtropical regions--with the surviving ferns, the new
Conifers, and certain trees of the ginkgo type, form the characteristic
Mesozoic vegetation.

A few words in the language of the modern botanist will show how this
vegetation harmonises with the story of evolution. Plants are broadly
divided into the lower kingdom of the Cryptogams (spore-bearing) and the
upper kingdom of the Phanerogams (seed-bearing). As we saw, the Primary
Era was predominantly the age of Cryptogams; the later periods witness
the rise and supremacy of the Phanerogams. But these in turn are broadly
divided into a less advanced group, the Gymnosperms, and a more advanced
group, the Angiosperms or flowering plants. And, just as the Primary Era
is the age of Cryptogams, the Secondary is the age of Gymnosperms, and
the Tertiary (and present) is the age of Angiosperms. Of about 180,000
species of plants in nature to-day more than 100,000 are Angiosperms;
yet up to the end of the Jurassic not a single true Angiosperm is found
in the geological record.

This is a broad manifestation of evolution, but it is not quite an
accurate statement, and its inexactness still more strongly confirms the
theory of evolution. Though the Primary Era was predominantly the age of
Cryptogams, we saw that a very large number of seed-bearing plants, with
very mixed characters, appeared before its close. It thus prepares the
way for the cycads and conifers and ginkgoes of