The
ginkgo trees seem to be even more closely related to the
Cordaites, and evolved from an early and generalised branch of
that group. The Cordaites, we may recall, more or less united in
one tree the characters of the conifer (in their wood) and the
cycad (in their fruit).
So much for the evolutionary aspect of the Jurassic vegetation in
itself. Slender as the connecting links are, it points clearly
enough to a selection of higher types during the Permian
revolution from the varied mass of the Carboniferous flora, and
it offers in turn a singularly varied and rich group from which a
fresh selection may choose yet higher types. We turn now to
consider the animal population which, directly or indirectly, fed
upon it, and grew with its growth. To the reptiles, the birds,
and the mammals, we must devote special chapters. Here we may
briefly survey the less conspicuous animals of the Mesozoic
Epoch.
The insects would be one of the chief classes to benefit by the
renewed luxuriance of the vegetation. The Hymenopters
(butterflies) have not yet appeared. They will, naturally, come
with the flowers in the next great phase of organic life.
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