tyledons, and Dicotyledons. Here is
a casual list of plants that then grew in the latitude of London and
Paris: the palm, magnolia, myrtle, Banksia, vine, fig, aralea, sequoia,
eucalyptus, cinnamon tree, cactus, agave, tulip tree, apple, plum,
bamboo, almond, plane, maple, willow, oak, evergreen oak, laurel, beech,
cedar, etc. The landscape must have been extraordinarily varied and
beautiful and rich. To one botanist it suggests Malaysia, to another
India, to another Australia.

It is really the last gathering of the plants, before the great
dispersion. Then the cold creeps slowly down from the Arctic regions,
and begins to reduce the variety. We can clearly trace its gradual
advance. In the Carboniferous and Jurassic the vegetation of the Arctic
regions had been the same as that of England; in the Eocene palms can
flourish in England, but not further north; in the Pliocene the palms
and bamboos and semi-tropical species are driven out of Europe; in the
Pleistocene the ice-sheet advances to the valleys of the Thames and the
Danube (and proportionately in the United States), every warmth-loving
species is annihilated, and our grasses, oaks, beeches, elms, apples,
plums, etc., linger on the green southern fringe of the Continent, and
in a few uncovered regions, ready to spread north once more as the ice
creeps back towards the Alps or the Arctic circle. Thus, in few words,
did Europe and North America come to have the vegetation we find in them
to-day.

The next broad characteristic of our landscape is the spreading carpet
of grass. The interest of the evolution of the grasses will be seen
later, when we shall find the evolution of the horse, for instance,
following very closely upon it. So striking, indeed, is the connection
between the advance of the grasses and the advance of the mammals that
Dr. Russel Wallace has recently claimed ("The World of Life," 1910)
that there is a clear purposive arrangement in the whole chain of
developments which leads to the appearance of the grasses. He says that
"the very puzzling facts" of the immense reptilian development in
the Mesozoic can only be understood on the supposition that they were
evolved "to keep down the coarser vegetation, to supply animal food for
the larger Carnivora, and thus give time for higher forms to obtain a
secure foothold and a sufficient amount of varied form and structure"
(p. 284).

Every insistence on the close connection of the different strands in t