mains, and then explaining the new types of
organisms by the cold climate. This, of course, we shall not do. The
difficulty is made greater by the extreme disinclination of many recent
geologists, and some recent botanists who have too easily followed the
geologists, to admit a plain climatic interpretation of the facts. Let
us first see what the facts are.

In the latter part of the Jurassic we find three different zones of
Ammonites: one in the latitude of the Mediterranean, one in the latitude
of Central Europe, and one further north. Most geologists conclude that
these differences indicate zones of climate (not hitherto indicated),
but it cannot be proved, and we may leave the matter open. At the same
time the warm-loving corals disappear from Europe, with occasional
advances. It is said that they are driven out by the disturbance of the
waters, and, although this would hardly explain why they did not spread
again in the tranquil chalk-ocean, we may again leave the point open.

In the early part of the Cretaceous, however, the Angiosperms (flowering
plants) suddenly break into the chronicle of the earth, and spread with
great rapidity. They appear abruptly in the east of the North American
continent, in the region of Virginia and Maryland. They are small in
stature and primitive in structure. Some are of generalised forms that
are now unknown; some have leaves approaching those of the oak, willow,
elm, maple, and walnut; some may be definitely described as fig,
sassafras, aralia, myrica, etc. Eastern America, it may be recalled, is
much higher than western until the close of the Cretaceous period. The
Angiosperms do not spread much westward; they appear next in Greenland,
and, before the middle of the Cretaceous, in Portugal. They have
travelled over the North Atlantic continent, or what remains of it. The
process seems very rapid as we write it, but it must be remembered that
the first half of the Cretaceous period means a million or a million and
a half years.

The cycads, and even the conifers, shrink before the higher type of
tree. The landscape, in Europe and America, begins to wear a modern
aspect. Long before the end of the Cretaceous most of the modern genera
of Angiosperm trees have developed. To the fig and sassafras are now
added the birch, beech, oak, poplar, walnut, willow, ivy, mulberry,
holly, laurel, myrtle, maple, oleander, magnolia, plane, bread-fruit,
and sweet-gum. Most of the American trees of