known as the Cretaceous or chalk
period. Now, for the first time, the forests begin to take on more of
the character of our forests of to-day. Plants like our willow and
beech, poplar and sassafras appear in great abundance. Their broad
leaves serve better than those of any earlier plants to catch the
sunlight. But in addition they offered such effective evaporating
surface that they cast off rapidly the moisture obtained from the
ground by the plant. Accordingly in the winter season, when the water
in the ground is frozen and not available for plant purposes, they
were forced to throw away their leaves. It is quite possible that up
to and including the time of the Carboniferous, plants were all
evergreen. There had been before this little variation in climate over
the globe. Life in the Cretaceous begins to take on distinctly its
modern form.

Among the reptiles of the forest there appear to have been a few small
creatures which to an observer of those times, if there could have
been an observer, would have seemed of the utmost insignificance
compared with their giant cousins.

These little creatures climbed up into the trees to escape their
enemies. There were some in whom the skin, in front of the elbow and
behind the wrist, was loose, and stretched across the joint a little
like the wing of a bat. This reptile, climbing into the trees to
escape its enemies, found that this loose flap of skin served it
nicely, and sailed out of the trees in a manner not unlike that of
the flying squirrel of to-day. Among these experimenters in aviation,
certain forms produced scales which became elongated and finally slit
up along the side. These slit scales slowly developed into the
feathers of the birds of to-day. Whether the steps by which the change
occurred have been correctly stated or not, the result is sure. In the
rocks of the chalk period we find the remains of an interesting
creature. If nothing but its bones had been found it would have been
called a reptile. It had a long tail, it had claws on its front limbs;
it had teeth in its mouth; it had a flexible backbone. All of these
are reptilian rather than bird characters. Yet on the rocks
surrounding these bones are the unmistakable impressions of the
feathers of the wings and of the tail. Nothing in the world to-day has
feathers excepting the birds, and in this "ancient winged thing," for
this is the significance of its name--archaeopteryx--we have perhaps
the most rema