LIFE IN THE PAST 181 
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 evaporat- 
ing 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 Car- 
boniferous, plants were all evergreen. There had 
been before this little variation in climate over the 
globe. Life in the Cretaceous begins to take on dis- 
tinctly 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 com- 
pared 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 
