Grasses also and palms
begin in the Cretaceous; though the grasses would at first be
coarse and isolated tufts. Even flowers, of the lily family
(apparently), are still detected in the crushed and petrified
remains.
We will give some consideration later to the evolution of the
Angiosperms. For the moment it is chiefly important to notice a
feature of them to which the botanist pays less attention. In his
technical view the Angiosperm is distinguished by the structure
of its reproductive apparatus, its flowers, and some recent
botanists wonder whether the key to this expansion of the
flowering plants may not be found in a development of the insect
world and of its relation to vegetation. In point of fact, we
have no geological indication of any great development of the
insects until the Tertiary Era, when we shall find them deploying
into a vast army and producing their highest types. In any case,
such a view leaves wholly unexplained the feature of the
Angiosperms which chiefly concerns us. This is that most of them
shed the whole of their leaves periodically, as the winter
approaches. No such trees had yet been known on the earth.
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