As the cycads shrank in the Cretaceous period, the Angiosperms
deployed with great rapidity, and, spreading at various levels
and in different kinds of soils and climates, branched into
hundreds of different types. We saw that the oak, beech, elm,
maple, palm, grass, etc., were well developed before the end of
the Cretaceous period. The botanist divides the Angiosperms into
two leading groups, the Monocotyledons (palms, grasses, lilies,
orchises, irises, etc.) and Dicotyledons (the vast majority), and
it is now generally believed that the former were developed from
an early and primitive branch of the latter. But it is impossible
to retrace the lines of development of the innumerable types of
Angiosperms. The geologist has mainly to rely on a few stray
leaves that were swept into the lakes and preserved in the mud,
and the evidence they afford is far too slender for the
construction of genealogical trees. The student of living plants
can go a little further in discovering relationships, and, when
we find him tracing such apparently remote plants as the apple
and the strawberry to a common ancestor with the rose, we foresee
interesting possibilities on the botanical side.
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