Others remained at the Alga-level, and grew in great
thickets along the sea bottoms, no doubt rivalling or surpassing
the giant sea-weeds, sometimes 400 feet long, off the American
coast to-day. Other lines which start from the level of the
primitive many-celled Algae develop into the Mosses (Bryophyta),
Ferns (Pteridophyta), Horsetails (Equisetalia), and Club-mosses
(Lycopodiales). The mosses, the lowest group, are not preserved
in the rocks; from the other three classes will come the great
forests of the Carboniferous period.
The early record of plant-life is so poor that it is useless to
speculate when the plant first left the water. We have somewhat
obscure and disputed traces of ferns in the Ordovician, and, as
they and the Horsetails and Club-mosses are well developed in the
Devonian, we may assume that some of the sea-weeds had become
adapted to life on land, and evolved into the early forms of the
ferns, at least in the Cambrian period. From that time they begin
to weave a mantle of sombre green over the exposed land, and to
play a most important part in the economy of nature.
We saw that at the beginning of the Devonian there was a
considerable rise of the land both in America and Europe, but
especially in Europe.
Pages:
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189