116 EVOLUTION DE EIFE 
Some years ago it was estimated, by Brown, that of the 
one thousand species of plants found in the rocks of the 
Primary Age, especially of the Carboniferous period, not 
less than eight hundred and seventy-two were Fern-like, 
the remaining species including about seventy-seven 
Conifere and Cycadz, forty Thallophytes, mostly Algae, 
and about twenty undetermined plants. We see from this 
estimate that the Fern-like plants were the characteristic 
feature of the Carboniferous period, and must have flour- 
ished in a much greater profusion than at the present day, 
the Tree-ferns of tropical climates, even, giving one ne 
idea of the luxuriance of their growth in those ancient 
days. Indeed, whole orders have passed away: the Cala- 
mites and Asterophyllites, resembling the Horse -tails, 
having no living representatives, while the Sigillariz and 
Lepidodendrons have degenerated into the Club-moss of 
our forests, As commonly known, the Lycopod of the 
woods is a delicate moss-like plant: that of the Supda 
Islands is often twenty-five feet high. The Lepidodendrons 
of the Carboniferous period, closely allied to living Club- 
moss, attained, however, a height of from forty to sixty feet, 
while their diameter at the roots was as much as twelve to 
fifteen feet. The Sigillariz are similar in many respects to 
the Lepidodendrons, often as high, though more slender. 
The general aspect of the Carboniferous period was that of 
a great Fern forest and a jungle of gigantic Club-mosses, 
with some Conifere and Cycade; these, however, but 
rarely seen, comparatively speaking. The gradual decom- 
position of these plants resulted in the formation of the 
vast coal-fields so characteristic of this period. In the 
marshes of these forests first appeared the Datrachia 
(Frogs, etc), together with the Centipedes, the May-fly, 
Locust, and Beetle orders among Insects. We see, there- 
fore, that the tree of the development of life, as proposed 
in the chapters on Botany and Zoology, is in perfect 
resembli 
we meet 
Permia il 
furnishin; 
saurus ha 
By looki 
it will be 
common. 
Carbonife 
stitute the 
