THE BEGINNINGS OF PLANT LIFE 
a great many periods. In a few instances, a type seems 
practically to defy time and age. But the history of a 
human individual, with its birth, youth, adulthood, sen¬ 
ility, and death, seems to repeat itself with considerable 
regularity in types of plants and animals, as well as in 
royal dynasties and human races. 
Since deposits of sediment from early Paleozic times 
are all of marine origin, we can reconstruct the aquatic 
life from facts. They are much richer, however, with 
regard to animals than to plants. It is more difficult, 
and entirely hypothetical, to try to picture the land life. 
The first fossil land plants are found in Lower Devonian 
times, and the first land animals in the Pennsylvanian 
period; but there must have been a land life at least along 
the seashore at a much earlier date, because in these first 
remains the land plants and land animals are already con¬ 
siderably developed. By the time of the Upper Devonian 
period, we find extensive forests of big trees which must 
have had behind them a long history of development, 
exceeding by far the length of a single geologic period. 
Some day we may find traces of this development in 
the rocks. Meanwhile, we have to be content with a 
theory. 
Perhaps in the Cambrian, surely not later than the 
Ordovician period, an amphibious type of land plants 
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