Evolution of Primitive Plants . 273 
slowly liberated by the earth itself, as “juvenile water,” through 
its volcanoes and thermal springs. What we see to-day of vadose 
(=old) waters is the accumulation of more than one thousand 
million years. Likewise the salts of the seas and oceans have been 
of slow gathering, for they have been gradually washed out of the 
land and have accumulated in the oceanic basins during the great 
length of geologic time. The rivers of to-day are known to be 
variably saline, and it is their small daily additions to the seas that 
have gone towards making up the vast amounts of salts contained 
in the latter, locked up in the rocks as rock-salt, or forming part of 
the enormous limestone and dolomite beds of the geologic formations. 
This subject is treated in detail in Chamberlin and Salisbury’s 
“ Geology ” or in shorter and more popular form in “ The Evolution 
of the Earth and its Inhabitants,” a series of papers by Yale 
instructors. 
We now know that the oceans did not always remain within 
their confines as at present delimited, for the many well known 
fossiliferous deposits on the continents attest that the marine 
waters have been over the latter. Since the beginning of the 
Paleozoic, the oceans have repeatedly flooded the lands more or 
less widely, but never have all the lands of any one time been 
beneath the seas. What has been true since the Cambrian 
was probably equally so for Archeozoic and Proterozoic times; 
but with this difference, that the water basins and the continental 
protuberances in the Archeozoic were probably smaller and by far 
greater in number than they are to-day. 
What is the bearing of these statements on Church’s theory ? 
Certainly they do not disprove his conclusions, rather do they 
appear to make all the more easy the solutions along his lines of 
thinking. We may therefore agree with him that nearly all life in 
the earliest Archeozoic consisted of oceanic micro-plankton, but 
that the oceans did not then have their present depth and that 
there were lands with shores and shallow-to-littoral seas, with 
sunlit bottoms, just as there are to-day. Accordingly some of the 
plankton, after it had evolved into nucleated cells living in colonial 
form, might easily have found a bottom where assimilation could 
have been continued, though probably more slowly than in the 
surface waters. With the finding of this favorable bottom for 
the continuance of life, a new factor in organic environment was 
introduced, and out of the struggle for adaptation to it there arose 
the plant benthos. 
