BROOKLYN BOTANIC GARDEN 
LEAFLETS 
Series VIII Brooklyn, N. Y., April 28, 1920. No. 3 — J 
THE ANCIENT HISTORY OF PLANTS* 
The earth has been estimated to be anywhere from 25,000,000 
to 400,000,000 years old. Man, in all probability, appeared upon it 
between two thousand and three thousand centuries ago. The 
historic record, as deciphered from the remains of ancient civil- 
izations, possibly extends back seven to eight thousand years. 
This record, contrasted with the age of the earth (conservatively 
estimated as 120,000,000 years), is as a quarter-second is to the 
passing of an hour, or, as some one has more graphically put it, 
“as the flashing of a meteor through the sea of night.” The 
oldest known plant remains are probably less than half the 
earth’s age, but antedate man by millions of years. The earliest 
vegetation which the rocks have shown us in any quantity, is far 
from simple in type, most of the forms being trees, shrubs, or 
woody ferns. Immense layers of rock strata still older than these 
exist, however, from which only the merest vestiges of plants 
have been taken. Hence, grounds exist for supposing these 
plants to have been already many stage-journeys along the road 
of evolutionary progress. Already they had an eon-old ancestral 
tree. 
During those first ages when the earth’s crust was forming, 
land was scarce, and the seas were new and filled with fresh water. 
Hence, the first plants were sea-born, distant relatives of our 
present-day pond-scums and slimes. As the centuries passed, 
land increased. Innumerable rivers filled the seas with decom- 
posed mineral matter. They lost their freshness. Only the more 
adaptable of the earlier vegetation remained, while the less 
adapted types existed only in the fresh-water areas of the slowly 
appearing continents. From the former, perhaps, came our 
present-day seaweeds; from the latter, our fresh-water green 
scums and slimes. Between the seaweeds, so far as the rock- 
written pages testify, and the rest of the plant kingdom, a great 
gulf exists — an almost entire absence of connecting links. A 
very few petrified moss and liverwort fragments have been found , 
but these furnish practically no clue as to their ancestral rela- 
tions, either to the pond-scums and seaweeds on the one hand, 
or to the ferns, conifers and flowering plants on the other. 
Mosses and seaweeds being rather delicate plants with no 
woody parts, the comparative scarcity of their petrified remains 
is rather to be expected. First, because only a relatively small 
portion of these most ancient plant graveyards have been ex- 
plored and only vegetation most favorably placed has been pre- 
served. Second, since the earliest types of vegetation arose, the 
land and sea areas which they inhabited have undergone great 
alterations. The earth’s crust has been repeatedly crumpled into 
mountain ranges and grooved into valleys, only to be rumpled 
and creased anew. Mountain chains have risen, only to sink and 
*This is largely a revised reprint of Leaflet No. 14. Series IV. 
