746 Evolution in the Vegetable Kingdom. [August, 
their existence to a limited extent, and live in hopes of yet bring- 
ing to light an important Upper Cretaceous flora. 
We are thus brought to the Laramie group of the Western 
Territories, which, though a brackish water deposit and difficult 
to correlate with other deposits, may be regarded as extreme 
Upper Cretaceous; 333 species have been thus far described from 
this group, which presents a flora of a still more Tertiary aspect 
than that of the Senonian proper, and fittingly ushers in the Ter- 
tiary flora. 
From the Paleocene of Sézanne and Gelinden to the Miocene 
the progress is uniform and rapid. The Eocene of the old world 
(Paris basin, Aix in Provence, Monte Bolca, Monte Promina, 
Monte Pastello, Isle of Wight, London clay, etc.) furnishes over 
650 species, while the Green River group of America, including 
the rich beds of Florissant, Colorado, probably of that age, has 
yielded more than two hundred. This is exclusive of the so- 
called Oligocene of the continent (Hering in Tyrol, Sotzka in 
Carniola, the Marseilles basin, Armissan near Narbonne, etc.) 
from which nearly 800 more have been taken. We thus have 
over 1800 pre-Miocene Tertiary plants, which is, however, much 
less than half of the Tertiary flora. The Miocene supplies 
nearly all the rest, yielding alone over 3000 species. It may be, 
as has been charged, that this number is too great, and that a 
portion of these plants belong to lower horizons. While Heer’s 
determinations in Switzerland have not been seriously questioned, 
his work on the arctic floras is doubtless open to revision, but this 
will not diminish the number of Tertiary plants, which, if we add 
to those already mentioned some 150 Pliocene species, will form 
an aggregate of nearly 5000. 
The Tertiary virtually closes the series for vegetable remains, 
the Quaternary having thus far furnished less than one hundred 
species of fossil plants. 
The development of plant life through the successive geologic 
ages may be graphically represented, so far as indicated by actual 
discovery, by the accompanying diagram or figure, in which the 
number of accredited species is taken as a measure of predom- 
7 ve —_— and the- space assigned to each horizon in the vertical 
. a ale sents its duration in so far as the thickness of the 
es cnet time. 
