eS ee 
GENERAL CONCLUSIONS. 53 
in all probability covered the higher slopes of the mountains of that epoch, 
has been destroyed everywhere, except in some deep valleys surrounded 
with walls of high granitic peaks, where it stands as a wonder of the 
vegetation of this continent. The other, S. sempervirens, left here and 
there, has again taken the ascendency under more favorable physical 
circumstances. Its present distribution explains its preservation until the 
present epoch. According to Professor Bolander, “the distribution of the 
Redwood depends upon sandstone and oceanic fogs. Where either one 
of these conditions is wanting there is no Redwood. The Redwoods 
begin in the northern part of Monterey County, in isolated groups, in 
deep, moist caiions. A short distance south of Monterey City, on the 
Monterey Bay, a white bituminous slate sets in, and extends nearly to 
Pajaro River. On this no Redwood is found but Pinus insigmis. At Pajaro 
River, eight to ten miles from the ocean, they set in again, and extend 
to nearly twenty-eight miles south of this city (San Francisco), either in 
deep cafions, or in groves extending over several ridges eastward as far 
as the fog may reach. Thus they continue in similar localities to latitude 
42°, the State boundary.” 
From these facts, as also from what is known of the general distribu- 
tion of Conifers, generally depending on a high degree of atmospheric 
moisture, the character of the flora of the Chalk Bluffs indicates the geo- 
graphical station of the localities where the Pliocene plants have been 
found, as that of a region sheltered by ranges of mountains against the 
influence of the Pacific fogs, and whose vegetation has been influenced 
by circumstances analogous to those governing it, as at the present 
time. 
The plants described here from the Pliocene clearly expose the climate 
of the period which they represent. They record a temperature a few 
degrees higher, in the average, than that of Middle California, or, like the 
species of the Chalk Bluffs of the Mississippi, they represent a latitude 
of a few degrees farther south. The Palms were very rare in this flota ; 
only a single specimen of a Sabai is found in the whole collection. 
Nevada County is on the 39th parallel of latitude, and a species of Palm 
still inhabits California under the 34th degree. For the Mississippi Valley, 
Sabal and Chamerops species have their northern limits also under this 
same latitude. The action of a warmer climate seems indicated by the 
Oaks of the Mexican type, and by species of Ficus; but this is counter- 
