234 THE AURIFEROUS GRAVELS OF THE SIERRA NEVADA. 
all the other trees comes P. albicaulis, or flexilis as it has been often called, 
which however occurs chiefly in scattered clumps, marking the upward limit 
of vegetation, but hardly forming a distinct zone. 
If now we inquire whether any arrangement or order of succession, of a 
character similar to that just indicated for the present vegetation, can be 
traced in that of the auriferous gravel series, we have, in the first place, to 
confess to poverty of material necessary for giving a definite answer. Still, 
what evidence has thus far been collected is decidedly in favor of a uniformity 
of vegetation, rather than of variety or separation into zones, during the 
epoch of the gravels. 
In illustration of this statement, the entire absence of any proof of the exist- 
ence of coniferous trees during the gravel period may be brought forward. 
In none of the collections made, so far as the same have been examined by 
Mr. Lesquereux, have any traces of the existence of conifers been observed. 
Neither has the writer any recollection of having observed such in his inves- 
tigations in the gravel region. Although further examinations may bring to 
light proofs of the former presence of coniferous trees in some portions of the 
gravel deposits, it seems almost certain that, if existing at all, they must 
have been very subordinate to the deciduous vegetation. 
We have now to inquire in regard to the vertical range of the fossil plants 
collected and examined by Mr. Lesquereux. Although leaves have been 
observed in many localities, as has already been explained, extremely few of 
these have yielded material in sufficiently perfect state for description. By 
far the most prolific locality is that of Chalk Bluffs, and the one next to it in 
importance is the Tuolumne Table Mountain. These two places are separated 
from each other by a distance of somewhat over eighty miles; the former is 
in latitude 39° 12’, the latter in 38°. Bowen’s Claim, the next locality mm im- 
portance, is fifteen miles south-southeast of Chalk Bluffs. The difference in 
altitude between the two principal localities is, however, considerable, the 
plant-bearing beds of Table Mountain being about 2,000 feet in elevation, 
and those of Chall Bluffs from 3,500 to 3,600 feet, the difference between the 
two being fully 1,500 feet. The fossil flora of the localities, thus seen to be 
considerably different both in latitude and altitude, would seem — from the 
investigations of Mr. Lesquereux— to be essentially the same. That is, 
nearly the same genera are represented, although the species are, in most 
cases, considered as differing. From the annexed tabular view of the species 
described by Mr. Lesquereux, in which the localities are designated, it will 
