GENERAL CONCLUSIONS. 45 
boldiu, etc.; Sakx Califormca with S. sessilifolia of Oregon; S. elliptica with 
S. capreoides of California; two species of Platanus with P. occidentalis, the 
form of the stipules of P. appendiculata, referring it more particularly to 
P. lindeniana, which, however, is considered a Southern or Mexican variety 
of P. occidentahs ; Liquidambar Californicum with L. acerifolium of Japan; 
Cornus Kelloggu with C. Nuttallii of California; Acer wguidentatum with A. 
spicatum ; A. Bolandert with A. tripartitum and grandidentatum of the Rocky 
Mountains; Juglans Oregoniana with J. rupestris of the mountains of New 
Mexico and California, and Cercocarpus antiquus, intermediate in the size 
of its leaves between (. fothergilloides of Mexico and C. ledifolius, now inhab- 
iting the slopes of the mountains from Colorado to California. Therefore 
types of the present flora are represented in that of the Chalk Bluffs 
by fourteen probably identical species, counting Cercocarpus and Juglans 
Californica, and by sixteen more or less intimately related ones, or in a 
relation more than double in degree of what it is in the Miocene. On the 
species of this list also, the same remark can be made as on those of 
the former; they represent most of all true American types. Indeed, of 
the fifty species of the table, there are none strange to the present North 
American flora, except the two species of /icus pertaining to a peculiar 
division of the genus, predominant in the Tertiary of both continents, but 
now disappeared, it seems, or merely represented by F. carica, everywhere 
cultivated in an infinity of varieties, and Juglans Californica, the offspring 
of J. acuminata, apparently the ancestor of J. regia, which is as generally 
known and cultivated, in Europe at least, as the Fig. I have compared 
Zanthoxylon diversifolium to Z. trphyllum on account of the peculiar similarity 
of its leaves to those of the Brazilian species; but the Pliocene form is 
as closely related by some of its characters to Z. wétegrifolium of the Mio- 
cene of (ningen, to which, according to Heer, Z. Americanum bears the 
nearest affinity. Hence it is evident that the general character of the 
Pliocene flora of the auriferous gravel deposits is truly North American, 
or that it is most nearly related to that of the present epoch. 
The assertion, however, does not apply to the present flora of California, 
where none of the more predominant genera recognized in the Pliocene 
plants are represented. Fugus, Quercus (of the subdivision of Q. vvrens, 
Q. castanea, and Q. lyrata), Liquidumbar, Ulnus, Persea, Magnolia, Acer (the 
section of A. spicatum and A. rubrum), Ilex, Rhus (with pinnately divided 
leaves), Zanthoxylum, are all generic divisions amply represented in the 
