44 FOSSTL FLORA OF THE SIERRA NEVADA. 



degree which cannot be fixed on account of the deficiency of the speci- 

 mens by which this last form is represented ; Juglans Calif arnica, com- 

 parable to J. acuminata, var. latifolia, Heer, a species of wide distribution 

 in the Tertiary, mostly Miocene, of Europe and of this country ; and J. 

 Orcgoniana, which bears the same degree of affinity to J. nigetta, Heer, of 

 Alaska. Thus the Miocene or Tertiary facies of the flora of the Chalk 

 Bluffs is manifested by four identical species, and by eight more or less 

 intimately related to Tertiary species of this country or of Europe. It 

 must be remarked, however, that, except the two species of Ficvs, these 

 last-named forms are truly intermediate in their relation, which, as seen 

 here below, is quite as close with types of the present flora as it is 

 with Tertiary ones. The comparison of these species, taken all together, 

 gives a propoition of less than twenty-five per cent, as indicative of the 

 Miocene character in the flora of the auriferous gravel. As the table 

 shows, the more evident relation of the above species is with those 

 recognized in the Tertiary of Alaska, and in the Lignitic of the Rocky 

 Mountains by identity, more or less distinct, with Fagus Antipqfi, Poputus 

 Zadclachi, Ficus tilicefolia, F. microphylla, F. Groenhndica, this one only from 

 Greenland ; and that, therefore, the oldest types of the flora of the Chalk 

 Bluffs are mostly American. Indeed, some of these types, as will be seen 

 hereafter, may be clearly traced up to the Cretaceous of the Dakota 

 group. 



The degree of relation of the plants of the above table with species 

 of the present flora is much higher. As identical, as far as leaves may 

 show identity, we find Bctula wquatis with B. occidentals ; Fagus pseudo- 

 ferrvginea intermediate between F. ferruginea and F. sylvatica ; Querent 

 Whitneyi with Q. bjrata; Castanca chrysophylloides with C. chrysophglla ; Ulmus 

 Californica with U. alala ; U. pseudo-fulva with TJ. fulva ; Pcrsca pscudo- Caroli- 

 nensis with P. Carolinensis ; Comas oralis with C. sessilis or C. Mas ; Mag- 

 nolia lanceolata and 31. Californica with M. acuminata and M. cor data ; Bhus 

 typhinoides and B. metopioides with B. typhind and B. metopium. Juglans 

 Californica is referable to the old type J. acuminata, now represented 

 only by the Asiatic J. regia, widely distributed by cultivation. Besides, 

 there is an evident, though less distinct relation between Qucrcus ekenoi- 

 des and Q. convene with Q. virens and its variety ; (f Nevadensis with Q. 

 castanea : <J. Bowcniana, Q. distincta, Q. Goepperti, and Q. Voyana with Q. agri- 

 folia of California, and a group of Mexican Oaks, Q. crassifoUa, Q. Hum- 



