150 UNITED STATES GEOLOGICAL SURVEY— TERTIARY FLORA. 



The fourth section, for lobato-crenate leaves and craspedoclrome secondary 

 veins, has only four species, which, I think, should be placed in the second 

 division ; for Quercus castanea and Q. furcinervis are evidently derivations 

 of Dryoj)h7jllmn, or referable to the same section ; while Q. elymodrys and 

 Q. Deuterogena, two species of Unger, are comparable to Q. prinoides and 

 Q. montana. a type of the North American flora, which, as seen above, 

 appears also derived from Dryophyllum. 



To the fifth section pertain the species with sinuate-lobed borders, like 

 those of our White Oaks. It has only twelve species, all Miocene, especially 

 Upper Miocene. As yet, this type is recognized in the Tertiary flora of this 

 continent by one .species only from the Pliocene of California. However, 

 Q. Furuhjelmi, Heer, from Alaska, is placed by Schimper in this section, and 

 as this species is closely allied on one side to the Cretaceous Dryophyllum 

 {Quercus) latifoUum, on the other to the present Q. bicolor, we may, without a 

 too hazardous hypothesis, consider this group as identical with the former, the 

 leaves passing, by the deepening of the obtuse teeth into lobes, to Q. alba, 

 Q. macrocarpa, etc., and, by narrowing them into mbre acute teeth, to Q.prinos, 

 or to the fossil species Q. pseudo-castanea, Q. furcine?-vis, etc. 



The last section of Schimper is reserved for the doubtful species, twenty- 

 four in number, two of them known only by fruits. 



From this it may be assumed that the diff'erent groups of Oaks of the 

 North American present flora, at least those of the eastern slope, have their origin 

 recorded in the Cretaceous by some related specific types; that the original 

 characters, those pertaining to the fourth section, are recognized in .species 

 of the Eocene of the Rocky Mountains; and that perhaps even the genus 

 takes its preponderance in North America, as in Europe, during the Miocene 

 period, especially in this country in the Pliocene. 



§ I. — Leaves ivith entire borders. 



Quercus neriifolia, Al. Br. 



Plate Xrx, Figs. 4,5. 



Quercus neriifolia, Heer, Fl. Tert. Helv., ii, p. 45, pi. Ixxiv, figs. 1-fi, 16 a, b, c, d (acorns), pi. Ixxv, fig. 

 2; iii, p. 178, pi. clii, fig. a.— Ung., Gen. et Sp., p. 403.— Ett., Foss. Fl. v. Bil., p. 54.— 

 Gaud., Cont., vi, p. 12, pi. ii, fig. 1.— Lesqx., Annual Report, 1873, p. 413. 



Quercus lignitum, Al. Br., Stizenb. Verz., p. 77. — Ileer, Ueber der Tert. Fl., p. 53. 



Quercus commutata, Heer, Fl. Tert. Helv.. pji. 14,21. 



Leaves coriaceous, with polished surface, narrowly lanceolate, gradually tapering toward the 

 base ; middle nerve thick and deep ; secondary veins on a very open angle of divergence, sparingly 

 branching toward the borders, where they are effaced ; generally separated by shorter intermediate 

 tertiary veins. 



