140 UNITED STATES GEOLOGICAL SURVEY— TERTIARY FLORA. 



Hamamelis, is described in the Eocene Flora of Sdzane. Considering, 

 then, the geological records in regard to the present distribution of 

 species in the North American flora, it would be more rational to refer 

 to Alnus those Cretaceous leaves, and to regard the origin of this genus as 

 Cretaceous. 



The paleontologists of Europe have to the present time described 

 twenty-nine species of Alnus, seven from the Lower Tertiary (Eocene and 

 Oligocene), and twenty-two from the Miocene formations. We have as yet 

 only five species referred to this genus, one from the Lower Eocene, and 

 four from the Miocene; of these, one is described by Dr. Newberry from 

 the Fort Union group, and two have been found in the Miocene of California 

 and Oregon. This apparent diiference in the distribution of this genus is 

 ascribable to our limited acquaintance with the North American Tertiary 

 floras. 



At the present time, fourteen species of Alnus are known and scattered 

 over the boreal hemisphere, except two inhabiting the mountains from South 

 Mexico to Chili. Two species are predominant in Europe, one south along 

 the Mediterranean shores from Italy to the Caucasus, another a northern one, 

 which also goes eastward to Western Asia; two others are still found in 

 Europe, more rarely, however, and none exclusively limited to that continent. 

 North America has five species, two of which exclusively belong to its flora, 

 one from the western slope, the other from the eastern slope only. This 

 distribution is therefore in accordance with that indicated by the Tertiary 

 flora of this continent, while it is the contrary for Europe, which counts 

 twenty-eight species in its Tertiary, and has none at our time exclusively 

 pertaining to its flora. 



Alnus Kef ei'steiuii, Gopp. 



Plate XVIII, Figs. 6-8; Plate LXIV, Fig. 11. 



Ahiiles Kefcrstdnii, Giipp., Nov. Act. N. C, xviii, 1, p. 364, pi. xli, figs. 1-19. 



Alnvs Kefcrsteinii, Ung., Chlor. Protog., p. 115, pi. xxxiii, figs. 1-4.— Heer, Fl. Tert. Helv., ii, p. 37, pi. Ixxi, 



figs. 6, 7. — Ludw., Palaiout., viii, p. 97, pi. xxxi, figs. 1-5, xxxii, figs. 1, 2. — Ett., Foss. 



Fl. V. Bil., p. 47, pi. xiv, figs. 17-20.— Heer, Fl. Foss. Arct., ii, p. 146, pi. xxv, figs. 4-9; Fl. 



Foss. Alask., p. 28, pi. iii, figs. 7, 8 ; Mioc. Bait. Flor., p. 67, pi. six, figs. 1-13.— Lesqx., Annual 



Report, 1871, p. 292; 1872, pp. 386, 401, 405. 



Leaves of medium size, ovate, obtusely pointed or acuminate, ronnded-subcordate at base, simply 

 or doubly serrate; lateral nerves and their divisions craspedodrome.. 



The leaves of this species are very variable, especially in the denticula- 

 tion of the borders. The most common variety is that represented in pi. xviii, 



