140 UNITED STATES GEOLOGICAL SURVEY— TERTIARY FLORA. 



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

 then, tlie 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 

 tour 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 CaHfornia 

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

 ascribable to our limited acquaintance with the North American Tertiary 

 floras 



At the present time, fourteen species oi 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 

 distril)ution is therefore in accordance with that indicated by the Tertiary 

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

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

 pertaining to its flora. 



Alniis Kcfcrsteinii, Gopp. 



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



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



Alnus Kefersteiuii, Ung., Chlor. Prolog., p. 115, pi. xxxiii, figs. 1-4. — Hcor, Fl. Tert. Helv., ii, p. 37, pi. Ixxi, 



iigs. (i, 7. — LikUv., Paluiout., 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. xix, figs. 1-13. — Lesqx., Annual 



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



Leaves of medinni size, ovate, obtusely pointed or acuminate, rounded-subcordate at base, simply 

 or doubly serrate ; lat(!ral nerves and their divisions craspedodrome. 



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

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



