76 



Populus ardica, Heer. 



Bib: Tert. F]., VII, 179, ph XXIII : Cret. and Tert. Fl., VIII, 225, pi. XLVI : Geol. Surv. 

 Can, 1877, 78, 186 B ; 1876-76 : 1887, 137 E; Is^ Ser. IV, 1888-89 ; VII, 1894, 36, 37 

 0; 231 B : Trans. R.S.G., IV, 1886; VII, 1889. 



This very abundant and well characterized species is found in the United States ranging 

 from the Laramie to the Miocene. It is an almost invariable element of all Tertiary collec- 

 tions. In Canada it is similarly abundant, having appeared in all collections from 1868 to the 

 present time. The localities recorded are Goal brook, Quesnel, Nine-mile creek, 

 Similkameen river, Eed Deer river. Bear river, Mackenzie basin, Omineca river and the Lignite 

 Tertiary of Porcupine creek and Great valley. 



Populus ardica latior, Heer. 



Bib: Geol. Surv. Can., N. Ser., IV. 1888-89 : Trans. E.S.C., VII, 1889. 



The only reference to this leaf is contained in Sir William Dawson's account of plants 

 from the Bear river, Mackenzie basin, collected in 1888. 



Populus halsamoides, Goepp. 

 Bib : Trans. R.S.G., I, 1895 : Fl. Foss. Alask., 1869, 26 : U.S. Geol. Surv. Terr., 1871, 299. 



So far as present records go, Populus halsamoides appears to be a somewhat unusual type 

 of poplar of restricted distribution. In the United States it has been met with at Yellowstone 

 lake and at Gorral Hollow, Galifornia ; and in Alaska it is recorded from Port Graham. In 

 Canada it is known only from Burrard inlet, British Columbia, where it was found 

 in 1895. 



Populus cor data, Newb. 



Bib: Lat. Ex. Fl., 1868, 60 : Cret and Tert.Fl., 1878, pi. XIV: Fl. Foss. Arct., II, 26, pi. 

 IL f. 5. 



■-} 



Although this is a well known arctic species, it has been recorded for only one station 

 in the United States — the Fort Union group of the Yellowstone riv^r, Montana. In Canada 

 it was obtained in the collections of 1906, from Quilchena and the Tulameen river, but it has 

 appeared nowhere else. This maybe due to the very striking resemblance it bears to, and 

 the difficulty of properly dijfferentiating it from, P. zaddachi. An examination of Heer's figures 

 of this latter species, as given in his Arctic Flora, shows a very wide variation of forms which 

 may belong to the same species, but which suggest that according to the limits usually 

 adopted in making species of fossil plants, there are really more than one : and there is a very 

 strong suggestion that P. eordata may be only a variant of P. zaddachi. 



Populus cordifolia, Newb. 



Bib : Trans. R.S.G., III, 1885, iv, 17 : Lat. Ex. Fl., 1868, 18. 



The Lignite Tertiary of Calgary, Alberta, is the only record of P. cordifolia for Canada' 

 and the Dakota group of Nebraska is the only locality in the United States. 



