452 THE AMERICAN NATURALIST [Vol. XLI 



western slopes of the Sierra Nevada Mountains where, according 

 to Gray ('89, II, 147) the two species now occupy an unstable 

 position of such character that "a little further drying of the 

 climate would precipitate their doom." 



The evidence afforded by the Pleistocene clays of Toronto is 

 therefore in accord, in this respect, with that furnished by certain 

 Pleistocene deposits at Elmira, New York, and by the conclusions 

 elsewhere stated with respect to the recession of Sequoia, Taxo- 

 dium, and probably also Pseudotsuga, from the present Great 

 Plains region of Saskatchewan and Alberta ('04, 64-(35). 



McGiLL University 

 Montreal ' 



LITERATURE. 

 Berry. Edward W. 



'06. Pleistocene Plants from ^'irginia. Torreya, ^'I, 190(3. pp. 88-90. 

 '07. A Tilia from the ?New Jersey Pleistocene. Torreya, VII, 1907. 

 p. 80. , ' 



Britton, N. L. and Brown, A. 



'97. Flora of the Northern States and Canada. II, 1897. 

 Gray, Asa. 



'89. Sequoia and Its History. Scientific Papers, II, 1889. 

 HoLLiCK, Arthur. 



'06. Systematic Palieontology of the Pleistocene Deposits of 

 Maryland. 



Cont. from the N. Y. Bot. Gard., No. 85, 1906. pp. 217-237, 

 PL LXVII-LXXV. 

 Knowlton, F. H. 



'98. Catalogue of the Cretaceous and Tertiary Plants of North America. 

 U. S. Geol. Surv., Bull. 152, 1898. 

 Lesquereux, Leo. 



'83. Cretaceous and Tertiary Flora of the United States. U. S. GeoL 

 Surv. of the Terr. VIII, 1883. PI. LIV, f. 10. 

 Macoun, John. 



'83. Catalogue of Canadian Plants. Geol. Surv. Can., 1883. 

 Penhallow, D. p. 



'90. The Pleistocene Flora of Canada. Bull. Geol. Soc. Amer., I,. 



1890. p. 327. 

 '04. Notes on Tertiary Plants. Trans. R. S. C, X, iv, 1904. pp. 57- 

 76. 

 Sargent, C. S. 



'02. Silva of North America. Ill & IX. 1902. 



