NO. 2151. FOSSIL PLANTS FROM FLORISSANT— KNOWLTON. 261 



POPULUS LESQUEREUXI Cockerell. 



Populus lesquereuxi Cockerell, Bull. Torr. Bot. Club, vol. 33, 1906, p. 307; 



Univ. of Colorado Studies, vol. 3, 1906, p. 172. 

 Populus heerii Saporta. Lesqueretjx, Rept. U. S. Geol. Surv. Terr., vol. 8 



(Cret. and Tert. FL), 1883, p. 157, pi. 30, figs. 1-8; pi. 31, fig. 11. [Not P. 



heerii Saporta]. 



This common and well-known Florissant species, which has been 

 correctly seggregated by Cockerell, is represented by a considerable 

 nmnber of well-preserved examples in the several collections. 



POPULUS PYRIFOLIA Klrchner. 



Populus pyrifoUa Kirchner, Trans. St. Louis Acad. Sci., vol. 8, 1898, p. 185, 



pi. 15, fig. 4. 

 Populus oxyphylla Saporta. Lesquereux, Rept. U. S. Geol. Surv. Terr., vol. 8 



(Cret. and Tert. Fl.) 1883, p. 159, pi. 38, figs. 9-11. 



Type of P. pyrifolia.—Csit. No. 33,687, U.S.N.M. 



After a comparison of all these specimens I have come to the con- 

 clusion that there is only a single species represented. The leaf 

 described by Kirchner as Populus pyrifolia is of precisely the same 

 character as the leaves figured by Lesquereux as P, oxypliyTla, the only 

 difference being in the size, the former being about twice as large as 

 the latter. The margin is not preserved in P. pyrifolia, but there is 

 every reason to suppose that it was toothed, as in the others. 



The proper name that should be given this species may be briefly 

 considered. If one could be certain that the leaves referred by Les- 

 quereux to P. oxyphylla were really Saporta's species, then of course 

 Kirchner's P. pyrifoliawould become a synonym of it, but, as Cockerell 

 has said,^ ''in view of the general improbabihty of our species being 

 identical with that of Saporta, I should prefer to use Kirchner's 

 name," I have acceded to this view and have placed these leaves 

 under the name given by Kirchner, where they may remain until 

 evidence to the contrary is forthcoming. 



There are two other specimens in the Hambach collection that I 

 refer here, though neither is as well preserved as the one figured. 



POPULUS MICBO-TREMULOroES, new species. 



Plate 19, fig. 2. 



A branch (4.5 cm. long) bearing prominent leaf scars and indicat- 

 ing a growth of three, and possibly four, seasons ; the presence of six 

 leaves is shown by the petioles which are crowded in a short space, 

 and are alternate in insertion; leaves apparently circular or short- 

 eUiptical in outline, truncate or slightly heart-shaped at base, and 

 there entire, possibly slightly toothed or undulate above; nervation 

 with a relatively strong midrib and several pairs of opposite, or sub- 



1 Univ. of Colorado Studies, vol. 3, 1906, p. 173. 



