FLOEA OF THE DAKOTA GEOTJP. 43 



POPULUS, Linn. 



Populus litigiosa, Heer. 

 "Phyll. Cr6t. du Neb.," p. 13, pi. i, fig. 2; Newby., "Illustr.," pi. iv, fig.l. 



Leaves round in outline, very entire at base ; the two pairs of lower lateral veins 

 opposite, the other alternate and distant ; nervilles curved, simple or forking. (Hr.) 



Hab. — Tekamah, Nebraska. Dr. Capellmi. 



Populus elliptica, Newby. 

 "Later Ext. Fl.," p. 16; "Illustr.," pi. iii, figs. 1, 2. 



Leaves long-petioled, suborbicular or transversely elliptical, slightly cuneate at 

 the base and apiculate at the summit; lower half of leaf entire, upper half or more 

 very regularly and rather finely obtusely serrate or crenate, the points of the teeth 

 inclining upward; primary nerves usually fine, sometimes three, radiating from the 

 base at equal angles; from them the secondary veins spring at acute angles. (Ny.) 



The species is remarkably similar, by the characters of the leaves, to 

 P. ciineata, Newby., loc. cit., p. 64, pi. xiv, figs. 1, 4, a Miocene species of 

 the type of P. arctica, or is, perhaps, one of its numerous varieties. 



Hab. — Blackbird Hills, Nebraska. Dr. F. V. Hayden. 



Populus mlcrophylla, Newby. 



"Later Ext. Fl.," p. 17 ; "Illustr.," pi. m, fig. 5. 



Leaves very small, scarcely an inch in length, broadly cuneate at the entire base, 

 rounded and deeply dentate from the middle upward ; teeth conical, acute or blunt at 

 the apex; uerves finely radiating from the base, branching above, the branches enter- 

 ing the teeth. (Ny.) 



Hab. — Same as the preceding. Dr. F. V. Hayden. 



Populus? cor di folia, Newby. 

 "Later Ext. Fl.," p. 18; "Illustr.," pi. iii, fig. 7. 



Leaves heart-shaped, slightly decurrent on the petiole ; margins entire; nervation 

 fine but distinctly defined; medial nerve straight or slightly curved, running to the 

 margin; lateral nerves, six on each side, diverging about 50°, nearly parallel, straight 

 or slightly curved near the apex, the lower branching ; nervilles at right angles or fork- 

 ing, rarely continuous. (Ny.) 



Hab. — Same locality as the preceding. Dr. F. V. Hayden. 



