CRETACEOUS FLORA. 11 



Populltes.l 



long petiole; borders entire, undulate; nervation obscurely tripalmate; and craspedodrome 

 primary lateral nerves emerging at a distance above the basal borders, 



I have figured two fragments of this species, in order to show the real form of 

 the leaves. In comparing the two figures it will be seen that in PI. A, fig. 2, the 

 primary lateral nerves are at a slightly greater distance above the basal border than 

 in PI. B, fig. 1, a fragment which has exactly the same characters as in the leaf in 

 Oret. Fl. loc. cit. The leaves are generally large, about 9 cm. long and nearly as broad. 

 The lateral nerves about parallel, at an angle of divergence of 40, branch under- 

 neath, or sometimes dichotomously, the ultimate division becoming very thin, but 

 running into the border as sub-craspedodrome, a character rarely remarked in 

 the living species of Populus. It is for this reason that I have preserved for the 

 leaves having this peculiar character the name of Populites. 



The genus Populus was abundantly represented in the Cretaceous of North 

 America. In his Phyllites de Nebraska, Heer has described one species. Prof. 

 Newberry has three, also from Nebraska, in his Notes on the Extinct Floras. I 

 have added to the number three in the Cret. Fl. from Kansas and Nebraska, and one 

 described here below, or already 8 species. And still Heer has found four species in 

 the specimens from the Cretaceous of Atane, Greenland, a formation which, by the 

 number of its species identical with those of the Dakota group, is evidently of the 

 same age. Even the first and only leaf of a dicotyledon found at Korne, a stage 

 of the Cretaceous of Greenland lower than Atane, is that of a Populus. It is 

 remarkable that all the species of Greenland have a camptodrome nervation. 



-Hob. North side of the Big Cottonwood river, near New Ulm, Minnesota. 

 M-ns. Beg. Nos. 5155 C, 5377. 



POPULITES CYCLOPHYLLUS? Heer. 



Proceed, of the Acad. of Nat. Sci. of Philadelphia, 1858, p. 266. Lesqx., Cret. Fl. p. 59, PL IV, f. 5; PL 

 XXIV, f. 4. 



Leaves round, entire, slightly undulate rounded or truncate to the petiole, texture 

 rather thin; nervation pinnate; lower lateral nerves, emerging at the base of the leaves all 

 craspedodrome, straight, simple, except the lowest pair branching underneath. 



The species is still uncertain, as I remarked in the first description I. c. I have 

 referred to it leaves answering to the description of Heer, but the author does not 

 consider my reference as right. I have not seen any original specimen nor any 

 figure of it. The specimens from Minnesota are mere fragments, not sufficient for a 

 positive determination. 



Hub. North side of the Big Cottonwood river, near New Ulm. 

 Mus. Eeg. No. 5155. 



