LEsyuEKEUx.l EEVIEW OF CRETACEOUS FLORA. 327 



tainly removed by the presence in our lignitic Eocene of some very 

 beauriiul and well characterized species of this geuus: Platanus 

 Haydcnii and P. Reynoldsii, Newby. These species, discovered first in 

 the Tertiary of the Upper Missouri River, near Fort Union, are predom- 

 iuant at Golden, Colo., by the number of specimens which represent 

 tliem, and are also found at Black Butte. The third Tertiary group, 

 that of Carbon, lias, for the more numerous representatives of its flora, 

 leaves of Platanus Aceroides and Fl. GtiiUelmce. 'No species of this 

 genus has been described from the Green River or fourth grouj) ; but 

 we have Irom the Upper Tertiary (Pliocene) of California very fine 

 specimens of leaves of two species of Platanus closely related by their 

 characters to the living Plaianus occidentalis. Therefore, and consider- 

 ing the geological records, we may trace tlie origin of Platanus as far 

 down as the North American Cretaceous, and follow its development 

 through nearly all the stages of the Tertiary to our present time, by a 

 number of closely-allied intermediate forms. 



Coming now to the Laurijiece, 1 have to remark somewhat more defi- 

 nitely on the Cretaceous species referred to this family. The relation 

 of some of them to the genera to which they have been referred is gen- 

 erally acknowledged, and the presence of the Laurineae in our Cretaceous 

 flora receives a kind of historical authority by that of a Sassafras in 

 a Cretaceous formation of Greenland ; of three species of Da^jhno- 

 phyllum in that of Tdoletin, and of Laurus cretacea^ Daphno(jene 

 primigenia, Daphnites Gopperti, in that of Niedershoena. Of the 

 species which have been described formerly in the flora of the Dakota 

 group, Laurus N€hrasce7icis is related to I)aphnophyllum elUpticum and 

 D. crassinervium of Heer, while Ginnamomum and Oreodaphne cretacea 

 are comparable to Daphnogene primigenia of Ettiughausen. Persea 

 Sternhergii is also evidently of the same family, and the two leaves, 

 described here below under the name of Laurus protewfoUa, are indeed 

 allied to species of Laurus or of Persea by their nervation, especially 

 by the more acute angle of divergence of the lower veins, though they 

 show in the grooved middle nerve a character often remarked in species 

 of Ficus, especially Ficus protogea Heer, of the Greenland Cretaceous 

 flora. Moreover, the fruit described (Fl. Cret., p. 74) as Laurus macro- 

 carpa satisfactorily completes the evidence afforded bj' the leaves, of 

 the existence of sjjecies of Laurince in the vegetable world of the Cre- 

 taceous epoch. We have, however, to eliminate of this family Lattro- 

 pliyllum retictdatum, which appears more properly referable to Ficus. 

 Its nervation, and especially its areolation, formed of square or irreg- 

 ularly polygonal meshes by the interposition of tertiary veins between 

 the secondary ones and parallel to them, and the rectangular subdi- 

 vision of its branches, are of the same character as in Ficus Geinitzi, 

 Ett., Ficus protogea, Heer, and many species of this genus now living 

 in Cuba, even Florida, like Ficus suffocans, F. lentiginosa, i: pertusa^ 

 F. dimidiata, etc. Numerous specimens recently touud in Kansas repre- 

 sent this fossil species in characters more precise than formerly, as seen 

 in its more detailed description under the name of Ficus laurophyllum. 



But if the reterence of some of the above-mentioned leaves to the 

 Laurinece is not contested, it is not the same in regard to those which, 

 at first appearance, were considered as more positively related to it, 

 and which have been described under the generic name of Sassafras. 

 The question of the relation of those leaves which, by their number, 

 seem to be the essential components of the North American Cretaceous 

 flora, has been already touched upon.* But since, I have obtained 



* Cretaceous Flora, p. 77. 



