* 



INTRODUCTION. H 



referred to the Araliaceoe by a more intimate affinity to Araliopsis species ;' 

 and Platanus affinis seems now, after the examination and comparison of 

 a number of specimens from Kansas, more evidently referable to the 

 Ampelideoe than to the Platanece. Therefore these last two species are 

 now eliminated from this generic division. The first is now Araliopsis 

 recurvatus, the second Cissites affinis. 



I persist in considering Platanus Heerii and P. obtusiloha as two dif- 

 ferent species, though it has been suggested that the last was probably a 

 mere variety of the first. The identity is denied not only by the size, 

 the fades, and the nervation of the leaves, but especially by the thinner 

 texture of those of P. obtusiloha. The fact that the numerous specimens 

 representing it are all from the same place in Nebraska, and that P. Heerii 

 has not been found in that State thus far, confirms this separation. In 

 regard to this last species Professor Geinitz has remarked in " Isis," 1875, 

 p. 558, that paleontologists might, perhaps, recognize in it a Credneria. 

 There is, indeed, some similarity in the general outline of the leaves. But 

 this might be said of many of the generic forms of the Cretaceous, which 

 seem referable to a few different types, or to present in one leaf the charac- 

 ters which are now generally found isolated in separate vegetable groups. 

 The genus Credneria, known as it is to me by what is described by Stiehler, 

 Vol. V of the " Paleontographica," includes species with cordate or sub- 

 cordate leaves (none narrowed to the petiole), and bearing above the base 

 two or three true secondary veins at right angles to the midrib. In P. 

 Heerii the leaves are cuneate at the base, even gradually narrowed or 

 decurrent on the petiole, which thus becomes slightly winged, and the 

 veins under the primary nerves are mere marginal veinlets. Perhaps the 

 relation of this species is more marked to the genus Ettingshausenia, which. 

 I regret to say, is known to me only by supposed synonyms Chondrophjllum 

 grandidentatum, as represented by Heer in the Cretaceous Flora of Moletein, 

 and by Phyllites repandus, Sternb., two forms which have no affinity to 

 Platanus. 



The typical character of the Cretaceous species of Platanus is more 

 evidently related to the Aralieae than to any other. This is proved by the 

 reference to that genus of leaves now generally admitted as species of 



'Hekr, in "Arctic Flora," vol. vi, part 2, admits it as Sassafras. 



