INTRODUCTION. 15 



specimens of this kind as representing species of Sassafras. In the last 

 volume of his superb work on Vegetable Paleontology/ Prof. W. P. Schim- 

 per, speaking of leaves of Sassafras cretaceum, of which I had sent him 

 photographical designs, remarks: "That those leaves, very variable in 

 size, present such a remarkable likeness to those of S. officinale, now living 

 in North America, that one would be disposed to consider them as belong- 

 ing to a homologous species." He rightly adds that the only difference 

 seems to be in the thicker substance of the fossil leaves. Even on this 

 point I have from Texas specimens of the present »S'. officinale, whose leaves 

 appear of a consistence nearly as thick as it seems to be in those of the 

 Dakota Group. 



On the other hand, no species of the Laurinece family living at our 

 time is known with dentate leaves; and it may be remarked, from the 

 figures, that the two leaves described as Sassafras cretaceum ("Cret. FL," 

 pi. xi, figs. 1 and 2) have the borders of the lobes somewhat dentate, and 

 some of the secondary veins running into the point of the teeth, or cras- 

 pedodrome. This character is still more marked in S. mirabile, loc. cit., 

 pi. xii, fig. 1, a form extremely common in Southern Kansas, and repre- 

 sented in very numerous and remarkable varieties. In some of the leaves 

 the secondary veins are all camptodrome, and therefore the borders of the 

 lobes are entire. In others, as seen, pi. xi, fig. 2, the outside lateral veins 

 are craspedodrome, and thus the borders are dentate, while on the inside 

 they curve along the borders, which are entire. In the fine complete leaf 

 (fig. 1 of the same plate) the middle lobe has the veins all camptodrome 

 on the left side, while on the right one, a few of them, one or two, reach to 

 the border, which has, therefore, one or two short indistinct teeth, and the 

 lateral lobes are clearly dentate on the outside only. This evidently shows 

 such a disposition to variations of nervation and border divisions, that I 

 formerly considered as unjustifiable a specific, and still more a generic, 

 division between the leaves of pi. xi, figs. 1 and 2, and those of pi. xii, 

 figs. 2 and 3, of the "Cret. Flora." When, therefore, we find the same 

 difference between the leaves which represent <S'. mirabile (pi. xii, fig. 1), 

 it seems that the same conclusion should follow. But in this case, with 

 the more generally predominant character of the indentation of the leaves, 



' Traite de PaMontologie v^g6tale, vol. iii, p. 298. 



