lesquereux.] EEVIEW OF CRETACEOUS FLORA. 329 



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 undistinct teeth, and the lateral lobes are clearly dentate on the out- 

 side only. This evidently shows such a disposition to variations of 

 nervation and border divisions, that I did formerly consider as unjusti- 

 fiable a specific, and still more a generic division between the leaves of 

 PI. XI, figs. 1 and 2, and those of PL XII, figs. 2 and 3, of the Cret. 

 Flora. When, therefore, we find the same differences between the 

 leaves which represent 8. 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, which, in some 

 larger specimens than the one figured, are more deeply cut by divisions, 

 like pointed lobes, there is still another one, remarked on a specimen 

 recently discovered, which seems to more forcibly separate these forms 

 from the Laurineas, and indicates a more evident relation to the Aralia- 

 cece. The specimen communicated by M. Chs. Sternberg, to whose 

 careful and zealous researches the flora of the Dakota group is indebted 

 for many important discoveries, represents a large leaf which, by its out- 

 lines, the nervation, and the dentate borders of its lobes, is exactly like 

 our 8. mirabile of PI. XII, fig. 1. The leaf, which is much larger, how- 

 ever, the lobes measuring ten centimeters in length from the point of 

 union of the primary nerves, greatly differs bj the forking of the lateral 

 nerves, from a point two and one-half centimeters above their base, and 

 thus forming, of course, a subdivision of these lobes into two equal parts, 

 or a palmately five-lobed leaf. Among the innumerable varieties in the 

 shape of the leaves of the living Sassafras officinale, we see a constant 

 and gradual mode of division passing from a round or oval and entire 

 shape to a bilobed and trilobed one; but, as yet, I have been unable to 

 observe a single case of subdivision of the lateral lobes, or to find a 

 palmately five-lobed Sassafras leaf. This character is, on the contrary, 

 far more generally seen in the Araliaceee of our time than in the trilo- 

 bate form of Sassafras. But in this section of Araliaceee, the Hedera, 

 which may be compared to our leaves, I do not know any with trilobate 

 leaves. Hedera turbascens, H. discolor, H. argentea, H. aurifolia, H. ja- 

 tropwfolia, have leaves five to seven palmately lobed, or, when occa- 

 sionally trifid, their segments are narrow and acuminate, of a type 

 related to that of Aralia tripartita of PI. I, fig. 1, of the memoir. The ref- 

 erence of these leaves to Araliaceee is, therefore, apparently obscure or 

 uncertain. And still, on another side, comparing the beautiful Aralia 

 saportanea represented in this memoir, fig. 2 of the same plate, we 

 see in its nervation, as well as in the indentation of the borders, &c, a 

 remarkable identity of characters with those of the five-lobate leaf of 

 Araliopsis mirabilis. Thus we have about the same degree of evidence 

 in regard to the relation of these fossil leaves to Aralia or to Sassafras. 

 Going further into this kind of investigation, we are met by a new 

 difficulty in the appearance of another modification in the characters of 

 this peculiar type of leaves. In examining the first specimens of the 

 species represented, PI. II, fig. 1, I could but consider them as repre- 

 senting either Sassafras (Araliopsis) obtusum, or 8. mirabile, for, the 

 specimens being fragmentary, had only the lobes or part of them. 

 As long as the auricled and peltate base was unknown, the reference 

 of the specimen could not be different. The nervation, the form of the 

 lobes, their size, all is of the same character as in 8. mirabile. But 

 in the peltate base of the leaves, which is figured from a leaf pre- 

 served entire, PI. II, fig. 1, and from fragment of much larger ones, 



