MARYLAND GEOLOGICAL SURVEY 881 



forms grade in several directions, culminating in quite dissimilar leaves. 

 Lesquereux's Sassafras cretaceum is a more planatoid leaf, with more 

 acute tips, a tendency to become dentate, and with the primaries inserted 

 nearer the base. Closely allied to the preceding is his Sassafras (Arali- 

 opsis} mirabile, which serves as a connecting link with his Platanus 

 recurvata. From the aforementioned Sassafras cretaceum of Lesquereux 

 it is but a step to such a leaf as the one shown on pi. viii, fig. 2, Later 

 Ext. FL, and to the trilobed forms referred to Cissites harkerianus, and 

 these in turn grade into the more Cissoid forms of this species, such as 

 those shown on pi. ii, fig. 3, Cret. Flora. The primaries are basal and of not 

 much greater caliber than the regularly succeeding straight secondaries. 

 It is but a step from this leaf to that of Cissites heerii on the one hand, 

 with its palmately five-pointed blade, and to such forms as Cissites 

 acuminatus on pi. v, fig. 4, Cret. and Tert. FL, on the other; which in 

 turn, by the elimination of the decreasing dentate points, gives us the 

 leaf shown on pi. v, fig. 3, Cret. and Tert. Fl. In the second series of 

 leaves diverging from the typical Sassafras cretaceum, pi. viii, fig. 1, 

 Later Ext. FL, is removed a slight distance by the shortening of the blade, 

 the thickening of the primaries and secondaries, and the shortening and 

 rounding of the lobes (Sassafras obtusum) ; while a smaller leaf would 

 be its logical descendant; and from these leaves to those referred to the 

 typical Cissites salisburicefolius is but a step. In the third series of 

 leaves diverging from the typical Sassafras cretaceum, we note that the 

 leaf has its lobes much produced, narrow and running to a sharp point, 

 as in the beautiful leaf on pi. vii, fig. 1, Later Ext. Fl., which, however, 

 is still referred to Sassafras cretaceum. Lesquereux's Sassafras acuti- 

 lolum does not differ greatly from the preceding except in the direction of 

 the lobes, which is a questionable specific character. From this leaf it is 

 no great jump to those trilobed forms which are referred to Aralia welling- 

 toniana, the chief difference being in the margin. Thus we have an inter- 

 related series connecting those leaves which seem to show affinity to 

 Sassafras with those which suggest Platanus on the one hand, and with 

 others which suggest Cissites and Aralia on the other. 



