1902] NOTES ON SASSAFIiAS 435 



rant its reference to Sassafras. Of rare occurrence, it probably 

 represents a young leaf of some unrelated species, or possibly of 

 the leaf which Fontaine describes under the followins: name. 



Sassafras cretaceum heterolobum resembles S.cretaceum obtu- 

 S7tm Lesq. from the Dakota formation and the Cheyenne sandstone, 

 but is considerably smaller and with more pointed lateral lobes. 



We 



to Cissites, its 



general outline (except the pointed lobes) being quite similar 

 to Cissites salisburiaefoliiis Lesq. from the Dakota formation, 

 which species Lesquereux determined as Populites, Sassafras, 

 and Cissites successively. Or we may consider it as related to 

 the ancestral form from which Platanus, so extensively devel- 

 oped in the succeeding strata, was developed. At any rate, I 

 see no reason why it should be considered a species of Sassafras. 

 Sassafras bilobatum. — While the outline of this leaf does 

 not exactly conform to any modern bilobed Sassafras leaf known 

 to me, it is nearer the latter than it is to any other leaf. The 

 right-angled sinus with straight sides and running to a point is 

 also a feature not seen in the modern leaf. In the latter, when 

 the sinus runs to a point it is narrow and deep ; and when it 

 forms a right angle it is curved and the resulting lobe is gener- 

 ally obtuse and but slightly produced. We have characters 

 which ally this ancient leaf to Sassafras in the decurrent base; 

 I the sub-opposite primaries, as they usually are in the bilobed 



leaves of the existing Sassafras ; the position of the secondaries ; 

 and especially in^the secondary running to the sinus, a feature 

 we would hardly expect to find in so primitive a leaf. We would 

 consider the bilobed leaf as a more ancient type than the tri- 

 lobed form, and removed from the ancestral simple leaf by a 

 series beginning with leaves with but a slight depression mark- 

 ing the position of the future sinus, and a slightly produced 

 obtuse lobe, through formspartially paralleled in the modern leaf, 

 in which these features were more and more emphasized. Just 

 why the leaf became lobed is largely conjectural. The primaries 

 form a more acute angle with the midrib than do the second- 

 aries, especially in the simple leaves ; they are the first and 

 largest arteries branching from the midrib; in the growing leaf 



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