1902] NOTES ON SASSAFRAS 449 



Ward suggestecl33 that they be referred to a new genus to be des- 

 ignated Protoplatanus, or some similar name indicative of their 

 ancestral character; but it seems to me that such a comprehen- 

 sive genus would be an unwieldy composite no more satisfactory 

 than the present state of affairs, for surely Platanus was not the 

 only modern form with this style of a leaf that has Cretaceous 

 ancestors. Other Spermatophytes are well represented in strata 

 of corresponding age, and analogy leads us to see no reason why 

 Sassafras, Aralia, Cissus, Liquidambar, etc., should not be pres- 

 ent. We may reasonably expect that the more we know of this 

 flora the more it will be found to resemble the existing flora of 

 North America ; in fact, the tendency of paleobotanists has 

 always been to underestimate the age of the American Creta- 

 ceous. All, or the majority of the Spermatophytes originally had, 

 in all probability, simple leaves; their origin was polyphyletic; 

 and it is very possible that a like environment caused lobation 

 which was thus more or less similar in all of these genera, 

 although the species were quite different in other respects. At 

 the present day a series of leaves of Vitis, Ampelopsis, Vibur- 

 num, Acer, Platanus, etc., could be obtained which would appear 

 to be as closely interrelated as are some of the Cretaceous forms. 



SUMMARY. 



Of the twenty-eight American forms which have been referred 

 to Sassafras the following disposition is made: 



Retained in Sassafras : S. bilobatum, from the Potomac for- 



Mudgi 



P 



ifc 



Hum, S. platanoides, and S. cretaceum (in part), all from the 

 Dakota formation. 



Referred to Aralia : Sassafras acutilobum, doubtfully. 



Referred to Cissites : S. harkeriamcm, S. obtustim, and S. creta- 

 ceum obttmifn. 



Referred to Platanus or Protoplatanus : 5. dissectiim, S. dis- 

 secium symmetric urn, S. mirabile, S. papillosum, S. cretaceum defita- 

 tum and grossedentatum, and S. recurvatum. 



"Bull. 17, U. S. Geol. Surv. 



