Gress: Fossil Plants of the Dakota. 307 



" Aralia in American Paleobotany " (Botanical Gazette, XXXVI, Dec, 

 1903, pp. 421-428), also in his "Notes on Sassafras" (Botanical Ga- 

 zette, XXXIV, Dec, 1902, pp. 426-450). It is also discussed by 

 Lester F. Ward in his '' Paleontological History of the Genus Plat- 

 anus " (Proceedings of the U. S. National jMuseum, XI, 1888, pp. 39^ 

 42, Pis. 17-22). 



Berry, in his " Notes on Sassafras," page 448, says : " The varying 

 similarity and interrelation of the forms heretofore referred to Sas- 

 safras, Aralia, Platanus, AspidiophyUmn, Cissitcs, etc., clearly in- 

 dicate that a change must soon be made in our conception of these 

 genera ; and this not only applies to Sassafras, but to various forms 

 referred to the other genera as well, including also Grczviopsis, Mcni- 

 spermites, Credneria, etc" 



Ward, op. cit., in speaking of Platanus, Aralia, Liquidambar, Sassa- 

 fras, Liriodendron, and Aspidiophylliim of the Dakota Group, says: 

 " It would, of course, be wrong to say that all these forms belong to 

 Platanus; but to predict that they will one day be recognized as in- 

 terrelated, and as representing the remote ancestry of the plane and 

 the sycamore, can, in the light of our present knowledge, scarcely be 

 considered rash." Ward believes that all those leaves with a basal 

 lobe like Aralia digifata should be referred to the Platanacccr and sug- 

 gests a new genus called Protoplatanus, or some other name indicative 

 of their ancestral character. (Ward, Bulletin ^j, U. S. Geological Sur- 

 ,vey, 1887, p. 63, under his discussion of Aralia digitata Ward.) 



Such a difference in the lobing, venation, and margin exists in 

 our modern Sassafras and Platanus, that, if strictly observed and 

 adhered to, a revision of these two genera would likely take place. 

 There are also differences in the venation of Platanus and Sassafras, 

 on the one hand, from the allied genera of Aralia. Stcrculia, Cissitcs, 

 etc., on the other hand, which, if accurately observed and strictly 

 adhered to, would, no doubt, place some fossil leaves, which have been 

 referred to these latter genera, in either Platanus or Sassafras, more 

 particularly in Platanus. 



One of the differences referred to is in the branching of the primary 

 veins at the base of the leaf, particularly in the five-lobed type. 

 Platanus and Sassafras are palmately three-veined. Each of the two 

 lateral primaries and the central one, which may be called the mid- 

 rib, go to lobes in the lobed form of the leaf. If the Platanus or 

 Sassafras leaf has five lobes, the veins extending into the two lower- 





