Gress : Fossil Plants of the Dakota. 309 



evidence of forming five lobes), and one was palmately five-veined 

 but seven-lobed, the veins running to these two extra lobes being 

 secondary veins. The three-lobed leaves have a tendency to form the 

 five palmate veins, as the two lowermost veins were present, but rather 

 delicate. 



/. Platanacecc. — Seven species of Platanns were examined, and all 

 leaves were of the three-palmate-veined form. In the five-lobed 

 leaves the veins extending to the two lowermost lateral lobes are 

 always secondary veins, branching from the two lateral primary veins 

 at some distance from the midrib. One species, Platanns Wrightii 

 Watson, resembles very closely Stcrciilia mucronata and StercuUa 

 Snowii, as figured by Lesquereux, " Flora of the Dakota Group," PI. 30, 

 figs. I, 2, 5, even in the fact that the margin of the lobes shows 

 little, if any,- tendency to serration at the time of blooming. I did 

 not have leaves of these species at the fruiting period. The leaves, 

 however, were large and appeared nearly mature. One species, P. 

 Lindeniana, showed only three-lobed leaves at the blooming period. 

 These leaves were decurrent a distance of from 0.5-1.0 cm. on the 

 inner face of the petiole. In several the base was indeed almost 

 peltate. 



g. Lanraccic. — No Sassafras leaves that I have seen are palmately 

 five-veined. The five-lobed leaves are traversed by secondary veins 

 originating from the two lateral primaries at some distance from the 

 midrib, as is the case with Platanns, but usually even farther from 

 the midrib than in Platanns. According to Sinnott and Bailey (Amer- 

 ican Journal of Botany, Investigations on the Phylogeny of the Angio- 

 sperms, II, 1915, pp. 1-22, Pis. i-iv), Sassafras and Platanns would 

 probably have the trilacunar type of node, and Aralia, Stcrculia, Cis- 

 sitcs,Menispermum, and Liqnidambar would have the trilacunar type, 

 or by amplification the multilacunar type. It seems to me that these 

 palmately three-veined and palmately five-veined methods of venation 

 might be very useful in separating Platanns and Sassafras on the 

 one hand from the other allied genera on the other hand, and that 

 differences, as pointed out by other investigators, particularly by 

 Berry, may be used in separating the genera from each other. Many 

 of the species of Platanns have been reduced to synonymy (see 

 Knowlton, Bulletin U. S. Geological Survey 152, 1898, pp. 168, 169). 

 Lesquereux, in the " Flora of the Dakota Group," p. 72, says : " Indeed 



