Palaeontologie. 509 



riodendron tulipifera, leaves on the same twigs as flowers tend 

 to an abbreviated blade, while by cutting off shoots of the 

 same year and forcing the development of next year's buds, 

 leaves, similar to them are also obtained. From this it is 

 argued that sterile soil, lack of humidity or similar adverse con- 

 ditions may have been responsible for the development of the 

 Liriophyllum type of leaf. 



With the progress of Dakota time, the warm and humid Cre- 

 taceous climate fostered rapid development of Llriodendron, and 

 with increase of size the leaves exhibited Variation in lobation 

 in direct response to varying conditions of nourishment. This 

 argument is supported by observations lipon L. tulipifera which 

 shows parallel variations under similar conditions. L. giganteum 

 Lesq. represents the culmination of a series of slight changes 

 originating in the more primitive L. Meekii through constantly 

 enlarging and more lobate forms induced by the con- 

 ditions noted above. L. oblongifolium lies in the direct line of 

 descent leading to L. tulipifera from which the latter has 

 deviated but slightly. 



American types appear to offer no connection between 

 L. oblongifolium and L. tulipifera, but European species appear 

 to establish a satisfactory and nearly complete series. The 

 curiously lobate forms from the American Cretaceous, embra- 

 cing four species and one variety, are unlike any modern spe- 

 cies and they evidently form a collateral branch to the ancestral 

 line. Of these, L. intermedium may have sprung from 

 L. giganteum and have led to L. Wellingtonii and L. acumi- 

 natum with its variety bilobatum. L. laramiense of Ward was 

 a comparatively simple form developed from the tulipifera form 

 and contemporaneous with it. L. Snowii from the Dakota 

 Group, differs widely from any of the other forms of Liriodendron, 

 and it probably represents an extreme development from 

 L. pinnatifidum, terminating a clolateral line of descent. With 

 the close of the Dakota period, the Liriodendron group appears to 

 have waned, leaving but one or possibly two species in the 

 Laramie and none in the American Tertiary or more recent 

 formations, although the tulip tree flourished in Europe throughout 

 the Tertiary. While the extremely lobate species may have be- 

 come extinct after the close of the Cretaceous, it is probable 

 that the ancestors of the modern tree still flourished, and the 

 imperfect geological record is probably accountable for the lack 

 of evidence of their existence. 



D. P. Penhallow. 



SELLARDS E. H., n the V a 1 i d i t y o f Idiophyllum rotundi- 

 folium Lesq., a FossilPlant from the Coal Measures 

 at Mazon Creek, Illinois. (Amer. Jn'l Soc. Vol. XIV. 

 Sept., 1902. p. 203 2 figures.) 



An examination of material from Mazon Creek, Illinois, now 

 in the Yale Museum, brought to light additional specimens of 



