468 
f 
margins; petioles long, stout and conspicuously winged; nerva- 
tion characteristic of the genus, consisting of two sets of parallel 
secondaries, one strong, connecting near the margins in festoons, 
the other weaker and intermediate with the former. 
Laramie group, Walsenberg, Colo. Collected by Mr. J. Mil- 
ligan under the direction of Mr. R. C. Hills. 
_* The genus Liriodendron is represented. in our living flora by a 
single species, L. Tulipifera L., our well known tulip tree, and a 
doubtful variety, L. Zulipifera Chinense Hemsl. from eastern Asia.* 
In the past, however, ranging from middle Cretaceous through 
the Tertiary, we find a great number of species referable to the 
genus and its immediate ancestors, the leaves of which indicate 
diversities in form equal to those of the oaks of to-day and with @ 
geographic range equally extensive. 
An enumeration of all the described forms is not necessary 
here, as several papers upon the subject have been already writ- 
ten, prominent among which may be mentioned those by Dr. J. 
S. Newberry+ and Mr. Theo. Holm.{ Incidental comments may 
also be found in the works of Heer, Massalongo, Lesquereux, 
Ward and others. 
If we examine the fossil species described under or referred 
to the genus we find the evolution of the leaf form to be exceed- 
_ ingly interesting and significant. The earliest ones (Liriodendrop- 
sis simplex Newb. mss., Phyllites obcordatus Heer, etc.) have little 
more than the characteristic emarginate apex by which to iden- 
tify them with the genus. Others are slightly lobed or merely 
constricted at the sides (L. primevum Newb., L. Meckii Heer, etc.). 
Yet others are conspicuously lobed (L. giganteum Lesq., L.acumr 
natum Lesq., etc.), while the Tertiary species (L. Procaccinu Ung» 
L. Helveticum Fisch., etc.) are hardly to be distinguished from te. 
living one. Attention may also be called, incidentally, to the “am | 
that there was a constant increase in the size of the leaves durmg 
*1. “Description of some new Phanerogamia collected by Dr. Shearer, at Ki 
kiang, China,” S. Le M. Moore, Journ Bot. 13: 225 (1875). inatly 
2, « Enumeration of all the plants known from China proper, Formosa, fom 
Corea, etc.” F. B, Forbes and W. B. Hemsley, Journ. Linn, Soc. 23: 
+The Ancestors of the Tulip-Tree,” Bull. Torr. Club, 14: 1-7. 4 6% 
oe + Notes on the Leaves of Liriodendron,” Proc. U. S. Nat. Mus. 13: 15-35. : 
