58 BOTANICAL GAZETTE [JULV 



alatmn of the Laramie, unless certain forms referred to Paliurus^^ 

 are the remains of stipules, they must have been developed early 

 in the history of the group, before the vernation became fixed 

 and the petioles lengthened. L. giganteum had a very large leaf, 

 5 by 16.5*^'", with consequently large veins, oblique or rectan- 

 gular, oblong, obtuse lobes, and deeply emarginate apex. We 

 have a number of leaf forms of L. Tulipifera from particularly 

 luxuriant saplings that greatly resemble L. gigaiitetim. The 

 venation is similar; the general contour is similar, the lobes m 

 L. Tulipifera being a trifle less obtuse; and, \\V^ L. giganteum, 

 these are very large leaves, in fact in all extra large leaves of 

 Z, Tulipifera the tendency is to assume a form that approximates 

 Z. gigantetitn in a general way, and we have a number of such 

 forms in our collection. L. giganteum cruciforme Lesq. differs 

 but slightly from Z. gigaiitetim, the lobes being more nearly at 

 right angles and the intervening sinuses deeper and narrower; 

 the lobes are also somewhat less obtuse and more like some of 

 our specimens of Z. Tulipifera, Dawson's L, praetulipiferum from 

 the Upper Cretaceous is evidently related to L, giga?iteum. It 

 also resembles some of the forms of Z. Meekii, and is without 

 doubt closely related to the then existing ancestor of our modern 

 tulip tree. 



The next species in the geological record is Z. oblongifolium 

 Newb. from the Amboy clays of New Jersey. Among the 

 various published figures of this species all are fragmentary and 

 of more or less uncertain affinity except one figure which shows 



Tulipifi 



ifoli 



direct line of descent leading to Z. Tulipifera, from which the 

 latter has changed but slightly. Z. oblongifolium is somewhat 

 less lobate than the modern leaf, and has the lateral veins nearly 

 straight, ascending, and approximately parallel. There is no 

 doubt that Z. oblongifolium, L.praetulipifertim, and L. giganteum 



'7 See Flora of Aniboy clays,//. 23. figs. 5, 9/ Flora of the Dakota group, //• J-5' 

 fi^s.6, 7; BulLTorr. Hot. Club 21 : pL lyj-fi^^S; Trans. N. Y. Acad. Sci. 12: //- ^• 

 figs. 12. 18, IQ. 



