1901.] NATURAL SCIENCES OF PHILADELPHIA. 309 



Liriodendron tulipifera (Tulip Poplar). 



The leaves of this tree ai*e extremely variable, aud different 

 forms of leaves are found by careful examination on the same tree, 

 as so clearly shown by Holm/ who has reduced many of the 

 fossil species established by Heer, Lesquereux and Saporta to the 

 tulipifera form, by finding that a large number of the fossil leaves 

 upon which specific characters were founded are duplicated by the 

 leaves from living trees. GoebeF has shown that it is necessary, 

 in studying leaf forms, to contrast the juvenile and adult condi- 

 tions, because these vary from each other within wide limits. It 

 is of course impossible to limit these sharply. The difference 

 between these juvenile stages and the adult form may be more or 

 less great. The present statistical inquiry is intended to mathe- 

 maticallv contrast these variations. The juvenile forms of leaves 

 in Liriodendron, beginning with the first leaf above the cotyle- 

 dons, may be described as follows : The first leaf is obreuiform, 

 i.e, two rounded lobes and rather deep angular sinus; the second 

 leaf is approximately bilobed, somewhat squarer than a typical 

 obcordate leaf; the third aud fourth leaves are deltoid with shallow 

 apical sinus, and therefore almost horizontal on top; the fifth 

 leaf from the cotyledons is four-lobsd with deep, rounded left and 

 right sinuses, shallow apical sinus and two distinct obtuse apical 

 lobes; the sixth leaf is entire, almost square, with two small lateral 

 lobes and narrowed apical portion. In general, the first four or 

 even five leaves on the very young tulip tree have the same form 

 as the oldest and youngest on the branches of the full-grown tree. 

 The best description of the adult leaf is by A, Michaux,^ as fol- 

 lows: " Foliis abscisso-truncatis, quadri-lobatis," and this descrip- 

 tion has been accepted by such authorities as Bentham and Hooker, 

 aud Gray. Britton' describes the leaves in this manner: " Leaves 

 glabrous, very broadly ovate or nearly orbicular in outline, trun- 

 cate or broadly notched at the apex, truncate, rounded or coi'date 

 at the base, 3'-6' long with 2 apical and 2-4 basal lobes with 

 rounded sinuses, or occasional!}^ entire." The juvenile leaves, as 

 above described, vary remarkably from those adult forms described 



* 1890. Holm, " Notes on the Leaves of Liriodendron," Proceedings of th& 

 Neitioned Museum, XIII, p. 15. 

 'Goebel, Organograpliie der Pflanzen, I. Theil, pp. 121-15L 

 ®1803, A. Michaax, Flora Boreali-Ainerkunn. p. 326. 

 ' 1897, Britton and Brown, Illustreited Flora, II, p. 49. 



