NOTES ON THE LEAVES OF LIRIODENDRON. 



KV 



Theodor Holm, 



Assistant in the Department of Botany. 

 (With Plates iv-ix.) 



Dnriug the spring of 1889, while engaged in studying the germina- 

 tion of some of our native phmts, I collected quite a large number of 

 germinating plantlets in the woods about Washington, especially along 

 the Potomac shore. In the pursuit of these studies I found many speci- 

 mens of our common Tulip-tree [Liriodendron Tulipifera), which, how- 

 ever, did not particularly attract my attention, since their germination 

 with the cotyledons above ground showed nothing especially remarka- 

 ble; nevertheless I collected a number of them and brought them home 

 for closer examination. I now observed, that although their germina- 

 tion did not present anything of particular interest, they showed a pe- 

 culiar fact in respect to their young foliage-leaves. The two or three 

 leav^es developed upon these young plants showed a great similarity 

 among themselves, and at the same time differed from those of the older 

 or full-grown tree. 1 then began the examination of the foliage of the 

 mature tree, and it was not long before I observed that there was a cer- 

 tain regularity, depending upon the position of the different forms of 

 leaves. 



It is a well known fact that there is a great variation in the leaves of 

 our recent Liriodendron^ not only on the same tree, but even on the 

 same branch, but as this circumstance does not seem to have been 

 much discussed heretofore, it may be of interest, at least to paleobota- 

 nists, to describe the Liriodendron leaf somewhat carefully. After 

 having collected many fine specimens of the leaves, from very young 

 trees and from the branches of some of the oldest ones in the vicinity 

 of Washington, I began to examine the course of the v^ariation. First, 

 however, I looked at the published descriptions of the tree, but it seems 

 to be a fact so well known that the sj'stematic authors have not thought 

 it necessary to mention it. I consulted Prof. Lester P. Ward about it, 

 but he did not remember where these variations were descrit)ed by any 

 author, but advised me to study certain paleobotaufcal publications, 

 and called my attention especially to a paper by Dr. J. a. Newberry, 



Proceediugs National Museum, Vol. XIII— No. 794. 



15 



