VOL. XlII 



] PROCEEDINGS OF THE NATIONAL MUSEUM. 21 



uormal sliai)e. This is, however, only a supposition, but as mentioned 

 above, the leaf shown in Fig. 23 was from a very young plant, of which 

 I observed many in the same locality, all of which were similar. 



If we look now at Plate ix, which represents a part of the foliage of a 

 shoot of the year and developed in the axil of the large leaf. Fig. 38, we 

 shall see, as stated in the explanation of the plates, that Fig. 41 is the 

 first and oldest one of this branch, after which followed a nearly uormal 

 four-lobed one, only a little smaller than usual; after this (Fig. 40), some- 

 what irregular, and still later two normal ones, both of the same shape 

 as Fig. 39, which was the next youngest; the youngest leaf of this 

 branch had again the same shape as that in Fig. 41 ; in short, the old- 

 est and the youngest leaf on the same branch showed an entirely dif- 

 ferent form from the intermediate ones, of which the form has been 

 taken as the normal one for our Liriodendron TnUpifera, viz : ''the four- 

 lobed leaf." It is to be pointed out that instead of the four-lobed leaves 

 it is not uncommon to find leaves with six or even eight lobes, like teeth, 

 as shown in Figs. 3 and 4. The fact that the oldest and youngest leaf 

 on the same branch can differ so much from the other ones seems to be 

 almost constant for the full-grown tree and especially on the lateral 

 branches ; it was at least the case with a very large number of branches, 

 which I examined for that j)urpose. And if we examine very young 

 specimens of our Liriodendron, only five months old, we shall certainly 

 see a still greater variation in the young foliage. In some of these not 

 less than five different forms were to be observed iu six leaves! The 

 first leaf after the cotyledons showed the sliape as given on Plate v, 

 Fig. 10, after this followed another one like Fig, 11, after this two, like 

 Fig. 12, and then two four-lobed ones, the youngest of which showed 

 the form as in Fig. 25, while the preceding was almost like Fig. 23. In 

 general the first four or even five leaves ou the very young Tulip tree 

 have the same curious form as the oldest and youngest on the branches 

 of the full-grown tree. This kind of variation in the foliage of many 

 other trees and even in herbs is not uncommon, and it may certainly 

 be considered as a constant character for many plants. 



What then is the principal character of the recent Liriodendron-\ea,f^ 

 and w^hat characters are to be looked for by the paleobotanists, when 

 identifying fossil leaves, supposed to belong to the genus Liriodendron ? 

 There is nothing more striking in the leaf than the notch at its apex, 

 which, as we have seen in the plates, is to be observed in all the leaves, 

 excepting Fig. 5, both large and small, whether they are lobed or not. 

 And if the paleobotanists do not find a completely preserved leaf, or 

 at least the apex of it, then it will certainly be a question, whether or 

 not they have the true Liriodendron before them, for I do not see any 

 essential difference in the lobes alone nor in the partial nervation, which 

 should be so characteristic as to guide the observer in identifying a 

 fossil Liriodendron, if he had not the summit of the leaf. The lobes, 

 considered by themselves, are not very different from those of many 



