30 LEAVES OP LIRIODENDEON HOLM. 



The uext species, L. acuminatum, is a small-leaved forin, of which 

 the two pairs of lobes were only 1"" broad, linear, and acuminate, all 

 curved upwards. It might represent a true species, if it did not be- 

 long to a young tree, for instance of L. intermedium, of which, as 

 mentioned, the lobes were very narrow with a deep sinus, and there is 

 a possibility that the lobes, or at least the upper one, have been di- 

 rected upwards. A similar form has been described as characteristic 

 of L. cruciforme, but the leaves of this species are large, the upper lobes 

 broad and at right angles to the midrib; the lower lobes were narrow 

 and turned upwards, a form that corresponds very closely to a leaf 

 figured on Plate vir, Fig. 28. L. semialatum had merely one pair of 

 short, rounded lobes at the base of the blade, and these were curved 

 upwards and enlarged into an obovate or spathulate entire lamina. 



1 hardly think that we have any leaf in our recent species corre- 

 sponding to this, unless the small, almost entire leaves, figured on Plate 

 V, Figs. 7, 9, 10, 13, etc., might represent a form of an almost similar 

 shape; but the author does not indicate any size of this peculiar leaf, 

 nor any indication of the proportional length and width of the lobes. 

 The last species, described by Lesquereux, is L. pinnatijidum, of which 

 only a single leaf has been found, showing, as remarked by the author, 

 the general fades of a Liriodendron, but subalternately trilobate on 

 each side. The only character of this form should then be that the 

 lobes were not opposite, and we might possibly have an abnormally 

 developed leaf, similar to that, figured on Plate vi. Fig. 24, of which 

 the lobes are to be called " approximately alternating." The top of the 

 leaf was, however, broken, so that the true character of a Liriodendroii, 

 the notched apex, was wanting, and it is therefore a question as to 

 whether the identification has been correct. It is interesting to see the 

 manner in which Lesquereux has considered these six species. It would 

 seem, though, as if he were not unwilling to consider them merely as 

 varieties, perhaps not of one, but of a few species. His remark that 

 the local distribution of the leaves may be relied upon to give some 

 directions for the separation of species is very precise; but, on the 

 other hand, our knowledge of the very distribution of these tyi)es is 

 proportionally far from sufliicient. Some leaves have only been found 

 ill Nebraska and Minnesota, some others in Kansas, but that seems only 

 <o sliow that they have occurred there ; by no means that they have not 

 existed in many other localities, and possibly even together. Another 

 qiU'Stion is that there is a probability that we might consider them as 

 local varieties of one or several species. It seems to me, that even if 

 the species described by Lesquereux are mutually different, then we 

 have seen above a similar variation in the foliage of but one species, and 

 that the recent one. It may not be too hazardous to draw some con- 

 clusions from the living species, and suppose that these ancient American 

 types have shown a liability to variation in the same degree as our re- 

 cent form. We have, in regard to that conclusion, a leaf called Lirio- 

 dendron laramieme by Professor Ward and found in the Laramie 



