Observations upon some Noteworthy Leaf Variations. 279 

 Observations upon some Noteworthy Leaf Variations, 



AND THEIR BEARING UPON PaLAEONTOLOGICAL 

 EVIDENCE. 



D. P. Penhallow. 



Our attention has been directed somewhat particularly of 

 late to one or two noteworthy instances of leaf variation 

 which seem worthy of record because of their important bear- 

 ing upon the character of palaeontological evidence, so far as 

 it is represented by fossil leaves. The present discussion is 

 not advanced with a view of proving any new idea, but in the 

 hope that it may serve to somewhat amplify our range of 

 facts as applicable to a view expressed by Ward as long ago as 

 1888, ' and since then amply proved by Holm" and Berry 3 

 with respect to Sassafras officinale and Liriodendron tulip- 

 ifera. While the evidence thus brought forward amply sup- 

 ports the opinion of botanists generally, that leaves, when 

 considered separately and wholly apart from the parent stem, 

 and especially when presented in a fragmentary condition, 

 afford no proper basis for the scientific recognition of species, 

 any extension of our knowledge which will tend to throw 

 light upon the extent of leaf variation among different species ; 

 the range of forms presented by the same species ; the dis- 

 tribution of these forms on the plant, and, above all, the 

 conditions under which such variations arise, will no doubt 

 serve a useful purpose in correcting one of the most fruit- 

 ful sources of error in the palaeontological record of the past, 

 since there is no doubt whatever, that the great multiplicity 

 of species recorded in such important works as those of 

 Lesquereux and Newberry and Heer, must eventually undergo 

 revision in the light of such evidence, when it will be found 

 that many forms now separately established are but variants 

 of one species. It is as a small contribution to this end that 

 the present notes are offered. 



1. The Palseontologic History of the Genus Platanus. Proc. U S. Nat. Mus., XI, 



1888. 



2. Notes on the Leaves of Lirio Jendron. Proc. U. S. Nat., Mus., XIII, 1890, 15-35 

 On the Va'idity of some fossil species of Liriodendron. Bot. Gaz., XX, 1895, 



312-316 



3. Additional Notes on Liriodendron Leaves. Torreya, vol. 2, 1902, 33-37 



