Vol. 2 No. 3 



TORREYA 



March, 1902 



ADDITIONAL NOTES ON LIRIODENDRON LEAVES 

 By Edward W. Berry 



(With Plates i and 2) 



Any attempt at tracing the phylogeny of a species or group 

 is always largely theoretical. The data upon which such specu- 

 lations are based are always insufficient, especially when dealing 

 with but one set of organs such as leaves. The extinct forms, 

 generally the most essential for the correct understanding of the 

 existing, are unknown for the most part and are represented by 

 but here and there a fragment. At the same time phylogenetical 

 hypotheses serve a coordinating purpose and are usually fertile 

 with suggestions for further research. 



The existing species of Liriodendron has never been adequately 

 studied ; especially is this true with regard to leaf-form, although 

 the leaves furnish the only basis for comparison with the numer- 

 ous fossil species. The response of organs such as leaves to 

 their environment is generally rapid and we may be sure that 

 similar changes in form may have appeared independently at any 

 time when the proper environment was furnished ; witness the 

 interrelations of the variously denominated lobed leaves of the 

 American Cretaceous. Thus it might seem that leaves afford 

 little support for arguments as to ancestry or identity ; and while 

 this may be true when views are based on individual speci- 

 mens or single "sports" it is not so far-reaching when argu- 

 ments are supported by innumerable specimens, or series of 

 specimens of a single species or genus showing constant gradations. 



In a forthcoming article in the Botanical Gazette I have at- 

 tempted a brief sketch of the probable relations of the various 



[The exact date of publication of each issue of Torkeya is given in the succeed- 

 ing number. Vol. 2, No. 2, comprising pages 17-32, was issued February 21, 1902.] 



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