On the Leaf Scars of Lepidodendron, 77 



VII.— On the Structure of Lepidodendron and Sigillaria. 



BY HERMAN L. FAIRCHILD. 



No. 2. — The Variations of the Leaf Scars of Lepidodendron 



Aculeatum, Sternberg. 



(With Plates V-IX.) 



Kead October 1, 1877. 



The determination of species of Lepidodendron is a matter 

 of extreme difficulty. Reasons lying in the fragmentary 

 character of the fossils have already been mentioned. But 

 this is not the only source of difficulty. The number of frag- 

 ments would not be so great an obstacle, if they commonly 

 presented recognizable characteristics, like animal remains, 

 or were even as invariable as some other fossil plants. The 

 chief source of trouble is the mutability of every feature or 

 marking of the leaf scars that has been used to distinguish 

 species. They are all alike unstable. Even the grouping of 

 these features affords no sure basis. The close relationship of 

 the species is another cause of difficulty, which perhaps pro- 

 duces the former. The species appear to blend or run into 

 one another in a manner very discouraging to the student. 

 M. Schimper's judgment, in his " Traite de Palseontologie 

 Vegetale," affords the best illustration I can give of the near 

 affinity of the species and the blending of their various forms. 

 Of Lepidodendron and identical genera, he mentions one hun- 

 dred and nineteen names. Sixty of these he suppresses ; 

 uniting a large number with L. Sternbergii, Brgt. and L. 

 aculeatum, Sternb., leaving only fifty -nine species. The ma- 

 jority of these he regards as closely allied to others; and 

 several of them as founded on differences which he thinks of 

 slight importance, or even worthless. Could he have ex- 

 amined our American species, there would probably be no oc- 

 casion for publishing this article. After enumerating those 

 described by Prof. Lesquereux, he says, " II est fort probable 

 qu'un examen fait sur les lieux memes reduirait ces huit es- 

 peces Pennsylvaniennes a deux ou trois." This sweeping 



