88 On the Leaf Scars of Lepidodendron. 



The degree of rugosity of the medial line is extremely 

 variable. The line is naturally smooth for some distance he- 

 low the vascular scar, and again for some distance above the 

 terminus of the leaf scar. But if the leaf scar is shortened, 

 the rugosity may reach to the extreme point. The line ex- 

 tending from the superior point of the leaf scar to the crown 

 is always quite smooth. 



The appendages are easily effaced, and upon leaf scars 

 having little relief they are either short or obsolete. Their 

 direction is less variable. 



Narrow portions of the surface of the leaf scars contiguous 

 to the superior sides of the vascular scars, are rarely elevated 

 with the latter. The lines bounding the superior sides of the 

 narrow areas have the appearance of an extra pair of append- 

 ages, particularly when they proceed from the superior angle 

 of the vascular scar. These lines are present in Fig. 4, PL 

 VIII, and are doubtless the upper appendages in distans (Fig. 

 6, PI. VI). It is scarcely necessary to add that they are of no 

 importance as a specific character. 



I suggest the possibility that the future thorough examina- 

 tion of these fossils will prove the identity of L. aculeatum, L. 

 Sternbergii, Brongt., L. crenatum, Sternb., and other so-called 

 species. I think this is not entirely contrary to Prof. 

 Schimper. Of L. aculeatum he says : " Se rencontre avec le pre- 

 cedent, dont il n'est probablement pas autrement distinct que 

 par les grandes cicatrices plus allongees vers le haut et vers 

 le bas." But I judge there is considerable variation in the 

 extremities of Sternbergii, as Prof. Schirnper identifies with it 

 L. obovatum, Sternb., and L. rugosum, Brongt. ; the former of 

 which was described as narrowed and acuminate below, and 

 the latter, if 1 am not mistaken, as narrowed and acuminate at 

 both ends. On the other hand, a large proportion of speci- 

 mens of aculeatum, as I have endeavored to show, are by 

 mutual pressure of the leaves in growth, much shortened at the 

 ends. Prof. Schimper says of L. crenatum, Sternb. : " Gette 

 espece ne se distingue dnLepid. Sternbergii, que par les cicatri- 

 cules un peu plus grandes et proportionnellement plus larges. 

 Ce caract>re me parait peu important." Fig. 4, PI. V, or Fig. 3, 



