LEPIDODENDRON 131 



marks or prints are seen, all of which lie in a hori- 

 zontal line, towards the lower edge of the scar. The 

 anatomy of specimens with their structure preserved 

 has shown that, of these three marks, the median one 

 alone represents the vascular bundle, which originally- 

 passed out into the leaf. The two lateral scars, as we 

 shall see presently, represent parenchymatous strands ; 

 together they bear the name of the parichnos. 



Besides the marks on the actual scar, there are 

 others on the surface of the leaf-cushion. The most 

 conspicuous of these are two large round prints or 

 depressions below the scar, lying one on each side of 

 the prominent angle of the pyramidal cushion (see 

 Fig- SS> a )- These, as is shown by anatomical investi- 

 gation, were connected internally with the parichnos. 



Immediately above the scar, and in the median line 

 of the cushion, is a small triangular print (Fig. 55, /), 

 which has been proved to mark the position of the 

 ligule; in Lepidodendron this organ was constantly present 

 on the upper side of the leaf-base, as in the genera Selagi- 

 nella and Isoetes at the present day. Other marks are 

 sometimes found on the leaf-cushions, but those already 

 described are the most constant and important. 



The above description is based on the most perfect 

 specimens preserved as casts, i.e. with the surface show- 

 ing its natural form. Where, as is often the case, the 

 specimen represents a " mould " of the exterior, the 

 depressions and elevations are, of course, reversed. 



We have a curious illustration of the difficulties of 

 nomenclature in fossil botany, in the fact that distinct 

 genera have been founded on specimens which are now 

 known to represent merely imperfect states of preserva- 



