,i6 WATSON, Two Species of Lepidodendron Harcourtii. 



Neither of these characters will suffice to distinguish 

 all specimens of Lepidophloios. 



Thus L. Hickii has transversely elongated leaf bases, 

 but is, as will be shown, a Lepidodendron, and specimens 

 of Lepidophloios acerosus (L. & H.) in the Williamson 

 collection have leaf bases twice as high as wide. 



Lepidophloios acerosus (L. & H.) has never been seen 

 with downwardly directed leaf bases, and Lepidophloios 

 Scoticus, Kidston, has its leaf bases at first directed 

 upward, and subsequently downward. 



In the Generic characters of Lepidophloios given by 

 Mr. Kidston ('93), there is one which will at once dis- 

 tinguish it from Lepidodendron, and which can be easily 

 determined from sections. This character is that the leaf 

 cushions imbricate. 



A simple rule applicable to sections and founded on 

 this character is the following : — 



" If a- normal radius of the stem can be drawn so as to 

 cut more than one leaf cushion, the specimen is a Lepi- 

 dophloios." 



This rule must be applied with care, and it must be 

 remembered that transverse sections are often 20 out, 

 and that longitudinal sections median for the axis are 

 not necessarily radial in the leaf bases. 



Applying the rule just given to L. Hickii, we find 

 that it is not a Lepidophloios, and reconstruction of the leaf 

 bases, by picking a series of sections from the transverse^ 

 tangential, and radial sections gives one a leaf base as in 

 the diagram on the next page. 



This leaf base agrees with certain specimens of 

 Lepidodendron obovatum. 



Comparison of other Lepidodendracece zvith L. Harcourtii. 

 Sections in my collection shew that the true L. Har- 



