LEPIDODENDREAE. 197 



because he sees in them the secreting extremities of small branches of the 

 vascular bundle which runs through the leaf-cushion. I should rather 

 compare them with the orifices, which are found variously disposed on the 

 base of the leaf- stalks of tree-ferns. But I believe that it will be best to 

 refrain from all hypotheses with respect to this point, and to wait till we 

 have gained the needful light from the anatomical examination of a well- 

 preserved stem-surface. There are still two other distinct marks to be 

 mentioned, which are inserted in the course of the median upper ridge 

 separating the two upper facets of the cushion, and which Stur was the 

 first to notice with the proper attention. One of these marks is close 

 to the upper angle of the scar, and forms in all cases according to Stur a 

 slight depression in the coal of the leaf-cushion ; it is triangular in shape, 

 with the point directed upwards. It must therefore be always seen on the 

 mould as a small protuberance. Nevertheless I have before me a particu- 

 larly well-preserved mould of a forked stem belonging probably to Lepido- 

 dendron Goppertianum which I found in the Dutweiler mine near Saar- 

 briacken, in which this mark appears as a deep pit-like depression. I must 

 presume therefore that a change has taken place in this object similar to 

 that which affects the trace-points in the lower faces. And when Stur appeals 

 to Selaginella and considers this pit to be the ligular pit of Lepidodendron, 

 the comparison is perhaps a just one, for the position does in fact agree 

 with that of the ligule in Selaginella. But no proof can be adduced for or 

 against this view, and both the absence of a ligula in Lycopodium and 

 the resemblance between the small trace and other small scars in the 

 cushion suggest caution, and make so wide an interpretation of minute facts 

 appear too imaginative. The second spot which is situated on the median 

 upper corner occupies the very uppermost angle of the leaf-cushion ; it is 

 raised and prominent, and like the other is triangular in form. Stur sees in 

 it a rudimentary indication of the point at the base of the leaf, on which 

 the sporangium is seated in the fertile leaves of Isoetes and Selaginella. 

 As this view is simply the logical consequence of the hypotheses just 

 described, it stands or falls with them. The object of the present work 

 does not require us to discuss the distribution into numerous species, which 

 is chiefly founded on the form of the cushion and the position of the scar. 

 Figure 19, A and D, will illustrate the above remarks. 



Hitherto*we have been engaged exclusively with the character of the 

 surface of the stem in- a perfect state of preservation. But specimens of 

 impressions are very frequently met with which have a different appearance, 

 and these were consequently grouped together by the older authors under 

 distinct genera ; but further research has had the result of showing with 

 greater or less certainty that these forms are nothing more than states of 

 preservation of stems of Lepidodendron. In the case of most of them this 

 view is generally accepted at the present day, and the old generic names 



