LYCOPODIALES— LEPIDODENDRE^— OMPHALOPHLOIOS. 225 



frequently deiiued in the carbon at the margin of the ovate-trianguhir, con- 

 cave areas, representing the compressed large bosses in those specimens. 



It remains also to note a minute mammilla, sometimes slightly depressed, 

 occasionally seen a little above the upper margin of the large boss. This trace 

 lies within a loop of the low, round, vertical ridges sometimes crossing the 

 large boss. Though these ridges are sometimes clear in the molds or impres- 

 sions, appearing as grooves or furrows, they are usually rather obscure on 

 the surface of the cortex, and may be entirely subcortical. 



Concerning the cicatricial traces within the leaf scar itself little can 

 yet be said. What appears to be a vascular trace is observable in many 

 instances. Also certain obscure depressions in the bolster, which occupy 

 the position of the respiratory appendages at the base of the leaf, seem to 

 be present; but I am far from certain that these appearances may'not really 

 be due to accident or other causes. 



In the slab, Mus. Reg. 5636, photographed in PI. LXVII, Fig. 1, we 

 have a large forked segment showing on the left the full width of the 

 branch, the cast of the lower portion of which is still in place. The upper 

 part or impression is the mold or counterpart of the fragment, PI. LXVIII, 

 Fig. 2, just discussed. The similarity of the preservation on the lower left 

 to that found in the lower right on the same slab is at once apparent. The 

 middle portion of the branch on the right presents, however, the same char- 

 acters as the lower portion of the other branch. In fact, we have at once 

 on this specimen impressions of the large central convex boss of the type 

 originally described as Lepidodendron cyclostigma, the quadrangular com- 

 pressed bolsters, and the flattened bosses, showing distinctly the details noted 

 on the surface of the preserved stem. I am not absolutely certain whether 

 in this slab we have a dichotomizing stem or trunk, or whether possibly two 

 trunks are superimposed. The facts that the bolsters below are in accord- 

 ance as to direction, that those on the right of the angle change the direc- 

 tion of curve, as is natural at a dichotomy, and that I find no intercalated 

 or separative zone or material, save numerous plications of the cortical 

 tissues, make it seem most probable that the two branches are in actual 

 union. Such plications are usually found in the angle of compressed 

 Lepidodendroid stems, and they are especially to be looked for in those in 

 which the cortical tissues are evidently spongy and therefore subject to 

 displacement under pressure. 



JION XXXVII 15 



