FOSSIL PLANTS. 429 



parts of a plant, but also to carefully note the variations of the same plant un- 

 der different circumstances. In this way it has been possible to ascertain the 

 reliability of some doubtful species of Lepidodendron, and to unite in one some 

 parts formerly referred to different species or even to different genera. 



LEPIDODENDRON RIGENS, Sp. nov. 



PI. xxvii, fig. 1 to 3. 



THE concretions of Mazon creek, which have generally pre- 

 served plants or their parts in their integrity, without deform- 

 ing them by compression, have furnished, among other very 

 interesting specimens, the branch of Lepidodendron which is 

 copied in our figure. It shows distinctly the bolster, the point, 

 and mode of attachment of the leaves, around the leaf scars, 

 and the vascular vessels, or bundles, in their disposition in pass- 

 ing from the stem to the leaves, as in fig. 2. At the same time 

 it proves that, in some species at least, the leaves of Lepido- 

 dendron were inflated, or somewhat cylindrical in their whole 

 length, as marked in fig. 3, and not flat, as they are generally 



seen on the shales. These leaves were not hollow or tubulose . 



j 



they are too stiff for that in this species at least, but were 

 probably filled by cellular tissue traversed by three bundles 

 of vessels. The form of these leaves does not appear to be 

 exactly like the outline of the leaf scar, as they seem to ex- 

 tend and become flat on the sides in joining the scar, fig. 2, 

 and in the cross section, fig. 3, enlarged, the leaf does not in- 

 dicate any angular compression on the sides. The bolsters 

 of this branch have not yet their definite form, and therefore 

 the specific affinity, considered from these characters, can not 

 be satisfactorily recognized. The narrower leaves and cica- 

 trices distinguish it evidently from the following species, which 

 it resembles by the length and straightness of the leaves. 



