OF THE WOODY ZONE OF CALAMITE. 175 



belong exclusively to medullary casts ; and_, 2nd, that they 

 are not the scars of leaves or branchlets. I am confirmed 

 in this conclusion by the fact that, though these scars are 

 very distinct on those joints of the pith of the specimen 

 represented in fig. i, from which the verticillate medullary 

 radii have been broken away, they are wholly absent from the 

 longitudinal ridges of the exterior of the specimen. If, as 

 I believe, mine is a correct interpretation of these scars, 

 we must abandon the notion that they were due to internal 

 vascular bundles, or that they were scars occasioned by 

 the separation of external branches ; and, as a consequence, 

 the verticillate arrangement of the branches suggested in 

 the restorations of Dr. Dawson will fail to be sustained, 

 so far as it rests upon the position of these scars, though 

 supported by other facts. Of the external appendages of 

 my plant as yet I know nothing. Since the axes of the 

 cones described by Mr. Binney are characterized by the 

 presence of scalariform tissue, they must belong to his plant 

 rather than to mine ; and there seems no reason to doubt 

 that some species oi Asterophyllites also represent the foliage 

 of the same. All that we know respecting the structure of 

 my plant externally to the woody zone is suggested by fig. i, 

 where we have a very thick layer of sandstone surrounding 

 the woody cylinder, and which must be regarded as repre- 

 senting an equally thick bark. Whether the longitudinal 

 flutings of its exterior really indicate the outermost part 

 of the bark, or whether this, in turn, has been invested 

 by an epidermal layer, represented by the thin cover- 

 ing of coal with which such Calamites are frequently 

 covered, has yet to be determined. Of its growth we 

 know nothing beyond the fact that the plant has de- 

 veloped offshoots from the base of its central stem, as ap- 

 pears obvious from the common occurrence of stems the 

 lower extremities of which exhibit a strongly marked 

 lateral curvature. 



