THE CALAMARIEAE i 7 



surface of the wood. Hence the superficial resemblance 

 of these specimens to the ribbed stem of an Equisetum 

 is fallacious, except that in both cases the marks on the 

 surface are related to the course of the vascular bundles. 

 In some specimens the tissue of the stem surrounding 

 the medullary cast is preserved, and the true cortical 

 surface shown. The latter is either smooth, or, if 

 ribbed, the ribs do not correspond to those of the 



HHHBWvn 



Fig. 2.— Catamites Suckovjit. Medullary cast, showing three nodes, on one of which 

 the cast of a branch is borne. Below each node, and between the furrows, the 

 prints of the infranodal canals are seen. About V of natural size. After Stur. 



medullary casts. 1 The characters which first suggested 

 Equisetaceous affinities having proved to a certain extent 

 deceptive, the whole question had to be reconsidered, 

 and the systematic position of these fossils has now 

 been determined by arguments of quite a different kind, 

 drawn from the fructifications and from the anatomy 

 of specimens with their structure preserved. 



1 The external surface of the wood, however, in decorticated pertrilied 

 specimens, is sometimes ribbed, and may bear a deceptive resemblance to 

 that of a medullary cast. 



2 



