﻿156 Canadian Record of Science. 



sions, and extends its differential characters to an 

 important extent. It thus becomes necessary to revise 

 our original diagnosis in conformity with the facts now at 

 hand. 



Xematophyton crassum (Dn.) Pen. 



Transverse. 



Concentric structure rather obscure. Eadial tracts 

 none. Medullary spots numerous, irregularly round or 

 oval, chiefly 174 ;z.-261 fx. broad, and connected by narrow 

 spaces which form a more or less distinct network, 

 enclosing groups of large, thick-walled cells. Cells of the 

 medulla not very compact, rather uniform, ranging from 

 23 U.-62 ^. broad, chiefly about 40 ^. 

 Lo7}gitudi7iaI. 



Cells of the medulla interlacing, often in groups. 

 Medullary spots vertically lenticular or oblong, crowded 

 with small hyphae, 2 //.-lO //. broad, which arise within 

 these areas from branching cells derived from the 

 surrounding structure. 



Highly crystalline forms often show a replacement 

 of the normal structure by a pseudo-cellular structure 

 (Celluloxylon.) 



Found as fragments, also the base of the stipe showing 

 root processes. 



Middle Erian (Devonian) of Gaspe (Bell) ; Hamilton 

 group (Middle Erian) of New York (Clarke and Prosser), 

 and the Upper Silurian (Lower Helderberg) of New York 

 (Mixer.) 



Description of Figures. 



Fig. ]. Transverse section of Nematophyton crassum, 

 showing the distribution of the medullary spots. 

 x45. 



Fig. 2. Transverse section of Nematophyton crassum, 

 showing distribution of the medullary spaces 

 connecting the medullary spots, x 45. 



