838 



J. W. DAWSON ON A SPECIMEN OF DIPLOX^LON 



greatest diameter, and consists of a central pith cylinder and two con- 

 centric coats of scalariform tissue (fig. 3). The pith cylinder is replaced 

 by sandstone, and is about one centimetre in diameter. The inner 



Fig. 2. — Longitudinal and Transverse Sections of the Trunk, showing 

 the position of the Axis. (Scale 2\ feet to 1 inch. Drawn by 

 Mr. Hill.) 



a, a, a. Internal axis. 



cylinder of scalariform tissue is perfectly continuous, not radiated, 

 and about one millimetre in thickness. Its vessels aro somewhat 

 crushed, but have been of large diameter. Its outer surface, which 



