258 



Scientific Proceedings , Royal Dublin Society. 



The Boot. — The structure of the root is that of a typical Fern. It is 

 diarch, and has a very definite pericycle and endodermis. The cells of the 

 cortex are brown-walled, but are hardly, if at all, sclerosed. 



The Petiole. — It has been seen already that the leaf-trace is formed by 

 the separation of a sector of the stele. Very early a perforation appears at 



Fig. 1. — Diagrammatic drawings showing structure of stele of Taenitis blechnoides. 



the middle of the leaf-trace, thus dividing it into separate straps. In some 

 cases this perforation may be formed before the leaf-trace is separated from 

 the stele (fig. 1, 14). There is no definite rule, and we may regard the 

 latter case as merely being a form in which the perforation is continued 

 downwards a little farther than in the former. The perforation continues 



