476 



R. KIDSTON AND D. T. GWYNNE-VAUGHAN ON 



until it reaches the pith, where it becomes an internal endodermis running just inside 

 the vascular ring and following closely the inner contour of the xylem strands 

 (fig. 36, in.en.). The internal endodermis curves deeply outwards into each 

 medullary ray, and it also passes far into the concavities of the arch-shaped xylem 

 strands (fig. 36). At the departure of each leaf-trace it communicates with the 

 outer endodermis round the margins of the leaf-gap. Thus, so far as the endo- 

 dermis is concerned, the vascular ring is divided up into a number of separate 



M.fl 



M.lo 



M.z. 



Text fig. 3. — Osmunditcs Carnieri, Schuster. Arrangement of meristeles (M. 1 to M. 8) in the type section 

 described by Schuster. The endodermis is shown by dotted lines, x 2J. 



meristeles each containing a varying number of xylem strands (fig. 35, and text- 

 fig. 3, M.). 



At one point in the vascular ring (x in fig. 35) there is a somewhat irregularly 

 shaped strand of xylem on the inside of which are two separate masses of xylem which 

 appear to have been nipped off from its inner margin. As shown in the enlargement 

 (fig. 38, x, x), each of these is completely surrounded by the internal endodermis. 

 Special significance is attached to this phenomenon because it offers a possible ex- 

 planation of the presence of a group of somewhat similar internal vascular strands 

 in Osmunditcs Skidegatensis described in Fart I. of this memoir,* and there regarded 



* Trans. Roy. Soc. Edin., vol. xlv. p. 772, pi. iv. fig. 23, 1907. 



