THE FOSSIL OSMUNDACE^E. 



773 



This phloem also projects into the spaces separating the internal xylem strands, and in 

 two cases the adjacent strands were further separated by a broad tract of sclerenchyma 

 (PI. IV., fig. 23, scl). It was not possible to make out definite protoxylem elements 



p.l. ph. par. 1 



xy. par. 1 ph. 



p.l. ph. pa 



Fig. 1. — Diagrammatic representation of a longitudinal section through the median region of a departing leaf-trace of Osmundites 

 skidegatensis. The xylem (xy. ) is evenly shaded ; the protoxylem (prx. ) is dead black ; the metaphloem (ph. ) is dotted ;. 

 the porose layers (p. I.) are shaded with short lines ; the sclerenchyma (sc. ) is cross-hatched, and the parenchyma (par. 1 

 and par. 2 ) is left unshaded. 



A transverse section taken at the level 1-1 corresponds to the xylem strand xy. 4 in fig. 23, PI. IV. ; at the level 2-2 to 

 the strand xy. 2 in fig. 23, PI. IV. ; at the level 3-3 to the strand marked l.g. sc. 1 hi fig. 24, PI. V. ; at the level 4-4 to the 

 departing leaf-trace U. 3 in fig. 23, PI. IV. ; at the level 5-5 to the leaf-gap Uj. in fig. 23, PL IV. ; and at the level 6-6 

 to the leaf-gap marked l.g. sc. in fig. 24, PI. V. 



in the strands, but in one of them there was a group of small tracheides near its outer 

 end which possibly represents protoxylem. 



These internal vascular strands have to be accepted as actually present in the living 

 plant, for the continuity of their elements with those of the pith is too perfect for their 

 occurrence to be accidental, or for them to be due to the displacement of a broken-off 

 portion of the normal ring which has slipped down from above, as, at first sight, seemed 

 to be the obvious explanation. At the same time, a letter which we have received from 

 Professor Penhallow informs us that this internal vascular tissue is not to be found 



