652 Ml! R. KIDSTON AND MR D. T. UWYNNE-VAUGHAN ON 



will become evident from the subsequent description that an unknown amount of its 

 coating of leaf-bases has been removed from it. Each leaf-base is clearly delimited 

 on the surface of the fossil, owing to the more persistent nature of the sclerotic tissues 

 of the petiole ; and in some of them, for similar reasons, the horseshoe-shaped leaf- 

 trace is also clearly visible. The spirally arranged leaf-traces increase in size quite 

 gradually towards without, not being interrupted by zones of reduced scale leaves as in 

 the living and in certain fossil Osmundacese (fig. 1). Numerous stout roots are seen 

 here and there boring their way through the leaf-bases in various directions. Im- 

 pressions of these roots are also to be seen on the outer surface of the fossil, 

 whose arrangement suggests that they frequently branched while still embedded 

 in the petiolar coating, as they also do in the living Osmundacese (fig. 4). Osmunda 

 cinnamomea presents an extreme case of this root-branching, as may be seen in 

 fig. 5 a and b, which is a photograph of a portion of a branch system dissected out. 



The Histology of the Stem. 



The transverse section of our specimen (fig. 1) shows that the plant possessed a 

 large central stele 13 mm. wide. The xylem mass alone measures 11 mm. in 

 diameter, and it consists of two distinct regions. There is an outer ring of normal 

 trachese surrounding a central mass of xylem elements of a very special and peculiar 

 type (fig. 1, o. xy. and c. xy.). These central elements constitute the greater part of 

 the xylem mass, forming a core about 8 mm. in diameter ; the width of the outer 

 xylem ring being therefore about 3 mm. The peripheral contour of the whole xylem is 

 somewhat uneven, owing to the progressive increase in prominence of the departing 

 leaf-trace xylems. On the outside of the stele there is a wide parenchymatous inner 

 cortex, the tissue of which has become almost completely disorganised (fig. 1, i.e.). This 

 is followed by a somewhat narrower zone of sclerotic outer cortex (fig. 1, sc. C), which 

 by its deep brown colour forms a prominent feature of the fossil and also marks the 

 limit of the stem proper, which is about 50 mm. in diameter. The remainder of 

 the specimen consists of a thick sheath of adpressed and more or less concrescent 

 petiole bases. Only the inner portion of this petiolar coating is present in our 

 specimen, which is bordered by well-preserved fragments of still more pheripheral 

 petioles. Its total extent can only be conjectured, but in the living plant it was 

 probably of considerably greater width. 



To return to the stele. The whole mass of the xylem is entirely without any 

 admixture of parenchyma. The elements of the outer xylem zone are very elon- 

 gated, sharp-pointed trachese with regular multiseriate pits (figs. 6-9). The pits are 

 transversely elongated, and two, three, or four vertical series usually occur on the 

 same facet of the tracheal wall (fig. 10). Five or even six series are also occasionally 

 met with, but simple scalariform tracheae with a single series of pits on each wall 

 are very rare. The trachese diminish slightly in size towards the periphery, without, 



