144 Mr Seward, Notes on the Binney Collection 



a. The stele. (Text-figure 1.) 



The central part of each stele is occupied by a mass of compact 

 parenchyma 3 mm. in diameter, of which several of the cells were 

 in a state of active growth at the time of fossilisation, as shown by 

 the presence of thin and evidently newly-formed walls. Enclosing 

 the pith there is a continuous cylinder of primary xylem con- 

 sisting of scalariform tracheids, which become smaller in diameter 

 towards the periphery, where the xylem is irregularly corrugated 

 and exhibits a series of more or less prominent points or teeth 

 separated by shallow grooves, agreeing closely with the corona as 

 described by Bertrand and others in Lepidophloios Harcourtii. 

 The edge of the primary xylem is represented in the micro- 

 photograph of Text-figure 1 by a distinct undulating dark line. 

 Next the inner face of the xylem there occur a few isodiametric 

 elements with reticulately pitted walls (PL iv. fig. 8 t) similar to 

 the well-known tracheal elements met with in the inner region of 

 the stele of Lepidodendron vasculare (Binney) 1 . Similar short 

 tracheae occur also in contact with the outer edge of the xylem 2 , 

 and here and there one of the elements is seen slightly internal to 

 the edge of the corona associated with the ordinary scalariform 

 tracheids. Abutting on the xylem there are 2 — 3 rows of very 

 dark polygonal parenchymatous cells, with an occasional isodiametric 

 tracheid ; beyond this we have a zone, about 8 cells deep, consisting 

 of small polygonal cells similar to those in contact with the 

 tracheids, but of lighter colour and more distinctly preserved ; this 

 band is spoken of as the meristematic zone (PI. ill. fig. 3 a, a). 

 Beyond this zone there is a conspicuous band made up in part of 

 large sacs, more or less circular in outline and limited by very thin 

 membranes, associated with smaller and partially disorganised 

 parenchymatous elements ; this region may be termed the secretory 

 zone (PI III. fig. 3, s, s; PL IV. fig. 12 and Text-figure 1). 



ft. Leaf-traces. 



The continuity of the tissues external to the corona is inter- 

 rupted at intervals by oval or circular leaf- traces which traverse 

 the cortical tissues in a gradually ascending course from the 

 periphery of the xylem, from which they appear to be given off in 

 the manner described in detail by Bertrand in the case of Lepido- 

 dendron Harcourtii 3 . A leaf-trace, as seen close to the edge of the 

 xylem, is approximately circular or somewhat elliptical in outline, 

 with an internal protoxylem group (It 1 and It 2, fig. 3, PI. in.) ; as 

 a leaf-trace in its outward course reaches the region of the secretory 

 zone the latter forms a bay in front of the tracheal strand of the 



1 =L. selaginoides Will. 



2 Cf. Maslen (99), p. 362, PI. xxxvi. fig. 2, st. 



3 Bertrand (91) pp. 87 e.t seq. 



