THE FOSSIL OSMUNDACE^. 765 



The xylem itself is not so well preserved as in Osmundites Dunlopi, but on the 

 broader walls of the tracheides dark marks are to be seen which indicate the presence 

 of more than one vertical series of pits. In this species the tracheides are about 

 the same size on the outside of the xylem ring as they are on the inside. There is 

 no parenchyma among the tracheides of the xylem, apart from that surrounding the 

 protoxylem elements. 



Although the peripheral tissues of the stele are very much disorganised, distinct 

 indications of the larger sieve-tubes are still to be made out on the outside of the xylem 

 ring (PI. III., fig. 19, S.T.). They occur as wedge-like groups projecting shortly into 

 the medullary rays, and they also form a row on the outside of most of the xylem 

 strands. The outer limit of the stele is clearly defined by the remains of an indubitable 

 endodermis (PI. III., fig. 19, en.), but the structure of the medullary tissue on the 

 inside of the xylem ring is no longer recognisable. 



In the inner cortex, just outside the stele, the leaf- traces are elliptic or slightly 

 reniform in section, and their xylem strands are of the same form, with a single median 

 adaxial protoxylem (PI. III., fig. 11, l.t. 2 ) The leaf- trace as a whole is clearly delimited 

 by the remains of an endodermis, and there are indications of a row of sieve-tubes on 

 the abaxial side of the xylem. The leaf-trace itself retains the same form until it has 

 passed through the sclerotic outer cortex of the stem, but its xylem strand becomes 

 more distinctly curved. 



Structure of the Leap-base. 



Passing out towards the periphery of the fossil, the leaf-trace undergoes the same 

 series of changes as in Osmundites Dunlopi, until in the outermost leaf-bases it has the 

 form of a horse-shoe with deeply inrolled ends. The xylem strand is thin, and so badly 

 preserved that the protoxylem groups are not to be distinguished (PI. IV., fig. 20, It. xy.). 

 It is usually surrounded by a sheath of crushed elements in which no distinct tissues 

 can be recognised. The thin-walled elements lying between the leaf-trace and the 

 sclerotic ring of the petiole have left no remains ; but several small strands of sclerenchyma 

 are present which are still preserved. They occur on all sides of the leaf-trace and also 

 in its concavity, but the two especially conspicuous strands lying in the bays formed 

 by the incurved ends of the leaf-trace in Osmundites Dunlopi are wanting in this species. 

 The leaf-base possessed the same stipular wings as in O. Dunlopi, but they are not so 

 thick, and the sclerotic strands they contain are not irregularly scattered, but are 

 arranged in a single series in each wing of the stipule (PI. IV., fig. 20, sc. St.). This is 

 best seen in PI. VI., fig. 4, which is a diagrammatic restoration of one of the outer 

 leaf-bases. The largest of these strands is nearest the sclerotic ring of the petiole, to 

 which it is often more or less attached, and they gradually decrease in size towards the 

 thin edge of the stipule. The larger strands are distinctly oblong in form, with the 

 long axis at right angles to the surface. The stipular wings were probably more or less 



