470 R. K1DSTON AND D. T. UWYNNE-VAUGHAN ON 



of the specimens consisted of the compacted coating of overlapping leaf-bases and 

 roots that once surrounded a stem. The stem itself was evidently included in the 

 other half of the block, which unfortunately was not found. The general appear- 

 ance of our half of the block showing the outer surface of the leaf-bases is seen on 

 PI. XLI. fig. 1. 



The closely packed leaf-bases possessed stipular wings, but the parenchymatous 

 tissues of which they were chiefly composed had almost completely disintegrated 

 before fossilisation took place, and the outline of the individual leaf-bases is entirely 

 lost except at a few favourable places (PI. XLI. fig. 2, a). In the inner region of the 

 leaf-coating, the sclerotic rings of the leaf-bases, though somewhat flattened and 

 crushed, are still fairly distinct. In the outer region they are so broken up and 

 fragmented that individual petioles are no longer recognisable (fig. 3), and this region 

 consists of irregularly scattered masses of sclerenchyma mixed up with crushed and 

 flattened roots in a matrix of detritus and humous material. 



A very interesting feature of this decomposed region is the presence of the 

 solenostelic rhizomes of an altogether different fern provisionally named Soleno- 

 stelopteris radicicula. They creep about in the disintegrated vegetable matter, and 

 four of them are seen in PL XLI. fig. 3, s, running in a more or less vertical direction. 



The petioles forming the coating of leaf-bases are all those of fully developed 

 leaves, there being no zones of abortive or scale leaves. In the larger petioles the 

 leaf-traces are clearly of the adaxially curved C-shaped Osmundaceous type, but they 

 are more or less deformed and distorted by pressure. The inner margin of the leaf- 

 coating in our specimen must have been very near the actual stem itself, for here 

 the xylem strands of the leaf-traces are oval in outline, with only a very small 

 adaxial bay and a single median protoxylem (fig. 4, prx.). They closely resemble 

 certain stages in the departing leaf-trace of Thamnopteris Schlechtendahlii figured 

 in Part III. of this memoir.* 



The ground tissue of the petiole lying between the leaf-trace and the sclerotic 

 ring is thin-walled, and for the most part very badly preserved except for a certain 

 amount of sclerenchyma that always occurs in the concavity of the leaf-trace. In 

 the inmost petioles this sclerenchyma forms a single subtriangular mass occupying 

 the whole space within the concavity of the leaf- trace (fig. 5, scl.). In the outer 

 petioles as the leaf-trace enlarges the sclerenchyma spreads out with it and eventually 

 divides (fig. G, scl.), forming two large and conspicuous masses, one of which occupies 

 the concavity of each of the incurved ends of the trace (fig. 7, scl.). The sclerotic 

 rings of the petiolar bases are stout and well preserved. At the very base they are 

 composed of homogeneous sclerenchyma throughout. At a point higher up two 

 lateral groups of specialised cells are seen at opposite sides of the ring, the cell-walls 

 of which are so much more densely thickened that they stand out in marked contrast 

 to the general appearance of the rest of the ring (text-fig. 1, and PL XL1I. figs. 8 and 



* Trans. Roij. Soc. Edin., vol. xlvi. pi. iv. lig. 23. 



