1870.] CARRUTHERS—OCENE FERN-STEM. 351 
its convex surface. The cells adjacent to the inner concave surface 
of the vascular bundle have a deposit of colouring-matter in them ; 
but this disappears towards the base of the petiole. I am able to 
confirm the correctness of Dr. Ogilvie’s description of this dark band 
in the petioles of Osmunda regalis; but it is probably not always 
present, as Prof. Church was not able to detect it in the specimens 
he examined (Linn. Soc. Journal, Botany, vol. vii. 1864, p. 88). 
Bundles of coloured cells occur, also, irregularly scattered through 
the parenchyma of the wings. 
The axis gives off in the older portions numerous adventitious 
roots. These proceed, as in tree ferns, from the interpetiolar spaces, 
and are not developed from the base of each petiole as figured and 
deseribed by Duval Jouve in the living plant (Billot’s Annotations 
a la Flore de France, 1855, p. 51, pl. 1. fig. 5 A). In the fossil I 
have a preparation showing their independent origin; and in the 
living Royal Fern I have dissected them out, tracing them into the 
vascular cylinder. They have a different structure from that of the 
petioles, being more or less circular in transverse section, and com- 
posed of a small central vascular bundle imbedded in a very little pale 
parenchyma, and both surrounded by a cylinder of very dark brown 
elongated cellular tissue. On issuing from the axis the root pushes 
through the cellular tissues of the petioles, until it is able to pass 
upwards between two. It then repeatedly branches; and when it 
escapes beyond the bases of the petioles the branches become long 
and wiry, and form a dense covering around the recent stems. This 
has disappeared from the fossil, because of the rubbing to which it 
has been subjected; but the branching roots are obvious among the 
petioles in the least-worn surface. 
The singularly perfect preservation of the tissues of this fossil is very 
remarkable. Not only are all the cells and vessels intact, but even 
the starch-granules, which abound in the parenchyma of ferns, still 
fill the cells in which they were originally formed ; or rather, I should 
say, the silica by which they are replaced, and which assumes their 
form,is there. In the form of the granules, and in the method in 
which they are packed in the cells, the fossil agrees exactly with 
the recent species. Many of the cells contain the mycelium 
threads of a parasitic fungus, which are inarticulate, and probably 
belong to the genus Peronospora, one species of which is too familiar 
from the injury it has brought on the potato crops. The dead stem 
of the fossil must have been at once attacked by this parasite; it 
could never have been desiccated, as the most delicate tissues are 
perfectly preserved. Buried in the moist clay, the silica must have 
speedily replaced the organic tissues before the most delicate cells, the 
mycelium threads, or even the starch-granules were disorganized. 
The position of the fossil cannot be doubted. It certainly belongs 
to Osmundacece, and most probably to the genus Osmunda. It would 
be referred without hesitation to this genus by some workers in fossil 
botany ; but it seems to me most desirable not to refer positively a 
fossil to a recent genus which has been established upon characters 
that are not present, and consequently cannot be determined, in the 
