in the ‘ Seedlings’ of Certain Leptosporangiate Ferns . 379 
The rhizome is creamy-white in colour and thickly clothed with long 
narrow brown ramenta, which at the growing point are greenish and so 
densely packed together that they may be removed en bloc as a firm conical 
cap, the protective value of which is obvious. After the removal of the 
ramenta, the surface of the rhizome is seen to be minutely pitted, each pit 
indicating the place of insertion of a ramentum. The ramenta are narrowly 
triangular in outline and consist of a single layer of cells with yellowish- 
brown walls. Each is inserted upon the rhizome at the base of the shallow 
pit by means of a short multicellular stalk, beyond which the base of the 
ramentum is produced backwards as two auricle-like lobes with densely 
papillose margins, sharply contrasting with the irregularly toothed margin 
of the body of the ramentum. The contour of the cell-walls differs in 
different parts of the scale ; in the lamina the cells are irregularly rect- 
angular in outline, contrasting with the cells in the region of the stalk, which 
are much smaller and hexagonal, with walls of a deep-brown colour. The 
cells of the auricular regions have sinuous contours. 
The primary root of Polypodium aureum is, as usual, diarch. The 
vascular strand is extremely simple, consisting of but a few elements, which 
are, however, very definite. In the transitional region a striking difference 
from the usual course of events is exhibited. Instead of the diarch plate 
gradually becoming rod-like to form the solid protostele of the young stem, 
the xylem extends laterally and becomes strongly curved. The phloem 
extends round the horns of the xylem, but the sieve-tubes are often absent 
from the extremities for a few sections. One or two root-traces join the 
cauline strand at or near the middle of its convex surface, and then the first 
leaf-trace is formed in a very simple and quite exceptional manner, by the 
nipping off of a small part of one of the vascular horns. The first trace is 
concentric, and in several plants was approximately equal to the remaining 
cauline strand. Thus, in striking contrast to other ferns examined, there 
is no central phloem differentiated at the centre of the solid protostele, 
and the first leaf-trace leaves no corresponding gap. The absence of early 
leaf-gaps is, of course, by no means exceptional outside the Polypodiaceae, 
familiar examples being afforded by the Schizaeaceae, Gleicheniaceae 
(Boodle), Osmundaceae ( Osmunda , Faull, Todea , Seward and Ford), and 
Marattiaceae ( Angiopteris , &c., Farmer and Hill). 
Poly podium aureum has already received the attention of Leclerc du 
Sablon 1 and Jeffrey 2 . The former investigator has correctly described the 
very earliest stages in the transition, but announces and figures the later 
appearance of a strand of parenchyma at the centre of the xylem rod. This 
however has been denied by Jeffrey, who was unable to find any such 
1 Loc. cit. 
2 Structure and development of the stem in the Pteridophyta and Gymnosperms. Phil. Trans., 
ser. B, vol. cxcv (1902). 
D d 2 
