A FERN FORMING A NEW GENUS — ETHERIDGE. 
143 
so that here alone among Ferns the bundles are capable of second- 
ary thickening. The whole cylinder is enclosed by a bundle-sheath 
(endodermis) consisting of a single layer of cells. The cortical 
part of the stem is mainly composed of starch-bearing parenchyma, 
but the outermost layers show a formation of cork.” An excellent 
diagramatic sketch of the several parts accompanies these remarks. 
I believe PI. xxvi., tig. 10, to practically represent the greater 
portion, if not all, of the stem or caudex, viewed transversely. It 
will be noticed that the central portions retain a fairly continuous 
oval contour, but the outer portions, possibly from extraneous 
causes, have been crushed together, and the contour broken or 
distorted. The dark centre in our figure, and from which the 
whole structure in the specimen has been obliterated, represents 
without doubt the pith (there is no evidence of primary wood), 
whilst the zone surrounding this is the secondary wood or xylem. 
The tw r o outer rings in PL xxvi., fig. 10, judging by Dr. Campbell’s, 
may possibly represent — the inner one the endodermis, and the 
outer the cork formation of the parenchyma. These rings in the 
fossil are of a dark orange-brown colour. In the enlarged figure, 
(PI. xxvi., fig. 11) the dark radiating lines perhaps represent the 
medullary rays. 
The following measurements were kindly made by Mr. T. 
Whitelegee : — 
Longer diameter of caudex 
Shorter ,, ,, ... 
Diameter of pith 
Width of ring of secondary wood 
Space between exo- and endoderm 
Space between endoderm and secondary 
18 mm. 
1*2 „ 
0-35 „ 
0-25 „ 
0T to 0 "2 mm. 
wood 
Width of exoderm ... 
Width of endoderm . . . 
0 - 0 to 0T ,, 
0 04 mm. 
0-03 „ 
In a longitudinal section of the caudex (PL xxvii., fig. 12) the 
same number of zones can be distinguished as in a transverse 
section (PI. xxvi., fig. 10). Thus, the central cylinder, without 
structure, is followed by the zone of secondary wood, in which 
faint longitudinal parallel lines can be discerned, answering to the 
radial lines in Plate xxvi., figs. 10 and 11, but no minute details 
can be made out. The edge of the secondary wood is of the same 
deep amber-brown colour already referred to in other parts of the 
organism, and between this and the layer corresponding to the 
endoderm in Dr. CampbelLs diagram of the stem in Botrychium , 
is a further narrow structureless zone (the inner of the two in 
PL xxvi., fig. 10), that varies so much in radial diameter. The 
endoderm and the exoderm are again of a deep amber-brown tint, 
and form strongly marked features of the section, the intermediate 
