A FERN FORMING A NEW GENUS — ETHERIDGE. 
137 
The fourth example (PI. xxvi., fig. 8) is supplementary in some 
points to PI. xxv., fig. 5, and is the longest portion of caudex in 
the collection, but much decorticated. At one end are portions of 
two fronds extended in opposite directions, and somewhat more 
than halfway down are traces of two others, one attached, the other 
protruding through the matrix, and although riot attached, as in 
the first instance, so clearly answering in position to the corres- 
ponding frond above, on the right hand side, as to leave little 
doubt that it also is in situ. 
Finally PI. xxiv., fig. 9, is the enlarged caudex of PI. xxiv., fig. 2, 
and displays the broken edges of the different zones of the stem 
which will be explained later on. 
The structure of the foregoing specimens may be summarised as 
follows : — 
The Caudex . — The caudex is round, varying from one to three 
millimetres in diameter, and in length from ten to forty-three 
millimetres, so far as preserved, sometimes in the round, at other 
times only as impressions, or both conditions may occur on the 
same example. When in the former state there is clear evidence 
of a peeling-ofi‘ of layers, thus reducing the general bulk of the 
caudex from what it must have really been in nature. At varied 
and inequidistant points may be seen the minute thorn-like pro- 
jections, when a caudex is seen in the round, or, in the case of an 
impression, as small depressions. T am unable to offer any definite 
explanation of these, but similar projections have been figured by 
Mr. R. Kidston on problematical stems from the Lanarkshire 
Goal-field, called Psilotites unilateral^* but as the name implies 
they are on one side only, nor do I, by calling attention to the 
resemblance mean to suggest any relation between the two plants. 
Mr. A. C. Seward has suggested that these may mark the positions 
of roots given off from a creeping rhizome. 
The inode of distribution of the fronds on the caudex is peculiar, 
and, so far as the specimens permit me to judge, constant. At 
intervals occur clusters or tufts of fronds, the intervening caudex 
surface being destitute of leaf clothing. A caudex is therefore 
divided into nodes and internodes (PI. xxv., fig. 5 ; PI. xxvi., 
fig. 8). In PI. xxv., fig. 5, we observe a cluster proceeding from 
an enlargement or corona, and at the other end a displaced cluster 
that has been accidentally pressed backwards. In PI. xxvi., 
fig. 8, traces of two of these nodes are visible, one a little below 
the middle of the caudex, the second at the upper end. The 
enlargement caused by the attachment of the frond bases has 
almost weathered away, but to the right and left of each the edge 
of a frond is traceable, particularly on the right of the lower tuft, 
where it is distinguishable by its re volute margin, and traces of 
# Ann. Mag. Nat. Hist., xvii. (5), 1886, p. 495. 
