68 
Seward. — A Contribution to our 
which are much like the sclerotic nests characteristic of the 
pith of Lyginodendron. On the whole, until some other fossil 
has been found which agrees better with this doubtful stem, 
we think there is a presumption that it really belonged to 
a Lyginodendron , , or to some plant of the same type of 
structure V 
An examination of additional sections cut from Mr. Nield’s 
specimen has furnished a few more facts as to the anatomical 
structure, and the main object of the present paper is to 
amplify and illustrate by means of a few figures the description 
given by Williamson and Scott. The material on which the 
following account is based consists of (i) the w^ater-worn block 
mentioned by Williamson in 1873, and now in the Botanical 
Department of the British Museum; (2) twelve sections in the 
Botanical Department ; and (3) the following sections in the 
Williamson Collection 1 2 (British Museum), viz. Nos. 1131, 1132, 
1133, 11 83, 1184, 1185. All the sections have been cut from 
the single specimen supplied to Professor Williamson by 
Mr. Nield. In PI. V, Fig. 1, is represented a photographic 
reproduction of a transverse section. The diameter of the 
pith and wood has already been given. The large pith is 
seen to be partially occupied by irregular patches of tissue, 
which in longitudinal section (Fig. 2) assume the form of 
broken transverse bands. The inner margin of the secondary 
wood consists of small dark bands separated by lighter 
radially-elongated spaces. This is more clearly seen in Fig. 6 
and in the lower part of Fig. 3 ; the lighter and broader 
patches were originally occupied by medullary-ray tissue, and 
the darker lines represent the internal limits of rows of 
secondary tracheids. In Fig. 1, and more clearly in Fig. 6, 
the continuity of the inner margin of the wood is interrupted 
at three points, t , t\ and which mark the position of out- 
going groups of xylem-elements, probably leaf-trace bundles 3 . 
1 Phil. Trans., Vol. 186 (1895) B, p. 742. 
2 There are also two small sections in a collection of fossil plants in the 
Botanical Museum, Cambridge. 
3 These groups of tracheids in passing through the secondary xylem of the stem 
