Penhallow . — Nematopkyton Ortoni , 5 /. 45 
that only short fragments appear (Figs. 2 and 3). A marked 
peculiarity of the cells in this plant is the frequency with 
which local expansions of the lumen occur. These we can 
only regard as representing the trumpet-hyphae and situations 
of sieve-plates so common in the Laminarieae. Although in 
the majority of cases no sieve-plate could be observed, in 
a few instances the fact of such structures having been 
present was quite obvious (Figs. 2 and 3). One of the 
trumpet-hyphae is shown on a much larger scale in Fig. 5. 
I have had no very good opportunity of instituting a com- 
parison between these structures and the forms occurring in 
the larger species of the Laminarieae. My chief comparison, 
therefore, has been with the forms common to the North 
Atlantic coast ; but through the kindness of Dr. W. G. Farlow, 
it has been possible to take into consideration Macrocystis 
pyrifera 1 . Although differing in detail, the general character 
of these structures in N ematophyton and Macrocystis is so 
similar as to suggest the belief that our fossil is related to 
those modern types of seaweeds of which Macrocystis is an 
example. As in the transverse section, no small hyphae are 
to be found between the large cells, but the latter are seen 
to branch somewhat frequently and always, so far as de- 
termined from the present material, in the immediate vicinity 
of a medullary spot (Fig. 4). 
From the details thus outlined it is clear that the plant is 
an Alga, and of an alliance with the Laminarias. Having 
regard to the general character of the stem-structure, it is 
evident from our specimens that the cortical layer was rela- 
tively thin, the medulla strongly predominating, and in these 
respects the stem presents features which are well represented 
by Laminaria digitata. 
This species differs from all others so far known, in the 
very loose character of the medulla, a feature which may be 
characteristic of the species as a whole, but which may belong 
more particularly to certain regions of the plant, and this 
1 In this connexion comparison may be made with the various forms of trumpet- 
hyphae in Macrocystis , as figured by Prof. F. W. Oliver in Ann. of Bot. I. 95. 
