332 Barber —On Nematophycus Storriei , nov. sp . 
The presence of these two well-marked kinds of cells is 
characteristic of Nematophycus Logani\ and, as will be seen 
in the sequel, this forms a separating character between this 
species and N. Storriei. 
The transverse section of Nematophycus Logani is charac- 
terised by the presence of a number of more or less radially 
arranged spaces. These appear like clefts in the tissue, of 
fairly constant width, but varying considerably in their radial 
extension (Fig. 4). 
At first sight they appear to be regions where the tissues 
have decayed, but a closer examination occasionally reveals 
the branching and subdivision of a larger tube — leading Pro- 
fessor Penhallow to suggest that these spaces are the points of 
junction between the otherwise distinct larger and smaller tubes. 
There appears, under a low power, in the transverse section, 
to be a series of well-marked concentric rings (Fig. 4). This 
is caused by the considerably diminished diameter of the 
larger tubes in these zones. It is natural, from our knowledge 
of exogenous stems, that the term 4 rings of growth ’ should 
be applied to these. There is always a gradual change in 
the diameter of the tubes in these regions, as opposed to the 
sudden widening of the spring-wood in dicotyledonous stems. 
Occasionally a double ring is met with, such as usually ac- 
companies the formation of new shoots during the summer in 
plants with secondary thickening. 
Beyond these peculiarities of structure, the whole trunk may 
be said to be fairly homogeneous. No distinction seems to 
have been noted between the structure of the central portions 
of the stem and that of the peripheral parts, such as would 
appear if there were a distinct bark 1 . 
The tissues described so far seem to belong to an alga of 
large size with general siphoneoid characters. 
No traces of leaves or roots seem to have been discovered. 
Possibly the thallus was not flattened into c leaves,’ although it 
is hardly probable that the plant was devoid of roots or hapteres. 
The anatomy thus indicated is derived from a careful 
Penhallow, loc. cit., p. 42. 
