242 Browne.—A Second Contribution to our Knowledge of the 
are, however, absent from about one-ninth of the circumference of the strand 
from the ninth that points straight outwards. A little later they die out, 
except on the inner side, and we get a medullary strand with inverted 
orientation, an orientation maintained throughout the rest of its course. 
At its inception the strand was intermediate in orientation between an 
inverted and a normal bundle, but nearer to the latter. Where the strand 
is largest, just before it branches (see Text-fig. 4 and PI. XIV, Fig. 2 ), it 
contains, in cross-section, rather more than thirty tracheides. As the small 
phloem-like cells are the first to appear, so they are also the last to die out. 
No traces of endodermal markings were observed in the cells round this 
medullary strand, but in E. maximum they are not usually recognizable 
outside the normal stele of the mature cones. The other much shorter 
medullary strand arises just as the lower one is dying out, and is about 
a millimetre in length. It lies about half-way between the normal stelar 
bundles and the centre of the pith. It is not surrounded by a marked ring 
of tannin-cells, but, at the level of its origin, scattered tannin-cells are 
exceptionally numerous in the pith. 
Though no other medullary strands were met with in Cone C, I found 
two or three patches of unlignified cells like those that occurred above and 
below the medullary vascular tissue (see PI. XIV, Fig. 2 , on the reader’s 
right); these seem to have been groups of cells that might, under conditions 
slightly more favourable to the development of xylem, have given rise to 
medullary tracheides. 
Structure of the Apex of the Cone. 
The apex of the stele of the cone of E. maximum resembles that of the 
cone of E. palustre rather than the apices of the steles of the cones 
of E. arve?ise or E. limosum. For in the last two species a certain number 
of the parenchymatous meshes of the cone persist round the strand or 
strands entering the terminal structure, while in E. palustre and in E. maxi¬ 
mum all the parenchymatous meshes of the cone seem to be closed at the 
apex. Further, in E. arvense two or more strands persist into the apex of 
the cone, and in E. limosum the terminal trace forms the continuation 
of one of the strands of the internode below. In E . palustre and E. maxi¬ 
mum there arises a closed ring of wood, which narrows rapidly, losing its 
£ pith ’, to form a large solid strand that passes into the apical structure. 
The actual diameter of this strand is greater in E. maximum than in 
E. palustre . 
Course of the Traces in the Cortex of the Cone. 
The traces entering the sporangiophores of E. maximum do not always 
pass out radially, but undergo torsion to the left or to the right. This 
is clearly the result of the poor development of the axial xylem at the 
fertile node; some tracts of parenchyma persist at this level in all cones of 
