424, MR. A. GC. SEWARD ON A NEW SPECIES OF CONIFER, 
Passing to the longitudinal sections: the radial walls of the 
tracheids show very clearly single or double rows of bordered 
pits, in the latter case the pits occur in opposite pairs as seen 10 
fig. 10. In fig. 11 is represented a slight modification of this 
arrangement: but this is exceptional. In fig. 6 a single 
bordered pit is shown on the tangential wall of a tracheid ; as a 
rule, however, the pits are confined to the radial walls. The 
filled-in cavities of the tracheid are traversed by numerous 
cracks, which occasionally extend across from one wall to the 
other; in addition to these apparent septa, there occur here 
and there, what are in all probability true transverse septa. 
Such walls are not confined to the xylem parenchyma, but also 
occur in the tracheids. Conwentz* notes the occurrence of 
transverse septa in the tracheids of Pinus succinifera, and 
recognises two kinds, comparatively thick walls and others 
much more delicate. In the Wealden species the preservation 
is less perfect than in Conwentz’s specimens, and no such 
distinction can be recognised; indeed it is always difficult in 
dealing with petrified plant tissues, to distinguish original from 
secondary structures. A thin wall in a fossil by no means 
necessarily means a thin wall in the living plant. The septa 
in a specimen of Cordaioxylon Brandlingi, Grand ’Eury, figured 
by Schenk in Zittel’s ‘Handbuch,’+ are probably transverse walls 
across the tracheids, and not the septa of tillen cells as is 
suggested in the description of the figure. 
The character of the medullary rays is clearly shown in 
fig. 7; the contents of the cells have in many cases been 
preserved as a dark coloured or carbonized substance in the 
cell cavity. In fig. 6 is represented one of the comparatively 
short and broad medullary rays, transversed by a horizontally 
running resin duct. In figs. 8 and 9 is shown the nature of the 
pits in the medullary ray cells, these vary somewhat in size and 
shape; no bordered pits have been detected in these cells. The 
connection between the parenchyma of the medullary rays and 
the xylem parenchyma in which the resin ducts occur, may be 
recognised in the radial longitudinal sections.t 
The histological characteristics brought out by the above 
brief description are, I believe, such as to justify the institution 
* ‘Mongraph. baltischen Bernsteinbiume,’ 1890, p. 44. pl. 4. 
+ P. 853, fig. 408. 
t Cf. Strasburger, Histologische Beitrige, Heft iii. p. 4. 
