342 Bower .—On the Structure of the Axis 
a parenchymatous sheath of two or more layers in thickness ; 
within this on the peripheral side (i. e. on the side nearer 
the arrow in Fig. 8 A) is a dark line, which is the probable 
limit between the sheath and the phloem ; the latter thus 
would consist of some two rows of elements on the side 
of the bundle nearer the periphery of the axis. The xylem 
in the bundles shown in Figs. 8, A and B , is rather irregular, 
and there is no clearly defined protoxylem. 
A longitudinal section through such a bundle, as it traverses 
the large air-space, shows such structure as is seen in Fig. 9. 
At the periphery are still to be seen the points (x) where 
trabeculae have broken away ; the tracheides show a closer 
reticulation on the central than on the peripheral side, but 
there is no more marked sign than this of a protoxylem. 
Finally, the Figs. 10, 11, show, as seen under a lower 
power, the structure which is found towards the apex of 
the cone, when cut in longitudinal section (compare Fig. 2) ; 
in this region the intercellular space is narrower, and the 
bundles more crowded, so that the section here shows some 
approach to the state of an earlier stage of development. 
It is easily seen that the connexion of the bundles to the 
other tissues by means of the trabeculae is here more 
complete, while numerous trabeculae are seen to be broken 
away ; such details are again shown under a higher power 
in Fig. 11, while some of the trabeculae appear to be marked 
by the transverse zone above alluded to. Certain of these 
points have been already illustrated by Sowerby in the plates 
attached to R. Brown’s memoir 1 , but have not been noticed 
by more recent writers. 
After traversing the large air-space, the bundles enter 
the outer dense band of the cortex and finally pass out 
into the sporophylls, but their further behaviour calls for 
no special notice. 
The details of structure above described show a remarkably 
perfect state of preservation, much better, in fact, than that 
Linn. Trans, vol. xx; see especially PI. XXIV, Fig. A. 
