906 PROFESSOR W. C. WILLIAMSON AND DR. D. H. SCOTT ON THE 
At the bractigerous nodes we also find a girdle of short reticulated tracheides, 
reproducing, on a small scale, the structure of a typical Calamitean node (see Plate 81, 
fig. 28, also photograph 10, on Plate 73). 
The bundles which pass out to the whorl of ‘bracts leave the cylinder with an 
obliquely upward course, but soon become perfectly horizontal. These bundles can 
very seldom be traced through the cortex, for they are usually broken away, in the 
region where the inner cortical tissue has perished. In one or two cases, however, 
the continuity is perfect. 
The fertile nodes, at which the sporangiophores were inserted, show scarcely any 
modification of structure, as compared with the internodes. Here the bundles passed 
out at a right angle, but are very seldom preserved throughout their whole course. 
‘The node through which the section shown in Plate 80, fig. 23, was taken, bore seven 
sporangiophores. It will be noticed that while the stele, as a whole, has an obtusely 
triangular section, the xylem shows seven small projecting points (sp. in the figure). 
To these were attached the bundles of the seven sporangiophores ; the bundle at sp* 
is partly preserved. 
It is not possible to give any regular scheme for the longitudinal course of the leaf- 
trace bundles in Calamostachys, for, as we have seen, the number of bundles in the 
axis bears no constant relation to the number of lateral appendages in a whorl. We 
may, however, point out that. the bundles appear to have passed up the axis in a 
straight line, and not to have alternated in successive internodes (see Plate 81, 
fig. 28). 
From what has been already said there can be little doubt that the structure of the 
bundles was collateral. For a long time, however, direct evidence of this was 
wanting, for in nearly all cases the whole tissue between the wood and the sclerotic 
outer cortex has perished. In one instance, however, we have found these tissues 
completely preserved at one side of the axis (see Plate 80, fig. 26). It is highly 
probable that here the group of smali delicate cells, ph., represents the phloém, while 
the larger thin-walled cells further to the exterior belong to the inner cortex, or 
rather perhaps to the pericycle. 
In some specimens the primary tissues already described are alone present. Often, 
however, a well-marked zone of secondary wood is added, as has been fully explained in 
previous memoirs” (see Plate 80, fig. 24). The secondary xylem is both fascicular and 
interfascicular ; it consists mainly of scalariform trachez, with a few parenchymatous 
rays between them. The radial arrangement of the elements is sufficiently regular to 
leave no doubt of their origin from a cambium; the secondary wood may attain a 
thickness of eight or more cells. 
In some specimens the growth in thickness had evidently stopped short at a very 
early stage, when only a few tangential divisions had taken place in the interfascicular 
* Wirtiamson, “ Organization,” Part V., Plate 10, &c. 
