376 Hickling . — The Anatomy of Palaeostachy a vera. 
importance of this course, and the interpretation to be placed on it, 
justifies the further particulars now to be given. The course of the bundle 
across the upper part of the sclerized disc is clearly seen in radial longi- 
tudinal section in Fig. 21. The figure also demonstrates the fact that the 
bundle approaches the axis in an ascending, not a descending path, and 
though it is difficult to distinguish tracheids elsewhere, sufficient traces may 
be found to prove that the bundle followed the outer edge of the triangular 
patch of sclerenchyma limited internally by the space S.Ptxy.C. At the 
apex of this triangle, traces of reflexed fibres may be seen, as indicated 
in the drawing. The space S.Ptxy.C \ I can only interpret as the pro- 
toxylem-canal of the ascending limb of the bundle. Any doubt which 
might be felt as to the bundle really passing round the sclerenchyma is 
completely removed by the numerous oblique-transverse sections, in which 
the sclerenchyma is seen forming the angular projections between alternate 
pairs of the main bundles, and showing the sporangiophore bundles hanging 
on to the projecting angles (Fig. 7, Sp. tr). It remains to prove that that 
point where the sporangiophore-trace comes into contact with the main 
bundle, at the apex of the triangle of sclerenchyma, is not the origin of the 
trace. The evident reflexion of the accompanying fibres (Fig. 21) and 
the existence of the canal S.Ptxy.C. suggest otherwise. Moreover, were 
that point a true node, one would expect the ground tissue cells to be 
‘ shortened-up,’ and the protoxylem canals of the main bundles to be 
obliterated as at the ordinary nodes. But no such modifications exist. 
Finally, the canal I have referred to in Fig. 21 as probably the protoxylem- 
canal of the trace, is a constant feature in the transverse sections, especially 
in those through the disc, where it appears as a small lacuna external to 
the main carinal canal, approaching nearer to the latter canal as the section 
gets closer to the node, till, immediately above that point, the two spaces 
become confluent, causing an 8-shaped space (see Figs. 12, 13, and 16). 
I think this leaves no doubt as to the correctness of the view here 
taken. 
Figs. 6 and 19 show the sporangiophore-trace crossing the c disc * in 
transverse section, and give a fair idea of the dimensions of the bundle. 
In Fig. 6 , M, a patch of dark tissue is seen at each end of the mass of 
tracheids. This tissue forms a strand accompanying the bundle, and 
crossing the * disc ’ immediately underneath it, so that in sections at 
a slightly lower level the separate patches here seen become confluent. 
These dark patches are very conspicuous features in sections of the ‘ disc 5 
(Fig. 7 ,M). One such patch is drawn in Fig. 18. The cells are elongated, 
with square or oblique ends, and are almost completely filled with a dense 
black material. At first I took this tissue for sclerenchyma, in consequence 
of its being always well preserved, but it is obviously not ordinary scleren- 
chyma, and is probably not sclerized at all. The c melanotic ’ cells of the 
