Stigmarian Rootlets. 563 
with the vascular strand, but also the continuity of the latter 
with the stele of the rootlet. 
This rootlet is unfortunately somewhat compressed, so that 
the space between the stele and the outer cortex is very much 
reduced, and the vascular strand is thrown into a fold. It will 
be seen that in this rootlet the strand on passing out from the 
protoxylem elements takes a very oblique direction, and would 
not in transverse section have had the appearance of the vas- 
cular strand figured by Renault. In structure, however, it 
shows the same features, and is surrounded by a sheath of 
parenchymatous cells, from which trabecular tissue ( trb .) runs 
to the parenchyma of the stele. On reaching the outer cortex 
the vascular branch communicates at first with some closely- 
set tracheids very similar to those at (b) in Fig. 2, and these 
are in their turn connected with wider spirally-marked tra- 
cheids {sp. tr.). From a comparison of Figs. 2 and 5 I have 
no hesitation in considering (b) in Fig. 2 as the point of 
entrance of the vascular strand into the outer cortex of that 
rootlet. Another feature shown by the longitudinal section 
represented in Fig. 5 is that the vascular strand seems to have 
been in some cases continued for a considerable distance 
beyond its entry into the outer cortex, and connected with 
several groups of spiral tracheids. Indeed, a branch (v. br.) 
is given off from the vascular strand close to its entry into the 
outer cortex, and this branch was in all probability connected 
with another patch of spiral tracheids at some other part of 
the root. It is difficult to ascertain what was the size and 
distribution of these' patches of spirally-marked cells of the 
outer cortex. As will be seen from Fig. 2, and as is apparent 
from other preparations, it was of some breadth. In one 
longitudinal section, indeed, such cells seem to have extended 
almost halfway round the root. In other cases, however, 
as can be seen in Fig. 4, the spiral tracheids extended only 
a little way on either side of the entrance of the vascular 
strand. No doubt there was considerable variation in this re- 
spect in the different types of rootlets, which belonged probably 
to different Lepidodendroid plants. 
Q q 
