736 Boodle . — Anatomy of the Gleicheniaceae . 
very strongly thickened in this specimen, but were brown, 
and its elements contained a mucilaginous substance, which 
was stained deeply with haematoxylene. The phloem 
contains typical Fern-sieve-tubes. 
Figs. 33 and 34 illustrate the mode of separation of the 
leaf-trace. A small peripheral tangential band of tracheides 
becomes marked out by the appearance of a group of 
parenchyma in the xylem below it (Fig. 33). In this section 
the group of parenchyma is unusually large, and happens to 
fit on to a chain of xylem-parenchyma (p.r .\ which is radially 
placed. The band of xylem mentioned above becomes free 
as the xylem of the leaf-trace. It may pass off straight, or 
may swing round slightly before separating. In Fig. 34 the 
same leaf-trace (/. 1 .) has reached the outer limit of the 
pericycle. It consists of the band of xylem and an arc of 
phloem, detached from that of the stele, which has already 
repaired the gap. After the leaf-trace passes the endodermis 
of the stele, it is invested with a complete endodermis. As it 
passes through the cortex of the stem, it remains collateral, 
its xylem becomes crescent-shaped, and acquires two proto- 
xylem groups on its inner side, not far from its ends. No 
median protoxylem-group could be recognized. No leaf-gap 
affecting the endodermis is present, and frequently the exit of 
the leaf-trace scarcely affects the xylem of the stele, beyond 
leaving a small external pit like that seen in Fig. 32. Figs. 33 
and 34 were drawn to show the nearest approach to a true 
leaf-gap met with. Longitudinal sections through the insertion 
of a leaf-trace did not show any passage of leaf-trace- 
parenchyma towards the centre of the stele. 
A diagram of the petiolar bundle is given in Fig. 35. It 
has an arched xylem with protoxylems on the inner face at 
the two sharp bends. The tissue within the arch appears to 
consist chiefly of phloem. 
In the rachis the xylem-arch is converted into a nearly 
straight band with a protoxylem immersed in it near each 
end. A little phloem is still found on the upper side, besides the 
arc of it on the lower. There is still no median protoxylem. 
