384 Boodle. — Anatomy of the Schizaeaceae. 
bundle in the base of the petiole in structure ; no fibres are 
present ; the pericycle forms a layer of nearly uniform thick- 
ness ; the phloem is continuous round the ends of the bundle, 
and three protoxylem-groups are present. As it passes in- 
wards through the cortex the phloem on the inner side of the 
xylem spreads from both ends towards the median point, 
where it ultimately meets. When the leaf-trace reaches the 
vascular cylinder a rounded stele fuses with one end of it, 
producing a knob at that end ; soon afterwards a long flat 
stele approaches the other end and fuses with it, thus produc- 
ing a long stele curved towards one end. The lower stele 
in Fig. 1 6 is an example of this. The knob is seen at the 
right-hand end ; the curved part is the leaf-trace, and the 
straight part on the left is the long flat stele just referred to. 
The little projection on the lower side is connected with 
a root, which is attached to the stele just as it fuses with 
the leaf-trace. Part of this flat stele remains as a knob on 
the left-hand end of the leaf-trace, and the remainder of the 
stele branches away again as a rounded stele ready to fuse 
with the next leaf-trace. The leaf-trace that we have been 
following has by this time a slightly curved form with a knob 
at each end, the phloem is interrupted at its ends, and the 
median protoxylem-group, which was present and contained 
spiral elements while the fusions were going on, now or a little 
lower down becomes lost. In passing downwards this strand 
becomes straightened out. and the enlargements at its ends 
less pronounced, while its protoxylem becomes scattered and 
largely external, as mentioned above when describing the 
stem ; that is, it gradually loses its leaf-trace characters. If 
one reverses the order of this series, one may say that, in 
following a stele upwards in the stem, it divides into three 
parts, of which the middle one, changing slightly in structure, 
becomes the leaf-trace. 
The petiolar bundle of A . Dregeana is not very different in 
type from that of A. Phyllitidis , except that, as Prantl (p. 25) 
observed, fibres are absent. The xylem forms a considerably 
flattened arch, with slightly hooked ends. The phloem has 
