Boodle . — Anatomy of the Gleicheniaceae . 735 
by Bower (’ 99 , p. 32), the leaf is occasionally forked, which 
points to its having been reduced from a dichotomous type, 
such as is found in Gleichenia . 
Platyzoma, structure. 
In Platyzoma microphyllum , as the leaves are crowded, 
numerous leaf-traces are seen in the cortex of the rhizome in 
any transverse section. The leaf-traces show spiral sedation, 
as is seen in Fig. 30. This was drawn from a section, which 
included rather less than half the cortex — the part with 
bundles on the right ; the dotted outline of the remainder 
of the cortex is added to complete the diagram. Fig. 31 is 
a diagram of the stele, giving the position of the outer 
endodermis, phloem, xylem and inner endodermis. Fig. 32 
is a photograph of about half the stele. On the outside of 
the figure are the pericycle (3-4 cells thick) and the phloem 
(phi) (seen in places as a dark line), each forming a continuous 
zone. Within these is the xylem, which resembles that of 
Gleichenia in being composed of scalariform tracheides 
together with chains and groups of parenchymatous cells, but 
differs from the xylem of all the species of Gleichenia except 
G. moniliformis in having no definite protoxylem-groups. 
The smallest tracheides occur in the outer region of the 
xylem, as seen in Fig. 32, so one may assume that the 
protoxylem-elements are distributed at or near the periphery. 
They are scalariform, and both in this respect and in being 
scattered at the periphery they resemble the corresponding 
elements in Lygodium. On the other hand the structure of 
the stem resembles what is found in G. pectinata , in that the 
xylem forms a ring, and that within it there is an inner 
endodermis enclosing a central mass of sclerenchyma. Of 
course it differs from that species in the absence of internal 
phloem, and of definite groups of spiral protoxylem-elements. 
The inner endodermis has its radial walls ruptured at most 
points in the photograph (Fig. 32, i. e .), and the central 
sclerotic tissue comes out as a dark mass. Its walls were not 
