Hymenophyllaceae , Sckizaeaceae and Gleicheniaceae. 535 
Summary. 
The mature rhizome of Schizaea dichotoma exhibits apparent 
dichotomy. In the region of dichotomy the stele (as seen 
in transverse section) undergoes elongation, constriction, and 
fission. The ring of xylem is open during the process, but 
no internal phloem is present. 
In the mature rhizome of vS. dichotoma endodermal pockets 
are often present at the nodes; an isolated internal endo- 
dermis is occasionally found and may contain brown sclerotic 
elements ; isolated internal tracheides sometimes occur. 
In the stem of the young plant of 5. pusilla no internal 
phloem is present in the transitional region. 
In two specimens of a small form of .S', dichotoma, which 
are probably seedling-plants, and at any rate have protostelic 
structure in their basal region, no internal phloem was present 
in the transitional region, but endodermal pockets or rudi- 
ments jof them were present early in the medullated stage. 
The deduction, which appears most natural, in the light 
of the various facts recorded, is that the inner endodermis 
is a vestigial structure, and that .S', dichotoma owes its typical 
(or more usual) structure to reduction from a medullated form 
with inner endodermis (‘ ectophloic siphonostelic ’). The 
same would probably be true for the other species of Schizaea. 
There is no evidence for the previous presence of an internal 
phloem. 
Conclusion. 
It is likely that a further structural examination of suf- 
ficiently numerous specimens of 5. dichotoma and of other 
specimens of Schizaea may give more safe grounds, than were 
obtainable from the material examined, for elaborating a 
theory as to the phylogenetic history of the stele of Schizaea ; 
and this may be helped by an extended comparison with 
certain species of Anemia, when their structure also has been 
examined in a large number of individuals. Both genera will 
