Boodle.—Anatomy of the Hymenophyllaceae. 461 
The phloem (ph) forms a continuous ring surrounding the 
xylem. The rhizome of H. fucoides , Swartz (Fig. 14), has 
a considerably smaller group of metaxylem-elements, with one 
protoxylem-group attached to its lower side. The group of 
small tracheides attached to the right-hand end of the 
metaxylem is derived from a root. The mass of xylem is 
still smaller in the rhizome of H. tunhridgense , Smith (Fig. 16). 
(This is seen by comparing Figs. 16 and 14, and allowing for 
the difference of magnification, Fig. 16 being about one and 
a half times the scale of Fig. 14.) The pericycle is one cell 
in thickness. The protoxylem is in contact with the meta¬ 
xylem, and is on the lower side. The stele has a phloem 
ring, which may be called continuous, but which tends to 
have larger elements on the upper side than on the lower, 
and is more liable to interruptions on the lower side. The 
xylem is monarch, with the protoxylem on the lower side. 
If the phloem were not developed on the lower side, the 
result would be a collateral bundle. To signify this, it is 
convenient to employ a special term for the type of structure 
found in H. tnnbridgense , and the term sub-collateral is 
suggested. 
A considerable number of species of Hymenophyllum have 
rhizomes belonging to this type; e. g. besides those just 
mentioned, the following :— H. polyanthos , Swartz, H. ciliatum , 
Swartz, H. Smithii , Hook, H. javanicum , Spreng. Other 
species have a similar xylem-mass, and are probably of the 
same type, but the material was not sufficiently well preserved 
in the following cases to show whether the phloem surrounded 
the xylem or was interrupted on the lower side :—H. denticu- 
latum , Swartz, H. Treubii , Raciborski, PI. fuscum , Bosch, 
H. varum, R. Br. 
In species with a sub-collateral stele, the tracheides from 
a root are inserted laterally on the metaxylem, that is in 
about the same region with regard to the outline of the 
entire xylem, as in the case of the species with two xylem- 
bands, e. g. H. scabrum. 
The two-banded stele of H. scabrum may be taken as 
