Boodle,—-Anatomy of the Hymenophyllaceae . 469 
are mostly fused, the roots are in direct connexion with both, 
being attached to the lines of junction of the two. 
Trxchomanes. 
In the genus Hymenophyllum , all the species have a creeping 
rhizome; but in Trichomanes , while many species have a 
similar habit, others have a short erect or oblique stem. The 
leaves are arranged distichously on the creeping rhizome, but 
have a two-fifth phyllotaxis in the case of upright stems, 
e. g. T. Prieurii , Kunze. The description of structure in the 
genus Trichomanes will be arranged under the different species, 
as it will be more convenient to take rhizome, petiole, and node 
of one species before going on to the rhizome of the next. 
T. reniforme i Forst. 
This species has a creeping rhizome and distichous arrange¬ 
ment of leaves and roots, as in Hymenophyllum , but it has 
a simple leaf, which is not very common in the order. The 
lamina is reniform in shape, and is unique in being four cells 
thick. 
The structure is of almost the same type as in the larger 
species of Hymenophyllum , so it will be suitable to begin with. 
The stele of the rhizome is shown in Fig. 22. It has much in 
common with the type of H. dilatatum or H scabrum , but 
differs in some points of detail. The xylem consists of an 
upper and lower band ; their limits, however, are sometimes 
not distinct, and the difference in the size of the tracheides 
is not conspicuous, but the upper xylem sometimes contains 
distinctly larger tracheides than the lower. Further the central 
mass of parenchyma contains, in addition to the evident proto- 
xylem-group or groups, several larger tracheides, which must 
be regarded as forming part of the metaxylem. There are 
some for instance in Fig. 22, separating the two protoxylem- 
groups there present. The root-steles are attached to the 
ends of the lower xylem-band (or to the junction of the two 
bands) as in Hymenophyllum. 
Fig. 23 shows a young stage of the rhizome in transverse 
