494 Boodle.—Anatomy of the Hymenophyllaceae. 
Summary. 
Some of the structural characters of the Hymenophyllaceae 
will now be summarized. 
The stem is monostelic, and one leaf-trace passes off to 
each leaf. The stele contains no pith, and is of several 
types, e. g. 
1. A xylem-mass with internal protoxylems, connected 
with leaf-traces. 
2. A xylem-mass with indefinite scattered protoxylem. 
3. A xylem-mass with peripheral protoxylem. 
4. Sub-collateral. 
5. A collateral bundle. 
The axillary branch is attached to the leaf-trace. 
The petiolar bundle is usually collateral, and very similar 
to the stele in the case of the sub-collateral and collateral 
types. 
In other types it often resembles stem-structure in its 
lower region, and higher up it usually has an arched xylem 
with two protoxylems at the ends, or with an additional one 
at the median dorsal point. 
As shown by Hymenophyllum } sub-collateral structure has 
probably been derived from a more complicated type by 
reduction. The filmy habit is probably not primitive. 
T. reniforme agrees more closely in structure with H . 
scabrum , &c., than with any species of its own genus. 
The investigations, which form the subject of the present 
paper, have been carried out at the suggestion of Dr. D. H. 
Scott, F.R.S., to whom I wish to express my thanks for 
his valuable advice throughout the work. I am also indebted 
to Mr. J. G. Baker, F.R.S., and Mr. C. B. Clarke, F.R.S., for 
their kind assistance in some systematic points, and to 
Mr. C. H. Wright, A.L.S., in this and in other ways. The 
material used in a considerable number of species was from 
living plants grown in the Royal Gardens, Kew. 
