Boodle.—Anatomy of the Hymenophyllaceae. 479 
The petiole has a large bundle, shaped like a squarish arch 
(Fig. 40). The endodermis, consisting of torn and crushed 
cells in the dried material, followed the outline of the xylem ; 
the protoxylem formed two groups in the dark tissue separat¬ 
ing the incurved tips of the xylem-arch from the uprights of 
the arch, and there may perhaps have been a third proto¬ 
xylem in the median region of the arch. 
T. ericoides , Hedw., &c. 
T. ericoides , Hedw., T. alatum , Swartz, and T. rigidum , 
Swartz, are species with a solid stele in the stem like that 
of T. spicatum or T. scandens. T. alatum rather resembles 
T. spicatum , but T. ericoides and T. rigidum have more the 
characters of T. scandens in the size of their tracheides, &c. 
The position of the protoxylem could unfortunately not be 
determined, as dried material was used, so it cannot be stated 
to which type these species belong. 
T. pyxidiferum , Linn., &c. 
Several species of Trichomanes show the sub-collateral type 
of structure in their rhizome ; e.g. T.pyxidiferum, Linn., where 
the phloem surrounds the small xylem mass. The xylem 
may consist of only eight tracheides, and in such cases the 
protoxylem cannot easily be determined. T. trichoideum , 
Swartz, is similar, and the protoxylem is here clearly peri¬ 
pheral. The petiolar bundle is somewhat similar in structure, 
but with fewer tracheides, and with diarch arrangement of 
protoxylem 1 ; it has the phloem slightly interrupted. 
T. reptans , Swartz, and T. Filicula , Bory, have a very 
small xylem-group, of five or six tracheides surrounded by 
phloem. 
T. pallidum , Blume, has a small xylem-band with the 
protoxylem possibly immersed, as seen in Hymenophyllum 
dilatatum in the^specimen shown in Fig. 21. Two species of 
Trichomanes among the series examined were found to have 
1 Prantl, 1 . c. 
