Boodle.- — Anatomy of the Schizaeaceae. 391 
the ground tissue outside. When the next leaf-trace passes 
off the horseshoe-shaped stele becomes broken in its arched 
region so that two sausage-shaped or reniform ‘steles’ are 
formed, each surrounded by an endodermis. These may 
be repaired again to form a horseshoe-stele once more, but 
at the next leaf-trace the two separate steles are re-formed, 
and subsequent leaf-gaps cause further division of them, and 
they become more distant from one another so as to form 
a broken ring round a fairly large mass of central ground- 
tissue. The mature stem-structure is then attained. Differ- 
ences occur in different seedlings as to the size of the xylem, 
the number of central phloem elements, and the stage reached 
at the level of a certain leaf-trace, but the above description 
may be taken as recording the successive changes in the 
arrangement of the tissues. The main facts as to the con- 
tinuity of the tissues up to the horseshoe-stage of the stele 
agree with what is found in another dialystelic Fern, Pteris 
aquilina , as described by Leclerc du Sablon (’ 90 , p. 3) and 
Jeffrey (’00, p. 9). 
The transitional region of the seedling having been described, 
a few remarks may be made on other structural points in the 
seedling. It could not be clearly made out whether the first 
one or two leaves had a collateral or a concentric petiolar 
bundle, but the bundle in the petiole of an early leaf (Fig. 33) 
shows the phloem (p/l.) surrounding the xylem. There is 
probably only one protoxylem group, the median one (px.), 
and the xylem forms a very slightly arched band. A few 
fibres (/.) are found in the phloem. Fig. 33 shows the petiolar 
bundle of a later leaf in an early stage of development. The 
median protoxylem-group (px'.) and two protophloems (pph! .) 
are differentiated. The incompletely differentiated phloem 
elsewhere is small-celled, and it can be seen that it is inter- 
rupted in the median region of the morphologically upper 
side, as in the leaves of the mature plant. Fig. 34 is a young 
stage of one of the steles in the dialystelic region of the stem 
in the seedling. The first formed tracheides are scattered. 
The first three or four leaves of the seedling are simple, with 
