Boodle. — Anatomy of the Schizaeaceae. 381 
band, interrupted by parenchyma. The sieve- tubes are not 
present at the ends of the xylem-mass. The sieve-tubes 
are in most places separated from the xylem by conjunctive 
parenchyma, 1-2 cells thick; this tissue also is better de- 
veloped on the inner than on the outer side. 
The xylem occupies the centre and has nearly the same 
form as the whole strand. In this region it consists entirely 
of scalariform tracheides and parenchyma ; spiral elements 
being absent. As seen in Fig. 40 the smaller tracheides are 
at or towards the outside (on the right in the figure), the 
largest ones being at the inner side. At the two ends of the 
xylem-strand there are rather numerous small tracheides 
taking up the greater part of the thickness of the xylem. 
Some of the small tracheides scattered along the outside of 
the xylem-band together with some at the ends, and one or 
two immersed in the xylem, are the first to differentiate. So 
the strand has rather irregular development, but a tendency 
to the exarch type l . Root-steles are attached to the ends 
of the stele, where the numerous small tracheides are present ; 
a root may fuse with one end of the strand, just before the 
attachment of a leaf-trace to that end. 
The scalariform tracheides are of a common type, with the 
pits often running the whole width of the wall. The sieve- 
tubes have inclined end-walls, and the sieve-plates are crowded 
on the longitudinal walls of the larger elements so as to give 
them a reticulate appearance. The strips of wall between 
the sieve-plates are narrow, but sometimes thickened to a 
remarkable extent, and the thickenings on the two sides of 
a longitudinal wall may together have a dumb-bell-shape in 
section, so that the sieve-plates are in these cases actually 
bordered. Granules are seen on some of the sieve-plates. 
In Fig. 40 some of the small tracheides are detached from 
the rest of the xylem, so as to be in contact with the sieve- 
tubes. This is rather exceptional. 
In the majority of species of Anemia (viz. excepting Prantfs 
subgenus Aneimiorrhizd) the structure of the stem appears 
5 That is, exarch with regard to the centre of the stem. 
