712 Boodle . — Anatomy of the Gleicheniaceae . 
mentions the rare occurrence of sclerotic cells among the 
scalariform tracheides in the rhizome of this species. 
In G. cryptocarpa mucilage occurs in the xylem- and 
phloem-parenchyma, and in G. dicarpa it is found in the 
same cells as well as in the pericycle. 
G. moniliformis is the most aberrant species in that no 
protoxylem-elements are distinguishable in the mature stem, 
and the tracheides all appear to be scalariform. The stele 
is small, the xylem measuring rather less than % mm. 
in diameter. The absence of spiral protoxylem-elements is 
interesting, because this species is the only one of its genus 
with an upright stem. It was noted among the Hymeno- 
phyllaceae, where spiral protoxylems are general, that their 
absence in certain species of Trichomanes appeared to be 
correlated with an upright habit [T, spicatum and T. Bern- 
er of tii). Both G. moniliformis and the species of Triclio - 
manes just mentioned have probably been derived from 
forms with a creeping rhizome, and the change to the 
upright stem has been accompanied with diminished length 
of the internodes and slower growth of the rhizome. This . 
makes it easy to understand the disappearance of the spiral 
elements. 
In the rhizome of G. Cnnninghami the xylem in transverse 
section presented a curious appearance on account of the 
presence of a rather neat uniseriate peripheral band of large 
tracheides, which was continued about half way round the 
circumference, with only four of five inconspicuous interrup- 
tions by parenchymatous cells. This was probably a band 
of tracheides ready to form the chief part of a leaf-trace, 
though at some distance from a node. 
The depth of the protoxylem-groups below the periphery 
of the xylem differs in the various species. G. vestita may 
be mentioned as a case in which they are deeply seated in 
proportion to the size of the xylem. 
Lignified sieve-tubes were observed by Poirault (’ 93 , p. 195) 
in the stem of G . polypodioides. Similar elements were not 
seen by the writer in the stem of this or any other species 
