Boodle . — Anatomy of the Gleicheniaceae . 713 
of Gleichenia, but this may be due to the rhizomes examined 
not being sufficiently old. 
When the rhizome branches, the stele divides in a simple 
manner as in Lygodium , but, in the cases observed, one stele 
is smaller than the other and passes off laterally. Both this 
character and the external appearance suggest monopodial 
branching, not dichotomy. 
Gleichenia, petiole. 
In most species of Gleichenia the cortex of the petiole bears 
a general resemblance to that of the stem. It consists largely 
of the usual brown-walled sclerotic tissue, which may be 
fairly uniform throughout, or may fall into two zones, one 
of which is formed of much thicker-walled elements than the 
other, or into three zones of which the middle is the thinnest- 
walled. The epidermis and sometimes one or two adjacent 
layers of the cortex may be comparatively thin-walled, as 
occurs in some rhizomes, or may be strongly sclerotic. 
The structure of the petiole has been described by Poirault 
(’ 93 , p. 176, &c.), and two detailed drawings (Figs. 17 and 18) 
are given by him of the petiolar bundles of G. Speluncae , Br., 
and G. rnpestris , Br. Both of these belong to Engleichenia . 
G. Speluncae is given by Hooker and Baker ( 74 , p. 11) as 
a synonym of G. circinata , and G . rnpestris as a separate but 
very nearly allied species. G. rnpestris has, however, been 
since reduced by Baker (’ 91 , p. 183) to a variety of G. circinata. 
The type of structure in the petiole is described by Poirault 
(’ 93 , p. 189) as being very different in the two subgenera of 
Gleichenia , and the difference is illustrated by his diagrams 
of the separated leaf-traces (Figs. 13 c and 14 d for Euglei- 
chenia and 16 d for Mertensia). The distinguishing point is 
that the bundle is circular or subcordiform in Engleichenia , 
but more or less shaped like a C in Mertensia. This dis- 
tinction appears to hold good for the majority of species ; 
however in G. (. Mertensia ) pedalis the indentation of the 
bundle is only slight, so that its form is about reniform, while 
