Affinities of Helminthostachys zeylanica . 429 
does not extend round the rhizome, and in this respect it 
differs from the Ophioglosseae as described by Holle, but 
the difference is probably to be ascribed, as are other features 
already alluded to, to the dorsiventral character of Helmintho- 
stachys, the spots where cork-formation originate not being, 
in this Fern, distributed at intervals around the stem but 
confined to one longitudinal strip of its surface. 
Beneath the external protective layers, there is to be seen 
a very well-developed cortical parenchyma, the cells of which are 
gorged with starch, at least at the season at which our plants 
were gathered. The cells are rounded in form, and thus 
necessarily leave intercellular spaces between each other. 
Their walls recall those of other Ophioglosseae in their pale 
colour, in their well-developed pits, and in their somewhat 
gelatinous appearance ; though in respect of this last character 
they are far less striking than are the cortical walls of e.g. 
Botrychium Lunar ia. 
The pits are remarkable, forming as they do not merely 
simple depressions in the walls, but rather being massed 
together in areas like the pores of a sieve-plate. Indeed they 
may be fairly termed pitted areolae, and they do not differ 
essentially from the actual sieve-plates of the sieve-tubes 
themselves in this plant. The areolae are of various forms, 
circular or oval, or they may be less regular in contour. 
They contain also a varying number of depressions or pits 
which are separated from each other by bars or ribs of 
thickening which thus divide up each areola into its thickened 
and unthickened portions. Of course the pits on either side 
of the middle lamella of two adjacent cells correspond, and 
we have in a few favourable cases been able to demonstrate 
fine protoplasmic continuity through the pit-membranes. 
The cortex of this plant offers a fine example of the occur- 
rence in the intercellular spaces of the substance identified 
by Russow, Terletzki, and others, as protoplasm, but deter- 
mined by Mangin to consist of pectose-compounds. 
The cortical parenchyma is limited internally by the outer 
endodermis, which is extremely well marked in Helmintho- 
