Insectivorous Plants | Page 5

of differently shaped ones, likewise filled with purple fluid,
but of a slightly different tint, and differently affected by chloride of
gold. These two layers are sometimes well seen when a gland has been
crushed or boiled in caustic potash. According to Dr. Warming, there is
still another layer of much more elongated cells, as shown in the
accompanying section (fig. 3) copied from his work; but these cells
were not seen by Nitschke, nor by me. In the centre there is a group of
elongated, cylindrical cells of unequal lengths, bluntly pointed at their
upper ends, truncated or rounded at their lower ends, closely pressed
together, and remarkable from being surrounded by a spiral line, which
can be separated as a distinct fibre.
These latter cells are filled with limpid fluid, which after long
immersion in alcohol deposits much brown matter. I presume that they
are actually connected with the spiral vessels which run up the tentacles,
for on several occasions the latter were seen to divide into two or three
excessively thin branches, which could be traced close up to the
spiriferous cells. Their development has been described by Dr.
Warming. Cells of the same kind have been observed in other plants, as
I hear from Dr. Hooker, and were seen by me in the margins of the
leaves of Pinguicula. Whatever their function may be, they are not
necessary for the secretion of a digestive fluid, or for absorption, or for
the communication of a motor impulse to other parts of the leaf, as we
may infer from the structure of the glands in some other genera of the
Droseraceae.
The extreme marginal tentacles differ slightly from the others. Their
bases are broader, and besides their own vessels, they receive a fine
branch from those which enter the tentacles on each side. Their glands
are much elongated, and lie embedded on the upper surface of the
pedicel, instead of standing at the apex. In other respects they do not

differ essentially from the oval ones, and in one specimen I found every
possible transition between the two states. In another specimen there
were no long-headed glands. These marginal tentacles lose their
irritability earlier than the others; and when a stimulus is applied to the
centre of the leaf, they are excited into action after the others. When
cut-off leaves are immersed in water, they alone often become
inflected.
The purple fluid or granular matter which fills the cells of the glands
differs to a certain extent from that within the cells of the pedicels. For
when a leaf is placed in hot water or in certain acids, the glands become
quite white and opaque, whereas [page 8] the cells of the pedicels are
rendered of a bright red, with the exception of those close beneath the
glands. These latter cells lose their pale red tint; and the green matter
which they, as well as the basal cells, contain, becomes of a brighter
green. The petioles bear many multicellular hairs, some of which near
the blade are surmounted, according to Nitschke, by a few rounded
cells, which appear to be rudimentary glands. Both surfaces of the leaf,
the pedicels of the tentacles, especially the lower sides of the outer ones,
and the petioles, are studded with minute papillae (hairs or trichomes),
having a conical basis, and bearing on their summits two, and
occasionally three or even four, rounded cells, containing much
protoplasm. These papillae are generally colourless, but sometimes
include a little purple fluid. They vary in development, and graduate, as
Nitschke* states, and as I repeatedly observed, into the long
multicellular hairs. The latter, as well as the papillae, are probably
rudiments of formerly existing tentacles.
I may here add, in order not to recur to the papillae, that they do not
secrete, but are easily permeated by various fluids: thus when living or
dead leaves are immersed in a solution of one part of chloride of gold,
or of nitrate of silver, to 437 of water, they are quickly blackened, and
the discoloration soon spreads to the surrounding tissue. The long
multicellular hairs are not so quickly affected. After a leaf had been left
in a weak infusion of raw meat for 10 hours, the cells of the papillae
had evidently absorbed animal matter, for instead of limpid fluid they
now contained small aggregated masses of protoplasm, which slowly

and incessantly changed their forms. A similar result followed from an
immersion of only 15 minutes in a solution of one part of carbonate of
ammonia to 218 of water, and the adjoining cells of the tentacles, on
which the papillae were seated, now likewise contained aggregated
masses of protoplasm. We may therefore conclude that when a leaf has
closely clasped a captured insect in the manner immediately to