was repeated with the same result; and on this occasion I observed that
the protoplasm had shrunk a little from the walls of the single
elongated cells forming the pedicels. In order to observe the process
of aggregation, a narrow strip of leaf was laid edgeways under the
microscope, and the glands were seen to be quite transparent; a little
of the stronger solution (viz. one part to 218 of water) was now added
under the covering glass; after an hour or two the glands contained
very fine granular matter, which slowly became coarsely granular and
slightly opaque; but even after 5 hrs. not as yet of a brownish tint.
By this time a few rather large, transparent, globular masses appeared
within the upper ends of the pedicels, and the protoplasm lining their
walls had shrunk a little. It is thus evident that the glands of
Pinguicula absorb carbonate of ammonia; but they do not absorb it, or
are not acted on by it, nearly so quickly as those of Drosera.
(13) Little masses of the orange-coloured pollen of the common pea,
placed on several leaves, excited the glands to secrete freely. Even a
very few grains which accidentally fell on a single gland caused the
drop surrounding it to increase so much in size, in 23 hrs., as to be
manifestly larger than the drops on the adjoining glands. Grains
subjected to the secretion for 48 hrs. did not emit their tubes; they
were quite discoloured, and seemed to contain less matter than before;
that [page 385] which was left being of a dirty colour, including
globules of oil. They thus differed in appearance from other grains
kept in water for the same length of time. The glands in contact with
the pollen-grains had evidently absorbed matter from them; for they had
lost their natural pale-green tint, and contained aggregated globular
masses of protoplasm.
(14) Square bits of the leaves of spinach, cabbage, and a saxifrage,
and the entire leaves of Erica tetralix, all excited the glands to
increased secretion. The spinach was the most effective, for it caused
the secretion evidently to increase in 1 hr. 40 m., and ultimately to
run some way down the leaf; but the glands soon began to dry, viz.
after 35 hrs. The leaves of Erica tetralix began to act in 7 hrs. 30
m., but never caused much secretion; nor did the bits of leaf of the
saxifrage, though in this case the glands continued to secrete for
seven days. Some leaves of Pinguicula were sent me from North Wales, to
which leaves of Erica tetralixand of an unknown plant adhered; and the
glands in contact with them had their contents plainly aggregated, as
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