for the glands were only slightly darkened by an immersion of 1 hr. 20
m., but became decidedly darker after 3 hrs. Leaves which had been left
for 7 hrs. in an infusion of raw meat or in saliva were placed in the
solution of carbonate of ammonia, and the glands now became greenish;
whereas, if they had been first placed in the carbonate, they would
have become black. In this latter case, the ammonia probably combines
with the acid of the secretion, and therefore does not act on the
colouring matter; but when the glands are first subjected to an organic
[page 339] fluid, either the acid is consumed in the work of digestion
or the cell-walls are rendered more permeable, so that the undecomposed
carbonate enters and acts on the colouring matter. If a particle of the
dry carbonate is placed on a gland, the purple colour is quickly
discharged, owing probably to an excess of the salt. The gland,
moreover, is killed.
Turning now to the action of organic substances, the glands on which
bits of raw meat were placed became dark-coloured; and in 18 hrs. their
contents were conspicuously aggregated. Several glands with bits of
albumen and fibrin were darkened in between 2 hrs. and 3 hrs.; but in
one case the purple colour was completely discharged. Some glands which
had caught flies were compared with others close by; and though they
did not differ much in colour, there was a marked difference in their
state of aggregation. In some few instances, however, there was no such
difference, and this appeared to be due to the insects having been
caught long ago, so that the glands had recovered their pristine state.
In one case, a group of the sessile colourless glands, to which a small
fly adhered, presented a peculiar appearance; for they had become
purple, owing to purple granular matter coating the cell-walls. I may
here mention as a caution that, soon after some of my plants arrived in
the spring from Portugal, the glands were not plainly acted on by bits
of meat, or insects, or a solution of ammonia a circumstance for which
I cannot account.
Digestion of Solid Animal Matter. Whilst I was trying to place on two
of the taller glands little cubes of albumen, these slipped down, and,
besmeared with secretion, were left resting on some of the small
sessile glands. After 24 hrs. one of these cubes was found [page 340]
completely liquefied, but with a few white streaks still visible; the
other was much rounded, but not quite dissolved. Two other cubes were
left on tall glands for 2 hrs. 45 m., by which time all the secretion
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