otherwise the colour would have been discharged. I have, however,
sometimes observed, especially with the long-headed tentacles on the
margins of very pale leaves immersed in a solution, that the glands as
well as the upper cells of the pedicels were discoloured; and in these
cases I presume that the unchanged carbonate had been absorbed. The
appearance above described, of the aggregating process being arrested
for a short time at each transverse partition, impresses the mind with
the idea of matter passing downwards from cell to cell. But as the
cells one beneath the other undergo aggregation when inorganic and
insoluble particles are placed on the glands, the process must be, at
least in these cases, one of molecular change, transmitted from the
glands, [page 45] independently of the absorption of any matter. So it
may possibly be in the case of the carbonate of ammonia. As, however,
the aggregation caused by this salt travels down the tentacles at a
quicker rate than when insoluble particles are placed on the glands, it
is probable that ammonia in some form is absorbed not only by the
glands, but passes down the tentacles.
Having examined a leaf in water, and found the contents of the cells
homogeneous, I placed it in a few drops of a solution of one part of
the carbonate to 437 of water, and attended to the cells immediately
beneath the glands, but did not use a very high power. No aggregation
was visible in 3 m.; but after 15 m. small spheres of protoplasm were
formed, more especially beneath the long-headed marginal glands; the
process, however, in this case took place with unusual slowness. In 25
m. conspicuous spherical masses were present in the cells of the
pedicels for a length about equal to that of the glands; and in 3 hrs.
to that of a third or half of the whole tentacle.
If tentacles with cells containing only very pale pink fluid, and
apparently but little protoplasm, are placed in a few drops of a weak
solution of one part of the carbonate to 4375 of water (1 gr. to 10
oz.), and the highly transparent cells beneath the glands are carefully
observed under a high power, these may be seen first to become slightly
cloudy from the formation of numberless, only just perceptible,
granules, which rapidly grow larger either from coalescence or from
attracting more protoplasm from the surrounding fluid. On one occasion
I chose a singularly pale leaf, and gave it, whilst under the
microscope, a single drop of a stronger solution of one part to 437 of
water; in this case the contents of the cells did not become cloudy,
39