32 TEB CAUSES OF FLUCTUATIONS IN TURCESCENCE
whicli they wore set. One of them, «, was now placed in an ammonia-chamber, and
tho other, b, in a chloroform one. The petals of a immediately began to show purplish
black spotting, which rapidly extended over their entire surface. The colour next
gradually assumed a greenish tint and ultimately became of a fine warm ochre.
Whilst those changes were occurring there were no signs of loss of tm-geseence, and
it was not until some hours after theii- full completion that a little exudation and a
trace of collapse manifested themsolvos. In the case of b the action of the abnormal
medium did not manifest itself for some time; but, when once initiated, alteration in
colour and loss of turgescence ran hand in hand, and after the close of a few hours
the colour was of a dull maroon red and tho tissues of tho flower were completely
flaccid and collapsed. Twenty-four hours after the mitiation of the experimeut, a was
slightly collapsed, but after this it remained apparently unaltered for some days.
Experiment XXII.—Two flowers of scarlet Hibiscus were taken, and one, a,
suspended free, apex downwards, in an ammonia-chamber, whilst the other, b, was
similarly hung in a chloroform-chamber. In the case of a, discolouration, in the form of
black spotting of the petals, made its appearance at once, and within an horn- the red
had entirely gone, save in a few isolated patches, and the rest of the tissue was deep
purpllsh-black, passing into deep greenish and ochre at the margins. There was, however,
no indication of any tendency to collapsc. In b discolouration was developed
much more slowly; but at the close of an hour the original vivid scarlet had
been replaced by a deep maroon, and the petals, which had originally been higlily
reflexed, were drooping downwards and rapidly collapsing. The first traces of collapse
in a did not appear until three hours after the beginning of the experiment, and even
then the petals remained highly reflexed. On the following day the petals of a were
drooped, but still widely divergent and firm in texture (plate I I I . fig. 3); whilst those
in b hung vertically downwards and were perfectly flaccid (plate I I I . fig. 4). Twentyfour
hours later the • petals of a were slightly less divergent than they had been, but
were still so divergent as to allow the stigmas to be visible beyond them in profile.
Both flowers were now removed from the chambers and hung in the open laboratory,
where they remained for days apparently unaltered, b being fully collapsed and a
retaining a considerable amount of turgidity.
Experiment X X / / / . — T w o flowers of scarlet Hibiscus were, as in the previous
case, placed respectively in ammonia and chloroform-chatqbers. They were not, however,
suspended, but were set with the freshly, subaqucously divided extremities of
their stalks immersed in water. As in the previous experiment, the flower in
the ammonia chamber began to show black spotting immediately, and rapidly passed
on through stages of deep purplish black and. deep greenish to a uniform warm ochi-e
without showing any signs of collapse; whilst that in the chlorofonn-chamber took
some time to show any signs of change in colour, but when it once had begun to
discolour, began also to collapse rapidly. On the following morning a slight amount of
collapse only was evident in a, whilst b was completely collapsed, flaccid, and soaked.
The ammonia-chamber was allowed to stand unopened for a week, and during
that period a remained almost in tho same condition as it was in after twenty-four
hours' exposure.
From the results obtained in tlie first of these experiments it is evident that tlie
retention of turgescence in such cases is not wholly due to the presence of free
IN THE MOTOR ORGANS OF LEAVES. 33
ammonia in the tissues, but that combinations must be formed within the cell-sap
which render it more or less permanently hygroscopic. The flower a did not undergo
complete collapse on removal from the ammonia chamber, but remained partially
turgid even after prolonged exposure in the open air. There can, therefore, be no
doubt that turgescence is mainly, if not solely, due to the osmotic properties of the
cell-sap, and that losses in turgescence are due to diminished osmotic capacity in the
latter, and not to any increased filtrative properties in the protoplasm. It is not,
however, quite clear that sü-uctural alterations in the protoplasm may not act in tho
contrary direction, in the way of retarding losses in turgescence by presenting an
abnormal resistance to the elastic recoil of the cell-walls. When we consider tho phenomena
presenting themselves in connection with death of tissues under the influence
of the vapour of osmic acid, there are many points suggesting that the abnormal
slowness with which loss of turgescence advances is due to such a causation. This
is shown by the data furnished by the next two experiments.
Experiment XXIV.—A leaf of Ealanchoe, weigliing 8-38 grammes, was enclosed
in a moist chamber containing a vessel of 2 per cent, solution of osmic acid. Visible blackening
of the surface became apparent within the course of half an hour, but the first
drop of exudation did not appear until two hours after exposure, and au hour later
only a certain number of scattered drops of black fluid had been excreted. On the
following day the leaf was coal-black and bore numerous large inky drops of fluid, but
the texture remained quite fii-m and the weight was still 7-9 grammes. It was now
placed in a simple moist chamber, where it remained for the next twelve days. The
successive losses in weight which occurred during the entire coiirse of the experiment
are recorded below :—
Date. Weight. Successive Total percentage
loss.
January 26th 8-38
27tb 7-90 0-48 5-7
28th 7-78 0-12 7-1
29th 7-64 0-14 8-6
„ 30tli 757 0'07 9-6
„ 31st 7-49 0'06 10-6
February 2nd 7-30 0-19 12-8
„ • 3rd 7-20 0-10 14-0
4th 7-05 0'15 15-6
5th 6'91 0-14 175
„ . 6th 6'84 0-07 18-3
8th 6-60 0-24 21-2
9lh 6-52 008 22-1
Here we have evidence of retarded loss in turgescence ; but the losses continued to
progress steadily, and there was no evidence of the absolute arrest of loss manifesting itself
m the case where death was caused by exposure to ammonia—vide experiment XIX.
The phenomenon appears rather to be the parallel of that presenting itself in cases
where the tissues are frozen, only that in this case the obstruction to tho escape of
volatile constituents and water from the tissues is a perinanent one and does not like
that established by cold, disappear on removal of the tissues from the conditions under
ANN. EOY. B o r . GAKK, CALCUTTA VOL. V I .