18 THE CAUSES OF FLUCTgATIONS IN TUEGESCENCE IN THE MOTOR ORGANS OF LEAVES. 19
was no general moistening of the surface or any indication of commencing flacciciity.
Tliree hours after the beginning o£ tho experiment it was very greatly blackened, but
was still quite rigid and had lost only 0 07 gi-nmrnes in weight. On tho following
morning it A\as perfectly black, but had discharged very little more fluid, the texture
remaining quite firui and the weiglit being 14'64 grammes. Twenty-four hours later,
I.e., forty-eight hours from the beginning of the experiment, a certain amount of further
exudation had occurred and the weight was 14-13 grammes, the total loss from tlie
boginuiiig of the experiment having oiily amounted to G-8 per cent. Tho slowness and
limitation of exudation attending exposure to this reagent as compared with tho
discharge taking place nnder ihe influence of the others is very remarkable. Tho
pheuumenon must bo due either to some alteration jn'oduced in the cell-.iap, whereby
stable in placo of unstable osmotic materials come to bo present in it, or more pmbably
to alterations in the protoplasm rendering it less filtrative than it is under ordiiiavy
circumstances.
E:epeninent XXI.—A leaf of Kaianchoe, weighing 26'87 grammes, was set in an
ammonia chamber. Conspicuous sweating took place in the lobes nearest to the vessel
containing the ammonia within the course of five minutes, and the tissues gradually
assumed an intense deep green colour. On the following day if. was of a very deep olive
green. The sm-face of the leaf was moist, but its testm-e was not flaccid. Twenty-four
hours later tho colour remained as before, and the weight was 23'43 grammes, equivalent
to a total loss of 13'8 per cent.
Experiment XXII.—A leaf of Ealmckoe, weighing 8-7 grammes, was set in a moist
ammonia chamber. AVithin ten minutes it became of a vivid deep green, and had begun
to sweat conspicuously. On the following day it was dark green and very moist, but still
rigid and smelling strongly of ammonia. The ammonia was removed so as to convert the
chamber into a simple moist one and the leaf replaced in it. 1'he weight of the leaf at
this timo was 8'52 grammes. It was kept under observation for three more days, during
which it continued to give off ammonia as indicated by the smell of the water in tho
chamber, wliich was renewed daily. The losses in weight for the successive periods of
twenty-four hours were O'SS, 0-29, and O'll grammes, giving a total loss for the entire
experiment of 1'56 grammes, or 17'9 per cent, of weight.
Experiment XXIII.—A leaf of Ealanchoe, weighing 29'22 grammes, was immersed
for forty minutes in a 2'5 per cent, alcoholic solution of corrosive sublimate. When
removed and gently dried, it weighed 29-3 grammes. It was now placed in a moist
chamber, and shortly began to sweat actively. On the following day it was partially flaccid,
nmch fluid had been already discharged, and active exudation was still going on. At
this time it weighed grammes. It continued to dischurge fluid, although kept
continuously in a sealed moist chamber, for tho next eight days, and at the close of
that period it was excessively flaccid, of a pale yellowish olive colour, and only
weighed 21-03 grammes, corresponding to a total loss of 8'19 grammes, or 28-3 per cent,
of weight.
Experiment XXIV.—A leaf of Kalmahoe, weighing 12 0 grammes, was immersed
in a saturated aqueous solution of corrosive sublimate, the extremity of the petiole being
fi-eshly divided after immersion in order to facilitate absorption. Twenty-two hours
later it was removed from tho solution and gently wipel diy.* It now weighed only
9-63 grammes, indicating a loss of 20-5 per cent, of total weight, and was flaccid and
of a pale ochreou.s colour, It was next placed in a simple moist chamber, and by the
following day had discliarged a considerable amount of fluid and weighed only 8'26
granmies. It would be hard to find a more striking demonstration of the fact that
turgidity is distinct from simple saturation than is afforded by the results of tJiis
experiment in which, whilst the leaf was actually submerged in the solution, such a
considerable loss of fluid occurred.
The most important points which are illustrated by the experimental data in the
present chapter are tlie following: —
lai.—That turgcsccnce implies saturation of tissue elements including osmotic
materials, and must therefore bo distinguished from simple saturation.
Tliat where tm'gescence is dependent on continued vitality, the relations of
coi-tain tissue elements to fluids are profoundly altered by conditions
which produce no appreciable effect on those of others.
^rd.—That where turgescence is dependent on continued vitality, its diminution
or total abolition may be determined by such varied conditions as
exposm-e to alkaline or acid vapours, to auieslhetics, poisonous substances
in solution, extremes of temperatm-e, and electrical currents.
4//i.—That the only other common effect which these different factors produce in
the tissues is the ultimate death of their living elements, or, in other
words, that depression or abolition of functional activity leads to diminution
or disappearance of turgidity. But this, taken along with the fact
that we have abundant evidence that certain forms of stimulation give
rise to increase in cell-turgescence, and no unequivocal evidence that
any forms of stinralation give rise to its decrease, almost forces us to
. believe that it is depression and not stimulation of functional activity
that is related to any movements which are determined by functional
causes and dependent on diminished cell-turgescence; and this finally
leads us to the conclusion already arrived at on independent grounds in
the previous chapter, that it is fluctuation in the activity of assimilatory
and respiratory function, and not fluctuations in the activity of contractile
function, that are essentially related to movements connocted
with alterations in the turgescence of cellular vegetable tissues.
C H A P T E R n i.
'iiilvc t c l d t i o i i sf i u r j t s c t n c t io i j r o t o i j l i i s m i c actiliifn.
The fads which have boon dofaUed in tlio pi-ocoding chapter might, if tal«n alone,
bo regarded as evidence lliat tm-gcsoence is a peculiarity of living tissaes, and therefore
directly and necessarily related to the presence of living protoplasm; and this opinion has
• la .11 ..... in r„,H„„. „[ a , „„ ¡„ jl,,
•S., carolull? proserrod aud inckdod in any aub.cqueiit w.igliment..
f esperimonts, l!iey •
Akn, Eg* Box, Giin. Cii.coTTA Vol. VI.