THE CAUSES OF FLUCTUATIOjS''S I N TUEGESCENCE
in tlic sap. In the case of blue OHtoria the tint is certainly related to relative alkalinity
of the sap, but this alkalinity is in great part due to the presence of non-fugitive,
fixed materials. In many yellow flowers, on the other hand, the persistence of the colour
after death of the tissues depends on much of the colom-ing matter being insoluble inthe
sap. In the African marigold, for example, the greater bulk of the pigment of the
corolla is not in solution, but is deposited in the form of resinous granules which are
quite insoluble in water, and therefore any changes in the reaction of the cell-sap do not
appreciably affect thehr eolour. The fact, therefore, that in certain cases wo do not find
loss in turgescence in the tissues to be accompanied by any conspicuous change in their
colour, cannot be taken as any evidence that chemical changes in the nature of the cellsap
have not occurred; wliilst the constancy with which we encounter evidences of the
presence of such changes, in cases where indices to theii- occurrence are present, sti-ongly
supports the belief in the normal coincidence of alterations in turgescence, which depend
on fluctuations in functional activity of the protoplasts, and chemical changes in the
Tlie chromatic change accompanying depression or abolition of function in vegetable
tissues is not, of course, an absolute proof of coincident alterations in their osmotic
properties, but merely of alterations in the composition of their cell-sap. It is,
however, highly probable that the processes leadmg to the latter may affect the
former also, and there are certain phenomena which to a certain extent appear to
indicate that they actually do so; for in cases in which depression and abolition
of functional activity is accompanied by very marked cliromatic changes, we find
the coincident loss in tm-gidity excessive, whilst in cases where chromatic changes
are inconspicuous, the loss in turgidity is not nearly so great. For example, when
the flowers of blue Clitma are killed by continued exposure to the vapom- of chloroform,
hardly any change manifests itself in their colour, whilst in the case of fîowers
of scarlet Sihisvus under similar circumstances the cliange is vciy great. A corresponding
difference occurs in relation to the coincident loss in turgidity, for, although
there is a considerable loss in Clitoria, it is limited in degree as compared with that
occurring in Ilihiscus, in wliicli the great change in colour is accompanied by absolute
ilaccidity of texture. The absence of conspicuous change in colour, and the limitation
in loss of turgescence, in Clitoria are at all events both ascribable to the presence of
certain stable constituents in the cell-sap which serve to maintain conditions in it
subsequent to the death of the tissues which can only be maintained in Ilibisous as
the result of the continued exercise of functional activity.
The experimental data which have been given above afford sufficient evidence that
alterations in turgescence following exposm'e to influences of the most diverse nature, and
which can hardly be supposed to produce any common effect on the nature of the protoplasts
of the tissues beyond depressing and ultimately abolishing their functional activities,
are accompanied by conspicuous alterations in the chemical constitution of the
cell-sap. This in itself is sufficient to suggest that it is to the properties of the latter,
and not to those of the protoplasts, that turgescence is immediately related; but we are
not obliged to remain content with any ambiguous evidence, as it is not hard to find
examples in which turgescence persists even in a very high degree quite apart from
the presence of any living protoplasts in the tissue. The tissue of the mesocai-p of
a ripe orange is one of the most striking of these. Here we certainly have a highly
turgid mass of tissue in which turgescence is maintained in spite of the absence of
IN THE iMOTOH OEGANS OP LEAVES. 27
any living protoplasm. During the process of maturation, the protoplasts of the cells
have been gi-adually expended with a proportionate accumulation of the products of
theii- functional activity in the ceU-sap ; and in the fully ripened tissue, if any living
protoplasm persists, its amount must evidently be extremely small. Whatever its amount
be, however, it certainly is not the cause of the tm-gidity of the tissue, as we
find the latter persisting under circumstances which involve the death of any living
protoplasts wliich have been exposed to them. When, for example, we expose portions
of the mesocarp of an orange to the influence of tlie conditions which we have just seen
to cause loss of turgescence where the latter is dependent on the presence of living
protoplasts, we do not find any evidence in these portioirs of the occun-ence of
parallel change. This is shown by the results of the following experiments:—
Experiment XIV.-A segment of the mesocai-p of a ripe orange, weighing 10-58
grammes, was exposed in a eliloroform-chamber for twenty-fom- hours. At the close of
this period it weighed 10-6 grammes and retained its turgidity unaltered.
E^perimeni XV.~A segment, weighing 9-52 gi-ammes, was exposed in a chloro-
¡ v Z t T the close of the experiment it weighed 9-53
_ Experiment XVI.-A segment, weighing 13-5 gi-ammes, was immersed for forty
mmutes m a 2-5 per cent, alcoholic solution of corrosive sublimate. On removal its
weight had increased to 13-73 grammes. It was now placed in a simple moist chamber
and on the following day was found apparently just as it had been at the beginning
of the expermient, quite turgid, the surface dry, and the weight 13-5 grammes. '
Experiment XVII.-A segment, weighing 20-U gi-ammes, was immersed in a 2-5
per cent, solution of corrosive sublimate for twenty-four hours. At the close of that
period it was excessively turgid, and when di-ied weighed 20-64 grammes It was
now placed in a simple moist chamber. Twenty-four liours later it was quite turbid
the surface dry, and the weight 19-87 gi-ammes. It was kept under observation foi
three days longer, and at the end of the experiment weighed 19'5 grammes.
Experiment ^ V I I I . - A segment of the mesocar-p of a ripe orange («), weighing
13 OS grammes, and a leaf of Kalanchoc {b), weighing 17-24 grammes, were immersed
or one mmute m boiling water. On removal («) weighed 13-5 gi-ammes and only
lo-6o. Forty-eigbt hom-s later, («) weighed 13-54 grammes; whilst {b) was flaccid,
yellowish olive, and weighed only 14-G grammes; the total loss in the former amountinc^
to 4-1 per cent, and in the latter to 15-3 per cent.
One of the most striking examples of the maintenance of an extremely hio-h
of tuj-gid.ty m cells, independent of the presence of any continuous s t i i m of
hvmg protoplasm, IS that which is afforded by the fertile filaments of PiMolus crustaU
Z ' J . r r ™ - ultimately leads to their rupture and
the violei^t discharge of the sporangia, arises only after they have been almost entii^ely
emptied of protoplasm by tho onward progress of the latter and its accumulation with n
the sporangium and certainly when no continuous stratum invests the interior of the cell
wall._ It IS certainly, herefore, independent of any anti-filtrative property of protoplasm
and nidecd . apparently independent of the action of any local protoplasm altogerhei, T
we find It to bo present in cases in wliich even the lower pai. of the stem immediaLly
ANX. EOY. BOT. GAKD. CALCUTTA VOL. V I.