CUKNINGHAM ON FLCTCTOATIO^S IN TUKGESCEXCE
III.—Exposure to the infliienae of tli'i vapoui' of ohlorofunn under eiroumstanoes favouriug
rapid treaspiratory removal of water from the tissues eonstautly occasions rapid
movements in piunules, but ouly esooptionally iaduoes rapid movemeuts of primary
petioles,
lY.—Neither exposure to a desiooatod atmospliore, unless the aridity bo very extreme, nor
esposui'e to a humid atmospUere oontainiug the vapour of ohloroform is ciipable
of iuducing rapid, sudden movements; but exposure to a desicoated atmospher
contaiuing the vapour of ohloroform is
; constantly attended by of suoh
movetnents.
Y,—The effects following exposure to the iufluei
e of the vapour of cliloroform, even in oases
I far as to cause actaul death, are piu'ely
where the treatment has been pushed
looalised to Ibose areas of a plant whic
the death of comparatively large i
I directly exposed to the vapour; and
ixis resulting from prolonged exposure
neither afieuts the oomluction of water by the water-condacting system, nor interferes
with the propagation of the conditions which give rise to the oeoun-ence of movemenfs.
These facts are quite inexplicable on nny theory which ascribes the occurrence of rapid movements
of the leaves to stimulation and active contraction of the protoplasts of the motor organs. "We
have no ground for believing that exposure to ansesthetio vapours leads to stimulation of protoplasmic
activity of any kind, but we liave distinct evidence that it acts in precisely opposite fashion. Were
the movements dependent on stimulation of contractile protoplasts in the motor organs by the
auListhetio vapoiu', thoy ought to retain tha same character, no matter what the hygi-ometrio properties
of the atmosphere be ; whereas as a faot sudden rapid movements never occur so long as the atmospliere
is humid, and ooustantly manifest themselves wliea it is desiccated, although similar atmospheric
aridity alone is incapable of iuducin? them, or indeed of inducing any movements whatever. Moreover,
were the movements dependent on protoplasmic stimulation and active contraction, the fact fliat
rapid piimular movement« are phenomena of normal occurrence on exposure to a desicoated atmosphere
containing vapour of chloroform, whilst rapid petiular movements are absolutely exceptional, would remain
a hopeless mj'stery.
But. on the theory that the movements are dependent on Josses in turgescenoe in the tissues of
the meter organs conneoted, not with any active protoplasmic contraction, but either with decrease
in the osmotic capacity of the cell-sap, or with influences facilifaHiig local filtration within the
tissues of the motor organs, or diitarhing pre-existent relations of equilibrium between general supply
and loss of water, all tlie phenomena become readily explicable. "Where plants or portions of plants
are exposed to the infiuenoe of the vapour of chloroform in a saturated or practically satui'ated
atmosptiore (as in the case of experiments T, VI, and 5 ) pinnular movements occur;- but they are of the
slow iusensihly progressive character normally present in cases where .liminatious in turgescenoe
occur iu connection with decrease or removal of normal stiiuulation. They are of the same character
as those ooeuriing periodically in connection with the diminution and cessation of solar stimulation
at sundown. They are evidently dependent; solely on the gradual loss of osmotic capacity in the
tissues of the motor organs attending the depression of assimilatory activity caused by the action
of the auEBSthetic. "Where (as in experiment YII) conditions favouring transpiratury lr>ss are considerably
greater, the rate of movement iunreases, because here the escape of liquid from the interior of the
cells of the motor organs accompanying depression of protophisiaio fuuctional activity is facilitated by
continuous evupoi-utive loss from the tissues generally. "Where, finally (as in experiments Y I I I , I X and XI),
depression in osmotic capacity is associated with exposure to a desiccated atmosphere, oooditions providing
for relatively rapid, considerable fluctuations in turgesoence ave manifestly present ; and with this
suddenly executed movements make their appearance. Suoli movements axe not, however, eveuly
distributed throughout the diSerout parts of the leaves. Thfy ocour coustantiy in the pinnules, quite
exceptionally in the primary petioles, and never, in so far as my espsrience goes, in the pinnas.
Are we to suppose that the vapour of chloroform under certain oircumstaiioes ocmstantly acts as a
sKmulant to the protoplasts of the tertiary pulvini, whilst it does so Only occasionally to those of the
primary pdvini and has no stimulunt effect whatever <m those of the secondary ones? It is surely
APPENDICES. 135
more reasonable to account for the phenomena as the result of a perfectly uniformly depressant factor
affecting iha assimilatory activity of the protoplasts of all the motor organs alike, but whose effects
manifest themselvts iu unlike I'oshion in parts which differ from one another in structural
peculiarities and in their relations to other parts of the leaf. Loss in osmotic capacity, and excessive
tranapiratory loss, work hand in hand in making for the elevation of the pinnules, which is determined
'by tlie excessive structural strength of the inferior mass of parenchyma in the tertiary pulvinus; tbo
tame factors come into play locally to give rise to a teudGiicy towards depressi(m of the primary
petiole, but here the weakening of the inferior mass of pulvinar parenchyma is discounted by the
coincident diminution in the resistance which it has to overcome ccnuHcted with the simultaneous
decrease in distal leverage attending excessive trailspiratory loss. Finally, in the secondary pulvini
there is an absenci of any highly developed differences in the structural and funcfionnl properties
in tliH masses of tissue which make respectively for divergence and convergence, nnd with this
any liability to the occurrence of rapid movements necessarily diminishes. Mere exposure to the influence
of vapour of chloroform is incapable of inducing sudden movements; exposure to a desiccated
atmosphere, unless the degree of aridity be very excessive, is equally inefficient; but tlie less of
osmotic properly connected with the depressiim of fimctional activity caused by the action of the
vapour of chloroform facilitates the occurrence of losses of turgescenoe to such aix extent us to ensure
the occurrence of rapid movements wherever conditions favouring active trauspiratory rewovul of
water are present in high degree.
APPENDIX D.
ON CEETAIN COMMONLY-ACCKPTED EUT ERIÎOKEOTJS STAÏKMENTS EEGAEDI.NG PHENOÎIEKA
PEIiSENXED Br iJIZIOSA FUDICA.
J. T/iai, in the initial ixocivrnal fosHim of the Icaics dvring the earw- portions of 11 ic iii(]I.l,
the prima^-j/ petioles are in a position oj deep depression*
The following notes give tlie results of observations iu regard to this point, which \
at various times of year;—
airitd out
Expeiumlnt L—January 27lh, C p.m. Pinnro aiul pinnules in maximal noctuinal position,
petioles higlily eltvalcd, but Leci-ming dei-iily depressed on cuiitaot impulses.
Exi'eiumhnt II,—January X'8th, 6-20 v.
Exi-niiiMKXT I I I . - F o b r u n r y 1st, G-20 i
lixPERiMEST lY.-Febvuary Sth, G p.m.
ExPEiiiME.N-r Y.-Fiibuiary lltli, 6 p.m.
ExnauMiiiiT YI.—May 30th, 7 p.m. Piiiiite and piunnles in maximal noctnrnnl posiiic
petioles hovizoniai or slightly elevated.
Results precisely siniilor to those of the {m
'rimary
Primary
Exi'KBiMiiN'i'YII-—October 11th, G p.m. Pinuro and pinnules almost in maximal nocturnal position.
Primary petioles horizmital or slightly eL^vated.
October l l t h , 8-30 J'.m. Pin-ira and pinnules iu maximal noctnrnnl position. Primary petioles
horizontal or slightly elevated.
October 12th, 12-15 a.m. Piunro and piunules as before. Marked increose in elevation of the
primary petioles.
The observations of the 27th and 28th January nnd of tho 1st, 8tb, and 11th February were
conducted in regai-d to very young plants in which the numb<-rs of pinnoe und of pinnules iu the
still small, the pinnce, as a rule, being only U o or three iu number and bearing only
,un.her of pinnules. This probably accounts for ihe fact that iu all cases the primary
e highly elevated, as in such leaves, apparently in connection with deficiency of distal
cessive elevation o£ the primary pctifle is of constant occurrence. The laminar portions
leaves we
a limited
kcl.a Torlcsnngon ; VorlesUDg, SXXYII. s. '
Akn. Roy. Bot. Gari-. Calcutta Yoi.. YI.