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INSECTIVOROUS PLANTS.
INSECTIVOROUS PLANTS
BY
CHARLES DARWIN, M.A., F.R.S.
ETC.
WITH ILLUSTRATIONS
NEW YORK
D. APPLETON AND COMPANY
1896
Authorised Edition.
CONTENTS.
CHAPTER I.
Drosera ROTUNDIFOLIA, OR THE Common SUN-DEW.
Number of insects captured — Description of the leaves and
their appendages or tentacles— Preliminary sketch of the
action of the various parts, and of the manner in which
insects are captured — Duration of the inflection of the
tentacles — Nature of the secretion — Manner “in which
insects are carried to the centre of the leaf — Evidence that
the glands have the power of absorption — Small size of
the TOOtS. sr Meee wa ae eam ee Pages 1-18
CHAPTER II.
Tue MovEMENTS OF THE TENTACLES FROM THE CONTACT OF
Sotip Bopres.
Inflection of the exterior tentacles owing to the glands of tho
disc being excited by repeated touches, or by objects left in
contact with them — Difference in the action of bodies yield-
ing and not yielding soluble nitrogenous matter — Inflection
of the exterior tentacles directly caused by objects left in
contact with their glands — Periods of commencing inflection
and of subsequent re-expansion — Extreme minuteness of
the particles causing inflection —Action under water —
Inflection of the exterior tentacles when their glands are
excited by los touches — ae drops of water do not.
cause inflection... .. . eh ea 19-37
vi CONTENTS.
CHAPTER ITI.
AGGREGATION OF THE PROTOPLASM WITHIN THE CELLS OF THE
TENTAOLES.
Nature of the contents of the cells before aggregation — Various
causes which excite aggregation — The process commences
within the glands and travels down the tentacles — Descrip-
tion of the aggregated masses and of their spontaneous
movements — Currents of protoplasm along the walls of the
cells — Action of carbonate of ammonia — The granules in
the protoplasm which flows along the walls coalesce with the
central masses — Minuteness of the quantity of carbonate of
ammonia causing aggregation — Action of other salts of
ammonia — Of other substances, organic fluids, &c—Of
water — Of heat — Redissolution of the aggregated masses —
Proximate causes of the aggregation of the protoplasm —
Summary and concluding remarks — Supplementary observa-
tions on aggregation in the roots of plants .. Pages 38-65
CHAPTER IV.
Tae Errrots oF Heat on THE LEAVES.
Nature of the experiments — Effects of boiling water — Warm
water causes rapid inflection — Water at a higher tempera-
ture does not cause immediate inflection, but does not kill
the leaves, as shown by their subsequent re-expansion and
by the aggregation of the protoplasm — A still higher
temperature kills the leaves and coagilates the albuminous
contents of the glands.. .. «2 «0. on owe) 66-75
CHAPTER V.
Tut Errects or NoN-NITROGENOUS AND NITROGENOUS
Oreanic FiLvips on THE LEAVES.
Non-nitrogenous fluids — Solutions of gum arabic — Sugar —
Starch — Diluted alcohol—Olive oil—Infusion and decoc-
tion of tea — Nitrogenous fluids — Milk — Urine — Liquid
albumen — Infusion of raw meat— Impure mucus — Saliva
—Solution of isinglass — Difference in the action of these
two sets of fluids — Decoction of green peas — Decoction
and infusion of cabbage — Decoction of grass leaves 76-84
CONTENTS. Vii
CHAPTER VI.
Tue Digestive Power oF THE SECRETION oF Drosera.
The secretion rendered acid by the direct and indirect excite-
ment of the glands— Nature of the acid — Digestible
substances — Albumen, its digestion arrested by alkalies,
recommences by the addition of an acid — Meat — Fibrin —
Syntonin — Areolar tissue — Cartilage — Fibro-cartilage —
Bone — Enamel and dentine — Phosphate of lime — Fibrous
basis of bone — Gelatine — Chondrin — Milk, casein and
cheese — Gluten — Legumin— Pollen — Globulin— Hasmatin
—Indigestible substances — Epidermic productions — Fibro-
elastic tissue — Mucin — Pepsin — Urea — Chitine— Cellulose
— Gun-cotton —Chlorophyll — Fat and oil — Starch — Action
of the secretion on living seeds —Summary and concluding
remarks .. 4. 6. 4 ue ew) Pages 85-185
CHAPTER VII.
Tue Errects or Sats or AMMONIA.
Manner of performing the experiments — Action of distilled
water in comparison with the solutions — Carbonate of-
ammonia, absorbed by the roots —The vapour absorbed by
the glands— Drops on the disc — Minute drops applied to
separate glands— Leaves immersed in weak solutions —
Minuteness of the doses which induce aggregation of the
protoplasm — Nitrate of ammonia, analogous experiments
with — Phosphate of ammonia, analogous experiments with
— Other salts of ammonia — Summary and concluding
remarks on the action of salts of ammonia .. .. 186-173
#
CHAPTER VIII
Tur EFFECTS OF VARIOUS OTHER SALTS, AND ACIDS, ON THE
LEAVES.
Salts of sodium, potassium, and other alkaline, earthy, and
metallic salts — Summary on the action of these salts—~—
Various acids — Summary on their action .. .. 174-198
viii CONTENTS.
CHAPTER IX.
Tue Errrcts OF OERTAIN ALKALOID POISONS, OTHER
SUBSTANCES AND VAPOURS.
Strychnine, salts of — Quinine, sulphate of, does not soon
arrest the mouvement of the protoplasm — Other salts of
quinine — Digitaline —. Nicotine — Atropine — Veratrine —
Colchicine — Theine — Curare — Morphia — Hyoscyamus —
Poison of the cobra, apparently accelerates the movements
of the protoplasm — Camphor, a powerful stimulant, its
vapour narcotic —- Certain essential oils excite movement —
Glycerine — Water and certain solutiong retard or prevent
the subsequent action of phosphate of ammonia—Alcohol
innocuous, its vapour narcotic and poisonous—Chloroform,
sulphuric and nitric ether, their stimulant, poisonous, and
narcotic power — Carbonic acid narcotic, not quickly
poisonous — Concluding remarks .. .. .. Pages 199-228
CHAPTER X.
ON THE SENSITIVENESS OF THE LEAVES, AND ON THE LINES
OF TRANSMISSION OF THE Motor IMPULSE.
Glands and summits of the tentacles alone sensitive — Trans-
mission of the motor impulse down the pedicels of the
tentacles, and across the blade of the leaf — Aggregation of
the protoplasm, a reflex action— First discharge of the
motor impulse sudden — Direction of the movements of the
tentacles — Motor impulse transmitted through the cellular
tissue — Mechanism of the movements — Nature of the
motor impulse — Re-expansion of the tentacles .. 229-261
CHAPTER XI.
REOAPITULATION OF THE CHIEF OBSERVATIONS ON
DROBERA ROTUNDIFOLIA.
262-277
CONTENTS. 13
CHAPTER XII.
ON Tuk STRUCTURE AND MoVEMENTS OF SOME OTHER
Sprores oF Drosera:
Drosera anglica—Drosera intermedia—Drosera capensis—Drosera
spathulata —Drosera filiformis—Drosera binata—Concluding
remarks «5 4. 6. 4. ue wee oe Pages 278-285
CHAPTER XIII.
DIoN@A MUSCIPULA.
Structure of the leaves — Sensitiveness of the filaments — Rapid
movement of the lobes caused by irritation of the filaments—
Glands, their power of secretion—Slow movement caused by
the absorption of animal matter — Evidence of absorption
from the aggregated condition of the glands— Digestive
power of the secretion— Action of chloroform, ether, and
hydrocyanic acid—The manner in which insects are captured
— Use of the marginal spikes — Kinds of insects captured —
The transmission of the motor impulse and mechanism of
the movements — Re-expansion of the lobes -- 286-820
CHAPTER XIV. *
ALDROVANDA VESIOULOSA,
Captures crustaceans — Structure of the leaves in comparison
with those of Dionwa— Absorption by the glands, by the
quadrifid processes, and points on the infolded margins —
Aldrovanda vesiculosa, var. australis — Captures prey —
Absorption of animal matter — Aldrovanda vesiculosa, var.
verticillata— Concluding remarks... .. .. .. 821-831
CHAPTER XV.
DrosopHyLLuM — Ror1puLA — ByBLis— GLANDULAR Hairs or
OTHER PLANTS—CONCLUDING REMARKS ON THE DROSERACER,
Drosophyllum—Structure of leaves—Nature of the secretion—
Manner of catching insects—Power of absorption— Digestion
of animal substances—Summary on Drosophyllum—Roridula
— Byblis— Glandular hairs of other plants, their power of
absorption — Saxifraga — Primula — Pelargonium — Erica—
Mirabilis — Nicotiana —Summary on glandular hairs—Con-
eluding remarks on the JWoseracee .. .. .. 832-367
x CONTENTS.
CHAPTER XVI.
PINGUIOULA.
Pinguicula vulgaris — Structure of leaves— Number of insects
and other objects caught—Movement of the margins of the
leaves — Uses of this movement — Secretion, digestion, and
absorption — Action of the secretion on various animal and
vegetable substances — The effects of substances not .con-
taining soluble nitrogenous matter on the glands—Pingwiculu
grandiflora — Pinguicula lusitanica, catches insects — Move-
ment of the leaves, secretion and digestion .. Pages 368-394
CHAPTER XVII.
UTRIOULARIA.
Utricularia neglecta — Structure of the bladder—The uses of the
several parts — Number of imprisoned animals — Manner of
capture — The bladders cannot digest animal matter, but
absorb the products of its decay— Experiments on the
absorption of certain fluids by the quadrifid processes —
Absorption by the glands — Summary of the observation on
absorption — Development of the bladders — Utricularia
vulgaris— Utricularia minor—Utricularia clandestina 395-430
CHAPTER XVIII.
UTRICULARIA (continued).
Utricularia montana — Description of the bladders on the sub-
terranean rhizomes — Prey captured by the bladders of
plants under culture and in a state of nature — Absorption
by the quadrifid processes and glands — Tubers serving as
reservoirs for water — Various other species of Utricularia —
Polypompholyx — Genlisea, different nature of the trap for
capturing prey — Diversified methods by which plants are
nourished .. 0. ee ewe 481-453
{NDEX ows ese wee saws «SHAG
INSECTIVOROUS PLANTS.
CHAPTER I.
DrosERA ROTUNDIFOLIA, OR THE COMMON Sun-prw.
Number of insects captured— Description of the leaves and their
appendages or tentacles — Preliminary sketch of the action of the
various parts, and of the manner in which insects are captured —
Duration of the inflection of the tentacles — Nature of the secre-
tion — Manner in which insects are carried to the centre of the
leaf — ividence that the glands have the power of absorption —
Small size of the roots.
Durina the summer of 1860, I was surprised by find-
ing how large a number of insects were caught by the
leaves of the common sun-dew (Drosera rotundifolia) on
a heath in Sussex.
I had heard that insects were thus
caught, but knew nothing further on the subject.* I
* As Dr. Nitschke has given
(‘Bot. Zeitung,’ 1860, p. 229) the
bibliography of Drosera, I need
not here go into details. Most of
the notices published before 1860
are brief and unimportant. The
oldest paper seems to have been
sne of the most valuable, namely,
by Dr. Roth, in 1782. There is
also an interesting though short
account of the habits of Drosera by
Dr. Milde, in the ‘ Bot. Zeitung,’
1852, p. 540. In 1855, in the‘ An-
nales des Sc. nat. bot.’ tom. iii. pp.
297 and 304, MM. Greenland and
Tréculeach published papers, with
figures, on the structure of the
leaves; but M. Trécul went so
far as to doubt whether they pos-
sessed any power of movement.
Dr. Nitschke’s papers in the ‘ Bot.
Zeitung’ for 1860 and 1861 are
by far the most important ones
which have been published, both
on the habits and structure of
this plant; and I shall frequently
have occasion to quote from
them. His discussions on several
points, for instance on the trans-
mission of an excitement from one
part of the leaf to another, are
excellent. On Dee. 11, 1862, Mr.
J. Scott read a paper before the
Botanical Society of Edinburgh,
2 DROSERA ROTUNDIFOLIA. Czar. I.
gathered by chance a dozen plants, bearing fifty-six
fully expanded leaves, and on thirty-one of these dead
insects or remnants of them adhered ; and, no doubt,
many more would have been caught afterwards by these
same leaves, and still more by those as yet not ex-
panded. On one plant all six leaves had caught their
prey; and on several plants very many leaves had
caught more than a single insect. On one large leaf
I found the remains of thirteen distinct insects.
Flies (Diptera) are captured much oftener than other
insects. The largest kind which I have seen caught
was a small butterfly (Cenonympha pamphilus); but
the Rev. H. M. Wilkinson informs me that he found a
large living dragon-fly with its body firmly held by
two leaves. As this plant is extremely common in
some districts, the number of insects thus annually
slaughtered must be prodigious. Many plants cause
the death of insects, for instance the sticky buds of
the horse-chestnut (Asculus hippocastanwm), without
thereby receiving, as far as we can perceive, any ad-
vantage; but it was soon evillent that Drosera was
which was published in the Gar-
dener’s Chronicle, 1863, p. 30.
Mr. Scott shows that gentle irrita-
tion of the hairs, as well as insects
placed on the dise of the leaf,
cause the hairs to bend in-
wards, Mr. A. W. Bennett also
gave another interesting account
of the movements of the leaves
before the British Association for
1873. In this same year Dr.
Warming published an essay, in
which he describes the structure
of the so-called hairs, entitled,
“Sur la Différence entre les Tri-
chomes,” &c., extracted from the
proceedings of the Soc. d’Hist.
Nat. de Copenhague. I shall also
have occasion hereafter to refer
to a paper by Mrs. Treat, of New
Jersey, on some American species
of Drosera. Dr. Burdon Sander-
son delivered a lecture on Dionxa,
before the Royal Institution (pub-
lished in ‘ Nature,’ June 14, 1874),
in which a short account of my
observations on the power of true
digestion possessed by Drosera
and Dioniea first appeared. Prof.
Asa Gray has done good service
by calling attention to Drosera,
and to other plants having similar
habits, in ‘ The Nation’ (1874, pp.
261 and 232), and in other publica-
tions. Dr. Hooker, also, in his
important address on Carnivorous
Plants (Brit. Assoo., Belfast, 1 874),
has given a history of the subject,
Cxar. L STRUCTURE OF THE LEAVES, 3
excellently adapted for the special purpose of catch-
ing insects, so that the subject seemed well worthy of
investigation.
The results have proved highly remarkable; the
wore important ones being-—firstly, the extraordinary
Q y T@ a
Qs ip ry
Fic, 1.*
(Drosera rotundifolia.)
Leaf viewed from above; enlarged four times.
sensitiveness of the glands to slight pressure and to
minute doses of certain nitrogenous fluids, as shown
by the movements of the so-called hairs or tentacles ;
* The drawings of Drosera and~ cularia, by my son Francis. They
Dionwa, given in this work, were have been excellently reproduced
made for me by my son George on wood by Mr. Cooper, 188
Tarwin: those of Aldrovanda, and Strard,
of the several specixs of Utri-
4 DROSERA ROTUNDIFOLIA. Crap. 1
sevondly, the power possessed by the leaves of render-
ing soluble or digesting nitrogenous substances, and
of afterwards absorbing them; thirdly, the changes
which take place within the cells of the tentacles, when
the glands are excited in various ways.
It is necessary, in the first place, to describe briefly
the plant. It bears from two or three to five or six
leaves, generally extended more or less horizontally,
but sometimes standing vertically upwards. The shape
and general appearance of a leaf is shown, as seen
from above, in fig. 1, and as seen laterally, in fig. 2.
The leaves are commonly a little broader than long,
Fre. 2.
(Drosera rotundifolia.)
Old leaf viewed laterally; enlarged about five times.
but this was not the case in the one here figured.
The whole upper surface is covered with gland-bearing
filaments, or tentacles, as I shall call them, from their
rmaanner of acting. The glands were counted on thirty-
one leaves, but many of these were of unusually large
size, and the average number was 192; the greatest
number being 260, and the least 130. The glands are
each surrounded by large drops of extremely viscid
secretion, which, glittering in the sun, have given rise
to the plant’s poetical name of the sun-dew.
The tentacles on the central part of the leaf or disc are
short and stand upright, and their pedicels are green. Towards
the margin they become longer and longer and more inclined
Ouar. 1. STRUCTURE OF THE LEAVES. 5
outwards, with their pedicels of a purple colour. Those on the
extreme margin project in the same plane with the leaf, or more
commonly (see fig. 2) are considerably reflexed. A few tentacles
spring from the base of the footstalk or petiole, and these are
the longest of all, being sometimes nearly 4 of an inch in length.
On a leaf bearing altogether 252 tentacles, the short ones on
the disc, having green pedicels, were in number to the longer
submarginal and marginal tentacles, having purple pedicels, as
nine to sixteen.
A tentacle consists of a thin, straight, hair-like pedicel, carry-
ing a gland on the summit. The pedicel is somewhat flattened,
and is formed of several rows of elongated cells, filled with purple
fluid or granular matter.* - There is, however, a narrow zone
close beneath the glands of the longer tentacles, and a broader
zone near their bases, of a green tint. Spiral vessels, accom-
panied by simple vascular tissue, branch off from the vascular
bundles in the blade of the leaf, and run up all the tentacles
into the glands.
Several eminent physiologists have discussed the homological
nature of these appendages or tentacles, that is, whether they
ought to be considered as hairs (trichomes) or prolongations of
the leaf. Nitschke has shown that they include all the elements
proper to the blade of a leaf; and the fact of their including
vascular tissue was formerly thought to prove that they were
prolongations of the leaf, but it is now known that vessels some-
times enter true hairs.t| The power of movement which they
possess is a strong argument against their being viewed as hairs.
The conclusion which seems to me the most probable will be
given in Chap. XV., namely that they existed primordially as
glandular hairs, or mere epidermic formations, and that their
upper part should still be so considered; but that their lower
* According to Nitschke (‘ Bot.
Zeitung,’ 1861, p. 224) the purple
fluid results from the metamor-
phosis of chlorophyll. Mr. Sorby
examined the colouring matter
with the spectroscope, and in-
forms me that it consists of the
commonest species of erythro-
phyll, “ which is often met with in
leaves with low vitality, and in
parts, like the petioles, which
earry on leaf-functions in a very
imperfect manner. All that can
be said, therefore, is that the hairs
(or tentacles) are coloured like
parts of a leaf which do not fulfil
their proper office.”
+ Dr. Nitschke has discussed
this subject in ‘Bot. Zeitung,’
1861, p. 241, &e. See also Dr.
Warming (‘Sur la Différence entre
les Trichomes,’ &c., 1873), who
gives references to various publi-
cations. See also Groonland and
Trécul, ‘ Annal. des Se. nat. bot.’
(4th series), tom. iii. 1855, pp.
297 and 303.
6 DROSERA ROTUNDIFOLIA, Cuar. L
part, which alone is capable of movement, consists of a prolon-
gation of the leaf; the spiral vessels being extended from this
to the uppermost part. We shall hereafter see that the ter-
minal tentacles of the divided leaves of Roridula are still in
an intermediate condition.
The glands, with the exception of those borne by the extreme
Fic. 3.
\Drosera rotundifolia.)
Longitudinal section of a gland; greatly magnified. From Dr. Warming.
marginal tentacles, are oval, and of nearly uniform size, viz.
about >45 of an inch in length. Their structure is remarkable,
and their functions complex, for they secrete, absorb, and are
acted on by various stimulants. They consist of an outer layer
of small polygonal cells, containing purple granular matter or
fluid, and with the walls thicker than those of the pedicels.
Onur. L SYRUCTURE OF THE LEAVES. 7
Within this layer of cells there is an inner one of differently
shaped ones, likewise filled with purple fluid, but of a slightly
different tint, and differently affected by chloride of gold. These
two layers are sometimes well seen when a gland has been
crushed or boiled in caustic potash. According to Dr. Warming,
there is still another layer of much more elongated cells, as
shown in the accompanying section (fig. 3) copied from his
work; but these cells were not seen by Nitschke, nor by me.
In the centre there is a group of elongated, cylindrical cells of
unequal lengths, bluntly pointed at their upper ends, truncated
or rounded at their lower ends, closely pressed together, and
remarkable from being surrounded by a spiral line, which can be
separated as a distinct fibre.
These latter cells are filled with limpid fluid, which after long
immersion in alcohol deposits much brown matter. I presume
that they are actually connected with the spiral vessels which run
up the tentacles, for on several occasions the latter were seen to
divide into two or three excessively thin branches, which could
be traced close up to the spiriferous cells. ‘Their development
has been described by Dr. Warming. Cells of the same kind
have been observed in other plants, as I hear from Dr. Hooker,
and were seen by me in the margins of the leaves of Pinguicula.
Whatever their function may be, they are not necessary for the
secretion of the digestive fluid, or for absorption, or for the
communication of a motor impulse to other parts of the leaf,
as we may infer from the structure of the glands in some other
genera of the Droseracez.
The extreme marginal tentacles differ slightly from the others.
Their bases aro broader, and besides their own vessels, they
receive a fine branch from those which enter the tentacles
on each side. Their glands are much elongated, and lie em-
bedded on the upper surface of the pedicel, instead of standing
at the apex. In other respects they do not differ essentially
from the oval ones, and in one specimen I found every possible
transition between the two states. In another specimen there
were no long-headed glands. These marginal tentacles lose
their irritability earlier than the others; and when a stimulus
is applied to the centre of the leaf, they are excited into action
after the others. When cut-off leaves are immersed in water,
they alone often become inflected.
The purple fluid or granular matter which fills the cells ot
the glands differs to a certain extent from that within the
cells of the pedicels. For when a leaf is placed in hot water or in
certain acids, the glands become quite white and opaque, whereaa
2
8 DROSERA ROTUNDIFOLIA. Cuar L
the cells of the pedicels are rendered of a bright red, with the
exception of those close beneath the glands. These latter cells
lose their pale red tint; and the green matter which they, as
well as the basal cells, contain, becomes of a brighter green.
The petioles bear many multicellular hairs, some of which
near the blade are surmounted, according to Nitschke, by a
few rounded cells, which appear to be rudimentary glands.
Both surfaces of the leaf, the pedicels of the tentacles, espe-
cially the lower sides of the outer ones, and the petioles, are
studded with minute papillze (hairs or trichomes), having a
conical basis, and bearing on their summits two, and occasion-
ally three or even four, rounded cells, containing much proto-
plasm. These papille are generally colourless, but sometimes
include a little purple fluid. They vary in development, and
graduate, as Nitschke* states, and as I repeatedly observed
into the long multicellular hairs. ‘Lhe latter, as well as the
papille, are probably rddiments of formerly existing tentacles.
I may here add, in order not to recur to the papille, that they
do not secrete, but are easily"permeated by various fluids: thus
when living or dead leaves are immersed in a solution of one
part of chloride of gold, or of nitrate of silver, to 437 of water,
they are quickly blackened, and the discoloration soon spreads
to the surrounding tissue. The long multicellular hairs are
not so quickly affected. After a leaf had been left in a weak
infusion of raw meat for 10 hours, the cells of the papillae had
evidently absorbed animal matter, for instead of limpid fluid
they now contained small aggregated masses of protoplasm,
which slowly and incessantly changed their forms. A similar
result followed from an immersion of only 15 minutes in a
solution of one part of carbonate of ammonia to 218 of water,
and the adjoining cells of the tentacles, on which the papilla
were seated, now likewise contained aggregated masses of proto-
plasm. We may therefore conclude that when a leaf has closely
clasped a captured insect in the manner immediately to be
described, the papillz, which project from the upper surface
of the leaf and of the tentacles, probably absorb some of the
animal matter dissolved in the secretion; but this cannot be
the case with the papilla on the backs of the leaves or on the
petioles.
* Nitschke has elaborately described and figured the
Bot. Zeitung,’ 1861, pp. 234, 253, 254. gu se papille,
Cuap. L ACTION OF THE 1 ARTS. 9
Preliminary Sketch of the Action of the several Parts, and
of the Manner in which Insects are Captured.
If a small organic or inorganic object be placed on
the glands in the centre of a leaf, these transmit a
motor impulse to the marginal tentacles. The nearer
ones are first affected and slowly bend towards the
centre, and then those farther off, until at last all
become closely inflected over the object. This takes
place in from one hour to four or five or more hours.
The difference in the time required depends on many
circumstances; namely on the size of the object and
on its nature, that is, whether it contains soluble
matter of the proper kind; on the vigour and age of
the leaf; whether it has lately been in action; and,
according to Nitschke,* on the temperature of the
day, as likewise seemed to me to be the case. A living
insect is a more efficient object than a dead one, as
in struggling it presses against the glands of many
tentacles. An insect, such as a fly, with thin integu-
ments, through which animal matter in solution can
readily pass into the surrounding dense secretion, is
more efficient in causing prolonged inflection than an
insect with a thick coat, such as a beetle. The inflec-
tion of the tentacles takes place indifferently in the
light and darkness; and the plant is not subject to
any nocturnal movement of so-called sleep.
If the glands on the disc are repeatedly touched or
brushed, although no object is left on them, the
marginal tentacles curve inwards. So again, if drops
of various fluids, for instance of saliva or of a solu-
tion of any salt of ammonia, are placed on the central
glands, the same result quickly follows, sometimes in
under half an hour.
* «Bot. Zeitung,’ 1860, p. 246.
10 DROSERA ROTUNDIFOLIA. Cuar. 1
The tentacles in the act of inflection sweep through
a wide space; thus a marginal tentacle, extended in
the same plane with the blade, moves through an angle
of 180°; and I have seen the much reflected tentacles
of a leaf which stood upright move through an angle
of not less than 270°. The bending part is almost
confined to a short space near the base ; but a rather
larger portion of the elongated exterior tentacles
Fie. 4. Fig. a.
(Drosera rotundifolia.) (Drosera rotundifolia.)
Leaf (enlarged) with all the tentacles Leaf (enlarged) with the tentacles on one
closely inflected, from immersion ina side inflected over a bit of meat placed
solution of phosphate of ammonia (one on the disc.
part to 87,500 of water).
becomes slightly incurved ; the distal half in all cases
remaining straight. The short tentacles in the centre
of the dise when directly excited, do not become in-
flected ; but they are capable of inflection if excited
by a motor impulse received from other glands at a
distance. Thus, if a leaf is immersed in an infusion
of raw meat, or in a weak solution of ammonia (if the
Oar. 1, ACTION OF THE PARTS. ll
solution is at all strong, the leaf is paralysed), all the
exterior tentacles bend inwards (see fig. 4), excepting
those near the centre, which remain upright ; but these
bend towards any exciting object placed on one side
of the disc, as shown in fig. 5. The glands in fig. 4
may be seen to form a dark ring round the centre ; and
this follows from the exterior tentacles increasing in
length in due proportion, as they stand nearer to the
circumference.
The kind of inflection which the tentacles undergo
is best shown when the gland of one of the long exterior
a
Fie. 6.
(Drosera rotundifolia.)
Piagram showing one of the exterior tentacles closely inflected; the two adjoining
ones in their ordinary position.
tentacles is in any way excited; for the surrounding
ones remain unaffected. In the accompanying outline
(fig. 6) we see one tentacle, on which a particle of
meat had been placed, thus bent towards the centre of
the leaf, with two others retaining their original
position. A gland may be excited by being simply
touched three or four times, or by prolonged contact |
with organic or inorganic objects, and various fluids. I
have distinctly seen, through a lens, a tentacle begin-
hing to bend in ten seconds, after an object had been
12 DROSERA ROTUNDIFOLIA. Cuap. L
placed on its gland; and I have often seeu strongly
pronounced inflection in under one minute. It is sur-
prising how minute a particle of any substance, such
as a bit of thread or hair or splinter of glass, if placed
in actual contact with the surface of a gland, suffices
to cause the tentacle to bend. If the object, which has
been carried by this movement to the centre, be not
very small, or if it contains soluble nitrogenous matter,
it acts on the central glands; and -these transmit a
motor impulse to the exterior tentacles, causing them
to bend inwards.
Not only the tentacles, but the blade of the leaf
often, but by no means always, becomes much in-
curved, when any strongly exciting substance or fluid
is placed on the disc. Drops of milk and of a solution
of nitrate of ammonia or soda are particularly apt to
produce this effect. The blade is thus converted into
a little cup. The manner in which it bends varies
greatly. Sometimes the apex alone, sometimes one
side, and sometimes both sides, become incurved. For
instance, I placed bits of hard-boiled egg on three
leaves; one had the apex bent towards the base; the
second had both distal margins much incurved, so
that it became almost triangular in outline, and this
perhaps is the commonest case ; whilst the third blade
was not at all affected, though the tentacles were as
closely inflected as in the two previous cases. The
whole blade also generally rises or bends upwards, and
thus forms a smaller angle with the footstalk than it
did before. This appears at first sight a distinct
kind of movement, but it results from the incurvation
of that part of the margin which is attached to the
footstalk, causing the blade, as a whole, to curve or
move upwards.
The length of time during which the tentacles as
Ounar. I. ACTION OF THE PARTS. 18
well as the blade remain inflected over an object placed
* on the disc, depends on various circumstances; namely
on the vigour and age of the leaf, and, according to
Dr. Nitschke, on the temperature, for during cold
weather when the leaves are inactive, they re-expand
at an earlier period than when the weather is warm.
But the nature of the object is by far the most
important circumstance; I have repeatedly found that
the tentacles remain clasped for a much longer average
time over objects which yield soluble nitrogenous
matter than over those, whether organic or inorganic,
which yield no such matter. After a period varying
from one to seven days, the tentacles and blade re-
expand, and are then ready to act again. I have seen
the same leaf inflected three successive times over
insects placed on the disc; and it would probably
have acted a greater number of times.
The secretion from the glands is extremely viscid,
so that it can be drawn out into long threads. It
appears colourless, but stains little balls of paper pale
pink. An object of any kind placed on a gland always
causes it, as I believe, to secrete more freely; but
the mere presence of the object renders this difficult
to ascertain. In some cases, however, the effect was
strongly marked, as when particles of sugar were
added; but the résult in this case is probably due
merely to exosmose. Particles of carbonate and phos-
phate of ammonia and:of some other salts, for instance
sulphate of zinc, likewise increase the secretion. Im-
mersion in a solution of one part of chloride of gold,
or of some other salts, to 437 of water, excites the
glands to largely increased secretion; on the other
hand, tartrate of antimony produces no such effect.
Lmmersion in many acids (of the strength of one part
to 437 uf water) likewise causes a wonderful amount of
14 DROSERA ROTUNDIFOLIA. Cuapr. L
secretion, so that when the leaves are lifted out, long
ropes of extremely viscid fluid hang from them. Some
acids, on the other hand, do not act in this manner.
Increased secretion is not necessarily dependent on
the inflection of the tentacle, for particles of sugar and
of sulphate of zinc cause no movement.
It is a much more remarkable fact that when an
object, such as a bit of meat or an insect, is placed on
-the dise of a leaf, as soon as the surrounding tentacles
become considerably inflected, their glands pour forth
an increased amount of secretion. I ascertained this
by selecting leaves with equal-sized drops on the two
sides, and by placing bits of meat on one side of the
disc; and as soon as the tentacles on this side became
much inflected, but before the glands touched the meat,
the drops of secretion became larger. This was re-
peatedly observed, but a record was kept of only
thirteen cases, in nine of which increased secretion was
plainly observed ; the four failures béing due either to
the leaves being rather torpid, or to the bits of meat
being too small to cause much inflection. We must
therefore conclude that the central glands, when
strongly excited, transmit some influence to the glands
of the circumferential tentacles, causing them to secrete
more copieusly.
It is a still more important fact (as we shall see
more fully when we treat of the digestive power of
the secretion) that when the tentacles become inflected,
owing to the central glands having been stimulated
mechanically, or by contact with animal matter, the
secretion not only increases in quantity, but changes
its nature and becomes acid; and this occurs before
the glands have touched the object on the centre of
the leaf. This acid is of a different nature from that
contained in the tissue of the leaves. As long as the
Ouar. 1. ACTION OF THE PARTS. 15
tentacles remain closely inflected, the glands continue
to secrete, and the secretion is acid; so that, if neu-
tralised by carbonate of soda, it again becomes acid
after a few hours. I have observed the same leaf with
the tentacles closely inflected over rather indigestible
substances, such as chemically prepared casein, pour-
ing forth acid secretion for eight successive days, and
over bits of bone for ten successive days.
The secretion seems to possess, like the gastric juice
of the higher animals, some antiseptic power. During
very warm weather I placed close together two equal-
sized bits of raw meat, one on a leaf of the Drosera,
and the other surrounded by wet moss. They were
thus left for 48 hrs., and then examined. The bit on
the moss swarmed with infusoria, and was so much
decayed that the transverse striae on the muscular
fibres could no longer be clearly distinguished ;
whilst the bit on the leaf, which was bathed by the
secretion, was free from infusoria, and its striz were
perfectly distinct in the central and undissolved por-
tion. In like manner small cubes: of albumen and
cheese placed on wet moss became threaded with
filaments of mould, and had their surfaces_ slightly
discoloured and disintegrated; whilst those on the
leaves of Drosera remained clean, the albumen being
changed into transparent fluid.
As soon as tentacles, which have remained closely
inflected during several days over an object, begin to
re-expand, their glands secrete less freely, or cease
to secrete, and are left dry. In this state they are
covered with a film of whitish, semi-fibrous matter,
which was held in solution by the secretion. The
drying of the glands during the act of re-expan
sion is of some little service to the plant; for I have
often observed that objecis adhering to the leaves
16 DROSERA ROTUNDIFOLIA. Cuap. L
sould then be blown away by a breath of air; the
leaves being thus left unencumbered and free for future
action. Nevertheless, it often happens that all the
glands do not become completely dry; and in this
ease delicate objects, such as fragile insects, are some-
times torn by the re-expansion of the tentacles into
fragments, which remain scattered all over the leaf.
After the re-expansion is complete, the glands quickly
begin to re-secrete, and as soon as fuli-sized drops
are formed, the tentacles are ready to clasp a new
object.
When an insect alights on the central disc, it is
instantly entangled by the viscid secretion, and the
surrounding tentacles after a time begin to bend, and
ultimately clasp it on all sides. Insects are generally
killed, according to Dr. Nitschke, in about a quarter
of an hour, owing to their trachee being closed by
the secretion. If an insect adheres to only a few of
the glands of the exterior tentacles, these soon
become inflected and carry their prey to the tentacles
next succeeding them inwards; these then bend in-
wards, and so onwards, until the insect is ultimately
carried by a curious sort of rolling movement to the
centre of the leaf. Then, after an interval, the ten-
tacles on all sides become inflected and bathe their
prey with their secretion, in the same manner as
if the insect had first alighted on the central disc. It
is surprising how minute an insect suffices to cause
this action: for instance, I have seen one of the
smallest species of gnats (Culex), which had just
settled with its excessively delicate feet on the
glands of the outermost tentacles, and these were
already beginning to curve inwards, though not a
single gland had as yet touched the body of the
insect. Had I not interfered, this minute gnat would
Cuar. I, ACTION OF THE PARTS. 17
assuredly have been carried to the centre of the leaf
and been securely clasped on all sides. We shall
hereafter see what excessively small doses of certain
organic fluids and saline solutions cause strongly
marked inflection.
Whether insects alight on the leaves by mere
chance, as a resting-place, or are attracted by the
odour of the secretion, I know not. I suspect from
the number of insects caught by the English species
of Drosera, and from what I have observed with some
exotic species kept in my greenhouse, that the odour
is attractive. In this latter case the leaves may be
compared with a baited trap; in the former case with
a trap laid in a run frequented by game, but without
any bait.
That the glands possess the power of absorption, is
shown by their almost instantaneously becoming dark-
coloured when given a minute quantity of carbonate of
ammonia; the change of colour being chiefly or exclu-
sively due to the rapid aggregation of their contents.
When certain other fluids are added, they become pale-
coloured. Their power of absorption is, however, best
shown by the widely different results which follow,
from placing drops of various nitrogenous and non-
nitrogenous fluids of tlie same density on the glands
of the disc, or on a single marginal gland; and like-
wise by the very different lengths of time during which
the tentacles remain inflected over objects, which yield
or do not yield soluble nitrogenous matter. This
same conclusion might indeed have been inferred from
the structure and movements of the leaves, which are
so admirably adapted for capturing insects.
The absorption of animal matter from captured
insects explains how Drosera can flourish in extremely
poor peaty soil,—in some cases where nothing but
18 DROSERA ROTUNDIFOLIA. Cuar. L
sphagnum moss grows, and mosses depend altogether
on the atmosphere for their nourishment. Although
‘the leaves at a hasty glance do not appear green, owing
to the purple colour of the tentacles, yet the upper and
lower surfaces of the blade, the pedicels of the central
tentacles, and the petioles contain chlorophyll, so that,
no doubt, the plant obtains and assimilates carbonic
acid from the air. Nevertheless, considering the
nature of the soil where it grows, the supply of nitrogen
would be extremely limited, or quite deficient, unless
the plant had the power of obtaining this important
element from captured insects. We can thus under-
stand how it is that the roots are so poorly developed.
These usually consist of only two or three slightly
divided branches, from half to one inch in length,
furnished with absorbent hairs. It appears, therefore,
that the roots serve only to imbibe water; though, no
doubt, they would absorb nutritious matter if present
in the soil; for as we shall hereafter see, they absorb
a weak solution of carbonate of ammonia. A plant
of Drosera, with the edges of its leaves curled in-
wards, so as to form a temporary stomach, with the
glands of the closely inflected tentacles pouring forth
their acid secretion, which dissolves animal matter,
afterwards to be absorbed, may be said to feed like an
animal. But, differently from an animal, it drinks’ by
means of its roots; and it must drink largely, so as to
retain many drops of viscid fluid round the glands,
sometimes as many as 260, exposed during the whole
day to a glaring sun.
Ouay. 11, INFLECTION INDINECTLY CAUSED. 19
CHAPTER IL
Tue Movements OF THE TENTACLES FROM THE ConTAcT oF SoLip
Bones.
Inflection of the exterior tentacles owing to the glands of the dise
being excited by repeated touches, or by objects left in contact
with them— Difference in the action of bodies yielding and not
yielding soluble nitrogenous matter —Inflection of the exterior
tentacles directly caused by objects left in contact with their
glands — Periods of commencing inflection and of subsequent re-
expansion — Extreme minuteness of the particles causing inflection
- —Action under water — Inflection of the exterior tentacles when
their glands are excited by repeated touches— Falling drops of
water do not cause inflection.
T wiLu give in this and the following chapters some of
the many experiments made, which best illustrate the
manner and rate of movement of the tentacles, when
excited in various ways. The glands alone in all
ordinary cases are susceptible to excitement. When
excited, they do not themselves move or change form,
but transmit a motor impulse to the bending part of
their own and adjoining tentacles, and are thus carried
towards the centre of the leaf. Strictly speaking, the
glands ought to be called irritable, as the term sensi-
tive generally implies consciousness; but no one sup-
poses that the Sensitive-plant is conscious, and as I
have found the term convenient, I shall use it without
seruple. I will commence with the movements of the
exterior tentacles, when indirectly excited by stimulants
applied to the glands of the short tentacles on the disc.
The exterior tentacles may be said in this case to be
indirectly excited, because their own glands are not
directly acted on. The stimulus proceeding from the
glands of the disc acts on the bending part of the
20 DROSERA ROTUNDIFOLIA. Caap. LL.
exterior tentacles, near their bases, and does not (as
will hereafter be proved) first travel up the pedicels to
the glands, to be then reflected back to the bending
place. Nevertheless, some influence does travel up to
the glands, causing them to secrete more copiously,
and the secretion to become acid. This latter fact
is, I believe, quite new in the physiology of plants;
it has indeed only recently been established that in
the animal kingdom an influence can be transmitted
along the nerves to glands, modifying their power of
secretion, independently of the state of the blood-
vessels.
The Inflection of the Exterior Tentacles from the Glands
of the Disc being excited by Repeated Touches, or by
Objects left in Contact with them.
The central glands of a leaf were irritated with a
small stiff camel-hair brush, and in 70 m. (minutes)
several of the outer tentacles were inflected; in 5 hrs.
(hours) all the sub-marginal tentacles were inflected ;
next morning after an interval of about 22 hrs. they were
fully re-expanded. In all the following cases the period
is reckoned from the time of first irritation. Another
leaf treated in the same manner had a few tentacles
inflected in 20 m.; in 4 hrs. all the submarginal and
some of the extreme marginal tentacles, as well as the
edge of the leaf itself, were inflected; in 17 hrs. they
had recovered their proper, expanded position. I then
put a dead fly in the centre of the last-mentioned leaf,
_and next morning it was closely clasped ; five days
afterwards the leaf re-expanded, and the tentacles,
with their glands surrounded by secretion, were ready
to act again.
Particles of meat, dead flies, bits of paper, wood,
dried moss, sponge, cinders, glass, &c., were repeatedly
Cnar. IL. INFLECTION [NDIRECTLY CAUSED. 2]
placed on leaves, and these objects were well e1ubraced
in various periods from 1 hr. to as long as 24 hrs., and
set free again, with the leaf fully re-expanded, in from
one or two, to seven or even ten days, according to
the nature of the object. On a leaf which had
naturally caught two flies, and therefore had already
closed and reopened either once or more probably
twice, I put a fresh fly: in 7 hrs. it was moderately,
and in 21 hrs. thoroughly well, clasped, with the
edges of the leaf inflected. In two days and a
half the leaf had nearly re-expanded ; as the exciting
object was an insect, this unusually short period of in-
‘flection was, no doubt, due to the leaf having recently
been in action. Allowing this same leaf to rest for
only a single day, I put on another fly, and it again
closed, but now vexy slowly ; nevertheless, in less than
two days it succeeded in thoroughly clasping the fly.
When a small object is placed on the glands of the
disc, on one side of a leaf, as near as possible to
its circumference, the tentacles on this side are first
affected, those on the opposite side much later, or, as
often occurred, not at all. This was repeatedly proved
by trials with bits of meat; but I will here give only
the case of a minute fly, naturally caught and still
alive, which I found adhering by its delicate feet to
the glands on the extreme left side of the central disc.
The marginal tentacles on this side closed inwards
and killed the fly, and after a time the edge of the
leaf on this side also became inflected, and thus
remained for several days, whilst neither the tentacles
nor the édge on the opposite side were in the least
affected.
If young and active leaves are selected, inorganic
particles not larger than the head of a small pin,
placed on the central glands, sometimes cause the
22 DROSERA ROTUNDIFOLIA. Cua. IL
outer tentacles to bend inwards. But this follows
much more surely and quickly, if the object contains
nitrogenous matter which can be dissolved by the
secretion. On one occasion I observed the follow-
ing unusual circumstance. Small bits of raw meat
(which acts more energetically than any other sub-
stance), of paper, dried moss, and of the quill of a
pen were placed on several leaves, and they were all
embraced equally well in about 2 hrs. On other
occasions the above-named substances, or more com-
monly particles of glass, coal-cinder (taken from the
fire), stone, gold-leaf, dried grass, cork, blotting-paper,
cotton-wool, and hair rolled up into little balls, were
used, and these substances, though they were some-
times well embraced, often caused no movement what-
ever in the outer tentacles, or an extremely slight and
slow movement. Yet these same leaves were proved to
be in an active condition, as they were excited to move
by substances yielding soluble nitrogenous matter,
such as bits of raw or roast meat, the yolk or white of
boiled eggs, fragments of insects of all orders, spiders,
&c. I will give only two instances. Minute flies were
placed on the discs of several leaves, and on others
balls of paper, bits of moss and quill of about the same
size as the flies, and the latter were well embraced
in a few hours; whereas after 25 hrs. only a very
few tentacles were inflected over the other objects.
The bits of paper, moss, and quill were then removed
from these leaves, and bits of raw meat placed on them ;
and now all the tentacles were soon energetically
inflected. x
Again, particles of coal-cinder (weighing rather more
than the flies used in the last experiment) were placed
on the centres of three leaves: after an interval of
19 hrs. one of the particles was tolerably well embraced;
Cap. I, INFLECTION INDIRECTLY CAUSED. 23
a second by a very few tentacles; and a third by none.
I then removed the particles from the two latter leaves,
and put on them recently killed flies. These were
fairly well embraced in 73 hrs. and thoroughly after
203 hrs.; the tentacles remaining inflected for many
subsequent days. On the other hand, the one leaf
which had in the course of 19 hrs. embraced the bit of
cinder moderately well, and to which no fly was given,
after an additional 33 hrs. (i.e. in 52 hrs. from the
time when the cinder was put on) was completely
re-expanded and ready to act again.
From these and numerous other experiments not
worth giving, it is certain that inorganic: substances,
or such organic substances as are not attacked by the
secretion, act much less quickly and efficiently than
organic substances yielding soluble matter which is
absorbed. Moreover, I have met with very few excep-
tions to the rule, and these exceptions apparently
depended on the leaf having been too recently in
action, that the tentacles remain clasped for a much
longer time over organic bodies of the nature just
specified than over those which are not acted on by
the secretion, or over inorganic objects.*
* Owing to the extraordinary
belief held by M. Ziegler (‘Comp-
tes rendus” May 1872, p. 122),
that albuminous substances, if
held for a moment between the
fingers, acquire the property of
making the tentacles of Drosera
contract, whereas, if not thus held,
they have no such power, I tried
some experiments with great care,
but the results did not confirm
this belief. Red-hot cinders were
taken out of the fire, and bits
of glass, cotton-thread, blotting
paper and thin slices of cork
were immersed in boiling water;
and particles were then placed
(every instrument with which
they were touched having been
previously immersed in boiling
water) on the glands of several
leaves, and they acted in exactly
the same manner as other par-
ticles, which had been purposely
handled for some time. Bits of
a boiled egg, cut with a knife
which had been washed in boiling
water, also acted like any other
animal substance. I breathed on
some leaves for above a minute,
and repeated the act two or three
times, with my mouth close tc
24 DROSERA ROTUNDIFOLIA. Cuar. IL
The Inflection of the Exterior Tentacles as directly caused
by Objects left in Contact with their Glands.
I made a vast number of trials by placing, by means
of a fine needle moistened with distilled water, and
with the aid of a lens, particles of various substances
on the viscid secretion surrounding the glands of the
outer tentacles. I experimented on both the oval and
long-headed glands. When a particle is thus placed
on a single gland, the movement of the tentacle is
particularly well seen in contrast with the stationary
condition of the surrounding tentacles. (See previous
fig. 6.) In four cases small particles of raw meat
caused the tentacles to be greatly inflected in between
5 and 6 m. Another tentacle similarly treated,
and observed with special care, distinctly, though
slightly, changed its position in 10 s. (seconds); and
this is the quickest movement seen by me. In 2m.
30s. it had moved through an angle of about 45°.
The movement as seen through a lens resembled that
of the hand of a large clock. In 5m. it had moved
through 90°, and when I looked again after 10 m,
the particle had reached the centre of the leaf; so
that the whole movement was completed in less
them, but this produced no effect. cause inflection. M. Ziegler
I may here add, as showing that
the leaves are not acted on by the
odour of nitrogenous substances,
that pieces of raw meat stuck on
needles were fixed as close as
possible, without actual contact,
to several leaves, but produced
no effect whatever. On the other
hand, as we shall hereafter see,
the vapours of certain volatile
substances and fluias, such as of
carbonate of ammonia, chloro-
form, certain essential oil2, &c.,
makes still more extraordinary
statements with respect to the
power of animal substances, which
have been left close to, but: not in
contact with, sulphate of quinine.
The action of salts of quinine will
be described in a future chapter.
Since the appearance of the paper
above referred to, M. Ziegler has
published a book on the same
subject, entitled, ‘Atonicité of
Zoicité,” 1874.
Snap, I. INFLECTION INDIRECTLY CAUSED 25
than 17 m. 30 s. In the course of some hours this
minute bit of meat, from having been brought into —
contact with some of the glands of the central disc,
acted centrifugally on the outer tentacles, which all be-
came closely inflected. Fragments of flies were placed
on the glands of four of the outer tentacles, ex-
tended in the same plane with that of the blade, and
.three of these fragments were carried in 35 m. through
an angle of 180° to the centre. The fragment on
the fourth tentacle was very minute, and it was
not carried to the centre until 3 hrs. had elapsed. In
three other cases minute flies or portions of larger
ones were carried to the centre in 1 hr. 30s. In
these seven cases, the fragments or small flies, which
had been carried by a single tentacle to the central
glands, were well embraced by the other tentacles
after an interval of from 4 to 10 hrs.
I also placed in the manner just described six small
balls of writing-paper (rolled up by the aid of pincers,
so that they were not touched by my fingers) on the
glands of six exterior tentacles on distinct leaves;
three of these were carried to the centre in about 1 hr.,
and the other three in rather more than 4 hrs.; but
after 24 hrs. only two of the six balls were well em-
braced by the other tentacles. It is possible that
the secretion may have dissolved a trace of glue or
animalised matter from the balls of paper. Four par-
ticles of coal-cinder were then placed on the glands
of four exterior tentacles; one of these reached
the centre in 3 hrs. 40 m.; the second in 9 hrs.; the
third within 24 hrs., but had moved only part of the
way in 9 hrs.; whilst the fourth moved only a very
short distance in 24 hrs.,and never moved any farther.
Of the above three bits of cinder which were ultimately
carried to the centre, one alone was well embraced. by
26 DROSERA ROTUNDIFOLIA. Cuar. IL
many of the other tentacles. We here see clearly that
such bodies as particles of cinder or little balls of
paper, after being carried by the tentacles to the
central glands, act very differently from fragments of
flies, in causing the movement of the surrounding
tentacles.
I made, without carefully recording the times of
movement, many similar trials with other substances,
such as splinters of white and blue glass, particles of
cork, minute bits of gold-leaf, &c.; and the propor-
tional number of cases varied much in which the
tentacles reached the centre, or moved only slightly,
or not at all. One evening, particles of glass and
cork, rather larger than those usually employed, were
placed on about a dozen glands, and next morning,
after 18 hrs., every single tentacle had carried its little
load to the centre; but the unusually large size of the
particles will account for this result. In another case
& of the particles of cinder, glass, and thread, placed
on separate glands, were carried towards, or actually
to, the centre; in another case 7, in another 4, and
in the last case only 33, were thus carried inwards, the
small proportion being here due, at least in part, to the
leaves being rather old and inactive. Occasionally a
gland, with its light load, could be seen through a
strong lens to move an extremely short distance and
then stop; this was especially apt to occur when ex-
cessively minute particles, much less than those of
which the measurements will be immediately given,
were placed on glands; so that we here have nearly
the limit of any action.
I was so much surprised at the smallness of the par-
ticles which caused the tentacles to become greatly
inflected that it seemed worth while carefully to
ascertain how minute a particle would plainly act.
Onap. IT. INFLECTION INDIRECTLY CAUSED. 27
Accordingly measured lengths of a narrow strip of
blotting paper, of fine cotton-thread, and of a woman’s
hair, were carefully weighed for me by Mr. Trenham
Reeks, in an excellent balance, in the laboratory in
Jermyn Street. Short bits of the paper, thread, and
hair were then cut off and measured by a micrometer,
so that their weights could be easily calculated. The
bits were placed on the viscid secretion surrounding the
glands of the exterior tentacles, with the precautions
already stated, and I am certain that the gland itself
was never touched; nor indeed would a single touch
have produced any effect. A bit of the blotting-paper,
weighing +4; of a grain, was placed so as to rest on
three glands together, and all three tentacles slowly
curved inwards; each gland, therefore, supposing the
weight to be distributed equally, could have been
pressed on by only ;,';5 of a grain, or ‘0464 of a milli-
gramme. Five nearly equal bits of cotton-thread were
tried, and all acted. The shortest of these was 1, of
an inch in length, and weighed ,2,, of a grain. The
tentacle in this case was considerably inflected in
1 hr. 30 m., and the bit of thread was carried to the
centre of the leaf in lhr.40m. Again, two particles
of the thinner end of a woman’s hair, one of these
being 43, of an inch in length, and weighing ,!-; of
a grain, the other +43, of an inch in length, and weigh-
ing of course a little more, were placed on two glands on
opposite sides of the same leaf, and these two tentacles
were inflected halfway towards the centre in 1 hr. 10m. ;
all the many other tentacles round the same leaf re-
maining motionless. The appearance of this one leaf
showed in an unequivocal manner that these minute
particles sufficed to cause the tentacles to bend. Allto-
gether, ten such particles of hair were placed on ten
glands on several leaves, and seven of them caused
28 DROSERA ROTUNDIFOLIA. Cuap. IT,
the tentacles to move in a conspicuous manner. The
smallest particle which was tried, and which acted
plainly, was only +,%5 of an inch (‘203 millimetre) in
length, and weighed the ;73,, of a grain, or 000822
milligramme. In these several cases, not only was the
inflection of the tentacles conspicuous, but the purple
fluid within their cells became aggregated into little
masses of protoplasm, in the manner to be described in
the next chapter; and the aggregation was so plain
that I could, by this clue alone, have readily picked
out under the microscope all the tentacles which had
carried their light loads towards the centre, from the
hundreds of other tentacles on the same leaves which
had not thus acted.
My surprise was greatly excited, not only by the
minuteness of the particles which caused movement,
but how they could possibly act on the glands; for it
must be remembered that they were laid with the
greatest care on the convex surface of the secretion.
At first I thought—but, as I now know, erroneously—
that particles of such low specific gravity as those of
cork, thread, and paper, would never come into contact
with the surfaces of the glands. The particles cannot
act simply by their weight being added to that of the
secretion, for small drops of water, many times heavier
than the particles, were repeatedly added, and never
produced any effect. Nor does the disturbance of the
secretion produce any effect, for long threads were
drawn out by a needle, and affixed to some adjoining
object, and thus left for hours; but the tentacles
remained motionless.
I also carefully removed the secretion from four
glands with a sharply pointed piece of blotting-paper,
so that they were exposed for a time naked to the air,
but this caused no movement; yet these glands were
aap, I INFLECTION INDIRECTLY CAUSED. 29
in an efficient state, for after 24 hrs. had elapsed, they
were tried with bits of meat, and all became quickly
inflected. It then occurred to me that particles float-
ing on the secretion would cast shadows on the glands,
which might be sensitive to the interception of the
light. Although this seemed highly improbable, as
“minute and thin splinters of colourless glass acted
powerfully, nevertheless, after it was dark, I put on,
by the aid of a single tallow candle, as quickly as
possible, particles of cork and glass on the glands of a
dozen tentacles, as well as some of meat on other
glands, and covered them up so that not a ray of light
could enter ; but by the next morning, after an interval
of 13 hrs., all the particles were carried to the centres
of the leaves.
These negative results led me to try many more
experiments, by placing particles on the surface of the
drops of secretion, observing, as carefully as I could,
whether they penetrated it and touched the surface of
the glands. The secretion, from its weight, generally
forms a thicker layer on the under than on the upper
sides of the glauds, whatever may be the position of
the tentacles. Minute bits of dry cork, thread, blotting
paper, and coal cinders were’ tried, such as those pre-
viously employed; and I now observed that they
absorbed much more of the secretion, in the course of
a few minutes, than I should have thought possible ; and
as they had been laid on the upper surface of the secre-
tion, where it is thinnest, they were often drawn down,
after a time, into contact with at least some one point
of the gland. With respect to the minute splinters
of glass and particles of hair, I observed that the
secretion slowly spread itself a little over their sur-
faces, by which means they were likewise drawn down-
wards or sideways, and thus one end, or some minute
.
30 DROSERA ROTUNDIFOLIA. Crap. IL
prominence, often came to touch, sooner or later, the
gland.
In the foregoing and following cases, it is probable
that the vibrations, to which the furniture in every
room is continually liable, aids in bringing the par-
ticles into contact with the glands. But as it was
sometimes difficult, owing to the refraction of the secre-
tion, to feel sure whether the particles were in contact,
I tried the following experiment. Unusually minute
particles of glass, hair, and cork, were gently placed or
the drops round several glands, and very few of the
tentacles moved. Those which were not affected were
left for about half an hour, and the particles were
then disturbed or tilted up several times with a fine
needle under the microscope, the glands not being
touched. And now in +h. course of a few minutes
almost all the hitherto motionless tentacles began to
move; and this, no doubt, was caused by one end or
some prominence of the particles having come into
contact with the surface of the glands. But as the
particles were unusually minute, the movement was
small.
Lastly, some dark blue glass pounded into fine
splinters was used, in order that the points of the par-
ticles might be better distinguished when immersed in
the secretion ; and thirteen such particles were placed
in contact with the depending and therefore thicker
part of the drops round so many glands. Five of the
tentacles began moving after an interval of a few
minutes, and in these cases I clearly saw that the par-
ticles touched the lower surface of the gland. A sixth
tentacle moved after 1 hr. 45 m., and the particle
was now in contact with the gland, which was not the
case at first. So it was with the seventh tentacle, but
its movement did not begin until 3 hrs. 45 m. had
unap. IL INFLECTION INDIRECTLY CAUSED. 31
elapsed. The remaining six tentacles never moved
as long as they were observed; and the particles
apparently never came into contact with the surfaces
of the glands.
From these experiments we learn that particles not
containing soluble matter, when placed on glands, often
cause the tentacles to begin bending in the course of
from one to five minutes; and that in such cases the
particles have been from the first in contact with the
surfaces of the glands. When the tentacles do not
begin moving for a much longer time, namely, from
half an hour to three or four hours, the particles
have been slowly brought into contact with the
glands, either by the secretion being absorbed by the
particles or by its gradual spreading over them, to-
gether with its consequent quicker evaporation.
When the tentacles do not move at all, the particles
have never come into contact with the glands, or in
some cases the tentacles may not have been in an
active condition. In order to excite movement, it is
indispensable that the particles should actually rest on
the glands; for a touch once, twice, or even thrice
repeated by any hard body is not sufficient to excite
movement.
Another experiment, showing that extremely mi-
nute particles act on the glands when immersed in
water, may here be given. A grain of sulphate of
quinine was added to an ounce of water, which was
not afterwards filtered; and on placing three leaves in
ninety minims of this fluid, I was much surprised to find
that all three leaves were greatly inflected in 15 m.;
for I knew from previous trials that the solution does
not act so quickly as this. It immediately occurred
to me that the particles of the undissolved salt, which
were so light as to float about, might have come
BY DROSERA ROTUNDIFOLIA. Guar. IL
into contact with the glands, and caused this rapid
movement. Accordingly I added to some distilled
water a pinch of a quite innocent substance, namely,
precipitated carbonate of lime, which consists of an
impalpable powder ; I shook the mixture, and thus got
a fluid like thm milk. Two leaves were immersed in
it, and in 6 m. almost every tentacle was much
inflected. I placed one of these leaves under the
microscope, and saw innumerable atoms of lime ad-
hering to the external surface of the secretion. Some,
however, had penetrated it, and were lying on the sur-
faces of the glands; and no doubt it was these particles
which caused the tentacles to bend. When a leaf is im-
mersed in water, the secretion instantly swells much;
and I presume that it is ruptured here and there, so
that little eddies of water rush in. If so, we can under-
stand how the atoms of chalk, which rested on the
surfaces of the glands, had penetrated the secretion.
Anyone who has rubbed precipitated chalk between
his fingers will have perceived how excessively fine
the powder is. No doubt there must be a limit, beyond
which a particle would be too small to act on a gland;-
but what this limit is, I know not. I have often seen
fibres and dust, which had fallen from the air, on the
glands of plants kept in my room, and these never
induced any movement; but then such particles lay
on the surface of the secretion and never reached the
gland itself.
Finally, it is an extraordinary fact that a little
bit of soft thread, =; of an inch in tength and weigh-
ing s7';; of a grain, or of a human hair, =8,, of an
inch in length and weighing only ,5!5, of a grain
(000822 milligramme), or particles of precipitated
chalk, after resting for a short time on a gland,
should induce some change in its cells, exciting them
Caar. IL INFLECTION DIRECTLY CAUSED. 33
0 transmit a motor impulse throughout the whole
length of the pedicel, consisting of about twenty cells,
to near its base, causing this part to bend, and the
tentacle to sweep through an angle of above 180°.
That the contents of the cells of the glands, and after-
wards those of the pedicels, are affected in a plainly
visible manner by the pressure of minute particles, we
shall have abundant evidence when we treat of the
aggregation of protoplasm. But the case is much more
remarkable than as yet stated ; for the particles are sup-
ported by the viscid and dense secretion ; nevertheless,
even smaller ones than those of which the measure-
ments have been given, when brought by an insensibly
slow movement, through the means above specified, into .
contact with the surface of a gland, act on it, and the
tentacle bends. The pressure exerted by the particle
of hair, weighing only -;!=; of a grain and supported
by a dense fluid, must have been inconceivably slight.
We may conjecture that it could hardly have equalled
the millionth of a grain; and we shall hereafter see
that far less than the millionth of a grain of phos-
phate of ammonia in solution, when absorbed by a
gland, acts on it and induces movement. A bit of
hair, =}, of an inch in length, and therefore much
larger than those used in the above experiments, was
not perceived when placed on my tongue; and it is
extremely doubtful whether any nerve in the human
body, even if in an inflamed condition, would be in
any way affected by such a particle supported in a
dense fluid, and slowly brought into contact with the
nerve. Yet the cells of the glands of Drosera are thus
excited to transmit a motor impulse to a distant point,
inducing movement. It appears to me that hardly
any more remarkable fact than this has been observed
in the vegetable kingdom.
34 DROSERA ROTUNDIFULIA. Cuar, IT
The Inflection of the Exterior Tentacles, when their Glands
are excited by Repeated Touches.
We have already seen that, if the central glands
are excited by being gently brushed, they trans-
mit a motor impulse to the exterior tentacles,
causing them to bend; and we have now to con-
sider the effects which follow from the glands of
the exterior tentacles being themselves touched. On
several occasions, a large number of glands were
touched only once with a needle or fine brush,
hard enough to bend the whole flexible tentacle;
and though this must have caused a thousand-
fold greater pressure than the weight of the above
described particles, not a tentacle moved. On
another occasion forty-five glands on eleven leaves
were touched once, twice, or even thrice, with a
needle or stiff bristle. This was done as quickly as
possible, but with force sufficient to bend the ten-
tacles; yet only six of them became inflected,—three
plainly, and three in a slight degree. In order to
ascertain whether these tentacles which were not
affected were in an efficient state, bits of meat were
placed on ten of them, and they all soon became greatly
incurved. On the other hand, when a large number of
glands were struck four, five, or six times with the
same force as before, a needle or sharp splinter of
glass being used, a much larger proportion of tentacles
became inflected; but the result was so uncertain
as to seem capricious. For instance, I struck in
the above manner three glands, which happened to
be extremely sensitive, and all three were inflected
almost as quickly as if bits of meat had been placed
on them. On another occasion I gave a single for
Cuar. II, THE EFFECTS OF REPEATED TOUCHES. 35
cible touch to a considerable number of glands, and
not one moved ; but these same glands, after an inter-
val of some hours, being touched four or five times
with a needle, several of the tentacles soon became
inflected.
The fact of a single touch or even of two or three
touches not causing inflection must be of some service
to the plant; as during stormy weather, the glands
cannot fail to be occasionally touched by the tall
blades of grass, or by other plants growing near; and
it would be a great evil if the tentacles were thus
brought into action, for the act of re-expansion takes
a considerable time, and until the tentacles are re-
expanded they cannot catch prey. On the other
hand, extreme sensitiveness to slight pressure is of the
highest service to the plant; for, as we have seen, if
the delicate feet of a minute struggling insect press
ever so lightly on the surfaces of two or three glands,
the tentacles bearing these glands soon curl inwards
and carry the insect with them to the centre, causing,
after a time, all the circumferential tentacles to
embrace it. Nevertheless, the movements of the
plant are not perfectly adapted to its requirements;
for if a bit of dry moss, peat, or other rubbish, is
blown on to the disc, as often happens, the tentacles
clasp it in a useless manner. They soon, however,
discover their mistake and release such innutritious
objects.
It is also a remarkable fact, that drops of water fall-
ing from a height, whether under the form of natural
or artificial rain, do not cause the tentacles to move;
yet the drops must strike the glands with considerable
force, more especially after the secretion has been all
washed away by heavy rain; and this often occurs,
36 DROSERA ROTUNDIFOLIA. Cuap. IL.
though the secretion is so viscid that it can be re-
moved with difficulty merely by waving the leaves in
water. If the falling drops of water are small, they
adhere to the secretion, the weight of which must be
increased in a much greater degree, as before re-
marked, than by the addition of minute particles of
solid matter ; yet the drops never cause the tentacles
to become inflected. It would obviously have been a
great evil to the plant (as in the case of occasional
touches) if the tentacles were excited to bend by
every shower of rain; but this evil has been avoided
by the glands either having become through habit
insensible to the blows and prolonged pressure of
drops of water, or to their having been originally
rendered sensitive solely to the contact of solid bodies.
We shall hereafter see that the filaments on the leaves
of Dionza are likewise insensible to the impact of
fluids, though exquisitely sensitive to momentary
touches from any solid body.
When the pedicel of a tentacle is cut off by a
sharp pair of scissors quite close beneath the gland,
the tentacle generally becomes inflected. I tried this
experiment repeatedly, as I was much surprised at the
fact, for all other parts of the pedicels are insensible to
any stimulus. These headless tentacles after a time
re-expand; but I shall return to this subject. On the
other hand, I .occasionally succeeded in crushing a
gland between a pair of pincers, but this caused no
inflection. In this latter case the tentacles seem
paralysed, as likewise follows from the action of too
strong solutions of certain salts, and by too great
heat, whilst weaker solutions of the same salts and a
more gentle heat cause movement. We shall also see
in future chapters that various other fluids, some
Ounar. IL.
DROPS OF WATER. 37
vapours, and oxygen (after the plant has been for some
time excluded from its action), all induce inflection,
and this likewise results from an induced galvanic
current.*
* My son Francis, guided by
the observations of Dr. Burdon
Sanderson on Dionza, finds that
if two needles are inserted into
the blade of a leaf of Drosera, the
tentacles do not move; but that if
similar needles in connection with
the secondary coil of a Du Bois
inductive apparatus are inserted,
the tentacles curve inwards rn the
course of a few minutes. My son
hopes soon to publish an account
of his observations.
38 DROSERA ROTUNDIFOLIA. Cuap. IIL
CHAPTER ITI.
ASGREGATION OF THE PRoTorLasM WITHIN THE CELLS OF THE
TENTACLES.
Nutuce of the contents of the cells before aggregation — Various
causes which excite aggregation—The process commences within
the glands and travels down the tentacles— Description of the
aggregated masses and of their spontaneous movements—Currents
of protoplasm along the walls of the cells—Action of carbonate
of ammonia—The granules in the protoplasm which flows along
the walls coalesce with the central masses—Minuteness of the
quantity of carbonate of ammonia causing aggregation — Action
of other salts of ammonia — Of other substances, organic fluids,
&c.—Of water—Of heat—Redissolution of the aggregated masses
—Proximate causes of the aggregation of the protoplasm—
Summary and concluding remarks—Supplementary observations
on aggregation in the roots of plants.
. I wii here interrupt my account of the movements
of the leaves, and describe the phenomenon of aggre-
gation, to which subject I have already alluded. If
the tentacles of a young, yet fully matured leaf, that
has never been excited or become inflected, be ex-
amined, the cells forming the pedicels are seen to be
filled with homogeneous, purple fluid. The walls are
lined by a layer of colourless, circulating protoplasm ;
but this can be seen with much greater distinctness
after the process of aggregation has been partly
effected than before. The purple fluid which exudes
from a crushed tentacle is somewhat coherent, and
does not mingle with the surrounding water; it con-
tains much flocculent or granular matter. But this
matter may have been generated by the cells having
been crushed; some degree of aggregation having
been thus almost instantly caused.
Ouap. ITI. THE PROCESS OF AGGREGATION. 39
If a tentacle is examined some hours after the gland
has been excited by repeated touches, or by an in-
organic or organic particle placed on it, or by the
absorption of certain fluids, it presents a wholly
changed appearance. The cells, instead of being filled
with homogeneous purple fluid, now contain variously
shaped masses of purple matter, suspended in a colour-
less or almost colourless fluid. The change is so
conspicuous that it is visible through a weak lens,
and even sometimes by the naked eye; the tentacles
now have a mottled appearance, so that one thus
affected can be picked out with ease from all the
others. The same result follows if the glands on the
disc are irritated in any manner, so that the exterior
tentacles become inflected; for their contents will
then be found in an aggregated condition, although
their glands- have not as yet touched any object. But
aggregation may occur independently of inflection, .
as we shall presently see. By whatever cause the
process may have been excited, it commences within
the glands, and‘then travels down the tentacles. It
can be observed much more distinctly in the upper
cells of the pedicels than within the glands, as these
are somewhat opaque. Shortly after the tentacles have
re-expanded, the little masses of protoplasm are all
redissolved, and the purple fluid within the cells be-
comes as homogeneous and transparent as it was at
first. The process of redissolution travels upwards
from the bases of the tentacles to the glands, and
therefore in a reversed direction to that of aggre-
gation. Tentacles in an aggregated condition were
shown to Prof. Huxley, Dr. Hooker, and Dr. Burdon
Sanderson, who observed the changes under the
microscope, and were much struck with the whole
phenomenon.
4
40 DROSERA ROTUNDIFOLIA. Cuap. U1.
The little masses of aggregated matter are of the
most diversified shapes, often spherical or oval, some-
times much elongated, or quite irregular with thread-
or necklace-like or club-formed projections. They
consist of thick, apparently viscid matter, which in
the exterior tentacles is of a purplish, and in the
short discal tentacles of a greenish, colour. These
little masses incessantly change their forms and posi-
tions, being never at rest. A single mass will often
separate into two, which afterwards reunite. Their
movements are rather slow, and resemble those of
. Amoebe or of the white corpuscles of the blood. We
Q@\2
Fic. 7.
(Drosera rotundifolia.)
Diagram of the same cell of a tentacle, showing the various forms successively
assumed by the aggregated masses of protoplasm.
may, therefore, conclude that they consist of proto-
plasm. If their shapes are sketched at intervals
of a few minutes, they are invariably seen to have
undergone great changes of form; and the same
cell has been observed for several hours. Eight rude,
though accurate sketches of the same cell, made at
intervals of between 2 m. or 3 m., are here given
(fig. 7), and illustrate some of the simpler and com-
monest changes. The cell A, when first sketched,
included two oval masses of purple protoplasm touch-
ing each other. These became separate, as shown
at B, and then reunited, as at C. After the next
interval a very common appearance was presented—-
Cuap, III. THE PROCESS OF AGGREGATION. 41
D, namely, the formation of an extremely minute
sphere at one end of an elongated mass. This rapidly
increased in size, as shown in E, and was then re-
absorbed, as at F, by which time another sphere had
been formed at the opposite end.
The cell above figured was from a tentacle of a dark
red leaf, which had caught a‘small moth, and was
examined under water. As I at first thought that the
movements of the masses might be due to the absorp-
tion of water, I placed a fly on a leaf, and when after
18 hrs. all the tentacles were well inflected, these were
examined without being immersed in water. The cell
Fie. 8.
(Drosera rotundifolia.)
Diagram of the same cell of a tentacle, showing the various forms successively
assumed by the aggregated masses of protoplasm.
here represented (fig. 8) was from this leaf, being
sketched eight times in the course of 15 m. These
sketches exhibit some of the more remarkable changes
which the protoplasm undergoes. At first, there was
at the base of the cell 1, a little mass on a short
footstalk, and a larger mass near the upper end, and
these seemed quite separate. Nevertheless, they may
have been connected by a fine and invisible thread of
protoplasm, for on two other occasions, whilst one
mass was rapidly increasing, and another in the same
cell rapidly decreasing, I was able by varying the
light and using a high power, to detect a connecting
thread of extreme tenuity, which evidently served as
42 DROSERA ROTUNDIFOLIA. Cuar. IIL.
the channel of communication between the two. On
the other hand, such connecting threads are some-
times seen to break, and their extremities then
quickly become club-headed. The other sketches in
fic. 8 show the forms successively assumed.
Shortly after the purple fluid within the cells has
become aggregated, the little masses float about in a
colourless or almost colourless fluid; and the layer
of white granular protoplasm which flows along the
walls can now be seen much more distinctly. The
stream flows at an irregular rate, up one wall and
down the opposite one, generally at a slower rate
across the narrow ends of the elongated cells, and so
round and round. But the current sometimes ceases.
The movement is often in waves, and their crests
sometimes stretch almost across the whole width of
the cell, and then sink down again. Small spheres of
protoplasm, apparently quite free, are often driven by
the current round the cells; and filaments attached
to the central masses are swayed to and fro, as if
struggling to escape. Altogether, one of these cells
with the ever changing central masses, and with the
layer of protoplasm flowing round the walls, presents
a wonderful scene of vital activity.
Many observations were made on the contents of the cells
whilst undergoing the process of aggregation, but I shall detail
only a few cases under different heads. A small portion of a
leaf was cut off, placed under a high power, and the glands
very gently pressed under a compressor. In 15 m. I distinctly
saw extremely minute spheres of protoplasm aggregating them-
selves in the purple fluid; these rapidly increased in size, both
within the cells of the glands and of the upper ends of the
pedicels. Particles of glass, cork, and cinders were also placed
on the glands of many tentacles; in 1 hr. several of them were
inflected, but after 1 hr. 35 m. there was no aggregation. Other
tentacles with these particles were examined after 8 hrs., and
Car. II, THE PROCESS OF AGGREGATION. 43
now all their cells had undergone aggregation; so had the cells
of the exterior tentacles which had become inflected through
the irritation transmitted from the glands of the disc, on which
the transported particles rested. This was likewise the case with
the short tentacles round the margins of the disc, which had not
as yet become inflected. This latter fact shows that the pro-
cess of aggregation is independent of the inflection of the ten-
tacles, of which indeed we have other and abundant evidence.
Again, the exterior tentacles on three leaves were carefully
examined, and found to contain only homogeneous purple fluid;
little bits of thread were then placed on the glands of three of
them, and after 22 hrs. the purple fluid in their cells almost
down to their bases was aggregated into innumerable, spherical,
elongated, or filamentous masses of protoplasm. The bits of
thread had been carried some time previously to the central
disc, and this had caused all the other tentacles to become
somewhat inflected; and their cells had likewise undergone
aggregation, which however, it should be observed, had not
as yet extended down to their bases, but was confined to the
cells close beneath the glands.
Not only do repeated touches on the glands* and the contact
of minute particles cause aggregation, but if glands, without
being themselves injured, are cut off from the summits of the
pedicels, this induces a moderate amount of aggregation in the
headless tentacles, after they have become inflected. On the
other hand, if glands are suddenly crushed between pincers, as
was tried in six cases, the tentacles seem paralysed by so great
a shock, for they neither become inflected nor exhibit any signs
of aggregation.
Carbonate of Ammonia.—Of all the causes inducing aggrega-
tion, that which, as far as I have seen, acts the quickest, and is
the most powerful, is a solution of carbonate of ammonia. What-
ever its strength may be, the glands are always affected first,
and soon become quite opaque,so as to appear black. For
instance, I placed a leaf in a few drops of a strong solution,
namely, of one part to 146 of water (or 3 grs. to 1 oz.), and
observed it under a high power. All the glands began to
* Judging from an account of
M. Heckel’s observations, which
I have only just seen quoted in
the ‘ Gardener’s Chronicle’ (Oct.
19, 1874), he appears to have
observed a similar phenomenon in
the stamens of Berberis, after
they have been excited by a
touch and have moved; for he
says, ‘the contents of each indi-
vidual cell are collected together
in the centre of the cavity.”
14 DROSERA ROTUNDIFOLIA. Cuar. IIT.
darken in 10 8. (seconds); and in 13 s. were conspicuously
darker. In 1 m. extremely small spherical masses of protoplasm
could be seen arising in the cells of the pedicels close beneath
the glands, as well as in the cushions on which the long-
headed marginal glands rest. In several cases the process
travelled down the pedicels for a length twice or thrice as great
as that of the glands, in about 10 m. It was interesting to
observe the process momentarily arrested at each transverse
partition between two cells, and then to see the transparent
contents of the cell next below almost flashing into a cloudy
mass. In the lower part of the pedicels, the action proceeded
slower, so that it took about 20 m. before the cells halfway
down the long marginal and submarginal tentacles became
aggregated.
We may infer that the carbonate of ammonia is absorbed by
the glands, not only from its action being so rapid, but from its
effect being somewhat different from that of other salts. As the
glands, when excited, secrete an acid belonging to the acetic
series, the carbonate is probably at once converted into a
salt of this series; and we shall presently see that the acetate
of ammonia causes aggregation almost or quite as energetically
as does the carbonate. If a few drops of a solution of one part of
the carbonate to 437 of water (or 1 gr. to 1 oz.) be added to the
purple fluid which exudes from crushed tentacles, or to paper
stained by being rubbed with them, the fluid and the paper are
changed into a pale dirty green. Nevertheless, some purple
colour could still be detected after 1 hr. 30 m. within the glands
of a leaf left in a solution of twice the above strength (viz.
2 ers. to 1 oz.); and after 24 hrs. the cells of the pedicels close
beneath the glands still contained spheres of protoplasm of a
fine purple tint. These facts show that the ammonia had not
entered as a carbonate, for otherwise the colour would have
been discharged. I have, however, sometimes observed, espe-
cially 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,
Cuar. IIL, THE PROCESS OF AGGREGATION, 45
independently of the absorption of any matter. So it may pos-
sibly be in the case of the carbonate of ammonia. As, how-
ever, 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 tue long-headed marginal glands; the process, how-
ever, in this case took place with unusual slowness. In 25m.
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 4875 of
water (1 gr. to 10 oz.), and thehighly 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, but after 10 m. minute irregular granules of
protoplasm could be detected, which soon increased into
irregular masses and globules of a greenish or very pale purple
tint; but these never formed perfect spheres, though incessantly
changing their shapes and positions.
With moderately red leaves the first effect of a solution of the
carbonate generally is the formation of two or three, or of
several, extremely minute purple spheres which rapidly increase
in size. To give an idea of the rate at which such spheres
increase in size, 1 may mention that a rather pale purple leaf
placed under a slip of glass was given a drop of a solution of
one part to 292 of water, and in 13 m. a few minute spheres of
protoplasm were formed; one of these, after 2 hrs. 30 m., was
about two-thirds of the diameter of the cell. After 4 hrs, 25 m.
46 DROSERA ROTUNDIFOLIA. Cuar. IIL.
it nearly equalled the cell in diameter; and a second sphérs
about half as large as the first, together with a few other
minute ones, were formed. After 6 hrs. the fluid in which these
spheres floated was almost colourless. After 8 hrs. 35 m. (always
reckoning from the time when the solution was first added) four
new minute spheres had appeared. Next morning, after 22 hrs.,
there were, besides the two large spheres, seven smaller ones,
floating in absolutely colourless fluid, in which some flocculent
greenish matter was suspended.
At the commencement of the process of aggregation, more
especially in dark red leaves, the contents of the cells often
present a different appearance, as if the layer of protoplasm
(primordial utricle) which lines the cells had separated itself
and shrunk from the walls; an irregularly shaped purple bag
being thus formed. Other fluids, besides a solution of the car-
bonate, for instance an infusion of raw meat, produce this same
effect. But the appearance of the primordial utricle shrinking
from the walls is certainly false ;* for before giving the solution,
I saw on several occasions that the walls were lined with colour-
less flowing protoplasm, and after the bag-like masses were
formed, the protoplasm was still flowing along the walls in a
conspicuous manner, even more so than before. It appeared
indeed as if the stream of protoplasm was strengthened by the
action of the carbgnate, but it was impossible to ascertain
whether this was really the case. The bag-like masses, when
once formed, soon begin to glide slowly round the cells, some-
times sending out projections which separate into little spheres ;
other spheres appear in the fluid surrounding the bags, and
these travel much more quickly. That the small spheres are
separate is often shown by sometimes one and then another
travelling in advance, and sometimes they revolve round each
other. I have occasionally seen spheres of this kind proceeding
up and down the same side of a cell, instead of round it. The
bag-like masses after a time generally divide into two rounded
or oval masses, and these undergo the changes shown in figs. 7
and 8. At other times spheres appear within the bags; and
these coalesce and separate in an endless cycle of change.
After leaves have been left for several hours in a solution of
the carbonate, and complete aggregation has been effected, the
* With other plants I have caused by a solution of carbonate
often seen what appears to be a of ammonia, as likewise follows
true shrinking of the primordial from mechanical injuries.
utricle from the walls of the cells,
Cuar. III, THE PROCESS OF AGGREGATION. 47
stream of protoplasm on the walls of the cells ceases to be
visible; I observed this fact repeatedly, but will give only one
instance. A pale purple leaf was placed in a few drops of a
solution of one part to 292 of water, and in 2 hrs. some fine
purple spheres were formed in the upper cells of the pedicels,
the stream of protoplasm round their walls being still quite
distinct; but after an additional 4 hrs., during which time
many more spheres were formed, the stream was no longer
distinguishable on the most careful examination; and this no
doubt was due to the contained granules having become united
with the spheres, so that nothing was left by which the move-
ment of the limpid protoplasm could be perceived. But minute
free spheres still travelled up and down the cells, showing that
there was still a current. So it was next morning, after 22 hrs.,
by which time some new minute spheres had been formed;
these oscillated from side to side and changed their positions,
proving that the current had not ceased, though no stream of
protoplasm was visible. On another occasion, however, a
stream was seen flowing round the cell-walls of a vigorous,
dark-coloured leaf, after it had been left for 24 hrs. in a rather
stronger solution, namely, of one part of the carbonate to 218 of
water. This leaf, therefore, was not much or at all injured by
an immersion for this length of time in the above solution of
two grains to the ounce; and on being afterwards left for 24 hrs,
in water, the aggregated masses in many of the cells were re-
dissolved, in the same manner as occurs with leaves in a state of
nature when they re-expand after having caught insects.
In a leaf which had been left for 22 hrs. in a solution of one
part of the carbonate to 292 of water, some spheres of proto-
plasm (formed by the self-division of a bag-like mass) were
gently pressed beneath a covering glass, and then examined
under a high power. They were now distinctly divided by
well-defined radiating fissures, or were broken up into separate
fragments with sharp edges; and they were solid to the centre.
In the larger broken spheres the central part was more opaque,
darker-coloured, and less brittle than the exterior; the latter
alone being in some cases penetrated by the fissures. In many
of the spheres the line of separation between the outer and
inner parts was tolerably well defined. The outer parts were of
exactly the same very pale purple tint, as that of the last
formed smaller spheres; and these latter did not include any
darker central core.
From these several facts we may conclude that when vigorous
dark-coloured leaves are subjected to the action of carbonate of
18 DROSERA ROTUNDIFOLIA. Cuar. IT}
ammonia, the fluid within the cells of the tentacles often aggre-
gates exteriorly into coherent viscid matter, forming a kind of
bag. Small spheres sometimes appear within this bag, and the
whole generally soon divides into two or more spheres, which
repeatedly coalesce and redivide. After a longer or shorter
time the granules in the colourless layer of protoplasm, which
flows round the walls, are drawn to and unite with the larger
spheres, or form small independent spheres ; these latter being of
a much paler colour, and more brittle than the first aggregated
masses. After the granules of protoplasm have been thus
attracted, the layer of flowing protoplasm can no longer be dis-
tinguished, though a current of limpid fluid still flows round
the walls.
If a leaf is immersed in a very strong, almost concentrated,
solution of carbonate of ammonia, the glands are instantly
blackened, and they secrete copiously; but no movement of the
tentacles ensues. ‘Two leaves thus treated became after 1 hr.
flaccid, and seemed killed; all the cells in their tentacles con-
tained spheres of protoplasm, but these were small and dis-
coloured. Two other leaves were placed in a solution not quite
so strong, and there was well-marked aggregation in 30 m.
After 24 hrs. the spherical or more commonly oblong masses of
protoplasm became opaque and granular, instead of being as
usual translucent; and in the lower cells there were only
innumerable minute spherical granules. It was evident that
the strength of the solution had interfered with the completion
of the process, as we shall see likewise follows from too great
heat.
All the foregoing observations relate to the exterior tentacles,
which are of a purple colour; but the green pedicels of the
short central tentacles are acted on by the carbonate, and by
an infusion of raw meat, in exactly the same manner, with the
sole difference that the aggregated masses are of a greenish
colour; so that the process is in no way dependent on the
colour of the fluid within the cells.
Finally, the most remarkable fact with respect to this salt is
the extraordinary small amount which suffices to cause aggre-
gation. Full details will be given in the seventh chapter, and
here it will be enough to say that with a sensitive leaf the
absorption by a gland of zs2ig5 Of a grain (*000482 mgr.) is
enough to cause in the course of one hour well-marked aggrega-
tion in the cells immediately beneath the gland.
The Kffects .f certain other Salts and Fluids——Two leaves were
placed in a solution of one part of acetate of ammonia to about
Cuap. ILL. THE PRUCESS OF AGGREGATION. 49
146 of water, and were acted on quite as energetically, but
perhaps not quite so quickly, as by the carbonate. After 10 m.
the glands were black, and in the cells beneath them there were
traces of aggregation, which after 15 m. was well marked, extend-
ing down the tentacles for a length equal to that of the glands.
After 2 hrs. the contents of almost all the cells in all the ten-
tacles were broken up into masses of protoplasm. A leaf was
immersed in a solution-of one part of oxalate of ammonia to
146 of water; and after 24 m. some, but not a conspicuous,
change could be seen within the cells beneath the glands.
After 47m. plenty of spherical masses of protoplasm were
formed, and these extended down the tentacles for about the
length of the glands. This salt, therefore, does not act so
quickly as the carbonate. With respect to the citrate of am-
monia, a leaf was placed in a little ‘solution of the above
strength, and there was not even a trace of aggregation in the
cells beneath the glands, until 56 m. had elapsed; but it was
well marked after 2 hrs. 20 m. On another occasion a leaf
was placed in a stronger solution, of one part of the citrate to
109 of water (4 grs. to 1 oz.), and at the same time another
leaf in a solution of the carbonate of the same strength. The
glands of the latter were blackened in less than 2 m., and
after 1 hr. 45 m. the aggregated masses, which were spherical
and very dark-coloured, extended down all the tentacles, for.
between half and two-thirds of their lengths; whereas in the
leaf immersed in the citrate the glands, after 30 m., were of
a dark red, and the aggregated masses in the cells beneath them
pink and elongated. After 1 hr. 45 m. these masses extended
down for only about one-fifth or one-fourth of the length of the
tentacles.
Two leaves were placed, each in ten minims of a solution of
one part of nitrate of ammonia to 5250 of water (1 gr. to
12 0z.), so that each leaf received 5}, of a grain ("1124 mgr.).
This quantity caused all the tentacles to be inflected, but after
94 hrs. there was only a trace of aggregation. One of these
same leaves was then placed in a weak solution of the car-
bonate, and after 1 hr. 45 m. the tentacles for half their lengths
showed’ an astonishing degree of aggregation. Two other
leaves were then placed in a much stronger solution of one part
of the nitrate to 146 of water (8 grs. to 1 oz.); in one of these
there was no marked change after 3 hrs.; but in the other
there was a trace of aggregation after 52 m., and this was
plainly marked after 1 hr. 22m, but even after 2 hrs. 12 m.
there was certainly not more aggregation than would have fol-
50 DROSERA ROTUNDIFOLIA. Cuap. IIL
lowed from an immersion of from 5 m. to 10 m. in an cqually
strong solution of the carbonate. ;
Lastly, a leaf was placed in thirty minims of a solution of
one part of phosphate of ammonia to 43,750 of water (1 gr. to
100 oz.), so that it received zJoq of a grain (04079 megr.); this
soon caused the tentacles to be strongly inflected; and after
94 hrs. the contents of the cells were aggregated into oval
and irregularly globular masses, with a conspicuous current of
protoplasm flowing round the walls. But after so long an
interval aggregation would have ensued, whatever had caused
inflection.
Only a few other salts, besides those of ammonia, were tried
in relation to the process of aggregation. A leaf was placed in
a solution of one part of chloride of sodium to 218 of water, and
after 1 hr. the contents of the cells were aggregated into small,
irregularly globular, brownish masses; these after 2 hrs. were
almost disintegrated and pulpy. It was evident that the proto-
plasm had been injuriously affected; and soon afterwards some
of the cells appeared quite empty. These effects differ alto-
gether from those produced by the several salts of ammonia,
as well as by various organic fluids, and by inorganic particles
placed on the glands. A solution of the same strength of car-
bonate of soda and carbonate of potash acted in nearly the same
manner as the chloride; and here again, after 2 hrs. 30 m., the
outer cells of some of the glands had emptied themselves of
their brown pulpy contents. We shall see in the eighth
chapter that solutions of several salts of soda of half the above
strength cause inflection, but do not injure the leaves. Weak
solutions of sulphate of quinine, of nicotine, camphor, poison of
the cobra, &c., soon induce well-marked aggregation; whereas
certain other substances (for instance, a solution of curare)
have no such tendency.
Many acids, though much diluted, are poisonous; and though,
as will be shown in the eighth chapter, they cause the ten-
tacles to bend, they do not excite true aggregation. Thus leaves
were placed in a solution of one part of benzoic acid to 437 of
water; and in 15m. the purple fluid within the cells had shrunk
a little from the walls, yet when carefully examined after 1 hr.
20 m., there was no true aggregation; and after 24 hrs. the leaf
was evidently dead. Other-leaves in iodic acid, diluted to the
same degree, showed after 2 hrs. 15 m. the same shrunken
appearance of the purple fluid within the cells; and these,
after 6 hrs. 15 m., were seen under a high power to be filled
with excessively minute spheres of dull reddish protoplasm,
Cuar. IIL THE PROCESS OF AGGREUATION. 51
which by the next morning, after 24 hrs., had almost dis-
appeared, the leaf being evidently dead. Nor was there any true
aggregation in leaves immersed in propionic acid of the same
strength; but in this case the protoplasm was collected in
irregular masses towards the bases of the lower cells of the
tentacles.
A filtered infusion of raw meat induces strong aggregation,
but not very quickly. In one leaf thus immersed there was a
little aggregation after 1 hr. 20 m., and in another after 1 hr.
50 m. With other leaves a considerably longer time was re-
quired: for instance, one immersed for 5 hrs. showed no aggre-
gation, but was plainly acted on in 5 m., when placed in a few
drops of a solution of one part of carbonate of ammonia to 146
of water. Some leaves were left in the infusion for 24 hrs.,
and these became aggregated to a wonderful degree, so that
the inflected tentacles presented to the naked eye a plainly
mottled appearance. The little masses of purple protoplasm
were generally oval or beaded, and not nearly so often spherical
as in the case of leaves subjected to carbonate of ammonia.
They underwent incessant changes of form; and the current of
colourless protoplasm round the walls was conspicuously plain
after an immersion of 25 hrs. Raw meat is too powerful a
stimulant, and even small bits generally injure, and sometimes
kill, the leaves to which they are given: the aggregated masses
of protoplasm become dingy or almost colourless, and present
an unusual granular appearance, as is likewise the case with
leaves which have been immersed in a very strong solution of
carbonate of ammonia. A leat placed in milk had the contents
of its cells somewhat aggregated in 1 hr. Two other leaves,
one immersed in human saliva for 2 hrs. 80 m., and another
in unboiled white of egg for 1 hr. 30 m., were not acted on in
this manner; though they undoubtedly would have been so,
had more time been allowed. These same two leaves, on being
afterwards placed in a solution of carbonate of ammonia (8 grs.
to 1 oz.), had their cells aggregated, the one in 10 m. and the
other in 5m. :
Several leaves were left for 4 hrs. 30 m. in a solution of one
part of white sugar to 146 of water, and no aggregation ensued
on being placed in a solution of this same strength of carbonate
of ammonia, they were acted on in 5m.; as was likewise a leaf
which had been left for 1 hr. 45 m. in a moderately thick solu-
tion of gum arabic. Several other leaves were immersed for
some hours in denser solutions of sugar, gum, and starch, and
they had the contents of their cells greatly aggregated. This
62 DROSERA ROTUNDIFOLIA. Cua. ILL
effect may be attributed to exosmose; for the leaves in the
syrup became quite flaccid, and those in the gum and starch
somewhat flaccid, with their tentacles twisted about in the
most irregular manner, the longer ones like corkscrews. We
shall hereafter see that solutions of ‘these substances, when
placed on the discs of leaves, do not incite inflection. Particles
of soft sugar were added to the secretion round several glands
and were soon dissolved, causing a great increase of the secre-
tion, no doubt by exosmose; and after 24 hrs. the cells showed
a certain amount of aggregation, though the tentacles wero
not inflected. Glycerine causes in a few minutes well-pro-
nounced aggregation, commencing as usual within the glands
and then travelling down the tentacles; and this I presume
may be attributed to the strong attraction of this substance
for water. Immersion for several hours in water causes some
degree of aggregation. Twenty leaves were first carefully
examined, and re-examined after having been left immersed
in distilled water for various periods, with the following results.
It is rare to find even a trace of aggregation until 4 or 5
and generally not until several more hours have elapsed.
When however a leaf becomes quickly inflected in water, as
sometimes happens, especially during very warm weather,
aggregation may occur in little over 1 hr. In all cases
leaves left in water for more than 24 hrs. have their glands
blackened, which shows that their contents are aggregated;
and in the specimens which were carefully examined, there
was fairly well-marked aggregation in the upper cells of the
pedicels. These trials were made with cut-off leaves, and it
occurred to me that this circumstance might influence the
result, as the footstalks would not perhaps absorb water quickly
enough to supply the glands as they continued to secrete.
But this view was proved erroneous, for a plant with uninjured
roots, bearing four leaves, was submerged in distilled water for
47 hrs., and the glands were blackened, though the tentacles
were very little inflected. In one of these leaves there was only
a slight degree of aggregation in the tentacles; in the second
rather more, the purple contents of the cells being a littlo
separated from the walls; in the third and fourth, which were
pale leaves, the aggregation in the upper parts of the pedicels
was well marked. In these leaves the little masses of proto-
plasm, many of which were oval, slowly changed their forms
and ‘positions so that a submergence for 47 hrs. had not killed
the protoplasm. In a previous trial with a submerged plant
the tentacles were not in the least indected.
Cuar. III. THE PROCESS OF AGGREGATION. 53
Heat induces aggregation. A leaf, with the cells of the
tentacles containing only homogeneous fluid, was waved about
for 1m. in water at 180° Fahr. (54°4 Cent.), and was then
examined under the microscope as quickly as possible, that
is in 2 m. or 3 m.; and by this time the conjents of the
cells had undergone some degree of aggregation. A second leaf
was waved for 2m. in water at 125° (51°-6 Cent.) and quickly
examined as before; the tentacles were well inflected; the
purple fluid in all the cells had shrunk a little from the walls,
and contained many oval and elongated masses of protoplasm,
with a few minute spheres. A third leaf was left in water at
125°, until it cooled, and when examined after 1 hr. 45 m., the
inflected tentacles showed some aggregation, which became
after 3 hrs. more strongly marked, but did not subsequently
increase. Lastly, a leaf was waved for 1 m. in water at 120°
(48°8 Cent.) and then left for 1 hr. 26 m.in cold water; the
tentacles were but little inflected, and there was only here and
there a trace of aggregation. In all these and other trials
with warm water the protoplasm showed much less tendency
to aggregate into spherical masses than when excited by car-
bonate of ammonia. :
Redissolution of the Aggregated Masses of Protoplasm.—As soon
as tentacles which have clasped an insect or any inorganic
object, or have been in any way excited, have fully re-expanded,
the aggregated masses of protoplasm are redissolved and dis-
appear; the cells being now refilled with homogeneous purple
fluid as they were before the tentacles were inflected. The
process of redissolution in all cases commences at the basts of the
tentacles, and proceeds up them towards the glands. In old
leaves, however, especially in those which have been several
times in action, the protoplasm in the uppermost cells of the
pedicels remains in a permanently-more or less aggregated con-
dition. In order to observe the process of redissolution, the
following observations were made: a leaf was left for 24 hrs. in
a little solution of one part of carbonate of ammonia to 218 of
water, and the protoplasm was as usual aggregated into number-
less purple spheres, which were incessantly changing their
forms. The leaf was then washed and placed in distilled water,
and after 3 hrs. 15 m. some few of the spheres began to show by
their less clearly defined edges signs of redissolution. After
9 hrs. many of them had become elongated, and the surround-
ing fluid in the cells was slightly more coloured, showing
plainly that redissolution had commenced. After 24 hrs.,
though many cells still contained spheres, here and there one
54 DROSERA ROTUNDIFOLIA. Cuap. III.
could be seen filled with purple fluid, without a vestige of
aggregated protoplasm; the whole having been redissolved. A
leaf with aggregated masses, caused by its having been waved
for 2 m. in water at the temperature of 125° Fahr., was left in
cold water, and after 11 hrs. the protoplasm showed traces
of incipient redissolution. When again examined three days
after its immersion in the warm water, there was a conspicuous
difference, though the protoplasm was still somewhat aggre-
gated. Another leaf, with the contents of all the cells strongly
aggregated from the action of a weak solution of phosphate of
ammonia, was left for between three and four days in a mixture
(known to be innocuous) of one drachm of alcohol to eight
drachms of water, and when re-examined every trace of aggre-
gation had disappeared, the cells being now filled with homo-
geneous fluid.
We have seen that leaves immersed for some hours in dense
solutions of sugar, gum, and starch, have the contents of their
cells greatly aggregated, and are rendered more or less flaccid,
with the tentacles irregularly contorted. These leaves, after
being left for four days in distilled water, became less flaccid,
with their tentacles partially re-expanded, and the aggre-
gated masses of protoplasm were partially redissolved. A leaf
with its tentacles closely clasped over a fly, and with the con-
tents of the cells strongly aggregated, was placed in a little
sherry wine; after 2 hrs. several of the tentacles had re-
expanded, and the others could by a mere touch be pushed back
into their properly expanded positions, and now all traces of
aggregation had disappeared, the cells being filled with perfectly
homogeneous pink fluid. The redissolution in these cases may,
I presume, be attributed to endosmose.
On the Prowimate Causes of the Process of Aggregation.
As most of the stimulants which cause the inflection
of the tentacles likewise induce aggregation in the
contents of their cells, this latter process might be
thought to be the direct result of inflection ; but this
is not the case. If leaves are placed in rather strong
solutions of carbonate of ammonia, for instance of
three or four, and even sometimes of only two grains
to the ounce of water (i.e. one part to 109, or 146, or
Cuar. Ul THE PROCESS OF AGGREGATION. 55
218, of water), the tentacles are paralysed, and do not
become inflected, yet they soon exhibit strongly
marked aggregation. Moreover, the short central
tentacles of a leaf which has been immersed in a
weak solution of any salt of ammonia, or in any
nitrogenous organic fluid, do not become in the least
inflected; nevertheless they exhibit all the pheno-
mena of aggregation. On the other hand, several
acids cause strongly pronounced inflection, but no
aggregation.
It is an important fact that when an organic or in-
organic object is placed on the glands of the disc,
and the exterior tentacles are thus caused to bend
inwards, not only is the secretion from the glands of
the latter increased in quantity and rendered acid,
but the contents of the cells of their pedicels become
aggregated. The process always commences in the
glands, although these have not as yet touched any
object. Some force or influence must, therefore, be
transmitted from the central glands to the exterior
tentacles, first to near their bases causing this part to
bend, and next to the glands causing them to secrete
more copiously. After a short time the glands, thus
indirectly excited, transmit or reflect some influence
down their own pedicels, inducing aggregation in cell
beneath cell to their bases.
It seems at first sight a probable view that aggrega-
tion is due to the glands being excited to secrete more
copiously, so that sufficient fluid is not left in their
cells, and in the cells of the pedicels, to hold the
protoplasm in solution. In favour of this view is the
fact that aggregation follows the inflection of the
tentacles, and during the movement the glands gener-
ally, or, as I believe, always, secrete more copiously
than they did before. Again, during the re-expansion
5
56 DROSERA ROTUNDIFOLIA. Cuar. IL
of the tentacles, the glands secrete less freely, or quite
cease to secrete, and the aggregated masses of proto-
plasm are then redissolved. Moreover, when leaves
are immersed in dense vegetable solutions, or in
glycerine, the fluid within the gland-cells passes out-
-wards, and there is aggregation; and when the leaves
are afterwards immersed in water, or in an innocuous
fluid of less specific gravity than water, the protoplasm
is redissolved, and this, no doubt, is due to endosmose.
Opposed to this view, that aggregation is caused by
the outward passage of fluid from the cells, are the
following facts. There seems no close relation between
the degree of increased secretion and that of aggre-
gation. Thus a particle of sugar added to the secre-
tion round a gland causes a much greater increase of
secretion, and much less aggregation, than does a
particle of carbonate of ammonia given in thé samo
manner. It does not appear probable that pure water
would cause much exosmose, and yet aggregation
often follows from an immersion in water of between
16 hrs. and 24 hrs., and always after from 24 hrs. to
48 hrs. Still less probable is it that water at a tempe-
rature of from 125° to 130° Fahr. (51°6 to 54°4 Cent.)
should cause fluid to pass, not only from the glands,
but from all the cells of the tentacles down to their
bases, so quickly that aggregation is induced within
2m. or 3 m. Another strong argument against
this view is, that, after complete aggregation, the
spheres and oval masses of protoplasm float about
in an abundant supply of thin colourless fluid; so
that at least the latter stages of the process cannot
be due to the want of fluid to hold the protoplasm
in solution. There is still stronger evidence that
aggregation is independent of secretion; for the pa-
pillz, described in the first chapter, with which the
Cur. UI. THE PROCESS OF AGGREGATION. 57
leaves are studded are not glandular, and do not
secrete, yet they rapidly absorb carbonate of ammonia
or an infusion of raw meat, and their contents then
quickly undergo aggregation, which afterwards spreads
into the cells of the surrounding tissues. We shall
hereafter see that the purple fluid within the sensi-
tive filaments of Dionza, which do not secrete, like-
wise undergoes aggregation from the action of a weak
solution of carbonate of ammonia.
The process of aggregation is a vital one; by which
I mean that the contents of the cells must be alive
and uninjured to be thus affected, and they must be in
an oxygenated condition for the transmission of the
process at the proper rate. Some tentacles in a
drop of water were strongly pressed beneath a slip of
glass; many of the cells were ruptured, and pulpy
matter of a purple colour, with granules of all sizes
and shapes, exuded, but hardly any of the cells were
completely emptied. I then added a minute drop of
a solution of one part of carbonate of ammonia to
109 of water, and after 1 hr. examined the specimens.
Here and there a few cells, both in the glands and in
the pedicels, had escaped being ruptured, and their
contents were well aggregated into spheres which were
constantly changing their forms and positions, and a
current could still be seen flowing along the walls;
so that the protoplasm was alive. On the other hand,
the exuded matter, which was now almost colourless
instead of being purple, did not exhibit a trace of
aggregation. Nor was there a trace in the many
cells which were ruptured, but which had not been
completely emptied of their contents. Though I
looked carefully, no signs of a current could be seen
within these ruptured cells. They had evidently been
killed by the pressure; and the matter which they
58 DROSERA ROTUNDIFOLIA. Crap. IL
still contained did not undergo aggregation any more
than that which had exuded. In these specimens, as
I may add, the individuality of the life of each cell
was well illustrated.
A full account will be given in the next chapter of
the effects of heat on the leaves, and I need here only
state that leaves immersed for a short time in water at
a temperature of 120° Fahr. (48°8 Cent.), which, as we
have seen, does not immediately induce aggregation,
were then placed in a few drops of a strong solution
of one part of carbonate of ammonia to 109 of water,
and became finely aggregated. On the other hand,
leaves, after an immersion in water at 150° (65°5
Cent.), on being placed in the same strong solution,
did not undergo aggregation, the cells becoming filled
with brownish, pulpy, or muddy matter. With leaves
subjected to temperatures between these two extremes
of 120° and 150° Fahr. (48°8 and 65°5 Cent.), there
were gradations in the completeness of the process ;
the former temperature not preventing aggregation
from the subsequent action of carbonate of ammonia,
the latter quite stopping it. Thus, leaves immersed
in water, heated to 130° (54°4 Cent.), and then in the
solution, formed perfectly defined spheres, but these
were decidedly smaller than in ordinary cases. With
other leaves heated to 140° (60° Cent.), the spheres
were extremely small, yet well defined, but many of
the cells contained, in addition, some brownish pulpy
matter. In two cases of leaves heated to 145° (62°7
Cent.), a few tentacles could be found with some of
their cells containing a few minute spheres; whilst
the other cells and other whole tentacles included
only the brownish, disintegrated or pulpy matter.
The fluid within the cells of the tentacles must be
in an oxygeuated condition, in order that the force or
Umar. II THE PROCESS OF AGGREGATION. 59
influence which induces aggregation should be trans-
mitted at the proper rate from cell to cell. A plant,
with its roots in water, was left for 45m. in a vessel
containing 122 oz. of carbonic acid.
bonate of ammonia induces aggregation in the cells of the roots
of Drosera; and this led me to make a few trials on the roots
of other plants. I dug up in the latter part of October the
first weed which ] met with, viz. Euphorbia peplus, being carer
64 DROSERA ROTUNDIFOLIA. Cuar. IN
ful not to injure the roots; these were washed and placed in a
little solution of one part of carbonate of ammonia to 146 of
water. In less than one minute I saw a cloud travelling from
cell to cell up the roots, with wonderful rapidity. After from
8m. to 9 m. the fine granules, which caused this cloudy appear-
ance, became aggregated towards the extremities of the roots
into quadrangular masses of brown matter; and some of these
soon changed their forms and became spherical. Some of the
cells, however, remained unaffected. I repeated the experi-
ment with another plant of the same species, but before I could
get the specimen into focus under the microscope, clouds of
granules and quadrangular masses of reddish and brown
matter were formed, and had run far up all the roots. A fresh
root was now left for 18 hrs. in a drachm of a solution of one
part of the carbonate to 487 of water, so that it received } of
a grain, or 27024 mg. When examined, the cells of all the
roots throughout their whole length contained aggregated
masses of reddish and brown matter. Before making these
experiments, several roots were closely examined, and not a
trace of the cloudy appearance or of the granular masses could
be seen in any of them. Roots were also immersed for 35 m.
in a solution of one part of carbonate of potash to 218 of water:
but this salt produced no effect. :
I may here add that thin slices of the stem of the Euphorbia
were placed in the same solution, and the cells which were
green instantly became cloudy, whilst others which were before
colourless were clouded with brown, owing to the formation of
numerous granules of this tint. I have also seen with various
kinds of leaves, left for some time in a solution of carbonate of
ammonia, that the grains of chlorophyll ran together and
partially coalesced; and this seems to be a form of aggregation.
Plants of duck-weed (Lemna) were left for between 30 m. and
45 m. in a solution of one part of this same salt to 146 of water,
and three of their roots were then examined. In two of them,
all the cells which had previously contained only limpid fluid
now included little green spheres. After from 13 hr. to 2 hrs,
similar spheres appeared in the cells on the borders of the
leaves; but whether the ammonia had travelled up the roots or
had been directly absorbed by the leaves, I cannot say. As one
species, Lemna arrhiza, produces no roots, the latter alternative
is perhaps the most probable. After about 23 hrs. some of the
little green spheres in the roots were broken up into small
granules which exhibited Brownian movements. Some duck.
weed was also left for 1 hr. 30 m. in a solution of one part of
Ouar. IL THE PROCESS OF AGGREGATION. 65
carbonate of potash to 218 of water, and no decided change
could be perceived in the cells of the roots; but when these
same roots were placed for 25 m. in a solution of carbonate of
ammonia of the same strength, little green spheres were formed.
A green marine alga was left for some time in this same solu-
tion, but was very doubtfully affected. On the other hand, a
red marine alga, with finely pinnated fronds, was strongly
affected. The contents of the cells aggregated themselves into
broken rings, still of a red colour, which very slowly and
slightly changed their shapes, and the central spaces within
these rings became cloudy with red granular matter. The
facts here given (whether they are new, I know not) indicate
that interesting results would perhaps be gained by observing
the action of various saline solutions and other fluids on the
roots of plants.
66 DROSERA ROTUNDIFOLIA. Cap IV.
CHAPTER IV.
Tur Errects or Heat on THE LEAVES.
Nature of the experiments — Effects of boiling water — Warm water
causes rapid inflection — Water at a higher temperature does not
cause immediate inflection, but does not kill the leaves, as shown
by their subsequent re-expansion and by the aggregation of the
protoplasm—A still higher temperature kills the leaves and
coagulates the albuminous contents of the glands.
In my observations on Drosera rotundifolia, the leaves
seemed to be more quickly inflected over animal sub-
stances, and to remain inflected for a longer period
during very warm than during cold weather. I
wished, therefore, to ascertain whether heat alone
would induce inflection, and what temperature was
the most efficient. Another interesting point pre-
sented itself, namely, at what degree life was extin-
guished ; for Drosera offers unusual facilities in this
respect, not in the loss of the power of inflection, but
in that of subsequent re-expansion, and more espe-
cially in the failure of the protoplasm to become
aggregated, when the leaves after being heated are
immersed in a solution of carbonate of ammonia.*
* When my experiments onthe cludes that the protoplasm with-
effects of heat were made, I was
not aware that the subject had
been carefully investigated by
several observers. For instance,
Sachs is convinced (‘Traité de
Botanique,’ 1874, pp. 772, 854)
that the most different kinds of
plants all perish if kept for 10m.
in water at 45° to 46° Cent., or
118° to 115° Fahr.; and he con-
in their cells always coagulates,
if in a damp condition, at a tem-
perature of between 50° and 60°
Cent., or 122° to 140° Fahr. Max
Schultze and Kiihne (as quoted
by Dr. Bastian in ‘Contemp.
Review,’ 1874, p. 528) “found
that the protoplasm of plant-
cells, with which they experi-
mented, was always killed and
Car. 1V. THE EFFECTS OF HEAT. 67
My experiments were tried in the following manner. Leaves
were cut off, and this does not in the least interfere with their
powers; for instance, three cut-off leaves, with bits of meat
placed on them, were kept in a damp atmosphere, and after
23 hrs. closely embraced the meat both with their ten-
tacles and blades; and the protoplasm within their cells was
well aggregated. Three ounces of doubly distilled water was
heated in a porcelain vessel, with a delicate thermometer
having a long bulb obliquely suspended in it. The water was
gradually raised to the required temperature by a spirit-lamp
moved about under the vessel; and in all cases the leaves
were continuaily waved for some minutes close to the bulb.
They were then placed in cold water, or in a solution of car-
bonate of ammonia. In other cases they were left in the water,
which had been raised to a certain temperature, until it cooled.
Again in other cases the leaves were suddenly plunged into
water of a certain temperature, and kept there for a specified
time. Considering that the tentacles are extremely delicate,
and that their coats are very thin, it seems scarcely possible
that the fluid contents of their cells should not have been
heated to within a degree or two of the temperature of the
surrounding water. Any further precautions would, I think,
have been superfluous, as the leaves from age or constitutional
causes differ slightly in their sensitiveness to heat.
It will be convenient first briefly to describe the effects of
immersion for thirty seconds in boiling water. The leaves are
rendered flaccid, with their tentacles bowed backwards, which,
as we shall see in a future chapter, is probably due to their
outer surfaces retaining their elasticity for a longer period than
their inner surfaces retain the power of contraction. The
purple fluid within the cells of the pedicels is rendered finely
granular, but there is no true aggregation; nor does this follow
altered by a very! brief expo-
sure to a temperature of 1183°
Fahy. as a maximum.” As my
results are deduced from special
phenomena, namely, the subse-
quent aggregation of the proto-
plasm and the re-expansion of
the tentacles, they seem to me
worth giving. We shall find that
Drosera resists heat somewhat
better than most other plants.
That there should be consider-
able differences in this respect is
not surprising, considering that
some low vegetable organisms
grow in hot springs—cases of
which have been collected by
Prof. Wyman (‘ American Journal
of Science,’ vol. xliv. 1867). Thus,
Dr. Hooker found Conferve in
water at 168° Fahr.; Humboldt,
at 185° Fahr.; and Descloizeaux,
at 208° Fahr.
68 DROSERA ROTUNDIFOLIA. Cuap IV.
when the leaves are subsequently placed in a solution of car-
bonate of ammonia. But the most remarkable change is that
the glands become opaque and uniformly white; and this may
be attributed to the coagulation of their albuminous contents.
My first and preliminary experiment consisted in putting
seven leaves in the same vessel of water, and warming it slowly
up to the temperature of 110° Fahr. (48°°3 Cent.); a leaf being
taken out as soon as the temperature rose to 80° (26°6 Cent.),
another at 85°, another at 90°, and so on. Each leaf, when taken
out, was placed in water at the temperature of my room, and
the tentacles of all soon became slightly, though irregularly,
inflected. They were now removed from the cold water and
kept in damp air, with bits of meat placed on their discs.
The leaf which had been exposed to the temperature of 110°
became in 15 m. greatly inflected; and in 2 hrs. every single
tentacle closely embraced the meat. So it was, but after rather
longer intervals, with the six other leaves. It appears, there-
fore, that the warm bath had increased their sensitiveness
when excited by meat. :
I next observed the degree of inflection which leaves under-
went within stated periods, whilst still immersed in warm
water, kept as nearly as possible at the same temperature; but
I will here and elsewhere-give only a few of the many trials
made. A leaf was left for 10 m. in water at 100° (87°-7 Cent.),
but no inflection occurred. A second leaf, however, treated in
the same manner, had a few of its exterior tentacles very
slightly inflected in 6 m., and several irregularly but not closely
inflected in 10 m. A third leaf, kept in water at 105° to 106°
(40°.5 to 41°1 Cent.), was very moderately inflected in 6 m.
A fourth leaf, in water at 110° (48°°3 Cent.), was somewhat in-
flected in 4 m., and considerably so in from 6 m. to 7 m.
Three leaves were placed in water which was heated rather
quickly, and by the time the temperature rose to 115°—116°
(46°1 to 46°-06 Cent.), all three were inflected. I then removed
the lamp, and in a few minutes every single tentacle was
closely inflected. The protoplasm within the cells was not
killed, for it was seen to be in distinct movement; and-the
leaves, having been left in cold water for 20 hrs., re-expanded.
Another leaf was immersed in water at 100° (87°7 Cent.), which
was raised to 120° (48°8 Cent.); and all the tentacles, except
the extreme marginal ones, soon became closely inflected.
The leaf was now placed in cold water, and in 7 hrs. 30 m. it
had partly, and in 10 hrs. fully, re-expanded. On the follow:
ing morning it was immersed in a weak solution of carbonate of
. Cnar. IV, THE EFFECTS OF HEAT. 69
ammonia, and the glands quickly became black, with strongly
marked aggregation in the tentacles, showing that the proto-
plasm was alive, and that the glands had not lost their power of
absorption. Another leaf was placed in water at 110° (48°3
Cent.) which was raised to 120° (48°'8 Cent.); and every ten-
tacle, excepting one, was quickly and closely inflected. This leaf
was now immersed in a few drops of a strong solution of car-
bonate of ammonia (one part to 109 of water); in 10 m. all the
glands became intensely black, and in 2 hrs. the protoplasm in
the cells of the pedicels was well aggregated. Another leaf was
suddenly plunged, and as usual waved about, in water at 120°,
and the tentacles became inflected in from 2m. to 3m., but
only so as to stand at right angles to the disc. The leaf was
now placed in the same solution (viz. one part of carbonate of
ammonia to 109 of water, or 4 grs. to 1 oz., which I will for
the future designate as the strong solution), and when I looked
at it again after the interval of an hour, the glands were
blackened, and there was well-marked aggregation. After an
additional interval of 4 hrs. the tentacles had become much
more inflected. It deserves notice that a solution as strong as
this never causes inflection in ordinary cases. Lastly a leaf
was suddenly placed in water at 125° (51°6 Cent.), and was
left in it until the water cooled; the tentacles were rendered
of a bright red and soon became inflected. The contents of
the cells underwent some degree of aggregation, which in
the course of three hours increased; but the masses of proto-
plasm did not become spherical, as almost always occurs with
leaves immersed in a solution of carbonate of ammonia.
We learn from these cases that a temperature of
from 120° to 125° (48°8 to 51°6 Cent.) excites the
tentacles into quick movement, but does not kill the
leaves, as shown either by their subsequent re-expansion
or by the aggregation of the protoplasm. We shall
now see that a temperature of 130° (54°-4 Cent.) is too
high to cause immediate inflection, yet does not kill
the leaves.
Experiment 1—A leaf was plunged, and as in all cases
waved about for a few minutes, in water at 180° (54°°4 Cent.),
but there was no trace of inflection; it was then placed in cold
water, and after an interval of 15 m. very slow movement wat
70 DROSERA ROTUNDIFOLIA. Cxar. LY
distinctly seen in a small mass of protoplasm in one of the cells
of a tentacle.* After a few hours all the tentacles and the
blade became inflected.
Experiment 2.—Another leaf was plunged into water at 130°
to 131°, and as before there was no inflection. After being kept
in cold water for an hour, it was placed in the strong solutior
of ammonia, and in the course of 55 m. the tentacles were con-
siderably inflected. The glands, which before had been rendered
of a brighter red, were now blackened. The protoplasm in the
cells of the tentacles was distinctly aggregated ; but the spheres
were much smaller than those usually generated in unheated
leaves when subjected to carbonate of ammonia. After an
additional 2 hrs. all the tentacles, excepting six or seven, were
closely inflected.
Experiment 3.—A similar experiment to the last, with exactly
the same results.
Experiment 4.—A fine leaf was placed in water at 100° (87°°7
Cent.), which was then raised to 145° (62°°7 Cent.). Soon after
immersion, there was, as might have been expected, strong
inflection. The leaf was now removed and left in cold water;
but from having been exposed to so high a temperature, it
never re-expanded.
Luperiment 5.—Leaf immersed at 130° (547-4 Cent.), and the
water raised to 145° (62°°7 Cent.), there was no immediate in-
flection; it was then placed in cold water, and after 1 hr. 20 m.
some of the tentacles on one side became inflected. This
leaf was now placed in the strong solution, and in 40 m. all
the submarginal tentacles were well inflected, and the glands
blackened. After an additional interval of 2 hrs. 45 m. all the
tentacles, except eight or ten, were closely inflected, with their
cells exhibiting a slight degree of aggregation; but the spheres
of protoplasm were very small, and the cells of the exterior
tentacles contained some pulpy or disintegratéd brownish
matter.
Experiments 6 and 7—Two leaves were plunged in water at
135° (57° 2 Cent.) which was raised to 145° (62°-7 Cent.); neither
became inflected. One of these, however, after having been left
for 31 m. in cold water, exhibited some slight inflection, which
increased after an additional interyal of 1 hr. 45 m., until
* Sachs states (‘Traité de Bo- after they were exposed for 1 m.
tanique,’ 1274, p. 855) that the in water to a temperature of 47°
movements of the protoplasm in to 48° Cent., or 117° to 119°
the hairs cf a Cucurbita ceased Fahr.
Cuar. IV. THE EFFECTS OF HEAT. 71
all the tentacles, except sixteen or seventeen, were more or less
inflected ; but the leaf was so much injured that it never re-
expanded. The other leaf, after having been left for half av
hour in cold water, was put into the strong solution, but no
inflection ensued; the glands, however, were blackened, and in
some cells there was a little aggregation, the spheres of proto-
plasm being extremely small; in other cells, especially in the
exterior tentacles, there was much greenish-brown pulpy
matter.
Experiment 8.—A leaf was plunged and waved about for a
‘few minutes in water at 140° (60° Cent.), and was then left for
half an hour in cold water, but there was no inflection. It was
now placed in the strong solution, and after 2 hrs. 30 m. the
inner submarginal tentacles were well inflected, with their
glands blackened, and some imperfect aggregation in the cells
of the pedicels. Three or four of the glands were spotted with
the white porcelain-like structure, like that produced by boiling
water. I have seen this result in no other instance after an
immersion of only a few minutes in water at so low a tempe-
rature as 140°, and in only one leaf out of four, after a similar
immersion at a temperature of 115° Fahr. On the other hand,
with two leaves, one placed in water at 145° (62°°7 Cent.), and
the other in water at 140° (60° Cent.), both being left therein
until the water cooled, the glands of both became white and
porcelain-like. So that the duration of the immersion is an
important element in the result.
Experiment 9.—A leaf was placed in water at 140° (60° Cent.),
which was raised to 150° (65°°5 Cent.); there was no inflection ;
on the contrary, the outer tentacles were somewhat bowed back-
wards. The glands became like porcelain, but some of them
were a little mottled with purple. The bases of the glands were
often more affected than their summits. This leaf having been
left in the strong solution did not undergo any inflection or
aggregation.
Eaperiment 10.—A leaf was plunged in water at 150° to 1502°
(65°°5 Cent.); it became somewhat flaccid, with the outer ten-
tacles slightly reflexed, and the inner ones a little bent inwards,
but only towards their tips; and this latter fact shows that the
Movement was not one of true inflection, as the basal part
alone normally bends. The tentacles were as usual rendered of
a very bright red, with the glands almost white like porcelain,
yet tinged with pink. The leaf having been placed in the
strong solution, the cell-contents of the tentacles became of a
muddy brown, with no trace of aggregation.
6
72 DROSERA ROTUNDiFOLIA. Cuap. IV
Experiment 11.—A leaf was immersed in water at 145° (62°°7
Cent.), which was raised to 156° (68°°8 Cent.). The tentacles
became bright red and somewhat reflexed, with almost all the
glands like porcelain; those on the disc. being still pinkish,
those near the margin quite white. The leaf being placed as
usual first in cold water and then in the strong solution, the
cells in the tentacles became of a muddy greenish brown, with
the protoplasm not aggregated. Nevertheless, four of the glands
escaped being rendered like porcelain, and the pedicels of these
glands were spirally curled, like a French horn, towards their
upper ends; but this can by no means be considered as a
case of true inflection. The protoplasm within the cells of the
twisted portions was aggregated into distinct though excessively
minute purple spheres. This case shows clearly that the proto-
plasm, after having been exposed to a high temperature for a
few minutes, is capable of aggregation when afterwards sub-
jected to the action of carbonate of ammonia, unless the heat
has been sufficient to cause coagulation.
Concluding Remarks.—As the hair-like tentacles are
extremely thin and have delicate walls, and as the
leaves were waved about for some minutes close to the
bulb of the thermometer, it seems scarcely possible
that they should not have been raised very nearly to
‘the temperature which the instrument indicated.
From the eleven last observations we see that a tem-
perature of 130° (54°4 Cent.) never causes the imme-
diate inflection of the tentacles, though a temperature
from 120° to 125° (48°8 to 51°6 Cent.) quickly pro-
duces this effect. But the leaves are paralysed only
for a time by a temperature of 130°, as afterwards,
whether left in simple water or in a solution of car-
bonate of ammonia, they become inflected and their
protoplasm undergoes aggregation. This great dif-
ference in the effects of a higher and lower tempera-
ture may be compared with that from immersion in
strong and weak solutions of the salts of ammonia; for
the former do not excite movement, whereas the latter
act energetically. A temporary suspension of the
Cuap. IV. THE EFFECTS OF HEAT. 13
power of movement due to heat is called by Sachs*
heat-rigidity ; and this in the case of the sensitive-
plant (Mimosa) is induced by its exposure for a few
minutes to humid air, raised to 120°—122° Fahr., or
49° to 50° Cent. It deserves notice that the leaves of
Drosera, after being immersed in water at 130° Fahr.,
are excited into movement by a solution of the car
bonate so strong that it would paralyse ordinary
leaves and cause no inflection.
The exposure of the leaves for a few minutes even
to a temperature of 145° Fahr. (62°'7 Cent.) does not
always kill them; as when afterwards left in cold
water, or in a strong solution of carbonate of ammo-
nia, they generally, though not always, become in-
flected ; and the protoplasm within their cells under-
goes aggregation, though the spheres thus formed are
extremely small, with many of the cells partly filled
with brownish muddy matter. In two instances, when
leaves were immersed in water, at a lower temperature
than 130° (54°-4 Cent.), which was then raised to 145°
(62°-7 Cent.), they became during the earlier period
of immersion inflected, but on being afterwards left
in cold water were incapable of re-expansion. Ex-
posure for a few minutes to a temperature of 145°
sometimes causes some few of the more sensitive
glands to be speckled with the porcelain-like appear-
ance; and on one occasion this occurred at a tempera-
ture of 140° (60° Cent.). On another occasion, when
a leaf was placed in water at this temperature of only
140°, and left therein till the water cooled, every
gland became like porcelain. Exposure for a few
minutes to a temperature of 150° (65°5 Genv.) gene-
tally produces this effect, yet many glands retain a
* ‘Traité de Bot.’ 1874, p. 1034.
“4 DROSERA ROTUNDIFOLIA. Cuap. IV
pinkish coleur, and many present a speckled appear-
ance. This high temperature never causes true inflec.
tion ; on the contrary, the tentacles commonly become
reflexed, though to a less degree than when immersed
in boiling water; and this apparently is due to their
passive power of elasticity. After exposure to a tem-
perature of 150° Fahr., the protoplasm, if subsequently
subjected to carbonate of ammonia, instead of under-
going aggregation, is converted into disintegrated or
pulpy discoloured matter. In short, the leaves are
generally killed by this degree of heat; but owing to
differences of age or constitution, they vary somewhat
in this respect. In one anomalous case, four out of
the many glands on a leaf, which had been immersed
in water raised to 156° (68°8 Cent.), escaped being
rendered porcellanous;* ‘and the protoplasm in the
cells close beneath these glands underwent some
slight, though imperfect, degree of aggregation.
Finally, it is a remarkable fact that the leaves of
Drosera rotundifolia, which flourishes on bleak upland
moors throughout Great Britain, and exists (Hooker)
within the Arctic Circle, should be able to withstand
for even a short time immersion in water heated to a
temperature of 145°.f
It may be worth adding that immersion in cold
* As the opacity and porcelain-
tike appearance of the glands is
differences in the results above
recorded.
probably due to the coagulation
of the albumen, I may add, on the
authority of Dr. Burdon Sander-
son, that albumen coagulates at
about 155°, but, in presence of
acids, the temperature of coagula-
tion is lower. The leaves of Dro-
sera contain an acid, and perhaps
a difference in the amount con-
tained may account for the slight
t It appears that cold-blooded
animals are, as might have been
expected, far more sensitive to an
increase of temperature than is
Drosera. Thus, as I hear from Dr.
Burdon Sanderson, a frog begins
to be distressed in water at a tem-
perature of only 85° Fahr. At 95°
the muscles become rigid, and the
animal dies in a stiffened condition
Cuap. IV. THE EFFECTS OF HEAT. 75
water does not cause any inflection: I suddenly placed
four leaves, taken from plants which had been kept for
several days at a high temperature, generally about
75° Fahr. (23°8 Cent.), in water at 45° (7°-2 Cent.), but
they were hardly at all affected; not so much as some
other leaves from the same plants, which were at the
same time immersed in water at 75°; for these became
in a slight degree inflected.
76 DROSERA ROTUNDIFOLIA. Crap. V
CHAPTER V.
Tue Errecrs or Non-NITROGENOUS AND NiTRocEenovus Orcanic Fiums
oN THE LEAVES.
?
Non-nitrogenous fluids—Solutions of gum arabic — Sugar — Starch
— Diluted alcohol — Olive oil—Infusion and decoction of tea —
Nitrogenous fluids — Milk — Urine— Liquid albumen — Infusion
of raw meat—Impure mucus — Saliva — Solution of isinglass—
Difference in the action of these two sets of fluids — Decootion of
green peas—Decoction and infusion of cabbage— Decoetion of
grass leaves.
WHEv, in 1860, I first observed Drosera, and was led to
believe that the leaves absorbed nutritious matter from
the insects which they captured, it seemed to me a
good plan to make some preliminary trials with a few
common fluids, containing and not containing nitro-
genous matter; and the results are worth giving.
In all the following cases a drop was allowed to fall
from the same pointed instrument on the centre of the
leaf; and by repeated trials one of these drops was
ascertained to be on an average very nearly half a
minim, or ;1,; of a fluid ounce, or ‘0295 ml. But these
measurements obviously do not pretend to any strict
accuracy ; moreover, the drops of the viscid fluids were
plainly larger than those of water. Only one leaf on
the same plant was tried, and the plants were col-
lected from two distant localities. The experiments
were made during August and September. In judging
of the effects, one caution is necessary: if a drop of
any adhesive fluid is placed on an old or feeble leaf,
the glands of which have ceased to secrete copiously,
the drop sometimes dries up, especially if the plant
Cuap. ¢. EFFECTS OF ORGANIC FLUIDS. 77
is kept in a room, and some of the central and sub-
marginal tentacles are thus drawn together, giving to
them the false appearance of having become inflected.
This sometimes occurs with water, as it is rendered
adhesive by mingling with the viscid secretion.
Hence the only safe criterion, and to this alone I
have trusted, is the bending inwards of the exterior
tentacles, which have not been touched by the fluid, or
at most only at their bases. In this case the move-
ment is wholly due to the central glands having been
stimulated by the fluid, and transmitting a motor
impulse to the exterior tentacles. The blade of the
leaf likewise often curves inwards, in the same manner
as when an insect or bit of meat is placed on the
disc. This latter movement is never caused, as far
as I have seen, by the mere drying up of an ad-
hesive fluid and the consequent drawing together of
the tentacles.
First for the non-nitrogenous fluids. As a pre-
liminary trial, drops of distilled water were placed on
between thirty and forty leaves, and no effect whatever
was produced; nevertheless, in some other and rare
cases, a few tentacles became for a short time in-
flected; but this may have been caused by the
glands having been accidentally touched in getting
the leaves into a proper position. That water should
produce no effect might have been anticipated, as
-otherwise the leaves would have been excited into
movement by every shower of rain.
Gum arabic.—Solutions of four degrees of strength were made ;
one of six grains to the ounce of water (one part to 78); a second
rather stronger, yet very thin; a third moderately thick, and a
fourth so thick that it would only just drop from a pointed
instrument. These were tried on fourteen leaves; the drops
being left on the discs from 24 hrs. to 44 hrs.; generally about
78 DKOSERA ROTUNDIFOLIA. Cuar. V
30 hrs. Inflection was never thus caused. It is necessary
to try pure gum arabic, for a friend tried a solution bought
ready prepared, and this caused the tentacles to bend; but he
afterwards ascertained that it contained much animal matter,
probably glue. \ :
Sugar.—Drops of a solution of white sugar of three strengths
(the weakest containing one part of sugar to 73 of water) were
left on fourteen leaves from 32 hrs. to 48 hrs.; but no effect was
produced. —
Starch—A mixture about as thick as cream was dropped on
six leaves and left on them for 30 hrs., no effect being produced.
I am surprised at this fact, as I believe that the starch of com-
merce generally contains a trace of gluten, and this nitrogenous
substance causes inflection, as we shall see in the next chapter.
Alcohol, Diluted.—One part of alcohol was added to seven of
water, and the usual drops were placed on the discs of three
leaves. No inflection ensued in the course of 48 hrs. To ascer-
tain whether these leaves had been at all injured, bits of meat
were placed on them, and after 24 hrs. they were closely inflected.
T also put drops of sherry-wine on three other leaves; no inflec-
tion was caused, though two of them seemed somewhat injured.
We shall hereafter see that cut-off leaves immersed in diluted
alcohol of the above strength do not become inflected.
Olive Oil.—Drops were placed on the discs of eleven leaves, and
no effect was produced in from 24 hrs, to 48 hrs. Four of these
leaves were then tested by bits of meat on their discs, and three
of them were found after 24 hrs, with all their tentacles and
blades closely inflected, whilst the fourth had only a few ten-
tacles inflected. It will, however, be shown in a future place,
that cut-off leaves immersed in olive oil are powerfully affected.
Infusion and Decoction of Tea.—Drops of a strong infusion and
decoction, as well as of a rather weak decoction, of tea were
placed on ten leaves, none of which became inflected. I after-
wards tested three of them by adding bits of meat to the drops
which still remained on their discs, and when I examined them
after 24 hrs. they were closely inflected. The chemical principle
of tea, namely theine, was subsequently tried and produced no
effect. The albuminous matter which the leaves must originally
have contuined, no doubt, had been rendered insoluble by their
having been completely dried.
We thus see that, excluding the experiments with
water, sixty-one leaves were tried with drops of the
Cuap. V. EFFECTS OF ORGANIC FLJIDs. 79
above-named non-nitrogenous fluids; and the tentacles
were not in a single case inflected.
With respect to nitrogenous fluids, the first which came to
hand were tried. The experiments were made at the same
time and in exactly the same manner as the foregoing.
As it was immediately evident that these fluids produced a
great effect, I neglected in most cases to record how soon the
tentacles became inflected. But this always occurred in less
than 24 hrs.; whilst the drops of non-nitrogenous fluids which
produced no effect were observed in every case during a
considerably longer period.
Milk.—Drops were placed on sixteen leaves, and the tentacles
of all, as well as the blades of several, soon became greatly
inflected. The periods were recorded in only three cases,
namely, with leaves on which unusually small drops had been
placed. Their tentacles were somewhat inflected in 45 m.;
and after 7 hrs. 45 m. the blades of two were so much curved
inwards that they formed little cups enclosing the drops.
These leaves re-expanded on the third day. On another occa-
sion the blade of a leaf was much inflected in 5 hrs. after a
drop of milk had been placed on it.
Human Urine.—Drops were placed on twelve leaves, and the
tentacles of all, with a single exception, became greatly inflected.
Owing, I presume, to differences in the chemical nature of the
urine on different occasions, the time required for the movements
of the tentacles varied much, but was always effected in under
24 hrs. In two instances I recorded that all the exterior ten-
tacles were completely inflected in 17 hrs., but not the blade of
the leaf. In another case the edges of a leaf, after 25 hrs,
30 m., became so strongly inflected that it was converted into a
cup. "The power of urine does not lie in the urea, which, as
we shall hereafter see, is inoperative.
Albumen (fresh from a hen’s egg), placed on seven . Teves,
caused the tentacles of six of them to be well inflected. In one
case the edge of the leaf itself became much curled in after
20 hrs. The one leaf which was unaffected remained so for
26 hrs., and was then treated with a drop of milk, and this
taused the tentacles to bend inwards in 12 hrs.
Cold Filtered Infusion of Raw Meat.—This was tried only on a
single leaf, which had most of its outer tentacles and the blade
inflected in 19 hrs. During subsequent years, I repeatedly
used this infusion to test leaves which had been experimented
80 DROSERA ROTUNDIFOLIA. Cuar. V
on with other substances, and it was found to act most ener-
getically, but as no exact account of these trials was kept, they
are not here introduced.
Mucus.—Thick and thin mucus from the bronchial tubes,
placed on three leaves, caused inflection, A leaf with thin
mucus had its marginal tentacles and blade somewhat curved
inward in 5 hrs. 30 m., and greatly so in 20 hrs. The action of
this fluid no doubt is due either to the saliva or to some_albu-
minous matter* mingled with it, and not, as we shall see in the
next chapter, to mucin or the chemical principle of mucus.
Saliva.—Human saliva, when evaporated, yieldst from 1:14 to
1:19 per cent. of residue; and this yields 0°25 per cent. of ashes,
so that the proportion of nitrogenous matter which saliva con-
tains must be small. Nevertheless, drops placed on the discs of
eight leaves acted on them all. In one case all the exterior ten-
tacles, excepting nine, were inflected in 19 hrs. 30m. ; in another
case a few became so in 2 hrs., and after 7 hrs. 30 m. all those
situated near where the drop lay, as well as the blade, were
acted on. Since making these trials, I have. many scores of
times just touched glands with the handle of my scalpel wetted
with saliva, to ascertain whether a leaf was in an active condi-
tion; for this was shown in the course of a few minutes by the
bending inwards of the tentacles. The edible nest of the Chinese
swallow is formed of matter secreted by the salivary glands; two
grains were added to one ounce of distilled water (one part to 218),
which was boiled for several minutes, but did not dissolve the
whole. The usual-sized drops were placed on three leaves, and
these in 1 hr. 80 m. were well, and in 2 hrs. 15 m. closely,
inflected.
Isinglass.—Drops of a solution about as thick as milk, and of
a still thicker solution, were placed on eight leaves,.and the ten-
tacles of all became inflected. In one case the exterior tentacles
were well curved in after 6 hrs. 30 m., and the blade of the leaf
to a partial extent after 24 hrs. As saliva acted so efficiently,
and yet contains so small a proportion of nitrogenous matter, I
tried how small a quantity of isinglass would act. One part was
dissolved in 218 parts of distilled water, and drops were placed
on four leaves. After 5 hrs. two of these were considerably and
two moderately inflected ; after 22 hrs. the former were greatly
and the latter much more inflected. In the course of 48 hrs.
* Mucus from the air-passages to contain some albumen.
is said in Marshall, ‘Outlines of + Miiller’s ‘ Elements of Physix
Physiology,’ vol. ii. 1867, p. 364, logy,’ Eng. Trans. vol. i. p. 514,
Cuar. V. EFFECTS OF ORGANIC FLUIDS. 81
from the time when the drops were placed on the leaves, all
four had almost re-expanded. They were then given little bits
of meat, and these acted more powerfully than the solution.
One part of isinglass was next dissolved in 437 of water; the
fluid thus formed was so thin that it could not be distinguished
from pure water. The usual-sized drops were placed on seven
leaves, each of which thus received ~4, of a grain (0295 mg.).
Three of them were observed for 41 hrs., but were in no way
affected; the fourth and fifth had two or three of their exterior
tentacles inflected after 18 hrs.; the sixth had a few more,
and the seventh had in addition the edge of the leaf just
perceptibly curved inwards. The tentacles of the four latter
leaves began to re-expand after an additional interval of only
8 hrs. Hence the 54, of a grain of isinglass is sufficient to affect
very slightly the more sensitive or active leaves. On one of the
leaves, which had not been acted on by the weak solution, and on
another, which had only two of its tentacles inflected, drops of
the solution as thick as milk were placed; and next morning,
after an interval of 16 hrs., both were found with all their ten-
tacles strongly inflected.
Altogether I experimented on sixty-four leaves
with the above nitrogenous fluids, the five leaves
tried only with the extremely weak solution of isin-
glass not being included, nor the numerous trials
subsequently made, of which no exact account was
kept. Of these sixty-four leaves, sixty-three had their
tentacles and often their blades well inflected. The
one which failed was probably too old and torpid.
But to obtain so large a proportion of successful
cases, care must be taken to select young and active
leaves. Leaves in this condition were chosen with
equal care for the sixty-one trials with non-nitro-
genous fluids (water not included); and we have seen
that not one of these was in the least affected. We
may therefore safely conclude that in the sixty-four
experiments with nitrogenous fluids the inflection of
the exterior tentacles was due to the absorption of
82 DROSERA ROTUNDIFOLIA. Cuar. V.
nitrogenous matter by the glands of the tentacles
on the disc.
Some of the leaves which were not affected by the
non-nitrogenous fiuids were, as above stated, imme-
diately afterwards tested with bits of meat, and were
thus proved to be in un active condition. But in
addition to these trials, twenty-three of the leaves,
with drops of gum, syrup, or starch, still lying on
their dises, which had produced no effect in the course
of between 24 hrs. and 48 hrs., were then tested with
drops of milk, urine, or albumen. Of the twenty-three
leaves thus treated, seventeen had their tentacles, and
in some cases their blades, well inflected; but their
powers were somewhat impaired, for the rate of move-
ment was decidedly slower than when fresh leaves
were treated with these same nitrogenous fluids. This
impairment, as well as the insensibility of six of the
leaves, may be attributed to injury from exosmose,
caused by the density of the fluids placed on their
dises.
The results of a few other experiments with nitrogenous fluids
may be here conveniently given. Decoctions of some vegetables,
known to be rich in nitrogen, were made, and these acted like
animal fluids. Thus, a few green peas were boiled for some time
in distilled water, and the moderately thick decoction thus made
was allowed to settle. Drops of the superincumbent fluid were
placed on four leaves, and when these were looked at after
16 hrs., the tentacles and blades of all were found strongly
inflected. I infer from a remark by Gerhardt* that legumin is
present in peas “in combination with an alkali, forming an
incoagulable solution,” and this would mingle with boiling
water. I may mention, in relation to the above and following
experiments, that according to Schifft certain forms of albumen
* Watts’ ‘Dict. of Chemistry,’ Digestion, tom. i. p. 379; tom
vol. iii. p. 568. ik, pp. 154, 166, on legumin.
t ‘Lecons sur la Phys. de la
Cuar. V. EFFECTS OF ORGANIC FLUIDS. 83
exist which are not coagulated by boiling water, but are con-
verted into soluble peptones.
On three occasions chopped cabbage-leaves* were boiled in
distilled water fcr 1 hr. or for 1} hr.; and by decanting the
decoction after it had been allowed to rest, a pale dirty green
fluid was obtained. The usual-sized drops were placed on
thirteen leaves. Their tentacles and blades were inflected after
4 hrs. to a quite extraordinary degree. Next day the protoplasm
within the cells of the tentacles was found aggregated in the
most strongly marked manner. I also touched the viscid secre-
tion round the glands of several tentacles with minute drops of
the decoction on the head of a small pin, and they became well
inflected in a few minutes. The fluid proving so powerful, one
part was diluted with three of water, and drops were placed on
the discs of five leaves; and these next morning were so much
acted on that their blades were completely doubled over. We
thus see that a decoction of cabbage-leaves is nearly or quite as
potent as an infusion of raw meat.
About the same quantity of chopped cabbage-leaves and of
distilled water, as in the last experiment, were kept in a vessel
for 20 hrs. in a hot closet, but not heated to near the boiling-
point. Drops of this infusion were placed on four leaves. One
of these, after 23 hrs., was much inflected ; a second slightly; a
third had only the submarginal tentacles inflected; and the
fourth was not at all affected. The power of this infusion is
therefore very much less than that of the decoction; and it is
clear that the immersion of cabbage-leaves for an hour in water
at the boiling temperature is much more efficient in extracting
matter which excites Drosera than immersion during many
hours in warm water. Perhaps the contents of the cells are
protected (as Schiff remarks with respect to legumin) by the
walls being formed of cellulose, and that until these are rup-
tured by boiling-water, but little of the contained albuminous
matter is dissolved. We know from the strong odour of cooked
cabbage-leaves that boiling water produces some chemical
change in them, and that they are thus rendered far more
digestible and nutritious to man. It is therefore an interesting
* The leaves of young plants, and the outer leaves of mature
before the heart is formed, such plants 1°6 per cent. Watts’ ‘Dict
as were used by me, contain 2°1 of Chemistry, vol. i. p. 653.
per cent. of albuminous matter,
84 DROSERA ROTUNDIFOLIA. Cuap. V.
fact that water at this temperature extracts matter from them
which excites Drosera to an extraordinary degree.
Grasses contain far less nitrogenous matter than do peas or
cabbages. The leaves and stalks of three common kinds were
chopped and boiled for some time in distilled water. Drops
of this decoction (after having stood for 24 hrs.) were placed
on six leaves, and acted in a rather peculiar manner, of which
other instances will be given in the seventh chapter on the
salts of ammonia. After 2 hrs. 30 m. four of the leaves had
their blades greatly. inflected, but not their exterior tentacles ;
and so it was with all six leaves after 24 hrs. Two days after-
wards the blades, as well as the few submarginal tentacles which
had been inflected, all re-expanded; and much of the fluid on
their discs was by this time absorbed. It appears that the de-
coction strongly excites the glands on the disc, causing the blade
to be quickly and greatly inflected; but that the stimulus, dif-
ferently from what occurs in ordinary cases, does not spread, or
only in a feeble degree, to the exterior tentacles.
I may here add that one part of the extract of belladonna
(procured from a druggist) was dissolved in 437 of water, and
drops were placed on six leaves. Next day all six were some-
what inflected, and after 48 hrs. were completely re-expanded.
It was not the included atropine which produced this effect, for
I subsequently ascertained that it is quite powerless. I also
procured some extract of hyoscyamus from three shops, and
made infusions of the same strength as before. Of these three
infusions, only one acted on some of the leaves, which were
tried. Though druggists believe that all the albumen is pre-
cipitated in the preparation of these drugs, I cannot doubt that
some is occasionally retained ; and a trace would be sufficient
to excite the more sensitive leaves of Drosera.
Cuar. VL DIGESTION. 85
CHAPTER VI.
Tus Dicrstrve Power oF THE SECRETION oF Drosera.
The secretion rendered acid by the direct and indirect excitement of
the glands— Nature of the acid -- Digestible substances — Albu-
men, its digestion arrested by alkalies, recommences by the addi-
tion of an acid — Meat — Fibrin — Syntonin — Areglar tissue —
Cartilage — Fibro-cartilage —Bone— Enamel and dentine — Phos-
phate of lime— Fibrous basis of bone — Gelatine — Chondrin —
Milk, casein and cheese — Gluten — Legumin — Pollen — Globulin
— Hematin — Indigestible substances — Epidermic productions —
Fibro-elastic tissue — Mucin — Pepsin — Urea — Chitine — Cellu-
lose — Gun-cotton — Chlorophyll — Fat and oil — Starch — Action
of the secretion on living seeds—Summary and concluding
remarks.
As we have seen that nitrogenous fluids act very
differently on the leaves of Drosera from non-nitro-
genous fluids, and as the leaves remain clasped for a
much lenger time over various organic bodies than
over inorganic bodies, such as bits of glass, cinder,
wood, &c., it becomes an interesting inquiry, whether
they can only absorb matter already in solution, or
render it soluble,—that is, have the power of digestion.
We shall immediately see that they certainly have this
power, and that they act on_albuminous compounds in
exactly the same manner as does the gastric juice of
mammals; the digested matter being afterwards ab-
sorbed. This fact, which will be clearly proved, is a
wonderful one in the physiology of plants. I must
here state that I have been aided throughout all my
later experiments by many valuable suggestions and
assistance given me with the greatest kindness by
Dr. Burdon Sanderson.
86 DROSERA ROTUNDIFOLIA. Ouar. VL
It may be well to premise for the sake of any reader
who knows nothing about the digestion of albuminous
compounds by animals that this is effected by means
of a ferment, pepsin, together with weak hydrochloric
acid, though almost any acid will serve. Yet neither
pepsin nor an acid by itself has any such power.*
We have seen that when the glands of the disc are
excited by the contact of any object, especially of
one containing nitrogenous matter, the outer ten-
stacles and often the blade become inflected ; the leaf
being thus converted into a temporary cup or sto-
mach. At the same time the discal glands secrete
more copiously, and the secretion becomes acid.
Moreover, they transmit some influence to the glands
of the exterior tentacles, causing them to pour forth
a more copious secretion, which also becomes acid or
more acid than it was before.
As this result is an important one, I will give the
evidence. The secretion of many glands on thirty
leaves, which had not been in any way excited, was
tested with litmus paper; and the secretion of twenty-
two of these leaves did not in the least affect the colour,
whereas that of eight caused an exceedingly feeble
and sometimes doubtful tinge of red. Two other
old leaves, however, which appeared to have been in-
flected several times, acted much more decidedly on
the paper. Particles of clean glass were then placed
on five of-the leaves, cubes of albumen on six, and
bits of raw meat on three, on none of which was the
secretion at this time in the least acid. After an
interval of 24 hrs., when almost all the tentacles on
_ * It appears, however, accord- though slowly, a very minute
ing to Schiff, and contrary to the quantity of coagulated albumen.
opinion of some physiologists, Schiff, ‘Phys. de la Digestion?
that weak hydrochloric dissolves, tom. il. 1867, p. 25
Cua. VI. DIGESTION. 37
these fourteen leaves had become more or less in-
flected, I again tested the secretion, selecting glands
which had not as yet reached the centre or touched
any object, and it was now plainly acid. The degree
of acidity of the secretion varied somewhat on the
glands of the same leaf. On some leaves, a few ten-
tacles did -not, from some unknown cause, become in-
flected, as often happens; and in five instances their
secretion was found not to be in ‘the least acid;
‘whilst the secretion of the adjoining and inflected
tentacles on the same leaf was decidedly acid. With
leaves excited by particles of glass placed on the
central glands, the secretion which collects on the
disc beneath them was much more strongly acid
than that poured forth from the exterior tentacles,
which were as yet only moderately inflected. When
bits of albumen (and this is naturally alkaline), or
bits of meat were placed on the disc, the secretion
collected beneath them was likewise strongly acid.
As raw meat moistened with water is slightly acid, I
compared its action on litmus paper before it was
placed on the leaves, and afterwards when bathed in
the secretion ; and there could not be the least doubt
that the latter was very much more acid. I have
indeed tried hundreds of times the state of the secre-
tion on the discs of leaves which were inflected over
various objects, and never failed to find it acid. We
may, therefore, conclude that the secretion from un-
excited leaves, though extremely viscid, is not acid or
only slightly so, but that it becomes acid, or mach
more strongly so, after the tentacles have begun to
bend over any inorganic or organic object; and still
more strongly acid after the tentacles have remained
for some time closely clasped over any object.
T may here remind the reader that the secretion
.
88 DROSERA ROTUNDIFOLIA. Cuap. VL
appears to be to a certain extent antiseptic, as it
checks the appearance of mould and infusoria, thus
preventing for a time the discoloration and decay of
such substances as the white of an egg, cheese, &c.
It therefore acts like the gastric juice of the higher
animals, which is known to arrest putrefaction by
destroying the microzymes.
As I was anxious to learn what acid the secretion contained,
445 leaves were washed in distilled water, given me by Prof,
Frankland; but the secretion is so viscid that it is scarcely
possible to scrape or wash off the whole. The conditions
were also unfavourable, as it was late in the year and the
leaves were small. Prof. Frankland with great kindness under-
took to test the fluid thus collected. The leaves were excited
by clean particles of glass placed on them 24 hrs. previously.
No doubt much more acid would have been secreted had the
1eaves been excited by animal matter, but this would have
rendered the analysis more difficult. Prof. Frankland informs
me that the fluid contained no trace of hydrochloric, sulphuric,
tartaric, oxalic, or formic acids. This having been, ascertained,
the remainder of the fluid was evaporated nearly to dryness, and
acidified with sulphuric acid; it then evolved volatile acid
vapour, which was condensed and digested with carbonate of
silver. “The weight of the silver salt thus produced was only
‘87 gr., much too small a quantity for the accurate determina-
tion of the molecular weight of the acid. The number obtained,
however, corresponded nearly with that of propionic acid; and
I believe that this, or a mixture of acetic and butyric acids, were
present in the liquid. The acid doubtless belongs to the acetic
or fatty series.”
Prof. Frankland, as well as his assistant, observed (and this
is an important fact) that the fluid, “ when aciditied with sul-
phuric acid, emitted a powerful odour like that of pepsin.”
The leaves from which the secretion had been washed were
also sent to Prof. Frankland; they. were macerated for some
hours, then acidified with sulphuric acid and distilled, but no
acid passed over. Therefore the acid which fresh leaves con-
tain, as shown by their discolouring litmus paper when crushed,
must be of a different nature from that present in the secretion.
Nor was any odour of pepsin emitted by them.
Crap. VI. DIGESTION. 89
Although it has long been known that pepsin with acetic
acid has the power of digesting albuminous compounds,
it appeared advisable to ascertain whether acetic acid could
be replaced, without the loss of digestive power, by tho
allied acids which are believed to occur in the secretion
of Drosera, namely, propionic, butyric, or valerianic. Dr.
Burdon Sanderson was so kind as to make for me the follow-
ing experiments, the results of which are valuable, indepen-
dently of the present inquiry. Prof. Frankland supplied the
acids.
“1. The purpose of the following experiments was to deter-
mine the digestive activity of liquids containing pepsin, when
acidulated with certain volatile acids belonging to the acetic
series, in comparison with liquids acidulated with hydrochloric
acid, in proportion similar to that in which it exists in gastric
juice.
«2. It has been determined empirically that the best results
are obtained in artificial digestion when a liquid containing two
per thousand of hydrochloric acid gas by weight is used. This
corresponds to about 6:25 cubic centimetres per litre of ordinary
strong hydrochloric acid. The quantities of propionic, butyric,
and valerianic acids respectively which are required to neutralise
as much base as 6°25 cubic centimetres of HCl, are in grammes
4:04 of propionic acid, 4°82 of butyric acid, and 5°68 of valerianic
acid. It was therefore judged expedient, in comparing the
digestive powers of these acids with that of hydrochloric acid, to
use them in these proportions.
“3. Five hundred cub. cent. of a liquid containing about
8 cub. cent. of a glycerine extract of the mucous membrane .of
the stomach of a dog killed during digestion having been pre-
pared, 10 cub. cent. of it were evaporated and dried at 110°.
This quantity yielded 0:0031 of residue.
“4. Of this liquid four quantities were taken which were
severally acidulated with hydrochloric, propivnic, butyric, and
valerianic acids, in the proportions above indicated. Each
liquid was then placed in a tube, which was allowed to float in
a water bath, containing a thermometer which indicated a
temperature of 388° to 40° Cent. Into each, a quantity of un-
yoiled fibrin was introduced, and the whole allowed to stand
for four hours, the temperature being maintained during the
whole time, and care being taken that each contained through-
out an excess of fibrin. At the end of the period each liquid
was filtered. Of the filtrate, which of course contained as
much of the fibrin as had been digested during the four hours,
9O DROSERA ROTUNDIFOLIA. Car. Vi.
10 cub. cent. were measured out and evaporated, and dried at
110° as before. The residues were respectively—
“Tn the liquid containing hydrochloric acid 0:4079
3 3s propionic acid -0-0601
butyric acid 01468
valerianic acid 0°1254
a” a
” a”
“Hence, deducting from each of these the above-mentioned
residue, left when the digestive liquid itself was evaporated,
viz. 0'0031, we have,
“For propionic acid .. .. as .. 0:0570
» butyricacid .. .. ae .. 01487
» Valerianic acid.. .. we .» 071228
as compared with 0°4048 for hydrochloric acid; these several
numbers expressing the quantities of fibrin by weight digested
in presence of equivalent quantities of the respective acids
under identical conditions.
“The results of the experiment may be stated thus :—If 100
represent the digestive power of a liquid containing pepsin with
the usual proportion of hydrochloric acid, 14:0, 35-4, and 30-2,
will represent respectively the digestive powers of the three
acids under investigation.
“5. In a second experiment in which the procedure was in
every respect the same, excepting that all the tubes were
plunged into the same water-bath, and the residues dried at
115° C., the results were as follows :—
* Quantity of fibrin dissolved in four hours by 10 cub. cent.
of the liquid—
“Propionic acid .. 2: « 0:0563
Butyric acid... oe - 00835
Valerianic acid .. rn « 0-0615
“The quantity digested by a similar liquid containing
hydrochloric acid was 0°3376. Hence, taking this as 100, the
following numbers represent the relative quantities digested
by the other acids:
4 Propionic acid .. aie « 165
Butyricacid .. be se 24-7
Valerianic acid .. sa zs 161
6. A third experiment of the same kind gave:
Cuap. VI. DIGESTION, 91
“Quantity of fibrin digested in four hours by 10 cub. cent,
of the liquid: :
“ Hydrochloric acid we - 02915
Propionic acid .. as . 071490
Butyricacid ., a « 0°1044
Valerianic acid .. ee .-, 0°0520
“ Comparing, as before, the three last numbers with the first
taken as 100, the digestive power of propionic acid is repre-
sented by 168; that of butyric acid by 35:8; and that of
valerianic by 17°8.
“The mean of these three sets of observations (hydrochloric
acid being taken as 100) gives for
“ Propionic acid .. 2 x 15:8
Butyric acid... bes gee 32:0
Valerianic acid .. <3 Pe 21-4
“7, A further experiment was made to ascertain whether the
digestive activity of butyric acid (which was selected as being
apparently the most efficacious) was relatively greater at ordinary
temperatures than at the temperature of the body. It was
found that whereas 10 cub. cent. of a liquid containing the ordi-
nary proportion of hydrochloric acid digested 0:1811 gramme,
a similar liquid prepared with butyric acid digested 0°0455
gramme of fibrin.
“ Hence, taking the quantities digested with hydrochloric acid
at the temperature of the body as 100, we have the digestive
power of hydrochloric acid at the temperature of 16° to 18°
Cent. represented by 44:9; that of butyric acid at the same
temperature being 15°6.”
We here see that at the lower of these two temperatures,
hydrochloric acid with pepsin digests, within the same time,
rather less than half the quantity of fibrin compared with
what it digests at the higher temperature; and the power of
butyric acid is reduced in the same proportion under similar
conditions and temperatures. We have also seen that butyric
acid, which is much more efficacious than propionic or vale-
rianic acids, digests with pepsin at the higher temperature less
than a third of the fibrin which is digested at the same tempera-
ture by hydrochloric acid.
92 DROSERA ROTUNDIFOLIA. Cuar. VL
I will now give in detail my experiments on the
digestive power of the secretion of Drosera, dividing
the substances tried into two series, namely those
which are digested more or less completely, and those
which are not digested. We shall presently see that
all these substances are acted on by the gastric juice
of the higher animals in the same manner. I beg
leave to call attention to the experiments under the
head albumen, showing that the secretion loses its
power when neutralised by an alkali, and recovers it
when an acid is added.
Substances which are completely or partially digested by
the Secretion of Drosera.
' Albumen.—After having tried various substances,
Dr. Burdon Sanderson suggested to me the use of cubes
of coagulated albumen or hard-boiled egg. I may pre-
mise that five cubes of the same size as those used in
the following experiments were placed for the sake of
comparison at the same time on wet moss close to the
plants of Drosera. The weather was hot, and after four
days some of the cubes were discoloured and mouldy,
with their angles a little rounded; but they were not
surrounded by a zone of transparent fluid as in the
case of those undergoing digestion. Other cubes
retained their angles and white colour. After eight
days all were somewhat reduced in size, discoloured,
with their angles much rounded. Nevertheless in
four out of the five specimens, the central parts were
still white and opaque. So that their state differed
widely, as we shall see, from that of the cubes sub-
jected to the action of the secretion.
Experiment 1.— Rather large cubes of albumen were first
tried the tentacles were well inflected in 24 hrs.; after an
Onap, VI. DIGESTION. 93
additional day the angles of the cubes were dissolved and
rounded ;* but the cubes were too large, so that the leaves
were injured, and after seven days one died and the others
were dying. Albumen which has been kept for four or five
days, and which, it may be presumed, has begun to decay
slightly, seems to act more quickly than freshly boiled eggs.
As the latter were generally used, I often moistened them
with a little saliva, to make the tentacles close more
quickly.
Heperiment 2.—A cube of J; of an inch (ie. with each side
js of an inch, or 2°54 mm., in length) was placed on a leaf, and
after 50 hrs. it was converted into a sphere about §; of an inch
(1905 mm.) in diameter, surrounded by perfectly transparent
fluid. After ten days the leaf re-expanded, but there was still
left on the disc a minute bit of albumen now rendered trans-
parent. More albumen had been given to this leaf than could
be dissolved or digested.
Experiment 38.—Two cubes of albumen of 3 of an inch
(1:27 mm.) were placed on two leaves. After 46 hrs. every
atom of one was dissolved, and most of the liquefied matter
was absorbed, the fluid which remained being in this, as in all
other cases, very acid and viscid. The other cube was acted
on at a rather slower rate.
Experiment 4.—Two cubes of albumen of the same size as
the last were placed on two leaves, and were converted in
50 hrs. into two large drops of transparent fluid; but when
these were removed from beneath the inflected tentacles, and
viewed by reflected light under the microscope, fine streaks of
white opaque matter could be seen in the one, and traces of
similar streaks in the other. ‘lhe drops were replaced on the
leaves, which re-expanded after 10 days; and now nothing
was left except a very little transparent acid fluid.
Experiment 5.—This experiment was slightly varied, so that
the albumen might be more quickly exposed to the action of the
secretion. Two cubes, each of about J; of an inch (635 mm.),
were placed on the same leaf, and two similar cubes on another
* In all my numerous experi-
ments on the digestion of cubes
of albumea, the angles and edges
were invariably first rounded.
Now, Schiff states (‘Lecons
phys. de la Digestion, vol. ii.
1867, p. 149) that this is charac-
*
teristic of the digestion of albu-
men by the gastric juice of ani-
mals. On the other hand, he
remarks, “les dissolutions, en
chimie, ont lieu sur toute la sur-
face des corps «n contact aveo
Yagent dissolvant.”
94 DROSERA ROTUNDIFOLIA. Cuap. VI
leaf. These were examined after 21 hrs. 30 m., and all four
were found rounded. After 46 hrs. the two cubes on the one
leaf were completely liquefied, the fluid being perfectly trans-
parent; on the other leaf some opaque white streaks could
still be seen in the midst of the fluid. After 72 hrs. these
streaks disappeared, but there was still a little viscid fluid
left on the disc; whereas it was almost all absorbed on the
first leaf. Both leaves were now beginning to re-expand.
The best and almost sole test of the presence of
some ferment analogous to pepsin in the secretion
appeared to be to neutralise the acid of the secretion
with an alkali, and to observe whether the process
of digestion ceased; and then to add a little acid
and observe whether the process recommenced. This
was done, and, as we shall see, with success, but it
was necessary first to try two control experiments ;
namely, whether the addition of minute drops of
water of the same size as those of the dissolved
alkalies to be used would stop the process of diges-
tion; and, secondly, whether minute drops of weak
hydrochloric acid, of the some strength and size as
those to be used, would injure the leaves. The
two following experiments were therefore tried :—
Experiment 6.—Small cubes of albumen were put on three
leaves, and minute drops of distilled water on the head of a pin
were added two or three times daily. These did not in the
least delay the process; for, after 48 hrs., the cubes were com-
pletely dissolved on all three leaves. On the third day the
leaves began to re-expand, and on the fourth day all the fluid
was absorbed.
Experiment 7—Small cubes of albumen were put on two
leaves, and minute drops of hydrochloric acid, of the strength of
one part to 437 of water, were added two or three times. This
did not in the least delay, but seemed rather to hasten, the
process of digestion ; for every trace of the albumen disappeared
in 24 hrs. 830 m. After three days the leaves partially re-
expanded, and by this time almost all the viscid fluid on their
discs was absorbed. It is almost superfluous to state that
Cuar. VI. DIGESTION. 95
cubes of albumen of the same size as those above used, left for
seven days ina little hydrochloric acid of the above strength,
retained all their angles as perfect as ever.
Experiment 8.—Cubes of albumen (of 4 of an inch, or 2°54
mm.) were placed on five leaves, and minute drops of a solu-
tion of one part of carbonate of soda to 487 of water were added
at intervals to three of them, and drops of carbonate of potash
of the same strength to the other two. The drops were given
on the head of a rather large pin, and | ascertained that
each was equal to about ~, of a minim (-0059 ml.), so that _
cach contained only gds5 of a grain (0185 mg.) of the alkali.
This was not sufficient, for after 46 hrs. all five cubes were
dissolved. yi
Eaperiment 9.—The last experiment was repeated on four
leaves, with this difference, that drops of the same solution of
carbonate of soda were added rather oftener, as often as the
secretion became acid, so that it was much more effectually
neutralised. And now after 24 hrs. the angles of three of
the cubes were not in the least rounded, those of the fourth
being so in a very slight degree. Drops of extremely weak
hydrochloric acid (viz. one part to 847 of water) were then ,
added, just enough to neutralise the alkali which was still
present; and now digestion immediately recommenced, so that
after 23 hrs. 30 m. three of the cubes were completely dis-
solved, whilst the fourth was converted into a minute sphere,
surrounded by transparent fluid; and this sphere next day
disappeared.
Kaperiment 10.—Stronger solutions of carbonate of soda and
of potash were next used, viz. one part to 109 of water; and as
the same-sized drops were given as before, each drop contained
robo Of a grain (0539 mg.) of either salt. Two cubes of albu-
men (each about 2, of an inch, or ‘635 mm.) were placed on the
same leaf, and two on another. Each leaf received, as soon as
the secretion became slightly acid (and this occurred four times
within 24 hrs.), drops either of the soda or potash, and the acid
was thus effectually neutralised. The experiment now succeeded
perfectly, for after 22 hrs. the angles of the cubes were as sharp
as they were at first, and we know from experiment 5 that such
small cubes would have been completely rounded within this
time by the secretion in its natural state. Some of the fluid was
now removed witb blotting-paper from the discs of the leaves,
and minute drops of hydrochloric acid of the strength of one
part to 200 of water was added. Acid of this greater strength
‘vas used as the solutions of the alkalies were stronger. The
96 ‘ DROSERA ROTUNDIFOLIA. Cuap. VI.
process of digestion now commenced, so that within 48 hrs. from
the time when the acid was given the four cubes were not only
completely dissolved, but much of the liquefied albumen was
absorbed.
Experiment 11—Two cubes of albumen (25 of an inch, or
‘635 mm.) were placed on two leaves, and were treated with
alkalies as inthe last experiment, and with the same result;
for after 22 hrs. they had their angles perfectly sharp, showing
that the digestive process had been completely arrested. I then
wished to ascertain what would be the effect of using stronger
hydrochloric acid ; so I added minute drops of the strength of
1 per cent. This proved rather too strong, for after 48 hrs.
from the time when the acid was added one cube was still
almost perfect, and the other only very slightly rounded, and
both were stained slightly pink. This latter fact shows that the
leaves were injured,* for during the normal process of digestion
the albumen is not thus coloured, and we can thus understand
why the cubes were not dissolved.
From these experiments we clearly see that the
secretion has the power of dissolving albumen, and
we further see that if an alkali is added, the process of
digestion is stopped, but immediately recommences as
soon as the alkali is neutralised by weak hydrochloric
acid. Even if J had tried no other experiments than
these, they would have almost sufficed to prove that
the glands of Drosera secrete some ferment analo-
gous to pepsin, which in presence of an acid gives
to the secretion its power of dissolving albuminous
compounds.
Splinters of clean glass were scattered on a large
number of leaves, and these became moderately in-
flected. They were cut off and divided into three
lots; two of them, after being left for some time in
a little distilled water, were strained, and some dis-
* Sachs remarks (‘Traité de agents, allow all their colouring
Bot.’ 1874, p. 774), that cells matter to escape into the sur
which are killed by freezing, by rounding water.
too great heat, or by chemical
Crap, VI. DIGESTION. 97
coloured, viscid, slightly acid fluid was thus obtained.
The third lot was well soaked in a few drops of
glycerine, which is well known to dissolve pepsin.
Cubes of albumen (75 of an inch) were now placed
in the three fluids in ‘watch-glasses, some of which
were kept for several days at about 90° Fahr.
( 32°2 Cent.), and others at the temperature of my
room; but none of the cubes were dissolved, the
angles remaining as sharp as ever. This fact pro-
bably indicates that the ferment is not secreted until
the glands are excited by the absorption of a minute
quantity of already soluble animal matter,—a con-
clusion which is supported by what we shall hereafter
see with respect to Dionza. Dr. Hooker likewise found
that, although the fluid within the pitchers of Ne-
penthes possesses extraordinary power of digestion, yet
when removed from the pitchers before they have
been excited and placed in a vessel, it has no such
power, although it is already acid; and we can
account for this fact only on the supposition that the
proper ferment is not secreted until some exciting
matter is absorbed.
On three other occasions eight leaves were strongly
excited with albumen moistened with saliva; they
were then cut off, and allowed to soak for several
hours or for a whole. day in a few drops of glycerine.
Some of this extract was added to a little hydro-
chloric acid of various strengths (generally one to
400 of water), and minute cubes of albumen were
placed in the mixture.* In two of these trials the
cubes were not in the least acted on; but in the third
* Aga control experiment bits the albumen, as might have been
of albumen were placed in the expected, was not in the least
same glycerine with hydrochloric affected after two days.
acid of the same strength; and
98 DROSERA ROTUNDIFOLIA. Cuar. V1
the experiment was successful. For in a vessel con-
taining two cubes, both were reduced in size in 3 hrs. ;
and after 24 hrs. mere streaks of undissolved albu-
men were left. In a second vessel, containing two
minute ragged bits of albumen, both were likewise
reduced in size in 3 hrs., and after 24 hrs. completely
disappeared. I then added a little weak hydro-
chlorie acid to both vessels, and placed fresh cubes
of albumen in them; but these were not acted on.
This latter fact is intelligible according to the high
authority of Schiff,* who has demonstrated, as he
believes, in opposition to the view held by some
physiologists, that a certain small amount of pepsin
is destroyed during the act of digestion. So that if
my solution contained, as is probable, an extremely
small amount of the ferment, this would have been
consumed by the dissolution of the cubes of albumen
first given; none being left when the hydrochloric
acid was added. The destruction of the ferment
during the process of digestion, or its absorption after
the albumen had been converted into a peptone, will
also account for only one out of the three latter sets
of experiments -having been successful.
Digestion of Roast Meat—Cubes of about 25 of an
inch (1:27 mm.) of. moderately roasted meat were
placed on five leaves which became in 12 hrs. closely
inflected. After 48 hrs. I gently opened one leaf, and
the meat now consisted of a minute central sphere,
partially digested and surrounded by a thick envelope
of transparent viscid fluid. The whole, without being
much disturbed, was zemoved and placed under the
microscope. In the central part the transverse stria
on the muscular fibres were quite distinct; and it was
* “Lecons pbvs. de la Digestion,’ 1867, tom. ii. pp. 114-126.
Onar. VL DIGESTION. 99
interesting to observe how gradually they disappeared,
when the same fibre was traced into the surrounding
fluid. They disappeared by the striae being replaced
by transverse lines formed of excessively minute dark
points, which towards the exterior could be seen only
under a very high power; and ultimately these points
were lost. When I made these observations, I had
not read Schiff’s account* of the digestion of meat
by gastric juice, and I did not understand the mean-
ing of the dark points. But this is explained in the
following statement, and we further see how closely
similar is the process of digestion by gastric juice and
by the secretion of Drosera.
“On a dit que le suc gastrique faisait perdre 4 la fibre muscu-
‘laire ses strics transversales. Ainsi énoncée, cette proposition
pourrait donner lieu 4 une équivoque, car ce qui se perd, ce n’est
que Vuspect extérieur de la striature et non les éléments anato-
miques qui la composent. On sait que les stries qui donnent un
aspect si caractéristique a la fibre musculaire, sont le résultat de
la juxtaposition et du parallélisme des corpuscules élémentaires,
placés, & distances égales, dans V’intérieur des fibrilles contigués.
Or, dés que le tissu connectif qui relie entre elles les fibrilles
élémentaires vient & se gonfler et & se dissoudre, et que les
fibrilles elles-mémes se dissocient, ce parallélisme est détruit et
avec lui l’aspect, le phénomeéne optique des stries. Si, aprés la
désagrégation des fibres, on examine au microscope les fibrilles
élémentaires, on distingue encore trés-nettement & leur intérieur
les corpuscules, et on continue & les voir, de plus en plus pales,
jusqu’au moment ot les fibrilles elles-mémes se liquéfient et dis-
paraissent dans le suc gastrique. Ce qui constitue la striature,
& proprement parler, n’est done pas détruit, avant Ja liqué-
faction de'la fibre charnue elle-méme.”
In the viscid fluid surrounding the central sphere of
undigested meat there were globules of fat and little
bits of fibro-elastic tissue; neither of which were in
* ‘Lecons phys. de la Digestion,’ tom. it. p. 145.
100 * DROSERA ROTUNDIFOLIA. Cuar, VI
the least digested. There were also little free paral-
lelograms of yellowish, highly translucent matter.
Schiff, in speaking of the digestion of meat by gastric
juice, alludes to such parallelograms, and says :—
“ Le gonflement par lequel commence la digestion de la viande,
résulte de l’action du suc gastrique acide sur le tissu connectif
qui se dissout d’abord, et qui, par sa liquéfaction, désagrége les
fibrilles. Celles-ci se dissolvent ensuite en grande partie, mais,
avant de passer 4 l’état liquide, elles tendent & se briser en
petits fragments transversaux. Les ‘sarcous clements’ de
Bowman, qui ne sont autre chose que les produits de cette
division transversale des fibrilles élémentaires, peuvent étre
préparés et isolés 4 Vaide du suc gastrique, pourvu qu’on
v’attend pas jusqu’a la liquéfaction compléte du muscle.”
After an interval of 72 hrs., from the time when
the five cubes were placed on the leaves, I opened the
four remaining ones. On two nothing could be seen
but little masses of transparent viscid fluid; but
when these were examined under a high power,
fat-globules, bits of fibro-elastic tissue, and some few
parallelograms of sarcous matter, could be distin-
guished, but not a vestige of transverse striae. On the
other two leaves there were minute spheres of only
partially digested meat in the centre of much trans-
parent fluid.
Fibrin.—Bits of fibrin were left in water during
four days, whilst the following experiments were
tried, but they were not in the least acted on. The
fibrin which I first used was not pure, and included
dark particles: it had either not been well prepared
or had subsequently undergone some change. Thin
portions, about +; of an inch square, were placed
on several leaves, and though the fibrin was soon
liquefied, the whole was never dissolved. Smaller
particles were then placed on four leaves, and minute
Cuar. VI. DIGESTION. 101
drops of hydrochloric acid (one part to 437 of
water) were added; this seemed to hasten the process
of digestion, for on one leaf all was liquefied and
absorbed after 20 hrs.; but on the three other leaves
some undissolved residue was left after 48 hrs. It
is remarkable that in all the above and following
experiments, as well as when much larger bits of
fibrin were used, the leaves were very little excited;
and it was sometimes necessary to add a little saliva
to induce complete inflection. The leaves, moreover,
began to re-expand after only 48 hrs., whereas they
would have remained inflected for a much longer
time had insects, meat, cartilage, albumen, &c., been
placed on them.
I then tried some pure white fibrin, sent me by Dr.
Burdon Sanderson.
Experiment 1.—Two particles, barely 35 of an inch (1:27 mm.)
square, were placed on opposite sides of the same leaf. One of
these did not excite the surrounding tentacles, and the gland
on which it rested soon dried. The other particle caused a few
of the short adjoining tentacles to be inflected, the more distant
-ones not being affected. After 24 hrs. both were almost, and
after 72 hrs. completely, dissolved.
Experiment 2.—The same experiment with the same result,
only one of the two bits of fibrin exciting the short surround-
ing tentacles. This bit was so slowly acted on that after a
day I pushed it on to some fresh glands. In three days from
the time when it was first placed on the leaf it was completely
dissolved.
Experiment 3.—Bits of fibrin of about the same size as before
were placed on the discs of two leaves; these caused very little
inflection in 23 hrs., but after 48 hrs. both were well clasped by
the surrounding short tentacles, and after an additional 24 hrs.
were completely dissolved. On the disc of one of these leaves
much clear acid fluid was left.
Experiment 4.—Similar bits of fibrin were placed on the discs
of two leaves; as after 2 hrs. the glands seemed rather dry,
they were freely moistened with saliva; this soon caused
strong inflection both of the tentacles and blades, with copious
102 DROSERA ROTUNDIFOLIA. Ouar. VI
secretion from the glands. In 18 hrs. the fibrin was com-
pletely liquefied, but undigested atoms still floated in the
liquid; these, however, disappeared in under twu additional
days.
From these experiments it is clear that the secre-
tion completely dissolves pure fibrin. The rate of
dissolution is rather slow; but this depends merely
on this substance not exciting the leaves sufficiently,
so that only the immediately adjoining tentacles are
inflected, and the supply of secretion is small.
Syntonin.—This substance, extracted from muscle,
was kindly prepared for me by Dr. Moore. Very
differently from fibrin, it acts quickly and energetic-
ally. Small portions placed on the discs of three
leaves caused their tentacles and blades to be strongly
inflected within 8 hrs.; but no further observations
were made. It is probably due to the presence of
this substance that raw mcat is too powerful a stimu-
lant, often injuring or even killing the leaves.
Areolar Tissue—Small portions of this tissue from a
sheep were placed on the discs of three leaves; these
became moderately well inflected in 24 hrs., but began
to re-expand after 48 hrs., and were fully re-expanded
in 72 hrs., always reckoning from the time when the
bits were first given. This substance, therefore, like
fibrin, excites the leaves for only a short time. The
residue left on the leaves, after they were fully re-
expanded, was examined under a high power and
found much altered, but, owing to the presence of a
quantity of elastic tissue, which is never acted on,
could hardly be said to be in a liquefied condition.
Some areolar tissue free from elastic tissue was next
procured from the visceral cavity of a toad, and
moderately sized, as well as very small, bits were
placed on five leaves. After 24 hrs. two of the bits
Cuap. VI. DIGESTION. 103
were completely liquefied; two others were rendered
transparent, but not quite liquefied; whilst the fifth
was but little affected. Several glands on the three
latter leaves were now moistened with a little saliva,
which soon caused much inflection and secretion,
with the result that in the course of 12 additional
hrs. one leaf alone showed a remnant of undigested
tissue. On the discs of the four other leaves (to one
of which a rather large bit had been given) nothing
was left except some transparent viscid fluid. I may
add that some of this tissue included points of black
pigment, and these were not at all affected. As a
control experiment, small portions of this tissue were
left in water and on wet moss for the same length of
time, and remained white and opaque. From these
facts it is clear that areolar tissue is easily and
quickly digested by the secretion; but that it does
not greatly excite the leaves.
Cartilage—Three cubes (,'5 of an inch or 1:27 mm.)
of white, translucent, extremely tough cartilage were .
cut from the end of a slightly roasted leg-bone of a
sheep. These were placed on three leaves, borne by
poor, small plants in my greenhouse during Novem-
ber; and it seemed in the highest degree improbable
that so hard a substance would be digested under
such unfavourable circumstances. Nevertheless, after
48 hrs., the cubes were largely dissolved and con-
verted into minute spheres, surrounded by trans-
parent, very acid fluid. Two of these spheres were
completely softened to their centres; whilst the third
still contained a very small irregularly shaped core
of solid cartilage. Their surfaces were seen under
the microscope to be curiously marked by prominent
ridges, showing that the cartilage had been un-
equally corroded by the secretion. I need hardly
8
104 DROSERA ROTUNDIFOLIA. Cuap. VI
say that cubes of the same cartilage, kept in water
for the same length of time, were not in the least
affected.
During a more favourable season, moderately sized
bits of the skinned ear of a cat, which includes
cartilage, areolar and elastic tissue, were placed on
three leaves. Some of the glands were touched with
saliva, which caused prompt inflection. Two of the
leaves began to re-expand after three days, and the
third on the fifth day. The fluid residue left on
their dises was now examined, and consisted in one
case of perfectly transparent, viscid matter; in the
other two cases, it contained some elastic tissue and
apparently remnants of half digested areolar tissue.
Fibro-cartilage (from between the vertebre of the
tail of a sheep). Moderately sized and small bits
(the latter about ~, of an inch) were placed on nine
leaves. Some of these were well and some very little
inflected. In the latter case the bits were dragged
over the discs, so that they were well bedaubed
with the secretion, and many glands thus irritated.
All the leaves re-expanded after only two days; so
that they were but little excited by this substance.
The bits were not liquefied, but were certainly in an
altered condition, being swollen, much more trans-
parent, and so tender as to disintegrate very easily.
My son Francis prepared some artificial gastric juice,
which was proved efficient by quickly dissolving
fibrin, and suspended portions of the fibro-cartilage
in it. These swelled and became hyaline, exactly like
those exposed to the secretion of Drosera, bit were
not dissolved. This result surprised me much, as
two physiologists were of opinion that fibro-cartilage
would be easily digested by gastric juice. I there-
fore asked Dr. Klein to examine the specimens; and
onap, VL DIGESTION. 105
he reports that the two which had been subjected to
- artificial gastric juice were “in that state of diges-
tion in which we find connective tissue when treated
with an acid, viz. swollen, more or less hyaline, the
fibrillar bundles having become homogeneous and lost
their fibrillar structure.” In the specimens which had
been left on the leaves of Drosera, until they re-
expanded, “parts were altered, though only slightly
so, in the same manner as those subjected to the
gastric juice, as they had become more transparent,
almost hyaline, with the fibrillation of the bundles
indistinct.” TF ibro-cartilage is therefore acted on in
nearly the same manner by gastric juice and by the
secretion of Drosera.
Bone.— Small smooth bits of the dried hyoidal
bone of a fowl moistened with saliva were placed on
two leaves, and a similarly moistened splinter of an
extremely hard, broiled mutton-chop bone on a third
leaf. These leaves soon became strongly inflected,
and remained so for an unusual length of time;
namely, one leaf for ten and the other two for nine
days. The bits of bone were surrounded all the time
by acid secretion. When examined under a weak
power, they were found quite softened, so that they
were readily penetrated by a blunt needle, torn into
fibres, or compressed. Dr. Klein was so kind as to
make sections of both bones and examine them. He
informs me that both presented the normal appearance
of decalcified bone, with traces of the earthy salts
occasionally left. The corpuscles with their processes
were very distinct in most parts; but in some parts,
especially near the periphery of the hyoidal bone,
none could be seen. , Other parts again appeared
amorphous, with even the longitudinal striation of
bone not distinguishable. This amorphous structure
106 DROSERA ROTUNDIFOLIA. Cuar, V1.
as Dr. Klein thinks, may be the result either of the
incipient digestion of the fibrous basis or of all the
animal matter having been removed, the corpuscles
being thus rendered invisible. A hard, brittle, yellow-
ish substance occupied the position of the medulla
in the fragments of the hyoidal bone.
As the angles and little projections of the fibrous
basis were not in the least rounded or corroded, two of
the bits were placed on fresh leaves. These by the
next morning were closely inflected, and remained
so,—the one for six and the other for seven days,—
therefore for not so long a time as on the first occasion,
but for a much longer time than ever occurs with
leaves inflected over inorganic or even over many
organic bodies. The secretion during the whole time
coloured litmus paper of a bright red; but this may
have been due to the presence of the acid super-
phosphate of lime. When the leaves re-expanded, the
angles and projections of the fibrous basis were as
sharp as ever. I therefore concluded, falsely as we
shall presently see, that the secretion cannot touch
the fibrous basis of bone. The more probable expla-
nation is that the acid was all consumed in decom.
posing the phosphate of lime which still remained;
so that mone was left in a free state to act in con-
junction with the ferment on the fibrous basis.
Enamel and Dentine—As the secretion decalcified
ordinary bone, I determined to try whether it would
act on enamel and dentine, but did not expect that it
would succeed with so hard a substance as enamel.
Dr. Klein gave me some thin transverse slices of
the canine tooth of a dog; small angular fragments
of which were placed on four leaves; and these were
examined each succeeding day at the same hour. The
results are, I think, worth giving in detail.
Ounar. V1. DIGESTION. 107
Experiment 1—May Ist, fragment placed on leaf; 3rd, ten-
tacles but little inflected, so a little saliva was added; 6th, as
the tentacles were not strongly inflected, the fragment was
transferred to another leaf, which acted at first slowly, but by
the 9th closely embraced it. On the llth this second leaf
began to re-expand; the fragment was manifestly softened, and
Dr. Klein reports, “a great deal of enamel and the greater
part of the dentine decalcified.”
Lcperiment 2.—May 1st, fragment placed on leaf; 2nd, ten-
tacles fairly well inflected, with much secretion on the disc, and
remained so until the 7th, when the leaf re-expanded. The
fragment was now transferred to a fresh leaf, which next day
(8th) was inflected in the strongest manner, and thus remained
until the 11th, when it re-expanded. Dr. Klein reports, “a great
deal of enamel and the greater part of the dentine decalcified.”
Experiment 3—May lst, fragment moistened with saliva and
placed on a leaf, which remained well inflected until 5th, when
it re-expanded. The enamel was not at all, and the dentine
only slightly, softened. The fragment was now transferred to a
fresh leaf, which next morning (6th) was strongly inflected, and
remained so until the 11th. The enamel and dentine both now
somewhat softened; and Dr. Klein reports, “less than half the
enamel, but the greater part of the dentine, decalcified.”
Eaperiment 4.—May lst, a minute and thin bit of dentine,
moistened with saliva, was placed on a leaf, which was soon
inflected, and re-expanded on the 5th. The dentine had become
as flexible as thin paper. It was then transferred to a fresh leaf,
which next morning (6th) was strongly inflected, and reopened
on the 10th. The decalcified dentine was now so tender that it
was torn into shreds merely by the force of the re-expanding
tentacles.
From these experiments it appears that enamel is
attacked by the secretion with more difficulty than
dentine, as might have been expected from its ex-
treme hardness; and both with more difficulty than
ordinary bone. After the process of dissolution has
once commenced, it is carried on with greater ease ;
this may be inferred from the leaves, to which the
fragments were transferred, becoming in all four cases
strongly inflected in the course of a single day ; whereas
the first set of leaves acted much less quickly and
108 DROSERA ROTUNDIFOLIA, Cuap. VI
energetically. The angles or projections of the fibrous
basis of the enamel and dentine (except, perhaps, in
No. 4, which could not be well observed) were not in
the least rounded; and Dr. Klein remarks that their
microscopical structure was not altered. But this
could not have been expected, as the decalcification
was not complete in the three specimens which were
carefully examined.
Fibrous Basis of Bone.—I at first concluded, as
already stated, that the secretion could not digest this
substance. I therefore asked Dr. Burdon Sanderson
to try bone, enamel, and dentine, in artificial gastric
juice, and he found that they were after a considerable
time completely dissolved. Dr. Klein examined some
of the small lamelle, into which part of the skull of a
cat became broken up after about a week’s immersion
in the fluid, and he found that towards the edges the
“matrix appeared rarified, thus producing the appear-
ance as if the canaliculi of the bone-corpuscles had
become larger. Otherwise the corpuscles and their
canaliculi were very distinct.” So that with bone
subjected to artificial gastric juice complete de-
calcification precedes the dissolution of the fibrous
basis. Dr. Burdon Sanderson suggested to me that
the failure of Drosera to digest the fibrous basis of
bone, enamel, and dentine, might be due to the acid
being consumed in the decomposition of the earthy
salts, so that there was none left for the work of
digestion. Accordingly, my son thoroughly decal-
cified the bone of a sheep with weak hydrochloric
acid; and seven minute fragments of the fibrous
basis were placed on so many leaves, four of the
fragments being first damped with saliva to aid
prompt inflection. All seven leaves became inflected,
but only very moderately, in the course of a day.
Omar, VL DIGESTION. 109
They quickly began to re-expand; five of them on
the second day, and the other two on the third day.
On all seven leaves the fibrous tissue was converted
into perfectly transparent, viscid, more or less lique-
fied little masses. In the middle, however, of one,
my son saw under a high power a few corpuscles,
with traces of fibrillation in the surrounding trans-
parent matter. From these facts it is clear that the
leaves are very little excited by the fibrous basis of
bone, but that the secretion easily and quickly lique-
fies it, if thoroughly decalcified. The glands which
had remained in contact for two or three days with
the viscid masses were not discoloured, and appa-
rently had absorbed little of the liquefied tissue,
or had been little affected by it.
Phosphate of Lime—As we have seen that the ten-
tacles of the first set of leaves remained clasped for
nine or ten days over minute fragments of bone, and
the tentacles of the second set for six or seven days
over the same fragments, I was led to suppose that
it was the phosphate of lime, and not any included
animal matter, which caused such long continued in-
flection. It is at least certain from what has just been
shown that this cannot have been due to the presence
of the fibrous basis. With enamel and dentine
(the former of which contains only 4 per cent. of
organic matter) the tentacles of two successive sets
of leaves remained inflected altogether for eleven
days. In order to test my belief in the potency of
phosphate of lime, I procured some from Prof. Frank-
land absolutely free of animal matter and of any acid.
A small quantity moistened with water was placed
on the discs of two leaves. One of these was only
slightly affected ; the other remained closely inflected
for ten days, when.a few of the tentacles began te
110 DROSERA ROTUNDIFOLIA. Cuar. VL
re-expand, the rest being much injured or killed. I
repeated the experiment, but moistened the phosphate
with saliva to insure prompt inflection ; one leaf re-
mained inflected for six days (the little saliva used
would not have acted for nearly so long a time) and
then died; the other leaf tried to re-expand on the
sixth day, but after nine days failed to do so, and
likewise died. Although the quantity of phosphate
given to the above four leaves was extremely small,
much was left in every case undissolved. A larger
quantity wetted with water was next placed on the
discs of three leaves; and these became most strongly
inflected in the course of 24 hrs. They never re-
expanded; on the fourth day they looked sickly,
and on the sixth were almost dead. Large drops
of not very viscid fluid hung from their edges during
the six days. This fluid was tested each day with
litmus paper, but never coloured it; and this cir-
cumstance J do not understand, as.the superphosphate
of lime is acid. I suppose that some superphosphate
must have been formed by the acid of the secretion
acting on the phosphate, but that it was all absorbed
and injured the leaves; the large drops which hung
from their edges being an abnormal and dropsical
secretion. Anyhow, it is manifest that the phos-
phate of lime is a most powerful stimulant. Even
small doses are more or less poisonous, probably on
the same principle that raw meat and other nutri-
tious substances, given in excess, kill the leaves.
Hence the conclusion, that the long continued in-
flection of the tentacles over fragments of bone,
enamel, and dentine, is caused by the presence of
phosphate of lime, and not of any included animal
matter, is no doubt correct.
Gelatine.—I used pure gelatine in thin sheets given
Onap. VI. DIGESTION. 111
mo by Prof. Hoffmann. For comparison, squares of
the same size as those placed on the leaves were left
close by on wet moss. These soon swelled, but re-
tained their angles for three days; after five days
they formed rounded, softened masses, but even on the
eighth day a trace of gelatine could still be detected.
Other squares were immersed in water, and these,
- though much swollen, retained their angles for six
days. Squares of 75 of an inch (2°54 mm.), just
moistened with water, were placed on two leaves; and
after two or three days nothing was left on them but
some acid viscid fluid, which in this and other cases
never showed any tendency to regelatinise; so that
the secretion must act on the gelatine differently
to what water does, and apparently in the same
manner as gastric juice.* Four squares of the same
size as before were then soaked for three days in water,
and placed on large leaves; the gelatine was liquefied
and rendered acid in two days, but did not excite
much inflection. The leaves began to re-expand after
four or five days, much viscid fluid being left on their
discs, as if but little had been absorbed. One of these
leaves, as soon as it re-expanded, caught a small fly,
and after 24 hrs. was closely inflected, showing how
much more potent than gelatine is the animal matter
absorbed from an insect. Some larger pieces of gela-
tine, soaked for five days in water, were next placed
on three leaves, but these did not become much in-
flected until the third day; nor was the gelatine
completely liquefied until the fourth day. On this
day one leaf began to re-expand ; the second on the
fifth ; and third on the sixth. These several facts
* Dr. Lauder Brunton, ‘Hand- phys. de la Digestion,’ 1867, p
book for the Phys. Laboratory, 249
1873, pp. 477, 487 ; Schiff, ‘ Legons
112 DROSERA ROTUNDIFOLIA. Crap. VL
prove that gelatine is far from acting energetically
on Drosera.
In the last. chapter it was shown that a solution of
isinglass of commerce, as thick as milk or cream,
induces strong inflection. I therefore wished to com-
pare its action with that of pure gelatine. Solutions
of one part of both substances to 218 of water were
made; and half-minim drops (‘0296 ml.) were placed
on the discs of eight leaves, so that each received
zt, of a grain, or ‘185 mg. The four with the isin-
glass were much more strongly inflected than the
other four. I conclude therefore that isinglass con-
tains some, though perhaps very little, soluble albu-
minous matter. As soon as these eight leaves re-
expanded, they were given bits of roast meat, and in
some hours all became greatly inflected; again show-
ing how much more meat excites Drosera than does
gelatine or isinglass. This is an interesting fact, as
it is well known that gelatine by itself has little
power of nourishing animals.*
Chondrin—This was sent me by Dr. Moore in a
gelatinous state. Some was slowly dried, and a small
chip was placed on a leaf, and a much larger chip on
a second leaf. The first was liquefied in a day; the
larger piece was much swollen and softened, but was
not completely liquefied until the third day. The
undried jelly was next tried, and as a control experi-
ment small cubes were left in water for four days
and retained their angles. Cubes of the same size
were placed on two leaves, and larger cubes on two
other leaves. The tentacles and lamine of the latter
were closely inflected after 22 hrs., but those of the
* Dr. Lauder Brunton gives view of the indirect part which
in the ‘Medical Record, January _ gelatine plays in nutrition.
1873, p. 36, an account of Voit’s
Cuar. VL DIGESTION. 113
two leaves with the smaller cubes only to a moderate
degree. The jelly on all four was by this time lique-
fied, and rendered very acid. The glands were
blackened from the aggregation of their protoplasmic
contents. In 46 hrs. from the time when the jelly
was given, the leaves had almost re-expanded, and
‘completely so after 70 hrs.; and now only a little
slightly adhesive fluid was left unabsorbed on their
discs.
One part of chondrin jelly was dissolved in 218
parts of boiling water, and half-minim drops were
given to four leaves; so that each received about 54,
of a grain (135 mg.) of the jelly; and, of course,
much less of dry chondrin. This acted most power-
fully, for after only 3 hrs. 30 m. all four leaves were
strongly inflected. Three of them began to re-
expand after 24 hrs., and in 48 brs. were completely
open; but the fourth had only partially re-expanded.
All the liquefied chondrin was by this time absorbed.
Hence a solution of chondrin seems to act far more
quickly and energetically than pure gelatine or isin-
glass; but I am assured by good authorities that it
is most difficult, or impossible, to know whether
chondrin is pure, and if it contained any albumi-
nous compound, this would have produced the above
effects. Nevertheless, I have thought these facts worth
giving, as there is so much doubt on the nutritious
value of gelatine; and Dr. Lauder Brunton does not
know of any experiments with respect to animals on
the relative value of gelatine and chondrin.
Milk.—We have seen in the last chapter that milk
acts most powerfully on the leaves; but whether this
‘s due to the contained casein or albumen, I know not.
Rather large drops of milk excite so much secretion
(which is very acid) that it sometimes trickles down
114 DROSERA ROTUNDIFOLIA. Cuap. VIL
from the leaves, and this is likewise characteristic of
chemically prepared casein. Minute drops of milk,
placed on leaves, were coagulated in about ten
minutes. Schiff denies* that the coagulation of milk
by gastric juice is exclusively due to the acid which
is present, but attributes it in part to the pepsin;.
and it seems doubtful whether with Drosera the
coagulation can be wholly due to the acid, as the
secretion does not commonly colour litmus paper
until the tentacles have become well inflected ;
whereas the coagulation commences, as we have seen,
in about ten minutes. Minute drops of skimmed
milk were placed on the discs of five leaves; and a
large proportion of the coagulated matter or curd
was dissolved in 6 hrs. and still more completely
in 8 hrs. These leaves re-expanded after two days,
and the viscid fluid left on their discs was then care-
fully scraped off and examined. It seemed at first
sight as if all the casein had not been dissolved, for
a little matter was left which appeared of a whitish
colour by reflected light. But this matter, when
examined under a high power, and when compared
with a minute drop of skimmed milk coagulated by
acetic acid, was seen to consist exclusively of oil-
globules, more or less aggregated together, with no
trace of casein. As I was not familiar with the
microscopical appearance of milk, I asked Dr. Lauder
Brunton to examine the slides, and he tested the
globules with ether, and found that they were dis-
solved. We may, therefore, conclude that the secretion
quickly dissolves casein, in the state in which it exists
in milk.
Chemically Prepared Casein.—This substance, which
* ‘Lecons,’ &c. tom. ii. p. 151.
Ouar. VI. DIGESTION. 115
is insoluble in water, is supposed by many chemists to
differ from the casein of fresh milk. I procured some,
consisting of hard globules, from Messrs. Hopkins and
Williams, and tried many experiments with it. Small
particles and the powder, both in a dry state and
moistened with water, caused the leaves on which they
were placed to be inflected very slowly, generally not
until two days had elapsed. Other particles, wetted
with weak hydrochloric acid (one part to 487 of
water) acted in a single day, as did some casein
freshly prepared for me by Dr. Moore. The ten-
tacles commonly remained inflected for from seven
to nine days; and during the whole of this time the
secretion was strongly acid. Even on the eleventh
day some secretion left on the disc of a fully re-
expanded leaf was strongly acid. The acid seems
to be secreted quickly, for in one case the secre-
tion from the discal glands, on which a little
powdered casein had been strewed, coloured litmus
paper, before any of the exterior tentacles were
inflected.
Small cubes of hard casein, moistened with water,
were placed on two leaves; after three days one cube
had its angles a little rounded, and after seven days
both consisted of rounded softened masses, in the
midst of much viscid and acid secretion; but it must
not be inferred from this fact that the angles were
dissolved, for cubes immersed in water were similarly
acted on. After nine days these leaves began to re-
expand, but in this and other cases the casein did not
appear, as far as could be judged by the eye, much, if
at all, reduced in bulk. According to Hoppe-Seyler
and Lubavin* casein consists of an albuminous, with
* Dr Lauder Bruntcn, ‘Handbook for Phys. Lab’ p. 529
116 DROSERA ROTUNDIFOLIA. Cuar. VL
a non-albuminous, substance; and the absorption of a
very small quantity of the former would excite the
leaves, and yet not decrease the casein to a percep-
tible degree. Schiff asserts*—and this is an import-
ant fact for us—that “la caséine purifiée des chimistes
est un corps presque complétement inattaquable par
le suc gastrique.” So that here we have another
point of accordance between the secretion of Drosera
and gastric juice, as both act so differently on the
fresh casein of milk, and on that prepared by
chemists.
A few trials were made with cheese; cubes of ; of
an inch (1°27 mm.) were placed on four leayes, and
these after one or two days became well inflected,
their glands pouring forth much acid secretion.
After five’ days they began to re-expand, but one
died, and some of the glands on the other leaves were
injured. Judging by the eye, the softened and sub-
sided masses of cheese, left on the discs, were very
little or not at all reduced in bulk. We may, how-
ever, infer from the time during which the tentacles
remained inflected,—from the changed colour of some
of the glands,—and from the injury done to others,
that matter had been absorbed from the cheese.
Legumin.—I did not procure this substance in a
separate state; but there can hardly be a doubt that
it would be easily digested, judging from the powerful
effect produced by drops of a decoction of green
peas, as described in the last chapter. Thin slices of
a dried pea, after being soaked in water, were placed
on two leaves; these became somewhat inflected in
the course of a single hour, and most strongly so in
21 hrs. They re-expanded after three or four days
* ‘Legons,’ &. tom. ii. p. 153.
Cuap. VI. DIGESTION. 117
The slices were not liquefied, for the walls of the cells,
composed of cellulose, are “not in the least acted on
by the secretion.
Pollen.—A little fresh pollen from the common pea
was placed on the discs of five leaves, which soon
became closely inflected, and remained so for two or
three days.
The grains being then removed, and examined under
the microscope, were found discoloured, with the oil-
globules remarkably aggregated. Many had their
contents much shrunk, and some were almost empty.
In only a few cases were the pollen-tubes emitted.
There could be no doubt that the secretion had
penetrated the outer coats of the grains, and had
partially digested their contents. So it must be
with the gastric juice of the insects which feed on
pollen, without masticating it.* Drosera in a state of
nature cannot fail to profit to a certain extent by this
power of digesting pollen, as innumerable grains from
the carices, grasses, rumices, fir-trees, and other wind-
fertilised plants, which commonly grow in the same
neighbourhood, will be inevitably caught by the viscid
secretion surrounding the many glands.
Gluten.—This substance is composed of two albu-
minoids, one soluble, the other insoluble in alcohol.t
Some was prepared by merely washing wheaten flour
in water. A provisional trial was made with rather
large pieces placed on two leaves; these, after 21 hrs.,
were Closely inflected, and remained so for four days,
when one was killed and the other had its glands
extremely blackened, but was not afterwards observed.
* Mr. A. W. Bennett foundthe Hort. Soc. of London,’ vol. iv.
undigested coats of the grainsin 1874, p. 158.
the intestinal canal of pollen- + Watts’ ‘Dict. of Chemistry,
eating Diptera; see ‘Journal of vol. ii. 1872, p. 873.
118 DROSERA ROTUNDIFOLIA. Cuar. VL
Smaller bits were placed on two leaves; these were
only slightly inflected in two days, but afterwards
became much more so. Their secretion was not so
strongly acid as that of leaves excited by casein.
The bits of gluten, after lying for three days on the
leaves, were more transparent than other bits left for
the same time in water. After seven days both leaves
re-expanded, but the gluten seemed hardly at all
reduced in bulk. The glands which had been in
contact with it were extremely black. Still smaller
bits of half putrid gluten were now tried on two
leaves; these were well inflected in 24 hrs. and
thoroughly in four days, the glands in contact being
much blackened. After five days one leaf began to
re-expand, and after eight days both were fully re-
expanded, some gluten being still left on their discs.
Four little chips of dried gluten, just dipped in
water, were next tried, and these acted rather dif-
ferently from fresh gluten. One leaf was almost
fully re-expanded in three days, and the other three
leaves in four days. The chips were greatly softened,
almost liquefied, but not nearly all dissolved. The
glands which had been in contact with them, instead
of being much blackened, were of a very pale colour,
and many of them were evidently killed.
In not one of these ten cases was the whole of the
gluten dissolved, even when very small bits were
given. I therefore asked Dr. Burdon Sanderson to
try gluten in artificial digestive fluid of pepsin with
hydrochloric acid; and this dissolved the whole.
The gluten, however, was acted on much more slowly
than fibrin; the proportion dissolved within four
hours being as 40°83 of gluten to 100 of fibrin.
Gluten was also tried in two other digestive fluids,
in which hydrochloric acid was replaced by propionis
Onar. VI. DIGESTION. 119
and butyric acids, and it was completely dissolved by
these fluids at the ordinary temperature of a room.
Here, then, at last, we have a case in which it appears
that there exists an essential difference in digestive
power between the secretion of Drosera and gastric
juice; the difference being confined to the ferment,
for, as we have just seen, pepsin in combination with
acids of the acetic series acts perfectly on gluten.
I believe that the explanation lies simply in the fact
that gluten is too powerful a stimulant (like raw
meat, or phosphate of lime, or even too large a piece
of albumen), and that it injures or kills the glands
before they have had time to pour forth a sufficient
supply of the proper secretion. That some matter is
absorbed from the gluten, we have clear evidence in
the length of time during which the tentacles remain
inflected, and in the greatly changed colour of the
glands. ~~
At the suggestion of Dr. Sanderson, some gluten
was left for 15 hrs. in weak hydrochloric acid (02 per
cent.), in order to remove the starch. It became
colourless, more transparent, and swollen. Small
portions were washed and placed on five leaves, which
were soon closely inflected, but to my surprise re-
expanded completely in 48 hrs. A mere vestige of
gluten was left on two of the leaves, and not a vestige
on the other three. The viscid and acid secretion,
which remained on the discs of the three latter
leaves, was scraped off and examined by. my son
under a high power; but nothing could be seen
except a little dirt, and a good many starch grains
which had not been dissolved by the hydrochloric
acid. Some of the glands were rather pale. We
thus learn that gluten, treated with weak hydro-
chloric acid, is not so powerful or so enduring a
9
120 DROSERA ROTUNDIFOLIA. Guar. V1
stimulant as fresh gluten, and does not much injure
the glands; and we further learn that it can be di-
gested quickly and completely by the secretion.
Globulin or Crystallin.—-This substance was kindly prepared
for me from the lens of .the eye by Dr. Moore, and consisted of
hard, colourless, transparent fragments. It is said* that globulin
ought to “swell up in water and dissolve, for the most part
forming a gummy liquid;” but this did not occur with the above
fragments, though kept in water for four days. Particles, some
moistened with water, others with weak hydrochloric acid,
others soaked in water for one or two days, were placed on
nineteen leaves. “Most of these leaves, especially those with the
long soaked particles, became strongly inflected in a few hours.
The greater number re-expanded after three or four days; but
three of the leaves remained inflected during one, two, or three
additional days. Hence some exciting matter must have been
absorbed; but the fragments, though perhaps softened in a
greater degree than those kept for the same time in water,
retained all their angles as sharp as ever. As globulin is an
albuminous substance, I was astonished at this result; and my
object being to compare the action of the secretion with that ot
gastric juice, I asked Dr. Burdon Sanderson to try some of the
globulin used by me. He reports that “it was subjected to a
liquid containing 0-2 per cent. of hydrochloric acid, and about
1 per cent. of glycerine extract of the stomach of a dog. It was
then ascertained that this liquid was capable of digesting 1:31
of its weight of unboiled fibrin in 1 hr.; whereas, during the
hour, only 0-141 of the above globulin was dissolved. In both
cases an excess of the substance to be digested was subjected to
the liquid.”t We thus see that within the same time less than
one-ninth by weight of globulin than of fibrin was dissolved ;
and bearing in mind that pepsin with acids of the acetic series
has only about one-third of the digestive power of pepsin with
hydrochloric acid, it is ngt surprising that the fragments of
* Watts’ ‘Dict. of Chemistry,’ that it was far more soluble than
vol. ii. p. 874.
+ I may add that Dr. Sander-
son prepared some fresh globulin
by Schmidt’s method, and of this
0°865 was dissolved within the
same time, namely, one hour; so
that which I used, though less
soluble than fibrin, of which, as
we have seen, 1°31 was dissolved.
I wish that I had tried on Dro-
sera globulin prepared by thie
method.
Ouap. VI. DIGESTION. 121
globulin were not corroded or rounded by the secretion of
Drosera, though some soluble matter was certainly extracted
from them and absorbed by the glands.
Hematin—Some dark red granules, prepared from bullock’s
blood, were given me; these were found by Dr. Sanderson to
be insoluble in water, acids, and alcohol, so that they were pro-
bably hematin, together with other bodies derived from the
blood. ~ Particles with little drops of water were placed on
four leaves, three of which were pretty closely inffected in two
days ; the fourth only moderdtely so. On the third day the
. glands in contact with the hematin were blackened, and some
of the tentacles seemed injured. After five days two leaves
died, and the third was dying; the fourth was beginning to re-
expand, but many of its glands were blackened and injured.
It is therefore clear that matter had been absorbed which was
either actually poisonous or of too stimulating a nature. The
particles were much more softened than those kept for the same
time in water, but, judging by the eye, very little reduced in
bulk. Dr. Sanderson tried this substance with artificial digestive
fluid, in the manner described under globulin, and found that
whilst 1°31 of fibrin, only 0456 of the hematin was dissolved
in an hour; but the dissolution by the secretion of even a less
amount would account for its action on Drosera. The residue
left by the artificial digestive fluid at first yielded nothing more
to it during several succeeding days. ~
Substances which are not Digested by the Secretion.
All the substances hitherto mentioned cause pro-
longed inflection of the tentacles, and are either com-
pletely or at least partially dissolved by the secretion.
But there are many other substances, some of them
containing nitrogen, which are not in the least acted
on by the secretion, and do not induce inflection for a
longer time than do inorganic and insoluble objects.
These unexciting and indigestible substances are, as
far as I have observed, epidermic productions (such
as bits of human nails, balls of hair, the quills of
feathers), fibro-elastic tissue, mucin, pepsin, urea,
chitine, chlorophyll, cellulose, gun-cotton, fat, oil, and
starch.
122 DROSERA ROTUNDIFOLIA. Cnap. VI
To these may be added dissolved sugar and gum,
diluted alcohol, and vegetable infusions not containing
albumen, for none of these, as shown in the last
chapter, excite inflection. Now, it is a remarkable
fact, which affords additional and important evidence,
that the ferment of Drosera is closely similar to or
identical with pepsin, that none of these same sub-
’ stances are, as far as it is known, digested by the gas-
tric juice of animals, though some of them are acted
on by the other secretions of the alimentary canal.
Nothing more need be said about some of the above
enumerated substances, excepting that they were re-
peatedly tried on the leaves of Drosera, and were not
in the least affected by the secretion. About the
others it will be advisable to give my experiments.
Fibro-elastic Tisswe.—We have already seen that when little
cubes of meat, &c., were placed on leaves, the muscles, areolar
tissue, and cartilage were completely dissolved, but the fibro-
elastic tissue, even the most delicate threads, were left without
the Icast signs of having been attacked. And it is well known
that this tissue cannot be digested by the gastric juice of
animals.*
Mucin—As this substance contains about 7 per cent. of
nitrogen, I expected that it would have excited the leaves
greatly and been digested by the secretion, but in this I
was mistaken. From what is stated in chemical wirks, it
appears extremely doubtful whether mucin can be prepared as
a pure principle. That which I used (prepared by Dr. Moore)
was dry and hard: Particles moistened with water were placed
on four leaves, but after two days there was only a trace of
inflection in the immediately adjoining tentacles. These leaves
were then tried with bits of meat, and all four soon became
strongly inflected. Some of the dried mucin was then soaked
in water for two days, and little cubes of the proper size
were placed on three leaves. After four days the tentacles
aoe for instance, Schiff, ‘Phys. de 2 Digestion, 1867, tom. ii
v. 38. ,
Onar. VIL DIGESTION. 123
round the margins of the discs were a little inflected, and
the secretion collected on the disc was acid, but the exterior
tentacles were not affected. One leaf began to re-expand on the
fourth day, and all were fully re-expanded on the sixth. Tho
glands which had been in contact with the mucin were a little
darkened. We may therefore conclude that a small amount of
some impurity of a moderately exciting nature had been
absorbed. That the mucin employed by me did contain some
soluble matter was proved by Dr. Sanderson, who on subjecting
it to artificial gastric juice found that in 1 hr. some was dis-
solved, but only in the proportion of 23 to 100 of fibrin during
the same time. The cubes, though perhaps rather softer than
those left in water for the same time, retained their angles as
sharp as ever. We may therefore infer that the mucin itself
was not dissolved or digested. Nor is it digested by the
gastric juice of living animals, and according to Schiff* it is a
layer of this substance which protects the coats of the stomach
from being corroded during digestion.
Pepsin—My experiments are hardly worth giving, as it is
scarcely possible to prepare pepsin free from other albuminoids ;
but I was curious to ascertain, as far as that was possible,
whether the ferment of the seeretion of Drosera would act on
the ferment of the gastric juice of animals. I first used the
common pepsin sold for medicinal purposes, and afterwards
some which was much purer, prepared for me by Dr. Moore.
Five leaves to which a considerable quantity of the former was
given remained inflected for five days; four of them then died,
apparently from too great stimulation. I then tried Dr. Moore’s
pepsin, making it into a paste with water, and placing such
small particles on the discs of five leaves that all would have
been quickly dissolved had it been meat or albumen. The
leaves were soon inflected; two of them began to re-expand
after only 20 hrs., and the other three were almost completely
re-expanded after 44 hrs. Some of the glands which had been
in contact with the particles of pepsin, or with the acid secre-
tion surrounding them, were singularly pale, whereas others
were singularly dark-coloured. Some of the secretion was
:eraped off and examined under a high power; and it abounded
with granules undistinguishable from those of pepsin left in
water for the same length of time. We may therefore infer,
as highly probable (remembering what small quantities were
given), that the ferment of Drosera does not act on or digest
* ‘Lecons phys. de la Digestion, 1867, tom. ii. p. 304
124 DROSERA ROTUNDIFOLIA. Cuap. VI
pepsin, but absorbs from it some albuminous impurity which
induces inflection, and which in large quantity is highly
injurious. Dr. Lauder Brunton at my request endeavoured to
ascertain whether pepsin with hydrochloric acid would digest
pepsin, and as far as he could judge, it had no such power.
Gastric juice, therefore, apparently agrees in this respect with
the secretion of Drosera.
Urea.—It seemed to me an interesting inquiry whether this
refuse of the living body, which contains much nitrogen,
would, like so many other animal fluids and substances, be
absorbed by the glands of Drosera and cause inflection. Half-
minim drops of a solution of one part to 487 of water were
placed on the discs of four leaves, each drop containing the
quantity usually employed by me, namely 535 of a grain, or
‘0674 mg.; but the leaves were hardly at all affected. They
were then tested with bits of meat, and soon became closely
inflected. I repeated the same experiment on four leaves
with some fresh urea prepared by Dr. Moore; after two days
there was no inflection; I then gave them another dose, but
still there was no inflection. These leaves were afterwards
tested with similarly sized drops of an infusion of raw meat,
and in 6 hrs. there was considerable inflection, which became
excessive in 24 hrs. But the urea apparently was not quite
pure, for when four leaves were immersed in 2 dr. (7:1 ml.) of
the solution, so that all the glands, instead of merely those on
the disc, were enabled to absorb any small amount of impurity
in solution, there was considerable inflection after 24 hrs.,
certainly more than would have followed from a similar im-
mersion in pure water. That the urea, which was not per-
‘fectly white, should have contained a sufficient quantity of
albuminous matter, or of some salt of ammonia, to have caused
the above effect, is far from surprising, for, as we shall see
in the next chapter, astonishingly small doses of ammonia
are highly efficient. We may therefore conclude-that urea itself
is not exciting or nutritious to Droscra; nor is it modified by
the secretion, so as to be rendered nutritious, for, had this been
the case, all the leaves with drops on their discs assuredly
would have been well inflected. Dr. Lauder Brunton informs
me that from experiments made at my request at St. Bartho-
lomew’s Hospital it appears that urea is not acted on by
artificial gastric juice, that is by pepsin with hydrochloric acid.
Chitine.—The chitinous coats of insects naturally captured by
the leaves do not appear in the least corroded. Small square
pieces of the delicate wing and of the elytron of a Staphylinus
Cuap. VI. DIGESTION. 125
were placed on some leaves, and after these had re-expanded,
the pieces were carefully examined. Their angles were as
sharp as ever, and they did not differ in appearance from the
other wing and elytron of the same insect which had been left
in water. The elytron, however, had evidently yielded somo
nutritious matter, for the leaf remained clasped over it for four
days ; whereas the leaves with bits of the true wing re-expanded
on the second day. Any one who will examine the excrement
of insect-eating animals will see how powerless their gastric
Juice is on chitine.
Cellulose—I did not obtain this substance in a separate state,
but tried angular bits of dry wood, cork, sphagnum moss, linen,
and cotton thread. None of these bodies were in the least
attacked by the secretion, and they caused only that moderate
amount of inflection which is common to all inorganic objects.
Gun-cotton, which consists of cellulose, with the hydrogen
replaced by nitrogen, was tried with the same result. We have
seen that a decoction of cabbage-leaves excites the most power-
ful inflection. I therefore placed two little square bits of the
blade of a cabbage-leaf, and four little cubes cut from the
midrib, on six leaves of Drosera. These became well inflected
in 12 hrs., and remained so for between two and four days;
the bits of cabbage being bathed all the time by acid secre-
tion. This shows that some exciting matter, to which I shall
presently refer, had been absorbed; but the angles of the
squares and cubes remained as sharp as ever, proving that the
framework of cellulose had not been attacked. Small square
bits of spinach-leaves were tried with the same result; the
glands pouring forth a moderate supply of acid secretion,
and the tentacles remaining inflected for three days. We have
also seen that the delicate coats of pollen grains are not dissolved
by the secretion. It is well known that the gastric juice of
animals does not attack cellulose.
Chlorophyll.—This substance was tried, as it contains nitrogen,
Dr: Moore sent me some preserved in alcohol; it was dried, but
soon deliquesced. Particles were placed on four leaves; after
3 hrs. the secretion was acid; after 8 hrs. there was a good deal
of inflection, which in 24 hrs. became fairly well marked. After
four days two of the leaves began to open, and the other two
were then almost fully re-expanded. It is therefore clear that
this chlorophyll contained matter which excited the leaves to a
moderate degree; but judging by the eye, little or none was dis-
solved ; so that in a pure state it would not probably have been
attacked by the secretion. Dr. Sanderson tried that which J
126 DROSERA ROTUNDIFOLIA. Cuar. VI
used, as well as some freshly prepared, with artificial digestive
liquid, and found that it was not digested. Dr. Lauder Brunton
likewise tried some prepared by the process given in the British
Pharmacopveia, and exposed it for five days at the temperature
of 37° Cent. to digestive liquid, but it was not diminished in
bulk, though the fluid acquired a slightly brown colour. It was
also tried with the glycerine extract of pancreas with a negative
result. Nor does chlorophyll seem affected by the intestinal
secretions of various animals, judging by the colour of their
excrement.
It must not be supposed from these facts that the grains of
chlorophyll, as they exist in living plants, cannot be attacked by
the secretion; for these grains consist of protoplasm merely
coloured by chlorophyll. My son Francis placed a thin slice of
spinach leaf, moistened with saliva, on a leaf of Drosera, and
other slices on damp cotton-wool, all exposed to the same
temperature. After 19 hrs. the slice on the leaf of Drosera was
bathed in much secretion from the inflected tentacles, and was
now examined under the microscope. No perfect grains of
chlorophyll could be distinguished ; some were shrunken, of a
yellowish-green colour, and collected in the middle of the cells;
others were disintegrated and formed a yellowish mass, likewise
in the middle of the cells. On the other hand, in the slices
surrounded by damp cotton-wool, the grains of chlorophyll were
green and as perfect as ever. My son also placed some slices
in artificial gastric juice, and these were acted on in nearly the
same manner as by the secretion. We have seen that bits of
fresh cabbage and spinach leaves cause the tentacles to be in-
flected and the glands to pour forth much acid secretion; and
there can be little doubt that it is the protoplasm forming the
grains of chlorophyll, as well as that lining the walls of the
cells, which excites the leaves.
Fat and Otl.—Cubes of almost pure uncooked fat, placed on
several leaves, did not have their angles in the least rounded.
We have also seen that the oil-globules in milk are not digested.
Nor does olive oil dropped on the discs of leaves cause any
inflection ; but when they are immersed in olive oil, they become
strongly inflected; but to this subject I shall have to recur.
Oily substances are not digested by the gastric juice of animals.
Starch.—Rather large bits of dry starch caused well-marked
inflection, and the leaves did not re-expand until the fourth
day; but I have no doubt that this was due to the prolonged
irritation of the glands, as the starch continued to absorb the
secretion, The particles were not in the least reduced in size:
Cuap. VI. DIGESTION. 127
and we know that leaves immersed in an emulsion of starch
are not at all affected. I need hardly say that starch is not
digested by the gastric juice of animals.
Action of the Secretion on Living Seeds,
The results of some experiments on living seeds, selected by
hazard, may here be given, though they bear only indirectly on
our present subject of digestion.
Seven cabbage seeds of the previous year were placed on the
same number of leaves. Some of these leaves were moderately,
but the greater number only slightly inflected, and most of
them re-expanded on the third day. One, however, remained
clasped till the fourth, and another till the fifth day. These
leaves therefore were excited somewhat more by the seeds than
by inorganic objects of the same size. After they re-expanded,
the seeds were placed under favourable conditions on damp
sand; other seeds of the same lot being tried at the same time
in the same manner, and found to germinate well. Of the seven
seeds which had been exposed to the secretion, only three ger-
minated; and one of the three seedlings soon perished, the tip
of its radicle being from the first decayed, and the edges of
its cotyledons of a dark brown colour; so that altogether five
out of the seven seeds ultimately perished.
Radish seeds (/aphanus sativus) of the previous year were
placed on three leaves, which became moderately inflected, and
re-expanded on the third or fourth day. Two of these seeds
were transferred to damp sand; only one germinated, and that
very slowly. This seedling had an extremely short, crooked,
diseased, radicle, with no absorbent hairs; and the cotyledons
were oddly mottled with purple, with the edges blackened and
partly withered.
Cress seeds (Lepidum sativum) of the previous year were
placed on four leaves; two of these next morning were mode-
rately and two strongly inflected, and remained so for four,
five, and even six days. Soon after these seeds were placed on
the leaves and had become damp, they secreted in the usual
manner a layer of tenacious mucus; and to ascertain whether
it was the absorption of this substance by the glands which
caused so much inflection, two seeds were put into water, and
as much of the mucus as possible scraped off. They were then
placed on leaves, which became very strongly inflected in the
course of 3 hrs., and were still closely inflected on the third
day; so that it evidently was not the mucus which excited sq
128 DROSERA ROTUNDIFOLIA. Cuar. VL
much inflection ; on the contrary, this served to a certain extent
as a protection to the seeds. Two of the six seeds germinated
whilst still lying on the leaves, but the seedlings, when trans-
ferred to damp sand, soon died ; of the other four seeds, only one
germinated.
Two seeds of mustard (Sinapis nigra), two of celery (Apium
graveolens)—both of the previous year, two seeds well soaked of
caraway (Carum carui), and two of wheat, did not excite the
leaves more than inorganic objects often do. Five seeds, hardly
ripe, of a buttercup (Ranunculus), and two fresh seeds of Ane-
mone nemorosa, induced only a little more effect. On the other
hand, four seeds, perhaps not quite ripe, of Carex sylvatica caused
the leaves on which they were placed to be very strongly in-
flected; and these only began to re-expand on the third day,
one remaining inflected for seven days.
It follows from these few facts that different kinds of seeds
excite the leaves in very different degrees ; whether this is
solely due to the nature of their coats is not clear. In the case
of the cress seeds, thé partial removal of the layer of mucus
hastened the inflection of the tentacles. Whenever the leaves
remain inflected during several days over seeds, it is clear that
they absorb some matter from them. That the secretion pene-
trates their coats is also evident from the large proportion of
cabbage, raddish, and cress seeds which were killed, and from
several of the seedlings being greatly injured. ‘This injury to
the seeds and seedlings may, however, be due solely to the acid
of the secretion, and not to any process of digestion; for Mr.
Traherne Moggridge has shown that very weak acids of the
acetic series are highly injurious to seeds. It never occurred
to me to observe whether seeds are often blown on to the viscid
leaves of plants growing in a state of nature; but this can
hardly fail sometimes to occur, as we shall hereafter see in the
case of Pingnicula. If so, Drosera will profit to a slight degree
by absorbing matter from such seeds.
Summary und Concluding Remarks on the Digestive
Power of Drosera.
When the glands on the disc are excited either
by the absorption of nitrogenous matter or by
mechanical irritation, their secretion increases in
quantity and becomes acid. They likewise transmit
Onar. VI. DIGESTION. 129
some influence to the glands of the exterior ten-
tacles, causing them to secrete more copiously; and
their secretion likewise becomes acid. With ani-
mals, according to Schiff,* mechanical irritation ex-
cites the glands of the stomach to secrete an acid,
but not pepsin. Now, I have every reason to be-
lieve (though the fact is not fully established), that
although the glands of Drosera are continually secret-
ing viscid fluid to replace that lost by evaporation,
yet they do not secrete the ferment proper for di-
gestion when mechanically irritated, but only after
absorbing certain matter, probably of a nitrogenous
nature. I infer that this is the case, as the secretion
from a large number of leaves which had been
irritated by particles of glass placed on their discs
did not digest albumen; and more especially from —
the analogy of Dionza and Nepenthes. In like
manner, the glands of the stomach of animals secrete
pepsin, as Schiff asserts, only after they have ab-
sorbed certain soluble substances, which he desig-
nates as peptogenes. There is, therefore, a remarkable
parallelism between the glands of Drosera and those
of the stomach in the secretion of their proper acid
and ferment.
The secretion, as we have seen, completely dissolves
albumen, muscle, fibrin, areolar tissue, cartilage, the
fibrous basis of bone, gelatin, chondrin, casein in the
state in which it exists in milk, and gluten which has
been subjected to weak hydrochloric acid. Syntonin
and legumin excite the leaves so powerfully and
quickly that there can hardly be a doubt that both
would be dissolved by the secretion. The secretion
IP cvceutecs Sec h he aeaee
* ‘Phys. de la Digestion,’ 1867, tom. ii. pp. 188, 245.
130 DROSERA ROTUNDIFOLIA. Cuap. VI
failed to digest fresh gluten, apparently from its
injuring the glands, though some was absorbed. Raw
meat, unless in very small bits, and large pieces of
albumen, &c., likewise injure the leaves, which seem
to suffer, like animals, from a surfeit. I know not
whether the analogy is a real one, but it is worth
notice that a decoction of cabbage leaves is far more
exciting and probably nutritious to Drosera than an
infusion made with tepid water; and boiled cabbages
are far more nutritious, at least to man, than the un-
cooked leaves. The most striking of all the cases,
though not really more remarkable than many others,
is the digestion of so hard and tough a substance as
cartilage. The dissolution of pure phosphate of lime,
of bone, dentine, and especially enamel, seems won-
derful ; but it depends merely on the long-continued
secretion of an acid; and this is secreted for a longer
time under these circumstances than under any others.
It was interesting to observe that as long as the acid
was consumed in dissolving the phosphate of lime, no
true digestion occurred; but that as soon as the bone
was completely decalcified, the fibrous basis was at-
tacked and liquefied with the greatest ease. The
twelve substances above enumerated, which are com-
pletely dissolved by the secretion, are likewise dis-
solved by the gastric juice of the higher animals;
and they are acted on in the same manner, as shown
by the rounding of the angles of albumen, and more
especially by the manner in which the transverse strice
of the fibres of muscle disappear.
The secretion of Drosera and gastric juice were
both able to dissolve some element or impurity out of
the globulin and hematin employed by me. ‘The
secretion also dissolved something out of chemically
Caap. V1. DIGESTION. 131
prepared casein, which is said to consist of two sub-
stances; and although Schiff asserts that casein in
this state is not attacked by gastric juice, he might
easily have overlooked a minute quantity of some
albuminous matter, which Drosera would detect and
absorb. Again, fibro- cartilage, though not properly
dissolved, is acted on in the same manner, both by
the secretion of Drosera and gastric juice. But this
substance, as well as the so-called hematin used by
me, ought perhaps to have been classed with indi-
gestible substances.
That gastric juice acts by means of its ferment,
pepsin, solely in the presence of an acid, is well
established ; and we have excellent evidence that a
ferment is present in the secretion of Drosera, which
likewise acts only in the presence of an acid; for we
have seen that when the secretion is neutralised by
minute drops of the solution of an alkali, the diges-
tion of albumen is completely stopped, and that on
the addition of a minute dose of hydrochloric acid it
immediately recommences.
The nine following substances, or classes of sub-
stances, namely, epidermic productions, fibro-elastic
tissue, mucin, pepsin, urea, chitine, cellulose, gun
cotton, chlorophyll, starch, fat and oil, are not acted
on by the secretion of Drosera; nor are they, as far as
is known, by the gastric juice of animals. Some
soluble matter, however, was extracted from the mucin,
pepsin, and chlorophyll, used by me, both by the
secretion and by artificial gastric juice.
The several substances, which are completely dis-
solved by the secretion, and which are afterwards
absorbed by the glands, affect the leaves rather dif-
ferently, They induce inflection at very different
132 DROSERA ROTUNDIFOLIA. Cuar. VL
rates and in very different degrees; and the ten-
tacles remain inflected for very different periods of
time. Quick inflection depends partly on the quan-
tity of the substance given, so that many glands are
simultaneously affected, partly on the facility with
which it is penetrated and liquefied by the secretion,
partly on its nature, but chiefly on the presence of
exciting matter already in solution. Thus saliva, or
a weak solution of raw meat, acts much more quickly
than even a strong solution of gelatine. So again
leaves which have re-expanded, after absorbing drops
of a solution of pure gelatine or isinglass (the latter
being the more powerful of the two), if given bits
of meat, are inflected much more energetically and
quickly than they were before, notwithstanding that
some rest is generally requisite between two acts
of inflection. We probably see the influence of tex-
ture in gelatine and globulin when softened by
having been soaked in water acting more quickly
than when merely wetted. It may be partly due to
changed texture, and partly to changed chemical
nature, that albumen, which has been kept for some
time, and gluten which has been subjected to weak
hydrochloric acid, act more quickly than these sub-
stances in their fresh state.
The length of time during which the tentacles re-
main inflected largely depends on the quantity of the
substance given, partly on the facility with which it is
penetrated or acted on by the secretion, and partly
on its essential nature. The tentacles always remain
inflected much longer over large bits or large drops
than over small bits or drops. Texture probably
plays a part in determining the extraordinary length
of time during which the tentacles remain inflected
Onar. V1, DIGESTION. 133
over the hard grains of chemically prepared casein.
But the tentacles remain inflected for an equally long
time over finely powdered, precipitated phosphate of
lime; phosphorus in this latter case evidently being
the attraction, and animal matter in the case of casein.
The leaves remain long inflected over insects, but it is
doubtful how far this is due to the protection afforded
by their chitinous integuments; for animal matter is
soon extracted from insects (probably by exosmose from
their bodies into the dense surrounding secretion),
as shown by the prompt inflection of the leaves. We
see the influence of the nature of different substances
in bits of meat, albumen, and fresh gluten acting very
differently from equal-sized bits of gelatine, areolar
tissue, and the fibrous basis of bone. The former
cause not only far more prompt and energetic, but
more prolonged, inflection than do the latter. Hence
we are, I think, justified in believing that gelatine,
areolar tissue, and the fibrous basis of bone, would be
far less nutritious to Drosera than such substances
as insects, meat, albumen, &c. This is an interest-
ing conclusion, as it is known that gelatine affords
but little nutriment to animals; and so, probably,
would areolar tissue and the fibrous basis of bone.
The chondrin which I used acted more powerfully
than gelatine, but then I do not know that it was
pure. It is a more remarkable fact that fibrin, which
belongs to the great class of Proteids,* including
albumen in one of its sub-groups, does not excite
the tentacles in a greater degree, or keep them in-
flected for a longer time, than does gelatine, or
* See the classifidation adopted by Dr. Michael Foster in Watts’
Dict. of Chemistry,’ Supplement 1872, p. 969.
134 DROSERA ROTUNDIFOLIA. Cuar. VL
areolar tissue, or the fibrous basis of bone. It is not
known how long an animal would survive if fed on
fibrin alone, but Dr. Sanderson has no doubt longer
than on gelatine, and it would be hardly rash to pre-
dict, judging from the effects on Drosera, that albu-
men would be found more nutritious than fibrin.
Globulin likewise belongs to the Proteids, forming
another sub-group, and this substance, though. con- ,
taining some matter which excited Drosera rather
strongly, was hardly attacked by the secretion, and
was very little or very slowly attacked by gastric
juice. How far globulin would be nutritious to ani-
mals is not known. We thus see how differently the
above specified several digestible substances act on
Drosera; and we may infer, as highly probable, that
they would in like manner be nutritious in very dif-
ferent degrees both to Drosera and to animals.
The glands of Drosera absorb matter from living
seeds, which are injured or killed by the secretion.
They likewise absorb matter from pollen, and from
fresh leaves; and this is notoriously the case with
the stomachs of vegetable-feeding animals. Drosera
is properly an insectivorous plant; but as pollen
cannot fail to be often blown on to the glands, as
will occasionally the seeds and leaves of surrounding
plants, Drosera is, to a certain extent, a vegetable-
feeder.
Finally, the experiments recorded in this chapter
show us that there is a remarkable accordance in the
power of digestion between the gastric juice of ani-
mals with its pepsin and hydrochloric acid and the
secretion of Drosera with its ferment and acid belong-
ing to the acetic series. We can, therefore, hardly
doubt that the ferment in both cases is closely similar,
Cuap. VI. DIGESTION, 135
if not identically the same. That a plant and an
animal should pour forth the same, or nearly the same,
complex secretion, adapted for the same purpose of
digestion, is a new and wonderful fact in physiology.
But I shall have to recur to this subject in the
fifteenth chapter, in my concluding remarks on the
Droseracee.
136 DROSERA ROTUNDIFOLIA. Cuar. VIL
CHAPTER VII.
Tue Errects ofr Satts or AMMONIA.
Manner of performing the experiments — Action of distilled water in
comparison with the solutions —Carbonate of ammonia, absorbed
by the roots — The vapour absorbed by the glands — Drops on the
disc — Minute drops applied to separate glands — Leaves im-
mersed in weak solutions — Minuteness of the doses which induce
aggregation of the protoplasm — Nitrate of ammonia, analogous
experiments with — Phosphate of ammonia, analogous experiments
with — Other salts of ammonia—-Summary and concluding re-
marks on the action of the salts of ammonia.
THE chief object in this chapter is to show how power-
fully the salts of ammonia act on the leaves of Drosera,
and more especially to show what an extraordinarily
small quantity suffices to excite inflection. I shall,
therefore, be compelled to enter into full details.
Doubly distilled water was always used; and for the
more delicate experiments, water which had been
prepared with the utmost possible care was given
me by Professor Frankland. The graduated measures
were tested, and found as accurate as such measures
can be. The salts were carefully weighed, and in all
the more delicate experiments, by Borda’s double
method. But extreme accuracy would have been
superfluous, as the leaves differ greatly in irritability,
according to age, condition, and constitution. Even
the tentacles on the same leaf differ in irritability
to a marked degree. My experiments were tried in
the following several ways.
Firstly.—Drops which were ascertained by repeated trials to
be on an average about half a minim, or the 54, of a fluid ounce
(0296 ml.), were placed by the same pointed instrument on the
Ounap. VIL, SALTS OF AMMONIA, 137
discs of the leaves, and the inflection of the exterior rows of
tentacles observed at successive intervals of time. It was first
ascertained, from between thirty and forty trials, that distilled
water dropped in this manner produces no effect, except that
sometimes, though rarely, two or three tentacles become in-
flected. In fact all the many trials with solutions which were
so weak as to produce no effect lead to the same result that
water is inefficient. :
Secondly.—The head of a small pin, fixed into a handle, was
dipped into the solution under trial. The small drop which
adhered to it, and which was much too small to fall off, was
cautiously placed, by the aid of a lens, in contact with the seere-
tion surrounding the glands of one, two, three, or four of the
exterior tentacles of the same leaf. Great care was taken that
the glands themselves should not be touched. I had supposed
that the drops were of nearly the same size; but on trial this
proved a great mistake. I first measured some water, and re-
moved 300 drops, touching the pin’s head each time on blotting-
paper; and on again measuring the water, a drop was found to
equal on an average about the 3, of a minim. Some water in a
small vessel was weighed (and this is a more accurate method),
and 800 drops removed as before; and on again weighing the
water, a drop was found to equal on an average only the 25
of a minim. I repeated the operation, but endeavoured this
time, by taking the pin’s head out of the water obliquely and
rather quickly, to remove as large drops as possible; and
the result showed that I had succeeded, for each drop on an
average equalled >; of a minim. I repeated the operation in
exactly the same manner, and now the drops averaged 335 of a
minim. Bearing in mind that on these two latter occasions
special pains were taken to remove as large drops as possible,
we may safely conclude that the drops used in my experiments
were at least equal to the » of a minim, or 0029 ml. One of
these drops could be applied to three or even four glands, and
if the tentacles became inflected, some of the solution must
have been absorbed by all; for drops of pure water, applied
in the same manner, never produced any effect. I was able to
hold the drop in steady contact with the secretion only for ten
to fifteen seconds; and this was not time enough for the diffu-
sion of all the salt in solution, as was evident, from three or
four tentacles treated successively with the same drop, often
becoming inflected. All the matter in solution was even then
probably not exhausted.
Thirdly.—Leaves were cut off and immersed in a measured
138 DROSERA ROTUNDIFOLIA. Cuap. VIL
quantity of the solution under trial; the same number of lezves
being immersed at the same time, in the same quantity of the
distilled water which had been used in making the solution.
The leaves in the two lots were compared at short intervals
of time, up to 24 hrs., and sometimes to 48 hrs. They were
Ammersed by being laid as gently as possible in numbered
watch-glasses, and thirty minims (1'775 ml.) of the solution
or of water was poured over each.
Some solutions, for instance that of carbonate of ammonia,
quickly discolour the glands; and as all on the same leaf were
discoloured simultaneously, they must all have absorbed some
of the salt within the same short period of time. This was
likewise shown by the simultaneous inflection of the several
exterior rows of tentacles. If we had no such evidence as
this, it might have been supposed that only the glands of the
exterior and inflected tentacles had absorbed the salt; or that
only those on the disc had absorbed it, and had then transmitted
a motor impulse to the exterior tentacles; but in this latter case
the exterior tentacles would not have become inflected until
some time had elapsed, instead of within half an hour, or even
within a few minutes, as usually occurred. All the glands on
the same leaf are of nearly the same size, as may best be seen
by cutting off a narrow transverse strip, and laying it on its
side; hence their absorbing surfaces are nearly equal. The
long-headed glands on the extreme margin must be excepted,
as they are much longer than the others; but only the upper
surface is capable of absorption. Besides the glands, both
surfaces of the leaves and the pedicels of the tentacles bear
numerous minute papille, which absorb carhonate of ammonia,
an infusion of raw meat, metallic salts, and probably many
other substances, but the absorption of matter by these papille
never induces inflection. We must remember that the move-
ment of each separate tentacle depends on its gland being
excited, except when a motor impulse is transmitted from the
glands of the disc, and then the movement, as just stated,
does not take place until some little time has elapsed. I have
made these remarks because they show us that when a, leaf is
immersed in a solution, and the tentacles are inflected, we can
judge with some accuracy how much of the salt each gland has
absorbed. For instance, if a leaf bearing 212 glands be immersed
in a measured quantity of a solution, containing ~, of a grain of
a salt, and all the exterior tentacles, except twelve, are inflected,
we may feel sure that each of the 200 glands can on an average
have absorbed at most g¢ggq of a grain of the salt. I say at
Caar. VIL. EFFECTS OF WATER. 139
most, for the papille will have absorbed some small amount,
and so will perhaps the glands of the twelve excluded tentacles
which did not become inflected. The application of this prin-
ciple leads to remarkable conclusions with respect to the
minuteness of the doses causing inflection.
On the Action of Distilled Water in causing Inflection.
Although in all the more important experiments the dii-
ference between the leaves simultaneously immersed in water
and in the several solutions will be described, nevertheless it
may be well here to give a summary of the effects of water.
The fact, moreover, of pure water acting on the glands deserves
in itself some notice. Leaves to the number of 141 were im-
mersed in water at the same time with those in the solutions,
and their state recorded at short intervals of time. Thirty-two
other leaves were separately observed in water, making alto-
gether 173 experiments. Many scores of leaves were also im-
mersed in water at other times, but no exact record of the
effects produced was kept; yet these cursory observations sup-
port the conclusions arrived at in this chapter. A few of the
long-headed tentacles, namely from one to about six, were
commonly inflected within half an hour after immersion; as
were occasionally a few, and rarely a considerable number of
the exterior round-headed tentacles. After an immersion of
from 5 to 8 hrs. the short tentacles surrounding the outer
parts of the disc generally become inflected, so that their glands
form a small dark ring on the disc; the exterior tentacles
not partaking of this movement. Hence, excepting in a few
cases hereafter to be specified, we can judge whether a solution
produces any effect only by observing the exterior tentacles
within the first 3 or 4 hrs. after immersion.
Now for a summary of the state of the 173 leaves after an
immersion of 3 or 4 hrs. in pure water. One leaf had almost
all its tentacles inflected; three leaves had most of them sub-
inflected; and thirteen had,on an average 36:5. tentacles in-
flected. Thus seventeen leaves out of the 173 were acted on in
a marked manner. Eighteen leaves had from seven to nineteen
tentacles inflected, the average being 9:3 tentacles for each
leaf. Forty-four leaves had from one to six tentacles inflected,
generally the long-headed ones. So that altogether of the 173
leaves carefully observed, seventy-nine were affected by the
water in some degree though commonly to a very slight degree;
and ninety-four were not affected in the least degree. This
140 DROSERA ROTUNDIFOLIA. Cnap, VII.
amount of inflection is utterly insignificant, as we shall here-
after see, compared with that caused by very weak solutions
of several salts of ammonia.
Plants which have lived for some time in a rather high
temperature are far more sensitive to the action of water than
these grown out of doors, or recently brought into a warm
greenhouse. Thus in the above seventeen cases, in which the
immersed leaves had a considerable number of tentacles in-
flected, the plants had been kept during the winter in a very
warm greenhouse; and they bore in the early spring remarkably
fine leaves, of a light red colour. Had I then known that the
sensitiveness of plants was thus increased, perhaps I should
not have used the leaves for my experiments with the very
weak solutions of phosphate of ammonia; but my experiments
are not thus vitiated, as I invariably used leaves from the same
plants for simultancous immersion in water. It often happened
that some leaves on the same plant, and some tentacles on the
same leaf, were more sensitive than others; but why this should
be so, Ido not know.
Resides the differences just indicated between the leaves im-
mersed in water and in weak
solutions of ammonia, the ten-
tacles of the latter are in most
cases much more closely in-
flected. The appearance of a
leaf after immersion in a few
drops of a solution of one grain
of phosphate of ammonia to
200 oz. of water (i.e. one part
to 87,500) is here reproduced :
such energetic inflection is
never caused by water alone.
With leaves in the weak solu-
tions, the blade or lamina often
becomes inflected; and this is
so rare a circumstance with
leaves in water that I have
Fic. 9. seen only two instances; and
(Drosera rotundifolia.) in both of these the inflec-
zeaf (enlarged) with all the tentacles tion was very feeble. Again
closely inflected, from immersion in a : :
solution of phosphate of ammonia (one with leaves the weak solu
part to 87,500 of water). tions, the inflection of the ten.
tacles and ‘blade often goes on
steadily, though slowly, increasing during many hours; and
Onar. VIL CARBONATE OF AMMONIA. 141
this again is so rare a circumstance with leaves in water that
I have seen only three instances of any such increase after the
first 8 to 12 hrs.; and in these three instances the two outer
rows of tentacles were not at all affected. Hence there is some-
times a much greater difference between the leaves in water and
in the weak solutions, after from 8 hrs. to 24 hrs., than there
was within the first 3 hrs.; though as a general rule it is best
to trust to the difference observed within the shorter time.
With respect to the period of the re-expansion of the leaves,
when left immersed either in water or in the weak solutions,
nothing could be more variable. In both cases the exterior
tentacles not rarely begin to re-expand, after an interval of
only from 6 to 8 hrs.; that is just about the time when the
short tentacles round the borders of the disc become inflected.
On the other hand, the tentacles sometimes remain inflected
for a whole day, or even two days; but as a general rule they
remain inflected for a longer period in very weak solutions than
in water. In solutions which are not extremely weak, they
never re-expand within nearly so short a period as six or
eight hours. From these statements it might be thought
difficult to distinguish between the effects of water and the
weaker solutions; but in truth there is not the slightest diffi-
culty until excessively weak solutions are tried; and then the
distinction, as might be expected, becomes very doubtful, and
at last disappears. But as in all, except the simplest, cases
the state of the leaves simultaneously immersed for an equal
length of time in water and in the solutions will be described,
the reader can judge for himself.
CARBONATE OF AMMONIA.
* This salt, when absorbed by the roots, does not cause
the tentacles to be inflected. A plant was so placed
in a solution of one part of the carbonate to 146 of
water that the young uninjured roots could be ob-
served. The terminal cells, which were of a pink
colour, instantly became colourless, and their limpid
contents cloudy, like a mezzo-tinto engraving, so that
some degree of aggregation was almost instantly
caused; but no further change ensued, and the ab-
sorbent hairs were not visibly affected. The tentacles
142 DROSERA ROTUNDIFOLIA. Cuap. VIL
did not bend. Two other plants were placed with
their roots surrounded by damp moss, in half an ounce
(14198 ml.) of a solution of one part of the carbo-
nate to 218 of water, and were observed for 24 hrs.
but not a single tentacle was inflected. In order to
produce this effect, the carbonate must be absorbed
by the glands. p 2
The vapour produces a powerful effect on the glands,
and induces inflection. Three plants with their roots
in bottles, so that the surrounding air could not have
become very humid, were placed under a bell-glass
(holding 122 fluid ounces), together with 4 grains
of carbonate of ammonia in a watch-glass. After an
interval of 6 hrs. 15 m. the leaves appeared unaffected ;
but next morning, after 20 hrs., the blackened glands
were secreting copiously, and most of the tentacles
were strongly inflected. These plants soon died.
Two other plants were placed under the same bell-
glass, together with half a grain of the carbonate, the
air being rendered as damp as possible; and in 2 hrs.
most of the leaves were affected, many of the glands
being blackened and the tentacles inflected. But it is
a curious fact that some of the closely adjoining ten-
tacles on the same leaf, both on the dise and round
the margins, were much, and some, apparently, not in
the least affected. The plants were kept under the
bell-glass for 24 hrs., but no further change ensued.
One healthy leaf was hardly at all affected, though .
other leaves on the same plant were much affected.
‘On some leaves all the tentacles on one side, but not
those on the opposite side, were inflected. I doubt
whether this extremely unequal action can be ex-
plained by supposing that the more active glands
absorb all the vapour as quickly as it is generated, se
that none is left for the others for we shall meet with
Cuap. VII. CARBONATE OF AMMONIA. 143
analogous cases with air thoroughly permeated with
the vapours of chloroform and ether.
Minute particles of the carbonate were added to the
secretion surrounding several glands. These instantly
became black and secreted copiously; but, except in
two instances, when extremely minute particles were
given, there was no inflection. This result is analo-
gous to that which follows from the immersion of
leaves in a strong solution of one part of the carbonate
to 109, or 146, or even 218 of water, for the leaves
are then paralysed and no inflection ensues, though
the glands are blackened, and the protoplasm in the
cells of the tentacles undergoes strong aggregation.
We will now turn to the effects of solutions of the carbonate.
Half-minims of a solution of one part to 437 of water were placed
on the discs of twelve leaves ; so that each received 54, of a grain
or ‘0675 mg. Ten of these had their exterior tentacles well
inflected ; the blades of some being also much curved inwards.
In two cases several of the exterior tentacles were inflected in
35 m.; but the movement was generally slower. These ten
leaves re-expanded in periods varying between 21 hrs. and
45 hrs., but in one case not until 67 hrs. had elapsed; so that
they re-expanded much more quickly than leaves which have
caught insects.
The same-sized drops of a solution of one part to 875 of water
were placed on the discs of eleven leaves; six remained quite
unaffected, whilst five had from three to six or, eight of their
exterior tentacles inflected; but this degree of movement can
hardly be considered as trustworthy. Each of these leaves
received y5 of a grain (°0337 mg.), distributed between the
glands of the disc, but this was too small an amount to produce
any decided effect on the exterior tentacles, the glands of which
had not themselves received any of the salt.
Minute drops on the head of a small pin, of a solution of one
part of the carbonate to 218 of water, were next tried in the
manner above described. A drop of this kind equals on an
average >, 0f a minim, and therefore contains -3;5 of a grain
(0135 mg.) of the carbonate. I touched with it the viscid
secretion round three glands, so that each gland received only
144 DROSERA ROTUNDIFOLIA Cuap. VIL
rele of a grain (:00445 mg.). Nevertheless, m two trials all
the glands were plainly blackened ; in one case all three tcntacles
were well inflected after an interval of 2 hrs. 40 m.; and in an.
other case two of the three tentacles were inflected. I then
tried drops of a weaker solution of one part to 292 of water on
twenty-four glands, always touching the viscid secretion round
three glands with the same little drop. Each gland thus received
only the zsh of a grain (°00387 mg.), yet some of them were
a little darkened; but in no one instance were any of the ten-
tacles inflected, though they were watched for 12 hrs. When a
still weaker solution (viz. one part to 437 of water) was tried on
six glands, no effect whatever was perceptible. We thus learn
that the zzigp of a grain (00445 mg.) of carbonate of ammonia,
if absorbed by a gland, suffices to induce inflection in the basal
part of the same tentacle; but as already stated, I was able to
hold with a steady hand the minute drops in contact with the
secretion only for a few seconds; and if more time had been
allowed for diffusion and absorption, a much weaker solution
would certainly have acted.
Some experiments were made by immersing cut-off leaves in
solutions of different strengths. Thus four leaves were left for
about 3 hrs. each in a drachm (8°549 ml.) of a solution of one
part of the carbonate to 5250 of water; two of these had almost
every tentacle inflected, the third had about half the tentacles
and the fourth about one-third inflected ; and all the glands were
blackened. Another leaf was placed in the same quantity of a
solution of one part to 7000 of water, and in 1 hr. 16 m. every.
single tentacle was well inflected, and all the glands blackened.
Six leaves were immersed, each in thirty minims (1:774 ml.) of
a solution of one part to 43875 of water, and the glands were all
blackened in 81m. All six leaves exhibited some slight inflec-
tion, and one was strongly inflected. Four leaves were then
immersed in thirty minims of a solution of one part to 8750 of
water, so that each leaf received the 535 of a grain (2025 mg.).
Only one became strongly inflected; but all the glands on all
the leaves were of so dark a red after one hour as almost to
deserve to be called black, whereas this did not occur with the
leaves which were at the same time immersed in water; nor did
water produce this effect on any other occasion in nearly so
short a time as an hour. These cases of the simultaneous
darkening or blackening of the glands from the action of weak
goiutions are important, as they show that all the glands absorbed
tno carbonate within the same time, which fact indeed there
was not the least reason to doubt. So again, whenever all the
Onar. VIL CARBONATE OF AMMONIA. 145
tentacles become inflected within the same time, we have
evidence, as before remarked, of simultaneous absorption. I
did not count the number of glands on these four leaves; but
as they were fine ones, and as we know that the average number
--of glands on thirty-one leaves was 192, we may safely assume
that each bore on an average at least 170; and if so, each
blackened gland could have absorbed only gzhg5 of a grain
(00119 mg.) of the carbonate.
A large number of trials had been previously made with
solutions of one part of the nitrate and phosphate of ammonia to
43750 of water (ie. one grain to 100 ounces), and these were
found highly efficient. Fourteen leaves were therefore placed,
each in thirty minims of a solution of one part of the carbonate
to the above quantity of water; so that each leaf received ~)55
of a grain (°0405 mg.). The glands were not much darkened.
Ten of the leaves were not affected, or only very slightly so.
Four, however, were strongly affected; the first having all the
tentacles, except forty, inflected in 47 m.; in 6 hrs. 30 m. all
except eight; and after 4 hrs. the blade itself. The second leaf
after 9 m. had all its tentacles except nine inflected; after 6 hrs.
80 m. these nine were sub-inflected; the blade having become
much inflected in 4 hrs. The third leaf after 1 hr. 6 m. had all
but forty tentacles inflected. . The fourth, after 2 hrs. 5 m., had
about half its teutacles and after 4 hrs. all.but forty-five in-
flected. ‘Leaves which were immersed in water at the same time
were not at all affected, with the exception of one; and this not
until 8-hrs. had elapsed. Hence there can be no doubt that a
highly sensitive leaf, if immersed in a solution, so that all the
glands are enabled to absorb, is acted on by zy of a grain of
the carbonate. Assuming that the leaf, which was a large one,
and which had all its tentacles excepting eight inflected, bore
170 glands, each gland could have absorbed only sgeyqq of a
grain (00024 mg.); yet this sufficed to act on each of the 162
tentacles which were inflected. But as only four out of the above
fourteen leaves were plainly affected, this is nearly the mini-
mum dose which is efficient.
Aggregation of the Protoplasm from the Action of Curbonate of
Ammonia.—I have fully described in the third chapter the
remarkable effects of moderately strong doses of this salt in
causing the aggregation of the protoplasm within the cells of
the glands and tentacles; and here my object is merely to show
what small doses suffice. A leaf was immersed in twenty
minims (1°183 ml.) of a solution of one part to 1750 of water.
146 DROSERA ROTUNDIFOLIA. Cuap. VIL
and another leaf in the same quantity of a solution of one part
to 3062; in the former case aggregation occurred in 4 m., in the
latter in 11m. A leaf was then immersed in twenty minims of
a solution of one part to 4375 of water, so that it received 52, of
a grain (‘27 mg.); in 5 m. there was a slight change of colour
in the glands, and in 15 m. small spheres of protoplasm were
formed in the cells beneath the glands of aii the tentacles. In
these cases there could not be a shadow of a doubt about the
action of the solution.
A solution was then made of one part to 5250 of water, and I
experimented on fourteen leaves, but will give only a few of the
cases. Eight young leaves were selected and examined with
care, and they showed no trace of aggregation. Four of these
were placed in a drachm (3°549 ml.) of distilled water ; and four
in a similar vessel, with a drachm of the solution. After a time
the leaves were examined under a high power, being taken alter-
nately from the solution and the water. The first leaf was taken
out of the solution after an immersion of 2 hrs. 40 m., and the
last leaf out of the water after 3 hrs. 50 m.; the examination
lasting for 1 hr.40 m. In the four leaves out of the water there
was no trace of aggregation except in one specimen, in which a
very few, extremely minute spheres of protoplasm were present
beneath some of the round glands. All the glands were trans-
lucent and red. ‘The four leaves which had been immersed in
the solution, besides being inflected, presented a widely different
appearance; for the contents of the cells of every single tentacle
on all four leaves were conspicuously aggregated ; the spheres
and elongated masses of protoplasm in many cases extending
halfway down the tentacles. All the glands, both those of the
central and exterior tentacles. were opaque and blackened; and
this shows that all had absorbed some of the carbonate. These
four leaves were of very nearly the same size, and the glands
were counted on one and found to be 167. This being the case,
and the four leaves having been immersed in a drachm of the
solution, each gland could have received on an average only
gaiss Of a grain (-001009 mg.) of the salt; and this quantity
sufficed to induce within a short time conspicuous aggregation
in the cells beneath all the glands.
A vigorous but rather small red leaf was placed in six
minims of the same solution (viz. one part to 5250 of water), so
that it received 53, of a grain (-0675 mg.). In 40 m. the glands.
appeared rather darker; and in 1 hr. from four to six spheres
of protoplasm were formed in the cells beneath the glands of
all the tentacles. I did not count the tentacles, but we maj
Cuar, VIL. CARBONATE OF AMMONIA. 147
safely assume that there were at least 140; and if so, each
gland could have received only the zy¢ygq Of a grain, or
“00048 mg.
A weaker solution was then made of one part to 7000 of water,
and four leaves were immersed in it; but I will give only one
case. A leaf was placed in ten minims of this solution; after
1 hr. 37 m. the glands became somewhat darker, and the cells
beneath all of them now contained ues spheres of aggregated
protoplasm. This leaf received 74, of a grain, and bore 166
glands. Each gland could, therefore, have received only a7s55
of a grain (°000507 mg.) of the carbonate.
Two other experiments are worth giving. A leaf was im-
mersed for 4 hrs. 15 m. in distilled water, and there was no
aggregation; it was then placed for 1 hr. 15 m. in a little solu-
tion of one part to 5250 of water; and this excited well-marked
aggregation and inflection. Another leaf, after having been
immersed for 21 hrs. 15 m. in distilled water, had its glands
blackened, but there was no aggregation in the cells beneath
them; it was then left in six minims of the same solution, and
in 1 hr. there was much aggregation in many of the tentacles;
in 2 hrs. all the tentacles (146 in number) were affected—the
aggregation extending down for a length equal to half or the.
whole of the glands. It is extremely improbable that these two
leaves would have undergone aggregation if they had been left
for a little longer in the water, namely for 1 br. and 1 hr. 15 m.,
during which time they were immersed in the solution ; for the
process of aggregation seems invariably to supervene slowly and
very gradually in water.
Summary of the Results with Carbonate of Ammonia.—
The roots absorb the solution, as shown by their changed
colour, and by the aggregation of the contents of their
cells. The vapour is absorbed by the glands; these
are blackened, and the tentacles are inflected. The
glands of the disc, when excited by a half-minim drop
(0296 ml.), containing 52; of a grain (0675 mg.),
transmit a motor impulse to the exterior tentacles,
causing them to bend inwards A minute drop, con-
taining z;4,5 of a grain (‘00445 mg.), if held for a
few seconds in contact with a gland, soon causes the
tentacle bearing it to be inflected. If a leaf is left
148 DROSERA ROTUNDIFOLIA. Cuar. VIL
immersed for a few hours in a solution, and a gland
absorbs the +s34;55 of a grain (00048 mg.), its colour
becomes darker, though not actually black; and the
contents of the cells beneath the gland are plainly
aggregated. Lastly, under the same circumstances,
the absorption by a gland of the erys00 Of a grain
(00024 mg.) suffices to excite the tentacle bearing this
gland into movement.
NITRATE OF AMMONIA.
With the salt I attended only to the inflection of the leaves,
for it is far less efficient than the carbonate in causing aggrega-
tion, although considerably more potent in causing inflection. I
experimented with half-minims (‘0296 ml.) on the discs of fifty-
two leaves, but will give only a few cases. A solution of one
part to 109 of water was too strong, causing little inflection, and
after 24 hrs. killing, or nearly killing, four out of six leaves
which were thus tried ; each of which received the 71, of a grain
(or ‘27 mg.). A solution of one part to 218 of water acted most
energetically, cansing not only the tentacles of all the leaves,
but the blades of some, to be strongly inflected. Fourteen
leaves were tried with drops of a solution of one part to 875
of water, so that the disc of each received the 755 of a grain
(0337 mg.). Of these leaves, seven were very strongly acted on,
the edges being generally inflected ; two were moderately acted
on; and five not at all. 1 subsequently tried three of these latter
five leaves with urine, saliva, and mucus, but they were only
slightly affected ; and this proves that they were not in an active
condition. 1 mention this fact to show how necessary it is to
experiment on several leaves. ‘Two of the leaves, which were
well inflected, re-expanded after 51 hrs.
In the following experiment I happened to select very sensi-
tive leaves. Half-minims of a solution of one part to 1094 ot
water (ie. 1 gr. to 25 oz.) were placed on the discs of nine leaves,
so that each received the 54,5 of a grain (027 mg.). Three of
them had their tentacles strongly inflected and their blades curled
inwards; five were slightly and somewhat doubtfully affected,
having from three to eight of their exterior tentacles inflected :
one leaf was not at all affected, yet was afterwards acted on by
saliva. In six of these cases, a trace of action was perceptible in
Cuap. VIL. NITRATE OF AMMONIA. 149
7 hrs., but the full effect was not produced until from 24 hrs. tc
30 hrs. had elapsed. Two of the leaves, which were only slightly
inflected, re-expanded after an additional interval of 19 hrs.
Half-minims of a rather weaker solution, viz. of one part tc
1812 of water (1 gr. to 3 0z.) were tried on fourteen leaves ; so that
each received z25q of a grain (0225 mg.), instead of, as in the last
experiment, sf55 Of a grain. The blade of one was plainly in-
flected, as were six of the exterior tentacles; the blade of a second
was slightly, and two of the exterior tentacles well, inflected, all
the other tentacles being curled in at right angles to the disc,
three other leaves had from five to eight tentacles inflected; five
others only two or three, and occasionally, though very rarely,
drops of pure water cause this much action; the four remaining
leaves were in no way affected, yet three of them, when subse-
quently tried with urine, became greatly inflected. In most of
these cases a slight effect was perceptible in from 6 hrs. to
7 hrs., but the full effect was not produced until from 24 hrs.
to 80 hrs. had elapsed. It is obvious that we have here reached
very nearly the minimum amount, which, distributed between
the glands of the disc, acts on the exterior tentacles; these
having themselves not received any of the solution.
In the next place, the viscid secretion round three of the
exterior glands was touched with the same little drop (j5 of a
minim) of a solution of one part to 437 of water; and after an
interval of 2 hrs. 50 m. all three tentacles were well inflected.
Each of these glands could have received only the ggi55 ofa
grain, or (00225 mg. A little drop of the same size and strength
was also applied to four other glands, and in 1 hr. two became
inflected, whilst the other two never moved. We here see, as in
the case of the half-minims placed on the discs, that the nitrate
of ammonia is more potent in causing inflection than the car-
bonate ; for minute drops of the latter salt of this strength pro-
’ duced no effect. I tried minute drops of a still weaker solution
of the nitrate, viz. one part to 875 of water, on twenty-one
glands, but no effect whatever was produced, except perhaps in
one instance.
Sixty-three leaves were immersed in solutions of various
strengths; other leaves being immersed at the same time in the
same pure water used insmaking the solutions. The results are
so remarkable, though less so than with phosphate of ammonia,
that I must describe the experiments in detail, but I will give
only a few. In speaking of the successive periods when
inflection occurred, I always reckon from the time of first
immersion.
{50 DROSERA ROTUNDIFOLIA. Cuar. VIL
Having made some preliminary trials as a guide, five leaves
were placed in the same little vessel in thirty minims of a solu-
tion of one part of the nitrate to 7875 of water (1 gr. to 18 0z.);
and this amount of fluid just sufficed to cover them. After
2 hrs. 10 m. three of the leaves were considerably inflected, and
the other two moderately. The glands of all became of so dark
a red as almost to deserve to be called black. After 8 hrs. four
of the leaves had all their tentacles more or less inflected ; whilst
the fifth, which I then perceived to be an old leaf, had only thirty
tentacles inflected. Next morning, after 23 hrs. 40 m., all the
leaves were in the same state, excepting that the old leaf had a
few more tentacles inflected. Five leaves which had been placed
at the same time in water were observed at the same intervals
of time; after 2 hrs. 10 m. two of them had four, one had seven,
one had ten, of the long-headed marginal tentacles, and the
fifth had four round-headed tentacles, inflected. After 8 hrs.
there was no change in these leaves, and after 24 hrs. all the
marginal tentacles had re-expanded ; but in one leaf, a dozen, and
in a second leaf, half a dozen, submarginal tentacles had become
inflected. As the glands of the five leaves in the solution were
simultaneously darkened, no doubt they had all absorbed a nearly
equal amount of the salt: and as 4, of a grain was given to the
five leaves together, each got 2,5 of a grain (045 mg.). I did
not count the tentacles on these leaves, which were moderately
fine ones, but as the average number on thirty-one leaves was
192, it would be safe to assume that each bore on an average at
least 160. If so, each of the darkened glands could have
received only sggyo5 Of a grain of the nitrate; and this caused
the inflection of a great majority of the tentacles.
This plan of immersing several leaves in the same vessel
is a bad one, as it is impossible to feel sure that the more
vigorous leaves do not rob the weaker ones of their share of
the salt. The glands, moreover, must often touch one another .
or the sides of the vessel, and movement may have been thus
excited; but the corresponding leaves in water, which were
little inflected, though rather more so than commonly occurs,
were exposed in an almost equal degree to these same sources
of error. I will, therefore, give only one other experiment mado
in this manner, though many were tried and all confirmed
the foregoing and following results.’ Four leaves were placed
in forty minims of a solution of one part to 10,500 of water;
and assuming that they absorbed equally, each leaf received
rosy of a grain (0562 mg.). After 1 hr. 20 m. many of the
tentacles on all four leaves were somewhat inflected. After
Cuap. VIL NITRATE OF AMMONIA. 151
5 hrs. 80 m. two leaves had all their tentacles inflected; a
third leaf all except the extreme marginals, which seemed old
and torpid; and the fourth a large number. After 21 hrs,
every single tentacle, on all four leaves, was closely inflected.
Of the four leaves placed at the same time in water, one had,
after 5 hrs. 45 m., five marginal tentacles inflected; a second,
ten; a third, nine marginals and submarginals; and the fourth,
twelve, chiefly submarginals, inflected. After 21 hrs. all these
marginal tentacles re-expanded, but a few of the submarginals
on two of the leaves remained slightly curved inwards. The
contrast was wonderfully great between these four leaves in
water and those in the solution, the latter having every one of
their tentacles closely inflected. Making the moderate assump-
tion that each of these leaves bore 160 tentacles, each gland
could have absorbed only zg2s55 Of a grain (000351 mg.).
This experiment was repeated on three leaves with the same
relative amount of the solution; and after 6 hrs. 15 m. all the
tentacles except nine, on all three leaves taken together, were
closely inflected. In this case the tentacles on each leaf were
counted, and gave an average of 162 per leaf.
The following experiments were tried during the summer of
1873, by placing the leaves, each in a separate watch-glass and
pouring over it thirty minims (1:775 ml.) of the solution; other
leaves being treated in exactly the same manner with the
doubly distilled water used in making the solutions. The
trials above given were made several years before, and when I
read over my notes, I could not believe in the results; so I
resolved to begin again with moderately strong solutions. Six
leaves were first immersed, each in thirty minims of a solution of
one’ part of the nitrate to 8750 of water (1 gr. to 20 0z.), so that
each received 54, of a grain (2025 mg.). Before 30 m. had
elapsed, four of these leaves were immensely, and two of them
moderately, inflected. The glands were rendered of a dark
red. The four corresponding leaves in water were not at all
affected until 6 hrs. had elapsed, and then only the short ten-
tacles on the borders of the disc; and their inflection, as
previously explained, is never of any significance.
Four leaves were immersed, each in thirty minims of a solu-
tion of one part to 17,500 of water (1 gr. to 40 0z.), so that each
received z=, of a grain (101 mg.); and in less than 45 m. three
of them had all their tentacles, except from four to ten, inflected ;
the blade of one being inflected after 6 hrs., and the blade of a
second after 21 hrs. The fourth leaf was not at all affected.
The glands of none were darkened. Of the corresponding leaves
11
152° DROSERA ROTUNDIFOLIA. Cuav. VIL
in water, only one had any of its éxterior tentacles, namely five, |
-inflected; after 6 hrs. in one case, and after 21 hrs, in two other
cases, the short tentacles on the borders of the disc formed a
ring, in the usual manner.
Four leaves were immersed, each in thirty minims of a solution
of one part to 48,750 of water (1 gr. to 100 oz.), so that each leaf
got sds of a grain (0405 mg.). Of these, one was much in--
flected in 8 m., and after 2 hrs. 7 m. had all the tentacles,
except thirteen, inflected. The second leaf, after 10 m., had all
except three inflected. The third and fourth were hardly at all
affected, scarcely more than the corresponding leaves in water.,
Of the latter, only one was affected, this having two tentacles
inflected, with those on the outer parts of the disc forming a
ring in the usual manner. In the leaf which had all its ten-
tacles except three inflected in 10 m., each gland (assuming that
the leaf bore 160 tentacles) could have absorbed only zszsoq of
a grain, or ‘000258 mg.
Four leaves were separately immersed as before in « solution
of one part to 131,250 of water (1 gr. to 300 0z.), so that each
received 2,5 of a grain, or 0185 mg. After 50 m. one leaf had
all its tentacles except sixteen, and after 8 hrs. 20 m. all but
fourteen, inflected. The second leaf, after 40 m., had all, but
twenty inflected; and after 8 hrs. 10 m. began to re-expand.
The third, in 3 hrs. had about half its tentacles inflected, which
began to re-expand after 8 hrs. 15 m. The fourth leaf, after
3 hrs. 7 m., had only twenty-nine tentacles more or less in-
flected. Thus three out of the four leaves were strongly acted
on. It is clear that very sensitive leaves had been accidentally
selected. The day moreover was hot. The four corresponding
jeaves in water were likewise acted on rather more than is usual;
for after 3 hrs. one had nine tentacles, another four, and
another two, and the fourth none, inflected. With respect to
the leaf of which all the tentacles, except sixteen, were inflected
after 50 m., each gland (assuming that the leaf bore 160 ten-
tacles) could have absorbed only ggzyqq of a grain (0000937
mg.), and this appears to be about the least quantity of the
nitrate which suffices to induce the inflection of a single tentacle,
As negative results are important-in confirming the foregoing
positive ones, eight leaves were immersed as before, each in thirty
minims of a solution of one part to 175,000 of water (1 gr. to
400 oz.), so that each received only ;,;5 of a grain (‘0101 mg.).
This minute quantity produced a slight effect on only four of
the eight leaves. One had fifty-six tentacles inflected after 2 hrs.
13 m.; a second, twenty-six inflected, or sub-inflected, after
Cuar. VIL: PHOSPHATE OF AMMONIA, 153
88 m.; a third, eighteen inflected, after 1 hr.; and u fourth,
ten inflected, after 35 m. The four other leaves were not in
the least affected. Of the eight corresponding leaves in water,
one had, after 2 hrs. 10 m., nine tentacles, and four others from
one to four long-headed tentacles, inflected; the remaining three
being unaffected. Hence, the zaj;5 of a grain given to a sensi-
tive leaf during warm weather perhaps produces a slight effect ;
but we must bear in mind that occasionally water causes as
great an amount of inflection as occurred in this last ex-
‘periment.
Summary of the Results with Nitrate of Ammonia.—
The glands of the disc, when excited by a half-minim
drop (0296 ml.), containing 7,55 of a grain of the
nitrate (027 mg.), transmit a motor impulse to the
exterior tentacles, causing them to bend inwards. A
minute drop, containing 4,4,, of a grain (00225 mg.),
if held for a few seconds in contact with a gland,
causes the tentacle bearing this gland to be inflected
If a leaf is left immersed for a few hours, and some-
times for only a few minutes, in a solution of such
strength that each gland can absorb only the 357505
of a grain (-0000937 mg.), this small amount is
enough to excite each tentacle into movement, and
it becomes closely inflected.
PHOSPHATE OF AMMONIA.
This salt is more powerful than the nitrate, even
in a greater degree than the nitrate is more powerful
than the carbonate. This is shown by weaker solu-
tions of the phosphate acting when dropped on the
discs, or applied to the glands of the exterior ten-
tacles, or when leaves are immersed. The difference
in the power of these three salts, as tried in three
different ways, supports the results presently to be
154 DROSERA ROTUNDIFOLIA. Ouap. VIL
given, which are so surprising that their credi-
bility requires every kind of support. In 1872 I
experimented on twelve immersed leaves, giving each
only ten minims of a solution; but this was a bad
method, for so small a quantity hardly covered them.
None of these experiments will, therefore, be given,
though they indicate that excessively minute doses
are efficient. When I read over my notes, in 1873,
I entirely disbelieved them, and determined to make
another set of experiments with scrupulous care, on
the same plan as those made with the nitrate; namely
by placing leaves in watch-glasses, and pouring over
each thirty minims of the solution under trial, treat-
ing at the same time and in the same manner other
leaves with the distilled water used in making the
solutions. During 1873, seventy-one leaves were thus
tried in solutions of various strengths, and the same
number in water. Notwithstanding the care taken
and the number of the trials made, when in the
following year I looked merely at the results, without
reading over my observations, I again thought that
there must have been some error, and thirty-five fresh
trials were made with the weakest solution; but
the results were as plainly marked as before. Al-
together, 106 carefully selected leaves. were tried,
both in water and in solutions of the phosphate.
Hence, after the most anxious consideration, I can
entertain no doubt of the substantial accuracy of my
results.
Before giving my experiments, it may be well to premise that
crystallised phosphate of ammonia, such as I used, contains
35°33 per cent. of water of crystallisation; so that in all the
following trials the efficient elements formed only 64°67 per
cent. of the salt used.
Extremely minute particles of the dry phosphate were placed
~
Cuap. VIL PHOSPHATE OF AMMONIA. 155
with the point of a needle on the secretion surrounding several
glands. These poured forth much secretion, were blackened,
and ultimately died; but the tentacles moved only slightly.
The dose, small as it was, evidently was too great, and the
result was the same as with particles of the carbonate of
ammonia.
Half-minims of a solution of one part to 487 of water were
placed on the discs of three leaves and acted most energetically,
causing the tentacles of one to be inflected in 15 m., and
the blades of all three to be much curved inwards in 2 hrs.
15m. Similar drops of a solution of one part to 1312 of water,
(1 gr. to 8 0z.) were then placed on the discs of five leaves,
so that each received the z2y5 of a grain (0225 mg.). After
8 hrs. the tentacles of four of them were considerably inflected,
and after 24 hrs. the blades of three. After 48 hrs. all five
were almost fully re-expanded. I may mention with respect
to one of these leaves, that a drop of water had been left
during the previous 24 hrs. on its disc, but produced no effect ;
and that this was hardly dry when the solution was added.
Similar drops of a solution of one part to 1750 of water (1 gr.
to 4 oz.) were next placcd on the discs of six leaves; so that
each received gy of a grain (0169 mg.); after 8 hrs. three of
them had many tentacles and their blades inflected; two others
had only a few tentacles slightly inflected, and the sixth was
not at all affected. After 24 hrs. most of the leaves had a few
more tentacles inflected, but one had begun to re-expand. We
thus see that with the more sensitive leaves the A;5 of a grain,
absorbed by the central glands, is enough to make many of the
exterior tentacles and the blades bend, whereas the z)5, of a
grain of the carbonate similarly given produced no effect; and
aeso Of a grain of the nitrate was only just sufficient to produce
a well-marked effect.
A minute drop, about equal to 4, of a minim, of a solution of
one part of the phosphate to 875 of water, was applied to the
secretion on three glands, each of which thus received only
srivo of a grain (00112 mg.), and all three tentacles became
inflected. Similar ‘drops of a solution of one part to 1312 of
water (1 gr. to 3 oz.) were now tried on three leaves; a drop
being applied to four glands on the same leaf. On the first
leaf, thfee of the tentacles became slightly inflected in 6 m., and
re-expanded after 8 hrs. 45m. On the second, two tentacles
became sub-inflected in 12m. And on the third all four ten-
tacles were decidedly inflected in 12 m.; they remained so for
8 hrs. 20 m., but by the next morning were fully re-expanded.
156 DROSERA ROTUNDIFOLIA. Cuap. VII
In this latter case each gland could have received only the
cresoo (or ‘000563 mg.) of a grain. Lastly, similar drops of a
solution of one part to 1750 of water (1 gr. to 4.0z.) were tried on
five leaves; a drop being applied to four glands on the same
leaf. The tentacles on three of these leaves were not in the
least affected ; on the fourth leaf, two became inflected; whilst
on the fifth, which happened to be a very sensitive one, all four
tentacles were plainly inflected in 6 hrs. 15 m.; but only one re-
mained inflected after 24 hrs. I should, however, state that in
this case an unusually large drop adhered to the head of the
pin. Each of these glands could have received very little more
than jsgso0 of a grain (or 000423); but this small quantity
sufficed to cause inflection. We must bear in mind that these
drops were applied to the viscid secretion for only from 10 to
15 seconds, and we have good reason to believe that all the
phosphate in the solution would not be diffused and absorbed in
this time. We have seen under the same circumstances that the
absorption by a gland of y5355 of a grain of the carbonate, and
of s7doo Of a grain of the nitrate, did not cause the tentacle bear-
ing the gland in question to be inflected; so that here again tho
phosphate is much more powerful than the other two salts.
We will now turn to the 106 experiments with immersed
leaves. Having ascertained by repeated trials that moderately
strong solutions were highly efficient, I commenced with sixteen
leaves, each placed in thirty minims of a solution of one part
to 48,750 of water (1 gr. to 100 oz.); so that each received
reso Of a grain, or 04058 mg. Of these leaves, eleven had
nearly all or a great number of their tentacles inflected in
1 hr., and the twelfth leaf in 3 hrs. One of the eleven had
every single tentacle closely inflected in 50 m. Two leaves out
of the sixteen were only moderately affected, yet more so
than any of those simultaneously immersed in water; and the
remaining two, which were pale leaves, were hardly at all
affected. Of the sixteen corresponding leaves in water, one
had nine tentacles, another six, and two others two tentacles
inflected, in the course of 5 hrs. So that the contrast ir
appearance between the two lots was extremely great.
Kighteen leaves were immersed, ,each in thirty minims of a
solution of one part to 87,500 of water (1 gr. to 200 0z.), so
that each received ss55 of a grain (0202 mg.). Fourteen ot
these were strongly inflected within 2 hrs, and some of them
within 15 m.; three out of the eighteen were only slightly
affected, having twenty-one, nineteen, and twelve tentacles in-
Car. VIL PHOSPHATE OF AMMONIA. 157
flected ; and one was not at all acted on. By an accident only
fifteen, instead of eighteen, leaves were immersed at the same
time in water; these were observed for 24 hrs.; one had six,
another four, and a third two, of their outer tentacles inflected ;
the remainder being quite unaffected.
The next experiment was tried under very favourable circum-
stances, fort he day (July 8) was very warm, and I happened
to have unusually fine leaves. Five were immersed as before in
a solution of one part to 131,250 of water (1 gr. to 300 oz.), sc
that each received z)55 of a grain, or 0135 mg. After an
immersion of 25 m. all five leaves were much inflected. After
1 hr. 25 m. one leaf had all but eight tentacles inflected; the
second, all but three; the third, all but five ; the fourth, all but
twenty-three; the fifth, on the other hand, never had more
than twenty-four inflected. Of the corresponding five leaves in
water, one had seven, a second two, a third ten, a fourth one,
and a fifth none inflected. Let it be observed what a contrast
is presented between these latter leaves and those in the solu-
tion. I counted the glands on the second leaf in the solution,
and the number was 217; assuming that the three tentacles
which did not become inflected absorbed nothing, we find
that each of the 214 remaining glands could have absorbed
only yostc00 Of a grain, or ‘0000631 mg. The third leaf bore
236 glands, and subtracting the five which did not become in-
flected, each of the remaining 231 glands could have absorbed
only ryohsc0 Of a grain (or ‘0000584 mg.), and this amount
sufficed to cause the tentacles to bend.
Twelve leaves were tried as before in a solution of one part to
175,000 of water (1 gr. to 400 0z.), so that each leaf received ¢255
of a grain (0101 mg.). My plants were not at the time in
a good state, and many of the leaves were young and pale.
Nevertheless, two of them had all their tentacles, except three
or four, closely inflected in under 1 hr, Seven were con-
siderably affected, some within 1 hr., and others not until 3 hrs.,
4 hrs. 30 m., and 8 hrs. had elapsed; and this slow action
may be attributed to the leaves being young and pale. Of
these nine leaves, four had their blades well inflected, and a
fifth slightly so. The three remaining leaves were not affected.
With respect to the twelve corresponding leaves in water, not
one had its blade inflected; after from 1 to 2 hrs. one had
thirteen of its outer tentacles inflected; a second six, and four
others either one or two inflected. After 8 hrs. the outer
tentacles did not become more inflected; whereas this occurred
with the leaves in the solution. I record in my notes that
158 DROSERA ROTUNDIFOLIA. Cuap. VIL
after the 8 hrs. it was impossible to compare the two lots, and
doubt for an instant the power of the solution.
Two of the above leaves in the solution had all their tentacles,
except three and four, inflected within an hour. I counted their
glands, and, on the same principle as before, each gland on one
leaf could have absorbed only z;ghg5q, and on the other leaf
only yz7i500: Of a grain of the phosphate.
Twenty leaves were immersed in the usual manner, each in
thirty minims of a solution of one part to 218,750 of water (1 gr.
to 500 oz.). So many leaves were tried because I was then
under the false impression that it was incredible that any
weaker solution could produce an effect. Each leaf received
xeon Of a grain, or ‘0081 mg. The first eight leaves which I
tried both in the solution and in water were either young and
pale or too old; and the weather was not hot. They were hardly
at all affected; nevertheless, it would be unfair to exclude them.
I then waited until I got eight pairs of fine leaves, and the
weather was favourable; the temperature of the room where the
leaves were immersed varying from 75° to 81° (23°8 to 27°-2
Cent.). In another trial with four pairs (included in the above
twenty pairs), the temperature in my room was rather low,
about 60° (15°°5 Cent.); but the plants had been kept for several
days in a very warm greenhouse and thus rendered extremely
sensitive. Special precautions were taken for this set of experi-
ments; a chemist weighed for me a grain in an excellent
‘balance; and fresh water, given me by Professor Frankland, was
carefully measured. The leaves were selected from a large
number of plants in the following manner: the four finest wero
immersed in water, and the next four finest in the solution, and
so on till the twenty pairs were complete. The water specimens
were thus a little favoured, but they did not undergo more in-
flection than in the previous cases, comparatively with those
in the solution.
Of the twenty leaves in the solution, eleven became inflected
within 40 m.; eight of them plainly and three rather doubt-
fully; but the latter had at least twenty of their outer tentacles
inflected. Owing to the weakness of the solution, inflection
occurred, except in No. 1, much more slowly than in the pre-
vious trials. The condition of the eleven leaves which were
considerably inflected will now be given at stated intervals,
always reckoning from the time of immersion :—
(1) After only 8 m. a large number of tentacles inflected,
and after 17 m. all but fifteen; after 2 hrs. all but eight in-
Guar. VIL PHOSPHATE OF AMMONIA. . 159
flected, or plainly sub-inflected. After 4 hrs. the tentacles
began to re-expand, and such prompt re-expansion is unusual;
after 7 hrs. 30 m. they were almost fully re-expanded.
(2) After 89 m. a large number of tentacles inflected; after
2 hrs. 18 m. all but twenty-five inflected ; after 4 hrs..17 m. all
but sixteen inflected. The leaf remained in this state for many
hours.
(3) After 12 m. a considerable amount of inflection; after
4 hrs. all the tentacles inflected except those of the two outer
rows, and the leaf remained in this state for some time; after
23 hrs. began to re-expand
(4) After 40 m. much inflection ; after 4 hrs. 13 m. fully half
the tentacles inflected ; after 23 hrs. still slightly inflected.
(5) After 40 m. much inflection; after 4 hrs. 22 m, fully half
the tentacles inflected ; after 23 hrs. still slightly inflected.
(6) After 40 m. some inflection; after 2 hrs. 18 m. about
twenty-eight outer tentacles inflected ; after 5 hrs.20 m. about a
third of the tentacles inflected ; after 8 hrs. much re-expanded.
(1 After 20 m. some inflection ; after 2 hrs. a considerable
number of tentacles inflected; after 7 hrs. 45 m. began to
re-expand.
(8) After 88 m. twenty-eight tentacles inflected; after 3 hrs.
45 m. thirty-three inflected, with most of the submarginal
tentacles sub-inflected ; continued so for two days, and then
partially re-expanded.
(9) After 38 m. forty-two tentacles inflected; after 3 hrs.
12 m. sixty-six inflected or sub-inflected ; after 6 hrs. 40 m. all
but twenty-four inflected or sub-inflected; after 9 hrs. 40 m. all
but seventeen inflected; after 24 hrs. all but four inflected or
sub-inflected, only a few being closely inflected; after 27 hrs.
40 m. the blade inflected. The leaf remained in this state for
two days, and then began to re-expand.
(10) After 38 m. twenty-one tentacles inflected ; after 3 hrs.
12 m. forty-six tentacles inflected or sub-inflected ; after 6 hrs.
40 m. all but seventeen inflected, though none closely; after
24 hrs. every tentacle slightly curved inwards ; after 27 hrs.
40 m. blade strongly ifflected, and so continued for two days,
and then the tentacles and blade very slowly re-expanded.
(11) This fine dark red and rather old leaf, though not very
large, bore an extraordinary number of tentacles (viz. 252), and
behaved in an anomalous manner. After 6 hrs. 40 m. only the
short tentacles round the outer part of the disc were inflected,
forming a ring, as so often occurs in from 8 to 24 hrs. with
leaves both in water and the weaker solutions. But after 9 hra
160 DROSERA ROTUNDIFOLIA. Cuar. VIL
410 m. all the outer tentacles except twenty-five were inflected,
as was the blade in a strongly marked manner. After 24 hrs.
every tentacle except one was closely inflected, and the blade
was completely doubled over. Thus the leaf remained for two
days, when it began to re-expand. 1 may add that the three
latter leaves (Nos. 9, 10, and 11) were still somewhat inflected
after three days. The tentacles in but few of these eleven leaves
became closely inflected within so short a time as in the pre-
vious experiments with stronger solutions.
We will now turn to the twenty corresponding leaves in water.
Nine had none of their outer tentacles inflected; nine others
had from one to three inflected; and these re-expanded after
8 hrs. The remaining two leaves were moderately affected; one
having six tentacles inflected in 34 m.; the other twenty-three
inflected in 2 hrs. 12 m.; and both thus remained for 24 hrs.
None of these leaves had their blades inflected. So that the con-
trast between the twenty leaves in water and the twenty in the
solution was very great, both within the first hour and after
from 8 to 12 hrs. had elapsed.
Of the leaves in the solution, the glands on leaf No. 1, which
in 2 hrs. had all its tenticles except eight inflected, were
counted and found to be 202. Subtracting the eight, each gland
could have received only the zss4oqo Of a grain (-0000411 mg.)
of the phosphate. Leaf No. 9 had 213 tentacles, all of which,
with the exception of four, were inflected after 24 hrs., but
none of them closely ; the blade was also inflected ; each gland
could have received only the zg74555 Of @ grain, or ‘0000387
mg. . Lastly, leaf No. 11, which had after 24 hrs. all its ten-
tacles, except one, closely inflected, as well as the blade, bore
the unusually large number of 252 tentacles; and on the same
principle as before, each gland could have absorbed only the
roorsoo Of a grain, or 0000322 mg.
With respect to the following experiments, I must premise
that the leaves, both those placed in the solutions and in water,
were taken from plants which had been kept in a very warm
greenhouse during the winter. They were thus rendered ex-
tremely sensitive, as was shown by water exciting them much
more than in the previous experiments. Before giving my
observations, it may be well to remind the reader that, judging
from thirty-one fine leaves, the average number of tentacles is
192, and that the outer or exterior ones, the movements of
which are alone significant, are to the short ones on the disc ia
the proportion of about sixteen to nine.
Cap. VII. PHOSPHATE OF AMMONIA. 161
Four leaves were immersed as before, each in thirty minima
of a solution of one part to 328,125 of water (1 gr. to 750 oz.).
Each leaf thus received ~45, of a grain (0054 mg.) of the salt;
and all four were greatly inflected.
(1) After 1 hr. all the outer tentacles but one inflected, and
the blade greatly so; after 7 hrs. began to re-expand.
(2) After 1 hr. all the outer tentacles but eight inflected ;
after 12 hrs. all re-expanded.
(8) After 1 hr. much inflection; after 2 hrs. 30 m. all the ten-
tacles but thirty-six inflected; after 6 hrs. all but twenty-two
inflected ; after 12 hrs, partly re-expanded.
(4) After 1 hr. all the tentacles but thirty-two inflected; after
2 hrs. 30 m. all but twenty-one inflected; after 6 hrs. almost
re-expanded.
Of the four corresponding leaves in water :—
(1) After 1 hr. forty-five tentacles inflected; but after 7 hrs.
so many had re-expanded that only ten remained much inflected.
(2) After 1 hr. seven tentacles inflected; these were almost
re-expanded in 6 hrs.
(8) and (4) Not affected, except that, as usual, after 11 hrs.
the short tentacles on the borders of the disc formed a ring.
There can, therefore, be no doubt about the efficiency of the
above solution ; and it follows as before that each gland of No. 1
could have absorbed only ggydoaq Of a grain (0000268 mg.)
and of No. 2 only gasdoao Of a grain (0000263 mg.) of the
phosphate.
Seven leaves were immersed, each in thirty minims of a
solution of one part to 487,500 of water (1 gr. to 1U00 oz.).
Each leaf thus 1eceived +g355 of a grain (00405 mg.). The day
was warm, and the leaves were very fine, so that all circum-
stances were favourable.
(1) After 30 m. all the outer tentacles except five inflected,
and most of them closely; after 1 hr. blade slightly inflected ;
after 9 hrs. 30 m. began to re-expand.
(2) After 83 m. all the outer tentacles but twenty-five in-
flected, and blade slightly so; after 1 hr. 80 m. blade strongly
inflected and remained so for 24 hrs.; but some of the tentacles
had then re-expanded.
(8) After 1 hr. all but twelve tentacles inflected ; after 2 hrs,
30 m. all but nine inflected; and of the inflected tentacles all
excepting four closely; blade slightly inflected. After & hrs,
blade quite doubled up, and now all the tentacles excepting
162 ‘ _ DROSERA ROTUNDIFOLIA. Cuar. VIL
eight closely inflected. The leaf remained in this state for two
days.
i) After 2 hrs. 20 m. only fifty-nine tentacles inflected ; but
after 5 hrs. all the tentacles closely inflected excepting two
which were not affected, and eleven which were only sub-in-
flected; after 7 hrs. blade considerably inflected; after 12 hrs,
much re-expansion.
(5) After 4 hrs. all the tentacles but fourteen inflected ; after
9 hrs. 80 m. beginning to re-expand.
(6) After 1 hr. thirty-six tentacles inflected; after 5 hrs. all
but fifty-four inflected ; after 12 hrs. considerable re-expansion.
(7) After 4 hrs. 30 m. only thirty-five tentacles inflected or
sub-inflected, and this small amount of inflection never increased.
Now for the seven corresponding leaves in water :—
(1) After 4 hrs. thirty-eight tentacles inflected; but after
7 brs. these, with the exception of six, re-expanded.
(2) After 4 hrs. 20 m. twenty inflected; these after 9 hrs.
partially re-expanded.
(8) After 4 hrs. five inflected, which began to re-expand after
7 rs.
(4) After 24 hrs. one inflected.
(5), (6) and (7) Not at all affected, though observed for
24 hrs., excepting the short tentacles on the borders of the disc,
which as usual formed a ring.
A comparison of the leaves in the solution, especially of
the first five or even six on the list, with those in the water,
after 1 hr. or after 4 hrs., and in a still more marked degree
after 7 hrs. or 8 hrs., could not leave the least doubt that the
solution had produced a great effect. This was shown not only
by the vastly greater number of mflected tentacles, but by
the degree or closeness of their inflection, and by that of their
blades. Yet each gland on leaf No. 1 (which bore 255 glands, all
of which, excepting five, were inflected in 30 m.) could not have
received more than one-four-millionth of a grain (-0000162
mg.) of the salt. Again, each gland on leaf No. 3 (which
bore 233 glands, all of which, except nine, were inflected in
2 hrs. 30 m.) could have received at most only the geghoaq of
a grain, or ‘0000181 mg.
Four leaves were immersed as before in a solution of one part
to 656,250. of water (1 gr. to 1500 oz.) ; but on this occasion I
happened to select leaves which were very little sensitive, as
on other occasions I chanced to select unusually sensitive
leaves. The leaves were not more affected after 12 hrs. than
Cuar. VII. PHOSPHATE OF AMMONIA. . 163
the four corresponding ones in water; but after 24 hrs. they
were slightly more inflected. Such evidence, however, is not at
all trustworthy.
Twelve leaves were immersed, each in thirty minims of a solu-
tion of one part to 1,312,500 of water (1 gr. to 3000 oz.); so that
each leaf received zghq5 of a grain (00135 mg.). The leaves were
not in very good condition ; four of them were too old and of a
dark red colour; four were too pale, yet one of these latter acted
well; the four others, as far as could be told by the eye, seemed
in excellent condition. The result was as follows :—
(1) This was a pale leaf; after 40 m. about thirty-eight ten-
tacles inflected; after 3 hrs. 830 m. the blade and many of the
outer tentacles inflected; after 10 hrs. 15 m. all the tentacles
but seventeen inflected, and the blade quite doubled up; after
24 hrs. all the tentacles but ten more or less inflected. Most
of them were closely inflected, but twenty-five were only sub-
inflected.
(2) After 1 hr. 40 m. twenty-five tentacles inflected; after
6 hrs. all but twenty-one inflected; after 10 hrs. all but sixteen
more or less inflected; after 24 hrs. re-expanded.
(8) After 1 hr. 40 m. thirty-five inflected; after 6 hrs. “a
large number” (to quote my own memorandum) inflected,
but from want of time they were not counted; after 24 hrs. re-
expanded.
(4) After 1 hr. 40 m. about thirty inflected ; after 6 hrs. “a
large number all round the leaf” inflected, but they were not
counted; after 10 hrs. began to re-expand.
(5) to (12) These were not more inflected than leaves often
are in water, having respectively 16, 8, 10, 8, 4, 9, 14, and 0 ten-
tacles inflected. ‘T'wo of these leaves, however, were remarkable
from having their blades slightly inflected after 6 hrs.
With respect to the twelve corresponding leaves in water, (1)
had, after 1 hr. 35 m., fifty tentacles inflected, but after 11 hrs.
only twenty-two remained so, and these formed a group, with the
blade at this point slightly inflected. It appeared as if this leaf
had been in some manner accidentally excited, for instance by a
particle of animal matter which was dissolved by the water.
(2) After 1 hr. 45 m. thirty-two tentacles inflected, but after
5 hrs. 80 m. only twenty-five inflected, and these after 10 hrs.
all re-expanded; (8) after 1 hr. twenty-five inflected, which
after 10 hrs. 20 m. were all re-expanded; (4) and (5) after
1 hr. 35 m. six and seven tentacles inflected, which re expanded
after 1] hrs.; (6), (7) and (8) from one to three inflected, which
164 | DROSERA ROTUNDIFOLIA. Crap. VIL
soon re-expanded ; (9),(10), (11) and (12) none inflected, though
observed for twenty-four hours.
Comparing the states of the twelve leaves in water with those
in the solution, there could be no doubt that in the latter a larger
number of tentacles were inflected, and these to a greater degree ;
but the evidence was by no means so clear as in the former ex-
periments with stronger solutions. It deserves attention that the
inflection of four of the leaves in the solution went on increasing
during the first 6 hrs.,and with some of them for a longer time;.
whereas in the water the inflection of the three leaves which
were the most affected, as well as of all the others, began to de-
crease during this same interval. It is also remarkable that the
blades of three of the leaves in the solution were slightly in-
flected, and this is a most rare event with leaves in water,
though it occurred to a slight extent in one (No. 1), which
seemed to have been in some mariner accidentally excited. All
this shows that the solution produced some effect, though less
and at a much slower rate than in the previous cases. The
small effect produced may, however, be accounted for in large
part by the majority of the leaves having been in a poor con-
dition.
Of the leaves in the solution, No. 1 bore 200 glands and received
zsboo Of a grain of the salt. Subtracting the seventeen tentacles
which were not inflected, each gland could have absorbed only
the g7shooo Of a grain (00000738 mg.). This amount caused
the tentacle bearing each gland to be greatly inflected. The
blade was also inflected.
Lastly, eight leaves were immersed, each in thirty minims of a
solution of one part of the phosphate to 21,875,000 of water (1 gr.
to 5000 oz.). Each leaf thus received sq45, of @ grain of the salt,
or 00081 mg. I took especial pains in selecting the finest leaves
from the hot-house for immersion, both in the solution and the
water, and almost all proved extremely sensitive. Beginning as
before with those in the solution :—
(1) After 2 hrs. 30 m. all the tentacles but twenty-two in-
flected, but some only sub-inflected ; the blade much inflected;
after 6 hrs. 80 m. all but thirteen inflected, with the blade
immensely inflected; and remained so for 48 hrs.
(2) No change for the first 12 hrs., but after 24 hrs. all the
tentacles inflected, excepting those of the outermost row, of which
only eleven were inflected. The inflection continued to increase,
and after 48 hrs. all the tentacles except three were inflected,
Chav. VIL PHOSPHATE OF AMMONIA. 164
and most of them rather closely, four or five being only sub-
inflected.
(3) No change for the first 12 hrs.; but after 24 hrs. all the
tentacles excepting those of the outermost row were sub-inflected,
with the blade ifflected. After 36 hrs. blade strongly inflected,
with all the tentacles, except three, inflected or sub-inflected.
After 48 hrs. in the same state. :
(4) to (8) These leaves, after 2 hrs. 30 m., had respectively
32, 17, 7, 4, and 0 tentacles inflected, most of which, after a few
hours, re-expanded, with the exception of No. 4, which retained
its thirty-two tentacles inflected for 48 hrs.
Now for the eight corresponding leaves in water :—
(1) After 2 hrs. 40 m. this had twenty of its outer tentacles
inflected, five of which re-expanded after 6 hrs. 30 m. After
10 hrs. 15 m. a most unusual circumstance occurred, namely,
the whole blade became slightly bowed towards the footstalk,
and so remained for 48 hrs. The exterior tentacles, excepting
those of the three or four outermost rows, were now also in-
flected to an unusual degree.
(2) to (8) These leaves, after 2 hrs. 40 m., had respectively 42,
12, 9, 8, 2,1, and 0 tentacles inflected, which all re-expanded
within 24 hrs., and most of them within a much shorter time.
When the two lots of eight leaves in the solution and in the
water were compared after the lapse of 24 hrs., they undoubt-
edly differed much in appearance. The few tentacles on the
leaves in water which were inflected had after this interval re-
expanded, with the exception of one leaf; and this presented
the very unusual case of the blade being somewhat inflected,
though in a degree hardly approaching that of the two leaves in
the solution. Of these latter leaves, No. 1 had almost all its
tentacles, together with its blade, inflected after an immersion
of 2 hrs. 30 m. Leaves No. 2 and 3 were affected at a much
slower rate; but after from 24 hrs. to 48 hrs. almost all their
tentacles were closely inflected, and the blade of one quite
doubled up. We must therefore admit, incredible as the fact
may at first appear, that this extremely weak solution acted on
the more sensitive leaves; each of which received only the
soeoo Of a grain (00081 mg.) of the phosphate. Now, leat
No. 8 bore 178 tentacles, and subtracting the three which were
not inflected, each gland could have absorbed only the ~o¢saa5
of a grain, or 00000463 mg. Leaf No. 1, which was strongly
acted on within 2 hrs. 30 m., and had all its outer tentacles,
except thirteen, inflected within 6 hrs. 30 m., bore 260 tentacles;
and on the same principle as before, each gland could have
166 DROSERA ROTUNDIFOLIA. Cuap. VIL
absorbed only s57dso50 Of a grain, or ‘00000328 mg.; and this
excessively minute amount sufficed to cause all the tentacles
bearing these glands to be greatly inflected. The blade was also
inflected.
Summary of the Results with Phosphate of Ammonia.—
The glands of the disc, when excited by a half-minim
drop (0296 ml.), containing 5,4, of a grain (‘0169
mg.) of this salt, transmit a motor impulse to the
exterior tentacles, causing them to bend inwards. A
minute drop, containing +5350 of a grain (000423
mg.), if held for a few seconds in contact with a
gland, causes the tentacle bearing this gland to_be
inflected. If a leaf is left immersed for a few hours,
and sometimes for a shorter time, in a solution so
weak that each gland can absorb only the +,-s005
of a grain (00000328 mg.), this is enough to excite
the tentacle into movement, so that it becomes
closely inflected, as does sometimes the blade. In
the general summary to this chapter a few remarks
will be added, showing that the efficiency of such
extremely minute doses is not so incredible as it
must at first appear. :
Sulphate of Ammonia.—The few trials made with this and the
following five salts of ammonia were undertaken merely to
ascertain whether they induced inflection. Half-minims of a
“solution of one part of the sulphate of ammonia to 487 of
water were placed on the discs of seven leaves, so that each
received 53, of a grain, or ‘0675 mg. After 1 hr. the tentacles
of five of them, as well as the blade of one, were strongly
inflected. ‘he leaves were not afterwards observed.
Citrate of Ammoniu.—Half-minims of a solution of one part
to 487 of water were placed on the discs of six leaves. In
l hr. the short outer tentacles round the discs were a little
inflected, with the glands on the discs blackened. After
3 hrs. 25 m. one leaf had its blade inflected, but none of the
exterior tentacles, All six leaves remained in nearly the same
state during the day, the submarginal tentacles, however,
Cuap. VIL, OTHER SALTS OF AMMONIA. 167
becoming more inflected. After 23 hrs. three of the leaves had
their blades somewhat inflected; and the submarginal tentacles
of all considerably inflected, but in none were the two, three, or
four outer rows affected. I have rarely seen cases like this,
except from the action of a decoction of grass. The glands on the
discs of the above leaves, instead of being almost black, as after
the first hour, were now after 23 hrs. very pale. I next tried
on four leaves half-minims of a weaker solution, of one part to
1312 of water (1 gr. to 3 0z.); so that each received 52,5 of
a grain (0225 mg.). After 2 hrs. 18 m. the glands on the disc
were very dark-coloured ; after 24 hrs. two of the leaves were
slightly affected ; the other two not at all.
Acetate of Ammonia.—Half-minims of a solution of about one
part to 109 of water were placed on the discs of two leaves, both
of which were acted on in 5 hrs. 30 m., and after 23 hrs. had
every single tentacle closely inflected.
Oxalate of Ammonia.—Half-minims of a solution of one part
to 218 of water were placed on two leaves, which, after 7 hrs.,
became moderately, and after 23 hrs. strongly, inflected. Two
other leaves were tried with a weaker solution of one part
to 487 of water; one was strongly inflected in 7 hrs.; the other
not until 30 hrs. had elapsed.
Tartrute of Ammonia.—Half-minims of a solution of one part
to 437 of water were placed on the discs of five leaves. In
31 m. there was a trace of inflection in the exterior tentacles o1
some of the leaves, and this became more decided after 1 hr.
with all the leaves; but the tentacles were never closely in-
flected. After 8 hrs. 30 m. they began to re-expand. Next
morning, after 23 hrs., all were fully re-expanded, excepting
one which was still slightly inflected. The shortness of the
period of inflection in this and the following case is remark-
able.
Chloride of Ammonium. — Half-minims of a solution of one
part to 437 of water were placed on the discs of six leaves.
A decided degree of inflection in the outer and submarginal
tentacles was perceptible in 25 m.; and this increased during
the next three or four hours, but never became strongly marked.
After only 8 hrs. 30 m. the tentacles began to re-expand, and
by the next morning, after 24 hrs., were fully re-expanded on
four of the leaves, but still slightly inflected on two.
General Summary and Concluding Remarks on the
Salis of Ammonia.—We have now seen that the nine
12
L68 DROSERA ROTUNDIFOLIA. Cuar. VIL
salts of ammonia which were tried, all cause the in-
flection of the tentacles, and often of the blade of
the leaf. As far as can be ascertained from the
superficial trials with the last six salts, the citrate is
the least powerful, and the phosphate certainly by far
the most. The tartrate-and chloride are remarkable
from the short duration of their action. ‘The rela-
tive efficiency of the carbonate, nitrate, and phos-
phate, is shown in the following table by the smallest
amount which suffices to cause the inflection of the
tentacles.
Solutions, how applied. Carhonate of ay itrate of puceDbate of
Placed on the glands of
the disc, so as to act aig. of el 0 ake sary of @
airs glam aa Dee Sor s r wie9" ‘3
tentacles . mg: mg. me.
Applied for a few se-),
eonds directly to the|! ss ie ge ida of
gland of an outer|’. 2 3 ’ : d
tentacle _),00445 mg. 0025 mg. 000423 mg.
Leaf immersed, with :
time allowed for each lagi ve he indo ee
gland to absorb all ’ : 2
thatutwan ss ) *00024 mg.| 0000937 mg. | *00000228 mg.
Amount absorbed by a
gland which suffices |
to cause the aggre-|' isfy of a
gation of the proto-\' grain, or
plasm in the adjoin-|,-00048 mg.
ing cells of the ten-
tacles. . ||
From the experiments tried in these three dif-
ferent ways, we see that the carbonate, which con-
tains 23°7 per cent. of nitrogen, is less efficient than
the nitrate, which contains 35 per cent. The phos
phate contains less nitrogen than either of these
salts, namely, only 21:2 per cent., and yet is far more
Cuap. VIL SUMMARY, SALTS OF AMMONIA. 169
efficient ; its power no doubt depending quite as much
on the phosphorus as on the nitrogen which it contains.
We may infer that this is the case, from the energetic
manner in which bits of bone and phosphate of lime
affect the leaves. The inflection excited by the other
salts of ammonia is probably due solely to their nitro-
gen,—on the same principle that nitrogenous organic ,
fluids act powerfully, whilst non-nitrogenous organic
fluids are powerless. As such minute doses of the
salts of ammonia affect the leaves, we may feel almost
sure that Drosera absorbs and profits by the amount,
though small, which is present in rain-water, in the
same manner as other plants absorb these same salts
by their roots.
The smallness of the doses of the nitrate, and
more especially of the phosphate of ammonia, which
cause the tentacles of immersed leaves to be inflected,
is perhaps the most remarkable fact recorded in this
volume. When we see that much less than the
millionth* of a grain of the phosphate, absorbed by
a gland of one of the exterior tentacles, causes it to
bend, it may be thought that the effects of the solu-
tion on the glands of the disc have been overlooked ;
namely, the transmission of a motor impulse from
them to the exterior tentacles. No doubt the move-
ments of the latter are thus aided; but the aid thus
rendered must be insignificant; for we know that a
drop containing as much as the ,,';, of a grain placed
on the disc is only just able to cause the outer ten-
tacles of a highly sensitive leaf to bend. It is cer-
* It is scarcely possible to real-
ise what a million means. The
best illustration which I have met
' with is that given by Mr. Croll,
who says,—Take a narrow strip of
paper 83 ft. 4 in. in length, and
stretch it along the wall of a large
hall; then mark off at one end
the tenth of an inch. This tenth
will represent a hundred, and the
entire strip a million.
170 DROSERA ROTUNDIFOLIA. Cuar. VIL
tainly a most surprising fact that the y57ss5000 of a
grain, or in round numbers the one-twenty-millionth
of a grain (0000033 mg.), of the phosphate should
affect any plant, or indeed any animal; and as this
salt contains 35:33 per cent. of water of crystallisation,
the efficient elements are reduced to s553s5705 Of a
grain, or in round numbers to one-thirty-millionth
of a grain (00000216 mg.). The solution, moreover,
in these experiments was diluted in the proportion of
one part of the salt to 2,187,500 of water, or one grain
to 5000 oz. The reader will perhaps best realise
this degree of dilution by remembering that 5000 oz.
would more than fill a 3l-gallon cask; and that to
this large body of water one grain of the salt was
added ; only half a drachm, or thirty minims, of the
solution being poured over a leaf. Yet this amount
sufficed to cause the inflection of almost every ten-
tacle, and often of the blade of the leaf.
I am well aware that this statement will at first
appear incredible to almost every one. Drosera is far
from rivalling the power of the spectroscope, but it
can detect, as shown by the movements of its leaves, a
very much smaller quantity of the phosphate of am-
monia than the most skilful chemist can of any
substance.* My results were for a long time incredible
* When my first observations ‘Treatise on Heat,’ 2nd edit.
were made on the nitrate of am-
monia, fourteen years ago, the
powers of the spectroscope had
not been discovered; and I felt
all the greater interest in the
then unrivalled powers of Drosera.
Now the spectroscope has al-
together beaten Drosera; for ac-
eee to Bunsen and Kirchhoff
probably less than one of
a grain of sodium can ee thus
detected \sce Balfour Biovark
1871, p. 228). With respect to
ordinary chemical tests, I -gather
from Dr. Alfred Taylor's work
on ‘Poisons’ that about yh, of a
grain of arsenic, ¥ib5 of a grain
of prussic acid, rm of iodine,
and x5 of tartarised antimony,
can be detected; but the power
of detection depends much on the
solutions under trial not being
extremely weak.
Cuar, VII. SUMMARY, SALTS OF AMMONIA. 171
even to myself, and I anxiously sought for every
source of error. The salt was in some cases weighed
for me by a chemist in an excellent balance ; and fresh
water was measured many times with care. The
observations were repeated during several years. T'wo
of my sons, who were as incredulous as myself, compared
several lots of leaves simultaneously immersed in the
weaker solutions and in water, and declared that there
could be no doubt about the difference in their ap-
pearance. I hape that some one may hereafter be in-
duced to repeat my experiments; in this case he should
select young and vigorous leaves, with the glands
surrounded by abundant secretion. The leaves should
be carefully cut off and laid gently in watch-glasses,
and a measured quantity of the solution and of water
poured over each. The water used must be as ab-
solutely pure as it can be made. It is to be especially
observed that the experiments with the weaker solu-
tions ought to be tried after several days of very
warm weather. Those with the weakest solutions
should be made on plants which have been kept
for a considerable time in a warm greenhouse, or cool
hothouse; but this is by no means necessary for trials
with solutions of moderate strength.
I beg the reader to observe that the sensitiveness or
irritability of the tentacles was ascertained by three
different methods—indirectly by drops placed on the
disc, directly by drops applied to the glands of the
outer tentacles, and by the immersion of whole leaves ;
and it was found by these three methods that the
nitrate was more powerful than the carbonate, and the
phosphate muck more powerful than the nitrate; this
result being intelligible from the difference in the
amount of nitrogen in the first two salts, and from the
presence of phosphorus in the third. It may aid the
172 DROSERA ROTUNDIFOLIA. Cuar. VIL
reader’s faith to turn to the experiments with a
solution of one grain of the phosphate to 1000 oz.
of water, and he will there find decisive evidence that
the one-four-millionth of a grain is sufficient to cause
the inflection of a single tentacle. There is, there-
fore, nothing very improbable in the fifth of this
weight, or the one-twenty-millionth of a grain, acting
on the tentacle of a highly sensitive leaf. Again, two
of the leaves in the solution of one grain to 3000
oz., and three of the leaves in the solution of one
grain to 5000 oz., were affected, not only far more
than the leaves tried at the same time in water, but
incomparably more than any five leaves which can be
picked out of the 173 observed by me at different
times in water.
There is nothing remarkable in the mere fact of the
one-twenty-millionth of a grain of the phosphate,
dissolved in above two-million times its weight of
water, being absorbed by a gland. All physiologists
admit that the roots of plants absorb the salts of
ammonia brought to them by the rain; and fourteen
gallons of rain-water contain* a grain of ammonia,
therefore only a little more than twice as much as in
the weakest solution employed by me. The fact
which appears truly wonderful is, that the one-twenty-
millionth of a grain of the phosphate of ammonia
(including less than the one-thirty-millionth of effi-
cient matter), when absorbed by a gland, should
induce some change in it, which leads to a motor
impulse being transmitted down the whole length of
the tentacle, causing the basal part to bend, often
through an angle of above 180 degrees.
Astonishing as is this result, there is no sound reason
Miller’s ‘Elements of Chemistry,’ part ii. p. 107, 3rd edit. 1864,
Cnar. VII. SUMMARY, SALTS OF AMMONIA.
173
why we should reject it as incredible. Prof. Donders,
of Utrecht, informs me that from experiments formerly
made by him and Dr. De Ruyter, he inferred that less
than the one-millionth of a grain of sulphate of atro-
pine, in an extremely diluted state, if applied directly
to the iris of a dog, paralyses the muscles of this organ.
But, in fact, every time that we perceive an odour, we
have evidence that infinitely smaller particles act on
our nerves. When a dog stands a quarter of a mile to
leeward of a deer or other animal, and perceives its
presence, the odorous particles produce some change in
the olfactory nerves; yet these particles must be in-
finitely smaller * than those of the phosphate of am-
monia weighing the one-twenty-millionth of a grain.
These nerves then transmit some influence to the brain
of the dog, which leads to action on its part. With Dro-
sera, the really marvellous fact is, that a plant without
any specialised nervous system should be affected by
such minute particles; but we have no grounds for
assuming that other tissues could not be rendered as
exquisitely susceptible to impressions from without if
this were beneficial to the organism, as is the nervous
system of the higher animals.
* My son, George Darwin, has
calculated for me the diameter of
a sphere of phosphate of ammonia
(specific gravity 1:678), weigh-
ing the one-twenty-millionth of
a grain, and finds it to be yy of
an inch. Now, Dr. Klein informs
me that the smallest Micrococci,
which are distinctly discernible
under a power of 800 diameters,
are estimated to be from -0002 to
0005 of a millimetre —that is,
from gako0 60 tr7ooo Of an inch
—in diameter. Therefore, an ob-
ject between #; and +, of the
size ‘of a sphere of the phos:
phate of ammonia of the above
weight can be seen under a high
power; and no one supposes
that odorous particles, such as
those emitted from the deer in
the above illustration, could be
seen under any power of the mi-
croscope.
L74 DROSERA ROTUNDIFOLIA. Cuar, VIIL
CHAPTER VIII.
Ture Errects or various SALTS AND ACIDS ON THE LEAVES,
Salts of sodium, potassium, and other alkaline, earthy, and metallic
salts Summary on the action of these salts— Various acids —
Summary on their action.
Havine found that the salts of ammonia were so
powerful, I was led to investigate the action of some
other salts. It will be convenient, first, to give a list
of the substances tried (including forty-nine salts and
two metallic acids), divided into two columns, showing
those which cause inflection, and those which do not
do so, or only doubtfully. My experiments were made
by placing half-minim drops on the discs of leaves, or,
more commonly, by immersing them in the solutions;
and sometimes by both methods. A summary of the
results, with some concluding remarks, will then be
given. The action of various acids will afterwards be
described.
Saxts oaustna InFLECTION. Sats nor oausinG INFLEcTION.
(Arranged in Groups according to the Chemical Classification in Watts?
* Dicti y of Chemistry.’)
Sodium carbonate, rapid inflec-
tion.
Sodium nitrate, rapid inflection.
Sodium sulphate,
rapid inflection.
Sodium phosphate, very rapid in-
flection.
Sodium citrate, rapid inflection.
Sodium oxalate, rapid inflection.
Sodium chloride, moderately rapid
inflection.
moderately
Potassium carbonate: slowly pol
sonous.
Potassium nitrate: somewhat poi:
sonous.
Potassium sulphate.
Potassium phosphate,
Potassium citrate.
Potassium chloride.
Cuar. VIII.
Satts causine Inriecrion.
EFFECTS OF VARIOUS SALTS.
175
SaLts Nov CAUSING INFLECTION.
(Arranged in Groups according to the Chemical Classification in Watts'
‘ Dictionary of Chemistry.’
Sodium iodide, rather slow inflec-
tion.
Sodium bromide, moderately rapid
inflection.
Potassium oxalate,
doubtful inflection.
Lithium nitrate, moderately rapid
inflection.
Cesium chloride, rather slow in-
flection.
Silver nitrate, rapid inflection:
quick poison.
slow and
Cadmium chloride, slow inflection.
Mercury perchloride, rapid inflec-
tion: quick poison.
Aluminium chloride, slow and
doubtful inflection.
Gold chloride, rapid inflection :
quick poison.
Tin chloride, slow inflection: poi-
sonous.
Antimony tartrate, slow inflec-
tion: probably poisonous.
Arsenious acid, quick inflection:
poisonous.
-ron chloride, slow inflection:
probably poisonous.
Chromic acid, quick inflection:
highly poisonous.
Copper chloride, rather slow in-
flection : poisonous.
Nickel chloride, rapid inflection :
probably poisonous.
Platinum chloride, rapid inflec-
tion: poisonous.
Potassium iodide, a slight and
doubtful amount of inflection
Potassium bromide.
Lithium acetate.
Rubidium chloride,
Calcium acetate.
Calcium nitrate.
Magnesium acetate.
Magnesium nitrate.
Magnesium chloride.
Magnesium sulphate.
Barium acetate.
Barium nitrate.
Strontium acetate.
Strontium nitrate.
Zine chloride.
Aluminium nitrate, a trace of in-
tection.
Aluminium and potassium eul-
phate.
Lead chloride.
Manganese chloride
Cobalt chloride.
176 DROSERA ROTUNDIFOLIA. Onar. VILL:
Sodium, Carbonate of (pure, given me by Prof. Hoffmann).—
Half-minims ( 0296 ml.) of a solution of one part to 218 of
water (2 grs. to 1 oz.) were placed on the discs of twelve leaves.
Seven of these became well inflected; three had only two or
three of their outer tentacles inflected, and the remaining two
were quite unaffected. But the dose, though only the 73, of a
grain (-185 mg.), was evidently too strong, for three of the
seven well-inflected leaves were killed. On the other hand, one
of the seven, which had only a few tentacles inflected, re-
expanded and seemed quite healthy after 48 hrs. By employing
a weaker solution (viz. one part to 437 of water, or 1 gr. to
loz.), doses of 535 of a grain (0675 mg.) were given to six
leaves. Some of these were affected in 37 m.; and in 8 hrs. the
outer tentacles of all, as well as the blades of two, were con-
siderably inflected. After 23 hrs. 15 m. the tentacles had
almost re-expanded, but the blades of the two were still just
perceptibly curved inwards. After 48 hrs. all six leaves were
fully re-expanded, and appeared perfectly healthy.
Three leaves were immersed, each in thirty minims of a solu-
tion of one part to 875 of water (1 gr. to 2 0z.), so that each
received z, of a grain (2°02 mg.); after 40 m. the three were
much affected, and after 6 hrs. 45 m. the tentacles of all and
the blade of one closely inflected. :
Sodium, Nitrate of (pure).—Half-minims of a solution of one
part to 4387 of water, containing 545 of a grain (°0675 mg.),
were placed on the discs of five leaves. After 1 hr. 25 m. tho
tentacles of nearly all, and the blade of one, were somewhat
inflected. The inflection continued to increase, and in 21 hrs.
15 m. the tentacles and the blades of four of them were greatly
affected, and the blade of the fifth to a slight extent. After an
additional 24 hrs. the four leaves still remained closely inflected,
whilst the fifth was beginning toexpand. Four days after the
solution had been applied, two of the leaves had quite, and one
had partially, re-expanded, whilst the remaining two remained
closely inflected and appeared injured.
Three leaves were immersed, each in thirty minims of a solu-
tion of one part to 875 of water; in 1 hr. there was great inflec-
tion, and after 8 hrs. 15 m. every tentacle and the blades of all
three were most strongly inflected.
Sodium, Sulphate of.—Half-minims of a solution of one part
to 437 of water were placed on the discs of six leaves. After
5 hrs. 30 m. the tentacles of three of them (with the blade of
one) were considerably, and those of the other three slightly,
inflected. After 21 hrs. the inflection had a little decreased.
Cuap. VIII, SALTS OF SODIUM. 177
and in 45 hrs. the leaves were fully expanded, appearing quite
healthy. :
Three leaves were immersed, each in thirty minims of a solu-
tion of one part of the sulphate to 875 of water; after 1 hr.
30 m. there was some inflection, which increased so much that
in 8 hrs. 10 m. all the tentacles and the blades of all three leaves
were closely inflected.
Sodium, Phosphate of.—Half-minims of a solution of one part
to 437 of water were placed on the discs of six leaves. ‘The
solution acted with extraordinary rapidity, for in 8 m. the outer
tentacles on several of the leaves were much incurved. After
6 hrs. the tentacles of all six leaves, and the blades of two, were
closely inflected. This state of things continued for 24 hrs.,
excepting that the blade of a third leaf became incurved. After
48 hrs. all the leaves re-expanded. It is clear that 54,5 of a
grain of phosphate of soda has great. power in causing in-
flection.
Sodium, Citrate of —Half-minims of a solution of one part to
437 of water were placed on the discs of six leaves, but these
were not observed until 22 hrs. had elapsed. The sub-
marginal tentacles of five of them, and the blades of four, were
then found inflected; but the outer rows of tentacles were not
affected. One leaf, which appeared older than the others, was
very little affected in any way. After 46 hrs. four of the leaves
were almost re-expanded, including their blades. Three leaves
were also immersed, each in thirty minims of a solution of one
part of the citrate to 875 of water; they were much acted
on in 25 m.; and after 6 hrs. 35 m. almost all the tentacles,
including those of the outer rows, were inflected, but not the
blades.
fodium, Oxalate of— Half-minims of a solution of one part to
487 of water were placed on the discs of seven leaves; after
5 hrs. 80 m. the tentacles of all, and the blades of most of them,
were much affected. In 22 hrs., besides the inflection of the
tentacles, the blades of all seven leaves were so much doubled
over that their tips and bases almost touched. On no other
occasion have I seen the blades so strongly affected. Three
leaves were also immersed, each in thirty minims of a solution of
one part to 875 of water; after 30 m. there was much inflection,
and after 6 hrs. 35 m. the blades of two and the tentacles of all
were closely inflected.
Sudium, Chloride of (best culinary salt).—Half-minims of a
solution of one part to 218 of water were placed on the diseg
178 DROSERA ROTUNDIFOLIA. Cuap. VIIL
of four leaves. Two, apparently, were not at all affected in
48 hrs.; the third had its tentacles slightly inflected; whilst
the fourth had almost all its tentacles inflected in 24 hrs., and
these did not begin to re-expand until the fourth day, and were
not perfectly expanded on the seventh day. I presume that
this leaf was injured by the salt. Half-minims of a weaker
solution, of one part to 487 of water, were then dropped on the
discs of six leaves, so that each received 53, of a grain. In
Lhr. 83 m. there was slight inflection; and after 5 hrs. 30 m.
the tentacles of all six leaves were considerably, but not closely,
inflected. After 23 hrs. 15 m. all had completely re-expanded,
and did not appear in the least injured.
Three leaves were immersed, each in thirty minims of a solu-
tion of one part to 875 of water, so that each received ¥, of a
grain, or 2°02 mg. After 1 hr. there was much inflection;
after 8 hrs. 80 m. all the tentacles and the blades of all three
were closely inflected. Four other leaves were also immersed
in the solution, each receiving the same amount of salt
as before, viz. 3, of a grain. They all soon became inflected ;
after 48 hrs. they began to re-expand, and appeared quite un-
injured, though the solution was sufficiently strong to taste
saline. :
Sodium, Iodide of.—Half-minims of a solution of one part to
487 of water were placed on the discs of six leaves. After
24 hrs. four of them had their blades and many tentacles in-
flected. he other two had only their submarginal tentacles
inflected; the outer ones in most of the leaves being but little
affected. After 46 hrs. the leaves had nearly re-expanded.
Three leaves were also immersed, each in thirty minims of a
solution of one part to 875 of water. After 6 hrs. 30 m. almost
all the tentacles, and the blade of one leaf, were closely inflected.
Sodium, Bromide of.—Half-minims of a solution of one part to
487 of water were placed on six leaves. After 7 hrs. there was
some inflection; after 22 hrs. three of the leaves had their blades
and most of their tentacles inflected ; the fourth leaf was very
slightly, and the fifth and sixth hardly at all, affected. Three
leaves were also immersed, each in thirty minims of a solution
of one part to 875 of water; after 40 m. there was some inflec-
tion; after 4 hrs. the tentacles of all three leaves and the blades
of two were inflected. These leaves were then plated in water,
and after 17 hrs. 80 m. two of them were almost completely,
and the third partially, re-expanded; so that apparently they
were not injured,
Onap. VILL SALTS OF POTASSIUM. 179
Potassium, Carbonate of (pure).—Half-minims of a solution
of one part to 437 of water were placed on six leaves. No
effect was produced in 24 hrs.; but after 48 hrs. some of the
leaves had their tentacles, and one the blade, considerably
inflected. This, however, seemed the result of their being in-
jured; for on the third day after the solution was given, three of
the leaves were dead, and one was very unhealthy; the other
two were recovering, but with several of their tentacles appa-
rently injured, and these remained permanently inflected. It
is evident that the 34; of a grain of this salt acts as a poison.
Three leaves were also immersed, each in thirty minims of a
solution of one part to 875 of water, though only for 9 hrs.; and,
very differently from what occurs with the salts of soda, no
inflection ensued. .
Potassium, Nitrate of —Walf-minims of a strong solution, of
one part to 109 of water (4 grs. to 1 oz.), were placed on the
discs of four leaves; two were much injured, but no inflection
ensued. Hight leaves were treated in the same manner, with
drops of a weaker solution, of one part to 218 of water. After
50 hrs. there was no inflection, but two of the leaves seemed in-
jured. Five of these leaves were subsequently tested with drops
of milk and a solution of gelatine on their discs, and only one
became inflected; so that the solution of the nitrate of the
above strength, acting for 50 hrs., apparently had injured or
paralysed the leaves. Six leaves were then treated in the same
manner with a still weaker solution, of one part to 487 of water,
and these, after 48 hrs., were in no way affected, with the excep-
tion of perhaps a single leaf. Three leaves were next immer-ed
for 25 hrs., each in thirty minims of a solution of one part to
875 of water, and this produced no apparent effect. They were
then put into a solution of one part of carbonate of ammonia
to 218 of water; the glands were immediately blackened, and
after 1 hr. there was some inflection, and the protoplasmic con-
tents of the cells became plainly aggregated. This shows that
the leaves had not been much injured by their immersion for
25 hrs. in the nitrate.
Potussium, Sulphate of—Half-minims of a solution of one part
to 487 of water were placed on the discs of six leaves. After
20 hrs. 30 m. no effect was produced; after an additional 24 hrs.
three remained quite unaffected; two seemed injured, and the
sixth seemed almost dead with its tentacles inflected. Never-
theless, after two additional days, all six leaves recovered. The
immersion of three leaves for 24 hrs., each in thirty minims of
4
180 . DROSERA ROTUNDIFOLIA. Car. VIIL
a solution of one part to 875 of water, produced no apparcut
effect. They were then treated with the same solution of car-
bonate of ammonia, with the same result as in the case of the
nitrate of potash.
Potassium, Phosphate of.—Half-minims of a solution of one
part to 487 of water were placed on the discs of six leaves,
which were observed during three days ; but no effect was pro-
duced. The partial drying up of the fluid on the disc slightly
drew together the tentacles on it, as often occurs in experi-
ments of this kind. The leaves on the third day appeared quite
healthy.
Potassium, Citrate of —Half-minims of a solution of one part
to 487 of water, left on the discs of six leaves for three days,
and the immersion of three leaves for 9 hrs., each in 80 minims
of a solution of one part to 875 of water, did not produce the
least effect.
Potassium, Oxalate of—Half-minims were placed on different
occasions on the discs of seventeen leaves; and the results per-
plexed me much, as they still do. Inflection supervened very
slowly. After 24 hrs. four leaves out of the seventeen were well
inflected, together with the blades of two; six were slightly
affected, and seven not at all. ‘Three leaves of one lot were
observed for five days, and all died; but in another lot of
six, all excepting one looked healthy after four days. Three
leaves were immersed during 9 hrs., each in 30 minims of
a solution of one part to 875 of water, and were not in the
least affected; but they ought to have heen observed for a
longer time.
Potassium, Chloride of. Neither half-minims of a solution of
one part to 437 of water, left on the dises of six leaves for three
days, nor the immersion of three leaves during 25 hrs., in
30 minims of a solution of one part to 875 of water, produced
the least effect. The immersed leaves were then treated with
carbonate of ammonia, as described under nitrate of potash, and
with the same result. :
Potassium, Iodide of—Half-minims of a solution of one part
to 437 of water were placed on the discs of seven leaves. In
30 m. one leaf had the blade inflected ; after some hours three
leaves had most of their submarginal tentacles moderately in-
flected; the remaining three being very slightly affected.
Hardly any of these leaves had their outer tentacles inflected.
After 21 hrs. all re-expanded, excepting two which still had a
few submarginal tentacles inflected. Three leaves were next
Cuap. VILL. EFFECTS OF VARIOUS SALTS. 181
immersed for 8 hrs. 40 m., each in 30 minims of a solution of
one part to 875 of water, and were not in the least affected. I
do not know what to conclude from this conflicting evidence ;
but it is clear that the iodide of potassium does not generally
produce any marked effect.
Potassium, Bromide of —Half-minims of a solution of one part
to 487 of water were placed on the discs of six leaves; after
22 hrs. one had its blade and many tentacles inflected, but I
suspect that an insect might have alighted on it and then
escaped; the five other leaves were in no way affected. I
tested three of these leaves with bits of meat, and after 24 hrs.
they became splendidly inflected. Three leaves were also im-
mersed for 21 hrs. in 30 minims of a solution of one part to 875
of water; but they were not at all affected, excepting that the
glands looked rather pale.
Lithium, Acetite of —Four leaves were immersed together in
a vessel containing 120 minims of a solution of one part to 487
of water; so that each received, if the leaves absorbed equally,
qs of a grain. After 24 hrs. there was no inflection. I then
added, for the sake of testing the leaves, some strong solution
(viz. 1 gr. to 20 oz., or one part to 8750 of water) of phosphate
of ammonia, and all four became in 30 m. closely inflected.
Lithium, Nitrute of.—Four leaves were immersed, as in the
last case, in 120 minims of a solution of one part to 487 of
water; after 1 h. 80 m. all four were a little, and after 24 hrs.
greatly, inflected. I then diluted the solution with some
water, but they still remained somewhat inflected on the third
day.
Cesium, Chloride of—Four leaves were immersed, as above, in
120 minims of a solution of one part. to 437 of water. After
l hr. 5 m. the glands were darkened; after 4 hrs. 20 m. there
was a trace of inflection; after 6 hrs. 40 m. two leaves were
greatly, but not closely, and the other two considerably inflected.
After 22 hrs, the inflection was extremely great, and two had
their blades inflected. I then transferred the leaves into water,
and in 46 hrs. from their first immersion they were almost re-
expanded. :
Rubidium, Chloride of.—Four leaves which were immersed, as
above, in 120 minims of a solution of one part to 437 of water,
were not acted on in 22 hrs. I then added some of the strong
solution (1 gr. to 20 oz.) of phosphate of ammonia, and in 30 m.
all were immensely inflected.
Silver, Nitrate of.— Three leaves were immersed in ninety
182 DROSERA ROTUNDIFOLIA. Crap. VIIL
minims of a solution of one part to 437 of water; so that each
received, as before, ~, of a grain. After 5 m. slight inflection,
and after 11 m. very strong inflection, the glands becoming
excessively black; after 40 m. all the tentacles were closely
inflected. After 6 hrs. the leaves were taken out of the solution,
washed, and placed in water; but next morning they were
evidently dead.
Calcium, Acctute of.—Four leaves were immersed in 120 minims
of a solution of one part to 487 of water; after 24 hrs. none of
the tentacles were inflected, excepting a few where the blade
joined the petiole; and this may have been caused by the
absorption of the salt by the cut-off end of the petiole. I then
added some of the solution (1 gr. to 20 oz.) of phospate of
ammonia, but this to my surprise excited only slight inflection,
even after 24 hrs. Hence it would appear that the acetate had
rendered the leaves torpid.
Calcium, Nitrate of —Four leaves were immersed in 120 minims
of a solution of one part to 487 of water, but were not affected
in 24 hrs. I then added some of the solution of phosphate of
ammonia (1 gr. to 20 oz.), but this caused only very slight in-
flection after 24 hrs. A fresh leaf was next put into a mixed
solution of the above strengths of the nitrate of calcium and
phosphate of ammonia, and it became closely inflected in between
5m.and10m. Half-minims of a solution of one part of the
nitrate of calcium to 218 of water were dropped on the discs of
three leaves, but produced no effect.
Magnesium, Acetute, Nitrate, and Chloride of. —Four leaves were
immersed in 120 minims of solutions, of one part to 437 of water,
of each of these three salts ; after 6 hrs. there was no inflection ;
but after 22 hrs. one of the leaves in the acetate was rather more
inflected than generally occurs from an immersion for this
length of time in water. Some of the solution (1 gr. to 20 oz.)
of phosphate of ammonia was then added to the three solutions.
The leaves in the acetate mixed with the phosphate underwent
some inflection; and this was well pronounced after 24 hrs.
Those in the mixed nitrate were decidedly inflected in 4 hrs.
30 m., but the degreé of inflection did not afterwards much
increase; whereas the four leaves in the mixed chloride were
greatly inflected in a few minutes, and after 4 hrs. had almost
every tentacle closely inflected. We thus see that the acetate
and nitrate of magnesium injure the leaves, or at least prevent
the subsequent action of phosphate of ammonia; whereas the
chloride has no such tendency.
Cuap. VIII. EFFECTS OF VARIOUS SALTS. 183
Magnesium, Sulphate of—Half-minims of a solution of one part
to 218 of water were placed on the discs of ten leaves, and pro-
duced no effect.
Barium, Acetate of —Four leaves were immersed in 120 ininims
of a solution of one part to 437 of water, and after 22 hrs. there
was no inflection, but the glands were blackened. The leaves
were then placed in a solution (1 gr. to 20 02.) of phosphate of
ammonia, which caused after 26 hrs. only a little inflection in
two of the leaves.
Barium, Nitrate of.—Four leaves were immersed in 120 minims
of a solution of one part to 437 of water; and after 22 hrs. there
was no more than that slight degree of inflection, which often
follows from an immersion of this length m pure water. I
then added some of the same solution of phosphate of ammonia,
and after 30 m. one leaf was greatly inflected, two others
moderately, and the fourth not at all. The leaves remained
in this state for 24 hrs.
Strontium, Acetate of.—Four leaves, immersed in 120 minims of
a solution of one part to 437 of water, were not affected in
22 hrs. They were then placed in some of the same solution
of phosphate of ammonia, and in 25 m. two of them were
greatly inflected; after 8 hrs. the third leaf was considerably
inflected, and the fourth exhibited a trace of inflection. They
were in the same state next morning.
Strontium, Nitrate of.—Five leaves were immersed in 120
minims of a solution of one part to 487 of water; after 22 hrs.
there was some slight inflection, but not more than sometimes
occurs with leaves in water. They were then placed in the
same solution of phosphate of ammonia; after 8 hrs. three of
them were moderately inflected, as were all five after 24 hrs.;
but not one was closely inflected. It appears that the nitrate of
strontium renders the leaves half torpid.
Cadmium, Chloride of.—Three leaves were immersed in ninety
minims of a solution of one part to 437 of water; after 5 hrs.
20 m. slight inflection occurred, which increased during the
next three hours. After 24 hrs. all three leaves had their
tentacles well inflected, and remained so for an additional 24
hrs.; glands not discoloured.
Mercury, Perchloride of.—Three leaves were immersed in ninety
minims of a solution of one part to 487 of water; after 22 m.
there was some slight inflection, which in 48 m. became well
pronounced; the glands were now blackened. After 5 hrs.
85 m. all the tentacles closely inflected; after 24 hrs. still
13
184 DROSERA ROTUNDIFOLIA. Onap. VILL.
inflected and discoloured. The leaves were then removed and
left for two days in water; but they never re-expanded, being
evidently dead.
Zinc, Chloride of—Three leaves immersed in ninety minims
of a solution of one part to 437 of water were not affected in
25 hrs. 30 m.
Aluminium, Chloride of—Four leaves were immersed in 120
minims of a solution of one part to 437 of water; after 7 hrs.
45 m. no inflection; after 24 hrs. one leaf rather closely, the
second moderately, the third and fourth hardly at all, inflected.
The evidence is doubtful, but I think some power in slowly
causing inflection must be attributed to this salt. These leaves
were then placed in the solution (1 gr. to 20 oz.) of phosphate
of ammonia, and after 7 hrs. 30 m. the three, which had been
but little affected by the chloride, became rather closely in-
flected.
Aluminium, Nitrate of—Four leaves were immersed in 120
minims of a solution of one part to 487 of water; after 7 hrs.
45 m. there was only a trace of inflection; after 24 hrs. one leaf
was moderately inflected. The evidence is here again doubtful,
as in the case of the chloride of aluminium. The leaves were
then transferred to the same solution, as before, of phosphate of
ammonia; this produced hardly any effect in 7 hrs. 30 m.; but
after 25 hrs. one leaf was pretty closely inflected, the three
others very slightly, perhaps not more so than from water.
Aluminium and Potassium, Sulphate of (common alum).—Half-
minims of a solution of the usual strength were placed on the
discs of nine leaves, but produced no effect.
Gold, Chloride of—Seven leaves were immersed in so much of
a solution of one part to 4387 of water that each received
30 minims, containing ;; of a grain, or 4048 mg., of the chloride.
There was some inflection in 8 m., which became extreme in
45 m. In 3 hrs. the surrounding fluid was coloured purple, and
the glands were blackened. After 6 hrs. the leaves were trans-
ferred to water; next morning they were found discoloured and
evidently killed. The secretion decomposes the chloride very
readily; the glands themselves becoming coated with the
thinnest layer of metallic gold, and particles float about on
the surface of the surrounding fluid.
Lead, Chloride of.— Three leaves were immersed in ninety
minims of a solution of one part to 437 of water. After 23 hrs.
there was nota trace of inflection ; the glands were not blackened,
and the leaves did not appear injured. They were then trans-
Caar VIIL EFFEROTS OF VARIOUS SALTS. 185
e
ferred to the solution (1 gr. to 20 oz.) of phosphate of ammonia,
and after 24 hrs. two of them were somewhat, the third very
little, inflected; and they thus remained for another 24 hrs.
Tin, Chloride of —Four leaves were immersed in 120 minims
of a solution of about one part (all not being dissolved) to 4387 of
water. After 4 hrs. no effect; after 6 hrs. 30 m. all four leaves
had their submarginal tentacles inflected; after 22 hrs. every
single tentacle and the blades were closely inflected. The sur-
rounding fluid was now coloured pink. The leaves were washed
and transferred to water, but next morning were evidently dead.
This chloride is a deadly poison, but acts slowly.
Antimony, Tartrute of.—Three leaves were immersed in ninety
minims of a solution of one part to 437 of water. After 8 hrs.
30 m. there was slight inflection; after 24 hrs. two of the leaves
were closely, and the third moderately, inflected; glands not
much darkened. The leaves were washed and placed in water,
but they remained in the same state for 48 additional hours.
This salt is probably poisonous, but acts slowly.
Arsenious Acid.—A solution of one part to 487 of water ; three
leaves were immersed in ninety minims; in 25 m. considerable
inflection ; in 1 h. great inflection; glands not discoloured. After
6 hrs. the leaves were transferred to water; next morning they
looked fresh, but after four days were pale-coloured, had not
re-expanded, and were evidently dead.
dron, Chloride of—Three leaves were immersed in ninety
minims of a solution of one part to 4387 of water; in 8 hrs. no
inflection; but after 24 hrs. considerable inflection; glands
blackened; fluid coloured yellow, with floating flocculent
particles of oxide of iron. The leaves were then placed in
water; after 48 hrs. they had re-expanded a very little, but I
think were killed; glands excessively black.
Chromic Acid.—One part to 487 of water; three leaves were
immersed in ninety minims; in 380 m. some, and in 1 hr. con-
siderable, inflection; after 2 hrs. all the tentacles closely in-
flected, with the glands discoloured. Placed in water, next
day leaves quite discoloured and evidently killed.
Manganese, Chloride of—Three leaves immersed in ninety
minims of a solution of one part to 437 of water; after 22 hrs.
no more inflection than often occurs in water; glands not
blackened. The leaves were then placed in the usual solution
of phosphate of ammonia, but no inflection was caused even
after 48 hrs.
Copper, Chloride of.—Three leaves immersed in ninety minima
186 DROSERA ROTUNDIFOLIA. Cuar. VILL
e
of a solution of one part to 437 of water; after 2 hrs. some inflec-
tion; after 8 hrs. 45 m. tentacles closely inflected, with the
glands blackened. After 22 hrs. still closely inflected, and the
leaves flaccid. Placed in pure water, next day evidently dead.
A rapid poison.
Nick l, Chloride of.—Three leaves immersed in ninety minims
of a solution of one part to 487 of water; in 25 m. considerable
inflection, and in 8 hrs. all the tentacles closely inflected. After
92 hrs. still closely inflected; most of the glands, but not all,
blackened. The leaves were then placed in water; after 24 hrs,
remained inflected; were somewhat discoloured, with the glands
and tentacles dingy red. Probably killed.
Cobalt, Chlor:de of.—Three leaves immersed in ninety minims
of a solution of one part to 487 of water; after 23 hrs. there
was not a trace of inflection, and the glands were not more
blackened than often occurs after an equally long immersion in
water.
Platinum, Chloride of.—Three leaves immersed in ninety
minims of a solution of one part to 487 of water; in 6 m. some
inflection, which became immense after 48m. After 3 hrs. the
zlands were rather pale. After 24 hrs. all the tentacles still
closely inflected; glands colourless; remained in same state for
four days; leaves evidently killed.
Concluding Remarks on the Action of the foregoing
Salts.—Of the fifty-one salts and metallic acids which
were tried, twenty-five caused the tentacles to be in-
flected, and twenty-six had no such effect, two rather
doubtful cases occurring in each series. In the table
at the head of this discussion, the salts are arranged
according to their chemical affinities; but their action
on Drosera does not seem to be thus governed. The
nature of the base is far more important, as far as can
be judged from the few experiments here given, than
that of the acid; and this is the conclusion at which
physiologists have arrived with respect to animals.
We see this fact illustrated in all the nine salts of
soda causing inflection, and in not being poisonous
except when given in large doses; whereas seven of
Cuar. VIO. CONCLUDING REMARKS, SALTS. 187
the corresponding salts of potash do not cause inflec-
tion, and some of them are poisonous. Two of them,
however, viz. the oxalate and iodide of potash, slowly
induced a slight and rather doubtful amount of inflec-
tion. This difference between the two series is inter-
esting, as Dr. Burdon Sanderson informs me that
sodium salts may be introduced in large doses into
the circulation of mammals without any injurious
effects; whilst small doses of potassium salts cause
death by suddenly arresting the movements of the
heart. An excellent instance of the different action
of the two series is presented by the phosphate of
soda quickly causing vigorous inflection, whilst phos-
phate of potash is quite inefficient. The great power
of the former is probably due to the presence of
phosphorus, as in the cases of phosphate of lime and
of ammonia. Hence we may infer that Drosera cannot
obtain phosphorus from the phosphate of potash. This
is remarkable, as I hear from Dr. Burdon Sanderson
that phosphate of potash is certainly decomposed
within the bodies of animals. Most of the salts of
soda act very rapidly ; the iodide acting slowest. The
oxalate, nitrate, and citrate seem to have a special
tendency to cause the blade of the leaf to be inflected.
The glands of the disc, after absorbing the citrate,
transmit hardly any motor impulse tc the outer
tentacles; and in this character the citrate of soda
resembles the citrate of ammonia, or a decoction of
grass-leaves; these three fluids all acting chiefly on
the blade.
It seems opposed to the rule of the preponderant
influence of the base that the nitrate of lithium
causes moderately rapid inflection, whereas the acetate
causes none; but this metal is closely allied to sodium
[88 DROSERA ROTUNDIFOLIA. Cuar. VIIL
and potassium,* which act so differently; therefore
we might expect that its action would be inter-
mediate. We see, also, that caesium causes inflection,
and rubidium does not; and these two metals are
allied to sodium and potassium. Most of the earthy
salts are inoperative. Two salts of calcium, four of
magnesium, two of barium, and two of strontium, did
not cause any inflection, and thus follow the rule of
the preponderant power of the base. Of three salts
of aluminium, one did not act, a second showed a
trace of action, and the third acted slowly and doubt-
fully, so that their effects are nearly alike.
Of the salts and acids of ordinary metals, seventeen
were tried, and only four, namely those of zinc, lead,
manganese, and cobalt, failed to cause inflection. The
salts of cadmium, tin, antimony, and iron, act slowly ;
and the three latter seem more or less poisonous. The
salts of silver, mercury, gold, copper, nickel, and
platinum, chromic and arsenious acids, cause great
inflection with extreme quickness, and are deadly
poisons. It is surprising, judging from animals, that
lead and barium should not be poisonous. Most of the
poisonous salts make the glands black, but chloride of
platinum made them very pale. I shall have occasion,
in the next chapter, to add a few remarks on the dif-
ferent effects of phosphate of ammonia on leaves pre-
viously immersed in various solutions.
ACIDS.
I will first give, as in the case of the salts, a list
of the twenty-four acids which were tried, divided into
two series, according as they cause or do not cause
* Miller’s ‘ Elements of Chemistry,’ 3rd edit. pp. 337, 448.
Cuapr. VIII.
inflection.
THE EFFECTS OF ACIDS.
189
After describing the experiments, a few
eoncluding remarks will be added.
Actps, MUCH DILUTED, WHICH CAUSE
_
oonondtdh nant Ww bw
a
non - S&S
13.
INFLECTION.
Nitric, strong inflection; poi-
sonous.
. Hydrochloric, moderate and
slowinflection; not poisonous.
. Hydriodic, strong inflection ;
poisonous.
. Iodic, strong inflection; poi-
sonous.
. Sulphuric, strong inflection ;
somewhat poisonous.
. Phosphoric, strong inflection ;
poisonous.
. Boracic, moderate and rather
slow inflection; not poisonous.
. Formic, very slight inflec-
tion; not poisonous.
. Acetic, strong and rapid in-
flection ; poisonous.
. Propionic, strong but not very
rapid inflection ; poisonous.
. Oleic, quick inflection; very
poisonous.
. Carbolic, very slow inflection ;
poisonous.
Lactic, slow and moderate in-
flection ; poisonous.
. Oxalic, moderately quick in-
flection ; very poisonous.
. Malic, very slow but consider-
able inflection; not poisonous.
. Benzoic, rapid inflection; very
poisonous.
. Succinic, moderately quick
inflection; moderately poi-
sonous.
. Hippuric, rather slow inflec-
tion; poisonous.
. Hydrocyanic, rather rapid in-
flection ; very poisonous.
op ope
Acts, DILUTED TO THE SAME
DscrEE, WHICH DO NOT OAUSH
INFLECTION.
. Gallic; not poisonous.
Tannic; not poisonous.
. Tartaric; not poisonous.
. Citric; not poisonous.
. Uric ; (?) not poisonous.
Nitric Acid.—Four leaves were placed, each in thirty minims
of one part by weight of the acid to 437 of water, so that each
received ;; of a grain, or 4048 mg. This strength was chosen
for this and most of the following experiments, as it is the same
L90 DROSERA ROTUNDIFOLIA. - Cuar. VIII.
as that of most of the foregoing saline solutions. In 2 hrs. 30 m.
some of the leaves were considerably, and in 6 hrs. 30 m: all
were immensely, inflected, as were their blades. The surround-
ing fluid was slightly coloured pink, which always shows that
the leaves have been injured. They were then left in water for
three days; but they remained inflected and were evidently
killed. Most of the glands had become colourless. Two leaves
were then immersed, each in thirty minims of one part to 1000
of water; in a few hours there was some inflection; and after
24 hrs. both leaves had almost all their tentacles and blades in-
flected; they were left in water for three days, and one partially
re-expanded and recovered. Two leaves were next immersed,
each in thirty minims of one part to 2000 of water; this pro-
duced very little effect, except that most of the tentacles close
to the summit of the petiole were inflected, as if the acid had
been absorbed by the cut-off end.
Hydroc: lorie Acid.—One part to 437 of water ; four leaves were
immersed as before, each in thirty minims. After 6 hrs. only
one leaf was considerably inflected. After 8 hrs. 15 m. one had
its tentacles and blade well inflected; the other three were
moderately inflected, and the blade of one slightly. The
surrounding fluid was not colourcd at all pink. After 25 hrs,
three of these four leaves began to re-expand, but their glands
were of a pink instead of a red colour; after two more days
they fully re-expanded; but the fuurth leaf remained inflected,
and seemed much injured or killed, with its glands white
Four leaves were then treated, each with thirty minims of one part
to 875 of water; after 21 hrs. they were moderately inflected;
and on being transferred to water, fully re-expanded in two days,
and seemed quite healthy.
Hydriodic Acid.—One to 487 of water; three leaves were im-
mersed as before, each in thirty minims. After 45 m. the glands
were discoloured, and the surrounding fluid became pinkish, but
there was no inflection. After 5 hrs. all the tentacles were
closely inflected; and an immense amount of mucus was secreted,
so that the fluid could be drawn out into long ropes. The leaves
were then placed in water, but never re-expanded, and were evi-
dently killed. Four leaves were next immersed in one part to 875
of water; the action was now slower, but after 22 hrs. all four
leaves were closely inflected, and were affected in other respects
as above described. These leaves did not re-expand, though
left for four days in water. This acid acts far more powerfully
than hydrochloric, and is poisonous.
Jodic Acid.—One to 437 of water; three leaves were immersed,
Cpnar. VILL THE EFFECTS OF ACIDS. 191
each in thirty minims; after 3 hrs. strong inflection; after 4 hrs.
glands dark brown; after 8 hrs. 30 m. close inflection, and the
leaves had become flaccid ; surrounding fluid not coloured pink.
These leaves were then placed in water, and next day were
evidently dead.
Sulphuric Acid—One to 437 of water; four leaves were im-
mersed, each in thirty minims; after 4 hrs. great inflection;
after 6 hrs. surrounding fluid just tinged pink; they were then
placed in water, and after 46 hrs. two of them were still closely
inflected, two beginning to re-expand; many of the glands
colourless. This acid is not so poisonous as hydriodic or iodic
acids.
Phosphoric Acid.—One to 437 of water; three leaves were
immersed together in ninety minims; after 5 hrs. 30 m. some
inflection, and some glands colourless; after 8 hrs. all the
tentacles closely inflected, and many glands colourless ; surround-
ing fluid pink. Left in water for two days and a half, remained
in the same state and appeared dead.
Boraciec Acid.—One to 437 of water; four leaves were im-
mersed together in 120 minims; after 6 hrs. very slight inflection ;
after 8 hrs. 15 m. two were considerably inflected, the other two
slightly. After 24 hrs. one leaf was rather closely inflected,
the second less closely, the third and fourth moderately. The
leaves were washed and put into water; after 24 hrs. they
were almost fully re-expanded and looked healthy. This acid
agrees closely with hydrochloric acid of the same strength in
its power of causing inflection, and in not being poisonous.
Formic Acid.—Four leaves were immersed together in 120
minims of one part to 437 of water; after 40 m. slight, and after
6 hrs. 30 m. very moderate inflection; after 22 hrs. only a little
more inflection than often occurs in water. Two of the leaves
were then washed and placed ‘in a solution (1 gr. to 20 oz.) of
phosphate of ammonia; after 24 hrs. they were considerably
inflected, with the contents of their cells aggregated, showing
that the phosphate had acted, though not to the full and
ordinary degree.
Acetic Acid.—Four leaves were immersed together in 120
minims of one part to 437 of water. In 1 hr. 20 m. the tentacles
of all four and the blades of two were greatly inflected. After
8 hrs. the leaves had become flaccid, but still remained closely
inflected, the surrounding fluid being coloured pink. They were
then washed and placed in water; next morning they were still
inflected and of a very dark red colour, but with their glands
colourless. After another day they were dingy-coloured, and
192 DROSERA ROTUNDIFOLIA Cuar. VIII
evidently dead. This acid is far more powerful than formic, and
is highly poisonous. Half-minim drops of a stronger mixture
(viz. oné part by measure to 320 of water) were placed on the
discs of five leaves; none of the exterior tentacles, only those
on the borders of the disc which actually absorbed the acid,
became inflected. Probably the dose was too strong and para-
lysed the leaves, for drops of a weaker mixture caused much
inflection; nevertheless the leaves ull died after two days.
Propionic Acid.—Three leaves were immersed in ninety minims
of a mixture of one part to 487 of water; in 1 hr. 50 m. there
was no inflection; but after 3 hrs. 40 m. one leaf was greatly
inflected, and the other two slightly. The inflection continued
to increase, so that in 8 hrs. all three leaves were closely in-
flected. Next morning, after 20 hrs., most of the glands were
very paie, but some few were almost black. No mucus had been
secreted, and the surrounding fluid was only just perceptibly
tinted of a pale pink. After 46 hrs. the leaves became slightly
flaccid and were evidently killed, as was afterwards proved to
be the case by keeping them in water. The protoplasm in the
closely inflected tentacles was not in the least aggregated, but
towards their bases it was collected in little brownish masses at
the bottoms of the:cells. This protoplasm was dead, for on
leaving the leaf in a solution of, carbonate of ammonia, no
aggregation ensued. Propionic acid is highly poisonous to
Drosera, like its ally acetic acid, but induces inflection at a
much slower rate.
Oleic Acid (given me by Prof. Frankland).—Three leaves were
immersed in this acid; some inflection was almost immediately
caused, which increased slightly, but then ceased, and the leaves
seemed killed. Next morning they were rather shrivelled, and
many of the glands had fallen off the tentacles. Drops of this
acid were placed on the discs of four leaves; in 40 m. all the
tentacles were greatly inflected, excepting the extreme marginal
ones; and many of these after 3 hrs. became inflected. I was
led to try this acid from supposing that it was present (which
does not seem to be the case)* in olive oil, the action of which
is anomalous. Thus drops of this oil placed on the disc do not
cause the outer tentacles to be inflected; yet when minute
drops were added to the secretion surrounding the glands of the
outer tentacles, these were.occasionally, but by means always,
inflected. Two leaves were also immersed in this oil, and there
* See articles on Giycerine and Oleic Acid in Watts’ ‘Dict. af
Chemistry.’
Cuar. VIIL THE EFfECTS OF ACIDS. 193
was no inflection for about 12 hrs.; but after 23 hrs. almost all
the tentacles were inflected. Three leaves were likewise im-
mersed in unboiled linseed oil, and soon became somewhat, and
in 3 hrs. greatly, inflected. After 1 hr. the secretion round the
glands was coloured pink. I infer from this latter fact that the
power of linseed oil to cause inflection cannot be attributed to
the albumin which it is said to contain.
Carbolic Acid.—Two leaves were immersed in sixty minims of
a solution of 1 gr. to 487 of water; in 7 hrs. one was slightly,
and in 24 hrs. both were closely, inflected, with a surprising
amount of mucus secreted. These leaves were washed and left
for two days in water; they remained inflected; most of their
glands became pale, and they seemed dead. This acid is
poisonous, but does not act nearly go rapidly or powerfully as
might have been expected from its known destructive power on
the lowest organisms. Half-minims of the same solution were
placed on the discs of three leaves; after 24 hrs. no inflection of the
outer tentacles ensued, and when bits of meat were given them,
they became fairly well inflected. Again half-minims of a
stronger solution, of one part to 218 of water, were placed on the
discs of three leaves; no inflection of the outer tentacles ensued ;
bits of meat were then given as before; one leaf alone became
well inflected, the discal glands of the other two appearing
much injured and dry. We thus see that the glands of
the discs, after absorbing this acid, rarely transmit any motor
impulse to the outer tentacles; though these, when their own
glands absorb the acid, are strongly acted on.
Lactic Acid.—Three leaves were immersed in ninety minims of
one part to 437 of water. After 48 m. there was no inflection,
but the surrounding fluid was coloured pink; after 8 hrs,
30 m. one leaf alone was a little inflected, and almost all
the glands on all three leaves were of a very pale colour,
The leaves were then washed and placed in a solution (1 gr.
to 20 oz.) of phosphate of ammonia; after about 16 hrs. there
was only a trace of inflection. They were left in the phosphate
for 48 hrs., and remained in the same state, with almost all
their glands discoloured. The prutoplasm within the cells
was not aggregated, except in a very few tentacles, the glands
of which were not much discoloured.. I believe, therefore,
that almost all the glands and tentacles had been killed by
the acid so suddenly that hardly any inflection was caused.
Four leaves were next immersed in 120 minims of a weaker
solution, of one part to 875 of water; after 2 hrs. 80 m. the
surrounding fluid was quite pink; the glands were pale, but
194 DROSERA ROTUNDIFOLIA. Cuar. VIIL
there was no inflection; after 7 hrs. 830 m. two of the leaves
showed some inflection, and the glands were almost white;
after 21 hrs. two of the leaves were considerably inflected,
and a third slightly; most of the glands were white, the others
dark red. After 45 hrs. one leaf had almost every tentacle in-
flected ; a second a large number ; the third and fourth very few ;
almost all the glands were white, excepting those on the discs of
two of the leaves, and many of these were very dark red. The
leaves appeared dead. Hence lactic acid acts in a very peculiar
manner, causing inflection at an extraordinarily slow rate, and
being highly poisonous. Immersion in even weaker solutions,
viz. of one part to 1812 and 1750 of water, apparently killed the
leaves (the tentacles after a time being bowed backwards), and
rendered the glands white, but caused no inflection.
Gallic, Tannic, Turtaric, and Citric Acids,—One part to 487 of
water. Three or four leaves were immersed, each in thirty
minims of these four solutions, so that each leaf received , of a
grain, or 4048 mg. No inflection was caused in 24 hrs., and the
leaves did not appear at all injured. Those which had been in
the tannic and tartaric acids were placed in a solution (1 gr. to
20 oz.) of phosphate of ammonia, but no inflection ensued in
24 hrs. On the other hand, the four leaves which had been in
the citric acid, when treated with the phosphate, became decidedly
inflected in 50 m. and strongly inflected after 5 hrs., and so
remained for the next 24 hrs.
Malic Acid —Three leaves were immersed in ninety minims of
a solution of one part to 437 of water; no inflection was caused
in 8 hrs. 20 m., but after 24 hrs. two of them were considerably,
and the third slightly, inflected—more so than could be ac-
counted for by the action of water. No great amount of mucus
was secreted. They were then placed in water, and after two
days partially re-expanded.. Hence this acid is not poisonous.
Oxalie Actd.—Three leaves were immersed in ninety minims of
a solution of 1 gr. to 487 of water; after 2 hrs. 10 m. there was
much inflection; glands pale; the surrounding fluid of a dark
pink colour; after 8 hrs. excessive inflection. The leaves were
then placed in water; after about 16 hrs. the tentacles were of
a very dark red colour, like those of the leaves in acetic acid.
After 24 additional hours, the three leaves were dead and their
glands colourless.
Benzoic Acid.—Five leaves were immersed, each in thirty
minims of a solution of 1 gr. to 487 of water. This solution was
so weak that it only just tasted acid, yet, as we shall see, was
highly poisonous to Drosera. After 52 m. the submargina:
Cuar. VIII. THE EFFECTS OF ACIDS. 195
tentacles were somewhat inflected, and all the glands very pale-
coloured; the surrounding fluid was coloured pink. On one
occasion the-fluid became pink in the course of only 12m., and
the glands as white as if the leaf had been dipped in boiling
water. After 4 hrs. much inflection; but none of the tentacles
were closely inflected, owing, as I believe, to their having been
paralysed before they had time to complete their movement.
An extraordinary quantity of mucus was secreted. Some of the
leaves were left in the solution; others, after an immersion of
6 hrs. 30 m., were placed in water. Next morning both lots
were quite dead; the leaves in the solution being flaccid, those
in the water (now coloured yellow) of a pale brown tint, and
their glands white. ;
Succinic Acid.—Three leaves were immersed in ninety minims
of a solution of 1 gr. to 437 of water; after 4 hrs. 15 m. consider-
able and after 23 hrs. great inflection; many of the glands
pale; fluid coloured pink. The leaves were then washed and
placed in water; after two days there was some re-expansion,
but many of the glands were still white. This acid is not
nearly so poisonous as oxalic or benzoic.
Uric Acid.—Three leaves were immersed in 180 minims of a
solution of 1 gr. to 875 of warm water, but all the acid was not
dissolved; so that each received nearly ~, of a grain. After
25 m. there was some slight inflection, but this never increased ;
after 9 hrs. the glands were not discoloured, nor was the solu-
tion coloured pink; nevertheless much mucus was secreted.
The leaves were then placed in water, and by next morning
fully re-expanded. I doubt whether this acid really causes
inflection, for the slight movement which at first occurred may
lave been due to the presence of a trace of albuminous matter.
But it produces some effect, as shown by the secretion of so
much mucus.
Hippuric Acid.—Four leaves were immersed in 120 minims of
a solution of 1 gr. to 487 of water. After 2 hrs. the fluid was
coloured pink; glands pale, but no inflection. After 6 hrs. some
inflection; after 9 hrs. all four leaves greatly inflected: much
mucus secreted; all the glands very pale. The leaves were then
left in water for two days; they remained closely inflected,
with their glands colourless, and I do not doubt were Pitted.
Hydrocyanic Acid.—Four leaves were immersed, each in thirty
minims of one part to 437 of water; in 2 hrs. 45 m. all the
tentacles were considerably inflected, with many of the glands
pale; after 3 hrs. 45 m. all stronyly inflected, and the surround-
ing fluid coloured pink; after 6 hrs. all closely inflected. After
196 DROSERA ROTUNDIFOLIA. Crap. VILL
an immersion of 8 hrs. 20 m. the leaves were washed and placed
in water; next morning, after about 16 hrs., they were still
inflected and discoloured; on the succeeding day they were
evidently dead. Two leaves were immersed in a stronger
mixture, of one part to fifty of water; in 1 hr. 15 m. the glands
became as white as porcelain, as if they had been dipped in boil-
ing water; very few of the tentacles were inflected; but after
4 hrs. almost all were inflected. These leaves were then placed
in water, and next morning were evidently dead. Half-minim
drops of the same strength (viz. one part to fifty of water) were
next placed on the discs of five leaves; after 21 hrs. all the
outer tentacles were inflected, and the leaves appeared much
injured. I likewise touched the secretion round a large number
of glands with minute drops (about =, of a minim, or ‘00296 ml.)
of Scheele’s mixture (6 per cent.); the glands first became bright
red, and after 3 hrs. 15 m. about two-thirds of the tentacles
bearing these glands were inflected, and remained so for the two
succeeding days, when they appeared dead.
Concluding Remarks on the Action of Acids.—It is
evident that acids have a strong tendency to cause the
inflection of the tentacles ;* for out of the twenty-four
acids tried, nineteen thus acted, either rapidly and
energetically, or slowly and slightly. This fact is
remarkable, as the juices of many plants contain more
acid, judging by the taste, than the solutions employed
in my experiments. From the powerful effects of so
many acids on Drosera, we are led to infer that those
naturally contained in the tissues of this plant, as well
as of others, must play some important part in their
economy. Of the five cases in which acids did not
cause the tentacles to be inflected, one is doubtful;
for uric acid did act slightly, and caused a copious
secretion of mucus. Mere sourness to the taste is no
* According to M. Fournier Berberis instantly to close; though
(‘De la Fécondation dans les drops of water have no such power,
Phanérogames.’ 1863, p. 61) drops _— which latter statement I can com
of acetic, hydrocyanic, and sul- firm.
phuric acid caye the stamens of
Cuar. VILL CONCLUDING REMARKS, ACIDS. 197
criterion of the power of an acid on Drosera, as citric
and tartaric acids are very sour, yet do not excite
inflection. It is remarkable how acids differ in
their power. Thus, hydrochloric acid acts far less
powerfully than hydriodic and many other acids of the
same strength, and is not poisonous. This is an in-
teresting fact, as hydrochloric acid plays so important
a part in the digestive process of animals. Formic
acid induces very slight inflection, and is not poison-
ous; whereas its ally, acetic acid, acts rapidly and
powerfully, and is poisonous. Malic acid acts slightly,
whereas citric and tartaric acids produce no effect.
Lactic acid is poisonous, and is remarkable from in-
ducing inflection only after a considerable interval of
time. Nothing surprised me more than that a solution
of benzoic acid, so weak as to be hardly acidulous to-
the taste, should act with great rapidity and be highly
poisonous; for I am informed that it produces no
marked effect on the animal economy. It may be
seen, by looking down the list at the head of this dis-
cussion, that most of the acids are poisonous, often
highly so. Diluted acids are known to induce nega-
tive osmose,* and the poisonous action of so many
acids on Drosera is, perhaps, connected with this
power, for we have seen that the fluids in which they
were immersed often became pink, and the glands
pale-coloured or white. Many of the poisonous acids,
such as hydriodic, benzoic, hippuric, and carbolic (but
I neglected to record all the cases), caused the secre-
tion of an extraordinary amount of mucus, so that
long ropes of this matter hung from the leaves when
they were lifted out of the solutions. Other acids,
such as hydrochloric and malic, have no such ten-
™ Miller’s ‘ Elements of Chemistry,’ part i. 1867, p. 87,
198 DROSERA ROTUNDIFOLIA. Cuar. VILL
dency ; in these two latter cases the surrounding fluid
was not coloured pink, and the leaves were not
poisoned. On the other hand, propionic acid, which
is poisonous, does not cause much mucus to be
secreted, yet the surrounding fluid became slightly
pink. Lastly, as in the case of saline solutions,
leaves, after being immersed in certain acids, were
soon acted on by phosphate of ammonia; on the
other hand, they were not thus affected after immer-
sion in certain other acids. To this subject, how-
ever, I shall have to recut.
Snap. IX. ALKALOID POISONS. 199
CHAPTER IX.
Tur EFrects OF CERTAIN ALKALOID PoIsoNns, OTHER SUBSTANCES AND
VAPpours.
Strychnine, salts of — Quinine, sulphate of, does not soon arrest the
movement of the protoplasm — Other salts of quinine — Digitaline
— Nicotine — Atropine— Veratrine—Colchicine—Theine— Curare
— Morphia — Hyoscyamus — Poison of the cobra, apparently acce-
lerates the movements of the protoplasm—Camphor, a powerful
stimulant, its vapour narcotic — Certain essential oils excite move-
ment — Glycerine — Water and certain solutions retard or prevent
the subsequent action of phosphate of ammonia — Alcohol inno-
cuous, its vapour narcotic and poisonous — Chloroform, sulphuric
and nitric ether, their stimulant, poisonous, and narcotic power —
Carbonic acid narcotic, not quickly poisonous — Concluding remarks,
As in the last chapter, I will first give my experiments,
and then a brief summary of the results with some
concluding remarks.
Acetate of Strychnine.—Half-minims of a solution of one part to
437 of water were placed on the discs of six leaves; so that
each received 54, of a grain, or.0675mg. In 2 hrs. 30m. the
outer tentacles on some of them were inflected, but in an irregu-
lar manner, sometimes only on one side of the leaf. The next
morning, after 22 hrs. 30 m., the inflection had not increased.
The glands on the central disc were blackened, and had ceased
secreting. After an additional 24 hrs. all the central glands
seemed dead, but the inflected tentacles had re-expanded and
appeared quite healthy. Hence the poisonous action of strych-
nine seems confined to the glands which have absorbed it;
nevertheless, these glands transmit a motor impulse to the
exterior tentacles. Minute drops (about 2, of a minim) of
the same solution applied to the glands of the outer tentacles
occasionally caused them to bend. The poison does not seem
to act quickly, for having applied to several glands similar
drops of a rather stronger solution, of one part to 292 of water,
this did not prevent the tentacles bending, when their glands
14
200 DROSERA ROTUNDIFOLIA. Cuar. IX.
were excited, after an interval of a quarter to three quarters of
an hour, by being rubbed or given bits of meat. Similar drops
of a solution of one part to 218 of water (2 grs. to 1 oz.) quickly
blackened the glands; some few tentacles thus treated moved,
whilst others did not. The latter, however, on being subse-
quently moistened with saliva or given bits of meat, became
incurved, though with extreme slowness; and this shows that
they had been injured. Stronger solutions (but the strength
was not ascertained) sometimes arrested all power of movement
very quickly ; thus bits of meat were placed on the glands of
several exterior tentacles, and as soon as they began to move,
minute drops of the strong solution were added. They con-
tinued for a short time to go on bending, and then suddenly
stood still; other tentacles on the same leaves, with meat
on their glands, but not wetted with the strychnine, continued
to bend and soon reached the centre of the leaf.
Citrate of Strychnine.—Half-minims of a solution of one part
to 487 of water were placed on the discs of six leaves; after
94 hrs. the outer tentacles showed only a trace of inflection.
Bits of meat were then placed on three of these leaves, but in
24 hrs. only slight and irregular inflection occurred, proving
that the leaves had been greatly injured. Two of the leaves to
which meat had not been given had their discal glands dry and
much injured. Minute drops of a strong solution of one part to
109 of water (4 grs. to 1 oz.) were added to the secretion round
several glands, but did not produce nearly so plain an effect as
the drops of a much weaker solution of the acetate. Particles of
the dry citrate were placed on six glands; two of these moved
some way towards the centre, and then stood still, being no
doubt killed; three others curved much farther inwards, and
were then fixed; one alone reached the centre. Five leaves
were immersed, each in thirty minims of a solution of one part
to 437 of water; so that each received ~, of a grain; after
about 1 hr. some of the outer tentacles became inflected, and
the glands were oddly mottled with black and white. These
glands, in from 4 hrs. to 5 hrs., became whitish and opaque,
and the protoplasm in the cells of the tentacles was well aggre-
gated. By this time two of the leaves were greatly inflected,
but the three others not much more inflected than they were
before. Nevertheless two fresh leaves, after an immersion re-
spectively for 2 hrs. and 4 hrs. in the solution, were not killed;
for on being left for 1 hr. 30 m. in a solution of one part of
carbonate of ammonia to 218 of water, their tentacles became
more inflected, and there was much aggregation. The glands
Ouap. IX. ALKALOID POISONS. 201
of two other leaves, after an immersion for 2 hrs. in a stronger
solution, of one part of the citrate to 218 of water, became of an
opaque, pale pink colour, which before long disappeared, leaving
them white. One of these two leaves had its blade and
tentacles greatly inflected; the other hardly at all; but the
protoplasm in the cells of both was aggregated down to the
bases of the tentacles, with the spherical masses in the cells
close beneath the glands blackened. After 24 hrs. one of these
leaves was colourless, and evidently dead.
Sulphate of Quinine—Some of this salt was added to
water, which is said to dissolve ;45 part of its weight.
Five leaves were immersed, each in thirty minims of this solu-
tion, which tasted bitter. In less than 1 hr. some of them had
a few tentacles inflected. In 3 hrs. most of the glands became
whitish, others dark-coloured, and many oddly mottled. After
6 hrs. two of the leaves had a good many tentacles inflected, but
this very moderate degree of inflection never increased. One of
the leaves was taken out of the solution after 4 hrs., and placed
in water; by the next morning some tew of the inflected
tentacles had re-expanded, showing that they were not dead;
but the glands were still much discoloured. Another leaf not
included in the above lot, after an immersion of 8 hrs. 15 m.,
was carefully examined; the protoplasm in the cells of the
outer tentacles, and of the short green ones on the disc, had
become strongly aggregated down to their bases ; and I distinctly
saw that the little masses changed their positions and shapes
rather rapidly ; some coalescing and again separating. I was
surprised at this fact, because quinine is said to arrest all move-
ment in the white corpuscles of the blood; but as, according to
Binz,* this is due to their being no longer supplied with oxygen
by the red corpuscles, any such arrestment of movement could
not be expected in Drosera. That the glands had absorbed some
of the salt was evident from their change of colour; but I at
first thought that the solution might not have travelled down
the cells of the tentacles, where the protoplasm was seen in
active movement. This view, however, I have no doubt, is
erroneous, for a leaf which had been immersed for 3 hrs, in the
quinine solution was then placed in a little solution of one part of
carbonate of ammonia to 218 of water; and in 30 m. the glands
and the upper cells of the tentacles became intensely black, with
the protoplasm presenting a very unusual appearance; for it
“ ‘Quarterly Journal of Microscopical Science, April 1874, p. 185.
202 DROSERA ROTUNDIFOLIA. Cuar. IX.
had become aggregated into reticulated dingy-coloured masses,
having rounded and angular interspaces. As I have never
seen this effect produced by the carbonate of ammonia alone,
it must be attributed to the previous action of the quinine.
These reticulated masses were watched for some time, but did
not change their forms; so that the protoplasm no doubt had
been killed by the combined action of the two salts, though
exposed to them for only a short time.
Another leaf, after an immersion for 24 hrs. in the quinine
solution, became somewhat flaccid, and the protoplasm in all
the cells was aggregated. Many of the aggregated masses were
discoloured, and presented a granular appearance; they were
spherical, or elongated, or still more commonly consisted of
little curved chains of small globules. None of these masses
exhibited the least movement, and no doubt were all dead.
Half-minims of the solution were placed on the discs of six
leaves; after 23 hrs. one had all its tentacles, two had a few,
and the others none inflected; so that the discal glands, when
irritated by this salt, do not transmit any strong motor impulse
to the outer tentacles. After 48 hrs. the glands on the discs of
all six leaves were evidently much injured or quite killed. It is
clear that this salt is highly poisonous.*
Acrtute of Quinine.—Four leaves were immersed, each in thirty
minims of a solution of one part to 487 of water. The solution
was tested with litmus paper, and was not acid. After only
10 m. all four leaves were greatly, and after 6 hrs. immensely,
inflected. They were then left in water for 60 hrs., but never
re-expanded; the glands were white, and the leaves evidently
dead. This salt is far more efficient than the sulphate in
causing inflection, and, like that salt, is highly poisonous.
Nitrate of Quinine.—Four leaves were immersed, each in thirty
minims of a solution of one part to 487 of water. After 6 hrs.
there was hardly a trace of inflection; after 22 hrs. three of the
leaves were moderately, and the fourth slightly inflected; sa
that this salt induces, though rather slowly, well-marked inflec-
tion.
These leaves, on being left in water for 48 hrs., almost
* Binz found several years ago
(as stated in ‘The Journal of
Anatomy and Phys.’ November
1872, p. 195) that quinia is an
energetic poison to low vege-
tuble and animal organisms. Even
one part added to £000 parts of
blood arrests the movements of the
white corpuscles, which become
“rounded and granular.” In the
tentacles of Droscra the aggre-
gated masses of protoplasm, which
appeared killed by the quinine,
likewise presented a granular
appearance.