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INSECTIVOROUS PLANTS.
By CHARLES DARWIN, M.A. F.R.S,
ETC.
SECOND EDITION
REVISED BY FRANCIS DARWIN.
WITH ILLUSTRATIONS.
Mo. Bot, Garden,
1893
LONDON:
JOHN MURRAY, ALBEMARLE STREET.
1888.
The right of Translation is reser ved,
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PREFACE TO THE SECOND EDITION.
Ix the present Edition I have not attempted to give a
complete account of the progress of the subject since 1875.
Nor have I called attention to those passages occurring
occasionally throughout the book wherein the Author makes
use of explanations, illustrations, or reference to authorities
which seem to me not perfectly satisfactory. I have merely
wished to indicate the more important points brought to
light by recent research. The additions are In some cases
placed in the text, but they are more commonly given as
footnotes. They are, in all cases, indicated by means of
square brackets.
Misprints, errors in numbers, &c., have been set right,
and a few verbal corrections have been taken from Charles
Darwin’s copy of the First Edition. Otherwise the text
remains unchanged.
Francis DARWIN.
CAMBRIDGE,
July, 1888.
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 roots 12 4. 5s te eek Pages 1-17
CHAPTER II.
Tue MOVEMENTS oF THE TENTACLES FROM THE CONTACT oF SOLID
Bovigs.
Inflection of the exterior tentacles owing to the glands of the disc
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 be ps a ee a 18-31
CHAPTER III.
AGGREGATION OF THE PROTOPLASM WITHIN THE CELLS OF THE
TENTACLES.
Nature of the contents of the cells before aggregation—Various causes
oo” 7O
which excite aggregation—The process commences within the
vili CONTENTS.
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, &e.—Of water—Of heat—
Redissolution of the aggregated masses—Proximate causes of the
aggregation of the protoplaam—Summary and concluding remarks
—Supplementary observations on aggregation in the roots of
pante. o we ve Oe ee i, ee
CHAPTER IV.
THe EFFECTS oF 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 coagu-
lates the albuminous contents of the glands Bias 56-63
CHAPTER V.
Tue EFFECTS or NoN-NITROGENOUS AND NITROGENOUS ORGANIC
FLUIDS oN THE LEAVES.
Non-nitrogenous fluids—Solutions of gum arabic—Sugar—Starch—
Diluted alcohoi—Olive oil—Infusion and decoction of tea—Nitro-
genous fluids—Milk—Urine—Liquid albumen—lInfusion 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 64-70
CHAPTER VI.
THE DIGESTIVE 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—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 — Hematin —
CONTENTS. ix
Indigestible substances — Epidermic productions — Fibro-elastic
tissue—M ucin—Pepsin— Urea—Chitine—Cellulose—Gun-cotton —
Chlorophyll—Fat and oil—Starch—Action of the secretion on
living seeds—Summary and concluding remarks Pages 71-110
CHAPEBReViIE
Tne EFFECTS oF SALTS oF 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
i ; in weak solutions—Minuteness of the doses which induce aggrega-
l tion 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
bate CF MORIA o n a ae e ee ee
CHAPTER VIII.
y THE 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—
unitary on their action .: e <e ao oe o o DEINE
CHAPTER IX.
THE EFFECTS OF CERTAIN ALKALOID POISONS, OTHER SUBSTANCES
AND VAPOURS.
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—H yoscyamus—Poison of the cobra, apparently
accelerates 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 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 ae s, e cae ky e oe cee 5 0 LO
x CONTENTS.
CHAPTER X.
ON THE SENSITIVENESS OF THE LEAVES, AND ON THE LINES OF
TRANSMISSION OF THE MOTOR IMPULSE.
Giands and summits of the tentacles alone sensitive—Transmission 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 Pages
187-211
CHAPTER XI.
RECAPITULATION OF THE CHIEF OBSERVATIONS ON DROSERA
ROTUNDIFOLIA n a o a ee eS
CHAPTER XII.
ON THE STRUCTURE AND MOVEMENTS OF SOME OTHER SPECIES OF
DROSERA.
Drosera anglica — Drosera intermedia — Drosera capensis — Drosera
spathulata — Drosera filiformis — Drosera binata — Concluding
remarks.. pe ees E ae Oe E ee e A
CHAPTER XIII.
DIONÆA MUSCIPULA.
Structure of the leaves—Sensitiveness of the filaments—Rapid move-
ment 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.. .. ., 231-259
CHAPTER XIV.
ALDROVANDA VESICULOSA.
Captures crustaceans—Structure of the leaves in comparison with
those of Dionawa—Absorption by the glands, by the quadrifid
CONTENTS. xi
processes, and points on the infolded margins — Aldrovanda
vesiculosa, var. australis—Captures prey—Absorption of animal
matter — Aldrovanda vesiculosa, var. verticillata — Concluding
POOR a o o e e as a =o — Pages 200-269
CHAPTER XV.
DROSOPHYLLUM—-RORIDULA—BYBLIS—GLANDULAR HAIRS OF OTHER
PLANTS—CONCLUDING REMARKS ON THE DROSERACE.
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 — Concluding remarks on the
SI o = a e ae n a eee
CHAPTER XVI.
PINGUICULA.
Pinguicula vulgavis—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
—tThe effects of substances not containing soluble nitrogenous
matter on the glands—Pinguicula grandiflora—Pinguicula lusi-
tanica, catches insects—Movement of the leaves, secretion and
daton e a aa es a a o e o
CHAPTER XVII.
UTRICULARIA.
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— Uftricu-
laria vulgaris—Utricularia minor— Utricularia clandestina
319-347
xil CONTENTS.
CHAPTER XVIII.
UTRICULARIA (continued).
Utricularia montana—Description of the bladders on the subterranean
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 .. -1 o e o: Pages 348-367
DoR- æ a r a‘ a Coen
f
LIST OF THE CHIEF ADDITIONS TO THE
SECOND EDITION.
Gardiner on the structure of the gland cells in Drosera dichotoma.
Evidence that Drosera profits by an animal diet.
The conclusions as to the sensitiveness of Drosera to a touch, modified
in accordance with Pfeffer’s views.
Gardiner on the rhabdoid,
On the nucleus in the tentacle-cells of Drosera.
The conclusion that the aggregated masses are protoplasmic, and execute
spontaneous movements, erroneous.
De Vries on the character of aggregation produced by carbonate of
ammonia.
Gardiner on the changes occurring during secretion, in the glands of
Drosera dichotoma.
Rees and Will on the nature of the acid in the secretion of Drosera.
Rees, Will, von Gorup, and Vines on the secretion of the acid and of
the ferment in Drosera and Nepenthes.
Results with syntonin untrustworthy.
Results with casein untrustworthy.
Schiffs peptogene theory.
Transmission of motor impulse.
Gardiner and Batalin on the mechanism of movement in Drosera.
Fraustadt and C. de Candolle on the stomata of Dionæa.
Fraustadt, C. de Candolle and Batalin on the sensitive filaments of
Dionæa.
Munk on the sensitiveness of Dionæa to the hygrometric state of the
air.
C. de Candolle on the effect of drops of water on the sensitive filaments
of Dionza.
Gardiner on the glands of Dionza.
J. D. Hooker on the early history of Dionza.
Munk on a movement of the edges of the leaf in Dionxa,
Batalin and Munk on the mechanism of the movement in Dionza.
ag Sanderson, Kunkel and Munk on the electrical phenomena in
Dionza.
Caspary on Aldrovanda.
Cohn and Caspary on Aldrovanda.
CHIEF ADDITIONS TO THE SECOND EDITION.
Mori on the seat of irritability in Aldrovanda.
Duval-Jouve on the function of certain glands in Aldrovanda.
Fraustadt, Penzig, and Pfeffer on the roots of Dionza and Droso-
phyllum.
Batalin on the yellow-green colour of Pinguicula.
Batalin on the pits or depressions in the leaves of Pinguicula.
| Pfeffer on the use of Pinguicula as rennet.
Kamienski on the absence of the root in Utricularia.
Schimper on the evidence of absorption of the products of decay in
Utricularia cornuta.
Hovelacque, Schenk, and Schimper on the morphology of Utricularia
montana.
Schimper on Utricularia cornuta.
Schimper on the evidence of absorption in Sarracenia.
De Bary on the vigorous growth of Utricularia when supplied with
animal food.
Treub on Dischidia Raffesiana.
EE OO ne T Re
INSECTIVOROUS PLANTS.
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, Md
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 roots.
Durine the summer of 1860, I was surprised by finding 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 gathered by chance a dozen plants,
* As Dr. Nitschke has given (‘ Bot.
Zeitung,’ 1860, p. 229) the biblio-
graphy 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 one of the most valuable,
namely, by Dr. Roth, in 1782. [In
the‘ Quarterly Journal of Science and
Art,’ 1829, G. T. Burnett expressed
his belief that Drosera profits by the
absorption of nutritive matter from
the captured insects.—F. D.] 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. Grænland and
Trécul each published papers, with
figures, on the structure of the leaves ;
but M. Trécul went so far as to doubt
whether they possessed 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 J shall frequently have
occasion to quote from them. His
discussions on several points, for in-
stance on the transmission of an
excitement from one part of the leaf
to another, are excellent. On Dec.
11, 1862, Mr. J. Scott read a paper
before the Botanical Society of Edin-
burgh, which was published in the
‘Gardener’s Chronicle,’ 1863, p. 30,
B
2 DROSERA ROTUNDIFOLIA. (Cuar. I.
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 expanded.
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 (Canonympha 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 inseets, for
instance the sticky buds of the horse-chestnut (Æsculus
hippocastanum), without thereby receiving, as far as we can
perceive, any advantage; but it was soon evident that
Drosera was excellently adapted for the special purpose of
catching insects, so that the subject seemed well worthy of
investigation.
The results have proved highly remarkable; the more
important ones being—firstly, the extraordinary 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; secondly, the power possessed by
Mr. Scott shows that gentle irrita-
tion of the hairs, as well as insects
placed on the disc of the leaf, cause
delivered a lecture on Dionæa, before
the Royal Institution (published in
‘Nature,’ June 14, 1874), in which a
the hairs to bend inwards. Mr. A.
W. Bennett also gave another inter-
esting account of the movements of
the leaves before the British Associa-
tion 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 Trichomes,” &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 Sanderson
short account of my observations on
the power of true digestion possessed
by Drosera and Dionza 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 publications, Dr.
Hooker also, in his important address
on Carnivorous Plants (Brit. Assoc.,
Belfast, 1874), has given a history of
the subject. [A paper on the com-
parative anatomy of the Droseracee
was published in 1879 by W. Oels as
a Dissertation at Breslau.]
4
x
è
4
f
{
Cuar. I.) STRUCTURE OF THE LEAVES. 3
the leaves of rendering 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
Fi L"
(Drosera rotundifolia.)
Leaf viewed from above ; enlarged four times.
plant. It bears from two or three to five or sıx leaves,
generally extended more or less horizontally, but sometimes
standing vertically upwards. The shape and general ap-
pearance 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
* The drawings of Drosera and several species of Utricularia, by my
Dionza, given in this work, were son Francis. They have been ex-
made for me by my son, George Dar- cellently reproduced on wood by Mr.
win; those of Aldrovanda, and of the Cooper, 188 Strand.
B 2
4 DROSERA ROTUNDIFOLIA. [Cuar. I.
broader than long, but this was not the case in the one here
figured. ‘The whole upper surface is covered with gland-
pearing filaments, or tentacles, as I shall call them, from their
manner 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.
(Drosera rotundifolia.)
4 Old leaf viewed laterally; enlarged about five times.
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 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 retiexed. A. few tentacles spring from the base of the
footstalk or petiole, and these are the longest of all, being sometimes
nearly + of an inch in length. Ona 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, carrying 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
* According to Nitschke (‘ Bot.
Zeitung,’ 1861, p. 224) the purple
fluid results from the metamorphosis
of chlorophyll. Mr. Sorby examined
the colouring matter with the spec-
with in leaves with low vitality, and
in parts, like the petioles, which
carry on leaf-functions in a very
imperfect manner. All that can be
said, therefore, is that the hairs (or
troscope, and informs me that it tentacles)are coloured like parts of a
consists of the commonest species of leaf which do not fulfil their proper
erythrophyll, “which is often met office.”
‘iceman T
a
Cuar. J.J STRUCTURE OF THE LEAVES. 5
glands of the longer tentacles, and a broader zone near their bases, of a
green tint. Spiral vessels, accompanied 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 sometimes enter true hairs.* 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 pri-
mordially as glandular hairs, or mere epidermic formations, and that
their upper part should still be so considered ; but that their lower
part, which alone is capable of movement, consists of a prolongation of
the leaf; the spiral vessels being extended from this to the uppermost
part. We shall hereafter see that the terminal tentacles of the
divided leaves of Roridula are still in an intermediate condition. _
The glands, with the exception of those borne by the extreme
marginal tentacles, are oval, and of nearly uniform size, viz. about 54, 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,t containing
purple granular matter or fluid, and with the walls thicker than those
of the pedicels. 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
* Dr. Nitschke has discusssd this
subject in ‘ Bot. Zeitung,’ 1861, p.
241, &e. See also Dr. Warming
(‘Sur la Différence entre les Tri-
chomes, &c., 1873), who gives refer-
ences to various publications. See
also Grænland and Trécul, ¢ Annal.
des Sc. nat. bot.’ (4th series), tom.
iii. 1855, pp. 297 and 303,
+ [Gardiner (¢ Proc. Royal Soc., No.
240, 1886) has pointed out that in
Drosera dichotoma “the gland-cells
of the head are provided with delicate
uncuticularised cell-walls, which are
remarkably pitted on their upper or
free surfaces.”—F. D.]
6 DROSERA ROTUNDIFOLIA. [Cuar. I.
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,
(Drosera rotundifolia.)
Longitudinal section of a gland; greatly magnified. From Dr. Warming.
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 loat as
we may infer from the structure of the glands in some other venera of
the Droseraceæ. : x
ee ee
Cuar. L] STRUCTURE OF THE LEAVES. 7
The extreme marginal tentacles differ slightly from the others
Their bases are 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 embedded on the wpper 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 of 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, whereas 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, especially the lower sides of
the outer ones, and the petioles, are studded with minute papilla (hairs
or trichomes), having a conical basis, and bearing on their summits
two, and occasionally three, or even four, rounded cells, containing
much protoplasm. ‘These papillæ are generally colourless, but some-
times include a little purple fluid. They vary in development, and
graduate, as Nitschke* states, and as I repeatedly observed, into the
long multicellular hairs. The latter, as well as the papillæ, are
probably rudiments of formerly existing tentacles.
I may here add, in order not to recur to the papillæ, 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 papilla had evidently absorbed animal matter, for instead of limpid
fluid they now contained small aggregated masses of protoplasm,t
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
* Nitschke has elaborately de- R. Microscop. Soc.’ Jan. 1876.—F. D.]
scribed and figured these papilla, t [With regard to the aggregated
‘Bot. Zeitung,’ 1861, pp. 234, 253, masses, see p. 34, footnote.—F. D.]
254. [See also A. W. Bennett, ‘ Trans.
8 DROSERA ROTUNDIFOLIA. [Cuar. I.
of the tentacles, on which the papilla were seated, now likewise
contained aggregated masses of protoplasm. We may therefore
conclude that, when a leaf has closely clasped a captured insect in the
manner immediately to be described, the papilla, 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 papillæ on the backs of the leaves or on the
petioles.
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 circum-
stances ; 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 integuments,
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 inflection 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 solution of any salt of ammonia, are
placed on the central glands, the same result quickly follows,
sometimes in under half an hour.
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
* ‘Bot, Zeitung,’ 1860, p. 246.
Agee
Cuar. L] ACTION OF THE PARTS. 9
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 becomes slightly incurved, the distal half in all
cases remaining straight. The short tentacles in the centre
of the disc, when directly excited, do not become inflected ;
but they are capable of inflection if excited by a motor
impulse received from other glands at a distance. Thus, if a
Fic. 4. Fic. 5.
(Drosera rotundifolia.) (Drosera rotundifolia.)
Leaf (enlarged) with all the tentacles Leaf (enlarged) with the tentacles on one
closely inflected, from immersion in a side inflected over a bit of meat placed
solution of phosphate of ammonia (one on the disc.
part to 87,500 of water).
jeaf is immersed in an infusion of raw meat, or in a weak
solution of ammonia (if the 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.
10 DROSERA ROTUNDIFOLIA. (Cuar. I.
The kind of inflection which the tentacles undergo is best
shown when the gland of one of the long exterior tentacles
is in any way excited; for the surrounding ones remain
unaffected. In the accompanying outline (fig. 6) we sce 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 beginning to bend
in ten seconds, after an object had been placed on its gland;
and I have often seen strongly pronounced inflection in under
one minute. It is surprising how minute a particle of any
b
Q
A
Sy
Frc. 6,
(Drosera rotundifolia.)
Diagram showing one of the exterior tentacles closely inflected; the two adjoining
ones in their ordinary position.
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 incurved, 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
sericea
Cuar. I,J ACTION OF THE PARTS. 11
varies greatly. Sometimes the apex alone, sometimes one
side, and sometimes both sides, become incurved. Forinstance,
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 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. Ihave 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 result in this case is probably due
merely to exosmose. Particles of carbonate and phosphate
of ammonia and of some other salts, for instance sulphate of
zinc, likewise increase the secretion. Immersion 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
12 DROSERA ROTUNDIFOLIA. [Cuap. I.
the other hand, tartrate of antimony produces no such effect.
Immersion in many acids (of the strength of one part to 437
of water) likewise causes a wonderful amount of 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 disc 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
repeatedly observed, but a record was kept of only thirteen.
cases, in nine of which increased secretion was plainly
observed; the four failures being 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 in-
fluence to the glands of the circumferential tentacles, causing
them to secrete more copiously.
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
tentacles remain closely inflected, the glands continue to
secrete, and the secretion is acid; so that, if neutralised by
carbonate of soda, it again becomes acid after a few hours. I
have observed the same leaf with the tentacles closely in-
flected over rather indigestible substances, such as chemi-
cally prepared casein,* pouring forth acid secretion for eight
* [These observations are not trustworthy, owing to the mode of preparation
of the casein. See p. 95.—F. D.]
An o
Cuar. LJ ACTION OF THE PARTS. is
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. Duri ing very warm
weather I placed close together two equal-sized ‘pits 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 striæ on the
muscular fibres could no longer be clearly distinguished ;
whilst the bit on the leaf, which was bathed by the secre-
tion, was free from infusoria, and its striae were perfectly
distinct in the central and undissolved portion. 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,
seml-fibrous matter, which was held in solution by the
secretion. The drying of the glands during the act of
re-expansion is of some little service to the plant; for I have
often observed that objects adhering to the leaves could 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 case delicate objects, such as fragile insects,
are sometimes 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 full-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
tracheæ 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
14 DROSERA ROTUNDIFOLIA. [Cuar. T.
next succeeding them inwards; these then bend inwards,
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 tentacles 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 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 exclusively 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 nitro-
genous and non-nitrogenous fluids of the same density on
the glands of the disc, or on a single marginal gland; and
likewise 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
identi
Cuar. IL] ACTION OF THE PARTS. 15
explains how Drosera can flourish in extremely poor peaty
soil, —in some cases where nothing but 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 assimi-
lates 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 understand 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 inwards,
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.
{Since the publication of the first edition, several experi-
ments have been made to determine whether insectivorous.
plants are able to profit by an animal diet. |
My experiments were published in ‘Linnean Society’s
Journal,’* and almost simultaneouly the results of Kellermann
and Yon Raumer were given in the ‘ Botanische Zeitung.’f
My experiments were begun in June 1877, when the plants
were collected and planted in six ordinary soup-plates. Each
plate was divided by a low partition into two sets, and the
* Vol. xvii., Francis Darwin on the fiitterung: ” ‘ Bot. Zeitung, 1878.
‘Nutrition of Drosera rotundifolia,’ Some account of the results was
t “ Vegetationsversuche an Drosera given before the Phys.-med. Soc.,
rotundifolia mit und ohne Fleisch- Erlangen, July 9, 1877.
16 DROSERA ROTUNDIFOLIA. [CHAR I.
least flourishing half of each cuiture was selected to be “ fed,”
while the rest of the plants were destined to be “starved.”
The plants were prevented from catching insects for them-
selves by means of a covering of fine gauze, so that the only
animal food which they obtained was supplied in very
minute pieces of roast meat given to the “ fed” plants but
withheld from the “starved” ones. After only 10 days the
difference between the fed and starved plants was clearly
visible: the fed plants were of brighter green and the
tentacles of a more lively red. At the end of August the
plants were compared by number, weight, and measurement,
with the following striking results :—
Starved. Fed.
Weight (without flower-stems) . . . 100 J215
Number of fowerstems o o 9.9. 100 164:9
Weight of stems .. 5 5 5 2 ne 100 231-9
Numberofcapsules > : > : - - 100 194:4
Total calculated weight of seed . . . 100 319:7
Total calculated number of seeds . : 100 241:5
These results show clearly enough that insectivorous
plants derive great advantage from animal food. It is of
interest to note that the most striking difference between the
two sets of plants is seen in what relates to reproduction—
i.e. in the flower-stems, the capsules, and the seeds.
After cutting off the flower-stems, three sets of plants were
allowed to rest throughout the winter, in order to test (by a
comparison of spring-growth) the amounts of reserve material
accumulated during the summer. Both starved and fed
plants were kept without food until April 3rd, when it was
found that the average weights per plant were 100 for the
starved, 213:0 for the fed. This proves that the fed plants
had laid by a far greater store of reserve material in spite of
having produced nearly four times as much seed.
In Kellermann and Von Raumer’s experiments (loc. cit.)
aphides were used as food instead of meat—a method which
adds greatly to the value of their results. Their conclusions
are similar to my own, and they show that not only is the
seed production of the fed plants greater, but they also form
much heavier winter-buds than the starved plants.
Dr. M. Büsgen has more recently published an interesting
paper* on the same subject. His experiments have the
* “ Die Bedeutung des Insectfanges für Drosera rotundifolia (L.),” ‘Bot.
Zeitung, 1883.
Cuar. I] ACTION OF THE PARTS. yi
advantage of having been made on young Droseras grown
from seed, The unfed plants are thus much more effectually
starved than in experiments on full-grown plants possessing
already a store of reserve matter. It is therefore not to be
wondered at that Biisgen’s results are more striking than
Kellermann’s and Von Raumer’s or my own—thus, for
instance, he found that the “fed” plants, as compared with
the starved ones, produced more than five times as many
capsules, while my figures are 100: 194. Büsgen gives a
good résumé of the whole subject, and sums up by saying
that the demonstrable superiority of fed over unfed plants is
great enough to render comprehensible the organisation of
the plants with reference to the capture of insects.—F. D.]
18 DROSERA ROTUNDIFOLIA. [Cuap. II.
CHAPTER IL.
THE MOVEMENTS OF THE TENTACLES FROM THE CONTACT OF SOLID
BODIES.
Inflection of the exterior tentacles owing to the glands of the disc 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 ex-
terior tentacles when their glands are excited by repeated touches—
Falling drops of water do not cause inflection.
I wit. 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 them-
selves 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
sensitive generally implies consciousness; but no one
supposes that the Sensitive-plant is conscious, and, as I have
found the term convenient, I shall use it without scruple. 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 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 esta-
blished that in the animal kingdom an influence can be trans-
Cuar. IL] INFLECTION INDIRECTLY CAUSED. 19
mitted 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 Jeaf 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 sub-
marginal 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 placed on
leaves, and these objects were well embraced 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 pro-
bably 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 inflection 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 very 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 dise, 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
c 2
20 DROSERA ROTUNDIFOLIA. (Cuar. IL.
repeatedly proved by trials with bits of meat ; but Iwill 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 edge 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 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 following unusual
circumstance. Small bits of raw meat (which acts more
energetically than any other substance), 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 commonly
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 sometimes well embraced, often caused no
movement whatever 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.
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; a second by a very
tew tentacles; and a third by none. I then removed the
aiiai te tia ital Nini
ong
Cuar. II] INFLECTION INDIRECTLY CAUSED. 21
particles from the two latter leaves, and put them on recently
killed flies. These were fairly well embraced in 74 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 addi-
tional 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 exceptions 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 be-
lief held by M. Ziegler (‘Comptes
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 particles, 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 to them,
but this produced no effect. 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 pro-
duced no effect whatever. On the
other hand, as we shall hereafter see,
the vapours of certain volatile sub-
stances and fluids, such as of carbonate
of ammonia, chloroform, certain es-
sential oils, &c., cause inflection. M.
Ziegler makes still more extra-
ordinary 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 et
Zoicité,’ 1874.
29 DROSERA ROTUNDIFOLIA. [Cuar. II.
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 experi-
mented 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 pre-
vious 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 2 m. 30 s. it had moved through an angle of about 45°.
* [The researches of Pfefer
( Unters. aus d. Bot. Institut zu
Tiibingen,’ vol. i., 1885, p. 483) on
the sensitiveness of various organs to
contact show that the conclusions as
to the sensitiveness of Drosera cannot
be maintained in their present form
(see p. 24).
Pfeffer shows, both in the case of
the tendrils of climbing plants, and
also in ‘that of the tentacles of
Drosera, that uniform pressure has
no stimulating action: the effect
which is ascribed simply to contact
is in reality due to unequal compres-
sion of closely neighbouring points.
Tendrils which move after having
been rubbed with a light stick fail
to be stimulated when they are
rubbed with a glass rod coated with
gelatine. The gelatine has the same
uniformity of action as drops of
water falling on the tendril, which
are known to produce no effect. If
the gelatine is sprinkled with fine
particles of sand, or if the water
holds particles of clay in suspension,
stimulation results. Analogous ex-
periments were made on Drosera
(p-511). It was found impossible to
produce movement of the tentacles
by rubbing the glands with a surface
of mercury, whereas by rubbing or
repeated touches with solid bodies
movement is called forth. Other
experiments of Pfeffer’s show con-
clusively that continuous uniform
pressure has no stimulating effect.
He placed small globules of glass om
the glands, and convinced himself
that, by examination with a lens,
that contact was affected. Some of
the tentacles moved, but the majority
showed no movement, as long as the
plants were so placed that no vibration
from the table or floor could reach
then. When they were exposed to
vibration, and when, therefore, the
glass globules must have rubbed
against or jarred the gland, the
tentacles moved. The results de-
tailed above in the text must pre-
sumably be set down to the same
cause, namely, the vibration of the
table and floor. The sensitiveness of
Drosera, therefore, by no means ceases
to be astonishing, Instead of believ-
ing in movements caused by the
steady pressure of very small weights,
we set down the results as being due
to the jarring of the gland by these
same minute bodies.—F, D.J
is an
Cuar. IL.) INFLECTION INDIRECTLY CAUSED. 20
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 than 17 m. 30s. 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 became closely
inflected. Fragments of flies were placed on the glands of
four of the outer tentacles, extended 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. 30 s. In these seven
cases, the fragments or small flies, which had been carried.
by a single tentacle to the central glands, were well em-
braced 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 embraced 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
particles of coal-cinder were then placed on the glands of
tour 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 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 move-
ment, many similar trials with other substances, such as
24 DROSERA ROTUNDIFOLIA. (Cuar. I.
splinters of white and blue glass, particles of cork, minute
bits of gold-leaf, &c.; and the proportional 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 13 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. Im 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 >, and in the last case only sẹ
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 excessively 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 particles
which caused the tentacles to become greatly inflected that
it seemed worth while carefully to ascertain how minute a
particle would plainly act. 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 l5 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 qyz of a grain, or -0464 of a milli-
gram. Five nearly equal bits of cotton-thread were tried,
and all acted. The shortest of these was =), of an inch in
length, and weighed ,,'5; of a grain. The tentacle in this
|
PRAA in
Cuar. II] INFLECTION INDIRECTLY CAUSED. 25
case was considerably inflected in 1 hr. 30 m., and the bit of
thread was carried to the centre of the leaf in 1 hr. 40 m.
Again, two particles of the thinner end of a woman’s hair,
one of these being +385 of an inch in length, and weighing
35714 Of a grain, the other ,}?,5 of an inch in length, and
weighing 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. 10 m.;
all the many other tentacles round the same leaf remaining
motionless. The appearance of this one leaf showed in an
unequivocal manner that these minute particles sufficed to
cause the tentacles to bend. Altogether, ten such particles
of hair were placed on ten glands on several leaves, and
seven of them caused the tentacles to move in a conspicuous
manner. The smallest particle which was tried, and which
acted plainly, was only +o‘ of an inch (+203 millimeter) in
length, and weighed the ş}4y of a grain, or *000822
milligram. 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 minute-
ness 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 secre-
tion 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
26 DROSERA ROTUNDIFOLIA. [CHar. II.
were exposed for a time naked to the air, but this caused no
movement; yet these glands were 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 floating 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 power-
fully, 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 experi-
ments, 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 glands, whatever
may be the position of the tentacles. Minute bits of dry
cork, thread, blotting-paper, and coal-cinders were tried, such
as those previously 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 secretion, 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 surfaces, by which means they were likewise
drawn downwards or sideways, and thus one end, or some
minute 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 particles into contact
with the glands. But as it was sometimes difficult, owing
to the refractich of the secretion, 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 on the drops round several glands, and very
Cuar. II] INFLECTION INDIRECTLY CAUSED. a
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
the course of a few minutes almost all the hitherto motion-
less 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 particles 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 particles 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 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 con-
taining 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, together 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, 1t 1s
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 minute par-
ticles act on the glands when immersed in water, may here
28 DROSERA ROTUNDIFOLIA. [Cuar II
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 into contact
with the glands, and caused this rapid movement. Accord-
ingly I added to some distilled water a pinch of a quite inno-
cent substance, namely, precipitated carbonate of lime, which
consists of an impalpable powder; I shook the mixture, and
thus got a fluid like thin 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 adhering to the external surface
of the secretion. Some, however, had penetrated it, and
were lying on the surfaces of the glands; and no doubt it
was these particles which caused the tentacles to bend.
When a leaf is immersed 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
understand how the atoms of chalk, which rested on the
surfaces of the glands, had penetrated the secretion. Any one
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, 5 of an inch in length and weighing yyy of a grain,
or of a human hair, oog of an inch in length and weighing
only ys+şy Of a grain (-000822 milligram), or particles of
precipitated chalk, after resting for a short time on a gland,
should induce some change in its cells, exciting them to
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
Cuar. Il.] THE EFFECTS OF REPEATED TOUCHES. 29
glands, and afterwards 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 the protoplasm. But the case is much more remarkable
than as yet stated; for the particles are supported by the
viscid and dense secretion; nevertheless, even smaller ones
than those of which the measurements 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 +ş}yy ofa 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 phosphate of ammonia in
solution, when absorbed by a gland, acts on it and induces
movement. A bit of hair, -ly of an inch in length, and there-
fore 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.
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 transmit a motor
impulse to the exterior tentacles, causing them to bend;
and we have now to consider 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 stifti
30 DROSERA ROTUNDIFOLIA. (Cuar. ID.
bristle. This was done as quickly as possible, but with force
sufficient to bend the tentacles ; 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 upon them. On
another occasion I gave a single forcible touch to a consider-
able number of glands, and not one moved; but these same
glands, after an interval 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 circum-
ferential tentacles to embrace it. Nevertheless, the move-
ments of the plant are not perfectly adapted to its require-
ments; 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 falling
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
IRAE Cbs, eria
Cuar. I.] THE EFFECTS OF REPEATED TOUCHES. Əl
after the secretion has been all washed away by heavy rain;
and this often occurs, though the secretion is so viscid that it
can be removed 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 remarked, 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 momen-
tary 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 of 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 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.f
* [Pfeffer’s experiments, given move; but that, if similar needles in
above (p. 22), explain the failure of connection with the secondary coil of
a Du Bois induction apparatus are
inserted, the tentacles curve inwards
in the course of a few minutes. My
son hopes soon to publish an account
of his observations.
rain to cause movement.—F. D.]
+ My son Francis, guided by the
observations of Dr. Burdon Sanderson
on Dionæa, finds that, if two needles
are inserted into the blade of a leaf
of Drosera, the tentacles do not
DROSERA ROTUNDIFOLIA. [Cuar. II.
CHAPTER III.
AGGREGATION OF THE PROTOPLASM WITHIN THE CELLS OF THE
TENTACLES.
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—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 wit here interrupt my account of the movements of the
leaves, and describe the phenomenon of aggregation, 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 examined, 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 ;f but
this can be seen with much
greater distinctness after the
* [The statement as to the absence
of a nucleus in the stalk-cells of
Drosera (Francis Darwin, ‘ Quarterly
Journal of Microscopical Science,’
1876) has been shown by Pfeffer to
be quite erroneous (‘ Osmotische
Untersuchungen,’ 1877, p. 197).—
F. Ds)
t (Mr. W. Gardiner (Proc. R. Soc.,
No. 240, 1886) has described a re-
markable body named by him the
“ rhabdoid,” which exists within the
epidermic cells of the stalk of the
tentacles. This body was discovered
in Drosera dichotoma, but exists also
in D. rotundifolia; in the former
species, in which it has been more
especially studied by its discoverer,
it is a more or less spindle-shaped
mass, stretching diagonally across
the cell, the two ends being embedded
in the cell-protoplasm. “It is
present in all the epidermic cells of
the leaf except the gland cells and
the cells immediately beneath the
same.” Further reference to the
rhabdoid will be found at p. 35.—
E D)
EREE ae N
qÃĂ o
Cuar. II.] THE PROCESS OF AGGREGATION. 38
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 contains 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.
If a tentacle is examined some hours after the gland has
been excited by repeated touches, or by an inorganic 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 colourless or almost colourless fluid. The change is so
conspicuous that it is visible through a weak lens, and even
sometimes with 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 becomes as homogeneous
and transparent as it was at first. The process of redissolu-
tion travels upwards from the bases of the tentacles to the
glands, and therefore in a reversed direction to that of
aggregation. ‘l'entacles 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.
The little masses of aggregated matter are of the most
diversified shapes, often spherical or oval, sometimes 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,
i - nm i
and in the short discal tentacles of a greenish, colour. ‘These
D
34 DROSERA ROTUNDIFOLIA. [Cnar. TIT.
little masses incessantly change their forms and positions,
being never at rest. A single mass will often separate into
two, which afterwards reunite. Their movements are rather
slow, and resemble those of Amæœbæ or of the white
corpuscles of the blood. We may therefore conclude that
they consist of protoplasm.* If their shapes are sketched at
(Drosera rotundifolia.)
Diagram of the same cell of a tentacle, showing the various forms successively
assumed by the aggregated masses of protoplasm.
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 2m.
or 3 m., are here given (fig. 7), and illustrate some of the
* [This conclusion has been shown
to be erroneous; there can be no
doubt that the aggregated masses
are concentrations or precipitations
of the cell-sap, and that their sup-
posed amæboid movements are the
result of the streaming protoplasm,
which moulds the passive masses into
a variety of forms.
Pfeffer was the first to insist on
this view of the nature of aggrega-
tion, in his ‘Osmotische Untersuch-
ungen’? (1877). Since then the
subject has been investigated by
Schimper (‘ Botanische Zeitung,’
1882, p. 233), who describes the
aggregated masses as concentrations
of cell-sap, rich in tannin, and float-
ing in the swollen and transparent
protoplasm.
Schimper’s observations are con-
firmed by Gardiner (‘ Proc. Royal Soe.,’
Nov. 19, 1885, No. 240, 1886), who
describes the protoplasm in the stalk-
cells of Drosera dichotoma as swelling
up by the absorption of the “ water
from its own vacuole,” and thus
leaving the tannin in cell-sap in &
concentrated condition. Gardiner
has added some curious observa-
tions on the connection between
aggregation and the condition of
the cell as regards turgidity. He
supposes that aggregation is connected
with a loss of water, and that an
aggregated cell is in a condition ot
diminished turgidity. This is sup-
ported by his observation that “ im-
jection of water into the tissue will
at once stop aggregation, and restore
the cell to its normal condition. ”
These changes are connected with
pone
FET EEE NATE one SO A
Cuar. HEJ THE PROCESS OF AGGREGATION. 35
simpler and commonest changes. The cell A, when first
sketched, included two oval masses of purple protoplasm
touching each other. These became separate, as shown at B,
and then reunited; as at ©. After the next interval a very
common appearance was presented—D, namely, the formation
of an extremely minute sphere at one end of an elongated
Fie. 8.
(Drosera rotundifolia.)
Diagram of the same cell of a tentacle, showing the various forms successively
assumed by the aggregated masses of protoplasm.
mass. This rapidly increased in size, as shown in E, and
was then reabsorbed, as at F, by which time another sphere
had been formed at the opposite end.
The cell drawn in fig. 7 was from a tentacle of a dark red
leaf, which had caught a small moth, and was examined
certain alterations of form occurring
in the above-mentioned body de-
scribed by Gardiner under the name
of rhabdoid, and which seems to be
peculiarly sensitive te changes in
the turgidity, so much so indeed that
the author utilises it as a “ turgo-
meter,” or index of the degree of
turgescence.
H. de Vries has also written on
the subject of aggregation (‘ Botan-
ische Zeitung,’ 1886, p. 1), and his
views agree with those of Pfeffer,
Schimper, and Gardiner as to the
main fact that the aggregated masses
are concentrations of cell-sap. In
some other respects they differ from
the conclusions of these authors.
De Vries believes that in Drosera
and in vegetable cells generally the
vacuoles are surrounded by a special
protoplasmic wall, distinct from
the layer of flowing protoplasm
which lines the walls. In the
process of aggregation the vacuole
expels a great part of its watery
contents, retaining, however, the
red colouring matter of the cell-
sap, as well as tannin and albu-
minous matter. The vacuole does
not remain a single body, but divides
into numerous secondary vacuoles.
These are the aggregated masses
which are rendered conspicuous by
being surrounded by the expelled
fluid which serves as a colourless
background to them. The move-
ments of the masses are, according to
De Vries, entirely passive, and are
accounted for by the currents of
protoplasm, stirring them and wash-
ing them to and fro.—F. D.)
D2
36 DROSERA ROTUNDIFOLIA. (Cuap. IIL.
under water. As I at first thought that the movements of
the masses might be due to the absorption 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 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 the channel of communication between the two. On the
other hand, such connecting threads are sometimes seen to
break, and their extremities then quickly become club-headed.
The other sketches in fig. 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
Cuar. I.) THE PROCESS OF AGGREGATION. 37
compressor, In 15 m. I distinctly saw extremely minute spheres of
protoplasm aggregating themselves 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 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 process of aggregation is independent of the inflection
of the tentacles, 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
ot 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 them-
selves 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 aggregation,
that which, as far as I have seen, acts the quickest, and is the most
powerful, isa solution of carbonate of ammonia, Whatever 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 darken in 10 s. (seconds); and in 13 s. were conspicuously
* Judging from an account of M. beris, after they have been excited by
Heckel’s observations, which I have a touch and have moved; for hesays,
only just seen quoted in the ‘Gar- ‘the contents of each individual cel]
dener’s Chronicle’ (Oct. 10, 1874), he are collected together in the centre
appears to have observed a similar ofthe cavity.”
phenomenon in the stamens of Ber-
38 DROSERA ROTUNDIFOLIA. (Cuar. III.
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 trans-
verse 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 ofone 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 by 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 grs. to 1 0z.); 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, especially 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, independently of the absorption of any matter. So it may
possibly be in the case of the carbonate of ammonia. As, however,
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 aggrega-
iii
z
Cuar. I] THE PROCESS OF AGGREGATION. 39
tion was visible in 3 m.; but after 15 m. small spheres of proto-
plasm were formed, more especially beneath the long-headed marginal
glands; the process, however, in this case took place with unusual
slowness. In 25 m. 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 4375 of water (1 gr. to 10 oz.),
and the highly 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 | 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, I may
mention that a rather pale purple leaf placed under a slip of grass was
given a drop of a solution of one part to 292 of water, and in 13 m. a
lew 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. it nearly*equalled the cell in diameter; and a
second sphere 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
* [De Vries (Joc. cit. p. 59) believes
that the form of aggregation pro-
duced by carbonate of ammonia is
radically different from ordinary
aggregation, e.g. that produced by
meat. He believes it to be due toa
precipitation of albuminous matter ;
the granules thus formed tend to
become packed into balls, and thus
dense masses are produced which it
is not always easy to distinguish
from the aggregated masses which
De Vries believed to be formed from
the vacuole. Glauer, in the ‘ Jahres-
Bericht der Schl. Gesell. für vater-
lind. Cultur, 1887, p. 167, also distin-
guishes ammonia—aggregation from
the ordinary form of the pheno-
menon.—F. D.]
40 DROSERA ROTUNDIFOLIA. (Cuar. IIL.
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 carbonate, 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
colourless flowing protoplasm, and, after the bag-like masses were
formed, the protoplasm was still flowing along the walls in a con-
spicuous manner, even more so than before. It appeared indeed as if
the stream of protoplasm was strengthened by the action of the
carbonate, 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, sometimes sending out projections which
separate into little spheres; other spheres appear in the fluid sur-
rounding 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 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 movement 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
* With other plants I have often a solution of carbonate of ammonia
seen what appears to be a true as likewise follows from mechanical
shrinking of the primordial utricle injuries.
from the walls of the cells, caused by
i
WHR Oy go
Car. III.] THE PROCESS OF AGGREGATION. 41
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 aggregatcd masses in many of the cells were
redissolved, 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 protoplasm (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 breoken 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 liue 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 ammonia,
the fluid within the cells of the tentacles often aggregates 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 distinguished, 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, ‘lwo
leaves thus treated became after 1 hr. flaccid, and seem killed; all the
cells in their tentacles contained spheres of protoplasm, but these were
small and discoloured. 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
42 DROSERA ROTUNDIFOLIA. (Cua. III.
granules. It was evident that the strength of the solution had inter-
fered 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
aggregate 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 aggregation. 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 yg3y55 of
a grain (*000482 mgr.) is enough to cause in the course of one hour
well-marked aggregation in the cells immediately beneath the gland.
The Effects of certain other Salts and Fluids.—Two leaves were
placed in a solution of one part of acetate of ammonia to about 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, extending 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 tentacles 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 47 m.
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 ammonia, a leaf was placed in a little solution
of the above strength, and there was not eveu 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. Aiter 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 oz.), so that each
leaf received =4,; of a grain (°1124 mgr.). This quantity caused all
the tentacles to be inflected, but atter 24 hrs. there was only a trace
f
Cuar. IIL.) THE PROCESS OF AGGREGATION. 43
of aggregation. One of these same leaves was then placed in a weak
solution of the carbonate, 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 (3 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. 22 m.,
but even after 2 hrs. 12 m. there was certainly not more aggregation
than would have followed from an immersion of from 5 m. to 10 m.
in an equally 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 5,45 of a grain (°04079 mgr.); this soon caused the
tentacles to be strongly inflected; and after 24 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 protoplasm had been injuriously
affected ; and soon afterwards some of the cells appeared quite empty.
These effects differ altogether 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
carbonate 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 (tor 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 tentacles 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 15 m. 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 aggrega-
tion; 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, which by
44 DROSERA ROTUNDIFOLIA. [Cuap. IIT.
the next morning, after 24 hrs., had almost disappeared, 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 aggre-
gation after 1 hr. 20 m., and in another after 1 hr. 50 m. With other
leaves a considerably longer time was required: for instance, one
immersed for 5 hrs. showed no aggregation, 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 fur 24 hrs., and these became aggregated to a wonderful
degree, so that the inflected tentacles presented to the naked eyea
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 under-
went incessant changes of form; and the current of colourless proto-
plasm 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 leaf 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 (3 grs. to 1 oz.), had their cells
aggregated, the one in 10 m. and the other in 5 m.
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 5 m.; as was likewise a leaf which had been
left for 1 hr. 45 m. in a moderately thick solution 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 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 secretion, no doubt by exosmose; and
after 24 hrs. the cells showed a certain amount of aggregation, though
Pane Pe ee
Car. IIL.] THE PROCESS OF AGGREGATION. 45
the tentacles were not inflected. Glycerine causes in a few minutes
well-pronounced 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 aggrega-
tion. 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 aggrega-
tion 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 little 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 proto-
plasm. In a previous trial with a submerged plant the tentacles were
not in the least inflected.
Heat induces aggregation. A leaf, with the cells of the tentacles
containing only homogeneous fluid, was waved about for 1 m. in water
at 130° Fahr. (54°°4 Cent.), and was then examined under the micro-
scope as quickly as possible, that is in 2 m. or 3 m.; and by this time
the contents of the cells had undergone some degree of aggregation.
A second leaf was waved for 2 m. 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
46 DROSERA ROTUNDIFOLIA. (Cap. III.
aggregate into spherical masses than when excited by carbonate 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 disappear; 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 bases 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
condition. 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 numberless 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 surrounding 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 could be
seen filled with purple fluid, without a vestige of aggregated proto-
plasm ; 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
aggregated. 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 aggregation had dis-
appeared, the cells being now filled with homogeneous fluid.
We have seen that leaves immersed for some hours in dense solu-
tions 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 aggregated masses of protoplasm were partially
redissolved. A leaf with its tentacles closely clasped over a fly, and
with the contents 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
tite A E EEE
Cuar. IHI.) THE PROCESS OF AGGREGATION. 47
fluid. The redissolution in these cases may, I presume, be attributed
to endosmose.
On the Proximate 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
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 phenomena 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 inorganic
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 tonched any
object. Some force or influence must, therefore, be trans-
mitted 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 aggregation 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 of the
tentacles, the glands secrete less freely, or quite cease to
48 DROSERA ROTUNDIFOLIA. (Cuap. III.
secrete, and the aggregated masses of protoplasm are then
redissolved. Moreover, when leaves are immersed in dense
vegetable solutions, or in glycerine, the fluid within the
gland-cells passes outwards, 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 aggregation. Thus a particle
of sugar added to the secretion round a gland causes a much
greater increase of secretion, and much less aggregation, than
does a particle of carbonate of ammonia given in the same
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 temperature 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.or3m. 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 proto-
plasm in solution. There is still stronger evidence that
aggregation is independent of secretion; for the papille,
described in the first chapter, with which the 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 sensitive 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
“gs
Cuap. HI.) THE PROCESS OF AGGREGATION. 49
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 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° (€5°°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° (547-4 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
E
Mo. Bot. Garden,
1202
50 DROSERA ROTUNDIFOLIA. [Cuar. IIL.
extremely small, yet well defined, but many of the cells con-
tained, 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
oxygenated condition, in order that the force or influence
which induces aggregation should be transmitted at the
proper rate from cell to cell. A plant, with its roots in
water, was left for 45 m. in a vessel containing 122 fluid oz.
of carbonic acid. A leaf from this plant, and, for comparison,
one from a fresh plant, were both immersed for 1 hr. in a
rather strong solution of carbonate of ammonia. They were
then compared, and certainly there was much less aggregation
in the leaf which had been subjected to the carbonic acid
than in the other. Another plant was exposed in the same
vessel for 2 hrs. to carbonic acid, and one of its leaves was
then placed in a solution of one part of the carbonate to 437
of water ; the glands were instantly blackened, showing that
they had absorbed, and that their contents were aggregated ;
but in the cells close beneath the glands there was no aggre-
gation even after an interval of 3 hrs. After 4 hrs. 15 m. a
few minute spheres of protoplasm were formed in these cells,
but even after 5 hrs. 30 m. the aggregation did not extend
down the pedicels for a length equal to that of the glands.
After numberless trials with fresh leaves immersed in a
solution of this strength, I have never seen the aggregating
action transmitted at nearly so slow a rate. Another plant
was left for 2 hrs. in carbonic acid, but was then exposed for
20 m. to the open air, during which time the leaves, being of
a red colour, would have absorbed some oxygen. One of
them, as well as a fresh leaf for comparison, were now
immersed in the same solution as before. The former were
looked at repeatedly, and after an interval 65 m. a few
spheres of protoplasm were first observed in the cells close
beneath the glands, but only in two or three of the longer
tentacles. After 3 hrs. the aggregation had travelled down
the pedicels of a few of the tentacles for a length equal to
that of the glands. On the other hand, in the fresh leaf
similarly treated, aggregation was plain in many of the
tentacles after 15 m.; after 65 m. it had extended down the
pedicels for four, five, or more times the length of the glands ;
see
Cuar. III.) THE PROCESS OF AGGREGATION. 51
and after 3 hrs. the cells of all the tentacles were affected for
one-third or one-half of their entire lengths. Hence there
can be no doubt that the exposure of leaves to carbonic acid
either stops for a time the process of aggregation, or checks
the transmission of the proper influence when the glands are
subsequently excited by carbonate of ammonia; and this
substance acts more promptly and energetically than any
other. It is known that the protoplasm of plants exhibits
its spontaneous movements only as long as it is in an
oxygenated condition ; and so it is with the white corpuscles of
the blood, only as long as they receive oxygen from the red
corpuscles ; * but the cases above given are somewhat different,
as they relate to the delay in the generation or aggregation
of the masses of the protoplasm by the exclusion of oxygen.
Summary and Concluding Remarks.—The process of aggre-
gation is independent of the inflection of the tentacles and
apparently of increased secretion from the glands. It
commences within the glands, whether these have been
directly excited, or indirectly by a stimulus received from
other glands. In both cases the process is transmitted from
cell to cell down the whole length of the tentacles, being
arrested for a short time at each transverse partition. With
pale-coloured leaves the first change which is perceptible,
but only under a high power, is the appearance of the finest
granules in the fluid within the cells, making it slightly
cloudy. These granules soon aggregate into small globular
masses. I have seen a cloud of this kind appear in 10 s.
after a drop of a solution of carbonate of ammonia had been
given to a gland. With dark red leaves the first visible
change often is the conversion of the outer layer of the fluid
within the cells into bag-like masses. The aggregated
masses, however they may have been developed, incessantly
change their forms and positions. They are not filled with
fluid, but are solid to their centres. Ultimately the colourless
granules in the protoplasm which flows round the walls
coalesce with the central spheres or masses; but there is still
a current of limpid fluid flowing within the cells. As soon
as the tentacles fully re-expand, the aggregated masses are
* With respect to plants, Sachs, ‘Quarterly Journal of Microscopical
‘Traité de Bot. 3rd edit., 1874, Science, April 1874, p. 185.
p- 864. On blood corpuscles, see
E 2
52 DROSERA ROTUNDIFOLIA. [Cuap, II.
redissolved, and the cells become filled with homogeneous
purple fluid, as they were at first. The process of redissolu-
tion commences at the bases of the tentacles, thence pro-
ceeding upwards to the glands; and, therefore, in a reversed
direction to that of aggregation.
Aggregation is excited by the most diversified causes, —
by the glands being several times touched,—by the pressure
of particles of any kind, and as these are supported by the
dense secretion, they can hardly press on the glands with the
weight of a millionth of a grain,*—by the tentacles being
cut off close beneath the glands,—by the glands absorbing
various fluids or matter dissolved out of certain bodies, —by
exosmose,—and by a certain degree of heat. On the other
hand, a temperature of about 150° Fahr. (65°°5 Cent.) does
not excite aggregation; nor does the sudden crushing of a
gland. Ifa cell is ruptured, neither the exuded matter nor
that which still remains within the cell undergoes aggrega-
tion when carbonate of ammonia is added. A very strong
solution of this salt and rather large bits of raw meat prevent
the aggregated masses being well developed. From these
facts we may conclude that the protoplasmic fluid within a
cell does not become aggregated unless it be in a living state,
and only imperfectly if the cell has been injured. We have
also seen that the fluid must be in an oxygenated state,
in order that the process of aggregation should travel from
cell to cell at the proper rate.
Various nitrogenous organic fluids and salts of ammonia
induce aggregation, but in different degrees and at very
different rates. Carbonate of ammonia is the most powerful
of all known substances; the absorption of j5,,55 of a
grain (*000482 mg.) by a gland suffices to cause all the cells
of the same tentacle to become aggregated. The first effect
of the carbonate and of certain other salts of ammonia, as well
as of some other fluids, is the darkening or blackening of the
glands. This follows even from long immersion in cold
* According to Hofmeister (as
quoted by Sachs, ‘Traité de Bot.,
1874, p. 958), very slight pressure
phenomenon, as it relates to the
contents of the cells, and only
on the cell-membrane arrests imme-
diately the movements of the pro-
toplasm, and even determines its
separation from the walls. But the
process of aggregation is a different
secondarily to the layer of protoplasm
which flows along the walls; though
no doubt the effects of pressure or of
a touch on the outside must be trans-
mitted through this layer.
Cuar. HI] THE PROCESS OF AGGREGATION. 53
distilled water. It apparently depends in chief part on
the strong aggregation of their cell-contents, which thus
become opaque and do not reflect light.* Some other fluids
render the glands of a brighter red; whilst certain acids,
though much diluted, the poison of the cobra-snake, &c.,
make the glands perfectly white and opaque; and this seems
to depend on the coagulation of their contents without any
aggregation. Nevertheless, before being thus affected, they
are able, at least in some cases, to excite aggregation in
their own tentacles.
That the central glands, if irritated, send centrifugally
some influence to the exterior glands, causing them to send
back a centripetal influence inducing aggregation, is perhaps
the most interesting fact given in this chapter. But the
whole process of aggregation is in itself a striking pheno-
menon. Whenever the peripheral extremity of a nerve i:
touched or pressed, and a sensation is felt, it is believed that
an invisible molecular change is sent from one end of the
nerve tothe other; but when a gland of Drosera is repeatedly
touched or gently pressed, we can actually see a molecular
change proceeding from the gland down the tentacle; though
this change is probably of a very different nature from that
in a nerve. Finally, as so many and such widely different
causes excite aggregation, it would appear that the living
matter within the gland-cells is in so unstable a condition
that almost any disturbance suffices to change its molecular
nature, as in the case of certain chemical compounds. And
this change in the glands, whether excited directly, or
indirectly by a stimulus received from other glands, is
transmitted from cell to cell, causing granules of protoplasm
either to be actually generated in the previously limpid fluid
or to coalesce and thus to become visible.
Supplementary Observations on the Process of Aggregation
in the Roots of Plants.
It will hereafter be seen that a weak solution of the carbonate 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 I met with, viz.
* [The words “which . ... light ” would probably have been omitted
by the author in a second edition.—F. D.]
54 DROSERA ROTUNDIFOLIA. [Caar. II,
Euphorbia peplus, being careful 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 8 m. to 9 m. the fine granules, which caused this cloudy
appearance, 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, how~
ever, remained unaffected. I repeated the experiment 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 re~
ceived § of a grain, or 2°024 mg. When examincd, 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 car-
bonate 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 14 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 24 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 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 solution,
but was very doubtfully affected. On the other hand, a red marine
alga, with finely pinnated fronds, was strongly affected. The contents
Cuar. III] THE PROCESS OF AGGREGATION. 55
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.*
* [See C. Darwin on “The Action also “The Action of Carbonate of
of Carbonate of Ammonia on the Ammonia on Chlorophyll-bodies:”
Roots of certain Plants: ” ‘Linn. Soc. ‘Linn. Soc. Journal’ (Bot.), vol. xix.
Journal’ (Bot.), vol. xix. 1882, p. 239; 1882, p. 262.—F. D.]
56 DROSERA ROTUNDIFOLIA. (Cuap. IV.
CHAPTER IV.
THE EFFECTS OF HEAT ON THE LEAVES.
Nature of the experiments—Etfects 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 substances 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 presented
itself, namely, at what degree life was extinguished; 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 especially in the failure of the proto-
plasm to become aggregated, when the leaves after being
heated are immersed in a solution of carbonate of ammonia.*
* When my experiments on the
effects of heat were made, I was not
aware that the subject had been
carefully investigated by several ob-
servers. For instance, Sachs is con-
vinced (‘Traité de Botanique, 1874,
pp. 772, 854) that the most different
kinds of plants all perish if kept for
10 m.in water at 45° to 46° Cent., or
113° to 115° Fahr. ; and he concludes
that the protoplasm within their cells
always coagulates, if in a damp condi-
tion,at a temperature of between 50°
and 60° Cent., or 122° to 140° Fahr.
Max Schultze and Kühne (as quoted
by Dr. Bastian in ‘ Contemp. Review,’
1874, p. 528) “found that the pro-
toplasm of plant-cells, with which
they experimented, was always killed
and altered by a very brief exposure
to a temperature of 1184° Fahr. as
a maximum.” As my results are
deduced from special phenomena,
namely, the subsequent aggregation
of the protoplasm 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 considerable differences in this re-
spect 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 Des-
cloizeaux, at 208° Fahr.
a a ee ee ee ee
seinen ii aiia
Cuap. IV] THE EFFECTS OF HEAT. or
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, wee
kept in a damp atmosphere, and after 23 hrs. closely embraced the
meat both with their tentacles 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 along bulb obliquely suspended init. ‘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 continually waved for
some minutes close to the bulb. They were then placed in cold water,
or in a solution of carbonate 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 con-
stitutional causes differ slightly in their sensitiveness to heat.
It will be convenient first briefly to describe the eflects 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 when the leaves are subsequently placed in a sclution of
carbonate of ammonia. But the most remarkable change is that the
glands become opaque and uniformly white; and this may be attri-
buted 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. (43°°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 soon. 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 rc-
moved 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 tem-
perature 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, therefore,
that the warm bath had increased their sensitiveness when excited by
meat.
I next observed the degree of inflection which leaves underwent
within stated periods, whilst still immersed in warm water, kept as
58 DROSERA ROTUNDIFOLIA. [Cuap. IV.
nearly as possible at the same temperature; but I will here and else-
where give only a few of the many trials made. A leaf was left for
10 m. in water at 100° (37°°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 40°°1 Cent.), was very moderately inflected in 6 m.
A fourth leaf, in water at 110° (43°°3 Cent.), was somewhat inflected
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 proto-
plasm 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 following morning it was
immersed in a weak solution of carbonate of ammonia, and the glands
quickly became black, with strongly marked aggregation in the
tentacles, showing that the protoplasm was alive, and that the glands
had not lost their power of absorption. Another leaf was placed in
water at 110° (43°°3 Cent.) which was raised to 120° (48°°8 Cent.) ;
and every tentacle, 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 2 m. to 3 m., 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 intlection
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 protoplasm 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°
Cuar. IV.] THE EFFECTS OF HEAT. 59
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 130° (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 was 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 solution of ammonia, and in the
course of 55 m. the tentacles were considerably 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° (37°°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,
Experiment 5.—Leaf immersed at 130° (54°°4 Cent.), and the water
raised to 145° (62°°7 Cent.), there was no immediate inflection; 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 disintegrated brownish
matter. =
Experiments 6 and 7.—Two leaves were plunged in water at 135
* Sachs states (‘Traité de Bə- were exposed for 1 m. in water to a
tanique,’ 1874, p. 855) that the temperature of 47° to 48° Cent., or
movements of the protoplasm in the 117° to 119° Fahr.
hairs of a Cucurbita ceased after they
60 DROSERA ROTUNDIFOLIA. (Cuar. IV.
(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 interval of 1 hr. 45 m., until 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 an 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 protoplasm
being extremely small; in other cells, especially in the exterior
tentacles, there was much greenish-brown pulpy matter.
Experiment 8.—A leat was plunged and waved about for a few
rninutes 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
temperature as 140°, and in only one leaf out of four, after a similar
immersion at a temperature of 145° 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 Tae of the immersion is an important clement 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 backwards.
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.
Experiment 10.—A leaf was plunged in water at 150° to 1503°
(65°°5 Cent.) ; it became somewhat flaccid, with the outer tentacles
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.
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
Cuar. IV.) THE EFFECTS OF HEAT. GI
then in the strong solution, the cells in the tentacles became of a
muddy greenish brown, with the protoplasm not aggregated. Never-
theless, 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 protoplasm, after having
been exposed to a high temperature for a few minutes, is capable of
aggregation when alterwards subjected to the action of carbonate of
ammonia, unless the heat has been sufficient to cause coagulation,
Concluding Remarks.—As the hair-like tentacles are ex-
tremely 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 temperature of 130° (54°°4 Cent.) never causes the
immediate inflection of the tentacles, though a temperature
from 120° to 125° (48°°8 to 51°:6 Cent.) quickly produces
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 carbonate of ammonia, they become
inflected and their protoplasm undergoes aggregation. This
great difference 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 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 carbonate 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 ammonia, they generally, though not
* «Traité de Bot.’ 1874, p. 1054.
62 DROSERA ROTUNDIFOLIA. (Cuar. IV.
always, become inflected; and the protoplasm within their
cells undergoes 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. Exposure 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 appearance ;
and on one occasion this occurred at a temperature 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. Ex-
posure for a few minutes to a temperature of 150° (65°°5
Cent.) generally produces this effect, yet many glands retain
a pinkish colour, and many present a speckled appearance.
This high temperature never causes true inflection; 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 temperature of 150° Fahr., the protoplasm, if
subsequently subjected to carbonate of ammonia, instead of
undergoing 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 proto-
plasm 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 through-
* As the opacity and porcelain-like of coagulation is lower. The leaves
appearance of the glands is probably
due to the coagulation of the albumen,
l may add, on the authority of Dr.
Burdon Sanderson, that albumen
coagulates at about 155°, but, in
presence of acids, the temperature
of Drosera contain an acid, and per-
haps a difference in the amount con-
tained may account for the slight
differences in the results above re-
corded.
pansy cs
Cuar. IV.) THE EFFECTS OF HEAT. 63
out 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°.*
It may be worth adding that immersion in cold 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.
* It appears the cold-blooded Burdon Sanderson, a frog begins to be
animals are, as might have been distressed in water at a temperature
expected, far more sensitive to an ofonly 85° Fahr. At 95° the muscles
increase of temperature than is become rigid, and the animal dies in a
Drosera. Thus, as I hear from Dr. stiffened condition.
64 DROSERA ROTUNDIFOLIA. [Cuar. V.
CHAPTER V.
THE EFFECTS OF NON-NITROGENOUS AND NITROGENOUS ORGANIC FLUIDS
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—Decoction of green peas—Decoction and infusion of cabbage—
Decoction of grass leaves.
Wuen, 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 nitrogenous 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 ,), of a fluid ounce,
or +0295 cc. 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
collected 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 is kept in a room, and some of the
central and submarginal 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
ee ENT ENNE E a
CHAP: V] EFFECTS OF ORGANIC FLUIDS. 65
this case the movement 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 adhesive fluid and the consequent
drawing together of the tentacles.
First for the non-nitrogenous fluids. As a preliminary
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 inflected; 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 73); 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 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 commerce
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 ascertain whether these
leaves had been at all injured, bits of meat were placed on them, and
after 24 hrs. they were closely inflected. I also put drops of sherry-
wine on three other leaves; no inflection 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.
F
66 DROSERA ROTUNDIFOLIA. [Cuar. V.
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 tentacles 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 afterwards 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 contained, 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 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
occasion 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 tentacles 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
> pe i
pee E eE
Cuap. V] EFFECTS OF ORGANIC FLUIDS. 67
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 leaves, 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
We a drop of milk, and this caused the tentacles to bend inwards in
12 hrs.
Cold Filtered Infusion of Raw Meat.—This was tried only ona
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 on with other substances, and
it was found to act most energetically, 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 inwards in 5 hrs. 80 m.
and greatly so in 20 hrs. The action of, this fluid no doubt is due
either to the saliva or to some albuminous 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 te
1°19 per cent. of residue; and this yields 0°25 per cent. of ashes, so
that the proportion of nitrogenous matter which saliva contains must
be small. Nevertheless, drops placed on the discs of eight leaves acted
on them all. In one case all the exterior tentacles, excepting nine,
were inflected in 19 hrs. 30 m.; in another case a few became so in 2
hrs., and after 7 hrs. 80 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 the glands with the handle of my
scalpel wetted with saliva, to ascertain whether a leaf was in an active
condition ; for this was shown in the course of a few minutes by the
bending inwards of the tentacies. The edible nest of the Chinese
swallow is formed of matter secreted by the salivary glands; two
grains were added to one ourice 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.
30 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 tentacles 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 cf
* Mucus from the air-passages is some albumen.
said in Marshall, ‘Outlines of Physi- t Miiller’s ‘ Elements of Physiology,’
ology,’ vol. ii. 1867, p. 364, to contain Eng. Trans. vcl. i. p. 514.
F 2
68 DROSERA ROTUNDIFOLIA. [Cuar. V.
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. from the time when the drops were placed on the leaves, atl
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 formes
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 51, 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 tertacles of the four
latter leaves began to re-expand after an additional interval of only
8 hrs. Hence the 515 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 tentacles 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 isinglass 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-nitrogenous 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 nitro-
genous matter by the glands of the tentacles on the disc.
Some of the leaves which were not affected by the non-
nitrogenous fluids were, as above stated, immediately after-
wards tested with bits of meat, and were thus proved to be
in an active condition. But in addition to these trials,
twenty-three of the leaves, with drops of gum, syrup, or
starch, still lying on their discs, which had produced no effect
—
es
Cuar. V.] EFFECTS OF ORGANIC FLUIDS. 69
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 movement 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 discs.
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 Schifff certain forms of albumen exist
which are not coagulated by boiling water, but are converted into
soluble peptones.
On three occasions chopped cabbage leaves f were boiled in distilled
water for 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, 1 also touched the viscid secretion
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.
* Watts’ ‘Dict. of Chemistry,’ before the heart is formed, such as
vol. iii. p. 568, were used by me, contain 2'1 per
t ‘Leçons sur la Phys. de la Di- cent. of albuminous matter, and the
gestion,’ tom. i. p. 379; tom. ii. pp. outer leaves of mature plants 1°6
154, 166, on legumin, per cent. Watts’ ‘ Dict. of Chemistry,
+ The leaves of young plants, vol. i. p. 653.
70 DROSERA ROTUNDIFOLIA. (Cuar. V
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 ruptured 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
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 tentacle ;
and so it was with all six leaves after 24 hrs. Two days afterwards
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 decoction strongly excites the glands
on the disc, causing the blade to be quickly and greatly inflected ; but
that the stimulus, differently 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 somewhat 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 precipi-
tated 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.
erate TAA
Cuar. VL] DIGESTION. 71
CHAPTER VI.
THE DIGESTIVE 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—Albumen, its diges-
tion 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—Hematin—lIndigestible 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.
As we have seen that nitrogenous fluids act very differ-
ently on the leaves of Drosera from non-nitrogenous fluids,
and as the leaves remain clasped for a much longer 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 mam-
mals; the digested matter being afterwards absorbed. 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 kind-
ness by Dr. Burdon Sanderson.
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 ofa 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
* It appears, however, according a very minute quantity of coagulated
to Schiff, and contrary to the opinion albumen. Schiff, ‘Phys. de la Di-
of some physiologists, that weak hy- gestion, 1867, tom. ii. p. 25.
drochloric dissolves, though slowly,
72 DROSERA ROTUNDIFOLIA. [Cuar. VI.
glands of the disc are excited by the contact of any object,
especially of one’ containing nitrogenous matter, the outer
tentacles and often the blade become inflected; the leaf
being thus converted into a temporary cup or stomach. 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
inflected 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 these fourteen leaves had become more or less
inflected, T 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 tentacles did not, from some unknown
cause, become inflected as often happens; and in five in-
stances 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
* [In the ‘ Proceedings of the Royal ing secretion, and gives evidence that
Society,’ 1886, No. 240, Gardiner has the secretion results from the break
described the changes which go on in ing downof the protoplasmic reti-
the glands of Drosera dichotoma dur- culum of the gland-cell.—F. D.]
egg gt ne eaman ncn
Cuar. VI] DIGESTION, 73
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
secretion 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 unexcited leaves,
though extremely viscid, is not acid or only slightly so, but
that it becomes acid, or much 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.
I may here remind the reader that the secretion 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 undertook 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 leaves 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
Gorup
* [Messrs Rees and Will (‘ Bot.
Zeitung,’ 1875, p. 716) stimulated the
glands of some thousand Drosera
plants with glass-dust and analysed
the secretion thus produced. They
found a variety of fatty acids present,
among which Formic acid was recog-
nised with certainty, and Propionic
and Butyric acids were suspected from
the eyidence of the smell.
and Will have shown that the neutral
secretion of Nepenthes becomes power-
fully digestive when acidulated with
formic acid (see ‘ Bot. Zeitung,’ 1876,
p- 476). It is therefore interesting
to find this acid naturally present in
the secretion of Drosera.—F.D.]
T4 DROSERA ROTUNDIFOLIA. [Cuap. VI.
digested with carbonate of silver. ‘The weight of the silver salt thus
produced was only °37 gr., much too small a quantity for the accurate
determination 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 acidified with sulphuric 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 contain, 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.
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 the 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 following ex-
periments, the results of which are valuable, independently of the
present inquiry. Prof. Frankland supplied the acids.
“1. The purpose of the following experiments was to determine 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 corre-
sponds 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 prepared, 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, propionic, 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 ther-
einen apn RR ts pstncn
Cuar. VL] DIGESTION. is
mometer which indicated a temperature of 38° to 40° Cent. Into
each, a quantity of unboiled 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
throughout 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, 10 cub. cent. were
measured out and evaporated, and dried at 110° as before. The residues
were respectively—
“ In the liquid containing hydrochloric acid 0°4079
propionic acid 0°0601
293
» 4 butyric acid 0°1468
> h valerianic acid 0:1254
“ 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 .. es 0:0570
sy Putyric add .. :: b ae 0:1437
„ Valerianic acid .. i ae ue 0°1223
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 repre-
sent 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. Ina 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 .. 5 — 0:0563
Butyric acid = Ss 2 0:0835
Valerianic acid .. z 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 :
“Propionic acid .. s> ef 16°5
Butyric acid. Ki F 24°7
Valerianic acid .. z$ A 16'1
“6, A third experiment of the same kind gave:
76 DROSERA ROTUNDIFOLIA. [Cuar. VI.
“Quantity of fibrin digested in four hours by 10 cub. cent. of the
liquid :
“ Hydrochloric acid = me 0° 2915
Propionic acid .. ae 0:1490
Butyric acid -i z 0:1044
Valerianic acid .. oC oc 0:0520
“Comparing, as before, the three last numbers with the first taken
as 100, the digestive power of propionic acid is represented by 16°8;
that of butyric acid by 85°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... es z 15°8
Butyric acid - PS = 32°0
Valerianic acid .. es - 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 ordinary proportion of
hydrochloric acid digested 0°1311 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°95 that of butyric acid at the same temperature being 15:6.”
We here see that at the lower of these two temperatures, hydro-
chloric 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 valerianic acids, digests with pepsin at the higher tem-
perature less than a third of the fibrin which is digested at the same
temperature by hydrochloric acid.
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
air fag:
Cuar. VLJ DIGESTION. 77
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 premise 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 speci-
mens, the central parts were still white and opaque. So
that their state differed widely, as we shall see, from that of
the cubes subjected 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 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.
Experiment 2.—A cube of 3 of an inch (i.e. with each side +1, 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 (1:905 mm.) in
diameter, surrounded by perfectly transparent fluid. After ten days
* In all my numerous experi-
ments on the digestion of cubes of
albumen, the angles and edges were
invariably first rounded. Now, Schiff
states (‘ Leçons Phys, de la Digestion,’
1867, tom. ii. p. 149) that this is
characteristic of the digestion of
albumen by the gastric juice of
animals, On the other hand, he
remarks, ‘ les dissolutions, en chimie,
ont lieu sur toute la surface des corps
en contact avec l'agent dissolvant.”
78 DROSERA ROTUNDIFOLIA. [Cuar. VI.
the leaf re-expanded, but there was still left on the disc a minute bit
of albumen now rendered transparent. More albumen had been given
to this leaf than could be dissolved or digested.
Experiment 3.—Two cubes of albumen of ṣẹ of an inch (1°27 mm.)
were placed on two leaves, After 46 hrs. every atom of one was dis-
solved, and most of the liquefied matter was absorbed, the fluid which
remained being in this, as in all other cases, very acid and viscid.
‘Lhe 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. The 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 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 transparent ; 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 recom-
menced. 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 digestion ; and, secondly, whether minute
drops of weak hydrochloric acid, of the same 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 ;
Cuar. VI] DIGESTION. 79
for, after 48 hrs., the cubes were completely 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 T.—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. 30 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 super-
fluous to state that cubes of albumen of the same size as those above
used, left for seven days in a little hydrochloric acid of the above
strength, retained all their angles as perfect as ever.
Experiment 8.—Cubes of albumen (of 35 of an inch, or 1°27 mm.)
were placed on five leaves, and minute drops of a solution of one part
of carbonate of soda to 437 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 I ascertained that each was equal to about 4, of a minim (-0059
c.c.), so that each contained only ṣọ of a grain (‘0135 mg.) of the
alkali. ‘This was not sufficient, for after 46 hrs. all five cubes were
dissolved.
Experiment 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 dissolved, whilst the fourth
was converted into a minute sphere, surrounded by transparent fluid;
and this sphere next day disappeared.
Experiment 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 5,55 of a grain
(°0539 mg.) of either salt. Two cubes of albumen (each about 75 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 with blotting-paper from the discs of the leaves, and minute
drops of hydrochloric acid of the strength of one part to 200 of water
80 DROSERA ROTUNDIFOLIA. [Cmar. VI.
was added. Acid of this greater strength was used as the solutions
of the alkalies were stronger. The process of digestion now com-
menced, 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.—T wo cubes of albumen (5 ofan inch, or *635 mm.)
were placed on two leaves, and were treated with alkalies as in the 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 I had tried
no other experiments than these, they would have almost
sufficed to prove that the glands of Drosera secrete some
ferment analogous 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 inflected. 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 discoloured, 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 (>ç 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. (82°-2 Cent.), and others at the
temperature of my room; but none of the cubes were
* Sachs remarks (‘Traité de Bot.’
1874, p. 774), that cells which are
killed by freezing, by too great heat,
or by chemical agents, allow all their
colouring matter to escape into the
surrounding water.
— ae
paete
Cuar. VI] DIGESTION. 81
dissolved, the angles remaining as sharp as ever. This fact
probably 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 conclusion which is sup-
ported by what we shall hereafter see with respect to Dionæa.
Dr. Hooker likewise found that, although the fluid within
the pitchers of Nepenthes 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.*
* [With regard to Drosera Messrs.
Rees and Will Ç Bot. Zeitung,’ 1875,
p- 715) state that a glycerine extract
of Drosera leaves in a state of unex-
cited secretion, and fairly free from
insects, had no digestive action. But
that the same extract, artificially acid-
ulated, digested fibrin thoroughly
well.
The authors believe that the natu-
ral acid of the glands was possibly
destroyed in the process of preparing
the extract. No conclusion can there-
fore be drawn from their results as
to the acidity of unexcited leaves. It
is probable, however, judging from
Von Gorup’s work on Nepenthes, that
Drosera does not secrete the requisite
amount of acid until it has been
stimulated by the capture of insects.
tees and Will’s experiments are not
quite conclusive on this point, but
they tend to show that what is want-
ing in the secretion of unexcited leaves
is the acid, not the ferment. The ex-
periments of Von Gorup and Will on
Nepenthes, as given in the ‘ Bot. Zei-
tung,’ 1876, p. 473, do not confirm
Hooker’s results on Nepenthes. The
authors state that the secretion col-
lected from pitchers which are free
from insects is neutral, while the
fluid of pitchers which contain the
remains of insects is distinctly acid.
The neutral secretion of the unexcited
pitchers has no digestive power until
it is acidulated, when it rapidly dis-
solves fibrin.
It seems, therefore, that the analogy
with animal digestion pointed out at
p. 106 does not altogether hold good.
For Schiff states that in the gastric
juice produced by mechanical irrita-
tion, the element absent is the fer-
ment, not the acid.
On the other hand an interesting
point of resemblance of a different
kind has been made out by Vines in
his paper on the digestive ferment of
Nepenthes (‘Journal of the Linn.
Soc.’ vol. xv. p. 427 ; also ‘ Journal of
Anatomy and Physiology,’ series ii.
vol. xi. p. 124).
The work was undertaken inde-
pendently of Von Gorup and carried
out by a different method, namely
the preparation ofa glycerine extract.
Vines having found that the extract
was far less active than the natural
secretion used by Von Gorup, was
led to an interesting explanation of
this fact by Ebstein and Griitzner’s
work on animal digestion. These
writers show that the glycerine ex-
tract gains in digestive activity if it
is prepared from mucous membrane
previously treated with acid. Vines
accordingly treated Nepenthes witi
one per cent acetic acid for 24 hrs.
previously to the preparation of the
extract, and thus obtained glycerine
of much greater peptic activity. This
82 DROSERA ROTUNDIFOLIA. [Cuap. VI.
On three other occasions eight leaves were strongly ex-
cited 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 hydrochloric 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 the
experiment was successful. For in a vessel containing two
cubes, both were reduced in size in 3 hrs; and after 24 hrs.
mere streaks of undissolved albumen 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. com-
pletely disappeared. I then added a little weak hydro-
chloric 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,t
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 -y 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,
fact would lead us to believe that the
act of secretion in Nepenthes is pre-
ceded by the production of a mother
substance, or pepsinogen, from which
the peptic ferment is formed by ac-
tion of acid—just as the pancreatic
ferment may, according to Heidenhain,
be produced by the action of acid on
zymogen—F, D.]
* As a control experiment bits of
albumen were placed in the same
glycerine with hydrochloric acid of
the same strength ; and the albumen,
as might have been expected, was
not in the least affected after two
days.
t ‘Leçons phys. de la Digestion,’
1867, tom. ii, pp. 114-126.
Cmar. VL] DIGESTION. 83
without being much disturbed, was removed and placed
under the microscope. In the central part the transverse
striz on the muscular fibres were quite distinct; and it was
interesting to observe how gradually they disappeared, when
the same fibre was traced into the surrounding fluid. They
disappeared by the striæ 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
meaning 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 à la fibre musculaire
ses stries transversales. Ainsi énoncée, cette proposition pourrait
donner lieu à une équivoque, car ce qui se perd, ce west que Paspect
extérieur de la striature et non les éléments anatomiques qui la com-
posent. Onsait que les stries qui donnent un aspect si caractéristique
à la fibre musculaire, sont le résultat de la juxtaposition et du
parallélisme des corpuscules élémentaires, placés, à distances égales, dans
Vintérieur des fibrilles contiguës. Or, dès que le tissu connectif qui
relie entre elles les fibrilles élémentaires vient à se gonfler et à se
dissoudre, et que les fibrilles elles-mêmes se dissocient, ce parallélisme
est détruit et avec lui laspect, le phénomène optique des stries. Si,
après la désagrégation des fibres, on examine au microscope les fibrilles
élémentaires, on distingue encore très-nettement à leur intérieur les
corpuscules, et on continue à les voir, de plus en plus pâles, jusqu’au
moment où les fibrilles elles-mêmes se liquéfient et disparaissent dans
le suc gastrique. Ce qui constitue la striature, à proprement parler,
n’est done pas détruit, avant la liquéfaction 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 the least
digested. There were also little free parallelograms of
yellowish, highly translucent matter. Schiff, in speaking of
the digestion of meat by gastric juice, alludes to such
parallelograms, and says :—
* t Leçons phys. de Ja Digestion,’ 1867, tom. ii. p. 145. i
G
84 DROSERA ROTUNDIFOLIA. [Cuap. VI.
“Le gonflement par lequel commence la digestion ‘de la viande,
résulte de laction 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
à létat liquide, elles tendent à se briser en petits fragments transver-
saux. Les ‘ sarcous elements’ de Bowman, qui ne sont autre chose que
les produits de cette division transversale des fibrilles élémentaires,
peuvent étre préparés et isolés à laide du suc gastrique, pourvu qu’on
n’attend pas jusqu’à la liquéfaction complète 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
distinguished, but not a vestige of transverse strie. On
the other two leaves there were minute spheres of only
partially digested meat in the centre of much transparent
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 „y 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 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.
jurdon Sanderson.
vipe
PET
Cuar. VI] DIGESTION. 85
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 adjoin-
ing tentacles to be inflected, the more distant ones not being affected.
After 24 hrs. both were almost, and after 72 hrs. completely, dis-
solved.
Experiment 2.—The same experiment with the same result, only
one of the two bits of fibrin exciting the short surrounding 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 dis-
solved. 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 secretion from the glands.
In 18 hrs. the fibrin was completely liquefied, but undigested atoms
still floated in the liquid; these, however, disappeared in under two
additional days.
From these experiments it is clear that the secretion
completely dissolves pure fibrin. ‘lhe 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 energetically. 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 meat is too powerful a stimulant,
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
* [These results cannot be considered trustworthy; it appears that the
syntonin prepared by the late Dr. Moore was far from pure.—F. D.
86 DROSERA ROTUNDIFOLIA. [Cuar. VI.
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 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 (>p 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 November; and it seemed in the
highest degree improbable that so hard a substance would be
digested under such unfavourable circumstances. Neverthe-
less, after 48 hrs., the cubes were largely dissolved and
converted into minute spheres, surrounded by transparent,
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 unequally corroded by the secretion. I need hardly say
Cuar. VI] DIGESTION. 87
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 in-
flection. Two of the leaves began to re-expand after three
days, and the third on the fifth day. The fluid residue left on
their discs 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
sly 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 transparent, and so tender as to disin-
tegrate very easily. Myson Francis prepared some artificial
gastric juice, which was proved efficient by quickly dis-
solving fibrin, and suspended portions of the fibro-cartilage
in it. These swelled and became hyaline, exactly like those
exposed to the secretion of Drosera, but 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 therefore asked Dr. Klein to examine the
specimens; and he reports that the two which had been
subjected to artificial gastric juice were “in that state of
digestion 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.” Fibro-cartilage is therefore acted on in
nearly the same manner by gastric juice and by the secretion
of Drosera.
88 DROSERA ROTUNDIFOLIA. [Cuar. VI.
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, as Dr. Klein thinks, may be the result
either of the incipient digestion of the fibrous basis or of all
the earthy matter having been removed, the corpuscles being
thus rendered invisible. A hard, brittle, yellowish 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 superphosphate of lime.
When the leaves re-expanded, the angles and projections of
the fibrous basis were as sharp as ever. I therefore con-
cluded, falsely, as we shall presently see, that the secretion
cannot touch the fibrous basis of bone. The more probable-
explanation is that the acid was all consumed in decomposing
the phosphate of lime which still remained ; so that none was
left in a free state to act in conjunction with the ferment
on the fibrous basis.
Enamel and Dentine.—As the secretion decalcified ordinary
PNE E
indice SE I EET
Cuar. VL] DIGESTION. 89-
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.
Experiment 1.—May Ist, fragment placed on leaf; 3rd, tentacles
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 11th 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.”
Experiment 2.—May 1st, fragment placed on leaf; 2nd, tentacles
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 llth, when it re-
expanded. Dr. Klein reports, “a great deal of enamel and the greater
part of the dentine decalcified.”
Experiment 3.—May 1st, 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.”
Experiment 4.—May 1st, a minute and thin bit of dentine, mois-
tened 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 decalci-
tied 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 extreme 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
90 DROSERA ROTUNDIFOLIA. [Cuar. VI.
first set of leaves acted much less quickly and 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 im-
mersion in the fluid, and he found that towards the edges the
“ matrix appeared rarified, thus producing the appearance 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 decalcification 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 con-
sumed in the decomposition of the earthy salts, so that there
was none left for the work of digestion. Accordingly, my
son thoroughly decalcified 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. 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 liquefied 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 transparent 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
liquefies it, if thoroughly decalcified. The glands which
had remained in contact for two or three days with the
viscid masses were not discoloured, and apparently had
I ee a A EA
Cuar. VL] DIGESTION. 91
absorbed little of the liquefied tissue, or had been little
affected by it.
Phosphate of Lime.—As we have seen that the tentacles 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 inflection. 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.
Frankland 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 to 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 remained 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 disc 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 circumstance I do not understand, as the super-
phosphate of lime is acid. I suppose that some superphos-
phate must have been formed by the acid of the secre-
tion 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 phosphate of lime is a most
powerful stimulant. Even small doses are more or less
92 DROSERA ROTUNDIFOLIA. [Cuar. VI.
poisonous, probably on the same principle that raw meat and
other nutritious substances, given in excess, kill the leaves.
Hence the conclusion, that the long-continued inflection 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 me 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 retained 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 ,!, 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 ab-
sorbed from an insect. Some larger pieces of gelatine, soaked
for five days in water, were next placed on three leaves,
but these did not become much inflected 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 prove
that gelatine is far from acting energetically on Drosera.
In the last chapter it was shown that a solution of isin-
glass of commerce, as thick as milk or cream, induces strong
inflection, I therefore wished to compare its action with that
of pure gelatine. Solutions of one part of both substances
* Dr. Lauder Brunton, ‘Handbook for the Phys. Laboratory,’ 1873, pp-
477, 487; Schiff, ‘ Leçons phys. de la Digestion,’ 1867, tom. ii. p. 249.
Cuar. VI] DIGESTION. 93
to 218 of water were made ; and half-minim drops (0296 c.c.)
were placed on the discs of eight leaves, so that each received
ip Of a grain, or ‘135 mg. The four with the isinglass
were much more strongly inflected than the other four. 1
conclude, therefore, that isinglass contains some, though per-
haps very little, soluble albuminous 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 showing
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 experiment 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 two leaves with the smaller
cubes only to a moderate degree. The jelly on all four was
by this time liquefied, 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 z1, of a grain (°135 mg.)
of the jelly; and, of course, much less of dry chondrin.
This acted most powerfully, 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 hrs. 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 ener-
* Dr. Lauder Brunton gives inthe indirect part which gelatine plays in
‘Medical Record,’ January 1873, p. nutrition. j
36, an account of Viot’s view of the
94 DROSERA ROTUNDIFOLIA. [Cuap. VI.
getically than pure gelatine or isinglass; 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 albu-
minous 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 re-
spect to animals on the relative value of gelatine and chrondrin.
Milk.—We have seen in the last chapter that milk acts
most powerfully on the leaves; but whether this is 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 from the leaves, and this is
likewise characteristic of chemically prepared casein. Minute
drops of milk, placed on Jeaves, 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 com-
pletely in 8 hrs. These leaves re-expanded after two days,
and the viscid fluid left on their discs was then carefully
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
dissolved. We may therefore conclude that the secretion
quickly dissolves casein, in the state in which it exists in
milk.t
* 6 Leçons, &c. tom. ii. p. 151. of cow’s milk contains a small pro-
+ (Professor Sanderson has called portion of nuclein, which is entirely
my attention to the fact that the casein indigestible by gastric juice—F. D.]}
ae
sete state
Oy aR
Cuar. VL] DIGESTION. 95
Chemically Prepared Casein.—This substance, which is in-
soluble 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 437 of water) acted in a
single day, as did some casein freshly prepared for me by Dr.
Moore. ‘The tentacles 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 discs of a fully re-expanded leaf was
strongly acid. ‘The acid seems to be secreted quickly, for in
one case the secretion from the discal glands, on which a
little powdered casein had been strewed, coloured litmus
paper, before any of the exterior tentacles were inflected.
Some 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 beinferred 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 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 perceptible degree. Schiff assertst—and this is
an important fact for us—that “la caséine purifiée des
chimistes est un corps presque complétement inattaquable
par le suc gastrique.” Sothat 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.t
* Dr. Lauder Brunton, ‘Handbook that this difference is no doubt due
for Phys. Lab.’ p. 529. to the action of the alcohol used
+ ‘Leçons; &c. tom, ii. p. 153. in making ‘chemically prepared
t [Professor Sanderson | tells me _ casein.’’—F. D.
96 DROSERA ROTUNDIFOLIA. [Cuar. VI.
A few trials were made with cheese; cubes of 55 of an
inch (1-27 mm.) were placed on four leaves, 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
subsided masses of cheese, left on the discs, were very little
or not at all reduced in bulk. We may, however, 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. 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 dises 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
* Mr. A. W. Bennett found the tera; see ‘Journal of Hort. Soc. of
undigested coats of the grains in the London, vol. iv. 1874, p. 158.
intestinal canal of pollen-eating Dip-
Te SA a OR IND se
Cuar. VI.] DIGESTION. 97
inevitably caught by the viscid secretion surrounding the
many glands.
Gluten.—This substance is composed of two albuminoids,
one soluble, the other insoluble in alcohol.* 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 cbserved. 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 differently
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 avery 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 there-
fore asked Dr. Burdon Sanderson to try gluten in artificial
digestive fluid of pepsin with hydrochloric acid; and this
di-solved the whole. The gluten, however, was acted on
much more slowly than fibrin; the proportion dissolved
within four hours being as 40°8 of gluten to 100 of fibrin.
Gluten was also tried in two other digestive fluids, in which
hydrochloric acid was replaced by propionic and butyric
acids, and it was completely dissolved by these fluids at the
* Watts’ ‘Dict. of Chemistry,’ vol. ii. 1872, p. 875.
H
98 DROSERA ROTUNDIFOLIA. [Cuar. VI.
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
toremove thestarch. 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 hydrochloric acid, is not so powerful or so
enduring a stimulant as fresh gluten, and does not much
injure the glands; and we further learn that it can be
digested 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,
* Watts’ ‘ Dict. of Chemistry,’ vol. ii. p. 874.
E
Cee a By Se
Cumar. VI] DIGESTION, 99
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 sub-
stance, I was astonished at this result;* and my object being to
compare the action of the secretion with that of 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 not
surprising that the fragments of 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 probably hamatin, to-
gether with other bodies derived from the blood. Particles with little
drops of water were placed on four leaves, three of which were pretty
closely inflected in two days; the fourth only moderately 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 0°456 of the hematin was
* [The result was no doubt due was dissolved within the same time,
(as I learn from Professor Sanderson)
to the fact that the globulin had
been treated with alcohol in the
course of its preparation—F, D.]
t I may add that Dr. Sanderson
prepared some fresh globulin by
Schmidt’s method, and of this 0°865
namely, one hour; so that it was far
more soluble than 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 Drosera globulin prepared by this
method.
H 2
100 DROSERA ROTUNDIFOLIA. [Cuar. VI.
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 prolonged
inflection of the tentacles, and are either completely 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 sub-
stances 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.
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 2 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
substances are, as far as it is known, digested by the gastric
juice of animals, though some of them are acted on by the
ther secretions of the alimentary canal. Nothing more
need be said about some of the above enumerated substances,
excepting that they were repeatedly 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 experi-
ments. 7
Fibro-elastic Tissue—We have already seen that when little cubes
of meat, &c., were placed on leaves, the muscles, areclar tissue, and
cartilage was completely dissolved, but the fibro-elastic tissue, even
the most delicate threads, were left without the least 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
.* See, for instance, Schiff, ‘ Phys. de la Digestion,’ 1867, tom. ii. p. 38.
Cuar. VL] DIGESTION. 101
stated in chemical works, 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 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. The 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 dissolved, 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 isa
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 secretion of Drosera would act on the ferment of the gastric juice
of animals. I first used the common pepsin sold for medicinal pur-
poses, 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 in-
tlected ; 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 secretion surrounding them, were singularly pale,
whereas others were singularly dark-coloured. Some of the secretion
was scraped 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
* < Leçons phys. de la Digestion,’ 1867, tom. ii. p. 304.
102 DROSERA ROTUNDIFOLIA. [CHAE VI.
(remembering what small quantities were given), that the ferment of
Drosera does not act on or digest 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 fiuids and substances, be absorbed by the glands of
Drosera and cause mflection. Half-minim drops of a solution of one
part to 437 of water were placed on the discs of four leaves, each drop
containing the quantity usually employed by me, namely 53, ofa 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 c.c.)
of the sotution, 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 immersion in pure water. ‘lhat
the urea, which was not perfectly 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 the urea itself is
not exciting or nutritious to Drosera; 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. Bartholomew’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 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 some nutritious matter, for the leaf remained clasped over it for
four days; whereas the leaves with bits of the true wing re-expanded on
SP ernie,
ENN NCE eg nee
lpi naa ENE PEPE OEA
Cuar. VL] DIGESTION. 103
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 powerful 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 secretion. ‘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 dissolved; so that in a pure state it would not
probably have been attacked by the seeretion. Dr. Sanderson tried that
which I 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 Phar-
macopeia, 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
chllorophyll, 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
104 DROSERA ROTUNDIFOLIA. [CHAE VI.
slice on the leaf of the 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 inflected 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 Oil—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 in-
flection, 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; 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 some-
what more by the seeds than by inorganic objects of the same size.
After they re-expanded, the seeds were placed under favourable con-
ditions 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, ,
Cuar. VI] DIGESTION. 105
Radish seeds (Raphanus 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 (Lepidium sativum) of the previous year were placed on
four leaves; two of these inext morning were moderately and two
strongly inflected, and remained so for four, five, and even six days.
Soon after these sceds 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 so much inflection; on the
contrary, this served to a certain extent as a protection to the sees.
Two of the six seeds germinated whilst still lying on the leaves, but
the seedlings, when transferred to damp sand, soon died; of the other
four seeds, only one germinated.
Two seeds of mustard (Sinapis nigra), two of celery (Apium grave-
olens)—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 Anemone nemorosd, 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 weie
placed to be very strongly inflected; 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 kinas of seeds excite
the leaves in very different degrees; whether this is solely due to the
nature of their coats is not clear. ln the case of the cress seeds, the
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 penetrates their coats is also evident from the large pro-
portion of cabbage, raddish, and cress seeds which were killed, ande
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 1n @
state of nature; but this can hardly fail sometimes to occur, as we
shall hereafter see in the case of Pinguicula. If so, Drosera will profit
to a slight degree by absorbing matter from such seeds,
106 DROSERA ROTUNDIFOLIA. [Cuap. VI.
Summary and 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 some influence to the glands of the
exterior tentacles, causing them to secrete more copiously ;
and their secretion likewise becomes acid. With animals,
according to Schiff,* mechanical irritation excites the glands
of the stomach to secrete an acid, but not pepsin. Now, I
have every reason to believe (though the fact is not fully
established), that although the glands of Drosera are con-
tinually secreting viscid fluid to replace that lost by
evaporation, yet they do not secrete the ferment proper for
digestion when mechanically irritated, but only after ab-
sorbing 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 absorbed
certain soluble substances, which he designates 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.t
* ‘Phys. de la Digestion,’ 1867, acid and pepsin make their appearance
tom. ii. pp. 188, 245.
+ [it will be seen from the facts
given in a footnote at p. 81, that
even if we accept Schiff’s peptogen
theory, the evidence on the bo-
tanical side is against the existence
of the above suggested parallelism.
Moreover, Schiffs peptogen theory
is not generally accepted by physio-
logists. Professor Sanderson has
called my attention to Ewald’s views
on this question as given in his
“Klinik der Verdauungs krankheiten,
(i) Die Lehre von der Verdauung,
1886, p. 91. Ewald does not believe
in any special action of the so-called
peptogens. He writes, “I find that
almost immediately after the intro-
duction of a starch solution into the
stomach. The same thing naturally
follows on the introduction of Schiff’s
peptogens, so that no inconsiderable
quantity of acid and pepsin is in
readiness for a subsequent act of
digestion, which is, in consequence,
rendered far more energetic.”
Haidenhain, in Hermann’s ‘ Hand-
buch der Physiologie,’ vol. v. part i.
p- 153, also criticises Schiff’s theory,
and shows that the observations on
which this theory is founded are to
some extent untrustworthy, owing to
a fault inthe method employed—F, D.]
Cuar. VL] DIGESTION. 107
The secretion, as we have seen, completely dissolves
albumen, muscle, fibrin, areolar tissue, cartilage, the fibrous
basis of bone, gelatine, 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. T'he secretion
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
fur 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 uncooked
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 wonderful; but it depends merely on the
jong-continued secretion of an acid; and this is secreted for a
longer time under these circumstances than under any other.
It was interesting to observe that as long as the acid was
consumed in dissolving the phosphate of lime, no true di-
gestion occurred; but that as soon as the bone was completely
decalcified, the fibrous basis was attacked and liquefied with
the greatest ease. The twelve substances above enumerated,
which are completely dissolved by the secretion, are likewise
dissolved 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 striæ 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 prepared casein which is said to
consist of two substances; 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 albu-
minous matter, which Drosera would detect and absorb.
Again, fibro-cartilage, though not properly dissolved, is
108 DROSERA ROTUNDIFOLIA. [Cuap. VI.
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 indigestible 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
digestion of albumen is completely stopped, and that on
the addition of a minute dose of hydrochloric acid it imme-
diately recommences.
The nine following substances, or classes of substances,
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 dissolved by
the secretion, and which are afterwards absorbed by the
glands, affect the leaves rather differently. They induce
inflection at very different rates, and in very different
degrees ; and the tentacles remain inflected for very different
periods of time. Quick inflection depends partly on the
quantity 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, and 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 gener-
ally requisite between two acts of inflection. We probably
see the influence of texture 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 tochanged chemical nature, that albumen,
Ne notes
JR. aaneen.
pe
sii T a E AS
popen Eea S aaa
Cuar. VI] DIGESTION. 109
which has been kept for some time, and gluten which has
been subjected to weak hydrochloric acid, act more quickly
than these substances in their fresh state.
The length of time during which the tentacles remain
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 extra-
ordinary length of time during which the tentacles remain
inflected 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; phos-
phorus 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 integu-
ments; for animal matter is soon extracted from insects
(probably by exosmose from their bodies into the dense sur-
rounding 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 flesh 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, justi-
fied 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
interesting 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 inflected for a
longer time, than does gelatine, or areolar tissue, or the
fibrous basis of bone. It is not known how long an animal
* See the classification adopted by Dr. Michael Foster in Watts’ ‘Dict. of
Chemistry,’ Supplement 1872, p. 969.
110 DROSERA ROTUNDIFOLIA. [CHAP VI.
would survive if fed on fibrin alone, but Dr. Sanderson has
no doubt longer than on gelatine, and it would be hardly
rash to predict, judging from the effects on Drosera, that
albumen would be found more nutritious than fibrin.
Globulin likewise belongs to the Proteids, forming another
sub-group, and this substance, though containing 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 animals 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 different
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 sur-
rounding 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 animals with its
pepsin and hydrochloric acid and the secretion of Drosera
with its ferment and acid belonging to the acetic series.
We can therefore hardly doubt that the ferment in both
cases is closely similar, 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 Droseracew,
Cuar. VIL] SALTS OF AMMONIA. 111
CHAPTER VII.
THE EFFECTS OF SALTS OF AMMONIA.
Manner of performing the experiments—Action of distilled water in com-
parison 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—Leayes immersed in weak solutions—Minute-
ness of the doses which induce aggregation of the protoplasm—Nitrate of
ammonia, analogous experiments with—Phosphate of ammonia, analogous
experiments with—Other saits of ammonia—Summary and concluding
remarks on the action of the salts of ammonia,
TuE chief object in this chapter is to show how powerfully
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 51, of a fluid ounce (*0296 c.c.),
were placed by the same pointed instrument on the dises of the leaves,
and the inflection of the exterior rows of tentacles observed at succes-
sive 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 inflected. 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
112 DROSERA ROTUNDIFOLIA. (Cuar. VII.
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 secretion 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;
Dut on trial this proved a great mistake. I first measured some water,
and removed 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 ṣẹ of a minim. Some water in a small vessel
Was weighed (and this is a more accurate method), and 300 drops re-
moved as before; and on again weighing the water, a drop was found
to equal on an average only the 3; ofa minim. I repeated the opera-
tion, 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 qz ofa minim. I repeated the operation in
19-4
exactly the same manner, and now the drops averaged 5235 of a
Ə
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 J, of a minim, or *0029 c.c. One of these drops could be applied
to three or even four glands, andif 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
tifteen seconds; and this was not time enough for the diffusion 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 quantity
of the solution under trial; the same number of leaves being im-
mersed 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 some-
times to 48 hrs. They were immersed by being laid as gently as
possible in numbered watchglasses, and thirty minims (1:775 c.c.) 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 ther
transmitted a motor impulse to the exterior tentacles; but in this
latter case the exterior tentacles would not have become inflected
aiaa patie
ee ye
—
Cumar. VIL] EFFECTS OF WATER. 113
until some time had elapsed, instead of within half an hour, or even
within a few minutes, as usually occurred. All the glands on tke
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 iong-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 papillæ, which absorb carbonate of ammonia,
an infusion of raw meat, metallic salts, and probably many other
substances, but the absorption of matter by these papillæ never induces
inflection. We must remember that the movement 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 sg, of a grain of the salt. I say at most, for the papilla
will have absorbed some small amount, and so will perhaps the glands
of the twelve excluded tentacles which did not become intlected. ‘The
application of this principle 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 difference
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. ‘lhe fact, moreover, of
pure water acting on the glands deserves in itself some notice. Leaves
to the number of 141 were immersed 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 altogether 173 experiments. Many scores of leaves were also
immersed in water at other times, but no exact record of the effects
produced was kept; yet these cursory observations support the con-
clusions arrived at in thischapter. 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 par-
I
114 DROSERA ROTUNDIFOLIA. [Cuar. VIL
taking of this movement. Hence, excepting iu a few cases hereafter
to be specified, we can judge whether a solution produces any efiect
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 inflected. Thus seventeen leaves out
of the 173 were acted on in a marked manner. Eighteen leaves bad
from seven to nineteen tentacles inflected, the average being 9°3 ten-
tacles 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 aflected by the
water in some degree, though
commonly toa very slight degree ;
and ninety-four were not affected
in the least degree. This amount
of inflection is utterly insignifi-
cant, as we shall hereafter 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 tem-
perature are far more sensitive to
the action of water than those
grown out of doors, or recently
brought inte a warm greenhouse.
ee Thus in the above seventeen cases,
(Drosera rotundifolia.) in which the immersed leaves had
dest (enlarked) with ail the tentacles a considerable number of tentacles
closely inflected, from immersion in a inflected, the plants had been kept
solution of phosphate of ammonia (one during the winter in a very warm
part to 87,500 of water). ~ c
greenhouse; and they bore in the
early spring remarkably fineleaves,
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 simultaneous immersion in water.
It often happened that some leaves on the same plant, and some ten-
tacles on the same leaf, were more sensitive than others; but why this
should be so, I do not know.
Besides the differences just indicated between the leaves immersed
in water and in weak solutions of ammonia, the tentacles of the latter
are in most cases much more closely inflected. The appearance of a
set seietieee ad en aR ae
TOE,
zep rey
We eee ee er
Cuar. VIL] CARBONATE OF AMMONIA. 115
leaf after immersion in a few drops of a solution of one grain of
phosphate of ammonia to 200 oz. of water (ùe. one part to 87,500) is
here reproduced: such energetic inflection is never caused by water
alone. With leaves in the weak solutions, the blade or lamina otten
becomes inflected; and this is so rare a circumstance with leaves in
water that I have seen only two instances; and in both of these the
inflection was very feeble. Again, with leaves in the weak solutions
the inflection of the tentacles and blade often goes on steadily, though
slowly, increasing during many hours; and this again is so rare a cir-
cumstance 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 sometimes 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 difficulty 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
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 observed. 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 absorbent hairs were
not visibly affected. The tentacles did not bend. Two
12
116 DROSERA ROTUNDIFOLIA. [Cuap. VII.
other plants were placed with their roots surrounded by
damp moss, in half an ounce (14:198 c.c.) of a solution of one
part of the carbonate 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.
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 isa curious fact that some
of the closely adjoining tentacles on the same leaf, both on the
disc 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 explained by supposing that the more active.
glands absorb all the vapour as quickly as it is generated,
so that none is left for the others; for we shall meet with
analogous cases with air thoroughly permeated with the
vapours of chloroform and ether.
Minute particles of the carbonate were added to the secre-
tion 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 analogous 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,
Cuar. VIL] CARBONATE OF AMMONIA. 117
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 545 ofa 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 themovement 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
intlected; but this degree of movement can hardly be considered as
trustworthy. Each of these leaves received sp 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 ;45 of a minim,
and therefore contains gsp of a grain (°0135 mg.) of the carbonate.
1 touched with it the viscid secretion round three glands, so that each
gland received only ;;19,5 of a grain (*00445 mg.). Nevertheless, in
two trials all the glands were plainly blackened ; in one case all three
tentacles were well inflected after an interval of 2 hrs. 40 m.; and in
another 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 z5455 of a grain
(°00337 mg.), yet some of them were a little darkened; but in no one
instance were any of the tentacles 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 z;15, 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
ior 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 (3°549 c.c.) of a solution of one part of the
carbonate to 5250 of water; two of these had almost every tentacle
intlected, 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 infected, and
118 DROSERA ROTUNDIFOLIA. [Cuar. VII.
all the glands blackened. Six leaves were immersed, each in thirty
minims (1°774. c.c.) of a solution of one part toj4375 of water, and the
glands were all blackened in 31 m. All six leaves exhibited some
slight inflection, 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 53; 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 solutions are important, as they show that all the
glands absorbed the carbonate within the same time, which fact indeed
there was not the least reason to doubt. So again, whenever all the
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
z147 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
(i. e. 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 -gpp of a grain (°0405 mg.). The glands
were not much darkened. ‘Ten of the leaves were not affected, cr
only very slightly so. Four, however, were strongly affected; the first
having all the tentacles, except forty, inflected in 47 m. ; in 6 hrs. 80m.
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. 30 m.
these nine were sub-inflected ; the blade having become much inflected
in4hrs. 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 tentacles
and after 4 hrs. all but forty-five inflected. 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 able to absorb, is acted on by 105p 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 33555 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 minimum dose which is efficient.
Aggregation of the Protoplasm from the Action of Carbonate of
remoting
Niles
Cuar. VIL] CARBONATE OF AMMONIA. 119
Ammonia.—I have fully described in the third chapter the remarkable
effects of moderately strong doses of this salt in causing the aggre-
gation 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 c.c.) of a solution of one
part to 1750 of water, 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
gis 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 all 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 F
experimented on fourteen leaves, but will give only a few of the cases.
Hight 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 c.c.) 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 alternately 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 translucent
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
conspicucusly aggregated; the spheres and elongated masses of proto-
plasm 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 g;455 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 5}5
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 may safely assume that there were at least 140; and
if so, each gland could have received only the z3dyo5 Of @ grain, or
-00048 mg.
A weaker solution was then made of one part to 7000 of water, and
120 DROSERA ROTUNDIFOLIA. [Cuar. VII.
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 many spheres of aggregated protoplasm. This leaf received
aig of a grain, and bore 166 glands. ach gland could, therefore, have
received only y37¢s¢ of a grain (*000507 mg.) of the carbonate.
‘wo other experiments are worth giving. A leaf was immersed 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 solution of one part to 5250 of
water; and this excited welf-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 len:th equal to half or the whole of the glands.
lt 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 hr. and 1 hr. 15 m., during which time they were
immersed in the solution; for the process of aggregation seems in-
variably to snpervene 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,
aud by the aggregation of the contents of their cells. The
vapour is absorbed by the glands; these are blackened, and
the tentacles are intiected. The glands of the disc, when
excited by a half-minim drop (‘0296 c.c.), containing 51, of
a grain (‘0675 mg.), transmit a motor impulse to the exterior
tentacles, causing them to bend inwards. A minute drop,
containing yz}, 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 immersed for a few
hours in a solution, and a gland absorbs the +y+ryy 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 s¢soy of a grain (-00024
mg.) suffices to excite the tentacle bearing this gland into
movement.
NITRATE OF AMMONIA.
With this salt I attended only to the inflection of the leaves, for it is
far less efficient than the carbonate in causing aggregation, although
considerably more potent in causing inflection. I experimented with
Se...
Cuar. VIL] NITRATE OF AMMONIA. 121
half-minims (+0296 c.c.) 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 zły of a grain (or *27 mg.). A solution of one part to 218 of
water acted most energetically, causing 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
diss of each received the +4, 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 notatail. I 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. I mention this fact to show how necessary it is to
experiment on several leaves. Two of the leaves, which were well
intiected, re-expanded after 51 hrs.
In the following experiment I happened to select very sensitive
leaves. Half-minims of a solution of one part to 1094 of water (i.e.
1 gr. to 23 oz.) were placed on the discs of nine leaves, so that each
received the 5345 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 7 hrs., but the full effect was not produced until
from 24 hrs, tu 80 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 to 1312
of water (1 gr. to 3 oz.) were tried on fourteen leaves; so that each
received 5,4, of a grain (*0225 mg.), instead of, as in the last experi-
ment, 5,455 of a grain. ‘lhe blade of one was plainly inflected, as were
3
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 trom
tive 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 subsequently 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 30
hrs. had elapsed. It is obvious that we have 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 (54; 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
a DROSERA ROTUNDIFOLIA. [Cuar. VIE.
could have received only the si55 of a grain, or 00225 mg. A
little drop of the same size and strength was also applied to four other
of this strength produced 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 in making 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.
Having made some preliminary trials as a guide, five leaves were
placed in the same little vessel in thirty minims of a solution of one
part of the nitrate to 7875 of water (1 gr. to 18 oz.); and this amount
of fluid just sufticed 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 a’most 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 alter 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 si;
of a grain was given to the five leaves together, each got -44y of a
grain (°045 mg.). 1 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 ssa4ao 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
cne, 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, more-
over, must often touch one another or the sides of the vessel, and
Cmar. VIL] NITRATE OF AMMONIA. 128
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 wiil, therefore, give only one other experiment
made 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 ;)55 of a grain (*0562 mg.).
After 1 hr. 20 m. many of the tentacles on all four leaves were
somewhat inflected. After 5 hrs. 30 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 sub-
marginals, 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
assumption that each of these leaves bore 160 tentacles, each gland
could have absorbed only , 7355 of a grain (*000351 mg.). This ex-
periment 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 intlected. In this case
the tentacles on each leaf were counted, and gave an average of 162
er 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 c.c.) 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 1, of a grain (*2025 mg.). Before 30 m. had
elapsed, four of these leaves were immensely, and two of them moder-
ately, 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 tentacles 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 solution of
one part to 17,500 of water (1 gr. to 40 oz.), so that each received 5},
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
124 DROSERA ROTUNDIFOLIA. [Ckar. VIL.
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 in water, only one had any of
its exterior 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 43,750 of water (1 gr. to 100 0z.), so that each leaf got
seo Of a grain (°0405 mg.). Of these, one was much inflected in 8 m.,
and after 2 hrs. 7m. had all the tentacles, except thirteen, inflected.
‘The second leaf, alter 10 m., had all except three inflected. The third
and fourth were hardly at ail affected, scarcely more than the cor-
responding 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 tentacles except three inflected in 10 m., each gland (assuming
that the leaf bore 160 tentacles) could have absorbed only 33~;o9 of
a grain, or *Q00258 mg.
four leaves were separately immersed as before in a sclution of one
part to 131,250 of water (1 gr. to 300 0z.), so that each received z355
of a grain, or 0135 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 inflected. Thus three out of the four leaves were strongly acted
on. Itis clear that very sensitive leaves had been accidentally
selected. The day moreover was hot. The four corresponding leaves
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 (as-
suming that the leaf bore 160 tentacles) could have absorbed only
Sorzo0 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 0z.), so that
each received only a5 of a grain (*0101 mg.). This minute quantity
produced a slight effect on only four of the cight leaves. One had
titty-six tentacles inflected after 2 hrs. 13 m.; a second, twenty-six
intlected, or sub-inflected, after 38 m.; a third, eighteen inflected, after
lhr.; and a 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
Cuar, VII.) PHOSPHATE OF AMMONIA. 125
unaffected. Hence, the 3yo of a grain given to a sensitive 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 experiment.
Summary of the Results with Nitrate of Ammonia—The
glands of the disc, when excited by a half-minim drop
oer c.c.), containing zy, 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
avon 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 sometimes for only a few minutes, in a solution of such
strength that each gland can absorb only the gyy'yg5 of a
grain (-0000937 mg.), this small amount is enough to excite
each tentacle into movement, and it becomes closely in-
flected.
PHOSPHATE OF AMMONIA.
This salt is more powerful than the nitrate, even in a
greater degree than the nitrate is more powerful than the car-
bonate. This is shown by weaker solutions of the phosphate
acting when dropped on the discs, or applied to the glands of
the exterior tentacles, 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 given,
which are so surprising that their credibility 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, treating at the same time and in the samo
ianuer 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
126 DROSERA ROTUNDIFOLIA, (Car. VIL
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. Altogether, 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 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 437 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. 15 m. Similar drops of a solution
of one part to 1312 of water (1 gr. to 3 oz.) were then placed on the
discs of five leaves, so that each received the zy, 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
iully 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 placed on the discs of six leaves; so that each received
geio 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 zg of a grain, absorbed by the central glands, is enough to make
many of the exterior tentacles and the blades bend, whereas the +355
of a grain of the carbonate similarly given produced no effect ; and
esp Of a grain of the nitrate was only just sufficient to produce a well-
marked effect.
A minute drop, about equal to ṣẹ of a minim, of a solution of one
Cuar. VIL] PHOSPHATE OF AMMONIA. 127
part of the phosphate to 875 of water, was applied to the secretion on
three glands, each of which thus received only 57155 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 three of the tentacles became slightly inflected in 6 m.,
and re-expanded after 8 hrs. 45 m. On the second, two tentacles
became sub-inflected in 12 m. And on the third all four tentacles
were decidedly inflected in 12 m.; they remained so for 8 hrs, 30 m.,
but by the next morning were fully re-expanded. In this latter case
each gland could have received only the +750 (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 remained 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 753500
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 5455 of a grain of the
carbonate, and of 5715y of a grain of the nitrate, did not cause the
tentacle bearing the gland in question to be inflected; so that here
again the 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 43,750 of water (1 gr. to 109
02.); so that each received z,55 of a grain, or *04058 mg. Of these
leaves, eleven had nearly ali 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 corre-
sponding 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 in appearance between the two lots was extremely great.
Eighteen leaves were immersed, each in thirty minims of a solution
of one part to 87,500 of water (1 gr. to 200 oz.), so that each received
gio Of a grain ('0202 mg.). Fourteen of these were strongly
inflected within 2 hrs., and some of them within 15 m.; three out of
128 DROSERA ROTUNDIFOLIA. [Cuar. VII:
the eighteen were only slightly affected, having twenty-one, nineteen,
and twelve tentacles inflected; 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 circumstances,
for the day (July 8) was very warm, and I happened to have
unusually tine leaves, Five were immersed as before in a solution of
one part to 131,250 of water (1 gr. to 300 oz.), so that each received
adua fa grain, or *0135 mg. Afteranimmersion 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 solution. 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 giands could
have absorbed only yga7uqo Of a grain, or *0000631 mg. The third
leaf bore 236 glands, and subtracting the five which did not become
inflected, each of the remaining 231 glands could have absorbed only
sioisoo 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 535, of 2
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 considerably 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.
record in my notes that 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 zzg¢so, and on the other leaf only 1474000
of a grain of the phosphate.
Cuar.. VIL] PHOSPHATE OF AMMONIA. 129-
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 im-
pression that it was incredible that any weaker solution could produce
an effect. Each leaf received oyy of a grain, or 0081 mg. ‘The first
eight leaves which I tried both in the solution and 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 had got eight pairs of fine leaves, and the
weather was favourable, the temperature of the room where the leaves
were immersed varyiug 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 experiments; a chemist weighed for me a grain in
an excellent balance; and fresh water, given me by Professor Frank-
land, was carefully measured. The leaves were selected from a large
number of plants in the following manuer: the four finest were
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 inflection 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 aud three rather doubtfully ; 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 previous 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 :—
L) After only 8 m. a large number of tentacles inflected, and after
17 m. all but fifteen; after 2 hrs. all but eight inflected, 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 39 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.
K
130 DROSERA ROTUNDIFOLIA. [Cuar. VII.
(T) 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 38 m. twenty-eight tentacles inflected; alter 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 5 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. l
(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; aiter 24 hrs. every tentacle
slightly curved inwards; after 27 hrs. 40 m. blade strongly inflected,
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 hrs. 40 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. 'l'hus the leaf remained
for two days, when it began to re-expand. | 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 previous experiments with
stronger solutions,
ove 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 contrast 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 tentacles except eight inflected, were counted and found
to be 202. Subtracting the eight, each gland could have received only
the ygs4o00 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 setivas of a grain,
weit. |
Cuar. VIL] PHOSPHATE OF AMMONIA. 131
or *0000387 mg. Lastly, leaf No. 11, which had after 24 hrs. all its
tentacles, 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 s55}o55 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 extremely. 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 in the proportion of about sixteen to nine.
Four leaves were immersed as before, each in thirty minims of a
solution of one part to 328,125 of water (1 gr. to 750 oz.). Each leaf
thus received z5455 Of a grain (*0054 mg.) of the salt; and all four
were greatly intlected.
(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.
(3) After 1 hr. much inflection; after 2 hrs. 30 m. all the tentacles
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 lirs, 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.
(3) and (4) Not affected, except that, as usual, after 11 hrs. the
short tentacles on the borders of the dise 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 3574559 Of a grain (*0000268 mg.) and of No. 2 only
szadoos Of a grain (0000263 mg.) of the phosphate.
Seven leaves were immersed, each in thirty minims of a solution of
one part to 437,500 of water (1 gr. to 1000 oz.). Each leaf thus
received +;355 of a grain (-00405 mg.). The day was warm, and the
leaves were very fine, so that all circumstances were favourable.
(1) After 30 m. all the outer tentacles except five inflected, and
K 2
132 DROSERA ROTUNDIFOLIA. [Cuar VII.
most of them closely ; after 1 hr. blade slightly inflected ; after 9 hrs.
30 m. began to re-expand.
(2) After 33 m. all the outer tentacles but twenty-five inflected, and
blade slightly so; after 1 hr. 30 m. blade strongly inflected and
remained so for 24 hrs.; but some of the tentacles had then re-
expanded.
(3) After 1 hr. all but twelve tentacles inflected; after 2 hrs. 80 m.
all but nine inflected ; and of the inflected tentacles all excepting four
closely ; blade slightly inflected. After 8 hrs. blade quite doubled up,
and now all the tentacles excepting eight closely inflected. The leaf
remained in this state for two days.
(4) After 2 hrs. 20 m. only fitty-nine tentacles inflected; but after
5 hrs. all the tentacles closely inflected excepting two which were not
affected, and eleven which were only sub-inflected ; 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.
30 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.
(T) After 4 hrs. 80 m. only thirty-five tentacles inflected or sub-
inflected, and this small amount of intlection never increased.
Now for the seven corresponding leaves in water :—
(1) After 4 hrs. thirty-eight tentacles inflected ; but after 7 hrs.
these, with the exception of six, re-expanded.
(2) After 4 hrs. 20 m. twenty inflected ; these after 9 hrs. partially
re-expanded.
(3) After 4 hrs. five inflected, which began to re-expand after 7 hrs.
(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 inflected
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 leat No. 3 (which bore 233 glands, all
of which, except nine, were inflected in 2 hrs. 80 m.) could have
received at most only the sgstoo5 Of a grain, or *0000181 mz.
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 1 happened
to select leaves which were very little sensitive, as on other occasions
I chanced to select unusually sensitive leaves. The leaves were not
ooo eee
iite i
Cuar. VIL] PHOSPHATE OF AMMONIA. igo
more affected after 12 hrs. than 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 solution
of one part to 1,812,500 of water (1 er. to 3000 oz.) ; so that each leaf
received = 7355 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 tentacles
inflected ; after 3 hrs. 30 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.
(3) 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; atter 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-ex pand,
(5) to (12) These were not more inflected than leaves often are in
water, having respectively 16, 8, 10, 8, 4, 9, 14, and O tentacles
inflected. Two 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, tor 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. 30 m. only twenty-five inflected,
and these after 10 hrs. all re-expanded; (3) 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 11 hrs.; (6), (7) and (8) from one to three inflected, which soon
re-expanded; (9), (10), (11) and (12) none inflected, though observed
for 24 hrs.
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 experiments with stronger
solutions. It deserves attention that the inflection of four of the leaves
134 DROSERA ROTUNDIFOLIA. (Cuar. VII.
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 decrease during this same interval. It is also re-
markable that the blades of three of the leaves in the solution were
slightly inflected, 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 manner 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 condition.
Of the leaves in the solution, No. 1 bore 200 glands and received
astoo Of a grain of the salt. Subtracting the seventeen tentacles
which were not inflected, each gland could have absorbed only the
5754000 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 21,875,000 of water 1 gr. to 5000
oz.). Each leaf thus received .545, of a 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 inflected,
but some only sub-inflected; the blade much inflected; after 6 hrs.
30 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 ten-
tacles 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, and most of them
rather closely, four or five being only sub-inflected.
(8) 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 inflected. 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,
T, 4, and O, 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 alter 6 hrs. 30m. After 10 hrs.
15 m. a most unusual circumstance occurred, namely, the whole
Cuap. VIL] PHOSPHATE OF AMMONIA. 135
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 inflected 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 undoubtedly 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 extremly weak solution acted on the more sensitive leaves ;
each of which received only the oboy Of a grain (*00081 mg.) of the
phosphate. Now, leaf No. 3 bore 178 tentacles, and, subtracting the
three which were not inflected, each gland could have absorbed only
the -1005007 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 absorbed only
ze7eooon 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
c.c.), containing 545 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 x53000
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. Ifa 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 y57¢yo00 Of a grain (00000328
ing.), 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.
136 DROSERA ROTUNDIFOLIA. [Cuar, VII.
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 437 of water were placed on the
discs of seven leaves, so that each received 54, 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. The leaves were not afterwards
observed.
Citrate of Ammonia.—Half-minims of a solution of one part to 437
of water were placed on the discs of six leaves. In 1 hr. the short
outer tentacles round the discs were a little inflected, with the glands
on the discs blackened. Aliter 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, becoming more and 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 grain to 3
0z.); so that each received z850 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. ‘lwo other leaves
were tried with a weaker solution of one part to 437 of water; one
was strongly inflected in 7 hrs.; the other not until 30 hrs. had
capsed.
Tartrate 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 of some of the leaves,
and this became more decided after 1 hr. with all the leaves; but
the tentacles were never closely inflected. 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
remarkable.
Chloride of Ammonia.—Hal{-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
Cm VIL] OTHER SALTS OF AMMONIA. — 137
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 Salts of
Ammonia.—We have now seen that the nine salts of ammonia
which were tried all cause the inflection of the tentacles,
and often of the blade of the leaf. As far as can be ascer-
tained 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 relative efficiency of
the carbonate, nitrate, and phosphate, is shown in the fol-
lowing table by the smallest amount which suffices to cause
the inflection of the tentacles.
|
P v .
io F ; Carbonate of | Nitrate of Phosphate of
Solutions, how applied. Ammonia. | Ammonia. Ammonia.
Placed on the glands of thej! as of a | 700 of a mw Ofa
disc, so as to act indirectly grain, or | grain, or grain, or
on the outer tentacles .) +0675 mg. -027 mg. *0169 mg.
. ji | .
Applied for a few seconds); yy\y5 0f 8 | aofa | asw of a
directly to the gland of an> grain, or | grain, or | grain, or
outer tentacle, . . .) 00445 mg.| °0025 mg. *000423 mg.
| |
Leaf immersed, with time]) sgg of a 301200 of a 10180000 of a
allowed for each gland tobi grain, or grain, or grain, or
absorb all that it can. .}) -00024mg.} *0000937 mg. | °00000328 mg.
|
|
Amount absorbed by a gland)!
which suffices to cause thef| yyy455 of a
aggregation of the proto->| grain, or
plasm in the my saa d Mosc mg.
cells of the tentacles . .
| |
From the experiments tried in these three different ways,
we see that the carbonate, which contains 23-7 per cent. of
nitrogen, is less efficient than the nitrate, which contains 35
per cent. The phosphate contains less nitrogen than either
of these salts, namely, only 21-2 per cent., and yet is far more
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
138 DROSERA ROTUNDIFOLIA. (Cuar. VII.
which bits of bone and phosphate of lime affect the leaves.
Theinflection excited by the other salts of ammonia is pro-
bably due solely to their nitrogen, —on the same principle that
nitrogenous organic fluids act powerfully, whilst non-nitro-
genous 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 ten-
tacles 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 solution
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 movements 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 3 J;, of a
grain placed on the disc is only just able to cause the outer
tentacles of a highly sensitive leaf to bend. It is certainly
a most surprising fact that the y57¢po09 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 BUSS 5130
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 31-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 the leaf. Yet this amount
* It is scarcely possible to realise
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 85 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.
i
i
-
E E E NE E
Cuar. VII.] SUMMARY, SALTS OF AMMONIA. 139
sufficed to cause the inflection of almost every tentacle, and
often of the blade of the leaf.
Iam 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 ammonia than the most skilful chemist can
of any substance.* My results were for a long time incredible
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. Two of my sons, who were as incre-
dulous as myself, compared several lots of leaves simultane-
ously immersed in the weaker solutions and in water, and
declared that there could be no doubt about the difference in
their appearance. I hope 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 absolutely pure as it can be made. It is to be
especially observed that the experiments with the weaker
solutions 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 irri-
tability of the tentacles was ascertained by three different
methods—indirectly by drops placed on the disc, directly by
* When my first observations were (see Balfour Stewart, ‘Treatise on
made on the nitrate of ammonia, Heat, 2nd edit. 1871, p. 228). With
fourteen years ago, the powers of respect to ordinary chemical tests, I
the spectroscope had not been dis- gather from Dr. Alfred Tay lor’s
covered ; and I felt all the greater work on ‘ Poisons’ that about 1055 Of
interest in the then unrivalled powers a grain of arsenic, 3/55 of a grain of
of Drosera. Now the spectroscope prussic acid, phy of iodine, and B05
has altogether beaten Drosera; for, of tartarised antimony, can be de-
according to Bunsen and Kirchhoff, tected; but the power of detection
probably less than one skg of a depends much on the solutions under
grain of sodium can be thus detected trial not being extremely weak.
140 DROSERA ROTUNDIFOLIA. (Cuar. VIL.
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 car-
bonate, and the phosphate much 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 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, therefore, 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
about 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 efficient 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 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
ofa grain of sulphate of atropine, in an extremely diluted
* Miller’s ‘Elements of Chemistry,’ part ii. p. 107, 3rd edit. 1864.
iiie
Cuar. VIL] SUMMARY, SALTS OF AMMONIA. 141
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 infinitely
smaller* than those of the phosphate of ammonia 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 Drosera, 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 ren-
dered 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 —that is, from 5155 to taby of an
calculated for me the diameter of |inch—in diameter. Therefore, an
a sphere of phosphate of ammonia object between 3; and J, of the size
(specific gravity 1:678), weighing of a sphere of the phosphate of
the one-twenty-millionth of a grain, | ammonia of the above weight can be
and finds it to be rdg Of an inch. seen under a high power; and no one
Now, Dr. Klein informs me that the
smallest Micrococci, which are dis-
tinctly discernible under a power of
800 diameters, are estimated to be
from +0002 to 0005 of a millimeter
supposes that odorous particles, such
as those emitted from the deer in the
above illustration, could be seen
under any power of the microscope.
142 DROSERA ROTUNDIFOLIA. (Cuar. VII.
CHAPTER VIII.
THE EFFECTS OF 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 experi-
ments 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 de-
scribed.
SALTS CAUSING INFLECTION. SALTS NOT CAUSING INFLECTION.
(Arranged in Groups according to the Chemical Classification in Watts’
< Dictionary of Chemistry.)
Sodium carbonate, rapid inflection. Potassium carbonate: slowly poison-
ous.
Sodium nitrate, rapid inflection. Potassium nitrate: somewhat poison-
ous.
Sodium sulphate, moderately rapid Potassium sulphate.
inflection.
Sodium phosphate, very rapid in- Potassium phosphate.
flection.
Sodium citrate, rapid inflection. Potassium citrate.
Sodium oxalate, rapid inflection.
Sodium chloride, moderately rapid Potassium chloride.
inflection.
Sodium iodide, rather slow inflection, Potassium iodide, a slight and doubt-
ful amount of inflection.
Sodium bromide, moderately rapid Potassium bromide.
inflection.
Potassium oxalate, slow and doubtful
inflection.
Cuar. VIIL]
SALTS CAUSING INFLECTION,
(Arranged in Groups according to the Chemical Classification in Watts
EFFECTS OF VARIOUS SALTS.
143
SALTS NOT CAUSING INFLECTION.
>
‘ Dictionary of Chemistry.’)
Lithium nitrate, moderately rapid
inflection.
Cæsium chloride, rather slow inflec-
tion. 5
Silver nitrate, rapid inflection: quick
poison,
Cadmium chloride, slow inflection.
Mercury perchloride, rapid inflection :
quick poison.
Aluminium chloride, slow and doubt-
ful inflection.
Gold chloride, rapid inflection : quick
poison.
Tin chloride, slow inflection: poison-
ous.
My
Antimony tartrate, slow inflection :
probably poisonous.
Arsenious acid, quick inflection : poi-
sonous.
Iron chloride, slow inflection: pro-
bably poisonous.
Chromic acid, quick inflection : highly
poisonous.
Copper chloride, rather slow inflec-
tion: poisonous,
Nickel chloride, rapid
probably poisonous.
Platinum chloride, rapid inflection :
poisonous.
inflection :
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-
flection.
Aluminium and potassium sulphate.
Lead chloride.
Manganese chloride
Cobalt chloride
Sodium, Carbonate of (pure, given me by Prof. Hoffmann).—Half-
minims (*0296 c.c.) 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
becaine well inflected; three had only two or three of their outer
tentacles inflectec, and the remaining two were quite unaffected. But
144 DROSERA ROTUNDIFOLIA. [Cuar. VIII.
the dose, though only the ;1; 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 457 of water, or 1 gr. to
1 0z.), doses of 545 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 considerably 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 solution of
one part to 875 of water (1 gr. to 2 0z.), so that each received 3} of a
grain (2°02 mg.); after 40 nı. the three were much affected, and
after 6 hrs. 45 m. the tentacles of alland the blade of one closely
inflected.
Sodium, Nitrate of (pure).—Half-minims of a solution of one part
to 437 of water, containing 515 of a grain (+0675 mg.), were placed on
the discs of five leaves. After 1 hr. 25 m. the 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 to expand.
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 solution of
one part to 875 of water; in 1 hr. there was great inflection, and after
8 hrs. 15 m. every tentacle and the blades of all three were most
strongly inflected.
Sodium, Sulphate of.—Nalf-ninims 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, and in 45 hrs. the leaves were fully
expanded, appearing quite healthy. :
Three leaves were immersed, each in thirty minims of a solution 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 leas
became incurved. After 48 hrs. all the leaves re-expanded. It is
Cmar.. VIII] SALTS OF SODIUM. 145
clear that 535 of a grain of phosphate of soda has great power in
causing inflection.
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 submarginal 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 mivims 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.
Sodium, Oxalate of.—Half-minims of a solution of one part to 487 of
water were placed on the disc of seven leaves; after 5 hrs. 30 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 brs. 35 m. the blades of two and the
tentacles or all were closely inflected.
Sodium, Chloride of (best culinary salt).—Half-minims of a solution
of one part to 218 of water were placed on the discs 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 ten-
tacles 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 437 of water, were then dropped on the
discs of six leaves, so that each received 51, ofa grain. In 1 hr. 33m.
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 solution of
one part to 875 of water, so that each received J, of a grain, or 2°02
mg. After 1 hr. there was much inflection; after 8 hrs. 30 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. 3y of a grain. They all soor became
inflected; after 48 hrs. they began to re-expand, aud appeared quite
uninjured, though the solution was sufficiently strong to taste saline.
Sodium, Jodide of.—Half-minims of a solution of one part to 437 of
water were placed on the discs of six leaves. After 24 hrs. four of them
had their blades and many tentacles inflected. The other two had
only their submarginal tentacles inflected ; the outer ones in most of
L
146 DROSERA ROTUNDIFOLIA. (Cuar. VIE
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 in-
flected.
Sodium, Bromide of.—Half-minims of a solution of one part to 437
of water were placed on six leaves. After 7 hrs. there was some in-
flection; 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 im-
mersed, each in thirty minims of a solution of one part to 875 of
water; after 40 m, there was some inflection; after 4 hrs. the tentacles
of all three leaves and the blades of two were inflected. These leaves.
were then placed in water, and after 17 hrs. 50 m. two of them were
almost completely, and the third partially, re-expanded; so that
apparently they were not injured.
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 injured; for, on the third day after the solutiom
was given, three of the leaves were dead, and one was very unhealthy ;
the other two were recovering, but with several of their tentacles
apparently injured, and these remained permanently inflected. It is:
evident that the 51, ofa grain ef 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—Half-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. Eight
leaves were treated in the same manner, with drops of a weaker solu--
tion, of one part to 218 of water. After 50 hrs. there was no inflection,
but two of the leaves seemed injured. 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 437 of water, and
these, after 48 hrs., were in no way affected, with the exception of
perhaps a single leaf. Three leaves were next immersed 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 contents of the cells became plainly aggregated.
This shows that the leaves had not been much injured. by their immer-
sion for 25 hrs. in the nitrate.
PO ere ec eats Ra
Cuar. VIL] SALTS OF POTASSIUM. 147
Potassium, Sulphate of.—Balf-minims of a solution of one part to
437 of water were placed on the discs of six leaves. After 20 hrs. 80 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. Nevertheless, after two additional
days, all six leaves recovered. The immersion of three leaves for 24
hrs., each in thirty minims of a solution of one part to 875 of water,
produced no apparent effect. They were then treated with the same
solution of carbonate 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
437 of water were placed on the discs of six leaves, which were observed
during three days; but no effect was produced. The partial drying up
of the fluid on the disc slightly drew together the tentacles on it, as
often occurs in experiments of this kind. ‘he leaves on the third day
appeared quite healthy.
Potassium, Citrate of —Half-ninims of a solution of one part to 437
of water, left on the discs of six leaves for three days, and the immer-
sion 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 etfect.
Potassium, Oxalate of.—Half-minims were placed on different occ2-
sions on the discs of seventeen leaves; and the results perplexed 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 been observed jor a longer time.
Potassium, Chloride of.—Neither half-minims of a solution of one
part to 437 of water, left on the discs of six leaves for three days, nor
the immersion of three leaves during 25 hrs., in 80 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.—Halt-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 inflected ; the remaining three
being very slightly affected. Hardly any of these leaves had their
outer tentactes inflected. After 21 hrs, all re-expanded, excepting two
which still had a few submarginal tentacles inflected. Three leaves
were next 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.
L 2
148 DROSERA ROTUNDIFOLLA. [Cuar. VIL.
Potassium, Bromide of.—Half-minims of a solution of one part to
437 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 alter 24 hrs. they became splendidly inflected.
Three leaves were also immersed 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, Acetate of.—Four leaves were immersed together in a
vessel containing 120 minims of a solution of one part to 437 of water;
so that each received, if the leaves absorbed equally, 34; 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, Nitrate of.—Four leaves were immersed, as in the last
case, in 120 minims of a solution of one part to 437 of water; after 1
hr. 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 —Your leaves were immersed, as above, in 120
minims of a solution of one part to 487 of water. After 1 hr. 5 m.
the glands were darkened; after + 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.—¥our 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 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.
Yalcium, Acetate of.—Four leaves were immersed in 120 minims of
a solution of one part to 437 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-oft end of the petiole. I then added some of the solution
(1 gr. to 20 oz.) of phosphate 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.
Cuar. VIIL] EFFECTS OF VARIOUS SALTS. 149
Calcium, Nitrate of —Four leaves were immersed in 120 minims of
a solution of one part to 437 of water, but were not affected in 24 hrs.
I then added some of the solution of phosphate of ammonia (1 gr. to
20 0z.), but this caused only very slight inflection 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 5 m. and 10m. 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, Acetate, 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 0z.) 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 degree 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.
Magnesium, Sulphate of.—Half-minims of a solution of one part to
218 of water were placed on the discs of ten leaves, and produced no
effect.
Barium, Acetate 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
inflection, but the glands were blackened. ‘The leaves were then
placed in a solution (1 gr. to 20 0z.) of phosphate of ammonia, which
caused after 26 hrs. only a little inflection in two of the leaves.
Barium, Nitrate of.—F¥our 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 in 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 g
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
150 DROSERA ROTUNDIFOLIA. (Cuar. VII.
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 —Vhree leaves were immersed in ninety
minims of a solution of one part to 437 of water; after 22 m. there
was some slight inflection, which in 48 m. became well pronounced ;
the giands were now blackened. After 5 hrs. 35 m. all the tentacles
closely inflected; after 24 hrs. still 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 inflected.
Aluminium, Nitrate of —Four leaves were immersed in 120 minims
of a solution of one part to 437 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 437 of water that each received 30 minims,
containing 5}; of a grain, or 4°048 mg., of the chloride. There was
some inflection in 8 m., which became extreme in 45 m. In 8 hrs. the
surrounding fluid was coloured purple, and the glands were blackened.
After 6 hrs. the leaves were transferred to water; next morning they
were found discoloured and evidently killed. The secretion decomposes
the chloride very readily ; the glands themselves becoming coated with
za
Otar, VIIL] EFFECTS OF VARIOUS SALTS. 151
the thinnest layer of metallic gold, and particles float about on the
surface of the surrounding fluid.
Lead, Chloride of.-—Yhree leaves were immersed in ninety minims
of a solution of one part to 437 of water. After 23 hrs. there was not
a trace of inflection; the glands were not blackened, and the leaves
did not appear injured. They were then transferred 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 437 of water.
After 4 hrs. no effect; after 6 hrs. 30 m. all four leaves had their sub-
marginal tentacles inflected; after 22 hrs. every single tentacle and
the blades were closely inflected. The surrounding fluid was now
coloured pink. The leaves were washed and transferred to water, but
next morning were evidently dead. ‘his chloride is a deadly poison,
but acts slowly.
Antimony, Tartrate of.—Three leaves were immersed in ninety
minims ofa 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 437 of water; three
leaves were immersed in ninety minims; in 25 m. considerable inflec-
tion; in 1 hr. 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.
Iron, Chloride of.—Three leaves were immersed in ninety minims of
a solution of one part to 437 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 437 of water; three leaves were
immersed in ninety minims; in 30 m. some, and in 1 hr. considerable,
inflection; after 2 hrs. all the tentacles closely inflected, 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. ee
Copper, Chloride of.—Three leaves immersed in ninety minims of a
solution of one part to 437 of water; after 2 hrs. some inflection ; after
152 DROSERA ROTUNDIFOLIA. [Cuar. VII.
3 hrs. 45 m. tentacles closely inflected, with the glands blackened.
After 22 hrs. still closely inflected, and the leaves flaccid. Placed im
pure water, next day evidently dead. A rapid poison.
Nickel, Chloride of.—Three leaves immersed in ninety minims of à
solution of one part to 437 of water; in 25 m. considerable inflection,
and in 3 hrs. all the tentacles closely inflected. After 22 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, Chloride ọf.—Three leaves immersed in ninety minims of a.
solution of one part to 437 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 437 of water; in 6 m. some inflection, which
became immense after 48 m. After 3 hrs. the glands 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 inflected, 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 the corresponding salts of potash do not cause
inflection, and some of them are poisonous. Two of them,
however, viz. the oxalate and iodide of potash, slowly in-
duced a slight and rather doubtful amount of inflection.
This difference between the two series is interesting, as Dr.
3urdon 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 potas-
sium 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 phosphate of potash is
Car. VHI] CONCLUDING REMARKS, SALTS. 153
quite inefficient. The great power of the former is probably
due to the presence of phosphorus, as in the cases of phos-
phate 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
to 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 and potassium,* which act
so differently; therefore we might expect that its action
would be intermediate. We see, also, that cæsium 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
doubtfully, 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 cad-
mium, 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 quick-
ness, 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
* Miller’s ‘ Elements of Chemistry,’ 3rd edit. pp. 337, 448.
154 DROSERA ROTUNDIFOLIA. [CHAF VIII.
different effects of phosphate of ammonia on leaves previously
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 inflection. After
describing the experiments, a few concluding remarks will
be added.
ACIDS, MUCH DILUTED, WHICH CAUSE ACIDS, DILUTED TO THE SAME
INFLECTION. DEGREE, WHICH DO NOT CAUSE
INFLECTION.
. Gallic; not poisonous.
. Tannic; not poisonous.
. Tartaric ; not poisonous.
. Citric ; not poisonous.
. Uric; (2) not poisonous.
1. Nitric, strong inflection; poi-
sonous.
2. Hydrochloric, moderate and slow
inflection ; not poisonous.
3. Hydriodic, strong inflection ;
poisonous.
4. lodic, strong inflection ; poisonous.
5. Sulphuric, strong inflection;
somewhat poisonous.
6. Phosphoric, strong inflection ;
poisonous,
7. Boracic, moderate and rather
slow inflection; not poisonous.
8. Formic, very slight inflection;
not poisonous.
9, Acetic, strong and rapid inflec-
tion ; poisonous.
10, Propionic, strong but not very
rapid inflection ; poisonous.
11. Oleic, quick inflection; very
poisonous.
12, Carbolic, very slow inflection;
poisonous,
13. Lactic, slow and moderate inflec-
tion ; poisonous.
14. Oxalic, moderately quick inflec-
tion; very poisonous.
15. Malic, very slow but considerable
inflection; not poisonous.
16. Benzoic,* rapid inflection; very
poisonous.
17. Succinic, moderately quick in-
flection ; moderately poisonous.
18. Hippuric, rather slow inflection ;
poisonous.
19. Hydrocyanic, rather rapid in-
flection ; very poisonous.
Cue Oboe
Car. VILL] THE EFFECTS OF ACIDS. 159
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 reccived >}, of
a grain, or 4°048 mg. This strength was chosen for this and most of
the following experiments, as it is the same 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 surrounding 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 inflected; 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 produced 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.
Hydrochloric 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 coloured
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 fourth 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 437 of water; three leaves were immersed
as before, each in thirty minims. After 45 m. the glands were dis-
coloured, 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 evidently 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.
lodic Acid.—One to 437 of water; three leaves were immersed, 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.
156 DROSERA ROTUNDIFOLIA. [Cuap. VIIE
Sulphuric Acid.—One to 487 of water; four leaves were immersed
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 begin-
ning 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 brs. all the tentacles closely inflected,
and many glands colourless : surrounding fluid pink. Left in water
for two days and a half, remained in the same state and appeared dead.
Boracic Acid.—One to 437 cf water; four leaves were immersed.
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 evidently dead. This acid is far more powerful than
formic, and is highly poisonous. Half-minim drops of a stronger
mixture (viz. one 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 paralysed the leaves, for drops
of a weaker mixture caused much inflection; nevertheless, the leaves
all died after two days.
Propionic Acid.—Three leaves were immersed in ninety minims of
a mixture of one part to 437 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
iu 8 hrs. all three leaves were closely inflected. Next morning, alter
ETIE
Cuar. VIIL] THE EFFECTS OF ACIDS. 157
20 hrs., most of the glands were very pale, 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 alterwards
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 no means always,
inflected. Two leaves were also immersed in this oil, and there was
no inflection for about 12 hrs.; but after 23 hrs. almost all the tentacles
were inflected. Three leaves were likewise immersed 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.—\wo leaves were immersed in sixty minims of a
solution of 1 gr. to 437 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 so
apidly or powerfully as might have been expected from its known de-
structive 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,
* See articles on Glycerine and Oleic Acid in Watts’ ‘ Dict. of Chemistry.’
158 DROSERA ROTUNDIFOLIA. [Cuap. VIII.
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 ;
thongh 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 inthe phosphate
for 48 hrs., and remained in the same state, with almest all their
glands disccloured. The protoplasm within the cells was not ag-
gregated, 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 there
was no inflection; after 7 hrs. 80 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 inflected ; 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 1312 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, Tartaric, and Citrie Acids.—One part to 437 of
water. Three or four leaves were immersed, each in 30 minims of these
four solutions, so that each leaf received jj; of a grain, or 4°048 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 accounted fer by the action
of water. No great amount of mucus was secreted. They were then
ce ee O E ee Te ee aT a ee T
Cuar. VIII.) THE EFFECTS OF ACIDS. 159
placed in water, and after two days partially re-expanded. Hence this
acid is not poisonous.
Oxalic Acid.—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 437 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 submarginal 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 12 m. 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 one gr. to 437 of water; after 4 hrs. 15 m. considerable,
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 4; 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 solution 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 have 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 437 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 killed.
160 DROSERA ROTUNDIFOLIA. [Cuar. VII.
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 strongly inflected, and the surrounding fluid coloured pink ;
alter 6 hrs. ail closely inflected. After 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 &
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
boiling 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-nsinim 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 zp of a minim,
or *00296 c.c.) of Scheele’s mixture (containing 4 per cent. of anhydrous
acid); 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 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 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
* According to M. Fournier (‘De cause the stamens of Berberis in-
la Fécondation dans les Phanéro- stantly to close; though drops of
games,’ 1863, p. 61) drops of acetic, water have no such power, which
hydrocyanic, and sulphuric acid latter statement I can confirm.
Pa
so eam ei Dis
$
f
$
H
Cuar. VIEL] CONCLUDING REMARKS, ACIDS. 161
and many other acids of the same strength, and is not
poisonous. This is an interesting 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 inducing 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 discussion, that
most of the acids are poisonous, often highly so. Diluted
acids are known to induce negative osmose,* and the
poisonous action of so many acids on Drosera is, perhaps,
connected with this power, for we have seen that the fluid in
which they were immersed often became pink, and the
glands pale-colonred or white. Many of the poisonous acids,
such as hydriodic, benzoic, hippuric, and carbolic (but I
neglected to record all the cases), caused the secretion 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 tendency; in these two latter cases the sur-
rounding 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 cer-
tain acids, were soon acted on by phosphate of ammonia; on
the other hand, they were not thus affected after immersion
in certain other acids. To this subject, however, I shall
have to recur.
* Miller’s ‘Elements of Chemistry,’ part i. 1867, p. 87,
162 . DROSERA ROTUNDIFOLIA. (Cuar. IX.
CHAPTER IX.
THE EFFECTS OF CERTAIN ALKALOID POISONS, OTHER SUBSTANCES AND
VAPOURS.
Strychnine, salts of—Quinine, sulphate of, does not soon arrest the move-
ment of the protoplasm—Other salts of quinine—Digitaline—Nicotine—
Atropine — Veratrine — Colchicine — Theine — Curare—Morphia—Hyos-
eyamus—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
solutions retard or prevent the subsequent action of phosphate of
ammonia—Aleohol innocuous, its vapour narcotic and poisonous—Chloro-
form, 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
ghz of a grain, or °0675 mg. In 2 hrs. 80 m. the outer tentacles on
some of them were inflected, but in an irregular 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-ex-
panded and appeared quite healthy. Hence the poisonous action of
strychnine seems confined to the glands which have absorbed it; never-
theless, these glands transmit a motor impulse to the exterior tentacles.
Minute drops (about 34 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
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
TARY rn
RIGA NAD aan asa reac emt ee
Cmar. IX] ALKALOID POISONS. 163
latter, however, on being subsequently 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 continued 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
437 of water were placed on the discs of six leaves; after 24 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 0z.) 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 487 of water; so that each received
Jj; 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 aggregated. 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 respectively 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 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 24,5 part of its weight. Five leaves were immersed,
each in thirty minims of this solution, which tasted bitter. In less
M 2
164 DROSERA ROTUNDIFOLIA. [Cuar. IX:
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 few 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,
afier an immersion of 3 hrs. 15 m., was carefully examined; the pro-
toplasm 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 movement 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 pro-
toplasm presenting a very unusual appearance; for it 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
* ‘Quarterly Journal of Microscopical Science,’ April 1874, p. 185.
Cmar. IX.) <. ALKALOID POISONS. 165
much injured or quite killed. It is clear that this salt is highly
poisonous.*
Acetate 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 437 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; so that this salt induces,
though rather slowly, well-marked inflection. ‘These leaves, on being
left in water for 48 hrs., almost completely re-expanded, but the glands
were much discoloured. Hence this salt is not poisonous in any high
degree. The different action of the three foregoing salts of quinine is
singular.
Digitaline—Half-minims of a solution of one part to 437 of water
were placed on the discs of five leaves. In 3 hrs. 45 m. some of them
had their tentacles, and one had its blade, moderately inflected. After
8 hrs. three of them were well inflected; the fourth had only a few
tentacles inflected, and the fifth (an old leaf) was not at all affected.
They remained in nearly the same state for two days, but the glands
on their discs became pale. On the third day the leaves appeared
much injured. Nevertheless, when bits of meat were placed on two of
them, the outer tentacles became inflected. A minute drop (about 3%
of a minim) of the solution was applied to three glands, and after 6
hrs. all three tentacles were inflected, but next day had nearly re-
expanded ; so that this very small dose of sslo5 of a grain (*00225
mg.) acts on a tentacle, but is not poisonous. lt appears from these
several facts that digitaline causes inflection, and poisons the glands
which absorb a moderately large amount.
Nicotine.—'The secretion round several glands was touched with a
minute drop of the pure fluid, and the glands were instantly blackened ;
the tentacles becoming inflected in a few minutes. Two leaves were
immersed in a weak solution of two drops to 1 oz., or 437 grains, of
water. When examined after 3 hrs. 20 m., only twenty-one tentacles
* Binz found several years ago corpuscles, which become * rounded
(as stated in ‘The Journal of and granular.” In the tentacles of
Anatomy and Phys.) November Drosera the aggregated masses of
1872, p. 195) that quinia is an protoplasm, which appeared killed
energetic poison to low vegetable by the quinine, likewise presented a
and animal organisms. Even one granular appearance. A similar
part added to 4000 parts of blood appearance is caused by very hot
arrests the movements of the white water.
166 DROSERA ROTUNDIFOLIA. (Cne. IX.
on one leaf were closely inflected, and six on the other slightly so; but
all the glands were blackened, or very dark coloured, with the pro-
toplasm in all the cells of all the tentacles much aggregated and dark
coloured. The leaves were not quite killed, for on being placed ina
little solution of carbonate of ammonia (2 grs. to 1 oz.) a few more
tentacles became inflected, the remainder not being acted on during
the next 24 hrs.
Half-minims of a stronger solution (two drops to 4 oz. of water) were
placed on the discs of six leaves, and in 30 m. all those tentacles
became inflected; the glands of which had actually touched the solu-
tion, as shown by their blackness; but hardly any motor influence was
transmitted to the outer tentacles. After 22 hrs. most of the glands on
the discs appeared dead; but this could not have been the case, as,
when bits of meat were placed on three of them, some few of the outer
tentacles were inflected in 24 hrs. Hence nicotine has a great tendency
to blacken the glandsard to induce aggregation of the protoplasm, but,
except when pure, has very moderate power of inducing inflection, and
still less power of causing a motor influence to be transmitted from the
discal glands to the outer tentacles. It is moderately poisonous.
Atropine.—A grain was added to 487 grains of water, but was not
all dissolved ; another grain was added to 437 grains of a mixture of
one part of alcohol to seven parts of water; and a third solution was
made by adding one part of valerianate of atropine to 437 of water.
Half-minims of these three solutions were placed, in each case, on the
discs of six leaves; but no effect whatever was produced, excepting
that the glands on the discs to which the valerianate was given were
slightly discoloured. The six leaves on which drops of the solution of
atiopine in diluted alcohol had been left for 21 hrs. were given bits of
meat, and all became in 24 hrs. fairly well inflected; so that atropine
does not excite movement, and is not poisonous. I also tried in the
same manner the alkaloid sold as daturine, which is believed not to
difier from atropine, and it produced no effect. Three of the leaves on
which drops of this latter solution had been left for 24 hrs. were like-
wise given bits of meat, and they had in the course of 24 hrs. a good.
many of their submarginal tentacles inflected.
Veratrine, Colchicine, Theine-—Solutions were made of these three
alkaloids by adding one part to 437 of water. Half-minims were
placed, in each case, on the discs of at least six leaves, but no inflection
was caused, except perhaps a very slight amount by the theine. Half-
minims of a strong infusion of tea likewise produced, as formerly
stated, no effect. I also tried similar drops of an infusion of one part
of the extract of colchicum, sold by druggists, to 218 of water; and the
leaves were observed for 48 hrs., without any effect being produced.
The seven leaves on which drops of veratrine had been left for 26 hrs.
were given bits of meat, and after 21 hrs. were well inflected. These
three alkaloids are therefore quite innocuous.
Curare.—One part of this famous poison was added to 218 of water,
and three leaves were immersed in ninety minims of the filtered solu-
Cuap. IX.] ALKALOID POISONS. 167
tion, In 3 hrs. 30 m. some of the tentacles were a little inflected ;
as was the blade of one, after 4 hrs. After 7 hrs. the glands were
wonderfully blackened, showing that matter of some kind had been
absorbed. In 9 hrs. two of the leaves had most of their tentacles sub-
inflected, but the inflection did not increase in the course of 24 hrs. One
of these leaves, after being immersed for 9 hrs. in the solution, was
placed in water, and by next morning had largely re-expanded; the
other two, after their immersion for 24 hrs., were likewise placed in
water, and in 24 hrs. were considerably re-expanded, though their
glands were as black as ever. Half-minims were placed on the discs of
six leaves, and no inflection ensued; but after three days the glands on
the discs appeared rather dry, yet to my surprise were not blackened.
On another occasion drops were placed on the discs of six leaves, and a
considerable amount of inflection was soon caused; but as I had not
filtered the solution, floating particles may have acted on the glands,
After 24 hrs. bits of meat were placed on the discs of three of these
leaves, and next day they became strongly inflected. As I at first
thought that the poison might not have been dissolved in pure water,
one grain was added to 437 grains of a mixture of one part of alcohol to
seven of water, and half-minims were placed on the discs of six leaves,
These were not at all affected, and when after a day bits of meat
were given them, they were slightly inflected in 5 hrs., and closely
after 24 hrs. It follows from these several facts that a solution of
curare induces a very moderate degree of inflection, and this may
perhaps be due to the presence of a minute quantity of albumen. It
certainly is not poisonous. The protoplasm in one of the leaves, which
had been immersed for 24 hrs., and which had become slightly in-
flected, had undergone a very slight amount of aggregation—not more
than often ensues from an immersion of this length of time in water.
Acetate of Morphia.—I tried a great number of experiments with
this substance, but with no certain result. A considerable number of
leaves were immersed from between 2 hrs. and 6 hrs. in a solution of
one part to 218 of water, and did not become inflected. Nor were
they poisoned; for when they were washed and placed in weak
solutions of phosphate and carbonate of ammonia, they soon became
strongly inflected, with the protoplasm in the cells well aggregated.
If, however, whilst the leaves were immersed in the morphia, phos-
phate of ammonia was added, inflection did not rapidly ensue.
Minute drops of the solution were applied in the usual manner to the
secretion round between thirty and forty glands; and when, after an
interval of 6 m., bits of meat, a little saliva, or particles of glass, were
placed on them, the movement of the tentacles was greatly retarded,
But on other occasions no such retardation occurred. Drops of water
similarly applied never have any retarding power. Minute drops of a
solution of sugar of the same strength (one part to 218 of water)
sometimes retarded the subsequent action of meat and of particles of
glass, and sometimes did not do so. At one time I felt convinced
that morphia acted as a narcotic on Drosera, but after having found in
168 DROSERA ROTUNDIFOLIA. (Cua. IX.
what a singular manner immersion in certain non-poisonous salts and
acids prevents the subsequent action of phosphate of ammonia,
whereas other solutions have no such power, my first conviction seems
very doubtful.
Extract of Hyoscyamus.—Several leaves were placed, each in thirty
minims of an infusion of 3 grs. of the extract sold by druggists to 1 oz.
of water. One of them, after being immersed for 5 hrs. 15 m., was
not inflected, and was then put into a solution (1 gr. to 1 oz.) of car-
bonate of ammonia; after 2 hrs. 40 m. it was found considerably
inflected, and the glands much blackened. Four of the leaves, after
being immersed for 2 hrs. 14 m., were placed in 120 minims of a
solution (1 gr. to 20 oz.) of phosphate of ammonia; they had already
become slightly inflected from the hyoscyamus, probably owing to the
presence of some albuminous matter, as formerly explained, but the
inflection immediately increased, and after 1 hr. was strongly pro-
nounced; so that hyoscyamus does not act as a narcotic or poison.
Poison from the Fang of a Living Adder.—Minute drops were
placed on the glands of many tentacles; these were quickly inflected,
just as if saliva had been given them. Next morning, after 17 hrs.
vO m., all were beginning to re-expand, and they appeared uninjured.
Poison from the Cobra.a—Dr. Fayrer, well known from his investi-
gations on the poison of this deadly snake, was so kind as to give me
some in a dried state. It is an albuminous substance, and is believed
to replace the ptyaline of saliva.* A minute drop (about 34 of a
minim) of a soluticn of one part to 437 of water was applied to the
secretion round four glands ; so-that each received only about ṣ5157y of
a grain (‘0016 mg.) The operation was repeated on four other
glands; and in 15 m. several of the eight tentacles became well
inflected, and all of them in 2 hrs. Next morning, after 24 hrs., they
were still inflected, and the glands of a very pale piak colour. After
an additional 24 hrs, they were nearly re-expanded, and completely so
on the succeeding day; but most of the glands remained almost
white.
Half-minims of the same solution were placed on the discs of three
leaves, so that each received 54, ofa grain (°0675 mg.); in 4 hrs. 15 m.
the outer tentacles were much inflected; and after 6 hrs. 30 m.
those on two of the leaves were closely inflected and the blade of one;
the third leaf was only moderately atfected. The leaves remained in
the same state during the next day, but after 48 hrs. re-expanded,
Three leaves were now immersed, each in thirty minims of the
solution, so that each received y% of a grain, or 4°048 mg. In 6 m.
there was some inflection, which steadily increased, so that after 2 hrs.
230 m. all three leaves were closely inflected; the glands were at first
somewhat darkened, then rendered pale; and the protoplasm within
the cells of the tentacles was partially aggregated. The little masses
* Dr. Fayrer, ‘The Thanatophidia of India,’ 1872, p. 150.
Cuap. IX] -POISON OF THE COBRA. 169
of protoplasm were examined after 3 hrs., and again after 7 hrs., and
on ne other occasion have | seen them undergoing such rapid changes
of form. After 8 hrs. 30 m. the glands had becume quite white; they
had not secreted any great quantity of mucus. The leaves were now
placed in water, and after 40 hre. re-expanded, showing that they were
not much or at all injured. During their immersion in water the
protoplasm within the cells of the tentacles was occasionally examined,
and always found in strong movement.
Two leaves were next immersed, each in thirty minims of a much
stronger solution, of one part to 109 of water; so that each received 4
of a grain, or 16°2 mg. After 1 hr. 45 m. the submarginal tentacles
were strongly inflected, with the glands somewhat pale; after 3 hrs.
50 m. both leaves had all their tentacles closely inflected and the
glands white. Hence the weaker solution, as in so many other cases,
induced more rapid inflection than the stronger one; but the glands
were sooner rendered white by the latter. After an immersion of
24 hrs. some of the tentacles were examined, and the protoplasm, still
of a fine purple colour, was found aggregated into chains of small
globular masses. These changed their shapes with remarkable
quickness. After an immersion of 48 hrs. they were again examined,
and their movements were so plain that they could easily be seen
under a weak power. The leaves were now placed in water, and after
24 hrs. (i.e. 72 hrs. from their first immersion) the little masses of pro-
toplasm, which had become of a dingy purple, were still in strong
movement, changing their shapes, coalescing, and again separating.
In 8 hrs, after these two leaves had been placed in water (i.e. in 56
hrs. after their immersion in the solution) they began to re-expand,
and by the next morning were more expanded. After an additional
day (i.e. on the fourth day after their immersion in the solution) they
were largely, but not quite fully, expanded. The tentacles were now
examined, and the aggregated masses were almost wholly re-dissolved ;
the cells being filled with homogeneous purple fluid, with the ex-
ception here and there of a single globular mass. We thus see how
completely the protoplasm bad escaped all injury from the poison. As
the glands were soon rendered quite white, it occurred to me that
their texture might have been modified in such a manner as to prevent
the poison passing into the cells beneath, and consequently that the
protoplasm within these cells had not been at all affected. Accordingly
I placed another leaf, which had been immersed for 48 hrs. in the
poison and afterwards for 24 hrs. in water, in a little solution of one
part of carbonate of ammonia to 218 of water; in 30 m. the protoplasm
in the cells beneath the glands became darker, and in the course of
24 hrs. the tentacles were filled down to their bases with dark-coloured
spherical masses. Hence the glands had not lost their power of
absorption, as far as the carbonate of ammonia is concerned,
From these facts it is manifest that the poison of the cobra, though
so deadly to animals, is not at all poisonous to Drosera; yet it causes
strong and rapid inflection of the tentacles, and soon discharges all
170 DROSERA ROTUNDIFOLIA. [Omar IX.
colour from the glands. It seems even to act as a stimulant to the
protoplasm, for after considerable experience in observing the move-
ments of this substance in Drosera, I have never seen it on any other
occasion in so active a state. I was therefore anxious to learn how
this poison affected animal protoplasm; and Dr. Fayrer was so kind as
to make some observations for me, which he has since published.*
Ciliated epithelium from the mouth of a frog was placed in a solution
of *03 gramm to 4°6 cubic cm. of water; others being placed at the
same time in pure water for comparison. The movements of the cilia
in tne solution seemed at first increased, but soon languished, and
after between 15 and 20 minutes ceased; whilst those in the water
were still acting vigorously. The white corpuscles of the blood of a
frog, and the cilia on two infusorial animals, a Paramecium and
Volvox, were similarly affected by the poison. Dr. Fayrer also found
that the muscle of a frog lost its irritability after an immersion of
20 m. in the solution not then responding to a strong electrical current.
On the other hand, the movements of the cilia on the mantle of an
Unio were not always arrested, even when left for a considerable time
in a very strong solution. On the whole, it seems that the poison of
the cobra acts far more injuriously on the protoplasm of the higher
animals than on that of Drosera.
There is one other point which may be noticed. I have occasionally
observed that the drops of secretion round the glands were rendered
somewhat turbid by certain solutions, and more especially by some
acids, a film being formed on the surfaces of the drops; but I never
saw this effect produced in so conspicuous a manner as by the cobra
poison. When the stronger solution was employed, the drops appeared
in 10 m. like little white rounded clouds. After 48 hrs. the secretion
was changed into threads and sheets of a membranous substance,
including minute granules of various sizes.
Camphor.—Some scraped camphor was left for a day in a bottle
with distilled water, and then filtered. A solution thus made is said
to contain 5y of its weight of camphor; it smelt and tasted of this
substance. ‘l’en leaves were immersed in this solution; after 15 m.
five of them were well inflected, two showing a first trace of movement
in 11 m. and 12 m.; the sixth leaf did not begin to move until 15 m.
had elapsed, but was fairly well inflected in 17 m. and quite closed in
24 m. ; the seventh began to move in 17 m., and was completely shut
in 26m. The eighth, ninth, and tenth leaves were old and of a very
dark red colour, and these were not inflected after an immersion of
24 hrs.; so that in making experiments with camphor it is necessary
to avoid such leaves. Some of these leaves, on being left in the
solution for 4 hrs., became of a rather dingy pink colour, and secreted
much mucus; although their tentacles were closely inflected, the
protoplasm within the cells was not at all aggregated. On another
* «Proceedings of Royal Society,’ Feb. 18, 1875.
ee
Cuar. IX.] CAMPHOR. 171
occasion, however, after a longer immersion of 24 hrs., there was well-
marked aggregation. A solution made by adding two drops of campho-
rated spirits to an ounce of water did not act on one leaf; whereas
thirty minims added to an ounce of water acted on two leaves immersed
together. -
S j | Length of
Z | Length of | | Time between
~ | ae the Immersion
s Immersion A Length of Time between the Act of Brushing | of the Leaves
8 | the Solution | and the Inflection of the Tentacles. peg EE
£ | of Camphor. | Sign of the
is | | Inflection of the
: | | Tentacles.
1 i 3m. considerable inflection; 4 m. all e
Pin t the tentacles except 3 or 4 inflected. :
2 5m. | 6 m. first sign of inflection. | 11 m.
6 m. 30 s. slight inflection; 7 m. 398.) 41 m. 30s.
a k
Co ico Tis Pee | . }
{ plain inflection. |
x 2 m. 30 s.a trace of inflection; 3 m. A
4 4m.30s. i 7m,
plain ; 4 m. strongly marked.
(9 2 ý Ps tan: R
2 m. 30 s. a trace of inflection m. : ?
5 4m. Heir z - F | 6m. 30s.
plain inflection. j
2 m. 30 s. decided inflection; 3 m. 50 s. ; 30 ¢
6 4m . é 6 m. 30 s.
strongly marked.
. 2 m. 30 s. slight inflection; 3 m. plain;) ș& aN a
7 4m. f eee >m. 30 s.
4 m. well marked. Í
8 2 (2 m. trace of inflection; 3 m. consider-) 5m
3 m. : : 5 5m.
, \ able, 6 m. strong inflection.
2m. trace of inflection; 3 m. consider-) -
9 3 m. ; : ae om.
able, 6 m. strong inflection.
M. Vogel has shown* that the flowers of various plants do not
wither so soon when their stems are placed in a solution of camphor
as when in water; and that if already slightly withered, they recover
more quickly. The germination of certain seeds is also accelerated by
the solution. So that camphor acts as a stimulant, and it is the only
known stimulant for plants. I wished, therefore, to ascertain whether
camphor would render the leaves of Drosera more sensitive to
mechanical irritation than they naturally are, Six leaves were left in
distilled water for 5 m. or 6 m., and then gently brushed twice or
thrice, whilst still under water, with a soft camel-hair brush; but no
movement ensued. Nine leaves, which had been immersed in the
above solution of camphor for the times stated in the above table,
* <Gardener’s Chronicle,’ 1874, p. 671. Nearly similar observations were
made in 1798 by B. S. Barton.
172 DROSERA ROTUNDIFOLIA. (Cuar. IX.
were next brushed only once with the same brush and in the same
manner us before; the results are given in the table. My first trials
were made by brushing the leaves whilst still immersed in the
solution; but it occurred to me that the viscid secretion round the
glands would thus be removed, and the camphor might act more
effectually on them. In all the above trials, therefore, each leaf
was taken out of the solution, waved for about 15 s. in water, then
placed in fresh water and brushed, so that the brushing would not
allow the freer access of the camphor; but this treatment made no
difference in the results.
Other leaves were left in the solution without being brushed; one
of these first showed a trace of inflection after 11 m.; a second after
12 m.; five were not inflected until 15 m. had elapsed, and two not
until a few minutes later. On the other hand, it will be seen in the
right-hand column of the table that most of the leaves subjected to the
solution, and which were brushed, became inflected in a much shorter
time. The movement of the tentacles of some of these leaves was so
rapid that it could be plainly seen through a very weak lens.
Two or three other experiments are worth giving. A large old leaf,
after being immersed for 10 m. in the solution, did not appear likely
to be soon inflected; so I brushed it, and in 2 m. it began to move,
and in 8 m. was completely shut. Another leaf, after an immersion
of 15 m., showed no signs of inflection, so was brushed, and in 4 m.
was grandly inflected. A third leaf, after an immersion of 17 m.,
likewise showed no signs of inflection; it was then brushed, but did
not move for 1 hr.; so that here was a failure. It was again brushed,
and now in 9 m. a few tentacles became inflected; the failure therefore
was not complete.
We may conclude that a small dose of camphor in solution is a
powerful stimulant to Drosera. Jt not only soon excites the tentacles
to bend, but apparently renders the glands sensitive to a touch, which
by itself does not cause any movement. Or it may be that a slight
mechanical irritation not enough to cause any inflection yet gives some
tendency to movement, and thus reinforces the action of the camphor.
This latter view would have appeared to me the more probable one,
had it not been shown by M. Vogel that camphor is a stimulant in
other ways to various plants and seeds,
Two plants bearing four or five leaves, and with their roots in a
little cup of water, were exposed to the vapour of some bits of camphor
(about as large as a filbert nut), under a vessel holding ten fluid
ounces. After 10 hrs. no inflection ensued; but the glands appeared
to be secreting more copiously. ‘The leaves were in a narcotised con-
dition, for on bits of meat being placed on two of them, there was no
inflection in 3 hrs..15 m., and even after 13 hrs. 15 m. only a few of
the outer tentacles were slightly inflected; but this degree of move-
ment shows that the leaves had not been killed by an ex posure during
10 hrs, to the vapour of camphor.
Oil of Caraway.—Water is said to dissolve about a thousandth
eters
E ESEE SA EEEN E ARE
Cuar. IX.) ESSENTIAL OILS, ETC. 173
part of its weight of this oil. A drop was added to an ounce of water
and the bottle occasionally shaken during a day; but many minute
globules remained undissolved. Five leaves were immersed in this
mixture; in from 4 m. to 5 m. there was some inflection, which
became moderately pronounced in two or three additional minutes.
After 14 m. all five leaves were well, and some of them closely,
inflected. After 6 hrs. the glands were white, and much mucus had
been secreted. The leaves were now flaccid, of a peculiar dull-red
colour, avd evidently dead. One of the leaves, after an immersion of
4 m. was brushed, like the leaves in the camphor, but this produced
no effect. A plant with its roots in water was exposed under a 10-o0z.
vessel to the vapour of this oil, and in 1 hr. 20 m. one leaf showed a
trace of inflection. After 5 hrs. 20 m. the cover was taken off and
the leaves examined; one had all its tentacles closely inflected, the
second about half in the same state; and the third all sub-inflected.
The plant was left in the open air for 42 hrs., but not a single tentacle
expanded ; all the glands appeared dead, except here and there one,
which was still secreting. It is evident that this oil is highly exciting
and poisonous to Drosera.
Oil of Cloves.—A mixture was made in the same manner as in the
last case, and three leaves were immersed in it. After 30 m. there
was only a trace of inflection which never increased. After 1 hr. 30 m.
the glands were pale, and after 6 hrs. white. No doubt the leaves
were much injured or killed.
Turpentine.—Small drops placed on the discs of some leaves killed
them, as did likewise drops of creosote. A plant was left for 15 m.
under a 12-oz. vessel, with its inner surface wetted with twelve drops
of turpentine; but no movement of the tentacles ensued. After 24 hrs.
the plant was dead.
Glycerine—Half-minims were placed on the discs of three leaves ;
in 2 hrs. some of the outer tentacles were irregularly inflected; and in
19 hrs. the leaves were flaccid and apparently dead ; the glands which
had touched the glycerine were celourless. Minute drops (about 4; of
a minim) were applied to the glands of several tentacles, and in a few
minutes these moved and soon reached the centre. Similar drops of a
mixture of four dropped drops to 1 oz. of water were likewise applied
to several glands; but only a few of the tentacles moved, and these
very slowly and slightly. Half minims of this same mixture placed
on the discs of some leaves caused, to my surprise, no inflection in the
course of 48 hrs. Bits of meat were then given them, and next day
they were well inflected; notwithstanding that some of the discal
glands had been rendered almost colourless. Two leaves were immersed
in the same mixture, but only for 4 hrs.; they were not inflected, and
on being afterwards left for 2 hrs, 30 m. in a solution (1 gr. to 1 0%.)
of carbonate of ammonia, their glands were blackened, their tentacles
inflected and the protoplasm within their cells aggregated. It appears
from these facts that a mixture of four drops of glycerine to an ounce
of water is not poisonous, and excites very little inflection; but that
174 DROSERA ROTUNDIFOLIA. [Cuar. IX.
pure glycerine is poisonous, and if applied in very minute quantities
to the glands of the outer tentacles causes their inflection.
The Effects of Immersion in Water and in various Solutions on
the subsequent Action of Phosphate and Carbonate of Ammonia.—
We have seen in the third and seventh chapters that immersion in
distilled water causes after a time some degree of aggregation of the
protoplasm, and a moderate amount of inflection, especially in the
case of plants which have been kept at a rather high temperature.
Water does not excite a copious secretion of mucus. We have here to
consider the effects of immersion in various fluids on the subsequent
action of salts of ammonia and other stimulants. Four leaves which
had been left for 24 hrs. in water were given bits of meat, but did not
clasp them. Ten leaves, after a similar immersion, were left for 24 hrs.
in a powerful solution (1 gr. to 20 oz.) of phosphate of ammonia, and
only one showed even a trace of inflection. Three of these leaves, on
being left for an additional day in the solution, still remained quite
unaffected. When, however, some of these leaves, which had been
first immersed in water for 24 hrs., and then in the phosphate for
24 hrs. were placed in a solution of carbonate of ammonia (one part
to 218 of water), the protoplasm in the cells of the tentacles became
in a few hours strongly aggregated, showing that this salt had been
absorbed and taken etfect.
A short immersion in water for 20 m. did not retard the subsequent
action of the phosphate, or of splinters of glass placed on the glands ;
but in two instances an immersion for 50 m. prevented any effect from
a solution of camphor. Several leaves which had been left for 20 m.
in a solution of one part of white sugar to 218 of water were placed in
the phosphate solution, the action of which was delayed; whereas a
mixed solution of sugar and the phosphate did not in the least interfere
with the effects of the latter. Three leaves, after being immersed for
20 m. in the sugar solution, were placed in a solution of carbonate of
ammonia (one part to 218 of water); in 2 m. or 3 m. the glands
were blackened, and after 7 m. the tentacles were considerably inflected,
so that the solution of sugar, though it delayed the action of the
phosphate, did not delay that of the carbonate. Immersion in a
similar solution of gum arabic for 20 m. had no retarding action on
the phosphate. Three leaves were left for 20 m. in a mixture of one
part of alcohol to seven parts of water, and then placed in the
phosphate solution: in 2 hrs. 15 m. there was a trace of inflection in
one leaf, and in 5 hrs. 80 m. a second was slightly affected; the
inflection subsequently increased, though slowly. Hence diluted
alcohol, which, as we shall see, is hardly at all poisonous, plainly
retards the subsequent action of the phosphate.
It was shown in the last chapter that leaves which did not become
inflected by nearly a day’s immersion in solutions of various salts and
acids behaved very differently from one another when subsequently
placed in the phosphate solution. I here give a table summing up
the results.
aiiai
Cuar. IX.] EFFECTS OF PREVIOUS IMMERSION. 175
fg
Name of tbe Salts and
Acids in Solution.
Immersion of
of one part to
Period of
the Leaves
in Solutions
437 of water.
Effects produced on the Leaves by their subse-
quent Immersion for stated periods in a
Solution of one part of phosphate of
ammonia to 8750 of water, or 1 gr. to
20 0z.
Rubidium chloride
Potassium carbonate
Calcium acetate .
Calcium nitrate .
Magnesium acetate
Magnesium nitrate
Magnesium chloride
Barium acetate .
Barium nitrate .
Strontium acetate
Strontium nitrate.
Aluminium chloride
Aluminium nitrate’
Lead chloride. .
Manganese chloride
Lactic acid .<<i + %
Tannic acid . . .
Tartaric acid. .
Citric acid é
Formic acid . .
24 hrs.
24 hrs.
22 hrs.
22 hrs.
22 hrs.
22 hrs.
22 hrs.
22 hrs.
22 hrs.
24 hrs.
24 hrs,
23 hrs,
22 hrs.
48 hrs.
24 hrs.
24 hrs.
24 hrs.
22 hrs.
After 30 m. strong inflection of the
tentacles.
Scarcely any inflection until 5 hrs. had
elapsed.
After 24 hrs. very slight inflection.
Do. do.
Some slight inflection, which became
well pronounced in 24 hrs.
After 4 hrs. 30 m. a fair amount of
inflection, which never increased.
After a few minutes great inflection ;
after 4 hrs. all four leaves with almost
every tentacle closely inflected.
After 24 hrs. two leaves out of four
slightly inflected.
| After 30 m. one leaf greatly, and two
others moderately, inflected; they
remained thus for 24 hrs,
| After 25 m. two leaves greatly in-
flected; after 8 hrs. a third lea
moderately, and the fourth very
slightly, inflected. All four thus
remained for 24 hrs.
After 8 hrs. three leaves out of five
moderately inflected; after 24 hrs.
all five in this state; but not one
closely inflected.
Three leaves which had either been
slightly or not at all affected by the
chloride became after 7 hrs. 30 m.
rather closely inflected.
After 25 hrs. slight and doubtful effect.
After 24 hrs. two leaves somewhat in-
flected, the third very little; and
thus remained.
After 48 hrs. not the least inflection.
After 24 hrs. a trace of inflection in a
few tentacles, the glands of which
had not been killed by the acid.
After 24 hrs. no inflection.
Do. do.
After 50 m. tentacles decidedly inflected,
and after 5 hrs. strongly inflected ;
so remained for the next 24 hrs.
Not observed until 24 hrs. had elapsed ;
tentacles considerably inflected, and
protoplasm aggregated.
176 DROSERA ROTUNDIFOLIA, [CHAF IX,
Tn a large majority of these twenty cases, a varying degree of
inflection was slowly caused by the phosphate. In four cases, however,
the inflection was rapid, occurring in less than half an hour or at most,
in 50m. Inthree cases the phosphate did net produce the least effect.
Now what are we to infer from these facts? We know from ten trials
that immersion in distilled water for 24 hrs. prevents the subsequent
action of the phosphate solution. It would therefore appear as if the
solutions of chloride of manganese, tannic and tartaric acids, which are
not poisonous, acted exactly like water, for the phosphate produced no
effect on the leaves which had been previously immersed in these three
solutions. ‘The majority of the other solutions behaved to a certain
extent like water, for the phosphate produced, after a considerable
interval of time, only a slight effect. On the other hand, the leaves
which had been immersed in the solutions of the chloride of rubidium
and magnesium, of acetate of strontium, nitrate of barium, and citric
acid, were quickly acted on by the phosphate. Now, was water absorbed
from these five weak solutions, and yet, owing to the presence of the
salts, did not prevent the subsequent action of the phosphate? Or
may we not suppose * that the interstices of the walls of the glands
were blocked up with the molecules of these five substances, so that they
were rendered impermeable to water; for had water entered, we know
from the ten trials that the phosphate would not afterwards have
produced any effect? It further appears that the molecules of the
carbonate of ammonia can quickly pass into glands which, from having
been immersed for 20 m. in a weak solution of sugar, either absorb the
phosphate very slowly or are acted on by it very slowly. On the other
hand, glands, however they may have been treated, seem easily to permit
the subsequent entrance of the molecules of carbonate of ammonia.
Thus leaves which had been immersed in a solution (of one part to 4387
of water) of nitrate of potassium for 48 hrs.—of sulphate of potassium for
24 hrs.—and of the chloride of potassium for 25 hrs.—on being placed in
a solution of one part of carbonate of ammonia to 218 of water, had their
* See Dr. M. Traube’s curious ex- precipitation of sulphate of barium
periments on the production of arti- to take place at the same time, the
ficial cells, and on their permeability membrane becomes “infiltrated ”
to various salts, described in his with this salt; and in consequence
papers: “ Experimente zur Theorie of the intercalation of molecules of
der Zellenbildung und Endosmose,” sulphate of barium among those of
Breslau, 1866; and * Experimente the gelatine precipitate, the mole-
zur physicalischen Erklärung der cular interstices in the membrane
Bildung der Zellhaut, ihres Wachs- are made smaller. In this altered
thums durch Intussusception,” Bres- condition, the membrane no longer
Jau, 1874. These researches perhaps allows the passare through it of
explain my results. Dr. Traube either sulphate of ammonia or nitrate
commonly employed as a membrane of barium, though it retains its per-
the precipitate formed when tannic meability for water and chloride of
acid comes into contact with a so- ammonia,
lution of gelatine. By allowing a
Bee US cs Cerner tensa at
PU
eee
Dee
EI
i
OKAR IX.] VAPOUR OF CHLOROFORM. aid
glands immediately blackened, and after 1 hr. their tentacles somewhat
inflected, and the protoplasm ageregated. But it would be an endless
task to endeavour to ascertain the wonderfully diversified effects of
various solutions on Drosera.
Alcohol (one part to seven of water).—It has already been shown
that half-minims of this strength placed on the discs of leaves do not
cause any inflection; and that when two days afterwards the leaves
were given bits of meat, they became strongly inflected. Four leaves
were immersed in this mixture, and two of them after 30 m. were
brushed with a camel-hair brush, like leaves in a solution of camphor,
but this produced no effect. Nor did these four leaves, on being left
for 24 hrs. in the diluted alcohol, undergo any inflection. They were
then removed; one being placed in an infusion of raw meat, and bits
of meat on the discs of the other three, with tbeir stalks in water.
Next day one seemed a little injured, whilst two others showed merely a
trace of inflection. We must, however, bear in mind that immersion
for 24 hrs. in water prevents leaves from clasping meat. Hence alcohol
of the above strength is not poisonous, nor does it stimulate the leaves
like camphor does,
The vapour of alcohol acts differently. A plant having three good
leaves was left for 25 m. under a receiver holding 19 oz, with sixty
minims of alcohol in a watch-glass. No movement ensued, but some
few of the glands were blackened and shrivelled, whilst many became
quite pale. These were scattered over all the leaves in the most
irregular manner, reminding me of the manner in which the glands
were affected by the vapour of carbonate of ammonia. Immediately
on the removal of the receiver particles of raw meat were placed on
many of the glands, those which retained their proper colour belng
chiefly selected. But not a single tentacle was inflected during the
next 4 hrs. After the first 2 hrs. the glands on all the tentacles
began to dry; and next morning, after 22 hrs., all three leaves
appeared almost dead, with their glands dry ; the tentacles on one leaf
alone being partially inflected. :
A second plant was left for only 5 m. with some alcohol in a watch-
glass, under a 12-oz. receiver, and particles of meat were then placed
on the glands of several tentacles. After 10 m.some of them began te
curve inwards, and after 55 m. nearly all were considerably inflected ;
but a few did not move. Some anesthethic effect is here probable, but
by no means certain. A third plant was also left for 5 m. under the
same small vessel, with its whole inner surface wetted with about a
dozen drops of alcohol. Particles of meat were now placed on the
glands of several tentacles, some of which first began to move in 25 m. ;
after 40 m. most of them were somewhat inflected, and after 1 hr.
10 m. almost all were considerably inflected. From their slow rate of
movement there can be no doubt that the glands of these tentacles
had been rendered insensible for a time by exposure during 5 m. to the
vapour of alcohol.
Vapour of Chloroform.—The action of this vapour on Drosera is
N
178 DROSERA ROTUNDIFOLIA. (Cuar. IX.
very variable, depending, I suppose, on the constitution or age of the
plant, or on some unknown condition. It sometimes causes the tentacles
to move with extraordinary rapidity, and sometimes produces no such
eflect. The glands are sometimes rendered for a time insensible to the
action of raw meat, but sometimes are not thus affected, or in a very
slight degree. A plant recovers from a small dose, but is easily killed
by a larger one.
A plant was left for 30 m. under a bell-glass holding 19 fluid oz.
(539°9 c.c.) with eight drops of chloroform, and before the cover was
removed, most of the tentacles became much inflected, though they
did not reach the centre. After the cover was removed, bits of meat
were placed on the glands of several of the somewhat incurved tentacles ;
these glands were found much blackened after 6 hrs. 80 m., but no
irae movement ensued. After 24 hrs. the leaves appeared almost
dead.
A smaller bell-glass, holding 12 fluid oz. (840°8 c.c.), was now em-
ployed, and a plant was left for 90 s. under it, with only two drops of
chloroform. Immediately on the removal of the glass all the tentacles
curved inwards so as to stand perpendicularly up; and some of them
could actually be seen moving with extraordinary quickness by little
starts, and therefore in an unnatural manner; but they never reached
the centre. After 22 hrs. they fully re-expanded, and on meat
being placed on their glands, or when roughly touched by a needle,
they promptly became inflected; so that these leaves had not been in
the least injured.
Another plant was placed under the same small bell-glass with three
drops of chloroform, and before two minutes had elapsed, the tentacles
began to curl inwards with rapid little jerks. The glass was then
removed, and in the course of two or three additional minutes almost
every tentacle reached the centre. On several other occasions the vapour
did not excite any movement of this kind.
‘There seems also to be great variability in the degree and manner
in which chloroform renders the glands insensible to the subsequent
action of meat. In the plant last referred to, which had been exposed
for 2m. to three drops of chloroform, some few tentacles curved up
only to a perpendicular position, and particles of meat were placed on
their glands; this caused them in 5 m. to begin moving, but they
moved so slowly that they did not reach the centre until 1 hr. 20 m-
had elasped. Another plant was similarly exposed, that is, for 2 m., to
three drops of chloroform, and on particles of meat being placed on the
glands of several tentacles, which had curved up into a perpendicular
position, one of these began to bend in 8 m., but afterwards moved
very slowly ; whilst none of the other tentacles moved for the next
40m. Nevertheless, in 1 hr. 45 m. from the time when the bits of
meat had been given, all the tentacles reached the centre. In this
case some slight anesthetic effect apparently had been produced. On
the following day the plant had perfectly recovered.
Another plant bearing two leaves was exposed for 2 m. under the
i Tc E AE ts
Cuar. IX.] VAPOUR OF ETHER. 179
19-02. vessel to two drops of chloroform; it was then taken out and
examined; again exposed for 2 m. to two drops; taken out, and re-
exposed for 3 m. to three drops; so that altogether it was exposed
alternately to the air and during 7 m. to the vapour of seven drops of
chloroform. Bits of meat were now placed on thirteen glands on the
two leaves. On one of these leaves, a single tentacle first began
moving in 40 m., and two others in 54m. On the second leaf some
tentacles first moved in 1 hr. 11 m. After 2 hrs. many tentacles on
both leaves were inflected; but none had reached the centre within
this time. In this case there could not be the least doubt that the
chloroform had exerted an anzesthetic influence on the leaves.
On the other hand, another plant was exposed under the same
vessel for a much longer time, viz. 20 m., to twice as much chloroform.
Bits of meat were then placed on the glands of many tentacles, and all
of them, with a single exception, reached the centre in from 13 m. to
14m. In this case, little or no anesthetic effect had been produced ;
and how to reconcile these discordant results, I know not.
Vapour of Sulphuric Ether—A plant was exposed for 30 m. to
thirty minims of this ether in a vessel holding 19 oz.; and bits of
raw meat were afterwards placed on many glands which had become
pale-coloured ; but none of the tentacles moved. After 6 hrs. 30 m,
the leaves appeared sickly, and the discal glands were almost dry. By
the next morning many of the tentacles were dead, as were all those
on which meat had been placed; showing that matter had been ab-
sorbed from the meat which had increased the evil effects of the
vapour. After four days the plant itself died. Another plant was
exposed in the same vessel for 15 m. to forty minims., One young,
small, and tender leaf had all its tentacles inflected, and seemed much
injured. Bits of raw meat were placed on several glands on two other
and older leaves. These glands became dry after 6 hrs., and seemed
injured; the tentacles never moved, excepting one was ultimately a
little inflected. The glands of which the other tentacles continued to
secrete, and appeared uninjured, but the whole plant after three days
became very sickly.
In the two foregoing experiments the doses were evidently too large
and poisonous. With weaker doses, the anesthetic effect was variable,
as in the case of chloroform. A plant was exposed for 5 m. to ten
drops under a 12-oz. vessel, and bits of meat were then placed on many
glands. None of the tentacles thus treated began to move in a decided
manner until 40 m. had elapsed; but then some of them moved very
quickly, so that two reached the centre after an additional interval of
only 10 m. In 2 hrs. 12 m. from the time when the meat was given,
all the tentacles reached the centre. Another plant, with two leaves,
was exposed in the same vessel for 5 m. to a rather large dose of ether,
and bits of meat were placed on several glands. In this case one
tentacle on each leaf began to bend in 5 m.; and after 12 m. two
tentacles on one leaf, and one on the second leaf, reached the centre.
In 30 m. after the meat had been given, all the tentacles, both those
N 2
180 DROSERA ROTUNDIFOLIA. (CHAP. IX.
with and without meat, were closely inflected; so that the ether
apparently had stimulated these leaves, causing all the tentacles to
bend.
Vapour of Nitric Ether.—This vapour seems more injurious than
that of sulphuric ether. A plant was exposed for 5 m.in a 12-07.
vessel to eight drops in a watch-glass, and I distinctly saw a few
tentacles curling inwards before the glass was removed, Immediately
afterwards bits of meat were placed on three glands, but no movement
ensued in the course of 18 m. ‘The same plant was placed again under
the same vessel for 16 m. with ten drops of the ether. None of the
tentacles moved, and next morning those with the meat were still in
the same position. After 48 brs. one leaf seemed healthy, but the
others were much injured.
Another plant, having two good leaves, was exposed for 6 m. under
a 19-oz. vessel to the vapour from ten minims of the ether, and bits of
meat were then placed on the glands of many tentacles on both leaves.
After 36 m. several of them on one leaf became inflected, and after
1 hr.almost all the tentacles, those with and without meat, nearly reached
the centre. On the other leaf the glands began to dry in 1 hr. 40 m.,
and after several hours not a single tentacle was inflected ; but by the
next morning, after 21 hrs., many were inflected, though they seemed
rnuch injured. In this and the previous experiment, it is doubtful,
owing to the injury which the leaves had suffered, whether any
anesthetic effect had been produced.
A third plant, having two good leaves, was exposed for only 4 m.
in the 19-0z. vessel to the vapour from six drops. Bits of meat were
then placed on the glands of seven tentacles on the same leaf. A
single tentacle moved after 1 hr. 23 m.; after 2 hrs. 3 m. several were
inflected; and after 3 hrs. 3 m. all the seven tentacles with meat were
well inflected. From the slowness of these movements it is clear that
this leaf had been rendered insensible for a time to the action of the
meat. A second leaf was rather differently affected; bits of meat
were placed on the glands of five tentacles, three of which were
slightly inflected in 28 m.; after 1 hr. 21 m. one reached the centre,
but the other two were still only slightly inflected; after 3 hrs. they
were much more inflected; but even after 5 hrs. 16 m. all five had
not reached the centre. Although some of the tentacles began to
move moderately soon, they afterwards moved with extreme slowness.
By next morning, after 20 hrs., most of the tentacles on both leaves
were closely inflected, but not quite regularly. After 48 hrs. neither
leaf appeared injured, though the tentacles were still inflected; after
72 hrs. one was almost dead, whilst the other was re-expanding and
recovering.
Carbonic Acid.—A plant was placed under a 122-oz. bell-glass
filled with this gas and standing over water; but I did not make
sufficient allowance for the absorption of the gas by the water, so that
towards the latter part of the experiment some air was drawn in.
After an exposure of 2 hrs. the plant was removed, and bits of raw
Cuar. IX.] CARBONIC ACID. 181
meat placed on the glands of three leaves. One of these leaves hung
a little down, and was at first partly and soon afterwards completely
covered by the water, which rose within the vessel as the gas was
absorbed. On this latter leaf the tentacles, to which meat had been
given, became well inflected in 2 m. 30 s., that is, at about the normal
rate; so that until I remembered that the leaf had been protected
from the gas, and might perhaps have absorbed oxygen from the water
which was continually drawn inwards, Į falsely concluded that the
carbonic acid had produced no effect. On the other two leaves, the
tentacles with meat behaved very differently from those on the first
leaf; two of them first began to move slightly in 1 hr. 50 m., always
reckoning from the time when the meat was placed on the glands—
were plainly inflected in 2 hrs. 22 m.—and in 3 hrs. 22 m. reached
the centre. Three other tentacles did not begin to move until 2 hrs.
20 m. had elapsed, but reached the centre at about the same time
with the others, viz. in 3 hrs. 22 m.
This experiment was repeated several times with nearly the same
results, excepting that the interval before the tentacles began to move
varied a little. I will give only one other case. A plant was exposed
in the same vessel to the gas for 45 m., and bits of meat were then
placed on four glands. But the tentacles did not move for 1 hr. 40 m. ;
after 2 hrs. 30 m, all four were well inflected, and after 3 hrs. reached
the centre.
The following singular phenomenon sometimes, but by no means
always, occurred. A plant was immersed for 2 hrs., and bits of meat
were then placed on several glands. In the course of 13 m. all the
submarginal tentacles on one leaf became considerably inflected ; those
with the meat not in the least degree more than the others. Ona
second leaf, which was rather oid, the tentacles with meat, as well as
a few others, were moderately inflected. On a third leaf all the
tentacles were closely inflected, though meat had not been placed on
any of the glands. ‘This movement, I presume, may be attributed to
excitement from the absorption of oxygen. The last-mentioned leaf,
to which no meat had been given, was fully re-expanded after 24 hrs. ;
whereas the two other leaves had all their tentacles closely inflected
over the bits of meat which by this time had been carried to their
centres. Thus these three leaves had perfectly recovered from the
effects of the gas in the course of 24 hrs.
On another occasion some fine plants, after having been left for
2 hrs. in the gas, were immediately given bits of meat in the usual
manner, and on their exposure to the air most of their tentacles became
in 12 m. curved into a vertical or sub-vertical position, but in an ex-
tremely irregular manner; some only on one side of the leaf and some
on the other, They remained in this position for some time; the
tentacles with the bits of meat not having at first moved more quickly
or farther inwards than the others without meat. But after 2 hrs,
20 m. the former began to move, and steadily went on bending until
they reached the centre. Next morning, after 22 hrs., all the tentacles
182 DROSERA ROTUNDIFOLIA. [Cuar. IX.
on these leaves were closely clasped over the meat which had been
carried to their centres; whilst the vertical and sub-vertical tentacles
on the other leaves to which no meat had been given had fully re-
expanded. Judging, however, from the subsequent action of a weak
solution of carbonate of ammonia cn one of these latter leaves, it had
not perfectly recovered its excitability and power of movement in 22
hrs.; but another leaf, after an additional 24 hrs., had completely re-
covered, judging from the manner in which it clasped a fly placed on
its disc.
I will give only one other experiment. After the exposure of a
plant for 2 hrs. to the gas, one of its leaves was immersed in a rather
strong solution of carbonate of ammonia, together with a fresh leaf
from another plant. The latter had most of its tentacles strongly
inflected within 80 m.; whereas the leaf which had been exposed to
the carbonic acid remained for 24 hrs. in the solution without under-
going any inflection, with the exception of two tentacles. ‘This leaf
had been almost completely paralysed, and was not able to recover its
sensibility whilst still in the solution, which from having been made
with distilled water probably contained little oxygen.
Concluding Remarks on the Effects of the foregoing Agents.—
As the glands, when excited, transmit some influence to the
surrounding tentacles, causing them to bend and their glands
to pour forth an increased amount of modified secretion, I
was anxious to ascertain whether the leaves included any
element having the nature of nerve-tissue, which, though
not continuous, served as the channel of transmission. This
led me to try the several alkaloids and other substances which
are known to exert a powerful influence on the nervous
system of animals. I was at first encouraged in my trials
by finding that strychnine, digitaline, and nicotine, which
all act on the nervous system, were poisonons to Drosera, and
caused a certain amount of inflection. Hydrocyanic acid,
again, which is so deadly a poison to animals, caused rapid
movement of the tentacles. But as several innocuous acids,
though much diluted, such as benzoic, acetic, &c., as well as
some essential oils, are extremely poisonous to Drosera, and
quickly cause strong inflection, it seems probable that
strychnine, nicotine, digitaline, and hydrocyanic acid, excite
inflection by acting on elements in no way analogous to
the nerve-cells of animals. If elements of this latter nature
had been present in the leaves, it might have been expected
that morphia, hyoscyamus, atropine, veratrine, colchicine,
curare, and diluted alcohol would have produced some marked
effect; whereas these substances are not poisonous and have
Cuar. IX.) 183
SUMMARY OF THE CHAPTER.
no power, or only a very slight one, of inducing inflection.
It should, however, be observed that curare, colchicine, and
veratrine are muscle-poisons—that is, act on nerves having
some special relation with the muscles, and, therefore, could
not be expected to act on Drosera. The poison of the cobra
is most deadly to animals, by paralysing their nerve-centres,*
yet is not in the least so to Drosera, though quickly causing
strong inflection.
Notwithstanding the foregoing facts, which show how
widely different is the effect of certain substances on the
health or life of animals and of Drosera, yet there exists a
certain degree of parallelism in the action of certain other
substances. We have seen that this holds good in a striking
manner with the salts of sodium and potassium. Again,
various metallic salts and acids, namely those of silver, mer-
cury, gold, tin, arsenic, chromium, copper, and platina, most
or all of which are highly poisonous to animals, are equally
so to Drosera. But it is a singular fact that the chloride of
lead and two salts of barium were not poisonous to this plant.
It is an equally strange fact, that, though acetic and pro-
pionic acids are highly poisonous, their ally, formic acid, is
not so; and that, whilst certain vegetable acids, namely
oxalic, benzoic, &c., are poisonous in a high degree, gallic,
tannic, tartaric, and malic (all diluted to an equal degree)
are not so. Malic acid induces inflection, whilst the three
other just named vegetable acids have no such power. But
a pharmacopceia would be requisite to describe the diversified
effects of various substances on Drosera.
Of the alkaloids and their salts which were tried, several
had not the least power of inducing inflection ; others, which
were certainly absorbed, as shown by the changed colour of
the glands, had but a very moderate power of this kind;
* Dr. Fayrer, ‘The Thanatophidia
of India,’ 1872, p. 4.
t Seeing that acetic, hydrocyanic,
and chromic acids, acetate of strych-
nine, and vapour of ether, are poison-
ous to Drosera, it is remarkable that
Dr. Ransom (‘ Philosoph. Transact.’
1867, p. 480), who used much
stronger solutions of these substances
than I did, states “that the rhyth-
mic contractility of the yolk (of the
ova of the pike) is not materiaily
influenced by any of the poisons used,
which did not act chemically, with
the exception of chloroform and car-
bonic acid.” I find it stated by
several writers that curare has no
influence on sarcode or protoplasm,
and we have seen that, though curare
excites some degree of inflection, it
causes very little aggregation of the
protoplasm,
184 DROSERA ROTUNDIFOLIA. [Cuar. IX.
others, again, such as the acetate of quinine and digitaline,
caused strong inflection.
The several substances mentioned in this chapter affect the
colour of the glands very differently. These often become dark
at first, and then very pale or white, as was conspicuously
the case with glands subjected to the poison of the cobra
and citrate of strychnine. In other cases they are from the
first rendered white, as with leaves placed in hot water and
several acids; and this, I presume, is the result of the coagu-
lation of the albumen. On the same leaf some glands become
white and others dark-coloured, as occurred with leaves in a
solution of the sulphate of quinine, and in the vapour of
alcohol. Prolonged immersion in nicotine, curare, and even
water, blackens the glands; and this, I believe, is due to the
aggregation of the protoplasm within their cells. Yet curare
caused very little aggregation in the cells of the tentacles,
whereas nicotine and sulphate of quinine induced strongly
marked aggregation down their bases. The aggregated
masses in leaves which had been immersed for 3 hrs. 15 m.
in a saturated solution of sulphate of quinine exhibited inces-
sant changes of form, but after 24 hrs. were motionless; the
leaf being flaccid and apparently dead. On the other hand,
with leaves subjected for 48 hrs. to a strong solution of the
poison of the cobra, the protoplasmic masses were unusually
active, whilst with the higher animals the vibratile cilia and
white corpuscles of the blood seem to be quickly paralysed
by this substance.
With the salts of alkalies and earths, the nature of the base,
and not that of the acid, determines their physiological action
on Drosera, as is likewise the case with animals; but this
rule hardly applies to the salts of quinine and strychnine, for
the acetate of quinine causes much more inflection than the
sulphate, and both are poisonous, whereas the nitrate of
quinine is not poisonous, and induces inflection at a much
slower rate than the acetate. The action of the citrate of
strychnine is also somewhat different from that of the
sulphate.
Leaves which have been immersed for 24 hrs. in water,
and for only 20 m. in diluted alcohol, or in a weak solution
of sugar, are afterwards acted on very slowly, or not at all,
by the phosphate of ammonia, though they are quickly acted
on by the carbonate. Immersion for 20 m. in a solution of
gum arabic has no such inhibitory power. The solutions of
mg ne =y
Cuar. IX.) SUMMARY OF THE CHAPTER. 185
certain salts and acids affect the leaves, with respect to the
subsequent action of the phosphate, exactly like water, whilst
others allow the phosphate afterwards to act quickly and
energetically. In this latter case, the interstices of the cell-
walls may have been blocked up by the molecules of the
salts first given in solution, so that water could not after-
wards enter, though the molecules of the phosphate could do
so, and those of the carbonate still more easily.
The action of camphor dissolved in water is remarkable,
for it not only soon induces inflection, but apparently renders
the glands extremely sensitive to mechanical irritation; for
if they are brushed with a soft brush, after being immersed
in the solution for a short time, the tentacles begin to bend
in about 2m. It may, however, be that the brushing, though
not a sufficient stimulus by itself, tends to excite movement
merely by reinforcing the direct action of the camphor.
The vapour of camphor, on the other hand, serves as a
narcotic.
Some essential oils, both in solution and in vapour, cause
rapid inflection, others have no such power; those which I
tried were all poisonous.
Diluted alcohol (one part to seven of water) is not poison-
ous, does not induce inflection, nor increase the sensitiveness
of the glands to mechanical irritation. The vapour acts as a
narcotic or anesthetic, and long exposure to it kills the
leaves.
The vapours of chloroform, sulphuric and nitric ether, act
in a singularly variable manner on different leaves, and on
the several tentacles of the same leaf. This, I suppose, is
owing to differences in the age or constitution of the
leaves, and to whether certain tentacles have lately been in
action. That these vapours are absorbed by the glands is
shown by their changed colour; but as other plants not
furnished with glands are affected by these vapours, 1t 1s
probable that they are likewise absorbed by the stomata of
Drosera. They sometimes excite extraordinarily rapid in-
flection, but this is not an invariable result. If allowed to act
for evena moderately long time, they kill the leaves; whilst
a small dose acting for only a short time serves as a narcotic
or anesthetic. In this case the tentacles, whether or not
they have become inflected, are not excited to further move-
ment by bits of meat placed on the glands, until some
considerable time has elapsed. It is generally believed that
186 DROSERA ROTUNDIFOLIA. [CHAR IX.
with animals and plants these vapours act by arresting
oxidation.
Exposure to carbonic acid for 2 hrs., and in one case for
only 45 m., likewise rendered the glands insensible for a
time to the powerful stimulus of raw meat. The leaves,
however, recovered their full powers, and did not seem in
the least injured, on being left in the air for 24 or 48 hrs.
We have seen in the third chapter that the process of
aggregation in leaves subjected for two hours to this gas and
then immersed in a solution of the carbonate of ammonia is
much retarded, so that a considerable time elapses before the
protoplasm in the lower cells of the tentacles becomes aggre-
gated. In some cases, soon after the leaves were removed
from the gas and brought into the air, the tentacles moved
spontaneously ; this being due, I presume, to the excitement
trom the access of oxygen. These inflected tentacles, how-
ever, could not be excited for some time afterwards to any
further movement by their glands being stimulated. With
other irritable plants it is known* that the exclusion of
oxygen prevents their moving, and arrests the movements of
the protoplasm within their cells, but this arrest is a different
phenomenon from the retardation of the process of aggre-
gation just alluded to. Whether this latter fact ought to be
attributed to the direct action of the carbonic acid, or to the
exclusion of oxygen, I know not.
* Sachs, ‘Traité de Bot. 1874, pp. 846, 1037.
Crar. X] SENSITIVENESS OF THE LEAVES. 187
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—Transmission 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.
We have seen in the previous chapters that many widely
different stimulants, mechanical and chemical, excite the
movement of the tentacles, as well as of the blade of the leaf;
and we must now consider, firstly, what are the points which
are irritable or sensitive, and secondly how the motor impulse
is transmitted from one point to another. The glands are
almost exclusively the seat of irritability, yet this irritability
must extend for a very short distance below them; for when
they were cut off with a sharp pair of scissors without being
themselves touched, the tentacles often became inflected.
These headless tentacles frequently re-expanded ; and when
afterwards drops of the two most powerful known stimulants
were placed on the cut-off ends, no effect was produced.
Nevertheless these headless tentacles are capable of sub-
sequent inflection if excited by an impulse sent from the disc.
I succeeded on several occasions in crushing glands between
fine pincers, but this did not excite any movement; nor did
raw meat and salts of ammonia, when placed on such crushed
glands. It is probable that they were killed so instantly
that they were not able to transmit any motor impulse; for
in six observed cases (in two of which, however, the gland
was quite pinched off) the protoplasm within the cells of the
tentacles did not become aggregated ; whereas in some
adjoining tentacles, which were inflected from having been
roughly touched by the pincers, it was well aggregated. In
like manner the protoplasm does not become aggregated
when a leaf is instantly killed by being dipped into boiling
188 DROSERA ROTUNDIFOLIA. (CHAF. X,
water. On the other hand, in several cases in which tentacles
became inflected after their glands had been cut off with
sharp scissors, a distinct though moderate degree of aggre-
gation supervened.
The pedicels of the tentacles were roughly and repeatedly
rubbed ; raw meat or other exciting substances were placed
on them, both on the upper surface near the base and else-
where, but no distinct movement ensued. Some bits of
meat, after being left for a considerable time on the pedicels,
were pushed upwards, so as just to touch the glands, and in
a minute the tentacles began to bend. I believe that the
blade of the leaf is not sensitive to any stimulant. I drove
the point of a lancet through the blades of several leaves,
and a needle three or four times through nineteen leaves: in
the former case no movement ensued; but about a dozen of
the leaves which were repeatedly pricked had a few tentacles
irregularly inflected. As, however, their backs had to be
supported during the operation, some of the outer glands, as
well as those on the disc, may have been touched ; and this
perhaps sufficed to cause the slight degree of movement
observed. Nitschke* says that cutting and pricking the leaf
does not excite movement. The petiole of the leaf is quite
insensible.
The backs of the leaves bear numerous minute papillæ,
which do not secrete, but have the power of absorption:
These papillæ are, I believe, rudiments of formerly existing
tentacles together with their glands. Many experiments
were made to ascertain whether the backs of the leaves could
be irritated in any way, thirty-seven leaves being thus tried.
Some were rubbed for a long time with a blunt needle, and
drops of milk and other exciting fluids, raw meat, crushed
flies, and various substances, placed on others. These sub-
stances were apt soon to become dry, showing that no
secretion had been excited. Hence I moistened them
with saliva, solutions of ammonia, weak hydrochloric acid,
and frequently with the secretion from the glands of other
leaves. I also kept some leaves, on the backs of which
exciting objects had been placed, under a damp bell-glass ;
but with all my care I never saw any true movement. I
was led to make so many trials because, contrary to my
previous experience, Nitschke statest that, after affixing
* ‘Bot. Zeitung,’ 1860, p. 234. + Ibid., p. 437.
l
CHAP. X.] SENSITIVENESS OF THE LEAVES. 18)
objects to the backs of leaves by the aid of the viscid
secretion, he repeatedly saw the tentacles (and in one instance
the blade) become reflexed. This movement, if a true one,
would be most anomalous; for it implies that the tentacles
receive a motor impulse from an unnatural source, and have
the power of bending in a direction exactly the reverse of
that which is habitual to them; this power not being of the
least use to the plant, as insects cannot adhere to the smooth
backs of the leaves.
I have said that no effect was produced in the above
cases ; but this is not strictly true, for in three instances a
little syrup was added to the bits of raw meat on the backs
of leaves, in order to keep them damp for a time; and after
36 hrs. there was a trace of reflexion in the tentacles of one
leaf, and certainly in the blade of another. After twelve
additional hours the glands began to dry, and all three leaves
seemed much injured. Four leaves were then placed under
a bell-glass, with their foot-stalks in water, with drops of
syrup or their backs, but without any meat. Two of these
leaves, after a day, had a few tentacles reflexed. The drops
had now increased considerably in size, from having imbibed
moisture, so as to trickle down the backs of the tentacles and
footstalks. On the second day, one leaf had its blade much
reflexed; on the third day the tentacles of two were much
reflexed, as well as the blades of all four to a greater or less
degree. The upper side of one leaf, instead of being, as at first,
slightly concave, now presented a strong convexity upwards.
Even on the fifth day the leaves did not appear dead. Now,
as sugar does not in the least excite Drosera, we may safely
attribute the reflexion of the blades and tentacles of the
above leaves to exosmose from the cells which were in
contact with the syrup, and their consequent contraction.
When drops of syrup are placed on the leaves of plants with
their roots still in damp earth, no inflection ensues, for the
roots, no doubt, pump up water as quickly as it is lost by
exosmose. But if cut-off leaves are immersed in syrup, or in
any dense fluid, the tentacles are greatly, though irregularly,
inflected, some of them assuming the shape of corkscrews ;
and the leaves soon become flaccid. If they are now
immersed in a fluid of low specific gravity, the tentacles
re-expand. From these facts we may conclude that drops ot
syrup placed on the backs of leaves do not act by exciting a
motor impulse which is transmitted to the tentacles; but
190 DROSERA ROTUNDIFOLIA. (Cuar, X.
that they cause reflection by inducing exosmose. Dr.
Nitschke used the secretion for sticking insects to the backs
of the leaves; and I suppose that he used a large quantity,
which from being dense probably caused exosmose. Perhaps
he experimented on cut-off leaves, or on plants with their
roots not supplied with enough water.
As far, therefore, as our present knowledge serves, we
may conclude that the glands, together with the immediately
underlying cells of the tentacles, are the exclusive seats of
that irritability or sensitiveness with which the leaves are
endowed. The degree to which a gland is excited can be
measured only by the number of the surrounding tentacles
which are inflected, and by the amount and rate of their
movement. Equally vigorous leaves, exposed to the same
temperature (and this is an important condition), are excited
in various degrees under the following circumstances. A
minute quantity of a weak solution produces no effect; add
more, or give a rather stronger solution, and the tentacles
bend. Touch a gland once or twice, and no movement
follows; touch it three or four times, and the tentacle
becomes inflected. But the nature of the substance which is
given is a very important element: if equal-sized particles
vf glass (which acts only mechanically), of gelatine, and
raw meat are placed on the discs of several leaves, the
meat causes far more rapid, energetic, and widely extended
movement than the two former substances. The number of
glands which are excited also makes a great difference in the
result : place a bit of meat on one or two of the discal glands,
and only a few of the immediately surrounding short tentacles
are inflected ; place it on several glands, and many more are
acted on ; place it on thirty or forty, and all the tentacles,
including the extreme marginal ones, become closely inflected.
We thus see that the impulses proceeding from a number of
glands strengthen one another, spread farther, and act on a
larger number of tentacles, than the impulse from any single
gland.
Transmission of the Motor Impulse.—In every case the impulse
from a gland has to travel for at least a short distance to the
basal part of the tentacle, the upper part and the gland
itself being merely carried by the inflection of the lower
part. The impulse is thus always transmitted down nearly
the whole length of the pedicel. When the central glands
are stimulated, and the extreme marginal tentacles become
D atana
ARIP st
Cuar. X.] TRANSMISSION OF MOTOR IMPULSE. 191
inflected, the impulse is transmitted across half the diameter
of the disc, and when the glands on one side of the disc are
stimulated, the impulse is transmitted across nearly the
whole width of the disc. A gland transmits its motor
impulse far more easily and quickly down its own tentacle
to the bending place than across the disc to neighbouring
tentacles. Thus a minute dose of a very weak solution of
ammonia, if given to one of the glands of the exterior
tentacles, causes it to bend and reach the centre; whereas a
large drop of the same solution, given to a score of glands
on the disc, will not cause through their combined influence
the least inflection of the exterior tentacles. Again, when a
bit of meat is placed on the gland of an exterior tentacle,
I have seen movement in ten seconds, and repeatedly within a
minute; but a much larger bit placed on several glands on
the disc does not cause the exterior tentacles to bend until
half an hour or even several hours have elapsed.
The motor impulse spreads gradually on all sides from one
or more excited glands, so that the tentacles which stand
nearest are always first affected. Hence, when the glands
in the centre of the disc are excited, the extreme marginal
tentacles are the last inflected. But the glands on different
parts of the leaf transmit their motor power in a somewhat
different manner. If a bit of meat be placed on the long-
headed gland of a marginal tentacle, it quickly transmits
an impulse to its own bending portion; but never, as far as
I have observed, to the adjoining tentacles ; for these are not
‘affected until the meat has been carried to the central glands,
which then radiate forth their conjoint impulse on all sides.
On four occasions leaves were prepared by removing some
days previously all the glands from the centre, so that these
could not be excited by the bits of meat brought to them by
the inflection of the marginal tentacles; and now these
marginal tentacles re-expanded after a time without any
other tentacle being affected. - Other leaves were similarly
prepared, and bits of meat were placed on the glands of two:
tentacles in the third row from the outside, and on the glands
of two tentacles in the fifth row. In these four cases the
impulse was sent in the first place laterally, that is, in the
same concentric row of tentacles, and then towards the
centre; but not centrifugally, or towards the exterior
tentacles. In one of these cases only a single tentacle on
each side of the one with meat was affected. In the three
192 DROSERA ROTUNDIFOLIA. [0r X
other cases, from half a dozen to a dozen tentacles, both
laterally and towards the centre, were well inflected, or
sub-inflected. Lastly, in ten other experiments, minute bits
of meat were placed on a single gland or on two glands in
the centre of the disc. In order that no other glands should
touch the meat, through the inflection of the closely
adjoining short tentacles, about half a dozen glands had been
previously removed round the selected ones. On eight of
these leaves from sixteen to twenty-five of the short
surrounding tentacles were inflected in the course of one or
two days; so that the motor impulse radiating from one or
two of the discal glands is able to produce this much effect.
The tentacles which had been removed are included in the
above numbers ; for, from standing so close, they would
certainly have been affected. On the two remaining leaves,
almost all the short tentacles on the disc were inflected.
With a more powerful stimulus than meat, namely a
little phosphate of lime moistened with saliva, I have seen
the inflection spread still farther from a single gland thus
treated; but even in this case the three or four outer rows
of tentacles were not affected. From these experiments it
appears that the impulse from a single gland on the disc acts
on a greater number of tentacles than that from a gland of
one of the exterior elongated tentacles; and this probably
follows, at least in part, from the impulse having to travel
a very short distance down the pedicels of the central
tentacles, so that it is able to spread to a considerable dis-
tance all round.
Whilst examining these leaves, I was struck with the fact
that in six, perhaps seven, of them the tentacles were much
more inflected at the distal and proximal ends of the leaf (ie.
towards the apex and base) than on either side; and yet
the tentacles on the sides stood as near to the gland where
the bit of meat lay as did those at the two ends. It thus
appeared as if the motor impulse was transmitted from the
centre across the disc more readily in a longitudinal than in
a transverse direction; and as this appeared a new and
interesting fact in the physiology of plants, thirty-five fresh
experiments were made to test its truth. Minute bits of
meat were placed on a single gland or on a few glands, on
the right or left side of the discs of eighteen leaves; other
bits of the same size being placed on the distal or proximal
ends of seventeen other leaves. Now if the motor impulse
Cuar. X.J* TRANSMISSION OF MOTOR IMPULSE. 193
were transmitted with equal force or at an equal rate through
the blade in all directions, a bit of meat placed at one side
or at one end of the disc ought to affect equally all the
tentacles situated at an equal distance from it; but this
certainly is not the case. Before giving the general results,
it may be well to describe three or four rather unusual
cases.
(1) A minute fragment of a fly was placed on one side of the disc,
and after 32 m. seven of the outer tentacles near the fragment were
inflected: after 10 hrs. several more became so, and after 23 hrs. a
still greater number ; and now the blade of the leaf on this side was
bent inwards so as to stand up at right angles to the other side.
Neither the blade of the leaf nor a single tentacle on the opposite side
was affected ; the line of separation between the two halves extending
from the footstalk to the apex. The leaf remained in this state for
three days, and on the fourth day began to re-expand; not a single
tentacle having been inflected on the opposite side.
(2) I will here give a case not included in the above thirty-five
experiments. A small fly was found adhering by its feet to the left
side of the disc. ‘The tentacles on this side soon closed in and killed
the fly: and owing probably to its struggle whilst alive, the leaf was
so much excited that in about 24 hrs, all the tentacles on the opposite
side became inflected; but as they found no prey, for their glands did
not reach the fly, they re-expanded in the course of 15 hrs.; the
tentacles on the left side remaining clasped for several days.
(3) A bit of meat, rather larger than those commonly used, was
placed in a medial line at the basal end of the disc, near the footstalk ;
after 2 hrs. 30 m. some neighbouring tentacles were inflected; after 6
hrs. the tentacles on both sides of the footstalk, and some way up both
sides, were moderately inflected; after 8 hrs. the tentacles at the
further or distal end were more inflected than those on either side;
after 23 hrs. the meat was well clasped by all the tentacles, excepting
by the exterior ones on the two sides.
(4) Another bit of meat was placed at the opposite or distal end of
another leaf, with exactly the same relative results.
(5) A minute bit of meat was placed on one side of the disc; next
day the neighbouring short tentacles were inflected, as well as in a
slight degree three or four on the opposite side near the footstalk, On
the second day these latter tentacles showed signs of re-expanding,
so I added a fresh bit of meat at nearly the same spot, and after
two days some of the short tentacles on the opposite side of the disc
were inflected. As soon as these began to re-expand, I added another
bit of meat, and next day all the tentacles on the opposite side
of the disc were inflected towards the meat; whereas we have seen
that those on the same side were affected by the first bit of meat which
was given.
0
194 DROSERA ROTUNDIFOLIA. (CHE X.
Now for the general results. Of the eighteen leaves on
which bits of meat were placed on the right or left sides of
the disc, eight had a vast number of tentacles inflected on
the same side, and in four of them the blade itself on this
side was likewise inflected ; whereas not a single tentacle
nor the blade was affected on the opposite side. These
leaves presented a very curious appearance, as if only the
inflected side was active, and the other paralysed. In the
remaining ten cases, a few tentacles became inflected beyond
the medial line, on the side opposite to that where the meat
lay; but, in some of these cases, only at the proximal or
distal ends of the leaves. The inflection on the opposite side
always occurred considerably after that on the same side,
and in one instance not until the fourth day. We have
also seen with No. 5 that bits of meat had to be added thrice
before all the short tentacles on the opposite side of the disc
were inflected.
The result was widely different when bits of meat were
placed in a medial line at the distal or proximal ends of the
disc. In three of the seventeen experiments thus made,
owing either to the state of the leaf or to the smallness of the
bit of meat, only the immediately adjoining tentacles were
affected ; but in the other fourteen cases the tentacles at the
opposite end of the leaf were inflected, though these were as
distant from where the meat lay as were those on one side of
the disc from the meat on the opposite side. In some of the
present cases the tentacles on the sides were not at all affected,
or in a less degree, or after a longer interval of time, than
those at the opposite end. One set of experiments is worth
giving in fuller detail. Cubes of meat, not quite so small as
those usually employed, were placed on one side of the discs
of four leaves, and cubes of the same size at the proximal or
distal end of four other leaves. Now, when these two sets
of leaves were compared after an interval of 24 hrs., they
presented a striking difference. Those having the cubes on
one side were very slightly affected on the opposite side ;
whereas those with the cubes at either end had almost every
tentacle at the opposite end, even the marginal ones, closely
inflected. After 48 hrs. the contrast in the state of the two
sets was still great; yet those with the meat on one side now
had their discal and submarginal tentacles on the opposite
side somewhat inflected, this being due to the large size of
the cubes. Finally we may conclude from these thirty-five
Cuar. X.] TRANSMISSION OF MOTOR IMPULSE. T99
experiments, not to mention the six or seven previous ones,
that the motor impulse is transmitted from any single gland
or small group of glands through the blade to the other ten-
tacles more readily and effectually in a longitudinal than in
a transverse direction.
As long as the glands remain excited, and this may last
for many days, even for eleven, as when in contact with
phosphate of lime, they continue to transmit a motor impulse
to the basal and bending parts of their own pedicels, for other-
wise they would re-expand. The great difference in the
length of time during which tentacles remain inflected over
inorganic objects, and over objects of the same size containing
soluble nitrogenous matter, proves the same fact. But the
intensity of the impulse transmitted from an excited gland,
which has begun to pour forth its acid secretion and is at the
same time absorbing, seems to be very small compared with
that which it transmits when first excited. Thus, when
moderately large bits of meat were placed on one side of the
disc, and the discal and submarginal tentacles on the opposite
side became inflected, so that their glands at last touched the
meat and absorbed matter from it, they did not transmit any
motor influence to the exterior rows of tentacles on the same
side, for these never became inflected. If, however, meat
had been placed on the glands of these same tentacles before
they had begun to secrete copiously and to absorb, they un-
doubtedly would have affected the exterior rows. Neverthe-
less, when I gave some phosphate of lime, which is a most
powerful stimulant, to several submarginal tentacles already
considerably inflected, but not yet in contact with some
phosphate previously placed on two glands in the centre
of the disc, the exterior tentacles on the same side were
acted on.
„When a gland is first excited, the motor impulse is dis-
charged within a few seconds, as we know from the bending
of the tentacle ; and it appears to be discharged at first with
much greater force than afterwards. Thus, in the case above
given of a small fly naturally caught by a few glands on one
side of a leaf, an impulse was slowly transmitted from them
across the whole breadth of the leaf, causing the opposite
tentacles to be temporarily inflected, but the glands which
remained in contact with the insect, though they continued
for several days to send an impulse down their own pedicels
to the bending place, did not prevent the teutacles on the
02
196 DROSERA ROTUNDIFOLIA. [Cuap. X.
opposite side from quickly re-expanding; so that the motor
discharge must at first have been more powerful than
afterwards.
When an object of any kind is placed on the disc, and the
surrounding tentacles are inflected, their glands secrete more
copiously and the secretion becomes acid, so that some in-
fluence is sent to them from the discal glands. This change
in the nature and amount of the secretion cannot depend on
the bending of the tentacles, as the glands of the short central
tentacles secrete acid when an object is placed on them,
though they do not themselves bend. Therefore I inferred
that the glands of the disc sent some influence up the sur-
rounding tentacles to their glands, and that these reflected.
back a motor impulse to their basal parts; but this view
was soon proved erroneous. It was found by many trials.
that tentacles with their glands closely cut off by sharp
scissors often become inflected and again re-expand, still
appearing healthy. One which was observed continued
healthy for ten days after the operation. I therefore cut the
glands off twenty-five tentacles, at different times and on
different leaves, and seventeen of these soon became inflected,
and afterwards re-expanded. The re-expansion commenced
in about 8 hrs. or 9 hrs., aud was completed in from 22 hrs.
to 30 hrs. from the time of inflection. After an interval of
a day or two, raw meat with saliva was placed on the discs
of these seventeen leaves, and when observed next day, seven
of the headless tentacles were inflected over the meat as
closely as the uninjured ones on the same leaves; and an
eighth headless tentacle became inflected after three addi-
tional days. The meat was removed from one of these leaves,
and the surface washed with a little stream of water, and
after three days the headless tentacle re-expanded for the
second time. These tentacles without glands were, however,
in a different state from those provided with glands and which
had absorbed matter from the meat, for the protoplasm within
the cells of the former had undergone far less aggregation.
From these experiments with headless tentacles it is certain
that the glands do not, so far as the motor impulse is concerned,.
act in a reflex manner like the nerve-ganglia of animals.
But there is another action, namely that of aggregation,
which in certain cases may be called reflex, and it is the only
known instance in the vegetable kingdom. We should bear
in mind that the process does not depend on the previous.
Cuar. X.] DIRECTION OF INFLECTED TENTACLES. 197
bending of the tentacles, as we clearly see when leaves are
immersed in certain strong solutions. Nor does it depend on
increased secretion from the glands, and this is shown by
several facts, more especially by the papillae, which do not
secrete, yet undergoing aggregation, if given carbonate of am-
monia or an infusion of raw meat. When a gland is directly
stimulated in any way, as by the pressure of a minute par-
ticle of glass, the protoplasm within the cells of the gland
first becomes aggregated, then that in the cells immediately
beneath the gland, and so lower and lower down the tentacles
to their bases ;—that is, if the stimulus has been sufficient
and not injurious. Now, when the glands of the disc are
excited, the exterior tentacles are affected in exactly the same
manner: the aggregation always commences in their glands,
though these have not been directly excited, but have only
received some influence from the disc, as shown by their
increased acid secretion. The protoplasm within the cells
immediately beneath the glands are next affected, and so
downwards from cell to cell to the bases of the tentacles.
This process apparently deserves to be called a reflex action,
in the same manner as when a sensory nerve is irritated, and
carries an impression to a ganglion which sends back some
influence to a muscle or gland, causing movement or increased
secretion; but the action in the two cases is probably of a
widely different nature. After the protoplasm in a tentacle
has been aggregated, its redissolution always begins in the
lower part, and slowly travels up the pedicel to the gland, so
that the protoplasm last aggregated is first redissolved.
This probably depends merely on the protoplasm being less
and less aggregated, lower and lower down in the tentacles,
as can be seen plainly when the excitement has been slight.
As soon, therefore, as the aggregating action altogether
ceases, redissolution naturally commences in the less strongly
aggregated matter in the lowest part of the tentacle, and is
there first completed. :
Direction of the Inflected Tentacles—When a particle of
any kind is placed on the gland of one of the outer tentacles,
this invariably moves towards the centre of the leaf; and so
it is with all the tentacles of a leaf immersed in any exciting
fluid. The glands of the exterior tentacles then form a ring
round the middle part of the disc, as shown in a previous
figure (fig. 4, p. 9). The short tentacles within this ring
still retain their vertical position, as they likewise do when
198 DROSERA ROTUNDIFOLIA. [Cmar X.
a large object is placed on their glands, or when an insect is
caught by them. In this latter case we can see that the
inflection of the short central tentacles would be useless, as
their glands are already in contact with their prey.
The result is very different when a single gland on one
side of the disc is excited, or a few in a group. These send
an impulse to the surrounding tentacles, which do not now
bend towards the centre of the leaf, but to the point of ex-
citement. We owe this capi-
tal observation to Nitschke,*
f and since reading his paper a
\ I 2 few years ago, I have repeat-
é > edly verified it. If a minute
bit of meat be placed by the
a aid of a needle on a single
gland, or on three or four
T together, halfway between
the centre and the circum-
i ference of the disc, the di-
5 rected movement of the sur-
rounding tentacles is well
exhibited. An accurate draw-
ing of a leaf with meat in
this position is here repro-
duced (fig. 10), and we see
the tentacles, including some
of the exterior ones, accu-
rately directed to the point
where the meat lay. But a
Leaf (enlarged) with the tentacles inflected much better plan as +0 place
over a bit of meat placed on one side of & particle of the phosphate
the disc. of lime moistened with saliva
on a single gland on one side
of the disc of a large leaf, and another particle on a single
gland on the opposite side. In four such trials the excitement
was not sufficient to affect the outer tentacles, but all those
near the two points were directed to them, so that two wheels
were formed on the disc of the same leaf; the pedicels of
the tentacles forming the spokes, and the glands united in
a mass over the phosphate representing the axles. The
precision with which each tentacle pointed to the particle
Fic. 10.
(Drosera rotundifolia.)
* ‘Bot. Zeitung,’ 1860, p. 240.
Cuar. X.) DIRECTION OF INFLECTED TENTACLES. 199
was wonderful; so that in some cases I could detect no
deviation from perfect accuracy. Thus, although the short
tentacles in the middle of the dise do not bend when their
glands are excited in a direct manner, yet if they receive
a motor impulse from a point on one side, they direct them-
selves to the point equally well with the tentacles on the
borders of the disc.
In these experiments, some of the short tentacles on the
disc, which would have been directed to the centre, had the
leaf been immersed in an exciting fluid, were now inflected in
an exactly opposite direction, viz. towards the circumference.
These tentacles, therefore, had deviated as much as 180°
from the direction which they would have assumed if their
. own glands had been stimulated, and which may be
considered as the normal one. Between this, the greatest
possible and no deviation from the normal direction, every
degree could be observed in the tentacles on these several
leaves. Notwithstanding the precision with which the ten-
tacles generally were directed, those near the circumference
of one leaf were not accurately directed towards some phos-
hate of lime at a rather distant point on the opposite side of
the disc. It appeared as if the motor impulse in passing
transversely across nearly the whole width of the disc had
departed somewhat from a true course, This accords with
what we have already seen of the impulse travelling less
readily in a transverse than in a longitudinal direction. In
some other cases, the exterior tentacles did not seem capable
of such accurate movement as the shorter and more central
ones.
Nothing could be more striking than the appearance
of the above four leaves, each with their tentacles pointing
truly to the two little masses of the phosphate on their discs.
We might imagine that we were looking at a lowly organised
animal seizing prey with its arms. In the case of Drosera
the explanation of this accurate power of movement, no
doubt, lies in the motor impulse radiating in all directions,
and whichever side of a tentacle it first strikes, that side
contracts, and the tentacle consequently bends towards the
oint of excitement. The pedicels of the tentacles are
flattened, or elliptic in section. Near the bases of the short
central tentacles, the flattened or broad face is formed of
about five longitudinal rows of cells; in the outer tentacles
of the disc, it consists of about six or seven rows; and in
200 DROSERA ROTUNDIFOLIA. [Cnar. X.
the extreme marginal tentacles of above a dozen rows. As
the flattened bases are thus formed of only a few rows of
cells, the precision of the movements of the tentacles is the
more remarkable; for when the motor impulse strikes the
base of a tentacle in a very oblique direction relatively to
its broad face, scarcely more than one or two cells towards
one end can be affected at first, and the contraction of these
cells must draw the whole tentacle into the proper direction.
It is, perhaps, owing to the exterior pedicels being much
flattened that they do not bend quite so accurately to the point
of excitement as the more central ones. The properly directed
movement of the tentacles is not an unique case in the
vegetable kingdom, for the tendrils of many plants curve
towards the side which is touched; but the case of Drosera
is far more interesting, as here the tentacles are not
directly excited, but receive an impulse from a distant point ;
nevertheless, they bend accurately towards this point.
On the Nature of the Tissues through which the Motor Impulse*
is Transmitted.—It will be necessary first to describe briefly
the course of the main fibro-vascular bundles. These are
shown in the accompanying sketch (fig. 11) of a small leaf.
Little vessels from the neighbouring bundles enter all the
many tentacles with which the surface is studded ; but these
are not here represented. The central trunk, which runs up
the footstalk, bifurcates near the centre of the leaf, each
branch bifurcating again and again according to the size of
the leaf. This central trunk sends off, low down on each
side, a delicate branch, which may be called the sublateral
branch. There is also, on each side, a main lateral branch or
bundle, which bifurcates in the same manner as the others.
Bifurcation does not imply that any single vessel divides,
but that a bundle divides into two. By looking to either
side of the leaf, it will be seen that a branch from the great
central bifurcation inosculates with a branch from the lateral
bundle, and that there is a smaller inosculation between the
* [In a letter (1862) to Sir Joseph
Hooker, in the ‘Life and Letters of
Charles Darwin,’ vol. iii. p. 321, the
writer speaks of the existence in
Drosera of “ diffused nervous matter,”
in some degree analogous in constitu-
tion and function to the nervous
matter of animals. Now, that
through the researches of Gardiner
(‘Phil. Trans.’ 1883) and others
the connection between plant-cells by
inter-cellular protoplasm has been
established, we can understand the
transmission of the motor impulse as
a molecular change in the protoplasm
from cell to cel]l.—F. D.]
nat
Cuar. X.] CONDUCTING TISSUES. 201
two chief branches of the lateral bundle. The course of the
vessels is very complex at the larger inosculation ; and here
vessels, retaining the same diameter, are often formed by the
union of the bluntly pointed ends of two vessels, but whether
these points open into each other by their attached surfaces,
I do not know. By means of the two inosculations all the
vessels on the same side of the leaf are brought into some sort
of connection. Near the circumference of the larger leaves
the bifurcating branches also come into close union, and then
separate again, forming a continuous zigzag line of vessels
round the whole circumfer-
ence. But the union of the
vessels in this zigzag line
seems to be much less inti-
mate than at the main in-
osculation. It should be
added that the course of the
vessels differs somewhat in
different leaves, and even on
opposite sides of the same
leaf, but the main inoscula-
tion is always present.
Now in my first experi-
ments with bits of meat
placed on one side of the disc,
it so happened that not a
single tentacle was inflected
on the opposite side; and
when I saw that the vessels
on the same side were all
connected together by the
two inosculations, whilst not Diagram showing the distribution of the
vascular tissue in a small leaf,
a vessel passed over to the
opposite side, it seemed pro- -
bable that the motor impulse was conducted exclusively
along them.
In order to test this view, I divided transversely with the
point of a lancet the central trunks of four leaves, just
beneath the main bifurcation; and two days afterwards
placed rather large bits of raw meat (a most powerful
stimulant) near the centre of the discs above the incision—
that is, a little towards the apex—with the following
results :—
Fic. 11,
(Drosera rotundifolia.)
202 DROSERA ROTUNDIFOLIA. [Cuar. X.
(1) This leaf proved rather torpid : after 4 hrs. 40 m. (in all cases
reckoning from the time when the meat was given) the tentacles at
the distal end were a little inflected, but nowhere else; they remained
so for three days, and re-expanded on the fourth day. The leaf was
then dissected, and the trunk, as well as the two sublateral branches,
were found divided.
(2) After 4 hrs. 30 m. many of the tentacles at the distal end were
well inflected. Next day the blade and all the tentacles at this end
were strongly inflected, and were separated by a distinct transverse line
from the basal half of the leaf, which was not in the least affected. On
the third day, however, some of the short tentacles on the disc near
the base were very slightly inflected. The incision was found on
dissection to extend across the leaf as in the last case.
(3) After 4 hrs. 30 m. strong inflection of the tentacles at the distal
end, which during the next two days never extended in the least to
the basal end. The incision as before.
(4) This leaf was not observed until 15 hrs. had elapsed, and then
all the tentacles, except the extreme marginal ones, were found
equally well inflected all round the leaf. On careful examination the
spiral vessels of the central trunk were certainly divided; but the
incision on one side had not passed through the fibrous tissue
surrounding these vessels, though it had passed through the tissue on
the other side.*
The appearance presented by the leaves (2) and (3) was
very curious, and might be aptly compared with that of a
man with his backbone broken and lower extremities
paralysed. Excepting that the line between the two halves
was here transverse instead of longitudinal, these leaves were
in the same state as some of those in the former experiments,
with bits of meat placed on one side of the disc. The case of
leaf (4) proves that the spiral vessels of the central trunk
may be divided, and yet the motor impulse be transmitted
from the distal to the basal end; and this led me at first to
suppose that the motor force was sent through the closely
surrounding fibrous tissue; and that if one half of this
tissue was left undivided, it sufficed for complete transmission.
3ut opposed to this conclusion is the fact that no vessels pass
directly from one side of the leaf to the other, and yet, as we
have seen, if a rather large bit of meat is placed on one side,
the motor impulse is sent, though slowly and imperfectly, in
* M. Ziegler made similar ex- rendus, 1874, p. 1417), but arrived
periments by cutting the spiral ves- at conclusions widely different from
sels of Drosera intermedia («Comptes mine.
Cuar. X.] CONDUCTING TISSUES, 203
a transverse direction across the whole breadth of the leaf.
Nor can this latter fact be accounted for by supposing that
the transmission is affected through the two inosculations, or
through the circumferential zigzag line of union, for had this
been the case, the exterior tentacles on the opposite side of
the disc would have been affected before the more central
ones, which never occurred. We have also seen that the
extreme marginal tentacles appear to have no power to
transmit an impulse to the adjoining tentacles; yet the little
bundle of vessels which enters each marginal tentacle sends
off a minute branch to those on both sides, and this I have
not observed in any other tentacles; so that the marginal
ones are more closely connected together by spiral vessels
than are the others, and yet have much less power of com-
municating a motor impulse to one another.
But besides these several facts and arguments we have
conclusive evidence that the motor impulse is not seni, at
least exclusively, through the spiral vessels, or through the
tissue immediately surrounding them. We know that if a
bit of meat is placed on a gland (the immediately adjoining
ones having been removed) on any part of the disc, all the
short surrounding tentacles bend almost simultaneously with
great precision towards it. Now there are tentacles on the
disc, for instance near the extremities of the sublateral
bundles (fig. 11), which are supplied with vessels that do not
come into contact with the branches that enter the sur-
rounding tentacles, except by a very long and extremely
circuitous course. Nevertheless, if a bit of meat is placed on
the gland of a tentacle of this kind, all the surrounding ones
are inflected towards it with great precision. Itis, of course,
possible that an impulse might be sent through a long and
circuitous course, but it is obviously impossible that the
direction of the movement could be thus communicated, so
that all the surrounding tentacles should bend precisely to
the point of excitement. The impulse no doubt is trans-
mitted in straight radiating lines from the excited gland to
the surrounding tentacles; it cannot, therefore, be sent along
the fibro-vascular bundles. The effect of cutting the central
vessels, in the above cases, in preventing the transmission of
the motor impulse from the distal to the basal end of a leaf,
may be attributed to a considerable space of the cellular
tissue having been divided. We shall hereafter see, when
we treat of Dionæa, that this same conclusion, namely that
204 DROSERA ROTUNDIFOLIA. (Cuar. X.
the motor impulse is not transmitted by the fibro-vascular
bundles, is plainly confirmed; and Professor Cohn has come
to the same conclusion with respect to Aldrovanda—both
members of the Droseraceæ.*
As the motor impulse is not transmitted along the vessels,
there remains for its passage only the cellular tissue; and
the structure of this tissue explains to a certain extent how
it travels so quickly down the long exterior tentacles, and
much more slowly across the blade of the leaf. We shall
also see why it crosses the blade more quickly in a longi-
tudinal than in a transverse direction; though with time it
can pass in any direction. We know that the same stimulus
causes movement of the tentacles and aggregation of the
protoplasm, and that both influences originate in and proceed
from the glands within the same brief space of time. It
seems therefore probable that the motor impulse consists of
the first commencement of a molecular change in the pro-
toplasm, which, when well developed, is plainly visible, and
has been designated aggregation ; but to this subject I shall
return. We further know that in the transmission of the
aggregating process the chief delay is caused by the passage
of the transverse cell-walls; for as the aggregation travels
down the tentacles, the contents of each successive cell seem
almost to flash into a cloudy mass. We may therefore infer
that the motor impulse is in like manner delayed chiefly by
passing through the cell-walls.
* [Batalin (‘ Flora, 1877) experi-
mented on the transmission of the
of Masdevallia muscosa the impulse
travels in a sheath of thin walled
motor impulse, and confirms the ob-
servations of Ziegler (‘Comptes ren-
dus,’ 1874), from which that natu-
ralist concluded that the vascular
bundles form the path for the trans-
mission of the impulse. Batalin
concludes that impulse travels with
far greater ease along the vessels than
across the parenchyma, and that the
course of the stimulus is normally
almost exclusively along the vessels.
If we believe that the motor im-
pulse travels as a molecular change
in the protoplasm, we cannot suppose
that it travels in the tracheids. Now
Oliver (‘Annals of Botany,’ Feb.
1888) has suggested that in the case
parenchyma accompanying the xylem.
If we make a similar assumption for
Drosera, we should get rid of a difti-
culty, for whether the impulse
travels in the course of the vascular
bundles or transversely across the
leaf, it would in either case. be
travelling in parenchymatous tissue ;
the only difference between the two
cases being that the parenchyma
accompanying the vessels would be
specially adapted for rapid transmis-
sion in a definite direction, whereas
the ordinary parenchyma has to
transmit the impulse in a variety
of directions.—F. D.]
CHAP. X] CONDUCTING TISSUES. 205
The greater celerity with which the impulse is transmitted
down the long exterior tentacles than across the dise may be
largely attributed to its being closely confined within the
narrow pedicel, instead of radiating forth on all sides as on
the dise. But besides this confinement, the exterior cells of
the tentacles are fully twice as long as those of the disc; so
that only half the number of transverse partitions have to
be traversed in a given length of a tentacle, compared with
an equal space on the disc; and there would be in the same
proportion less retardation of the impulse. Moreover, in
sections of the exterior tentacles given by Dr. Warming,*
the parenchymatous cells are shown to be still more elon-
gated; and these would form the most direct line of com-
munication from the gland to the bending place of the
tentacle. Ifthe impulse travels down the exterior cells, it
would have to cross from between twenty to thirty trans-
verse partitions: but rather fewer if down the inner paren-
chymatous tissue. In either case it is remarkable that the
impulse is able to pass through so many partitions down
nearly the whole length of the pedicel, and to act on the
bending place, in ten seconds. Why the impulse, after
having passed so quickly down one of the extreme marginal
tentacles (about >} of an inch in length), should never, as
far as I have seen, affect the adjoining tentacles, I do not
understand. It may be in part accounted for by much
energy being expended in the rapidity of the transmission.
Most of the cells of the disc, both the superficial ones and’
the larger cells which form the five or six underlying layers,
are about four times as long as broad. They are arranged
almost longitudinally, radiating from the footstalk. The
motor impulse, therefore, when transmitted across the disc, has
to cross nearly four times as many cell-walls as when trans-
mitted in a longitudinal direction, and would consequently be
much delayed in the former case. The cells of the disc
converge towards the bases of the tentacles, and are thus
fitted to convey the motor impulse to them from all sides.
On the whole, the arrangement and shape of the cells, both
those of the disc and tentacles, throw much light on the rate
and manner of diffusion of the motor impulse. But why the
impulse proceeding from the glands of the exterior rows of
* ¢Videnskabelige Meddelelser de la Soc, d’Hist. nat. de Copenhazue,”
Nos, 10-12, 1872, woodcuts iv. and v.
206 DROSERA ROTUNDIFOLIA. [Cuar. X.
tentacles tends to travel laterally and towards the centre of
the leaf, but not centrifugally, is by no means clear.
Mechanism of the Movements, and Nature of the Motor
Impulse.—W hatever may be the means of movement, the
exterior tentacles, considering their delicacy, are inflected
with much force. <A bristle, held so that a length of 1 inch
projected from a handle, yielded when I tried to lift with it
an inflected tentacle, which was somewhat thinner than the
bristle. The amount or extent, also, of the movement is
great. Fully expanded tentacles in becoming inflected
sweep through an angle of 180°; and if they are beforehand
reflexed, as often occurs, the angle is considerably greater.
It is probably the superficial cells at the bending place
which chiefly or exclusively contract; for the interior cells
have very delicate walls, and are so few in number that
they could hardly cause a tentacle to bend with precision
toa definite point. Though I carefully looked, I could never
detect any wrinkling of the surface at the bending place,
even in the case of a tentacle abnormally curved into a com-
plete circle, under circumstances hereafter to be mentioned.
All the cells are not acted on, though the motor impulse
passes through them. When the gland of one of the long
exterior tentacles is excited, the upper cells are not in the
least affected ; about half-way down there is a slight bending,
but the chief movement is confined to a short space near the
base; and no vart of the inner tentacle bends except the
basal portion. With respect to the blade of the leaf, the
motor impulse may be transmitted through many cells, from
the centre to the circumference, without their being in the
least affected, or they may be strongly acted on and the
blade greatly inflected. In the latter case the movement
seems to depend partly on the strength of the stimulus, and
partly on its nature, as when leaves are immersed in certain
fluids.
The power of movement which various plants possess,
when irritated, has been attributed by high authorities to
the rapid passage of fluid out of certain cells, which, from
their previous state of tension immediately contract.*
Whether or not this is the primary cause of such movements,
fluid must pass out of closed cells when they contract or are
" * Sachs, ‘ Traitéde Bot.’ 3rd edit. 1874, p. 1038. This view was, I believe,
first suggested by Lamarck.
Cmar. X.J MEANS OF MOVEMENT. 207
pressed together in one direction, unless they, at the same
time, expand in some other direction. For instance, fluid can
be seen to ooze from the surface of any young and vigorous
shoot if slowly bent into a semi-circle.* In the case of
Drosera there is certainly much movement of the fluid
throughout the tentacles whilst they are undergoing inflec-
tion. Many leaves can be found in which the purple fluid
within the cells is of an equally dark tint on the upper and
lower sides of the tentacles, extending also downwards on
both sides to equally near their bases. If the tentacles of
such a leaf are excited into movement, it will generally be
found after some hours that the cells on the concave side are
much paler than they were before, or are quite colourless,
those on the convex side having become much darker. In
two instances, after particles of hair had been placed on
glands, and when in the course of 1 hr. 10 m. the tentacles
were incurved halfway towards the centre of the leaf, this
change of colour in the two sides was conspicuously plain.
In another case, after a bit of meat had been placed on a
gland, the purple colour was observed at intervals to be
slowly travelling from the upper to the lower part, down
the convex side of the bending tentacle. But it does not
follow from these observations that the cells on the convex side
become filled with more fluid during the act of inflection than
they contained before ; for fluid may all the time be passing
into the disc or into the glands which then secrete freely.
The bending of the tentacles, when leaves are immersed
in a dense fluid, and their subsequent re-expansion in a less
dense fluid, show that the passage of fluid from or into the
cells can cause movements like the natural ones. But the
inflection thus caused is often irregular; the exterior ten-
tacles being sometimes spirally curved. Other unnatural
movements are likewise caused by the application of dense
fluids, as in the case of drops of syrup placed on the backs
of leaves and tentacles. Such movements may be compared
with the contortions which many vegetable tissues undergo
when subjected to exosmose. It is therefore doubtful
whether they throw any light on the natural movements.
If we admit that the outward passage of fluid is the cause
of the bending of the tentacles, we must suppose that the
cells, before the act of inflection, are in a high state of
* Sachs, ibid, p. 919.
208 DROSERA ROTUNDIFOLIA. (Cuap. X.
tension, and that they are elastic to an extraordinary degree ;
tor otherwise their contraction could not cause the tentacles
often to sweep through an angle of above 180°. Professor
Cohn, in his interesting paper* on the movements of the
stamens of certain Composit, states that these organs, when
dead, are as elastic as threads of india-rubber, and are then
only half as long as they were when alive. He believes
that the living protoplasm within their cells is ordinarily in
a state of expansion, but is paralysed by irritation, or may
be said to suffer temporary death; the elasticity of the cell-
walls then coming into play, and causing the contraction of
the stamens. Now the cells on the upper or concave side of
the bending part of the tentacles of Drosera do not appear
to be in a state of tension, nor to be highly elastic; for
when a leaf is suddenly killed, or dies slowly, it is not the
upper but the lower sides of the tentacles which contract
from elasticity. We may therefore conclude that their
movements cannot be accounted for by the inherent elasticity
of certain cells, opposed as long as they are alive and not
irritated by the expanded state of their contents.
A somewhat different view has been advanced by other
physiologists—namely that the protoplasm, when irritated,
contracts like the soft sarcode of the muscles of animals,
In Drosera the fluid within the cells of the tentacles at the
bending place appears under the microscope thin and homo-
geneous, and after aggregation consists of small, soft masses
of matter, undergoing incessant changes of form and floating
in almost colourless fluid. These masses are completely
redissolved when the tentacles re-expand. Now it seems
scarcely possible that such matter should have any direct
mechanical power; but if through some molecular change it
were to occupy less space than it did before, no doubt the
cell-walls would close up and contract. But in this case it
might be expected that the walls would exhibit wrinkles,
and none could ever be seen. Moreover, the contents of all
the cells seem to be of exactly the same nature, both before
and after aggregation; and yet only a few of the basal cells
contract, the rest of the tentacle remaining straight.
A third view maintained by some physiologists, though
* ¢ Abhand. der Schles. Gesell. fiir given in the ‘Annals and Mag. of
vaterl, Cultur, 1861, Heft i, An Nat. Hist.’ 3rd series, 1863, vol, ix.
excellent abstract of this paper is pp. 188-197.
Cuar. X.] NATURE OF THE MOTOR IMPULSE. 209
rejected by most others, is that the whole cell, including the
walls, actively contracts. If the walls are composed solely
of non-nitrogenous cellulose, this view is highly improbable ;
but it can hardly be doubted that they must be permeated
by proteid matter, at least whilst they are growing. Nor
does there seem any inherent improbability in the cell-walls
of Drosera contracting, considering their high state of organi-
sation ; as shown in the case of the glands by their power of
absorption and secretion, and by being exquisitely sensitive
so as to be affected by the pressure of the most minute
particles. The cell-walls of the pedicels also allow various
impulses to pass through them, inducing movement, increased
secretion and aggregation. On the whole the belief that the
walls of certain cells contract, some of their contained fluid
being at the same time forced outwards, perhaps accords best
with the observed facts. If this view is rejected, the next
most probable one is that the fluid contents of the cells shrink,
owing to a change in their molecular state, with the con-
sequent closing in of the walls. Anyhow, the movement can
hardly be attributed to the elasticity of the walls, together
with a previous state of tension.*
With respect to the nature of the motor impulse which is
transmitted from the glands down the pedicels and across
the disc, it seems not improbable that it is closely allied to
that influence which causes the protoplasm within the cells
of the glands and tentacles to aggregate. We have seen that
both forces originate in and proceed from the glands within
a few seconds of the same time, and are excited by the same
causes. The aggregation of the protoplasm lasts almost as
long as the tentacles remain inflected, even though this be
for more than a week; but the protoplasm is redissolved at
the bending place shortly before the tentacles re-expand,
* [See Gardiner’s interesting paper
tt On the Contractility of the Proto-
plasm of Plant Cells ”(* Proc. R. Soc.’
Nov. 24, 1887, vol. xliii.), in which he
gives evidence tending to show that
the curvature of the tentacles of
Drosera is brought about by contrac-
tion of the protoplasm.
Batalin (‘Flora 1877) experi-
mented on the curvature of the
tentacles as well as on the bending
of the blade of the leaf. He made
marks on the lower surface and found
that when the curvature takes place,
the distance between the marks on
what becomes the convex surface of
the leaf or tentacle increases. When
the leaf opens, or the tentacle
straightens, the distance between the
marks does not return to what it was
at first, and this permanent increase
shows that the curvature is connected
with actual growth.—F. D.J
p
210 DROSERA ROTUNDIFOLIA. [OBAR X-
showing that the exciting cause of the aggregating process
has then quite ceased. Exposure to carbonic acid causes both
the latter process and the motor impulse to travel very slowly
down the tentacles. We know that the aggregating process
is delayed in passing through the cell-walls, and we have
good reason to believe that this holds good with the motor
impulse; for we can thus understand the different rates of its
transmission in a longitudinal and transverse line across the
disc. Under a high power the first sign of aggregation is
the appearance of a cloud, and soon afterwards of extremely
fine granules, in the homogeneous purple fluid within the
cells; and this apparently is due to the union of molecules of
protoplasm. Now it does not seem an improbable view that
the same tendency—namely for the molecules to approach
each other—should be communicated to the inner surface of
the cell-walls which are in contact with the protoplasm; and
if so, their molecules would approach each other, and the cell-
wall would contract.
To this view it may with truth be objected that when
leaves are immersed in various strong solutions, or are
subjected to a heat of above 130° Fahr. (54°°4 Cent.), aggre-
gation ensues, but there is no movement. Again, various
acids and some other fluids cause rapid movement, but no
aggregation, or only of an abnormal nature, or only after a
long interval of time; but as most of these fluids are more or
less injurious, they may check or prevent the aggregating
process by injuring or killing the protoplasm. There is
another and more important difference in the two processes ;
when the glands on the dise are excited, they transmit some
influence up the surrounding tentacles, which acts on the
cells at the bending place, but does not induce aggregation
until it has reached the glands; these then send back some
other influence, causing the protoplasm to aggregate first in
the upper and then in the lower cells.
The Re-expansion of the Tentacles. -This movement is always
slow and gradual. When the centre of the leaf is excited, or
a leaf is immersed in a proper solution, all the tentacles bend
directly towards the centre, and afterwards directly back
from it. But when the point of excitement is on one side of
the disc, the surrounding tentacles bend towards it, and
therefore obliquely with respect to their normal direction ;
when they afterwards re-expand, they bend obliquely back,
so as to recover their original positions. The tentacles
Cuar. X.] RE-EXPANSION OF THE TENTACLES. ees
farthest from an excited point, wherever that may be, are
the last and the least affected, and probably in consequence
of this they are the first to re-expand. The bent portion of
a Closely inflected tentacle is in a state of active contraction,
as Shown by the following experiment. Meat was placed on
a leaf, and after the tentacles were closely inflected and had
quite ceased to move, narrow strips of the disc, with a few of
the outer tentacles attached to it, were cut off and laid on
one side under the microscope. After several failures, I
succeeded in cutting off the convex surface of the bent portion
of a tentacle. Movement immediately re-commenced, and
the already greatly bent portion went on bending until it
formed a perfect circle; the straight distal portion of the
tentacle passing on one side of the strip. The convex surface
must therefore have previously been in a state of tension,
sufficient to counterbalance that of the concave surface,
which, when free, curled into a complete ring.
The tentacles of an expanded and unexcited leaf are
moderately rigid and elastic; if bent by a needle, the upper
end yields more easily than the basal and thicker part, which
alone is capable of becoming inflected. The rigidity of this
basal part seems due to the tension of the outer surface
balancing a state of active and persistent contraction of the
cells of the inner surface. I believe that this is the case,
because, when a leaf is dipped into boiling water, the ten-
tacles suddenly become reflexed, and this apparently indicates
that the tension of the outer surface is mechanical, whilst
that of the inner surface is vital, and is instantly destroyed
by the boiling water. We can thus also understand why the
tentacles as they grow old and feeble slowly become much
reflexed. If a leaf with its tentacles closely inflected is
dipped into boiling water, these rise up a little, but by no
means fully re-expand. This may be owing to the heat
quickly destroying the tension and elasticity of the cells of
the convex surface; but I can hardly believe that their
tension, at any one time, would suffice to carry back the
tentacles to their original position, often through an angle of
above 180°. It is more probable that fluid, which we know
travels along the tentacles during the act of inflection, is
slowly re-attracted into the cells of the convex suriace, their
tension being thus gradually and continually increased. __
A recapitulation of the chief facts and discussions in this
chapter will be given at the close of the next chapter.
P2
912 DROSERA ROTUNDIFOLIA. [Cuap. XI.
CHAPTER XI.
RECAPITULATION OF THE CHIEF OBSERVATIONS ON
DROSERA ROTUNDIFOLIA.*
As summaries have been given to most of the chapters, it
will be sufficient here to recapitulate, as briefly as I.can, the
chief points. In the first chapter a preliminary sketch was
given of the structure of the leaves, and of the manner in
which they capture insects. This is effected by drops of
extremely viscid fluid surrounding the glands and by the
inward movement of the tentacles. As the plants gain most
of their nutriment by this means, their roots are very poorly
developed; and they often grow in places where hardly any
other plant except mosses can exist. The glands have the
power of absorption, besides that of secretion. They are
extremely sensitive to various stimulants, namely repeated
touches, the pressure of minute particles, the absorption of
animal matter and of various fluids, heat, and galvanic
action. A tentacle with a bit of raw meat on the gland has
been seen to begin bending in 10 s., to be strongly incurved
in 5 m., and to reach the centre of the leaf in half an hour.
The blade of the leaf often becomes so much inflected that it
forms a cup, enclosing any object placed on it.
A gland, when excited, not only sends some influence
down its own tentacle, causing it to bend, but likewise
to the surrounding tentacles, which become incurved; so
that the bending place can be acted on by an impulse
received from opposite directions, namely from the gland on
the summit of the same tentacle, and from one or more
glands of the neighbouring tentacles. Tentacles, when
inflected, re-expand after a time, and during this process the
glands secrete less copiously or become dry. As soon as
they begin to secrete again, the tentacles are ready to re-act ;
and this may be repeated at least three, probably many
more times,
* [The reader consulting this list of additions in the present
chapter without having read the edition given at the beginning of the
foregoing pages should look at the book.—F, D.]
Cuar, XL] GENERAL SUMMARY. 213
It was shown in the second chapter that animal substances
placed on the discs cause much more prompt and energetic
inflection than do inorganic bodies of the same size, or mere
mechanical irritation; but there is a still more marked
difference in the greater length of time during which the
tentacles remain inflected over bodies yielding soluble and
nutritious matter, than over those which do not yield such
matter. Extremely minute particles of glass, cinders, hair,
thread, precipitated chalk, &c., when placed on the glands of
the outer tentacles, cause them to bend. A particle, unless
it sinks through the secretion and actually touches the
surface of the gland with some one point, does not produce
any effect. A little bit of thin human hair ,,8,5 of an inch
(:203 mm.) in length, and weighing only +,+,5 of a grain
(-000822 mg.), though largely supported by the dense
secretion, suffices to induce movement. It is not probable
that the pressure in this case could have amounted to
that from the millionth of a grain. Even smaller particles
cause a slight movement, as could be seen through a lens.
Larger particles than those of which the measurements
have been given cause no sensation when placed on the
tongue, one of the most sensitive parts of the human
body.
Movement ensues if a gland is momentarily touched three
or four times; but if touched only once or twice, though with
considerable force and with a hard object, the tentacle does
not bend. ‘The plant is thus saved from much useless
movement, as during a high wind the glands can hardly
escape being occasionally brushed by the leaves of sur-
rounding plants. Though insensible to a single touch, they
are exquisitely sensitive, as just stated, to the slightest
pressure if prolonged for a few seconds; and this capacity is
manifestly of service to the plant in capturing small insects.
Even gnats, if they rest on the glands with their delicate
feet, are quickly and securely embraced. The glands are
insensible to the weight and repeated blows of drops of
heavy rain, and the plants are thus likewise saved from much
useless movement. :
The description of the movements of the tentacles was
interrupted in the third chapter for the sake of describing
the process of aggregation. ‘This process always commences
in the cells of the glands, the contents of which first become
214 DROSERA ROTUNDIFOLIA. [Cuap. XL
cloudy; and this has been observed within 10 s. after a
gland has been excited. Granules just resolvable under a
very high power soon appear, sometimes within a minute, in
the cells beneath the glands; and these then aggregate into
minute spheres. The process afterwards travels down the
tentacles, being arrested for a short time at each transverse
partition. The small spheres coalesce into larger spheres, or
into oval, club-headed, thread- or necklace-like, or otherwise
shaped masses of protoplasm, which, suspended in almost
colourless fluid, exhibit incessant spontaneous changes of
form. These frequently coalesce and again separate. If a
gland has been powerfully excited, all the cells down to the
base of the tentacle are affected. In cells, especially if filled
with dark red fluid, the first step in the process often is the
formation of a dark red, bag-like mass of protoplasm which
afterwards divides and undergoes the usual repeated changes
of form. Before any aggregation has been excited, a sheet
of colourless protoplasm, including granules (the primordial
utricle of Mohl), flows round the walls of the cells; and this
becomes more distinct after the contents have been partially
aggregated into spheres or bag-like masses. But after a
time the granules are drawn towards the central masses and
unite with them; and then the circulating sheet can no
longer be distinguished, but there is still a current of trans-
parent fluid within the cells.
Aggregation is excited by almost al! the stimulants which
induce movement; such as the glands being touched two or
three times, the pressure of minute inorganic particles, the
absorption of various fluids, even long immersion in distilled
water, exosmose, and heat. Of the many stimulants tried,
carbonate of ammonia is the most energetic and acts the
quickest; a dose of 37:55 of a grain (00048 mg.) given to
a single gland suffices to cause in one hour well-marked
aggregation in the upper cells of the tentacle. The process
goes on only as long as the protoplasm is in a living, vigorous,
and oxygenated condition.
The result is in all respects exactly the same, whether a
gland has been excited directly, or has received an influence
from other and distant glands. But there is one important
difference; when the central glands are irritated, they
transmit centrifugally an influence up the pedicels of the
exterior tentacles to their glands; but the actual process of
aggregation travels centripetally, from the glands of the
fm
Cuar. XE] GENERAL SUMMARY. 219
exterior tentacles down their pedicels. The exciting
influence, therefore, which is transmitted from one part of
the leaf to another must be different from that which
actually induces aggregation. The process does not depend
on the glands secreting more copiously than they did before ;
and is independent of the inflection of the tentacles. It
continues as long as the tentacles remain inflected, and as
soon as these are fully re-expanded, the little masses of
protoplasm are all redissolved; the cells becoming filled with
homogeneous purple fluid, as they were before the leaf was
excited.
As the process of aggregation can be excited by a few
touches, or by the pressure of insoluble particles, it is
evidently independent of the absorption of any matter, and
must be of a molecular nature. Even when caused by the
absorption of the carbonate or other salt of ammonia, or an
infusion of meat, the process seems to be of exactly the same
nature. The protoplasmic fluid must, therefore, be in a
singularly unstable condition, to be acted on by such slight
and varied causes. Physiologists believe that when a nerve
is touched, and it transmits an influence to other parts of the
nervous system, a molecular change is induced in it, though
not visible to us. Thereforeit is a very interesting spectacle
to watch the effects on the cells of a gland, of the pressure of
a bit of hair, weighing only +455 of a grain and largely
supported by the dense secretion, for this excessively slight
pressure soon causes a visible change in the protoplasm,
which change is transmitted down the whole length of the
tentacle, giving it at last a mottled appearance, distinguish-
able even by the naked eye.
In the fourth chapter it was shown that leaves placed for
a short time in water at a temperature of 110° Fahr. (438°°3
Cent.) become somewhat inflected; they are thus also
rendered more sensitive to the action of meat than they
were before. If exposed to a temperature of between 115°
and 125° (46° -1—51°-6 Cent.), they are quickly inflected, and
their protoplasm undergoes aggregation; when afterwards
placed in cold water, they re-expand. Exposed to 130° (54°°4
Cent.), no inflection immediately occurs, but the leaves are
only temporarily paralysed, for on being left in cold water,
they often become inflected and afterwards re-expand. In
one leaf thus treated, I distinctly saw the protoplasm in
movement. In other leaves treated in the same manner, and
216 DROSERA ROTUNDIFOLIA. (Cmar. XI.
then immersed in a solution of carbonate of ammonia, strong
aggregation ensued. Leaves placed in cold water, after an
exposure to so high a temperature as 145° (62°-7 Cent. ),
sometimes become slightly, though slowly inflected; and
afterwards have the contents of their cells strongly aggre-
gated by carbonate of ammonia. But the duration of the
immersion is an important element, for if left in water at 145°
(62°-7 Cent.), or only at 140° (60° Cent.), until it becomes cool,
they are killed, and the contents of the glands are rendered
white and opaque. This latter result seems to be due to the
coagulation of the albumen, and was almost always caused
by even a short exposure to 150° (65°°5 Cent.) ; but different
leaves, and even the separate cells in the same tentacle,
differ considerably in their power of resisting heat. Unless
the heat has been sufficient to coagulate the albumen,
carbonate of ammonia subsequently induces aggregation.
In the fifth chapter, the results of placing drops of various
nitrogenous and non-nitrogenous organic fluids on the discs
of leaves were given, and it was shown that they detect with
almost unerring certainty the presence of nitrogen. A de-
coction of green peas or of fresh cabbage-leaves acts almost
as powerfully as an infusion of raw meat, whereas an infusion
of cabbage-leaves made by keeping them for a long time in
merely warm water is far less efficient. A decoction of grass-
leaves is less powerful than one of green peas or cabbage-
leaves.
These results led me to inquire whether Drosera possessed
the power of dissolving solid animal matter. The experi-
ments proving that the leaves are capable of true digestion,
and that the glands absorb the digested matter, are given in
detail in the sixth chapter. These are, perhaps, the most
interesting of all my observations on Drosera, as no such
power was before distinctly known to exist in the vegetable
kingdom. It is likewise an interesting fact that the glands
of the disc, when irritated, should transmit some influence
to the glands of the exterior tentacles, causing them to se-
crete more copiously and the secretion to become acid, as if
they had been directly excited by an object placed on them.
The gastric juice of animals contains, as is well known, an
acid and a ferment, both of which are indispensable for diges-
tion, and so it is with the secretion of Drosera. When the
stomach of an animal is mechanically irritated, it secretes an
acid, and when particles of glass or other such objects were
egy
Cuar. XL] GENERAL SUMMARY. 217
placed on the glands of Drosera, the secretion, and that of
the surrounding and untouched glands, was increased in
quantity and became acid. But according to Schiff, the
stomach of an animal does not secrete its proper ferment,
pepsin, until certain substances, which he calls peptogenes,
are absorbed; and it appears from my experiments that some
matter must be absorbed by the glands of Drosera before
they secrete their proper ferment. That the secretion does
contain a ferment which acts only in the presence of an acid
on solid animal matter, was clearly proved by adding minute
doses of an alkali, which entirely arrested the process of
digestion, this immediately recommencing as soon as the
alkali was neutralised by a little weak hydrochloric acid.
From trials made with a large number of substances, it was
found that those which the secretion of Drosera dissolves
completely, or partially, or not at all, are acted on in exactly
the same manner by gastric juice. We may therefore con-
clude that the ferment of Drosera is closely analogous to, or
identical with, the pepsin of animals.
The substances which are digested by Drosera act on the
leaves very differently. Some cause much more energetic
and rapid inflection of the tentacles, and keep them inflected
for a much longer time, than do others. We are thus led to
believe that the former are more nutritious than the latter,
asis known to be the case with some of these same substances
when given to animals; for instance, meat in comparison
with gelatine. As cartilage is so tough a substance and is
so little acted on by water, its prompt dissolution by the
secretion of Drosera, and subsequent absorption, is, perhaps,
one of the most striking cases. But it is not really more
remarkable than the digestion of meat, which is dissolved by
this secretion in the same manner and by the same stages as
by gastric juice. The secretion dissolves bone, and even the
enamel of teeth, but this is simply due to the large quantity
of acid secreted, owing, apparently, to the desire of the
plant for phosphorus. In the case of bone, the ferment does
not come into play until all the phosphate of lime has been
decomposed and free acid is present, and then the fibrous
basis is quickly dissolved. Lastly, the secretion attacks and
dissolves matter out of living seeds, which it sometimes kills,
or injures, as shown by the diseased state of the seedlings. It
also absorbs matter from pollen, and from fragments of leaves.
The seventh chapter was devoted to the action of the
218 DROSERA ROTUNDIPFOLIA. [Cuar. XI.
‘salts of ammonia. ‘These all cause the tentacles, and often
the blade of the leaf, to be inflected, and the protoplasm to
be aggregated. They act with very different power; the
citrate being the least powerful, and the phosphate, owing,
no doubt, to the presence of phosphorus and nitrogen, by far
the most powerful. But the relative efficiency of only three
salts of ammonia was carefully determined, namely the car-
bonate, nitrate, and phosphate. The experiments were made
by placing half-minims (°0296 c.c.) of solutions of different
strengths on the discs of the leaves,—by applying a minute
drop (about the >p of a minim, or -00296 c.c.) for a few
seconds to three or four glands,—and by the immersion of
whole leaves in a measured quantity. In relation to these
experiments it was necessary first to ascertain the effects of
distilled water, and it was found, as described in detail, that
the more sensitive leaves are affected by it, but only ina
slight degree.
A solution of the carbonate is absorbed by the roots and
induces aggregation in their cells, but does not affect the
leaves. The vapour is absorbed by the glands, and causes
inflection as well as aggregation. A drop of a solution con-
taining „ły of a grain (°0675 mg.) is the least quantity
which, when placed on the glands of the disc, excites the
exterior tentacles to bend inwards. Buta minute drop, con-
taining yy455 of a grain (00445 mg.), if applied for a few
seconds to the secretion surrounding a gland, causes the
inflection of the same tentacle. When a highly sensitive
leaf is immersed in a solution, and there is ample time for
absorption, the s¢Jsj5 of a grain (°00024 mg.) is sufficient
to excite a single tentacle into movement.
The nitrate of ammonia induces aggregation of the
protoplasm much less quickly than the carbonate, but is
more potent in causing inflection. A drop containing 5755
of a grain (+027 mg.) placed on the disc acts powerfully
on all the exterior tentacles, which have not themselves
received any of the solution ; whereas a drop with ,.,5 of a
grain caused only a few of these tentacles to bend, but
affected rather more plainly the blade. A minute drop ap-
plied as before, and containing 5,1), of a grain (+0025 mg.),
caused the tentacle bearing this gland to bend. By the
immersion of whole leaves, it was proved that the absorp-
tion by a single gland of syrsyo of a grain (0000937 mg.)
was sufficient to set the same tentacle into movement.
Cuar. XI.] GENERAL SUMMARY. 219
The phosphate of ammonia is much more powerful than
the nitrate. A drop containing 55 of a grain (+0169 mg.)
placed on the disc of a sensitive leaf causes most of the ex-
terior tentacles to be inflected, as well as the blade of the leaf.
A minute drop containing y53\59y of a grain (-000423 mg.),
applied for a few seconds to a gland, acts, as shown by
the movement of the tentacle. When a leaf is immersed in
thirty minims (1°7748 c.c.) of a solution of one part by
weight of the salt to 21,875,000 of water, the absorption by
a gland of only the tørevovy Of a grain (-00000328 mg.),
that is, a little more than the one-twenty-millionth of a
grain, is suflicient to cause the tentacle bearing this gland
to bend to the centre of the leaf. In this experiment, owing
to the presence of the water of crystallisation, less than the
one-thirty-millionth of a grain of the efficient elements
could have been absorbed. There is nothing remarkable in
such minute quantities being absorbed by the glands, for all
physiologists admit that the salts of ammonia, which must
be brought in still smaller quantity by a single shower of
rain to the roots, are absorbed by them. Nor is it surprising
that Drosera should be enabled to profit by the absorption of
these salts, for yeast and other low fungoid forms flourish in
solutions of ammonia, if the other necessary elements are
present. But it is an astonishing fact, on which I will not
here again enlarge, that so inconceivably minute a quantity
as the one-twenty-millionth of a grain of phosphate of
ammonia should induce some change in a gland of Drosera,
sufficient to cause a motor impulse to be sent down the
whole length of the tentacle; this impulse exciting move-
ment often through an angle of above 180°. I know not
whether to be most astonished at this fact, or that the
pressure of a minute bit of hair, supported by the dense
secretion, should quickly cause conspicuous movement.
Moreover, this extreme sensitiveness, exceeding that of the
most delicate part of the human body, as well as the power
of transmitting various impulses from one part of the leaf to
another, have been acquired without the intervention of any
nervous system.
As few plants are at present known to possess glands
specially adapted for absorption, it seemed worth while to
try the effects on Drosera of various other salts, besides
those of ammonia, and of various acids. Their action, as
described in the eighth chapter, does not correspond at all
220 DROSERA ROTUNDIFOLIA. [Omir XI.
strictly with their chemical affinities, as inferred from the
classification commonly followed. The nature of the base is
far more influential than that of the acid; and this is known
to hold good with animals. For instance, nine salts of
sodium all caused well-marked inflection, and none of them
were poisonous in small doses; whereas seven of the nine
corresponding salts of potassium produced no effect, two
causing slight inflection. Small doses, moreover, of some of
the latter salts were poisonous. The salts of sodium and
potassium, when injected into the veins of animals, likewise
differ widely in their action. The so-called earthy salts
produce hardly any effect on Drosera. On the other hand,
most of the metallic salts cause rapid and strong inflection,
and are highly poisonous; but there are some odd exceptions
to this rule; thus chloride of lead and zinc, as well as two
salts of barium, did not cause inflection, and were not
poisonous.
Most of the acids which were tried, though much diluted
(one part to 437 of water), and given in small doses, acted
powerfully on Drosera; nineteen, out of the twenty-four,
causing the tentacles to be more or less inflected. Most of
them, even the organic acids, are poisonous, often highly so ;
and this is remarkable, as the juices of so many plants
contain acids. Benzoic acid, which is innocuous to animals,
seems to be as poisonous to Drosera as hydrocyanic. On the
other hand, hydrochloric acid is not poisonous either to
animals or to Drosera, and induces only a moderate amount
of inflection. Many acids excite the glands to secrete an
extraordinary quantity of mucus; and the protoplasm
within their cells seems to be often killed, as may be inferred .
from the surrounding fluid soon becoming pink. It is
strange that allied acids act very differently: formic acid
induces very slight inflection, and is not poisonous; whereas
acetic acid of the same strength acts most powerfully and is
poisonous. Lactic acid is also poisonous, but causes inflection
only after a considerable lapse of time. Malic acid acts
slightly, whereas citric and tartaric acids produce no effect.
In the ninth chapter the effects of the absorption of
various alkaloids and certain other substances were de-
scribed. Although some of these are poisonous, yet as
several, which act powerfully on the nervous system of
animals, produce no effect on Drosera, we may infer that the
extreme sensibility of the glands, and their power of trans-
‘Sah ainiaan ananasai
AA
CHAP. XL) GENERAL SUMMARY. 221
mitting an influence to other parts of the leaf, causing
movement, or modified secretion, or aggregation, does not
depend on the presence of a diffused element, allied to nerve-
tissue. One of the most remarkable facts is that long
immersion in the poison of the cobra-snake does not in the
least check, but rather stimulates, the spontaneous move-
ment of the protoplasm in the cells of the tentacles.
Solutions of various salts and acids behave very differently
in delaying or in quite arresting the subsequent action of a
solution of phosphate of ammonia. Camphor dissolved in
water acts as a stimulant, as do small doses of certain
essential oils, for they cause rapid and strong inflection.
Alcohol is not a stimulant. The vapours of camphor,
alcohol, chloroform, sulphuric and nitric ether, are poisonous
in moderately large doses, but in small doses serve as
narcotics or anæsthetics, greatly delaying the subsequent
action of meat. But some of these vapours also act as
stimulants, exciting rapid, almost spasmodic movements in
the tentacles. Carbonic acid is likewise a narcotic, and
retards the aggregation of the protoplasm when carbonate
of ammonia is subsequently given. The first access of air to
plants which have been immersed in this gas sometimes acts
as a stimulant and induces movement. But, as before
remarked, a special pharmacopceia would be necessary to
describe the diversified effects of various substances on the
leaves of Drosera.
In the tenth chapter it was shown that the sensitiveness
of the leaves appears to be wholly confined to the glands and
to the immediately underlying cells. It was further shown
that the motor impulse and other forces or influences,
proceeding from the glands when excited, pass through the
cellular tissue, and not along the fibro-vascular bundles. A
gland sends its motor impulse with great rapidity down the
pedicel of the same tentacle to the basal part which alone
bends. The impulse, then passing onwards, spreads on all
sides to the surrounding tentacles, first affecting those which
stand nearest and then those farther off. But by being thus
spread out, and from the cells of the disc not being so much
elongated as those of the tentacles, it loses force, and here
travels much more slowly than down the pedicels. Owing
also to the direction and form of the cells, it passes with
greater ease and celerity in a longitudinal than in a
transverse line across the disc. The impulse proceeding
222 DROSERA ROTUNDIFOLIA. [Cuar. XI.
from the glands of the extreme marginal tentacles does not
seem to have force enough to affect the adjoining tentacles ;
and this may be in part due to their length. The impulse
from the glands of the next few inner rows spreads chiefly
to the tentacles on each side and towards the centre of the
leaf; but that proceeding from the glands of the shorter
tentacles on the disc radiates almost equally on all sides.
When a gland is strongly excited by the quantity or
quality of the substance placed on it, the motor impulse
travels farther than from one slightly excited; and if
several glands are simultaneously excited, the impulses from
all unite and spread still farther. As soon as a gland is
excited, it discharges an impulse which extends to a con-
siderable distance; but afterwards, whilst the gland is
secreting and absorbing, the impulse suffices only to keep
the same tentacle inflected; though the inflection may last
for many days.
If the bending place of a tentacle receives an impulse
from its own gland, the movement is always towards the
centre of the leaf; and so it is with all the tentacles, when
their glands are excited by immersion in a proper fluid.
The short ones in the middle part of the disc must be
excepted, as these do not bend at all when thus excited. On
the other hand, when the motor impulse comes from one
side of the disc, the surrounding tentacles, including the
short ones in the middle of the disc, all bend with precision
towards the point of excitement, wherever this may be
seated. This is in every way a remarkable phenomenon ;
for the leaf falsely appears as if endowed with the senses of
an animal. It is all the more remarkable, as when the
motor impulse strikes the base of a tentacle obliquely with
respect to its flattened surface, the contraction of the cells
must be confined to one, two, or a very few rows at one end.
And different sides of the surrounding tentacles must be
acted on, in order that all should bend with precision to the
point of excitement.
The motor impulse, as it spreads from one or more glands
across the disc, enters the bases of the surrounding tentacles,
and immediately acts on the bending place. It does not in
the first place proceed up the tentacles to the glands,
exciting them to reflect back an impulse to their bases.
Nevertheless, some influence is sent up to the glands, as
their secretion is soon increased and rendered acid; and
a a E ON
Cair. XI] GENERAL SUMMARY. 225
then the glands, being thus excited, send back some other
influence (not dependent on increased secretion, nor on the
inflection of the tentacles), causing the protoplasm to
aggregato in cell beneath cell. This may be called a reflex
action, though probably very different from that proceeding
from the nerve-ganglion of an animal; and it is the only
known case of reflex action in the vegetable kingdom. :
About the mechanism of the movements and the nature of
the motor impulse we know very little. During the act of
inflection fluid certainly travels from one part to another of
the tentacles. But the hypothesis which agrees best with
the observed facts is that the motor impulse is allied in nature
to the aggregating process; and that this causes the mole-
cules of the cell-walls to approach each other, in the same
manner as do the molecules of the protoplasm within the
cells; so that the cell-walls contract, But some strong
objections may be urged against this view. The re-expansion
of the tentacles is largely due to the elasticity of their outer
cells, which comes into play as soon as those on the inner
side cease contracting with prepotent force; but we have
reason to suspect that fluid is continually and slowly attracted
into the outer cells during the act of re-expansion, thus
increasing their tension.*
I have now given a brief recapitulation of the chief points
observed by me, with respect to the structure, movements,
constitution, and habits of Drosera rotundifolia ; and we see
how little has been made out in comparison with what
remains unexplained and unknown.
* [Increase of fluid iv the external (convex) cells would tend to prevent
re-expansion, not to facilitate it—F. D.]
224. DROSERA ANGLICA. . [Cuar. XIE
CHAPTER XII.
ON THE STRUCTURE AND MOVEMENTS OF SOME OTHER SPECIES OF
DROSERA,
Drosera anglica—Drosera intermedia—Drosera capensis—Drosera spathulata—
Drosera filiformis—Drosera binata—Concluding remarks.
J EXAMINED six other species of Drosera, some of them in-
habitants of distant countries, chiefly for the sake of ascer-
taining whether they caught insects. This seemed the more
necessary as the leaves of some of the species differ to an
extraordinary degree in shape from the rounded ones of
Drosera rotundifolia. In functional powers, however, they
differ very little.
Drosera anglica (Hudson).*—The leaves of this species, which was
sent to me from Ireland, are much elongated, and gradually widen from
the footstalk to the bluntly pointed apex. They stand almost erect,
and their blades sometimes exceed 1 inch in length, whilst their
breadth is only the t of an inch. The glands of all the tentacles have
the same structure, so that the extreme marginal ones do not differ
from the others, as in the case of Drosera rotundifolia. When they
are irritated by being roughly touched, or by the pressure of minute
inorganic particles, or by contact with animal matter, or by the
absorption of carbonate of ammonia, the tentacles become inflected;
the basal portion being the chief seat of movement. Cutting or
pricking the blade of the leaf did not excite any movement. They
frequently capture insects, and the glands of the inflected tentacles
pour forth much acid secretion. Bits of roast meat were placed on
some glands, and the tentacles began to move in 1 m. or 1 m. 308.3
and in 1 hr. 10 m. reached the centre. "Two bits of boiled cork, one of
boiled thread, and two of coal-cinders taken from the fire, were placed,
by the aid of an instrument which had been immersed in boiling
water, on five glands ; these superfluous precautions having been taken
on account of M. Ziegler’s statements. One of the particles of cinder
* Mrs. Treat has given an ex- of Drosera longifolia (which is a syn-
cellent account in ‘The American onym in part of Drosera anglica), of
Naturalist,’ December 1873, p. 705, Drosera rotundifolia and filiformis,
Cuar. XIL] DROSERA CAPENSIS. 225
caused some inflection in 8 hrs. 45 m., as did after 23 hrs. the other
particle of cinder, the bit of thread, and both bits of cork. Three
glands were touched half a dozen times with a needle; one of the
tentacles became well inflected in 17 m., and re-expanded after 24
hrs.; the two others never moved. The homogeneous fluid within the
cells of the tentacles undergoes aggregation after these have become
inflected ; especially if given a solution of carbonate of ammonia; and
I observed the usual movements in the masses of protoplasm. In one
case, aggregation ensued in 1 hr. 10 m. after a tentacle had carried
a bit of meat to the centre. From these facts it is clear that the
tentacles of Drosera anglica behave like those of Drosera rotundi-
folia.
If an insect is placed on the central glands, or has been naturally
caught there, the apex of the leaf curls inwards. For instance, dead
flies were placed on three leaves near their bases, and after 24 hrs. the
previously straight apices were curled completely over, so as to embrace
and conceal the flies; they had therefore moved through an angle of
180°. After three days the apex of one leaf, together with the tentacles,
began to re-expand. But as far as I have seen—and I made many
trials—the sides of the leaf are never inflected, and this is the one
functional ditference between this species and Drosera rotundifolia.
Drosera intermedia (Hayne). ‘This species. is quite as common in
some parts of England as Drosera rotundifolia. It differs from
Drosera anglica, as far as the leaves are concerned, only in their
smaller size, and in their tips being generally a little reflexed. They
capture a large number of insects. ‘he tentacles are excited into
movement by all the causes above specified; and aggregation ensues,
vith movement of the protoplasmic masses. I have seen, through a
lens, a tentacle beginning to bend in less than a minute after a
particle of raw meat had been placed on the gland. The apex of the
leaf curls over an exciting object as in the case of Drosera anglica.
Acid secretion is copiously poured over captured insects. A leaf which
had embraced a fly with all its tentacles re-expanded after nearly three
days.
Drosera capensis.—This species, a native of the Cape of Good Hope,
was sent to me by Dr. Hooker. The leaves are elongated, slighty
concave along the middle and taper towards the apex, which is bluntly
pointed and reflexed. ‘They rise from an almost woody axis, and their
greatest peculiarity consists in their foliaceous green footstalks, which
are almost as broad and even longer than the gland-bearing blade.
This species, therefore, probably draws more nourishment from the air,
and less from captured insects, than the other species of the genus.
Nevertheless, the tentacles are crowded together on the disc, and are
extremely numerous; those on the margins being much longer than
the central ones. All the glands have the same form ; their secretion
is extremely,viscid and acid.
The specimen which I examined had only just recovered from a
weak state of health, This may account for the téntacles moving
Q
226 DROSERA FILIFORMIS. (Cmar. XII.
very slowly when particles of meat were placed on the glands, and
perhaps for my never succeeding in causing any movement by
repeatedly touching them with a needle. But with all the species of
the genus this latter stimulus is the least effective of any. articles
of glass, cork, and coal-cinders, were placed on the glands of six
tentacles; and one alone moved after an interval of 2 hrs. 30 m.
Nevertheless, two glands were extremely sensitive to very small doses
of the nitrate ofammonia, namely to about 54; of a minim of a solution
(one part to 5250 of water), containing only y;3555 Of a grain
(-000562 mg.) of the salt. Fragments of flies were placed on two
leaves near their tips, which became incurved in 15 hrs. A fly was
also placed in the middle of the leaf; in a few hours the tentacles on
each side embraced it, and in 8 hrs. the whole leaf directly beneath
the fly was a little bent transversely. By the next morning, after
23 hrs., the leaf was curled so completely over that the apex rested
on the upper end of the footstalk. In no case did the sides of the
leaves become inflected. A crushed fly was placed on the foliaceous
footstalk, but produced no effect.
Drosera spathulata (sent to me by Dr. Hooker),—I made only a
few observations on this Australian species, which has long, narrow
leaves, gradually widening towards their tips. The glands of the
extreme marginal tentacles are elongated and differ from the others, as
in the case of Drosera rotundifolia. A fly was placed on a leaf, and
in 18 hrs. it was embraced by the adjoining tentacles. Gum-water
dropped on several leaves produced no effect. A fragment of a leaf
was immersed in a few drops of a solution of one part of carbonate of
ammonia to 146 of water; all the glands were instantly blackened ;
the process of aggregation could be seen travelling rapidly down the
cells of the tentacles; and the granules of protoplasm soon united into
spheres and variously shaped masses, which displayed the usual
movements. Half a minim of a solution of one part of nitrate of
ammonia to 146 of water was next placed on the centre of a leaf;
after 6 hrs. some marginal tentacles on both sides were inflected, and
after 9 hrs. they met in the centre. The lateral edges of the leaf also
became incurved, so that it formed a half-cylinder; but the apex of
the leaf in none of my few trials was inflected. The above dose of
the nitrate (viz. ył of a grain or *202 mg.) was too powerful, for in
the course of 23 hrs. the leaf died.
Drosera filiformis.—This North American species grows in such
abundance in parts of New Jersey as almost to cover the ground. It
catches, according to Mrs, Treat,* an extraordinary number of small and
large insects,—even great flies of the genus Asilus, moths, and butter-
flies. The specimen which I examined, sent me by Dr. Hooker, had
thread-like leaves, from 6 to 12 inches in length, with the upper surface
convex and the lower fiat and slightly channelled. The whole convex
* ¢ American Naturalist,’ Dec. 1873, p. 705.
Cuar. XIIL] DROSERA BINATA. wae
surface, down to the roots—for there is no distinct footstalk—is covered
with short gland-bearing tentacles, those on the margins being the
longest and reflexed. Bits of meat placed on the glands of some
tentacles caused them to be slightly inflected in 20 m.; but the plant
was not in a vigorous state. After 6 hrs. they moved through an
angle of 90°, and in 24 hrs. reached the centre. The surrounding
tentacles by this time began to curve inwards. Ultimately a large drop
of extremely viscid, slightly acid secretion was poured over the meat
from the united glands. Several other glands were touched with a
little saliva, and the tentacles became incurved in under 1 hr., and
re-expanded after 18 hrs. Particles of glass, cork, cinders, thread, and
gold-leaf, were placed on numerous glands on two leaves; in about
1 hr. four tentacles became curved, and four others after an additional
interval of 2 hrs. 30 m. I never once succeeded in causing any
movement by repeatedly touching the glands with a needle; and
Mrs. Treat made similar trials for me with no success. Small tlies
were placed on several leaves near their tips, but the thread-like blade
became only on one occasion very slightly bent, directly beneath the
insect. Perhaps this indicates that the blades of vigorous plants
would bend over captured insects, and Dr. Canby informs me that
this is the case; but the movement cannot be strongly pronounced, as
it was not observed by Mrs. Treat.
Drosera binata (or dichotoma).*—I am much indebted to Lady
Dorothy Nevill for a fine plant of this almost gigantic Australian species,
which differs in some interesting points from those previously described.
In this specimen the rush-like footstalks of the leaves were 20 inches
in length. The blade bifurcates at its junction with the footstalk, and
twice or thrice afterwards, curling about in an irregular manner. It is
narrow, being only 4, of an inch in breadth. One blade was 73 inches
long, so that the entire leaf, including the footstalk, was above 27
‘inches in length. Both surfaces are slightly hollowed out. The upper
surface is covered with tentacles arranged in alternate rows; those in
the middle being short and crowded together, those towards the margins
longer, even twice or thrice as long as the blade is broad. The glands
of the exterior tentacles are of a much darker red than those of the
central ones. The pedicels of all are green. The apex of the blade is
attenuated, and bears very long tentacles. Mr. Copland informs me
that the leaves of a plant which he kept for some years were generally
covered with captured insects before they withered.
The leaves do not differ in essential points of structure or of function
from those of the previously described species. Bits of meat or a little
saliva placed on the glands of the exterior tentacles caused well-marked
movement in 3 m., and particles of glass acted in 4m. The tentacles
with the latter particles re-expanded after 22 hrs. A piece of leaf
immersed in a few drops of a solution of one part of carbonate of
* [See E. Morren, ‘Bull. de Acad. Royale de Belgique,’ 2™° série, tom
40, 1875, where the plant is figured, and some experiments described.— F. D,}
Q 2
228 DROSERA BINATA. [Cuar. XIL
ammonia to 437 of water had all the glands blackened and all the
tentacles inflected in 5 m. A bit of raw meat, placed on several glands
in the medial furrow, was well clasped in 2 hrs. 10 m. by the marginal
tentacles on both sides. Bits of roast meat and small flies did not act
quite so quickly; and albumen and fibrin still less quickly. One of
the bits of meat excited so much secretion (which is always acid) that
it flowed some way down the medial furrow, causing the inflection of
the tentacles on both sides as far as it extended. Particles of glass
placed on the glands in the medial furrow did not stimulate them
sufliciently for any motor impulse to be sent to the outer tentacles.
In no case was the blade of the leaf, even the attenuated apex, at all
inflected.
On both the upper and lower surface of the blade there are numerous
minute, almost sessile glands, consisting of four, eight, or twelve cells.
On the lower surface they are pale purple, on the upper, greenish.
Nearly similar organs occur on the foot-stalks, but they are smaller and
often in a shrivelled condition. The minute glands on the blade can
absorb rapidly: thus, a piece of leaf was immersed in a solution of one
part of carbonate of ammonia to 218 of water (2 gr. to 1 oz.), and in
5 m. they were all so much darkened as to be almost black, with their
contents aggregated. They do not, as far as I could observe, secrete
spontaneously ; but in between 2 and 3 hrs. after a leaf had been
rubbed with a bit of raw meat moistened with saliva, they seemed
to be secreting freely ; and this conclusion was afterwards supported by
other appearances. ‘They are, therefore, homologous with the sessile
glands hereafter to be described on the leaves of Dionwa and Droso-
phyllum. In this latter genus they are associated, as in the present
case, with glands which secrete. spontaneously, that is, without being
excited.
Drosera binata presents another and more remarkable peculiarity,
namely, the presence of a few tentacles on the backs of the leaves, near
their margins. ‘These are perfect in structure; spiral vessels run up
their pedicels; their glands are surrounded by drops of viscid secretion,
and they have the power of absorbing. This latter fact was shown by
the glands immediately becoming black, and the protoplasm aggregateu,
when a leaf was placed in a little solution of one part of carbonate
of ammonia to 437 of water. These dorsal tentacles are short, not being.
nearly so long as the marginal ones on the upper surface; some of them
are so short as almost to graduate into the minute sessile glands. Their
presence, number, and size, vary on different leaves, and they are
arranged rather irregularly. On the back of one leaf I counted as
many as twenty-one along one side.
These dorsal tentacles differ in one important respect from those on
the upper surface, namely, in not possessing any power of movement,.
in whatever manner they may be stimulated. Thus, portions of four
leaves were placed at different times in solutions of carbonate of
ammonia (one part to 437 or 218 of water), and all the tentacles on the:
upper surface soon became closely inflected; but the dorsal ones did
Cumar. XII] CONCLUDING REMARKS. 229
not move, though the leaves were left in the solution for many hours,
and though their glands from their blackened colour had obviously
absorbed some of the salt. Rather young leaves should be selected
for such trials, for the dorsal tentacles, as they grow old and begin to
Wither, often spontaneously incline towards the middle of the leaf. If
these tentacles had possessed the power of movement, they would not
have been thus rendered more serviceable to the plant ; for they are not
long enough to bend round the margin of the leaf so as to reach an
insect caught on the upper surface. Nor would it have been of any
use if these tentacles could have moved towards the middle of the
lower surface, for there are no viscid glands there by which insects
can be caught. Although they have no power of movement, they are
probably of some use by absorbing animal matter from any minute
insect which may be caught by them, and by absorbing ammonia from
the rain-water. But their varying presence and size, and their irregular
position, indicate that they are not of much service, and that they are
tending towards abortion. In a future chapter we shall see that
Drosophyllum, with its elongated leaves, probably represents the
condition of an early progenitor of the genus Drosera; and none of the
tentacles of Drosophyllum, neither those on the upper nor lower surface
of the leaves, are capable of movement when excited, though they
capture numerous insects, which serve as nutriment. Therefore it
seems that Drosera binata has retained remnants of certain ancestral
characters—namely, a few motionless tentacles on the backs of the
leaves, and fairly well developed sessile glands—which have been lost
by most or all of the other species of the genus.
Concluding Remarks.—F rom what we have now seen, there
can be little doubt that most or probably all the species of
Drosera are adapted for catching insects by nearly the same
means. Besides the two Australian species above described,
it is said* that two other species from this country, namely
Drosera pallida and Drosera sulphurea, “close their leaves
upon insects with great rapidity: and the same phenomenon
is manifested by an Indian species, D. lunata, and by several
of those of the Cape of Good Hope, especially by D. trinervis.”
Another Australian species, Drosera heterophylla (made by
Lindley into a distinct genus, Sondera) is remarkable from
its peculiarly shaped leaves, but I know nothing of its power
of catching insects, for I have seen only dried specimens.
The leaves form minute flattened cups, with the footstalks
attached not to one margin, but to the bottom. The inner
* ¢Gardener’s Chronicle,’ 1874, p. 209.
230 CONCLUDING REMARKS. (Cuar. XI.
surface and the edges of the cups are studded with tentacles,
which include fibro-vascular bundles, rather different from
those seen by me in any other species: for some of the vessels.
are barred and punctured, instead of being spiral. The
glands secrete copiously, judging from the quantity of dried
secretion adhering to them.
j
Cuar. XIII] DIONÆA MUSCIPULA. 2P
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 hydro-
cyanic 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.
Tus plant, commonly called Venus’ fly-trap, from the rapidity
and force of its movements, is one of the most wonderful in
the world.* It is a member of the small family of the
Droseracex, and is found only in the eastern part of North
Carolina, growing in damp situations. The roots are small ;
those of a moderately fine plant which I examined consisted
of two branches about 1 inch in length, springing from a
bulbous enlargement. They probably serve, as in the case
of Drosera, solely for the absorption of water ; fora gardener,
who has been very successful in the cultivation of this plant,
grows it, like an epiphytic orchid, in well-drained damp
moss without any soil.t The form of the bilobed leaf, with
its foliaceous footstalk, is shown in the accompanying drawing
(fig. 12). The two lobes stand at rather less than a right
angle to each other. Three minute pointed processes or fila-
ments, placed triangularly, project from the upper surfaces of
both ; but I have seen two leaves with four filaments on each
side, and another with only two. These filaments are
* Dr. Hooker, in his address to [A good account of the early
the British Association at Belfast, literature is given by Kurtz in Reich-
1874, has given so full an historical ert and Du Bois-Reymond’s ‘ Archiv.’
account of the observations which 1876.—F. D.]
have been published on the habits of + ‘Gardener’s Chronicle,’ 1874, p.
this plant, that it would be super- 464,
fluous on my part to repeat them.
232 DIONÆA MUSCIPULA. [Cuar. XII.
remarkable from their extreme sensitiveness to a touch, as
shown not by their own movement, but by that of the lobes.
The margins of the leaf are prolonged into sharp rigid pro-
jections which I will call spikes, into each of which a bundle
of spiral vessels enters. The spikes stand in such a position
that, when the lobes close, they interlock like the teeth
of arat-trap. The midrib of the leaf, on the lower side, is
strongly developed and prominent.
The upper surface* of the leafis thickly covered, excepting
towards the margins, with minute glands of a reddish or
Fic. 12.
(Dionza muscipula.)
Leaf viewed laterally in its expanded state.
purplish colour, the rest of the leaf being green. There are
no glands on the spikes, or on the foliaceous footstalk. The
glands are formed of from twenty to thirty polygonal cells,
filled with purple fluid. Their upper surface is convex.
They stand on very short pedicels, into which spiral vessels
do not enter, in which respect they differ from the tentacles
of Drosera. They secrete, but only when excited by the
absorption of certain matters; and they have the power of
* (A. Fraustadt, in his Breslau dis- fact. It is easy to see that the lower
sertationon Dionza (Mar. 1876) states
that the upper surface of the leaf
is devoid of stomata. C. De Candolle,
‘Archives des Sciences Phys. et Nat.’
Geneva, April 1876, mentions the same
surface of the leaf is a better one for
the development of stomata than the
upper surfaee, which is liable to be
constantly bathed in secretion.—
FE; D)
LE ETE I TT a TEL EY a
Cuar. XII.] SENSITIVENESS OF FILAMENTS. ase
absorption. Minute projections, formed of eight divergent
arms of a reddish-brown or orange colour, and appearing
under the microscope like elegant little flowers, are scattered
in considerable numbers over the footstalk, the backs of the
leaves, and the spikes, with a few on the upper surface of the
lobes. These octofid projections are no doubt homologous
with the papille on the leaves of Drosera rotundifolia. There
are also a iew very minute, simple, pointed hairs,* about
17407 Of an inch (+0148 mm.) in lengih on the backs of the
eaves,
The sensitive filamentst are formed of several rows of
elongated cells, filled with purplish fluid. They are a little
above the >} of an inch in length; are thin and delicate, and
taper toa point. I examined the bases of several, making
sections of them, but no trace of the entrance of any vessel
could be seen. The apex is sometimes bifid or even trifid,
owing to a slight separation between the terminal pointed
cells. Towards the base there is constriction, formed of
broader cells, beneath which there is an articulation, supported
on an enlarged base, consisting of differently shaped poly-
gonal cells. As the filaments project at right angles to the
surface of the leaf, they would have been lable to be broken
whenever the lobes closed together, had it not been for the
articulation which allows them to bend flat down.
These filaments, from their tips to their bases,f are ex-
quisitely sensitive to a momentary touch. It is scarcely
possible to touch them ever so lightly or quickly with any
hard object without causing the lobes to close. A piece of
very delicate human hair, 24 inches in length, held dangling
over a filament, and swayed to and fro so as to touch it, did
not excite any movement. But when a rather thick cotton
thread of the same length was similarly swayed, the lobes
closed. Pinches of fine wheaten flour, dropped from a height,
produced no effect. The above-mentioned hair was then fixed
into a handle, and cut off so that 1 inch projected; this
* [These hairs were absent in the
specimens examined by Kurtz (Reich-
ert and Du Bois-Reymond’s ‘ Archiv.’
1876).—F. D.]
+ [Both Fraustadt and De Candolle
have described the structure of these
tilaments, and have shown that their
morphological rank is that of “ emer-
gencies.””—F. D.]
t [Batalin (‘ Flora,’ 1877) quotes
Oudemans (R. Academy of Sciences of
Amsterdam, 1859), to the effect that
the filaments are much more sensitive
at the base than elsewhere. Batalin
confirms the fact from his own obser-
vations.—F, D.]
234 DIONEA MUSCIPULA. [Cuap. XII.
length being sufficiently rigid to support itself in a nearly
horizontal line. The extremity was then brought by a slow
movement laterally into contact with the tip of a filament,
and the leaf instantly closed. On another occasion two or
three touches of the same kind were necessary before any
movement ensued. When we consider how flexible a fine
hair is, we may form some idea how slight must be the touch
given by the extremity of a piece, 1 inch in length, moved
slowly.
Although these filaments are so sensitive to a momentary
and delicate touch, they are far less sensitive than the glands
of Drosera to prolonged pressure. Several times I succeeded
in placing on the tip of a filament, by the aid of a needle
moved with extreme slowness, bits ot rather thick human
hair, and these did not excite movement, although they were
more than ten times as long as those which caused the ten-
tacles of Drosera to bend; and although in this latter case
they were largely supported by the dense secretion. On the
other hand, the glands of Drosera may be struck with a needle
or any hard object, once, twice, or even thrice, with consider-
able force, and no movement ensues. This singular differenc
in the nature of the sensitiveness of the filaments of Dionxa
and of the glands of Drosera evidently stands in relation to
the habits of the two plants. Ifa minute insect alights with
its delicate feet on the glands of Drosera, it is caught by the
viscid secretion, and the slight, though prolonged pressure,
gives notice of the presence of prey, which is secured by the
slow bending of the tentacles. On the other hand, the
sensitive filaments of Dionæa are not viscid, and the capture
of insects can be assured only by their sensitiveness to a
momentary touch, followed by the rapid closure of the lobes.*
As just stated, the filaments are not glandular, and do not
secrete. Nor have they the power of absorption, as may be
inferred from drops of a solution of carbonate of ammonia
(one part to 146 of water), placed on two filaments, not pro-
ducing any effect on the contents of their cells, nor causing
the lobes to close. When, however, a small portion of a leaf
with an attached filament was cut off and immersed in the
* [Munk (Reichert and du Bois- covering them was removed. It is
Reymond’s ‘Archiv.’ 1876, p. 105) remarkable that the change from a
states that the leaves of his plants damp to a dry atmosphere should
frequently closed when the bell-jar produce this effect.—F. D.]
Cuar, XIUI.] SENSITIVENESS OF FILAMENTS. 235
same solution, the fluid within the basal cells became almost.
instantly aggregated into purplish or colourless, irregularly
shaped masses of matter. The process of aggregation grad-
ually travelled up the filaments from cell to cell to their ex-
tremities, thatis in a reverse course to what occurs in the ten-
tacles of Drosera when their glands have been excited. Several
other filaments were cut off close to their bases, and left for
1hr. 30 m.in a weaker solution of one part of the carbonate to
218 of water, and this caused aggregation in all the cells,
commencing as before at the bases of the filaments.
Long immersion of the filaments in distilled water likewise
causes aggregation. Nor is it rare to find the contents of
a few of the terminal cells in a spontaneously aggregated
condition. The aggregated masses undergo incessant slow
changes of form, uniting and again separating; and some of
them apparently revolve round their own axes. A current
of colourless granular protoplasm could also be seen travelling
round the walls of the cells. This current ceases to be
visible as soon as the contents are well aggregated; but it
probably still continues, though no longer visible, owing to
all the granules in the flowing layer having become united
with the central masses. In all these respects the filaments
of Dionza behave exactly like the tentacles of Drosera.
Notwithstanding this similarity there is one remarkable
difference. The tentacles of Drosera, after their glands have
been repeatedly touched, or a particle of any kind has been
placed on them, become inflected and strongly aggregated.
No such effect is produced by touching the filaments of
Dionæa ; I compared, after an hour or two, some which had
been touched and some which had not, and others after
twenty-five hours, and there was no difference in the contents
of the cells. The leaves were kept open all the time by clips;
so that the filaments were not pressed against the opposite
lobe.
Drops of water,* or a thin broken stream, falling from a
height on the filaments, did not cause the blades to close;
though these filaments were afterwards proved to be highly
* [C. De Candolle (‘Archives des late the leaf, but that it may be made
Sc. Phys. et Nat.’ Geneva, April 1876) to close by a current of water directed
states that drops of water which in- at right angles to the filament.—
fringe on the filaments in the direc- F, D.J
tion of their length do not stimu-
236 DIONEA MUSCIPULA. (Car. XIII.
sensitive. No doubt, as in the case of Drosera, the plant is
indifferent to the heaviest shower of rain. Drops ofa solution
of half an ounce of sugar to a fluid ounce of water were
repeatedly allowed to fall from a height on the filaments, but
produced no effect, unless they adhered to them. Again, I
blew many times through a fine pointed tube with my utmost
force against the filaments without any effect; such blowing
heing received with as much indifference as no doubt is a
heavy gale of wind. We thus see that the sensitiveness of
the filaments is of a specialised nature, being related to a
momentary touch rather than to prolonged pressure ; and the
touch must not be from fluids, such as air or water, but from
some solid object.
Although drops of water and of a moderately strong solu-
tion of sugar, falling on the filaments, does not excite them,
yet the immersion of a leaf in pure water sometimes caused
the lobes to close. One leaf was left immersed for 1 hr. 10m.
and three other leaves for some minutes, in water at tem-
peratures varying between 59° and 65° (15° to 18°°3 Cent.)
without any effect. One, however, of these four leaves, on
being gently withdrawn from the water, closed rather quickly.
The three other leaves were proved to he in good condition,
as they closed when their filaments were touched. Never-
theless two fresh leaves on being dipped into water at 75°
and 625° (23°°8 and 16°-9 Cent.) instantly closed. These
were then placed with their footstalks in water, and after
23 hrs. partially re-expanded ; on touching their filaments one
of them closed. This latter leaf after an additional 24 hrs.
again re-expanded, and now, on the filaments of both leaves
being touched, both closed. We thus see that a short immer-
sion in water does not at all injure the leaves, but sometimes
excites the lobes to close. The movement in the above cases
was evidently not caused by the temperature of the water.
It has been shown that long immersion causes the purple
fluid within the cells of the sensitive filaments to become
aggregated; and the tentacles of Drosera are acted on in the
same manner by long immersion, often being somewhat
inflected. In both cases the result is probably due to a
slight degree of exosmose.
I am confirmed in this belief by the effects of immersing a
leaf of Dionæa in a moderately strong solution of sugar; the
leaf having been previously left for 1 hr. 10 m. in water
without any effect; for now the lobes closed rather quickly,
PAO ie E es
Cuar. XIII.] SENSITIVENESS OF FILAMENTS. O51
the tips of the marginal spikes crossing in 2 m. 30 s., and
the leaf being completely shut in 3 m. Three leaves were
then immersed in a solution of half an ounce of sugar to a
fluid ounce of water, and all three leaves closed quickly.
As I was doubtful whether this was due to the cells on the
upper surface of the lobes, or to the sensitive filaments, being
acted on by exosmose, one leaf was first tried by pouring a
little of the same solution in the furrow between the lobes
over the midrib, which is the chief seat of movement. It
was left there for some time, but no movement ensued. The
whole upper surface of leaf was then painted (except close
round the bases of the sensitive filaments, which I could not
do without risk of touching them) with the same solution,
but no effect was produced. So that the cells on the upper
surface are not thus affected. But when, after many trials,
I succeeded in getting a drop of the solution to cling to one
of the filaments, the leaf quickly closed. Hence we may, I
think, conclude that the solution causes fluid to pass out of
the delicate cell of the filaments by exosmose; and that this
sets up some molecular change in their contents, analogous
to that which must be produced by a touch.
The immersion of leaves .in a solution of sugar affects them
for a much longer time than does an immersion in water, or
a touch on the filaments; for in these latter cases the lobes
begin to re-expand in less than a day. On the other hand,
of the three leaves which were immersed for a short time in
the solution, and were then washed by means of a syringe
inserted between the lobes, one re-expanded after two days;
a second after seven days; and the third after nine days.
The leaf which closed, owing to a drop of the solution
having adhered to one of the filaments, opened after two days.
I was surprised to find on two occasions that the heat from
the rays of the sun, concentrated by a lens on the bases of
several filaments, so that they were scorched and discoloured,
did not cause any movement; though the leaves were active,
as they closed, though rather slowly, when a filament on the
opposite side was touched. On a third trial, a fresh leaf
closed after a time, though very slowly; the rate not being
increased by one of the filaments, which had not been
injured, being touched. After a day these three leaves
opened, and were fairly sensitive when the uninjured fila-
ments were touched. The sudden immersion of a leaf into
boiling water does not cause it to close. Judging from the
238 DIONÆA MUSCIPULA. (Cap. XIII.
analogy of Drosera, the heat in these several cases was too
great and too suddenly applied. The surface of the blade is
very slightly sensitive; it may be freely and roughly handled,
without any movement being caused. A leaf was scratched
rather hard with a needle, but did not close; but when the
triangular space between the three filaments on another leaf
was similarly scratched, the lobes closed. They always
closed when the blade or midrib was deeply pricked or cut.
Inorganic bodies, even of large size, such as bits of stone,
glass, &c.—or organic bodies not containing soluble nitro-
genous matter, such as bits of wood, cork, moss, or bodies
containing soluble nitrogenous matter, if perfectly dry, such
as bits of meat, albumen, gelatine, &c., may be long left (and
many were tried) on the lobes, and no movement is excited.
The result, however, is widely different, as we shall presently
see, if nitrogenous organic bodies which are at all damp, are
left on the lobes; for these then close by a slow and gradual
movement, very different from that caused by touching one
of the sensitive filaments. The footstalk is not in the least
sensitive; a pin may be driven through it, or it may be cut
off, and no movement follows.
‘The upper surface of the lobes, as already stated, is
thickly covered with small purplish, almost sessile glands.*
These have the power both of secretion and absorption ; but,
unlike those of Drosera, they do not secrete until excited
by the absorption of nitrogenous matter. No other excite-
ment, as far as I have seen, produces this effect. Objects,
such as bits of wood, cork, moss, paper, stone, or glass, may
be left for a length of time on the surface of a leaf, and it
remains quite dry. Nor does it make any difference if the
lobes close over such objects. For instance, some little balls
of blotting-paper were placed on a leaf, and a filament was
touched; and when after 24 hrs. the lobes began to re-open,
* [Gardiner has described these protoplasm is much less granular
glands in the ‘ Proceedings of the R.
Society,’ vol xxxvi. p.180. When at
rest the gland-cells show a granular
protoplasm, containing in most cases
a single large vacuole; the nucleus is
situated at the base of the cell. At
the end of the secreting period the
following changes have occurred, The
nucleus seems to diminish in size, it
has assumed a central position; the
than before, and contains a number
of small vacuoles, so that the nucleus
appears suspended by radiating
strands of protoplasm in the centre
of the cell.
Another change produced by the
feeding the leaf is the appearance, in
the parenchyma, of tufts of greenish
yellow crystals of unknown nature.—
F, D]
Car. XIIL] SECRETION AND ABSORPTION. 239
the balls were removed by the aid of thin pincers, and were
found perfectly dry. On the other hand, if a bit of damp
meat or a crushed tly is placed on the surface of an expanded
leaf, the glands after a time secrete freely. In one such
case there was a little secretion directly beneath the meat in
4 hrs. ; and atier an additional 3 hrs. there was a consider-
able quantity both under and close round it. In another
case, after 3 hrs. 40 m., the bit of meat was quite wet. But
none of the glands secreted, excepting those which actually
touched the meat or the secretion containing dissolved
animal matter.
If, however, the lobes are made to close over a bit of meat
or an insect, the result is different, for the glands over the
whole surface of the leaf now secrete copiously. As in this
case the glands on both sides are pressed against the meat or
insect, the secretion from the first is twice as great as when
a bit of meat is laid on the surface of one lobe; and as the
two lobes come into almost close contact, the secretion,
containing dissolved animal matter, spreads by capillary
attraction, causing fresh glands on both sides to begin
secreting in a continually widening circle. The secretion is
almost colourless, slightly mucilaginous, and, judging by the
manner in which it coloured litmus paper, more strongly
acid than that of Drosera. It is so copious that on one
occasion, when a leaf was cut open, on which a small cube
of albumen had been placed 45 hrs. before, drops rolled off
the leaf. On another occasion, in which a leaf with an
enclosed bit of roast meat spontaneously opened after eight
days, there was so much secretion in the furrow over the
midrib that it trickled down. A large crushed fly (Tipula)
was placed on a leaf from which a small portion at the base
of one lobe had previously been cut away, so that an opening
was left; and through this, the secretion continued to run
down the footstalk during nine days,—that is, for as long a
time as it was observed. By forcing up one of the lobes, I
was able to see some distance between them, and all the
glands within sight were secreting freely.
We have seen that inorganic and non-nitrogenous objects
placed on the leaves do not excite any movement; but
nitrogenous bodies, if in the least degree damp, cause after
several hours the lobes to close slowly. Thus bits of quite
dry meat and gelatine were placed at opposite ends of the
same leaf, and in the course of 24 hrs. excited neither
240 DIONEA MUSCIPULA, (Cuap. XIII.
secretion nor movement. They were then dipped in water,
their surfaces dried on blotting-paper, and replaced on the
same leaf, the plant being now covered with a bell-glass.
After 24 hrs. the damp meat had excited some acid secretion,
and the lobes at this end of the leaf were almost shut. At
the other end, where the damp gelatine lay, the leaf was
still quite open, nor had any secretion been excited ; so that,
as with Drosera, gelatine is not nearly so exciting a sub-
stance as meat. The secretion beneath the meat was tested
by pushing a strip of litmus paper under it (the filaments
not being touched), and this slight stimulus caused the leaf
to shut. On the eleventh day it reopened; but the end
where the gelatine lay, expanded several hours before the
opposite end with the meat.
A second bit of roast meat, which appeared dry, though it
had not been purposely dried, was left for 24 hrs. on a leaf,
caused neither movement nor secretion. The plant in its
pot was now covered with a bell-glass, and the meat absorbed
some moisture from the air; this sufficed to excite acid
secretion, and by the next morning the leaf was closely shut.
A third bit of meat, dried so as to be quite brittle, was
placed on a leaf under a bell-glass, and this also became in
24 hrs. slightly damp, and excited some acid secretion, but
no movement.
A rather large piece of perfectly dry albumen was left at
one end of a leaf for 24 hrs. without any effect. It was then
soaked for a few minutes in water, rolled about on blotting-
paper, and replaced on the leaf; in 9 hrs. some slightly acid
secretion was excited, and in 24 hrs. this end of the leaf was
partially closed. The bit of albumen, which was now
surrounded by much secretion, was gently removed, and
although no filament was touched, the lobes closed. In this
and the previous case, it appears that the absorption of
animal matter by the glands renders the surface of the leaf
much more sensitive to a touch than it is in its ordinary
state; and this is a curious fact. Two days afterwards the
end of the leaf where nothing had been placed began to
open, and on the third day was much more open than the
opposite end where the albumen had lain.
Lastly, large drops of a solution of one pari of carbonate
of ammonia to 146 of water were placed on some leaves, but
no immediate movement ensued. I did not then know of
the slow movement caused by animal matter, otherwise £
4
Te
Cuar. XIII] SECRETION AND ABSORPTION. 241
should have observed the leaves for a longer time, and they
would probably have been found closed, though the solution
(judging from Drosera) was, perhaps, too strong.
From the foregoing cases it is certain that bits of meat
and albumen, if at all damp, excite not only the glands to
secrete, but the lobes to close. This movement is widely
different from the rapid closure caused by one of the
filaments being touched. We shall see its importance when
we treat of the manner in which insects are captured.
There is a great contrast between Drosera and Dionza in the
effects produced by mechanical irritation on the one hand,
and the absorption of animal matter on the other. Particles
of glass placed on the glands of the exterior tentacles of
Drosera excite movement within nearly the same time, as
do particles of meat, the latter being rather the most
efficient ; but when the glands of the disc have bits of meat
given them, they transmit a motor impulse to the exterior
tentacles much more quickly than do these glands when
bearing inorganic particles, or when irritated by repeated
touches. On the other hand, with Dionea, touching the
filaments excites incomparably quicker movement than the
absorption of animal matter by the glands. Nevertheless, in
certain cases, this latter stimulus is the more powerful of the
two. On three occasions leaves were found which from
some cause were torpid, so that their lobes closed only
slightly, however much their filaments were irritated ; but
on inserting crushed insects between the lobes, they became
in a day closely shut.
The facts just given plainly show that the glands have
the power of absorption, for otherwise it is impossible that
the leaves should be so differently affected by non-nitro-
genous and nitrogenous bodies, and between these latter in a
dry and damp condition. It is surprising how slightly
damp a bit of meat or albumen need be in order to excite
secretion and afterwards slow movement, and equally
surprising how minute a quantity of animal matter, when
absorbed, suffices to produce these two effects. It seems
hardly credible, and yet it is certainly a fact, that a bit of
hard-boiled white of egg, first thoroughly dried, then soaked
for some minutes in water and rolled on blotting-paper,
should yield in a few hours enough animal matter to the
glands to cause them to secret>, and afterwards the lobes to
close. That the glands have the power of absorption is
R
242 DIONÆA MUSCIPULA. [Cuap. XIII.
likewise shown by the very different lengths of time (as we
shall presently see) during which the lobes remain closed
over insects and other bodies yielding soluble nitrogenous
matter, and over such as do not yield any. But there is
direct evidence of absorption in the condition of the glands
which have remained for some time in contact with animal
matter. Thus bits of meat and crushed insects were several
times placed on glands, and these were compared after some
hours with other glands from distant parts of the same leaf.
The latter showed not a trace of aggregation, whereas those
which had been in contact with the animal matter were well
ageregated. Aggregation may be seen to occur very quickly
if a piece ofa leaf is immersed in a weak solution of carbonate
of ammonia. Again, small cubes of albumen and gelatine
were left for eight days on a leaf, which was then cut open.
The whole surface was bathed with acid secretion, and every
cell in the many glands which were examined had its
contents aggregated in a beautiful manner into dark or pale
purple, or colourless globular masses of protoplasm. These
underwent incessant slow changes of forms; sometimes
separating from one another and then reuniting, exactly as
in the cells of Drosera, Boiling water makes the contents
of the gland-cells white and opaque, but not so purely white
and porcelain-like as in the case of Drosera. How living
insects, when naturally caught, excite the glands to secrete
so quickly as they do, I know not; but I suppose that the
great pressure to which they are subjected forces a little
excretion from either extremity of their bodies, and we have
seen that an extremely small amount of nitrogenous matter
is sufficient to excite the glands.
Before passing on to the subject of digestion, I may state
that I endeavoured to discover, with no success, the functions
of the minute octofid processes with which the leaves are
studded. From facts hereafter to be given in the chapters
on Aldrovanda and Utricularia, it seemed probable that they
served to absorb decayed matter left by the captured insects ;.
but their position on the backs of the leaves and on the
footstalks rendered this almost impossible. Nevertheless,
leaves were immersed in a solution of one part of urea to 437
of water, and after 24 hrs. the orange layer of protoplasm
within the arms of these processes did not appear more
aggregated than in other specimens kept in water. I then
tried suspending a leaf in a bottle over an excessively putrid
Pe SSN Straten eneon,
Cuar. XIU] DIGESTION, 243
infusion of raw meat, to see whether they absorbed the
vapour, but their contents were not affected.
Digestive Power of the Secretion.*—When a leaf closes over
any object, it may be said to form itself into a temporary
stomach; and if the object yields ever so little animal
matter, this serves, to use Schiff’s expression, as a peptogene, t
and the glands on the surface pour forth their acid secretion,
which acts like the gastric juice of animals. As so many ex-
periments were tried on the digestive power of Drosera, only
a few were made with Dionæa, but they were amply sufficient
to prove that it digests. This plant, moreover, is not so
* Dr. W. M. Canby, of Wilmington,
to whom I am much indebted for
information regarding Dionza in its
native home, has published in the
‘Gardener’s Monthly,’ Philadelphia,
August 1868, some interesting ob-
servations. He ascertained that the
secretion digests animal matter, such
as the contents of insects, bits of
meat, &c.; and that the secretion is
reabsorbed. He was also well aware
that the lobes remain closed for a
much longer time when in contact
with animal matter than when made
to shut by a mere touch, or over
objects not yielding soluble nutri-
ment; and that in these latter cases
the glands do not secrete. The Rey.
Dr. Curtis first observed (¢ Boston
Journal Nat. Hist.’ vol. i. p. 123)
the secretion from the glands. I
may here add that a gardener, Mr.
Knight, is said (Kirby and Spence’s
‘Introduction to Entomology,’ 1818,
vol. i. p. 295) to have found that a
plant of the Dionza, on the leaves of
which “ he laid fine filaments of raw
beef, was much more luxuriant in its
growth than others not so treated.”
[The earlier history of the subject
is given in Sir Joseph Hooker’s “ Ad-
dress to the Department of Botany
and Zoology,” ‘British Association
Report,’ 1874, p. 102, whence the
following facts are taken.
About 1768 Ellis, a well-known
English naturalist, sent to Linnzus a
drawing and specimens of Dionea
with the following remarks (“ A Bo-
tanical Description of the Ponza
muscipula.... in a letter to Sir
Charles Linnzeus,” p. 37) :—
“The plant, of which I now enclose
you an exact figure. . . . shows that
Nature may have some views towards
its nourishment, in forming the upper
joint of its leaf like a machine to
catch food.”
Linnzus was unable to believe that
the plant could profit by the captured
insects ; he only saw in the phenomena
“an extreme case of sensitiveness in
the leaves which causes them to fold
up where irritated, just as the sensi-
tive plant does; and he consequently
regarded the capture of the disturb-
ing insect as something merely
accidental and of no importance to
the piant. . . . Linnzus’s authority
overbore criticism if any was offered ;
and his statement about the behaviour
of the leaves was copied from book to
book. ... Dr. [Erasmus] Darwin
(1791) was contented to suppose that
Dionæa surrounded itself with insect-
traps to prevent depredations upon
its flowers. Dr. Curtis, whose con-
tribution to the subject has been
already mentioned, describes the
captured insects as enveloped in a
fluid of a mucilaginous consistence
which seems to act as a solvent, the
insects being more or less consumed
by it.”—F. D.]
t [See footnote, p. 106.—F. D.]
E2
244 DIONZA MUSCIPULA. [Cuar. XIII.
well fitted as Drosera for observation, as the process goes on
within the closed lobes. Insects, even beetles, after being
subjected to the secretion for several days, are surprisingly
softened, though their chitinous coats are not corroded.
Experiment 1.—A cube of albumen of 54, of an inch (2:540 mm.)
was placed at one end of a leaf, and at the other end an oblong piece
of gelatine, 4 of an inch (5°08 mm.) long, and ṣẹ broad; the leaf was
then made to close. It was cut open after 45 hrs. The albumen was
hard and compressed, with its angles only a little rounded; the gelatine
was corroded into an oval form; and both were bathed in so much
acid secretion that it drepped off the leaf. ‘The digestive process
apparently is rather slower than in Drosera, and this agrees with the
length of time during which the leaves remain closed over digestible
objects.
Experiment 2.—A bit of albumen + of an inch square, but only
zy in thickness, and a piece of gelatine of the same size as before, were
placed on a leaf, which eight days afterwards was cut open. The sur-
face was bathed with slightly adhesive, very acid secretion, and the
glands were all in an aggregated condition. Not a vestige of the
albumen or gelatine was left. Similarly sized pieces were placed at
the same time on wet moss on the same pot, so that they were sub-
jected to nearly similar conditions ; after eight days these were brown,
decayed, and matted with fibres of mould, but had not disappeared.
Experiment 3.—A piece of albumen ;3, of an inch (3°81 mm.) long,
and 55 broad and thick, and a piece of gelatine of the same size as
before, were placed on another leaf, which was cut open after seven
days; not a vestige of either substance was left, and only a moderate
amount of secretion on the surface.
Experiment 4.—Pieces of albumen and gelatine, of the same size as
in the last experiment, were placed on a leaf, which spontaneously
opened after twelve days, and here again not a vestige of either was
left, and only a little secretion at one end of the midrib.
Experiment 5.—Pieces of albumen and gelatine of the same size were
placed on another leaf, which after twelve days was still firmly closed,
but had begun to wither; it was cut open, and contained nothing
except a vestige of brown matter where the albumen had lain.
Experiment 6.—A cube of albumen of zo Of an inch and a piece of
gelatine of the same size as before were placed on a leaf, which opened
spontaneously after thirteen days. The albumen, which was twice as
thick as in the latter experiments, was too large; for the glands in
contact with it were injured and were dropping off; a film also of
albumen of a brown colour, matted with mould, was left. All the
gelatine was absorbed, and there was only a little acid secretion left on
the midrib.
Experiment 7.—A bit of half roasted meat (not measured) and a
Lit of gelatine were placed on the two ends of a leaf, which opened
eae
—
itamo, asii ARRIE
Cuap. XIILJ DIGESTION. 245
spontaneously after eleven days; a vestige of the meat was left, and
the surface of the leaf was here blackened ; the gelatine had all dis-
appeared.
Experiment 8.—A bit of half roasted meat (not measured) was
placed on a leaf which was forcibly kept open by a clip, so that it was
moistened with the secretion (very acid) only on its lower surface.
Nevertheless, after -only 224 hrs. it was surprisingly softened, when
Suet age with another bit of the same meat which had been kept
amp.
Experiment 9.—A cube of 54, of an inch of very compact roasted
beef was placed on a leaf, whicn opened spontaneously after twelve
days; so much feebly acid secretion was left on the leaf that it trickled
off. The meat was completely disintegrated, but not all dissolved ;
there wasno mould, The little mass was placed under the microscope ;
some of the fibrillea in the middie still exhibited transverse striæ ;
others showed not a vestige of striae; and every gradation could -be
traced between these two states. Globules, apparently of fat, and some
undigested fibro-elastic tissue remained. The meat was thus in the
same state as that formerly described, which was half digested by
Drosera. Here, again, as in the case of albumen, the digestive process
seems slower than in Drosera. At the opposite end of the same leaf, a
firmly compressed pellet of bread had been placed; this was completely
disintegrated, I suppose, owing to the digestion of the gluten, but
seemed very little reduced in bulk.
Experiment 10.—A cube of 3 of an inch of checse and another of
albumen were placed at opposite ends of the same leaf. After nine
days the lobes opened spontaneously a little at the end enclosing the
cheese, but hardly any or none was dissolved, though it was softened
and surrounded by secretion. Two days subsequently the end with
the albumen also opened spontaneously (i.e. eleven days after it was
put on), a mere trace in the blackened and dry condition being left.
Experiment 11.—The same experiment with cheese and albumen
repeated on another and rather torpid leaf. ‘The lobes at the end with
the cheese, after an interval of six days, opened spontaneously a little ;
the cube of cheese was much softened, but not dissolved, and but little,
if at all reduced in size. Twelve hours afterwards the end with the
albumen opened, which now consisted of a large drop of transparent,
not acid, viscid fluid.
Experiment 12.—Same experiment as the two last, and here
again the leaf at the end enclosing the cheese opened before the oppo-
site end with the albumen; but no further observations were made,
Experiment 13.—A globule of chemically prepared casein, about 75
of an inch in diameter, was placed on a leaf, which spontaneously
opened after eight days. The casein now consisted of a soft sticky
mass, very little, if at all, reduced in size, but bathed in acid secretion.
These experiments are sufficient to show that the secretion
from the glands of Dionæa dissolves albumen, gelatine, and
246 DION. ZA MUSCIPULA. (Cuap. XIII.
meat, if too large pieces are not given. Globules of fat and
fibro-elastic tissue are not digested. The secretion, with its
dissolved matter, if not in excess, is subsequently absorbed.
On the other hand, although chemically prepared casein and
cheese (as in the case of Drosera) excite much acid secretion,
owing, I presume, to the absorption of some included
albuminous matter, these substances are not digested, and
are not appreciably, if at all, reduced in bulk.
Effects of the Vapours of Chloroform, Sulphuric Ether, and Hydro-
cyanic Acid.—A plant bearing one leaf was introduced into a large
bottle with a drachm (3°549 c.c.) of chloroform, the mouth being im-
perfectly closed with cotton-wool. The vapour caused in 1 m. the
lobes to begin moving at an imperceptibly slow rate; but in 3 m. the
spikes crossed, and the leaf was soon completely shut. The dose,
however, was much too large, for in between 2 and 3 hrs. the leaf
appeared as if burnt, and soon died.
Two leaves were exposed for 30 m. in a 2-oz. vessel to the vapour
of 30 minims (1:774 c.c.) of sulphuric ether. One leaf closed alter a
time, as did the other whilst being removed from the vessel without
being touched. Both leaves were greatly injured. Another leaf,
exposed for 20 m. to 15 minims of ether, closed its lobes to a certain
extent, and the sensitive filaments were now quite insensible. After
24 hrs. this leaf recovered its sensibility, but was still rather torpid.
A leaf exposed in a large bottle for only 3 m. to ten drops was
rendered insensible. After 52 m. it recovered its sensibility, and when
one of the filaments was touched, the lobes closed. It began to
reopen after 20 hrs. Lastly another leaf was exposed for 4 m. to only
four drops of the ether; it was rendered insensible, and did not close
when its filaments were repeatedly touched, but closed when the end
of the open leaf was cut off. This shows either that the internal
parts had not been rendered insensible, or that an incision is a more
powerful stimulus than repeated touches on the filaments. Whether
the larger doses of chloroform and ether, which caused the leaves to
close slowly, acted on the sensitive filaments or on the leaf itself, I do
not know.
Cyanide of potassium, when left in a bottle, generates prussic or
hydrocyanic acid. A leaf was exposed for 1 hr. 35 m. to the vapour
thus formed ; and the glands became within this time so colourless and
shrunken as to be scarcely visible, and I at first thought that they had
all dropped off. The leaf was not rendered insensible ; for as soon as
one of the filaments was touched it closed. It had, however, suffered,
for it did not reopen until nearly two days had passed, and was not
even then in the least sensitive. After an additional day it recovered
its powers, and closed on being touched and subsequently re-opened.
Another leaf behaved in nearly the same manner after a shorter
exposure to this vapour.
Cuar. XIII] MANNER OF CAPTURING INSECTS. 247
On the Manner in which Insects are caught.—We will now
consider the action of the leaves when insects happen to
touch one of the sensitive filaments. This often occurred in
my greenhouse, but I do not know whether insects are
attracted in any special way by the leaves. They are caught
in large numbers by the plant in its native country. As
soon as a filament is touched, both close with astonishing
quickness ; and as they stand at less than a right angle to
each other, they have a good chance of catching any intruder.
The angle between the blade and footstalk does not
change when the lobes close. The chief seat of movement is
near the midrib, but is not confined to this part; for, as the
lobes come together, each curves inwards across its whole
breadth ; the marginal spikes, however, not becoming curved.*
This movement of the whole lobe was well seen in a leaf to
which a Jarge fly had been given, and from which a large
portion had been cut off the end of one lobe; so that the
opposite lobe, meeting with no resistance in this part, went
on curving inwards much beyond the medial line. The
whole of the lobe, from which a portion had been cut, was
afterwards removed, and the opposite lobe now curled
completely over, passing through an angle of from 120° to
130°, so as to occupy a position almost at right angles to
that which it would have held had the opposite lobe been
present.
From the curving inwards of the two lobes, as they
move towards each other, the straight marginal spikes inter-
cross by their tips at first, and ultimately by their bases.
The leaf is then completely shut and encloses a shallow
cavity. Ifit has been made to shut merely by one of the
sensitive filaments having been touched, or if it includes an
object not yielding soluble nitrogenous matter, the two lobes
retain their inwardly concave form until they re-expand.
The re-expansion under these circumstances—that is when
no organic matter is enclosed—was observed in ten cases.
In all of these, the leaves re-expanded to about two-thirds
of the full extent in 24 hrs. from the time of closure. Even
the leaf from which a portion of one lobe had been cut off
opened to a slight degree within this same time. In one
* (Munk (Reichert and Du Bois’- at the edge of the leaf, by which the
_Reymond’s ‘ Archiv.’ 1876, p. 108) teeth are carried inwards.—F. D.J
states that a special movement occurs
248 DIONÆA MUSCIPULA. (Omir. XMI
case a leaf re-expanded to about two-thirds of the full extent
in 7 hrs., and completely in 32 lrs.; but one of its filaments
had been touched merely with a hair just enough to cause
the leaf to close. Of these ten leaves only a few re-expanded
completely in less than two days, and two or three required
even a little longer time. Before, however, they fully
re-expand, they are ready to close instantly if their sensitive
filaments are touched. How many times a leaf is capable
of shutting and opening if no animal matter is left enclosed,
Ido not know; but one leaf was made to close four times,
reopening afterwards, within six days. On the last occasion
it caught a fly, and then remained closed for many days.
This power of reopening quickly after the filaments have
been accidentally touched by blades of grass, or by objects
blown on the leaf by the wind, as occasionally happens in its
native place,* must be of some importance to the plant; for
as long as a leaf remains closed, it cannot of course capture
an insect.
When the filaments are irritated and a leaf is made to
shut over an insect, a bit of meat, albumen, gelatine, casein,
and, no doubt, any other substance containing soluble
nitrogenous matter, the lobes, instead of remaining concave,
thus including a concavity, slowly press closely together
throughout their whole breadth. As this takes place, the
margins gradually become a little everted, so that the
spikes, which at first intercrossed, at last project in two
parallel rows. The lobes press against each other with such
force that I have seen a cube of albumen much flattened,
with distinct impressions of the little prominent glands; but
this latter circumstance may have been partly caused by the
corroding action of the secretion. So firmly do they become
pressed together that, if any large insect or other object has
been caught, a corresponding projection on the outside of the
leaf is distinctly visible. When the two lobes are thus
completely shnt, they resist being opened, as by a thin
wedge being driven between them, with astonishing force,
and are generally ruptured rather than yield. If not
ruptured, they close again, as Dr. Canby informs me in a
letter, “ with quite a loud flap.” But if the end ofa leaf is
held firmly between the thumb and finger, or by a clip, so
* According to Dr. Curtis, in ‘ Boston Journal of Nat. Hist.’ vol. i. 1837,
p: 123.
a scent
Cuar. XIII] MANNER OF CAPTURING INSECTS. 249
that the lobes cannot begin to close, they exert, whilst in
this position, very little force.
I thought at first that the gradual pressing together of the
lobes was caused exclusively by captured insects crawling
over and repeatedly irritating the sensitive filaments; and
this view seemed the more probable when I learnt from Dr.
Burdon Sanderson that whenever the filaments of a closed
leaf are irritated, the normal electric current is disturbed.
Nevertheless, such irritation is by no means necessary, for a
dead insect, or a bit of meat, or of albumen, all act equally
well; proving that in these cases it is the absorption of
animal matter which excites the lobes slowly to press close
together. We have seen that the absorption of an extremely
small quantity of such matter also causes a fully expanded
leaf to close slowly ; and this movement is clearly analogous to
the slow pressing together of the concave lobes. This latter
action is of high functional importance to the plant, for the
glands on both sides are thus brought into contact with a
captured insect, and consequently secrete. ‘The secretion
with animal matter in solution is then drawn by capillary
attraction over the whole surface of the leaf, causing all the
glands to secrete and allowing them to absorb the diffused
animal matter. The movement, excited by the absorption of
such matter, though slow, suffices for its final purpose, whilst
the movement excited by one of the sensitive tilaments being
touched is rapid, and this is indispensable for the capturing
of insects. These two movements, excited by two such
widely different means, are thus both well adapted, like all the
other functions of the plant, for the purposes which they
subserve.
There is another wide difference in the action of leaves
which enclose objects, such as bits of wood, cork, balls of
paper, or which have had their filaments merely touched,
and those which enclose organic bodies yielding soluble
nitrogenous matter. In the former case the leaves, as we
have seen, open in under 24 hrs. and are then ready, even
before being fully expanded, to shut again. But if they
have closed over nitrogen-yielding bodies, they remain
closely shut for many days; and after re-expanding are
torpid, and never act again, or only after a considerable
interval of time. In four instances, leaves after catching
insects never re-opened, but began to wither, remaining
closed—in one case for fifteen days over a fly; in a second,
250 DIONÆA MUSCIPULA. (Car. XIII.
for twenty-four days, though the fly was small; in a third
for twenty-four days over a woodiouse; and in a fourth, for
thirty-five days over a large Tipula. In two other cases
leaves remained closed for at least nine days over flies, and
for how many more I do not know. It should, however, be
added that in two instances in which very small insects had
been naturally caught the leaf opened as quickly as if
nothing had been caught ; and I suppose that this was due
to such small insects not having been crushed or not having
excreted any animal matter, so that the glands were not
excited. Small angular bits of albumen and gelatine were
placed at both ends of three leaves, two of which remained
closed for thirteen and the other for twelve days. Two
other leaves remained closed over bits of meat for eleven
days, a third leaf for eight days, and a fourth (but this had
been cracked and injured) for only six days. Bits of cheese,
or casein, were placed at one end and albumen at the other
end of three leaves; and the ends with the former opened
after six, eight, and nine days, whilst the opposite ends
opened a little later. None of the above bits of meat,
albumen, &c., exceeded a cube of -y of an inch (2°54 mm.)
in size, and were sometimes smaller ; yet these small portions
sufficed to keep the leaves closed for many days. Dr. Canby
informs me that leaves remain shut for a longer time over
insects than over meat; and from what I have seen, I can
well believe that this is the case, especially if the insects are
large.
In all the above cases, and in many others in which leaves
remained closed for a long but unknown period over insects
naturally caught, they were more or less torpid when they
re-opened, Generally they were so torpid during many
succeeding days that no excitement of the filaments caused
the least movement. In one instance, however, on the day
after a leaf opened which had clasped a fly, it closed with
extreme slowness when one of its filaments was touched ; and
although no object was left enclosed, it was so torpid that it
did not re-open for the second time until 44 hrs. had elapsed.
In a second case, a leaf which had expanded after remaining
closed for at least nine days over a fly, when greatly irritated,
moved one alone of its two lobes, and retained this unusual
position for the next two days. A third case offers the
strongest exception which I have observed; a leaf, after
1emaining clasped for an unknown time over a fly, opened,
Cuar. XIII.] MANNER OF CAPTURING INSECTS. 205
and when one of its filaments was touched, closed, though
rather slowly. Dr. Canby, who observed in the United
States a large number of plants which, although not in their
native site, were probably more vigorous than my plants,
informs me that he has “several times known vigorous
leaves to devour their prey several times; but ordinarily
twice, or quite often, once was enough to render them
unserviceable.” Mrs. Treat, who cultivated many plants in
New Jersey, also informs me that “ several leaves caught
successively three insects each, but most of them were not
able to digest the third fly, but died in the attempt. Five
leaves, however, digested each three flies, and closed over the
fourth, but died soon after the fourth capture. Many leaves
did not digest even one large insect,” 1t thus appears that
the power of digestion is somewhat limited, and it is certain
that leaves always remain clasped for many days over an
insect, and do not recover their power of closing again for
many subsequent days. In this respect Dionæa differs from
Drosera, which catches and digests many insects after shorter
intervals of time.
We are now prepared to understand the use of the mar-
ginal spikes, which form so conspicuous a feature in the
appearance of the plant (fig. 12, p. 232), and which at first
seemed to me in my ignorance useless appendages. From
the inward curvature of the lobes as they approach each
other, the tips of the marginal spikes first intercross, and
ultimately their bases. Until the edges of the lobes come
into contact, elongated spaces between the spikes, varying
from the ;!; to the ;, of an inch (1:693 to 2:540 mm.) in
breadth, according to the size of the leaf, are left open.
Thus an insect, if its body is not thicker than these measure-
ments, can easily escape between the crossed spikes, when
disturbed by the closing lobes and increasing darkness; and
one of my sons actually saw a small insect thus escaping.
A moderately large insect, on the other hand, if it tries to
escape between the bars will surely be pushed back again
into its horrid prison with closing walls, for the spikes
continue to cross more and more until the edges of the lobes `
come into contact. A very strong insect, however, would be
able to free itself, and Mrs. Treat saw this effected by a
rose-chafer (Macrodactylus subspinosus) in the United States.
Now it would manifestly be a great disadvantage to the
plant to waste many days in remaining clasped over a
252 DIONZA MUSCIPULA. [Ome XIII.
minute insect, and several additional days or weeks in
afterwards recovering its sensibility; inasmuch as a minute
insect would afford but little nutriment. It would be far
better for the plant to wait for a time until a moderately
large insect was captured, and to allow all the little ones to
escape ; and this advantage is secured by the slowly inter-
crossing marginal spikes, which act like the large meshes of
a fishing-net, allowing the small and useless fry to escape.
As I was anxious to know whether this view was correct—
and as it seems a good illustration of how cautious we ought
to be in assuming, as I had done with respect to the marginal
spikes, that any fully developed structure is useless—I
applied to Dr. Canby. He visited the native site of the
plant, early in the season, before the leaves had grown to
their full size, and sent me fourteen leaves, containing
naturally captured insects. Four of these had caught rather
small insects, viz. three of them ants, and the fourth a rather
small fly, but the other ten had all caught large insects,
namely, five elaters, two chrysomelas, a curculio, a thick and
broad spider, and a scolopendra. Out of these ten insects,
no less than eight were bevtles,* and out of the whole four-
teen there was only one, viz. a dipterous insect, which could
readily take flight. Drosera, on the other hand, lives chiefly
on insects which are good flyers, especially Diptera, caught
by the aid of its viscid secretion. But what most concerns
us is the size of the ten larger insects. Their average length
from head to tail was +256 of an inch, the lobes of the leaves
being on an average *53 of an inch in length, so that the
insects were very nearly half as long as the leaves within
which they were enclosed. Only a few of these leaves,
therefore, had wasted their powers by capturing small prey,
though it is probable that many small insects had crawled
over them and been caught, but had then escaped through
the bars.
The Transmission of the Motor Impulse, and means of Move-
* Dr. Canby remarks (‘Gardener’s elaters, for the five which I examined
Monthly,’ Aug. 1868), “as a general were in an extremely fragile and
thing beetles and insectsof that kind, empty condition, as if all their in-
though always killed, seem to be ternal parts had been partially di-
too hard-shelled to serve as food, gested. Mrs. Treat informs me that
and after a short time are rejected.” the plants which she cultivated in
I am surprised at this statement, at New Jersey chiefly caught Diptera.
least with respect to such beetles as
Cuar. XIIL] TRANSMISSION OF MOTOR IMPULSE. 253
ment.—It is sufficient to touch any one of the six filaments to
cause both lobes to close, these becoming at the same time
incurved throughout their whole breadth. The stimulus
must therefore radiate in all directions from any one filament.
It must also be transmitted with much rapidity across the
leaf, for in all ordinary cases both lobes close simultaneously,
as far us the eye can judge. Most physiologists believe that
in irritable plants the excitement is transmitted along, or in
close connection with, the fibro-vascular bundles. In Dionzxa,
the course of these vessels (composed of spiral and ordinary
vascular tissue) seems at first sight to favour this belief; for
they run up the midrib in a great bundle, sending off small
bundles almost at right angles on eachside. These bifurcate
occasionally as they extend towards the margin, and close to
the margin small branches from adjoining vessels unite and
enter the marginal spikes. At some of these points of union
the vessels form curious loops, like those described under
Drosera. A continuous zigzag line of vessels thus runs
round the whole circumference of the leaf, and in the midrib
all the vessels are in close contact; so that all parts of the
leaf seem to be brought into some degree of communication.
Nevertheless, the presence of vessels is not necessary for the
transmission of the motor impulse, for it is transmitted from
the tips of the sensitive filaments (these being about the 5\,
of an inch in length), into which no vessels enter; and these
could not have been overlooked, as I made thin vertical
sections of the leaf at the bases of the filaments.
On several occasions, slits about the 4‘; ofan inch in length
were made with a lancet, close to the bases of the filaments,
parallel to the midrib, and, therefore, directly across the
course of the vessels. These were made sometimes on the
inner and sometimes on the outer side of the filaments; and
after several days, when the leaves had reopened, these
filaments were touched roughly (for they were always ren-
dered in some degree torpid by the operation), and the lobes
then closed in the ordinary,manner, though slowly, and some-
times not until after a considerable interval of time. These
cases show that the motor impulse is not transmitted along
the vessels, and they further show that there is no necessity
for a direct line of communication from the filament which
is touched towards the midrib and opposite lobe, or towards
the outer parts of the same lobe.
Two slits near each other, both parallel to the midrib,
254 DIONÆA MUSCIPULA. (Cuap. XIII.
were next made in the same manner as before, one on each
side of the base of a filament, on five distinct leaves, so that
a little slip bearing a filament was connected with the rest
of the leaf only at its two ends. These slips were nearly of
the same size; one was carefully measured ; it was *12 of an
inch (3:048 mm.) in length, and +08 of an inch (2-032 mm.)
in breadth ; and in the middle stood the filament. Only one
of these slips withered and perished. After the leaf had
recovered from the operation, though the slits were still
open, the filaments thus circumstanced were roughly touched,
and both lobes, or one alone, slowly closed. In two instances
touching the filament produced no effect; but when the
point of a needle was driven into the slip at the base of the
filament, the lobes slowly closed. Now in these cases the
impuise must have proceeded along the slip in a line parallel
to the midrib, and then have radiated forth, either from both
ends or from one end alone of the slip, over the whole surface
of the two lobes.
Again, two parallel slits, like the former ones, were made,
one on each side of the base of a filament, at right angles to
the midrib. After the leaves (two in number) had recovered,
the filaments were roughly touched, and the lobes slowly
closed; and here the impulse must have travelled for a short
distance in a line at right angles to the midrib, and then
have radiated forth on all sides over both lobes. These
several cases prove that the motor impulse travels, in all
directions through the cellular tissue, independently of the
course of the vessels.
With Drosera we have seen that the motor impulse is
transmitted in like manner in all directions through the
cellular tissue; but that its rate is largly governed by the
length of the cells and the direction of their longer axes.
Thin sections of a leaf of Dionæa were made by my son, and
the cells, both these of the central and of the more superficial
layers, were found much elongated, with their longer axes
directed towards the midrib; and it is in this direction that
the motor impulse must be sent with great rapidity from one
lobe to the other, as both close simultaneously. ‘I'he central
parenchymatous cells are larger, more loosely attached
together, and have more delicate walls than the more super-
ficial cells. A thick mass of cellular tissue forms the upper
surface of the midrib over the great central bundle of
vessels.
i cuneate
Cuar. XIII] TRANSMISSION OF MOTOR IMPULSE. 255
When the filaments were roughly touched, at the bases of
which slits had been made, either on both sides or on one
side, parallel to the midrib or at right angles to it, the two
lobes, or only one, moved. In one of these cases, the lobe
on the side which bore the filament that was touched moved,
but in three other cases the opposite lobe alone moved: so
that an injury which was sufficient to prevent a lobe moving
did not prevent the transmission from it of a stimulus which
excited the opposite lobe to move. We thus also learn that,
although normally both lobes move together, each has the
power of independent movement. A case, indeed, has
already been given of a torpid leaf that had lately re-opened
after catching an insect, of which one lobe alone moved when
irritated. Moreover, one end of the same lobe can close and
re-expand, independently of the other end, as was seen in
some of the foregoing experiments.
When the lobes, which are rather thick, close, no trace of
wrinkling can be seen on any part of their upper surfaces.
It appears therefore that the cells must contract. The chief
seat of the movement is evidentiy in the thick mass of cells
which overlies the central bundle of vessels in the midrib.
To ascertain whether this part contracts, a leaf was fastened
on the stage of the microscope in such a manner that the two
lobes could not become quite shut, and having made two
minute black dots on the midrib, in a transverse line and a
little towards one side, they were found by the micrometer
to be -44y of an inch apart. One of the filaments was then
touched and the lobes closed; but as they were prevented
from meeting, I could still see the two dots, which now were
+i3, of an inch apart, so that a small portion of the upper
surface of the midrib had contracted in a transverse line +7755
of an inch (*0508 mm.).
We know that the lobes, whilst closing, become slightly
incurved throughout their whole breadth. This movement.
appears to be due to the contraction of the superficial layers
of cells over the whole upper surface. In order to observe
their contraction, a narrow strip was cut out of one lobe at
right angles to the midrib, so that the surface of the opposite
lobe could be seen in this part when the leaf was shut.
After the leaf had recovered from the operation and had re-
expanded, three minute black dots were made on the surface
opposite to the slit or window, in a line at right angles tu
the midrib. The distance between the dots was found to be
256 DIONÆA MUSCIPULA. (Cuar, XII.
142v of an inch, so that the two extreme dots were 75} of
an inch apart. One of the filaments was now touched and
the leaf closed. On again measuring the distances between
the dots, the two next to the midrib were nearer together
by 14y% of an inch, and the two further dots by ?j3% of an
5
now stood about y¢%;5 of an inch (*127 mm.) nearer together
than before. If we suppose the whole upper surface of the
lobe, which was 429% of an inch in breadth, to have con-
tracted in the same proportion, the total contraction will
have amounted to about +235 or 4p of an inch (°635 mm.):
but whether this is sufficient to account for the slight inward
curvature of the whole lobe, I am unable to say.*
Finally, with respect to the movement of the leaves the
wonderful discovery made by Dr. Burdon Sanderson} is now
universally known ; namely that there exists a normal elec-
trical current in the blade and footstalk; and that when the
leaves are irritated, the current is disturbed in the same
manner as takes place during the contraction of the muscle
of an animal.t
* [Batalin has discussed the me-
chanism of closure in Dionza in his
interesting essay in ‘Flora,’ 1877.
He agrees in general with the state-
ments above given, but as in the case
of Drosera, so here he believes that
the movements are associated with a
small amount of actual growth.
Marks are made on the lower or
external surface of the leaf, and the
distance between them is found to
increase when the leaf closes. When
the leaf opens the distance does not
perfectly return to its former dimen-
sions, and thus shows a certain
amount of permanent growth has
taken place. It will be seen that
Batalin’s observations do not support
the idea (see p. 258) that the re-open-
ing of the leaf is due to the return of
the outer cells to their natural size
when the tension put on them by the
contraction of the inner surface is re-
moved. Munk (loc. cit.) and Pfeffer
(‘Osmotische Untersuchungen,’ 1877,
p- 196) have with justice called at-
tention to the unsatisfactory nature
of the discussion in the text on the
mechanism of the movement. Batalin
shows further that the ultimate
closure of the leaf by which the two
valves are closely pressed together is
effected by the shortening or con-
traction of the outer surface of the
leaf. He records a curious fact which
has not elsewhere been noted, namely,
that the midrib becomes more curved
after the closure of the leaf. Munk
(Reichert and Du Bois-Reymond,
‘Archiv.’ 1876, p. 121), on the other
hand, is inclined to believe that the
curvature of the midrib diminishes
when the leaf closes.—F, D.]
t ‘Proc. Royal Soc.’ vol. xxi. p.
495; and lecture at the Royal In-
stitution, June 5, 1874, given in
‘Nature,’ 1874, pp. 105 and 127.
t [Professor Sanderson’s work has
been criticised by Professor Munk in
Reichert and Du _ Bois-Reymond’s
‘Archiv.’ 1876, and by Professor
Kunkel in Sachs’ ‘Arbeiten a. d.
bot. Institut in Wiizburg,’ Bd. ii. p. 1.
Professor Sanderson. has continued
RETEST ena antag AR ~
Cuar. XIIL]
RE-EXPANSION. ZFT
The Re-expansion of the Leaves.-—This is effected at an in-
sensibly slow rate, whether or not any object is enclosed.*
to work at the subject, and has given
his results in an elaborate paper in
‘Phil. Transactions,’ 1882. It will
be sufficient to note his conclusions
with regard to the two points men-
tioned in the text.. First, for the
electrical condition of the leaf at rest.
Sanderson rejects Munk’s method of
cxplaining the state of the leaf by a
mechanical schema—an arrangement
of copper and zine cylinders. He does
so, not only because he accepts “as
fundamental the doctrine that what-
ever physiological properties the leaf
possesses, it possesses by virtue of its
being a system of living cells;” but
also because the facts of the case are
not in accordance with Professor
Munk’s theoretical deductions. He in-
clines to admit that the electrical
differences observed between different
parts of the unexcited leaf may be
partly explained by the migration of
water. “ For on the one hand we know
that in consequence of the surface
evaporation, migration of water cer-
tainly exists, while on the other we
have proof in the experiments of Dr.
Kunkel that such migration cannot
occur without producing electrical
differences.” In a similar way he is in-
clined to believe that the gradual elec-
trical change resulting from repeated
excitation, as well as the after effect-of
a single excitation, are to be explained
by migration of water accompanying
the motion of the leaf. On the other
hand he believes that the primary,
and rapidly propagated electrical
disturbance which is the immediate
effect of excitation cannot be due to
water-migration, but that it is the
expression of molecular changes in
the protoplasm of the leaf. Prof.
Sanderson takes occasion to correct
the impression produced by certain
expressions in his lecture at the Royal
Institution in 1874. Prof. Munk,
among others, seems to have believed
that Professor Sanderson claimed
absolute identity between muscular
action and the movement of the leaf
of Dionza. It need hardly be stated
that no such implication was intended
by Prof. Sanderson; the view which
he held in 1874 he still adheres to,
namely, that the rapidly propagated
molecular change in an excited Dionga ©
leaf can only be identified with the
corresponding process in the excitable
tissues of animals.
Certain unpublished researches
made during the last two years have
led Professor Sanderson to extend his
views in the direction above indicated,
and to conclude that the “ leaf-
current,” i.e. the electrical difference
between the upper and lower surfaces
of the leaf, is intimately} connected
with the physiological conditions of
that part of the upper surface from
which spring the sensitive filaments :
thus it will probably be established
that the “leaf-current ” and the ex-
citatory disturbance are different
manifestations of the same property.
From measurements made with his
Rheotome, of six carefully chosen
leaves, taken from vigorous plants
(Aug. 1887), Professor Sanderson
found that the electrical disturbance
produced in one lobe by stimulation
of the other by an induction current,
begins in the course of the second
tenth of a second following the ex-
citation. In five out of the six leaves
no effect was perceptible during the
first tenth. If we assume that the
distance travelled by the disturbance
is one centimeter, this gives 100
millimeters per second as the rate of
propagation. This, as Professor San-
derson has pointed out, happens to be
just about the rate of propagation of
the excitatory electrical disturbance
in the muscular tissue of the heart of
the frog.—F. D.]
* Nuttall, in his ‘Gen. American
S
258 DION A MUSCIPULA.
One lobe can re-expand by itself, as occurred with the torpid
leaf of which one lobe alone had closed. We havealso seen in
the experiments with cheese and albumen that the two ends of
the same lobe can re-expand to a certain extent independently
of each other. But in all ordinary cases both lobes open
at the same time. The re-expansion is not determined by
the sensitive filaments; all three filaments on one lobe were
cut off close to their bases; and the three leaves thus treated
re-expanded,—one to a partial extent in 24 hrs.,—a second to
the same extent in 48 hrs.,—and the third, which had been
previously injured, not until the sixth day. These leaves
after their re-expansion closed quickly when the filaments on
the other lube were irritated. These were then cut off one
of the leaves, so that none were left. This mutilated leaf,
notwithstanding the loss of all its filaments, re-expanded in
two days in the usual manner. When the filaments have
been excited by immersion in a solution of sugar, the lobes
do not expand so soon as when the filaments have been
merely touched ; and this, I presume, is due to their having
been strongly affected through exosmose, so that they con-
tinue for some time to transmit a motor impulse to the upper
surface of the leaf.
The following facts make me believe that the several
layers of cells forming the lower surface of the leaf are
always in a state of tension; and that it is owing to this
mechanical state, aided probably by fresh fiuid being
attracted into the cells, that the lobes begin to separate or
expand as soon as the contraction of the upper surface
diminishes. A leaf was cut off and suddenly plunged
perpendicularly into boiling water: I expected that the
lobes would have closed, but instead of doing so, they
diverged a little. I then took another fine leaf, with the
lobes standing at an angle of nearly 80° to each other; and
on immersing it as before, the angle suddenly increased to
90°. A third leaf was torpid from having recently re-
Plants,’ p. 277 (note), says that, cilia, accompanied by a partial open-
[Cuar. XIII.
whilst collecting this plant in its
native home, “1 had occasion to ob-
serve that a detached leaf would
make repeated efforts towards dis-
closing itself to the influence of the
sun ; these attempts consisted in an
undulatory motion ef the marginal
ing and succeeding collapse of the
lamina, which at length terminated
in a complete expansion and in the
destruction of sensibility.” I am
indebted to Prof. Oliver for this
reference; but I do not understand
what took place.
fo ESE: a Se
Car. XIIL] RE-EXPANSION. 259
expanded after having caught a fly, so that repeated touches
of the filaments caused not the least movement ; nevertheless
when similarly immersed, the lobes separated a little. As
these leaves were inserted perpendicularly into the boiling
water, both surfaces and the filaments must have been
equally affected; and I can understand the divergence of the
lobes only by supposing that the cells on the lower side,
owing to their state of tension, acted mechanically and thus
suddenly drew the lobes a little apart, as soon as the cells on
the upper surface were killed and lost their contractile power.
We have seen that boiling water in like manner causes the
tentacles of Drosera to curve backwards; and this is an
analogous movement to the divergence of the lobes of
Dionzea.
Tn some concluding remarks in the fifteenth chapter on the
Droseraceæ, the different kinds of irritability possessed by
the several genera, and the different manner in which they
capture insects, will be compared.
260 ALDROVANDA VESICULOSA. (CHar. XIV.
CHAPTER XIV.
ALDROVANDA VESICULOSA.
Captures erustaceans—Structure of the leaves in comparison with those of
Dionza—Absorption by the glands, by the quadrifid processes, and points
on the infolded margins—Aldrovanda vesiculosa, var. australis—Captures
prey—Absorption of animal matter—A/drovanda vesiculosa, var. verticillata
—Concluding remarks.
Tuts plant may be called a miniature aquatic Dionæa. Stein
discovered in 1873 that the bilobed leaves, which are
generally found closed in Europe, open under a sufficiently
high temperature, and, when touched, suddenly close.*
They re-expand in from 24 to 36 hrs., but only, as it appears,
when inorganic objects are enclosed. The leaves sometimes
contain bubbles of air, and were formerly supposed to be
bladders; hence the specific name of vesiculosa. Stein
observed that water-insects were sometimes caught, and
Prof. Cohn has recently found within the leaves of naturally
growing plants many kinds of crustaceans and larvæ.f
Plants which have been kept in filtered water were placed
by him in a vessel containing numerous crustaceans of the
genus Cypris, and next morning many were found imprisoned
and alive, still swimming about within the closed leaves,
but doomed to certain death.
* Since his original publication,
alec nan
Stein has found out that the irrita-
bility of the leaves was observed by
De Sassus, as recorded in * Bull. Bot.
Soc. de France,’ in 1861. Delpino
states in a paper published in 1871
(‘Nuovo Giornale Bot. Ital.’ vol. iii.
p- 174) that “una quantita di chioc-
cioline e di altri animalcoli acquatici ”
are caught and suffocated by the
leaves. I presume that chioccioline
are fresh-water molluscs. It would
be interesting to know whether their
shells are at all corroded by the acid
of the digestive secretion. |
[The late Professor Caspary pub-
lished in the ‘Bot. Zeitung,’ 1859,
p. 117, an elaborate paper on Aldro-
vanda, dealing chiefly with its morpho-
logy, anatomy, systematic position
and geographical distribution. The
early literature of the species is also
fully given.—F. D.
t+ I am greatly indebted to this
distinguished naturalist for having
sent me a copy of his memoir on
Aldrovanda, before its publication in
his ‘ Beiträge zur Biologie der Pflan-
zen,’ drittes Heft, 1875, p. 71.
ee
Cuar. XIV.] ALDROVANDA VESICULOSA. 261
Directly after reading Prof. Cohn’s memoir, I received
through the kindness of Dr. Hooker living plants from
Germany. As I can add nothing to Prof. Cohn’s excellent
description, I will give only two illustrations, one of a
whorl of leaves copied from his work, and the other of a leaf
pressed flat open, drawn by my son Francis. I will, how-
ever, append a few remarks on the differences between this
plant and Dionza.
Aldrovanda is destitute of roots and floats freely in the
water. The leaves are arranged in whorls round the stem.
Their broad petioles terminate in from four to six rigid
projections,* each tipped with a stiff, short bristle. ‘lhe
bilobed leaf, with the midrib likewise tipped with a bristle,
stands in the midst of these projections, and is evidently
defended by them. The lobes are formed of very delicate
tissue, so as to be translucent ; they open, according to Cohn,
about as much as the two valves of a living mussel-shell,
therefore even less than the lobes of Dionæə ; and this must
make the capture of aquatic animals more easy. The
outside of the leaves and the petioles are covered with minute
two-armed papillæ, evidently answering to the eight-rayed
papille of Dionza.
Each lobe rather exceeds a semi-circle in convexity, and
consists of two very different concentric portions ; the inner
and lesser portion, or that next to the midrib, is slightly
concave, and is formed, according to Cohn, of three layers of
cells. Its upper surface is studded with colourless glands
like, but more simple than, those of Dionxa; they are
supported on distinct footstalks, consisting of two rows of
cells. The outer and broader portion of the lobe is flat and
very thin, being formed of only two layers of cells.{ Its
upper surface does not bear any glands, but, in their place,
smail quadrifid processes, each consisting of four tapering
projections, which rise from a common prominence. These
* There has been much discussion 1850) and Caspary (‘Bot. Zei-
by botanists on the homological nature
of these projections. Dr. Nitschke
(‘ Bot. Zeitung,’ 1861, p. 146) believes
that they correspond with the ftim-
briated scale-like bodies found at the
bases of the petioles ot Drosera,
t [According to Cohn (¢Fiora,’
tung,’ 1859), the two layers of cells
are so combined as to produce the
effect of a single layer. The three
layers of which the central part is
made up consist of external and
internal epidermic layers, and a single
layer of parenchyma.—F. D.]
262 ALDROVANDA VESICULOSA. (Cuapr. XIV.
processes are formed of very delicate membrane lined with a
layer of protoplasm ; and they sometimes contain aggregated
globules of hyaline matter. Two of the slightly diverging
arms are directed towards the circumference, and two
towards the midrib, forming together a sort of Greek cross.
Occasionally two of the arms are replaced by one, and then
Fic. 13.
(Aldrovanda vesicutosa.y'
Upper figure, whorl of leaves (from Prof, Cohn.)
Lower figure, leaf pressed flat open and greatly enlarged.
the projection is trifid. We shall see in a future chapter
that these projections curiously resemble those found within
the bladders of Utricularia, more especially of Utricularia
montana, although this genus is not related to Aldrovanda.
A narrow rim of the broad flat exterior part of each lobe is
Cuar, XIV] ALDROVANDA VESICULOSA. 263
turned inwards, so that, when the lobes are closed, the
exterior surfaces of the infolded portions come into contact.
The edge itself bears a row of conical, flattened, transparent
points with broad bases, like the prickles on the stem ofa
bramble or Rubus. As the rim is infolded, these points are
directed towards the midrib, and they appear at first as if
they were adapted to prevent the escape of prey; but this
can hardly be their chief function, for they are composed of
very delicate and highly flexible membrane, which can be
easily bent or quite doubled back without being cracked.
Nevertheless, the infolded rims, together with the points,
must somewhat interfere with the retrograde movement of
any small creature, as soon as the lobes begin to close. The
circumferential part of the leaf of Aldrovanda thus differs
greatly from that of Dionza; nor can the points on the rim
be considered as homologous with the spikes round the leaves
of Dionæa, as these latter are prolongations of the blade, and
not mere epidermic productions. They appear also to serve
for a widely different purpose.
On the concave gland-bearing portion of the lobes, and
especially on the midrib, there are numerous long, finely
pointed hairs, which, as Prof. Cohn remarks, there can be
little doubt are sensitive to a touch,* and, when touched,
cause the leaf toclose. They are formed of two rows of cells,
or, according to Cohn, sometimes of four, and do not include
any vascular tissue. They differ also from the six sensitive
filaments of Dionwa in being colourless, and in having a
medial as well as a basal articulation. No doubt it is owing
to these two articulations that, notwithstanding their length,
they escape being broken when the lobes close.
The plants which I received during the early part of
October from Kew never opened their leaves, though sub-
jected toa high temperature. After examining the structure
of some of them, I experimented on only two, as I hoped that
the plants would grow; and I now regret that I did not
sacrifice a greater number.
A leaf was cut open along the midrib, and the glands
examined under a high power. It was then placed in a few
drops of an infusion of raw meat. After 3 hrs. 20 m. there
* [In a paper in the ‘Nuovo Gior- case, namely that the irritability
nale Botanico Italiano,’ vol. viii. 1876, resides exclusively in the central
p. 62, Mori states that this is the glandular region of the leafi—F, D.]
264 ALDROVANDA VESICULOSA. [Cuar. XIV.
was no change, but when next examined after 23 hrs. 20 mM
the outer cells of the glands contained, instead of limpid
fluid, spherical masses of a granular substance, showing that
matter had been absorbed from the infusion. That these
glands secrete a fluid which dissolves or digests animal
matter out of the bodies of the creatures which the leaves
capture, is also highly probable from the analogy of Dionzea.
If we may trust to the same analogy, the concave and inner
portions of the two lobes probably close together by a slow
movement, as soon as the glands have absorbed a slight
amount of already soluble animal matter. The included
water would thus be pressed out, and the secretion conse-
quently not be too much diluted to act. With respect to
the quadrifid processes on the outer parts of the lobes, I was
not able to decide whether they had been acted on by the
infusion ; for the lining of protoplasm was somewhat shrunk
before they were immersed. Many of the points on the
infolded rims also had their lining of protoplasm similarly
shrunk, and contained spherical granules of hyaline matter.
A solution of urea was next employed. This substance
was chosen partly because it is absorbed by the quadrifid
processes and more especially by the glands of Utricularia—
a plant which, as we shall hereafter see, feeds. on decayed
animal matter. As urea is one of the last products of the
chemical changes going on in the living body, it seems fitted
to represent the early stages of the decay of the dead body. IL
was also led to try urea irom a curious little fact mentioned
by Prof. Cohn, namely that when rather large crustaceans
are caught between the closing lobes, they are pressed so
hard whilst making their escape that they often void their
sausage-shaped masses of excrement, which were found
within most of the leaves. These masses, no doubt, contain
urea. They would be left either on the broad outer surfaces
of the lobes where the quadrifids are situated, or within the
closed concavity. In the latter case, water charged with
excrementitious and decaying matter would be slowly forced
outwards, and would bathe the quadrifids, if I am right in
believing that the concave lobes contract after a time like
those of Dionza. Foul water would also be apt to ooze out
at all times, especially when bubbles of air were generated
within the concavity.
A leaf was cut open and examined, and the outer cells of
the glands were found to contain only limpid fluid. Some
:
Cuar. XIV.] ALDROVANDA VESICULOSA. 265
of the quadrifids included a few spherical granules, but
several were transparent and empty, and their positions
were marked. This leaf was now immersed in a little
solution of one part of urea to 146 of water, or three grains
to the ounce. After 3 hrs. 40 m. there was no change either
in the glands or quadrifids; nor was there any certain change
in the glands after 24 hrs.; so that, as far as one trial goes,
urea does not act on them in the same manner as an infusion
of raw meat. It was different with the quadrifids ; for the
lining of protoplasm, instead of presenting a uniform texture,
was now slightly shrunk, and exhibited in many places
minute, thickened, irregular, yellowish specks and ridges,
exactly like those which appear within the quadrifids of
Utricularia when treated with this same solution. More-
over, several of the quadrifids, which were before empty,
now contained moderately sized or very small, more or less
aggregated, globules of yellowish matter, as likewise occurs
under the same circumstances with Utricularia. Some of
the points on the infolded margins of the lobes were
similarly affected; for their lining of protoplasm was a little
shrunk and included yellowish specks; and those which
were before empty now contained small spheres and irregular
masses of hyaline matter, more or less aggregated ; so that
both the points on the margins and the quadrifids had
absorbed matter from the solution in the course of 24 hrs.;
but to this subject I shall recur. In another rather old leaf,
to which nothing had been given, but which had been kept
in foul water, some of the quadrifids contained aggregated
translucent globules. These were not acted on by a solution
of one part of carbonate of ammonia to 218 of water: and
this negative result agrees with what I have observed under
similar circumstances with Utricularia.
Aldrovanda vesiculosa, var. australis—Dried leaves of this
plant from Queensland in Australia were sent me by Prof.
Oliver from the herbarium at Kew. Whether it ought to be
considered as a distinct species or a variety, cannot be told
until the flowers are examined by a botanist. The pro-
jections at the upper end of the petiole ape four to six in
number) are considerably longer relatively to the blade, and
much more attenuated than those of the European form.
They are thickly covered for a considerable space near their
extremities with the upcurved prickles, which are quite
absent in the latter form; and they generally bear on their
266 ALDROVANDA VESICULOSA. (Cuar. XIV.
tips two or three straight prickles instead of one. The
bilobed leaf appears also to be rather larger and somewhat
broader, with the pedicel by which it is attached to the
upper end of the petiole a little longer. The points on the
infolded margins likewise differ; they have narrower bases,
and are more pointed; long and short points also alternate
with much more regularity than in the European form.
The glands and sensitive hairs are similar in the two forms.
No quadrifid processes could be seen on several of the
leaves, but I do not doubt that they were present, though
indistinguishable from their delicacy and from having
shrivelled; for they were quite distinct on one leaf under
circumstances presently to be mentioned.
Some of the closed leaves contained no prey, but in one
there was rather a large beetle, which from its flattened
tibiz I suppose was an aquatic species, but was not allied to
Colymbetes. All the softer tissues of this beetle were com-
pletely dissolved, and its chitinous integuments were as
clean as if they had been boiled in caustic potash ; so that it
must have been enclosed for a considerable time. The glands
were browner and more opaque than those on other leaves
which had caught nothing; and the quadrifid processes,
from being partly filled with brown granular matter, could
be plainly distinguished, which was not the case, as already
stated, on the other leaves. Some of the points on the
infolded margins likewise contained brownish granular
matter. We thus gain additional evidence that the glands,
the quadrifid processes, and the marginal points, all have the
power of absorbing matter, though probably of a different
nature.
Within another leaf disintegrated remnants of a rather
small animal, not a crustacean, which had simple, strong,
opaque mandibles, and a large unarticulated chitinous coat,
were present. Lumps of black organic matter, possibly of
a vegetable nature, were enclosed in two other leaves; but
in one of these there was also a small worm much decayed.
But the nature of partially digested and decayed bodies,
which have been pressed flat, long dried, and then soaked in
water, cannot be recognised easily. All the leaves contained
unicellular and other Alga, still of a greenish colour, which
had evidently lived as intruders, in the same manner as
occurs, according to Cohn, within the leaves of this plant in
Germany.
Cmar. XIV.) CONCLUDING REMARKS. 267
Aldrovanda vesiculosa, var. verticillata.—Dyr, King, Superin-
tendent of the Botanic Gardens, kindly sent me dried
specimens collected near Calcutta. This form was, 1 believe,
considered by Wallich as a distinct species, under the name
of verticillata. It resembles the Australian form much more
nearly than the European; namely in the projections at the
upper end of the petiole being much attenuated and covered
with upcurved prickles; they terminate also in two straight
little prickles. The bilobed leaves are, I believe, larger and
certainly broader even than those of the Australian form; so
that the greater convexity of their margins was conspicuous.
The length of an open leaf being taken at 100, the breadth
of the Bengal form is nearly 173, of the Australian form 147,
and of the German 134. The points on the infolded margins
are like those in the Australian form. Of the few leaves
which were examined, three contained entomostracan crus-
taceans, .
Concluding Remarks.—The leaves of the three foregoing
closely allied species or varieties are manifestly adapted for
catching living creatures. With respect to the functions of
the several parts, there can be little doubt that the long
jointed hairs are sensitive, like those of Dionæa, and that,
when touched, they cause the lobes to close. That the glands
secrete a true digestive fluid and afterwards absorb the
digested matter, is highly probable from the analogy of
Dionza,—from the limpid fluid within their cells being
aggregated into spherical masses, after they had absorbed an
infusion of raw meat,—from their opaque and granular
condition in the leaf, which had enclosed a beetle for a long
time,—and from the clean condition of the integuments of
this insect, as well as of crustaceans (as described by Cohn),
which have been long captured. Again, from the effect
produced on the quadrifid processes by an immersion for
24 hrs. in a solution of urea,—from the presence of brown
granular matter within the quadrifids of the leaf in which
the beetle had been caught,—and from the analogy of
Utricularia,—it is probable that these processes absorb
excrementitious and decaying animal matter. It is a more
curious fact that the points on the infolded margins ap-
parently serve to absorb decayed animal matter in the same
manner as the quadrifids. We can thus understand the
meaning of the infulded margins of the lobes furnished with
delicate points directed inwards, and of the broad, flat, outer
268 CONCLUDING REMARKS. [Cuar. XIV.
portions, bearing quadrifid processes; for these surfaces must
be liable to be irrigated by foul water flowing from the
concavity of the leaf when it contains dead animals.* This
would follow from various causes,—from the gradual con-
traction of the concavity,—from fluid in excess being secreted,
—and from the generation of bubbles of air. More observa-
tions are requisite on this head; but if this view is correct,
we have the remarkable case of different parts of the same
leaf serving for very different purposes—one part for true
digestion, and another for the absorption of decayed animal
matter. We can thus also understand how, by the gradual
loss of either power, a plant might be gradually adapted for
the one function to the exclusion of the other: and it will
hereafter be shown that two genera, namely Pinguicula and
Utricularia, belonging to the same family, have been adapted
for these two different functions.
* [Duval-Jouve’s observations
throw some doubt on this point. He
has shown (‘Bull. Soc. Bot. de
France,’ t. xxiii. p. 130) that in the
lar structures are described by Duval-
Jouve as occurring on the leaves of
Callitriche, Nuphar luteum and Nym-
phea alba, and similar observations
winter buds of Aldrovanda the leaves
are reduced to a petiole, the lamina
being absent. Now the lamina bears
both the glands for which a peptic
function is suggested in the text, and
also the quadrifid processes which
are believed to absorb the products
of decay. Since the leaves of the
winter buds have no lamina, and
cannot therefore capture prey, we
must believe that the glands on the
petioles have merely general absorp-
tive function, and are not specialised
in relation to the products of the
decaying victims of the plant. Ximi-
were made by the late E. Ray Lan-
kester (‘ Brit. Assoc, Report,’ 1850,
published 1851, 2nd part of volume,
p. 113). This being so we must sus-
pend judgment as to the function of
the quadrifid processes on the outer
region of the lamina of the leaves of
Aldrovanda. Charles Darwin appears
to have been impressed with the im-
portance of these facts, as I infer
from a note pencilled in Prof. Mar-
tin’s tranlation of ‘ Insectivorous
Plants,’ where Duval-Jouve’s paper
is discussed in a note by the trans-
lator.—F, D.]
Cuar. XV.] DROSOPHYLLUM LUSITANICUM. 269
CHAPTER XV.
DROSOPHYLLUM—RORIDULA—-BYBLIS—GLANDULAR HAIRS OF OTHER
PLANTS—CONCLUDING REMARKS ON THE DROSERACEÆ.
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—Concludine
remarks on the Droseracez.
DrosopHYLLUM LusiTaNnicuM.—This rare plant has been found!
only in Portugal, and, as I hear from Dr. Hooker, in Morocco.
I obtained living specimens through the great kindness of
Mr. W. C. Tait, and afterwards from Mr. G. Maw and Dr.
Moore. Mr. Tait informs me that it grows plentifully on
the sides of dry hills near Oporto, and that vast numbers of
flies adhere to the leaves. This latter fact is well known to
the villagers, who call the plant the “ fly-catcher,” and hang
it up in their cottages for this purpose. A plant in my hot-
house caught so many insects during the early part of April,
although the weather was cold and insects scarce, that it
must have been in some manner strongly attractive to them.
On four leaves of a young and small plant, 8, 10, 14, and 16
minute insects, chiefly Diptera, were found in the autumn
adhering to them. I neglected to examine the roots, but I
hear from Dr. Hooker that they are very small, as in the case
of the previously mentioned members of the same family of
the Droseraceie.
The leaves arise from an almost woody axis; they are
linear, much attenuated towards their tips, and several inches
in length. The upper surface is concave, the lower convex,
with a narrow channel down the middle. Both surfaces,
with the exception of the channel, are covered with glands,
supported on pedicels and arranged in irregular longitudinal
rows. These organs I shall call tentacles, from their close
resemblance to those of Drosera, though they have no power
of movement, Those on the same leaf differ much in length.
270 DROSOPHYLLUM LUSITANICUM. [Cmar. XV.
The glands also differ in size, and are of a bright pink or of
a purple colour; their upper surfaces are convex, and the
lower flat or even concave, so that they resemble miniature
mushrooms in appearance. They are formed of two (as I
believe) layers of delicate angular cells, enclosing eight or
ten larger cells with thicker zigzag walls. Within these
larger cells there are others marked by spiral lines, and
apparently connected with the spiral vessels which run up
the green multicellular pedicels. The glands secrete large
drops of viscid secretion. Other glands, having the same
general appearance, are found on the flower-peduncles and
calyx.
Besides the glands which are borne on longer or shorter
pedicels, there are numerous ones, both on
the upper and lower surfaces of the leaves,
so small as to be scarcely visible to the
naked eye. They are colourless and almost
sessile, either circular or oval in outline;
the latter occurring chiefly on the backs of
the leaves (fig. 14). Internally they have
exactly the same structure as the larger
glands which are supported on pedicels;
and indeed the two sets almost graduate
into one another. But the sessile glands
differ in one important respect, for they
never secrete spontaneously, as far as I
_ have seen, though I have examined them
ee lusi- under a high power on a hot day, whilst
Part of leaf, enlargea the glands on pedicels were secreting co-
seven times, show- piously. Nevertheless, if little bits of damp
ing lower surface. ™
albumen or fibrin are placed on these
sessile glands, they begin after a time to
secrete, in the same manner as do the glands of Dionæa
when similarly treated. When they were merely rubbed
with a bit of raw meat, I believe that they likewise secreted.
Both the sessile glands and the taller ones on pedicels have
the power of rapidly absorbing nitrogenous matter.
The secretion from the taller glands differs in a remarkable
manner from that of Drosera, in being acid before the glands
have been in any way excited; and judging from the changed
colour of litmus paper, more strongly acid than that of
Drosera. This fact was observed repeatedly; on one
oceasion I chose a young leaf, which was not secreting freely,
Ciar. XV.] SECRETION. 271
and had never caught an insect, yet the secretion on all the
glands coloured litmus paper of a bright red. From the
quickness with which the glands are able to obtain animal
matter from such substances as well-washed fibrin and
cartilage, I suspect that a small quantity of the proper
ferment must be present in the secretion before the glands
are excited, so that a little animal matter is quickly
dissolved.
Owing to the nature of the secretion or to the shape of
the glands, the drops are removed from them with singular
facility. It is even somewhat difficult, by the aid of a finely
pointed polished needle, slightly damped with water, to place
a minute particle of any kind on one of the drops; for on
withdrawing the needle, the drop is ‘generally withdrawn;
whereas with Drosera there is no such difficulty, though the
drops are occasionally withdrawn. From this peculiarity,
when a small insect alights on a leaf of Drosophyllum, the
drops adhere to its wings, feet, or body, and are drawn from
the gland ; the insect then crawls onward and other drops
adhere to it; so that at last, bathed by the viscid secretion,
it sinks down and dies, resting on the small sessile glands
with which the surface of the leaf is thickly covered. In
the case of Drosera, an insect sticking to one or more of the
exterior glands is carried by their movement to the centre of
the leaf; with Drosophyllum, this is effected by the crawling
of the insect, as from its wings being clogged by the secretion
it cannot fly away.
There is another difference in function between the glands
of ‘these two plants: we know that the glands of Drosera
secrete more copiously when properly excited. But when
minute particles of carbonate of ammonia, drops of a solution
of this salt or of the nitrate of ammonia, saliva, small insects,
bits of raw or roast meat, albumen, fibrin or cartilage, as well
as inorganic particles, were placed on the glands of Droso-
phyllum, the amount of secretion never appeared to be in
the least increased. As insects do not commonly adhere to
the taller glands, but withdraw the secretion, we can see
that there would be little use in their having acquired the
habit of secreting copiously when stimulated; whereas with
Drosera this is of use, and the habit has been acquired.
Nevertheless, the glands of Drosophyllum, without being
stimulated, continually secrete, so as to replace the loss by
evaporation. Thus when a plant was placed under a small
272 DROSOPHYLLUM LUSITANICUM. [Cmar. XV.
bell-glass with its inner surface and support thoroughly
wetted, there was no loss by evaporation, and so much
secretion was accumulated in the course of a day that it ran
down the tentacies and covered large spaces of the leaves.
The glands to which the above named nitrogenous
substances and liquids were given did not, as just stated,
secrete more copiously ; on the contrary, they absorbed their
own drops of secretion with surprising quickness. Bits of
damp fibrin were placed on five glands, and when they were
looked at after an interval of 1 hr. 12 m., the fibrin was
almost dry, the secretion having been all absorbed. So it
was with three cubes of albumen after 1 hr. 19 m., and with
four other cubes, though these latter were not looked at
until 2 hrs. 15 m. had elapsed. The same result followed in
between 1 hr. 15 m. and 1 hr. 30 m. when particles both of
cartilage and meat were placed on several glands. Lastly, a
minute drop (about „y of a minim) of a solution of one part
of nitrate of ammonia to»146 of water was distributed between
the secretion surrounding three glands, so that the amount
of fluid surrounding each was slightly increased ; yet when
looked at after 2 hrs., all three were dry. On the other
hand, seven particles of glass and three of coal-cinders, of
nearly the same size as those of the above-named organic
substances, were placed on ten glands; some of them being
observed for 18 hrs., and others for two or three days; but
there was not the least sign of the secretion being absorbed.
Hence, in the former cases, the absorption of the secretion
must have been due to the presence of some nitrogenous
matter, which was either already soluble or was rendered so
by the secretion. As the fibrin was pure, and had been well
washed in distilled water after being kept in glycerine, and
as the cartilage had been soaked in water, I suspect that
these substances must have been slightly acted on and
rendered soluble within the above stated short periods.
The glands have not only the power of rapid absorption,
but likewise of secreting again quickly; and this latter
habit has perhaps been gained, inasmuch as insects, if they
touch the glands, generally withdraw the drops of secretion,
which have to be restored. The exact period of re-secretion
was recorded in only a few cases. The glands on which
bits of meat were placed, and which were nearly dry after
about 1 hr. 30 m., when looked at after 22 additional hours,
were found secreting ; so it was after 24 hrs. with one gland
Cuar. XV.] ABSORPTION. 273
on which a bit of albumen had been placed. The three
glands to which a minute drop of a solution of nitrate of
ammonia was distributed, and which became dry after 2 hrs.,
were beginning to re-secrete after only 12 additional hours.
Tentacles Incapable of Movement.—Many of the tall ten-
tacles, with insects adhering to them, were carefully ob-
served ; and fragments of insects, bits of raw meat, albumen,
&c., drops of a solution of two salts of ammonia and of
saliva, were placed on the glands of many tentacles; but
not a trace of movement could ever be detected. I also
repeatedly irritated the glands with a needle, and scratched
and pricked the blades, but neither the blade nor the
tentacles became at all inflected. We may therefore con-
clude that they are incapable of movement.
On the Power of Absorption possessed by the Glands.—It has
already been indirectly shown that the glands on pedicels
absorb animal matter; and this is further shown by their
changed colour, and by the aggregation of their contents,
after they have been left in contact with nitrogenous
substances or liquids. The following observations apply
both to the glands supported on pedicels and to the minute
sessile ones. Before a gland has been in any way stimu-
lated, the exterior cells commonly contain only limpid purple
fluid; the more central ones including mulberry-like masses
of purple granular matter. A leaf was placed in a little
solution of one part of carbonate of ammonia to 146 of water
(3 grs. to 1 oz.), and the glands were instantly darkened
and very soon became black; this change being due to the
strongly marked aggregation of their contents, more especially
of the inner cells. Another leaf was placed in a solution of
the same strength of nitrate of ammonia, and the glands
were slightly darkened in 25 m., more so in 50 m., and after
1 hr. 30 m. were of so dark a red as to appear almost black.
Other leaves were placed in a weak infusion of raw meat
and in human saliva, and the glands were much darkened
in 25 m., and after 40 m. were so dark as almost to deserve
to be called black. Even immersion for a whole day in
distilled water occasionally induces some aggregation within
the glands, so that they become of a darker tint. In all
these cases the glands are affected in exactly the same
manner as those of Drosera. Milk, however, which
acts so energetically on Drosera, seems rather less effective
on Drosophyllum, for the glands were only slightly
T
274 DROSOPHYLLUM LUSITANICUM. ([Cuar. XV
darkened by an immersion ¢f 1 hr. 20 m., but became decidedly
darker after 3 hrs. Leaves which had been left for 7 hrs.
in an infusion of raw meat or in saliva were placed in the
solution of carbonate of ammonia, and the glands now be-
came greenish ; whereas, if they had been first placed in the
carbonate, they would have become black. In this latter
case, the ammonia probably combines with the acid of the
secretion, and therefore does not act on the colouring matter ;
but when the glands are first subjected to an organic fluid,
either the acid is consumed in the work of digestion or the
cell-walls are rendered more permeable, so that the undecom-
posed carbonate enters and acts on the colouring matter. If
a particle of the dry carbonate is placed on a gland, the purple
colour is quickly discharged, owing probably to an excess of
the salt. The gland, moreover, is killed.
Turning now to the action of organic substances, the
glands on which bits of raw meat were placed became dark-
coloured; and in 18 hrs. their contents were conspicuously
aggregated. Several glands with bits of albumen and fibrin
were darkened in between 2 hrs. and 3 brs. ; but in one case
the purple colour was completely discharged. Some glands
which had caught flies were compared with others close by ;
and though they did not differ much in colour, there was a
marked difference in their state of aggregation. In some
few instances, however, there was no such difference, and
this appeared to be due to the insects having been caught
long ago, so that the glands had recovered their pristine
state. In one case, a group of the sessile colourless glands,
to which a small fly adhered, presented a peculiar appear-
ance; for they had become purple, owing to purple granular
matter coating the cell-walls. I may here mention as a
caution that, soon after some of my plants arrived in the
spring from Portugal, the glands were not plainly acted on
by bits of meat, or insects, or a solution of ammonia—a
circumstance for which I cannot account.
Digestion of Solid Animal Matter.—Whilst I was trying to
place on two of the taller glands little cubes of albumen,
these slipped down, and, besmeared with secretion, were left
resting on some of the small sessile glands. After 24 hrs.
one of these cubes was found completely liquefied, but with
a few white streaks still visible; the other was much
rounded, but not quite dissolved. Two other cubes were left
on tall glands for 2 hrs. 45 m., by which time all the
Cuar. XV.J DIGESTION. 275
secretion was absorbed ; but they were not perceptibly acted
on, though no doubt some slight amount of animal matter had
been absorbed from them. They were then placed on the small
sessile glands, which being thus stimulated secreted copiously
in the course of 7 hrs. One of these cubes was much
liquefied within this short time; and both were completely
liquefied after 21 hrs. 15 m.; the little liquid masses, how-
ever, still showing some white streaks. These streaks
disappeared after an additional period of 6 hrs. 30 m.; and
by next morning (i.e. 48 hrs. from the time when the cubes
were first placed on the glands) the liquefied matter was
wholly absorbed. A cube of albumen was left on another tall
gland, which first absorbed the secretion and after 24 hrs.
poured forth a fresh supply. This cube, now surrounded
by secretion, was left on the gland for an additional 24 hrs.,
but was very little, if at all, acted on. We may therefore
conclude, either that the secretion from the tall glands has
little power of digestion, though strongly acid, or that the
amount poured forth froma single gland is insufficient to dis-
solve a particle of albumen which within the same time
would have been dissolved by the secretion from several of
the small sessile glands. Owing to the death of my last
plant, I was unable to ascertain which of these alternatives
is the true one.
Four minute shreds of pure fibrin were placed, each
resting on one, two, or three of the taller glands. In the
course of 2 hrs. 30 m. the secretion was all absorbed, and the
shreds were left almost dry. They were then pushed on to
the sessile glands. One shred, after 2 hrs. 30 m., seemed
quite dissolved, but this may have been a mistake. A
second, when examined after 17 hrs. 25 m., was liquefied,
but the liquid as seen under the microscope still contained
floating granules of fibrin. The other two shreds were com-
pletely liquefied after 21 hrs. 30 m.; but in one of the drops
a very few granules could still be detected. These, however,
were dissolved after an additional interval of 6 hrs. 30 m.;
and the surface of the leaf for some distance all round was
covered with limpid fluid. It thus appears that Drosophyllum
digests albumen and fibrin rather more quickly than
Drosera can ; and this may perhaps be attributed to the acid,
together probably with some small amount of the ferment,
being present in the secretion, before the glands have been
stimulated ; so that digestion begins at once.
T 2
276 RORIDULA. [Cmar. XV.
Concluding Remarks—The linear leaves of Drosophyllum
differ but slightly from those of certain species of Drosera ;
the chief differences being, firstly, the presence of minute,
almost sessile, glands, which, like those of Dionea, do not
secrete until they are excited by the absorption of nitro-
genous matter. But glands of this kind are present on the
leaves of Drosera binata, and appear to be represented by the
papille on the leaves of Drosera rotundifolia. Secondly,
the presence of tentacles on the backs of the leaves; but we
have seen that a few tentacles, irregularly placed and
tending towards abortion, are retained on the backs of the
leaves of Drosera binata. There are greater differences in
function between the two genera. The most important one
is that the tentacles of Drosophyllum have no power of
movement ; this loss being partially replaced by the drops
of viscid secretion being readily withdrawn from the glands ;
so that, when an insect comes into contact with a drop, it is
able to crawl away, but soon touches other drops, and then,
smothered by the secretion, sinks down on the sessile glands
and dies. Another difference is, that the secretion from the
tall glands, before they have been in any way excited, is
strongly acid, and perhaps contains a small quantity of the
proper ferment. Again, these glands do not secrete more
copiously from being excited by the absorption of nitro-
genous matter; on the contrary, they then absorb their own
secretion with extraordinary quickness. In a short time
they begin to secrete again. All these circumstances are
probably connected with the fact that insects do not
commonly adhere to the glands with which they first come
into contact, though this does sometimes occur; and that it
is chiefly the secretion from the sessile glands which dissolves
animal matter out of their bodies.
RORIDULA.
Roridula dentata.—This plant, a native of the western
parts of the Cape of Good Hope, was sent to me in a dried
state from Kew. It has an almost woody stem and branches,
and apparently grows to a height of some feet. The leaves
are linear, with their summits much attenuated. Their
upper and lower surfaces are concave, with a ridge in the
middle, and both are covered with tentacles, which differ
greatly in length; some being very long, especially those
Cuar. XV.] BYBLIS. ya af
on the tips of the leaves, and some very short. The glands
also differ much in size and are somewhat elongated. They
are supported on multicellular pedicels.
This plant, therefore, agrees in several respects with
Drosophyllum, but differs in the following points. I could
detect no sessile glands; nor would these have been of any
use, as the upper surface of the leaves is thickly clothed
with pointed, unicellular hairs directed upwards. The
pedicels of the tentacles do not include spiral vessels; nor
are there any spiral cells within the glands. The leaves
often arise in tufts and are pinnatifid, the divisions pro-
jecting at right angles to the main linear blade. These
lateral divisions are often very short and bear only a single
terminal tentacle, with one or two short ones on the sides.
No distinct line of demarcation can be drawn between the
pedicels of the long terminal tentacles and the much attenu-
ated summits of the leaves. We may, indeed, arbitrarily fix
on the point to which the spiral vessels proceeding from the
blade extend; but there is no other distinction.
It was evident from the many particles of dirt sticking to
the glands that they secrete much viscid matter. A large
number of insects of many kinds also adhered to the leaves.
I could nowhere discover any signs of the tentacles having
been inflected over the captured insects; and this probably
would have been seen even in the dried specimens, had they
possessed the power of movement. Hence, in this negative
character, Roridula resembles its northern representative,
Drosophyllum.
BYBLIS.
Byblis gigantea (Western Australia)—A dried specimen,
about 18 inches in height, with a strong stem, was sent me
from Kew. The leaves are some inches in length, linear,
slightly flattened, with a small projecting rib on the lower
surface. They are covered on all sides by glands of two
kinds—sessile ones arranged in rows, and others supported
on moderately long pedicels. Towards the narrow summits
of the leaves the pedicels are longer than elsewhere, and
here equal the diameter of the leaf. The glands are purplish,
much flattened, and formed of a single layer of radiating
cells, which in the larger glands are from forty to fifty in
number. The pedicels consist of single elongated cells, with
colourless, extremely delicate walls, marked with the finest
278 GLANDULAR HAIRS: [Cuar. XV.
intersecting spiral lines. Whether these lines are the result
of contraction from the drying of the walls, I do not know,
but the whole pedicel was often spirally rolled up. ‘These
glandular hairs are far more simple in structure than the so-
called tentacles of the preceding genera, and they do not
differ essentially from those borne by innumerable other
plants. The flower-peduncles bear similar glands. The
most singular character about the leaves is that the apex is
enlarged into a little knob, covered with glands, and about
a third broader than the adjoining part of the attenuated
leaf. In two places dead flies adhered to the glands. As
no instance is known of unicellular structures having any
power of movement,* Byblis, no doubt, catches insects solely
by the aid of its viscid secretion. These probably sink down
besmeared with the secretion and rest on the small sessile
glands, which, if we may judge by the analogy of Droso-
phyllum, then pour forth their secretion and afterwards
absorb the digested matter.
Supplementary Observations on the Power of Absorption by the
Glandular Hairs of other Plants—A few observations on this
subject may be here conveniently introduced. As the glands
of many, probably of all, the species of Droseraceze absorb
various fluids or at least allow them readily to enter,f it
seemed desirable to ascertain how far the glands of other
plants which are not specially adapted for capturing insects,
had the same power. Plants were chosen for trial at hazard,
with the exception of two species of saxifrage, which were
selected from belonging to a family allied to the Droseracez.
Most of the experiments were made by immersing the glands
either in an infusion of raw meat or more commonly in a
solution of carbonate of ammonia, as this latter substance
acts so powerfully and rapidly on protoplasm. It seemed
also particularly desirable to ascertain whether ammonia
was absorbed, as a small amount is contained in rain-water.
With the Droseraceæ the secretion of a viscid fluid by the
glands does not prevent their absorbing; so that the glands
of other plants might excrete superfluous matter, or secrete
an odoriferous fluid as a protection against the attacks of
* Sachs, ‘Traité de Bot.’ 3rd edit. imbibition, is by no means clearly
1874, p. 1026. understood: see Miiller’s ‘ Physio-
ł The distinction between true logy; Eng. translat. 1838, vol. i. p.
absorption and mere permeation, or 280.
paa
Cuar. XV.] THEIR POWER OF ABSORPTION. 279
insects, or for any other purpose, and yet have the power of
absorbing. I regret that in the following cases I did not
try whether the secretion could digest or render soluble
animal substances, but such experiments would have been
difficult on account of the small size of the glands and the
small amount of secretion. We shall see in the next chapter
that the secretion from the glandular hairs of Pinguicula
certainly dissolves animal matter.
Saxifraga umbrosa.—The flower-peduncles and petioles of the
leaves are clothed with short hairs, bearing pink-coloured glands,
formed of several polygonal cells, with their pedicels divided by partitions
into distinct cells, which are generally colourless, but sometimes pink.
The glands secrete a yellowish viscid fluid, by which minute Diptera
are sometimes, though not often, caught.* The cells of the glands
contain bright pink fluid, charged with granules or with globular
masses of pinkish pulpy matter. This matter must be protoplasm,
for it is seen to undergo slow but incessant changes of form if a gland
be placed in a drop of water and examined. Similar movements were
observed after glands had been immersed in water for 1, 3, 5, 18, and
27 hrs. Even after this latter period the glands retained their bright
pink colour; and the protoplasm within their cells did not appear to
have become more aggregated. The continually changing forms of
the little masses of protoplasm are not due to the absorption of water,
as they were seen in glands kept dry.
A flower-stem, still attached to a plant, was bent (May 29) so as to
remain immersed for 23 hrs. 30 m. in a strong infusion of raw meat.
The colour of the contents of the glands was slightly changed, being
now of a duller and more purple tint than before. ‘The contents also
appeared more aggregated, for the spaces between the little masses of
protoplasm were wider; but this latter result did not follow in some
other and similar experiments. ‘The masses seemed to change their
forms more rapidly than did those in water; so that the cells had a
different appearance every four or five minutes. Elongated masses
became in the course of one or two minutes spherical; and spherical
ones drew themselves out and united with others. Minute masses
rapidly increased in size, and three distinct ones were seen to unite.
The movements were, in short, exactly like those described in the case
of Drosera. The cells of the pedicels were not affected by the infusion ;
nor were they in the following experiment.
Another flower-stem was placed in the same manner and for the
same length of time in a solution of one part of nitrate of ammonia to
* In the case of Sarifraga tri- and in almost every instance remnants
dactylites, Mr. Druce says (‘Phar- of insects adhered to the leaves. So
maceutical Journal,’ May 1875) that it is, as I hear from a friend, with
he examined some dozens of plants, this plant in Ireland,
280 GLANDULAR HAIRS: [Cuar. XV.
146 of water (or 3 grs. to 1 oz.), and the glands were discoloured in
exactly the same manner as by the infusion of raw meat.
Another flower-stem was immersed, as before, in a solution of one
part carbonate of ammonia to 109 of water. The glands, after 1 hr.
30 m., were not discoloured, but after 3 hrs. 45 m. most of them had
become dull purple, some of them blackish-green, a few being still
unaffected. The little masses of protoplasm within the cells were
seen in movement. The cells of the pedicels were unaltered. ‘The
experiment was repeated, and a fresh flower-stem was left for 23 hrs.
in the solution, and now a great effect was produced; all the glands
were much blackened, and the previously transparent fluid in the cells
of the pedicels, even down to their bases, contained spherical masses of
granular matter. By comparing many different hairs, it was evident
that the glands first absorb the carbonate, and that the effect thus
produced travels down the hairs from cell to cell, The first change
which could be observed is a cloudy appearance in the fluid, due to
the formation of very fine granules, which afterwards aggregate into
larger masses. Altogether, m the darkening of the glands, and in the
process of aggregation travelling down the cells of the pedicels, there is
the closest resemblance to what takes place when a tentacle of Drosera
is immersed in a weak solution of the same salt. ‘The glands, however,
absorb very much more slowly than those of Drosera. Besides the
glandular hairs, there are star-shaped organs which do not appear to
secrete, and which were not in the least affected by the above
solutions.
Although in the case of uninjured flower-stems and leaves the
carbonate seems to be absorbed only by the glands, yet it enters a cut
surface much more quickly than a gland. Strips of the rind of a
flower-stem were torn off, and the cells of the pedicels were seen to
contain only colourless transparent fluid ; those of the glands including
as usual some granular matter. These strips were then immersed in
the same solution as before (one part of the carbonate to 109 of water),
and in a few minutes granular matter appeared in the lower cells of all
the pedicels. The action invariably commenced (for I tried the ex-
periment repeatedly) in the lowest cells, and therefore close to the torn
surface, and then gradually travelled up the hairs until it reached the
glands, in a reversed direction to what occurs in uninjured specimens.
The glands then became discoloured, and the previously contained
granular matter was aggregated into larger masses. Two short bits of
a flower-stem were also left for 2 hrs. 40 m. ina weaker solution of one
part of the carbonate of 218 of water; and in both specimens the
pedicels of the hairs near the cut ends now contained much granular
matter; and the glands were completely discoloured.
Lastly, bits of meat were placed on some glands; these were
examined after 23 hrs., as were others, which had apparently not long
before caught minute flies; but they did not present any difference
from the glands of other hairs. Perhaps there may not have been
time enough for absorption. I think so, as some glands, on which
W
oF
Cuar. XV.] THEIR POWER OF ABSORPTION. 281
dead flies had evidently long lain, were of a pale dirty purple colour or
even almost colourless, and the granular matter within them presented.
an unusual and somewhat peculiar appearance. That these glands. had
absorbed animal matter from the flies, probably by exosmose into the
viscid secretion, we may infer, not only from their changed colour, but
because, when placed in a solution of carbonate of ammonia, some of
the cells in their pedicels become filled with granular matter ; whereas
the cells of other hairs, which had not caught flies, after being treated
with the same solution for the same length of time, contained only a
small quantity of granular matter. But more evidence is neces-ary
before we fully admit that the glands of this saxifrage can absorb,
even with ample time allowed, animal matter from the minute insects
which they occasionally and accidentally capture.
Saxifraga rotundifolia (?).—The hairs on the flower-stems of this
species are longer than those just described, and bear pale brown glands.
Many were examined, and the cells of the pedicels were quite trans-
parent. A bent stem was immersed for 30 m. in a solution of one
part of carbonate of ammonia to 109 of water, and two or three of the
uppermost cells in the pedicels now contained granular or aggregated
matter; the glands having become of a bright yellowish-green. ‘The
glands of this species therefore absorb the carbonate much more
quickly than do those of Saxifraga umbrosa, and the upper cells of the
pedicels are likewise atiected much more quickly. Pieces of the stem
were cut off and immersed in the same solution; and now the process
of aggregation travelled up the hairs in a reversed direction ; the cells
close to the cut surfaces being first affected.
Primula sinensis.—Vhe flower-stems, the upper and lower surfaces
of the leaves and their footstalks, are all clothed with a multitude of
longer and shorter hairs. The pedicels of the longer hairs are divided
by transverse partitions into eight or nine cells. The enlarged ter-
minal cell is globular, forming a gland which secretes a variable amount
of thick, slightly viscid, not acid, brownish-yellow matter.
A piece of a young flower-stem was first immersed in distilled water
for 2 hrs. 30 m., and the glandular hairs were not at all affected.
Another piece, bearing twenty-five short and nine long hairs, was
carefully examined. ‘lhe glands of the latter contained no solid or
semi-solid matter; and those of only two of the twenty-five short hairs
contained some globules. This piece was then immersed for 2 hrs.
in a solution of one part of carbonate of ammonia to 109 of water,
and now the glands of the twenty-five shorter hairs, with two or three
exceptions, contained either one large or from two to five smaller
spherical masses of semi-solid matter. Three of the glands of the
nine long hairs likewise included similar masses. In a few hairs there
were also globules in the cells immediately beneath the glands.
Looking to all thirty-fonr hairs, there could be no doubt that the
glands had absorbed some of the carbonate. Another piece was left
for only 1 hr. in the same solution, and aggregated matter appeared
in all the glands. Myson Francis examined some glands of the longer
282 GLANDULAR HAIRS: [Cuar. XV.
hairs, which contained little masses of matter, before they were
immersed in any solution; and these masses slowly changed their
forms, so that no doubt they consisted of protoplasm. He then
irrigated these hairs for 1 hr. 15 m., whilst under the microscope,
with a solution of one part of the carbonate to 218 of water; the
glands were not perceptibly affected, nor could this have been expected,
as their contents were already aggregated. But in the cells of the
pedicels numerous, almost colourless, spheres of matter appeared,
which changed their forms and slowly coalesced; the appearance of
the cells being thus totally changed at successive intervals of time.
The glands on a young flower-stem, after having been left for 2 hrs.
45 m. in a strong solution of one part of the carbonate to 109 of water,
contained an abundance of aggregated masses, but whether generated
by the action of the salt, Ido not know. This piece was again placed
in the solution, so that it was immersed altogether for 6 hrs. 15 m.,
and now there was a great change; for almost all the spherical masses
within the gland-cells had disappeared, being replaced by granular
matter of a darker brown. The experiment was thrice repeated with
nearly the same result. On one occasion the piece was left immersed
for 8 hrs. 80 m., and though almost all the spherical masses were
changed into the brown granular matter, a few still remained. If the
spherical masses of aggregated matter had been originally produced
merely by some chemical or physical action, it seems strange that a
somewhat longer immersion in the same solution should so completely
alter their character. But as the masses which slowly and sponta-
neously changed their forms must have consisted of living protoplasm,
there is nothing surprising in its being injured or killed, and its
appearance wholly changed by long immersion in so strong a solution
of the carbonate as that employed. A solution of this strength
paralyses all movement in Drosera, but does not kill the protoplasm ;
a still stronger solution prevents the protoplasm from aggregating into
the ordinary full-sized globular masses, and these, though they do not
disintegrate, become granular and opaque. In nearly the same
manner, too, hot water and certain solutions (for instance, of the salts
of soda and potash) canse at first an imperfect kind of aggregation in the
cells of Drosera ; the little masses afterwards breaking ‘up into granular
or pulpy brown matter. All the foregoing experiments were made on
tlower-stems, but a piece of a leaf was immersed for 30 m. in a strong
solution of the carbonate (one part to 109 of water), and little globular
masses of matter appeared in all the glands, which before contained
only limpid fluid.
I made also several experiments on the action of the vapour of the
carbonate on the glands; but will give only a few cases. The cut end
of the footstalk of a young leaf was protected with sealing-wax, and was
then placed under a small bell-glass, with a large pinch of the carbon-
ate. After 10 m. the glands showed a considerable degree of aggrega-
tion, and the protoplasm lining the cells of the pedicels was a little
separated from the walls. Another leaf was left for 50 m. with the
Cuar. XV. THEIR POWER OF ABSORPTION. 283
same result, excepting that the hairs became throughout their whole
length of a brownish colour. In a third leaf, which was exposed for
1 hr. 50 m., there was much aggregated matter in the glands; and
some of the masses showed signs of breaking up into brown granular
matter. This leaf was again placed in the vapour, so that it was
exposed altogether for 5 hrs. 80 m.; and now, though I examined
a large number of glands, aggregated masses were found in only two
or three; in all the others, the masses, which before had been globular,
were converted into brown, opaque, granular matter. We thus see
that exposure to the vapour for a considerable time produces the same
effects as long immersion in a strong solution. In both cases there
could hardly be a doubt that the salt had been absorbed chiefly or
exclusively by the glands.
On another occasion bits of damp fibrin, drops of a weak infusion of
raw meat and of water, were left fur 24 hrs. on some leaves ; the hairs
were then examined, but to my surprise differed in no respect from
others which had not been touched by these fluids. Most of the cells,
however, included hyaline, motionless little spheres, which did not
seem to consist of protoplasm, but, 1 suppose, of some balsam or
essential oil.
Pelargonium zonale (var. edged with white),—The leaves are clothed
with numerous multicellular hairs; some simply pointed; others
bearing glandular heads, and differing much in length. The glands
on a piece of leaf were examined and found to contain only a limpid
fluid; most of the water was removed from beneath the covering glass,
and a minute drop of one part of carbonate of ammonia to 146 of water
was added; so that an extremely small cose was given. After an
interval of only 3 m. there were signs of aggregation within the glands
of the shorter hairs; and after 5 m. many small globules of a pale
brown tint appeared in all of them; similar giobules, but larger, being
found in the large glands of the longer hairs. After the specimen had
been left for 1 hr. in the solution, many of the smaller globules had
changed their positions; and two or three vacuoles or small spheres
(for 1 know not which they were) of a rather darker tint appeared
within some of the larger globules. Little globules could now be seen
in some of the uppermost cells of the pedicels, and the protoplasmic
lining was slightly separated from the walls of the lower cells. After
2 hrs. 30 m. from the time of first immersion, the large globules
within the glands of the longer hairs were converted into masses of
darker brown granular matter. Hence from what we have seen with
Primula sinensis, there can be little doubt that these masses originally
consisted of living protoplasm,
A drop of a weak infusion of raw meat was placed on a leaf, and
after 2 hrs, 30 m. many spheres could be seen within the glands.
These spheres, when looked at again after 30 m., had slightly changed
their positions and forms, and one had separated into two; but the
changes were not quite like those which the protoplasm of Drosera
undergves. These hairs, moreover, had not been examined before
284 GLANDULAR HAIRS: [Cuar. XV.
immersion, and there were similar spheres in some glands which had
not been touched by the infusion.
Erica tretraliv.—A few long glandular hairs project from the
margins of the upper surfaces of the leaves. The pedicels are formed
of several rows of cells, and support rather large globular heads,
secreting viscid matter, by which minute insects are occasionally
though rarely, caught. Some leaves were left for 23 hrs. in a weak
infusion of raw meat and in water, and the hairs were then com-
pared, but they differed very little or not at all. In both cases the
contents of the cells seemed rather more granular than they were
before; but the granules did not exhibit any movement. Other
leaves were left for 23 hrs. in a solution of one part of carbonate of
ammonia to 218 of water, and here again the granular matter appeared
to have increased in amount; but one such mass retained exactly the
same form as before after an interval of 5 hrs., so that it could hardly
have consisted of living protoplasm. These glands seem to have very
little or no power of absorption, certainly much less than those of the
foregoing plants.
Mirabilis longiflora.—The stems and both surfaces of the leaves
bare viscid hairs. Young plants, from 12 to 18 inches in height in
my greenhouse, caught so many minute Diptera, Coleoptera, and
larva, that they were quite dusted with them. ‘lhe hairs are short,
of unequal lengths, formed of a single row of cells, surmounted by an
enlarged cell which secretes viscid matter. These terminal cells or
glands contain granules and often globules of granular matter.
Within a gland which had caught a small insect, one such mass
was observed to undergo incessant changes of form, with the occa-
sional appearance of vacuoles. But 1 do not believe that this
protoplasm had been generated by matter absorbed from the dead
insect; for, on comparing several glands which had and had not
caught insects, not a shade of difference could be perceived between
them, and they all contained fine granular matter. A piece of leaf
was immersed for 24 hrs. in a solution of one part of carbonate of
ammonia to 218 of water, but the hairs seemed very little affected by
it, excepting that perhaps the glands were rendered rather more
opaque. In the leaf itself, however, the grains of chlorophyll near
the cut surfaces had run together, or become aggregated. Nor were
the glands on another leaf, after an immersion ‘for 24 hrs. in an in-
fusion of raw meat, in the least affected; but the protoplasm luing
the cells of the pedicels had shrunk greatly from the walls. This
latter effect may have been due to exosmose, as the infusion was
strong. We may therefore conclude that the glands of this plant
either have no power of absorption or that the protoplasm which they
contain is not acted on by a solution of carbonate of ammonia (and
this seems scarcely credible) or by an infusion of meat.
Nicotiana tabacum.—This plant is covered with innumerable hairs
of unequal lengths, which catch many minute insects. ‘The pedicels
of the hairs are divided by transverse partitions, and the secreting
Cuar. XV.] THEIR POWER OF ABSORPTION. 285
glands are formed of many cells, containing greenish matter with little
globules of some substance. Leaves were left in an infusion of raw
meat and in water for 26 hrs., but presented no difference. Some of
these same leaves were then left tor above 2 hrs. in a solution of
carbonate of ammonia, but no effect was produced. I regret that
other experiments were not tried with more care, as M. Schloesing has
shown* that tobacco plants supplied with the vapour of carbonate of
ammonia yield on analysis a greater amount of nitrogen than other
plants not thus treated ; and, from what we have seen, it is probable
that some of the vapour may be absorbed by the glandular hairs.
Summary of the Observations on Glandular Hairs—From
the foregoing observations, few as they are, we see that the
glands of two species of Saxifraga, of a Primula and Pelar-
gonium, have the power of rapid absorption; whereas the
glands of an Erica, Mirabilis, and Nicotiana, either have no
such power, or the contents of the cells are not affected by
the fluids employed, namely a solution of carbonate of
ammonia and an infusion of raw meat. As the glands of
the Mirabilis contain protoplasm, which did not become
aggregated from exposure to the fluids just named, though
the contents of the cells in the blade of the leaf were greatly
affected by carbonate of ammonia, we may infer that they
cannot absorb. We may further infer that the innumerable
insects caught by this plant are of no more service to it
than are those which adhere to the deciduous and sticky
scales of the leaf-buds of the horse-chestnut.
The most interesting case for us is that of the two species
of Saxifraga, as this genus is distantly allied to Drosera.
Their glands absorb matter from an infusion of raw meat,
from solutions of the nitrate and carbonate of ammonia, and
apparently from decayed insects. This was shown by the
changed dull purple colour of the protoplasm within the cells
of the glands, by its state of aggregation, and apparently by
its more rapid spontaneous movements. ‘The aggregating
process spreads from the glands down the pedicels of the
hairs; and we may assume that any matter which is absorbed
ultimately reaches the tissues of the plant. On the other
hand, the process travels up the hairs whenever a surface
is cut and exposed to a solution of the carbonate of ammonia.
* «Comptes rendus, June 15, 1874. A good abstract of this paper is
given in the ‘Gardener’s Chronicle,’ July 11, 1874,
286 GLANDULAR HAIRS. (Cuar, XV.
The glands on the flower-stalks and leaves of Primula
sinensis quickly absorb a solution of the carbonate of ammonia,
and the protoplasm which they contain becomes aggregated.
The process was seen in some cases to travel from the glands
into the upper cells of the pedicels. Exposure for 10 m. to
the vapour of this salt likewise induced aggregation. When
leaves were left from 6 hrs. to 7 hrs. in a strong solution,
or were long exposed to the vapour, the little masses of
protoplasm became disintegrated, brown, and granular, and
were apparently killed. An infusion of raw meat produced
no effect on the glands.
The limpid contents of the glands of Pelargonium zonale
became cloudy and granular in from 3 m. to 5 m. when they
were immersed in a weak solution of the carbonate of am-
monia ; and in the course of 1 hr. granules appeared in the
upper cells of the pedicels. As the aggregated masses
slowly changed their forms, and as they sutfered disintegra-
tion when left for a considerable time in a strong solntion,
there can be little doubt that they consisted of protoplasm.
It is doubtful whether an infusion of raw meat produced any
effect.
The glandular hairs of ordinary plants have generally
been considered by physiologists to serve only as secreting
or excreting organs, but we now know that they have the
power, at least in some cases, of absorbing both a solution
and the vapour of ammonia. As rain-water contains a small
percentage of ammonia, and the atmosphere a minute quantity
of the carbonate, this power can hardly fail to be beneficial.
Nor can the benefit be quite so insignificant as it might at
first be thought, for a moderately fine plant of Primula sinensis
bears the astonishing number of above two millions and a
half of glandular hairs,* all of which are able to absorb
* My son Francis counted the (the larger ones being a little more
hairs on a space measured by means than 2 inches in diameter) was now
of a micrometer, and found that selected, and the area of all the
there were 35,336 on a square inch leaves, together with their footstalks
of the upper surface of a leaf, and (the flower-stems not being included)
30,035 on the lower surface; that is, was found by a planimeter to be
in about the proportion of 100 on the 39°285 square inches; so that the
upper to 85 on the lower surface. area of both surfaces was 78°57
On a square inch of both surfaces square inches. Thus the plant (ex-
there were 65,371 hairs. A moder- cluding the flower-stems) must have
ately fine plant bearing twelve leaves
borne the astonishing number of
Cuar. XV.] DROSERACE®. 287
ammonia brought to them by the rain. It is moreover
probable that the glands of some of the above-named plants
obtain animal matter from the insects which are occasionally
entangled by the viscid secretion.
ConcLuDING REMARKS ON THE DROSERACEÆ.
The six known genera composing this family have now
been described in relation to our present subject, as far as
my means have permitted. They all capture insects. This
is effected by Drosophyllum, Roridula, and Byblis, solely by
the viscid fluid secreted from their glands; by Drosera,
through the same means, together with the movements of
the tentacles; by Dionæa and Aldrovanda, through the
closing of the blades of the leaf. In these two last genera
rapid movement makes up for the loss of viscid secretion.
In every case it is some part of the leaf which moves. In
Aldrovanda it appears to be the basal parts alone which
contract and carry with them the broad, thin margins of the
lobes. In Dionza the whole lobe, with the exception of the
marginal prolongations or spikes, curves inwards, though
the chief seat of movement is near the midrib. In Drosera
the chief seat is in the lower part of the tentacles, which,
homologically, may be considered as prolongations of the
leaf; but the whole blade often curls inwards, converting
the leaf into a temporary stomach.
There can hardly be a doubt that all the plants belonging
to these six genera have the power of dissolving animal
matter by the aid of their secretion, which contains an acid,
together with a ferment almost identical in nature with
pepsin; and that they afterwards absorb the matter thus
digested. This is certainly the case with Drosera, Droso-
phyllum, and Dionea; almost certainly with Aldrovanda ;
and, from analogy, very probable with Roridula and Byblis.
We can thus understand how it is that the three first-named
2,568,099 glandular hairs. The hairs
were counted late in the autumn, and
by the following spring (May) the
leaves of some other plants of the
same lot were found to be from one-
third to one-fourth broader and
longer than they were before; so
that no doubt the glandular hairs
had increased in number, and }ro-
bably now much exceeded three
millions.
288 CONCLUDING REMARKS [Cuar, XV.
genera are provided with such small roots,* and that Aldro-
vanda is quite rootless; about the roots of the two other
genera nothing is known. It is, no doubt, a surprising fact
that a whole group of plants (and, as we shall presently see,
some other plants not allied to the Droseraceæ) should
subsist partly by digesting animal matter, and partly by
decomposing carbonic acid, instead of exclusively by this
latter means, together with the absorption of matter from
the soil by the aid of roots. We have, however, an equally
anomalous case in the animal kingdom ; the rhizocephalous
crustaceans do not feed like other animals by their mouths,
for they are destitute of an alimentary canal; but they live
by absorbing through root-like processes the juices of the
animals on which they are parasitic.t
Of the six genera, Drosera has been incomparably the
most successful in the battle for life; and a large part of its
success may be attributed to its manner of catching insects.
It is a dominant form, for it is believed to include about 100
species,t which range in the Old World from the Arctic
regions to Southern India, to the Cape of Good Hope,
*(Fraustadt (Dissertation, Breslau, cirripede, the Anelasma squalicola,
1876) shows that the roots of Dionwa had become extinct, it would have
are by no means small. In another been very difficult to conjecture how
Breslau Dissertation (1887) Otto so enormous a change could have
Penzig shows that the roots of been gradually effected. But, as
Drosophyllum lusitanicum are also Fritz Müller remarks, we have in
well developed. Pfeffer (‘Landwirth. Anelasma an animal in an almost
Jahrbucher, 1877) points out thatthe exactly intermediate condition, for it
argument from the small develop- has root-like processes embedded in
ment of roots in some carnivorous the skin of the shark on which it is
plants is valueless, because the same parasitic, and its prehensile cirri and
state of things is found in many mouth (as described in my monograph
marsh and aquatic plants which on the Lepadide, ‘Ray Soc.’ 1851,
neither catch nor digest insects— p. 169) are in a most feeble and
F. DJ almost rudimentary condition. Dr.
+ Fritz Müller, ‘Facts for Darwin, R. Kossmann has given a very in-
Eng. trans. 1869, p. 139. The rhizo- teresting discussion on this subject
cephalous crustaceans are allied to in his ‘Suctoria and Lepadidæ, 1873.
the cirripedes. It is hardly possible See also, Dr. Dohrn, ‘ Der Ursprung
to imagine a greater difference than der Wirbelthiere,’ 1875, p. 77.
that between an animal with pre- } Bentham and Hooker, ‘Genera
hensile limbs, a well-constructed Plantarum.’
mouth and alimentary canal, and one tropolis of the genus, forty-one
destitute of all these organs and species having been described from
feeding by absorption through branch- this country, as Prof. Oliver informs
ing root-like processes. If one rare me.
Australia is the me-
Cuar, XYV.] ON THE DROSERACE®. 289
Madagascar, and Australia; and in the New World from
Canada to Tierra del Fuego. In this respect it presents a
marked contrast with the five other genera, which appear
to be failing groups. Dionæa includes only a single species,
which is confined to one district in Carolina. The three
varieties or closely allied species of Aldrovanda, like so many
water-plants, have a wide range from Central Europe to
Bengal and Australia. Drosophyllum includes only one
species, limited to Portugal and Morocco, Roridula and
Byblis each have (as I hear from Prof. Oliver) two species ;
the former confined to the western parts of the Cape of Good
Hope, and the latter to Australia. It is a strange fact that
Dionza, which is one of the most beautifully adapted plants
in the vegetable kingdom, should apparently be on the high
road to extinction. This is all the more strange as the
organs of Dionza are more highly differentiated than those
of Drosera; its filaments serve exclusively as organs of
touch, the lobes for capturing insects, and the glands, when
excited, for secretion as well as for absorption ; whereas with
Drosera the glands serve all these purposes, and secrete
without being excited.
By comparing the structure of the leaves, their degree of
complication, and their rudimentary parts in the six genera,
we are led to infer that their common parent form partook
of the characters of Drosophyllum, Roridula, and Byblis.
The leaves of this ancient form were almost certainly linear,
perhaps divided, and bore on their upper and lower surfaces
glands which had the power of secreting and absorbing.
Some of these glands were mounted on pedicels, and others
were almost sessile; the latter secreting only when stimu-
lated by the absorption of nitrogenous matter. In Byblis
the glands consist of a single layer of cells, supported on a
unicellular pedicel; in Roridula they have a more complex
structure, and are supported on pedicels formed of several
rows of cells; in Drosophyllum they further include spiral
cells, and the pedicels include a bundle of spiral vessels.
But in these three genera these organs do not possess any
power of movement, and there is no reason to doubt that
they are of the nature of hairs or trichomes. Although in
innumerable instances foliar organs move when excited, no
case is known of a trichome having such power.* We are
* Sachs, ‘Traité de Botanique, 3rd edit. 1874, p. 1026.
U
290 CONCLUDING REMARKS [Cuar. XV.
thus led to inquire how the so-called tentacles of Drosera,
which are manifestly of the same general nature as the
glandular hairs of the above three genera, could have
acquired the power of moving. Many botanists maintain
that these tentacles consist of prolongations of the leaf,
because they include vascular tissue, but this can no longer
be considered as a trustworthy distinction.* The possession
of the power of movement on excitement would have been
safer evidence. But when we consider the vast number of
the tenacles on both surfaces of the leaves of Drosophyllum,
and on the upper surface of the leaves of Drosera, it seems
searcely possible that each tentacle could have aboriginally
existed as a prolongation of the leaf. Roridula, perhaps,
shows us how we may reconcile these difficulties with respect
to the homological nature of the tentacles. The lateral
divisions of the leaves of this plant terminate in long ten-
tacles; and these include spiral vessels which extend for
only a short distance up them, with no line of demarcation
between what is plainly the prolongation of the leaf and
the pedicel of a glandular hair. Therefore there would be
nothing anomalous or unusual in the basal parts of these
tentacles, which correspond with the marginal ones of
Drosera, acquiring the power of movement; and we know
that in Drosera it is only the lower part which becomes
inflected. But in order to understand how in this latter
genus not only the marginal but all the inner tentacles have
become capable of movement, we must further assume, either
that through the principle of correlated development this
power was transferred to the basal parts of the hairs, or that
the surface of the leaf has been prolonged upwards at numer-
ous points, so as to unite with the hairs, thus forming the
bases of the inner tentacles,
The above-named three genera, namely Drosophyllum,
Roridula, and Byblis, which appear to have retained a
primordial condition, still bear glandular hairs on both
surfaces of their leaves; but those on the lower surface
have since disappeared in the more highly developed genera,
with the partial exception of one species, Drosera binata.
The small sessile glands have also disappeared in some of
* Dr. Warming, ‘Sur la Différence belige Meddelelser de la Soc. d’Hist.
entre les Trichomes,’ Copenhague, nat. de Copenhague, Nos. 10-12,
1873, p. 6. ‘Extrait des Videnska- 1872.
CHAF. XV.) ON THE DROSERACE. 291
the gerera, being replaced in Roridula by hairs, and in
most species of Drosera by absorbent papillae. Drosera
binata, with its linear and bifurcating leaves, is in an inter-
mediate condition. It still bears some sessile glands on both
surfaces of the leaves, and on the lower surface a few
irregularly placed tentacles, which are incapable of move-
ment. A further slight change would convert the linear
leaves of this latter species into the oblong leaves of Drosera
anglica, and these might easily pass into orbicular ones
with footstalks like those of Drosera rotundifolia. The
footstalks of this latter species bear multicellular hairs,
which we have good reason to believe represent aborted
tentacles.
The parent form of Dionæa and Aldrovanda seems to have
been closely allied to Drosera, and to have had rounded
leaves, supported on distinct footstalks, and furnished with
tentacles all round the circumference, with other tentacles
and sessile glands on the upper surface. I think so because
the marginal spikes of Dionza apparently represent the
extreme marginal tentacles of Drosera, the six (sometimes
eight) sensitive filaments on the upper surface, as well as
the more numerous ones in Aldrovanda, representing the
central tentacles of Drosera, with their glands aborted, but
their sensitiveness retained. Under this point of view we
should bear in mind that the summits of the tentacles of
Drosera, close beneath the glands, are sensitive.
The three most remarkable characters possessed by the
several members of the Droseracez consist in the leaves of
some having the power of movement when excited, in their
glands secreting a fluid which digests animal matter, and in
their absorption of the digested matter. Can any light be
thrown on the steps by which these remarkable powers were
gradually acquired ?
As the walls of the cells are necessarily permeable to
fluids, in order to allow the glands to secrete, it is not
surprising that they should readily allow fluids to pass in-
wards; and this inward passage would deserve to be called
an act of absorption, if the fluids combined with the contents
of the glands. Judging from the evidence above given, the
secreting glands of many other plants can absorb salts of
ammonia, of which they must receive small quantities from
the rain. This is the case with two species of Saxifraga.
U2
292 CONCLUDING REMARKS.
[CHAP. XV.
and the glands of one of them apparently absorb matter from
captured insects, and certainly from an infusion of raw meat.
There is, therefore, nothing anomalous in the Droseraceæ
having acquired the power of absorption in a much more
highly developed degree.
It is a far more remarkable problem how the members of
this family, and Pinguicula, and, as Dr. Hooker has recently
shown, Nepenthes, could all have acquired the power of
secreting a fluid which dissolves or digests animal matter.
The six genera of the Droseracew have probably inherited
this power from a common progenitor, but this cannot apply
to Pinguicula or Nepenthes, for these plants are not at all
closely related to the Droseracexw. But the difficulty is not
nearly so great as it at first appears. Firstly, the juices of
many plants contain an acid, and, apparently, any acid
serves for digestion. Secondly, as Dr. Hooker has remarked
in relation to the present subject in his address at Belfast
(1874), and as Sachs repeatedly insists,* the embryos of some
plants secrete a fluid which dissolves albuminous substances
out of the endosperm ; although the endosperm is not actually
united with, only in contact with, the embryo. All plants,
moreover, have the power of dissolving albuminous or proteid
substances, such as protoplasm, chlorophyll, gluten, aleurone,
and of carrying them from one part to other parts of their
tissues. This must be effected by a solvent, probably con-
sisting of a ferment together with an acid.t Now, in the
case of plants which are able to absorb already soluble matter
from captured insects, though not capable of true digestion,
the solvent just referred to, which must be occasionally
present in the glands, would be apt to exude from the glands
together with the viscid secretion, inasmuch as endosmose
is accompanied by exosmose. If such exudation did ever
occur, the solvent would act on the animal matter contained
within the captured insects, and this would be an act of true
digestion. As it cannot be doubted that this process would
* ¢Traité de Botanique, 3rd edit.
1874, p. 844. See also for following
facts pp. 64, 76, 828, 831.
+ Since this sentence was written,
I have received a paper by Gorup-
Besanez (‘Berichte der Deutschen
Chem. Gesellschaft,’ Berlin, 1874, p.
1478), who, with the aid of Dr. H.
Will, has actually made the discovery
that the seeds of the vetch contain a
ferment, which, when extracted by
glycerine, dissolves albuminous sub-
stances, such as fibrin, and converts
them into true peptones. [See, how-
ever, Vines’ ‘Physiology of Plants,”
p. 190.—F. D)
Cuar. XV] ON THE DROSERACE:. 293
be of high service to plants growing in very poor soil, it
would tend to be perfected through natural selection. There-
fore, any ordinary plant having viscid glands, which
occasionally caught insects, might thus be converted under
favourable circumstances into a species capable of true
digestion. It ceases, therefore, to be any great mystery how
several genera of plants, in no way closely related together,
have independently acquired this same power.
As there exist several plants the glands of which cannot,
as far as is known, digest animal matter, yet can absorb salts
of ammonia and animal fluids, it is probable that this latter
power forms the first stage towards that of digestion. It
might, however, happen, under certain conditions, that a
plant, after having acquired the power of digestion, should
degenerate into one capable only of absorbing animal matter
in solution, or in a state of decay, or the final products of
decay, namely the salts of ammonia. It would appear that
this has actually occurred to a partial extent with the leaves
of Aldrovanda; the outer parts of which possess absorbent
organs, but no glands fitted for the secretion of any digestive
fluid, these being confined to the inner parts.
Little light can be thrown on the gradual acquirement of
the third remarkable character possessed by the more highly
developed genera of the Droseraceæ, namely the power of
movement when excited. It should, however, be borne in
mind that leaves and their homologues as well as flower-
peduncles, have gained this power, in innumerable instances,
independently of inheritance from any common parent form ;
for instance, in tendril-bearers and leaf-climbers (i.e. plants
with their leaves, petioles and flower-peduncles, &c., modified
for prehension) belonging to a large number of the most
widely distinct orders,—in the leaves of the many plants
which go to sleep at night, or move when shaken,—and in
irritable stamens and pistils of not a few species. We may
therefore infer that the power of movement can be by some
means readily acquired. Such movements imply irritability
or sensitiveness, but, as Cohn has remarked,* the tissues of
the plants thus endowed do not differ in any uniform manner
* See the abstract of his memoir on the contractile tissues of plants, in the
* Annals and Mag. of Nat, Hist.’ 3rd series, vol. xi. p. 188.
294 CONCLUDING REMARKS (Cmar. XV.
from those of ordinary plants; it is therefore probable that
all leaves are to a slight degree irritable. Even if an insect
alights on a leaf, a slight molecular change is probably trans-
mitted to some distance across its tissue, with the sole
difference that no perceptible effect is produced. We have
some evidence in favour of this belief, for we know that a
single touch on the glands of Drosera does not excite inflec-
tion; yet it must produce some effect, for if the glands have
been immersed in a solution of camphor, inflection follows
within a shorter time than would have followed from the
effects of camphor alone. So again with Dionwa, the blades
in their ordinary state may be roughly touched without
their closing; yet some effect must be thus caused and trans-
mitted across the whole leaf, for if the glands have recently
absorbed animal matter, even a delicate touch causes them
to close instantly. On the whole we may conclude that
the acquirement of a high degree of sensitiveness and of
the power of movement by certain genera of the Drose-
race presents no greater difficulty than that presented by
the similar but feebler powers of a multitude of other plants.
The specialised nature of the sensitiveness possessed by
Drosera and Dionwa, and by certain other plants, well deserves
attention. A gland of Drosera may be forcibly hit once,
twice, or even thrice, without any effect being produced,
whilst the continued pressure of an extremely minute particle
excites movement. On the other hand, a particle many
times heavier may be gently laid on one of the filaments of
Dionea with no effect ; but if touched only once by the slow
movement of a delicate hair, the lobes close; and this differ-
ence in the nature of the sensitiveness of these two plants
stands in manifest adaptation to their manner of capturing
insects. So does the fact, that when the central glands of
Drosera absorb nitrogenous matter, they transmit a motor
impulse to the exterior tentacles much more quickly than
when they are mechanically irritated; whilst with Dionza
the absorption of nitrogenous matter causes the lobes to press
together with' extreme slowness, whilst a touch excites rapid
movement. Somewhat analogous cases may be observed, as
I have shown in another work, with the tendrils of various
plants ; some being most excited by contact with fine fibres,
others by contact with bristles, others with a flat or a
creviced surface. The sensitive organs of Drosera and Dionæa
are also specialised, so as not to be uselessly affected by the
Car. XV.] ON THE DROSERACE. 295
weight or impact of drops of rain, or by blasts of air. This
may be accounted for by supposing that these plants and
their progenitors have grown accustomed to the repeated
action of rain and wind, so that no molecular change is thus
induced; whilst they have been rendered more sensitive by
means of natural selection to the rarer impact or pressure
of solid bodies. Although the absorption by the glands
of Drosera of various fluids excites movement, there is a
great difference in the action of allied fluids; for instance,
between certain vegetable acids, and between citrate and
phosphate of ammonia. The specialised nature and per-
fection of the sensitiveness in these two plants is all the
more astonishing as no one supposes that they possess
nerves; and by testing Drosera with several substances
which act powerfully on the nervous system of animals, it
does not appear that they include any diffused matter
analogous to nerve-tissue.
Although the cells of Drosera and Dionza are quite as
sensitive to certain stimulants as are the tissues which
surround the terminations of the nerves in the higher animals,
yet these plants are inferior even to animals low down in the
scale, in not being affected except by stimulants in contact
with their sensitive parts. They would, however, probably
be affected by radiant heat; for warm water excites energetic
movement. When a gland of Drosera, or one of the filaments
of Dionza, is excited, the motor impulse radiates in all direc-
tions, and is not, as in the case of animals, directed towards
special points or organs. This holds good even in the case
of Drosera when some exciting substance has been placed at
two points on the disc, and when the tentacles all round are
inflected with marvellous precision towards the two points.
The rate at which the motor impulse is transmitted, though
rapid in Dionæa, is much slower than in most or all animals.
This fact, as well as that of the motor impulse not being
specially directed to certain points, are both no doubt due to
the absence of nerves. Nevertheless we perhaps see the pre-
figurement of the formation of nerves in animals in the trans-
mission of the motor impulse being so much more rapid down
the confined space within the tentacles of Drosera than else-
where, and somewhat more rapid in a longitudinal than ina
transverse direction across the disc. These plants exhibit
still more plainly their inferiority to animals in the absence
of any reflex action, except in so far as the glands of Drosera,
296 CONCLUDING REMARKS. [Cuar. XV.
when excited from a distance, send back some influence which
causes the contents of the cells to become aggregated down
to the bases of the tentacles. But the greatest inferiority of
all is the absence of a central organ, able to receive impressions
from all points, to transmit their effects in any definite
direction, to store them up and reproduce them.
Cuar. XVI] PINGUICULA VULGARIS. | 297
CHAPTER XVI.
PINGUICULA.
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 containing
soluble nitrogenous matter on the glands—Pinguicula grandiflora—Pin-
guicula lusitanica, catches insects—Movement of the leaves, secretion and
digestion, r
PINGUICULA VULGARIS.— This plant grows in moist places,
generally on mountains. It bears on an average eight,
rather thick, oblong, light green * leaves, having scarcely
any footstalk. A full-sized leaf is about 1} inch in length
and } inch in breadth. The young central leaves are deeply
concave, and project upwards; the older ones towards the
outside are flat or convex, and lie close to the ground, form-
ing a rosette from 3 to 4 inches in diameter. The margins
of the leaves are incurved. Their upper surfaces are thickly
covered with two sets of glandular hairs, differing in the
size of the glands and in the length of their pedicels. The
larger glands have a circular outline as seen from above, and
are of moderate thickness; they are divided by radiating
partitions into sixteen cells, containing light-green, homo-
geneous fluid. They are supported on elongated, unicellular
pedicels (containing a nucleus with a nucleolus) which rest
on slight prominences. The small glands differ only in being
formed of about half the number of cells, containing much
paler fluid, and supported on much shorter pedicels. Near
the midrib, towards the base of the leaf, the pedicels are
multicellular, are longer than elsewhere, and bear smaller
glands. All the glands secrete a colourless fluid, which is
so viscid that I have seen a fine thread drawn out toa length
* (According to Batalin (¢ Flora,’ green in plants grown in shady places.
1877) the yellowish-green colour is It is due to a yellow homogeneous
peculiar to plants grown in strong substance found in the epidermal
light, being replaced bya more lively cells andin the glands.—F. D.J]
298 PINGUICULA VULGARIS. (Cuar. XVI.
of 18 inches; but the fluid in this case was secreted by a
gland which had been excited. The edge of the leaf is
translucent, and does not bear any glands; and here the
spiral vessels, proceeding from the midrib, terminate in cells
marked by a spiral line, somewhat like those within the
glands of Drosera.
The roots are short. Three plants were dug up in North
Wales on June 20, and carefully washed ; each bore five or
six unbranched roots, the longest of which was only 1+2 of
an inch. ‘Two rather young plants were examined on
September 28; these had a greater number of roots, namely
eight and eighteen, all under 1 inch in length, and very little
branched.
I was led to investigate the habits of this plant by being
told by Mr. W. Marshall that on the mountains of Cumber-
land many insects adhere to the leaves.
A friend sent me on June 23 thirty-nine leaves from North Wales,
which were selected owing to objects of some kind adhering to them.
Of these leaves, thirty-two had caught 142 insects, or on an average
4'4 per leaf, minute fragments of insects not being included. Besides
the insects, small leaves belonging to four different kinds of plants,
those of Erica tetralix being much the commonest, and three minute
seedling plants, blown by the wind, adhered to nineteen of the leaves.
One had caught as many as ten leaves of the Erica. Seeds or fruits,
commonly of Carex and one of Juncus, besides bits of moss and other
rubbish, likewise adhered to six of the thirty-nine leaves. The same
friend, on June 27, collected nine plants bearing seventy-four leaves,
and all of these, with the exception of three young leaves, had caught
insects; thirty insects were counted on one leaf, eighteen on a second,
and sixteen on a third. Another friend examined on August 22 some
plants in Donegal, Ireland, and found insects on 70 out of 157 leaves;
fifteen of these leaves were sent me, each having caught on an average
2°4 insects. To nine of them, leaves (mostly of Erica tetralix) ad-
hered ; but they had been specially selected on this latter account. I
may add that early in August my son found leaves of this same Erica
and the fruits of a Carex on the leaves of a Pinguicula in Switzerland,
probably Pinguicula alpina; some insects, but no great number, also
adhered to the leaves of this plant, which had much better developed
roots than those of Pinguicula vulgaris. In Cumberland, Mr.
Marshall, on September 3, carefully examined for me ten plants
bearing eighty leaves; and on sixty-three of these (i.e. on 79 per
cent.) he found insects, 143 in number; so that each leaf had on an
average 2°27 insects. A few days later he sent me some plants with
sixteen seeds or fruits adhering to fourteen leaves. There was a seed
on three leaves on the same plant. The sixteen seeds belonged to
Cuar. XVI.] MOVEMENTS OF THE LEAVES. 299
nine different kinds, which could not be recognised, excepting one of
Ranunculus, and several belonging to three or four distinct species of
Carex. It appears that fewer insects are caught late in the year than
earlier; thus in Cumberland from twenty to twenty-four insects were
observed in the middle of July on several leaves, whereas in the
beginning of September the average number was only 2°27. Most of
the insects, in all the foregoing cases, were Diptera, but with many
minute Hymenoptera, including some ants, a few small Coleoptera,
larvee, spiders, and even small moths.
We thus see that numerous insects and other objects are
caught by the viscid leaves ; but we have no right to infer
from this fact that the habit is beneficial to the plant, any
more than in the before-given case of the Mirabilis, or of
the horse-chestnut. But it will presently be seen that dead
insects and other nitrogenous bodies excite the glands to
increased secretion; and that the secretion then becomes
acid and has the power of digesting animal substances, such
as albumen, fibrin, &c. Moreover, the dissolved nitrogenous
matter is absorbed by the glands, as shown by their limpid
contents being aggregated into slowly moving granular
masses of protoplasm. The same results follow when insects
are naturally captured, and as the plant lives in poor soil
and has small roots, there can be no doubt that it profits by
its power of digesting and absorbing matter from the prey
which it habitually captures in such large numbers. It will,
however, be convenient first to describe the movements of
the leaves.
Movements of the Leaves.—That such thick, large leaves as
those of Pinguicula vulgaris should have the power of curving
inwards when excited has never even been suspected. It is
necessary to select for experiment leaves with their glands
secreting freely, and which have been prevented from cap-
turing many insects; as old leaves, at least those growing
in a state of nature, have their margins already curled so
much inwards that they exhibit little power of movement,
or move very slowly. I will first give in detail the more
important experiments which were tried, and then make
some concluding remarks,
Experiment 1.—A young and almost upright leaf was selected, with
its two lateral edges equally and very slightly incurved. A row of
small flies was placed along one margin. When looked at next day,
after 15 hrs., this margin, but not the other, was found folded inwards,
300 PINGUICULA VULGARIS. (Cuar. XVI.
like the helix of the human ear, to the breadth of 345 of an inch, so as
to lie partly over the row of flies (fig. 15). The glands on which the
flies rested, as well as those on the over-lapping margin which had
been brought into contact with the flies, were all secreting copiously.
Experiment 2.—A row of flies was placed on one margin of a rather
old leaf, which lay flat on the ground; and in this case the margin,
after the same interval as before, namely 15 hrs., had only just begun
to curl inwards; but so much secretion had been poured forth that the
spoon-shaped tip of the leaf was filled with it.
Experiment 3,—Fragments of a large fly were placed close to the
apex of a vigorous leaf, as well as along half one margin. After 4 hrs.
20 m. there was decided incurvation, which increased a little during
the afternoon, but was in the same state on the following morning.
Near the apex both margins were inwardly
curved. I have never seen a case of the apex
itself being in the least curved towards the base
of the leaf. After 48 hrs. (always reckoning
from the time when the flies were placed on the
leaf) the margin had everywhere begun to unfold.
Experiment 4.—A large fragment of a fly was
placed on a leaf, in a medial line, alittle beneath
the apex. Both lateral margins were perceptibly
incurved in 3 hrs., and after 4 hrs. 20 m. to such
a degree that the fragment was clasped by both
margins. After 24 hrs. the two infolded edges
near the apex (for the lower part of the leaf was
not at all affected) were measured and found to
be *11 of an inch (2°795 mm.) apart. The fly
was now removed, and a stream of water poured
over the leaf so as to wash the surface; and after
Fig. 15. 24 hrs. the margins were *25 of an‘inch (6°349
(Pinguicula vulgaris.) mm.) apart, so that they were largely unfolded.
Outline of leaf with left After an additional 24 hrs. they were completely
margin inflected over a ynfolded. Another fly was now put on the same
Aa a e spot to see whether this leaf, on which the first
fly had been left 24 hrs., would move again;
after 10 hrs. there was a trace of incurvation, but this did not increase
during the next 24 hrs. <A bit of meat was also placed on the
margin of a leaf, which four days previously had become strongly in-
curved over a fragment of a fly and had afterwards re-expanded ; but
the meat did not cause even a trace of incurvation. On the contrary,
the margin became somewhat reflexed, as if injured, and so remained
for the three following days, as long as it was observed.
Experiment 5.—A large fragment of a fly was placed halfway be-
tween the apex and base of a leaf and halfway between the midrib and
one margin. A short space of this margin, opposite the fly, showed a
trace of incurvation after 3 hrs., and this became strongly pronounced in
T hrs. After 24 hrs. the infolded edge was only ‘16 of an inch
~~
Cmar. XVI] MOVEMENTS OF THE LEAVES. 301
(4:064 mm.) from the midrib. The margin now began to unfold,
though the fly was left on the leaf; so that by the next morning
(i.e. 48 hrs. from the time when the fly was first put on) the infolded
edge had almost completely recovered its original position, being now
*3 of an inch (7°62 mm.), instead of *16 of an inch, from the midrib.
A trace of flexure was, however, still visible.
Experiment 6.—A young and concave leaf was selected with its
margins slightly and naturally incurved. Two rather large, oblong,
rectangular pieces of roast meat were placed with their ends touching
the infolded edge, and *46 of an inch (11°68 mm.) apart from one
another. After 24 hrs. the margin was greatly and equally incurved
(see fig. 16) throughout this space, and for a length of °12 or °13 of an
inch (3°048 or 3°302 mm.) above and below each
bit; so that the margin had been affected over a
greater length between the two bits, owing to
their conjoint action, than beyond them. The
bits of meat were too large to be clasped by the
margin, but they were tilted up, one of them so
as to stand almost vertically. After 48 hrs. the
margin was almost unfolded, and the bits had
sunk down. When again examined after two
days, the margin was quite unfolded, with the
exception of the naturally inflected edge; and
one of the bits of meat, the end of which had at
first touched the edge, was now ‘067 of an inch
(1:70 mm.) distant from it; so that this bit had
been pushed thus far across the blade of the leaf.
Experiment 7.—A bit of meat was placed close
to the incurved edge of a rather young leaf, and
after it had re-expanded, the bit was left lying
"11 of an inch (2°795 mm.) from the edge. The
distance from the edge to the midrib of the fully ue a:
expanded leaf was *35 of an inch (8°89 mm.); pati ar bees
so that the bit had been pushed inwards and across right prt ge es
nearly one-third of its semi-diameter. against two square bits
Experiment 8.—Cubes of sponge, soaked in a °f™eat.
strong infusion of raw meat, were placed in close
contact with the incurved edges of two leaves,—an older and younger
one. The distance from the edges to the midribs was carefully
measured. After 1 hr. 17 m. there appeared to be a trace of incur-
vation. After 2 hrs. 17 m. both leaves were plainly inflected; the
distance between the edges and midribs being now only half what it
was at first. The incurvation increased slightly during the next 42
Fic. 16.
` hrs., but remained nearly the same for the next 17 hrs. 30 m. In
35 hrs. from the time when the sponges were placed on the leaves, the
margins were a little unfolded—to a greater degree in the younger than
in the older leaf. The latter was not quite unfolded until the third
day, and now both bits of sponge were left at the distance of *1 of an
302 PINGUICULA VULGARIS. [Cuar. XVI.
inch (2°54 mm.) from the edges; or about a quarter of the distance
between the edge and midrib. A third bit of sponge adhered to the
edge, and, as the margin unfolded, was dragged backwards, into its
original position.
Experiment 9.—A chain of fibres of roast meat, as thin as bristles
and moistened with saliva, were placed down one whole side, close to
the narrow, naturally incurved edge of a leaf. In 3 hrs. this side was
greatly incurved along its whole length, and after 8 hrs. formed a
cylinder, about =, of an inch (1°27 mm.) in diameter, quite concealing
the meat. This cylinder remained closed for 32 hrs., but after 48 hrs.
was half unfolded, and in 72 hrs. was as open as the opposite margin
where no meat had been placed. As the thin fibres of meat were
completely overlapped by the margin, they were not pushed at all
inwards, across the blade.
Experiment 10.—Six cabbage seeds, soaked for a night in water,
were placed in a row close to the narrow incurved edge of a leaf. We
shall hereafter see that these seeds yield soluble matter to the glands.
In 2 hrs. 25 m. the margin was decidedly inflected; in 4 hrs. it
extended over the seeds for about half their breadth, and in 7 hrs. over
three-fourths of their breadth, forming a cylinder not quite closed
along the inner side. After 24 hrs. the inflection had not increased,
perhaps had decreased. The glands which had been brought into
contact with the upper surfaces of the seeds were now secreting freely.
In 36 hrs. from the time when the seeds were put on the leaf the
margin had greatly, and after 48 hrs. had completely, re-expanded.
As the seeds were no longer held by the inflected margin, and as the
secretion was beginning to fail, they rolled some way down the
marginal channel.
Experiment 11.—Fragments of glass were placed on the margins of
two fine young leaves. After 2 hrs. 30 m. the margin of one certainly
became slightly incurved; but the inflection never increased, and dis-
appeared in 16 hrs. 30 m. from the time when the fragments were
first applied. With the second leaf there was a trace of incurvation
in 2 hrs. 15 m., which became decided in 4 hrs. 30 m., and still more
strongly pronounced in 7 hrs., but after 19 hrs. 30 m. had plainly
decreased. The fragments excited at most a slight and doubtful in-
crease of the secretion; and in two other trials, no increase could be
perceived. Bits of coal-cinders, placed on a leaf, produced no effect,
either owing to their lightness or to the leaf being torpid.
Experiment 12.—We will now turn to fluids, A row of drops of a
strong infusion of raw meat were placed along the margins of two
leaves; squares of sponge soaked in the same infusion being placed on
the opposite margins. My object was to ascertain whether a fluid
would act as energetically as a substance yielding the same soluble
matter to the glands. No distinct difference was perceptible; certainly
none in the degree of incurvation; but the incurvation round the bits
of sponge lasted rather longer, as might perhaps have been expected
from the sponge remaining damp and supplying nitrogenous matter
Cuar. XVI.] MOVEMENTS OF THE LEAVES. 303
fora longer time. The margins, with the drops, became plainly
incurved in 2 hrs. 17 m. The incurvation subsequently increased
somewhat, but after 24 hrs. had greatly decreased.
Experiment 13.—Drops of the same strong infusion of raw meat
were placed along the midrib of a young and rather deeply concave
leaf. The distance across the broadest part of the leaf, between the
naturally incurved edges, was *55 of an inch (13°97 mm.). In 3 hrs.
27 m. this distance was a trace less; in 6 hrs. 27 m. it was exactly
°45 of an inch (11°43 mm.), and had therefore decreased by ‘1 of
an inch (2°54 mm.). After only 10 hrs. 37 m. the margin began
to re-expand, for the distance from edge to edge was now a trace
wider, and after 24 hrs. 20 m. was as great, within a hair’s breadth,
as when the drops were first placed on the leaf. From this experi-
ment we learn that the motor impulse can be transmitted to a dis-
tance of +22 of an inch (5°590 mm.) in a transverse direction from
the midrib to both margins; but it would be safer to say *2 of an inch
(5°08 mm.), as the drops spread a little beyond the midrib. The
incurvation thus caused lasted for an unusually short time.
Experiment 14.—Three drops of a solution of one part of carbonate
of ammonia to 218 of water (2 grs. to 1 oz.) were placed on the margin
of a leaf. These excited so much secretion that in 1 hr. 22 m. all
three drops ran together; but although the leaf was observed for 24
hrs., there was no trace of inflection. We know that a rather strong
solution of this salt, though it does not injure the leaves of Drosera,
paralyses their power of movement, and I have no doubt, from [this
and] the following case, that this holds good with Pinguicula.
Experiment 15.—A row of drops of a solution of one part of
carbonate of ammonia to 875 of water (1 gr. to 2 oz.) was placed on
the margin of a leaf. In 1 hr. there was apparently some slight
incurvation, and this was well marked in 3 hrs. 80m. After 24 hrs,
the margin was almost completely re-expanded.
Experiment 16.—A row of large drops of a solution of one part of
phosphate of ammonia to 4375 of water (1 gr. to 10 oz.) was placed
along the margin of a leaf. No effect was produced, and after 8 hrs,
fresh drops were added along the same margin without the least effect.
We know that a solution of this strength acts powerfully on Drosera,
and it is just possible that the solution was too strong. I regret that
I did not try a weaker solution.
Experiment 17.—As the pressure from bits of glass causes incurvation,
I scratched the margins of two leaves for some minutes with a blunt
needle, but no effect was produced. The surface of a leaf beneath a
drop of a strong infusion of raw meat was also rubbed for 10 m. with
the end of a bristle, so as to imitate the struggles of a captured insect ;
but this part of the margin did not bend sooner than the other parts
with undisturbed drops of the infusion.
We learn from the foregoing experiments that the margins
of the leaves curl inwards when excited by the mere pressure
304 PINGUICULA VULGARIS. (Cmr. XVI.
of objects not yielding any soluble matter, by objects yield-
ing such matter, and by some fluids—namely an infusion of
raw meat and a weak solution of carbonate of ammonia. A
stronger solution of two grains of this salt to an ounce of
water, though exciting copious secretion, paralyses the leaf.
Drops of water and of a solution of sugar or gum did not
cause any movement. Scratching the surface of the leaf for
some minutes produced no effect. Therefore, as far as we at
present know, only two causes—namely slight continued
pressure and the absorption of nitrogenous matter—excite
movement. It is only the margins of the leaf which bend,
for the apex never curves towards the base. The pedicels
of the glandular hairs have no power of movement. I
observed on several occasions that the surface of the leaf
became slightly concave where bits of meat or large flies had
long lain, but this may have been due to injury from over-
stimulation.*
The shortest time in which plainly marked movement was
observed was 2 hrs. 17 m., and this occurred when either
nitrogenous substances or fluids were placed on the leaves;
but I believe that in some cases there was a trace of move-
ment in 1 hr. or 1 hr. 30 m. The pressure from fragments
of glass excites movement almost as quickly as the absorption
of nitrogenous matter, but the degree of incurvation thus
caused is much less. After a leaf has become well incurved
and has again expanded, it will not soon answer to a fresh
stimulus. The margin was affected longitudinally, upwards
or downwards, for a distance of +13 of an inch (3:302 mm.)
from an excited point, but for a distance of +46 of an inch
between two excited points, and transversely for a distance
of -2 of an inch (5°08 mm.). The motor impulse is not
accompanied, as in the case of Drosera, by any influence
causing increased secretion; for when a single gland was
strongly stimulated and secreted copiously, the surrounding
glands were not in the least affected. The incurvation of
the margin is independent of increased secretion, for frag-
ments of glass cause little or no secretion, and yet excite
movement: whereas a strong solution of carbonate of am-
monia quickly excites copious secretion, but no movement.
* [Batalin (‘ Flora,’ 1887) believes accompanied by actual growth, and
that the depressions are due to the thus a permanent alteration in the
fact that the curvature of the leaf is form of the leaf is effected.—F. D.]
Cuar. XVI] MOVEMENTS OF THE LEAVES. 305
One of the most curious facts with respect to the move-
ment of the leaves is the short time during which they
remain incurved, although the exciting object is left on them.
In the majority of cases there was well-marked re-expansion
within 24 hrs. from the time when even large pieces of meat,
&c., were placed on the leaves, and in all cases within 48
hrs. In one instance the margin of a leaf remained for 32
hrs. closely inflected round thin fibres of meat; in another
instance, when a bit of sponge, soaked in a strong infusion
of raw meat, had been applied to a leaf, the margin began to
unfold in 35 hrs. Fragments of glass keep the margin
incurved for a shorter time than do nitrogenous bodies ; for
in the former case there was complete re-expansion in 16 hrs.
30m. Nitrogenous fluids act for a shorter time than nitro-
genous substances ; thus, when drops of an infusion of raw
meat were placed on the midrib of a leaf, the incurved
margins began to unfold in only 10 hrs. 37 m., and this
was the quickest act of re-expansion observed by me; but
it may have been partly due to the distance of the margins
from the midrib where the drops lay.
We are naturally led to inquire what is the use of this
movement which lasts for so short atime? If very small
objects, such as fibres of meat, or moderately small objects,
such as little flies or cabbage-seeds, are placed close to the
margin, they are either completely or partially embraced by
it. The glands of the overlapping margin are thus brought
into contact with such objects and pour forth their secretion,
afterwards absorbing the digested matter. Butas the incur-
vation lasts for so short a time, any such benefit can be of
only slight importance, yet perhaps greater than at first
appears. The plant lives in humid districts, and the insects
which adhere to all parts of the leaf are washed by every
heavy shower of rain into the narrow channel formed by the
naturally incurved edges. For instance, my friend in North
Wales placed several insects on some leaves, and two days
afterwards (there having been heavy rain in the interval)
found some of them quite washed away, and many others
safely tucked under the now closely inflected margins, the
glands of which all round the insects were no doubt secret-
ing. We can thus, also, understand how it is that so many
insects, and fragments of insects, are generally found lying
within the incurved margins of the leaves.
The incurvation of the margin, due to the presence of an
x
306 PINGUICULA VULGARIS. [Cnar. XVI.
exciting object, must be serviceable in another and probably
more important way. We have-seen that when large bits
of meat, or of sponge soaked in the juice of meat, were placed
on a leaf, the margin was not able to embrace them, but, as
it became incurved, pushed them very slowly towards the
middle of the leaf, to a distance from the outside of fully > 1
of an inch (2°54 mm.), that is, across between one-third and
one-fourth of the space between the edge and midrib. Any
object, such as a moderately sized insect, would thus be
brought slowly into contact with a far larger number of
glands, inducing much more secretion and absorption, than
would otherwise have been the case. That this would be
highly serviceable to the plant, we may infer from the fact
that Drosera has acquired highly developed powers of move-
ment, merely for the sake of bringing all its glands Into
contact with captured insects. So again, after a leaf of
Dionæa has caught an insect, the slow pressing together of
the two lobes serves merely to bring the glands on both
sides into contact with it, causing also the secretion charged
with animal matter to spread by capillary attraction over
the whole surface. In the case of Pinguicula, as soon as an
insect has been pushed for some little distance towards the
midrib, immediate re-expansion would be beneficial, as the
margins could not capture fresh prey until they were un-
folded. The service rendered by this pushing action, as
well as that from the marginal glands being brought into
contact for a short time with the upper surfaces of minute
captured insects, may perhaps account for the peculiar move-
ments of the leaves: otherwise, we must look at these move-
ments as a remnant of a more highly developed power for-
merly possessed by the progenitors of the genus.
In the four British species, and, as I hear from Prof. Dyer,
in most or all the species of the genus, the edges of the
leaves are in some degree naturally and permanently
incurved. This incurvation serves, as already shown, to
prevent insects from being washed away by the rain; but it
likewise serves for another end. When a number of glands
have been powerfully excited by bits of meat, insects, or any
other stimulus, the secretion often trickles down the leaf, and
is caught by the incurved edges, instead of rolling off and
being lost. As it runs down the channel, fresh glands are
able to absorb the animal matter held in solution. Moreover,
the secretion often collects in little pools within the channel,
Cuar. XVI] SECRETION, ABSORPTION, DIGESTION. 307
or in the spoon-like tips of the leaves; and I ascertained that
bits of albumen, fibrin, and gluten are here dissolved more
quickly and completely than on the surface of the leaf,
where the secretion cannot accumulate; and so it would be
with naturally caught insects. The secretion was repeatedly
seen thus to collect on the leaves of plants protected from the
rain; and with exposed plants there would be still greater need
of some provision to prevent, as far as possible, the secretion,
with its dissolved animal matter, being wholly lost.
It has already been remarked that plants growing in a
state of nature have the margins of their leaves much more
strongly incurved than those grown in pots and prevented
from catching many insects. We have seen that insects
washed down by the rain from all parts of the leaf often
lodge within the margins; which are thus excited to curl
farther inwards ; and we may suspect that this action, many
times repeated during the life of the plant, leads to their
permanent and well-marked incurvation. I regret that this
view did not occur to me in time to test its truth.
It may here be added, though not immediately bearing on
our subject, that when a plant is pulled up, the leaves
immediately curl downwards so as to almost conceal the
roots,—a fact which has been noticed by many persons.
I suppose that this is due to the same tendency which causes
the outer and older leaves to lie flat on the ground. It
further appears that the flower-stalks are to a certain extent
irritable, for Dr. Johnson states that they “bend backwards
if rudely handled.” *
Secretion, Absorption, and Digestion —I will first give my
observations and experiments, and then a summary of the
results.
The Effects of Objects containing Soluble Nitrogenous Matter.
(1) Flies were placed on many leaves, and excited the glands to
secrete copiously; the secretion always becoming acid, though not so
vefore. After a time these insects were rendered so tender that their
imbs and bodies could be separated by a mere touch, owing no doubt
* ‘English Botany,’ by Sir J. E. bending or shaking a turgescent stem.
Smith; with coloured figures by J. This would be likely to occur in the
Sowerby ; edit. of 1832, tab. 24, 25, course of the “rough handling,” and
26. [It is well known that perma- we may perhaps thus account for
nent curvatures may be produced by Dr, Johnson’s curvatures.—F, D,]
I2
308 PINGUICULA VULGARIS. [Cuar. XVI.
to the digestion and disintegration of their muscles. The glands in
contact with a small fly continued to secrete for four days, and then
became almost dry. A narrow strip of this leaf was cut off, and the
glands of the longer and shorter hairs, which had lain in contact for
the four days with the fly, and those which had not touched it, were
compared under the microscope, and presented a wonderful contrast.
Those which had been in contact were filled with brownish granular
matter, the others with homogeneous fluid. There could therefore be
no doubt that the former had absorbed matter from the fly.
(2) Small bits of roast meat, placed on a leaf, always caused much
acid secretion in the course of a few hours—in one case within 40 m.
When thin fibres of meat were laid along the margin of a leaf which
stood almost upright, the secretion ran down to the ground. Angular
bits of meat, placed in little pools of the secretion near the margin,
were in the course of two or three days much reduced in size, rounded,
rendered more or less colourless and transparent, and so much softened
that they fell to pieces on the slightest touch. In only one instance
was a very minute particle completely dissolved, and this occurred
within 48 hrs. When only a small amount of secretion was excited,
this was generally absorbed in from 24 hrs. to 48 hrs.; the glands
being left dry. But when the supply of secretion was copious, round
either a single rather large bit of meat, or round several small bits,
the glands did not become dry until six or seven days had elapsed.
The most rapid case of absorption observed by me was when a small
drop of an infusion of raw meat was placed on a leaf, for the glands
here became almost dry in3 hrs. 20 m. Glands excited by small
articles of meat, and which have quickly absorbed their own secretion,
gin to secrete again in the course of seven or eight days from the
time when the meat was given them.
(8) Three minute cubes of tough cartilage from the leg-bone of a
sheep were laid on a leaf. After 10 hrs, 30 m. some acid secretion was
excited, but the cartilage appeared little or not at all affected. After
24 hrs. the cubes were rounded and much reduced in size; after 32 hrs.
they were softened to the centre, and one was quite liquefied; after
35 hrs. mere traces of solid cartilage were left; and after 48 hrs. a
trace could still be seen through a lens in only one of the three. After
82 hrs. not only were all three cubes completely liquefied, but all the
secretion was absorbed and the glands left dry.
(4) Small cubes of albumen were placed on a leaf; in 8 hrs. feebly
acid secretion extended to a distance of nearly 3, of an inch round
them, and the angles of one cube were rounded. After 24 hrs. the
angles of all the cubes were rounded, and they were rendered through-
out very tender; after 30 hrs. the secretion began to decrease, and
after 48 hrs. the glands were left dry; but very minute bits of albumen
were still left undissolved.
(5) Smaller cubes of albumen (about sy or a of an inch, -508
or +423 mm.) were placed on four glands; after 18 hrs. one cube was
completely dissolved, the others being much reduced in size, softened
Cuar. XVI.] SECRETION, ABSORPTION, DIGESTION. 309
and transparent. After 24 hrs. two of the cubes were completely
dissolved, and already the secretion on these glands was almost wholly
absorbed. After 42 hrs, the two other cubes were completely dissolved.
These four glands began to secrete again after eight or nine days.
(6) Two large cubes of albumen (fully 5 of an inch, 1°27 mm.)
were placed, one near the midrib and the other near the margin
of a leaf; in 6 hrs. there was much secretion, which after 48 hrs.
accumulated in a little pool round the cube near the margin. This
cube was much more dissolved than that on the blade of the leaf; so
that after three days it was greatly reduced in size, with all the angles
rounded, but it was too large to be wholly dissolved. ‘The secretion
was partially absorbed after four days. The cube on the blade was
much less reduced, and the glands on which it rested began to dry
after only two days.
(7) Fibrin excites less secretion than does meat or albumen.
Several trials were made, but I will give only three of them. Two
minute shreds were placed on some glands, and in 3 hrs. 45 m. their
secretion was plainly increased. The smaller shred of the two was
completely liquefied in 6 hrs. 15 m., and the other in 24 hrs.; but even
after 48 hrs. a few granules of fibrin could still be seen through a
lens floating in both drops of secretion. After 56 hrs. 30 m. these
granules were completely dissolved. A third shred was placed ina little
pool of secretion, within the margin of a leaf where a seed had been
lying, and this was completely dissolved in the course of 15 hrs. 80 m.
(8) Five very small bits of gluten were placed on a leaf, and they
excited so much secretion that one of the bits glided down into the
marginal furrow. After a day all five bits seemed much reduced in
size, but none were wholly dissolved. On the third day | pushed two
of. them which had begun to dry, on to fresh glands. On the fourth
day undissolved traces of three out of the five bits could still be
detected, the other two having quite disappeared ; but I am doubtful
whether they had really been completely dissolved. Two fresh bits
were now placed, one near the middle and the other near the margin
of another leaf; both excited an extraordinary amount of secretion;
that near the margin had a little pool formed round it, and was much
more reduced in size than that on the blade, but after four days was not
completely dissolved. Gluten, therefore, excites the glands greatly,
but is dissolved with much difficulty, exactly as in the case of
Drosera. I regret that I did not try this substance after having been
immersed in weak hydrochloric acid, as it would then probably have
been quickly dissolved.
(9) A small square thin piece of pure gelatine, moistened with
water, was placed on a leaf, and excited very little secretion in 5 hrs.
30 m., but later in the day a greater amount. After 24 hrs. the whole
square was completely liquefied; and this would not have occurred
had it been left in water. The liquid was acid.
(10) Small particles of chemically prepared casein excited acid
secretion, but were not quite dissolved after two days; and the glands
310 PINGUICULA VULGARIS. [Cuar. XVI.
then began to dry. Nor could their complete dissolution have been
expected from what we have seen with Drosera.
(11) Minute drops of skimmed milk were placed on a leaf, and these
caused the glands to secrete freely. After 3 hrs. the milk was found
curdled, and after 23 hrs. the curds were dissolved. On placing the
now clear drops under the microscope, nothing could be detected except
some oil-globules. The secretion, therefore, dissolves fresh casein.
(12) Two fragments of a leaf were immersed for 17 hrs., each in a
drachm of a solution of carbonate of ammonia, of two strengths,
namely of one part to 437 and 218 of water. The glands of the
longer and shorter hairs were then examined, and their contents found
aggregated into granular matter of a brownish-green colour. These
granular masses were seen by my son slowly to change their forms,
and no doubt consisted of protoplasm. The aggregation was more
strongly pronounced, and the movements of the protoplasm more rapid,
within the glands subjected to the stronger solution than in the others.
The experiment was repeated with the same result; and on this
occasion I observed that the protoplasm had shrunk a little from the
walls of the single elongated cells forming the pedicels. In order to
observe the process of aggregation, a narrow strip of leaf was laid
edgeways under the microscope, and the glands were seen to be quite
transparent; a little of the stronger solution (viz. one part to 218 of
water) was now added under the covering glass; after an hour or two
the glands contained very fine granular matter, which slowly became
coarsely granular and slightly opaque; but even after 5 hrs. not as yet
of a brownish tint. By this time a few rather large, transparent,
globular masses appeared within the upper ends of the pedicels, and the
protoplasm lining their walls had shrunk a little. It is thus evident
that the glands of Pinguicula absorb carbonate of ammonia; but they
do not absorb it, or are not acted on by it, nearly so quickly as
those of Drosera.
(13) Little masses of the orange-coloured pollen of the common pea,
placed on several leaves, excited the glands to secrete freely. Even a
very few grains which accidentally fell on a single gland caused the
drop surrounding it to increase so much in size, in 23 hrs., as to
be manifestly larger than the drops on the adjoining glands. Grains
subjected to the secretion for 48 hrs, did not emit their tubes; they
were quite discoloured, and seemed to contain less matter than before;
that which was left being of a dirty colour, including globules of oil.
‘They thus differed in appearance from other grains kept in water for
the same length of time. The glands in contact with the pollen-grains
had evidently absorbed matter from them; for they had lost their
natural pale-green tint, and contained aggregated globular masses of
protoplasm.
(14) Square bits of the leaves of spinach, cabbage, and a saxifrage,
and the entire leaves of Erica tetralix, all excited the glands to
increased secretion. The spinach was the most effective, for it caused
the secretion evidently to increase in 1 hr. 40 m., and ultimately to run
Cuar. XVI.] SECRETION, ABSORPTION, DIGESTION. 311
some way down the leaf; but the glands soon began to dry, viz. after
35 hrs. The leaves of Erica tetralix began to act in 7 hrs. 30 m., but
never caused much secretion; nor did the bits of leaf of the saxifrage,
though in this case the glands continued to secrete for seven days.
Some leaves of Pinguicula were sent me from North Wales, to which
leaves of Erica tetralix and of an unknown plant adhered; and the
glands in contact with them had their contents plainly aggregated, as
if they had been in contact with insects; whilst the other glands on
the same leaves contained only clear homogeneous fluid.
(15) Seeds.—A considerable number of seeds or fruits selected by
hazard, some fresh and some a year old, some soaked for a short time
in water and some not soaked, were tried. ‘The ten following kinds,
namely, cabbage, radish, Anemone nemorosa, Rumex acetosa, Carex
sylvatica, mustard, turnip, cress, Ranunculus acris, and Avena pubescens,
all excited much secretion, which was in several cases tested and found
always acid. The five first-named seeds excited the glands more than
the others. The secretion was seldom copious until about 24 hrs. had
elapsed, no doubt owing to the coats of the seeds not being easily
permeable. Nevertheless, cabbage seeds excited some secretion in 4 hrs.
30 m.; and this increased so much in 18 hrs. as to run down the leaves.
The seeds, or properly the fruits, of Carex are much oftener found
adhering to leaves in a state of nature than those of any other genus ;
and the fruits of Carex sylvatica excited so much secretion that in
15 hrs. it ran into the incurved edges; but the glands ceased to secrete
after 40 hrs. On the other hand, the glands on which the seeds of the
Rumex and Avena rested continued to secrete for nine days.
The nine following kinds of seeds excited only a slight amount of
secretion, namely, celery, parsnip, caraway, Linum grandiflorum, Cassia,
Trifolium pannonicum, Plantago, onion, and Bromus. Most of these
seeds did not excite any secretion until 48 hrs. had elapsed, and in the
case of the Trifolium only one seed acted, and this not until the third
day. Although the seeds of the Plantago excited very little secretion,
the glands continued to secrete for six days. Lastly, the five following
kinds excited no secretion, though left on the leaves for two or three
days, namely, lettuce, Erica tetralix, Atriplex hortensis, Phalaris
canariensis, and wheat.. Nevertheless, when the seeds of the lettuce,
wheat, and Atriplex were split open and applied to leaves, secretion was
excited in considerable quantity in 10 hrs., and I believe that some
was excited in six hours. In the case of the Atriplex the secretion ran
down to the margin, and after 24 hrs. I speak of it in my notes “as
immense in quantity, and acid.” The split seeds also of the Trifolium
and celery acted powerfully and quickly, though the whole seeds
caused, as we have scen, very little secretion, and only after a long
interval of time. A slice of the common pea, which however was not
tried whole, caused secretion in 2 hrs, From these facts we may
conclude that the great difference in the degree and rate at which
various kinds of seeds excite secretion, is chiefly or wholly due to the
different permeability of their coats.
312 PINGUICULA VULGARIS. [Cuar. XVI.
Some thin slices of the common pea, which had been previously
soaked for 1 hr. in water, were placed on a leaf, and quickly excited
much acid secretion. After 24 hrs. these slices were compared under a
high power with others left in water for the same time; the latter
contained so many fine granules of legumin that the slide was rendered
muddy; whereas the slices which had been subjected to the secretion
were much cleaner and more transparent, the granules of legumin
apparently having been dissolved. A cabbage seed which had lain for
two days on a leaf and had excited much acid secretion, was cut into
slices, and these were compared with those of a seed which had been
left for the same time in water. Those subjected to the secretion were
of a paler colour; their coats presenting the greatest differences, for
they were of a pale dirty tint instead of chestnut-brown. The glands
on which the cabbage seeds had rested, as well as those bathed by the
surrounding secretion, differed greatly in appearance from the other
glands on the same leaf, for they all contained brownish granular
matter, proving that they had absorbed matter from the seeds.
That the secretion acts on the seeds was also shown by some of
them being killed, or by the seedlings being injured. Fourteen cabbage
seeds were left for three days on leaves and excited much secretion ;
they were then placed on damp sand under conditions known to be
favourable for germination. ‘Three never germinated, and this was a
far larger proportion of deaths than occurred with seeds of the same lot,
which had not been subjected to the secretion, but were otherwise
treated in the same manner. Of the eleven seedlings raised, three had
the edges of their cotyledons slightly browned, as if scorched; and the
cotyledons of one grew into a curious indented shape. Two mustard
seeds germinated; but their cotyledons were marked with brown
patches and their radicles deformed. Of two radish seeds, neither
germinated; whereas of many seeds of the same lot not subjected to
the secretion, all, excepting one, germinated. Of the two Rumex seeds,
one died and the other germinated ; but its radicle was brown and soon
withered. Both seeds of the Avena germinated, one grew well, the
other had its radicle brown and withered. Of six seeds of the Erica
none germinated, and when cut open after having been left for five
months on damp sand, one alone seemed alive. ‘Twenty-two seeds of
various kinds were found adhering to the leaves of plants growing in a
state of nature; and of these, though kept for five months on damp
sand, none germinated, some being then evidently dead.
The Effects of Objects not containing Soluble Nitrogenous Matter.
(16) It has already been shown that bits of glass, placed on leaves,
excite little or no secretion. The small amount which lay beneath the
fragments was tested and found not acid. A bit of wood excited
no secretion; nor did the several kinds of seeds of which the coats are
not permeable to the secretion, and which, therefore, acted like inorganic
bodies. Cubes of fat, left for two days on a leaf, produced no effect.
Cnar, XVI] SECRETION, ABSORPTION, DIGESTION. 313
(17) A particle of white sugar, placed on a leaf, formed in 1 hr. 10 m.
a large drop of fluid, which in the course of 2 additional hours ran
down into the naturally inflected margin. This fluid was not in the
least acid, and began to dry up, or more probably was absorbed,
in 5 hrs. 830m. The experiment was repeated; particles being placed
on a leaf, and others of the same size on a slip of glass in a moistened
state; both being covered by a bell-glass. This was done to see
whether the increased amount of fluid on the leaves could be due to
mere deliquescence; but this was proved not to be the case. The
particle on the leaf caused so much secretion that in the course of 4 hrs.
it ran down across two-thirds of the leaf. After 8 hrs. the leaf, which
was concaye, was actually filled with very viscid fluid; and it particu-
larly deserves notice that this, as on the former occasion, was not in the
least acid. This great amount of secretion may be attributed to exosmose.
The glands which had been covered for 24 hrs, by this fluid did not
differ, when examined under the microscope, from others on the same leaf,
which had not come into contact with it. This is an interesting fact in
contrast with the invariably aggregated condition of glands which have
been bathed by the secretion, when holding animal matter in solution.
(18) Two particles of gum arabic were placed on a leaf, and they
certainly caused in 1 hr. 20 m, a slight increase of secretion. This
continued to increase for the next 5 hrs., that is for as long a time as
the leaf was observed.
(19) Six small particles of dry starch of commerce were placed on a
leaf, and one of these caused some secretion in 1 hr. 15 m., and the
others in from 8 hrs. to 9 hrs. The glands which had thus been
excited to secrete soon became dry, and did not begin to secrete again
until the sixth day. A larger bit of starch was then placed on a leaf,
and no secretion was excited in 5 hrs. 30 m.; but after 8 hrs. there
was a considerable supply, which increased so much in 24 hrs. as to
run down the leaf to the distance of ? of an inch. This secretion,
though so abundant, was not in the least acid. As it was so copiously
excited, and as seeds not rarely adhere to the leaves of naturally
growing plants, it occurred to me that the glands might perhaps have
the power of secreting a ferment, like ptyaline, capable of dissolving
starch; so I carefully observed the above six small particles during
several days, but they did not seem in the least reduced in bulk. A
particle was also left for two days in a little pool of secretion, which
had run down from a piece of spinach leaf; but although the particle
was so minute no diminution was perceptible. We may therefore
conclude that the secretion cannot dissolve starch. The increase caused
by this substance may, I presume, be attributed to exosmose. But
lam surprised that starch acted so quickly and powerfully as it did,
though in a less degree than sugar. Colloids are known to possess some
slight power of dialysis; and on placing the leaves of a Primula in
water, and others in syrup and diffused starch, those in the starch
became flaccid, but to a less degree and at a much slower rate than the
leaves in the syrup ; those in water remaining all the time crisp.
9
314 PINGUICULA VULGARIS. (Cuar. XVI.
From the foregoing experiments and observations we see
that objects not containing soluble matter have little or no
power of exciting the glands to secrete. Non-nitrogenous
fluids, if dense, cause the glands to pour forth a large supply
of viscid fluid, but this is not in the least acid. On the
other hand, the secretion from glands excited by contact
with nitrogenous solids or liquids is invariably acid, and is
so copious that it often runs down the leaves and collects
within the naturally incurved margins. The secretion in
this state has the power of quickly dissolving, that is of
digesting, the muscles of insects, meat, cartilage, albumen,
fibrin, gelatine, and casein as it exists in the curds of milk.*
The glands are strongly excited by chemically prepared
casein and gluten; but these substances (the latter not
having been soaked in weak hydrochloric acid) are only
partially dissolved, as was likewise the case with Drosera.
The secretion, when containing animal matter in solution,
whether derived from solids or from liquids, such as an
infusion of raw meat, milk, or a weak solution of carbonate
of ammonia, is quickly absorbed; and the glands, which
were before limpid and of a greenish colour, become brownish
and contain masses of aggregated granular matter. This
matter, from its spontaneous movements, no doubt consists of
protoplasm. No such effect is produced by the action of non-
nitrogenous fluids. After the glands have been excited to
secrete freely, they cease for a time to secrete, but begin
again in the course of a few days.
Glands in contact with pollen, the leaves of other plants,
and various kinds of seeds, pour forth much acid secretion,
and afterwards absorb matter probably of an albuminous
nature from them. Nor can the benefit thus derived be
insignificant, for a considerable amount of pollen must be
blown from the many wind-fertilised carices, grasses, &c.,
growing where Pinguicula lives, on to the leaves thickly
covered with viscid glands and forming large rosettes. Even
* [Pfeffer (‘Ueber fleischfessende same use in the Italian Alps. The
Pflanzen,’ in the ‘Landwirthschaft. property of the plant seems to be
Jahrbücher, 1877) quotes Linneus widely known among primitive
(‘ Flora Lapponica,’ 1737, p.10) tothe people, for, within the last 30 years,
effect that certain Lapland tribes use it was used as rennet by mountain
the leaves of Pinguicula to coagulate farmers in North Wales. I have
milk. Pfeffer learnt from an old myself succeeded in curdling milk
shepherd that they are put to the with this vegetable rennet.—F. D.]
Cuar. XVL] PINGUICULA LUSITANICA. 315
a few grains of pollen on a single gland causes it to secrete
copiously. We have also seen how frequently the small
leaves of Erica tetralix and of other plants, as well as various
kinds of seeds and fruits, epecially of Carex, adhere to the
leaves. One leaf of the Pinguicula had caught ten of the
little leaves of the Erica; and three leaves on the same
plant had each caught a seed. Seeds subjected to the action
of the secretion are sometimes killed, or the seedlings injured.
We may therefore conclude that Pinguicula vulgaris, with its
small roots, is not only supported to a large extent by the
extraordinary number of insects which it habitually captures,
but likewise draws some nourishment from the pollen, leaves,
and seeds of other plants which often adhere to its leaves.
It is therefore partly a vegetable as well as an animal
feeder.
PINGUICULA GRANDIFLORA.
This species is so closely allied to the last that it is ranked
by Dr. Hooker as a sub-species. It differs chiefly in the
larger size of its leaves, and in the glandular hairs near the
basal part of the mid-rib being longer. But it likewise
differs in constitution; I hear from Mr. Ralfs, who was so
kind as to send me plants from Cornwall, that it grows in
rather different sites; and Dr. Moore, of the Glasnevin
Botanic Gardens, informs me that it is much more manage-
able under culture, growing freely and flowering annually ;
whilst Pinguicula vulgaris has to be renewed every year.
Mr. Ralfs found numerous insects and fragments of insects
adhering to almost all the leaves. These consisted chiefly
of Diptera, with some Hymenoptera, Homoptera, Coleoptera,
and a moth; on one leaf there were nine dead insects, besides
a few still alive. He also observed a few fruits of Carex
pulicaris, as wellas the seeds of this same Pinguicula, adhering
to the leaves. I tried only two experiments with this species ;
firstly, a fly was placed near the margin of a leaf, and after
16 hrs. this was found well inflected. Secondly, several
small flies were placed in a row along one margin of another
leaf, and by the next morning this whole margin was curled
inwards, exactly as in the case of Pinguicula vulgaris.
PINGUICULA LUSITANICA.
This species, of which living specimens were sent me by
Mr. Ralfs from Cornwall, is very distinct from the two fore-
316 PINGUICULA LUSITANICA. [Cuar. XVI.
going ones. The leaves are rather smaller, much more
transparent, and are marked with purple branching veins.
The margins of the leaves are much more involuted ; those of
the older ones extending over a third of the space between
the midrib and the outside. As in the two other species, the
glandular hairs consist of longer and shorter ones, and have
the same structure; but the glands differ in being purple,
and in often containing granular matter before they have
been excited. In the lower part of the leaf, almost half the
space on each side between the midrib and margin is destitute
of glands; these being replaced by long, rather stiff, multi-
cellular hairs, which intercross over the midrib. These hairs
perhaps serve to prevent insects from settling on this part of
the leaf, where there are no viscid glands by which they
could be caught; but it is hardly probable that they were
developed for this purpose. The spiral vessels proceeding
from the midrib terminate at the extreme margin of the leaf
in spiral cells; but these are not so well developed as in the
two preceding species. The flower-peduncles, sepals, and
petals, are studded with glandular hairs, like those on the
leaves.
The leaves catch many small insects, which are found
chiefly beneath the involuted margins, probably washed there
by the rain, The colour of the glands on which insects have
long lain is changed, being either brownish or pale purple,
with their contents coarsely granular ; so that they evidently
absorb matter from their prey. Leaves of the Erica tetralix,
flowers of a Galium, scales of grasses, &c., likewise adhered to
some of the leaves. Several of the experiments which were
tried on Pinguicula vulgaris were repeated on Pinguicula
lusitanica, and these will now be given.
(1) A moderately sized and angular bit of albumen was placed on
one side of a leaf, halfway between the midrib and the naturally
involuted margin. In 2 hrs. 15 m. the glands poured forth much
secretion, and this side became more infolded than the opposite one.
The inflection increased, and in 3 hrs. 30 m. extended up almost to the
apex. After 24 hrs. the margin was rolled into a cylinder, the outer
surface of which touched the blade of the leaf and reached to within
the 5 of an inch of the midrib. After 48 hrs. it began to unfold, and
in 72 hrs. was completely unfolded. The cube was rounded and
greatly reduced in size; the remainder being in a semi-liquefied
state.
(2) A moderately sized bit of albwmen was placed near the apex of
Cuar. XVL] PINGUICULA LUSITANICA. 317
a leaf, under the naturally incurved margin. In 2 hrs. 30 m. much
secretion was excited, and next morning the margin on this side was
more incurved than the opposite one, but not to so great a degree
as in the last case. The margin unfolded at the same rate as before.
aF proportion of the albumen was dissolved, a remnant being stil!
eit.
(3) Large bits of albumen were laid in a row on the midribs of two
leaves, but produced in the course of 24 hrs. no effect; nor could this
have been expected, for even had glands existed here, the long bristles
would have prevented the albumen from coming in contact with them.
On both leaves the bits were now pushed close to one margin, and in
3 hrs. 30 m. this became so greatly inflected that the outer surface
touched the blade; the opposite margin not being in the least affected.
After three days the margins of both leaves with the albumen were
still as much inflected as ever, and the glands were still secreting
copiously. With Pinguicula vulgaris I have never seen inflection
lasting so long.
(4) Two cabbage seeds, after being soaked for an hour in water, were
placed near the margin of a leaf, and caused in 3 hrs. 20 m. increased
secretion and incurvation. After 24 hrs. the leaf was partially
unfolded, but the glands were still secreting freely. These began to
dry in 48 hrs., and after 72 hrs. were almost dry. The two seeds were
then placed on damp sand under favourable conditions for growth ; but
they never germinated, and after a time were found rotten. They had
no doubt been killed by the secretion.
(5) Small bits of a spinach leaf caused in 1 hr. 20 m. increased se-
cretion; and after 3 hrs. 20 m. plain incurvation of the margin. The
margin was well inflected after 9 hrs. 15 m., but after 24 hrs. was
almost fully re-expanded. The glands in contact with the spinach
became dry in 72 hrs. Bits of albumen had been placed the day
before on the opposite margin of this same leaf, as well as on that of a
leaf with cabbage seeds, and these margins remained closely inflected
for 72 hrs., showing how much more enduring is the effect of albumen
than of spinach leaves or cabbage seeds.
(6) A row of small fragments of glass was laid along one margin of
a leaf; no effect was produced in 2 hrs. 10 m., but after 3 hrs. 25 m.
there seemed to be a trace of inflection, and this was distinct, though
not strongly marked, after 6 hrs. The glands in contact with the
fragments now secreted more freely than before; so that they appear
to be more easily excited by the pressure of inorganic objects
than are the glands of Pinguicula vulgaris. The above slight
inflection of the margin had not increased after 24 hrs., and the glands
were now beginning to dry. The surface of a leaf, near the midrib
and towards the base, was rubbed and scratched for some time,
but nomovement ensued. The long hairs which are situated here were
treated in the same manner, with no effect. This latter trial was made
because I thought that the hairs might perhaps be sensitive to a touch,
like the filaments of Dionza,
318 PINGUICULA LUSITANICA. [Cuar. XVI.
(7) The flower-peduncles, sepals and petals bear glands in general
appearance like those on the leaves. A piece of a flower-peduncle was
therefore left for 1 hr. in a solution of one part of carbonate of
ammonia to 437 of water, and this caused the glands to change from
bright pink to a dull purple colour; but their contents exhibited no
distinct aggregation. After 8 hrs. 30 m. they became colourless. Two
minute cubes of albumen were placed on the glands of a flower-
peduncle, and another cube on the glands of a sepal; but they were
not excited to increased secretion, and the albumen after two days was
not in the least softened. Hence these glands apparently differ greatly
in function from those on the leaves.
From the foregoing observations on Pinguicula lusitanica we
see that the naturally much incurved margins of the leaves
are excited to curve still farther inwards by contact with
organic and inorganic bodies; that albumen, cabbage seeds,
bits of spinach leaves, and fragments of glass, cause the
glands to secrete more freely ; that albumen is dissolved by
the secretion, and cabbage seeds killed by it; and lastly that
matter is absorbed by the glands from the insects which are
caught in large numbers by the viscid secretion. The glands
on the flower-peduncles seem to have no such power. ‘This
species differs from Pinguicula vulgaris and grandiflora in the
margins of the leaves, when excited by organic bodies, being
inflected to a greater degree, and in the inflection lasting for
a longer time. ‘The glands, also, seem to be more easily
excited to increased secretion by bodies not yielding soluble
nitrogenous matter. In other respects, as far as my observa-
tions serve, all three species agree in their functional powers.
Cuar. XVIL] UTRICULARIA NEGLECTA. 319
CHAPTER XVII.
UTRICULARIA.
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 observations on absorption—Development
of the bladders— Utricularia vulgaris — Utricularia minor — Utricularia
clandestina,
I was led to investigate the habits and structure of the
species of this genus partly from their belonging to the same
natural family as Pinguicula, but more especially by Mr.
Holland’s statement, that “water insects are often found
imprisoned in the bladders,” which he suspects “are destined
for the plant to feed on.” * The plants which I first received
as Utricularia vulgaris from the New Forest in Hampshire
and from Cornwall, and which I have chiefly worked on,
have been determined by Dr. Hooker to be a very rare
British species, the Utricularia neglecta of Lehm.t I subse-
quently received the true Utricularia vulgaris from Yorkshire.
Since drawing up the following description from my own
observations and those of my son, Francis Darwin, an
important memoir by Prof. Cohn on Utricularia vulgaris has
appeared ;{ and it has been no small satisfaction to me to
find that my account agrees almost completely with that of
this distinguished observer. I will publish my description
as it stood before reading that by Prof. Cohn, adding
occasionally some statements on his authority.
* The ‘Quart. Mag. of the High
Wycombe Nat. Hist. Soc.’ July 1868,
p. 5. Delpino (‘ Ult. Osservaz. sulla
Dicogamia,’ &c. 1868-1869, p. 16)
also quotes Crouan as having found
(1858) crustaceans within the blad-
ders of Utricularia vulgaris.
t+ Iam much indebted to the Rey.
H. M. Wilkinson, of Bistern, for
having sent me several fine lots of
this species from the New Forest.
Mr. Ralfs was also so kind as to send
me living plants of the same species
from near Penzance in Cornwall.
+ ‘ Beiträge zur Biologie der Pflan-
zen,’ drittes Heft, 1875.
D
320 UTRICULARIA NEGLECTA. [Cmar. XVII.
Utricularia neglecta.—The general appearance of a branch
(about twice enlarged), with the pinnatifid leaves bearing
bladders, is represented in the following sketch (fig. 17).
The leaves continually bifurcate, so that a full-grown one
terminates in from twenty to thirty points. Each point is
tipped by a short, straight bristle ; and slight notches on the
Fic. 17.
(Utricularia neglecta.)
Branch with the divided leaves bearing bladders; about twice enlarged.
sides of the leaves bear similar bristles. On both surfaces
there are many small papille, crowned with two hemi-
spherical cells in close contact. The plants float near the
surface of the water, and are quite destitute of roots, even
during the earliest period of growth.* They commonly
* Linfer that this is the case from from the ‘ Videnskabelige Meddelel-
a drawing of a seedling given by Dr. ser; Copenhagen, 1874, Nos. 3-7, pp.
Warming in his paper, “ Bidrag til 33-58. [Cf. Kamienski, ‘ Bot. Zeit.’
Kundskaben om Lentibulariacee,” 1877, p. 765.]
Cair. XVII.] STRUCTURE OF THE BLADDER. 821
inhabit, as more than one observer has remarked to me,
remarkably foul ditches.
The bladders offer the chief point of interest. There are
often two or three on the same divided leaf, generally near
the base ; though I have seen a single one growing from the
stem. ‘They are supported on short footstalks. When fully
grown, they are nearly 75 of an inch (2°54 mm.) in length.
They are translucent, of a green colour, and the walls are
formed of two layers of cells. The exterior cells are poly-
gonal and rather large; but at many of the points where the
angles meet, there are smaller rounded cells. These latter
support short conical projections, surmounted by two hemi-
spherical cells in such close apposition that they appear
Fig. 18.
(Utricularia neglecta.)
Bladder; much enlarged. c, collar indistinctly seen through the walls.
united ; but they often separate a little when immersed in
certain fluids. The papille thus formed are exactly like
those on the surfaces of the leaves. Those on the same
bladder vary much in size; and there are a few, especially
on very young bladders, which have an elliptical instead of
a circular outline. The two terminal cells are transparent,
but must hold much matter in solution, judging from the
area coagulated by prolonged immersion in alcohol or
ether.
The bladders are filled with water. They generally, but
by no means always, contain bubbles of air. According to
the quantity of the contained water and air, they vary much
f è
822 UTRICULARIA NEGLECTA. (Cuar. XVII.
in thickness, but are always somewhat compressed. At an
early stage of growth, the flat or ventral surface faces the
axis or stem; but the footstalks must have some power of
movement; for in plants kept in my greenhouse the ventral
surface was generally turned either straight or obliquely
downwards. The Rev. H. M. Wilkinson examined plants for
me in a state of nature, and found this commonly to be the
case, but the younger bladders often had their valves turned
upwards.
The general appearance of a bladder viewed laterally, with
the appendages on the near side alone represented, is shown
on the preceding page (fig. 18). The lower side, where
the footstalk arises, is nearly straight, and I have called it
Mn DDN
Qe an Ala
(nf SERRA
SN PSR AINIS WARS OLN TIA
(NAMES ENTS ZL,
Aa ee
Fia. 19.
(Utricularia neglecta.)
Valve of bladder; greatly enlarged.
the ventral surface. The other or dorsal surface is convex,
and terminates in two long prolongations, formed of several
rows of cells, containing chlorophyll, and bearing, chiefly on
the outside, six or seven long, pointed, multicellular bristles.
These prolongations of the bladder may be conveniently
called the antenne, for the whole bladder (sce fig. 17)
curiously resembles an entomostracan crustacean, the short
footstalk representing the tail. In fig. 18, the near antenna
alone is shown. Beneath the two antenne the end of the
bladder is slightly truncated, and here is situated the most
important part of the whole structure, namely the entrance
and valve. On each side of the entrance from three to rarely
seven long, multicellular bristles project outwards; but only
oe
Czar. XVII.] STRUCTURE OF THE BLADDER. 323
those (four in number) on the near side are shown in the
drawing. These bristles, together with those borne by the
antenne, form a sort of hollow cone surrounding the
entrance.
The valve slopes into the cavity of the bladder, or upwards
in fig. 18. It is attached on all sides to the bladder,
excepting by its posterior margin, or the lower one in fig.
19, which is free, and forms one side of the slit-like orifice
leading into the bladder. This margin is sharp, thin, and
smooth, and rests on the edge of a rim or collar, which dips
deeply into the bladder, as shown in the longitudinal section
(fig. 20) of the collar and valve; it is also shown at c, in
fig. 18. The edge of the valve can thus open only inwards.
Fic. 20.
(Utricularia neglecta.)
Longitudinai vertical section through the ventral portion of a bladder; sbowing valve and
collar. v, valve; the whole projection above c forms the collar; b, bifid processes; $,
ventral surface of bladder,
As both the valve and collar dip into the bladder, a hollow
or depression is here formed, at the base of which lies the
slit-like orifice.
The valve is colourless, highly transparent, flexible and
elastic. It is convex in a transverse direction, but has been
drawn (fig. 19) in a flattened state, by which its apparent
breadth is increased. It is formed, according to Cohn, of two
layers of small cells, which are continuous with the two
layers of larger cells forming the walls of the bladder, of
which it is evidently a prolongation. Two pairs of trans-
parent pointed bristles, about as long as the valve itself,
arise from near the free posterior margin (fig. 19), and point
obliquely outwards in the direction of the antennæ. There
Y2
324 UTRICULARIA NEGLECTA. (Gaar. XVII.
are also on the surface of the valve numerous glands, as I
will call them; for they have the power of absorption,
though I doubt whether they ever secrete. They consist of
three kinds, which to a certain extent graduate into one
another. Those situated round the anterior margin of the
valve (upper margin in fig. 19) are very numerous and
crowded together; they consist of an oblong head on a long
pedicel. The pedicel itself is formed of an elongated cell,
surmounted by a short one. The glands towards the free
posterior margin are much larger, few in number, and almost
spherical, having short footstalks ; the head is formed by the
confluence of two cells, the lower one answering to the short
upper cell of the pedicel of the oblong glands. The glands of
the third kind have transversely elongated heads, and are
seated on very short footstalks; so that they stand parallel
and close to the surface of the valve; they may be called
the two-armed glands. The cells forming all these glands
contain a nucleus, and are lined by a thin layer of more or
less granular protoplasm, the primordial utricle of Mohl.
They are filled with fluid, which must hold much matter in
solution, judging from the quantity coagulated after they
have been long immersed in alcohol or ether. The depression
in which the valve lies is also lined with innumerable glands;
those at the sides having oblong heads and elongated pe-
oe exactly like the glands on the adjoining parts of the
valve.
The collar (called the peristome by Cohn) is evidently
formed, like the valve, by an inward projection of the walls
of the bladder. The cells composing the outer surface, or
that facing the valve, have rather thick walls, are of a
brownish colour, minute, very numerous, and elongated; the
‘ower ones being divided into two by vertical partitions.
The whole presents a complex and elegant appearance. The
cells forming the inner surface are continuous with those
over the whole inner surface of the bladder. The space be-
tween the inner and outer surface consists of coarse cellular
tissue (fig. 20). The inner side is thickly covered with
delicate bifid processes, hereafter to be described. The collar
is thus made thick; and it is rigid, so that it retains the
same outline whether the bladder contains little or much air
and water. This is of great importance, as otherwise the
thin and flexible valve would be liable to be distorted, and
in this case would not act properly.
Cuar. XVII.] STRUCTURE OF THE BLADDER. 325
Altogether the entrance into the bladder, formed by the
transparent valve, with its four obliquely projecting bristles,
its numerous diversely shaped glands, surrounded by the
collar, bearing glands on the inside and bristles on the out-
side, together with the bristles borne by the antennæ, presents
an extraordinary complex appearance when viewed under the
microscope.
We wiil now consider the internal structure of the bladder.
The whole inner surface, with the exception of the valve, is
seen under a moderately high power to be covered with a
serried mass of processes (fig. 21). Each of these consists of
jFic. 21, Fic, 22
(Utricularia neglecta.) ue lecta.)
` En riculart cla.
Small portion of inside of bladder, oe sh z
much enlarged, showing quadrifid One of the quadrifid processes
processes, greatly enlarged,
four divergent arms; whence their name of quadrifid
processes. They arise from small angular cells, at the
Junctions of the angles of the larger cells which form the
interior of the bladder. The middle part of the upper
surface of these small cells projects a little, and then con-
tracts into a very short and narrow footstalk which bears the
four arms (fig. 22). Of these, two are long, but often of not
quite equal length, and project obliquely inwards and
towards the posterior end of the bladder. The two others
are much shorter, and project at a smaller angle, that is, are
more nearly horizontal, and are directed towards the anterior
326 UTRICULARIA NEGLECTA. [Cuar. XVII.
end of the bladder. These arms are only moderately sharp ;
they are composed of extremely thin transparent membrane,
so that they can be bent or doubled in any direction without
being broken. They are lined with a delicate layer of
protoplasm, as is likewise the short conical projection from
which they arise. Each arm generally (but not invariably)
contains a minute, faintly brown particle, either rounded
or more commonly elongated, which exhibits incessant
3rownian movements. These particles slowly change their
positions, and travel from one end to the other of the arms,
but are commonly found near their bases. They are present
in the quadrifids of young bladders, when only about a third
of their full size. They do not resemble ordinary nuclei, but
I believe that they are nuclei in a modified condition, for
when absent, I could occasionally just distinguish in their
places a delicate halo of matter, including a darker spot.
Moreover, the quadrifids of Utricularia montana contain
rather larger and much more regularly spherical, but
otherwise similar, particles, which closely resemble the
nuclei in the cells forming the walls of the bladders. In the
present case there were sometimes two, three, or even more,
nearly similar particles within a single arm; but, as we shall
hereafter see, the presence of more than one seemed always
to be connected with the absorption of decayed matter.
The inner side of the collar (see the previous fig. 20) is
covered with several crowded rows of processes, differing in
no important respect from the quadrifids, except in bearing
only two arms instead of four; they are, however, rather
narrower and more delicate. I shall call them the bifids.
They project into the bladder, and are directed towards its
posterior end. The quadrifid and bifid processes no doubt
are homologous with the papillee on the outside of the bladder
and of the leaves; and we shall see that they are developed
from closely similar papille.
The Uses of the several Parts— After the above long but
necessary description of the parts, we will turn to their uses.
The bladders have been supposed by some authors to serve
as floats; but branches which bore no bladders, and others
from which they had been removed, floated perfectly, owing
to the air in the intercellular spaces. Bladders containing
dead and captured animals usually include bubbles of air, but
these cannot have been generated solely by the process of
decay, as I have often seen air in young, clean, and empty
Cmar. XVII.] MANNER OF CAPTURING PREY. oat
bladders; and some old bladders with much decaying matter
had no bubbles.
The real use of the bladders is to capture small aquatic
animals, and this they do on a large scale. In the first lot of
plants, which I received from the New Forest early in July,
a large proportion of the fully grown bladders contained prey ;
in a second lot, received in the beginning of August, most of
the bladders were empty, but plants had been selected which
had grown in unusually pure water. In the first lot, my son
examined seventeen bladders, including prey of some kind,
and eight of these contained entomostracan crustaceans, three
larvæ of insects, one being still alive, and six remnants of
animals so much decayed that their nature could not be
distinguished, I picked out five bladders which seemed very
full, and found in them four, five, eight, and ten crustaceans,
and in the fifth a single much elongated larva. In five other
bladders, selected from containing remains, but not appearing
very full, there were one, two, four, two, and five crustaceans.
A plant of Utricularia vulgaris, which had been kept in almost
pure water, was placed by Cohn one evening into water
swarming with crustaceans, and by the next morning most
of the bladders contained these animals entrapped and
swimming round and round their prisons. They remained
alive for several days; but at last perished, asphyxiated, as I
suppose, by the oxygen in the water having been all con-
sumed, Freshwater worms were also found by Cohn in some
bladders. In all cases the bladders with decayed remains
swarmed with living Alge of many kinds, Infusoria, and
other low organisms, which evidently lived as intruders.
Animals enter the bladders by bending inwards the pos-
terior free edge of the valve, which from being highly elastic
shuts again instantly. As the edge is extremely thin, and
fits closely against the edge of the collar, both projecting into
the bladder (see section, fig. 20), it would evidently be very
difficult for any animal to get out when once imprisoned, and
apparently they never do escape. To show how closely the
edge fits, I may mention that my son found a Daphnia which
had inserted one of its antennæ into the slit, and it was thus
held fast during a whole day. On three or four occasions I
have seen long narrow larve, both dead and alive, wedged
between the corner of the valve and collar, with half their
bodies within the bladder and half out.
As I felt much difficulty in understanding how such
328 UTRICULARIA NEGLECTA. (Cuar. XVII.
minute and weak animals, as are often captured, could force
their way into the bladders, I tried many experiments to
ascertain how this was affected. The free margin of the
valve bends so easily that no resistance is felt when a needle
or thin bristle is inserted. A thin human hair, fixed to a
handle, and cut off so as to project barely } of an inch, en-
tered with some difficulty ; a longer piece yielded instead of
entering. On three occasions minute particles of blue glass
(so as to be easily distinguished) were placed on valves
whilst under water; and on trying gently to move them
with a needle, they disappeared so suddenly that, not see-
ing what had happened, I thought that I had flirted them
off; but on examining the bladders, they were found safely
enclosed. ‘The same thing occurred to my son, who placed
little cubes of green box-wood (about z} of an inch, 423 mm.)
on some valves; and thrice in the act of placing them on, or
whilst gently moving them to another spot, the valve sud-
denly opened and they were engulfed. He then placed
similar bits of wood on other valves, and moved them about
for some time, but they did not enter. Again, particles of
blue glass were placed by me on three valves, and extremely
minute shavings of lead on two other valves ; after 1 or 2 brs.
none had entered, but in from 2 to 5 hrs. all five were
enclosed. One of the particles of glass was a long splinter,
of which one end rested obliquely on the valve, and after a
few hours it was found fixed, half within the bladder and
half projecting out, with the edge of the valve fitting closely
all round, except at one angle, where a small open space was
left. It was so firmly fixed, like the above-mentioned larve,
that the bladder was torn from the branch and shaken, and
yet the splinter did not fall out. My son also placed little
cubes (about s of an inch, +391 mm.) of green box-wood,
which were just heavy enough to sink in water, on three
valves. ‘These were examined after 19 hrs. 30 m., and were
still lying on the valves; but after 22 hrs. 30 m. one was
found enclosed. I may here mention that I found in a
bladder on a naturally growing plant a grain of sand, and
in another bladder three grains; these must have fallen by
some accident on the valves, and then entered like the par-
ticles of glass.
The slow bending of the valve from the weight of particles
of glass and even of box-wood, though largely supported by
the water, is, I suppese, analogous to the slow bending of
Cuir. XVII] MANNER OF CAPTURING PREY. 329
colloid substances. For instance, particles of glass were
placed en various points of narrow strips of moistened gela-
tine, and these yielded and hecame bent with extreme slow-
ness. It is much more difficult to understand how gently
moving a particle from one part of a valve to another causes
it suddenly to open. To ascertain whether the valves were
endowed with irritability, the surfaces of several were
scratched with a needle or brushed with a fine camel-hair
brush, so as to imitate the crawling movement of small
crustaceans, but the valve did not open. Some bladders,
before being brushed, were left for a time in water at tem-
peratures between 80° and 130° F. (26°-6—54°°4 Cent.), as,
judging from a wide-spread analogy, this would have ren-
dered them more sensitive to irritation, or would by itself
have excited movement; but no effect was produced. We
may therefore conclude that animals enter merely by forcing
their way through the slit-like orifice; their heads serving
as a wedge. But I am surprised that such small and weak
creatures as are often captured (for instance, the nauplius ot
a crustacean, and a tardigrade) should be strong enough to
act in this manner, seeing that it was difficult to push in one
end of a bit of hair 4 of an inch in length. Nevertheless,
it is certain that weak and small creatures do enter, and
Mrs. Treat, of New Jersey, has been more successful than any
other observer, and has often witnessed in the case of
Utriculria clandestina the whole process.* She saw a tardi-
grade slowly walking round a bladder, as if reconnoitring ;
at last it crawled into the depression where the valve lies,
and then easily entered. She also witnessed the entrapment
of various minute crustaceans. Cypris “was quite wary,
“ but nevertheless was often caught. Coming tothe entrance
“of a bladder, it would sometimes pause a moment, and then
“dash away ; at other times it would come close up, and even
“venture part of the way into the entrance and back out as
“if afraid. Another, more heedless, would open the door
“and walk in; but it was no sooner in than it manifested
“alarm, drew in its feet and antenne, and closed its shell.”
Larve, apparently of gnats, when “feeding near the en-
“trance, are pretty certain to run their heads into the net,
“ whence there is no retreat. A large larva is sometimes
* «New York Tribune,’ reprinted in the ‘Gard. Chron.’ 1875, p. 303.
390 UTRICULARIA NEGLECTA. (Cuar. XVII.
“three or four hours in being swallowed, the process bring-
“ing to mind what I have witnessed when a small snake
“makes a large frog its victim.” But as the valve does
not appear to be in the least irritable,* the slow swallowing
process must be the effect of the onward movement of the
larva.
It is*difficult to conjecture what can attract so many
creatures, animal- and vegetable-feeding crustaceans, worms,
tardigrades, and various larve, to enter the bladders.
Mrs. Treat says that the larve just referred to are vegetable
feeders, and seem to have a special liking for the long
bristles round the valve, but this taste will not account for
the entrance of animal-feeding crustaceans. Perhaps small
aquatic animals habitually try to enter every small crevice,
like that between the valve and collar, in search of food or
protection. Itis not probable that the remarkable trans-
parency of the valve is an accidental circumstance, and the
spot of light thus formed may serve as a guide. The long
bristles round the entrance apparently serve for the same
purpose. I believe that this is the case, because the bladders
of some epiphytic and marsh species of Utricularia which
live embedded either in entangled vegetation or in mud, have
no bristles round the entrance, and these under such condi-
tions would be of no service as a guide. Nevertheless, with
these epiphytic and marsh species, two pairs of bristles pro-
ject from the surface of the valve, as in the aquatic species ;
and their use probably is to prevent too large animals from
trying to force an entrance into the bladder, thus rupturing
the orifice.
As under favourable circumstances most of the bladders
succeed in securing prey, in one case as many as ten crusta-
ceans ;—as the valve is so well fitted to allow animals to
enter and to prevent their escape ;—and as the inside of the
bladder presents so singular a structure, clothed with innu-
merable quadrifid and bifid processes, it is impossible to
doubt that the plant has been specially adapted for securing
prey. From the analogy of Pinguicula, belonging to the
saine family, I naturally expected that the bladders would
* [Guided by her observations (‘ Harper’s Magazine,’ Feb. 1876) on the act
of capture, Mrs, Treat concludes that the valve is irritable.—F. D.]
Car. XVII] MANNER OF CAPTURING PREY. 831
have digested their prey; but this is not the case, and there
are no glands fitted for secreting the proper fluid. Never-
theless, in order to test their power of digestion, minute
fragments of roast meat, three small cubes of albumen, and
three of cartilage, were pushed through the orifice into the
bladders of vigorous plants. They were left from one day
to three days and a half within, and the bladders were then
cut open: but none of the above substances exhibited the
least signs of digestion or dissolution; the angles of the
cubes being as sharp as ever. These observations were made
subsequently to those on Drosera, Dionza, Drosophyllum,
and Pinguicula; so that I was familar with the appearance
of these substances when undergoing the early and final
stages of digestion. We may therefore conclude : that
Utricularia cannot digest the animals which it habitually
captures.
In most of the bladders the captured animals are so much
decayed that they form a pale brown, pulpy mass, with
their chitinous coats so tender that they fall to pieces with
the greatest ease. The black pigment of the eye-spots is
preserved better than anything else. Limbs, jaws, &c. are
often found quite detached ; and this I suppose is the result
of the vain struggles of the later captured animals. I have
sometimes felt surprised at the small proportion of im-
prisoned animals in a fresh state compared with those utterly
decayed.* Mrs. Treat states with respect to the larvae above
referred to, that “ usually in less than two days after a large
“one was captured the fluid contents of the bladders began
“ to assume a cloudy or muddy appearance, and often became
“so dense that the outline of the animal was lost to view.”
This statement raises the suspicion that the bladders secrete
some ferment hastening the process of decay. There is no
inherent improbability in this supposition, considering that
meat soaked for ten minutes in water mingled with the
milky juice of the papaw becomes quite tender and soon
passes, as Browne remarks in his ‘Natural History of
Jamaica,’ into a state of putridity.
Whether or not the decay of the imprisoned animals is in
any way hastened, it is certain that matter is absorbed from
* [Schimper (‘ Botanische Zeitung,’ 1882, p. 245) was struck by the same
fact in the case of U. cornuta.—F. D.]
332 UTRICULARIA NEGLECTA. (Cuar. XVI.
them by the quadrifid and bifid processes. The extremely
delicate nature of the membrane of which these processes
are formed, and the large surface which they expose, owing
to their number crowded over the whole interior of the
bladder, are circumstances all favouring the process of
absorption. Many perfectly clean bladders which had never
caught any prey were opened, and nothing could be distin-
guished with a No. 8 object-glass of Hartnack within the
delicate, structureless protoplasmic lining of the arms, ex-
cepting in each a single yellowish particle or modified
nucleus. Sometimes two or even three such particles were
present; but in this case traces of decaying matter could
generally be detected. On the other hand, in bladders con-
taining either one large or several small decayed animals,
the processes presented a widely different appearance. Six
such bladders were carefully examined; one contained an
elongated, coiled-up larva; another a single large entomo-
stracan crustacean, and the others from two to five smaller
ones, all in a decayed state. In these six bladders, a large
number of the quadrifid processes contained transparent,
often yellowish, more or less confluent, spherical or irregu-
larly shaped, masses of matter. Some of the processes,
however, contained only fine granular matter, the particles
of which were so small that they could not be defined clearly
with No. 8 of Hartnack. The delicate layer of protoplasm
lining their walls was in some cases a little shrunk.* On three
occasions the above small masses of matter were observed
and sketched at short intervals of time; and they certainly
changed their positions relatively to each other and to the
walls of the arms. Separate masses sometimes became con-
fluent, and then again divided. A single little mass would
send out a projection, which after a time separated itself.
Hence there could be no doubt that these masses consisted of
protoplasm. Bearing in mind that many clean bladders
were examined with equal care, and that these presented no
such appearance, we may confidently believe that the pro-
* [Schimper (loc. cit. p. 247) ob-
empty bladders, but the commonest
served a marked difference in the
change is a collection of the pro-
appearance of the hairs in those
bladders of U. cornuta which contain
captured prey. ‘The protoplasm is
sometimes more granular than in
toplasm in the axis of the cell where
it is suspended by radiating strands
to the delicate layer of protoplasm
lining the walls.—F. D.]
Osmar. XVII] ABSORPTION BY THE QUADRIFIDS. 333
toplasm in the above cases had been generated by the
absorption of nitrogenous matter from the decaying animals.
In two or three other bladders, which at first appeared quite
clean, on careful search a few processes were found, with
their outsides clogged with a little brown matter, showing
that some minute animal had been captured and had de-
cayed, and the arms here included a very few more or less
spherical and aggregated masses; the processes in other
parts of the bladders being empty and transparent. On the
other hand, it must be stated that in three bladders con-
taining dead crustaceans, the processes were likewise empty.
This fact may be accounted for by the animals not having
been sufficiently decayed, or by time enough not having
been allowed for the generation of protoplasm, or by its
subsequent absorption and transference to other parts of the
plant. It will hereafter be seen that in three or four other
species of Utricularia the quadrifid processes in contact with
decaying animals likewise contained aggregated masses of
protoplasm.
On the Absorption of certain Fluids by the Quadrifid and
Bifid Processes—These experiments were tried to ascertain
whether certain fluids, which seemed adapted for the purpose
would produce the same effects on the processes as the
absorption of decayed animal matter. Such experiments are,
however, troublesome ; for it is not sufficient merely to place
a branch in the fluid, as the valve shuts so closely that the
fluid apparently does not enter soon, if at all. Even when
bristles were pushed into the orifices, they were in several
cases wrapped so closely round by the thin flexible edge of
the valve that the fluid was apparently excluded ; so that
the experiments tried in this manner are doubtful and not
worth giving. The best plan would have been to puncture
the bladders, but I did not think of this till too late,
excepting in a few cases. In all such trials, however, it
cannot be ascertained positively that the bladder, though
translucent, does not contain some minute animal in the
last stage of decay. Therefore most of my experiments were
made by cutting bladders longitudinally into two; the
quadrifids were examined with No. 8 of Hartnack, then
irrigated, whilst under the covering glass, with a few drops
of the fluid under trial, kept in a damp chamber, and re-
examined after stated intervals of time with the same power
as before.
334 UTRICULARIA NEGLECTA. [Cuar. XVII.
Four bladders were first tried as a control experiment, in the manner
just described, in a solution of one part of gum arabic to 218 of water,
and two bladders in a solution of one part of sugar to 437 of water ;
and in neither case was any change perceptible in the quadrifids or
bifids after 21 hrs. Four bladders were then treated in the same
manner with a solution of one part of nitrate of ammonia to 487 of
water, and re-examined after 21 hrs. In two cf these the quadrifids
now appeared full of very finely granular matter, and their protoplasmic
lining or primordial utricle was a little shrunk. In the third bladder,
the quadrifids included distinctly visible granules, and the primordial
utricle was a little shrunk after only 8 hrs. In the fourth bladder the
primordial utricle in most of the processes was here and there
thickened into little irregular yellowish specks ; and from the gradations
which could be traced in this and other cases, these specks appear to give
rise to the larger free granules contained within some of the processes.
Other bladders, which, as far as could be judged, had never caught, any
prey, were punctured and left in the same solution for 17 hrs.; and
their quadrifids now contained very fine granular matter.
A bladder was bisected, examined, and irrigated with a solution of
one part of carbonate of ammonia to 437 of water. After 8 hrs. 30 m.
the quadrifids contained a good many granules, and the primordial
utricle was somewhat shrunk; after 23 hrs. the quadrifids and bifids
contained many spheres of hyaline matter, and in one arm twenty-four
such spheres of moderate size were counted. Two bisected bladders,
which had been previously left for 21 hrs. in the solution of gum (one
part to 218 of water) without being affected, were irrigated with the
solution of carbonate of ammonia; and both had their quadrifids
modified in nearly the same manner as just described,—one after only
9 hrs. and the other after 24 hrs. Two bladders which appeared
never to have caught any prey were punctured and placed in the
solution ; the quadrifids of one were examined after 17 hrs., and found
slightly opaque ; the quadrifids of the other, examined after 45 hrs., had
their primordial utricles more or less shrunk with thickened yellowish
specks like those due to the action of nitrate of ammonia. Several un-
injured bladders were left in the same solution, as well as in a weaker
solution of one part to 1750 of water, or 1 gr. to 4 oz. ; and after two days
the quadrifids were more or less opaque, with their contents finely
granular; but whether the solution had entered by the orifice, or had
been absorbed from the outside, I know not.
Two bisected bladders were irrigated with a solution of one part
of urea to 218 of water; but when this solution was employed, I forgot
that it had been kept for some days in a warm room, and had there-
fore probably generated ammonia; anyhow, the quadrifids were
affected after 21 hrs. as if a solution of carbonate of ammonia had been
used; for the primordial utricle was thickened in specks, which seemed
to graduate into separate granules. Three bisected bladders were also
irrigated with a fresh solution of urea of the same strength; their
quadrifids after 21 hrs. were much less affected than in the former
Cmar. XVII.] ABSORPTION BY THE QUADRIFIDS. 300
case; nevertheless, the primordial utricle in some of the arms was a
little shrunk, and in others was divided into two almost symmetrical
sacks.
Three bisected bladders, after being examined, were irrigated with
a putrid and very offensive infusion of raw meat. After 23 hrs. the
quadrifids and bifids in all three specimens abounded with minute,
hyaline, spherical masses; and some of their primordial utricles were
a little shrunk. Three bisected bladders were also irrigated with
a fresh infusion of raw meat; and to my surprise the quadrifids in
one of them appeared, after 23 hrs., finely granular, with their
primordial utricles somewhat shrunk and marked with thickened yellow-
ish specks; so that they had been acted on in the same manner as by
the putrid infusion or by the salts of ammonia. In the second
bladder some of the quadrifids were similarly acted on, though to
a very slight degree ; whilst the third bladder was not at all affected.
From these experiments it is clear that the quadrifid and
bifid processes have the power of absorbing carbonate and
nitrate of ammonia, and matter of some kind from a putrid
infusion of meat. Salts of ammonia were selected for trial,
as they are known to be rapidly generated by the decay of
animal matter in the presence of air and water, and would
therefore be generated within the bladders containing cap-
tured prey. The effect produced on the processes by these
salts and by a putrid infusion of raw meat differs from that
produced by the decay of the naturally captured animals
only in the aggregated masses of protoplasm being in the
latter case of larger size; but it is probable that the fine
granules and small hyaline spheres produced by the solutions
would coalesce into larger masses, with time enough allowed.
We have seen with Drosera that the first effect of a weak
solution of carbonate of ammonia on the cell-contents is the
production of the finest granules, which afterwards aggre-
gate into larger, more or less rounded, masses; and that the
granules in the layer of protoplasm which flows round the
walls ultimately coalesce with these masses. Changes of
this nature are, however, far more rapid in Drosera than in
Utricularia. Since the bladders have no power of digesting
albumen, cartilage, or roast meat, I was surprised that matter
was absorbed, at least in one case, from a fresh infusion
of raw meat. I was also surprised, from what we shall
presently see with respect to the glands round the orifice,
that a fresh solution of urea produced only a moderate effect
on the quadrifids.
336 UTRICULARIA NEGLECTA. LCnar. XVII.
As the quadrifids are developed from papille which at
first closely resemble those on the outside of the bladders
and on the surfaces of the leaves, I may here state that the
two hemispherical cells with which these latter papille are
crowned, and which in their natural state are perfectly
transparent, likewise absorb carbonate and nitrate of am-
monia; for, after an immersion of 23 hrs. in solutions of one
part of both these salts to 437 of water, their primordial
utricles were a little shrunk and of a pale brown tint, and
sometimes finely granular. The same result followed from
the immersion of a whole branch for nearly three days in a
solution of one part of the carbonate to 1750 of water. The
grains of chlorophyll, also, in the cells of the leaves on this
branch became in many places aggregated into little green
masses, which were often connected together by the finest
threads.
On the Absorption of certain Fluids by the Glands on the
Valve and Collar.—The glands round the orifices of bladders
which are still young, or which have been long kept in
moderately pure water, are colourless ; and their primordial
utricles are only slightly or hardly at all granular. But in
the greater number of plants in a state of nature—and we
must remember that they generally grow in very foul water,
—and with plants kept in an aquarium in foul water, most
of the glands were of a pale brownish tint; their primordial
utricles were more or less shrunk, sometimes ruptured, with
their contents often coarsely granular or aggregated into
little masses. That this state of the glands is due to their
having absorbed matter from the surrounding water, I
cannot doubt; for, as we shall immediately see, nearly the
same results follow from their immersion for a few hours in
various solutions. Nor is it probable that this absorption is
useless, seeing that it is almost universal with plants grow-
ing in a state of nature, excepting when the water is remark-
ably pure.
The pedicels of the glands which are situated close to the
slit-like orifice, both those on the valve and on the collar,
are short; whereas the pedicels of the more distant glands
are much elongated and project inwards. The glands are
thus well placed so as to be washed by any fluid coming out
of the bladder through the orifice. The valve fits so closely,
judging from the result of immersing uninjured bladders in
various solutions, that it is doubtful whether any putrid
Cuar. XVIIL] ABSORPTION BY THE GLANDS. oor
fluid habitually passes outwards. But we must remember that
a bladder generally captures several animals; and that each
time a fresh animal enters, a puff of foul water must pass
out and bathe the glands. Moreover, I have repeatedly
found that, by gently pressing bladders which contained air,
minute bubbles were driven out through the orifice; and if
a bladder is laid on blotting paper and gently pressed, water
oozes out. In this latter case, as soon as the pressure is
relaxed, air is drawn in, and the bladder recovers its proper
form. If it is now placed under water and again gently
pressed, minute bubbles issue from the orifice and nowhere
else, showing that the walls of the bladder have not been
ruptured. I mention this because Cohn quotes a statement
by Treviranus, that air cannot be forced out of a bladder
without rupturing it. We may therefore conclude that
whenever air is secreted within a bladder already full of
water, some water will be slowly driven out through the
orifice. Hence I can hardly doubt that the numerous glands
crowded round the orifice are adapted to absorb matter from
the putrid water, which will occasionally escape from
bladders including decayed animals.
In order to test this conclusion, I experimented with various
solutions on the glands. As in the case of the quadrifids, salts of
ammonia were tried, since these are generated by the final decay of
animal matter under water. Unfortunately the glands cannot be
carefully examined whilst attached to the bladders in their entire
state. Their summits, therefore, including the valve, collar, and
antenny, were sliced off, and the condition of the glands observed ;
they were then irrigated, whilst beneath a covering glass, with the
solutions, and after a time re-examined with the same power as before,
aed No. 8 of Hartnack. The following experiments were thus
made.
As a control experiment solutions of one part of white sugar and of
one part of gum to 218 of water were first used, to see whether these
produced any change in the glands. It was also necessary to observe
whether the glands were affected by the summits of the bladders having
been cut off. The summits of four were thus tried; one being exam-
ined after 2 hrs. 30 m., and the other three after 23 hrs.; but there
was no marked change in the glands of any of them. — :
Two summits bearing quite colourless glands were irrigated with a
solution of carbonate of ammonia of the same strength (viz. one part
to 218 of water), and in 5 m. the primordial utricles of most of the
glands were somewhat contracted; they were also thickened in specks
or patches, and had assumed a pale brown tint. When looked at
Z
338 UTRICULARIA NEGLECTA. [Cuar. XVII.
again after 1 hr. 30 m., most of them presented a somewhat different
appearance. A third specimen was treated with a weaker solution
of one part of the carbonate to 437 of water, and after 1 hr. the glands
were pale brown and contained numerous granules.
Four summits were irrigated with a solution of one part of nitrate
of ammonia to 437 of water. One was examined after 15 m., and the
glands seemed affected ; after 1 hr. 10 m. there was a greater change,
and the primordial utricles in most of them were somewhat shrunk,
and included many granules. In the second specimen, the primordial
utricles were considerably shrunk and brownish after 2 hrs. Similar
effects were observed in the two other specimens, but these were not
examined until 21 hrs. had elapsed. The nuclei of many of the
glands apparently had increased in size. Five bladders on a branch,
which had been kept for a long time in moderately pure water, were
cut off and examined, and their glands found very little modified.
The remainder of this branch was placed in the solution of the nitrate,
and after 21 hrs. two bladders were examined, and all their glands
were brownish, with their primordial utricles somewhat shrunk and
finely granular.
The summit of another bladder, the glands of which were in a
beautifully clear condition, was irrigated with a few drops of a mixed
solution of nitrate and phospate of ammonia, each of one part to 437
of water. After 2 hrs. some few of the glands were brownish. After
8 hrs. almost all the oblong glands were brown and much more opaque
than they were before ; their primordial utricles were somewhat shrunk
and contained a little aggregated granular matter. The spherical
glands were still white, but their utricles were broken up into three or
four small hyaline spheres, with an irregularly contracted mass in the
middle of the basal part. These smaller spheres changed their forms
in the course of a few hours, and some of them disappeared. By the
next morning, after 23 hrs. 80 m., they had all disappeared, and the
glands were ‘brown; their utricles now formed a globular shrunken
mass in the middle. The utricles of the oblong glands had shrunk
very little, but their contents were somewhat aggregated. Lastly, the
summit of a bladder which had been previously irrigated for 21 hrs.
with a solution of one part of sugar to 218 of water without being
affected, was treated with the above mixed solution; and after 8 hrs.
30 m. all the glands became brown, with their primordial utricles
slightly shrunk.
Four summits were irrigated with a putrid infusion of raw meat.
No change in the glands was observable for some hours, but after
24 hrs. most of them had become brownish, and more opaque and
granular than they were before. In these specimens, as in those
irrigated with the salts of ammonia, the nuclei seemed to have
increased both in size and solidity, but they were not measured. Five
summits were also irrigated with a fresh infusion of raw meat; three
of these were not at all affected in 24 hrs., but the glands of the other
two had perhaps become more granular, One of the specimens which
Cmar. XVII.] ABSORPTION BY THE GLANDS. 339
was not affected was then irrigated with the mixed solution of the
nitrate and phosphate of ammonia, and after only 25 m. the glands
contained from four or five toa dozen granules, After six additional
hours their primordial utricles were greatly shrunk.
The summit of a bladder was examined, and all the glands found
colourless, with their primordial utricles not at all shrunk ; yet many
of the oblong glands contained granules just resolvable with No. 8 of
Hartnack. It was then irrigated with a few drops of a solution
of one part of urea to 218 of water.’ After 2 hrs. 25 m. the
spherical glands were still colourless; whilst the oblong and two-armed
ones were of a brownish tint, and their primordial utricles much
shrunk, some containing distinctly visible granules. After 9 hrs.
some of the spherical glands were brownish, and the oblong glands
were still more changed, but they contained fewer separate granules ;
their nuclei, on the other hand, appeared larger, as if they had absorbed
the granules. After 23 hrs. all the glands were brown, their pri-
mordial utricles greatly shrunk, and in many cases ruptured.
A bladder was now experimented on, which was already somewhat
affected by the surrounding water; for the spherical glands, though
colourless, had their primordial utricles slightly shrunk; and the
oblong glands were brownish, with their utricles much, but irregularly,
shrunk. ‘The summit was treated with the solution of urea, but was
little affected by it in 9 hrs.; nevertheless, after 23 hrs. the spherical
glands were brown, with their utricles more shrunk; several of the
other glands were still browner, with their utricles contracted into
irregular little masses.
Two other summits, with their glands colourless and their utricles
not shrunk, were treated with the same solution of urea. After 5 hrs.
many of the glands presented a shade of brown, with their utricles
slightly shrunk. After 20 hrs. 40 m. some few of them were quite
brown, and contained irregularly aggregated masses; others were still
colourless, though their utricles were shrunk; but the greater number
were not much affected. This was a good instance of how unequally
the glands on the same bladder are sometimes affected, as likewise
often occurs with plants growing in foul water. Two other summits
were treated with a solution which had been kept during several days
in a warm room, and their glands were not at all affected when
examined after 21 hours. ;
A weaker solution of one part of urea to 437 of water was next tried
on six summits, all carefully examined before being irrigated. The
first was re-examined after 8 hrs. 30 m., and the glands, including the
spherical ones, were brown; many of the oblong glands having their
primordial utricles much shrunk and including granules. The second
summit, before being irrigated, had been somewhat affected by the
Surrounding water, for the spherical glands were not quite uniform in
appearance; and a few of the oblong ones were brown, with their
utricles shrunk. Of the oblong glands, those which were before colour-
less, became brown in 3 hrs, 12 m. after irrigation, with their utricles
Z 2
340 UTRICULARIA NEGLECTA. [Cuar. XVII.
slightly shrunk. The spherical glands did not become brown, but their
contents seemed changed in appearance, and after 23 hrs. still more
changed and granular. Most of the oblong glands were now dark
brown, but their utricles were not greatly shrunk. The four other
specimens were examined after 3 hrs. 80 m., after 4 hrs. and 9 hrs. ;
a brief account of their condition will be sufficient. The spherical glands
were not brown, but some of them were finely granular. Many of the
oblong glands were brown; and these, as well as others which still
remained colourless, had their utricles more or less shrunk, some of
them including small aggregated masses of matter.
Summary of the Observations on Absorption.—-From the facts
now given there can be no doubt that the variously shaped
glands on the valve and round the collar have the power of
absorbing matter from weak solutions of certain salts of
ammonia and urea, and from a putrid infusion of raw meat.
Prof. Cohn believes that they secrete slimy matter; but I
was not able to perceive any trace of such action, excepting
that, after immersion in alcohol, extremely fine lines could
sometimes be seen radiating from their surfaces. The glands
are variously affected by absorption: they often become of a
brown colour; sometimes they contain very fine granules, or
moderately sized grains, or irregularly aggregated little
masses; sometimes the nuclei appear to have increased in
size; the primordial utricles are generally more or less
shrunk and sometimes ruptured. Exactly the same changes
may be observed in the glands of plants growing and
flourishing in foul water. The spherical glands are generally
affected rather differently from the oblong and two-armed
ones. The former do not so commonly become brown, and
are acted on more slowly. We may therefore infer that
they differ somewhat in their natural functions.
It is remarkable how unequally the glands on the bladders
on the same branch, and even the glands of the same kind
on the same bladder, are affected by the foul water in which
the plants have grown, and by the solutions which were
employed. In the former case I presume that this is due
either to little currents bringing matter to some glands and
not to others, or to unknown differences in their constitution.
When the glands on the same bladder are differently affected
‘by a solution, we may suspect that some of them had
previously absorbed a small amount of matter from the
water. However this may be, we have seen that the glands
ey eee
Cuar. XVII.] SUMMARY ON ABSORPTION. 341
on the same leaf of Drosera are sometimes very unequally
affected, more especially when exposed to certain vapours.
If glands which have already become brown, with their
primordial utricles shrunk, are irrigated with one of the
effective solutions, they are not acted on, or only slightly and
slowly. If, however, a gland contains merely a few coarse
granules, this does not prevent a solution from acting. I
have never seen any appearance making it probable that
glands which have been strongly affected by absorbing matter
of any kind are capable of recovering their pristine, colour-
less, and homogeneous condition, and of regaining the power of
absorbing.
From the nature of the solutions which were tried, I
presume that nitrogen is absorbed by the glands; but the
modified, brownish, more or less shrunk, and aggregated
contents of the oblong glands were never seen by me or by
my son to undergo those spontaneous changes of form
characteristic of protoplasm. On the other hand, the contents
of the larger spherical glands often separated into small
hyaline globules or irregularly shaped masses, which changed
their forms very slowly and ultimately coalesced, forming a
central shrunken mass. Whatever may be the nature of the
contents of the several kinds of glands, after they have been
acted on by foul water or by one of the nitrogenous solutions,
it is probable that the matter thus generated is of service to
the plant, and is ultimately transferred to other parts.
The glands apparently absorb more quickly than do the
quadrifid and bifid processes; and on the view above main-
tained, namely that they absorb matter from putrid water
occasionally emitted from the bladders, they ought to act
more quickly than the processes; as these latter remain in
permanent contact with captured and decaying animals.
Finally, the conclusion to which we are led by the fore-
going experiments and observations is that the bladders have
no power of digesting animal matter, though it appears that
the quadrifids are somewhat affected by a fresh infusion of
raw meat. It is certain that the processes within the
bladders, and the glands outside, absorb matter from salts of
ammonia, from a putrid infusion of raw meat, and from urea,
Lhe glands apparently are acted on more strongly by a
solution of urea, and less strongly by an infusion of raw
meat, than are the processes. The case of urea is particularly
interesting, because we have seen that it produces no effect
342 UTRICULARIA NEGLECTA. (Cuap. XVII.
on Drosera, the leaves of which are adapted to digest fresh
animal matter. But the most important fact of all is, that
in the present and following species the quadrifid and bifid
processes of bladders containing decayed animals generally
include little masses of spontaneously moving protoplasm ;
whilst such masses are never seen in perfectly clean bladders.
Development of the Bladders.—My son and I spent much
time over this subject with small success. Our observations
apply to the present species and to Utricularia vulgaris, but
were made chiefly on the latter, as the bladders are twice as
large as those of Utricularia neglecta. In the early part of
autumn the stems terminate in large buds, which fall off and
lie dormant during the winter at the bottom. The young
leaves forming these buds bear bladders
in various stages of early development.
When the bladders of Utricularia vul-
garis are about +1, inch (+254 mm.)
in diameter (or 5), in the case of
Utricularia neglecta), they are circular
in outline, with a narrow, almost
closed, transverse orifice, leading into
a hollow filled with water; but the
bladders are hollow when much under
14y of an inch in diameter. The
orifices face inwards or towards the
Fic, 23. axis of the plant. At this early age
(Utricularia vulgaris.) the bladders are flattened in the plane
Longitudinal section through in Which the orifice lies, and therefore
in length, With te oie we at right angles to that of the mature
widely open, bladders. They are covered exteriorly
with papillz of different sizes, many
of which have an elliptical outline. A bundle of vessels,
formed of simple elongated cells, runs up the short footstalk,
and divides at the base of the bladder. One branch extends
up the middle of the dorsal surface, and the other up the
middle of the ventral surface. In full-grown bladders the
ventral bundle divides close beneath the collar, and the two
branches run on each side to near where the corners of the
valve unite with the collar; but these branches could not be
seen in very young bladders.
The accompanying figure (fig. 23) shows a section, which
happened to be strictly medial, through the footstalk and
between ihe nascent antenne of a bladder of Utricularia
Cuar. XVII.] DEVELOPMENT OF THE BLADDERS. 343
vulgaris, +1, inch in diameter. The specimen was soft, and
the young valve became separated from the collar toa greater
degree than is natural, and is thus represented. We here
clearly see that the valve and collar are infolded prolon-
gations of the wall of the bladder. Even at this early age,
glands could be detected on the valve. The state of the
quadrifid processes will presently be described. The antenne
at this period consist of minute cellular projections (not
shown in the above figure, as they do not lie in the medial
plane), which soon bear incipient bristles. In five instances
the young antennæ were not of quite equal length; and this
Fic. 24.
(Utricularia vulgaris.)
Young leaf from a winter bud, showing on the left side a bladder in its earliest stage
of development.
fact is intelligible if I am right in believing that they
represent two divisions of the leaf, rising from the end of the
bladder ; for, with the true leaves, whilst very young, the
divisions are never, as far as I have seen, strictly opposite;
they must therefore be developed one after the other, and so
1t would be with the two antenne.
At a much earlier age, when the half formed bladders are
only ly inch (+0846 mm.) in diameter or a little more, they
present a totally different appearance. One is represented
on the left side of the accompanying drawing (fig. 24). The
young leaves at this age have broad flattened segments, with
344 UTRICULARIA NEGLECTA. ([Cuar, XVII.
their future divisions represented by prominences, one of
which is shown on the right side. Now, in a large number
of specimens examined by my son, the young bladders
appeared as if formed by the oblique folding over of the apex
and of one margin with a prominence, against the opposite
margin. The circular hollow between the infolded apex and
infolded prominence apparently contracts into the narrow
orifice, wherein the valve and collar will be developed; the
bladder itself being formed by the confluence of the opposed
margins of the rest of the leaf. But strong objections may
be urged against this view, for we must in this case suppose
that the valve and collar are developed as symmetrically from
the sides of the apex and prominence. Moreover, the bundles
of vascular tissue have to be formed in lines quite irre-
spective of the original form of the leaf. Until gradations
can be shown to exist between this the earliest state and a
young yet perfect bladder, the case must be left doubtful.
As the quadrifid and bifid processes offer one of the
greatest peculiarities in the genus, I carefully observed their
development in Utricularia neglecta. In bladders about 44>
of an inch in diameter, the inner surface is studded with
papillx, rising from small cells at the junctions of the larger
ones. ‘These papille consist of a delicate conical protuber-
ance, which narrows into a very short footstaik, surmounted
by two minute cells. They thus occupy the same relative
position, and closely resemble, except in being smaller and
rather more prominent, the papille on the cutside of the
bladders, and on the surfaces of the leaves. The two terminal
cells of the papillx first become much elongated in a line
parallel to the inner surface of the bladder. Next, each is
divided by a longitudinal partition. Soon the two half-cells
thus formed separate from one another; and we now have
four cells or an incipient quadrifid process. As there is not
space for the two new cells to increase in breadth in their
original plane, the one slides partly under the other. Their
manner of growth now changes, and their outer sides,
instead of their apices, continue to grow. The two lower
cells, which have slid partly beneath the two upper ones,
form the longer and more upright pair of processes: whilst
the two upper cells form the shorter and more horizontal
pair; the four together forming a perfect quadrifid. A trace
of the primary division between the two cells on the
summits of the papille can still be seen between the bases
Cmar. XVIL] UTRICULARIA MINOR. 845
of the longer processes. The development of the quadrifids
is very liable to be arrested. I have seen a bladder y of
an inch in length including only primordial papillae; and
another bladder, about half its full size, with the quadrifids
in an early stage of development.
As far as I could make out, the bifid processes are de-
veloped in the same manner as the quadrifids, excepting that
the two primary terminal cells never become divided, and
only increase in length. The glands on the valve and collar
appear at so early an age that I could not trace their develop-
ment; but we may reasonably suspect that they are developed
from papille like those on the outside of the bladder, but
with their terminal cells not divided into two. The two
segments forming the pedicels of the glands probably answer
to the conical protuberance and short footstalk of the quadri-
fid and bifid processes. I am strengthened in the belief that
the glands are developed from papille like those on the
outside of the bladders, from the fact that in Utricularia
amethystina the glands extend along the whole ventral surface
of the bladder close to the footstalk.
UTRICULARIA VULGARIS.
Living plants from Yorkshire were sent me by Dr. Hooker. This
Species differs from the last in the stems and leaves being thicker or
coarser; their divisions form a more acute angle with one another;
the notches on the leaves bear three or four short bristles instead of
one ; aud the bladders are twice as large, or about 4 of an inch (5°08
mm.) in diameter. In all essential respects the bladders resemble those
of Utricularia neglecta, but the sides of the peristome are perhaps a
little more prominent, and always bear, as far as I have seen, seven or
eight long multicellular bristles. There are eleven long bristles on
each antenna, the terminal pair being included. Five bladders, con-
taining prey of some kind, were examined. ‘The first included five
Cypris, a large copepod and a Diaptomus; the second, four Cypris;
the third, a single rather large crustacean; the fourth, six crustaceans ;
and the fifth, ten. My son examined the quadrifid processes in a
bladder containing the remains of two crustaceans, and found some of
them full of spherical or irregularly shaped masses of matter, which
were observed to move and to coalesce. These masses therefore con-
sisted of protoplasm.
UTRICULARIA MINOR.
This rare species was sent me in a living state from Cheshire, through
the kindness of Mr. John Price. The leaves and bladders are much
346 UTRICULARIA CLANDESTINA. [OmiP. XVII.
smaller than those of Utricularia neglecta. The leaves bear fewer
and shorter bristles, and the bladders are more globular. ‘The antenna,
instead of projecting in front of the bladders, are curled under the
valve, and are armed with twelve or fourteen extremely long multi-
cellular bristles, generally arranged in pairs. These, with seven or
eight long bristles on both sides of the peristome, form a sort of net
over the valve, which would tend to prevent all animals, excepting
very small ones, entering the bladder. ‘The valve and collar have the
same essential structure as in the two previous species; but the glands
are not quite so numerous; the oblong ones are rather more elongated,
whilst the two-armed ones are rather less elongated. The four bristles
which project obliquely from the lower edge of the valve are short.
Their shortness, compared with those on the valves of the foregoing
species, is intelligible if my view is
correct that they serve to prevent too
large animals forcing an entrance
through the valve, thus injuring it;
for the valve is already protected to a
certain extent by the incurved antenne,
together with the lateral bristles. ‘The
bifid processes are like those in the
previous species; but the quadrifids
differ in the four arms (fig. 25) being
ig 6s directed to the same side; the two
ee longer ones being central, and the two
shorter ones on the outside.
The plants were collected in the
middle of July; and the contents of
five bladders, which from their opacity seemed full of prey were
examined. ‘lhe first contained no less than twenty-four minute fresh-
water crustaceans, most of them consisting of empty shells, or includ-
ing only a few drops of red oily matter; the second contained twenty ;
the third, fifteen; the fourth, ten, some of them being rather larger
than usual; and the fifth, which seemed stuffed quite full, contained
only seven, but five of these were of unusually large size. The prey,
therefore, judging from these five bladders, consists exclusively of
fresh-water crustaceans, most of which appeared to be distinct species
from those found in the bladders of the two former species. In one
bladder the quadrifids in contact with a decaying mass contained
numerous spheres of granular matter, which slowly changed their
forms and positions.
(Uiricularia minor.)
Quadrifid process; greatly enlarged.
UTRICULARIA CLANDESTINA.
This North American species, which is aquatic like the three fore-
going ones, has been described by Mrs. Treat, of New Jersey, whose
excellent observations have already been largely quoted. I have not
as yet seen any full description by her of the structure of the bladder,
Cuar. XVII] UTRICULARIA CLANDESTINA. 347
but it appears to be lined with quadrifid processes. A vast number
of captured animals were found within the bladders; some being
crustaceans, but the greater number delicate, elongated larvae, I sup-
pose of Culicide. On some stems, “ fully nine out of every ten bladders
contained these larve or their remains.” The larve “ showed signs
of life from twenty-four to thirty-six hours after being imprisoned,”
and then perished.
348 UTRICULARIA MONTANA. [Cuar. XVIII.
CHAPTER XVIII.
UTRICULARIA (continued).
Utricularia montana—Description of the bladders on the subterranean
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 Utricu-
laria—Poly pompholyx—Genlisea, different nature of the trap for capturing
prey—{Sarracenia]—Diversified methods by which plants are nourished.
UTRICULARIA MoNTANA.—This species inhabits the tropical
parts of South America, and is said to be epiphytic; but,
judging from the state of the roots (rhizomes) of some dried
specimens from the herbarium at Kew, it likewise lives in
earth, probably in crevices of rocks. In English hot-houses
it is grown in peaty soil. Lady Dorothy Nevill was so kind
as to give me a fine plant, and I received another from Dr.
Hooker. The leaves are entire, instead of being much divided,
as in the foregoing aquatic species. They are elongated,
about 14 inch in breadth, and furnished with a distinct foot-
stalk, The plant produces numerous colourless rhizomes,* as
thin as threads, which bear minute bladders, and occasionally
swell into tubers, as will hereafter be described. These
rhizomes appear exactly like roots, but occasionally throw up
* [Hovelacque, in the ‘Comptes mountains of Dominica. Utricularia
Rendus, vols. cv. p. 692, and cvi. p.
310, has discussed the nature of the
underground runners; he considers
them to be morphologically leaves, in
opposition to Schenk (Pringsheim’s
‘Jahrbiicher,’ vol. xviii. p. 218),
who rgards them as rhizomes.
Schimper, in his paper on the West
Indian Epiphytes (‘ Bot. Central-
blatt,’ vol. xvii. p. 257), takes a
view similar to Schenk’s as to stolons
or runners in the new species, U.
Schimperi, discovered by him in the
cornuta, described by Schimper in
the ‘Bot. Zeitung,’ 1882, p. 241,
has similar underground runners,
as well as aerial organs usually
described as leaves. He discusses
the possibility of a morphological
identity between the runners and
the “leaves” from a point of view
opposite to that of Hovelacque’s—
namely, that the “leaves” as well
as the stolons may be morphologically
stems,—F. D,]
Onar: XVIII] STRUCTURE OF THE BLADDERS. 549
green shoots. They penetrate the earth sometimes to the
depth of more than 2 inches: but when the plant grows as
an epiphyte, they must creep amidst the mosses. roots,
decayed bark, &c., with which
the trees of these countries are
thickly covered.
As the bladders are attached
to the rhizomes, they are neces-
sarily subterranean. They are
produced in extraordinary num-
bers. One of my plants, though
young, must have borne several
hundreds; for a single branch
out of an entangled mass had
thirty-two, and another branch,
about 2 inches in length (but,
with its end and one side
branch broken off), had seventy-
three bladders.* The bladders
are compressed and rounded, with
the ventral surface, or that be-
tween the summit of the long
delicate footstalk and valve, ex-
tremely short (fig. 27). They
are colourless and almost as transparent as glass, so that they
appear smaller than they really are, the largest being under
the s> of an inch (1°27 mm.) in its longer diameter. They
are formed of rather large angular cells, at the junctions of
which oblong papille project, corresponding with those on
the surfaces of the bladders of the previous species. Similar
papille abound on the rhizomes, and even on the entire leaves,
but they are rather broader on the latter. Vessels, marked
with parallel bars instead of by a spiral line, run up the
footstalks, and just enter the bases of the bladders; but they
Frc. 26.
(Utricularia montana.)
Rhizome swollen into a tuber; the
branches bearing minute bladders; of
natural size.
* Prof. Oliver has figured a plant that the bladders on the rhizomes of
of Utricularia Jamesoniana (‘ Proc.
Linn. Soc.’ vol. iv. p- 169) having
entire leaves and rhizomes, like those
of our present species; but the mar-
gins of the terminal halves of some
of the leaves are converted into
bladders, This fact clearly indicates
the present and following species are
modified segments of the leaf; and
they are thus brought into accordance
with the bladders attached to the
divided and floating leaves of the
aquatic species.
350 UTRICULARIA MONTANA. [Cmar. XVIII.
do not bifurcate and extend up the dorsal and ventral
surfaces, as in the previous species.
The antennæ are of moderate length, and taper to a fine
point; they differ conspicuously from those before described,
in not being armed with bristles. Their bases are so
abruptly curved that their tips generally rest one on each
side of the middle of the bladder, but sometimes near the
margin. Their curved bases thus form a roof over the cavity
in which the valve lies; but there is always left on each
side a little circular passage into the cavity, as may be seen
Fig. 27.
(Utricularia montana.)
Bladder; about 27 times enlarged.
in the drawing, as well as a narrow passage between the
bases of the two antennz. As the bladders are subterranean,
had it not been for the roof, the cavity in which the valve
lies would have been liable to be blocked up with earth and
rubbish; so that the curvature of the antenns is a service-
able character. There are no bristles on the outside of the
collar or peristome, as in the foregoing species.
The valve is small and steeply inclined, with its free pos-
terior edge abutting against a semicircular, deeply depending
Cuap. XVIII.] CAPTURED ANIMALS. 351
collar. Itis moderately transparent, and bears two pairs of
short stiff bristles, in the same position as in the other
species. The presence of these four bristles, in contrast with
the absence of those on the antennæ and collar, indicates that
they are of functional importance, namely, as I believe, to
prevent too large animals forcing an entrance through the
valve. The many glands of diverse shapes attached to the
valve and round the collar in the previous species are here
absent, with the exception of about a dozen of the two-armed
or transversely elongated kind, which are seated near the
borders of the valve, and are mounted on very short foot-
stalks. These glands are only the şov of an inch (019
mm.,) in length; though so small, they act as absorbents.
The collar is thick, stiff, and almost semicircular ; it is formed
of the same peculiar brownish tissue as in the former species.
The bladders are filled with water, and sometimes include
bubbles of air. They bear internally rather short, thick,
quadrifid processes arranged in approximately concentric
Fig. 28.
(Utricularia montana.)
One of the quadrifid processes; much enlarged.
rows. The two pairs of arms of which they are formed
differ only a little in length, and stand in a peculiar position
(fig. 28); the two longer ones forming one line, and the
two shorter ones another parallel line. Each arm includes a
small spherical mass of brownish matter, which, when crushed,
breaks into angular pieces. I have no doubt that these
spheres are nuclei, for closely similar ones are present in the
cells forming the walls of the bladders. Bifid processes,
having rather short oval arms, arise in the usual position on
the inner side of the collar.
These bladders, therefore, resemble in all essential respects
the larger ones of the foregoing species. They differ chiefly
in the absence of the numerous glands on the valve and
round the collar, a few minute ones of one kind alone being
present on the valve. They differ more conspicuously in
the absence of the long bristles on the antennæ and on the
outside of the collar. ‘The presence of these bristles in the
352 UTRICULARIA MONTANA. [Cuar. XVIII.
previously mentioned species probably relates to the capture
of aquatic animals.
It seemed to me an interesting question whether the
minute bladders of Utricularia montana served, as in the
previous species, to capture animals living in the earth, or
in the dense vegetation covering the trees on which this
species is epiphytic; for in this case we should have a new
sub-class of carnivorous plants, namely, subterranean feeders.
Many bladders, therefore, were examined, with the following
results :—
(1) A small bladder, less than {1 of an inch (*847 mm.) in diameter
contained a minute mass of brown, much decayed matter; and in this,
a tarsus with four or five joints, terminating in a double hook, was
clearly distinguished under the microscope. I suspect that it was a
remnant of one of the Thysanoura. The quadrifids in contact with
this decayed remnant contained either small masses of translucent,
yellowish matter, generally more or less globular, or fine granules. In
distant parts of the same bladder, the processes were transparent and
quite empty, with the exception of their solid nuclei. My son made
at short intervals of time sketches of one of the above aggregated
masses, and found that they continually and completely changed their
forms; sometimes separating from one another and again coalescing.
Evidently protoplasm had been generated by the absorption of some
element from the decaying animal matter.
(2) Another bladder included a still smaller speck of decayed brown
matter, and the adjoining quadrifids contained aggregated matter,
exactly as in the last case.
(3) A third bladder included a larger organism, which was so much
decayed that I could only make out that it was spinose or hairy. The
quadrifids in this case were not much affected, excepting that the
nuclei in the several arms differed much in size ; some of them contain-
ing two masses having a similar appearance.
(4) A fourth bladder contained an articulate organism, for I distinctly
saw the remnant of a limb, terminating in a hook. The quadrifids
were not examined.
(5) A fifth included much decayed matter apparently of some
animal, but with no recognisable features. The quadrifids in contact
contained numerous spheres of protoplasm.
(6) Some few bladders on the plant which I received from Kew
were examined; and in one, there was a worm-shaped animal very
little decayed, with a distinct remnant of a similar one greatly decayed.
Several of the arms of the processes in contact with these remains
contained two spherical masses, like the single solid nucleus which is
properly found in each arm. In another bladder there was a minute
grain of quartz, reminding me of two similar cases with Utricularia
neglecta,
ameman
3
CHAP. XVIL] ABSORPTION. Soe
©
As it appeared probable that this plant would capture a greater
number of animals in its native country than under culture, I obtained
permission to remove small portions of the rhizomes from dried speci-
mens in the herbarium at Kew. I did not at first find out that it was
advisable to soak the rhizomes for two or three days, and that it was
necessary to open the bladders and spread out their contents on glass:
as from their state of decay and from having been dried and pressed,
their nature could not otherwise be well distinguished. Several
bladders on a plant which had grown in black earth in New Granada
were first examined; and four of these included remnants of animals.
The first contained a hairy Acarus, so much decayed that nothing was
left except its transparent coat; also a yellow chitinous head of some
animal with an internal fork, to which the cesophagus was suspended,
but I could see no mandibles; also the double hook of the tarsus of
some animal; also an elongated greatly decayed animal; and lastly, a
curious flask-shaped organism, having the walls formed of rounded cells.
Professor Claus has looked at this latter organism, and thinks that it
is the shell of a rhizopod, probably one of the Arcellidæ. In this
bladder, as well as in several others, there were some unicellular
Alge, and one multicellular Alga, which no doubt had lived as
intruders.
A second bladder contained an Acarus much less decayed than the
former one, with its eight legs preserved; as well as remnants ot
several other articulate animals. A third bladder contained the end
of the abdomen with the two hinder limbs of an Acarus, as I believe.
A fourth contained remnants of a distinctly articulated bristly animal,
and of several other organisms, as well as much dark brown organic
inatter, the nature of which could not be made out. : ;
Some bladders from a plant, which had lived as an epiphyte in
Trinidad, in the West Indies, were next examined, but not so carefully
as the others; nor had they been soaked long enough. Four of them
contained much brown, translucent granular matter, apparently organic,
with no distinguishable parts. The quadrifids in two were brownish,
with their contents granular; and it was evident that they had
absorbed matter. In a fifth bladder there was a flask-shaped organism,
like that above mentioned. A sixth contained a very long, much
decayed, worm-shaped animal. Lastly, a seventh bladder contained
an organism, but vf what nature could not be distinguished.
Only one experiment was tried on the quadrifid processes
and glands with reference to their power of absorption. A
bladder was punctured and left for 24 hrs. in a solution of
one part of urea to 437 of water, and the quadrifid and bifid
processes were found much affected. In some arms there
was only a single symmetrical globular mass, larger than
the proper nucleus, and consisting of yellowish matter,
generally translucent but sometimes granular ; Pa others
k
354 UTRICULARIA MONTANA. [Cuar. XVIII.
there were two masses of different sizes, one large and the
other small; and in others there were irregularly shaped
globules; so that it appeared as if the limpid contents of
the processes, owing to the absorption of matter from the
solution, had become aggregated sometimes round the
nucleus, and sometimes into separate masses; and that
these then tended to coalesce. The primordial utricle or
protoplasm lining the processes was also thickened here and
there into irregular and variously shaped specks of yellowish
translucent matter, as occurred in the case of Utricularia
neglecta under similar treatment. These specks apparently
did not change their forms.
The minute two-armed glands on the valve were also
affected by the solution; for they now contained several,
sometimes as many as six or eight, almost spherical masses
of translucent matter, tinged with yellow, which slowly
changed their forms and positions. Such masses were never
observed in these glands in their ordinary state. We may
therefore infer that they serve for absorption. Whenever a
little water is expelled from a bladder containing animal
remains (by the means formerly specified, more especially
by the generation of bubbles of air), it will fill the cavity
in which the valve lies; and thus the glands will be able
to utilise decayed matter which otherwise would have been
wasted.
Finally, as numerous minute animals are captured by this
plant in its native country and when cultivated, there can
be no doubt that the bladders, though so small, are far from
being in a rudimentary condition; on the contrary, they
are highly efficient traps. Nor can there be any doubt that
matter is absorbed from the decayed prey by the quadrifid
and bifid processes, and that protoplasm is thus generated.
What tempts animals of such diverse kinds to enter the
cavity beneath the bowed antenne, and then force their
way through the little slit-like orifice between the valve
and collar into the bladders filled with water, I cannot
conjecture.
Tubers.—These organs, one of which is represented in 4
previous figure (fig. 26) of the natural size, deserve a few
remarks. Twenty were found on the rhizomes of a single
plant, but they cannot be strictly counted ; for, besides the
twenty, there were all possible gradations between a short
length of a rhizome just perceptibly swollen and one 80
Cuar. XVIIL] RESERVOIRS FOR WATER. 899
much swollen that it might be doubtfully called a tuber.
When well developed, they are oval and symmetrical, more
so than appears in the figure. The largest which I saw was
1 inch (25-4 mm.) in length and +45 inch (11°43 mm.) in
breadth. They commonly lie near the surface, but some
are buried at the depth of 2 inches. The buried ones are
dirty white, but those partly exposed to the light become
greenish from the development of chlorophyll in their
superficial cells. They terminate in a rhizome, but this
sometimes decays and drops off. They do not contain any
air, and they sink in water; their surfaces are covered with
the usual papillæ. The bundle of vessels which runs up
each rhizome, as soon as it enters the tuber, separates into
three distinct bundles, which reunite at the opposite end.
A rather thick slice of a tuber is almost as transparent as
glass, and is seen to consist of large angular cells, full of
water and not containing starch or any other solid matter.
Some slices were left in alcohol for several days, but only a
few extremely minute granules of matter were precipitated
on the walls of the cells; and these were much smaller and
fewer than those precipitated on the cell-walls of the
rhizomes and bladders. We may therefore conclude that
the tubers do not serve as reservoirs for food, but for water
during the dry season to which the plant is probably exposed.
The many little bladders filled with water would aid towards
the same end.
To test the correctness of this view, a small plant, growing
in light peaty earth in a pot (only 45 by 44 inches outside
measure) was copiously watered, and then kept without a
drop of water in the hothouse. Two of the upper tubers were
beforehand uncovered and measured, and then loosely covered
up again. In a fortnight’s time the earth in the pot appeared
extremely dry ; but not until the thirty-fifth day were the
leaves in the least affected; they then became slightly
reflexed, though still soft and green. This plant, which
bore only ten tubers, would no doubt have resisted the
drought for even a longer time, had I not previously removed
three of the tubers and cut off several long rhizomes. When,
on the thirty-fifth day, the earth in the pot was turned out,
it appeared as dry as the dust on the road. All the tubers
had their surfaces much wrinkled, instead of being smooth
and tense. They had all shrunk, but I cannot say accurately
ow much ; for as they were at first EE ed lem I
aA
356 UTRICULARIA MONTANA. (Cuar. XVIIL
measured only their length and thickness; but they con-
tracted in a transverse line much more in one direction than
in another, so as to become greatly flattened. One of the
two tubers which had been measured was now three-fourths
of its original length, and two-thirds of its original thickness
in the direction in which it had been measured, but in
another direction only one-third of its former thickness.
The other tuber was one-fourth shorter, one-eighth less thick
in the direction in which it had been measured, and only
half as thick in another direction.
A slice was cut from one of these shrivelled tubers and
examined. The cells still contained much water and no air,
but they were more rounded or less angular than before, and
their walls not nearly so straight; it was therefore clear
that the cells had contracted. The tubers, as long as
they remain alive, have a strong attraction for water ;
the shrivelled one, from which a slice had been cut, was
left in water for 22 hrs. 30 m., and its surface became as
smooth and tense as it originally was. On the other hand,
a shrivelled tuber, which by some accident had been separated
from its rhizome, and which appeared dead, did not swell in
the least, though left for several days in water.
With many kinds of plants, tubers, bulbs, &c., no doubt
serve in part as reservoirs for water, but I know of no case,
besides the present one, of such organs having been developed
solely for this purpose. Prof. Oliver informs me that two or
three other species of Utricularia are provided with these
appendages; and the group containing them has in conse-
quence received the name of orchidioides. All the other
species of Utricularia, as well as of certain closely related
genera, are either aquatic or marsh plants; therefore, on the
principle of nearly allied plants generally having a similar
constitution, a never-failing supply of water would probably
be of great importance to our present species. We can thus
understand the meaning of the development of its tubers,
and of their number on the same plant, amounting in one
instance to at least twenty.
UTRICULARIA NELUMBIFOLIA, AMETHYSTINA, GRIFFITHH,
CERULEA, ORBICULATA, MULTICAULIS [CORNUTA].
As I wished to ascertain whether the bladders on ithe
rhizomes of other species of Utricularia, and of the species
Cuar. XVIII.) UTRICULARIA AMETHYSTINA. 3857
of certain closely allied genera, had the same essential
structure as those of Utricularia montana, and whether they
captured prey, I asked Prof. Oliver to send me fragments
from the herbarium at Kew. He kindly selected some of
the most distinct forms, having entire leaves, and believed
to inhabit marshy ground or water. My son, Francis
Darwin, examined them, and has given me the following
observations; but it should be borne in mind that it is
extremely difficult to make out the structure of such minute
and delicate objects after they have been dried and pressed.*
Utricularia nelumbifolia (Organ Mountains, Brazil).—The
habitat of this species is remarkable. According to its
discoverer, Mr. Gardner,f it is aquatic, but “is only to be
found growing in the water which collects in the bottom
of the leaves of a large Tillandsia, that inhabits abundantly
an arid rocky part of the mountain, at an elevation of about
5000 feet above the level of the sea. Besides the ordinary
method by seed, it propagates itself by runners, which it
throws out from the base of the flower-stem; this runner is
always found directing itself towards the nearest Tillandsia,
when it inserts its point into the water and gives origin to
a new plant, which in its turn sends out another shoot. In
this manner I have seen not less than six plants united.”
The bladders resemble those of Utricularia montana in all
essential respects, even to the presence of a few minute two-
armed glands on the valve. Within one bladder there was
the remnant of the abdomen of some larva or crustacean of
large size, having a brush of long sharp bristles at the apex.
Other bladders included fragments of articulate animals, and
many of them contained broken pieces of a curious organism,
the nature of which was not recognised by any one to whom
it was shown. :
Utricularia amethystina (Guiana).—This species has small
entire leaves, and is apparently a marsh plant ; but it must
grow in places where crustaceans exist, for there were two
small species within one of the bladders. The bladders are
nearly of the same shape as those of Utricularia montana, and
* Prof. Oliver has given (‘ Proc. appear to have paid particular atten-
Linn. Soc.’ vol. iv. p. 169) figures of tion to these organs. Í a
the bladders of two South American t ‘Travels in the Interior of Brazil,
species, namely, Utricularia Jameso- 1836-41; p. 527.
niana and peltata; but he does not
358 UTRICULARIA ORLICULATA. ([Cuar. XVIII.
are covered outside with the usual papille ; but they differ
remarkably in the antenne being reduced to two short
points, united by a membrane hollowed out in the middle.
This membrane is covered with innumerable oblong glands
supported on long footstalks ; most of which are arranged in
two rows converging towards the valve. Some, however,
are seated on the margins of the membrane; and the short
ventral surface of the bladder, between the petiole and
valve, is thickly covered with glands. Most of the heads
had failen off, and the footstalks alone remained; so that
the ventral surface and the orifice, when viewed under a
weak power, appeared as if clothed with fine bristles. The
valve is narrow, and bears a few almost sessile glands. The
collar against which the edge shuts is yellowish, and presents
the usual structure. From the large number of glands on
the ventral surface and round the orifice, it is probable that
this species lives in very foul water, from which it absorbs
matter, as well as from its captured and decaying prey.
Utricularia grifithii (Malay and Borneo).—The bladders
are transparent and minute; one which was measured being
only ;25, of an inch (+711 mm.) in diameter. The antenne
are of moderate length, and project straight forward; they
are united fur a short space at their bases by a membrane ;
and they bear a moderate number of bristles or hairs, not
simple as heretofore, but surmounted by glands. ‘he
bladders also differ remarkably from those of the previous
species, as within there are no quadrifid, only bifid processes.
In one bladder there was a minute aquatic larva; in another
the remains of some articulate animal; and in most of them
grains of sand.
Utricularia cærulea (India).—The bladders resemble those
of the last species, both in the general character of the
antenne and in the processes within being exclusively bifid.
They contained remnants of entomostracan crustaceans.
Utricularia orbiculata (India).—The orbicular leaves and
the stems bearing the bladders apparently float in water.
The bladders do not differ much from those of the two last
species. The antenne, which are united for a short distance
at their bases, bear on their outer surfaces and summits
numerous, long, multicellular hairs, surmounted by glands.
The processes within the bladders are quadrifid, with the
four diverging arms of equal length. The prey which they
had captured consisted of entomostracan crustaceans.
—
Cuar. XVIIL] POLYPOMPHOLYX. 359
Utricularia multicaulis (Sikkim, India, 7000 to 11,000 feet).
—The bladders, attached to rhizomes, are remarkable from
the structure of the antennæ. These are broad, flattened,
and of large size; they bear on their margins multicellular
hairs, surmounted by glands. Their bases are united into a
single, rather narrow pedicel, and they thus appear like a
great digitate expansion at one end of the bladder. Inter-
nally the quadrifid processes have divergent arms of equal
length. The bladders contained remnants of articulate
animals.
| Utricularia cornuta, Michx. (United States).—This species
has been studied by A. Schimper in America, and is the sub-
ject of a short paper in the ‘ Botanische Zeitung.’ * It grows
in swampy ground, and presents a remarkable appearance ;
the aerial part of the plant seems at first sight to consist of
nothing but almost naked flower-stems a foot in height,
bearing from two to five large yellow flowers. U. cornuta
has no roots, its underground stem or rhizome is much
branched and bears numerous minute bladders. The
branches of the rhizome throw up here and there grass-like
leaves which cover the ground without having any apparent
connection with the flower-stem. The structure of the blad-
ders is not in any way remarkable, resembling in its general
features that of the European species. The bladders generally
contain organic remains; out of 114 only 11 contained no
débris. The contents include diatoms and small animals,—
worms, rotifers, small crustaceans; and the hairs lining the
inside of the bladders give evidence of having absorbed
matter from the decaying mass.—F. D. |
PoLYPOMPHOLYX.
This genus, which is confined to Western Australia, is
characterised by having a “quadripartite calyx.” In other
respects, as Prof. Oliver remarks,t “it is quite a
Utricularia.” i
Polypompholyx multifida.—The bladders are attached in
whorls round the summits of stiff stalks. The two antennæ
are represented by a minute membranous fork, the basal
part of which forms a sort of hood over the orifice. This
[* “ Notizen über Insectfressende Pflanzen,” 1882, p. 241.]
t ‘Proc. Linn. Soe.’ vol. iv. p. 171.
360 GENLISEA ORNATA. [Cuar. XVIII.
hood expands into two wings on each side of the bladder. A
third wing or crest appears to be formed by the extension of
the dorsal surface of the petiole; but the structure of these
three wings could not be clearly made out, owing to the
state of the specimens. The inner surface of the hood is
lined with long simple hairs, containing aggregated matter,
like that within the quadrifid processes or the previously
described species when in contact with decayed animals.
These hairs appear therefore to serve as absorbents. A valve
was seen, but its structure could not be determined. On the
collar round the valve there are in the place of glands
numerous one-celled papillw, having very short footstalks.
The quadrifid processes have divergent arms of equal length.
Remains of entomostracan crustraceans were found within the
bladders.
Polypompholyx tenella—The bladders are smaller than
those of the last species, but have the same general structure.
They were full of débris, apparently organic, but no remains
of articulate animals could be distinguished.
GENLISEA.
This remarkable genus is technically distinguished from
Utricularia, as I hear from Prof. Oliver, by having a five-
partite calyx. Species are found in several parts of the
world, and are said to be “ herbee annuz paludose.”
Genlisea ornata (Brazil).—This species has been described
and figured by Dr. Warming,* who states that it bears two
kinds of leaves, called by him spathulate and utriculiferous.
The latter include cavities; and as these differ much from
the bladders of the foregoing species, it will be convenient
to speak of them as utricles. The accompanying figure
(fig. 29) of one of the utriculiferous leaves, about thrice en-
larged, will illustrate the following description by my son,
which agrees in all essential points with that given by Dr.
Warming. The utricle (b) is formed by a slight enlarge-
ment of the narrow blade of the leaf. A hollow neck (n), no
less than fifteen times as long as the utricle itself, forms a
passage from the transverse slit-like orifice (o) into the
cavity of the utricle. A utricle which measured 3}; of an
* “Bidrag til Kundskaben om Lentibulariacee,” Copenhagen, 1874.
Cuar. XVIII] STRUCTURE OF THE LEAVES. 361
inch (+705 mm.) in its longer diameter had a neck 14 of an
inch (10:583 mm.) in length, and +}, of an inch (+254 mm.)
in breadth. On each side of the orifice there is a long spiral
arm or tube (a); the structure of which will be best under-
stood by the following illustration. Take a narrow ribbon
and wind it spirally round a thin
cylinder, so that the edges come
into contact along its whole
length; then pinch up the two
edges so as to form a little crest,
which will of course wind spirally
round the cylinder like a thread
round a screw. If the cylinder is
now removed, we shall have a
tube like one of the spiral arms.
The two projecting edges are not
actually united, and a needle can
be pushed in easily between
them. They are indeed in many
places a little separated, forming
narrow entrances into the tube ;
but this may be the result of the
drying of the specimens. The
lamina of which the tube is 4
LTR n sad
formed seems to be a lateral pro-
longation of the lip of the orifice ;
and the spiral line between the
two projecting edges is contin-
vous with the corner of the orifice.
If a fine bristle is pushed down i
one of the arms, it passes into Fio. 2.
the top of the hollow neck. (Genlisea ornata.)
Whether the arms are open Or Utriculiferous leaf; enlarged about
closed at their extremities could : ee
not be determined, as all the T Upper part of lamina of leaf.
Specimens were broken; nor does n Neck of utricle.
it appear that Dr. Warming 5 Spirally wound arms, with their
ascertained this point. ends broken off.
So much for the external struc- :
ture. Internally the lower part of the utricle is covered with
spherical papille, formed of four cells (sometimes eight
according to Dr. Warming), which evidently answer to the
quadrifid processes within the bladders of Utricularia. These
362 GENLISEA ORNATA. [Ciir X VILL
papille extend a little way up the dorsal and ventral surfaces
of the utricle; and a few, according to Warming, may be
found in the upper part. This upper region is covered by
many transverse rows, one above the other, of short, closely
approximate hairs, pointing downwards. These hairs have
broad bases, and their tips are formed by a separate cell.
They are absent in the lower
part of the utricle where the
papille abound. The neck is
likewise lined throughout its
whole length with transverse
rows of long, thin, transparent
hairs, having broad bulbous
(fig. 30) bases, with similarly
constructed sharp points. They
arise from little projecting
ridges, formed of rectangular
epidermic cells. The hairs vary
a little in length, but their
points generally extend down
to the row next below; so that
if the neck is split open and
laid flat, the inner surface re-
sembles a paper of pins,—the
hairs representing the pins, and
the little transverse ridges re-
presenting the folds of paper
through which the pins are
thrust. These rows of hairs are
indicated in the previous figure
(29) by numerous transverse
Fic. 30. lines crossing the neck. The
(Genlisea ornata.) inside of the neck is also studded
Portion of inside of neck leading With papille; those in the lower
into the utricle, greatly enlarged, show- :
ing the downward pointed bristles, and part are spherical and formed
small quadrifid cells or processes. of four cells, as in the lower
part of the utricle ; those in the
upper part are formed of two cells, which are much elongated
downwards beneath their points of attachment. These two-
celled papille apparently correspond with the bifid process
in the upper part of the bladders of Utricularia. The narrow
transverse orifice (0, fig. 29) is situated between the bases of
the two spiral arms. No valve could be detected here, nor
Cuar. XVIIL] CAPTURED PREY. 363
was any such structure seen by Dr. Warming. The lips of
the oritice are armed with many short, thick, sharply pointed,
somewhat incurved hairs or teeth.
The two projecting edges of the spirally wound lamina,
forming the arms, are provided with short incurved hairs or
teeth, exactly like those on the lips. These project inwards
at right angles to the spiral line of junction between the
two edges. The inner surface of the lamina supports two-
celled, elongated papille, resembling those in the upper
part of the neck, but differing slightly from them, according
to Warming, in their footstalks being formed by prolonga-
tions of large epidermic cells; whereas the papillae within
the neck rest on small cells sunk amidst the larger ones.
These spiral arms form a conspicuous difference between the
present genus and Utricularia.
Lastly, there is a bundle of spiral vessels which, running
up the lower part of the linear leaf, divides close beneath
the utricle. One branch extends up the dorsal and the
other up the ventral side of both the utricle and neck. Of
these two branches, one enters one spiral arm, and the other
branch the other arm. e
The utricles contained much débris or dirty matter, which
seemed organic, though no distinct organisms could þe
recognised. It is, indeed, scarcely possible that any object
could enter the small orifice and pass down the long narrow
neck, except a living creature. Within the necks, however,
of some specimens, a worm with retracted horny jaws, the
abdomen of some articulate animal, and specks of dirt, pro-
bably the remnants of other minute creatures, were found.
Many of the papillæ within both the utricles and necks
were discoloured, as if they had absorbed matter.
From this description it is sufficiently obvious how Genlisea
secures its prey. Small animals entering the narrow orifice
—but what induces them to enter is not known any more
than in the case of Utricularia—would find their egress
rendered. difficult by the sharp incurved hairs on the lips,
and as soon as they passed some way down the neck, it
would be scarcely possible for them to return, owing to the
many transverse rows of long, straight, downward pointing
airs, together with the ridges from which these project.
Such creatures would, therefore, perish either within the
neck or utricle; and the quadrifid and bifid papilla would
absorb matter from their decayed remains. The transverse
364 GENLISEA FILIFORMIS. [Cuar. XVIII.
rows of hairs are so numerous that they seem superfluous
merely for the sake of preventing the escape of prey, and as
they are thin and delicate, they probably serve as additional
absorbents, in the same manner as the flexible bristles on
the infolded margins of the leaves of Aldrovanda. The
spiral arms no doubt act as accessory traps. Until fresh
leaves are examined, it cannot be told whether the line ot
junction of the spirally wound lamina is a little open along
its whole course, or only in parts, but a small creature which
forced its way into the tube at any point, would be prevented
from escaping by the incurved hairs, and would find an open
path down tue tube into the neck, and so into the utricle.
If the creature perished within the spiral arms, its decaying
remains would be absorbed and utilised by the bifid papille.
We thus see that animals are captured by Genlisea, not by
means of an elastic valve, as with the foregoing species,
but by a contrivance resembling an eel-trap, though more
complex. : i
Genlisea africana (South Africa).—Fragments of the utri-
culiferous leaves of this species exhibited the same structure
as those of Genlisea ornata. A nearly perfect Acarus was
found within the utricle or neck of one leaf, but in which
of the two was not recorded.
Genlisea aurea (Brazil).—A fragment of the neck of a
utricle was lined with transverse rows of hairs, and was fur-
nished with elongated papillæ, exactly like those within the
neck of Genlisea ornata. It is probable, therefore, that the
whole utricle is similarly constructed.
Genlisea filiformis (Bahia, Brazil)—Many leaves were
examined and none were found provided with utricles,
whereas such leaves were found without difficulty in the
three previous species. On the other hand, the rhizomes
bear bladders resembling in essential character those on the
rhizomes of Utricularia. These bladders are transparent,
and very small, viz. only +}, of an inch (+254 mm.) in length.
The antenne are not united at their bases, and apparently
bear some long hairs. On the outside of the bladders there
are only a few papille, and internally very few quadrifid
processes. These latter, however, are of unusually large
size, relatively to the bladder, with the four divergent arms
of equal length. No prey couid be seen within these =
bladders. As the rhizomes of this species were furnishe
with bladders, those of Genlisea africana, ornata, and aurea
Cuar. XVIIL] CONCLUSION. 365
were carefully examined, but none could be found. What
are we to infer from these facts? Did the three species just
named, like their close allies, the several species of Utricu-
laria, aboriginally possess bladders on their rhizomes, which
they afterwards lost, acquiring in their place utriculiferous
leaves? In support of this view it may be urged that the
bladders of Genlisea filiformis appear from their small size and
from the fewness of their quadrifid processes to be tending
towards abortion; but why has not this species acquired
utriculiferous leaves, like its congeners ?
ConcLuston.—It has now been shown that many species of
Utricularia and of two closely allied genera, inhabiting the
most distant parts of the world—Kurope, Africa, India, the
Malay Archipelago, Australia, North and South America—
are admirably adapted for capturing by two methods small
aquatic or terrestrial animals, and that they absorb the pro-
ducts of their decay. =
Ordinary plants of the higher classes procure the requisite
inorganic elements from the soil by means of their roots, and
absorb carbonic acid from the atmosphere by means of their
leaves and stems. But we have seen in a previous part of
this work that there is a class of plants which digest and
afterwards absorb animal matter, namely, all the Droseracewx,
Pinguicula, and, as discovered by Dr. Hooker, Nepenthes,
and to this class other species will almost certainly soon be
added. These plants can dissolve matter out of certain
vegetable substances, such as pollen, seeds, and bits of leaves.
No doubt their glands likewise absorb the salts of ammonia
brought to them by the rain. It has also been shown that
some other plants can absorb ammonia by their glandular
hairs ; and these will profit by that brought to them by the
rain. There is a second class of plants which, as we have
just seen, cannot digest, but absorb the products of the
decay of the animals which they capture, namely, Utricularia*
and its close allies; and from the excellent observations of
[* The late Professor de Bary grown in water swarming with
showed me at Strasburg two dried
specimens of Utricularia (vulgaris ?)
which clearly demonstrated the ad-
vantage which this plant derives from
captured insects. One had been
minute crustaceans, the other in clean
water ; the difference in size between
the “fed” and the “starved” plants
was most striking.—F. D.]
366 : CONCLUSION. (Cuar. XVIII.
Dr. Mellichamp and Dr. Canby, there can scarcely be a doubt
that Sarracenia and Darlingtonia may be added to this class,
though the fact can hardly be considered as yet fully proved.
[A. Schimper, in an interesting paper,* gives evidence that
the products of decay are absorbed by the pitchers of Sarra-
cenia purpurea.t In the epidermic cells at the base of the
pitcher the changes produced by the presence of decaying
animal matter are strikingly evident, and bear a strong
resemblance to the process of aggregation as seen in Drosera.
The cell-sap is rich in tannin (as in Drosera), and when
aggregation takes place the single vacuole containing the
cell-sap is replaced by several highly refractive drops. The
process resembles in fact the division and concentration of
the vacuole as described by De Vries (see footnote, p. 35).
Schimper supposes that the cell-sap gives up to the proto-
plasm part of its water, and he describes the concentrated,
tannin-containing drops which are thus formed, as lying in
the swollen watery protoplasm which now takes up more
space than in the unstimulated condition. Schimper’s paper
also contains a good general description of the pitchers of
Sarracenia.—F’. D. |
There is a third class of plants which feed, as is now .
generally admitted, on the products of the decay of vegetable
matter, such as the bird’s-nest orchis (Neottia), &c.t Lastly,
* [“ Notizen über Insectfressende
Pflanzen,” ‘Bot. Zeitung, 1882, p.
225.
+ [In the ‘Quarterly Journal of
Science and Art,’ 1829, vol. ii. p. 290,
Burnett (as Mr. Thiselton Dyer
points out to me) wrote as follows:
“Sarracenia, if kept from the access
of flies, are said to be less flourishing
in their growth than when each
pouch is truly a sarcophagus.”
According to Faivre (‘Comptes ren-
dus,’ vol. Ixxxiii. 1876, p. 1155) both
Nepenthes and Sarracenia flourish
better when their pitchers are sup-
plied with water, and Wiesner states
that Sarracenia can be kept fresh for
months without watering the roots
if the pitchers are well supplied.
(‘Elemente der Anat. und Phys. der
Pflanzen, 2nd Edit. 1885, p. 226).—
F. D.] .
t [Dischidia Rafflesiana, Wall., is
sometimes doubtfully mentioned as
an insectivorous plant. The re-
searches of Treub (¢ Annales du Jardin
botanique de Buitenzorg, vol. iii.1885,
p. 13) show that this is not the case.
Dischidia grows as a climbing epi-
phyte on trees, and bears clusters of
modified leaves or pitchers. They
are of interest morphologically be-
cause it is the inside of the pitcher
which corresponds to the lower sur-
face of the leaf, so that, the pitchers
are involutions or pouchings of the
leaf from the lower instead of from
the upper surface as in Nepenthes,
Sarracenia and Cephalotus (see Dick-
son, ‘Journal of Botany,’ 1881, p.
133). The pitchers of Dischidia are
covered, both inside and out, with a
waxy coating which is heaped up in
a curious manner round the stomata,
Cuar. XVIIL] CONCLUSION. 367
there is the well-known fourth class of parasites (such as the
mistletoe), which are nourished by the juices of living plants.
Most, however, of the plants belonging to these four classes
obtain part of their carbon like ordinary species, from the
atmosphere. Such are the diversified means, as far as at
present known, by which higher plants gain their subsis-
tence.
forming a tower-like structure round
each of these openings. There are
no glands on the surface of the
pitchers, and the fluid with which
they are often partially filled is
simply collected rain-water. Adven-
titious roots are numerous and com-
monly enter the cavities of the
pitchers. Delpino (quoted by Treub)
believes that the pitchers serve to
collect ants, &c., whose dead bodies
may supply food tothe roots. Treub
on the other hand believes that the
drowning of ants within the pitchers
is accidental rather than wilful on
the part of the plant. He points out
that no arrangement for retaining
the ants exists, and that the adven-
titious roots supply ladders by which
they may escape; moreover the ants
are as often as not found alive and
well within the pitchers. Treub is
inclined to consider that the pitchers’
function is as stores or cisterns of
water; but their use in the economy
of the plant cannot be considered as
definitely settled.—F. D.]
( 369 )
INDEX.
ABSORPTION.
A.
ABSORPTION by Dionza, 238
—— by Drosera, 1, 14
—— by Drosophyllum, 273
—— by Pinguicula, 307
—— by glandular hairs, 278
—— by glands of Utricularia, 336,
340
—— by quadrifids of Utricularia,
333, 340
—— by Utricularia montana, 353
Acid, nature of, in digestive secretion
of Drosera, 73
—— present in digestive fluid of
various species of Drosera, Dionza,
Drosophyllum, and Pinguicula,
224, 243, 274, 307
Acids, various, action of, on Drosera,
154
of the acetic series replacing
hydrochloric in digestion, 74
—, arsenious and chromic, action
on Drosera, 151
, diluted,
osmose, 161
Adder’s poison, action on Drosera,
168
Aggregation of protoplasm in Dro-
sera, 32
inducing negative
— in Drosera induced by salts of |
ammonia, 37
caused by small doses of
carbonate of ammonia, 119
— of protoplasm in Drosera, a
reflex action, 196
in various species of Dro-
—
me
sera, 224
AMMONIA.
Aggregation of protoplasm in Dionæa,
235, 243
in Drosophyllum, 273, 274
—— —— in Pinguicula, 299, 314
in Utricularia, 332, 335,
345, 346, 352
Albumen, digested by Drosera, 77
, liquid, action on Drosera, 67
Alcohol, diluted, action of, on Dro-
sera, 65, 177
Aldrovanda vesiculosa, 260
, absorption and digestion by,
264
, varieties of, 265
Algæ, aggregation in fronds of, 54
Alkalies, arrest digestive process in
Drosera, 78
Aluminium, salts of, action on Dro-
sera, 150
Ammonia, amount of, in rain water,
140
, carbonate, action on heated
leaves of Drosera, 58
i , smallness of doses causing
aggregation in Drosera, 119
s „its action on Drosera, 115
; , vapour of, absorbed by
glands of Drosera, 116
y , smallness of doses causing
inflection in Drosera, 119, 137
, phosphate, smallness of doses
causing inflection in Drosera, 125,
137
—, , size of particles affecting
Drosera, 141
, nitrate, smallness of doses
causing inflection in Drosera, 120,
137
—__
2 B
INDEX.
AMMONIA.
Ammonia, salts of, action on Drosera,
13
x , their action affected by
previous immersion in water and
various solutions, 174
’ , induce aggregation in
Drosera, 37
» various salts of,
inflection in Drosera, 135
Antimony, tartrate, action on Dro-
sera, 15
Areolar tissue, its digestion by Dro-
sera, 85
Arsenious acid, action on Drosera, 151
Atropine, action on Drosera, 166
causing
B.
Barium, salts of, action on Drosera,
149
Bases of salts, preponderant action of,
on Drosera, 152
Basis, fibrous, of bone, its digestion
by Drosera, 90
Batalin, on motor impulse in Drosera,
204
, on bending of tentacles of
Drosera, 209
, on Dionxa, 233
, on mechanism of closure in
Dionæa, 256
, on colour of Pinguicula leaves,
297
, on movement in Pinguicula, 304
Belladonna, extract of, action on
Drosera, 70
Bennett, Mr. A. W., on Drosera, 1, 2,7
, coats of pollen grains not
digested by insects, 96
Binz, on action of quinine on white
blood-corpuscles, 164
, On poisonous action of quinine
on low organisms, 165
Bone, its digestion by Drosera, 88
Brunton, Lauder, on digestion of
gelatine, 92
—, on the composition of casein,
95
CHROMIC.
Brunton, Lauder, on the digestion of
urea, 102
id
of chlorophyll, 103
of pepsin, 102
nutrition of
?
Biisgen, Dr. M., on
Drosera, 16
Burnett, on Sarracenia, 366
Byblis, 277
C.
Cabbage, decoction
Drosera, 70
Cadmium chloride, action on Drosera,
150
Cæsium, chloride of, action on Dro-
sera, 148
Calcium, salts of, action on Drosera,
148
Camphor, action of Drosera, 170 _
Canby, Dr., on Dionæa, 243, 250, 252
, on Drosera filiformis, 227
Caraway, oil of, action on Drosera,
172
Carbonic acid, action on Drosera, 180
delays aggregation in Drosera,
of, action on
50
Cartilage, its digestion by Drosera,
86
Casein, its digestion by Drosera, 95
Caspary, on Aldrovanda, 260, 261
Cellulose, not digested by Drosera,
103
Chalk, precipitated, causing inflec-
tion of Drosera, 28
Cheese, its digestion by Drosera, 96
Chitine, not digested by Drosera,
102
Chloroform, effects of, on Drosera
1?
. , on Dionæa, 246 i
Chlorophyll, grains of, in living
plants, digested by Drosera, 103
, pure, not digested by Drosera,
Chondrin, its digestion by Drosera,
93
Chromic acid, action on Drosera,
151
INDEX.
CLOVES.
Cloves, oil of, action on Drosera, 173
Cobalt chloride, action on Drosera,
152
Cobra poison, action on Drosera, 168
Cohn, Prof., on Aldrovanda, 260
, on contractile tissues in plants,
293
, on movements of stamens of
Composite, 208
, on Utricularia, 319
Colchicine, action on Drosera, 166
Copper chloride, action on Drosera,
151
Crystallin, its digestion by Drosera,
98 Co,
Curare, action on Drosera, 166
Curtis, Dr., on Dionza, 243
p.
Darwin, C., papers on action of
ammonia on roots, 55
, Erasmus, on Diongæa, 243
, Francis, on the effect of an
induced galvanic current on Dro-
sera, 31
, on aggregation in Drosera, 32,
39
, on nutrition of Drosera, 15
„on the digestion of grains of
chlorophyll, 103
De Bary, effect of animal food on
Utricularia, 365
De Candolle, on Dionæa, 232, 233,
235
Delpino, on Aldrovanda, 260
, on Utricularia, 319, 366
, on Dischidia, 367
Dentine, its digestion by Drosera, 88
Digestion of various substances by
Dionæa, 243
by Drosera, 71
—— —— by Drosophyllum, 274
by Pinguicula, 307
, origin of power of, 291
Digitaline, action on Drosera, 165
Dionza, early literature of, 231
—_—,
_——
DROSOPHYLLUM.
Dionza, muscipula, small size of roots,
231
-
» structure of leaves, 232
, Sensitiveness of filaments, 254
, absorption by, 238
, secretion by, 238
—, digestion by, 243
, effects on, of chloroform, 246
» manner of capturing insects,
247
, transmission of motor impulse,
253
, re-expansion of lobes, 257
Direction of inflected tentacles of
Drosera, 197
Dischidia. Rafflesiana, 366
Dohrn, Dr., on rhizocephalous crus-
taceans, 288
Donders, Prof, small amount of
atropine affecting the iris of the
dog, 140
Dragonfly caught by Drosera, 2
Drosera, absorption by, 1, 14
anglica, 224
binata, vel dichotoma, 227
capensis, 225
dichotoma, 5
—— filiformis, 226
heterophylla, 229
—— intermedia, 225
, sensitiveness of, 22
Drosera rotundifolia, structure of
leaves, 3
, artificial feeding of, 15
, effects on, of nitrogenous
fluids, 64
, effects of heat on, 56
, its power of digestion, 71
——, backs of leaves not sensitive, 188
——, transmission of motor impulse,
190.
——, general summary, 212
spathulata, 226
Droseraceez concluding remarks on,
287
——, their sensitiveness compared
with that of animals, 295
Drosophyllum, structure of leaves,
269
, secretion by, 270
INDEX.
DROSOPHYLLUM.
Drosophyllum, absorption by, 273
, digestion by, 274
Duval-Jouve, on Aldrovanda, 268
E.
Ellis, on Dionga, 245
Enamel, its digestion by Drosera,
88
Erica, tetralix, glandular hairs of,
284
Ether, effects of, on Drosera, 179
$ , on Dionæa, 246
Euphorbia, process of aggregation in
roots of, 53
Ewald, on peptogenes, 106
Exosmose from backs of leaves of Dro- |
sera, 188
F.
Faivre, on Nepenthes and Sarra-
cenia, 366
Fat not digested by Drosera, 104
Fayrer, Dr., on the nature of cobra
poison, 168
yon the action of cobra poison
on animal protoplasm, 170
» on cobra poison paralysing
nerve centres, 185
Ferment, nature of, in secretion of
Drosera, 78, 81
Fibrin, its digestion by Drosera, 84
Fibro-cartilage, its digestion by
Drosera, 87
Fibro-elastic tissue, not digested by
Drosera, 100
Fibrous basis of bone, its digestion by
Drosera, 90
Fluids, nitrogenous, effects of, on
Drosera, 64
Fournier, on acids causing movements
in stamens of Berberis, 160,
Frankland, Prof., on nature of acid in
secretion of Drosera, 73
Fraustadt, A., on Dionæa, 232, 233
——, on roots of Dionæa, 288
HAIDENHAIN,
G.
Galyanism, current of, causing in-
flection of Drosera, 31
, effects of, on Dionza, 256
Gardiner, W., on Drosera dichotoma, 5
, on the Rhabdoid, 32
, on aggregation, 34 :
» on process of secretion in
Drosera, 72
» on intercellular protoplasm,
200
„on contractility of plant-cells,
209
, on gland-cells of Dionæa, 238
Gardner, Mr., on Utricularia nelum-
bifolia, 357
Gelatine, impure, action on Drosera,
67
—, pure, its digestion by Drosera,
92
~
Genlisea africana, 364
filiformis, 364
ornata, structure of, 360 :
, manner of capturing prey, 369
Glandular hairs, absorpion by, 278
, Summary on, 285
Glauer, on aggregation, 39
Globulin, its digestion by Drosera, 98
Gluten, its digestion by Drosera, 97
Glycerine, inducing aggregation m
Drosera, 45
» action on Drosera, 173 :
Gold chloride, action on Drosera, 150
Gorup-Besanez, on the presence of &
solvent in seeds of the vetch, 292
Grass, decoction of, action on Dro-
sera, 70
Gray, Asa, on the Droseracez, 2
Greenland, on Drosera, 1, 5
Gum, action of, on Drosera, 65
Gun-cotton, not digested by Drosera,
103
H.
Hæmatin, its digestion by Drosera,
9
Haidenhain, on peptogenes, 106
INDEX.
373
HAIRS,
Hairs, glandular, absorption by, 278
—, , Summary on, 285 -
Heat, inducing aggregation in Dro-
sera, 45
——, effect of, on Drosera, 56
—, , on Dionæa, 237, 258
Heckel, on state of stamens of Ber-
beris after excitement, 37
Hofmeister, on pressure arresting
movements of protoplasm, 52
Holland, Mr., on Utricularia, 319
Hooker, Dr., on carnivorous plants, 2
———, on power of digestion by Ne-
penthes, 81
—, history of observations on
Dionza, 231, 243
Hovelacque, on Utricularia, 348
Hydrocyanic acid, effects of, on
Dionæa, 246
apa action on Drosera, 70,
it
Iron chloride, action on Drosera,
151
Isinglass, solution of, action on Dro-
sera, 67
J.
Johnson, Dr., on movement of flower-
stems of Pinguicula, 307
K.
Kellermann and Von Raumer, on
_ nutrition of Drosera, 15
Klein, Dr., on microscopic character
of half digested bone, 88
——,, on state of half digested fibro-
cartilage, 87
—, on size of micrococci, 141
Knight, Mr., on feeding Dionxa, 243
Kossman, Dr., on rhizocephalous
crustaceans, 288
MORI.
Kunkel, on electric phenomena in
Dionea, 256
Kurtz, on Dionæa, 231, 253
L.
Lankester, E. Ray, on glands of water
plants, 268
Lead chloride, action on Drosera, 151
Leaves of Drosera, backs of, not
sensitive, 188
Legumin, its digestion by Drosera, 96
Lemna, aggregation in leaves of, 54
Lime, carbonate of, precipitated,
causing inflection of Drosera, 28
, phosphate of, its action on
Drosera, 91
Linnæus, on Dionæa, 243
Lithium, salts of, action on Drosera,
148
M.
Magnesium, salts of, action on Dro-
sera, 149
Manganese chloride, action on Dro-
sera, 151
Marshall, Mr. W., on Pinguicula,
298
Means of movement in Dionæa, 253
in Drosera, 206
Meat, infusion of, causing aggrega-
tion in Drosera, 44
, action on Drosera, 67
, its digestion by Drosera, 82
Mercury perchloride, action on Dro-
sera, 150
Milk, inducing aggregation in Dro-
sera, 44
, action on Drosera, 66
, its digestion by Drosera, 94
Mirabilis longiflora, glandular hairs
of, 284
Moggridge, Traherne, on acids in-
juring seeds, 105
Moore, Dr., on Pinguicula, 315
Mori, on Aldrovanda, 263
?
374
INDEX.
MORPHIA.
Morphia acetate, action on Drosera,
167
Morren, E., on Drosera binata, 227
Motor impulse in Drosera, 190, 209
in Dionæa, 252
Movement, origin of power of, 293
Movements of leaves of Pinguicula,
299
of tentacles of Drosera, means
of, 206
of Dionæa, means of, 252
Mucin, not digested by Drosera, 100
Mucus, action on Drosera, 67
Müller, Fritz, on rhizocephalous
crustaceans, 288
Munk, on Dionæa, 234, 247
, onelectric phenomena in Dionæa,
ose
256
N.
Nepenthes, its power of digestion, 81
Nickel chloride, action on Drosera,
152
Nicotiana tabacum, glandular hairs
of, 284
Nicotine, action on Drosera, 165
Nitric ether, action on Drosera, 180
Nitschke, Dr., references to his papers
on Drosera, 1 :
, On sensitiveness of backs of
leaves of Drosera, 188
, on direction of inflected ten-
tacles in Drosera, 198
, on Aldrovanda, 261
Nourishment, various means of, by
plants, 365
Nuttall, Dr., on re-expansion of Dionza,
257
0.
Odour of pepsin, emitted from leaves
of Drosera, 74
Oels, W., on comp, anatomy of Dro-
seraceæ, 2
Oil, olive, action of, on Drosera, 66,
104
POISON.
Oliver, F., on motor impulse, 204
, Prof, on Utricularia, 349,
356-360 a
Oudemans, on Dionæa, 233
P.
Papaw, juice of, hastening putrefac-
tion, 331
Particles, minute size of, causing
inflection in Drosera, 24, 28
Peas, decoction of, action on Drosera,
69
Pelargonium zonale, glandular hairs
of, 283
Penzig, Otto, on roots of Droso-
phyllum, 288
Pepsin, odour of, emitted from Dro-
sera leaves, 74
, not digested by Drosera, 101
, its secretion by animals excited
only after absorption, 107
Peptogenes, 106
Pfeffer, on sensitiveness of Drosera to
contact, 22, 31
, on nucleus in Drosera, 32
, on aggregation, 34
, on Dionzea, 256
, on roots of carnivorous plants,
288
, on Pinguicula, 314
Pinguicula grandiflora, 315
lusitanica, 315
vulgaris, structure of leaves
and roots, 297
, number of insects caught by,
298
<
, power of movement, 299 :
, Secretion and absorption by, 307
——-, digestion by, 307 ‘
, leaves of, used to curdle milk,
314
, effects of secretion on living
seeds, 315
Platinum chloride, action on Drosera,
152
Poison of cobra and adder, their
action on Drosera, 168
INDEX.
(Jt)
-~
Or
POLLEN.
Pollen, its digestion by Drosera, 96
Polypompholyx, structure of, 359
Potassium, salts of, inducing aggre-
gation in Drosera, 43
’ , action on Drosera, 146
phosphate, not decomposed by
Drosera, 147, 153
Price, Mr. John, on Utricularia, 345
Primula sinensis, glandular hairs of,
281
, number of glandular hairs of,
286
Protoplasm, aggregated, re-dissolu-
tion of, 46
——, aggregation of, in Drosera, 32,
34, 35
—, „in Drosera, caused by
small doses of carbonate of am-
monia, 119
3 , in Drosera, a reflex
action, 196
—, , in various species of Dro-
sera, 224
, in Dionæa, 235, 242
——, ——, in Drosophyllum, 273,
274
——, —, in Pinguicula, 299, 314
, in Utricularia, 352, 335,
_
—_—,
?
346, 352
Q.
Quinine, salts of, action on Drosera,
163
R.
Rain-water, amount of ammonia in,
140
Ralts, Mr., on Pinguicula, 315
Ransom, Dr., action of poisons on the
yolk of eggs, 183
Rees and Will, on digestive action in
Drosera, 73, 81
Re-expansion of headless tentacles of
Drosera, 187
— of tentacles of Drosera, 210
—— of Dionæa, 257
SCHIFF.
Roots of Drosera, 17
» process of aggregation
x
in, 53
— , absorb carbonate of am-
monia, 115
of Dionga, 231
of Drosophyllum, 269
of Pinguicula, 298
Roridula, 276
Rubidium chloride, action on Drosera,
148
Sachs, Prof., effects of heat on pro-
toplasm, 56, 59
, on the dissolution of proteid
compounds in the tissues of plants,
292
Saliva, action on Drosera, 67
Salts and acids, various, effects of,
on subsequent action of ammonia,
175
Sanderson, Burdon, on coagulation of
albumen from heat, 62
» on acids replacing
chloric in digestion, 74
, on the digestion of fibrous
basis of bone, 90
of gluten, 97
of globulin, 99
of chlorophyll, 103
„on different effect of sodium
and potassium on animals, 152
, on electric currents in Dionza,
256
Sarracenia, 365, 366
Saxifraga umbrosa, glandular hairs
of, 279
Schenk, on Utricularia, 348
Schiff, on hydrochloric acid dis-
solying coagulated albumen, 71
„on manner of digestion of
albumen, 77
, on changes in meat during
digestion, 83
on the coagulation of milk,
hydro-
?
,
?
——
,
94
INDEX.
SCHIFF.
Schiff, on the digestion of casein, 95
, on the digestion of mucus, 101
, on peptogenes, 106
Schimper, on aggregation, 34
, on Utricularia, 331, 332
, on Sarracenia purpurea, 365
Schloesing, on absorption of nitro-
gen by Nicotiana, 285
Scott, Mr., on Drosera, 1
Secretion of Drosera, general account
of, 11
, its antiseptic power, 13
, becomes acid from excite-
ment, 72
——, nature of its ferment, 78,
81
— by Dionza, 238
—— by Drosophyllum, 271
— by Pinguicula, 307
Seeds, living, acted on by Drosera,
104
—, , acted on by Pinguicula, |
311, 314
Sensitiveness, localisation of, in Dro-
sera, 187
of Dionæa, 233
of Pinguicula, 299
Silver nitrate, action on Drosera, 148
Sodium, salts of, action on Drosera,
143
—, , inducing aggregation in
Drosera, 43
Sondera heterophylla, 229
Sorby, Mr., on colouring matter of
Drosera, 4
Spectroscope, its power compared
with that of Drosera, 139
Starch, action of, on Drosera, 65,
104
Stein, on Aldrovanda, 260
Strontium, salts of, action on Dro-
sera, 149
Strychnine, salts of, action on Dro-
sera, 162
Sugar, solution of, action of, on Dro-
sera, 65
s , inducing aggregation in
Drosera, 44
Sulphuric ether, action on Drosera,
179
}
UTRICULARIA.
Sulphuric ether, action on Dionæa, 246
Syntonin, its action on Drosera, 85
T.
Tait, Mr., on Drosophyllum, 269
Taylor, Alfred, on the detection of
minute doses of poisons, 139
Tea, infusion of, action on Drosera,
65
Tentacles of Drosera, move when
glands cut off, 31, 187
, inflection, direction of, 197
——, means of movement, 206
, Te-expansion of, 210
Theine, action on Drosera, 166
Tin chloride, action on Drosera, 151
Tissue, areolar, its digestion by
Drosera, 85
, fibro-elastic, not digested by
Drosera, 100
| Tissues through which impulse is
transmitted in Drosera, 200
in Dionæa, 252 :
Touches repeated, causing inflection
in Drosera, 29 :
Transmission of motor impulse in
Drosera, 190
in Dionæa, 252
Traube, Dr., on artificial cells, 176
Treat, Mrs., on Drosera filiformis, 226
, on Dionæa, 251
„on valve in Utricularia, 329,
330, 346
| Trécul, on Drosera, 1, 5
Treub, on Dischidia, 366, 367 __
Tubers of Utricularia montana, 354
Turpentine, action on Drosera, 173
v.
Urea, not digested by Drosera, 102
Urine, action on Drosera, 66
Utricularia clandestina, 346
minor, 345
-— montana, structure of bladders,
348
INDEX.
377
UTRICULARIA,
Utricularia, montana animals caught
by, 352
, absorption by, 353
, tubers of, serving as reservoirs,
354
Utricularia neglecta, structure of
bladders, 321
, animals caught by, 327
, absorption by, 333
——, summary on absorption, 340
, development of bladders, 342
Utricularia, various species of, 356
Utricularia vulgaris, 345
V.
Veratrine, action on Drosera, 166
Vessels in leaves of Drosera, 200
Vessels of Dionæa, 253
Vines, on digestive fluid of Nepen-
thes, 81
——, on the ferment of the Vetch, 292
Vogel, on effects of camphor on
plants, 171
Von Gorup and Will, on digestive
action in Drosera, 73, 81
Vries, H. de, on aggregation, 35, 39
ZINC.
W.
Warming, Dr., on Drosera, 2, 6
|! ——, on roots of Utricularia, 320
|
——, on trichomes, 289
, on Genlisea, 360
» on parenchymatous cells in
tentacles of Drosera, 205
Water, drops of, nòt causing inflec-
tion in Drosera, 30
, its power in causing aggrega-
tion in Drosera, 45
, its power in causing inflection
in Drosera, 113
and various solutions, effects of,
on subsequent action of ammonia,
174
Wiesner, on Sarracenia, 366
Wilkinson, Rev. H. M., on Utricularia,
Z.
Ziegler, his statements with respect
to Drosera, 21, 204
, experiments by cutting vessels
of Drosera, 202
| Zinc chloride, action on Drosera, 150
to
Q
te...
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c2
20 LIST OF WORKS
LYELL (K.M.). Handbook of Ferns, Post 8vo. 7s. 6d.
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[In the Press.
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24 LIST OF WORKS
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28 LIST OF WORKS
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