Insectivorous plants

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Theological Seminary,

PRINCETON, N. J.

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INSECTIVOEOUS PLANTS.

BY THE SAME AUTHOR.

ON THE ORIGIN OF SPECIES BY MEANS OF NATURAL SE-

LECTION"; or, The Peeservation of Favored Eaces in the Struggle fob
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THE THEORY OF DESCENT, AND DARWINISM. By Prof. Oscar
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INSECTIVOROUS PLANTS

By CHAELES DAEWIN, M.A., F.E.S.,

ETC.

WITH ILLUSTRATIONS.

NEW YORK:
D. APPLETON AND COMPANY,

549 AND 551 Broadway.

1875.

CONTENTS.

CHAPTER I.

Drosera kotundifolia, 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 Pages 1-18

CHAPTER 11.

The Movements of the Tentacles from the Contact op
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 yield-
ing and not yielding soluble nitrogenous matter — Inflection
of the exterior tentacles directly caused by objects left in
contact with their glands — Periods of commencing inflection
and of subsequent re-expansion — Extreme minuteness of
the particles causing inflection — Action under water —
Inflection of the exterior tentacles when their glands are
excited by repeated touches — Falling drops of water do not
cause inflection 19-37

VI CONTENTS.

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 — Descrip-
tion of the aggregated masses and of their spontaneous
movements — Currents of protoplasm along the walls of the
cells — Action of carbonate of ammonia — The granules in
the protoplasm which flows along the walls coalesce with the
central masses — Minuteness of the quantity of carbonate of
ammonia causing aggregation — Action of other salts of
ammonia — Of other substances, organic fluids, &c. — Of
water — Of heat — Eedissolution of the aggregated masses —
Proximate causes of the aggregation of the protoplasm —
Summary and concluding remarks — Supplementary observa-
tions on aggregation in the roots of plants . . Pages 33-G5

CHAPTEK IV.

The Effects of Heat on the Leaves.

Nature of the experiments — Effects of boiling water — Warm
water causes raj^id inflection — Water at a higher tempera-
ture does not cause immediate inflection, but does not kill
the leaves, as shown by their subsequent re-exi:)ansion and
by the aggregation of the protoplasm — A still higher
temperature kills the leaves and coagulates the albuminous
contents of the glands 66-75

CHAPTER V.

The Effects of Non-niteogenous and Nitrogenous
Organic Fluids on the Leaves.

Non-nitrogenous fluids — Solutions of gum arable — Sugar —
Starch — Diluted alcohol — Olive oil — Infusion and decoc-
tion of tea — Nitrogenous fluids — Milk — Urine — Liquid
albumen — Infusion of raw meat — Impure mucus — Saliva
— Solution of isinglass — Difference in the action of these
two sets of fluids — Decoction of green peas — Decoction
and infusion of cabbage — Decoction of grass leaves 76-84

CONTENTS. VU

CHAPTER VI.

The Digestive Power of the Secretion of Drosera.

The secretion rendered acid by tlie direct and indirect excite-
ment of ttie 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 — Hsematin
—Indigestible substances — Epidermic productions — Fibro-
elastic tissue — Mucin — Pepsin — Urea — Chit ine — Cellulose

— Gun-cotton— Chlorophyll — Fat and oil — Starch —Action
of the secretion on living seeds — Summary and concluding
remarks Pages 85-135

CHAPTER VII.

The 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 in weak solutions —
Minuteness of the doses which induce aggregation of the
protoplasm — Nitrate of ammonia, analogous experiments
with — Phosphate of ammonia, analogous experiments with

— Other salts of ammonia — Summary and concluding
remarks on the action of salts of ammonia .. .. 136-173

CHAPTER VIII.

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 — Summary on their action 174-198

Vlll CONTENTS.

CHAPTER IX.

The Effects of certain Alkaloid Poisons, other
Substances and Vapours.

Stryclinine, salts of — Quinine, sulphate of, does not soon
arrest tlie movement of the protoplasm — Other salts of
quinine — Digitaline — Nicotine — Atropine — Vera trine —
Colchicine — Theine — Curare — Morphia — Hyoscyamus —
Poison of the cobra, apparently accelerates the movements
of the protoplasm — Camphor, a powerful stimulant, its
vapoui" narcotic — Certain essential oils excite movement —
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 Pages 199-228

CHAPTER X.

On the Sensitiveness op the Leaves, and on the Lines
OF Transmission of the Motor Impulse.

Glands and summits of the tentacles alone sensitive — Trans-
mission of the motor impulse down the pedicels of the
tentacles, and across the blade of the leaf — Aggregation of
the protoplasm, a reflex action — First discharge of the
motor impulse sudden — Direction of the movements of the
tentacles — Motor impulse transmitted through the cellular
tissue — Mechanism of the movements — Nature of the
motor impulse — Ee-expansion of the tentacles .. 229-261

CHAPTER Xr.

Eeoapitulation of the Chief Observations on
, Drosera rotundifolia.

262-277

CONTENTS. IX

CHAPTER XII.

On the Structuee and Movements of some other
Species of Drosera.

Drosera anglica — Drosera intermedia — Drosera capensis — Drosera
spathulata— Drosera filiformis — Drosera Unata — Concluding
remarks Pages 278-285

CHAPTER XIII.

DlON^A MUSCIPULA.

Structure of tlie leaves — Sensitiveness of the filaments — Kapid
movement of the lobes caused by irritation of the filaments —
Glands, their power of secretion— Slow movement caused by
the absorption of animal matter — Evidence of absorption
from the aggregated condition of the glands — Digestive
power of the secretion — Action of chloroform, ether, and
hydrocyanic acid— The manner in which insects are captured
— Use of the marginal spikes — Kinds of insects captured —
The transmission of the motor impulse and mechanism of
the movements — Ee-expansion of the lobes .. 286-320

CHAPTER XIV.

Aldrovanda vesiculosa.

Captures crustaceans — Structure of the leaves in comparison
with those of Dionsea— Absorption by the glands, by the
quadrifid processes, and points on the infolded margins —
Aldrovanda vesiculosa, var. australis — Captures prey —
Absorption of animal matter — Aldrovanda vesiculosa, var.
ver^ic^7?ato — Concluding remarks 321-381

CHAPTER XY.

DrOSOPHYLLUM — RORIDULA — BVBLIS — GLANDULAR HaiES OF

OTHER Plants— Concluding Kemarks on the DROSERACEiE.
Drosophyllum— Structure of leaves— Nature of the secretion-
Manner of catching insects— Power of absorption— Digestion
of animal substances— Summary on Drosophyllum— Eoridula
— Byblis — Glandular hairs of other plants, their power of
absorption — Saxifraga — Primula — Pelargonium — Erica—
Mirabilis — Nicotiana — Summary on glandular hairs— Con-
cluding remarks on the Droseracese .. :, .. 332-367

X CONTENTS.

CHAPTER XYI.

PlNGUICULA.

Fmgukula vulgaris — Structure of leaves — Number of iusects
and other objects canglit — Movement of the margins of tlie
leaves — Uses of this movement — Secretion, digestion, and
absorption — Action of the secretion on various animal and
vegetable substances — The effects of substances not con-
taining soluble nitrogenous matter on the glands — Pinguicula
grandiflora — Pinguicula lusitanica, catches' insects — Move-
ment of the leaves, secretion and digestion . . Pages 368-394

CHAPTER XYII.
Uteiculaeia.

Utricularia veglecta — Structure of the bladder — The uses of the
several parts — Number of imprisoned animals — Manner of
capture — The bladders cannot digest animal matter, but
absorb the products of its decay — Experiments on the
absorption of certain fluids by the quadrifid processes —
Absorption by the glands — Summary of the observation on
absorption — Development of the bladders — Utricularia
vulgaris — Utricularia minor — Utricularia clandestina 395-430

CHAPTER XVIII.

Utkiculakia (continued').

Utricularia montana — Description of the bladders on the sub-
terranean rhizomes — Prey captured by the bladders of
plants under culture and in a state of nature — Absorption
by the quadrifid processes and glands — Tubers serving as
reservoirs for water — Various other species of Utricularia —
Polypompholyx — Genlisea, different nature of the trap for
capturing prey — Diversified methods by which plants are
nourished 431-453

Index 455-462

INSECTIVOEOUS PLANTS

CHAPTEB I.

Dkosera rotundifolia, ok 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 secre-
tion—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.

During the summer of 1860, I was surprised by find-
ing liow large a number of insects were caught by the
leaves of the common sun-dew (Drosera rotundifolia) on
a heath in Sussex. I had heard that insects were thus
caught, but knew nothing further on the subject.* I

* As Dr. Nitschke has given leaves; but M. Trc'cul went so

('Bot. Zeitung,' 18G0, p. 229) the far as to doubt whether they pos-

bibliography of Drosera, I need sessed any power of movement,

not here go into details. Most of Dr. Nitschke's papers in the ' Bot.

the notices published before 1860 Zeitung' for 1860 and 1861 are

are brief and unimportant. The by far the most important ones

oldest paper seems to have been which have been published, both

one of the most valuable, namely, on the habits and structure of

by Dr. Roth, in 1782. There is this plant; and I shall frequently

also an interesting though short have occasion to quote from

account of the habits of Drosera by them. His discussions on several

Dr. Milde, in the ' Bot. Zeitung,' points, for instance on the trans-

1852, p. .540. la 1S55, in the ' An- mission of an excitement from one

nales des Sc. nat. bot^' torn. iii. pp. part of the leaf to another, are

297 and 304, MM. Greenland and excellent. On Dec. 11, 1862, Mr.

Tre'cul each published papers, with J. Scott read a paper before the

figures, on the structure of the Botanical Society of Edinburgh,

2 DEOSERA EOTUNDIFOLIA. CiiAP. I.

gathered by cjiance a dozen plants, bearing fifty-six
fully expanded leaves, and on thirty-one of these dead
insects or remnants of them adhered ; and, no doubt,
many more would have been caught afterwards by these
same leaves, and still more by those as yet not ex-
panded. On one plant all six leaves had caught their
prey; and on several plants very many leaves had
caught more than a single insect. On one large leaf
I found the remains of thirteen distinct insects.
Flies (Diptera) are captured much oftener than other
insects. The largest kind which I have seen caught
was a small butterfly {Cwnomjmpha j)amphihis) ; but
the Eev. H. M. AVilkinson informs me that he found a
large living dragon-fly with its body firmly held by
two leaves. As this plant is extremely common in
some districts, the number of insects thus annually
slaughtered must be prodigious. Many plants cause
the death of insects, for instance the sticky buds of
the horse-chestnut {Msculus hippocastanum), without
thereby receiving, as far as we can perceive, any ad-
vantage; but it was soon evident that Drosera was

which was published in the Gar- to a paper by Mrs. Treat, of New

flener's Chronicle,' 1863, p. 30. Jersey, on some American species

;Mr. Scott shows that gentle irrita- of Drosera. Dr. Burdon Sander-

tion of the hairs, as well as insects son delivered a lecture on Diontea,

placed on the disc of the leaf, before the Royal Institution I'pub-

cause the haii-s to bend in- lishedin'Nature,' June 14, 1874),

wards. Mr. A. W. Bennett also in which a short account of my

gave another interesting account observations on the power of true

of the movements of the leaves digestion possessed by Drosera

before the British Association for and Diunrea first appeared. Prof.

1873. In this same year Dr. Asa Gray has done good service

Warming published an essay, in by calling attention to Drosera,

which he describes the structure and to other plants having similar

of the so-called hairs, entitled, habits, in 'The Nation '(1874, pp.

" Sur la Difterence entre les Tri- 261 und 232), and in other publica-

chomes," &c., extracted from the tions. Dr. Hooker, also, in his

proceedings of the Soc. d'Hist. important acklress on Carnivorous

Nat. de Copenhague. I shall also Plants(Brit. Assoc, Belfast, 1874),

have occasion hereafter to refer has given a history of the subject.

Chap. I.

STRUCTURE OF THE LEAVES.

excellently adapted for the special purpose of catch-
ing insects, so that the subject seemed well worthy of
investigation.

The results have proved highly remarkable ; the
more important ones being — firstly, the extraordinary

Fig. 1.* -
{Drosera rotundifoUa.)
Leaf viewed from above ; enlarged four times.

sensitiveness of the glands to slight pressure and to
minute doses of certain nitrogenous fluids, as shown
by the movements of the so-called hairs or tentacles ;

* The drawings of Drosera and
Dionsea, given in this vrork, were
made for me by my son George
Darwin ; those of Aldrovanda, and
of the several species of Utri-

cnlaria, by my son Francis. They
have been excellently reproduced
on wood by Mr. Cooper, 188
Strand.

DROSERA ROTUNDIFOLIA.

Chap. I.

secoiiflly, the power possessed by the leaves of render-
ing]^ soluble or digesting nitrogenous substances, and
of ai'terwards absorbing them; thirdly, the changes
which take phice within the cells of the tentacles, when
the glands are excited in various ways. .

It is necessary, in the first place, to describe briefly
tlie plant. It bears from two or three to five or six
loaves, generally extended more or less horizontally,
but sometimes standing vertically upwards. The shape
and general appearance of a leaf is shown, as seen"
from above, in fig. 1, and as seen laterally, in fig. 2.
The leaves are commonly a little broader than long.

.«fe^£&Mi*r

Fig. 2.

(Drosera rotundi folia.')

Old leaf viewed laterally ; enlarged about five times.

l)iit tliis was not the case in the one here figured.
The whole upper surface is covered with gland-bearing
lilament.s, or tentacles, as I shall call them, from their
ni a liner of acting. The glands were counted on thirty-
on(,' leaves, but many of these were of unusually large
size, and the average number was 192; the greatest
number being 2(30, and the least 130. The glands are
each surrounded by large drops of extremely viscid
s<M.Totion, which, glittering in the sun, have given rise
lo the plant's poetical name of the sun-dew.

The tcntadcs on tlic central part of the leaf or disc are
sliort and stand ni)nVdit, and tlieir ixdiccls are green. Towards
the mari,'iu tliey become longer and longer and more inclined

CiiAP. I. STRUCTUEE OF THE LEAVES. 5

outwards, with their pedicels of a purple colour. Those on the
extreme margin project in the same plane with the leaf, or more
commonly (see fig. 2) are considerably reflexed. A few tentacles
spring from the base of the footstalk or petiole, and these are
the longest of all, being sometimes nearly i of an inch in length.
On a leaf bearing altogether 252 tentacles, the short ones on
the disc, having green pedicels, were in number to the longer
submarginal and marginal tentacles, having purple pedicels, as
nine to sixteen.

A tentacle consists of a thin, straight, hair-like pedicel, carry-
ing a gland on the summit. The pedicel is somewhat flattened,
and is formed of several rows of elongated cells, filled with purple
fluid or granular matter.* There is, however, a narrow zone
close beneath the glands of the longer tentacles, and a broader
zone near their bases, of a green tint. Sjjiral vessels, accom-
panied by simple vascular tissue, branch off from the vascular
bundles in the blade of the leaf, and run up all the tentacles
into the glands.

Several eminent physiologists have discussed the homological
nature of these appendages or tentacles, that is, whether they
ought to be considered as hairs (trichomes) or prolongations of
the leaf. Nitschke has shown that they include all the elements
proper to the blade of a leaf; and the fact of their including
vascular tissue was formerly thought to prove that they were
prolongations of the leaf, but it is now known that vessels some-
times enter true hairs.f The power of movement which they
possess is a strong argument against their being viewed as hairs.
The conclusion which seems to me the most probable will be
given in Chap. XV., namely that they existed primordially as
glandular hairs, or mere epidermic formations, and that their
upper i^art should still be so considered ; but that their lower

* According to Nitschke (' Bot. (or tentacles) are coloured like

Zeitung,' IbGl, p. 224) the purple parts of a leaf which do not fulfil

fluid results from the metamor- their proper office."

pilosis of chlorophyll. Mr. Sorby f Dr. Nitschke has discussed

examined the colouring matter this subject in 'Bot. Zeituug,'

■with the spectroscope, and in- 1861, p. 241, &c. See also Dr.

forms me that it consists of the Warming ('Sur la Difference eutre

commonest species of erythro- les Trichomes,' &c., 1873;, who

phyll, " which is often met with in gives references to various publi-

leaves with low vitality, and in cations. See also Greenland and

parts, like the petioles, which Trt'cul, * Annal. des Sc. nat. bot.'

carry on leaf-functions in a very (4tli series), torn. iii. 1855, pp.

imperfect manner. All that can 297 and 303.
be said, therefore, is that the hahs

6 DROSERA ROTUNDIFOLIA. Chap. 1.

part, which alone is capable of movement, consists of a prolon-
gation of the leaf; the spiral vessels being extended from this
to the uppermost part. We shall hereafter see that the ter-
minal tentacles of the divided leaves of Eoridula are still in
an intermediate condition.
The glands, with the exception of those borne by the extreme

Fig. 3.

{Drosera rotundifolia.)

lA>ngitudlnal section of a gland ; greatly magnilied. From Dr. Warming.

marginal tentacles, are oval, and of nearly uniform size, viz.
nlxjut 5^*0 of an inch in length. Their structure is remarkable,
and their functions complex, for they secrete, absorb, and are
artcd on by various stimulants. They consist of an outer layer
of siiijill iK)lyg()nal cells, containing purj)le granular matter or
lluid, and ^\ith the walls thicker than those of the pedicels.

Chap. I. STKUCTUEE OF THE LEAVES. 7

Within this layer of cells there is an inner one of differently-
shaped ones, likewise filled with pnrple fluid, but of a slightly
different tint, and differently affected by chloride of gold. These
two layers are sometimes well seen when a gland has been
crushed or boiled in caustic potash. According to Dr. Warming,
there is still another layer of much more elongated cells, as
shown in the accompanying section (fig. 3) copied from his
work; but these cells were not seen by Nitschke, nor by me.
In the centre there is a group of elongated, cylindrical cells of
unequal lengths, bluntly pointed at their upper ends, truncated
or rounded at their lower ends, closely pressed together, and
remarkable from being surrounded by a spiral line, which can be
separated as a distinct fibre.

These latter cells are filled with limpid fluid, which after long
immersion in alcohol deposits much bro^^n matter. I presume
that they are actually connected with the spiral vessels which run
up the tentacles, for on several occasions the latter were seen to
divide into two or three excessively thin branches, which could
be traced close up to the spiriferous cells. Their development
has been described by Dr. Warming. Cells of the same kind
have been observed in other plants, as I hear from Dr. Hooker,
and were seen by me in the margins of the leaves of Pinguicula.
Whatever their function may be, they are not necessary for the
secretion of the digestive fluid, or for absorption, or for the
communication of a motor impulse to other parts of the leaf,
as we may infer from the structure of the glands in some other
genera of the Droseracese.

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 em-
bedded on the upper surface of the pedicel, instead of standing
at the apex. In other respects they do not differ essentially
fi-om 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

8 DROSERA ROTUNDIFOLIA. Chap. I.

the cells of tlie 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.
IJoth surfaces of the leaf, the pedicels of the tentacles, espe-
cially the lower sides of the outer ones, and the petioles, are
studded with minute papillie (hairs or trichomes), having a
conical basis, and bearing on their summits two, and occasion-
ally three or even four, rounded cells, containing much proto-
])lasm. These papilla} are generally colourless, but sometimes
include a little purple fluid. They vary in development, and
graduate, as Kitschke * states, and as I repeatedly observed
into the long multicellular hairs. The latter, as well as the
l>a]Mllaj, are probably rudiments of formerly existing tentacles.

I may here add, in order not to recur to the papillss, 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 afi"ected. After a leaf had been left in a weak
infusion of raw meat for 10 hours, the cells of the papillae had
evidently absorbed animal matter, for instead of limpid fluid
tlu-y now contained small aggregated masses of protoplasm,
which slowly and incessantly changed their forms. A similar
result followed from an immersion of only 15 minutes in a
sohition of one part of carbonate of ammonia to 218 of water,
and the adjoining cells of the tentacles, on which the papillas
were seated, now likewise contained aggregated masses of proto-
plasm. We may therefore conclude that when a leaf has closely
clasped a captured insect in the manner immediately to be
described, the 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 papilla) on the backs of the leaves or on the
petioles.

* Nitsclikc has elaborately described and figured these papilla),
*13ot. Zeitun-,' ISGI, pp. 2;]4, 25:^, 251.

Chap. L ACTION OF THE PAKTS. 9

Preliminary Sketch of the Action of the several Farts, and
of the Manner in ivJiich 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, nntil at last all
become closely inflected over the object. This takes
place in from one hour to four or five or more hours.
The difference in the time required depends on many
circumstances ; namely on the size of the object and
on its nature, that is, whether it contains soluble
matter of the proper kind ; on the vigour and age of
the leaf ; whether it has lately been in action ; cfnd,
according to Nitschke,* on the temperature of the
day, as likewise seemed to me to be the case. A living
insect is a more efficient object than a dead one, as
in struggling it presses against the glands of many
tentacles. An insect, such as a fly, with thin integu-
ments, through which animal matter in solution can
readily pass into the surrounding dense secretion, is
more efficient in causing prolonged inflection than an
insect with a thick coat, such as a beetle. The inflec-
tion of the tentacles takes place indifferently in the
light and darkness; and the plant is not subject to
any nocturnal movement of so-called sleep.

If the glands on the disc are repeatedly touched or
brushed, although no object is left on them, the
marginal tentacles curve inwards. So again, if drops
of various fluids, for instance of saliva or of a solu-
tion of any salt of ammonia, are placed on the central
glands, the same result quickly follows, sometimes in
under half an hour.

Bot. Zeitung,' 18G0, p. 246.

10

DROSERA ROTUNDIFOLIA.

Chap. 1.

The tentacles in the act of inflection sweep through
a wide space ; thus a marginal tentacle, extended in
the same plane with the blade, moves through an angle
of 180^ ; and I have seen the much reflected tentacles
of a leaf which stood upright move through an angle
of not less than 270^ The bending part is almost
confined to a short space near the base ; but a rather
larrrer portion of the elongated exterior tentacles

Fio. 4.

{Drosera rotundifolia.)

Loaf (onliirgod) with all the tentacles
closely intic ctcd, from immorsion in a
Bolutioti of i)hosplKit(' of ammonia (one
part to 87,500 of water).

Fig. 5.

(Dmsera rotundifolia.')

Leaf (enlarged) with the tentacles on one
side inflected over a bit of meat placed
ou the disc.

becomes sliglitly incurved ; the distal half in all cases
remaining straight. The short tentacles in the centre
of the disc when directly excited, do not become in-
flected ; but they are capable of inflection if excited
by a motor impulse received from other glands at a
distance. Thus, if a leaf is immersed in an infusion
of raw meat, or in a weak solution of ammonia (if the

Chaf. I. ACTION OF THE PARTS. 11

solution is at all strong, the leaf is paralysed), all the
exterior tentacles bend inwards (see fig. 4), excepting
those near the centre, which remain upright ; but these
bend towards any exciting object placed on one side
of the disc, as shown in fig. 5. The glands in fig. 4
may be seen to form a dark ring round the centre ; and
this follows from the exterior tentacles increasing in
length in due proportion, as they stand nearer to the
circumference.

. The kind of inflection which the tentacles undergo
is best shown when the gland of one of the long exterior

Fig. 6.
(Brosera rotundifolia.)

Diagram showing one of the exterior tentacles closely inflected ; the two adjoining
ones in their ordinary position.

tentacles is in any way excited ; for the surrounding
ones remain unaffected. In the accompanying outline
(fig. 6) we see one tentacle, on which a particle of
meat had been placed, thus bent towards the centre of
the leaf, with two others retaining their original
position. A gland may be excited by being simply
touched three or four times, or by prolonged contact
with organic or inorganic objects, and various fluids. I
have distinctly seen, through a lens, a tentacle begin-
ning to bend in ten seconds, after an object had been

12 DROSERA EOTUNDirOLIA. Chap. I,

placed on its gland ; and I have often seen strongly
pronounced inflection in under one minute. It is sur-
prising liow minute a particle of any substance, such
as a bit of thread or hair or splinter of glass, if placed
in actual contact with the surface of a gland, suffices
to cause the tentacle to bend. If the object, which has
been carried by this movement to the centre, be not
very small, or if it contains soluble nitrogenous matter,
it acts on the central glands ; and these transmit a
motor impulse to the exterior tentacles, causing them
to bend inwards.

Not only the tentacles, but the blade of the leaf
often, but by no means always, becomes much in-
carved, when any strongly exciting substance or fluid
is placed on the disc. Droj)s of milk and of a solution
of nitrate of ammonia or soda are particularly apt to
produce this effect. The blade is thus converted into
a little cup. The manner in which it bends varies
greatly. Sometimes the apex alone, sometimes one
side, and sometimes both sides, become incurved. For
instance, I placed bits of hard-boiled egg on three
leaves ; one had the apex bent towards the base ; the
second had both distal margins much incurved, so
that it became almost triangular in outline, and this
perhaps is the commonest case ; whilst the third blade
was not at all affected, though the tentacles were as
closely inflected as in the two previous cases. The
whole blade also generally rises or bends upwards, and
thus forms a smaller angle with the footstalk than it
did before. This appears at first sight a distinct
kind of movement, but it results from the incurvation
of that part of the margin which is attached to the
footstalk, causing the blade, as a whole, to curve or
move upwards.
• The length of time during which the tentacles as

Chap. I. ACTION OF THE PARTS. 13

well as the blade remain inflected over an object placed
on the disc, depends on various circumstances ; namely
on the vigour and age of the leaf, and, according to
Dr. Nitschke, on the temperature, for during cold
weather when the leaves are inactive, they re-expand
at an earlier period than when the weather is warm.
But the nature of the object is by far the most
important circumstance ; I have repeatedly found that
the tentacles remain clasped for a much longer average
time over objects which yield soluble nitrogenous
matter than over those, whether organic or inorganic,
which yield no such matter. After a period varying
from one to seven days, the tentacles and blade re-
expand, and are then ready to act again. I have seen
the same leaf inflected three successive times over
insects placed on the disc; and it would probably
have acted a greater number of times.

The secretion from the glands is extremely viscid,
so that it can be drawn out into long threads. It
appears colourless, but stains little balls of paper pale
pink. An object of any kind placed on a gland always
causes it, as I believe, to secrete more freely ; but
the mere presence of the object renders this difficult
to ascertain. In some cases, however, the effect was
strongly marked, as when particles of sugar were
added; but the result in this case is probably due
merely to exosmose. Particles of carbonate and phos-
phate of ammonia and of some other salts, for instance
sulphate of zinc, likewise increase the secretion. Im-
mersion in a solution of one part of chloride of gold,
or ■ of some other salts, to 437 of water, excites the
glands to largely increased secretion; on the other
hand, tartrate of antimony produces no such effect.
Immersion in many acids (of the strength of one part
to 437 of water) likewise causes a wonderful amount of

14 DEOSEEA EOTUNDIFOLIA. Chap. I.

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 dejDendent 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 dro]3S on the two
sides, and by placing bits of meat on one side of the
disc ; and as soon as the tentacles on this side became
much inflected, but before the glands touched the meat,
the drops of secretion became larger. This was re-
peatedly observed, but a record was kept of only
thirteen cases, in nine of which increased secretion was
phxinly 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 influence 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 ghinds have touched the object on the centre of
tlui leaf. This acid is of a different nature from that
contained in the tissue of the leaves. As long as the

Chap. I. ACTION OF THE PAETS. 15

tentacles remain closely inflected, the glands continue
to secrete, and the secretion is acid ; so that, if neu-
tralised by carbonate of soda, it again becomes acid
after a few hours. I have observed the same leaf with
the tentacles closely inflected over rather indigestible
substances, such as chemically prepared casein, pour-
ing forth acid secretion for eight successive days, and
over bits of bone for ten successive days.

The secretion seems to possess, like the gastric juice
of the higher animals, some antiseptic power. During
very warm weather I placed close together two equal-
sized bits of raw meat, one on a leaf of the Drosera,
and the other surrounded by wet moss. They were
thus left for 48 hrs., and then examined. The bit on
the moss swarmed with infusoria, and was so much
decayed that the transverse striae on the muscular
fibres could no longer be clearly distinguished;
whilst the bit on the leaf, which was bathed by the
secretion, was free from infusoria, and its stri« were
perfectly distinct in the central and undissolved por-
tion. In like manner small cubes of albumen and
cheese placed on wet moss became threaded with
filaments of mould, and had their surfaces slightly
discoloured and disintegrated; whilst those on the
leaves of Drosera remained clean, the albumen being
changed into transparent fluid.

As soon as tentacles, which have remained closely
inflected during several days over an object, begin to
re-expand, their glands secrete less freely, or cease
to secrete, and are left dry. In this state they are
covered with a film of whitish, semi-fibrous matter,
which was held in solution by the secretion. The
drying of the glands during the act of re-expan-
sion is of some little service to the plant ; for I have
often observed that objects adhering to the leaves
2

16 DROSERA ROTUNDIFOLIA. Chap. 1.

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 some-
times torn by the re-expansion of the tentacles into
fragments, which remain scattered all over the leaf.
After the re-expansion is complete, the glands quickly
begin to re-secrete, and as soon as 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 tracheae being closed by
the secretion. If an insect adheres to only a few of
the glands of the exterior tentacles, these soon
become inflected and carry their prey to the tentacles
next succeeding them inwards; these then bend in-
wards, and so onwards, until the insect is ultimately
carried by a curious sort of rolling movement to the
centre of the leaf. Then, after an interval, the ten-
tacles on all sides become inflected and bathe their
prey with their secretion, in the same manner as
if the insect had first alighted on the central disc. It
is surprising how minute an insect suffices to cause
this action : for instance, I have seen one of the
smallest species of gnats (Culex), which had just
settled with its excessively delicate feet on the
glands of the outermost tentacles, and these were
ah-eady 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

Chap. I. ACTION OF TUE PARTS. 17

assuredly have been carried to tlie centre of tlie leaf
and been securely clasped on all sides. We shall
hereafter see what excessively small doses of certain
organic fluids and saline solutions cause strongly
marked inflection.

Whether insects alight on the leaves by mere
chance, as a resting-place, or are attracted by the
odour of the secretion, I know not. I suspect from
the number of insects caught by the English species
of Drosera, and from what I have observed with some
exotic species kept in my greenhouse, that the odour
is attractive. In this latter case the leaves may be
compared with a baited trap ; in the former case with
a trap laid in a run frequented by game, but without
any bait.

That the glands possess the power of absorption, is
shown by their almost instantaneously becoming dark-
coloured when given a minute quantity of carbonate of
ammonia ; the change of colour being chiefly or exclu-
sively due to the rapid aggregation of their contents.
When certain other fluids are added, they become pale-
coloured. Their power of absorption is, however, best
shown by the widely different results which follow,
from placing drops of various nitrogenous and non-
nitrogenous fluids of the same density on the glands
of the disc, or on a single marginal gland ; and like-
wise by the very different lengths of time during which
the tentacles remain inflected over objects, which yield
or do not yield soluble nitrogenous matter. This
same conclusion might indeed have been inferred from
the structure and movements of the leaves, which are
so admirably adapted for capturing insects.

The absorption of animal matter from captured
insects explains how Drosera can flourish in extremely
poor peaty soil, — in some cases where nothing but

18 DROSERA ROTUNDIFOLIA. Chap. I.

sphagnum moss grows, and mosses depend altogether
on the atmosphere for their nourishment. Although
the leaves at a hasty glance do not appear green, owing
to the purple colour of the tentacles, yet the upper and
lower surfaces of the blade, the pedicels of the central
tentacles, and the petioles contain chlorophyll, so that,
no doubt, the plant obtains and assimilates carbonic
acid from the air.' JSTeyertheless, , considering the
nature of the soil where it grows, the supply of nitrogen
would be extremely limited, or quite deficient, unless
the plant had the power of obtaining this important
element from captured insects. We can thus under-
stand how it is that the roots are so poorly developed.
These usually consist of only two or three slightly
divided branches, from half to one inch in length,
furnished with absorbent hairs. It appears, therefore,
that the roots serve only to imbibe water ; though, no
doubt, they would absorb nutritious matter if present
in the soil ; for as we shall hereafter see, they absorb
a weak solution of carbonate of ammonia. A plant
of Drosera, with the edges of its leaves curled in-
wards, so as to form a temporary stomach, with the
glands of the closely inflected tentacles poiu-ing 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.

Chap. II. INFLECTION INDIRECTLY CAUSED. 19

CHAPTEK II.

The Movements of the Tentacles feom 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 — Difterence in the action of bodies yiekUng 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.

I WILL give in this and the following chapters some of
the many experiments made, which best illustrate the
manner and rate of movement of the tentacles, when
excited in various ways. The glands alone in all
ordinary cases are susceptible to excitement. When
excited, they do not themselves move or change form,
but transmit a motor impulse to the bending part of
their own and adjoining tentacles, and are thus carried
towards the centre of the leaf. Strictly speaking, the
glands ought to be called irritable, as the term sensi-
tive generally implies consciousness ; but no one sup-
poses that the Sensitive-plant is conscious, and as I
have found the term convenient, I shall use it without
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

20 DROSERA ROTUNDIFOLIA. Chap. H.

exterior tentacles, near their bases, and does not (as
will hereafter be proved) first travel up the j)edicels to
the glands, to be then reflected back to the bending
place. Nevertheless, some influence does travel up to
the glands, causing them to secrete more copiously,
and the secretion to become acid. This latter fact
is, I believe, quite new in the physiology of plants ;
it has indeed only recently been established that in
the animal kingdom an influence can be transmitted
along the nerves to glands, modifying their power of
secretion, independently of the state of the blood-
vessels.

Th6 Inflection of the Exterior Tentacles from the Glands
of the Disc heing excited hy Bepeated Touches, or hj
Objects left in Contact with them.

The central glands of a leaf were irritated with a
small stiff camel-hair brush, and in 70 m. (minutes)
several of the outer tentacles were inflected ; in 5 hrs.
(hours) all the sub-marginal tentacles were inflected ;
next morning after an interval of about 22 hrs. they were
fully re-expanded. In all the following cases the period
is reckoned from the time of first irritation. Another
leaf treated in the same manner had a few tentacles
inflected in 20 m. ; in 4 hrs. all the submarginal and
some of the extreme marginal tentacles, as well as the-
edge of the leaf itself, were inflected ; in 17 hrs. they
had recovered their proper, expanded position. I then
put a dead fly in the centre of the last-mentioned leaf,
and next morning .it was closely clasped; five days
afterwards the leaf re-expanded, and the tentacles,
with their glands surrounded by secretion, were ready
to act again.

Particles of meat, dead flies, bits of paper, wood,
dried moss, sponge, cinders, glass, &c., were repeatedly

Chap. n. INFLECTION INDIKECTLY CAUSED. 21

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 probably
twice, I put a fresh fly : in 7 hrs. it was moderately,
and in 21 hrs. thoroughly well, clasped, with the
edges of the leaf inflected. In two days and a
half the leaf had nearly re-expanded ; as the exciting
object was an insect, this unusually short period of in-
flection was, no doubt, due to the leaf having, recently
been in action. Allowing this same leaf to rest for
only 'a single day, I put on another fly, and it again
closed, but now 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
disc, on one side of a leaf, as near as possible to
its circumference, the tentacles on this side are first
afl*ected, those on the opposite side much later, or, as
often occurred, not at all. This was repeatedly proved
by trials with bits of meat ; but I will here give only
the case of a minute fly, naturally caught and still
alive, which I found adhering by its delicate feet to
the glands on the extreme left side of the central disc.
The marginal tentacles on this side closed inwards
and killed the fly, and after a time the edge of the
leaf on this side also became inflected, and thus
remained for several days, whilst neither the tentacles
nor the 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

22 DEOSERA ROTUNDIFOLIA. Chap. II.

outer tentacles to bend inwards. But this follows
much more surely and quickly, if the object contains
nitrogenous matter which can be dissolved by the
secretion. On one occasion I observed the follow-
in or unusual circumstance. Small bits of raw meat
(which acts more energetically than any other sub-
stance), of paper, dried moss, and of the quill of a
pen were placed on several leaves, and they were all
embraced equally well in about 2 hrs. On other
occasions the above-named substances, or more com-
monly particles of glass, coal-cinder (taken from the
fire), stone, gold-leaf, dried grass, cork, blotting-paper,
cotton- wool, and hair rolled up into little balls, were
used, and these substances, though they were some-
times well embraced, often caused no movement what-
ever in the outer teiitacles, 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,
<Scc. I will give only two instances. Minute flies were
l)laced 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 those 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 tlie flies used in the last experiment) were placed
on the centres of three leaves: after an interval of
19 hrs. one of the j^articles was tolerably well embraced;

Chap. II. INFLECTION INDIRECTLY CAUSED. 23

a second by a very few tentacles ; and a tliird by none.
I then removed the particles from the two latter leaves,
and put on them recently killed flies. iThese were
fairly well embraced in 7 J hrs. and thoroughly after
20 J hrs. ; the tentacles remaining inflected for many
subsequent days. On the other hand, the one leaf
which had in the course of 19 hrs. embraced the bit of
cinder moderately well, and to which no fly was given,
after an additional 33 hrs. (i. e. in 52 hrs. from the
time when the cinder was put on) was completely
re-expanded and ready to act again.

From these and numerous other experiments not
worth giving, it is certain that inorganic substances,
or such organic substances as are not attacked by the
secretion, act much less quickly and efficiently than
organic substances yielding soluble matter which is
absorbed. Moreover, I have met with very few excep-
tions to the rule, and these exceptions apparently
depended on the leaf having been too recently in
action, that the tentacles remain clasped for a much
longer time over organic bodies of the nature just
specified than over those which are not acted on by
the secretion, or over inorganic objects.*

* Owinj? to the extraordinary and particles were then placed
belief held by M. Zieglcr (' Comp- (every iustriiment with which
tes rendus,' May 1872, p. 122), they were touched havincf been
that albuminous substances, if previously immersed in boiling
held for a moment between the water) on the glands of several
fingers, acquire the property of leaves, and they acted in exactly
making the tentacles of Drosera the same manner as other par-
contract, whereas, if not thus held, tides, which had been purposely
they have no such power, I tried handled for some time. Bits of
some experiments with great care, a boiled egg, cut with a knife
but the results did not confirrn which had been washed in boiling
this belief. Eed-hot cinders were water, also acted like any other
taken out of the fire, and bits animal substance. I breathed on
of glass, cotton-thread, blotting some leaves for above a minute,
paper and thin slices of cork and repeated the act two or three
were immersed in boiling water ; times, with my mouth close to

24 DROSEEA EOTUNDIFOLIA. Chap. II.

The Inflection of the Exterior Tentacles as directly caused
hij Objects left in Contact with their Glands.
I made a vast number of trials by placing, by means
of a fine needle moistened with distilled water, and
with the aid of a lens, particles of various substances
on the viscid secretion surrounding the glands of the
outer tentacles. I experimented on both the oval and
long-headed glands. When a particle is thus placed
on a single gland, the movement of the tentacle is
particularly well seen in contrast with the statioi^ary
condition of the surrounding tentacles. (See previous
fig. C.) 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 movement as seen through a lens resembled that
of the hand of a large clock. In 5 m. it had moved
through 90°, and when I looked again after 10 m.,
the particle had reached the centre of the leaf; so
that the whole movement was completed in less

them, but this protluccd no effect. cause inflection. M. Ziegler

I niiiy here add, as showing that makes still more extraordinary

the leaves are not acted on by the statements with respect to the

otlour of nitrogenous substances, powerof animal substances, which

that pieces of raw meat stuck on have been left close to, but not in
needles were fixed as close as . contact with, sulphate of quinine.

iw)s.sihle, without actual contact, The action of salts of quinine will

to several leaves, but produced be described in a future chapter,

no eflfect whatever. On the other ^ince the appearance of the paper

hand, as we shall hereafter see, above referred to, M. Ziegler has

the vapours of certain volatile published a book on the same

substances and fluids, such as of subject, entitled, 'Atonicite et

oirbonate of ammonia, chloro- Zuicite,' 1874.
form, certain essential oils, &c..

Chap. II. INFLECTION INDIKECTLY CAUSED. 25

than 17 m. 30 s. In the course of some hours this
minute bit of meat, from ha^dng been brought into
contact with some of the glands of the central disc,
acted centrifugally on the outer tentacles, which all be-
came closely inflected. Fragments of flies were placed
on the glands of four of the outer tentacles, ex-
tended in the same plane with that of the blade,. and
three of these fragments were carried in 35 m. through
an angle of 180° to the centre. The fragment on
the fourth tentacle was very minute, and it was
not carried to the centre until 3 hrs. had elapsed. In
three other cases minute flies or portions of larger
ones were carried to the centre in 1 hr. 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 embraced by the other tentacles
after an interval of from 4 to 10 hrs.

I also placed in the manner just described six small
balls of writing-paper (rolled up by the aid of pincers,
so that they were not touched by my fingers) on the
glands of six exterior tentacles on distinct leaves;
three of these were carried to the centre in about 1 hr.,
and the other three in rather more than 4 hrs. ; but
after 24 hrs. only two of the six balls were well em-
braced by the other tentacles. It is possible that
the secretion may have dissolved a trace of glue or
animalised matter from the balls of paper. Four par-
ticles of coal-cinder were then placed on the glands
of four exterior tentacles ; one of these reached
the centre in 3 hrs. 40 m. ; the second in 9 hrs. ; the
third within 24 hrs., but had moved only part of the
way in 9 hrs. ; whilst the fourth moved only a very
short distance in 24 hrs., and never moved any farther.
Of the above three bits of cinder which were ultimately
carried to the centre, one alone was well embraced by

2(j DROSERA ROTUNDIFOLTA. Chap. II.

many of the other tentacles. We here see clearly that
such bodies as particles of cinder or little balls of
paper, after being carried by the tentacles to the
central glands, act very differently from fragments of
flies, in causing the movement of the surrounding
tentacles.

I made, without carefully recording the times of
movement, many similar trials with other substances,
such as splinters of white and blue glass, particles of
cork, minute bits of gold-leaf, &c. ; and the propor-
tional number of cases varied much in which the
tentacles reached the centre, or moved only slightly,
or not at all. One evening, particles of glass and
cork, rather larger than those usually employed, were
placed on about a dozen glands, and next morning,
after 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. In another case
4 of the particles of cinder, glass, and thread, placed
on separate glands, were carried towards, or actually
to, the centre ; in another case ^, in another -f^, and
in the last case only -^ were thus carried inwards, the
small proportion being here due, at least in part, to the
leaves being rather old and inactive. Occasionally a
gland, with its light load, could be seen through a
strong lens to move an extremely short distance and
then stop ; this was especially apt to occur when ex-
cessively minute particles, miich less than those of
which the measurements will be immediately given,
were placed on glands ; so that we here have nearly
the limit of any action.

I was so much surprised at the smallness of the par-
ticles which caused the tentacles to become greatly
inflected that it seemed worth while carefully to
ascertain how minute a particle would plainly act.

Chap. II. INFLECTION INDIRECTLY CAUSED. 27

Accordingly measured lengths of a narrow strip of
blotting paper, of fine cotton-tliread, and of a woman's
hair, were carefully weighed for me by Mt. 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 ^-^ 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 -nnrT of a grain, or -0464 of a* milli-
gramme. Five nearly equal bits of cotton-thread were
tried, and all acted. The shortest of these was -3^ of
an inch in length, and weighed g ^\^ ^ of a grain. The
tentacle in this case was considerably inflected in
1 hr. 30 m., and the bit of thread was carried to the
centre of the leaf in 1 hr. 40 m. Again, two particles
of the thinner end of a woman's hair, one of these
being -j-^f-o of an inch in length, and weighing xf^Itt o^
a grain, the other -i%-o of an inch in length, and weigh-
ing of course a little more, were placed on two glands on
opposite sides of the same leaf, and these two tentacles
were inflected halfway towards the centre in 1 hr. 10m.;
all the many other tentacles round the same leaf re-
maining motionless. The appearance of this one leaf
showed in an unequivocal manner that these minute
particles sufiiced to cause the tentacles to bend. Alto-
gether, ten such particles of hair were j)laced on ten
glands on several leaves, and seven of them caused

28 DROSERA. ROTUNDIFOLIA. Chap. II.

the tentacles to move in a conspicuous manner. Tlie
smallest particle which was tried, and which acted
plainly, was only -^yVo of an inch ('203 millimetre) in
lenf^th, and weighed the yrtr-o of a grain, or -000822
milligramme. In these several cases, not only was the
inflection of the tentacles conspicuous, but the purple
fluid within their cells became aggregated into little
masses of protoplasm, in the manner to be described in
the next chajDter ; 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
liundreds of other tentacles on the same leaves which
had not thus acted.

My surprise was greatly excited, not only by the
minuteness of the particles which caused movement,
but how they could possibly act on the glands ; for it
must be remembered that they were laid with the
greatest care on the convex surface of the secretion.
At first I thought — but, as I now know, erroneously —
that particles of such low specific gravity as those of
cork, thread, and paper, would never come into contact
with the surfaces of the glands. The particles cannot
act simply by their weight being added to that of the
secretion, for small drops of water, many times heavier
than the particles, were repeatedly added, and never
produced any efi'ect. Nor does the disturbance of the
secretion produce any effect, for long threads were
drawn out by a needle, and aflixed to some adjoining
object, and thus left for hours ; but the tentacles
remained motionless.

I also carefully removed the secretion from four
glands with a sharply pointed piece of blotting-paper,
so that they were exposed for a time naked to the air,
but this caused no movement ; yet these glands were

Chap. II. INFLECTION INDIRECTLY- CAUSED. 29

in an efficient state, for after- 24 hrs. had elapsed, they
were tried with bits of meat, and all became quickly
inflected. It then occurred to me that particles float-
ing on the secretion would cast shadows on the glands,
which might be sensitive to the interception of the
light. Although this seemed highly improbable, as
minute and thin splinters of colourless glass acted
powerfully, nevertheless, after it was dark, I put on,
by the aid of a single tallow candle, as quickly as
possible, particles of cork and glass on the glands of a
dozen tentacles, as well as some of meat on other
glands, and covered them up so that not a ray of light
could enter ; but by the next morning, after an interval
of 13 hrs., all the particles were carried to the centres
of the leaves.

These negative results led me to try many more
experiments, by placing particles on the surface of the
drops of secretion, observing, as carefully as I could,
whether they penetrated it and touched the surface of
the glands. The secretion, from its weight, generally
forms a thicker layer on the under than on the upper
sides of the 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 pre-
viously employed ; and I now observed that they
absorbed much more of the secretion, in the course of
a few minutes,. than I should have thought possible ; and
as they had been laid on the upper surface of the secre-
tion, where it is thinnest, they were often drawn down,
after a time, into contact with at least some one point
of the gland. With respect to the minute splinters
of glass and particles of hair, I observed that the
secretion slowly spread itself a little over their sur-
faces, by which means they were likewise drawn down-
wards or sideways, and thus one end, or some minute

30 DEOSERA ROTUNDIFOLIA. Chap. II.

prominence, often came to touch, sooner or later, the
ghind.

In the foregoing and following cases, it is probable
that the vibrations, to which the furniture in every
room is continually liable, aids in bringing the par-
ticles into contact with the glands. But as it was
sometimes difficult, owing to the refraction of the secre-
tion, to feel sure whether the particles were in contact,
I tried the following experiment. Unusually minute
particles of glass, hair, and cork, were gently placed on
the drops round several glands, and very few of the
tentacles moved. Those which were not affected were
left for about half an hour, and the particles were
then disturbed or tilted up several times wdth a fine
needle under the microscope, the glands not being
touched. And now in the course of a few minutes
almost all the hitherto motionless tentacles began to
move ; and this, no doubt, was caused by one end or
some prominence of the particles having come into
contact with the surface of the glands. But as the
particles were unusually minute, the movement was
small.

Lastly, some dark blue glass pounded into fine
splinters was used, in order that the points of the par-
ticles might be better distinguished when immersed in
the secretion ; and thirteen such particles were placed
in contact with the depending and therefore thicker
part of the drops round so many glands. Five of the
tentacles began moving after an interval of a few
minutes, and in these cases I clearly saw that the par-
ticles touched the lower surface of the gland. A sixth
tentacle moved after 1 hr. 45 m., and the particle
was now in contact with the gland, which was not the
case at first. So it was with the seventh tentacle, but
its movement did not begin until 3 hrs. 45 m. had

Chap. II. INFLECTION INDIRECTLY CAUSED. 31

elapsed. Tlie remaining six tentacles never moved
as long as they were observed; and the particles
apparently never came into contact with the surfaces
of the glands.

From these experiments we learn that particles not
containing soluble matter, when placed on glands, often
cause the tentacles to begin bending in the course of
from one to five minutes ; and that in such cases the
particles have been from the first in contact with the
surfaces of the glands. When the tentacles do not
begin moving for a much longer time, namely, from
half an hour to three or four hours, the particles
have been slowly brought into contact with the
glands, either by the secretion being absorbed by the
particles or by its gradual spreading over them, to-
gether with its consequent quicker evaporation.
When the tentacles do not move at all, the particles
have never come into contact with the glands, or in
some cases the tentacles may not have been in an
active condition. In order to excite movement, it is
indispensable that the particles should actually rest on
the glands; for a touch once, twice, or even thrice
repeated by any hard body is not sufficient to excite
movement.

Another experiment, showing that extremely mi-
nute particles act on the glands when immersed in
water, may here be given. A grain of sulphate of
quinine was added to an ounce of water, which was
not afterwards filtered ; and on placing three leaves in
ninety minims of this fluid, I was much surprised to find
that all three leaves were greatly inflected in 15 m. ;
for I knew from previous trials that the solution does
not act so quickly as this. It immediately occurred
to me that the particles of the undissolved salt, which
were so light as to float about, might have come

32 DKOSEKA EOTUNDIFOLIA. Chap. H.

into contact witli the glands, and caused this rapid
movement. Accordingly I added to some distilled
^vater a pinch of a quite innocent substance, namely,
precipitated carbonate of lime, which consists of an
impalpable powder ; I shook the mixture, and thus got
a fluid like 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 ad-
hering to the external surface of the secretion. Some,
however, had penetrated it, and were lying on the sur-
faces of the glands ; and no doubt it was these particles
which caused the tentacles to bend. When a leaf is im-
mersed in water, the secretion instantly swells much ;
and I presume that it is ruptured here and there, so
that little eddies of water rush in. If so, we can under-
stand how the atoms of chalk, which rested on the
surfaces of the glands, had j)enetrated the secretion.
Anyone who has rubbed precipitated chalk between
his fingers will have perceived how excessively fine
tlic powder is. No doubt there must be a limit, beyond
wliich a particle would be too small to act on a gland ;
]»ut what this limit is, I know not. I have often seen
iilnx'S and dust, which had fallen from the air, on the
ghmds 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
ghind itself.

Finally, it is an extraordinary fact that a little
bit of soft thread, -^V of an inch in length and weigh-
ing -^\j-^ of a grain, or of a human hair, ■y-J'-j^-^ of an
inch in length and weighing only --^i— ^ of a grain
(•000822 milligramme), or particles of precipitated
chalk, after resting for a short time on a gland,
should induce some change in its cells, exciting them

Chap. II. INFLECTION DIRECTLY CAUSED. 33

to transmit a motor impulse througliout tlie whole
length of the j^edicel, consisting of about twenty cells,
to near its base, causing this part to bend, and the
tentacle to sweep through an angle of above 180°.
That the contents of the cells of the glands, and after-
wards those of the pedicels, are affected in a plainly-
visible manner by the pressure of minute particles, we
shall have abundant evidence when we treat of the
aggregation of protoplasm. But the case is much more
remarkable than as yet stated ; for the particles are sup-
ported by the viscid and dense secretion ; nevertheless,
even smaller ones than those of which the measure-
ments have been given, when brought by an insensibly
slow movement, through the means above specified, into
contact with the surface of a gland, act. on it, and the
tentacle bends. The pressure exerted by the particle
of hair, weighing only -y-gJ^-o of a grain and supported
by a dense fluid, must have been inconceivably slight.
We may conjecture that it could hardly have equalled
the millionth of a grain; and we shall hereafter see
that far less than the millionth of a grain of phos-
phate of ammonia in solution, when absorbed by a
gland, acts on it and induces movement. A bit of
hair, -^ of an inch in length, and therefore much
larger than those used in the above experiments, was
not perceived when placed on my tongue ; and it is
extremely doubtful whether any nerve in the human
body, even if in an inflamed condition, would be in
any way affected by such a particle supported in a
dense fluid, and slowly brought into contact with the
nerve. Yet the cells of the glands of Drosera are thus
excited to transmit a motor impulse to a distant point,
inducing movement. It appears to me that hardly
any more remarkable fact than this has been observed
in the vegetable kingdom.

DEOSEEA EOTUNDIFOLIA. Chap. II

The Inflection of the Exterior Tentacles, when their Glands
are excited hy Repeated Touches.

We have already seen that, if the central glands
are excited by being gently brushed, they trans-
mit a motor impulse to the exterior tentacles,
causing them to bend; and we have now to con-
sider the effects which follow from the glands of
the exterior tentacles being themselves touched. On
several occasions, a large number of glands were
touched only once with a needle or fine brush,
hard enough to bend the whole flexible tentacle ;
and though this must have caused a thousand-
fold greater pressure than the weight of the above
described particles, not a tentacle moved. On
another occasion forty-five glands on eleven leaves
were touched once, twice, or even thrice, with a
needle or stiff bristle. This was done as quickly as
possible, but with force sufficient to bend the ten-
tacles ; yet only six of them became inflected, — three
phiinly, 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
tlie al)ove manner three glands, which happened to
be extremely sensitive, and all three were inflected
almost as quickly as if bits of meat had been placed
on them. On another occasion I gave a single for-

Chap. II. THE EFFECTS OF REPEATED TOUCHES. 35

cible touch to a considerable number of glands, and
not one moved ; but these same glands, after an inter-
val of some hours, being touched four or five times
with a needle, several of the tentacles soon became
inflected.

The fact of a single touch or even of two or three
touches not causing inflection must be of some service
to the plant ; as during stormy weather, the glands
cannot fail to be occasionally touched by the tall
blades of grass, or by other plants growing near ; and
it would be a great evil if the tentacles were thus
brought into action, for the act of re-expansion takes
a considerable time, and until the tentacles are re-
expanded they cannot catch prey. On the other
hand, extreme sensitiveness to slight pressure is of the
highest service to the plant ; for, as we have seen, if
the delicate feet of a minute struggling insect press
ever so lightly on the surfaces of two or three glands,
the tentacles bearing these glands soon curl inwards
and carry the insect with them to the centre, causing,
after a time, all the circumferential tentacles to
embrace it. Nevertheless, the movements of the
plant are not perfectly adapted to its requirements;
for if a bit of dry moss, peat, or other rubbish, is
blown on to the disc, as often happens, the tentacles
clasp it in a useless ilianner. They soon, however,
discover their mistake and release such innutritions
objects.

It is also a remarkable fact, that drops of water fall-
ing from a height, whether under the form of natural
or artificial rain, do not cause the tentacles to move ;
yet the drops must sta'ike the glands with considerable
force, more especially after the secretion has been all
washed away by heavy rain ; and this often occurs,

3G DKOSEEA EOTUNDIFOLIA. Chap. II.

tlioiijxh the secretion is so yiscid that it can be re-
moved with difficulty merely by waving the leaves in
water. If the falling drops of water are small, they
adhere to the secretion, the w^eight of which must be
increased in a much greater degree, as before re-
marked, than by the addition of minute particles of
solid matter ; yet the drops never cause the tentacles
to become inflected. It would obviously have been a
great evil to the plant (as in the case of occasional
touches) if the tentacles were excited to bend by
every shower of rain ; but this evil has been avoided
by the glands either having become through habit
insensible to the blows and prolonged pressure of
drops of water, or to their having been originally
rendered sensitive solely to the contact of solid bodies.
AVe shall hereafter see that the filaments on the leaves
of Dionaca are likewise insensible to the impact of
fluids, though es^quisitely sensitive to momentary
touches from any solid body.

When the pedicel, of a tentacle is cut off by a
sharp pair of scissors quite close beneath the gland,
the tentacle generally becomes inflected. • I tried this
experiment repeatedly, as I was much surprised at the
fact, for all other parts of the pedicels are insensible to
any stimulus. These headless tentacles after a time
re-expand ; but I shall return to this subject. On the
other hand, I occasionally succeeded in crushing a
gland between a pair of pincers, 'but this caused no
inflection. In this latter case the tentacles seem
l)aralysed, as likewise follows from the action of too
strong solutions of certain salts, and by too great
heat, whilst weaker solutions of the same salts and a
more gentle heat cause movement. We shall also see
in future chapters that various other fluids, some

Chap. II. DEOPS OF WATER. 37

vapours, and oxygen (after the plant has been for some
time excluded from its action), all induce inflection,
and this likewise results from an induced galvanic
current.*

* My son Francis, guided by the secondary coil of a Du Bois

the observations of Dr. Burdon inductive apparatus are inserted,

Sanderson on Dionsea, finds that the tentacles curve inwards in the

if two needles are inserted into course of a few minutes. My son

the blade of a leaf of Drosera, the hopes soon to publish an account

tentacles do not move ; but that if of his observations,
similar needles in connection with

38 DEOSERA KOTUNDIFOLIA. Chap. III.

CHAPTEK III.

Aggregation op the Protoplasm -vnTHiN 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 WILL here interrupt my account of the movements
of the leaves, and describe the phenomenon of aggre-
gation, to which subject I have already alluded. If
the tentacles of a young, yet fully matured leaf, that
has never been excited or become inflected, be ex-
amined, the cells forming the pedicels are seen to be
filled with homogeneous, purple fluid. The walls are
lined by a layer of colourless, circulating protoplasm ;
but this can be seen with much greater distinctness
after the process of aggregation has been partly
effected than before. The purple fluid which exudes
from a crushed tentacle is somewhat coherent, and
does not mingle with the surrounding water; it con-
tains much flocculent or granular matter. But this
matter may have been generated by the cells having
been crushed; some degree of aggregation having
been thus almost instantly caused.

Chap. III. THE PKOCESS OF AGGREGATION. 39

If a tentacle is examined some hours after the gland
has been excited by repeated touches, or by an in-
organic or organic particle placed on it, or by the
absorption of certain fluids, it presents a wholly
changed appearance. The cells, instead of being filled
with homogeneous purple fluid, now contain variously
shaped masses of purple matter, suspended in a colour-
less or almost colourless fluid. The change is so
conspicuous that it is visible through a weak lens,
and even sometimes by the naked eye ; the tentacles
now have a mottled appearance, so that one thus
affected can be picked out with ease from all the
others. The same result follows if the glands on the
disc are irritated in any manner, so that the exterior
tentacles become inflected; for their contents will
then be found in an aggregated condition, although
their glands have not as yet touched any object. But
aggregation may occur independently of inflection,
as we shall presently see. By whatever cause the
process may have been excited, it commences within
the glands, and then travels down the tentacles. It
can be observed much more distinctly in the upper
cells of the pedicels than within the glands, as these
are somewhat opaque. Shortly after 'the tentacles have
re-expanded, the little masses of protoplasm are all
redissolved, and the purple fluid within the cells be-
comes as homogeneous and transparent as it was at
first. The process of redissolution travels upwards
from the bases of the tentacles to the glands, and
therefore in a reversed direction to that of aggre-
gation. Tentacles in an aggregated condition were
shown to Prof. Huxley, Dr. Hooker, and Dr. Burdon
Sanderson, who observed the changes under the
microscope, and were much struck with the whole
phenomenon.

• 3

40

DKOSEEA ROTUNDIFOLIA.

Chap. III.

The little masses of aggregated matter are of the
most diversified shapes, often spherical or oval, some-
times much elongated, or quite irregular with thread-
er necklace-like or club-formed projections. They
consist of tliick, apparently viscid matter, which in
the exterior tentacles is of a purplish, and in the
short discal tentacles of a greenish, colour. These
little masses incessantly change their forms and posi-
tions, being never at rest. A single mass will often
separate into two, which afterwards reunite. Their
movements are rather slow, and resemble those of
Amoeba3 or of the white corpuscles of the blood. We

Fig. 7.

[Drosera rotundifolia.)

Diagram of the same cell of a tentacle, showing the various forms successively
assumed by the aggregated masses of protoplasm.

may, therefore, conclude that they consist of proto-
plasm. If their shapes are sketched at intervals
of a few minutes, they are invariably seen to have
undergone great changes of form ; and the same
cell has been observed for several hours. Eight rude,
though accurate sketches of the same cell, made at
intervals of between 2 m. or 3 m., are here given
(fig. 7), and illustrate some of the simpler and com-
monest changes. The cell A, when first sketched,
included two oval masses of purple protoplasm touch-
ing each other. These became separate, as shown
at B, and then reunited, as at C. After the next
interval a very common appearance was presented —

Chap. III.

THE PEOCESS OF AGGREGATION.

41

D, namely, llie formation of an extremely minute
sphere at one end of an elongated mass. This rapidly
increased in size, as shown in E, and was then re-
absorbed, as at F, by which time another sphere had
been formed at the opposite end.

The cell above figured was from a tentacle of a dark
red leaf, which had caught a small moth, and was
examined under water. As I at first thought that the
movements of the masses might be due to the absorp-
tion of water, I placed a fly on a leaf, and when after
18 hrs. all the tentacles were well inflected, these were
examined without being immersed in water. The cell

0

Fig. 8.

{Drosera rotundifolia.')

Diagram of the same cell of a tentacle, showing the various forms successively
assumed by the aggregated masses of protoplasm.

here represented (fig. 8) was from this leaf, being
sketched eight times in the course of 15 m. These
sketches exhibit some of the more remarkable changes
which the protoplasm undergoes. At first, there was
at the base of the cell 1, £w little mass on a short
footstalk, and a larger mass near the upper end, and
these seemed quite separate. Nevertheless, they may
have been connected by a fine and invisible thread of
protoplasm, for on two other occasions, whilst one
mass was rapidly increasing, and another in the same
cell rapidly decreasing, I was able by varying the
light and using a high power, to detect a connecting
thread of extreme tenuity, which evidently served as

42 DROSERA ROTUNDIFOLTA. Chap. III.

the channel of communication between the two. On
the other hand, such connecting threads are some-
times seen to break, and their extremities then
quickly become club-headed. The other sketches in
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.

]\Iany observations were made on the contents of the cells
whilst undergoing the process of aggregation, but I shall detail
only a few cases under different heads. A small portion of a
leaf was cut off, placed under a high power, and the glands
very gently pressed under a compressor. In 15 m. I distinctly
saw extremely minute spheres of protoplasm aggregating them-
selves in the purple fluid ; these rapidly increased in size, both
within the cells of the glands and of the upper ends of the
pedicels. Particles of glass, cork, and cinders were also placed
on the glands of many tentacles ; in 1 hr. several of them were
inflected, but after 1 hr. 35 m. there was no aggregation. Other
tentacles with these particles were examined after 8 hrs., and

Chap. III. THE PROCESS OF AGGREGATION. 43

now all their cells had undergone aggregation ; so had the cells
of the exterior tentacles which had become inflected through
the irritation transmitted from the glands of the disc, on which
the transported particles rested. Tliis was likewise the case with
the short tentacles round the margins of the disc, which had not
as yet become inflected. This latter fact shows that the pro-
cess of aggregation is independent of the inflection of the ten-
tacles, of which indeed we have other and abundant evidence.
Again, the exterior tentacles on three leaves were carefully
examined, and found to contain only homogeneous purple fluid ;
little bits of thread were then placed on the glands of three of
them, and after 22 hrs. the purple fluid in their cells almost
down to their bases was aggregated into innumerable, spherical,
elongated, or filamentous masses of protoplasm. The bits of
thread had been carried some time previously to the central
disc, and this had caused all the other tentacles to become
somewhat inflected; and their cells had likewise undergone
aggregation, which however, it should be observed, had not
as yet extended down to their bases, but was confined to the
cells close beneath the glands.

Not only do repeated touches on the glands* and the contact
of minute particles cause aggregation, but if glands, without
being themselves injured, are cut off from the summits of the
pedicels, this induces a moderate amount of aggregation in the
headless tentacles, after they have become inflected. On the
other hand, if glands are suddenly crushed between pincers, as
was tried in six cases, the tentacles seem paralysed by so great
a shock, for they neither become inflected nor exhibit any signs
of aggregation.

Carbonate of Ammonia. — Of all the causes inducing aggrega-
tion, that which, as far as I have seen, acts the quickest, and is
the most powerful, is a solution of carbonate of ammonia. AVhat-
ever its strength may be, the glands are always affected first,
and soon become quite opaque, so as to appear black. For
instance, I placed a leaf in a few drops of a strong solution,
namely, of one part to 146 of water (or 3 grs. to 1 oz.), and
observed it under a high power. AH the glands began to

* Judging from an account of the stamens of Berberis, after

INI. Heckel's observations, which they have been excited by a

I have only just seen quoted in touch and liave moved; for he

the ' Gardener's Chronicle ' (Oct. says, " the contents of each indi-

10, 1874), he appears to have vidual cell are collected together

observed a similar phenomenon in in the centre of the cavity."

44 DROSERA ROTUNDIFOLIA. Chap. HI.

darken in 10 s. (seconds); and in 13 s. were conspicnonsly
darker. In 1 m. extremely small splierical masses of protoplasm
could be seen arising in the cells of the pedicels close beneath
the glands, as well as in the cushions on which the long-
headed marginal glands rest. In several cases the process
travelled down the pedicels for a length twice or thrice as great
as that of the glands, in about 10 m. It was interesting to
observe the process momentarily arrested at each transverse
partition between two cells, and then to see the transparent
contents of the cell next below almost flashing into a cloudy
mass. In the lower part of the pedicels, the action proceeded
slower, so that it took about 20 m. before the cells halfway
down the long marginal and submarginal tentacles became
aggregated.
^ We may infer that the carbonate of ammonia is absorbed by
the glands, not only from its action being so rapid, but from its
eifcct being somewhat different from that of other salts. As the
glands, when excited, secrete an acid belonging to the acetic
series, the carbonate is probably at once converted into a
salt of this series ; and we shall presently see that the acetate
of ammonia causes aggregation almost or quite as energetically
as does the carbonate. If a few drops of a solution of one part of
the carbonate to 437 of water (or 1 gr. to 1 oz.) be added to the
purple fluid which exudes from crushed tentacles, or to paper
stamed by being rubbed with them, the fluid and the paper are
changed into a pale dirty green. Nevertheless, some purple
colour could still be detected after 1 hr. 30 m. within the glands
of a leaf left in a solution of twice the above strength (viz.
2 gi"s. to 1 oz.) ; and after 24 hrs. the cells of the pedicels close
beneath the glands still contained spheres of protoplasm of a
fine purple tint. These facts show that the ammonia had not
entered as a carbonate, for otherwise the colour would have
been discharged. I have, however, sometimes observed, espe-
cially with the long-headed tentacles on the margins of very pale
leaves immersed in a solution, that the glands as well as the
upper cells of the pedicels were discoloured; and in these cases
I presume that the unchanged carbonate had been absorbed.
The appearance above described, of the aggregating process
lx}ing 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.

Chap. III. THE PKOCESS OF AGGKEGATION. 45

independently of the absorption of any matter. So it may pos-
sibly be in the case of the carbonate of ammonia. As, how-
ever, the aggregation caused by this salt travels down the
tentacles at a quicker rate than when insoluble particles are
placed on the glands, it is probable that ammonia in some form
is absorbed not only by the glands, but passes down the
tentacles.

Having examined a leaf in water, and found the contents of the
cells homogeneous, I placed it in a few drops of a solution of one
part of the carbonate to 437 of water, and attended to the cells
immediately beneath the glands, but did not use a very high
power. No aggregation was visible in 3 m. ; but after 15 m.
small spheres of protoplasm were formed, more especially
beneath the long-headed marginal glands; the process, how-
ever, 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
protojDlasm from the surrounding fluid. On one occasion I
chose a singularly pale leaf, and gave it, whilst under the
microscope, a single drop of a stronger solution of one part to
437 of water; in this case the contents of the cells did not
become cloudy, but after 10 m. minute irregular granules of
protoplasm could be detected, which soon increased into
irregular masses and globules of a greenish or very pale purple
tint ; but these never formed perfect spheres, though incessantly
changing their shapes and positions.

With moderately red leaves the first efiiect of a solution of the
carbonate generally is the formation of two or three, or of
several, extremely minute purj^le 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 glass w\as given a drop of a solution of
one part to 292 of water, and in 13 m. a few minute spheres of
protoplasm were formed ; one of these, after 2 hrs. 30 m., was
about two -thirds of the diameter of the cell. After 4 lirs. 25 m.

46 DROSEEA EOTUNDIFOLIA. Chap. III.

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 ^yas first added) four
new minute spheres had appeared. Next morning, after 22 hrs.,
there were, besides the two large spheres, seven smaller ones,
floating in absolutely colourless fluid, in which some flocculent
greenish matter was suspended.

At the commencement of the process of aggregation, more
especially in dark red leaves, the contents of the cells often
present a different appearance, as if the layer of protoplasm
(primordial utricle) which lines the cells had separated itself
and shrunk from the walls ; an irregularly shaped purple bag
being thus formed. Other fluids, besides a solution of the cai^
bonate, for instance an infusion of raw meat, produce this same
effect. But the appearance of the primordial utricle shrinking
from the walls is certainly false ; * for before giving the solution,
I saw on several occasions that the walls were lined with colour-
less flowing protoplasm, and after the bag-like masses were
formed, the protoplasm was still flowing along the walls in a
conspicuous manner, even more so than before. It appeared
indeed as if the stream of protoplasm was strengthened by the
action of the 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, some-
times sending out projections which separate into little spheres ;
other spheres appear in the fluid surrounding the bags, and
these travel much more quickly. That the small spheres are
separate is often shown by sometimes one and then another
travelling in advance, and sometimes they revolve round each
other. I have occasionally seen spheres of this kind proceeding
up and down the same side of a cell, instead of round it. The
bag-like masses after a time generally divide into two rounded
or oval masses, and these undergo the changes shown in figs. 7
and 8. At other times spheres appear within the bags; and
these coalesce and separate in an endless cycle of change.

After leaves have been left for several hours in a solution of
the carbonate, and complete aggregation has been effected, the

* With otlior plants I have caused by a solution of carbonate

often seen what appears to be a of ammonia, as likewise follows

true slirinking of tlie i>rimor(lial from mechanical injuries,
utricle from the walls of the cells,

Chap. III. THE PROCESS OF AGGREGATION. 47

stream of protoplasm on tlie 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
})urple spheres were formed in the upper cells of the pedicels,
the stream of protoplasm round their walls being still quite
distinct; but after an additional 4 hrs., during which time
many more spheres were formed, the stream was no longer
distinguishable on the most careful examination; and this no
doubt was due to the contained granules having become united
with the spheres, so that nothing was left by which the move-
ment of the limpid protoplasm could be perceived. But minute
free spheres still travelled up and down the cells, showing that
there was still a current. So it was next morning, after 22 hrs.,
by which time some new minute spheres bad 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 2-4 hrs. in a rather
stronger solution, namely, of one part of the carbonate to 218 of
water. This leaf, therefore, was not much or at all injured by
an immersion for this length of time in the above solution of
two grains to the ounce ; and on being afterwards left for 24 hrs.
in water, the aggregated masses in many of the cells were re-
dissolved, in the same manner as occurs with leaves in a state of
natui-e when they re-expand after having caught insects.

In a leaf which had been left for 22 hrs. in a solution of one
part of the carbonate to 292 of water, some spheres of proto-
plasm (formed by the self-division of a bag-like mass) were
gently pressed beneath a covering glass, and then examined
under a high power. They were now distinctly divided by
well-defined radiating fissures, or were broken up into separate
fragments with sharp edges ; and they were solid to the centre.
In the larger broken spheres the central part was more opaque,
darker -coloured, and less brittle than the exterior; the latter
alone being in some cases penetrated by the fissures. In many
of the spheres the line of separation between the outer and
inner parts was tolerably well defined. The outer parts were of
exactly the same very pale purple tint, as that of the last
formed smaller spheres; and these latter did not include any
darker central core.

From these several facts we may conclude that when vigorous
dark-coloured leaves are subjected to the action of carbonate of

48 DROSERA ROTUNDIFOLIA. Chap. Ill

ammonia, the fluid within the cells of the tentacles often aggre-
gates exteriorly into coherent viscid matter, forming a kind of
bag. Small spheres sometimes appear within this bag, and the
whole generally soon divides into two or more sj^heres, 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 di'awn to and unite with the larger
spheres, or form small independent spheres ; these latter being of
a much paler colour, and more brittle than the first aggregated
masses. After the granules of protoplasm have been thus
attracted, the layer of flowing protoplasm can no longer be dis-
tinguished, though a current of limpid fluid still flows round
the walls.

If a leaf is immersed in a very strong, almost concentrated,
solution of carbonate of ammonia, the glands are instantly
blackened, and they secrete copiously ; but no movement of the
tentacles ensues. Two leaves thus treated became after 1 hr.
flaccid, and seemed killed ; all the cells in their tentacles con-
tained spheres of protoplasm, but these were small and dis-
coloured. Two other leaves were placed in a solution not quite
so strong, and there was well-marked aggregation in 30 m.
After 24 hrs. the spherical or more commonly oblong masses of
protoplasm became opaque and granular, instead of being as
usual translucent; and in the lower cells there were only
innumerable minute spherical granules. It was evident that
the strength of the solution had interfered with the completion
of the process, as we shall see likewise follows from too great
heat.

All the foregoing observations relate to the exterior tentacles,
which are of a purple colour ; but the green pedicels of the
short central tentacles are acted on by the carbonate, and by
an infusion of raw meat, in exactly the same manner, with the
sole difference that the aggregated masses are of a greenish
. colour ; so that the process is in no way dependent on the
colour of the fluid within the cells.

Finally, the most remarkable fact with respect to this salt is
the extraordinary small amount which suffices to cause aggre-
gation. Full details will be given in the seventh chapter, and
liere it. will be enough to say that with a sensitive leaf the
aUsorption by a gland of ystVoo of ^ S^^^^ ('000482 mgr.) is
enough to cause in the course of one hour well-marked aggrega-
tion in the cells immediately beneath the gland.

The Effects of certain otJier Salts and Fluids. — Two leaves were
placed in a solution of one part of acetate of ammonia to about

Chap. III. THE PKUCESS OF AGGREGATION. 49

146 of water, and were acted on quite as energetically, but
perhaps not quite so quickly, as by the carbonate. After 10 m.
the glands were black, and iii the cells beneath them there were
traces of aggregation, which after 15 m. was well marked, extend-
ing down the tentacles for a length equal to that of the glands.
After 2 hrs. the contents of almost all the cells in all the ten-
tacles were broken up into masses of protoplasm. A leaf was
immersed in a solution of one part of oxalate of ammonia to
146 of water; and after 24 m. some, but not a conspicuous,
change could be seen within the cells beneath the glands.
After 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 am-
monia, a leaf was placed in a little solution of the above
strength, and there was not even a trace of aggregation in the
cells beneath the glands, until 56 m. had elapsed ; but it was
well marked after 2 hrs. 20 m. On another occasion a leaf
was placed in a stronger solution, of one part of the citrate to
109 of water (4 grs. to 1 oz.), and at the same time another
leaf in a solution of the carbonate of the same strength. The
glands of the latter were blackened in less than 2 m., and
after 1 hr. 45 m. the aggregated masses, which were spherical
and very dark-coloured, extended down all the tentacles, for
between half and two-thirds of their lengths ; whereas in the
leaf immersed in the citrate the glands, after 30 m., were of
a dark red, and the aggregated masses in the cells beneath them
pink and elongated. After 1 hr. 45 m. these masses extended
down for only about one-fifth or one -fourth of the length of the
tentacles.

Two leaves were placed, each in ten minims of a solution of
one part of nitrate of ammonia to 5250 of water (1 gr. to
12 oz.), so that each leaf received -^ of a grain (-1124 mgr.).
This quantity caused all the tentacles to be inflected, but after
24 hrs. there was only a trace of aggregation. One of these
same leaves was then placed in a weak solution of the car-
bonate, and after 1 hr. 45 m. the tentacles for half their lengths
showed an astonishing degree of aggregation. Two other
leaves were then placed in a much stronger solution of one part
of the nitrate to 146 of water (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 fol-

50 DEOSERA EOTUNDIFOLIA. CiiAr. III.

lowed 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 d3,750 of water (1 gr. to
100 oz.), so that it received ^ho o^ a gi'ain (-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 proto-
plasm had been injui-iously "affected; and soon afterwards some
of the cells appeared quite empty. These effects differ alto-
gether from those produced by the several salts of ammonia,
as well as by various organic fluids, and by inorganic particles
placed on the glands. A solution of the same strength of car-
bonate of soda and carbonate of potash acted in nearly the same
manner as the chloride ; and here again, after 2 lirs. 30 m., the
outer cells of some of the glands had emptied themselves of
their brown pulpy contents. We shall see in the eighth
chapter that solutions of several salts of soda of half the above
strength cause inflection, but do not injure the leaves. Weak
solutions of sulphate of quinine, of nicotine, camphor, poison of
the cobra, &c., soon induce well-marked aggregation ; whereas
certain other substances (for instance, a solution of curare)
have no such tendency.

Many acids, though much diluted, are poisonous ; and though,
as will he shown in the eighth chapter, they cause the ten-
tacles to bend, they do not excite true aggregation. Thus leaves
were placed in a solution of one part of benzoic acid to 437 of
water ; and in 15 m. the purple fluid within the cells had shrunk
a little from the walls, yet when carefully examined after 1 hr.
20 m., tliere was no true aggi-egation ; and after 24 hrs. the leaf
was evidently dead. Other leaves in iodic acid, diluted to thb
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,

Chap. III. THE PROCESS OF AGGREGATION. 51

which by the next morning, after 24 hrs., had almost dis-
appeared, the leaf being evidently dead. Nor was there any true
aggregation in leaves immersed in propionic acid of the same
strength; but in this case the protoplasm was collected in
irregular masses towards the bases of the lower cells of the
tentacles.

A filtered infusion of raw meat induces strong aggregation,
but not very quickly. In one leaf thus immersed there was a
little aggregation after 1 hr. 20 m., and in another after 1 hr.
50 m. With other leaves a considerably longer time was re-
quired : for instance, one immersed for 5 hrs. showed no aggre-
gation, but was plainly acted on in 5 m., when placed in a few
drops of a solution of one part of carbonate of ammonia to 146
of water. Some leaves were left in the infusion for 24 hrs.^
and these became aggregated to a wonderful degree, so that
the inflected tentacles presented to the naked eye a plainly
mottled appearance. The little masses of purple protoplasm
were generally oval or beaded, and not nearly so often spherical
as in the case of leaves subjected to carbonate of ammonia.
They underwent incessant changes of form ; and the current of
colourless protoplasm round the walls was conspicuously plain
after an immersion of 25 hrs. Eaw 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
?in 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. 30 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 solu-
tion of gum arabic. Several other leaves were immersed for
some hours in denser solutions of sugar, gum, and starch, and
they had the contents of their cells greatly aggregated. This

52 DEOSERA ROTUNDIFOLIA. Chap. 111.

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 tho
most irregular manner, the longer ones like corkscrews. We
shall hereafter see that solutions of these substances, vfhen
placed on the discs of leaves, do not incite inflection. Particles
of soft sugar were added to the secretion round several glands
and were soon dissolved, causing a great increase of the secre-
tion, no doubt by exosmose ; and after 2-1 hrs. the cells showed
a certain amount of aggi'egation, though the tentacles were
not inflected. Glycerine causes in a few minutes well-pro-
nounced aggregation, commencing as usual within the glands
and then travelling down the tentacles; and this I presume
may be attributed to the strong attraction of this substance
for water. Immersion for several hours in water causes some
degree of aggregation. Twenty leaves were first carefully
examined, and re-examined after having been left immersed
in distilled water for various periods, with the following results.
It is rare to find even a trace of aggregation until 4 or 5
and generally not until several more hours have elapsed.
When however a leaf becomes quickly inflected in water, as
sometimes happens, especially during very warm weather,
aggregation may occur in little over 1 hr. In all cases
leaves left in water for more than 24 hrs. have their glands
blackened, which shows that their contents are aggregated;
and in the specimens which were carefully examined, there
was fairly well-marked aggregation in the upper cells of the
pedicels. These trials were made with cut-oif 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-
y)lasm, many of which were oval, slowly changed their forms
acd positions; so that a submergence for 47 hrs. had not killed
the protoplasm. In a previous trial with a submerged plant,
the tentacles were not in the least inflected.

Chap. III. THE PROCESS OF AGGREGATION. 53

Heat induces aggregation. A leaf, with the cells of tho
tentacles containing only homogeneous fluid, was waved about
for 1 m. in Y/ater at 130° Fahr. (54:°-4 Cent.), and was then
examined under the microscope as quickly as possible, that
is in 2 m. or 3 m. ; and by this time the 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 Httle from the walls, '
and contained many oval and elongated masses of protoplasm,
with a few minute spheres. A third leaf was left in water at
125°, until it cooled, and when examined after 1 hr. 45 m., the
inflected tentacles showed some aggregation, which became
after 3 hrs. more strongly marked, but did not subsequently
increase. Lastly, a leaf was waved for 1 m. in water at 120°
(48°-8 Cent.) and then left for 1 hr. 26 m. in cold water ; the
tentacles were but little inflected, and there was only here and
there a trace of aggregation. In all these and other trials
with warm water the protoplasm showed much less tendency
to aggregate into spherical masses than when excited by car-
bonate of ammonia.

Redissolutlon of the Aggregated Masses of Protojdasm.—As soon
as tentacles which have clasped an insect or any inorganic
object, or have been in any way excited, have fully re-expanded,
the aggregated masses of protoplasm are redissolved and dis-
appear ; the cells being now refilled with homogeneous purple
fluid as they were before the tentacles were inflected. The
process of redissolution in all cases commences at the 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 con-
dition. In order to observe the process of redissolution, the
following observations were made : a leaf was left for 24 hrs. m
a little solution of one part of carbonate of ammonia to 218 of
water, and the protoplasm was as usual aggregated into number-
less purple spheres, which were incessantly changing their
forms. The leaf was then washed and placed in distilled water,
and after 3 hrs. 15 m. some few of the spheres began to show by
their less clearly defined edges signs of redissolution. After
9 hrs. many of them had become elongated, and the surround-
ing fluid in the cells was slightly more coloured, showing
plainly that redissolution had commenced. After 24 hrs.,
though many cells still contained spheres, here and there one

r)4 DROSERA ROTUNDIFOLIA. Chap. III.

could be scon filled with purple fluid, without a vestige of
aggregated protoplasm ; the whole having been redissolved. A
leaf witli aggregated masses, caused by its having been waved
for 2 m. in water at the temperature of 125° Fahr., was left in
cold water, and after 11 hrs. the protoplasm showed traces
of incipient redissolution. When again examined three days
after its immersion in the warm water, there was a conspicuous
difference, though the protoplasm was still somewhat aggre-
gated. Another leaf, with the contents of all the cells strongly
aggregated from the action of a weak solution of phosphate of
ammonia, was left for between three and four days in a mixture
(known to be innocuous) of one drachm of alcohol to eight
drachms of water, and when re-examined every trace of aggre-
gation had disappeared, the cells being now filled with homo-
geneous fluid.

We have seen that leaves immersed for some hours in dense
solutions of sugar, gum, and starch, have the contents of their
cells greatly aggregated, and are rendered more or less flaccid,
with tlie tentacles irregularly contorted. These leaves, after
being left for four days in distilled water, became less flaccid,
with tlieir tentacles partially re-expanded, and the aggi'e-
gated masses of protoplasm were partially redissolved. A leaf
with its tentacles closely clasped over a fly, and with the con-
tents of the cells strongly aggregated, was placed in a little
sherry wine ; after 2 hrs. several of the tentacles had re-
expanded, and the others could by a mere touch be pushed back
into their properly expanded positions, and now all traces of
aggregation had disappeared, the cells being filled with perfectly
liomogeneous pink 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
thouglit 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

Chap. III. THE PROCESS OF AGGEEGATION. 55

218, of water), the tentacles are paralysed, and do not
become inflected, yet they soon exhibit strongly
marked aggregation. Moreover, the short central
tentacles of a leaf which has been immersed in a
weak solution of any salt of ammonia, or in any
nitrogenous organic fluid, do not become in the least
inflected; nevertheless they exhibit all the pheno-
mena of aggregation. On the other hand, several
acids cause strongly pronounced inflection, but no
aggregation.

It is an important fact that when an organic or in-
organic object is placed on the glands of the disc,
and the exterior tentacles are thus caused to bend
inwards, not only is the secretion from the glands of
the latter increased in quantity and rendered acid,
but the contents of the cells of their pedicels become
aggregated. The process always commences in the
glands, although these have not as yet touched any
object. Some force or influence must, therefore, be
transmitted from the central glands to the exterior
tentacles, first to near their bases causing this part to
bend, and next to the glands causing them to secrete
more copiously. After a short time the glands, thus
indirectly excited, transmit or reflect some influence
down their own pedicels, inducing aggregation in cell
beneath cell to their bases.

It seems at first sight a probable view that aggrega-
tion is due to the glands being excited to secrete more
copiously, so that sufficient fluid is not left in their
cells, and in the cells of the pedicels, to hold the
protoplasm in solution. In favour of this view is the
fact that aggregation follows the inflection of the
tentacles, and during the movement the glands gener-
ally, or, as I believe, always, secrete more copiously
than they did before. Again, during the re-expansion

56 DEOSEEA EOTUNDIFOLIA. Chap. III.

of the tentacles, tlie glands secrete less freely, or quite
cease to secrete, and the aggregated masses of proto-
plasm are then redissolved. Moreover, when leaves
are immersed in dense vegetable solutions, or in
glycerine, the fluid within the gland-cells passes out-
wards, and there is aggregation ; and when the leaves
are afterwards immersed in water, or in an innocuous
fluid of less specific gravity than water, the protoplasm
is redissolved, and this, no doubt, is due to endosmose.
Opposed to this view, that aggregation is caused by
the outward passage of fluid from the cells, are the
following facts. There seems no close relation between
the degree of increased secretion and that of aggre-
gation. Thus a particle of sugar added to the secre-
tion round a gland causes a much greater increase of
secretion, and much less aggregation, than does a
particle of carbonate of ammonia given in the samo
manner. It does not appear probable that pure water
would cause much exosmose, and yet aggregation
often follows from an immersion in water of between
16 hrs. and 24 hrs., and always after from 24 hrs. to
48 hrs. Still less probable is it that water at a tempe-
rature of from 125'' to 130° Fahr. (51°-6 to 54°-4 Cent.)
should cause fluid to pass, not only from the glands,
but from all the cells of the tentacles down to their
bases, so quickly that aggregation is induced within
2 m. or 3 m. Another strong argument against
this view is, that, after complete aggregation, the
spheres and oval masses of protoplasm float about
in an abundant supply of thin colourless fluid; so
that at least the latter stages of the process cannot
be due to the want of fluid to hold the protoplasm
in solution. There . is still stronger evidence that
aggregation is independent of secretion ; for the pa-
pillcc, described in the first chapter, with which the

Chap. m. THE PEOCESS OF AGGREGATION. 57

leaves are studded are not glandular, and do not
secrete, yet they rapidly absorb carbonate of ammonia
or an infusion of raw meat, and their contents then
quickly undergo aggregation, which afterwards spreads
into the cells of the surrounding tissues. We shall
hereafter see that the purple fluid within the sensi-
tive filaments of Dionsea, which do not secrete, like-
wise undergoes aggregation from the action of a weak
solution of carbonate of ammonia.

The process of aggregation is a vital one ; by which
I mean that the contents of the cells must be alive
and uninjured to be thus affected, and they must be in
an oxygenated condition for the transmission of the
process at the proper rate. Some tentacles in a
drop of watei; 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
com23letely emptied. I then added a minute drop of
a solution of one part of carbonate of ammonia to
109 of water, and after 1 hr. examined the specimens.
Here and there a few cells, both in the glands and in
the pedicels, had escaped being ruptured, and their
contents were well aggregated into spheres which were
constantly changing their forms and positions, and a
current could still be seen flowing along the walls ;
so that the protoplasm was alive. On the other hand,
the exuded matter, which was now almost colourless
instead of being purple, did not exhibit a trace of
aggregation. Nor was there a trace in the many
cells which were ruptured, but which had not been
completely emptied of their contents. Though I
looked carefully, no signs of a current could be seen
within these ruptured cells. They had evidently been
killed by the pressure ; and the matter which they

58 DROSERA ROTUNDIFOLIA. Chap. TIL

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"^ (Go'^'S
Cent.), on being placed in the same strong solution,
did not undergo aggregation, the cells becoming filled
with bro^Tiish, pulpy, or muddy matter. With leaves
subjected to temperatures between these two extremes
of 120^ and 150° Fahr. (48°-8 and 65°-5 Cent.), there
were gradations in the completeness of the process ;
the former temperature not preventing aggregation
from the subsequent action of carbonate of ammonia,
the latter quite stopping it. Thus, leaves immersed
in water, heated to 130° (54°'4 Cent.), and then in the
solution, formed perfectly defined spheres, but these
were decidedly smaller than in ordinary cases. AVith
other leaves heated to 140° (60° Cent.), the spheres
were extremely small, yet well defined, but many of
the cells contained, in addition, some brownish pulpy
matter. In two cases of leaves heated to 145° (62°-7
Cent.), a few tentacles could be found with some of
tlieir 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

Chap. III. THE PROCESS OF AGGEEGATION. 59 *

influence which induces aggregation shouhl be trans-
mitted 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 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 Jess 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 in-
stantly 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. ^fter 4 hrs.
15 m. a few minute spheres of protoplasm were formed
in these cells, but even after 5 hrs. 30 m. the aggre-
gation 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 solu-
tion as before. The former were looked at repeatedly,
and after an interval of 65 m. a few spheres of
protoplasm were first observed in the cells close be-
neath 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

GO DROSEEA EOTUNDIFOLIA. Chap. III.

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 15m.; after
65 m. it had extended down the pedicels for four, five,
or more times the lengths of the glands ; 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 fts
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 protoplasm by the exclusion of oxygen.

Summary and Concluding Bemarls.— The process of
aggregation is independent of the inflection of the
tentacles and 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 pro-
cess is transmitted from cell to cell down the whole
length of the tentacles, being arrested for a short
tmie at each transverse partition. With pale-coloured
leaves the first change which is perceptible, but only

'Traiy'^l'/Tf'^J^^^''v!'^?S?' 'Q^^^terly Journal of Micro-
p. »b4. On blood corpuscles, see 185.' > f it"

CuAP. III. THE PEOCESS OF AGGREGATION. 61

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 car-
bonate 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 redis-
solved, and the cells become filled with homogeneous
purple fluid, as they were at first. The process of re-
dissolution commences at the bases of the tentacles,
thence proceeding upwards to the glands ; and, there-
fore, 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

* According to Hofmeister (as gation is a different phenomenon,

quoted by Sachs, ' Traite de Bot.' as it relates to the contents of the

J 874, p. 958), very slight pres- cells, and only secondarily to the

sure on the cell-membrane arrests layer of protoplasm which flows

immediately the movements of along the walls ; though no doubt

the protoplasm, and even deter- the effects of pressure or of a

mines its separation from the touch on the outside must be

walls. But the process of aggre- transmitted through this layer.

62 DROSERA ROTUNDIFOLIA. Chap. III.

the glands, — by the glands absorbing various fluids or
matter dissolved out of certain bodies, — by exosmose, —
and by a certain degree of beat. 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. If a cell is ruptured, neither the exuded
matter nor that which still remains within the cell
undergoes aggregation 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 con-
clude that the protoplasmic fluid within a cell does
H'jt 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 oxygen-
ated state, in order that the process of aggregation
should travel from cell to cell at the j)roper rate.

Various nitrogenous organic fluids and salts of am-
monia induce aggregation, but in different degrees
and at very different rates. Carbonate -of ammonia is
the most powerful of all known substances; the ab-
sorption of TTm-o 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 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

Chap. III. THE PROCESS OF AGGEEGATION. 63

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 centri-
fugally 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 aggrega-
tion is. in itself a striking phenomenon. Whenever
the peripheral extremity of a nerve is touched or
pressed, and a sensation is felt, it is believed that an
invisible molecular change is sent from one end of the
nerve to the 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. .

Sup^Iementarij Ohservations on the Process of Aggre-
gation in the Boots of Plants.

It will hereafter be seen that a weak solution of the car-
bonate of ammonia induces aggregation in the cells of the roots
of Drosera ; and this led me to make a few trials on the roots
of other* plants. I dug up in the latter part of October the
first weed which 1 met with, viz. Euphorbia peplus, being care-
4

61 DEOSERA ROTUNDIFOLIA. Chap. III.

ful not to injure the roots ; these were wasked 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 appear-
ance, became aggregated towards the extremities of the roots
into quadrangular masses of brown matter ; and some of these
soon changed their forms and became spherical. Some of the
cells, however, remained unaffected. I repeated the experi-
ment with another plant of the same species, but before I could
get the specimen into focus under the microscope, clouds of
granules and quadrangular masses of reddish and brown
matter were formed, and had run far up all the roots. A fresh
root tsras now left for 18 hrs. in a drachm of a solution of one
part of the carbonate to 437 of water, so that it received | of
a grain, or 2" 024 mg. When examined, the cells of all the
roots throughout their whole length contained aggregated
masses of reddish and brown matter. Before making these
experiments, several roots were closely examined, and not a
trace of the cloudy appearance or of the granular masses could
be seen in any of them. Eoots were also immersed for 35 m.
in a solution of one part of carbonate of potash to 218 of water;
but this salt produced no effect.

I may here add that thin shces 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
4.5 m. in a solution of one part of this same salt to 146 of water,
and tlu'ce of their roots were then examined. In two of them,
all the cells which had previously contained only limj^id fluid
now included little green spheres. After from 1^ 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 a rrA^'za, produces no roots, the latter alternative
is perhaps the most probable. After about 2^ 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

Chap. m. THE PROCESS OF AGGREGATION. 65

carbonate of potash to 218 of water, and no decided change
could be perceived in the cells of the roots; but when these
same roots were placed for 25 m. in* a solution of carbonate of
ammonia of the same strength, little green spheres were formed.
A green marine alga was left for some time in this same solu-
tion, but was very doubtfully affected. On the other hand, a
red marine alga, with finely pinnated fronds, was strongly
affected. The contents of the cells aggregated themselves into
broken rings, still of a red colour, which very slowly and
slightly changed their shapes, and the central spaces within
these rings became cloudy with red granular matter. The
facts here given (whether they are new, I know not) indicate
that interesting results would perhaps be gained by observing
the action of various saline solutions and other fluids on the
roots of plants.

66 DROSERA ROTUNDIFOLIA. Chap IV.

CHAPTEE ly.

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
coagulates the albuminous contents of the glands.

In my observations on Drosera rotwidifolia, the leaves
seemed to be more quickly inflected over animal sub-
stances, and to remain inflected for a longer period
during very warm than during cold weather. I
wished, therefore, to ascertain whether heat alone
would induce inflection, and what temperature was
the most efficient. Another interesting point pre-
sented itself, namely,- at what degree life was extin-
guished ; for Drosera offers unusual facilities in this
respect, not in the loss of the power of inflection, but
in that of subsequent re-expansion, and more espe-
cially in the failure of the protoplasm to become
aggregated, when the leaves after being heated are
immersed in a solution of carbonate of ammonia.*

* When my experiments on the eludes that the protoplasm with-
eflfects of heat were made, I was in their cells always coagulates,
not aware that the subject had if in a damp condition, at a tem-
been carefully investigated by perature of between 50° and 60°
several observers. For instance, Cent., or 122° to 140° Fahr. Max
Sachs is convinced (' Traite do Schultze and Kiihue (as quoted
I3otani(iue,' 1874, pp. 772, 854) by Dr. Bastian in 'Coutemp.
that the most ditfercnt kinds of Review,' 1874, p. 528) " found
plants all perish if kt'pt for 10 m. that the protoplasm of plant-
in water at 45° to 40° Cent., or cells, with which they experi-
113° to 115° Fahr. ; and he con- mented, was always killed and

CuAi'. IV. THE EFFECTS OF HEAT. 67

My experiments were tried in the following manner. Lccaves
were cut oS, and this does not in the least interfere with their
powers; for instance, three cut-off leaves, with bits of meat
placed on them, were kept in a damp atmosphere, and after
23 hrs. closely embraced the meat both with their ten-
tacles and blades ; and the protoplasm within their cells was
well aggregated. Three ounces of doubly distilled water was
heated in a porcelain vessel, with a delicate thermometer
having a long bulb obliquely suspended in it. The water was
gradually raised to the required temperature by a spirit-lamp
moved about under the vessel; and in all cases the leaves
were continually waved for some minutes close to the bulb.
They were then placed in cold water, or in a solution of car-
bonate of ammonia. In other cases they were left in the water,
which had been raised to a certain temperature, until it cooled.
Again in other cases the leaves were suddenly plunged into
water of a certain temperature, and kept there for a specified
time. Considering that the tentacles are extremely delicate,
and that their coats are very thin, it seems scarcely possible
that the fluid contents of their cells should not have been
heated to within a degree or two of the temperature of the
surrounding water. Any further precautions would, I think,
have been superfluous, as the leaves from age or constitutional
causes differ slightly in their sensitiveness to heat.

It will be convenient first briefly to describe the effects of
immersion for thirty seconds in boiling water. The leaves are
rendered flaccid, with their tentacles bowed backwards, which,
as we shall see in a future chapter, is probably due to their
outer surfaces retaining their elasticity for a longer period than
their inner surfaces retain the power of contraction. The
purple fluid within the cells of the pedicels is rendered finely
granular, but there is no true aggregation ; nor does this follow

altered by a very brief expo- able differences in this respect is

Bure to a temperature of 118J° not surprising, considering that

Fahr. as a maximum." As my some low vegetable organisms

results are deduced from special grow in hot springs — cases of

phenomena, namely, the subse- which have been collected by

quent aggregation of the proto- Prof. Wyman (' American Journal

plasm and the re-expansion of of Science,' vol. xli v. 1867). Thus,

the tentacles, they seem to me Dr. Hooker found Confervre in

worth giving. We shall find that water at 168° Fahr. ; Humboldt,

Drosera resists heat somewhat at 185° Fahr. ; and Descloizeaux,

better than most other plants. at 208° Fahr.
That there should be consider-

68 DROSEKA ROTUNDIFOLIA. Chap IV.

when tho leaves are subsequently placed in a solution of car-
bonate of ammonia. But the most remarkable change is that
the glands become opaque and uniformly white ; and this may
be attributed to the coagulation of their albuminous contents.

My first and preliminary experiment consisted in putting
seven leaves in the same vessel of water, and warming it slowly
up to the temperature of 110° Fahr. (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 so on. Each leaf, when taken
out, was placed in water at the temperature of my room, and
"the tentacles of all soon became slightly, though iii-egularly,
inflected. They were now removed fi'om the cold water and
kept in damp air, with bits of meat placed on their discs.
The leaf which had been exposed to the temperature of 110°
became in 15 m. greatly inflected ; and in 2 hrs. every single
tentacle closely embraced the meat. So it was, but affer rather
longer intervals, with the six other leaves. It appears, there-
fore, that the warm bath had increased their sensitiveness
when excited by meat.

I next observed the degree of inflection which leaves under-
went within stated periods, whilst still immersed in warm
water, kept as nearly as possible at the same temperature ; but
I will here and elsewhere give only a few of the many trials
made. A leaf was left for 10 m. in water at 100° (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 41°-1 Cent.), was very moderately inflected in 6 m.
A fourth leaf, in water at 110° (43°-3 Cent.), was somewhat in-
flected in 4 m., and considerably so in from 6 m. to 7 m.

Three leaves were placed in water which was heated rather
quickly, and by the time the temperature rose to 115°— 116°
(46°"1 to 46°'06 Cent.), all three were inflected. I then removed
the lamp, and in a few minutes every single tentacle was
closely inflected. The protoplasm within the cells was not
killed, for it was seen to be in distinct movement; and the
leaves, having been left in cold water for 20 hrs., re-expanded.
Another leaf was immersed in water at 100° (37°-7 Cent.), which
was raised to 120° (48°-8 Cent.); and all the tentacles, except
tho extreme marginal ones, soon became closely inflected.
Tho leaf was now placed in cold water, and in 7 hrs. 30 m. it
had partly, and in 10 hrs. fully, re-expanded. On the follow-
ing morning it was immersed in a weak solution of carbonate of

Chap. IV. THE EFFECTS OF HEAT. 69

ammonia, and the glands quickly became black, with strongly
marked aggregation in the tentacles, showing that the proto-
plasm was alive, and that the glands had not lost their power of
absorption. Another leaf was placed in water at 110^ (43"-3
Cent.) w^hich was raised to 120° (48°-8 Cent.) ; and every ten-
tacle, excepting one, was quickly and closely inflected. This leaf
was now immersed in a few drops of a strong solution of car-
bonate of ammonia (one i3art 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 inflection in ordinary cases. Lastly a leaf
was suddenly placed in water at 125° (51°-6 Cent.), and was
left in it until the water cooled ; the tentacles were rendered
of a bright red and soon became inflected. The contents of
the cells underwent some degree of aggregation, which in
the course of three hours increased ; but the masses of proto-
plasm did not become spherical, as almost always occurs with
leaves immersed in a solution of carbonate of ammonia.

We learn from these cases tliat a temperature of
from 120° to 125° (48°-8 to 5r-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 1*30° (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

70 DEOSERA ROTUNDIFOLIA. Chap. IV.

distinctly seen in a small mass of protoplasm in one of the cells
of a tentacle.* After a few houi's all the tentacles and the
blade became inflected.

Krpiriment 2.— Another leaf was plunged into water at 130°
to ISl"", 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 coui'se of 55 m. the tentacles were con-
siderably inflected. The glands, which before had been rendered
of a brighter red, wefe 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
closelyinflected.

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.

Exp)eriment 5. — Leaf immersed at 130° (54:°-'i Cent.), and the
water raised to 145° (62° "7 Cent.), there was no immediate in-
flection ; it was then placed in cold water, and after 1 hi\ 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.

Exjv'riments 6 and 7. — Two leaves were plunged in water at
135° (57° • 2 Cent.) which was raised to 145° (62° • 7 Cent.) ; neither
became inflected. One of these, however, after having been left
for 31 m. in cold water, exhibited some slight inflection, which
increased after an additional interval of 1 hr. 45 m., until

* Saclis states (' Traite de Bo- after they were exposed for 1 m.

taiii(iue,' 1874, p. 85.1) tliat tlie in water to a temperature of 47°

luoveineiits of tlie proto})lasm in to 48° Cent., or 117° to 119°

the hairs of a Cucurbita ceased Fahr.

Chap. IV. THE EFFECTS OF HEAT. 71

all the tentacles, except sixteen or seventeen, were more or less
inflected ; but the leaf was so much injured that it never re-
expanded. The other leaf, after having been left for half 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 proto-
plasm being extremely small; in other cells, especially in the
exterior tentacles, there was much greenish-brown pulpy
matter.

Experiraent 8. — A leaf was plunged and waved about for a
few minutes in water at 140° (60° Cent.), and was then left for
half an hour in cold water, but there was no inflection. It was
now placed in the strong solution, and after 2 hrs. 30 m. the
inner submarginal tentacles were well inflected, with their
glands blackened, and some imperfect aggregation in the cells
of the pedicels. Three or four of the glands were spotted with
the white porcelain- like structure, like that produced by boihng
water. I have seen this result in no other instance after an
immersion of only a few minutes in water at so low a tempe-
rature as 140°, and in only one leaf out of four, after a similar
immersion at a temperature of 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-hke. So that the duration of the immersion is an
important element in the result.

Experiment 9. — A leaf was placed in water at 140° (60° Cent.),
which was raised to 150° (65° '5 Cent.); there was no inflection ;
on the contrary, the outer tentacles were somewhat bowed back-
wards. The glands became like porcelain, but some of them
were a little mottled with purple. The bases of the glands were
often more affected than their summits. This leaf having been
left in the strong solution did not undergo any inflection or
aggregation.

Experiment 10.— A leaf was plunged in water at 150° to 150^°
(65° • 5 Cent.) ; it became somewhat flaccid, with the outer ten-
tacles slightly reflexed, and the inner ones a little bent inwards,
but only towards thek 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.

72 DROSERA ROTUNDIFOLIA. Chap. rV>

Experiment 11. — A leaf was imrDersed 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
usnal first in cold water and then in the strong solution, the
cells in the tentacles became of a muddy greenish brown, with
the protoplasm not aggregated. Nevertheless, four of the glands
escaped being rendered like porcelain, and the pedicels of these
glands were spirally curled, like a French horn, towards their
upper ends; but this can by no means be considered as a
case of true inflection. The protoplasm within the cells of the
twisted portions was aggregated into distinct though excessively
minute purple spheres. This case shows clearly that the proto-
plasm, after having been exposed to a high temperature for a
few minutes, is capable of aggregation when afterwards sub-
jected to the action of carbonate of ammonia, unless the heat
has been suflGicient to cause coagulation.

Concluding RemarJcs. — As the hair-like tentacles are
extremely thin and have delicate walls, and as the
leaves were waved about for some minutes close to the
bulb of the thermometer, it seems scarcely possible
that they should not have been raised very nearly to
the temperature which the instrument indicated.
From the eleven last observations we see that a tem-
perature of 130*^ (54°-4 Cent.) never causes the imme-
diate inflection of the tentacles, though a temperature
from 120" to 125° (48°-8 to 51°-6 Cent.) quickly pro-
duces this effect. But the leaves are paralysed only
for a time by a temperature of 130°, as afterwards,
whether left in simple water or in a solution of car-
bonate of ammonia, they become inflected and their
protoplasm undergoes aggregation. This great dif-
ference in the efiects 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

Chap. IV. THE EFFECTS OF HEAT. 73

power of movement due to heat is called by Sachs*
heat-rigidity ; and this in the case of the sensitive-
plant (Mimosa) is induced by its exposure for a few
minutes to humid air, raised to 120° — 122° Fahr., or
49° to 50° Cent. It deserves notice that the leaves of
Drosera, after being immersed in water at 130° Fahr.,
are excited into movement by a solution of the car-
bonate so strong that it would paralyse ordinary
leaves and cause no inflection.

The exposure of the leaves for a few minutes even
to a temperature of 145° Fahr. (62°-7 Cent.) does not
always kill them ; as when afterwards left in cold
water, or in a strong solution of carbonate of ammo-
nia, they generally, though not always, become in-
flected; and the protoplasm within their cells under-
goes aggregation, though the spheres thus formed are
extremely small, with many of the cells partly filled
with brownish muddy matter. In two instances, when
leaves were immersed in water, at a lower temperature
than 130° (54°-4 Cent.), which was then raised to 145°
(62°-7 Cent.), they became during the earlier period
of immersion inflected, but on being afterwards left
in cold water were incapable of re-expansion. Ex-
posure for a few minutes to a temperature of 145°
sometimes causes some few of the more sensitive
glands to be speckled with the porcelain-like appear-
ance ; and on one occasion this occurred at a tempera-
ture of 140° (60° Cent.). On another occasion, when
a leaf was placed in water at this temperature of only
140°, and left therein till the water cooled, every
gland became like porcelain. Exposure for a few
minutes to a temperature of 150° (65°-5 Cent.) gene- '
rally produces this effect, yet many glands retain a

Traite de Bot.' 1874, p. 1034.

74 DROSEKA EOTUNDIFOLIA. Chap. IV.

piukish colour, and many present a speckled appear-
ance. This liigli temperature never causes true inflec-
tion ; on the contrary, the tentacles commonly become
reflexed, though to a less degree than when immersed
in boiling water ; and this apparently is due to their
passive power of elasticity. After exposure to a tem-
perature of 150^ Fahr., the protoplasm, if subsequently
subjected to carbonate of ammonia, instead of under-
going aggregation, is coliverted 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 tJie protoplasm in the
cells close beneath these glands underwent some
slight, though imperfect, degree of aggregation.

Finally, it is a remarkable fact that the leaves of
Drosera rotundifolia, which flourishes on bleak upland
moors throughout Great Britain, and exists (Hooker)
within the Arctic Circle, should be able to withstand
for even a short time immersion in water heated to a
temperature of 145°.t

It may be worth adding that immersion in cold

* As tlie opacity and porcelain- differences in the results above

like appearance of the glands is recorded.

j)rnl)iil)ly tluc to the coai^ulation f It appears that cold-blooded

of the albumen, I may add, on tlie animals are, .as might have been

authority of Dr. liurdon Sander- expected, far more sensitive to an

son, that albumen coagulates at increase of temperature than is

about 155°, but, in presence of Drosera. Thus, as I hear from Dr.

acids, the temperature of coagula- Burden Sanderson, a frog begins

tion is lower. The leaves of Dro- to be distressed in water at a tem-

tera contain an acid, and perhaps perature of only 85° Fahr. At 95°

a difference in the amount con- the muscles become rigid, and the

tuined may account for the slight animal dies in a stiffened condition.

CiiAP. IV. THE EFFECTS OF HEAT. 75

water does not cause any inflection : I suddenly placed
four leaves, taken from plants which had been kept for
several days at a high temperature, generally about
75° Fahr. (23°-8 Cent.), in water at 45° (7°-2 Cent.), but
they were hardly at all affected ; not so much as some
other leaves from the same plants, which were at the
same time immersed in water at 75° ; for these became
in a slight degree inflected.

76 " DROSEKA ROTUNDIFOLIA. Cilvp. V.

CHAPTEK 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 muciis — 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.

AYhen, in 1860, 1 first observed Drosera, and was led to
believe that the leaves absorbed nutritious matter from
the insects which they captured, it seemed to me a
good plan to make some preliminary trials with a few
common fluids, containing and not containing nitro-
genous matter ; and the results are worth giving.

In all the following cases a drop was allowed to fall
from the same pointed instrument on the centre of the
leaf; and by repeated trials one of these drops was
ascertained to be on an average very nearly half a
minim, or ^^ of a fluid ounce, or '0295 ml. But these
measurements obviously do not pretend to any strict
accuracy ; moreover, the drops of the viscid fluids were
plainly larger than those of water. Only one leaf on
the same plant was tried, and the plants were col-
lected from two distant localities. The experiments
were made during August and September. In judging
of the effects, one caution is necessary : if a drop of
any adhesive fluid is placed on an old or feeble leaf,
the glands of which have ceased to secrete copiously,
the drop sometimes dries up, especially if the plant

Chap. V. EFFECTS OF ORGANIC FLUIDS. 77

is kept in a room, and some of the central and sub-
marginal tentacles are thus drawn together, giving to
them the false appearance of having become inflected.
This sometimes occurs with water, as it is rendered
adhesive by mingling with the viscid secretion.
Hence the only safe criterion, and to this alone I
have trusted, is the bending inwards of the exterior
tentacles, w hich have not been touched by the fluid, or
at most only at their bases. In this case the move-
ment is wholly due to the central glands having been
stimulated by the fluid, and transmitting a motor
impulse to the exterior tentacles. The blade of the
leaf likewise often curves inwards, in the same manner
as when an insect or bit of meat is placed on the
disc. This latter movement is never caused, as far
as I have seen, by the mere drying up of an ad-
hesive fluid and the consequent drawing together of
the tentacles.

First for the non-nitrogenous fluids. As a pre-
liminary trial, drops of distilled water were placed on
between thirty and forty leaves, and no effect whatever
was produced; nevertheless, in some other and rare
cases, a few tentacles became for a short time in-
flected; but this may have been caused by the
glands having been accidentally touched in getting
the leaves into a proper position. That water should
produce no effect might have been anticipated, as
otherwise the leaves would have been excited into
movement by every shower of rain.

Gum arahic— 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 M hrs. ; generally about

78 DROSEEA ROTUNDIFOLIA. Chap. V.

30 hrs. Inflection was never thus caused. It is necessary
to try pure gum arabic, for a friend tried a solution bought
ready prepared, and this caused the tentacles to bend ; but he
afterwards ascertained that it contained much animal matter,
probably glue.

Sugar. — Drops of a solution of white sugar of three strengths
(the weakest containing one part of sugar to 73 of water) were
left on fourteen leaves from 32 hrs. to 48 hrs. ; but no effect was
produced.

Starch. — A mixture about as thick as cream was dropped on
six leaves and left on them for 30 hrs., no effect being produced.
I am surprised at this fact, as I believe that the starch of com-
merce generally contains a trace of gluten, and this nitrogenous
substance causes inflection, as we shall see in the next chapter.

Alcohol, Diluted. — One part of alcohol was added to seven of
water, and the usual di'ops were placed on the discs of three
leaves. No inflection ensued in the course of 48 hrs. To ascer-
tain whether these leaves had been at all injui'ed, 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 inflec-
tion was caused, though two of them seemed somewhat injured.
We shall hereafter see that cut-off leaves immersed in diluted
alcohol of the above strength do not become inflected.

Olive Oil. — Drops were placed on the discs of eleven leaves, and
no effect was produced in from 24 hrs. to 48 hi's. Four of these
leaves were then tested by bits of meat on their discs, and three
of them were found after 24 hrs. with all their tentacles and
blades closely inflected, whilst the fourth had only a few ten-
tacles inflected. It will, however, be shown in a future place,
that cut-off leaves immersed in olive oil are powerfully affected.

Infusion and Decoction of Tea. — Drops of a strong infusion and
decoction, as well as of a rather weak decoction, of tea were
placed on ten leaves, none of which became inflected. I after-
wards tested three of them by adding bits of meat to the drops
which still remained on their discs, and when I examined them
after 24 hrs. they were closely inflected. The chemical principle
of tea, namely theine, was subsequently tried and produced no
effect. The albuminous matter which the leaves must originally
have contained, no doubt, had been rendered insoluble by their
having been completely dried.

We thus see tliat, excluding the experiments with
water, sixty-one leaves were tried with drops of the

Chap. V. EFFECTS OF OEGANIC FLUIDS. 79

above-named non-nitrogenous fluids ; and the tentacles
were not in a single case inflected.

With respect to nitrogenous fluids, the first which came to
hand were tried. The experiments were made at the same
time and in exactly the same manner as the foregoing.
As it was immediately evident that these fluids produced a
great efiect, I neglected in most cases to record how soon tho
tentacles became inflected. But this always occurred in less
than 24 hrs. ; whilst the drops of non-nitrogenous fluids which
produced no effect were observed in every case during a
considerably longer period.

Milk. — Drops were placed on sixteen leaves, and the tentacles
of all, as well as the blades of several, soon became greatly
inflected. The periods were recorded in only three cases,
namely, with leaves on which unusually small drops had been
placed. Their tentacles were somewhat inflected in 45 m. ;
and after 7 hrs. 45 m. the blades of two were so much curved
inwards that they formed little cups enclosing the drops.
These leaves re-expanded on the third day. On another occa-
sion the blade of a leaf was much inflected in 5 hrs. after a
drop of milk had been placed on it.

Human Urine. — Drops were placed on twelve leaves, and the
tentacles of all, with a single exception, became greatly inflected.
Owing, I presume, to differences in the chemical nature of the
urine on different occasions, the time required for the movements
of the tentacles varied much, but was always effected in under
24 hrs. In two instances I recorded that all the exterior ten-
tacles were completely inflected in 17 hrs., but not the blade of
the leaf. In another case the edges of a leaf, after 25 hrs.
30 m., became so strongly inflected that it was converted into a
cup. The power of urine does not lie in the urea, which, as
we shall hereafter see, is inoperative.

Albumen (fresh from a hen's egg), placed on seven 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 with 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 on a
single leaf, which had most of its outer tentacles and the blade
inflected in 19 hrs. During subsequent years, I repeatedly
used this infusion to test leaves which had been experimented

80 DROSERA ROTUNDIFOLIA. Chap. V.

on with other substances, and it was found to act most ener-
getically, but as no exact account of these trials was kept, they
are not here introduced.

Mucus. — Tliick and thin mucus from the bronchial tubes,
placed on three leaves, caused inflection. A leaf with thin
mucus had its marginal tentacles and blade somewhat curved
inward in 5 hrs. 30 m., and greatly so in 20 hrs. The action of
this fluid no doubt is due either to the saliva or to some albu-
minous matter* mingled with it, and not, as we shall see in the
next chapter, to mucin or the chemical principle of mucus.

Saliva. — Human saliva, when evaporated, yieldsf from 1-14 to
1*19 per cent, of residue ; and this yields 0*25 per cent, of ashes,
so that the proportion of nitrogenous matter which saliva eon-
tains must be small. Nevertheless, drops placed on the discs of
eight leaves acted on them all. In one case all the exterior ten-
tacles, excepting nine, were inflected in 19 hrs. 30 m. ; in another
case a few became so in 2 hrs., and after 7 hrs. 30 m. all those
situated near where the drop lay, as well as the blade, were
acted on. Since making these trials, I have many scores of
times just touched glands with the handle of my scalpel wetted
with saliva, to ascertain whether a leaf was in an active condi-
tion ; for this was shown in the course of a few minutes by the
bending inwards of the tentacles. The edible nest of the Chinese
swallow is formed of matter secreted by the salivary glands ; two
grains were added to one ounce of distilled water (one part to 218),
which was boiled for several minutes, but did not dissolve the
whole. The usual-sized drops were placed on three leaves, and
these in 1 hr. 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 ten-
tacles of all became inflected. In one case the exterior tentacles
were well curved in after 6 hrs. 30 m., and the blade of the leaf
to a partial extent after 24 hrs. As saliva acted so efficiently,
and yet contains so small a proportion of nitrogenous matter, I
tried how small a quantity of isinglass would act. One part was
dissolved in 218 parts of distilled water, and drops were placed
on four leaves. After 5 hrs. two of these were coEsiderably and
two moderately inflected ; after 22 hrs. the former were greatly
q,nd the latter much more inflected. In the course of 48 hrs.

* Mucus from the air-passages to contain some albumen,
is said in Marshall, 'Outlines of f Miiller's 'Elements of Phy sio-

Phy Biology,' vol. ii. 18G7, p. 364, logy,' Eng. Trans, vol. i. p. 514.

Chap. V. EFFECTS OF ORGANIC FLUIDS, 81

from the time when the drops were placed on the leaves, all
four had almost re-expanded. They were then given little bits
of meat, and these acted more powerfully than the solution.
One part of isinglass was next dissolved in 437 of water ; the
fluid thus formed was so thin that it could not be distinguished
from pure water. The usual-sized drops were placed on seven
leaves, each of which thus received gi^ of a grain (-0295 mg.).
Three of them were observed for 41 hrs., but were in no way
affected ; the fourth and fifth had two or three of their exterior
tentacles inflected after 18 hrs. ; the sixth had a few more ;
and the seventh had in addition the edge of the leaf just
perceptibly curved inwards. The tentacles of the four latter
leaves began to re-expand after an additional interval of only
8 hrs. Hence the g-|o of a grain of isinglass is sufficient to affect
very slightly the more sensitive or active leaves. On one of the
leaves, which had not been acted on by the weak solution, and on
another, which had only two of its tentacles inflected, drops of
the solution as thick as milk were placed ; and next morning,
after an interval of 16 hrs., both were found with all their ten-
tacles strongly inflected.

Altogether I experimented on sixty-four leaves
with the above nitrogenous fluids, the five leaves
tried only with the extremely weak solution of isin-
glass not being included, nor the numerous trials
subsequently made, of which no exact account was
kept. Of these sixty-four leaves, sixty- three had their
tentacles and often their blades well inflected. The
one which failed was probably too old and torpid.
But to obtain so large a proportion of successful
cases, care must be taken to select young and active
leaves. Leaves in this condition were chosen with
equal care for the sixty-one trials with non-nitro-
genous fluids (water not included) ; and we have seen
that not one of these w^as in the least affected. We
may therefore safely conclude that in the sixty-four
experiments with nitrogenous fluids the inflection of
the exterior tentacles was due to the absorption of

82 DEOSERA ROTUNDIFOLIA. Chat. V.

nitrogenous 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, imme-
diately afterwards 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 in the course
of between 24 hrs. and 48 hrs., were then tested with
drops of milk, urine, or albumen. Of the twenty-three
leaves thus treated, seventeen had their tentacles, and
in some cases their blades, well inflected; but their
powers were somewhat impaired, for the rate of move-
ment was decidedly slower than when fresh leaves
were treated with these same nitrogenous fluids. This
impairment, as well as the insensibility of six of the
leaves, may be attributed to injury from exosmose,
caused by the density of the fluids placed on their
discs.

■ The results of a few otlier 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 tliick decoction thus made
was allowed to settle. Drops of the superincumbent fluid were
placed on four leaves, and when these were looked at after
IG 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

* "Watts' 'Diet, of Chemistry,' Digestion,' torn. 1. p. 370; torn,
vol. lit. p. 568. ii. pp. 154, 166, on legumin.

t 'Leyons sur la Phys. do la

Chap. V. EFFECTS OF OEGANIC FLUIDS. 83

exist wMcli are not coagulated by boiling water, but are con-
verted into soluble peptones.

On three occasions chopped cabbage-leaves* 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. I also touched the viscid secre-
tion round the glands of several tentacles with min,ute 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 di'ops were placed on
the discs of five leaves ; and these next morning were so much
acted on that their blades were completely doubled over. We
thus see that a decoction of cabbage-leaves is nearly or quite as
potent as an infusion of raw meat.

About the same quantity of chopped cabbage-leaves and of
distilled water, as in the last experiment, were kept in a vessel
for 20 hrs. in a hot closet, but not heated to near the boiling-
point. Drops of this infusion were placed on four leaves. One
of these, after 23 hrs., was much inflected ; a second slightly ; a
third had only the submarginal tentacles inflected; and the
fourth was not at all affected. The power of this infusion is
therefore very much less than that of the decoction ; and it is
clear that the immersion of cabbage-leaves for an hour in water
at the boihng temperature is much more efficient in extracting
matter which excites Drosera than immersion during many
hours in warm water. Perhaps the contents of the cells are
protected (as Schiff remarks with respect to legumin) by the
walls being formed of cellulose, and that until these are rup-
tured by boiling-water, but little of the contained albuminous
matter is dissolved. We know from the strong odour of cooked
cabbage-leaves that boiling water produces some chemical
change in them, and that they are thus rendered far more
digestible and nutritious to man. It is therefore an interesting

* The leaves of young plants, and the outer leaves of mature

before the heart is formed, such plants 1 • 6 per cent. Watts' ' Diet,

as were used by me, contain 2-1 of Chemistry,' vol. i. p. 653.
per cent of albuminous matter,

84 DEOSERA EOTUNDIFOLIA. Chap. V.

fact that water at this temperature extracts matter from them
which excites Drosera to an extraordinary degree.

Grasses contain far less nitrogenous matter than do peas or
cabbages. The leaves and stalks of three common kinds were
chopped and boiled for some time in distilled water. Drops
of this decoction (after having stood for 24 hi's.) were placed
on six leaves, and acted in a rather peculiar manner, of which
other instances will be given in the seventh chapter on the
salts of ammonia. After 2 hrs. 30 m. four of the leaves had
their blades greatly inflected, but not their exterior tentacles ;
and so it was with all six leaves after 24 hrs. Two days after-
wards the blades, as well as the few submarginal tentacles which
had been inflected, all re-expanded ; and much of the fluid on
their discs was by this time absorbed. It appears that the de-
coction strongly excites the glands on the disc, causing the blade
to be quickly and greatly inflected ; but that the stimulus, dif-
ferently from what occurs in ordinary cases, does not spread, or
only in a feeble degree, to the exterior tentacles.

I may here add that one part of the extract of belladonna
(procured from a di-uggist) was dissolved in 437 of water, and
drops were placed on six leaves. Next day all six were some-
what inflected, and after 48 hrs. were completely re-expanded.
It was not the included atropine which produced this effect, for
I subsequently ascertained that it is quite powerless. I also
procured some extract of hyoscyamus from three shops, and
made infusions of the same strength as before. Of these three
infusions, only one acted on some of the leaves, which were
tried. Though druggists believe that all the albumen is pre-
cipitated in the preparation of these di'ugs, I cannot doubt that
some is occasionally retained ; and a trace would be sufficient
to excite the more sensitive leaves of Drosera.

Chap. VL DIGESTION. 85

CHAPTER YI.

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 — Albu-
men, its digestion arrested by alkalies, recommences by the addi-
tion of an acid — Meat — Fibrin — Syntonin — Areolar tissue —
Cartilage — Fibro-cartilage — Bone — EQamel and dentine — Phos-
phate of lime — Fibrous basis of bone — Gelatine — Chondrin —
Milk, casein and cheese — Gluten — Legumin — Pollen — Globulin
— Hsematin — Indigestible substances — Epidermic productions —
Fibro-elastic tissue — Mucin — Pepsin — Urea — Chitine — Cellu-
lose — Gun-cotton — Chlorophyll — Fat and oil — Starch — Action
of the secretion on living seeds — Summary and concluding
remarks.

As we have seen that nitrogenous fluids act very
differently on the leaves of Drosera from non-nitro-
genous fluids, and as the leaves remain clasped for a
much 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
mammals ; the digested matter being afterwards ab-
sorbed. This fact, which will be clearly proved, is a
wonderful one in the physiology of plants. I must
here state that I have been aided throughout all my
later experiments by many valuable suggestions and
assistance given me with the greatest kindness by
Dr. Burdon Sanderson.

86 DROSEEA ROTUNDIFOLIA. Chap. VI.

It may be well to premise for the sake of any reader
wlio knows nothing about the digestion of albuminous
compounds by animals that this is effected by means
of a ferment, pepsin, together with weak hydrochloric
acid, though almost any acid will serve. Yet neither
pepsin nor an acid by itself has any such power.*
We have seen that when the glands of the disc are
excited by the contact of any object, especially of
one containing nitrogenous matter, the outer ten-
tacles and often the blade become inflected ; the leaf
being thus converted into a temporary cup or sto-
mach. At the same time the discal glands secrete
more copiously, and the secretion becomes acid.
Moreover, they transmit some influence to the glands
of the exterior tentacles, causing them to pour forth
a more copious secretion, which also . becomes acid or
more acid than it was before.

As this result is an important one, I will give the
evidence. The secretion of many glands on thirty
leaves, which had not been in any way excited, was
tested with litmus paper ; and the secretion of twenty-
two of these leaves did not in the least affect the colour,
whereas that of eight caused an exceedingly feeble
and sometimes doubtful tinge of red. Two other
old leaves, however, which appeared to have been in-
flected several times, acted much more decidedly on
the paper. Particles of clean glass were then placed
on five of the leaves, cubes of albumen on six, and
bits of raw meat on three, on none of which was the
secretion at this time in the least acid. After an
interval of 24 hrs., when almost all the tentacles on

* It appears, however, accord- though slowly, a very minute

ing to Schilf, and contrary to tho quantity of coagulated albumen.,

opinion of some physiologists, 8chitf, 'Phys. de la Digestion,'

that weak liydrochloric dissolves, torn. ii. 1867, p. 25.

Chap. VI. DIGESTION. 87

these fourteen leaves had become more or less in-
flected, I again tested the secretion, selecting glands
which had not as yet reached the centre or touched
any object, and it was now plainly acid. The degree
of acidity of the secretion varied somewhat on the
glands of the same leaf. On some leaves, a few ten-
tacles did not, from some unknown cause, become in-
flected, as often happens ; and in five instances their
secretion was found not to be in the least acid;
whilst the secretion of the adjoining and inflected
tentacles on the same leaf was decidedly acid. With
leaves excited by particles of glass placed on the
central glands, the secretion which collects on the
disc beneath them was much more strongly acid
than that poured forth from the exterior tentacles,
which were as yet only moderately inflected. When
bits of albumen (and this is naturally alkaline), or
bits of meat were placed on the disc, the secretion
collected beneath them was likewise strongly acid.
As raw meat moistened with water is slightly acid, I
compared its action on litmus paper before it was
placed on the leaves, and afterwards when bathed in
the secretion ; and there could not be the least doubt
that the latter was very much more acid. I have
indeed tried hundreds of times the state of the secre-
tion on the discs of leaves which were inflected over
various objects, and never failed to find it acid. We
may, therefore, conclude that the secretion from un-
excited leaves, though extremely viscid, is not acid or
only slightly so, but that it becomes acid, or 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
5

88 DEOSEEA BOTUNDIFOLIA. Chap. VI.

appears to be to a certain extent antiseptic, as. it
checks the appearance of monld and infusoria, thus
preyentino- 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 anxions 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 vrith great kindness under-
took to test the fluid thus collected. The leaves were excited
by clean particles of glass placed on them 24 hrs. previously.
No doubt much more acid would have been secreted had the
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 hydi'ochloric, sulphuric,
tartaric, oxalic, or formic acids. This having been ascertained,
the remainder of the fluid was evaporated nearly to dryness, and
acidified with sulphuric acid ; it then evolved volatile acid
vapour, which was condensed and digested with carbonate of
silver. ■ " The weight of the silver salt thus produced was only
'37 gr., much too small a quantity for the accurate determina-
tion of the molecular weight of the acid. The number obtained,
however, corresponded nearly with that of propionic acid ; and
I believe that this, or a mixture of acetic and butyric acids, were
present in the liquid. The acid doubtless belongs to the acetic
or fatty series."

Prof. Frankland, as well as his assistant, observed (and this
is an important fact) that the fluid, " when acidified with sul-
phuric acid, emitted a powerful odour like that of pepsin."
The leaves from which the secretion had been washed were
also sent to Prof. Frankland; they were macerated for some
hours, then acidified with sulphuric acid and distilled, but no
acid passed over. Therefore the acid which fresh leaves con-
tain, as shown by their discolouring litmus paper when crushed,
must bo of a different nature from that present in the secretion.
Nor was any odour of pepsin emitted by them.

Chap. VI. DIGESTION. 89

Althougli 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 follow-
ing experiments, the results of which are valuable, indepen-
dently of the present inquiry. Prof. Frankland supplied the
acids.

" 1. The purpose of the following experiments was to deter-
mine the digestive activity of liquids containing pepsin, when
acidulated with certain volatile acids belonging to the acetic
series, in comparison with liquids acidulated with hydrochloric
acid, in proportion similar to that in which it exists in gastric
juice.

" 2. It has been determined empirically that the best results
are obtained in artificial digestion when a liquid containing two
per thousand of hydrochloric acid gas by weight is used. This
corresponds to about 6'25 cubic centimetres per litre of ordinary
strong hydrochloric acid. The quantities of propionic, butyric,
and valerianic acids respectively which are required to neutralise
as much base as 6'25 cubic centimetres of HCl, are in grammes
4-04 of propionic acid, 4-82 of butyric acid, and 5'68 of valerianic
acid. It was therefore judged expedient, in comparing the
digestive powers of these acids with that of hydrochloric acid, to
use them in these proportions.

"3. Five hundred cub. cent, of a liquid containing about
8 cub. cent, of a glycerine extract of the mucous membrane of
the stomach of a dog killed during digestion having been pre-
pared, 10 cub. cent, of it were evaporated and dried at 110°.
This quantity yielded 0-0031 of residue.

"4. Of this liquid four quantities were taken which were
severally acidulated with hydrochloric, 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 thermometer which indicated a
temperature of 38° to 40° Cent. Into each, a quantity of un-
boiled fibrin was introduced, and the whole allowed to stand
for four hours, the temperature being maintained during the
whole time, and care being taken that each contained through-
out an excess of fibrin. At the end of the period each liquid
was filtered. Of the filtrate, which of course contained as
much of the fibrin as had been digested during the four hours,

90 DBOSEEA BOTr^T)IFOLIA. Chap. YI.

10 cub. cent were measnred ont and evaporated, and dried at
110' as before. The residues were resi)ectiyelv—

*' In the liqnid containing hydrochloric acid 04079

„ „ propionic acid 0-0601

butyric acid 0-1468

„ „ 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 0-0570

„ butyric acid 01437

„ valerianic acid . . . . . . . . 0-1223

as compared with 0-4043 for hydrochloric acid; these several
numbers expressing the quantities of fibrin by weight digested
in presence of equivalent quantiti^ of the respective acids
under identical conditions,

" The results of the experiment may be stated thus : — If 100
represent the digestive power of a Hquid containing pepsin with
the usual proportion of hydrochloric acid, 14-0, 35'4, and 30*2,
will represent respectively the digestive powers of the three
acids under investigation.

" 5. In a second experiment in which the procedure was in
every respect the same, excepting that all the tubes were
plunged into the same water-bath, and the residues dried at
115^ C, the results were as follows : —

" Quantity of fibrin dissolved in four hours by 10 cub. cent,
of the Uquid —

" Propionic acid 0-0563

Butyric acid 0-0S35

Yalerianic acid .. .. .. 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 .. .. .. 165

Butyric acid 247

Yalerianic acid 16-1

" 6. A third experiment of the same kind gave :

Chap. VI. DIGESTION. 91

" Quantity of fibrin digested in four hours by 10 cub. cent.
of the liquid :

" Hydrochloric acid .. .. 0-2915

Propionic acid 0*1490

Butyric acid 01044

Valerianic acid .. .. .. 0*0520

" Comparing, as before, the three last numbers with the first
taken as 100, the digestive power of propionic acid is repre-
sented by 16*8; that of butyi'ic acid by 35-8; and that of
valerianic by 17-8.

" The mean of these three sets of observations (hydrochloric
acid being taken as 100) gives for

" Propionic acid 158

Butyric acid 32-0

Valerianic acid 21-4

" 7. A further experiment was made to ascertain whether tho
digestive activity of butyric acid (which was selected as being
apparently the most eflBcacious) was relatively greater at ordinary
temperatures than at the temperature of the body. It was
found that whereas 10 cub. cent, of a liquid containing the ordi-
nary proportion of hydrochloric acid digested 0*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*9; that of butyric acid at the same
temperature being 15*6."

We here see that at the lower of these two temperatures,
hydrochloric acid with pepsin digests, within the same time,
rather less than half the quantity of fibrin compared with
what it digests at the higher temperature; and the power of
butyric acid is reduced in the same proportion under similar
conditions and temperatures. We have also seen that butyric
acid, which is much more eflBcacious than propionic or vale-
rianic acids, digests with pepsin at the higher temperature less
than a third of the fibrin which is digested at the same tempera-
ture by hydrochloric acid.

92 DROSEEA EOTUNDIFOLIA. Chap, VI.

I will now give in detail my experiments on the
digestive power of the secretion of Drosera, dividing
the substances tried into two series, namely those
which are digested more or less completely, and those
which are not digested. We shall presently see that
all these substances are acted on by the gastric juice
of the higher animals in the same manner. I beg
leave to call attention to- the experiments under the
head albumen, showing that the secretion loses its
power when neutralised by an alkali, and recovers it
when an acid is added.

Suhstances which are eomjoletehj or jpartially digested hj
the Secretion of Drosera.

Albumen. — After having tried various substances,
Dr. Burden Sanderson suggested to me the use of cubes
of coagulated albumen or hard-boiled egg. I may pre-
.mise that five cubes of the same size as those used in
the following experiments were placed for the sake of
comparison at the same time on wet moss close to the
plants of Drosera. The weather was hot, and after four
days some of the cubes were discoloured and mouldy,
with their angles a little rounded ; but they were not
surrounded by a zone of transparent fluid as in the
case of those undergoing digestion. Other cubes
retained their angles and white colour. After eight
days all were somewhat reduced in size, discoloured,
with their angles much rounded. ISTevertheless in
four out of the five specimens, the central parts were
still white and opaque. So that their state differed
widely, as we shall see, from that of the cubes sub-
jected to the action of the secretion.

Experiment 1. — Eathcr largo cubes of albnmen wero first
tried; tlie teutaclcs were well inflcct-od in 24 hrs. ; after an

Chap. VI. DIGESTION. 93

additional day the angles of the cubes were dissolved and
rounded;* but the cubes were too large, so that the leaves
were injured, and after seven days one died and the others
were dying. Albumen which has been kept for four or five
days, and which, it may be presumed, has begun to decay
slightly, seems to act more quickly than freshly boiled eggs.
As the latter were generally used, I often moistened them
with a little saliva, to make the tentacles close more
quickly.

Experiment 2. — A cube of -^^ of an inch (i.e. with each side
yV 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 the leaf re-expanded, but there was still
left on the disc a minute bit of albumen now rendered trans-
parent. More albumen had been given to this leaf than could
be dissolved or digested.

Experiment 3. — Two cubes of albumen of ^\j of an inch
(1*27 mm.) were placed on two leaves. After 46 hrs. every
atom of one was dissolved, and most of the liquefied matter
was absorbed, the fluid which remained being in this, as in all
other cases, very acid and viscid. The other cube was acted
on at a rather slower rate.

Experiment 4. — Two cubes of albumen of the same size as
the last were placed on two leaves, and were converted in
50 hrs. into two large drops of transparent fluid ; but when
these were removed from beneath the inflected tentacles, and
viewed by reflected light under the microscope, fine streaks of
white opaque matter could be seen in the one, and traces of
similar streaks in the other. 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 -^ of an inch ( • 635 mm.),
were placed on the same leaf, and two similar cubes on another

* In all my numerous cxperi- teristic of the digestion of albu-

ments on the digestion of cubes men by the gastric juice of ani-

of albumen, the angles and edges mals. On the other hand, he

were invariably first rounded. remarks, "les dissolutions, en

Now, Schitf states ( ' Le90U3 chimie, ont lieu sur toute la sur-

phys. de la Digestion,' vol. ii. face des corps en contact avcc

18U7, p. 149) that this is charac- I'agent dissolvant."

94 DROSERA ROTUNDIFOLIA. Chap. VI.

leaf. These were examined after 21 hrs. 30 m., and all four
were found roimdcd. After 46 hrs. the two cubes on the one
leaf were completely liquefied, the fluid being perfectly trans-
parent; on the other leaf some opaque white streaks could
still be seen in the midst of the fluid. After 72 hrs. these
streaks disappeared, but there was still a little viscid fluid
left on the disc; whereas it was almost all absorbed on the
first leaf. Both leaves were now beginning to re-expand.

The best and almost sole test of the presence of
some ferment analogous to pepsin in the secretion
appeared to be to neutralise the acid of the secretion
with an alkali, and to observe whether the process
of digestion ceased ; and then to add a little acid
and observe whether the process recommenced. This
was done, and, as we shall see, with success, but it
was necessary first to try two control experiments ;
namely, whether the addition of minute drops of
water of the same size as those of the dissolved
alkalies to be used would stop the process of diges-
tion ; and, secondly, whether minute drops of weak
hydrochloric acid, of the some strength and size as
those to be used, would injure the leaves. The
two following experiments were therefore tried : —

Eocperlment 6. — Small cubes of albumen were put on three
leaves, and minute drops of distilled water on the head of a pin
were added two or three times daily. These did not in the
least delay the process ; for, after 48 hrs., the cubes were com-
pletely dissolved on all three leaves. On the third day the
leaves began to re-expand, and on the fourth day all the fluid
was absorbed.

Experiment 7.— Small cubes of albumen, were put on two
leaves, and minute drops of hydrochloric acid, of the strength of
one part to 437 of water, were added two or three times. This
did not in the least delay, but seemed rather to hasten, the
process of digestion ; for every trace of the albumen chsappeared
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 ahnost superfluous to state that

Chap. VI. DIGESTION. 95

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 -^ of an inch, or 2-54:
mm.) were placed on five leaves, and minute drops of a solu-
tion of one part of carbonate of soda to 437 of water were added
at intervals to three of them, and di'ops 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 ^^ of a minim (-0059 ml.), so that
each contained only -^^ 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 dis-
solved, 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
y^ of a grain (-0539 mg.) of either salt. Two cubes of albu-
men (each about J^ 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 was added. Acid of this greater strength
was used as the solutions of the alkalies were stronger. The

96 DROSERA ROTUNDIFOLIA. Ckap. VI.

process of digestion now commenced, so that within 48 hrs. from
the time when tlie acid was given the four cubes were not only
completely dissolved, but much of the liquefied albumen was
absorbed.

Experiment 11. — Two cubes of albumen (^ of an inch, or
•C35 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
hydi'ochloric 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 tho
leaves were injured,* for during the normal process of digestion
the albumen is not thus coloured, and we can thus understand
why tho 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 analo-
gous to pepsin, which in presence of an acid gives
to the secretion its power of dissolving albuminous
compounds.

Splinters of clean glass were scattered on a large
number of leaves, and these became moderately in-
flected. They were cut off and divided into three
lots; two of them, after being left for some time in
a little distilled water, were strained, and some dis-

* Sachs remarks ('Traite do agents, allow all their colouring

Bot.' 1874, p. 774), tliat cells matter to escapo into the Bur-

■NvLich are killed by freezing, by rounding water,
too great heat, or by chemical

Chap. VI. DIGESTION. 97

coloured, viscid, slightly acid fluid was thus obtained.
The third lot was well soaked in a few drops of
glycerine, which is well known to dissolve pepsin.
Cubes of albumen (^^g- of an inch) were now placed
in the three fluids in watch-glasses, some of which
were kept for several days at about 90° Fahr.
( 32°-2 Cent.), and others at the temperature of my
room; but none of the cubes were dissolved, the
angles remaining as sharp as ever. This fact pro-
bably indicates that the ferment is not secreted until
the glands are excited by the absorption of a minute
quantity of already soluble animal matter, — a con-
clusion which is supported by what we shall hereafter
see with respect to Dionaea. Dr. Hooker likewise found
that, although the fluid within the pitchers of Ne-
penthes possesses extraordinary power of digestion, yet
when removed from the' pitchers before they have
been excited and placed in a vessel, it has no such
power, although it is already acid; and we can
account for this fact only on the supposition that the
proper ferment is not secreted until some exciting
matter is absorbed.

On three other occasions eight leaves were strongly
excited with albumen moistened with saliva; they
were then cut off, and allowed to soak for severaJ
hours or for a whole day in a few drops of glycerine.
Some of this extract was added to a little hydro-
chloric acid of various strengths (generally one to
400 of water), and minute cubes of albumen were
placed in the mixture.* In two of these trials the
cubes were not in the* least acted on ; but in the third

* As a control experiment bits the albumen, as might have been

of albumen were placed in the expected, was not in the least

same glycerine with hydrochloric aflected after two days.
acid of the same strength; and

98 DROSERA ROTUNDIFOLIA. Chap. VI.

the experiment was successful. For in a vessel con-
taining two cubes, both were reduced in size in 3 hrs. ;
and after 24 hrs. mere streaks of undissolved albu-
men were left. In a second vessel, containing two
minute ragged bits of albumen, both were likewise
reduced in size in 3 hrs., and after 24 hrs. completely
disappeared. I then added a little weak hydro-
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,* 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 Boast Meat. — Cubes of about -^ of an
inch (1-27 mm.) of moderately roasted meat were
placed on five leaves which became in 12 hrs. closely
inflected. After 48 hrs. I gently opened one leaf, and
the meat now consisted of a minute central sphere,
partially digested and surrounded by a thick envelope
of transparent viscid fluid. The whole, without being
much disturbed, was removed and placed under the
microscope. In the central part the transverse striae
on the musciihir fibres were quite distinct ; and it was

* 'Le^oDS phys. do la Digestion,' 18G7, torn. ii. pp. 114-126.

Chap.VL

DIGESTION. 99

interesting to observe how gradually they disappeared,
when the same fibre was traced into the surrounding
jluid. Thejf disappeared by the striae being replaced
by transverse lines formed of excessively minute dark
points, which towards the exterior could be seen only
under a very high power ; and ultimately these points
were lost. When I made these observations, I had
not read Schiff's account* of the digestion of meat
by gastric juice, and I did not understand the mean-
ing of the dark points. But this is explained in the
following statement, and we further see how closely
similar is the process of digestion by gastric juice and
by the secretion of Drosera.

" On a dit que le sue gastrique faisait perdre a la fibre muscu-
laire ses stries transversales. Ainsi enoncee, cette proposition
pourrait donner lieu a une equivoque, car cequi se perd, ce n'est
que Vaspect exterieur de la striature et non les elements anato-
miques qui la composent. On sait que les stries qui donnent un
aspect si caracteristique a la fibre musculaire, sent le resultat do
la juxtaposition et du parallelisme des corpuscules elementau-es,
places, a distances egales, dans Tinterieur des fibrilles contigues.
Or, des que le tissu connectif qui relie entre elles les fibrilles
elementaires vient a se gonfler et a se dissoudre, et que les
fibrilles elles-memes se dissocient, ce parallelisme est detruit et
avec lui I'aspect, le phenomene optique des stries. Si, apres la
desagregation des fibres, on examine au microscope les fibrilles
elementaires, on distingue encore tres-nettement a leur interieur
les corpuscules, et on continue a les voir, de plus en plus pales,
jusqu'au moment oil les fibrilles elles-memes se liquefient et dis-
paraissent dans le sue gastrique. Ce qui constitue la striature,
a proprement parler, n'est done pas detruit, avant Ja Uque-
faction de la fibre cliarnue elle-meme."

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

* ' Le9ons phys. de la Digestion,* torn. ii. p. 145.

100 DROSEEA KOTUNDIFOLIA. Chap. VI

the least digested. There were also little free paral-
lelograms of yellowish, highly translucent matter.
Schiff, in speaking of the digestion of meat by gastric
juice, alludes to such parallelograms, and says : —

" Le gonflement par lequel commence la digestion de la viande,
resulte de Taction du sue gastrique acide snr le tissu connectif
qui se dissout d'abord, et qui, par sa liquefaction, desagrege les
fibrilles. Celles-ci se dissolvent ensuite en grande partie, mais,
avant de passer a I'etat liquide, elles tendent a se briser en
petits fragments transversaux. Les ' sarcous elements' de
Bo^vman, qui ne sont autre chose que les produits de cette
division transversale des fibrilles elcmentaires, peuvent etre
prepares et isolos a I'aide du sue gastrique, pourvu qu'on
n'attcnd pas jusqu'a la liquefaction complete du muscle."

After an interval of 72 hrs., from the time when
the five cubes were placed on the leaves, I opened the
four remaining ones. On two nothing could be seen
but little masses of transparent viscid fluid ; but
when these were examined under a high power,
fat-globules, bits of fibro-elastic tissue, and some few
parallelograms of sarcous matter, could be distin-
guished, but not a vestige of transverse striae. On the
other two leaves there were minute spheres of only
partially digested meat in the centre of much trans-
parent fluid.

Fibrin. — Bits of fibrin were left in water during
four days, whilst the following experiments were
tried, but they were not in the least acted on. The
fibrin which I first used was not pure, and included
dark particles : it had either not been well prepared
or had subsequently undergone some change. Thin
portions, about --pV 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

Chap. VI. DIGESTION. 101

drops of hydrochloric acid (one part to 437 of
water) were added ; this seemed to hasten the process
of digestion, for on one leaf all was liquefied and
absorbed after 20 hrs. ; but on the three other leaves
some undissolved residue was left after 48 hrs. It
is remarkable that in all the above and following
experiments, as well as when much larger bits of
fibrin were used, the leaves were very little excited ;
and it was sometimes necessary to add a little saliva
to induce complete inflection. The leaves, moreover,
began to re-expand after only 48 hrs., whereas they
would have remained inflected for a much longer
time had insects, meat, cartilage, albumen, &c., been
placed on them.

I then tried some pure white fibrin, sent me by Dr.
Burden Sanderson.

Experiment 1. — Two particles, barely gV of an incli (1-27 mm.)
square, were x)laced on opposite sides of the same leaf. One of
these did not excite the surrounding tentacles, and the gland
on which it rested soon dried. The other particle caused a few
of the short adjoining tentacles to be inflected, the more distant
ones not being affected. After 24 hrs. both were almost, and
after 72 hrs, completely, dissolved.

Experimeiit 2. — The same experiment with the same result,
only one of the two bits of fibrin exciting the short surround-
ing tentacles. This bit was so slowly acted on that after a
day I pushed it on to some fresh glands. In three days from
the time when it was first placed on the leaf it was completely
dissolved.

Experiment 3. — Bits of fibrin of about the same size as before
were placed on the discs of two leaves ; these caused very little
inflection in 23 hrs., but after 48 hrs. both were well clasped by
the surrounding short tentacles, and after an additional 24 hrs.
were completely dissolved. On the disc of one of these leaves
much clear acid fluid was left.

Experiment 4 — Similar bits of fibrin were placed on the discs
of two leaves ; as after 2 hrs. the glands seemed rather dry,
they were freely moistened with saliva; this soon caused
strong inflection both of the tentacles and blades, with copious

102 DROSERA ROTUNDIFOLIA. Chap. VI.

secretion from the glands. In 18 hrs. tho fibrin was com.
pletely 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 secre-
tion completely dissolves pure fibrin. The rate of
dissolution is rather slow; but this depends merely
on this substance not exciting the leaves sufficiently,
so that only the immediately adjoining tentacles are
inflected, and the supply of secretion is small.

Syntonin. — This substance, extracted from muscle,
was kindly prepared for me by Dr. Moore. Very
differently from fibrin, it acts quickly and energetic-
ally. Small portions placed on the discs of three
leaves caused their tentacles and blades to be strongly
inflected within 8 hrs. ; but no further observations
were made. It is probably due to the presence of
this substance that raw meat is too powerful a stimu-
lant, often injuring or even killing the leaves.

Areolar Tissue. — Small portions of this tissue from. a
sheep were placed on the discs of three leaves ; these
became moderately well inflected in 24 hrs., but began
to re-expand after 48 hrs., and were fully re-expanded
in 72 hrs., always reckoning from the time when the
bits were first given. This substance, therefore, like
fibrin, excites the leaves for only a short time. The
residue left on the leaves, after they were fully re-
expanded, was examined under a high power and
found much altered, but, owing to the presence of a
quantity of elastic tissue, which is never acted on,
could hardly be said to be in a liquefied condition.

Some areolar tissue free from elastic tissue was next
procured from the visceral cavity of a toad, and
moderately sized, as well as very small, bits were
placed on five leaves. After 24 hrs. two of the bits

Chap. VI. DIGESTION. 103

were completely liquefied; two others were rendered
transparent, but not quite liquefied; whilst the fifth
was but little affected. Several glands on the three
latter leaves were now moistened with a little saliva,
which soon caused much inflection and secretion,
with the result that in the course of 12 additional
hrs. one leaf alone showed a remnant of undigested
tissue. On the discs of the four other leaves (to one
of which a rather large bit had been given) nothing
was left except some transparent viscid fluid. I may-
add that some of this tissue included points of black
pigment, and these were not at all affected. As a
control experiment, small portions of this tissue were
left in water and on wet moss for the same length of
time, and remained white and opaque. From these
facts it is clear that areolar tissue is easily and
quickly digested by the secretion; but that it does
not greatly excite the leaves.

Cartilage. — Three cubes (^ of an inch or 1-27 mm.)
of white, translucent, extremely tough cartilage were
cut from the end of a slightly roasted leg-bone of a
sheep. These were placed on three leaves, borne by
poor, small plants in my greenhouse during Novem-
ber ; and it seemed in the highest degree improbable
that so hard a substance would be digested under
such unfavourable circumstances. Nevertheless, after
48 hrs., the cubes were largely dissolved and con-
verted into minute spheres, surrounded by trans-
parent, very acid fluid. Two of these spheres were
completely softened to their centres ; whilst the third
still contained a very small irregularly shaped core
of solid cartilage. Their surfaces were seen under
the microscope to be curiously marked by prominent
ridges, showing that the cartilage had been un-
equally corroded by the secretion. I need hardly

104 DROSEEA ROTUNDIFOLIA. Chap. VI.

say that cubes of the same cartilage, kept in water
for the same length of time, were not in the least
aflected.

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 leayes. Some of the glands were touched with
saliva, which caused prompt inflection. Two of the
leaves began to re-expand after three days, and the
third on the fifth day. The fluid residue left on
their 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 vertebrae of the
tail of a sheep). Moderately sized and small bits
(the latter about -^ of an inch) were placed on nine
leaves. Some of these were well and some very little
inflected. In the latter case the bits were dragged
over the discs, so that they were well bedaubed
with the secretion, and many glands thus irritated.
All the leaves re-expanded after only two days ; so
that they were but little excited by this substance.
The bits were not liquefied, but were certainly in an
altered condition, being swollen, much more trans-
parent, and so tender as to disintegrate very easily.
My son Francis prepared some artificial gastric juice,
which was proved efficient by quickly dissolving
fibrin, and suspended portions of the fibro-cartilage
in it. These swelled and became hyaline, exactly like
those exposed to the secretion of Drosera, 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 there-
fore asked Dr, Klein to examine the specimens ; and

Chap. VL DIGESTION. 105

lie reports that the two which had been subjected to
artificial gastric juice were " in that state of diges-
tion in which we find connective tissue when treated
with an acid, yiz. swollen, more or less hyaline, the
fibrillar bundles haying 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." Eibro-cartilage is therefore acted on in
nearly the same manner by gastric juice and by the
secretion of Drosera.

Bone. — Small smooth bits of the dried hyoidal
bone of a fowl moistened with saliva were placed on
two leaves, and a similarly moistened splinter of an
extremely hard, broiled mutton-chop bone on a third
leaf. These leaves soon became strongly inflected,
and remained so for an unusual length of time ;
namely, one leaf for ten and the other two for nine
days. The bits of bone were surrounded all the time
by acid secretion. When examined under a weak
power, they were found quite softened, so that they
were readily penetrated by a blunt needle, torn into
fibres, or compressed. Dr. Klein was so kind as to
make sections of both bones and examine them. He
informs me that both presented the normal appearance
of decalcified bone, with traces of the earthy salts
occasionally left. The corpuscles with their processes
were very distinct in most parts ; but in some parts,
especially near the periphery of the hyoidal bone,
none could be seen. Other parts again appeared
amorphous, with even the longitudinal striation of
bone not distinguishable. This amorphous structure,

106 DEOSEKA ROTUNDIFOLIA. Chap. VI.

as Dr. Klein tliinks, may be the result either of the
incipient digestion of the fibrous basis or of all the
animal matter having been removed, the corpuscles
being thus rendered invisible. A hard, brittle, yellow-
ish substance occupied the position of the medulla
in the fmgments of the hyoidal bone.

As the angles and little projections of the fibrous
basis were not in the least rounded or corroded, two of
the bits were placed on fresh leaves. These by the
next morning were closely inflected, and remained
so, — the one for six and the other for seven days, —
therefore for not so long a time as on the first occasion,
but for a much longer time than ever occurs with
leaves inflected over inorganic or even over many
organic bodies. The secretion during the whole time
coloured litmus paper of a bright red ; but this may
have been due to the presence of the acid super-
phosphate of lime. When the leaves re-expanded, the
angles and projections of the fibrous basis were as
sharp as ever. I therefore concluded, falsely as we
shall presently see, that the secretion cannot touch
the fibrous basis of bone. The more probable expla-
nation is that the acid was all consumed in decom-
posing the phosphate of lime which still remained;
so that none was left in a free state to act in con-
junction with the ferment on the fibrous basis.

Enamel and Dentine. — As the secretion decalcified
ordinary bone, I determined to try whether it would
act on enamel and dentine, but did not expect that it
would succeed with so hard a substance as enamel.
Dr. Klein gave me some thin transverse slices of
the canine tooth of a dog; small angular fragments
of which were placed on four leaves; and these were
examiijed each succeeding day at the same hour. The
results are, I think, worth giving in detail.

Chap. VI. DIGESTION. 107

Experiment 1. — May 1st, fragment placed on leaf; 3rd, ten-
tacles but little inflected, so a little saliva was added ; 6tli, 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, ten-
tacles fairly well inflected, with much secretion on the disc, and
remained so until the 7th, when the leaf re-expanded. The
fragment was now transferred to a fresh leaf, which next day
(8th) was inflected in the strongest manner, and thus remained
until the 11th, when it re-expanded. Dr. Klein reports, " a great
deal of enamel and the greater part of the dentine decalcified."

Experiment 3. — May 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,
moistened with saliva, was placed on a leaf, which was soon
inflected, and re-expanded on the 5th. The dentine had become
as flexible as thin paper. It was then transferred to a fresh leaf,
which next morning (6th) was strongly inflected, and reopened
on the 10th. The decalcified dentine was now so tender that it
was torn into shreds merely by the force of the re-expanding
tentacles.

From these experiments it appears that enamel is
attacked by the secretion with more difficulty than
dentine, as might have been expected from its ex-
treme hardness ; and both with more difficulty than
ordinary bone. After the process of dissolution has
once commenced, it is carried on with greater ease ;
this may be inferred from the leaves, to which the
fragments were transferred, becoming in all four cases
strongly inflected in the course of a single day ; whereas
the first set of leaves acted much less quickly and

108 DEOSERA EOTUNDIFOLIA. Chap. VI

energetically. The angles or projections of the fibrous
basis of the enamel and dentine (except, perhaps, in
No. 4, which could not be well observed) were not in
the least rounded ; and Dr. Klein remarks that their
microscopical structure was not altered. But this
could not have been expected, as the decalcification
was not complete in the three specimens which were
carefully examined.

Fibrous Basis of Bone. — I at first concluded, as
already stated, that the secretion could not digest this
substance. I therefore asked Dr. Burden 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 lamellae, into which part of the skull of a
cat became broken up after about a week's immersion
in the fluid, and he found that towards the edges the
" matrix appeared rarified, thus producing the appear-
ance as if the canaliculi of the bone-corpuscles had
become larger. ' Otherwise the corpuscles and their
canaliculi were very distinct." So that with bone
subjected to artificial gastric juice complete de-
calcification precedes the dissolution of the fibrous
basis. Dr. Burden Sanderson suggested to me that
the failure of Drosera to digest the fibrous basis of
bone, enamel, and dentine, might be due to the acid
being consumed in the decomposition of the earthy
salts, so that there was none left for the work of
digestion. Accordingly, my son thoroughly decal-
cified the bone of a sheep with weak hydrochloric
acid; and seven minute fragments of the fibrous
basis were placed on so many leaves," four of the
fragments being first damped with saliva to aid
prompt inflection. All seven leaves became inflected,
but only very moderately, in the course of a day.

Chap. VI.

DIGESTION. 109

They quickly began to re-expand ; five of them on
the second day, and the other two on the third day.
On all seven leaves the fibrous tissue was converted
into perfectly transparent, viscid, more or less lique-
fied little masses. In the middle, however, of one,
my son saw under a high power a few corpuscles,
with traces of fibrillation in the surrounding trans-
parent matter. From these facts it is clear that the
leaves are very little excited by the fibrous basis of
bone, but that the secretion easily and quickly lique-
fies it, if thoroughly decalcified. The glands which
had remained in contact for two or three days with
the viscid masses were not discoloured, and appa-
rently had absorbed little of the liquefied tissue,
or had been little affected by it.

Fliosi^hate of Lime.— As we have seen that the ten-
tacles of the first set of leaves remained clasped for
nine or ten days over minute fragments of bone, and
the tentacles of the second set for six or seven days
over the same fragments, I was led to suppose that
it was the phosphate of lime, and not any included
animal matter, which caused such long continued in-
flection. It is at least certain from what has just been
shown that this cannot have been due to the presence
of the fibrous basis. With enamel and dentine
(the former of which contains only 4 per cent, of
organic matter) the tentacles of two successive sets
of leaves remained inflected altogether for eleven
days. In order to test my belief in the potency of
phosphate of lime, I procured some from Prof. Frank-
land absolutely free of animal matter and of any acid.
A small quantity moistened with water was placed
on the discs of two leaves. One of these was only
slightly affected ; the other remained closely inflected
for ten days, when a few of the tentacles began to

110 DEOSEEA ROTUNDIFOLIA. Chap. VI.

re-expand, the rest being much injured or killed. I
repeated the experiment, but moistened the phosphate
with saliva to insure prompt inflection ; one leaf re-
mained inflected for six days (the little saliva used
would not have acted for nearly so long a time) and
then died; the other leaf tried to re-expand on the
sixth day, but after nine days failed to do so, and
likewise died. Although the quantity of phosphate
given to the above four leaves was extremely small,
much was left in every case undissolved. A larger
quantity wetted with water was next placed on the
discs of three leaves ; and these became most strongly
inflected in the course of 24 hrs. They never re-'
expanded ; on the fourth day they looked sickly,
and on the sixth were almost dead. Large drops
of not very viscid fluid hung from their edges during
the six days. This fluid was tested each day with
litmus paper, but never coloured it ; and this cir-
cumstance I do not understand, as the superphosphate
of lime is acid. I suppose that some superphosphate
must have been formed by the acid of the secretion
acting on the phosphate, but that it was all absorbed
and injured the leaves ; the large drops which hung
from their edges being an abnormal and dropsical
secretion. Anyhow, it is manifest that the phos-
phate of lime is a most powerful stimulant. Even
small doses are more or less poisonous, probably on
the same principle that raw meat and other nutri-
tious substances, given in excess, kill the leaves.
Hence the conclusion, that the long continued in-
flection of the tentacles over fragments of bone,
enamel, and dentine, is caused by the presence of
phosphate of lime, and not of any included animal
matter, is no doubt correct.

Gelatine, — I used pure gelatine in thin sheets given

Chap. VI. DIGESTION. Ill

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 re-
tained their angles for three days; after five days
they formed rounded, softened masses, but even on the
eighth day a trace of gelatine could still be detected.
Other squares were immersed in water, and these,
though much swollen, retained their angles for six
days. Squares of -^q 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 2-1 hrs. was closely inflected, showing how
much more potent than gelatine is the animal matter
absorbed from an insect. Some larger pieces of gela-
tine, soaked for five days in water, were next placed
on three leaves, but these did not become much in-
flected until the third day ; nor was the gelatine
completely liquefied until the fourth day. On this
day oile leaf began to re-expand ; the second on the
fifth ; and third on the sixth. These several facts

* Dr. Lauder Brimton, ' Hand- phys. de la Digestion,' 1867, p.
book for the Phys. Laboratory,' 249
1873, pp. 477, 487 ; Schiif, ' Leyons

112 DROSERA ROTUNDIFOLIA. Chap. VI.

prove that gelatiae is far from acting energetically
on Drosera.

In the last chapter it was sho^\-n that a solution of
isinglass of commerce, as thick as milk or cream,
induces strong inflection. I therefore wished to com-
pare its action with that of pure gelatine. Solutions
of one part of both substances to 218 of water were
made; and half-minim drops (-0296 ml.) were placed
on the discs of eight leaves, so that each received
-^ of a grain, or '135 mg. The four with the isin-
glass were much more strongly inflected than the
other four. I conclude therefore that isinglass con-
tains some, though perhaps very little, soluble albu-
minous matter. As soon as these eight leaves re-
expanded, they were given bits of roast meat, and in
some hours all became greatly inflected ; again show-
in «• how much moTO meat excites Drosera than does
gelatine or isinglass. This is an interesting fact, as
it is well known that gelatine by itself has little
power of nourishing animals.*

Chondrin. — This was sent me by Dr. Moore in a
gelatinous state. Some was slowly dried, and a small
chip was placed on a leaf, and a much larger chip on
a second leaf. The first was liquefied in a day ; the
larger piece was much swollen and softened, but was
not completely liquefied until the third day. The
undried jelly was next tried, and as a control experi-
ment small cubes were left in water for four days
and retained their angles. Cubes of the same size
were placed on two leaves, and larger cubes on two
other leaves. The tentacles and laminae of the latter
were closely inflected after 22 hrs., but those of the

* Dr. Lauder Brunton gives view of the indirect part \vliich
in the 'Medical Record,' January gelatine plays in nutrition.
1873, p. 30, an- account of Voit'a

Chap. VI. DIGESTION. 113

two leaves with the smaller cubes only to a moderate
degree. ' The jelly on all four was by this time lique-
fied, and rendered very acid. The glands were
blackened from the aggregation of their protoplasmic
contents. In 46 hrs. from the time when the jelly
was given, the leaves had almost re-expanded, and
completely so after 70 hrs. ; and now only a little
slightly adhesive fluid was left unabsorbed on their
discs.

One part of chondrin jelly was dissolved in 218
parts of boiling water, and half-minim drops were
given to four leaves ; so that each received about -^-l-^
of a grain (-135 mg.) of the jelly ; and, of course,
much less of dry chondrin. This acted most power-
fully, for after only 3 hrs. 30 m. all four leaves were
strongly inflected. Three of them began to re-
expand after 24 hrs., and in 48 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 energetically than pure gelatine or isin-
glass; but I am assured by good authorities that it
is most difficult, or impossible, to know whether
chondrin is pure, and if it contained any albumi-
nous compound, this would have produced the above
effects. Nevertheless, I have thought these facts worth
giving, as there is so much doubt on the nutritious
value of gelatine ; and Dr. Lauder Brunton does not
know of any experiments with respect to animals on
the relative value of gelatine and chondrin.

31ilk. — 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.
Eather large drops of milk excite so much secretion
(which is very acid) that it sometimes trickles down

114 DROSERA ROTUNDIFOLIA. Chap. VI.

from the leaves, and this is likewise characteristic of
chemically prepared casein. Minute drops of milk,
placed on leaves, were coagulated in about ten
minutes. Schiff denies* that the coagulation of milk
by gastric juice is exclusively due to the acid w^hich
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
secretioii does not commonly colour litmus paper
until the tentacles have become well inflected ;
whereas the coagulation commences, as we have seen,
in about ten minutes. Minute drops of skimmed
milk were placed on the discs of five leaves ; and a
large proportion of the coagulated matter or curd
was dissolved in 6 hrs. and still more completely
in 8 hrs. These leaves re-expanded after two days,
and the viscid fluid left on their discs was then care-
fully scraped off and examined. It seemed at first
sight as if all the casein had not been dissolved, for
a little matter was left which appeared of a whitish
colour by reflected light. But this matter, when
examined under a high power, and when compared
with a minute drop of skimmed milk coagulated by
acetic acid, was seen to consist exclusively of oil-
globules, more or less aggregated together, with no
trace of casein. As I was not familiar with the
microscopical appearance of milk, I asked Dr. Lauder
Brunton to examine the slides, and he tested the
globules with ether, and found that they were dis-
solved. We may, therefore, conclude that the secretion
quickly dissolves casein, in the state in which it exists
in milk.

Chemically Prepared Casein.--T\i\^ substance, which

♦ 'Le9ons,' &c. torn. ii. p. 151.

Chap. VI. DIGESTION. 115

is insoluble in water, is supposed by many chemists to
differ from the casein of fresh milk. I procured some,
consisting of hard globules, from Messrs. Hopkins and
Williams, and tried many experiments with it. Small
particles and the powder, both in a dry state and
moistened with water, caused the leaves on which they
were placed to be inflected very slowly, generally not
until two days had elapsed. Other particles, wetted
with weak hydrochloric acid (one part to 437 of
water) acted in a single day, as did some casein
freshly prepared for me by Dr. Moore. The ten-
tacles commonly remained inflected for from seven
to nine days ; and during the whole of this time the
secretion was strongly acid. Even on the eleventh
day some secretion left on the disc of a fully re-
expanded leaf was strongly acid. The acid seems
to be secreted quickly, for in one case the secre-
tion from the discal glands, on which a little
powdered casein had been strewed, coloured litmus
paper, before any of the exterior tentacles were
inflected.

Small cubes of hard casein, moistened with water,
were placed on two leaves ; after three days one cube
had its angles a little rounded, and after seven days
both consisted of rounded softened masses, in the
midst of much viscid and acid secretion ; but it must
not be inferred from this fact that the angles were
dissolved, for cubes immersed in water were similarly
acted on. After nine days these leaves began to re-
expand, but in this and other cases the casein did not
appear, as far as could be judged by the eye, much, if
at all, reduced in bulk. According to Hoppe-Seyler
and Lubavin* casein consists of an albuminous, with

* Dr. Lauder Brimton, ' Haiulbook for Phys. Lab.' jj. 529.

11(3 DEOSEEA ROTUNDIFOLIA. Chap. VI.

a non-albuminous, substance ; and the absorption of a
very small quantity of the former would excite the
leaves, and yet not decrease the casein to a percep-
tible degree. Schiff asserts*— and this is an import-
ant fact for us— that " la caseine purifiee des chimistes
est un corps presque completement inattaquable par
le sue gastrique." So that here we have another
point of accordance between the secretion of Drosera
and gastric juice, as both act so differently on the
fresh casein of milk, and on that prepared by
chemists.

A few trials were made with cheese ; cubes of ^V o^
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 sub-
sided masses of cheese, left on the discs, were very
little or not at all reduced in bulk. We may, how-
ever, infer from the time during which the tentacles
remained inflected, — from the changed colour of some
of the glands, — and from the injury done to others,
that matter had been absorbed from the cheese.

Legumin. — I did not procure this substance in a
separate state ; but there can hardly be a doubt that
it would be easily digested, judging from the powerful
effect produced by drops of a decoction of green
peas, as described in the last chapter. Thin slices of
a dried pea, after being soaked in water, were placed
on two leaves ; these became somewhat inflected in
the course of a single hour, and most strongly so in
21 hrs. They re-expanded after three or four days.

* 'Lemons,' &c. torn. ii. p. 153.

Chap. VI. DIGESTION. 117

The slices were not liquefied, for tlie walls of the cells,
composed of cellulose, are not in the least acted on
by the secretion.

Pollen. — A little fresh pollen from the common pea
was placed on the discs of five leaves, which soon
became closely inflected, and remained so for two or
three days.

The grains being then removed, and examined under
the microscope, were found discoloured, with the oil-
globules remarkably aggregated. Many had their
contents much shrunk, and some were almost empty.
In only a few cases were the pollen-tubes emitted.
There could be no doubt that the secretion had
penetrated the outer coats of the grains, and had
partially digested their contents. So it must be
with the gastric juice of the insects which feed on
pollen, without masticating it.* Drosera in a state of
nature cannot fail to profit to a certain extent by this
power of digesting pollen, as innumerable grains from
the carices, grasses, rumices, fir-trees, and other wind-
fertilised plants, which commonly grow in the same
neighbourhood, will be inevitably caught by the viscid
secretion surrounding the many glands.

Gluten, — This substance is composed of two albu-
minoids, one soluble, the other insoluble in alcohol.f
Some was prepared by merely washing wheaten flour
in water. A provisional trial was made with rather
large pieces placed on two leaves ; these, after 21 hrs.,
were closely inflected, and remained so for four days,
when one was killed and the other had its glands
extremely blackened, but was not afterwards observed.

* Mr. A. W. Bennett found the Hort. Soc. of London,' vol. iv.

undigested coats of the grains in 1874, p. 158.
the intestinal canal of pollen- f Watts' ' Diet, of Chemistry,'

eating Diptera; see 'Journal of vol. ii. 1872, p. 873.

118 DROSERA ROTUNDIFOLIA. Chap. VI.

Smaller bits were placed on two leaves; these were
only slightly inflected in two days, but afterwards
became much more so. Their secretion was not so
strongly acid as that of leaves excited by casein.
The bits of gluten, after lying for three days on the
leaves, were more transparent than other bits left for
the same time in water. After seven days both leaves
re-expanded, but the gluten seemed hardly at all
reduced in bulk. The glands which had been in
contact with it were extremely black. Still smaller
bits of half putrid gluten were now tried on two
leaves ; these were well inflected in 24 hrs., and
thoroughly in four days, the glands in contact being
much blackened. After five days one leaf began to
re-expand, and after eight days both were fully re-
expanded, some gluten being still left on their discs.
Four little chips of dried gluten, just dipped in
water, were next tried, and these acted rather dif-
ferently from fresh gluten. One leaf was almost
fully re-expanded in three days, and the other three
leaves in four days. The chips were greatly softened,
almost liquefied, but not nearly all dissolved. The
glands which had been in contact with them, instead
of being much blackened, were of a very pale colour,
and many of them were evidently killed.

In not one of these ten cases was the whole of the
gluten dissolved, even when very small bits were
given. I therefore asked Dr. Burden Sanderson to
try gluten in artificial digestive fluid of pepsin with
hydrochloric acid ; and this dissolved the whole.
The gluten, however, was acted on much more slowly
than fibrin ; the proportion dissolved within four
hours being as 40-8 of gluten to 100 of fibrin.
Gluten was also tried in two other digestive fluids,
in which hydrochloric acid was replaced by propionic

Chap. VI. DIGESTION. 119

and butyric acids, and it was completely dissolved by
these fluids at the ordinary temperature of a room.
Here, then, at last, we have a case in which it appears
that there exists an essential difference in digestive
power between the secretion of Drosera and gastric
juice; the difference being confined to the ferment,
for, as we have just seen, pepsin in combination with
acids of the acetic series acts perfectly on gluten.
I believe that the explanation lies simply in the fact
that gluten is too powerful a stimulant (like raw
meat, or phosphate of lime, or even too large a piece
of albumen), and that it injures or kills the glands
before they have had time to pour forth a sufficient
supply of the proper secretion. That some matter is
absorbed from the gluten, we have clear evidence in
the length of time during which the tentacles remain
inflected, and in the greatly changed colour of the
glands.

At the suggestion of Dr. Sanderson, some gluten
was left for 15 hrs. in weak hydrochloric acid (-02 per
cent.), in order to remove the starch. It became
colourless, more transparent, and swollen. Small
portions were washed and placed on five leaves, which
were soon closely inflected, but to my surprise re-
expanded completely in 48 hrs. A mere vestige of
gluten was left on two of the leaves, and not a Vestige
on the other three. The viscid and acid secretion,
which remained on the discs of the three latter
leaves, was scraped off and examined by my son
under a high power ; but nothing could be seen
except a little dirt, and a good many starch grains
which had not been dissolved by the hydrochloric
acid. Some of the glands were rather pale. We
thus learn that gluten, treated with weak hydro-
chloric acid, is not so powerful or so enduring a

120 DROSERA ROTUNDIFOLIA. Chap. VI.

stimulant as fresh gluten, and does not much injure
the glands ; and we further learn that it can be di-
gested quickly and completely by the secretion.

Globulin or CrtjstaUin.—This substcance was kiDdly prepared
for me from the lens of the eye by Dr. Moore, and consisted of
hard, colourless, transparent fragments. It is said* that globulin
ought to "swell up in water and dissolve, for the most part
forming a gummy liquid ;" but this did not occur with the above
fragments, though kept in water for four days. Particles, some
moistened with water, others with weak hydrochloric acid,
others soaked in water for one or two days, were placed on-
nineteen leaves. Most of these leaves, especially those with the
long soaked particles, became strongly inflected in a few hours.
The gi-eater number re-expanded after three or four days ; hut
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 theii- angles as sharp as ever. As globulin is an
albuminous substance, I was astonished at this result ; and my
object being to compare the action of the secretion with that 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 hydi'ochloric 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 ia 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 surj^rising that the fragments of

* Watts' ' Diet, of Chemistry,' that it was far more soluble than

vol. ii. p. 874. that Nvliich I used, though less

t I may add tliat Dr. Sander- soluble than fibrin, of which, as

son prepared sonic fresh globulin we have seen, 1'31 was dissolved.

V)y {Schmidt's method, and of this I wish that I had tried ouDro-

()-865 was dissolved within the sera globulin prepared by this

same time, namely, one hour ; so method.

Chap. VI. DIGESTION. 121

globulin were not corroded or rounded by the secretion of
Drosera, though some soluble matter was certainly extracted
from them and absorbed by the glands.

Ummatin. — 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 i)ro-
bably hsematin, together with other bodies derived from the
blood. Particles with little drops of water were placed on
four leaves, three of which were pretty closely inflected in two
days ; the fourth only moderately so. On the third day the
glands in contact with the hsematin 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 globuhn, and found that
whilst 1'31 of fibrin, only 0456 of the hsematin was dissolved
in an hour ; but the dissolution by the secretion of even a less
amount would account for its action on Drosera. The residue
left by the artificial digestive fluid at first yielded nothing more
to it during several succeeding days.

Substances which are not Digested hj the Secretion.

All the substances hitherto mentioned cause pro-
longed inflection of the tentacles, and are either com-
pletely or at least partially dissolved by the secretion.
But there are many other substances, some of them
containing nitrogen, which are not in the least acted
on by the secretion, and do not induce inflection for a
longer time than do inorganic and insoluble objects.
These unexciting and indigestible substances are, as
far as I have observed, epidermic productions (such
as bits of human nails, balls of hair, the quills of
feathers), fibro-elastic tissue, mucin, pepsin, urea,
chitine, chlorophyll, cellulose, gun-cotton, tat, oil, and
starch.

122 . DEOSEIiA ROTUNDIFOLIA. Cjiap. VI.

To. these may be added dissolved sugar and gum,
diluted alcohol, and vegetable infusions not containing
albumen, for none of these, as shown in the last
chapter, excite inflection. Now, it is a remarkable
fact, which affords additional and important evidence,
that the ferment of Drosera is closely similar to or
identical with pepsin, that none of these same sub-
stances are, as far as it is known, digested by the gas-
tric juice of animals, though some of them are acted
on by the other secretions of the alimentary canal.
Nothing more need be said about some of the above
enumerated substances, excepting that they were re-
peatedly tried on the leaves of Drosera, and were not
in the least affected by the secretion. About the
others it will be advisable to give my experiments.

Fibro-elastlc Tissue. — "We have already seen that when little
cubes of meat, &c.,' were placed on leaves, the muscles, areolar
tissue, and cartilage were completely dissolved, but the fibro-
elastic tissue, even the most delicate threads, were left without
the 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 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

* See, for instance, Schiff, * Phys. de la Digestion,' 1867, torn, ii
p. 38.

Chap. VI.

DIGESTION. 123

round the margins of the discs were a little inflected, and
the secretion collected on the disc was acid, but the exterior
tentacles were not affected. One leaf began to re-expand on the
fourth day, and all were fully re-expanded on the sixth. 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 dis-
solved, but only in the proportion of 23 to 100 of fibrin during
the same time. The cubes, though perhaps rather softer than-
those left in water for the same time, retamed their angles as
sharp as ever. We may therefore infer that the mucin itself
was not dissolved or digested. Nor is it digested by the
gastric juice of living animals, and according to Schiff* it is a
layer of this substance which protects the coats of the stomach
from being corroded during digestion.

Pepsin.— M-Y 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 purposes, and afterwards
some which was much purer, prepared for me by Dr. Moore.
Five leaves to which a considerable quantity of the former was
given remained inflected for five days; four of them then died,
apparently from too great stimulation. I then tried Dr. Moore's
pepsin, making it into a paste with water, and placing such
small particles on the discs of five leaves that all would have
been quickly dissolved had it been meat or albumen. The
leaves were soon inflected; two of them began to re-expand
after only 20 hrs., and the other three were almost completely
re-expanded after 44 hrs. Some of the glands which had been
in contact with the particles of pepsin, or with the acid secre-
tion surrounding them, were singularly pale, whereas others
were singularly dark-coloured. Some of the secretion was
scraped off and examined under a high power; and it abounded
with granules undistinguishable from those of pepsin left m
water for the same length of time. We may therefore infer,
as highly probable (remembering what small quantities were
given), that the ferment of Drosera does not act on or digest

♦ 'Le9ons phys. de la Digestion,' 1867, torn. ii. p. 304.

124 DROSEEA llOTUNDIFOLIA. Chap. VI.

pepsin, but absorbs from it some aUmminous impurity which
induces inflection, and which in large quantity is highly
injurious. Dr. Lauder Brunton at my request endeavoured to
ascertain whether pepsin with hydrochloric acid would digest
pepsin, and as far as he could judge, it had no such power.
Gastric juice, therefore, apparently agrees in this respect with
the secretion of Drosera.

Urea.— It seemed to me an interesting inquiry whether this
refuse of the living body, which contains much nitrogen,
would, like so many other animal fluids and substances, be
absorbed by the glands of Drosera and cause inflection. Half-
mi uim drops of a solution of one part to 437 of water were
l.laced on the discs of four leaves, each drop contaming the
quantity usually employed by me, namely g^o of a grain, or
•0u7-i 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
l)ure, for when four leaves were immersed in 2 dr. (I'l ml.) of
tJie solution, so that all the glands, instead of merely those on
the disc, were enabled to absorb any small amount of impurity
in solution, there was considerable inflection after 24 hrs.,
certainly more than would have followed from a similar im-
mersion in pure water. That the urea, which was not per-
fectly white, should have contained a sufficient quantity of
albuminous matter, or of some salt of ammonia, to have caused
the above effect, is far from surprising, for, as we shall see
in the next chapter, astonishingly small doses of ammonia
are highly efficient. We may therefore conclude that urea itself
is not exciting or nutritious to 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 Brunt on informs
me that from experiments made at my request at St. Bartho-
lomew's Hospital it appears that urea is not acted on by
artificial gastric juice, that is by pepsin with hydrochloric acid.

Chitine. — The chitinous coats of insects naturally captured by
the leaves do not appear in the least corroded. Small square
pieces of the deUcate wing and of the elytron of a Staphylinus

CUAl". VI.

DIGESTION. 125

were placed on some leaves, and after these had re-expanded,
the pieces were carefully examined. Their angles were as
sharp as ever, and they did not differ in appearance from the
other wing and elytron of the same insect which had been left
in water. The elytron, however, had evidently yielded 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 the* second day. Any one who will examine the excrement
of insect-eating animals will see how powerless their gastric
juice is on chitine.

Cellulose. — I did not obtain this substance in a separate state,
but tried angular bits of dry wood, cork, sphagnum moss, linen,
and cotton thread. None of these bodies were in the least
attacked by the secretion, and they caused only that moderate
amount of inflection which is common to all inorganic objects.
Gun-cotton, which consists of cellulose, with the hydrogen
replaced by nitrogen, was tried with the same result. We have
seen that a decoction of cabbage-leaves excites the most power-
ful inflection. I therefore placed two little square bits of the
blade of a cabbage-leaf, and four little cubes cut from the
midrib, on six leaves of Drosera. These became well inflected
in 12 hrs., and remained so for between two and four days;
the bits of cabbage being bathed all the time by acid secre-
tion. This shows that some exciting matter, to which I shall
presently refer, had been absorbed ; but the angles of the
squares and cubes remained as sharp as ever, proving that the
framework of cellulose had not been attacked. Small square
bits of spinach-leaves were tried with the same result; the
glands pouring forth a moderate supply of acid secretion,
and the tentacles remaining inflected for three days. We have
also seen that the delicate coats of pollen grains are not dissolved
by the secretion. It is well known that the gastric juice of
animals does not attack cellulose.

ChlorophylL — This substance was tried, as it contains nitrogen.
Dr. Moore sent me some preserved in alcohol ; it was dried, but
soon deliquesced. Particles were placed on four leaves; after
3 hrs. the secretion was acid ; after 8 hrs. there was a good deal
of inflection, which in 24 hrs. became fairly well marked. After
four days two of the leaves began to open, and the other two
were then almost fully re-expanded. It is therefore clear that
this chlorophyll contained matter which excited the leaves to a
moderate degree ; but judging by the eye, little or none was dis-
solved ; so that in a pure state it would not probably have been
attacked by the secretion. Dr. Sanderson tried that which I

126 DROSERA ROTUNDIFOLIA. Chap. VI.

used, as well as some freshly prepared, with artificial digestive
liquid, and found that it was not digested. Dr. Lauder Brunton
likewise tried some prepared by the process given in the British
Pharmacopoeia, and exposed it for five days at the temperature
of 37° Cent, to digestive liquid, but it was not diminished in
bulk, though the fluid acquired a slightly brown colour. It was
also tried with the glycerine extract of pancreas with a negative
result. Nor does chlorophyll seem affected by the intestinal
secretions of various animals, judging by the colour of their
excrement.

It must not be supposed from these facts that the grains of
chlorophyll, as they exist in living plants, cannot be attacked by
the secretion; for these gTains consist of protoplasm merely
coloured by chlorophyll. My son Francis placed a thin slice of
spinach leaf, moistened with saliva, on a leaf of Drosera, and
other slices on damp cotton-wool, all exposed to the same
temperature. After 19 hrs. the slice on the leaf of Drosera was
bathed in much secretion from the inflected tentacles, and was
now examined under the microscope. No perfect grains of
chlorophyll could be distinguished ; some were shrunken, of -a
yellowish-green colour, and collected in the middle of the cells ;
others were disintegrated and formed a yellowish mass, likewise
in the middle of the cells. On the other hand, in the slices
surrounded by damp cotton-wool, the grains of chlorophyll were
green and as perfect as ever. My son also placed some slices
in artificial gastric juice, and these were acted on in nearly the
same- manner as by the secretion. We have seen that bits of
fresh cabbage and spinach leaves cause the tentacles to be in-
flected and the glands to pour forth much acid .secretion ; and
there can be little doubt that it is the protoplasm forming the
grains of chlorophyll, as well as that lining the walls of the
cells, which excites the leaves.

Fat and OiJ. — 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. — Eather large bits of dry starch caused well-marked
inflection, and the leaves did not re-expand until the fourth
day ; but I have no doubt that this was due to the prolonged
irritation of the glands, as the starch continued to absorb the
secretion. The particles were not in the least reduced in size ;

Chap. VI.

DIGESTION. 127

and we know that leaves immersed in an emulsion of starch
are not at all affected. I need hardly say that starch is not
digested by the gastric juice of animals.

Action of the Secretion on Living Seeds.

The results of some experiments on living seeds, selected by
hazard, may here be given, though they bear only indirectly on
our present subject of digestion.

Seven cabbage seeds of the previous year were placed on the
same number of leaves. Some of these leaves were moderately,
but the greater number only slightly inflected, and most of
them re-expanded on the third day. One, however, remained
clasped till the fourth, and another till the fifth day. These
leaves therefore were excited somewhat more by the seeds than
by inorganic objects of the same size. After they re-expanded,
the seeds were placed under favourable conditions on damp
sand ; other seeds of the same lot being tried at the same time
in the same manner, and found to germinate well. Of the seven
seeds which had been exposed to the secretion, only three ger-
minated ; and one of the three seedlings soon perished, the tip
of its radicle being from the first decayed, and the edges of
its cotyledons of a dark brown colour; so that altogether five
out of the seven seeds ultimately perished.

Eadish seeds (Baphanus sativus) of the previous year were
placed on three leaves, which became moderately inflected, and
re-expanded on the third or fourth day. Two of these seeds
were transferred to damp sand ; only one germinated, and that
very slowly. This seedling had an extremely short, crooked,
diseased, radicle, with no absorbent hairs ; and the cotyledons
were oddly mottled with purple, with the edges blackened and
partly withered.

Cress seeds (Lepidum sativum) of the previous year were
placed on four leaves ; two of these next morning were mode-
rately and two strongly inflected, and remained so for four,
five, and even six days. Soon after these seeds were placed on
the 'leaves and had become damp, they secreted in the usual
manner a layer of tenacious mucus ; and to ascertain whether
it was the absorption of this substance by the glands which
caused so much inflection, two seeds were put into water, and
as much of the mucus as possible scraped off. They were then
placed on leaves, which became very strongly inflected in the
course of 3 hrs., and were still closely inflected on the third
day ; so that it evidently was not the mucus which excited so

128 DEOSERA EOTUNDIFOLIA. Chap. VI.

much inflection ; on the contrary, this served to a certain extent
as a protection to the seeds. Two of the six seeds germinated
whilst still lying on the leaves, but the seedlings, when trans-
ferred to damp sand, soon died ; of the other four* seeds, only one
germinated.

Two seeds of mustard (Sinajns nigra), two of celery {Apiiim
graveolens) — both of the previous year, two seeds well soaked of
caraway (Carum carui), and two of wheat, did not excite the
leaves more than inorganic objects often do. Five seeds, hardly
ripe, of a buttercup (Eanunculus), and two fresh seeds of Ane-
mone nemorosa, induced only a little more effect. On the other
hand, four seeds, perhaps not quite ripe, of Carex sylvatica caused
the leaves on which they were placed to be very strongly in-
flected; and these only began to re-expand on the third day,
one remaining inflected for seven days.

It follows from these few facts that different kinds of seeds
excite the leaves in very different degrees; whether this is
solely due to the nature of their coats is not clear. In the case
of the cress seeds, 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 pene-
trates their coats is also evident from the large proportion of
cabbage, raddish, and cress seeds which were killed, and from
several of the seedlings being greatly injured. This injury to
the seeds and seedlings may, however, be due solely to the acid
of the secretion, and not to any process of digestion ; for Mr.
Traherne Moggridge has shown that very weak acids of the
acetic series are highly injurious to seeds. It never occurred
to me to observe whether seeds are often blown on to the viscid
leaves of plants growing in a state of nature ; but this can
hardly fail sometimes to occur, as we shall hereafter see in the
case of Pinguicula. If so, Drosera will profit to a slight degree
by absorbing matter from such seeds.

Summary and Concluding Remarks on tJie Digestive
Foiver 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

Chap. VI. DIGESTION. 129

some influence to the glands of the exterior ten-
tacles, causing them to secrete more copiously ; and
their secretion likewise becomes acid. With ani-
mals, according to Schiff,* mechanical irritation ex-
cites the glands of the stomach to secrete an acid,
but not pepsin. Now, I have every reason to be-
lieve (though the fact is not fully established), that
although the glands of Drosera are continually secret-
ing viscid fluid to replace that lost by evaporation,
yet they do not secrete the ferment proper for di-
gestion when mechanically irritated, but only after
absorbing certain matter, probably of a nitrogenous
nature. I infer that this is the case, as the secretion
from a large number of leaves which had been
irritated by particles of glass placed on their discs
did not digest albumen; and more especially from
the analogy of Dionaea and Nepenthes. In like
manner, the glands of the stomach of animals secrete
pepsin, as Schiff asserts, only after they have ab-
sorbed certain soluble substances, which he desig-
nates as peptogenes. There is, therefore, a remarkable
parallelism betw^een the glands of Drosera and those
of the stomach in the secretion of their proper acid
and 'ferment.

The secretion, as we have seen, completely dissolves
albumen, muscle, fibrin, areolar tissue, cartilage, the
fibrous basis of bone, gelatin, chondrin, casein in the
state . in which it exists in milk, and gluten which has
been subjected to weak hydrochloric acid. Syntonin
and legumin excite the leaves so powerfully and
quickly that there can hardly be a doubt that both
would be dissolved by the secretion. The secretion

* ' Phys. de la Digestion,' 1867, torn. ii. pp. 188, 245.

130 DEOSEEA ROTUNDIFOLIA. • Chap. VI.

failed to digest fresh gluten, apparently from its
injuring the glands, though some was absorbed. Eaw
meat, unless in very small bits, and large pieces of
albumen, &c., likewise injure the leaves, which seem
to suffer, like animals, from a surfeit. I know not
whether the analogy is a real one, but it is worth
notice that a decoction of cabbage leaves is far more
exciting and probably nutritious to Drosera than an
infusion made with tepid water ; and boiled cabbages
are far more nutritious, at least to man, than the un-
cooked leaves. The most striking of all the cases,
though not really more remarkable than many others,
is the digestion of so hard and tough a substance as
cartilage. The dissolution of pure phosphate of lime,
of bone, dentine, and especially enamel, seems won-
derful ; but it depends merely on the long-continued
secretion of an acid ; and this is secreted for a longer
time under these circumstances than under any others.
It was interesting to observe that as long as the acid
was consumed in dissolving the 'phosphate of lime, no
true digestion occurred ; but that as soon as the bone
was completely decalcified, the fibrous basis was at-
tacked and liquefied with the greatest ease. The
twelve substances above enumerated, which are com-
pletely dissolved by the secretion, are likewise dis-
solved by the gastric juice of the higher animals ;
and they are acted on in the same manner, as shown
by the rounding of the angles of albumen, and more
especially by the manner in which the transverse striae
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 hoematin employed by me. The
secretion also dissolved something out of chemically

Chap. VI. DIGESTION. 131

prepared casein, which is said to consist of two sub-
stances ; and although Schiff asserts that casein in
this state is not attacked by gastric juice, he might'
easily have overlooked a minute quantity of some
albuminous matter, which Drosera would detect and
absorb. Again, fibro-cartilage, though not properly
dissolved, is acted on in the same manner, both by
the secretion of Drosera and gastric juice. But this
substance, as well as the so-called haematin used by
me, ought perhaps to have been classed with indi-
gestible substances.

That gastric juice acts by means of its ferment,
pepsin, solely in the presence of an acid, is well
established ; and we have excellent evidence that a
ferment is present in the secretion of Drosera, which
likewise acts only in the presence of an acid ; for we
have seen that when the secretion is neutralised by
minute drops of the solution of an alkali, the diges-
tion of albumen is completely stopped, and that on
the addition of a minute dose of hydrochloric acid it
immediately recommences.

The nine following substances, or classes of sub-
stances, namely, epidermic productions, fibro-elastic
tissue, mucin, pepsin, urea, chitine, cellulose, gun-
cotton, chlorophyll, starch, fat and oil, are not acted
on by the secretion of Drosera ; nor are they, as far as
is known, by the gastric juice of animals. Some
soluble matter, however, was extracted from the mucin,
pepsin, and chlorophyll, used by me, both by the
secretion and by artificial gastric juice.

The several substances, which are completely dis-
solved by the secretion, and which are afterwards
absorbed by the glands, affect the leaves rather dif-
ferently. They induce inflection at very different

132 DROSERA ROTUNDIFOLIA. Chap. VL

rates and in very diiferent degrees ; and the ten-
tacles remain inflected for very dilBferent periods of
time. Quick inflection depends partly on the quan-
tity of the substance given, so that many glands are
simultaneously affected, partly on the facility with
which it is penetrated and liquefied by the secretion,
partly on its nature, but chiefly on the presence of
exciting matter already in solution. Thus saliva, or
a weak solution of raw meat, acts much more qui<ikly
than even a strong solution of gelatine. So again
leaves which have re-exj)anded, after absorbing drops
of a solution of pure gelatine or isinglass (the latter
being the more powerful of the two), if given bits
of meat, are inflected much more energetically and
quickly than they were before, notwithstanding that
some rest is generally requisite between two acts
of inflection. AYe probably see the influence of tex-
ture in gelatine and globulin when softened by
having been soaked in water acting more quickly
than when merely wetted. It may be partly due to
changed texture, and partly to changed chemical
nature, that albumen, which has been kept for some
time, and gluten which has been subjected to weak
hydrochloric acid, act more quickly than these sub-
stances in their fresh state.

The length of time during which the tentacles re-
main inflected largely depends on the quantity of the
substance given, partly on the facility with which it is
penetrated or acted on by the secretion, and partly
on its essential nature. The tentacles always remain
inflected much longer over large bits or large drops
than over small bits or drops. Texture probably
plays a part in determining the extraordinary length
of time during which the tentacles remain inflected

CuAP. VI. DIGESTION. 133

over the hard grains of chemically prepared casein.
But the tentacles remain inflected for an equally long
time over finely powdered, precipitated phosphate of
lime ; phosphorus in this latter case evidently being
the attraction, and animal matter in the case of casein.
The leaves remain long inflected over insects, but it is
doubtful how far this is due to the protection afforded
by their chitinous integuments ; for animal matter is
soon extracted from insects (probably by exosmose from
their bodies into the dense surrounding secretion),
as shown by the prompt inflection of the leaves. We
see the influence of the nature of different substances
in bits of meat, albumen, and fresh gluten acting very
differently from equal-sized bits of gelatine, areolar
tissue, and the fibrous basis of bone. The former
cause not only far more prompt and energetic, but
more prolonged, inflection than do the latter. Hence
we are, I think, justified in believing that gelatine,
areolar tissue, and the fibrous basis of bone, would be
far less nutritious to Drosera than such substances
as insects, meat, albumen, &c. This is an interest-
ing conclusion, as it is known that gelatine affords
but little nutriment to animals ; and so, probably,
would areolar tissue and the fibrous basis of bone.
The chondrin which I used acted more powerfully
than gelatine, but then I do not know that it was'
pure. It is a more remarkable fact that fibrin, which
belongs to the great class of Proteids,* including
albumen in one of its sub-groups, does not excite
the tentacles in a greater degree, or keep them in-
flected for a longer time, than does gelatine, or

* See the classification adopted by Dr. Michael Foster in Watts*
Diet, of Chemistry,' Supplement 1872, p. 969.

134 DROSEEA ROTUNDIFOLIA. Chap. VL

areolar tissue, or the fibrous basis of bone. It is not
known liow long an animal would survive if fed on
fibrin alone, but Dr. Sanderson has no doubt longer
than on gelatine, and it would be hardly rash to pre-
dict, judging from the effects on Drosera, that albu-
men would be found more nutritious than fibrin.
Globulin likewise belongs to the Proteids, forming
another sub-group, and this substance, though con-
taininof some matter which excited Drosera rather
strongly, was hardly attacked by the secretion, and
was very little or very slowly attacked by gastric
juice. How far globulin would be nutritious to ani-
mals is not known. We thus see how differently the
above specified several digestible substances act on
Drosera ; and we may infer, as highly probable, that
they would in like manner be nutritious in very dif-
ferent degrees both to Drosera and to animals. •

The glands of Drosera absorb matter from living
seeds, which are injured or killed by the secretion.
They likewise absorb matter from pollen, and from
fresh leaves ; and this is notoriously the case with
the stomachs of vegetable-feeding animals. Drosera
is i^roperly an insectivorous plant; but as pollen
cannot fail to be often blown on to the glands, as
will occasionally the seeds and leaves of surrounding
'plants, Drosera is, to a certain extent, a vegetable-
feeder.

Finally, the experiments recorded in this chapter
show us that there is a remarkable accordance in the
power of digestion between the gastric juice of ani-
mals with its pepsin and hydrochloric acid and the
secretion of Drosera with its ferment and acid belong-
ing to the acetic series. We can, therefore, hardly
doubt that the ferment in both cases is closely similar,

Chap. VI. DIGESTION. 135

if not identically the same. That a plant and an
animal should pour forth the same, or nearly the same,
complex secretion, adapted for the same purpose of
digestion, is a new and wonderful fact in physiology.
But I shall have to recur to this subject in the
fifteenth chapter, in my concluding remarks on the
Droseraceae.

136 DEOSEKA ROTUNDIFOLIA. Chap. VIL

CHAPTER VII.

The 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 im-
mersed in weak solutions — Minuteness of the doses which induce
aggregation of the protoplasm — Nitrate of ammonia, analogous
experiments with — Phosphate of ammonia, analogous experiments
with — Other salts of ammonia — Summary and concluding re-
marks on the action of the salts of ammonia.

The chief object in this chapter is to show how power-
fully the salts of ammonia act on the leaves of Drosera,
and more especially to show what an extraordinarily
small quantity suffices to excite inflection. I shall,
therefore, be compelled to enter into full details.
Doubly distilled water was always used ; and for the
more delicate experiments, water which had been
prepared with the utmost possible care was given
me by Professor Frankland. The graduated measures
were tested, and found as accurate as such measures
can be. The salts were carefully weighed, and in all
the more delicate experiments, by Borda's double
method. But extreme accuracy would have been
superfluous, as the leaves differ greatly in irritability,
according to age, condition, and constitution. Even
the tentacles on the same leaf differ in irritability
to a marked degree. My experiments were tried in
the following several ways.

Firsihj.— Droits which were ascertained by repeated trials to
be on an average about half a minim, or the q-}^ of a fluid ounce
(-0296 ml.), were placed by the same pointed instrument on the

Chap. VII. SALTS OF AMMONIA. 137

discs of the leaves, and the inflection of the exterior rows of
tentacles observed at successive intervals of tiine. It was first
ascertained, from between thirty and forty trials, that distilled
water dropped in this manner produces no effect, except that
sometimes, though rarely, two or three tentacles become in-
flected. In fact all the many trials with solutions which were
60 weak as to produce no effect lead to the same result that
water is inefficient.

Secondly. — The head of a small pin, fixed into a handle, was
dipped into the solution under trial. The small drop which
adhered to it, and which was much too small to fall off, was
cautiously placed, by the aid of a lens, in contact with the secre-
tion surroundiiig the glands of one, two, three, or four of the.
exterior tentacles of the same leaf. Great care was taken that
the glands themselves should not be touched. I had supposed
that the drops were of nearly the same size ; but on trial this
proved a great mistake. I first measured some water, and re-
moved 300 drops, touching the pin's head each time on blotting-
paper ; and on again measuring the water, a drop was found to
equal on an average about the ^ of a minim. Some water in a
small vessel was weighed (and this is a more accurate method),
and 300 dro23S removed as before ; and on again weighing the
water, a drop was found to equal on an average only the ^^
of a minim. I repeated the operation, but endeavoured this
lime, 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 7^ of a minim. I repeated the operation in
exactly the same manner, and now the drops averaged ^3 .^ of a
minim. Bearing in mind that on these two latter occasions
special pains were taken to remove as large drops as possible,
we may safely conclude that the drops used in my experiments
were at least equal to the 2V of a minim, or "0029 ml. One of
these drops could be applied to three or even four glands, and
if the tentacles became inflected, some of the solution must
have been absorbed by all; for drops of pure water, applied
in the same manner, never produced any effect. I was able to
hold the drop in steady contact with the secretion only for ten
to fifteen seconds ; and this was not time enough for the diffu-
sion of all the salt in solution, as was evident, from three or
four tentacles treated successively with the same drop, often
becoming inflected. All the matter in solution was even then
probably not exhausted.

Thirdly. — Leaves were cut off and immersed in a measured

138 DKOSERA EOTUNDIFOLIA. CllAP. ML

quantity of the solution under trial ; the same number of leaves
being immersed at the same time, in the same quantity of the
distilled water which had been used in making the solution.
The leaves in the two lots were compared at short intervals,
of time, up to 24 hrs., and sometimes to 48 hrs. They were
immersed by being laid as gently as possible in numbered
watch-glasses, and thirty minims (1-775 ml.) of the solution
or of water was poured over each.

Some solutions, for instance that of carbonate of ammonia,
quickly discolour the glands ; and as all on the same leaf were
discoloured simultaneously, they must all have absorbed some
of the salt within the same short period of time. This was
likewise shown by the simultaneous inflection" of the several
exterior rows of tentacles. If we had no such evidence as
tliis, it might have been supposed that only the glands of the
exterior and inflected tentacles had absorbed the salt ; or that
only those on the disc had absorbed it, and had then transmitted
a motor impulse to the exterior tentacles ; but in this latter case
the exterior tentacles would not have become inflected until
some time had elapsed, instead of within half an hour, or even
within a few minutes, as usually occurred. All the glands on
the same leaf are of nearly the same size, as may best be seen
by cutting oif a narrow transverse strip, and laying it on its
side; hence theii* absorbing surfaces are nearly equal. The
long-headed glands on the extreme margin must be excepted,
as they are much longer than the others; but only the upper
surface is capable of absorption. Besides the glands, both
surfaces of the leaves and the pedicels of the tentacles bear
numerous minute papillae, which absorb carbonate of ammonia,
an infusion of raw meat, metallic salts, and probably many
other substances, but the absorption of matter by these papillae
never induces inflection. We must remember that the move-
ment of each separate tentacle depends on its gland being
excited, except when a motor impulse is transmitted from the
glands of the disc, and then the movement, as just stated,
does not take place until some little time has elapsed. I have
made these remarks because they show us that when a leaf is
immersed in a solution, and the tentacles are inflected, we can
judge with some accuracy how much of the salt each gland has
absorbed. For instance, if a leaf bearing 212 glands be immersed
in a measured quantity of a solution, containing ^^ of a grain of
a salt, and all the exterior tentacles, except twelve, are inflected,
we may feel sure that each of the 200 glands can on an average
have absorbed at most ayVo ^^ ^ grain of the salt. I say at

Chap. VII. EFFECTS OF WATER. 139

most, for the papillfe will have absorbed some small amount,
and so will perhaps the glands of the twelve excluded tentacles
which did not become inflected. The application of this prin-
ciple leads to remarkable conclusions with respect to the
minuteness of the doses causing inflection.

On the Action of Distilled Water in causing Inflection.

Although in all the more important experiments the dif-
ference between the leaves simultaneously immersed in water
and in the several solutions will be described, nevertheless it
may be well here to give a summary of the effects of water.
The fact, moreover, of pure water acting on the glands deserves
in itself some notice. Leaves to the number of 111 were im-
mersed in water at the same time with those in the solutions,
and their state recorded at short intervals of time. Thirty-two
other leaves were separately observed in water, making alto-
gether 173 experiments. Many scores of leaves were also im-
mersed in water at other times, but no exact record of the
effects produced was kept ; yet these cursory observations sup-
port the conclusions arrived at in this chapter. A few of the
long-headed tentacles, namely from one to about six, were
commonly inflected within half an hour after immersion ; as
were occasionally a few, and rarely a considerable number of
the exterior round-headed tentacles. After an immersion of
from 5 to 8 hrs. the short tentacles surrounding the outer
parts of the disc generally become inflected, so that their glands
form a small dark ring on the disc; the exterior tentacles
not partaking of this movement. Hence, excepting in a few
cases hereafter to be specified, we can judge whether a solution
produces any effect only by observing the exterior tentacles
within the first 3 or 4 hrs. after immersion.

Now for a summary of the state of the 173 leaves after an
immersion of 3 or 4 hrs. in pure water. One leaf had almost
all its tentacles inflected ; three leaves had most of them sub-
inflected; and thirteen had on an average 36'5 tentacles in-
flected. Thus seventeen leaves out of the 173 were acted on in
a marked manner. Eighteen leaves had from seven to nineteen
tentacles inflected, the average being 9*3 tentacles for each
leaf. Forty-four leaves had from one to six tentacles inflected,
generally the long-headed ones. So that altogether of the 173
leaves carefully observed, seventy-nine were affected by the
water in some degree, though commonly to a very slight degree;
and ninety-four were not affected in the least degree. This

140

DROSEKA EOTUNDIFOLIA.

Chap. VII.

amount of inflection is utterly insignificant, as we shall here-
after see, compared with that caused by very weak solutions
of several salts of ammonia.

Plants which have lived for some time in a rather high
temperature are far more sensitive to the action of water than
those grown out of doors, or recently brought into a warm
greenhouse. Thus in the above seventeen cases, in which the
immersed leaves had a considerable number of tentacles in-
flected, the plants had been kept during the winter in a very
warm greenhouse ; and they bore in the early spring remarkably
fine leaves, of a light red colour. Had I then known that the
sensitiveness of plants was thus increased, perhaps I should
not have used the leaves for my experiments with the very
weak solutions of phosphate of ammonia ; but my experiments
are not thus vitiated, as I invariably used leaves from the same
plants for simultaneous immersion in water. It often happened
that some leaves on the same plant, and some tentacles on the
same leaf, were more sensitive than others ; but why this should
be so, I do not know.
Resides the differences just indicated between the leaves im-
mersed in water and in weak
solutions of ammonia, the ten-
tacles of the latter are in most
cases much more closely in-
flected. The appearance of a
leaf after immersion in a few
drops of a solution of one grain
of phosphate of ammonia to
200 oz. of water (i.e. one part
to 87,500) is here reproduced :
such energetic inflection is
never caused by water alone.
With leaves in the weak solu-
tions, the blade or lamina often
becomes inflected ; and this is
so rare a circumstance with
leaves in water that I have
seen only two instances; and
in both of these the inflec-
tion was very feeble. Again,
with leaves in the weak solu-
tions, the inflection of the ten-
tacles and blade often goes on
steadily, though slowly, increasing during many hours; and

(^Drosera rotundifoUa.)

Leaf (enlarged) with all the tentacles

closely inflected, from immersion in a

solution of phosphate of ammonia (one

part to 87,500 of water).

Chap. yil. CAEBONATE OF AMMONIA. 141

tliis again is so rare a circumstance with leayes in water that
I have seen only three instances of any such increase after tlie
first 8 to 12 hrs. ; and in these three instances the two outer
rows of tentacles were not at all affected. Hence there is some-
times a much greater diiference 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,
notliing could be more variable. In both cases the exterior
tentacles not rarely begin to re-expand, after an interval of
only from 6 to 8 hrs. ; that is just about the time when the
short tentacles round the borders of the disc become inflected.
On the other hand, the tentacles sometimes remain inflected
for a whole day, or even two days ; but as a general rule they
remain inflected for a longer period in very weak solutions than
in water. In solutions which are not extremely weak, they
never re-expand within nearly so short a period as six or
eight hours. From these statements it might be thought
difficult to distinguish between the effects of water and the
weaker solutions ; but in truth there is not the slightest diffi-
culty until excessively weak solutions are tried ; and then the
distinction, as might be expected, becomes very doubtful, and
at last disappears. But as in all, except the simplest, cases
the state of the leaves simultaneously immersed for an equal
length of time in water and in the solutions will be described,
the reader can judge for himself.

Caebonate of Ammonia.

This salt, when absorbed by the roots, does not cause
the tentacles to be inflected. A plant was so placed
in a solution of one part of the carbonate to 146 of
water that the young uninjured roots could be ob-
served. The terminal cells, which were of a pink
colour, instantly became colourless, and their limpid
contents cloudy, like a mezzo-tinto engraving, so that
some degree of aggregation was almost instantly
caused; but no further change ensued, and the ab-
sorbent hairs were not visibly affected. The tentacles

142 DEOSEKA EOTUNDIFOLIA. Chap. VII.

did not bend. Two other plants were placed with
their roots surrounded by damp moss, in half an ounce
(14*198 ml.) of a solution of one part of the carbo-
nate to 218 of water, and were observed for 24 hrs. ;
but not a single tentacle was inflected. In order to
produce this effect, the carbonate must be absorbed
by the glands.

The vapour produces a powerful effect on the glands,
and induces inflection. Three plants with their roots
in bottles, so that the surrounding air could not have
become very humid, were placed under a bell-glass
(holding 122 fluid ounces), together with 4 grains
of carbonate of ammonia in a watch-glass. After an
interval of 6 hrs. 15 m. the leaves appeared unaffected ;
but next morning, after 20 hrs., the blackened glands
were secreting copiously, and most of the tentacles
were strongly inflected. These plants soon died.
Two other plants were placed under the same bell-
glass, together with half a grain of the carbonate, the
air being rendered as damp as possible ; and in 2 hrs.
most of the leaves were affected, many of the glands
being blackened and the tentacles inflected. But it is
a curious fact that some of the closely adjoining ten-
tacles on the same leaf, both on the disc and round
the margins, were much, and some, a]3parently, not in
the least affected. The plants were kept under the
bell-glass for 24 hrs., but no further change ensued.
One healthy leaf was hardly at all affected, though
other leaves on the same plant were much affected.
On some leaves all the tentacles on one side, but not
those on the opposite side, were inflected. I doubt
whether this extremely unequal action can be ex-
plained by supposing that the more active glands
absorb all the vapour as quickly as it is generated, so
that none is left for the others for we shall meet with

Chap. VII. CAEBONATE OF AMMONIA. 143

analogous cases with air tlioroughly permeated with
the vapours of chloroform and ether.

Minute particles of the carbonate were added to the
secretion surrounding several glands. These instantly
became black and secreted copiously ; but, except in
two instances, when extremely minute particles were
given, there was no inflection. This result is analo-
pfous to that which follows from the immersion of
leaves in a strong solution of one part of the carbonate
to 109, or 146, or even 218 of water, for the leaves
are then paralysed and no inflection ensues, though
the glands are blackened, and the protoplasm in the
cells of the tentacles undergoes strong aggregation.

We will now turn to the effects of solutions of the carbonate.
Half-minims of a solution of one part to 437 of water were placed
on the discs of twelve leaves ; so that each received -gig of a grain
or "0675 mg. Ten of these had their exterior tentacles well
inflected ; the blades of some being also much curved inwards.
In two cases several of the exterior tentacles were inflected in
35 m. ; but the movement was generally slower. These ten
leaves re-expanded in periods varying between 21 hrs. and
45 hrs., but in one case not until 67 hrs. had elapsed ; so that
they re-expanded much more quickly than leaves which have
caught insects.

The same-sized drops of a solution of one part to 875 of water
were placed on the discs of eleven leaves; six remained quite
unaffected, whilst five had from three to six or eight of their
exterior tentacles inflected ; but this degree of movement can
hardly be considered as trustworthy. Each of these leaves
received j,;^ 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 ^L of a minim, and therefore contaius :^^l_ of a grain
(•0135 mg.) of the carbonate. I touched with it the viscid
secretion round tlii-ee glands, so that each gland received only

144 DROSEEA ROTUNDIFOLIA. Chap. VIL

14400 Q^ ^ gi'ain ('0044:5 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 an-
other case two of the three tentacles were inflected. I then
tried drops of a weaker solution of one part to 292 of water on
twenty-four glands, always touching the viscid secretion round
three glands with the same little drop. Each gland thus received
only the ygioo of a gi'ain ( ' 00337 mg.), yet some of them were
a little darkened ; but in no one instance were any of the ten-
tacles inflected, though they were watched for 12 hrs. When a
still weaker solution (viz. one part to 437 of water) was tried on
six glands, no effect whatever was perceptible. We thus learn
that the ttto o of a grain ( • 00145 mg.) of carbonate of ammonia,
if absorbed by a gland, suflQces to induce inflection in the basal
part of the same tentacle ; but as already stated, I was able to
hold with a steady hand the minute drops in contact with the
secretion only for a few seconds; and if more time had been
allowed for diffusion and absorption, a much weaker solution
Avould 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 ml.) of a solution of one
part of the carbonate to 5250 of water ; two of these had almost
every tentacle inflected, the third had about half the tentacles
and the fourth about one-thii'd inflected ; and all the glands were
blackened. Another leaf was placed in the same quantity of a
solution of one part to 7000 of water, and in 1 hr. 16 m. every
single tentacle was well inflected, and all the glands blackened.
Six leaves were immersed, each in thirty minims (1'774 ml.) of
a solution of one part to 4375 of water, and the glands were all
blackened in 31 m. All six leaves exhibited some slight inflec-
tion, and one was strongly inflected. Four leaves were then
immersed in thirty minims of a solution of one part to 8750 of
water, so that each leaf received the ^ko 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

CiiAP. VII. CARBONATE OF AMMONIA. 145

tentacles become inflected within the same time, we have
evidence, as before remarked, of simultaneous absorption. I
did not count the number of glands on these four leaves ; but
as they were fine ones, and as we know that the average number
of glands on thirty-one leaves was 192, we may safely assume
that each bore on an average at least 170; and if so, each
blackened gland could have absorbed only g-j^o 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 y g^o
of a grain ("OlOS mg.). The glands were not much darkened.
Ten of the leaves were not affected, or only very slightly so.
Four, however, were strongly affected ; the first having all the
tentacles, except forty, inflected in 47 m. ; in 6 hrs. 30 m. all
except e.ight ; 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 in 4 hrs. The third leaf after 1 hr. 6 m. had all
but forty tentacles inflected. The fourth, after 2 hrs. 5 m., had
about half its tentacles and after 4 hrs. all but forty-five in-
flected. Leaves which were immersed in water at the same time
were not at all affected, with the exception of one ; and this not
until 8 hrs. had elapsed. Hence there can be no doubt that a
highly sensitive leaf, if immersed in a solution, so that all the
glands are enabled to absorb, is acted on by y^Vo of n- 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 ^gg^QQ of a
grain ('00024 mg.); yet this sufficed to act on each of the 162
tentacles which were inflected. But as only four out of the above
fourteen leaves were plainly affected, this is nearly the mini-
mum dose which is efficient.

Aggregation of the Protoplasm from the Action of Carhonate of
Ammonia. — I have fully described in the third chapter the
remarkable effects of moderately strong doses of this salt in
causing the aggregation of the protoplasm within the cells of
the glands and tentacles ; and here my object is merely to show
what small doses suffice. A leaf was immersed in twenty
minims (1 • 183 ml.) of a solution of one part to 1750 of water.

146 DROSERA ROTUNDIFOLIA. ' Chap. VII.

and another leaf in the same quantity of a solution of one part
to 3062 ; in the former case aggrepjation occurred in 4 m., in the
latter in 11 m. A leaf was then immersed in twenty minims of
a solution of one part to 4375 of water, so that it received -2^ 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 I
experimented on fourteen leaves, but will give only a few of the
cases. Eight young leaves were selected and examined with
care, and they showed no trace of aggregation. Four of those
were placed in a drachm (3 ' 549 ml.) of distilled water ; and four
in a similar vessel, with a drachm of the solution. After a time
the leaves were examined under a high power, being taken alter-
nately from the solution and the water. The first leaf was taken
out of the solution after an immersion of 2 hrs. 40 m., and the
last leaf out of the water after 3 hrs. 50 m. ; the examination
lasting for 1 hr. 40 m. In the four leaves out of the water there
was no trace of aggregation except in one specimen, in which a
very few, extremely minute spheres of protoplasm were present
beneath some of the round glands. All the glands were trans-
lucent and red. The four leaves which had been immersed in
the solution, besides being inflected, presented a widely difl"erent
appearance ; for the contents of the cells of every single tentacle
on all four leaves were conspicuously aggregated ; the spheres
and elongated masses of protoplasm in many cases extending
halfway down the tentacles. All the glands, both those of the
central and exterior tentacles, were opaque and blackened ; and
this shows that all had absorbed some of the carbonate. These
fi)ur 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
■^^28 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 9^0 of a grain ( -0675 mg.). In 40 m. the glands
appeared rather darker; and in 1 hr, from four to six spheres
of i^rotoplasm were formed in the cells beneath the glands of
all the tentacles. I did not count the tentacles, but we may

Chap. VII. CARBONATE OF AMMONIA. 147

safely assume that there were at least 140; and if so, each
gland could have received only the xaiVoo of a grain, or
•00048 mg.

A weaker solution was then made of one part to 7000 of water,
and four leaves were immersed in it ; but I will give only one
case. A leaf was placed in ten minims of this solution ; after
1 hr. 37 m. the glands became somewhat darker, and the cells
beneath all of them now contained many spheres of aggregated
protoplasm. This leaf received -^-^^ of a grain, and bore 166
glands. Each gland could, therefore, have received only YY^iWs
of a grain ( • 000507 mg.) of the carbonate.

Two other experiments are worth giving. A leaf was im-
mersed for 4 hrs. 15 m. in distilled water, and there was no
aggregation ; it was then placed for 1 hr. 15 m. in a little solu-
tion of one part to 5250 of water ; and this excited well-marked
aggregation and inflection. Another leaf, after having been
immersed for 21 hrs. 15 m. in distilled water, had its glands
blackened, but there was no aggregation in the cells beneath
them ; it was then left in six minims of the same solution, and
in 1 hr. there was much aggregation in many of the tentacles ;
in 2 hrs. all the tentacles (146 in number) were affected — the
aggregation extending down for a length equal to half or the
whole of .the glands. It is extremely improbable that these two
leaves would have undergone aggregation if they had been left
for a little longer in the water, namely for 1 hr. and 1 hr. 15 m.,
during which time they were immersed in the solution ; for the
process of aggregation seems invariably to supervene slowly and
very gradually in water.

Summary of the Results with Carhonafe of Ammonia. —
The roots absorb the solution, as shown by their changed
colour, and by the aggregation of the contents of their
cells. The vapour is absorbed by the glands ; these
are blackened, and the tentacles are inflected. The
glands of the disc, when excited by a half-minim drop
(•0296 ml.), containing -^^ of a grain (•0675 mg.),
transmit a motor impulse to the exterior tentacles,
causing them to bend inwards. A minute drop, con-
taining -xiiT-o of a grain (-00445 mg.), if held for a
few seconds in contact with a gland, soon causes the
tentacle bearing it to be inflected. If a leaf is left

148 DROSERA EOTUNDIFOLIA. Chap. VII.

immersed for a few hours in a solution, and a gland
absorbs the ttAito 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 ^ ^ ^\ „ „ of a grain
(•00024 mg.) suffices to excite the tentacle bearing this
o-land into movement.

Nitrate of Ammonia.

With the salt I attended only to the inflection of the leaves,
for it is far less efficient than the carbonate in causing aggrega-
tion, although considerably more potent in causing inflection. I
experimented with half-minims ('0296 ml.) on the discs of fifty-
two leaves, but will give only a few cases. A solution of one
part to 109 of water was too strong, causing httle inflection, and
after 21 hrs. killing, or nearly killing, four out of six leaves
which were thus tried ; each of which received the g-i ^ 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 disc of each received the ygVo of a grain
(•0337 mg.). Of these leaves, seven were very strongly acted on,
the edges being generally inflected ; two were moderately acted
on ; and five not at all. I subsequently tried three of these latter
five leaves with urine, saliva, and mucus, but they were only
slightly afi'ected ; 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 inflected, re-expanded after 51 hrs.

In the following exi^eriment I happened to select very sensi-
tive leaves. Ilalf-minims of a solution of one part to 1094 of
water (i.e. 1 gr. to 2h oz.) were placed on the discs of nine leaves,
so that each received the 2T00 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

CiiAP. VII. NITKATE OF AMMONIA. 149

7 lirs., but the full eifect was not produced until from 24 brs. to
30 lirs. 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 -gsVo o^ ^ grain (-0225 mg.), instead of, as in the last
experiment, a^Vo ^^ ^ grain. The blade of one was plainly in-
flected, as were six of the exterior tentacles ; the blade of a second
was slightly, and two of the exterior tentacles well, inflected, all
the other tentacles being curled in at right angles to the disc ;
three other leaves had from five to eight tentacles inflected ; five
others only two or three, and occasionally, though very rarely,
drops of pure water cause this much action ; the four remaining
leaves were in no way afiected, yet three of them, when subse-
quently tried with urine, became greatly inflected. In most of
these cases a slight effect was perceptible in from 6 hrs. to
7 hrs., but the full effect was not produced until from 24 hrs.
to 30 hrs. had elapsed. It is obvious that we have here reached
very nearly the minimum amount, which, distributed between
the glands of the disc, acts on the exterior tentacles ; these
having themselves not received any of the solution.

In the next place, the viscid secretion round three of the
exterior glands was touched with the same little drop (J^ of a
minim) of a solution of one part to 437 of water ; and after an
interval of 2 hrs. 50 m. all three tentacles were well inflected.
Each of these glands could have received only the -gs^oo ^^ ^
grain, or "00225 mg. A little drop of the same size and strength
was also applied to four other glands, and in 1 hr. two became
inflected, whilst the other two never moved. We here see, as in
the case of the half-minims placed on the discs, that the nitrate
of ammonia is more potent in causing inflection than the car-
bonate ; for minute drops of the latter salt of this strength pro-
duced no effect. I tried minute drops of a still weaker solution
of the nitrate, viz. one part to 875 of water, on twenty-one
glands, but no effect whatever was produced, except perhaps in
one instance.

Sixty-three leaves were immersed in solutions of various
strengths ; other leaves being immersed at the same time in the
same pure water used 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.

150 DROSEKA EOTUNDIFOLIA. Chap. VII.

Having made some preliminary trials as a guide, five leaves
were placed in the same little vessel in thirty minims of a solu-
tion of one part of the nitrate to 7875 of water (1 gr. to 18 oz.);
and this amount of fluid just sufficed to cover them. After
2 hrs. 10 m. three of the leaves were considerably inflected, and
the other two moderately. The glands of all became of so dark
a red as almost to deserve to be called black. After 8 hrs. four
of the leaves had all their tentacles more or less inflected ; whilst
the fifth, wliich I then perceived to be an old leaf, had only thirty
tentacles inflected. Next morning, after 23 hrs. 40 m., all the
leaves were in the same state, excepting that the old leaf had a
few more tentacles inflected. Five leaves which had been placed
at the same time in water were observed at the same intervals
of time ; after 2 hrs. 10 m. two of them had four, one had seven,
one had ten, of the long-headed marginal tentacles, and the
fifth had four round-headed tentacles, inflected. After 8 hrs.
there was no change in these leaves, and after 21 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 -^-^ of a grain was given to the
five leaves together, each got y^ of a grain (-015 mg.). I did
not count the tentacles on these leaves, which were moderately
fine ones, but as the average number on thii-ty-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 y 3 oVoo ^^ ^ grain of the nitrate ; and this caused
the inflection of a great majority of the tentacles.

This plan of immersing several leaves in the same vessel
is a bad one, as it is impossible to feel sure that the more
vigorous leaves do not rob the weaker ones of their share of
the salt. The glands, moreover, must often touch one another
or the sides of the vessel, and movement may have been thus
excited; but the corresponding leaves in water, which were
little inflected, though rather more so than commonly occurs,
were exposed in an almost equal degree to these same sources
of error. I will, therefore, give only one other experiment 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
__i_ of a grain (-0562 mg.). After 1 hr. 20 m. many of the
tentacles ou all four leaves were somewhat inflected. After

Chap. VII. NITRATE OF AMMONIA. 151

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 submarginals, inflected. After 21 hrs. all these
marginal tentacles re-expanded, but a few of the submarginals
on two of the leaves remained slightly curved inwards. The
contrast was wonderfully great between these four leaves in
water and those in the solution, the latter having every one of
their tentacles closely inflected. Making the moderate assump-
tion that each of these leaves bore 160 tentacles, each gland
could have absorbed only ^ g ^^3 ^ ^ of a grain (-000351 mg.).
This experiment was repeated on three leaves with the same
relative amount of the solution ; and after 6 hrs. 15 m. all the
tentacles except nine, on all three leaves taken, together, were
closely inflected. In this case the tentacles on each leaf were
counted, and gave an average of 162 per leaf.

The following experiments were tried during the summer of
1873, by placing the leaves, each in a separate watch-glass and
pouring over it thirty minims (1775 ml.) of the solution; other
leaves being treated in exactly the same manner with the
doubly distilled water used in making the solutions. The
trials above given were made several years before, and when I
read over my notes, I could not beheve 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 oz.), so that
each received -^ of a grain (2025 mg.). Before 30 m. had
elapsed, four of these leaves were immensely, and two of them
nfoderately, inflected. The glands were rendered of a dark
red. The four corresponding leaves in water were not at all
affected until 6 hrs. had elapsed, and then only the short ten-
tacles on the borders of the disc; and their inflection, as
previously explained, is never of any significance.

Four leaves were immersed, each in thirty minims of a solu-
tion of one part to 17,500 of water (1 gr. to 40 oz.), so that each
received qIq of a grain (lOl mg.); and in less than 45 m. three
of them had all their tentacles, except from four to ten, inflected ;
the blade of one being inflected after 6 hi's., 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

152 DROSEEA EOTUNDIFOLIA. Chap. VII.

in water, only one bad any of its exterior tentacles, namely five,
inflected ; after 6 lirs. 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 oz.), so that each leaf
got ^JL^ of a grain (-0105 mg.). Of these, one was much in-
flected in 8 m., and after 2 hrs. 7 m. bad all the tentacles,
except thirteen, inflected. The second leaf, after 10 m., had all
except three inflected. The third and fourth were hardly at all
affected, scarcely more than the corresponding leaves in water.
Of the latter, only one was affected, this having two tentacles
inflected, with those on the outer parts of the disc forming a
ring in the usual manner. In the leaf which bad all its ten-
tacles except three inflected in 10 m., each gland (assuming that
the leaf bore 160 tentacles) could have absorbed only asiVoo of
a grain, or -000258 mg.

Four leaves were separately immersed as before in a solution
of one part to 131,250 of water (1 gr. to 300 oz.), so that each
received -^^ 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 8 hrs. had about half its tentacles inflected, which
began to re-expand after 8 hrs. 15 m. The fourth leaf, after
3 hrs. 7 m., had only twenty-nine tentacles more or less in-
flected. Thus three out of the four leaves were strongly acted
on. It is clear that very sensitive leaves had been accidentally
selected. The day moreover was hot. The four corresponding
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 (assuming that the leaf bore 160 ten-
tacles) could have absorbed only 6^2 oo ^^ ^ 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 imjDortant in confirming the foregoing
positive ones, eight leaves were immersed as before, each in thirty
minims of a solution of one part to 175,000 of water (1 gr. to
400 oz.), so that each received only -^ Jg^ of a grain (-0101 mg.).
This minute quantity produced a slight effect on only four of
the eight leaves. One had fifty-six tentacles inflected after 2 hrs,
13 m. ; a second, twenty-six inflected, or sub-inflected, after

Chap. VII. PHOSPHATE OF AMMONIA. 153

38 m.; a third, eighteen inflected, after 1 hr. ; and a fourth,
ten inflected, after 85 m. The four other leaves were not in
the least affected. Of the eight corresponding leaves in water,
one had, after 2 hrs. 10 m., nine tentacles, and four others from
one to four long-headed tentacles, inflected ; the remaining three
being unaffected. Hence, the -g^o of a grain given to a sensi-
tive leaf during warm weather perhaps produces a slight effect;
but we must bear in mind that occasionally water causes as
great an amount of inflection as occurred in this last ex-
23eriment.

Summary of the Besults tvitJi Nitrate of Ammonia. —
The glands of the disc, when excited by a half-minim
drop (-0296 ml.), containing -2T0-0 of ^ grain of the
nitrate ('027 mg.), transmit a motor impulse to the
exterior tentacles, causing them to bend inwards. A
minute drop, containing ^3 ^^^ of a grain (-00225 mg.),
if held for a few seconds in contact with a gland,
causes the tentacle bearing this gland to be inflected
If a leaf is left immersed for a few hours, and some-
times for only a few minutes, in a solution of such
strength that each gland can absorb only the -g-g-rWo
of a grain ('0000937 mg.), this small amount is
enough to excite each tentacle into movement, and
it becomes closely inflected.

Phosphate of Ammonia.

This salt is more powerful than the nitrate, even
in a greater degree than the nitrate is more powerful
than the carbonate. This is shown by weaker solu-
tions of the phosphate acting when dropped on the
discs, or applied to the glands of the exterior ten-
tacles, or when leaves are immersed. The difference
in the power of these three salts, as tried in three
different ways, supports the results presently to be

154 DROSEKA EOTUNDIFOLIA. Chap. VII.

given, Avliicli are so surprising that their credi-
bility requires every kind of support. In 1872 I
experimented on twelve immersed leaves, giving each,
only ten minims of a solution; but this was a bad
method, for so small a quantity hardly covered them.
None of these experiments will, therefore, be given,
though they indicate that excessively minute doses
are efficient. AVhen I read over my notes, in 1873,
I entirely disbelieved them, and determined to mako
another set of experiments with scrupulous care, on
the same plan as those made with the nitrate ; namely
by placing leaves in watch-glasses, and pouring over
each thirty minims of the solution under trial, treat-
ing at the same time and in the same manner other
leaves with the distilled water used in making the
solutions. During 1873, seventy-one leaves were thus
tried in solutions of various strengths, and the same
number in water. Notwithstanding the care taken
and the number of the trials made, when in the
following year I looked merely at the results, without
reading over my observations, I again thought that
there must have been some error, and thirty-five fresh
trials were made with the weakest solution ; but
the results were as plainly marked as before. Al-
together, 106 carefully selected leaves were tried,
both in water and in solutions of the phosphate.
Hence, after the most anxious consideration, I can
entertain no doubt of the substantial accuracy of my
results.

Before giving my experiments, it may he 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 61"67 per
cent, of the salt used.

Extremely minute particles of the dry phosphate were placed

Chap. VII. PHOSPHATE OF AMMONIA. 155

with the point of a needle on the secretion surronnding 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 -^-^-^ 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 fi^ie
were almost fully re-expanded. I may mention with respect
to one of these leaves, that a drop of water had been left
during the previous 24 hrs. on its disc, but produced no effect ;
and that this was hardly dry when the solution was added.

Similar drops of a solution of one part to 1750 of water (1 gr.
to 4 oz.) were next placed on the discs of six leaves ; so that
each received ^-^^ 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 3 g\o of a grain,
absorbed by the central glands, is enough to make many of the
exterior tentacles and the blades bend, whereas the ^oVo ^^ ^
grain of the carbonate similarly given produced no effect ; and
_j__ of a grain of the nitrate was only just sufficient to produce
a well-marked effect.

A minute drop, about equal to ^V of ^ minim, of a solution of
one part of the phosphate to 875 of water, was applied to the
secretion on three glands, each of which thus received only
■gyJL— 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 ten-
tacles were decidedly inflected in 12m.; they remained so for
8 hrs. 30 m., but by the next morning were fully re-expanded.

156 DKOSEJRA ROTUNDIFOLIA. Chap. VII.

In this latter case each gland could have received only the
^^^^QQ (or -000563 mg.) of a grain. Lastly, similar drops of a
solution of one part to 1750 of water (1 gr. to 4 oz.) were tried on
five leaves ; a drop being applied to four glands on the same
leaf. The tentacles on three of these leaves were not in the
least affected ; on the fourth leaf, two became inflected ; whilst
on the fifth, which happened to be a very sensitive one, all four
tentacles were plainly inflected in 6 hrs. 15 m. ; but only one re-
mained inflected after 21 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 issVoo of ^ gi'ain (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 yg-^ of a grain of the carbonate, and
of "sYWo of ^ gi'ain of the nitrate, did not cause the tentacle bear-
ing the gland in question to be inflected ; so that here again the
phosj)hate 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 tliirty minims of a solution of one part
to 43,750 of water (1 gr. to 100 oz.) ; so that each received
T^oo of a grain, or '04058 mg. Of these leaves, eleven had
nearly all or a great number of their tentacles inflected in
1 hr., and the twelfth leaf in 3 hrs. One of the eleven had
every single tentacle closely inflected in 50 m. Two leaves out
of the sixteen were only moderately affected, yet more so
than any of those simultaneously immersed in water ; and the
remaining two, which were pale leaves, were hardly at all
affected. Of the sixteen corresponding leaves in water, one
had nine tentacles, another six, and two others two tentacles
inflected, in the course of 5 hrs. So that the contrast 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 32V0 of a grain (-0202 mg.). Fourteen of
these were strongly inflected within 2 hrs., and some of them
within 15 m. ; three out of the eighteen were only slightly
affected, having twenty-one, nineteen, and twelve tentacles in-

Chap. VII. PHOSPHATE OF AMMONIA. 157

fleeted ; 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 onter tentacles inflected ;
the remainder being quite unaffected.

The next experiment was tried under very favourable circum-
stances, fort he day (July 8) was very warm, and I happened
to have unusually fine leaves. Five were immersed as before in
a solution of one part to 131,250 of water (1 gr. to 300 oz.), so
that each received ^^Vo of a grain, or -0135 mg. After arf
immersion of 25 m. all five leaves were much inflected. After
1 hr. 25 m. one leaf had all but eight tentacles inflected; the
second, all but three ; the third, all but five ; the fourth, all but
twenty- three ; the fifth, on the other hand, never had more
than twenty-four inflected. Of the corresponding five leaves in
water, one had seven, a second two, a third ten, a fourth one,
and a fifth none inflected. Let it be observed what a contrast
is presented between these latter leaves and those in the solu-
tion. I counted the glands on the second leaf in the solution,
and the number was 217; assuming that the three tentacles
which did not become inflected absorbed nothing, we find
that each of the 214 remaining glands could have absorbed
only 1027200 of a grain, or -0000631 mg. The third leaf bore
236 glands, and subtracting the five which did not become in-
flected, each of the remaining 231 glands could have absorbed
only j^iolsoo of a grain (or '0000584 mg.), and this amount
sufiiced 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 oz.), so that each leaf received g^^
of a grain ('0101 mg.). My plants were not at the time in
a good state, and many of the leaves were young and pale.
Nevertheless, two of them had all their tentacles, except three
or four, closely inflected in under 1 hr. Seven were con-
siderably affected, some within 1 hr., and others not until 3 hrs.,
4 hrs. 30 m., and 8 hrs. had elapsed; and this slow action
may be attributed to the leaves being young and pale. Of
these nine leaves, four had their blades well inflected, and a
fifth slightly so. The three remaining leaves were not affected.
With respect to the twelve corresponding leaves in water, not
one had its blade inflected; after from 1 to 2 hrs. one had
thirteen of its outer tentacles inflected ; a second six, and four
others either one or two inflected. After 8 hrs. the outer
tentacles did not become more inflected ; whereas this occurred
with the leaves in the solution. I record in my notes that

158 DROSERA ROTUXDIFOLIA. Chap. VII.

after the 8 lirs. 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 TTeisoo. and on the other leaf
only i^rlooo. of ^ Sixain of the phosphate.

Twenty leaves were immersed in the usual manner, each in
thirty minims of a solution of one part to 218,750 of water (1 gr.
to 500 oz.). So many leaves were tried because I was then
under the false impression that it was incredible that any
weaker solution could produce an effect. Each leaf received
_j__ of a grain, or -0081 mg. The first eight leaves which I
tried both in the solution and in water were either young and
pale or too old ; and the weather was not hot. They were hardly
at all affected ; nevertheless, it would be unfair to exclude them.
I then waited until I got eight pairs of fine leaves, and the
weather was favourable ; the temperature of the room where the
leaves were immersed varying from 75° to 81° (23°-8 to 27°-2
Cent.). In another trial with four pairs (included in the above
twenty pairs), the temperature in my room was rather low,
about 60° (15°*5 Cent.) ; but the plants had been kept for several
days in a very warm greenhouse and thus rendered extremely
sensitive. Special precautions were taken for this set of experi-
ments; a chemist weighed for me a grain in an excellent
balance ; and fresh water, given me by Professor Frankland, was
carefully measured. The leaves were selected from a large
niTmber of plants in the followiug manner : 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 in-
flection than in the previous cases, comparatively with those
in the solution.

Of the twenty leaves in the solution, eleven became inflected
within 40 m. ; eight of them plainly and three rather doubt-
fully; but the latter had at least twenty of their outer tentacles
inflected. Owing to the weakness of the solution, inflection
occurred, except in No. 1, much more slowly than in the pre-
vious trials. The condition of the eleven leaves which were
considerably inflected will now be given at stated intervals,
always reckoning from the time of immersion : —

(1) After only 8 m. a large number of tentacles inflected,
and after 17 m. all but fifteen; after 2 hrs. all but eight in-

CuAP. VII. PHOSPHATE OF AMMONIA. 159

fleeted, or plainly sub-inflected. After 4 hrs. the tentacles
began to re-expand, and such prompt re-expansion is unusual ;
after 7 hrs. 30 in. 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 mflected.

(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.

(7) After 20 m. some inflection ; after 2 hrs. a considerable
number of tentacles inflected; after 7 hi's. 45 m. began to
re-expand.

(8) After 38 m. twenty-eight tentacles inflected ; after 3 hrs.
45 m. thirty-three mflected, with most of the submarginal
tentacles sub-inflected ; contmued so for two days, and then
partially re-expanded.

(9) After 38 m. forty-two tentacles inflected; after 3 hrs.
12 m. sixty-six inflected or sub-inflected ; after 6 hrs. 40 m. all
but twenty-four inflected or sub-inflected ; after 9 hrs. 40 m. all
but seventeen inflected ; after 24 hrs. all but four inflected or
sub-inflected, only a few being closely inflected; after 27 hrs.
40 m. the blade inflected. The leaf remained in this state for
two days, and then began to re-expand.

(10) After 38 m. twenty-one tentacles inflected ; after 3 hrs.
12 m. forty-six tentacles inflected or sub-inflected ; after 6 hrs.
40 m. all but seventeen mflected, though none closely; after
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 wator and the weaker solutions. But after 9 hrs.

160 DEOSERA EOTUNDIFOLIA. Chap. VII.

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. Thus the leaf remained for two
days, when it began to re-expand. I 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 dosehj inflected within so short a time as in the pre-
vious experiments with stronger solutions.

We will now turn to the twenty corresponding leaves in water.
Nine" had none of their outer tentacles inflected ; nine others
had from one to three inflected; and these re-expanded after
8 hrs. The remaining two leaves were moderately afi'ected ; one
having six tentacles inflected in 34 m. ; the other twenty-three
inflected in 2 hrs. 12 m. ; and both thus remained for 24 hrs.
None of these leaves had their blades inflected. So that the. con-
trast between the twenty leaves in water and the twenty in the
solution was very gi'cat, 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 teoIooo ^^ ^ grain ('0000411 mg.)
of the iDhosphate. 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 YGihioo of a grain, or "0000387
mg. Lastly, leaf No. 11, which had after 24 hrs. all its ten-
tacles, except one, closely inflected, as well as the blade, k^e
the unusually large number of 252 tentacles ; and on the same
principle "as before, each gland could have absorbed only the
2^]^ 000 of a grain, or '0000322 mg.

With respect to the following experiments, I must premise
that the leaves, both those placed in the solutions and in water,
were taken from plants which had been kept in a very warm
greenhouse during the winter. They were thus rendered ex-
tremely sensitive, as was shown by water exciting them much
more than in the previous experiments. Before giving my
observations, it may be well to remind the reader that, judging
from thirty-one fine leaves, the average number of tentacles is
192, and that the outer or exterior ones, the movements of
which are alone significant, are to the short ones on the disc in
the proportion of about sixteen to nine.

Chap. VII. PHOSPHATE OF AMMONIA. 161

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 y^^oo ^f a grain (-0054 mg.) of the salt ;
and all four were greatly inflected.

(1) After 1 hr. all the outer tentacles but one inflected, and
the blade greatly so ; after 7 hrs. began to re-expand.

(2) After 1 hr. all the outer tentacles but eight inflected;
after 12 hrs. all re-expanded.

(3) After 1 hr. much inflection ; after 2 hrs. 30 m. all the ten-
tacles but thirty-six inflected ; after 6 hrs. all but twenty-two
inflected ; after 12 hrs. partly re-expanded.

(4) After 1 hr. all the tentacles but thirty-two inflected; after
2 hrs. 30 m. all but twenty-one inflected ; after 6 hrs. almost
re-expanded.

Of the four corresponding leaves in water : —

(1) After 1 hr. forty-five tentacles inflected ; but after 7 hrs.
so many had re-expanded that only ten remained much inflected.

(2) After 1 hr. seven tentacles inflected; these were almost
re -expanded in G hrs.

(3) and (4) Not affected, except that, as usual, after 11 hrs.
the short tentacles on the borders of the disc formed a ring.

There can, therefore, be no doubt about the efiicicncy of the
above solution ; and it follows as before that each gland of No. 1
could have absorbed only g^i^opQ of a grain (0000268 mg.)
and of No. 2 only aioiooo 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 ICOO oz.).
Each leaf thus received tq^oo of a grain (-00105 mg.). The day
was warm, and the leaves were very. fine, so that all circum-
stances were favourable.

(1) After 30 m. all the outer tentacles except five inflected,
and most of them closely ; after 1 hr. blade slightly inflected ;
after 9 hrs. 30 m. began to re-expand.

(2) After 33 m. all the outer tentacles but twenty-five in-
flected, and blade shghtly so ; after 1 hr. 30 m. blade strongly
inflected and remained so for 21 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

162 DROSEKA EOTUNDIFOLIA. Chap. VII.

eight closely inflected. The leaf remained in this state for two
days.

(4) After 2 hrs. 20 m. only fifty-nine tentacles inflected ; but
after 5 hrs. all the tentacles closely inflected excepting two
which were not affected, and eleven wliich were only sub-in-
flected ; after 7 hrs. blade considerably inflected ; after 12 hrs.
much re-expansion.

(5) After 4 hrs. all the tentacles but fourteen inflected ; after
9 hrs. 30 m. beginning to re-expand.

(6) After 1 hr. thirty- six tentacles inflected; after 5 hrs. all
but fifty-foui' inflected ; after 12 hrs. considerable re-expansion.

(7) After 4 hrs. 30 m. only thirty-five tentacles inflected or
sub-inflected, and this small amount of inflection never increased.

Now for the seven corresponding leaves in water : —

(1) After 4 hrs. thirty-eight tentacles inflected ; but after
7 hrs. these, with the exception of six, re-expanded.

(2) After 4 hrs. 20 m. twenty inflected; these after 9 hrs.
partially re-expanded.

(8) After 4 hrs. five inflected, which began to re-expand after
7 hrs.

(4) After 24 hrs. one inflected.

(5), (6) and (7) Not at all affected, though observed for
24 hrs., excei^ting the short tentacles on the borders of the disc,
wliich as usual formed a ring.

A comparison of the leaves in the solution, especially of
the first five or even six on the Kst, with those in the water,
after 1 hr. or after 4 hrs., and in a still more marked degi-ee
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 leaf No. 3 (which
bore 233 glands, all of which, except nine, were inflected in
2 hi*s. 30 m.) could have received at most only the g-^-^QQQ of
a gi'ain, or 'OOOOIBI mg.

Four leaves were immersed as before in a solution of one part
to 656,250 of water (1 gr. to 1500 oz.) ; but on this occasion I
happened to select leaves which were very little sensitive, as
on other occasions I chanced to select unusually sensitive
leaves. The leaves were not more affected after 12 hrs. than

CuAP. VII. PHOSPHATE OF AMMONIA. 163

the four corresponding ones in water; but after 24 hrs. they
were slightly more inflected. Such evidence, however, is not at
all trustworthy.

Twelve leaves were immersed, each in thirty minims of a solu-
tion of one part to 1,312,500 of water (1 gr. to 3000 oz.); so that
each leaf received ^oo of ^ grain (-00135 mg.). The leaves were
not in very good condition ; four of them were too old and of a
dark red colour ; four were too pale, yet one of these latter acted
well ; the four others, as far as could be told by the eye, seemed
in excellent condition. The result was as follows :—

(1) This was a pale leaf; after 40 m. about thirty-eight ten-
tacles inflected; after 3 hrs. 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
21 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. thkty-five inflected; after 6. hrs. ''a
large number" (to quote my own memorandum) inflected,
but from want of time they were not counted ; after 24 hrs. rcr
expanded.

(4) After 1 hr. 40 m. about thirty inflected ; after 6 hr«. " a
large number all round the leaf" inflected, but they were not
counted ; after 10 hrs. began to re-expand.

(5) to (12) These were not more inflected than leaves often
-are m water, having respectively 16, 8, 10, 8, 4, 9, 14, and 0 ten-
tacles inflected. Two of these leaves, however, were remarkable
from having their blades slightly inflected after 6 hrs.

AYith respect to the twelve corresponding leaves in water, (1)
had, after 1 hr. 35 m., fifty tentacles inflected, but after 11 hrs.
only twenty-two remained so, and these formed a group, with the
blade at this point slightly inflected. It appeared as if this leaf
had been in some manner accidentally excited, for instance by a
particle of animal matter which was dissolved by the water.
(2) After 1 hr. 45 m. thirty-two tentacles inflected, but .after
5 hrs. 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

164 DROSERA ROTUNDIFOLIA. Chap. Vn.

soon re-expanded ; (9), (10), (11) and (12) none inflected, though
observed for twenty-four hours.

Comparing the states of the twelve leaves in water with those
in the sohition, there could be no doubt that in the latter a larger*
number of tentacles were inflected, and these to a greater degree ;
but the evidence was by no means so clear as in the former ex-
periments with stronger solutions. It deserves attention that the
inflection of four of the leaves in the solution went on increasing
during the first 6 hrs., and with some of them for a longer time ;
whereas in the water the inflection of the three leaves which
were the most affected, as well as of all the others, began to de-
crease during this same interval. It is also remarkable that the
blades of three of the leaves in the solution were slightly in-
flected, and this is a most rare event with leaves in w\ater,
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
antl at a much slower rate than in the previous cases. The
small effect produced may, however, be accounted for in large
part by the majority of the leaves having been in a poor con-
dition.

Of the leaves in the solution. No. 1 bore 200 glands and received
4s 000 ^^ ^ grain of the salt. Subtracting the seventeen tentacles
which were not inflected, each gland could have absorbed only
the "sYs+ooo of ^ grain (-00000738 mg.). This amount caused
the tentacle bearing each gland to be greatly inflected. The
blade was also inflected.

Lastly, eight leaves were immersed, each in thirty minims of a
solution of one part of the phosphate to 21,875,000 of water (1 gr.
to 5000 oz.). Each leaf thus received « o^oo ^^ ^ 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
w^ater, and almost all proved extremely sensitive. Beginning as
before with those in the solution : —

(1) After 2 hrs. 30 m. all the tentacles but twenty- two in-
flected, but some only sub-inflected ; the blade much inflected ;
after 6 hrs. 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
tentacles inflected, excepting those of the outermost row, of which
only eleven were inflected. The inflection continued to increapc,
and after 48 hrs. aU the tentacles except three were inflected.

Chap. VII. PHOSPHATE OF AMMONIA. 165

and most of them rather closely, four or five being only sub-
inflected.

(3) No change for the first 12 hrs. ; but after 24 hrs. all the
tentacles excepting those of the outermost row were sub-inflected,
with the blade 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, 7, 4, and 0 tentacles inflected, most of which, after a few
hours, re-expanded, with the exception of No. 4, which retained
its thirty-two tentacles inflected for 48 hi-s.

Now for the eight corresponding leaves in water : —

(1) After 2 hi's. 40 m. this had twenty of its outer tentacles
inflected, five of which re-expanded after 6 hrs. 30 m. After
10 hrs. 15 m. a most unusual circumstance occurred, namely,
the whole blade became slightly bowed towards the footstalk,
and so remained for 48 hrs. The exterior tentacles, excepting
those of the three or four outermost rows, were now also in-
flected to an unusual degree.

(2) to (8) These leaves, after 2 hrs. 40 m., had respectively 42,
12, 9, 8, 2, 1, and 0 tentacles inflected, which all re-expanded
within 24 hrs., and most of them within a much shorter time.

When the two lots of eight leaves in the solution and in the
water were compared after the lapse of 24 hrs., they undoubt-
edly differed much in appearance. The few tentacles on the
leaves in water which were inflected had after this interval re-
expanded, with the exception of one leaf; and this presented
the very unusual case of the blade being somewhat inflected,
though in a degree hardly approaching that of the two leaves in
the solution. Of these latter leaves, No. 1 had almost all its
tentacles, together with its blade, inflected after an immersion
of 2 hrs. 30 m. Leaves No. 2 and- 3 were affected at a much
slower rate ; but after from 24 hrs. to 48 hrs. almost all their
tentacles were closely inflected, and the blade of one quite
doubled up. We must therefore admit, incredible as the fact
may at first appear, that this extremely weak solution acted on
the more sensitive leaves; each of which received only the
soooo of a S^^^^ (-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 t4oooooo
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 hi-s. 30 m., bore 260 tentacles ;
and on the same principle as before, each gland could have

166 DEOSERA ROTUNDIFOLIA. Chap. VII.

absorbed only ^..^'oooo of a gram, or '00000328 mg.; and this
excessively minnto amount snABced to cause all tlie tentacles
bearing these glands to be greatly inflected. The blade was also
inflected.

Summary of the Besults tvWi Phosphate of Ammonia. —
The glands of the disc, when excited by a half-minim
drop (-0296 ml.), containing 3V4-0 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 ttxtoI) of a grain (-000423
mg.), if held for a few seconds in contact with a
gland, causes the tentacle bearing this gland to be
inflected. If a leaf is left immersed for a few hours,
and sometimes for a shorter time, in a solution so
weak that each gland can absorb only the

1 9 7 1> 0 0

of a grain (-00000328 mg.), this is enough to excite
the tentacle into movement, so that it becomes
closely inflected, as does sometimes the blade. In
the general summary to this chapter a few remarks
will be added, showing that the efiiciency of such
extremely minute doses is not so incredible as it
must at first appear.

Sulphate of Ammonia, — The few trials made with this and the
following five salts of ammonia were undertaken merely to
ascertain whether they induced inflection. Half-minims of a
solution of one part of the sulphate 'of ammonia to 437 of
water were placed on the discs of seven leaves, so that each
received ^^ 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. After
3 hrs. 25 m. one leaf had its blade inflected, but none of the
exterior tentacles. All six leaves remained in nearly the same
state during the day, the submarginal tentacles, however.

Chap. VII. OTHER SALTS OF AMMONIA. 167

becoming more inflected. After 23 hrs. three of tlie leaves had
tlieir blades somewhat inflected ; and the submarginal tentacles
of all considerably inflected, but in none were the two, three, or
four outer rows affected. I have rarely seen cases like this,
except from the action of a decoction of grass. The glands on the
discs of the above leaves, instead of being almost black, as after
the first hour, were now after 23 hrs. very pale. I next tried
on four leaves half-minims of a weaker solution, of one part to
1312 of water (1 gr. to 3 oz.) ; so that each received ^^^ of
a grain (-0225 mg.). After 2 hrs. 18 m. the glands on the disc
were very dark-coloured ; after 21 hrs. two of the leaves were
slightly affected ; the other two not at all.

Acetate of Ammonia. — Half-minims of a solution of ahout one
part to 109 of water were placed on the -discs of two leaves, both
of which were acted on in 5 hrs. 30 m., and after 23 hrs. had
every single tentacle closely inflected.

Oxalate of Ammonia. — Half-minims of a solution of one part
to 218 of water were placed on two leaves, which, after 7 hrs.,
became moderately, and after 23 hrs. strongly, inflected. Two
other leaves were tried with a weaker solution of one part
to 437 of water ; one was strongly inflected in 7 hrs. ; the other
not until 30 hrs. had elapsed.

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 in-
flected. After 8 hrs. 30 m. they began to re-expand. Next
morning, after 23 hrs., all were fully re-expanded, excepting
one which was still slightly inflected. The shortness of the
period of inflection in this and the following case is remark-
able.

Chloride of Ammonium. — Half-minims' of a solution of one
part to 437 of water were placed on the discs of six leaves.
A decided degree of inflection in the outer and. submarginal
tentacles was perceptible in 25 m. ; and this increased during
the next three or four hours, but never became strongly marked.
After only 8 hrs. 30 m. the tentacles began to re-expand, and
by the next morning, after 24 hrs., were fully re-expanded on
four of the leaves, but still slightly inflected on two.

General Summary and Concluding BemarJcs on the
Salts of Ammonia. — We have now seen that the nine

168

DROSEKA ROTUNDIFOLIA.

CUAP. VII.

salts of ammonia which were tried, all cause the in-
flection of the tentacles, and often of the blade of
the leaf. As far as can be ascertained from the
superficial trials with the last six salts, the citrate is
the least powerful, and the phosphate certainly by far
the most. The tartrate and chloride are remarkable
from the short duration of their action. The rela-
tive efficiency of the carbonate, nitrate, and phos-
phate, is shown in the following table by the smallest
amount which suffices to cause the inflection of the
tentacles.

Solutions, bow applied.

Carbonate of
I Ammonia.

Nitrate of
Ammonia.

Phosphate of
Ammonia.

Placed on the glauds of j
the disc, so as to act [
iudii-ectly on the outer j
tentacles ... J

Applied for a few se-]
conds directly to the I
gland of an outer |
tentacle . . . .j

Leaf immersed, with]! ^

time allowed for each ' ' ^dss
gland to absorb all
that it can

Amount absorbed by a
gland which suffices
to cause the aggre-
gation of the proto-
plasm in the adjoin-
ing cells of the ten-
tacles

965 of a
grain, or
•0675 mg.

nW of a

grain, or

■00445 mg.

of a
gram, or
00024 mg.

ishm of a

grain, or

■00048 mtr

51155 of a
grain, or
•027 mg.

553755 of a

grain, or
•0025 m^.

mhm of a

grain, or

•0000937 mj

5515 of a
grain, or
•01G9 msc.

133555 of a

grain, or
•000423 mg.

T97B5555 of a

grain, or
•00000328 m<

From the experiments tried in these three dif-
ferent ways, we see that the carbonate, which con-
tains 23'7 per cent, of nitrogen, is less efficient than
the nitrate, which contains 35 per cent. The phos-
phate contains less nitrogen than either of these
salts, namely, only 21*2 per cent., and yet is far more

Chap. VII. SUMMAKY, SALTS OF AMMONIA. 169

efficient ; its power no doubt depending quite as much
on the phosphorus as on th^ nitrogen which it contains.
We may infer that this is the case, from the energetic
manner in which bits of bone and phosphate of lime
affect the leaves. The inflection excited by the other
salts of ammonia is probably due solely to their nitro-
gen,— on the same principle that nitrogenous organic
fluids act powerfully, whilst non-nitrogenous organic
fluids are powerless. As such minute doses of the
salts of ammonia affect the leaves, we may feel almost
sure that Drosera absorbs and profits by the amount,
though small, which is present in rain-water, in the
same manner as other plants absorb these same salts
by their roots.

The smallness of the doses of the nitrate, and
more especially of the phosphate of ammonia, which
cause the tentacles of immersed leaves to be inflected,
is perhaps the most remarkable fact recorded in this
volume. When we see that much less than the
millionth* of a grain of the phosphate, absorbed by
a gland of one of the exterior tentacles, causes it to
bend, it may be thought that the effects of the solu-
tion on the glands of the disc have been overlooked ;
namely, the transmission of a motor impulse from
them to the exterior tentacles. No doubt the move-
ments of the latter are thus aided ; but the aid thus
rendered must be insignificant; for we know that a
drop containing as much as the 3V4-0 of a grain placed
on the disc is only just able to cause the outer ten-
tacles of a highly sensitive leaf to bend. It is cer-

* It is scarcely possible to real- stretch it along the wall of a large

ise what a million means. The hall; then mark ofl* at one end

best illustration which I have met the tenth of an inch. This tenth

with is that given by Mr. Croll, will represent a hundred, and the

who says, — Take a narrow strip of entire strip a million,
paper 83 ft. 4 in. in length, and

170 DROSERA EOTUNDIFOLIA. CiiAr. VII.

taiuly a most surprising fact that the TT7TTr'oirrr-o- 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 ai'e reduced to 3-TT^^Vmr 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 a leaf. Yet this amount
sufficed to cause the inflection of almost every ten-
tacle, and often of the blade of the leaf.

I am well aware that this statement will at first
appear incredible to almost every one. Drosera is far
from rivalling the power of the spectroscope, but it
can detect, as shown by the movements of its leaves, a
very much smaller quantity of the phosphate of am-
monia than the most skilful chemist can of any
substance.* My results were for a long time incredible

* When my first observations ' Treatise on Heat,' 2nd edit.

wore inado on the nitrate of am- 1871, p. 228). With respect to

monia, fourteen years ago, the ordinary chemical tests, I gather

powers of the spectroscope had from Dr. Alfred Taylor's work

not Leen discovered; and I felt on 'Poisons' that about 5^ of a

all the greater interest in the grain of arsenic, ^^ of a grain

then unrivalled powers of Drosera. of prussic acid, -^ of iodine,

Now the spectroscope has al- and ^^ of tartarised antimony,

together beaten Drosera; for ac- can be detected; but the power

cording to Bunsen and Kirchhoff of detection depends much on the

probaljly less than one sijTmnniWo of solutions under trial not being

a grain of sodium can be thus extremely weak,
detected (see Balfour Stewart,

Chap. VII. SUMMARY, SALTS OF AMMONIA. 171

even to myself, and I anxiously sought for every
source of error. The salt was in some cases weighed
for me by a chemist in an excellent balance ; and fresh
water was measured many times with care. The
observations were repeated during several years. Two
of my sons, who were as incredulous as myself, compared
several lots of leaves simultaneously immersed in the
weaker solutions and in water, and declared that there
could be no doubt about the difference in their ap-
pearance. I 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 Jaid gently in watch-glasses,
and a measured quantity of the solution and of water
poured over each. The water used must be as ab-
solutely pure as it can be made. It is to be especially
observed that the experiments with the weaker solu-
tions ought to be tried after several days of very
warm weather. Those with the weakest solutions
should be made on plants which have been kept
for a considerable time in a warm greenhouse, or cool
hothouse ; but this is by no means necessary for trials
with solutions of moderate strength.

I beg the reader to observe that the sensitiveness or
irritability of the tentacles was ascertained by three
different methods — indirectly by drops placed on the
disc, directly by drops applied to the glands of the
outer tentacles, and by the immersion of whole leaves ;
and it was found by these three methods that the
nitrate was more powerful than the carbonate, and the
phosphate 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

172 DEOSEKA ROTUNDIFOLIA. Chap. VII.

reader's faith to turn to the experiments with a
solution of one grain of the phosphate to 1000 oz.
of water, and he will there find decisive evidence that
the one-four-millionth of a grain is sufficient to cause
the inflection of a single tentacle. There is, there-
fore, nothing very improbable in the fifth of this
weight, or the one-twenty-millionth of a grain, acting
on the tentacle of a highly sensitive leaf. Again, two
of the leaves in the solution of one grain to 3000
oz., and three of the leaves in the solution of one
grain to 5000 oz., were affected, not only far more
than the leaves tried at the same time in water, but
incomparably more than any five leaves which can be
pickecl out of the 173 observed by me at different
times in water.

There is nothing remarkable in the mere fact of the
one-twenty-millionth of a grain of the phosphate,
dissolved in above two-million times, its weight of
water, being absorbed by a gland. All physiologists
admit that the roots of plants absorb the salts of
ammonia brought to them by the rain ; and fourteen
gallons of rain-water contain* a grain of ammonia,
therefore only a little more than twice as much as in
the weakest solution employed by me. The fact
which appears truly wonderful is, that the one-twenty-
millionth of a grain of the phosphate of ammonia
(including less than the one-thirty-millionth of effi-
cient matter), when absorbed by a gland, should
induce some change in it, which leads to a motor
impulse being transmitted down the whole length of
the tentacle, causing the basal part to bend, often
through an angle of above 180 degrees.

Astonishing as is this result, there is no sound reason

Miller's ' Elements of Chemistry,' part ii. p. 107, 3rd edit. 1864.

CuAP. VII. SUMMARY, SALTS OF AMMONIA. 173

why we should reject it as incredible. Prof. Donders,
of Utrecht, informs me that from experiments formerly
made by him and Dr. De Knyter, he inferred that less
than the one-millionth of a grain of sulphate of atro-
pine, in an extremely diluted state, if applied directly
to the iris of a dog, paralyses the muscles of this organ.
But, in fact, every time that we perceive an odour, we
have evidence that infinitely smaller particles act on
our nerves. When a dog stands a quarter of a mile to
leeward of a deer or other animal, and perceives its
presence, the odorous particles produce some change in
the olfactory nerves ; yet these particles must be in-
finitely smaller * than those of the phosphate of am-
monia weighing the one-twenty-millionth of a grain.
These nerves then transmit some influence to the brain
of the dog, which leads to action on its part. With Dro-
sera, the really marvellous fact is, that a plant without
any specialised nervous system should be affected by
such minute particles; but we have no grounds for
assuming that other tissues could not be rendered as
exquisitely susceptible to imj)ressions from without if
this, were beneficial to the organism, as is the nervoiLs
system of the higher animals.

* My son, George Darwin, has from g^fro to Trrowij of an inch

calculated for me the diameter of — in diameter. Therefore, an ob-

a sphere of phosphate of ammonia ject between -^ and ^ of the

(specific gravity 1-G78), weigh- size of a sphere of the phos-

ing the one-twenty-millionth of phate of ammonia of the above

a grain, and finds it to be -j^ of weight can be seen under a high

an inch. Now, Dr. Klein informs power ; and no one supposes

me that the smallest Micrococci, that odorous particles, such as

which are distinctly discernible those emitted from the deer in

under a power of 800 diameters, the above illustration, could be
are estimated to be from • 0002 to

•0005 of a millimetre — that is, croscope

174 DEOSEKA EOTUNDIFOLIA. Chap. VIII.

CHAPTEE VIII.

The Effects of various Salts and Acids on the Leaves.

Salts of sodium, potassium, and other alkaline, earthy, and metallic
gaits — Summary on the action of these salts — Various acids —
Summary on their action.

Having found that the salts of ammonia were so
powerful, I was led to investigate the action of some
othe» salts. It will be convenient, first, to give a list
of the substances tried (including forty -nine salts and
two metallic acids), divided into two columns, showing
those which cause inflection, and those which do not
do so, or only doubtfully. My experiments were made
by placing half-minim drops on the discs of leaves, or,
more commonly, by immersing them in the solutions ;
and sometimes by both methods. A summary of the
results, with some concluding remarks, will then be
given. The action of various acids will afterwards be
described.

Salts causing Inflection. Salts not causing Inflection.

{Arranged in Groups according to the Chemical Classification in Watts*
' Dictionary of Chemistry.*')

Sodium carbonate, rapid inflec- Potassium carbonate : slowly poi-

tion. sonous.

Sodium nitrate, rapid inflection. Potassiima nitrate : somewhat poi™

sonous.

Sodium sulphate, moderately Potassium sulphate.

rapid inflection.

Sodium phosphate, very rapid in- Potassium phosphate.

flection.

Sodiiun citrate, rapid inflection. Potassium citrate.
Sodium oxalate, rapid inflection.

Sodium chloride, moderately rapid Potassium chloride.

inflection.

ClIAP. VIII.

EFFECTS OF VARIOUS SALTS.

175

Salts causing Inflection. Salts not causing Inflection.

(^Arranged in Groups according to the Chemical Classification in Watts'
' Dictionary of Chemistry.'

Potassium iodide, a slight and

doubtful amount of inflection.
Potassium bromide.

Sodium iodide, rather slow inflec-
tion.

Sodium bromide, moderately rapid
inflection.

Potassium oxalate, slow and
doubtful inflection.

Lithium nitrate, moderately rapid • Lithium acetate,
inflection.

Caesium chloride, rather slow in- Kubidium chloride,
flection.

Silver nitrate, rapid inflection :
quick poison.

Cadmium chloride, slow inflection.
Mercury perchloride, rapid inflec-
tion : quick poison.

Aluminium chloride, slow and

doubtful inflection.
Gold chloride, rapid inflection :
quick poison.

Calcium acetate.
Calcium nitrate.

Magnesium acetate.
Magnesium nitrate.
Magnesium chloride.
Magnesium sulphate.
Barium acetate.
Barium nitrate.
Strontium acetate.
Strontium nitrate.
Zinc chloride.

Alimainium nitrate, a trace of in-
flection.

Aluminium and potassium sul-
phate.

Tin chloride, slow inflection :
sonous.

poi- Lead chloride.

Antimony tartrate, slow inflec-
tion : probably poisonous.

Arsenious acid, quick inflection :
poisonous.

Iron chloride, slow inflection :
probably poisonous.

Chromic acid, quick inflection :
highly poisonous.

Copper chloride, rather slow in-
flection : poisonous.

Nickel chloride, rapid inflection :
probably poisonous.

Platinum chloride, rapid inflec-
tion: poisonous.

Manganese chloride.

Cobalt chloride.

176 DROSEEA EOTUNDIFOLIA. Ch^p. Vm.

Sodium, Carbonate of (pure, given me by Prof. Hoflfmann). —
Half-minims ("0296 ml.) of a solution of one part to 218 of
■water (2 grs. to 1 oz.) were placed on the discs of twelve leaves.
Seven of these became well inflected; three had only two or
tliree of their outer tentacles inflected, and the remaining two
were quite unafiected. But the dose, though only the ^^ of a
grain {'13b mg.), was evidently too strong, for thi-ee of the
seven well-inflected leaves were kiUed. On the other hand, one
of the seven, which had only, a few tentacles inflected, re-
expanded and seemed quite healthy after 48 hrs. By employing
a weaker solution (viz. one part to 437 of water, or 1 gr. to
1 oz.), doses of 9^0 of a grain ('0075 mg.) were given to six
leaves. Some of these were affected in 37 m. ; and in 8 hrs. the
outer tentacles of all, as well as the blades of two, were con-
siderably inflected. After 23 hi's. 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 thii'ty minims of a solu-
tion of one part to 875 of water (1 gr. to 2 oz.), so that each
received gV of a grain (2-02 mg.); after 40 m. the three wero
much afl'ected, and after 6 hrs. 45 m. the tentacles of all and
the blade of one closely inflected.

Sodium, Nitrate of (pure).— Half-minims of a solution of one
part to 437 of water, containing g^ of a grain (-0675 mg.),
were placed on the discs of five leaves. After 1 hr. 25 m. tho
tentacles of nearly all, and the blade of one, were somewhat
inflected. The imQection continued to increase, and in 21 hi'S.
15 m. the tentacles and the blades of four of them were greatly
aflected, 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 tho
solution had been applied, two of the leaves had quite, and ono
liad partially, re-expanded ; whilst the remaining two remained
closely inflected and appeared injiu-ed.

Three leaves were immersed, each in thirty minims of a solu-
tion of one part to 875 of water ; in 1 hr. there was great inflec-
tion, and after S hrs. 15 m. every tentacle and the blades of all
thi-ee were most strongly inflected.

Sodium, Sulphate of — Half-minims of a solution of one part
to 437 of water were placed on the discs of six leaves. After
5 hrs. 30 m. the tentacles of three of them (with the blade of
one) were considerably, and those of the other three slightly,
inflected. After 21 hi's. the inflection had a little decreased.

CuAP. Vm. SALTS OF SODIUM. 177

and in 45 hrs. the leaves were fully expanded, appearing quite
healthy.

Three leaves were immersed, each in thirty minims of a solu-
tion of one part of the sulphate to 875 of water ; after 1 hr.
30 m. there was some inflection, which increased so much that
in 8 hrs. 10 m. all the tentacles and the blades of all three leaves
were closely inflected.

Sodium, Phosphate of. — Half-minims of a solution of one part
to 437 of water were placed on the discs of six leaves. The
solution acted with extraordinary rajjidity, for in 8 m. the outer
tentacles on several of the leaves were much incurved. After
6 hrs. the tentacles of all six leaves, and the blades of two, were
closely inflected. This state of things continued for 24 hrs.,
excepting that the blade of a third leaf became incurved. After
48 hrs. all the leaves re-expanded. It is clear that -^ of a
grain of phosphate of soda has great power in' causing in-
flection.

Sodium, Citrate of. — Half-minims of a solution of one part to
437 of water were placed on the discs of six leaves, but these
were not observed until 22 hrs. had elapsed. The sub-
marginal tentacles of five of them, and the blades of four, were
then found inflected; but the outer rows of tentacles were not
affected. One leaf, which appeared older than the others, was
very little affected in any way. After 46 hrs. foui* of the leaves
were almost re-expanded, including their blades. Three leaves
were also immersed, each in thirty minims of a solution of one
part of the citrate to 875 of water; they were much acted
on in 25 m. ; and after 6 hrs. 35 m. almost all the tentacles,
including those of the outer rows, were inflected, but not the
blades.

Sodium, Oxalate of. — Half-minims of a solution of one part to
437 of water were placed on the discs 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 hrs. 35 m. the blades of two and the tentacles of 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

178 DROSEKA EOTUNDIFOLIA. Chap. VIIL

of four leaves. Two, apparently, were not at all affected in
48 lirs. ; the third had its tentacles slightly inflected; whilst
the fourth had almost all its tentacles inflected in 24 hrs., and
these did not begin to re-expand until the foui'th 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 g^ of a grain. In
1 lir. 33 m. there was slight inflection ; and after 5 hrs. 30 m.
the tentacles of all six leaves were considerably, but not closely,
inflected. After 23 hrs. 15 m. all had completely re-expanded,
and did not appear in the least injured.

Three leaves were immersed, each in thirty minims of a solu-
tion of one part to 875 of water, so that each received g^ of a
grain, or 2-02 mg. After 1 hr. there was much inflection;
after 8 hi*s. 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. ^ of n grain. They all soon became inflected ;
after 48 hrs. they began to re-expand, and appeared quite un-
injured, though the solution was sufiiciently strong to taste
saline.

Sodium, Iodide 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 in-
flected. The other two had only their submarginal tentacles
inflected ; the outer ones in most of the leaves being but little
affected. After 46 hrs. the leaves had nearly re-expanded.
Three leaves were also immersed, each in thirty minims of a
solution of one part to 875 of water. After 6 hrs. 30 m. almost
all the tentacles, and the blade of one leaf, were closely inflected.
Sodium, Bromide of. — Half-minims of a solution of one part to
437 of water were placed on six leaves. After 7 hrs. there was
some inflection ; after 22 hrs. three of the leaves had their blades
and most of theii* tentacles inflected ; the fourth leaf was very
slightly, and the fifth and sixth hardly at all, affected. Three
leaves were also immersed, each in thirty minims of a solution
of one part to 875 of water ; after 40 m. there was some inflec-
tion ; after 4 hrs. the tentacles of all three leaves and the blades
of two were inflected. These leaves were then placed in water,
and after 17 hrs. 30 m. two of them were almost completely,
and the third partially, re-expanded ; so that apparently they
were not injured.

Chap. Vin. SALTS OF POTASSIUM. 179

Potassium, Carhonate of (pure). — Half-minims of a solution
of one part to 437 of water were placed on six leaves. No
effect was produced in 24 hrs. ; but after 48 hrs. some of the
leaves had their tentacles, and one the blade, considerably
inflected. This, however, seemed the result of their being in-
jured ; for on the third day after the solution was given, three of
the leaves were dead, and one was very unhealthy ; the other
two were recovering, but with several of their tentacles appa-
rently injured, and these remained permanently inflected. It
is evident that the g^^ of a grain of this salt acts as a poison.
Three leaves were also immersed, each in thirty minims of a
solution of one part to 875 of water, though only for 9 hrs. ; and,
very differently from what occurs with the salts of soda, no
inflection ensued.

Fotassium, 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 solution, of one part to 218 of water. After
50 hrs. there was no inflection, but two of the leaves seemed in-
jured. Five of these leaves were subsequently tested with drops
of milk and a solution of gelatine on their discs, and only one
became inflected; so that the solution of the nitrate of the
above strength, acting for 50 hrs., apparently had injured or
paralysed the leaves. Six leaves were then treated in the same
manner with a still weaker solution, of one part to 437 of water,
and these, after 48 hrs., were in no way affected, with the excep-
tion of perhaps a single leaf. Three leaves were next 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 amnionia
to 218 of water ; the glands were immediately blackened, and
after 1 hr. there was some inflection, and the protoplasmic con-
tents of the cells became plainly aggregated. This shows that
the leaves had not been much injured by their immersion for
25 hrs. in the nitrate.

Fotassium, Sulphate of. — Half-minims of a solution of one part
to 437 of water were placed on the discs of six leaves. After
20 hrs. 30 m. no effect was produced ; after an additional 24 hrs.
three remained quite unaffected ; two seemed injured, and the
sixth seemed almost dead with its tentacles inflected. Never-
theless, after two additional days, all six leaves recovered. The
immersion of three leaves for 24 hrs., each in thirty minims of

180 DROSEKA ROTUNDIFOLIA. Chap. VIII.

a solution of one part to 875 of water, produced no apparent
effect. They were then treated with the same solution of car-
bonate of ammonia, with the same result as in the case of the
nitrate of potash.

Fotassium, 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 pro-
duced. The partial drying up of the fluid on the disc slightly
drew together the tentacles on it, as often occui's in experi-
ments of this kind. The leaves on the third day appeared quite
healthy.

Fota^siuin, Citrate of. — Half-minims of a solution of one part
to 437 of water, left on the discs of six leaves for three days,
and the immersion of three leaves for 9 hrs., each in 30 minims
of a solution of one part to 875 of water, did not jDroduce the
least effect.

Fotassium, Oxalate of. — Half-minims were placed on different
occasions on the discs of seventeen leaves ; and the results per-
plexed me much, as they still do. Inflection supervened very
slowly. After 24 hrs. four leaves out of the seventeen were well
inflected, together with the blades of two; six were slightly
affected, and seven not at all. Three leaves of one lot were
observed for five days, and all died; but in another lot of
six, all excepting one looked healthy after four days. Three
leaves were immersed during 9 lirs., 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 for a
longer time.

Fotassium, Chloride of. Neither half-minims of a solution of
one imrt to 437 of water, left on the discs of six leaves for three
days, nor the immersion of three leaves during 25 hrs., in
30 minims of a solution of one part to 875 of water, produced
the least effect. The immersed leaves were then treated with
carbonate of ammonia, as described under nitrate of potash, and
with the same result.

Fotassium, Iodide of. — Half-minims of a solution of one part
to 437 of water were placed on the discs of seven leaves. In
30 m. one leaf had the blade inflected ; after some liours three
leaves had most of their submarginal tentacles moderately in-
flected; the remaining three being very slightly affected.
Hardly any of these leaves had their outer tentacles inflected.
After 21 hrs. all re-expanded, excepting two which still had a
few submarginal tentacles inflected. Three leaves were next

Chap. Vm. EFFECTS OF VAEIOUS SALTS. 181

immersed for 8 hrs. 40 m., each in 30 minims of a solntion of
one part to 875 of water, and were not in the least affected. I
do not know what to conclude from this conflicting evidence ;
but it is clear that the iodide of potassium does not generally
produce any marked effect.

Potassium, Bromide of. — Half-minims of a solution of one part
to 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 after 24 hrs.
they became splendidly inflected. Three leaves were also im-
mersed for 21 hrs, in 30 minims of a solution of one part to 875
of water ; but they were not at all affected, excepting that the
glands looked rather pale.

Lithium, Acetate o/.— 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,
yV of a grain. After 24 hrs. there was no inflection. I then
added, for the sake of testing the leaves, some strong solntion
(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 h. 30 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.

Ccesium, Chloride of — Four leaves were immersed, as above, in
120 minims of a solution of one part to 437 of water. After
1 hr. 5 m. the glands were darkened ; after 4 hrs. 20 m. there
was a trace of inflection ; after 6 hrs. 40 m. two leaves were
greatly, bjit 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.

Bubidium, Chloride of. — Four leaves which were immersed, as
above, in 120 minims of a solution of one part to 437 of water,
were not acted on in 22 hrs. I then added some of the strong
solution (1 gr. to 20 oz.) of phosphate of ammonia, and in 30 m.
all were immensely inflected.

Silver, Nitrate of. — Three leaves were immersed in ninety

182 DEOSERA EOTUNDIFOLIA. Chap. Vni.

minims of a solution of one part to 437 of water ; so that each
received, as before, yV of a grain. After 5 m. shght inflection,
and after 11 m. very strong inflection, the glands becoming
excessively black; after 40 m. all the tentacles were closely
inflected. After 6 hrs. the leaves were taken out of the solution,
washed, and placed in water ; but next morning they were
evidently dead.

Calcium^ 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-off end of the petiole. I then
added some of the solution (1 gr. to 20 oz.) of phospate of
ammonia, but this to my surprise excited only slight inflection,
even after 24 hrs. Hence it would appear that the acetate had
rendered the leaves torpid.

Calcium, Nitrate of.—Foux 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 oz.), but this caused only very slight in-
flection after 24 hrs. A fresh leaf was next put into a mixed
solution of the above strengths of the nitrate of calcium and
phosphate of ammonia, and it became closely inflected in between
6 m. and 10 m. Half-minims of a solution of one part of the
nitrate of calcium to 218 of water were droi)ped 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 oz.)
of phosphate of ammonia was then added to the three solutions.
The leaves in the acetate mixed with the phosphate underwent
some inflection; and this was well pronounced after 24 hrs.
Those in the mixed nitrate were decidedly inflected in 4 hrs.
30 m., but the 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.

Chap. VIIL EFFECTS OF VARIOUS SALTS. 183

Magnesium, Sulphate of. — Half-minims of a solution of one part
to 218 of water were placed on the discs of ten leaves, and pro-
duced no effect.

Barium, Acetate of. — Four leaves were immersed in 120^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 oz.) of phosphate of
ammonia, which caused after 26 hi's. only a little inflection in
two of the leaves.

Barium, Nitrate of. — Four leaves were immersed in 120 minims
of a solution of one part to 437 of water ; and after 22 hrs. there
was no more than that slight degree of inflection, which often
follows from an immersion of this length in pure water. I
then added some of the same solution of phosjDhate of ammonia,
and after 30 m. one leaf was greatly inflected, two others
moderately, and the fourth not at all. The leaves remained
in this state for 24 hrs.

Strontium, Acetate of. — Four leaves, immersed in 120 minims of
a solution of one part' to 437 of water, were not affected in
22 hrs. They were then placed in some of the same solution
of phosphate of ammonia, and in 25 m. two of them were
greatly inflected ; after 8 hrs. the third leaf was considerably
inflected, and the fourth exhibited a trace of inflection. They •
were in the same state next morning.

Strontium, Nitrate of. — Five leaves were immersed in 120
minims of a solution of one part to 437 of water ; after 22 hrs.
there was some slight inflection, but not more than sometimes
occurs with leaves in water. They were then placed in the
same solution of phosphate of ammonia ; after 8 hrs. three of
them were moderately inflected, as were all five after 24 hrs. ;
but not one was closely inflected. It appears that the nitrate of
strontium renders the leaves half torpid.

Cadmium, Chloride of. — Three leaves were immersed in ninety
minims of a solution of one part to 437 of water ; after 5 hrs.
20 m. slight inflection occurred, which increased during the
next three hours. After 24 hrs. all three leaves had their
tentacles well inflected, and remained so for an additional 24
hrs.; glands not discoloured.

Mercury', Perchloride of. — Three leaves were immersed in ninety
minims of a solution of one part to 437 of water ; after 22 m.
there was some slight inflection, which in 48 m. became well
pronounced; the glands were now blackened. After 5 hrs.
35 m. all the tentacles closely inflected; after 24 hrs. still

184 DROSERA ROTUNDIFOLIA. Chap. VIII.

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^ Chlwide of. — Four leaves were immersed in 120
minims of a solution of one part to 437 of water ; after 7 brs.
45 m. no inflection; after 24 hrs. one leaf rather closely, the
second moderately, the third and fourth hardly at all, inflected.
The evidence is doubtful, but I think some power in slowly
causing inflection must be attributed to this salt. These leaves
were then placed in the solution (1 gr. to 20 oz.) of phosphate
of ammonia, and after 7 hrs. 30 m. the three, which had been
but little affected by the chloride, became rather closely in-
flected.

Aluminium, Nitrate of. — Four leaves were immersed in 120
minims of a solution of one part to 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,

Oold, 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 Jg of a grain, or 4-048 mg,, of the chloride.
There was some inflection in 8 m., which became extreme in
45 m. In 3 hrs.- the surrounding fluid was coloured purple, and
the glands were blackened. After 6 hrs. the leaves were trans-
ferred to water; next morning they were found discoloured and
evidently killed. The secretion decomposes the chloride very
readily; the glands themselves becoming coated with the
thinnest layer of metallic gold, and particles float about on
the surface of the surrounding fluid.

Lead, Chloride of. — Three leaves were immersed in ninety
minims of a solution of one part to 437 of water. After 23 hrs.
there was not a trace of inflection ; the glands were not blackened,
and the leaves did not appear injured. They were then trans-

Chap. VUI. EFFECTS OP VARIOUS SALTS. 185

ferred to the solution (1 gr. to 20 oz.) of phosphate of ammonia,
and after 24 hrs. two of them were somewhat, the third very
little, inflected ; and they thus remained for another 24 hrs.

Tin, Chloride of. — Four leaves were immersed in 120 minims
of a solution of about one part (all not being dissolved) to 437 of
water. After 4 hrs. no effect ; after 6 hrs. 30 m. all four leaves
had their submarginal tentacles inflected ; after 22 hrs. every
single tentacle and the blades were closely inflected. The sur-
rounding fluid was now coloured pink. The leaves were washed
and transferred to water, but next morning were evidently dead.
This chloride is a deadly poison, but acts slowly.

Antimmiy, Tartrate of. — Three leaves were immersed in ninety
minims of a solution of one part to 437 of water. After 8 hrs.
30 m. there was slight inflection; after 24 hrs. two of the leaves
were closely, and the thii'd 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
inflection ; in 1 h. great inflection ; glands not discoloured. -After
6 hrs. the leaves were transferred to water ; next morning they
looked fresh, but after four days were pale-coloured, had not
re- expanded, and were evidently dead.

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. con-
siderable, inflection; after 2 hrs. all the tentacles closely in-
flected, with the glands discoloured. Placed in water, next
day leaves quite discoloured and evidently killed.

Manganese^ Chloride of. — Three leaves immersed in ninety
minims of a solution of one part to 437 of water ; after 22 hrs.
no more inflection than often occurs in water; glands not
blackened. The leaves were then placed in the usual solution
of phosphate of ammonia, but no inflection was caused even
after 48 hrs.

Copper, Chloride of, — Three leaves immersed in ninety minims

186 DROSEKA ROTUNDIFOLIA. Chap. YIU.

of a solution of one part to 437 of water ; after 2 hrs. some inflec-
tion ; after 3 hrs. 45 m. tentacles closely inflected, with the
glands blackened. After 22 lu's. still closely inflected, and the
leaves flaccid. Placed in pure water, next day evidently dead.
A rapid poison.

Nick'^^1, Chloride of. — Tliree leaves immersed in ninety minims
of a solution of one part to 437 of water ; in 25 m. considerable
inflection, and in 3 hi's. 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 of. — 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 o/.— 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 in-
flected, and twenty-six had no such effect, two rather
doubtful cases occurring in each series. In the table
at the head of this discussion, the salts are arranged
according to their chemical affinities ; but their action
on Drosera does not seem to be thus governed. The
nature of the base is far more important, as far as can
be judged from the few experiments here given, than
that of the acid ; and this is the conclusion at which
physiologists have arrived with respect to animals.
AVe 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

Chap. Vni. CONCLUDING REMARKS, SALTS. 187

the corresponding salts of potash do not cause inflec-
tion, and some of them are poisonous. Two of them,
however, viz. the oxalate and iodide of potash, slowly
induced a slight and rather doubtful amount of inflec-
tion. This difference between the two series is inter-
esting, as Dr. Burden Sanderson informs me that
sodium salts may be introduced in large doses into
the circulation of m^ammals without any injurious
effects ; whilst small doses of potassium salts cause
death by suddenly arresting the movements of the
heart. An excellent instance of the different action
of the two series is presented by the phosphate of
soda quickly causing vigorous inflection, whilst phos-
phate of potash is quite inefficient. The great power
of the former is probably due to the presence of
phosphorus, as in the cases of phosphate of lime and
of ammonia. Hence we may infer that Drosera cannot
obtain phosphorus from the phosphate of potash. This
is remarkable, as I hear from Dr. Burden 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

188 DROSEEA EOTUNDIFOLIA. Chap. YIII.

and potassium,* which act so differently ; therefore
we might expect that its action would be inter-
mediate. We see, also, that caesium causes inflection,
and rubidium does not; and these two metals are
allied to sodium and potassium. Most of the earthy
salts are inoperative. Two salts of calcium, four of
magnesium, two of barium, and two of strontium, did
not cause any inflection, and thus follow the rule of
the preponderant power of the base. Of three salts
of aluminium, ,one did not act, a second showed a
trace of action, and the third acted slowly and doubt-
fully, so that their effects are nearly alike.

Of the salts and acids of ordinary metals, seventeen
were tried, and only four, namely those of zinc, lead,
manganese, and cobalt, failed to cause inflection. The
salts of cadmium, tin, antimony, and iron, act slowly ;
and the three latter seem more or less poisonous. The
salts of silver, mercury, gold, copper, nickel, and
platinum, chromic and arsenious acids, cause great
inflection with extreme quickness, and are deadly
poisons. It is surprising, judging from animals, that
lead and barium should not be poisonous. Most of the
poisonous salts make the glands black, but chloride of
platinum made them very pale. I shall have occasion,
in the next chapter, to add a few remarks on the dif-
ferent effects of phosphate of ammonia on leaves j)re-
viously immersed in various solutions.

Acids.

I will first give, as in the case of the salts, a list
of the twenty -four acids which were tried, divided into
two series, according as they cause or do not cause

* ]\Iiller's ' Elements of Chcmiatry,' Srd edit. pp. 337, 4i8.

Chap. VIII.

THE EFFECTS OF ACIDS.

189

inflection. After describing the experiments, a few
concluding remarks will be added.

Acids, much diluted, which cause
Inflection.

1. Nitric, strong inflection ; poi-

sonous.

2. Hydrochloric, moderate and

slow inflection; not poisonous.

3. Hydriodic, strong inflection;
poisonous.

4. Iodic, strong inflection; poi-

sonous.

5. Sulphuric, strong inflection ;
somewhat poisonous.

6. Phosphoric, strong inflection ;
poisonous.

7. Boracic, moderate and rather
slow inflection; not poisonous.

8. Formic, very slight inflec-
tion ; not poisonous.

9. Acetic, strong and rapid in-
flection ; 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 in-

flection; poisonous.

14. Oxalic, moderately quick in-
flection ; very poisonous.

15. 51 alio, very slow but consider-
able inflection; not poisonous.

16. Benzoic, rapid inflection; very

poisonous.

17. Succinic, moderately quick
inflection ; moderately poi-
sonous.

18. Hippuric, rather slow inflec-

tion; poisonous.

19. Hydrocyanic, rather rapid in-

flection ; very poisonous.

Acids, diluted to the sajie
Degree, which do not cause
Inflection.

1. Gallic; not poisonous.

2. Tannic ; not poisonous.

3. Tartaric ; not poisonous.

4. Citric^* not poisonous.

5. Uric ; (?) not poisonous.

Nitric Acid.—FoMY leaves were placed, each in thirty minims
of one part by weight of the acid to 437 of water, so that each
received yV of a grain, or 4-048 mg. This strength was chosen
for this and most of the following experiments, as it is the same

190 DKOSERA EOTUNDIFOLIA. Chap. YIII.

as that of most of the foregoing sahne solutions. In 2 hrs. 30 m.
some of the leaves were considerably, and in 6 hrs. 30 m. all
were immensely, inflected, as were their blades. The surround-
ing fluid was slightly coloured pink, which always shows that
the leaves have been injured. They were then left in water for
three days; but they remained inflected and were evidently
killed. Most of the glands had become coloui-less. 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
21 hrs. both leaves had almost all their tentacles and blades in-
flected ; they were left in water for three days, and one partially
re-expanded and recovered. Two leaves were next immersed,
each in thirty minims of one part to 2000 of water ; this jDro-
duced very little effect, except that most of the tentacles close
to the summit of the petiole were inflected, as if the acid had
been absorbed by the cut-off end.

Hydrod.loric 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 hi-s. 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 im-
mersed as before, each in thirty minims. After 45 m. the glands
were discoloured, and the surrounding fluid became pinkish, but
there was no inflection. After 5 hrs. all the tentacles were
closely inflected; and an immense amount of mucus was secreted,
so that the fluid could be drawn out into long ropes. The leaves
were then placed in water, but never re-expanded, and were evi-
dently killed. Four leaves were next immersed in one part to 875
of water ; the action was now slower, but after 22 hrs. all four
leaves were closely inflected, and were affected in other respects
as above described. These leaves did not re-expand, though
left for four days in water. Tliis acid acts far more powerfully
than hydrochloric, and is poisonous.

Iodic Acid. — One to 437 of water ; three leaves were immersed.

X

Chap. VIII. THE EFFECTS OF ACIDS. 191

each in thirty minims ; after 3 hrs. strong inflection ; after 4 hrs.
glands dark brown ; after 8 hrs. 30 m. close inflection, and the
leaves had become flaccid ; surrounding fluid not coloured pink.
These leaves were then placed in water, and next day were
evidently dead.

Sulphuric Acid. — One to 437 of water; four leaves were im-
mersed, each in thirty minims; after 4 hrs. great inflection;
after 6 hrs. surrounding fluid just tinged pink ; they were then
placed in water, and after 46 hrs. two of them were still closely
inflected, two beginning to re-expand; many of the glands
colourless. This acid is not so poisonous as hydi'iodic or iodic
acids.

Phosphoric Acid. — One to 437 of water ; three leaves were
immersed together in ninety minims; after 5 hrs. 30 m. some
inflection, and some glands colourless; after 8 hrs. all the
tentacles closely inflected, and many glands colourless ; surround-
ing fluid pink. Left in water for two days and a half, remained
in the same state and appeared dead.

Boracic Acid. — One to 437 of water; four leaves were im-
mersed together in 120 minims ; after 6 hrs. very slight inflection f
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 httle
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 gi'eatly inflected. After
8 hrs. the leaves had become flaccid, but still remained closely
inflected, the suiTounding fluid being coloured pink. They were
then washed and placed in water ; next morning they were still
inflected and of a very dark red colour, but with their glands
colourless. After another day they were dingy-coloured, and

192 DKOSERA EOTUNDIFOLIA. CnAr. VIIL

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 para-
lysed 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. 60 m. there
was no inflection ; but after 3 hrs. 40 m. one leaf was greatly
inflected, and the other two slightly. The inflection continued
to increase, so that in 8 hrs. all three leaves were closely in-
flected. Next mormng, after 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 shghtly
flaccid and were evidently killed, as was afterwards proved to
be the case by keeping them in water. The protoplasm in the
closely inflected tentacles was not in the least aggregated, but
towards their bases it was collected in little brownish masses at
the bottoms of the cells. This protoplasm was dead, for on
leaving the leaf in a solution of carbonate of ammonia, no
aggregation ensued. Propionic acid is highly poisonous to
Drosera, like its ally acetic acid, but induces inflection at a
much slower rate.

Oleic Acid (given me by Prof. Frankland). — Three leaves were
immersed in this acid ; some inflection was almost immediately
caused, which increased slightly, but then ceased, and the leaves
seemed killed. Next morning they were rather shrivelled, and
many of the glands had fallen off the tentacles. Drops of this
acid were placed on the discs of four leaves ; in 40 m. all the
tentacles were greatly inflected, excepting the extreme marginal
ones ; and many of these after 3 hrs. became inflected. I was
led to try this acid from supposing that it was present (which
does not seem to be the case)* in olive oil, the action of which
is anomalous. Thus drops of this oil placed on the disc do not
cause the outer tentacles to be inflected ; yet when minute
drops were added to the secretion surrounding the glands of the
outer tentacles, these were occasionally, but by means always,
inflected. Two leaves were also immersed in this oil, and there

* See articles on Glycerine and Oleic Acid in Watts' 'Diet, of
Chemistry.'

Chat. VIII. THE EFFECTS OF ACIDS. 193

was no inflection for about 12 hrs. ; but after 23 hrs. almost all
the tentacles were inflected. Three leaves were likewise im-
mersed in unboiled hnseed oil, and soon became somewhat, and
in 3 hrs. greatly, inflected. After 1 hr. the secretion round the
glands was coloured pink. I infer from this latter fact that the
power of linseed oil to cause inflection cannot be attributed to
the albumin which it is said to contain.

Carbolic Acid. — Two leaves were immersed in sixty minims of
a solution of 1 gr. to 437 of water ; in 7 hrs. one was slightly,
and in 24 hrs. both were closely, inflected, mth 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 rapidly or powerfully as
might have been expected from its known destructive power on
the lowest organisms. Half -minims of the same solution were
placed on the discs of three leaves ; after 24 hrs. no inflection of the
outer tentacles ensued, and when bits of meat were given them,
they became fairly well inflected. Again half-minims of a
stronger solution, of one part to 218 of water, were placed on the
discs of three leaves ; no inflection of the outer tentacles ensued ;
bits of meat were then given as before ; one leaf alone became
well inflected, the discal glands of the other two appearing
much injured and dry. We thus see that the glands of
the discs, after absorbing this acid, rarely transmit any motor
impulse to the outer tentacles; though these, when their own
glands absorb the acid, are strongly acted on.

Lactic Acid. — Three leaves were immersed in ninety minims of
one part to 437 of water. After 48 m. there was no inflection,
but the surrounding fluid was coloured pink; after 8 hrs.
30 m. one leaf alone was a little inflected, and almost all
the glands on all three leaves were of a very ^jale colour.
The leaves were then washed and placed in a solution (1 gr.
to 20 oz.) of phosphate of ammonia; after about 16 hrs. there
was only a trace of inflection. They were left in the phosphate
for 48 hrs., and remained in the same state, with almost all
their glands discoloured. The protoplasm within the cells
was not aggregated, except in^a very few tentacles, the glands
of which were not much discoloured. I believe, therefore,
that almost all the glands and tentacles had been killed by
the acid so suddenly that hardly any inflection was caused.
Four leaves were next immersed in 120 minims of a weaker
solution, of one part to 875 of water; after 2 hrs. 30 m. the
surrounding fluid was quite pink ; the^ glands were pale, but

194 DROSERA ROTUNDIFOLIA. Chap. VIII.

there was no inflection; after 7 hrs. 30 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 4=5 hrs. one leaf had almost every tentacle in-
flected ; a second a large number ; the third and foni-th 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 Citric Acids.— Ohq part to 437 of
water. -Three or four leaves were immersed, each in thirty
minims of these four solutions, so that each leaf received y^ of a
grain, or 4-04:8 mg. No inflection was caused in 24 hrs., and the
leaves did not appear at all injui-ed. 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 hi-s., and so
remained for the next 24 hrs.

Malic Acid.—ThvQQ leaves were immersed in ninety minims of
a solution of one part to 437 of water; no inflection was caused
in 8 hrs. 20 m., but after 24 hrs. two of them were considerably,
and the third slightly, inflected— more so than could be ac-
counted for by the action of water. No great amount of mucus
was secreted. They were then placed in water, and after two
days partially re-expanded. Hence this acid is not poisonous.

Oxalic Acid. — Three leaves were immersed in ninety minims of
a solution of 1 gr. to 437 of water ; after 2 hrs. 10 m. there was
much inflection; glands pale; the surrounding fluid of a dark
2^ink 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 additiocal hours, the tlii'ee leaves were dead and their
glands colourless.

Benzoic Acid. — Five leaves were immersed, each in thirty
minims of a solution of 1 gi*. 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 62 m. the submarginal

CuAP. VIII. THE EFFECTS OF ACIDS. 195

tentacles were somewhat inflected, and all the glands yery 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 le^ft in the solution ; others, after an immersion of
6 hi-s. 30 m., were placed in water. Next morning both lots
were quite dead; the leaves in the solution being flaccid, those
in the water (now coloured yellow) of a pale brown tint, and
their glands white.

Succinic Acid. — Three leaves were immersed in ninety minims
of a solution of 1 gr. to 437 of water ; after 4 hrs. 15 m. consider-
able and after 23 hi's. 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 oxahc 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 y\ of a grain. After
25 m. there was some slight inflection, but this never increased ;
after 9 hrs. the glands were not discoloured, nor was the solu-
tion coloured pink; nevertheless much mucus was secreted.
The leaves were then placed in water, and by next morning
fully re-expanded. I doubt whether this acid really causes
inflection, for the shght 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.

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 surround-
ing fluid coloured pink ; after 6 hrs. all closely inflected. After

196 DROSERA ROTUNDIFOLIA. Chap. Vm.

an immersion of 8 hrs. 20 m. the leaves were washed and placed
in water; next morning, after about 16 hrs., they were still
inflected and discoloured ; on the succeeding day they were
evidently dead. Two leaves were immersed in a stronger
mixture, of one part to fifty of water ; in 1 hr. 15 m. the glands
became as white as porcelain, as if they had been dipped in boil-
ing water ; very few of the tentacles were inflected ; but after
4 hrs. almost all were inflected. These leaves were then placed
in water, and next morning were evidently deadt Half-minim
drops of the same strength (viz. one part to fifty of water) were
next placed on the discs of five leaves ; after 21 hrs. all the
outer tentacles were inflected, and the leaves appeared much
injured. I likewise touched the secretion round a large number
of glands with minute drops (about ^^ of a minim, or '00296 ml.)
of Scheele's mixture (6 per cent.) ; the glands first became bright
red, and after 3 hrs. 15 m. about two-thirds of the tentacles
bearing these glands were inflected, and remained so for the two
succeeding days, when they appeared dead.

Concluding RemarJcs on the Action of Acids. — It is
evident that acids have a strong tendency to cause the
inflection of the tentacles ; * for out of the twenty-four
acids tried, nineteen thus acted, either rapidly and
energetically, or slowly and slightly. This fact is
remarkable, as the juices of many plants contain more
acid, judging by the taste, than the solutions employed
in my experiments. From the powerful effects of so
many acids on Drosera, we are led to infer that those
naturally contained in the tissues of this plant, as well
as of others, must play some important part in their
economy. Of the five cases in which acids did not
cause the tentacles to be inflected, one is doubtful ;
for uric acid did act slightly, and caused a copious
secretion of mucus. Mere sourness to the taste is no

* According to IM. Fouriiier Berberis instantly to close; though

(' De la Fecondation dans les drops of water have no such power,

rhancrogames,' 1863, p. 61) drops which latter statement I can con-

of acetic, hydrocyanic, and sul- firm,
phuric acid cause the stamens of

Chap. VIII. CONCLUDING REMARKS, ACIDS. 197

criterion of the power of an acid on Drosera, as citric
and tartaric acids are very sour, yet do not excite
inflection. It is remarkable how acids differ in
their power. Thus, hydrochloric acid acts far less
powerfully than hydriodic and many other acids of the
same strength, and is not poisonous. This is an in-
teresting fact, as hydrochloric acid plays so important
a part in the digestive process of animals. Formic
acid induces very slight inflection, and is not poison-
ous ; whereas its ally, acetic acid, acts rapidly and
powerfully, and is poisonous. Malic acid acts slightly,
whereas citric and tartaric acids produce no effect.
Lactic acid is poisonous, and is remarkable from in-
ducing inflection only after a considerable interval of
time. Nothing surprised me more than that a solution
of benzoic acid, so weak as to be hardly acidulous to
the taste, should act with great rapidity and be highly
poisonous; for I am informed that it produces no
marked effect on the animal economy. It may be
seen, by looking down the list at the head of this dis-
cussion, that most of the acids are poisonous, often
highly so. Diluted acids are known to induce nega-
tive osmose,* and the poisonous action of so many
acids on Drosera is, perhaps, connected with this
power, for we have seen that the fluids in which they
were immersed often became pink, and the glands
pale-coloured or white. Many of the poisonous acids,
such as hydriodic, benzoic, hippuric, and carbolic (but
I neglected to record all the cases), caused the secre-
tion of an extraordinary amount of mucus, so - that
long ropes of this matter hung from the leaves when
they were lifted out of the solutions. Other acids,
such as hydrochloric and malic, have no such ten-

* Miller's ' Elements of Chemistry,' part i. 1867, p. 87.

198 DROSERA ROTUNDIFOLIA. Chap. VIII

dency ; in these two latter cases the surrounding fluid
was not coloured pink, and the leaves were not
poisoned. On the other hand, propionic acid, which
is poisonous, does not cause much mucus to be
secreted, yet the surrounding fluid became slightly
pink. Lastly, as in the case of saline solutions,
leaves, after being immersed in certain acids, were
soon acted on by phosphate of ammonia ; on the
other hand, they were not thus affected after immer-
sion in certain other acids. To this subject, how-
ever, I shall have to recur.

Chap. IX. ALKALOID POISONS. 199

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 — Hyoscyamus — Poison of the cobra, apparently acce-
lerates the movements of the protoplasm — Camphor, a powerful
stimulant, its vapour narcotic — Certain essential oils excite move-
ment — Glycerine — Water and certain solutions retard or prevent
the subsequent action of phosphate of ammonia — Alcohol inno-
cuous, its vapour narcotic and poisonous — Chloroform, sulphuric
and nitric ether, their stimulant, poisonous, and narcotic power —
Carbonic acid narcotic, not quickly poisonous — Concluding remarks.

As in the last chapter, I will first give my experiments,
and then a brief summary of the results with some
concluding remarks.

Acetate of Strychnine. — Half-minims of a solution of one part to
437 of water were placed on the discs of six leaves ; so that
each received -^q of a grain, or .0675 mg. In 2 hrs. 30 m. the
outer tentacles on some of them were inflected, but in an irregu-
lar manner, sometimes only on one side of the leaf. The next
morning, after 22 hrs. 30 m., the inflection had not increased.
The glands on the central disc were blackened, and had ceased
secreting. After an additional 24 hrs. all the central glands
seemed dead, but the inflected tentacles had re-expanded and
appeared quite healthy. Hence the poisonous action of strych-
nine seems confined to the glands which have absorbed it ;
nevertheless, these glands transmit a motor impulse to the
exterior tentacles. Minute drops (about -^-^ 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

200 DROSERA ROTUNDIFOLIA. Chap. IX.

were excited, after an interval of a quarter to three quarters of
an hour, by being rubbed or given bits of meat. Similar drops
of a solution of one part to 218 of water (2 grs. to 1 oz.) quickly-
blackened the glands ; some few tentacles thus treated moved,
whilst others did not. The latter, however, on being subse-
quently moistened with saliva or given bits of meat, became
incurved, though with extrepie slowness; and this shows that
they had been injured. Stronger solutions (but the strength
was not ascertained) sometimes arrested all power of movement
very quickly ; thus bits of meat were placed on the glands of
several exterior tentacles, and as soon as they began to move,
minute drops of the strong solution were added. They con-
tinued for a short time to go on bending, and then suddenly
stood still; other tentacles on the same leaves, with meat
on their glands, but not wetted with the strychnine, continued
to bend and soon reached the centre of the leaf.

Citrate of Strychnine. — Half-minims of a solution of one 23art
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 oz.) were added to the secretion round
several glands, but did not produce nearly so plain an effect as
the drops of a much weaker solution of the acetate. Particles of
the dry citrate were placed on six glands ; two of these moved
some way towards the centre, and then stood still, being no
doubt killed ; three others curved much farther inwards, and
were then fixed; one alone reached the centre. Five leaves
were immersed, each in thirty minims of a solution of one part
to 437 of water; so that each received -^ of & 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 hi's., became whitish and opaque,
and the protoplasm in the cells of the tentacles was well aggre-
gated. By this time two of the leaves were greatly inflected,
but the three others not much more inflected than they were
before. Nevertheless two fresh leaves, after an immersion re-
spectively for 2 hi's. 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

Chap. IX, ALKALOID POISONS. 201

of two other leaves, after an immersion for 2 hrs. in a stronger
solution, of one part of the citrate to 218 of water, became of an
opaque, pale pink colour, which before long disappeared, leaving
them white. One of these two leaves had its blade and
tentacles greatly inflected; the other hardly at all; but the
protoplasm in the cells of both was aggregated down to the
bases of the tentacles, with the spherical masses in the cells
close beneath the glands blackened. After 24 hrs. one of these
leaves was colourless, and evidently dead.

Sulphate of Quinine. — Some of this salt was added to
water, which is said to dissolve yooo P^^^ ^^ i^s weight.
Five leaves were immersed, each in thirty minims of this solu-
tion, which tasted bitter. In less than 1 hr. some of them had
a few tentacles inflected. In 3 hrs. most of the glands became
whitish, others dark-coloured, and many oddly mottled. After
6 hrs. two of the leaves had a good many tentacles inflected, but
this very moderate degree of inflection never increased. One of
the leaves was taken out of the solution after 4 hrs., and placed
in water; by the next morning some lew of the inflected
tentacles had re-expanded, showing that they were not dead;
but the glands were still much discoloured. Another leaf not
included in the above lot, after an immersion of 3 hrs. 15 m.,
was carefully examined; the protoplasm in the cells of the
outer tentacles, and of the short green ones on the disc, had
become strongly aggregated down to their bases ; and I distinctly
saw that the little masses changed their positions and shapes
rather rapidly ; some coalescing and again separating. I was
surprised at this fact, because quinine is said to arrest all move-
ment in the white corpuscles of the blood ; but as, according to
Binz,* this is due to their being no longer supplied with oxygen
by the red corpuscles, any such arrestment of movement could
not be expected in Drosera. That the glands had absorbed some
of the salt was evident from their change of colour ; but I at
first thought that the solution might not have travelled down
the cells of the tentacles, where the protoplasm was seen in
active movement. This view, however, I have no doubt, is
erroneous, for a leaf which had been immersed for 3 hrs. in the
quinine solution was then placed in a little solution of one part of
carbonate of ammonia to 218 of water ; and in 30 m. the glands
and the upper cells of the tentacles became intensely black, with
the protoplasm presenting a very unusual appearance; for it

'Quarterly Journal of Microscoj)ical Scieuce,' April 1874, i^. 185.

202 DKOSEPvA EOTUNDIFOLIA. Chap. IX.

had become aggregated into reticulated dingy-coloured masses,
haying rounded and angular interspaces. As I have never
seen this efifect 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 oh the discs of six
leaves; after 23 hrs. one had all its tentacles, two had a few,
and the others none inflected ; so that the discal glands, when
irritated by this salt, do not transmit any strong motor impulse
to the outer tentacles. After 48 hrs. the glands on the discs of
all six leaves were evidently much injui'ed or quite killed. It is
clear that this salt is highly poisonous.*

Aci'fate of Quinine. — Four leaves were immersed, each in thirty
minims of a solution of one part to 487 of water. The solution
vvas 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 inflec-
tion. These leaves, on being left in water for 48 hrs., almost

* Binz found several years ago white corpuscles, which become

(as stated in ' The Journal of " rounded and granular." In the

Anatomy and Phys.' November tentacles of Drosera the agsrre-

1872, p. 195) that quinia is an gated masses of protoplasm, which

energetic poison to low veg-e- appeared killed by the quinine,

table and animal orijanisms. Even likewise presented a granular

one part added to 4000 parts of appearance. A similar appear-

l)lood arrests the movements of the ance is caused by very hot water.

Chap. rx. ALKALOID POISONS. 203

completely re-expanded, but tlie 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 sin-
gular.

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 in-
flected ; the fourth had only a few tentacles inflected, and the
fifth (an old leaf) was not at all affected. They remained in
nearly the sam.e 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 yV ^f ^ 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 g^^oo of a grain (-00225 mg.) acts oil a tentacle, but is not
poisonous. It 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 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 in a 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 i 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 solution, 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 ap-
peared 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 glands and to induce aggregation

204 DROSERA ROTUNDIFOLIA. Chap. IX

of the protoplasm, but, except when pm-e, 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.— K grain was added to 437 grains of water, but
was not all dissolved ; another grain was added to 437 grains of
a mixture of one part of alcohol f o 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 jDlaced, 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 di-ops of the solution
of atropine 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 differ 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 likewise
given bits of meat, and they had in the course of 24 hrs. a good
many of their submarginal tentacles inflected.

Verafrine, 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 like-
wise 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 solution. 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 kiud had been absorbed. In 9 hrs. two of the
leaves had most of their tentacles sub-inflected, but the inflec-
tion 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 ;

Chap. IX. ALKALOID POISONS. 205

the other two, after their immersion for 24 hrs., were likewise
placed in water, and in 24 hrs. were considerably re-exj^anded,
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 afl^ected,
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 pro-
toplasm in the cells well aggregated. If, however, whilst the
leaves were immersed in the morphia, phosphate of am-
monia 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 retar-
dation 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

2U6 DROSERA ROTUNDIFOLIA. Chap. IX.

sometimes did not do so. At one time I felt convinced that
morphia acted as a narcotic on Drosera, but after having found
in 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.

Kxtracf, of Ilyosci/umus. — 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 carbonate 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 pronounced ; so that hyoscyamus does not act as a
narcotic or poison.

Puiso7ifrom 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. 30 m., all were beginning to re-expand, and they
ai^pcared uninjured.

Foison from the Cobra. — Dr. Fayrer, well known from his
investigations 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 Jq of a minim) of a solution of one part to
437 of water was applied to the secretion round four glands ; so
that each received only about g^^oo ^^ ^ 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 pink 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 ^^ of a grain (*0675 mg.) ; in

Dr. Fayrer, ' The Thanatophidia of India,' 1872, p. 150.

CiiAr. IX. POISON OF THE COBEA. 207

4 lirs. .15 m, the outer tentacles were mucli inflected ; and after
6 lirs. 30 m. those on two of the leaves were closely inflected and
the blade of one ; the third leaf was only moderately affected.
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 -^^ of a grain, or 4*048 mg. In
6 m. there was some inflection, which steadily increased, so that
after 2 hrs. 30 m. all three leaves were closely inflected; the
glands were at first somewhat darkened, then rendered pale ; and
the protoplasm tvithin the cells of the tentacles was partially
aggregated. The little masses of protoplasm were examined
after 3 hrs., and again after 7 hrs., and on no other occasion
have I seen them undergoing such rapid changes of form.
After 8 hrs. 30 m. the glands had become quite white ; they had
not secreted any great quantity of mucus. The leaves were
now placed in water, and after 40 hrs. 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 tliirty minims of a
much stronger solution, of one part to 109 of water ; so that each
received ^ of a grain, or 16-2 mg. After 1 hr. 45 m. the sub-
marginal tentacles were strongly inflected, with the glands some-
what pale ; after 3 hrs. 30 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 inflec-
tion 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 protoplasm, 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 immer-
sion in the solution) they were largely, but not quite fully
10

208 DROSEKA ROTUNDIFOLIA. Chap. IX.

expanded. The tentacles were now examined, and the aggregated
masses were almost wholly' redissolved ; the cells being filled with
homogeneous pnrple fluid, with the exception here and there of
a single globular mass. We thus see how completely the proto-
plasm had 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 conse-
quently 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 hi*s. 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 jDoison 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 colour from the glands. It seems even to act
as a stimulant to the protoplasm, for after considerable expe-
rience in observing the movements 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 obser-
vations for me, which he has since jDublished.* Ciliated epi-
thelium from the mouth of a frog was placed in a solution of
•03 gramme to 4*6 cubic cm. of water ; others being placed
at the same time in pure water for comparison. The move-
ments of the cilia in the solution seemed at first increased,
but soon languished, and after between 15 and 20 minutes
ceased ; wdiilst 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 ParamEecium and Yolvox, 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 consider-

Proceedings of Eoyal Society,' Feb. IS, 1875.

Chap. IX. CAMPHOR. 209

able 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 occa-
sionally 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 con-
spicuous a manner as by the cobra poi^son. 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 yooo ^f its weight of camphor; it smelt and
tasted of this substance. Ten 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
26 m. 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 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.

M. Vogel has shown* that the flowers of various plants do not
wither so soon when their stems are placed in a solution of cam-
phor 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

* ' Gardener's Chronicle,' 1874, p. G71. Nearly similar observations
were made in 1798 by B. S. Barton.

210

DKOSERA ROTUNDIFOLIA.

Chap. IX.

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 following
table, were next brushed only once with the same brush and in
the same manner as before ; the results are given in the table.
]\Iy first trials were made by brushing the leaves whilst still
immersed in the solution ; but it occiu'red 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
following trials, therefore, each leaf was taken out of the solu-
tion, 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 camj)hor ; but this treatment made no difference
in the results.

rA

Length of

s

Time between

c3

Length of

the Immersion

i

Immersion in

Length of Time between the Act of Brushing

of the Leaves in
tbe Solution

tlie Solution

and the Inflection of the Tentacles.

and the First

M

of Camphor.

Sign of the

?.

Inflection of the

^

Tcntacks.

1

5 m.

2

5 m.

3

5 m.

4

4 m.

5

4 m.

G

4 m.

7

4 m.

8

3 m.

9

3 m.

30

("3 m. considerable inflection ; 4 m. all)'
\ the tentacles except 3 or 4 inflected./
G m. first sign of inflection.
6 m. 30 s. slight inflection ; 7 m. 30 s.V

plain inflection. /

2 m. 30 s. a trace of inflection ; 3 m.V

plain ; 4 m. strongly marked. /
2 m. 30 s. a trace of inflection; 3 m.V

plain inflection. j,

2 m. 30 s. decided inflection ; 3 m. 30 s.'i

strongly marked. /

2 ra. 30 s. slight inflection; 3 mA

plain ; 4 m. well marked. /

2 m. trace of inflection ; 3 m. con-\

siderable, 6 m. strong inflection. J
2 m. trace of inflection ; 3 m. con- 1

siderable, G m. strong inflection, f

8 m.
11 m.
11m. 30 s.

7 m.

G m. 30 s.

G m. 30 s.

G m.30 s.

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

CnAr. IX. ESSENTIAL OILS, ETC. 211

elapsed, and two not until a few minntes 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 move-
ment of the tentacles of some of tliese 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 3 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 in-
flection; 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. It not only soon excites the ten-
tacles to bend, but apparently renders the glands sensitive to a
touch, Tvhich 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 condition, 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 movement
shows that the leaves had not been killed by an exposure
during 10 hrs. to the vapour of camphor.

Oil of Caraway.— Wsbter is said to dissolve about a thousandth
part of its weight of this oil. A drop w^as added to an ounce
of water and the bottle occasionally shaken during a day;
but many minute globules remained undissolved. Five leaves
w^ere immersed in this mixture ; in from 4 m. to 5 m. there was
Bome inflection, which became moderately pronounced in two or

212 DROSEEA EOTUNDIFOLIA. Chap. IX.

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 pecuHar dull-red colour, and 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-oz. 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— Bmnll 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 ten-
tacles 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 colour-
less. Minute drops (about J^ 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 mix-
ture 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 colour-
less. 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 oz.) of carbonate of
ammonia, their glands were b]acken<3d, their tentacles inflected,
and the protoplasm within their cells aggregated. It appears

CiiAP. IX. EFFECTS OF niEVIOUS IMMERSION. 213

from these facts that a mixture of four drops of glycerine to
an ounce of water is not poisonous, and excites very little in-
flection; but that pure glycerine is poisonous, and if applied
in very minute quantities to the glands of the outer tentacles
causes their inflection.

Tiie 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, espe-
cially 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 pro-
toplasm in the cells of the tentacles became in a few hours
strongly aggregated, showing that this salt had been absorbed
and taken effect.

A short immersion in water for 20 m. did not retard the sub-
sequent action of the phosphate, or of splinters of glass placed
on the glands ; but in two instances an immersion for 50 m. pre-
vented 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 arable 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,

214

DROSEKA EOTUNDIFOLIA.

CUAP. IX.

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. 30 m. a second
was slightly afifected ; 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 an-
other when subsequently placed in the phosphate solution. I
Jiere give a table summing up the results.

Name of the Salts and
Acids in Solution.

Rubidium chloride

Potassium carbonate

Calcium acetate
Calcium nitrate .
Magnesium acetate.

Magnesium nitrate .

Magnesium chloride

Barium acetate .
Barium nitrate .

Strontium acetate .

Strontium nitrate .

Alti minium chloride

Period of
Immersion

of the

Leaves in

Solutions

of one part

to 437 of

■water.

22 hrs.

20 m.

24 hrs.
24 hrs.
22 hi-s.

22 hrs.

22 hrs.

22 hrs.
22 hrs.

22 hrs.

22 hrs.

24 hrs.

Effects produced on the Leaves by their siibsc-
quent Immersion for stated periods in a
Solution of one part of phosphate of
ammonia to 8750 of water, or 1 gr. to
20 oz.

After 30 m. strong inflection of the

tentacles.
Scarcely any inflection until 5 hrs.

had elapsed.
After 24 hrs. very slisrht 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 leaf

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 whiih had either bten

slii^htly or not at all afleeted by tho

chloride became after 7 hrs. 30 m.

rather closely inflected.

Chap. IX. EFFECTS OF rEEVIOUS IMMERSION.

215

Name of the Salts and
Atids in Solution.

Aluminium nitrate .
L(nid chloride .

IMauGranese chloride
Lactic acid .

Tannic acid .
Tartaric acid
Citric acid .

Formic acid

Period of
Immersion

of the

Leaves in

Solutions

of one part

to 437 of

water.

Effects produced on the Leaves by their sub-
sequent Immersion for stated periods in a
Solution of one part of phosphate of
ammonia to 8750 of water, or 1 gr. to
20 oz.

After 25 hrs. slight and doubtful effect.

After 24 hrs. two leaves somewhat
inflected, 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. teutacles decidedly in-
flected, 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.

- In a large majority of these twenty cases, a varying degree of
injflection was slowly caused by the phosphate. In fonr cases,
however, the inflection was rapid, occurring in less than half an
hour or at most in 50 m. In three cases the phosphate did not
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 phos-
phate sohition. 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 pro-
duced, 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

216 DEOSEEA EOTUNDIFOLIA. Chap. IX.

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 phos-
phate 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 437 of water) of nitrate of potas-
sium 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 glands immediately blackened, and after 1 hr. their
tentacles somewhat inflected, and the protoplasm aggregated.
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 in-
flected. Four leaves were immersed in this mixture, and two of
them after 30 m. were brushed with a camel-hair brush, like the
leaves in the solution of camphor, but this produced no effect.

* See Dr. M. Traiibe's curious By allowing a precipitation of
experiments on the production of sulphate of barium to take place
artificial cells, and on their per- at the same time, the membrane
meability to various salts, de- becomes "infiltrated" with this
scribed in his papers : " Experi- salt ; and in consequence of the
mente zur Theorie der Zellenbil- intercalation of molecules of sul-
dung und Endosmose," Breslau, phate of barium among those of
.1860; and " Experimente zur the gelatine precijDitate, the mole-
physicalischen Erklarung der Bil- cular interstices in the membrane
dung der Zellhaut, ihres AVachs- are made smaller. In this altered
thums durch Intussusception," condition, the membrane no longer
Breslau, 1874. These researclies allows the passage through it of
perhaps explain my results. Dr. either sulphate of ammonia or
Traube commonly employed as a nitrate of barium, though it re-
membrane the precipitate formed tains its permeability for water
when tannic acid comes into con- and chloride of ammonia,
tact with a solution of gelatine.

Chap. IX. VAPOUR OF CHLOROFOKM. 217

Nor did these four leaves, on being left for 24 hrs. in tlie 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 their 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 afi'ected 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 being 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 to curve inwards, and after 55 m. nearly
all were considerably inflected ; but a few did not move. Some
ansesthethic 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
exposui'e during 5 m. to the vapour of alcohol.

Vapour of Chloroform.— The action of this vapour on Drosera
is 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 effect. The glands are sometimes

218 DROSERA ROTUNDIFOLIA. Chap. IX.

rendered for a time insensible to the action of raw meat, bnt
sometimes are not thus affected, or in a very slight degi-ee. 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. (539-6 ml.) 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. 30 m., but no further
movement ensued. After 21 hrs. the leaves appeared almost
dead.

A smaller bell-glass, holding 12 fluid oz. (340-8 ml.), was now
employed, 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 perpen-
dicularly 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 Tinder 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 coui'se 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 2 m. 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. 30 m. had elapsed.
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

Chap. IX." VArOUR OF ETUER. 219

moved for the next 40 m. 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 anaesthetic 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 19-oz. 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 altei-nately 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 nioving in 40 m.,
and two others in 54 m. 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 tliis case there could not be the least doubt that
the chloroform had exerted an anaesthetic 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 14 m. In this case, little or no
anaesthetic effect had been produced ; and how to reconcile-
these discordant results, I know not.

Vapour of Sul2'>linric 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 absorbed 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, except-
ing one which was ultimately a little inflected. The glands of
the other tentacles continued to secrete, and appeared uninjured,
but the whole i)lant after three days became very sickly.

220 DEOSEKA EOTUNDIFOLIA. Chap. IX.

In the two foregoing experiments the doses were evidently too
large and poisonous. With weaker doses, the anaesthetic 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 larger 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
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-
oz. 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 hrs. 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 much injured. In this and the previous experiment,
it is doubtful, owing to the injury w^hich the leaves had sufl"ered,
whether any anaesthetic effect had been produced.

A third plant, having two good leaves, was exposed for only
4 m. in the 19-oz. vessel to the vapour from six drops. Bits of
meat were then placed on the glands of seven tentacles on the

Chap. IX. CARBONIC ACID. 221

same leaf. A single tentacle moved after 1 hr, 23 m. ; after
2 lirs. 3 m. several were inflected ; and after 3 hrs. 3 m. all the
seven tentacles with meat were well inflected. From the slow-
ness 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
8 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.

Carho7nc 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 meat placed on the glands of three leaves. One of
these leaves hung a little down, and was at first partly and soon
afterwards comi3letely 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, I 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.

222 DKOSEEA KOTUNDIFOLIA. Chap. IX.

A plant was exposed in the same vessel to the gas for 45 m., and
bits of meat were then placed on four glands. Bnt the ten-
tacles 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 con-
siderably inflected ; those with the meat not in the least degree
more than the others. On a second leaf, which was rather
old, 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 ten-
tacles 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 extremely 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 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 on one of these latter
leaves, it had not perfectly recovered its excitability and x^wer
of movement in 22 hrs. ; but another leaf, after an additional
24 hrs., had completely recovered, 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

Chap. IX. SUMMARY OF THE CIIArTEIl. -22.^)

a fresh leaf from another plant. The latter had most of its
tentacles strongly inflected within 30 m. ; whereas the leaf which
had been exposed to the carbonic acid remained for 24 hrs, in
the solution without undergoing any inflection, with the excep-
tion 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 tJie 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 in-
fluence on the nervous system of animals. I was at
first encouraged in my trials by finding that strych-
nine, digitaline, and nicotine, which all act on the
nervous system, were poisonous 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 in-
nocuous acids, though much diluted, such as benzoic,
acetic, &c., as well as some essential oils, are ex-
tremely poisonous to Drosera, and quickly cause
strong inflection, it seems probable that strychnine,
nicotine, digitaline, and hydrocyanic acid, excite in-
flection 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, atro-
pine, veratrine, colchicine, curare, and diluted alcohol
would have produced some marked effect; whereas

224' DROSERA ROTUNDIFOLIA. Chap. IX.

these substances are not poisonons and have 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, mercury, 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 j)oisonous to
this plant. It is an equally strange fact, that, though
acetic and propionic 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 pharmacopoeia would be requisite ta describe the
diversified efl'ects of various substances on Drosera. t

* Dr. Fayrer, 'The Thanato- cyanic, and chromic acids, ace-

phidia of India,' 1872, p. 4. tate of strychnine, and -vapour of

t Seeing that acetic, hydro- ether, are poisonous to Drosera,

Chap. IX. SUMMARY OF THE CIIAPTEK. 225

Of tlie 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 mode-
rate power of this kind; others, again, such as the
acetate of quinine and digitaline, caused strong in-
flection.

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
coagulation 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 im-
mersion in nicotine, curare, and even water, blackens
the glands ; and this, I believe, is due to the aggre-
gation 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 solu-
tion of sulphate of quinine exhibited incessant

it is remarkable that Dr. Eansom cally, with the exception of chloro-

(Thilosoph. Transact.' 18G7, p. form and carbonic acid." I find

480), who used mnch stronprer it stated by several writers that

solutions of these substances than curare has no influence on sarcode

I did, states " that the rhythmic or protoplasm, and we have seen

contractility of the yolk (of the that, though curare excites some

ova of the pike) is not materially degree of inflection, it causes very

influenced by any of the poisons little aggregation of the proto-

UBed, wliich did not act chemi- plasm.

226 DEOSERA ROTUNDIFOLIA. Chap. IX.

changes of form, but after 24 lirs. were motionless;
the leaf bemg 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 proto-
plasmic masses were unusually active, whilst with
the hio-her animals the vibratile cilia and white

o

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 a^^plies 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 arable has
no such inhibitory power. The solutions of 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 uj)
by the molecules of the salts first given in solution,
so that water could not afterwards enter, though the
molecules of the phosphate could do so, and those of
the carbonate still more easily.

CuAP. IX SUMMARY OF THE CHAPTER. 227

The action of camphor dissolved in water is remark-
able, for it not only soon induces inflection, but
apj^arently 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
2 m. 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
poisonous, does not induce inflection, nor increase the
sensitiveness of the glands to mechanical irritation.
The vapour acts as a narcotic or anaesthetic, 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, it is
probable that they are likewise absorbed by the sto-
mata of Drosera. They sometimes excite extraordi-
narily rapid inflection, but this is not an invariable
result. If allowed to act for even a moderately long
time, they kill the leaves ; whilst a small dose acting
for only a short time serves as a narcotic or ansesthetic.
In this case the tentacles, whether or not they have

228 DEOSEKA KOTUNDIFOLIA. Chap. IX.

become inflected, are not excited to further move-
ment by bits of meat placed on the glands, imtil
some considerable time has elapsed. It is generally
believed that 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 sub-
jected for two hours to this gas and then immersed in
a solution of the carbonate of ammonia is much re-
tarded, so that a considerable time elapses before the
protoplasm in the lower cells of the tentacles becomes
aggregated. 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 pre-
sume, to the excitement from the access of oxygen.
These inflected tentacles, however, could not be ex-
cited for some time afterwards to any further move-
ment by their glands being stimulated. With other
irritable plants it is known* that the exclusion of
oxygen prevents their moving, and arrests the move-
ments of the protoplasm within their cells, but this
arrest is a different phenomenon from the retardation
of the process of aggregation 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, ' Traitd de Bot.' 1874, pp. 846, 1037.

Chap. X. SENSITIVENESS OF THE LEAVES. 229

CHAPTEK 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 move-
ments — Nature of the motor impulse — Ee-expansion of the ten-
tacles.

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 ten-
tacles often became inflected. These headless ten-
tacles frequently re-expanded ; and when afterwards
dropa 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
subsequent 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.

230 DROSERA ROTUNDIFOLIA. Chap. X.

It is probable lliat they were killed so instantly that
they were not able to transmit any motor imj^nlse ; 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 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 aggregation supervened.

The pedicels of the tentacles were roughly and re-
peatedly rubbed; raw meat or other exciting sub-
stances were placed on them, both on the upper
surface near the base and elsewhere, but no dis-
tinct movement ensued. Some bits of meat, after
beijag 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 sufiiced to cause the
slight degree of movement observed. Nitschke* says

Bot. Zeitung,' 1860, p. 234.

Chap. X. SENSITIVENESS OF THE LEAVES. 231

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
papillae, which do not secrete, but have the power of
absorption. These papillae 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, crtished flies, and various substances, placed on
others. These substances 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, Mtschke states* that, after
affixing objects to the backs of leaves by the aid of
the viscid secretion, he repeatedlij saw the tentacles
(and in one instance the blade) become reflexed.
This movement, if a true one, would be most ano-
malous; 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

* * Bot. Zeitung,' 1860, p. 437.
11

232 DEOSERA KOTUNDIFOLIA. Chap. X.

cases ; but this is not strictly true, for in three in-
stances 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 cer-
tainly in the blade of another. After twelve addi-
tional hours, the glands began to dry, and all three
leaves seemed much injured. Four leaves were then
placed under a bell-glass, with their footstalks in
water, with drops of syrup on their backs, but without
any meat. Two of these leaves, after a day, had a few
tentacles reflexed. The drops had now increfised con-
siderably 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

CuAP. X. SENSITIVENESS OP THE LEAVES. 233

facts we may conclude that drops of syrup placed on
the backs of leaves do not act by exciting a motor
impulse which is transmitted to the tentacles ; but
that they cause reflexion 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 pro-
bably 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 in-
flected, and by the amount and rate of their move-
ment. Equally vigorous leaves, exposed to the same
temperature (and this is an important condition),
are excited in different degrees under the following
circumstances. A minute quantity of a weak solu-
tion 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 par-
ticles of glass (which acts only mechanically), of
gelatine, and raw meat, are placed on the discs of
several leaves, the meat causes far more rapid, ener-
getic, and widely extended movement than the two
former substances. The number of glands which are
excited also makes a great diflerence in the result :
place a bit of meat on one or two of the discal

234 DROSEKA EOTUNDIFOLIA. Chap. X.

glands, and only a few of the immediately surround-
ing sliort 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 im-
pulse 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 ten-
tacles become 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 neigh-
bouring 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

Chap. X. TRANSMISSION OF MOTOR IMPULSE. 235

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 ten-
tacles 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 ten-
tacles 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 out-
side, 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 ex-
terior tentacles. In one of these cases only a single
tentacle on each side of the one with meat was
affected. In the three other cases, from half a dozen
to a dozen tentacles, both laterally and towards the
centre, were well inflected or sub-inflected. Lastly, in

236 DKOSERA EOTUNDIFOLIA. Chap. X.

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 adjoin-
ing 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 radiat-
ing 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 ten-
tacles 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 ten-
tacles, so that it is able to spread to a considerable
distance 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 proxi-
mal ends of the leaf (i. e. towards the apex and base)
than on either side ; and yet the tentacles on the sides
stood as near to the gland M-here the bit of meat lay
as did those at the two ends. It thus appeared as

Chap. X. TRANSMISSION OF MOTOR IMPULSE. 237

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
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 miniite fragment of a fly was placed on one side of the
disc, and after 32 m. seven of tlie outer tentacles near the frag-
ment were inflected ; after 10 hi-s. 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 ten-
tacle 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.

238 DEOSEEA EOTUNDIFOLIA. Chap. X.

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 in-
flected; 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 thi-ee 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.

Now for the general results. Of the eigliteen 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 itseK on this side was likewise in-
flected ; whereas not a single tentacle nor the blade
was affected on the opposite side. These leaves pre-
sented a very curious appearance, as if only the in-
flected 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 con-
siderably after that on the same side, and in one in-
stance not until the fourth day. We have also seen

Chap. X. TRANSMISSION OF MOTOR IMPULSE. 239

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 experi-
ments thus made, owing either to the state of the leaf
or to the smallness of the bit of meat, only the im-
mediately 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 em-
ployed, 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 difierence. 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 in-
flected. 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 ten-
tacles on the opposite side somewhat inflected, this
being due to the large size of the cubes. Finally we
may conclude from these thirty-five experiments, not
to mention the six or seven previous ones, that the
motor impulse is transmitted from any single gland

240 DEOSEEA EOTUXDIFOLIA. Chap. X

or small group of glands through the blade to the
other tentacles 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 otherwise 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 nitro-
genous 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 ex-
cited. Thus, when moderately large bits of meat were
placed on one side of the disc, and the discal and sub-
marginal tentacles on the opposite side became in-
flected, 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 undoubtedly would have
affected the exterior rows. Nevertheless, 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
discharp^ed within a few seconds, as we know from the

Chap. X. TEANSMISSION OF MOTOR IMPULSE. 241

bending of tlie tentacle; and it appears to be dis-
charged at first with much greater force than after-
wards. 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 tentacles on the 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 influence 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 surrounding 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 con-
tinued healthy for ten days after the operation. I
therefore cut the glands off twenty-five tentacles,
at different times and on different leaves, and seven-
teen of these soon became inflected, and afterwards
re-expanded. The re-expansion commenced in about

242 DKOSEKA ROTUNDIFOLIA. Chap. X.

8 hrs. or 9 hrs., and 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 additional 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, how-
ever, 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 under-
gone far less aggregation. From these experiments
with headless tentacles it is certain that the glands
do not, as 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 aggrega-
tion, which in certain cases may be called reflex, and
it is the only known instance in the vegetable king-
dom. We should bear in mind that the process does
not depend on the previous 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 ammonia or an infusion of raw meat. When a gland
is directly stimulated in any way, as by the pressure of
a minute particle 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 ; —

Chap. X. DIEECTION OF INFLECTED TENTACLES. 243

that is, if tlie 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 com-
mences in their glands, though these have not been
directly excited, but have only received some influ-
ence from the disc, as shown by their increased acid
secretion. The protoplasm within the cells immedi-
ately 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 protopla'sm last
aggregated is first redissolved. This probably depends
merely on the protoplasm being less and less aggre-
gated, 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.

244

DROSEKA EOTUNDIFOLIA.

Chap. X.

p. 10). The short tentacles within this ring still
retain their vertical position, as they likewise do when
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 con-
tact 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 excitement. We owe
this capital observation to
Kitschke,* and since read-
ing his paper a few years
ago, I have repeatedly
verified it. If a minute bit
of meat be placed by the
aid of a needle on a single
gland, or on three or four
together, halfway between
the centre and the circum-
ference of the disc, the
directed movement of the

^bir of meat placed on one side of g^rOUudiug tCntaclcS is

well exhibited. An accu-
rate drawing of a leaf with meat in this position is
here reproduced (fig. 10), and we see the tentacles, in-
cluding some of the exterior ones, accurately directed
to the point where the meat lay. But a much better

Fig. 10.

(^Drosera rotundifolia.')

Leaf (enlarged) with the tentacles inflected

over
thei

* *Bot. Zeitimg,' 18G0, p. 240.

CuAP. X. DIRECTION OF INFLECTED TENTACLES. 245

plan is to place a particle of the pliospliate 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 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 disc 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 themselves 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 tentacles
generally were directed, those near the circumference
of one leaf were not accurately directed towards some
phosphate of lime at a rather distant point on the
opposite side of the disc. It appeared as if the motor

246 DKOSERA EOTUNDIFOLIA. Chap. X.

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 appear-
ance of the above four leaves, each with their ten-
tacles 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 point 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 the extreme marginal tentacles
of above a dozen rows. As the flattened bases are
thus foiTQed of only a few rows of cells, the precision
of the movements of the tentacles is the more remark-
able ; 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 fii'st, 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

Chap. X.

CONDUCTING TISSUES.

247

^V.A

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 to-
wards 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 ivhich the Motor
Lrqmlse is Transmitted. — It will be necessary first
to describe briefly the
course of the main fibro-
vascular bundles. These
are shown in the accom-
panying sketch (fig. 11)
of a small leaf. Little
vessels from the neigh-
bouring bundles enter
all the many tentacles
with which the surface
is studded; but these
are not liere 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

Fig. 11.

(Drosera rotundi/olia.')

Diagram showing the distribution of the

vascular tissue in a small leaf.

248 DKOSEKA KOTUNDIFOLIA. Chap. X.

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 inoscu-
lation between the two chief branches of the lateral
bundle. The course of the vessels is very complex
at the larger inosculation ; and here vessels, retain-
ing 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 circumference.
But the union of the vessels in this zigzag line seems
to be much less intimate than at the main inoscula-
tion. 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
inosculation is always present.

Now in my first experiments 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 a vessel passed over to the opposite side, it seemed
probable that the motor impulse was conducted ex-
clusively 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

Chap. X. CONDUCTING TISSUES. 249

(a most powerful stimulant) near the centre of the
disc above the incision — that is, a little towards the
apex — with the following results : —

(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 dis-
tinct 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. 80 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 cer-
tainly 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 ex-
tremities paralysed. Excepting that the line between
the two halves was here transverse instead of longitu-
dinal, 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)

* M. Ziegler made similar ex- ('Comptes rendiis,' 1874, p. 1417),
periments by cutting the spiral fcut arrived at eonclusioua widely
vessels of Drosera inter inedia different from mine.

250 DKOSEEA ROTUNDIFOLIA. Chap. X.

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. But 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 a transverse direction across the whole breadth of
the leaf. JSTor can this latter fact be accounted for
by supposing that the transmission is effected 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 ten-
tacles; so that the marginal ones are more closely
connected together by spiral vessels than are the
others, and yet have much less power of communi-
cating a motor impulse to one another.

But besides these several facts and arguments we
have conclusive evidence that the motor impulse is
not sent, 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 sur-

Chap. X. CONDUCTING TISSUES. 251

rounding tentacles bend almost simnltaneously 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 surrounding 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. It is, of course, pos-
sible 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 transmitted in straight radiating
lines from the excited gland to the surrounding ten-
tacles ; it cannot, therefore, be sent along the fibro-
vascular bundles. The effect of cutting the central
vessels, in the above cases, in preventing the transmis-
sion 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 Dionaea, that this same
conclusion, namely that 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 Droseracese.

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

252 DROSERA ROTUNDIFOLIA. Chap. X.

the blade more quickly in a longitudinal 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 game brief
space of time. It seems therefore probable that the
motor impulse consists of the first commencement of
a molecular change in the protoplasm, which, when
well developed, is plainly visible, and has been desig-
nated aggregation ; but to this subject I shall return.
We further know that in the transmission of the aggre-
gating 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 suc-
cessive 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.

The greater celerity with which the impulse is
transmitted down the long exterior tentacles than
across the disc may be largely attributed to its being
closely confined within the narrow pedicel, instead
of radiating forth on all sides as on the disc. But
besides this confinement, the exterior cells of the ten-
tacles 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 ten-
tacles given by Dr. Warming,* the parenchymatous

* ' Videnskabelige Meddelelser de la Soc. d'Hist. nat. de Copen
hague,' No3. 10-12, 1872, woodcuts iv. and v.

CiiAT. X. CONDUCTING TISSUES. 253

cells are shown to be still more elongated ; and these
would form the most direct line of communication from
the gland to the bending place of the tentacle. If the
impulse travels down the exterior cells, it would have
to cross from between twenty to thirty transverse par-
titions ; but rather fewer if down the inner parenchy-
matous tissue. In either case it is remarkable that
the impulse is able to pass through so many par-
titions 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
transmitted 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 ex-
terior rows of tentacles tends to travel laterally and
towards the centre of the leaf, but not centrifugally, is
by no means clear.

254 DliOSERA EOTUNDIFOLIA. Chap. X.

Mechanism of the Movements, and Nature of the
Motor Impulse. — Whatever 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 in-
flected tentacle, which was somewhat thinner than the
bristle. The amount or extent, also, of the moA^ement
is great. Fully expanded tentacles in becoming in-
flected sweep through an angle of 180^; and if they
are beforehand reflexed, as often occurs, tile 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 to a 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 complete 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 afi'ected ; about half-
way down there is a slight bending, but the chief
movement is confined to a short space near the base ;
and no part of the inner tentacles 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

Chap. X. MEAN3 OF MOVEMENT. " 25D

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 con-
tract.* Whether or not this is the primary cause of
such movements, fluid must pass out of closed cells
when they contract or are 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.t In the case
of Drosera there is certainly much movement of the
fluid throughout the tentacles whilst they are under-
going inflection. 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

* Sachs, 'Traite de Bot.' 3rd Lamarck,
edit. 1874, p. 1038. This view f Sachs, ibid. p. 919.

was, I believe, first suggested by

12

256 DKOSERA ROTUNDIFOLIA. Chap. X.

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 in-
flection 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 im-
mersed in a dense fluid, and their subsequent re-
expansion in a less dense fluid, show that the passage
of fluid from or into the celJs can cause movements
like the natural ones. But the inflection thus caused
is often irregular^ the exterior tentacles being some-
times 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 tension, and that they are
elastic to an extraordinary degree ; for 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 Compositse, 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

* ' Abhand. der Schles. Gesell. is given in the * Annals and Mag.
fiir vaterl. Cultur/ 18G1, Heft i. of Nat. Hist.' 3rd series, 18G"3,
An excellent abstract of this paper vol. xi. pp. 188-197.

Ci!Ai>. X. MEANS OF MOVEMENT. 257

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 irri-
tated 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 homogeneous, 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,

258 DROSEKA KOTUNDIFOLIA. Chap. X.

though 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 organisa-
tion ; 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 aggrega-
tion. 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 consequent closing in of the walls.
Anyhow, the movement can hardly b*e 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 pedi-
cels 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 ten-
tacles 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

Chap. X. ' NATURE OF THE MOTOR IMPULSE. 259

protoplasm is redissolvecl at the bending -place shortly
before the tentacles re-expand, showing that the ex-
citing 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 aggre-
gating 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 htgh power the first sign of aggregation is the ap-
pearance 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 com-
municated to the inner surfaces 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
wdien leaves are immersed in various strong solu-
tions, or are subjected to a heat of above 130°
Fahr. (54°4 Cent.), aggregation 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 aggre-
gating process by injuring or killing the protoplasm.
There is another and more important difference in the
two processes : when the glands on the disc are ex-
cited, they transmit some influence up the surrounding

260 DROSEEA EOTUNDIFOLIA. Chap. X.

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 in-
fluence, causing the protoplasm to aggregate, first in
the upper and then in the lower cells.

The Be-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 solu-
*tion, 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 ten-
tacles 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 recom-
menced, 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 pre-
viously been in a state of tension, sufficient to counter-
balance that of the concave surface, which, when free,
curled into a complete ring.

The tentacles of an expanded and unexcited leaf

Chap. X. EE-EXPANSION OF THE TENTACLES. 261

• 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 in-
flected. 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 tentacles
suddenly become reflexed, and this apparently indi-
cates that the tension of the outer surface is mecha-
nical, 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 suflice 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 surface, their
tension being thus gradually and continually in-
creased.

A recapitulation of the chief facts and discussions
in this chapter will be given at the close of the next
chapter.

2()2 DROSERA ROTUNDIFOLIA. Chap. XI.

CHAPTEE 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 sen-
sitive to various stimulants, namely repeated touches,
the pressure of minute particles, the absorption of
animal matter and of various fluids, heat, and gal-
vanic 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 in-
fluence 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,

Chap. XI GENERAL SUMMARY. 263

namely from the gland on the summit of the same
tentacle, and from one or more glands of the neigh-
bouring tentacles. Tentacles, when inflected, re-ex-
pand 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.

It was shown in the second chapter that animal sub-
stances 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 in-
flected 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 xoVo of an inch ('203 mm.) in
length, and weighing only y^|4-o of a grain (-000822
mg.), though largely supported by the dense secre-
tion, 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.

264 DEOSERA EOTUNDIFOLIA. Chap. XI.

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 surrounding plants. Though
insensible to a single touch, they are exquisitely sensi-
tive, as just stated, to the slightest pressure if pro-
longed for a few seconds ; and this capacity is ma-ni-
festly 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 con-
tents of which first become 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-
er necklace-like, or otherwise shaped masses of proto-
plasm, 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 aifected. In cells, especially
if filled with dark red fluid, the first step in the

Chap. XI. GENERAL SUMMARY. 265

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 prim-
ordial utricle of Mohl), flows round the walls of the
cells; and this becomes more distinct after the con-
tents 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 all 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 ttAu^ 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 centri-
fugally 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 exterior tentacles down their pedicels. The ex-
citing influence, therefore, which is transmitted from

266 DKOSERA ROTUNDIFOLIA. Chap. XL

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 inde-
pendent of the inflection of the tentacles. It con-
tinues 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 proto-
plasmic fluid must, therefore, be in a singularly un-
stable 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. Therefore it
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 -j-^ywu o^ ^ grain and largely supported
by the dense secretion, for this excessively slight
pressure soon causes a visible change in the proto-
plasm, which change is transmitted down the whole
length of the tentacle, giving it at last a mottled
appearance, distinguishable 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. (43°*3 Cent.) become somewhat inflected ;
they are thus also rendered more sensitive to the action

Chap. XL GENERAL SUMMARY. 2G7

of meat than they were before. If exposed to a tem-
perature of between 115° and 125° (46°-l— 51°-6 Cent.),
they are quickly inflected, and their protoplasm under-
goes aggregation ; when afterwards placed in cold water,
they re-expand. Exposed to 130° (54°-4 Cent.), no in-
flection 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 then immersed in a solution of carbonate
of ammonia, strong aggregation ensued. Leaves placed
in cold water, after an exposure to so high a tem-
perature as 145° (62°-7 Cent.), sometimes become
slightly, though slowly, inflected ; and afterwards have
the contents of their cells strongly aggregated by car-
bonate of ammonia. But the duration of the immer-
sion 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 albu-
men,, 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 con-
siderably in their power of resisting heat. Unless the
heat has been sufficient to coagulate the albumen, car-
bonate 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 decoction of green peas or
of fresh cabbage-leaves acts almost as powerfully as an
infusion of raw meat ; whereas an infusion of cabbage-

208 DKOSERA ROTUNDIFOLIA. Chap. XI.

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 j)eas
or cabbage-leaves.

These results led me to inquire whether Drosera
130ssessed the power of dissolving solid animal matter.
The experiments proving that the leaves are capable
of true digestion, and that the glands absorb the di-
gested 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 secrete more copiously and the secretion to be-
come acid, as if they had been directly excited by
an object placed on them. The gastric juice of ani-
mals contains, as is well known, an acid and a fer-
ment, both of which are indispensable for digestion^
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 gther
such objects were placed on the glands of Drosera,
the secretion, and that of the surrounding and un-
touched 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 jDeptogenes,
are absorbed; and it apj^ears 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

Chai-. XL " GENERAL SUMMARY. 2G9

an alkali, which entirely arrested the process of diges-
tion, 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, conclude 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, as is
known to "be the case with some of these same sub-
stances 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 simj^ly 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 some-
times kills, or injures, as shown by the diseased state

270 DKOSEKA ROTUNDIFOLIA. Chap. XI.

of the seedlings. It also absorbs matter from pollen,
and from fragments of leaves.

The seventh chapter was devoted to the action of
the 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.
Biit 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 ml.) of solutions
of different strengths on the discs of the leaves, — by
applying a minute drop (about the -^^ of a minim, or
•00296 ml.) 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 in a 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 containing -^^ of a grain
(•0675 mg.) is the least quantity which, when placed
on the glands of the disc, excites the exterior ten-
tacles to bend inwards. But a minute drop, contain-
ing TTT-o-i7 of a grain (•OOMo mg.), if applied for a few
seconds to the secretion surrounding a gland, causes
tlie inflection of the same tentacle. When a highly
sensitive leaf is immersed in a solution, and there is
ample time for absorption, the ^^,^\oo of a grain

Chap. XL GENEEAL SUMMARY. 271

(•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 contain-
ing -2-rV-o 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 -^-g^'^j ^^ ^ grain caused only a few of these
tentacles to bend, but affected rather more plainly the
blade. A minute drop applied as before, and contain-
ing ^^l^^Q of a grain (-0025 mg.), caused the tentacle
bearing this gland to bend. By the immersion of
whole leaves, it was proved that the absorption by a
single gland of ^ .^ I'o o o ^^ ^ grain ('0000937 mg.) was
sufficient to set the same tentacle into movement.

The phosphate of ammonia is much more powerful
than the nitrate. A drop containing ^Vt-o of a grain
(•0169 mg.) placed on the disc of a sensitive leaf
causes most of the exterior tentacles to be inflected,
as well as the blade of the leaf. A minute drop con-
taining ■, ^ s'tj 0 0 of a grain (-000423 mg.), applied for a
few seconds to a gland, acts, as shown by the move-
ment of the tentacle. When a leaf is immersed in
thirty minims (1-7748 ml.) of a solution of one part by
weight of the salt to 21,875,000 of water, the absorp-
tion by a gland of only the -rgTuVo-cro of a grain
(-00000328 mg.), that is, about the one-twenty-mil-
lionth of a grain, is sufficient 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,

272 DROSERA ROTUNDIFOLIA. Chap. XL

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 othpr necessary elements are pre-
sent. 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 movement 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 transmit-
ting 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 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 poison-
ous in small doses ; whereas seven of the nine corre-

Chap. XL GENERAL SUMMARY. 273

sponding 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 widelv 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 in-
flection, and is not poisonous ; whereas acetic acid of
the same strength acts most powerfully and is poi-
sonous. 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.

274: DEOSEKA EOTUNDIFOLIA. Chap. XL

In the ninth chapter the effects of the absorption of
various alkaloids and certain other substances were
described. 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 transmitting 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-
ments of the protoplasm in the cells of the tentacles.
Solutions of various salts and acids behave very dif-
ferently in delaying or in quite arresting the sub-
sequent 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 stimu-
lant. The vapours of camphor, alcohol, chloroform,
sulphuric and nitric ether, are poisonous in moderately
laro:e doses, but in small doses serve as narcotics or
anaesthetics, greatly delaying the subsequent action
of meat. But some of these vapours also act as stimu-
lants, 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 pharma-
copoeia 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 sensitive-

Chap. XL GENEKAL SUMMAEY. 275

ness of the leaves apj)ears 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-yascular 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 cele-
rity in a longitudinal than in a transverse line across
the disc. The impulse proceeding 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 considerable, distance ; but after-
wards, whilst the gland is secreting and absorbing,
the impulse suffices only to keep the same tentacle

276 DEOSERA ROTUNDIFOLIA. Chap. XI.

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 immer-
sion 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 pre-
cision 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 en-
dowed 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 diff'erent sides of the surrounding tentacles must
be acted on, in order that all should bend with pre-
cision to the point of excitement.

The motor impulse, as it spreads from one or more
glands across the disc, enters the bases of the sur-
rounding tentacles, and immediately acts on the bend-
ing 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 secre-
tion is soon increased and rendered acid; and 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 proto-
plasm to aggregate in cell beneath cell. This may

Chap. XL GENERAL SUMMARY. 277

be called a reflex action, though probably very dif-
ferent 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 hypo-
thesis 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 con-
tracting 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 struc-
ture, movements, constitution, and habits of Drosera
rotuiidifolia ; and we see how little has been made out
in comparison with what" remains unexplained and
unknown.

278 DKOSEKA ANGLIOA. Chap. XH.

CHAPTEK XII.

On the STKrCTUKE AND MOTEME^"TS OF SOME OTHER SpECIES OF

Droseka.

Drosera anglica — Drosera intermedia — Drosera capensis — Drosera
spathulata — Drosera filiformis — Drosera hinata — Concluding
remarks.

I EXAMINED six other species of Drosera, some of
them inhabitants of distant countries, chiefly for the
sake of ascertaining 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 tMs 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 | 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 par-
ticles, 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 fi'e-
quently 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

♦ Mrs. Treat has given an ex- synonym in part of Drosera an-

cellent account in ' The American glica), of Drosera rotundifolia and

NaturaHst,' December 1873, p. 705, filiformis.
oi Drosera longifolia (which is a

Chap. XII. DROSERA CAPENSIS. 279

1 m. 30 s. ; 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 super-
fluous precautions having been taken on account of M. Ziegler's
statements. One of the particles of cinder 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 proto-
plasm. 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 anglua behave like
those of Drosera rotund/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 differ-
ence 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. The tentacles are excited
into movement by all the causes above specified ; and aggregation
ensues, with 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,
shghtly concave along the middle and taper towards the apex.

280 DKOSERA SPATHULATA. Chap. XII.

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. Never-
theless, 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 tentacles
moving 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. Particles 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 ex-
tremely sensitive to very small doses of the nitrate of ammonia,
namely to about -^^ of a minim of a solution (one part to 5250
of water), containing only yy-Voo ^f 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.
■ Brosera 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 aggrega-
tion could be seen travelling rapidly down the cells of the ten-
tacles ; and the granules of protoplasm soon united into spheres
and variously shaped masses, which displayed the usual move-

Chap. XII. DEOSEEA FILIFORMIS. 281

ments. 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. gio 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 butterflies. 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 flat and slightly channelled. The whole convex
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 liWle
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 flies 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 hinata (or dichotoma).—! am much indebted to Lady

American Naturalist,* Dec. 1873, p. 705.

282 DROSEEA BINATA. Chap. XII.

Dorothy Nevill for a fine plant of this almost gigantic Australian
species, which differs in some interesting points from those pre-
viously 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, curl-
ing about in an irregular manner. It is narrow, being only -^
of an inch in breadth. One blade was 7^ 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 particies
of glass acted in 4 m. 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 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 mar-
ginal 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 iDlaced on the glands in the
medial furrow did not stimulate them sufficiently 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

Chap. XIL DEOSEKA BINATA. 283

of ammonia to 218 of water (1 gr. to 2 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 Dion sea and Drosophyllum. In
this latter genus they are associated, as in the present case, with
glands which secrete spontaneously, that is, without being
excited.

Drosera bhiata presents another and more remarkable pecu-
liarity, 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 sur-
rounded by drops of viscid secretion, and they have the power of
absorbing. This latter fact was shown by the glands imme-
diately becoming black, and the protoplasm aggregated, 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 irre-
gularly. 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 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. Eather 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

284 CONCLUDING EEMAKKS. Chap. Xn.

moved towards the middle of the lower surface, for there aro
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 chap-
ter we shall see that Drosophyllum, with its elongated leaves,
probably represents the condition of an early j^rogenitor of the
genus Drosera; and none of the tentacles of Droso^Dhyllum, 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
h'lnata 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 RemarJcs. — From what we have now sec;i,
there can be little doubt that most or probably all the
species gf 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 2>ciUida and
Drosera sulj)hurea, " close their leaves upon insects with
" great rapidity : and the same phenomenon is mani-
" fested by an Indian species, D. lunata, and by several
" of those of the Cape of Good Hope, especially by
"D. trinervisJ' Another Australian species, Drosera
lieterojplujila (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. Th'e

Gardener's Chronicle,' 1874, p. 209.

CuAr. XII. CONCLUDING KEMAKKS. 285

inner surface and the edges of the cups are studded
with tentacles, which include fibro-vascular bundles,
rather diiferent from those seen by me in any other
species ; for some of the vessels are barred and punc-
tured, instead of being spiral. The glands secrete
copiousl}^ judging from the quantity of dried secretion
adhering to them.

286 DION^A MUSCIPULA. Chap. XIII.

CHAPTER XIII.

DiONiEA MUSCIPULA.

Structure of the leaves — Sensitiveness of the filaments — Eapid
movement of the lobes caused by irritation of the filaments —
Glands, their power of secretion — Slow movement caused by the
absorption of anmial matter — Evidence of absorption from the
aggregated condition of the glands — Digestive power of the secre-
tion— Action of chloroform, ether, and hydrocyanic acid — The
manner in which insects are captured — Use of the marginal
spikes — Kinds of insects captured — The transmrssion of the motor
impulse and mechanism of the movements — Ke-expansion of the
lobes.

This 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 Droseraceae, and is found only in
the eastern part of North Carolina, growing in damp
situations. The roots are small ; those of a mo-
derately 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;
for a gardener, who has been very successful in the
cultivation of this plant, growls it, like an epiphytic
orchid, in well-drained damp moss without any soil.f
The form of the bilobed leaf, with its foliaceous foot-
stalk, is shown in the accompanying drawing (fig. 12).

* Dr. Hooker, in his address to the habits of this plant, that it

the British Association at Belfast, would be superfluous on my part

1874, has given so full an.histori- to repeat them.
cal account of the observations f 'Gardener's Chronicle,' 1874,

which have been published on p. 464.

Chap. XIII. STRUCTURE OF THE LEAVES. 287

The two lobes stand at rather less than a right angle
to each other. Three minute pointed processes or
filaments, placed triangularly, project from the upper
surfaces of both ; but I hav0 seen two leaves with four
filaments on each side, and another with only two.
These filaments are 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 projections
which I will call spikes, into each of which a bundle

Fig, 12.

(Bionaa muscipula.')

Leaf viewed latcrallj- in its expanded state.

of spiral vessels enters. The spikes stand in sucli
a position that, when the lobes close, they inter-lock
like the teeth of a rat-trap. The midrib of the
leaf, on the lower side, is strongly developed and
prominent.

The upper surface of the leaf is thickly covered,'
excepting towards the margins, with minute glands of
a reddish or 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

288 DION^A MUSCIPULA. Chap. XIII.

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 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
foot-stalk, 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
papillae on the leaves of Drosera rotundifolia. There
are also a few very minute, simple, pointed hairs,
about T^hro ("0148 mm.) of an inch in length on the
backs of the leaves.

The sensitive filaments 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 to a 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 constrictiojQ, 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 liable
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, are ex-
quisitely sensitive to a momentary touch. It is scarcely

Chap. XIII. SENSITIVENESS OF FILAMENTS. 289

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, 2J inches
in length, held dangling over a filament, and swayed
to and fro so as to touch it, did not excite any move-
ment. 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 length being sufficiently rigid to sup-
port 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 momen-
tary 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 of rather thick human hair, -and these did not.,
excite movement, although they were more than ten
times as long as those which caused the tentacles 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 considerable force, and no movement
ensues. This singular difference in the nature of
the sensitiveness of the filaments of Dionsea and of

290 DIONiEA MUSCIPULA. Chap. XIII.

the glands of Drosera eyidently stands in relation to
the habits of the two plants. If a 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 Diontea 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 dro23S of a solution of car-
bonate of ammonia (one part to 146 of water), placed
on two filaments, not producing 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 same
solution, the fluid within the basal cells became almost
instantly aggregated into purplish or colourless, irre-
gularly shaped masses of matter. The process of
aggregation gradually travelled up the filaments from
cell to cell to their extremities, that is in a reverse
course to what occurs in the tentacles of Drosera when
their glands have been excited. Several other fila-
ments were cut off close to their bases, and left for 1 hr.
oO m. in a w^eaker 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

Chap. XIIL SENSITIVENESS OP FILAMENTS. 291

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 Dionasa behave exactly
like the tentacles of Drosera.

Notwithstanding this similarity there is one re-
markable 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 pro-
duced by touching the filaments of Dionsea ; I com-
pared, 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 sensitive. No doubt, as in the
case of Drosera, the plant is indifferent to the heaviest
shower of rain. Drops of a solution of a 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 being received

292 DION^A MUSCIPULA. Chap. XI 11.

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
solution 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. 10 m., and three other leaves for
some minutes, in water at temperatures varying be-
tween 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 be in
good condition, as they closed when their filaments
were touched. Nevertheless two fresh leaves on being
dipped into water at 75° and 62^° (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 immersion 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.

Chap. XIII. SENSITIVENESS OF FILAMENTS. 293

I am confirmed in this belief by the effects of
immersing a leaf of Dionaea 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, the tips of the marginal
spikes crossing in 2 m. 30 s., and the leaf being com-,
pletely 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 fila-
ments, 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 cells 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-exj)and 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

294 DIONiEA MUSCIPULA. Chap. XIII.

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 move-
ment ; 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
filaments were touched. The sudden immersion of a
leaf into boiling water does not cause it to close.
Judging from the 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, with-
out 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 nitrogenous 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

Chap. XIII. SECRETION AND ABSORPTION. 295

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 fila-
ments. 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 excitement, 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, 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
fly 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 after an additional 3 hrs. there was a
considerable 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, except-
ing 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.

296 DION^^Li MUSCIPULA. Chap. Xni.

As in this case the glands on both sides are pressed
against the meat or insect, the secretion from the first
is tAvice as orreat as when a bit of meat is kid on the
surface of one lobe ; and as the two lobes come into
almost close contact, the secretion, containing dis-
solved aninial matter, spreads by capilUiry 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 do\^"n. 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 do^vn 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 move-
ment ; but nitrogenous bodies, if in the least degree
damp, cause after several hoirrs 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 2-i hrs. excited neither secretion nor move-
ment. They were then dipped in water, their sur-
faces dried on blotting paper, and replaced on the same

Chap. XIII. SECRETION AND ABSORPTION. 297

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 gela-
tine lay, the leaf was still quite open, nor had any
secretion been excited ; so that, as with Drosera, gela-
tine is not nearly so exciting a substance as meat.
The secretion beneath the meat was tested by push-
ing 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 secre-
tion. 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

298 DION^A MUSCIPULA. Chap. Xm.

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 part of car-
bonate 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 I 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 move-
ment is widely different from the rapid closure caused
by one of the filaments being touched. AVe shall see
its importance when we treat of the manner in Avhich
insects are captured. There is a great contrast be-
tween Drosera and Dionsea in the effects produced by
mechanical irritation on the one hand, and the absorp-
tion of animal matter on the other. Particles of glass
placed on the glands of the exterior tentacles of Dro-
sera 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 Dionaea, touching the filaments excites
incomparably quicker movement than the absorption
of animal matter by the glands. Nevertheless, in

Chap. XIII. SECKETION AND ABSORPTION. 299

certain cases, tliis latter stimulus is the more powerful
of the two. On three occasions leaves were found
which from some cause were torpid, so tliat 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 im-
possible that the leaves should be so differently af-
fected by non-nitrogenous and nitrogenous bodies, and
between these latter in a dry and damp condition. It
is surprising how slightly damp a bit of meat or albu-
men 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, t'hen 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 secrete, and
afterwards the lobes to close. That the glands have
the power of absorption is 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

300 DION^A MUSCIPULA. Chaf. Xin.

well aggregated. Aggregation may be seen to occur
very quickly if a piece of a 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 w^ater 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 Utricu-
laria, 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. Never-
theless, 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 thafi in other speci-

Chap. XIII. DIGESTION. 301

mens kept in water. I then tried suspending a leaf
in a bottle over an excessively putrid infusion of
raw meat, to see Avhether 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 expres-
sion, as a peptogene, and the glands on the surface
pour forth their acid secretion, which acts like the
gastric juice of animals. As so many experiments
were tried on the digestive power of Drosera, only a
few were made with Dionsea, but they were amply
sufficient to prove that it digests. This plant, more-
over, is not so 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 -^ of an inch (2"540
mm.) was placed at one end of a leaf, and at the other end
an oblong piece of gelatine, ^ of an inch (5*08 mm.) long, and

* Dr. W. M. Canby, of Wil- not yielding- soluble nutriment;

mington, to whom I am much and that in these latter cases the

indebted for information regard- glands do not secrete. The Rev.

iug Dionfca in its lative home, Dr. Curtis first observed (' Boston

has published in the 'Gardener's Journal Nat. Hist.' vol. i. p. 123)

Monthly,' Philadelphia, August the secretion from the glands. I

18tj8, some interesting observa- may here add that a gardener,

tions. He ascertained that the Mr. Knight, is said (Kirby and

secretion digests animal matter, Spencer's 'Introduction to Ento-

such as the contents' of insects, mology,' 1818, vol. i. p. 295) to

bits of meat, &c. ; and that the have found that a plant of tlio

secretion is reabsorbed. He was Dionsea, on the leaves of which

also well aware that the lobes "he laid fine filaments of raw

remain closed for a much longer beef, was much more luxuriant

time when in contact with animal in its growth than others not so

matter than when made to shut treated."
by a mere touch, or over objects

802 DIONJEA MUSCIPULA. Chap. XIII.

■^ broad; the leaf was tlien 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 dropped oif the leaf. The digestive process apparently
is rather slower than in Drosera, and this agi'ees with the length
of time dui'ing which the leaves remain closed over digestible
objects.

Experiment 2. — A bit of albumen -^ of an inch square, but
only ^ 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 surface was bathed with slightly adhesive, very
acid secretion, and the glands were all in an aggregated condi-
tion. Not a vestige of the albumen or gelatine was left. Simi-
larly sized pieces were placed at the same time on wet moss on
the same pot, so that they were subjected to nearly similar con-
ditions ; after eight days these were brown, decayed, and matted
with fibres of mould, but had not disappeared.

Experiment 3. — A piece of albumen -^-^ pf an inch (3*81 mm.)
long, and -^ 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.

Experimerd 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.

Expjerimerd 6. — A cube of albumen of -^^ 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 bit of gelatine were placed on the two ends of a leaf, which

Chap. XIIL

DIGESTION. 303

opened spontaneously after eleven days ; a vestige of the meat
was left, and the surface of the leaf was here blackened ; the
gelatine had all disappeared.

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 22 1 hrs. it was sur-
prisingly softened, when compared with another bit of the
same meat which had been kept damp.

Experiment 9.— A cube of Jq of an inch of very compact
roasted beef was placed on a leaf, which 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 was no mould. The little mass was
placed under the microscope ; some of the fibrillse in the middle
still exhibited transverse stri»; others showed not a vestige
of stria) ; 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 di-
gested by Drosera. Here, again, as in the case of albumen,
the digestive process seems slower than in Drosera. At tho
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 -^ of an inch of cheese 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 secre-
tion. Two days subsequently the end with the albumen also
opened spontaneously (i.e. eleven days after it was put on), a
mere trace in a blackened and dry condition being left.

Experiment 11. — The same experiment with cheese and albu-
men repeated on another and rather torpid leaf. The lobes at the
end with the cheese, after an interval, of six days, opened spon-
taneously 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 droj) of transparent, not acid, viscid
fluid.

Experiment 12. — Same experiment as the two last, and hero
again the leaf at the end enclosing the cheese opened before tho
14

304 DION^A MUSCIPULA. Chaj. XIII.

opposite end with the albumen ; but no further observationa
were made.

Ex^ieriment 13. — A globule of chemically prepared casein,
about -^ of an inch in diameter, was placed on a leaf, which
spontaneously opened after eight days. The casein now con-
sisted 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 Dionsea dissolves albu-
men, gelatine, and 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 (3'54:9 ml.) of chloroform, the mouth
being imperfectly 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 com-
pletely shut. The dose, however, was much too large, for in
between 2 and 3 hi's. the leaf appeared as if burnt, and soon
died.

Two leaves were exposed for 30 m. in a S-oz. vessel to the
vapour of 30 minims (l'77-4 ml.) of sulphuric ether. One leaf
closed after 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 sensibihty, but vras 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

CHAP.Xm. MANNEE OF OAPTURINa INSECTS. 305

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 chloro-
form and ether, which caused the leaves to close slowly,
acted on the sensitiye 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.

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 lobes 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 in-
truder. 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 move-

306 DION^A MUSCIPULA. Chap. XUL

ment of the whole lobe was well seen in a leaf to
which a large 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 re-
sistance 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 t© 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
intercross by their tips at first, and ultimately by their
bases. The leaf is then completely shut and encloses
a shallow cavity. If it has been made to shut merely
by one of the sensitive filaments having been touched,
or if it includes an object not yielding soluble nitro-
genous 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 case a leaf re-expanded to about two-
thirds of the full extent in 7 hrs., and comj)letely in
32 hrs. ; but one of its filaments had been touched
merely with a haii 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, how-
ever, they fully re-expand, they are ready to close

Chap.XIIL MANNEK OF CAPTURING INSECTS.

307

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, I do
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, gela-
tine, casein, and, no doubt, any other substance con-
taining 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 pro-
jection on the outside of the leaf is distinctly visible.
When the two lobes are thus completely shut, they

* According to Dr. Cui-tis, in 'Boston Journal of Nat. Hist.'
vol. i. 1837, p.l23.

308 DION^A MUSCIPULA. Chap. XIH.

resist being opened, as by a thin wedge driven
between them, with astonishing force, and are gene-
rally 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 of a leaf
is held firmly between the thumb and finger, or by a
clip, so 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. Burden Sanderson
that whenever the filaments of a closed leaf are irri-
tated, the normal electric current is disturbed. Never-
theless, 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
filaments being touched is rapid, and this is indis-

Chap. XIII. MANNER OF CAPTURINa INSECTS. 309

pensable for the capturing of insects. These two move-
ments, 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 consider-
able interval of time. In four instances, leaves after
catching insects never reopened, but began to wither,
remaining closed — in one case for fifteen days over
a fly ; in a second, for twenty-four days, though
the fly was small ; in a third for twenty-four days over
a woodlouse ; 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, bo
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

310 DION^A MUSCIPULA. Chap. XIII.

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 oj^ened 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 -^ 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 reopened. Generally they
were so torpid during many succeeding days that no
excitement of the filaments caused the least move-
ment. In one instance, however, on the day after a
leaf oj)ened which had clasped a fly, it closed with ex-
treme 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 remaining clasped for an unknown time
over a fly, opened, and when one of its filaments was
touched, closed, though rather slowly. Dr. Canby,

Chap. Xni. MANNER OF CAPTURING INSECTS. 311

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." It 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 Dionsea differs from Drosera, which catches
and digests many insects after shorter intervals of
time.

We are now prepared to understand the use of the
marginal spikes, which form so conspicuous a feature
in the appearance of the plant (fig. 12, p. 287), 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, elon-
gated spaces between the spikes, varying from the ^r
to the -yV of an inch (1'693 to 2*54 mm.) in breadth,
according to the size of the leaf, are left open. Thus
an insect, if its body is not thicker than these mea-
surements, can easily escape between the crossed
spikes, when disturbed by the closing lobes and in

312 DION^A MUSCIPULA. Chap. XIII.

creasing darkness ; and one of my sons actually saw a
small insect thus escaping. A moderately large in-
sect, on the other hand, if it tries to escape between
the Lars will surely be pushed back again into its
horrid prison with closing walls, for the spikes con-
tinue to cross more and more until the edges of the
lobes come into contact. A very strong insect, how-
ever, would be able to free itself, and Mrs. Treat saw
this effected by a rose-chafer (Macrodactylus siibspi-
nosiis) in the United States. N'ow it would manifestly
be a great disadvantage to the plant to waste many
days in remaining clasped over a minute insect, and
several additional days or weeks in afterwards re-
covering its sensibility; inasmuch as a minute insect
would afford but little nutriment. It would bo
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 intercrossing 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 gro^vn 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 scolo-
pendra. Out of these ten insects, no less than eight

Chap. XIII. TRANSMISSION OF MOTOR IMPULSE. 313

were beetles,* and out of the whole fourteen 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 Movement. — It is sufiicient to touch any one of the
six filaments to cause both lobes to close, these becom-
ing 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 as the eye can judge. Most physiologists be-
lieve that in irritable plants the excitement is trans-
mitted along, or in close connection with, the fibro-
vascular bundles. In Dion?ea, the course of these
vessels (composed of spiral and ordinary vascular

* Dr. Canhy remarks (' Gar- as elaters, for the five which I

dener's Monthly,' August 18(J8), examined were in an extremely

" as a general thing beetles and fragile and empty condition, as if

insects of that kind, though al- all their internal parts had been

ways killed, seem to be too hard- partially digested. Mrs. Treat

shelled to serve as food, and after informs me that the plants which

a short time are rejected." I am she cultivated in New Jersey

surprised at this statement, at chiefly caught Diptera.
least with respect to such beetles

314 DION^A MUSCIPULA. Chap. XIII.

tissue) seems at first sight to fayour tliis belief; for
they run up the midrib in a great bundle, sending
off small bundles almost at right angles on each side.
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 com-
munication. 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 -^ 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 fila-
ments.

On several occasions, slits about the -^ of an inch
in length were made with a lancet, close to the bases
of the filaments, parallel to the midrib, and, there-
fore, directly across the course of the vessels. These
were made sometimes on the inner and sometimes
on the outer sides of the filaments ; and after several
days, when the leaves had reopened, these filaments
were touched roughly (for they were always rendered
in some degree torpid by the operation), and the
lobes then closed in the ordinary manner, though
slowly, and sometimes 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 v/hich is

Chap. XIII. TRANSMISSION OF MOTOR IMPULSE. 315

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 mid-
rib, 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 con-
nected with the rest of the leaf only at its two ends.
These slips were nearly of the same size ; one was care-
fully 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 pro-
duced 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 impulse
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

316 DION^A MUSCIPULA. Chap. XIII.

is transmitted in like manner in all directions tlirough
the cellular tissue ; but that its rate is largely governed
by the length of the cells and the direction of their
longer axes. Thin sections of a leaf of Dionaea were
made by my son, and the cells, both those of the
central and of the more superficial layers, were found
much elongated, with their longer axes directed to-
wards 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.
The central parenchymatous cells are larger, more
loosely attached together, and have more delicate walls
than the more superficial cells. A thick mass of cel-
lular tissue forms the upper surface of the midrib
over the great central bundle of vessels.

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 tonched 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 to-
gether, 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 bo seen on any part of their upper

Chap. XIIL TRANSMISSION OF MOTOR IMPULSE. 317

surfaces. It appears therefore that the cells must con-
tract. The chief seat of the moyement is evidently
in the thick mass of cells which oyerlies 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 ^H^- 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 -rkwo of ^^ i^^ch apart,
so that a small portion of the upper surface of the
midrib had contracted in a transverse line two 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 nar-
row 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 to the midrib. The distance between
the dots was found to be two of an inch, so that the
two extreme dots were two- 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
\ o"o 0 of an inch, and the two further dots by -f^ of
an inch, than they were before ; so that the two extreme

318 DIONiEA MUSCIPULA. Chap. XHI.

dots now stood about tijVo ^^ ^^ i^oli ('127 mm.)
nearer together than before. If we suppose the whole
upper surface of the lobe, which was -^^^ of an inch
in breadth, to have contracted in the same proportion,
the total contraction will have amounted to about
-^-^^ or ^V 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. Burden Sander-
son* is now universally known ; namely that there
exists a normal electrical 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.

The Re-ex]pansion of the Leaves. — This is effected at an
insensibly slow rate, whether or not any object is
enclosed.t One lobe can re-expand by itself, as oc-
curred with the torpid leaf of which one lobe alone had
closed. We have also 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

* 'Proc. Royal Soc' vol. xxi. influence of the sim; these at-

p. 405 ; and lecture at the Royal tempts consisted in an undula-

Institution, June 5, 1874, given in tory motion of the marginal cilia3,

'Nature,' 1874, pp. 105 and 127. accompanied by a partial open-

t Nuttall, in his 'Gen. Ame- ing and succeeding collapse of

rican Plants,' p. 277 (note), says the lamina, wliich at length ter-

that, whilst collecting this plant minated in a complete expansion

in its native home, " I had occa- and in the destruction of sensi-

Bion to observe that a detaclicd bility." I am indebted to Prof,

leaf would make repeated efibrta Oliver for this reference ; but I do

towards disclosing itself to the not understand what took place.

Chap. XIIL RE-EXPANSION. 319

leaves thus treated re-expanded, — one to a partial ex-
tent in 24 lirs., — a second to the same extent in 48
hrs., — and the third, which had been previously in-
jured, not until the sixth day. .These leaves after
their re-expansion closed quickly when the filaments
on the other lobe 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 fila-
ments, 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 continue 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 fluid 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-expanded
after having caught a fly, so that repeated touches of
the filaments caused not the least movement; never-
theless, when similarly immersed, the lobes separated a
little. As these leaves were inserted perpendicularly
into the boiling water, both surfaces and the filaments

320 DIONiEA MUSCIPULA. Chap. XIH.

must liaye been equally affected ; and 1 can under-
stand the divergence of the lobes only by supposmg
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 back-
wards ; and this is an analogous movement to the
divergence of the lobes of Dionsea.

In some concluding remarks in the fifteenth chapter
on the Droseracese, the different kinds of irritability
possessed by the several genera, and the different
manner in which they capture insects, will be com-
pared.

CHAP. XIV. ALDROVANDA VESICULOSA. 321

CHAPTER XIV.

Aldroyanda vesiculosa.

Captures crustaceans — Structure of the leaves in comparison witH
those of Dionsea — Absorption by the glands, by the quadriiid pro-
cesses, and points on the infolded margins — Aldrovanda vesiculosa,
var. aiistralis — Captures prey — Absorption of animal matter —
Aldrovanda vesiculosa, var. verticillata — Concluding remarks.

This plant may be called a miniature aqnatic Dionsea.
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 inor-
ganic 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 larva3.t Plants which had been kept
in filtered water were placed by him in a vessel con-

* Since his original publication, cliioccioline are fresh-water mol-

Stein has found out that the irri- luscs. It would be interesting to

tability of the leaves was observed know whether their shells are at

by De Sassus, as recorded in all corroded by the acid of the

* Bull. Bot. Soc. de France,' in digestive secretion.

I8G1. Delpino states in a paper f I am greatly indebted to this

published in 1871 ('Nuovo (alio r- distinguished naturalist for having

nale Bot. Ital.' vol. iii. p. 174) sent me a copy of his memoir on

that "una quantita di chioccio- Aldrovanda, before its publica-

line e di altri animalcoli acqua- tion in his ' Beitriige zur Biologie

tici" are caught and suffocated der Pflanzen/ drittes Heft, 1875,

by the leaves. I presume that p. 71.

322 ALDEOVANDA VESICULOSA. Chap. XIV.

taming numerous crustaceans of the genus Cyj)ris, and
next morning many were found imprisoned and alive,
still swimming about within the closed leaves, but
doomed to certain death.

Directly after reading Prof. Cohn's memoir, I re-
ceived 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, however, append a few
remarks on the differences between this plant and
Dionsea.

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. The bilobed leaf, with the midrib like-
•wise 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 Dion£ea ; 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 papillaB, evidently
answering to the eight-rayed papillsB of Dionsea.

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.

* There has been much discus- 1861, p. 146) believes that they

sion by botanists on the homologi- correspond with the fimbriated

cal nature of these projections. scale-like bodies found at the

Dr. Nitschke (' Bot. Zeitung,' bases of the petioles of Drosera.

Chap. XFV.

ALDROVANDA VESICULOSA.

323

is slightly concave, and is formed, according to Cobn,
of three layers of cells. Its upper surface is studded
with colourless glands like, but more simple than,
those of Dioneaa; they are supported on distinct
footstalks, consisting of two rows of cells. The outer

Fig. 13.
{Aldrovanda vesiculosa.)
Upper figure, whorl of leaves (from Prof. Cohn).
Lower figure, leaf pressed flat open and greatly enlarged.

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, small quadriiid processes, each consisting of
four tapering projections, which rise from a common

324 ALDROVANDA VESICULOSA. Chap. XIV.

prominence. These 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 the projection is trifid. We shall see in
a future chapter that these projections curiously re-
semble 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 turned inwards, so that, when the lobes are
closed, the exterior surfaces of the in-folded portions
come into contact. The edge itself bears a row of
conical, flattened, transparent points with broad bases,
like the prickles on the stem of a bramble or Eubus.
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 com-
posed of very delicate and highly flexible membrane,
which can be easily bent or quite doubled back with-
out 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 circum-
ferential part of the leaf of Aldrovanda thus differs
greatly from that of Dionaea ; nor can the points on
the rim be considered as homologous with the spikes
round the leaves of Dion?ea, as these latter are pro-
longations of the blade, and not mere epidermic
productions. They appear also to serve for a widely
different purpose.

Chap. XIV. ALDEOVANDA VESICULOSA. 325

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 re-
marks, there can be little doubt are sensitive to a
touch, and, when touched, cause the leaf to close.
They are formed of two rows of cells, or, according to
Cohn, sometimes of four, and do not include any vas-
cular tissue. They differ also from the six sensitive
filaments of Dionsea in being colourless, and in having
a medial as well as a basal articulation. No doubt it
is owing to these two articulations that, notwithstand-
ing 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 subjected to a high temperature. After ex-
amining 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 was no change, but when
next examined after 23 hrs. 20 m., 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 Dionsea. 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

326 ALDROVANDA VESICULOSA. Chap. XIV

already soluble animal matter. Tlie 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 proto-
plasm was somewhat shrunk before they w^ere im-
mersed. 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 sub-
stance 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. I was also led to try
urea from 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 quad-
rifids 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 Dionaea. 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

Chap. XIV. ALDKOVANDA VESICULOSA. 327

cells of the glands were found to contain only limpid
fluid. Some of the quadrifids included a few spherical
granules, but several were transparent and empty, and
their positions were marked. This leaf was now im-
mersed 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, irre-
gular, yellowish specks and ridges, exactly like those
which appear within the quadrifids of Utricularia
when treated with this same solution. Moreover, several
of the quadrifids, which were before empty, now con-
tained 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 proto-
plasm was a little shrunk and included yellowish
specks ; and those which were before empty now con-
tained 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 con-
tained 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
15

328 ALDEOVANDA VESICULOSA. Chat. XIV.

agrees with what I have observed under similar cir-
stances with Utricularia.

Aldrovanda vesiculosa, var. australls. — 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 ex-
amined by a botanist. The projections at the upper
end of the petiole (from 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 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 indistinguish-
able from their delicacy and from having shrivelled ;
for they were quite distinct on one leaf under circum-
stances presently to be mentioned.

Some of the closed leaves contained no prey, but in
one there was a rather large beetle^ which from its
flattened tibire I suppose was an aquatic species, but
was not allied to Colymbetes. All the softer tissues
of this beetle were completely dissolved, and its chiti-
nous integuments were as clean as if they had been

Chap. XIV. ALDROVANDA VESICULOSA. 329

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 pro-
cesses, 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 con-
tained brownish granular matter. We thus gain
additional evidence that the glands, the quadrifid pro-
cesses, 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 unarti-
culated 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 Algse, still of a green-
ish colour, which had evidently lived as intruders, in
the same manner as occurs, according to Cohn, within
the leaves of this plant in Germany.

Aldrovanda vesiculosa, var. verticillata. — Dr. King,
Superintendent of the Botanic Gardens, kindly sent
me dried specimens collected near Calcutta. This
form was, I believe, considered by Wallich as a distinct
species, under the name of verticillata. It resembles
the Australian form much more nearly than the Euro-
pean ; namely in the projections at the upper end of
the petiole being much attenuated and covered with

330 ALDROVANDA VESICULOSA. Chap. XIV.

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 crustaceans.

Concluding Bemarhs. — The leaves of the three fore-
going 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 Dionaea, 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 Dio-
nsea, — 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 con-
dition 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 pro-
cesses absorb excrementitious and decaying animal
matter. It is a more curious fact that the points on

Chap. XIV. CONCLUDING REMARKS. 331

the infolded margins apparently serve to absorb de-
cayed animal matter in the same manner as the quad-
rifids. We can thus understand the meaning of the
infolded margins of the lobes furnished with delicate
points directed inwards, and of the broad, flat, outer
portions, bearing quadrifid processes ; for these sur-
faces must be liable to be irrigated by foul water
flowing from the concavity of the leaf when it con-
tains dead animals. This would follow from various
causes, — from the gradual contraction of the concavity,
— from fluid in excess being secreted, — and from the
generation of bubbles of air. More observations 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 under-
stand 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 Utri-
cularia, belonging to the same family, have been
adapted for these two different functions.

332 DROSOPIIYLLUM LUSITANICUM. Chap. XV.

CHAPTEE XV.

Dkosopiitlloi — RoRiDULA — Byblis — Glandular Hairs of other
Plants — Concluding Eemarks on the Droserace^.

Drosophyllum — Structure of leaves — Nature of the secretion — Man-
ner of catching insects — Power of absorption — Digestion of animal
substances — Siunmary on Drosophyllum — Roridula — Byblis —
Glandular hairs of other plants, their power of absorption — Saxi-
fraga — Primula — Pelargonium — Erica — Mirabilis — Nicotiana
— Summary on glandular hairs — Concluding remarks on the Dro-
eeracese.

Deosophyllum lusitanicum. — 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 w^ell 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 men-
tioned members of the same family of the Droseracea).
The leaves arise from an almost woody axis ; they

Chap. XV. STRUCTURE OF LEAVES. 333

are linear, miicli attenuated towards their tips, and
several inches in length. The upper surface is con-
cave, 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 resem-
blance to those of Drosera, though they have no power
of movement. Those on the same leaf differ much in
length. The glands also differ in size, and are of a
bright pink or of a purple colour; their upper sur-
faces are convex, and the lower flat or even concave,
so that they resemble miniature mushrooms in appear-
ance. 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 multi-
cellular pedicels. The glands secrete ^^"^^
large drops of viscid secretion. Other p ^ ^ ^" -1
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 '^ , ^^'J
are numerous ones, both on the upper tj^ u\^
and lower surfaces of the leaves, so
small as to be scarcely visible to the '^^^- ^^^

naked eye. They are colourless and tanicum.)

almost sessile, either circular or oval P^^-t of leaf, enlarged

' ^ Beven times, shovv-

in outline ; the latter occurring chiefly i"s lo^^r surface.
on the backs of the leaves (fig. 14).
Internally they have exactly the same structure as
the larger glands which are supported on pedicels ;

334 DROSOPHYLLUM LUSITANICUM. Chap. XV.

and indeed the two sets almost graduate into one
another. But the sessile glands differ in one im-
portant respect, for they never secrete spontaneously,
as far as I have seen, though I have examined
them under a high power on a hot day, whilst
the glands on pedicels were secreting copiously.
Nevertheless, if little bits of damp 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 Dionsea 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 occasion I chose a young
leaf, which was not secreting freely, 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

Chap. XV. SECRETION. 335

needle, tlie 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 Dro-
sophyllum, 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, continu-
ally secrete, so as to replace the loss by evaporation.
Thus when a plant was placed under a small bell-
glass with its inner surface and support thoroughly
wetted, there was no loss by evaporation, and so much

336 DROSOPHYLLUM LUSITANICUM. Chap. XV.

secretion was accumulated in the course of a day that
it ran down the tentacles 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 secre-
tion 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 -^ 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 ren-
dered 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

Chap. XV. ABSORPTION. 337

have been slightly acted on and rendered soluble
within the above stated short periods.

The glands have not only the power of rapid absorp-
tion, 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 on which a bit
of albumen had been placed. The three glands to
which a minute drojD of a solution of nitrate of
ammonia was distributed, and which became dry after
2 hrs., were beginning to re-secrete after only 12 addi-
tional hours.

Tentacles Licapahle of Movement. — Many of the tall
tentacles, with insects adhering to them, were care-
fully observed ; 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 tentac'les became
at all inflected. We may therefore conclude that
they are incapable of movement.

On. the Poiuer of Absorption i^ossessed hj 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

338 DROSOPHYLLUM LUSITANICUM. Chap. XV.

pedicels and to tlie minute sessile ones. Before a
gland lias been in any way stimulated, 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 Droso-
phyllum, for the glands were only slightly darkened
by an immersion of 1 h^;. 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 became 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

Chap. XV. DIGESTION. 339

fluid, either the acid is consumed in the work of di-
gestion or the cell-walls are rendered more permeable,
so that the undecomposed 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 con-
tents were conspicuously aggregated. Several glands
with bits of albumen and fibrin were darkened in
between 2 hrs. and 3 hrs. ; 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 appearance ;
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

340 DEOSOPHYLLUM LUSITANICUM. Chap. XV.

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 secre-
tion 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 com-
pletely liquefied after 21 hrs. 15 m. ; the little liquid
masses, however, 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 sur-
rounded 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 diges-
tion, though strongly acid, or that the amount poured
forth from a single gland is insufficient to dissolve 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 alter-
natives 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

Chap. XV. CONCLUDING REMARKS. 341

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 completely
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 wdth 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.

Concluding BemarJcs. — The linear leaves of Droso-
phyllum 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 Dionsea, do not secrete until they are
excited by the absorption of nitrogenous matter. But
glands of this kind are present on the leaves of
Drosera hinafa, and appear to be represented by the
papilloG 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 Di'-osera hinata. There are
greater difl'erences in function between the two ge-
nera. 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

342 • ROEIDULA. Chap. XV.

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
nitrogenous 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 se-
cretion from the sessile glands which dissolves animal
matter out of their bodies.

KORIDULA.

Boridiila 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 w^ith tentacles, which differ greatly in length ;
some being very long, especially those 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

Chap. XV. , BYBLIS. 343

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 pin-
natifid, the divisions projecting 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 pedi-
cels of the long terminal tentacles and the much
attenuated 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 stick-
ing 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 cap-
tured insects ; and this probably would have been seen
even in the dried specimens, had they possessed the
power of movement. Hence, in this negative cha-
racter, Koridula resembles its northern representative,
Drosophyllum.

Byblis. •

Bijhlis 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

344 GLANDULAK HAIES, . Chap. XV.

— sessile ones arranged in rows, and others sup-
ported 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 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 sin-
gular 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 fourth their secretion and after-
wards absorb the digested matter.

Siip2^Iementary Observations on the Power of Absorp-
tion 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,

* Sachs, ' Traite do Bot.' 3rd edit. 1874, p. 1026.

CiiAP. XV. THEIR POWER OF ABSORPTION. 345

the species of Droseraceae absorb various fluids or
at least allov/ tliem readily to enter,* it seemed desir-
able 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 saxi-
frage, which were selected from belonging to a family
allied to the Droseracese. Most of the experiments
were made by immersing the glands either in an in-
fusion 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 Droseraceoe the secretion of a viscid
fluid by the glands does not prevent their absorbing ; so
that the glands of other plants might excrete super-
fluous matter, or secrete an odoriferous fluid as a
protection against the attacks of 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

* The distinction between true clearly iinderstood : see Miiller's
absorption and mere permeation, ' Physiology,' Eng. trauslat. 1838,
or imbibition, is by no means vol. "i. p. 280.

346 GLANDULAR HAIRS, Chap. XV.

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 aggi-egated, 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 differ-
ent 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 146 of water (or 3 grs. to 1 oz.), and the glands
we]-e 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 of 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 pui-ple, some of them blackish-

* In the case of Saxifraga tri- stance remnants of insects ad-

(Jactylites, Mr. Druce says (' Phar- hered to the leaves. So it is, as

maceutical Journal,' May 1S75) I hear from a friend, with this

that he examined some dozens of plant in Ireland,
plants, and in almost every in-

Chap. XV. THEIR POWER OF ABSORPTION. 347

green, a few being still unaffected. The little masses of proto-
plasm within the cells were seen in movement. 1'he 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 after-
wards aggregate into larger masses. Altogether, in the darken-
ing 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 o^ 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 loioer cells of all the
pedicels. The action invariably commenced (for I tried the
experiment 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 dis-
coloured, 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. in a weaker solution of one part
of the carbonate to 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

348 GLANDULAE HAIRS, Chap. XV.

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 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 some-
what 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 necessary 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 captm-e.

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 transparent. 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 affected 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 sur-
faces being first affected.

Primula sinensis. — The flower-stems, the upi^er and lower sur-
faces 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 terminal 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. The glands of the latter
contained no solid or semi-solid matter ; and those of only two

Chap. XV. THEIR POWER OP ABSORPTION. 349

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, con-
tained 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-four 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. My son Francis examined
some glands of the longer 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, I do 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 sjjherical masses within
the gland-cells had disappeared, being replaced by granular
matter of a darker brown. The experiment was thrice re-
peated with nearly the same result. On one occasion the piece
was left immersed for 8 hrs. 30 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
spontaneously 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

350 GLANDULAR HAIRS, Chap. XV.

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) cause 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 flower-
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
seahng-wax, and was then placed under a small bell-glass, with
a large pinch of the carbonate. After 10 m. the glands showed
a considerable degree of aggregation, 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 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 aggTegated 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. 30 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 in-
fusion of raw meat and of water, were left for 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, I suppose, of some balsam or essential oil.

Pelargonium zonale (var. edged with white). — The leaves

CiiAP. XV. THEIR POWER OF ABSORPTION. 351

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 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 dose 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 globules, but larger, being
found in the large glands of the longer hairs. After the speci-
men 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 I 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 shghtly
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 sepa-
rated into two ; but the changes were not quite like those which
the protoplasm of Drosera undergoes. These hairs, moreover,
had not been examined before immersion, and there were similar
spheres in some glands which had not been touched by the
infusion.

Erica tetralix. — 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 compared, 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
16

852 GLANDULAK HAIRS,' Chap. XV.

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.

Mirahilis longiflora. — The stems and both surfaces of the
leaves bear viscid hairs. Young plants, from 12 to 18 inches
in height in my greenhouse, caught so many minute Diptera,
Coleoptera, and larvae, that they were quite dusted with them.
The 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 occasional appearance of
vacuoles. But I 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 car-
bonate 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 infusion of raw meat, in
the least affected; but the protoplasm lining 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 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 for 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

Chap. XV. THEIR POWER OF ABSORPTION. 353

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 Ohservations 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 Pelargonium, 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 am-
monia 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 appa-
rently by its more rapid spontaneous movements.

' Comptes rendus,' June 15, 1874. A good abstract of this paper
iven in the 'Gardener's Chronicle,' July 11, 1874.

IS given

354 GLANDULAK HAIES. Chap. XV.

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 ex-
posed to a solution of the carbonate of ammonia.

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 Felargonium
zo7iaIe became cloudy and granular in from 3 m. to 5 m.
when they were immersed in a weak solution of the car-
bonate of ammonia ; 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 suffered disintegration when left for a consider-
able time in a strong solution, 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 gene-
rally 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

Chap. XV. DROSEKACEiE. 355

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 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 Kemaeks on the Dkoserace^.

The six kno^va 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, Eoridula,
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
Dionaea and Aldrovanda, through the closing of the
blades of the leaf. In these two last genera rapid

* My son Francis counted the planimeter to be 39-285 square
hairs on a space measured by inches ; so that the area of both
means of a micrometer, and found surfaces was 78 • 57 square inches,
that there were 35,336 on a Thus the plant (excluding the
square inch of the upper surface flower-stems) must have borne
of a leaf, and 30,035 on the lower the astonishing number of
surface ; that is, in about the pro- 2,568,099 glandular hairs. Tiie
portion of 100 on the upper to 85 hairs were counted late in the
on the lower surface. On a square autumn, and by the following
inch of both sm-faces there were spring (May) the leaves of some
65,371 hairs. A moderately fine other plants of the same lot were
plant bearing twelve leaves (the found to be from one-third to one-
larger ones being a little more fourth broader and longer than
than 2 inches in diameter) was they were before ; so that no
now selected, and the area of all doubt the glandular hairs had
the leaves, together with their increased in number, and pro-
foot-stalks (the flower-stems not bably now much exceeded three
being included), was found by a millions.

356 CONCLUDING REMARKS Chap. XV.

ruoyement 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 Dionsea 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 dis-
solving 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, Drosophyllum, and
Dionsea ; almost certainly with Aldrovanda ; and, from
analogy, very probable with Koridula and Byblis. We
can thus understand how it is that the three first-
named genera are provided with such small roots, and
that Aldrovanda 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 Droseraceoe) 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

Chap. XV. ON THE DEOSERACE^. 357

alimentary canal ; but they live by absorbing through
root-like processes the juices of the animals on which
they are parasitic*

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,! which range in
the Old World from the Arctic regions to Southern
India, to the Cape of Good Hope, 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. Diona3a 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. Droso-
phyllum includes only one species, limited to Portugal
and ]\torocco. Eoridula and Byblis each have (as I

* Fritz Miiller, ' Facts for Dar- condition, for it has root-like pro-
win,' Eu<^. trans. 1809, p. 1 39. Tlie cesses embedded in the skin of the
rhizocephalous crustaceans are shark on which it is parasitic, and
allied to the cirripedes. It is hardly its prehensile cirri and mouth (as
possible to imagine a greater dif- described in my monograph on
ference than that between an ani- the Lepadidaj, 'Ray Soc' 1851,
mal with prehensile limbs, a well- p., 169) are in a most feeble and
constructed mouth and alimentary almost rudimentary conditign.
canal, and one destitute of all Dr. R. Kossmann has given a very
these organs and feeding by ab- interesting discussion on this
sorption through branching root- subject in his ' Suctoria anJ Lc-
like processes. If one rare cirri- padida^,' 1873. See also, Dr.
■pede, the Anelas7nasquaUcola, had Dolirn, ' Der Ursprung der Wir-
become extinct, it would have belthiere,' 1875, p. 77.
been very difficult to conjecture f Bentham and Hooker, ' Genera
how so enormous a change could Plantarum.' Australia is the me-
have been gradually eftected. tropolis of the genus, forty-ono
But, as Fritz Miiller remarks, we species having been described
have in Anelasma an animal in from this country, as Prof. Oliver
an almost exactly intermediate informs me.

858 CONCLUDING KEMAEKS Chap. XV.

hear from Prof. Oliver) two species ; the former con-
fined to the western parts of the Cape of Good Hope,
and the latter to Australia. It is a strange fact that
Dionsea, 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 Dion?ea 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,
Koridula, 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 Koridula they
have a more complex structure, and are supported on
pedicels formed of several rows of cells; in Droso-
phyllum they further include spiral cells, and the pedi-
cels 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 ex-
cited, no case is kno^^n of a trichome having such

Chap. XV. ON THE DROSERACEiE. 359

power.* We are 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 vas-
cular 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 tentacles on both surfaces of the leaves of Droso-
phyllum, and on the upper surface of the leaves of
Drosera, it seems scarcely 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 homo-
logical nature of the tentacles. The lateral divisions
of the leaves of this plant terminate in long tentacles ;
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 mar-
ginal but all the inner tentacles have become capable
f)f movement, we must further assume, either that
through the principle of correlated development this

♦ Sachs, ' Traite de Botanique,' hasfue, 1873, p. 6. * Extrait des

3rd edit. 1874, p. 1026. Vi'denskabeli^'^-e Meddelelser de

t Dr. Warminc:, ' Sur la Difife- la Soc. d'Hist. nat. de Copeu-

rence entre lea Trichomes,' Copen- hague,' Nof. 10-12, 1872.

860 CONCLUDING REMARKS Chap. XV.

power was transferred to the basal parts of tlie hairs,
or that the surface of the leaf has been prolonged
upwards at numerous points, so as to unite with the
hairs, thus forming the bases of the inner tentacles.

The above named three genera, namely Droso-
phyllum, Eoridula, and Byblis, which appear to have
retained a prinjordial 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 excej)tion
of one species, Drosera hinata. The small sessile
glands have also disappeared in some of the genera,
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 intermediate 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 movement. 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 rotundifoUa. The footstalks of this
latter species bear multicellular hairs, which we have
good reason to believe represent aborted tentacles.

The parent form of Dionaea 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 uppef
surface. I think so because the marginal spikes of
Dionaea 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

Chap. XV. ON THE DEOSERACE^. 861

tentacles of Drosera, with their glands aborted, but their
sensitiveness retained. linger this point of view we
should bear in mind that the summits of the tentacles
of Drosera, close beneath tlie glands, are sensitive.

The three most remarkable characters possessed by
the several members of the Droseraceas 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 inwards ; and this inward passage would deserve
to be called an act of absorption, if the fluids com-
bined 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
Avhich they must receive small quantities from the rain.
This is the case with two s]3ecies of Saxifraga, 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
Droseracese 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 dis-
solves or digests animal matter. The six genera of
the Droseraceae have probably inherited this power
from a common progenitor, but this cannot apply to

362 CONCLUDING KEMAEKS Chap. XV.

Pinguicula or Nepenthes, for these plants are not at all
closely related to the Droseraceae. 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 albu-
minous 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 consisting 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 secre-
tion, 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 be of high service to plants

* ' Traite de Botanique,' 3rd Berlin, 1874, p. 1478), who, with

edit. 1874, p. 844. See also for the aid of Dr. H. Will, has ac-

foUowing facts pp. 64, 76, 828, tually made the discovery that the

831. seeds of the vetch contain a fer-

t Since this sentence was writ- ment, which, when extracted by

ten, I have reseived a paper by glycerine, dissolves albuminous

Gorup-Besanez ('Bcrichte der substances, such as fibrin, and

Deutschen Chem. Gesellschaft,' converts them into true peptones.

Chap. XV. ON THE DROSEKACE^. 363

growing in very poor soil, it would tend to be perfected
through natural selection. Therefore, any ordinary
plant having viscid glands, which occasionally caught
insects, might thus be converted under favourable cir-
cumstances 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 acquire-
ment of the third remarkable character possessed by
the more highly developed genera of the Droseraceae,
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, indepen-
dently 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

364 CONCLUDING REMAEKS Chap. XV.

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 the 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 irri-
tability or sensitiveness, but, as Cohn has remarked,*
the tissues of the plants thus endowed do not differ
in any uniform manner 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 transmitted
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 inflection ; 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
w^ould have followed from the effects of camphor
alone. So again with Dionaea, the blades in their
ordinary state may be roughly touched without their
closing ; yet some effect must be thus caused and
transmitted 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 Droseraceae presents no greater difiiculty
than that presented by the similar but feebler powers
of a multitude of other plants.

* See the abstract of his me- Map;, of Nat. Hist.' 3rd series,
moir on the contractile tissues vol. xi. p. 188.
of plants, in the ' Annals and

CuAP. XV. ON THE DEOSERACE^. 365

The specialised nature of the sensitiveness possessed
by Drosera and Dionsea, 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
Dionsea with no effect ; but if touched only once by
the slow movement of a delicate hair, the lobes close ;
and this difference 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 nitro-
genous matter, they transmit a motor impulse to the
exterior tentacles much more quickly than when they
are mechanically irritated; whilst with Dionaea the
absorption of nitrogeneous 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 Dionsea
are also specialised, so as not to be uselessly affected
by the weight or impact of drops of rain, or by
blasts of air. This may be accounted for by sup-
posing 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 move-

366 CONCLUDING REMARKS Chap. XV.

ment, 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 perfection of the sensitive-
ness 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 Dionsea 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 move-
ment. "When a gland of Drosera, or one of the fila-
ments of Dionsea, is excited, the motor impulse radiates
in all directions, 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 Dionsea, 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. Never-
theless we perhaps see the prefigurement of the forma-
tion of nerves in animals in the transmission of the
motor impulse being so much more rapid down the
confined space within the tentacles of Drosera than

Chap. XV. ON THE DROSEEACEiE. 367

elsewhere, and somewhat more rapid in a longitudinal
than in a 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, 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 repro-
duce them.

368 PINGUICULA VULGARIS. Chap. XVI.

CHAPTEK XYl.

PlXGUICrLA.

Tinguicula vulgaris — Strticture 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 — Finguicida hi-si-
tanica, catches insects — Movement of the leaves, secretion and
digestion.

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 H
inch in length and J 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, forming 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, homogeneous fluid. They are
supported on elongated, unicellular pedicels (contain-
ino- 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 pedi-
cels. Near the midrib, towards the base of the leaf, the

CflAP.XVL CAPTURED INSECTS. " 369

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 to a length 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 Cumberland 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 ad-
liering 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 167 leaves; fifteen of

370 PINGUICULA VULGARIS. Chap. XVI.

these leaves were sent me, each haying canght 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 vul-
garis. 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 nine
different kinds, which could not be recognised, excepting one
of Eanunculus, 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 Hyme-
noptera, including some ants, a few small Coleoptera, larvse,
spiders, and even small moths.

We tlius 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 <3ase of
the Mirabilis, or of the horse-chestnut. But it will pre-
sently 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 gra-
nular 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

CHAr. XVI.

MOVEMENTS OF THE LEAVES.

871

doubt that it profits by its power of digesting and
absorbing matter from the prey which it habitually cap-
tures in such large numbers. It will, however, be con-
venient first to describe the movements of the leaves.

Movements of the Leaves. — That such thick, large leaves
as those of Pinguicida 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 capturing 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, like the helix of the
human ear, to the breadth of -^ 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 be-
fore, 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.

Fig. 15,

(Pinguicula vulgaris.)

Outline of leaf with left
margin inflected over a
row of small flies.

372 PINGUICDLA VULGARIS. Chap. XVI.

After 4 hrs. 20 m. there was decided incurvation, whicli in-
creased 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, a little beneath the apex. Both lateral mar-
gins were perceptibly incurved in 3 hrs., and after 4 hrs. 20 m.
to such a degi'ee 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 24 hrs. the margins were "25 of an
inch (6-349 mm.) apai't, so that they were largely unfolded. After
an additional 24 hrs. they were completely unfolded. Another
fly was now put on the same 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 incurved over a fragment of a fly and had aft-.rwards
re-expanded ; but the meat did not cause even a trace of incur-
vation. 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
between 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 incuiwation after 3 hrs,, and this
became strongly pronounced in 7 hrs. After 24 hrs. the infolded
edge was only -16 of an inch (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 ^G of an inch (11-68 mm.)

Chat. XVI.

MOVEMENTS OF THE LEAVES.

373

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 exa-
mined after two days, the margin was quite
unfolded, with the exception of the natu-
rally 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 'll of an inch (2*795 mm.)
from the edge. The distance from the edge
to the midrib of the fully expanded leaf
was "35 of an inch (8'89 mm.); so that the
bit had been pushed inwards and across
nearly one-third of its semi-diameter.

Experiment 8. — Cubes of sponge, soaked in a 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 incurvation. 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
4:2 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 spoDge were
left at the distance of "1 of an 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.

Fig 16.
{Pinguicula vulgaris.)

Outline of leaf, with
right margin inflected
against two square bits
of meat.

374 PINGUICULA VULGAEIS. Chap. XVI.

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 conceahng 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 com-
pletely overlapped by the margin, they were not pushed at all
inwards, across the blade.

Exferiment 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, and
about "7 of an inch (1*778 mm.) in diameter. 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 soijie way
down the marginal channel.

E.rperime7it 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 disappeared 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
increase of the secretion; and in two other trials, no increase
could be perceived. Bits of coal-cinders, placed on a leaf, pro-
duced 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 ascer-

Chap. XVI. MOVEMENTS OF THE LEAVES. 875

tain 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 in-
curvation ; 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 for a
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
l^laced on the leaf. From this experiment we learn that the
motor impulse can be transmitted to a distance 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 I h. 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 the following case, that
this holds good with Pinguicula.

Expei'iment 15. — A row of drops of a solution of one part ot
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. 30 m.
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

ir

376 PINGUIOULA VULGARIS. Chap. XVI.

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 of objects not yielding any soluble
matter, by objects yielding such matter, and by some
fluids — namely an infusion of raw meat and a weak
solution of carbonate of ammonia. A stronger solu-
tion 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 nitro-
genous 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 glan-
dular hairs have no power of movement. I observed
on several occasions that the surface of the leaf be-
came 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 move-
ment 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

Chap. XVI. MOVEMENTS OF THE LEAVES. 377

there was a trace of movement in 1 hr. or 1 hr. 30 m.
The pressure from fragments of glass excites move-
ment almost as quickly as the absorption of nitro-
genous 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 accom-
panied, 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 in-
creased secretion, for fragments of glass cause little
or no secretion, and yet excite movement ; whereas
a strong solution of carbonate of ammonia quickly
excites copious secretion, but no movement.

One of the most curious facts with respect to the
movement 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 in-
fusion 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

878 PINGUICULA VULGARIS. Chap. XVI.

complete re-expansion in 16 hrs. 30 m. Nitrogenous
fluids act for a shorter time than nitrogenous sub-
stances ; thus, when drops of an infusion of raw meat
were placed on the midrib of a leaf, the incurvefl
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 a time ? 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 over-
lapping margin are thus brought into contact with
such objects and pour forth their secretion, afterwards
absorbing the digested matter. But as the incurvation
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
secreting. 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 exciting object, must be serviceable in another

Chap. XYI. MOVEMENTS OF THE LEAVES. 379

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 ser-
viceable 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 Dionaea 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 sur-
face. 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 unfolded. 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 movements of the leaves ;
otherwise, we must look at these movements as a
remnant of a more highly developed power formerly
possessed by the progenitors of the genus.

In the four British species, and, as I hear from

380 PINGUICULA VULGARIS. Chap. XYI.

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 dovm. 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, or in the spoon-like
tips of the leaves ; and I ascertained that bits of albu-
men, 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'secre-
tion 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 pro-
vision 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

Chap. XVI. SECRETION, ABSORPTION, DIGESTION. 881

bearing on our subject, that when a phint is pulled
up, the leaves immediately curl downwards so as
almost to 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, Ahsori)tion, and Digestion. — I will first give
my observations and experiments, and then a summary
of the results.

The Effects of Ohjects 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 before. After a time these insects were rendered so
tender that their limbs and bodies could be separated by a
mere touch, owing no doubt to the digestion and disintegration
of their muscles. The glands in contact with a small fly cod-
tinued 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 won-
derful 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

* * Eno^lish Botany,' liy Sir J. E. Smith ; with coloured figures by
J. Sowerby; edit, of 1832, tab. 24, 25, 26.

PINGUICULA VULGAKIS. Chap. XVI.

two or three days mucli 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 yery 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 di*y. But when the supply ot
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 in 3 hrs. 20 m. Glands excited by small
particles of meat, and which have quickly absorbed their own
secretion, begin to secrete again in the course of seven or eight
days from the time when the meat was given them.

(3) Three minute cubes of tough curtilage 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 hi's. 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 secre-
tion 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 -Jq 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 throughout 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 -gV or ^^ 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, 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 gV of an inch, 1 • 27 mm.)
were placed, one near the midrib and the other near the margin

Chap. XVI. SECRETION, ABSOEPTION, DIGESTION. 383

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 in a 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. 30 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 I 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 diificulty,
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 v/ould 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 secre-
tion 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

384 PINGUICULA VULGARIS. Chap. XVL

acid secretion, but were not quite dissolved after two days ; and
the glands then began to dry. Nor could their complete dis-
solution have been expected from what we have seen with
Drosera.

(11) Minute drops of skimmed m^7^ 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 airhonate 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 solu-
tion (viz. one part to 218 of water) was now added under the
covering glass ; after an hour or two the glands contained very
fine gi-anular 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 foil
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 dis-
coloured, and seemed to contain less matter than before; that

Chap. XVI. SECEETION, ABSOKPTION, DIGESTION. 385

which was left being of a dirty colonr, 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 aggre-
gated 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 effec-
tive, for it caused the secretion evidently to increase in 1 hr.
40 m., and ultimately to run 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 se-
lected 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 nemo-
ro^a, Bumex acetosa, Carex sylvatica, mustard, turnip, cress,
lianunculus acris, and Avena puhtscens, all excited much secre-
tion, whic'i 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 Eumex 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
grandijiorum, Cassia, Trifulium pannonicum, Plantago, onion.

386 PINGUICULA VULGAKIS. Chap. XYl.

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, Atriphx hortensis,
Fhalaris cunarierisis, 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 jDOwerfully and quickly, though the whole seeds
caused, as w^e have seen, very little secretion, and only after a
long interval of time. A slice of the common pea, which how-
ever 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 secre-
tion, is chiefly or wholly due to the different permeability
of their coats.

Some thin slices of the common pea, which had been pre-
viously 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 appa-
rently 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 sur-
rounding 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 thi-ee days on leaves and excited

Chap. XVI. SECRETION, ABSOEPTION, DIGESTION. 387

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 tv/o radish
seeds, neither germinated ; whereas of many seeds of the same
lot not subjected to the secretion, all, excepticg one, germinated.
Of the two Eumex 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 Ohjecis not containing Soluble Nitrorjenous 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.

(17) A particle of white sugar, j^laced 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. 30 m. 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
ieliquescence ; 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 concave, was actually filled with very viscid

888 PINGUICULA VULGARIS. Chap. XVI.

fluid ; and it particularly 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 arahic 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 jDarticles 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 f 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 I am 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 sjTup; those in
water remaining all the time crisp.

From the foregoing experiments and observations we

Chap. XVI. SECEETION, ABSOEPTION, DIGESTION. 389

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 secre-
tion 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 secre-
tion 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 w^eak 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

390 PINGUICULA GRANDIFLOEA. Chap. XVI.

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 a few
grains of pollen on a single gland causes it to
secrete copiously. We have also seen how fre-
quently the small leaves of Erica tetralix and of
other plants, as well as various kinds of seeds and
fruits, especially 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, con-
clude that Finguicula vulgaris, with its small roots,
is not only supported to a large extent by the extra-
ordinary number of insects which it habitually cap-
tures, 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 geandiflora.

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 midrib
being longer. But it likewise differs in constitution;
I hear from ]\Ir. Kalfs, who was so kind as to send
me plants from Cornwall, that it grows in rather
difierent sites ; and Dr. Moore, of the Glasnevin
Botanic Gardens, informs me that it is much more
manageable under culture, growing freely and flower-
ing annually ; whilst Finguicula vulgaris has to be
renewed every year. Mr. Ralfs found numerous

Chap. XVI. PINGUICULA LUSITANICA. 391

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 aliye. He also observed a few fruits
of Careoc piiUcaris, as well as 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 Pinguicala vulgaris.

Pinguicula lusitanica.

This species, of which living specimens were sent me
by Mr. Kalfs from Cornwall, is very distinct from the
two foregoing 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, multicellular 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 pro-

892 PINGUICULA LUSITANICA. Chap. XATE.

ceeding 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 ex-
periments 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
l^lactd 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 2^0 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 serai-liquefied state.

(2) A moderately sized bit of albumen was placed near the
apex of 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. A large proportion of the
albumen was dissolved, a remnant being still left.

(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 ;

Ohap. XVI. PINGUICULA LUSITANICA. 393

nor Could tliis 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 favoui'able conditions for growth; but they never ger-
minated, and a-fter a time were found rotten. They had no
doubt been killed by the secretion.

(5) Small bits of a spniach leaf caused in 1 hr. 20 m.
increased secretion ; 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 Fi7i-
guicula vulgaris. The above shght 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 no
movement 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 Dionsea.

894 PINGUICULA LUSITANICA. Chap. XVI.

(7) The flower-pednncles, 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 aggre-
gation. After 8 hrs. 30 m. they became colourless. Two minuto
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 obseryations on Finguicula lusi-
tanica we see that the naturally much incurved mar-
gins of the leaves are excited to curve still farther in-
wards 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 Pin-
guicala 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 observations serve, all three species agree in
their functional powers.

Chap. X\n. UTEICULARIA NEGLECTA. 395

CHAPTER XVII.

Utriculakia.

Utricularia neglecta — Structure of the bladder — The uses of the several
parts — Number of imprisoned animals — Manner of capture —
The bladders cannot digest animal matter, but absorb the products
of its decay — Experiments on the absorption of certain fluids by
the quadrifid processes — Absorption by the glands — Summary
of the observation on absorption — Development of the bladders —
Utricularia vulgaris — Utricularia minor — Utricularia clandestina.

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.f I
subsequently 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

* The 'Quart. Mag. of the f I am much indebted to the

High Wycombe Nat. Hist. Soc' Rev. H. M. Wilkinson, of Bistern,

July 1868, p. 5. Delpino (' Ult. for having sent me several fine

Osservaz. sulla Dicogamia,' &c. lots of this species from the New

1868-1869, p. 16) also quotes Forest. Mr. Ealfs was also so kind

Crouan as having found (1858) as to send me living plants of the

crustaceans within the bladders same species from near Penzance

of Utricularia vulgaris. in Cornwall.

396

UTRICULARIA NEGLECTA.

Chap. XVII.

on TJtricularia vulgaris has appeared ; * and it has been
no small satisfaction to me to find that my account
agrees almost completely with that of this distin-
guished observer. I will publish my description as
it stood before reading that by Prof. Cohn, adding
occasionally some statements on his authority.

Fig. 17.

(JJtricularia neglecta.')

Branch with the divided leaves bearing bladders ; about twice enlarged,

TJtricularia neglecta. — The general appearance of a
branch (about twice enlarged), with the pinnatifid leaves
bearing bladders, is represented in the above sketch
(fig. 17). The leaves continually bifurcate, so that
a full-grown one terminates in from twenty to thirty

'Beitrage zur Biologie der Pflauzen, ' drittes Heft, 1875.

Chap. XVn. STEUCTURE OF THE BLADDER. 397

points. Each point is tipped by a short, straight
bristle ; and slight notches on the sides of the
leaves bear similar bristles. On both surfaces there
are many small papillae, crowned with two hemi-
6j)herical 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 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
-iV of an inch (2*54 mm.) in length. They are trans-
lucent, 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, sur-
mounted by two hemispherical cells in such close
apposition that they appear united; but they often
separate a little when immersed in certain fluids. The
papillae 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 tw^o terminal cells are
transparent, but must hold much matter in solution,
judging from the quantity coagulated by prolonged
immersion in alcohol or ether.

* I infer that this is the case om Lentibiilariacese," from the

from a drawing of a seedling ' Videnskabelige Meddelelser,'

given by Dr. Warming in his Copenhagen, 1874, Nos. 3-7, pp.

paper, " Bidi-ag til Kundskaben 33-58.

398

UTEICULARIA NEGLECTA.

Chap. XVIL

The bladders are filled with water. They generally,
but by no means always, contain bubbles of air. Ac-
cording to the quantity of the contained water and
air, they vary much in thickness, but are always some-
what 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 Kev. H. M. Wilkinson examined

Fig. is.

( Utricularia neglecta.)

Bladder ; much enlarged, c, collar indistinctly seen through the walls.

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 late-
rally, with the appendages on the near side alone
represented, is sho^vn in the accompanying figure
(fig. 18). The lower side, where the footstalk arises, is
nearly straight, and I have called it 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

Chap. XVII. STRUCTUEE OF THE BLADDER.

399

the outside, six or seven long, pointed, multicellular
bristles. These prolongations of the Madder may be
conveniently called the antenna, for the whole bladder
(see fig. 17) curiously resembles an entomostracan crus-
tacean, the short footstalk representing the tail. In
fig. 18, the near antenna alone is shown. Beneath
the two antennae 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 out-

Fia. 19,

(^Utricularia neglecta.')

Valve of bladder ; greatly enlarged.

wards ; but only those (four in number) on the near
side are shown in the drawing. These bristles, to-
gether with those borne by the antennae, 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
18

400 UTEICULAEIA NEGLECTA. Chap. XVII.

bladder, as shown in the longitudinal section (fig. 20)
of the collar and yalve ; it is also shown at e, in fig. 18.
The edge of the vah^e can thus open only inwards.
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.

Fig. 20.
( rtricularia neglecta.)
Longitudinal vertical section through the A-entral portion of a bladder; showing valve
and collar, v, valve ; the whole projection above c forms the collar; h, bifid pro-
cesses ; s, ventral surface of bladder.

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 evi-
dently a prolongation. Two pairs of transparent
pointed bristles, about as long as the valve itself,
arise from near the free posterior margin (fig. 18),
and point obliquely outwards in the direction of the
antennae. There 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

Chap. XVII. STRUCTUEE OF THE BLADDER. 401

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 form-
ing 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 depres-
sion in which the valve lies is also lined with innu-
merable glands; those at the sides having oblong
heads and elongated pedicels, exactly like the glands
on the adjoining parts of the valve.

The collar (called the peristome by Cohn) is evi-
dently 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 lower 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-

402 UTKICULAKIA NEGLECTA. Chap. XVII

tween the inner and outer surface consists of coarse
cellular tissue (fig. 20). The inner side is thickly
covered ^yith 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.

Altogether the entrance into the bladder, formed by
the transparent valve, with its four obliquely project-
ing bristles, its numerous diversely shaped glands,
surrounded by the collar, bearing glands on the
inside and bristles on the outside, together with the
bristles borne by the antennae, presents an extra-
ordinarily complex appearance when viewed under
the microscope.

We will 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 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 contracts 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 end of the bladder. These arms
are only moderately sharp ; they are composed of ex-

Chap. XVIL STRUCTURE OF THE BLADDER.

403

tremely 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 proto-
plasm, as is likewise the short conical projection from
which they arise. Each arm generally (but not in-
variably) contains a minute, faintly brown particle,
either rounded or more commonly elongated, which
exhibits incessant Brownian movements. These par-

FiG. 21.

\JJtricularia neglecta.')

Small portion of inside of blad-
der, much enlarged, showing quad-
rifid processes.

Fig. 22.
{rtricularia neylecta.)
■ One of the quadrifid processes
greatly enlarged.

tides 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 quad-
rifids 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 con-
dition, for when absent, I could occasionally just dis-
tinguish in their places a delicate halo of matter,
including a darker spot. Moreover, the quadrifids of
Vtricularia montana contain rather lari^er and much

404 UTRICULAEIA NEGLECTA. Chap. XVII.

more regularly spherical, but otherwise similar, par-
ticles, 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, dif-
fering 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 j^i'oject into the bladder,
and are directed towards its posterior end. The quad-
rifid and bifid processes no doubt are homologous
with the papillae on the outside of the bladder and
of the leaves; and we shall see that they are de-
veloped from closely similar papilla?.

TJie Uses of the several Farts. — After the above long
but necessary description of the parts, we will turn to
their nses. 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 pro-
cess of decay, as I have often seen air in young, clean,
and empty bladders ; and some old bladders with much
decaying matter had no bubbles.

The real use of the bladders is to capture small
a<|uatic animals, and this they do on a large scale. In
tlie first lot of plants, which I received from the New
Forest early in July, a large proportion of the fully

Chap. XVII. MANNER OF CArTUEING PREY. 405

grown bladders contained prey ; in a second lot, re-
ceived 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, in-
cluding prey of some kind, and eight of these con-
tained entomostracan crustaceans, three larvse of in-
sects, 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 TJtricularia 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 consumed. Freshwater worms w^ere
also found by Cohn in some bladders. In all cases
the bladders with decayed remains swarmed with
living Algse of many kinds. Infusoria, and other low
organisms, which evidently lived as intruders.

Animals enter the bladders by bending inwards the
posterior 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

406 TJTKICULAEIA NEGLECTA. Chap. XVII

fits, I may mention that my son found a Daplmia
which had inserted one of its antennae into the slit,
and it was thus held fast during a whole day. On
three or four occasions I have seen long narrow larvae,
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
minute and weak animals, as are often captured,
could force their way into the bladders, I tried many
experiments to ascertain how this was eifected. 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,
entered with some difficulty ; a longer piece yielded
instead of entering. On three occasions minute par-
ticles 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 disap-
peared so suddenly that, not seeing what had happened,
I thought that I had flirted them off; but on ex-
amining the bladders, they were found safely enclosed.
The same thing occurred to my son, who placed little
cubes of green box-wood (about -^J^ 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 suddenly oj)ened and they were en-
gulfed. 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 hrs.
none had entered, but in from 2 to 5 hrs. all five
were enclosed. One of the particles of glass was a

Chap. XVII. MANNER OF CAPTURING PREY. 407

long splinter, of whicli 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 larvae, 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 -^V 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 particles
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 suppose, analogous to the
slow bending of colloid substances. For instance,
particles of glass were placed on various points of
narrow strips of moistened gelatine, and these yielded
and became bent with extreme slowness. 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 move-
ment of small crustaceans, but the valve did not
open. Some bladders, before being brushed, were left
for a time in water at temperatures between 80^ and
130° F. (26°-6— 54°-4 Cent.), as, judging from a wide-

408 UTPvICULAEIA NEGLECTA. Chap. XVII.

spread analogy, this would have rendered 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 Aveak creatures as are often captured
(for instance, the nauplius of a crustacean, and a tardi-
grade) should be strong enough to act in this manner,
seeing that it was difficult to push in one end of a
bit of a hair i 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 suc-
cessful than any other observer, and has often wit-
nessed in the case of TJtricularia clandestina the
whole process.* She saw a tardigrade slowly walk-
ing 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 entrap-
ment of various minute crustaceans. Cypris "was
" quite wary, but nevertheless was often caught.
" Coming to the entrance of a bladder, it would some-
" times pause a moment, and then dash away ; at
" other times it would come close up, and even ven-
" ture 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 antennae,
and closed its shell." Larvae, apparently of gnats,
when "feeding near the entrance, are pretty certain
" to run their heads into the net, whence there is no
" retreat. A large larva is sometimes three or four
" hours in being swallowed, the process bringing to

New York Tribune,' reprinted in the ' Gard. Chron.' 1875, p. 303.

Chap. XVII. MANNEE OF CAPTURING TEEY. 400

" 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 larvae, to enter the
bladders. Mrs. Treat says that the larva? just
referred to are vegetable-feeders, and seem to have a
sj)ecial 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 pro-
tection. It is 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 ap-
parently serve for the same purpose. I believe that
this is the case,^ because the bladders of some epi-
phytic 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 conditions would be of no service as a guide.
Nevertheless, with these epiphytic and marsh species,
two pairs of bristles project from the surface of the
valve, as in the aquatic species ; and their use pro-
bably 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 blad-
ders succeed in securing prey, in one case as many as
ten crustaceans ; — as the valve is so well fitted to

410 UTRICULAEIA NEGLECTA. Chap. XYIL

allow auimals to enter and to prevent their escape ; —
and as the inside of the bladder presents so singular
a structure, clothed with innumerable 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 same
family, I naturally expected that the bladders would
haye digested their prey ; but this is not the case, and
there are no glands fitted for secreting the j)roper
fluid. Nevertheless, 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, Diona3a, Droso-
phyllum, and Pinguicula ; so that I was familiar with
the appearance of these substances when under-
going the early and final stages of digestion. We may
therefore conclude that TJtricularia 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 any-
thing 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
imprisoned animals in a fresh state compared with
those utterly decayed. Mrs. Treat states with respect

Chat. XVIL ABSORPTION BY THE QUADRIFIDS. 411

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 them by the quadrifid and bifid pro-
cesses. The extremely delicate nature of the mem-
brane 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, excepting in each a single yellowish particle or
modified nucleus. Sometimes two or even three such
particles were present ; but in this case traces of decay-
ing matter could generally be detected. On the other
hand, in bladders containing either one large or several
small decayed animals, the processes presented a widely
different appearance. Six such bladders were care-
fully examined; one contained an elongated, coiled-
up larva ; another a single large entomostracan crusta-
cean, and the others from two to five smaller ones, all

412 UTRICULARIA NEGLECTA. Chap. XVU.

in a decayed state. In these six bladders, a large
number of the quadrifid processes contained transpa-
rent, often yellowish, more or less confluent, spherical
or irregularly 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 confluent, 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 appear-
ance, we may confidently believe that the protoplasm
in the above cases had been generated by the absorp-
tion 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 bro^\Ti
matter, showing that some minute animal had been
captured and had decayed, 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 containing dead
crustaceans, the processes were likewise empty. This
fact may be accoimted for by the animals not having
been sufficiently decayed, or by time enough not
having been allowed for the generation of proto-

Chap. XVII. ABSOKPTION BY THE QUADEIFIDS. 413

plasm, 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 Ahsorption of certain Fluids hy 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 appa-
rently 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 ascer-
tained 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.

Four bladders were first tried as a control experiment, in
the manner jnst described, in a solution of one part of gum
arable 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

41 -i UTKICULAEIA NEGLECT A. Chap. XYIL

change perceptible in the qnadrifids 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 437 of water, and
re-examined after 21 hrs. In two of these the qnadrifids now
appeared full of very finely gi-anular matter, and their proto-
plasmic lining or primordial utricle was a Uttle shrunk. In the
third bladder, the qnadrifids 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 pro-
cesses. 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 qnadrifids now contained very
fine granular matter.

A Wadder 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 qnadrifids contained a good many granules,
and the primordial utricle was somewhat shrunk ; after 23 hrs.
the qnadrifids and bifids contained many si^heres 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 qnadrifids
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 qnadrifids of one were examined
after 17 hrs., and found slightly opaque ; the quadi'ifids 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. SeveiM! uninjured bladders
were left in the same solution, as well as a v.eaker solution
of one part to 1750 of water, or 1 gr. to 4 oz. ; and after two
days the qnadrifids were more or less opaque, with their con-
tents 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 em-
ployed, I forgot that it had been kept for some days in a warm
room, and had therefore probably generated ammonia ; anyhow

Chap. XVII. ABSORPTION BY THE QUADRIFIDS. 415

the quadrifids were affected after 21 hrs. as if a solution of car-
bonate of ammonia had been used ; for the i^rimordial 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 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 blad-
ders 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 yellowish 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 qiiad-
rifid 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 contain-
ing captured prey. The effect produced on the pro-
cesses 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.

416 UTRICULAEIA NEGLECTA. Chap. XVII.

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 aggregate 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 l\ave 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.

As the quadrifids are developed from paj)ill8e 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 papillae are crowned, and which in their natural
state are perfectly transparent, likewise absorb car-
bonate and nitrate of ammonia ; 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 hy the Glands on
the Valve and Collar. — The glands round the orifices of
bladders which are still young, or which have been

Chap. XVII. ABSOKPTION BY THE GLANDS. 417

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 prim-
ordial 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 growing
in a state of nature, excepting when the water is re-
markably 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 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 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 blad-
ders 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.

418 UTRICULAEIA NEGLECTA. Chap. XVIL

In this latter case, as soon as the pressure is relaxed, air
is dra^Yn in, and the bladder recovers its proper form.
If it is now placed nnder 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 concln-ion, I experimeuted 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 antennae, 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-ex-
amined with the same power as before, namely No. 8 of Hart-
nack. 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 examined 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 i^rimordial
utricles of most of the glands were somewhat contracted ; they
were also thickened in specks or patches, and had assumed a pale

Chap. XVII. ABSOKPTION BY THE GLANDS. 419

brown tint. When looked at again after 1 hr. 30 m., most of
them presented a somewhat different appearance. A third
specimen w^as treated with a ^veaker solntion of one part of the
carbonate to 437 of w'ater, 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 consider-
ably shrunk and brownish after 2 hrs. Similar effects were
observed in the two other specimens, but these were not ex-
amined 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 mode-
rately 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 blad-
ders were examined, and all their glands w-ere 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 phosphate 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 w^ere 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. 30 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

420 UTRICULAEIA NEGLECTA. Chap. XVII.

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 speci-
mens, 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 w^ere 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
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 to a 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 ii-rigated wath
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 w^ere 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 primordial 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 sliglitly
shrunk; and the oblong glands were brownish, with their
utricles much, but irregularly, shrunk. The summit was
treated with the solution of ui'ea, 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.
4.0 m. some few of them were quite brown, and contained

Ohap. XVII. SUMMAEY ON ABSOKPTION. 42l

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 hrs.

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 in-
cluding 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 colourless, be-
came brown in 3 hrs. 12 m. after irrigation, with their utricles
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. 30 m., after 4 hrs,, and 9 hrs. ; a brief account of their
condition will be suflBcient. 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.

Sum7nary 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, ex-
cepting that, after immersion in alcohol, extremely
fine lines could sometimes be seen radiating from their

422 UTEICULAEIA NEGLECTA. Ciiap. XVII.

surfaces. The glands are variously affected by absorp-
tion ; they often become of a brown colour ; sometimes
they contain very fine granules, or moderately sized
grains, or irregularly aggregated little masses ; some-
times 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 sj)herical 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 some-
what 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 unknow^n 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 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

CiiAP. XVII. SUMMAKY ON ABSORPTION. 423

any appearance making it probable that glands which
have been strongly afiectcd by absorbing matter of
any kind are capable of recovering their pristine,
colourless, and homogeneous condition, and of regain-
ing 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 spon-
taneous 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 maintained, namely that they absorb matter
from putrid water occasionally emitted from the
bladder>', they ought to act more quickly than the
processes ; as these latter remain in permanent con-
tact with captured and decaying animals.

Finally, the conclusion to which we are led by
the foregoing 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
19

424 UTKICULAEIA NEGLECTA. Chap. XVII.

ammonia, from a putrid infusion of raw meat, and from
urea. The 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 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 sj)ecies the quadrifid
and bifid processes of bladders containing decayed
animals generally include little masses of spontane-
ously 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 Utri-
cularia vulgaris, but were made chiefly on the latter, as
the bladders are twice as large as those of TJtricularia
neglecta. In the early part of autumn the stems ter-
minate 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
vulgaris are about -p^ inch ('254 mm.) in diameter
(or ^-^ in the case of TJtricularia neglecta), they are
circular in outline, with a narrow, almost closed, trans-
verse orifice, leading into a hollow filled with water ;
but the bladders are hollow when much under -j-^ of
an inch in diameter. The orifices face inwards or
towards the axis of the plant. At this early age the
bladders are flattened in the plane in which the orifice
lies, and therefore at right angles to that of the
mature bladders. They are covered exteriorly with
papillae of different sizes, many of which have an
elliptical outline. A bundle of vessels, formed of

Chap. XVII. DEVELOPMENT OF THE BLADDEKS. 425

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 foot-
stalk and between the nascent antennae of a bladder
of Utricularia vulgaris, -p^ inch
in diameter. The specimen was
soft, and the young valve be-
came separated from the collar
to a greater degree than is
natural, and is thus represented.
We here clearly see that the
valve and collar are infolded
prolongations of the walls 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 antennte 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 antennae were not of quite equal
length; and this 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

Fig. 23.

{Utricularia vulgaris.)

Longitudinal section through

a young bladder, -^ of an inch

in length, with the orifice too

widely open.

426

UTKICULAEIA NEGLECTA.

Chap. XYII.

must therefore be developed one after the other, and
so it wonld be with the two antennee.

At a much earlier age, when the half formed
bladders are only 3-^ inch ('0846 mm.) in diameter
or a little more, they present a totally different ap-
pearance. One is represented on the left side of the
accompanying drawing (fig. 24). The young leaves

Fig. 24.

{Utricularia vulgaris.')

Young leaf from a wiuter bud, showing on the left side a bladder in its earliest stage

of development.

at this age have broad flattened segments, with their
future divisions represented by prominences, one of
which is shoT^^l 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 aj)ex 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

Chap. XVII. DEVELOPMENT OF THE BLADDEKS. 427

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
asymmetrically from the sides of the apex and pro-
minence. Moreover, the bundles of vascular tissue
have to be formed in lines quite irrespective 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 m Utricularia neglecta. In bladders
about -j-^ of an inch in diameter, the inner surface
is studded with papillae, rising from small cells at the
junctions of the larger ones. These papillae consist of
a delicate conical protuberance, which narrows into
a very short footstalk, surmounted by two minute
cells. They thus occupy the same relative position,
and closely resemble, except in being smaller and
rather more prominent, the papillae on the outside of
the bladders, and on the surfaces of the leaves. The
two terminal cells of the papilla3 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 sepa-
rate 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

428 UTKICULAEIA VULGAEIS. Chap. XVII.

and more horizontal pair; the four together forming
a perfect quadriiid. A trace of the primary division
between the two cells on the summits of the papillae can
still be seen between the bases of the longer processes.
The development of the quadriiids is very liable to
be arrested. I have seen a bladder -^ 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
developed 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 development ; but
w^e may reasonably suspect that they are developed
from papillae 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 quadrifid and bifid processes. I am
strengthened in the belief that the glands are de-
veloped from papillae like those on the outside of the
bladders, from the fact that in Utricular i a amethystina
the glands extend along the whole ventral surface
of the bladder close to the footstalk.

Utriculaeia vulgaris.

Living plants from Torksliire were sent me by Dr. Hooker.
This species dififers 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 ; and the bladders are twice
as large, or about i of an inch (5*08 mm.) in diameter. In
all essential respects the bladders resemble those of Utricularia
negleda, but the sides of the peristome are perhaps a little more

Chap. XVn. UTEICULARIA MINOE. 429

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, containing prey of some kind, were examined. The
first included five Cypris, a large copepod and a Diaptomus ;
the second, four CyiDris ; the third, a single rather large crus-
tacean ; 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.

UtKICULAEIA MINOE.

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 smaller than those of Utricnlaria neglecta.
The leaves bear fewer and shorter bristles, and the bladders are
more globular. The antennse, instead of projecting in front
of the bladders, are curled under the valve, and are armed with
twelve or fourteen extremely long
multicellular 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 ani-
mals, excepting very small ones,
entering the bladder. The valve
and collar have the same essential Fig. 25.

structure as in the two previous ( Ctricularia minor.)

species; but the glands are not QnadriM process ; greatly enlarged.

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 antennse, 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)

430 UTKICULAKIA CLANDESTINA. Chap. XVII.

being directed to the same side ; tlie two 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. The first contained no less than
twenty-four minute fresh-water crustaceans, most of them con-
sisting of empty shells, or including 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 stufi"ed 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 decay-
ing mass contained numerous spheres of granular matter,
which slowly changed their forms and positions.

Utkicularia clandestina.

This North American species, which is aquatic like the three
foregoing 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, 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 suppose of Culicidse. On
some stems, "fully nine out of every ten bladders contained
these larvae or their remains." The larvae " showed signs of life
from twenty-four to thii'ty-six hours after being imprisoned,"
and then perished.

Ch\p. XVIII.

UTRICULARIA MONTANA.

431

CHAPTEK XVIII.

Utkicitlakia (continued).

Utricularia montana — Description of the bladders on the subter-
ranean rhizomes — Prey captiu'ed by the bladders of plants under
culture and in a state of nature — Absorption by the quadrifid pro-
cesses 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.

Uteiculaeia 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 spe-
cimens 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 IJ inch in breadth,
and furnished with a dis-
tinct footstalk. The phint produces numerous colour-
less rhizomes, as thin as threads, which bear minute
bladders, and occasionally swell into tubers, as will

Fig. 26.

( Utricularia montana.')

Rhizome swollen into a tuber; the
branches bearing minute bladders ; of
natural size.

432 UTEICULAEIA MONTANA. Chap. XVILT.

hereafter be described. These rhizomes aj^pear ex-
actly like roots, but occasionally throw np green
shoots. They penetrate the earth sometimes tp 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 necessarily subterranean. They are produced in
extraordinary numbers. 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 between the summit
of the long delicate footstalk and valve, extremely
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 ^ of an
inch (1-27 mm.) in its longer diameter. They are
formed of rather large angular cells, at the junctions
of which oblong papillae project, corresponding with
those on the surfaces of the bladders of the previous
species. Similar papillae 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

* Prof. Oliver has figured a clearly indicates that the bladders

plant of Utricularia Jamesoniana on the rliizomes of the present and

('Proc. Linn. Soc' vol. iv. p. I(i9) following species are modified seg-

having entire leaves and rhizomes, ments of the leaf; and they are

like those of our present species ; thus brought into accordance with

but the margins of the terminal the bladders attached to the di-

halves of some of the leaves are vided and floating leaves of the

converted into bladders. This fact aquatic species.

Chap. XVIII. STKUCTURE OF THE BLADDERS. 433

just enter the bases of the bladders ; but they do not
bifurcate and extend up the dorsal and ventral sur-
faces, as in the previous species.

The antennae 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

Fig. 27.

( Utricularia montana.)

Bladder; about 27 times enlarged.

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 in the drawing,
as well as a narrow passage between the bases of the
two antennse. 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

434 UTRICULAEIA MONTANA. Chap. XVIIL

and rubbish ; so that the curvature of the antennae is
a serviceable 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
posterior edge abutting against a semicircular, deeply-
depending collar. It is 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 antennae 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 footstalks. These
glands are only the -^-^^ of an inch ('019 mm.) in
length ; though so small, they act as absorbents.
The collar is thick, stiff, and almost semi-circular ; 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 approxi-
mately concentric 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

Chap. XVIII. CAPTUKED ANIMALS. 435

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 antenna3 and on the outside of
the collar. The presence of these bristles in the pre-
viously mentioned species probably relates to the
capture of aquatic animals.

Fig. 28.

(JJtricularia montana.')

One of the quadrifid processes ; much enlarged.

It seemed to me an interesting question whether
the minute bladders of Utricularia montana served, as in
the previous s]3ecies, 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, there-
fore, were examined, with the following results : —

(1) A small bladder, less than J^of an inch ('847 mm.) in dia-
meter, contained a minute mass of brown, mnch. 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

436 UTEICULAKIA MONTANA. Chap. XVIII.

or less globular, or fine grannies. 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 aggre-
gated 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 afiocted,
excepting that the nuclei in the several arms differed much in
size; some of them containing 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, remind-
ing me of two similar cases with Utricidaria negUcta.

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 specimens 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 exceiDt its transparent coat ;

Chap. XVIII. ABSORPTION. 437

also a yellow chitinoiis 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 Glaus has looked at this latter organism,
and thinks that it is the shell of a rhizopod, probably one of the
Arcellidse. In this bladder, as well as in several others, there
were some unicellular Algae, 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 of 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 organ-
isms, as well as much dark brown organic matter, 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, but with no distinguish-
able 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 of what nature could not be dis-
tinguished.

Only one experiment was tried on the quadrifid pro-
cesses and glands with reference to their f)Ower 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; in others there
were two masses of different sizes, one large and the

438 UTEICULARIA MONTANA. Chap. XVIII.

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 sepa-
rate masses; and that these then tended to coalesce.
The primordial utricle or protoplasm lining the pro-
cesses was also thickened here and there into irregular
and variously shaped specks of yellowish translucent
matter, as occurred in the case of TJtricularia 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 posi-
tions. 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 culti-
vated, there can be no doubt that the bladders, though
so small, are far from being in a rudimentary con-
dition ; 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

Chap. XVIII. EESERVOIES FOR WATER. 439

the cavity beneath the bowed antennae, 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 a 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 pos-
sible gradations between a short length of a rhizome
just perceptibly swollen and one so 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
(1143 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 papillae. 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 con-

440 UTRICULARIA MONTANA. Ghap. XVIII.

elude that tlie tubers do not serve as reservoirs for
food, but for water during the dry season to which the
phint 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 4^ by 4^
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 ex-
tremely 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 a road. All the
tubers had their surfaces much wrinkled, instead of
being smooth and tense. They had all shrunk, but I
cannot say accurately how much ; for as they were at
first symmetrically oval, I measured only their length
and thickness ; but they contracted 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 thick-
ness 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

Chap. XVIII. UTEICULAEIA NELUMBIFOLIA. 441

and examined. The cells still contained mnch 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.

AVith 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 consequence
received the name of orcliidioides. 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.

UtKICULAEIA NELUMBIFOLIA, AMETHYSTINA, GKIF-
FITHII, C^RULEA, ORBICULATA, MULTICAULIS.

As I wished to ascertain whether the bladders on
the rhizomes of other species of Utricularia, and of the

442 UTKICULAEIA NELUMBIFOLIA. Chap. XVIII.

species of certain closely allied genera, had the same
essential structure as those of TJtricularia montana, and
whether they caj)tured prey, I asked Prof. Oliver to send
me fragments from the herbarium at Kew. He kindly
selected some of the most distinct forms, haying 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.*

TJtricularia nelimibifolia (Organ Mountains, Brazil). —
The habitat of this sjDecies is remarkable. According
to its discoverer, Mr. Gardner,! 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 moun-
tain, 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 JJtricidaria 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,

* Prof. Oliver has given (' Proc. but he does not appear to have

Linn. Soc.' vol. iv. p. 169) figures paid particular attention to these

of the bladders of two South organs.

American species, namely, Utri- f ' Travels in the Interior of

cularia Jamesoniana and peltata; Brazil, 1836-41,' p. 527.

Chap. XVIII. UTRICULARIA AMETIIYSTINA. 443

having a brush of long sharp bristles at the apex.
Other bladders included fragments of articulate ani-
mals, and many of them contained broken pieces of a
curious organism, the nature of which was not recog-
nised by anyone to whom it was shown.

Utricularia ametliystina (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 are covered outside
wdth the usual papilla? ; but they differ remarkably in
the antennae 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 mem-
brane; and the short ventral surface of the' bladder,
between the petiole and valve, is thickly covered with
glands. Most of the heads had fallen off, and the foot-
stalks 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
w^hich 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 decay-
ing prey.

Utricularia griffitliii (Malay and Borneo). — The
bladders are transparent and minute; one which was
measured being only ^H^ of an inch (-711 mm.)
in diameter. The antennae are of moderate length, and

444 UTRICULARIA MULTICAULIS. Chap. XVIII.

project straight forward ; they are united for 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. The bladders
also differ remarkably from those of the j)revious 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.

UtriculariOf cserulea (India). — The bladders re-
semble those of the last species, both in the general
character of the antennae and in the processes with-
in being exclusively bifid. They contained remnants
of entomostracan crustaceans.

Vtricularia orhiculata (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 antennae, 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 wdthin
the bladders are quadrifid, with the four diverging
arms of equal length. The prey which they had
captured consisted of entomostracan crustaceans.

Utrieularia multicaulis (Sikkim, India, 7000 to
11,000 feet). — The bladders, attached to rhizomes,
are remarkable from the structure of the antennae.
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 ap]3ear like a
great digitate expansion at one end of the bladder.
Internally the quadrifid processes have divergent arms
of equal length. The bladders contained remnants of
articulate animals.

Chap. XVIII. POLYPOMPHOLYX. 445

POLYPOMPHOLYX.

This genus, which is confined to Western Australia,
is characterised by having a " quadripartite calyx." In
other respects, as Prof. Oliver remarks,* " it is quite a
Utricularia."

Pohjpo7n]oholj/x multifida. — The bladders are attached
in whorls round the summits of stiff stalks. The two
antennae are represented by a minute membranous
fork, the basal part of which forms a sort of hood over
the orifice. This 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 speci-
mens. The inner surface of the hood is lined with
long simple hairs, containing aggregated matter, like
that within the quadrifid processes of the previously
described species when in contact with decayed ani-
mals. These hairs appear therefore to serve as absor-
bents. 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 papillae,
having very short footstalks. The quadrifid processes
have divergent arms of equal length. Remains of
entomostracan crustaceans were found within the
bladders.

Polypomphohjx tenella. — The bladders are smaller
than those of the last species, but have the same
general structure. They were full of debris, apparently
organic, but no remains of articulate animals could
be distinguished.

Proc. Linn. Soc' vol. iv. p. 171.

446 GENLISEA OENATA. Chap. XVIIL

Genlisea.

This remarkable genus is teclinically clistingiiislied
from Utricularia, as I hear from Prof. Oliver, Ly
having a five-partite calyx. Species are found in
several parts of the world, and are said to be " herbse
annuae paludos?e."

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 (h) is formed
by a slight enlargement 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 -^V of an inch
(•705 mm.) in its longer diameter had a neck 44
(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 understood 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

* " Bidrag til Kundskaben om Lentibulariaceoe," Copenhagen, 1874.

Chap. XVIII. STEUCTURE OF THE LEAVES.

447

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 be-
tween them. They are in-
deed in many places a little
separated, forming narrow
entrances into the tube ;
but this may be the result
of the drying of the speci-
mens. The lamina of which
the tube is formed seems
to be a lateral prolongation
of the lip of the orifice ;
and the spiral line between
the two projecting edges is
continuous with the corner
of the orifice. If a fine
bristle is pushed down one
of the arms, it passes into
the top of the hollow neck.
Whether the arms are open
or closed at their extre-
mities could not be deter-
mined, as all the specimens
were broken; nor does it
appear that Dr. Warming
ascertained this point.

So much for the external
structure. Internally the

lower part of the utricle is covered with spherical
papillae, formed of four cells (sometimes eight accord-
ing to Dr. Warming), which evidently answer to the
quadrifid processes withjn the bladders of Utricularia.
20

Q-- — - 6

1

Fig, 29.

{Genlisea ornata.)

Utriculiferous leaf; onlarged about

three times.

I Upper part of lamina of leaf,
& Utricle or bladder.
n Neck of utricle.
0 Orifice.

a Spirally wound arms, with their
ends broken off.

448

GENLISEA OKNATA.

Chap. XYIII.

These papillae 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 pa-
pillae abound. The neck
is likewise lined throughout
its whole length with trans-
verse 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 epi-
dermic 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 sjDlit open and laid
flat, the inner surface re-
sembles a paper of pins, —
the hairs representing the
pins, and the little transverse
ridges representing the folds
of paper through which the
pins are thrust. These rows of hairs are indicated
in the previous figure (29) by numerous transverse
lines crossing the neck. The inside of the neck is

Fig. 30.

{Genlisea ornata.')

Portion of inside of neck leading
into the utricle, greatly enlarged, show-
ing the downward pointed bristles,
and small quadrifid cells or processes.

Chap. XVIIT. CAPTURED PREY. 449

also studded with papillae ; those in the lower part are
spherical and formed 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 papillae
apparently correspond with the bifid process in the
upper part of the bladders of Utricularia. The narrow
transverse orifice (o, fig. 29) is situated between the
bases of the two spiral arms. JSTo valve could be
detected here, nor was any such structure seen by
Dr. Warming. The lips of the orifice 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, elon-
gated papillae, resembling those in the upper part of
the neck, but differing slightly from them, according
to Warming, in their footstalks being formed by
prolongations 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.

The utricles contained much debris or dirty matter,
which seemed organic, though no distinct organisms

450 GENLISEA OKNATA. Chap. XVIII,

could be recognised. It is, indeed, scarcely possible
that any object could enter the small orifice and pass
down the long narrow neck, excej)t 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, probably the
remnants of other minute creatures, were found.
Many of the papillae 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 w^ay down the neck, it would be scarcely possible
for them to return, owing to the many transverse rows
of long, straight, downward pointing hairs, together
with the ridges from which these project. Such crea-
tures would, therefore, perish either within the neck
or utricle ; and the quadrifid and bifid papillae would
absorb matter from their decayed remains. The
transverse 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 of
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

Chap. XVIII. GENLISEA FILIFORMIS. 451

the tube into tlie 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
papillae. 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.

Genlisea afrieana (South Africa). — Fragments of the
utriculiferous 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 furnished with elongated papillce, exactly
like those within the neck of Genlisea ornata. It is
probable, therefore, that the whole utricle is similarly
constructed.

Genlisea filiforniis (Bahia, Brazil). — Many leaves
were examined and none were found jDrovided with
utricles, whereas such leaves were found without diffi-
culty in the three previous species. On the other
hand, the rhizomes bear bladders resembling in essen-
tial character those on the rhizomes of Utricularia.
These bladders are transparent, and very small, viz.
only -j-^ of an inch ('254: mm.) in length. The
antennae are not united at their bases, and apparently
bear some long hairs. On the outside of the bladders
there are only a few papillae, and internally very few
quadrifid processes. These latter, however, are of un-
usually large size, relatively to the bladder, with the
four divergent arms of equal length. No prey could
be seen within these minute bladders. As the rhizomes
of this species were furnished with bladders, those of
Genlisea afrieana, ornata, and aurea were carefully

452 CONCLUSION. Chap. XVIII.

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
XJtricularia, 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 ?

Conclusion. — It has now been shown that many
species of XJtricularia and of two closely allied genera,
inhabiting the most distant parts of the world —
Europe, Africa, India, the Malay Archipelago, Austra-
lia, North and South America — are admirably adapted
for capturing by two methods small aquatic or terres-
trial animals, and that they absorb the products 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
Droseracese, 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 sub-
stances, such as pollen, seeds, and bits of leaves. No
doubt their glands likewise absorb the salts of am-
monia brought to them by the rain. It has also been
shown that some other plants can absorb ammonia by

Chap. XVIII. CONCLUSION. 453

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 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. 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. Lastly, 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 subsistence.

INDEX.

ABSORPTION.

A.

Absorption by Diongea, 295

by Drosera, 17

by Drosophyllum, 337

by Pinguicula, 381

by glandular hairs, 344

by glands of Utricularia, 416,

421

• by quadrifids of Utricularia,

413, 421
— — by Utricularia montana, 437
Acid, nature of, in digestive secre-
tion of Drosera, 88

present in digestive fluid of

various species of Drosera, Dio-
nsea, Drosophyllum, and Pingui-
cula, 278, 301, 339, 381

Acids, various, action of, on Drosera,
188

of the acetic series replacing

hydrochloric in digestion, 89

, arsenious and chromic, action

on Drosera, 185

, diluted, inducing negative

osmose, 197

Adder's poison, action on Drosera,
206

Aggregation of protoplasm in Dro-
sera, 38

in Drosera induced by salts of

ammonia, 43

caused by small doses of

carbonate of ammonia, 145

of protoplasm in Drosera, a

reflex action, 242

— — in various species of

Drosera, 278
in Dionsea, 290, 300

Aggregation of protoplasm in Dro-
sophyllum, 337, 339

in Pinguicula, 370, 389

in Utricularia, 411, 415,

429, 430, 436

Albumen, digested by Drosera, 92

, liqiiid, action on Drosera, 79

Alcohol, diluted, action of, on Dro-
sera, 78, 216

Aldrovanda vesiculosa, 321

, absorption and digestion by,

325

■ , varieties of, 329

Algfe, aggregation in fronds of, 65

Alkalies, arrest digestive process in
Drosera, 94

Aluminium, salts of, action on
Drosera, 184

Ammonia, amount of, in rain vyater,
172

, carbonate, action on heated

leaves of Drosera, 69

, , smallness of doses caus-
ing aggregation in Drosera, 145

— — , , its action on Drosera,

141

, , vapour of, absorbed by

glands of Drosera, 142

', , smallness of doses caus-
ing inflection in Drosera, 145,
168

, phosphate, smallness of doses

causing inflection in Drosera,
153, 168

, , size of particles afiecting

Drosera, 173

, nitrate, smallness of doses

causing inflection in Drosera, 148,
168

, salts of, action on Drosera, 136

456

mDEX.

AMMONIA.

Ammonia, salts of, their action
affected by previous immersion in
water and various solutions, 213

, , induce aggregation in

Drosera, 43

• , various salts of, causing in-
flection in Drosera, 166

Antimony, tartrate, action on Dro-
sera, 185

Areolar tissue, its digestion by
Dro.<era, 102

Ari^enious acid, action on Drosera,
185

Atropine, action on Drosera, 204

B.

Barium, salts of, action on Drosera,

183
Bases of salts, preponderant action

of, on Drosera, 186
Basis, fibrous, of bone, its digestion

by Drosera, 108
Belladonna, extract of, action on

Drosera, 84
Bennett, Mr. A. "W., on Drose a, 2
• , coats of pollen-grains not

digested by insects, 117
Binz, on action of quinine on white

blood-corpuscles, 201
, on poisonous action of quinine

on low organisms, 202
Bone, its digestion by Drosera, 105
Brunton, Lauder, on digestion of

gelatine, 111
, on the composition of casein,

115

, on the digestion of urea, 124

, of chlorophyll, 126

■, of pepsin, 124

Byblis, 343

C.

Cabbage, decoction of, action on
Drosera, 83

Catlmium chloride, action on Dro-
sera, 183

Caesium, chloride of, action on
Drosera, 181

Calcium, salts of, action on Drosera,

182
Camphor, action on Drosera, 209
Canby, Dr., on Dionsea, 301, 310,

313

, on Drosera filiformis, 281

Caraway, oil of, action on Drosera,

211
Carbonic acid, action on Drosera, 221
, delays aggregation in Drosera,

59
Cartilage, its digestion by Drosera,

103
Casein, its digestion by Drosera, 114
Cellulose, not digested by Drosera,

125
Chalk, precipitated, causing inflec-
tion of Drosera, 32
Cheese, its digestion by Drosera,

116
Chitine, not digested by Drosera,

124
Chloroform, effects of, on Drosera,

217

, , on Dionaa, 304

Chlorophyll, grains of, in living

plants, digested by Drosera, 126
, pure, not digested by Drosera,

125
Chondrin, its digestion by Drosera,

112
Chromic acid, action on Drosera,

185
Cloves, oil of, action on Drosera, 212
Cobalt chloride, action on Drosera,

186
Cobra poison, action on Drosera,

206
Cohn, Prof., on Aldrovanda, 321
, on contractile tissues in plants,

364
, on movements of stamens of

Compositse, 256

, on Utricularia, 395

Colchicine, action on Drosera, 204
Copper chloride, action on Drosera,

185
Crystallin, its digestion by Drosera,
• 120

Curare, action on Drosera, 204
Curtis, Dr., on Dionaea, 301

INDEX.

457

DAKWDf.

Darwin, Francis, on the effect of an

induced galvanic current on Dro-

sera, 37
, on the digestion of grains of

chlorophyll, 126

■ , on Utricularia, 442

Delpino, on Aldrovanda, 321

, on Utricularia, 395

Dentine, its digestion by Drosera,

106
Digestion of various substances by

Dionsea, 301

by Drosera, 85

by Drosophyllum, 339

by Pinguicula, 381

, origin of power of, 361

Digitaline, action on Drosera, 203
Dionaea muscipula, small size of

roots, 286

, structure of leaves, 287

, sensitiveness of filaments,

289

, absorption by, 295

• , secretion by, 295

, digestion by, 301

, effects on, of chloroform, 304

, manner of caplmiug insects,

305
, transmission of motor impulse,

313

■ , re-expansion of lobes, 318

Direction of inflected tentacles of

Drosera, 243
Dohrn, Dr., on rhizocephalous crus-
taceans, 357
Donders, Prof., small amount of

atropine affecting the iris of the

dog, 172
Dragonfly caught by Drosera, 2
Drosera anglica, 278

binata, vel dichotoma, 281

capensis, 279

filiformis, 281

heterophylla, 284

intermedia, 279

Drosera rotundifolia, structure of

leaves, 4
, effects on, of nitrogenous

fluids, 76

FIBROUS.

Drosera rotundifolia, effects of heat

on, 66

, its power of digestion, 85

, backs of leaves not sensitive,

231
, transmission of motor impulse,

234

, general summary, 262

spathulata, 280

Droseracese, concluding remarks on,

355
, their sensitiveness compared

with that of animals, 366
Drosophyllum, structure of leaves,

333

, secretion by, 334

, absorption by, 337

, digestion by, 339

Enamel, its digestion by Drosera,

106
Erica tetralix, glandular hairs of,

351
Ether, effects of, on Drosera, 219

, , on Dionsea, 304

Euphorbia, process of aggregation

in roots of, 63
Exosmose from backs of leaves of

Drosera, 231

F.

Fat not digested by Drosera, 126
Fayrer, Dr., on the nature of cobra

poison, 206
, on the action of cobra poison

on animal protoplasm, 208
, on cobra poison paralysing

nerve centres, 224
Ferment, nature of, in secretion of

Drosera, 94, 97
Fibrin, its digestion by Drosera, 100
Fibro-cartilage, its digestion by

Drosera, 104
Fibro-elastic tissue, not digested by

Drosera, 122
Fibrous ba&is of bone, its digestion

by Drosera, 108

458

INDEX.

FLUIDS.

Fluids, nitrogenous, effects of, on
Drosera, 76

Fournier, on acids causing move-
ments in stamens of Berberis, 19G

Franklaud, Prof., on nature of acid
in secretion of Drosera, 88

Galvanism, current of, causing in-
flection of Drosera, 37

, effects of, on Dionsea, 318

Gardner, Mr., on Utricularia nelum-
bifolia, 442

Gelatine, impure, action on Drosera,
80

, pure, its digestion by Drosera,

110

Genlisea africana, 451

filiformis, 451

Genlisea ornata, structure of, 446

, manner of capturing prey,

450

Glaudular hairs, absorption by, 344

, summary on, 353

Globulin, its digestion by Drosera,
1^0

Gluten, its digestion by Drosera,
117

Glycerine, inducing aggregation in
Drosera, 52

, action on Drosera, 212

Gold chloride, action on Drosera,
184

Gorup-Besanez on the presence of a
solvent in seeds of the vetch, 362

Grass, decoction of, action on Dro-
sera, 84

Gray, Asa, on the Droseracese, 2

Greenland, on Drosera, 1, 5

Gum, action of, oa Drosera, 77

Gun-cotton, not digested by Dro-
sera, 125

Hsoraatin, its digestion by Drosera,

121
Hairs, glandular, absorption by, 344
, , summary on, 353

Heat, inducing aggregation in Dro-
sera, 53

, effect of, on Drosera, G6

, , on Dionsea, 291, 319

Heckel, on state of stamens of Ber-
beris after excitement, 43
Hofmeister, on pressure arresting

movements of protoplasm, 61
Holland, Mr., on Utricularia, 395
Hooker, Dr., on carnivorous plants, 2
, on power of digestion by Ne-
penthes, 97

, history of observations on

Dionsea, 286
Hydrocyanic acid, effects of, on

Dionaea, 305
Hyoscyamus, action on Drosera, 84,
206

Iron chloride, action on Drosera,

185
Isinglass, solution of, action on

Drosera, 80

J.

Johnson, Dr., on movement of flower-
stems of Pinguicula, 381

Klein, Dr., on microscopic character
of half digested bone, 106

, on state of half digested fibro-

cartilage, 104

■ , on size of micrococci, 173

Knight, Mr., on feeding Dionaja, 301
Kossmann, Dr., on rhizocephalous
crustaceans, 357

Lead chloride, action on Drosera,

184
Leaves of Drosera, backs of, not

sensitive, 231

INDEX.

459

LEGUMIN.

PINGUICULA.

Legumin, its digestion by Drosera,

116
Lemna, aggregation in leaves of, 64

N.

Nepenthes, its power of digestion,

Lime, carbonate of, precipitated,

97

causing inflection of Drosera, 32

Nickel chloride, action on Drosera,

, pliosphate of, its action on

186

Drosera, 109

Nicotiana-tabacum, glandular hairs

Lithium, salts of, action on Drosera,

of, 352

181

Nicotine, action on Drosera, 203

Nitric ether, action on Drosera, 220

Nitschke, Dr., references to his

.M.

papers on Drosera, 1

, on sensitiveness of backs of

Magnesium, salts of, action on Dro-

leaves of Drosera, 231

sera, 182

— -, on direction of inflected ten-

Manganese chloride, action on Dro-

tacles in Drosera, 244

sera, 1S5

, on Aldrovanda, 322

Marshall, Mr. "W., on Pinguicula,

Nourishment, various means of, by

369

plants, 452

Means of movement in Diontea, 313

Nuttall, Dr., on re-expansion of

in Drosera, 254

Dionaea, 318

Meat, infusion of, causing aggrega-

tion in Drosera, 51

■ , , action on Drosera, 79

0.

■ , its digestion by Drosera, 98

Mercury perchloride, action on

Odour of pepsin, emitted from leaves

Drosera, 183

of Drosera, 88

Milk, inducing aggregation in Dro-

Oil, olive, action of, on Drosera, 78,

sera, 51

126

, action on Drosera, 79

Oliver, Prof., on Utricularia, 432,

, its digestion by Drosera, 113

441-446

Mirabilis longiflora, glandular hairs

of, 352

Moggridge, Traherne, on acids in-

P.

juring seeds, 128

Moore, Dr., on Pinguicula, 390

Papaw, juice of, hastening putrefac-

Morphia acetate, action on Drosera,

tion, 411

205

Particles, mimite size of, causing

Motor impulse in Drosera, 234, 258

inflection in Drosera, 27, 32

in Dionsea, 313

Peas, decoction of, action on Dro-

Movement, origin of power of, 363

sera, 82

Movements of leaves of Pinguicula,

Pelargonium zonale, glandular hairg

371

of, 350

of tentacles of Drosera, means

Pepsin, odour of. emitted from Dro-

of, 254

sera leaves, 88

of Dionsea, means of, 313

, not digested by Drosera, 123

jMucin, not digested by Drosera,

, its secretion by animals ex-

122

cited only after absorption, 129

Mucus, action on Drosera, 80

Peptogenes, 129

Muller, Fritz, on rhizocephalous

Pinguicula grandiflora, 390

crustaceans, 357

460

INDEX.

PINQUICULA.

SAXIFKAGA.

Pinguicula vulgaris, structure of

leaves and roots, 368

E.

, number of insects caught by,

369

Eain -water, amount of ammonia in.

, power of movement, 371

172

, secretion and absorption by,

Ralfs, iRIr , on Pinguicula, 390

381

Ransom, Dr., action of poisons on

, digestion by, 381

the yolk of eggs, 225

, eflects of secretion on living

Re-expansion of headless tentacles

seeds, 390

of Drosera, 229

Platinum chloride, action on Dro-

of tentacles of Drosera, 260

sera, 186

of Dionsea, 318

Poison of cobra and adder, their

Roots of Drosera, 18

action on Drosera, 206

of Drosera, process of aggrega-

Pollen, its digestion by Drosera,

tion in, 63

117

■^ of Drosera, absorb carbonate of

Polypompholyx, structure of, 445

ammonia, 141

Potassium, salts of, inducing ag-

of Diona3a, 286

gregation in Drosera, 50

of Drosophyllum, 332

, , action on Drosera, 179

of Pinguicula, 369

phosphate, not decomposed by

Pvoridula, 342

Drosera, ISO, 187

Rubidimn chloride, action on Dro-

Price, Mr. John, on Utricularia,

429
Primula sinensis, glandular hairs

sera, 181

of, 348

S.

, number of glandular hairs of,

355

Sachs, Prof, effects of heat on pro-

Protoplasm, aggregation of, in Dro-

toplasm, 66, 70

sera, 38

, on the dissolution of proteid

, , in Drosera, caused by

compounds in the tissues of

small doses of carbonate of am-

plants, 362

monia, 145

Saliva, action on Drosera, 80

, , in Drosera, a reflex

Salts and acids, various, effects of.

action, 242

on subsequent action of ammonia,

aggregated, re-dissolution of,

214

53

Sanderson, Burden, on coagulation

, aggregation of, in- various

of albumen from heat, 74

species of Drosera, 278

, on acids replacing hydro-

, in Dionsea, 290, 300

chloric in digestion, 89

, , in Drosophyllum, 337,

, on the digestion of fibrous

339

basis of bone, 108

, , in Pinguicula, 370, 389

, of gluten, 118

, , ill Utricularia, 411, 415,

, of <2;lobulin, 120

429, 430, 436

, of chlorophyll, 126

, on different effect of soilium

and potassium on animals, 187

Q.

, on electric currents in Dionsea,

318
Saxifraga umbrosa, glandular hairs

Quinine, salts of, action on Drosera,

201

of, 345

INDEX.

461

SCHIFF.

TURPENTINE.

Schiff, on hydrochloric acid dis-

Strychnine, salts of, action on

solvhig cQagulated albumen,

Drosera, 199

86

Sugar, solution of, action of, on

• , on manner of digestion of

Drosera, 78

albumen, 93

, , inducing aggregation in

■ , on changes in meat during

Drosera, 51

digestion, 99

Sulphuric ether, action on Drosera,

■ , on the coagulation of milk,

219

114

, on Dionaea, 304

, on the digestion of casein,

116
, of mucus, 123

Syntonin, its action on Drosera, 102

, on peptogenes, 129

Schloesing, on absorption of nitro-

T.

gen by Nicotiana, 352

Scott, Mr., on Drosera, 1

Tait, Mr., on Drosophyllum, 332

Secretion of Drosera, general ac-

Taylor, Alfred, on the detection of

count of, 13

minute doses of poisons, 170

, its antiseptic power,

Tea, infusion of, action on Drosera,

15

78

, becomes acid from ex-

Tentacles of Drosera, move when

citement, 86

glands cut of, 36, 229

■ , nature of its ferment,

, inflection, direction of, 243

94,97

, means of movement, 254

by Dionsea, 295

, re-expansion of, 260

by Drosophyllum, 335

Theine, action on Drosera, 204

by Pinguicula, 381

Tin chloride, action on Drosera,

Seeds, living, acted on by Drosera,

185

127

Tissue, areolar, its digestion by

• , , acted on by Pinguicula,

Drosera, 102

385, 390

, fibro-elastic, not digested by

Sensitiveness, localisation of, in

Drosera, 122

Drosera, 229

Tissues through which impulse is

of Diona^a, 289

transmitted in Drosera, 247

of Pinguicula, 371

in Dionsea, 313

Silver nitrate, action on Drosera,

Touches repeated, causing inflec-

181

tion in Drosera. 34

Sodium, salts of, action on Drosera,

Tr;msmission of motor impulse in

176

Drosera, 234

, , inducing aggregation in

in Dionsea, 313

Drosera, 50

Traube, Dr., on artificial cells, 216

Sondera hetero^hylla, 284

Treat, Mrs., on Drosera filiformis,

Sorby, Mr., on colouring matter of

281

Drosera, 5

, on Dionsea, 311

Spectroscope, its power compared

, on Utricularia, 408, 430

with that of Drosera, 170

Tre'cul, on Drosera, 1, 5

Starch, action of, on Drosera, 78,

Tubers of Utricularia montana, 439

126

Turpentine, action on Drosera, 212

Stein, on Aldrovanda, 321

Strontium, salts of, action on Dro- ,

sera, 183

462

INDEX.

UKEA.

ZINC.

u.

W.

Urea, not digested by Drosera, 124

Warming, Dr., on Drosera, 2, 6

Urine, action on Drosera, 79

, on roots of Utricularia, 397

Utricularia clandestina, 430

, on trichomes, 359

minor, 429

, on Genlisea, 446

Utricularia montana, structure of

, on parenchymatous cells in

bladders, 431

tentacles of Drosera, 252

, animals caught by, 435

Water, drops of, not causing inflec-

, absorption by, 437

tion in Drosera, 35

, tubers of, serving as reservoirs,

, its power in causing aggrega-

439

tion in Drosera, 52

Utricularia neglecta, structure of

, its ppwer in causing inflection

bladders, 397

in Drosera, 139

, animals caugbt by, 405

and various solutions, effects

, absorption by, 413

of, on subsequent action of am-

, summary on absorption, 421

monia, 213

, development of bladders, 424

Wilkinson, Eev., on Utricularia,

Utricularia, various species of, 441

398

Utricularia vulgaris, 428

Z

Ziegler, his statements with respect

V.

Veratrine, action on Drosera, 2^4

to Drosera, 23

Vessels in leaves of Drosera, 247

, experiments by cutting ves-

of Diona^a, 314

sels of Drosera, 249

Vogel, on eflects of camphor on

Zinc chloride, action on Drosera,

plants, 209

184

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Prof William Odlong, F. R. S., The Old
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W. L.^uder Lindsay, M. D., F. R. S. E.,
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Sir John Lubbock, Bart., F. R. S., The
A ntiqnity of Man.

Prof W. T. Th'iselton Dyer, B. A.,
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Mr. J. N. Lockyer, F. R. S., Spectrum
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Prof. Michael Foster, M. D., Proto-
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Prof. W. Stanley Jevons, Money : and
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H. Charlton Bastian, M. D., F. R. S.,
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Prof C. A. Young, Ph. D. (of Dartmouth
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Prof. Hermann (University of Zurich),
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Prof Liebreich (University of Berlin),
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Prof Rees (University of Erlangen), On
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E. Alglave (Professor of Constitutional
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