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INSECTIVOROUS PLANTS 



CHARLES DARWIN'S WORKS. 



Origin of Species by Means of Natural Selection ; or, The Preservation of 
Favored Races in the Struggle for Life. From sixth and last London edition. 
2 voIb. i2mo. Cloth, $4.00. 

Descent of Man, and Selection in Relation to Sex, With many Illustra- 
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described, chiefly from sketches taken on the spot, by R. 1', Phitchu'it. 8vo. 
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The Structure and Distribution of Coral Reefs. Baned on Observations 
made during the Voyage of the " Heagle," With Charts and Illustrations, 
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Geological Observations on the Volcanic Islands and Parts of South America 
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Emotional Expressions of Man and the Lower Animals. i2mo. Cloth, 
$3-50. 

The Variations of Animals and Plants under Domestication. With a 
Preface by Professor AsA GiiAV. 2 vols. Illustrated Cloth, $5.00. 

Insectivorous Plants, ismo. Cloth, $2.00. 

Movements and Habits of Climbing Plants. With Illustrations. i2mo. 
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The Various Contrivances by which Orchids are Fertilized by Insects. 
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The Effects of Cross and Self Fertilization in the Vegetable Kingdom. 
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Different Forms of Flowers on Plants of the same Species. With Illus- 
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The Power of Movement in Plants. By Charles Darwin, LL, D., F. R. S., 
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The Formation of Vegetable Mould through the Action of Worms, 
with Observations on their Habits, With lltustrations. i2mo. Cloth, $1.50. 



New York: D. APPLETON & CO., Publishers. 



INSECTIVOROUS PLANTS, 



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



WITH ILLUSTRATIONS. 



NEW YORK: 

D. APPLETON AND COMPANY, 

1895. 



CONTENTS. 



CHAPTEE I. 

DeOSBEA EOTUNDIPOLIA, OB THE CoMMON SUN-DEW. 

Ifumber of insects captured — Description of the leayes 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 



CHAPTEE II. 

The Movements op the Tentacles from the Contact of 
Solid Bodieb. 

tuflection 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 ia 
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 — Palling drops of water do not 
cause inflection 19^7 



n CONTENTS. 



CHAPTER III. 

Aggbegation 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 — Descrij)- 
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 38-65 

CHAPTEE IV. 

The Effects of Heat on the Leaves. 

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

CHAPTER V. 

The Effects of Non-nitbogbnous and Niteogbnous 
Obganic Eluidb on the Leaves. 

Kon-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 70-84 



CONTENTS. VU 

CHAPTER VI. 

The Digkstivb Powbe of the Secketion of Dboseba. 

the secretion rendered acid by the direct and indirect excite- 
ment of the glands — Nature of the acid — Digestible 
substances — Albumen, its digestion arrested by alkahes, 
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 — Chii ine — Cellulose 

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

CHAPTEE 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 othee 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 — Stmimary on their action .. .. 174-198 



VIU CONTENTS. 



CHAPTER IX. 

The Effects of certain Alkaloid Poisons, othek 

SUESTANCES AND VAPOUKS. 

strychnine, salts of — Quinine,- sulphate of, does not soon 
arrest the movement of the protoplasm — Other salts oi 
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 
vapour 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. 

Ok the Sensitiveness of the Leaves, and on the Links 
OF Transmission of the Motor Impdlbe. 

Srlands 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 XL 

EkoapituIiAtion of the Chief Observations on 
Drosera rotcndibolia. 

262-277 



CONTENTS. IS 

CHAPTEE XII. 

On tub Stuuctukb and Movsmbnts of some othee 
Speoieb of Dboseba. 

Drosera anglica — Drosera intermedia — Drosera capensis — Drosera 
spathulata — Drosera flU/mmis — Drosera binata — Concluding 
remarks Pages 278-285 

CHAPTER XIII. 

DiONffiA MUSCIPULJ.. 

Structure of the leaves — Sensitiveness of the filaments — Bapid 
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 

CHAPTEE XIV. 

Aldeovahda vesiculosa. 

Captures crustaceans — Structure of the leaves in comparison 
with those of Dionsea — Absorption by the glands, by the 
quadrifld processes, and points on the infolded margins — 
Aldrouari'ia vesiculosa, var. australis — Captures prey • — ■ 
Absorption of animal matter — Aldrovanda vesiculosa, var. 
verticillata — Concluding remarks 321-331 

CHAPTER XV. 

DBOSOPHTIiLUM — EOBIDULA — ByBLIS — GLANDULAR HaIBB OF 
OTHER Plants — CoNCLTJDING EeMAEKS on the DBOSEEAOBiE. 

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 — JSicotiana — Summary on glandular liairs — Con- 
cluding remarks on the JTloseracese 332-367 



X CONTENTS. 

CHAPTER XVI. 

PlNGDIOULA. 

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

CHAPTER XVII. 

Utbioulaeia. 

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

CHAPTER XVIII. 

UtkicuIiAEIA (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. 

DrOSEEA BOTUNDIFOLIA, OB THE COMMON SuN-DEW. 

tfumber of insects oaptuied — Description of the leaves and theii 
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. 

DuEiNG the summer of 1860, 1 was surprised by find- 
ing how large a number of insects were caught by the 
leaves of the common sun-dew (Brosera 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. Tre'cul went so 

(' Bot. Zeitung,' 1860, 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 18(50 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 

o.ie of the most valuable, namely, on the habits and structure of 

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

alKO 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. Inl^".55, inthe' An- mission of an excitement from one 

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

297 and 301, MM. Greenland and excellent. On Deo. 11, 1862, Mr. 

Treoul each published papers, with J. Scott read a paper before the 

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



2 DEOSEEA EOTUNDIFOLIA. OhAP. L 

gathered by chance a dozen plants, bearing fifty-six 
fully expanded leayes, 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 {Caenomynvpha paiwphilus) ; but 
the Eev. H. M. Wilkinson informs me that he found a 
large living dragon-fly with its body firmly held by 
two leaves. As this plant is extremely common in 
some districts, the number of insects thus annually 
slaughtered must be prodigious. Many plants cause 
the death of insects, for instance the sticky buds of 
the horse-chestnut {Mseulus hifpocastanum), 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 
doner's Chronicle,' 1863, p. 30. Jersey, on some American species 
Mr. Scott shows that gentle iriita- of Drosera. Dr. Burden Sander- 
tion of the hairs, as well as insects son delivered a lecture on Dionsea, 
placed on the disc of the leaf, before the Eoyal Institution (pub- 
cause the hairs to bend in- lished in ' 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 thn leaves digestion possessed by Drosera 
before the British Association for and Dionsea 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 Difference entre les Tri- 261 and 232), and in other publica- 
ahomes," &c., extracted from the tions. Dr. Hooker, also, in his 
proceedings of the Soc. d'Hist. important address on Carnivorous 
Nat. de Copenhague. I shall also Plants(Brit.Assoc.,Bolfast,1874), 
have occasion hereafter to refer has given a history of the subject 



Chap. I. STEUCTUKE OF THE LEAYES. 3 

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

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




Fig. 1* 

{Drosera rotwndiftAia.) 

Leftf Tiewed 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 eularia, by my son Francis. They 

BionsoB. given in this vork, were have been excelleully reprodnoed 

made for me by my son George on wood by Mr, Cooper, IS8 

I larwin ; those of Aldrovanda, and Strai d. 
of the several species of Utri- 



4 DEOSEEA EOTUNDIPOLIA. Chap. 1 

secondly, the power possessed by the leaves of render- 
ing soluble or digesting nitrogenous substances, and 
of afterwards absorbing them; thirdly, the changes 
which take place within the cells of the tentacles, when 
the glands are excited in various ways. 

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




Fio. 2. 

(Drosera rotwndifolia.) 

Old leaf viewed laterally ; enlarged about five times. 

but this was not the case in the one here figured. 
The whole upper surface is covered with gland-bearing 
filaments, or tentacles, as I shall call them, from their 
manner of acting. The glands were counted on thirty- 
one leaves, but many of these were of unusually large 
size, and the average number was 192; the greatest 
number being 260, and the least 130. The glands are 
each surrounded by large drops of extremely viscid 
secretion, which, glittering in the sun, have given rise 
to the plant's poetical name of the sun-dew. 

The tentacles on the central part of the leaf or disc are 
short and stand upright, and their pedicels are green. Towards 
the margin they become longer and longer and more inclinen 



Chat I. STRUCTUEB 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 flg. 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. Spiral vessels, accom- 
panied by simple vascular tissue, branch off from the vascular 
bundles in the blade of the leaf, and run up all the tentacles 
into the glands. 

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



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

Zeitimg,' 1861, p. 224) the purple parts of a leaf which do not fulfil 

fluid results from the metamor- their proper office." 

phosis of chlorophyll. Mr. Sorby t Dr. Nitsohke has discussed 

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

with the spectroscope, and in- 3861, p. 241, &c. See also Dr. 

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

commonest species of erythro- les Triviomes,' &o., 1873), who 

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

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

parts, like the petioles, which 'J'recul, ' Annal. des So. nat. bot.' 

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

imperfect manner. All that can 297 and 303. 
be 8aid, therefore, is that the hairs 



6 



DEOSERA KOTUNDIFOLIA. 



Chap. L 



part, which alone is capable of moTement, consists of a prolon- 
gation of the leaf; the spiral vessels being extended from this 
to the uppermost part. We shall hereafter fee that th« 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 raiumdi/olia.) 
longitudinal section of a gland; greatly magnified. 



From Dr. Warming. 



marginal tentacles, are oval, and of nearly uniform size viz. 
about ^ of an inch in length. Their structure is remarkable, 
and their functions complex, for they secrete, absorb, and are 
acted on by various stimulants. They consist of an outer layer 
of small polygonal cells, containing purple granular matter or 
fluid, and with the walls thicker than those of the pedicels. 



Chap. I. STKUOTUEE OF THE LEAVES. 7 

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

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

The extreme marginal tentacles differ slightly from the others. 
Their bases arc broader, and besides their own vessels, they 
receive a fine branch from those which enter the tentacles 
on each side. Their glands are much elongated, and lie em- 
bedded on the upper surface of the pedicel, instead of standing 
at the apex. In other respects they do not differ essentially 
from the oval ones, and in one specimen I found every possible 
transition between the two states. In another specimen there 
were no long-headed glands. These marginal tentacles lose 
their irritability earlier than the others ; and when a stimulus 
is applied to the centre of the leaf, they are excited into action 
after the others. When cut-off leaves are immersed in water, 
they alone often become inflected. 

The purple fluid or granular matter which fills the cells ot 

the glands differs to a certain extent from that within the 

cells of the pedicels. For when a leaf is placed in hot water or in 

certain acids, the glands become quite white and opaque, whereas 

2 



S DEOSEEA KOTUNPIFOLIA. Chap. I. 

the cells of the pedicels are rendered of a bright red, with the 
exception of those close beneath the glands. These latter cells 
lose their pale red tint ; and the green matter which they, as 
well as the basal cells, contain, becomes of a brighter green. 
The petioles bear many multicellular hairs, some of which 
near the blade are surmounted, according to Nitschke, by a 
few rounded cells, which appear to be rudimentary glands. 
Both surfaces of the leaf, the pedicels of the tentacles, espe- 
cially the lower sides of the outer ones, and the petioles, are 
studded with minute papillae (hairs or trichomes), having a 
conical basis, and bearing on their summits two, and occasion- 
ally three or even four, rounded cells, containing much proto- 
plasm. These papillae are generally colourless, but sometiines 
include a little purple fluid. They vary in development, and 
graduate, as Nitschke * states, and as I repeatedly observed 
into the long multicellular hairs. The latter, as well as the 
papillae, are probably rudiments of formerly existing tentacles. 

I may here add, in order uot to recur to the papillae, that they 
do not secrete, but are easily permeated by various fluids : thus 
when living or dead leaves are immersed in a solution of one 
part of chloride of gold, or of nitrate of silver, to 437 of water, 
they are quickly blackened, and the discoloration soon spreads 
to the surrounding tissue. The long multicellular hairs are 
not so quickly affected. After a leaf had been left in a weak 
infusion of raw meat for 10 hours, the cells of the papillae had 
evidently absorbed animal matter, for instead of limpid fluid 
they now contained small aggregated masses of protoplasm, 
which slowly and incessantly changed their forms. A similar 
result followed from an immersion of only 15 minutes in a 
solution of one part of carbonate of ammonia to 218 of water, 
and the adjoining cells of the tentacles, on which the papillae 
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 papillae, 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 papillae on the backs of the leaves or on the 
petioles. 

* Nitschke has elaborately described and figured these papillaiL 
Bot. Zeitung,' 1861, pp. 234, 253, 254. 



Chap. I. ACTION OF THE PAKTS. 9 

Preliminary Sketch of the Action of the several Parts, and 
of the Manner in which Insects are Captured. 

If a small organic or inorganic object be placed on 
the glands in the centre of a leaf, these transmit a 
motor impulse to the marginal tentacles. The nearer 
oiies are first affected and slowly bend towards the 
centre, and then those farther off, until at last all 
become closely inflected over the object. This takes 
place in from one hour to four or five or more hours. 
The difference in the time required depends on many 
circumstances ; namely on the size of the object and 
on its nature, that is, whether it contains soluble 
matter of the proper kind ; on the vigour and age of 
the leaf; whether it has lately been in action; and, 
according to Nitschke,* on the temperature of the 
day, as likewise seemed to me to be the case. A living 
insect is a more efficient object than a dead one, as 
in struggling it presses against the glands of many 
tentacles. An insect, such as a fly, with thin integu- 
ments, through which animal matter in solution can 
readily pass into the surrounding dense secretion, is 
more efficient in causing prolonged inflection than an 
insect with a thick coat, such as a beetle. The inflec- 
tion of the tentacles takes place indifferently in the 
light and darkness; and the plant is not subject to 
any nocturnal movement of so-called sleep. 

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



' Bot. Zeitung,' 1860, p. 2-16. 



10 DBOSEEA BOTUNDIPOLIA. Ohap. I 

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





Fig. 4. Fig. 5. 

(Bnnera rotwndifoUa.') (Droiera rotundifoUa.) 

Iieaf (enlarged) with all tbe tentacles Leaf (enlarged) with the tentacles on one 

cloflely inflected, from immersion in a side inflected over a bit of meat placed 

solution of phosphate of asimonla (one on tbe disc, 
part to 87,500 of water). 

becomes slightly incurved ; the distal half in all cases 
remaining straight. The short tentacles in the centre 
of the 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 



Obap. 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 reimain 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 




Fio. 6. 
(Brosera rotundifolia.) 

Diagram showing one of the exterior tentacles closely infiected ; 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 DEOSEEA ROTUNDIFOLIA. Chap. I 

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

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

The length of time curing which the tentacles aa 



Chap. I. ACTION OF THE PAETS. I'S 

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, 
^mmersion in many acids (of the strength of one part 
to 43R of water) likewise causes a wonderful amount of 



14 DEOSEEA EOTUNDIFOLIA. Chap. I. 

Becrotion, so that when the leaves are lifted out, long 
ropes of extremely viscid fluid hang from them. Some 
acids, on the other hand, do not act in this manner. 
Increased secretion is not necessarily dependent on 
the inflection of the tentacle, for particles of sugar and 
of sulphate of zinc cause no movement. 

It is a much more remarkable fact that when an 
object, such as a bit of meat or an insect, is placed on 
the disc of a leaf, as soon as the surrounding tentacles 
become considerably inflected, their glands pour forth 
an increased amount of secretion. I ascertained this 
by selecting leaves with equal-sizec^ drops on the two 
sides, and by placing bits of meat on one side of the 
disc ; and as soon as the tentacles on this side became 
much inflected, but before the glands touched the meat, 
the drops of secretion became larger. This was re- 
peatedly observed, but a record was kept of only 
thirteen cases, in nine of which increased secretion was 
plainly observed; the four failures 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 glands have touched the object on the centre of 
the leaf. This acid is of a different nature from that 
contained in the tissue of the leaves. As long as the 



CUAP. I. ACTION OF THE PARTS. 15 

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

The secretion seems to possess, like the gastric juice 
of the higher animals, some antiseptic power. During 
very warm weather I placed close together two equal- 
sized bits of raw .meat, one on a leaf of the Drosera, 
and the other surrounded by wet moss. They were 
thus left for 48 hrs., and then examined. The bit on 
the moss swarmed with infusoria, and was so much 
decayed that the transverse striae on the muscular 
fibres could no longer be clearly distinguished; 
whilst the bit on the leaf, which was bathed by the 
secretion, was free from infusoria, and its strise 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 



1^ nEOSEEA EOTDNDIFOLIA. OhaP. L 

tould 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 
surroimding 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 sufiices to cause 
this action : for instance, I have seen one of the 
smallest species of gnats (Culex), which had just 
settled with its excessively delicate feet on the 
glands of the outermost tentacles, and these were 
already beginning to curve inwards, though not a 
single gland had as yet touched the body of the 
inse(;t. Had I not interfered, this minute gnat would 



Chap. I. ACTION OF THE PAKTS. 17 

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

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

That the glands possess the power of absorption, is 
shown by their almost instantaneously becoming dark- 
coloured when given a minute quantity of carbonate of 
ammonia ; the change of colour being chiefly or exclu- 
sively due to the rapid aggregation of their contents. 
When certain other fluids are added, they become pale- 
coloured. Their power of absorption is, however, best 
shown by the widely different results which follow, 
from placing drops of various nitrogenous and non- 
nitrogenous fluids of 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 sohrble 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 DEOSERA EOTDNDIFOLIA. 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. Nevertheless, considering the 
nature of the soil where it grows, the supply of nitrogen 
would be extremely limited, or quite deficient, unless 
the plant had the power of obtaining this important 
element from captured insects. We can thus under- 
stand how it is that the roots are so poorly developed. 
These usually consist of only two or three slightly 
divided branches, from half to one inch in length, 
furnished with absorbent hairs. It appears, therefore, 
that the roots serve only to imbibe water ; though, no 
doubt, they would absorb nutritious matter if present 
in the soil ; for as we shall hereafter see, they absorb 
a weak solution of carbonate of ammonia. A plant 
of Drosera, with the edges of its leaves curled in- 
wards, so as to form a temporary stomach, with the 
glands of the closely inflected tentacles pouring forth 
their acid secretion, which dissolves animal matter, 
afterwards to be absorbed, may be said to feed like an 
animal. But, differently from an animal, it drinks by 
means of its roots ; and it must drink largely, so as to 
retain many drops of viscid fluid round the glands, 
sometimes as many as 260, exposed during the whole 
day to a glaring svm. 



Ohap. U. INFLECTION INDIRECTLY CAUSED. 19 



CHAPTEE II. 

The Movements or the Tentacles fbom the Contact of Solid 
Bodies. 

Infleotion of the exterior tentacles owing to the glands of the disa 
being excited by repeated touches, or by objects left in contact 
•with them — Difference in the action of bodies yielding and not 
yielding soluble nitrogenous matter — Inflection of the exterior 
tentacles directly caused by objects left in contact with their 
glands — Periods of commencing inflection and of subsequent re- 
expansion — Extreme minuteness of the particles causing inflection* 
— Action under water — Inflection of the exterior tentacles when 
their glands are excited by repeated touches — Falling drops of 
water do not cause inflection. 

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 DEOSEKA EOTUNDIFOLIA. Chap. II. 

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

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

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

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



Ghap. ii. inflection indirectly 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 
affected, those on the opposite side much later, or, as 
often occurred, not at all. This was repeatedly proved 
by trials with bits of meat ; but I will here give only 
the case of a minute fly, naturally caught and still 
alive, which I found adhering by its delicate feet to 
the glands on the extreme left side of the central disc. 
The marginal tentacles on this side closed inwards 
and killed the fly, and after a time the edge of the 
leaf on this side also became inflected, and thus 
remained for several days, whilst neither the tentacles 
nor the 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 DROSEKA EOTUNDIFOI.IA. CHAP. H. 

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 obserred the follow- 
ing unusual circumstance. Small bits of raw meat 
(which acts more energetically than any other sub- 
stance), of paper, dried moss, and of the quill of a 
pen were placed on several leaves, and they were all 
embraced equally well in about 2 hrs. On other 
occasions the above-named substances, or more com- 
monly particles of glass, coal-cinder (taken from the 
fire), stone, gold-leaf, dried grass, cork, blotting-paper, 
cotton- wool, and hair rolled up into little balls, were 
used, and these substances, though they were some- 
times well embraced, often caused no movement what- 
ever in the outer tentacles, or an extremely slight and 
slow movement. Yet these same leaves were proved to 
be in an active condition, as they were excited to move 
by substances yielding soluble nitrogenous matter, 
such as bits of raw or roast meat, the yolk or white of 
boiled eggs, fragments of insects of all orders, spiders, 
&o. I will give only two instances. Minute flies were 
placed on the discs of several leaves, and on others 
balls of paper, bits of moss and quill of about the sam.e 
size as the flies, and the latter were well embraced 
in a few hours ; whereas after 25 hrs. only a very 
few tentacles were inflected over the other objects. 
The bits of paper, moss, and quill were then removed 
from these leaves, and bits of raw meat placed on them ; 
and now all the tentacles were soon energetically 
inflected. 

Again, particles of coal-cinder (weighing rather more 
than the flies used in the last experiment) were placed 
on the centres of three leaves : after an interval of 
19 hrs. one of the particles was tolerably well embraced ; 



Chap. U. INFLECTION INDIRECTLY CAUSED, 23 

a second by a very few tentacles ; and a third by none. 
I then removed the particles from the two latter leaves, 
and put on them recently killed flies. These were 
fairly well embraced in 7 J hrs. and thoroughly after 
20J 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 completelv 
re-expanded and ready to act again. 

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



* Owing to the extraordinary and particles were then placed 

belief held bv M. Ziegler ('Comp- (every instrument with which 

tes rendns,' May 1872, p. 122 1, they were touched having been 

that albuminous siibstanoes, if previously immersed in boiling 

held for a moment between the water) on the glands of several 

fingers, aoquii-e the property of leaves, and they acted in exactly 

making the tentacles of Drosera the same manner as other par- 

eontraot, whereas, if not thus held, tides, which had been purposely 

they have no such power, I tried handled for some time. Bits o( 

some experiments with great care, a boiled egg, out with a knife 

but the results did not confirm which had been washed ia boiling 

this belief. Eed-hot cinders were water, also acted lik« 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 immerseil in boiling water ; times, with my mouth close to 



24 DEOSEEA EOTTJNDIFOLIA. Chap. H. 

The Infleetion of the Exterior Tentacles as directly caused 
hi/ 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 Tiscid secretion surrounding the glands of the 
outer tentacles. I experimented on both the oval and 
long-headed glands. When a particle is thus placed 
on a single gland, the movement of the tentacle is 
particularly well seen in contrast with the stationary 
condition of the surrounding tentacles. (See previous 
fig. 6.) In four cases small particles of raw meat 
caused the tentacles to be greatly inflected in between 
5 and 6 m. Another tentacle similarly treated, 
and observed with special care, distinctly, though 
slightly, changed its position in 10 s. (seconds) ; and 
this is the quickest movement seen by me. In 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 produced no effect. cause inflection. M. Ziegler 

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

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

odour 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. 

possible, without actual contact. The action of salts of quinine will 

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

no eifect whatever. On the other Since 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 fluias, such as of subject, entitled, ' Atonicite' ot 

carbonate of ammonia, chloro- Zoicit^,' 1874. 
form, certain essential oili, &c., 



Ohap. n. INFLECTION INDIRECTLY CAUSED 25 

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



26 DKOSERA EOTUNDIFOLTA. 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 
.f. of the particles of cinder, glass, and thread, placed 
on separate glands, were carried towards, or actually 
to, the centre ; in another case i, in another -^, 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, much less than those of 
which the measurements will be immediately given, 
were placed on glands ; so that we here have nearly 
the limit of any action. 

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



Chap. II. INFLECTION INDIEECTLY CAUSED. 27 

Accordingly measured lengths of a narrow strip of 
blotting paper, of fine cotton-thread, and of a woman's 
hair, were carefully weighed for me by Mr. Trenham 
Eeeks, 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 -j-gigr 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 -^^ of 
an inch in length, and weighed ^ ^\, 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-^fo of ^^ ^'^^ ^^ length, and weighing 3-3-7x4- o^ 
a grain, the other yH-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. 10 m. ; 
all the many other tentacles round the same leaf re- 
maining motionless. The appearance of this one leaf 
showed in an unequivocal manner that these minute 
particles sufficed to cause the tentacles to bend. Alto- 
gether, ten such particles of hair were placed on ten 
glands on several leaves, and seven of them ca,used 



28 DROSERA EOTUNDIFOLIA. CuAP- H. 

the tentacles to moye in a conspicuous manner. The 
smallest particle which was tried, and which acted 
plainly, was only -rwo of an inch (-203 millimetre) in 
length, and weighed the -yTfro of a grain, or -000822 
milligramme. In these several cases, not only was the 
inflection of the tentacles conspicuous, but the purple 
fluid within their cells became aggregated into little 
masses of protoplasm, in the manner to be described in 
the next chapter ; and the aggregation was so plain 
that I could, by this clue alone, hare readily picked 
out under the microscope all the tentacles which had 
carried their light loads towards the centre, from the 
hundreds of other tentacles on the same leaves which 
had not thus acted. 

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

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



Chj»p, 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 glauds, whatever may be the position of 
the tentacles. Minute bits of dry cork, thread, blotting 
paper, and coal cinders were tried, such as those pre- 
viously employed ; and I now observed that they 
absorbed much more of the secretion, in the course of 
a few minutes, than I should have thought possible ; and 
as they had been laid on the upper surface of the secre- 
tion, where it is thinnest, they were often drawn down, 
after a time, into contact with at least some one point 
of the gland. With respect to the minute splinters 
of glass and particles of hair, I observed that the 
secretion slowly spread itself a little over their sur- 
faces, by which means they were likewise drawn down- 
wards or sideways, and thus one end, or some minute 



30 DEOSEKA BOTUNDIFOLIA. Chap. H. 

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

In the foregoing and following cases, it is probable 
that the vibrations, to which the furnitm-e in every 
room is continually liable, aids in bringing the par- 
ticles into contact with the glands. But as it was 
sometimes difScult, 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 with a fine 
needle under the microscope, the glands not being 
touched. And now in the course of a few minutes 
almost all the hitherto 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- - 
tides 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 



UHAP. n. INFLECTION INDIRECTLY CAUSED. 31 

elapsed. The remaining six tentacles never moYed 
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 ; |ind 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 conseqiient 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 sufScient 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 DKOSEEA KOTUNDIFOLIA. Chap. H- 

into contact with the glands, and caused this rapid 
movement. Accordingly I added to some distilled 
water a pinch of a quite innocent substance, namely, 
precipitated carbonate of lime, which consists of an 
impalpable powder ; I shook the mixture, and thus got 
a iluid like thm milk. Two leaves were immersed in 
it, and in 6 m. almost every tentacle was much 
iniiected. I placed one ctf these leaves under the 
microscope, and saw innumerable atoms of lime ad- 
hering to the external surface of the secretion. Some, 
however, had penetrated it, and were lying on the sur- 
faces of the glands ; and no doubt it was these particles 
which caused the tentacles to bend. When a leaf is im- 
mersed in water, the secretion instantly swells much ; 
and I presume that it is ruptured here and there, so 
that little eddies of water rush in. If so, we can under- 
stand how the atoms of chalk, which rested on the 
surfaces of the glands, had penetrated the secretion. 
Anyone who has rubbed precipitated chalk between 
his fingers will have perceived how excessively fine 
the powder is. No doubt there must be a limit, beyond 
which a particle would be too small to act on a gland ; 
but what this limit is, I know not. I have often seen 
fibres and dust, which had fallen from the air, on the 
glands of plants kept in my room, and these never 
induced any movement ; but then such particles lay 
on the surface of the secretion and never reached the 
gland itself. 

Finally, it is an extraordinary fact that a little 
bit of soft thread, -J-^ of an inch in length and weigh- 
ing itW of a grain, or of a human hair, -ro%-o of an 
inch in length and weighing only -,-^-)-^„- 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 DIKECTLY CAUSED. 33 

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



34. DEOSEEA EOTUNDIFOLIA. Chap. II 

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

We have already seen that, if the central glands 
are excited by being gently brushed, they trans- 
mit a motor impulse to the exterior tentacles, 
causing them to bend; and we have now to con- 
sider the effects which follow from the glands of 
the exterior tentacles being themselves touched. On 
several occasions, a large number of glands were 
touched only once with a needle or fine brush, 
hard enough to bend the whole flexible tentacle; 
and though this must have caused a thousand- 
fold greater pressure than the weight of the above 
described particles, not a tentacle moved. On 
another occasion forty-five glands on eleven leaves 
were touched once, twice, or even thrice, with a 
needle or stiff bristle. This was done as quickly as 
possible, but with force sufficient to bend the ten- 
tacles ; yet only six of them became inflected, — three 
plainly, and three in a slight degree. In order to 
ascertain whether these tentacles which were not 
affected were in an efBcient state, bits of meat were 
placed on ten of them, and they all soon became greatly 
incurved. On the other hand, when a large number of 
glands were struck four, five, or six times with the 
same force as before, a needle or sharp splinter of 
glass being used, a much larger proportion of tentacles 
became inflected; but the result was so uncertain 
as to seem capricious. For instance, I struck in 
the above manner three glands, which happened to 
be extremely sensitive, and all three were inflected 
almost as quickly as if bits of meat had been placed 
on them. On another occasion I gave a single for- 



Chap. II. THE EFFECTS OP REPEATED TOUCHES. 35 

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

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



36 DEOSERA EOTUNDIFOLIA. ChaP. H. 

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

When the pedicel of a tentacle is cut off by a 
sharp pair of scissors quite close beneath the gland, 
the tentacle generally becomes inflected. I tried this 
experiment repeatedly, as I was much surprised at the 
fact, for all other parts of the pedicels are insensible to 
any stimulus. These headless tentacles after a time 
re-expand ; but I shall return to this subject. On the 
other hand, I occasionally succeeded in crushing a 
gland between a pair of pincers, but this caused no 
inflection. In this latter case the tentacles seem 
paralysed, as likewise foUows 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 



ClIAl'. II. 



DROPS OF WATEK. 



37 



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



* My son Francis, guided by 
the observations of Dr. Burden 
Sanderson on Dionsea, finds that 
if two needles are inserted into 
the blade of a leaf of Drosera, the 
tentacles do not move ; but that if 
similar needles in connection with 



the secondary coil of a Du Boia 
inductive apparatus are insrrted, 
the tentacles curve inwards lu the 
course of a few minutes, ilj son 
hopes soon to publish an aoooiir^ 
of his observations. 



38 DEOSEEA EOTUNDIFOLIA. GhAP. HI. 



CHAPTEE III. 

ASOEEGATION OP THE PhOTOPLASM WITHIlf THE CeLIS OP THE 

Tentacles. 

Jiuture 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, 
ifec. — Of water — Of heat — Eedissolution 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 ah-eady 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 PROCESS OF AGGEEGATION. 39 

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

4 



40 



DEOSEKA KOTUNDIFOLIA. 



CiIAP. [II- 



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



Fie. 1. 

{Drosera rotwndifoUa.) 

Diagram of the same rell 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 TROCESS OF AGGREGATION. 



41 



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

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



Fig. 8. 

(Drosera rotundifvliu.) 

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



here represented (fig. 8) was from this leaf, being 
sketched eight times in the course of 15 m. These 
sketches exhibit some of the more remarkable changes 
which the protoplasm undergoes. At first, there was 
at the base of the cell 1, a little mass on a short 
footstalk, and a larger mass near the upper end, and 
these seemed quite separate. Nevertheless, they may 
have been connected by a fine and invisible thread of 
protoplasm, for on two other occasions, whilst one 
n\ass 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 tenaity, which evidently served as 



i2 DROSEKA KOTUNDIFOLIA. Chap. HI. 

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. 



Many observations were made on the contents of the cells 
whilst undergoing the process of aggregation, but I shall detail 
only- a few cases under different heads. A small portion of a 
leaf was out oflF, 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 Ihe 
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 rh. there was no aggregation. Other 
tentacles with these particles were examined after 8 hrs., and 



Chap. III. THE PKOCESS OF AGGREGATION. 43 

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

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

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



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

M. 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 togethej 

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



44 DEOSEEA EOTUNUIFOLIA. Chap. IIT. 

darken in 10 s, (seconds); and in 13 s. were conspicuously 
darker. In 1 m. extremely small spherical masses of protoplasm 
could be seen arising in the cells of the pedicels close beneath 
the glands, as well as in the cushions on which the long- 
headed marginal glands rest. In several cases the process 
travelled down the pedicels for a length twice or thrice as great 
as that of the glands, in about 10 m. It was interesting to 
observe the process momentarily arrested at each transverse 
partition between two cells, and then to see the transparent 
contents of the cell next below almost flashing into a cloudy 
mass. In the lower part of the pedicels, the action proceeded 
slower, so that it took about 20 m. before the cells halfway 
down the long marginal and submarginal , tentacles became 



We may infer that the carbonate of ammonia is absorbed by 
the glands, not only from its action being so rapid, but from its 
effect being somewhat different from that of other salts. As the 
glands, when excited, secrete an acid belonging to the acetic 
series, the carbonate is probably at once converted into a 
salt of this series ; and we shall presently see that the acetate 
of ammonia causes aggregation almost or quite as energetically 
as does the carbonate. If a few drops of a solution of one part of 
the carbonate to 437 of water (or 1 gr. to 1 oz.) be added to the 
purple fluid which exudes from crushed tentacles, or to paper 
stained by being rubbed with them, the fluid and the paper are 
changed into a pale dirty green. Nevertheless, some purple 
colour could still be detected after 1 hr. 30 m. within the glands 
of a leaf left in a solution of twice the above strength (viz. 
2 grs. 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 margias of very pale 
leaves immersed in a solution, that the glands as well as the 
upper cells of the pedicels were discoloured ; and in these cases 
I presume that the unchanged carbonate had been absorbed. 
The appearance above described, of the aggregating process 
being arrested for a short time at each transverse partition, 
impresses the mind with the idea of matter passing downwards 
from cell to cell. But as the cells one beneath the other 
undergo aggregation when inorganic and insoluble particles are 
placed on the glands, the process must be, at least in these 
cases, one of molecular change, transmitted from the glands 



Chap. 111. THE PROCESS OF AGGEEGATION. 45 

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

Having examined a leaf in water, and found the contents of the 
cells homogeneous, I placed it in a few drops of a solution of one 
part of the carbonate to 437 of water, and attended to the cells 
immediately beneath the glands, but did not use a very high 
power. No aggregation was visible in 3 m. ; but after 15 m. 
small spheres of protoplasm were formed, more especially 
beneath tue long-headed marginal glands; the process, how- 
ever, in this case took place with unusual slowness. In 25 m. 
conspicuous spherical masses were present in the cells of the 
pedicels for a length about equal to that of the glands ; and 
in 3 hrs. to that of a third or half of the whole tentacle. 

If tentacles with cells containing only very pale pink fluid, 
and apparently but little protoplasm, are placed in a few drops 
of a weak solution of one part of the carbonate to 4375 of 
water (1 gr. to 10 oz.), and the highly transparent cells beneath 
the glands are carefully observed under a high power, these 
may be seen first to become slightly cloudy from the formation 
of numberless, only just perceptible, granules, which rapidly 
grow larger either from coalescence or from attracting more 
protoplasm from the surrounding fluid. On one occasion 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, thbugh incessantly 
changing their shapes and positions. 

With moderately red leaves the first effect of a solution of the 
carbonate generally is the formation of two or three, or of 
several, extremely minute purple spheres which rapidly increase 
in size. To give an idea of the rate at which such spheres 
increase in size, I may mention that a rather pale purple leaf 
placed under a slip of glass was given a drop of a solution of 
one part to 292 of water, and in 13 m. a few minute spheres of 
protoplasm were formed ; one of these, after 2 hrs. 30 m., was 
about two thirds of the diameter of the cell. After 4 hrs. 25 m. 



16 DKOSEEA EOTUNDIFOLIA. CsAr. Ill- 

it nearly equalled the cell in diameter; and a second sphiiirf 
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 hi-s. 35 m. (always 
reckoning from the time when the solution was first added) four 
new minute spheres had appeared. Next morning, after 22 hrs., 
there were, besides the two large spheres, seven smaller ones, 
floating in absolutely colourless fluid, in which some flocculent 
greenish matter was suspended. 

At the commencement of the process of aggregation, more 
especially in dark red leaves, the contents of the cells often 
present a different appearance, as if the layer of protoplasm 
(primordial utricle) which lines the cells had separated itself 
and shrunk from the walls ; an irregularly shaped purple bag 
being thus formed. Other fluids, besides a solution of the cai^ 
bonate, for instance an infusion of raw meat, produce this same 
effect. But the appearance of the primordial utricle slu-inking 
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 
those 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, tlie 



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

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

true shrinking of the primordial from mechanical injuries, 
ntriole from ti.e walls of tlie cells, 



OuAP. III. THE PROCESS OF AGGEEGATION. 47 

stream of protoplasm on the walls of the cells coases to be 
visible ; I observed this fact repeatedly, but will give only one 
instance. A pale pnrple leaf was placed in a few drops of a 
Bolution of one part to 292 of water, and in 2 hrs. some fine 
purple spheres were formed in the upper cells of the pedicels, 
the stream of protoplasm round their walls being still quite 
distinct; but after an aMitiorial 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 coQtained granules having become united 
with the spheres, so that nothing was left by which the move- 
ment of the limpid protoplasm could be perceived. But minute 
free spheres still travelled up and down the cells, showing that 
there was still a current. So it was next morning, after 22 hrs., 
by which time some new minute spheres had been formed ; 
these oscillated from side to side and changed their positions, 
proving that the current had not ceased, though no stream of 
protoplasm was visible. On another occasion, however, a 
stream was seen flowing round the cell-walls of a vigorous, 
dirk- coloured leaf, after it had been left for 24 hrs. in a rather 
stronger solution, namely, of one part of the carbonate to 218 of 
water. This leaf, therefore, was not much or at all injured by 
an immersion for this length of time in the above solution of 
two grains to the ounce ; and on being afterwards left for 24 hrs. 
in water, the aggregated masses in many of the cells were re- 
dissolved, in the same manner as occurs with leaves in a state of 
nature when they re-expand after having caught insects. 

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

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



48 DKOSEEA KOTUNDIFOLIA. 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 gentrally soon divides into two or more spheres, which 
repea.tedly coalesce and redivide. After a longer or shorter 
time the granules in the colourless layer of protoplasm, which 
flows round the walls, are drawn to and unite with the larger 
spheres, or form small independent spheres ; these latter being of 
a much paler colour, and more brittle than the first aggregated 
masses. After the granules of protoplasm have been thus 
attracted, the layer of flowing protoplasm can no longer be dis- 
tinguished, though a current of limpid fluid still flows round 
the walls. 

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

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

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

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



Chap. IU. THE PKUCESS OF AGGEEGATION. 49 

146 of water, and were acted on quite as energetically, but 
perhaps not quite so quickly, as by the carbonate. After 10 m. 
the glands were black, and in the cells beneath them there were 
traces of aggregation, which after 15 m. was well marked, extend- 
ing down the tentacles for a length equal to that of the glands. 
After 2 hrs. the contents of almost all the cells in all the ten- 
tacles were broken up into masses of protoplasm. A leaf was 
immersed in a solution of one part of oxalate of ammonia to 
146 of water ; and after 24 m. some, but not a conspicuous, 
change could be seen within the cells beneath the glands. 
After 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 
loaf 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 -g^ 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 aggrejjation 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 DKOSEEA BOTUNDIFOLIA. Gu^^. 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 43,750 of water (1 gr. to 
100 oz.), so that it received tts'oo of a grain (-04079 mgr.); this 
soon caused the tentacles to be strongly inflected ; and after 
24 hrs. the contents of the cells were aggregated into oval 
and irregularly globular masses, with a conspicuous current of 
protoplasm flowing round the walls. But after so long an 
interval aggregation would have ensued, whatever had caused 
inflection. 

Only a few other salts, besides those of ammonia, were tried 
in relation to the process of aggregation. A leaf was placed in 
a solution of one part of chloride of sodium to 218 of water, and 
after 1 hr. the contents of the cells were aggregated into small, 
irregularly globular, brownish masses ; these after 2 hrs. were 
almost disintegrated and pulpy. It was evident that the proto- 
plasm had been injuriously affected ; and soon afterwards some 
of the cells appeared quite empty. These effects differ alto- 
gether from those produced by the several salts of ammonia, 
as well as by various organic fluids, and by inorganic particles 
placed on the glands. A solution of the same strength of car- 
bonate of soda and carbonate of potash acted in nearly the same 
manner as the chloride ; and here again, after 2 hrs. 30 m., the 
outer cells of some of the glands had emptied themselves of 
their brown pulpy contents. We shall see in the eighth 
chapter that solutions .of several salts of soda of half the above 
strength cause inflection, but do not injure the leaves. Weak 
solutions of sulphate of quinine, of nicotine, camphor, poison of 
the cobra, &c., soon induce well-marked aggregation; whereas 
certain other substances (for instance, a solution of curare) 
have no such tendency. 

Many acids, though much diluted, are poisonous ; and though, 
as will be shown in the eighth chapter, they cause the ten- 
tacles to bend, they do not excite true aggregation. Thus leaves 
were placed in a solution of one part of benzoic acid to 437 of 
water ; and in 15 m. the purple fluid within the cells had shrunk 
a little from the walls, yet when carefully examined after 1 hr. 
20 m., there was no true aggregation ; and after 24 hrs. the leaf 
was evidently dead. Other leaves in iodic acid, diluted to the 
same degree, showed after 2 hrs. 15 m. the same shrunken 
appearance of the purple fluid within the cells ; and these, 
after 6 hrs. 15 m., wore seen under a high power to be filled 
with excessively minute spheres of dull reddish protoplasm. 



Chap. IIL THE PROCESS OF AGGEBUATION. 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 oi 
colourless protoplasm round the walls was conspicuously plain 
after an immersion of 25 hrs. Raw meat is too pow.erful 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 
jin 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 aggrega,ted, 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 arable. 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. Thie 



52 DEOSERA ROTUNDIFOLIA. Ohap. III. 

effect may be attributed to exosniose ; for the leaves in tlie 
Byrup became quite flaccid, and those in the gum and starch 
somewhat flaccid, with their tentacles twisted about in the 
most irregular manner, the longer ones like corkscrews. We 
shall hereafter see that solutions of these substances, when 
placed on the discs of leaves, do not incite inflection. Particles 
of soft sugar were added to the secretion round several glands 
ati'l were soon dissolved, causing a great increase of the secre- 
tion, no doubt by exosmose ; and after 24 hrs. the cells showed 
a certain amount of aggregation, though the tentacles wero 
not inflected. Glycerine causes in a few minutes well-pro- 
nounced aggregation, commencing as usual within the glands 
and then travelling down the tentacles ; and this I presume 
may bo attributed to the strong attraction of this substance 
for water. Immersion for several hours in water causes some 
degree of aggregation. Twenty leaves were first carefully 
examined, and re-examined after having been left immersed 
in distilled water for various periods, with the following results. 
It is rare to find even a trace of aggregation until 4 or 5 
and generally not until several more hours have elapsed. 
When however a leaf becomes quickly inflected in water, as 
sometimes happens, especially during very warm weather, 
aggregation may occur in little over 1 hr. In all cases 
leaves left in water for more than 24 hrs. have their glands 
blackened, which shows that their contents are aggregated ; 
and in the specimens which were carefully examined, there 
was fairly well-marked aggregation in the upper cells of the 
pedicels. These trials were made with cut-off leaves, and it 
occurred to me that this circumstance might influence the 
result, as the footstalks would not perhaps absorb water quickly 
enough to supply the glands as they continued to secrete. 
But this view was proved erroneous, for a plant with uninjured 
roots, bearing four leaves, was submerged in distilled water for 
47 hrs., and the glands were blackened, though the tentacles 
were very little inflected. In one of these leaves there was only 
a slight degree of aggregation in the tentacles; in the second 
rather more, the purple contents of the cells being a little 
separated from the walls ; in the third and fourth, which were 
pale leaves, the aggregation in the upper parts of the pedicels 
was well marked. In these leaves the little masses of proto- 
plasm, many of which were oval, slowly changed their forms 
and positions so that a submergence for 47 hrs. had not killed 
the protoplasm. In a previous trial with a submerged plants 
the tentacles were not in the least injected. 



Chap. IH. THE PROCESS OF AGGKEGATION. 53 

Heat induces aggregation. A leaf, with tlie cells of the 
tentacles containing only homogeneous fluid, was waved about 
for 1 m. in water at 130° Pahr. (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 little from the walls, 
and contained many oval and elongated masses of protoplasm, 
with a few minute spheres. A third leaf was left in water at 
125°, until it cooled, and when examined after 1 hr. 45 m., the 
inflected tentacles showed some aggregation, which became 
after 3 hrs. more strongly marked, btit 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. 

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



54 DKOSERA EOTUNDIFOLIA. Ohap. III. 

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

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



On the Proximate Causes of the Process of Aggregation. 

As most of the stiimilants which cause the inflection 
of the tentacles likewise induce aggregation in the 
contents of their cells, this latter process might be 
thought to be the direct result of inflection ; but this 
is not the case. If leaves are placed in rather strong 
solutions of carbonate of ammonia, for instance of 
three or four, and even sometimes of only two grains 
to the ounce of water (i.e. one part to 109, or 146, oi 



Chap, UI. THE PROCESS OF AGGREGATION. 55 

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

It is an important fact that when an organic or in- 
organic object is placed on the glands of the disc, 
and the exterior tentacles are thus caused to bend 
inwards, not only is the secretion from the glands of 
the latter increased in quantity and rendered acid, 
but the contents of the cells of their pedicels become 
aggregated. The process always commences in the 
glands, although these have not as yet touched any 
object. Some force or iafluence must, therefore, be 
transmitted from the central glands to the exterior 
tentacles, flrst 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 sufiicient 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 EOTDNDIFOLIA. OhAP. Ill, 

of the tentacles, the glands secrete less freely, or quite 
cease to secrete, and the aggregated masses of proto- 
plasm are then redissolved. Moreover, when leaves 
are immersed in dense vegetable solutions, or in 
glycerine, the fluid within the gland-cells passes out- 
wards, and there is aggregation ; and when the leaves 
are afterwards immersed in water, or in an innocuous 
fluid of less specific gravity than water, the protoplasm 
is redissolved, and this, no doubt, is due to endosmose. 
Opposed to this view, that aggregation is caused by 
the outward passage of fluid from the cells, are the 
following facts. There seems no close relation between 
the degree of increased secretion and that of aggre- 
gation. Thus a particle of sugar added to the secre- 
tion round a gland causes a much greater increase of 
secretion, and much less aggregation, than does a 
particle of carbonate of ammonia given in 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- 
pillae, described in the first chapter, with which the 



Chap. III. THE PEOCESS OF AGGREGATION. 57 

leaves are studded are not glandular, and do not 
secrete, yet they rapidly absorb carbonate of amjnonia 
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 water were strongly pressed beneath a slip of 
glass; many of the cells were ruptured, and pulpy 
matter of a purple colour, with granules of all sizes 
and shapes, exuded, but hardly any of the cells were 
completely emptied. I then added a minute drop of 
a solution of one part of carbonate of ammonia to 
109 of water, and after 1 hr. examined the specimens. 
Here and there a few cells, both in the glands and in 
the pedicels, had escaped being ruptured, and their 
contents were well aggregated into spheres which were 
constantly changing their forms and positions, and a 
current could still be seen flowing along the walls ; 
so that the protoplasm was alive. On the other hand, 
the exuded matter, which was now almost colourless 
instead of being purple, did not exhibit a trace of 
aggregation. Nor was there a trace in the many 
cells which were ruptured, but which had not been 
completely emptied of their contents. Though I 
looked carefully, no signs of a current could be seen 
within these ruptured cells. They had evidently been 
killed by the pressure ; and the matter which they 



58 DKOSEKA BOTUNDIFOLIA. Chap. IU 

Btill contained did not undergo aggregation any more 
than that which had exuded. In these specimens, as 
I may add, the individuality of the life of each cell 
was well illustrated. 

A full account will be given in the next chapter of 
the effects of heat on the leaves, and I need here only 
state that leaves immersed for a short time in water at 
a temperature of 120° Fahr. (48°-8 Cent.), which, as we 
have seen, does not immediately induce aggregation, 
were then placed in a few drops of a strong solution 
of one part of carbonate of ammonia to 109 of water, 
and became finely aggregated. On the other hand, 
leaves, after an immersion in water at 150° (65°'5 
Cent.), on being placed in the same strong solution, 
did not undergo aggregation, the cells becoming filled 
with brownish, pulpy, or muddy matter. With leaves 
subjected to temperatures between these two extremes 
of 120° and 150° Fahr. (48°-8 and 65°-5 Cent.), there 
were gradations in the completeness of the process ; 
the former temperature not preventing aggregation 
from the subsequent action of carbonate of ammonia, 
the latter quite stopping it. Thus, leaves immersed 
in water, heated to 130° (54°'4 Cent.), and then in the 
solution, formed perfectly defined spheres, but these 
were decidedly smaller than in ordinary cases. With 
other leaves heated to 140° (60° Cent.), the spheres 
were extremely small, yet well defined, but many of 
the cells contained, in addition, some brownish pulpy 
matter. In two cases of leaves heated to 145° (62°-7 
Cent.), a few tentacles could be found with some of 
their cells containing a few minute spheres; whilst 
the other cells and other whole tentacles included 
only the brownish, disintegrated or pulpy matter. 

Tl>e fluid within the cells of the tentacles must be 
in an oxygenated condition, in order that the force ot 



Chap. III. THE PEOCESS OF AGGREGATION. 59 

influence which induces aggregation should Ibe 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 less aggregation in the 
leaf which had been subjected to the carbonic acid 
than in the other. Another plant was exposed in 
the same vessel for 2 hrs. to carbonic acid, and one of 
its leaves was then placed in a solution of one part of 
the carbonate to 437 of water; the glands were 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. After 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 



60 DEOSEEA EOTDNDIFOLIA. Chap. Ill 

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 its 
spontaneous movements only as long as it is in an 
oxygenated condition; and so it is with the white 
corpuscles of the blood, only as long as they receive 
oxygen from the red corpuscles ;* but the cases above 
given are somewhat different, as they relate to the 
delay in the generation or aggregation of the masses 
of protoplasm by the exclusion of oxygen. 

Summary and Concluding Remarks. — 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 
time at each transverse partition. With pale-coloured 
leaves the first change which is perceptible, but only 



♦ Witli respect to plants. Sachs, ' Quarterly Journal of Micro- 
'Truite de Bot.,' 3rd edit., 1874, ecopioal Science,' April 1874, p 
0. 8U4. On blood corpuscles, see IS.*!.' 



Chap. III. THE PBOCESS OF AGGEEGATION. 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 

1871, p. 95*i), very slight pros- cells, and only secondarily to the 

sure oil the oell-menibrane 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 sepaTatiou from the touch on the outside must be 

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



62 DEOSERA EOTUNDIFOLIA. 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 heat. On the other hand, 
a temperature of about 150° Fahr. (65°-5 Cent.) does 
not excite aggregation ; nor does the sudden crushing 
of a gland. 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 
not become aggregated unless it be in a living state, 
and only imperfectly if the cell has been injured. We 
have also seen that the fluid must be in an oxygen- 
ated state, in order that the process of aggregation 
should travel from cell to cell at the proper rate. 

Various nitrogenous organic fluids and salts of am- 
monia induce aggregation, but in difi'erent degrees 
and at very different rates. Carbonate of ammonia is 
the most powerful of all known substances; the ab- 
sorption of TTm-o of ^ 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- 
cuntents, 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. m. THE PROCESS OF AGGREGATION. 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. 

Supplementary Observations on the Process of Aggre- 
gation in the Roots of Plants. 

It will hereafter be seen that a weak solution oi the car- 
bonate of ammonia induces aggregation in the cells of the roots 
of Dropera ; 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 
flidt weed which 1 met with, viz. Ev/phorhia peplus, being care- 



64 DEOSEEA. EOTUNDIFOLIA. OiIAV. lU 

ful not to injure the roots ; these were washed and placed in a 
little solution of one part of carbonate of ammonia to 146 of 
water. In less than one minute I saw a cloud travelling from 
cell to cell up the roots, with wonderful rapidity. After from 
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 was 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 J ol 
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. Roots were also immersed for 35 m. 
in a solution of one part of carbonate of potash to 218 of water'- 
but this salt produced no effect. 

I may here add that thin 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 
45 m. in a solution of one part of this same salt to 146 of water, 
and three of their roots were then examined. ]n two of them, 
all the cells which had previously contained only limpid fluid 
now included little green spheres. After from li hr. to 2 hrs. 
similar spheres appeared in the cells on the borders of the 
leaves ; but whether the ammonia had travelled up the rctots or 
had been directly absorbed by the leaves, I cannot say. As one 
species, Lemna arrhiza, produces no roots, the latter alternative 
is perhaps the most probable. After about 2J 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 o* 



Chap. ni. 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. 



fifi DKOSERA BOTUNDIFOLIA. OhAP IV. 



CHAPTEE IV. 

TuE Effects of Heat on the Leaves. 

Nature of the experiments — Effects of boiling water — Warm watei 
causes rapid inflection — Water at a iiigher temperature does not 
cause immediate inflection, but does not kill the leaves, as shov^n 
by their subsequent re-expansion and by the aggregation of the 
protoplasm — A still higher temperature kills the leaves and 
coagulates the albuminous contents of the glands. 

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



* When my experiments on the eludes that the protoplasm with- 
effects 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 de Schultze and Kiihne (as quoted 
Botanique,' 1874, pp. 772, 854) by Dr. Bastian in 'Contemp. 
that the most different kinds of Eeview,' 1874, p. 528) " found 
plants all perish if kept for 10 m. that the protoplasm of plant- 
in water at 45° to 4B° Cent., or cells, with which they experi- 
113° to 115° Fahr. ; and he con- mented, was always killed am? 



CiLiJ-. IV. THE EFFECTS OF HEAT. 67 

My experiments were tried in the following manner. Leaves 
were out off, and this does not in the least interfere with their 
powers; for instaneo, three cut-off leayes, 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 13 

Biire to a temperature of 118 J° 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. Wy man ('American Journal 

plasm and the re-expansion of of Science,' vol. xliv. 18fi7). Thus, 

the tentacles, they seem to me Dr. Hooker found Confervas 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 DBOSEKA ROTUNDIFOIilA. Chap IV. 

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

My first and preliminary experiment consisted in putting 
seven leaves in the same vessel of water, and warming it slowly 
up to the temperj-ture 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 irregularly, 
inflected. They were now removed from the cold water and 
kept in damp air, with bits of meat placed on their discs. 
The leaf which had been exposed to ths temperature of 110° 
became in 15 m. greatly inflected ; and in 2 hrs. every single 
tentacle closely embraced the meat. So it was, but after rather 
longer intervals, with the six other leaves. It appears, there- 
fore, that the warm bath had increased their sensitiveness 
when excited by meat. 

I next observed the degree of inflection which leaves under- 
went within stated periods, whilst still immersed in warm 
water, kept as nearly as possible at the same temperature ; but 
I will here and elsewhere give only a few of the many trials 
made. A leaf was left for 10 m. in water at 100° (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 
the extreme marginal ones, soon became closely inflected. 
The leaf was now placed in cold water, and in 7 hrs 30 m. it 
had partly, and in 10 hrs. fully, re-expanded. On the follow- 
ing morning it was immersed in a weak solution of carbonate oi 



Chap. IV. THE EFFECTS OF HEAT. 69 

aromonia, 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.) which was raissed to 120° (48°'8 Cent.) ; and every ten- 
tacle, excepting one, was quickly and closely inflected. This leaf 
was now immersed in a few drops of a strong solution of car- 
bonate of ammonia (one part to 109 of water) ; in 10 m. all the 
glands became intensely black, and in 2 hrs. the protoplasm in 
the cells of the pedicels was well aggregated. Another leaf was 
suddenly plunged, and as usual waved about, in water at 120°, 
and the tentacles became inflected in from 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 that a temperature of 
from 120° to 125° (48°-8 to 51°-6 Cent.) excites the 
tentacles into quick movement, but does not kill the 
leaves, as shown either by their subsequent re-expansion 
or by the aggregation of the protoplasm. We shall 
now see that a temperature of 130° (54°"4 Cent.) is too 
high to cause immediate inflection, yet does not kill 
the leaves. 

Experimeni 1. — A leaf was plunged, and as in all eases 
waved aboiit for a few minutes, in water at 130° (54° '4 Gent.), 
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 DEOSEEA EOTUNDIFOLIA. Chap. H' 

distinctly seen in a small mass of protoplasm in one of the oells 
of a tentacle.* After a few hours all the tentacles and thf 
blade became inflected. 

E-xp^riment 2.— Another leaf was plunged into water at 130' 
to 131°, and as before there was no inflection. After being ker< 
in cold water for an hour, it was placed in the strong solutior. 
of ammonia, and in the course of 55 m. the tentacles, were con- 
siderably inflected. The glands, which before had been rendered 
of a brighter red, were now blackened. The protoplasm in the 
cells of the tentacles was distinctly aggregated ; but the spheres 
were much smaller than those usually generated in unheated 
leaves when subjected to carbonate of ammonia. After an 
additional 2 hrs. all the tentacles, excepting six or seven, were 
closely inflected. 

Experiment 3. — A similar experiment to the last, with exactly 
the same results. 

Experiment 4. — A fine leaf was placed in water at 100° (37° '7 
Cent.), which was then raised to 145° (62° -7 Cent.). Soon after 
immersion, there was, as might have been expected, strong 
inflection. The leaf was now removed and left in cold water ; 
but from having been exposed to so high a temperature, it 
never re-expanded. 

Experiment b. — Leaf immersed at 130° (54°-4 Cent.), and the 
wat€r raised to 145° (62°"7 Cent.), there was no immediate in- 
flection ; it was then placed in cold water, and after 1 hr. 20 m. 
some of the tentacles on one side became inflected. This 
leaf was now placed in the strong solution, and in 40 m. all 
the submarginal tentacles were well inflected, and the glands 
blackened. After an additional interval of 2 hrs. 45 m. all the 
tentacles, except eight or ten, were closely inflected, with their 
cells exhibiting a slight degree of aggregation ; but the spheres 
of protoplasm were very small, and the cells of the exterior 
tentacles contained some pulpy or disintegrated brownish 
matter. 

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



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

tanique,' 1?74. p. S.i.i) that the in water to a temperature.of 47° 

movements of the protopIa.sm in to -(8° Cent., or 117° to H9° 

the hairs cf a Cucurbita ceased Falir. 



Chaf. IV. THE EFFECTS OF HEAT. 71 

all the tentacles, except sixteen or seventeen, were more or lesa 
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 gi-eenish-brown pulpy 
matter. 

Experiment 8. — A leaf was plunged and waved aboixt for a 
few minutes in water at 140° (60° Cent.), and was then left for 
half an hour in cold water, but there was no inflection. It was 
now placed in the strong solution, and after 2 hrs. 30 m. the 
inner submarginal tentacles were well inflected, with their 
glands blackened, and some imperfect aggregation in the cells 
of the pedicels. Three or four of the glands were spotted with 
the white porcelain-like structure, like that produced by boiling 
water. I have seen this result in no other instance after an 
immersion of only a few minutes in water at so low a tempe- 
rature as 140°, and in only one leaf out of four, after a similar 
immersion at a temperature of 115° Fahi-. On the other hand, 
with two leaves, one placed in water at 145° (62° • 7 Cent.), and 
the other in water at 140° (60° Cent.), both being left therein 
until the water cooled, the glands of both became white and 
porcelain-like. So that the duration of the immersion is an 
important element in the result. 

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

Experiment 10. — A leaf was plunged in water at 150° to 150i° 
(65° '5 Cent.); it became somewhat flaccid, with the outer ten- 
tacles slightly reflexed, and the inner ones a little bent inwards, 
but only towards their tips ; and this latter fact shows that the 
movement was not one of true inflection, as the baSal part 
alone normally bends. The tentacles were as usual rendered of 
a very bright red, with the glands almost white like porcelain, 
yet tinged with pink. The leaf having been placed in the 
strong solution, the cell-contents of the tentacles became of a 
muddy brown, with no trace of aggregation. 



72 DKOSEKA EOTUNDiFOLIA. Chap. IV. 

Experiment 11. — A leaf was immersed in water at 145° (62° '7 
CeDt), which was raised to 156° (68° '8 Cent.). The tentacles 
became bright red and somewhat reflexed, with almost all the 
glands like porcelain; those on the disc being still pinkish, 
those near the margin quite white. The leaf being placed as 
usual first in cold water and then in the strong solution, the 
cells in the tentacles became of a muddy greenish lirown, with 
the protoplasm not aggregated. Nevertheless, four of the glands 
escaped being rendered like porcelain, and the pedicels of these 
glands were spirally curled, like a French horn, towards their 
upper ends; but this can by no means be considered as a 
case of true inflection. The protoplasm within the cells of the 
twisted portions was aggregated into distinct though excessively 
minute purple spheres. This case shows clearly that the proto- 
plasm, after having been exposed to a high temperature for a 
few minutes, is capable of aggregation when afterwards sub- 
jected to the action of carbonate of ammonia, unless the heat 
has been sufficient to cause coagulation. 

Conduding Remarks. — As the hair-like tentacles are 
extremely thin and have delicate walls, and as the 
leaves were waved about for some minutes close to the 
bulb of the thermometer, it seems scarcely possible 
that they should not have been raised very nearly to 
the temperature which the instrument indicated. 
From the eleven last observations we see that a tem- 
perature of 130° (54°'4 Cent.) never causes the imme- 
diate inflection of the tentacles, though a temperature 
from 120° to 125° (48°-8 to 51°-6 Cent.) quickly pro- 
duces this effect. But the leaves are paralysed only 
for a time by a temperature of 130°, as afterwards, 
whether left in simple water or in a solution of car- 
bonate of ammonia, they become inflected and their 
protoplasm undergoes aggregation. This great dif- 
ference in the effects of a higher and lower tempera- 
ture may be compared with that from immersion in 
strong and weak solutions of the salts of ammonia ; for 
the former do not excite movement, whereas the latter 
act energetically. A temporary suspension of tha 



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 whfen 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 KOTUNDIFOLTA. Chap. IV, 

pinkish colour, and many present a speckled appear- 
ance. This high temperature never causes true inflec- 
tion ; on the contrary, the tentacles commonly become 
reflexed, though to a less degree than when immersed 
in boiling water ; and this apparently is due to their 
passive power of elasticity. After exposure to a tem- 
perature of 150° Tahr., the protoplasm, if subsequently 
subjected to carbonate of ammonia, instead of under- 
going aggregation, is converted into disintegrated or 
pulpy discoloured matter. In short, the leaves are 
generally killed by this degree of heat ; but owing to 
differences of age or constitution, they vary somewhat 
in this respect. In one anomalous case, four out of 
the many glands on a leaf, which had been immersed 
in water raised to 156° (68°'8 Cent.), escaped being 
rendered porcellanous ; * and the protoplasm in the 
cells close beneath these glands underwent some 
slight, though imperfect, degree of aggregation. 

Finally, it is a remarkable fact that the leaves of 
Drosera rotv/ndifolia, which flourishes on bleak upland 
moors throughout Great Britain, ahd 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 the opacity and porcelain- differences in the results above 

like appearance of the glands is recorded. 

probably due to the coagulation t It appears that cold-blooded 

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

authority of Dr. Burdon 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- Burdon Sanderson, a frog begins 

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

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

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

tained may account for the slight animal dies in a stiffened conditioa 



OllAP. rV. 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 DEOSEKA EOTUNDIFOLIA. OhaP. V 



CHAPTER V. 

The Effects of Non-nitkooenoos and Nitrogenous Oeoanio Fluids 
ON the Leaves. 

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

When, 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 prelimipary 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 OEGANIC FLUIDS. 77 

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

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

Gum 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 44 hrs. ; generally about 



78 UBOSEBA llOTUNDJirOLIA. OllAI'. V 

30 hrs. Inflection was novor thus caused, It in neoossarj 
to try pure gum arable, 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 78 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 80 hrs., no effect being produced, 
I am surprised at thjs fact, as I believe that the starch of com- 
merce generally contains a trace of gluten, and this nitrogenous 
substance causes inflection, as we shall see in the next chapter. 

Alcohol, Diluted. — One part of alcohol was added to seven of 
water, and the usual drops were placed on the discs of three 
leaves. No inflection ensued in the course of 48 hrs. To ascer- 
tain whether these leaves had been at all injured, bits of meat 
were placed on them, and after 21 hrs, they wore 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 hrs. Four of these 
leaves were then tested by bits of moat 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, bo shown in a future place, 
that cut-off leaves immersed in olive oil are powerfully affected. 

JnfuBvm and DecocHon uf Tea. — Di'opH of a strong infusion and 
decoction, as well as of a rather weak decoction, of tea were 
placed on ten loaves, 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 thu8 see that, excluding the experiments with 
water, sixty-oue leaves were tried with drops of the 



Chat. V. EFFECTS OF OKGAXIC FLZID&. 79 

aU)ve-named non-nitrogenoTis fluids ; and the tentacles 
were not in a single case inflected. 

With lespect to nitrogaioiis fluids, the fiist which came to 
hand were tried. The eEperiments were made at the same 
time and in exacti; the same mamier as the foi^oicg. 
As it was immediately eTident that these fluids pmdnoed a 
gr^t efiect, I neglected in most cases to record how soon the 
tentacles became inflected. Bnt this alwajs occnned in less 
than 24 hrs. ; whilst the drops of non-nitiogenons fluids which 
produced no e&ct weie observed in every case dnrii^ a 
Gousideialdf longer poiod. 

JiUk. — Drops were jdaced on sucteen leaves, and the tentacles 
of an, as well as the blades of sevraal, soon became greatly 
inflected. The i)mods were lecorded in only fliree cases, 
namely, with leaves <hi which unusually anaU drops had beoi 
placed. Their tentacles were smnewbat inflected in ^ m.; 
aad after 7 hrs. 4o m. the blades ol two were so much carved 
inwards that they formed little cups enclosing the drops. 
These leaves re-espanded on the third day. On another occa- 
sion the blade of a leaf was much inflected in 5 hrs. aito a 
drop of milk had been placed on it. 

human Urine. — Drops were placed on twelve leaves, aad 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, bnt was always effected in under 
21 hrs. In two instances I recorded that all the estedcK ten- 
tacles were completely inflected in 17 hrs., but not flie blade of 
the lea£ In another case the edges of a leaf, after ii hrst 
30 SL, became so strongly inflected that it was converted into a 
cup. The power of urine does not lie in the niea, whidi, as 
we shall hereafter see, is inoperative. 

Albumen (firesh from a hens e^X placed on seven leaves, 
caused the tentacles of six of them to be well infl»^ed. 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 vf milk, and this 
caused the tentacles to bend inwards in 13 hrs. 

C'oW Filtered InfasUm of Bi ■ Heat. — ^This was tried cmly on a 
single leaf, which had most of its outer tentacles and the blade 
inflected in 19 hrs. Dnrii^ subse<:jtient years, I repeatedly 
Bsed this infusion to test leaves which had been experimented 



80 DROSEBA EOTUNDIFOLIA. OuAP. V 

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

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

Saliva. — ^Human saliva, when evaporated, yieldsf from 114 to 
1*19 per cent, of residue ; and this yields 0'25 per cent, of ashes, 
so that the proportion of nitrogenous matter which saliva con- 
tains must be small. Nevertheless, drops placed on the discs of 
eight leaves acted on them all. In one case all the exterior ten- 
tacles, excepting nine, were inflected in 19 hrs. 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. 

Idnglais. — ^Drops of a solution about as thick as milk, and of 
a still thicker solution, were placed on eight leaves, and the ten- 
tacles of all became inflected. In one case the exterior tentacles 
were well curved in after 6 hrs. 30 m., and the blade of the leaf 
to a partial extent after 24 hrs. As saliva acted so efficiently, 
and yet contains so small a proportion of nitrogenous matter, I 
tried how small a quantity of isinglass would act. One part was 
dissolved in 218 parts of distilled water, and drops were placed 
on four leaves. After 5 hrs. two of these were considerably and 
two moderately inflected ; after 22 hrs. the former were greatly 
and the latter much more inflected. In the course of 48 hrs. 



» Mucus from the air-paegageB to contain some albumen, 
is said in Marshall, 'Outlines of t Mailer's 'Elements of Phygio" 

Physiology,' vol. 11. 1867, 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 th(5 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 f-Ju 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^ of a grain of isinglass is sufBcient 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 aboTe nitrogenous fluids, the five leaves 
tried only with the extremely weak solution of isin- 
glass not being included, nor the numerous trials 
subsequently made, of which no exact account was 
kept. Of these sixty-four leaves, sixty-three had their 
tentacles and often their blades well inflected. The 
one which failed was probably too old and torpid. 
But to obtain so large a" proportion of successful 
cases, care must be taken to select young and active 
leaves. Leaves in this condition were chosen with 
equal care for the sixty-one trials with non-nitro- 
genous fluids (water not included) ; and we have seen 
that not one of these was. in the least affected. We 
may therefore safely conclude that in the sixty-four 
experiments with nitrogenous fluids the inflection of 
ihe exterior tentacles was due to the absorption of 



82 DEOSERA KOTUNDirOLIA. 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 aBerwards tested wii^^h 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 other experiments with nitrogenous fluids 
may be here conveniently given. Decoctions of some vegetables, 
known to be rich in nitrogen, were made, and these acted like 
animal fluids. Thus, a few green peas were boiled for some time 
in distilled water, and the moderately thick decoction thus made 
was allowed to settle. Drops of the superincumbent fluid were 
placed on four leaves, and when these were looked at after 
16 hrs., the tentacles and blades of all were found strongly 
inflected. I infer from a remark by Gerhardt* that legumin is 
present in peas " in combination with an alkali, forming an 
incoagulable solution," and this would mingle with boiling 
water. I may mention, in relation to the above and following 
experiments, that according to Schifff certain forms of albumen 



* Watts' ' Diet, of Chemistry,' Digestion,' torn. L p. 379 ; torn 
vol. ill. p. 568. ii. pp. 154, 166, on legnmin. 

f 'Lemons sor la Phys. de la 



Ohap. V. EFFECTS OF ORGANIC FLtJIDS. 83 

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

On three occasions chopped cabbage-leaves* were boiled in 
distilled water for 1 hr. or for IJ hr. ; and by decanting the 
decoction after it had been allowed to rest, a pale dirty green 
fluid was obtained. The usual-sized drpps were placed on 
thirteen leaves. Their tentacles and blades were inflected after 
4 hrs. to a quite extraordinary degree. Next day the protoplasm 
within the cells of the tentacles was found aggregated in the 
most strongly marked manner. I also touched the viscid secre- 
tion round the glands of several tentacles with minute drops of 
the decoction on the head of a small pin, and they became well 
inflected in a few minutes. The fluid proving so powerful, one 
part was diluted with three of water, and drops were places] 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 baiMng 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 loaves 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. 1. p. 653. 
per cent of albuminous matter, 



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

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



CiiAP. YL DIGESTION. 85 



OHAPTEE VI. 

The Digestive Power of the Secretion of Dkobera. 

The seoretion rendered aoid by the du-ect and indirect excitement of 
the glands — Natui'e 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 — 
Cai'tilage — Fibro-cartilage — Bone — Biiamel 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 
who -knows nothing about the digestion of albiuninous 
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 litiiius paper ;. and the secretion of twenty- 
two of these leaves did not in the least affect the colour, 
whereas that of eight caused an exceedingly feeble 
and sometimes doubtful tinge of red. Two other 
old leaves, however, which appeared to have been in- 
flected several times, acted much more decidedly on 
the paper. Particles of clean glass were then placed 
on five of the leaves, cubes of albumen on six, and 
bits of raw meat on three, on none of which was the 
secretion at this time in the least acid. After an 
interval of 24 hrs., when almost all the tentacles on 



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

ing to Schiff, and contrary to the quantity of coagulated albumen, 

opinion of some physiologists, Sehiff, 'Phys. de la Digestion,' 

that weak hydrochloric dissolves, tom. ii. 1867, p. 25 



Chap. VL 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 
7 



88 DEOSERA EOTUNDIFOLIA. Oh4P. VI. 

appears to be to a certain extent antiseptic, as it 
checks the appearance of mould and infusoria, thus 
preventing for a time the discoloration and decay of 
such substances as the white of an egg, cheese, &c. 
It therefore acts like the gastric juice of the higher 
animals, which is known to arrest putrefaction by 
destroying the microzymes. 



As I was anxious to learn what acid the secretion contained, 
445 leaves were washed in distilled water, given me by Prof. 
Prankland; but the secretion is so viscid that it is scarcely 
possible to scrape or wash off the whole. The conditions 
were also unfavourable, as it was late in the year and the 
leaves were small. Prof. Frankland with great kindness under- 
took to test the fluid thus collected. The leaves were excited 
by clean particles of glass placed on them 24 hrs. previously. 
No doubt much more acid would have been secreted had the 
leaves been excited by animal matter, but this would have 
rendered the analysis more difficult. Prof. Frankland informs 
me that the fluid contained no trace of hydrochloric, sulphuric, 
tartaric, oxalic, or formic acids. This having been ascertained, 
the remainder of the fluid was evaporated nearly to dryness, and 
acidified with sulphuric acid ; it then evolved volatile acid 
vapour, which was condensed and 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 determinar 
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 be of a different nature from that present in the secretion. 
Nor was any odour of pepsin emitted by them. 



Chap. VI. 



DIGESTION. 89 



Although it has long been known that pepsin with acetic 
acid has the power of digesting albuminous compounds, 
it appeared adyisable 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. 
Burden 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 625 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 O'OOSl 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 hquid 
was filtered. Of the filtrate, which of course contained as 
much of the fibrin as had been digested during the four hours, 



90 DEOSEBA EOTUNDIPOLIA. Chap, VL 

10 eub. cent, were measured out and eTaporated, and dried at 
110° as before. The residues were respectively — 

" In the liquid containing hydrochloric acid 0'4:079 

„ „ 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 .. 0-1437 

„ valerianic acid 0-1223 

as compared with 0-4048 for hydrochloric acid; these several 
numbers expressing the quantities of fibrin by weight digested 
in presence of equivalent quantities of the respective acids 
under identical conditions. 

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

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

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

"Propionic acid 0-0563 

Butyric acid 0-0835 

Valerianic 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 .. .. .. 16-5 

Butyric acid .. .. .. 24-7 

Valerianic 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 eub. cent, 
of the liquid : 



" Hydrochloric acid 


.. 0'2915 


Propionic acid .. 


.. 0-1490 


Butyric acid 


.. 0-1044 


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 butyric acid by 35'8; and that of 
valerianic by 17-8. 

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

" Propionic acid .. .. .. 15-8 

Butyric acid . . . . . . 32-0 

Valerianic acid .. .. .. 21-4 

" 7. A further experiment was made to ascertain whether the 
digestive activity of butyric acid (which was selected as being 
apparently the most eflcacious) 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 0-13H gramme, 
a similar liquid prepared with butyric acid digested 0-0455 
gramme of fibrin. 

" Hence, taking the quantities digested with hydrochloric acid 
at the temperature of the body as 100, we have the digestive 
power of hydrochloric acid at the temperature of 16° to 18° 
Cent, represented by 44-9 ; that of butyric acid at the same 
temperature being 15-6." 

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



92 DEOSEEA 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. 

Substances which are completeh/ or jpartiaHy digested hy 
the Secretion of Drosera. 

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

Experiment 1. — Bather large cubes of albumen were first 
tried the tentacles were well inflected 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. 

Exi.eriment 2. — A cube of ^ of an inch (i.e. with each side 
jJg 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 /g 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. 

Expeiiment 3. — Two cubes of albumen of -^ of an inch 
(127 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. — Tvro 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. 'I'he drops were replaced on the 
leaves, which re-expanded aft«r 10 days; and now nothing 
was left except a very little transparent acid fluid. 

Experiment 5. — This experiment was sb'ghtly 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, Sohiff states ( 'Lemons ohimie, ont lieu sur taute la snr- 

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

1867, p. Ii9; that this is charac- I'agent dissolvaut." 



94 DEOSERA EOTUNDIFOLIA. Chap. VI. 

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

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

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

Exjurlmeiit 7.— Small cubes of albumen were put on two 
leaves, and minute drops of hydrochloric acid, of the strength of 
one part to 437 of water, were added two or three times. This 
did not in the least delay, but seemed rather to hasten, the 
process of digestion ; for every trace of the albumen disappeared 
in 24 hrs. 30 m. After three days the leaves partially re- 
expanded, and by this time almost all the viscid fluid on theii 
discs was absorbed. It is almost superfluous to state thai 



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 1 ascertained that 
each was equal to about j^ of a minim ('0059 ml.), so that 
each contained only ^^ of a grain ('OISS 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 tho 
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 sphwe 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 
■j-Jg^ of a grain (-0539 mg.) of either salt. Two cubes of albu- 
men (each about -^ 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 shghtly 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 lirs. 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 wns 
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 DROSEKA EOTUNDIFOLIA. Chap. VI. 

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

Experiment 11. — Two cubes of albumen (Jg of an inch, or 
•0^5 mm.) were placed on two leaves, and were treated with 
alkalies as in the last experiment, and with the same result ; 
for after 22 hrs. they had their angles perfectly sharp, showing 
that the digestive process had been completely arrested. I then 
wished to ascertain what would be the effect of using stronger 
hydrochloric acid ; so I added minute drops of the strength of 
1 per cent. This proved rather too strong, for after 48 hrs. 
from the time when the acid was added one cube was still 
almost perfect, and the other only very slightly rounded, and 
both were stained slightly pink. This latter fact shows that the 
leaves were injured,* for during the normal process of digestion 
the albumen is not thus coloured, and wo can thus understand 
why the cubes were not dissolved. 

From these experiments we clearly see that the 
secretion has the power of dissolving albumen, and 
we further see that if an alkali is added, the process of 
digestion is stopped, but immediately recommences as 
soon as the alkali is neutralised by weak hydrochloric 
acid. Even if I had tried no other experiments than 
these, they would have almost sufficed to prove that 
the glands of Drosera secrete some ferment 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 (' Traits de agents, allow all their colouring 

Bot.' 1874, p. 774), that cells matter to escape into the snr- 

which arfi killed by freezing, by rounding water, 
joo great heat, or by cheinbal 



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 (-^V 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 Dionsea. Dr. Hooker likewise found 
that, although the fluid within the pitchers of Ne- 
penthes possesses extraordinary power of digestion, yet 
when removed from the pitchers before they have 
been excited and placed in a vessel, it has no such 
power, although it is already acid ; and we can 
account for this fact only on the supposition that the 
proper ferment is not secreted until some exciting 
matter is absorbed. 

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



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

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

tame glycerine with hydi-ochlorio affected after two days. 
noid of the same strength; and 



98 DROSEEA KOTUNDIFOLIA. Chap. VL 

the expferiment 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 leafj 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 tlie central part the transverse striae 
on the muscular fibres were quite distinct; and it was 



• 'Lecons pl-vs. de la Digestion,' 1867, torn. ii. pp. 114-126. 



CHA.r. VI. DIGESTION. 99 

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

" On a dit que le sue gastrique faisait perdre a la fibre muscu- 
laire ses stries transversales. Ainsi enoncee, cette proposition 
pourrait dormer lieu a une equivoque, car ce qui se perd, ce n'est 
que I'aspect exterieur de la striature et non las elements anato- 
miques qui la composent. On salt que les stries qui donnent un 
aspect si oaracteristique a la fibre musoulaire, sont le resultat de 
la juxtaposition et du parallelisme des corpuscules elementaires, 
places, a distances egales, dans I'interieur 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 
aveo lui I'aspect, le phenomene optique des stries. Si, apres la 
d&agregation 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 ou les fibrilles elles-mgmes se liquefient et dis- 
paraissent dans le sue gastrique. Ce qui constitue la striature, 
a proprement parler, n'est done pas detruit, avant la lique- 
faction de la fibre cbarnue 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 



* ' Le5ons phys. de la Digestion,' torn. ii. p. 145. 



too DEOSEEA ROTUNDIFOLIA. 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 1 'action du sue gastriqne acide sur le tissu connect! f 
qui se dissout d'abord, et qui, par sa liquefaction, desagrege les 
fibril les. 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 demsrits' de 
Bowman, qui ne sont autre chose que les produits de cette 
division transversals des fibrilles elementaires, peuvent etre 
prepares et isoles a I'aide du sue gastrique, pourvu qu'on 
n'attend 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 ^„- 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 tho process 
of digestion, for on one leaf all was liquefied and 
absorbed after 20 hrs. ; but on the three other leaves 
some undissolved residue was left after 48 hrs. It 
is remarkable that in all the above and following 
experiments, as well as when much larger bits of 
fibrin were used, the leaves were very little excited ; 
and it was sometimes necessary to add a little saliva 
to induce complete inflection. The leaves, moreover, 
began to re-expand after only 48 hrs., whereas they 
would have remained inflected for a much longer 
time had insects, meat, cartilage, albumen, &c., been 
placed on them. 

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

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

Experiment 2. — The same experiment with the same result, 
only one of the two bits of fibrin exciting tfhe 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 DROSEEA EOTUNDIFOLIA. Chat. VI, 

secretion from the glands. In 18 hrs. the fibrin was com- 
pletely liquefied, but undigested atoms still floated in the 
liquid; these, however, disappeared in under two additional 
days. 

Prom 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 
8 



104 DllOSEBA ROTUNDIFOLIA. Ohap. VL 

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

During a more favourable season, moderately sized 
bits of the skinned ear of a cat, which includes 
cartilage, areolar and elastic tissue, were placed on 
three leaves. Some of the glands were touched with 
saliva, which caused prompt inflection. Two of the 
leaves began to re-expand after three days, and the 
third on the fifth day. The fluid residue left on 
their 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-cartilaffe (from between the vertebrae of the 
tail of a sheep). Moderately sized and small bits 
(the latter about -g-V 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, sq 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 

he reports that the two which had been subjected to 
artificial gastric juice were "in that state of diges- 
tion in which we find connective tissue when treated 
with an acid, viz. swollen, more or less hyaline, the 
fibrillar bundles having become homogeneous and lost 
their fibrillar structure." In the specimens which had 
been left on the leaves of Drosera, until they re- 
expanded, "parts were altered, though only slightly 
so, in the same manner as those subjected to the 
gastric juice, as they had become more transparent, 
almost hyaline, with the fibrillation of the bundles 
indistinct." Fibro-cartilage is therefore acted on in 
nearly the same manner by gastric j^lice 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 DEOSEEA EOTI3NDIFOLIA. Chap. A? I. 

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

As the angles and little projections of the fibrous 
basis were not in the least rounded or corroded, two of 
the bits were placed on fresh leaves. These by the 
next morning were closely inflected, and remained 
so, — the one for six and the other for seven days, — 
therefore for not so long a time as on the first occasion, 
but for a much longer time than ever occurs with 
leaves inflected over inorganic or even over many 
organic bodies. The secretion during the whole time 
coloured litmus paper of a bright red; but this may 
have been due to the presence of the acid super- 
phosphate of lime. When the leaves re-expanded, the 
angles and projections of the fibrous basis were as 
sharp as ever. I therefore concluded, falsely as we 
shall presently see, that the secretion cannot touch 
the fibrous basis of bone. The more probable expla- 
nation is that the acid was all consumed in decom- 
posing the phosphate of lime which still remained; 
so that 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 
examined each succeeding day at the same hour. The 
results are, I think, worth giving in detail. 



Chap. VI. DIGESTION. 107 

Experimevt 1. — May 1st, fragment placed on leaf ; 3rd, ten- 
tacles but little inflected, so a little saliva was added ; 6th, as 
the tentacles were not strongly inflected, the fragment was 
transferred to another leaf, which acted at first slowly, but by 
the 9th closely embraced it. On the 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 difSculty 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 aad 



108 DEOSEEA EOTUNDIFOLIA. Chap. \l 

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 rarifled, thus producing the appear- 
ance as if the canaliculi of the bone-corpuscles had 
become larger. Otherwise the corpuscles and theii- 
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. 

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



110 DEOSEEA EOTUNDIFOLIA. Chap. VL 

re-expand, the rest being much injured or killed. I 
repeated the experiment, but moistened the phosphate 
with saliva to insure prompt inflection ; one leaf re- 
mained inflected for six days (the little saliva used 
would not have acted for nearly so long a time) and 
then died; the other leaf tried to re-expand on the 
sixth day, but after nine days failed to do so, and 
likewise died. Although the quantity of phosphate 
given to the above four leaves was extremely small, 
much was left in every case undissolved. A larger 
quantity wetted with water was next placed on the 
discs of three leaves ; and these became most strongly 
inflected in the course of 24 hrs. They never re- 
expanded ; on the fourth day they looked sickly, 
and on the sixth were almost dead. Large drops 
of not very viscid fluid hung from their edges during 
the six days. This fluid was tested each day with 
litmus paper, but never coloured it ; and this cir- 
cumstance 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. YI. 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 -^V o^ ^^ ^^^^ ( 2'54 mm.), just 
moistened with water, were placed on two leaves ; and 
after two or three days nothing was left on them but 
some acid viscid fluid, which in this and other cases 
never showed any tendency to regelatinise ; so that 
the secretion must act on the gelatine differently 
to what water does, and apparently in the same 
manner as gastric juice.* Four squares of the same 
size as before were then soaked for three days in water, 
and placed on large leaves ; the gelatine was liquefied 
and rendered acid in two days, but did not excite 
much inflection. The leaves began to re-expand after 
four or five days, much viscid fluid being left on their 
discs, as if but little had been absorbed. One of these 
leaves, as soon as it re-expanded, caught a small fly, 
and after 24 hrs. was closely inflected, showing how 
much more potent than gelatine is the animal matter 
absorbed from an insect. Some larger pieces of gela- 
tine, soaked for five days in water, were next placed 
on three leaves, but these did not become much in- 
flected until the third day ; nor was the gelatine 
completely liquefied until the fourth day. On this 
day one leaf began to re-expand ; the second on the 
fifth ; and third on the sixth. These several facts 



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



112 DEOSEBA ROTUNDIFOLIA. ChaP. VI. 

prove that gelatiae is far from acting energetically 
on Drosera. 

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

Ghondrin. — 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 whiclr 
in the ' Medical Record,' Janiary gelatine plays in nutrition. 
1873, p. 36, an account of Voit's 



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 ^-J-^ 
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. 

Milli. — We have seen in the last chapter that milk 
acts most powerfully on the leaves ; but whether this 
Is due to the contained casein or albumen, I know not. 
Rather large drops of milk excite so much secretion 
(which is very acid) that it sometimes trickles down 



114 DEOSEKA EOTUNDIFOLIA. Chap. VI. 

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

Chemically Prepared Casein. — This substance, which 



• 'Le9onB,' &o. 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-Seylei 
and Lubavin* casein consists of an albuminous, with 



• Di. Lauder Bruntcn, ' Handbook for Phys. Lab.' p. .529 



116 DEOSEEA EOTUNDIFOLIA. Chap. VI, 

a non-albumiuous, 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. Sphiff 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 of 
an inch (1'27 mm.) were placed on four leaves, and 
these after one or two days became well inflected, 
their glands pouring forth much acid secretion. 
After five days they began to re-expand, but one 
died, and some of the glands on the other leaves were 
injured. Judging by the eye, the softened and 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. 

Leffimiin. — I did not procure this substance in a 
geparate 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 daya 



' Lejons,' &o. torn. ii. p. 153. 



CnAP. YI. DIGESTION. 117 

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

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

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

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



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

undigested coats of the grains in 1874, p. 158. 
the intestinal canal of pollen- t Watts' ' Diet, of Chemistry, 

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



118 DEOSERA EOTUNDIFOLIA. 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 w-ere 
given. I therefore asked Dr. Burdon Sanderson to 
try gluten in artificial digestive fluid of pepsin with 
hydrochloric acid ; and this dissolved the whole. 
The gluten, however, was acted on much more slowly 
than fibrin ; the proportion dissolved within four 
hours being as 40'8 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 lattei 
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 liad 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 DEObJEKA EOTUNDIFOLIA. 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. 

Oldbulin or Crystallin. — This substance was kindly prepared 
for me from the lens of the eye by Dr. Moore, and consisted of 
hard, colourless, transparent fragments. It is said* that globulin 
ought to " swell up in water and dissolve, for the most part 
forming a gummy liquid ;" but this did not occur with the above 
fragments, though kept in water for four days. Particles, some 
moistened with water, others with weak hydrochloric acid, 
others soaked in water for one or two days, were placed on 
nineteen leaves. Most of these leaves, especially those with the 
long soaked particles, became strongly inflected in a few hours. 
The greater number re-expanded after three or four days ; but 
three of the leaves remained inflected during one, two, or three 
additional days. Hence some exciting matter must have been 
absorbed; but the fragments, though perhaps softened in a 
greater degree than those kept for the same time in water, 
retained all their angles as sharp as ever. As globulin is an 
albuminous substance, I was astonished at this result ; and my 
object being to compare the action of the secretion with that of 
gastric juice, I asked Dr. Burdon Sanderson to try some of the 
globulin used by me. He reports that " it was subjected to a 
liquid containing 0''2 per cent, of hydrochloric acid, and about 
1 per cent, of glycerine extract of the stomach of a dog. It was 
then ascertained that this liquid was capable of digesting 1-31 
of its weight of unboiled fibrin in 1 hr. ; whereas, during the 
hour, only 0'14l of the above globulin was dissolved. In both 
cases an excess of the substance to be digested was subjected to 
the liquid."t We thus see that within the same time less than 
one-ninth by weight of globulin than of fibrin was dissolved ; 
and bearing in mind that pepsin with acids of the acetic series 
has only about one-third of the digestive power of pepsin with 
hydrochloric acid, it is not surprising that the fragments of 



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

vol li. p. 874. that which I used, though less 

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

son prepared some fresh globulin we have seen, 1-31 was dissolved. 

by Schmidt's method, and of this I wish that I had tried on Dro- 

0-865 WHS dissolved within the sera globulin prepared by thii 

same time, namely, one hour ; so method. 



Chap. VI. DIGESTION, 121 

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

Bxmatin.- — Some dark red granules, prepared from bullock's 
blood, were given me ; these were found by Dr. Sanderson to 
be insoluble in water, acids, and alcohol, so that they were pro- 
bably 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 globulin, 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. 

Suhstances which are not Digested hy 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 
feir as I have observed, epidermic productions (such 
as bits of human nails, balls of hair, the quills of 
feathers), fibro-elastic tissue, mucin, pepsin, urea, 
chitine, chlorophyll, cellulose, gun-cotton, fat, oil, and 
starch. 



122 DEOSEEA EOTUNDIFOLIA. Chap. 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. 



Fihro-elastic 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 flbro- 
elastio 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.-^Ks 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. Prom what is stated in chemical works, it 
appeals 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, Sshiff, 'Phys. de .a Digestion,' 1867, torn, ii 
0.98. 



uhap. ■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, retained their angles as 
sharp as ever. We may therefore infer that the mucin itself 
was not dissolved or digested. Nor is it digested by the 
gastric juice of living animals, and according to Schiff* it is a 
layer of this substance which protects the coats of the stomach 
from being coreoded during digestion. 

Fepsin. — ^My experiments are hardly worth giving, as it is 
scarcely possible to prepare pepsin free from other albuminoids ; 
but I was curious to ascertain, as far as that was possible, 
whether the ferment of the secretion of Drosera would act on 
the ferment of the gastric juice of animals. I first used the 
common pepsin sold for medicinal purposes, and afterwards 
some which was much purer, prepared for me by Dr. Moore. 
Kve 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 ax:id secre- 
tion surrounding them, were singularly pale, whereas others 
were singularly dark-coloured. Some of the secretion was 
i craped off and examined under a high power ; and it abounded 
with granules undistinguishable from those of pepsin left in 
water for the same length of time. We may therefore infer, 
as highly probable (remembering what small quantities were 
given), that the ferment of Drosera does not act on or digest 

* 'licgons phys. de la Digestion,' 1867, torn. ii. p. 304. 



t24 DROSEKA KOTUNDIFOLIA. Chap. VT 

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

Urea. — It seemed to me an interesting inquiry whether this 
refuse of the living body, which contains much nitrogen, 
would, like so many other animal fluids and substances, be 
absorbed by the glands of Drosera and cause inflection. Half- 
minim drops of a solution of one part to 437 of water were 
placed on the discs of four leaves, each drop containing the 
quantity usually employed by me, namely -g^ of a grain, or 
•0674 mg. ; but the leaves were hardly at all affected. They 
were then tested with bits of meat, and soon became closely 
inflected. I repeated the same experiment on four leaves 
with some fresh urea prepared by Dr. Moore ; after two days 
there was no inflection; I then gave them another dose, but 
still there was no inflection. These leaves were afterwards 
tested with similarly sized drops of an infusion of raw meat, 
and in 6 hrs. there was considerable inflection, which became 
excessive in 24 hrs. But the urea apparently was not quite 
pure, for when four leaves were immersed in 2 dr. (7'1 ml.) of 
the solution, so that all the glands, instead of merely those on 
the disc, were enabled to absorb any small amount of impurity 
in solution, there was considerable inflection after 24 hrs., 
certainly more than would have followed from a similar im- 
mersion in pure water. That the urea, which was not per- 
fectly white, should have contained a sufficient quantity of 
albuminous matter, or of some salt of ammonia, to have caused 
the above effect, is far from surprising, for, as we shall see 
in the next chapter, astonishingly small doses of ammonia 
are highly efficient. We may therefore conclude that urea itself 
is not exciting or nutritious to Drosera ; nor is it modified by 
the secretion, so as to be rendered nutritious, for, had this been 
the case, all the leaves with drops on their discs assuredly 
would have been well inflected. Dr. Lauder Brunton informs 
me that from experiments made at my request at St. Bartho- 
lomew's Hospital it appears that urea is not acted on by 
artificial gastric juice, that is by pepsin with hydrochloric acid. 

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



Chap. VI. DIGESTION. 126 

■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. 
£>r. 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 DKOSEEA EOT0NDIFOLIA. Chap. VL 

used, as well as some freshly prepared, with arliflcial 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 grains consist of protoplasm merely 
coloured by chlorophyll. My son Francis placed a thin slice of 
spinach leaf, moistened with saliva, on a leaf of Drosera, and 
other slices on damp cotton-wool, all exposed to the same 
temperature. After 19 hrs. the slice on the leaf of Drosera was 
bathed in much secretion from the inflected tentacles, and was 
now examined under the microscope. No perfect grains of 
chlorophyll could be distinguished ; some were shrunken, of a 
yellowish-green colour, and collected in the middle of the cells ; 
others were disintegrated and formed a yellowish mass, likewise 
in the middle of the cells. On the other hand, in the slices 
surrounded by damp cotton-wool, the grains of chlorophyll were 
green and as perfect as ever. My son also placed some slices 
in artificial gastric juice, and these were acted on in nearly the 
same manner as by the secretion. We have seen that bits of 
fresh cabbage and spinach leaves cause the tentacles to be in- 
flected and the glands to pour forth much acid secretion ; and 
there can be little doubt that it is the protoplasm forming the 
grains of chlorophyll, as well as that lining the walls of the 
cells, which excites the leaves. 

Fut and Oil. — Cubes of almost pure uncooked fat, placed on 
several leaves, did not have their angles in the least rounded. 
We have also seen that the oil-globules in milk are not digested. 
Nor does olive oil dropped on the discs of leaves cause any 
inflection ; but when they are immersed in olive oil, they become 
strongly inflected ; but to this subject I shall have to recur. 
Oily substances are not digested by the gastric juice of animals. 

Starch. — Bather 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 satiuus) 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 tho 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 loaves 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 ot 3 hrs., and were still closely inflected on the third 
day ; so that it evidently was not the mucus which excited so 



128 DEOSEKA KOTUNDIFOLIA. ClUP. VI. 

much inflection ; on the contrary, this served to a certain exteni 
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 {Si'vapis rngra), two of celeiy (^Apium 
graveolens) — ^both of the previous year, two seeds well soaked of 
caraway \Carum carui), and two of wheat, did not excite the 
leaves more than inorganic objects often do. Five seeds, hardly 
ripe, of a buttercup (Eanunculus), and two fresh seeds of Ane- 
wone nemorosn, induced only a little more effect. On the other 
hand, four seeds, perhaps not quite ripe, of Ca/rtx 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 Pingnicula. If so, Drosera will profit to a slight degree 
by absorbing matter from such seeds. 



Summary and Concluding Remarhs on the Digestive 
Power of Drosera. 

When the glands on the disc are excited either 
by the absorption of nitrogenous matter or by 
mechanical irritation, their secretion increases in 
quantity and becomes acid. They likewise transmit 



CliAP. 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 Dioneea and Nepenthes. In like 
manner, the glands of the stomach of animals secrete 
pepsin, as Schiff asserts, only after they have ab- 
sorbed certain soluble substances, which he desig- 
nates as peptogenes. There is, therefore, a remarkable 
parallelism between the glands of Drosera and those 
of the stomach in the secretion of their proper acid 
and ferment. 

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



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



130 DEOSEEA EOTUNDIFOLIA. CuAP. 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. 1 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 au 
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 string 
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 haematin 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-elastie 
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. 

Tlie 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 DKORERA ROTDNDIFOLIA. Chap. YL 

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

The length of time during which the tentacles re- 
main inflected largely depends on the quantity of the 
substance given, partly on the facility with which it is 
penetrated or acted on by the secretion, and partly 
on its essential natiu'e. 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 



Chap. 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 ■nas 
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 Poster in Watts' 
Diet, of Chemistry,' Supplement 1872, p. 969. 



134 DKOSEKA EOTUNDIFOLIA. Chap. VI. 

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

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

Finally, the experiments recorded in this chapter 
show us that there is a remarkable accordance in the 
power of digestion between the gastric juice of ani- 
raals 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, 



Ohap. 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 pmpose 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. 



10 



136 DEOSEKA EOTUNDIFOLIA. Chap. Vli 



CHAPTEE VII. 

The Effects op Salts op AMMOinA. 

Manner of performing the experiments — Action of distilled water in 
comparison with the solutions — Carbonate of ammonia, absorbed 
by the roots — The vapour absorbed by the glands — Drops on the 
disc — Minute drops applied to separate glands — Leaves im- 
mersed in weak solutions — Minuteness of the doses which induce 
aggregation of the protoplasm — Nitrate of ammonia, analogous 
experiments with — Phosphate of ammonia, analogous experiments 
with — Other salts of ammonia — Summary and concluding re- 
marks on the action of the salts of ammonia. 

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

Firstly. — Drops which were ascertained by repeated trials to 
be on an average about half a minim, or the -^ 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 time. It was first 
ascertained, from between thirty and forty trials, that distilled 
water dropped in this manner produces no effect, except that 
sometimes, though rarely, two or three tentacles become in- 
flected. In fact all the many trials with solutions which were 
so weak as to produce no effect lead to the same result that 
water is inefficient. 

Secondly. — The head of a small pin, fixed into a handle, was 
dipped into the solution under trial. The small drop which 
adhered to it, and which was much too small to fall off, was 
cautiously placed, by the aid of a lens, in contact with the secre- 
tion surrounding the glands of one, two, three, or four of the 
exterior tentacles of the same leaf. Great care was taken that 
the glands themselves should not be touched. I had supposed 
that the drops were of nearly the same size ; hut 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 drops 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 
time, by taking the pin's head out of the water obliquely and 
rather quickly, to remove as large drops as possible ; and 
the result showed that I had succeeded, for each drop on an 
average equalled 7^ of a minim. I repeated the operation in 
exactly the same manner, and now the drops averaged 5^.5 of a 
minim. Bearing in mind that on these two latter occasions 
special pains were taken to remove as large drops as possible, 
we may safely conclude that the drops used in my experiments 
were at least equal to the -^ of a minim, or '0029 ml. One of 
these drops could be apphed 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 DEOSEEA ROTUNDIFOLIA. CllAP. '^11 

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 (1775 ml.) of the solution 
or of water was poured over each. 

Some solutions, for instance that of carbonate of ammonia, 
quickly discolour the glands ; and as all on the same leaf were 
discoloured simultaneously, they must all have absorbed some 
of the salt within the same short period of time. This was 
likewise shown by the simultaneous inflection of the several 
exterior rows of tentacles. If we had no such evidence as 
this, it might have been supposed that only the glands of the 
exterior ajid inflected tentacles had absorbed the salt ; or that 
only those on the disc had absorbed it, and had then transmitted 
a motor impulse to the exterior tentacles ; But in this latter case 
the exterior tentacles would not have become inflected until 
some time had elapsed, instead' of within half an hour, or even 
within a few minutes, as usually occurred. All the glands on 
the same leaf .are of nearly the same size, as may best be seen 
by cutting off a narrow transverse strip, and laying it on its 
side; hence their absorbing surfaces are nearly equal. The 
long-headed glands on the extreme margin must be excepted, 
as they are much longer than the others; but only the upper 
surface is capable of absorption. Besides the glands, both 
surfaces of the leaves and the pedicels of the tentacles bear 
numerous minute 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 ia 
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 -^^ of a grain of the salt. 1 say at 



Ohap. VII. EFFECTS OF WATER. 139 

most, for the papilto 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 dil- 
ference between the leaves simultaneously immersed in water 
and in the several solutions will be described, nevertheless it 
may be well here to give a summary of the effects of water. 
The fact, moreover, of pure water acting on the glands deserves 
in itself some notice. Leaves to the number of 141 were im- 
mersed in water at the same time with those in the solutions, 
and their state recorded at short intervals of time. Thirty-two 
other leaves were separately observed in water, making alto- 
gether 173 experiments. Many scores of leaves were also im- 
mersed in water at other times, but no exact record of the 
effects produced was kept ; yet these cursory observations sup- 
port the conclusions arrived at in this chapter. A few of the 
long-headed tentacles, namely from one to about six, were 
commonly inflected within half an hour after immersion; as 
were occasionally a few, and rarely a considerable number of 
the exterior round-headed tentacles. After an immersion of 
from 5 to 8 hrs. the short tentacles surrounding the outer 
parts of the disc generally become inflected, so that their glands 
form a small dark ring on the disc; the exterior tentacles 
not partaking of this movement. Hence, excepting in a few 
cases hereafter to be specified, we can judge whether a solution 
produces any effect only by observing the exterior tentacles 
within the first 3 or 4 hrs. after immersion. 

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



140 



DEOSEBA 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 gTown 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. 
Besides 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 




Fig. 9. 

(^Drosera rotiindi/olia.) 

jcar (enlarged) with all the tentacles 
closely inflected, from immersion in a 
solution of phosphaLC of ammonia (one 
part to 87,500 of water). 



Chap. VII. CAEBONATE OF AMMONIA. 141 

this again is so rare a circumstance with leaves in water that 
I have seen only three instances of any such increase after the 
first 8 to 12 hrs. ; and in these three instances the two outer 
rows of tentacles were not at all affected. Hence there is some- 
times a much greater difference between the leaves in water and 
in the weak solutions, after from 8 hrs. to 24 hrs., than there 
was within the first 3 hrs. ; though as a general rule it is best 
to trust^o the difference observed within the shorter time. 

With respect to the period of the re-expansion of the leaves, 
when left immersed either in water or in the weak solutions, 
nothing could be more variable. In both cases the exterior 
tentacles not rarely begin to re-expand, after an interval of 
only from 6 to 8 hrs.; that is just about the time when the 
short tentacles round the borders of the disc become inflected. 
On the other hand, the tentacles sometimes remain inflected 
for a whole day, or even two days ; but as a general rule they 
remain inflected for a longer period in very weak solutions than 
in water. In solutions wliich 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 simplestj cases 
the state of the leaves simultaneously immersed for an equal 
length of time in water and in the solutions will be described, 
tho reader can judge for himself. 



Carbonate of Ammonia. 

TMs salt, when absorbed by tlie 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 
caiised; but no further change ensued, and the ab- 
sorlient hairs were not ^•isibly aflfected. The tcntacleg 



142 DEOSERA KOTUNDIFOLIA. 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 ajjsorbed 
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, apparently, not in 
the least affected. The plants were kept under the 
bell-glass for 24 hrs., but no further change ensued. 
One healthy leaf was hardly at all affected, though 
other leaves on the same plant were much affected. 
On some leaves all the tentacles on one side, but not 
those on the opposite side, were inflected. I doubt 
whether this extremely unequal action can be ex- 
plained by supposing that the more active glands 
absorb all the vapour as quickly as it is generated, so 
that none is left for the others for we shall meet with 



Chap. VII. CAKBONATE OF AMMONIA. 143 

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

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



We will now turn to the effects of solutions of the carbonate. 
Half-minims of a solution of one part to 437 of water were placed 
on the discs of twelve leaves ; so that each received -g^ of a grain 
or "0675 mg. Ten of these had their exterior tentacles well 
inflected ; the blades of some beinj; 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 ; s» 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 ^'ra 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 ^lo o^ 8, minim, and therefore contains ^^^ of a grain 
(•0135 mg.) of the carbonate. I touched with it the viscid 
jecretion round three glands, so that each gland received onlj 



144 DROSEEA EOTUNDIFOLIA. Chap. VU. 

i4^o of a grain (• 00445 mg.). Nevertheless, in two trials all 
the glands were plainly blackened ; in one case all three tentacles 
were well inflected after an interval of 2 hrs. 40 m. ; and in 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 xraoo °^ ^ grain ( • 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 Tiioo "^ * grain ("00445 mg.) of carbonate of ammonia, 
if absorbed by a gland, suffices to induce inflection in the basal 
part of the same tentacle ; but as already stated, I was able to 
hold with a steady hand the minute drops in contact with the 
secretion only for a few seconds; and if more time had been 
allowed for diffusion and absorption, a much weaker solution 
would certainly have acted. 

Some experiments were made by immersing cut-off leaves in 
solutions of different strengths. Thus four leaves were left for 
about 3 hrs. each in a drachm (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-third inflected ; and all the'^glands were 
blackened. Another leaf was placed in the same quantity of a 
solution of one part to 7000 of water, and in 1 hr. 16 m. every 
single tentacle was well inflected, and all the glands blackened. 
Six leaves were immersed, each in thirty minims (1'774 ml.) of 
a solution of one part to 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 g^g of a grain ('2025 mg.). 
Only one became strougly 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 cuses 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 



Chap. VII. CAEBONATE 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-jloo of "■ gi'ain 
(■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 YaVo 
of a grain ('0405 mg.). The glands were not much darkened. 
Ten of the leaves were not affected, or only very slightly so. 
Four, however, were strongly affected ; the first having all the 
tentacles, except forty, inflected in 47 m. ; in 6 hi's. 30 m. all 
except eight ; and after 4 hrs. the blade itself. The second leaf 
after 9 m. had all its tentacles except nine inflected; after 6 hrs. 
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-ftve 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 tsW of * 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 jeAoo 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 Ourhonaie 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 (] '183 ml.) of a solution of one part to 1750 of water. 



146 DEOSEKA KOTUNDIPOLIA. Ohap. VII, 

and another leaf in the same quantity of a solution of one part 
to 30G2 ; in the former case aggregation 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 -^ 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 oases 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 
eases. 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 bad been immersed in 
the solution, besides being inflected, presented a widely different 
appearance ; for the contents of the cells of every single tentacle 
on all four leaves were conspicuously aggregated ; the spheres 
and elongated masses of protoplasm in many oases extending 
halfway down the tentacles. All the glands, both those of the 
central and exterior tentacles, were opaque and blackened ; and 
this shows that all had absorbed some of the carbonate. These 
four leaves were of very nearly the same size, and the glands 
were counted on one and found to be 167. This being the case, 
and the four leaves having been immersed in a drachm of the 
solution, each gland could have received on an average only 
siriTS of 8, 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 ^^ of a grain ^^'0675 mg.). In 40 m. the glands 
appeared rather darker ; and in 1 hr. from four to six spheres 
of protoplasm were formed in the cells beneath the glands of 
all the tentacles. I did not count the tentacles, but w^e may 



Chap. VII. CARBONATE OF AMMONIA. 147 

safely assume that there were at least 140; and if so, each 
gland could have leeeived only the T34V00 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 yos °^ ^ grain, and bore 166 
glands. Each gland could, therefore, have received only -j-a-iVss 
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 Carbonate of Ammonia. — 
The roots absorb the solution, as shown by their changed 
colour, and by the aggregation of the contents of their 
cells. The vapour is absorbed by the glands; these 
are blackened, and the tentacles are inflected. The 
glands of the disc, when excited by a half-minim drop 
(•0296 ml.), containing -^^ of a grain (-0675 mg.), 
transmit a motor impulse to the exterior tentacles, 
causing them to bend inwards. A minute drop, con- 
taining TTTo-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 DROSEEA EOTUNDIFOLIA. Ohai'. VII. 

immersed for a few hours in a solntion, and a gland 
absorbs the ttV^tto 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 -nj^Vor oi a grain 
(•00024 mg.) suffices to excite the tentacle bearing this 
gland into moTcment. 



NiTEATE OP Ammonia. 

With the salt I attended only to the inflection of the leaves, 
for it is far less efficient than the carbonate in causing aggrega- 
tion, although considerably more potent in causing inflection. I 
experimented with half-minims (-0296 ml .) on the discs of fifty- 
two leaves, but will give only a few cases. A solution of one 
part to 109 of water was too strong, causing little inflection, and 
after 24 hrs. killing, or nearly killing, four out of six leaves 
which were thus tried ; each of which received the ^^ of a grain 
(or '2? 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 yo^o of a grain 
(■0337 mg.). Of these leaves, seven were very strongly acted on, 
the edges being generally inflected ; two were moderately acted 
on ; and five not at all. 1 subsequently tried three of these latter 
five leaves with urine, saliva, and mucus, but they were only 
slightly affected ; and this proves that they were not in an active 
condition. 1 mention this fact to show how necessary it is to 
experiment on several leaves. Two of the leaves, which were 
well inflected, re-expanded after 51 hrs. 

In the following experiment I happened to select very sensi- 
tive leaves. Half-minims of a solution of one part to 1094 of 
water (i e. 1 gr. to 2i oz.) were placed on the discs of nine leave.", 
so that each received the -^^ of a grain ( 027 mg.). Three of 
them had their tentacles strongly inflected and their blades curled 
inwards ; five were slightly and someVhat doubtfully affected, 
having from three to eight of their ext|erior 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 io 



Chap. VII. NITRATE OF AMMONIA. 149 

7 hrs., but the full effect was not produced until from 24 hrs. tc 
30 hrs. had elapsed. Two of the leaves, which were only slightly 
inflected, re-expanded after an additional interval of 19 hrs. 

Half-minims of a rather weaker solution, viz. of one part tc 
] 312 of water (1 gr. to 3 oz.) were tried on fourteen leaves ; so that 
each received -y^ of a grain ('0225 mg.), instead of, as in the last 
experiment, -5-^5^ of a grain. The blade of one was plainly in- 
flected, as were six of the exterior tentacles ; the blade of a second 
was slightly, and two of the exterior tentacles well, inflected, all 
the other tentacles being curled in at right angles to the disc ; 
three other leaves had from five to eight tentacles inflected ; five 
others only two or three, and occasionally, though very rarely, 
drops of pure water cause this much action ; the four remaining 
leaves were in no way affected, yet three of them, when subse- 
quently tried with urine, became greatly inflected. In most of 
these cases a slight effect was perceptible in from 6 hrs. to 
7 hrs., but the full effect was not produced until from 24 hrs. 
to 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 (^l 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 inflect«'d. 
Each of these glands could have received only the -as Joq of a 
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 iu 
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 DROSEEA EOTDNDIFOLIA. Chap. \II. 

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 787 ) of water (1 gr. to 18 oz.); 
and this amount of fluid just sufBoed to cover them. After 
2 hrs. 10 m. three of the leaves were considerably inflected, and 
the other two moderately. The glands of all became of so dark 
a red as almost to deserve to be called' black. After 8 hrs. four 
of the leaves had all their tentacles more or less inflected ; whilst 
the fifth, which I then perceived to be an old Ipaf, had only thirty 
tentacles inflected. Next morning, after 23 hrs. 40 m., all the 
leaves were in the same state, excepting that the old leaf had a 
few more tentacles inflected. Five leaves which had been placed 
at the same time in water were observed at the same intervals 
of time ; after 2 hrs. 10 m. two of them had four, one had seven, 
one had ten, of the long-headed marginal tentacles, and the 
fifth had four round-headed tentacles, inflected. After 8 hrs. 
there was no change in these leaves, and after 24 hrs. all the 
marginal tentacles had re-expanded ; but in one leaf, a dozen, and 
in a second leaf, half a dozen, submarginal tentacles had become 
inflected. As the glands of the five leaves in the solution were 
simultaneously darkened, no doubt they hnd all absorbed a nearly 
equal amount of the salt : and as ^ig- of a grain was given to the 
five leaves together, each got ^liW of ^ grain (-04.5 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 ,, 30^00 of a grain of the nitrate ; and this caused 
the inflection of a great majority of the tentacles. 

This plan of immersing several leaves in the same vessel 
is a bad one, as it is impossible to feel sure that the more 
vigorous leaves do not rob the weaker ones of their share of 
the salt. The glands, moreover, must often touch one another 
or the sides of the vessel, and movement may have been thus 
excited; but the corresponding leaves in water, which were 
little inflected, though rather more so than commonly occurs, 
were exposed in an almost equal degree to these same sources 
of error. I will, therefore, give only one other experiment mado 
in this manner, though many were tried and all confirmed 
the foregoing and following results. Four leaves were placed 
in forty minims of a solution of one part to 10,500 of water; 
and assuming that they absorbed equally, each leaf received 
■Y^ of a grain (■0562 mg. 1. After 1 hr. 20 m. many of the 
tentacles on all tour leaves were somewhat inflected. After 



Chap. VU. 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 siibmarginals 
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 ^^^^3^0 of a grain ('000351 mg.). 
This experiment was repeated on three leaves with the same 
relative amount of the solution ; and after 6 hrs. 15 m. all the 
tentacles except nine, on all three leaves taken together, were 
closely inflected. In this case, the tentacles on each leaf were 
counted, and gave an average of 162 per leaf. 

The following experiments were tried during the summer of 
1873, by placing the leaves, each in a separate watch-glass and 
pouring over it thirty minims (1-775 ml.) of the solution ; other 
leaves being treated in exactly the same manner with the 
doubly distilled water used in making the solutions. The 
trials above given were made several years before, and when I 
read over my notes, 1 could not believe in the results; so 1 
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 ^5 of a grain (2025 mg). Before 30 m. had 
elapsed, four of these leaves were immensely, and two of them 
moderately, inflected. The glands were rendered of a dark 
red. The four corresponding leaves in water were not at all 
affected until 6 hrs. had elapsed, and then only the short ten- 
tacles on the borders of the disc; and their inflection, as 
previously explained, is never of any significance. 

four leaves were immersed, each in thirty minims of a solu- 
tion of one part to 17,500 of water (1 gr. to 40 oz.), so that each 
received -^ 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 hrs., and the blade of a 
second after 21 hrs. The fourth leaf was not at all affected. 
The glands of none were darkened. Of the corresponding leaves 

11 



152 DBOSEEA EOTUNDIFOLIA. Cum: VIL 

in water, only one had any of its exterior tentacles, namely five, 
inflected ; after 6 hrs. in one case, and after 21 hrs. in two other 
cases, the short tentacles on the borders of the disc formed a 
ring, in the usual manner. 

Four leaves were immersed, each in thirty minims of a solution 
of one part to 43,750 of water (.1 gr, to 100 oz.), so that each leaf 
got yJgo of a grain (-0405 mg.). Of these, one was much in- 
flected in 8 m., and after 2 hrs. 7 m. had all the tentacles, 
except thirteen, inflected. The second leaf, after 10 m., had all 
except three inflected. The third and fourth were hardly at all 
affected, scarcely more than the corresponding leaves in water. 
Of the latter, only one was affected, this having two tentacles 
inflected, with those on the outer parts of the disc forming a 
ring in the usual manner. In the leaf which had all its ten- 
tacles except three inflected in 10 m., each gland (assuming that 
the leaf bore 160 tentacles) could have absorbed only s^-jVoo "^ 
a grain, or -000258 mg. 

Four leaves were separately immersed as before in ii solution 
of one part to 131,250 of water (1 gr. to 800 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 3 hrs. had about half its tentacles inflected, which 
began to re-expand after 8 hrs. 15 m. The fourth leaf, after 
3 hrs. 7 m , had only twenty-nine tentacles more or less in- 
flected. Thus three out of the four leaves were strongly acted 
on. It is clear that very senoitive 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 ostaoo °f ^ grain (0000937 
mg.), and this appears to be about the least quantity of the 
nitrate which suffices to induce the inflection of a single tentacle. 

As negative results are important in confirming the foregoing 
positive ones, eight leaves were immersed as before, each in thirty 
minims of a solution of one part to 175,000 of water (1 gr. to 
400 oz.), so that each received only -g^ of a grain (0101 mg,;. 
This minute quantity produced a slight effect on only four of 
the eight leaves. One had flfty-six tentacles inflected after 2 hrs. 
13 m.; a second, twenty-six inflected, or sub-inflected, after 



Chap. VII. PHOSPHATE OP AMMONIA. 153 

38 m.; a third, eighteen inflected, after 1 hr. ; and a fourth, 
ten inflected, after 35 m. The four other leaves were not in 
the least affected. Of the eight corresponding leaves in water, 
one had, after 2 hrs. 10 m., nine tentacles, and four others from 
one to four long-headed tentacles, inflected : the remaining three 
being unaffected. Hence, the -g^ of a grain given to a sensi- 
tive leaf during warm weather perhaps produces a slight effect; 
but we must bear in mind that occasionally water causes as 
great an amount of inflection as occurred in this last ex- 
periment. 



Summary of the Results with Nitrate of Ammonia. — 
The glands of the disc, when excited by a half-minim 
drop ("0296 ml.), containing -a^Vo of ^ grain of the 
nitrate ('027 mg.), transmit a motor impulse to the 
exterior tentacles, causing them to bend inwards. A 
minute drop, containing -^ ^loo of ^ 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 hoiu's, 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 op 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 diiference 
in the power of these three salts, as tried in three 
different ways, supports the results presently to be 



154 DEOSEEA KOTUNDIFOLIA. Chap. VH. 

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



Before giving my experiments, it may be well to premise that 
crystallised phosphate of ammonia, such as I used, contains 
35'33 per cent, of water of crystallisation; so that in all the 
following trials the eflBcient elements formed only 6i'67 per 
cent, of the salt used. 

Extremely minute particles of the dry phosphate were placed 



OiiAP. VU. PHOSPHATE OF AMMONIA. 155 

■with, the point of a needle on the secretion surrounding several 
glands. These poured forth much secretion, were blackened, 
and ultimately died; but the tentacles moved only slightly. 
The dose, small as it was, evidently was too great, and the 
result was the same as with particles of the carbonate of 
ammonia. 

Half-minims of a solution of one part to 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 8 oz.) were then placed on the discs of five leaves, 
so that each received the a-fSo "^ ^ grain ('0225 mg.). After 
8 hrs. the tentacles of four of them were considerably inflected, 
and after 24 hrs. the blades of three. After. 48 hrs. all five 
were almost fully re-expanded. I may mention with respect 
to one of these leaves, that a drop of water had been left 
during the previous 24 hrs. on its disc, but produced no effect ; 
and that this was hardly dry when the solution was added. 

Similar drops of a solution of one part to 1750 of water (1 gr. 
to 4 oz.) were next placed on the discs of six leaves ; so that 
each received jg^^ 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 -j ■^'jo of a grain, 
absorbed by the central glands, is enough to make many of the 
exterior tentacles and the blades bend, whereas the xAo "^ ^ 
grain of the carbonate similarly given produced no effect ; and 
•asVo of ^ grain of the nitrate was only just suffloient to produce 
a well-marked effect. 

A minute drop, about equal to -Jj of a minim, of a solution of 
one part of the phosphate to 875 of water, was applied to the 
secretion on three glands, each of which thus received onlj 
57000 of ^ g™i^ (-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 12 m. ; they reroained so for 
8 hrs. 30 m., but by the next morning were fully re-expanded. 



156 DROSEEA EOTUNDIFOLIA. Chap. V II- 

In this latter case each gland could have received only the 
j^^^^og (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 24 hrs. I should, however, state that in 
this case an unusually large drop adhered to the head of the 
pin. Each of these glands could have received very little more 
than 1 s^Voo o^ ^ grain (or '000423) ; but this small quantity 
sufficed to cause inflection. We must bear in mind that these 
drops were applied to the viscid secretion for only from 10 to 
15 seconds, and we have good reason to believe that all the 
phosphate in the solution would not be diffused and absorbed in 
this time. We have seen under the same circumstances that tho 
absorption by a gland of j-rsoo °f ^ grain of the carbonate, and 
of 5,^00 of a grain of the nitrate, did not cause the tentacle bear- 
ing the gland in question to be inflected ; so that here again the 
phosphate is much more powerful than the other two salts. 

We will now turn to the 106 experiments with immersed 
leaves. Having ascertained by repeated trials that moderately 
strong solutions were highly efficient, I commenced with sixteen 
leaves, each placed in thirty minims of a solution of one part 
to 43,750 of water (1 gr. to 100 oz.); so that each received 
jg'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 ir 
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 jJ^o "^ ^ grain (-0202 mg.). Fourteen ol 
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 outer tentacles inflected ; 
the remainder being quite unaffected. 

The next experiment was tried under very favourable circum- 
stances, fort he day (July 8) was very warm, and I happened 
tu 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 5^5^ of a grain, or "0135 mg. After an 
immersion of 25 m. all five leaves were much inflected. After 
1 hr. 25 m. one leaf had all but eight tentacles inflected; the 
second, all but three ; the third, all but five ; the fourth, all but 
twenty-three; the fifth, on the othef 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. 1 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 loajaoo of a grain, or -0000631 mg. The third leaf bore 
236 gland.s, and subtracting the five which did not become in- 
flected, each of the remaining 231 glands could have absorbed 
oily iiossoo of ^ grain (or '0000584 mg.), and this amount 
sufficed to cause the tentacles to bend. 

Twelve leaves were tried as before in a solution of one part to 
175,000 of water (1 gr. to 400 oz.), so that each leaf received -g^-^ 
of a grain ('OlOl 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 DKOSBEA EOTUWDIFOLIA. Chap. VII 

after the 8 hrs. it was impossible to compare the two lots, and 
doubt for an instant the power of the solution. 

Two of the above leaves in the solution had all their tentacles, 
except three and four, inflected within an hour. I counted their 
glands, and, on the same principle as before, each gland on one 
leaf could have absorbed only ^leiiibo . a-^d on the other leaf 
only 1^,^000 - of a grain of the phosphate. 

Twenty leaves were immersed in the usual manner, each in 
thirty minims of a solution of one part to 218,750 of water (1 gr. 
to. 500 02.). 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 
Woo of a grain, or '0081 mg. The first eight leaves which I 
tried both in the solution and in water were either young and 
pale or too old ; and the weather was not hot. They were hardly 
at all affected ; nevertheless, it would be unfair to exclude them. 
I then waited until I got eight pairs of fine leaves, and the 
weather was favourable ; the temperature of the room where the 
leaves were immersed varying from 75° to 81° (23°-8 to 27°-2 
Cent.). In another trial with four pairs (included in the above 
twenty pairs), the temperature in my room was rather low, 
about 60° (15°'5 Cent.) ; but the plants had been kept for several 
days in a very warm greenhouse and thus rendered extremely 
sensitive. Special precautions were taken for this set of experi- 
ments; a chemist weighed for me a grain in an excellent 
balance ; and fresh water, given me by Professor Frankland, was 
carefully measured. The leaves were selected from a large 
number of plants in the following manner : the four finest 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 tentaclfes inflected, 
and after 17 m. all but fifteen; aftei- 2 hrs. all but eight in- 



Chap. VII. PHOSPHATE OF AMMONIA. 159 

fleeted, or plainly sub-inflected. After i hrs. the tentacles 
began to re-expand, and such prompt re-expansion is nnnsual ; 
after 7 hrs. 30 m. they were almost fully re-expanded. 

(2) After "39 m. a large number of tentacles inflected ; after 
'2 hrs. 18 m. all but twenty-five inflected ; after 4 hrs. 17 m. all 
but sixteen inflected. The leaf remained in this state for many 
hours. 

(3) After 12 m. a considerable amount of inflection; after 
4 hrs. all the tentacles inflected except those of the two outer 
rows, and the leaf remained in this state for some time ; after 

23 hrs. began to re-expand. 

(4) After 40 m. much inflection ; after 4 hrs. 13 m. fully half 
the tentacles inflected ; after 23 hrs. still slightly inflected. 

(5) After 40 m. much inflection ; after 4 hrs. 22 m. fully half 
the tentacles inflected ; after 23 hrs. still slightly inflected. 

(6) After 40 m. some inflection ; after 2 hrs. 18 m. about 
twenty-eight outer tentacles inflected ; after 5 hrs. 20 m. about a 
third of the tentacles inflected ; after 8 hrs. much re-expanded. 

(7) After 20 m. some inflection ; after 2 hrs. a considerable 
number of tentacles inflected; after 7 hrs. 4.5 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 ; continued so for two days, and then 
partially re-expanded. 

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

(10) After 38 m. twenty-one tentacles inflected ; after 3 hrs. 
12 m. forty- six tentacles inflected or sub-inflected ; after 6 hrs. 
40 m. all but seventeen inflected, though none closely; after 

24 hrs. every tentacle slightly curved inwards ; after 27 hrs. 
40 m. blade strongly inflected, and so continued for two days, 
and then the tentacles and blade very slowly re-expanded. 

(11) This fine dark red and rather old leaf, though not very 
large, bore an extraordinary number of tentacles (viz. 252), and 
behaved in an anomalous manner. After 6 hrs. 40 m. only the 
short tentacles round the outer part of the disc were inflected, 
forming a ring, as so often occurs in from 8 to 24 hrs. with 
leaves both in water and the weaker solutions. But after 9 hra 



160 DEOSEKA KOTUNDIFOLIA. Chap. VII. 

iO m. all the outer tentacles except twenty-five were inflected, 
as was the blade in a strongly marked manner. After 24 hrs. 
every tentacle except one was closely inflected, and the blade 
was completely doubled over. Thus the leaf remained for two 
days, when it began to re-expand. 1 may add that the three 
latter leaves (Nos. 9, 10, and 11) were still Somewhat inflected 
after three days. The tentacles in but few of these eleven leaves 
became closaly inflected within so short a time as in the pre- 
vious experiments with stronger solutions. 

We will now turn to the twenty corresponding leaves in water. 
Nine had none of their outer tentacles inflected; nine others 
had from one to three inflected; and these re-expanded after 
8 hrs. The remaining two leaves were moderately affected ; one 
having six tentacles inflected in 34 m. ; the other twenty-three 
inflected in 2 hrs. 12 m. ; and both thus remained for 24 hrs. 
None of these leaves had their blades inflected. So that the con- 
trast between the twenty leaves in water and the twenty in the 
solution was very great, both within the first hour and after 
from 8 to 12 hrs. had elapsed. 

Of the leaves in the solution, the glands on leaf No. 1, which 
in 2 hrs. had all its tenticles except eight inflected, were 
counted and found to be 202. Subtracting the eight, each gland 
could have received only the Tssiooo of ^ grain (-0000411 mg.) 
of the phosphate. Leaf No. 9 had 213 tentacles, all of which, 
with the exception of four, were inflected after 24 hrs., but 
none of them closely ; the blade was also inflected ; each gland 
could have received only the ^^ailooo o^ ^ grain, or -0000387 
mg. Lastly, leaf No. 11, which had after 24 hrs. all its ten- 
tacles, except one, closely inflected, as well as the blade, bore 
the unusually large number of 252 tentacles ; and on the same 
principle as before, each gland could have absorbed only the 
j^g^ of a grain, or -0000822 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 
]92, 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 minima 
of a solution of one part to ;-{28,125 of water (1 gr. to 750 oz. i. 
Each leaf thus reoeiTed rrooo of ^ grain (•0054 mg.) of the salt ; 
and all four were greatly inflected. 

(1) After 1 lir. 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. aU but twent.y-two 
inflected ; after 12 hrs. partly re-expanded. 

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

Of the four corresponding leaves in water : — 

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

(2) After 1 hr. seven tentacles inflected; these were almost 
re -expanded in 6 hrs. 

(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 efficiency of the 
above solution ; and it follows as before that each gland of No. 1 
could have absorbed only a^i^oo,, of a grain (0000268 mg.) 
and of No. 2 only 345^000 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 lUOO oz.). 
Each leaf thus leceived xsboo o' ^ grain ('00405 mg.). The day 
was warm, and the leaves were very fine, so that all circum- 
stances were favourable. 

(1) After 30 m. all the outer tentacles except five inflected, 
and most of them closely ; after 1 hr. blade slightly inflected ; 
after 9 hrs. 80 m. began to re-expand. 

(2) After 33 m. all the outer tentacles but twenty-five in- 
flected, and blade sUghtly so; after 1 hr. 30 m. bla^le strongly 
inflected and remained so for 24 hrs. ; but some of the tentacles 
had then re-expanded. 

(3) After 1 hr. all but twelve tentacles inflected ; after 2 hrs. 
30 m. all but nine inflected ; and of the inilected tentacles all 
excepting four closely; blade slightly inflected. After 8 hrs.' 
blade quite doubled up, and now all the tentacles excepting 



162 DKOSEKA KOTUNDIFOLIA. Chap. Vll. 

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 which were only sub-in- 
flected ; after 7 hrs. blade considerably inflected ; after 12 hrs. 
much re-expansion. 

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

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

(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. 

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

(4) After 24 hrs. one inflected. 

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

A comparison of the leases in the solution, especially of 
the first five or even six on the list, with those in the water, 
after 1 hr. or after 4 hrs., and in a still more marked degree 
after 7 hrs. or 8 hrs., could not leave the least doubt that the 
solution had produced a great effect. This was shown not only 
by the vastly greater number of mflected tentacles, but by 
the degree or closeness of their inflection, and by that of their 
blades. Yet each gland on leaf No. 1 (which bore 255 glands, all 
of which, excepting five, were inflected in 30 m.) could not have 
received more than one-four-millionth of a grain (-0000162 
mg.) of the salt. Again, each gland on leaf No. 3 (which 
bore 233 glands, all of which, except nine, were inflected in 
2 hrs. 30 m.) could have received at most only the jssiooo of 
a grain, or -0000181 mg. 

Four leaves were immersed as before in a solution of one part 
to 656,2-50 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 



Chap. VII. THOSPHATE OF AMMONIA. 163 

the fotir correspondiBg 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 ^^^po °^ ^ g^3,in (-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 
24 hrs. all the tentacles but ten more or less inflected. Most 
of them were closely inflected, but twenty-five were only sub- 
inflected. 

(2) After 1 hr. 40 m. twenty-five tentacles inflected; after 
6 hrs. all but twenty-one inflected ; after 10 hrs. all but sixteen 
more or less inflected ; after 24 hrs. re-expanded. 

(3) After 1 hr. 40 m. thirty-five inflected; after 6 hrs. "a 
large number" (to quote my own memorandum) inflected, 
but from want of time they were not counted ; after 24 hrs. re- 
eipanded. 

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

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

With respect to the twelve corresponding leaves in water, (1) 
had, after 1 hr. 35 m., fifty tentacles inflected, but after 11 hrs. 
only twenty- two remained so, and these formed a group, with the 
blade at this point slightly inflected. It appeared as if this leaf 
had been in some manner accidentally excited, 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 infl^joted, which 
after 10 hrs. 20 m. were all re-expanded ; (4) and (6) 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 DEOSERA EOTDNDIFOMA. Chap. VII 

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

Comparing the states of the twelve leaves in water with those 
in the solution, there could be no doubt that in the latter a larger 
number of tentacles were inflected, and those to a greater degree ; 
but the evidence was by no means so clear as in the former ex- 
periments with stronger solutions. It deserves attention that the 
inflection of four of the leaves in the solution went on increasing 
during the first 6 hrs., and with some of them for a longer time ; 
whereas in the water the inflection of the three leaves which 
were the most affected, as well as of all the others, began to de- 
crease during this same interval. It is also remarkable that the 
blades of three of the leaves in the solution were slightly in- 
flected, and this is a most rare event with leaves in water, 
though it occurred to a slight extent in one (No. 1), which 
seemed to have been in some manner accidentally excited. All 
this shows that the solution produced some effect, though less 
and at a much slower rate than in the previous cases. The 
small effect produced may, however, be accounted for in large 
part by the majority of the leaves having been in a poor con- 
dition. 

Of the leaves in the solution, No. 1 bore 200 glands and received 
TsTOo °^ ^ grain of the salt. Subtracting the seventeen tentacles 
which were not inflected, each gland could have absorbed only 
*li6 ft,sj,ooo of a grain (00000738 mg.). This amount caused 
the tentacle bearing each gland to be greatly inflected. The 
blade was also inflected. 



Lastly, eight leaves were immersed, each in thirty minims of a 
solution of one part of the phosphate to 21,875,000 of water (1 gr. 
to 5000 oz.). Each leaf thus received so^o^ of a grain of the salt, 
or '00081 mg. I took especial pains in selecting the finest leaves 
from the hot-house for immersion, both in the solution and the 
water, and almost all proved extremely sensitive. Beginning as 
before with those in the solution : — 

(1) After 2 hrs. 30 m. all the tentacles but twenty- two in- 
fiected, 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 increase, 
and after 48 hrs. all the tentacles except three were inflected. 



Chap. VII. PHOSPHATE OF AMMONIA. 165 

and most of thorn rather closely, fom 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 respectiTely 
82, 17, 7, 4, and tentacles inflected, most of which, after a few 
hours, re-expanded, with the exception of No. 4, which retained 
its thirty-two tentacles inflected for 48 hrs. 

Now for the eight corresponding leaves in water : — 

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

(2) to (8) These leaves, after 2 hrs. 40 m., had respectively 42, 
12, 9, 8, 2, 1, and 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 
eo^oo of a grain (-00081 mg.) of the phosphate. Now, leaf 
No. 3 bore 178 tentacles, and subtracting the three which were 
not inflected, each gland could have absorbed only the ttooVobs 
of a grain, or '00000463 mg. Leaf No. 1, which was strongly 
acted on within 2 hrs. 30 m., and had all its outer tentacles, 
except thirteen, inflected within 6 hrs. 30 m., bore 260 tentacles; 
and on the same principle as befoi;e, each gland could have 



166 DEOSERA EOTUNDIFOLIA. Chap. VII. 

absorbed only rrTeWro °^ ^ g'"*!"' °^ '00000328 mg. ; and this 
excessively minute amount sufBced to cause all the tentacles 
bearing these glands to be greatly inflected. The blade was also 
inflected. 

Svmmary of the Results with Phosphate of Ammonia. — 
The glands of the disc, when excited by a half-minim 
drop (-0296 ml.), containing -^-^'^s 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 tjtW-o 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 



I t> 7 G 



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

Sulphate of Ammonia. — The few trials made with this and the 
following five salts of ammonia were undertaken merely to 
ascertain whether they induced inflection. Half-minims of a 
solution of one part of the sixlphato of ammonia to 437 of 
water were placed on the discs of seven leaves, so that each 
received -g^g 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. 'Ihe 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 littlfe 
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. VU. OTHEE SALTS OF AMMONIA. 1 67 

becoming more inflected. After 23 hrs. three of the leaves had 
their blades somewhat inflected ; and the submarginal tentacles 
of all considerably inflected, but in none were the two, three, or 
four outer rows affected. I have rarely seen cases like this, 
except from the action of a decoction of grass. The glands on the 
discs of the above leaves, instead of being almost black, as after 
the first hour, were now after 23 hrs. very pale. I next tried 
on four leaves half-minims of a weaker solution, of one part to 
131'2 of water (1 gr. to 3 oz.) ; so that each received ^^Vo °^ 
a grain (-0225 mg.). After 2 hrs. 18 m. the glands on the disc 
were very dark-coloured ; after 24 hrs. two of the leaves were 
slightly affected ; the other two not at all. 

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

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

Tartrate of Aw,monia. — Half-minims of a solution of one part 
to 487 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 EemarJcs mi the 
SaUs of Ammonia. — We have now seen that the nine 

13 



L68 



DKOSEEA EOTUNDIFOLIA. 



Chap. Vn. 



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



Solutions, how applied. 



Carbonate of 
Ammonia. 



Nitrate of 
Ammonia, 



Phosphate of 
Ammonia. 



Placed on the glands of i 
the disc, so as to act | 
indirectly on the outer | 
tentacles .... J 

Applied for a few se-j 
conds directly to the 
gland of an outer 
tentacle . . . .1 



grain, or 
•0675 mg. 



gram, or 
00445 mg. 



Leaf immersed, with] , „ 
time allowed for each! ^^^^^ 
gland to absorb all L ^ ' 
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 



grain, or 
■00048 mg. 



iOTiiOfa 
grain, or 
•027 mg. 



IB531! ™ a 

gram, or 
•0025 mg. 



grain, or 
• 0000937 mg. 



sAsOfa 
grain, or 
•0169 mg. 



■mim °' a 

grain, or 

• 000423 mg. 



T5160()60 ^^ a 

gram, or 
•00000328 mg. 



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. SUMMAEY, SALTS OF AMMONIA. 1()9 

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

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

who says, — Take a narrow strip of entire strip a million, 
paper H3 ft. 4 in. in length, and 



170 DEOSEEA KOTUNDIFOLIA. Chap. VH 

taiuly a most surprising fact that the , g , ^'„ „ „ „ of a 
grain, or in round numbers the one-twenty-millionth 
of a grain (-0000033 mg.), of the phosphate should 
affect any plant, or indeed any animal ; and as this 
salt contains 35'33 per cent, of water of crystallisation, 
the efficient elements are reduced to ^ „ , ^'^ , ^ ^ 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 
sufSced to cause the inflection of almost every ten- 
tacle, and often of the blade of the leaf. 

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



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

were made on the nitrate of am- 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 been discovered ; and I felt on ' Poisons ' that about ^ of a 

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

then unrivalled powers of Drosera. of prussic acid, ym "^ iodine, 

Now the spectroscope has al- and 5^ 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 

probably less than one tanti - oai) of solutions under trial not betug 

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



CliAP. VII. BUMMAEY, 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 laid gently in watch-glasses, 
And a measured quantity of the solution and of water 
poured over each. The water used must be as ab- 
solutely pure as it can be made. It is to be especially 
observed that the experiments with the weaker solu- 
tions ought to be tried after several days of very 
warm weather. Those with the weakest solutions 
should be made on plants which have been kept 
for a considerable time in a warm greenhouse, or cool 
hothouse ; but this is by no means necessary for trials 
with solutions of moderate strength. 

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

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

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

Astonishing as is this result, there is no sound reason 



• Miller'ri ' Elen^onts of Chemistry,' part ii. p. 107, 3rd edit. 18G4, 



Chap. Vn. SUMMARY, SALTS OF AMMONIA. 173 

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



* My son, George Darwin, has from s-jrhnr to TT^ffW of an inch 

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

a sphere of phosphate of ammonia jeot between ^ and ^V of the 

(specific gravity 1 ■ 678), 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 fjm °^ 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 8(10 diameters, the above illustration, could be 

are estimated to be from -0002 to seen under any power of the mi' 

•0005 of a millimetre — that is, crosoope. 



174 DHOSEEA KOTUNDIFOLIA. Chap. VUL 



CHAPTEE VIII. 

The Effects of various Salts and Aoids on the Leaves. 

Baits of sodium, potassium, and other alkaline, earthy, and metallic 
salts — Summary on the action of these salts — Various aoids — 
Summary on their action. 

Having found that the salts of ammouia were so 
powerful, I was led to investigate the action of some 
other salts. It will be convenient, first, to give a list 
of the substances tried (including forty-nine salts and 
two metallic acids), divided into two columns, showing 
those which cause inflection, and those which do not 
do so, or only doubtfully. My experiments were mado 
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 Cliemical Classification in WaM 
' Dictionary of Chemistry.') 

Sodium carbonate, rapid inflec- Potassium carbonate : sluwly poi" 

tion. sonous. 

Sodium nitrate, rapid inflection. Potassium nitrate : somewhat poi' 

sonous. 

Sodium sulphate, moderately Potassium sulphate. 

rapid inflection. 

Sodium phosphate, very rapid iu- Potassium phosphate. 

flection. 

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

Sodium chloride, moderately rapid Potassiiun chloride. 

inflection. 



CuAP. vin. 



EFFECTS OF VAEIOUS SALTS. 



175 



Salts caijsisg Inflection. 



Salts not CArsisG Inflection. 



^Arranged in Groups according to (he Cliemical Classification in WaM 
' Dictionary of Chemistry.' 



Sodium iodide, rather slow inflec- 
tion. 

Sodium bromide, moderately rapid 
inflection. 

Potassium oxalate, slow and 
doubtful inflection. 

Lithium nitrate, moderately rapid 
inflection. 

Caesium chloride, rather slow in- 
flection. 

Silver nitrate, rapid inflection: 
quick poison. 



Potassium iodide, a slight and 

doubtful amount of inflection 
Potassium bromide. 



Lithium acetate. 
Rubidium chloride. 



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



Calcium acetate. 
Calcium nitrate. 

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



Aluminium chloride, slow and 

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



Aluminium nitrate, a trace of in- 
flection. 

A hiTniTiiiiTn and potassium sul« 
phate. 



Tin chloride, slow inflection : poi- 
sonous. 



Lead chloride. 



Antimony tartrate, slow inflec- 
tion : probably poisonous. 

Arsenious acid, quick inflection: 
poisonous. 

jon 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. Chap. VI II 

Sodium, Carbonate of (pure, given me by Prof. HoflEmann). — 
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 leaven. 
Seven of these became well inflected ; three had only two or 
three of their outer tentacles inflected, and the remaining two 
were quite unaffected. But the dose, though only the jIq of a 
grain ("IBS mg.), was evidently too strong, for three of the 
seven well-inflected leaves were killed. On the other hand, one 
of the seven, which had only a few tentacles inflected, re- 
expanded and seemed quite healthy' after 48 hrs. By employing 
a weaker solution (viz. one part to 437 of water, or 1 gr. to 
1 oz.), doses of gij of a grain ('OGTo mg.) were given to six 
leaves. Some of these were affected in 37 m. ; and in 8 hrs. the 
outer tentacles of all, as well as the blades of two, were con- 
siderably inflected. After 23 hrs. 15 m. the tentacles had 
almost re-expanded, but the blades of the two were still just 
perceptibly curved inwards. After 48 hrs. all six leaves were 
fully re-expanded, and appeared perfectly healthy. 

Three leaves were immersed, each in thirty minims of a solu- 
tion of one part to 875 of water (1 gr. to 2 oz.), so that each 
received -J^ of a grain (2 ■ 02 mg.) ; after 40 m. the three were 
much affected, and after 6 hrs. 45 m. the tentacles of all and 
the blade of one closely inflected. 

Sodium, Nitrate of (pure). — Half-minims of a solution of one 
part to 437 of water, containing -g^ of a grain ('0675 mg.), 
were placed on the discs of five leaves. After 1 hr. 25 m. the 
tentacles of nearly all, and the blade of one, were somewhat 
inflected. The inflection continued to increase, and in 21 hrs. 
15 m. the tentacles and the blades of four of them were greatly 
affected, and the blade of the fifth to a slight extent. After an 
additional 24 hrs. the four leaves still remained closely inflected, 
whilst the fifth was beginning to expand. Pour days after the 
solution had been applied, two of the leaves had quite, and one 
had partially, re-expanded ; whilst the remaining two remained 
closely inflected and appeared injured. 

Three leaves were immersed, each in thirty minims of a solu- 
tion of one part to 875 of water; in 1 hr. there was great inflec- 
tion, and after 8 hrs. 15 m. every tentacle and the blades of all 
three were most strongly inflected. 

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



Chap. Vin. SALTS OF SODIUM. 177 

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

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

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

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

f^odium, 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 aflfected. 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 



i78 DEOSEKA EOTUNDIFOLIA. Chap. Vm, 

of four leaves. Two, apparently, were not at all affected in 
48 brs. ; the third had its tentacles slightly inflected ; whilst 
the fourth had almost all its tentacles inflected in 24 hrs., and 
these did not begin to re-expand until the fourth day, and were 
not perfectly expanded on the seventh day. I presume that 
this leaf was injured by the salt. Half-minims of a weaker 
solution, of one part to 437 of water, were then dropped on the 
discs of six leaves, so that each received -g^ of a grain. In 
1 hr. 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 ^-^ of a 
grain, or 2 '02 mg. After 1 hr. there was much inflection; 
after 8 hrs. 30 m. all the tentacles and the blades of all three 
were closely inflected. Four other leaves were also immersed 
in the solution, each receiving the same amount of salt 
as before, viz. ^ of a grain. They all soon became inflected ; 
after 48 hrs. ttey began to re-expand, and appeared quite un- 
injured, though the solution was sufflciently 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 their tentacles inflected'; the fourth leaf was very 
slightly, and the fifth and sixth hardly at all, affected. Three 
leaves were also immersed, each in thirty minims of a solution 
of one part to 875 of water ; after 40 m. there was some inflec- 
tion ; after 4 hrs. the tentacles of all three leaves and the blades 
of two were inflected. These leaves were then 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. Vm, 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 
iiiflected. 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. 

Potassium, Nitrate of. — Half-minims of a strong solution, of 
one part to 109 of water (4 grs. to 1 oz.), were placed on the 
discs of four leaves ; two were much injured, biit 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 immer^ed 
for 25 hrs., each in thirty minims of a solution of one part to 
875 of water, and this produced no apparent effect. They were 
then put into a solution of one part of carbonate of ammonia 
to 218 of water ; the glands were immediately blackened, and 
after 1 hr. there was some inflection, and the protoplasmic con- 
tents of the cells became plainly aggregated. This shows that 
the leaves had not been much injured by their immersion for 
25 hrs. in the nitrate. 

Potassium, Sulfihate 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 oi 



180 DEOSEEA EOTUNDIFOLIA. 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. 

Potassium, Phosphate of. — Half-minims of a solution of one 
part to 437 of water were placed on the discs of six leaves, 
which were observed during three days ; but no effect was pro- 
duced. The partial drying up of the fluid on the disc slightly 
drew together the tentacles on it, as often occurs in experi- 
ments of this kind. The leaves on the third day appeared quite 
healthy. 

Puta^sium, 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 produce the 
least effect. 

Potassium, Oxalate of. — Half-minims were placed on different 
occasions on the discs of seventeen leaves ; and the results per- 
plexed me much, as they still do. Inflection supervened very 
slowly. After 24 hrs. four leaves out of the seventeen were well 
inflected, together with the blades of two ; six were slightly 
affected, and seven not at all. Three leaves of one lot were 
observed for five days, and all died; but in another lot of 
six, all excepting one looked healthy after four days. Three 
leaves were immersed during 9 hrs., each in 30 minims of 
a solution of one part to 875 of water, and were not in the 
least affected; but they ought to have lieen observed for a 
longer time. 

Potassium, Chloride of. Neither half-minims of a solution of 
one part to 437 of water, left on the discs of six leaves for three 
days, nor the immersion of three leaves during 25 hrs., in 
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. 

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



Chap. Vm. EFFECTS OF VAEIOUS SALTS. 181 

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

Potassium, Bromide of. — Half-minims of a solution of one part 
to 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 of. — ^Four leaves were immersed together in 
a vessel containing 120 minims of a solution of one part to 437 
of water ; so that each received, if the leaves absorbed equally, 
■jpg- of a grain. After 24 hrs. there was no inflootion. I then 
added, for the sake of testing the leaves, some strong solution 
(viz. 1 gr. to 20 oz., or one part to 8750 of water) of phosphate 
of ammonia, and all four became in 30 m. closely inflected. 

Lithium, Nitrate of. — Four leaves were immersed, as in the 
last case, in 120 minims of a solution of one part to 437 of 
water ; after 1 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 tliird 
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, but not closely, and the other two considerably inflected. 
After 22 hrs. the inflection was extremely great, and two had 
their blades inflected. I then transferred the leaves into water, 
and in 46 hrs. from their first immersion they were almost re- 
expanded. 

Rubidium, Chloride of. — Four leaves which were immersed, as 
above, in 120 minims of a solution of one part to 437 of water, 
were not acted on in 22 hrs. I then added some of the strong 
solution (1 gr. to 20 oz.) of phosphate of ammonia, and in 30 m. 
r11 were immensely intlected. 

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



182 DKOSEEA KOTUNDIPOLIA. Chap. VIIL 

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

Calcium, Acetate of. —Pour 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. — Pour 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 
5 m. and 10 m. Half-minims of a solution of one part of the 
nitrate of calcium to 218 of water were dropped on the discs of 
three leaves, but produced no effect. 

Magnesium, Acetate, Nitrate, and Chloride of. — Pour 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. VIU. EFFECTS OF VARIOUS SALTS. 183 

Magnenum, Sulphate cf. — 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. 

Baiiun, Acetate cf. — 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 hrs. only a little inflection in 
two of the leaves. 

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

Strontium, Acetate of. — Pour 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. — Tlxree 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. stiU 

13 



184 DEOSEEA EOTUNDIFOLIA. Chap. VIXI. 

inflected and discoloured. The leaves were then removed and 
left for two days in water ; but they never re-expanded, being 
evidently dead. 

Zinc, Chloride of. — Three leaves immersed in ninety minims 
of a solution of one part to 437 of water were not affected in 
25 hrs. 30 m. 

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

Aluminium, Nitrate nf. — ^Pour 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 Potasnium, 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 J^ of a grain, or 4-048 mg., of the chloride. 
There was some inflection in 8 m., which became extreme in 
45 ra. 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 VIU. EFFECTS OF VARIOUS SALTS. 185 

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

Till, Ohhride of. — Pour 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. 

AnUmmiy, Tartr.itt rf. — Three leaves were immersed in ninety 
minims of a solution of one part to 437 of water. After 8 hrs. 
30 m. there was shght inflection; after 24 hrs. two of the leaves 
were closely, and the third moderately, inflected ; glands not 
much darkened. The leaves were washed and placed ih 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, Chluride 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 flocoulent 
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 



<86 DEOSEEA EOTUNDIFOLIA. Chap. VIU 

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 hrs. still closely inflected, and the 
leaves flaccid. Placed in pure water, next day evidently dead. 
A rapid poison. 

Nick.l, Chloride of. — Three leaves immersed in ninety minims 
of a solution of one part to 437 of water ; in 25 m. considerable 
inflection, and in 3 hrs. all the tentacles closely inflected. After 
22 hrs. still closely inflected; most of the glands, but not all, 
blackened. The leaves were then placed in water ; after 24 hrs. 
remained inflected ; were somewhat discoloured, with the glands 
and tentacles dingy red. Probably killed. 

Cobalt, Chloride 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 Aetion of the foregoing 
Salts. — Of the fifty-one salts and metallic acids which 
were tried, twenty-five caused the tentacles to be in- 
flected, and twenty-six had no such effect, two rather 
doubtful cases occurring in each series. In the table 
at the head of this discussion, the salts are arranged 
according to their chemical affinities ; but their action 
on Drosera does not seem to be thus governed. The 
nature of the base is far more important, as far as can 
be judged from the few experiments here given, than 
that of the acid ; and this is the conclusion at which 
physiologists have arrived with respect to animals. 
We see this fact illustrated in all the nine salts of 
soda causing inflection, and in not being poisonous 
except when given in large doses; whereas seven of 



Chap. VUI. CONCLUDING EEMAEKS, SALTS. 187 

the corresponding salts of potash do not cause inflec- 
tion, and some of them are poisonous. Two of them, 
however, vi?. 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 mammals without any injurious 
effects ; whilst smaU 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 tc the outer 
tentacles ; and in this character the citrate of soda 
resembles the citrate of ammonia, or a decoction of 
grass-leaves; these three fluids all acting chiefly on 
the blade. 

It seems opposed to the rule of the preponderant 
influence of the base that the nitrate of lithium 
causes moderately rapid inflection, whereas the acetate 
causes none ; but this metal is closely allied to sodium 



188 DROSEEA EOTUNDIFOLIA. OuAP. VIU. 

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- 
smalts are inoperative. Two salts of calcium, four of 
magnesium, two of barium, and two of strontium, did 
not cause any inflection, and thus follow the rule of 
the preponderant power of the base. Of three salts 
of aluminium, one did not act, a second showed a 
trace of action, and the third acted slowly and doubt- 
fully, so that their effects are nearly alike. 

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

Acids. 

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



* Miller's ' Elements of Chemistry,' 3rd edit. pp. 337, 448. 



Chap. VIII. 



THE EFFECTS OF ACIDS. 



189 



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



Acids, much i)ilt;ted, which cause 
Inflection. 



1. Nitric, strong inflection; poi- 
sonous. 

2. Hydrochloric, moderate and 

slow inflection ; not poisonous. 

3. Hydi'iodic, strong inflection; 
poisonous. 

4. Iodic, strong inflection ; poi- 

sonous. 

5. Sulphuric, strong inflection; 
somewhat poisonous. 

6. Phosphoric, strong inflection ; 
poisonous. 

7. Boraoio, 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. 55 alic, 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 same 
Degeee, 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. — Four leaves were placed, each in thirty minims 
of one part by weight of the acid to 437 of water, so that each 
received J^ 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. OahP. VIII. 

as that of most of the foregoing saline solutions. In 2 hr s. 30 ra. 
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 loft in water for 
three days; but they remained inflected and were evidently 
killed. Most of the glands had become colourless. Two leaves 
were then immersed, each in thirty minims of one part to 1000 
of water ; in a few hours there was some inflection ; and after 
24 hrs. both leaves had almost all their tentacles and blades in- 
flected ; they were left in water for three days, and one partially 
re-expanded and recovered. Two leaves were next immersed, 
each in thirty minims of one part to 2000 of water ; this pro- 
duced very little effect, except that most of the tentacles close 
to the summit of the petiole were inflected, as if the acid had 
been absorbed by the cut-ofl' end. 

Hydroc- 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 i-ed colour ; after two more days 
they fully re -expanded; but the f )urth leaf remained inflected, 
and seemed much injured or killed, with its glands white. 
Four leaves were then treated, each with thirty minims of one part 
to 875 of water ; after 21 hrs. they were moderately inflected ; 
and on being transferred to water, fully re -expanded in two days, 
and seemed quite healthy. 

Hydriodic Acid. — One to 437 of water; three leaves were im- 
mersed as before, each in thirty minims. After 45 m. the glands 
were discoloured, and the surrounding fluid became pinkish, but 
there was no inflection. After 5 hrs. all the tentacles were 
closely inflected; and an immense amount of mucus was secreted, 
so that the fluid could be drawn out into long ropes. The leaves 
were then placed in water, but never re-expanded, and were evi- 
dently killed. Four leaves were next immersed in one part to 875 
of water ; the action was now slower, but after 22 hrs. all four 
leaves were closely inflected, and were affected in other respects 
as above described. These leaves did not re-expand, though 
left for four days in water. This acid acts far more powerfully 
than hydrochloric, and is poisonous. 

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



Cbap. VIII. THE EFFECTS OP 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. 
Tliese leaves were then placed in water, and next day were 
evidently dead. 

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

I'hoaphoric 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 ; 
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 aiid 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. 

Ftyrmic Acid. — Four leaves were immersed together in 120 
minims of one part to 437 of water ; after 40 m. slight, and after 
6 hrs. 30 m. very moderate inflection ; after 22 hrs. only a little 
more inflection than often occurs in water. Two of the leaves 
were then washed and placed in a solution (1 gr. to 20 oz.) of 
phosphate of ammonia; after 24 hrs. they were considerably 
inflected, with the contents of their cells aggregated, showing 
that the phosphate had acted, though ]iot to the full and 
ordinary degree. 

Acetic Acid. — Four leaves were immersed together in 120 
minims of one part to 437 of water. In 1 hr. 20 m. the tentacles 
of all four and the blades of two were greatly inflected. After 
8 hrs. the leaves had become flaccid, but still remained closely 
inflected, the surrounding fluid being coloured pink. They were 
then washed and placed in water ; next morning they were still 
inflected and of a very dark red colour, but with their glands 
colourless. After another Jay they were dingy-coloured, and 



192 DKOSEKA EOTUNDIFOLIA Chap. VIU 

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 ftve 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. 

Fropioidc Acid. — Three leaves were immersed in ninety minims 
of a mixture of one part to 437 of water; in 1 hr. 50 m. there 
was no inflection; but after 3 hrs. 40 m. one leaf was greatly 
inflected, and the other two slightly. The inflection continued 
to increase, so that in 8 hrs. all three leaves were closely in- 
flected. Next morning, 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 slightly 
flaccid and were evidently killed, as was afterwards proved to 
be the case by keeping them in water. The protoplasm in the 
closely inflected tentacles was not in the least aggregated, but 
towards their bases it was collected in little brownish masses at 
the bottoms of the cells. This protoplasm was dead, for on 
leaving the leaf in a solution of carbonate of ammonia, no 
aggregation ensued. Propionic acid is highly poisonous to 
Drosera, like its ally acetic acid, but induces inflection at a 
much slower rate. 

Oleic Acid (given me by Prof. Frankland). — Three leaves were 
immersed in this acid ; some inflection was almost immediately 
caused, which increased slightly, but then ceased, and the leaves 
seemed killed. Next morning they were rather shrivelled, and 
many of the glands had fallen ofi' 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 G.ycerine and Oleic Acid in Watts' 'Diet, of 
Chemistry.' 



Chap. Vin. THE EFFECTS OF ACIDS. 193 

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

Carbolic Acid. — Two leaves were immersed in sixty minims of 
a solution of 1 gr. to 437 of water ; in 7 hrs. one was slightly, 
and in 24 hrs. both were closely, inflected, with a surprising 
amount of mucus secreted. These leaves were washed and left 
tor 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 
wen inflected, the diseal 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 ail 
the glands on all three leaves were of a very pale colour. 
The leaves were then washed and placed in a solution (1 gr. 
to 20 oz.) of phosphate of ammonia ; after about 16 hrs. there 
was only a trace of inflection. They were left in the phosphate 
for 48 hrs., and remained in the same state, with almost all 
their glands discoloured. The 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 DEOSEKA KOTUNDIFOLIA. Chap. Vlli 

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 45 hrs. one leaf had almost- every tentacle in- 
flected; a second a large number ; the third and fourth very few ; 
almost all the glands were white, excepting those on the discs of 
two of the leaves, and many of these were very dark red. The 
leaves appeared dead. Hence lactic acid acts in a very peculiar 
manner, causing inflection at an extraordinarily slow rate, and 
being highly poisonous. Immersion in even weaker solutions, 
viz. of one part to 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. 

OalUc, Tannic, Tartaric, and Citric Acids. — One part to 487 of 
water. Three or four leaves were immersed, each in thirty 
minims of these four solutions, so that each leaf received ^ of a 
grain, or 4'048 mg. No inflection was caused in 24 hrs., and the 
leaves did not appear at all injured. Those which had been in 
the tannic and tartaric acids were placed in a solution (1 gr. to 
20 oz.) of phosphate of ammonia, but no inflection ensued in 
24 hrs. On the other hand, the four leaves which had been in 
the citric acid, when treated with the phosphate, became decidedly 
inflected in 50 m. and strongly inflected after 5 hrs., and so 
remained for the next 24 hrs. 

Malic Acid. — Three leaves were immersed in ninety minims of 
a solution of one part to 437 of water; no inflection was caused 
in 8 hrs. 20 m., but after 24 hrs. two of them were considerably, 
and the third slightly, inflected — more so than could be 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 
pink colour ; after 8 hrs. excessive inflection. The leaves were 
then placed in water ; after about 16 hrs. the tentacles were of 
a very dark red colour, like those of the leaves in acelic acid. 
After 24 additional hours, the three leaves were dead and thciv 
glands colourless. 

Benzoic Acid. — Five leaves were immersed, each in thirty 
minims of a solution of 1 gr. to 437 of water. This solution was 
BO weak that it only just tasted acid, yet, as we shall see, was 
highly poisonous to Drosera. After 52 m. the submarginai 



CuAr. VIII. THE EFFECTS OF ACIDS. 195 

tentacles were somewhat inflected, and all tlie glands very pale- 
coloured; the surrounding fluid was coloured pink. On one 
occasion the fluid became pink in the course of only 12 m., and 
the glands as white as if the leaf had been dipped in boiling 
water. After 4 hrs. much inflection ; but none of the tentacles 
were closely inflected, owing, as I believe, to their having been 
paralysed before they had time to complete their movement. 
An extraordinary quantity of mucus was secreted. Some of the 
leaves were left in the solution; others, after an immersion of 
6 hrs. 30 m., were placed in water. Next morning both lots 
were quite dead; the leaves in the solution being flaccid, those 
in the water (now coloured yellow) of a pale brown tint, and 
their glands white. 

Succinic Acid. — Three leaves were immersed in ninety minims 
of a solution of 1 gr. to 437 of water ; after 4 hrs. 15 m. consider- 
able and after 23 hrs. great inflection; many of the glands 
pale ; fluid coloured pink. The leaves were then washed and 
placed in water ; after two days there was some re-expansion, 
but many of the glands were still white. This acid is not 
nearly so poisonous as oxalic or benzoic. 

Uric Acid. — Three leaves were immersed in 180 minims of a 
solution of 1 gr. to 875 of warm water, but all the acid was not 
dissolved; so that each received nearly -^^ of a grain. After 
25 m. there was some slight inflection, but this never increased; 
after 9 hrs. the glands were not discoloured, nor was the solu- 
tion coloured pink; nevertheless much mucus was secreted. 
The leaves were then placed in water, and by ~next morning 
fully re-expanded. I doubt whether this acid really causes 
inflection, for the 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 DROSEEA EOTUNDIFOLIA. Ohap. 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 discoloTjred ; on the succeeding day they were 
evidently dead. Two leaves were immersed in a stronger 
mixture, of one part to fifty of water ; in 1 hr. 15 m. the glands 
became as white as porcelain, as if they had been dipped in boil- 
ing water ; very few of the tentacles were inflected ; but after 
4 hrs. almost all were inflected. These leaves were then placed 
in water, and next morning were evidently dead. Half-minim 
drops of the same strength (viz. one part to fifty of water) were 
next placed on the discs of five leaves ; after 21 hrs. all the 
outer tentacles were inflected, and the leaves appeared much 
injured. I likewise touched the secretion round a large number 
of glands with minute drops (about ^ of a minim, or "00296 ml.) 
of Scheele's mixture (6 per cent.) ; the glands first became bright 
red, and after 3 hrs. 15 m. about two-thirds of the tentacles 
bearing these glands were inflected, and remained so for the two 
succeeding days, when they appeared dead. 

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



* According to M. Foumler Berberis instantly to close; though 

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

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

of acetic, hydrocyanic, and snl- firm. 
phnric acid cave the stamens of 



Chap. VIII. CONCLUDING EEMAEKS, ACIDS. 197 

criterion of the power of an acid on Drosera, as citric 
and tartaric acids are very sonr, 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 vshich 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 DEOSERA ROTUNDIFOLIA. Ghap. 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, 
leayes, 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- 
■^ver, I shall have to recur. 



OlUP. IX. ALKALOID POISONS. 199 



CHAPTEK IX. 

Tub Effects of certain Alkaloid Poisons, other Substances and 
Vafouus. 

Btryohnine, salts of — Quinine, sulphate of, does not soon arrest the 
moTement of the protoplasm — Other salts of quinine — Digitaline 

— Nicotine — Atropine — Veratrine — Colohioine — Theine — Curare 

— Morphia — Hyosoyamus — 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 -g^ 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 -jL of a minim) of 
the same solution applied to the glands of the outer tentacles 
occasionally caused them to bend. The poison does not seem 
to act quickly, for having applied to several glands similar 
drops of a rather stronger solution, of one part to 292 of water, 
this did not prevent the tentacles bending, when their glands 
14 



200 DEOSERA EOTUNDIPOLIA. 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 i218 of water (2 grs. to 1 oz.) quickly 
blackened the glands; some few tentacles thus treated moved, 
whilst others did not. The latter, however, on being subse- 
quently moistened with saliva or given bits of meat, became 
incurved, though with extreme slowness; and this shows that 
they had been injured. Stronger solutions (but the strength 
was not ascertained) sometimes arrested all power of movement 
very quickly ; thus bits of meat were placed on the glands of 
several exterior tentacles, and as soon as they began to move, 
minute drops of the strong solution were added. They con- 
tinued for a short time to go on bending, and then suddenly 
stood still; other tentacles on the same leaves, with meat 
on their glands, but not wetted with the strychnine, continued 
to bend and soon reached the centre of the leaf. 

Ci'rate nf Strychnine. — Half-minims of a solution of one part 
to 437 of water were placed on the discs of six leaves ; after 
24 hrs. the outer tentacles showed only a trace of inflection. 
Bits of meat were then placed on three of these leaves, but in 
24 hrs. only slight and irregular inflection occurred, proving 
that the leaves had been greatly injured. Two of the leaves to 
which meat had not been given had their discal glands dry and 
much injured. Minute drops of a strong solution of one part to 
109 of water (4 grs. to 1 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 
weie immersed, each in thirty minims of a solution of one part 
to 437 of water; so that each received jL of a grain; after 
about 1 hr. some of the outer tentacles became inflected, and 
the glands were oddly mottled with black and white. These 
glands, in from 4 hrs. to 5 hrs., became whitish and opaque, 
and the protoplasm in the cells of the tentacles was well aggre- 
gated. By this time two of the leaves were greatly inflected, 
but the three others not much more inflected than they were 
befoi'e. Nevertheless two fresh leaves, after an immersion re- 
spectively for 2 hrs. and 4 hrs. in the solution, were not killed ; 
for on being left for 1 hr. 30 m. in a solution of one part of 
carbonate of ammonia to 218 of water, their tentacles became 
more inflected^ and there was much aggregation. The glands 



Chap. IX. ALKALOID POISOKS. 201 

of two other leaves, after an immersion for 2 lirs. in a stronger 
solution, of one part of the citrate to 318 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^^'* of ^^ 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 increa.=,ed. One of 
the leaves was taken out of the solution after 4 hrs., and placed 
in water ; by the next morning some few of the inflected 
tentacles had re-expanded, showing that they were not dead; 
but the glands were still much discoloured. Another leaf not 
included in the above lot, 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 supphed 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 



'Qi^artt'ily Joui'nal of Microscopical Science,' April 1S71, p. 185. 



202 DKOSEEA EOTUNDIFOLIA. Chap. IX. 

had become aggregated into reticulated dingy-cjoloured masses, 
haying rounded and angular interspaces. As I have never 
seen this effect produced by the carbonate of ammonia alone, 
it must be attributed to the previous action of the quinine. 
These reticulated masses were watched for some time, but did 
not change their forms ; so that the protoplasm no doubt had 
been killed by the combined action of the two salts, though 
exposed to them for only a short time. 

Another leaf, after an immersion for 24 hrs. in the quinine 
solution, became somewhat flaccid, and the protoplasm in all 
the cells was aggregated. Many of the aggregated masses were 
discoloured, and presented a granular appearance ; they were 
spherical, or elongated, or still more commonly consisted of 
little curved chains of small globules. None of these masses 
exhibited the least movement, and no doubt were all dead. 

Half-minims of the solution were placed on the discs of six 
leaves; after 23 hrs. one had all its tentacles, two had a few, 
and the others none inflected; so that the discal glands, when 
irritated by this salt, do not transmit any strong motor impulse 
to the outer tentacles. After 48 hrs. the glands on the discs of 
all six leaves were evidently much injured or quite killed. It is 
clear that this salt is highly poisonous.* 

Acetate of Quinine. — Pour leaves were immersed, each in thirty 
minims of a solution of one part to 437 of water. The solution 
was tested with litmus paper, and was not acid. After only 
10 m. all four leaves were greatly, and after 6 hrs. immensely, 
inflected. They were then left in water for 60 hrs., but never 
re-expanded; the glands were white, and the leaves evidently 
dead. This salt ip 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 

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

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

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

energetic poison to low vege- appeared killed by the quinine, 

tiible and animal organisms. Even likewise presei.ted a granular 

one part added to 4(100 parts of appearance. A similar appear- 

Wood arrests the movemeuta of the ance is caused by very hot water 



Chap. IX. ALKALOID POISONS. 203 

completely re-expanded, but the glands were much discoloured. 
Hence this salt is not poisonous in any high degree. The 
different action of the three foregoing salts of quinine is sin- 
gular. 

Dif/italine. — 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 same state for two days, but the glands on their discs 
became pale. On the third day the leaves appeared much 
injured. Nevertheless, when bits of meat were placed on two 
of them, the outer tentacles became inflected. A minute drop 
(about Jg of a minim) of the solution was applied to three 
glands, and after 6 hrs. all three tentacles were inflected, but 
next day had nearly re-expanded ; so that this very small dose 
of 2sioo of a grain (-00225 mg.) acts on 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 shghtly 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 4 oz. of 
water) were pjaced 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 DKOSERA EOTUNDIFOIJA. Chap. IX 

of the protoplasm, but, except when pure, has very moderate 
power of inducing inflection, and still less power of causing 
a motor influence to be transmitted from the discal glands to 
the outer tentacles. It is moderately poisonous. 

Atnipine.—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 to seven parts of water; and 
a third solution was made by adding one part of valerianate of 
atropine to 437 of water. Half-minims of these three solutions 
were placed, in each case, on the discs of six leaves ; but no 
effect whatever was produced, excepting that the glands on 
the discs to which the valerianate was given were slightly 
discoloured. The six leaves on which 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 rib 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. 

Verakrine, 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 waterr 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 kiod had been absorbed. In 9 hrs. two of the 
loaves 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-expanded, 
though their glands were as black as ever. Half-minims were 
placed on the discs of six leayes, and no inflection ensued ; tut 
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 glauds. 
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. Those were not at all affected, 
and when after a day bits of meat were given them, they were 
slightly inflected in 5 hrs., and closely after 24 hrs. It follows 
from these several facts tliat 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 strerigth (one part to 218 of water) sometimes retarded 
the subsequent action of meat and of particles of glass, and 



206 DROSEEA EOTUNDIFOLIA. Ohap. 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. 

Extract of Hyoscyamus. — Several leaves were placed, each in 
thirty minims of an infusion of 3 grs. of the extract sold by 
druggists to 1 oz. of water. One of them, after being immersed 
for 5 hrs. 15 m., was not inflected, and was then put into a 
solution (1 gr. to 1 oz.) of carbonate of ammonia ; after 2 hrs. 
40 m. it was found considerably inflected, and the glands 
much blackened. Tour 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 
uarcotic or poison. 

Poison from the Fang of a Living Adder. — Minute drops were 
placed on the glands of many tentacles; these were quickly 
inflected, just as if saliva had been given them. Next morning, 
after 17 hrs. 30 m., all were beginning to re-expand, and they 
appeared uninjured. 

Poison 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 Jj 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^io^ °f ^ 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.) ; iu 



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



Chap. IX. POISON OF THE COBKA. 207 

4 lirs. 15 m. the outer tentacles were much inflected ; and after 
6 hrs. 30 m. those on two of the leaves were closely inflected and 
the blade of one ; the third leaf was only moderately 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 t'o °^ '•' 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 within 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 iu 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 -J- of a grain, or 16'iJ 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, a ad 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 



208 DEOSEEA EOTUNDIFOLIA. Chap. IX- 

expanded. The tentacles were now examined, and the aggregated 
masses were almost wholly redissolved ; the cells being filled with 
homogeneous purple 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 hrs. in 
water, in a little solution of one part of carbonate of ammonia 
to 218 of water ; in 30 m. the protoplasm in the cells beneath 
the glands became darker, and in the course of 24 hrs. the 
tentacles were filled down to their bases with dark-coloured 
spherical masses. Hence the glands had not lost their 
power of absorption, as far as the carbonate of ammonia is 
concerned. 

From these facts it is manifest that the poison of the cobra, 
though so deadly to animals, is not at all poisonous to Drosera ; 
yet it causes strong and rapid inflection of the tentacles, and 
soon discharges all 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 animai 
protoplasm ; and Dr. Fayrer was so kind as to make some .obser- 
vations for me, which he has since published.* 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 ; whilst those in the water were still acting vigorously. 
The white corpuscles of the blood of a frog, and the cilia on two 
infusorial animals, a Paramsecium and Volvox, were similarly 
affected by the poison. Dr. Fayrer also found that the muscle 
of a frog lost its irritability after an immersion of 20 m. in 
the solution, not then responding to a strong electrical current. 
On the other hand, the movements of the cilia on the mantle of 
an Unio were not always arrested, even when left for a consider- 



' ProetedingB of Koyal Society ' Feb. 18, 1875. 



Chap. IX. CAMPHOK. 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 poison. When the stronger 
solution was employed, the drops appeared in 10 m. like little 
white rounded clouds. After 48 hrs. the secretion was changed 
into threads and sheets of a membranous substance, including 
minute granules of various sizes. 

Camplwr. — 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 y^ijo of 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. 671. Nearly uimilar observationi 
wore made in 1798 bv B. S. Barton. 



210 



DKOSEBA KOTUNDIFOLIA. 



OUAP. tX. 



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. 
My first trials were made by brushing the leaves whilst still 
immersed in the solution ; but it occurred to me that the viscid 
secretion round the glands would thus be removed, and the 
camphor might act more effectually on them. In all the 
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 camphor ; but this treatment made no difference 
in the results. 



I 



Length of 
Immersion in 
the Solution 
of Camphor. 



Length of Time between the Act of Brushing 
and tbe Inflection of the Tentaclcij, 



Length of 

Time between 

the Immersion 

of the Ijeaves in 

tlie Solution 

and the First 

Sign of the 

'Inflection of the 

Tentacles. 



5 m. 
5 m. 
5 m. 



4 I 4 m. 30 s. 



5 


4 m. 


6 


4 m. 


7 


4 m. 


8 


3 m. 



9 I 3 m. 



f 

G 

r 

2 

2 

r 



m. ooDBiderable inflection ; 4 m. all 

the tentacles except 3 or 4 inflected, 

m. first sign of inflection. 

m. 30 s. slight inflection ; 7 m. 30 s. 
plain inflection. 

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

m. 30 s. a trace of inflection ; 3 ni. 
plain inflection. 

m. 30 s. decided inflection; 3 m. 30 s. 
strongly marked, 
m. 30 s. slight inflection ; 3 m, 
plain ; 4 m. well marked. 

m. trace of inflection ; 3 m. con- 
siderable, m. strong inflection, 
m. trace of inflection ; 3 m. con- 
siderable, m. strong inflection. 



H 

}" 
} ' 

! ' 
} • 



I » 



m. 
m. 
m. 30 8. 

m. 

m. 30 8. 

m. 30 8. 

m. 30 s. 

m. 

m. 



Other leaves were loft 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 



Obap. IX. ESSENTIAL OILS, ETC. 211 

elapsed, and two not until a few minutes later. On the other 
hand, it will be seen in the right-hand column of the table that 
most of the leaves subjected to the solution, and which were 
brushed, became inflected in a much shorter time. The move- 
ment of the tentacles of some of these leaves was so rapid that 
it could be plainly seen through a very weak lens. 

Two or three other experiments are worth giving. A largo 
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, which by itself does not cause any movement. Or it may 
be that a slight mechanical irritation not enough to cause any 
inflection yet gives some tendency to movement, and thus 
reinforces the action of the camphor. This latter view would 
have appeared to me the more probable one, had it not been 
shown by M. Vogel that camphor is a stimulant in other ways to 
various plants and seeds. 

Two plants bearing four or five leaves, and with their roots 
in a little cup of water, were exposed to the vaponr 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 vaponr of camphor. 

Oil of Cartnoay. — Water is said to dissolve about a thousandth 
part of its weight of this oil. A drop was added to an ounce 
of water and the bottle occasionally shaken during a day ; 
but many minute globules remained undissolved. Five leaves 
were immersed in this mixture; in from 4 m. to 5 m. there was 
Bome inflection, which became moderately pronounced in two o.i 



212 DEOSEEA 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 peculiar 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. — Small drops placed on the discs of some leaves 
killed them, as did likewise drops of creosote. A plant was left 
for 15 m. under a 12-oz. vessel, wibh its inner surface wetted 
with twelve drops of turpentine ; but no movement of the ten- 
tacles ensued. After 24 hrs. the plant was dead. 

O/ycerme.— 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 ^^ 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- 
loss. 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 blackened, their tentacles inflected, 
and the protoplasm within their colls aggregated. Tt appears 



Chap. IX. EFFECTS OF PKEVIOUS 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 piire glycerine is poisonous, and if applied 
in very minute quantities to the glands of the outer tentacles 
causes their inflection. 

Tiie Effects of hmnersion 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 tMs 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 vn. pro- 
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 ra. 
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 



DROSEKi. KOTUNDIFOLIA. 



Chap. 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 affected ; the inflection subsequently increased, 
though slowly. Hence diluted alcohol, which, as we shall see, is 
hardly at all poisonous, plainly retards the subsequent action of 
the phosphate. 

It was shown in the last chapter that leaves which did not 
become inflected by nearly a day's immersion in solutions of 
various salts and acids behaved very differently from one an- 
other when subsequently placed in the phosphate solution. I 
here give a table summing up the results. 



Name of the Salts add 
Acids in Solution. 



Period of 
Immersion 

of the 

Leaves In 

Solutions 

of one part 

to 43Y of 

water. 



Effects produced on the Leaves by their subse- 
quent Immersion f(ir stated pi-riods in a 
Solution of one part of photjihate of 
ammonia to 8750 of water, or 1 gr. to 
20 oz. 



Eubidium chloride 

Potassium carbonate 

Calcium acetate 
Calcium nitrate . 
Magnesium acetate . 

Magnesium nitrate . 

Magnesium chloride 

Barium acetate . 
Barium nitrate . 

Strontium acetate 



Strontium nitrate 



Aluminium chloride 



22 hrs. 

20 m. 

24 hrs. 
24 hrs. 
22 hrs. 

22 hrs. 

22 hrs. 

22 hrs. 
22 hrs. 

22 hrs. 



22 hrs. 



24 hrs. 



After 30 m. strong inflection of the 

tentacles. 
Scarcely any inflection until 5 hrs. 

had elapsed. 
After 24 hrs. very slight inflection. 

D.). 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 Ave in this state; but not one 

closely inflected. 
Three leaves which had either been 

slightly or uot at all afferited by the 

chloriile became after 7 hrs. 30 m 

rather closely inflected. 



Chap. IX. EFFECTS OP PREVIOUS IMMEESION. 



215 





Period of 






Immersion 


Effects produced on the Leaves by their sul)- 




of the 


spquent Immersion for stated periods in a 


Name of the Salts and 


Leaves in 


Solution of one part of phosphate of 


Aiids in Solution. 


Solutions 


ammonia to 8750 of water, or 1 gr. to 




of one part 


20 02. 




to 437 of 






water. 




Aluminium nitrate . 


24 hrs. 


After 25 hrs. slight and doubtful effect . 


Lead chloride . . 


23hrs. 


After 24 hrs. two leaves somewhat 
inflected, the third very little ; and 
thus remained. 


Manganese chloride 


22 hrs. 


After 48 hrs. not the least inflection. 


Tiactic acid . . . 


48 hrs. 


After 24 hrs. a trace of inflection in 
a few tentacles, the glands of 
which had not been killed by the 
acid. 


Tannic acid . 


24 hrs. 


After 24 hrs. no inflection. 


Tartaric acid 


24 hrs. 


Do. do. 


Citric acid . . . 


24 hre. 


After 50 m. tentacles decidedly in- 
flected, and after 5 hrs. strongly 
inflected ; so remained for the next 
24 hrs. 


Formic acid . 


22 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 
inflection was slowly caused by the phosphate. In four cases, 
however, the inflection was rapid, occurring in less than half an 
hour or at most in 50 m. In three oases the phosphate did not 
produce the least eflfect. 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 solution. It would, therefore, appear as if the solutions of 
"chloride of manganese, tannic and tartaric acids, which are not 
poisonous, acted exactly like water, for the phosphate produced 
no effect on the leaves which had been previously immersed 
in these three solutions. The majority of the other solutions 
behaved to a certain extent like water, for the phosphate pro- 
duced, after a considerable interval of time, only a slight eflfect. 
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, 
iid not prevent the subsequent action of the phosphate? Ox 
15 



216 DEOSEBA ^OTUNDIFOLIA. OhAP. 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 
'jan 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 tlie 
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 mixtuie, 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. Traube's curious By allowing a precipitation of 
sxperiments 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 : " Expert- salt ; and in consequence of the 
mente zur Theorie der Zellenbil- intercalation of molecules of sul- 
dung und Rndosmose," Breslau, phate of barium among those of 
IH6B ; and " Experimente zur the gelatine precipitate, the mole- 
physicalischen Erklarung der Bil- cular interstices in the membrane 
dung der Zellhaut, ihres Waehs- are made smaller. In this altered 
thums duroh Intussusception," condition, the membrane no longer 
Breslau, 1874. Thestj researches allows the passage through it of 
perhaps explain my results. Dr. either sulphate of ammonia ot 
Traube commonly employed as a nitrate of barium, though it re- 
membrane the precipitate formed tains its permeability for watci 
when tannic acid comes into con- and chloride of ammonia, 
tact with a solution of gelatine. 



Chap. IX. VAPOUR OF CHLOKOFOEM. 217 

Nor did these four leaves, on being left for 24 hrs. in the diluted 
alcohol, undergo any inflection. They were then removed ; one 
being placed in an infusion of raw meat, and bits of meat on 
the discs of the other three, with their stalks in water. Next 
day one seamed 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 io. which the glands were affected by the vapour 
of carbonate of ammonia. Immediately on the removal of the 
receiver particles of raw meat were placed on many of the glands, 
those which retained their proper colour 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, a,nd after 
1 hr. 10 m. almost all were considerably inflected. From their 
slow rate of movement there can be no doubt that the glands of 
these tentacles had been rendered insensible for a time by 
exposure during 5 m. to the vapour of alcohol. 

Vapiiur of Cliloroform.~The action of this vapour on Drosera 
is very variable, depending, I suppose, on the constitution or age 
of tlie 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 DEOSEEA KOTUNDIFOLIA. Chap. IX. 

rendered for a time insensible to the action of raw meat, but 
sometimes are not thus affected, or in a very slight degree. A 
plant recovers from a small dose, but is easily killed by a larger 
one. 

A plant was left for 30 m. under a bell-glass holding 
19 fluid oz. (539'6 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 24 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 under the same small bell-glass 
with three drops of chloroform, and before two minutes had 
elapsed, the tentacles began to curl inwards with rapid httle 
jerks. The glass was then removed, and in the course of two 
or three additional minutes almost every tentacle reached the 
centre. On several other occasions the vapour did not excite 
any movement of this kind. 

There seems also to be great variabihty 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., bxit 
afterwards moved very slowly ; whilst none of the other tentacles 



Chap. IX. VAPOUR OF ETHEK. 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 ansssthetic 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 moving 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 this case there could not be the least doubt that 
the chloroform had exerted an ansesthetic influence on the 



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 
ansesthetic effect had been produced; and how to reconcile 
these discordant results, I know not. 

Vapour of Sulphuric Kthrr. — 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 oi 
the other tentacles continued to secrete, and appeared uninjured, 
Out the whole plant after three days became very sickly. 



220 DEOSEKA ROTUNDIFOLIA. Chap. IX. 

In the two foregoing experiments the doses were evidently too 
large and poisonous. With weaker doses, the anassthetic 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 Kther, — This vapour seems more injurious than 
that of sulphuric ether. A plant was exposed for 5 ra. 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 vrithout meat, nearly reached the centre. On 
the other leaf the glands began t<) 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 which the leaves had suffered, 
whether any ansBsthetic 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 wore then placed on the glands of seven tentacles on the 



Chap. IX. CAE.BONIC ACID. 221 

eame leaf. A single tentacle moved after 1 hr. 23 m. ; after 

2 hrs. 3 m. seTeral 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 teniacles, three of which were 
slightly inflected in 28 m.; after 1 hr. 21 m. one reached the 
centre, but the other two were still only slightly inflected; after 

3 hrs. they were much more inflected; but even after 5 hrs. 
16 m. all five had not reached the centre. Although some of 
the tentacles began to move moderately soon, they afterwards 
moved with extreme slowness. By next morning, after 20 hrs., 
most of the tentacles on both leaves were closely inflected, but 
not quite regularly. After 48 hrs. neither leaf appeared injured, 
though the tentacles were still inflected ; after 72 hrs. one 
was almost dead, whilst the other was re-expanding and 
recovering. 

Carhmic Acid. — A plant was placed under a 122-oz. bell-glass 
filled with this gas and standing over water; but I did not make 
suflBcient allowance for the absorption of the gas by the water, 
so that towards the latter part of the experiment sorLe 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 completely covered by the water, which rose within 
the vessel as the gas was absorbed. On this latter leaf the 
tentacles, to which meat had been given, became well inflected 
in 2 m. 30 s., that is, at about the normal rate ; so that until 
I remembered that the leaf had been protected from the gas, 
and might perhaps have absorbed oxygen from the water 
which was continually drawn inwards, 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 
I'n 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 caso. 



322 DEOSEKA EOTUNDIFOLIA. Ohap. IX. 

&. plant was exposed in the same vessel to the gas for 45 m., and 
bits of meat were then placed on four glands. But the 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 powei 
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 racner strong solution of carbonate of ammonia, together with 



Chap. IX. SUMMARY OP THE CHAPTER. 223 

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 Bemarhs on the Effects of the foregoing 
Agents. — As the glands, when excited, transmit some 
influence to the surrounding tentacles, causing them 
to bend and their glands to pour forth an increased 
amount of modified secretion, I was anxious to 
ascertain whether the leaves included any element 
having the nature of nerve-tissue, which, though 
not continuous, served as the channel of transmission. 
This led me to try the several alkaloids and other 
substances which are known to exert a powerful 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, colchiciae, curare, and diluted alcohol 
would have produced some marked effect; whereas 



224 DROSERA ROTUNDIFOLIA. Chap. IX. 

these substances are not poisonous 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 poisonous 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 to describe the 
diversified effects of various substances on Drosera.f 



* Dr. Fayrer, 'The Thanato- cyanic, and chromic acids, ace- 

phidia of India,' 1872, p. 4. tate of strychnine, and vapour of 

+ Sei;iiig that acetic, hydro- ether, are poisonous to Drosera, 



Chap. IX. SUMMAKY OF THE CHAPTEK. 225 

Of the alkaloids and their salts which were tried, 
several had not the least power of inducing inflection ; 
others, which were certainly absorbed, as shown by the 
changed colour of the glands, had but a very mode- 
rate power of this kind ; others, again, such as the 
•icetate 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 chloio- 
( ' Philosoph. Transact.' 1867, p. form and carbonic acid." I iind 
480), who used much stronger 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 prote- 
ased, which did not act chemi- plasm. 



226 DEOSBRA KOTUNDIFOLIA. OiLiP. IX 

changes of form, but after 24 hrs. were motionless; 
the leaf being flaccid and apparently dead. On the 
other hand, with leaves subjected for 48 hrs. to a 
strong solution of the poison of the cobra, the proto- 
plasmic masses were unusually active, whilst with 
the higher . animals the vibratile cilia and white 
corpuscles of the blood seem to be quickly paralysed 
by this substance. 

With the salts of alkalies and earths, the nature of 
the base, and not that of the acid, determines their 
physiological action on Drosera, as is likewise the case 
with animals ; but this rule hardly applies to the salts 
of quinine and strychnine, for the acetate of quinine 
causes much more inflection than the sulphate, and 
both are poisonous, whereas the nitrate of quinine is 
not poisonous, and induces inflection at a much slower 
rate than the acetate. The action of the citrate of 
strychnine is also somewhat diiferent 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 up 
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. 



Chap. IX SUMMARY OF THE CHAPTER. 227 

The action of camphor dissolved in water is remark- 
able, for it not only soon induces inflection, but 
apparently renders the glands extremely sensitive to 
mechanical irritation ; for if they are brushed with a 
soft brush, after being immersed in the solution for 
a short time, the tentacles begin to bend in about 
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 DEOSEEA ROTUNDIFOLIA. Chat. IX. 

become inflected, are not excited to further move- 
ment by bits of meat placed on the glands, until 
some considerable time has elapsed. It is generally 
believed that 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, ' Traite de Bot.' 1874, pp. 846, 1037. 



Chap. X. SENSITIVENESS OF THE LEAVES. 229 



CHAPTEE X. 

On the Sensitttfness op the Leaves, and on the Lines of 
Tbansmtssion of the Motor Impulse. 

Otiaude and summits af 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 — Fii'st 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 iii 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 iniiected. These headless ten- 
tacles frequently re-expanded ; and when afterwards 
drops of the two most powerful known stimulants were 
placed on the cut-off ends, no effect was produced. 
Nevertheless these headless tentacles are capable of 
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 DROSEKA KOTTJNDIFOLIA. Chap. X. 

It is probable that they were killed so instantly that 
they were not able to transmit any motor impulse ; for 
in six observed cases (in two of which however the 
gland was quite pinched off) the protoplasm within 
the cells of the tentacles did not become aggregated ; 
whereas in some adjoining tentacles, which were 
inflected from having been roughly touched by the 
pincers, it was well aggregated. In like manner the 
protoplasm does not become aggregated when a leaf is 
instantly killed by being dipped into boiling 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 
being left for a considerable time on the pedicels, 
were pushed upwards, so as just to touch the glands, 
and in a minute the tentacles began to bend. I 
believe that the blade of the leaf is not sensitive to 
any stimulant. I drove the point of a lancet through 
the blades of several leaves, and a needle three or four 
times through nineteen leaves : in the former case 
no movement ensued ; but about a dozen of the leaves 
which were repeatedly pricked had a few tentacles 
irregularly inflected. As, however, their backs had 
to be supported during the operation, some of the 
outer glands, as well as those on the disc, may have 
been touched; and this perhaps sufficed to cause the 
slight degree of movement observed. Nitschke* says 



'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 
papillse, which do not secrete, but have the power of 
absorption. These papillse are, I believe, rudiments 
of formerly existing tentacles together with their 
glands. Many experiments were made to ascertain 
whether the backs of the leaves could be irritated in 
any way, thirty-seven leaves being thus tried. Some 
were rubbed for a long time with a blunt needle, 
and drops of milk and other exciting fluids, raw 
meat, crushed flies, and various substances, placed on 
others. These substances were apt soon to become 
dry, showing that no secretion had been excited. 
Hence I inoistened them with saliva, solutions of 
ammonia, weak hydrochloric acid, and frequently with 
the secretion from the glands of other leaves. I 
also kept some leaves, on the backs of which exciting 
objects had been placed, under a damp bell-glass ; but 
with all my care I never saw any true movement. I 
was led to make so many trials because, contrary to 
my previous experience, Nitschke states* that, after 
affixing objects to the backs of leaves by the aid of 
the viscid secretion, he repeatedly saw the tentacles 
(and in one instance the blade) become reflexed. 
This movement, if a true one, would be most 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. 
16 



232 DEOSEKA EOTUNDIFOLIA. Ohai'. 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 increased 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 



Chap. 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 motoi' 
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), oi 
gelatine, and raw meat, are placed on the discs ot 
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 difference in the result: 
place a bit of meat on one or two of the discaJ 



234 DKOSEKA KOTUNDIPOLIA. Chap. X, 

glands, and only a few of the immediately surround- 
ing short tentacles are inflected ; place it on several 
glands, and many more are acted on ; place it on 
thirty or forty, and all the tentacles, including the 
extreme marginal ones, become closely inflected. We 
thus see that the impulses proceeding from a number 
of glands strengthen one another, spread farther, and 
act on a larger number of tentacles, than the 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 Jnflection 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 iafluence 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 MOTOE 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 teutacles 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 ceutrifugally, 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 DKOSEEA 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 where the bit of meat lay 
as did those at the two ends. It thus appeared as 



Chap. X. TEANSMISSION 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 fotu- rather unusual cases. 



(1) A minute fragment of a fly was placed on one side of the 
disc, and after 32 m. seven of the outer tentacles near the frag- 
ment were inflected ; after 10 hrs. several more became so, and 
after 23 hrs. a still greater number ; and now the blade of the 
leaf on this side was bent inwards so as to stand up at right 
angles to the other side. Neither the blade of the leaf nor a 
single tentacle on the opposite side was affected; the line of 
separation between the two halves extending from the footstalk 
to the apex. The leaf remained in this state for three days, 
and on the fourth day began to re-expand; not a single 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 DROSEEA EOTUNDIFOLIA. CliAP. 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 three or four on the opposite side 
near the footstalk. On the second day these latter tentacles 
showed signs of re-expanding, so I added a fresh bit of meat 
at nearly the same spot, and after two days some of the short 
tentacles on the opposite side of the disc were inflected. As 
soon as these began to re-expand, 1 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 ths first bit of meat 
which was given. 



Now for the general results. Of the eighteen leaves 
on which bits of. meat were placed on the right 
or left sides of the disc, eight had a vast number of 
tentacles inflected on the same side, and in four of 
them the blade itself on this side was likewise 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 



OHAr. X. TEANSMISSION 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 difference. Those 
having the cubes on one side were very slightly 
affected on the opposite side ; whereas those with the 
cubes at either end had almost every tentacle at the 
opposite end, even the marginal ones, closely 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 EOTUNDIFOLIA. Ohap.X, 

or small group of glands through the b'ade 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 
discharged within a few seconds, as we know from the 



Chap. X. TEANSMISSIOK OF MOTOE IMPULSE. 241 

bending of the 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 acioss 
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, tJieir 
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 impulso 
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 DBOSEEA 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 jorotoplasm 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. DIRECTION OF INFLECTED TENTACLES. 243 

that is, if the stimulus has been sufficient and not 
injurious. Now, when the glands of the disc are 
excited, the exterior tentacles are affected in exactly 
the same manner : the aggregation always 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 protoplasm 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 



DEOSEEA EOTUNDIFOLIA. 



Chap. 3.. 



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 
Nitschke,* 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 

(Drosera rottmazfolub.) 
Leaf (enlarged) with the tentacles inflected directed mOVCmCUt of the 

ttTdLf °' "'" '"^'' ™ ""' "" "' surrounding tentacles 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, iu- 
sluding some of the exterior ones, accurately directed 
to the point where the meat lay. But a much bettei 




* 'Bot. Zeituug,' 1860, p. 240. 



Chap. X. DIKECTION OF INFLECTED TENTACLES. 245 

plan is to place a particle of the phosphate 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 DEOSEKA 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 formed 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 first, and the contraction 
of these cells must draw the whole tentacle into the 
proper direction. It is, perhaps, owing to the exterior 
pedicels being much flattened that they do not bend 
quite so accurately to the point of excitement as the 



Chap. X. 



CONDUCTING TISSUES. 



247 



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 which the Motor 
Impulse is Transmitted. — It will be necessary first 
to describe briefly the 
course of the main fibro- 
vascular bundles. These 
are shown in the 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. 

(Drotera rotimdi/oliaS) 

Diagram showing the distribution of the 
vascular tissue in a small leaf. 



248 DEOSEEA KUTUNDIFOLIA. 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, hut 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. 30 m. strong inflection of the tentacles at 
the distal end, which during the next two days never extended 
in the least to the basal end. The incision as before. 

(4) This leaf was not observed until 15 hrs. had elapsed, and 
then aU 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 rendus,' 1874, p. 1417), 
perimcnts by cutting the spiral feut arrived at conclusijonB widely 
vessels of Drosera intermedia different from mine. 



250 DKOSEEA KOTUNDIFOLIA. Chap. X. 

proves that the spiral vessels of the cen tral 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 Nor 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 simultaneously with 
great precision towards it. Now there are tentacles 
on the disc, for instance near the extremities of the 
sublateral bundles (fig. 11), which are supplied with 
vessels that do not come into contact with the branches 
that enter the 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 Dionsea, 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 DBOSEKA BOTUNDIFOLIA. 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 same brief 
space of time. It seems therefore probable that the 
motor impulse consisttj 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 Meddelolser ile la Soo.. d'Hist. nat. de Copen- 
hague,' Nos. 10-J2, 1872, woodcuts iv. and v. 



Ohai'. 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 -Jj- 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 diifusion 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 DEOSEEA KOTUNDIFOLIA. 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 movement 
is great. Fully expanded tentacles in becoming in- 
flected sweep through an angle of 180°; and if they 
are beforehand reflexed, as often occurs, the angle is 
considerably greater. It is probably the superficial 
cells at the bending place which chiefly or exclusively 
contract; for the interior cells have very delicate 
walls, and are so few in number that they could hardly 
cause a tentacle to bend with precision 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 affected; about half- 
way down there is a slight bending, but the chief 
movement is confined to a short space near the base ; 
and no 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 ou 



Chap. X. MEANS OF MOVEMENT. 25b 

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 esipand 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.f In the case 
of Drosera there is certainly much movement of the 
flaid 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 I 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 
Hieat had been placed on a gland, the purple colour 
was observed at intervals to be slowly travelling from 
tlie upper to the lower part, down the convex side of 



* Paohs, 'Traite de Bot.' Srd Lamarclr. 
edit. 1871, p. 1038. Tliie view t Sachs, ibid. p. 919. 

viae, I believe, first BUggceted by 



25(5 DKOSEEA EOTUNDI FOLIA. Chap. X. 

the bending tentacle. But it does not follow from 
these observations that the cells on the convex side 
become filled with more iluid 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 iluid, and their subsequent re- 
expansion in a less dense fluid, show that the passage 
of fluid from or into the cells can cause movements 
like the natural ones. But the inflection thus caused 
is often irregular ; the exterior 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 
Oohn, in his interesting paper* on the movements 
of the stamens of certain Compositae, 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, 1861, Heft 1. of Nat. Hist.' 3rd series, 1863, 
An excoUent abstract of this paper vol. xi. pp. 188-197. 



CiiAi: 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 tlie 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 1 hat 
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 DEOSEBA EOTUNDIFOLIA. Chap. X 

thougii 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 be attributed to 
the elasticity of the walls, together with a previous 
state of tension. 

With respect to the nature of the motor impulse 
which is transmitted from the glands down the 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. NATUKE OF THE MOTOR IMPULSE. 259 

protoplasm is redissolved 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 iuxpulse 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 high 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 ^^hould 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 
when 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 DKOSEEA 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-exparision 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 lea/ 



Chap. X. EE-EXFANSION 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 suffice to 
carry back the tentacles to their original position, 
often through an angle of above 180". It is more 
probable that fluid, which we know travels along the 
tentacles during the act of inflection, is slowly re- 
attracted into the cells of the convex 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. 



262 DROSERA ROTUNDIFOLIA. Chap. JO. 



CHAPTER XI. 

BECAPITDLATrON OF THE ChIEP OBSERVATIONS ON 

Droseba kotundifolia. 

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, tborr-rootis 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 , aosorption, 
besides that of secretion. They are extrp^iely sen- 
sitive to various stimulants, namelyj;e,ptf«£od touches, 
the pressiire 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 Lalf 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 SUMMABT. 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 two- o^ ^^ iiich (-203 mm.) in 
length, and weighing only yttj-o of a grain (-000822 
ing.), though largely supported by the dense secre- 
tion, suiHces 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, 
18 



2(J4 DEOSEEA EOTUNDITOLIA. 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 mani- 
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 necklaceJike, 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 affected. In cells, especially 
if filled with dark red fluid, the first step in the 



Chap. XI. GENERAL SUMMAET. 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 -s-tV-o-o 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 DEOSEEA EOTUNDIFOLIA. Chap. XI 

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-s-rss of a 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 



CiSAP. XL GENEEAL SUMMARY. 267 

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 exposm-e 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- 



268 DEOSEEA EOTUNDIPOLIA. 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 peas 
or cabbage-leaves. 

These results led me to inquire whether Drosera 
possessed the power of dissolving solid animal matter. 
The experiments proving that the leaves are caj)able 
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 other 
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 Schiif, the stomach of an 
animal does not secrete its proper ferment, pepsin, 
until certain substances, which he calls peptogenes, 
are absorbed ; and it appears from my experiments 
that some matter must be absorbed by the glands 
of Drosera before they secrete their proper ferment. 
That the secretion does contain a ferment which acts 
only in the presence of an acid on solid animal 
matter, was clearly proved by adding minute doses of 



Chap. XI. GENEKAL SUMMARY. 269 

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 boqe, and 
even the enamel of teeth, but this is simply due to 
the large quantity of acid secreted, owing, apparently, 
to the desire of the plant for phosphorus. In the 
case of bone, the ferment does not come into play 
until all the phosphate of lime has been decomposed 
and free acid is present, and then the fibrous basis is 
quickly dissolved. Lastly, the secretion attacks and 
dissolves matter out of living seeds, which it some- 
times kills, or injures, as shown by the diseased state 



270 DKOSEEA EOTUNDIFOLIA. Chap. XI 

of the seedlings. It also absorbs matter irom 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. 
But the relative efficiency of only three salts of 
ammonia was carefully determined, namely the car- 
bonate, nitrate, and phosphate. The experiments were 
made by placing half-minims ('0296 ml.) of solutions 
of different strengths on the discs of the leaves, — by 
applying a minute drop (about the -j-'^ 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 -g-^ 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^^ of a grain (^00445 mg.), if applied for a few 
seconds to the secretion surrounding a gland, causes 
the inflection of the same tentacle. When a highly 
sensitive leaf is immersed in a solution, and there is 
ample time for absorption, the g^„'^„„ of a grain 



Chap. XI. 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 -stVo- 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 ttfo-o- of ^ 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- 
™g 38800 of ^ 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 ■j-g-ra-ro of * 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 -^j-g 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 -3-3-'ro-o 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 ttttoo-cto 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 ROTUN DIFOLIA. Chap. XI. 

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 sarprising that Drosera should be 
enabled to profit by the absorption of these salts, for 
yeast and other low fungoid forms flourish in solutions 
of ammonia, if the other necessary elements are 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. XI. GENERAL SUMMARY. 273 

spending salts of potassium produced no effect, two 
causing slight inflection. Small doses, moreover, of 
some of the latter salts were poisonous. The salts 
of sodium and potassium, when injected into the veins 
of animals, likewise differ widely in their action. The 
so-called earthy salts produce hardly any effect on 
Drosera. On the other hand, most of the metallic 
salts cause rapid and strong inflection, and are highly 
poisonous ; but there are some odd exceptions to this 
rule; thus chloride of lead and zinc, as well as two 
salts of barium, did not cause inflection, and were not 
poisonous. 

Most of the acids which were tried, though much 
diluted (one part to 437 of water), and given in small 
doses, acted powerfully on Drosera ; nineteen, out of the 
twenty-four, causing the tentacles to be more or less 
inflected. Most of them, even the organic acids, are 
poisonous, often highly so ; and this is remarkable, as 
the juices of so many plants contain acids. Benzoic 
acid, which is innocuous to animals, seems to be as 
poisonous to Drosera as hydrocyanic. On the other 
hand, hydrochloric acid is not poisonous either to 
animals or to Drosera, and induces only a moderate 
amount of inflection. Many acids excite the glands to 
secrete an extraordinary quantity of mucus; and the 
protoplasm within their cells seems to be often killed, 
as may be inferred from the surrounding fluid soon 
becoming pink. It is strange that allied acids act 
very differently : formic acid induces very slight 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 tartari<! 
acids produce no effect. 



274 DKOSEKA BOTUNDIFOLIA. Chap. XI. 

In the niutli 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 
large 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- 
copceia 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. XI. GENEKAL SDMMAET. 275 

ness of the leaves appears to be wholly confined to 
the glands and to the immediately underlying cells. 
It was further shown that the motor impulse and other 
forces or influences, proceeding from the glands when 
' excited, pass through the cellular tissue, and not along 
the fibro-vascular bundles. A gland sends its motor 
impulse with great rapidity down the pedicel of the 
same tentacle to the basal part which alone bends. The 
impulse, then passing onwards, spreads on all sides to 
the surrounding tentacles, first affecting those which 
stand nearest and then those farther off. But by, being 
thus spread out, and from the cells of the disc not 
being so much elongated as those of the tentacles, it 
loses force, and here travels much more slowly than 
down the pedicels. Owing also to the direction and 
form of the cells, it passes with greater ease and 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 DEOSEKA EOTUNDIFOLIA. Cbap. XI 

inflected ; though the inflection may last for many 



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 different 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 



ClUP. XI. GENERAL SUMMAET. 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 
rotundifolia ; and we see how little has been made out 
in comparison with what remains unexplained and 
anknown. 



278 DKOSEKA ANGLIOA. Ohap. Xli. 



CHAPTEE XII. 

On the Stkuctuhe and Movements of some othee Species oe 
Dboseka. 

Drosera angliea — Drosera intermedia — Drosera capensis — Drosera 
spaihulata — Drosera filiformii — Drosera binata — 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 antilica (Hudson).* — The leaves of this species, which 
was sent to me from Ireland, are much elongated, and gradually 
widen from the footstalk to the bluntly pointed apex. They 
stand almost erect, and their blades sometimes exceed 1 inch 
in length, whilst their breadth is only the | 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 inilected ; the basal 
portion being the chief seat of movement. Cutting or pricking 
the blade of the leaf did not excite any movement. They fre- 
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- 

ccUent account in ' The American gliea), of Drosera rotundifolia and 

N aturalist,' December 1873, p. 70.5, fiUfomds. 
oi Drosera longifolia (which is a 



Ch4I'. XII. DEOSEEA CAPENSIS. 279 

1 m. 30 s. ; and in 1 hr. 10 m. readied 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 anc/lua behave like 
those oi Drosera rotundifolia. 

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 anylica. 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, 
Blightly concave along the middle and taper towards the apex, 
19 



280 DEOSEEA SPATHULATA. OaiP. XIL 

wMclt is bluntly pointed and reflexed. They rise from an almost 
woody axis, and their greatest peculiarity consists in their 
foliaceous green footstalks, -wnich 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), containmg only 1,^^00 of a grain ('000562 mg.) of 
the salt. Fragments of flies were placed on two leaves near their 
tips, which became incurved in 15 hrs. A fly was also placed in 
the middle of the leaf ; in a few hours the tentacles on each side 
embraced it, and in 8 hrs. the whole leaf directly beneath the 
fly was a little bent transversely. By the next morning, after 
23 hrs., the leaf was curled so completely over that the apex 
rested on the upper end of the footstalk. In no case did the 
sides of the leaves become inflected. A crushed fly was placed 
on the foliaceous footstalk, but produced no effect. 

Drosera spathulata (sent to me by Dr. Hooker). — I made only a 
few observations on this Australian species, which has long, 
narrow leaves, gradually widening towards their tips. The 
glands of the extreme marginal tentacles are elongated and differ 
from the others, as in the case of Drosera rotundifolia. A fly was 
placed on a leaf, and in 18 hrs.- it was embraced by the adjoining 
tentacles. Gum-water dropped on several leaves produced no 
effect. A fragment of a leaf was immersed in a few drops of a 
solution of one part of carbonate of ammonia to 146 of water ; 
all the glands were instantly blackened ; the process of 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. Xn. DEOSEEA PILIFORMIS. 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 his. 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 jbut 
the apex of the leaf in none of my few trials was inflected. The 
above dose of the nitrate (viz. ^ 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 
Buch 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 little 
saliva, and the tentacles became incurved in under 1 hi"., 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 obfierved by Mrs. Treat. 

Drosera binata (or dicfiotoma). — I am much indebted to Ladj 



* ' American Naturalist,' Deo. 1873, p. 705. 



282 DEOSTSKA BINATA. Chap. Xlt 

Dorothy Nevill for a flue 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 particles 
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 placed on the glands in the 
medial furrow did not stimulate them suflBciently 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 ai-e 
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 nart of carbonate 



Chap. XU. deoseea 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 Dionsea and Drosophyllimi. In 
this latter genus they are associated, as in the present case, with 
glands which secrete spontaneously, that is, without being 
excited. 

Drosera binata presents another and more remarkable pecu- 
liarity, namely, the presence of a few tentacles on the backs o^ 
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 foixr 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 obvioTisly 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. Xlt 

moved towards the middle of tlie lower surface, for there are 
no viscid glands there by which insects can be caught. 
Although they have no power of movement, they are probably 
of some use by absorbing animal matter from any minute insect 
which may be caught by them, and by absorbing ammonia from 
the rain-water. But their varying presence and size, and their 
irregular position, indicate that they are not of much senica, 
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 progenitor of the 
genus Drosera ; and none of the tentacles of Drosophyllum, neither 
those on the upper nor lower surface of the leaves, are capable of 
movement when excited, though they capture numerous insects, 
which serve as nutriment. Therefore it seems that Drosera 
hmata 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. 



Gonduding Remarks. — From what we have now seen, 
there can be little doubt that most or probalily all the 
species of Drosera are adapted for catching insects by 
nearly the same means. Besides the two Australian 
species above described, it is said* that two other 
species from this country, namely Drosera pallida and 
Drosera sulfhv/rea, " 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. trinervis." Another Australian species, Drosera 
heterophylla (made by Lindley into a distinct genus, 
Sondera) is remarkable from its peculiarly shaped 
leaves, l3ui I know nothing of its power of catching 
insects, for I have seen only dried specimens. The 
leaves form minute flattened cups, with the footstalks 
attached not to one margin, but to the bottom. The 



' Gardener's Cliroiiicle,' 1874, p. 209. 



Chap. XII. CONCLUDING EEMAEKS. 285 

inner surface and the edges of the cups are studded 
with tentacles, which include fibro-vascular bundles, 
rather different from those seen by me in any other 
species ; for some of the vessels are barred and punc- 
tured, instead of being spiral. The glands secrete 
copiously, judging from the quantity of dried secretion 
adhering to them. 



286 DION^A MUSCIPULA. Chap. XIIL 



CHAPTEK XIII. 

DiONiEA MCSCIPULA. 

structure of the leaves — Sensitiveness of the filaments — Rapid 
movement of the lobes caused by irritation of the filaments — 
Glands, their power of secretion — Slow movement caused by the 
absorption of animal matter — Evidence of absorption from the 
aggregated condition of the glands — Digestive power of the 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 transmission of the motor 
impulse and mechanism of the movements — Be-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 Droseracese, 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, grows it, like an epiphytic 
orchid, in well-drained damp moss without any soil.t 
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 t ' Gardener's Chioniclu,' 1874. 

s^iiich have been published on p. 464. 



Chap. XHL 



STKUOTUKE 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 have 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 




FlO. 12. 

(BioncEa mtigcipula.'^ 

Leaf viewed laterally in its e\paiKli\l state. 



of spiral vessels enters. The spikes stand in such 
a position that, when the lobes close, they inter-lock 
like the teeth of a rat-trap. The midi-ib 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 DIOTSMA MUSCIPULA. Chaf. Xlll 

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 
papillas on the leaves of Drosera rotundifolia. There 
are also a few very minute, simple, pointed hairs, 
about ,aooo ('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 constriction, formed of broader cells, 
beneath which there is an articulation, supported on 
an enlarged base, consisting of differently shaped poly- 
gonal cells. As the filaments project at right angles 
to the surface of the leaf, they would have been 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. Kill. 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 yery 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 sufSciently 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 Dionaea and of 



290 DIONiEA MUSCIPULA. OuAr. XIIL 

the glands of Diosera evidently 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 yiscid 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 Dionsea are not viscid, and the capture of insects 
can be assured only by their sensitiveness to a 
momentary touch, followed by the rapid closure of 
the lobes. 

As just stated, the filaments are not glandular, and 
do not secrete. Nor have they the power of absorption, 
as may be inferred from drops of a solution of car- 
bonate of ammonia (one part to 146 of water), placed 
on two filaments, not producing any efi'ect 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 o£f 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. 
30 m. in a weaker solution of one part of the carbonate 
to 218 of water, and this caused aggregation in all 
the cells, commencing as before at the bases of the 
filaments. 

Long immersion of the filaments in distilled water 
likewise causes aggregation. Nor is it rare to find 
the contents of a few of the terminal cells in a 
spontaneously aggregated condition. The aggregated 



Chap. Xni. SENSITIVENESS OP FII A.MENTS. 29] 

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 Dionsea 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. 
A-gain, I blew many times through a fine pointed 
tube with my utmost force against the filaments 
without any effect; such blowing being received 



292 DIONiEA MUSCIPULA. CniJ>. XUI. 

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. 
Tt 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 tht 
result is probably due to a slight degree of exosmose. 



, Ihap. 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-expand in less 
than a day. On the other hand, of the three leaves 
which were immersed for a short time in the solution, 
and were then washed by means of a syringe inserted 



294 DION^A 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 difierent, as we 



Chap. XIU. SECEETION AND ABSORPTION. 295 

shall presently see, if nitrogenous organic bodies which 
are at all damp, are left on the lobes ; for thes(; 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 thfe 
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. 
20 



296 mON^A MUSCIPUIA. Chap. XIII. 

As in this case the glands on both sides are pressed 
against the meat or insect, the secretion from the first 
is twice as great as when a bit of meat is laid on the 
surface of one lobe ; and as the two lobes come into 
almost close contact, the secretion, containing dis- 
solved animal matter, spreads by capillary attraction, 
causing fresh glands on both sides to begin secreting 
in a continually widening circle. The secretion is 
almost colourless, slightly mucilaginous, and, judging 
by the manner in which it coloured litmus paper, 
more strongly acid than that of Drosera. It is so 
copious that on one occasion, when a leaf was cut 
open, on which a small cube of albumen had been 
placed 45 hrs. before, drops rolled off the leaf. On 
another occasion, in which a leaf with an enclosed bit 
of roast meat spontaneously opened after eight days, 
there was so much secretion in the furrow over the 
midrib that it trickled down. A large crushed fly 
(Tipula) was placed on a leaf from which a small 
portion at the base of one lobe had previously been 
cut away, so that an opening was left ; and through 
this, the secretion continued to run down the footstalk 
during nine days, — that is, for as long a time as it was 
observed. By forcing up one of the lobes, I was able 
to see some distance between them, and all the glands 
within sight were secreting freely. 

We have seen that inorganic and non-nitrogenous 
objects placed on the leaves do not excite any move- 
ment ; but nitrogenous bodies, if in the least degree 
damp, cause after several hours the lobes to close 
slowly. Thus bits of quite dry meat and gelatine were 
placed at opposite ends of the same leaf, and in the 
course of 24 hrs. excited neither secretion nor move- 
ment. They were then dipped in water, their sur- 
faces dried on blotting paper, and replaced on the same 



Chap. Xm. SECRETION AND ABSOEPTION. 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. XIIL 

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 leaTes, 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. We shall see 
its importance when we treat of the manner in which 
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. SECRETION A.ND ABSOEPTION. 299 

certain cases, this latter stimulus is the more powerful 
of the two. Ou three occasions leaves were found 
which from some cause were torpid, so that their lobes 
closed only slightly, however much their filaments 
were irritated ; but on inserting crushed insects 
between the lobes, they became in a day closely shut. 
The facts just given plainly show that the glands 
have the power of absorption, for otherwise it is 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, sufSces to 
produce these two effects. It seems hardly credible, 
and yet it is certainly a fact, that a bit of hard-boiled 
white of egg, first thoroughly dried, then soaked 
for some minutes in water and rolled on blotting 
paper, should yield in a few hours enough animal 
matter to the glands to cause them to 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 DIONJEA MUSCIPULA, Chaf XUI. 

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 leafj which was then cut open. The 
whole surface was bathed with acid secretion, and 
every cell in the many glands which were examined 
had its contents aggregated in a beautiful manner 
into dark or pale purple, or colourless globular 
masses of protoplasm. These underwent incessant 
slow changes of forms ; sometimes separating from 
one another and then reuniting, exactly as in the 
cells of Drosera. Boiling water makes the contents 
of the gland-cells white and opaque, but not so 
purely white and porcelain-like as in the case of 
Drosera. How living insects, when naturally caught, 
excite the glands to secrete so quickly as they do, I 
know not; but I suppose that the great pressure to 
which they are subjected forces a little excretion 
from either extremity of their bodies, and we have 
seen that an extremely small amount of nitrogenous 
matter is sufficient to excite the glands. 

Before passing on to the subject of digestion, I may 
state that I endeavoured to discover, with no success, 
the functions of the minute octofld processes with 
which the leaves are studded. From facts hereafter to 
be given in the chapters on Aldrovanda and Utrieu- 
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 than in other speci- 



Ciiii'. 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 whether they absorbed the vapour, 
but their contents were not affected. 

Digestive Power of the Secretion.*— When a leaf closes 
over any object, it may be said to form itself into a 
temporary stomach ; and if the object yields ever so 
little animal matter, this serves, to use SchifPs 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 Dionaea, 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. 



Expenment 1. — A cube of albumen of Jg of an inch (2-540 
mm.) was placed at one end of a leaf, and at the other end 
an oblong piece of gelatine, i 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 oases the 

indebted for information regard- glands do not secrete. The Rev. 

ing Dionrea 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 secretioo from the glands. I 

18t>8, some interesting observa- may here add tliat a gardener, 

tions. He ascertained that the Mr. Knight, is said (Kirby and 

secretion digests animal matter, Spencer's 'Introduction to Ento- 

such £is the contents of insects, mology,' 1818, vol. i. p. 295) to 

bits of meat, &c. ; and that the have foimd that a plant of the 

secretion is reabsorbed. He was Dionssa, 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 luximaut 

time when in contact with animal in its growth than otlicrs not so 

matter than when made to shut treated." 
by a mere touch, or over objects 



302 DION^A MUSCIPULA. Chap. XUI 

1^ broad ; the leaf was then made to close. It was cut open 
after 45 hrs. The albumen was hard and compressed, with 
its angles only a little rounded ; the gelatine was corroded into 
an oval form ; and both were bathed in so much acid secretion 
that it dropped off the leaf The digestive process apparently 
is rather slower than in Urosera, and this agrees with the length 
of time during which the leaves remain closed over digestible 
objects. 

Experiment 2. — A bit of albumen -^ of an inch square, but 
only Jg 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. 

Kxperimeiit 3. — A piece of albumen -^ of 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. 

Experimeni 4. — Pieces of albumen and gelatine, of the same 
size as in the last experiment, were placed on a leaf, which 
spontaneously opened after twelve days, and here again not a 
vestige of either was left, and only a little secretion at one end 
of the midrib. 

Experiment 5. — Pieces of albumen and gelatine of the same 
size were placed on another leaf, which after twelve days was 
still firmly closed, but had begun to wither ; it was cut open, 
and contained nothing except a vestige of brown matter where 
the albumen had lain. 

Experiment 6. — A cube of albumen of -^ of an inch and a 
piece of gelatine of the same size as before were placed on a 
It-af, 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. XTT T. 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. 

Eayperiment 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^ 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 -^ 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 tricliled 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 iibrillse in the middle 
stOl exhibite .1 transverse striae; others showed not a vestige 
of strise; 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 the 
opposite end of the same leaf, a firmly compressed pellet of 
bread had been placed ; this was completely disintegrated, I 
suppose, owing to the digestion of the gluten, but seemed veiy 
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 spoutaneously 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. 

Exprriment 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 drop of transparent, not acid, viscid 
fluid. 

Exi erimcnt 12. — Same experiment as the two last, and here 
again the leaf at the end enclosing the cheese opened before the 



304 DION^A MUSCIFULA. CiUP. XIH 

opposite end with the albumen ; bnt no farther observations 
were made. 

Experiment 13. — A globule of chemically prepared casein, 
about Jjj 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 suiEcient 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 (3-549 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 hrs. the leaf appeared as if burnt, and soon 
died. 

Two leaves were exposed for 30 m. in a 2-oz. vessel to the 
vapour of 30 minims (r774 ml.) of sulphuric ether. One leaf 
c]osed 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 
wore now quite insensible. After 24 hrs. this leaf recovered 
its sensibility, but was still rather torpid. A leaf exposed 
in a large bottle for only 3 m. to ten drops was rendered 
insensible. After 52 m. it recovered its sensibility, and when 
one of the filaments was touched, the lobes closed. It begaD 



Ohap. xiii. manner of captueing 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 sensitive filaments or on the leaf itself, I do not 
know. 

Cyanide of potassium, when left in a bottle, generates prussic 
or hydrocyanic acid. A leaf was exposed for 1 hr. 35 m. to the 
vapour thus formed; and the glands became within this time 
so colourless and shrunken as to be scarcely visible, and I at 
first thought that they had all dropped off. The leaf was not 
rendered insensible; for as soon as one of the filaments was 
touched it closed. It had, however, suffered, for it did not 
reopen until nearly two days had passed, and was not even 
then in the least sensitive. After an additional day it recovered 
its powers, and closed on being touched and subsequently re- 
opened. Another leaf behaved in nearly the same manner after 
a shorter exposure to this vapour. 



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 becomiiig curved. This move- 



306 DION^A MUSCIPULA. Chap. XHL 

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 to occupy a position almost at right angles to 
that which it would have held had the opposite lobe 
been present. 

From the curving inwards of the two lobes, as they 
move towards each other, the straight marginal spikes 
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 completely 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. XIII. MANNEE 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. Curtis, in 'Boston Joxirnal of Nat. Hist 
vol. i. 1837, p. 123. 



308 DION^A MUSCIPULA. Chap. XIIX 

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 exclusiTely 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. Xm. MANNER OF CAPTUEING 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 1 do not know. It should, however, be 
added that in two instances in which very small 
insects had been naturally caught the leaf opened 
as quickly as if nothing had been caught ; and I 
suppose that this was due to such small insects not 
having been crushed or not having excreted any 
animal matter, so that the glands were not excited. 
Small angular bits of albumen and gelatine were 
placed at both ends of three leaves, two of which 
remained closed for thirteen and the other for twelve 
days. Two other leaves remained closed over bits of 



310 DIOKJiiA MUSCIPTTLA. Chap. XEO. 

meat for eluven days, a third leaf for eight days, and 
a fourth (but this had been cracked and injured) for 
only six days. Bits of cheese, or casein, were placed 
at one end and' albumen at the other end of three 
leaves; and the ends with the former opened after 
six, eight, and nine days, whilst the opposite ends 
opened a little later. None of the above bits of meat, 
albumen, &c., exceeded a cube of -jL. 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. Cxenerally 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 opened 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, an:l when one of its filaments was 
touched, closed, though rather slowly. Dr. Canby, 



Chap. Xm. MANNER OF CAPTUEING INSECTS. 311 

who observed in the United States a large number of 
plants which, although not in their uative 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 Dionaea 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 featui-e 
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 -^-^ 
to the -rV 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 

SI 



312 mON^.A iffUSCtPULA. Ohap, xiil 

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 bars 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 {Macrodaetylus subspi- 
nosus) in the United States. Now 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 be 
far better for the plant to wait for a time until a 
moderately large insect was captured, and to allow all 
the little ones to escape ; and this advantage is 
secured by the slowly 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 grown to their full size, 
and sent me fourteen leaves, containing naturally 
captured insects. Four of these had caught rather 
small insects, viz. three of them ants, and the fourth 
a rather small fly, but the other ten had all caught 
large insects, namely, five elaters, two chrysomelas, 
a curculio, a thick and broad spider, and a scolo- 
pendra. Out of these ten irsects, no less than eight 



3hap. XIII. TRANSMISSION OP MOTOR IMPULSE. 313 

were beetles,* and out of tlie 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 Impube, and Means 
of Movement. — It is sufficient 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 Dionsea, the course of these 
vessels (composed of spiral and ordinary vascular 



» Dr. Canby remarks (' Gar- as elaters, for the five which I 
dener's Monthly,' August 1868), examined were in an exb 



"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. 
feast with respect to such beetles 



314 DIONiEA MUSCIPULA. Chap. XIH 

tissue) seems at first sight to favour this belief; for 
they run up the midi-ib 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 -jL 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 which i» 



Ohap. XIU. TEANSMISSION of MOTOB IMPULbiC. 315 

touched towards tlie 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 filameut. 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 thS 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 dionjEA muscipula. Chap. xiii. 

is transmitted in like manner in all directions through 
the cellular tissue ; but that its rate is largely governed 
by the length of the cells and the direction of their 
longer axes, rhin sections of a leaf of Dionsea 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 touched moved, but in three other 
cases the opposite lobe alone moved ; so that an injury 
which was sufficient to prevent a lobe moving did not 
prevent the transmission from it of a stimulus which 
excited the opposite lobe to move. We thus also 
learn that, although normally both lobes move 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 be seen on any part of their uppei 



Chap. Xin. TRANSMISSION OF MOTOE IMPULSE. 317 

surfaces. It appears therefore that the cells must con- 
tract. The chief seat of the movement is evid^intly 
in the thick mass of cells which overlies the central 
bundle of vessels in the midrib. To ascertain whether 
this part contracts, a leaf was fastened on the stage of 
the microscope in such a manner that the two lobes 
could not become quite shut, and having made two 
minute black dots on the midrib, in a transverse line 
and a little towards one side, they were found by the 
micrometer to be -two oi 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 -rwo of an inch apart, 
so that a small portion of the upper surface of the 
midrib had contracted in a transverse line two of ^^ 
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 -rrs-o of an inch, so that the 
f wo extreme dots were t-|-§-o 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 
■ ', il'o I of an inch, and the two further dots by t-jw of 
an inch, than they were before ; so that the two extreme 



318 DION^A MUSCIPULA. Chap. XIIL 

dots now stood about two oi an inch (•127 mm.) 
nearer together than before. If we suppose the whole 
upper surface of the lobe, which was -rrrV o^ ^^ iiich 
in breadth, to have contracted in the same proportion, 
the total contraction will have amounted to about 
, '^ •; „ or tV 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 Be-expansion of the Leaves. — This is effected at an 
insensibly slow rate, whether or not any object is 
enclosed.f 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 on-^ 
lobe were cut off close to their bases ; and the three 



' ' Proo. Koyal Soc' vol. xxi. influence of the sun ; these at- 

p. 495 ; and lecture at the Koyal tempts consisted in an undula- 

Institution, June 5, 1874, given in tory motion of the marginal cilise, 

' Nature,' 1874, pp. 105 and 127. accompanied by a partial open- 

t Nuttall, iu his ' Gen. Arae- ing and succeeding collapse o( 

rican Plants,' p. 277 (note), says the lamina, which at length ter- 

tliat, whilst collectirg this plant minated in a complete expansion 

in its native home, " I had oooa- and in the destruction of sensi' 

sion to observe that a detached bility." I am indebted to Prof, 

leaf would make repeated efforts Oliver for this reference ; but I d« 

tov/ards disclosing itself to the not understand what took place. 



Okap. XIII. EE-EXPANSION. 319 

leaves thus treated re-expanded, — one to a partial ex- 
tent in 24 hrs., — 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 
Segin 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 filamenta 



320 DION^A MUSCIPULA. Chap. XUT. 

must have been equally affected ; and I can under- 
stand the divergence of the lobes only by supposing 
that the cells on the lower side, owing to their state of 
tension, acted mechanically and thus suddenly drew 
the lobes a little apart, as soon as the cells on the 
upper surface were killed and lost their contractile 
power. We have seen that boiling water in like 
manner causes the tentacles of Drosera to curve 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.xtv. aldbovanda vesiculosa. 321 



OHAPTEE XIV. 

Aldkovanda vesiculosa. 

Captures crustaceans — Structure of the leaves in comparison with 
those of Dionuea — Absorption by the glands, by the quadrifld pro- 
cesses, and points on the iafolded margins — Aldrovanda vesieulosa, 
var. australia — Captures prey — Absorption of animal matter — 
Aldrovanda vesiculosa, var. verticillata — Concluding remarks. 

This plant may be called a miniature aquatic 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 larvee.t Plants which had been kept 
in filtered water were placed by him in a vessel con- 



* Since his original publication, chioccioline are fresh-water niol- 

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. Soo. de France,' in digestive secretion. 

1861. Delpino states in a paper t I am greatly indebted to this 

published in 1871 ('Nuovo (jior- distinguished naturalist for haring 

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 6 di altri animalcoli aequa- tion in his ' Beitriige zur Biologie 

tioi" are caught and suffocated der Pflanzen,' drittes Heft, 1875, 

by the leaves. I presume that p. 71. 



322 ALDKOVANDA VESICULOSA. Chap. XIV, 

taiiiiug numerous crustaceans of the genus Cypris, and 
next morning many were found imprisoned and alive, 
still swimming about within the closed leaves, but 
doomed to certain death. 

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, djrawn 
by my son Francis. I will, however, append a few 
remarks on the differences between this plant and 
Dionaea. 

Aldrovanda is destitute of roots and floats freely in 
the water. The loaves 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 Dionaea ; 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 papillae, evidently 
answering to the eight-rayed papillae of Dionaea. 

Each lobe rather exceeds a semi-circle in convexity, 
iind 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 

oal nature of these projections scale-like bodies found at the 

Dr. Nitsehl^e (■ Bot. Zeitung, bases of the petioles of Drosera. 



Chap. XrV'. ALDEOVANDA VESICULOSA. 323 

is slightly concave, and is formed, according to Colin, 
of three layers of cells. Its upper surface is studded 
with colourless glands like, but more simple than, 
those of Dionsea; they are supported on distinct 
footstalks, consisting of two rows of cells. The outer 





Fig. 13. 
{Aldrovanda vesieuUisa.) 
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 quadrifid processes, each consisting of 
four tapering projections, which rise from a common 



324 ALDEOVANDA VESICULOSA. Chap. XIV. 

promineuce. 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 Rubus. 
As the rim is infolded, these points are directed 
towards the midrib, and they appear at first as if they 
were adapted to prevent the escape of prey ; but this 
can hardly be their chief function, for they are 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 Dioneea; nor can the points on 
the rim be considered as homologous with the spikes 
round the leaves of Dionsea, 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 Dionaea 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 diu-ing 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 examiued 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 dissolve's 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 rnay 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 ALDEOVANDA VESICULOSA. Chap. XIV 

already soluble animal matter. The included water 
would thus be pressed out, and the secretion conse- 
quently not be too much diluted to act. With respect 
to the quadrifld 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 were 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 
quadrifld 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 outei 



Chap. XrV. ALDEOVANDA 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 diiferent 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 
23 



328 ALDEOVANDA VESICULOSA. Chat. XIV 

agrees with what I have observed under similar cir- 
stances with Utricularia. 

Aldrovanda vesiculosa, var. australis. — Dried leaves of 
this plant from Queensland in Australia were sent 
me by Prof. Oliver from the herbarium at Kew. 
Whether it ought to be considered as a distinct species 
or a variety, cannot be told until the flowers are 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 tibiae 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- 
aous integuments were as clean as if they had been 



Chap. XIV. ALIiEOVANDA VESICULOSA. 329 

boiled in caustic potash; so that it must hare been 
enclosed for a considerable time. The glands were 
browner and more opaque than those on other leaves 
which had caught nothing; and the quadrifld pro- 
copses, from being partly filled with brown granular 
■/imtter, 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 quadrifld 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 Algae, 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. verticiUata. — 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 ALDKOVANDA VESICULOSA. Chap. XIV. 

upcTirred 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 Remarks. — 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 Dionsea, 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 EEMAEKS. 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 DBOSOPHYLIitJM LUSITANiOUM. Chap XV 



CHAPTEK XV. 

DkOSOPHTLWJM ^ EOEIDCLA — -BtBLIS — GlANDTJLAB HjUBb OP OTHEB 

Plants — Conoludinq Eemabks on the DBosEBAOBa;. 

DroBophyllum — Structure of leaves — ^ Nature of the secretion — Man- 
ner of catching insects — Power of absorption — Digestion of animal 
substances — Summary on Drosophyllum — Eoridula — Byblis — 
Glandular hairs of other plants, their power of absorption — Saxi- 
fraga — Primula — Pelargonium — Erica — Mirabilis — Niootiana 
— Summary on glandular hairs — Concluding remarks on the Dro- 



Deosophtllum LUSITANIOUM. — This rare plant has 
been found only in Portugal, and, as I hear from 
Dr. Hooker, in Morocco. I obtained living specimens 
through the great kindness of Mr. W. C. Tait, and 
afterwards from Mr. G. Maw and Dr. Moore. Mr. Tait 
informs me that it grows plentifully on the sides of 
dry hills near Oporto, and that vast numbers of flies 
adhere to the leaves. This latter fact is well known 
to the villagers, who call the plant the " fly-catcher," 
and hang it up in their cottages for this purpose. A 
plant in my hot-house caught so many insects during 
the early part of April, although the weather was 
cold and insects scarce, that it must have been in 
some manner strongly attractive to theni. 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 Droseracese. 
The leaves arise from an almost woody axis; thev 



Chap. XV. 



STRUCTURE OF LEAVES. 



333 



are linear, much 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 
glands, having the same general 
appearance, are found on the flower- 
peduncles and calyx. 

Besides the glands which are borne 
on longer or shorter pedicels, there 
are numerous ones, both on the upper 
and lower surfaces of the leaves, so 
small as to be scarcely visible to the 
naked eye. They are colourless and 
almost sessile, either circular or oval 
in outline ; the latter occurring chiefly 
on the backs of the leaves (fig. 14). 
Internally they have exactly the same structure as 
the larger glands which are supported on pedicels ; 




Fig. 11. 

{DrosQphyllum lusi- 
tamicwm.) 

Part of leaf, enlargeii 
seven times, show- 
ing lower sulfa e. 



334 DEOSOPHYLLUM 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 withdrawiag the 



Chap. XV. SECEETION. 335 

aeedle, the drop is generally withdrawn ; whereas with 
Drosera there is no such difficulty, though the drops 
are occasionally withdrawn. From this peculiarity, 
when a small insect alights on a leaf of Drosophyllum, 
the drops adhere to its wings, feet, or body, and are 
drawn from the gland ; the insect then crawls onward 
and other drops adhere to it ; so that at last, bathed 
by the viscid secretion, it sinks down and dies, resting 
on the small sessile glands with which the surface of 
the leaf is thickly covered. In the case of Drosera, 
an insect sticking to one or more of the exterior 
glands is carried by their movement to the centre of 
the leaf; with Drosophyllum, this is effected by the 
crawling of the insect, as from its wings being clogged 
by the secretion it cannot iiy 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 DROSOPHTLLUM Ll-glTANICUM. 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 -^ oi 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 -ji glycerine, and as the cartilage had been 
soaked in water, I suspect that these substances must 



Chap. XV. ABSOEPTION. 337 

hsive 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 drop of a solution of nitrate of 
ammonia was distributed, and which became dry after 
2 hrs., were beginning to re-secrete after only 12 addi- 
tional hours. 

Tentacles Incapable 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 tentacles became 
at all inflected. We may therefore conclude that 
they are incapable of movement. 

On. the Power of Absorption possessed by the Glands. — 
It has already been indirectly shown that the glands 
on pedicels absorb animal matter ; and this is furth*."- 
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 DKOSOPHYLLUM LUSITANICUM. Chap. XV. 

pedicels and to the minute sessile ones. Before a 
gland has 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 iii a little solution 
of one part of carbonate of ammonia to 146 of water (c 
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 ol 
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 efiective on Droso- 
phyllum, for the glands were only slightly darkened 
by an immersion of 1 hr. 20 m., but became decidedly 
darker after 3 hrs. Leaves which had been left for 
7 hrs. in an infusion of raw meat or in saliva were 
placed in the solution of carbonate of ammonia, and 
the glands now 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 ^vhen 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; theii- 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 
•juite 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. Tliey 



Chap.xv. concluding eemaeks. 841 

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 with limpid fluid. It 
thus appears that Drosophyllum digests albumen 
and fibrin rather more quickly than Drosera can ; 
and this may perhaps be attributed to the acid, 
together probably with some small amount of the 
ferment, being present in the secretion, before the 
glands have been stimulated ; so that digestion begins 
at once. 

Goneluding Bemarks. — 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 hinata, and appear to be represented by the 
papillse on the leaves of Drosera rotundifolia. Secondly, 
the presence of tentacles on the backs of the leaves ; 
but we have seen that a few tentacles, irregularly placed 
and tending towards abortion, are retained on the 
backs of the leaves of Drosera hinata. There are 
greater differences 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 EOEIDULA. 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. 



KOBIDULA. 

Boridula dentata. — This plant, a native of the -western 
parts of the Cape of Good Hope, was sent to me in a 
dried state from Kew. It has an almost woody stem 
and branches, and apparently grows to a height of 
some feet. The leaves are linear, with their summits 
much attenuated. Their upper and lower surfaces 
are concave, with a ridge in the middle, and both are 
covered with tentacles, which differ greatly in length ; 
some being very long, especially those 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, Eoridula resembles its northern representative, 
Drosophyllum. 

Byblis. 

Byhlis 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 
S3 



344 GLANDULAE HAIES, Ohap. 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. 

Supplementary 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, ' Tvaite de Bot.' 3rd edit. 1874, p. 1020. 



Chap. XV. THEIE POWER OF ABSORPTION. 345 

the species of Droseracese absorb various fluids or 
at least allow them 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 Droseraceae. 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 Droseracese 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. 

S ixi/raga umhrosa. — 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 
Bometimes pink. The glands secrete a yellowish viscid fluid, by 



* The distinction between true clearly understood : see Miiller's 
absorption and mere permeation, ' Physiology,' Eng. translat. 1838 
or imbiliition, is by no means vol. i. p. 280. 



846 GLANDULAR HAIRS, Ohap. XV 

which mimite 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 protoplasi^ 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) 
BO as to remain immersed for 23 hrs. 30 m. in a strong infusion 
of raw meat. The colour of the contents of the glands was 
slightly changed, being now of a duller and more purple tint 
than before. The contents also appeared more aggregated, for 
the spaces between the little masses of protoplasm were wider ; 
but this latter result did not follow in some other and similar 
experiments. The masses seemed to change their forms more 
rapidly than did those in water ; so that the cells had a 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 
were discoloured in exactly the same manner as by the infusion 
of raw meat. 

Another flower-stem was immersed, as before, in a solution of 
one part 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 purple, some of them blackish- 



* In the case of Saxifraga tri- stance remnants of insects ad- 

daeiyUtes, Mr. Druoe says (' Phar- liered to the leaves. So it is, as 

maoeutioal Journal,' M.iy lt<75) I hear from a friend, with this 

that he examined some dozens of plant in Ireland, 
pltinte, and in almost eveiy in- 



Chap. XV. THEIE POWER OF ABSORPTION. 347 

green, a few being still unaffected. The little masses of proto- 
plasm within the cells were seen in movement. The cells of the 
pedicels were unaltered. The experiment was repeated, and a 
fresh flower-stem was left for 23 hrs. in the solution, and now a 
great effect was produced ; all the glands were much blackened, 
and the previously transparent fluid in the cells of the pedicels, 
even down to their bases, contained spherical masses of granular 
matter. By comparing many different hairs, it was evident that 
the glands first absorb the carbonate, and that the effect thus 
produced travels down the hairs from cell to cell. The first 
change which could be observed is a cloudy appearance in the 
fluid, due to the formation of very fine granules, which 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 of the 
pedicels were seen to contain only colourless transparent fluid ; 
those of the glands including as usual some granular matter. 
These strips were then immersed in the same solution as before 
(one part of the carbonate to 109 of water), and in a few 
minutes granular matter appeared in the lower cells of all the 
pedicels. The action invariably commenced (for I tried the 
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 ; thepe were 
examined after 23 hrs., as were others, which had apparently 
not long before caught minute flics; but they did not present any 



348 GLANDULAK HAIKS, 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 captui-e. 

Siixifriga 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 thau do those of Saxifraga umbrnsa, 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 upper 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. 'AQ 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 



OHAt. XV. THEIE POWER OF ABSORPTION. 349 

of i,he twenty-flve 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. 
Ijooking to all thirty-four hairs, there could be no doubt that 
the glands had absorbed some uf 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 mas-ses 
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 lir. 
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 tjie 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 spherical 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 lew 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 theii- forms must have consisted of 
living protoplasm, there is nothing surjirising 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 HAIES, 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. AH 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 
sealing-wax, and was then placed ui der 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 aggregated matter in the glands ; and 
some of the masses showed signs of breaking up into brown 
granular matter. This leaf was again placed in the vapour, 
so that it was exposed altogether for 5 hrs. 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 thxis 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 zonaU (var. edged with wliife). — The leaves 



Chap. XV. THEIB POWER OF ABSOEPTION. 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 bo seen in some of the uppermost 
cells of the pedicels, and the protoplasmic lining was slightly 
separated from the walls of the lower cells. After 2 hrs. 30 m. 
from the time of first immersion, the large globules within 
the glands of the longer hairs were converted into masses of 
darker brown granular matter. Hence from what we have seen 
with Primula sinensis, there can be little doubt that . these 
masses originally consisted of living protoplasm. 

A drop of a weak infusion of raw meat was placed on a leaf, 
and after 2 hrs. 30 m. many spheres could be seen within the 
glands. These spheres, when looked at again after 30 m., had 
slightly changed their positions and forms, and one had 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 
tlie hairs were then compared, but they differed very little or 
not at all. In both cases the contents of the cells seemed rather 
more grau'ilar 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 



352 GLANDULAE HAIKS, OhAP. 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 beeii due to exosmose, as the infusion was strong. 
We may, therefore, conclude that the glands of this plant either 
have no power of absorption of 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 trisd with more care, as M. Schloosing 



Chap. XV. THEIR PCtWEE OF ABSOEPTION. 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 Observations on Glandular Hairs. — 
From the foregoing observations, few as they are, we 
see that the glands of two species of Saxifraga, of a 
Primula and 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. 



Is given 



Comptee rendus,' June 15, 1S74. A good abstract of this papei 
en in the 'Gardener's Chronicle,' July H, 1874. 



354 GLANDULAR 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 
Primida sinensis quickly absorb a solution of the 
carbonate of ammonia, and the protoplasm which they 
contain becomes aggregated. The process was seen 
in some cases to travel from the glands into the upper 
cells of the pedicels. Exposure for 10 m. to the 
vapour of this salt likewise induced aggregation. 
When leaves were left from 6 hrs. to 7 hrs. in a strong 
solution, or were long exposed to the vapour, the little 
masses of protoplasm became disintegrated, brown, and 
granular, and were apparently killed. An infusion of 
raw meat produced no effect on the glands. 

The limpid contents of the glands of Pelargonium 
zonaJe 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 
fiiiS 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, tliis 



Chap. XV. DEOSEEACEiE. 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 Eemaeks on the Deoseeace^. 

The. six known genera composing this, family have 
now been described in relation to our present subject, 
as far as my means have permitted. They all capture 
insects. This is effected by Drosophyllum, Roridula, 
and Byblis, solely by the viscid fluid secreted from 
their glands ; by Drosera, through the same means, 
together with the movements of the tentacles ; by 
Dionsea and Aldrovanda, through the closing of the 
blades of the leaf. In these two last genera rapid 



* My sou Francis counted the planimeter to be 39285 square 

hail's on a space measured by iuohes ; 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 ilower-stems) must have borne 

of a leaf, and 30,035 on the lower the astonishing number of 

surface ; that is, in about the pro- 2,56S,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 surfaces there were spring i 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 op." 

larger ones being a little more fom-th broader and longer .uan 

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 

D6mg included;, was found by a millions. 



356 CONCLUDING EEMARKS Chap. XT 

movement makes up for the loss of Tiscid 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 Eoridula 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 Droseracese) 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 othei 
animals by their mouths, for they are destitute of an 



Chap. XV. ON THE DEOSEEACE^. 357 

alimentary canal ; but they liye 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,t 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. Dionsea 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 Morocco. Eoridula and Byblis each have (as I 



* Fritz Miiller, ' Facts for Dar- condition, for it has root lite pro- 
win,' Eng. trans. 1869, p. 139. Tlie cesses embedded in the skin of the 
rhizooephalous crustaceans are shark on which it is parasitic, and 
allied to the oirripedes. It is hardly its prehensile cirri and mouth (as 
possible to imagine a greater dif- described in my monograph on 
ferenoe than that between an aui- the Lepadidae, "Ray Soc' 1851, 
mal with prehensile limbs, a well- p. 169) axe in a most feeble and 
constructed mouth and alimentary almost rudimentary condition, 
canal, and one destitute of all Dr. K. Kossmann has given a very 
these organs and feeding by ab- interesting discussion on this 
sorption through branching root- subject in his ' Suctoria and Le- 
like processes. If one rare oii-ri- padidse,' 1873. See also, Dr. 
jieAe,the Anelasmaxcjualicola, had Dohrn, ' Der Ursprung der Wir- 
become extinct, it woul I have belthiere,' 1875, p. 77. 
been very difficult to conjecture f Bentham and Hooker, ' Genera 
how so enormous a change could Plantariin;.' Australia is the me- 
have been gi-adually effected. tropolis of the genus, forty-one 
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. 



358 CONCLUDING EEMAEKS ChAP. XV. 

hear from Prof. Oliver) two species ; the former con- 
fined to the western parts of the Cape of G-ood Hope, 
and the latter to Australia. It is a strange fact that 
Dionaea, 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 Dionaea 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 nidimentary parts 
in the six genera, we are led to infer that their common 
parent form partook of the characters of Drosophyllum, 
Roridula, and Byblis. The leaves of this ancient form 
were almost certainly linear, perhaps divided, and bore 
on their upper and lower surfaces glands which had 
the power of secreting and absorbing. Some of these 
glands were mounted on pedicels, and others were 
almost sessile ; the latter secreting only when stimu- 
lated by the absorption of nitrogenous matter. In 
Byblis the glands consist of a single layer of cells, 
supported on a unicellular pedicel ; in Eoridula 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 known of a trichome having such 



Chap. XV. ON THE DKOSEKACE^. 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.f 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. Eoridula, 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 
of movement, we must further assume, either that 
through the principle of correlated development this 



* Sachs, ' Traite cle Botanique,' hagut, 1 87:-!, p. 6. ' Extrait des 

3rd edit. 1874, p. 11126. Vldeiiskabelifre Meddelelser de 

t Dr. Wai-minir. • Sur la Diffe- la iroc. d' Hist. nat. de Copen 

sencc en tro les Trie homes,' Copen- hagiie,' Nos. 10-12, 1872. 

24 



360 CONCLUDING EEMAEKS Chap. XV. 

power was transferred to the basal parts of the 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, Roridula, and Byblis, which appear to have 
retained a primordial condition, still bear glandular 
hairs on both surfaces of their leaves ; but those on 
the lower surface have since disappeared in the more 
highly developed genera, with the partial exception 
of one species, Drosera 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 papillas. Drosera 
hinata, 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 Dionsea and Aldrovanda seems to 
have been closely allied to Drosera, and to have had 
rounded leaves, supported on distinct footstalks, and 
furnished with tentacles all round the circumference, 
with other tentacles and sessile glands on the upper 
surface. I think so because the marginal spikes of 
Dionsea 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 DBOSEKACE^. 361 

tentacles of Drosera, with their glands aborted, but their 
sensitiveness retained. Under this point of view we 
should bear in mind that the summits of the tentacles 
of Drosera, close beneath the glands, are sensitive. 

The three most remarkable characters possessed by 
the several members of the Droseracese 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 
which they must receive small quantities from the rain. 
This is the case with two species 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 Droseracese have probably inherited this power 
from a common progenitor, but this cannot apply to 



362 CONCLUDING EEMAEKS Chap. XV. 

Pinguicula or Nepenthes, for tHese plants are not at all 
closely related to the Droseracese. 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.f Now, in the case of 
plaats 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 



* 'Traitd de Botaniqiie,' 3rd Berlin, 1874, p. 1478), who, with 

edit. 1874, p. 844. See also for the aid of Dr. H. Will, has ao- 

foUowing facts pp. 64, 76, 828, tually made the discovery that the 

8:^l. seeds of the vetch contain a fer- 

t Since this sentence was writ- meut, which, when extracted by 

ten, I have reseived a paper by glycerine, dissolves albuminous 

Gorup-Besanez ('Beriohte der substances, such as fibrin, and 

Deutschen Chem. Gese.'eohaft,' converts them into true peptones 



Chap. XV. ON THE DEOhBEACE^. 363 

growing in yery 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 independent^ ■lioquired this same power. 

As there exist sever^ 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 Droseracese, 
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 REMARKS 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 readUy acquired. Such movements imply irri- 
tability or sensitiveness, but, as Cphn has remarked,* 
the tissues of the plants thus eudd^ed 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 
would have followed from the effects of camphor 
alone. So again with Dionsea, 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 difficulty 
than that presented by tne similar but feebler powers 
of a multitude of other plants. 



* See the abstract of his me- Mag. of Nat. Hist.' 3rd series, 
mnir on the contractile tissues vol. xi. p. 188. 
of plants, in the ' Annals and 



Chap. XV. ON THE DEOSEEACE^. 365 

Tlie specialised nature of the sensitiveness possessed 
by Drosera and Dionaa, 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 
Dionaea 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 Dionsea 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 Dionaea 
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 OONOLUDING KEMAKKS Ohap. 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. Cf^ THE DEOSEEACE^. 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 stori tbem up and repro- 
duce them. 



368 PINGUICULA VULGARIS. Chap. XVL 



CHAPTEE XVI. 

PiNGUIOrLA. 

Finguicttla vulgaris — Structure of leaves — Number of insects and 
other objects caught — Movement of the margins of the leaves — 
Uses of this movement — Secretion, digestion, and absorption — 
Action of the secretion on various animal and vegetable substances 
— The eifeots of substances not containing soluble nitrogenous 
matter on the glands — Pinguicula grandiflora — Pinguioula lusi- 
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 1^ 
inch in length and | inch in breadth. The young 
central leaves are deeply concave, and project upwards ; 
the older ones towards the outside are flat or convex, 
and lie close to the ground, 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- 
ing 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 



ClaAP.XVI. CAPTURED INSECTS. 369 

pedicels are multicellular, are longer than elsewLere, 
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 Nortli 
Wales, which were selected owing to objects of some kind ad- 
hering 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 lirica 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. St-eds 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 wore 
counted on one leaf, eighteen on a second, and sixteen on a third. 
Another friend examined on August 22 some plants in Donegal, 
lieland, and found insects on 70 out of 157 leaves; fifteen of 



370 PINGUICULA VOIiGAEIS. Chap. XVI 

these leaves were sent me, each having caught on an average 2-4 
insects. To nine of them, leaves (mostly of Erica tetralix) ad- 
hered ; but they had been specially selected on this latter account. 
I may add that early in August my son found leaves of this same 
Erica and the fruits of a Carex on the leaves of a Pinguicula 
in Switzerland, probably Pinguicula alpina ; some insects, but no 
great number, also adhered to the leaves of this plant, which 
had much better developed roots than those of Pinguv-ula 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 Ranunculus, and several belonging to three or four distinct 
species of Carex. It appears that fewer insects are caught late 
in the year than earlier ; thus in Cumberland from twenty to- 
twenty-four insects were observed in the middle of July on 
several leaves, whereas in the beginning of September the 
average number was only 2'27. Most of the insects, in all the 
foregoing cases, were Diptera, but with many minute Hyme- 
noptera, including some ants, a few small Coleoptera, larvae, 
spiders, and even small moths. 

We thus see that numerous insects and other objects 
are caught by the viscid leaves ; but we have no right 
to infer from this fact that the habit is beneficial to 
the plant, any more than in the before given case of 
the Mirabilis, or of the horse-chestnut. But it will 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 foots, there can be no 



Chap. XVI. 



MOVEMENTS OF THE LEAVES. 



371 



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 Pinguioula 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 captui-ing 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. 1 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 -j^ 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. 

Kxperiment 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- 
ehaped 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. 




Fin, l.',. 

(^Pinguicula vulgaris,) 

Outline of leaf with left 
margin inflected ovei a 
row of small flies. 



372 PINGDICOLA VULGAEIS. Chap. XVI. 

After 4 hrs. 20 m. there was decided incurvation, which in- 
creased a little diiring 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. 

KxpeHmtnt 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 woie perceptibly incurved in 3 hrs., and after 4 hrs. 20 m. 
to such a degree that the fragment was clasped by both margins. 
After 24 hrs. the two infolded edges near the apex (for the lower 
part of the leaf was not at all affected) were measured and 
found to be 'll 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.) apart, 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 afterwards 
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. 

Ea-periment 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 incurvation after 3 hrs., and this 
became strongly pronounced in 7 hrs. After 24 hrs. the infolded 
edge was only '16 of an inch (4064 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. 

Expi rimtnt 6. — A young and concave leaf was selected with 
its margins slightly and natui-ally incurved. Two rather large, 
oblong, rectangular pieces of roast meat were placed with their 
ends touching the infolded edge, and -40 of an inch (11-68 mm.) 



Chat. XVI. 



MOVEMENTS OF THE LEAVES. 



373 




ajjart from ono 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 (3-0i8 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 io 
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 
4i hrs., but remained nearly the same for the next 17 hrs. 30 m 
In 35 hrs. from the time when the sponges were placed on the 
leaves, the margins were a little unfolded — to a greater degree 
in the younger than in the older leaf. The latter was not quite 
unfolded until the third day, and now both bits of sponge were 
left at the distance of '1 of an 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. 



Fio 16. 
(Pinguicula vulgarii.) 
Outline of leaf, witli 
right margin inflected 
against two square iJits 
of meat. 



374 PINGUICULA VULGARIS. Ohap. XVL 

Experiment 9. — A chain of fibres of roast meat, as thin as 
bristles and moistened with saliva, were placed down one whole 
side, close to the narrow, naturally incurved edge of a leaf. 
In 3 hrs. this side was greatly incurved along its whole length, 
and after 8 hrs. formed a cylinder, about -^ of an inch (1-27 
mm.) in diameter, quite concealing tlie 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. 

Experiment 10. — Six cabbage seeds, soaked for a night in 
water., were placed in a row close to the narrow incurved edge of 
a leaf. We shall hereafter see that these seeds yield soluble 
matter to the glands. In 2 hrs. 25 m. the margin was decidedly 
inflected; in 4 hrs. it extended over the seeds for about half 
their breadth, and in 7 hrs. over thrt- e-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 some way 
down the marginal channel. 

Experiment 11. — Fragments of glass were placed on the 
margins of two fine young leaves. After 2 hrs. 30 m. the 
margin of one certainly became slightly incurved; but the 
inflection never increased, and 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 asceiv 



OuAP. XVI. MOVEMENTS OF THE LEAVES. {J75 

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 (1143 mm.), and had therefore 
decreased by '1 of an inch (2'54 mm.). After only 10 hrs. 37 m. 
the margin began to re-expand, for the distance from edge to 
edge was now a trace wider, and after 24 hrs. 20 m. was as 
great, within a hair's breadth, as when the drops were first 
placed on the leaf. From this 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. 

JCxperim.erit 14.— Three drops of a solution of one part of 
carbonate of ammonia to 218 of water (2 grs. to 1 oz.) were 
placed on the margin of a leaf. These excited so much secretion 
that in 1 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 Pinguioula. 

Experiment 15. — A row of drops of a solution of one part ol 
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 4875 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 

25 



376 PINGUIOULA VULGARIS. Chap. XVX 

strength acts pc werfuUy on Drosera, and it is just possible that 
tho solution was too strong. I regret that I did not try a weaker 
solution. 

Ex/ieri.nent, 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 tlie 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 eitlier nitrogenous substances or fluids were 
placed on the leaves ; but I believe that in some cases 



Chap. XVL 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 afifected 
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 
Veep the margin incurved for a shorter time than do 
nitrogenous bodies ; for in the former case there was 



378 PINGUIOULA VULCAEIS. Chap. XVL 

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 incurved 
margins began to unfold in only 10 hrs. 87 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 i& 
that so many insects, and fragments of insects, are 
generally found lying wiihin the incurved margins 
of the leaves. 

The incurvation of the margin, due to the presence 
of an exciting object, must be serviceable in anothei 



Chap. XVI. 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 middk 
of the leaf, to a distance from the outside of fuUj 
•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 Dionsea 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 PINGUICUIA VULGARIS. Chap. XVI. 

Prof. Dyer, in most or all the species of the genus, 
the edges of the leaves are in some degree naturally 
and permanently incurved. This incurvation serves, 
as already shown, to prevent insects from being 
washed away by the rain ; but it likewise serves for 
another end. When a number of glands have been 
powerfully excited by bits of meat, insects, or any other 
stimulus, the secretion often trickles down the leaf, 
and is caught by the incurved edges, instead of rolling 
off and being lost. As it runs down the channel, fresh 
glands are able to absorb the animal matter held in 
solution.' Moreover, the secretion often collects in 
little pools within the channel, 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 immedi.itely 



CJhap. XVI. SECRETION, ABSOKPTION, DIGESTION. 381 

bearing on. our subject, that wben a plant 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, Absorption, and Digestion. — I will first give 
my observations and experiments, and then a summary 
of the results. 



The Effects of Objects containing Soluble Nitrogmous Mutter. 

(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 con- 
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 hafl 
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 mai-gin, were in the course of 



* ' English Botany,' liv Sir J. E. Smith ; with colourea liguree by 
J. Sowerby ; edit. of'lSS'i, lab. 24, 2.% 26. 



382 PINGUICDLA VULGARIS. Chap. XVI. 

two or three days much reduced in size, rounded, rendered 
more or less colourless anl transparent, and so much softened 
that they fell to pieces on the slightest touch. In only one 
instance was a very minute particle completely dissolved, and 
this occurred within 48 hrs. When only a small amount of 
secretion was excited, this was generally absorbed in from 24 hrs. 
to 48 hrs. ; the glands being left dry. But when the supply 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 cartilaye from the leg- bone 
of a sheep were laid on a leaf. After 10 hrs. 30 m. some acid 
secretion was excited, but the cartilage appeared little or not at 
all affected. After 24 hrs. the cubes were rounded and much 
reduced in size ; after 32 hrs. they were softened to the centre, 
and one was quite liquefied ; after 35 hrs. mere traces of solid 
cartilage were left ; and after 48 hrs. a trace could still be seen 
through a lens in only one of the three. After 82 hrs. not 
only were all three cubes completely liquefied, but all the 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 -fj 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 ^ 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 ol albumen (fully -^ of an inch, 1*27 mm.) 
were placed, one near the midrib and the other near the margia 



Chap. XVL SECRETION, ABSORPTION, DIGESTION. 383 

of a leaf ; in 6 his. 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 iiiuoh less reduced, and the glands 
on which it rested began to dry after only two days. 

(7) b'lhrin 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. 
4 J 111. their secretion was plainly increased. The smaller shred 
of the two was completely liquefied in 6 hrs. 15 m., and the other 
ill 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 difficulty, 
exactly as in the case of Drosera. I regret that I did not try 
this substance after having been immersed in weak hydrochloric 
acid, as it would thon probably have been qtuckly 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. 

(lOj Small particles of chemically prepared casein excited 



384 PINGUICULA VULGAEIS. Chap. XVI 

acid secretion, aut were not quite dissolved after two days ; and 
the glandsi then began to dry. Nor could their complete dis- 
solution have Deen expected from what we have seen with 
Drosera. 

(11) Minute drops of skimmed mi7/fc 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 
3oulJ 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 curbonate 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 granular matter, which slowly became coarsely granular 
and slightly opaque; but even after 5 hrs. not as yet of a 
brownish tint. By this time a few rather large, transparent, 
globular masses appeared within the upper ends of the pedicels, 
and the protoplasm lining their walls had shrunk a little. It 
is thus evident that the glands of Pinguicula absorb carbonate 
of ammonia ; but they do not absorb it, or are not acted on by 
it, nearly so quickly as those of Drosera. - 

(13) Little masses of the orange-coloured poUen of the 
common pea, placed on several leaves, excited the glands to 
secrete freely. Even a very few grains which accidentally fell 
on a single gland caused the drop surrounding it to increase so 
much in size, in 23 hrs., as to be manifestly larger than the 
drops on the adjoining glands. Grains subjected to the secretion 
for 48 hrs. did not emit their tubes; they were quite dis- 
coloured, and seemed to contain less matter than before; that 



Chap. XVL SECKETION, ABSORPTION, DIGESTION. 385 

■which was left being of a dirty colotir, 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-greon 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 tetiaiix, 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 bad 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- 
roxa, Bumex acetosa, Oarex syloatica, mustard, turnip, cress, 
Ranunculus acris, undi Avena puh scena, all excited much secre- 
tion, whic I was in several cases tested and found always acid. 
The iive 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 Kumex 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, Liuura 
grandiflorum, Cassia, Trifulium pannonicum, Plantago, onion, 



386 PINGUICULA VULGARIS. Chap. XVL 

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, Krica tetralir, Atriplex hortensis, 
I'halaris canariensis, and wheat. Nevertheless, when the seeds 
of the lettuce, wheat, and Atriplex were split open and applied 
to leaves, secretion was excited in considerable quantity in 
10 hrs., and I believe that some was excited in six hours. In 
the case of the Atriplex the secretion ran down to the margin, 
and after 24 hrs. I speak of it in my notes " as immense in 
quiintity and acid." The split seeds also of the Trifolium and 
celery acted powerfully and quickly, though the whole seeds 
caused, as we 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 Icgumin 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 lepumin appa- 
rently having been dissolved. A cabbage seed which had lain 
for two days ou a loaf 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 ; thtir 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 graniilar 
matter, proving that they had absorbed matter from the seeds. 

That the secretion acts on the seeds was also shown by some 
of them being killed, or by the seedlings being injured. Fourteen 
cabbage seeds were left for three days on leaves and excited 



Chap. XVI. SECRETION, ABSORPTION, DIGESTION. 387 

mtich 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 proportioti of deaths 
than occurred with seeds of the same lot, which had not been 
subjected to the secretion, but were otherwise treated in the 
same manner. Of the eleven seedlings raised, three had the 
edges of their cotyledons slightly browned, as if scorched; and 
the cotyledons of one grew into a curious indented shape. Two 
mustard seeds germinated; but their cotyledons were marked 
with brown patches and their radicles deformed. Of two radish 
seeds, neither germinated ; whereas of many seeds of the same 
lot not subjected to the secretion, all, excepting one, germinated. 
Of the two Rumex seeds, one died and the other germinated ; 
but its radicle was brown and soon withered. Both seeds of the 
Avena germinated, one grew well, the other had its radicle brown 
and withered. Of six seeds of the Erica none germinated, and 
when cut open after having been left for five months on damp 
sand, one alone seemed alive. Twenty-two seeds of various 
kinds were found adhering to the leaves of plants growing in a 
state of nature ; and of these, though kept for five months on 
damp sand, none germinated, some being then evidently dead. 

The Effects nf Ohjeots not containing Soluble Nitrogenous Matter. 

(16) It has already been shown that bits of glass, placed on 
leaves, excite little or no secretion. The small amount which 
lay beneath the fragments was tested and found not acid. A 
bit of wood excited no secretion ; nor did the several kinds of 
seeds of which the coats are not permeable to the secretion, and 
which, therefore, acted like inorganic bodies. Cubes of fat, left 
for two days on a leaf, produced no effect. 

(17) A particle of white sugar, placed on a leaf, formed in 
1 hr. 10 m. a large drop of fluid, which in the course of 2 
additional hours ran down into the naturally inflected margin. 
This fluid was not in the least acid, and began to dry up, or 
more probably was absorbed, in 5 hrs. 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 
ieliquesoence ; but this was proved not to be the ease. 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 



388 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 difler, 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 particles of dry starch of commerce were placed 
on a leaf, and one of these caused some secretion in 1 lir. 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 degi'ce 
and at a much slower rate than the leaves in the syrup; those in 
water remaining all the time crisp. 



From the foregoing experiments and observations w« 



CHApiXVL SECBETION, 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 caseia 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 fi-om solids 
or from liquids, such as an infusion of raw meat, 
mUk, or a weak solution of carbonate of ammonia, 
is quickly absorbed; and the glands, which were 
before limpid and of a greenish colour, become brownish 
and contain masses of aggregated granular matter. 
This matter, from its spontaneous movements, no doubt 
consists of protoplasm. No such effect is produced 
by the action of non-nitrogenous fluids. After the 
glands have been excited to secrete freely, they cease 
for a time to secrete, but begin again in the course of 
a few days. 

Glands in contact with pollen, the leaves of other 
plants, and various kinds of seeds, pour forth much 
acid secretion, and afterwards absorb matter probably 
of an albuminous nature from them. Nor can the 
benefit thus derived be insignificant, for a considerable 



390 PINGUICULA GEANDIPLOEA. Chap.'XVI 

amount of pollen miist be blown from the many 
wind-fertilised carices, grasses, &c., growing where 
Pinguicula lives, on to the leaves thickly covered with 
viscid glands and fomiing 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 Pinguicula vulgaris, with its small roots, 
is not only supported to a large extent by the extra- 
oj'dinary 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 gkandifloka. 

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 Mr. Ralfs, who was so kind as to send 
me plants from Cornwall, that it grows in rather 
different sites ; and Dr. Moore, of the GlasTievin 
Botanic Gardens, informs me that it is much more 
inanageable under culture, growing freely and flower- 
iug annually ; whilst Pinguicula vulgaris has to be 
renewed every year. Mr. Ealfs found numerous 



Ohap. 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 alive. He also observed a few fruits 
of Garex puliearis, 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 Pingmeala vulgaris. 

Pinguicula lusitanica. 

This species, of which living specimens were sent me 
by Mr. Ealfs 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 pui-ple, 
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- 
26 



392 PINGUICULA LUSITANICA. Chap. XVL 

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 tetraUx, 
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 
pi act d 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 Jg of an inch of the midrib. After 48 hrs. it began to 
unfold, and in 72 hrs. was completely unfolded. The cube was 
rounded and greatly reduced in size; the remainder being in 
a Semi-liquefied state. 

(2) A moderately sized bit of albumen was placed near the 
apex of a leaf, under the naturaUy 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. 

(8) Large bits of aZJitmcra were laid in a row on the midriba 
of two leaves, but produced in the course of 24 hrs. no effect ; 



Chap. XVI. PmGUICUT.A LTJSITANICA. 393 

nor could this have been expected, for even had glands 
existed here, the long bristles would have prevented the 
albumen from coming iu contact with them. On both leaves 
the bits were now pushed close to one margin, and in 3 hrs. 
30 m. this became so greatly inflected that the outer surface 
touched the blade ; the opposite margin not being in the least 
affected. After three days the margins of both leaves with the 
albumen were still as much inflected as ever, and the glands 
were still secreting copiously. With Pinguicula vulgaris I have 
never seen inflection lasting so long. 

(4) Two cabbage seeds, after being soaked for an hour in water, 
were placed near the margin of a leaf, and caused in 3 hrs. 
20 m. increased secretion and incurvation. After 24 hrs. the 
leaf was partially unfolded, but the glands were still secreting 
freely. These began to dry in 48 hrs., and after 72 hrs. were 
almost dry. The two seeds were then placed on damp sand 
under favourable conditions for growth; but they never ger- 
minated, and after a time were found rotten. They had no 
doubt been killed by the secretion. 

(6) Small bits of a spinach Uaf 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 
ui 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 Pin- 
guicula vulgaris. The above slight inflection of the margin had 
not increased after 24 hrs., and the glands were now beginning 
to dry. The surface of a leaf, near the midrib and towards 
the base, was rubbed and scratched for some time, but 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 1 thought that the hairs might perhaps 
be sensitive to a touch, like the iilaments of Dionsea. 



394 PINGUICULA LUSITANICA. Chap. XVI 

(7) The flower-peduncles, sepals and petals, bear glands it 
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 observations on Finguieula 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 diifers 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 secretior. 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 NEGLEOTA. 395 



CHAPTER XVII. 

TJtkioulaeia. 

Utricttlaria 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 — 
Vtricularia vulgaris — Utricularia minor — Vtrimlaria dandestina. 

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 \ 1 am much indebted to the 

High Wycombe Nat. Hist. Soo.' Eev. H. M. Wilkinson, of Bistern, 

July 1868, p. 5. Delpino ('tilt. for having sent me several fine 

Osservaz. suUa Dioogamia,' &o. lots of this species from the New 

1868-1869, p. 16) also quotes Forest. Mr. Balfs was also so kind 

Crouan as having found (1858) as to send me living plants of the 

crustaceans within the bLidders same species from near Penzance 

of Jjtrioularia vulgaris. in Cornwall. 



396 



UTEICULAEIA NEGLECTA. 



Chap. XVII. 



on Utrioularia 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 obserTer. I will publish my description as 
it stood before reading that by Prof. Cohn, adding 
occasionally some statements on his authority. 




Fig. xr. 

(CTricwZaria neglecta.') 

Branch with the divided leaves bearing bladders; abont twice enlarged, 

Utrioularia 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 



' Beitrago zur Biologie der Pflanzen, ' drittes Heft, 1875. 



Chap. XVn. ,STEDCTUEE OF THE BLADDEE. 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 papillsB, crowned with two hemi- 
spherical cells in close contact. The plants float 
near the surface of the water, and are quite destitute 
of roots, even during the earliest period of growth.* 
U'hey 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 
y'-o 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 iluids. The 
papillge thus formed are exactly like those on the 
surfaces of the leaves. Those on the same bladder 
vary much in size ; and there are a few, especially on 
very young bladders, which have an elliptical instead 
of a circular outline. The two terminal cells are 
transparent, but must hold much matter in solution, 
judging from the quantity coagulated by prolonged 
immersion in alcohol or ether. 



* I infer that this is the case om Lentibulariaeeaj," from the 

from a drawing of a seedling ' Videnskabelige Meddelelaer,' 

given by Dr. Warming in his Copenhagen, 1874, Nos. 3-7, pp. 

paper, " Bidrag til Kuudskaben 33-58. 



398 UTEIOULAEIA NEGLECTA. Chap. XVII. 

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 Rev. H. M. Wilkinson examined 




Fio. 18. 

(^Utricularia iKglecta.') 

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 bad their valves turned upwards. 

The general appearance of a bladder viewed late- 
rally, with the appendages on the near side alone 
represented, is shown 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 lons" prolongations, formed of several rows of 
cells, confer uing chlorophyll, and bearing, chiefly on 



Chap. XVU. STEDCTUEE OF THE BLADDEE. 399 

the outside, six or seven long, pointed, multicellular 
bristles. These prolongations of the bladder may be 
conveniently called the antennae, for the whole bladder 
(^ee 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 antennas 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- 




Fm. 19. 

( Utricu^na negkcta.) 

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 antennse, 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 
lovrer 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 



400 UTKICULAEIA NEGLECTA. Chap. XVIX 

bladder, as shown in the longitudinal section (fig. 20) 
of the collar and valve ; it is also shown at e, in fig. 18. 
The edge of the valve 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. 
(^Utricularia Tieglecta.) 
Fjongiludinal vertical Bection through the ventral portion of a bladder; showing valve 
and collar, ti, valve ; the whole projection atiove c forms the collarj b, bifid pro- 
cesses ; 8, 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. STEUOTUEE OF THE BLADDEE. 401 

to a certain extent graduate into one another. Those 
situated found 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 TTrBICULAKIA NEGLEOTA. Chap. XVU 

tween the inner and outer surface consists of coarse 
cellular tissue (fig. 20). The inner side is thickly 
covered with delicate bifid processes, hereafter to be 
described. The collar is thus made thick; and it is 
rigid, so that it retains the same outline whether the 
bladder contains little or much air and water. This 
is of great importance, as otherwise the thin and 
flexible valye 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. XVII. 



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- 





FlO. 21. 

;^ Utricularia negUcta.) 

Small portion of inside of blad- 
der, mucU enlargt d, showing quad- 
rifid processes. 



KiG. 22. 

(^Utricularia 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 
Vtrieularia tnontana contain rather larger and much 



404 UTEICITLAEIA NBGLEOTA. Ohap. XVH 

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 project 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 papillae. 

The Uses of the several Parts. — After the above long 
but necessary description of the parts, we will turn to 
their uses. The bladders have been supposed by some 
authors to serve as floats; but branches which bore 
no bladders, and others from which they had been 
removed, floated perfectly, owing to the air in the 
intercellular spaces. Bladders containing dead and 
captured animals usually include bubbles of air, but 
these cannot have been generated solely by the 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 
aquatic 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 



CiiAK XVII. MANNEE OF CAPTURING PEET. 405 

grown bladders contained prey ; in a second lot, re- 
ceived in the beginning vi 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 larvae 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 Vtricularia 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 were 
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 



106 UTEICULABIA NEGLECTA. Chap. XVII 

fits, I may mention that my son found a Daphnia 
whicn 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 effected. 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 undgr 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 ^l of ^^^ 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 opened 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 OAPTUEING PKET. 407 

long splinter, of which one end rested obliquely on 
the valve, and after a few hours it was found fixed, half 
within the bladder and half projecting out, with the 
edge of the valve fitting closely all rouud, 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 -^ of an inch, 'SQl 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- 
27 



t08 UTEICDLAEIA NEGIECTA. Ohap. XVIl 

spread analogy, this would have rendered them more 
sensitive to irritation, or would by itself have excited 
movement ; but no eifect was produced. We may, 
therefore, conclude that animals enter merely by 
forcing their way through the slit-like oriiice ; their 
heads serving as a wedge. But I am surprised that 
such small and weak 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 ^ 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 Utricularia 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 Trib-me, reprinted in the ' Gard. Chron.' 1875, p. 303 



Chap. XVII. MAHNEB OF CAPTURING FEET. 409 

" mind what I have witnessed when u 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 larvae just 
referred to are vegetable-feeders, and seem to have a 
special liking for the long bristles round the valve, but 
this taste will not account for the entrance of animal- 
feeding crustaceans. Perhaps small aquatic animals 
habitually try to enter every small crevice, like that 
between the valve and collar, in search of food or 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 piu-pose. 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 fcircumstances 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 



no UTBICU LABIA NEGLECTA. Chap. XTII 

allow auimais to enter and to prevent their escape ;— 
and as the inside of the bladder presents so singular 
a structure, clothed with innumerable quadriiid 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 
have digested their prey ; but this is not the case, and 
there are no glands fitted for secreting the proper 
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, Dionisa, 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 Utricularia cannot digest the 
animals which it habitually captures. 

In most of the bladders the captured animals are so 
much decayed that they form a pale brown, pulpy 
mass, with their chitinous coats so tender that they 
fall to pieces with the greatest ease. The black 
pigment of the eye-spots is preserved better than 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 



Dhap, XVII. ABSOEPTION BT THE QUADBIFIDS. 411 

to the larvse 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 CTEIOULAEIA NEGLECTA. Chap. XVIL 

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 brown 
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 accounted for by the animals not having 
been sufficiently decayed, or by time enough not 
having been allowed for the generation of proto- 



Ohap. XVII. ABSORPTION BY THE QUADEIFIDS. 41d 

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 Absorption 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. 

I'our bladders were iirst tried as a control experiment, in 
the manner just dr^scribed,, in a solution of one part of gum 
arabic to 218 of walcr, and two bladders in a solution of one 
part of sugar to 437 of water; and in neither case was anj 



il4 UTKICULAEIA NEGLECTA. Chap. XVII. 

shange perceptible in the quadrifids or bifids after 21 hrs. 
Four bladders were then treated in the same manner with a 
solution of one part of nitrate of ammonia to 437 of water, and 
re-examined after 21 hrs. In two of these the quadrifids now 
appeared full of very finely granular matter, and their proto- 
plasmic lining or primordial utricle was a little shrunk. lu the 
third bladder, the quadrifids included distinctly Tisible 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 quadrifids now contained very 
fine granular matter. 

A bladder was bisected, examined, and irrigated with a 
solution of one part of carbonate of ammonia to 437 of water. 
After 8 hrs. 30 m. the quadrifids contained a good many granules, 
and the primordial utricle was somewhat shrunk ; after 23 hrs. 
the quadrifids and bifids contained many spheres of hyaline 
matter, and in one arm twenty-four such spheres of moderate 
size were counted. Two bisected bladders, which had been 
previously left for 21 hrs. in the solution of gum (one part to 
218 of water) without being affected, were irrigated with the 
solution of carbonate of ammonia; and both had their quadrifids 
modified in nearly the same manner as just described,— one 
after only 9 hrs., and the other after 24 hrs. Two bladders 
which appeared never to have caught any prey were punctured 
and placed in the solution ; the quadrifids of one were examined 
after 17 hrs., and found slightly opaque ; the quadrifids of the 
other, examined after 45 hrs., had their primordial utricles more 
or less shrunk with thickened yellowish specks, like those due 
to the action of nitrate of ammonia. Several uninjured bladders 
were left in the same solution, as well as a weaker solution 
of one part to 1750 of water, or 1 gr. to 4 oz. ; and after twu 
days the quadrifids 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 ; anjhow 



CBiP. XVn. ABSOEPTION BY THE QUADEIFIDS. 415 

the quadrifids were affected after 21 hrs. as if a solution of car- 
bonate of ammonia had been used ; for the primordial utricle 
was thickened in specks, which seemed to graduate into separate 
granules. Three bisected bladders were also irrigated with a 
fresh solution of urea of the same strength; their quadrifids 
after 21 hrs. were much less affected than in the former 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 quad- 
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 prodiiced 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 lime enough allowed. 



416 UTEICTTLAEIA NEGLECTA. Chap. XVH 

We have seeu with Drosera that the first eifect 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 have no power of digesting albumen, 
cartilage, or roast meat, I was surprised that matter 
was absorbed, at least in one case, from a fresh infusion 
of raw meat. I was also surprised, from what we shall 
presently see with respect to the glaads round the 
orifice, that a fresh solution of urea produced only a 
moderate effect on the quadrifids. 

As the quadrifids are developed from papillae 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 par- 
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 by the Glands on 
tlie Valve and Collar. — The glands round the orifices of 
bladders which are still young, or which have been 



Ohap. XVn. AJBSOBPTIO.N BY THE GLAiNDS. 41T 

long kept in moderately pure water, are colourless; 
and tlieir 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 
olotting paper and gently pressed, water oozes out. 



418 UTEICULAEIA NEGLECTA. Chap. XVIL 

In this latter case, as soon as the pressure is relaxed, air 
is drawn in, and the bladder recovers its proper form.. 
If it is now placed under water and again gently 
pressed, minute bubbles issue from the orifice and 
nowhere else, showing that the walls of the bladder 
have not been ruptured. I mention this because Cohii 
quotes a statement by Treviranus, that air cannot bf« 
forced out of a bladder without rupturing it. We may 
therefore conclude that whenever air is secreted within 
a bladder already full of water, some water will be 
slowly driven out through the orifice. Hence I can 
hardly doubt that the numerous glands crowded round 
the orifice are adapted to absorb matter from the 
putrid water, which will occasionally escape from 
bladders including decayed animals. 

In order to test this conclusion, I experimented with various 
solutions on the glands. As in the case of the quadrifids, salts 
of ammonia were tried, since these are generated by the final 
decay of animal matter under water. Unfortunately the glands 
cannot be carefully examined whilst attached to the bladders 
in their entire state. Their summits, therefore, including the 
valve, collar, and antennse, 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 contro] 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 primordial 
utricles of most of the glands were somewhat contracted ; they 
were also thickened in specks or patches, and had assumed a pale 



Chap XVIL ABSOEPTION 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 was treated with a weaker solution of one part of the 
carbonate to 437 of water, and after 1 hr. the glands were pale 
brown and contained numerous granules. 

Pour 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 his. 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 were brownish, with 
their primordial utricles somewhat shrunk and finely granular. 

The summit of another bladder, the glands of which were in a 
beautifully clear condition, was irrigated with a few drops of 
a mixed solution of nitrate and pho.sphate of ammonia, each 
of one part to 437 of water. After 2 hrs. some few of the 
glands were brownish. After 8 hrs. almost all the oblong glands 
were brown and much more opaque than they were before; 
their primordial utricles were somewhat shrunk and contained a 
little aggregated granular matter. The spherical glands were 
still white, but their utricles were broken up into three or 
four small hyaline spheres, with an irregularly contracted mass 
in the middle of the basal part. These smaller spheres changed 
their forms iii 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 



^0 ' UTEICULAEIA NEGLECTA. Chap. XVIL 

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 were also irrigated 
with a fresh infusion of raw meat ; three of these were not at 
all affected in 24 hrs., but the glands of the other two had 
perhaps become more granular. One of the specimens which 
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 irrigated with 
a few drops of a solution of one part of urea to 218 of water. 
After 2 hrs. 25 m. the spherical glands were still colourless ; 
whilst the oblong and two-armed ones were of a brownish tint, 
and their primordial utricles much shrunk, some containing 
distinctly visible granules. After 9 hrs. some of the spherical 
glands were brownish, and the oblong glands were still more 
changed, but they contained fewer separate granules; their 
nuclei, on the other hand, appeared larger, as if they had 
absorbed the granules. After 23 hrs. all the glands were 
brown, their 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 slightly 
shrunk; and the oblong glands were brownish, with their 
utricles much, but irregularly, shrunk. Ihe summit was 
treated with the solution of urea, but was little affected by it in 
9 hrs.; nevertheless, after 23 hrs. the spherical glands were 
brown, with their utricles more shrunk; several of the other 
glands were still browner, with their utricles contracted into 
irregular little masses. 

Two other summits, with their glands colourless and their 
utricles not shrunk, were treated with the same solution of 
urefi- After 5 hrs. many of the glands presented a shade of 
brown, with their utricles slightly shrunk. After 20 hrs. 
40 m. some few of thsm were quite brown, and contaiood 



Chip. XVn. STJMMAKY ON ABSOEPTlCN. 42i 

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 whicli 
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 .nppearance; 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 sufficient. The spherical glands were not 
brown, but some of them were finely granular. Many of the 
oblong glands were brown ; and these, as well as others which 
still remained colourless, had their utricles more or less shrunk, 
some of them including small aggregated masses of matter. 

Summary of the Observations on Absorption. — From 
the facts now given there can be no doubt that the 
variously shaped glands on the valve and round the 
collar have the power of absorbing matter from weak 
solutions of certain salts of ammonia and urea, ancJ 
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 UTEIODLAEIA NEGLEOTA. Chap. XVII. 

surfaces. The glands are variously affected by absorp- 
tion ; they often become of a brown colour ; sometimes 
they contain Tery 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 spherical glands 
are generally affected rather differently from the 
oblong and two-armed ones. The former do not so 
commonly become brown, and are acted on more 
slowly. We may therefore infer that they differ 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 unknown differences in their constitution. When 
the glands on the same bladder are differently affected 
by a solution, we may suspect that some of them 
had previously absorbed a small amount of matter 
from the water. However this may be, we have 
seen that the glands 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 



Chap. XVn. SUMMARY ON ABSORPTION. 423 

any appearance making it probable that glands which 
have been strongly affected 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 
bladd'r , 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 



424 tFTEICULAKIA NEGLECTA. Chap. XVIL 

ammoma, 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 particidarly 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 species 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 Utrieularia 
negleeta. 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 Utrieularia 
vulgaris are about -^^ inch (-254 mm.) in diameter 
(or -g-Lj. in the case of Utrieularia negleeta), they are 
circular in outline, with a narrow, almost closed, trans- 
verse orifice, leadiiig 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 BLADDERS. 



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 THricularia vulgaris, -pi-j- 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 
Jage, glands could be detected' 
on the valve. The state of the 
quadrifld processes will presently 
be described. The antennae at this 
period consist of minute cellular projections (not shown 
in the above figure, as they do not lie in the medial 
piano), 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. 

(TTtHoilaria vulgaris.') 

Longitudinal section through 

a young bladder, -mj of an incb 

in length, with the orifice too 

widely open. 



426 UTRICULAEIA NEGLECTA. Chap. XVII. 

must therefore be developed one after the other, and 
so it would be with tne two antennee. 

At a much earlier age, when the half formed 
bladders are only -j-i-j^ 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 




FlO. 24. 

(^Utricularia vtUgaHt.') 

Yoang leaf from i winter bnd, sttowing on the left side a bladder in its earliest stage 

of development. 

at this age have broad flattened segments, with theii- 
future divisions represented by prominences, one of 
which is shown on the right side. Now, ia a large 
number of specimens examined by my son, the young 
bladders appeared as if formed by the oblique folding 
over of the apex and of one margin with a prominence, 
against the opposite margin. The circular hollow 
between the infolded apex and infolded prominence 
apparently contracts into the narrow orifice, wherein 
the valve and collar will be developed ; the bladder 
itself being formed by the confluence of the opposed 



Chap. XVII. DEVELOPMENT OF THE BLADDEES. 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 qiiadrifld and bifid processes offer one of the 
greatest peculiarities in the genus, I carefully observed 
their development in Uirieularia neghcta. In bladders 
about -j-i-^ of an inch in diameter, the inner surface 
is studded with papillBB, 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 papillae 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 UTEICDLAEIA VDLGAKIS. Chap. XVIL 

and more horizontal pair; the four together forming 
a perfect quadrifid. A trace of the primary division 
between the two cells on the summits of the papillae can 
still be seen between the bases of the longer processes. 
The doTelopment of the quadrifids is very liable to 
be arrested. I have seen a bladder -5^- of an inch 
in length including only primordial papillas ; and 
another bladder, about haK 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 
we may reasonably suspect that they are developed 
from papillse 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 papillse like those on the outside of the 
bladders, from the fact that in Utricularia amethystina 
the glands extend along the whole ventral surface 
of the bladder close to the footstalk. 

Uteiculaeia vulgaeis. 

Living plants from Yorkshire were sent me by Dr. Hooker. 
This species differs from the last in the stems and leaves being 
thicker or coarser; their divisions form a more acute angle 
with one another; the notches on the leaves hear three or 
four short bristles instead of one ; and the bladders are twice 
as large, or about \ of an inch (5'08 mm.) in diameter. In 
all essential respects the bladders resemble those of Utiicularia 
negleda, but the siaes of the peristome are perhaps a little more 



OHAP.XVn. UTEICULAEIA 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 InoluderL Five 
bladders, containing prey of some kind, were examined. The 
first included five Cypris, a large copepod and a Diaptomus ; 
the second, four Cypris; the third, a single rather large 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. 

UtEICULAEIA 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 L'tiiculmia neghcta. 
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 (^ctrumlana minor.') 

species; but the glands are not QnadiiM 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 ah'eady protected to a certain 
extent by the incurved antennse, together with the lateral 
bristles. The bifid processes are hke those in the previous 
species; but the quadrifids differ in the four arms (fig. 25) 




430 UTEIOULAEIA OLANDESTINA. Chap. XVIL 

being directed to the same side ; tlie two longer ones beiug 
central, and the two shorter ones on the outside. 

The plants were collected in the middle of July; and the 
contents of Ave 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 stuffed quite full, contained only seven, 
but five of these were of unusually large size. The prey, 
therefore, judging from these five bladders, consists exclusively 
of fresh- water crustaceans, most of which appeared to be distinct 
species from those found in the bladders of the two foimer 
species. In one bladder the quadriflds in contact with a decay- 
ing mass contained numerous spheres of granular matter, 
which slowly changed their forms and positions. 

TJteiculaeia 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 liaed with quadrifid 
processes. A vast number of captured animals were found 
within the bladders; some being crustaceans, but the greatei 
number delicate, elongated larvse, I suppose of Culicidse. On 
some stems, "fully nine out of every ten bladders contained 
these larvae or their remains." The larvse " showed signs of hfe 
from twenty-four to thirty-six hours after being imprisoned," 
and then perished. 



Obap. XVIU. 



UTEIOULAEIA MONTANA. 



431 



CHAPTEE XVIII. 

Utkiohlaeia (continued). 

Vliiculana montana — Description of the bladders on the subter- 
ranean rhizomes — Prey captured 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 XJtricularia — Polypompholyx — Geulisea, 
different nature of the trap for capturing prey — Diversified 
methods by which plants are noxirished. 

Uteiculakia 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 fig. 26. 

species. They are elongated, (.uMeuiaria montana.) 

about n inch in breadth, teS^ohrbe'SngT '"''° "'"''"' *'' 




natural size. 



; minute, bladders : of 



and furnished with a dis- 
tinct footstalk. The plant produces numerous colour- 
less rhizomes, as thin as threads, which bear minute 
bladders, and occasionally swell into tubers, as will 



432 UTEICUIAKIA MONTANA, Chap. X VIII. 

hereafter be described. These rhizomes appear ex- 
actly like roots, but occasionally throw up green 
shoots. They penetrate the earth sometimes to the 
depth of more than 2 inches ; but when the plant 
grows as an epiphyte, they must creep amidst the 
mosses, roots, decayed bark, &c., with which the trees 
of these countries are thickly covered. 

As the bladders are attached to the rhizomes, they 
are 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 JaTnesoniana on the rhizomes of the present and 

(' Proe. Linn. Soc.' vol. iv. p. 169) 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 acoordauce 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 

oonverted into bladders. This fact aquatic species. 



Chap. XVni. STEUCTUEE 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 




Fio. 2». 

^Utricularia numtana.) 

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 eai-th 



434 UTBIOULABIA MONTANA. Chap. XVIH. 

and rubbist ; 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 
dependiug 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. XVUL CAPTUEED ANTMAI-S. 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 antennae 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. 

(JTtriciUaria vumtanaJ) 

One of the quadrifid processes ; much eiUan^. 

It seemed to me an interesting question whether 
the minute bladders of JJiricularia montana served, as in 
the previous species, to capture animals living in the 
earth, or in the dense vegetation covering the trees on 
which this species is epiphytic ; for in this case we 
should have a new sub-class of carnivorous plants^ 
namely, subterranean feeders. Many bladders, there- 
fore, were examined, with the following results : — 

(1) A small bladder, less than ^ of an inch (-847 mm.) in dia- 
meter, contained a minnte mass of brown, much decayed matter; 
and in this, a tarsus with four or five joints, terminating in a 
double hook, was clearly distinguished under the microscope. 
I suspect that it was a remnant of one of the Thysanoura. The 
^uadriflds in contact with this decayed remnant contained either 
email masses of translucent, yellowish matter, generally more 



436 DTEICULAEIA MONTANA. Ohap. XVIH 

or less globular, or fine granules. In distant parts of the samo 
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 affected, 
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 Utricularia neglecta. 

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 
bladder.s on a plant which had grown in black earth in New 
Granada were first examined ; and four of these included 
remnants of animals. The first contained a hairy Acarus, so 
much decayed that nothing was left except its transparent coat; 



Chap. XVUI. ABSOEPTION. 437 

also a yellow chitinous head of some animal with an internal 
fork, to which the oesophagus 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 
ArcellidsB. In this bladder, as well as in several others, there 
were some unicellular Algss, 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 ia 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 power of 
absorption. A bladder was punctured and left for 
24 hrs. in a solution of one part of urea to 437 of 
water, and the quadrifid and bifid processes were found 
much affected. In some arms there was only a single 
symmetrical globular mass, larger than the proper 
nucleus, and consisting of yellowish matter, generally 
translucent but sometimes granular; in others there 
were two masses of different sizes, one large and the 



t38 UTRICULAEIA MONTANA. CnAl-. XVIH 

other small; and in others there were irregularly 
shaped globules ; so that it appeared as if the limpid 
contents of the processes, owing tc 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 Utricularia neglecta 
under similar treatment. These specks apparently did 
not change their forms. 

The minute two-armed glands on the valve were 
also affected by the solution ; for they now contained 
several, sometimes as many as six or eight, almost 
spherical masses of translucent matter, tinged with 
yellow, which slowly changed their forms and 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 wiU 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 uf such diverse kinds to enter 



Chap. XVIU. BESEEVOIES FOE WATER. 439 

* 

the cavity beneath the bowed antennae, and then force 
their way through the little sHt-like orifice between 
the Talve 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 
(11-43 mm.) in breadth. They commonly lie near 
the surface, but some are buried at the depth of 
2 inches. The buried ones are dirty white, but those 
partly exposed to the light become greenish from the 
development, of chlorophyll in their superficial cells. 
They terminate in a rhizome, but this sometimes 
decays and drops off. They do not contain any air, 
and they sink in water; their surffi«es are covered 
with the usual papillse. 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- 
29 



440 UTBIOTOAEIA MONTANA. Ohap. XVIII 

clud(} that the tubers do not serve as reservoirs for 
food, but for water during the diy season to which the 
plant is probably exposed. The many little bladders 
filled with water would aid towards the same end. 

To test the correctness of this view, a small plant, 
growing in light peaty earth in a pot (only 4-i- by 4-i- 
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 accurS,tely 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. xviu. uteiculaeia nelumbifolia. 441 

and examined. The cells still contained much water 
and no air, but they were more rounded or less angular 
than before, and their walls not nearly so straight ; it 
svas 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 ta water for 22 hrs. 30 m., 
and its surface became as smooth and tense as it 
originally was. On the other hand, a shrivelled tuber, 
which by some accident had been separated from its 
rhizome, and which appeared dead, did not swell in 
the least, though left for several days in water. 

With many kinds of plants, tubers, bulbs, &c. no 
doubt serve in part as reservoirs for water, but I 
know of no case, besides the present one, of such 
organs having been developed solely for this purpose. 
Prof. Oliver informs me that two or three other species 
of Utricularia are provided with these appendages ; 
and the group containing them has in consequence 
received the name of orchidioides. All the other 
species of Utricularia, as well as of certain closely 
related genera, are either aquatic or marsh plants; 
therefore, on the principle of nearly allied plants 
generally having a similar constitution, a never failing 
supply of water would probably be of great importance 
to our present species. We can thus understand the 
meaning of the development of its tubers, and of their 
number on the same plant, amounting in one instance 
to at least twenty. 

Uteiculaeia nelumbifolia, amethtstina, geif- 
fithii, c^eulea, oebiculata, multicaulis. 

As I wished to ascertain whether the bladders on 
the rhizomes of other species of Utricularia, and of the 



442 UTRICUTAEIA NELUMBIFOLIA. Chap. XVHL 

species of certain closely allied genera, had the same 
essential structure as those of Utricularia montana, and 
whether they captured prey, I asked Prof. Oliver to send 
me fragments from the herbarium at Kew. He kindly 
selected some of the most distinct forms, having entire 
leaves, and believed to inhabit marshy ground or 
water. My son, Francis Darwin, examined them, and 
has given me the following observations; but it 
should be borne in mind that it is extremely difficult 
to make out the structure of such minute and delicate 
objects after they have been dried and pressed.* 

Utricularia nelimbifolia (Organ Mountains, Brazil). — 
The habitat of this species is remarkable. According 
to its discoverer, Mr. Gardner,t 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 Utricula/ria montwna 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 (' Proo. but he does not appear to have 

Linn. Soo.' vol. iv. p. 169) figures paid particular attention to these 

of the bladders of two South organs. 

American species, namely, Vtri- t 'Travels in the Interior of 

oularia Jameecmiana and peltata; Brazil, 1836-11,' p. 527. 



Chap. XVIII. UTEICULAEIA AMETHTSTINA. 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. 

JJtricularia amethystma (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 Utrieularia moniana, and are covered outside 
with the usual papillae ; but they differ remarkably in 
the antennas 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 
which the edge shuts is yellowish, and presents the 
usual structure. From the large number of glands on 
the ventral surface and round the orifice, it is probable 
that this species lives in very foul water, from which it 
absorbs matter, as well as from its captured and decay- 
ing prey. 

Utrieularia griffithii (Malay and Borneo). — The 
bladders are transparent and minute; one which was 
measured being only xfI-o of ^^ inch. ('Til mm.) 
in diameter. The antennae are of moderate length, and 



444 UTHICULAEIA MULTIOAULIS. Ohap. XVIIt 

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 previous species, 
as within there are no quadrifid, only bifid, processes. 
In one bladder there was a minute aquatic larva; 
in another the remains of some articulate animal ; 
and in most of them grains of sand. 

Utricularia emrulea (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, 

Vtriouhria orUculata (India). — The orbicular leaves 
and the stems bearing the bladders apparently float in 
water. The bladders do not differ much from those oJ 
the two last species. The antennas, which are united 
for a short distance at their bases, bear on their outer 
surfaces and summits numerous, long, multicellular 
hairs, surmounted by glands. The processes within 
the bladders are quadrifid, with the four diverging 
arms of equal length. The prey which they had 
captured consisted of entomostracan crustaceans. 

Utricula/na mvlticaulw (Sikkim, India, 7000 to 
11,000 feet). — The bladc/ers, attached to rhizomes, 
are remarkable from the structure of the antenna. 
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, 
rath(a- narnjw pedicel, and they thus appear 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 o/ 
articulate animals. 



OflAP. XVin. POLTPOMPHOLYX. 



U5 



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." 

Polypompholyx 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 papillas, 
having very short footstalks. The quadrifid processes 
have divergent arms of equal length. Remains of 
entomostracan crustaceans were found within the 
bladders. 

Polypompholyx tenella. — The bladders are smaller 
than those of the last species, but have the same 
general structure. They were full of debris, apparently 
organic, but no remains of articulate animals could 
be distinguished. 



'Proo. Linn. Sco.' vol. iy. p. 171. 



446 OENLISEA OBNATA, OhAP. XVni. 



Genlisea. 

This remarkable genus is technically distinguished 
from Utricularia, as I hear from Prof. Oliver, by 
having a five-partite calyx. Species are found in 
several parts of the world, and are said to be " herbas 
annuae paludosse." 

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 (V) 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 -g-V of an inch 
(■705 mm.) in its longer diameter had a neck -^-^ 
(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 
narr«w ribbon and wind it spirally round a thin 
cylinder, so that the edges come into contact along its 
\vhole length ; then pinch up the two edges so as to 
form a little crest, which will of course wind spirally 



' Bidrag til Kundskaben om Lentibulariaeese," Copenhagen, 1874 



Chap. XVm. STEUOTUEE 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- 
d eed 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 within the bladders of Utricularia. 



Fig. 29. 

{GeinUsea omcbtti.') 

Utriculiferous leaf; enlarged about 

three times, 

I Up^er part of lamina of leaf. 
6 Utricle OT bladder. 
n Neck of utricle. 
o Orifice. 

a Spirally wound arms, with theil 
ends broken off. 



448 



GENLISEA OENATA. 



Ohap. XVIIL 



These papilla 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 foimed 
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 split 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 
These rows of hairs are indicated 
in the previous figure (29) by numerous transverse 
lines crossing the neck. The inside of the neck is 




Fio. 30. 
{Genlisea omata.') 
Portion of inside of neck leading 
nto '.lie utricle, greatly enlarged, show- 
ing the downward pointed bristles, 
aud small quadrifid cells or processes. 



pins are thrust. 



Chap. XVIII. CAPTURED PEET. 449 

also studded with papillse ; 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 
uj)per part of the bladders of Utricularia. The narrow 
transverse orifice (o, fig. 29) is situated between the 
bases of the two spiral arms. No 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 papillse, 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 
papillse 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, divide? 
close beneath the utricle. One branch extends up the 
dorsal and the other up the ventral side of both tlie 
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, 
trhich 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 nepk, except a living creature. 
Within the necks, however, of some specimens, a worm 
with retracted horny jaws, the abdomen of some 
articulate animal, and specks of dirt, 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 sufiiciently 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 Utricidaria — 
would find their egress rendered difficult by the sharp 
incurved hairs on the lips, and as soon as they passed 
some way down the neck, it would be scarcely possible 
for them to return, owing to the many transverse rows 
of long, straight, downward pointing 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 papillaa 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 02)en 
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. XVm. GENLISEA FILIFOEMIS. 451 

the tube into the neck, and so into the utricle. If the 
creature perished within the spiral arms, its decaying 
remains would be absorbed and utilised by the bifid 
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 papillse, exactly 
like those within the neck of Genlisea ornata. It is 
probable, therefore, that the whole utricle is similarly 
constructed. 

Genlisea filiformis (Bahia, Brazil). — Many leaves 
were examined and none were found provided with 
utricles, whereas such leaves were found without diffi- 
culty in the three previous species. On the other 
hand, the rhizomes bear bladders resembling in essen- 
tial character thdSe on the rhizomes of Utricularia. 
These bladders are transparent, and very small, viz. 
only -rro of ^^ 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 papillse, 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 COSCLUSION. Chaf. 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 
Utricularia, 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 
fiUformis 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 Utricularia 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 teaves 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 
Droseraceae, 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 



Ohap. xviil 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. 



ABBOSFnON. 



Absorption by Dionsea, 395 

— — by Drosera, 17 

— — by Drosophyllum, 337 

by Pinguicula, 381 

■ by glandular hairs, 344 

■ by glands of Utiictdaiia, 416, 

421 

• by quadrifids of Utrioiilaria, 

413, 421 

by Utricularla montnna, 437 

Acid, nature of, in digestive secre- 
tion of Drosera, 88 

present in digestive duid of 

various species of Drosera, Dio- 
nsea, Drodopliyllum, 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 

cai-bonate of ammonia, 145 
-^— of protoplasm in Drosera, a 

reflex action, 242 
— — in variout species ot 

Drosera, 278 
in Dionsea, 290, 300 

30 



Aggregation of protoplasm in Dro- 
sophyllum, 337, 339 

in Pinguiuula, 370, 389 

in Utrioulajia, 411, 41.'5, 

429, 430, 436 
Albumen, digested by Drosera, 92 

, liquid, action on Drosera, 79 

Alcohol, diluted, action of, on Dro- 
sera, 78, 216 
Aldrovanda vesiculosa, 321 
, absorption and digestion by, 

, varieties of, 829 

Algss, aggregation in fronds of, 65 
Alkalies, arrest digestive process in 

Drosera, 94 
Aluminium, salts of, action on 

Drosera, 184 
Ammonia, amount of, in rain water, 

172 
, carbonate, action on heated 

leaves of Drossra, 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 infl. ot;on in Drosera, 

153, 108 
, , size of particles affecting 

Drosera, 173 
, nitrate, smallness of doses 

causing inflection in Drosera, US, 

168 
^1 salts of, action on Drosera, 136 



^6 



TSTDEX. 



Ammonia, salts of, their action 
affected by previous immersion in 
water and varioue solutions, 21 3 

, , induce aggre^tion in 

Dr^sera, 13 

, various salts of, causing in- 
flection in Drosera ltJ6 

Antimony, tartrate, action on Dro- 
bera, 185 

Areolar tissue, its dgestion by 
Dro. era, 102 

Ar.-en'.ous acid, action on Drosera, 
185 

Atroi)ine, 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.. ou Dross a, 2 
, coats of pollen-grains not 

digested by insects, 117 
Binz, on action of quinine on white 

blood-corpuselea, 201 
, on pi lisonous action of quinine 

on low orgaidsms, 202 
Bom-, its digestion by Drosera, 105 
Bruiiton, Lauder, on digestion of 

gelatine, 111 
, on the composition of casein, 

115 

• , on tbe digestion of urea, 124 

, of cidorophyll, 126 

, of pepsin, 124 

Bvblia, 343 



Cabbage, decoction of, action on 

Drosera, 83 
Cadmium chloride, action on Dro- 

seia, 183 
Ciesiiim, chloride of action on 

Drosera, 181 



OUETIS. 

Calcium, salts of, action on Drosera, 

182 
Camphor, action on Drosera, 209 
Canby, Dr., ou Diunsea, 301, 310, 

313 

, on Drosera filiformis, 281 

Caraway, oil of, action on Droseia, 

211 
Carbonic acid, action on Drosera, 221 
, delays aggregation in Drosera, 

59 
Cartilage, its digestion by Dro^era, 

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 

, , ou Dion sea, 304 

Chlorophyll, grains of, in living 

plants, digested by Uroaera, 126 
, pure, not digested by Drostra, 

125 
Chondrin, its digestion by Drosera, 

112 
Chromic acid, action on Drosera, 

185 
Cloves, oil of, action on Droseia, 212 
Cobalt chloride, action on Drosera, 

186 
Cobra poison, action on Diosera, 

206 
Cohn, Prof, on Aldrnvanda, 321 
, on contractile tissues in plants, 

364 
, on movements of stamens of 

Compnsitaj, 256 

, on Utricularia, 395 

Cololiicine, action on Drosera, 201 
Copper chloride, action on Droser.i, 

185 
Cry>tallin, its digestion by Drosera 

120 
Curare, action on Drosera, 204 
Curtis, Dr., on Dionsea, 301 



INDEX. 



457 



D. 

D»rwin, Francis, on the effect of an 

induced galvanic current on Dro- 

sera, 37 
— , on the digestion of grains of 

chlorophyll, 126 

■ , on Utricularia, 442 

Dclpino, on Aldrovanda, 321 

, on Utricularia, 895 

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 

Digitaliue, action on Drosera, 203 
DionsBa 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 capturing insects, 

305 
, transmission of motor impulse, 

313 

, re-expansion of lobea, 318 

Direction of inflected tentacles of 

Drosera, 243 
Dolim, 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 



PIBEOUS. 

Drosera rotundifolia, effects of heat 

on, 66 

, its power of digestion, 8.t 

, backs of leaves not sensitive, 

231 
■ , transmission of motor impulse, 

234 

, general summary, 262 

spathulata, 280 

DroseracesB, concluding remarks on, 

355 
, their sensitiveness compared 

vrith 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 o*', 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 pEiralysing 

nerve centres, 224 
Ferment, nature of, in secretion of 

Drosera, 94, 97 
Fibrin, its digestion by Droicra, 100 
Pibro-cartilage, its digestion by 

Drosera, 104 
Fibro-eleistic ti^sue, not digested by 

Drosera, 122 
Fibrous ba.-i3 of bone, its digestion 

by Drosera, 108 



158 



INDEX. 



Fluids, nitrogenous, effects of, on 
Drosera, 76 

Fournier, on acids causing move- 
ments in stamens of Berberis, 196 

Frankl.iud, Prof., on nature of acid 
in secretion of Drosera. 88 



0. 

Galvanism, current of, causing in- 
flection of Drosera, 37 

, effects of, on Diojisea, 318 

Gardner, Mr., on Utricularia nelum- 
bifolia, 442 

Gelatine, impure, action on Drosera, 
80 

, pure, its digestion by Drosera, 

110 

Genliaea africana, 451 

filiformls, 451 

Genlisea ornata, structure of, 446 

, manner of capturing prey, 

Glandular hairs, absorption by, 344 

, summary on, 353 

Globulin, its digestion by Drosera, 

120 
Gluten, its digestion by Drosera, 

117 
Glycerine, inducing aggregation in 

Drosera, 52 

, action on Drosera, 212 

Gold chloride, action on Drosera, 

184 
Gorup-Besaiiez on the presence of a 

solvent in seeds of the vetch, 362 
Grass, decoction of, action on Dro- 
sera, 84 
Gray, Asa, on the Droseraeese, 2 
Greenland, on Drosera, 1, 5 
Gum, action of, on Drosera, 77 
Gun-cotton, not digested by Dro. 

sera, 125 



Haimatin, its digestion by Drosera, 

fiairs, glandular, absorption by, 344 
, , summary on, 353 



Heat, inducing aggregalion in Dro- 
sera, 53 

, effect of, on Drosera, 66 

, • , on Dionsea, 291, 319 

Heckel, on state of stamens of Ber- 
beris after excitement, 43 
Hofiueistir, on pressure arresting 

movements of protoplasin, 61 
Holland, Mr., on Utricularia, 395 
Hooker, Dr., on carnivorous plants. 2 
, on power of digestion by Ne- 
penthes, 97 

, history of observations on 

Dioneea, 286 
Hydrocyanic acid, effects of, on 

Dionsea, 305 
Hyoscyamus, action on Drosera, 84, 
206 



Iron chloride, action on Drosera, 

185 
Isinglass, solution of, action on 

Drosera, 80 



Johnson, Dr., on movement of flower- 
stems of Pinguicula, 381 



K. 

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 Dionsea, 301 
Kossmann, Dr., on rhizocephaluus 
crustaceans, 357 



Lead chloride, action on Drosera, 

184 
Leaves of Drosera, backs of, uo< 

sensitive, 231 



INDEX. 



459 



I.ogumin, its digestion by Drosera, 

116 
I.emna, aggregation in leaves of, 64 
Lime, carbonate of, precipitated, 

causing inflection of Drosera, 32 
, pliospliate of, its action on 

Drosera, 109 
Lithium, salts of, action on Drosera, 

181 



Magnesium, salts of, action on Dro- 
sera, 182 

Manganese chloride, action on Dro- 
sera, ISo 

Marshall, Mr. W., on Pinguicula, 
369 

Mians of movement in Dionssa, 313 

in Drosera, 254 

Meat, infusion of, causing aggrega- 
tion in Drosera, 51 

, , action on Drosera, 79 

, its digestion by Drosera, 98 

Mercury perchloride, action on 
Drosera. 183 

Milk, inducing aggregation in Dro- 
sera, 51 

, action on Drosera, 79 

, its digestion by Drosera, 113 

Mirabilis longiflora, glandular hairs 
of, 352 

Mo^giidge, Traherne, on acids in- 
juring seeds, 128 

Moore, Dr., on Pinguicula, 390 

Morphia acetate, action on Drosera, 
205 

Motor impulse in Drosera, 234, 258 

in Dionsea, 313 

Movement, origin of power of, 363 

Movements of leaves of Pinguicula, 
371 

of tentacles of Drosera, means 

of, 254 

of Dionsea, means of, 313 

Mucin, not digeoted by Drosera, 
122 

Mucus, action on Drosera, 80 

Miiller, Fritz, on rhizocepbalous 
crustaceans. 357 



PINGUICOLA. 



H. 



Nepenthijs, its power of digestion, 

97 
Nickel chloride, action on Drosera, 

186 
Nicotiana tabaoum, glandular hairs 

of, 352 
Nicotine, action on Drosera, 203 
Nitric ether, action on Drosera, 220 
Nitschke, Dr., refennces to his 

papers on Drosera, 1 
, on sensitiveness of backs of 

leaves of Droj-era, 231 
, on direction of inflected ten- 
tacles in Drosera, 244 

, on Aldrovanda, 322 

Nourishment, various means of, by 

plants, 452 
Nuttall; Dr., on re-expansion of 

Dioneea, 318 



0. 

Odour of pepsin, emitted from leaves 

of Drosera, 88 
Oil, olive, action of, on Drosera, 78, 

126 
Oliver, Prof., on TJtricularia, 432, 

441-446 



Papaw, juice of, hastening putrefac- 
tion, 411 

Particles, minute size of. causing 
inflection in Drosera, 27, 32 

Peas, decoction of, action on Dro- 
sera, 82 

Pelargonium zonale, glandular hiiii-s 
of, 350 

Pepsin, odour of emitted frcim Dro- 
sera leaves, 88 

, not digested by Drosera, 123 

, its secretion by animals ex- 
cited only after absorption, 129 

Peptogenes, 129 

Pinguicula grandiflora, 390 

lusitanioa, 391 



i60 



INDEX. 



PINGtIIOULA. 


SAXIFBAOA. 


Pingaicula vulgaris, structure of 




kaves and roots, 368 


B. 


, number of insects caught by, 




369 


Rain-wiiter, amount of ammonia in, 


, power of movement, 371 


172 


, secretion and absorption by. 


Ralfs, Mr , on Pinguicula, 390 


381 


Eansom, Dr., action of poisons on 


, digestion by, 381 


the yolk of eggs, 225 


, efteots of secretion on Jiving 


He-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 


Koots 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 Dion^a, 286 


gngation in Drosera, 50 


of Drosophyllum, 332 


, , action on Drosera, 179 


of Pinguicula, 369 


phnspliate, not decomposed by 


Eoridula, 342 


Drosera, 180, 187 


Eubidium chloride, action on Dro- 


Price, Mr. John, on Utricjilaria, 

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 tlie dissolution of proteid 


, , in Drosera, cuused 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, Burdon, 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 globulm, 120 


429. 430. 436 


, ofchloiophyll, 126 




, on different effect of solium 




and potassium un animals. 187 


Q. 


, on electric currents in Dionssa, 




318 


Quinine, salts of, action on Drosera, 


Saxifraga umbrosa. glaudular hairs 


201 


of, 345 



IITDEX. 



461 



Schiff, on hydrochloric acid dis- 
solving coagulated albumen, 
8B 

- — , on manner of digestion of 
albumen, 93 

■ , on changes in meat during 

d giBtion, 99 

' , on the coagulation of milk, 

114 

, on the digestioi. of casein, 

116 

, of mucus, 123 

, on peptogenea, 129 

Schloesing, on absorption of nitro- 
gen by Nicotianit, 352 

Scott, Mr., On Drosera, 1 

Secretion of Drosera, general ac- 
count of, 13 

, its antiseptic power, 

15 

■ — — , becomes acid from ex- 
citement, 86 

' • , nature of its feiment, 

94,97 

■ by Dionaea, 295 

by Drosophyllum, 335 

■ by Pinguicula, 381 

Seeds, living, acted on by Drosera, 
127 

■ , , acted on by Pinguicula, 

385, 390 

Sensitiveness, localisation of, in 
Drosera, 229 

of Dionffia, 289 

of Pinguicula, 871 

Silver nitrate, action on Drosera, 
181 

Sodium, salts of, action on Drosera, 
176 

, ■, inducing aggregation in 

Drosera, 50 

Sondera heterophylla, 284 

Sorby, Mr., on culouiing matter of 
Drosera, 5 

Spectroscope, its power compared 
with that of Drosera. 170 

Starch, action of, on Drosera, 78, 
126 

Stein, on Aldrovand i, 32] 

Strontium, salts of, uctiun on Dro- 
8tra, 183 



TUBPENTINE. 

Strychnine, salts of, action on 

Drosera, 199 
Sugar, solution of, action of, on 

Drosera, 78 
, , inducing aggregation in 

Drosera, 51 
Sulphuric ether, action on Drosera, 

219 

, on Dionsea, 304 

Syntonin, its action on Drosera, 102 



T. 

Tait, Mr., on Drosophyllum, 332 
Taylor. Alfred, on the detection of 

minute doses of poisons, 170 
Tea, infusion of, action on Drosera, 

78 
Tentacles of Drosera, move when 

glands cut of, 36, 229 

, inflection, direction of, 243 

, means of movement, 254 

, rp,-uxpansiun of, 260 

Theine, action on Drosera, 204 
Tin chloride, action on Drosera, 

185 
Tissue, areolar, its digeol]ion by 

Drodcra, 102 
, fibro-eliistic, not digested by 

Drosera, 122 
Tissues through which impulse is 

transmitted in Drosera, 2J7 

in Dionaea, 813 

Touches repeated, causing inflec- 
tion iu Droseja, 34 
Transmission of motor impulse in 

Droseia, 234 

iu Dionaja, 313 

Traube, Dr., on artiHci.il cells, 216 
Treat, Mrs., on Dro.=eia filiforiiiis, 

281 

, on Dionsea, 311 

, on Utriciilaria. 408, 430 

Tje'cul, on Diosera, 1,5 
Tnbersof Utiirularia raontana, 439 
Turpentine, action on Drooer:i, 212 



462 



INDEX. 



UBKA. 


zrso. 


V. 


W. 


Un a, not digested by Drpsera, 124 


■Warming, Dr., on Drosera, 2, 6 


Urine, action on Drosera, 79 


, on roots of Utricularia, 397 


Utiioularia olandestina, 430 


, on trifhomes, 359 


minor, 429 


, on Genlisea, 446 


Utricularia raontiina, stnioture of 


, on parenchymatous ctlls in 


bladders, 431 


tentacles of Dro^rerii, 252 


, animals caught by, 435 


Water, drops of, not causing inflec- 


, absorption by, 437 


tion in Drpsera, 35 


, tubers of, serving as reservoirs. 


, its power in causing aggrega- 


439 


tion in Drosera, 52 


Utricularia negleota, structure of 


, its power in causing inflection 


bladders, 397 


in Drosera, 139 


, animals caught 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 Droseia, 2j04 


to Drosera, 23 


Vessels in leaves of Drosera, 247 


, expenmi nts by cutting ves- 


of Dionsea, 314 


sels of Drosera, 249 


Vogel, on effects of camphor on 


Zinc chloride, notion on Drosera, 


plants, 209 


184 



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MEMOIRS OF PROF. E. L. YOUMANS. 

EDWARB lilVlNGSTON YOUMANS, Interpreter of Science 
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