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Full text of "Insectivorous plants"

CORNELL 

UNIVERSITY 

LIBRARY 




Bequest of 
Prof. Wilder D. Bancroft 





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Cornell University Library 




3 1924 031 177 961 
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INSECTIVOROUS PLANTS. 



WORKS BY THE SAME AUTHOR. 



X XATUEALIST'S JOURNTAL OF EESEAECHES INTO 

THE Natural HrSTORT and Groldgy of Countrcks visited during a Voyage 
Bound the World. Eighteenth Thousand, Woodcuts. Murray. 

THE ORIGIN OP SPECIES BY MEANS OP NATURAL 
SELECTION; or. The Preservation op Favoured Races in ™b 
Struggle for Life. Thirty-third Thousand. Woodcuts, Large Typa 
Edition. 2 vols. Crown 8vo., 12s. Cheap Edition, 6s. JMUbray. 

THE VARIOUS CONTRIVANCES BY WHICH ORCHIDS 
ARE FERTILIZED BY INSECTS. Fourth Thmisand. Woodcuts. 7s. 6d. 

Murray. 

THE VARIATION OP ANIMALS AND PLANTS UNDER 
DOMESTICATION. Sixth Thousand. Illustrations. 15s. Muerat. 

THE DESCENT OP MAN, AND SELECTION IN RELA- 
TION TO SEX. Twenty-first Thousand. Ulu-tratlons. Large Type Edition. 
2 vols. Crown 8vo., 15s. Cheap Edition, 7s. 6d. Muerav. 

THE EXPRESSION OP THE EJIOTIONS IN MAN AND 
ANIMALS, ninth Thousand. Illustrations. Mureay. 

INSECTIVOROUS PLANTS. Fifth Thousand. lUuetrations. 9s. 

JIURItAY. 

THE MOVEMENTS AND HABITS OP CLIMBING PLANTS. 

Third Thousand. Woodcut-j. 6s. Murray. 

THE EPFECTS OP CROSS AND SELP-PEETILIZATION 

IN THE VEGETABLE KINGDOM. Third Ilmisand. Illustrations. 9«. 

Murray. 
THE DIFFERENT FORMS OF FLOWERS ON PLANTS OP 

THE SAMU SPECIES. Third Thousand. Illustrations. 7s. 6d. Murray. 

THE POWER OP MOVEMENT IN PLANTS. Third Thousand. 

Woodcuts. Mureay. 

THE FORMATION OP VEGETABLE MOULD THROUGH 

THK ACTION OF WORMS, lenth Thousand. Woodcuts. Crown 8vo., 6s. 

MnSEAT. 

LIFE OP ERASMUS DARWIN. With a Study of his Scientific 
Works. Portrait. 7s. Sd. Mureay. 

THE STRUCTURE AND DISTRIBUTION OP CORAL 
REEFS. Second Wition, revised. Smith, Eldee, & Co. 

GEOLOGICAL OBSERVATIONS ON VOLCANIC ISLANDS 
AND OS PARTS OP SOUI'H AMERICA, visited during the Voyaiie of 
H.M.S. * Beagle.' Second Edition. Smith, Eldee, & Co. 

A MONOGRAPH OP THE OIRRIPEDIA. With numerous 
Illustrations. 2 vols. 8vo. Rat Societt. Hardwickb. 

A MONOGRAPH OF THE FOSSIL LEPADIDiE, OR 
PEDUNCULiTED CIRRIPEDS OF GREAT' BaiTAIN. 

PAL.ffiONT0GEAPnrCAL SOCIETY. 

A MONOGRAPH OP THE FOSSIL BALANIDJi! AND 

VERRUCIU/E OF GRUAT BRITAIN. Pal^ontogeapkioal Society. 



FACTS AND ARGUMENTS FOR DARWIN. By Fritz 

MtJLLEE. From the German, with Additions by the Author. Translated by 
W. S. Dallas, F.L.S. Illustrations. 65. Muekat. 



INSECTIVOROUS PLANTS, 



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



SECOND EDITION 
REVISED BY FRANCIS DARWIN. 



WITH ILLUSTRATIONS. 



LONDON: 

JOHN MUEEAY, ALBEMAELE STEEET. 

1888. 

Th& right of Translation is reserved. 






A, ^^3^5"^ 



LONDON: 
PBINTED BY WILLIAM CLOWES AND SONS, Limited, 

STAMFOaD STBEET AND CHABING CB0S3, 



PEEFACE TO THE SECOND EDITION. 



In the present Edition I have not attempted to give a 
complete account of the progress of the suhject since 1875. 
Nor have I called attention to those passages occurring 
occasionally throughout the book wherein the Author makes 
use of explanations, illustrations, or reference to authorities 
which seem to me not perfectly satisfactory. I have merely 
wished to indicate the more important points brought to 
light by recent research. The additions are in some cases 
placed in the text, but they are more commonly given as 
footnotes. They are, in all cases, indicated by means of 
square brackets. 

Misprints, errors in numbers, &c., have been set right, 
and a few verbal corrections have been taken from Charles 
Darwin's copy of the First Edition. Otherwise the text 



remains unchanged. 



Cambridge, 
July, 1888. 



Francis Darwin. 



CONTENTS. 

CHAPTER I. 

Dkosera eotundifolia, or tub Common Sun-dew. 

Number of insects captured — Description of the leaves and their 
appendages or tentacles — Preliminary sketch of the action of the 
various parts, and of the manner in which insects are captured — 
Duration of the inflection of the tentacles — Nature of the secretion 
— Manner in which insects are carried to the centre of the leaf — 
Evidence that the glands have the power of absorption — Small size 
of the roots Pages 1-17 

CHAPTER 11. 

The Movements of the Testacles fbom the Contact of Solid 

Bodies. 

Inflection of the exterior tentacles owing to the glands of the disc 
being excited by repeated touches, or by objects left in contact 
with them — Difference in the action of bodies yielding and not 
yielding soluble nitrogenous matter — Inflection of the exterior 
tentacles directly caused by objects left in contact with their glands 
— Periods of commencing inflection and of subsequent re-expansion 
— Extreme minuteness of the particles causing inflection — Action 
imder water — Inflection of the exterior tentacles when their glands 
are excited by repeated touches — Falling drops of water do not 
cause inflection 18-31 

CHAPTER III. 

Aggregation op 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 



VIU CONTENTS. 

glands and travels down the tentacles — Description of tlie 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 iiows 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 aggi'egated masses — Proximate causes of the 
aggregation of the protoplasm — Summary and concluding remarks 
— Supplementary observations on aggregation in the roots of 
plants Pages 32-55 



CHAPTEE IV. 

The Effects of Heat on the Leaves. 

N.iture of the experiments — Effects of boiling water — Warm water 
causes rapid inflection — Water at a higher temperature does not 
cause immediate inflection, but does not kill the leaves, as shown 
by their subsequent re-expansion and by the aggregation of the 
protoplasm — A still higher temperature kills the leaves and coagu- 
lates the albuminous contents of the glands . . . . 56-63 



CHAPTER V. 

The Effects of Non-niteogenous akd Nitkogenous Orgakic 
Fluids on the Leaves. 

Non-nitrogenous fluids — Solutions of gum arable — Sugar — Starch — 
Diluted alcohol — Olive oil — Infusion and decoction of tea — Nitro- 
genous fluids — MUk — 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 64-70 



CHAPTER VI. 

The Digestive Power of the Secretion op Dbosera. 

The secretion rendered acid by the direct and indirect excitement of 
the glands — Nature of the acid — Digestible substances — Albumen, 
its digestion arrested by alkalies, recommences by the addition of 
an acid — Meat — Fibrin — Syntonin — ^Areolar tissue — Cartilage — 
Fibro-cartilage — Bone — Enamel and dentine — Phosphate of hme — 
Fibrous basis of bone — Gelatine — Chondrin — MUk, casein and 
cheese — Gluten — Legumin — Pollen — Globulin — Hajmatin — 



CONTENTS. IX 

Indigestible substances — Epidermio productions — Fibre-elastic 
tissue — Mucin — Pepsin — Urea — Ohitine — Cellulose — Gun-cotton — 
Chlorophyll — Fat and oil — Starch — Action of the secretion on 
living seeds — Summary and concluding remarks Pages 71-110 



CHAPTER VII. 

The Effects of Salts op Ammokia. 

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 aggrega- 
tion of the protoplasm— Nitrate of ammonia, analogous experiments 
with — Phosphate of ammonia, analogous experiments with — Other 
salts of ammonia — Summary and concluding remarks on the action 
of salts of ammoaia 111-141 



CHAPTER VIII. 
The Effects of vakiocs other Salts, and Acids, on the Leaves. 

Salts of sodium, potassium, and other alkaline, earthy, and metallic 
salts — Summary on the action of these salts — Various acids — 
Summary on their action 142-161 

CHAPTER IX. 

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

Strychnine, salts of — Quinine, sulphate of, does not soon arrest 
the movement of the protoplasm — Other salts of quinine — 
Digitaline — Nicotine — Atropine — Veratrine — Colchicine — Theine 
— Curare — Morphia — Hyosoyamus — Poison of the cobra, apparently 
accelerates the movements of the protoplasm — Camphor, a powerful 
stimulant, its vapour narcotic — Certain essential oils excite move- 
ment — Glycerine — ^Water and certain solutions retard or prevent 
the subsequent action of phosphate of ammonia — Alcohol innocuous, 
its vapour narcotic and poisonous — Chloroform, sulphuric and 
nitric ether, their stimulant, poisonous, and narcotic power — 
Carbonic acid narcotic, not quickly poisonous — Concluding 
remarks 162—186 



CONTENTS. 



CHAPTER X. 

On the Senshtveness of the Leaves, and on the Lines op 
Tbansmission of the Motor Impulse. 

Glands and summits of the tentacles alone sensitive — ^Transmission of 
the motor impulse down the pedicels of the tentacles, and across 
the blade of the leaf — Aggregation of the protoplasm, a reflex 
action — First discharge of the motor impulse sudden — ^Direction 
of the movements of the tentacles — Motor impulse transmitted 
through the cellular tissue — Mechanism of the movements — Nature 
of the motor impulse — Re-expansion of the tentacles Pages 

187-211 

CHAPTER XL 

Recapitulation of the Chief Observations on Dkosera 
rotukdifolia 212-223 

CHAPTER XIL 

On the Structure and Movements of some other Species of 
Dboseea. 

Drosera anglica — Brosera intermedia — Drosera capensis — -Drosera 
spathulata ■ — Drosera filiformis — Dronera hinata — Concluding 
remarks 224r-230 



CHAPTER XIIL 

DlON^aSA muscipula. 

Structure of the leaves — Sensitiveness of the filaments — Rapid move- 
ment of the lobes caused by irritation of the filaments — Glands, 
their power of secretion— Slow movement caused by the absorption 
of animal matter — Evidence of absorption from the aggregated 
condition of the glands — Digestive power of the secretion — Action 
of chloroform, ether, and hydrocyanic acid — The manner in which 
insects are captured — ^Use of the marginal spikes — Kinds of insects 
captured — The transmission of the motor impulse and mechanism 
of the movements — Re-expansion of the lobes 231-259 

CHAPTER XIV. 

Aldrovanda vesiculosa. 

Captures crustaceans — Structure of the leaves in comparison with 
those of Dionsea — Absorption by the glands, by the quadrifid 



CONTENTS. XI 

processes, and points on the infolded margins — Aldrovanda 
vesicidosa, var. australis — Captures prey — Absorption of animal 
matter — Aldrovanda vesiculosa, var. verticillata — Concluding 
remarks Pages 260-268 



CHAPTER XV. 

DnosopHTLLUM — EoniDTjLA — Byblis — Glandular Hairs op other 
Plants — Ooncldding Remarks on the UsosERACEiE. 

Drosophyllum — Structure of leaves — Nature of the secretion — Manner 
of catching insects — Power of absorption — Digestion of animal 
substances — Summary on Drosophyllum — Eoridula — Byblis — 
Glandular hairs of other plants, their power of absorption — 
Saxifraga — Primula — Pelargonium — Erica — Mirabilis — Nicotiana 
— Summary on glandular hairs — Concluding remarks on the 
Droseracea; 269-296 



CHAPTER XVI. 

PiNGUIOCLA. 

Pinguicula vulgaris — Structure of leaves — Number of insects and 
other objects caught — Movement of the margins of the leaves — 
Uses 'Of this movement — Secretion, digestion, and absorption — 
Action of the secretion on various animal and vegetable substances 
— The effects of substances not containing soluble nitrogenous 
matter on the glands — Pinguicula grandiflora — Pinguicula lusi- 
tanica, catches insects — Movement of the leaves, secretion and 
digestion 297-318 



CHAPTER XVII. 

Utricularia. 

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

319-347 



XU CONTENTS. 

CHAPTER XVIII. 

Uteiculaeia (continued). 

Uiricularia montana — Description of the bladders on the subterranean 
rhizomes — Prey captured by the bladders of plants under culture 
and in a state of nature — Absorption by the quadrifid processes 
and glands — Tubers serving as reservoirs for water — Various other 
species of Utricularia — Polypompholyx — Genlisea, different nature 
of the trap for capturing prey — Diversified methods by which 
plants are nourished Pages 348-3C7 



Index 369-377 



LIST OF THE CHIEF ADDITIONS TO THE 
SECOND EDITION. 



Page 

5 

15 

22 

32 
32 
34 

39 

72 

73 
81 

85 
95 
106 
200 
204 
209 
232 
233 

234 

235 

238 
243 
247 
256 
256 
257 
260 
261 



Gardiner on the structure of the gland cells in Drosera dichotama. 

Evidence that Drosera profits by an animal diet. 

The conclusions as to the sensitiveness of Drosera to a touch, modified 

in accordance with Pfeffer's views. 
Gardiner on the rhabdoid. 
On the nucleus in the tentacle-cells of Drosera. 
The conclusion that the aggregated masses are protoplasmic, and execute 

spontaneous movements, erroneous. 
De Vriea on the character of aggregation produced by carbonate of 

ammonia. 
Gardiner on the changes occurring during secretion, in the glands of 

Drosera dichotama. 
Eees and Will on the nature of the acid in the secretion of Drosera. 
Eees, Will, von Gorup, and Vines on the secretion of the acid and of 

the ferment in Drosera and Kepenthes. 
Results with syntonin untrustworthy. 
Results with casein untrustworthy. 
SchifFs peptogene theory. 

[Transmission of motor impulse. 

Gardiner and Batalin on the mechanism of movement in Drosera. 

Fraustadt and C. de CandoUe on the stomata of Dionsca. 

Fraustadt, C. de CandoUe and Batalin on the sensitive filaments of 

Dioucca. 
Mnnk on the sensitiveness of Dionsea to the hygrometric state of the 

air. 
C. de CandoUe on the effect of drops of water on the sensitive filaments 

of Dionaea. 
Gardiner on the glands of Dion*a. 
J. D. Hooker on the early history of Dionasa. 
Munk on a movement of the edges of the leaf in Diona;a. 
Batalin and Munk on the mechanism of the movement in Dionsea. 

)Burdon Sanderson, Kunkel and Munk on the electrical phenomena in 
Dionaea. 
Caspary on Aldrovanda. 
Cohn and Caspavy on Aldrovanda. 



XIV CHIEF ADDITIONS TO THE SECOND EDITION. 



PAGE 

263 
268 
288 

297 
304 
314 
320 
332 

348 

359 
365 
365 

366 



Mori on the seat of irritability in Aldroranda. 

Duval-Jouve on the function of certain glands in Aldrovanda. 

Fraustadt, Penzig, and Pfefier on the roots of Dionsa and Droso- 

phyllum. 
Eatalin on the yellow-green colour of Pinguicula. 
Batalin on the pits or depressions in the leaves of Pinguicula. 
PfefFer on the use of Pinguicula as rennet. 
Kamieuski on the absence of the root in Utricularia. 
Schimper on the evidence of absorption of the products of decay in 

Vtricularia comvia. 
Hovelacque, Schenfc, and Schimper on the morphology of Utricularia 

montana. 
Schimper on Utricularia cornuta. 

Schimper on the evidence of absorption in Sarracenia. 
De Bary on the vigorous growth of Utricularia when supplied with 

animal food. 
Treub on Dischidia Rafflesiana. 



INSECTIYOEOUS PLANTS. 



CHAPTEE I. 

DeOSERA nOTtJNDIFOLIA, OR THE COMMON SUX-DEW. 



Number of insects captured — Description of the leaves and their appendages 
or tentacles — Preliminary sketch of the action of the various parts, JTnd 
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 gland^ have the 
power of absorption — Small size of the roots. 

DuEiNG the summer of 1860, 1 was surprised by finding how 
large a number of insects were caught by the leaves of the 
common sun-dew (JJrosera rotundifolia) on a heath in Sussex. 
I had heard that insects were thus caught, but knew nothing 
further on the subject.* I gathered by chance a dozen plants. 



* As Dr. Nitsohke has given (' Bot. 
Zeitung,' 1860, p. 229) the biblio- 
graphy of Drosera, I need not here 
go into details. Most of the notices 
published before 1860 are brief and 
unimportant. The oldest paper seems 
to have been one of the most valuable, 
namely, by Dr. Roth, in 1782. [In 
■the ' Quarterly Journal of Science and 
Art,' 1829, G. T. Burnett expressed 
his belief that Drosera profits by the 
absorption of nutritive matter from 
the captured insects. — F. D.] There 
is also an interesting though short 
account of the habits of Drosera by 
Dr. Milde, in the 'Bot. Zeitung,' 
1852, p. 540. In 1855, in the 'An- 
nales des Sc. nat. bot.,' torn. iii. pp. 
297 and 304, MM. Greenland and 



Trdcul each published papers, with 
figures, on the structure of the leaves ; 
but M. Tr^cul went so far as to doubt 
whether they possessed any power of 
movement. Dr. Nitschke's papers in 
the 'Bot. Zeitung' for 1860 and 
1861 are by far the most important 
ones which have been published, both 
on the habits and structure of this 
plant ; and I shall frequently have 
occasion to quote from them. His 
discussions on several points, for in- 
stance on the transmission of an 
excitement from one part of the leaf 
to another, are excellent. On Dec. 
11, 1862, Mr. J. Scott read a paper 
before the Botanical Society of Edin- 
burgh, which was published in the 
' Gardener's Chronicle,'" 1863, p. 30. 
B 



2 DEOSEEA KOTUNDIFOLIA. [Chap. I. 

bearing fifty-six fully expanded leaves, and on thirty-one of 
these dead insects or remnants of them adhered; and, no 
doubt, many more would have been caught afterwards by 
these same leaves, and still more by those as yet not expanded. 
On one plant all six leaves had caught their prey ; and on 
several plants very many leaves had caught more than a 
single insect. On one large leaf I found the remains of 
thirteen distinct insects. Flies (Diptera) are captured much 
oftener than other insects. The largest kind which I have 
seen caught was a small butterfly (Gaenonympha pamphilus) ; 
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 {Msculus: 
hippocastanum), without thereby receiving, as far as we can 
perceive, any advantage ; but it was soon evident that 
Drosera was excellently adapted for the special purpose of 
catching insects, so that the subject seemed well worthy of 
investigation. 

The results have proved highly remarkable ; the more 
important ones being — firstly, the extraordinary sensitiveness- 
of the glands to slight pressure and to minute doses of certain 
nitrogenous fluids, as shown by the movements of the so- 
called hairs or tentacles ; secondly, the power possessed by 



Mr. Scott shows that gentle irrita- delivered a lecture on Dionsea, before 

tion of the hairs, as well as insects the Royal Institution (published in 

placed on the disc of the leaf, cause 'Nature,' June 14, 1874), in which a 

the hairs to bend inwards. Mr. A. short account of my observations on^ 

W. Bennett also gave another inter- the power of true digestion possessed 

esting account of the movements of by Drosera and Dionasa first appeared, 

the leaves before the British Associa- Prof. Asa Gray has done good service 

tion for 1873. In this same year Dr. by calling attention to Drosera, and 

Warming published an essay, in which to other plants having similar habits,. 

he describes the structure of the in ' The Nation ' (1874, pp. 261 and 

so-called hairs, entitled, " Sur la 232), and in other publications. Dr. 

Diifurence entre, les Trichomes," &c., Hooker also, in his important address 

extracted from the proceedings of on Carnivorous Plants (Brit. Assoc, 

the Soc. d'Hist. Nat. de Copenhague. Belfast, 1874), has given a history of 

I shall also have occasion hereafter the subject. [A paper on the com- 

to refer to a paper by Mrs. Treat, of parative anatomy of the Droseraceai 

New Jersey, on some American species was published in 1879 by W. Oels as- 

of Drosera. Dr. Bnrdon Sanderson a Dissertation at Breslau-] 



Chai'. I.] 



STKUCTUEE OF THE LEAVES. 



the leaves of rendering soluble or digesting nitrogenous 
substances, and of afterwards absorbing them ; thirdly, the 
changes which take place within the cells of the tentacles, 
when the glands are excited in various ways. 

It is necessary, in the first place, to describe briefly the 




Fig. I* 

^Drosera rotundifolia.') 

Leaf viewed from above ; enlarged four times. 



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 ap- 
pearance of a leaf is shown, as seen from above, in fig. 1, and 
as seen laterally, in fig. 2. The leaves are commonly a little 



* The drawings of Drosera and 
Bionsca, given in this work, were 
made for me by my son, George Dar- 
win ; those of Aldrovanda, and of the 



several species of Utrlcularia, by my 
son Francis. They have been ex- 
cellentlv reproduced on wood by Mr. 
Cooper," 188 Strand. 

B 2 



DEOSEEA KOTUNDIFOLIA. 



[Chap. I. 



iDroader than long, but this was not the case in the one here 
figured. The whole upper surface is covered with gland- 
hearing filaments, or tentacles, as I shall call them, from their 
manner of acting. The glands were counted on thirty-one 
kaves, but many of these were of unusually large size, and 
the average number was 192 ; the gi-eatest number being 260, 
and the least 130. The glands are each suiTounded 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. 




Fig. 2. 

(Drosei-a rotundifolia.) 

Old leaf viewed laterally; enlarged alKiut five times. 



The tentacles on the central part of the leaf or disc are short and 
stand upright, and their pedicels are green. Towards the margin they 
become longer and longer and more inclined outwards, with their 
pedicels of a purple colour. Those on the extreme margin project in 
the same plane with the leaf, or more commonly (see fig. 2) are 
considerably 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 m 
number to the longer submarginal and marginal tentacles, having 
purple pedicels, as nine to sixteen. 

A tentacle consists of a thin, straight, hair-like pedicel, carrying a 
gland on the summit. The pedicel is somewhat flattened, and is 
formed of several rows of elongated cells, filled with purple fltiid or 
granular matter.* There is, however, a narrow zone close beneath the 



* According to Nitschke ('Bot. 
Zeitung,' 1861, p. 224) the purple 
fluid results from the metamorphosis 
of chlorophyll. Mr. Sorby examined 
the colouring matter with the spec- 
troscope, and informs me that it 
consists of the commonest species of 
erythrophyll, " which is often met 



with in leaves with low vitality, and 
in parts, like the petioles, which 
carry on leaf-functions in a very 
Imperfect mauner. All that can be 
said, therefore, is that the hairs (or 
tentacles) are coloured like parts of a 
leaf which do not fulfil their proper 
office." 



Chap. I.], STEUCTUEE OF THE LEAVES. 5 

glands^ of the longer tentacles, and a broader zone near their bases, of a 
green tint. Spiral vessels, accompanied by simple vascular tissue, 
branch oif 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 (triohomes) or prolongations of the leaf. Nitschke 
has shown that they include all the elements proper to the blade of a 
leaf; and the fact of their including vascular tissue was formerly 
thought to prove that they were prolongations of the leaf, but it is 
now known that vessels sometimes enter true hairs.* The power of 
movement which they possess is a strong argument against their being 
viewed as hairs. The conclusion which seems to me the most 
probable will be given in Chap. XV., namely that they existed pri- 
mordially as glandular hairs, or mere epidermic formations, and that 
their upper part should still be so considered ; but that their lower 
part, which alone is capable of movement, consists of a prolongation of 
the leaf; the spiral vessels being extended from this to the uppermost 
part. We shall hereafter see that the terminal tentacles of the 
divided leaves of Eoridula are still in an intermediate condition. 

The glands, with the exception of those borne by the extreme 
marginal tentacles, are oval, and of nearly uniform size, viz. about -g^ of 
an inch in length. Their structure is remarkable, and their functions 
complex, for they secrete, absorb, and are acted on by various stimulants. 
They consist of an outer layer of small polygonal cells,t containing 
purple granular matter or fluid, and with the walls thicker than those 
of the pedicels. Within this layer of cells there is an inner one of 
differently shaped ones, likewise filled with purple fluid, but of a 
slightly difierent tint, and differently affected by chloride of gold. 
These two layers are sometimes well seen when a gland has been 
crushed or boiled in caustic potash. According to Dr. Warming, there 
is still another layer of much more elongated cells, as shown in the 
accompanying section (fig. 3) copied from his work ; but these cells 
were not seen by Nitschke, nor by me. In the centre there is a group 
of elongated, cylindrical cells of unequal lengths, bluntly pointed at 
their upper ends, truncated or rounded at their lower ends, closely 
pressed together, and remarkable from being surrounded by a spiral 
line, which can be separated as a distinct fibre. 

These latter cells are filled With limpid fluid, which after long 



* Dr. Nitschke has discusssd this iii. 1855, pp. 297 and 303. 

subject in ' Bot. Zeitung,' 1861, p. f [Gardiner (' Proc. Eoyal Soc.,' No. 

241, &c. See also Dr. Warming 240, 1886) has pointed out that in 

('Stir la Difference entre les Tri- Drosera dichotoma "the gland-cells 

chomcs,' &c., 1873), who gives refer- of the head are provided with delicate 

ences to various publications. See uncuticularised cell-walls, which are 

also Greenland and Tr&ul, ' Annal. remarkably pitted on their upper Or 

des Sc. nat. bot.' (4th series), torn. free surfaces." — F. D.] 



DROSEEA EOTUNDIFOLIA. 



[Chap. I. 



immersion in alcohol deposits much brown matter. I presume that 
they are actually connected with the spiral vessels which run up the 
tentacles, for on several occasions the latter were seen to divide into 
two or three excessively thin branches, which could be traced close up 
to the spiriferous cells. Their development has been described by Dr. 
Wanning. Cells of the same kind have been observed in other plants. 




Fig. 3. 

(2>ro5em rotundifolia.') 

Iiongitadinal section of a gland ; greatly magnified. From Dr. Warming. 

as I hear from Dr. Hooker, and were seen by me in the margins of the 
leaves of Pingaicula. Whatever their fimction 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 o^enera of 
the Droseracese. 



CiiAr. I.] STEUOTURE OF THE LEAVES. 7 

The extreme marginal tentacles differ slightly from the others 
Their bases are broader, and, besides their own vessels, they receive a 
fine branch from those which enter the tentacles on each side. Their 
glands are much elongated, and lie embedded on the 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 of the 
glands, differs to a certain extent from that within the cells of the 
pedicels. For, when a leaf is placed in hot water or in certain acids, 
the glands become quite white and opaque, whereas the cells of the 
pedicels are rendered of a bright red, with the exception of those close 
beneath the glands. These latter cells lose their pale red tint ; and the 
green matter which they, as well as the basal cells, contain, becomes of 
a bri'ihter green. The petioles boar many multicellular hairs, some of 
which near the blade are surmounted, according to Nitschke, by a few 
rounded cells, which appear to be rudimentary glands. Both surfaces 
of the leaf, the pedicels of the tentacles, especially the lower sides of 
the outer ones, and the petioles, are studded with minute papillse (hairs 
or triohomes), having a conical basis, and bearing on their summits 
two, and occasionally three, or even four, rounded cells, containing 
much protoplasm. These papillas are generally colourless, but some- 
times include a little pur^ile 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 not to recur to the papilliE, 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 lor 10 hours, the cells of 
the papillas had evidently absorbed animal matter, for instead of limpid 
fluid they now contained small aggregated masses of protoplasm,t 
which slowly and incessantly changed their forms. A similar result 
ibllowed from an immersion of only 15 minutes in a solution of one 
part of carbonate of ammonia to 218 of water, and the adjoining cells 



* Nitschke has elaborately de- K. Microscop. Soc' Jan. 1876.— F. D.] 
scribed and figured these papilla;, t [With regard to the aggregated 

' Bet. Zeitung,' 1861, pp. 234, 253, masses, see p. 34, footnote.— F. D.] 
254. [See also A. W. Bennett, ' Trans. 



8 DEOSEEA EOTUNDIFOLIA. [CHAr. I. 

of tlie tentacles, on which the papillse were seated, now likewise 
contained -aggregated masses of protoplasm. We may therefore 
conclude that, when a leaf has closely clasped a captured insect in the 
manner immediately to be described, the papilte, 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 papillie on the backs of the leaves or on the 
petioles. 

Preliminary Shetch of the Action of the Several Parts, and of the 
Manner in which Insects are Captured. 

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

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

The tentacles in the act of inflection sweep through a wide 
space ; thus a marginal tentacle, extended in the same plane 
with the blade, moves through an angle of 180°; and I have 



* 'Bot. Zeitung,' 1860, p. 246. 



Chap. I.] 



ACTION OF THE PAETS. 



9 



seen the mucli reflected tentacles of a leaf wiiicli stood 
upright move through an angle of not less than 270°. The 
bending part is almost confined to a short space near the 
base ; but a rather larger portion of the elongated exterior 
tentacles becomes slightly incurved, the distal half in all 
cases remaining straight. The short tentacles in the centre 
of the disc, when directly excited, do not become inflected ; 
but they are capable of inflection if excited by a motor 
imj)ulse received from other glands at a distance. Thus, if a 





Fig. 4. 

(Drosera votundifolia.') 

Leaf (enLirged) with all the tentacles 
cloaely inflected, from immersion in a 
solution of pbosphaie of ammonia (one 
part to 87,600 of water). 



Fig. 6. 

(Z>j*osej'a votundifolia.) 

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



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



10 



DKOSERA EOTUNDIFOLIA. 



[ClIAP. I. 



The kind of inflection which the tentacles undergo is best 
shown when the gland of one of the long exterior tentacles 
is in any way excited; for the surrounding ones remain 
unaffected. In the accompanying outline (fig. 6) we 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 beginning to bend 
in ten seconds, after an object had been placed on its gland ; 
and I have often seen strongly pronounced inflection in under 
one minute. It is surprising how minute a particle of any 




-i. 



iMG. C. 

{Ih-osera rotandifoUa.') 

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



substance, such as a bit of thread or hair or splinter of glass, 
if placed in actual contact with the surface of a gland, 
suffices to cause the tentacle to bend. If the object, which 
has been can-ied 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 extei-ior tentacles, causing them to bend inwards. 

Not only the tentacles, but the blade of the leaf often, 
but by no means always, becomes much incurved, when any 
strongly exciting substance or fluid is placed on the disc. 
Drops of milk and of a solution of nitrate of ammonia or soda 
are particularly apt to produce this effect. The blade is thus 
converted into a little cup. The manner in which it bends 



Chap. I.] ACTION OF THE PAETS. 11 

varies greatly. Sometimes the apex alone, sometimes one 
side, and sometimes both sides, become incurved. For instance, 
I placed bits of bard-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 aifected, though the tentacles 
were as closely inflected as in the two previous cases. The 
whole blade also generally rises or bends upwards, and thus 
forms a smaller angle with the footstalk than it did before. 
This appears at first sight a distinct kind of movement, but 
it results from the incurvation of that part of the margin 
which is attached to the footstalk, causing the blade, as a 
whole, to curve or move upwards. 

The length of time during which the tentacles as well as 
the blade remain inflected over an object placed on the disc, 
depends on various circumstances; namely on the vigour 
and uge 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 ibr 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 ntimber 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 di£Bcult to ascertain. In some cases, however, 
the effect was strongly marked, as when particles of sugar 
were added; but the result in this case is probably due 
merely to exosmose. Particles of carbonate and phosphate 
of ammonia and of some other salts, for instance sulphate of 
zinc, likewise increase the secretion. Immersion in a solution 
of one part of chloride of gold, or of some other salts, to 437 
of water, excites the glands to largely increased secretion ; on 



12 DKOSEEA EOTUNDIFOLIA. [CHAr. I. 

the other hand, tartrate of antimony produces no such effect. 
Immersion in many acids (of the strength of one part to 437 
of water) likewise causes a wonderful amount of secretion, so 
that, when the leaves are lifted out, long ropes of extremely 
viscid fluid hang from them. Some acids, on the other hand, 
do not act in this manner. Increased secretion is not 
necessarily dependent on the inflection of the tentacle, for 
particles of sugar and of sulphate of zinc cause no movement. 

It is a much more remarkable fact, that when an object, 
such as a bit of meat or an insect, is placed on the disc of a 
leaf, as soon as the surrounding tentacles become considerably 
inflected, their glands pour forth an increased amount of 
secretion. I ascertained this by selecting leaves with equal- 
sized drops on the two sides, and by placing bits of meat on 
one side of the disc ; and as soon as the tentacles on this side 
became much inflected, but before the glands touched the 
meat, the drops of secretion became larger. Thi8_ was 
repeatedly observed, but a record was kept of only thirteen 
cases, in nine of which increased secretion was plainly 
observed; the four failures being due either to the leaves 
being rather torpid, or to the bits of meat being too small to 
cause much inflection. We must therefore conclude that the 
central glands, when strongly excited, transmit some in- 
fluence to the glands of the circumferential tentacles, causing 
them to secrete more copiously. 

It is a still more important fact (as we shall see more fuUy 
when we treat of the digestive power of the secretion), that 
when the tentacles become inflected, owing to the central 
glands having been stimulated mechanically, or by contact 
with animal matter, the secretion not only increases in 
quantity, but changes its nature and becomes acid ; and this 
occurs before the glands have touched the object on the 
centre of the leaf. This acid is of a different nature from 
that contained in the tissue of the leaves. As long as the 
tentacles remain closely inflected, the glands continue to 
secrete, and the secretion is acid ; so that, if neutralised by 
carbonate of soda, it again becomes acid after a few hours. I 
have observed the same leaf with the tentacles closely in- 
flected over rather indigestible substances, such as chemi- 
cally prepared casein,* pouring forth acid secretion for eight 



* [These obsei-viitions are not trustworthy, owing to the mode of preparation 
of the casein. See p. 95. — F. D.] 



Chap. I.] ..ACTION OF THE PAETS. 13 

successive days, and over bits of bone for ten successive 
days. 

The secretion seems to possess, like tbe 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 secre- 
tion, was free from infusoria, and its strias were perfectly 
distinct in the central and undissolved portion. In like 
manner small cubes of albumen and cheese placed on wet 
moss became threaded with filaments of mould, and had 
their surfaces slightly discoloured and disintegrated ; whilst 
those on the leaves of Drosera remained clean, the albumen 
being changed into transparent fluid. 

As soon as tentacles, which have remained closely inflected 
during several days over an object, begin to re-expand, their 
glands secrete loss 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-expansion is of some little service to the plant ; for I have 
often observed that objects adhering to the leaves could then 
be blown away by a breath of air ; the leaves being thus 
left unencumbered and free for future action. Nevertheless, 
it often happens that all the glands do not become completely 
dry ; and in this case delicate objects, such as fragile insects, 
are sometimes torn by the re-expansion of the tentacles into 
fragments, which remain scattered all over the leaf. .After 
the re-expansion is complete, the glands quickly begin to 
re-secrete, and, as soon as full-sized drops are formed, the 
tentacles are ready to clasp a new object. 

When an insect alights on the central disc, it is instantly 
entangled by the viscid secretion, and the surrounding 
tentacles after a time begin to bend, and ultimately clasp it 
on all sides. Insects are generally killed, according to 
Dr. Nitschke, in about a quarter of an hour, owing to their 
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 



14 DROSEEA KOTUNDIFOLIA. [Chap. I. 

next succeeding tliem inwards ; these then hend inwards, 
and so onwards, until the insect is ultimately carried by a 
curious Sort of rolling movement to the centre of the leaf. 
Then, after an interval, the tentacles on all sides become 
inflected and bathe their prey with their secretion, in the 
same manner as if the insect had iirst alighted on the central 
disc. It is surprising how minute an insect suffices to cause 
this action : for instance, I have seen one of the smallest 
species of gnats (Culex), which had just settled with its 
excessively delicate feet on the glands of the outermost 
tentacles, and these were already beginning to curve 
inwards, though not a single gland had as yet touched the 
body of the insect. Had I not interfered, this minute gnat 
would assuredly have been carried to the centre of the leaf 
and been securely clasped on all sides. We shall hereafter 
see what excessivelj' small doses of certain organic fluids 
and saline solutions cause strongly marked inflection. 

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

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

The absorption of animal matter from captured insects 



Chap. I.] ACTION OF THE PAETS. 15 

explains how Drosera oau flourish in extremely poor peaty- 
soil, — in some cases wliei'e nothing but sphagnum moss 
grows, and mosses depend altogether on the atmosphere for 
their nourishment. Although the leaves at a hasty glance 
do not appear green, owing to the purple colour of the 
tentacles, yet the upper and lower surfaces of the blade, the 
pedicels of the central tentacles, and the petioles contain 
chlorophyll, so that, no doubt, the plant obtains and assimi- 
lates carbonic acid from the air. Nevertheless, considering 
the nature of the soil where it grows, the supply of nitrogen 
would be extremely limited, or quite deficient, unless the 
plant had the power of obtaining this important element 
from captured insects. We can thus understand how it is 
that the roots are so "jioorly developed. These usually 
consist of only two or three slightly divided branches, fiom 
half to one inch in length, furnished with absorbent hairs. 
It apijears, therefore, that the roots serve only to imbibe 
water; though, no doubt, they would absorb nutritious 
matter if present in the soil ; for as we shall hereafter see, 
they absorb a weak solution of carbonate of ammonia. A 
plant of Drosera, with the edges of its leaves curled inwards, 
so as to form a temporarj' stomach, with the glands of the 
closely inflected tentacles pouring forth their acid secretion, 
which dissolves animal matter, afterwards to be absorbed, 
may be said to feed like an animal. But, differently from 
an animal, it drinks by means of its roots ; and it must 
drink largely, so as to retain many drops of viscid fluid 
round the glands, sometimes as many as 260, exposed during 
the whole day to a glaring sun. 

[Since the publication of the first edition, several experi- 
ments have been made to determine whether insectivorous 
plants are able to profit by an animal diet.] 

My experiments were published in 'Linnean Society's 
Journal,'* and almost simultaneouly the results of Kellermann 
and Von Eaumer were given in the ' Botanische Zeitung.'t 
My experiments were begun in June 1877, when the plants 
were collected and planted in six ordinary soup-plates. Each 
plate was divided by a low jjartition into two sets, and the 



* Vol. xvii., Francis Darwin on the fiitternng : " ' Bot. Zeitung,' 1878. 

' Nutrition of Drosera rotandifolia.' Some account of the results was 

t "Vegetationsversuche an Z>ros«'a given before the Phys.-med. Soc, 

rotundifolia mit uud ohne Fleisch- Erlangen, July 9, 1877. 



100 


121-5 


100 


164-9 


100 


231-9 


100 


194-4 


100 


379-7 


100 


241-5 



16 DEOSEEA EOTUNDIFOLIA. [Chap. I. 

least flourishing half of each culture -was selected to be " fed/' 
while the rest of the plants -were destined to he "starved." 
The plants were prevented from catching insects for them- 
selves by means of a covering of fine gauze, so that the only- 
animal food which they obtained was supplied in very 
minute pieces of roast meat given to the " fed " plants but 
withheld from the " starved" ones. After only 10 days the 
difference between the fed and starved plants was clearly 
visible: the fed plants were of brighter green and the 
tentacles of a more lively red. At the end of August the 
plants were compared by number, weight, and measurement, 
with the following striking results : — 

starved. Fed. 

Weight (without flower-stems) 
Number of flower-stems . 
Weight of stems .... 
Number of capsules 
Total calculated weight of seed 
Total calculated number of seeds 

These results show clearly enough that insectivorous 
plants derive great advantage from animal food. It is of 
interest to note that the most striking difference between the 
two sets of plants is seen in what relates to reproduction— 
i.e. in the flower-stems, the capsules, and the seeds. 

After cutting off the flower-stems, three sets of plants were 
allowed to rest throughout the winter, in order to test (by a 
comparison of spring-growth) the amounts of reserve material 
accumulated during the summer. Both starved and fed 
plants were kept without food until April 3rd, when it was 
found that the average weights per plant were 100 for the 
starved, 213-0 for the fed. This proves that the fed plants 
had laid by a far greater store of reserve material in spite of 
having produced nearly four times as much seed. 

In Kellermann and Von Eaumer's experiments (loc. cit.) 
aphides were used as food instead of meat — a method which 
adds greatly to the value of their results. Their conclusions 
are similar to my own, and they show that not only is the 
seed production of the fed plants greater, but they also form 
much heavier winter-buds than the starved plants. 

Dr. M. Biisgen has more recently published an interesting 
paper* on the same subject. His experiments have the 

* " Die Bedeutung des Insectfanges fiir Drosera rotundifolia (L.)," ' Bot. 
Zeitung,' 1883. 



Chap. IJ ACTION OF THE PAETS. 17 

advantage of having been made on young Droseras grown 
fi'om seed. The unfed plants are thus much more effectually 
starved than in experiments on full-grown plants possessing 
already a store of reserve matter. It is therefore not to be 
■wondered at that Busgen's results are more striking than 
Kellermann's and Von Kaumer's or my own — thus, for 
instance, he found that the " fed " plants, as compared with 
the starved ones, produced more than five times as many 
capsules, while my figures are 100 : 194. Busgen gives a 
good resume of the whole subject, and sums up by saying 
that the demonstrable superiority of fed over unfed plants is 
great enough to render comprehensible the organisation of 
the plants with reference to the capture of insects. — P. D.] 



18 DBOSEKA EOTUNDIFOLI4. [Chap. II. 



CHAPTEE II. 

The Movements of the Tektacles from the Contact of Solid 
Bodies. 

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

I 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 them- 
selves move or change form, but transmit a motor impulse to 
the bending part of their own and adjoining tentacles, and 
are thus carried towards the centre of the leaf. Strictly 
speaking, the glands ought to be called irritable, as the term 
sensitive generally implies consciousness ; but no one 
supposes that the Sensitive-plant is conscious, and, as I have 
found the term convenient, I shall use it without scruple. I 
will commence with the movements of the exterior tentacles, 
when indirectly excited by stimulants applied to the glands 
of the short tentacles on the disc. The exterior tentacles 
may be said in this case to be indirectly excited, because 
their own glands are not directly acted on. The stimulus 
proceeding from the glands of the disc acts on the bending 
part of the exterior tentacles, near their bases, and does not 
(as will hereafter be proved) first travel up the pedicels to 
the glands, to be then reflected back to the bending place. 
^Nevertheless, some influence does travel up to the glands, 
causing them to secrete more copiously, and the secretion to 
become acid. This latter fact is, I believe, quite new in the 
physiology of plants ; it has indeed only recently been esta- 
blished that in the animal kingdom an influence can be trans- 



Chap. II.] INFLECTION INDIRECTLY CAUSED. 19 

mitted along the nerves to glands, modifying their power 
ot" secretion, independently of the state of the blood-vessels. 

The Inflection of the Exterior Tentacles from the Glands of the 
Disc being excited by Repeated Touches, or by Objects left in 
Contact with them^ 

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

Particles of meat, dead flies, bits of paper, wood, dried 
moss, sponge, cinders, glass, &c., were repeatedly placed on 
leaves, and these objects were well embraced in various 
periods from 1 hr. to as long as 24 hrs., and set free again, 
with the leaf fully re-expanded, in from one or two, to seven 
or eyen ten days, according to the nature of the object. On 
a leaf which had naturally caught two flies, and therefore 
had already closed and reopened either once, or more pro- 
bably twice, I put a fresh fly : in 7 hrs. it was modei'ately, 
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 
nnnsually short period of inflection was, no doubt, due to 
the leaf having recently been in action. Allowing this same 
leaf to rest for only a single day, I put on another fly, and 
it again closed, but now very slowly ; nevertheless, in less 
than two days it succeeded in thoroughly clasping the fly. 

When a small object is placed on the glands of the 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 

c 2 



20 DEOSEEA EOTUNDIFOLIA. [Chap. II. 

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 afiected. 

If young and active leaves are selected, inorganic particles 
not larger than the head of a small pin, placed on the central 
glands, sometimes cause the outer tentacles to bend inwards. 
But this follows much more surely and quickly, if the object 
contains nitrogenous matter which can be dissolved by the 
secretion. On one occasion I observed the following unusual 
circumstance. Small bits of raw meat (which acts more 
energetically than any other substance), of paper, dried moss, 
and of the quill of a pen were placed on several leaves, and 
they were all embraced equally well in about 2 hrs. On 
other occasions the above-named substances, or more commonly 
particles of glass, coal-cinder (taken from the fire), stone, 
gold-leaf, dried grass, cork, blotting-paper, cotton-wool, and 
hail- rolled up into little balls, were used, and these substances, 
though they were sometimes well embraced, often caused no 
movement whatever in the outer tentacles, or an extremely 
slight and slow movement. Yet these same leaves were 
proved to be in an active condition, as they were excited to 
move by substances yielding soluble nitrogenous matter, such 
as bits of raw or roast meat, the yolk or white of boiled eggs,, 
fragments of insects of all orders, spiders, &c. I will give 
only two instances. Minute flies were placed on the discs of 
several leaves, and on others balls of paper, bits of moss and 
quill of about the same size as the flies, and the latter were 
well embraced in a few hours ; whereas after 25 hrs. only a 
veiy 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 intei-val of 19 hrs. one of the 
particles was tolerably well embraced; a second by a very 
few tentacles ; and a third by none. T then removed the 



Chap. II.] INFIiECTION INDIEECTLY CAUSED. 



21 



particles from tlie two latter leaves, and put them on recently 
killed flies. These were fairly well embraced in 7^ hrs. and 
thoroughly after 20^ hrs. ; the tentacles remaining inflected 
for many subsequent days. On the other hand, the one leaf 
which had in the course of 19 hrs. embraced the bit of cinder 
moderately well, and to which no fly was given, after an addi- 
tional 33 hrs. (i.e. in 52 hrs. from the time when the cinder was 
put on) was completely re-expanded and ready to act again. 
From these and numerous other experiments not worth 
giving, it is certain that inorganic substances, or such organic 
substances as are not attacked by the secretion, act much less 
quickly and efficiently than organic substances yielding 
soluble matter which is absorbed. Moreover, 1 have met 
with very few exceptions to the rule, and these exceptions 
apparently depended on the leaf having been too recently in 
action, that the tentacles remain clasped for a much longer 
time over organic bodies of the nature just specified than 
over those which are not acted on by the secretion, or 
(Over inorganic objects.* 



* Owing to the extraordinary be- 
lief held by M. Ziegler ('Comptes 
rendus,' May 1872, p. 122), that 
albuminous substances, if held for a 
moment between the fingers, acquire 
the property of malcing the tentacles 
of Drosera contract, wliereas, if not 
■thus held, they have no such power, 
I tried some experiments with great 
care, but the results did not confirm 
this belief. Red-hot cinders were 
taken out of the fire, and bits of 
glass, cotton-thread, blotting paper 
and thin slices of cork were immersed 
in boiling water ; and particles were 
then placed (every instrument with 
which they were touched having been 
previously immersed in boiling water) 
on the glands of several leaves, and 
■they acted in exactly the same 
manner as other particles, which had 
been purposely handled for some 
time. Bits of a boiled egg, cut with 
a knife which had been washed in 
boiling water, also acted like any 
ether animal substance. I breathed 
on some leaves for above a minute, 



and repeated the act two or three 
times, with my mouth close to them, 
but this produced no effect. I may 
here add, as showing that the leaves 
are not acted on by the odour of 
nitrogenous substances, that pieces of 
raw meat stuck on needles were fixed 
as close as possible, without actual 
contact, to several leaves, but pro- 
duced no effect whatever. On the 
other hand, as we shall hereafter see, 
the vapours of certain volatile sub- 
stances and fluids, such as of carbonate 
of ammonia, chloroform, certain es- 
sential oils, &c., cause inflection. M. 
Ziegler makes still more extra- 
ordinary statements with respect to 
the power of animal substances, 
which have been left close to, but 
not in contact with, sulphate of 
quinine. The action of salts of 
quinine will be described in, a future 
chapter. Since the appearance of 
the paper above referred to, M. 
Ziegler has published a book on the 
same subject, entitled, 'Atonicit^ et 
Zoicitc!,' 1874. 



22 



DEOSEEA EOTUNDIFOLIA. 



[Chap. II. 



The Inflection of the Exterior Tentacles as directly caused hif 
Objects left in Contact with their Glands.* 
1 made a vast number of trials by placing, by means of a 
fine needle moistened with distilled water, and with the aid 
of a lens, particles of various substances on the viscid secretion 
surrounding the glands of the outer tentacles. I experi- 
mented on both the oval and long-headed glands. When a 
particle is thus placed on a single gland, the movement of 
the tentacle is particularly well seen in contrast with the 
stationary condition of the surrounding tentacles. (See pre- 
vious fig. 6.) In four cases small particles of raw meat caused 
the tentacles to be greatly inflected in between 5 and 6 m. 
Another tentacle similarly treated, and observed with special 
care, distinctly, though slightly, changed its position in 10 s. 
(seconds) ; and this is the quickest movement seen by me. 
In 2 m. 30 s. it had moved through an angle of about 45°. 



* [The researches of Pfeffer 
(' Unters. aus d, Bot, Institut zu 
Tiibingen,' vol. i., 1885, p. 483) on 
the -sensitiveness of various organs to 
contact show that the conclusions as 
to the sensitiveness of Drosera cannot 
be maintained in their present form 
(see p. 24). 

Pfeffer shows, both in the case of 
the tendrils of climbing plants, and 
also in that of the tentacles of 
Drosera, that uniform pressure has 
no stimulating action : the effect 
which is ascribed simply to contact 
is in reality due to unequal compres- 
sion of closely neighbouring points. 
Tendrils which move after having 
been rubbed with a light stick fail 
to be stimulated when tliey are 
rubbed with a glass rod coated with 
gelatine. The gelatine has the same 
uniformity of action as drops of 
water falling on the tendril, which 
are known to produce no eifect. If 
the gelatine is sprinliled with iine 
particles of sand, or if the water 
liolds particles of clay in suspension, 
stimulation results. Analogous ex- 
periments were made on Drosera 
(p. 511). It was found impossible to 
produce movement of the tentacles 



by rubbing the glands with a surface 
of mercury, whereas by rubbing or 
repeated touches with solid bodies 
movement is called forth. Other 
experiments of Pfeffer's show con- 
clusively that continuous uniform 
pressure has no stimulating effect. 
He placed small globules of glass on 
the glands, and convinced himself 
that, by examination with a lens, 
that contact was affected. Some of 
the tentacles moved, but the majority 
showed no movement, as Icmg as the- 
plants uere so placed that no vibration 
from the table or floor could reach 
them. When they were exposed to 
vibration, and when, therefore, the 
glass globules must have rubbed 
against or jarred the gland, the 
tentacles moved. The results de- 
tailed above in the text must pre- 
sumably be set down to the same 
cause, namely, the vibration of the 
table and floor. The sensitiveness of 
Drosera, therefore, by no means ceases 
to be astonishing. Instead of believ- 
ing in movements caused by the 
steady pressure of very small v/eights, 
we set down the results as being due 
to the jarring of the gland by these 
same minute bodies. — F. D.] 



CiiAi'. II.] INFLECTION INDIRECTLY CAUSED. 23 

The movement as seea 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 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 became closely 
inflected. Fragments of flies were placed on the glands of 
four of the outer tentacles, extended in the same plane with 
that of the blade, and three of these fragments were carried 
in 35 m. through an angle of 180° to the centre. The 
fragment on the fourth tentacle was very minute, and it 
was not carried to the centre until 3 hrs. had elapsed. In 
three other cases minute flies or portions of larger ones 
were earned to the centre in 1 hr. 30 s. In these seven 
cases, the fragments or small flies, which had been carried 
by a single tentacle to the central glands, were well em- 
braced by the other tentacles after an interval of from 4 to 
10 hrs. 

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

I made, without carefully recording the times of move- 
ment, many similar trials with other substances, such as 



24 DEOSEEA KOTUNDIFOLIA. [Chap. H. 

splinters of white and blue glass, particles of cork, minute 
bits of gold-leaf, &c. ; and the proportional number of cases 
varied much in which the tentacles reached the centre, or 
moved only slightly, or not at all. One evening, particles of 
glass and cork, rather larger than those usually employed, 
were placed on about a dozen glands, and next morning, 
after 13 hrs., every single tentacle had carried its little load 
to the centre ; but the unusually large size of the particles 
will account for this result. In another case -^ of the 
particles of cinder, glass, and thread, placed on separate 
glands, were carried towards, or actually to, the centre ; in 
another case ^, in another -f^, and in the last case_ only ^ 
were thus carried inwards, the small proportion being here 
due, at least in part, to the leaves being rather old and 
inactive. Occasionally a gland, with its light load, could be 
seen through a strong lens to move an extremely short 
distance and then stop ; this was especially apt to occur 
when excessively minute particles, much less than those of 
which the measurements will be immediately given, were 
placed on glands ; so that we here have nearly the limit of 
any action. 

I was so much surprised at the smallness of the particles 
which caused the tentacles to become greatly inflected that 
it seemed worth while carefully to ascertain how minute a 
particle would plainly act. Accordingly, measured lengths 
of a narrow strip of blotting-paper, of iine cotton-thread, and 
of a woman's hair, were carefully weighed for me by 
lyir. 1'renham Eeeks, in an excellent balance, in the laboratory 
in Jermyn Street. Short bits of the paper, thread, and hair 
were then cut oif 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 -5-3^3^ of * grain, or '0464 of a milli- 
gram. Five nearly equal bits of cotton-thread were tried, 
and all acted. The shortest of these was J„^ of an inch in 
length, and weighed stVt of a grain. The tentacle in this 



Chap. II.] INFLECTION INDIRECTLY CAUSED. 25 

caso 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 y-J-g-ij- of an inch in length, and weighing 
■szTn of ^ grain, the other y^U^ of an inch in length, and 
weighing of course a little more, were placed on two glands 
on opposite sides of the same leaf, and these two tentacles 
were inflected halfway towards the centre in 1 hr. 10 m. ; 
all the many other tentacles round the same leaf remaining 
motionless. The appearance of this one leaf showed in an 
unequivocal manner that these minute particles sufficed to 
cause the tentacles to bend. Altogether, ten such particles 
of hair were placed on ten glands on several leaves, and 
seven of them caused the tentacles to move in a conspicuous 
manner. The smallest particle which was tried, and which 
acted plainly, was only ytPits o^ ^^ i°<2l^ ("203 millimeter) in 
length, and weighed the T^-ffxr of a grain, or '000822 
milligram. In these several cases, not only was the 
inflection of the tentacles conspicuous, but the purple fluid 
■within their cells became aggregated into little masses of 
protoplasm, in the manner to be described in the next 
chapter ; and the aggregation was so plain that I could, by 
this clue alone, have readily picked out under the microscope 
all the tentacles which had carried their light loads towards 
the centre, from the hundreds of other tentacles on the same 
leaves which had not thus acted. 

My surprise was greatly excited, not only by the minute- 
ness of the particles which caused movement, but how they 
oould 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 
pr6duced any effect. Nor does the disturbance of the secre- 
tion produce any effect, for long threads were drawn out by 
a needle, and affixed to some adjoining object, and thus left 
for hours; but the tentacles remained motionless. 

I also careiuUy removed the secretion from four glands 
with a sharply pointed piece of blotting-paper, so that they 



26 DEOSBKA ROTUNDIFOLIA. [Chap. II. 

were exposed for a time naked to the air, but this caused no 
movement ; yet these glands were in an efficient state, for, 
after 24 hrs. had elapsed, they were tried with hits of meat, 
and all became quickly inflected. It then occurred to me 
that particles floating on the secretion would cast shadows 
on the glands which might be sensitive to the interception 
of the light. Although this seemed highly improbable, as 
minute and thin splinters of colourless glass acted power- 
fully, nevertheless, after it was dark, I put on, by the_ aid of 
a single tallow candle, as quickly as possible, particles of 
cork and glass on the glands of a dozen tentacles, as well as 
some of meat on other glands, and covered them up so that 
not a ray of light could enter ; but by the next morning, 
after an interval of 13 hrs., all the particles were carried to 
tlie centres of the leaves. 

These negative results led me to try many more experi- 
ments, by placing particles on the surface of the drops of 
secretion, observing-, as carefully as I could, whether they 
penetiated it and touched the surface of the glands. The 
secretion, from its weight, generally forms a thicker layer 
on the under than on the upper sides of the glands, whatever 
may be the position of the tentacles. Minute bits of dry 
cork, thread, blotting-paper, and coal-cinders were tried, such 
as those previously employed ; and I now observed that they 
absorbed much more of the secretion, in the course of a few 
minutes, than I should have thought possible ; and as they 
had been laid on the upper surface of the secretion, where it 
is thinnest, tliey were often drawn down, after a time, into 
contact with at least some one point of the gland. With 
respect to the minute splinters of glass and particles of hair, 
I observed that the secretion slowly spread itself a little 
over their surfaces, by which means they were likewise 
drawn downwards or sideways, and thus one end, or some 
minute prominence, often came to touch, sooner or later, the 
gland. 

In the foregoing and following cases, it is probable that 
the vibrations, to which the furniture in every room is 
continually liable, aids in bringing the particles into contact 
with the glands. But as it was sometimes diflScult, owing 
to the refraction of the secretion, to feel sure whether the 
particles were in contact, I tried the following experiment. 
Unusually minute particles of glass, hair, and cork were 
gently placed on the drops round several glands, and very 



Chap. II.;! INFLECTION INDIEECTLY CAUSED. 27 

few of the tentacles moved. Those which were not aifected 
were left for about half an hour, and the particles were then 
disturhed or tilted up several times with a fine needle under 
the microscope, the glands not being touched. And now in 
the course of a few minutes almost all the hitherto motion- 
less tentacles began to move ; and this, no doubt, was caused 
by one end or some prominence of the particles having come 
into contact with the surface of the glands. But, as the 
particles were unusually minute, the movement was small. 

Lastly, some dark blue glass pounded into fine splinters 
was used, in order that the points of the particles might be 
better distinguished when immersed in the secretion; and 
thirteen such particles were placed in contact with the 
depending and therefore thicker part of the drops round so 
many glands. Five of the tentacles began moving after an 
interval of a few minutes, and in these cases I clearly saw 
that the particles touched the lower surface of the gland. A 
t.ixth tentacle moved after 1 hr. 45 m., and the particle wa.s 
now in contact with the gland, which was not the case at 
first. So it was with the seventh tentacle, but its movement 
did not begin until 3 hrs. 45 m. had elapsed. The remaining 
six tentacles never moved as long as they were observed ; 
and the particles apparently never came into contact with 
the surfaces of the glands. 

From these experiments we learn that particles not con- 
taining soluble matter, when placed on glands, often cause 
the tentacles to begin bending in the course of from one to 
five minutes ; and that in such cases the particles have been 
from the first in contact with the surfaces of the glands. 
When the tentacles do not begin moving for a much longer 
time, namely, from half an hour to three or four hours, the 
particles have been slowly brought into contact with the 
glands either by the secretion being absorbed by the particles 
or by its gradual spreading over them, together with its 
consequent quicker evaporation. When the tentacles do not 
move at all, the particles have never come into contact with 
the glands, or in some cases the tentacles may not have been 
in an active condition. In order to excite movement, 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 suificient to excite movement. 

Another experiment, showing that extremely minute par^ 
tides act on the glands when immersed in water, may here 



28 DEOSEEA EOTUNDIFOLIA. [Chap. II. 

he given. A grain of sulphate of quinine was added to an 
ounce of water, which was not afterwards filtered ; and, on 
placing three leaves in ninety minims of this fluid, I was 
much surprised to find that all three leaves were greatly- 
inflected in 15 m. : for I knew from previous trials that the 
solution does not act so quickly as this. It immediately 
occurred to me that the particles of the undissolved salt, which, 
were so light as to float about, might have come into contact 
with the glands, and caused this rapid movement. Accord- 
ingly I added to some distilled water a pinch of a quite inno- 
cent substance, namely, precipitated carbonate of lime, which 
consists of an impalpable powder ; I shook the mixture, and 
thus got a fluid like thin milk. Two leaves were immersed 
in it, and in 6 m. almost every tentacle was much inflected. 
I placed one of these leaves under the microscope, and saw 
innumerable atoms of lime adhering to the external surface 
of the secretion. Some, however, had penetrated it, and 
were lying on the surfaces of the glands ; and no doubt it 
was these particles which caused the tentacles to bend. 
When a leaf is immersed in water, the secretion instantly 
swells much ; and I presume that it is ruptured here and 
there, so that little eddies of water rush in. If so, we can 
understand how the atoms of chalk, which rested on the 
surfaces of the glands, had penetrated the secretion. Any one 
who has rubbed precipitated chalk between his flngers 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, Jy of an inch in length and weighing -g-iVr of a grain, 
or of a human hair, yw^^ o^ ^^ inch in length and weighing 
only ygj^j, of a grain ('000822 milligram), or particles of 
precipitated chalk, after resting for a short time on a gland, 
should induce some change in its cells, exciting them to 
transmit a motor impulse throughout the whole length of the 
pedicel, consisting of about twenty cells, to near its base, 
causing this part to bend, and the tentacle to sweep through 
an angle of above 180°. That the contents of the cells of the 



Chap. II.] THE EFFECTS OF REPEATED TOUCHES. 2[) 

glands, and afterwards those of the pedicels, are affected in a 
plainly visible manner by the pressure of minute particles, we 
shall have abundant evidence when we treat of the aggregation 
of the protoplasm. But the case is much more remarkable 
than as yet stated; for the particles are supported by the 
viscid and dense secretion ; nevertheless, even smaller ones 
than those of which the measurements have been given, when 
brought by an insensibly slow movement, through the means 
above specified, into contact with the surface of a gland, act 
on it, and the tentacle bends. The pressure exerted by the 
particle of hair, weighing only T-gr^u of a grain and supported 
by a dense fluid, must have been inconceivably slight. We 
may conjecture that it could hardly have equalled the 
millionth of a grain ; and we shall hereafter see that far less 
than the millionth of a grain of phosphate 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 there- 
fore much larger than those used in the above experiments, 
was not perceived when placed on my tongue; and it is 
extremely doubtful whether any nerve in the human body, 
even if in an inflamed condition, would be in any way 
affected by such a particle supported in a dense fluid, and 
slowly brought into contact with the nerve. Yet the cells of 
the glands of Drosera are thus excited to transmit a motor 
impulse to a distant point, inducing movement. It appears 
to me that hardly any more remarkable fact than this has 
been observed in the vegetable kingdom. 

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

We have already seen that, if the central glands are 
excited by being gently brushed, they transmit a motor 
impulse to the exterior tentacles, causing them to bend; 
and we have now to consider the effects which follow from 
the glands of the exterior tentacles being themselves touched. 
On several occasions, a large number of glands were touched 
only once with a needle or fine brush, hard enough to bend 
the whole flexible tentacle; and, though this must have 
caused a thousand-fold greater pressure than the weight of 
the above-described particles, not a tentacle moved. On 
another occasion forty-five glands on eleven leaves were 
touched once, twice, or even thrice, with a needle or stiff 



30 DEOSERA EOTUNDIFOLIA. [Cuap. II. 

bristle. This was done as quickly as possible, but with force 
sufficient to bend the tentacles ; yet only six of them became 
inflected, — three pMinly, and three in a slight degree. In 
order to ascertain whether these tentacles which were not 
affected were in an efficient state, bits of meat were placed 
on ten of them, and they all soon became greatly incurved. 
On the other hand, when a large number of glands were 
struck four, five, or six times with the same force as before, 
a needle or sharp splinter of glass being used, a much larger 
proportion of tentacles became inflected ; but the result was 
so uncertain as to seem capricious. For instance, I struck 
in the above manner three glands, which happened to be 
extremely sensitive, and all three were inflected almost as 
quickly as if bits of meat had been placed upon them. On 
another occasion I gave a single forcible touch to a consider- 
able number of glands, and not one moved ; but these same 
glands, after an interval of some hours, being touched four 
or five times with a needle, several of the tentacles soon 
became inflected. 

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

It is also a remarkable fact, that drops of water falling 
from a height, whether under the form of natural or artificial 
rain, do not cause the tentacles to move ; yet the drops must 
strike the glands with considerable force, more especially 



Chap. II.] THE EFFECTS OF REPEATED TOUCHES. 31 

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

When the pedicel of a tentacle is cut off by a sharp pair of 
scissors quite close beneath the gland, the tentacle generalh' 
becomes inflected. I tried this experiment repeatedly, as 1 
was much surprised at the fact, for all other parts of the 
pedicels are insensible to any stimulus. These headless 
tentacles after a time re-expand ; but I shall return to this 
subject. On the other hand, I occasionally succeeded in 
crushing a gland between a pair of pincers, but this caused 
no inflection. In this latter case the tentacles seem paralysed, 
as likewise follows from the action of too strong solutions of 
certain salts, and of too great heat, whilst weaker solutions 
of the same salts and a more gentle heat cause movement. 
We shaU also see in future chapters that various other fluids, 
some vapours, and oxygen (after the plant has been for some 
time excluded from its action), all induce inflection, and this 
likewise results from an induced galvanic current.j 



* [PfefFev's experiments, given move ; but that, if similar needles in 

above (p. 22), explain tiie failure of connection with the secondary coil of 

rain to cause movement. — F. D.] a Du Bois induction apparatus are 

t My son Francis, guided by the inserted, the tentacles curve inwards 

observations of Dr. Burdon Sanderson in the course of a few minutes. My 

on Dionica, finds that, if two needles son hopes soon to publish an account 

are inserted into the blade of a leaf of his observations, 
of Drosera, the tentacles do not 



32 DBOSERA ROTUNDIFOLIA. [Cuap. III. 



CHAPTEK III. 

Agoeegation of the Pkotoplasm withix the Cells of the 
Tentacles. 

Nature of the contents of the cells before aggregation — Various causes which 
excite aggregation — The process commences within the glands and travels 
down the tentacles — Description of the aggregated masses and of their 
spontaneous movements — Currents of protoplasm along the walls of the 
cells — Action of carbonate of ammonia — The granules in the protoplasm 
which flows along the walls coalesce with the central masses — Minuteness 
of the quantity of carbonate of ammonia causing aggregation — Action of 
other salts of ammonia — Of other substances, organic fluids, &c. — Of 
water — Of heat — 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 accoTint of the movements of the 
leaves, and describe the phenomenon of aggregation, to which 
subject I have already alluded. If the tentacles of a young, 
yet fully matured leaf, that has never been excited or become 
inflected, be examined, the cells forming the pedicels are seen 
to be filled with homogeneous, purple fluid.* The walls are 
lined by a layer of colourless, circulating protoplasm ;f but 
this can be seen with much greater distinctness after the 



* [The statement as to the absence in Droscra dichotoma, but e.\ists also 

of a nucleus in the stalk-cells of in D. rotundifolia ; in the former 

Drosera (Francis Darwin, ' Quarterly species, in which it has been more 

Journal of Microscopical Science,' especially studied by its discoverer, 

1876) has been shown by Pfeffer to it is a more or less spindle-shaped 

be quite erroneous (' Osmotische mass, stretching diagonally across 

Untersuchungen,' 1877, p. 197). — the cell, the two ends being embedded 

F. D.] in the cell-protoplasm. " It is 

t [Mr. W.Gardiner ('Proc. E. Soc.,' present in all the epidermic cells of 

No. 240, 1886) has described a re- the leaf except the gland cells and 

markable body named by him the the cells immediately beneath the 

*' rhabdoid," which exists within the same." Further reference to the 

epidermic cells of the stalk of the rhabdoid will be found at p. 35. — 

tentacles. This body was discovered F. D.] 



CiiAr. III.] THE PROCESS OF AGGREGATIOX. 33 

process of aggregation has been partly effected than before. 
The purple fluid which exudes from a crushed tentacle is 
somewhat coherent, and does not mingle with the surrounding 
water ; it contains much flocculent or granular matter. But 
this matter may have been generated by the cells having 
been crushed ; some degree of aggregation having been thus 
almost instantly caused. 

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

The little masses of aggregated matter are of the most 
diversified shapes, often spherical or oval, sometimes much 
■elongated, or quite irregular with thread- or necklace-like or 
club-formed projections. They consist of thick, apparently 
viscid matter, which in the exterior tentacles is of a purplish, 
and in the short discal tentacles of a greenish, colour. These 

D 



34 



DROSEEA EOTUNDIFOLIA. 



[Chap. III. 



little masses incessantly change their forms and positions, 
being never at rest. A single mass will often separate into 
two, which afterwards reunite. Their movements are rather 
slow, and resemble those of Amoebss or of the white 
corpuscles of the blood. We may therefore conclude that 
they consist of protoplasm.* If their shapes are sketched at 





Fig. 1. 

(JDro&era rotwndifolia.') 

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



intervals of a few minutes, they are invariably seen to have 
imdergone 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 



* [This conclusion has been shown 
to be erroneous ; there can be no 
doubt that the aggregated masses 
are concentrations or precipitations 
of the cell-sap, and that their sup- 
posed amoeboid movements are the 
result of the streaming protoplasm, 
which moulds the passive masses into 
a variety of forms. 

Pfeffer was the first to insist on 
this view of the nature of aggrega- 
tion, in his ' Osmotische Untersuch- 
ungen' (1877). Since then the 
subject has been investigated by 
Schimper (' Botanische Zeitung,' 
1882, p. 233), who describes the 
aggregated masses as concentrations 
of cell-sap, rich in tannin, and float- 
ing in the swollen and transparent 
protoplasm. 

Schimper's observations are con- 



firmed by Gardiner ('Proc. Eoyal Soc.,' 
Nov. 19, 1885, No. 240, 1886), who 
describes the protoplasm in the stalk- 
cells of Drosera dichotoma as swelling 
up by the absorption of the " water 
from its own vacuole," and thus 
leaving the tannin in cell-sap in a 
concentrated condition. Gardiner 
has added some curious observa- 
tions on the connection between 
aggregation and the condition of 
the cell as regards turgidity. He 
supposes that aggregation is connected 
with a loss of water, and that an 
aggregated cell is in a condition of 
diminished turgidity. This is sup- 
ported by his observation that " in- 
jection of water into the tissue will 
at once stop aggregation, and restore 
the cell to its normal condition." 
These changes are connected with 



Chap. III.] THE PEOCESS OP AOaEEGATION. 



35 



simpler and commonest changes. Tlie cell A, when first 
sketched, included two oval masses of purple protoplasm 
touching each other. These became separate, as shown at B, 
and then reunited, as at C. After the next interval a very 
common appearance was presented — D, namely, the formation 
of an extremely minute sphere at one end of an elongated 



^Al 



G 
9 



Fio. 8. 

{Drosera rotundifolia.) 

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



mass. This rapidly increased in size, as shown in E, and 
was then reabsorbed, as at P, by which time another sphere 
had been formed at the opposite end. 

The cell drawn in fig. 7 was from a tentacle of a dark red 
leaf, which had caught a small moth, and was examined 



certain alterations of form occurring 
in the above-mentioned body de- 
scribed by Gardiner under the name 
of rhabdoid, and which seems to be 
peculiarly sensitive to changes in 
the turgidity, so much so indeed that 
the author utilises it as a " turgo- 
meter," or index of the degree of 
turgescence. 

H. de Vries has also written on 
the subject of aggregation (' Botan- 
ische Zeitung,' 1886, p. 1), and his 
views agree with those of Pfeffer, 
Schimper, and Gardiner as to the 
main fact that the aggregated masses 
are concentrations of cell-sap. In 
some other respects they differ from 
the conclusions of these authors. 

De Vries believes that in Droscra 
and in vegetable cells generally the 
vacuoles are surrounded by a special 



protoplasmic wall, distinct from 
the layer of flowing protoplasm 
which lines the walls. In the 
process of aggregation the vacuole- 
expels a great part of its watery 
contents, retaining, however, the 
red colouring matter of the cell- 
sap, as well as tannin and albu- 
minous matter. The vacuole does 
not remain a single body, but divides 
into numerous secondary vacuoles. 
These are the aggregated masses 
which are rendered conspicuous by 
being surrounded by the expelled 
fluid which serves as a colourless 
background to them. The move- 
ments of the masses are, according to 
De Vries, entirely passive, and are 
accounted for by the currents of 
protoplasm, stirring them and wash- 
ing them to and fro. — F. D.] 
D 2 



36 DROSEEA EOTUNDIFOLIA. [Chap. III. 

under -wtlter. As I at first thought that the movements of 
the masses might be due to the absorption of water, I placed 
a fly on a leaf, and, when after 18 hrs. all the tentacles were 
well inflected, these were examined without being immersed 
in water. The cell here represented (fig. 8) was from this 
leaf, being sketched eight times in the course of 15 m. 
These sketches exhibit some of the more remarkable changes 
which the protoplasm undergoes. At first, there was at the 
base of the ^cell 1 a little mass on a short footstalk, and a 
larger mass near the upper end, and these seemed quite 
separate. Nevertheless, they may have been connected by a 
fine and invisible thread of protoplasm, for on two other 
occasions, whilst one mass was rapidly increasing, and 
another in the same ceU rapidly decreasing, I was able, by 
varying the light and using a high power, to detect a 
connecting thread of extreme tenuity, which evidently served I 
as the channel of communication between the two. On the 
other hand, such connecting threads are sometimes seen to 
break, and their extremities then quickly become club-headed. 
The other sketches in fig. 8 show the forms successively 
assumed. 

Shortly after the purple fluid within the cells has become 
aggregated, the little masses float about in a colourless or 
almost colourless fluid; and the layer of white granular 
protoplasm which flows along the walls can now be seen much 
more distinctly. The stream flows at an irregular rate, up 
one wall and down the opposite one, generally at a slower 
rate across the naiTow 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 oliservations were made on the contents of the cells whilst 
undergoing the process of aggregation, but I shall detail only a few 
cases imder different heads. A small portion of a leaf was cut oif, 
placed under a high power, and the glands very gently pressed under a 



Chap. III.] THE PKOCBSS OP AGGBEGATION. 37 

compressor. In 15 m. I distinctly saw extremely minute spheres of 
protoplasm aggregating themselves in the purple fluid ; these rapidly 
increased in size, both within the cells of the glands and of the upper 
ends of the pedicels. Particles of glass, cork, and cinders were also 
placed oa the glands of many tentacles ; in 1 hr. several of them were 
inflected, but after 1 hr. 35 m. there was no aggregation. Other 
tentacles with these particles were examined after 8 hrs., and now all 
their cells had undergone aggregation ; so had the cells of the exterior 
tentacles which had become inflected through the irritation transmitted 
from the glands of the disc, on which the transported particles rested. 
This was likewise the case with the short tentacles round the margins 
of the disc, which had not as yet become inflected. This latter fact 
shows that the process of aggregation is independent of the inflection 
of the tentacles, of which indeed we have other and abundant evidence. 
Again, the exterior tentacles on three leaves were carefully examined, 
and found to contain only homogeneous purple fluid; little bits of 
thread were then placed on the glands of three of them, and after 22 
hrs.' the purple fluid in their cells almost down to their bases was 
aggregated into innumerable spherical, elongated, or filamentous masses 
of protoplasm. The bits of thread had been carried some time 
previously to the central disc, and this had caused all the other 
tentacles to become somewhat inflected ; and their cells had likewise 
undergone aggregation, which, however, it should be observed, had not 
as yet extended down to their bases, but was confined to the cells close 
beneath the glands. 

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

Carbonate of Ammonia. — Of all the causes inducing aggregation, 
that which, as far as I have seen, acts the quickest, and is the most 
powerful, is a solution of carbonate of ammonia. Whatever its strength 
may be, the glands are always affected first, and soon become quite 
opaque, so as to appear black. For instance, I placed a leaf in a few 
drops of a strong solution, namely, of one part to 146 of water (or 3 
grs. to 1 oz.), and observed it under a high power. All the glands 
began to darken in 10 s. ( seconds) ; and in 13 s. were conspicuously 



* Judging from an account of M. beris, after they have been excited by 

Heckel's observations, which I have a touch and have moved ; for he says, 

only just seen quoted in the ' Gar- " the contents of each individual cell 

dener's Chronicle ' (Oct. 10, 1874), he are collected together in the centre 

appears to have observed a similar of the cavity." 
phenomenon in the stamens of Ber- 



38 DEOSEEA EOTUNDIFOLIA. [Chap. III. 

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

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

Having examined a leaf in water, and found the contents of the 
cells homogeneous, I placed it in a few drops of a solution of one part 
of the carbonate to 437 of water, and attended to the cells immediately 
beneath the glands, but did not use a very high power. No aggrega- 



Chap. III.] THE PROCESS OP AGGEEGATION. 39 

tion was visible in 3 m. ; but after 15 m. small spheres of proto- 
plasm were formed, more especially beneath the long-headed marginal 
glands ; the process, however, in this case took place with unusual 
slowness. In 25 m. conspicuous spherical masses were present in the 
cells of the pedicels for a length about equal to that of the glands ; 
aad in 3 hi-s. 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 gi-. 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 1 chose a singularly pale leaf, and gave it, whilst imder the 
microscope, a single drop of a stronger solution of one part to 437 
of water; in this case the contents of the cells did not become 
cloudy, but after 10 m. minute irregular granules of protoplasm 
could be detected, which soon increased into irregular masses and 
globules of a greenish or very pale purple tint; but these never 
formed perfect spheres, though incessantly changing their shapes and 
positions. 

With moderately red leaves the first effect of a solution of the 
carbonate generally is the formation of two. or three, or of several, 
extremely minute pmple spheres which rapidly increase in size. To 
give an idea of the rate at which such spheres increase in size, I may 
mention that a rather pale purple leaf placed under a slip of grass was 
given a drop of a solution of one part to 292 of water, and in 13 m. a 
lew minute spheres of protoplasm were formed; one of these, after 
2 hrs. 30 m., was about two-thirds of the diameter of the cell. 
After 4 hrs. 25 m. it nearly equalled the cell in diameter; and a 
second sphere about half as large as the first, together with a few 
other minute ones, were formed. After 6 hrs. the fluid in which 
these spheres floated was almost colourless. After 8 hrs. 35 m. (always 
reckoning from the time when the solution was first added) four new 
minute spheres had appeared. Next morning, after 22 hrs., there 
were, besides the two large spheres, seven smaller ones, floating in 



* [De Vries (loc. cit. p. 59) believes is not always easy to distinguish 

that the form of aggregation pro- from the aggregated masses which 

(luced by carbonate of ammonia is De Vries believed to be formed from 

radically different from ordinary the vacuole. Glauer, in the ' Jahres- 

aggregation, e.g. that produced by Bericht der Schl. Gesell. fiir vater- 

meat.° He believes it to be due to a land. Cultur,' 1887, p. 167, also distin- 

precipitation of albuminous matter ; guishes ammonia— aggregation from 

the granules thus formed tend to the ordinary form of the pheno- 

hecome packed into balls, and thus menon. — F. D.] 
dense masses are produced which it 



40 DEOSEEA KOTUNDIFOLIA. [Chap. III. 

absolutely colourless fluid, in which some flocculent greenish matter 
was suspended. 

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

After leaves have been left for several hours in a solution of the 
carbonate, and complete aggregation has been effected, the stream of 
protoplasm on the walls of the cells ceases to be visible ; I observed 
this fact repeatedly, but will give only one instance. A pale purple, 
leaf was placed in a few drops of a solution of one part to 292 of water, 
and in 2 hrs. some fine purple spheres were formed in the upper cells, 
of the pedicels, the stream of protoplasm round their walls being still 
quite distinct ; but after an additional 4 hrs., during which time many 
more spheres were formed, the stream was no longer distinguishable on 
the most careful examination ; and this no doubt was due to the 
contained granules having become united with the spheres, so that 
nothing was left by which the movement of the limpid protoplasm 
could be perceived. But minute free spheres still travelled up and 
down the cells, showing; that there was still a current. So it was next 



* With other plants I have often a solution of carbonate of ammonia 

seen what appears to be a true as likewise follows from mechanical 

shrinliiug of the primordial utricle injuries, 
from the walls of the cells, caused by 



Chap. III.] THE PROCESS OF AGGEEGATION. 41 

morniug, after 22 hrs., by whicla time some new minute spheres had 
been formed; these oscillated from tide to side and changed their 
positions, proving that the curreut had not ceased, though no stream of 
protoplasm was visible. On another occasion, however, a stream was 
seen flowing round the cell-walls of a vigorous, dark-coloured leaf, 
after it bad 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 
redissolved, in the same manner as occurs with leaves in a state of 
nature when they re-expand after having caught insects. 

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

From these several facts we may conclude that, when vigorous dark- 
coloured leaves are subjected to the action of carbonate of ammonia, 
the fluid within the cells of the tentacles often aggregates exteriorly 
into coherent viscid matter, forming a kind of bag. Small spheres 
sometimes appear within this bag, and the whole generally soon divides 
into two or more spheres, which repeatedly coalesce and redivide. After 
a longer or shorter time the granules in the colourless layer of protoplasm, 
which flows round, the walls, are drawn to and unite with the larger 
spheres, or form small independent spheres ; these latter being of a 
much paler colour, and more brittle than the first aggregated masses. 
After the granules of protoplasm have been thus attracted, the layer 
of flowing protoplasm can no longer be distinguished, though a current 
of limpid fluid still flows round tlie 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 seem killed ; all the 
cells in their tentacles contained spheres of protoplasm, but these were 
small and discoloured. Two other leaves were placed in a solution not 
quite so strong, and there was well-marked aggregation in 30 m. After 
24 hrs. the spherical or more commonly oblong masses of protoplasm 
became opaque and granular, instead of being as usual translucent : 
and in the lower cells there were only innumerable minute spherical 



42 DEOSEEA EOTUNDIFOLIA. [Chap. HI. 

granules. It was evident that the strength of the solution had inter- 
fered with the completion of the process, as we shall see likewise 
follows from too great heat. 

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

Finally, the most remarkable fact with respect to this salt is the 
extraordinary small amount which suffices to cause aggregation. Pull 
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 13/^05 of 
a grain ('000482 mgr.) is enough to cause in the course of one tour 
well-marked aggregation ia the cells immediately beneath the gland. 

The Effects of certain other Salts and Fluids. — Two leaves were 
placed in a solution of one part of acetate of ammonia to about 146 of 
water, and were acted on quite as energetically, but perhaps not quite 
so quickly as by the carbonate. After 10 m. the glands were black, and 
in the cells beneath them there were traces of aggregation, which 
after 15 m. was well marked, extending down the tentacles for a length 
equal to that of the glands. After 2 hrs. the contents of almost all 
the cells in all the tentacles were broken up into masses of protoplasm. 
A leaf was immersed in a solution of one part of oxalate of ammonia 
to 146 of water; and after 24 m. some, but not a conspicuous, change 
eould be seen within the cells beneath the glands. After 47 lu. 
plenty of spherical masses of protoplasm were formed, an^ these 
extended down the tentacles for about the length of the glands. 
This salt, therefore, does not act so quickly as the carbonate. With 
respect to the citrate of ammonia, a leaf was placed in a little solution 
of the above strength, and there wa^ not even a trace of aggregation 
in the .cells beneath the glands, until 56 m. had elapsed ; but it was 
well marked after 2 hrs. 20 m. On another occasion a leaf was 
placed in a stronger solution, of one part of the citrate to 109 of 
water (4 grs. to 1 oz.), and at the same time another leaf in a 
solution of the carbonate of the same strength. The glands of the 
latter were blackened in less than 2 m., and after 1 hr. 45 m. the 
aggregated masses, which were spherical and very dark-coloured, 
extended down all the tentacles, for between half and two-thirds of 
their lengths ; whereas in the leaf immersed in the citrate the glands, 
after 30 m., were of a dark red, and the aggregated masses in the 
cells beneath them pink and elongated. Alter 1 hr. 45 m. these 
masses extended down for only about one-lifth or one-fourth of the 
length of the tentacles. 

Two leaves were placed, each in ten minims of a solution of one part 
of nitrate of ammonia to 5250 of water (1 gr. to 12 oz.), so that each 
leaf received -^ of a grain ("1124 mgr.). This quantity caused all 
the tentacles to be inflected, but after 24 hrs. there was only a trace 



CiiAP. III.] THE PKOOESS OF AGGEE6ATI0N. 43 

of aggregation. One of these same leaves was then placed in a weak 
solution of the carbonate, and after 1 hr. 45 m. the tentacles for half 
their lengths showed an astonishing degree of aggregation. Two other 
leaves were then placed in a much stronger solution of one part of the 
nitrate to 14G of water (3 grs. to 1 oz.) ; in one of these there was no 
marked change after 3 hrs. ; but in the other there was a trace of 
aggregation after 52 m., and this was plainly marked after 1 hr. 22 m., 
but even after 2 hrs. 12 m. there was certainly not more aggregation 
than would have followed from an immersion of from 5 m. to 10 m. 
in an equally strong solution of the carbonate. 

Lastly, a leaf was placed in thirty minims of a solution of one part 
of phosphate of ammonia to 43,750 of water (1 gr. to 100 oz.), so that 
it received -j^jto °f ^ 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 fiowing round the walls. 
But after so long an interval aggregation would have ensued, whatever 
had caused inflection. 

Only a few other salts, besides those of ammonia, were tried in 
relation to the process of aggregation. A leaf was placed in a solution 
of one part of chloride of sodium to 218 of water, and after 1 hr. the 
contents of the cells were aggregated into small, irregularly globular, 
brownish masses ; these after 2 hrs. were almost disintegrated and 
pulpy. It was evident that the protoplasm had been injuriously 
affected ; and soon afterwards some of the cells appeared quite empty. 
These effects differ altogether from those produced by the several salts 
of ammonia, as well as by various organic fluids, and by inorganic 
particles placed on the glands. A solution of the same strength of 
carbonate of soda and carbonate of potash acted in nearly the same 
maimer 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 (lor instance, a solution 
of curare) have no such tendency. 

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



44 DKOSEEA EOTUNDIFOLIA. [Chap. III. 

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

A filtered infusion of raw meat induces strong aggregation, but not 
very quickly. In one leaf thus immersed there was a little aggre- 
gation after 1 hr. 20 m., and in another after 1 hr. 50 m. With other 
leaves a considerably longer time was required : for instance, one 
immersed for .5 hrs. showed no aggregation, but was plainly acted on 
in 5 m., when placed in a few drops of a solution of one part of 
carbonate of ammonia to 146 of water. Some leaves were left in the 
infusion 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 under- 
went incessant changes of form ; and the current of colourless proto- 
plasm round the walls was conspicuously plain after an immersion of 
25 hrs. Eaw meat is too powerful a stimulant, and even small bits, 
generally injure, and sometimes kill, the leaves to which they are 
given : the aggregated masses of protoplasm become dingy or almost 
colourless, and present an unusual granular appearance, as is likewise 
the case with leaves which have been immersed in a very strong 
solution of carbonate of ammonia. A leaf placed in milk had the 
contents of its cells somewhat aggregated in 1 hr. Two other leaves, 
one immersed in human saliva for 2 hrs. 30 m., and another in unboUed 
white of egg for 1 hr. 30 m., were not acted on in this manner ; 
though they undoubtedly would have been so, had more time been 
allowed. These same two leaves, on being afterwards placed in a 
solution of carbonate of ammonia (3 grs. to 1 oz.), had their cells- 
aggregated, the one in 10 m. and the other in 5 m. 

Several leaves v/ere left for 4 hrs. 30 m. in a solution of one part of 
white sugar to 146 of water, and no nggregation ensued ; on being 
placed in a solution of this same strength of carbonate of ammonia, 
they were acted on in 5 m.; as was likewise a leaf which had been 
left for 1 hr. 45 m. in a moderately thick solution of gum 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. This effect may be attributed to exosmose ; for 
the leaves in the syrup became quite flaccid, and those in the gum and 
starch somewhat flaccid, with their tentacles twisted about in the 
most irregular manner, the longer ones like corkscrews. We shall 
hereafter see that solutions of these substances, when placed on the 
discs of leaves, do not incite inflection. Particles of soft sugar were 
added to the secretion round several glands and were soon dissolved, 
causing a great increase of the secretion, no doubt by exosmose ; and 
after 24 hra. the cells showed a certain amount of aggregation, though 



Chap. III.] THE PROCESS OF AGGKEGATION. 45 

the tentacles were not inflected. Glycerine causes in a few minutes 
well-pronounccil aggregation, commencing as usual within the glands 
and then travelling down the tentacles ; and this I presume may be 
attributed to the strong attraction of this substance for water. 
Immersion for several hours in water causes some degree of aggrega- 
tion. Twenty leaves were first carefully examined, and re-examined 
after having been left immersed in distilled water for various periods, 
with the following results. It is rare to find even a trace of aggrega- 
tion until 4 or 5 and generally not until several more hours have 
elapsed. When, however, a leaf becomes quickly inflected in water, as 
sometimes happens, especially during very warm weather, aggregation 
may occur in little over 1 hr. In all cases leaves left in water for 
more than 24 hrs. have their glands blackened, which shows that 
their contents are aggregated ; and in the specimens, which were 
carefully examined, there was fairly well-marked aggregation in the 
upper cells of the pedicels. These trials were made with cut-off leaves, 
and it occurred to me that this circumstance might influence the 
result, as the footstalks would not perhaps absorb water quickly 
enough to supply the glands as they continued to secrete. But this 
view was proved erroneous, for a plant with uninjured roots, bearing 
four leaves, was submerged in distilled water for 47 hrs., and the 
glands were blackened, though the tentacles were very little inflected. 
In one of these leaves there was only a slight degree of aggregation in 
the tentacles ; iu the second rather more, the pui-ple contents of the 
cells being a little separated from the walls ; in the third and fourth, 
which were pale leaves, the aggregation in the upper parts of the 
pedicels was well marked. In these leaves the little masses of proto- 
plasm, many of which were oval, slowly changed their forms and 
positions ; so that a submergence for 47 hrs. had not killed the proto- 
plasm. In a previous trial with a submerged plant the tentacles were 
not in the least inflected. 

Heat induces aggregation. A leaf, with the cells of the tentacles 
containing only homogeneous fluid, was waved about for 1 m. in water 
at 130° Pahr. (54° "4 Cent.), and was then examined under the micro- 
scope as quickly as possible, that is in 2 m. or 3 m. ; and by this time 
the contents of the cells had undergone some degree of aggregation. 
A second leaf was waved for 2 m. in water at 125° (51° "6 Cent.) and 
quickly examined as before; the tentacles were well inflected; the 
purple fluid in all the cells had shrunk a little from the walls, and 
contained many oval and elongated masses of protoplasm, with a few 
minute spheres. A third leaf was left in water at 125°, until it cooled, 
and, when examined after 1 hr. 45 m., the inflected tentacles showed 
some aggregation, which became after 3 hrs. more strongly marked, 
but did not subsequently increase. Lastly, a leaf was waved for 1 m. 
in water at 120° (48° '8 Cent.) and then left for 1 hr. 26 m. in cold 
water; the tentacles were but little inflected, and there was only 
here and there a trace of aggregation. In all these and other trials 
with warm water the protoplasm showed much less tendency to 



46 DEOSEEA EOTUNDIFOLIA. [Chap. III. 

aggregate into spherical masses than when excited by carbonate of 
ammonia. 

Eedissolution of the Aggregated Masses of Protojjlasm.—As soon as 
tentacles which have clasped an insect or any inorganic object, or have 
been in any way excited, have fully re-expanded, the aggregated 
masses of protoplasm are redissolved and disappear; the cells being 
now refilled with homogeneous purple fluid as they were before the 
tentacles were inflected. The process of redissolution in all cases 
commences at the bases of the tentacles, and proceeds up them 
towards the glands. In old leaves, however, especially in those which 
have been several times in action, the protoplasm in the uppermost 
cells of the pedicels remains in a permanently more or less aggregated 
condition. In order to observe the process of redissolution, the 
following observations were made : a leaf was left for 24 hrs. in a little 
solution of one part of carbonate of ammonia to 218 of water, and the 
protoplasm -^as as usual aggregated into numberless purple spheres, 
which were incessantly changing their forms. The leaf was then 
washed and placed in distilled water, and after 3 hrs. 15 m. some few 
of the spheres began to show by their less clearly defined edges signs 
of redissolution. After 9 hrs. many of them had become elongated, 
and the surrounding fluid in the cells was slightly more coloured, 
showing plainly that redissolution had commenced. After 24 hrs., 
though many cells still contained spheres, here and there one could be 
seen filled with purple fluid, without a vestige of aggregated proto- 
plasm ; the whole having been redissolved. A leaf witii aggregated 
masses, caused by its having been waved for 2 m. in water at the 
temperature of 125° Fahr., was left in cold water, and after 11 hrs. the 
protoplasm showed traces of incipient redissolution. When again 
examined three days after its immersion in the warm water, there was 
a conspicuous difference, though the protoplasm was still somewhat 
aggregated. Another leaf, with the contents of all the cells strongly 
aggregated from the action of a weak solution of phosphate of 
ammonia, was left for between three and four days in a mixture 
(known to be innocuous) of one drachm of alcohol to eight drachms of 
water, and when re-examined every trace of aggregation had dis- 
appeared, the cells being now filled with homogeneous fluid. 

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



Chap. III.] THE WIOCESS OP AGGEEGATIOK. 47 

fluid. Tbe redissolntion in these cases may, I presume, be attributed 
to endosmoso. 

On the Proximate Causes of the Process of Aggregation. 

As most of the stimulants which cause the inflection of the 
tentacles likewise induce aggi-egation in the contents of their 
cells, this latter process might be thought to bo the direct 
result of inflection ; but this is not the case. If leaves are 
placed in rather strong solutions of carbonate of ammonia, for 
instance of three or four, and even sometimes of only two 
grains to the ounce of water (i.e. one part to 109, or 146, or 
218, of water), the tentacles are paralysed, and do not become 
inflected, yet they soon exhibit strongly marked aggregation. 
Moreover, the short central tentacles of a leaf which has been 
immersed in a weak solution of any salt of ammonia, or in 
any nitrogenous organic fluid, do not become in the least 
inflected; nevertheless, they exhibit all the phenomena of 
aggregation. On the other hand, several acids cause strongly 
pronounced inflection, but no aggregation. 

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

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



48 DEOSEEA EOTUNDIFOLIA. [Chap. III. 

secrete, and the aggregated masses of protoplasm are then 
redissolved. Moreover, when leaves are immersed in dense 
vegetable solutions, or in glycerine, the fluid vrithin the 
gland-cells passes outwards, and there is aggregation; and 
when the leaves are afterwards immersed in water, or in an 
innocuous fluid of less specific gravity than water, the 
protoplasm is redissolved, and this, no doubt, is due to 
endosmose. 

Opposed to this view, that aggregation is caused by the 
•outward passage of fluid from the cells, are the following 
facts. There seems no close relation between the degree of 
increased secretion and that of aggregation. Thus a particle 
of sugar added to the secretion round a gland causes a much 
greater increase of secretion, and much less aggregation, than 
does a particle of carbonate of ammonia given in the same 
manner. It does not appear probable that piire water would 
cause much exosmose, and yet aggregation often follows from 
an immersion in water of between 16 hrs. and 24 hrs., and 
always after from 24 hrs. to 48 hrs. Still less probable is it 
that water at a temperature of from 125° to 130° !Fahr. 
(51° • 6 to 54° -4 Cent.) should cause fluid to pass, not only 
from the glands, but from all the cells of the tentacles down 
to their bases, so quickly that aggregation is induced within 
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 proto- 
plasm in solution. There is still stronger evidence that 
aggregation is independent of secretion; for the papillae, 
described in the first chapter, with which the leaves are 
studded are not glandular, and do not secrete, yet they 
rapidly absorb carbonate of ammonia or an infusion of raw 
meat, and their contents then quickly undergo aggregation, 
which afterwards spreads into the cells of the surrounding 
tissues. We shall hereafter see that the purple fluid within 
the sensitive filaments of 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 
iminjured to be thus aifected, and they must be in an 
oxygenated condition for the transmission of the process at 



Chap. III.] THE PROCESS OF AGGREGATION. 49 

the proper rate. Some tentacles in a drop of -water were 
strongly pressed beneath a slip of glass ; many of the cells 
were ruptured, and puljjy matter of a purple colour, 
with granules of all sizes and shapes, exuded, but hardly 
any of the cells were completely emptied. I then added 
a minute drop of a solution of one part of carbonate of 
ammonia to 109 of water, and after 1 hr. examined the 
specimens. Here and there a few cells, both in the glands 
and in the pedicels, had escaped being ruptured, and their 
contents were well aggregated into spheres which were 
constantly changing their forms and positions, and a current 
could still be seen flowing along the walls ; so that the 
protoplasm was alive. On the other hand, the exuded 
matter, which was now almost colourless instead of being 
purple, did not exhibit a trace of aggregation. Nor was 
there a trace in the many cells which were ruptured, but 
which had not been completely emptied of their contents. 
Though I looked carefully, no signs of a current could be 
seen within these ruptured cells. They had evidently been 
killed by the pressure; and the matter which they still 
contained did not undergo aggregation any more than that 
which had exuded. In these specimens, as I may add, the 
individuality of the life of each cell was well illustrated. 

A full account will be given in the next chapter of the 
effects of heat on the leaves, and I need here only state that 
leaves immersed for a short time in water at a temperature 
of 120° Fahr. (48°- 8 Cent.), which, as we have seen, does not 
immediately induce aggregation, were then placed in a few 
drops of a strong solution of one part of carbonate of 
ammonia to 109 of water, and became finely aggregated. 
On the other hand, leaves, after an immersion in water at 
150° (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 



50 DEOSEEA EOTUNDIFOLIA. [Chap. III. 

extremely small, yet well defined, but many of the cells con- 
tained, in .addition, some brownish pnlpy matter. In two 
cases of leaves heated to 145° (62° • 7 Cent.), a few tentacles 
could he found with some of their cells containing a fewminute 
spheres ; whilst the other cells and other whole tentacles 
included only the brownish, disintegrated or pulpy matter. 

The fluid within the cells of the tentacles must be in an 
oxygenated condition, in order that the force or influence 
which induces aggregation should be transmitted at the 
proper rate from cell to cell. A plant, with its roots in 
water, was left for 45 m. in a vessel containing 122 fluid oz. 
of carbonic acid. A leaf from this plant, and, for comparison, 
one from a fresh plant, were both immersed for 1 hr. in a 
rather strong solution of carbonate of ammonia. They were 
then compared, and certainly there was much less aggregation 
in the leaf which had been subjected to the carbonic acid 
than in the other. Another plant was exposed in the same 
vessel for 2 hrs. to carbonic acid, and one of its leaves was 
then placed in a solution of one part of the carbonate to 437 
of water ; the glands were instantly blackened, showing that 
they had absorbed, and that their contents were aggregated ; 
but in the cells close beneath the glands there was no aggre- 
gation even after an interval of 3 hrs. After 4 hrs. 16 m. a 
few minute spheres of protoplasm were formed in these cells, 
but even after 5 hrs. 30 m, the aggregation did not extend 
down the pedicels for a length equal'to that of the glands. 
After numberless trials with fresh leaves immersed in a 
solution of this strength, I have never seen the aggregating 
action transmitted at nearly so slow a rate. Another plant 
was left for 2 hrs. in carbonic acid, but was then exposed for 
20 m. to the open air, during which time the leaves, being of 
a red colour, would have absorbed some oxygen. One of 
them, as well as a fresh leaf for comparison, were now 
immersed in the same solution as before. The former were 
looked at repeatedly, and after an interval 65 m. a few 
spheres of protoplasm were first observed in the cells close 
beneath the glands, but only in two or three of the longer 
tentacles. After 3 hrs. the aggregation had travelled down 
the pedicels of a few of the tentacles for a length equal to 
that of the glands. On the other hand, in the fresh leaf 
similarly treated, aggregation was plain in many of the 
tentacles after 15 m. ; after 65 m. it had extended down the 
pedicels for four, five, or more times the length of the glands ; 



Chap. III.] THE PROCESS OF AGGKEGATIOJf. 51 

and after 3 hrs. the cells of all the tentacles were affected for 
one-third or one-half of their entire lengths. Hence there 
can he no doubt that the exposure of leaves to carbonic acid 
cither stops for a time the process of aggregation, or checks 
the transmission of the proper influence when the glands are 
subsequently excited by carbonate of ammonia; and this 
substance acts more promptly and energetically than any 
other. It is known that the protoplasm of plants exhibits 
its spontaneous movements only as long as it is in an 
oxygenated condition ; and so it is with the white corpuscles of 
the blood, only as long as they receive oxygen from the red 
corpuscles ; * but the cases above given are somewhat different, 
as they relate to the delay in the generation or aggregation 
of the masses of the protoplasm by the exclusion of oxygen. 

Summary and Concluding EemarJcs. — The process of aggre- 
gation is independent of the inflection of the tentacles and 
apparently of increased secretion from the glands. It 
commences within the glands, whether these have beep, 
directly excited, or indirectly by a stimulus received from 
other glands. In both cases the process is transmitted from 
cell to cell down the whole length of the tentacles, being 
arrested for a short time at each transverse partition. With 
pale-coloured leaves the first change which is perceptible, 
but only under a high power, is the appearance of the finest 
granules in the fluid within the cells, making it slightly 
cloudy. These granules soon aggregate into small globular 
masses. I have seen a cloud of this kind appear in 10 s. 
after a drop of a solution of carbonate of ammonia had been 
given to a gland. With dark red leaves the first visible 
change often is the conversion of the outer layer of the fluid 
within the cells into bag-like masses. The aggregated 
masses, however they may have been -developed, incessantly 
change their forms and positions. They are not filled with 
fluid, but are solid to their centres. Ultimately the colourless 
granules in the protoplasm which flows round the walls 
coalesce with the central spheres or masses ; but there is still 
a current of limpid fluid flowing within the cells. As soon 
as the tentacles fully re-expand, the aggregated masses are 



* With respect to plants, Sachs, 'Quarterly Journal of Microscopical 
'Traitd de Bot.,' 3rd edit., 1874, Science,' ApriI1874, p. 185. 



p. 864. On blood corpuscles, see 



E 2 



52 DEOSERA EOTUNDIFOLIA. [Chap. III. 

redissolved, and tlie cells become filled with homogeneous 
purple fluid, as they were at first. The process of redissolu- 
tion commences at the hases of the tentacles, thence pro- 
ceeding upwards to the glands ; and, therefore, in a reversed 
direction to that of aggregation. 

Aggregation is excited by the most diversified causes, — 
by the glands being several times touched, — by the pressure 
of particles of any kind, and as these are supported by the 
dense secretion, they can hardly press on the glands with the 
weight of a millionth of a grain,* — by the tentacles being 
cut off close beneath the glands, — by the glands absorbing 
various fluids or matter dissolved out of certain bodies, — by 
exosmose, — and by a certain degree of heat. On the other 
hand, a temperature of about 150° Fahr. (65° • 6 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 aggrega- 
tion when carbonate of ammonia is added. A very strong 
solution of this salt and rather large bits of raw meat prevent 
the aggregated masses being well developed. From these 
facts we may conclude that the protoplasmic fluid within a 
cell does not become aggregated unless it be in a living state, 
and only imperfectly if the cell lias been injured. We have 
also seen that the fluid must be in an oxygenated state, 
in order that the process of aggregation should travel from 
cell to cell at the proper rate. 

Various nitrogenous organic fluids and salts of ammonia 
induce aggregation, but in different degrees and at veiy 
different rates. Carbonate of ammonia is the most powerful 
of all known substances; the absorption of xWtott of a 
grain ( ■ 000482 mg.) by a gland suffices to cause all the cells 
of the same tentacle to become aggregated. The first effect 
of the carbonate and of certain other salts of ammonia, as well 
as of some other fluids, is the darkening or blackening of the 
glands. This follows even from long immersion in coli^ 



* According to Hofmeister (as phenomenon, as it relates to the 
quoted by Sachs, 'Traits de Bot.,' contents of the cells, and only 
1874, p. 958), very slight pressure secondarily to the layer of protoplasm 
on the cell-membrane arrests imme- "which flows along the walls ; though 
diately the movements of the pro- no doubt the effects of pressure or of 
toplasm, and even determines its a touch on the outside must be trans- 
separation from the walls. But the mitted through this layer, 
process of aggregation is a different 



Chap. III.] THE PEOCESS OF AGGKEGATIOK. 53 

distilled water. It apparently depends in chief part on 
the strong aggregation of their cell-contents, which thus 
become opaque and do not reflect light.* Some other fluids 
render the glands of a brighter red ; whilst certain acids, 
though much diluted, the poison of the cobra-snake, &o., 
make the glands perfectly white and opaque ; and this seems 
to depend on the coagulation of their contents without any 
aggregation. Nevertheless, before being thus afi'ected, they 
are able, at least in some cases, to excite aggregation in 
their own tentacles. 

That the central glands, if irritated, send centrifugally 
6ome influence to the exterior glands, causing them to send 
back a centripetal influence inducing aggregation, is perhaps 
the most interesting fact given in this chapter. But the 
whole process of aggregation is in itself a striking pheno 
menon. Whenever the peripheral extremity of a nerve i^ 
touched or pressed, and a sensation is felt, it is believed that 
an invisible molecular change is sent from one end of the 
nerve 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 Aggregation 
in the Boots of Plants. 

It will hereafter be seen that a weak solution of the carbonate of 
•ammonia induces aggregation in the cells of the roots of Drosera ; and 
this led me to make a few trials on the roots of other plants. I dug 
up in the latter part of October the first weed which I met with, viz. 



* [The words " which .... light " would probably have been omitted 
by the author iii a second edition. — F. D.] 



54 DEOSEEA EOTUNDIFOLIA. [Chap. III. 

FjuphorUa peplus, being careful not to injure tlie roots ; these were 
washed and placed in a little solution of one part of carbonate of 
ammonia to 146 of water. In less than one minute I saw a cloud 
travelling from cell to cell up the roots, with wonderful rapidity. 
After from 8 m. to 9 m. the fine granules, which caused this cloudy 
appearance, became aggregated towards the extremities of the roots 
into quadrangular masses of brown matter ; and some of these soon 
changed their forms and became spherical. Some of the cells, how* 
ever, remained unaffected. I repeated the experiment with another 
plant of the same species, but before I could get the specimen into 
focus under the microscope, clouds of granules and quadrangular 
masses of reddish and brown matter were formed, and had run far up 
all the roots. A fresh root was now left for 18 hrs. in a drachm of a 
solution of one part of the carbonate to 437 of water, so that it re- 
ceived i of a grain, or 2-024 mg. When examined, the cells of all 
the roots throughout their whole length contained aggregated massed 
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 themj 
Boots were also immersed for 35 m. in a solution of one part of car- 
bonate of potash to 218 of water ; but this salt produced no effect. 

I may here add that thin slices of the stem of the Euphorbia were 
placed in the same solution, and the cells which were green instantly 
became cloudy, whilst others which were before colourless were clouded 
with brown, owing to the formation of nmnerous granules of this tint. 
I have also seen with various kinds of leaves, left for some time in a 
solution of carbonate of ammonia, that the grains of chlorophyll ran 
together and partially coalesced ; and this seems to be a form of 
aggregation. 

Plants of duck-weed (Lemna) were left for between 30 m. and 45 m. 
in a solution of one part of this same salt to 146 of water, and three of 
their roots were then examined. In two of them, all the cells which 
had previously contained only limpid iiuid now included little green 
spheres. After from 1-J hr. to 2 hrs. similar spheres appeared in the 
cells on. the borders of the leaves; but whether the ammonia had 
travelled up the roots or had been directly absorbed by the leaves, I 
cannot say. As one species, Lemna arrhiza, produces no roots, the 
latter alternative is perhaps the most probable. After about 2^ hrs. 
some of the little green spheres in the roots were broken up into small 
granules which exhibited Brownian movements. Some duck-weed 
was also left for 1 hr. 30 m. in a solution of one part of carbonate of 
potash to 218 of water, and no decided change could be perceived in 
the cells of the roots : but when these same roots were placed for 25 m. 
in a solution of carbonate of ammonia of the same strength, little green 
spheres were formed. 

A green marine alga was left for some time in this same solution, 
but was very doubtfully, affected. On the other hand, a red marine 
alga, with finely pinnated fronds, was strongly affected. The contents 



Chap. III.] THE PROCESS OF AGGREGATION. 55 

of the cells aggregated themselves into broken rings, still of a red 
colour, which very slowly and slightly changed their shapes, and the 
central spaces within these rings became cloudy with red granular 
matter. The facts here given (whether they are new, I know not) 
indicate that interesting results would perhaps be gained by observing 
the action of various saline solutions and other fluids on the roots of 
plants.* 

*[See C. Darwin on "The Action also "Tlie Action of Carbonate of 

of Carbonate of Ammonia on tlie Ammonia on Chlorophyll-bodies : " 

Roots of certain Plants : " ' Linn. Soc. ' Linn. See. Jonrnal ' (Bot.), vol. lix. 

Journal ' (Bot.), vol. xix. 1882, p. 239 ; 1882, p. 262.— F. D.] 



56 DKOSEEA EOTUNDIFOLIA. [Chap. IV. 



CHAPTER IV. 

The Effects of Heat on the Leaves. 

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

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



* When my experiments on the to a temperature of 118^° Fahr. as 

effects of heat were made, I was not a maximum." As my results are 

aware that the subject had been deduced from special phenomena, 

carefully investigated by several ob- namely, the subsequent aggiegation 

servers. For instance, Sachs is con- of the protoplasm and there-expansion 

vinced ('Traite de Botanique,' 1874, of the tentacles, they seem to me worth 

pp. 772, 854) that the most different giving. We shall find that Drosera 

kinds of plants all perish if kept for resists heat somewhat better than 

10 m. in water at 45° to 46° Cent., or most other plants. That there should 

113° to 115° Fahr. ; and he concludes be considerable differences in this re- 

that the protoplasm within their cells spect is not surprising, considering 

always coagulates, if in a damp condi- that some low vegetable organisms 

tion, at a temperature of between 50° grow in hot springs — cases of which 

and 60° Cent., or 122° to 140° Fahr. have been collected by Prof. Wyman 

Max Schultze and Kiihne (as quoted (' American .Journal of Science,' vol. 

by Dr. Bastian in ' Contemp. Review,' xliv. 1867). Thus, Dr. Hooker found 

1874, p. 528) " found that the pro- Conferva; in water at 168° Fahr. ; 

toplasm of plant-cells, with which Humboldt, at 185° Fahr. ; and Des- 

they experimented, was always killed cloizeaux, at 208° Fahr. 
and altered by a very brief exposure 



CuAP. IV.] THE EFFECTS OF HEAT. 57 

My experiments were tried in the following manner. Leaves were 
cut off, and this does not in the least interfere with their powers ; for 
instance, three cut-off leaves, with bits of meat placed on them, weie 
kept in a damp atmosphere, and after 23 hrs. closely embraced the 
meat both with their tentacles and blades ; and the protoplasm within 
their cells was well aggregated. Three ounces of doubly distilled 
water was heated in a porcelain vessel, with a delicate thermometer 
having a long bulb obliquely suspended in it. The water was gradiinllj' 
raised to the required temperature by a spirit-lamp moved about under 
the vessel ; and in all cases the leaves were continually waved for 
some minutes close to the bulb. They were then placed in cold water, 
or in a solution of carbonate of ammonia. In other cases they were 
left in the water, which had been raised to a certain temperature, imtil 
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 tliink, have been superfluous, as the leaves from age or con- 
stitutional causes differ slightly in their sensitiveness to heat. 

It will be convenient first briefly to describe the eflects of immersion 
for thirty seconds in boiling water. The leaves are rendered flaccid 
with their tentacles bowed backwards, which, as we shall see in a 
future chapter, is probably due to their outer surfaces retaining their 
elasticity for a longer period than their inner s\irfaces retain the power 
of contraction. 'J'he purjile fluid within Ihe cells of the pedicels is 
rendered finely granular, but there is no true aggregation ; nor docs 
this follow when the leaves are subsequently placed in a solnticin of 
carbonate of ammonia. But the most remarkable change is that the 
glands become opaque and uniformly white ; and this may be attri- 
liuted to the coagulation of their albuminous contents. 

My first and preliminary experiment consisted in putting seven 
leaves in the same vessel of water, and warming it slowly up to the 
temperature of 110° Fahr. (43° -3 Cent.); a leaf being taken out as 
soon as the temperature rose to 80° (26° "6 Cent.), another at 8h°, 
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 re- 
moved from the cold water and kept in damp air, with bits of meat 
placed on their discs. The leaf which had been exposed to the tem- 
perature of 110° became in 15 m. greatly inflected ; and in 2 hrs. every 
single tentacle closely embraced the meat. So it was, but after rather 
longer intervals, with the six other leaves. It aiipears, therefore, 
that the warm bath had increased their sensitiveness when excited by 
meat. 

1 next observed the degree of inflection which leaves underwent 
•within stated periods, whilst still immersed in warm water, kept as 



58 DROSEEA EOTUNDIFOLIA. [Chap. IV. 

nearly as possible at the same temperature ; but I will here and else- 
where give only a few of the many trials made. A leaf was left for 
10 m. in water at 100° (37° -7 Cent.), but no infleotiou 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 10.5° 
to 106° (40° • 5 to 40° • 1 Cent.), was very moderately infiectad in 6 m. 
A fourth leaf, in water at 110° (43° -3 Cent.), was somewhat inflected 
in 4 m., and considerably so in from 6 m. to 7 m. 

Three leaves were placed in water which was heated rather quickly, 
and by the time the temperature rose to 115°— 116° (46°-l to 46°-06 
Cent.), all three were inflected. I then removed the lamp, and in a, 
few minutes every single tentacle was closely inflected. The proto- 
plasm within the cells was not killed, for it was seen to be in distinct 
movement ; and the leaves, having been left in cold water for 20 hrs., 
re-expanded. Another leaf was immersed in water at 100° (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 following morning it was 
immersed in a weak solution of carbonate of ammonia, and the glands 
quickly became black, with strongly marked aggregation in the 
tentacles, showing that the protoplasm was alive, and that the glands 
had not lost their power of absorption. Another leaf was placed in 
water at 110° (43° -3 Cent.) which was raised to 120° (48° -8 Cent.); 
and every tentacle, excepting one, was quickly and closely inflected. 
This leaf was now immersed in a few drops of a strong solution of car- 
bonate of ammonia (one part to 109 of water) ; in 10 m. all the glands 
became intensely black, and in 2 hrs. the protoplasm in the cells of 
the pedicels was well aggregated. Another leaf was suddenly plunged, 
and as usual waved about, in water at 120°, and the tentacles became 
inflected in from 2 m. to 3 m., but only so as to stand at right angles 
to the disc. The leaf was now placed in the same solution (viz. 
one part of carbonate of ammonia to 109 of water, or 4 grs. to 1 oz., 
which I will for the future designate as the strong solution), and when 
I looked at it again after the interval of an hour, the glands were 
blackened, and there was well-marked aggregation. After an additional 
interval of 4 hrs. the tentacles had become much more inflected. It 
deserves notice that a solution as strong as this never causes 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 protoplasm did not become 
spherical, as almost always occurs with leaves immersed in a solution 
of carbonate of ammonia. 

We learn from these cases that a temperature of from 120° 



Chap. IV.] THE EFFECTS OF HEAT. 59 

to 125° (48°- 8 to ol°-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 
lorotoplasm. We shall now sea that a temperature of 130° 
(54° '4 Cent.) is too high to cause immediate inflection, yet 
does not kill the leaves. 

Experiment 1. — A leaf was plunged, and as in all cases waved about 
for a few minutes, in water at 130° (54° -4 Cent.), but there was no 
trace of inflection ; it was then placed in cold water, and after an 
interval of 15 m. very slow movement was distinctly seen in a small 
mass of protoplasm in one of the cells of a tentacle.* After a few- 
hours all the tentacles and the blade became inflected. 

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

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

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

Experiment 5. — Leaf immersed at 130° (54° '4 Cent.), and the water 
raised to 145° (62° '7 Cent.), there was no immediate inflection; it 
was then placed in cold water, and after 1 hr. 20 m. some of the 
tentacles on one side became inflected. This leaf was now placed in 
the strong solution, and in 40 m. all the submarginal tentacles were 
well inflected, and the glands blackened. After an additional interval 
of 2 hrs. 45 m. all the tentacles, except eighi; or ten, were closely 
inflected, with their cells exhibiting a slight degree of aggregation; 
but the spheres of protoplasm were very small, and the cells of the 
exterior tentacles contained some pulpy or disintegrated brownish 
matter. 

Experiments 6 and 7. — Two leaves were plunged in water at 135° 



* Sachs states (' Traitd de Bo- were exposed for 1 m. in water to a 

tanique,' 1874-, p. 855) that the temperature of 47° to 48° Cent., oi' 

movements of the protoplasm in the 117° to 119° Fahr. 
hairs of a Cucurbita ceased after they 



60 DKOSEEA KOTUNDIFOLIA. [Chap. IV. 

(u7°-2 Cent.) which was raised to 145° (62° '7 Cent.) ; neither becaine 
inflected. One of these, however, after having been left for 31 m. in 
cold water, exhibited some slight inflection, which increased after an 
additional interval of 1 hr. 45 m., xintil all the tentacles, except sixteen 
or seventeen, were more or less inflected ; but the leaf was so much 
injured that it never re-expanded. The other leaf, after having been 
left for half an hour in cold water, was put into the strong solution, 
but no inflection ensued ; the glands, however, were blackened, and in 
some cells there was a little aggregation, the spheres of protoplasm 
being extremely small ; in other cells, especially in the exterior 
tentacles, there was much greenish-brown pulpy matter. 

Experiment 8. — A leaf was plunged and waved about for a few 
minutes in water at 140° (60° Cent.), and was then left for half an 
hour in cold water, but there was no inflection. It was now placed in 
I he strong solution, and alter 2 hrs. 30 m. the inner submarginal 
tentacles were well inflected, with their glands blackened, and some 
imperfect aggregation in the cells of the pedicels. Three or four of 
the glands were spotted with the white porcelain-like structure, like 
that produced by boiling water. I have seen this result in no other 
instance after an immersion of only a few minutes in water at so low a 
temperature as 140°, and in only one leaf out of four, after a similar 
immersion at a temperature of 145° Fahr. On the other hand, with 
two leaves, one placed in water at 145° (62° '7 Cent.), and the other in 
water at 140° (60° Cent.), both being left therein until the water 
cooled, the glands of both became white and porcelain-like. So that 
the 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 backwards. 
The glands became like porcelain, but some of them were a little • 
mottled with purple. The bases of the glands were often moru 
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 150J° 
(65° "5 Cent.); it became somewhat flaccid, with the outer tentacles 
slightly reflexed, and the inner ones a little bent inwards, but only 
towards their tips ; and this latter fact shows that the movement was 
not one of true inflection, as the basal part alone normally bends. The 
tentacles were as usual rendered of a very bright red, with the glands 
almost white like porcelain, yet tinged with pink. The leaf having 
been placed in the strong solution, the cell-contents of the tentacles 
became of a muddy brown, with no trace of aggregation. 

Experiment 11.' — A leaf was immersed in water at 145° (62° '7 
Cent.), which was raised to 156° (68° "8 Cent.). The tentacles became 
bright red and somewhat reflexed, with almost all the glands like 
porcelain ; those on the disc being still pinkish, those near the margin 
quite white. The leaf being placed as usual first in cold water and 



Chap. IV.] THE EFFECTS OF HEAT. 61 

then in the strong solution, the cells in the tentacles became of a 
muddy greenish brown, with the protoplasm not aggregated. Never- 
tlieless, four of the glands escaped being rendered like porcelain, and 
the pedicels of these glands were spirally curled, like a French horn, 
towards their upper ends ; but this can by no means be considered as a 
case of true inflection. The protoplasm within the cells of the twisted 
portions was aggregated into distinct though excessively minute purple 
.spheres. This case shows clearly that the protoplasm, after having 
been exposed to a high temperature for a few minutes, is capable of 
aggregation when alterward.s subjected to the action of carbonate of 
ammonia, unless the heat has been sufficient to cause coagulation. 

Concluding BemarJcs. — As the hair-liko tentacles are ex- 
tremely th-in and have delicate walls, and as the leaves were 
waved about for some minutes close to the hulb of tho- 
thermometer, it seems scarcely possible that they should not 
have been raised very nearly to the temperature which the 
instrument indicated. From the eleven last observations we 
see that a temperature of 130° (54° "4 Cent.) never causes the 
immediate inflection of the tentacles, though a temperature 
from 120° to 125° (48° -8 to 51° -6 Cent.) quickly produces 
this eifect. But the leaves are paralysed only for a time by 
a temperature of 130°, as afterwards, whether left in simple 
water or in a solution of carbonate of ammonia, they become 
inflected and their protoplasm undergoes aggregation. This 
great difference in the effects of a higher and lower tempera- 
ture may be compared with that from immersion in strong 
and weak solutions of the salts of ammonia ; for the former 
do not excite movement, whereas the latter act energetically. 
A temporary suspension of the power of movement due to 
heat is called by Sachs* heat rigidity ; and this in the case 
of the sensitive plant (Mimosa) is induced by its exposure 
for a few minutes to humid air, raised to 120°^ — 122° Fahr., 
or 49° to 60° Cent. It deserves notice that the leaves of 
Drosera, after being immersed in water at 130° Fahr., are 
excited into movement by a solution of the carbonate so 
strong that it would paralyse ordinary leaves and cause no 
inflection. 

The exposure of the leaves for a few minutes even to a 
temperature of 145° Fahr. (62°* 7 Cent.) does not always kill 
them ; as, when afterwards left in cold water, or in a strong 
solution of carbonate of ammonia, they generally, though not 



' Traits de Bot.' 1874, p. 1034. 



62 DEOSEEA EOTUNDIFOLIA. [Chap. IV. 

always, become inflected; and tte protoplasm witliin their 
cells undergoes aggregation, tlLongh 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 virere incapable of 
re-expansion. Exposure for a few minutes to a temperature 
of 145° sometimes causes some few of the more sensitive 
glands to be speckled with the porcelain-like appearance; 
and on one occasion this occurred at a temperature of 140° 
(60° Cent.). On another occasion, when a leaf was placed in 
water at this temperature of only 140°, and left therein till 
the water cooled, every gland became like porcelain. Ex- 
posure for a few minutes to a temperature of 150° (65°*5 
Cent.) generally produces this effect, yet many glands retain 
a pinkish colour, and many present a speckled appearance. 
This high temperature never causes true inflection ; on the 
contrary, the tentacles commonly become reflexed, though to 
a less degree than when immersed in boUing water ; and this 
apparently is due to their passive power of elasticity. After 
exposure to a temperature of 150° Eahr., the protoplasm, if 
subsequently subjected to carbonate of ammonia, instead of 
undergoing aggregation, is converted into disintegrated or 
pulpy discoloured matter. In short, the leaves are generally 
killed by this degree of heat; but owing to differences of 
age or constitution, they vary somewhat in this respect. In 
one anomalous case, four out of the many glands on a leaf, 
which had been immersed in water raised to 156° (68° -8 
Cent.), escaped being rendered porcellanous ; * and the proto- 
plasm in the cells close beneath these glands underwent some 
slight, though imperfect, degree of aggregation. 

Finally, it is a remarkable fact that the leaves of Drosera 
rotundifolia, which flourishes on bleak upland moors through- 



* As the opacity and porcelain-like of coagulation is lower. The leaves 
appearance of the glands is probably of Drosera contain an acid, and per- 
due to the coagulation of the albumen, haps a difference in the amount con- 
1 may add, on the authority of Dr. tained may account for the slight 
Burden Sanderson, that albumen differences in the results above re- 
coagulates at about 155°, but, in corded, 
presence of acids, the temperature 



CuAP. IV.] THE EFFECTS OF HEAT. 63 

out Great Britain, and exists (Hooker) within the Arctic 
Circle, should he ahle to withstand for even a short time 
immersion in water heated to a temperature of 145°.* 

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



* It appears the cold-blooded Burdon Sanderson, a frog begins to be 

animals are, as might have been distressed in water at a temperature 

expected, far more sensitive to an of only 85° Fahr. At 95° the muscles 

increase of temperature than is become rigid, and the animal dies in ;i 

Drosera. Thus, as I hear from Dr. stiffened condition. 



64 DKOSEEA EOTUNDIFOLIA. [Chap. V. 



CHAPTER V. 

Tub ErrECTS or Nox-sitrogenous and Nitrogenous Organic Fujids 
ON THE Leaves. 

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

WHEiif, in 1860, I first observed Drosera, and was led to 
believe tliat the leaves absorbed nutritious matter from the 
insects -which they captured, it seemed to me a good plan 
to make some preliminary trials with a few common fluids, 
containing and not containing nitrogenous matter : and the 
results are worth giving. 

In all the following cases a drop was allowed to fall from, 
the same pointed instrument on the centre of the leaf; and 
by repeated trials one of these drops was ascertained to be on 
an average very nearly half a minim, or tj-|^ of a fluid ounce,, 
or -0295 cc. But these measurements obviously do not 
pretend to any strict accuracy ; moreover, the drops of the 
viscid fluids were plainly larger than those of water. Only 
one leaf on the same plant was tried, and the plants were 
collected from two distant localities. The experiments were- 
made during August and September. In judging of the- 
efiects, one caution is necessary : if a drop of any adhesive- 
fluid is placed on an old or feeble leaf, the glands of which 
have ceased to secrete copiously, the drop sometimes dries up, 
especially if the plant is kept in a room, and some of the- 
central and submarginal tentacles are thus drawn together, 
giving to them the false appearance of having become 
inflected. This sometimes occurs with water, as it is rendered 
adhesive by mingling -with the viscid secretion. Hence the 
only safe criterion, and to this alone I have trusted, is the 
bending inwards of the exterior tentacles, which have not 
been touched by the fluid, or at most only at their bases. In 



Chap. V.] EFFECTS OF ORGANIC FLUIDS. 65 

this case the movement is wholly due to the central glands 
having been stimulated by the fluid, and transmitting a 
motor impulse to the exterior tentacles. The blade of the 
leaf likewise often curves inwards, in the same manner as 
when an insect or bit of meat is placed on the disc. This 
latter movement is never caused, as far as I have seen, by 
the mere drying up of an adhesive fluid and the consequent 
drawing together of the tentacles. 

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

Oum arable. — 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 heing left on the discs from 24 hrs. 
to 44 hrs. ; generally about 30 hrs. Inflection was never thus caused. 
It is necessary to try pure gum arabic, for a friend tried a solution 
bought ready prepared, and this caused the tentacles to bend; 
hut he afterwards ascertained that it contained much animal matter, 
probably glue. 

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

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

Alcohol, Diluted. — One part of alcohol was added to seven of water, 
•nnd the usual drops were placed on the discs of three leaves. No 
inflection ensued in the course of 48 hrs. To ascertain whether these 
leaves had been at all injured, bits of meat were placed on them, and 
after 24 hrs. they were closely inflected. I also put drops of sherry- 
wine on three other leaves ; no inflection was caused, though two of 
them seemed somewhat injured. We shall hereafter see that cut-off 
leaves immersed in diluted alcohol of the above strength do not become 
inflected. 



66 DBOSERA EOTUNDIFOLIA. [Chap. T. 

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

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

■We thus see that, excluding the experiments with water, 
sixty-one leaves were tried with drops of the ahove-named 
non-nitrogenous fluids ; and the tentacles were not in a 
single case inflected. 

■With respect to nitrogenous fluids, the first which came to hand 
-were tried. The experiments were made at the same time and in 
exactly the same manner as the foregoing. As it was immediately 
evident that these fluids produced a great effect, I neglected in most 

• cases to record how soon the tentacles became inflected. But this 
always occurred in less than 24 hrs. ; whilst the drops of non- 
nitrogenous fluids which produced no effect were observed in every case 

. during a considerably longer period. 

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

Human UriTts. — Drops were placed on twelve leaves, and the 
tentacles of all, with a single exception, became greatly inflected. 
Owing, I presume, to differences in the chemical nature of the urine 
on different occasions, the time required for the movements of the 
tentacles varied much, but was always effected in under 24 hrs. In 
two instances I recorded that all the exterior tentacles were completely 
inflected in 17 hrs., but not the blade of the leaf. In another case the 
edges of a leaf, after 25 hrs. 30 m., became so strongly inflected that it 



Chap. V;.] EFFECTS OF OEGANIC FLUIDS. 67 

was converted into a cup. The power of urine does not lie in the 
urea, .which, as we, shall hereafter see, is inoperative. 

. Albumen (fresli from a hen's egg), placed on seven leaves, caused 
the tentacles of six of them .to he well iriflected. In one case the edge 
of the leaf itself became much curled in after 20 hrs. The one leaf 
which veas , unaffected remained so for 26 hrs., and was then treated 
with a drop of milk, and this caused the tentacles to bend inwards in 
12 hrs.. 

. Cold Filtered Infusion of Saw Meat. — This was tried only on a 
single leaf, which hM most of its outer tentacles and the blade inflected 
in 19 hrs. .During subsequent years I repeatedly used this infusion to 
test leaves vhich had been experimented on with other substances, and 
, it was fgund to act most energetically, but as no exact account of these 
trials was kept, they are not .here iDtroduced. 

^wcws.7— Thick and thin mucus from the bronchial tubes, placed on 
three leaves, caused Inflection. A, leaf with thin mucus had its 
marginal tentacles and blade somewhat curved inwards in 5 hrs. 30 m. 
and greatly so in 20 hrs. The action of, this fluid no doubt is due 
either to the saliva or to some albuminous matter* mingled with it, 
and not, as we shall see in the next chapter, to mucin or the chemical 
piinoiple of mucus. 

Saliva. — Human saliva, when evaporated, yieldst from 1*14 to 
1'19 per cent, of residue; and this yields 0'25 per cent, of ashes, so 
that the proportion of nitrogenous matter which saliva contains must 
be small. Nevertheless, drops placed on the discs of eight leaves acted 
on them all. In one case all the exterior tentacles, excepting nine, 
were inflected in 19 hrs. 30 m. ; in another case a few became so in 2 
hrs., and after 7 hrs. 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 the glands with the handle of my 
scalpel wetted with saliva, to ascertain whether a leaf was in an active 
condition ; for this was shown in the course of a few minutes by the 
bending inwards of the tentacles. The edible nest of the Chinese 
swallow is foi'med 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 mihntes, but did not dissolve the whole. 
The usual-sized drops were placed on three leaves, and these in 1 hr. 
30 m. were well, and in 2 hrs. 15 m. closely, inflected. 

Isinglass. — Drops of a solution about as thick as milk, and of a still 
thicker solution, were placed on eight leaves, and the tentacles of all 
became inflected. In one case the exterior tentacles were well curved 
in after 6 hrs. 30 m., and the blade of the leaf to a partial extent after 
24 hrs. As saliva acted so efficiently, and yet contains so small a 
proportion of nitrogenous matter, I tried how small a quantity cf 



* Mucus from the air-passages is some albumen, 
said in Marshall, ' Outlines of Physi- t Muller's ' Elements of Physiology,' 

ology,' vol ii. 1867, p. 364-, to contain Eng. Trans, vd. i. p. 514. 

F 2 



68 DEOSEEA EOTUNDIFOLIA. [Ciiai>. T. 

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 the.-iu 
were considerably and two moderately inflected; after 22 hrs. -the 
former were greatly and the latter much more inflected. In the coursu 
of 48 hrs. from the time when the drops were placed on the leaves, all 
four had almost re-expanded. They were then given little biis of 
meat, and these acted more powerfully than the solution. One'part oiT 
isinglass was next dissolved in 437 of water; the fluid thus formed 
was so thin that it could not be distinguished from jxire water. The 
usual-sized drops were placed on seven leaves, each of which thus- 
received -yjo of * grain (-0295 mg.). Three of them were observed for 
41 hrs., but were in no way aifected ; 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 sufficient to affect very 
slightly the more sensitive or active leaves.. On one of the leaves, 
which had not been acted on by the weak solution, and on another, 
which had only two of its tentacles inflected, drops of the solution as 
thick as milk were placed ; and next morning, after an interval of lli 
hrs., both were found with all their tentacles strongly inflected. 

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

Some of the leaves which were not affected by the non- 
nitrogenous fluids were, as above stated, immediately after- 
wards tested with bits of meat, and were thus proved to be 
in an active condition. But in addition to these trials, 
twenty-three of the leaves, with drops of gum, syrup, or 
starch, still lying on their discs, which had produced no effect 



OiiAi-. v.] £1''FECTS OF ORGANIC FLUIDS. 69 

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

The results of » few other experimenta 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 incoagulalsle solution," and this would mingle with 
boiling water. I may mention, in relation to the above and following 
experiments, that according to Schifff certain ibrms of albumen exist 
which are not coagulated by boiling water, but are converted into 
soluble peptones. ■ , 

On three occasions chopped cabbage leaves % were boiled in distilled 
water for 1 hr. or for li hr. ; and by decanting the decoction after it had 
been allowed to rest, a pale dirty green fluid was obtained. The usual- 
sized drops were, placed on thirteen leaves. Their tentacles and blades 
were inflected after 4 hrs. to a quite extraordinary degree. Next day the 
protoplasm, within the cells of the tentacles was found aggregated in 
the most strongly-marked manner. 1 also touched the viscid secretion 
round the' glands of several' tentacles with minute drops of the 
decoction on the head of a small pin, and they became well inflected 
in a few ■ minutes. The fluid proving so powerful, one part was 
diluted with three of water, and drops were placed on the discs of five 
leaves ; and these next morning were so much acted on that their 
blades were completely doubled over. We thus see that a decoction 
of cabbage leaves is nearly or quite as potent as an infusion of raw 
meat. 



• Watts' ' Diet, of Chemistry,' before the heart is formed, such as 

vol. iii. p. 568. were used by me, contain 2-1 per 

t ' Lemons sur la Phys. de la Di- cent, of albuminous matter, and the 

gestion,' torn. i. p. 379; tom. ii. pp. outer leaves of mature plants 1-6 

J Ui, 1G6, on legumin. per cent. Watts' ' Diet, of Chemistry, 

X The leaves of young plants, vol. i. p. 053. 



70 DKOSEKA BOTUNDIFOLIA. [Chap. V 

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

Grasses contain far less nitrogenous matter than do peas or cabbages. 
The leaves and stalks of three .common kinds were chopped and boilec^ 
for some time in distilled water. , Drops of this decoction (after having 
stood for 2i 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. SO.m. four of the 
leaves had their blades greatly inflected, but not their exterior, tentacle j 
and so it was with.all.six, leaves .after ,24 hrs. ■ T.wo^ days afterwards 
the blades, as well as the few submarginal ' tentacles which had heeg 
inflected, all re-expanded ; and much of the fluid on their discs was by this 
time absorbed. It appears' that the (leooction strongly excites^the gland^ 
on the disc, causing the blade to be quickly and greatly inflected ;^but 
that the stimulus, differently frorn whatpccurs in , ordinary .oases, does 
not spread, or only in a feeble degree, to the exteripr.1 tentacles. , , , , 

I may here add that one partoC 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 werei somewhat inflected, and after 
48 hrs. were completely re-expanded. . It .was , not ,the included 
atropine which produced . this ., effect, for, I, subsequently ascertained 
that it is quite powerless. I also procured some extract of liyosdyamus 
from three, shops, and made infusions of the same strength as before. 
Of these three infusions, only one acted oh some of the leaves,' whicli 
were tried. Though.druggists I)elieve_that all the albumen is precipi- 
tated in ,the preparation of these drugs, I cannot doubt th?it some is 
occasionally retained ; and a trace would be 'sufficient to excite the 
more sensitive leaves of Drosera. 



Chap. VI.] DIGESTION. 71 



CHAPTEE VT. 

The Digestive Power op the Secretion op Dkoseea. 

The secretion rendered .icid by the direct and indirect excitement of the 
glands — Nature of the acid — Digestible substances — Albumen, its diges- 
tion arrested by alkalies, recommences by the addition of an acid — Meat 
— Fibrin— Syntonin — Areolar tissue — Cartilage — Fibro-cartilage — Bone 

— Enamel and dentine — Phosphate of lime^Fibrous basis of bone 

Gelatine — Chondrin — Milk, casein and cheese — Gluten — Legumin — Pollen 
— Globulin — Hsematin — Indigestible substances — Epidermic productions 
— Fibro-elastic tissue — Mucin — Pepsin — Urea— Chitine — Cellulose — Gun- 
cotton — Chlorophyll — Fat and oil — Starch — Action of the secretion on 
living seeds— Summary and concluding remarks. 

As we liave seen that nitrogenous fluids act very differ- 
ently on the leaves of Drosera from non-nitrogenous fluids, 
ajid 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, &o., it becomes an interesting 
inquiry,, whether they can only absorb matter already in 
solution, or, render it. soluble,— that is, have the power of 
digestipn. We shall immediately see that they certainly have 
this power, and that they, act on albuminous compounds in 
exactly the same manner as does the gastric juice, of mam- 
mals ; the digested matter. being afterwards absorbed. This 
fact, which :will be clearly proved, is a wonderful one in the 
p.hysiology.i of plants. I must here state that I have been 
aided throughout all my later, experiments by many valuable 
suggestions and assistance given me with the greatest kind- 
npss by Dr. Burdon, Sanderson. 

■ It may be well |;o premise for the sake of any reader who 
knows nothing about the digestion of albuminous compounds 
by animals that this js. eifected by means of a ferment, 
pepsin, together with weak hydrochloric acid, though almost 
any acid wij.1 _ serve. , Yet neither pepsin nor an, acid by 
itself has any such power.* We have seen that when the 

* It appears, however, according a very minute quantity of coagulated 

to Schiff, and contrary to the opinion albumen. SchifF, 'Phys. de la Di- 

of some physiologists, that weak hy- gestion,' 1867, torn. ii. p. 25. 
drochloric dissolves, though slowly. 



72 DEOSEEA KOTUNDIFOLIA. [Cuap. VI. 

glands of the disc are excited by the contact of any object, 
especially of one containing nitrogenous matter, the outer 
tentacles and often the blade become inflected ; the leaf 
being thus converted into a temporary cup or stomach. At 
the same time the discal glands secrete * more copiously, and 
the secretion becomes acid. Moreover, they transmit some 
influence to the glands of the exterior tentacles, causing 
them to pour forth a more copious secretion, which also 
becomes acid or more acid than it was before. 

As this result is an important one, 1 will give the evidence. 
The secretion of many glands on thirty leaves, which had 
not been in any way excited, was tested with litmus paper ; 
and the secretion of twenty-two of these leaves did not in 
the least affect the colour, whereas that of eight caused an 
exceedingly feeble and sometimes doubtful tinge of red. 
Two other old leaves, however, which appeared to have been 
inflected several times, acted much more decidedly on the 
paper. Particles of clean glass were then placed on five of 
the leaves, cubes of albumen on six, and bits of raw meat on 
three, on none of which was the secretion at this time in the 
least acid. After an interval of 24 hrs., when almost all the 
tentacles on these fourteen leaves had become more or less 
inflected, 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 tentacles did hot, from some unknown 
cause, become inflected as often happens ; and in five in- 
stances their secretion was found not to be in the least acid ; 
whilst the secretion of the adjoining and inflected tentacles 
on the same leaf was decidedly acid. With leaves excited by 
particles of glass placed on the central glands, the secretion 
which collects on the disc beneath them was much more 
strongly acid than that poured forth from the exterior 
tentacles, which were as yet only moderately inflected. 
When bits of albumen (and this is nflturally alkaline), or 
bits of meat were placed on the disc, the secretion collected 
beneath them was likewise strongly acid. As raw meat 



* [In the ' Proceedings of the Royal ing secretion, and gives evidence that 

Society,' 1886, No. 240, Gardiner has the secretion results from the break 

described the changes which go on in ing down of the protoplasmic reti- 

the glands of Drosera dichotoma dur- culum of the gland-cell. — F. D.] 



Chap. VI.] DIUE.STIOX. 73 

moistened with water is slightly acid, I compared its action 
on litmus paper before it was placed on the leaves, and 
afterwards when bathed in the secretion ; and there could 
not be the least doubt that the latter was very much more 
acid. I have indeed tried hundreds of times the state of the 
secretion on the discs of leaves which were inflected over 
various objects, and never failed to find it acid. We may, 
therefore, conclude that the secretion from unexcited leaves, 
though extremely viscid, is not acid or only slightly so, but 
that it becomes acid, or much more strongly so, after the 
tentacles have begun to bend over any inorganic or organic 
object ; and still more strongly acid after the tentacles have 
remained for some time closely clasped over any object. 

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

As I was anxious to learn what acid* the secretion contained, 4'^5 
leaves were washed in distilled water, given me by Prof. Frankland; 
but the secretion is so viscid that it is scarcely possible to scrape or 
wash off the wliole. The conditions were also unfavourable, as it was 
late in the year and the leaves were small. Prof. Frankland with 
great kindness undertook to test the fluid thus collected. ' The leaves 
were excited by clean particles of glass placed on them 24 hrs. 
]ireviously. 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 ihe 
fluid was evaporated nearly to dryness, and acidified with sulphuric 
acid ; it then evolved volatile acid vapour, which was condensed and 



* [Messrs Rees and Will (' Bot. the evidence of the smell. Gorup 
Zeitung,' 1875, p. 716) stimulated the and Will have shown that the neutral 
glands of some thousand Drosera secretion of Nepenthes becomes power- 
plants with glass-dust and analysed fully digestive when acidulated with 
the secretion thus produced. They formic acid (see 'Bot. Zeitung,' 1876, 
found a variety of fatty acids present, p. 476). It is therefore interesting 
.nmong which Formic acid was recog- to 6nd this acid naturally present in 
nised 'with certainty, and Propionic the secretion of Drosera.— F.D.] 
and Butyric acids were suspected from 



1 4: DEOSEKA ROTUNDIFOLIA. [Chap. VI.' 

digested witla' carbonate of silver. " The weight bf the silver salt thus 
produced was only • 37 gr., much too small a quantity for the accurate 
determination^ of the molecular weight of the acid. The number, 
obtained, however, corresponded nearly with that of propionic acid ; 
and I believe that this, or a mixture of acetic and butyric acids, were 
present in the liquid. The acid doubtless belongs to the acetic or 
fetty series." 

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

Although it has long been known that pepsin with acetic acid has 
the power of digesting albuminous compounds, it appeared advisable 
to ascertain whether acetic acid could be replaced, without the loss of 
digestive power, by the allied acids which are believed to occur in the - 
secretion of Drosera, namely, propionic, butyric, or valerianic. Dr. 
Burden Sanderson was so kind as to make for me the following ex-, 
periments, the results of which are valuable, independently of the 
present inquiry. Prof. Frankland supplied the acids. 

" 1. The, purpose of the .following experiments was to determine the 
digestive activity of liquids containing ipepsin, 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. , i - 

, "2. It has been determined empirically that the best results, are; 
obtained in artifipia,l digestion. Vi'hen- a liquid' containing two per' 
thousand of .hydrochloric' acid gas by weight is used. , This- cone-' 
spends to. about 6 •,25, cubic centimetres per litre of ordinary strong 
hydrochloric acid. The quantities of propionic, butyric, and valerianic: 
acids respectively which are required to neutralise as much base as 6 .' 25 ■ 
cubic centimetres (?f HCl, are in grammes 4 '04 of propibnio acid, -.4 ■82, 
of butyric acid, and 5',68 of valerianic acid. It' was therefore judged! 
expedient, in coinpa,ring 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' ^lyeerih'e 'extra;ct of 'the taucous deinbrane of 'the sfoinachV , 
a dog killed during digestion haviftg been prepared, 10 cub. cent, 'of if 
were evaporated and' dried 'at 110°. This qualntit^r yielded O"0O31 of' 
rfesiduei. ■> ■ ; i ■ > . ','.., 

■ "4. Of this liquid 'four quantities were taken which were severally,, 
acidulated with hydroctloric, propionic, butyric, and valerianic, acids,, 
in the proportions above indicated,. Each liquid was then placed iu a- 
tube, 'Tvhich was allowed to float in a water bath, containing a ther-. 



Chap. VI.] DIGESTION. 76 

mometer which indicated a temperature of 38° to 40° Cent. Into 
each, a quantity of unboiled fibrin was introduced, and the whole, 
allowed to stand for four hours, the temperature being maintained 
during the whole time, and care being taken that each contained 
throughout an excess of fibrin. At the end of the period each hquid 
was filtered.' Of the filtrate, which of course contained as much of the 
fibrin as had been digested during the four hours, 10 cub. cent, were 
nieasured out and evaporated, and dried at 110° as before. The lesidues 
were respectively — 

" In the liquid containing hydrochloric acid 0*4079 
„ „ propionic acid 0*0601 

„ „ butyric acid 0'1488 

„ „ valerianic acid 0"1254 

"Hence, deducting from each of these the above-mentioned residue, 
left when the digestive, liquid jtself was evaporated, viz. O'OOSl, 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 quaiititios of the respective acids under identical conditions.' 

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

" S. In a seciond 'experinient in which the procedure was in' eVei y 
respect the same, excepting that all the tubes, were plunged into.tjie 
same water-balh, and'. the residues dried'at'115° 0'., the rcisiilts were as 
follows: — ■ ■ ' 

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

" Propionic, acid ' „ .. .. 0"0563 

Btiiyric'aoid ' .. .. .. 0-0835 

Valerianic acid".; .. .. 0"0615 

" The quantity digested by a similar liquid containing hydrochloric 
.icid'was '0-3376.i-.Hehce,-talring. this as lOO, the following itumhers 
represent the relative quantities digested. by .the other acids:. 

" Propionic acid .. .. ., 16,5 

Butyric acid .. .1 .;. 24 '7 

Valerianic acid ... . . . . 16 ' 1 

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



"■6 DROSEEA EOXUNDIFOLIA. [Chap. VI. 

" Quantity of fibrin digested in four hours by 10 cub. 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 v/ith the first taken 
as 100, the digestive power of propionic acid is represented 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 efficacious) was relatively greater at ordinary 
temperatures than at the temperature of the body. . It was found that 
whereas 10 cub. cent, of a liquid containing the ordinary proportion of 
Ijydrochloric acid digested 0-1311 gramme, a similar liquid prepared 
with butyric acid digested 0-0455 gramme of fibrin. , . 

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

We here see that at the lower of these two temperatures, hydro- , 
chloric acid with pepsin digests, within the same time, rather less than' 
half the quantity of fibrin compared with what it digests at the 
higher temperature : and the power of butyric acid is reduced in the 
same proportion imder similar conditions and temperatures.- We have 
also seen that butyric acid, which is niuch more, efficacious than 
propionic or valerianic acids, digests with pepsin at the higher tem- 
perature less than a third of the fibrin which is digested at the same 
temperature by hydrochloric acid. 

I will now give in detail my experiments on. the digestive 
power of the secretion of Drosera, dividing the substances 
tried into two series, namely those which are (^igested 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 iinder the 



Chap. VI.] DIGESTION. 77 

head albumen, showing that the secretion loses its power 
when neutralised by an alkali, and recovers it when an acid 
is added. 

Substances which are completely or partially Digested by the 
Secretion of Drosera. 

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

Experiment 1. — Bather large cubes of albumen were first tried; 
the tentacles wore well inflected in 24 hrs ; after an additional day the 
angles of the cubes were dissolved and rounded ;* but the cubes were 
too large, so that the leaves were injured, and after seven days one 
died and the others were dying. Albumen which has been kept for 
four or five days, and which, it may be presumed, has begun to decay 
slightly, seems to act more quickly than freshly boiled eggs. As the 
.latter were generally used, I often moistened them with a little saliva,, 
to make the tentacles close more quickly. 

Experiment 2. — A cube of -^ of an inch {i.e. with each side ^ 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 J^ of an inch (1'905 mm.) Id 
diameter, surrounded by perfectly transparent fiuid. After ten days 



* In all my numerous experi- characteristic of the digestion of 

ments on the digestion of cubes of albumen by the gastric juice of 

albumen, the angles and edges were animals. On the other hand, he 

invariably first rounded. Now, Schiff remarks, " les dissolutions, en chimie, 

states (' Leijons Phys. de la Digestion,' ont lieu sur tmte la surface des corps- 

1867, tom. ii. p. 149) that this is en contact aveo I'agent dissolvant." 



78 DEOSEEA EOTUNDIFOLIA. [Chap. VI. 

theleaf re-exparided, but there wa^ still left on the disc a minute bit 
, of albumen now iiendered. transparent. Mora albumen had been given 
to this leaf than could be dissolved or digested. 

Experiment 3. — Two cubes of albumen of ^ of an inch (1 • 27 mm.) 
were placed on two leaves. After 46 hrs. every atqm of one was dis- 
solved, arid most of the liquefied matter was a;bSorbed, 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. 

'Experiinent 4. — Two cubes of albumen of the same size as the last 
were placed' on two leaves, and were converted in 50 hrs. into two 
large drops of transparent fluid ; but when these were removed from 
beneath the inflected tentacles, and viewed by reflected light under the 
microscope, fine streaks of white opaque matter could be seen in the 
one, and traces of Similar streaks' in the other. The drops were 
replaced on the leaves, which re-expanded after' 10 days ; and now 
nothing was left except a very little transparent acid fluid. 

Experiment 5. — This experiment was ■ slightly varied, so that the 
albumen might, be more quickly exposed. to the action of the secretion. 
Two cubes, each of about ^ of an inch ( • 635 mm.) were placed on 
. the same leaf,- and two similar cubes on another leaf. ■ These were 
examined after, 21 hrs. 30 m., and aU four were found rounded. After 
46 hrs. the two cubes on the one leaf were completely liquefied, the 
fluid' being perfectly tiansparent ; on the other leaf Some opaque white 
streaks ■ coidd 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 flrst leaf.. Both 
leaves were now beginning to re-expand. 

The test and almost sole test of tlae presence of some 
ferment analogous to pepsin in tlie secretion appeared to be 
to neutralise the acid of the secretion with an alkali, and to 
observe whether the process of digestion ceased ; and then to 
add a little acid and observe whether the process recom- 
menced. This v?as 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 
t-top the process of digestion ; and, secondly, whether minute 
drops of weak hydrochloric acid, of the same strength and 
size as those to be used, would injure the leaves. The two 
following experiments were therefore tried : — 

Experiment 6. — Small cubes of albumen were put on three leaves, 
and minute drops of distilled water on the head of a pin were added 
two or three times daily. These did not in the least delay the process ; 



Chap. VI.] DIGESTION. 79 

for, after 48 hrs., the cubes were completely dissolved on all three 
leaves. On the third day the leaves began to ro-expand, and on the 
fourth day all the fluid was absorbed." 

. Experiment 7. — Small cubes of albumen were put on two leaves, 
and minute drops of hydrochloric acid, of the strength of one part to 
437 of water, were added two oi: three times. This did not in the 
least delay, but seemed rather to hasten, the process of digestion ; 
for every trace of the albumen disappeared in 24 hrs. 30 m. After 
three days the leaves partially re-expanded, and by this time almost 
all the viscid fluid on their discs was absorbed. It is almost super- 
' fluous to state that cubes of albumen of the same size as those above 
used, left for seven days la a little hydrochloric acid of the above 
streiigth, retained all their angles as jierfect as ever. 

Experiment 8.^-Cubes of albumen (of -jV of- an inch, .or 1'27 mm.) 
werciplaced on^five leaves, and minute drops of a solution of one part 
of carbonate of soda to 437 of water were added at intervals to three 
.of them, and drops of carbonate of potashj of the same strength to the 
other two. The drops were given on the head of a rather large pin, 
and I ascertained that each was equal to about Jj of a minim (-0059 
c.f.), so that, each .contained only -j^W f^ ^ g™"! ('OlSd-mg.) of the 
'alkali. This was not sufficient, for after 46 hrs. all five cubes were 
■ dissolved. 

Experiment 9. — The last experiment was repeated on four leaves, 
with this difference, that • drops ■ of the same solution of carbonate of 
soda were added rather oftener, as often as the secretion became acid, 
.so that it was much. more effectually neutralised. And now after 24 
hrs. the angles of three of the cubes were not in the least rounded, 
those of the fourth being so in a very, slight degree. Drops of 
extremely weak hydrochloric acid (viz. one part to 847 of water) were 
' then added, just enough to ileutralise the alkali which was still present ; 
and now digestion immediately recommenced, so . that after 23 hrs. 
30 m. three of the cubes were completely dissolved, whilst the fourth 
was converted into a minute sphere, surrounded by transparent fluid'; 
and this sphere next day disappeared. 

Experiment 10. — Stronger solutions of carbonate of soda and of 
potash were next used, viz. one part to 109 of water ; and as the same- 
sized drops were given as before, each drop contained rsVo °f ^ grain 
(•0539 mg.) of either salt. Two cubes of albumen (each about -^ of 
an inch, or • 635 mm.) were placed on the same leaf, and two on another. 
Bach leaf received, as soon as the secretion became slightly acid (and 
this occurred four times within 24 hrs.), drops either of the soda or 
potash, and the acid was thus effectually neutralised. 1'he experiment 
now succeeded perfectly, for after 22 hrs. the angles of the cubes were 
as sharp as they were at first, and we know from experiment o that 
such small cubes would have been completely rounded within this time 
by the secretion in its natural state. Some of the fluid was now 
removed with blotting-paper from the discs of the leaves, and minute 
drops of hydrochloric acid of the strength of one part to 200 of water 



80 DEOSERA KOTUNDIFOLIA. [Ciiap. VI. 

■was added. Aciil of this greater strength was used as the solutions 
of the alkalies were stronger. The process of digestion now com- 
menced, so that within 48 hrs. from the time when the acid was given 
the four cubes were not only completely dissolved, but much of the 
liquefied albumen was absorbed. 

Experiment 11. — 'fwo cubes of albumen (Jg of an inch, or • 635 mm.) 
were placed on two leaves, and were treated with alkalies as in the last 
experiment, and with the same result ; for after 22 hrs. they had their 
angles perfectly sharp, showing that the digestive process had been 
completely arrested. I then wished to ascertain what would be the 
effect of using stronger hydrochloric acid ; so I added minute drops of 
the strength of 1 per cent. This proved rather too strong, for after 48 
hrs. from the time when the acid was added one cube was still alnlost 
perfect, and the other only very slightly rounded, and both wero 
stained slightly pink. This latter fact shows that the leaves were 
injured,* for during the normal process of digestion the albumen is 
not thus coloured, and we can thus understand why the cubes were 
not dissolved. 

From these experiments we clearly see that the secretion 
has the power of dissolving albumen, and we further see 
that if an alkali is added, the process of digestion is stopped, 
but immediately recommences as soon as the alkali is 
neutralised by weak hydrochloric acid. Even if I had tried 
no other experiments than these, they would have almost 
sufficed to prove that the glands of Drosera secrete some 
ferment analogous to pepsin, which in presence of an acid 
gives to the secretion its power of dissolving albuminous 
compounds. 

Splinters of clean glass were scattered on a large number 
of leaves, and these became moderately inflected. They 
were cut off and divided into three lots ; two of them, after 
being left for some time in a little distilled water, were 
strained, and some discoloured, viscid, slightly acid fluid was 
thus obtained. The third lot was well soaked in a few drops 
of glycerine, which is well known to dissolve pepsin. Cubes 
of albumen (^ 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 



* Sachs remarks (' Traite de Bot.' or by chemical agents, allow all their 
1874, p. 774), that cells which are colouring matter to escape into the 
killed by freezing, by too great heat, surrounding water. 



Chap. VI.] 



DIGESTION. 



81 



dissolved, tile aagles remaining as sharp as ever. This fact 
probably indicates that the ferment is not secreted until the 
glands are excited by the absorption of a minute quantity of 
already soluble animal matter, — a conclusion which is sup- 
ported by what we shall hereafter see with respect to Dionssa. 
Dr. Hooker likewise found that, although the fluid within 
the pitchers of Nepenthes possesses extraordinary power of 
•digestion, yet when removed from the pitchers before they 
have been excited and placed in a vessel, it has no such 
power, although it is already acid ; and we can account for 
this fact only on the supposition that the proper ferment is 
not secreted until some exciting matter is absorbed.* 



* [With regard to Drosera Messrs. 
Rees and Will (' Bot. Zeitung,' 1875, 
ji. 715) state that a glycerine extract 
of Drosera leaves in a state of unex- 
cited secretion, and fairly free from 
insects, had no digestive action. But 
that the same extract, artificially acid- 
ulated, digested fibrin thoroughly 
well. 

The authors believe that the natu- 
lal acid of the glands was possibly 
destroyed in the process of preparing 
the extract. No conclusion can there- 
fore be drawn from their results as 
to the acidity of unexcited leaves. It 
is probable, however, judging from 
VonGorup'sworkon Nepenthes, that 
Drosera does not secrete the requisite 
«mount of acid until it has been 
stimulated by the capture of insects. 
Rees and Will's experiments are not 
quite conclusive on this point, but 
they tend to show that what is want- 
ingin the secretion of unexcitedleaves 
is the acid, not the ferment. The ex- 
periments of Von Gorup and Will on 
Nepenthes, as given in the ' Bot. Zei- 
tung,' 1876, p. 473, do not confirm 
Hooker's results on Nepenthes. The 
authors state that the secretion col- 
lected from pitchers which are free 
from insects is neutrdly while the 
Huid of pitchers which contain the 
remains of insects is distinctly acid. 
The neutral secretion of the xinexcited 
pitchers has no digestive power until 



it is acidulated, when it rapidly dis- 
solves fibrin. 

It seems, therefore, tliat the analogy 
with animal digestion pointed out at 
p. 106 does not altogether hold good. 
For SchifF states that in the gastric 
juice produced by mechanical irrita- 
tion, the element absent is the fer- 
ment, not the acid. 

On the other hand an interesting 
point of resemblance of a different 
kind has been made out by Vines in 
his paper on the digestive ferment of 
Nepenthes (' Journal of the Linn. 
Soc' vol. XV. p. 427 ; also ' Journal of 
Anatomy and Physiology,' series ii. 
vol. xi. p. 124). 

The work was undertaken inde- 
pendently of Von Gorup and carried 
out by a . different method, namely 
the preparation of a glycerine extract. 
Vines having found that the extract 
was far less active than the natural 
secretion used by Von Gorup, was 
led to an interesting explanation of 
this fact by Ebstein and Griitzner's 
work on animal digestion. These 
writers show that the glycerine ex- 
tract gains in digestive activity if it 
is prepared from mucous membrane 
previously treated with acid. Vines 
accordingly treated Nepenthes with 
one per cent acetic acid for 24 hrs. 
previously to the preparation of the 
extract, and thus obtained glycerine 
of much greater peptic activity. This 
G 



82 DEOSEEA KOTUNDIFOLIA. [Chap. VI'. 

On three other occasions eight leaves were strongly ex- 
cited with albumen moistened with saliva ; they were then 
CTit off, and allowed to soak for several hours or for a whole 
.day in a few drops of glycerine. Some of this extract was 
added to a little hydrochloric acid of various strengths 
(generally one to 400 of water), and minute cubes of albumen 
were placed ia the mixture.* In two of these trials the 
cubes were not in the least acted on ; but in the third the 
experiment was successful. .For in a vessel containing two 
cubes, both were reduced in size in 3 hrs ; and after 24 hrs. 
mere streaks of undissolved albumen were left. In a second 
vessel, containing two minute ragged bits of albumen, both 
were likewise reduced in size in 3 hrs. and after 24 hrs. com- 
pletely disappeared. I then added a little weak hydro- 
chloric acid to both vessels, and placed fresh cubes of 
albumen in them ; but these were not acted on. This latter 
fact is intelligible according to the high authority of Schiff,| 
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 -^jj of an inch 
(1 • 27 mm.) of moderately roasted meat were placed on five 
leaves which became in 12 hrs. closely inflected. After 48 
hrs. I gently opened one leaf, and the meat now consisted of 
a minute central sphere, partially digested and surrounded 
by a thick envelope of transparent viscid fluid. The whole, 



fact would lead us to believe that the * As a control experiment bits of 

act of secretion in Nepenthes is pre- albumen were placed in the same 

ceded by- the production of a mother glycerine with hydrochloric acid ol' 

substance, or pepsinogen, from which the same strength ; and the albumen, 

the peptic ferment is formed by ac- as might have been expected, was 

tion of acid — just as the pancreatic not in the least affected after two 

ferment may, according to Heidenhain, .days. 

be produced by the action of acid on t 'Le9ons phys;' de la Digestion,' 

zymogen— F. D.] , 1867, torn. ii. pp. 114-126. - 



Chap. VI.] DIGESTION. 83 

witliout being much disturbed, was removed and placed 
Tinder the microscope. In the central part the transverse 
striae on the mnscular fibres were quite distinct ; and it was 
interesting to observe how gradually they disappeared, when 
the same fibre was traced into the surrounding fluid. They 
disappeared by the strias being replaced by transverse lines 
formed of excessively minute dark points, which towards the 
exterior could bo seen only under a very high power; and 
ultimately these points were lost. When I made these 
observations, I had not read Schiff's account* of the digestion 
of meat by gastric juice, and I did not understand the 
meaning of the dark points. But this is explained in the 
following statement, and we further see how closely similar 
is the process of digestion by gastric juice and by the 
secretion of Drosera. 

" On a dit que le sue gastrique faisait perdre b, la fibre musculaire 
ses stries transvevsales. Ainsi enonoe'e, cette proposition pourrait 
donner lieu i uue Equivoque, car ce qui se perd, co n'est que I'aspect 
ext&ieur de la striature et non les elements anatomiques qui la com- 
posent. On salt que les stries qui donnent un aspect si caract&istique 
u la fibre musculaire, sont le r&ultat de la juxtaposition et du 
parall^lisme dea corpuscules 61ementaires, places, k distances egales, dans 
I'intdrieur des fibrilles contigues. Or, des que le tissu connectif qui 
relie entre elles les fibrilles dldmentaires vient a se gonfler et 3, se 
dissoudre, et que les fibrilles elles-memes se dissocient, ce parallelisme 
est d^truit et aveo ' lui I'aspect, le pbdnorafine optique des stries. Si, 
aprSs la d&agrdgation des fibres, on examine au microscope les fibrilles 
^Wmentaires, on distingue encore trSs-nettement a leur intdrieur les 
corpusoules, et on continue £l les voir, de plus en plus pMes, jusqu'au 
moment ou les fibrilles elles-memes se liqu^fient et disparaissent dans 
le sue gastrique. Ce qui constitue la striature, i. proprement parler,. 
n'est done pas detruit, avant la liquefaction de la fibre cbarnue elle- 



In the viscid fluid surrounding the central sphere of 
undigested meat there were globules of fat and little bits 
of fibro-elastic tissue ; neither of which were in the least 
digested. There were also little free parallelograms of 
yellowish, highly translucent matter. Schifif, in speaking of 
the digestion of meat by gastric juice, alludes to such 
parallelograms, and says : — 



* 'Le9ons phys. de la Digestion,' 1867, torn. ii. p. 145. 

G 2 



84 DROSERA ROXUNDIFOLIA. [Chap. VI. 

" Le gonfiement par lequel commence la digestion de la viande, 
resulte de Taction du sue gastrique aoide sur le tissu conaeotif qui su 
dissout d'abord, et qui, par sa liquefaction, desagrege les fibrilles. 
Celles-ci'se dissolvent ensuite en grande partie, mais, avant de passer 
^ r^tat liquide, elles tendent k se briser en petits fragments transyer- 
saux. Les ' sarcous elements ' de Bowman, qui ne sont autre cbose que 
les produits de cette division transversale des fibrilles el^mentaires, 
peuvent §tre prepares et isoles a I'aide du sue gastrique, pourvu qu'oa 
n'attend pas jusqu'^ 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 
distinguished, 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 transparent 
fluid. 

Fibrin. — Bits of fibrin were left in water during four days, 
whilst the following experiments were tried, but they were 
not in the least acted on. The fibrin which I first used was 
not pure, and included dark particles : it had either not been 
well prepared or had subsequently undergone some change. 
Thin portions, about -^ of an inch square, were placed on 
several leaves, and though the fibrin was soon liquefied, the 
whole was never dissolved. Smaller particles were then 
placed on four leaves, and minute drops of hydrochloric acid 
(one part to 437 of water) were added ; this seemed to hasten 
the process of digestion, for on one leaf all was liquefied and 
absorbed after 20 hrs. ,- but on the three other leaves some 
undissolved residue was left after 48 hrs. It is remarkable 
that in all the above and following experiments, as well as 
when much larger bits of fibrin were used, the leaves were 
very little excited ; and it was sometimes necessary to add 
a little saliva to induce complete inflection. The leaves, 
moreover, began to re-expand after only 48 hrs., whereas 
they would have remained inflected for a much longer time 
had insects, meat, cartilage, albumen, &c., been placed on 
them. 

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



Chap. VI.] DIGESTION. 85 

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

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

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

Experiment 4. — Similar bits of fibrin were placed on the discs of 
two leaves ; as after 2 hrs. the glands seemed rather dry, they were 
freely moistened with saliva ; this soon caused strong infleotioa both 
of the tentacles and blade.s, with copious secretion from the glands. 
In 18 hrs. the fibrin was completely liquefied, but undigested atoms 
still floated in the liquid ; these, however, disappeared in under two 
additional days. 

Prom these experiments it' is clear that the secretion 
completely dissolves pure fibrin. The rate of dissolution 
is rather slow; hut this depends merely on this substance 
not exciting the leaves suflSciently, so that only the 
immediately adjoining tentacles are inflected, and the 
supply of secretion is small. 

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

Areolar Tissue. — Small portions of this tissue from a sheep 
were placed on the discs of three leaves ; these became 



* [These results cannot be considered trustworthy; it .ippeavs that the 
syntonin prepared by the late Dr. Moore was far from pure. — V. D.] 



86 DEOSERA EOTUNDIFOLIA. [CHAr. VI, 

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

Some areolar tissue free from elastic tissue was next 
procured from the visceral cavity of a toad, and moderately 
sized, as well as very small, bits were placed on five leaves. 
After 24 hrs. two of the bits were completely liquefied ; two 
others were rendered transparent, but not quite liquefied ; 
whilst the fifth was but little affected. Several glands on the 
three latter leaves were now moistened with a little saliva, 
which soon caused much inflection and secretion, with the 
result that in the course of 12 additional hrs. one leaf alone 
showed a remnant of undigested tissue. On the discs of the 
four other leaves (to one of which a rather large bit had 
been given) nothing was left except some transparent viscid 
fluid. I may add that some of this tissue included points of 
black pigment, atid these were not at all afiected. 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 Q^ of an inch or 1*27 mm.) of 
white, translucent, extremely tough cartilage were cut from 
the end of a slightly roasted leg-bone of a sheep. These 
were placed on three leaves, borne by poor, small plants in 
my greenhouse during November ; and it seemed in the 
highest degree improbable that so hard a substance would be 
digested under such unfavourable circumstances. Neverthe- 
less, after 48 hrs., the cubes were largely dissolved and 
converted into minute spheres, surrounded by transparent, 
very acid fluid. Two of these spheres were completely 
softened to their centres ; whilst the third still contained a 
very small irregularly shaped core of solid cartilage. Their 
surfaces were seen under the microscope to be curiously 
marked by prominent ridges, showing that the cartilage had 
been unequally corroded by the secretion. I need hardly say 



CiiAP. \1.2 DIGESTION. 87 

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

During a more favourable season, moderately sized bits of 
the skinned ear of a cat, which includes cartilage, areolar 
and elastic tissue, were placed on three loaves. Some of the 
glands were touched with saliva, which caused prompt in- 
flection. Two of the leaves began to re-expand after three 
days, and the third on the fifth day. The fluid residue left on 
their discs was now examined, and consisted in one case of 
perfectly transparent, viscid matter ; in the other two cases, 
it contained some elastic tissue and apparently remnants of 
half digested areolar tissue. 

Fibro-Cartilage (from between the vertebras of the tail of a 
sheep). Moderately sized and small bits (the latter about 
-}^ of an inch) were placed on nine leaves. Some of these 
were well and some very little inflected. In the latter case 
the bits were dragged over the discs, so that they were well 
bedaubed with the secretion, and many glands thus irritated. 
All the leaves re-expanded after only two days ; so that they 
wei-e but little excited by this substance. Tlie bits were not 
liquefied, but were certainly in an altered condition, being 
swollen, much more transparent, and so tender as to disin- 
tegrate very easily. My son Francis prepared some artificial 
gastric juice, which was proved efficient by quickly dis- 
solving fibrin, and suspended portions of the fibro-cartilage 
in it. These swelled and became hyaline, exactly like those 
exposed to the sectetion of Drosera, but were not dissolved. 
This result surprised me nmch, as two physiologists were of 
opinion that fibro-cartilage would be easily digested by 
gastric juice. I therefore asked Dr. Klein to examine the 
specimens ; and he reports that the two which had been 
subjected to artificial gastric juice were " in that state of 
digestion in which we find connective tissue when treated 
with an acid, viz. swollen, more or less hyaline, the fibrillar 
bundles having become homogeneous and lost their fibrillar 
structure." In the specimens which had been left on the 
leaves of Drosera, tmtil they re-expanded, "parts were 
altered, though only slightly so, in the same manner as those 
subjected to the gastric juice, as they had become more 
transparent, almost hyaline, with the fibrillation of the 
bundles indistinct." Fibro-cartilage is therefore acted on in 
nearly the same manner by gastric juice and by the secretion 
of Drosera. 



88 DEOSEEA EOTUNDIFOLIA. [Chap. VI. 

Bone.- — Small smooth bits of the dried hyoidal bone of a 
fowl moistened 'with saliva were placed on two leaves, and a 
similarly moistened splinter of an extremely hard, broiled 
mntton-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 aU the time by acid 
secretion. When examined under a weak power, they were 
found quite softened, so that they were readily penetrated by 
a blunt needle, torn into fibres, or compressed. Dr. Klein 
was so kind as to make sections of both bones and examine 
them. He informs me that both presented the normal 
appearance of decalcified bone, with traces of the earthy 
salts occasionally left. The corpuscles with their processes 
were very distinct in most parts ; but in some parts, 
especially near the periphery of the hyoidal bone, none could 
be seen. Other parts again appeared amorphous, with even 
the longitudinal striation of bone not distinguishable. This 
amorphous structure, as Dr. Klein thinks, may be the result 
either of the incipient digestion of the fibrous basis or of all 
the earthy matter having been removed, the corpuscles being 
thus rendered invisible. A hard, brittle, yellowish substance 
occupied the position of the medulla in the fragments of the 
hyoidal bone. 

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

Enamel and Dentine. — As the secretion decalcified ordinary 



Chap. VI.] DIGESTION. 89 

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

Experiment 1. — May 1st, fragment placed on leaf ; 3rd, tentacles 
but little inflected, so a little saliva was added ; Cth, 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 loaf; 2nd, tentacles 
fairly well inflected, with much secretion on the disc, and remained so 
until the 7th, when the leaf re-expanded. The iragment 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 ve-expanded. 
The enamel was not at all, and the dentine only slightly, softened. 
The fragment was now transferred to a fresh leaf, which next mornint;; 
(6th) was strongly inflected, and remained so until the 11th. The 
enamel and dentine both now somewhat softened ; and Dr. Klein 
reports, " less than half the enamel, but the greater part of the dentine 
decalcified." 

Experiment 4. — May 1st, a minute and thin bit of dentine, mois- 
tened with saliva, was placed on a leaf, which was soon inflected, and 
re-expanded on the 5th. The dentine had become as flexible as thin 
paper. It was then transferred to a fresh leaf, which next morning 
(6th) was strongly inflected, and reopened on the lOib. The decalci- 
fied dentine was now so tender that it was torn into shreds merely by 
the force of the re-expanding tentacles. 

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



90 DKOSEEA EOTUNDIFOLIA. [Chap. VI. 

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

Fibrous Basis of Bone. — I at first concluded, as already 
stated, that the secretion could not digest this substance. I 
therefore asked Dr. 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 lamellee, into which part of 
the skull of a cat became broken up after about a week's im- 
mersion in the fluid, and he found that towards the edges the 
" matrix appeared rarified, thus producing the appearance as 
if the canaliculi of the bone-corpuscles had become largeri 
Otherwise the corpuscles and their canaliculi were very 
distinct." So that with bone subjected to artificial gastric 
juice complete decalcification precedes the dissolution of the 
fibrous basis. Dr. 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 con- 
sumed in the decomposition of the earthy salts, so that there 
was none left for the work of digestion. Accordingly, my 
son thoroughly decalcified the bone of a sheep with weak 
hydrochloric acid; and seven minute fragments of the fibrous 
basis were placed on so many leaves, four of the fragments 
being first damped with saliva to aid prompt inflection. All 
seven leaves became inflected, but only 'very moderately, in 
the course of a day. They quickly began to re-expand ; five 
of them on the second daj', and the other two on the third 
day. On all seven leaves the fibrous tissue was converted 
into perfectly transparent, viscid, more or less liquefied little 
masses. In the middle, however, of one, my son saw under 
a high power a few corpuscles, with traces of fibrillation in 
the surrounding. transparent matter. From these facts it is 
clear that the leaves are very little excited by the fibrous 
basis of bone, but that the secretion easily and quickly 
liquefies, it, if thoroughly decalcified. The glands which 
had remained in contact for two or three days with the 
viscid masses were not discoloured, and apparently had, 



Chap. VI.] DIGESTION. 91 

absorbed little of the liquefied tissue, or bad been little 
affected by it. 

Phospliate of Lime. — As we have seen that tbe tentacles of 
the first set of leaves remained clasped for nine or ten days 
over minute fragments of bone, and the tentacles of the 
second set for six or seven days over the same fragments, I 
was led to suppose that it was the phosphate of lime, and 
not any included animal matter, which caused such long- 
continued inflection. It is at least certain from what has 
just been shown that this cannot have been due to the 
presence of the fibrous basis. With enamel and dentine (the 
former of which contains only 4 per cent, of organic matter) 
the tentacles of two successive sets of leaves remained inflected 
altogether for eleven days. In order to test my belief in the 
potency of phosphate of lime, I procured some from Prof. 
Frankland absolutely free of animal matter and of any 
acid. A small quantity moistened with -water was placed on 
the discs of two leaves. One of these was only slightly 
affected; the other remained closely inflected for ten days, 
when a few of the tentacles began to re-expand, the rest 
being much injured or killed. I repeated the experiment, 
but moistened the phosphate with saliva to insure prompt 
inflection ; one leaf remained inflected for six days (the little 
saliva used would not have acted for nearly so long a time) 
and then died ; the other leaf tried to re-expand on the sixth 
day, but after nine days failed to do so, and likewise died. 
Although the quantity of phosphate given to the above four 
leaves was extremely small, much was left in every case 
undissolved. A larger quantity wetted with water was next 
placed on the disc of three leaves ; and these became most 
strongly inflected in the course of 24 hrs. They never re- 
expanded ; on the fourth day they looked sickly, and on the 
sixth were almost dead. Large drops of not very viscid fluid 
hung from their edges during the six days. This fluid was 
tested each day with litmus paper, but never coloured it; 
and this circumstance I do not understand, as the super- 
phosphate of lime is acid. I suppose that some superphos- 
phate must have been formed by the acid of the secre- 
tion acting on the phosphate, but that it was all absorbed 
and injured the leaves; the large drops which hung from 
their edges being an abnormal and dropsical secretion. 
Anyhow, it is manifest that the phosphate of lime is a most 
powerful stimulant. Even small doses are more or less 



92 DEOSEHA EOTUNDIFOLIA.' [Chap. VI. 

poisonous, protably on tlie same principle that raw meat and 
other nutritious substances, given in excess, kill tlie leaves. 
Hence the conclusion, that the long-continued inflection of 
the tentacles over fragments of bone, enamel and dentine, is 
caused by the presence of phosphate of lime, and not of any 
included animal matter, is no doubt correct. 

Gelatine. — I used pure gelatine in thin sheets given me by 
Prof. Hoffmann. For comparison, squares of the same size as 
those placed on the leaves were left close by on wet moss. 
These soon swelled, but retained their angles for three days ; 
after five days they formed rounded, softened masses, but 
even on the eighth day a trace of gelatine could still he 
detected. Other squares were immersed in water, and these, 
though much swollen, retained their angles for six days. 
Squares of -jij^ of an inch (2 • 54 mm.), just moistened with 
water, were placed on two leaves ; and after two or three 
days nothing was left on them but some acid viscid fluid, 
which in this and other cases never showed any tendency to 
regelatinise ; so that the secretion must act on the gelatine 
difierently to what water does, and apparently in the same 
manner as gastric juice.* Pour 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 ipflected, showing how 
much more potent than gelatine is the animal matter ab- 
sorbed from an insect. Some larger pieces of gelatine, soaked 
for five days in water, were next placed on three leaves, 
but these did not become much inflected until the third day, 
nor was the gelatine completely liquefied until the fourth day. 
On this day one leaf began to re-expand ; the second on the 
fifth; and third on the sixth. These several facts prove 
that gelatine is far from acting energetically on Drosera. 

In the 'last chapter it was shown that a solution of isin- 
glass of commerce, as thick as milk or cream, induces strong 
inflection, I therefore wished to compare its action with that 
of pure gelatine. Solutions of one part of both substances 



* Dr. Lander Brunton, 'Handbook for the Phys. Laboratory,' 1873, pp. 
477, 487 ; Sohiff, ' Le9oiis phys. de la Digestion,' 1867, torn. ii. p. 249. 



CuAP. VI.] DIGESTION. 93 

to 218 of water were made ; and half-minim drops ( • 0296 c.c.) 
were placed on tlie discs of eight leaves, so that each received 
jjI^^ of a grain, or -135 mg. The four with the isinglass 
were much more strongly inflected than the other four. 1 
conclude, therefore, that isinglass contains some, though per- 
haps very little, soluble albuminous matter. As soon as these 
eight leaves re-expanded, they were given bits of roast meat, 
and in some hours all became greatly inflected ; again showing 
how much more meat excites Drosera than does gelatine or 
isinglass. This is an interesting fact, as it is well known 
that gelatine by itself has little power of nourishing animals. 

Chondrin. — This was sent me by Dr. Moore in a gelatinous 
state. Some was slowly dried, and a small chip was placed 
on a leaf, and a much larger chip on a second leaf. The first 
was liquefied in a day ; the larger piece was much swollen 
and softened, but was not completely liquefied until the 
third day. The undried jelly was next tried, and as a 
control experiment small cubes were left in water for four 
days and retained their angles. Cubes of the same size were 
placed on two leaves, and larger cubes on two other leaves. 
The tentacles and laminae of the latter were closely inflected 
after 22 hrs. but those of the two leaves with the smaller 
cubes only to a moderate degree. The jelly on all four was 
by this time liquefied, and rendered very acid. The glands 
were blackened from the aggregation of their protoplasmic 
contents. In 46 hrs. from the time when the jelly was given, 
the leaves had almost re-expanded, and completely so after 
70 hrs. ; and now only a little slightly adhesive fluid was 
left unabsorbed on their discs. 

One part of chondrin jelly was dissolved in 218 parts of 
boiling water, and half-minim drops were given to four 
leaves ; so that each received about ^-^^ of a grain (• 135 mg.) 
of the jelly ; and, of course, much less of dry chondrin. 
This acted most powerfully, for after only 3 hrs. 30 m. all 
four leaves were strongly inflected. Three of them began to 
re- expand after 24 hrs., and in 48 hrs. were completely open ; 
but the fourth had only partially re-expanded. All the 
liquefied chondrin was by this time absorbed. Hence a 
solution of chondrin seems to act far more quickly and ener- 



* Dr. Lauder Brunton gives in the indirect pai-t which gelatine plays in 
'Medical Record,' January 1873, p. nutrition, i 
36, an account of Viot's view of the 



94 DEOSEEA EOTUNDIFOLIA. [CHAr. VI. 

getically than pure gelatine or isinglass ; but I am assured 
by good authorities that it is most difficult,' or impossible, to 
know whether chondrin is pure, and if it contained any albu- 
minous compound, this would have produced the above effects. 
Nevertheless, I have thought these facts worth giving, as there 
is so much doubt on the nutritious value of gelatine ; and Dr. 
Lauder Brunton does not know of any experiments with re- 
spect to animals on the relative value of gelatine and chrondrin. 
Milk:- — -We have seen in the last chapter that milk acts 
anost powerfully on the leaves ; but whether this is due to 
the contained casein or albumen, I know not. Eather large 
drops of milk excite so much secretion (which is very acid) 
that it sometimes trickles down from the leaves, and this is 
likewise characteristic of chemically prepared casein. Minute 
drops of milk, placed on leaves, were coagulated in about ten 
miniites. Schiff denies* that the coagulation of milk by 
gastric juice is exclusively due to the acid which is present, 
but attributes it in part to the pepsin ; and it seems doubtful 
whether with Drosera the coagulation can be wholly due to 
the acid, as the secretion does not commonly colour litmus 
paper until the tentacles have become well inflected ; whereas 
the coagulation commences, as we have seen, in about ten 
minutes. Minute drops of skimmed milk were placed on the 
discs of five leaves ; and a large proportion of the coagulated 
matter or curd was dissolved in 6 hrs. and still more com- 
pletely in 8 hrs. These leaves re-expanded after two days, 
and the viscid fl.uid left on their discs was then carefully 
scraped off and examined. It seemed at first sight as if all 
the casein had not been dissolved, for a little matter was left 
which appeared of a whitish colour by reflected light. But 
this matter, w;hen examined under a high power, and when 
compared with a minute drop of skimmed milk coagulated 
by acetic acid, was seen to consist exclusively of oil-globules, 
more or less aggregated together, with no trace of casein. 
As I was not familiar with the microscopical appearance of 
milk, I asked Dr. Lauder Brunton to examine the slides, and 
he tested the globules with ether, and found that they were 
dissolved. We may therefore conclude that the secretion 
quickly dissolves casein, in the state in which it exists in 

milk.t 

* ' Lepons,' &o. torn. ii. p. 151. of cow's milk contains a small pro- 

t [Professor Sanderson Jias called portion of nuclein, which is entirely 

my attentionto the fact that the casein indigestible by gastric juice — F. D.]| 



Chap. VI.]' DIGESTION. 95 

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

Some cubes of hard casein, moistened with water, were 
placed on two leaves; after three days one cube had its 
angles a little rounded, and after seven days both consisted of 
rounded softened masses, in the midst of much viscid and 
acid secretion ; but it must not be inferred from this fact that 
the angles were dissolved, for cubes immersed in water were 
similarly acted on. After nine days these leaves began to 
re-expand, but in this and other cases the casein did not 
appear, as far as could be judged by the eye, much, if at all, 
reduced in bulk. According to Hoppe-Seyler and Lubavin* 
caseiu consists of an albuminous, with a non-albuminous, 
substance ; and the absorption of a very small quantity of the 
former would excite the leaves, and yet not decrease the 
casein to a perceptible degree. Schiff assertsf — and this is 
an important 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.! 



* Dr. Lauder Brunton, 'Handbook that this difference is no doubt due 

for Phys. Lab.' p. 529. to the action of the alcohol used 

t ' Le5ons,' &c. torn. ii. p. 153. in making " chemically prepared 

X [Professor Sanderson tells me casein." — F. D.] 



96 DEOSEEA EOTUNDIFOLIA. [Chap. VI. 

A few trials were made witli cheese ; cubes of -^-^ of an 
incli (1 • 27 mm.) were placed on four leaves, and these after 
one or two days became well inflected, their glands pouring 
forth much acid secretion. After five days they began to re- 
expand, but one died, and some of the glands on the other 
leaves were injured. Judging by the eye, the softened and 
subsided masses of cheese, left on the discs, were very little 
or not at all reduced in bulk. We may, however, infer from 
the time during which the tentacles remained iaflected, — 
from the changed colour of some of the glands, — and from 
the injury done to others, that matter had been absorbed from 
the cheese. 

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

Pollen. — A little fresh pollen from the common pea was 
placed on the 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 



* Mr. A. W. Bennett found the tera ; see ' Journal of Hort. Soc. of 
■(indigested coats of the grains in the London,' yol. iv. 1874, p. 158. 
intestinal canal of pollen-eating Dip- 



Chap. VI.] DIGESTIOX. 97 

inevitably cauglit by the viscid secretion surrounding the 
many glands. 

Gluten. — This substance is composed of two albuminoids, 
one soluble, the other insoluble in alcohol.* Some was 
prepared by merely washing wheaten flour in water. A 
provisional trial was made with rather large pieces placed on 
two leaves ; these, after 21 hrs., were closely inflected, and 
remained so for four days, when one was killed and the 
other had its glands extremely blackened, but was not 
afterwards observed. 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 leuf 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 diiferently 
from fresh gluten. One leaf was almost fully re-expanded in 
three days, and the other three leaves in four days. The 
■chips were greatly softened, almost liquefied, but not nearly 
all dissolved. The glands which had been in contact with 
them, instead of being much blackened, were of a very pale 
•colour, and many of them were evidently killed. 

In not one of these ten cases was the whole of the gluten 
■dissolved, even when very small bits were given. I there- 
fore asked Dr. Burdon Sanderson totry 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 and butyric 
acids, and it was completely dissolved by these fluids at the 



* Watts' 'Diet, of Chemistry,' toI. ii. 1S72, p. 873. 

H 



98 DEOSEEA EOTUNDIFOLIA. [Chap. VI'. 

ordinary temperature of a room. Here, then, at last, we 
have a case in which it appears that there exists an essential 
difference in digestive power between the secretion of Drosera 
and gastric jnice ; 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 Isefore they have had time 
to pour forth a sufScient 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. SmSU portions were washed and placed on five 
leaves, which were soon closely inflected, but to my surprise 
re-expanded completely in 48 hrs. A mere vestige of gluten 
was left on two of the leaves, and not a vestige on the other 
three. The viscid and acid secretion, which remained on the 
discs of the three latter leaves, was scraped off and examined 
by my son under a high power ; but nothing could be seen 
except a little dirt, and a good many starch grains which 
had not been dissolved by the hydrochloric acid. Some of 
the glands were rather pale. We thus learn that gluten, 
treated with weak hydrochloric acid, is not so powerful or so 
enduring a stimulant as fresh gluten, and does not much 
injure the glands ; and we further learn that it can be 
digested quickly and completely by the secretion. 

Glohulin or Crystallin.—1\as feulstance was kindly prepared for 
me from the lens of the eye by Dr. Moore, and consisted of liard, 
colourless, transparent fragments. It is said * that globulin ought to 
"swell up in water and dissolve, for the most p^rt 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 hydrochlorio acid, others soaked in water for one or 
two days, were placed on nineteen leaves. Most of these leaves. 



Watts' ' Diet, of Chemistry,' vol. ii. p. 874. 



Chap. VI.] DIGESTIOX. 99 

especially those with the long soaked particles, became strongly 
inflected in a few hours. The greater number re-expanded after three 
or four days ; but three of the leaves remained inflected during one, 
two, or three additional days. Hence some exciting matter must have 
been absorbed ; but the fragments, though perhaps softened in a 
greater degree than those kept for the same time in water, retained 
all their angles as sharp as ever. As globulin is an albuminous sub- 
stance, I was astonished at this result ; * and my object beins; 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 • 141 of the above globulin was dissolved. In. 
both cases an excess of the substance to be digested was subjected to- 
the liquid." f We thus see that within the same time less than one- 
ninth by weight of globulin than of fibrin was dissolved : and bearing 
in mind that pepsin with acids of the acetic series has only about one- 
third of the digestive power of pepsin with hydrochloric acid, it is not 
surprising that the fragments of globulin were not corroded or rounded 
by the secretion of Urosera, though some soluble matter was certainly 
e.'ctracted from them and absorbed by the glands. 

Hcematin. — Some dark red granules, prepared from bullock's blood, 
were given me ; these were found by Dr. Sanderson to be insoluble in 
water, acids, and alcohol, so that they were probably hfematin, to- 
gether with other bodies derived from the blood. Particles with little- 
drops of water were placed on four leaves, three of which were pretty 
closely inflected in two days ; the fourth only moderately so. On the 
third day the glands in contact with the hajmatin were blackened, and 
some of the tentacles seemed injured. After five rlays 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 witii 
artificial digestive fluid, in the manner described under globulin, and 
found that whilst 1"31 of fibrin, only 0"456 of the hasmatin was 



* [The result was no doubt due was dissolved within the same time, 

(as I learn from Professor Sanderson) namely, one hour ; so that it was far 

to the fact that the globulin had more soluble than that which I used, 

been treated with alcohol in the though less soluble than fibrin, of 

course of its preparation — F. D.] which, as we have seen, 1'31 wag 

t I may add that Dr. Sanderson dissolved. I wish that I had tried 

prepared some fresh globulin by on Drosera globulin prepared by this 

Schjnidt's method, and of this 0'865 method. 

H 2 



100 DKOSEIJA KOTUXBIFOLIA. [Chap. VI. 

dissolved in an hour ; but the dissolution by the secretion of even a 
less amount would account for its action on Drosera. The residue 
left by the artificial digestive fluid at first yielded nothing more to it 
during several succeeding daj-s. 

Substances loliich are not Digested by the Secretion. 

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

To these may be added dissolved sugar and gum, diluted 
alcohol, and vegetable infusions not containing albumen, for 
none of these, as shown in the last chapter, excite inflection. 
Now, it is 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 
substances are, as far as it is known, digested by the gastric 
juice of animals, though some of them are acted on by the 
other secretions of the alimentary canal. Nothing mure 
need be said about some of the above enumerated substances, 
excepting that they were repeatedly tried on the leaves of 
Drosera, and were not in the least affected by the secretion. 
About the others it will be advisable to give my experi- 
ments. 

Fibro-elastic Tissue. — We have already seen that when little cubes 
of meat, &c., were placed on leaves, the muscles, areolar tissue, and 
cartilage was completely dissolved, but the fibro-elastic tissue, even 
the most delicate threads, were left without the least signs of having 
been attacked. And it is well known that this tissue cannot be 
digested by the gastric juice of animals.* 

Mucin. — As this substance contains about 7 per cent, of nitrogen, I 
expected that it would have excited the leaves greatly and been 
digested by the secretion, but in this I was mistaken. Prom what is 



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



Chap. VI.] DIGESTION. 101 

stated in cliemical works, it appears extremely doubtful -whether 
mucin can be prepared as a pure principle. That which I used 
(prepared by Dr. Moore) was dry and hard. Particles moistened 
with water were placed on four loaves, but after two days there was 
only a trace of inflection in the immediately adjoining tentacles. 
These leaves wero then tried with bits of meat, and all four soon 
became strongly inflected. Some of the dried mucin was then soaked 
in water for two days, and little cubes of the proper size were placed 
on three leaves. After four days the tentacles round the margins of 
the discs wore a little inflected, and the secretion collected on the disc 
was acid, but the exterior tentacles were not affected. One leaf began 
to re-expand on the fourth day, and all were fully re-expanded on the 
sixth. The glands which had been in contact with the mucin were 
a little darkened. We may therefore conclude that a small amount of 
some impurity of a moderately exciting nature had been absorbed. 
That the mucin employed by me did contain some soluble matter was 
proved by Dr. Sanderson, who on subjecting it to artificial gastric 
juice found that in 1 hr. .some was dissolved, but ooly in the proportion 
of 23 to 100 of fibrin during the same time. The cubes, though 
perhaps rather softer than those left in water for the same time, 
retained their angles as sharp as ever. We may therefore infer that 
the mucin itself was not dissolved or digested. Nor is it digested by 
the gastric juice of living animals, and according to Schiff* it is a 
layer of this substance which protects the coats of the stomach from 
being corroded during digestion. 

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 pur- 
poses, and afterwards some which was much purer, prepared for me 
by Dr. Moore. Five leaves to which a considerable quantity of the 
former was given remained inflected for five days ; four of them then 
died, apparently from too great stimulation. I then tried Dr. Moore's 
pepsin, making it into a paste with water, and placing such small 
particles on the discs of five leaves that all would have been quickly 
dissolved had it been meat or albumen. The leaves were soon in- 
flected ; two of them began to re-expand after only 20 hrs., and the 
other three were almost completely re-expanded alter 44 hrs. Some 
of the glands which had been in contact with the particles of pepsin, 
or with the acid secretion surrounding them, were singularly pale, 
whereas others were singularly dark-coloured. Some of the secretion 
was scraped off and examined rmder a high power ; and it abovmded 
with granules undistinguishable from those of pepsin left in water for 
the same length of time. We may therefore infer, as highly probable 



' Lemons phys. de la Digestion,' 1867, torn. ii. p. 30-t. 



102 DEOSEEA EOTUNDIFOLIA. [Chap. VI. 

(remembering what small quantities were given), that the ferment of 
Drosera does not act on or digest pepsin, but absorbs from it some 
albuminous impurity which induces inflection, and which in large 
quantity is highly injurious. Dr. Lauder Brunton at my request 
endeavoured to ascertain whether pepsin with hydrochloric acid would 
digest pepsin, and as far as he could judge, it had no such power. 
Gastric juice, therefore, apparently agrees in this respect wiih the 
secretion of Diosera. 

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 aflected. 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; alter two days there was no inflection; 
I then gave them another dose, but still there was no inflection. 
These leaves were afterwards tested with similarly sized drops of an 
infusion of raw meat, and in 6 hrs. there was considerable inflection, 
which became excessive in 24 hrs. But the urea apparently was not 
quite pure, for when four leaves were immersed in 2 dr. (7'1 c.c.) 
of the 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 immersion in pure water. 'Jhat 
the urea, which was not perfectly white, should have contained a 
sufiicient quantity of albuminous matter, or of some salt of ammonia, 
to have caused the above efi'ect, is far from surprising, for, as we shall 
see in the next chapter, astonishingly small doses of ammonia are 
highly efficient. We may therefore conclude that the urea itself is 
not exciting or nutritious to Drosera; nor is it modified by the 
secretion, so as to be rendered nutritious, for, had this been the case, 
all the leaves with drops on their discs assuredly would have been 
well inflected. Dr. Lauder Brunton informs me that from experiments 
made at my request at St. Bartholomew's Hospital it appears that uren. 
is not acted on by artificial gastric juice, that is by pepsin with 
hydrochloric acid. 

Chitine. — The chitinous coats of insects naturally captured by the 
leaves do not appear in the least corroded. Small square pieces of the 
delicate wing and of the elytron of a Staphylinus were placed on some 
leaves, and after these bad re-expanded, the pieces were carefully 
examined. Their angles were as sharp as ever, and tbey 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 
lour days ; whereas the leaves with bits of the true wing re-expanded on 



Chap. VI.] DIGESTION, 103 

the second day. Any one who will examine the excrement of inseot- 
eatins animals will see how powerless their gastric-juice is on ohitine. 

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. G-un-cotton, which consists 
of cellulose, with the hydrogen replaced by nitrogen, was tried with the 
same result. We have seen that a decoction of cabbage leaves excites 
the most powerful inflection. I therefore placed two little square bits 
of the blade of a cabbage leaf, and four little cubes cut from the 
midrib, on six leaves of Drosera. These became well inflected in 12 
hrs., and remained so for between two and four days; the bits of 
cabbage being bathed all the time by acid secretion. This shows that 
some exciting matter, to which I shall presently refer, had been 
absorbed ; but the angles of the squares and cubes remained as sharp 
as ever, proving that the framework of cellulose had not been attacked. 
Small square bits of spinach leaves were tried with the same result ; 
the glands pouring forth a moderate supply of acid secretion, and the 
tentacles remaining inflected for three days. We have also seen 
that the delicate coats of pollen grains are not dissolved by the 
secretion. It is well known that the gastric juice of animals does 
not attack cellulose. 

Chlorophyll. — This substance was tried, as it contains nitrogen. 
Dr. Moore sent me some preserved in alcohol ; it was dried, but soon 
deliquesced. Particles were placed on four leaves ; after 3 hrs. the 
secretion was acid ; after 8 hrs. there was a good deal of inflection, 
which in 24 hrs. became fairly well marked. After four days two of 
the leaves began to open, and the other two were then almost fully re- 
expanded. It is therefore clear that this chlorophyll contained matter 
\vliich excited the leaves to a moderate degree ; but judging by the 
eye, little or none was dissolved ; so that in a pure state it would not 
probably have been attacked by the secretion. Dr. Sanderson tried that 
which I used, as well as some freshly prepared, with artificial digestive 
liquid, and found that it was not digested. Dr. Lauder Bruntou 
likewise tried some prepared by the process given in the British Phar- 
macopoeia, and exposed it for five days at the temperature of 37° 
Cent, to digestive liquid, but it was not diminished in bulk, though 
the fluid acquired a slightly brown colour. It was also tried with 
.the glycerine extract of pancreas with a negative result. Nor does 
chlorophyll seem affected by the intestinal secretions of various animals, 
judging by the colour of their excrement. 

It must not be supposed from these facts that the grains of 
chllorophyll, as they exist in living plants, cannot he attacked by the 
secretion; for these grains consist of protoplasm merely coloured by 
chlorophyll. My son Francis placed a thin slice of spinach leaf, 
moistened with saliva, on a leaf of Drosera, and other slices on damp 
cotton-wool, all exposed to the same temperature. After 19 hrs. the 



104 DEOSEEA KOTUNDIFOLIA. [Chap. VI. 

slice on the leaf of the Drosera was bathed in much' secretion from 
the inflected tentacles, and was now examined under the microscope. 
JNo perfect grains of chlorophyll could be distinguished ; some were 
shrunken, of a yellowish-green colour, and collected in the middle of 
the cells; others were disintegrated and formed a yellowish mass, 
likewise in the middle of the cells. On the other hand, in the 
slices surrounded by damp cotton-wool, the grains of chlorophyll were 
green and as perfect as ever. My son also placed some slices in 
artificial gastric juice, and these were acted on in nearly the same 
manner as by the secretion. We have seen that bits of fresh cabbage 
and spinach leaves cause the tentacles to be inflected and the glands 
to pour forth much acid secretion ; and there can be little doubt that 
it is the protoplasm forming the grains of chlorophyll, as well as that 
lining the walls of the cells, which excites the leaves. 

Ji'at 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 iuflection : but when they 
are immersed in olive oil they become strongly inflected; but to this 
subject I shall have to recur. Oily substances are not digested by 
the gastric juice of animals. 

Starch. — Rather large bits of dry starch caused well-marked in- 
flection, and the leaves did not re-expand until the fourth day; but I 
have no doubt that this was due to the prolonged irritation of the 
glands, as the starch continued to absorb the secretion. The particles 
were not in the least reduced in size; and we know that leaves 
immersed in an emulsion of starch are not at all affected. I need 
hardly say that starch is not digested by the gastric juice of animals. 

Action of the Secretion on Living Seeds. 

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

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



Chap. VI.] DIGESTION. 105 

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

Cress seeds (Lepidimn sativum) of the previous year were placed on 
four leaves ; two of these 'next morning were moderately and two 
strongly inflected, and remained so for four, five, and even six days. 
Soon after these seeds were placed on the leaves and had become damp,, 
they secreted in the usual manner a layer of tenacious mucus ; and to 
ascertain whether it was the absorption of this substance by the glands- 
which caused so much inflection, two seeds were put into water, 
and as much of the mucus as possible scraped ofl". They were then 
plao( d on leaves, which became very stronjily inflected in the course 
of 3 hrs., and were still closely inflected on the third day ; so that ic 
evidently was not the nmcus which excited so much inflection ; on tho 
contrary, this served to a certain extent as a protection to the seeiis. 
Two of the six seeds germinated whilst still lying on the leave.", but 
the seedlings, when transferred to damp sand, soon died ; of the other 
four seeds, only one germinated. 

Two seeds of mustard (Sinapis nigra), two of celery {Api.um grave- 
olens) — both of the previous year, two seeds well soaked of caraway 
(fiarum carui), and two of wheat, did not excite the leaves more thau 
inorganic objects often do. Five seeds, hardly ripe, of a buttercup 
(Ranunculus), and two fresh seeds of Anemone nemorosa, induced 
only a little more effect. On the other hand, four seeds, perhaps not 
quite ripe, of Carex sylvatica caused the leaves on which they wei e- 
placed to be very strongly inflected ; and these only began to re-e.\pand 
on the third day, one remaining inflected for seven days. 

It follows from these few facts that difi'erent kinas of seeds exciie 
the leaves in very different degrees ; whether this is solely due to tho 
nature of their coats is not clear. In the case of the cress seeds, tlie 
partial removal of the layer of mucus hastened the inflection of tlio 
tentacles. Whenever the leaves remain inflectfd during several days 
over seeds, it is clear that they absorb some matter from them. Tliat 
the secretion penetrates their coats is also evident from the large pro- 
portion of cabbage, raddish, and cress seeds which were killed, and 
from several of the seedlings being greatly injured. This injury to 
the seeds and seedlings may, however, be due solely to the acid of the 
secretion, and not to any process of digestion; for Mr. Traherne 
Moggridge has shown that very weak acids of the acetic series are 
highly injurious to seeds. It never occurred to me to observe whether 
seeds are often blown on to the viscid leaves of plants growing in a. 
state of nature ; but this can hardly fail sometimes to occur, as we 
shall hereafter see in the case of Pinguicula. If so, Drosera will profit 
to a slight degree by absorbing matter Irom such seeds. 



106 DKOSEEA EOTUXDIFOLIA. [Chap. VI. 



Summary and Concluding Bemarks on the Digestive Power of 

Drosera. 

When the glands on the disc are excited either by the 
absorption of nitrogenous matter or by mechanical irritation, 
their secretion increases in quantity and becomes acid. 
They likewise transmit some influence to the glands of the 
exterior tentacles, causing them to secrete more copiously; 
and their secretion likewise becomes acid. With animals, 
according to Schiff,* mechanical irritation excites the glands 
•of the stomach to secrete an acid, but not pepsin. Now, I 
have every reason to believe (though the fact is not fully 
established), that although the glands of Drosera are con- 
tinually secreting viscid fluid to replace that lost by 
evaporation, yet they do not secrete the ferment proper for 
digestion when mechanically irritated, but only after ab- 
sorbing certain matter, probably of a nitrogenous nature. I 
infer that this is the case, as the secretion from a large 
number of leaves which had been irritated by particles of 
glass placed on their discs did not digest albumen ; and 
more especially from the analogy of Dionasa and Nepenthes. 
In like manner, the glands of the stomach of animals secrete 
pepsin, as Schiff asserts, only after they have absorbed 
certain soluble substances, which he designates as peptogenes. 
There is, therefore, a remarkable parallelism between the 
glands of Drosera and those of the stomach in the secretion 
of their proper acid and ferment.f 

* 'Phys. dc la Digestion,' 1867, acid and pepsin make tlieir appearance 

torn. ii. pp. 188, 245. almost immediately after tlie intro- 

f [It will be seen from the facts duction of a starch solution into the 
given in a footnote at p. 81, that stomach. The same thing naturally 
even if we accept Schift's peptogeu follows on the introduction of SchifFs 
theory, the evidence on the bo- peptogens, so that no inconsiderable 
tanical side is against the existence quantity of acid and pepsin is in 
of the above suggested parallelism. readiness for a subsequent act of 
Moreover, ScliifF's peptogen theory digestion, which is, in consequence, 
is not generally accepted by physio- rendered far more energetic." 
legists. Professor Sanderson has Haideuhain, in Hermann's ' Hand- 
called my attention to Ewald's views buch der Physiologic,' vol. v. part i. 
on this question as given in his p. 153, also criticises SchifTs theory, 
' Klinik der Verdauungs krankheiten, and shows that the observations on 
(i) Die Lehre von der Verdauung,' which this theory is founded are to 
1886, p. 91. Ewald does not believe some extent untrustworthy, owing to 
an any speci'aZ action of the so-called a fault in the method employed — F. D.] 
lieptogens. He writes, " I find that 



Chap. VI.] DIGESTION. 107 

The secretion, as we liave seen, completely dissolves 
albumen, muscle, fibrin, areolar tissue, cartilage, the fibrous 
basis of bone, gelatine, chondrin, casein in the state in which it 
exists in milk, and gluten which has been subjected to weak 
hydrochloric acid. Syntonin and legumin excite the leaves 
eo powerfully and quickly that there can hardly be a doubt 
that both would be dissolved by the secretion. The secretion 
failed to digest fresh gluten, apparently from its injuring 
the glands, though some was absorbed. Raw meat, unless 
in very small bits, and large pieces of albumen, &c., likewise 
injure the leaves, which seem to suffer, like animals, from 
a surfeit. I know not whether the analogy is a real one, 
but it is worth notice that a decoction of cabbage leaves is 
fur more exciting and probably nutritious to Drosera than 
an infusion made with tepid water ; and boiled cabbages are 
far more nutritious, at least to man, than the uncooked 
leaves. The most striking of all the cases, though not really 
more remarkable than many others, is the digestion of so 
hard and tough a substance as cartilage. The dissolution of 
pure phosphate of lime, of bone, dentine, and especially 
enamel, seems wonderful ; but it depends merely on the 
long-continued secretion of an acid; and this is secreted for a 
longer time under these circumstances than under any other. 
It was interesting to observe that as long as the acid was 
consumed in dissolving the phosphate of lime, no true di- 
gestion occurred ; but that as soon as the bone was completely 
decalcified, the fibrous basis was attacked and liquefied with 
the greatest ease. The twelve substances above enumerated, 
which are completely dissolved by the secretion, are likewise 
dissolved by the gastric juice of the higher animals ; and 
they are acted on in the same manner, as shown by the 
rounding of the angles of albumen, and more especially by 
the manner in which the transverse stri» 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 
h»matin employed by me. The secretion also dissolved 
something out of chemically prepared casein which is said to 
consist of two substances ; and although Schiff asserts that 
casein in this state is not attacked by gastric juice, he might 
easily have overlooked a minute quantity of some albu- 
minous matter, which Drosera would detect and absorb. 
^'Igain, fibro-cartilage, though not properly dissolved, is 



108 DROSEEA EOTUNDIFOLIA. [Chap. VI. 

acted on in the same manner, both by the secretion of Drosera 
and gastric juice. But this substance, as well as the so- 
called hssraatin used by me, ought perhaps to have been 
classed with indigestible substances. 

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

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

The several substances, which are completely dissolved by 
the secretion, and which are afterwards absorbed by the 
glands, affect the leaves rather differently. They induce 
inflection at very different rates, and in very different 
degrees ; and the tentacles remain inflected for very different 
periods of time. Quick inflection depends partly on the 
quantity of the substance given, so that many glands are 
Kimultaneously affected, partly on the facility with which it 
is penetrated, and liquefied by the secretion, and partly on 
its nature, but chiefly on the presence of exciting matter 
already in solution. Thus saliva, or a weak solution of raw 
meat, acts much more quickly than even a strong solution of 
gelatine. So again leaves which have re-expanded, after 
absorbing drops of a solution of pure gelatine or isinglass 
(the latter being the more powerful of the two), if given bits 
of meat, are inflected much more energetically and quickly 
than they were before, notwithstanding that some rest is gener- 
ally requisite between two acts of inflection. We probably 
see the influence of texture in gelatine and globulin when 
softened by having been soaked in water acting more quickly 
than when merely wetted. It may be partly due to changed 
texture, and partly to changed chemical nature, that albumen, 



Chap. VI.] DIGESTION. 109 

whicli has been kept for some time, and gluten which has 
been subjected to weak hydrochloric acid, act more quickly 
than these substances in their fresh state. 

The length of time during which the tentacles remain 
inflected largely depends on the quantity of the substance 
given, partly on the facility with which it is penetrated or 
acted on by the secretion, and partly on its essential nature. 
The tentacles always remain inflected much longer over 
large bits or large drops than over small bits or drops. 
Texture probably plays a part in determining the extra- 
ordinary length of time during which the tentacles remain 
inflected over the hard grains of chemically prepared casein. 
J5ut the tentacles remain inflected for an equally long time 
over finely powdered, precipitated phosphate of lime ; phos- 
phorus iti 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 aiforded by their chitinous integu- 
ments ; for animal matter is soon extracted from insects 
(probably by exosmose from their bodies into the dense sur- 
rounding secretion), as shown by the prompt inflection of 
the leaves. We see the influence of the nature of different 
substances in bits of meat, albumen, and flesh gluten acting 
very differently from equal-sized bits of gelatine, areolar 
tissue, and the fibrous basis of bone. The former cause not 
only far more prompt and energetic, but more prolonged, 
inflection than do the latter. Hence we are, I think, justi- 
fied in believing that gelatine, areolar tissue, and the fibrous 
basis of bone, would be far less nutritious to Drosera than 
such substances as insects, meat, albumen, &c. This is an 
interesting conclusion, as it is known that gelatine affords 
but little nutriment to animals ; and so, probably would 
areolar tissue and the fibrous basis of bone. The chondrin 
which I used acted more powerfully than gelatine, but then 
1 do not know that it was pure. It is a more remarkable fact 
that fibrin, which belongs to the great class of Proteids,* 
including albumen in one of its sub-groups, does not excite 
the tentacles in a greater degree, or keep them inflected for a 
longer time, than does gelatine, or areolar tissue, or the 
fibrous basis of bone. It is not known how long an animal 



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



110 DEOSERA EOTUNDIFOLIA. [Chap. VI. 

would survive if fed on fibrin alone, but Dr. Sanderson has; 
no doubt longer than on gelatine, and it would be bardly 
rasb to predict, judging from the effects on Drosera, that 
albumen would be found more nutritious than fibrin. 
Globulin likewise belongs to the Proteids, forming another 
sub-group, and this substance, though containing some 
matter which excited Drosera rather strongly, was hardly 
attacked by the secretion, and was very little or very slowly 
attacked by gastric juice. How far globulin would be 
nutritious to animals is not known. We thus see how 
differently the above specified several digestible substances 
act on Drosera ; and we may infer, as highly probable, that 
they would in like manner be nutritious in very different 
degrees both to Drosera and to animals. 

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

Finally the experiments recorded in this chapter show 
us that there is a remarkable accordance in the power of 
digestion between the gastric juice of animals with its 
pepsin and hydrochloric acid and the secretion of Drosera 
with its ferment and acid belonging to the acetic series. 
We can therefore hardly doubt that the ferment in both 
cases is closely similar, if not identically the same. That 
a plant and an animal should pour forth the same, or nearly 
tlje same, complex secretion, adapted for the same purpose of 
digestion, is a new and wonderful fact in physiology. But 
I shall have to recur to this subject in the fifteenth chapter, 
in my concluding remarks on the Droserace®. 



Chap. Vn.] SALTS OF AMMONIA. 1 1 1 



CHAPTEE VII. 

The Effects op Salts of Amjiomia. 

Wanner of performing the experiments — Action of distilled water in com- 
parison with the solutions — Carbonate of ammonia, absorbed by the roots 
— The vapour absorbed by the glands — Drops on the disc — Minute drop» 
applied to separate glands — Leaves immersed in weak solutions — Minute- 
ness of the doses which induce aggregation of the protoplasm — Nitrate of 
ammonia, analogous experiments with — Phosphate of ammonia, analogous- 
experiments with — Other salts of ammonia — Summary and concluding 
remarks on the action of the salts of ammonia. 

The chief object in this chapter is to show how powerfully 
the salts of ammonia act on the leaves of Drosera, and more 
especially to show what an extraordinarily small quantity 
suffices to excite inflection. I shall therefore he 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 extrem e 
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 iu 
irritability to a marked degree. My experiments were tried 
in the following several ways. 

Firstly. — Drops which were ascertained by repeated trials to he on 
an average about half a minim, or the 5^0°^"' ^^i*^ ounce (-0296 c.c), 
were placed by the same pointed instrument on the discs of the leaves, 
and the inflection of the exterior rows of tentacles observed at succes- 
sive intervals of time. It was first ascertained, from between thirty 
and forty trials, that distilled water dropped in this manner produces 
no effect, except that sometimes, though rarely, two or three tentacles 
become inflected. In fact all the many trials with solutions which 
were so weak as to produce no effect lead to the same result that 
water is inefficient. 

Secondly.— Ihe head of a small pin, fixed into a handle, was dipped 



112 DEOSEEA EOTUXDIFOLIA. [Cuap. YII. 

into the solution un'ler trial. The small drop which adhered to it, 
iind which was much too small to fall off, was cautiously placed, by 
the aid of a lens, in contact with the secretion surrounding the glands 
(if one, two, three, or four of the exterior tentacles of the same leaf. 
Oreat care was taken that the glands themselves should not be 
touched. I had supposed that the di-ops were of nearly the same size; 
ll)ut on trial this proved a great mistake. I first measured some water, 
iind removed 300 drops, touching the pin's head each time on blotting- 
paper ; and on again measuring the water, a drop was found to equal 
•on an average about the Jj of a minim. Some water in a small vessel 
■was weighed (and this is a more accurate method), and 300 drops re- 
moved as before ; and on again weighiag the water, a drop was found 
to equal on an average only the -^ oi a, minim. 1 repeated the opera- 
tion, but endeavoured this time, by taking the pin's head out of the 
water obliquely and rather quickly, to remove as large drops as 
possible; and the result showed that I had succeeded, for each drop 
on an average equalled Ys-i of ^ minim. I repeated the operation in 
■exactly the same manner, and now the drops averaged ^.-^ 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 c.c. One of these drops could be applied 
to three or even four glands, and if the tentacles became inflected, some 
.<jf the solution must have been absorbed by all ; for drops of pure water, 
iipplied 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 diffusion of all 
the salt in solution, as was evident, from three or four tentacles treated 
iiuccessively with the same drop, often becoming inflected. All the 
matter in solution was even then probably not exhausted. 

Thirdly. — Leaves were cut off and immersed in a measured quantity 
of the solution under trial; the same number of leaves being im- 
mersed at the same time, in the same quantity of the distilled water 
which had bsen used in making the solution. The leaves in the two 
lots were compared at short intervals of time, up to 24 hrs., and some- 
times to 48 hrs. They were immersed by being laid as gently as 
)iossible in numbered watchglasses, and thirty minims (1'775 c.c.) of 
the solution or of water was poured over each. 

Some solutions, for instance that of carbonate of ammonia, quickly 
discolour the glands ; and as all on the same leaf were discoloured 
simultaneously, they must all have absorbed some of the salt within 
the same short period of time. This was likewise shown by the 
simultaneous inflection of the several exterior rows of tentacles. If 
we had no such evidence as this, it might have been supposed that 
only the glands of the exterior and inflected tentacles had absorbed the 
salt ; or that only those on the disc had absorbed it, and had then 
transmitted a motor impulse to the exterior tentacles ; but in this 
latter case the exterior tentacles would not have become inflected 



Ghap. VII.] EFFECTS OF WATEB. 113 

until some time had elapsed, instead of within half an hour, or even 
within a few minutes, as usually occurred. All the glands on the 
same leaf are of nearly the same size, as may best he 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 papilla, which absorb carbonate of ammonia, 
an infusion of raw meat, metallic salts, and probably many other 
substances, but the absorption of matter by these papillaj never induces 
inflection. We must remember that the movement of each separate 
tentacle depends on its gland being excited, except when a motor 
impulse is transmitted from tlie glands of the disc, and then the 
movement, as just stated, does not take place imtil some little time 
has elapsed. 1 have made these remarks because they show us that 
when a leaf is immersed in a solution, and the tentacles are inflected, 
we can judge with some accuracy how much of the salt each gland 
hiis absorbed. For instance, if a leaf bearing 212 glands, be immersed 
in a measured quantity of a solution, containing ■j'o 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 absorbai 
at most ^oVo "^ '''■ gr^iii o' *-^8 s^l''- I ^^7 ^^ most, for the papillas 
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 principle leads to remarkable conclusions with 
respect to the minuteness of the doses causing inflection. 

On the Action of Distilled Water in causing Inflection. 

Although in all the more important experiments the difference 
between the leaves simultaneously immersed in water and in the 
several solutions will be described, nevertheless it may be well here 
to give a summary of the effects of water. The fact, moreover, of 
pure water acting on the glands deserves in itself some notice. Leaves 
to the number of 141 were immersed in water at the same time with 
those in the solutions, and- their state recorded at short intervals of 
time. Thirty-two other leaves were separately observed in water, 
making altogether 173 experiments. Many scores of leaves were also 
immersed in water at other times, but no exact record of the effects 
produced was kept ; yet these cursory observations support the con- 
clusions arrived at in 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 surroundmg the 
outer parts of the disc generally become inflected, so that their glands 
form a small dark ring on the disc ; the exterior tentacles not par- 

I 



114 



DROSEEA EOTUNEIFOLIA. 



[Chap. VIL 



taking of this movement. Hence, excepting in a few cases hereafter 
to be specified, we can judge whether a solution produces any efiect 
only by observing the exterior tentacles ^v■ithin the first 3 or 4 hrs. 
after immersion. 

Now for a summary of the state of the 173 leaves after an immersion 
©f 3 or 4 hrs. in pure water. One leaf had almost all its tentacles 
inflected ; three leaves had most of them sub-infiected ; and thirteen 
had on an average 36 '5 tentacles inflected. Thus seventeen leaves out 
of the 173 were acted on in a marked manner. Eighteen leaves had 
from seven to nineteen tentacles inflected, the average being 9 '3 ten- 
tacles for each leaf. Forty-four leaves had from one to six tentacles 

inflected, generally the long-headed 
ones. So that altogether of the 
173 leaves carefully observed, 
seventy-nine were atlected by tlie 
water in some degree, though 
commonly to a very slight degree ; 
and ninety-four were not affected 
in the least degree. This amount 
of inflection is vitterly insignifi- 
cant, as we shall hereafter see, 
compared with that caused by 
very weak solutions of several 
salts of ammonia. 

Plants which have lived for 
some time in a rather high tem- 
perature are far more sensitive to 
the action of water than those 
grown out of doors, or recently 
brought into a warm greenhouse. 
Thus in the above seventeen cases, 
in which the immersed leaves had 
a considerable number of tentacles 
inflected, the plants had been kept 
during the winter in a very warm 
greenhouse ; and they bore in the 
early spring remarkably fineleaves, 
of a light red colour. Had I then known that the sensitiveness of 
plants was thus increased, perhaps I should not have used the leaves 
for my experiments with the very weak solutions of phosphate of 
ammonia ; but my experiments are not thus vitiated, as I invariably 
used leaves from the same plants for simultaneous immersion in water. 
It often happened that some leaves on the same plant, and some ten- 
tacles on the same leaf, were more sensitive than others ; but why this 
should be so, I do not know. 

Besides the differences just indicated between the leaves immersed 
in water and in weak solutions of ammonia, the tentacles of the latter 
are in most cases much more closely inflected. The appearance of a 




Fig. 9. 

(_Drosei-a rotundifolia.') 

Leaf (enlarged) with all the tentacles 
closely inflected, from Immersion in a 
solution of phosphate of ammonia (one 
part to 8>,600 of water). 



Ghap. Vir.] OAKBOKATE OF AMMOXIA. Il5 

leaf after immersion in ,1 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 solutions, the blade or lamina olten 
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 thp 
inflection was very feeble. Again, with leaves in the weak solutions 
the inflection of the tentacles and blade often goes on steadily, though 
slowly, increasing during many hours ; and this again is so rare a cir- 
cumstance with leaves in water that I have seen only three instances 
of any such increase after the first 8 to 12 hrs. ; and in these three 
instances the two outer rows of tentacles were not at all affected. 
Hence there is sometimes a much greater difference between the leaves 
in water and in the weak solutions, after from 8 hrs. to 24 hrs., than 
there was within the iirst 3 hrs. ; though as a general rule it is best 
to trust to the difference observed within the shorter time. 

With respect to the period of the re-expansion of the leaves, when 
left immersed either in water or in the weak solutions, nothing could 
be more variable. In both cases the exterior tentacles not rarely 
begin to re-expand, after an interval of only from 6 to 8 hrs. ; that is 
just about the time when the short tentacles round the borders of the 
disc become inflected. On the other hand the tentacles sometimes 
remain inflected for a whole day or even two days; but as a general 
rule they remain inflected for a longer period in very weak solutions 
than in water. In solutions which are not extremely weak, they never 
re-expand within nearly so short a period as six or eight hours. From 
these statements it might be thought difficult to distinguish between 
the effects of water and the weaker solutions ; but in truth there is not 
the slightest difficulty until excessively weak solutions are tried ; and 
then the distinction, as might be expected, becomes very doubtful, 
and at last disappears. But as in all, except the simplest, cases the 
state of the leaves simultaneously immersed for an equal length of time 
in water and in the solutions will be described, the reader can judge for 
himself. 



Carbonate of Ammonia. 

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



116 DEOSEEA EOTUNDIFOLIA. [Chap. VII. 

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

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

Minute particles of the carbonate were added to the secre- 
tion surrounding several glands. These instantly became 
black and secreted copiously ; but, except in two instances, 
when extremely minute particles were given, there was no 
inflection. This result is analogous to that which follows- 
i'rom 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. 



CHAr. VII.] CAEBONATE OF AMMONIA. 117 

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

The same- sized drops of a solution of one part to 875 of water were 
placed on the discs of eleven leaves ; six remained quite unafl'ected, 
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 ^^^ of a grain ('0337 
uig.), distributed , between the glands of the disc, but this was too 
small an amount to ]iroduce 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 21S of water, were next tried in the manner above 
described. A drop of this kind equals on an average ^ of a minim, 
and therefore contains -j^q of a grain (•0135 mg.) of the carbonate. 
1 touched with it the viscid secretion round three glands, so that each 
gland received only y^Jgo 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 
[mother 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 yolots °^ ^ grain 
("00337 mg.), yet some of them were a little darkened; but in no one 
instance were any of the tentacles inflected, though they were watched 
for 12 hrs. When a still weaker solution (viz. one part to 437 of 
water) was tried on six glands, no effect whatever was perceptible. 
We thus leain that the Trioo of ^ S™!! ("00445 mg.) of carbonate of 
ammonia, if absorbed by a rfand, suffices to induce inflection in the 
ba.^i>l 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 
lor diffusion and absorption, a much weaker solution would certainly 
have acted. 

Some expeiiments were made by immersing cut-off leaves in 
solutions of different strengths. Thus four leaves were left for about 
3 hrs. each in a drachm (3 "549 c.c.) of a solution of one part of the 
carbonate to 5250 of water ; two of these had almost every tentacle 
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 



118 DEOSEEA EOTUNDIFOLIA. [Chap. Vn. 

all the glands blackened. Six leaves were immersed, each in thirty- 
minims (1 • 774. c.c.) of a solution of one part to[4375 of water, and the 
gknds were all blackened in 31 m. All six leaves exhibited some 
slight inflection, and one was strongly inflected. Pour leaves were 
then immersed in thirty minims of a solution of one part to 8750 of 
water, so that each leaf received the -gig of a grain ('2025 mg.). 
Only one became strongly inflected ; but all the glands on all the 
leaves were of so dark a red after one hour as almost to deserve to be 
called black, whereas this did not occur with the leaves which were at 
the same time immersed in water ; nor did water produce this effect 
on any other occasion in nearly so short a time as an hour. These 
cases of the simultaneous darkening or blackening of the glands from 
the action of weak solutions are important, as they show that all the 
glands absorbed the carbonate within the same time, which fact indeed 
there was not the least reason to doubt. So again, whenever all the 
tentacles become inflected within the same time, we have evidence, as 
before remarked, of simultaneous absorption. I did not count the 
number of glands on these four leaves ; but as they were fine ones, 
and as we know that the average number of glands on thirty-one 
leaves was 192, we may safely assume that each bore on an average 
at least 170 ; and if so, each blackened gland could have absorbed only 
5^'|oo of * grain ('00119 mg.) of the carbonate. 

A large number of trials had been previously made with solutions of 
one part of the nitrate and phosphate of ammonia to 43750 of water 
(i. e. one grain to 100 ounces), and these were found highly efficient. 
Fourteen leaves were therefore placed, each in thirty minims of a 
solution of one part of the carbonate to the above quantity of water ; so 
that each leaf received ^^Vo "f ^ grain (-0405 mg.). The glands 
were not much darkened. Ten of the leaves were not affected, cr 
only very slightly so. Four, however, were strongly affected ; the first 
having all the tentacles, except forty, inflected in 47 m. ; in 6 hrs. 80 m. 
aU 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-five inflected. Leaves which were 
immersed in water at the same time were not at all affected, with the 
exception of one ; and this not until 8 hrs. had elapsed. Hence there 
can be no doubt that a highly sensitive leaf, if immersed in a solution, 
so that all the glands are able to absorb, is acted on by ysVo "^ * 
grain of the carbonate. Assuming that the leaf, which was a large one, 
and which had all its tentacles excepting eight inflected, bore 170 glandsy 
each gland could have absorbed only ^n^'gpq 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 afiected, this is nearly the minimum dose which is efficient. 
Agyregation of the Protoplasm from the Action of Carbonate of 



Chap. VII.] CARBONATE OF AMMONIA. 119 

Ammonia.— I have fully described in the third chapter the remarkahle 
effects of moderately strong doses of this salt in caiising the aggre- 
gation of the protoplasm within the cells of the glands and tentacles ; 
and here my object is merely to show what small doses suflSoe. A 
leaf was immersed in twenty minims (1 • 183 c.c.) of a solution of one 
part to 1750 of water, and another leaf in the same quantity of a 
solution of one part to 3062 ; in the former case aggregation occurred 
in 4 m., in the latter in 11 m. A leaf was then immersed in twenty 
minims of a solution of one part to 4375 of water, so that it received 
2^ of a grain ( • 27 mg.) ; in 5 m. there was a slight change of colour 
in the glands, and in 15 m. small spheres of protoplasm were formed in 
the cells beneath the glands of all the tentacles. In these cases there 
could not be a shadow of a doubt about the action of the solution. 

A solution was then made of one part to 5250 of water, and I 
experimented on fourteen leaves, but will give only a few of the cases. 
Eight young leaves were selected and examined with care, and they 
showed no trace of aggregation. Four of these were placed in a 
drachm (3 ■ 549 c.c.) of distilled water ; and four in a similar vessel, 
with a drachm of the solution. After a time the leaves were examined 
under a high power, being taken alternately from the solution and the 
water. The first leaf was taken out of the solution after an immersion 
of 2 hrs. 40 m., and the last leaf out of the water after 3 hrs. 50 m. ; 
the examination lasting for 1 hr. 40 m. In the four leaves out of the 
water there was no trace of aggregation except in one specimen, in 
which a very few extremely minute spheres of protoplasm were present 
beneath some of the round glands. All the glands were translucent 
and red. The four leaves which had been immersed in the solution, 
besides being inflected, presented a widely different appearance ; for 
the contents of the cells of every single tentacle on all four leaves were 
conspicuously aggregated ; the spheres and elongated masses of proto- 
plasm in many cases extending halfway down the tentacles. All the 
glands, both those of the central and exterior tentacles, were opaque 
and blackened; and this shows that all had absorbed some of the 
carbonate. These four leaves were of very nearly the same size, and the 
glands were counted on one and found to be 167. This being the case, 
and the four leaves having been immersed in a drachm of the solution, 
each gland could have received on an average only -b-j-J-js of ^ 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 -g^ 
of a grain (•0675 mg). In 40 m. the glands appeared rather darker; 
and in 1 hr. from four to six spheres of protoplasm were formed in the 
cells beneath the glands of all- the tentacles. I did not count the 
tentacles ; but we may safely assume that there were at least 140; and 
if so, each gland could have received only the xfiSoo °f ^ g™n, or 
•00048 mg. 

A weaker solution was then made of one part to 7000 of water, and 



120 DEOSEEA EOTUNDIFOLIA. [Chap. VII. 

four leaves were immersed in it ; but I will give only one case. A leaf 
was placed in ten minims of tHs solution ; after 1 hr. 37 m. the glands 
became somewhat darker, and the cells beneath all of tliem now 
contained many spheres of aggregated protoplasm. This leaf received 
yjg- of a grain, and bore 166 glands, liaoh gland could, therefore, have 
received only ^^,1^^^ of a grain ( ■ 000507 mg.) of the carbonate. 

Two other experiments are worth giving. A leaf was immersed for 
4 hrs. 15 m. in distilled water, and there was no aggregation ; it was 
then placed for 1 hr. 15 m. in a little solution of one part to 5250 of 
water; and this excited welf-marked aggregation and inflection. 
Another leaf, after having been immersed for 21 hrs. 15 rii. ia 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 mnny 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 tlie 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 tliey were 
immersed in the solution; for the process of aggregation seems in- 
variably to supervene slowly and very gradually in water. 

Summary of the Besults with Carbonate of Ammonia.- — The 
roots absorb the solution, as showrn 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 (-0291) c.c), containing -g^ of 
a grain ('OtiTS mg.), transmit a motor impulse to the exterior 
tentacles, causing them to bend invrards. A minute drop, 
containing t^^tht o^ ^ grain (-00445 mg.), if held for a few 
seconds in contact with a gland, soon causes the tentacle 
bearing it to be inflected. If a leaf is left immersed for a few 
hours in a solution, and a gland absorbs the ysAinr °^ ^ grain 
(•00048 mg.), its colour becomes darker, though not actually 
black ; and the contents of the cells beneath the gland are 
jjlainly aggregated. Lastly, under the same circumstances, 
the absorption by a gland of the ^TrsVinr "^ ^ grain (-00024 
mg.) suffices to excite the tentacle bearing this gland into 
movement. 

Nitrate of Ammonia. 

With this salt I attended only to the inflection of the leaves, for it is 
far less efficient than the carbonate in causing aggregation, although 
considerably more potent in causing inflection. I experimented with 



.Chap. VII.] NITRATE OF AMMONIA. 121 

half-minims ("0296 c.c.) on the discs of fifty-two leaves, but will give 
only a few cases. A solution of one part to 109 of water was too strong, 
causing little inflection, nnd after 24 hrs. killing, or nearly killing, 
lour out of six leaves v/hich were thus tried ; each of which received 
tlie -j-J^ of a grain (or '27 mg.). A solution of one part to 218 of 
water acted most energetically, causing not only the tentacles of all the 
leaves, but the blades of some to be strongly inflected. I'ourteen leaves 
were tried with dropsof asolutionofonepartto875 of water, so that the 
<lis3 of each received the ysVs °^ ^ grain ("OSST mg.). Of these leaves, 
seven were very strongly acted on, the edges being generally inflected ; 
two were moderately acted on ; and five not at all. I subsequently tried 
three of these latter five leaves with urine, saliva, and mucus, but they 
were only slightly affected ; and this proves that they were not in an 
active condition. I mention this fact to show how necessary it is to 
e.speriment on several leaves. Two of the leaves, which were well 
inllected, re-expanded after 51 hrs. 

In the following experiment I happened to select very sensitive 
leaves. Half-minims of a solution of one part to 1094 of water (i.e. 
1 gr. to 2i oz.) were placed on the discs of nine leaves, so that each 
received the 2-j"og of a grain ("027 mg.). Three of them had their 
tentacles strongly inflected and their blades curled inwards; five were 
slightly and somewhat doubtfully affected, having from three to eight 
of their exterior tentacles inflected ; one leaf was not at all affected, 
yet was afterwards acted on by saliva. In six of these cases, a trace of 
action was perceptible in 7 hrs., but the full effect was not produced until 
fiom 24 hrs. to 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 to 1312 
of water (1 gr. to 3 oz.) were tried on fourteen leaves ; so that each 
received -^-^^ of a grain (■022.5 mg.), instead of, as in the last experi- 
ment, -g-^^ of a grain. The blade of one was plainly inflected, 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 
live 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 afi'ected, yet three of 
them, when subsequently tried with urine, became greatly inflected. 
In most of these cases a slight effect was perceptible in from 6 hrs. to 
7 hrs., but the full effect was not produced until from 24 hrs. to 30 
Jirs. had elapsed. It is obvious that we have reached very nearly the 
minimum amount, which, distributed between the glands of the disc, 
acts on the exterior tentacles ; these having themselves not received 
any of the solution. 

In the next place, the viscid secretion round three of the exterior 
g'ands was touched with the same little drop (-jV of a minim) of a 
solution of one part to 437 of water; and after an interval of 2 hrs. 
£0 m. all three tentacles were well inflected. Each of these glands 



122 DEOSEEA KOTUNDIFOLIA. [Chap. VII. 

could have received only tlie ttboo °^ ^ 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, wliilst the other two never 
moved. We here see, as in the case of the half-minims placed on 
the discs, that the nitrate of ammonia is more potent in causing 
inflection than the carbonate; for minute drops of the latter salt 
of this strength produced no effect. I tried minute drops of a still 
weaker solution of the nitrate, viz. one part to 875 of water, on 
twenty-one glands, but no eflect whatever was produced, except 
perhaps in one instance. 

Sixty-three leaves were immersed in solutions of various strengths ; 
other leaves being immersed at the same time in the same pure water 
used in making the solutions. The results are so remarkable, though 
less so than with phosphate of ammonia, that I must describe the 
experiments in detail, but I will give only a few. In speaking of the 
successive periods when inflection occurred, I always reckon from the 
time of first immersion. 

Having made some preliminary trials as a guide, five leaves were 
placed in the same little vessel in thirty minims of a solution of one 
part of the nitrate to 7875 of water (1 gr. to 18 oz.) ; and this amount 
of fluid just sufficed to cover them. After 2 hrs. 10 m. three of the 
leaves were considerably inflected, and the other two moderately. The 
glands of all became of so dark a red as almost to deserve to be called 
black. After 8 hrs. four of the leaves had all their tentacles more or 
less inflected ; whilst the fifth, which I then perceived to be an old 
leaf, had only thirty tentacles inflected. Next morning, after 23 hrs. 
40 m., all the leaves were in the same state, excepting that the old 
leaf had a few more tentacles inflected. Five leaves which bad 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 
ronnd-headed tentacles, inflected. After 8 hrs. there was no chanae 
in these leaves, and alter 24 hrs. all the marginal tentacles had re- 
expanded; but in one leaf, -a dozen, and in a second leaf, half a dozen, 
submarginal tentacles had become inflected. As the glands of the 
five leaves in the solution were simultaneously darkened, no doubt 
they had all absorbed a nearly equal amount of the salt: and as j-Jg- 
of a grain was given to the five leaves together, each got -j^o of a 
grain ( '045 mg.). I did not count the tentacles on these leaves, which 
were moderately fine ones, but as the average number on thirty-one 
leaves was 192, it would be sate to assume that each bore on an average 
at least 160. If so, each of the darkened glands could have received 
only -jaoVoo °f 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, more- 
over, must often touch one another or the sides of the vessel, and 



Chap. VU.] NITRATE OF AMMONIA. 123 

itiovement may have been thus excited ; but the corresponding leaves- 
in water, which were little inflected, though rather more so than 
commonly occurs, were exposed in an almost equal degree to these 
same sources of error. I will, therefore, give only one other experiment 
made m this manner, though many were tried and all confirmed tlicf 
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 ^^^ of a grain (•05(12 mg.). 
After 1 hr. 20 m. many of the tentacles on all four leaves wer& 
somewhat inflected. After 5 hrs. 30 m. two leaves had all their 
tentacles inflected; a third leaf all except the extreme marginals, 
which seemed old and torpid ; and the fourth a large number. After 
21 hrs. every .single tentacle, on all four leaves, was closely inflected. 
Of the four leaves placed at the same time in water, one had, after 
5 hrs. 45 m., five marginal tentacles inflected ; a second, ten ; a third, 
nine marginals and submarginals ; and the fourth, twelve, chiefly sub- 
marginals, inflected. After 21 hrs. all these marginal tentacles re- 
expanded, but a few of the submarginals on two of the leaves remained 
slightly curved inwards. The contrast was wonderfully great between 
these four leaves in water and those in the solution, the latter having 
every one of their tentacles closely inflected. Making the moderate 
assinnption that each of these leaves bore 160 tentacles, each gland 
could have absorbed only i ^^^ ./p of a grain ('OOOSSl mg.). This ex- 
periment was repeated on three leaves with the same relative amount 
of the solution ; and after 6 hrs. 15 m. all the tentacles except nine, 
on all three leaves taken together, were closely inflected. In this ca'-.e 
the tentacles on each leaf were counted, and gave an average of 1C2 
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 c.c.) of the solution; other leaves being 
treated in exactly the same manner with the doubly distilled water 
used in making the solutions. The trials above given were made 
several years before, and when I read over my notes, I could not believe 
in the results ; so I resolved to begin again with moderately strong 
solutions. Six leaves were first immersed, each in thirty minims of 
a solution of one part of the nitrate to 8750 of water (1 gr. to 20 oz.), 
so that each received 3^ of a grain (•2025 mg.). Before 30 m. had 
elapsed, four of these leaves were immensely, and two of them moder- 
ately, inflected. The glands were rendered of a dark red. The ' four 
corresponding leaves in water were not at all affected until 6 hrs. 
had elapsed, and then only the short tentacles on the borders of the 
disc ; and their inflection, as previously explained, is never of any 
significance. 

Four leaves were immersed, each in thirty minims of a solution of 
one part to 17,500 of water (1 gr. to 40 oz.), so that each received -^^ 
of a grain (•lOl mg.) ; and in less than 45 m. three of them had all 
their tentacles, ex'cept from four to ten, inflected; the blade of or.6 



124 DKOSERA EOTDNDIFOLIA. [Chap. VII. 

beiug inflected after C hrs., and the blade of a second after 21 hrs. 
The fourth leaf was not at all affected. The glands of none wore 
darkened. Of the corresponding leaves in water, only onp 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 
Tern °f ^ grain ( ■ 0405 mg.). Of these, one was much inflected in 8 m., 
and after 2 hr.s. 7 m. had all the tentacles, except thirteen, inflected. 
The second leaf, alter 10 m., had all except three inflected. The third 
and fourth were hardly at all affected, scarcely more than the cor- 
responding leaves in water. Of the latter, only one was affected, this 
having two tentacles inflected, with those on the outer parts of the 
disc forxning a ring in tlie usual manner. In the leaf which had all 
its tentaclts except thi'ee inflected in 10 m., each gland (assuming 
th^t the leaf bore 160 tentacles) could have absorbed only ^^^\oq of 
a grain, or "000258 mg. 

Four leaves were separately imniorsed as before in a solution of one 
part to 131,250 of water (1 gr. to yOO oz.), so that each received -jg^ 
of a grain, or •0135 mg. After 50 m. one leaf had all its tentacles 
except sixteen, and after 8 hrs. 20 m. all but fourteen, inflected. The 
second leaf, after 40 m , had all but twenty inflected ; and after 8 hrs. 
10 m. began to re-expand. The third, in 3 hrs. had about half its 
tentacles inflected, which began to re-expand after 8 hrs. 15 m. The 
fourth leaf, after 3 hrs. 7 m., had only twenty-nine tentacles more or 
less inflected. Thus three out of the four leaves were strongly acted 
on. It is clear that very sensitive leaves had been accidentally 
selected. The day moreover was hot. The four corresponding leaves 
in water were likewise acted on rather more than is usual ; for after 
3 hrs. one had nine tentacles, another four, and another two, and the 
fourth none, inflected. With respect to the leaf of which all the 
tentacles, except sixteen, were inflected after 50 m., each gland (as- 
suming that the leaf bore 160 tentacles) could have absorbed only 
SaiToo "^ ^ grain ("0000937 mg.), and this appears to be about the 
least quantity of the nitrate which suflioes 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 
oach received only -g-^^ of a grain ( " 0101 mg.). This minute quantity 
produced a slight eflect on only lour of the eight leaves. One had 
fifty-six tentacles inflected after 2 hrs. 13 m.; a second, twenty-six 
inflected, or sub-inflected, after 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 



Chap. VII.] PHOSPHATE OF AMMONIA. 125 

unaffected. Hence, tho Tf^'j^ of a grain given to a sensitive leaf during- 
warm weather perhaps produces a slight effect ; but we must bear in 
mind that occasionally water causes as great an amount of hifleciii n 
as occurred in this last experiment. 

Summary of the Besults with Nitrate of Ammonia. — The 
glands of the disc, when excited hy a half-minim drop 
r0296 c.c), containing Tr^Vir of * grain of the nitrate 
(•027 mg.), transmit a motor impulse to the exterior tentacles, 
causing tnem to bend inwards. A minute drop, containing 
issisTT of a, grain (-00225 mg.), if held for a few seconds in. 
contact with a gland, causes the tentacle bearing this gland 
to be inflected. If a leaf is left immersed for a few hours, 
and sometimes for only a few minutes, in a solution of such 
strength that each gland can absorb only the TruTVinr of * 
grain (-OOOOGS? mg.), this small amount is enough to excite 
each tentacle into movement, and it becomes closely in- 
flected. 

Phosphate of Ammonia. 

This salt is more powerful than the nitrate, even in a 
greater dejijree than the nitrate is more powerful than the car- 
bonate. This is shown by weaker solutions of the phosphate 
acting when dropped on the discs, or applied to the glands of 
the exterior tentacles, or when leaves are immersed. Tho 
difference in the power of these three salts, as tried in three 
different ways, supports the results presently to be given^ 
which are so surprising that their credibility requires every 
kind of support. In 1872 1 experimented on twelve immersed 
leaves, giving each only ten minims of a solution : but this- 
was a bad method, for so small a quantity hardly covered 
them. None of these experiments will, therefore, be given, 
though they indicate that excessively minute doses ^ are 
efficient. When I read over my notes, in 1873, I entirely 
disbelieved them, and determined to make another set of 
experiments with scrupulous care, on the same plan as those 
made with the nitrate ; namely by placing leaves in watch 
glasses, and pouring over each thirty minims of the solution 
under trial, treating at the same time and in the 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 



126 DROSEHA EOTUNDIFOLIA. [Chap. YII, 

in water. Notwitlistanding the care taken and the number of 
the trials made, when in the following year I looked merely 
at the results, without reading over my observations, I again 
thought that there must have been some error, and thirty-five 
fresh trials were made with the weakest solution ; but the 
results were as plainly marked as before. Altogether, 106 
carefully selected leaves were tried, both in water and in 
solutions of the phosphate. Hence, after the most anxious 
consideration, I can entertain no doubt of the substantial 
accuracy of my results. 

Before giving my experiments, it may be well to premise that 
crystallised phosphate of ammonia, such as I used, contains 35 "SB 
iper cent, of water of crystallisation; so that in all the following 
trials tlie efficient elements formed only 64 -67 per cent, of the 
salt used. 

Extremely minute particles of the dry phosphate were placed with 
the point of a needle on the secretion surrounding several glands. 
These poured forth much secretion, were blackened, and ultimately 
died ; hut 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 tlie 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 
he much curved inwards in 2 hrs. 15 m. Similar drops of a solution 
of one part to 1312 of water (1 gr. to 3 oz.) were then placed on the 
Jiscs of five leaves, so that each received the •jaVo °f ^ 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 
luUy 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 
3-J55 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 
iSlightly 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 
hegunto re-expand. We thus see that with the more sensitive leaves 
the 3g'^p of a grain, absorbed by the central glands, is enough to make 
many of the exterior tentacles and the blades bend, whereas the xAo 
of a grain of the carbonate similarly given produced no effect ; and 
•j-g'g^ of a grain of the nitrate was only just sufficient to produce a well- 
marked effect. 

A minute drop, about equal to ^ of a minim, of a solution of one 



Chap. VII.] PHOSPHATE OF AMMONIA. 127 

part of the phosphate to 875 of water, was applied to the secretion on 
three glands, each of which thus received only -g^^ of a grain ( • 00112 
rig.), 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 heing applied to four glands on the same leaf. 
On the first leaf three of the tentacles became slightly inflected iu 6 m., 
and re-expanded after 8 hrs. 45 m. On the second, two tentacles 
tecame sub-inflected in 12 m. And on the third all four tentacles 
were decidedly inflected in 12m.; they remained so for 8 hrs. 30 m., 
but by the next morning were fully re-expanded. In this latter case 
each gland could have received only the ttsVoo (P^ '000563 mg.) of a 
grain. Lastly, similar drops of a solution of one part to 1750 of 
water (1 gr. to i 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 
infiected ; whilst on the fifth, which happened to be a very sensitive 
one, all four tentacles were plainly inflected in 6 hrs. 15 m. ; but only 
one remained inflected after 24 hrs. I should, however, state that in 
this case an unusually large drop adhered to the head of the pin. 
Each of these glands could have received very little more than i^^^gg 
of a grain (or •0004:23); but this small quantity sufficed to cause 
inflection. We must bear in mind that these drops were applied to 
the viscid secretion for only from 10 to 15 seconds, and we have 
good reason to believe that all the phosphate in the solution would not 
be diffused and absorbed in this time. We have seen under the same 
circumstances that the absorption by a gland of Ywkoo of ^ grain of the 
carbonate, and of ■^yo'So "f S. grain of the nitrate, did not cause the 
tentacle bearing the gland in question to be inflected; so that here 
again the phosphate is much more powerful than the other two salts. 

We will now turn to the 106 experiments with immersed leaves. 
Having ascertained by repeated trials that moderately strong solutions 
were highly efficient, I commenced with sixteen leaves, each placed in 
thirty minims of a solution of one part to 43,750 of water (1 gr. to 100 
oz.) ; so that each received -j-boo °^ ^ 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 corre- 
sponding leaves in water, one had nine tentacles, another six, and two 
others two tentacles inflected, in the course of 5 hrs. So that the 
contrast in appearance between the two lots was extremely great. 

Eighteen leaves were immersed, each in thirty minims of a solution 
of one part to 87,500 of water (1 gr. to 200 oz.), so that each received 
^3^5^ of a grain (-0202 mg.). Fourteen of these were strongly 
inflected within 2 hrs., and some of them within 15 m.; three out of 



128 DEOSEEA EOTUNDIFOLIA. [Chap. VII. 

the eighteen were only slightly affected, having twenty-one, nineteen, 
and twelve tentacles inflected; and one was not at all acted on. By 
an accident only fifteen, instead of eighteen leaves were immersed at 
the same time in water; these were observed for 24 hrs. ; one had six, 
another four, and a third two, of their outer tentacles inflected ; the 
remainder being quite unaffected. 

The next experiment was tried under very favourable circumstances, 
for the day (July 8) was very warm, and I hajipened to have 
unusually fine leaves. Five were immersed as before in a solution of 
one part to 131,250 of water (1 gr. to 300 oz.), so that each received 
•jgij^ ofa grain, or "0135 mg. After an immersion of 25 m. all flve leaves 
were mucli inflected. After 1 hr. 25 m. one leaf had all but eight 
tentacles inflected ; the second, all but three ; the third, all but five ; 
the fourth, all but twenty-three ; the fifth, on the other hand, never 
had more than twenty-four inflected. Of the corresponding five leaves 
in water, one had seven, a second two, a third ten, a fourth one, and a 
fifth none inflected. Let it be observed what a contrast is presented 
between these latter leaves and those in the solution. I counted the 
glands on the second leaf in the solution, and the number was 217 ; 
assuming that the three tentacles which did not become inflected 
absorbed nothing, we find that each of the 214 remaining glands could 
have absorbed only io27' ' 2oo °^ ^ graifj or '0000631 mg. The third 
leaf bore 236 glands, and subtracting the five which did not become 
inflected, each of the remaining 231 glands could have absorbed only 
TToBBoo °f ^ grain (or '0000584 mg.), and this amount suflSced to 
cause the tentacles to bend. 

Twelve leaves were tried as before in a solntion of one part to 
175,000 of water (1 gr. to 400 oz.), so that each leaf received -g-^^g of a 
grain ("0101 mg.). My plants were not at the time in a good state, 
and many of the leaves were young and pale. Nevertheless, two of 
them had all their tentacles, except three or four, closely inflected in 
under 1 hr. Seven were considerably affected, some within 1 hr., and 
others not until 3 hrs., 4 hrs. 30 m., and 8 hrs. had elapsed ; and this 
slow action may be attributed to the leaves being young and pale. 
Of these nine leaves, four had their blades well inflected, and a fiflh 
slightly so. The three remaining leaves were not afi'ected. 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 outtr 
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 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 ttoisoo> ^^^ °o ^^^ other leaf only ■j:jyi(iog 
of a grain of the phosphate. 



CHAf. VII.] PHOSPHATE OF AMMONIA. 129 

Twenty leaves were immersed in the usual manner, each in thirty 
minims of a solution of one part to 218,750 of water (1 gr. to 500 oz.). 
So many leaves were tried because I was then under the false im- 
pression that it was incredible that any weaker solution could produce 
an effect. Bach leaf received -5^5^ of a grain, or '0081 mg. 'J'he first 
eight leaves which I tried both in the solution and water were either 
young and pale or too old ; and the weather was not hot. They were 
hardly at all affected; nevertlieless, it would be unfair to exclude 
them. I then waited until I had got eight pairs of fine leaves, and the 
weather was favourable, the temperature of the room where the leaves 
were immersed varying from 75° to 81° (2;-!°-8 to 27°-2 Cent.). In 
another trial with lour jiairs (included in the above twenty pairs), the 
temperature in my room was rather low, about 60° (15°'5 Cent.) ; but 
the plants had been kept for several days in a very warm greenhouse 
and thus rendered extremely sensitive. Special precautions were 
taken for this set of experiments ; a chemist weighed tV>r me a grain in 
an excellent balance ; and fresh water, piven me by Professor Frank- 
land, was carefully measured. The leaves were selected from a large 
number of plants in the followinj; manner : the four finest were 
immersed in water, and tiie next four finest in the solution, and so on 
till the twenty pairs wore complete. The water specimens were thus a 
little favoured, but they did not undergo more inflection than in the 
previous cases, comparatively with those in the solution. 

Of the twenty leaves in the solution, eleven became inflected within 
40 m. ; eight of tliem plainly and three rather doubtfully ; but the 
latter had at least twenty of their outer tentacles inflected. Owing to 
the weakness of the solution, inflection oocurred, except in No. 1, 
much more slowly than in the previous trials. I'he condition of the 
eleven leaves which were considerably inflected will now be given at 
stated intervals, always reckoning from the time of immersion : — 

(1) After only 8 m. a large number of tentacles inflected, and after 

17 m. all but fifteen ; after 2 hrs. all but eight inflected, or plainly 
sub-inflected. After 4 hrs. the tentacles began to re- expand, and such 
prompt re-expansion is unusual ; after 7 hrs. 30 m. they were almost 
fully re-expanded. 

(2) After 39 m. a largo number of lenlacles inflected; after 2 hrs, 

18 m. all but twenty-five inflected ; after i 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 hi's. 13 m. fully half the 
tentacles inflected ; after 23 hrs. still shghtly 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. 



130 DEOSEEA EOTUNDIFOLIA. [Chap. VII. 

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

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

(9) After 38 m. forty-two tentacles inflected ; after 3 hrs. I'A m. 
sixty-six inflected or sub-infleoted ; 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; afier 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 ; alter 24 hrs. every tentacle 
slightly curved inwards ; after 27 hrs. 40 m. blade strongly inflected, 
and so continued for two days, and then the tentacles and blade very 
slowly re-expanded. 

(11) This fine dark red and rather old leaf, though not very large, 
bore an extraordinary number of tentacles (viz. 252), and behaved in 
an anomalous manner. After 6 hrs. 40 m. only the short tentacles 
round the outer part of the disc were inflected, forming a ring as so 
often occurs in from 8 to 24 hrs. with leaves both in water and the weaker 
solutions. But after 9 hrs. 40 m. all the outer tentacles except 
twenty-five were inflected, as was the blade in a strongly marked 
manner. After 24 hrs. every tentncle 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) weie still somewhat inflected after three 
days. The tentacles in but few of these eleven leaves became closely 
inflected within so short a time as in the previous experiments with 
stronger solutions. 

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 contrast between the twenty leaves in 
water and the twenty in the solution was very great, both within the 
first hour and after from 8 to 12 hrs. had elapsed. 

Of the leaves in the solution, the glands on leaf No. 1, which in 2 
hrs. had all its tentacles except eight inflected, were counted and found 
to be 202. Subtracting the eight, each gland could have received only 
the -isriooo °f ^ 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 ytj— Jpoo o^ ''■ S^^^j 



CiiAP. YII.] PHOSPHATE OF AMMONIA. 131 

or -0000387 mg. Lastly, leaf No. 11, which had after 24 hrs. all its 
tentacles, except one, closely inflected, as well as the blade, bore the 
unusually large number of 252 tentacles ; and, on the same principle 
as before, each gland could have absorbed only the -^ oosooo °^ ^ grain, 
or -0000322 mg. 

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

Four leaves were immersed as before, each in thirty minims of a 
solution of one part to 328,125 of water (1 gr. to 750 oz.). Each leaf 
thus received y¥ooo "^ * S''^'™ ("0054: mg.) of the salt; and all four 
were greatly inflected. 

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

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

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

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

Of the four corresponding leaves in water : — 

(1) After 1 hr. forty-five tentacles inflected ; but after 7 lirs. so 
many bad 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 ^^jipm, of a grain (-0000268 mg.) and of No. 2 only 
ataooo ' o °^ ^ grain (-0000263 mg.) of the phosphate. 

Seven leaves were immersed, each in thirty minims of a solution of 
one part to 437,500 of water (1 gr. to 1000 ok.). Each leaf thus 
received ^^ooo '^^^ grain (-00405 mg.). The day was warm, and the 
leaves were very fine, so that all cirormistances were favourable. 

(1) After 30 m. all the outer tentacles except five infiected, and 

K 2 



182 DEOSERA EOTUKDIFOLIA. [Chap. VII. 

most of them closely ; after 1 hr. blade slightly inflected ; after 9 hrs. 
30 m. began to re-expand. 

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

(3) After 1 hr. all but twelve tentacles inflected ; after 2 hrs. 30 m. 
all but nine inflected ; and of the inflected tentacles all excepting four 
closely ; blade slightly inflected. After 8 hrs. blade quite doubled up, 
and now all the tentacles excepting eight closely inflected. The leaf 
remained in this state for two days. 

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

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

(6) After 1 hr. thirty-six tentacles inflected; after 5 hrs. all but 
flfty-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 obsei-ved for 24 hrs.y 
excepting the short tentacles on. the borders of the disc, which as usual 
formed a ring. 

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

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



Chap. VII.] PHOSPHATE OF AMMONIA. 133 

more affected after 12 hrs. than ihe fonr corresponding ones in 
water; but after 24 hrs. they were slightly more iuflected. Such 
evidence, however, is not at all trustworthy. 

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

(1) This was a pale leaf; after 40 m. about thirty-eight tentacles 
inflected ; after 3 hrs. 30 m. the blade and many of the outer tentacles 
inflected; after 10 hrs. 15 m. all the tentacles hut 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 suh-inflected. 

(2) After 1 hr. 40 m. twenty-five tentacles inflected ; after 6 hrs. sdl 
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; alter 24 hrs. re-expanded. 

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

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

With respect to the twelve corresponding leaves in water, (1) had, 
after 1 hr. 35 m., fifty tentacles inflected, but after 11 hrs. only twenty- 
two remained so, and these formed a group, with the blade at this 
point sli.iihtly inflected. It appeared as if this leaf had been in some 
manner accidentally excited, for instance by a particle of animal matter 
which was dissolved by the water. (2) After 1 hr. 45 m. thirty-two 
tentacles inflected, but after 5 hrs. 30 m. only twenty-five inflected, 
and these after 10 hrs. all re-expanded; (3) after 1 hr. twenty- five 
inflected, which after 10 hrs. 20 m. were all re-expanded ; (4) and (5) 
after 1 hr. 35 m. six and seven tentacles inflected, which re-expanded 
after 11 hrs. ; (6), (7) and (8) from one to three inflected, which soon 
re-expanded ; (9), (10), (11) and (12) none inflected, though observed 
for 24 hrs. 

Comparing the states of the twelve leaves in water with those in the 
solution, there cotold be no doubt that in the latter a larger number of 
tentacles were inflected, and these to a greater degree; but the evidencfi 
was by no means so clear as in the former experiments with stronger 
solutions. It deserves attention that the inflection of four of the leaves 



134 DEOSEEA EOTUNDIFOLIA. [Ohap. VII. 

in the solution went on increasing during the fii'st 6 hra., and with 
some of them for a longer time ; whereas in the water the inflection of 
the three leaves which were the most affected, as well as of all the 
others, began to decrease during this same interval. It is also re- 
markable that the blades of three of the leaves in the solution were 
slightly inflected, and this is a most rare event with leaves in water, 
though it occurred to a slight extent in one (No. 1), which seemed to 
have been in some maimer accidentally excited. All this shows that 
the solution produced some effect, though less and at a much slower 
rate than in the previous oases. The small effect produced may, 
however, be accounted for in large part by the majority of the leaves 
having been in a poor condition. 

Of the leaves in the sobition. No. 1 bore 200 glands and received 
Tsooo o^ ''' grain of the salt. Subtracting the seventeen tentacles 
which were not inflected, each gland could have absorbed only the 
);,(,|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 21,875,000 of water 1 gr. to 5000 
oz.). Bach leaf thus received ,.^1^0 of a grain of the salt, or • 00081 
mg. I tooii; especial pains in selecting the finest leaves from the hot- 
house for immersion, both in the solution and the water, and almost all 
j)roved extremely sensitive. Beginning as before with those in the 
solution : — 

(1) After 2 hrs. 30 m. all the tentacles but twenty-two inflected, 
but some only sub-inflected ; the blade much inflected ; after G hrs.. 
30 m. all but thirteen inflected, with the blade immensely inflected ;, 
and remained so for 48 hrs. 

(2) No change for the first 12 hrs., but after 24 hrs. all the ten- 
tacles inflected, excepting those of the outermost row, of which only 
eleven were inflected. The inflection continued to increase, and after 
48 hrs. all the tentacles except three were inflected, and most of them 
rather closely, four or five being only sub-inflected. 

(3) No change for the first 12 hrs. ; but after 24 hrs. all the 
tentacles excepting those of the outermost row were sub-inflected, 
with the blade inflected. After 36 hrs. blade strongly inflected, with 
all the tentacles, except three, inflected or sub-inflected. After 48- 
hrs. in the same state. 

(4) to (8) These leaves, after 2 hrs. 30 m., had respectively 32, 17, 
7, 4, and 0, tentacles inflected, most of which, after a few hours, re- 
expanded, with the exception of No. 4, which retained its thirty-two- 
tentacles inflected for 48 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 occvu:red, namely, the whola 



Chap. VII.] rilOSPHATE OF AMMONIA. 135 

blade became slightly bowed towards the footstalk, and so remained 
for 48 hrs. The exterior tentacles, excepting those of the three or 
four outermost rows, were now also inflected to an unusual degree. 

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

\¥hen the two lots of eight leaves in the solution and in the water 
were compared after the lapse of 24 hrs., they undoubtedly differed 
much in appearance. The few tentacles on the leaves in water which 
were inflected had after this interval re-expanded, with the exception 
of one leaf; and this presented the very unusual case of the blade 
being somewhat inflected, though in a degree hardly approaching that 
of the two leaves in the solution. Of these latter leaves. No. 1 had 
almost all its tentacles, together with its blade, inflected after an 
immersion of 2 hrs. 30 m. Leaves No. 2 and 3 were afi'eoted at a 
much slower rate ; but after from 24 hrs. to 48 hrs. almost all their 
tentacles were closely inflected, and the blade of one quite doubled up. 
We must therefore admit, incredible as the fact may at first appear, 
that this extremly weak solution acted on the more sensitive leaves ; 
each of which received only the -jfoooo °^ * 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 
tlis TiooWoo o'' ^ g™™> °^ "00000403 mg. Leaf No. 1, which was 
strongly acted on within 2 hrs. 30 m., and had all its outer tentacles, 
except thirteen, inflected within 6 hrs. 30 m., bore 260 tentacles ; and, 
on the same principle as before, each gland could have absorbed only 
TroTaoSoo of ^ grain, or '00000328 mg. ; and this excessively minute 
amount sufficed to cause all the tentacles bearing these glands to be 
greatly inflected. The blade was also inflected. 

Summary of the Results with Phosphate of Ammonia. — The 
glands of ilie disc, when excited by a half-minim drop (-0296 
CO.), containing ^^^^ 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 TTBVinr 
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 s 7 c'o o o u o^ * 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. 



136 DROSEEA BOTUNDIFOLIA. [Chap. VII. 

Sulphate of Ammonia. — The few trials made with this and the 
following five salts of ammonia were undertaken merely to asoertaia 
whether they induced inflection. Half-minims of a solution of one 
part of the sulphate of ammonia to 437 of water were placed on the 
discs of seven leaves, so that each received -g^-^ of a o:rain, or • 0675 
mg. After 1 hr. the tentacles of fi\'e of them, as well as the blade 
of one, were strongly inflected. The leaves were not afterwards 
observed. 

Citrate of Ammonia. — Half-minims of a solution of one part to 437 
of water were placed on the discs of six leaves. In 1 hr. the short 
outer tentacles round the discs weie a little inflected, with the glands 
on the discs blackened. Alter 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 subniargiual tentacles, 
however, becoming more arid 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. '1 he glands on the discs of the 
above leaves, instead of being almost black, as after the first hour, 
were now, after 23 hrs., very pale. I next tried on four leaves half- 
minims of a weaker solution, of one part to 1312 of water (1 grain to 3 
oz.) ; so that each received j-g^g-g of a grain ('0225 mg.). After 2 hrs. 
18 m. the glands on the disc were very dark-coloured ; after 24 hrs. 
two of the leaves were sli;ihtly affected; the other two not at all. 

Acetate if 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, wliich, after 7 hrs., became 
'moderately, and after 23 hrs. strongly, inflected. 1'wo other leaves 
were tried with a weal;er solution of one part to 437 of water ; one 
was strongly inflected in 7 hrs. ; the other not until 30 hrs. had 
elapsed. 

Tartrate of Ammonia. — Half-minims of a solution of one part to 
437 of water were placed on the discs of five leaves. In 31 m. there 
was a trace of inflection in the exterior tentacles of some of the leaves, 
and this became more decided after 1 hr. with all the leaves ; hut 
the tentacles were never closely inflected. After 8 hrs. 30 m. they 
began to re-expand. Next morning, after 23 hrs., all were fully re- 
expanded, excepting one which was still slightly inflected. The 
shortness of the period of inflection in this and the following case is 
remarkable. 

Chloride of Ammonia. — 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 liours, but never 



Ciur. VII.] 



OTHEK SALTS OF AMMONIA. 



137 



Lccamo strongly marked. After only 8 hrs. 30 m. the tentacles bepan 
to re-expand, and by the next morning, after 24 hrs., were fully 
le-expanded on four of the leaves, but still slightly inflected oa two. 

General Summary and Concluding JRemarJcs on the Salts of 
Ammonia. — We have now seen that the nine salts of ammonia 
which were tried all cause the inflection of the tentacles, 
and often of the blade of the leaf. As far as can be ascer- 
tained from the superficial trials with the last six salts, the 
citrate is the least powerful, and the phosphate certainly by 
far the most. The tartrate and chloride are remarkable from 
the short duration of their action. The relative efficiency of 
the carbonate, nitrate, and phosphate, is shown in the fol- 
lowing table by the smallest amount which suffices to cause 
the inflection of the tentacles. 



Sulutlons. how applied. 



Carbonate of 
Ammonia. 



Nitrate of 
Ammonia. 



Phosphate of 
Ammonia. 



Placed on the glands of the 
disc, su as to act indirectly 
on the outer tentacles 

Applied for a few seconds] 
directly to the gland of an 
outer tentacle ... . | 

Leaf immersed, with time 
allowed for each gland to 
absorb all that it can . 

Amount absorbed by a glandl 
which suffices to cause the 
aggregation of the proto- 
plasm in the adjoining! 
cells of the tentacles . 



m of a 
grain, or 
■ 0675 ma;. 



n4i!ii°f<i 

grain, or 

•00445 mg. 

mms °f ^ 

grain, or 

•00024 mg. 



TSTOn "f * 
grain, or 
00048 mg. 



■n'lro of a 
grain, or 
•027 mg. 

•SBBijT of •'' 
grain, or 
•0025 mg. 

mms of * 

grain, or 

•0000937 mg. 



3515 of a 
grain, or 
•0169 mg. 

T33531I of a 

grain, or 

•000423 mg. 

T515!i!ilil! of a 

grain, or 
•00000328 mg 



From the experiments tried in these three different ways, 
we see that the carbonate, which contains 2.'5*7 per cent, of 
nitrogen, is less efficient than the nitrate, which contains 35 
per cent. The phosphate contains less nitrogen than either 
of these salts, namely, only 21-2 per cent., and yet is far more 
efficient ; its power, no doubt, depending quite as much on 
the phosphorus as on the nitrogen which it contains. We 
may infer that this is the case, from the energetic manner in 



138 DROSEKA EOTUNDIirOIJA. [Chap. VII. 

whicli bits- of iDOiie and phosphate of lime affect the leaves. 
The inflection excited hy the other salts of ammonia is pro- 
hahly due solely to their nitrogen, — on the same principle that 
nitrogenous organic fluids act powerfully, whilst non-nitro- 
genous organic fluids are powerless. As such minute doses, 
of the salts of ammonia affect the leaves, we may feel almost 
sure that Drosera absorbs and profits by the amount, though 
small, which is present in rain-water, in the same manner as- 
other plants absorb these same salts by their roots. 

The smallness of the doses of the nitrate, and more 
especially of the phosphate of ammonia, which cause the ten- 
tacles of immersed leaves to be inflected, is perhaps the most 
remarkable fact recorded in this volume. When we see that 
much less than the millionth* of a grain of the phosphate, 
absorbed by a gland of one of the exterior tentacles, causes- 
it to bend, it may be thought that the effects of the solution 
on the glands of the disc have been overlooked ; namely, the 
transmission of a motor impulse from them to the exterior 
tentacles. No doubt the movements of the latter are thus, 
aided ; but the aid thus rendered must be insignificant ; for 
we know that a drop containing as much as the ^^fVir °^ ^ 
grain placed on the disc is only just able to cause the outer 
tentacles of a highly sensitive leaf to bend. It is certainly 
a most surprising fact that the i a 7 d'o i) o o "^ * 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 7; s a's 1 2 li 
of a grain, or in round numbers to one-thirty-millionth of a 
grain ("00000216 mg.). The solution, moreover, in these 
experiments was diluted in the proportion of one part of the- 
salt to 2,187,500 of water, or one grain to 5000 oz. The 
reader will perhaps best realise this degree of dilution by 
remembering that 5000 oz. would more than fill a 31-gallon 
cask ; and that to this large body of water one grain of the 
salt was added ; only half a drachm, or thirty minims, of the 
solution being poured over the leaf. Yet this amount 



* It is scarcely possible to realise 4 in. in length, and stretch it along 
what a million means. The best the wall of a large hall ; then mark 
illustration which I have met with is off at one end the tenth of an inch- 
that given by Mr. Croll, who says. This tenth will represent a hundred,. 
— Take a narrow strip of paper S'd ft. and the entire strip a million. 



Chap. VII.] SUMMARY, SALTS OF AMMONIA. 139 

suflSced to cause the inflection of almost every tentacle, and 
often of the hlade 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 ammonia than the most skilful chemist can 
of any substance.* My results were for a long time incredible 
even to myself, and I anxiously sought for every source of 
error. The salt was in some cases weighed for me by a 
chemist in an excellent balance ; and fresh water was measured 
many times with care. The observations were repeated 
during several years. Two of my sons, who were as incre- 
dulous as myself, compared several lots of leaves simultane- 
ously immersed in the weaker solutions and in water, and 
declared that there could be no doubt about the difference in 
their appearance. I hope that some one may hereafter be in- 
duced to repeat my experimenis ; in this case he should select 
young and vigorous leaves, with the glands surrounded by 
abundant secretion. The leaves should be carefully cut off 
and laid gently in watch-glasses, and a measured quantity of 
the solution and of water poured over each. The water used 
must be as absolutely pure as it can be made. It is to be 
especially observed that the experiments with the weaker 
solutions ought to be tried after several days of very warm 
weather. Those with the weakest solutions should be made 
on plants which have been kept for a considerable time in a 
warm greenhouse, or cool hothouse ; but this is by no means 
necessary for trials with solutions of moderate strength. 

I beg the reader to observe that the sensitiveness or irri- 
tability of the tentacles was ascertained by three different 
methods — indirectly by drops placed on the disc, directly by 



* When my first observations were (see Balfour Stewart, ' Treatise on 
made on the nitrate of ammonia, Heat,' 2nd edit. 1871, p. 228). With 
fourteen years ago, the powers of respect to ordinary chemical tests, I 
the spectroscope had not been dis- gather from Dr. Alfred Taylor's 
covered ; and I felt all the greater work on ' Poisons ' that about ^^ of 
interest in the then unrivalled powers a grain of arsenic, jj'jj of a grain of 
of Drosera. Now the spectroscope prussic acid, -^^ of iodine, and ^^ 
has altogether beaten Drosera ; for, of tartarised antimony, can be de- 
according to Bunsen and KirchhofF, tected ; but the power of detection 
probably less than one jjjisjinro "^ "■ depends much on the solutions under 
grain of sodium can be thus detected trial not being extremely weali. 



140 DEOSEEA EOTUNDIFOLIA. [Chap. VII. 

drops applied to the glands of the outer tentacles, and ty the 
immersion of whole leaves ; and it was found hy these three 
methods that the nitrate was more powerful than the car- 
bonate, and the phosphate much more powerful than the 
nitrate ; this result heing intelligible from the difference in 
the amount of nitrogen in the first two salts, and from the 
presence of phosphorus in the third. It may aid the reader's 
faith to turn to the experiments with a solution of one grain 
of the phosphate to 1000 oz. of water, and he will there find 
decisive evidence that the one-four-millionth of a grain is 
sufiicient to cause the inflection of a single tentacle. There 
is, therefore, nothing very improbable in the fifth of this 
weight, or the one-twenty-millionth of a grain, acting on the 
tentacle of a highly sensitive leaf. Again, two of the leaves 
in the solution of one grain to 3000 oz., and three of the 
leaves in the solution of one grain to 5000 oz., were affected, 
not only far more than the leaves tried at the same time in 
water, but incomparably mote than any five leaves which 
can be picked out of the 173 observed by me at different 
times in water. 

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

Astonishing as is this result, there is no sound reason why 
we should reject it as incredible. Prof. 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 atropine, in an extremely diluted 



' Miller's 'Elements of Chemistrj-,' part ii. p. 107, 3i-d edit. 1864, 



CnAi\ VII.] STJMMAKY, SALTS OF AMMONIA. 141 

state, if applied directly to tlie iris of a dog, paralyses the 
muscles of this organ. But, in fact, every time that we 
perceive an odour, we have evidence that infinitely smaller 
particles act on our nerves. When a dog stands a quarter of 
a mile to leeward of a deer or other animal, and perceives its 
presence, the odorous particles produce some change in the 
olfactory nerves; yet these particles must be infinitely 
smaller* than those of the phosphate of ammonia weighing 
the one-twenty-millionth of a grain. These nerves thea 
transmit some influence to the brain of the dog, which leads 
to action on its part. With Drosera, the really marvellous 
fact is, that a plant without any specialised nervous system 
should be affected by such minute particles ; but we have no 
grounds for assuming that other tissues could not be ren- 
dered as exquisitely susceptible to impressions from without, 
if this were beneficial to the organism, as is the nervous 
system of the higher animals. 



* My son, George Darwin, has — that is, from jjjju to tj,'555 of an. 

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

a sphere of phosphate of ammonia object between j'j and ,'7 of the size 

(specific grayity 1'678), weighing of a sphere of the phosphate of 

the one-twenty-milliouth of a grain, ammonia of the above weight can be 

and finds it to be yg',; of an inch. seen under a high power ; and no one 

Now, Dr. Klein informs me that the supposes that odorous particles, such 

smallest Micrococci, which are dis- as those emitted from the deer in the 

tinctly discernible under a power of above illustration, could be seen 

800 diameters, are estimated to be under any power of the microscope, 
from • 0002 to • 0005 of a millimeter 



14-2 DROSEKA EOTUNDIFOLIA. [Chap. VIII. 



CHAPTEE VIII. 

The Effects of various Salts and Acids on the Leaves. 

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

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

Salts causing Inflection. Salts not causing Inflection. 

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

Sodium carhonate, rapid inflection. Potassium carbonate : slowly poison- 

ous. 
Sodium nitrate, rapid inflection. Potassium nitrate : somewhat poison- 

ous. 
Sodium sulphate, moderately rapid Potassium sulphate. 

inflection. 
Sodium phosphate, very rapid in- Potassium phosphate. 

flection. 
Sodium citrate, rapid inflection. Potassium citrate. 

Sodium oxalate, rapid inflection. 
Sodium chloride, moderately rapid Potassium chloride. 

inflection. 
Sodium iodide, rather slow inflection. Potassium iodide, a slight and doubt- 
ful amount of inflection. 
Sodium bromide, moderately rapid Potassium bromide. 

inflection. 
Potassium oxalate, slow and donbtful 

inflection. 



Chap. VIII.] EFFECTS OP VARIOUS SALTS. 



143 



Salts causing Ixflection, 

■(^Arranrjcd in Groups according to the 
' Dictionanj of 

Lithium nitrate, moderately rapid 
inflection. 

OiEsium chloride, rather slow inflec- 
tion. 

Silver nitrate, rapid inflection : quick 
poison. 

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



Salts not causing Inflection. 

C/icmical Classification in WMs' 
Chemistry.*) 

Lithium acetate. 
Uubidium chloride. 



Calcium acetate. 
Calcium nitrate. 

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

Aluminium nitrate, a trace of in- 
flection. 
Aluminium and potassium sulphate. 



Aluminium chloride, slow and doubt- 
ful inflection. 

Gold chloride, rapid inflection ; quick 
poison. 

Tin chloride, slow inflection : poison- 
ous. 

Antimony tartrate, slow inflection : 
probably poisonous. 

Arsenious acid, -quick inflection: poi- 
sonous; • , 

Iron chloride, , slow inflection : pro- 
bably poisonous. 

Chromic acid, quick inflection : highly 
poisonous. 

Copper chloride, rather slow inflec- 
tion : poisonous. 

Nickel chloride, rapid inflection : 
probably poisonous. 

Platinum chloride, rapid inflection : 
poisonous. 

Sodium, Carhonate of (pure, given me by Prof. Hoffmann). — Half- 
minims ('0296 c.c.) of a solution of one part to 218 of water (2 grs. to 
1 oz.) were placed on the discs of twelve leaves. Seven of these 
became well inflected ; three had only two or three of their outer 
tentacles inflected, and the remaining two were quite unaffected. But 



Lead chloride. 



Manganese chloride 



Cobalt chloride 



144 DEOSEEA EOTUNDIFOLIA. [Chap. VIII. 

the dose, though only the -g^ of a grain (-ISS mg.), was evidently 
too strong, for three of the seven well-inflected leaves were killed. Oa 
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 ol' water, or 1 gr. to 
1 oz.), doses of -j^Q of a grain ('0675 mg.) were given to six leaves- 
Some of these were afiected in 37 m. ; and in 8 hrs. the outer tentacles 
of nil, as well as the blades of two, were considerably inflected. After, 
23 hrs. 15 m. the tentacles had almost re-expanded, but. the blades of 
the two were still just perceptibly curved inwards. After 48 hrs. all 
*ix leaves were fully re-expanded, and appeared perfectly healthy. 

Three leaves were immersed, each in thirty minims of a solution of 
one part to 875 of water (1 gr. to 2 oz.), so that each received ^l of a 
grain (2 '02 mg.) ; after 40 ni. the three were much affected, and 
alter G 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. Alter 1 hr. 25 m. the tentacles of nearly all, 
and the blade of one, were somewhat inflected. The inflection 
continued to increase, and in 21 hrs. 15 m. the tentacles and the blades 
of four of them were greatly affected, and the blade of the fifth to a 
slight extent. After an additional 24 hrs. the four leaves still 
remained closely inflected, whilst the fifth was beginning to expand. 
Four days after the solution had been applied, two of the leaves had 
quite, and one had partially, re-expanded ; whilst the remaining two 
remained closely inflected and appeared injured. 

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

Sodium, Sulphate of. — Half-minims of a solution of one part to 437 
of water were placed on the discs of six leaves. After 5 hrs. 30 m. the; 
tentacles of three of them (with the blade of one) were considerably, 
and those of the other three slightly, inflected. After 21 hrs. the 
inflection had a little decreased, and in 45 hrs. the leaves were fully 
expanded, appearing quite healthy. 

Three leaves were immers' d, each in thirty minims of a solution of 
one part of the stilphate 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 [Jaced on the discs of six leaves. The solution acted 
with extraordinary rapidity, lor 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 his., excepting that the blude of a third leas 
became incurved. After 48 hrs. all the leaves re-expanded. It is 



Chav. VIII.] SALTS OF SODITJM. 145 

clear that -^^ of a grain of phosphate of soda has great power in 
causing inflection! 

Sodium, Citrate of. — Half-minims of a solution of one part to 437 of 
water were placed on the discs of six leaves, but these were not 
observed until 22 hrs. had elapsed. Tlie submarginal tentacles of five 
of them, and the bludes 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. 
'J'hree leaves were also immersed, each in thirty minims of a solution 
of one part of the citrate to 875 of water ; they were much acted on in* 
25 m. ; and after 6 hrs. 35 m. almost all the tentacles, including those 
of the outer rows, were inflected, but not the blades. 

Sodium, Oxalate of. — Half-minims of a solution of one part to 437 of 
water were placed on the disc of seven leaves ; after 5 hrs. 30 m. the 
tentacles of all, and the blades of most of them, Avere much affected. 
In 22 hrs., besides the inflection of the tentacles, the blades of all 
seven leaves were so much doubled over that their tips and bases 
almost touched. On no other occasion have I seen the blades so 
strongly affected. Three leaves were also immersed, each in thirty 
minims of a solution of one part to 875 of water ; after 30 m. there 
was much inflection, and after 6 hrs. 35 m. the blades of two and the 
tentacles or all were closely inflected. 

Sodium, Chloride of (best culinary salt). — ^Half-minims of a solution 
of one part to 218 of water were placed on the discs of four leaves. 
Two, apparently, were not at all affected in 48 hrs. ; the third had its 
tentacles slightly inflected ; whilst the fourth had almost all its ten- 
tacles inflected in 24 hrs., and these did not begin to re-expand until 
the fourth day, and were not perfectly expanded on the seventh day. 
I presume that this leaf was injured by the salt. Half-minims of a 
weaker solution, of one part to 437 of water, were then dropped on the 
discs of six leaves, so that each received -g^-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 2o 
hrs. 15 m. all had completely re-expanded, and did not appear in the 
least injured. 

Three leaves were immersed, each in thirty minims of a solution of 
one part to 875 of water, so that each received ^ij of a grain, or 2'02 
m;;. After 1 hr. there was much inflection ; after 8 hrs. 30 ni. 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. -j^ of a grain. They all sdon became 
inflected ; after 48 hrs. they began to re-expand, and appeared quite 
iminjured, though the solution was sufficiently 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 inflected. The other two had 
only their submarginal tentacles inflected ; the outer ones in most of 



146 DEOSERA ROTUNDIFOLIA. [Chap. VIIL 

the leaves being but little affected. After 46 lirs. 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. SO m., 
almost all the tentacles, and the blade of one leaf, were closely in- 
flected. 

Sodium, Bromide of. — Half-minims of a solution of one part to 43T 
of water were placed on six leaves. After 7 hrs. there was some in- 
flection ; after 22 hrs. three of the leaves had their blades and most oiT 
their tentacles inflected; the fourth leaf was very slightly, and the 
fifth and sixth hardly at all, affected. Three leaves were also im- 
mersed, each in thirty minims of a solution of one part to 875 of 
water ; after 40 m. there was some inflection ; after 4 hrs. the tentacles 
of all three leaves and the blades of two were inflected. These leaves- 
were then placed in water, and after 17 hrs. 30 m. two of them were 
almost completely, and the third partially, re-expanded ; so that 
apparently they were not injured. 

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

Potassium, Nitrate of. — Half-minims of a strong solution, of one- 
part to 109 of water (4 grs. to 1 oz. ), were placed on the discs of four 
leaves ; two were much injured, but no inflection ensued. Eight 
leaves were treated in the same manner, with drops of a weaker solu- 
tion, of one part to 218 of water. After 50 hrs. there was no inflection, 
but two of the leaves seemed injured. Five of these leaves were 
subsequently tested with drops of milk and a solution of gelatine on 
their discs, and only one became inflected ; so that the solution of the- 
nitrate of the above strength, acting for 50 hi-s., apparently had injured, 
or paralysed the leaves. Six leaves were then treated in the same 
manner with a still weaker solution, of one part to 437 of water, and 
these, after 48 hrs., were in no way affected, with the exception of 
perhaps a single leaf. Three leaves were next immersed for 25 hrs.v 
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 iiart of carbonate of ammonia to 218 of water ; the glands were 
immediately blackened, and after 1 hr. there was some inflection, and 
the protoplasmic contents of the cells became plainly aggregated- 
This shows that the leaves had not been much injured by their immer- 
sion for 25 hrs. in the nitrate. 



Chap. VIII.] SALTS OF POTASSIUM. 147 

Potassium, Sulphate of. — Tlalf-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 lirs. three remained 
quite unaffected; two seemed injured, and the sixth seemed almost 
dead, with its tentacles inflected. Nevertheless, after two additional 
days, all six leaves recovered. The immersion of thi-ee leaves for 24 
hrs., each in thirty minims of a solution of one part to 875 of water, 
produced no apparent effect. Thej'- were then treated with the same 
solution of carbonate of ammonia, with the same result as in the case 
of the nitrate of potash. 

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

Potassium, 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 immer- 
sion 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 occa- 
sions on the discs of seventeen leaves ; and the results perplexed roe 
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., eacii in 30 minims of a 
solution of one part to 875 of water, and were not in the least affected ; 
but they ought to have been observed for a longer time. 

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. 

Potassium, Iodide of. — Half-minims of a solution of one part to 437 
of water were placed on the discs of seven leaves. In 30 m. one leaf 
had the blade inflected; after some hours three leaves had most of 
their submarginal tentacles moderately inflected ; 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 immersed for 8 hrs. 40 m., each in 30 minims of a solution 
of one part to 875 of water, and were not in the least affected. I do 
not know what to conclude from this conflicting evidence ; but it is 
clear that the iodide of potassium does not generally produce any 
marked effect. 

L 2 



148 DEOSEEA EOTUNDIFOLIA. [Chap. VIII. 

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 
Lad 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 witli 
bits of meat, and after 24 hrs. they became splendidly inflected. 
Three leaves were also immersed for 21 hrs. in 30 minims of a solution 
of one part to 875 of water ; but they were not at all affected, 
excepting that the glands looked rather pale. 

Lithium, Acetate of. — Four leaves were immersed together in a 
vessel containing 120 minims of a solution of one part to 437 of water; 
so that each received, if the leaves absorbed equally, -jig- of a grain. 
After 24 hrs. there was no inflection. I then added, for the sake of 
testing the leaves, some strong solution (viz. 1 gr. to 20 oi., or one 
part to 8750 of water) of phosphate of ammonia, and all four became 
in 30 m. closelj' inflected. 

Lithium, Nitrate of. — Four leaves were immersed, as in the last 
case, in 120 minims of a solution of one part to 437 of water ; after 1 
hr. 30 m. all four were a little, and after 24 hrs. greatly, inflected, I 
then diluted the solution with some water, but they still remained 
somewhat inflected on the third day. 

Ceesium, 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 e.\tremely 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 rc-expandcd. 

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

Silver, Nitrate of. — Three leaves were immersed in ninety minims 
of a solution of one part to 437 of water ; so that each received, as 
before, -^ oi a grain. After 5 m. slight inflection, and after 1 1 m. 
very strong inflection, the glands becoming excessively black; after 
40 m. all the tentacles were closely inflected. After 6 hrs. the leaves 
were taken out of the solution, washed, and placed in water ; but 
next morning they were evidently dead. 

Calcium, Acetate of. — Four leaves were immersed in 120 minims of 
a solution of one part to 437 of water ; after 24 hrs. none of the 
tentacles were inflected, excepting a few where the blade joined the 
petiole ; and this may have been caused by the absorption of the salt 
by the cut-off end of the petiole. I then added some of the solution 
(1 gr. to 20 oz.) of phosphate of ammonia, but this to my surprise 
excited only slight inflection, even after 24 hrs. Hence it would 
appear that the acetate had rendered the leaves torpid. 



Cdap. VIIL] effects OF VAEIOUS SALTS. 149 

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 inflection after 24 hrs. A 
fresh leaf was next put into a mixed solution of the above strengths of 
the nitrate of calcium and phosphate of ammonia, and it became 
closely inflected in between !j 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. — Four leaves were 
immersed in 120 minims of solutions, of one part to 437 of water, of 
each of these three salts ; after 6 hrs. there was no inflection ; but 
after 22 hrs. one of the leaves in the acetate was rather more inflected 
than generally occurs from an immersion for this length of time in 
water. Some of the solution (1 gr. to 20 oz.) of phosphate of ammonia 
was then added to the three solutions. The leaves in the acetate 
mixed with the phosphate underwent some inflection ; and this was 
well pronounced after 24 hrs. Those in the mixed nitrate were 
decidedly inflected in 4 hrs. 30 m., hut the degree of inflection did not 
afterwards much increase ; whereas the four leaves in the mixed 
chloride were greatly inflected in a few minutes, and after 4 hrs. had 
almost every tentacle closely inflected. We thus see that the acetate 
and nitrate of magnesium injure the leaves, or at least prevent the 
subsequent action of phosphate of ammonia ; whereas the chloride has 
no such tendency. 

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

Barium, Acetate of. — Four leaves were immersed in 120 minims of 
a solution of one part to 437 of water, and after 22 hrs. there was no 
inflection, but the glands were blackened. The leaves were then 
placed in a solution (1 gr. to 20 oz.) of phosphate of ammonia, which 
caused after 2H 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. 
'J'he leaves remained in this state for 24 hrs. 

Strontium, Acetate of. — Four leaves, immersed in 120 minims of a 
solution of one part to 437 of water, were not affected in 22 hrt. 
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 



150 DEOSEKA EOTUNDIFOLIA. [Chap. VIII. 

slight inflection,. but not more than sometimes occurs with leaves in 
water. They were then placed in the same solution of phosphate of 
ammonia ; after 8 hrs. three of them were moderately inflected, as 
were all five after 24 hrs. ; but not one was closely inflected. It 
appears that the nitrate of strontium renders the leaves half torpid. 

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

Mercury, Perchloride of. — Three leaves were immersed in ninety 
minims of a solution of one part to 437 of water ; after 22 m. there 
was some slight inflection, which in 48 m. became well pronounced ; 
the glands were now blackened. After 5 hrs. 35 m. all the tentacles 
closely inflected ; after 24 hrs. still 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 afl'ected in 25 hrs. 30 m. 

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

Aluminium, Nitrate of. — Four leaves were immersed in 120 minims 
of a solution of one part to 437 of water ; after 7 hrs. 45 m. there was 
only a trace of inflection ; after 24 hrs. one leaf was moderately 
inflected. The evidence is here again doubtful, as in the case of the 
chloride of aluminium. The leaves were then transferred to the same 
solution as before, of phosptiate of ammonia ; this produced hardly any 
effect in 7 hrs. 30 m. ; but after 25 his. one leaf was pretty closely 
inflected, the three others very slightly, perhaps not more so than 
from water. 

Aluminium and Potassium, Sulphate of (common alum). — Half- 
minims of a solution of the usual strength were placed on the discs of 
nine leaves, but produced no effect. 

Gold, Chloride of. — Seven leaves were immersed in so much of a 
solution of one part to 437 of water that each received 30 minims, 
contaimng --^g of a grain, or 4 '048 mg., of the chloride. There was 
some inflection in 8 m., which became extreme in 45 m. In 3 hrs. the 
surrounding fluid was coloured purple, and the glands were blackened. 
After 6 hrs. the leaves were transferred to water ; next morning they 
were found discoloured and evidently killed. The secretion decomposes 
the chloride very readily ; the glands themselves becoming coated with 



Ohap. VIII.] EFFECTS OF VAKIOUS SALTS. 151 

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 
fi trace of inflection ; the glands were not blackened, and the leaves 
•did not appear injured. They were then transferred to the solution (1 
^r. to 20 oz.) of phosphate of ammonia, and after 24 hrs. two of them 
were somewiiat, the third very little, inflected ; and they thus remained 
for another 24 hrs. 

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

Antimony, Tartrate of. — Three leaves were immersed in ninety 
minims of a solution of one part to 437 of water. After 8 hrs. 30 m. there 
was slight inflection ; after 24 hrs. two of the leaves were closely, and 
the third moderately, inflected; glands not much darkened. The 
leaves were washed and placed in water, but they remained in the same 
state for '48 additional hours. This salt is probably poisonous, but 
acts slowly. 

Arsenious Acid. — A solution of one part to 437 of water; three 
leaves were immersed in ninety minims ; in 25 m. considerable inflec- 
tion ; in 1 hr. great inflection ; glands not discoloured. After 6 hrs. 
the leaves were transferred to water ; next morning they looked fresh, 
but after four days were pale-coloured, had not re-expanded, and were 
■evidently dead. 

Iron, Chloride of. — Three leaves were immersed in ninety minims of 
a solution of one part to 437 of water ; in 8 hrs. no inflection ; but 
after 24 hrs. considerable inflection ; glands blackened ; fluid coloured 
yellow, with floating flocculent particles of oxide of iron. The leaves 
were then placed in water ; after 48 hrs. they had re-expanded a very 
little, but I think were killed ; glands excessively black. 

Chromic Acid. — One part to 437 of water ; three leaves were 
immersed in ninety minims ; in 30 m. some, and in 1 hr. considerable, 
inflection ; after 2 hrs. all the tentacles closely inflected, with the 
glands discoloured. Placed in Avater, next day leaves quite discoloured 
and evidently killed. 

Manganese, Chloride of. — Three leaves immersed in ninety minims 
of a solution of o^e 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 of a 
solution of one part to 437 of watar ; after 2 hrs. some inflection ; after 



152 DROSERA ROTUNDIFOLIA. [Chap. VIII. 

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. 

Nickel, 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 -^vas not a 
trace of inflection, and the glands were not more blackened than often 
occurs after an equally long immersion in water. 

Platinum, Chloride of. — Three leaves immersed in ninety minims of 
a solution of one part, to 437 of water ; in 6 m. some inflection, which 
became immense after 48 m. After 3 hrs. the glands were rather pale. 
After 24 hrs. all the tentacles still closely inflected ; glands colourless ; 
remained in same state for four days ; leaves evidently killed. 

Concluding BemarTcs on the Action of the foregoing Salts. — Of 
the fifty-one salts and metallic acids vfliich. were tried, 
twenty-five caused the tentacles to te inflected, and twenty- 
six had no such effect, two rather doubtful cases occurring in 
each series. In the table at the head of this discussion, the 
salts are arranged according to their chemical affinities ; but 
their action on Drosera does not seem to he thus governed. 
The nature of the base is far more important, as far as can be 
judged from the few experiments here given, than that of the 
acid ; and this is the conclusion at which physiologists have 
arrived with respect to animals. We see this fact illustrated 
in all the nine salts of soda causing inflection, and in not 
being poisonous except when given in large doses ; whereas 
seven of the corresponding salts of potash do not cause 
inflection, and some of them are poisonous. Two of them, 
however, viz. the oxalate and iodide of potash, slowly in- 
duced a slight and rather doubtful amount of inflection. 
This difference between the two series is interesting, as Dr. 
Burden Sanderson informs me that sodium salts may be 
introduced in large doses into the circulation of mammals, 
without any injurious effects; whilst small doses of potas- 
sium salts cause death by suddenly arresting the movements 
of the heart. An excellent instance of the different action of 
the two series is presented by the phosphate of soda quickly 
causing vigorous inflection, whilst phosphate of potash is 



Chai'. VIII.] CONCLUDING REMARKS, SALTS. 153 

quite inefficient. The great power of the former is pro'ba'bly 
due to the presence of phosphorus, as in the cases of phos- 
phate of lime and of ammonia. Hence we may infer that 
Drosera cannot obtain phosphorus from the phosphate of 
potash. This is remarkable, as I hear from Dr. Burden 
Sanderson that phosphate of potash is certainly decomposed 
within the bodies of animals. Most of the salts of soda act 
very rapidly; the iodide acting slowest. The oxalate, nitrate, 
and citrate seem to have a special tendency to cause the 
blade of the leaf to be inflected. The glands of the disc, 
after absorbing the citrate, transmit hardly any motor impulse 
to the outer tentacles ; and in this character the citrate of 
soda resembles the citrate of ammonia, or a decoction of 
grass-leaves; these three fluids all acting chiefly on the 
blade. 

It seems opposed to the rule of the preponderant influence 
of the base that the nitrate of lithium causes moderately 
rapid inflection, whereas the acetate causes none ; but this 
metal is closely allied to sodium and potassium,* which act 
so differently; therefore we might expect that its action 
would be intermediate. We see, also, that ceesium causes 
inflection, and rubidium does not ; and these two metals are 
allied to sodium and potassium. Most of the earthy salts are 
inoperative. Two salts of calcium, four of magnesium, two 
of barium, and two of strontium, did not cause any inflection, 
and thus follow the rule of the preponderant power of the 
base. Of three salts of aluminium, one did not act, a second 
nhowed a trace of action, and the third acted slowly and 
doubtfully, so that their effects are nearly alike. 

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

* Miller's ' Elements of Chemistr)-,' 3rd edit. pp. 337, 448. 



154 



DROSEEA EOTUNDIFOLIA. 



[Ohap. VIII. 



■differont effects of phosphate of ammonia on leaves previously- 
immersed in various solutions. 



Acids. 

I will first give, as in the case of the salts, a list of the 
twenty-four acids which were tried, divided into two series, , 
according as they cause or do not cause inflection. After 
describing the experiments, a few concluding remaris will 
be added. 



Acids, much diluted, whioh cause 
Inflection. 

1. Nitric, strong inflection; poi- 
sonous. 

2. Hydrochloric, moderate and slow 

inflection ; not poisonous. 

3. Hydriodio, strong inflection ; 
poisonous. 

4. Iodic, strong inflection ; poisonous. 

5. Sulphuric, strong inflection; 

somewhat poisonous. 

6. Phosphoric, strong inflection ; 
poisonous. 

7. Boracic, moderate and rather 

slow inflection ; not poisonous. 

S. Formic, very slight inflection; 
not poisonous. 

9. Acetic, strong and rapid inflec- 
tion ; poisonous. 

10. Propionic, strong but not very 
rapid inflection ; poisonous. 

11. Oleic, quick inflection; very 
poisonous. 

12. Carbolic, very slow inflection; 

poisonous. 

13. Lactic, slow and moderate inflec- 
tion ; poisonous. 

14. Oxalic, moderately quick inflec- 

tion ; very poisonous. 
13. Walic, very slow but considerable 
inflection ; not poisonous. 

16. Benzoic,' rapid inflection ; very 
poisonous. 

17. Succinic, moderately quick in- 
flection ; moderately poisonous. 

18. Hippuric, rather slow inflection; 

poisonous. 

19. Hydrocyanic, rather rapid in- 
flection ; very poisonous. 



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

1. Gallic ; not poisonous. 

2. Tannic ; not poisonous. 

3. Tartaric ; not poisonous. 

4. Citric ; not poisonous. 

5. Uric ; (?) not poisonous. 



■CuAP. Vlir.] THE EFFECTS OF ACIDS. 155 

Xilric Acid. — rour leaves were placed, each in thirty minims of one 
part by weight of the acid to -ioT 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 tlie same as that of rnoi-t of the 
foregoing saline solutions. In 2 hrs. 30 m. some of the leaves were 
considerably, and in 6 hrs. 30 m. all were immensely, inflected, as were 
their blades. The surrounding fluid was slightly coloured pink, which 
always shows that the leaves have been injured. They were then left 
in water for three days ; but they remained inflected and were evidently 
Jiilled. Most of the glands had become colourless. Two leaves were 
then immersed, each in thirty minims of one part to 1000 of water ; in 
.a few hours there was some inflection ; and after 24 hrs. both leaves 
had almost all their tentacles and blades inflected ; they were left in 
water for three days, and one partially re-expanded and recovered. 
Two leaves were next immersed, each in thirty minims of one part to 
'2000 of water ; this produced very little effect, except that most of the 
tentacles close to the summit of the petiole were inflected, as if the acid 
had been absorbed by the cut-off end. 

Hydrochloric Acid. — One part to 437 of water; four leaves were 
immersed as before, each in thirty minims. After 6 hrs. only one leaf 
was considerably inflected. After 8 hrs. 15 m. one had its tentacles 
and blade well inflected; the other three were moderately inflected, 
:and the blade of one slightly. The surrounding fluid was not coloured 
at all pink. After 25 hrs. three of these four leaves began to re- 
«xpand, but their glands were of a pink instead of a red colour ; after 
two more days they fully re-expanded ; but the fourth leaf remained 
inflected, and seemed much injured or killed, with its glands white. 
JPour 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. 

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

Iodic Acid. — One to 437 of water ; three leaves were immersed, each 
in thirty minims ; after 3 hrs. strong inflection ; after 4 hrs. glands 
■dark brown; after 8 hrs. 30 m. close inflection, and the leaves had 
become flaccid; surrounding fluid not coloured pink. These leaves 
•were then placed in water, and next day were evidently dead. 



156 DEOSEEA EOTUNDIFOLIA. [Chap. VIII. 

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

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

Sorac'c Acid. — One to 437 of water ; four leaves were immersed 
together in 120 minims ; after 6 hrs. very slight inflection ; after 8 
hrs. 15 m. two were considerably inflected, the other two slightly. 
After 24 hrs. one leaf was rather closely inflected, the second less 
closely, the third and fourth moderately. The leaves were washed and 
put into water; after 24 hrs. they were almost fully re-expanded .ind 
looked healthy. This acid agrees closely with hydrochloric acid of 
the same strength in its power of causing inflection, and in not being 
poisonous. 

Formic Add.- — 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 contsiits of their 
cells aggregated, showing that the phosphate had acted, though not to 
the full and ordinary degree. 

Acetic Acid. — Four leaves were immersed together in 120 minims of 
one purt 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, 
hut with their glands colourless. After another day they were dingy- 
coloured, and evidently dead. This acid is far more powerful than 
formic, and is highly poisonous. Half-minim drops of a stronger 
mixture (viz. one part by measm-e to 320 of water) were placed on the 
discs of flve leaves ; none of the exterior tentacles, only those on the 
borders of the disc which actually absorbed the acid, became inflected". 
Probably the dose was too strong and paralysed the leaves, for drops 
of a weaker mixture caused much inflection ; nevertheless, the leaves 
all dird after two days. 

Propionic Acid. — Three leaves were immersed in ninety minims of 
a mixture of one part to 437 of water ; in 1 hr. 50 m. there was no 
inflection ; but after 3 hrs. 40 m. one leaf was greatly inflected, andi 
the other two slightly. The inflection continued to increase, so that 
iu 8 hrs. all three leaves were closely inflected. Next morning, alter 



Chap. VIII.] THE EFFECTS OF ACIDS. 157 

20 lirs., most of the glands were very pale, but some few wern almost 
black. No mucus had been secreted, and the surroimding fluid was 
only just perceptibly tinted of a pale pink. After 46 hrs. the leaves 
became slightly flaccid and were evidently killed, as was alterwaids 
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 mucli slower rate. 

Oleic Acid (given me by Prof. Frankland). — Three leaves were 
immersed in ttiis acid ; some inflection was almost immediately 
caused, which increased slightly, but then ceased, and the leaves 
seemed killed. Next morning they were rather shrivelled, and many 
of the glands had fallen off the tentacles. Drops of this acid were 
placed on the discs of four leaves ; in 40 m. all the tentacles were 
greatly inflected, excepting the extreme marginal ones ; and many of 
these after 3 hrs. became inflected. I was led to try this acid from 
supposing that it was present (which does not seem to be the case)* 
in olive oil, the action of which is anomalous. Thus drops of this oil 
placed on the disc do not cause the outer tentacles to be inflected ; yet, 
when minute drops were added to the secretion surrounding the glands 
of the outer tentacles, these were occasionally, but by no means always, 
inflected. Two leaves were also immersed in this oil, and there was 
no inflection for about 12 hrs. ; but after 23 hrs. almo.st all the tentacles 
were inflected. Three leaves were likewise immersed in unboiled 
linseed oil, and soon became somewhat, and in 3 hrs. greatly inflected . 
After 1 hr. the secretion round the glands was coloured pink. I infer 
from this latter fact that the power of linseed oil to cause inflection 
cannot be attributed to the albumin which it is said to contain. 

Carbolic Acid. — Two leaves were immersed in f-ixty minims of a 
solution of 1 gr. to 437 of water ; in 7 hrs. one was slightly, and in 24 
hrs. both were closely, inflected, with a surprising amount of mucus 
secreted. These leaves were washed and left for two days in water; 
they remained inflected ; most of their glands became pale, and they 
seemed dead. Tiiis acid is poisonous, but does not act nearly so 
rapidly or powerfully as might have been expected from its known de- 
structive power on the lowest organisms. Half-minims of the same 
solution were placed on the discs of three leaves ; after 24 hrs. no 
inflection of the outer tentacles ensued, and when bits of meat Avere 
given them they became fairly well inflected. Again half-minims of 
a stronger solution, of one part to 218 of water, were placed on the discs 
of three leaves ; no inflection of the outer tentacles ensued ; bits of 
meat were then given as before ; one leaf alone became well inflected. 



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



158 DEOSEKA KOTUNDIFOLIA. [Chap. VIII. 

the discal glands of the other two appearing much injured and dry. 
We thus see that the glands of the discs, after absorbing this- 
acid, rarely transmit any motor impulse to the outer tentacles ; 
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 inilectiun, but the 
surrounding fluid was coloured pink ; after 8 hrs. 30 m. one leaf alone 
was a little inflected, and almost all the glands on all three leaves were- 
of a very pale colour. The leaves were then washed and placed in a 
solution (1 gr. to 20 oz.) of phosphate of ammonia; after about 16 hrs. 
there was only a trace of inflection. They were left in the phosphate 
for 48 hrs., and remained in the same state, with, almost all their 
glands discoloured. The protoplasm within the cells was not ag^ 
gregated, except in a very few tentacles, the glands of which were not 
much discoloured. I believe, therefore, that almost all the glands and 
tentacles had been killed by the acid so suddenly that hardly any 
inflection was caused. Four leaves were next immersed in 120 minims 
of a weaker solution, of one part to 875 of water; after 2 hvs. 30 m. 
the surrounding fluid was quite pink ; the glands were pale, but 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 inflected ; a second a large number ; the third 
and fourth very few ; almost all the glands were white, excepting those 
on the discs of two of the leaves, and many of these were very dark red. 
The leaves appeared dead. Hence lactic acid acts in a very peculiar 
manner, causing inflection at an extraordinarily slow rate, and being 
highly poisonous. Immersion in even weaker solutions, viz. of one 
part to 1312 and 1750 of water, apparently killed the leaves (the 
tentacles after a time being bowed backwards), and rendered the 
glands white, but caused no inflection. 

Gallic, Tannic, Tartaric, and Citric Acids. — ^One part to 437 of 
water. Three or four leaves were immersed, each in 30 minims of these 
four solutions, so that each leaf received -jij of a grain, or 4'048 mg. No 
inflection was caused in 24 hrs., and the leaves did not appear at all 
injured. Those which had been in the tannic and tartaric acids were 
placed in a solution (1 gr. to 20 oz.) of phosphate of ammonia, but no 
inflection ensued in 24 hrs. On the other hand, the four leaves which 
had been in the citric acid, when treated with, the phosphate, became 
decidedly inflected in 50 m., and strongly inflected after 5 hrs., and so 
remained for the next 24 hrs. 

Malic acid. — Three leaves were immersed in ninety minims of a 
solution of one part to 437 of water ; no inflection was caused in 8 hrs.. 
20 m., but after 24 hrs. two of them were considerably, and the third 
slightly, inflected — ^more so than could be accounted for by the action 
of water. No great amount of mucus was secreted. They were then 



CiiAP. Vlir.] THE EFFECTS OF ACIDS. 159 

placed in water, and after two days partially re-expanded. Hence this 
acid is not poisonous. 

Oxalia Acid. — Three leaves were immersed in ninety minims of a 
solution of 1 gr. to 437 of water ; after 2 hvs. 10 m. there was much 
inflection ; glands pale ; the surrounding fluid of a dark pink colour ; 
after 8 hrs. excessive inflection. The leaves were then placed in water ; 
after about 16 hrs. the tentacles were of a very dark red colour, like 
those of the leaves in acetic acid. After 24 additional hours, the three 
leaves were dead and their glands colourless. 

Benzoic Acid. — ^Five leaves were immersed, each in thirty minims 
of a solution of 1 gr. to 437 of water. This solution was so ^veak that 
it only just tasted acid, yet, as we shall see, was highly poisonous to 
Drosera. After 52 m. the submarginal tentacles were somewhat 
inflected, and all the glands very pale-coloured ; the surrounding fluid 
was coloured pink. On one occasion the fluid laecame pink in the 
course of only 12 m. and the glands as white as if the loaf had been 
dipped in boiling water. After 4 hrs. much mflection ; 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 muous 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 ; tho 
leaves in the solution being flaccid, those in the water (now colom-ed 
yellow) of a pale brown tint, and their glands white. 

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

Uric Acid. — Three leaves were immersed in 180 minims of a solution 
of 1 gr. to 875 of warm water, but all the acid was not dissolved ; so 
that each received nearly ^^ of a grain. After 25 m. there was some 
slight inflection ; but this never increased ; after 9 hrs. the glands 
were not discoloured, nor was the solution coloured pink ; nevertheless, 
much mucus was secreted. The leaves were then placed in water, and 
by next morning fully re-expanded. I doubt whether this acid really 
causes inflection, for the slight movement which at first occurred 
may have been due to the presence of a trace of albuminous matter. 
But it produces some effect, as shown by tho secretion of so much 
mucus. 

Eippuric Acid. — Four leaves were immersed in 120 minims of a 
solution of 1 gr. to 437 of water. After 2 hrs. the fluid was coloured 
pink ; glands pale, but no inflection. After 6 hrs. some inflection ; 
after 9 hrs. all four leaves greatly inflected ; much mucus secreted ; all 
the glands very pale. The leaves were then left in water for two days ; 
they remained closely inflected, with their glands colourless, and I do- 
not doubt were killed. 



160 DEOSERA EOTUNDIFOLIA. [Chap. VIII. 

Hydrocyanic Acid. — Pour 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 hr.s. 
45 m. all strongly inflected, and the surrounding fluid coloured pink ; 
after 6 hrs. all closely inflected. After an immersion of 8 hrs. 20 m. 
the leaves were washed and placed in water; next morning, after about 
16 hrs., they were still inflected and discoloured; on the succeeding 
day they were evidently dead. Two leaves were immersed in 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 
boiling water ; very few of the tentacles were inflected ; but after 4 
hrs. almost all were inflected. These leaves were then placed in water 
and next morning were evidently dead. Half-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 -^oia, minim, 
or '00296 c.c.) of Scheele's mixture (containing 4 per cent, of anhydrous 
acid) ; the glands first became bright red, and after 3 hrs. 15 m. 
about two-thirds of the tentacles bearing these glands were inflected, 
and remained so for the two succeeding days, when they appeared 
dead. 

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



'■ According to M. Fournier (' De cause the stamens of Berberis in- 

la F&ondation daus les Phandro- stantly to close; though drops of 

games,' 1863, p. 61) drops of acetic, water have no such power, which 

hydrocyanic, and sulphuric acid latter statement I can confirm. 



Chap. VIII.] COXCLUDING KEMAKKS, ACIDS. 161 

and many other acids of the same strength, and is not 
poisonous. This is an interesting fact, as hydrochloric acid 
plays so important a part in the digestive process of animals. 
Formic acid induces very slight inflection, and is not poison- 
ous ; whereas its ally, acetic acid, acts rapidly and powerfully, 
and is poisonous. Malic acid acts slightly, whereas citric 
and tartaric acids produce no effect. Lactic acid is poisonous, 
and is remarkable from inducing inflection only after a 
considerable interval of time. Nothing surprised me more 
than that a solution of benzoic acid, so weak as to be hardly 
acidulous to the taste, should act with great rapidity and be 
highly poisonous; for I am informed that it produces no 
marked effect on the animal economy. It may be seen, by 
looking down the list at the head of this discussion, that 
most of the acids are poisonous, often highly so. Diluted 
acids are known to induce negative osmose,* and the 
poisonous action of so many acids on Drosera is, perhaps, 
connected with this power, for we have seen that the fluid in 
which they were immersed often became pink, and the 
glands pale-coloured or white. Many of the poisonous acids, 
such as hydriodio, benzoic, hippuric, and carbolic (but I 
neglected to record all the cases), caused the secretion of an 
extraordinary amount of mucus, so that long ropes of this 
matter hung from the leaves when they were lifted out of 
the solutions. Other acids, such as hydrochloric and malic, 
have no such tendency ; in these two latter cases the sur- 
rounding fluid was not coloured pink, and the leaves were 
not poisoned. On the other hand, propionic acid, which is 
poisonous, does not cause much mucus to be secreted, yet the 
surrounding fluid became slightly pink. Lastly, as in the 
case of saline solutions, leaves, after being immersed in cer- 
tain acids, were soon acted on by phosphate of ammonia ; on 
the other hand, they were not thus affected after immersion 
in certain other acids. To this subject, however, I shall 
have to recur. 



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



162 DEOSEEA EOTUNDIFOLIA. [Chap. IX, 



CKAPTEK IX. 

The Effects of cektaix Alkaloid Poisoxs, other Suustaxces and 
Vapours. 

Strychnine, salts of — Qhmine, sulphate of, does not soon arrest the move- 
ment of the protoplasm — Other salts of quinine — Digitaline — Nicotine — 
Atropine — Veratrine — Colchicine — Theine — Curare — Morphia — Hyos- 
cyamus — 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 — Chloro- 
form, sulphuric and nitric ether, their stimulant, poisonous, and narcotic 
power — Carbonic acid narcotic, not quiclcly poisonous — Concluding 
remarks. 

As in the last chapter, I will first give my experiments and 
tlien a bj'ief 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 
■gig of a grain, or "OeVS mg. In 2 hrs. 30 m. the outer tentacles on 
some of them were inflected, but in an irregular manner, sometimes 
only on one side of the leaf. The next morning, after 22 hrs. 30 m., 
the inflection had not increased. The glands on the central disc were 
blackened, and had ceased secreting. After an additional 24 hrs. all 
the central glands seemed dead, but the inflected tentacles had re-ex- 
panded and appeared quite healthy. Hence the poisonous action of 
strychnine seems confined to the glands which have absorbed it; never- 
theless, these glands transmit a motor impulse to the exterior tentacles. 
Minute drops (about jij of a minim) of the same solution applied to 
the glands of the outer tentacles occasionally caused them to bend. 
The poison does not seem to act quickly, for having applied to several 
glands similar drops of a rather stronger solution, of one part to 292 of 
water, this did not prevent the tentacles bending, when their glands 
■were excited, after an interval of a quarter to three quarters of an hour, 
■ by being rubbed or given bits of meat. Similar drops of a solution of 
one part to 218 of water (2 grs. to 1 oz.) quickly blackened the glands ; 
some few tentacles thus treated moved, whilst others did not. The 



Chap. IX.] ALKALOID POISONS. 163 

latter, however, on being subsequently moistened with saliva or given 
bits of meat, became incurved, though with extreme slowness ; and 
this shows that they had been injured. Stronger solutions (but the 
strength was not ascertained) sometimes arrested all power of movement 
very quickly; thus bits of meat were placed on the glands of several 
exterior tentacles, and as soon as they began to move, minute drops of 
the strong solution were added. They continued for a short time to 
go on bending, and then suddenly stood still ; other tentacles on the 
same leaves, with meat on their glands, but not wetted with the 
strychnine, continued to bend and soon reached the centre of the 
leaf. 

Citrate of Strychnine. — Half-minims of a solution of one part to 
437 of water were placed on the discs of six leaves ; after 24 hrs. the 
outer tentacles showed only a trace of inflection. Bits of meat were 
then placed on three of these leaves, but in 24 hrs. only slight and 
irregular inflection occurred, proving that the leaves had been greatly 
injured. Two of the leaves to which meat had not been given had 
their discal glands dry and much injured. Minute drops of a strong 
solution of one part to 109 of water (4 grs. to 1 oz.) were added to the 
secretion round several glands, but did not produce nearly so plain an 
effect as the drops of a much weaker solution of the acetate. Particles 
of the dry citrate were placed on six glands ; two of these moved some 
way towards the centre, and then stood still, being no doubt killed ; 
three others curved much farther inwards, and were then fixed ; one 
alone reached the centre. Five leaves were immersed, each in thirty 
minims of a solution of one part to 437 of water ; so that each received 
jij- 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 tlie cells of the tentacles was well aggregated. By 
this time two of the leaves were greatly inflected, but the three others 
not much more inflected than they were before. Nevertheless two 
fresh leaves, after an immersion respectively for 2 hrs. and 4 hrs. in 
the solution, were not killed ; for on being left for 1 hr. 30 m. in a 
solution of one part of carbonate of ammonia to 218 of water, their 
tentacles became more inflected, and there was much aggregation. 
The glands of two other leaves, after an immersion for 2 hrs. in a 
stronger solution, of one part of the citrate to 218 of water, became of 
an opaque, pale pink colour, which before long disappeared, leaving 
them white. One of these two leaves had its blade and tentacles 
greatly inflected ; the other hardly at all ; but the protoplasm in the 
cells of both was aggregated down to the bases of the tentacles, 
with the spherical masses in the cells close beneath the glands 
blackened. After 24 hrs. one of these leaves was colourless, and 
evidently dead. 

Sulphate of Quinine^ — Some of this salt was added to water, which 
is said to dissolve j-oSo P^''* of its weight. Five leaves were immersed, 
each in thirty minims of this solution, which tasted bitter. In less 

M 2 



164 DEOSEEA EOTUNDirOLIA. [Chap. IX. 

than 1 hr. some of them had a few tentacles inflected. In 3 hrs. most 
of the glands became -whitish, others dark-coloured, and many oddly- 
mottled. After 6 hrs. t-wo of the leaves had a good many tentacles 
inflected, hut this very moderate degree of inflection never increased. 
One of the leaves -was taken out of the solution after 4 hrs., and placed 
in -water ; by the next morning some fe-vv of the inflected tentacles had 
re-expanded, sho-wing 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 pro- 
toplasm in the cells of the outer tentacles, and of the short green ones 
on the disc, had become strongly aggregated down to their bases ; and 
I distinctly saw that the little masses changed their positions and 
shapes rather rapidly ; some coalescing and again separating. I was 
surprised at this fact, because quinine is said to aiTest all movement in 
the white corpuscles of the blood ; but as, according to Binz,* this is 
due to their being no longer supplied with oxygen by the red corpuscles, 
any such arrestment of movement could not be expected in Diosera. 
That the glands had absorbed some of the salt was evident from their 
change of coloxir ; but I at first thought that the solution might not 
have travelled do^vn the cells of the tentacles, where the protoplasm 
was seen in active movement. This view, ho-wever, I have no doubt, 
is erroneous, for a leaf which had been immersed for 3 hrs. in the 
quinine solution was then placed in a, little solution of one part of 
carbonate of ammonia to 218 of water; and in 30 m. the glands and 
the upper cells of the tentacles became intensely black, with the pro- 
toplasm presenting h very unusual appearance ; for it had become 
aggregated into reticulated dingy-coloured masses, having rounded and 
angular interspaces. As I have never seen this effect produced by the 
carbonate of ammonia alone, it must be attributed to the previous 
action of the quinine. These reticulated masses were watched for 
some time, but did not change their forms ; so that the protoplasm no 
doubt had been killed by the combined action of the two salts, though 
exposed to them for only a short time. 

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

Half-minims of the solution were placed on the discs of six leaves ;. 
after 23 hrs. one had all its tentacles, two had a few, and the others 
none inflected ; so that the disoal 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 aU six leaves were evidently 



' Quarterly Journal of Microscopical Science,' April 1874, p. 185. 



Chap. IX.] ALKALOID POISONS, 165 

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 is far more efficient 
than the sulphate in causing inflection, and, like that salt, is highly 
poisonous. 

Nitrate of Quinine. — Four leaves were immersed, each in thirty 
minims of a solution of one part to 437 of water. After 6 hrs. thei'e 
was hardly a trace of inflection ; after 22 hrs. three of the leaves were 
moderately, and the fourth slightly inflected ; so that this salt induces, 
though rather slowly, well-marked inflection. These leaves, on being 
left in water for 48 hrs., almost completely re-expanded, but the glands 
were much discoloured. Hence this salt is not poisonous in any high 
degree. The different action of the three foregoing salts of quinine is 
singular. 

jfijritoZirae.— Half-minims of a solution of one part to 437 of water 
were placed on the discs of five leaves. In 3 hrs. 45 m. some of them 
had their tentacles, and one had its blade, moderately inflected. After 
8 hrs. three of them were well inflected ; the fourth had only a few 
tentacles inflected, and the fifth (an old leaf) was not at all affected. 
They remained in nearly the same state for two days, but the glands 
on their discs became pale. On the third day the leaves appeared 
much injured. Nevertheless, when bits of meat were placed on two of 
them, the outer tentacles became inflected. A minute drop (about -^ 
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 -^shro of * 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 



• Binz found several years ago corpuscles, which become "rounded 

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

Anatomy and Phys.,' November Drosera the aggregated masses of 

1872, p. 195) that quinia is an protoplasm, which appeared killed 

■energetic poison to low vegetable by the quinine, likewise presented a 

and animal organisms. Even one granular appearance. A similar 

part added to 4000 parts of blood appearance is caused by very hot 

arrests the movements of the white water. 



166 DROSEKA EOTUNDIFOLIA. [Chap. IX. 

on one leaf were closely inflected, and six on the other slightly so ; but 
all the glands were blackened, or very dark coloured, with the pro- 
toplasm in all the cells of all the tentacles much aggregated and dark 
coloured. The leaves were not quite killed, for on being placed in a 
little solution of carbonate of ammonia (2 grs. to 1 oz.) a few more 
tentacles became inflected, the remainder not being acted on during 
the next 24 hrs. 

Half-minims of a stronger solution (two drops to i oz. of water) were 
placed on the discs of six leaves, and in 30 m. all those tentacles 
became inflected ; the glands of which bad actually touched the solu^ 
tion, as shown by their blackness; but hardly any motor influence was 
transmitted to the outer tentacles. After 22 hrs. most of the glands on 
the discs appeared dead; but this could not have been the case, as, 
when bits of meat were placed on three of them, some few of the outer 
tentacles were inflected in 24 hrs. Hence nicotine has a great tendency 
to blacken the glands and to induce aggregation of the ])rotoplasm, but, 
except when pure, has very moderate power of inducing inflection, and 
still less power of causing a motor influence to be transmitted from the 
discal glands to the outer tentacles. It is moderately poisonous. 

Atropine. — A grain was added to 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 drops of the solution of 
ati opine 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 
diH'er from atropine, and it produced no effect. Tliree of the leaves on 
which drops of this latter solution had been left for 24 hrs. were like- 
wise given bits of meat, and they had in tlie course of 24 hi'Si a good 
many of their submarginal tentacles inflected. 

Veratrine, Colchicine, Theine.- — Solutions were made of tkese three 
alkaloids by adding one part to 437 of water. Half-mimiims were 
placed, in each case, on the discs of at least six leaves, but no inflection 
was caused, except perhaps a very slight amount by the theine. Half-^ 
minims of a strong infusion of tea likewise produced, as formerly 
stated, no effect. I also tried similar drops of an infusion of one part 
of the extract of colchicum, sold by druggists, to 218 of water ; and the 
leaves were observed for 48 hrs., without any effect being produced. 
The seven leaves on which drops of veratrine had been left for 26 hrs. 
were given bits of meat, and after 21 hrs. were well inflected. ITiese 
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 sola- 



Chap. IX.] ALKALOID POISONS. 167 

tion. In 3 hrs. 30 m. some of the tentacles were a little inflected ; 
as was the hlade of one, after 4 hrs. After 7 hrs. the glands were 
wonderfully blackened, showing that matter of some kind had been 
absorbed. In 9 hrs. two of the leaves had most of their tentacles sub- 
inflected, but the inflection did not increase in the course of 24 hrs. One 
of these leaves, after being immersed for 9 hrs. in the solution, wai 
placed in water, and by next morning had largely re-expanded ; the 
other two, after their immersion for 24 hrs., were likewise placed in 
water, and in 24 hrs. were considerably re-expanded, though their 
glands were as black as ever. Half-minims were placed on the discs of 
six leaves, and no inflection ensued ; but after three days the glands on 
the discs appeared rather dry, yet to my surprise were not blackened. 
On another occasion drops were placed on the discs of six leaves, and a 
considerable amount of inflection was soon caused ; but as I had not 
filtered the solution, floating particles may have acted on the glands. 
After 24 hrs. hits 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 balf-minims were placed on the discs of six leaves. 
These were not at all affected, and when after a day bits of meat 
were given them, they were slightly inflected in 5 hrs., and closely 
after 24 hrs. It follows from these several facts that a solution of 
curare induces a very moderate degree of inflection, and this may 
perhaps be due to the presence of a minute quantity of albumen. It 
certainly is not poisonous. The protoplasm in one of the leaves, which 
had been immersed for 24 hrs., and which had become slightly in- 
flected, had undergone a very slight amount of aggregation — not more 
than often ensues from an immersion of this length of time in water. 

Acetate of Morphia. — I tried a great number of experiments with 
this substance, but with no certain result. A considerable number of 
leaves were immersed from between 2 hrs. and 6 hrs. in a solution of 
one part to 218 of water, and did not become inflected. Nor were 
they poisoned; for when they were washed and placed in weak 
solutions of phosphate and carbonate of ammonia, they soon became 
strongly inflected, with the protoplasm in the cells well aggregated. 
If, however, whilst the leaves were immersed in the morphia, phos- 
phate of ammonia was added, inflection did not rapidly ensue. 
Minute drops of the solution were applied in the usual manner to the 
secretion round between thirty and forty glands ; and when, after an 
interval of 6 m., bits of meat, a little saliva, or particles of glass, were 
placed on them, the movement of the tentacles was greatly retarded. 
But on other occasions no such retardation occurred. Drops of water 
similarly applied never have any retarding power. Minute drops of a 
solution of sugar of the same strength (one part to 218 of water) 
sometimes retarded the subsequent action of meat and of particles of 
glass, and sometimes did not do so. At one time I felt convinced 
that morphia acted as a narcotic on Drosera, but after having foimd in 



168 DBOSEEA EOTUNDIFOLIA. [Chap. IX. 

what a singular manner immersion in certain non-poisonous salts and 
acids prevents the subsec[uent action of phosphate of ammonia, 
whereas other solutions have no such power, my first conviction seems 
very doubtful. 

Extract of Byoscyamus. — Several leaves were placed, each in thirty 
minims of an infusion of 3 grs. of the extract sold by druggists to 1 oz. 
of water. One of them, after being immersed for 5 hrs. 15 m., was 
not inflected, and was then put into a solution (1 gr. to 1 oz.) of car- 
bonate of ammonia; after 2 hrs. 40 m. it was found considerably 
inflected, and the glands much blackened. Four of the leaves, after 
being immersed for 2 hrs. 14 m., were placed in 120 minims of a 
solution (1 gr. to 20 oz.) of phosphate of ammonia ; they had already 
become slightly inflected from the byoscyamus, probably owing to the 
presence of some albuminous matter, as formerly explained, but the 
inflection immediately increased, and after 1 hr. was strongly pro- 
nounced; so that byoscyamus does not act as a narcotic or poison. ' 

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

Poison from the Cobra. — -Dr. Fayrer, well known from his investi- 
gations on the poison of this deadly snake, was so kind as to give me 
some in a dried state. It is an albuminous substance, and is believed 
to replace the ptyaline of saliva.* A minute drop (about ^ oi 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-fjoo °f 
a grain ('0016 mg.). The operation was repeated on four other 
glands; and in 15 m. several of the eight tentacles became well 
inflected, and all of them in 2 hrs. Next morning, after 24 hrs., they 
were still inflected, and the glands of a very pale 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 -gi^ of a grain ( • 0675 mg.) ; in 4 hrs. 15 m. 
the outer tentacles were much inflected ; and after 6 hrs. 30 m. 
those on two of the leaves were closely inflected and the blade of one ; 
the third leaf was only moderately 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 j^j of a grain, or 4*048 mg. In 6 m. 
there was some inflection, whicu 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 



* Dr. Fayrer, 'The Thauatophidia of India,' 1872, p. 150'. 



Chap. IX.] POISON OF THE COBRA. 169 

of protoplasm were examined after 3 lirs., and again after 7 hrs., and 
on ne other occasion have 1 seen them imdergoing such rapid clianges 
of form. After 8 hrs. 30 m. the ghands had become quite white ; they 
liad not secreted any great quantity of mucus. The leaves were now 
placid in water, and after 40 hr.°. re-expanded, showing that they were 
not much or at all injured. During their immersion in water the 
protoplasm within the cells of the tentacles was occasionally examined, 
and always found in strong movement. 

Two leaves were next immersed, each in thirty minims of a much 
stronger solution, of one part to 109 of water ; so that each received J7 
of a grain, or 16"2 mg. After 1 hr. 45 m. ths submarginal tentacles 
were strongly inflected, with the glands somewhat 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 inflection than the strotiger 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 jirotoplasm, still 
of a fine purple colour, was found aggregated into chains of small 
globular masses. These changed their shapes with remarkable 
quickness. After an immersion of 48 hrs. they were again examined, 
and their movements were so plain that they could easily be seen 
under a weak power. The leaves were now placed in water, and after 
24 hrs. (i.e. 72 hrs. from their first immersion) the little masses of pro- 
toplasm, which had become of a dingy purple, were still in strong 
movement, changing their shapes, coalescing, and again separating. 

In 8 hrs. after these two leaves had been placed in water (i.e. in 56 
hrs. after their immersion in the solution) they began to re-expand, 
and by the next morning were more expanded. After an additional 
day (i.e. on the fourth day after their immersion in the solution) they 
were largely, but not quite fully, expanded. The tentacles were now 
•examined, and the aggregated masses were almost wholly re-dissolved ; 
the cells being filled with homogeneous purple fluid, with the ex- 
ception here and there of a single globular mass. We thus see how 
•completely the protoplasm 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 consequently that the 
protoplasm within these cells had not been at all affected. Accordingly 
I placed another leaf, which had been immersed for 48 hrs. in the 
poison and afterwards for 24 hrs. in water, in a little solution of one 
part of carbonate of ammonia to 218 of water ; in 30 m. the protoplasm 
in the cells beneath the glands became darker, and in the course of 
24 hrs. the tentacles were filled down to their bases with dark-coloured 
■epherical 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 jjoisonous to Drosera ; yet it causes 
strong and rapid inflection of the tentacles, and soon discharges all 



170 DEOSEEA EOTUNDIFOLIA. [Chap. IX. 

colour from the glands. It seems even to act as a stimulant to the 
protoplasm, for after considerable experience in observing the move- 
ments of this substance in Drosera, I have never seen it on any other 
occasion in so active a state. I was therefore anxious to learn how 
this poison aifeoted animal protoplasm ; and Dr. Fayrer was so kind as 
to make some observations for me, which be has since published.* 
Ciliated epithelium from the mouth of a frog was placed in a solution 
of "03 gramm to 4' 6 cubic cm. of water; others being placed at the 
same time in pure water for comparison. The movements of the cilia 
in the solution seemed at iirst increased, but soon languished, and 
after between 15 and 20 minutes ceased ; whilst those in the water 
were still acting vigorously. The white corpuscles of the blood of a 
frog, and the cilia on two infusorial animals, a Paramecium and 
Volvox, were similarly affected by the poison. Dr. Payrer also found 
that the muscle of a frog lost its irritability after an immersion of 
20 m. in the solution not then responding to a strong electrical current. 
On the other hand, the movements of the cilia on the mantle of an 
Unio were not always arrested, even when left for a considerable time 
in a very strong solution. On the whole, it seems that the poison of 
the cobra acts far more injuriously on the protoplasm of the higher 
animals than on that of Drosera. 

There is one other point which may be noticed. I have occasionally 
observed that the drops of secretion round the glands were rendered 
somewhat turbid by certain solutions, and more especially by some 
acids, a film being formed on the surfaces of the drops ; but I never 
saw this effect produced in so conspicuous a manner as by the cobra 
poison. When the stronger solution was employed, the drops appeared 
in 10 m. like little white rounded clouds. After 48 hrs. the secretion 
was changed into threads and sheets of a membranous substance, 
including minute granules of various sizes. 

Gamplwr. — 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 yo^o '^^ i*^ 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 coloin-, and these were not inflected after an immersion of 
24: hrs. ; so that in making experiments with camphor it is necessary 
to avoid such leaves. Some of these leaves, on being left in the 
solution for 4 hrs., became of a rather dingy pink colour, and secreted 
much mucus ; although their tentacles were closely inflected, the 
protoplasm within the cells was not at all aggregated. On another 



* 'Proceedings of Royal Society,' Feb. 18, 1875. 



Chap. IX.] 



CAMPHOE. 



171 



occasion, however, after a lonaer immersion of 24 hrs., there was well- 
marked aggregation. A solution made by adding two drops of campho- 
rated spiiits 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. 









Length of 


% 


Length of 




Time between 


,2 




the Itnmerslon 


o 


Immersion in 


Lengtli of Timo Ijetween the Act of Brushing 


of the Leaves 


% 


the Solution 


and the Inflection of the Tentacles. 


in the Solution 
and the First 


1 


of Camplior. 




Sign of the 


S, 






Inflection of the 






Tentacles. 


1 




l'3 m. considerable inflection ; 4 m. all" 
\ the tentacles except 3 or 4 inflected. , 


8 m. 


5 m. 


2 


5 m. 


6 m. first sign of inflection. 


11 m. 


3 


5 m. 


f6 m. 30 s. sliglit inflection; 7 m. 30 s.\ 
\ plain inflection. j 


11 m. 30 s. 






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




4 


4 m. 30 s. 


7 m. 






(3 m. 30 s. a trace of inflection; 3 m. i 
\ plain inflection. J 




5 


4 m. 


6 m. 30 s. 


6 


4 m. 


f2 m. 30 s. decided inflection; 3 m. 30 s.| 
\ strongly marked. J 


6 m. 30 s. 


7 


4ra. 


(2 m. 30 s. slight inflection ; 3 m. plain ;\ 
1 4 m. well marked. J 


6 m. 30 s. 


8 




(2 m. trace of inflection ; 3 m. consider-' 
\ able, 6 m. strong inflection. 




3 m. 


5 m. 


y 




(2 m. trace of inflection ; 3 m. consider-' 
able, 6 m. strong inflection. 




o m. 


5 m. 



M. Vogel has shown* that the flowers of various plants do not 
wither so soon when their stems are placed in a solution of camphor 
as when in water ; and that if already slightly withered, they recover 
more quickly. The germination of certain seeds is also accelerated by 
the solution. So that camphor acts as a stimulant, and it is the only 
known stimulant for plants. I wished, therefore, to ascertain whether 
camphor would render the leaves of Drosera more sensitive to 
mechanical irritation than they naturally are. Six leaves were left in 
distilled water for 5 m. or 6 m., and then gently brushed twice or 
tlirice, whilst still under water, with a soft camel-hair brush ; but no 
movement ensued. Nine leaves, which had been immersed In the 
above solution of camphor for the times stated in the above table. 



' 'Gardener's Chronicle,' 1874, p. 671. Nearly similar observations were 
made in 1798 by B. S. Barton. 



172 DEOSERA EOTUNDIFOLIA. [Chap. IX. 

■were next bnished 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 above trials, therefore, each leaf 
was taken out of the solution, waved for about 15 s. in water, then 
placed in fresh water and brushed, so that the brushing would not 
allow the freer access of the camphor ; but this treatment made no 
difference in the results. 

Other leaves were left in the solution without being brushed ; one 
of these first showed a trace of inflection after 11 m. ; a second after 
12 m. ; five were not inflected until 15 m. had elapsed, and two not 
until a few minutes later. On the other hand, it will be seen in the 
right-hand column of the table that most of the leaves subjected to the 
solution, and which were brushed, became inflected in a much shorter 
time. The movement of the tentacles of some of these leaves was so 
rapid that it could be plainly seen through a very weak lens. 

Two or three other experiments are worth giving. A large old leaf, 
after being immersed for 10 m. in the solution, did not apijear 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 ni., 
likewise showed no signs of inflection ; it was then brushed, but did 
not move for 1 hr. ; so that here was a failure. It was again brushed, 
and now in 9 m. a few tentacles became inflected; the failure therefore 
was not complete. 

We may conclude that a, small dose of camphor in solution is a 
powerful stimulant to Drosera. It not only scon excites the tentacles 
to bend, but apparently renders the glands sensitive to a touch, which 
hy itself does not cause any movement. Or it may be that a slight 
mechanical irritation not enough to cause any inflection yet gives some 
tendency to movement, and thus reinforces the action of the camphor. 
This latter view would have appeared to me the more probable one, 
had it not been shown by M. Vogel that camphor is a stimulant in 
other ways to various plants and seeds. 

Two plants bearing four or five leaves, and with their roots in a 
little cup of water, were exposed to the vapour of some bits of camphor 
{about as large as a filbert nut), under a vessel holding ten fluid 
ounces. After 10 hrs. no inflection ensued ; but the glands appeared 
to be secreting more copiously. The leaves were in a narcotised con- 
dilinn, for on bits of meat being placed on two of them, there was no 
inflection in 3 hrs. 15 m., and even after 13 hrs. 15 m. only a few of 
the outer tentacles were slightly inflected; but this degree of move- 
ment shows that the leaves had not been killed by an exposure during 
10 hrs. to the vapour of camphor. 

Oil of Caraway. — Water is said to dissolve about a thousandth 



Chap. IX.] ESSENTIAL OILS, ETC. 173 

part of its weight of this oil. A drop was added to an ounce of water 
and the hottle occasionally shaken during a day ; but many minute 
globules remained undissolved. Five leaves were immersed in this 
mixture ; in from 4 m. to 5 m. there was some inflection, which 
became moderately pronounced in two or three additional minutes. 
After 14 m. all five leaves were well, and some of them closely, 
inflected. After 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 eftect. 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 lialf in the same state ; and the third all sub-inflected. 
The plant was left in the open air for 42 hrs., but not a single tentacle 
expanded ; all the glands appeared dead, except here and there one, 
which was still secreting. It is evident that this oil is highly exciting 
and poisonous to Drosera. 

Oil of Cloves. — A mixture was made in the same manner as in the 
last case, and three leaves were immersed in it. After 30 m. there 
was only a trace of inflection which never increased. After 1 hr. 30 m. 
the glands were pale, and after 6 hrs. white. No doubt the leaves 
were much injured or killed. 

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

Olycerine. — 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 colourless. 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 mixture placed 
ou the discs of some leaves caused, to my surprise, no inflection in the- 
course of 48 hrs. Bits of meat were then given them, and next day 
they were well inflected; notwithstanding that some of the discal 
glands had been rendered almost colourless. Two leaves were immersed 
in the same mixture, but only for 4 hrs. ; they were not inflected, and 
on being afterwards left for 2 hrs. 30 m. in a solution (1 gr. to 1 oz.) 
of carbonate of ammonia, their glands were blackened, their tentacles 
inflected and the protoplasm within their cells aggregated. It appears 
from these facts that a mixture of four drops of glycerine to an ounce- 
of water is not poisonous, and excites very little inflection ; but that 



174 DEOSERA ROTUNDIFOIJA. [Chap. IX. 

pure glycerine is poisonous, and if applied in very minute quantities 
to the glands of the outer tentacles causes their inflection. 

The affects of Immersion in Water and in various Solutions on 
the subsequent Action of Phosphate and Qarhonate of Ammonia. — 
We have seen in the third and seventh chapters that immersion in 
distilled water causes after a time some degree of aggregation of the 
protoplasm, and a moderate amount of inflection, especially in the 
case of plants which have been kept at a rather high temperature. 
Water does not excite a copious secretion of mucus. We have here to 
consider the effects of immersion in various fluids on the subsequent 
action of salts of ammonia and other stimulants. Four leaves which 
had been left for 24 hrs. in water were given bits of meat, but did not 
clasp them. Ten leaves, after a similar immersion, were left for 24 hrs. 
in a powerful solution (1 gr. to 20 oz.) of phosphate of ammonia, and 
only one showed even a trace of inflection. Three of these leaves, on 
being left for an additional day in the solution, still remained quite 
unaileoted. When, however, some of these leaves, which had been 
first immersed in water for 24 hrs., and then in the phosphate for 
24 hrs. were placed in a solution of carbonate of ammonia (one part 
to 218 of water), the protoplasm in the cells of the tentacles became 
in a few hours strongly aggregated, showing that this salt had been 
absorbed and taken effect. 

A short immersion in water for 20 m. did not retard the subsequent 
action of the phosphate, or of splinters of glass placed on the glands ; 
but in two instances an immersion for 50 m. prevented any effect from 
a solution of camphor. Several leaves which had been left for 20 m. 
in a solution of one part of white sugar to 218 of water were placed in 
the phosphate solution, the action of which was delayed ; whereas a 
mixed solution of sugar and the phosphate did not in the least interfere 
with the effects of the latter. Three leaves, after being immersed for 
20 m. in the sugar solution, were placed in a solution of carbonate of 
ammonia (one part to 218 of water) ; in 2 m. or 3 m. the glands 
were blackened, and after 7 m. the tentacles were considerably inflected, 
so that the solution of sugar, though it delayed the action of the 
phosphate, did not delay that of the carbonate. Immersion in a 
similar solution of gum 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, 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 another when subsequently 
placed in the phosphate solution. I here give a table summing up 
the results. 



Chap. IX.] EFFECTS OF PREVIOUS IMMERSION. 



175 



Name of the Salts and 
Acids in Solution. 



Period of 

Immersion of 

the Leaves 

in Solutions 

of one part to 

43Y of water. 



Effects produced on tlie Leaves by their subse- 
quent Immersion for stated periods in a 
Solution of one part of phospbate of 
ammonia to 8Y50 of water, or 1 gr. to 
20 oz. 



Rubidium chloride 

Potassium carbonate 

Calcium acetate . 
Calcium nitrate . 
Magnesium acetate 

Magnesium nitrate 

Magnesium chloride 

Barium acetate 
Barium nitrate 

Strontium acetate 



Strontium nitrate. 



.Aluminium chloride 



Aluminium nitrate 
Lead chloride , 



Manganese chloride 
Lactic acid 



Tannic acid . 
Tartaric acid . 
Citric acid 



Formic acid 



22 hrs. 

20 m. 

24 hrs. 
24 hrs. 
22 hrs. 

22 hrs. 

22 hrs. 

22 hrs. 
22 hrs. 

22 hrs. 



22 hrs. 



24 hrs. 



24 hrs 
23 hrs 



22 hrs 
48 hrs 



24 hrs, 
24 hrs 
24 hrs 



22 hrs. 



After 30 m. strong inflection of the 
tentacles. 

Scarcely any inflection until 5 hrs. had 
elapsed. 

After 24 hrs. very slight inflection. 
Do. do. 

Some slight inflection, which became 
well pronounced in 24 hrs. 

After 4 hrs. 30 m. a fair amount of 
inflection, which never increased. 

After a few minutes great inflection ; 
after 4 hrs. all four leaves with almost 
every tentacle closely inflected. 

After 24 hrs. two leaves out of four 
slightly inflected. 

After 30 m. one leaf greatly, and two 
others moderately, inflected ; they 
remained thus for 24 hrs. 

After 25 m. t%vo leaves greatly in- 
flected ; after 8 hrs. a third lea 
moderately, and the fourth very 
slightly, inflected. All four thus 
remained for 24 hrs. 

After 8 hrs. three leaves out of five 
moderately inflected ; after 24 hrs. 
all five in this state ; but not one 
closely inflected. 

Three leaves which had either been 
slightly or not at all afiected by the 
chloride became after 7 hrs. 30 m. 
rather closely inflected. 

After 25 hrs. slight and doubtful effect. 

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

After 48 hrs. not the least inflection. 

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

After 24 hrs. no inflection. 
Do. do. 

After 50 ra. tentacles decidedly inflected, 
and after 5 hrs. strongly inflected; 
so remained for the next 24 hrs. 

Not observed until 24 hrs. had elapsed ; 
tentacles considerably inflected, and 
protoplasm aggregated. 



176 DEOSEEA EOTUNDIFOLIA. [Chap. IX. 

Tu a large majority of these twe}ity 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 cases the phosphate did not produce the least effect. 
Now what are we to infer from these facts? We know from ten trials 
that immersion in distilled water for 24 hrs. prevents the subsequent 
action of the phosphate solution. It would therefore appear as if the 
solutions of chloride of manganese, tannic and tartaric acids, which are 
not poisonous, acted exactly like water, for the phosphate produced no 
effect on the leaves which had been previous!}' immersed in these three 
solutions. The majority of the other solutions behaved to a certain 
extent like water, for the phosphate produced, after a considerable 
interval of time, only a slight effect. On the other hand, the leaves 
which had been immersed in the solutions of the chloride of rubidium 
and magnesium, of acetate of strontium, nitrate of barium, and citric 
acid, were quickly acted on by the phosphate. Now, was water absorbed 
from these five weak solutions, and yet, owing to the presence of the 
salts, did not prevent the subsequent action of the phosphate ? Or 
may we not suppose * that the interstices of the walls of the glands 
were blocked up with the molecules of these five substances, so that they 
were rendered impermeable to water ; for had water entered, we know 
from the ten trials that the phosphate would not afterwards have 
produced any effect ? It further appears that the molecules of the 
carbonate of ammonia can quioklj' pass into glands which, from having 
been immersed for 20 m. in a weak solution of sugar, either absorb the 
phosphate very slowly or are acted on by it very slowly. On the other 
hand, glands, however they may have been treated, seem easily to permit 
the subsequent entrance of the molecules of carbonate of ammonia. 
Thus leaves which had been immersed in a solution (of one part to 437 
of water) of n itrate of potassium for 48 hrs. — of sulphate of potassium for 
24 hrs. — and of the chloride of potassium for 25 hrs. — on being placed in 
a solution of one part of carbonate of ammonia to 218 of water, had their 



* See Dr. M. Traube's curious ex- precipitation of sulphate of barium 

periments on the production of arti- to take place at the same time, the 

ficial cells, and on their permeability membrane becomes " infiltrated " 

to various salts, described in his with this salt ; and in consequence 

papers : " Experimente zur Theorie of the intercalation of molecules of 

der Zellenbildung und Endosmose," sulphate of barium among those of 

Breslau, 1866 ; and " Experimente the gelatine precipitate, the mole- 

zur physicalischen Erkliirung der cular interstices in the membrane 

Bildung der Zellhaut, ihres Wachs- are made smaller. In this altered 

thums durch Intussusception," Bres- condition, the membrane no longer 

lau, 1874. These researches perhaps allows the passage through it of 

explain my results. Dr. Traube either sulphate of ammonia or nitrate 

commonly employed as a membrane of barium, though it retains its per- 

the precipitate formed when tannic meability for water and chloride of 

acid comes into contact with a so- ammonia, 
lution of gelatine. By allowing a 



Chap. IX.] VAPOUE OF CHLOROFORM. 177 

plands 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 inflected. Four leaves 
were immersed in this mixture, and two of them after 30 m. were 
brushed with a camel-hair brush, like leaves in a solution of camphor, 
but this produced no effect. Nor did these four leaves, on being left 
for 24 hrs. in the diluted alcohol, undergo any inflection. They were 
then removed ; one being placed in au infusion of raw meat, and bits 
of meat on the discs of the other three, with their stalks in water. 
Next day one seemed a little injured, whilst two others showed merely a 
trace of inflection. We must, however, bear in mind that immersion 
for 24 hrs. in water prevents leaves from clasping meat. Hence alcohol 
of the above strength is not poisonous, nor does it stimulate the leaves 
like camphor does. 

The vapour of alcohol acts differently. A plant having three good 
leaves was left for 25 m. under a receiver holding 19 oz. with sixtj' 
minims of alcohol in a watch-glass. No movement ensued, but some 
few of the glands were blackened and shrivelled, whilst many became 
quite pale. These were scattered over all the leaves in the most 
irregular manner, reminding me of the manner in which the glands 
were affected by the vapour of carbonate of ammonia. Immediately 
on the removal of the receiver particles of raw meat were placed on 
many of the glands, those which retained their proper colour 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 tc 
curve inwards, and after 55 m. nearly all were considerably inflected ; 
but a few did not move. Some anasthethic effect is here probable, but 
by no means certain. A third plant was also left for 5 m. under the 
same small vessel, with its whole inner surface wetted with about a 
dozen drops of alcohol. Particles of meat were now placed on the 
glands of several tentacles, some of which first began to move in 25 m. ; 
after 40 m. most of them were somewhat inflected, and after 1 hr. 
10 m. almost all were considerably inflected. From their slow rate of 
movement there can be no doubt that the glands of these tentacles 
had been rendered insensible for a time by exposure during 5 m. to the 
vapour of alcohol. 

Vapour of Chloroform. — The action of this vapour on Drosera is 



178 DEOSEEA EOTUNDIFOLIA. [Chap. IX. 

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 
ei3'ect. The glands are sometimes rendered for a time insensible to the 
action of raw meat, but sometimes are not thus affected, or in a very 
slight degree. A plant recovers from a small dose, but is easily killed 
by a larger one. 

A plant was left for 30 m. under a bell-glass holding 19 fluid oz. 
(539 "9 c.c.) with eight drops of chloroform, and before the cover was 
removed, most of the tentacles became much inflected, though they 
did not reach the centre. After the cover was removed, bits of meat 
were placed on the glands of several of the somewhat incurved tentacles ; 
these glands were found much blackened after 6 hrs. 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 c.c), was now em- 
ployed, and a plant was left for 90 s. under it, with only two drops of 
chloroform. Immediately on the removal of the glass all the tentacles 
curved inwards so as to stand perpendicularly up ; and some of them 
could actually be seen moving with extraordinary quickness by little 
starts, and therefore in an unnatural manner ; but they never reached 
the centre. After 22 hrs. they fully re-expanded, and on meat 
being placed on their glands, or when roughly touched by a needle, 
they promptly became inflected ; so that these leaves had not been in 
the least injured. 

Another plant was placed under the same small bell-glass with three 
drops of chloroform, and before two minutes bad elapsed, the tentacles 
began to curl inwards with rapid little jerks. The glass was then 
removed, and in the course of two or three additional minutes almost 
every tentacle reached the centre. On several other occasions the vapour 
did not excite any movement of this kind. 

There seems also to be great variability in the degree and manner 
in which chloroform renders the glands insensible to the subsequent 
action of meat. In the plant last referred to, which had been exposed 
for 2 m. to three drops of chloroform, some fev/ tentacles cm-ved 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 elasped. Another plant was similarly exposed, that is, for 2 m., to 
three drops of chloroform, and on particles of meat being placed on the 
glands of several tentacles, which had curved up into a perpendicular 
position, one of these began to bend in 8 m., but afterwards moved 
very slowly ; whilst none of the other tentacles moved for the next 
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 shght ansesthetic 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 



Chap. IX.] VAPOUR OF ETHEK. 179 

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 
alternately to the air and during 7 m. to the vapour of seven drops of 
cliloroform. 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 anaesthetic influence on the leaves. 

On the other hand, another plant was exposed under the same 
vessel for a much longer time, viz. 20 m., to twice as much chloroform. 
Bits of meat were then placed on the glands of many tentacles, and all 
of them, with a single exception, reached the centre in from 13 m. to 
14 m. In this case, little or no anresthetic effect had been produced ; 
and how to reconcile these discordant results, I know not. 

Vapour of Sulphuric Ether. — A plant was exposed for 30 m. to 
thirty minims of this ether in a vessel holding 19 oz. ; and bits of 
raw meat were aftei'wards placed on many glands which had become 
pale-coloured ; but none of the tentacles moved. After 6 hrs. 30 m. 
the leaves appeared sickly, and the discal glands were almost dry. By 
the next morning many of the tentacles were dead, as were all those 
on which meat had been placed ; showing that matter had been ab- 
sorbed from the meat which had increased the evil effects of the 
vapour. After four days the plant itself died. Another plant was 
exposed in the same vessel for 15 m. to forty minims. One young, 
small, and tender leaf had all its tentacles inflected, and seemed much 
injured. Bits of raw meat were placed on several glands on two other 
and older leaves. These glands became dry after 6 hrs., and seemed 
injured ; the tentacles never moved, excepting one was ultimately a 
little inflected. The glands of which the other tentacles continued to 
secrete, and appeared uninjured, but the whole plant after three days 
became very sickly. 

In the two foregoing experiments the doses were evidently too large 
and poisonous. With weaker doses, the anresthetio effect was variable, 
as in the case of chloroform. A plant was exposed for 5 m. to ten 
drops under a 12-oz. vessel, and bits of meat were then placed on many 
glands. None of the tentacles thus treated began to move in a decided 
manner until 40 m. had elapsed ; but then some of them moved very 
quickly, so that two reached the centre after an additional interval of 
only 10 m. In 2 hrs. 12 m. from the time when the meat was given, 
all the tentacles reached the centre. Another plant, with two leaves, 
was exposed in the same vessel for 5 m. to a rather large dose of ether, 
and bits of meat were placed on several glands. In this case one 
tentacle on each leaf began to bend in 5 m. ; and after 12 m. two 
tentacles on one leaf, and one on the second leaf, reached the centre. 
In 30 m. after the meat had been given, all the tentacles, both those 

N 2 



180 DEOSEEA EOTUNDIFOLIA. [Chap. IX. 

with and without meat, were closely inflected ; so that the ether 
apparently had stimulated these leaves, causing all the tentacles to 
bend. 

Vapour of Nitric Ether. — This vapour seems more injurious (han 
that of sulphuric ether. A plant was exposed for 5 m. in a 12-oz. 
vessel to eight drops in a watch-glass, and I distinctly saw a few 
tentacles curling inwards before the glass was removed. Immediately 
afterwards bits of meat were placed on three glands, but no movement 
ensued in the course of 18 m. The same plant was placed again under 
the same vessel for 16 m. with ten drops of the ether. None of the 
tentacles moved, and next morning those with the meat were still in 
the same position. After 48 hrs. one leaf seemed healthy, but the 
others were much injured. 

Another plant, having two good leaves, was exposed for 6 m. under 
a 19-oz. vessel to the vapour from ten minims of the ether, and bits of 
meat were then placed on the glands of many tentacles on both leaves. 
After 36 m. several of them on one leaf became inflected, and after 
1 hr. almost all the tentacles, those with and without meat, nearly reached 
the centre. On the other leaf the glands began to dry in 1 hr. 40 m., 
and after several hours not a single tentacle was inflected ; but by the 
next morning, after 21 hrs., many were inflected, though they seemed 
much injured. In this and the previous experiment, it is doubtful, 
owing to the injury which the leaves had suffered, whether any 
anaesthetic effect had been produced. 

A third plant, having two good leaves, was exposed for only 4 m. 
in the 19-oz. vessel to the vapour from six drops. Bits of meat were 
then placed on the glands of seven tentacles on the same leaf. A 
single tentacle moved after 1 hr. 23 m. ; after 2 hrs. 3 m. several were 
inflected ; and after 3 hrs. 3 m. all the seven tentacles with meat were 
well inflected. Prom the slowness of these movements it is clear that 
this leaf had been rendered insensible for a time to the action of the 
meat. A second leaf was rather differently aflFeoted ; bits of meat 
were placed on the glands of five tentacles, three of which were 
slightly inflected in 28 m. ; after 1 hr. 21 m. one reached the centre, 
but the other two were still only slightly inflected; after 3 hrs. they 
were much more inflected; but even after 5 hrs. 16 m. all five had 
not reached the centre. Although some of the tentacles began to 
move moderately soon, they afterwards moved with extreme slowness. 
By next morning, after 20 hrs., most of the tentacles on both leaves 
were closely inflected, but not quite regularly. After 48 hrs. neither 
leaf appeared injured, though the tentacles were still inflected; after 
72 hrs. one was almost dead, whilst the other was re-expanding and 
recovering. 

Carbonic Acid.- — A plant was placed under a 122-oz. bell-glass 
filled with this gas and standing over water; but I did not make 
sufficient allowance for the absorption of the gas by the water, so that 
.towards the latter part of the experiment some air was drawn in. 
After an exposm-e of 2 hrs. the plant was removed, and bits of raw 



CiiAr. IX.] CARBONIC ACID. 181 

meat placed on the glands of three leaves. One of these leaves hung 
a little down, and was at first partly and soon afterwards completely 
covered by the water, which rose within the vessel as the gas was 
absorbed. On this latter leaf the tentacles, to which meat had been, 
given, became well inflected in 2 m. 30 s., that is, at about the normal 
rate; so that until I remembered that the leaf had been protected 
from the gas, and might perhaps have absorbed oxygen from the water 
which was continually drawn inwards, I falsely concluded that the 
carbonic acid had produced no effect. On the other two leaves, the 
tentacles with meat behaved very differently from those on the first 
leaf; two of them first began to move slightly in 1 hr. 50 m., always 
reckoning from the time when the meat was placed on the glands — • 
were plainly inflected in 2 hrs. 22 m. — -and in 3 hrs. 22 m. reached 
the centre. Three other tentacles did not begin to move until 2 hrs. 
20 m. had elapsed, but reached the centre at about the same time 
with the others, viz. in 3 hrs. 22 m. 

This experiment was repeated several times with nearly the same 
results, excepting that the interval before the tentacles began to move 
varied a little. I will give only one other case. A plant was exposed 
in the same vessel to the gas for 45 m., and bits of meat were then 
placed on four glands. But the tentacles did not move for 1 hr. 40 m. ; 
after 2 hrs. 30 m. all four were well inflected, and after 3 hrs. reached 
the centre. 

The following singular phenomenon sometimes, but by no means 
always, occurred. A plant was immersed for 2 hrs., and bits of meat 
Avcrc then placed on several glands. In the course of 13 m. all the 
submarginal tentacles on one leaf became considerably inflected ; those 
with the meat not in the least degree more than the others. 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 tentacles closely inflected 
over the bits of meat which by this time had been carried to their 
centres. Thus these three leaves had perfectly recovered from the 
effects of the gas in the course of 24 hrs. 

On another occasion some fine plants, after having been left for 
2 hrs. in the gas, were immediately given bits of meat in the usual 
manner, and on their exposure to the air most of their tentacles became 
in 12 m. curved into a vertical or sub- vertical position, but in an ex- 
tremely irregular manner ; some only on one side of the leaf and some 
on tlie other. They remained in this position for some time; the 
tentacles with the bits of meat not having at first moved more quickly 
or farther inwards than the others without meat. But after 2 hrs. 
20 m. the former began to move, and steadily went on bending until 
they reached the centre. Next morning, after 22 hrs., all the tentacles 



182 DROSEBA EOTUNDIFOLIA.. [Chap. IX. 

on these leaves were closely clasped over the meat which had been 
carried to their centres ; whilst the vertical and sub-vertical tentacles 
on the other leaves to which no meat had been given had fully re- 
expanded. Judging, however, from the subsequent action of a weak 
solution of carbonate of ammonia en one of these latter leaves, it had 
not perfectly recovered its excitability and power of movement in 22 
hrs. ; but another leaf, after an additional 24 hrs., had completely re- 
covered, judging from the manner in which it clasped a fly placed on 
its disc. 

I will give only one other experiment. After the exposure of a 
plant for 2 hrs. to the gas, one of its leaves was immersed in a rather 
strong solution of carbonate of ammonia, together with a fresh leaf 
from another plant. The latter had most of its tentacles strongly 
inflected within 30 m. ; whereas the leaf which had been exposed to 
the carbonic acid remained for 24 hrs. in the solution without under- 
going any inflection, with the exception of two tentacles. 'J'his leaf 
had been almost completely paralysed, and was not able to recover its 
sensibility whilst still in the solution, which from havihg 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 influence on the nervous 
system of animals. I was at first encouraged in my trials 
by finding that strychnine, digitaline, and nicotine, which 
all act on the nervous system, were 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 innocuous acids, 
though much diluted, such as benzoic, acetic, &c., as well as 
some essential oils, are extremely poisonous to Drosera, and 
quicldy cause strong inflection, it seems probable that 
strychnine, nicotine, digitaline, and hydrocyanic acid, excite 
inflection by acting on elements in no way analogous to 
the nerve-cells of animals. If elements of this latter nature 
had been present in the leaves, it might have been expected 
that morphia, hyosoyamus, atropine, veratrine, colchicine, 
curare, and diluted alcohol would have produced some marked 
effect ; whereas these substances are not poisonous and have 



Chap. IX.] SUMMARY OF THE CHAPTBE. 183 

no power, or only a very sliglit one, of inducing inflection. 
It should, however, he observed that curare, colchicine, and 
veratrine are muscle-poisons — that is, act on nerves having 
eome special relation with the muscles, and, therefore, could 
not be expected to act on Drosera. The poison of the cobra 
is most deadly to animals, by paralysing their nerve-centres,* 
yet is not in the least so to Drosera, though quickly causing 
strong inflection. 

Notwithstanding the foregoing facts, which show how 
widely different is the effect of certain substances on the 
health or life of animals and of Drosera, yet there exists a 
certain degree of parallelism in the action of certain other 
substances. We have seen that this holds good in a striking 
manner with the salts of sodium and potassium. Again, 
various metallic salts and acids, namely those of silver, mer- 
cury, gold, tin, arsenic, chromium, copper, and platina, most 
or all of which are highly poisonous to animals, are equally 
80 to Drosera. But it is a singular fact that the chloride of 
lead and two salts of barium were not poisonous to this plant. 
It is an equally strange fact, that, though acetic and pro- 
pionic acids are highly poisonous, their ally, formic acid, is 
not so ; and that, whilst certain vegetable acids, namely 
oxalic, benzoic, &c., are poisonous in a high degree, gallic, 
tannic, tartaric, and malic (all diluted to an equal degree) 
are not so. Malio 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.l 

Of the alkaloids and their salts which were tried, several 
had not the least power of inducing inflection ; others, which 
were certainly ahsorbed, as shown by the changed colour of 
the glands, had but a very moderate power of this kind ; 



* Dr. Fayrer, 'The Thanatophidia ova of the pike) is not materially 

of India,' 1872, p. 4. influenced by any of the poisons used, 

t Seeing that acetic, hydrocyanic, which did not act chemically, with 
and chromic acids, acetate of strych- the exception of chloroform and car- 
nine, and vapour of ether, are poison- bonlc acid." I find it stated by 
ous to Drosera, it is remarkable that several writers that curare has no 
Dr. Kansom (' Philosoph. Transact.' influence on sarcode or protoplasm, 
1867, p. 480), who used much and we have seen that, though curare 
stronger solutions of these substances excites some degree of inflection, it 
than I did, states " that the rhyth- causes very little aggregation of the 
mic contractility of the yolk (of the protoplasm. 



184 DEOSEEA EOTUNDIFOLIA. [Chap. IX. 

others, again, such as the acetate of quinine and digitaline, 
caused strong inflection. 

The severar substances mentioned in this chapter afiectthe 
colour of the glands very differently. These often hecome dark 
at first, and then very pale or white, as was conspicuously 
the case with glands subjected to the poison of the cobra 
and citrate of strychnine. In other cases they are from the 
first rendered white, as with leaves placed in hot water and 
several acids ; and this, I presume, is the result of the coagu- 
lation of the albumen. On the same leaf some glands become 
white and others dark-coloured, as occurred with leaves in a 
solution of the sulphate of quinine, and in the vapour of 
alcohol. Prolonged immersion in nicotine, curare, and even 
water, blackens the glands ; and this, I believe, is due to the 
aggregation of the protoplasm within their cells. Yet curare 
caused very little aggregation in the cells of the tentacles, 
whereas nicotine and sulphate of quinine induced strongly 
marked aggregation down their bases. The aggregated 
masses in leaves which had been immersed for 3 hrs. 15 m. 
in a saturated solution of sulphate of quinine exhibited inces- 
sant changes of form, but after 24 hrs. were motionless ; the 
leaf being flaccid and apparently dead. On the other hand, 
with leaves subjected for 48 hrs. to a strong solution of the 
poison of the cobra, the protoplasmic masses were unusually 
active, whilst with the higher animals the vibratile cilia and 
white corpuscles of the blood seem to be quickly paralysed 
by this substance. 

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

Leaves which have been immersed for 24 hrs. in water, 
and for only 20 m. in diluted alcohol, or in a weak solution 
of sugar, are afterwards acted on very slowly, or not at all, 
by the phosphate of ammonia, though they are quickly acted 
on by the carbonate. Immersion for 20 m. in a solution of 
gum arable has no such inhibitory power. The solutions of 



Chap. IX.] SUMMARY OF THE CHAPTER. 185 

certain salts and acids affect the leaves, with respect to the 
subsequent action of the phosphate, exactly like water, whilst 
others allow the phosphate afterwards to act quickly and 
energetically. In this latter case, the interstices of the cell- 
walls may have been blocked up by the molecules of the 
salts first given in solution, so that water could not after- 
wards enter, though the molecules of the [jhosphate could do 
80, and those of the carbonate still more easily. 

The action of camphor dissolved in water is remarkable, 
for it not only soon induces inflection, but apparently renders 
the glands extremely sensitive to mechanical irritation ; for 
if they are brushed with a soft brush, after being immersed 
in the solution for a short time, the tentacles begin to bend 
in about 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 tlie other hand, serves as a 
narcotic. 

Some essential oils, both in solution and in vapour, cause 
rapid inflection, others have no such power; those which I 
tried were all poisonous. 

Diluted alcohol (one part to seven of water) is not poison- 
ous, does not induce inflection, nor increase the sensitiveness 
of the glands to mechanical irritation. The vapour acts as a 
narcotic or antiasthetic, 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 difi'erences 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 stomata of 
Drosera. They sometimes excite extraordinarily rapid in- 
flection, 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 anajsthetic. In this case the tentacles, whether or not 
they have become inflected, are not excited to further move- 
ment by bits of meat placed on the glands, until some 
considerable time has elapsed. It is generally believed that 



186 DEOSEKA EOTUNDIFOLIA. [Chap. IX. 

■with animals and plants these vapours act by arresting 
oxidation. 

Exposure to carhonic acid for 2 hrs., and in one ease for 
only 45 m., likewise rendered the glands insensible for a 
time to the powerful stimulus of raw meat. The leaves, 
however, recovered their full powers, and did not seem in 
the least injured, on being left in the air for 24 or 48 hrs. 
We have seen in the third chapter that the process of 
aggregation in leaves subjected for two hours to this gas and 
then immersed in a solution of the carbonate of ammonia is 
much retarded, so that a considerable time elapses before the 
protoplasm in the lower cells of the tentacles becomes aggre- 
gated. In some cases, soon after the leaves were removed 
from the gas and brought into the air, the tentacles moved 
spontaneously ; this being due, I presume, to the excitement 
from the access of oxygen. These inflected tentacles, how- 
ever, could not be excited for some time afterwards to any 
further movement by their glands being stimulated. With 
other irritable plants it is known* that the exclusion of 
oxygen prevents their moving, and arrests the movements of 
the protoplasm within their cells, but this arrest is a different 
phenomenon from the retardation of the process of aggre- 
gation just alluded to. Whether this latter fact ought to be 
attributed to the direct action of the carbonic acid, or to the 
exclusion of oxygen, I know not. 



Sachs, 'Traits de Bot.' 1874, pp. 846, 1037. 



Chap. X.] SENSITIVENESS OF THE LEAVES. 187 



CHAPTEE X. 

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

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

We have seen in the previous chapters that many vyidely 
•different stimulants, mechanical and chemical, excite the 
movement of the tentacles, as well as of the blade of the leaf ; 
and v^e must now consider, firstly, what are the points which 
are irritable or sensitive, and secondly how the motor impulse 
is transmitted from one point to another. The glands are 
almost exclusively the seat of irritability, yet this irritability 
must extend for a very short distance below them ; for when 
they were cut off with a sharp pair of scissors without being 
themselves touched, the tentacles often became inflected. 
These headless tentacles frequently re-expanded ; and when 
afterwards drops of the two most powerful known stimulants 
were placed on the cut-off ends, no effect was produced. 
Nevertheless these headless tentacles are capable of sub- 
sequent inflection if excited by an impulse sent from the disc. 
I succeeded on several occasions in crushing glands between 
fine pincers, but this did not excite any movement ; nor did 
raw meat and salts of ammonia, when placed on such crushed 
glands. It is probable that they were killed so instantly 
that they were not able to transmit any motor impulse ; for 
in six observed cases (in two of which, however, the gland 
was quite pinched off) the protoplasm within the cells of the 
tentacles did not become aggregated ; whereas in some 
adjoining tentacles, which were inflected from having been 
roughly touched by the pincers, it was well aggregated. In 
like manner the protoplasm does not become aggregated 
when a leaf is instantly killed by being dipped into boiling 



188 DROSEEA EOTUNDIFOLIA. [Chap. X. 

water. On. the other hand, in several cases in which tentacles 
became inflected after their glands had been cut off with 
sharp scissors, a distinct though moderate degree of aggre- 
gation supervened. 

The pedicels of the tentacles were roughly and repeatedly- 
rubbed ; raw meat or other exciting substances were placed 
on them, both on the upper surface near the base and else- 
where, but no distinct movement ensued. Some bits of 
meat, after being left for a considerable time on the pedicels, 
were pushed upwards, so as just to touch the glands, and in 
a minute the tentacles began to bend. I believe that the 
blade of the leaf is not sensitive to any stimulant. I drove 
the point of a lancet through the blades of several leaves, 
and a needle three or four times through nineteen leaves : in 
the former case no movement ensued ; but about a dozen of 
the leaves which were repeatedly pricked had a few tentacles 
irregularly inflected. As, however, their backs had to be 
supported during the operation, some of the outer glands, as 
well as those on the disc, may have been touched ; and this 
perhaps sufficed to cause the slight degree of movement 
observed. Nitschke* says that cutting and pricking the leaf 
does not excite movement. The petiole of the leaf is quite 
insensible. 

The backs of the leaves bear numerous minute papilla, 
which do not secrete, but have the power of absorption. 
These papillas are, I believe, rudiments of formerly existing 
tentacles together with their glands. Many experiments 
were made to ascertain whether the backs of the leaves could 
be irritated in any way, thirty-seven leaves being thus tried. 
Some were rubbed for a long time with a blunt needle, and 
drops of milk and other exciting fluids, raw meat, crushed 
flies, and various substances, placed on others. These sub- 
stances were apt soon to become dry, showing that no 
secretion had been excited. Hence I moistened them 
with saliva, solutions of ammonia, weak hydrochloric acid, 
and frequently with the secretion from the glands of other 
leaves. I also kept some leaves, on the backs of which 
exciting objects had been placed, under a damp bell-glass ; 
but with all my care I never saw any true movement. I 
was led to make so many trials because, contrary to my 
previous experience, Nitschke statesf that, after affixing 



' Bot. Zeitung,' 1860, p. 234. j Ibid., p. 437. 



Chap. X.] SENSITIVENESS OF THE LEAVES. 180 

objects to the backs of leaves by the aid of the viscid 
secretion, he repeatedly sa,w the lentacles (and in one instance 
the blade) become reflexed. This movement, if a true one, 
would be most anomalous ; for it implies that the tentacles 
receive a motor impulse from an unnatural source, and have 
the power of bending in a direction exactly the reverse of 
that which is habitual to them ; this power not being of the 
least use to the plant, as insects cannot adhere to the smooth 
backs of the leaves. 

I have said that no effect was produced in the above 
cases ; but this is not strictly true, for in three instances a 
little syrup was added to the bits of raw meat on the backs 
of leaves, in order to keep them damp for a time ; and after 
36 hrs. there was a trace of reflexion in the tentacles of one 
leaf, and certainly in the blade of another. After twelve 
additional hours the glands began to dry, and all three leaves 
seemed much injured. Four leaves were then placed under 
a bell-glass, with their foot-stalks in water, with drops of 
syrup on their backs, but without any meat. Two of these 
leaves, after a day, had a few tentacles reflexed. The drops 
had now increased considerably in size, from having imbibed 
moisture, so as to trickle down the backs of the tentacles and 
footstalks. On the second day, one leaf had its blade much 
reflexed ; on the third day the tentacles of two were much 
reflexed, as well as the blades of all four to a greater or less 
degree. The upper side of one leaf, instead of being, as at first, 
slightly concave, now presented a strong convexity upwards. 
Even on the fifth day the leaves did not appear dead. Now, 
as sugar does not in the least excite Drosera, we may safelj' 
attribute the reflexion of the blades and tentacles of the 
above leaves to exosmose from the cells which were in 
contact with the syrup, and their consequent contraction. 
When drops of syrup are placed on the leaves of plants with 
their roots still in damp earth, no inflection ensues, for the 
roots, no doubt, pump up water as quickly as it is lost by 
exosmose. But if cut-off leaves are immersed in syrup, or in 
any dense fluid, the tentacles are greatly, though irregularly, 
inflected, some of them assuming the shape of corkscrews ; 
and the leaves soon become flaccid. If they are now 
immersed in a fluid of low specific gravity, the tentacles 
re-expand. From these facts we may conclude that drops of 
syrup placed on the backs of leaves do not act by exciting a 
motor impulse which is transmitted to the tentacles ; but 



190 ' DBOSEEA BOTUNDIFOLIA. [Chap. X. 

that they cause reflection hy inducing exosmose. Dr. 
Nitschke used the secretion for sticking insects to the hacks 
of the leaves ; and I suppose that he used a large quantity, 
which from being dense probably caused exosmose. Perhaps, 
he experimented on cut-off leaves, or on plants with their 
roots not supplied with enough water. 

As far, therefore, as our present knowledge serves, we 
may conclude that the glands, together with the immediately- 
underlying cells of the tentacles, are the exclusive seats of 
that irritability or sensitiveness with which the leaves are 
endowed. The degree to which a gland is excited can be 
measured only by the number of the surrounding tentacles 
which are inflected, and by the amount and rate of their 
movement. Equally vigorous leaves, exposed to the same 
temperature (and this is an important condition), are excited 
in various degrees under the following circumstances, A 
minute quantity of a weak solution produces no effect ; add 
more, or give a rather stronger solution, and the tentacles 
bend. Touch a gland once or twice, and no movement 
follows; touch it three or four times, and the tentacle 
becomes inflected. But the nature of the substance which is 
given is a very important element : if equal-sized particles 
of glass (which acts only mechanically), of gelatine, and 
raw meat are placed on the discs of several leaves, the 
meat causes far more rapid, energetic, and widely extended 
movement than the two former substances. The number of 
glands which are excited also makes a great difference in the 
result : place a bit of meat on one or two of the discal glands, 
and only a few of the immediately surrounding short tentacles 
are inflected ; place it on several glands, and many more are 
acted on ; place it on thirty or forty, and all the tentacles, 
including the extreme marginal ones, become closely inflected. 
We thus see that the impulses proceeding from a number of 
glands strengthen one another, spread farther, and act on a 
larger number of tentacles, than the impulse from any single 
gland. 

Transmission of the Motor Impulse. — In every case the impulse 
from a gland has to travel for at least a short distance to the 
basal part of the tentacle, the upper part and the gland 
itself being merely carried by the inflection of the lower 
part. The impulse is thus always transmitted down nearly 
the whole length of the pedicel. When the central glands 
are stimulated, and the extreme marginal tentacles become 



Chap. X.] TRANSMISSION OF MOTOR IMPULSE. 191 

inflected, tlie impulse is transmitted across half the diameter 
of the disc, and when the glands on one side of the disc are 
stimulated, the impulse is transmitted across nearly the 
whole width of the disc. A gland transmits its motor 
impulse far more easily and quickly down its own. tentacle 
to the bending place than across the disc to neighbouring 
tentacles. Thus a minute dose of a very weak solution of 
ammonia, if given to one of the glands of the exterior 
tentacles, causes it to bend and reach the centre ; whereas a 
large drop of the same solution, given to a score of glands 
on the disc, will not cause through their combined influence 
the least inflection of the exterior tentacles. Again, when a 
bit of meat is placed on the gland of an exterior tentacle, 
1 have seen movement in ten seconds, and repeatedly within a 
minute ; but a much larger bit placed on several glands on 
the disc does not cause the exterior tentacles to bend until 
half an hour or even several hours have elapsed. 

The motor impulse spreads gradually on all sides from one 
or more excited glands, so that the tentacles which stand 
nearest are always first affected. Hence, when the glands 
in the centre of the disc are excited, the extreme marginal 
tentacles are the last inflected. But the glands on different 
parts of the leaf transmit their motor power in a somewhat 
different manner. If a bit of meat be placed on the long- 
headed gland of a marginal tentacle, it quickly transmits 
an impulse to its own bending portion ; but never, as far as 
I have observed, to the adjoining tentacles ; for these are not 
affected until the meat has been carried to the central glands, 
which then radiate forth their conjoint impulse on all sides. 
On four occasions leaves were prepared by removing some 
days previously all the glands from the centre, so that these 
could not be excited by the bits of meat brought to them by 
the inflection of the marginal tentacles; and now these 
marginal tentacles re~expanded after a time without any 
other tentacle being affected. Other leaves were similarly 
prepared, and bits of meat were placed on the glands of two- 
tentacles in the third row from the outside, and on the glands- 
of two tentacles in the fifth row. In these four cases the 
impulse was sent in the first place laterally, that is, in the 
same concentric row of tentacles, and then towards the 
centre; but not centrifugally, or towards the exterior 
tentacles. In one of these cases only a single tentacle on 
each side of the one with meat was affected. In. the three= 



192 DEOSEEA EOTUN'DIPOLIA. [Chap. X. 

other cases, from half a dozen to a dozen tentacles, hotli 
laterally and towards the centre, were well inflected, or 
STih-inflected. Lastly, in ten other experiments, minute hits 
of meat were placed on a single gland or on two glands in 
the centre of the disc. In order that no other glands should 
touch the meat, through the inflection of the closely 
adjoining short tentacles, about half a dozen glands had been 
previously removed round the selected ones. On eight of 
these leaves from sixteen to twenty-fi.ve of the short 
surrounding tentacles were inflected in the course of one or 
two days ; so that the motor impulse radiating from one or 
two of the discal glands is able to produce this much effect. 
The tentacles which had been removed are included in the 
above numbers ; for, from standing so close, they would 
certainly have been affected. On the two remaining leaves, 
almost all the short tentacles on the disc were inflected. 
With a more powerful stimulus than meat, namely a 
little phosphate of lime moistened with saliva, I have seen 
the inflection spread still farther from a single gland thus 
treated ; but even in this case the three or four outer rows 
of tentacles were not affected. Prom these experiments it 
appears that the impulse from a single gland on the disc acts 
on a greater number of tentacles than that from a gland of 
one of the exterior elongated tentacles ; and this probably 
follows, at least in part, from the impulse having to travel 
a very short distance down the pedicels of the central 
tentacles, so that it is able to spread to a considerable dis- 
tance all round. 

Whilst examining these leaves, I was struck with the fact 
that in six, perhaps seven, of them the tentacles were much 
more inflected at the distal and proximal ends of the leaf {ie. 
towards the apex and base) than on either side; and yet 
the tentacles on the sides stood as near to the gland where 
the bit of meat lay as did those at the two ends. It thus 
appeared as if the motor impulse was transmitted from the 
centre across the disc more readily in a longitudinal than in 
a transverse direction ; and as this appeared a new and 
interesting fact in the physiology of plants, thirty-five fresh 
experiments were made to test its truth. Minute bits of 
meat were placed on a single gland or on a few glands, on 
the right or left side of the discs of eighteen leaves ; other 
bits of the same size being placed on the distal or proximal 
ends of seventeen other leaves. Now if the motor impulse 



CHAr. X.] TEANSSnSSION OF MOTOR IMPULSE. 193 

were transmitted -with equal force or at an equal rate through 
the blade in all directions, a bit of meat placed at one side 
or at one end of the disc ought to aifect equally all the 
tentacles situated at an equal distance from it ; but this 
certainly is not the case. Before giving the general results, 
it may be well to describe three or four rather unusual 



(1) A minute fragment of a fly was placed on one side of the disc, 
and after 32 m. seven of the outer tentacles near the fragment were 
inflected: after 10 hrs. several more became so, and after 23 hrs. a 
['.till greater number ; and now the blade of the leaf on this side was 
bent inwards so as to stand up at right angles to the other side. 
Neither the blade of the leaf nor a single tentacle on the opposite side 
was affected ; the line of separation between the two halves extending 
from the footstalk to the apex. The leaf remained in this state for 
three days, and on the fourth day began to re-expand ; not a single 
tentacle having been inflected on the opposite side. 

(2) I will here give a case not included in the above thirty-five 
experiments. A small fly was found adhering by its feet to the left 
side of the disc. The tentacles on this side soon closed in and killed 
the fly : and owing probably to its struggle whilst alive, the leaf was 
so much excited that in about 24 hrs. all the tentacles on the opposite 
side became inflected ; but as they found no prey, for their glands did 
not reach the fly, they re-expanded in the course of 15 hrs.; the 
tentacles on the left side remaining clasped for several days. 

(3) A bit of meat, rather larger than those commonly used, was 
placed in a medial line at the basal end of the disc, near the footstalk ; 
after 2 hrs. 30 m. some neighbouring tentacles were inflected ; after G 
hrs. the tentacles on both sides of the footstalk, and some way up both 
sides, were moderately inflected; after 8 hrs. the tentacles at the 
further or distal end were more inflected than those on either side ; 
after 23 hrs. the meat was well clasped by all the tentacles, excepting 
by the exterior ones on the two sides. 

(4) Another bit of meat was placed at the opposite or distal end of 
another leaf, with exactly the same relative results. 

(5) A minute bit of meat was placed on one side of the disc ; next 
day the neighbouring short tentacles were inflected, as well as in a 
slight degree tliree or four on the opposite side near the footstalk. On 
the second day these latter tentacles showed signs of re-expanding, 
so I added a fresh bit of meat at nearly the same spot, and after 
two days some of the short tentacles on the opposite side of the disc 
were inflected. As soon as these began to re-expand, I added another 
bit of meat, and next day all the tentacles on the opposite side 
of the disc were inflected towards the meat ; whereas we have .seen 
that those on the same side were affected by the first bit of meat which 
was given. 





194 DEOSEEA EOTUNDIFOLIA. [Chap. X. 

Now for tlie general results. Of the eighteen leaves on 
■which, bits of meat were placed on the right or left sides of 
the disc, eight had a vast number of tentacles inflected on 
the same side, and in four of them the blade itself on this 
side was likewise inflected ; whereas not a single tentacle 
nor the blade was affected on the opposite side. These 
leaves presented a very curious appearance, as if only the 
inflected side was active, and the other paralysed. In the 
remaining ten cases, a few tentacles became inflected beyond 
the medial line, on the side opposite to that where the meat 
lay; but, in some of these cases, only at the proximal or 
distal ends of the leaves. The inflection on the opposite side 
always occurred considerably after that on the same side, 
and in one instance not until the fourth day. We have 
also seen with No. 5 that bits of meat had to be added thrice 
before all the short tentacles on the opposite side of the disc 
were inflected. 

The result was widely different when bits of meat were 
placed in a medial line at the distal or proximal ends of the 
disc. In three of the seventeen experiments thus made, 
owing either to the state of the leaf or to the smallness of the 
bit of meat, only the immediately adjoining tentacles were 
affected ; but in the other fourteen cases the tentacles at the 
opposite end of the leaf were inflected, though these were as 
distant from where the meat lay as were those on one side of 
the disc from the meat on the opposite side. In some of the 
present cases the tentacles on the sides were not at all affected, 
or in a less degree, or after a longer interval of time, than 
those at the opposite end. One set of experiments is worth 
giving in fuller detail. Cubes of meat, not quite so small as 
those usually employed, were placed on one side of the discs 
of four leaves, and cubes of the same size at the proximal or 
distal end of four other leaves. Now, when these two sets 
of leaves were compared after an interval of 24 hrs., they 
presented a striking difference. Those having the cubes on 
one side were very slightly affected on the opposite side ; 
whereas those with the cubes at either end had almost every 
tentacle at the opposite end, even the marginal ones, closely 
inflected. After 48 hrs. the contrast in the state of the two 
sets was still great ; yet those with the meat on one side now 
had their discal and submarginal tentacles on the opposite 
side somewhat inflected, this being due to the large size of 
the cubes. Finally we may conclude from these thirty-five 



Chap. X.] TKANSMISSION OF MOTOR IMPULSE. 195 

experiments, not to mention tlie six or seven previous ones, 
that the motor impulse is transmitted from any single gland 
or small group of glands through the blade to the other ten- 
tacles more readily and effectually in a longitudinal than in 
a transverse direction. 

As long as the glands remain excited, and this may last 
for many days, even, for eleven, as when in contact with 
phosphate of lime, they continue to transmit a motor impulse 
to the basal and bending parts of their own pedicels, for other- 
wise they would re-expand. The great difference in the 
length of time during which tentacles remain inflected over 
inorganic objects, and over objects of the same size containing 
soluble nitrogenous matter, proves the same fact. But the 
intensity of the impulse transmitted from an excited gland, 
which has begun to pour forth its acid secretion and is at the 
same time absorbing, seems to be very small compared with 
that which it transmits when first excited. Thus, when 
moderately large bits of meat were placed on one side of the 
disc, and the discal and submarginal tentacles on the opposite 
side became inflected, so that their glands at last touched the 
meat and absorbed matter from it, they did not transmit any 
motor influence to the exterior rows of tentacles on the same 
side, for these never became inflected. If, however, meat 
had been placed on the glands of these same tentacles before 
they had begun to secrete copiously and to absorb, they un- 
doubtedly would have affected the exterior rows. Neverthe- 
less, when I gave some phosphate of lime, which is a most 
powerful stimulant, to several submarginal tentacles already 
considerably inflected, but not yet in contact with some 
phosphate previously placed on two glands in the centre 
of the disc, the exterior tentacles on the same side were 
acted on. 

When a gland is first excited, the motor impulse is dis- 
charged within a few seconds, as we know from the bending 
•of the tentacle ; and it appears to be discharged at first with 
much greater force than afterwards. Thus, in the case above 
given of a small fly naturally caught by a few glands on one 
side of a leaf, an impulse was slowly transmitted from them 
across the whole breadth of the leaf, causing the opposite 
tentacles to be temporarily inflected, but the glands which 
remained in contact with the insect, though they continued 
for several days to send an impulse down their own pedicels 
to the bending place, did not prevent the tentacles on th& 

2 



196 DEOSEKA EOTUNDIFOLIA. [Chap. X, 

opposite side from quickly re-expanding ; so that the motor 
discharge must at first have been more powerful than 
afterwards. 

When an object of any kind is placed on the disc, and the 
surrounding tentacles are inflected, their glands secrete more 
copiously and the secretion becomes acid, so that some in- 
fluence is sent to them from the discal glands. This change 
in the nature and amount of the secretion cannot depend on 
the bending of the tentacles, as the glands of the short central 
tentacles secrete acid when an object is placed on them, 
though they do not themselves bend. Therefore I inferred 
that the glands of the disc sent some influence up the sur- 
rounding tentacles to their glands, and that these reflected 
back a motor impulse to their basal parts ; but this view 
was soon proved erroneous. It was found by many trials 
that tentacles with their glands closely cut off by sharp 
scissors often become inflected and again re-expand, still 
appearing healthy. One which was observed continued 
healthy for ten days after the operation. I therefore cut the 
glands off twenty-five tentacles, at different times and on 
different leaves, and seventeen of these soon became inflected, 
and afterwards re-expanded. The re-expansion commenced 
in about 8 hrs. or 9 hrs., 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 addi- 
tional days. The meat was removed from one of these leaves, 
and the surface washed with a little stream of water, and 
after three days the headless tentacle re-expanded for the 
second time. These tentacles without glands were, however, 
in a different state from those provided with glands and which 
had absorbed matter from the meat, for the protoplasm within, 
the cells of the former had undergone far less aggregation. 
From these experiments with headless tentacles it is certain 
that the glands do not, so far as the motor impulse is concerned,, 
act in a reflex manner like the nerve-ganglia of animals. 

But there is another action, namely that of aggregation, 
which in certain cases may be called reflex, and it is the only 
known instance in the vegetable kingdom. We should bear 
in mind that the process does not depend on the previous- 



Chap. X.] DIRECTION OF INFLECTED TENTACLES. 197 

bending of the tentacles, as we clearly see when leaves are 
immersed in certain strong solutions. Nor does it depend on 
increased secretion from the glands, and this is shown by 
several facts, more especially by the papilla, which do not 
secrete, yet undergoing aggregation, if given carbonate of am- 
monia or an infusion of raw meat. When a gland is directly 
stimulated in any way, as by the pressure of a minute par- 
ticle of glass, the protoplasm within the cells of the gland 
first becomes aggregated, then that in the cells immediately 
beneath the gland, and so lower and lower down the tentacles 
to their bases ; — that is, if the stimulus has been sufficient 
and not injurious. Now, when the glands of the disc are 
excited, the exterior tentiicles are affected in exactly the same 
manner : the aggregation always commences in their glands, 
though these have not been directly excited, but have only 
received some influence from the disc, as shown by their 
increased acid secretion. The protoplasm within the cells 
immediately beneath the glands are next affected, and so 
downwards from cell to cell to the bases of the tentacles. 
This process apparently deserves to be called a reflex action, 
in the same manner as when a sensory nerve is irritated, and 
carries an impression to a ganglion which sends back some 
influence to a muscle or gland, causing movement or increased 
secretion ; but the action in the two cases is probably of a 
widely different nature. After the protoplasm in a tentacle 
has been aggregated, its redissolution always begins in the 
lower part, and slowly travels up the pedicel to the gland, so 
that the protoplasm last aggregated is first redissolved. 
This probably depends merely on the protoplasm being less 
and less aggregated, lower and lower down in the tentacles, 
as can be seen plainly when the excitement has been slight. 
As soon, therefore, as the aggregating action altogether 
ceases, redissolution naturally commences in the less strongly 
aggregated matter in the lowest part of the tentacle, and is 
there first completed. 

Direction of the Inflected Tentacles. — When a particle of 
any kind is placed on the gland of one of the outer tentacles, 
this invariably moves towards the centre of the leaf; and so 
it is with all the tentacles of a leaf immersed in any exciting 
fluid. The glands of the exterior tentacles then form a ring 
round the middle part of the disc, as shown in a previous 
figure (fig. 4, p. 9). The short tentacles within this ring 
still retain their vertical position, as they likewise do when 



198 



DEOSEEA EOTUNDIFOLIA. 



[Chap. X. 



a large object is placed on their glands, or when an insect is 
caught by them. In this latter case we can see that the 
inflection of the short central tentacles would he useless, as 
their glands are already in contact with their prey. 

The result is very different when a single gland on one 
side of the disc is excited, or a few in a group. These send 
an impulse to the surrounding tentacles, which do not now 
bend towards the centre of the leaf, but to the point of ex- 
citement. We owe this capi- 
tal observation to Nitschke,* 
and since reading his paper a 
few years ago, I have repeat- 
edly 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 
togethei', halfway between 
the centre and the circum- 
ference of the disc, the di- 
rected movement of the sur- 
rounding tentacles is well 
exhibited. An accurate draw- 
ing of a leaf with meat in 
this position is here repro- 
duced (fig. 10), and we see 
the tentacles, including some 
of the exterior ones, accu- 
rately directed to the point 
where the meat lay. But a 
much better 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 




Fig. 10. 

{Drosera rotundifolui.') 

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



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



Chap. X.] DIEECTION OF INFLECTED TENTACLES. 199 

was wonderful; so that in some cases I could detect no 
deviation from perfect accuracy. Thus, although the short 
tentacles in the middle of the 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 them- 
selves to the point equally well with the tentacles on the 
borders of the disc. 

In these experiments, some of the short tentacles on the 
disc, which would have been directed to the centre, had the 
leaf been immersed in an exciting fluid, were now inflected in 
an exactly opposite direction, viz. towards the circumference. 
These tentacles, therefore, had deviated as much as 180° 
from the direction which they would have assumed if their 
own glands had been stimulated, and which may be 
considered as the normal one. Between this, the greatest 
possible and no deviation from the normal direction, every 
degree could be observed in the tentacles on these several 
leaves. Notwithstanding the precision with which the ten- 
tacles generally were directed, those near the circumference 
of one leaf were not accurately directed towards some phos- 
phate of lime at a rather distant point on the opposite side of 
the disc. It appeared as if the motor impulse in passing 
transversely across nearly the whole width of the disc had 
departed somewhat from a true course. This accords with 
what we have already seen of the impulse travelling less 
readily in a transverse than in a longitudinal direction. In 
some other cases, the exterior tentacles did not seem capable 
of such accurate movement as the shorter and more central 
ones. 

Nothing could be more striking than the appearance 
of the above four leaves, each with their tentacles pointing 
truly to the two little masses of the phosphate on iheir 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 



200 DEOSEEA EOTUNDIFOLIA. [Chap. X. 

the extreme marginal tentacles of above a dozen rows. As 
the flattened bases are thus formed of only a few rows of 
cells, the precision of the movements of the tentacles is the 
more remarkable ; for when the motor impulse strikes the 
base of a tentacle in a very oblique direction relatively to 
its broad face, scarcely more than one or two cells towards 
one end can be affected at first, and the contraction of these 
cells must draw the whole tentacle into the proper direction. 
It is, perhaps, owing to the exterior pedicels being much 
flattened that they do not bend quite so accurately to the point 
of excitement as the more central ones. The properly directed 
movement of the tentacles is not an unique case in the 
vegetable kingdom, for the tendrils of many plants curve 
towards the side which is touched ; but the case of Drosera 
is far more interesting, as here the tentacles are not 
directly excited, but receive an impulse from a distant point ; 
nevertheless, they bend accurately towards this point. 

On the Nature of the Tissues through which the Motor Impulse* 
is Transmitted. — It will be necessary first to describe briefly 
the course of the main fibro-vascular bundles. These are 
shown in the accompanying sketch (fig. 11) of a small leaf. 
Little vessels from the neighbouring bundles enter all the 
many tentacles with which the surface is studded ; but these 
are not here represented. The central trunk, which runs up 
the footstalk, bifurcates near the centre of the leaf, each 
branch bifurcating again and again according to the size of 
the leaf. This central trunk sends off, low down on each 
side, a delicate branch, which may be called the sublateral 
branch. There is also, on each side, a main lateral branch or 
bundle, which bifurcates in the same manner as the others. 
Bifurcation does not imply that any single vessel divides, 
but that a bundle divides into two. By looking to either 
side of the leaf, it will be seen that a branch from the great 
central bifurcation inosculates with a branch from the lateral 
bundle, and that there is a smaller inosculation between the 



* [In a letter (1862) to Sir Joseph through the researches of Gardiner 

Hooker, in the 'Life and Letters of ('Phil. Trans.' 1883) and others 

Charles Darwin,' toI. iii. p. 321, the the connection between plant-cells by 

writer speaks of the existence in inter-cellular protoplasm has been 

Drosera of " diffused nervous matter," established, we can understand the 

in some degree analogous in constitu- transmission of the motor impulse as 

tion and function to the nervous a molecular change in the protoplasm 

matter of animals. Now, that from cell to cell. — F. D.] 



Chap. X.] 



CONDUCTING TISSUES. 



201 



two chief branches of the lateral bundle. The course of the 
vessels is very complex at the larger inosculation ; and here 
vessels, retaining the same diameter, are often formed by the 
union of the bluntly pointed ends of two vessels, but whether 
these points open into each other by their attached surfaces, 
I do not know. By means of the two inosculations aU the 
vessels on the same side of the leaf are brought into some sort 
of connection. Near the circumference of the larger leaves 
the bifurcating branches also come into close union, and then 
separate again, forming a continuous zigzag line of vessels 
round the whole circumfer- 
ence. But the union of the 
vessels in this zigzag line 
seems to be much less inti- 
mate than at the main in- 
osculation. It should be 
added that the course of the 
vessels differs somewhat in 
different leaves, and even on 
opposite sides of the same 
leaf, but the main inoscula- 
tion is always present. 

Now in my first experi- 
ments with bits of meat 
placed on one side of the disc, 
it so happened that not a 
single tentacle was inflected 
on the opposite side ; and 
when I saw that the vessels 
on the same side were all 
connected together by the 
two inosculations, whilst not 
a vessel passed over to the 
opposite side, it seemed pro- 
bable that the motor impulse was conducted exclusively 
along them. 

In order to test this view, I divided transversely with the 
point of a lancet the central trunks of four leaves, just 
beneath the main bifurcation; and two days afterwards 
placed rather large bits of raw meat (a most powerful 
stimulant) near the centre of the discs above the incision — 
that is, a little towards the apex — with the following 
results : — 




I'lG. 11. 

(^Droseiu rotundi folia.') 

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



202 DBOSEKA EOTUNDIFOLIA. [Chap. X. 

(1) This leaf proved rather torpid : after i hrs. 40 m. (in all cases 
reckoning from the time when the meat was given) the tentacles at 
the distal end were a little inflected, but nowhere else ; they remained 
so for three days, and re-expanded on the fourth day. The leaf was 
then dissected, and the trunk, as well as the two sublateral branches, 
were found divided. 

(2) After 4 hrs. 30 m. many of the tentacles at the distal end were 
well inflected. Next day the blade and all the tentacles at this end 
were strongly inflected, and were separated by a distinct transverse line 
from the basal half of the leaf, which was not in the least affected. On 
the third day, however, some of the short tentacles on the disc near 
the base were very slightly inflected. The incision was found on 
dissection to extend across the leaf as in the last case. 

(3) After 4 hrs. 30 nj. strong inflection of the tentacles at the distal 
end, which during the next two days never extended in the least to 
the basal end. The incision as before. 

(4) This leaf was not observed until 15 hrs. had elapsed, and then 
all the tentacles, except the extreme marginal ones, were found 
equally well inflected all round the leaf. On careful examination the 
spiral vessels of the central trunk were certainly divided; but the 
incision on one side had not passed through the fibrous tissue 
surrounding these vessels, though it had passed through the tissue on 
the other side.* 

The appearance presented by the leaves (2) and (3) was 
very curious, and might he aptly compared with that of a 
man with his backbone broken and lower extremities 
paralysed. Excepting that the line between the two halves 
was here transverse instead of longitudinal, these leaves were 
in the same state as some of those in the former experiments, 
with bits of meat placed on one side of the disc. The case of 
leaf (4) proves that the spiral vessels of the central trunk 
may be divided, and yet the motor impulse be transmitted 
from the distal to the basal end ; and this led me at first to 
suppose that the motor force was sent through the closely 
surrounding fibrous tissue ; and that if one half of this 
tissue was left undivided, it sufficed for complete transmission. 
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 



* M. Ziegler made similar ei- rendus,' 1874, p. 1417), but arrived 
periments by cutting the spiral ves- at conclusions widely different from 
sels of Drosera iniermsdia (' Comptes mine. 



Chat. X.] CONDUCTING TISSUES. 203 

a transverse direction across the whole hreadth of the leaf. 
Nor can this latter fact he accounted for by supposing that 
the transmission is affected through the two inosculations, or 
through the circumferential zigzag line of union, for had thiS' 
been the case, the exterior tentacles on the opposite side of 
the disc would have been affected before the more central 
ones, which never occurred. We have also seen that thei 
extreme marginal tentacles appear to have no power to 
transmit an impulse to the adjoining tentacles ; yet the little 
bundle of vessels which enters each marginal tentacle sends^ 
off a minute branch to those on both sides, and this I have 
not observed in any other tentacles; so that the marginal 
ones are more closely connected together by spiral vessels 
than are the others, and yet have much less power of com- 
municating a motor impulse to one another. 

But besides these several facts and arguments we have 
conclusive evidence that the motor impulse is not 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 surrounding tentacles bend almost simultaneously with 
great precision towards it. Now there are tentacles on the 
disc, for instance near the extremities of the sublateral 
bundles (fig. 11), which are supplied with vessels that do not 
come into contact with the branches that enter the sur- 
rounding tentacles, except by a very long and extremely 
circuitous course. Nevertheless, if a bit of meat is placed on 
the gland of a tentacle of this kind, all the surrounding ones 
are inflected towards it with great precision. It is, of course, 
possible that an impulse might be sent through a long and 
circuitous course, but it is obviously impossible that the 
direction of the movement could be thus communicated, so 
that all the surrounding tentacles should bend precisely to 
the point of excitement. The impulse no doubt is trans- 
mitted in straight radiating lines from the excited gland to 
the surrounding tentacles ; it cannot, therefore, be sent along 
the fibro- vascular bundles. The effect of cutting the central 
vessels, in the above cases, in preventing the transmission of 
the motor impulse from the distal to the basal end of a leaf, 
may be attributed to a considerable space of the cellular' 
tissue having been divided. We shall hereafter see, when 
we treat of Dionsea, that this same conclusion, namely that- 



;204 DROSEEA ROTUNDIFOLIA. [Chap. X. 

the motor impulse is not transmitted by the fihro-vascular 
Inindles, is plainly confirmed ; and Professor Cohn has come 
ito the same conclusion with respect to Aldrovanda — both 
members of the Droseraceas.* 

As the motor impulse is not transmitted along the vessels, 
there remains for its passage only the cellular tissue ; and 
the structure of this tissue explains to a certain extent how- 
it travels so quickly down the long exterior tentacles, and 
much more slowly across the blade of the leaf. We shall 
also see why it crosses the blade more quickly in a longi- 
tudinal than in a transverse direction; though with time it 
-can pass in any direction. We know that the same stimulus 
causes movement of the tentacles and aggregation of the 
protoplasm, and that both influences originate in and proceed 
from the glands within the same brief space of time. It 
.seems therefore probable that the motor impulse consists of 
the first commencement of a molecular change in the pro- 
toplasm, which, when well developed, is plainly visible, and 
has been designated aggregation ; but to this subject I shall 
return. We further know that in the transmission of the 
aggregating process the chief delay is caused by the passage 
of the transverse cell-walls; for as the aggregation travels 
down the tentacles, the contents of each successive cell seem 
almost to flash into a cloudy mass. We may therefore infer 
that the motor impulse is in like manner delayed chiefly by 
passing through the cell-walls. 



* [Batalin (' Flora,' 1877) experi- of MasdevalUa muscosa the impulse 

mented ou the transmission of the travels in a sheath of thin walled 

motor impulse, and confirms the ob- parenchyma accompanying thexylem. 

.servations of Ziegler (' Comptes ren- If we make a similar assumption for 

dus,' 1874), from which that natu- Drosera, we should get rid of a diffi- 

ralist concluded that the vascular culty, for whether the impulse 

bundles form the path for the trans- travels in the course of the vascular 

mission of the impulse. Batalin bundles or transversely across tlie 

concludes that impulse travels with leaf, it would in either case be 

far greater ease along the vessels than travelling in parenchymatous tissue ; 

across the parenchyma, and that the the only difference between the two 

.course of the stimulus is normally cases being that the parenchyma 

almost exclusively along the vessels. accompanying the vessels would be 

If we believe that the motor im- specially adapted for rapid transmis- 

pulse travels as a molecular change sion in a definite direction, whereas 

in the protoplasm, we cannot suppose the ordinary parenchyma has to 

that it travels in the tracheids. Now transmit the impulse in a ^variety 

Oliver (' Annals of Botany,' Feb. of directions. — F. D.J 
1888) has suggested that in the case 



Chap. X.] CONDUCTING TISSUES. 205- 

The greater celerity witli 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 tentacles are fully twice as long as those of the disc ; so 
that only half the number of transverse partitions have to- 
be traversed in a given length of a tentacle, compared with 
an equal space on the disc ; and there would be in the same- 
proportion less retardation of the impulse. Moreover, in 
sections of the exterior tentacles given by Dr. Warming,* 
the parenchymatous cells are shown to be still more elon- 
gated ; and these would form the most direct line of com- 
munication from the gland to the bending place of the 
tentacle. If the impulse travels down the exterior cells, it 
would have to cross from between twenty to thirty trans- 
verse partitions : but rather fewer if down the inner paren- 
chymatous tissue. In cither case it is remarkable that the 
impulse is able to pass through so many partitions down 
nearly the whole length of the pedicel, and to act on the 
bending place, in ten seconds. Why the impulse, after 
having passed so quickly down one of the extreme marginal 
tentacles (about -^ of an inch in length), should never, as 
far as I have seen, afiect the adjoining tentacles, I do not- 
understand. It may be in part accounted for by much 
energy being expended in the rapidity of the transmission. 

Most of the cells of the disc, both the superficial ones and 
the larger cells which form the five or six underlying layers,, 
are about four times as long as broad. They are arranged 
almost longitudinally, radiating from the footstalk. The 
motor impulse, therefore, when transmitted across the disc, has 
to cross nearly four times as many cell-walls as when trans- 
mitted in a longitudinal direction, and would consequently be 
much delayed in the former case. The cells of the disc 
converge towards the bases of the tentacles, and are thus 
fitted to convey the motor impulse to them from all sides. 
On the whole, the arrangement and shape of the cells, both 
those of the disc and tentacles, throw much light on the rate 
and manner of diffusion of the motor impulse. But why the 
impulse proceeding from the glands of the exterior rows of 

* ' Videnskabelige Meddelelser de la Soc. d'Hist. nat. de Copenhague,*' 
Nos. 10-12, 1B72, woodcuts iv. and v. 



206 DEOSEEA EOTUNDIFOLIA. [Chap. X. 

tentacles tends to travel laterally and towards tlie centre of 
the leaf, but not centrifugally, is by no means clear. 

Mechanism of the Movements, and Nature of the Motor 
Impulse. — Whatever may be the means of moyement, the 
•exterior tentacles, considering their delicacy, are inflected 
vrith much force. A bristle, held so that a length of 1 inch 
projected from a handle, yielded when I tried to lift with it 
an inflected tentacle, which was somewhat thinner than the 
bristle. The amount or extent, also, of the movement is 
great. Fully expanded tentacles in becoming inflected 
sweep through an angle of 180° ; and if they are beforehand 
reflexed, as often occurs, the angle is considerably greater. 
It is probably the superficial cells at the bending place 
which chiefly or exclusively contract ; for the interior cells 
have very delicate walls, and are so few in number that 
they could hardly cause a tentacle to bend with precision 
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 com- 
plete circle, under circumstances hereafter to be mentioned. 

All the cells are not acted on, though the motor impulse 
passes through them. When the gland of one of the long 
exterior tentacles is excited, the upper cells are not in the 
least affected ; about half-way down there is a slight bending, 
but the chief movement is confined to a short space near the 
base; and no part of the inner tentacle bends except the 
basal portion. With respect to the blade of the leaf, the 
motor impulse may be transmitted through many cells, from 
the centre to the circumference, without their being in the 
least affected, or they may be strongly acted on and the 
blade greatly inflected. In the latter case the movement 
seems to depend partly on the strength of the stimulus, and 
partly on its nature, as when leaves are immersed in certain 
fluids. 

The power of movement which various plants possess, 
when irritated, has been attributed by high authorities to 
the rapid passage of fluid out of certain cells, which, from 
their previous state of tension immediately contract.* 
Whether or not this is the primary cause of such movements, 
fluid must pass out of closed cells when they contract or are 



* Sachs, ' TraiU de Bot.' 3rd edit. 1874, p. 1038.' This view was, I belieye, 
first suggested by Lamarck. 



Chap. X.] MEANS OP MOVEMENT. 207 

pressed together in one direction, unless they, at the same 
time, expand in some other direction. For instance, fluid can 
be seen to ooze from the surface of any young and vigorous 
shoot if slowly hent into a semi-circle.* In the case of 
Drosera there is certainly much movement of the fluid 
throughout the tentacles whilst they are undergoing inflec- 
tion. Many leaves can he found in which the purple fluid 
within the cells is of an equally dark tint on the upper and 
lower sides of the tentacles, extending also downwards on 
both sides to equally near their bases. If the tentacles of 
such a leaf are excited into movement, it will generally be 
found after some hours that the cells on the concave side are 
much paler than they were before, or are quite colourless, 
those on the convex side having become much darker. In 
two instances, after particles of hair had been placed on 
glands, and when in the course of 1 hr. 10 m. the tentacles 
were incurved halfway towards the centre of the leaf, this 
change of colour in the two sides was conspicuously plain. 
In another case, after a bit of meat had been placed on a 
gland, the purple colour was observed at intervals to be 
slowly travelling from the upper to the lower part, down 
the convex side of the bending tentacle. But it does not 
follow from these observations that the cells on the convex side 
become filled with more fluid during the act of inflection than 
they contained before ; for fluid may all the time be passing 
into the disc or into the glands which then secrete freely. 

The bending of the tentacles, when leaves are immersed 
in a dense fluid, and their subsequent re-expansion in a less 
dense fluid, show that the passage of fluid from or into the 
cells can cause movements like the natural ones. But the 
inflection thus caused is often irregular ; the exterior ten- 
tacles being sometimes spirally curved. Other unnatural 
movements are likewise caused by the application of dense 
fluids, as in the case of drops of syrup placed on the backs 
of leaves and tentacles. Such movements may be compared 
with the contortions which many vegetable tissues undergo 
when subjected to exosmose. It is therefore doubtful 
whether they throw any light on the natural movements. 

If we admit that the outward passage of fluid is the cause 
of the bending of the tentacles, we must suppose that the 
cells, before the act of inflection, are in a high state of 



* Sachs, ibid. p. 919> 



208 DEOSEEA KOTUNDIFOLIA. [Chap. X, 

tension, and tliat they are elastic to an extraordinary degree ; 
for otherwise their contraction could not cause the tentacles 
often to sweep through an angle of above 180°. Professor 
Cohn, in his interesting paper* on the movements of the 
stamens of certain Compositas, states that these organs, when 
dead, are as elastic as threads of india-rubber, and are then 
only half as long as they were when alive. He believes 
that the living protoplasm within their cells is ordinarily in 
a state of expansion, but is paralysed by irritation, or may 
be said to suifer 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 
iiTitated by the expanded state of their contents. 

A somewhat different view has been advanced by other 
physiologists — namely that the protoplasm, when irritated, 
contracts like the soft sarcode of the muscles of animals. 
In Drosera the fluid within the cells of the tentacles at the 
hending place appears under the microscope thin and homo- 
geneous, and after aggregation consists of small, soft masses 
of matter, undergoing incessant changes of form and floating 
in almost colourless fluid. These masses are completely 
redissolved when the tentacles re-expand. Now it seems 
scarcely possible that such matter should have any direct 
mechanical power ; but if through some molecular change it 
were to occupy less space than it did before, no doubt the 
cell-walls would close up and contract. But in this case it 
might be expected that the walls would exhibit wrinkles, 
and none could ever be seen. Moreover, the contents of all 
the cells seem to be of exactly the same nature, both before 
and after aggregation ; and yet only a few of the basal cells 
contract, the rest of the tentacle remaining straight. 

A third view maintained by some physiologists, though 



* ' Abhand. der Schles. Gesell. fiiv giren in the ' Annals and Mag. of 
vaterl. Cultur,' 1861, Heft i. An Nat. Hist.' 3rd series, 1863, vol. ix. 
excellent abstract of this paper is pp. 188-197. 



Chap. X.] NATIJKE OF THE MOTOR IMPULSE. 209 

rejected by most others, is that the whole cell, including the 
walls, actively contracts. If the walls are composed solely 
of non-nitrogenous cellulose, this view is highly improhable ; 
but it can hardly be doubted that they must be permeated 
by proteid matter, at least whilst they are growing. Nor 
does there seem any inherent improbability in the cell-walls 
of Drosera contracting, considering their high state of organi- 
sation ; as shown in the case of the glands by their power of 
absorption and secretion, and by being exquisitely sensitive 
so as to be affected by the pressure of the most minute 
particles. The cell-walls of the pedicels also allow various 
impulses to pass throughthem, inducing movement, increased 
secretion and aggregation. On the whole the belief that the 
walls of certain cells contract, some of their contained fluid 
being at the same time forced outwards, perhaps accords best 
with the observed facts. If this view is rejected, the next 
most probable one is that the fluid contents of the cells shrink, 
owing to a change in their molecular state, with the con- 
sequent closing in of the walls. Anyhow, the movement can 
hardly be attributed to the elasticity of the walls, together 
with a previous state of tension.* 

With respect to the nature of the motor impulse which is 
transmitted from the glands down the pedicels and across 
the disc, it seems not improbable that it is closely allied to 
that influence which causes the protoplasm within the cells 
of the glands and tentacles to aggregate. We have seen that 
both forces originate in and proceed from the glands within 
a few seconds of the same time, and are excited by the same 
causes. The aggregation of the protoplasm lasts almost as 
long as the tentacles remain inflected, even though this be 
for more than a week ; but the protoplasm is redissolved at 
the bending place shortly before the tentacles re-expand, 

* [See Gardiner's interesting paper marks on tlie lower surface and found 

" On the Contractility of the Proto- that when the curvature takes place, 

plasm of Plant Cells "('Proe. R. Soc' the distance between the marks on 

Nov. '24, 1887, vol. xliii.), in which he what becomes the convex surface of 

gives evidence tending to show that the leaf or tentacle increases. When 

the curvature of the tentacles of the leaf opens, or the tentacle 

Drosera is brought about by contrac- straightens, the distance between the 

tion of the protoplasm. marks does not return to what it was 

Batalin (' Flora,' 1877) experi- at first, and this permanent increase 

mented on the curvature of the shows that the curvature is connected 

tentacles as well as on the bending with actual growth. — F. D.] 
of the blade of the leaf. He made _ 

1> 



210 DEOSERA EOTUNDIFOLIA. [Chap. X. 

showmg that the exciting cause of the aggregating process 
has then quite ceased. Exposure to cartonic acid causes both 
the latter process and the motor impulse to travel very slowly 
down the tentacles. We know that the aggregating process 
is delayed in passing through the cell-walls, and we have 
good reason to believe that this holds good with the motor 
impulse ; for we can thus understand the different rates of its 
transmission in a longitudinal and transverse line across the 
disc. Under a high power the first sign of aggregation is 
the appearance of a cloud, and soon afterwards of extremely 
fine granules, in the homogeneous purple fluid within the 
cells ; and this apparently is due to the union of molecules of 
protoplasm. Now it does not seem an improbable view that 
the same tendency — namely for the molecules to approach 
each other — should be communicated to the inner surface of 
the cell-walls which are in contact with the protoplasm ; and 
if so, their molecules would approach each other, and the cell- 
wall woTild contract. 

To this view it may with truth be objected that when 
leaves are immersed in various strong solutions, or are 
subjected to a heat of above 130° Fahr. (54° -4 Cent.), aggre- 
gation ensues, but there is no movement. Again, various 
acids and some other fluids cause rapid movement, but no 
aggregation, or only of an abnormal nature, or only after a 
long interval of time ; but as most of these fluids are more or 
less injurious, they may check or prevent the aggregating 
process by injuring or killing the protoplasm. There is 
another and more important difference in the two processes ; 
when the glands on the disc are excited, they transmit some 
influence up the surrounding tentacles, which acts on the 
cells at the bending place, but does not induce aggregation 
until it has reached the glands ; these then send back some 
other influence, causing the protoplasm to aggregate first in 
the upper and then in the lower cells. 

The Se-expandon of the Tentacles.- -This movement is always 
slow and gradual. When the centre of the leaf is excited, or 
a leaf is immersed in a proper solution, all the tentacles bend 
directly towards the centre, and afterwards directly back 
from it. But when the point of excitement is on one side of 
the disc, the surrounding tentacles bend towards it, and 
therefore obliquely with respect to their normal direction; 
when they afterwards re-expand, they bend obliquely back, 
so as to recover their original positions. The tentacles 



Chap. X.] EE-BXPANSION OF THE TENTACLES. 2ll 

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 
11 closely inflected tentacle is in a state of active contraction, 
as shown by the following experiment. Meat was placed on 
a leaf, and after the tentacles were closely inflected and had 
quite ceased to move, narrow strips of the disc, with a few of 
the outer tentacles attached to it, were cut off and laid on 
one side under the microscope. After several failures, I 
succeeded in cutting off the convex surface of the bent portion 
of a tentacle. Movement immediately re-commenced, and 
the already greatly bent portion went on bending until it 
formed a perfect circle; the straight distal portion of the 
tentacle passing on one side of the strip. The convex surface 
must therefore have previously been in a state of tension, 
sufficient to counterbalance that of the concave surface^ 
which, when free, curled into a complete ring. 

The tentacles of an expanded and unexcited leaf are 
moderately rigid and elastic ; if bent by a needle, the upper 
end yields more easily than the basal and thicker part, which 
alone is capable of becoming inflected. The rigidity of this 
basal part seems due to the tension of the outer surface 
balancing a state of active and persistent contraction of the 
cells of the inner surface. I believe that this is the case, 
because, when a leaf is dipped into boiling water, the ten- 
tacles suddenly become reflexed, and this apparently indicates 
that the tension of the outer surface is mechanical, whilst 
that of the inner surface is vital, and is instantly destroyed 
by the boiling water. We can thus also understand why the 
tentacles as they grow old and feeble slowly become much 
reflexed. If a leaf with its tentacles closely inflected is 
dipped into boiling water, these rise up a little, but by no 
means fuUy 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 suifice 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 increased. 

A recapitulation of the chief facts and discussions in thi.« 
chapter will be given at the close of tho next chapter. 

p 2 



212 DEOSEEA EOTUNDIFOLIA. [Chap. XI. 



CHAPTEE XI. 

Eeoapitulation of the Chief Obseevatioxs on 
Dboseea botundifolia.* 

As summaries have been given to most of the chapters, it 
■will be sufficient here to recapitulate, as briefly as I can, the 
chief points. In the first chapter a preliminary sketch was 
given of the structure of the leaves, and of the manner in 
which they capture insects. This is effected by drops of 
extremely viscid fluid surrounding the glands and by the 
inward movement of the tentacles. As the plants gain most 
of their nutriment by this means, their roots are very poorly 
developed ; and they often grow in places where hardly any 
other plant except mosses can exist. The glands have the 
power of absorption, besides that of secretion. They are 
extremely sensitive to various stimulants, namely repeated 
touches, the pressure of minute particles, the absorption of 
animal matter and of various fluids, heat, and galvanic 
action. A tentacle with a bit of raw meat on the gland has 
been seen to begin bending in 10 s., to be strongly incurved 
in 5 m., and to reach the centre of the leaf in half an hour. 
The blade of the leaf often becomes so much inflected that it 
forms a cup, enclosing any object placed on it. 

A gland, when excited, not only sends some influence 
down its own tentacle, causing it to bend, but likewise 
to the surrounding tentacles, which become incurved; so 
that the bending place can be acted on by an impulse 
received from opposite directions, namely from the gland on 
the summit of the same tentacle, and from one or more 
glands of the neighbouring tentacles. Tentacles, when 
inflected, re-expand after a time, and during this process the 
glands secrete less copiously or become dry. As soon as 
they begin to secrete again, the tentacles are ready to re-act ; 
and this may be repeated at least three, probably many 
more times. 

* [The reader consulting this list of additions in the present 
chapter without having read the - edition given at the beginning of the 
foregoing pages should look at the boolj. — F. D.] 



CuAP. XI.] GEKEEAL SUMMARY. 213 

It was shown in the second chapter that animal substances 
placed on the discs cause much more prompt and energetic 
inflection than do inorganic bodies of the same size, or mere 
mechanical irritation ; but there is a still more marked 
difference in the greater length of time during which the 
tentacles remain inflected over bodies yielding soluble and 
nutritious matter, than over those which do not yield such 
matter. Extremely minute particles of glass, cinders, hair, 
thread, precipitated chalk, &c., when placed on the glands of 
the outer tentacles, cause them to bend. A particle, unless 
it sinks through the secretion and actually touches the 
surface of the gland with some one point, does not produce 
any effect. A little bit of thin human hair -nAnr ^^ ^^ inch 
0203 mm.) in length, and weighing only ^g^^a of a grain 
(•000822 mg.), though largely supported by the dense 
secretion, suffices to induce movement. It is not probable 
that the pressure in this case could have amounted to 
that from the millionth of a grain. Even smaller particles 
cause a slight movement, as could be seen through a lens. 
Larger particles than those of which the measurements 
have been given cause no sensation when placed on the 
tongue, one of the most sensitive parts of the human 
body. 

Movement ensues if a gland is momentarily touched three 
or four times ; but if touched only once or twice, though with 
considerable force and with a hard object, the tentacle does 
not bend. The plant is thus saved from much useless 
movement, as during a high wind the glands can hardly 
escape being occasionally brushed by the leaves of sur- 
rounding plants. Though insensible to a single touch, they 
are exquisitely sensitive, as just stated, to the slightest 
pressure if prolonged for a few seconds ; and this capacity is 
manifestly of service to the plant in capturing small insects. 
Even gnats, if they rest on the glands with their delicate 
feet, are quickly and securely embraced. The glands are 
insensible to the weight and repeated blows of drops of 
heavy rain, and the plants are thus likewise saved from much 
useless movement. 

The description of the movements of the tentacles was 
interrupted in the third chapter for the sake of describing 
the process of aggregation. This process always commences 
in the cells of the glands, the contents of which first become 



214 DROSERA EOTUNDIFOLIA. [Chap. XI. 

cloudy ; and this lias been observed witliin 10 s. after a 
gland has been excited. Granules just resolvable under a 
very high power soon appear, sometimes within a minute, in 
the cells beneath the glands ; and these then aggregate into 
minute spheres. The process afterwards travels down the 
tentacles, being arrested for a short time at each transverse 
partition. The small spheres coalesce into larger spheres, or 
into oval, club-headed, thread- or necklace-like, or otherwise 
shaped masses of protoplasm, which, suspended in almost 
colourless fluid, exhibit incessant spontaneous changes of 
form. These frequently coalesce and again separate. If a 
gland has been powerfully excited, all the cells down to the 
base of the tentacle are affected. In cells, especially if filled 
with dark red fluid, the first step in the process often is the 
formation of a dark red, bag-like mass of protoplasm which 
afterwards divides and undergoes the usual repeated changes 
of form. Before any aggregation has been excited, a sheet 
of colourless protoplasm, including granules (the primordial 
utricle of Mohl), flows round the walls of the cells ; and this 
becomes more distinct after the contents have been partially 
aggregated into spheres or bag-like masses. But after a 
time the granules are drawn towards the central masses and 
unite with them; and then the circulating sheet can no 
longer be distinguished, but there is still a current of trans- 
parent fluid within the cells. 

Aggregation is excited by almost all the stimulants which 
induce movement ; such as the glands being touched two or 
throe 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 t^^ttit ^^ ^ grain ( • 00048 mg.) given to 
a single gland suffices to cause in one hour well-marked 
aggregation in the upper cells of the tentacle. The process 
goes on only as long as the protoplasm is in a living, vigorous, 
and oxygenated condition. 

The result is in all respects exactly the same, whether a 
gland has been excited directly, or has received an influence 
from other and distant glands. But there is one important 
difference; when the central glands are irritated, they 
transmit centrifugally an influence up the pedicels of the 
exterior tentacles to their glands ; but the actual process of 
aggregation travels centripetally, from the glands of the 



Chap. XI.] GENEBAL SUMMARY. 215 

exterior tentacles down their pedicels. The exciting 
influence, therefore, which is transmitted from one part of 
the leaf to another must be different from that which 
actually induces aggregation. The process does not depend 
on the glands secreting more copiously than they did hefore ; 
and is independent of the inflection of the tentacles. It 
continues as long as the tentacles remain inflected, and as 
soon as these are fully re-expanded, the little masses of 
protoplasm are all redissolved ; the cells becoming filled with 
homogeneous purple fluid, as they were before the leaf was 
excited. 

As the process of aggregation can be excited by a few 
touches, or by the pressure of insoluble particles, it is 
evidently independent of the absorption of any matter, and 
must be of a molecular nature. Even when caused by the 
absorption of the carbonate or other salt of ammonia, or an 
infusion of meat, the process seems to be of exactly the same 
nature. The protoplasmic fluid must, therefore, be in a 
singularly unstable condition, to be acted on by such slight 
and varied causes. Physiologists believe that when a nerve 
is touched, and it transmits an influence to other parts of the 
nervous system, a molecular change is induced in it, though 
not visible to us. 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 i^^oo of a grain and largely 
supported by the dense secretion, for this excessively slight 
pressure soon causes a visible change in the protoplasm, 
which change is transmitted down the whole length of the 
tentacle, giving it at last a mottled appearance, distinguish- 
able even by the naked eye. 

In the fourth chapter it was shown that leaves placed for 
a short time in water at a temperature of 110° Fahr. (43°'3 
Cent.) become somewhat inflected ; they are thus also 
rendered more sensitive to the action of meat than they 
were before. If exposed to a temperature of between 115° 
and 125° (46° • 1—51° • 6 Cent.), they are quickly inflected, and 
their protoplasm undergoes aggregation ; when afterwards 
placed in cold water, they re-expand. Exposed to 130° (54° • 4 
Cent.), no inflection immediately occurs, but the leaves are 
only temporarily paralysed, for on being left in cold water, 
they often become inflected and afterwards re-expand. In 
one leaf thus treated, I distinctly saw the protoplasm in 
movement. In other leaves treated in the same manner, and 



216 DEOSEEA KOTUNDIFOLIA. [Chap. XI. 

then immersed in a solution of carbonate of ammonia, strong 
aggregation ensued. Leaves placed in cold water, after an 
exposure to so high a temperature as 145° (62°-7 Cent.), 
sometimes become slightly, though slowly inflected; and 
afterwards have the contents of their cells strongly aggre- 
gated by carbonate of ammonia. But the duration of the 
immersion is an important element, for if left in water at 145° 
(62° • 7 Cent.), or only at 140° ((50° Cent.), until it becomes cool, 
they are killed, and the contents of the glands are rendered 
white and opaque. This latter result seems to be due to the 
coagulation of the albumen, and was almost always caused 
by even, a short exposure to 150° (65° "5 Cent.) ; but different 
leaves, and even the separate cells in the same tentacle, 
differ considerably in their power of resisting heat. Unless 
the heat has been sufficient to coagulate the albumen, 
carbonate of ammonia subsequently induces aggregation. 

In the fifth chapter, the results of placing drops of various 
nitrogenous and non -nitrogenous organic fluids on the discs 
of leaves were given, and it was shown that they detect with 
almost unerring certainty the presence of nitrogen. A de- 
coction of green peas or of fresh cabbage-leaves acts almost 
as powerfully as an infusion of raw meat, whereas an infusion 
of cabbage-leaves made by keeping them for a long time in 
merely warm water is far less efficient. A decoction of grass- 
leaves is less powerful than one of green peas or cabbage- 
leaves. 

These results led me to inquire whether Drosera possessed 
the power of dissolving solid animal matter. The experi- 
ments proving that the leaves are capable of true digestion, 
and tha,t the glands absorb the digested matter, are given in 
detail in the sixth chapter. These are, perhaps, the most 
ititeresting of all my observations on Drosera, as no such 
power was before distinctly known to exist in the vegetable 
kingdom. It is likewise an interesting fact that the glands 
of the disc, when irritated, should transmit some influence 
to the glands of the exterior tentacles, causing them to se- 
crete more copiously and the secretion to become acid, as if 
they had been directly excited by an object placed on them. 
The gastric juice of animals contains, as is well known, an 
acid and a ferment, both of which are indispensable for diges- 
tion, and so it is with the secretion of Drosera. When the 
stomach of an animal is mechanically irritated, it secretes an 
acid, and when particles of glass or other such objects were 



Chat. XI.] GENEEAL SUMMARY. 217 

placed on the glands of Drosera, the secretion, and that of 
the fiiirrounding and untouched glands, was increased in 
quantity and became acid. But according to Schiff, the 
stomach of an animal does not secrete its proper ferment, 
pepsin, until certain substances, which he calls peptogenes, 
are absorbed; and it appears from my experiments that some 
matter must bo absorbed by the glands of Drosera before 
they secrete their proper ferment. That the secretion does 
contain a ferment which acts only in the presence of an acid 
on solid animal matter, was clearly proved by adding minute 
doses of an alkali, which entirely arrested the process of 
digestion, this immediately recommencing as soon as the 
alkali was neutralised by a little weak hydrochloric acid. 
From trials made with a large number of substances, it was 
found that those which the secretion of Drosera dissolves 
completely, or partially, or not at all, are acted on in exactly 
the same manner by gastric juice. We may therefore con- 
clude that the ferment of Drosera is closely analogous to, or 
identical with, the pepsin of animals. 

The substances which are digested by Drosera act on the 
leaves very differently. Some cause much more energetic 
and rapid inflection of the tentacles, and keep them inflected 
for a much longer time, than do others. We are thus led to 
believe that the former are more nutritious than the latter, 
as is known to be the case with some of these same substances 
when given to animals ; for instance, meat in comparison 
with gelatine. As cartilage is so tough a substance and is 
so little acted on by water, its prompt dissolution by the 
secretion of Drosera, and subsequent absorption, is, perhaps, 
one of the most striking cases. But it is not really more 
remarkable than the digestion of meat, which is dissolved by 
this secretion in the same manner and by the same stages as 
by gastrip juice. The secretion dissolves bone, and even the 
enamel of teeth, but this is simply due to the large quantity 
of acid secreted, owing, apparently, to the desire of the 
plant for phosphorus. In the case of bone, the ferment does 
not come into play until all the phosphate of lime has been 
decomposed and free acid is present, and then the fibrous 
basis is quickly dissolved. Lastly, the secretion attacks and 
dissolves matter out of living seeds, which it sometimes kills, 
or injures, as shown by the diseased state of the seedlings. It 
also absorbs matter from pollen, and from fragments of leaves. 

The seventh chapter was devoted to the action of the 



218 DEOSEEA EOTUNDIFOLIA. [Chap. XI. 

•salts of ammonia. These all cause the tentacles, and often 
the blade of the leaf, to be inflected, and the protoplasm to 
be, aggregated. They act with very different power; the 
citrate being the least powerful, and the phosphate, owing, 
no doubt, to the presence of phosphorus and nitrogen, by far 
the most powerful. But the relative efficiency of only three 
salts of ammonia was carefully determined, namely the car- 
honate, nitrate, and phosphate. The experiments were made 
by placing half-minims ('0296 c.c.) of solutions of different 
strengths on the discs of the leaves, — by applying a minute 
drop (about the ^V of a minim, or •00296 c.c.) for a few 
.seconds to three or four glands, — and by the immersion of 
■whole leaves in a measured quantity. In relation to these 
experiments it was necessary first to ascertain the effects of 
distilled water, and it was found, as described in detail, that 
the more sensitive leaves are affected by it, but only 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 con- 
taining ff^-ff of a grain (-OGTS mg.) is the least quantity 
which, when placed on the glands of the disc, excites the 
exterior tentacles to bend inwards. But a minute drop, con- 
taining i4^l(,t) 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 sensitiTe 
leaf is immersed in a solution, and there is ample time for 
absorption, the -^s-stwu of a grain ('00024 mg.) is sufficient 
to excite a single tentacle into movement. 

The nitrate of ammonia induces aggregation of the 
protoplasm much less quickly than the carbonate, but is 
more potent in causing inflection. A drop containing ytwo 
■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 -^-^ of a 
grain caused only a few of these tentacles to bend, but 
affected rather more plainly the blade. A minute drop ap- 
plied as before, and containing ^j^^,^ of a grain (•0025mg.), 
•caused the tentacle bearing this gland to bend. By the 
immersion of whole leaves, it was proved that the absorp- 
tion by a single gland of ^ ^ ^^^ d o °^ ^ grain ( • 0000937 mg.) 
•was sufScient to set the same tentacle into movement. 



Chap. XI.] GENERAL SUMMAEY. 219 

The plaosphate of ammonia is much more powerful than 
the nitrate. A drop containing ^-g^T "^ * grain ('OieO mg.) 
placed on the disc of a sensitive leaf causes most of the ex- 
terior tentacles to be inflected, as well as the blade of the leaf. 
A minute drop containing xs-strrs o^ ^ grain ( • 000423 mg.), 
applied for a few seconds to a gland, acts, as shown by 
the movement of the tentacle. When a leaf is immersed in 
thirty minims (1*7748 c.c.) of a solution of one part by 
weight of the salt to 21,876,000 of water, the absorption by 
a gland of only the 1 6 7 a'o a o o of ^ grain ('00000328 mg.), 
that is, a little more than the one-twenty-millionth 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 tlio 
one-thirty-millionth of a grain of the efficient elements 
could have been absorbed. There is nothing remarkable in 
such minute quantities being absorbed by the glands, for all 
physiologists admit that the salts of ammonia, which must 
be brought in still smaller quantity by a single shower of 
rain to the roots, are absorbed by them. Nor is it surprising 
that Drosera should be enabled to profit by the absorption of 
these salts, for yeast and other low fungoid forms flourish in 
solutions of ammonia, if the other necessary elements are 
present. But it is an astonishing fact, on which I will not 
here again enlarge, that so inconceivably minute a quantity 
as the one-twenty-millionth of a grain of phosphate of 
ammonia should induce some change in a gland of Drosera, 
sufficient to cause a motor impulse to be sent down the 
whole length of the tentacle ; this impulse exciting move- 
ment often through an angle of above 180°. I know not 
whether to be most astonished at this fact, or that the 
pressure of a minute bit of hair, supported by the dense 
secretion, should quickly cause conspicuous movement. 
Moreover, this extreme sensitiveness, exceeding that of the 
most delicate part of the human body, as well as the power 
of transmitting various impulses from one part of the leaf to 
another, have been acquired without the intervention of any 
nervous system. 

Aa few plants are at present known to possess glands 
specially adapted for absorption, it seemed worth while to 
try the efiiects on Drosera of various other salts, besides 
those of ammonia, and of various acids. Their action, as 
described in the eighth chapter, does not correspond at all 



220 DEOSEEA EOTUNDIFOLIA. [Chap. XI. 

strictly with their chemical affinities, as inferred from the 
classification commonly followed. The nature of the base is 
far more influential than that of the acid ; and this is known 
to hold good with animals. Tor instance, nine salts of 
sodium all caused well-marked inflection, and none of them 
were poisonous in small doses; whereas seven of the nine 
corresponding salts of potassium produced no effect, two 
causing slight inflection. Small doses, moreover, of some of 
the latter salts were poisonous. The salts of sodium and 
potassium, when injected into the veins of animals, likewise 
differ widely in their action. The so-called earthy salts 
produce hardly any effect on Drosera. On the other hand, 
most of the metallic salts cause rapid and strong inflection, 
and are highly poisonous ; but there are some odd exceptions 
to this rule ; thus chloride of lead and zinc, as well as two 
salts of barium, did not cause inflection, and were not 
poisonous. 

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

In the ninth chapter the effects of the absorption of 
various alkaloids and certain other substances were de- 
scribed. Although some of these are poisonous, yet as 
several, which act powerfully on the nervous system of 
animals, produce no effect on Drosera, we may infer that the 
extreme sensibility of the glands, and their power of trans- 



CiLiP. XI.] GENERAL SUMMARY. 221 

mitting an influence to other parts of the leaf, causing 
movement, or modified secretion, or aggregation, does not 
depend on the presence of a diffused element, allied to nerve- 
tissue. One of the most remarkable facts is that long 
immersion in the poison of the cobra-snake does not in the 
least check, but rather stimulates, the ppontaneous move- 
ment of the protoplasm in the cells of the tentacles. 
Solutions of various salts and acids behave very differently 
in delaying or in quite arresting the subsequent action of a 
solution of phosphate of ammonia. Camphor dissolved in 
water acts as a stimulant, as do small doses of certain 
essential oils, for they cause rapid and strong inflection. 
Alcohol , is not a stimulant. The vapours of camphor, 
alcohol, chloroform, sulphuric and nitric ether, are poisonous 
in moderately large doses, but in small doses serve as 
narcotics or anajsthetios, greatly delaying the subsequent 
action of meat. But some of these vapours also act as 
stimulants, exciting rapid, almost spasmodic movements in 
the tentacles. Carbonic acid is likewise a narcotic, and 
retards the aggregation of the protoplasm when carbonate 
of ammonia is subsequently given. The first access of air to 
plants which have been immersed in this gas sometimes acts 
as a stimulant and induces movement. But, as before 
remarked, a special pharmacopoeia would be necessary to 
describe the diversified effects of various substances on the 
leaves of Drosera. 

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



222 DBOSEEA EOTUNDIFOLIA. [Chap. XI. 

from the glands of the extreme marginal tentacles does not 
seem to have force enough to affect the adjoining tentacles ; 
and this may be in part due to their length. The impulse 
from the glands of the next few inner rows spreads chiefly 
to the tentacles on each side and towards the centre of the 
leaf; but that proceeding from the glands of the shorter 
tentacles on the disc radiates almost equally on all sides. 

When a gland is strongly excited by the quantity or 
quality of the substance placed on it, the motor impulse 
travels farther than from one slightly excited ; and if 
several glands are simultaneously excited, the impulses from 
all unite and spread still farther. As soon as a gland is 
excited, it discharges an impulse which extends to a con- 
siderable distance ; but afterwards, whilst the gland is 
secreting and absorbing, the impulse suffices only to keep 
the same tentacle inflected ; though the inflection may last 
for many days. 

If the bending place of a tentacle receives an impulse 
from its own gland, the movement is always towards the 
centre of the leaf ; and so it is with all the tentacles, when 
their glands are excited by immersion in a proper fluid: 
The short ones in the middle part of the disc must be 
excepted, as these do not bend at all when thus excited. On 
the other hand, when the motor impulse comes from one 
side of the disc, the surrounding tentacles, including the 
short ones in the middle of the disc, all bend with precision 
towards the point of excitement, wherever this may he 
seated. This is in every way a remarkable phenomenon; 
for the leaf falsely appears as if endowed with the senses of 
an animal. It is all the more remarkable, as when the 
motor impulse strikes the base of a tentacle obliquely with 
respect to its flattened surface, the contraction of the cells 
must be confined to one, two, or a very few rows at one end. 
And different sides of the surrounding tentacles must [be 
acted on, in order that all should bend with precision to the 
point of excitement. 

The motor impulse, as it spreads from one or more glands 
across the disc, enters the bases of the surrounding tentacles, 
a,nd immediately acts on the bending place. It does not in 
the first place proceed up the tentacles to the glands, 
exciting them to reflect back an impulse to their bases. 
Nevertheless, some influence is sent up to the glands, as 
their secretion is soon increased and rendered acid; and 



Chap. XL] GENERAL SUMMARY. 223^ 

then the glands, being thus excited, send back some other 
influence (not dependent on increased secretion, nor on the 
inflection of the tentacles), causing the protoplasm to 
aggregate in cell beneath cell. This may be called a reflex 
action, though probably very different from that proceeding 
from the nerve-ganglion of an animal; and it is the only 
known case of reflex action in the vegetable kingdom. 

About the mechanism of the movements and the nature of 
the motor impulse we know very little. During the act of 
inflection fluid certainly travels from one part to another of 
the tentacles. But the hypothesis which agrees best with 
the observed facts is that the motor impulse is allied in nature 
to the aggregating process ; and that this causes the mole- 
cules of the cell-walls to approach each other, in the same 
manner as do the molecules of the protoplasm within the 
cells ; so that the cell- walls contract. But some strong 
objections may be urged against this view. The re-expansion 
of the tentacles is largely due to the elasticity of their outei" 
cells, which comes into play as soon as those on the inner 
side cease contracting with prepotent force; but we haver 
reason to suspect that fluid is continually and slowly attracted 
into the outer cells during the act of re-expansion, thus 
increasing their tension.* 

I have now given a brief recapitulation of the chief points 
observed by me, with respect to the structure, movements,, 
constitution, and habits of Drosera rotundifolia ; and we see 
how little has been made out in comparison with what 
remains unexplained and unknown. 



♦ [Increase of fluid in the external (convex) cells would tend to prevent 
re-expansion, not to facilitate it. — F. D.] 



224 DKOSEEA ANGLICA. [Chap. XU. 



CHAPTER XII. 

On the Structore and Movements of some other Species op 
Dkoseba. 

Srosera anglica — Drosera intermedia — Drosera capensis — Drosera spathulata — 
Jjroscra filiformis — Drosera hiiiata — Concluding remarks. 

I EXAMINED six otHer species of Drosera, some of tliem in- 
habitants of distant countries, chiefly for the sake of ascer- 
taining whether they caught insects. This seemed.the more 
necessary as the leaves of some of the species differ to an 
extraordinary degree in shape from the rounded ones of 
Drosera rotundifolia. In functional powers, however, they 
differ very little. 

Drosera anglica (Hudson).* — The leaves of this species, which was 
sent to me from Ireland, are much elongated, and gradually widen from 
the footstalk to the bluntly pointed apex. They stand almost erect, 
and their hlades sometimes exceed 1 inch in length, whilst their 
breadth is only the -J of an inch. The glands of all the tentacles have 
the same structure, so that the extreme marginal ones do not differ 
from the others, as in the case of Drosera rotundifolia. When they 
are irritated by, being roughly touched, or by the pressure of minute 
inorganic particles, or by contact with animal matter, or by the 
absorption of carbonate of ammonia, the tentacles become inflected; 
the basal portion being the chief seat of movement. Cuttinj or 
Tfficking the blade of the leaf did not excite any movement. They 
frequently capture insects, and the glands of the inflected tentacles 
pour forth much acid secretion. Bits of roast meat were placed on 
some glands, and the tentacles began to move in 1 m. or 1 m. 30 s. ; 
and in 1 hr. 10 m. reached the centre. Two bits of boiled cork, one of 
boiled thread, and two of coal-cinders taken from the Are, were placed, 
by the aid of an instrument which had been immersed in boiling 
•water, on five glands ; these superfluous precautions having been taken 
•on account of M. Ziegler's statements. One of the particles of cinder 



* Mrs. Treat has given an ex- of Drosera longifoUa (which is a syn- 
.cellent account in * The American onym in part of Drosera anglica), of 
iJaturalist,' December 1873, p. 705, Drosera rotundifolia uni filiformis. 



Chap. XII.] DROSEEA CAPENSIS. 225 

caused some inflection in 8 hrs. 45 m., as did after 23 hrs. the other 
jiarticle of cinder, the bit of thread, and both bits of cork. Thiee 
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 wiihin the 
cells of the tentacles undergoes aggregation after these have become 
inflected ; especially if given a solution of carbonate of ammonia; and 
I observed the usual movements in the masses of protoplasm. In one 
case, aggregation ensued in 1 hr. 10 m. after a tentacle had carried 
a bit of meat to the centre. From these facts it is clear that the 
tentacles of Drosera anglica behave like those of Drosera rotundi- 
folia. 

If an insect is placed on the central glands, or has been naturally- 
caught there, the apex of the leaf curls inwards. For instance, dead 
flies were placed on three leaves near their bases, and after 24 hrs. the 
previously straight apices were curled completely over, so as to embrace 
and conceal the flies ; they had therefore moved through an angle of 
180°. After three days the apex of one leaf, together with the tentacles, 
began to re-expand. But as far as I have seen — and I made many 
trials — the sides of the leaf are never inflected, and this is the one 
functional difference between tliis species and Drosera rotundifulia. 

Drosera intermedia (Hayne). This species is quite as common in 
some parts of England as Drosera rotundifolia. It differs from 
Drosera anglica, as far as the leaves are concerned, only in their 
.smaller size, and in their tips being generally a little reflexed. They 
capture a large number of insects. The tentacles are excited into 
movement by all the causes above specified; and aggregation ensues, 
with movement of the protoplasmic masses. I have seen, through a 
lens, a tentacle beginning to bend in less than a minute after a 
particle of raw meat had been placed on the gland. The apex of the 
leaf curls over an exciting object as in the case of Drosera anglica. 
Acid secretion is copiously poured over captured insects. A leaf which 
had embraced a fly with all its tentacles re-expanded after nearly three 
days. 

Drosera capensis. — This species, a native of the Cape of Good Hope, 
was sent to me by Dr. Hooker. The leaves are elongated, slightly 
concave along the middle and taper towards the apex, which is bluntly 
pointed and reflexed. They rise from an almost woody axis, and tlieir 
greatest peculiarity consists in their foliaceous green footstalks, which 
are almost as broad and even longer than the gland-bearing blade. 
This species, therefore, probably draws more nourishment from the air, 
and less from captured insects, than the other species of the genus. 
Xevertheless, 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 



226 I^ROSERA FILIFORMIS. [Chap. XII. 

very slowly when particles of meat were placed on the glands, and 
perhaps for my never succeeding in causing any movement by 
repeatedly touching them with a needle. But with all the species of 
the genus this latter stimulus is the least effective of any. Panicles 
of glass, cork, and coal-cinders, were placed on the glands of six 
tentacles; and one alone moved after an interval of 2 hrs. 30 m. 
Nevertheless, two glands were extremely sensitive to very small doses 
of the nitrate of ammonia, namely to about ^ of a minim of a solution 
(one part to 5250 of water), containing only TrJaoo °^ ^ 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 foliaoeous 
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, narrmv 
leaves, gradually widening towards their tips. The glands tf the 
extreme marginal tentacles are elongated and differ from the others, as 
in the case oi Drosera rotundifolia. A fly was placed on a leaf, and 
in 18 hrs. it was embraced by the adjoining tentacles. Grum-wiiter 
dropped on several leaves produced no effect. A fragment of a leaf 
was immersed in a few drops of a solution of one part of carbonate of 
ammonia to 146 of water ; all the glands were instantly blackened ; 
the process of aggregation could be seen travelling rapidly down the 
cells of the tentacles ; and the granules of protoplasm soon united into 
spheres and variously shaped masses, which displayed the usual 
movements. Half a minim of a solution of one part of nitrate of 
ammonia to 146 of water was next placed on the centre of a leaf; 
after 6 hrs. some marginal tentacles on both sides were inflected, and 
after 9 hrs. they met in the centre. The lateral edges of the leaf also 
became incurved, so that it formed a half-cylinder ; but the apex of 
the leaf in none of my few trials was inflected. The above dose of 
the nitrate (viz. ^-Jg of a grain or '202 mg.) was too poweiful, for in 
the course of 23 hrs. the leaf died. 

Drosera filiformis. — This North American species grows in such 
abundance in parts of Kew Jersey as almost to cover the ground. It 
catches, according to Mrs. Treat,* an extraordinary number of small and 
large insects, — even great flies of the genus Asilus, moths, and butter- 
flies. The specimen which I examined, sent me by Dr. Hooker, had 
thread-like leaves, from 6 to 12 inches in length, with the upper surface 
convex and the lower flat and shghtly channelled. The whole convex 



' American Naturalist,' Dec. 1873, p. 705. 



Chap. XII.] DROSERA BINATA. 227 

surface, down to the roots — for there is no distinct footstalk — is covered 
witli short gland-bearing tentacles, those on the margins being the 
longest and refiexed. 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 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 meal 
from the united glands. Several other glands were touched with a 
little saliva, and the tentacles became incurved in under 1 hr., and 
re-expanded after 18 hrs. Particles of glass, cork, cinders, thread, and 
gold-leaf, were placed on numeious glands on two leaves; in aliout 
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 ; ami 
Mrs. Treat made similar trials for me with no success. Small tiies 
were placed on several leaves near their tips, but the thread-like blade 
became only on one occasion very slightly bent, directly beneath thu 
insect. Perhaps this indicates that the blades of vigorous plants 
would bend over captured insects, and Dr. Canby informs me that 
this is the case ; but the movement cannot be strongly pronounced, as 
it was not observed by Mrs. Treat. 

Drosera hinata (or didhotoma).*^-! am much indebted to Lady 
Dorothy Nevill for a fine plant of this almost gigantic Australian species, 
which differs in some interesting points from those previously described. 
In this specimen the rush-like footstalks of the leaves were 20 inches 
iin length. The blade bifurcates at its junction with the footstalk, and 
twice or thrice afterwards, curling about in an irregular manner. It is 
narrow, being only -^ of an inch in breadth. One blade was 74 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 blaile 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 exlerior 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 



* [See E. Morren, 'Bull, de I'Acad. Royale de Belgique,' 2™ s^rie, tnm. 
40, 1875, where the plant is figured, and some cxreriments described. — F. D.] 

Q 2 



228 DEOPBEA BINATA. [Chap. XII. 

ammonia to 437 of water had all the glands blackened and all the 
tentacles inflected in 5 m. A bit of raw meat, placed on several glands 
in the medial furrow, was well clasped in 2 hrs. 10 m. by the marginal 
tentacles on both sides. Bits of roast meat and small flies did not act 
quite so quickly ; and albumen and fibrin still less quickly. One of 
the bits of meat excited so much secretion (which is always acid) that 
it flowed some way down the medial furrow, causing the inflection of 
the tentacles on both sides as far as it extended. Particles of glass 
placed on the glands in the medial furrow did not stimulate them 
suificiently for any motor impulse to be sent to the outer tentacles. 
In no case was the blade of the leaf, even the attenuated apex, at all 
inflected. 

On both the upper and lower surface of the blade there are numerous 
minute, almost sessile glands, consisting of four, eight, or twelve cells. 
On the lower surface they are pale purple, on the upper, greenish. 
Nearly similar organs occur on the foot-stalks, but they are smaller and 
often in a shrivelled condition. The minute glands on the blade can 
absorb rapidly : thus, a piece of leaf was immersed in a solution of one 
part of carbonate of ammonia to 218 of water (2 gr. to 1 oz.), and in 
5 m. they were all so much darkened as to be almost black, with their 
contents aggregated. They do not, as far as I could observe, secrete 
spontaneously ; but in between 2 and 3 hrs. after a leaf had been 
rubbed with a bit of raw meat moistened with saliva, they seemed 
to be secreting freely ; and this conclusion w as afterwards supported by 
other appearances. They are, therefore, homologous with the sessile 
glands hereafter to be described on the leaves of Dionaja and Droso- 
phyllum. In this latter genus they are associated, as in the present 
case, with glands which secrete spontaneously, that is, without beiiig 
excited. 

Brosera hinata presents another and more remarkable peculiarity, 
namely, the presence of a few tentacles on the backs of the leaves, near 
their margins. These are perfect in structure ; spiral vessels run up 
their pedicels ; their glands are surrounded by drops of viscid secretion, 
and they have the power of absorbing. This latter fact was shown by 
the glands immediately becoming black, and the protoplasm aggregateii, 
when a leaf was placed in a little solution of one part of carbonate 
of ammonia to 437 of water. These dorsal tentacles are short, not being 
nearly so long as the marginal ones on the upper surface ; some of them 
are so short as almost to graduate into the minute sessile glands. Their 
presence, number, and size, vary on different leaves, and they are 
arranged rather irregularly. On the back of one leaf I counted as- 
many as twenty-oue along one side. 

These dorsal tentacles differ in one important respect from those on 
the upper surface, namely, in not possessing any power of movement, 
in whatever manner they may be stimulated. Thus, portions of four 
leaves were placed at different times in solutions of carbonate of 
ammonia (one part to 437 or 218 of water), and all the tentacles on the 
upper surface soon became closely inflected ; but the dorsal ones did 



Chap. XII.] GONCLUDING REMARKS. 229 

not move, though the leaves were left in the solution for many hours, 
and tliough their glands from their blackened colour had obviously- 
absorbed some of the salt. Rather young leaves should be selected 
for such trials, for the dorsal teotacles, as they grow old and begin to 
wither, often spontaneously incline towards the middle of the leaf. If 
these tentacles had possessed the power of movement, they would not 
have been thus rendered more .serviceable to the plant ; for they are not 
long enough to bend round the margin of the leaf so as to reach an 
insect caught on the upper surface. Nor would it have been of any 
use if these tentacles could have moved towards the middle of the 
lower surface, for there are no viscid glands there by which insects 
can be cauglit. Although they have no power of movement, they are 
probably of some use by absorbing animal matter from any minute 
insect which may be caught by them, and by absorbing ammonia from 
the rain-water. But their varying presence and size, and their irregular 
position, indicate that they are not of much service, and that they are 
tending towards abortion. In a future chapter we shall see that 
Drosophyllum, with its elongated leaves, probably represents tho 
condition of an early progenitor of the genus Drosera ; and none of the 
tentacles of Drosophyllum, neither those on the upper nor lower surface 
of the leaves, are capable of movement when excited, though they 
capture numerous insects, which serve as nutriment. Therefore it 
seems that Drosera binata has retained remnants of certain ancestral 
characters — namely, a few motionless tentacles on the backs of the 
leaves, and fairly well developed sessile glands — which have been lost 
by most or all of the other species of the genus. 



Concluding Memarks. — From what we liave now seen, there 
can be little doubt that most or probably all the species of 
Drosera are adapted for catching insects by nearly the same 
means. Besides the two Australian species above described, 
it is said* that two other species from this country, namely 
Drosera pallida and Drosera sulphurea, " close their leaves 
upon insects with great rapidity : and the same phenomenon 
is manifested by an Indian species, D. lunata, and by several 
of those of the Cape of Good Hope, especially by D. trinervis." 
Another Australian species, Drosera heterophylla (made by 
Lindley into a distinct genus, Sondera) is remarkable from 
its peculiarly shaped leaves, but I know nothing of its power 
of catching insects, for I have seen only dried specimens. 
The leaves form minute flattened cups, with the footstalks 
attached not to one margin, but to the bottom. The inner 



* ' Gardener's Chronicle,' 1874, p. 209. 



230: CONCLUDING EEMAEKS. [Chap. XII. 

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



Chap. XIH.] DION^EA JIUSCIPULA. 231 



CHAPTEE XIII. 

DlON^A MUSOIPULA. 

Structure of the leaves — Sensitiveness of the filaments — Rapid movement of 
the lobes caused by irritation of the filaments — Glands, their power of 
secretion — Slow movement caused by the absorption of animal matter — 
Evidence of absorption from the aggregated condition of the glands- 
Digestive power of the secretion — Action of chloroform, ether, and hydro- 
cyanic acid — The manner in which insects are captured — 0se of the 
marginal spikes — Kinds of insects captured — The transmission of the 
motor impulse and mechanism of the movements — Ee-expansion of the 
lobes. 

This plant, commonly called Venus' fly-trap, from the rapidity 
and force of its movements, is one of tlie 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 moderately fine plant which I examined consisted 
of two branches about 1 inch in length, springing from a 
bulbous enlargement. They probably serve, as in the case 
of Drosera, solely for the absorption of water ; 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.f Tho form of the bilobed leaf, with 
its foliaceous footstalk, is shown in the accompanying drawing 
(fig. 12). The two lobes stand at rather less than a right 
angle to each other. Three minute pointed processes or fila- 
ments, placed triangularly, project from the ilpper surfaces of 
both ; but I have seen two leaves with four filaments on each 
side, and another with only two. These filaments are 



* Dr. Hooker, in his address to [A good account of the early 

the British Association at Belfast, literature is given by Kurtz in Ueich- 

1S74, has given so full an historical ert and Du Bois-Reymond's ' Arohiv.' 

account of the observations which 1876. — F. D.] 

have been published on the habits of t 'Gardener's Chronicle,' 1874, p. 

this plnnt, that it would be super- 464. 
iiuous on my part to repeat them. 



232 



DIONiEA MUSCIPULA. 



[Chap. XIII. 



remarkable from their extreme sensitiveness to a toucli, as 
Btown uot by tlieir own movement, but by that of the lobes. 
The margins of the leaf are prolonged into sharp rigid pro- 
jections which I will call spikes, into each of which a bundle 
of spiral vessels enters. The spikes stand in such a position 
that, when the lobes close, they interlock like the teeth 
of a rat-trap. The midrib of the leaf, on the lower side, is 
strongly developed and prominent. 

The upper surface* of the leaf is thickly covered, excepting 
towards the margins, with minute glands of a reddish or 




Fig. 12. 

(_Dion8ea muscipula,) 

LeaT viewed laterally in its expanded state. 



purplish colour, the rest of the leaf being green. There are 
no glands on the spikes, or on the foliaceous footstalk. The 
glands are formed of from twenty to thirty polygonal cells, 
filled with purple fluid. Their upper surface is convex. 
They stand on very short pedicels, into which spiral vessels 
do not enter, in which respect they differ from the tentacles 
of Drosera. They secrete, but only when excited by the 
absorption of certain matters ; and they have the power of 



* [A. Fraustadt, in his Sreslau dis- 
sertation on Dionaja (Mar. 1876) states 
that the upper surface of the leaf 
is devoid of stomata. C. De Candolle, 
'Archive.s des Sciences Phys. et Nat,' 
Geneva, April 1876, mentions the same 



fact. It is easy to see that the lower 
surface of the leaf is a better one for 
the development of stomata than the 
upper surface, which is liable to be 
constantly bathed in secretion. — 
F. D.] 



Chap. Xm.] SENSITIVENESS OF FILAMENTS. 233 

absorption. Minute projections, formed of eight divergent 
arms of a reddish-brown or orange colour, and appearing 
under the microscoj)e like elegant little flowers, are scattered 
in considerable numbers over the footstalk, the backs of the 
leaves, and the spikes, with a few on the upper surface of the 
lobes. These octofid projections are no doubt homologous 
with the papillsB on the leaves of Brosera rotundifolia. There 
are also a few very minute, simple, pointed hairs,* about 
i^^oj) of an inch (•0148 mm.) in length on the backs of the 
leaves. 

The sensitive filamentsf 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 celLf. 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,:f are ex- 
quisitely sensitive to a momentary touch. It is scarcely 
possible to touch them ever l^o lightly or quickly with any 
hard object without causing the lobes to close. A piece of 
very delicate human hair, 2^ inches in length, held dangling 
over a filament, and swayed to and fro so as to touch it, did 
not excite any movement. But when a rather thick cotton 
thread of the same length was similarly swayed, the lobes 
closed. Pinches of fine wheaten flour, dropped from a height, 
jiroduced no efiect. The above-mentioned hair was then fixed 
into a handle, and cut off so that 1 inch projected ; this 



* [These hairs were absent in the gencies." — F. D.] 

sjiecimeus examined by Kurtz (Reich- J [Batalin ('Flora,' 1877) quotes 

ert and Du Bois-Keymond's ' Archiv.' Oudemans (E. Academy of Sciences of 

1876).— F. D.] Amsterdam, 1859), to the efiect that 

t [Both Fraustadt and De Candolle the filaments are much more sensitive 

have described the structure of these at the base than elsewhere. Batalin 

filaments, and have shown that their confirms the fact from his own obser- 

morphological rank is that of " emer- rations. — F. D.] 



234 DION^A MUSCIPULA. [Chap. Xni. 

length being sufficiently rigid to STij)port itself in a nearly- 
horizontal line. The extremity was then brought by a Blow- 
movement laterally into contact with the tip of a filament, 
and the leaf instantly closed. On another occasion two or 
three touches of the same kind were necessary before any 
movement ensued. When we consider how flexible a fine 
hair is, we may form some idea how slight must be the touch 
given by the extremity of a piece, 1 inch in length, moved 
slowly. 

Although these filaments are so sensitive to a momentary 
and delicate touch, they are far less sensitive than the glands 
of Drosera to prolonged pressure. Several times I succeeded 
in placing on the tip of a filament, by the aid of a needle 
moved with extreme slowness, bits 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 ten- 
tacles of Drosera to bend ; and although in this latter case 
they were largely supported by the dense secretion. On the 
other hand, the glands of Drosera may be struck with a needle 
or any hard object, once, twice, or even thrice, with consider- 
able force, and no movement ensues. This singular differencj 
in the nature of the sensitiveness of the filaments of Dionsea 
and of the glands of Drosera evidently stands in relation to 
the habits of tho two plants. If a minute insect alights with 
its delicate feet on the glands of Drosera, it is caught by the 
viscid secretion, and the slight, though prolonged pressure, 
gives notice of the presence of prey, which is secured by the 
slow bending of the tentacles. On the other hand, the 
sensitive filaments of 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 carbonate of ammonia 
(one part to 146 of water), placed on two filaments, not pro- 
ducing any effect on the contents of their cells, nor causing 
the lobes to close. When, however, a small portion of a leaf 
^vith an attached filament was cut off and immersed in the 



* [Munk (Reichert and du Bois- covering them was removed. It is 

Reymond's ' Archiv.' 1876, p. 105) remarkable that the change from a 

states that the leaves of his plants damp to a dry atmosphere should 

frequently closed when the bell-jar produce this effect. — F. 0.] 



Chap. XIH.] SENSITIVENESS OF FILAMENTS. 235 

same solution, tte fluid within the basal cells became almost 
instantly aggregated into purplish or colourless, irregularly- 
shaped masses of matter. The process of aggregation grad- 
ually travelled up the filaments from cell to cell to their ex- 
tremities, that is in a reverse course to what occurs in the ten- 
tacles of Droserawhen their glands have been excited. Several 
other filaments 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. Nur is it rare to find the contents of 
a few of the terminal cells in a spontaneously aggregated 
condition. The aggregated masses undergo incessant slow 
changes of form, uniting and again separating ; and some of 
them apparently revolve round their own axes. A current 
of colourless granular protoplasm could also be seen travelling 
round the walls of the cells. This current ceases to be 
visible as soon as the contents are well aggregated ; but it 
probably still continues, though no longer visible, owing to- 
all the granules in the flowing layer having become united 
with the central masses. In all these respects the filaments- 
of Dionsea behave exactly like the tentacles of Drosera. 

Notwithstanding this similarity there is one remarkable 
difference. The tentacles of Drosera, after their glands have 
been repeatedly touched, or a particle of any kind has been 
placed on them, become inflected and stronglj- aggregated. 
No such effect is produced by touching the filaments of 
DionEea ; I compared, after an hour or two, some which had 
been touched and some which had not, and others after 
twenty-five hours, and there was no difference in the contents 
of the cells. The leaves were kept open all the time by clips ; 
so that the filaments were not pressed against the opposite 
lobe. 

Drops of water,* or a thin broken stream, falling from a, 
height on the filaments, did not cause the blades to close; 
though these filaments were afterwards proved to be highly 



* [C. De Candolle (' Archives des late the leaf, but that it may be made 

Sc. Phys. et Nat.' Geneva, April 1876) to close by a current o£ water directed 

states that drops of water which in- at right angles to the filament. — 

fringe on the filaments in the direc- F. D.] 
tion of their length do not stimu- 



236 DIONiEA MUSCIPULA. [Chap. Xin. 

sensitive. No donbt, as in tlie case of Drosera, the plant is 
indifferent to the heaviest shower of rain. Drops of a solution 
•of half an ounce of sugar to a fluid ounce of water were 
repeatedly allowed to fall from a height on the filaments, hut 
produced no effect, unless they adhered to them. Again, I 
Islew many times through a fine pointed tube with my utmost 
force against tho filaments without any effect ; such blowing 
being received with as much indifference as no doubt is a 
heavy gale of wind. "We thus see that the sensitiveness of 
the filaments is of a specialised nature, being related to a 
momentary touch rather than to prolonged pressure ; and the 
touch must not be from fluids, such as air or water, but from 
some solid object. 

Although drops of water and of a moderately strong solu- 
tion of sugar, falling on the filaments, does not excite them, 
yet the immersion of a leaf in pure water sometimes caused 
the lobes to close. One leaf was left immersed for 1 hr. 10 m. 
and three other leaves for some minutes, in water at tem- 
peratures varying between 69° and 65° (15° to 18° -3 Cent.) 
without any effect. One, however, of these four leaves, on 
being gentlj' 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. Never- 
theless two fresh leaves on being dipped into water at 75° 
and 62i° (23°-8 and 16°-9 Cent.) instantly closed. These 
were then placed with their footstalks in water, and after 
23 hrs. partially re-expanded ; on touching their filaments one 
of them closed. This latter leaf after an additional 24 hrs. 
again re-expanded, and now, on the filaments of both leaves 
being touched, both closed. We thus see that a short immer- 
sion in water does not at all injure the leaves, but sometimes 
excites the lobes to close. The movement in the above cases 
was evidently not caused by the temperature of the water. 
It has been shown that long immersion causes the purple 
fluid within the cells of the sensitive filaments to become 
aggregated ; and the tentacles of Drosera are acted on in the 
same manner by long immersion, often being somewhat 
inflected. In both cases the result is probably due to a 
slight degree of exosmose. 

I am confirmed in this belief by the effects of immersing a 
leaf of Dionasa 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, 



Chap. XIII.] SENSITIVENESS OF FILAMENTS. 237 

the tips of the marginal spikes crossing in 2 m. 30 s., and 
the leaf being completely shut in 3 m. Three leaves were 
then immersed in a solution of half an ounce of sugar to a 
fluid ounce of water, and all three leaves closed quickly. 
As I was doubtful whether this was due to the cells on the 
upper surface of the lobes, or to the sensitive iilaments, being 
acted on by exosmose, one leaf was first tried by pouring a 
little of the same solution in the furrow between the lobes, 
over the midrib, which is the chief seat of movement. It 
was left there for some time, but no movement ensued. The 
whole upper surface of leaf was then painted (except close 
round the bases of the sensitive filaments, which I could not 
do without risk of touching them) with the same solution, 
but no effect was produced. So that the cells on the upper 
surface are not thus affected. But when, after many trials, 
I succeeded in getting a drop of the solution to cling to one 
of the filaments, the leaf quickly closed. Hence we may, I 
think, conclude that the solution causes fluid to pass out of 
the delicate cell of the filaments by exosmose ; and that this 
sets up some molecular change in their contents, analogous 
to that which must be produced by a touch. 

The immersion of leaves in a solution of sugar affects them 
for a much longer time than does an immersion in water, or 
a touch on the filaments ; for in these latter cases the lobes 
begin to re-expand in less than a day. On the other hand, 
of the three leaves which were immersed for a short time in 
the solution, and were then washed by means of a syringe 
inserted between the lobes, one re-expanded after two days ; 
a second after seven days; and the third after nine days. 
The leaf which closed, owing to a drop of the solution 
having adhered to one of the filaments, opened after two days. 

I was surprised to find on two occasions that the heat from 
the rays of the sun, concentrated by a lens on the bases of 
several filaments, so that they were scorched and discoloured, 
did not cause any movement ; though the leaves were active, 
as they closed, though rather slowly, when a filament on the 
opposite side was touched. On a third trial, a fresh leaf 
closed after a time, though very slowly; the rate not being 
increased by one of the filaments, which had not been 
injured, being touched. After a day these three leaves- 
opened, and were fairly sensitive when the uninjured fila- 
ments were touched. The sudden immersion of a leaf into 
boiling water does hot cause it to close. Judging from the 



^238 DIONiEA MUSCIPULA. [Chap. XIII. 

a,nalogy of Drosera, the heat in these several cases was too 
great and too suddenly applied. The surface of the blade is 
very slightly sensitive ; it may be freely and roughly handled, 
■without any movement being caused. A leaf was scratched 
Tather hard with a needle, but did not close ; but when the 
triangular space between the three filaments on another leaf 
was similarly scratched, the lobes closed. They always 
■closed when the blade or midrib was deeply pricked or cut. 
Inorganic bodies, even of large size, such as bits of stone, 
glass, &c. — or organic bodies not containing soluble nitro- 
genous matter, such as bits of wood, cork, moss, or bodies 
■containing soluble nitrogenous matter, if perfectly dry, such 
-as bits of meat, albumen, gelatine, &c., may be long left (and 
many were tried) on the lobes, and no movement is excited. 
The result, however, is widely different, as we shall presently 
■see, if nitrogenous organic bodies which are at all damp, are 
left on the lobes ; for these then close by a slow and gradual 
movement, very different from that caused by touching one 
of the sensitive filaments. The footstalk is not in the least 
■sensitive ; a pin may be driven through it, or it may be cut 
off, and no movement follows. 

The upper surface of the lobes, as already stated, is 
thickly covered with small purplish, almost sessile glands.* 
These have the power both of secretion and absorption ; but, 
unlike those of Drosera, they do not secrete until excited 
by the absorption of nitrogenous matter. No other excite- 
ment, as far as I have seen, produces this effect. Objects, 
such as bits of wood, cork, moss, paper, stone, or glass, may 
be left for a length of time on the surface of a leaf, and it 
remains quite dry. Nor does it make any difference if the 
lobes close over such objects. For instance, some little balls 
of blotting-paper were placed on a leaf, and a filament was 
touched; and when after 24 hrs. the lobes began to re-open, 



* [Gardiner has described these protoplasm is much less granular 

•glands in the * Proceedings of the R. than before, and contains a number 

Society,' vol xxxvi. p. 180. When at of small vacuoles, so that the nucleus 

rest the gland-cells show a granular appears suspended by radiating 

protoplasm, containing in most cases strands of protoplasm in the centi'e 

a single large vacuole ; the nucleus is of the cell. 

situated at the base of the cell. At Another change produced by the 

the end of the secreting period the feeding the leaf is the appearance, in 

following changes have occuri'ed. The the parenchyma, of tufts of greenish 

nucleus seems to diminish in size, it yellow crystals of unknown nature. — 

has assumed a central position ; the F. D.] 



Chap. XIU.] SECBETION AND ABSORPTION. 239 

the tails -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, ihe glands after a time secrete freely. In one such 
case there was a little secretion directly beneath the meat in 
4 hrs. ; and aiier an additional 3 hrs. there was a consider- 
able quantity both under and close round it. In another 
case, after 3 hrs. 40 m., the bit of meat was quite wet. But 
none of the glands secreted, excepting those which actually 
touched the meat or the secretion containing dissolved 
animal matter. 

If, however, the lobes are made to close over a bit of meat 
or an insect, the result is different, for the glands over the 
whole surface of the leaf now secrete copiously. As in this 
case the glands on both sides are pressed against the meat or 
insect, the secretion from the first is twice as great as when 
a bit of meat is laid on the surface of one lobe ; and as the 
two lobes come into almost close contact, the secretion, 
containing dissolved animal matter, spreads by capillary 
attraction, causing fresh glands on both sides to begin 
secreting in a continually widening circle. TLe 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, hO that an opening 
was left ; and through this, the secretion continued to run 
down the footstalk during nine days, — that is, for as long a 
time as it was observed. By forcing up one of the lobes, I 
was able to see some distance between them, and all the 
glands within sight were secreting freely. 

We have seen that inorganic and non-nitrogenous objects 
placed on the leaves do not excite any movement; but 
nitrogenous bodies, if in the least degree damp, cause after 
several hours the lobes to close slowly. Thus bits of quite 
dry meat and gelatine were placed at opposite ends of the 
same leaf, and in the course of 24 hrs. excited neither 



240 DIOXiEA MUSCIPULA. [Chap. Xin. 

secretion nor movement. They were tlien dipped in water, 
their surfaces dried on blotting-paper, and replaced on the 
same leaf, the plant being now covered with a bell-glass. 
After 24 hrs. the damp meat had excited some acid secretion, 
and the lobes at this end of the leaf were almost shut. At 
the other end, where the damp gelatine lay, the leaf was 
still quite open, nor had any secretion been excited ; so that, 
as with Drosera, gelatine is not nearly so exciting a sub- 
stance as meat. The secretion beneath the meat was tested 
by pushing a strip of litmus paper under it (the filaments 
not being touched), and this slight stimulus caused the leaf 
to shut. On the eleventh day it reopened ; but the end 
where the gelatine lay, expanded several hours before the 
opposite end with the meat. 

A second bit of roast meat, which appeared dry, though it 
had not been purposely dried, was left for 24 hrs. on a leaf, 
caused neither movement nor secretion. The plant in its 
pot was now covered with a bell-glass, and the meat absorbed 
some moisture from the air; this sufficed to excite acid 
secretion, and by the next morning the leaf was closely shut. 
A third bit of meat, dried so as to be quite brittle, was 
placed on a leaf under a bell-glass, and this also became in 
24 hrs. slightly damp, and excited some acid secretion, but 
no movement. 

A rather large piece of perfectly dry albumen was left at 
one end of a leaf for 24 hrs. without any effect. It was then 
soaked for a few minutes in water, rolled about on blotting- 
paper, and replaced on the leaf; in 9 hrs. some slightly acid 
secretion was excited, and in 24 hrs. this end of the leaf was 
partially closed. The bit of albumen, which was now 
surrounded by much secretion, was gently removed, and 
although no filament was touched, the lobes closed. In this 
and the previous case, it appears that the absorption of 
animal matter by the glands renders the surface of the leaf 
much more sensitive to a touch than it is in its ordinary 
state ; and this is a curious fact. Two days afterwards the 
end of the leaf where nothing had been placed began to 
open, and on the third day was much more open than the 
opposite end where the albumen had lain. 

Lastly, large drops of a solution of one part of carbonate 
of ammonia to 146 of water were placed on some leaves, but 
no immediate movement ensued. I did not then know of 
the slow movement caused by animal matter, otherwise I 



Chap. XIII.] SECRETION AND ABSORPTION. 241 

elioTild have otseirvred. tLe leaves for a longer time, and they 
would probably have been found closed, though the solution 
(judging from Drosera) was, perhaps, too strong. 

From the foregoing cases it is certain that bits of meat 
and albumen, if at all damp, excite not only the glands to 
secrete, but the lobes to close. This movement is widely 
different from the rapid closure caused by one of the 
filaments being touched. We shall see its importance when 
we treat of the manner in which insects are captured. 
There is a great contrast between Drosera and Dionasa in the 
effects produced by mechanical irritation on the one hand, 
and the absorption of animal matter on the other. Particles 
<if glass placed on the glands of the exterior tentacles of 
Drosera excite movement within nearly the same time, as 
do particles of meat, the latter being rather the most 
efficient ; but when the glands of the disc have bits of meat 
given them, they transmit a motor impulse to the exterior 
tentacles much more quickly than do these glands when 
bearing inorganic particles, or when irritated by repeated 
touches. On the other hand, with DionKa, touching the 
filaments excites incomparably quicker movement than the 
.absorption of animal matter by the glands. Nevertheless, in 
certain cases, this latter stimulus is the more powerful of the 
two. On three occasions leaves were found which from 
some cause were torpid, so that their lobes closed only 
slightly, however much their filaments were irritated ; but 
on inserting crushed insects between the lobes, they became 
in a day closely shut. 

The facts just given plainly show that the glands have 
the power of absorption, for otherwise it is impossible that 
the leaves should be so differently affected by non-nitro- 
genous and nitrogenous bodies, and between these latter in a 
dry and damp condition. It is surprising how slightly 
damp a bit of meat or albumen need be in order to excite 
secretion and afterwards slow movement, and equally 
surprising how minute a quantity of animal matter, when 
absorbed, suffices to produce these two effects. It seems 
hardly credible, and yet it is certainly a fact, that a bit of 
liard-boiled white of egg, first thoroughly dried, then soaked 
for some minutes in water and rolled on blotting-paper, 
should yield in a few hours enough animal matter to the 
glands to cause them to secret 3, and afterwards the lobes to 
close. That the glands hava the power of absorption is 

K 



242 DIONJEA MUSCIPULA, [Chap. XHI. 

likewise shown by the very different lengths of time (as we 
shall presently see) during which the lohes remain closed 
over insects and other bodies yielding soluble nitrogenous 
matter, and over such as do not yield any. But there is 
direct evidence of absorption in the condition of the glands 
which have remained for some time in contact with animal 
matter. Thus bits of meat and crushed insects were several 
times placed on glands, and these were compared after some 
hours with other glands from distant parts of the same leaf. 
The latter showed not a trace of aggregation, whereas those 
which had been in contact with the animal matter were well 
aggregated. Aggregation may be seen to occur very quickly 
if a piece of a leaf is immersed in a weak solution of carbonate 
of ammonia. Again, small cubes of albumen and gelatine 
were left for eight days on a leaf, which was then cut open. 
The whole surface was bathed with acid secretion, and every 
cell in the many glands which were examined had its 
contents aggregated in a beautiful manner into dark or pale 
purple, or colourless globular masses of protoplasm. These 
underwent incessant slow changes of forms ; sometimes 
separating from one another and then reuniting, exactly as 
in the cells of Drosera. Boiling water makes the contents 
of the gland -cells white and opaque, but not so purely white 
and porcelain-like as in the case of Drosera. How living 
insects, when naturally caught, excite the glands to secrete 
so quickly as they do, I know not ; but I suppose that the 
great pressure to which they are subjected forces a little 
excretion from either extremity of their bodies, and we have 
seen that an extremely small amount of nitrogenous matter 
is sufficient to excite the glands. 

Before passing on to the subject of digestion, I may state 
that I endeavoured to discover, with no success, the functions 
of the minute octofid processes with which the leaves are 
studded. From facts hereafter to be given in the chapters, 
on Aldrovanda and Utricularia, it seemed probable that they 
served to absorb decayed matter left by the captured insects ;. 
but their position on the backs of the leaves and on the 
footstalks rendered this almost impossible. Nevertheless,, 
leaves were immersed in a solution of one part of urea to 437 
of water, and after 24 hrs. the orange layer of protoplasm 
within the arms of these processes did not appear more- 
aggregated than in other specimens kept in water. I then 
tried suspending a leaf in a bottle over an excessively putrid 



Chap. XUI.] 



DIGESTION. 



243 



infusion of raw meat, to see whetlier they alisorbed tlio 
vapour, but their contents were not affected. 

Digestive Power of the Secretion.* — When a leaf closes over 
any object, it may be said to form itself into a temporary 
stomach ; and if the object yields ever so little animal 
matter, this serves, to use Schiff's expression, as a peptogene, I 
and the glands on the surface pour forth their acid secretion, 
which acts like the gastric juice of animals. As so many ex- 
periments were tried on the digestive power of Drosera, only 
a few were made with Dionaea, but they were amply sufficient 
to prove that it digests. This plant, moreover, is not so 



* Dr. W. M. Canby, of Wilmington, 
to whom I am mucli indebted for 
information regarding Dionaia in its 
native home, has published in the 
'Gardener's Monthly,' Philadelphia, 
August 1868, some interesting ob- 
servations. He ascertained that the 
secretion digests animal matter, such 
as the contents of insects, bits of 
meat, &o. ; and that the secretion is 
reabsorbed. He was also well aware 
that the lobes remain closed for a 
much longer time when in contact 
with animal matter than when made 
to shut by a mere touch, or over 
objects not yielding soluble nutri- 
ment ; and that in these latter cases 
the glands do not secrete. The Kev. 
Dr. Curtis first observed (' Boston 
Journal Nat. Hist.' vol. i. p. 123) 
the secretion from the glands. I 
may here add that a gardener, Mr. 
Knight, is said (Kirby and Spence's 
'Introduction to Entomology,' 1818, 
vol. i. p. 295) to have found that a 
plant of the Dionsea, on the leaves of 
which " he laid fine filaments of raw 
beef, was much more luxuriant in its 
growth than others not so treated." 

[The earlier history of the subject 
is given in Sir Joseph Hooker's " Ad- 
dress to the Department of Botany 
and Zoology," ' British Association 
Report,' 1874, p. 10'-', whence the 
following facts are taken. 

About 1768 Ellis, a well-known 
English naturalist, sent to Linnaeus a 
drawing and specimens of Dionasa 



with the following remarks (" A Bo- 
tanical Description of the D.onxa 
■muscipula. ... in a letter to Sir 
Charles Linnceus," p. 37) : — 

" The plant, of which I now enclose 
you an exact figure. . . . shows that 
Nature may have some views towards 
its nourishment, in forming the upper 
joint of its leaf like a machine to 
catch food." 

Linnaeus was unable to believe that 
the plant could profit by the captured 
insects ; he only saw in the phenomen.i 
" an extreme case of sensitiveness in 
the leaves which causes them to fold 
up where irritated, just as the sensi- 
tive plant does ; and he consequently 
regarded the capture of the disturb- 
ing insect as something merely 
accidental and of no importance to 
the plant. . . . Linnjeus's authority 
overbore criticism if any was offered ; 
and his statement about the behaviour 
of the leaves was copied from book to 
book. . . . Dr. [Erasmus] Darwin 
(1791) was contented to suppose that 
Dionsea surrounded itself with insect- 
traps to prevent depredations upon 
its flowers. Dr. Curtis, whose con- 
tribution to the subject has been 
already mentioned, describes the 
captured insects as enveloped in a 
fluid of a mucilaginous consistence 
which seems to act as a solvent, the 
insects being more or less consumed 
by it."— F. D.] 

t [See footnote, p. 106.— F. D.] 

R 2 



24 i DIOX^A MUSCIPULA. [Chap. XIII. 

well fitted as Drosera for observation, as tlie process goes on 
within the closed lobes. Insects, even beetles, after being 
subjected to the secretion for several days, are surprisingly- 
softened, though their chitinous coats are not corroded. 

Experiment 1. — A cube of albumen of -^ of an inch (2-540 mm.) 
was placed at one end of a leaf, and at the other end an oblong piece 
of gelatine, -i of an inch (5 '08 mm.) long, and ^ 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 Diosera, and tliis agrees with thp 
length of time during which the leaves remain closed over digestible 
objects. 

Experiment 2. — A bit of albumen ^ of an inch square, but only 
-^ in thickness, and a piece of gelatine of the same size as before, were 
placed on a leaf, which eight days afterwards was cut open. The sur- 
face was bathed with slightly adhesive, very acid secretion, and tlie 
glands were all in an aggregated condition. Not a ve.stige of the 
albumen or gelatine was left. Similarly sized pieces were placed at 
the same time on wet moss on the same pot, so that they were sub- 
jected to nearly similar conditions ; after eight days these were brown, 
decayed, and matted with fibres of mould, bat had not disappeared. 

Experiment 3. — ^A piece of albumen -fg of an inch (3 ■ 81 mm.) long, 
and 2V broad and thick, and a piece of gelatine of the same size as 
before, were placed on another leaf, which was cut open after seven 
days ; not a vestige of either substance was left, and only a moderate 
amount of secretion on the surface. 

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

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

Experiment 6. — ^A cube of albumen of -j^ of an inch and a piece of 
gelatine of the same size as before were placed on a leaf, which opened 
spontaneously after thirteen days. The albtnnen, 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 httle 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 opened 



Chap. Xin.] DIGESTION. 245 

spontaneously after eleven days ; a vestige of tke meat was left, and 
tlie surfuce of the leaf was here blackened ; the gelatine had all dis- 
appeared. 

Experiment 8. — A bit of half roasted meat (not measured) was 
placed on a leaf which was forcibly kept open by a clip, so that it was 
moistened with the secretion (very acid) only on its lower surface. 
Kevertheless, after only 22^ hrs. it was surprisingly softened, when 
compared with another bit of the same meat which had been kept 
damp. 

Experiment 9. — A cube of •j'o of ^° inch of very compact roasted 
beef was placed on a leaf, whicd opened spontaneously after twelve 
days ; so much feebly acid secretion was left on the leaf that it trickled 
off. The meat was completely disintegrated, but not all dissolved ; 
there was no mould. The little mass was placed under the microscope ; 
some of the fibrillss in the middle still exhibited transverse stri^ ; 
others showed nut 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 
pame state as that formerly described, which was half digested by 
Drosera. Here, again, as in the case of albumen, the digestive process 
seems slower than in Drosera. At theoi)posite end of the same leaf, a 
firmly comi)ressed pellet of bread had been placed; this was completely 
disintegrated, I suppose, owing to the digestion of the gluten, but 
seemed very little reduced in bulk. 

Experiment 10.— A cube of Jj of an inch of cheese and another of 
albumen were placed at opposite ends of the same leaf. After nine 
days the lobes opened spontaneously a little at the end enclosing the 
cheese, but hardly any or none was dissolved, though it was softened 
and suri'ounded by secretion. Two days subsequently the end with 
the albumen also opened spontaneously (t'.e. eleven days after it was 
put on), a mere trace in the blackened and dry condition being left. 

Experiment 11. — The same experiment with cheese and albumen 
repeated on another and rather torpid leaf. The lobes at the end with 
the cheese, after an interval of six days, opened spontaneously a little ; 
the cube of cheese was much softened, but not dissolved, and but little, 
if at all reduced in size. Twelve hours afterwards the end with the 
albumen opened, which now consisted of a large drop of transparent, 
not acid, viscid fluid. 

Experiment 12. — Same experiment as the two last, and here 
again the leaf at the end enclosing the cheese opened before the oppo- 
site end with the albumen ; but no further observations were made. 

Experiment 13. — A globule of chemically prepared casein, about Jg 
of an inch in diameter, was placed on a leaf, which spontaneously 
opened after eight days. The casein now consisted of a soft sticky 
mass, very little, if at all, reduced in size, but bathed in acid secretion. 

These experiments are sufficient to show that the secretion 
from the glands of Dionsea dissolves albumen, gelatine, and 



246 DION^SIA MUSCIPULA. [Chap. XIII. 

meat, if too large pieces are not given. Globules of fat and 
fibro-elastic tissiie 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 JDrosera) excite much acid secretion, 
owing, I presume, to the absorption of some included 
albuminous matter, these substances are not digested, and 
are not appreciably, if at all, reduced in bulk. 

Effects of the Vapours of Chloroform, Sulphuric Ether, and Hydro- 
cyanic Acid. — A plant bearing one leaf was introduced into a large 
bottle with a drachm (3 ■ 549 c.c.) of chloroform, the mouth being im- 
perfectly closed with cotton-wool. The vapour caused in 1 m. the 
lobes to begin moving at an imperceptibly slow rate ; but in 3 m. the 
spikes crossed, and the leaf was soon completely shut. The dose, 
however, was much too large, for in between 2 and 3 hrs. the leaf 
appeared as if burnt, and soon died. 

Two leaves were exposed for 30 m. in a 2-oz. vessel to the vapour 
of 30 minims (1'774 c.c.) of sulphuric ether. One leaf closed alter a 
time, as did the other whilst being removed from the vessel without 
being touched. Both leaves were greatly injured. Another leaf, 
exposed for 20 m. to 15 minims of ether, closed its lobes to a certain 
extent, and the sensitive filaments were now quite insensible. After 
24 hrs. this leaf recovered its sensibility, but was still rather torpid. 
A leaf exposed in a large bottle for only 3 m. to ten drops was 
rendered insensible. After 52 m. it recovered its sensibility, and when 
one of the filaments was touched, the lobes closed. It began to 
reopen after 20 hrs. Lastly another leaf was exposed for 4 m. to only 
four drops of the ether ; it was rendered insensible, and did not close 
when its filaments were rcpeatedlv touched, but closed when the end 
of the open leaf was cut off. This shows either that the internal 
parts had not been rendered insensible, or that an incision is a more 
powerful stimulus than repeated touches on the filaments. Whether 
the larger doses of chloroform and ether, which caused the leaves to 
close slowly, acted on the sensitive filaments or on the leaf itself, I do 
not know. 

Cyanide of potassium, when left in a bottle, generates prussic or 
hydrocyanic acid. A leaf was exposed for 1 hr. 35 m. to the vapour 
thus formed ; and the glands became within this time so colourless and 
shrunken as to be scarcely visible, and I at first thought that they had 
all dropped off. The leaf was not i-endered 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. 



Chap. XIII.] MANNER OF CAPTURING INSECTS. 247 

On the Manner in which Insects are caught. — We will now 
consider the action of the leaves when insects happen to 
touch one of the sensitive filaments. This often occurred in 
my greenhouse, but I do not know whether insects are 
attracted in any special way by the leaves. They are caught 
in large numbers by the plant in its native country. As 
Koon as a filament is touched, both close with astonishing 
quickness ; and as they stand at less than a right angle to 
each other, they have a good chance of catching any intruder. 
The angle between the blade and footstalk does not 
change when the lobes close. The chief seat of movement is 
near the midrib, but is not confined to this part ; for, as the 
lobes come together, each curves inwards across its whole 
breadth ; the marginal spikes, however, not becoming curved.* 
This movement of the whole lobe was well seen in a leaf to 
which a 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 resistance in this part, went 
on curving inwards much beyond the medial line. The 
whole of the lobe, from which a portion had been cut, was 
afterwards removed, and the opposite lobe now curled 
completely over, passing through an angle of from 120° to 
130°, so as to occupy a position almost at right angles to 
that which it would have held had the opposite lobe been 
present. 

From the curving inwards of the two lobes, as they 
move towards each other, the straight marginal spikes inter- 
cross by their tips at first, and ultimately by their bases. 
The leaf is then completely shut and encloses a shallow 
cavity. 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 nitrogenous matter, the two lobes 
retain their inwardly concave form until they re-expand. 
The re-expansion under these circumstances — that is when 
no organic matter is enclosed — was observed in ten cases. 
la all of these, the leaves re-expanded to about two-thirds 
of the full extent in 24 hrs. from the time of closure. Even 
the leaf from which a portion of one lobe had been cut off 
opened to a slight degree within this same time. In one 



' [Munk (Reichert and Du Bois'- at the edge of the leaf, by which the 
Reymond's ' Archiv.' 1876, p. 108) teeth are carried inwards.— P. D.] 
states that a special movement occurs ■ i^ 



24S' DIOXJCA MUSCIPULA. [Chap. XIH. 

case a leaf re-expanded to about two-tTiirds of tlie full extent 
in 7 lirs., and completely in 32 hrs. ; but one of its filaments 
iad been toncbed merely with a bair just enougb to cause 
tbe leaf to close. Of tbese ten leaves only a few re-expanded 
completely in less tban two days, and two or tbree required 
even a little longer time. Before, however, they fully 
re-expand, tbey are ready to close instantly if their sensitive 
filaments are touched. How many times a leaf is capable 
of shutting and opening if no animal matter is left enclosed, 
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, gelatine, casein, 
and, no doubt, any other substance containing soluble 
nitrogenous matter, the lobes, instead of remaining concave, 
thus including a concavity, slowly press closely together 
throughout their whole breadth. As this takes place, the 
margins gradually become a little everted, so that tbe 
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 fiattened, 
with distinct impressions of the little prominent glands ; but 
this latter circumstance may have been partly caused by the 
corroding action of the secretion. So firmly do they become 
pressed together that, if any large insect or other object has 
been caught, a corresponding projection on the outside of the 
leaf is distinctly visible. When the two lobes are thus 
completely shut, they resist being opened, as by a thin 
wedge being driven between them, with astonishing force, 
and are generally ruptured rather than yield. If not 
ruptured, they close again, as Dr. Canby informs me in a 
letter, " with quite a loud flap." But if the end of a leaf is 
held firmly between the thumb and finger , or by a clip, so 



* According to Dr. Curtis, in ' Boston Journal of Nat. Hist.' vol. i. 1837, 
p. 123. 



Chap. XIII.] MANNER OP CAPTUEING INSECTS. 24D 

that -the lotes cannot begin to close, they exert, whilst ia 
this position, very little force. 

I thought at first that the gradual pressing together of the 
lobes was caused exclusively by captured insects crawling 
over and repeatedly irritating the sensitive filaments ; and 
this view seemed the more probable when I learnt from Dr. 
Burdon Sanderson that whenever the filaments of a closed 
leaf are irritated, the normal electric current is disturbed. 
Nevertheless, such initatlon 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 f een 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 indispensable for the capturing 
of insects. These two movements, excited by two such 
widely different means, are thus both well adapted, like all the 
other functions of the plant, for the purposes wliich they 
subserve. 

There ia another wide difference in the action of leaves 
which enclose objects, such as bits of wood, cork, balls of 
paper, or which have had their filaments merely touched, 
and those which enclose organic bodies yielding soluble 
nitrogenous matter. In the former case the leaves, as we 
have seen, open in under 24 hrs. and are then ready, even 
before being fully expanded, to shut again. But if they 
have closed over nitrogen-yielding bodies, they remain 
closely shut for many days; and after re-expanding are 
torpid, and never act again, or only after a considerable 
interval of time. In four instances, leaves after catching 
insects never re-opened, but began to wither, remaining 
closed — in one case for fifteen days over a fly ; in a second. 



250 DION^A MUSCIPULA. [Chap. Xni. 

for twenty-four days, thougli 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 oases 
leaves remained closed for at least nine daj's over flies, and 
for how many more I do not know. It should, however, be 
added that in two instances in which very small insects had 
heen naturally canght the leaf opened as quickly as if 
nothing had been caught ; and I suppose that this was due 
to such small insects not having been crushed or not having 
excreted any animal matter, so that the glands were not 
excited. Small angular bits of albumen and gelatine were 
placed at both ends of three leaves, two of which remained 
closed for thirteen and the other for twelve days. Two 
other leaves remained closed over bits of meat for eleven 
days, a thiid leaf for eight days, and a fourtli (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 -ji^ of an inch ( 2-54 mm.) 
in size, and were sometimes smaller ; yet these small portions 
eufSced to keep the leaves closed for many days. Dr. Canby 
informs me that leaves remain shut for a longer time over 
insects than over meat ; and from what I have seen, I can 
well believe that this is the case, especially if the insects are 
large. 

In all the above cases, and in many others in which leaves 
remained closed for a long but unknown period over insects 
naturally caught, they were more or less torpid when they 
re-opened. Generally they were so torpid during many 
eucceeding days that no excitement of the filaments caused 
the least movement. In one instance, however, on the day 
after a leaf opened which had clasped a fly, it closed with 
extreme slowness when one of its filaments was touched ; and 
although no object was left enclosed, it was so torpid that it 
did not re-open for the second time until 44 hrs. had elapsed . 
In a second case, a leaf which had expanded after remaining 
closed for at least nine days over a fly, when greatly irritated, 
moved one alone of its two lobes, and retained this unusual 
position for the next two days. A third case offers the 
strongest exception which I have observed ; a leaf, after 
lemaining clasped for an unknown time over a fly, opened, 



Chap. XIII.] MANNEE OF CAPTURING INSECTS. 251 

and when one of its filaments was touched, closed, though 
rather slowly. Dr. Canby, who observed in the United 
States a large number of plants which, although not in their 
native site, were probably more vigorous than my plants, 
informs me that he has " several times known vigorous 
leaves to devour their prey several times ; but ordinarily 
twice, or quite often, once was enough to render them 
unserviceable." Mrs. Treat, who cultivated many plants in 
New Jersey, also informs me that " several leaves caught 
successively three insects each, but most of them were not 
able to digest the third fly, but died in the attempt. Five 
leaves, however, digested each three flies, and closed over the 
fourth, but died soon after the fourth capture. Many leaves 
did not digest even one large insect." 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 Dionasa differs from 
Drosera, which catcljes and digests many insects after shorter 
intervals of time. 

We are now prepared to understand the use of the mar- 
ginal spikes, wiiich form so conspicuous a feature in the 
appearance of the plant (fig. 12, p. 232), and which at first 
seemed to me in my ignorance useless appendages. From 
the inward curvature of the lobes as they approach each 
other, the tips of the marginal spikes first intercross, and 
ultimately their bases. Until the edges of the lobes come 
into contact, elongated spaces between the spikes, varying 
from the -[Jj- to the -rV of ^^ inch (1 • 693 to 2 • 540 mm.) in 
breadth, according to the size of the leaf, are left open. 
Thus an insect, if its body is not thicker than these measure- 
ments, can easily escape between the crossed spikes, when 
disturbed by the closing lobes and increasing darkness; and 
one of my sons actually saw a small insect thus escaping. 
A moderately large insect, on the other hand, if it tries to 
escape between the bars will surely be pushed back again 
into its horrid prison with closing walls, for the spikes 
continue to cross more and more until the edges of the lobes 
come into contact. A very strong insect, however, would be 
able to free itself, and Mrs. Treat saw this effected by a 
rose-chafer (Macrodactylus suhspinosus) in the United States. 
Now it would manifestly be a great disadvantage to the 
plant to waste many days in remaining clasped over a 



252 DION^A MUSCIPULA. [Chap. XIII. 

minute insect, and several additional days or weeks in 
afterwards recovering its sensibility; inasmuch as a minute 
insect would afford but little nutriment. It would be far 
better for the plant to wait for a time until a moderately 
large insect was captured, and to allow all the little ones to 
escape; and this advantage is secured by ±he slowly inter- 
crossing marginal spikes, which act like the large meshes of 
a fishing-net, allowing the small and useless fry to escape. 

As I was anxious to know whether this view was correct — 
and as it seems a good illustration of how cautious we ought 
to be in assuming, as I had done with respect to the marginal 
spikes, that any fully developed structure is useless — I 
applied to Dr. Canby. He visited the native site of the 
plant, early in the season, before the leaves had grown to 
their full size, and sent me fourteen leaves, containing 
naturally captured insects. Four of these had caught rather 
small in.-.ects, 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 cuiculio, a thick and 
broad spider, and a scolopendra. Out of these ten insects, 
no less than eight were beetles,* and out of the whole foui-- 
teen there was only one, viz. a dipterous insect, which could 
readily take flight. Drosera, on the other hand, lives chiefly 
on insects which are good flyers, especially Diptera, caught 
by the aid of its viscid secretion. But what most concerns 
us is the size of the ten larger insects. Their average length 
from head to tail was "256 of an inch, the lobes of the leaves 
being on an average '53 of an inch in lengtli, so that the 
insects were very nearly half as long as the leaves within 
which they were enclosed. Only a few of these leaves, 
therefore, had wasted their powers by capturing small prey, 
though it is probable that many small insects had crawled 
over them and been caught, but had then escaped through 
the bars. 

The Transmission of the Motor Impulse, and means of Move- 



* Dr. Canby remarks (* Gardener^s elaters, for the five which I examined 

Monthly,' Aug. 1868), "as a general were in an extremely fragile and 

thing beetles and insects of that Ivind, empty condition, as if all their in- 

though always killed, seem to be ternal parts had been partially di- 

too hard-shelled to serve as food, gested. Mrs. Treat informs me that 

and after a short time are rejected." the plants which she cultivated in 

I am surprised at this statement, at New Jersey chiefly caught Diptera. 
least with respect to such beetles as 



Chap. XIII.] TEANSMISSION OF MOTOR IMPULSE. 253 

ment. — It is sufficient to touch any one of the six filaments to 
cause hoth lobes to close, these becoming at the same time 
incurved throughout their whole breadth. The stimulus 
must therefore radiate in all directions from any one filament. 
It must also be transmitted with much rapidity across the 
leaf, for in all ordinary cases both lobes close simultaneously, 
ns far as the eye can judge. Most physiologists believe that 
in irritable plants the excitement is transmitted along, or in 
close connection with, the fibro-vascular bundles. In Diontea, 
the course of these vessels (composed of spiral and ordinary 
vascular tissue) seems at first sight to favour this belief; for 
they run up the midrib in a great bundle, sending off small 
bundles almost at right angles on 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 zigEag line of vessels thus runs 
round the whole circumference of the leaf, and in the midrib 
all the vessels are in close contact ; so that all parts of the 
leaf seem to be brought into some degree of communication. 
Nevertheless, the presence of vessels is not necessary for the 
transmission of the motor impulse, for it is transmitted from 
the tips of the sensitive filaments (these being about the -.^ 
of an inch in length), into which no vessels enter ; and these 
could not have been overlooked, as I made thin vertical 
sections of the leaf at the bases of the filaments. 

On several occasions, slits about the -j'^ of an inch in length 
were made with a lancet, close to the bases of the filaments, 
parallel to the midrib, and, therefore, directly across the 
course of the vessels. These were made sometimes on the 
inner and sometimes on the outer iside of the filaments ; and 
after several days, when the leaves had reopened, these 
filaments were touched roughly (for they were always ren- 
dered in some degree torpid by the operation), and the lobes 
then closed in the ordinaryjmanner, though slowly, and some- 
times not until after a considerable interval of time. These 
cases show that the motor impulse is not transmitted along 
the vessels, and they further show that there is no necessity 
for a direct line of communication from the £lament which 
is touched towards the midrib and opposite lobe, or towards 
the outer parts of the same lobe. 

Two slits near each other, both parallel to the midrib, 



254 diontea muscipula. [Chap. xnr. 

were next made in tlie same manner as before, one on each 
side of the base of a filament, on five distinct leaves, so that 
a little slip bearing a filament was connected with the rest 
of the leaf only at its two ends. These slips were nearly of 
the same size ; one was carefully measured ; it was -12 of an 
inch (3 • 048 mm.) in length, and • 08 of an inch (2 ■ 032 mm.) 
in breadth ; and in the middle stood the filament. Only one 
of these slips withered and perished. After the leaf had 
recovered from the operation, though the slits were still 
open, the filaments thus circumstanced were roughly touched, 
and both lobes, or one alone, slowly closed. In two instances 
touching the filament produced no effect ; but when the 
point of a needle was driven into the slip at the base of the 
filament, the lobes slowly closed. Now in these cases the 
impulse must have proceeded along the slip iri a line parallel 
to the midrib, and then have radiated forth, either from both 
ends or from one end alone of the slip, over the whole surface 
of the two lobes. 

Again, two parallel slits, like the former ones, were made, 
one on each side of the base of a filament, at right angles to 
the midrib. After the leaves (two in number) had recovered, 
the filaments were roughly touched, and the lobes slowly 
closed ; and here the impulse must have travelled for a short 
distance in a line at right angles to the midrib, and then 
have radiated forth on all sides over both lobes. These 
several cases prove that the motor impulse travels, in all 
directions through the cellular tissue, independently of the 
course of the vessels. 

With Drosera we have seen that the motor impulse is 
transmitted in like manner in all directions through the 
cellular tissue ; but that its rate is largly governed- by the 
length of the cells and the direction of their longer axes. 
Thin sections of a leaf of Dionsea were made by my son, and 
the cells, both these of the central and of the more superficial 
layers, were found much elongated, with Iheir longer axes 
directed towards the midrib ; and it is in this direction that 
the motor impulse must be sent with great rapidity from one 
lobe to the other, as both close simultaneously. The central 
parenchymatous cells are larger, more loosely attached 
together, and have more delicate walls than the more super- 
ficial cells. A thick mass of cellular tissue forms the upper 
surface of the midrib over the great central bundle of 
vessels. 



Chap. XIII.] TRANSMISSION OF MOTOR IMPULSE, 255 

When tte 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 sufiicient to prevent a lobe moving 
did not prevent the transmission from it of a stimulus which 
excited the opposite lobe to move. We thus also learn that, 
although normally both lobes move together, each has the 
power of independent movement. A case, indeed, has 
already been given of a torpid leaf that had lately re-openeil 
after catching an insect, of which one lobe alone moved when 
irritated. Moreover, one end of the same lobe can close and 
re-expand, independently of the other end, as was seen in 
some of the foregoing experiments. 

When the lobes, which are rather thick, close, no trace of 
wrinkling can be seen on any part of their upper surfaces. 
It appears therefore that the cells must contract. The chief 
seat of the movement is evidently 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 raw °f *^ 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 
j^go of an inch apart, so that a small portion of the upper 
surface of the midrib had contracted in a transverse line -[jf^jy 
of an inch (-0508 mm.). 

We know that the lobes, whilst closing, become slightly 
incurved throughout their whole breadth. This movement 
appears to be due to the contraction of the superficial layers 
of cells over the whole upper surface. In order to observe 
their contraction, a narrow strip was cut out of one lobe at 
right angles to the midrib, so that the surface of the opposite 
lobe could be seen in this part when the leaf was shut. 
After the leaf had recovered from the operation and had re- 
expanded, three minute black dots were made on the surface 
opposite to the slit or window, in a line at right angles to 
the midrib. The distance between the dots was found to be 



256 



DIONiEA MUSOIPULA. 



[Chap. Xni. 



-j-^^ of an inch, so that the two extreme dots were xwir of 
an inch apart. One of the jfilaments 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 J-J^ of an inch, and the two further dots by Yvh% of ^^ 
inch, than they were before ; so that the two extreme dots 
now stood about tswu of ^''^ inch (-127 mm.) nearer together 
than before. If we suppose the whole upper surface of the 
lobe, which was T*xnn7 of an inch in breadth, to have con- 
tracted in the same proportion, the total contraction will 
bave amounted to about y-^l^j- or -^-^ 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 Sandersonf is now 
universally known ; namely that there exists a normal elec- 
trical current in the blade and footstalk ; and that when the 
leaves are irritated, the current is disturbed in the same 
manner as takes place during the contraction of the muscle 
of an animal, f 



* [Batalin has discussed the me- 
chanism of closure in Dionasa in his 
interesting essay in 'Flora,' 1877. 
He agrees in general with the state- 
ments above given, but as in the case 
of Drosera, so here he believes that 
the movements are associated with a 
■small amount of actual growth. 
Marks are made on the lower or 
external surface of the leaf, and the 
distance between them is found to 
increase when the leaf closes. When 
-the leaf opens the distance does not 
perfectly return to its former dimen- 
sions, and thus shows a certain 
-amount of permanent growth has 
taken place. It will be seen that 
Batalin's observations do not support 
the idea (see p. 258) that the re-open- 
ing of the leaf is due to the return of 
the outer cells to their natural size 
when the tension put on them by the 
contraction of the inner surface is re- 
moved. JIunk (Joe. cit.) and Pfefifer 
('Osmotische Untersuchungen,' 1877. 
p. 196) have with justice called at- 
tention to the unsatisfactory nature 



of the discussion in the text on the 
mechanism of the movement. Batalin 
shows further that the ultimate 
closure of the leaf by which the two 
valves are closely pressed together is 
etfected by the shortening or con- 
traction of the outer surface of the 
leaf. He records a curious fact which 
has not elsewhere been noted, namely, 
that the midrib becomes more curved 
after the closure of the leaf. Munk 
(Reichert and Du Bois-Keymond, 
' Archiv.' 1876, p. 121), on the other 
hand, is inclined to believe that the 
curvature of the midrib diminishes 
when the leaf closes. — F. D.] 

t 'Proo. Royal Soc' vol. .\xi. p. 
495 ; and lecture at the Royal In- 
stitution, June 5, 1874, given in 
'Nature,' 1874, pp. 105 and 127. 

J [Professor Sanderson's work has 
been criticised by Professor Munk in 
Reichert and Du Bois-Eeymond's 
'Archiv.' 1876, and by Professor 
Kunkel in Sachs' 'Arbeiten a. d. 
bot. Institut in Wiizburg,' Bd. ii. p. 1- 

Professor Sanderson has continued 



Chap. XIII.] 



EE-EXPANSIOX. 



257 



The Be-expansion of the Leaves. — This is eEEeoted at an in- 
sensibly slow rate, whether or not any object is enclosed.* 



to work at the subject, and has given 
his results in an elaborate paper in 
'Phil. Transactions,' 1882. It will 
be sufficient to note his conclusions 
with regard to the two points men- 
tioned in the text. First, for the 
electrical condition of the leaf at rest. 
Sanderson rejects Munk's method of 
explaining the state of the leaf by a 
mechanical schema — an arrangement 
of copper and zinc cylinders. He does 
so, not only because he accepts " as 
fundamental the doctrine tliat what- 
ever physiological properties the leaf 
possesses, it possesses by virtue of its 
being a system of living cells ;" but 
also because the facts of the case are 
not in accordance with Professor 
Munk's theoretical deductions. He in- 
clines to admit that the electrical 
differences observed between different 
parts of the unexcited leaf may be 
partly explained by the migration of 
water. " For on the one hand we know 
that in consequence of the surface 
evaporation, migration of water cer- 
tainly exists, while on the other we 
have proof in the experiments of Dr. 
Kunkel that such migration cannot 
occur without producing electrical 
differences." In a similar way he is in- 
clined to believe that the gradual elec- 
trical change resulting from repeated 
excitation, -as well as the after effect of 
a single excitation, are to be explained 
by migration of water accompanying 
the motion of the leaf. On the other 
hand he believes that the primary, 
and rapidly propagated electrical 
disturbance which is the immediate 
effect of excitation cannot be due to 
water-migration, but that it is the 
expression of molecular changes in 
the protoplasm of the leaf. Prof 
Sanderson takes occasion to correct 
the impression produced by certain 
expressions in his lecture at the Royal 
Institution in 1874. Prof. Munk, 
among others, seems to have believed 



that Professor Sanderson claimed 
absolute identity between muscular 
action and the movement of the leaf 
of Dioniea. It need hardly be stated 
that no such implication was intended 
by Prof. Sanderson ; the view which 
he held in 1874 he still adheres to, 
namely, that the rapidly propagated 
molecular change in an excited Dionsea 
leaf can only be identified with the 
corresponding process in the excitable 
tissues of animals. 

Certain unpublished researches 
made during the last two years have 
led Professor Sanderson to extend his 
views in the direction above indicated, 
and to conclude that the " leaf- 
current," i.e. the electrical difference 
between the upper and lower surfaces 
of the leaf, is intimately connected 
with the physiological conditions of 
that part of the upper surface from 
which spring the sensitive filaments; 
thus it will probably be establishedl 
that the ** leaf-current " and the ex- 
citatory disturbance are different 
manifestations of the same property. 
From measurements made with his 
Kheotome, of six carefully chosen 
leaves, taken from vigorous plants 
(Aug. 1887), Professor Sanderson 
found that the electrical disturbance 
pi'oduced in one lobe by stimulation 
of the other by an induction current, 
begins in the course of the second 
tenth of a second following the ex- 
citation. In five out of the six leaves 
no effect was perceptible during the 
first tenth. If we assume that the 
distance travelled by the disturbance 
is one centimeter, this gives 100 
millimeters per second as the rate of 
propagation. This, as Professor San- 
derson has pointed out, happens to be 
just about the rate of propagation of 
the excitatory electrical disturbance 
in the muscular tissue of the heart of 
the frog.— F. D.] 

* Nuttall, in his ' Gen, American 
S 



258 DI0NJ5A MUSCIPULA. [Chap. XIIl. 

One lolie can re-expand Tdj itself, as occurred with tBe torpid 
leaf of which one lobe alone had closed. We have also seen in 
the experiments with cheese and albumen that the two ends of 
the same lobe can re-expand to a certain extent independently 
of each other. But in all ordinary cases both lobes open 
at the same time. The re-expansion is not determined by 
the sensitive filaments; all three filaments on one lobe were 
cut off close to their bases ; and the three leaves thus treated 
re-expanded, — one to a partial extent in 24 hrs., — a second to 
the same extent in 48 hrs., — and the third, which had been 
previously injured, not until the sixth day. These leaves 
after their re-expansion closed quickly when the filaments on 
the other 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 filaments, re-expanded in 
two days in the usual manner. When the filaments have 
been excited by immersion in a solution of sugar, the lobes 
do not expand so soon as when the filaments have been 
merely touched ; and this, I presume, is due to their having 
been strongly affected through exosmose, so that they con- 
tinue for some time to transmit a motor impulse to the upper 
surface of the leaf. 

The following facts make me believe that the several 
layers of cells forming the lower surface of the leaf are 
always in a state of tension; and that it is owing to this 
mechanical state, aided probably by fresh fluid being 
attracted into the cells, that tlie lobes begin to separate or 
expand as soon as the contraction of the upper surface 
diminishes. A leaf was cut off and suddenly plunged 
perpendicularly into boiling water : I expected that the 
lobes would have closed, but instead of doing so, they 
diverged a little. I then took another fine leaf, with the 
lobes standing at an angle of nearly 80° to each other ; and 
on immersing it as before, the angle suddenly increased to 
90°. A third leaf was torpid from having recently re- 



Plants,' p. 277 (note), says that, ciliic, accompanied by a partial open- 

whilst collecting this plant in its ing and succeeding collapse of the 

native home, " I had occasion to oh- lamina, which at length terminated 

serve that a detached leaf would in a complete expansion and in the 

make repeated efforts towards dis- destruction of sensibility." I am 

closing itself to the influence of the indebted to Prof. Oliver for this 

sun ; these attempts consisted in an reference ; but I do not understand 

nndulatoiy motion of the marginal what took place. 



Chap. XIII.] EE-EXPANSION. 259 

expanded after having caught a fly, so that repeated touches 
of the filaments caused not the least movement ; nevertheless 
when similarly immersed, the lohes separated a little. As 
these leaves were inserted perpendicularly into the boiling 
water, both surfaces and the filaments must have been 
equally affected ; and I can understand the divergence of the 
lobes only by supposing that the cells on the lower side, 
owing to their state of tension, acted mechanically and thus 
suddenly drew the lobes a little apart, as soon as the cells on 
the upper surface were killed and lost their contractile power. 
We have seen that boiling water in like manner causes the 
tentacles of Drosera to curve backwards ; and this is an 
analogous movement to the divergence of the lobes of 
Dionaaa. 

In some concluding remarks in the fifteenth chapter on the 
DroseraceiB, the different kinds of irritability possessed by 
the several genera, and the different m.anner in which they 
capture insects, will be compared. 



260 ALDEOVANDA VESICULOSA. [Chap. XIV. 



CHAPTEE XIV. 

Aldrovanda vesiculosa. 

Caiitiires orustaoeans — Structure of the leaves in comparison with those of 
Dionica — Absorption by the glands, by the quadrifid processes, and points 
on the infolded margins — Aldrovanda vesiculosa, var, australis — Captures 
prey — Absorption of animal rasAi^v—Aldrovanda vesiculosa, var. verticillata 
— Concluding remarks. 

This plant may be called a miniature aquatic Dionsea. Stein 
discovered in 1873 that the bilohed leaves, which are 
generally found closed in Europe, open under a sufficiently 
high temperature, and, when touched, suddenly close.* 
They re-expand in from 24 to 36 hrs., but only, as it appears, 
when inorganic objects are enclosed. The leaves sometimes 
contain bubbles of air, and were formerly supposed to be 
bladders ; hence the specific name of vesiculosa. Stein 
observed that water-insects were sometimes caught, and 
Prof. Cohn has recently found within the leaves of naturally 
growing plants many kinds of crustaceans and larvse.f 
Plants which have been kept in filtered water were placed 
by him in a vessel containing numerous crustaceans of the 
genus Cypris, and next morning many were found imprisoned 
and alive, still swimming about within the closed leaves, 
but doomed to certain death. 



* Since his original publication, [The late Professor Caspary pub- 
Stein has found out that the irrita- lished in the ' Bot. Zeitung,' 1859, 
Wlity of the leaves was observed by p. 117, an elaborate paper on Aldro- 
De Sassus, as recorded in 'Bull. Bot. vanda, dealing chiefly with its morpho- 
Soo. de France,* in 1861. Delpino logy, anatomy, systematic position 
states in a paper published in 1871 and geographical distribution. The 
(' Nuovo Giornale Bot. Ital.' vol. iii. early literature of the species is also 
p. 174) that " una quantiti di chioc- fully given. — F. D.] 
cioline e di altrianimalcoliacquatici" f I am greatly indebted to this 
are caught and suffocated by the distinguished naturalist for having 
leaves. I presume that chioccioline sent me a copy of his memoir on 
are fresh-water molluscs. It would Aldrovanda, before its publication in 
be interesting to know whether their his ' Beitrage zur Biologic der Pflan- 
shells are at all corroded by the acid zen,' drittes Heft, 1875, p. 71. 
of the digestive secretion. 



Chap. XIV.] ALDKOVANDA VESICULOSA. 261 

Directly after reading Prof. Cohn's memoir, I received 
through the kindness of Dr. Hooker living plants from 
Oermany. As I can add nothing to Prof. Cohn's excellent 
description, I will give only two illustrations, one of a 
whorl of leaves copied from his work, and the other of a leaf 
pressed flat open, drawn by my son Francis. I will, how- 
over, append a few remarks on the differences between this 
plant and Dionsea. 

Aldrovanda is destitute of roots and floats freely in the 
water. The leaves are arranged in whorls round the stem. 
Their broad petioles terminate in from four to six rigid 
projections,* each tipped with a stiff, short bristle. The 
bilobed leaf, with the midrib likewise tipped with a bristle, 
stands in the midst of these projections, and is evidently 
defended by them. The lobes are formed of very delicate 
tissue, so as to be translucent ; they open, according to Cohn, 
about as much as the two valves of a living mussel-shell, 
therefore even less than the lobes of Dionsea ; 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 
papillaa of Dioneea. 

Each lobe rather exceeds a semi-eircle in convexity, and 
consists of two very different concentric portions; the inner 
and lesser portion, or that next to the midrib, is slightly 
concave, and is formed, according to Cohr, of three layers of 
cells. Its upper surface is studded with colourless glands 
like, but more simple than, those of Dionaea; they are 
■supported on distinct footstalks, consisting of two rows of 
cells. The outer and broader portion of the lobe is flat and 
very thin, being formed of only two layers of cells.f 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 prominence. These 



* There has been much discussion 1850) and Caspary (' Bot. Zei- 

lybotanists on the homological nature tung,' 1859), the two layers of cells 

•of these projections. Ur. Nitschke are so combined as to produce the 

('Bot.Zeitung,'1861, p. 146) believes effect of a single layer. The three 

that they correspond with the fim- layers of which the central part is 

briated scale-like bodies found at the made up consist of external and 

fcases of the petioles of Drosera. internal epidermic layers, and a single 

t [According to Cohn ('Flora,' layer of parenchyma. — K. D.] 



262 



ALDEOVANDA VESICULOSA. [Chap. XIV. 



processes are formed of very delicate membrane lined •with a 
layer of protoplasm ; and they sometimes contain aggregated 
globules of hyaline matter. Two of the slightly diverging 
arms are directed towards the circumference, and two 
towards the midrib, forming together a sort of Greek cross. 
Occasionally two of the arms are replaced by one, and then 





Fig. 13. 

(^Aldrovanda vesuulosa.y, 

Upper figure, wliorl of leaves (from Prof. Cohn.) 
Lower figure, leaf pressed Eat open and greatly enlarged. 



the projection is trifid. "We shall see in a future chapter 
that these projections curiously resemble those found within 
the bladders of Utricularia, more especially of Utricularia 
montana, allhough this genus is not related to Aldrovanda. 
A narrow rim of the broad flat exterior part of each lobe is 



Chap. XIV.] ALDEOVANDA VESICULOSA. 263 

turned inwards, so that, when the lohes are closed, the 
exterior surfaces of the infolded portions come into contact. 
The edge itself hears a row of conical, flattened, transparent 
points with hroad bases, like the prickles on the stem of a 
bramble or Eubus. As the rim is infolded, these points are 
directed towards the midrib, and they appear at first as if 
they were adapted to prevent the escape of prey; but this 
can hardly be their chief function, for they are composed of 
very delicate and highly flexible membrane, which can be 
easily bent or quite doubled back without being cracked. 
Nevertheless, the infolded rims, together with the points, 
must somewhat interfere with the retrograde movement of 
any small creature, as soon as the lobes begin to close. The 
circumferential part of the leaf of Aldrovanda thus diSers 
greatly from that of Diona3a ; nor can the points on the rim 
be considered as homologous with the spikes round the leaves 
of Dionrea, as these latter are prolongations of the blade, and 
not mere epidermic productions. They appear also to serve 
for a widely different purpose. 

On the concave gland-bearing portion of the lobes, and 
especially on the midrib, there are numerous long, finely 
pointed hairs, which, as Prof. Oohn remarks, 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 vascular tissue. They differ also from the six sensitive 
filaments of Dionsea in being colourless, and in having a 
medial as well as a basal articulation. No doubt it is owing 
to these two articulations that, notwithstanding their length, 
they escape being broken when the lobes close. 

The plants which I received during the early part of 
October from Kew never opened their leaves, though sub- 
jected to a high temperature. After examining the structure 
of some of them, I experimented on only two, as I hoped that 
the plants would grow; and I now regret that I did not 
sacrifice a greater number. 

A leaf was cut open along the midrib, and the glands 
examined under a high power. It was then placed in a few 
drops of an infusion of raw meat. After 3 hrs. 20 m. there 



* [In a paper in the ' Nuovo Gior- case, namely that the irritability 
naleBotanicoItaliano.'Tol.viii. 1876, resides exclusively in the central 
p. 62, Mori states that this is the glandular region of the leaf. — F. D.] 



264 ALDBOVANDA VESICULOSA. [Chap. XIV. 

■was no change, tut when next examined after 23 Jbrs. 20 m., 
the outer cells of the glands contained, instead of limpid 
fluid, spherical masses of a granular substance, showing that 
matter had been absorbed from the infusion. That these 
glands secrete a fluid which dissolves or digests animal 
matter out of the bodies of the creatures which the leaves 
capture, is also highly probable from the analogy of Dioiiaaa. 
If we may trust to the same analogy, the concave and inner 
portions of the two lobes probably close together by a slow 
movement, as soon as the glands have absorbed a slight 
amount of already soluble animal matter. The included 
water would thus be pressed out, and the secretion conse- 
quently not be too much diluted to act. With respect to 
the quadrifid processes on the outer parts of the lobes, I was 
not able to decide whether they had been acted on by the 
infusion ; for the lining of protoplasm was somewhat shrunk 
before they were immersed. Many of the points on the 
infolded rims also had their lining of protoplasm similarly 
shrunk, and contained spherical granules of hyaline matter. 

A solution of urea was next employed. This substance 
was chosen partly because it is absorbed by the quadrifid 
processes and more especially by the glands of Utricularia — 
a plant which, as we shall hereafter see, feeds on decayed 
animal matter. As urea is one of the last products of the 
chemical changes going on in the living body, it seems fitted 
to represent the early stages of the decay of the dead body. I 
was also led to try urea trom a curious little fact mentioned 
by Prof. Cohn, namely that when rather large crustaceans 
are caught between the closing lobes, they are pressed so 
hard whilst making their escape that they often void their 
sausage-shaped masses of excrement, which were found 
within most of the leaves. These masses, no doubt, contain 
urea. They would be left either on the broad outer surfaces 
of the lobes where the quadrifids are situated, or within the 
closed concavity. In the latter case, water charged with 
excrementitious and decaying matter would be slowly forced 
outwards, and would bathe the quadrifids, if I am right in 
believing that the concave lobes contract after a time like 
those of Dionaja. Foul water would also be apt to ooze out 
at all times, especially when bubbles of air were generated 
within the concavity. 

A leaf was cut open and examined, and the outer cells of 
the glands were found to contain only limpid fluid. Some 



Chap. XIV.] ALDROVANDA VESICULOSA. 265 

of tho quadrifids included a few spherical granules, but 
several were transparent and empty, and their positions 
were marlced. This leaf was now immersed in a little 
solution of one part of urea to 146 of water, or three grains 
to the ounce. After 3 hre. 40 m. there was no change either 
in the glands or quadrifids ; nor was there any certaiu 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 au infusion 
of raw meat. It was different with the quadrifids ; for the 
lining of protoplasm, instead of presenting a uniform texture, 
was now slightly shrunk, and exhibited in many places 
minute, thickened, irregular, yellowish specks and ridges, 
exactly like those which appear within the quadrifids of 
Utricularia when treated with this same solution. More- 
over, several of the quadrifids, which were before empty, 
now contained moderately sized or very small, more or less 
aggregated, globules of yellowish matter, as likewise occurs 
under the same circumstances with Utricularia. Some of 
the points on the infolded margins of the lobes were 
similarly affected ; for their lining of protoplasm was a little 
shrunk and included yellowish specks; and those which 
were before empty now contained small spheres and irregular 
masses of hyaline matter, more or less aggregated ; so that 
both the points on the margins and the quadrifids had 
absorbed matter from the solution in the course of 24 hrs. ; 
but to this subject I shall recur. In another I'ather old leaf, 
to which nothing bad been given, but which had been kept 
in foul water, some of the quadrifids contained aggregated 
translucent globules. These were not acted on by a solution 
of one part of carbonate of ammonia to 218 of water: and 
this negative result agrees with what I have observed under 
similar circumstances with Utricularia. 

Aldrovanda vesiculosa, var. australis. — Dried leave ■* of this 
plant from Queensland in Australia were sent me by Prof. 
Oliver from the herbarium at Kew. Whether it ought to be 
considered as a distinct species or a variety, cannot be told 
until the flowers are examined by a botanist. The pro- 
jections at the upper end of the petiole (from four to six in 
number) are con.-iderably longer relatively to the blade, and 
much more attenuated than those of the European form. 
They are thickly covered for a considerable space near their 
extremities with the upcurved prickles, which are quite 
absent in the latter form ; and they generally bear on their 



266 ALDEOVANDA VESICULOSA. [Chap. XIV. 

tips two or three straight prickles instead of one. The 
bilobed leaf appears also to he rather larger and somewhat 
broader, with the pedicel by which it is attached to the 
tipper 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 seeu on several of the 
leaves, but I do not doubt that they were present, though 
indistinguishable from their delicacy and from having 
shrivelled ; for they were quite distinct on one leaf under 
circumstances presently to be mentioned. 

Some of the closed leaves contained no prey, but in one 
there was rather a large beetle, which from its flattened 
tibias I suppose was an aquatic species, but was not allied to 
Colymbetes. All the softer tissues of this beetle were com- 
pletely dissolved, and its chitinous integuments were as 
clean as if they had been boiled in caustic potash ; so that it 
must have been enclosed fur a considerable time. Tlie glands 
were browner and more opaque than those on other leaves 
which had caught nothing; and the quadrifid processes, 
from being partly filled with brown granular matter, could 
be plainly distinguished, which was not the case, as already 
stated, on the other leaves. Some of the points on the 
infolded margins likewise contained brownish granular 
matter. We thus gain additional evidence that the glands, 
the quadrifid processes, and the marginal points, all have the 
power of absorbing matter, though probably of a different 
nature. 

Within another leaf disintegrated remnants of a rather 
small anitual, not a crustacean, which had simple, strong, 
opaque mandibles, and a large unarticulated chitinous coat, 
were present. Lumps of black organic matter, possibly of 
a vegetable nature, were enclosed in two other leaves ; but 
in one of these there was also a small worm much decayed. 
But the nature of partially digested and decayed bodies, 
which have been pressed flat, long dried, and then soaked in 
water, cannot be recognised easily. All the leaves contained 
unicellular and other Algse, t>till of a greenish colour, which 
had evidently lived as intruders, in the same manner as 
occurs, according to Cohn, within the leaves of this plant in 
Germany. 



Chap. XIV.] CONCLUDING EEMAEKS. 267 

Aldrovanda vesiculosa, var. verticillata. — Dr. King, Superin- 
tendent of the Botanic Gardens, kindly sent me dried 
specimens collected near Calcutta. This furm was, 1 believe, 
considered by Wallich as a distinct species, under the name 
of verticillata. It resembles the Austi alian form much more 
nearly than the European ; namely in the projections at the 
upper end of the petiole being much attenuated and covered 
with upcurved prickles ; they terminate also in two straight 
little prickles. The bilobed leaves are, I believe, larger and 
certainly broader even than those of the Australian form ; s.> 
that the greater convexity of their margins was conspicuous. 
The lengih of an open leaf being taken at 100, the breadth 
of the Bengal form is nearly 173, of the Australian form 147, 
and of the German 134. The points on the infolded margins 
are like those in the Australian form. Of the few leaves 
which were examined, three contained entomostracan crus- 
taceans. 

Concluding Eemarlcs. — The leaves of the three foregoing 
closely allied species or varieties are manifestly adapted for 
catching living creatures. With respect to the functions of 
the several parts, there can be little doubt that the long 
jointed hairs are sensitive, like those of Dionaea, and that, 
when touched, thfy 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 
Diontea, — from the limpid fluid within their cells being 
aggregated into spherical masses, after they had absorbed an 
infusion of raw meat,— from their opaque and granular 
condition in the leaf, which had enclosed a beetle for a long 
time, — and from the clean condition of the integuments of 
this insect, as well as of crustaceans (as described by Cohn), 
which have been long captured. Again, from the eflect 
produced on the quadrifid processes by an immersion for 
!i4 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 ciught, — and from the analogy of 
Utricularia, — it is probable that these processes absorb 
excrementitious and decaying animal matter. It is a more 
curious fact that the points on the infolded margins ap- 
parently serve to absorti decnyed animal matter in the same 
manner as the quadrifids. We can thus understand the 
meaning of the infulded margins of the lobes furnished with 
delicate points directed inwards, and of the broad, flat, outer 



268 CONCLUDING EEMAEKS. [Chap. XIV. 

portions, bearing quadrifid processes ; for these surfaces must 
be liable to be irrigated by foul water flowing from the 
concavity of the leaf when it contains dead animals.* This 
would follow from various causes, — from the gradual con- 
traction of the concavity, — from fluid in excess being secreted, 
— and from the generation of bubbles of air. More observa- 
tions are requisite on this head ; but if this view is correct, 
we have the remarkable case of different parts of the same 
leaf serving for very different purposes — one part for true 
'digestion, and another for the absorption of decayed animal 
matter. We can thus also understand how, by the gradual 
loss of either power, a plant might be gradually adapted for 
the one function to the exclusion of the other : and it will 
hereafter be shown that two genera, namely Pinguicula and 
Utricular ia, belonging to the same family, have been adapted 
for these two different functions. 



* [Duval - Jouve's observations lar structures are described by Duval- 
throw some doubt on this point. He Jouve as occurring on the leaves of 
has shown (' Bull. Soo. Bot. de Callitriche, Nuphar luteum and Nym- 
France,' t. xxiii. p. 130) that in the phcea alba, and similar observations 
winter buds of Aldrovanda the leaves were made by the late E. Kay Lan- 
are reduced to a petiole, the lamina kester (' Brit. Assoc. Keport,' 1850, 
being absent. Now the lamina bears published 1851, 2nd part of volume, 
both the glands for which a peptic p. 113). This being so we must sus- 
function is suggested in the text, and pend judgment as to the function of 
also the quadrifid processes which the quadrifid processes on the outer 
are believed to absorb the products region of the lamina of the leaves of 
of decay. Since the leaves of the Aldrovanda. Charles Darwin appears 
winter buds have no lamina;, and to have been impressed with the im- 
cannot therefore capture prey, we portance of these facts, as I infer 
must believe that the glands on the from a note pencilled in Prof. Mar- 
petioles have merely general absorp- tin's tranlation of ' Insectivorous 
live function, and are not specialised Plants,' where Duval-Jouve's paper 
in relation to the products of the is discussed in a note by the trans- 
decaying victims of the plant. Simi- lator. — F. D.] 



Chap. XV.] DROSOPHYLLUM LUSITANICUM. 269i 



CHAPTER XV. 

Deosophyllum — EoEiDULA — Byblis — Glandulak Hairs of other 
Plants — Concluding Remarks on the Droserace.i:. 

Drosophyllam — Structure of leaves — Nature of the secretion — JIanner of 

catching insects — Power of absorption — Digestion of animal substances 

Summary on Drosophyllum — Uoridula— Byblis — Glandular hairs of other 

plants, their power of absorption — Saxifraga — Primula — Pelargonium 

Erica — Mirabilis — Nicotiana — Summary on glandular hairs — Concludino- 
remarks on the Droseraceaj. 

Dbosophyllum LUSITANICUM. — This rare plant has been found: 
only in Portugal, and, as I hear from Dr. Hooker, in Morocco. 
I obtained living specimens through the great kindness of 
Mr. W. C. Tait, and afterwards from Mr. G. Maw and Dr. 
Moore. Mr. Tait informs me that it grows plentifully on 
tlie sides of dry hills near Oporto, and that vast numbers of 
flies adhere to the leaves. This latter fact is well known to 
the villagers, who call the plant the " fly-catcher," and hang 
it up in their cottages for this purpose. A plant in my hot- 
house caught so many insects during the early part of April,, 
although the weather was cold and insects scarce, that it 
must have been in some manner strongly attractive to them. 
On four leaves of a young and small plant, 8, 10, 14, and 16' 
minute insects, chiefly Diptera, were found in the autumn 
adhering to them. I neglected to examine the roots, but I 
hear from Dr. Hooker that they are very small, as in the case 
of the previously mentioned members of the same family of 
the Droseracese. 

The leaves arise from an almost woody axis ; they are 
linear, much attenuated towards their tips, and several inches 
in length. The upper surface is concave, the lower convex, 
with a narrow channel down the middle. Both surfaces, 
with the exception of the channel, are covered with glands, 
supported on pedicels and arranged in irregular longitudinal 
rows. These organs I shall call tentacles, from their close- 
resemblance to those of Drosera, though they have no power 
of movement. Those on the same leaf differ much.in length- 



270 



DEOSOPHYLLUM LUSITANICUM. [Chap. XV. 



Tlie glands also differ in size, and are of a briglit pink or of 
a purple colour ; tlieir upper surfaces are convex, and the 
lower flat or even concave, so that they resemble miniature 
mushrooms in appearance. They are formed of two (as I 
believe) layers of delicate angular cells, enclosing eight or 
ten larger cells with thicker zigzag walls. Within these 
larger cells there are others marked by spiral lines, and 
apparently connected with the spiral vessels which run up 
the green multicellular pedicels. The glands secrete large 
drops of viscid secretion. Other glands, having the same 
general appearance, are found on the flower-peduncles and 
calyx. 

Besides the glands which are borne on longer or shorter 
pedicels, there are numerous ones, both on 
the upper and lower surfaces of the leaves, 
so small as to be scarcely visible to the 
naked eye. They are colourless and almost 
sessile, either circular or oval in outline; 
the latter occurring chiefly on the backs of 
the leaves (fig. 14). Internally they have 
exactly the same structure as the larger 
glands which are supported on pedicels; 
and indeed the two sets almost graduate 
into one another. But the sessile glands 
differ in one important respect, for they 
never secrete spontaneously, as far as I 
have seen, though I have examined them 
under a high power on a hot day, whilst 
the glands on pedicels were secreting co- 
piously. 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 Dionasa 
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, 




Fro. 14. 

^ Drosophyllum lusi- 
tanicum.) 

Part of leaf, enlarged 
seven timeo, bIiow- 
ing lower surface. 



Chap. XV.] SECRETION. 271 

and had never caught an insect, yot the secretion on all the 
glands coloured litmus paper of a bright red. From the 
quickness with which the glands are able to obtain animal 
matter from such substances as well-washed fibrin and 
cartilage, I suspect that a small quantity of the proper 
ferment must be present in the secretion before the glands 
are excited, so that a little animal matter is quickly 
dissolved. 

Owing to the nature of the secretion or to the shape of 
the glands, the drops are removed from them with singular 
facility. It is even somewhat difficult, by the aid of a finely 
pointed polished needle, slightly damped with water, to place 
a minute particle of any kind on one of the drops ; for on 
withdrawing the needle, the drop is fgenerally withdrawn ; 
whereas with Drossra there is no such difficulty, though the 
drops are occasionally withdrawn. From this peculiarity, 
when a small insect alights on a leaf of Drosophyllum, the 
drops adhere to its wings, feet, or body, and are drawn from 
the gland ; the insect then crawls onward and other drops 
adhere to it ; so that at last, bathed by the viscid secretion, 
it sinks down and dies, resting on the small sessile glands 
with which the surface of the leaf is thickly covered. In 
the case of Drosera, an insect sticking to one or more of the 
exterior glands is carried by their movement to the centre of 
the leaf; with Drosophyllum, this is effected by the crawling 
of the insect, as from its wings being clogged by the secretion 
it cannot fly away. 

There is another difference in function between the glands 
of 'these two plants : we know that the glands of Drosera 
secrete more copiously when properly excited. But when 
minute particles of carbonate of ammonia, drops of a solution 
of this salt or of the nitrate of ammonia, saliva, small insects, 
bits of raw or roast meat, albumen, fibrin or cartilage, as well 
as inorganic particles, were placed on the glands of Droso- 
phyllum, the amount of secretion never appeared to be in 
the least increased. As insects do not commonly adhere to 
the taller glands, but withdraw the secretion, we can see 
that there would be little use in their having acquired the 
habit of secreting copiously when stimulated ; whereas with 
Drosera this is of use, and the habit has been acquired. 
Nevertheless, the glands of Drosophyllum, without being 
stimulated, continually secrete, so as to replace the loss by 
evaporation. Thus when a plant was placed under a small 



272 DEOSOPHYLLTJM LUSITANICUM. [Chap. XV. 

bell-glass with its inner surface and support thorougHy 
wetted, there was no loss by evaporation, and so much 
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 w^hen they were 
looked at after an interval of 1 hr. 12 m., the fibrin was 
almost dry, the secretion having been all absorbed. So it 
was with three cubes of albumen after 1 hr. 19 m., and witli 
four other cubes, though these latter were not looked at 
until 2 hrs. 15 m. had elapsed. The same result followed in 
between 1 hr. 15 m. and 1 hr. 30 m. when particles both of 
cartilage and meat were placed on several glands. Lastly, a 
minute drop (about ^ of a minim) of a solution of one part 
of nitrate of ammonia to 146 of water was distributed between 
the secretion surrounding three glands, so that the amount 
of fiuid surrounding each was slightly increased ; yet when 
looked at after 2 hrs., all three were dry. On the other 
hand, seven particles of glass and three of coal-cinders, of 
nearly the same size as those of the above-named organic 
substances, were placed on ten glands ; some of them being 
observed for 18 hrs., and others for two or three days ; but 
there was not the least sign of the secretion being absorbed. 
Hence, in the former cases, the absorption of the secretion 
must have been due to the presence of some nitrogenous 
matter, which was either already soluble or was rendered so 
by the secretion. As the fibrin was pure, and had been well 
washed in distilled water after being kept in glycerine, and 
as the cartilage had been soaked in water, I suspect that 
these substances must have been slightly acted on and 
rendered soluble within the above stated short periods. 

The glands have not only the power of rapid absorption, 
but likewise of secreting again quickly; and this latter 
habit has perhaps been gained, inasmuch as insects, if they 
touch the glands, generally withdraw the drops of secretion, 
which have to be restored. The exact period of re-secretion 
was recorded in only a few cases. The glands on which 
bits of meat were placed, and which were nearly dry after 
about 1 hr. 30 m., when looked at after 22 additional hours, 
were found secreting ; so it was after 24 hrs. with one gland 



Chap. XV.] ABSORPTION. 273 

on whicli a bit of albumen had been placed. The three 
glands to which a minute drop of a solution of nitrate of 
ammonia was distributed, and which became dry after 2 hrs., 
were beginning to re-secrete after only 12 additional hours. 

Tentacles Incapable of Movement. — Many of the tall ten- 
tacles, with insects adhering to them, were carefully ob- 
served ; and fragments of insects, bits of raw meat, albumen, 
&c., drops of a solution of two salts of ammonia and of 
saliva, were placed on the glands of many tentacles ; but 
not a trace of movement could ever be detected. I also 
repeatedly irritated the glands with a needle, and scratched 
and pricked the blades, but neither the blade nor the 
tentacles became at all inflected. We may therefore con- 
clude that they are incapable of movement. 

On the Power of Absorption possessed by the Glands. — It has 
already been indirectly shown that the glands on pedicels 
absorb animal matter ; and this is further shown by their 
changed colour, and by the aggregation of their contents, 
after they have been left in contact with nitrogenous 
substances or liquids. The following observations apply 
both to the glands supported on pedicels and to the minute 
sessile ones. Before a gland has been in any way stimu- 
lated, the exterior cells commonly contain only limpid purple 
fluid; the more central ones including mulberry-like masses 
of purple granular matter. A leaf was placed in a little 
S'llution of one part of carbonate of ammonia to 146 of water 
(3 grs. to 1 oz.), and the glands were instantly darkened 
and very soon became black ; this change being due to the 
etrongly 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 
weie slightly darkened in 25 m., more so in 50 m., and after 
1 hr. 30 m. were of so dark a red as to appear almost black. 
Other leaves were placed in a weak infusion of raw meat 
and in human saliva, and the glands, were much darkened 
in 25 m., and after 40 m. were so dark as almost to deserve 
io 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 afi'ected in exactly the same 
manner as those of Drosera. Milk, however, which 
acts so energetically on Drosera, seems rather less efiective 
on Drosophyllum, for the glands were only slightly 

T 



274 DEOSOPHYLLUM LUSITANICUM. [CuAr. XV 

darkened by an immersion of 1 hr. 20 m., but became decidedly- 
darker after 3 brs. Leaves wbich liad been left for 7 hrs. 
in an infusion of raw meat or in saliva were placed in the 
solution of carbonate of ammonia, and tbe glands now be- 
came greenish ; whereas, if they had been first placed in the 
carbonate, they would have become black. In this latter 
case, the ammonia probably combines with the acid of the 
secretion, and therefore does not act on the colouring matter ,- 
but when the glands are first subjected to an organic fluid,, 
either the acid is consumed in the work of digestion or the 
cell-walls are rendered more permeable, so that the undeoom- 
posed carbonate enters and acts on the colouring matter. If 
a particle of the dry carbonate is placed on a gland, the purple 
colour is quickly discharged, owing probably to an excess of 
the salt. The gland, moreover, is killed. 

Turning now to the action of organic substances, the 
glands on which bits of raw meat were placed became dark- 
coloured; and in 18 hrs. their contents were conspicuously 
aggregated. Several glands with bits of albumen and fibrin 
were darkened in between 2 hrs. and 3 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 appear- 
ance ; for they had become purple, owing to purple granular 
matter coating the cell-walls. I may here mention as a 
caution that, soon after some of my plants arrived in the 
spring from Portugal, the glands were not plainly acted on 
by bits of meat, or insects, or a solution of ammonia— a 
circumstance for which I cannot account. 

Digestion of Solid Animal Matter. — Whilst I was trying to- 
place on two of the taller glands little cubes of albumen,, 
these slipped down, and, besmeared with secretion, were left 
resting on some of the small sessile glands. After 24 hrs. 
one of these cubes was found completely liquefied, but with 
a few white streaks still visible ; the other was muck 
rounded, but not quite dissolved. Two other cubes were left- 
on tall glands for 2 hrs. 45 m., by which time all the. 



Chap. XV.] DIGESTION. 275 

secretion was absorbed ; but tbey were not perceptibly acted 
on, tbougb no doubt some slight amount of animal matter had 
been absorbed from them. They were then placed on the small 
sessile glands, which being thus stimulated secreted copiously 
in the course of 7 hrs. One of these cubes was much 
liquefied within this short time ; and both were completely 
liquefied after 21 hrs. 15 m. ; the little liquid masses, how- 
ever, stiU showing some white streaks. These streaks 
disappeared after an additional period of 6 hrs. 30 m. ; and 
by next morning (i.e. 48 hrs. from the time when the cubes 
were first placed on the glands) the liquefied matter was 
wholly absorbed. A cube of albumen was left on another tall 
gland, which first absorbed the secretion and after 24 hrs. 
poured forth a fresh supply. This cube, now surrounded 
by secretion, was left on the gland for an additional 24 hrs., 
but was very little, if at all, acted on. "We may therefore 
conclude, either that the secretion from the tall glands has 
little power of digestion, though strongly acid, or that the 
amount poured forth from a single gland is insufBcient to dis- 
solve a particle of albumen which within the same time 
would have been dissolved by the secretion from several of 
the small sessile glands. Owing to the death of my last 
plant, I was unable to ascertain which of these alternatives 
is the true one. 

Four minute shreds of pure fibrin were placed, each 
resting on one, two, or three of the taller glands. In the 
course of 2 hrs. 30 m. the secretion was all absorbed, and the 
sbreds were left almost dry. They were then pushed on to 
the sessile glands. One shred, after 2 hrs. 30 m., seemed 
quite dissolved, but this may have been a mistake. A 
second, when examined after 17 hrs. 25 m., was liquefied, 
but the liquid as seen under the microscope still contained 
floating granules of fibrin. The other two shreds were com- 
pletely liquefied after 21 hrs. 30 m. ; but in one of the drops 
a very few granules could still be detected. These, however, 
were dissolved after an additional interval of 6 hrs. 30 m. ; 
and the surface of the leaf for some distance all round was 
covered with limpid fluid. It thus appears that Drosophyllum 
digests albumen and fibrin rather more quickly than 
Drosera can ; and this may perhaps be attributed to the acid, 
together probably with some small amount of the ferment, 
being present in the secretion, before the glands have been 
stimulated ; so that digestion begins at once. 

T 2 



27.6 EOKIDULA. [Chap. XV. 

Concluding BemarTcs. — The linear leaves of Drosophyllum 
differ but slightly from those of certain species of Drosera ; 
the chief differences being, firstly, the presence of minute, 
almost sessile, glands, which, like those of Dionaea, do not. 
secrete until they are excited by the absorption of nitro- 
genous matter. But glands of this kind are present on the 
leaves of Drosera hinata, and appear to be represented by the 
papilla 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 hinala. There are greater differences in 
function between the two genera. The most important one 
is that the tentacles of Drosophyllum have no power of 
movement ; this loss being partially replaced by the drops 
of viscid secretion being readily withdrawn from the glands ; 
so that, when an insect comes into contact with a drop, it is 
able to crawl away, but soon touches other drops, and then, 
smothered by the secretion, sinks down on the sessile glands 
and dies. Another difference is, that the secretion from the 
tall glands, before they have been in any way excited, is 
strongly acid, and perhaps contains a small quantity of the 
proper ferment. Again, these glands do not secrete more 
copiously from being excited by the absorption of nitro- 
genous matter ; on the contrary, they then absorb their own 
secretion with extraordinary quickness. In a short time 
they begin to secrete again. All these circumstances are 
probably connected with the fact that insects do not 
commonly adhere to the glands with which they first come 
into contact, though this does sometimes occur ; and that it 
is chiefly the secretion from the sessile glands which dissolves 
animal matter out of their bodies. 

EoEIDULi. 

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 



Chap. XV.] BYBLIS. 277 

on the tips of the leaves, and some very short. The glands 
also differ much in size and are somewhat elongated. They 
are supported on multicellular pedicels. 

This plant, therefore, agrees in several respects with 
Drosophyllum, but differs in the following points. I could 
detect no sessile glands ; nor would these have been of any 
use, as the upper surface of the leaves is thickly clothed 
with pointed, unicellular hairs directed upwards. The 
pedicels of the tentacles do not include spiral vessels ; nor 
are there any spiral cells within the glands. The leaves 
often arise in tufts and are pinnatifid, the divisions pro- 
jecting at right angles to the main linear blade. These 
lateral divisions are often very short and bear only a single 
terminal tentacle, with one or two short ones on the sides. 
No distinct line of demarcation can be drawn between the 
pedicels of the long tenninal tentacles and the much attenu- 
ated summits of the leaves. We may, indeed, arbitrarily fix 
on the point to which the spiral vessels proceeding from the 
blade extend ; but there is no other distinction. 

It was evident from the many particles of dirt sticking to 
the glands that they secrete much viscid matter. A large 
number of insects of many kinds also adhered to the leaves. 
I could nowhere discover any signs of the tentacles having 
been inflected over the captured insects ; and this probably 
would have been seen even in the dried specimens, had they 
possessed the power of movement. Hence, in this negative 
character, 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 — sessile ones arranged in rows, and others supported 
on moderately long pedicels. Towards the narrow summits 
of the leaves the pedicels are longer than elsewhere, and 
here equal the diameter of the leaf. The glands are purplish, 
much flattened, and formed of a single layer of radiating 
cells, which in the larger glands are from forty to fifty in 
number. The pedicels consist of single elongated cells, with 
colourless, extremely delicate walls, marked with the finest 



278 GLANDULAR HAIES : [Chap. XV. 

intersecting spiral lines. WhetHer these lines are the result 
of contraction from the diying of the walls, I do not know, 
but the whole pedicel was often spirally rolled np. 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 home by innumerable other 
plants. The flower-peduncles bear similar glands. The 
most singular character about the leaves is that the apex is 
enlarged into a little knob, covered with glands, and about 
a third broader than the adjoining part of the attenuated 
leaf. In two places dead flies adhered to the glands. As 
no instance is known of unicellular structures having any 
power of movement,* Byblis, no doubt, catches insects solely 
by the aid of its viscid secretion. These probably sink down 
besmeared with the secretion and rest on the small sessile 
glands, which, if we may judge by the analogy of Droso- 
phyllum, then pour forth their secretion and afterwards 
absorb the digested matter. 

Supplementary Observations on the Power of Absorption hy the 
Glandular Hairs of other Plants. — A few observations on this 
subject may be here conveniently introduced. As the glands 
of many, probably of all, the species of Droseracese absorb 
various fluids or at least allow them readily to enter, ■{■ it 
seemed desirable to ascertain how far the glands of other 
plants which are not specially adapted for capturing insects, 
had the same power. Plants were chosen for trial at hazard, 
with the exception of two species of saxifrage, which were 
selected from belonging to a family allied to the Droseracese. 
Most of the experiments were made by immersing the glands 
either in an infusion of raw meat or more commonly in a 
solution of carbonate of ammonia, as this latter substance 
acts so powerfully and rapidly on protoplasm. It seemed 
also particularly desirable to ascertain whether ammonia 
was absorbed, as a small amount is contained in rain-water. 
With the Droseraceas the secretion of a viscid fluid by the 
glands does not prevent their absorbing ; so that the glands 
of other plants might excrete superfluous matter, or secrete 
an odoriferous fluid as a protection against the attacks of 



* Sachs, 'Trait(5 de Bot.' 3rd edit. imbibition, is by no means clearly 

1874, p. 1026. understood : see MiiUer's ' Physio- 

t The distinction between true logy,' Eng. translat. 1838, vol. i. p. 

absorption and mere permeation, or 280. 



Chap. XV.] THEIE POWER OF ABSORPTION. 279 

insects, or for any other purpose, and yet have the power of 
absorbing. I regret that in the following cases I did not 
try whether the secretion could digest or render soluble 
animal substances, but such experiments would have been 
difficult on account of the small size of the glands and the 
.small amount of secretion. We shall see in the next chapter 
that the secretion from the glandular hairs of Pinguicula 
certainly dissolves animal matter. 

Saxifraga umbrom. — The flower-peduncles and petioles of the 
leaves are clothed with short hairs, bearing pink-coloured glands, 
formed of several polygonal cells, vidth their pedicels divided by partitions 
into distinct cells, which are generally colourless, but sometimes pink. 
The glands secrete a yellowish viscid fluid, by which minute Diptera 
are sometimes, though not often, caught.* The cells of the glands 
contain bright pink fluid, charged with granules or with globular 
masses of pinkish pulpy matter. This matter must be protoplasm, 
for it is seen to undergo slow but incessant changes of form if a gland 
be placed in a drop of water and examined. Similar movements were 
observed after glands had been immersed in water for 1, 3, 5, 18, and 
27 hrs. Even after this latter period the glands retained their bright 
pink colour ; and the protoplasm within their cells did not appear to 
have become more aggregated. The continually changing forms of 
the little masses of protoplasm are not due to the absorption of water, 
as they were seen in glands kept dry. 

A flower-stem, still attached to a plant, was bent (May 29) so as to 
remain immersed for 23 hrs. 30 m. in a strong infusion of raw meat. 
The colour of the contents of the glands was slightly changed, being 
now of a duller and more purple tint than before. The contents also 
appeared more aggregated, for the spaces between the little masses of 
protoplasm were wider ; but this latter result did not follow in some 
other and similar experiments. The masses seemed to change their 
forms more rapidly than did those in water ; so that the cells had a 
different appearance every four or flve minutes. Elongated masses 
became in the course of one or two minutes spherical ; and spherical 
ones drew themselves out and united with others. Minute masses 
rapidly increased in size, and three distinct ones were seen to unite. 
The movements were, in short, exactly like those described in the case 
of Drosera. The cells of the pedicels were not affected by the infusion ; 
nor were they in the following experiment. 

Another flower-stem was placed in the same manner and for the 
same length of time in a solution of one part of nitrate of ammonia to 



* In the case of Saxifraqa tri- and in almost every instance remnants 

dactylites, Mr. Druce says (' Phar- of insects adhered to the leaves. So 

niaceutical Journal,' May 1875) that it is, as I hear from a friend, with 

he examined some dozens of plants, this plant in Ireland. 



280 GLANDULAE HAIES : [CnAr. XV. 

146 of water (or 3 grs. to 1 oz.), and the glands were discoloured in 
exactly the same manner as by the infusion of raw meat. 

Another flower-stem was immersed, as before, in a solution of one 
part carbonate of ammonia to 109 of water. The glands, after 1 hr. 
30 m., were not discoloured, but after 3 hrs. 45 m. most of them had 
become dull purple, some of them blacldsh-green, a few being still 
unaffected. The little masses of protoplasm within the cells were 
seen in movement. The cells of the pedicels were unaltered. The 
experiment was repeated, and a fresh flower-stem was left for 23 hrs. 
in the solution, and now a great effect was produced ; all the glands 
were much blackened, and the previously transparent fluid in the cells 
of the pedicels, even down to their bases, contained spherical masses of 
granular matter. By comparing many difi'erent hairs, it was evident 
that the glands first absorb the carbonate, and that the effect thus, 
produced travels down the hairs from cell to cell. The first change 
which could be observed is a cloudy appearance in the fluid, due to 
the formation of very fine granules, which afterwards aggregate into 
larger masses. Altogether, m the darkening of the glands, and in the 
process of aggregation travelling down the cells of the pedicels, thei e 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 wtich do not appear to 
secrete, and which were not in the least affected by the above 
solutions. 

Although in the case of uninjured flower-stems and leaves the 
carbonate seems to be absorbed only by the glands, yet it enters a cut 
surface much more quickly than a gland. Strips of the rind of a 
flower-stem were torn off, and the cells of the pedicels were seen to 
contain only colourless transparent fluid ; those of the glands including 
as usual some granular matter. These strips were then immersed in 
the same solution as before (one part of the carbonate to 109 of water), 
and in a few minutes granular matter appeared in the lower cells of all 
the pedicels. The action invariably commenced (for I tried the ex- 
periment repeatedly) in the lowest cells, and therefore close to the torn 
surface, and then gradually travelled up the hairs until it reached the 
glands, in a reversed direction to what occurs in uninjured specimens. 
The glands then became discoloured, and the previously contained 
granular matter was aggregated into larger masses. Two short bits of 
a flower-stem were also left for 2 hrs. 40 m. in a weaker solution of one 
part of the carbonate of 218 of water ; and in both specimens the 
pedicels of the hairs near the out ends now contained much granular 
matter ; and the glands were completely discoloured. 

Lastly, bits of meat were placed on some glands; these were 
examined after 23 hrs., as were others, which had apparently not long 
before caught minute flies ; but they did not present any diflerence 
from the glands of other hairs. Perhaps there may not have been 
time enough for absorption. I think so, as some glands, on which 



Chap. XV.] THEIK POWER OF ABSORPTION. 281 

dead flies had evidently long lain, were of a pale dirty purple colour or 
even almost colourless, and ihe granular matter within them presented 
an unusual and somewhat i:eculiar 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 
tlie cells in their pedicels become /Kei^ with granular matter ; whereas 
the cells of other hairs, which had not caught flies, after being treated 
with the same solution lor the same length of time, contained only a. 
small cfuantity of granular matter. But more evidence is necestaiy 
before we fully admit that the glands of this t-axifrage Ciin absorb,, 
even with ample time allowed, animal matter from the minute insects 
which they occasionally and accidentally capture. 

Saxifraga rotundifolia (?). — The hairs on the flower-stems of this- 
species are longer than those just described, and hear pale brown glands. 
Many were examined, and the cells of the pedicels were quite trans- 
parent. A bent stem was immersed for 30 m. in a solution of one 
part of carbonate of ammonia to 109 of water, and two or three of the 
uppermost cells in the pedicels now contained granular or aggregated 
matter ; the glands having become of a bright yellowish-green. The 
glands of this species therefore absorb the carbonate much more 
quickly than do those of Saxifraga umbrosa, and the upper cells of the 
pedicels are likewise aHected much more quickly. Pieces of the stem 
were cut off and immersed in the same solution ; and now the process- 
of aggregation travelled up the hairs in a reversed direction ; the cells 
close to the cut surfaces being first affected. 

I'rimula sinensis. — Tlie flower-stems, the upper and lower surfaces- 
of the leaves and their footstalks, are all clothed with a multitude of 
longer and shorter hairs. The pedicels of the longer hairs are divided 
by transverse partitions into eight or nine cells. The enlarged ter- 
minal cell is globular, forming a gland which secretes a variable amount 
of thick, shghtly viscid, not acid, brownish-yellow matter. 

A piece of a young flower-stem was first immersed in distilled water 
for 2 hrs. 30 m., and the glandular hairs were not at all affected. 
Another piece, bearing twenty-five short and nine long hairs, was- 
■carefully examined. 'Ihe glands of the latter contained no solid or 
semi-solid matter ; and those of only two of the twenty-five short hairs- 
contained some globules. Tlrs piece was then immersed for 2 hrs. 
in a solution of one part of carbonate of ammonia to 109 of water^ 
and now the glands of the twenty-five shorter hairs, with two or three 
exceptions, contained either one large or from two to five smaller 
-spherical masses of semi-solid matter. Three of the glands of the 
nine long hairs likewise included similar masses. In a few hairs there 
were also globules in the cells immediately beneath the glands. 
Lookinij; to all thirty-four hairs, there could be no doubt that the- 
glands had absorbed some of the carbonate. Another piece was left 
for only 1 hr. in the same solution, and aggregated matter appeared 
in all the glands. My son Francis examined some glands of the longer 



282 GLANDULAR HAIES : [Chap. XV. 

hairs, whicli contained little masses of matter, before they were 
immersed in any solution; and these masses slowly changed their 
forms, so that no doubt they consisted of protoplasm. He then 
irrigated these hairs for 1 hr. 15 m., whilst under the microscope, 
with a solution of one part of the carbonate to 218 of water ; the 
iglands were not perceptibly affected, nor could this have been expected, 
as their contents were already aggregated. But in the cells of the 
pedicels numerous, almost colourless, spheres of matter appeared, 
■which changed their forms and slowly coalesced ; the appearance of 
the cells being thus totally changed at successive intervals of time. 

The glands on a young flower-stem, after having been left for 2 hrs. 
45 m. in a strong solution of one part of the carbonate to 109 of water, 
contained an abundance of aggregated masses, but whether generated 
by the action of the salt, I do not know. This piece was again placed 
in the solution, so that it was immersed altogether for 6 hrs. 15 m., 
and now there was a great change ; for almost all the spherical masses 
withia the gland-cells had disappeared, being replaced by granular 
matter of a darker brown. The experiment was thrice repeated with 
nearly the same result. On one occasion the piece was left immersed 
for 8 hrs. 30 m., and though almost all the spherical masses were 
changed into the Ijrown granular matter, a few still remained. If the 
spherical masses of asgregated matter had been originally produced 
merely by some chemical or physical action, it seems strange that a 
somewhat longer immersion in the same solution should so completely 
alter their character. But as the masses which slowly and sponta- 
neously changed their forms must have consisted of living protoplasm, 
there is nothing surprising in its being injured or killed, and its 
appearance wholly changed by long immersion in so strong a solution 
of the carbonate as that employed. A s-olution of this strength 
paralyses all movement in Drosera, but does not kill the protoplasm; 
a still stronger solution prevents the protoplasm from aggregating into 
the ordinary full-sized globular masses, and these, though they do not 
disintegrate, become granular and opaque. In nearly the same 
manner, too, hot water and certain solutions (for instance, of the salts 
of soda and potash) cause at first an imperfect kind of aggregation in the 
cells of Drosera ; the little masses afterwards breaking up into granular 
or pulpy brown matter. All the foregoing experiments were made on 
flower-stems, but a piece of a leaf was immersed for 30 m. in a strong 
solution of the carbonate (one part to 109 of water), and little globular 
masses of matter appeared in all the glands, which before contained 
only limpid fluid. 

I made also several experiments on the action of the vapour of the 
carbonate on the glands ; but will give only a few cases. The cut end 
of the footstalk of a young leaf was protected with sealing-wax, and was 
then placed under a small bell-glass, with a large pinch of the carbon- 
ate. After 10 m. the glands showed a considerable degree of aggrega- 
tion, and the protoplasm lining the cells of the pedicels was a little 
separated from the walls. Another leaf was left for 50 m. with the 



Chap. XV.] THEIR POWER OF ABSORPTION. 283 

same result, excepting that the hairs became throughout their whole 
length of a brownish colour. In a third leaf, which was exposed for 

1 hr. 50 m., there was much aggregated matter in the glands ; and 
some of the masses showed signs of breaking up into brown granular 
matter. This leaf was again placed in the vapour, so that it was 
exposed altogether for 5 hrs. 30 m. ; and now, though I examined 
a large number of glands, aggregated masses were found in only two 
or three ; in all the others, the masses, which before had been globular, 
were converted into brown, opaque, granular matter. We thus see 
that exposure to the vapour for a considerable time produces the same 
effects as long immersion in a strong solution. In both cases there 
could hardly be a doubt that the salt had been absorbed chiefly or 
exclusively by the glands. 

On another occasion bits of damp fibrin, drops of a weak infusion of 
raw meat and of water, were left fur 24 hrs. on some leaves ; the hairs 
were then examined, but to my surprise differed in no respect from 
others which had not been touched by these fluids. Most of the cells, 
however, included hyaline, motionless little spheres, which did not 
seem to consist of protoplasm, but, I suppose, of some balsam or 
essential oil. 

Pelargonium zonale (var. edged with white). — The leaves are clothed 
with numerous multicellular hairs; some simply pointed; others 
bearing glandular heads, and differing much in length. The glands 
on a piece of leaf were examined and found to contain only a limpid 
fluid; most of the water was removed from beneath the covering glaus, 
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 specimen had 
been left for 1 hr. in the solution, many of the smaller globules had 
changed their positions ; and two or three vacuoles or small spheres 
(for I know not which they were) of a rather darker tint appeared 
within some of the larger globules. Little globules could now be seen 
in some of the uppermost cells of the pedicels, and the protoplasmic 
lining was 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 ot 
darker brown granular matter. Hence from what we have seen with 
Primula sinensis, there can be little doubt that these masses originally 
consisted of living protoplasm. 

A drop of a weak infusion of raw meat was placed on a leaf, and 
after 2 hrs. 30 m. many spheres could be seen within the glands. 
These spheres, when looked at again after 30 m., had slightly changed 
their positions and forms, and one had separated into two ; but the 
changes were not quite like those which ttie protoplasm of Drosera 
undergoes. These hairs, moreover, had not been examined before 



284 GLANDULAR HAIRS : [Chap. XV. 

immersion, and there were similar spheres in some glands which had 
not been touched by the infusion. 

Erica tretralix. — A few long glandular hairs project from the 
margins of the upper surfaces of the leaves. The pedicels are formed 
of several rows of cells, and support rather large globular heads, 
secreting viscid matter, by which minute insects are occasionally 
though rarely, caught. Some leaves were left for 23 hrs. in a weak 
infusion of raw meat and in water, and the hairs were then com- 
pared, but they differed very little or not at all. In both cases the 
contents of the cells seemed rather more granular than they were 
before ; but the granules did not exhibit any movement. Other 
leaves were left for 23 hrs. in a solution of one part of carbonate of 
ammonia to 218 of water, and here again the granular matter appeared 
to have increased in amount ; but one such mass retained exactly the 
same form as before after an interval of 5 hrs., so that it could hardly 
have consisted of living protoplasm. These glands seem to have very 
little or no power of absorption, certainly much less than those of the 
foregoing plants. 

Mirdbilis longifiora.^The stems and both surfaces of the leaves 
bare viscid hairs. Young plants, from 12 to 18 inches in height ia 
my greenhouse, caught so many minute Diptera, Coleoptera, and 
larvas, 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 olten globules of granuhir matter. 
Within a gland which had caught a small insect, one such mass 
was observed to undergo incessant changes of form, with the occa- 
sional appearance of vacuoles. But 1 do not believe that tiiis 
protoplasm had been generated by matter absorbed from the dead 
insect; for, on comparing several glands which had and had not 
caught insects, not a shade of difference could be perceived between 
them, and they all contained fine granular matter. A piece of leaf 
was immersed for 24 hrs. in a solution of one part of carbonate of 
ammonia to 218 of water, but the hairs seemed very httle aHected 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. Kor were 
the glands on another leaf, after an immersion for 'li hrs. in an in- 
fusion of raw meat, in the least affected ; but the protoplasoi lining 
the cells of the pedicels had shrunk greatly from the walls. This 
latter effect may have been due to exosmose, as the infusion was 
strong. We may therefore conclude that the glands of this plant 
either have no power of absorption or that the protoplasm which they 
contain is not acted on by a solution of carbonate of ammonia (and 
this seems scarcely credible) or by an infusion of meat. 

JVicotiana 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 



Chap. XV.] THEIIl POWER OF ABSORPTION. 285 

glands are formed of many cells, containing greenish matter with little 
globules of some substance. Leaves were left in an infusion of raw 
meat and in water for 26 hrs., but presented no ditlerenoe. Some of 
these same leaves were then left for above 2 lirs. in a solution of 
carbonate of ammonia, but no effect was produced. I regret that 
other experiments were not tried with more care, as M. Schloesing has 
shown* that tobacco plants supplied with the vapour of carbonate of 
ammonia yield on analysis a greater amount of nitrogen than other 
plants not thus treated ; and, from what we have seen, it is probable 
that some of the vapour may be absorbed by the glandular hairs. 

Summary of the Observations on Glandular Hairs. — From 
the foregoing observations, few as tliey are, we see that the 
glands of two species of Saxifraga, of a Primula and Pelar- 
gonium, have the power of rapid absorption ; whereas the 
glands of an Erica, Mirahilis, and Nicotiana, either have no 
such power, or the contents of the cells are not affected by 
the fluids employed, namely a solution of carbonate of 
ammonia and an infusion of raw meat. As the glands of 
the Mirabilis contain protoplasm, which did not become 
aggregated from exposure to the fluids just named, though 
the contents of the cells in the blade of the leaf were greatly 
affected by carbonate of ammonia, we may infer that they 
cannot absorb. We may further infer that the innumerable 
insects caught by this plant are of no more service to it 
than are those which adhere to the deciduous and sticky 
scales of the leaf-buds of the horse-chestnut. 

The most interesting case for us is that of the two species 
of Saxifraga, as this genus is distantly allied to Drosera. 
Their glands absorb matter from an infusion of raw meat, 
from solutions of the nitrate and carbonate of ammonia, and 
apparently from decayed insects. This was shown by the 
changed dull purple colour of the protoplasm within the cells 
of the glands, by its state of aggregation, and apparently by 
its more rapid spontaneous movements. The aggregating 
process sjireads from the glands down the pedicels of the 
hairs ; and we may assume that any matter which is absorbed 
ultimately reaches the tissues of the plant. On the other 
hand, the process travels up the hairs whenever a surface 
is cut and exposed to a solution of the carbonate of ammonia. 



* 'Comptes rendus,' June 15, 1874. A good abstract of this paper is 
given in the ' Gardener's Chronicle,' July 11, 1874. 



286 GLANDULAR HAIES. [Chap. XY. 

The glands on the flower-stalks and leaves of Primula- 
sinensis quickly absorb a solution of tbe carbonate of ammonia, 
and the protoplasm which they contain becomes aggregated. 
The process was seen in some cases to travel from the glands 
into the upper cells of the pedicels. Exposure for 10 m. to 
the vapour of this salt likewise induced aggregation. When 
leaves were left from 6 hrs. to 7 hrs. in a strong solution, 
or were long exposed to the vapour, the little masses of 
protoplasm became disintegrated, brown, and granular, and 
were apparently killed. An infusion of raw meat produced 
no effect on the glands. 

The limpid contents of the glands of Pelargonium zonale 
became cloudy and granular in from 3 m. to 5 m. when they 
were immersed in a weak solution of the carbonate of am- 
monia ; and in the course of 1 hr. granules appeared in the 
upper cells of the pedicels. As the aggregated masses 
slowly changed their forms, and as they suffered disintegra- 
tion when left for a considerable 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 generally 
been considered by physiologists to serve only as secreting 
or excreting organs, but we now know that they have the 
power, at least in some cases, of absorbing both a solution 
and the vapour of ammonia. As rain-water contains a small 
percentage of ammonia, and the atmosphere a minute quantity 
of the carbonate, this power can hardly fail to be beneficial. 
Nor can the benefit be quite so insignificant as it might at 
first be thought, for a moderately fine plant of Primula sinensis 
bears the astonishing number of above two millions and a 
half of glandular hairs,* all of which are able to absorb 



* My son Francis counted the (the larger ones being a little more- 
hairs on a space measured by means than 2 inches in diameter) was now 
of a micrometer, and found that selected, and the area of all the 
there were 35,336 on a square inch leaves, together with their footstalks 
of the upper surface of a leaf, and (the flower-stems not being included)' 
30,035 on the lower surface ; that is, was found by a planimeter to be- 
in about the proportion of 100 on the 39 '285 square inches; so that the 
upper to 85 on the lower surface. area of both surfaces was 78 "57 
On a square inch of both surfaces square inches. Thus the plant (ex- 
there were 65,371 hairs. A moder- eluding the flower-stems) must have 
ately fine plant bearing twelve leaves borne the astonishing number o6 



Chap. XV.] DROSERAOEiE. 287 

ammonia brought to them by the rain. It is moreover 
probable that the glands of some of the above-named plants 
obtain animal matter from the insects which are occasionally- 
entangled by the viscid secretion. 



Concluding Eemarks on the Droserace.e. 

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, Eoridula, and Byblis, solely by 
the viscid fluid secreted from their glands ; by Drosera, 
through the same means, together with the movements of 
the tentacles ; by Dionaea and Aldrovanda, through the 
closing of the blades of the leaf. In these two last genera 
rapid movement makes up for the loss of viscid secretion. 
In every case it is some part of the leaf which moves. In 
Aldrovanda it appears to be the basal parts alone which 
contract and carry with them the broad, thin margins of the 
lobes. In Dionasa the whole lobe, with the exception of the 
marginal prolongations or spikes, curves inwards, though 
the chief seat of movement is near the midrib. In Drosera 
the chief seat is in the lower part of the tentacles, which, 
homologically, may be considered as prolongations of the 
leaf; but the whole blade often curls inwards, converting 
the leaf into a temporary stomach. 

There can hardly be a doubt that all the plants belonging- 
to these six genera have the power of dissolving animal 
matter by the aid of their secretion, which contains an acid, 
together with a ferment almost identical in nature with 
pepsin; and that they afterwards absorb the matter thus 
digested. This is certainly the case with Drosera, Droso- 
phyllum, and Diona3a ; almost certainly with Aldrovanda i. 
and, from analogy, very probable with Eoridula and Byblis. 
We can thus understand how it is that the three first-named 



2,568,099 glandular hairs. The hairs longer than they were before ; sr> 
were counted late in the autumn, and that no doubt the glandular haiis 
by the following spring (May) the had increased in numbei-, and fro- 
leaves of some other plants of the bably now much exceeded three- 
same lot were found to be from one- millions, 
third to one-fourth broader and 



288 



CONCLUDIXG EEMAEKS 



[Chap. XV. 



genera are provided with sucli small roots,* and that Aldro- 
-vanda is quite rootless; about the roots of the two other 
genera nothing is known. It is, no doubt, a surprising fact 
that a whole group of plants (and, as we shall presently see, 
some other plants not allied to the 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 rhizooephalous 
crustaceans do not feed like other animals by their mouths, 
for they are destitute of an alimentary canal ; but they live 
by absorbing through root-like processes the juices of the 
animals on which they are parasitic.f 

Of the six genera, Drosera has been incomparably the 
most successful in the battle for life ; and a large part of its 
success may be attributed to its manner of catching insects. 
It is a dominant form, for it is believed to include about 100 
species,! which range in the Old World from the Arctic 
regions to Southern India, to the Gape of Good Hope, 



* [Fraustadt (Dissertation, iVreslau, 
1876) shows that the roots of Diona;a 
are by no means small. In another 
Breslau Dissertation (1887) Otto 
Penzig shows that the roots of 
Zfrosophyllum lusitanicmn are also 
well deTeloped. Pfeffer (' Landwirth. 
Jahrbucher,' 1877) points out that the 
■argument from the small develop- 
ment of roots in some carnivorous 
plants is valueless, because the same 
state of things is found in many 
marsh and aquatic plants which 
neither catch nor digest insects. — 
T. D.] 

t Fritz MuUer, ' Facts for Darwin,' 
Eng. trans. 1869, p. 139. The rhizo- 
oephalous crustaceans are allied to 
the cirripedes. It is hardly possible 
-to imagine a greater difference than 
that between an animal with pre- 
hensile Jirabs, a well - constructed 
mouth and alimentary canal, and one 
•destitute of all these organs and 
feeding by absorption through branch- 
ing root-like processes. If one rare 



cirripede, the Anelasma squalicola^ 
had become extinct, it would have 
been very difficult to conjecture how 
so enormous a change could have 
been gradually effected. But, as 
Fritz MuUer remarks, we have in 
Anelasma an animal in an almost 
exactly intermediate condition, for it 
has root-like processes embedded in 
the skin of the shark on which it is 
parasitic, and its prehensile cirri and 
mouth (as described in my monograph 
on the Lepadidse, ' Ray Soc' 1851, 
p. 169) are in a most feeble and 
almost rudimentary condition. Dr. 
R. Kossmann has given a very in- 
teresting discussion on this subject 
in his ' Suctoria and Lepadidae,' 1873. 
See also, Dr. Dohrn, ' Der Drsprung 
der Wirbelthiere,' 1875, p. 77. 

X Bentham and Hooker, * Genera 
Plantarum.' Australia is the me- 
tropolis of the genus, forty - one 
species having been described from 
this country, as Prof. Oliver informs 
me. 



Chap. XV.] ON THE DKOSEEACE^. 289 

Madagascar, and Australia; and in the New World from 
Canada to Tierra del Tuego. In this respect it presents a 
marked contrast with the five other genera, which appear 
to be failing groups. Dionaea includes only a single species, 
which is confined to one district in Carolina. The three 
varieties or closely allied species of Aldrovanda, like so many 
water-plants, have a wide range from Central Europe to 
Bengal and Australia. Drosophyllum includes only one 
species, limited to Portugal and Morocco. Eoridula and 
Byblis each have (as I hear from Prof. Oliver) two species ; 
the former confined to the western parts of the Cape of Good 
Hope, and the latter to Australia. It is a strange fact that 
Dionaa, 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 Dionsea 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 weU as for absorption ; whereas with 
Drosera the glands serve all these purposes, and secrete 
without being excited. 

By comparing the structure of the leaves, their degree of 
complication, and their rudimentary parts in the six genera, 
we are led to infer that their common parent form partook 
of the characters of Drosophyllum, Eoridula, 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 Drosophyllum they further include spiral 
cells, and the pedicels include a bundle of spiral vessels. 
But in these three genera these organs do not possess any 
power of movement, and there is no reason to doubt that 
they are of the nature of hairs or trichomes. Although in 
innumerable instances foliar organs move when excited, no 
case is known of a trichome having such power.* We are 



Sachs, 'Traite de Botaniqiie,' 3rd edit. 1874, p. 1026. 

V 



290 CONCLUDING EBMAEKS [Chap. XV. 

thus led to inquire how the so-called tentacles of Drosera, 
which are manifestly of the same general nature as the 
glandular hairs of the above three genera, could have 
acquired the power of moving. Many botanists maintain 
that these tentacles consist of prolongations of the leaf, 
because they include vascular tissue, but this can no longer 
be considered as a trustworthy distinction.* The possession 
of the power of movement on excitement would have been 
safer evidence. But when we consider the vast number of 
the tenacles on both surfaces of the leaves of Drosophyllum, 
and on the upper surface of the leaves of Drosera, it seems 
scarcely possible that each tentacle could have aboriginally 
existed as a prolongation of the leaf. Eoridula, perhaps, 
shows us how we may reconcile these difSculties with respect 
to the homological nature of the tentacles. The lateral 
divisions of the leaves of this plant terminate in long ten- 
tacles ; and these include spiral vessels which extend for 
only a short distance up them, with no line of demarcation 
between what is plainly the prolongation of the leaf and 
the pedicel of a glandular hair. Therefore there would be 
nothing anomalous or unusual in the basal parts of these 
tentacles, which correspond with the marginal ones of 
Drosera, acquiring the power of movement ; and we know 
that in Drosera it is only the lower part which becomes 
inilected. But in order to understand how in this latter 
genus not only the marginal but all the inner tentacles have 
become capable of movement, we must further assume, either 
that through the principle of correlated development this 
power was transferred to the basal parts of the hairs, or that 
the surface of the leaf has been prolonged upwards at numer- 
ous points, so as to unite with the hairs, thus forming the 
bases of the inner tentacles. 

The above-named three genera, namely Drosophyllum, 
Eoridula, 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 



* Dr. Warming, ' Sur la Difference belige Meddelelser de la Soc. d'Hist. 
entre les Trichomes,' Copenhague, nat. de Copenhague,' Nos. 10-12, 
1873, p. 6. ' Extrait des Videnska- 1872. 



Chap. XV.] ON THE DEOSEEAOE^. 291 

the genera, being replaced in Eoridula by hairs, and in 
most species of Drosera by absorbent papillae. Drosera 
hinata, with its linear and bifurcating leaves, is in an inter- 
mediate condition. It still bears some sessile glands on both 
surfaces of the leaves, and on the lower surface a few 
irregularly placed tentacles, which are incapable of move- 
ment. A further slight change would convert the linear 
leaves of this latter species into the oblong leaves of Drosera 
anglica, and these might easily pass into orbicular ones 
with footstalks like those of Drosera rotundifolia. The 
footstalks of this latter species bear multicellular hairs, 
which we have good reason to believe represent aborted 
tentacles. 

The parent form of Dionasa 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 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 Droseraceas consist in the leaves of 
some having the power of movement when excited, in their 
glands secreting a fluid which digests animal matter, and in 
their absorption of the digested matter. Can any light be 
thrown on the steps by which these remarkable powers were 
gradually acquired ? 

As the walls of the cells are necessarily permeable to 
fluids, in order to allow the glands to secrete, it is not 
surprising that they should readily allow fluids to pass in- 
wards ; and this inward passage would deserve to be called 
an act of absorption, if the fluids combined with the contents 
of the glands. Judging from the evidence above given, the 
secreting glands of many other plants can absorb salts of 
ammonia, of which they must receive small quantities from 
the rain. This is the case with two species of Saxifraga. 

2 



292 CONCLUDING REMARKS. [Chap. XV. 

and the glands of one of them apparently absorb matter from 
captured insects, and certainly from an infusion of raw meat. 
There is, therefore, nothing anomalous in the Droserace» 
having acquired the power of absorption in a much more 
highly developed degree. 

It is a far more remarkable problem how the members of 
this family, and Pinguicula, and, as Dr. Hooker has recently 
shown, Nepenthes, could all have acquired the power of 
secreting a fluid which dissolves or digests animal matter. 
The six genera of the Droseracesa have probably inherited 
this power from a common progenitor, but this cannot apply 
to Pinguicula or Nepenthes, for these plants are not at all 
closely related to the Droseraoese. But the difficulty is not 
nearly so great as it at first appears. Firstly, the juices of 
many plants contain an acid, and, apparently, any acid 
serves for digestion. Secondly, as Dr. Hooker has remarked 
in relation to the present subject in his address at Belfast 
(1874), and as Sachs repeatedly insists,* the embryos of some 
plants secrete a fluid which dissolves albuminous substances 
out of the endosperm ; although the endosperm is not actually 
united with, only in contact with, the embryo. All plants, 
moreover, have the power of dissolving albuminous or proteid 
substances, such as protoplasm, chlorophyll, gluten, aleurone, 
and of carrying them from one part to other parts of their 
tissues. This must be efiected by a solvent, probably con- 
sisting of a ferment together with an acid.f Now, in the 
case of plants which are able to absorb already soluble matter 
from captured insects, though not capable of true digestion, 
the solvent just referred to, which must be occasionally 
present in the glands, would be apt to exude from the glands 
together with the viscid secretion, inasmuch as endosmose 
is accompanied by exosmoso. 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 



* ' Traits de Botanique,' 3rd edit. Will, has actually made the discovery 

1874, p. 844. See also for following that the seeds of the vetch contain a 

facts pp. 64, 76, 828, 831. ferment, which, when extracted by 

f Since this sentence was written, glycerine, dissolves albuminous sub- 

I have received a paper by Gorup- stances, such as fibrin, and converts 

Besanez (' Berichte der Deutschen them into true peptones, [See, how- 

Chem. Gesellschaft,' Berlin, 1874, p. ever. Vines' ' Physiology of Plants,' 

1478), who, with the aid of Dr. H. p. 190.— F. D.] 



Chap. XV ] ON THE DEOSEEACEJi. 293 

be of Mgh service to plants growing in very poor soil, it 
would tend to be perfected through, natural selection. There- 
fore, any ordinary plant having viscid glands, which 
occasionally caught insects, might thus be converted under 
favourable circumstances into a species capable of true 
digestion. It ceases, therefore, to be any great mystery how 
several genera of plants, in no way closely related together, 
have independently acquired this same power. 

As there exist several plants the glands of which cannot, 
as far as is known, digest animal matter, yet can absorb salts 
of ammonia and animal fluids, it is probable that this latter 
power forms the first stage towards that of digestion. It 
might, however, happen, under certain conditions, that a 
plant, after having acquired the power of digestion, should 
degenerate into one capable only of absorbing animal matter 
in solution, or in a state of decay, or the final products of 
decay, namely the salts of ammonia. It would appear that 
this has actually occurred to a partial extent with the leaves 
of Aldrovanda ; the outer parts of which possess absorbent 
organs, but no glands fitted for the secretion of any digestive 
fluid, these being confined to the inner parts. 

Little light can be thrown on the gradual acquirement of 
the third remarkable character possessed by the more highly 
developed genera of the Droseracess, namely the power of 
movement when excited. It should, however, be borne in 
mind that leaves and their homologues as well as flower- 
peduncles, have gained this power, in innumerable instances, 
independently of inheritance from any common parent form ; 
for instance, in tendril-bearers and leaf-climbers (i.e. plants 
with their leaves, petioles and flower-peduncles, &c., modified 
for prehension) belonging to a large number of the most 
widely distinct orders, — in the leaves of the many plants 
which go to sleep at night, or move when shaken,— and in 
irritable stamens and pistils of not a few species. We may 
therefore infer that the power of movement can be by some 
means readily acquired. Such movements imply irritability 
or sensitiveness, but, as Cohn has remarked,* the tissues of 
the plants thus endowed do not difi'er in any uniform manner 



* See the abstract of his memoir on the contractile tissues of plants, in the 
'Annals and Mag. of Nat. Hist.' 3rd series, vol. xi. p. 183. 



294 CONCLUDING EEMAEKS [Chap. XV. 

from those of ordinarj'- plants ; it is therefore prohahle that 
all leaves are to a slight degree irritable. Even if an insect 
alights on a leaf, a slight molecular change is prohahly trans- 
mitted to some distance across its tissue, with the sole 
difference that no perceptible effect is produced. "We have 
some evidence in favour of this belief, for we know that a 
single touch on the glands of Drosera does not excite inflec- 
tion ; yet it must produce some effect, for if the glands have 
been immersed in a solution of camphor, inflection follows 
within a shorter time than would have followed from the 
effects of camphor alone. So again with Dionaaa, the blades 
in their ordinary state may be roughly touched without 
their closing ; yet some effect must be thus caused and trans- 
mitted across the whole leaf, for if the glands have recently 
absorbed animal matter, even a delicate touch causes them 
to close instantly. On the whole we may conclude that 
the acquirement of a high degree of sensitiveness and of 
the power of movement by certain genera of the Drose- 
raceee presents no greater difficulty than that presented by 
the similar but feebler powers of a multitude of other plants. 
The specialised nature of the sensitiveness possessed by 
Drosera and Dionasa, 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 
Dion»a with no effect ; but if touched only once by the slow 
movement of a delicate hair, the lobes close ; and this differ- 
ence in the nature of the sensitiveness of these two plants 
stands in manifest adaptation to their manner of capturing 
insects. So does the fact, that when the central glands of 
Drosera absorb nitrogenous matter, they transmit a motor 
impulse to the exterior tentacles much more quickly than 
when they are mechanically irritated ; whilst with Dionsea 
the absorption of nitrogenous matter causes the lobes to press 
together with' extreme slowness, whilst a touch excites rapid 
movement. Somewhat analogous cases may be observed, as 
I have shown in another work, with the tendrils of various 
plants ; some being most excited by contact with fine fibres, 
others by contact with bristles, others with a flat or a 
creviced surface. The sensitive organs of Drosera and Dionsea 
are also specialised, so as not to be uselessly affected by the 



Chap. XV.] ON THE DEOSEEACE^. 295 

weight or impact of drops of rain, or by Hasts of air. This 
may be accounted for by supposing that these plants and 
their progenitors have grown accustomed to the repeated 
action of rain and wind, so that no molecular change is thus 
induced ; whilst they have been rendered more sensitive by 
means of natural selection to the rarer impact or pressure 
of solid bodies. Although the absorption by the glands 
of Drosera of various fluids excites movement, there is a 
great difference in the action of allied fluids ; for instance, 
between certain vegetable acids, and between citrate and 
phosphate of ammonia. The specialised nature and per- 
fection of the sensitiveness in these two plants is all the 
more astonishing as no one supposes that they possess 
nerves ; and by testing Drosera with several substances 
which act powerfully on the nervous system of animals, it 
does not appear that they include any diffused matter 
analogous to nerve-tissue. 

Although the cells of Drosera and Dionaea are quite as 
sensitive to certain stimulants as are the tissues which 
surround the terminations of the nerves in the higher animals, 
yet these plants are inferior even to animals low down in the 
scale, in not being affected except by stimulants in contact 
with their sensitive parts. They would, however, probably 
be affected by radiant heat ; for warm water excites energetic 
movement. When a gland of Drosera, or one of the filaments 
of Dionaea, is excited, the motor impulse radiates in all direc- 
tions, and is not, as in the case of animals, directed towards 
special points or organs. This holds good even in the case 
of Drosera when some exciting substance has been placed at 
two points on the disc, and when the tentacles all round are 
inflected with marvellous precision towards the two points. 
The rate at which the motor impulse is transmitted, though 
rapid in 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. Nevertheless we perhaps see the pre- 
figurement of the formation of nerves in animals in the trans- 
mission of the motor impulse being so much more rapid down 
the confined space within the tentacles of Drosera than else- 
where, and somewhat more rapid in a longitudinal than m 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, 



296 CONCLUDING EEMAEKS. [Chap. XV. 

when excited from a distance, send back some influence which 
causes the contents of the cells to become aggregated down 
to the bases of the tentacles. But the greatest inferiority of 
all is the absence of a central organ, able to receive impressions 
from all points, to transmit their effects in any definite 
direction, to store them up and reproduce them. 



Chap. XVI.] PINGUICULA VULGAEIS. ' 297 



CHAPTEE XVI. 

PlNGUICULA. 

Pinguimla vulgaris — Structure of leaves — Number of insects and other objects 
caught — Movement of the margins of the leaves — Uses of this movement 
— Secretion, digestion, and absorption — Action of the secretion on various 
animal and vegetable substances — The effects of substances not containing 
soluble nitrogenous matter on the glands — Pinguicula grandiflora — Pin- 
guicula liisitanica, catches insects — Movement of the leaves, secretion and 
digestion, 

Pinguicula vulgaeis. — This plant grows iu moist places, 
generally on moiintains. 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 f inch in breadth. The young central leaves are deeply 
concave, and project upwards ; the older ones towards the 
outside are flat or convex, and lie close to the ground, form- 
ing a rosette from 3 to 4 inches in diameter. The margins 
of the leaves are incurved. Their upper surfaces are thickly 
covered with two sets of glandular hairs, diflering in the 
size of the glands and in the length of their pedicels. The 
larger glands have a circular outline as seen from above, and 
are of moderate thickness ; they are divided by radiating 
partitions into sixteen cells, containing light-green, homo- 
geneous fluid. They are supported on elongated, unicellular 
pedicels (containing a nucleus with a nucleolus) which rest 
on slight prominences. The small glands differ only in being 
formed of about half the number of cells, containing much 
paler fluid, and supported on much shorter pedicels. Near 
the midrib, towards the base of the leaf, the pedicels are 
multicellular, are longer than elsewhere, and bear smaller 
glands. All the glands secrete a colourless fluid, which is 
so viscid that I have seen a fine thread drawn out to a length 



* [According to Batalin (' Flora,' green in plants grown in shady places. 

1877) the yellowish-green colour is It is due to a yellow homogeneous 

peculiar to plants grown in strong substance found in the epidermal 

light, being replaced by a more lively cells and in the glands. — F. D.] 



298 PINGUICULA VULGARIS. [Chap. XVI. 

of 18 inciies ; bixt the fluid in this case was secreted ty a 
gland wHch had been excited. The edge of the leaf is 
translucent, and does not bear any glands ; and here the 
spiral vessels, proceeding from the midrib, terminate in cells 
marked by a spiral line, somewhat like those within the 
glands of Drosera. 

The roots are short. Three plants were dug up in North 
Wales on June 20, and carefully washed ; each bore five or 
six unbranched roots, the longest of which was only 1*2 of 
an inch. Two rather young plants were examined on 
September 28 ; these had a greater number of roots, namely 
eight and eighteen, all under 1 inch in length, and very little 
branched. 

I was led to investigate the habits of this plant by being 
told by Mr. W. Marshall that on the mountains of Cumber- 
land many insects adhere to the leaves. 

A friend sent me on June 23 thirty-nine leaves from North Wales, 
whicli were selected owing to objects of some kind adhering to them. 
Of these leaves, thirty-two had caught 142 insects, or on an average 
4'4 per leaf, minute fragments of insects not heing included. Besides 
the insects, small leaves belonging to four different kinds of plants, 
those of Erica ietralix being much the commonest, and three minute 
seedling plants, blown by the wind, adhered to nineteen of the leaves. 
One had caught as many as ten leaves of the Erica. Seeds or fruits, 
commonly of Carex and one of Juncus, besides bits of moss and other 
rubbish, likewise adhered to six of the thirty-nine leaves. The same 
friend, on June 27, collected nine plants bearing seventy-four leaves, 
and all of these, with the exception of three young leaves, had caught 
insects ; thirty insects were counted on one leaf, eighteen on a second, 
and sixteen on a third. Another friend examined on August 22 some 
plants in Donegal, Ireland, and found insects on 70 out of 157 leaves ; 
fifteen of these leaves were sent me, each having caught on an average 
2 '4 insects. To nine of them, leaves (mostly of Erica tetrdlix) ad- 
hered ; but they had been specially selected on this latter account. I 
may add that early in August my son found leaves of this same Erica 
and the fruits of a Carex on the leaves of a Pinguicula in Switzerland, 
probably Pinguicula alpina; some insects, but no great number, also 
adhered to the leaves of this plant, which had much better developed 
roots than those of Pinguicula vulgaris. In Cumberland, Mr. 
Marshall, on September 3, carefully examined for me ten plants 
bearing eighty leaves; and on sixty-three of these (i.e. on 79 per 
cent.) he found insects, 143 in number ; so that each leaf had on an 
average 2 "27 insects. A few days later he sent me some plants with 
sixteen seeds or fruits adhering to fourteen leaves. There was a seed 
on three leaves on the same plant. The sixteen seeds belonged to 



Chap. XVI.] MOVEMENTS OF THE LEAVES. 299 

nine different kinds, whioli could not be recognised, excepting one of 
Eanunoulus, and several belon^ng to three or four distinct species of 
Carex. It appears that fewer insects are caught late in the year than 
earlier ; thus in Cumberland from twenty to twenty-four insects were 
observed in the middle of July on several leaves, whereas in the 
beginning of September the average number was only 2 • 27. Most of 
the insects, in all the foregoing cases, were Diptera, but with many 
minute Hymenoptera, including some ants, a few small Coleoptera, 
larviE, spiders, and even small moths. 

We tlius see that numerous insects and other objects are 
caught by the viscid leaves ; but we have no right to infer 
from this fact that the habit is beneficial to the plant, any- 
more than in the before-given case of the Mirabilis, or of 
the horse-chestnut. But it will presently be seen that dead 
insects and other nitrogenous bodies excite the glands to 
increased secretion; and that the secretion then becomes 
acid and has the power of digesting animal substances, such 
as albumen, fibrin, &c. Moreover, the dissolved nitrogenous 
matter is absorbed by the glands, as shown by their limpid 
contents being aggregated into slowly moving granular 
masses of protoplasm. The same results follow when insects 
are naturally captured, and as the plant lives in poor soil 
and has small roots, there can be no doubt that it profits by 
its power of digesting and absorbing matter from the prey 
which it habitually captures in such large numbers. It will, 
however, be convenient first to describe the movements of 
the leaves. 

Movements of the Leaves. — That such thick, large leaves as 
those of Pinguicula vulgaris should have the power of curving 
inwards when excited has never even been suspected. It is 
necessary to select for experiment leaves with their glands 
secreting freely, and which have been prevented from cap- 
turing many insects ; as old leaves, at least those growing 
in a state of nature, have their margins already curled so 
much inwards that they exhibit little power of movement, 
or move very slowly. I will first give in detail the more 
important experiments which were tried, and then make 
some concluding remarks. 

Experiment 1. — A yoimg 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. 



303 



PINGUICULA VULGARIS. 



[Chap. XVI. 



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. 

Experiment 2. — A row of flies was placed on one margin of a rather 
old leaf, which lay flat on the ground ; and in this case the margin, 
after the same interval as before, namely 15 hrs., had only just begun 
to curl inwards ; but so much secretion had been poured forth that the 
spoon-shaped tip of the leaf was filled with it. 

Experiment 3. — Fragments of a large fly were placed close to the 
apex of a vigorous leaf, as well as along half one margin. After 4 hrs. 
20 m. there was decided incurvation, which increased a little during 
the afternoon, but was in the same state on the following morning. 
Near the apex both margins were inwardly 
curved. I have never seen a case of the apex 
itself being in the least curved towards the base 
of the leaf. After 48 hrs. (always reckoning 
from the time when the flies were placed on the 
leaf) the margin had everywhere begun to unfold. 
Experiment 4. — A large fragment of a fly was 
placed on a leaf, in a medial line, a little beneath 
the apex. Both lateral margins were perceptibly 
incurved in 3 hrs., and after 4 hrs. 20 m. to such 
a degree that the fragment was clasped by both 
margins. After 24 hrs. the two infolded edges 
near the apex (for the lower part of the leaf was 
not at all affected) were measured and found to 
be • 11 of an inch (2 • 795 mm.) apart. The fly 
was now removed, and a stream of water poured 
over the leaf so as to wash the surface ; and after 
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 in- 
cui-ved over a fragment of a fly and had afterwards re-expanded ; but 
the meat did not cause even a trace of incurvation. On the contrary, 
the margin became somewhat reflexed, as if injured, and so remained 
for the three following days, as long as it was observed. 

Experiment 5. — A large fragment of a fly was placed halfway be- 
tween the apex and base of a leaf and halfway between the midrib and 
one margin. A short space of this margin, opposite the fly, showed a 
trace of incurvation after 3 hrs., and this became strongly pronounced in 
7 hrs. After 24 hrs. the infolded edge was only '16 of an inch 




Fig. 16. 

(Pinguicula vulgarii.') 

Outline of leaf with left 
margin infiected over a 
row of small flies. 



Chap. XVI.] MOVEMENTS OF THE LEAVES. 



301 



(4 "064 mm.) from the midrib. The margin now began to unfold, 
though the fly was left on the leaf; so that by the next morning 
{i.e. 48 hrs. from the time when the fly was first put on) the infolded 
edge had almost completely recovered its original position, being now 
•3 of an inch (7 "62 mm.), instead of -16 of an inch, from the midrib, 
A trace of flexure was, however, still visible. 

Experiment 6. — A young and concave leaf was selected with its 
margins slightly and naturally incurved. Two rather large, oblong, 
rectangular pieces of roast meat were placed with their ends touching 
the infolded edge, and '46 of an inch (11 -68 mm.) apart from one 
another. After 24 hrs. the margin was greatly and equally incurved 
(see fig. 16) throughout this space, and for a length of '12 or "13 of an 
inch (3 •048 or 3 "302 mm.) above and below each 
bit ; so that the margin had been afiected over a 
greater length between the two bits, owing to 
their conjoint action, than beyond them. The 
bits of meat were too large to be clasped by the 
margin, but they were tilted up, one of them so 
as to stand almost vertically. After 48 hrs. the 
margin was almost unfolded, and the bits had 
sunk down. When again examined after two 
days, the margin was quite unfolded, with the 
exception of the naturally inflected edge ; and 
one of the bits of meat, the end of which had at 
first touched the edge, was now " 067 of an inch 
(1'70 mm.) distant from it; so that this bit had 
been pushed thus far across the blade of the leaf. 

Experiment 7. — A bit of meat was placed close 
to the incurved edge of a rather young leaf, and 
after it had re-expanded, the bit was left lying 
• 11 of an inch (2 • 795 mm.) from the edge. The 
distance from the edge to the midrib of the fully 
expanded leaf was "35 of an inch (8*89 mm.); 
so that the bit had been pushed inwards and across ri^"''"m'argin"'Tn'flecteiJ 
nearly one-third of its semi-diameter. aguinst two square bits 

Experiment 8. — Cubes of sponge, soaked in a "f™*"*- 
strong infusion of raw meat, were placed in close 
contact with the incurved edges of two leaves, — an older and younger 
one. The distance from the edges to the midribs was carefully 
measured. After 1 hr. 17 m. there appeared to be a trace of incur- 
vation. After 2 hrs. 17 m. both leaves were plainly inflected ; the 
distance between the edges and midribs being now only half what it 
was at first. The incurvation increased sUghtly durmg 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 




Fio. 16. 

(^Pinguicula vulgaris.) 

Outline of leaf, with 



302 PINGUICULA VULGAEIS. [Chap. XVI. 

inch (2 "54 mm.) from the edges; or about a quarter of the distance 
between the edge and midrib. A third bit of sponge adhered to the 
edge, and, as the margin unfolded, was dragged backwards, into its 
original position. 

Experiment ^9. — A chain of fibres of roast meat, as thin as bristles 
and moistened with saliva, were placed down one whole side, close to 
the narrow, naturally incurved edge of a leaf. In 3 hrs. this side was 
greatly incurved along its whole length, and after 8 hrs. formed a 
cyhnder, about -^ of an inch (1 ■ 27 mm.) in diameter, quite concealing 
the meat. This cylinder remained closed for 32 hrs., but after 48 hrs. 
was half unfolded, and in 72 hrs. was as open as the opposite margin 
where no meat had been placed. As the thin fibres of meat were 
completely overlapped by the margin, they were not pushed at all 
inwards, across the blade. 

Experiment 10. — Six cabbage seeds, soaked for a night in water, 
were placed in a row close to the narrow incurved edge of a leaf. We 
shall hereafter see that these seeds yield soluble matter to the glands. 
In 2 hrs. 25 m. the margin was decidedly inflected ; in 4 hrs. it 
extended over the seeds for about half their breadth, and in 7 hrs. over 
three-fourths of their breadth, forming a cylinder not quite closed 
along the inner side. After. 24 hrs. the inflection had not increased, 
perhaps had decreased. The glands which had been brought into 
contact with the upper surfaces of the seeds were now secreting freely. 
In 36 hrs. from the time when the seeds were put on the leaf the 
margin had greatly, and after 48 hrs. had completely, re-expanded. 
As the seeds were no longer held by the inflected margin, and as the 
secretion was beginning to fail, they rolled some way down the 
marginal channel. 

Experiment 11. — Fragments of glass wore placed on the margins of 
two fine young leaves. After 2 hrs. 30 m. the margin of one certainly 
became slightly incurved ; but the inflection never increased, and dis- 
appeared in 16 hrs. 30 m. from the time when the fragments were 
first applied. With the second leaf there was a trace of incurvation 
in 2 hrs. 15 m., which became decided in 4 hrs. 30 m., and still more 
strongly pronounced in 7 hrs., but after 19 hrs. 30 m. had plainly 
decreased. The fragments excited at most a slight and doubtful in- 
crease of the secretion ; and in two other trials, no increase could be 
perceived. Bits of coal-cinders, placed on a leaf, produced no effect, 
either owing to their lightness or to the leaf being torpid. 

Experiment 12. — We will now turn to fluids. A row of drops of a 
strong infusion of raw meat were placed along the margins of two 
leaves ; squares of sponge soaked in the same infusion being placed on 
the opposite margins. My object was to ascertain whether a fluid 
would act as energetically as a substance yielding the same soluble 
matter to the glands. No distinct difference was perceptible ; certainly 
none in the degree of incm-vation ; 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 



Chap. XVI.] MOVEMENTS OF THE LEAVES. 303 

for a longer time. The margins, with, the drops, became plainly- 
incurved in 2 hrs. 17 m. The incurvation subsequently increased 
somewhat, but after 24 hrs. had greatly decreased. 

Experiment 13. — Drops of the same strong infusion of raw meat 
were placed along the midrib of a young and rather deeply concave 
leaf. The distance across the broadest part of the leaf, between the 
naturally incurved edges, was '55 of an inch (13 '97 mm.). In 3 hrs. 
27 m. this distance was a trace less ; in 6 hrs. 27 m. it was exactly 
■45 of an inch (11 "43 mm.), and had therefore decreased by "1 of 
an inch (2*54 mm.). After only 10 hrs. 37 m. the margin began 
to re-expand, for the distance from edge to edge was now a trace 
wider, and after 24 hrs. 20 m. was as great, within a hair's breadth, 
as when the drops were first placed on the leaf. From this experi- 
ment we learn that the motor impulse can be transmitted to a dis- 
tance of ■ 22 of an inch (5 • 590 mm.) in a transverse direction from 
the midrib to both margins ; but it would be safer to say "2 of an inch 
(5 • 08 mm.), as the drops spread a little beyond the midrib. The 
incurvation thus caused lasted for an unusually short time. 

ExperiTnent 14.— Three drops of a solution of one part of carbonate 
of ammonia to 218 of water (2 grs. to 1 oz.) were placed on the margin 
of a leaf. These excited so much secretion that in 1 hr. 22 m. all 
three drops ran together ; but although the leaf was observed for 24 
hrs., there was no trace of inflection. We know that a rather strong 
solution of this salt, though it does not injure the leaves of Drosera, 
paralyses their power of movement, and I have no doubt, from [this 
and] the following case, that this holds good with Pinguicula. 

Experiment 15. — A row of drops of a solution of one part of 
carbonate of ammonia to 875 of water (1 gr. to 2 oz.) was placed on 
the margin of a leaf. In 1 hr. there was apparently some slight 
incurvation, and this was well marked in 3 hrs. 30 m. After 24 hrs. 
the margin was almost completely re-expanded. 

Experiment 16. — A row of large drops of a solution of one part of 
phosphate of ammonia to 4375 of water (1 gr. to 10 oz.) was placed 
along the margin of a leaf. No effect was produced, and after 8 hrs. 
fresh drops were added along the same margin without the least effect. 
We know that a solution of this strength acts powerfully on Drosera, 
and it is just possible that the solution was too strong. I regret that 
I did not try a weaker solution. 

Experiment 17. — As the pressure from bits of glass causes incurvation, 
I scratched the margins of two leaves for some minutes with a blant 
needle, but no effect was produced. The surface of a leaf beneath a 
drop of a strong infusion of raw meat was also rubbed for 10 m. with 
the end of a bristle, so as to imitate the struggles of a captured insect ; 
but this part of the margin did not bend sooner than the other parts 
with undisturbed drops of the infusion. 

We learn from the foregoing experiments that the margins 
of the leaves curl inwards when excited by the mere pressure 



304 PINGITICULA VULGAEIS. [Chap. XVI. 

of objects not yielding any soliilDle matter, by objects yield- 
ing such matter, and by some fluids — ^namely an infusion of 
raw meat and a weak solution of carbonate of ammonia. A 
stronger solution of two grains of this salt to an ounce of 
water, though exciting copious secretion, paralyses the leaf. 
Drops of water and of a solution of sugar or gum did not 
cause any movement. Scratching the surface of the leaf for 
some minutes produced no effect. Therefore, as far as we at 
present know, only two causes— namely slight continued 
pressure and the absorption of nitrogenous matter — excite 
movement. It is only the margins of the leaf which bend, 
for the apex never curves towards the base. The pedicels 
of the glandular hairs have no power of movement. I 
observed on several occasions that the surface of the leaf 
became slightly concave where bits of meat or large flies had 
long lain, but this may have been due to injury from over- 
stimulation.* 

The shortest time in which plainly marked movement was 
observed was 2 hrs. 17 m., and this occurred when either 
nitrogenous substances or fluids were placed on the leaves ; 
biit 1 believe that in some cases there was a trace of move- 
ment in 1 hr. or 1 hr. 30 m. The pressure from fragments 
of glass excites movement almost as quickly as the absorption 
of nitrogenous matter, but the degree of incurvation thus 
caused is much less. After a leaf has become well incurved 
and has again expanded, it will not soon answer to a fresh 
stimulus. The margin was affected longitudinally, upwards 
or downwards, for a distance of -13 of an inch (3-302 mm.) 
from an excited point, but for a distance of • 46 of an inch 
between two excited points, and transversely for a distance 
of -2 of an inch (5 • 08 mm.). The motor impulse is not 
accompanied, as in the case of Drosera, by any influence 
causing increased secretion; for when a single gland was 
strongly stimulated and secreted copiously, the surrounding 
glands were not in the least affected. The incurvation of 
the margin is independent of increased secretion, for frag- 
ments of glass cause little or no secretion, and yet excite 
movement : whereas a strong solution of carbonate of am- 
monia quickly excites copious secretion, but no movement. 



* [Batalin (' Flora,' 1887) believes accompanied by actual growth, and 
that the depressions are due to the thus a permanent alteration in the 
fact that the curvature of the leaf is form of the leaf is effected. — F. D.] 



Chap. XVI.] MOVEMENTS OF THE LEAVES. 305 

One of the most curious facts with respect to the move- 
ment of the leaves is the short time during which they 
remain incurved, although the exciting ohject 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 hit of sponge, soaked in a strong infusion 
of raw meat, had been applied to a leaf, the margin began to 
unfold in 35 hrs. Fragments of glass keep the margin 
incurved for a shorter time than do nitrogenous bodies ; for 
in the former case there was complete re-expansion in 16 hrs. 
30 m. Nitrogenous fluids act for a shorter time than nitro- 
genous substances ; thus, when drops of an infusion of raw 
meat were placed on the midrib of a leaf, the incurved 
margins began to unfold in only 10 hrs. 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 overlapping margin are thus brought 
into contact with such objects and pour forth their secretion, 
afterwards absorbing the digested matter. But as the incur- 
vation lasts for so short a time, any such benefit can be of 
only slight importance, yet perhaps greater than at first 
appears. The plant lives in humid districts, and the insects 
which adhere to all parts of the leaf are washed by every 
heavy shower of rain into the narrow channel formed by the 
naturally incurved edges. For instance, my friend in North 
Wales placed several insects on some leaves, and two days 
afterwards (there having been heavy rain in the interval) 
found some of them quite washed away, and many others 
safely tucked under the now closely inflected margins, the 
glands of which all round the insects were no doubt secret- 
ing. We can thus, also, understand how it is that so many 
insects, and fragments of insects, are generally found lying 
within the incurved margins of the leaves. 

The incurvation of the margin, due to the presence of an 

X 



306 PINGUICULA YULGAEIS. [Chap. XYI. 

exciting object, must he serviceable in another and probably 
more important way. We have seen that when large bits 
of meat, or of sponge soaked in the juice of meat, were placed 
on a leaf, the margin was not able to embrace them, but, as 
it became incurved, pushed them very slowly towards the 
middle of the leaf, to a distance from the outside of fully • 1 
of an inch (2 • 54 mm.), that is, across between one-third and 
one-fourth of the space between the edge and midrib. Any 
object, such as a moderately sized insect, would thus be 
brought slowly into contact with a far larger number of 
glands, inducing much more secretion and absorption, than 
would otherwise have been the case. That this would be 
highly serviceable to the plant, we may infer from the fact 
that Drosera has acquired highly developed powers of move- 
ment, merely for the sake of bringing all its glands into 
contact with captured insects. So again, after a leaf of 
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 surface. In the case of Pinguicula, as soon as an 
insect has been pushed for some little distance towards the 
midrib, immediate re-expansion would be beneficial, as the 
margins could not capture fresh prey until they were un- 
folded. The service rendered by this pushing action, as 
well as that from the marginal glands being brought into 
contact for a short time with the upper surfaces of minute 
captured insects, may perhaps account for the peculiar move- 
ments of the leaves : otherwise, we must look at these move- 
ments as a remnant of a more highly developed power for- 
merly possessed by the progenitors of the genus. 

In the four British species, and, as I hear from Prof. Dyer, 
in most or all the species of the genus, the edges of the 
leaves are in some degree naturally and permanently 
incurved. This incurvation serves, as already shown, to 
prevent insects from being washed away by the rain ; but it 
likewise serves for another end. When a number of glands 
have been powerfully excited by bits of meat, insects, or any 
other stimulus, the secretion often trickles down the leaf, and 
is caught by the incurved edges, instead of rolling off and 
being lost. As it runs down the channel, fresh glands are 
able to absorb the animal matter held in solution. Moreover, 
the secretion often collects in little pools withia the channel. 



Chap. XVI.] SECRETION, ABSORPTION, DIGESTION. 307 

or in tlie spoon-like tips of the leaves ; and I ascertained that 
hits of albumen, fibrin, and gluten are here dissolved more 
quickly and completely than on the surface of the leaf, 
■where the secretion cannot accumulate ; and so it would be 
with naturally caught insects. The secretion was repeatedly 
seen thus to collect on the leaves of plants protected from the 
rain ; and with exposed plants there would be still greater need 
of some provision to prevent, as far as possible, the secretion, 
with its dissolved animal matter, being wholly lost. 

It has already been remarked that plants growing in a 
state of nature have the margins of their leaves much more 
strongly incurved than those grown in pots and prevented 
from catching many insects. We have seen that insects 
washed down by the rain from all parts of the leaf often 
lodge within the margins ; which are thus excited to curl 
farther inwards ; and we may suspect that this action, many 
times repeated during the life of the plant, leads to their 
permanent and well-marked incurvation. I regret that this 
view did not occur to me in time to test its truth. 

It may here be added, though not immediately bearing on 
our subject, that when a plant is pulled up, the leaves 
immediately curl downwards so as to almost conceal the 
roots, — a fact which has been noticed by many persons. 
I suppose that this is due to the same tendency which causes 
the outer and older leaves to lie flat on the ground. It 
further appears that the flower-stalks are to a certain extent 
irritable, for Dr. Johnson states that they " bend backwards 
if rudely handled." * 

Secretion, Absorption, and Digestion. — I will first give my 
observations and experiments, and then a summary of the 
results. 

The Effects of Objects containing Soluble Nitrogenous Matter. 

(1) Flies were placed on many leaves, and excited the glands to 
secrete copiously ; the secretion always becoming acid, though not so 
iefore. After a time these insects were rendered so tender that their 
limbs and bodies could be separated by a mere touch, owing no doubt 



* ' English Botany,' by Sir J. E. bending or shaking a turgesoent stem. 

Smith ; with coloured figures by J. This would be likely to occur in the 

Sowerby ; edit, of 1832, tab. 24, 25, course of the " rough handling," and 

26. [It is well known that perma- we may perhaps thus account for 

nent curvatures may be produced by Dr. Johnson's curvatures. — F. D.] 

X 2 



308 PINGUICULA VUL6AEIS. [Chap. XVI. 

to the digestion and disintegration of their muscles. The glands in 
contact with a small fly continued to secrete for four days, and then 
became almost dry. A narrow strip of this leaf was cut off, and the 
glands of the longer and shorter hairs, which had lain in contact for 
the four days with the fly, and those which had not touched it, were 
compared under the microscope, and presented a wonderful contrast. 
Those which had been in contact were filled with brownish granular 
matter, the others with homogeneous fluid. There could therefore he 
no doubt that the former had absorbed matter from the fly. 

(2) Small bits of roast meat, placed on a leaf, always caused much 
acid secretion in the course of a few hours — in one case within 40 m. 
When thin fibres of meat were laid along the margin of a leaf which 
stood almost upright, the secretion ran down to the ground. Angular 
bits of meat, placed in little pools of the secretion near the margin, 
were in the course of two or three days much reduced in size, rounded, 
rendered more or less colourless and transparent, and so much softened 
that they fell to pieces on the slightest touch. In only one instance 
was a very minute particle completely dissolved, and this occurred 
within 48 hrs. When only a small amount of secretion was excited, 
this was generally absorbed in from 24 hrs. to 48 hrs. ; the glands 
being left dry. But when the supply of secretion was copious, round 
either a single rather large bit of meat, or roimd 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 cartilage from the leg-bone of a 
sheep were laid on a leaf. After 10 hrs, 30 m. some acid secretion was 
excited, but the cartilage appeared little or not at all affected. After 
24 hrs. the cubes were rounded and much reduced in size ; after 32 hrs. 
they were softened to the centre, and one was quite liquefied ; after 
35 hrs. mere traces of solid cartilage were left; and after 48 hrs. a 
trace could still be seen through a lens in only one of the three. After 
82 hrs. not only were all three cubes completely liquefied, but all the 
secretion was absorbed and the glands left dry. 

(4) Small cubes of albumen were placed on a leaf ; in 8 hrs. feebly 
acid secretion extended to a distance of nearly J^ of an inch round 
them, and the angles of one cube were rounded. After 24 hrs. the 
angles of all the cubes were rounded, and they were rendered through- 
out very tender; after 30 hrs. the secretion began to decrease, and 
after 48 hrs. the glands were left dry ; but very minute bits of albumen 
were still left undissolved. 

(5) Smaller cubes of albumen (about J^ or -^5 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 



Chap. XVI.] SECEETION, ABSOKPTION, DIGESTION. 309 

and transparenS After 24 hrs. two of the cubes were completely 
dissolved, and already the secretion on these glands was almost wholly 
absorbed. After 42 hrs. the two other cubes were completely dissolved. 
These four glands began to secrete again after eight or nine days. 

(6) Two large cubes of albumen, (fully -^ of an inch, 1'27 mm.) 
were placed, one near the midrib and the other near the margin 
of a leaf; in 6 hrs. there was much secretion, which after 48 hrs. 
accumulated in a little pool round the cube near the margin. This 
cube was much more dissolved than that on the blade of the leaf ; so 
that after three days it was greatly reduced in size, with all the angles 
roimded, but it was too large to be wholly dissolved. The secretion 
was partially absorbed after four days. The cube on the blade was 
much less reduced, and the glands on which it rested began to dry 
after only two days. 

(7) Fibrin excites less secretion than does meat or albumen. 
Several trials were made, but I will give only three of them. Two 
minute shreds were placed on some glands, and in 3 hrs. 45 m. their 
secretion was plainly increased. The smaller shred of the two was 
completely liquefied in 6 hrs. 15 m., and the other in 24 hrs. ; but even 
after 48 hrs. a few granules of fibrin couLl .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 then probably have 
been quickly dissolved. 

(9) A small square thin piece of pure gelatine, moistened with 
water, was placed on a leaf, and excited very little secretion in 5 hrs. 
30 m., but later in the day a greater amount. After 24 hrs. the whole 
square was completely liquefied; and this would not have occurred 
had it been left in water. The liquid was acid. 

(10) Small particles of chemically prepared casein excited acid 
secretion, but were not quite dissolved after two days ; and the glands 



310 PINGUICULA VULGAEIS. [Chap. XVI. 

then began to dry. Nor could their complete dissolution have heen 
expected from what we have seen with Drosera. 

(11) Minute drops of skimmed milk were placed on a leaf, and these 
caused the glands to secrete freely. After 3 hrs. the milk was found 
curdled, and after 23 hrs. the curds were dissolved. On placing the 
now clear drops under the microscope, nothing could be detected except 
some oil-globules. The secretion, therefore, dissolves fresh casein. 

(12) Two fragments of a leaf were immersed for 17 hrs., each in a 
drachm of a solution of carbonate of ammonia, of two strengths, 
namely of one part to 437 and 218 of water. The glands of the 
longer and shorter hairs were then examined, and their contents found 
aggregated into granular matter of a brownish-green colour. These 
granular masses were seen by my son slowly to change their forms, 
and no doubt consisted of protoplasm. The aggregation was more 
strongly pronounced, and the movements of the protoplasm more rapid, 
within the glands subjected to the stronger solution than in the others. 
The experiment was repeated with tlie same result ; and on this 
occasion I observed that the protoplasm had shrunk a little from the 
walls of the single elongated cells forming the pedicels. In order to 
observe the process of aggregation, a narrow strip of leaf was laid 
edgeways under the microscope, and the glands were seen to be quite 
transparent; a little of the stronger solution (viz. one part to 218 of 
water) was now added under the covering glass ; after an hour or two 
the glands contained very fine granular matter, which slowly became 
coarsely granular and slightly opaque ; but even after 5 hrs. not as yet 
of a brownish tint. By this time a few rather large, transparent, 
globular masses appeared within the upper ends of the pedicels, and the 
protoplasm lining their walls had shrunk a little. It is thus evident 
that the glands of Pinguicula absorb carbonate of ammonia ; but they 
do not absorb it, or are not acted on by it, nearly so quickly as 
those of Drosera. 

(13) Little masses of tho orange-coloured pollen of the common pea, 
placed on several leaves, excited the glands to secrete freely. Even a 
very few grains which accidentally fell on a single gland caused the 
drop surrounding it to increase so much in size, in 23 hrs., as to 
be manifestly larger than the drops on the adjoining glands. Grains 
subjected to the secretion for 48 hrs. did not emit their tubes ; they 
were quite discolouj'ed, and seemed to contain less matter than before ; 
that which was left being of a dirty colour, including globules of oil. 
They thus differed in appearance from other grains kept in water for 
the same length of time. The glands in contact with the pollen-grains 
had evidently absorbed matter from them; for they had lost their 
natural pale-green tint, and contained aggregated globular masses of 
protoplasm. 

(14) Square bits of the leaves of spinach, cabbage, and a saxifrage, 
and the entire leaves of Erica tetralix, all excited the glands to 
increased secretion. The spinach was the most effective, for it caused 
the secretion evidently to increase in 1 hr. 40 m., and ultimately to run 



Chap. XVI.] SECEETION, ABSORPTION, DIGESTION. 311 

some way down the leaf ; but tlie glands soon began to dry, viz. after 
35 hrs. The leaves of Erica telralix began to act in 7 hrs. 30 m., but 
never caused much secretion ; nor did the bits of leaf of the saxifrage, 
though in this case the glands continued to secrete for seven days. 
Some leaves of Pinguicula were sent me from North Wales, to which 
leaves of Erica tetralix and of an unknown plant adhered ; and the 
glands in contact with them had their contents plainly aggregated, as 
if they had been in contact with insects ; whilst the other glands on 
the same leaves contained only clear homogeneous fluid. 

(15) Seeds. — A considerable number of seeds or fruits selected by 
hazard, some fresh and some a year old, some soaked for a short time 
in water and some not soaked, were tried. The ten following kinds, 
namely, cabbage, radish, Anemone ncmorosa, Suinex acetosa, Carex 
sylvaticoi, mustard, turnip, cress, lianunculus acris, and Avena pubescens, 
all excited much secretion, which was in several cases teste! and formd 
always acid. The five first-named seeds excited the glands more than 
the others. The secretion was seldom copious until about 24 hrs. had 
elapsed, no doubt owing to the coats of the seeds not being easily 
permeable. Nevertheless, cabbage seeds excited some secretion in 4 hrs. 
30 m. ; and this increased so much in 18 hrs. as to run down the leaves. 
Tlie 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 lirs. 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 amotmt of 
secretion, namely, celery, parsnip, caraway, Linum grandiflorum, Cassia, 
Tri/olium pannonicum, Flantago, onion, and Bromus. Most of these 
seeds did not excite any secretion until 48 hrs. had elapsed, and in the 
case of the Trifolium only one seed acted, and this not until the third 
day. Althougli the seeds of the Flantago excited very little secretion, 
the glands continued to secrete for six days. Lastly, the five following 
kinds excited no secretion, though left on the leaves for two or three 
days, namely, lettuce. Erica tetralix, Atriplex hortensis, Phalaris 
canariensis, and wheat. Nevertheless, when the seeds of the lettuce, 
wheat, and Atriplex were split open and applied to leaves, secretion was 
excited in considerable quantity in 10 hrs., and I believe that some 
was excited in six hours. In the case of the Atriplex the secretion ran 
down to the margin, and after 24 hrs. I speak of it in my notes " as 
immense in quantity, and acid." The split seeds also of the Trifolium 
and celery acted powerfully and quickly, though the whole seeds 
caused, as we have seen, very little secretion, and only after a long 
interval of time. A slice of the common pea, which however was not 
tried whole, caused secretion in 2 hrs. From these facts we may 
conclude that the great difference in the degree and rate at which 
various kinds of seeds excite secretion, is chicfiy or wholly due to the 
different permeability of their coats. 



312 PINGUICULA VULGAEIS. [Chap. XVI. 

Some tliin slices of the common pea, which had been previously 
soaked for 1 hr. in water, were placed on a leaf, and quickly excited 
much acid secretion. After 24 hrs. these slices were compared under a 
high power with others left in water for the same time; the latter 
contained so many fine granules of legumin that the slide was rendered 
muddy ; whereas the slices which had been subjected to the secretion 
were much cleaner and more transparent, the granules of legumin 
apparently having been dissolved. A cabbage seed which had lain for 
two days on a leaf and had excited much acid secretion, was cut into 
slices, and these were compared with those of a seed which had been 
left for the same time in water. Those subjected to the secretion were 
of a paler colour; their coats presenting the greatest differences, for 
they were of a pale dirty tint instead of chestnut-brOwn. The glands 
on which the cabbage seeds had rested, as well as those bathed by the 
surrounding secretion, differed greatly in appearance from the other 
glands on the same leaf, for they all contained brownish granular 
matter, proving that they had absorbed matter from the seeds. 

That the secretion acts on the seeds was also shown by some of 
them being killed, or by the seedlings being injured. Fourteen cabbage 
seeds were left for three days on leaves and excited much secretion ; 
they were then placed on damp sand under conditions known to be 
favourable for germination. Three never germinated, and this was a 
far larger proportion of deaths than occurred with seeds of the same lot, 
which had not been subjected to the secretion, but were otherwise 
treated in the same manner. Of the eleven seedlings raised, three had 
the edges of their cotyledons slightly browned, as if scorched ; and the 
cotyledons of one grew into a curious indented shape. Two mustard 
seeds germinated ; but their cotyledons were marked with brown 
patches and their radicles deformed. Of two radish seeds, neither 
germinated ; whereas of many seeds of the same lot not subjected to 
the secretion, all, excepting one, germinated. Of the two Rumex seeds, 
one died and the other germinated ; but its radicle was brown and soon 
withered. Both seeds of the Avena germinated, one gi'ew 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 cf 
various kinds were found adhering to the leaves of plants growing in a 
state of nature ; and of these, though kept for five months on damp 
sand, none germinated, some being then evidently dead. 

The Effects of Objects not containing Soluble Nitrogenous Matter. 

(16) It has already been shown that bits of glass, placed on leaves, 
excite little or no secretion. The small amount which lay beneath the 
fragments was tested and found not acid. A bit of wood excited 
no secretion ; nor did the several kinds of seeds of which the coats are 
not permeable to the secretion, and which, therefore, acted like inorganic 
bodies. Cubes of fat, left for two days on a leaf, produced no effect. 



CiiAP. XVI.] SECRETION, ABSORPTION, DIGESTION. 313 

(17) A particle of white sugar, placed on a leaf, formed in 1 hr. 10 ni. 
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 deliquescence ; but this was proved not to be the case. The 
particle on the leaf caused so much secretion that in the course of 4 hrs. 
it ran down across two-thirds of the leaf. After 8 hrs. the leaf, which 
was concave, was actually fllled with very viscid fluid ; and it particu- 
larly deserves notice that this, as on the former occasion, was not in the 
least acid. This great amount of secretion may be attributed to exosmose. 
The glands which had been covered for 24 hrs. by this fluid did not 
difi'er, 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 arable were placed on a leaf, and they 
certainly caused in 1 hr. 20 m. a slight increase of secretion. This 
continued to increase for the next 5 hrs., that is for as long a time as 
the leaf was observed. 

(19) Six small particles of dry starch of commerce were placed on a 
leaf, and one of these caused some secretion in 1 hr. 15 m., and the 
others in from 8 hrs. to 9 hrs. The glands which bad 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 dinunution was perceptible. We may therefore 
conclude that the secretion cannot dissolve starch. The increase caused 
by this substance may, I presume, be attributed to exosmose. But 
I am surprised that starch acted so quickly and powerfully as it did, 
though in a less degree than sugar. Colloids are known to possess some 
slight power of dialysis; and on placing the leaves of a Primula in 
water, and others in syrup and diffused starch, those in the starch 
became flaccid, but to a less degree and at a much slower rate than the 
leaves in the syrup ; those in water remaining all the time crisp. 



314 PINGUIOULA VULGARIS, [Chap. XVI. 

Prom tlie foregoing experiments and observations we see 
tliat objects not containing soluble matter have little or no 
power of exciting the glands to secrete. Non-nitrogenous 
fluids, if dense, cause the glands to pour forth a large supply 
of viscid fluid, but this is not in the least acid. On the 
other hand, the secretion from glands excited by contact 
with nitrogenous solids or liquids is invariably acid, and is 
so copious that it often runs down the leaves and collects 
within the naturally incurved margins. The secretion in 
this state has the power of quickly dissolving, that is of 
digesting, the muscles of insects, meat, cartilage, albumen, 
fibrin, gelatine, and casein as it exists in the curds of milk.* 
The glands are strongly excited by chemically prepared 
casein and gluten ; but these substances (the latter not 
having been soaked in weak hydrochloric acid) are only 
partially dissolved, as was likewise the case with Drosera. 
The secretion, when containing animal matter in solution, 
whether derived from solids or from liquids, such as an 
infusion of raw meat, milk, or a weak solution of carbonate 
of ammonia, is quickly absorbed ; and the glands, which 
were before limpid and of a greenish colour, become brownish 
and contain masses of aggregated granular matter. This 
matter, from its spontaneous movements, no doubt consists of 
protoplasm. No such effect is produced by the action of non- 
nitrogenous fluids. After the glands have been excited to 
secrete freely, they cease for a time to secrete, but begin 
again in the course of a few days. 

Glands in contact with pollen, the leaves of other plants, 
and various kinds of seeds, pour forth much acid secretion, 
and afterwards absorb matter probably of an albuminous 
nature from them. Nor can the benefit thus derived be 
insignificant, for a considerable amount of pollen must be 
blown from the many wind-fertilised carices, grasses, &c., 
growing where Pinguicula lives, on to the leaves thickly 
covered with viscid glands and forming large rosettes. Even 



* [Pf^ffer (' Ueber fleischfessende same use in the Italian Alps. The 

Pflanzen,' in the ' Landwirthsohaft. property of the plant seems to be 

Jahrbiicher,' 1877) quotes Linnaeus widely known among primitive 

(' Flora Lapponica,' 1737, p. 10) to the people, for, within the last 30 years, 

effect that certain Lapland tribes use it was used as rennet by mountain 

the leaves of Pinguicula to coagulate farmers in North Wales. I have 

milk. PfefFer learnt from an old myself succeeded in curdling milk 

shepherd that they are put to the with this vegetable rennet. — F. D.] 



Chap. XVI.] PINGUICULA LUSITANICA. 315 

a few grains of pollen on a single gland causes it to secrete 
copiously. We have also seen how frequently tli6 small 
leaves of Erica tetralix and of other plants, as well as various 
kinds of seeds and fruits, epecially of Carex, adhere to the 
leaves. One leaf of the Pinguicula had caught ten of the 
little leaves of the Erica; and three leaves on the same 
plant had each caught a seed. Seeds subjected to the action 
of the secretion are sometimes killed, or the seedlings injured. 
We may therefore conclude that Pinguicula vulgaris, with its 
small roots, is not only supported to a large extent by the 
extraordinary number of insects which it habitually captures, 
but likewise draws some nourishment from the pollen, leaves, 
and seeds of other plants which often adhere to its leaves. 
It is therefore partly a vegetable as well as an animal 
feeder. 

Pinguicula geandiflora. 

This species is so closely allied to the last that it is ranked 
by Dr. Hooker as a sub-species. It differs chiefly in the 
larger size of its leaves, and in the glandular hairs near the 
basal part of the mid-rib being longer. But it likewise 
differs in constitution; I hear from Mr. Ealfs, who was so 
kind as to send me plants from Cornwall, that it grows in 
rather different sites ; and Dr. Moore, of the Glasnevin 
Botanic Gardens, informs me that it is much more manage- 
able under culture, growing freely and flowering annually ; 
whilst Pinguicula vulgaris has to be renewed every year. 
Mr. Ealfs found numerous insects and fragments of insects 
adhering to almost all the leaves. These consisted chiefly 
of Diptera, with some Hymenoptera, Homoptera, Coleoptera, 
and a moth ; on one leaf there were nine dead insects, besides 
a few still alive. He also observed a few fruits of Carex 
pulicaris, as 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 i-ow along one margin of another 
leaf, and by the next morning this whole margin was curled 
inwards, exactly as in the case of Pinguicula vulgaris. 

Pinguicula lusitanica. 

This species, of which living specimens were sent me by 
Mr. Ealfs from Cornwall, is very distinct from the two fore- 



316 PINGUIOULA LTJSITANICA. [Chap. XVI. 

going ones. The leaves are rather smaller, much more 
transparent, and are marked with purple branching veins. 
The margins of the leaves are much more involuted ; those of 
the older ones extending over a third of the space between 
the midrib and the outside. As in the two other species,, the 
glandular hairs consist of longer and shorter ones, and have 
the same structure ; but the glands differ in being purple, 
and in often containing granular matter before they have 
been excited. In the lower part of the leaf, almost half the 
space on each side between the midrib and margin is destitute 
of glands ; these being replaced by long, rather stiff, multi- 
cellular hairs, which intercross over the midrib. These hairs 
perhaps serve to prevent insects from settling on this part of 
the leaf, where there are no viscid glands by which they 
could be caught ; but it is hardly probable that they were 
developed for this purpose. The spiral vessels proceeding 
from the midrib terminate at the extreme margin of the leaf 
in spiral cells ; but these are not so well developed as in the 
two preceding species. The flower-peduncles, sepals, and 
petals, are studded with glandular hairs, like those on the 



The leaves catch many small insects, which are found 
chiefly beneath the involuted margins, probably washed there 
by the rain. The colour of the glands on which insects have 
long lain is changed, being either brownish or pale purple, 
with their contents coarsely granular ; so that they evidently 
absorb matter from their prey. Leaves of the Erica tetralix, 
flowers of a Galium, scales of grasses, &c., likewise adhered to 
some of the leaves. Several of the experiments which were 
tried on Pinguicula vulgaris were repeated on Pinguicula 
lusiianica, and these will now be given. 

(1) A moderately sized and angular bit of albumen was placed on 
one side of a leaf, halfway tetween 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 ■g'g 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-iiqueSed 
state. 

(2) A moderately sized hit of albumen was placed near the apex of 



Chap. XVI.] PINGUICULA LUSITANICA. 317 

a leaf, under the naturally incurved margin. In 2 hrs. 30 m. much 
secretion was excited, and next morning the margin on this side was 
more incurved than the opposite one, but not to so great a degree 
as m the last case. The margin unfolded at the same rate as before. 
A large proportion of the albumen was dissolved, a remnant beino- stiU 
left. 

(3) Large bits of albumen were laid in a row on the midi'ibs of two 
leaves, but produced in the course of 24 hrs. no effect ; nor could this 
have been expected, for even had glands existed here, the long bristles 
would have prevented the albumen from coming in contact with them. 
On both leaves the bits were now pushed close to one margin, and in 
3 hrs. 30 m. this became so greatly inflected that the outer surface, 
touched the blade ; the opposite margin not being in the least affected. 
After three days the margins of both leaves with the albumen were 
still as much infieoted as ever, and the glands were still secreting 
copiously. With Pinguicula vulgaris I have never seen inflection 
lasting so long. 

(4) Two callage seeds, after being soaked for an hour in water, were 
placed near the margin of a leaf, and caused in 3 hrs. 20 m. increased 
secretion and incurvation. After 24 hrs. the leaf was partially 
unfolded, but the glands were still secreting freely. These began to 
dry in 48 hrs., and after 72 hrs. were almost dry. The two seeds were 
then placed on damp sand under favourable conditions for growth ; but 
they never germinated, and after a time were found rotten. They had 
no doubt been killed by the secretion. 

(5) Small bits of a spinach leaf caused in 1 hr. 20 m. increased se- 
cretion ; and after 3 hrs. 20 m. plain incurvation of the margin. The 
margin was well inflected after 9 hrs. 15 m., but after 24 hrs. was 
almost fully re-expanded. The glands in contact with the spinach 
became dry in 72 hrs. Bits of albumen had been placed the day 
before on the opposite margin of this same leaf, as well as on that of a 
leaf with cabbage seeds, and these margins remained closely inflected 
for 72 hrs., showing how much more enduring is the effect of albumen 
than of spinach leaves or cabbage seeds. 

(6) A row of small fragments of glass was laid along one margin of 
a leaf ; no effect was produced in 2 hrs. 10 m., but after 3 hrs. 25 m. 
there seemed to be a trace of inflection, and this was distinct, though 
not strongly marked, after 6 hrs. The glands in contact with the 
fragments now secreted more freely than before ; so that they appear 
to be more easily excited by the pressure of inorganic objects 
than are the glands of Finguicula 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. Tliis latter trial was made 
because I thought that the hairs might perhaps be sensitive to a touch, 
like the filaments of Dionsea. 



318 PINGUICULA LTJSITANICA. [Chap. XVI. 

(7) The flower-peduncles, sepals and petals bear glands in general 
appearance like those on the leaves. A piece of a flower-peduncle was 
therefore left for 1 hr. in a solution of one part of carbonate of 
ammonia to 437 of water, and this caused the glands to change from 
bright pink to a dull purple colour ; but their contents exhibited no 
distinct aggregation. After 8 hrs. 30 m. they became colourless. Two 
minute cubes of albumen were placed on the glands of a flower- 
peduncle, and another cube on the glands of a sepal ; but they were 
not excited to increased secretion, and the albumen after two days was 
not in the least softened. Hence these glands apparently differ greatly 
in function from those on the leaves. 

From the foregoing observations on Pinguicula lusitanica we 
see that the naturally muoh incurved margins of the leaves 
are excited to curve still farther inwards by contact vrith 
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 v^hich are 
caught in large numbers by the viscid secretion. The glands 
on the flower-peduncles seem to have no such power. This 
species differs from Pinguicula vulgaris and grandiflora in the 
margins of the leaves, when excited by organic bodies, being 
inflected to a greater degree, and in the inflection lasting for 
a longer time. The glands, also, seem to be more easily 
excited to increased secretion by bodies not yielding soluble 
nitrogenous matter. In other respects, as far as my observa- 
tions serve, all three species agree in their functional powers. 



Chap. XVII.] UTEICULAEIA NE6LECTA. 319 



CHAPTEE XVII. 

Uteioulahia. 

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

I WAS led to investigate the habits and structure of the 
species of this genus partly from their helonging 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 Lehrn,']- I subse- 
quently received the true Utricularia vulgaris from Yorkshire. 
Since drawing up the following description from my own 
observations and those of my son, Francis Darwin, an 
important memoir by Prof. Cohn on Utricularia vulgaris has 
appeared ; f and it has been no small satisfaction to me to 
find that my account agrees almost completely with that of 
this distinguished observer. I will publish my description 
as it stood before reading that by Prof. Cohn, adding 
occasionally some statements on his authority. 



» The ' Quart. Mag. of the High H. M. Wilkinson, of Bistern, for 

Wycombe Nat. Hist. Soc' July 1868, having sent me several fine lots of 

p. 5. Delpino (' Ult. Osservaz. suUa this species from the New Forest. 

Dicogamia,' &c. 1868-1869, p. 16) Mr. Kalfs was also so kind as to send 

also quotes Crouan as having found me living plants of the same species 

(1858) crustaceans within the blad- from near Penzance in Cornwall, 

ders of Utricularia vulgaris. + ' Beitrage zur Biologic der Pflan- 

t I am much indebted to the Rev. zen,' drittes Heft, 1875. 



320 



UTEICULAEIA NEGLECTA. 



[Chap. XVII. 



Utricularia neglecta. — -The general appearance of a branch, 
(atout twice enlarged), with the pinnatifid leaves hearing 
bladders, is represented in the following sketch (fig. 17). 
The leaves continually bifurcate, so that a full-grown one 
terminates in from twenty to thirty points. Each point is 
tipped by a short, straight bristle ; and slight notches on the 




Fig. 11. 

(UtriaiXaria neglecta.) 

Branch with the divided leaves bearing bladders ; about twice enlarged. 



sides of the leaves bear similar bristles. On both surfaces 
there are many small papillae, crowned with two hemi- 
spherical cells in close contact. The plants float near the 
surface of the water, and are quite destitute of roots, even 
during the earliest period of growth.* They commonly 



* I infer that this is the case from 
a drawing of a seedling given by Dr. 
Warming in his paper, " Bidrag til 
Kundskaben om Lentibulariacese," 



from the ' Videnskabelige Meddelel- 
ser,' Copenhagen, 1874, Nos. 3-7, pp. 
33-58. [Cf. Kamienski, ' Bot. Zeit.' 
1877, p. 765.] 



Chap. XVII.] STRUCTUEE OP THE BLADDER. 



321 



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'^ of an inch (2 '64 mm.) in length. 
They are translucent, of a green colour, and the walls are 
formed of two layers of cells. The exterior cells are poly- 
gonal and rather large ; but at many of the points where the 
angles meet, there are smaller rounded cells. These latter 
support short conical projections, surmounted by two hemi- 
spherical cells in such close apposition that thoy appear 




Fig. 18. 

i^Utriculariu neglecta.) 

Bladdcv ; much enlarged, c, collar indistinctly seen through the walls. 



united ; but they often separate a little when immersed in 
certain fluids. The papilla 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. 

The bladders are filled with water. They generally, but 
by no means always, contain bubbles of air. According to 
the quantity of the contained water and air, they vary much 



'322 



UTEICULAKIA NEGLECTA. 



[CHAr. XVII. 



in tMc];ness, but are always somewliat 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 Eev. H. M. 'Wilkinson examined plants for 
me in a state of nature, and found this commonly to be the 
case, but the younger bladders often had their valves turned 
upwards. 

The general appearance of a bladder viewed laterally, with 
the appendages on the near side alone represented, is shown 
on the preceding page (fig. 18). The lower side, where 
the ■ footstalk arises, is nearly straight, and I have called it 




FiG. 19. 

( UtHculai-ia neglecta.) 

Valve of bladder; greatly enlarged. 



the ventral surface. The other or dorsal surface is convex, 
and terminates in two long prolongations, formed of several 
rows of cells, containing chlorophyll, and bearing, chiefly on 
the outside, six or seven long, pointed, multicellular bristles. 
These prolongations of the bladder may be conveniently 
called the antennas, for the whole bladder (see fig. 17) 
curiously resembles an entomostracan crustacean, the short 
footstalk representing the tail. In fig. 18, the near antenna 
alone is shown. Beneath the two antennaa 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 bristleiS project outwards j but only 



Chap. XVH.] STRUCTURE OF THE BLADDER. 



323 



those (four in number) on the near side are shown in the 
drawing. These bristles, together with those borne by the 
antennss, form a sort of hollow cone surrounding the 
entrance. 

The valve slopes into the cavity of the bladder, or upwards 
in fig. 18. It is attached on all sides to the bladder, 
excepting by its posterior margin, or the lower one in fig. 
19, which is free, and forms one side of the slit-like orifice 
leading into the bladder. This margin is sharp, thin, and 
smooth, and rests on the edge of a rim or collar, which dips 
deeply into the bladder, as shown in the longitudinal section 
(fig. 20) of the collar and valve ; it is also shown at c, in 
fig. 18. The edge of the valve can thus open only inwards. 




Fig. 20. 
( UtricuJarki neglecta.) 
Longitudinal vertical section through the ventral portion of a bladder; showing valve and 
collar. V, valve ; the whole projection above c forms the collar ; b, bifid processes ; s, 
ventral surface of bladder. 



As both the valve and collar dip into the bladder, a hollow 
or depression is here formed, at the base of which lies the 
slit-like orifice. 

The valve is colourless, highly transparent, flexible and 
elastic. It is convex in a transverse direction, but has been 
drawn (fig. 19) in a flattened state, by which its apparent 
breadth is increased. It is formed, according to Cohn, of two 
layers of small cells, which are continuous with the two 
layers of larger cells forming the walls of the bladder, of 
which it is evidently a prolongation. Two pairs of trans- 
parent pointed bristles, about as long as the valve itself, 
arise from near the free posterior margin (fig. 19), and point 
obliquely outwards in the direction of the antennae. There 

Y 2 



324 UTBICULAEIA NEGLECTA. [Chap. XVU. 

are also on the surface of the valve numerous glands, as I 
will call them; for they have the power of absorption, 
though I doubt whether they ever secrete. They consist of 
three kinds, which to a certain extent graduate into one 
another. Those situated round the anterior margin of the 
valve (upper margin in fig. 19) are very numerous and 
crowded together ; they consist of an oblong head on a long 
pedicel. The pedicel itself is formed of an elongated eel], 
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 tihort 
upper cell of the pedicel of the oblong glands. The glands of 
the third kind have transversely elongated heads, and are 
seated on very short footstalks ; so that they stand parallel 
and close to the surface of the valve; they may be called 
the two-armed glands. The cells forming all these glands 
contain a nucleus, and are lined by a thin layer of more or 
less granular protoplasm, the primordial utricle ofMohl. 
They are filled with fluid, which must hold much matter in 
solution, judging from the quantity coagulated after they 
have been long immersed in alcohol or ether. The depression 
in which the valve lies is also lined with innumerable glands; 
those at the sides having oblong heads and elongated pe- 
dicels, exactly like the glands on the adjoining parts of the 
valve. 

The collar (called the peristome by Cohn) is evidently 
formed, like the valve, by an inward projection of the walls 
of the bladder. The cells composing the outer surface, or 
that facing the valve, have rather thick walls, are of a 
brownish colour, minute, very numerous, and elongated ; the 
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- 
tween the inner and outer surface consists of coarse cellular 
tissue (fig. 20). The inner side is thickly covered with 
delicate bifid processes, hereafter to be described. The collar 
is thus made thick ; and it is rigid, so that it retains the 
same outline whether the bladder contains little or much air 
and water. This is of great importance, as otherwise the 
thin and flexible valve would be liable to be distorted, and 
in this case would not act properly. 



CiiAP. XVII.] STEUCTURE OF THE BLADDEE. 



325 



Altogether the entrance into the hladder, formed by the 
transparent valve, with its four obliquely projecting bristles, 
its numerous diversely shaped glands, surrounded by the 
collar, bearing glands on the inside and bristles on the out- 
side, together with the bristles borne by the antennae, presents 
an extraordinarj' complex appearance when viewed under the 
microscope. 

We will now consider the internal structure of the bladdur. 
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 




'|FlG. 21. 

(^Utricularia neglecta.) 

Small portion of inside of bladder, 
much enlarged, sbowing quadritid 
processes. 




Fig. 22. 
(ririculatna neglecta.) 
One of the quadrii5d processes 
greatly enlarged. 



four divergent arms ; whence their name of quadrifid 
processes. They arise from small angular cells, at the 
junctions of the angles of the larger cells which form the 
interior of the bladder. The middle part of the upper 
surface of these small cells projects a little, and then con- 
tracts into a very short and narrow footstalk which bears the 
four arms (fig. 22). Of these, two are long, but often of not 
quite equal length, and project obliquely inwards and 
towards the posterior end of the bladder. The two others 
are much shorter, and project at a smaller angle, that is, are 
more nearly horizontal, and are directed towards the anterior 



326 UTEICULAEIA NEGLECTA. [Chap. XVII. 

end of tlie bladder. These arms are only moderate^ sharp ; 
they are composed of extremely thin transparent membrane, 
so that they can be bent or doubled in any direction without 
being broken. They are lined with a delicate layer of 
protoplasm, as is likewise the short conical projection from 
which they arise. Each arm generally (but not invariably) 
contains a minute, faintly brown particle, either rounded 
or more commonly elongated, which exhibits incessant 
Brownian movements. These particles slowly change their 
positions, and travel from one end to the other of the arms, 
but are commonly found near their bases. They are present 
in the quadrifids of young bladders, when only about a third 
of their full size. They do not resemble ordinary nuclei, but 
I believe that they are nuclei in a modified condition, for 
when absent, I could occasionally just distinguish in their 
places a delicate halo of matter, including a darker spot. 
Moreover, the quadrifids of TJtricularia montana contain 
rather larger and much more regularly spherical, but 
otherwise similar, particles, which closely resemble the 
nuclei in the cells forming the walls of the bladders. In the 
present case there were sometimes two, three, or even more, 
nearly similar particles within a single arm ; but, as we shall 
hereafter see, the presence of more than one seemed always 
to be connected with the absorption of decayed matter. 

The inner side of the collar (see the previous fig. 20) is 
covered with several crowded rows of processes, difi'ering in 
no important respect from the quadrifids, except in bearing 
only two arms instead of four; they are, however, rather 
narrower and more delicate. I shall call them the bifids. 
They project into the bladder, and are directed towards its 
posterior end. The quadrifid and bifid processes no doubt 
are homologous with the papillss on the outside of the bladder 
and of the leaves ; and we shall see that they are developed 
from closely similar papillse. 

The Uses of the several Parts. — After the above long but 
necessary description of the parts, we will turn to their uses. 
The bladders have been supposed by some authors to serve 
as floats ; but branches which bore no bladders, and others 
from which they had been removed, floated perfectly, owing 
to the air in the intercellular spaces. Bladders containing 
dead and captured animals usually include bubbles of air, but 
these cannot have been generated solely by the process of 
decay, as I have often seen air in young, clean, and empty 



CiiAi'. XVII.] MANNEE OF CAPTURING PREY. 327 

nladders ; and some old bladders with much decaying matter 
had no bubbles. 

The real use of the bladders is to capture small aquatic 
animals, and this they do on a large scale. In the first lot of 
plants, which I received from the New Forest early in July, 
a large proportion of the fully grown bladders contained prey ; 
in a second lot, received in the beginning of August, most of 
the bladders were empty, but plants had been selected which 
had grown in unusually pure water. In the first lot, my son 
examined seventeen bladders, including prey of some kind, 
and eight of these contained entomostracan crustaceans, three 
larvas of insects, one being still alive, and six remnants of 
animals so much decayed that their nature could not be 
distinguished. I picked out five bladders which seemed very 
full, and found in them four, five, eight, and ten crustaceans, 
and in the fifth a single much elongated larva. In five other 
bladders, selected from containing remains, but not appearing 
very full, there were one, two, four, two, and five crustaceans. 
A plant of Utricularia vulgaris, which had been kept in almost 
pure water, was placed by Cohn one evening into water 
swarming with crustaceans, and by the next morning most 
of the bladders contained these animals entrapped and 
swimming round and round their prisons. They remained 
alive for several days ; but at last perished, asphyxiated, as I 
suppose, by the oxygen in the water having been all con- 
sumed. Freshwater worms were also found by Cohn in some 
bladders. In all cases the bladders with decayed remains 
swarmed with living Algas of many kinds, Infusoria, and 
other low organisms, which evidently lived as intruders. 

Animals enter the bladders by bending inwards the pos- 
terior free edge of the valve, which from being liighly 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 
tdge fits, I may mention that my son found a Daphnia which 
had inserted one of its antennee into the slit, and it was thus 
held fast during a whole day. On three or four occasions I 
have seen long narrow Jarvas, both dead and alive, wedged 
between the corner of the valve and collar, with half their 
bodies within the bladder and half out. 

As I felt much difficulty in understanding how such 



328 UTEICULAEIA XEGLECTA. [Chap. XVII. 

minute and weak animals, as are often captured, could force 
their way into the bladders, I tried many experiments to 
ascertain how this was affected. The free margin of the 
valve bends so easily that no resistance is felt when a needle 
or thin bristle is inserted. A thin human hair, fixed to a 
handle, and cut off so as to project barely ^ of an inch, en- 
tered with some dif&culty ; a longer piece yielded instead of 
entering. On three occasions minute particles of blue glass 
(so as to be easily distinguished) were placed on valves 
whilst under water ; and on trying gently to move them 
with a needle, they disappeared so suddenly that, not see- 
ing what had happened, I thought that I had flirted them 
ofi'; but on examining the bladders, they were found safely 
enclosed. The same thing occurred to my son, who placed 
little cubes of green box-wood (about ^^5^ of an inch, • 423 mm.) 
on some valves; and thrice in the act of placing them on, or 
whilst gently moving them to another spot, the valve sud- 
denly opened and they were engulfed. He then placed 
similar bits of wood on other valves, and moved them about 
for some time, but they did not enter. Again, particles of 
blue glass were placed by me on three valves, and extremely 
minute shavings of lead on two other valves ; after 1 or 2 hrs. 
none had entered, but in from 2 to 5 hrs. all five were 
enclosed. One of the particles of glass was a long splinter, 
of which one end rested obliquely on the valve, and after a 
few hours it was found fixed, half within the bladder and 
half projecting out, with the edge of the valve fitting closely 
all round, except at one angle,, where a small open space was 
left. It was so firmly fixed, like the above-mentioned larvse, 
that the bladder was torn from the branch and shaken, and 
yet the splinter did not fall out. My son also placed little 
cubes (about -^V of an inch, -SOI 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 mubt have fallen by 
some accident on the valves, and then entered like the par- 
ticles of glass. 

The slow bending of the valve from the weight of particles 
of glass and even of box-wood, though largely supported by 
tbo water, is, I suppose, analogous to the slow bending of 



CnAr. XVII.] BIANNEE OF CAPTURING PEEY. 329 

colloid substances. For instance, particles of glass were 
placed on various points of narrow strips of moistened gela- 
tine, and these yielded and became bent with extreme slow- 
ness. It is much more difficult to understand how gently- 
moving a particle from one part of a valve to another causes 
it suddenly to open. 'J"o ascertain whether the valves were 
endowed with irritability, the surfaces of several were 
scratched with a needle or brushed with a fine camel-hair 
brush, so as to imitate the crawling movement of small 
crustaceans, but the valve did not open. Some bladders, 
before being brushed, were left for a time in water at tem- 
peratures between 80° and 130° P. (26° -6— 54° -4 Cent.), as, 
judging from a wide-spread analogy, this would have ren- 
dered them more sensitive to irritation, or would by itself 
have excited movement ; but no effect was produced. AN'e 
may therefore conclude that animals enter merely by forcing 
their way through the slit-like orifice ; their heads serving 
as a wedge. But I am surprised that such small and weak 
creatures as are often captured (for instance, the nauplius of 
a crustacean, and a tardigrade) should be strong enough to 
act in this manner, seeing that it was difficult to push in one 
end of a bit of hair ^ of an inch in length. Nevertheless, 
it is certain that weak and small creatures do enter, and 
Mrs. Treat, of New Jersey, has been more successful than any 
other observer, and has often witnessed in the case of 
Utriculria clandestina the whole process.* She saw a tardi- 
grade slowly walking round a bladder, as if reconnoitring ; 
at last it crawled into the depression where the valve lies, 
and then easily entered. She also witnessed the entrapment 
of various minute crustaceans. Cypris " was quite wary, 
" but nevertheless was often caught. Coming to the entrance 
" of a bladder, it would sometimes pause a moment, and then 
" dash away ; at other times it would come close up, and even 
" venture part of the way into the entrance and back out as 
" if afraid. Another, more heedless, would open the door 
" and walk in ; but it was no sooner in than it manifested 
" alarm, drew in its feet and antenna, and closed its shell." 
LarvK, apparently of gnats, when " feeding near the en- 
" trance, are pretty certain to run their heads into the net, 
" whence there is no retreat. A large larva is sometimes 



* ' Xeiv York Tribune,' reprinted iu tlie ' Card. Cliron.' 1875, p. 303. 



330 UTEICULAEIA NEGLECTA. [Chap. XVII. 

" ttree or four hours in being swallowed, the process hring- 
"ing to mind what I have witnessed when a small snake 
" makes a large frog its victim." But as the valve does 
not appear to be in the least irritable,* the slow swallowing 
process must be the effect of the onward movement of the 
larva. 

It is^difficult to conjecture what can attract so many- 
creatures, animal- and vegetable-feeding crustaceans, worms, 
tardigrades, and various larvfe, to enter the bladders. 
Mrs. Treat says that the larvse just referred to are vegetable 
feeders, and seem to have a special liking for the long 
bristles round the valve, but this taste will not account for 
the entrance of animal- feeding crustaceans. Perhaps small 
aquatic animals habitually try to enter every small crevice, 
like that between the valve and collar, in search of food or 
protection. 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 apparently serve for the same 
purpose. I believe that this is the case, because the bladders 
of some epiphytic and marsh species of Utricularia which 
live embedded either in entangled vegetation or in mud, have 
no bristles round the entrance, and these under such condi- 
tions would be of no service as a guide. Nevertheless, with 
these epiphytic and marsh species, two pairs of bristles pro- 
ject from the surface of the valve, as in the aquatic species ; 
and their use probably is to prevent too large animals from 
trying to force an entrance into the bladder, thus rupturing 
the orifice. 

As under favourable circumstances most of the bladders 
succeed in securing prey, in one case as many as ten crusta- 
ceans ; — as the valve is so well fitted to allow animals to 
enter and to prevent their escape ; — and as the inside of the 
bladder presents so singular a structure, clothed with innu- 
merable quadrifid and bifid processes, it is impossible to 
doubt that the plant has been specially adapted for securing 
prey. From the analogy of Pinguicula, belonging to the 
same family, I naturally expected tbat the bladders would 



* [Guided by her observations (' Harper's Magazine,' Feb. 1876) on the act 
of capture, Mrs. Treat concludes that the valve is irritable. — F. D.] 



CuAP. XVII.] MAJSfNER OF CAPTURING PREY. 331 

have digested their prey ; but this is not the case, and there 
are no glands fitted for secreting the proper fluid. Never- 
theless, in order to test their power of digestion, minute 
fragments of roast meat, three small cubes of albumen, and 
three of cartilage, ^vere pushed through the orifice into the 
bladders of vigorous plants. They vfere 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 
subsequentlj' to those on Drosera, Dionsea, Drosophyllum, 
and Pinguicula ; so that I was familar with the appearance 
of these substances when undergoing the early and final 
stages of digestion. We may ^therefore conclude that 
Utrioularia cannot digest the animals which it habitually 
captures. 

In most of the bladders the captured animals are so much 
decayed that they form a pale brown, pulpy mass, with 
their chitinous coats so tender that they fall to pieces with 
the greatest ease. The black pigment of the eye-spots is 
preserved better than anything else. Limbs, jaws, &c. are 
often found quite detached ; and this I suppose is the result 
of the vain struggles of the later captured animals. I have 
sometimes felt surprised at the small proportion of im- 
piisoned animals in a fresh state compared with those utterly 
decayed.* Mrs. Treat states with respect 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 m^itter is absorbed from 



* [Schimper (' Botanische Zeitung,' 1.882, p. 245) was struck by the same 
fact in the case of V. cornuta. — F. D.] 



332: UTEICULAEIA NEGLEGTA, [CIhap. XVII. 

them by tlio quadrifid and bifid processes. The extreme] y 
delicate nature of the membrane of which these processes 
are formed, and the large surface which they expose, owing 
to their number crowded over the whole interior of the 
bladder, are circumstances all favouring the process of 
absorption. Many perfectly clean bladders which had never 
caught any prey were opened, and nothing could be distin- 
guished with a No. 8 object-glass of Hartnack within the 
delicate, structureless protoplasmic lining of the arms, ex- 
cepting in each a single yellowish particle or modified 
nucleus. Sometimes two or even three such particles were 
present; but in this case traces of decaying matter could 
generally be detected. On the other hand, in bladders con- 
taining either one large or several small decayed animals, 
the processes presented a widely different appearance. Six 
such bladders were carefully examined ; one contained an 
elongated, coiled-up larva ; another a single large entomo- 
stracan crustacean, and the others from two to five smaller 
ones, all in a decayed state. In these s-ix bladders, a large 
number of the quadrifid processes contained transparent, 
often yellowish, more or less confluent, spherical or irregu- 
larly shaped, masses of matter. Some of the processes, 
however, contained only fine granular matter, the particles 
of which were so small that they could not be defined clearly 
with No. 8 of Hartnack. The delicate layer of protoplasm 
lining their walls was in some cases a little shrunk.* On three 
occasions the above small masses of matter were observed 
and sketched at short intervals of time ; and they certainly 
changed their positions relatively to each other and to the 
walls of the arms. Separate masses sometimes became con- 
fluent, and then, again divided. A single little mass would 
send out a projection, which after a time separated itself. 
Hence there could be no doubt that these masses consisted of 
protoplasm. Bearing in mind that many clean bladders 
were examined with equal care, and that these presented no 
such appearance, we may confidently believe tiiat the pro- 



* [Schimper (loc. cit. p. 247) ob- empty bladders, but the commonest 
served a marked difference in the change is a collection of the pro- 
appearance of the hairs in those toplasm in the axis of the cell where 
bladders of U. cornuta which contain it is suspended by radiating strands 
captured prey. The protoplasm is to the delicate layer of protoplasm 
sometimes more granular than in lining the walls. — K. D.] 



C'uAr. XVII.] ABSOEPTION BY THE QUADEIFIDS. 333 

toplasm in the above cases had been generated by the 
absorption of nitrogenous matter from the decaying animals. 
In two or three other bladders, which at first appeared quite 
clean, on careful search a few processes were found, with 
their outsides clogged with a little brown matter, showing 
that some minute animal had been captured and had de- 
cayed, a;ad the arms here included a very few more or less 
spherical and aggregated masses ; the processes in other 
parts of the bladders being empty and transparent. On the 
other hand, it must be stated that in three bladders con- 
taining dead crustaceans, the processes were likewise empty. 
This fact may be accounted for by the animals not having 
been suESciently decayed, or by time enough not having 
been allowed for the generation of protoplasm, or by its 
subsequent absorption and transference to other parts of the 
plant. It will hereafter be seen that in three or four other 
species of Utricularia the quadrifid processes in contact with 
decaying animals likewise contained aggregated masses of 
protoplasm. 

On the Absorption of certain Fluids by the Quadrifid and 
Bifid Processes. — These experiments were tried to ascertain 
whether certain fluids, which seemed adapted for the purpose 
would produce the same effects on the processes as the 
absorption of decayed animal matter. Such experiments are, 
however, troublesome ; for it is not sufficient merely to place 
a branch in the fluid, as the valve shuts so closely that the 
fluid apparently does not enter soon, if at all. Even when 
bristles were pushed into the orifices, they were in several 
cases wrapped so closely round by the thin flexible edge of 
the valve that the fluid was apparently excluded ; so that 
the experiments tried in this manner are doubtful and not 
worth giving. The best plan would have been to puncture 
the bladders, but I did not think of this till too late, 
excepting in a few cases. In all such trials, however, it 
cannot be ascertained positively that the bladder, though 
translucent, does not contain some minute animal in the 
last stage of decay. Therefore most of my experiments were 
made by cutting bladders longitudinally into two ; the 
quadrifids were examined with No. 8 of Hartnack, then 
irrigated, whilst under the covering glass, with a few drops 
of the fluid under trial, kept in a damp chamber, and re- 
examined after stated intervals of time with the same power 
as before. 



334 UTEICULAEIA NEGLECTA. [Chap. XVn. 

Four bladders were first tried as a cortrol experiment, in the manner 
just described, in a solution of one part of gum arable to 218 of water, 
and two bladders in a solution of one part of sugar to 437 of water ; 
and in neither case was any change perceptible in the quadrifids or 
biflds after 21 hrs. Pour 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 protoplasmic 
lining or primordial utricle was a little shrunk. In the third bladder, 
the quadrifids included distinctly visible granules, and the primordial 
utricle was a little shrunk after only 8 hrs. In the fourth bladder the 
primordial utricle in most of the processes was here and there 
thickened into little irregular yellowish specks ; and from the gradations 
which could be traced in this and other cases, these specks appear to give 
rise to the larger free granules contained within some of the processes. 
Other bladders, which, as far as could be judged, had never caught any 
prey, were punctured and left in the same solution for 17 hrs.; and 
their quadrifids now contained very fine granular matter. 

A bladder was bisected, examined, and irrigated with a solution of 
one part of carbonate of ammonia to 487 of water. After 8 hrs. 30 m. 
the quadrifids contained a good many sranules, and the primordial 
utricle was somewhat shrunk ; after 23 hrs. the quadrifids and bifids 
contained many spheres of hyaline matter, and ia one arm twenty-four 
such spheres of moderate size were counted. Two bisected bladders, 
which had been previously left for 21 hrs. in the solution of gum (one 
part to 218 of water) without being affected, were irrigated with the 
solution of carbonate of ammonia; and both had their quadrifids 
modified in nearly the same manner as just described, — one after only 
9 hrs., and the other after 24 hrs. Two bladders which appeared 
never to have caught any prey were punctured and placed in the 
solution ; the quadrifids of one were examined after 17 hrs., and found 
slightly opaque ; the quadrifids of the other, examined after 45 hrs., had 
their primordial utricles more or less shrunk with thickened yellowish 
specks like those due to the action of nitrate of ammonia. Several un- 
injured bladders were left in the same solution, as well as in a weaker 
solution of one part to 1750 of water, or 1 gr. to 4 oz. ; and after two days 
the quadrifids were more or less opaque, with their contants finely 
granular ; but whether the solution had entered by the orifice, or had 
been absorbed from the outside, I know not. 

Two bisected bladders were irrigated with a solution of one part 
of urea to 218 of water; but when this solution was employed, I forgot 
that it had been kept for some days in a warm room, and had there- 
fore probably generated ammonia; anyhow, the quadrifids were 
affected after 21 hrs. as if a solution of carbonate of ammonia had been 
used ; for the primordial utricle was thickened in specks, which seemed 
to graduate into separate granules. Three bisected bladders were also 
irrigated with a fresh solution of urea of the same strength ; their 
quadrifids after 21 hrs. were much less affected than in the former 



Chap. XVn.] ABSORPTION BY THE QUADEIFIDS. 335 

case ; nevertheless, tlie primordial utricle in some of tte 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 ia all three specimens abounded with minute, 
hyaline, spherical masses ; and some of their primordial utricles were 
a little shrunk. Three bisected bladders were also irrigated with 
a fresh infusion of raw meat ; and to my surprise the quadrifids in 
one of them appeared, after 23 hrs., finely granular, with their 
primordial utricles somewhat shrunk and marked with thickened yellow- 
ish specks ; so that they had been acted on in the same manner as by 
the putrid infusion or by the salts of ammonia. In the second 
bladder some of the quadrifids were similarly acted on, though to 
a very slight degree ; whilst the third bladder was not at all affected. 

From these experiments it is clear that the quadrifid and 
hifid processes have the power of absorbing carbonate and 
nitrate of ammonia, and matter of some kind from a putrid 
infusion of meat. Salts of ammonia were selected for trial, 
as they are known to be rapidly generated by the decay of 
animal matter in the presence of air and water, and would 
therefore be generated within the bladders containing cap- 
tured prey. The effect produced on the processes by these 
salts and by a putrid infusion of raw meat differs from that 
produced by the decay of the naturally captured animals 
only in the aggregated masses of protoplasm being in the 
latter case of larger size ; but it is probable that the fine 
granules and small hyaline spheres produced by the solutions 
would coalesce into larger masses, with time enough allowed. 
We have seen with Drosera that the first effect of a weak 
solution of carbonate of ammonia on the cell-contents is the 
production of the finest granules, which afterwards aggre- 
gate into larger, more or less rounded, masses ; and that the 
granules in the layer of protoplasm which flows round the 
walls ultimately coalesce with these masses. Changes of 
this nature are, however, far more rapid in Drosera than in 
Utricularia. Since the bladders have no power of digesting 
albumen, cartilage, or roast meat, I was surprised that matter 
was absorbed, at least in one case, from a fresh infusion 
of raw meat. I was also surprised, from what we shall 
presently see with respect to the glands round the orifice, 
that a fresh solution of urea produced only a moderate effect 
on the quadrifids. 



o36 UTEICULAEIA NEGLECTA. [Chap. XVII. 

As the quadrifids are developed from papilla 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 carbonate and nitrate of am- 
monia ; for, after an immersion of 23 hrs. in solutions of one 
part of both these salts to 437 of water, their primordial 
utricles were a little shrunk and of a pale brown tint, and 
sometimes finely granular. The same result followed from 
the immersion of a whole branch for nearly three days in a 
solution of one part of the carbonate to 1750 of water. The 
grains of chlorophyll, also, in the cells of the leaves on this 
branch became in many places aggregated into little green 
masses, which were often connected together by the finest 
threads. 

On the Absorption of certain Fluids hy the Glands on tlie 
Valve and Collar. — The glands round the orifices of bladders 
which are still young, or which have been long kept in 
moderately pure water, are colourless ; and their primordial 
utricles are onlj' slightly or hardly at all granular. But in 
the greater number of plants in a state of nature — and we 
must remember that they generally grow in very foul water, 
— and with plants kept in an aquarium in foul water, most 
of the glands were of a pale brownish tint ; their primordial 
utricles were more or less shrunk, sometimes ruptured, with 
their contents often coarsely granular or aggregated into 
little masses. That this state of the glands is due to their 
having absorbed matter from the surrounding water, I 
cannot doubt ; for, as we shall immediately see, nearly the 
same results follow from their immersion for a few hours in 
various solutions. Nor is it probable that this absorption is 
useless, seeing that it is almost universal with plants grow- 
ing in a state of nature, excepting when the water is remark- 
ably pure. 

The pedicels of the glands which are situated close to the 
slit-like orifice, both those on the valve and on the collar, 
are short ; whereas the pedicels of the more distant glands 
are much elongated and project inwards. The glands are 
thus well placed so as to be washed by any fluid coming out 
of the bladder through the orifice. The valve fits so closely, 
judging from the result of immersing uninjured bladders in 
various solutions, that it is doubtful whether any putrid 



Chap. XVII.] ABSORPTION BY THE GLANDS. 337 

fluid habitually passes outward s. But we must rememlier that 
a bladder generally captures several animals ; and that each 
time a fresh animal enters, a puff of foul water must pass 
out and bathe the glands. Moreover, I have repeatedly 
found that, by gently pressing bladders which contained air, 
minute bulDbles were driven out through the orifice ; and if 
a bladder is laid on blotting paper and gently pressed, water 
oozes out. In this latter case, as soon as the pressure is 
relaxed, air is drawn in, and the bladder recovers its proper 
form. If it is now placed under water and again gently 
pressed, minute bubbles issue from the orifice and nowhere 
else, showing that the walls of the bladder have not been 
ruptured. I mention this because Cohn quotes a statement 
by Treviranus, that air cannot be forced out of a bladder 
without rupturing it. We may therefore conclude that 
whenever air is secreted within a bladder already full of 
water, some water will be slowly driven out through the 
orifice. Hence I can hardly doubt that the numerous glands 
crowded round the orifice are adapted to absorb matter from 
the putrid water, which vrill 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 
antennai, were sliced off, and the condition of the glands observed ; 
they were then irrigated, whilst beneath a covering glass, with the 
solutions, and after a time re-examined with the same power as before, 
namely No. 8 of Hartnack. The following experiments were thus 
made. 

As a control experiment solutions of one part of white sugar and of 
one part of gum to 218 of water were first used, to see whether these 
produced any change in the glands. It was also neoessaiy to observe 
whether the glands were affected by the summits of the bladders having 
been cut off. The summits of four were thus tried ; one being exam- 
ined after 2 hrs. 30 m., and the other three after 23 hrs. ; but there 
was no marked change in the glands of any of them. 

Two summits bearing; quite colourless glands were irrigated with a 
solution of carbonate of ammonia of the same strength (viz. one part 
to 218 of water), and ia 5 m. the primordial utricles of most of the 
glands were somewhat contracted ; they were also thickened in specks 
or patches, and had assumed a pale brown tint. When looked at 



338 UTEICULAEIA NEGLECTA. [Chap. XVH. 

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 considerably shrunk and brownish after 2 hrs. Similar 
effects were observed in the two other specimens, but these were not 
examined until 21 hrs. had elapsed. The nuclei of many of the 
glands apparently had increased in size. Five bladders on a branch, 
which had been kept for a long time in moderately pure water, were 
cut off and examined, and their glands found very little modified. 
The remainder of this branch was placed in the solution of the nitrate, 
and after 21 hrs. two bladders were examined, and all their glands 
were brownish, with their primordial utricles somewhat shrunk and 
finely granular. 

The summit of another bladder, the glands of which were in a 
beautifully clear condition, was irrigated with a few drops of a mixed 
solution of nitrate and phospate of ammonia, each of one part to 437 
of water. After 2 hrs. some few of the glands were brownish. After 
8 hrs. almost all the oblong glands were brown and much more opaque 
than they were before ; their primordial utricles were somewhat shrunk 
and contained a little aggregated granular matter. The spherical 
glands were still white, but their utricles were broken up into three or 
four small hyaline spheres, with an irregularly contracted mass in the 
middle of the basal part. These smaller spheres changed their forms 
ia 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 meat. 
No change in the glands was observable for some hours, but after 
24 hrs. most of them had become brownish, and more opaque and 
granular than they were before. In these specimens, as in those 
irrigated with the salts of ammonia, the nuclei seemed to have 
increased both in size and solidity, but they were not measured. Five 
summits were also irrigated with a fresh infusion of raw meat ; three 
of these were not at all affected in 24 hrs., but the glands of the other 
two had perhaps become more granular. One of the specimens which 



Chap. XVII.] ABSOEPTION BY THE GLANDS. 339 

wag 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 dozeii granules. After six additional 
hours their primordial utricles wore 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 contaiuing distinctly visible granules. After 9 hrs. 
some of the spherical glands were brownish, and the oblong glands 
were still more changed, but they contained fewer separate granules ; 
their nuclei, on the other hand, appeared larger, as if they had absorbed 
the granules. After 23 hrs. all the glands were brown, their pri- 
mordial utricles greatly shrunk, and in many cases ruptured. 

A bladder was now experimented on, which was already somewhat 
afl'ected 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, 
i-hrunk. The summit was treated with the solution of urea, but was 
little affected by it in 9 hrs. ; nevertheless, after 23 hrs. the spherical 
glands were brown, with their utricles more shrunk ; several of the 
other glands were still browner, with their utricles contracted into 
irresfular little masses. 

Two other summits, with their glands colourless and their utricles 
not shrunk, were treated with the same solution of urea. After 5 hrs. 
many of the glands presented a shade of brown, with their utricles 
slightly shrunk. After 20 hrs. 40 m. some few of them were quite 
brown, and contained irregularly aggregated masses ; others were still 
colourless, though their utricles were shrunk ; but the greater number 
were not much affected. This was a good instance of how imequally 
the glands on the same bladder are sometimes affected, as hkewise 
often occurs with plants growing in foul water. Two other summits 
were treated with a solution which had been kept during several days 
in a warm room, and their glands were not at all affected when 
examined after 21 hours. 

A weaker solution of one part of urea to 437 of water was next tried 
on six summits, all carefully examined before being irrigated. The 
first was re-examined after 8 hrs. 30 m., and the glands, including the 
spherical ones, were brown ; many of the oblong glands having their 
primordial utricles much shrunk and including granules. The second 
summit, before being irrigated, had been somewhat affected by the 
surrounding water, for the spherical glands were not quite uniform in 
appearance; and a few of the oblong ones were brown, with their 
utricles shrunk. Of the oblong glands, those which were before colour- 
less, became brown in 3 hrs. 12 m. after irrigation, vntk their utricles 

z 2 



340 IJTEICULAEIA NEGLEOTA. [Chap. XVII. 

sligMly shiTink. 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 .'pherioal 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 he no douht that the variously shaped 
glands on the valve and round the collar have the power of 
absorbing matter from weak solutions of certain salts of 
ammonia and urea, and from a putrid infusion of raw meat. 
Prof. Cohn believes that they secrete slimy matter ; but I 
was not able to perceive any trace of such action, exceptinj;; 
that, after immersion in alcohol, extremely fine lines could 
sometimes be seen radiating from their surfaces. The glands 
are variously affected by absorption : they often become of a 
brown colour ; sometimes they contain very fine granules, or 
moderately sized grains, or irregularly aggregated little 
masses ; sometimes the nuclei appear to have increased in 
size; the primordial utricles are generally more or less 
shrunk and sometimes ruptured. Exactly the same changes 
may be observed in the glands of plants growing and 
flourishing in foul water. The spherical glands are generally 
aifected rather differently from the oblong and two-armed 
ones. The former do not so commonly become brown, and 
are acted on more slowly. We may therefore infer that 
they differ somewhat in their natural functions. 

It is remarkable how unequally the glands on the bladders 
on the same branch, and even the glands of the same kind 
on the same bladder, are affected by the foul water in which 
the plants have grown, and by the solutions which were 
employed. In the former case I presume that this is due 
either to little currents bringing matter to some glands and 
not to others, or to unknown differences in their constitution. 
"When the glands on the same bladder are differently affected 
by a solution, we may suspect that some of them had 
previously absorbed a small amount of matter from the 
water. However this may be, we have seen that the glands 



Chap. XVII.] SUMMARY ON ABSOKPTIOX. 341 

on tlie same leaf of Drosera are sometimes very unequally 
affected, more especially when exposed to certain vapours. 

If glands wliicli have already become brown, with their 
primordial utricles shrunk, are irrigated with one of the 
effective solutions, they are not acted on, or only slightly and 
slowly. If, however, a gland contains merely a few coarse 
granules, this does not prevent a solution from acting. I 
have never seen any appearance making it probable that 
glands which have been strongly affected by absorbing matter 
of any kind are capable of recovering their pristine, colour- 
less, and homogeneous condition, and of regaining the power of 
absorbing. 

From the nature of the solutions which were tried, I 
presume that nitrogen is absorbed by the glands ; but the 
modified, brownish, more or less shrunk, and aggregated 
contents of the oblong glands were never seen by me or by 
my son to undergo those spontaneous changes of form 
characteristic of protoplasm. On the other hand, the contents 
of the larger spherical glands often separated into small 
hyaline globules or irregularly shaped masses, which changed 
their forms very slowly and ultimately coalesced, forming a 
central shrunken mass. Whatever may be the nature of the 
contents of the several kinds of glands, after they have been 
acted on by foul water or by one of the nitrogenous solutions, 
it is probable that the matter thus generated is of service to 
the plant, and is ultimately transferred to other parts. 

The glands apparently absorb more quickly than do the 
quadrifid and bitid processes ; and on the view above main- 
tained, namely that they absorb matter from putrid water 
occasionally emitted from the bladders, they ought to act 
more quickly than the processes ; as these latter remain in 
permanent contact with captured and decaying animals. 

Finally, the conclusion to which we are led by the fore- 
going experiments and observations is that the bladders have 
no power of digesting animal matter, though it appears that 
the quadrifids are somewhat affected by a fresh infusion of 
raw meat. It is certain that the processes within the 
bladders, and the glands outside, absorb matter from salts of 
ammonia, from a putrid infusion of raw meat, and from urea. 
The glands apparently are acted on more strongly by a 
solution of urea, and less strongly by an infusion of raw 
meat, than are the processes. The case of urea is particularly 
interesting, because we have seen that it produces no effect 



342 



UTEICULAKIA NEGLECTA. 



[Chap. XVII. 



on Drosera, the leaves of -wliicli are adapted to digest fresh 
animal matter. But the most important fact of all is, that 
in the present and following species the quadrifid and bifid 
processes of bladders containing decayed animals generally 
include little masses of spontaneously moving protoplasm ; 
whilst such masses are never seen in perfectly clean bladders. 
Development of the Bladders. — My son and I spent much 
time over this subject with small succesi». Our observations 
apply to the present species and to TJtricularia vulgaris, but 
were made chiefly on the latter, as the bladders are twice as 
large as those of Utricularia neglecta. In the early part of 
autumn the stems terminate in large buds, which fall oif 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 TJtricularia vul- 
garis are about -j-Jtt inch ('254 mm.) 
in diameter (or -^^ in the case of 
Utricularia neglecta'), they are circular 
in outline, with a narrow, almost 
closed, transverse orifice, leading into 
a hollow filled with water; but Ihe 
bladders are hollow when much under 
y^^ of an inch in diameter. The 
orifices face inwards or towards the 
Fig. 23. axis of tho plant. At this early age 

(Utricularia vulgaris.) the bladders are flattened in the plane 
Longitudinal eection through in which the orjflce lies, and therefore 

rnTng^th'','"^?th-t^°oviS?e'ro'^ f* ^}^^^ angles to that of the mature 
■widely o^ien. bladders. They are covered exteriorly 

with papillfB of different sizes, many 
of which have an elliptical outline. A bundle of vessels, 
formed of simple elongated cells, runs up the short footstalk, 
and divides at the base of the bladder. One branch extends 
up the middle of the dorsal surface, and the other up the 
middle of the ventral surface. In full-grown bladders the 
ventral bundle divides close beneath the collar, and the two 
branches run on each side to near where the corners of the 
valve unite with the collar ; but these branches could not bo 
seen in very young bladders. 

The accompanying figure (fig. 23) shows a section, which 
happened to be strictly medial, through the footstalk and 
between the nascent antennae of a bladder of Utricularia 




Chap. XVII.] DEVELOPJIENT OF THE BLADDERS. 343 

vulgaris, -j-^ inch in diameter. The specimen was soft, and 
the young valve became 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 prolon- 
gations of the wall of the hladder. Even at this early age, 
glands could be detected on the valve. The state of the 
quadrifid processes will presently be described. The antennas 
at this period consist of minute cellular projections (not 
shown in the above figure, as they do not lie in the medial 
plane), which soon bear incipient bristles. In five instances 
the young antennas were not of quite equal length ; and this 




Fig. 24. 

(Uti^icularia vulgaris.) 

YoungVat trom a winter bud, showing on the left side a bladder in its earliest stage 
of development. 



fact is intelligible if I am right in believing that they 
represent two divisions of the leaf, rising from the end of the 
bladder; for, with the true leaves, whilst very young, the 
divisions are never, as far as I have seen, strictly opposite ; 
they must therefore be developed one after the other, and so 
it would be with the two antennas. 

At a much earlier age, when the half formed bladders are 
only ^^ inch ( • 0846 mm.) in diameter or a little more, they 
present a totally different appearance. One is represented 
on the left side of the accompanying drawing (fig. 24). The 
young leaves at this age have broad flattened segments, with 



344 UXEICULAEIA NEGLECTA. [Chap. XVII. 

their future divisions represented by prominences, one of 
which is shown on the right side. Now, in a large number 
of specimens examined by my son, the young bladders 
appeared as if formed by the oblique folding over of the apex 
and of one margin with a prominence, against the opposite 
margin. The circular hollow between the infolded apex and 
infolded prominence apparently contracts into the narrow 
orifice, wherein the valve and collar will be developed ; the 
bladder itself being formed by the confluence of the opposed 
margins of the rest of the leaf. But strong objections may 
be urged against this view, for we must in this case suppose 
that the valve and collar are developed as symmetrically from 
the sides of the apex and prominence. Moreover, the bundles 
of vascular tissue have to be formed in lines quite irre- 
spective of the original form of the leaf. Until gradations 
can be shown to exist between this the earliest state and a 
young yet perfect bladder, the case must be left doubtful. 

As the quadrifid and bifid processes ofier one of the 
greatest peculiarities in the genus, I carefully observed their 
development iu Utricularia neglecta. In bladders about tJ^ 
of an inch in diameter, 1he inner surface is studded with 
papillas, rising from small cells at the junctions of the larger 
ones. These papillae consist of a delicate conical protuber- 
ance, 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 papillas first become much elongated in a line 
parallel to the inner surface of the bladder. Next, each is 
divided by a longitudinal partition. Soon the two half-cells 
thus formed separate from one another; and we now have 
four cells or an incipient quadrifid process. As there is not 
space for the two new cells to increase in breadth in their 
original plane, the one slides partly under the other. Their 
manner of growth now changes, and their outer sides, 
instead of their apices, continue to grow. The two lower 
cells, which have slid partly beneath the two upper ones, 
form the longer and more upright pair of processes : whilst 
the two upper cells form the shoi-ter 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 



Chap. XVII.] UTEICULAEIA MINOE. 345 

of the longer processes. The development of the qtiadrifids 
is very liable to he arrested. I have seen a hladder ^V of 
an inch in length including only primordial papillje ; and 
another bladder, about half its full size, with the quadrifids 
in an early stage of development. 

As far as I could make out, Ihe bifid processes are de- 
veloped in the same manner as the quadrifids, excepting that 
the two primary terminal cells never become divided, and 
only increase in length. The glands on the valve and collar 
appear at so early an age that I could not trace their develop- 
ment ; but we may reasonably suspect that thej' are developed 
from papillaa like those on the outside of the bladder, but 
with their terminal cells not divided into two. The two 
segments forming the pedicels of the glands probably answer 
to the conical protuberance and short footstalk of the quadri- 
fid and bifid processes. I am strengthened in the belief that 
the glands are developed from papillae 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. 

TJxKICnLAEIA VULGARIS, 

Living plants from Yorkshire were sent me by Dr. Hooker. This 
species differs from the last in the stems and leaves being thicker or 
coarser ; their divisions forra a more acute argle with one another ; 
the notches on the leaves bear three or four short bristles instead of 
one ; and the bladders are twice as large, or about i of an inch (5*08 
mm.) in diameter. In all essential respects the bladders resemble those 
of Utricularia neglecta, but the sides of the peiistome are perhaps a 
little more prominent, and always bear, as far as I have seen, seven or 
eight long multicellular bristles. There are eleven long bristles ou 
each antenna, the terminal pair being included. Five bladders, con- 
taining prey of some kind, were examined. The first included five 
Cypris, a large copepod and a Diaptomus ; the second, four Cypris ; 
the third, a single rather large crustacean ; the fourth, six crustaceans ; 
and the fifth, ten. My son examined the quadrifid processes in a 
bladder containing the remains of two crustaceans, and found some of 
them full of spherical or irregularly shaped masses of matter, which 
were observed to move and to coalesce. These masses therefore con- 
sisted of protoplasm. 

Uteiculaeia minor. 

This rare species was sent me in a living state from Cheshire, through 
the kindness of Mr. John Price. The leaves and bladders are much 



346 



UTEICULAEIA CLANDESTINA. [Chap. XVII. 



smaller than those of Utricularia neglecta. The leaves bear fewer 
and shorter bristles, and the bladders are more globular. The antennas, 
instead of projecting in front of the bladders, are curled under tlie 
valve, and are armed with twelve or fourteen extremely long multi- 
cellular bristles, generally arranged ia pairs. These, with seven or 
eight long bristles on both sides of the peristome, form a sort of net 
over the valve, which would tend to prevent all animals, excepting 
very small ones, entering the bladder. The valve and collar have the 
same essential structure as in the two previous species ; but the glands 
are not quite so numerous ; the oblong ones are rather more elongated, 
whilst the two-armed ones are rather less elongated. The four bristles 
which project obliquely from the lower edge of the valve are short. 
Their shortness, compared with those on the valves of the foregoing 

species, is intelligible if my view is 
correct that they serve to prevent too 
large animals forcing an entrance 
through the valve, thus injuring it; 
for the valve is already protected to a 
certain extent by the incurved antennae, 
together with the lateral bristles. The 
bifid processes are like those in the 
previous species; but the quadrifids 
differ in the four arms (fig. 25) being 
directed to the same side ; the two 
longer ones being central, and the two 
shorter ones on the outside. 

The plants were collected in the 
middle of July; and the contents of 
five bladders, which from their opacity seemed fviU of prey were 
examined. The first contained no less than twenty-four minute fresh- 
water crustaceans, most of them consisting of empty shells, or includ- 
ing only a few drops of red oily matter ; the second contained twenty ; 
the third, fifteen ; the fourth, ten, some of them being rather larger 
than usual ; and the fifth, which seemed stuffed quite full, contained 
only seven, but five of these were of tmusually large size. The prey, 
therefore, judging from these five bladders, consists exclusively of 
fresh-water crustaceans, most of which appeared to be distinct species 
from those found in the bladders of the two former species. In one 
bladder the quadrifids in contact with a decaying mass contained 
numerous spheres of granular matter, which slowly changed their 
forms and positions. 




Fig. 2j. 

( FLriciilaria minor,) 

Quadritid procoss ; greatly enlarged. 



Uteicdlaeia clandestine. 

This North American species, which is aquatic like the three fore- 
going ones, has been described by Mrs. Treat, of New Jersey, whose 
excellent observations have already been largely quoted. I have not 
as yet seen any full description by her of the structure of the bladder, 



Chap. XVIL] UTRICULAEIA CLANDESTINA. 347 

but it appears to be lined with quadrifid processes. A vast mimber 
of captured animals were found witliin the bladders ; some being 
crustaceans, but the greater number delicate, elongated larvas, I sup- 
pose of Culicidae. On some stems, " fully nine out of every ten bladders 
contained these larvte or their remains." The larvaa " showed signs 
of life from twenty-four to thirty-six hours after being imprisoned," 
and then perished. 



348 UTEICULAEIA MONTANA. [Chap. XVIII. 



CHAPTER XVIir. 

Uteiculaeia (continuect). 

Utricularia montmia — Description of the bladders on the subterranean 
rhizomes — Prey captured by the bladders of plants under culture and in 
a state of nature — Absorption by the quadrifid processes and glands — 
Tubers serving as reservoirs for water — Various other species of Utricu- 
laria — Polypompholyx — Genlisea, different nature of "the trap for capturing 
prey — [Sarracenia] — Diversified methods by which plants are nourished. 

Utricularia Montana. — This species inhabits the tropical 
parts of South America, and is said to be epiphytic ; but, 
judging from the state of the roots (rhizomes) of some dried 
specimens from the herbarium at Kew, it likewise lives in 
earth, probably in crevices of rocks. la English hot-houses 
it is grown in peaty soil. Lady Dorothy Nevill was so kind 
as to give me a fine plant, and I received another from Dr. 
Hooker. The leaves are entire, instead of being much divided, 
as in the foregoing aquatic species. They are elongated, 
about IJ inch in breadth, and furnished with a distinct foot- 
stalk. The plant produces numerous colourless rhizomes,* as 
thin as threads, which bear minute bladders, and occasionally 
swell into tubers, as will hereafter be described. These 
rhizomes appear exactly like roots, but occasionally throw up 



* [Hovelacque, in the * Comptes mountains of Dominica. Uiricularia 

Rendus,' vols. cv. p. 692, and cvi. p. cornuta, described by Schimper in 

310, has discussed the nature of the the ' Bot. Zeitung,' 1882, p. 241, 

underground runners; he considers has similar underground runners, 

them to be morphologically leaves, in as well as aerial organs usually 

opposition to Schenk (Pringsheim's described as leaves. He discusses 

' Jahrbiicher,' vol. xviii. p. 218), the possibility of a morphological 

who rgards them as rhizomes. identity between the runners and 

Schimper, in his paper on the West the " leaves " from a point of view 

Indian Epiphytes (' Bot. Central- opposite to that of Hovelacque's — 

blatt,' vol. xvii. p. 257), takes a namely, that the "leaves" as well 

view similar to Schenk's as to stolons as the stolons may be morphologically 

or runners in the new species, U. stems, — F. D.] 
Schimpci'i, discovered by him in the 



CiiAr. XVIII.] STRUCTURE OF THE BLADDERS. 



3W 



green shoots. They penetrate the earth sometimes to the 
depth of more than 2 inches : but when the plant grows as 
an epiphyte, they must creep amidst the mosses, roots, 
decayed bark, &c., with which 
the trees of these countries are 
thickly covered. 

As the bladders are attached 
to the rhizomes, they are neces- 
sarily subterranean. They are 
produced in extraordinary num- 
bers. One of my plants, though 
young, must have borne several 
hundreds ; for a single branch 
out of an entangled mass had 
thirty-two, and another branch, 
about 2 inches in length (but 
with its end and one side 
branch broken off), had seventy- 
three bladders.* The bladders 
are compressed and rounded, with 
the ventral surface, or that be- 
tween the summit of the long 
delicate footstalk and valve, ex- 
tremely short (fig. 27). They 

are colourless and almost as transparent as glass, so that they 
appear smaller than they really are, the largest being under 
the ^ of an inch (1'27 mm.) in its longer diameter. They 
are formed of rather large angular cells, at the junctions of 
which oblong papillse project, corresponding with those on 
the surfaces of the bladders of the previous species. Similar 
papillss abound on the rhizomes, and even on the entire leaves, 
hut they are rather broader on the latter. Vessels, marked 
with parallel bars instead of by a spiral line, run up the 
footstalks, and just enter the bases of the bladders ; but they 




Fig. 26. 
( Utricularw, montana.) 
Bhizome swollen into a tuber; tlie i 
branches bearing minute bladders j of '' 
natural size. 



* Prof. Oliver has figured a plant 
iif Utricularia Jamesoniana (' Proc. 
Linn. See' toI. ir. p. 169) having 
entire leaves and rhizomes, like those 
of our present species ; but the mar- 
gins of the terminal halves of some 
of the leaves are converted into 
bladders. This fact clearly indicates 



that the bladders on the rhizomes of 
the present and following species are 
modified segments of the leaf; and 
they are thus brought into accordance 
with the bladders attached to the 
divided and floating leaves of the 
aquatic species. 



350 UTEICULAEIA MONTANA. [Chap. XVIII. 

do not bifurcate and extend iip the dorsal and ventral 
surfaces, 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 sometimes near the 
margin. Their curved bases thus form a roof over the cavity 
in which the valve lies ; but there is always left on each 
side a little circular passage into the cavity, as may be seen 




Fig. 2V. 

(^UtricuJaria monfana,) 

Bladder; about 27 times enlarged. 

in the drawing, as well as a narrow passage between the 
bases of the two antennae. As the bladders are subterranean, 
had it not been for the roof, the cavity in which the valve 
lies would have been liable to be blocked up with earth and 
rubbish ; so that the curvature of the antennae is a service- 
able character. There are no bristles on the outside of the 
collar or peristome, as in the foregoing species- 

The valve is small and steeply inclined, with its free pos- 
terior edge abutting against a semicircular, deeply depending 



Chap. XYIII.] CAPTURED ANIMALS. 351 

collar. It is moderately transparent, and bears two pairs of 
hliort stiff bristles, in tbe same position as in tlie other 
species. Tbe 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 foot- 
stalks. These glands are only the ^ ^( ,f, of an inch (-019 
mm.,) in length ; though so small, they act as absorbents. 
The collar is thick, stiff, and almost semicircular ; it is formed 
of the same peculiar brownish tissue as in the former species. 
The bladders are filled with water, and sometimes include 
bubbles of air. They bear internally rather short, thick, 
quadrifid processes arranged in approximately concentric 



Fig. 23. 

{Utncularia •montana.') 

One of the quadrifid processes; much enlarged. 

rows. The two pairs of arms of which they are formed 
differ only a little in length, and stand in a peculiar position 
(fig. 28) ; the two longer ones forming one line, and the 
two shorter ones another parallel line. Each arm includes a 
small spherical mass of brownish matter, which, when cru.shed, 
breaks into angular pieces. I have no doubt that these 
spheres are nuclei, for closely similar ones are present in the 
cells forming the walls of the bladders. Bifid processes, 
having rather short oval arms, arise in the usual position on 
the inner side of the collar. 

These bladders, therefore, resemble in all essential respects 
the larger ones of the foregoing species. They differ chiefly 
in the absence of the numerous glands on the valve and 
round the collar, a few minute ones of one kind alone being 
present on the valve. They differ more conspicuously in 
the absence of the long bristles on the antennas and on the 
outside of the collar. The presence of these bristles in the 



352 UTRICULARIA MONTANA. [Chap. XVIII. 

previously mentioned Species probably relates to the capture 
of aquatic animals. 

It seemed to me an interesting question whetlier the 
minute bladders of Utricularia montana served, as in the 
previous species, to capture animals living in the earth, or 
in the dense vegetation covering the trees on which this 
species is epiphytic ; for in this case we should have a new 
sub-class of carnivorous plants, namely, subterranean feeders. 
Many bladders, therefore, were examined, with the following 
results : — 

(1) A small bladder, less than ^^ of an inch (■847 mm.) in diameter 
contained a miaute mass of brown, much decayed matter ; and ia 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 oae of the Thysanoura. Tlie quadrifids in contact with 
this decayed remnant contained either small masses of translucent, 
yellowish, matter, generally more or less globular, or fine granules. In 
distant parts of the same bladder, the processes were transparent and 
quite empty, with the exception of their solid nuclei. My son made 
at short intervals of time sketches of one of the above aggregated 
masses, and found that they continually and completely changed their 
forms ; sometimes separating from one another and again coalescing. 
Evidently protoplasm had been generated by the absorption of some 
element from the decaying animal matter. 

(2) Another bladder included a still smaller speck of decayed brown 
matter, and the adjoining quadrifids contained aggregated matter, 
exactly as in the last case. 

(3) A third bladder included a larger organism, which was so much 
decayed that I could only make out that it was spinose or hairy. The 
quadrifids in this case were not much affected, excepting that the 
nuclei in the several arms differed much in size ; some of them contain- 
ing two masses having a similar appearance. 

(4) A fourth bladder contained an articulate organism, for I distinctly 
saw the remnant of a limb, terminating in a hook. The quadrifids 
were not examined. 

(5) A fifth included much decayed matter apparently of some 
animal, but with no recognisable features. The quadrifids in contact 
contained numerous spheres of protoplasm. 

(6) Some few bladders on the plant which I received from Kew 
were examined ; and in one, there was a worm-shaped animal very 
little decayed, with a distinct remnant of a similar one greatly decayed. 
Several of the arms of the processes in contact with these remains 
contained two spherical masses, like the single solid nucleus which is 
properly found in eaoharm. In another bladder there was a minute 
grain of quartz, reminding me of two similar cases with Utricularia 
neghcta. 



Chap, XVIII.] ABSORPTIOX. 353 

As it appeared probable that this plant would capture a greater 
number of animals in its native country than under culture, I obtained 
permission to remove small portions of the rhizomes from dried speci- 
mens in the herbarium at Kew. I did not at first find out that it was 
advisable to soak the rhizomes for two or three days, and that it was 
necessary to open the bladders and spread out their contents on glass : 
as from their state of decay and from having been dried and pressed, 
their nature could not otherwise be well distinguished. Several 
bladders on a plant which had grown in black earth in New Granada 
were first examined ; and four of these included remnants of animals. 
The first contained a hairy Acarus, so much decayed that nothing was 
left except its transparent coat ; also a yellow chitinous head of some 
animal with an internal fork, to which the ccsophagus was suspended, 
but I could see no mandibles ; also the double hook of the tarsus of 
some animal ; also an elongatedgreatly 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 Arcellida;. In this 
bladder, as well as in several others, there were some unicellular 
Alga?, 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 organisms, 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, 
with no distinguishable parts. The quadrifids in two were brownish, 
with their contents granular; and it was evident that they had 
absorbed matter. In a fifth bladder there was a flask-shaped organism, 
like that above mentioned. A sixth contained a very long, much 
decayed, worm-shaped animal. Lastly, a seventh bladder contained 
an organism, but of what nature could not be distinguished. 

Only one experiment was tried on tlie quadrifid processes 
and glands with reference to their power of absorption. A 
bladder was punctured and left for 24 hrs. in a solution of 
one part of urea to 437 of water, and the quadrifid and bifid 
processes were found much affected. In some arms there 
was only a single symmetrical globular mass, larger than 
the proper nucleus, and consisting of yellowish matter, 
generally translucent but sometimes granular; in others 

2 a 



354 UTEICULAEIA MONTANA. [Chap. XVIII. 

there were two masses of different sizes, one large and the 
other small; and in others there were irregularly shaped 
globules; so that it appeared as if the limpid contents of 
the processes, owing to the absorption of matter from the 
solution, had become aggregated sometimes round the 
nucleus, and sometimes into separate masses ; and that 
these then tended to coalesce. The primordial utricle or 
protoplasm lining the processes was also thickened here and 
there into irregular and variously shaped specks of yellowish 
translucent matter, as occurred in the case of Utrioularia 
neglecta under similar treatment. These specks apparently 
did not change their forms. 

The minute two-armed glands on the valve were also 
affected by the solution; for they now contained several, 
sometimes as many as six or eight, almost spherical masses 
of translucent matter, tinged with yellow, which slowly 
changed their forms and positions. Such masses were never 
observed in these glands in their ordinary state. We may 
therefore infer that they serve for absorption. Whenever a 
little water is expelled from a bladder containing animal 
remains (by the means formerly specified, more especially 
by the generation of bubbles of air), it will fill the cavity 
in which the valve lies ; and thus the glands will be able 
to utilise decayed matter which otherwise would have been 
wasted. 

Finally, as numerous minute animals are captured by this 
plant in its native country and when cultivated, there can 
be no doubt that the bladders, though so small, are far from 
being in a rudimentary condition ; on the contrary, they 
are highly efficient traps. Nor can there be any doubt that 
matter is absorbed from the decayed prey by the quadrifid 
and bifid processes, and that protoplasm is thus generated. 
What tempts animals of such diverse kinds to enter the 
cavity beneath the bowed antennas, and then force their 
way through the little slit-like orifice between the valve 
and collar into the bladders filled with water, I cannot 
conjecture. 

tubers. — These organs, one of which is represented in a 
previous figure (fig. 26) of the natural size, deserve a few 
remarks. Twenty were found on the rhizomes of a single 
plant, but they cannot be strictly counted ; for, besides the 
twenty, there were all possible gradations between a short 
length of a rhizome just perceptibly swollen and one so 



Chap. XVIII.] EESERVOIES FOR WATER. 355 

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 ofi:, They do not contain any 
air, and they sink in water ; their surfaces are covered with 
the usual papillae. The bundle of vessels which runs up 
each rhizome, as soon as it enters the tuber, separates into 
three distinct bundles, which feunite at the opposite end. 
A rather thick slice of a tuber is almost as transparent as 
glass, and is seen to consist of large angular cells, full of 
water and not containing starch or any other solid matter. 
Some slices were left in alcohol for several days, but only a 
few extremely minute granules of matter were precipitated 
on the walls of the cells ; and these were much smaller and 
fewer than those precipitated on the cell-walls of the 
rhizomes and bladders. We may therefore conclude that 
the tubers do not serve as reservoirs for food, but for water 
during the dry season to which the plant is probably exposed. 
The many little bladders filled with water would aid towards 
the same end. 

To test the correctness of this view, a small plant, growing 
in light peaty earth in a pot (only 4^ by 4^ inches outside 
measure) was copiously watered, and then kept without a 
drop of water in the hothouse. Two of the upper tubers were 
beforehand uncovered and measured, and then loosely covered 
up again. In a fortnight's time the earth in the pot appeared 
extremely dry ; but not until the thirty-fifth day were the 
leaves in the least affected ; they then became slightly 
reflexed, though still soft and green. This plant, which 
bore only ten tubers, would no doubt have resisted the 
<lrought for even a longer time, had I not previously removed 
three of the tubers and cut off several long rhizomes. When, 
on the thirty-fifth day, the earth in the pot was turned out, 
it appeared as dry as the dust on the road. All the tubers 
had their surfaces much wrinkled, instead of being smooth 
and tense. They had all shrunk, but I cannot say accurately 
how much ; for as they were at first symmetrically oval, I 

2 A 2 



356 UTRICULAEIA MONTANA. [Chap. XYIII. 

measured only their length and thickness; but they con- 
tracted in a transverse line much more in one direction than 
in another, so as to become greatly flattened. One of the 
two tubers -which had been measured was now three-fourths 
of its original length, and two-thirds of its original thickness 
in the direction in which it had been measured, but in 
another direction only one-third of its former thickness. 
The other tuber was one-fourth shorter, one-eighth less thick 
in the direction in which it had been measured, and only 
half as thick in another direction. 

A slice was cut from one of these shrivelled tubers and 
examined. The cells still contained much water and no air, 
biit they were more roimded or less angular than before, and 
their walls not nearly so straight ; it was therefore clear 
that the cells had contracted. The tubers, as long as 
they remain alive, have a strong attraction for water ; 
the shrivelled one, from which a slice had been cut, was 
left in water for 22 hrs. 30 m., and its surface became as 
smooth and tense as it originally was. On the other hand, 
a shrivelled tuber, which by some accident had been separated 
from its rhizome, and which appeared dead, did not swell in 
the least, though left for several days in water. 

With many kinds of plants, tubers, bulbs, &c., no doubt 
serve in part as reservoirs for water, but I know of no case, 
besides the present one, of such organs having been developed 
solely for this purpose. Prof. Oliver informs me that two or 
three other species of Utricularia are pi'ovided with these 
appendages ; and the group containing them has in conse- 
quence received the name of orchidioides. All the other 
species of Utricularia, as well as of certain closely related 
genera, are either aquatic or marsh plants ; therefore, on the 
principle of nearly allied plants generally having a similar 
constitution, a never-failing supply of water would probably 
be of great importance to our present species. "VVe 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 helumbifolia, amethystina, geiffithii, 

CiERULEA, OEBICULATA, MULTICAULIS [cORNUTA]. 

As I wished to ascertain whether the bladders on the 
rhizomes of other species of Utricularia, and of the species 



Chap. XVIII.] UTBICULAEIA AMETHYSTINA. 357 

of certain closely allied genera, had the same essential 
structure as those of Utricularia montana, and whether they 
captured prey, I asked Prof. Oliver to send me fragments 
from the herbarium at Kew. He kindly selected some of 
the most distinct forms, having entire leaves, and believed 
to inhabit marshy ground or water. My son, Francis 
Darwin, examined them, and has given me the following 
observations; but it should be borne in mind that it is 
extremely difficult to make out the structure of such minute 
and delicate objects after they have been dried and pressed.* 

Utricularia nelumbifolia (Organ Mountains, Brazil). — The 
habitat of this species is remarkable. According to its 
discoverer, Mr. Gardner,f it is aquatic, but " is only to be 
found growing in the water which collects in the bottom 
of the leaves of a large Tillandsia, that inhabits abundantly 
an arid rooky part of the mountain, at an elevation of about 
6000 feet above the level of the sea. Besides the ordinary 
method by seed, it propagates itself by runners, which it 
throws out from the base of the flower-stem ; this runner is 
always found directing itself towards the nearest Tillandsia, 
when it inserts its point into the water and gives origin to 
a new plant, which in its turn sends out another shoot. In 
this manner I have seen not less than six plants united." 
The bladders resemble those of Utricularia montana in all 
essential respects, even to the presence of a few minute two- 
armed glands on the valve. Within one bladder there was 
the remnant of the abdomen of some larva or crustacean of 
large size, having a brush of long sharp bristles at the apex. 
Other bladders included fragments of articulate animals, and 
many of them contained broken pieces of a curious organism, 
the nature of which was not recognised by any one to whom 
it was shown. 

Utricularia amethystina (Guiana). — This species has small 
entire leaves, and is apparently a marsh plant ; but it must 
grow in places where crustaceans exist, for there were two 
small species within one of the bladders. The bladders are 
nearly of the same shape as those of Utricularia montana, and 



* Prof. Oliver has givea (' Proc. appear to have paid particular atteu- 

Linn. Soc' vol. iv. p. 169) figures of tion to these organs, 

the bladders of two South American t ' Travels in the Interior of Brazil, 

species, namely, Utricularia Jameso- 1836-41,' p. 527. 
niana and peltata; but he does not 



358 UTEICULABIA OKUICULATA. [Chap. X\1II. 

are covered outside with the usual papillas ; but they differ 
remarkably in the antennse being reduced to two short 
points, united by a membrane hollowed out in the middle. 
This membrane is covered with innumerable oblong glands 
supported on long footstalks ; most of which are arranged in 
two rows converging towards the valve. Some, however, 
are seated on the margins of the membrane ; and the short 
ventral surface of the bladder, between the petiole and 
valve, is thickly covered with glands. Most of the heads 
had fallen off, and the footstalks alone remained ; so that 
the ventral surface and the orifice, when viewed under a 
weak power, appeared as if clothed with fine bristles. The 
valve is narrow, and bears a few almost sessile glands. The 
collar against which the edge shuts is yellowish, and presents 
the usual structure. From the large number of glands on 
the ventral surface and round the orifice, it is probable that 
this species lives in very foul water, from which it absorbs 
matter, as well as from its captured aind decaying prey. 

Utricularia griffithii (Malay and Borneo). — The bladders 
are transparent and minute ; one which was measured being 
only xIot of ^^ inch ( • 711 mm.) in diameter. The antennse 
are of moderate length, and 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 cserulea (India).- — The bladders resemble those 
of the last species, both in the general character of the 
antennas and in the processes within being exclusively bifid. 
They contained remnants of entomostracan crustaceans. 

Utricularia orhiculata (India). — The orbicular leaves and 
the stems bearing the bladders apparently float in water. 
The bladders do not differ much from those of the two last 
species. The antennse, 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 anus of equal length. The prey which they 
had captured consisted of entomostracan crustaceans. 



Chap. XVIII.] POLYPOMPHOLYX. 359 

Utricularia multicaulis (Sikkim, India, 7000 to 11,000 feet). 
— The bladders, attached to rhizomes, are remarkaUe from 
the structure of the antennas. These are broad, flattened, 
and of large size ; they bear on their margins multicellular 
hairs, surmounted by glands. Their bases are united into a 
single, rather narrow pedicel, and they thus appear like a 
great digitate expansion at one end of the bladder. Inter- 
nally the qnadrifid processes have divergent arms of equal 
length. The bladders contained remnants of articulate 
animals. 

[ Utricularia cornuta, Michx. (United States). — This species 
has been studied by A. Schimper in America, and is the sub- 
ject of a short paper in the ' Botanische Zeitung.' * It grows 
in swampy ground, and presents a remarkable appearance ; 
the aerial part of the plant seems at first sight to consist of 
nothing but almost naked flower-stems a foot in height, 
bearing from two to five large yellow flowers. U. cornuta 
has no roots, its underground stem or rhizome is much 
branched and bears numerous minute bladders. The 
branches of the rhizome throw up here and there grass-like 
leaves which cover the ground without having any apparent, 
connection with the flower-stem. The structure of the blad- 
ders is not in any way remarkable, resembling in its general 
features that of the European species. The bladders generally 
contain organic remains; out of 114 only 11 contained no- 
debris. The contents include diatoms and small animals, — 
worms, rotifers, small crustaceans ; and the hairs lining the 
inside of the bladders give evidence of having absorbed 
matter from the decaying mass. — F. D.] 

POLYPOMPHOLYX. 

This genus, which is confined to Western Australia, is 
characterised by having a "quadripartite calyx." In other 
respects, as Prof. Oliver remarks, | " it is quite a 
Utricularia." 

Polypompholyx muUifida. ^^The bladders are attached in 
whorls round the summits of stiff stalks. The two antenna3 
are represented by a minute membranous fork, the basal 
part of which forms a sort of hood over the orifice. This 



[* " NotizeQ ubei- Insectfressende Pflanzen," 1882, p. 241.] 
t ' Proc. Linn. Soc' toI. iv. p. 171. 



360 GENLISEA OENATA. [Chap. XVIII. 

hood expands into two wings on each side of the bladder. A 
third wing or crest appears to be formed by the extension of 
the dorsal surface of the petiole ; but the structure of these 
three wings could not be clearly made out, owing to the 
state of the specimens. The inner surface of the hood is 
lined with long simple hairs, containing aggregated matter, 
like that within the quadrifid processes or the previously 
described species when in contact with decayed animals. 
These hairs appear therefore to serve as absorbents. A valve 
was seen, but its structure could not be determined. On the 
collar round the valve there are in the place of glands 
numerous one-celled papillse, having very short footstalks. 
The quadrifid processes have divergent arms of equal length. 
Eemains of entomostracan crustraceans were found within the 
bladders. 

Polypompholyx tenella. — The bladders are smaller than 
those of the last species, but have the same general structure. 
They were full of debris, apparently organic, but no remains 
of articulate animals could be distinguished. 



Genlisea. 

This remarkable genus is technically distinguished from 
Utrioularia, 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 " herba3 annuse paludosse." 

Oenlisea 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 (6) is formed by a slight enlarge- 
ment of the narrow.blade of the leaf. A hollow neck (ji), 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 ■^\ of an 



" Bidrag til Kundskaben om Lentibulariacese," Copenhagen, 1874. 



Chap. XVIII.] STEUOTUEE OF THE LEAVES. 



361 




inch ( ■ 705 mm.) in its longer diameter had a neck ^ of an 
inch (10-583 mm.) in length, and y^ of an inch (-254 mm.) 
in breadth. On each side of the orifice there is a long spiral 
arm or tube (o) ; the structure of which will be best under- 
stood by the following illustration. Take a narrow ribbon 
and wind it spirally round a thiu 
cylinder, so that the edges come 
into contact along its whole 
length ; then pinch up the two 
edges so as to form a little crest, 
which will of course wind spirally 
round the cylinder like a thread 
round a screw. If the cylinder is 
now removed, we shall have a 
tube like one of the spiral arms. 
The two projecting edges are not 
actually united, and a needle can 
be pushed in easily between 
them. They are indeed in many 
places a little separated, forming 
narrow entrances ioto the tube ; 
but this may be the result of the 
drjiing of the specimens. The 
lamina of which the tube is 
formed seems to be a lateral pro- 
longation of the lip of the orifice ; 
and the spiral line between the 
two projecting edges is contin- 
uous 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 extremities could 
not be determined, as all the 
specimens were broken ; nor does 
it appear that Dr. "Warming 
ascertained this point. 

So much for the external struc- 
ture. Internally the lower part of the utricle is covered with 
spherical papillee, formed of four cells (sometimes , eight 
according to Dr. Warming), which evidently answer to the 
quadrifid processes within the bladders of Utricularia. These 



w 



Fig. 29. 

{Genlisea oimata.') 

UtrlcuLiferous leaf; enlarged about 
three times. 

I Upper part of lamiua of leaf. 
h Utricle or bladder. 
n Neck of utricle. 
o Orifice. 

a Spirally wound arms, with their 
ends broken off. 



362 



GENLISEA OENATA. 



[Chap. XVUI. 



papillae extend a little way up the dorsal and ventral surfaces 
of the utricle ; and a few, according to Warming, may be 
found in the upper part. This upper region is covered by 
many transverse rows, one above the other, of short, closely 
approximate hairs, pointing downwards. These hairs have 
broad bases, and their tips are formed by a separate cell. 

They are absent in the lower 
part of the utricle where the 
papillae abound. The n^ct is 
likewise lined throughout its 
whole length with transverse 
rows of long, thin, transparent 
hairs, having broad bulbous 
(fig. 30) bases, with similarly 
constructed sharp points. They 
arise from little projecting 
ridges, formed of rectangular 
epidermic cells. The hairs vary 
a little in length, but their 
points generally extend down 
to the row next below ; so that 
if the neck is split open and 
laid flat, the inner surface re- 
sembles a paper of pins, — the 
hairs representing the pins, and 
the little transverse ridges re- 
presenting the folds of paper 
through which the pins are 
thrust. These rows of hairs are 
indicated in the previous figure 
(29) by numerous transverse 
lines crossing the neck. The 
inside of the neck is also studded 
with papillae ; those in the lower 
part are spherical and formed 
of four cells, as in the lower 
part of the utricle ; those in the 
upper part are formed of two cells, which are much elongated 
downwards beneath their points of attachment. These two- 
celled papillas apparently correspond with the bifid process 
in the upper part of the bladders of Utricularia. The narrow 
transverse orifice (o, fig. 29) is situated between the bases of 
the two spiral arms. No valve could be detected here, nor 




Fie. 31). 

(^Genlisea ornata.^ 

Portion of inside of neck leading 
into tlie utricle, greatly enlarged, Bhow- 
ing the downward pointed bristles, and 
small quadrifid cells or processes. 



Chap. XVIH.] CAPTURED PREY. 363 

was any such structure seen by Dr. Wanning. The lips of 
the oritice are armed with many short, thick, sharply pointed, 
somewhat incurved hairs or teeth. 

The two projecting edges of the spirally wound lamina, 
forming the arms, are provided with short incurved hairs or 
teeth, exactly like those on the lips. These project inwards 
at right angles to the spiral line of junction between the 
two edges. The inner surface of the lamina supports two- 
celled, elongated papilles, resembling those in the upper 
part of the neck, but differing slightly from them, according 
to Warming, in their footstalks being formed by prolonga- 
tions of large epidermic cells ; whereas the papillaa within 
the neck rest on small cells sunk amidst the larger ones. 
These spiral arms form a conspicuous difference between the 
present genus and Utricularia. 

Lastly, there is a bundle of spiral vessels which, running 
up the lower part of the linear leaf, divides close beneath 
the utricle. One branch extends up the dorsal and the 
other up the ventral side of both the utricle and neck. Of 
these two branches, one enters one spiral arm, and the other 
branch the other arm. 

The utricles contained much debris or dirty matter, which 
seemed organic, though no distinct oi-ganisms could be 
recognised. It is, indeed, scarcely possible that any object 
could enter the small orifice and pass down the long narrow 
neck, except a living creature. Within the necks, however, 
of some specimens, a worm with retracted horny jaws, the 
abdomen of some articulate animal, and specks of dirt, pro- 
bably the remnants of other minute creatures, were found. 
Many of the papillee within both the utricles and necks 
were discoloured, as if they had absorbed matter. 

From this description it is sufficiently obvious how Genlisea 
secures its prey. Small animals entering the narrow orifice 
— but what induces them to enter is not known any more 
than in the case of Utricularia — would find their egress 
rendered difficult by the sharp incurved hairs on the lips, 
and as soon as they passed some way down the neck, it 
would be scarcely possible for them to return, owing to the 
many transverse rows of long, straight, downward pointing 
hairs, together with the ridges from which these project. 
Such creatures would, therefore, perish either within the 
neck or utricle ; and the quadrifid and bifid papillae would 
absorb matter from their decayed remains. The transverse 



364 GENLISEA FILIFOEMIS. [Chap. XVIII. 

rows of hairs are so numerous that they seem superfluous 
merely for the sake of preventing the escape of prey, and as 
they are thin and delicate, they prohahly serve as additional 
absorbents, in the same manner as the flexible bristles on 
the infolded margins of the leaves of Aldrovanda. The 
spiral arms no doubt act as accessory traps. Until fresh 
leaves are examined, it cannot be told whether the line of 
junction of the spirally wound lamina is a little open along 
its whole course, or only in parts, but a small creature which 
forced its way into the tube at any point, would be prevented 
from escaping by the incurved hairs, and would find an open 
path down 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 africana (South Africa). — Fragments of the utri- 
ouliferous leaves of this species exhibited the same structure 
as those of Genlisea ornata. A nearly perfect Acarus was 
found within the utricle or neck of one leaf, but in which 
of the two was not recorded. 

Genlisea aurea (Brazil). — A fragment of the neck of a 
utricle was lined with transverse rows of hairs, and was fur- 
nished with elongated papillas, exactly like those within the 
neck of Genlisea ornata. It is probable, therefore, that the 
whole utricle is similarly constructed. 

Genlisea filiformis (Bahia, Brazil). — Many leaves were 
examined and none were found provided with utricles, 
whereas such leaves were found without difficulty in the 
three previous species. On the other hand, the rhizomes 
bear bladders resembling in essential character those on the 
rhizomes of Utricularia. These bladders are transparent, 
and very small, viz. only -j^ of an inch ( • 254 mm.) in length. 
The antennae are not united at their bases, and apparently 
bear some long hairs. On the outside of the bladders there 
are only a few papillae, and internally very few quadrifid 
processes. These latter, however, are of unusually 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 africana, ornata, and aurea 



Chap. XVIU.] COXCLUSIOK. 365 

were carefully examined, but none could be found. What 
are we to infer from these facts ? Did the three species just 
named, like their close allies, the several species of Utricu- 
laria, aboriginally possess bladders on their rhizomes, which 
they afterwards lost, acquiring in their place utriculiferous 
leaves? In support of this view it may be urged that the 
bladders of Genlisea 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, Australia, North and South America- 
are admirably adapted for capturing by two methods small 
aquatic or terrestrial animals, and that they absorb the pro- 
ducts of their decay. 

Ordinary plants of the higher classes procure the requisite 
inorganic elements from the soil by means of their roots, and 
absorb carbonic acid from the atmosphere by means of their 
leaves and stems. But we have seen in a previous part of 
this work that there is a class of plants which digest and 
afterwards absorb animal matter, namely, all the 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 substances, such as pollen, seeds, and bits of leaves. 
No doubt their glands likewise absorb the salts of ammonia 
brought to them by the lain. It has also been shown that 
some other plants can absorb ammonia by their glandular 
hairs ; and these will profit by that brought to them by the 
rain. There is a second class of plants which, as we have 
just seen, cannot digest, but absorb the products of the 
decay of the animals which they capture, namely, Utricularia* 
and its close allies ; and from thfe excellent observations of 



[* The late Professor de Bary grown in water swarming with 

showed me at Strasburi' two dried minute crustaceans, the other in clean 

specimens of Utricularia (vulgcms ?) water ; the difference in size between 

which clearly demonstrated the ad- the "fed" and the "starved" plants 

vantage which this plant derives from was most striking. — F. D.] 
captured insects. One had been 



366 " CONCLUSION. [Chap. XVIII. 

Dr. Mellichamp and Dr. Canby, there can scarcely he a doubt 
that Sarracenia and Darlingtonia may be added to this class, 
though the fact can hardly be considered as yet fully proved. 

[A. Schimper, in an interesting paper,* gives evidence that 
the products of decay are absorbed by the pitchers of Sarra- 
cenia purpurea.^ In the epidermic cells at the base of the 
pitcher the changes produced by the presence of decaying 
animal matter are strikingly evident, and bear a strong 
resemblance to the process of aggregation as seen in Drosera. 
The cell-sap is rich in tannin (as in Drosera), and when 
aggregation takes place the single vacuole containing the 
cell-sap is replaced by several highly refractive drops. The 
process resembles in fact the division and concentration of 
the vacuole as described by De Vries (see footnote, p. 35). 
Schimper supposes that the cell-sap gives up to the proto- 
plasm part of its water, and he describes the concentrated, 
tannin-containing drops which are thus formed, as lying in 
the swollen watery protoplasm which now takes up more 
space than in the unstimulated condition. Schimper's paper 
also contains a good general description of the pitchers of 
Sarracenia. — ¥. I).] 

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, 



* [" Notizen tibcr Insectfressende J [_Dischidia Safflesiana, Wall., is 

Pflanzen," *Bot. Zeitung,' 1882, p. sometimes doubtfully ' mentioned as 

225.] an insectivorous plant. The re- 

■]• [In the 'Quarterly Journal of searches of Treub (' Annales duJardin 
Science and Art,' 1829, vol. ii. p. 290, botaniquedeBuitenzorg,'Tol.iii.l883, 
Burnett (as Mr. Thiselton Dyer p. 13) shbw that this is not the case, 
points out to me) wrote as follows : Dischidia grows as a climbing epi- 
" SarraceniiE, if kept from the access phyte on trees, and bears clusters of 
of flies, are said to be less flourishing modified leaves or pitchers. They 
in their growth than when each dre of interest morphologically be- 
pouch is truly a sarcophagus." cause it is the inside of the pitcher 
According to Faivre (' Comptes ren- which corresponds to the lower sur- 
dus,' vol. Ixxxiii. 1876, p. 1155) both face of the leaf, so that, the pitchers 
Nepenthes and Sarracenia flourish are involutions or ponchings of the 
better when their pitchers are sup- leaf from the lower instead of from 
plied with water, and Wiesner states the upper surface as in Nepenthes, 
that Sarracenia can be kept fresh for Sarracenia and Cephalotus (see Dick- 
months without watering the roots son, 'Journal of Botany,' 1881, p. 
if the pitchers are well supplied. 133). The pitchers of Dischidia are 
(' Elemente der Anat. und Phys. der covered, both inside and out, with a 
Pflanzen,' 2nd Edit. 1885, p. 226). — waxy coating which is heaped up in 
F. D.] a curious manner round the stomata. 



Ciur. XVIII.] 



CONCLUSION. 



367 



ttere is the well-known fourtli class of parasites (such as the 
mistletoe), which are nourished by the juices of living plants. 
Most, however, of the plants belonging to these four classes 
obtain part of their carbon like ordinary species, from the 
atmosphere. Such are the diversified means, as far as at 
present known, by which higher plants gain their subsis- 
tence. 



forming a tower-like structure round 
each of these openings. There are 
no glands on the surface of the 
pitchers, and the fluid with which 
they are often partially filled is 
simply collected rain-water. Adven- 
titious roots are numerous and com- 
monly enter the cavities of the 
pitchers. Delpino (quoted by Treub) 
believes that the pitchers serve to 
collect ants, &c., whose dead bodies 
may supply food to the roots. Treub 
on the other hand believes that the 
drowning of ants within the pitchers 



is accidental rather than wilful on 
the part of the plant. He points out 
that no arrangement for retaining 
the ants exists, and that the adven- 
titious roots supply ladders by which 
they may escape ; moreover the ants 
are as often as not found alive and 
well within the pitchers. Treub is 
inclined to consider that the pitchers' 
function is as stores or cisterns of 
water ; but their use in the economy 
of the plant cannot be considered as 
definitely settled.— F. D.] 



( 369 ) 



INDEX. 



ABSORPTION. 



AnsORPTiON by Dionaia, 238 

by Drosera, 1, 14 

by Drosophyllum, 273 

by Pinguicula, 307 

by glandular hairs, 278 

by glands of Utricularia, 336, 

340 
by quadrifids of Utricularia, 

333, 340 
— ^ by Utricularia montana, 353 
Acid, nature of, in digestive secretion 

of Drosera, 73 

— present in digestive fluid of 
various species of Drosera, Dionaia, 
Drosophyllum, and Pinguicula, 
224, 243, 274, 307 

Acids, various, action of, on Drosera, 

154 
of the acetic series replacing 

hydrochloric in digestion, 74 
, arsenious and chromic, action 

on Drosera, 151 
, diluted, inducing negative 

osmose, 161 
Adder's poison, action on Drosera, 

168 
Aggregation of protoplasm in Dro- 
sera, 32 
— — in Drosera induced by salts of 

ammonia, 37 
caused by small doses of 

carbonate of ammonia, 119 

of protoplasm in Drosera, a 

reflex action, 196 

in various species of Dro- 
sera, 224 



AMMONIA. 

Aggregation of protoplasm in DioniEa, 

235, 243 

in Drosophyllum, 273, 274 

in Pinguicula, 299, 314 

in Utricularia, 332, 335, 

345, 346, 352 
Albumen, digested by Drosera, 77 

, liquid, action on Drosera, 67 

Alcohol, diluted, action of, on Dro- 
sera, 65, 177 
Aldrovanda vesiculosa, 260 
, absorption and digestion by, 

264 

, varieties of, 265 

Alga;, aggregation in fronds of, 54 
Alkalies, arrest digestive process in 

Drosera, 78 
Aluminium, salts of, action on Dro- 
sera, 150 
Ammonia, amount of, in rain water, 

140 
, carbonate, action on heated 

leaves of Drosera, 58 
, , smallness of doses causing 

aggregation in Drosera, 119 

, , its action on Drosera, 1 1 5 

• -, , vapour of, absorbed by 

glands of Drosera, 116 

, ■, smallness of doses causing 

inflection in Drosera, 119, 137 
, phosphate, smallness of doses 

causing inflection in Drosera, 125, 

137 
, , size of particles afifecting 

Drosera, 141 
, nitrate, smallness of dosos 

causing inflection in Drosera, 120, 

137 

2 B 



370 



INDEX. 



AMMONIA. 


CHROMIC. 


Ammonia, salts of, action on Drosera, 


Brunton, Lauder, on the digestion of 


11 


urea, 102 


, , their action affected by 


, of chlorophyll, 103 


previous immersion in water and 


, of pepsin, 102 


various solutions, 174 


Biisgen, Dr. M., on nuti'ition of 


, , induce aggregation in 


Drosera, 16 


Drosera, 37 


Burnett, on Sarracenia, 366 


, various salts of, causing 


Byblis, 277 


inflection in Drosera, 135 




Antimony, tartrate, action on Dro- 




sera, 15 


C. 


Areolar tissue, its digestion by Dro- 




sera, 85 


Cabbage, decoction of, action on 


Arsenious acid, action on Drosera, 151 


Drosera, 70 


Atropine, action on Drosera, 166 


Cadmium chloride, action on Drosera, 

150 
CiEsium, chloride of, action on Dro- 






sera, 148: ■ . 


B. 


Calcium, salts of,. action on Drosera, 




148 


Barium, salts of, action on Drosera, 


Camphor, action of Drosera, 170 


149 


Canby, Dr., on Dionasa, 243, 250, 252 


Bases of salts, preponderant action of. 


, on Drosera filiformis, 227 


on Drosera, 152 


Caraway, oil of, action on Drosera, 


Basis, fibrous, of bone, its digestion 


172 


by Drosera, 90 


Carbonic acid, action on Drosera, 180 


Batalin, on motor impulse in Drosera, 


delays aggregation in Drosera, 


204 


50 


, on bending of tentacles of 


Cartilage, its digestion by Drosera, 


Drosera, 209 


86 


, on Dionaaa, 233 


Casein, its digestion by Drosera, 95 


■ , on mechanism of closure in 


Caspary, on Aldrovanda, 260, 261 


Diona;a, 256 


Cellulose, not digested by Drosera, 


, on colour of Pinguicula leaves, 


103 


297 


Chalk, precipitated, causing inflec- 


■ , on movement in Pinguicula, 304 


tion of Drosera, 28 


Belladonna, extract of, action on 


Cheese, its digestion by Drosera, 96 


Drosera, 70 


Chitine, not digested by Drosera, 


Bennett, Mr. A. W., on Drosera, 1, 2, 7 


102 


' , coats of pollen grains not 


Chloroform, effects of, on Drosera 


digested by insects, 96 


177 


Binz, on action of quinine on white 


, , on Diona;a, 246 


blood-corpuscles, 164 


Chlorophyll, grains of, in living 


■ , on poisonous action of quinine 


plants,"iJigested by Drosera, 103 


on low organisms, 165 


, pure, not digested by Drosera, 


Bone, its digestion by Drosera, 88 


103 


Brunton, Lauder, on digestion of 


Chondrin, its digestion by Drosera. 


gelatine, 92 ' 


93 


, on the composition of casein, 


Chromic acid, action on Drosera, 


95 


151 



INDEX. 



371 



Cloves, oil of, action on Crosera, 173 
Cobalt chloride, action on Drosera, 

152 
Cobra poison, action on Drosera, 168 
Cohn, Prof., on Aldrovanda, 260 . 
— , on contractile tissues in plants, 

293 
— -, on movements of stamens of 

Composite, 208 

, on Utricularia, 319 

Colchicine, action on Drosera, 166 
Copper chloride, action on Drosera, 

151 
Crystallin, its digestion by Droscrn, 

98 
Curare, action on Drosera, 166 
Curtis, Dr., on Diona;a, 243 



Darwin, C, papers on action of 

ammonia on roots, 55 
— .— , Erasmus, on Dionsca, 2'l-3 
— — , Francis, on the effect of an 

induced galvanic current on Dro- 
sera, 31 
, on aggregation in Drosera, 32, 

39 

, on nutrition of Drosera, 15 

1 , on the. digestion of grains of 

chlorophyll, 103 
De Bavy, effect of animal food on 

Utricularia, 363. • j 
De Candolle, on, Dismpa, 232, 23.3, 

235 
Delpino, on Aldrovanda, 260 

, on Utricularia, 319, 366 

, on Dischidia, 367 

Dentine, its digestion by Drosera, 88 
Digestion of various substances by 

Dionaea, 243 

by Drosera, 71 

by Drosophyllum, 274 

. by Pinguicula, 307 

, origin of power of, 291 

Digitaline, action on Drosera, 163 
Dionsea, early literature o^ 231 



DEOSOPIIYLLUM. 

Dionaja, muscipula, small size of roots, 
231 

, structure of leaves, 232 

, sensitiveness of filaments, 234 

, absorption by, 238 

, secretion by, 238 

, digestion by, 243 

, effects on, of chloroform, 246 

, maimer of capturing insects, 

247 

, transmission of motor impulse, 

258 

, re-e.xpansion of lobes, 257 

Direction of inHected tentacles of 

Drosera, 197 
Dischidia Rafilesiana, 366 
Dohrn, Dr., on rhizocephalous crus- 
taceans, 288 
Donders, Prof, small amount of 
atropine affecting the iris of the 
dog, 140 
Dragonfly caught by Drosera, 2 
Drosera, absorption by, 1, 14 

anglica, 224 

binata, rel dichotomn, 227 

capensis, 223 

dichotoma, 5 

filiformis, 226 

heterophylla, 229 

intermedia, 225 

, sensitiveness of, 22 

Drosera rotundilblia, structure of 
leaves, 3 

, artificial feeding of, 15 

, effects on, of nitrogenous 

fluids, 64 

, effects of heat on, 56 

, its power of digestion, 71 

, backs of leaves not sensitive, 1 88 

, transmission of motor impulse, 

190 

, general summary, 212 

spathulata, 226 

Droseracese concluding remarks on, 
287 

, their sensitiveness compared 

with that of animals, 295 
Drosophyllum, structure of leaves, 

269 
, secretion by, 270 



372 



INDEX. 



DROSOPHTLLUM. 



Drosophyllum, absorption by, 273 

, digestion by, 274 

Puval-Jouve, on Aldroyanda, 268 



Ellis, on Dionaea, 243 

Enamel, its digestion by Drosera, 
88 

Erica, tetralix, glandular hairs of, 
284 

Ether, effects of, on Drosera, 179 

, , on Dioniea, 246 

Euphorbia, process of aggregation in 
roots of, 53 

Ewald, on peptogenes, 106 

Exosmose from backs of leaves of Dro- 
sera, 188 



r. 

Faivre, on Nepenthes and Sarra- 

cenia, 366 
Fat not digested by Drosera, 104 
Fayrer, Dr., on the nature of cobra 

poison, 168 
, on the action of cobra poison 

on animal protoplasm, 170 
, on cobra poison paralysing 

nerve centres, 183 
Ferment, nature of, in secretion of 

Drosera, 78, 81 
Fibrin, its digestion by Drosera, 84 
Fibro-cartilage, its digestion by 

Drosera, 87 
Fibro-elastic tissue, not digested by 

Drosera, 100 
Fibrous basis of bone, its digestion by 

Drosera, 90 
Fluids, nitrogenous, effects of, on 

Drosera, 64 
Fouruier, on acids causing movements 

in stamens of Berberis, 160| 
Frankland, Prof., on nature of acid in 

secretion of Drosera, 73 
Fraustadt, A., on Diona;a, 232, 233 
, on roots of Dionsea, 288 



HAIDENHAIN. 



G. 



Galvanism, current of, causing in- 
flection of Drosera, 31 

, effects of, on Dioneea, 256 

Gardiner, W., on Drosera dichotoma, 5 

, on the Rhabdoid, 32 

, on aggregation, 34 

, on process of secretion in 

Drosera, 72 

, on intercellular protoplasm, 

200 

, on contractility of plant-cells, 

209 

, on gland-cells of Dionaja, 238 

Gardner, Mr., on Utricularia nelum- 

bifolia, 357 
Gelatine, impure, action on Drosera, 
67 

, pure, its digestion by Drosera, 

92 
Genlisea africana, 364 

filiformis, 364 

ornata, structure of, 360 

, manner of capturing prey, 363 

Glandular hairs, absorpion by, 278 

, summary on, 285 

Glauer, on aggregation, 39 
Globulin, its digestion by Drosera, 98 
Gluten, its digestion by Drosera, 97 
Glycerine, inducing aggregation in 
Drosera, 45 

, action on Drosera, 173 
Gold chloride, action on Drosera, 150 
Gorup-Besanez, on the presence of ii 

solvent in seeds of the vetch, 292 
Gra.ss, decoction of, action on Dro- 
sera, 70 
Gray, Asa, on the Droseracea;, 2 
Greenland, on Drosera, 1, 5 
Gum, action of, on Drosera, 65 
Gun-cotton, not digested by Drosera, 
103 



H. 

Hffimatin, its digestion by Drosera, 

99 
Haidenhain, on peptogenes, 106 



INDEX. 



373 



Hail's, glandular, absorption by, 278 

— — , , summary on, 285 

Heat, inducing aggregation in Dro- 

sera, 45 
— , effect of, on Drosera, 56 

, , on Dionaja, 237, 258 

Hockel, on state of stamens of Bcr- 

beris after excitement, 37 
Hofmeister, on pressure arresting 

movements of protoplasm, 52 
Holland, Mr., ou Utricularia, 319 
Hooker, Dr., on carnivorous plants, 1! 
, on power of digestion by Ne- 
penthes, 81 
, history of observations on 

Dioniea, 231, 243 
Hovelacque, on Utricularia, 348 
Hydrocyanic acid, effects of, on 

Dionica, 246 
Hyoscyamus, action on Drosera, 70, 

168 



Iron chloride, action on Drosera, 
151 

Isinglass, solution of, action on Dro- 
sera, 67 



Johnson, Dr., on movement of flower- 
stems of Pinguicula, 307 



X. 

Kellerraann and Von Raumer, on 

nutrition of Drosera, 15 
Klein, Dr., on microscopic character 

of half digested bone, 88 
— . — , on state of half digested fibro- 

cartilage, 87 
■ .. , on size of micrococci, 141 
Knight, Mr., on feeding Dionasa, 243 
Kossman, Dr., ou rhizocephalous 

crustaceans, 288 



Kunkel, on electric phenomena in 

Diona;a, 256 
Kurtz, on Dionasa, 231, 233 



Lankester, E. Ray, on glands of water 

plants, 268 
Lead chloride, action on Drosera, 151 
Leaves of Drosera, backs of, not 

sensitive, 188 
Legumin, its digestion by Drosera, fl6 
Lemna, aggregation in leaves of, 54 
Lime, carbonate of, precipitated, 

causing inflection of Drosera, 28 
, phosphate of, its action on 

Drosera, 91 
Linna:us, on Dionxn, 243 
Lithium, salts of, action ou Drosera, 

148 



Magnesium, salts of, action on Dro- 
sera, 149 

Manganese chloride, action on Dro- 
sera, 151 

Marshall, Mr. W., on Pinguicula, 
298 

Means of movement in Dionaia, 253 

in Drosera, 206 

Meat, infnsion of, causing aggrega- 
tion in Drosera, 44 

, , action on Drosera, 67 

, its digestion by Drosera, 82 

Mercury perchloride, action on Dro- 
sera, 150 

Milk, inducing aggregation in Dro- 
sera, 44 

, action on Drosera, 66 

, its digestion by Drcsera, 94 

Mirabilis longiflora, glandular hairs 
of, 284 

Moggridge, Traherne, on acids in- 
juring seeds, 105 

Moore, Dr., on Pinguicula, 315 

Mori, on Aldrovanda, 263 



374 



INDEX. 



Morphia acetate, action on Srosera, 

167 
Morren, E., on Drosera binata, 227 
Motor impulse in Drosera, 190, 209 

in Dion^ea, 252 

Movement, origin of power of, 293 
Movements of leaves of Pinguicula, 

299 
of tentacles of Drosera, means 

of, 206 

of Dionsen, means of, 252 

Mucin, not digested by DroSera, 100 
Mucus, action on Drosera, 67 
Miiller, Fritz, on rhizocephalous 

crustaceans, 288 
Munk, on Diona:a, 234, 247 

, on electric phenomena in Dionosa, 

• 256 



N. 

Nepenthes, its power of digestion, 81 
Nickel chloride, action on Drosera, 

152 
Nicotiana tabacum, glandular hairs 

of, 284 
Nicotine, action on Drosera, 165 
Nitric ether, action on Drosera, 180 
Nitschke, Dr., references to his papers 

on Drosera, 1 
, on sensitiveness of backs of 

leaves of Drosera, 188 
, on direction of inflected ten- 
tacles in Drosera, 198 

, on Aldrovanda, 261 

Nourishment, various moans of, by 

plants, 365 
Nuttall,I)r.,onre-e.tpansionofDion8Ea, 

257 



Odour of pepsin, emitted from leaves 

of Drosera, 74 
Oels, W., on comp. anatomy of Dro- 

seraceie, 2 
Oil, olive, action of, on Drosera, 66, 

104 



Oliver, F., on motor impulse, 204 

, Prof., on Utricularia, 349, 

356-360 
Oudemans, on Dionsea, 233 ' 



Papaw, juice of, hastening putrefac- 
tion, 331 
Particles, minute size of, causing 

inflection in Drosera, 24, 28 
Peas, decoction of, action on Drosera, 

6& 
Pelargonium zonale, glandular hairs 

of,. 283 
Penzig, Otto, on roots of Droso- 

phyllum, 288 
Pepsin, odour of, emitted from Dro- 
sera leaves, 74 

, not digested by Drosera, 101 

, its secretion by animals excited 

only after absorption, 107 
Peptogenes, 106 
Pfeffer, on sensitiveness of Drosera to 

contact, 22, 31 

, on nucleus in Drosera, 32 

. ; on aggregation, 34 

•, on Dionsea, 256 

; on roots of carnivorous plants, 

288 

, on Pinguicula, 314 

Pinguicula grandiflora, 315 

lusitanica, 315 

vulgaris, structure of leaves 

and roots, 297 
, number of insects caught by, 

298 

, power of movement, 299 

, secretion and absorption by, 307 

, digestion by, 307 

, leaves of, used to curdle milk, 

314 
, effects of secretion on living 

seeds, 315 
Platinum chloride, action on Drosera, 

152 
Poison of cobra and adder, their 

action on Drosera, 1S8 



INDEX. 



375 



Pollen, its digestion by Drosera, 96 
Polypompholyx, structure of, 359 
Pntnssium, salts of, inducing aggre- 
gation in Drosera, 43 

, , action on Drosera, 146 

■ ' phosphate, not decomposed by 

Drosera, 147, 153 
Price, Mr. John, on Utricularia, 345 
Primula sinensis, glandular hairs of, 
281 

, number of glandular hairs of, 

286 
Protoplasm, aggregated, re-dissolu- 
tiou of, 46 

, aggregation of, in Drosera, 32, 

34,35 

, , in Drosera, caused by 

small doses of carbonate of am- 
monia, 119 

, , iu Drosera, a reflex 

action, 196 
, , in various species of Dro- 
sera, 224 

, in Dionaia, 235, 242 

, , in Drosophyllum, 273, 

274 

, , in Pinguicula, 299, 314 

, , in Utricularia, 332, 335, 

346, 352 



Quinine, salts of, action on Drosern, 
- 163 



B. 

Rain-water, amount of ammonia in, 

140 
Ralls, Mr., on Pinguicula, 315 
Kansom, Dr., action of poisons on the 

yolk of eggs, 183 
Rees and Will, on digestive action in 

Drosera, 73, 81 
Re-expansion of headless tentacles of 

Drosera, 187 

of tentacles of Drosera, 210 

of Dionsea, 257 



Roots of Drosera, 17 

, process of aggregation 

in, 53 

■ , absorb carbonate of am- 
monia, 115 

of Dionica, 231 

of Drosophyllum, 269 

of Pinguicula, 298 

Koridula, 276 

Rubidium chloride, action on Drosera, 
148 



Sachs, Prof, effects of heat on pro- 
toplasm, 56, 59 

, on the dissolution of protei'd 

compounds in the tissues of plant;, 
292 

Saliva, action on Drosera, 67 

Salts and acids, various, effects of, 
on subsequent action of ammonia, 
175 

Sanderson, Burdon, on coagulation of 
albumen from heat, 62 

, on acids replacing hydro- 
chloric in digestion, 74 

, on the digestion of fibrous 

basis of bone, 90 

, of gluten, 97 

, of globulin, 99 

, of chlorophyll, 103 

, on different effect of sodium 

and potassium on animals, 152 

, on electric currents iu Dionaia, 

256 

Sarracenia, 365, 366 

Saxifraga umbrosa, glandular hairs 
of, 279 

Schenk, on Utricularia, 348 

Schiff, on hydrochloric acid dis- 
solving coagulated albumen, 71 

, on manner of digestion <)( 

alljumen, 77 

, on changes in meat during 

digestion, 83 

, on the coagulation of milk, 

94 



376 



INDEX. 



Schifif, on the digestion of casein, 95 

, on the digestion of mucus, 101 

, on peptogenes, 106 

Schimper, on aggregation, 34 
, on Utricularia, 331, 332 

, on Sarracenia purpurea, 365 

Schloesing, on absorption of nitro- 
gen by Nicotiana, 285 

Scott, Mr., on Drosera, 1 

Secretion of Drosera, general account 
of, 11 

, its antiseptic power, 13 

, becomes acid from excite- 
ment, 72 

, nature of its ferment, 78, 

81 

by Dionaja, 238 

by Drosophyllum, 271 

by Pinguicula, 307 

Seeds, living, acted on by Drosera, 
104 

, , acted on by Pinguicula, 

311, 314 

Sensitiveness, localisation of, in Dro- 
sera, 187 

-ofDionrea, 233 

of Pinguicula, 299 

Silver nitrate, action on Drosei'a, 148 

Sodium, salts of, action on Drosera, 
143 

— — , , inducing aggregation in 

Drosera, 43 

Sondera heterophylla, 229 

Sorby, Mr., on colouring matter of 
Drosera, 4 

Spectroscope, its power compared 
with that of Drosera, 139 

Starch, action of, on Drosera, 65, 
104 

Stein, on Aldrovanda, 260 

Strontium, salts of, action on Dro- 
sera, 149 

Strychnine, salts of, action on Dro- 
sera, 162 

Sugar, solution of, action of, on Dro- 
sera, 65 

, , inducing aggregation in 

Drosera, 44 
Sulphuric ether, action on Drosera, 
179 



UTEICOLAEIA. 



Sulphuric ether, action on Dionsea, 246 
Syntonin, its action on Drosera, 85 



Tait, Mr., on Drosophyllum, 269 
Taylor, Alfred, on the detection of 

minute doses of poisons, 139 
Tea, infusion of, action on Drosera, 

66 
Tentacles of Drosera, move when 

glands cut off, 31, 187 

, inflection, direction of, 197 

, means of movement, 206 

, re-expansion of, 210 

Tlieine, action on Drosera, 166 
Tin chloride, action on Drosera, 151 
Tissue, areolar, its digestion by 

Drosera, 85 
, fibro-elastic, not digested by 

Drosera, 100 
Tissues through which impulse is 

transmitted in Drosera, 200 

in Diona;a, 252 

Touches repeated, causing inflection 

in Drosera, 29 
Transniission of motor impulse in 

Drosera, 190 

' in Dionaja, 252 

Traube, Dr., on artificial cells, 176 
Treat, Mrs., on Drosera filiformis, 226 

, on Dionaja, 251 

, on valve in Utricularia, 829, 

330, 346 
Trecul, on Drosera, 1, 5 
Treub, on Dischidia, 366, 367 
Tubers of Utricularia montana, 354 
Turpentine, action on Drosera, 173 



V. 

Urea, not digested by Drosera, 102 
Urine, action on Drosera, 66 
Utricularia clandestina, 346 

minor, 345 

montana, structure of bladders, 

348 



INDEX. 



UTKICULARIA. 

Utricularia, montana animals caught 

by, 352 

, absorption by, 353 
, tubers of, senring as reserroirs, 

354 
Utricularia neglecta, structure of 

bladders, 321 

, animals caught by, 327 

, absorption by, 333 

, summary on absorption, 340 

, development of bladders, 342 

Utricularia, various species of, 356 
Utricularia vulgaris, 345 



Veratrine, action on Drosera, 166 

Vessels in leaves of Drosera, 200 

Vessels of Dionsea, 253 

Vines, on digestive fluid of Nepen- 
thes, 81 

, on the ferment of the Vetch, 292 

Vogel, on effects of camphor on 
plants, 171 

Von Gorup and Will, on digestive 
action in Drosera, 73, 81 

Vries, H. de, on aggregation, 35, 39 



Warming, Dr., on Drosera, 2, 6 

, on roots of Utricularia, 320 

, on trichomcs, 289 

, on Genlisea, 360 

, on parenchymatous cells in 

tentacles of Drosera, 205 

Water, drops of, not causing inflec- 
tion in Drosera, 30 

, its pov^er in causing aggrega- 
tion in Drosera, 45 

, its power in causing inflection 

in Drosera, 113 

and various solutions, effects of, 

on subsequent action of ammonia, 
174 

Wiesner, on Sarracenia, 366 

Willcinson, Rev. H. M., on Utricularia, 



Z. 

Ziegler, his statements with respect 

to Drosera, 21, 204 
, experiments by cutting vessels 

of Drosera, 202 
Zinc chloride, action on Drosera, 150 



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