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INSECTIVOROUS PLANTS 



INSECTIVOROUS 

PLANTS 



BY 

CHARLES DARWIN, M. A., R R. S. 



IVITH ILLUSTRylTIONS 



NEW YORK 

D. APPLETON AND COMPANY 

1899 



Authorized Edition. 




PREFACE TO THE SECOND EDITION. 



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

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

Francis Darwin. 

CAMBUDaE, July, 1888. 

T 



CONTENTS. 



CHAPTER I. 

Drosera rotukdifolia, or the Common Sun-dew. 

Number of insects captured Description of the leaves and their append- 
ages 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 II. 

The Movements of the Tentacles from the Contact of 
Solid Bones. 

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 com- 
mencing inflection and of subsequent re-expansion Extreme minute- 
ness of the particles causing inflection Action under water Inflec- 
tion of the exterior tentacles when their glands are excited by 
repeated touches Falling drops of water do not caus inflection. 

18-32 

CHAPTER III. 

Agqreoation of the Protoplasm within the Cells of 
the Tentacles, 

Nature of the contents of the cells before aggregation Various causes 
which excite aggregation The process commences within the glands 
and travels down the tentacles Description of the aggregated masses 
and of their spontaneous movements Currents of protoplasm along 
the walls of the cells Action of carbonate of ammonia The granules 
in the protoplasm which flows along the walls coalesce with the cen- 



iii CONTENTS. 

tnl nuuMM MinuteneflB of the quantity of carbonate of ammonia 
earning aggrcfcation Action uf other huIIm uf ammonia ()f other sub- 
stances, organic fluidti, &c. ()f water ()f heat Uedissolution of the 
aggregated maoaes l^roxinmte cauM^ of the aKgrcKution of the proto- 
plMm Summary and concludinK remarks Supplementary observa- 
tions on aggregation in the roots of plants . . . Phages 33-5S 



CHAPTER IV. 

The Effects of Heat on the Leaves. 

Nature of the cxperimentB Effects of boiling water Warm water canaea 
rapid inflection Water at a higher temperature does not cause imme- 
diate inflection, but does not kill the leaves, as shown by their subse- 
quent re-expansion and by the aggregation of the protoplasm A still 
higher tenipi^raturc kills the leaves and coagulates the albuminous 
contents of the glands 5&-(i3 

CHAPTER V. 

The Effects of Non-niteoqenous and Nitrogenous Oboanic 
Fluids on the Leaves. 

Non-nitrogenons fluids Solutions of gum arable 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 infu- 
sion of cabbage Decoction of grass leaves .... 64-70 



CHAPTER VL 

The Digestive Power of the Secretion of Droseea. 

The secretion rendered acid by the direct and indirect excitement of the 
glands Nature of the acid Digestible substances Albumen, its di- 
gestion 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 Qluten Legu- 
min Pollen globulin Uecmatin Indigestible substances Epider- 
mic productions Fibro-elastic tissue Mucin Pepsin Urea Chitine 
Cellulose Gun-cotton Chlorophyll Fat and oil Starch Action 
of the secretion on living aeeda Summary and concluding remarks. 

71-110 

CHAPTER VH. 

The Effects of Salts of Akmonia. 

Manner of performing the experimenta Action of distilled water in com- 
parison with the solutions Cbrbonate of ammonia, absorbed by the 



CONTENTS. ix 

roots The vaponr absorbed by the glands Drops on the disc Minnte 
drops applied to separate glands Leaves immersed in weak solutions 
Minuteness of the doses which induce aggregation of the protoplasm 
Nitrate of ammonia, analogous experiments with Phosphate of 
ammonia, analogous experiments with Other salts of ammonia Sum- 
mary and concluding remarks on the action of the salts of ammonia. 

Pages 111-141 

CHAPTER. VIII. 

The Effects of various other Salts, and Acids, on the Leaves. 

Salts of sodium, potassium, and other alkaline, earthy, and metallic salta 
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 move- 
ment of the protoplasm Other salts of quinine Digitaline Nicotine 
Atropine Veratrine Colchicine Theine Curare Morphia 
Hyoscyamus Poison of the cobra, apparently accelerates the move- 
ments 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 phos- 
phate of ammonia Alcohol innocuous, its vapour narcotic and poison- 
ous Chloroform, sulphuric and nitric ether, their stimulant, poison- 
ous, and narcotic power Carbonic acid narcotic, not quickly poisonous 
Concluding remarks 162-186 



CHAPTER X. 

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

Glands and summitB 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 dis- 
charge of the motor impulse suqden 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 . 187-212 



CHAPTER XI. 

Recapitulation of the Chief Observations on Drosera rotun- 
difolia 213-225 



X CONTENTS. 

CHAPTER XII. 

On the Structure and Movements of some other Spbciis 
OF Drosera. 

Droaera anglica Drotera intfrmfdia Dronera capen$i Drostra spathulata 
DroMera JUiformU Drosrra binata Cuncluding remarks. 

Pages 228-231 



CHAPTER XIII. 

DlON.A MUSCIPULA. 

Structure of the leaves Sensitiveness of the filaments Rapid movement 
of the lobes caused by irritation of the filaments Glands, their jwwer 
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 insecte are cap- 
tured Use of the marginal spikes Kinds of insects captured The 
transmission of the motor impulse and mechanism of the movements 
Be-expansion of the lobes 232-260 

CHAPTER XIV. 

Aldrotanda vesiculosa. 

Oaptnres crustaceans Structure of the leaves in comparison with those of 
Dionsea Absorption by the glands, by the quadrifid processes, and 
points on the infolded margins- -/l/rfroranda vesiailosa, var. australis 
Captures prey Absorption of animal matter Aldrovanda vesieulo*a, 
var. verttaUata Concluding remarks 261-269 

CHAPTER XV. 

Drosophtllux RoRiDULA Byblis Glandular Hairs of other 
Plants Concluding Remarks on the Droserace^. 

Drosophyllum Structure of leaves Nature of the secretion Manner of 
catching insects Power of absorption Digestion of animal sub- 
stances Summary on Drosophyllum Roridula Byblis Glandular 
hairs of other plants, their power of abRori>tion Saxifraga Primula 
Pelargonium Erica Mirabilis Nicotiana Summary on glandular 
hain Concluding remarks on the Druseraccte . 270-297 



CHAPTER XVI. 

Pinouicula. 

Ptnguiaddi vulgarit Structure of leaves Number of insects and other 
ot(iects caught Movement of the margins of the leaves Uses of this 



CONTEXTS. xi 

movement Secretion, digestion, and absorption Action of the secre- 
tion on various animal and vegetable substances The effects of sub- 
stances not containing soluble nitrogenous matter on the glands 
Pinguicula graudiflora Pinguicula lunitanica, catches insects Move- 
ment of the leaves, secretion and digestion . . Pages 298-319 

CHAPTER XVIL 

Utkiculaeia. 

Utrieularia 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 quad- 
rifid processes Absorption by the glands Summary of the observa- 
tions on absorption Development of the bladders Utrieularia vul- 
garis Utrieularia minor Utrieularia dandestina . . . 320-348 



CHAPTER XVIII. 

Uteiculakia (continued). 

Utrieularia VMntana 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 Utrieularia Polypompholyx Grenlisea, different nature of the 
trap for capturing prey [Sarracenia] Diversified methods by which 
plants are nourished 348-368 



Index 36&-3r6 



LIST OF THE CHIEF ADDITIONS TO THE 
SECOND EDITION. 



FAGS 
5 

15 

22 

83 
33 
35 

40 

72 

73 

81 

85 
96 
106 
200 
205 
210 

233 
234 

235 

236 

239 
244 
248 
257 
258 
258 
259 
261 



Gardiner on the structure of the gland cells in Drosera dichot' 

oma. 
Evidence that Drosera profits by an animal diet. 
The conclusions as to the sensitiveness of Drosera to a touch, 

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

and execute spontaneous movements, erroneous. 
De Vries on the character of aggregation produced by carbo- 
nate of ammonia. 
Gardiner on the changes occurring during secretion, in the 

glands of Drosera dichotoma. 
Rees and Will on the nature of the acid in the secretion of 

Drosera. 
Rees, Will, von Gorup, and Vines on the secretion of the acid 

and of the ferment in Drosera and Nepenthes. 
Results with syntonin untrustworthy. 
Results with casein untrustworthy. 
Schiff's 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 Dionaea. 
Fraustadt, C. de Candolle, and Batalin on the sensitive filaments 

of Dionaea. 
Munk on the sensitiveness of Diontea to the hygrometric state 

of the air. 
C. de Candolle on the effect of drops of water on the sensitive 

filaments of Dionaea. 
Gardiner on the glands of Dionaea. 
J. D. Hooker on the early history of Dionapa. 
Munk on a movement of the edges of the leaf in Dionaea. 

i Batalin and Munk on the mechanism of the movement in 
Dionaea. 
Burdon Sanderson, Kunkel, and Munk on the electrical phe- 
nomena in Dionaea. 
Caspary on Aldrovanda. 



xiv CHIEF ADDITIONS TO THE SECOND EDITION. 



PAfll 

282 
264 
269 



805 
815 

321 
833 

849 

860 
867 
367 

868 



Cohn and Casparj on Aldroyanda. 

Mori on the neat of irritability in Aldrovanda. 

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

Fraustadt, Penzig, and Pfefler on the roots of Dionaea and 
Drosophjllum. 

Batalin on the yellow-green colour of Pinguicula. 

Batalin on the pits or depressions in the leaves of Pinguicula. 

Pfeffer on the use of Pinguicula as rennet. 

Kamienski on the absence of the root in Utricularia. 

Schimper on the evidence of absorption of the products of decay 
in Vtricularia cornuta. 

Hovelacque, Schenk, and Schimper on the morphology of Utric- 
ularia 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 Diachidia Rafflesiana. 



IXSECTIYOROUS PLANTS. 



CHAPTER I. 



DROSEBA ROTUNDIFOLIA, OB THE COMMON SUN-DEW. 

Number of insects captured Description of the leaves and their append- 
ages 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. 

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



* As Dr. Xitschke has given 
(' Bot. Zeltung,' 1860, p. 229) the 
bibliography of Drosera, I need 
not here go Into details. Most 
of the notices published before 
1860 are brief and unimportant. 
The oldest paper seems to have 
been 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 cap- 
tured Insects. F. I).] There Is 
also an Interesting though short 
account of the habits of Drosera 
by Dr. Mllde, In the ' Bot. Zelt- 
ung,' 1852, p. 540. In 185.5, In 
the ' Annales des Sc. nat. bot.,' 
torn. 111. pp. 297 and 304, MM. 
-Greenland and Tr^cul each pub- 
lished 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. 
Nltscnke's papers In the ' Bot. 
Zeltung 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 sev- 
eral points, for instance on the 
transmission of an excitement 
from one part of the leaf to an- 
other, are excellent. On Dec. 
11, 1862, Mr. J. Scott read a 
paper before the Botanical So- 
ciety of Edinburgh, which was 
published In the ' Gardener's 
Chronicle,' 1863, p. 30. Mr. Scott 
shows that gentle Irritation of 
the hairs, as well as insects 
placed on the disc of the leaf, 
cause the hairs to bend Inwards. 
Mr. A. W. Bennett also gave an- 
other Interesting account of the 
movements of the leaves before 
the British As.socIatlon for 1873. 
In this same year Dr. Warming 

Subllshed an essay. In which he 
escribes the structure of the so- 
called hairs, entitled, " Sur la 
Difference entre les 'Trlchomes," 
&c., extracted from the proceed- 
ings of the Soc. d'HIst. Nat. de 
Copenhague. I shall also have 

1 



2 DROSBRA ROTUNDIPOLIA. [Chap. I. 

a dozen plants, bearing fifty-six fully expanded leaves, and 
on thirty-one of these dead insects or remnants of them 
adhered; and, no doubt, many more would have been caught 
afterwards by these same leaves, and still more by those as 
yet not expanded. On one plant all six leaves had caught 
their prey; and on several plants very many leaves had 
caught more than a gingle 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 (CcBnonympha 
pamphilus) ; but the Rev. H. M. Wilkinson informs me that 
he found a large living dragon-fly with its body firmly held 
by two leaves. As this plant is extremely common in some 
districts, the number of insects thus annually slaughtered 
must be prodigious. Many plants cause the death of insects, 
for instance the sticky buds of the horse-chestnut (^sculus 
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 in- 
sects, 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 
the leaves of rendering soluble or digesting nitrogenous sub- 
stances, and of afterwards absorbing them; thirdly, the 
changes which take place within the cells of the tentacles, 
when the glands are excited in various ways. 

It is necessary, in the first place, to describe briefly the 
plant. It bears from two or three to five or six leaves, gfener- 
ally extended more or less horizontally, but sometimes stand- 

oocaKlon heronfter to refer to a onlllnR attention to Drosera, and 

Saper by MrH. Trent, of New to other plantH having similar 

eney, on Home American Ki>e- hnliltH, In The Nation ' (1S74, 

cles of Drosera. Dr. Itiinlnn pp. 2itl nnd 2.TJ), and In other 

Bandpraon delivered a lecture on puhllcatlonH. Dr. Hooker also, 

DIooaea. before the Royal lUHtItu- In his Important address on Car- 

tion (publlHhe<l In ' Nature,' June nivorous rinuts (Itrlt. Assoc., 

14, 174), In which a short nc- Helfnst, 1874). has KlVen a hls- 

count of my observntlons on the tory of the 8nbje<"t. [A paper on 

power of true digestion pos- the comparative anatomy of the 



eased by Drosera and Dlona?a Droseracejp was published In 
nmt app(>ared. Professor Asa 1870 br W. Oels "" 

Gray has done good service by tlon at Brealau.] 



Chap. I.] 



STRUCTURE OP THE LEAVES. 



3 



ing vertically upwards. The shape and general appearance 
of a leaf is shown, as seen from above, in Fig. 1, and as seen 
laterally, in Fig. 2. The leaves are commonly a little broader 
than long, but this was not the case in the one here figured. 
The whole upper surface is covered with gland-bearing 




Fig. 1. 

(Drosera rotundifolut.) 

Leaf viewed from above ; enlarged four times. 

filaments, or tentacles, as I shall call them, from their man- 
ner of acting. The glands were counted on thirty-one leaves, 
but many of these were of unusually large size, and the aver- 
age number was 192; the greatest number being 260, and 
the least 130. The glands are each surrounded by large drops 
of extremely viscid secretion, which, glittering in the sun, 
have given rise to the plant's poetical name of the sun-dew. 



' The drawlnjjs of Drosera and 
Dionaea, given In this work, were 
made for me by my son, George 
Darwin; those of Aldrovanda, 
and of the several species of 
o 



Utrlcularla, by my son Francis. 

They have been excellently re- 

pro(niced on wood by Mr. Cooper, 
188 Strand. 



DROSERA ROTUNDI FOLIA. 



[Chap. I. 



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 

froject in the same plane with the leaf, or more commonly (see 
ig 2.) are considerably rettexed. A few tentacles spring from the 
base of the footstalk or petiole, and these are the longest of all, 




Fig. 2. 

{Drosera rotiindifolia.) 

Old leaf viewed laterally ; enlarged about five times. 

being sometimes nearly i of an inch in length. On a leaf bearing 
altogether 252 tentacles, the short ones on the disc, having green 
pedicels, were in number to the longer submarginal and marginal 
tentacles, having purple pedicels, as nine to sixteen. 

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

Several eminent physiologists have discussed the homological 
nature of these appendages or tentacles, that is, whether they ought 
to be considered as hairs (trichomes) or prolongations of the leaf. 
Nitschke has shown that they include all the elements proper to 
the blade of a leaf; and the fact of their including vascular tissue 
was fonnerly thought to prove that they were prolongations of the 
leaf, but it is now known that vessels sometimes enter true hairs.* 



According to Nitschke (' Bot. 
Zeltunj?.' 181. p. 224) the purple 
Hiikl results from the motanntr- 
phoKls of chlorophyll. Mr. Sorby 
<>x:iiiiln'<] the coiourlnK mutter 
with the spectroscope, and In- 
forms me that It consists of the 
commonest species of erythro- 
nhyll, " which Is often met with 
In leaves with low vitality, nnil 
In parts, like the petioles, which 
carry on leaf-functions In a very 
Imperfect manner. All that can 
be said, therefore, Is that the 



hairs (or tentacles) are coloured 
like parts of a leaf which do not 
fulHI their proper ofBco." 

* Dr. Nitschke has <llscus8e(l 
tills subject In ' Hot. Zeltung,' 
isdl. n. 241, &c. 8cc also Dr. 
WarmniK C Sur la Dlffi^rence 
entre les Trichomes,' &c., 1873), 
who jjlves references to various 
publications. See also Groen- 
land and Tr^cul, Annal. de 8c. 
nat. hot.' (4th series), torn. 111. 
18o5, pp. 297 and 303. 



Chap. I.] STRUCTURE OF THE LEAVES. $ 

The power of movement which they possess is a strong argument 
against their being viewed as hairs. The conclusion which seems 
to me the most probable will be given in Chap. XV., namely that 
they existed primordially as glandular haire, 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 ex- 
tended from this to the uppermost part. We shall hereafter see 
that the terminal tentacles of the divided leaves of Roridula are 
still in an intermediate condition. 

The glands, with the exception of those borne by the extreme 
marginal tentacles, are oval, and of nearly uniform size, viz. about 
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,* 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 ofles, like- 
wise filled with purple fluid, but of a slightly different tint, and 
differently affected by chloride of gold. These two layers are some- 
times well seen when a gland has been crushed or boiled in caustic 
potash. According to Dr. Warming, there is still another layer of 
much more elongated cells, as shown in the accompanying section 
(Fig. 3) copied from his work; but these cells were not seen by 
Nitschke, nor by me. In the centre there is a group of elongated, 
cylindrical cells of unequal lengths, bluntly pointed at their upper 
ends, truncated or rounded at their lower ends, closely pressed 
together, and remarkable from being surrounded by a spiral line, 
which can be separated as a distinct fibre. 

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

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 

[Gardiner (' Proc. Roynl provided with delicate nncntlcu- 
Soc.,' No. 240, 188C) han pointed Inrlsed cell-wallR, which are re- 
out that In DroMrra dichotomn markably pitted on their upper 
" the gland-cells of the head are or free surface*." F. D.] 



DROSERA ROTUNDIFOLIA. 



[Chap. L 



renpects they do not differ essentially from the oval ones, and in 
one specimen 1 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 




Fio. 3. 
(Dronern rotundifolin.) 
J/Ongitudinal section of a gland ; greatly magnified. 



From Dr. Warming. 



others, and, when a stimulus is applied to the centre of the leaf, 
they are excited into action after the others. When cut-oflT leaves 
are immersed in water, they alone often become inflected. 

The purple fluid, or granular matter which fills the cells of the 
glands, ditferH to a certain extent from that within the cells of the 
pelicels. For, when a leaf is pla<-ed 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 



Chap. I.] ACTION OF THE PARTS. 7 

cells, contain, becomes of a brighter green. The petioles bear many 
multicellular hairs, some of which near the blade are surmounted, 
according to Nitsohke, by a few rounded cells, which appear to be 
rudimentary glands. Both surfaces of the leaf, the pedicels of the 
tentacles, especially the lower sides of the outer ones, and the 
petioles, are studded with minute papilla; (hairs or trichomes), hav- 
ing a conical basis, and bearing on their summits two, and occa- 
sionally three, or even four, rounded cells, containing much proto- 
plasm. These papillae are generally colourless, but sometimes in- 
clude a little purple fluid. They vary in development, and gradu- 
ate, as Nitschke" states, and as I repeatedly observed, into the 
long multicellular hairs. The latter, as well as the papillte, are 
probably rudiments of formerly existing tentacles. 

I may here add, in order not to recur to the papillae, that they 
do not secrete, but are easily permeated by various fluids : thus, 
when living or dead leaves are immersed in a solution of one part 
of chloride of gold, or of nitrate of silver, to 437 of water, they 
are quickly blackened, and the discoloration soon spreads to the 
surrounding tissue. The long multicellular hairs are not so quickly 
affected. After a leaf had been left in a weak infusion of raw 
meat for 10 hours, the cells of the papillae had evidently absorbed 
animal matter, for instead of limpid fluid they now contained small 
aggregated masses of protoplasm,' which slowly and incessantly 
changed their forms. A similar result followed from an immersion 
of only 15 minutes in a solution of one part of carbonate of 
ammonia to 218 of water, and the adjoining cells of tl.e tentacles, 
on which the papillae were seated, now likewise contained aggre- 
gated masses of protoplasm. We may therefore conclude that, 
Avhen a leaf has closely clasped a captured insect in the manner 
immediately to be described, the papillae, which project from the 
upper surface of the leaf and of the tentacles, probably absorb 
some of the animal matter dissolved in the secretion; but this 
cannot be the case with the papillae on the backs of the leaves or 
on the petioles. 

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

If a small organic or inorganic object be placed on the 
glands in the centre of a leaf, these transmit a motor impulse 
to the marginal tentacles. The nearer ones are first affected 
and slowly bend towards the centre, and then those farther 
off, until at last all become closely inflected over the object. 
This takes place in from one hour to four or five or more 

Nitschke has elaborately de- ' Trans. R. Mlcroscop. Soc' Jan. 
scribed and figured these piiplllfe, 1876. F. D.] 

* Bot. Zeltung,' 181, pp. 234, 233, MWIth regard to the nggre- 

254. [See also A. W. Bennett, gated masses, aee p. 34, footnute. 

F. D.] 



8 DROSERA EOTUNDIPOLIA. [Chap. I. 

hours. The difference in the time required depends on many 
circumstances; namely, on the size of the object and on its 
nature, that is, whether it contains soluble matter of the 
proper kind; on the vigour and age of the leaf; whether it 
has lately been in action; and, according to Nitschke,* on 
the temperature of the day, as likewise seemed to me to be the 
case. A living insect -is a more eflBcient 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 movements of so-called sleep. 

If the glands en 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 in- 
stance of saliva or of a solution of any salt of ammonia, are 
placed on the central glands, the same result quickly follows, 
sometimes in under half an hour. 

The tentacles in the act of inflection sweep through a wide 
space; thus a marginal tentacle, extended in the same plane 
with the blade, moves through an angle of 180 ; and I have 
seen the much reflected tentacles of a leaf which stood up- 
right move through an angle of not less than 270". The bend- 
ing 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 re- 
maining straight. The short tentacles in the centre of the 
disc, when directly excited, do not become inflected; but they 
are capable of inflection if excited by a motor impulse received 
from other glands at a distance. Thus, if a 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 to- 
wards 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 ex- 

Bot. ZeltUDg,' 1800. p. 240. 



Chap. I.] 



ACTION OP THE PARTS. 



9 



terior tentacles increasing in length in due proportion, as they 
stand nearer to the circumference. 

The kind of inflection which the tentacles undergo is best 
shown when the gland of one of the long exterior tentacles is 
in any way excited; for the surrounding ones remain un- 




FlG. 4. 
{Drosera rotundifolia.) 
Leaf (enlarged) with all the tenta- 
cles closely inflected, from immer- 
sion in a solution of phosphate of 
ammonia (one part to 87,500 of 
water). 




Fig. 5. 
(Drosera rotundifolia.) 
Leaf (enlarged) with the tentacles 
on one side inflected over a bit 
of meat placed on the disc. 



affected. 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 
substance, such as a bit of thread or hair or splinter of glass, 
if placed in actual contact with the surface of a gland, suf- 
fices to cause the tentacle to bend. If the object, which has 



10 DROSERA ROTUNDIFOLIA. [Cbap. I. 

been carried by this movement to the centre, be not very 
small, or if it contains soluble nitrogenous matter, it acts on 
the central glands ; and these transmit a motor impulse to the 
exterior tentacles, causing them to bend inwards. 

Not only the tentacles, but the blade of the leaf often, 
but by no means always, becomes much incurved, when any 




Fig. 6. 

(Drosera rotundifolia.) 

Diagram showing one of the exterior tentacles closely inflected ; the two 

adjoining ones in their ordinary position. 

strongly exciting substance or fluid is placed on the disc. 
Drops of milk and of a solution of nitrate of ammonia or soda 
are particularly apt to produce this effect. The blade is thus 
converted into a little cup. The manner in which it bends 
varies greatly. Sometimes the apex alone, sometimes one 
side, and sometimes both sides, become incurved. For in- 
stance, I placed bits of hard-boiled egg on three leaves; one 
had the apex bent towards the base; the second had both dis- 
tal margins much incurved, so that it became almost tri- 
angular in outline, and this perhaps is the commonest case; 
whilst the third blade was not at all affected, though the ten- 
tacles 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 be- 
fore. 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. 



Chap. I.] ACTION OF THE PARTS. 11 

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

The secretion from the glands is extremely viscid, so that 
it can be drawn out into long threads. It appears colourless, 
but stains little balls of paper pale pink. An object of any 
kind placed on a gland always causes it, as I believe, to 
secrete more freely; but the mere presence of the object 
renders this difiicult 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 solu- 
tion of one part of chloride of gold, or of some other salts, to 
437 of water, excites the glands to largely increased secretion ; 
on the other hand, tartrate of antimony produces no such 
effect. Immersion in many acids (of the strength of one part 
to 437 of water) likewise causes a wonderful amount of secre- 
tion, so that, when- the leaves are lifted out, long ropes of ex- 
tremely 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 



18 DROSERA ROTUNDIFOLIA. [Chap. I. 

secretion. I ascertained this by selecting leaves with equal- 
sized drops on the two sides, and by placing bits of meat on 
one side of the disc; and as soon as the tentacles on this side 
became much inflected, but before the glands touched the 
meat, the drops of secretion became larger. This was re- 
peatedly observed, but a record was kept of only thirteen 
cases, in nine of which increased secretion was plainly ob- 
served; 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 cen- 
tral glands, when strongly excited, transmit some influence 
to the glands of the circumferential tentacles, causing them 
to secrete more copiously. 

It is a still more important fact (as we shall see more fully 
when we treat of the digestive power of the secretion), that 
when the tentacles become inflected, owing to the central 
glands having been " stimulated mechanically, or by contact 
with animal matter, the secretion not only increases in quan- 
tity, but changes its nature and becomes acid; and this oc- 
curs before the glands have touched the object on the centre 
of the leaf. This acid is of a different nature from that con- 
tained 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 ob- 
served the same leaf with the tentacles closely inflected over 
rather indigestible substances, such as chemically prepared 
casein,* pouring forth acid secretion for eight successive days, 
and over bits of bone for ten successive days. 

The secretion seems to possess, like the gastric juice of 
the higher animals, some antiseptic power. During very 
warm weather I placed close together two equal-sized bits of 
raw meat, one on a leaf of the Drosera, and the other sur- 
rounded 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 stria3 on the 
muscular fibres could no longer be clearly distinguished; 
whilst the bit on the leaf, which was bathed by the secretion, 
was free from infusoria, and its strias were perfectly distinct 

[These obBervntlooH are not of preparation of the casein. See 
truBtwortbjr, owing to the mode p. 65. F. D.] 



Chap. I.] ACTION OP THE PARTS. 13 

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; Avhilst those on the 
leaves of Drosera remained clean, the albumen being changed 
into transparent fluid. 

As soon as tentacles, which have remained closely inflected 
during several days over an object, begin to re-expand, their 
glands secrete less freely, or cease to secrete, and are left 
dry. In this state they are covered with a film of whitish, 
semi-fibrous matter, which was held in solution by the se- 
cretion. 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 tenta- 
cles 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 tenta- 
cles after a time begin to bend, and ultimately clasp it on all 
sides. In^pcts are generally killed, according to Dr. Nitschke, 
in about a quarter of an hour, owing to their tracheae being 
closed by the secretion. If an insect adheres to only a 
few of the glands of the exterior tentacles, these soon become 
inflected and carry their prey to the tentacles next succeeding 
them inwards; these then bend inwards, and so onwards, 
until the insect is .ultimately carried by a curious sort of roll- 
ing movement to the centre of the leaf. Then, after an inter- 
val, the tentacles on all sides become inflected and bathe their 
prey with their secretion, in the same manner as if the insect 
had first alighted on the central disc. It is surprising how 
minute an insect sufiices to cause this action : for instance, I 
have seen one of the smallest species of gnats (Culex), which 
had just settled with its excessively delicate feet on the glands 
of the outermost tentacles, and these were already beginning 



14 DROSERA ROTUNDIFOLIA. [Chap. I. 

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 cen- 
tre of the leaf and been securely clasped on all sides. We 
shall hereafter see what excessively small doses of certain 
organic fluids and saline solutions cause strongly marked in- 
flection. 

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 aggre- 
gation 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 different results which 
follow, from placing drops of various nitrogenous and non- 
nitrogenous fluids of the same density on the glands of the 
disc, or on a single marginal gland ; and likewise by the very 
different lengths of time during which the tentacles remain 
inflected over objects, which yield or do not yield soluble ni- 
trogenous matter. This same conclusion might indeed have 
been inferred from the structure and movements of the leaves, 
which are so admirably adapted for capturing insects. 

The absorption of animal matter from captured insects 
explains how Drosera can flourish in extremely poor peaty 
soil, in some cases where nothing but sphagnum moss grows, 
and mosses depend altogether on the atmosphere for their 
nourishment. Although the leaves at a hasty glance do not 
appear green, owing to the purple colour of the tentacles, yet 
the upper and lower surfaces of the blade, the pedicels of the 
central tentacles, and the petioles contain chlorophyll, so that, 
no doubt, the plant obtains and assimilates carbonic acid 
from the air. Nevertheless, considering the nature of the 
soil where it grows, the supply of nitrogen would be extremely 



Chap. I.] ACTION OP THE PARTS. 16 

limited, or quite deficient, unless the plant had the power of 
obtaining this important element from captured insects. We 
can thus understand how it is that the roots are so poorly 
developed. These usually consist of only two or three slightly 
divided branches from half to one inch in length, furnished 
with absorbent hairs. It appears, therefore, that the roots 
serve only to imbibe water; though, no doubt, they would 
absorb nutritious matter if present in the soil ; for as we shall 
hereafter see, they absorb a weak solution of carbonate of am- 
monia. A plant of Drosera, with the edges of its leaves 
curled inwards, so as to form a temporary stomach, with the 
glands of the closely inflected tentacles pouring forth their 
acid secretion, which dissolves animal matter, afterwards to 
be absorbed, may be said to feed like an animal. But, differ- 
ently 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 simultaneously the results of Keller- 
mann and Von Raumer were given in the * Botanische Zeit- 
ting." My experiments were begun in June 1877, when the 
plants were collected and planted in six ordinary soup-plates. 
Each plaie was divided by a low partition into two sets, and 
the least flourishing half of each culture was selected to be 
" fed," while the rest of the plants were destined to be 
" starved." The plants were prevented from catching insects 
for themselves 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 ten days 
the difference between the fed and starved plants was clearly 
visible: the fed plants were of brighter green and the tenta- 
cles of a more lively red. At the end of August the plants 

" Vol. xvH.. Francis Dnrwln FlelschftttteninR: " ' Bot. Zelt- 

on the ' Nutrition of Drosera unj?,' 1878. 8om(^ account of the 

rotundifoUa.' resnlts was given before the 

" " VeRetatlonBversuche an rhy.-med. Soc., Erlangen, July 

Drosera rotundifolia mlt und ohne 0, 1877. 



16 DROSERA ROTUNDIFOLIA. [Chap. I. 

were compared by number, weight, and measurement, with the 
following striking results : 

SUured. Fed. 
Weight (without flower-stems) ... 100 121.5 

Number of flower-stems . 
Weight of stems 
Numljer of capsules . 
Total calculated weight of seed 
Total calculated number of seeds 



100 164.9 

100 231.9 

100 194.4 

100 379.7 

100 241.5 



These results show clearly enouph 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 t. 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 ma- 
terial accumulated during the summer. Both starved and 
fed plants were kept without food until April 3rd, when 
it was found that the average weights per plant were 
100 for the starved, 213.0 for the fed. This proves that 
the fed plants had laid by a far greater store of reserve 
material in spite of having produced nearly four times as 
much seed. 

In Kellermann and Von Raumer's experiments (loc. cit.) 
aphides were used as food instead of meat a method 
which adds greatly to the value of their results. Their con- 
clusions 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 ad- 
vantage of having been made on young Droseras grown from 
seed. The unfed plants are thus much more effectually 
starved than in experiments on full-grown plants possessing 
already a store of reserve matter. It is therefore not to be 
wondered at that Biisgen's results are more striking than Kel- 
lermann's and Von Raumer's or my own thus, for instance, 
he found that the " fed " plants, as compared with the starved 

" *' Dl* BMentvng des Insectfanges fUr Droaera rotundifolia (L.)," 
Bot. Zeltung.' 188a 



Chap. L] AC3TI0N OP THE PARTS. 17 

ones, produced more than five times as many capsules, while 
my figures are 100 : 194. Biisgen gives a good resume of 
the whole subject, and sums up by saying that the demon- 
strable superiority of fed over unfed plants is great enough to 
render comprehensible the organisation of the plants with 
reference to the capture of insects. F. D.] 



18 DROSERA ROTUNDIFOLIA. [Chap. II. 



CHAPTER II. 

THE MOVEMENTS OF THE TENTACLES FROM THE CONTACT 
OF SOLID BODIES. 

Inflection of the exterior tentacles owing to the glands of the disc being 
excited by repeated touches, or by objects left in contact with thenj 
Difli'rence 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 com- 
mencing inflection and of subsequent re-expansion Extreme minute- 
ness of the particles causing inflection Action under water Inflec- 
tion of the exterior tentacles when their glands are excited by 
repeated touches Falling drops of water do not cause inflection. 

I WILL give in this and the following chapters some of the 
many experiments made, which best illustrate the manner 
and rate of movement of the tentacles, when excited in vari- 
ous ways. The glands alone in all ordinary cases are sus- 
ceptible to excitement. When excited they do not themselves 
move or change form, but transmit a motor impulse to the 
bending part of their own and adjoining tentacles, and are 
thus carried towards the centre of the leaf. Strictly speaking, 
the glands ought to be called irritable, as the term 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 tenta- 
cles 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 copious- 
ly, and the secretion to become acid. This latter fact is, I 
believe, quite new in the physiology of plants; it has indeed 
only recently been established that in the animal kingdom an 



Chap. II.] INFLECTION INDIRECTLY CAUSED. 19 

influence can be transmitted along the nerves to glands, 
modifying their power of secretion, independently of the 
state of the blood-vessels. 

The Inflection of the Exterior Tentacles from the Glands of 

the Disc being excited hy Repeated Touches, or hy 

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, were inflected; in 17 hrs. 
they had recovered their proper, expanded position. I then 
put a dead fly in the centre of the last-mentioned leaf, and 
next morning it was closely clasped; five days afterwards the 
leaf re-expanded, and the tentacles, with their glands sur- 
rounded by secretion, were ready to act again. 

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

When a small object is placed on the glands of the disc, on 
3 



20 DROSERA ROTUNDIFOLIA. [Chap. II. 

one side of a leaf, as near as possible to its circumference, the 
tentacles on this side are first affected, those on the opposite 
side much later, or, as often occurred, not at all. This was 
repeatedly proved by trials with bits of meat; but I will here 
give only the case of a minute fly, naturally caught and still 
alive, which I found adhering by its delicate feet to the 
glands on the extreme left side of the central disc. The mar- 
ginal tentacles on this side closed inwards and killed the 
fly, and after a time the edge of the leaf on this side also be- 
came inflected, and thus remained for several days, whilst 
neither the tentacles nor the edge on the opposite side were in 
the least affected. 

If young and active leaves are selected, inorganic particles 
not larger than the head of a small pin, placed on the central 
glands, sometimes cause the outer tentacles to bend inwards. 
But this follows much more surely and quickly, if the object 
contains nitrogenous matter which can be dissolved by the 
secretion. On one occasion I observed the following unusual 
circumstance. Small bits of raw meat (which acts more 
energetically than any other substance), of paper, dried moss, 
and of the quill of a pen were placed on several leaves, and 
they were all embraced equally well in about 2 hrs. On other 
occasions the above-named substances, or more commonly par- 
ticles of glass, coal-cinder (taken from the fire), stone, gold- 
leaf, dried grass, corlj^ blotting-paper, cotton-wool, and hair 
rolled up into little balls, were used, and these substances, 
though they were sometimes well embraced, often caused no 
movement whatever in the outer tentacles, or an extremely 
slight and slow movement. Yet these same leaves were 
proved to be in an active condition, as they were excited to 
move by substances yielding soluble nitrogenous matter, such 
as bits of raw or roast meat, the yolk or white of boiled egg^, 
fragments of insects of all orders, spiders, <S: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 moes and 
quill of about the same size as the flies, and the latter were 
well embraced in a few hours; whereas after 25 hrs. only a 
very few tentacles were inflected over the other objects. The 
bits of paper, moss, and quill were then remove<l from these 
leaves, and bits of raw meat placed on them ; and now all the 
tentacles were soon energetically inflected. 



Chap. II.] INFLECTION INDIRECTLY CAUSED. 



21 



Again, particles of coal cinder (weighing rather more than 
the flies used in the last experiment) were placed on the 
centres of three leaves : after an interval of 19 hrs. one of the 
particles was tolerably well embraced; a second by a very 
few tentacles; and a third by none. I then removed the 
particles from the two latter leaves, and put them on recently 
killed flies. These were fairly well embraced in 7i hrs. and 
thoroughly after 20i 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 exi)eriment8 not worth 
giving, it is certain that inorganic substances, or such or- 
ganic substances as are not attacked by the secretion, act 
much less quickly and efficiently than, organic substances, 
yielding soluble matter which is absorbed. Moreover, I have 
met with very few exceptions to the rule, and these exceptions 
apparently depended on the leaf having been too recently in 
action, that the tentacles remain clasped for a much longer 
time over organic bodies of the nature just specified than 
over those which are not acted on by the secretion, or over in- 
organic objects.* 



Owing to the extraordinary 
belief held by M. Zlcjrler 
(' Comptes rendtiB.' May 1872. p. 
122), that albuminous substances. 
If held for a moment between 
the fingers, acquire the property 
of making the tentacles of 
Drosera contract, whereas. If not 
thus held, they have no such 
power, I tried some experiments 
with great care, but the results 
did not confirm this belief. Red- 
hot cinders were taken out of 
the fire, an<l 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 iMlllng water* on the glands of 
Beveral 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, cat with a 
kiilfe which had been washed lo 
boiling water, also acted like any 
other animal substance. I 
breathed on some leaves for 
above a minute, and repeated the 
act two or three times, with my 
mouth close to them, but this 
produced no effect. I may here 
add, as showing that the leaves 
are not acted on by the odour 
of nitrogenous substances, that 
pieces of raw meat stuck on 
needles were fixed as close as 
possible, without actual contact, 
to several leaves, but produced 
no effect whatever. On the 
other hand, as we shall hereafter 
see, the vapours of certain vola- 
tile substances and flubis, such 
as of carbonate of ammonia, 
chloroform, certain essential oils. 
&c., cause Inflection. M. Zlegler 
makes still more extraordinary 
statements with respect to the 



^2 



DROSERA ROTUNDIFOLIA. 



[COAP. II. 



The Inflection of the Exterior Tentacles as directly caused 
by Objects left in Contact with their Glands* 

I made a vast number of trials by placing, by means of a 
fine needle moistened with distilled water, and with the aid 
of a lens, particles of various substances on the viscid secre- 
tion 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 



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 ap- 
pearance or the paper above re- 
ferred to, M. ZfcKler has pub- 
lished a book on the same sub- 
ject, entitled, ' Atonlcit6 et Zol- 
clt^,' 1874. 

* [The researches of Pfeffor 
(' IJnters. aus d. Hot. Instltut zu 
Tilbingeu.' vol. I., 1885, p. 483) on 
the sensitiveness of various or- 
gans to contact show that the 
conclusions as to the sensitive- 
ness of Drosera cannot be nmin- 
talned in their present form (ace 
p. 24). 

I'feffcr shows. l>oth In the 
case of the tendrils of climbing 
plants, and also In that of the 
tentacles of Drosera, that uni- 
form pressure hns no stimulating 
action; tle effect which is 
ascribc>d simply to contact is in 
reality due to unequal compres- 
sion of closely neighbouring 
points. Tendrils which move 
after having been rubbeil with a 
light stick fall to be stimulated 
when they are rubbed with a 
glass rod coated with gelatine. 
The gelatine hns the sMme uni- 
formity of action ns drops of 
water falling on the tendril, 
which are known to produce no 
effect. If the gelatine Is sprin- 
kled with flne particles of sand, 
or If the water holds particles 



of clay In suspension, stimula- 
tion results. Analogous experi- 
ments were made on Drosera (p, 
511). It was found impossible to 
produce movement of the ten- 
tacles by rubbing the glands 
with a surface of mercury, 
whereas bv rubbing or repeated 
touches with solid bodies move- 
ment is called forth. Other ex- 
periments of Pfeffer's show con- 
clusively that continuous uni- 
form pressure has no stimulating 
effect. He placed small glob- 
ules of glass on the glands, and 
convinced himself, by examina- 
tion with a lens, that contact 
was effected. Some of the ten- 
tacles moved, Imt the majority 
showed no movement, a lonrj ns 
the plnnlt tcrrc i>o plnrnl thai no 
vibration from the tabl' or floor 
rould rrarh thrm. When they 
were exposed to vibration, and 
when, therefore, the glass glob- 
ules must have rubbed against 
or Jarred the gbind. the ten- 
tacles moved. The results de- 
taile<l above in the text nmst 
presumably be set down to the 
same cause, namely, the vibra- 
tion of the table and floor. The 
sensitiveness of Drosera. there- 
fore, by no means ceases to be 
astonishing. Instead of liellev- 
Ing In movements caused by the 
steady pressure of very small 
weights, we set down the results 
ns iK'Ing due to the Jarring r>f 
the gland by these same minute 
bodies. P. D.] 



CuAP. U.] INFLECTION DIRECTLY CAUSED. 23 

me. In 2 m. 30 s.it had moved through an angle of about 45**. 
The movement as seen through a lens resembled that of the 
hand of a large clock. In 5 m, it had moved through 90, 
and when I looked again after 10 m., the particle had reached 
the centre of the leaf; so that the whole movement was com- 
pleted in less than 17 m. 30 s. In the course of some hours 
this minute bit of meat, from having been brought into con- 
tact with some of the glands of the central disc, acted 
centrif ugally 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 frag- 
ment on the fourth tentacle was very minute, and it was not 
carried to the centre until 3 hrs. had elapsed. In three other 
cases minute flies or portions of larger ones were carried to 
the centre in 1 hr. 30 s. In these seven cases, the fragments 
or small flies, which had been carried by a single tentacle to 
the central glands, were well embraced by the other tentacles 
after an interval of from 4 to 10 hrs. 

I also placed in the manner just described six small balls 
of writing paper (rolled up by the aid of pincers, so that 
they were not touched by my fingers) on the glands of six 
oxterior tentacles on distinct leaves; three of these were car- 
ried to the centre in about 1 hr., and the other three in rather 
more than 4 hrs.; but after 24 hrs. only two of the six balls 
were well embraced by the other tentacles. It is possible that 
the secretion may have dissolved a trace of glue or animalised 
matter from the balls of paper. Four particles of coal-cinder 
were then placed on the glands of 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 frag- 
ments of flies, in causing the movement of the surrounding 
tentacles. 



24 DEOSERA ROTUNDIFOLIA. [Chap. IL 

I made, without carefully recording the times of move- 
ment, many similar trials with other substances, such as 
splinters of white and blue glass, particles of cork, minute bits 
of gold-leaf, &c. ; and the 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 ac- 
count for this result. In another case f of the particles of 
cinder, glass, and thread, placed on separate glands, were car- 
ried towards, or actually to, the centre ; in another case V, in 
another ^j, and in the last case only A 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 im- 
mediately given, were placed on glands ; so that we here have 
nearly the limit of any action. 

I was so much surprised at the smallness of the particles 
which caused the tentacles to become greatly inflected that 
it seemed worth while carefully to ascertain how minute a 
particle would plainly act. Accordingly, measured lengths 
of a narrow strip of blotting-paper, of fine cotton-thread, and 
of a woman's hair, were carefully weighed for me by Mr. 
Trenham Reeks, in an excellent balance, in the laboratory in 
Jermyn Street. Short bits of the paper, thread, and hair 
were then cut off and measured by a micrometer, so that 
their weights could be easily calculated. The bits were placed 
on the viscid secretion surrounding the glands of the exterior 
tentacles, with the precautions already stated, and I am 
certain that the gland itself was never touched; nor indeed 
would a single touch have produced any effect. A bit of the 
blotting-paper, weighing j\t 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 
i/rr of a grrain, or .0464 of a milligram. Five nearly equal 



Chap. II.] INFLECTION DIRECTLY CAUSED. 25 

bits of cotton-thread were tried, and all acted. The shortest 
of these was jV of an inch in length, and weighed tt'st of a 
grain. The tentacle in this case was considerably inflected in 
1 hr. 30 m., and the bit of thread was carried to the centre of 
the leaf in 1 hr. 40 m. Again, two particles of the thinner 
end of a woman's hair, one of these being rihs of an inch 
in length, and weighing yjfiT of a grain, the other tMtt 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 
suflaced 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 conspicu- 
ous manner. The smallest particle which was tried, and 
which acted plainly, was only tAtt of an inch (.203 milli- 
meter) in length, and weighed the tbtts 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 chap- 
ter; and the aggregation was so plain thaj; I could, by this 
clue alone, have readily picked out under the microscope all 
the tentacles which had carried their light loads towards the 
centre, from the hundreds of other tentacles on the same 
leaves which had not thus acted. 

My surprise was greatly excited, not only by the minute- 
ness of the particles which caused movement, but how they 
could possibly act on the glands; for it must be remembered 
that they were laid with the greatest care on the convex sur- 
face 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 se- 
cretion, for small drops of water, many times heavier than the 
particles, were repeatedly added, and never produced any 
effect. Nor does the disturbance of the secretion produce any 
effect, for long threads were drawn out by a needle, and 



26 DROSERA ROTUNDIFOLIA. [Chap. II. 

affixed to some adjoining object, and thus left for hours; but 
the tentacles remained motionless. 

I also carefully removed the secretion from four glands 
with a sharply pointed piece of blotting-paper, so that they 
were exposed for a time naked to the air, but this caused no 
movement; yet these glands were in an efficient state, for, 
after 24 hrs. had elapsed, they were tried with bits of meat, 
and all became quickly inflected. It then occurred to me that 
particles floating on the secretion would cast shadows on the 
glands which might be sensitive to the interception of the 
light. Although this seemed highly improbable, as minute 
and thin splinters of colourless glass acted powerfully, never- 
theless, after it was dark, I put on, by the aid of a single 
tallow candle, as quickly as possible, particles of cork and 
glass on the glands of a dozen tentacles, as well as some of 
meat on other glands, and covered them up so that not a 
ray of light could enter; but by the next morning, after an 
interval of 13 hrs., all the particles were carried to the centres 
of the leaves. 

These negative results led me to try many more experi- 
ments, by placing particles on the surface of the drops of 
secretion, observing, as carefully as I could, whether they 
penetrated it and touched the surface of the glands. The 
secretion, from its weight, generally forms a thicker layer on 
the under than on the upi)er 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 b<H?n laid on the upper surface of the secretion, where it 
is thinnest, they were often drawn down, after a time, into 
contact with at least some one point of the gland. With 
respect to the minute splinters of glass and particles of hair, I 
observed that the secretion slowly spread itself a little over 
their surfaces, by which means they were likewise drawn 
downwards or sideways, and thus one end, or some minute 
prominence, often came to touch, sooner or later, the gland. 

In the foregoing and following cases, it is probable that 
the vibrations, to which the furniture in every room is con- 
tinually liable, aids in bringing the particles into contact 



Chap. II.] INFLECTION DIRECTLY CAUSED. 27 

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

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

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



28 DROSERA ROTUNDIFOLIA. [Chap. IL 

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 suflScient to excite movement. 

Another experiment, showing that extremely minute par- 
ticles act on the glands when immersed in water, may here 
be given. A grain of sulphate of quinine was added to an 
ounce of water, which was not afterwards filtered; and, on 
placing three leaves in ninety minims of this fluid, I was 
much surprised to find that all three leaves were greatly in- 
flected in 15 m.: for I knew from previous trials that the 
solution does not act so quickly as this. It immediately oc- 
curred 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 surface of the glands; and no doubt it was 
these particles which caused the tentacles to bend. When a 
leaf is immersed in water, the secretion instantly swells 
much; and I presume that it is ruptured here and there so 
that little eddies of water rush in. If so, we can understand 
how the atoms of chalk, which rested on the surfaces of the 
glands, had penetrated the secretion. Any one who has 
rubbed precipitated chalk between his fingers will have per- 
ceived 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 in- 
duced 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, iV of an inch in length and weighing nVr of a grain. 



Chap. II.] THE EFFECTS OP REPEATED TOUCHES. 29 

or of a human hair, tAt of an inch in length and weighing 
only rrfiff 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 tentficle to sweep through 
an angle of above 180. That the contents of the cells of the 
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 aggre- 
gation of the protoplasm. But the case is much more re- 
markable 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 ex- 
erted by the particle of hair, weighing only Tshns 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, A 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 -ex- 
tremely doubtful whether any nerve in the human body, 
even if in an inflamed condition, would be in any way af- 
fected by such a particle supported in a dense fluid, and 
slowly brought into contact with the nerve. Yet the cells of 
the glands of Drosera are thus excited to transmit a motor 
impulse to a distant point, inducing movement. It appears 
to me that hardly any more remarkable fact than this has 
been observed in the vegetable kingdom. 

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

We have already seen that, if the central glands are ex- 
cited by being gently brushed, they transmit a motor impulse 



80 DROSERA ROTUNDIFOLIA, [Chap. II. 

to the exterior tentacles, causing them to bend ; and we have 
now to consider the efccts 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 thou- 
sand-fold greater pressure than the weight of the above- 
described particles, not a tentacle moved. On another oc- 
casion forty-five glands on eleven leaves were touched once, 
twice, or even thrice, with a needle or stiff bristle. This was 
done as quickly as possible, but with force sufficient to bend 
the tentacles; yet only six of them became inflected, three 
plainly, and three in a slight degree. In order to ascertain 
whether these tentacles which were not affected were in an 
eflScient 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 be- 
came 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 considerable 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 oc- 
casionally 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-expandcd 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 



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

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 mis- 
take 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 
after the secretion has been all washed away by heavy rain; 
and this often occurs, though the secretion is so viscid that it 
can be removed with difficulty merely by waving the leaves 
in water. If the falling drops of water are small, they ad- 
here 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 ob- 
viously 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 Qf 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 Dionroa are likewise insensible to the impact of 
fluids, though exquisitely sensitive to momentary touches 
from any solid body. 

When the pedicel of a tentacle is cut off by a sharp pair 
of scissors quite close beneath the gland, the tentacle gener- 
ally becomes inflected, I tried this experiment repeatedly, 
as I was much surprised at the fact, for all other parts of the 
pedicels are insensible to any stimuliis. These headless ten- 
tacles 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 par- 
alysed, as likewise follows from the action of too strong soln- 

[Pfoffer'H experiments, given nre of rnin to cause movement. 
al)ove <p. 22), explain the fail- F. D.] 



82 DROSERA ROTUNDIFOLIA. [Cdap. IL 

tions of certain salts, and of too great heat, whilst weaker 
solutions of the same salts and a more gentle heat cause 
movement. We shall also see in future chapters that various 
other fluids, some vapours, and oxygen (after the plant has 
been for some time excluded from its action), all induce in- 
flection, and this likewise results from an induced galvanic 
current.* 

* My son Francis, Ruklod by nection with the Becondary coll 

the observations of Dr. Burdon of a I)u Bois Induction apparatus 

Sanderson on Dionsca, flnds that, are inserted, the tentacles curve 

If two needles are Inserted Into Inwards In the course of a few 

the blade of a leaf of Drosera, minutes. My son hones soon to 

the tentacles do not move; but publish an account of his obser- 

that, if similar needles in con- vutlous. 



Chap. III.] THE PROCESS OF AGGREGATION. 33 



CHAPTER in. 

AGGREGATION OP THE PROTOPLASM WITHIN THE CELLS OF 
THE TENTACLES. 

Nature of the contents of the cells before aggregation Various causes 
which excite aggregJition The process comniences within the glands 
and travels down the tentacles Description of the aggregated masses 
and of their spontaneous movementsCurrents 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 cen- 
tral masses Minuteness of the quantity of carbonate of ammonia 
causing aggregation Action of other salts of ammonia Of other sub- 
stances, organic fluids, &c. Of water Of heat Redissolution of the 
aggregated masses Proximate causes of the aggregation of the proto- 
plasm Summary and concluding remarks Supplementary observa- 
tions on aggregation in the roots of plants. 

I WILL here interrupt my account of the movements of the 
leaves, and describe the phenomenon of aggregation, to which 
subject I have already alluded. If the tentacles of a young, 
yet fully matured leaf, that has never been excited or be- 
come 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, circultfting protoplasm ; * 
but this can be seen with much greater distinctness after the 
process of aggregation has been partly effected than before. 
The purple fluid which exudes from a crushed tentacle is 
somewhat coherent, and does not mingle with the surrounding 
water; it contains much flocculent or granular matter. But 
this matter may have been generated by the cells having been 

> [The statement as to the ab- ered In Dmnera dichotoma. but ex- 
sence of n nucleus lii the stalk- Ists also In D. rotundifolia: In 
cells of Drosera (Francis Dar- the former species. In which It 
win. ' Quarterly Journal of Ml- has been more especially studied 
croseopleiil Solenee.' 1876) has by Its discoverer. It la a more or 
been shown by I'fefTer to be qtilte less spindle-shaped mass, stretch- 
erroneous (' Osmotlsche , TJnter- Ing diagonally across the cell, 
Buchnntten.' 1877, p. 107). F. D.] the two ends being embedded In 

* [Mr. W. Gardiner (' Proc. R. the cell-protoplasm. " It la prcs- 

Soc.,' No. 240, 1880) has de- ent In all the epidermic cells of 

scribed a remarkable bodv the leaf except the gland cells 

named by him the " rhabdoid, and the cells Immediately be- 

whlch exists within the eplder- neath the same." Further refer- 

mlc cells of the stalk of the ten- ence to the rhabdoid will be 

tacles. This body was dlscov- found at p. 35. F. I).] 



34 DROSERA ROTUNDIFOLIA. [Chap. TTT. 

crushed; some degree of aggrregation having been thus al- 
most instantly caused. 

If a tentacle is examined some hours after the gland has 
been excited by repeated touches, or by an inorganic or or- 
ganic 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 mot- 
tled 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 aggre- 
gation. Tentacles in an aggregated condition were shown 
to Prof. Huxley, Dr. Hooker, and Dr. Burdon Sanderson, 
who observed the changes under the microscope, and were 
much struck with the whole phenomenon. 

The little masses of aggregated matter are of the most 
diversified shapes, often spherical or oval, sometimes much 
elongated, or quite irr^^lar with thread- or necklace-like or 
club-formed projections. They consist of thick, apparently 
viscid matter, which in the exterior tentacles is of a purplish, 
and in the short discal tentacles of a greenish, colour. These 
little masses incessantly change their forms and positions, be- 
ing nevet at rest. A single mass will often separate into two, 
which afterwards reunite. Their movements are rather 



Chap. III.] THE PROCESS OP AGGREGATION. 



35 



slow, and resemble those of Amcebse or of the white corpuscles 
of the blood. We may therefore conclude that they consist 
of protoplasm.* If their shapes are sketched at intervals of 



mm 



Fig. 7. 

(Drosera rotundifolia.) 

Diagram of the same cell of a tentacle, showing the Tarions forms saoces- 

sively assumed by the aggregated masses of protoplasm. 

a few minutes, they are invariably seen to have undergone 
great changes of form; and the same cell has been observed 
for several hours. Eight rude, though accurate sketches of 
the same cell, made at intervals of between 2 m. or 3 m.. 



* [This conclusion has been 
shown to be erroneous: there can 
be no doubt that the aggregated 
masses are concentrations or pre- 
cipitations of the cell-sap, and 
that their supposed 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 
apjrregatlon. In his ' Osmotlsche 
Untersuchunpen ' (1877). Since 
then the subject has been Inves- 
tigated by Schluiper (' Bota- 
nlsche Zeltung.' 1SS2. p. 2), who 
deserilies the appregjited masses 
as concentrations of cell-sjip, 
rich In tannin, and floating in the 
swollen and transparent proto- 
plasm. 

Sehimper's observations are 
confirmed by Oardlner (' Proc. 
Royal Soc.,' Nov. 19. 1885,' No. 
240. 1880), who describes the 
protoplasm In the stalk-cells of 
Drofifra dichotnma as swelling up 
by the absorption of the " water 
from Its own vacnole," and thus 
leaving the tannin In cell-sap in 
a concentrateil condition. Oar- 
diner has addefl some curious ob- 
servations on the connection le- 
tween aggregation and the cn- 
dltlon of the cell as regards tnr- 
gtdlty. ne supposes that aggrc- 

. 4 



gatlon Is connected with a loss 
of water, and that an aggregated 
ceil is in a condition of dimin- 
ished turgldlty. This Is sup- 
ported by his observation that 
" Injection of water Into the tis- 
sue will at once stop aggrega- 
tion, and restore the cell to Its 
normal condition." These 

changes are Connected with cer- 
tain alterations of form occur- 
rlnir in the above-mentioned Imdy 
described by Oardlner under the 
name of rhabdoid, and which 
seems to be peculiarly sensitive 
to changes In the tarKldity, so 
much so Indeed that the author 
utilises It as a " turgometer," or 
index of the degree of tur- 
gescence. 

H. de Vrles has also written 
on the subject of aggreeation 
(' Botanische Zeltung,' 1880, p. 
1), and hfs views agree with 
those of Pfeffer, Schlmper, and 
Gardiner as to the main fact 
that the ncrpregated masses are 
concentrations of cell-snp. In 
some other respects they differ 
from the conclusions of these au- 
thors. 

De Vrles believes that In Dro- 
pcrn and In vegetable cells gen- 
era Ily the vacuoles are sur- 
roiindetl by n special proto- 

1>lasmie wall, distinct from the 
nyer of flowing protoplnsui 



86 



DROSERA ROTUNDIPOLIA. 



[Chap. HI. 



are here given (Fig. 7), and illustrate some of the simpler 
and commonest changes. The cell A, when first sketched, in- 
cluded 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 



1 



vm 



Fig. 8. 

(Drotera rotundifolia) 

Diagram of the same cell of a tentacle, showing the various forms saceoh 

sively assumed by the aggregated masiies of protoplasm. 

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

The cell drawn in Fig. 7 was from a tentacle of a dark red 
leaf, which had caught a small moth, and was examined under 
water. As I at first thought that the movements of the 
masses might be due to the absorption of water, I placed 
a fly on a leaf, and, when after 18 hrs. all the tentacles were 
Well inflected, these were examined without being immersed 
in water. The cell here represented (Fig. 8) was from this 
leaf, being sketched eight times in the course of 15 m. These 
sketches exhibit some of the more remarkable changes which 
the protoplasm undergoes. At first, there was at the base of 
the cell 1 a little mass on a short footstalk, and a larger mass 
near the upper end, and these seemed quite separate. Never- 



whlcb Hnrs tho wnlln. In the 
procefM of ntrjtroKiitlon the vacu- 
ole expelH n ;rt>nt part of Its 
watery contenlK. rotnlnlnir, how- 
ever, the red colouring matter of 
the cell-Hap. an wi>ll ns tannin 
and alhnmlnoud matter. The 
vncuole doe not remain a siuKle 
body, hut divldoH Into numerous 
neoondnry vacuoles. These are 
the aggregated masses which are 



rendered conspicuous bv being 
surrounded by the expelie<l fluid 
which servos as a colourless 
backjrrotmfl to them. The ujove- 
ments of the masses are, accord- 
lUK to I)e Vrlcs, >nflrply passive, 
and are accounfeil for by the cur- 
rents of protoplasm, stirring 
them and washing them to and 
fro.-P. D.] 



Chap. III.] THE PROCESS OP AGGREGATION. 37 

theless, they may have been connected by a fine and invisible 
thread of protoplasm, for on two other occasions, whilst one 
mass was rapidly increasing, and another in the same cell 
rapidly decreasing, I was able, by varying the light and using 
a high power, to detect a connecting thread of extreme ten- 
uity, which evidently served as the channel of communication 
between the two. On the other hand, such connecting 
threads are sometimes seen to break, and their extremities 
then quickly become club-headed. The other sketches in 
Fig. 8 show the forms successively assumed. 

Shortly after the purple fluid within the cells has become 
aggregated, the little masses float about in a colourless or 
almost colourless fluid; and the layer of white granular 
protoplasm which flows along the walls can now be seen much 
more distinctly. The stream flows at an irregular rate, up 
one wall and down the opposite one, generally at a slower 
rate across the narrow ends of the elongated cells, and so 
round and round. But the current sometimes ceases. The 
movement is often in waves> and their crests sometimes 
stretch almost across the whole width of the cell, and then 
sink down again. Small spheres of protoplasm, apparently 
quite free, are often driven by the current round the cells; 
and filaments attached to the central masses are swayed to 
and fro, as if struggling to escape. Altogether, one of these 
cells with the ever-changing central masses, and with the 
layer of protoplasm flowing round the walls, presents a won- 
derful scene of vital activity. 

Many observations were made on the contents of the cells whilst 
undergoing the process of aggregation, but I shall detail only a 
few cases under different heads. A small portion of a leaf was 
cut off, placed under a high power, and the glands very gently 
pressed under a compressor. In 15 m. I distinctly saw extremely 
minute spheres of protoplasm aggregating 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 placc<i on the glands of many tentacles; 
in 1 hr. several of them were inflected, but after 1 hr. 35 m. there 
was no aggregation. Other tentacles with these particles were ex- 
amined after 8 hrs., and now all their cells had undergone aggre- 
gation ; 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. 



88 DEOSERA ROTUNDIFOLIA. [Chap. III. 

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 evi- 
dence. 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, elon- 
gated, 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 in- 
flected; and their cells had likewise undergone aggregation, 
which, however, it should be observed, had not as yet extended 
down to their bases, but was confined to the cells close beneath 
the glands. 

Not only do repeated touches on the glands* and the contact 
of minute particles cause aggregation, but if glands, without being 
themselves injured, are cut off from the summits of the pedicels, 
this induces a moderate amount of agp-egation 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 aggrega- 
tion. 

Carbonate of Ammonia. Of all the causes inducing aggrega- 
tion, that which, as far as I have seen, acts the quickest, and is 
the most powerful, is a solution of carbonate of ammonia. What- 
ever its strengtli may be, the glands are always afl"ected 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 

fart to 14G of water (or 3 grs. to 1 oz.), and observed it under a 
igh power. All the glands began to darken in 10 s. (seconds) ; 
and in 13 s. were conspicuously darker. In 1 m. extremely small 
spherical masses of protoplasm could be seen arising in the cells of 
the pedicels close l)eneath the glands, as well as in the cushions on 
which the long-headed marginal glamls rest. In several cases the 
process travelled down the pedicels for a length twice or thrice as 
gpreat as that of the glands, in about 10 m. It was interesting to 
observe the process momentarily arrcstetl at each transverse par- 
tition between two cells, and then to see the transparent contents 
of the cell next Inflow almost flashing into a cloudy mass. In the 
lower part of the pedicels, the action i)rocec<led slower, so that it 
took about 20 m. l>efore the cells halfway down the long marginal 
and submarginal tentacles became aggregated. 

We may infer that the carbonate of ammonia is absorbed by the 

* Jiidfflns from nn nrconnt of thoy have been excited by a 

M. Hocki'rH oliHorvntlons. which touch nnd have moved; for he 

I have only Jiint won <iiioted In nnyn, " the i-ontcnts of oiwh In- 

the ' ClnrdcnT's Chronicle ' (Oct. (Mvldiitil cell nro oollccfod to- 

10, 1K74), he nnponrH to have pother In the <i*nlre of the cav- 

observofl n Klmllnr phoiumjonon Ity." 
In the stamens of Rorborl.H, after 



CuAP. III.] THE PROCESS OF AGGREGATION. 89 

glands, not only from its action being so rapid, but from' its effect 
being somewhat different from tl;at of oilier 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. 
Ii 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 hi"8. 
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 veiy 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 par- 
ticles are placed on the glands, it is probable that ammonia in 
some form is absorbed not only by the glands, but passes dpwn 
the tentacles. 

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

If tentacles with cells containing only very pale pink fluid, and 
apparently but little protoplasm, are placed in a few drops of a 
weak solution of one part of the carbonate to 4375 of water (1 
gr. to 10 oz.), and the highly transparent cells beneath the glands 
are carefully observe*! under a high power, the.se may be seen 
first to become slightly cloudy from the formation of numberleM^ 



40 DROSERA EOTUNDIFOLIA. [Chap. IIL 

only just perceptible granules,* which rapidly grow larger cither 
from coalescence or from attracting more protoplasm from the sur- 
rounding fluid. On one occasion I chose a singularly pale leaf, and 
gave it, whilst under the microscope, a single drop of a stronger 
solution of one part to 437 of water; in this case the contents of 
the cells did not become cloudy, but after 10 m. minute irregular 
granules of protoplasm could be detected, which soon increased 
into irregular masses and globules of a greenish or very pale purple 
tint; but these never formed jwrfect spheres, though incessantly 
changing their shapes and positions. 

With moderately red leaves the first efTect of a solution of the 
carbonate generally is the formation of two or three, or of several, 
extremely minute purple spheres which rapidly increase in size. To 
give an idea of the rate at which such spheres increase in size, I 
may mention that a rather pale purple leaf placed under a slip 
of grass was given a drop of a solution of one part to 292 of 
water, and in 13 m. a few minute spheres of protoplasm were 
formed; one of these, after 2 hrs. 30 m., was about two-tliirds of the 
diameter of the cell. After 4 hrs. 25 m. it nearly e<iualled 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 solu- 
tion was first added) four new minute spheres had appeared. Next 
morning, after 22 hrs., there were, besides the two large spheres, 
seven smaller ones, floating in absolutely colourless fluid, in which 
some flocculent greenish matter was suspended. 

At the commencement of the process of aggregation, more espe- 
cially 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 irr^ularly shaped purple bag being thus formed. 
Other fluids, besides a solution of the carbonate, for instance an in- 
fusion of raw meat, produce this same efTect. 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 line<i with colourless flowing protoplasm, and, 
after the bag-like masses were formed, the protoplasm was still 
flowing along the walls in a conspicuous manner, even more so than 

[I)e Vrles (loc. cit. p. 50) J)e- Olnuer, In the ' Jnlires-Berlcht 

llovos that the form of nRKregH- dor Schl. Oesell. fdr vntorlilnd. 

tlon produced by carbonate of Ciiltur,' 1887, p. 107, also dlstln- 

aintnonia Is radlrnlly different fniixbes nmnionla nKKrcfcatton 

from ordinary aKirretcatlon. r. g. from the ordinary form of the 

that produced by meat. He be- phenomenon. F. I).] 

lleves It to he due to a preclplta- With other plants I bare 

tlon of albnnilnonH matter: the often seen what apiear to be a 

IcrnnuleB tbuH fornierl tend to be- true Hhrlnking of tlie primordial 

come packed Into baltn, and tinis utricle from the walln of the 

dense masses are produced which celln. cnusefl by a Holutlon of 

It Is not always easy to dls- cart>onate of amninnia, as like- 

tlmculnh from the aKKrexated wise follows from mechanical la- 

niaKKen which De VrioH bellevcnl Juries, 
to be formed from the vacuole. 



Chap. UI.] THE PROCESS OP AGGREGATION. 41 

before. It appeared indeed as if the stream of protoplasm- was 
strengthened by the action of the carbonate, but it was impossible 
to ascertain whether this was really the case. The bag-like masses, 
when once formed, soon begin to glide slowly round the cells, some- 
times sending out projections which separate into little spheres; 
other spheres appear in the fluid surrounding the bags, and these 
travel much more quickly. That the small spheres are separate 
is often shown by sometimes one and then another travelling in 
advance, and sometimes they revolve round each other. I have 
occasionally seen spheres of this kind proceeding up and down 
the same side of a cell, instead of round it. The bag-like masses 
after a time generally divide into two rounded or oval masses, and 
these undergo the changes shown in Figs. 7 and 8. At other times 
spheres appear within the bags; and these coalesce and separate in 
an endless cycle of change. 

After leaves have been left for several hours in a solution of 
the carbonate, and complete aggregation has been eflfected, 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 examina- 
tion; 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 nest morning, after 22 
hrs., by which time some new minute spheres had been formed; 
these oscillated from side to side and changed their positions, prov- 
ing that the current had not cease<l, though no stream of proto- 
plasm was visible. On another occasion, however, a stream was 
seen flowing round the cell-walls of a vigorous, dark -coloured leaf, 
after it had been left for 24 hrs. in a rather stronger solution, 
namely, of one part of the carbonate to 218 of water. This leaf, 
therefore, was not much oi" 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 leaif which had been left for 22 hrs. in a solution of one 
part of the carbonate to 292 of water, some spheres of protoplasm 
(formed by the self-division of a bag-like mass) were gently pressed 
beneath a covering glass, and then examined under a high power. 
They were now distinctly divided by well-defined radiating fissures, 
or were broken up into separate fragments with sharp e<lges, and 
they were solid to the centre. In the larger broken spheres the 
central part was more opaque, darker-coloured, and less brittle tlian 



42 DROSERA ROTUNDIFOLIA. [Chap. III. 

the exterior; the latter alone being in some cases penetrated by the 
fissures. In niiiny of the spheres the line of separation iKdween 
the outer and inner parts was tolerably well deiined. The outer 
parts were of exactly the same very pale purple tint, as that of 
the last- formed smaller spheres; and these latter did not include 
any darker central core. 

From these several facts we may conclude that, when vii^orous 
dark-coloured leaves are subjected to the action of carbonate of 
ammonia, the fluid within the cells of the tentacles often aggre- 
gates exteriorly into coherent viscid matter, forming a kind of 
bag. Small spheres sometimes appear within this bag, and the 
whole generally soon divides into two or more spheres, which re- 
peatedly coalesce and redividc. 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; those 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 cur- 
rent of limpid fluid still flows round the walls. 

If a leaf is immersed in a very strong, almost concentrated, solu- 
tion of carbonate of ammonia, the glands are instantly blackened, 
and they secrete copiously; but no movement of the tenUicles en- 
sues. Two leaves thus treated became after 1 hr. flaccid, and 
seem killed; all the cells in their tentacles contained spheres of 

f)rotoplasm, but these were small and discoloured. Two other ^ 
eaves were placed in a sohition not quite so strong, and there was * 
well-marked aggregation in 30 m. After 24 hrs. the spherical or 
more commonly oblong masses of protoplasm became opaque and 
granular, instead of being as usual translucent: and in the lower 
cells there were only innumerable minute spherical granules. It 
was evident that the strength of the solution had interfered with 
the completion of the process, as we shall see likewise follows from 
too great heat. 

All the foregoing observations relate to the exterior tentacles, 
which are of a purple colour; but the green petlicels 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 dilFerence 
that the aggregate masses are of a greenish colour; m tliat 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 suflTices to cause aggrega- 
tion. Full details will be given in the seventh chai)ter, and here 
it will be enough to say that with a .sensitive leaf the absorption 
by a gland of TxAinr "f a grain (.000 tS2 mgr.) is enough to cau.se 
in the course of one hour well-marked aggregation in the cells ira- 
nieiliately l)eneath the gland. 

The Kffrctn of certain other Salts and Fluids. Two leaves were 
placetl in a solutir>n of one part of acetate of ammonia to about 
140 of water, and were acted on quite as energetically, but perhaps 



Chap. III.] THE PROCESS OF AGGREGATION. 43 

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 ni. 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 immei-setl in a 
solution of one part of oxalate of ammonia to 14G of water; and 
after 24 ra. some, but not a conspicuous, change could be seen 
within the cells beneath the glands. After 47 m. plenty of spher- 
ical masses of protoplasm were formed, and these extended down 
the tentacles for about the length of the glands. This salt, there- 
fore, does not act so quickly as the carbonate. With respect to 
the citrate of ammonia, a leaf was place<i in a little solution of 
the above strength, and there was not even a trace of aggiegation 
in the cells beneath the glands, until 56 m. had elapsed; but it was 
well marked after 2 hrs. 20 m. On another occasion a leaf was 
placed in a stronger solution, of one part of the citrate to 109 of 
water (4 grs. to 1 oz.), and at the same time another leaf in a 
solution of the carbonate of the same strength. The glands of the 
latter were blackened in less than 2 m., and after 1 hr. 45 m. the 
aggregated masses, which were spherical and very dark-coloured, 
extended down all the tentacles, for between half and two-thirds of 
their lengths; whereas in the leaf immersed in the citrate the 
glands, after 30 m., were of a dark red, and the aggregated masses 
in the cells beneath them pink and elongated. After 1 hr. 45 m. 
these masses extended down for only about one-fifth or one-fourth 
of the length of the tentacles. 

Two leaves were placed, each in ten minims of a solution of one 
part of nitrate of ammonia to 5250 of water (1 gr. to 12 oz.), so 
that each leaf received yj^ of grain (.1124 njgr.). This quantity 
caused all the tentacles to be inflected, but after 24 hrs. there was 
only a trace of aggregation. One of these same leaves was then 
placed in a weak solution of the carbonate, and after 1 hr. 45_ m. 
the tentacles for half their lengths showed an astonishing degree 
of aggregation. Two other leaves were then placed in a much 
stronger solution of one part of the nitrate to 146 of water (3 
grs. to 1 oz.) ; in one of these there was no marked change after 3 
hrs. ; but in the other there was a trace of aggregation after 52 m., 
and this was plainly marked after 1 hr. 22 m., but even after 
2 hrs. 12 m. there was certainly not more aggregation than would 
have followed from an immersion of from 5 m. to 10 m. in an 
equally strong solution of the carbonate. 

Lastly, a leaf was placed in thirty minims of a solution of one 
part of phosphate of ammonia to 43,750 of water (1 gr. to 100 oz.), 
so that it received i^TT of a grain (.04079 mgr.) ; this soon caused 
the tentacles to be strongly inflected ; and after 24 hrs. the contents 
of the cells were aggregated into oval and irregularly globular 
masses, \^-ith a conspicuous current of protoplasm flowing round 
the walls. But after so long an inter^'al aggregation would have 
ensued, whatever had caused inflection. 

Only a few other salts, besides those of ammonia, were tried in 



44 DROSERA ROTUNDIPOLIA. [Chap. III. 

relation to the process of aggregation. A leaf was placed in a solu- 
tion of one part of chloride of sodium to 218 of water, and after 
1 hr. the contents of the cells were aggregated into small, irregu- 
larly globular, brownish masses; these after 2 hrs. were almost dis- 
integrated and pulpy. It was evident that the protoplasm had 
been injuriously affected; and soon afterwards some of the cells 
appeared quite empty. These effects differ altogether from those 
produced by the several 'salts of ammonia, as well as by various 
organic fluids, and by inorganic particles placed on the glands. A 
solution of the same strength of carbonate of soda and carbonate 
of potash acted in nearly the same manner as the chloride; and 
here again, after 2 hrs. 30 m., the outer cells of some of the glands 
had emptied themselves of their brown pulpy contents. We shall 
see in the eighth chapter that solutions of several salts of soda 
of half the above strength cause inflection, but do not injure the 
leaves. Weak solutions of sulphate of quinine, of nicotine, cam- 
phor, poison of the cobra, &c., soon induce well-marked aggrega- 
tion; whereas certain other substances (for instance, u 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 e.xcite true aggregation. Thus leaves were 
placed in a solution of one part of benzoic acid to 437 of water; 
and in 15 m. the purple fluid within the cells had shrunk a little 
from the walls; yet, when carefully examined after 1 hr. 20 m., 
there was no true aggregation; and after 24 hrs. the leaf was evi- 
dently dead. Other leaves in iodic acid, diluted to the same d^ree, 
showed after 2 hrs. 15 m. the same shrunken appearance of the 
purple fluid within the cells; and these, after 6 hrs. 15 m., were 
seen under a high power to be filled with excessively minute 
spheres of dull reddish protoplasm, which by the next morning, 
after 24 hrs., had almost disappeareil, the leaf being evidently 
dead. Nor was there any true aggregation in leaves immersed in 
propionic acid of the same strength; but in this case the proto- 

f>Iasm was collecte<l in irregular masses towards the bases of the 
ower cells of the tentacles. 

A filtered infusion of raw meat induces strong aggregation, but 
not very quickly. In one leaf thus immersed there was a little 
aggregation after 1 br. 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 waa 
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., ond these l)ecame aggregated 
to a wonderful degree, so that the inflectp<l tentacles presented to 
the nake<l eye a plainlj' mottled appearnnce. The little masses of 
purple protoplasm were generally oval or l)eaded, and not nearly so 
often spherical as in the case of leaves subjected to carbonate of 
ammonia. They undenvent incessant changes of form; and the 
current of colourless protoplasm round the walls was conspicuously 
plain after an immersion of 25 hrs. Raw meat is too powerful a 



Chap. III.] THE PROCESS OF AGGREGATION. 45 

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 iraniei-sed in a very strong solution of carbonate 
of ammonia. A leaf placed in milk had the contents of its cells 
somewhat aggregated in 1 hr. Two other leaves, one immersed in 
human saliva for 2 hrs. 30 m., and another in unboiled white of egg 
for 1 hr. 30 m., were not acted on in this manner; though they 
undoubtedly would have been so, had more time been allowed. 
These same two leaves, on being afterwards placed in a solution of 
carbonate of ammonia (3 grs. to 1 oz.), had their cells aggregated, 
the one in 10 m. and the other in 5 m. 

Several leaves were left for 4 hrs. 30 m. in a solution of one part 
of white sugar to 146 of water, and no aggregation ensued; on 
being placed in a solution of this same strength of carbonate of 
ammonia, they were acted on in 5 m. ; as was likewise a leaf which 
had been left for 1 hr. 45 m. in a moderately thick solution of gum 
arable. Several other leaves were immersed for some hours in 
denser solutions of sugar, gum, and starch, and they had the con- 
tents of their cells greatly aggregated. This effect may be attrib- 
uted to exosmose; for the leaves in the syrup became quite flac- 
cid, 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 excite 
inflection. Particles of soft sugar were added to the secretion 
round several glands and were soon dissolved, causing a great in- 
crease of the secretion, no doubt by exosmose; and after 24 hrs. 
the cells showed a certain amount of aggregation, though the ten- 
tacles were not inflected. Glycerine causes in a few minutes well- 
pronounced aggregation, commencing as usual within the glands 
and then travelling down the tentacles; and this I presume may be 
attributed to the strong attraction of this substance for water. 
Immersion for several hours in water causes some degree of aggre- 
gation. Twenty leaves were first carefully examined, and re- 
examined after having been left immersed in distilled water for 
various periods, with the following results. It is rare to find even 
a trace of aggregation until 4 or 5 and generally not until several 
more hours have elapsed. When, however, a leaf becomes quickly 
inflected in water, as sometimes happens, especially during very 
warm weather, aggregation may occur in little over 1 hr. In all 
cases leaves left in water for more than 24 hrs. have their glands 
blackened, which shows that their contents are aggregated ; and in 
the specimens, which were carefully examined, there was fairly 
well-marked aggregation in the upper cells of the pedicels. These 
trials were made with cut-ofT leaves, and it occurred to mo 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. 



46 DROSERA ROTUNDIFOLIA. [Chap. III. 

wfts submerged in distilled water for 47 hre., and the frlnnds were 
MackeniHl, though the tentat'lcs were very little inflected. In one 
of these leaves there was only a slight degree of aggregation in 
the tentacles; in the second rather more, the purple contents of the 
cells being a little separated from the walls; in the third and 
fourth, which were pale leaves, the aggregation in the upper parta 
of the iHHlicels was well niarkwl. In these leaves the little masses 
of protoplasm, many of which were oval, slowly changed their 
fomis and positions; so that a submergence for 47 hrs. had not 
killed the protoplasm. In a previous trial with a submerged plant 
the tentacles were not in the least inflected. 

Heat induces aggregation. A leaf, with the cells of the ten- 
tacles containing only homogeneous fluid, was wave<l about for 1 m. 
in water at 130 Fahr. {54*'.4 Cent.), and was then examineil under 
the microscope as quickly as possible, that is in 2 m. or 3 m. ; and 
by this time the contents of the cells had undergone some degree 
of aggregation. A second leaf was waved for 2 m. in water at 
12,5 (51.0 Cent.) and quickly examined as before; the tentacles 
were well inflectetl ; 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 di(l not subsecjuently 
increase. Lastly, a leaf was waved for 1 m. in water at 120 (4S.8 
Cent.) and then left for 1 hr. 20 m. in cold water; the tentacles 
were but little inflecte<l, and there was only here and there a trace 
of aggregation. In all these and other trials with warm water the 
protoplasm showetl much less tendency to aggregate into spherical 
masses than when excited by carbonate of ammonia. 

Redissohition <if the Angrrynted ManKcn of Prntnphmm. As soon 
as tentacles which have clasped an insect or any inorganic object, or 
have been in any way excited, have fully re-expan<led, the aggre- 
gated mas-ses of protoplasiH are redissolved and disappear; the cells 
being now refille<l 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 proce<Mls up 
them towards the glands. In old leaves, however, es|>ecially 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 
redisaolution, the following observations were made: a leaf was 
left for 24 hrs. in a little solution of one part of carbonate of am- 
monia to 218 of water, and the protoplasm was as usual aggregated 
into numl>erles8 purple spheres, which were incessantly changing 
their forms. The leaf was then washe<l an<l place<l in distilled 
water, and after 3 hrs. 15 m. some few of the spheres l>egan to 
show by their less clearly defined edges signs of redissolution. 
After O' hrs. many of them had become elongate<l, and the sur- 
rounding fluid in the cells was slightly more coloure<l, showing 
plainly that redissolution bad commenced. After 24 hrs., though 



Chap. III.] THE PROCESS OP AGGREGATION. 47 

many cells still contained spheres, here and there one could be 
seen filled with purple fluid, without a vestige of aggregated proto- 
plasm; the whole having been redissolved. A leaf with aggre- 
gated 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 solu- 
tion 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 disappeared, the cells being now filled 
with homogeneous fluid. 

We have seen that leaves immersed for some hours in dense 
solutions of sugar, gum, and starch have the contents of their cells 
greatly aggregated, and are rendered more or less flaccid, with the 
tentacles irregularly contorted. These leaves, after being left for 
four days in distilled water, became less flaccid, with their ten- 
tacles partially re-expanded, and the aggregated masses of proto- 
plasm 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 sheny wine; after 2 hrs. several 
of the tentacles had re-expanded, and the others could by a mere 
touch be pushed back into their properly expanded positions, and 
now all traces of aggregation had disappeared, the cells being filled 
with perfectly homogeneous pink fluid. The redissolution in these 
cases may, I presume, be attributed to endosmose. 

On the Proximate Causes of the Process of Aggregation. 

As most of the stimulants which cause the inflection ai 
the tentacles likewise induce aggregation in the contents of 
their cells, this latter process might be thought to be the 
direct result of inflection ; but this is not the case. If leaves 
are placed in rather strong solutions of carbonate of am- 
monia, 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 paralyzed, 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 phe- 
nomena of aggregation. On the other hand, several acids 
cause strongly pronoimccd inflection, but no aggregation. 



48 DROSERA ROTUNDIPOLU, [Chap. III. 

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, induc^g 
aggregation in cell beneath cell to their bases. 

It seems at first sight a probable view that aggregation is 
due to the glands being excited to secrete more copiously, so 
that sufficient fluid is not left in their cells, and in the cells 
of the pedicels, to hold the protoplasm in solution. In favour 
of this view is the fact that aggregation follows the inflection 
of the tentacles, and during the movement the glands gener- 
ally, or, as I believe, always, secrete more copiously than 
they did before. Again, during the re-expansion of the -ten- 
tacles, the glands secrete less freely, or quite cease to secrete, 
and the aggregated masses of protoplasm are then redissolved. 
Moreover, when leaves are immersed in dense vegetable solu- 
tions, or in glycerine, the fluid within the gland-cells passes 
outwards, and there is aggregation; and when the leaves are 
afterwards immersed in water, or in an innocuous fluid of less 
specific gravity than water, the protoplasm is redissolved, and 
this, no doubt, is due to endosmose. 

Opposed to this view, that aggregation is caused by the 
outward passage of fluid from the cells, are the following 
facts. There seems no close relation between the degree of 
increased secretion and that of aggregation. Thus a particle 
of sugar added to the secretion round a gland causes a much 
greater increase of secretion, and much less aggregation, 
than does a particle of carbonate of ammonia given in the 
same manner. It does not appear probable that pure water 
would cause much exosmose, and yet aggregation often fol- 
lows from an immersion in water of between 16 hrs. and 
24 hrs., and always after from 24 hrs. to 48 hrs. Still less 



Chap. III.] THE PROCESS OF AGGREGATION. 49 

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 protoplasm in solution. There is still 
stronger evidence that aggregation is independent of se- 
cretion; 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 Di- 
onsea, which do not secrete, likewise undergoes aggregation 
from the action of a weak solution of carbonate of ammonia. 
The process of aggregation is a vital one; by which I 
mean that the contents of the cells must be alive and 
uninjured to be thus affected, and they must be in an oxy- 
genated condition for the transmission of the process at 
the proper rate. Some tentacles in a dfop of water were 
strongly pressed beneath a slip of glass; many of the cells 
were ruptured, and pulpy matter of a purple colour, with 
^granules of all sizes and shapes, exuded, but hardly any of 
the cells were completely emptied. I then added a minute 
drop of a solution of one part of carbonate of ammonia to 
109 of water, and after 1 hr. examined the specimens. Here 
and there a few cells, both in the glands and in the pedicels, 
had escaped being ruptured, and their contents were well 
aggregated into spheres which were constantly changing 
their forms and positions, and a current could still be seen 
flowing along the walls; so that the protoplasm was alive. 
On the other hand, the exuded matter, which was now al- 
most 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 been completely 
emptied of their contents. Though I looked carefully, no 



50 DROSERA ROTUNDIPOLIA. [Chap. II L 

sigrns 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 aggre- 
gation 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 may 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** {Q5.5 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 subse- 
quent action of carbonate of ammonia, the latter quite stop- 
ping 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 or- 
dinary cases. With other leaves heated to 140** (60** Cent.), 
the spheres were extremely small, yet well defined, but many 
of the cells contained, in addition, some brownish pulpy 
matter. In two cases of leaves heated to 145 (G2.7 Cent.), 
a few tentacles could be found with some of their cells con- 
taining a few minute spheres; whilst the other cells and 
other whole tentacles included only the brownish, disinte- 
grated 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 com- 
parison, one from a fresh plant, were both immersed for 1 hr. 
in a rather strong solution of carbonate of ammonia. They 



Chap. III.] THE PROCESS OP AGGREGATION. 51 

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 car- 
bonate to 437 of water; the glands were instantly blackened, 
showing that they had absorbed, and that their contents were 
aj^gregated; but in the cells close beneath the glands there 
was no aggregation even after an interval of 3 hrs. After 
4 hrs. 15 m. a few minute spheres of protoplasm were formed 
in these cells, but even after 5 hrs. 30 m. the aggregation did 
not extend down the pedicels for a length equal to that of 
the glands. After numberless trials with fresh leaves im- 
mersed 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 com- 
parison, were now immersed in the same solution as before. 
The former were looked at repeatedly, and after an interval 
of 65 m. a few spheres of protoplasm were first observed 
in the cells close 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, iu 
the fresh leaf similarly treated, aggregation was plain in 
many of the tentacles after 15 m.; after 65 m. it had ex- 
tended down the pedicels for four, five, or more times the 
length of the glands; and after 3 hrs. the cells of all the 
tentacles were affected for one-third or one-half of their 
entire lengths. Hence there can be no doubt that the ex- 
posure of leaves to carbonic acid either stops for a time the 
process of aggrregation, 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 move- 
ments 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 corpus- 
6 



62 DROSERA ROTUNDIPOLIA. [Chip, IIL 

cles ; * but the casc?s above given are somewhat different, as 
they relate to the delay in the generation or aggregation 
of the masses of the protoplasm by the exclusion of oxygen. 

Summary and Concluding Remarks. The process of 
aggregation is independent of the inflection of the tentacles 
and apparently of increased secretion from the glamls. It 
commences within the glands, whether these have been di- 
rectly 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 higher power, is the appearance of the 
finest granules in the fluid within the cells, making it 
slightly cloudy. These granules soon aggregate intp 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 colour- 
less 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 redissolved, and the cells become filled with homo- 
geneous purple fluid, as they were at first. The process of 
redissolution commences at the bases of the tentacles, thence 
proceeding upwards to the glands; and, therefore, in a re- 
versed 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 

* with resppct to plnntn Snobn, Acoorrtlnjr to Hofmolster (as 

Trnltft de Rot..' 3rrl. wilt.. 1874, quoted bv .Sachn. ' Trnit* de 

p. K4fl. On l)lood corpiiKclM. tfe Bot..' 1874. p. 958). rpry Blljrht 

'(jiiartorly JournnI of Sllcroncopl- proHnnre on tho oell-monil)rane 

cal Science,' April 1874, p. 185. arrests Immediately the move- 



Chap. III.] THE PROCESS OP AGGREGATION. 53 

cut off close beneath the glands, by the glands absorbing 
various fluids or matter dissolved out of certain bodies, by 
exosmose, and by a certain degree of heat. On the other 
hand a temperature of about 150 Fahr. (65.5 Cent.) does 
not excite aggregation; nor does the sudden crushing of a 
gland. If a cell is ruptured, neither the exuded matter nor 
that which still remains within the cell undergoes aggrega- 
tion when carbonate of anunonia is added. A very strong 
solution of this salt and rather large bits of raw meat pre- 
vent the aggregated masses being well developed. From 
these facts we may conclude that the protoplasmic fluid with- 
in a cell does not become aggregated unless it be in a living 
state, and only imperfectly if the cell has been injured. We 
have also seen that the fluid must be in an oxygenated state, 
in order that the process of aggregation should travel from 
cell to cell at the proper rate. 

Various nitrogenous organic fluids and salts of ammonia 
induce aggregation, but in different degrees and at very 
different rates. Carbonate of ammonia is the most power- 
ful of all known substances; the absorption of it^^i^^ of a 
grain (.000482 mg.) by a gland suflSces 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 Ibng immersion in 
cold distilled water. It apparently depends in chief part on 
the strong aggregation of their cell-contents, which thus 
become opaque and, do not reflect light.* Some other fluids 
render the glands of a brighter red; whilst certain acids, 
though much diluted, the poison of the cobra-snake, fec., 
make the glands perfectly white and opaque; and this seems 
to depend on the coagulation of their contents without any 
aggr^ation. Nevertheless, before being thus affected, they 
are able, at least in some cases, to excite aggregation in 
their own tentacles. 

ments of the protoplnsm, nnd wnlls; thon^^h no doiiht th> ef- 
pven dPtermlnes Its soparntlon fects of pressure or of a touch 
from the wnlls. But the process on the outside must be trans- 
of aKf^reg^tlon Is a different phe- mitted through this Inyer. 
nomenon. ns It relates to the [The words " which .... 
contents of the cells, and only light " would probably have been 
secondarily to the Inyer of proto- omitted bv the author In a sec- 
plasm which flows along the ond edition. F. D.] 



54 DROSERA ROTUNDIPOLU. [Chap. III. 

That the central glands, if irritated, send centrifugally 
some influence to the exterior glands, causing them to send 
back a centripetal influence inducing aggregation, is per- 
haps the most interesting fact given in this cnapter. But 
the whole process of aggregation is in itself a striking phe- 
uomenon. Whenever the peripheral extremity of a nerve is 
touched or pressed, and a sensation is felt, it is believed that 
an invisible molecular change is sent from one end of the 
nerve to the other; but when a gland of Drosera is re- 
peatedly touched or gently pressed, we can actually see a 
molecular change proceeding from the gland down the tenta- 
cle ; 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 com- 
pounds. And this change in the glands, whether excited 
directly, or indirectly by a stimulus received from other 
glands, is transmitted from cell to cell, causing granules of 
protoplasm either to be actually generated in the previously 
limpid fluid or to coalesce and thus to become visible. 

Supplementary Observations on the Process of 
Aggregation in the Roots of Plants. 

It will hereafter be seen that a weak solution of the carbonate 
of ammonia induces aggregation in the cells of the roots of 
Drosera; and this led me to make a few trials on the roots of 
other plants. I dug up in the latter part of October the first 
weed which I met with, viz. Euphorbia peplua, being careful not 
to injure the roots; these were washed and placed in a little solu- 
tion 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 quadranf;ular masses of 

Sown matter; and some of these soon changed their forms and 
came spherical. Some of the cells, however, remained unaffected. 
I repeated the experiment with another plant of the same species, 
but before I could get the specimen into focus under the micro- 
scope, clouds of granules and quadrangular masses of reddish and 
brown matter were formed, and had run far up all the roots. A 
fresh root was now left for 18 hrs. in a drachm of a solution of 
one part of the carbonate to 437 of water, so that it received i of 



Chap. III.] THE PROCESS OP AGGREGATION. 55 

a grain, or 2.024 mg. When examined, the cells of all the roots 
throughout their whole length contained aggregated masses of 
reddish and brown matter. Before making these experiments, sev- 
eral roots were closely examined, and not a trace of the cloudy 
appearance or of the granular masses could be seen in any of them. 
Roots were also immersed for 35 m. in a solution of one part of car- 
bonate of potash to 218 of water; but this salt produced no effect. 

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

Plants of duck- weed (Lemna) were left for between 30 m. and 
45 m. in a solution of one part of this same salt to 146 of water, 
and three of their roots were then examined. In two of them, all 
the cells which had previously contained only limpid fluid now in- 
cluded little green spheres. After from H 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 can not say. As one species, 
Lemna arrhiza, produces no roots, the latter alternative is per- 
haps the most probahle. After 2J hrs. some of the little green 
spheres in the roots were broken up into small granules which ex- 
hibited 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 wero,placed for 25 m. in 
a solution of carbonate of ammonia of the same strength, little 
green spheres were formed. 

A green marine alga was left for some time in this same solu- 
tion, but was very doubtfully affected. On the other hand, a red 
marine alga, with finely pinnated fronds, was strongly affected. 
The contents of the cells aggregated themselves into broken rings, 
still of a red colour, which very slowly and slightly changed their 
shapes, and the central spaces within these rings became cloudy 
with red granular matter. The facts here given (whether they are 
new, I know not) indicate that interesting results would perhaps 
be gained by observing the action of various saline solutions and 
other fluids on the roots of plants." 

" [Bee C. Darwin on " The Ac- tlon of Carbonate of Ammonia 

tlon of Carbonate of Ammonia on Chioroph.vli-l)o<lles: " * Linn. 

on the Roots of certain Plants: " Soc. Jonrmil ' (Rot.), vol. xlx. 

' Linn. Soc. Jonrnnl ' (Bot.), vol. 1882, p. 2G2. F. D.l 
xlx. 1882, p. 230; also The Ac- 



66 



DROSEllA ROTUNDIFOLIA, 

\ 



[Chap. IV. 



CHAPTER IV. 



THE EFFECTS OF HEAT ON THE LEA^'E8. 

Nntnre of the experiments Effecta of boiling water Warm water muses 
nipid inflection Water at a hipher temperature (1(h>.s not cause iiinin'- 
diute inflection, but Awa not kill the leaves, as shown by their suhw- 
quent re-expansion and by the aggregation of the protoplasm A still 
higher temperature kills the leaves and coagulates the albuminous 
contents of the glands. 

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



' When my experiments on the 
efTects of heat were made. I wus 
not aware that the ul>Jeot had 
been carefully Investigated by 
several observers. For Instance, 
Sachs Is convlnce<l (' Trnltf' de 
Botanlque,' 1874. pp. 772. KA) 
that the most different kinds of 
plants all perish If kept for 10 
m. In water at 40 to id' Cent., 
or ll.T to 115 Fahr.; and he 
concludes that the protoplasm 
within their cells always <'oaKU- 
lates. If In n dump coinlltlon, nt 
n temperature or between IV)'' 
and (50 Cent., or l'J*J to 140' 
Fnhr. Max S<-hultze and Kllhne 
(ns (|iioted by Dr. liastlan In 
Conlemp. Review,' 1874. p. 5281 
* found that the protoplasm of 
plnntcells. with which thev ex- 
perlmenleil. was always killed 
and altercl by a very brief vx- 



posure to a temperature of 118}* 
Fiihr. as a maximum." As my 
results are de<liiced from special 
phenomena, namely, the subse- 
quent aggregation of the proto- 
plasm and the re-expanslon of 
the tentacles, they seem to me 
worth giving. We shall find that 
Drosera resists heat somewhat 
better than most other plants. 
That there should be couslder- 
able differences In this respect Is 
not surprising, considering that 
some low vegetable organisms 
grow In hot springs -cases cf 
which have been collected by 
I'rofessor Wyman C American 
Journal of Science.' vol. xllv. 
1807). Thus. Dr. Hooker found 
Confervac In water at m8 Fahr.; 
Ilntnbcildt. at 1S." Fahr.; and 
Desclolzeauz, at 'MS Fahr. 



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, were 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 gradually raised to the required temperature by a 
spirit-lamp moved about under the vessel ; and in all cases the 
leaves were continually waved for some minutes close to the bulb. 
They were then placed in cold water, or in a solution of carbonate 
of ammonia. In other cases they were left in the water, which 
had been raised to a certain temperature, until it cooled. Again, 
in other cases the leaves were suddenly plunged into water of a 
certain temperature, and kept there for a specified time. Consider- 
ing that the tentacles are extremelj' delicate, and that their coats 
are very thin, it seems scarcely possible that the fluid contents 
of their cells should not have been heated to within a degree or 
two of the temperature of the surrounding water. Any further 
precautions would, I think, have been superfluous, as the leaves 
from age or constitutional causes differ slightly in their sensitive- 
ness to heat. 

It will be convenient first briefly to describe the effects of im- 
mersion for thirt}"^ seconds in boiling water. The leaves are ren- 
dered 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 sur- 
faces retain the power of contraction. The purple fluid within 
the cells of the pedicels is rendered flnely granular, but there is 
no true aggregation ; nor does this follow wheifl the leaves are sub- 
sequently placed, in a solution of carbonate of ammonia. But the 
most remarkable change is that the glands become opaque and 
uniformly white; and this may be attributed to the coagulation 
of their albuminous contents. 

My first and preliminary experiment consisted in putting seven 
leaves in the same vessel of water, and warming it slowly up to the 
temperature of 110 Fahr. (43''.3 Cent.); a leaf being taken out 
as soon as the temperature rose to 80" (26''.6 Cent.), another at 
85, another at 90, and so on. Each leaf when taken out, was 
placed in water at the temperature of my room, and the tentacles 
of all soon became slightly, though irregularly, inflected. They 
were now removed from the cold water and kept in damp air, with 
bits of meat placed on their discs. The leaf which had been ex- 
posed to the temperature of 110 became in 15 ni. greatly in- 
flected; and in 2 hrs. every single tentacle closely embraced the 
meat. So it was, but after rather longer intervals, with the six 
other leaves. It appears, therefore, that the warm bath had in- 
creased their sensitiveness when excited by meat. 

I next observe<l the degree of inflection which leaves underwent 
within stated periods, whilst still immersed in warm water, kept as 



58 DEOSERA ROTUNDIFOLI4. [( UAP. IV. 

nearly as possible at the same temperature; but I will here and 
elsewhere give only a few of the many trials made. A leaf was 
left for 10 m. in water at 100 (37.7 Cent.), but no inflection oc- 
curred. A second leaf, however, treated in the same manner, had 
a few of its e.xterior tentacles very slightly inflected in G m., anl 
several irregularly but not closely inflected in 10 m. A third leaf, 
kept in water at 105" to 106 (40.5 to 40.l Cent.), was very 
moderately inflected in -C 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 protoplasm within the cells was not killed, for it 
was seen to be in distinct movement; and the leaves, having been 
left in cold water for 20 hrs., re-expanded. Another leaf was im- 
mersed 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 become 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 marke<l 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 carbonate 
of ammonia (one part to 109 of water) ; in 10 m. all the glands be- 
came intensely black, and in 2 hrs. the protoplasm in the cells of the 
pedicels was well aggregate<l. Another leaf was suddenly plunged, 
and as usual waved about, in water at 120, and the tentacles be- 
came 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 sudden- 
ly placed in water at 125 (51.0 Cent.), and was left in it until the 
water coole<l ; the tentacles were rendennl of a bright red and soon 
became inflected. The contents of the ceils 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 leam from these cases that a temperature of from 
120 to 125* (48**.8 to 51*.6 Cent.) excites the tentacles 



Chap. IV.] THE EFFECTS OP HEAT. 69 

into quick movement, but does not kill the leaves, as shown 
either by their subsequent re-expansion or by the aggregation 
of the protoplasm. We shall now see that a temperature of 
130 (54.4 Cent.) is too high to cause immediate inflection, 
yet does not kill the leaves. 

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

Experiment 2. Another leaf was plunged into water at 130' to 
131", and, as before, there was no inflection. After being kept in 
cold water for an hour, it was placed in the strong solution of am- 
monia, 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 ten- 
tacles was distinctly aggr^ated ; but the spheres were much smaller 
than those usually generated in unheated leaves when subjected to 
carbonate of ammonia. After an additional 2 hrs. all the tentacles, 
excepting six or seven, were closely inflected. 

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

Experiment 4- A fine leaf was placed in water at 100 (37.7 
Cent.), which was then raised to 145" (62.7 Cent.). Soon after 
immersion, there was, as might have been expected, strong in- 
flection. 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 inflec- 
tion ; it was then placed in cold water, and after 1 hr. 20 m. some of 
the tentacles on one side became inflected. This leaf was now placed 
in the strong solution, and in 40 m. all the submarginal tentacles 
were well inflected, and the glands blackened. After an additional 
interval of 2 hrs. 45 m. all the tentacles, except eight or ten, were 
closely inflectetl, with their cells exhibiting a slight degree of aggre- 
gation; but the spheres of protoplasm were very small, and the cells 
of the exterior tentacles contained some pulpy or disintegrated 
brownish matter. 

Experiments 6 and 7. Two leaves were plunged in water at 135" 
(57".2 Cent.) which was raised to 145" (fl2".7 Cent.); neither be- 
came inflectetl. One of these, however, after having been left for 31 
m. in cold water, exhibited some slight inflection, which increased 
after an additional interval of 1 hr. 45 m., until all the tentacles, ex- 

* Sacbs Btnten (' Tralt<' de Bo- after the.v were exposed for 1 m. 

tnnlqiie," 1784, p. STw) that the in water to a temperature of 47* 

movements -of the protoplasm In to 48* Cent., or 117' to 119 Fabr. 
the balrs of a Cucurblta ceased 



CO DROSEKA ROTUNDIFOLIA. [Chap. IV. 

cept 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, espe- 
cially in the exterior tentacles, there was much greenish-brown 
pulpy matter. 

Experiment 8. A leaf was plunged and waved about for a few 
minutes in water at 140" (60" Cent.), and was then left for half an 
hour in cold water, but there was no inflection. It was now placed 
in the strong solution, and after 2 hrs. 3U m. the inner submarginal 
tentacles were well inflecte<l, 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 immei-sion 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 porce- 
Inin-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 (05.5 Cent.) ; there whs no inflection; on 
the contrary, the outer tentacles were somewhat bowed backwards. 
The glands became like porcelain, but some of them were a little 
mottletl with purple. The bases of the glands were often more af- 
fected than their summits. This leaf having been left in the strong 
solution did not undergo any inflection or aggregation. 

Experiment 10. A leaf was plunged in water at 150 to 150} 
(65.5 Cent.) ; it became somewhat flaccid, with the outer 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 place<l 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 imnierse<l in water at 145 (62.7 
Cent), which was raised to 1.56 (68.8 Cent.). The tentacles be- 
came bright red and somewhat reflexed, with almost all the glands 
like porcelain; those on the disc Ix-ing still pinkish, those near the 
margin quite white. The leaf being placed as usual first in cold 
water and then in the strong solution, the cells in the tentacles be- 
came of a muddy greenish brown, with the protoplasm not aggre- 
gated. Nevertheless, four of the glands escaped In-ing 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 



Chap. IV.] THE EFFECTS OF HEAT. 61 

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 afterwards subjected 
to the action of carbonate of ammonia, unless the heat has been suffi- 
cient to cause coagulation. 

Concluding Remarks. As the hair-like tentacles are ex- 
tremely thin and have delicate walls, and as the leaves were 
waved about for some minutes close to the bulb of the 
thermometer, it seems scarcely possible that they should not 
have been raised very nearly to the temperature which the 
instrument indicated. From the eleven last observations we 
see that a temperature of 130 (54,4 Cent.) never causes 
the immediate inflection of the tentacles, though a tem- 
perature from 120 to 125 (48.8 to 51.6 Cent.) quickly 
produces this effect. But the leaves are paralysed only for a 
time by a temperature of 130, as afterwards, whether left in 
simple water or in a solution of carbonate of ammonia, they 
become inflected and their protoplasm undergoes aggregation. 
This great difference in the effects of a higher and lower tem- 
perature 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 ener- 
getically. A temporary suspension of the power of move- 
ment due to heat is called by Sachs* heat 'rigidity; and this 
in the case of the sensitive plant (Mimosa) is induced by its 
exposure for a few minutes to humid air, raised to 120 
122 Fahr., or 49 to 50 Cent. It deserves notice that the 
leaves of Drosera, after being immersed in water at 130 
Fahr., are excited into movement by a solution of the carbon- 
ate so strong that it would paralyze 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 always, become inflected; and the protoplasm 
within their cells undergoes aggregation, though the spheres 
thus formed are extremely small, with many of the cells 
partly filled with brownish muddy matter. In two instances, 

* Tralte de Bot.' 1874, p. 1034. 



62 DROSERA ROTUNDIPOLIA. [Chap. IV. 

when leaves were immersed in water, at a lower temperature 
than 130" (54 .4 Cent.), which was then raised to 145* 
(62** .7 Cent.), they became during . the earlier period of 
immersion inflected, but on being afterwards left in cold 
water were incapable of re-expansion. Exposure for a few 
minutes to a temperature of 145 sometimes causes some few 
of thfe more sensitive glands to be speckled with the porce- 
lain-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 tempyerature of only 
140, and left therein till the water cooled, every gland be- 
came like porcelain. Exposure for a few minutes to a tem- 
perature of 150 (65.5 Cent.) generally produces this 
effect, yet many glands retain a pinkish colour, and many 
present a speckled appearance. This high temperature 
never causes true inflection; on the contrary, the tentacles 
commonly become reflexed, though to a less degree than when 
immersed in boiling water; and this apparently is due to 
their passive power of elasticity. After exposure to a tem- 
perature of 150 Fahr., the protoplasm, if subsequently sub- 
jected to carbonate of ammonia, instead of undergoing 
aggregation, is converted into disintegrated or pulpy dis- 
coloured matter. In short, the leaves are generally killed 
by this degree of heat; but owing to diflferences 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 
rolundifolia, which flourishes on bleak upland moora 
throughout Great Britain, and exists (Hooker) within the 
Arctic Circle, should be able to withstand for even a short 
time immersion in water heated to a temperature of 145.* 

Ah the opnolty and porce- ture of ronpnlntlon Is lower. 

Inln-liko apponraiioe of the The leaves of Drosera contain an 

Klands Is prol)nl)ly due to the co- acid, and perhaps n dilToreuce In 

a^rnlatlon of the alhutneD, I may the amount contained may ac- 

ndd. on the authority of Dr. count for the slight dirferencea In 

Ilnrdon Sanderson, that albumen the results above recorded, 

coatrnlates at nlM>i't 1S5*, but. In It appears the cold-blooded 

presence of acids, the tempera- animals are. as might have l>een 



Chap. IV.] THE EFFECTS OF HEAT. 63 

It may be worth adding that immersion in cold water 
does not cause any inflection : I suddenly placed four leaves, 
taken from plants which had been kept for several days at a 
high temperature, generally about 75 Fahr. (28.8 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. 

expected, far more sensitive to at a temperature of only 85' 
an Increase of temperature than Fahr. At 95" the muscles be- 
ts Drosera. Thus, as I bear from come rigid, and the animal dies 
r>r. Burdon Sanderson, a frog in a stiffened condition, 
begins to be distressed in water 



C4 DKOSERA ROTUNDIFOLIA. [Cuap. V. 



CHAPTER V. 

THE EFFECTS OF NON-NITROOENOUS AND NITROGENOUS ORGANIO 
FLUIDS ON THE LEAVES. 

Non-nitrogenous fluids Solutions of gum arabic Sugar Starch Diluted 
alcohol Olive oil Infusion and decot-tion of tt-a Nitrogenous fluids 
Milk Urine Liquid albumen Infusion of raw meat Impurti 
mucus Saliva Solution of isinglass DiUbrcncc in the action of 
these two sets of fluids EKicoction of green peas Decoction and infu- 
sion of cabbage Decoction of grass leaves. 

When, in 1860, I first observed Drosera, and was led to 
believe that the leaves absorbed nutritious matter from in- 
sects 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 f\^ of a fluid 
ounce, or .0295 cc. But these measurements obviously do 
not pretend to any strict accuracy; moreover, the drops of 
the viscid fluids were plainly larger than those of water. 
Only one leaf on the same plant was tried, and the plants 
were collected from two distant localities. The experiments 
were made during August and September. In judging of 
the effects, one caution is necessary: if a drop of any ad- 
hesive 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 to- 
gether, giving to them the false appearance of having become 
inflected. This sometimes occurs with water, as it is ren- 
dered 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. 



Chap, v.] EFFECTS OF ORGANIC FLUIDS. 65 

In 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 lat- 
ter movement is never caused, as far as I have seen, by the 
mere drying up of an adhesive fluid and the consequent 
drawing together of the tentacles. 

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

Gvtn 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 instru- 
ment. These were tried on fourteen leaves ; the drops being left on 
the discs from 24 hrs. to 44 hrs. ; generally about 30 hrs. Inflection 
was never thus caused. It is necessary to try pure gum arable, for a 
friend tried a solution bought ready prepared^and this caused the 
tentacles to bend; but he afterwards ascertained that it contained 
much animal matter, probably glue. 

Sugar. Drops of a solution of white sugar of three strengths 
(the weakest containing one part of sugar to 73 of water) M'ere left 
on fourteen leaves from 32 hrs. to 48 hrs.; but no effect was pro- 
duced. 

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 gen- 
erally contains a trace of gluten, and this nitrogenous substance 
causes inflection, as we shall see in the next chapter. 

Alcohol, Diluted. One part of alcohol was added to seven of 
water, and the usual drops were placed on the discs of three leaves. 
No inflection ensued in the course of 48 hrs. To ascertain whether 
these leaves had been at all injured, bits of meat wtre 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. 



6G DROSERA EOTUNDIFOIJA. [Chap. V. 

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

Infusion and Decoction of Tea. Drops of a strong infusion and 
decoction, as well as of a rather weak decoction, of tea were placed 
on ten leaves, none of which became infected. I afterwards tested 
three of them by adding bits of meat to the drops which still re- 
mained 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 produceii no effect. The albuminous 
matter which the leaves must riginally have contained, no doubt, 
had been rendered insoluble by their having been completely dried. 

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

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

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

Human Urine. Drops were placed on twelve leaves, and the ten- 
tacles of all, with a single exception, became greatly inflected. Ow- 
ing, I presume, to differences in the chemical nature of the urine 
on different occasions, the time required for the movements of the 
tentacles varie<l much, but was always effected in under 24 hrs. In 
two instances I recorded that all the exterior tentacles were com- 
pletely 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 in- 
flected that it was converte<l into a cup. The power of urine does 
not lie in the urea, which, as we shall hereafter see, is inoperative. 

Albumen (fresh from a hen's egg), placed on seven leaves, caused 



Chap. V.] EFFECTS OF ORGANIC FLUID. 67 

the tentacles of six of them to be well inflected. In one case the edge 
of the leaf itself became much curled in after 20 hrs. The one leaf 
which was unaffected remained so for 26 hrs., and was then treated 
with a drop of milk, and this caused the tentacles to bend inwards 
in 12 hrs. 

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

Mucus. Thick and thin mucus from the bronchial tubes, placed 
on three leaves, caused inflection, A leaf with thin mucus had its 
marginal tentacles and blade somewhat curved inwards in 5 hrs. 
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 principle of mucus. 

Saliva. Human saliva, when evaporated, yields* 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 ease all the exterior tentacles, ex- 
cepting 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 mak- 
ing 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 inwa^ls of the tentacles. 
The edible nest of the Chinese swallow is formed of matter secreted 
by the salivary glands; two grains were added to one ounce of dis- 
tilled water (one part to 218), which was boiled for several minutes, 
but did not dissolve the whole. The usual-sized drops were placed 
on three leaves, and these in 1 hr. 30 m. were well, and in 2 hrs. 15 m. 
closely, inflected. 

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

' Mucus from the air-passages * MUIIer's * Elements of Physl- 

is snld in MarHhall, * Outlines of olofry,' Eng. translatioD, vol. I. 
I'hysloloBV.' vol. il. 1867, p. 304, p. 514. 
to coutaiu some albumen. 
6 



6S DROSERA ROTUNDIFOLIA. [Chap. V. 

on the leavea, all four had almost re-expanded. They were then 
given little bits of meat, and tlu-sc acted more i)owerfuny than the 
solution. One part of isinglass was next dissolved in 437 of water: 
the fluid thus formed was so thin that it could not be distinguished 
from pure water. The usual-sized drops were placed on seven 
leaves, each of which thus received 7^0 of a grain (.0295 mg.). 
'I'luee of them were observed for 41 hrs., but were in no way af- 
fected; the fourth and fifth had two or three of their exterior ten- 
tacles 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 -^ of a 
grain of isinglass is suilicicnt to affect very slightly the more sen- 
sitive or active leaves. On one of the leaves, which had not been 
acted on by the weak solution, and on another, which had only 
two of its tentacles inflected, drops of the solution as thick as 
milk were placed; and next morning, after an interval of 16 hrs., 
both were found with all their tentacles strongly inflected. 



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

Some of the leaves which were not affected by the non- 
nitrogenous fluids were, as above stated, 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 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 



Chap. V.] EFFECTS OF ORGANIC FLUIDS. 69 

in some cases their blades, well inflected; but their powers 
were somewhat impaired, for the rate of movement was de- 
cidedly slower than when fresh leaves were treated with 
these same nitrogenous fluids. This impairment, as well as 
the insensibility of six of the leaves, may be attributed to 
injury from exosmose, caused by the density of the fluids 
placed on their discs. 

The results of a few other experiments with nitrogenous fluids 
may be here conveniently given. Decoctions of some vegetables 
known to be rich in nitrogen, were made, and these acted like animal 
fluids. Thus, a few green peas were boiled for some time in distilled 
water, and the moderately thick decoction thus made was allowed to 
settle. Drops ofthe 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 Ger- 
hardt * that legumin is present in peas " in combination with an 
alkali, forming an incoagulable solution," and this would mingle 
with boiling water. I may mention, in relation to the above and 
following experiments, that according to Schiff * certain forms of al- 
bumen exist which are not coagulated by boiling water, but are con- 
verted into soluble peptones. 

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

About the same quantity of chopped cabbage leaves and of dis- 
tilled 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 2.3 
hrs., was much inflected; a second slightly; a third had only the 
submarginal tentacles inflected; and the fourth was not at all af- 

Watts' ' Diet, of Chemistry,' as were used bv me. contnln 2.1 

vol. ill. p. 568. per cent, of alniinilnous matter. 

* ' Lemons ur la Phys. de la and the outer leaves of mntiire 

Digestion.' torn. I. p. 370; torn. 11. pinnts 1.6 per cent. Watts' 

pp. l.'M, 160, on lepuniln. ' IHct. of Chemistry,' vol. 1. p. 

The leaves of yodug pinnts. 653. 
before the heart is foriued, sucb 



70 DROSERA ROTUNDIPOLIA. [Chap. V. 

fected. The power of this infusion is therefore very much less than 
that of the det-oc-tion ; and it is clear that the immersion of cabbage 
leaves for an hour in water at the boiling temperature is much more 
etiicient in extracting matter which excites Drosera than immersion 
during many hours in wai-m water. Perhaps the contents of the 
cells are protected (as Schiff remarks with respect to legumin) by 
the walls being formed of .cellulose, and that until these are ruptured 
by boiling-water, but little of the contained albuminous matter is 
dissolved. We know from the strong odour of cooked cabbage leaves 
that boiling-water produces some chemical change in them, and that 
they are thus rendered far more digestible and nutritious to man. 
It is therefore an interesting fact that water at this temperature ex- 
tracts matter from them which excites Drosera to an extraor- 
dinary degree. 

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

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



Chap. VI.] DIGESTION. 71 



CHAPTER VI. 

THE DIGESTIVE POWER OF THE SECRETION OF DROSERA. 

The secretion rendered acid by the direct and indirect excitement of the 
glands Nature of the acid Digestible substances Albumen, it8 di- 
gestion 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 Legu- 
min Pollen Globulin Usematin Indigestible substances Epider- 
mic productions Fibro-elastic tissue Mucin Pepsin Urea Chitine 
Cellulose Gun-cotton Chlorophyll Fat and oil Stareh Action 
of the secretion on living seeds Summary and concluding remarks. 

As we have seen that nitrogenous fluids act very differ- 
ently on the leaves of Drosera from non-nitrogenous fluids, 
and as the leaves remain clasped for a much longer time 
over various organic bodies than over inorganic bodies, such 
as bits of glass, cinder, wood, &c., it becomes an interesting 
inquiry, whether they can only absorb matters already in 
solution, or render it soluble, that is, have the power of di- 
gestion. We shall immediately see that they certainly have 
this power, and that they act on albuminous compounds in 
exactly the same manner as does the gastric juice of mam- 
mals; the digested matter being afterwards absorbed. This 
fact, which will be clearly proved, is a wonderful one in the 
physiology of plants. I must here state that I have been 
aided throughout all my later experiments by many valuable 
suggestions and assistance given me with the greatest kind- 
ness by Dr. Burdon Sanderson. 

It may be well to premise for the sake of any reader who 
knows nothing about the digestion of albuminous compounds 
by animals that this is effected by means of a ferment, pep- 
sin, together with weak hydrochloric acid, though almost 
any acid will serve. Yet neither pepsin nor an acid by itself 
has any such power.* We have seen that when the glands of 

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

Ing to Scbiff, and contrary to the quantity of coagulated albumen. 

o|>inion of- 8oroe physiologists, Schlff, ' I'hvs. do la Digestion,' 

that weak hydrochloric dissolves, 18C7, torn. li. p. 25. 



72 DROSERA ROTUNDIFOLIA. [Cdap. VI. 

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 secre- 
tion becomes acid. Moreover, they transmit some influence 
to the glands of the exterior tentacles, causing them to pour 
forth a more copious secretion, which also becomes acid or 
more acid than it was before. 

As this result is an important one, I will give the evi- 
dence. 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 afiFect 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 wore 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 secre- 
tion varied somewhat on the glands of the same leaf. On 
some leaves, a few tentacles did not, from some unknown 
cause, become inflected as often happens; and in five in- 
stances their secretion was found not to be in the least acid ; 
whilst the secretion of the adjoining and inflected tentacles 
on the same leaf was decidedly acid. With leaves excited by 
particles of glass placed on the central glands, the secretion 
which collects on the disc beneath them was much more 
strongly acid than that poured forth from the exterior 
tentacles, which were as yet only moderately inflected. When 
bits of albumen (and this is naturally alkaline), or bits of 
meat were placed on the disc, the secretion collected beneath 

[In the ' Proceodlngs of the Injt seoretlon, nnd (flve evidence 

Royal Society,' 188(J, No. 240, that the secretion reHultH from 

Gardiner baa described the the breakhiK down of the proto- 

chnnsefl which go on in the plaHnilc reticulum of the gland- 

glands of Droacra dichotoma dur- celL F. D.] 



Chap. VI.] DIGESTION. 73 

them was likewise strongly acid. As raw meat moistened 
with water is slightly acid, I compared its action on litmus 
paper before it was placed on the leaves, and afterwards when 
bathed in the secretion; and there could not be the least 
doubt that the latter was very much more acid. I have in- 
deed 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 be- 
gun to bend over any inorganic or organic object; and still 
more strongly acid after the tentacles have remained for 
gome 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 appear- 
ance 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 putre- 
faction by destroying the microzymes. 

As I was anxious to leam what acid * the secretion contained, 445 
leaves were washed in distilled water, given me by Professor Frank- 
land; but the secretion is so viscid that it is' scarcely possible to 
scrape or wash off the whole. The conditions were also unfavour- 
able, as it was late in the year and the leaves were small. Pro- 
fessor Frankland with great kindness undertook to test the ffuid 
thus collected. The leaves were excited by clean particles of glass 
placed on them 24 hrs. previously. No doubt much more acid would 
have been secreted had the leaves been excited by animal matter, 
but this would have rendered the analysis more difficult. Professor 
Frankland informs me that the fluid contained no trace of hydro- 
chloric, sulphuric, tartaric, oxalic, or formic acids. This having been 
ascertained, the remainder of the fluid was evaporated nearly to dry: 
ness, and acidified with sulphuric acid ; it then evolved volatile acid 

* [Messrs. Rees and Will the evidence of the smell. Gornp 

(' Bot. Zeltnng,' 1875, p. 716) and Will have shown that the 

stimulated the glands of some nentral secretion of Nepenthes 

thousand Drosera plants with becomes powerfully digestive 

glass-dust and analysed the se- when aclanlated with formic 

cretion thus produced. Thoy acid (see ' Bot. Zeltung,' 1870, p. 

found a variety of fatty a'id8 470). It Is therefore Interesting 

present, among which Formic to find this noid naturally pres- 

acld was recognised with cer- ent In the secretion of Drosera. 

talnty, and Propionic and Bu- F. D.] 
tyric adds were suspected from 



74 DROSERA ROTUNDIFOLIA. [Chap. VI. 

rapour, which was condensed and digested with carbonate of silver. 
" The weight of the silver salt thus produced was only .37 gr., much 
too small a quantity for the accurate determination of the mo- 
lecular weight of the acid. The number obtained, however, corre- 
sponded nearly with that of propionic acid ; and I believe that this, 
or a mixture of acetic and butyric acids, were present in the liquid. 
The acid doubtless belongs to the acetic or fatty series." 

Professor Frankland, as well as his assistant, observed (and this 
is an important fact) tliat the fluid, " when acidified with sulphuric 
acid, emitted a powerful odour like that of pepsin." The leaves from 
which the secretion had been washed were also sent to Professor 
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 lit- 
mus 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 ad- 
visable 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 vale- 
rianic. Dr. Burdon Sanderson was so kind as to make for me the 
following experiments, the results of which are valuable, independ- 
ently of the present inquiry. Professor Frankland supplied the 
acids. 

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

" 2. It has been determined empirically that the best results are 
obtained in artificial digestion when a liquid containing two per 
thousand of hydrochloric acid gas by weight is used. This corre- 
sponds to about 6,25 cubic centimetres per litre of ordinary strong 
hydrochloric acid. The quantities of propionic, butyric, and vale- 
rianic acids respectively which are required to neutralise as much 
base as 6.25 cubic centimetres of HCl, are in grammes 4.04 of pro- 
pionic acid, 4.82 of butyric acid, and 5.68 of valerianic acid. It was 
therefore judged expe<lient, in comparing the digestive powers of 
these acids with that of hydrochloric acid, to use them in these pro- 
portions. 

" 3. Five hundred cub. cent, of a liquid containing about 8 cub. 
cent, of a glycerine extract of the mucous membrane of the stomach 
of a dog killed during digestion having been prepared, 10 cub. cent, 
of it were evaporated and dried at 110. This quantity yielded 
0.0031 of residue. 

" 4. Of this liauid four quantities were taken which were sever- 
ally acidulated with hydrocnloric, propionic, butyric, and valerianic 
acids, in the proportions above indicated. Each liquid was then 
placed in a tube, which was allowed to float in a water bath, con- 



Chap. VI.] DIGESTION. 75 

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

" In the liquid containing hydrochloric acid 0.4079 

" " propionic acid O.OGOl 

" " butyric acid 0.1468 

" " valerianic acid 0.1254 

" Hence, deducting from each of these the above-mentioned resi- 
due, left when the digestive liquid itself was evaporated, viz. 0.0031, 
we have, 

" For propionic acid . . . . . . . . 0.0570 

" butyric acid 0.1437 

" valerianic acid . . ' 0.1223 

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

" The results of the experiment may be stated thus: If 100 rep- 
resent the digestive power of a liquid containing pepsin with the 
usual proportion of hydrochloric acid, 14.0, 35.4, and 30.2, will repre- 
sent respectively the digestive powers of the three acids under in- 
vestigation. 

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

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

"Propionic acid 0.0563 

Butyric acid 0.0835 

Valerianic acid 0.0615 

"The quantity digested by a similar liquid containing hydro- 
chloric acid was 0.3376. Hence, taking this as 100, the following 
numbers represent the relative quantities digested by the other 
acids : 

" Propionic acid . . . . . 16.5 

Butyric acid . . . . . . 24.7 

Valerianic acid 16.1 



76 DROSERA ROTUNDIPOLIA. [Chap. VL 

" fl. A third experiment of the same kind gave: 
" Quantity of librin 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 with 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 eflicacious) 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 pro- 
portion of hydrochloric acid digested 0.1311 gramme, a similar 
liquid prepared with butyric acid digested 0.0455 gramme of fibrin. 

" Hence, taking the quantities digested with hydrochloric acid 
at the temperature of the body as 100, we have the digestive power 
of hydrochloric acid at the temperature of 16" to 18 Cent, repre- 
sented 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 under similar conditions and temperatures. 
We have also seen that butyric acid, which is mtich more effica- 
cious than propionic or valerianic acids, digests with pepsin at the 
higher temperature less than a third of the fibrin which is digested 
at the same temperature by hydrochloric acid. 

I will now give in detail my experiments on the digestive 
power of the secretion of Drosera, dividing the substances 
tried into two series; namely, those which are digested more 
or less completely, and those which are not digested. We 
shall presently see that all these substances are acted on by 
the gastric juice of the higher animals in the same manner. 
I b% leave to call attention to the experiments under 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 hy the 
Secretion of Drosera. 

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

Experiment 1. Eather large cubes of albumen were first tried; 
the tentacles were well inflected in 24 hrs.; after an additional day 
the angles of the cubes were dissolved and rounded ; * but the 
cubes were too large, so that the leaves were injured, and arfter 
seven days one died and the others were dying. Albumen which 
has been kept for four or five days, and which, it may be pre- 
sumed, has begim 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 tV 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 -^g of an inch 
(1.905 mm.) in diameter, surrounded by perfectly transparent fluid. 
After ten days the leaf re-expanded, but there was still left on 
the disc a minute bit of albumen now rendered transparent. More 

* In all my numerous experl- Istlc of the dtgeRtlon of nibnmen 

ments on the digestion of cubes by the gnstrlc Juice of anIuiiilH. 

of albumen, the anjrles and t'<l.t?e8 On the other hand, ho roniarkH, 

were Invariably tlrst rounded. " les dlssolntlons, en chimb', ont 

Now, Schlff states (' Lof.-ons lieu sur toute la surface d8 

Phys. de la' Digestion,' 1807, toin. corps en contact avec Tugent Ul- 

il.. p. 140) that this is character- solvaut." 



78 DROSERA ROTUNDIFOLIA. [Chap. VI. 

albumen had been given to this lea| than could be dissolved or 
digested. 

Experiment S. Two cubes of albumen of ^ of an inch 
(1.27 mm.) were placed on two leaves. After 40 hrs. every atom of 
one was dissolved, and most of the liquefied matter was absorbed, 
the fluid which remained being in this, as in all other cases, very 
acid and viscid. The other cube was acted on at a rather slower 
rate. 

Experiment Jf. 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 secre- 
tion. Two cubes, each of about ^ of an inch (.035 mm.) were 
placed on the same leaf, and two similar cubes on another leaf. 
These were examined after 21 hrs. 30 m., and all four were found 
rounded. After 40 hrs, the two cubes on the one leaf were com- 
pletely liquefied, the fluid being perfectly transparent; on the 
other leaf some opaque white streaks could still be seen in the 
midst of the fluid. After 72 hrs. these streaks disappeared, but 
there was still a little viscid fluid left on the disc; whereas it was 
almost all absorbed on the first leaf. Both leaves were now begin- 
ning to re-expand. 

The best and almost sole test of the presence of some 
ferment analogous to pepsin in the secretion appeared to be 
to neutralise the acid of the secretion with an alkali, and to 
observe whether the process of digestion ceased ; and then to 
add a little acid and observe whether the process recom- 
menced. This was done, and, as we shall see, with success, 
but it was necessary first to try two control experiments; 
namely, whether the addition of minute drops of water of 
the same size as those of the dissolved alkalies to be used 
would stop the process of digestion; and, secondly, whether 
minute drops of weak hydrochloric acid, of the same strength 
and size as those to be used, would injure the leaves. The 
two following exi)eriments 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 sidded two or three times daily. These did not in the least de- 



Chap. VI.] DIGESTION. 79 

lay the process; for, after 48 hrs., the cubes were completely dis- 
solved on all three leaves. On the third day the leaves began to 
re-expand, and on the fourth day all the fluid was absorbed. 

Experiment 7. Small cubes of albumen were put on two leaves, 
and minute drops of hydrochloric acid, of the strength of one part 
to 437 of water, were added two or three times. This did not in 
the least delay, but seemed rather to hasten, the process of diges- 
tion; 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 al- 
most superfluous to state that cubes of albumen of the same 
size as those above used, left for seven days in a little hydro- 
chloric acid of the above strength, retained all their angles as per- 
fect as ever. 

Experiment 8. Cubes of albumen (of ^ of an inch, or 1.27 mm.) 
were placed on five leaves, and minute drops of a solution of one 
part of carbonate of soda to 437 of water were added at intervals 
to three of them, and drops of carbonate of potash of the same 
strength to the other two. The drops were given on the head of 
a rather large pin, and I ascertained that each was equal to about 
I'i,^ of a minim (.0059 c.c), so that each contained only -^^ of a 
grain (.0135 mg.) of the alkali. This was not sufficient, for after 
46 hrs. all five cubes were dissolved. 

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

Experiment 10. Stronger solutions of carbonate of soda and of 
potash were next used, viz. one part to 109 of water; and as the 
same-sized drops were given as before, each drop contained Tj^ifff of 
a 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. Each leaf received, as soon as the secretion became 
slightly acid (and this occurred four times within 24 hrs.), drops 
either of the soda or potash, and the acid was thus effectually neu- 
tralised. The experiment now succeeded perfectly, for after 22 hrs. 
the angles of the cubes were as sharp as they were at first, and we 
know from experiment 5 that such small cubes would have been 
completely rounded within this time by the secretion in its natural 
state. Some of the fluid was now removed with blotting-paper from 
the discs of the leaves and minute drops of hydrochloric acid of the 
strength of one part to 200 of water was added. Acid of this 
greater strength was used as the solutions of the alkalies were 



80 DROSERA ROTDNDIFOLIA. [Chap. VI. 

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

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

From these experiments we clearly see that the secretioH 
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 neu- 
tralised by weak hydrochloric acid. Even if I had tried no 
other experiments than these, they would have almost suf- 
ficed to prove that the glands of Drosera secrete some fer- 
ment analogous to pepsin, which in presence of an acid gives 
to the secretion its power of dissolving albuminous com- 
pounds. 

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 dis- 
solved, the angles remaining as sharp as ever. This fact 
probably indicates that the ferment is not secreted until the 

* Sachs remarks (' Tniit4 de agents, allow all their colouring 

Bot.' 1874, p. 774), thnt cells matter to escape Into the sur- 

wbich are klllf>d by freezing, by rounding water, 
too great beat, or by chemical 



Chap. VL] 



DIGESTION. 



81 



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

On three other occasions eight leaves were strongly ex- 
cited with albumen moistened with saliva; they were then 
cut off, and allowed to soak for several hours or for a whole 



[With regard to Drosera 
Messrs. Rees and Will C Bot. 
Zeitung,* 1875, p. 715) state that 
a glycerine extract of Drosera 
leaves In a state of unexcited 
secretion, and fairly free from 
Insects, had no digestive action. 
But that the same extract, arti- 
ficially acidulated, digested fibrin 
thoroughly well. 

The authors believe that the 
natural acid of the glands was 
possibly destroyed in the process 
of preparing the extract. No 
conclusion can therefore be 
drawn from their results as to 
the acidity of unexcited leaves. 
It is probable, however, Judging 
from Von Gorup's work on Ne- 
penthes, that Drosera does not 
secrete the requisite amount 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 wanting In the secretion of 
unexcited leaves is the acid, not 
the ferment. The experiments 
of Von Gorup and Will on Ne- 
penthes, as given In the ' Bot. 
Zeltung,' 1876, p. 473, do not con- 
firm Hooker's results on Nepen- 
thes. The authors state that the 
secretion collected from pitchers 
which are free from Insects is 
neutral, while the fluid of pitch- 
ers which contain the remains 
of insects is distinctly acid. The 
neutral secretion of the unex- 
cited pitchers has no digestive 
power until It Is acidulated, 
when It rapldiv dissolves fibrin. 

It seems, therefore, that the 
analogr with animal digestion 
polnteo out at p. 106 does not 



altogether hold good. For Schlff 
states that in the gastric juice 
produced by mechanical irrita- 
tion, the element absent is the 
ferment, not the acid. 

On the other hand an Inter- 
esting point of resemblance of a 
dififerent kind has been made out 
by Vines in his paper on the di- 

festlve ferment of Nepenthes 
Journal of the Linn. Soc' vol. 
XV. p. 427; also, ' Journal of 
Anatomy and Physiology,' series 
II. vol. xl. p. 124). 

The work was undertaken In- 
dependently of Von Gorup and 
carried out by a different meth- 
od, namely, the preparation of a 
glycerine extract. Vines having 
found that the extract was far 
less active than the natural se- 
cretion used by Von Gorup, was 
led to an Interesting explanation 
of this fact by Ebsteln and Grtttz- 
ner's work on animal digestion. 
These writers show that the 
glycerine extract gains in diges- 
tive activity If It is prepared 
from mucous membrane previ- 
ously treated with acid. Vines 
accordingly treated Nepenthes 
with one per cent, acetic add 
for 24 hrs. previously to the 
preparation of the extract, and 
thus obtained glycerine of much 
greater peptic activity. This 
fact would lead us to believe 
that the act of secretion In Ne- 
penthes Is preceded by the pro- 
duction of a mother substance, 
or pepsinogen, from which the 
peptic ferment Is formed by ac- 
tion of add Just as the pancre- 
atic ferment may, according to 
Heldenhaln, be produce<l by the 
action of addon zymogen. F. D.] 



82 DROSERA ROTUNDIPOLIA. [Chap. VL 

day in a few (frops of glycerine. Some of this extract was 
added to a little hydrochloric acid of various strengths (gen- 
erally one to 400 of water), and minute cubes of albumen 
were placed in the mixture.' In two of these trials the cubes 
were not in the least acted on ; but in the third the experiment 
was successful. For in a vessel containing two cubes, both 
were reduced in size in 3 hrs. ; and after 24 hrs. mere streaks 
of undissolved albumen were left. In a second vessel, con- 
taining two minute ragged bits of albumen, both were like- 
wise reduced in size in 3 hrs. and after 24 hrs. completely 
disappeared. I then added a little weak hydrochloric 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 demon- 
strated, as he believes, in opposition to the view held by some 
physiologists, that a certain small amount of pepsin is de- 
stroyed 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 fer- 
ment during the process of digestion, or its absorption after 
the albumen had been converted into a peptone, will also ac- 
count for only one out of the three latter sets of exi)eriment8 
having been successful. 

Digestion of Roast Meat. Cubes of about -^ of an inch 
(1.27 mm.) of moderately roasted meat were placed on five 
leaves which became in 12 hrs. closely inflected. After 48 
hrs. I gently opened one leaf, and the meat now consisted of 
a minute central sphere, partially digested and surrounded 
by a thick envelope of transparent viscid fluid. The whole, 
without being much disturbed, was removed and placed 
under the microscope. In the central part the transverse 
striee on the muscular fibres were quite distinct; and it was 
interesting to observe how gradually they disappeared, when 
the same fibre was traced into the surrounding fluid. They 
disappeared by the striae being replaced by transverse lines 

* As a control pxpprlment t>lt8 expectod. was not In the least 

of albumen were nlnceel In the affected nfter two clays, 
same (rljrcprlne with hydrochloric 'Lecons phys. de la Disres- 

add of the same strenKth; and tlon,' 18U7, torn. il. pp. 114-120. 
the albumen, as might have been 



Chap. VI.] DIGESTION. 88 

formed of excessively minute dark points, which towards 
the exterior could be seen only under a very high power ; and 
ultimately these points were lost. When I made these obser- 
vations, I had not read Schiffs 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 pro- 
cess of digestion by gastric juice and by the secretion of 
Drosera. 

"On a dit que le sue gastrique faisait perdre h la fibre mus- 
culaire ses stries transversales. Ainsi 6nonc6e, cette proposition 
pourrait donner lieu a une Equivoque, car ce qui se perd, ce n'est 
que Vaspect extCrieur de la striature et non les 6l6ments anato- 
miques qui la composent. On salt que les stries qui donnent un 
aspect si caract6ristique a la fibre musculaire, sont le r^sultat de la 
juxtaposition et du parallfilisme des corpuscules 6l6mentaires, places, 
a distances ^gales, dans I'intfirieur des fibrilles contigues. Or, d6s 
que le tissu connectif qui relie entre elles les fibrilles ClSmentaires 
vient a se gonfler et a se dissoudre, et que les fibrilles elles-m6mes se 
dissocient, ce parallelisme est d6truit et avec lui I'aspect, le ph6no- 
m^ne optique des stries. Si, apr&s la d^sagrfigation des fibres, on ex- 
amine au microscope les fibrilles 6l6mentaires, on distingue encore 
tr&s-nettement a leur intfrieur les corpuscules, et on continue a les 
voir, de plus en plus pales, jusqu'au moment oil les fibrilles elles- 
mt^mes se liquf'fient et disparaissent dans le sue gastrique. Ce qui 
constitue la striature, a proprement parler, n'est done pas dCtruit, 
arant la liquefaction de la fibre charnue elle-mf^me." 

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 yel- 
lowish, highly translucent matter. Schiff, in speaking of 
the digestion of meat by gastric juice, alludes to such par- 
allelograms, and says: 

" Le gonflement par lequel commence la digestion de la viande, 
r^ulte de I'action du sue gastrique acide sur le tissu connectif qui 
se dissout d'abord, et qui, par sa liquefaction, desagrCge les fibrilles. 
Celles-ci se dissolvent ensuite en grande partie, mais, avant de 
passer a I'etat liquide, elles tendent a se briser en petits fragments 
transversaux. Les ' sarcoufi elements ' de Bowman, qui ne sont 
autre chose que les produits de cette division transversale des 
fibrilles elementaires, peuvent etre prepares et Isolds a i'aide du 

* ' LecoDS pbys. de la Digestion,' 1867, torn. 11. p. 145. 

7 



84 DROSBRA ROTIJNDIPOLIA. [Ciiap. VI. 

sue gastrique, pourvu qu'on n'attend pas jiuqu'fi. 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 striaj. On the 
other two leaves there were minute spheres of only par- 
tially 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 hy- 
drochloric 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 exi)eri- 
ments, 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 \o 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. Bur- 
don Sanderson. 

FjTperiment 1. Two particlefl, bnrely Vn of an inch (1.27 mm.) 
nquarp, 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 cause<l a few of the 
short adjoining tentacles to be inflected, the more distant ones not 
bein); affected. After 24 hrs. both were almost, and after 72 hrs. 
completely, dissolved. 



Chap. VI.] DIGESTION. 85 

Experiment 2. The same experiment with the same result, only 
one of the two bits of fibrin exciting the short surrounding tenta- 
cles. 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 S. Bits of fibrin of about the same size as before 
were placed on the discs of two leaves; these caused very little in- 
flection in 23 hrs., but after 48 hrs. both were well clasped by the 
surrounding short tentacles, and after an additional 24 hrs. were 
completely dissolved. On the disc of one of these leaves much clear 
acid fluid was left. 

Experiment J/. Similar bits of fibrin were placed on the discs of 
two leaves; as after 2 hrs. the glands seemed rather dry, they were 
freely moistened with saliva; this soon caused strong inflection 
both of the tentacles and blades, with copious secretion from the 
glands. In 18 hrs. the fibrin was completely liquefied, but un- 
digested atoms still floated in the liquid; these, however, disap- 
peared in under two additional days. 

From these experiments it is clear that the secretion 
completely dissolves pure fibrin. The rate of dissolution is 
rather slow; but 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 por- 
tions placed on the discs of three leaves caused their tentacles 
and blades to be strongly inflected within 8 hrs. ; but no fur- 
ther observations were made. It is probably due to the pres- 
ence of this substance that raw meat is too powerful a stimu- 
lant, often injuring or even killing the leaves. 

Areolar Tissue. Small portions of this tissue from a 
sheep were placed on the discs of three leaves; these became 
moderately well inflected in 24 hrs., but began to re-expand 
after 48 hrs., and were fully re-expanded in 72 hrs., always 
reckoning from the time when the bits were first given. This 
substance, therefore, like fibrin, excites the leaves for only a 
short time. The residue left on the leaves, after they were 
fully re-expanded, was examined under a high power and 
found much altered, but, owing to the presence of a quantity 

* [These results cnnnot be by the late Dr. Moore waa far 
considered' trustworthy; it ap- from pure. F. D.J 
pears that the syntooia prepared 



86 DROSERA ROTUNDIPOLIA. [Chap. VL 

of elastic tissue, which is never acted on, could hardly be 
said to be in a liquetied 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 ^e 
four other leaves (to one of which a rather large bit had been 
given) nothing was left except some transparent viscid 
fluid. I may add that some of this tissue included points of 
black pigment, and that these were not at all affected. As a 
control exi)eriment, 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 se- 
cretion ; but that it does not greatly excite the leaves. 

Cartilage. Three cubes (^ of an inch or 1.27 mm.) of 
white, translucent, extremely tough cartilage were cut from 
the end of a slightly roasted leg-bone of a sheep. These 
were placed on three leaves, born 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 con- 
verted into minute spheres, surrounded by transparent, very 
acid fluid. Two of these spheres were completely softened 
to their centres; whilst the third contained a very small 
irregularly shaped core of solid cartilage. Their surfaces 
were seen under the microscope to be curiously marked by 
prominent ridges, showing that the cartilage had been un- 
equally corroded by the secretion. I need hardly say that 
the cubes of the same cartilage, kept in water for the same 
length of time, were not in the least affected. 

During a more favourable season, moderately sized bits of 
the skinned ear of a cat, which includes cartilage, areolar 
and elastic tissue, were placed on throe leaves. Some of the 



Chap. VI.] DIGESTION. 87 

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 rem- 
nants of half digested areolar tissue. 

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

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 



88 DROSERA ROTUNDIPOLIA. [Chap. VI. 

mutton-chop bone on a third leaf. These leaves soon be- 
came strongly inflected, and remained so for an unusual 
length of time; namely, one leaf for ten and the other two 
for nine days. The bits of bone were surrounded all the 
time by acid secretion. When examined under a weak 
power, they were found quite softened, so that they were 
readily penetrated by a blunt needle, torn into fibres, or 
compressed. Dr. Klein was so kind as to makQ 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 distinguish- 
able. 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 col- 
oured litmus paper of a bright ro<l; but this may have been 
due to the presence of the acid superphosphate of lime. 
When the leaves re-expanded, the angles and projections of 
the fibrous basis were as sharp as ever. I therefore concluded 
falsely, as we shall presently see, that the secretion cannot 
touch the fibrous basis of bone. The more probable explana- 
tion is that the acid was all consumed in decomposing the 
phosphate of lime which still remained; so that none was 
left in a free state to act in conjunction with the ferment on 
the fibrous basis. 

Enamel and Dentine. As the secretion decalcified or- 
dinary bone, I determined to try whether it would act on 



Chap. VI.] DIGESTION. 89 

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

Experiment 1. May Ist, fragment placed on leaf; 3rd, tentacles 
but little inflected, so a little saliva was added; 6th, as the tenta- 
cles were not strongly inflected, the fragment was transferred to 
another lerff, which acted at first slowly, but by the 9th closely 
embraced it. On the 11th this second leaf began to re-expand; the 
fragment was manifestly softened, and Dr. Klein reports, " a great 
deal of enamel and the greater part of the dentine decalcified." 

Experiment 2. May 1st, fragment placed on leaf; 2nd, tentacles 
fairly well inflected, with much secretion on the disc, and remained 
BO until the 7th, when the leaf re-expanded. The fragment was 
now transferred to a fresh leaf, which next day (8th) was inflected 
in the strongest manner, and thus remained until the 11th,. when it 
re-expanded. Dr. Klein reports, " a great deal of enamel and the 
greater part of the dentine decalcified." 

Experiment 3. May 1st, fragment moistened with saliva and 
placed on a leaf, which remained well inflected until 5th, when it 
re-expanded. The enamel was not at all, and the dentine only 
slightly, softened. The fragment was now transferred to a fresh 
leaf, which next morning (6th) was strongly inflected, and re- 
mained so until the 11th. The enamel and dentine both now some- 
what softened ; and Dr. Klein reports, " less than half the enamel, 
but the greater part of the dentine decalcified." 

Experiment .'/. May 1st, a minute and thin bit of dentine, 
moistened with saliva, was placed on a leaf , v.'hich was soon inflected, 
and re-expanded on the 5th. The dentine had become as flexible as 
thin paper. It was then transferred to a fresh leaf, which next 
morning (6th) was strongly inflected, and reopened on the 10th. 
The decalcified dentine was now so tender that it was torn into 
shreds, merely by the force of the re-expanding tentacles. 

From these experiments it appears that enamel is at- 
tacked 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 bo inferred from the leaves, to 
which the fragments were transferred, becoming in all four 
cases strongly inflected in the course of a single day; where- 
as the first set of leaves acted much less quickly and ener- 
getically. The angles or projections of the fibrous basis of 



90 DROSERA ROTUNDIFOLIA. [Chap VI. 

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. 

Fibroiis Basis of Bone. I at first concluded, as already 
stated, that the secretion could not digest this substance. I 
therefore asked Dr. Burdon Sanderson to try bone, enamel, 
and dentine, in artificial gastric juice, and he found that 
they were after a considerable time completely dissolved. 
Dr. Klein examined some of the small lamellae, into which 
part of the skull of a cat became broken up after about a 
week's immersion in the fluid, and he found that towards 
the edges the " matrix appeared rarefied, thus producing the 
appearance as if the canaliculi of the bone-corpuscles had 
become larger. Otherwise the corpuscles and their canali- 
culi were very distinct." So that with bone subjected to 
artificial gastric juice complete decalcification precedes the 
dissolution of the fibrous basis. Dr. Burdon Sanderson sug- 
gested to me that the failure of Drosera to digest the fibrous 
basis of bone, enamel, and dentine, might be due to the acid 
being consumed in the decomposition of the earthy salts, so 
that there was none left for the work of digestion. Accord- 
ingly, 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 frag- 
ments being first damped with saliva to aid prompt inflec- 
tion. All seven leaves became inflected, but only very mod- 
erately, in the course of a day. They quickly began to re- 
expand; five of them on the second day, and the other two 
on the third day. On all seven leaves the fibrous tis- 
sue 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 



CoAP. VI.] DIGESTION. 91 

absorbed little of the liquefied tissue, or had been little af- 
fected by it. 

Phosphate of Lime. As we have seen that the tentacles 
of the first set of leaves remained clasped for nine or ten days 
over minute fragments of bone, and the tentacles of the 
second set for six or seven days over the same fragments, I 
was led to suppose that it was the phosphate of lime, and 
not any included animal matter, which caused such long- 
continued inflection. It is at least certain from what has 
just been shown that this cannot have been due to the pres- 
ence 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 in- 
flected altogether for eleven days. In order to test my belief 
in the latency 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 be- 
ing much injured or killed. I repeated the experiment, but 
moistened the phosphate with saliva to insure prompt in- 
flection; 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 un- 
dissolved. 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 secretion 
acting on the phosphate, but that it was all absorbed and in- 
jured the leaves; the large drops which hung from their 
edges being an abnormal and dropsical secretion. Anyhow, it 



92 DROSERA ROT UNDI FOLIA. [CnAP. VI. 

is manifest that the phosphate of lime is a most powerful 
stimulant. Even small doses are more or less poisonous, 
probably on the same principle that raw meat and other nu- 
tritious substances, given in excess, kill the leaves. Hence 
the conclusion, that the long-continued inflection of the 
tentacles over fragments of bone, enamel and dentine, is 
caused by the presence of phosphate of lime, and not of any 
included animal matter, is no doubt correct. 

Oelatine. I used pure gelatine in thin sheets given me 
by Prof. Hoffmann. For comparison, squares of the same 
size as those placed on the leaves were left close by on wet 
moss. These soon swelled, but retained their angles for 
three days; after five days they formed rounded, softened 
masses, but even on the eighth day a trace of gelatine could 
still be detected. Other squares were immersed in water, 
and these, though much swollen, retained their angles for six 
days. Squares of ^ of an inch (2.54 mm,), just moistened 
with water, were placed on two leaves ; and after two or three 
days nothing was left on them but some acid viscid fluid, 
which in this and other cases never showed any tendency to 
regelatinise ; so that the secretion must act on the gelatine 
differently to what water does, and apparently in the same 
manner as gastric juice." Four squares of the same size as 
before were then soaked for three days in water, and placed 
on large leaves; the gelatine was liquefied and rendered acid 
in two days, but did not excite much inflection. The leaves 
began to re-expand after four or five days, much viscid fluid 
being left on their discs, as if but little had been absorbed. 
One of these leaves as soon as it re-expanded, caught a small 
fly, and after 24 hrs. was closely inflected, showing how much 
more potent than gelatine is the animal matter absorbed 
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. 

" Dr. Lander Brmiton, ' Ilnnd- phys. <1p la Digestion,' 1867, torn, 
book for the I'hj-H. I^Jwmtory,' U. p. 249. 
1878. pp.477. 487: Srblfr, 'Levona 



Chap. VI.] DIGESTION. 93 

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 
to 218 of water were made; and half -minim drops (.0296 c.c.) 
were placed on the discs of eight leaves, so that each received 
ths of a grain, or .135 mg. The four with the isinglass 
were much more strongly inflected than the other four. I 
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 gela- 
tine 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 gelati- 
nous state. Some was slowly dried, and a small cliip 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 laminse 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 proto- 
plasmic 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 rlr of a grain (.135 mg.) 
of the jelly; and, of course, much less of dry chondrin. 

* Dr. Lander Brunton Rives In view of the Indirect pnrt which 
the ' Me<llcnl Record,' January, gelatine plays In nutrition. 
1873, p. 36, an accoant of Ylot'a 



94 DROSERA ROTUNDIFOLIA. [Chap. VI. 

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 lique- 
fied chondrin was by this time absorbed. Hence a solution 
of chondrin seems to act far more quickly and energetically 
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 albuminous 
compound, this would have produced the above effects. 
Nevertheless, I have thought these facts worth giving, as 
there is so much doubt on the nutritious value of gelatine; 
and Dr. Lauder Brunton does not know of any experiments 
with respect to animals on the relative value of gelatine and 
chondrin. 

Milk. We have seen in the last chapter that milk acts 
most powerfully on the leaves; but whether this is due to 
the contained casein or albumen, I know not, liather 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. Min- 
ute drops of milk, placed on leaves, were coagulated in about 
ten minutes. SchiF 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; where- 
as 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 1'. 8 hrs. Those leaves re-expanded after two days, 
and thJ viscid fluid left on their discs was then carefully 
scrap. 4 off and examined. It seemed at first sight as if all 
the C4^ein had not been dissolved, for a little matter was 
left vifcich appeared of a whitish colour by reflected light. 
But this matter, when examined under a high power, and 
when compared with a minute drop of skimmed milk coagru- 
latcd i>y acetic acid, was seen to consist exclusively of oil- 
** ' Lecons,' &c. torn. li. p. 15L 



Chap. VI.] DIGESTION. 95 

globules, more or less aggregated together, with no trace of 
casein. As I was not familiar with the microscopical ap- 
pearance 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." 

Chemically Prepared Casein. This substance, which is 
insoluble in water, is supposed by many chemists to differ 
from the casein of fresh milk. I procured some, consisting 
of hard globules, from Messrs. Hopkins and Williams, and 
tried many experiments with it. Small particles and the 
pjowder, both in a dry state and moistened with water, caused 
the leaves on which they were placed to be inflected very slow- 
ly, generally not until two days had elapsed. Other parti- 
cles, 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 re- 
mained inflected for from seven to nine days ; and during the 
whole of this time the secretion was strongly acid. Even on 
the eleventh day some secretion left on the discs of a fully 
re-expanded leaf was strongly acid. The acid seems to be 
secreted quickly, for in one case the secretion from the discal 
glands, on which a little powdered casein had been strewed, 
coloured litmus paper, before any of the exterior tentacles 
were inflected. 

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

'* [Professor Sanderson has nncleln. which Is entirely ln<'l- 
Cftlled my attention to the fact gentlMe by frastric Juice. F. I>.1 
that the casein of cow's milk ' Dr. I-nnder Prnnton. ' Hand- 
contains h sniull pruporllou of book for I'hys. Lab.,' p. 520. 



00' DROSERA ROTUNDIPOLIA. [Chap. VI. 

the former would excite the leaves, and yet not decrease the 
casein to a j>erceptible degree. Schiff asserts " and this is 
an important fact for us that " la caseine purifiee des 
chimistes est un corps presque completement inattaquablc 
par le sue gastrique." So that here we have another point 
of accordance between the secretion of Drosera and gastric 
juice, as both act so differently on the fresh casein of milk, 
and on that prepared by chemists." 

A few trials were made with cheese; cubes of i^ of an 
inch (1.27 mm.) were placed on four leaves, and these after 
one or two days became well inflected, their glands pouring 
forth much acid secretion. After five days they began to re- 
expand, but one died, and some of the glands on the other 
leaves were injured. Judging by the eye, the softened and 
subsided masses of cheese, left on the discs, were very little 
or not at all reduced in bulk. We may, however, infer from 
the time during which the tentacles remained inflected, 
from the changed colour of some of the glands, and from 
the injury done to others, that matter had been absorbed 
from the cheese. 

Legumin. I did not procure this substance in a separate 
state; but there can hardly be a doubt that it would bo 
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 in- 
flected 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 re- 
markably 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 

' ' Tjornnn,' *c. fom. II. p. 153. doiiht rtne to the notion of the 
" [I'rofewRor HnmlorHon tells alcohol 8e(l In mnkltiT " chnil- 
me that tbla difference la no cally preiiared cuiielu." K. D.] 



Chap. VI.] DIGESTION. 97 

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 na- 
ture cannot fail to profit to a certain extent by this power of 
digesting pollen, as innumerable grains from the carices, 
grasses, rumices, fir-trees, and other wind-fertilised plants, 
which commonly grow in the same neighbourhood, will be 
inevitably caught by the viscid secretion surrounding the 
many glands. 

Gluten. This substance is composed of two albuminoids, 
one soluble, the other insoluble in alcohol." Some was pre- 
pared by merely washing wheaten flour in water. A pro- 
visional trial was made with rather large pieces placed on two 
leaves; these, after 21 hrs., were closely inflected, and re- 
mained 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 afterwai-ds be- 
came 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 trans- 
parent than other bits left for the same time in water. After 
seven days both leaves re-expanded, but the gluten seemed 
hardly at all reduced in bulk. The glands which had been 
in contact with it were extremely black. Still smaller bits 
of half putrid gluten were now tried on two leaves ; these 
were well inflected in 24 hrs., and thoroughly in four days, 
the glands in contact being much blackened. After five days 
one leaf began to re-expand, and after eight days both were 
fully re-expanded, some gluten being still left on their discs. 
Four little chips of dried gluten, just dipped in water, were 
next tried, and these acted rather differently from fresh 
gluten. One leaf was almost fully re-expanded in three 
days, and the other three leaves in four days. The chips 
were greatly softened, almost liquefied, but not nearly all 
dissolved. The glands which had been in contact with them, 
instead of being much blackened, . were of a very pale col- 
our, and many of them were evidently killed. 

' Mr. A. W. Bennett fonnd nal of Hort. Soc. of London,' 

the nndlgcHted conta of the vol. Iv. 1874. p. LVi. 
grnlns In the Inteslinnl canal of ' Watts' ' Diet, of Chemistry,' 

pollen-eating Dlptera; see 'Jour- vol. li. 1872, p. 873. 



98 DROSERA ROTUNDIPOUA. [Cuap. VI. 

In not one of these ten cases was the whole of the gluten 
dissolved, even when very small bits were given. I there- 
fore asked Dr. Burdon Sanderson to try gluten in artificial 
digestive fluid of pepsin with hydrochloric acid; and this 
dissolved the whole. The gluten, however, was acted on 
much more slowly than fibrin ; the proportion dissolved with- 
in four hours being as 40.8 of gluten to 100 of fibrin. Gluten 
was also tried in two other digestive fluids, in which hydro- 
chloric acid was replaced by propionic and butyric acids, and 
it was completely dissolved by these fluids at the ordinary 
temperature of a room. Here, then, at last, we have a case in 
which it appears that there exists an essential difference in 
digestive pyower between the secretion of Drosera and gastric 
juice ; the difference being confined to the ferment, for, as we 
have just seen, pepsin in combination with acids of the acetic 
series acts perfectly on gluten. I believe that the explana- 
tion lies simply in the fact that gluten is too powerful a 
stimulant (like raw meat, or phosphate of lime, or even too 
large a piece of albumen), and that it injures or kills the 
glands before they have had time to pour forth a sufficient 
supply of the proper secretion. That some matter is ab- 
sorbed 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 transpar- 
ent, and swollen. Small portions were washed and placed 
on five leaves, which were soon closely inflected, but to my 
surprise re-expanded completely in 48 hrs. A mere vestige 
of gluten was left on two of the leaves, and not a vestige 
on the other three. The viscid and acid secretion, which re- 
mained 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 power- 
ful or so enduring a stimulant as fresh gluten, and docs not 
much injure the glands; and we further learn that it can be 
digested quickly and completely by the secretion. 



Chap. VI.] DIGESTION. 99 

Olobulin or Crystallin. This substance was kindly prepared for 
me from the lens of the eye by Dr. Moore, and consisted of hard, 
colourless, transparent fragments. It is said *" that globulin ought 
to " swell up in water and dissolve, for the most part forming a 
gummy liquid; " but this did not occur with the above fragments, 
though kept in water for four days. Particles, some moistened 
with water, others with weak hydrochloric acid, others soaked in 
water for one or two daj's, were placed on nineteen leaves. Most 
of these leaves, especially those with the long soaked particles, be- 
came 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 d^ree than those kept for the 
same time in water, retained all their angles as sharp as ever. As 
globulin is an albuminous substance, I was astonished at this re- 
sult ; " and my object being to compare the action of the secre- 
tion with that of gastric juice, I asked Dr. Burdon Sanderson to try 
some of the globulin used by me. He reports that " it was sub- 
jected 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 M'eight of unboiled fibrin in 1 hr. ; whereas, during the hour, 
only 0.141 of the above globulin was dissolved. In both cases an 
excess of the substance to be digested was subjected to the liquid.*^ 
We thus see that within the same time less than one-ninth by 
weight of globulin than of fibrin was dissolved: and bearing in 
mind that pepsin with acids of the acetic series has only about 
one-third of the digestive power of pepsin with hydrochloric acid, it 
is not surprising that the fragments of globulin were not corroded 
or rounded by the secretion of Drosera, though some soluble matter 
was certainly extracted from them and absorbed by the glands. 

Ilamatin. Some dark red granules, prepared from bullock's 
blood, were given me ; these were found by Dr. Sanderson to be in- 
soluble in water, acids, and alcohol, so that they were prohalily 
haematin, together with other bodies derived from the blood. Par- 
ticles 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 
lia>matin were blackened, and some of the tentacles seemed injured. 
After five days two leaves died, and the third was dying; the 
fourth was beginning to re-expand, but many of its glands were 
blackened and injured. It is therefore clear that matter had been 

* Watts' ' Diet, of Cheuilstry,' by Schmidt's method, and of this 

vol. II. p. 874. 0.80.5 was dissolved within the 

" [The result was no doubt same time, namely, one hour: so 

due (as I learn from Professor that It was far more soluble than 

Sanderson) to the fact that the that which I used, thon^rh less 

globulin had boen trontod with soluble than flbrin, of which, as 

alcohol In the course of Its prep- we have soen. 1.31 was dissolved, 

aratlon. F. D.] I wl.sh that I had tried on 

" I may add that Dr. Snuder- Drosera globulin prepareil by 

on prepared some fresh Rlobulln this method. 

8 



100 DROSERA ROTUNDIFOLIA. [Chap. VI. 

absorbed which was either actually poisonous or of too stimulating 
a nature. The particlea were much more softened than those kept 
for the same time in water, but, judging by tlie eye, very little 
reduc(Hl in bulk. Dr. Sanderson tried tliis substance with artifu-ial 
digestive fluid, in the manner described under globulin, and found 
that whilst 1.31 of fibrin, only 0.456 of the hsenuitin was dissolved 
in an hour; but the di.ssolution by the secretion of even a less 
amount would account for its action on Drosera. The residue left 
by the artificial digestive fluid at first yielded nothing more to it 
during several succeeding days. 

Substances which are not Digested by the Secretion. 

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

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 more 
need be said about some of the above enumerated substances, 
excepting that they were repeatedly tried on the leaves of 
Drosera, and were not in the least affected by the secretion. 
About the others it will be advisable to give my experi- 
ments. 

Fihroelnstic 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 tbreadsj were left without the least 



Chap. VI.J DIGESTION. 101 

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 nitro- 
gen, I expected that it would have excited the leaves greatly and 
been digested by the secretion, but in this I was mistaken. From 
what is stated in chemical works, it appears extremely doubtful 
whether mucin can be prepared as a pure principle. That which I 
used (prepared by Dr. Moore) was dry and hard. Particles mois- 
tened with water were placed on four leaves, but after two days 
there was only a trace of inflection in the immediately adjoining 
tentacles. These leaves were then tried with bits of meat, and all 
four soon became strongly inflected. Some of the dried mucin was 
then soaked in water for two days, and little cubes of the proper 
size were placed on three leaves. After four days the tentacles 
round the margins of the discs were a little inflected, and the secre- 
tion 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 artiflcial gastric juice found 
that in 1 hr. some was dissolved, but only in the proportion of 23 
to 100 of fibrin during the same tijne. 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 beinqr corroded during digestion. 

Pepsin. My experiments are hardly worth giving, as it is 
scarcely possible to prepare pepsin free from other albuminoids; 
but I was curious to ascertain, as far as that was possible, whether 
the ferment of the secretion of Drosera would act on the ferment of 
the gastric juice of animals. I first used the common pepsin sold 
for medicinal purposes, and afterwards some which was much purer, 
prepared for me by Dr. Moore. Five leaves to which a considerable 
quantity of the former was given remained inflected for five days; 
four of them then died, apparently from too great stimulation. I 
then tried Dr. Moore's pepsin, making it into a paste with water, 
and placing such small particles on the discs of five leaves that all 
would have been quickly dissolved had it been meat or albumen. 
The leaves were soon inflected; two of them began to re-expand 
after only 20 hrs., and the other three were almost completely re- 
expanded' after 44 hrs. Some of the glands which had been in con- 
tact with the particles of pepsin, or with the aci<l secretion sur- 
rounding them, were singularly pale, whereas others were singular- 

** 8re, tor Instance. Schlff. " * Lecons phys. de la Dlge- 

' Phvs. de la Digestion,' 1867, tlon,' 1867, torn. 11. p. 304. 
torn. II. p. 38. 



102 DROSERA ROTUxNDIFOLIA. [Chap. VI. 

ly dark-coloured. Some of the Becrction was scraped off and ex- 
amined under a high power; and it abounded with granules undis- 
tinguishable from those of pepsin left in water for the same length 
of time. VVc may therefore infer, as highly probable (remembering 
what small quantities were given), that the ferment of Drosera 
does not act on or digest pepsin, but absorbs from it some albu- 
minous impurity which induces inflection, and which in large 
quantity is highly injurious. Dr. Lauder Brunton at my request 
endeavoured to ascertain whether pepsin with hydrochloric acid 
would digest pepsin, and as far as he could judge, it had no such 
power. Gastric juice, therefore, apparently agrees in this respect 
with the secretion of Drosera. 

Urea. It seemed to me an interesting inquiry whether this re- 
fuse 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. Hnlf-minim drops of a solu- 
tion 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 ^^^ of a grain, or .0074 mg.; but the leaves were hardly at 
all afTected. They were then tested with bits of meat, and soon be- 
came closely inflected. I repeated the same experiment on four 
leaves with some fresh urea prepared by Dr. Moore: after two days 
there was no inflection; I then gave them another dose, but still 
there was no inflection. These leaves were afterwards tested with 
similarly sized drops of an infusion of raw meat, and in 6 hrs. 
there was considerable inflection, which became excessive in 24 hrs. 
But the urea apparently was not quite pure, for when four leaves 
were immersed in 2 dr. (7.1 c.c.) of the 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. That the urea, which 
was not perfectly white, should have contained a sufficient quantity 
of albuminous matter, or of some salt of ammonia, to have caused 
the alx)ve effect, is far from surprising, for, as we shall see in the 
next chapter, astonishingly small doses of ammonia are highly 
efficient. We may therefore conclude that the urea itself is not 
exciting or nutritious to Drosera; nor is it modified by the secre- 
tion, 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. liartholomew's Hospital it appears that 
urea is not acted on by artificial gastric juice, that is by pepsin 
with hydrochloric acid. 

Chitine. The chitinous coats of insects naturally captured by 
the leaves do not appear in the least corroded. Small square pieces 
of the delicate wing and of the elytron of a Staphylinus were placed 
on some leaves, and after these had re-expanded, the pieces were 
carefully examine<l. Their angles were as sharp as ever, and they 
did not differ in appearance from the other wing and elytron of the 
same insect which had Inrn left in water. The elytron, however. 



Chap. VI.] DIGESTION. 103 

had evidently j-ielded some nutritious matter, for the leaf remained 
clasped over it for four days; whereas the leaves with bits of the 
true wing re-expanded on the second day. Any one who will ex- 
amine the excrement of insect-eating animals will see how powerless 
their gastric-juice is on chitine. 

Cellulose. I did not obtain this substance in a separate state, 
but tried angular bits of dry wood, cork, sphagnum moss, linen, 
and cotton thread. None of these bodies were in the least attacked 
by tle secretion, and they caused only that moderate amount of 
inflection which is common to all inorganic objects. Gun-cotton, 
which consists of cellulose, with the hydrogen replaced by nitrogen, 
was tried with the same result. We have seen that a decoction of 
cabbage leaves excites the most powerful inflection. I therefore 
placed two little square bits of the blade of a cabbage leaf, and four 
little cubes cut from the midrib, on six leaves of Drosera. These 
became well inflected in 12 hrs., and remained so for between two 
and four days; the bits of cabbage being bathed all the time by 
acid secretion. This shows that some exciting matter, to which I 
shall presently refer, had been absorbed; but the angles of the 
squares and cubes remained as sharp as ever, proving that the 
framework of cellulose had not been attacked. Small square 
bits of spinach leaves were tried with the same result; the glands 
pouring forth a moderate supply of acid secretion, and the tenta- 
cles remaining inflected for three days. We have also seen that 
the delicate coats of pollen grains are not dissolved by the se- 
cretion. 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 in- 
flection, 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 chloro- 
phyll contained matter which excited the leaves to a motlerate de- 
gree; 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 usetl, as well as 
some freshly prepared, with artificial digestive liquid, and found 
that it was not digested. Dr. Lauder Bmnton likewise trie<l some 
prepared by the process given in the British Pharmacopoeia, and 
exposed it for five days at the temperature of 37 Cent, to digestive 
liquid, but it was not diminishe<l in bulk, though the fluid accjuiretl 
a slightly brown colour. It was also tried with the glycerine ex- 
tract of pancreas with a negative result. Nor docs chloropliyli 
seem affected by the intestinal secretions of various animals, judg- 
ing by the colour of their excrement. 

It must not be supposed from these facts that the grains of 
chlorophyll, as they exist in living plants, cannot be attacked by 
the secretion; for these grains consist of protoplasm merely col- 
oured by chlorophyll. My son Francis placed a thin slice of 



104 DROSERA ROTUNDIPOLIA. [Chap. VL 

spinach leaf, moistened with saliva, on a leaf of Drosera, and other 
slices on damp cotton-wool, all exposed to the same teni|K'ruture. 
After 10 hrs. the slice on the leaf of the Drosera was bathed in 
much secretion from the inflected tentacles, and was now examined 
under the microscope. No perfect grains of chlorophyll could be 
distinguished; some were shrunken, of a yellowish-green colour, 
and collected in the middle of the cells; others were disintegrated 
and formed a yellowish mass, likewise in the middle of the cells. 
On the other hand, in the slices surrounded by damp cotton-wool, 
the grains of chlorophyll were green and as perfect as ever. My 
son also placed some slices in artificial gastric juice, and these were 
acted on in nearly the same manner as by the secretion. We have 
seen that bits of fresh cabbage and spinach leaves cause the ten- 
tacles to be inflected and the glands to pour forth much acid secre- 
tion; and there can be little doubt that it is the protoplasm form- 
ing the grains of chlorophyll, as well as that lining tne walls of 
the cells, which excites the leaves. 

f^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 dig&sted. Nor 
does olive oil dropped on the discs of leaves cause any inflection; 
but when they are immersed in olive oil they become strongly in- 
flected; 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 afl'ected. 
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 haz- 
ard, may here be given, though they bear only indirectly on our 
present subject of digestion. 

Seven cabbage seeds of the previous year were placed on the 
same number of leaves. Some of these leaves were moderately, but 
the greater number only slightly inflected, and most of them re- 
expanded on the third day. One, however, remained clasped till 
the fourth, and another till the fifth day. These leaves therefore 
were excited somewhat more by the seeds than by inorganic ob- 
jects of the same size. After they re-cxpandetl, the seeds were 
placed under favourable conditions on damp sand ; other seeds of 
the same lot being trie<I at the same time in the same manner, and 
found to germinate well. Of the seven seeds which had been ex- 
posc<l to the secretion, only three germinated ; and one of the three 
seedlings soon perished, the tip of its radicle being from the first 



Chap. VI.] DIGESTION. 105 

decayed, and the edges of its cotyledons of a dark brown colour; 
so that altogetlier live out of the seven seeds ultimately perished. 

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

Cress seeds {Lepidium sativum) of the previous year were 
placed on four leaves; two of these 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 tena- 
cious mucus; and to ascertain whether it was the absorption of 
this substance by the glands which caused so much inflection, two 
seeds were put into water, and as much of the mucus as possible 
scraped off. They were then placed on leaves, which became very 
strongly inflected in the course of 3 hrs., and were still closely in- 
flected on the third day; so that it evidently was not the mucus 
which excited so much inflection; on the contrary, this served to 
a certain extent as a protection to the seeds. Two of the six seeds 
germinated whilst still lying on the leaves, but the seedlings, when 
transferred to damp sand, soon died; of the other four se^s, only 
one germinated. 

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

It follows from these few facts that different kinds of seeds 
excite the leaves in very different degrees; whether this is solely 
due to the nature of their coats is not clear. In the case of the 
cress seeds, the partial removal of the layer of mucus hastened the 
inflection of the tentacles. Whenever the leaves remain inflected 
during several days over seeds, it is clear that they absorb some 
matter from them. That the secretion penetrates their coats is also 
evident from the large proportion of cabbage, radish, and cress 
seeds which were killed, and from several of the seedlings being 
greatly injured. This injury to the seeds and seedlings may, how- 
ever, be due solely to the acid of the secretion, and not to any pro- 
cess of digestion ; for Mr. Traherne Moggridge has shown that very 
weak acids of the acetic series arc highly injurious to seeds. It 
never occurred to me to obser>'e 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 



106 DROSERA EOTUNDIPOLIA. [Chap. VL 

case of Pinguicula. If so, Drosera will profit to a slight degree 
by absorbing mutter from such seeds. 

Summary and Concluding Remarks on the Digestive Power 
of Drosera. 

When the glands on the disc are excited either by the 
absorption of nitrogenous matter or by mechanical irritation, 
their secretion increases in quantity and becomes acid. 
They likewise transmit some influence to the glands of the 
exterior tentacles, causing them to secrete more copiously; 
and their secretion likewise becomes acid. With animals, 
according to SchiflF,** 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 es- 
tablished), that although the glands of Drosera are continu- 
ally 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 absorbing certain mat- 
ter, 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 Dionsea and Nepenthes. In like manner, the 
glands of the stomach of animals secrete pepsin, as Schiff 
asserts, only after they have absorbed certain soluble sub- 
stances, which he designates as peptogenes. There is, there- 
fore, a remarkable parallelism between the glands of Drosera 
and those of the stomach in the secretion of their proper acid 
and ferment." 

** ' Phys. de la Digestion/ any special action of the so-called 

18C7, torn. II. pp. 188. 245. peptoRPHs. He wrItPH. " I find 

[It will be seen from the that ac-ld and popain make tholr 

facts given In a footnote at p. appenrnnce nImoHt IniiiKMllatclr 

81, that even If we accept after the Introduction of a stiirrh 

Scblff's peptoeen theory, the evi- solution Into the Ktoniiwh. The 

dence on the botanical side In unnjc thln>r nnturnllv followH on 

against the existence of the the Introduction of SchltT's jjcpto- 

ai>ove suggeHted pnrnllelltni. gens, ho that no ln<-onsli|i>riib1e 

Moreover, RchlffB peptogcn the- (|unntlty of acid and pepsin Is In 

ory Is not generally accciifcd by readiness for a subseiiuent act of 

physiologists. Professor Sander- dicesllon, whirh Is. In conse- 

son has called my attention to qiience, rendered far more ener- 

Ewnld's views on this i|uestlon getlc." 

ns given In his ' Kllnik der V'er- lialilenhaiu. In Hermann's 

dannngs krankhelten. (I) Die ITandbuch der I'hvslolojjle.' vol. 

Lcbre von der VenlauunK.' 18sn. v. part I. p. 1.5.% also criticises 

p. OL Ewald does not believe In Schiff's theory, and shows that 



Cbap. VI.] DIGESTION. 107 

The secretion, as we have seen, completely dissolves 
albumen, muscle, fibrin, areolar tissue, cartilage, the fibrous 
basis of bone, gelatine, chondrin, casein in the state in which 
it exists in milk, and gluten which has been subjected to 
weak hydrochloric gcid, Syntonin and legumin excite the 
leaves so powerfully and quickly that there can hardly be a 
doubt that both would be dissolved by the secretion. The 
secretion failed to digest fresh gluten, apparently from its 
injuring the glands, though some was absorbed. Raw meat, 
unless in very small bits, and large pieces of albumen, &c., 
likewise injure the leaves, which seem to suffer, like animals, 
from a surfeit. I know not whether the analogy is a real 
one, but it is worth notice that a decoction of cabbage leaves 
is far more exciting and probably nutritious to Drosera than 
an infusion made with tepid water; and boiled cabbages are 
far more nutritious, at least to man, than the 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 en- 
amel, 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 complete- 
ly decalcified, the fibrous basis was attacked and liquefied 
with the greatest ease. The twelve substances above enu- 
merated, 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 striaj 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 
hcematin employed by me. The secretion also dissolved 
something out of chemically prepared casein which is said to 

the observntlonn on which this a fault in the method employed, 
theory is foiindwl nre to some F. D,] 
extent untrustworthy, owiug to 



108 DROSEBA EOTUNDIPOLIA. [Chap. VL 

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 albumi- 
nous matter, which Drosera would detect and absorb. Again, 
fibro-cartilage, though not properly dissolved, is acted on in 
the same manner, both by the secretion of Drosera and gas- 
tric juice. But this substance, as well as the so-called 
hsematin 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 likwise acts only in the pres- 
ence 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 ex- 
tracted 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 in- 
flection at very different rates, and in very different de- 
grees; and the tentacles remain inflected for very different 
periods of time. Quick inflection depends partly on the 
quantity of the substance given, so that many glands are 
simultaneously affected, partly on the facility with which it 
is penetrated, and liquefied by the secretion, and partly on 
its nature, but chiefly on the presence of exciting matter 
already in solution. Thus saliva, or a weak solution of 
raw meat, acts much more quickly than even a strong solu- 
tion of gelatine. So again leaves which have re-expanded, 
after absorbing drops of a solution of pure gelatine or isin- 
glass (the latter being the more powerful of the two), if 



Chap. VI.] DIGESTION. 109 

given bits of meat, are inflected much more energetically and 
quickly than they were before, notwithstanding that some 
rest is generally requisite between two acts of inflection. We 
probably see the influence of 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, which has been kept for some time, and gluten 
which has been subjected to weak hydrochloric acid, act 
more quickly than these substances in their fresh state. 

The length of time during which the tentacles remain 
inflected largely depends on the quantity of the substance 
given, partly on the facility with which it is penetrated or 
acted on by the secretion, and partly on its essential nature. 
The tentacles always remain inflected much longer over 
large bits or lai^e drops than over small bits or drops. Tex- 
ture probably plays a part in determining the extraordinary 
length of time during which the tentacles remain inflected 
over the hard grains of chemically prepared casein. But the 
tentacles remain inflected for an equally long time over 
finely powdered, precipitated phosphate of lime ; phosphorus 
in this latter case evidently being the attraction, and animal 
matter in the case of casein. The leaves remain long in- 
flected over insects, but it is doubtful how far this is due 
to the protection afforded by their chitinous integuments; 
for animal matter is soon extracted from insects (probably 
by exosmose from their bodies into the dense surrounding 
secretion), as shown by the prompt inflection of the leaves. 
We see the influence of the nature of different substances in 
bits of meat, albumen, and fresh gluten acting very different- 
ly from equal-sized bits of gelatine, areolar tissue, and the 
fibrous basis of bone. The former cause not only far more 
prompt and energetic, but more prolonged, inflection than 
do the latter. Hence we are, I think, justified in believing 
that gelatine, areolar tissue, and the fibrous basis of bone, 
would be far less nutritious to Drosera than such substances 
as insects, meat, albumen, <fec. This is an interesting con- 
clusion, as it is known that gelatine affords but little nutri- 
ment to animals; and so, probably would areolar tissue and 
the fibrous basis of bone. The chondrin which I used acted 
more powerfully than gelatine, but then I do not know that 



110 DROSERA ROTUNDIFOLIA. [Cbap. VL 

it was pure. It is a more remarkable fact that fibrin, which 
belongs to the great class of Protcids," 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 would survive if 
fed on fibrin alone, but Dr. Sanderson has no doubt longer 
than on gelatine, and it would be hardly rash to predict, 
judging from the effects of Drosera, that albumen would be 
found more nutritious than fibrin. Globulin likewise be^ 
longs to the Proteids, forming another sub-group, and this 
substance, though containing some matter which excited 
Drosera rather strongly, was hardly attacked by the secre- 
tion, 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 surrounding plants, 
Drosera is, to a certain extent, a vegetable-feeder. 

Finally the experiments recorded in this chapter show 
us that there is a remarkable accordance in the power of 
digestion between the gastric juice of animals with its pep- 
sin and hydrochloric acid and the secretion of Drosera with 
its ferment and acid belonging to the acetic series. We can 
therefore hardly doubt that the ferment in both cases is 
closely similar, if not identically the same. That a plant 
and an animal should pour forth the same, or nearly the 
same, complex secretion, adapted for the same purpose of di- 
gestion, 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 Droseraccm. 

"flfw tho rlnBBlflcntlon adoptpd ' Diet, of Clipmlstry,' Supple* 
by Dr. Mlihaol Foster In Watts' ment 1872, p. 000. 



Chap.VIL] salts op AMMONIA. HI 



CHAPTER VII. 

THE EFFECTS OF SALTS OF AMMONIA. 

Manner of performing the experiments Action of distilled water in com- 
parison with the solutions Carbonate of ammonia, absorbed by the 
roots The vapour absorbed by the glands Drops on the disc Minute 
drops applied to si-paratc glands Leaves immersed in weak solutions 
Minuteness of the doses which induce aggregation of the protoplasm 
Nitrate of ammonia, analogous experiments with Phosphate of 
ammonia, analogous experiments with Other salts of ammoniac-Sum- 
mary 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 be compelled 
to enter into full details. Doubly distilled water was always 
used; and for the more delicate experiments, water which 
had been prepared with the utmost possible care was given 
me by Professor Frankland. The graduated measures were 
tested, and found as accurate as such measures can be. The 
salts were carefully weighed, and in all the more delicate 
experiments, by Borda's double method. But extreme ac- 
curacy would have been superfluous, as the leaves differ great- 
ly in irritability, according to age, condition, and constitu- 
tion. Even the tentacles on the same leaf differ in irrita- 
bility to a marked decree. My experiments were tried in 
the following several ways. 

Firstly. Drops which were ascertained by repeated trials to be 
on an average about half a minim, or the -i>^p of a fluid ounce 
(.0296 CO.), were placed by the same pointecl instrument on the 
discs of the leaves, and the inflection of the exterior rows of tenta- 
cles observed at successive intervals of time. It was first ascer- 
tained, from between thirty and forty trials, that distille<l water 
dropped in this manner produces no efTect, 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 efTect lead to the same result that water is ineflTicient. 

Secondly. The hesid of a small pin, fixed into a handle, waa 
dipped into the solution under trial. The small drop which ad- 



112 DROSERA ROTUNDIFOLIA. [Chap. VIL 

hered to it, and which was much too small to fall off, was cautious- 
ly placed, by the aid of a lens, in contact with the secretion sur- 
ToundfnL; the glands of one, two, three, or four of the exterior tentar 
clcs of the same leaf. Great care was taken that the glands them-^ 
selves should not be touched. I had supposed that the drops were 
of nearly the same size; but on trial this proved a great mistake. 
I first measured some water, and 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 i^ 
of a minim. Some water in a small vessel was weighed (and this 
is a more accurate method ) , and 300 drops removed as before ; and 
on again weighing the water, a drop was found to equal on an aver- 
age only the ^ of a minim. I repeated the operation, but en- 
deavoured 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 j-J^j of a minim. I repeated the operation in 
exactly the same manner, and now the drops averaged g^ 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 of the solution must have been absorbed by all; 
for drops of pure water, applied in the same manner, never produced 
any effect. I was able to hold the drop in steady contact with 
the secretion only for ten to fifteen seconds; and this was not time 
enough for the diffusion of all the salt in solution, as was evi- 
dent, from three or four tentacles treated successively with the 
same drop, often becoming inflected. All the matter in solution 
was even then probably not exhausted. 

Thirdly. Leaves were cut off and immersed in a measured 
quantity of the solution under trial; the same number of leaves 
being immersed at the same time, in the same quantity of the 
distilled water which had been used in making the solution. The 
leaves in the two lots were compared at short intervals of time, 
up to 24 hrs., and sometimes to 48 hrs. They were immersed by 
being laid as gently as possible in numbered watchglasses, and 
thirty minims (1.776 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 dis- 
coIoure<l 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 ten- 
tacles. 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 tenta- 
cles; but in this latter case the exterior tentacles would not have 
become inflected until some time had elapsed, instead of within 



Chap. VII.] EFFECTS OP WATER. 113 

half an hour, or even within a few minutes, as usually occurred. 
AH the glands on the same leaf are of nearly the same size, as may 
best be seen by cutting off a narrow transverse strip, and laying it 
on its side; hence their absorbing surfaces are nearly equal. The 
long-headed glands on the extreme margin must be excepted, as 
they are mucli 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 pa- 
pillae, which absorb carbonate of ammonia, an infusion of raw meat, 
metallic salts, and probably many other substances, but the ab- 
sorption of matter by these papillae never induces inflection. We 
must remember that the movement of each separate tentacle de- 
pends on its gland being excited, except when a motor impulse is 
transmitted from the glands of the disc, and then the movement, aa 
just stated, does not take place until some little time has elapsed. 
I have made these remarks because they show us that when a leaf 
is immersed in a solution, and the tentacles are inflected, we can 
judge with some accuracy how much of the salt each gland has ab- 
sorbed. For instance, if a leaf bearing 212 glands, be immersed in 
a measured quantity of a solution, containing -j^f of a grain of a 
salt, and all the exterior tentacles, except twelve, are inflected, we 
may feel sure that each of the 200 glands can on an average have 
absorbed at most n/jny of a grain of the salt. I say at most, for the 
papilhe will have absorbed some small amount, and so will per- 
haps the glands of the twelve excluded tentacles which did not be- 
come inflected. The application of this principle leads to remark- 
able conclusions with respect to the minuteness of the doses caus- 
ing 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 
interA'als of time. Thirty-two other leaves were separately ob- 
served in water, making altogether 173 experiments. Alany scores 
of leaves were also immersed in water at other times, but no exact 
record of the effects produced was kept; yet these cursory obser- 
vations support the conclusions arrived at in this chapter. A few 
of the long-headed tentacles, namely from one to about six, were 
commonly inflected within half an hour after immersion; as were 
occasionally a few, and rarely a considerable number of the ex- 
terior round-headed tentacles. After an immersion of from 5 to 
8 hrs. the short tentacles surrounding the outer parts of the disc 
generally become inflected, so that their glands form a small dark 
ring on the disc; the exterior tentacles not partaking of this move- 
ment. H^nce, excepting in a few cases hereafter to be specified, 



114 



DROSERA ROTUNDIFOLIA. 



[Chap. VII. 



we can judge whether a solution produces any effect only by ob- 
serving the exterior tentacles M'itfaiin the first 3 or 4 hrs. after im- 
mersion. 

Now for a summary of the state of the 173 leaves after an im- 
mersion of 3 or 4 hrs. in pure water. One leaf had almost all 
its tentacles inflected ; three leaves had most of them sub-inflected ; 
and thirteen had on an average 3G.5 tentacles inflected. Thus seven- 
teen leaves out of the 173 were acted on in a marked manner. 
Eighteen leaves had from- seven to nineteen tentacles inflected, the 
average being 9.3 tentacles for each leaf. Forty-four leaves had 
from one to six tentacles inflected, generally the long-headed ones. 
So that altogether of the 173 leaves carefully observed, seventy- 
nine were affected by the water in 
some degree, though commonly 
to a very slight degree; and nine- 
ty-four were not affected in the 
least degree. This amount of in- 
flection is utterly insignificant, as 
we shall hereafter see, compared 
with that caused by very weak 
solutions of several salts of am- 
monia. 

Plants which have lived for 
some time in a rather high tem- 
perature are far more sensitive to 
the action of water than those 
giown out of doors, or recently 
brought into a warm greenhouse. 
Thus in the above seventeen cases, 
in which the immersed leaves hod 
a considerable number of ten- 
tacles inflected, the plants had 
been kept during the winter in a 
very warm greenhouse; and they 
bore in the early spring remark- 
obly fine leaves, of a light red col- 
our. Had 1 then known that the 
sensitiveness of plants was thus 
increased, perhaps 1 should not 
have use<l the leaves for my experiments with the very weak solu- 
tions of phosphate of ammonia; but my experimenta are not thus 
vitiatecl, as I invariably used leaves from the same plants for simul- 
taneous immersion in water. It often hapiH-'ned that some leaves 
on the same plant, and some tentacles on the same leaf, were more 
sensitive than others; but why this should be so, I do not know. 
Besides the differences just indicated between the leaves im- 
mersed in water and in weak solutions of ammonia, the tentacles of 
the latter are in most cases much more closely inflected. The ap- 
pearance of a leaf after immersion in a few drops of a solution of 
one grain of phosphate of ammonia to 200 oz. of water (i. e. one 
part to 87,500) is here reproduced: such energetic inflection is never 




Fio. 9. 
(Drogera rotundifolia.) 
Leaf (enlarged) with all the ten- 
tacles cl()(H-Iy infltH-tcd, frum im- 
mersion in a solution of phos- 
phate of ammonia (one part to 
87,500 of water). 



Chap. VII J CARBONATE OP AMMONIA. 115 

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

With respect to the period of the re-expansion of the leaves, 
when left immersed either in water or in the weak solutions, noth- 
ing could be more variable. In both cases the exterior tentacles 
not rarely b^n 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 diflScult 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 M-ater and in the solutions will be described, the 
reader can judge for himself. 



C^BONATE OF AMMONIA. 

This salt, when absorbed by the roots, does not cause the 
tentacles to be inflected. A plant was so placed in a solution 
of one part of the carbonate to 146 of water that the young 
uninjured roots could be observed. The terminal cells, which 
were of a pink colour, instantly became colourless, and their 
limpid contents cloudy, like a mezzo-tinto engraving, so that 
some degree of aggregation was almost instantly caused; 
but no further change ensued, and the absorbent hairs were 
not visibly affected. The tentacles did not bend. Two 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 
9 



116 DROSERA ROTUNDIFOLIA. [Chap. VII. 

24 hrs. ; but not a single tentacle was inflected. In order 
to produce this efiFect, 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 to- 
gether with half a grain of the carbonate, the air being ren- 
dered 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, apparent- 
ly, not in the least affected. The plants were kept under the 
bell-glass for 24 hrs., but no further change ensued. One 
healthy leaf was hardly at all affected, though other leaves on 
the same plant were much affected. On some leaves all the 
tentacles on one side, but not those on the opposite side, 
were inflected. I doubt whether this extremely unequal ac- 
tion 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 
anal(^ous cases with air thoroughly permeated with the 
vapours of chloroform and ether. 

Minute particles of the carbonate were added to the secre- 
tion surrounding several glands. These instantly became 
black and secreted copiously; but, except in two instances, 
when extremely minute particles were given, there was 
no inflection. This result is analogous to that which 
follows from the inunersion 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 inflec- 
tion ensues, though the glands are blackened, and the 
protoplasm in the cells of the tentacles undergoes strong 
aggregatioo. 



Chap. VII.] CARBONATE OP 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 g^g of a grain 
or .0675 mg. Ten of these had their exterior tentacles well in- 
flected; the blades of some being also much curved inwards. In 
two cases several of the exterior tentacles were inflected in 35 m.; 
but the movement was generally slower. These ten leaves re- 
expanded in periotls 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 un- 
affected, 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 yg^ir of a 
grain (.0337 mg.), distributed between the glands of the disc, but 
this was too small an amount to produce any decided effect on the 
exterior tentacles, the glands of which had not themselves received 
any of the salt. 

Minute drops on the head of a small pin, of a solution of one 
part of the carbonate to 218 of water, were next tried in the man- 
ner above described. A drop of this kind equals on an average ^ 
of a minim, and therefore contains j-g^-g- of a grain (.0135 mg.) of 
the carbonate. I touched with it the viscid secretion round three 
glands, so that each gland received only uioo of a grain (.00445 
mg). Nevertheless, in two trials all the glands were plainly black- 
ened ; in one case all three tentacles were well inflected after an in- 
terval of 2 hrs. 40 m. ; and in another case two of the three tentacles 
were inflected. I then tried drops of a weaker solution of one part 
to 292 of water on twenty-four glands, always touching the viscid 
secretion round three glands with the same little drop. Each gland 
thus received only the -rgimr of a grain (.00337 mg.), yet some of 
them were a little darkened; but in no one instance were any of 
the tentacles inflected, though they were watched for 12 hrs. 
When a still weaker solution (viz. one part to 437 of water) was 
tried on six glands, no effect whatever was perceptible. We thus 
learn that the -j-riinr of a grain (.00445 mg.) of carbonate of am- 
monia, if absorbed by a gland, suffices to induce inflection in the 
basal part of the same tentacle; but as already stated, I was able 
to hold with a steady hand the minute drops in contact with the 
secretion only for a few seconds; and if more time had been allowed 
for diffusion and absorption, a much weaker solution would cer- 
tainly have acted. 

Some experiments were made by immersing cut-off leaves in 
solutions of different strengths. Thus four leaves were left for 
about 3 hrs. each in a drachm (3.549 c.c.) of a solution of one part 
of the carbonate to 5250 of water; two of these had almost every 
tentacle inflected, the third had about half the tentacles and the 
fourth about one-third inflected ; and all the glands were blackened. 
Another leaf was place<I in the same quantity of a solution of one 
part to 7000 of water, and in 1 hr. 10 m. every single tentacle was 



118 DROSERA ROTUNDIFOLIA. [Chap. VIL 

well inflectwl, and all the glands blackened. Six leaves were im- 
nioi-sed, each in thirty minims (1.774 c.e.) of a solution of one 
part to 4375 of water, and the glands were all blackened in 31 m. 
All six leaves exhibited some slight inflection, and one was strongly 
inflected. Four leaves were then immersed in thirty minims ot a 
solution of one part to 8750 of water, so that each leaf received the 
x^ of a grain (.2025 nig.). 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 so* 
lutions 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 be- 
come 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 ko, each blackened gland could have absorbed 
o^^Jy rriini ^ * grain (.00119 mg.) of the carbonate. 

A large number of trials had been previously made with solu- 
tions of one part of the nitrate and phosphate of ammonia to 
43750 of water (t. c. one grain to 100 ounces), and these were found 
highly efTicient. Fourteen leaves were therefore placed, each in 
thirty minims of a solution of one part of the carbonate to the 
above quantity of water; so that each leaf received y^ of a 
grain (.0405 mg.). The glands were not much darkened. Ten of 
the leaves were not affected, or only very slightly so. Four, how- 
ever, were strongly affected; the first having all the tentacles, ex- 
cept forty, inflected in 47 m. ; in 6 hrs. 30 m. all except eight; and 
after 4 hrs. the blade itself. The second leaf after 9 m. had all its 
tentacles except nine inflected; after 6 hrs. 30 m. these nine were 
sub-inflected ; the blade having become much inflected in 4 hrs. 
The third leaf after 1 hr. 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 im- 
mersed 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 
yg\nr ^^ ^ grain of the carbonate. Assuming that the leaf, which 
was a large one, and which had all its tentacles excepting eight 
inflected, bore 170 glands, each gland could have absorbed only 
rstVirff of * grain (.(X)024 mg.) ; yet this sufTiced to act on each of 
the 162 tentacles which were inflected. But as only four out of 
the above fourteen leaves were plainly affected, this is nearly the 
minimum dose which is efficient. 

Aggregation of the Protoplasm from the Action of Carbonate of 



Chap. VII.] CARBONATE OP AMMONIA. 110 

Ammonia. I have fully described in the third chapter the remark- 
able effects of moderately strong doses of this salt in causing the 
aggregation of the protoplasm within the cells of the glands and 
tentacles; and here my object is merely to show what small doses 
suffice. A leaf was immersed in twenty minims (1.183 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 aggre- 
gation 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 ^hs 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 in- 
flected, presented a widely different appearance; for the contents 
of the cells of every single tentacle on all four leaves were con- 
spicuously 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 ^^irr o^ ^ grain (.001009 mg.) of the salt: and this 
quantity sufficed to induce within a short time conspicuous aggre- 
gation in the cells beneath all the glands. 

A vigorous but rather small red leaf was placed in six minims 
of the same solution (viz. one part to 5250 of water), so that it 
received 5^u 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 forme<l 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 TTAnff of a grain, or .00048 mg. 

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



120 DROSERA ROTUNDIFOLIA. [Coap. VIL 

and four leaves were immersed in it ; but I will give only one case. 
A leaf was placed in ten minims of this solution; after 1 hr. 37 m. 
the glands became somewhat darker, and the cells beneath all 
of them now contained many spheres of aggregated protoplasm. 
This leaf received y^ of a grain, and bore IGti glands. Each gland 
could, therefore, have received only n ^' ^gg of a grain (.000507 mg.) 
of the carbonate. 

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

Summary of the Results with Carbonate of Ammonia. 
The roots absorb the solution, as shown by their changed col- 
our, and by the aggregation of the contents of their cells. 
The vapour is absorbed by the glands; these are blackened, 
and the tentacles are inflected. The glands of the disc, when 
excited by a half minim drop (.0296 c.c), containing fiv of 
a grain (.0675 mg.), transmit a motor impulse to the exterior 
tentacles, causing them to bend inwards. A minute drop, 
containing -rriinr of a grain (.00445 mg.), if held for a few 
seconds in contact with a gland, soon causes the tentacle 
bearing it to be inflected. If a leaf is left immersed for a 
few hours in a solution, and a gland absorbs the Trt'nnr of a 
grain (.00048 mg.), its colour becomes darker, though not 
actually black; and the contents of the cells beneath the 
gland are plainly aggregated. Lastly, under the same cir- 
cumstances, the absorption by a gland of the wr^rez of a 
grain (.00024 mg.) suflBces to excite the tentacle bearing this 
gland into movement. 

NITRATE OF AMHONTA. 

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 ex- 



Chap. VII.] NITRATE OF AMMONIA. 121 

perimented with half-minims (.0296 c.c.) on the discs of fifty- two 
leaves, but will give only a few cases. A solution of one part to 
109 of water was too strong, causing little inflection, and after 24 
hrs. killing, or nearly killing, four out of six leaves which were 
thus tried; each of which received the yio of a grain (or .27 mg.). 
A solution of one part to 218 of water acted most energetically, 
causing not only the tentacles of all the leaves, but the blades of 
some to be strongly inflected. Fourteen leaves were tried with 
drops of a solution of one part to 875 of water, so that the disc 
of each received the tjVo of a grain (.0337 mg.). Of these leaves, 
seven were very strongly acted on, the edges being generally in- 
flected; 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 experiment on several leaves. 
Two of the leaves, which were well inflected, re-expanded after 
61 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 2 J oz.) were placed on the discs of nine leaves, so that each 
received the j-^j of a grain (.027 mg.). Three of them had their 
tentacles strongly inflected and their blades curled inwards; five 
were slightly and somewhat doubtfully affected, having from three 
to eight of their exterior tentacles inflected; one leaf was not at 
all affected, yet was afterwards acted on by saliva. In six of these 
cases, a trace of action was perceptible in 7 hrs., but the full effect 
was not produced until from 24 hrs. 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 jVnr of a grain (.0225 mg.), instead of, as in the 
last experiment, jj^ of a grain. The blade of one was plainly in- 
flected, as were six of the exterior tentacles; the blade of a second 
was slightly, and two of the exterior tentacles well inflected, all 
the other tentacles being curled in at right angles to the disc ; three 
other leaves had from five to eight tentacles inflected; five others 
only two or three, and occasionally, though very rarely, drops of 
pure water cause this much action ; the four remaining leaves were 
in no way affected, yet three of them, when subsequently tried 
with urine, became greatly inflected. In most of these cases a 
slight effect was perceptible in from 6 hrs. to 7 hrs., but the full 
effect was not produced until from 24 hrs. to 30 hrs. had elapsed. 
It is obvious that we have reached very nearly the minimum 
amount, which, distributed between the glands of the disc, acts on 
the exterior tentacles; these having themselves not received any 
of the solution. 

In the next place, the viscid secretion round three of the ex- 
terior glands was touched with the same little drop (j^j of a 
minim) of a solution of one part to 437 of water; and after an in* 



122 DROSERA ROTUNDIFOLIA. [Chap. VII. 

tcrval of 2 hrs. 50 m. all three tentacles were well inflected. Each 
of these glands could have received only the jrijnf ^^ * grain, or 
.00225 mg. A little drop of the same size and strength was also 
applied to four other glands, and in 1 hr. two became inflected, 
whilst the other two never moved. We here see, as in the case of 
the half-minims placed on the discs, that the nitrate of ammonia 
is more potent in causing inflection than the 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 elfect 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 
BO 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 oc- 
curred, 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 suflTiced 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 in- 
flected. Next morning, after 23 hrs. 40 m., all the leaves were in 
the same state, excepting that the old leaf had a few more ten- 
tacles inflected. Five leaves which had been placed at the same 
time in water were observed at the same intervals of time; after 
2 hrs. 10 m. two of them had four, one had seven, one had ten, of 
the long-headed marginal tentacles, and the fifth had four round- 
headed tentacles, inflected. After 8 hrs. there was no change in 
these leaves, and after 24 hrs. all the marginal tentacles had re- 
expanded; but in one leaf, a dozen, and in a second leaf, half a 
dozen, submarginal tentacles had become inflected. As the glands 
of the five leaves in the solution were simultaneously darkened, no 
doubt they had all absorbed a nearly equal amount of the salt: 
and as -y^ of a grain was given to the five leaves together, each 
got j^f-g 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 102, it would be safe to assume 
that each bore on an average at least 160. If so, each of the dark- 
ened glands could have received only rsT/^^nr of * grain of the 
nitrate; and this caused the inflection of a great majority of the 
tentacles. 

This plan of immersing several leaves in the same vessel is a 
bad one, as it is impossible to feel sure that the more vigorous 
leaves do not rob the weaker ones of their share of the salt. The 
glands, moreover, must often touch one another or the sides of the 



Chap. Vn.] NITRATE OP AMMONIA. 123 

vessel, and movement may have been thus excited; but the cor- 
responding leaves in water, which were little inflected, though 
rather more so than commonly occurs, were exposed in an almost 
equal degree to these same sources of error. I will, therefore, give 
only one other experiment made in this manner, though many 
were tried and all confirmed the foregoing and following results. 
Four leaves were placed in forty minims of a solution of one part 
to 10,500 of water; and assuming that they absorbed equally, each 
leaf received -j-j^y^ of a grain (.0562 mg.). After 1 hr. 20 m. many 
of the tentacles on all four leaves were somewhat inflected. After 
5 hrs. 30 m. two leaves had all their tentacles inflected; a third 
leaf all except the extreme marginals, which seemed old and torpid ; 
and the fourth a large number. After 21 hrs. every single tentacle, 
on all four leaves, was closely inflected. Of the four leaves placed 
at the same time in water, one had, after 5 hrs. 45 m., five mar- 
ginal tentacles inflected; a second, ten; a third, nine marginals 
and submarginals ; and the fourth, twelve, chiefly submarginals, 
inflected. After 21 hrs. all these marginal tentacles re-expanded, 
but a few of the submarginals on two of the leaves remained slight- 
ly curved inwards. The contrast was wonderfully great between 
these four leaves in water and those in the solution, the latter 
having every one of their tentacles closely inflected. Making the 
moderate assumption that each of these leaves bore 160 tentacles, 
each gland could have absorbed only i^^^ia of a grain (.000351 
mg.). This experiment was repeated on three leaves with the same 
relative amount of the solution; and after 6 hrs. 15 m. all the ten- 
tacles except nine, on all three leaves taken together, were closely 
inflected. In this case the tentacles on each leaf were counted, and 
gave an average of 162 per leaf. 

The following experiments were tried during the summer of * 
1873, by placing the leaves, each in a separate watch-glass and 
pouring over it thirty minims (1.775 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 
y^ of a grain (.2025 mg.). Before 30 m. had elapsed, four of 
these leaves were immensely, and two of them moderately, in- 
flected. The glands were rendered of a dark red. The four cor- 
responding leaves in water were not at all aflfected 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 solu- 
tion of one part to 17,500 of water (1 gr. to 40 oz.), so that each 
received -g^ of a grain (.101 mg.) ; and in less than 45 m. three 
of them had all their tentacles, except from four to ten, inflected; 
the blade of one being inflected after 6 hrs., and the blade of a 



124 DROSERA ROTUNDIPOLU. [Chap. VII. 

second after 21 hre. The fourth leaf was not at all aflTected. The 
glands of none were durkene<I. Of the corresponding leaves in 
water, only one had any of its exterior tentacles, namely Ave, in- 
flected; after (3 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 T^xs of a grain (.0405 mg.). Of these, one was much in- 
llected in 8 m., and after 2 hrs. 7 m. had all the tentacles, except 
thirteen, inflected. The second leaf, after 10 m., had all except 
three inflected. The third and fourth were hardly at all afTectcd, 
scarcely more than the corresponding leaves in water. Of the lat- 
ter, only one was afl"ected, this having two tentacles inflected, with 
those on the outer parts of the disc forming a ring in the usual 
manner. In the leaf which had all its tentacles except three in- 
flected in 10 m., each gland (assuming that the leaf bore 160 ten- 
tacles) could have absorbed only Tj-i^gTrff of a grain, or .000258 mg. 

Four leaves were separately immersed as before in a solution 
of one part to 131,250 of water (1 gr. to 300 oz.), so that each re- 
ceived xAff 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 in- 
flected; 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, in- 
flected. With respect to the leaf of which all the tentacles, except 
sixteen, were inflected after 50 m., each gland (assuming that the 
leaf bore 100 tentacles) could have absorbed only ^v^'fon o^ * 
grain (.0000937 mg.), and this appears to be about the least quan- 
tity of the nitrate which suflBces to induce the inflection of a 
single tentacle. 

As negative results are important in confirming the foregoing 
positive ones, eight leaves were immersed as before, each in thirty 
minims of a solution of one part to 175,000 of water (1 gr. to 
400 oz.), so that each received only ^Jt^ of a grain (.0101 mg.). 
This minute quantity pro<luced a slight efToct on only four of 
the eight leaves. One had fifty-six tentacles inflected after 2 hrs. 
13 m. ; a sec-ond, twenty-six inflected, or sub-inflected, after 33 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 afl'ected. 
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 unaflTectecl. Hence, 
the y'i)5 of a grain given to a sensitive leaf during warm weather 



Chap. VII.] PHOSPHATE OF AMMONIA. 125 

perhaps produces a slight eflFect; but we must bear in mind that 
occasionally water causes as great an amount of inflection as oc- 
curred in this last experiment. 

.' . 

Summary of the Results with Nitrate of Ammonia. The 

glands of the disc, when excited by a half-minim, drop 
(.0296 C.C.), containing yjVjr of a grain of the nitrate (.027 
mg.), transmit a motor impulse to the exterior tentacles, 
causing them to bend inwards. A minute drop, containing 
trkvv 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 tWsTs of a 
grain (.0000937 mg.), this small amount is enough to excite 
each tentacle into movement, and it becomes closely in- 
flected. 

PHOSPHATE OP AMMONTA. 

This salt is more powerful than the nitrate, even in a 
greater degree than the nitrate is more powerful than the 
carbonate. This is shown by weaker solutions of the phos- 
phate acting when dropped on the discs, or applied to the 
glands of the exterior tentacles, or when leaves are im- 
mersed. The difference in the power of these three salts, as 
tried in three different ways, supports the results presently 
to be given, which are so surprising that their credibility re- 
quires every kind of support. In 1872 I experimented on 
twelve immersed leaves, giving each only ten minims of a 
solution : but this was a bad method, for so small a quantity 
hardly covered them. None of these Qxi)eriments will, there- 
fore, 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 



126 DROSERA ROTUNDIFOLIA. [Cdap. VII. 

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

Before giving my experiments, it may be well to premise that 
crystallised phosphate of ammonia, such as I used, contains 35.33 
per cent, of water of crystallisation; so that in all the following 
trials the eflBcient elements formed only 64.07 per cent, of the salt 
used. 

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

Half-minims of a solution of one part to 437 of water were 
placed on the discs of three leaves and acted most energetically, 
causing the tentacles of one to be inflected in 15 m., and the blades 
of all three to be much curved inwards in 2 hrs. 15 m. Similar 
drops of a solution of one part to 1312 of water (1 gr. to 3 oz.) 
were then placed on the discs of live leaves, so that each received 
the yg'fj of a grain (.0225 mg.). After 8 hrs. the tentacles of four 
of them were considerably inflected, and after 24 hra. the blades 
of three. After 48 hrs. all five were almost fully re-expanded. I 
may mention with respect to one of these leaves, that a drop of 
water had been left during the previous 24 hrs. on its disc, but 
produced no effect; and that this was hardly dry when the solu- 
tion 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 re- 
ceived ^Vrff o' * grain (.0109 nig.) ; after 8 hrs. three of them had 
many tentacles and their blades inflected; two others had only a 
few tentacles slightly inflected, and the sixth was not at all af- 
fected. After 24 hrs. most of the leaves had a fev^ more tentacles 
inflected, but one had begun to re-expand. We thus see that with 
the more sensitive leaves the y^f^f of a grain, absorbed by the 
central glands, is enough to make many of the exterior tentacles 
and the blades bend, whereas the y^,r of a grain of the carbonate 
similarly given produced no efl'ect; and j^ of a grain of the 
nitrate was only just sulFicient to produce a well-marked effect. 

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



Chap. VII.] PHOSPHATE OF AMMONIA. 127 

one part of the phosphate to 875 of water, was applied to the secre- 
tion on three glands, each of which thus received only rrhsv o^ * 
grain (.00112 rag.), and all three tentacles became inllected. Sim- 
ilar drops of a solution of one part to 1312 of water (1 gr. to 3 oz.) 
were now tried on three leaves; a drop being applied to four glands 
on the same leaf. On the first leaf three of the tentacles became 
slightly inflected in 6 m., and re-expanded after 8 hrs. 45 m. On 
the second, two tentacles became sub-inflected in 12 m. And on 
the third all four tentacles were decidedly inflected in 12 m. ; they 
remained so for 8 hrs. 30 m., but by the next morning were fully 
re-expanded. In this latter case each gland could have received 
only the -[- [^ o g (or .000563 mg.) of a grain. Lastly, similar drops 
of a solution of one pari to 1750 of water (1 gr. to 4 oz.) were 
tried on five leaves; a drop being applied to four glands on the 
same leaf. The tentacles on three of these leaves were not in the 
least alTected ; on the fourth leaf two became inflected ; whilst on the 
fifth, which happened to be a very sensitive one, all four tentacles 
were plainly inflected in 6 hrs. 15 m. ; but only one remained in- 
flected 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 rs^Vifff of 
a grain (or .000423); but this small quantity sufficed to cause in- 
flection. 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 TriTro 9^ 
a grain of the carbonate, and of ^-7-^ of ^ 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 ^^ of a grain, or 
.04058 mg. Of these leaves, eleven had nearly all or a great 
number of their tentacles inflected in 1 hr., and the twelfth leaf in 
3 hrs. One of the eleven had every single tentacle closely inflected 
in 50 m. Two leaves out of the sixteen were only moderately af- 
fected, yet more so than any of those simultaneously immersed in 
water; and the remaining two, which were pale leaves, were hard- 
ly at all alTected. Of the sixteen corresponding leaves in water, 
one had nine tentacles, another six, and two others two tentacles 
inflected, in the course of 5 hrs. So that the contrast in appear- 
ance 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 y,'o, of a grain (.0202 mg.). Fourteen of these were 
strongly inflected within 2 hrs., and some of them within 15 m.; 



128 DROSERA ROTUNDIPOLIA. [Chap. Vn. 

three out of 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 
unafTected. 

The next experiment was tried under very favourable circum- 
stances, for the day (July 8) was very warm, and I happened to 
have unusually fine leaves. Five were immersed as before in a 
solution of one part to 131,250 of water (1 gr. to 300 oz.), so that 
each received ts^ot o^ * gi'^iinj or .0135 mg. After an immersion of 
25 m. all five leaves were much inflected. After 1 hr, 25 m. 
one leaf had all but eight tentacles inflected; the second, all 
but three; the third, all but five; the fourth, all but twenty-three; 
the fifth, on the other hand, never had more than twenty-four in- 
flected. Of the corresponding five leaves in water, one had seven, 
a second two, a third ten, a fourth one, and a fifth none inflected. 
I^et 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 rnrfnnj of a grain, or .0000631 mg. The third leaf 
bore 23G glands, and subtracting the five which did not become 
inflected, each of the remaining 231 glands could have absorbed 
only itfllgoo of a grain (or .0000584 mg.), and this amount suf- 
ficed to cause the tentacles to bend. 

Twelve leaves were tried as before in a solution of one part to 
175,000 of water (1 gr. to 400 oz.), so that each leaf received -g^fni 
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 in- 
flected 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 be- 
ing young and pale. Of these nine leaves, four had their blades 
well inflected, and a fifth slightly so. The three remaining leaves 
were not affected. With respect to the twelve corresponding leaves 
in water, not one had its blade infleoto<l; after from I to 2 hrs. one 
had thirteen of its outer tentacles inflected; a second six, and four 
others either one or two inflected. After 8 hrs. the other 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 tor 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 plnnd on one 
leaf could have absorbed only riiiTrnr* "^^^ ^^ ^^^ other leaf only 
TTrWa of a grain of the phosphate. 



Chap. VII.] PHOSPHATE OP 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 impression that it was incredible that any weaker solu- 
tion could produce an effect. Each leaf received -gT^gjf of a grain, 
or .0081 mg. The first eight leaves which I tried both in the solu- 
tion and water were either young and pale or too old; and the 
weather was not hot. They were hardly at all affected; never- 
theless, 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 vary- 
ing from 75 to 81 (23.8 to 27.2 Cent.). In another trial with 
four pairs (included in the above twenty pairs), the temperature in 
my room was rather low, about 60 (15.5 Cent.); but the plants 
had been kept for several days in a very warm greenhouse and 
thus rendered extremely sensitive. Special precautions were taken 
for this set of experiments; a chemist weighed for me a grain in 
an excellent balance; and fresh water, given me by Professor 
Frankland, was carefully measured. The leaves were selected from 
a large number of plants in the following manner: the four finest 
were immersed in water, and the next four finest in the solution, 
and so on till the twenty pairs were complete. The wjater speci- 
mens were thus a little favoured, but they did not undergo more 
inflection than in the previous cases, comparatively with those in 
the solution. , 

Of the twenty leaves in the solution, eleven became inflected 
within 40 m.; eight of them plainly and three rather doubtfully; 
but the latter had at least twenty of their outer tentacles inflected. 
Owing to the weakness of the solution, inflection occurred, except 
in No. 1, much more slowly than in the previous trials. The con- 
dition 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 inflec'ted, or 
plainly sub-inflected. After 4 hrs. the tentacles began to re-ex- 
pand, and such prompt re-expansion is unusual; after 7 hrs. 30 m. 
they were almost fully re-expanded. 

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

(3) After 12 m. a considerable amount of inflection; after 4 hrs. 
all the tentacles inflected except those of the two outer rows, and 
the leaf remained in this state for some time; after 23 hrs. began 
to re-expand. 

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

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

(6) After 40 m. some inflection; after 2 hrs. 18 m. about 



130 DROSERA ROTUNDIFOLIA. [Chap. VII. 

twenty-eight outer tentacles inflected; after 5 hrs. 20 m. about a 
third of the tentacles inllected ; after 8 hrs. much re-expanded. 

(7) After 20 ui. some inflection; after 2 hrs. a considerable 
number of tentacles inllected; after 7 hrs. 45 m. b^^n to re- 
expand. 

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

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

(10) After 38 m. twenty-one tentacles inflected; after 3 hrs. 
12 m. forty-six tentacles inflected or sub-inflected; after 6 hrs. 
40 m. all but seventeen inflected, though none closely; after 24 hrs. 
every tentacle slightly cur\ed 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 be- 
haved in an anomalous manner. After 6 hrs. 40 m. only the short 
tentacles round the outer part of the disc were inflected, forming a 
ring as so often occurs in from 8 to 24 hrs. with leaves both in 
water and the weaker solutions. But after 9 hrs. 40 m. all the 
outer tentacles except twenty-five were inflected, as was the blade 
in a strongly marked manner. After 24 hrs. every tentacle except 
one was closely inflected, and the blade was completely doubled 
over. Thus the leaf remained for two days, when it began to re- 
expand. I may add that the three latter leaves (Nos. 9, 10, and 
11) were still somewhat inflected after three days. The tentacles 
in but few of these eleven leaves became 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 moilerately afl^eoted ; 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 onlv the rnrinon o' grain (.0000411 mg.) of the phos- 
phate. Leaf No. 9 had 213 tentacles, all of which, with the ex- 



Chap. VII.] PHOSPHATE OF AMMONIA. 131 

ception of four, were inflected after 24 hrs., but none of them 
closely; the blade was also inflected; each gland could have re- 
ceived only the is T iggo of a grain, 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 ;o oi u ffo of a grain, or .0000322 mg. 

With respect to the following experiments, I must premise that 
the leaves, both those placed in the solutions and in water, were 
taken from plants which had been kept in a very warm greenhouse 
during the winter. They were thus rendered extremely sensitive, 
as was shown by water exciting them much more than in the 
previous experiments. Before giving my observations, it may be 
well to remind the reader that, judging from thirty-one fine leaves, 
the average number of tentacles is 192, and that the outer or ex- 
terior 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 jgo ^ ooo of a grain (.0054 mg.) of the saltr 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 hrs. so 
many had re-expanded that only ten remained much inflected. 

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

(3) and (4) Not aflfected, except that, as usual, after 11 hrs. 
the short tentacles on the borders of the disc fcrme<l 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 y^riTnnr of a grain (.0000208 mg.) and 
of No. 2 only r^oims of a grain (.0000263 mg.) of the phosphate. 

Seven leaves were immersed, each in thirty minims of a solu- 
tion of one part to 437,500 of water (1 gr. to ioOO oz.). Each leaf 
thus received i-eoinr of a grain (.00405 mg.). The day was warm, 
and the leaves were very fine, so that all circumstances were 
favourable. 

(1) After 30 m. all the outer tentacles except five inflected, and 
10 



132 DROSERA ROTUNDIFOLIA. [Cuap. VII. 

most of them closely; after 1 hr. blade slightly inflected; after 
y hrs. 30 in. bcfj^an to re-e.\j)and. 

(2) After 33 m. ull the outer tentacles but twenty-five inflecteil, 
and blade slij^htly so; after 1 hr. 30 m. blade strongly inllected 
and remained so for 24 hrs.; but some of tlie tentacles hud tlicn 
re-expanded. 

(3) After 1 lir. all but twelve tentacles inflected; after 2 hrs. 
30 m. all but nine inflected; and of the inflected tentacles all ex- 
cepting 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 fifty-nine tentacles inflected; but 
after 5 hrs. all the tentacles closely inflected excepting two which 
were not allected, and eleven which were only sub-inflected; after 
7 hrs. blade considerably inflected; after 12 hrs. much re-ex- 
pansion. 

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

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

(7) After 4 hrs. 30 m. only thirty-five tentacles inflected or sub- 
inflecte<l, 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. par- 
tially re-e.\panded. 

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

7 hrs. 

(4) After 24 hrs. one inflected. 

(5), (G) and (7) Not at all alFccted, though obseri-ed for 24 
lirs., excepting the short tentacles on the borders of the disc, which 
as usual formed a ring. 

A comparison of the leaves in the solution, especially of the 
first five or even six on the list, with those in the water, after 1 hr. 
or after 4 hrs., and in a still more marked degree after 7 hrs. or 

8 hrs., could not leave the least doubt that the solution had pro- 
duced a great effect. This was shown, not only by the vastly 
greater number of inflected tentacles, but by the degree or close- 
ness of their inflection, and by that of their blades. Yet each 
gland on leaf No. 1 (wliich bore 255 glands, all of which, except- 
ing five, were inflected in 30 m.) could not have received more than 
one-four-millionth of a grain (.00001G2 mg.) of the salt. Again, 
each gland on leaf No. 3 (which bore 233 glands, all of which, ex- 
cept nine, were inflected in 2 hrs. 30 m.) could have received at 
most only the jrrhfim ^^ * grain, or .0000181 mg. 

Foxir leaves were immersed as before in a solution of one part 
to G.'>G.2.50 of water (1 gr. to 1500 oz.) ; but on this occasion I hap- 
pened to select leaves which were very little sensitive, as on other 
occasions I chanced to select unusually sensitive leaves. The 



CuAP. VII.] PHOSPHATE OP AMMONIA. I33 

leaves were not more affected after 12 hrs. than the four corre- 
sponding ones in water; but after 24 lirs. tliey were sliglitly more 
intiected. Such evidence, however, is not at all trustworthy. 

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

(1) This was a pale leaf; after 40 m. about thirty-eight tenta- 
cles inflected; after 3 hrs. 30 m. the blade and many of the outer 
tentacles inflected; after 10 hrs. 15 m. all the tentacles but seven- 
teen inflected, and the blade quite doubled up; after 24 hrs. all 
the tentacles but ten more or less inflected, ilost of them were 
closely inflected, but twenty-five were only sub-inflected. 

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

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

(4) After 1 hr. 40 m. about thirty infleete<l; 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 10, 8, 10, 8, 4, 9, 14, and tenta- 
cles inflected. Two of these leaves, however, were remarkable from 
having their blades slightly inflected after G hrs. 

With respect to the twelve corresponding leaves in water, (I) 
had, after 1 hr. 35 m., fifty tentacles inflected, but after 11 hrs. only 
twenty-two remained so, and these formed a group, with the -blade 
at this point slightly inflected. It appeared as if this leaf had been 
in some manner accidentally excited, for instance by a particle of 
animal matter wliich 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-ex- 
panded; (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; (0), 
(10), (11) and (12) none inflected, though observed for 24 hrs. 

Comparing the states of the twelve leaves in water with those 
in the solution, there could be no doubt that in the latter a larger 
number of tentacles were inflected, and these to a greater degree; 
but the evidence was by no means so clear as in the former ex- 
periments with stronger solutions. It deserves attention that the 
inflection of four of the leaves in the solution went on increasing 
during the first G hrs., and with some of them for a longer time; 



134 DROSERA ROTUNDIFOLIA. [Chap. VII. 

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 remarkable that the blades 
of three of the leaves in the solution were slightly inflected, and 
this is a most rare event with leaves in water, though it occurred 
to a slight extent in one (No. 1), which seemed to have been in 
some manner accidentally excited. All this shows that the solu- 
tion produced some effect, though less and at a much slower rate 
than in the previous cases. The small effect produced may, how- 
ever, be accounted for in large part by the majority of the leaves 
having been in a poor condition. 

Of the leaves in the solution, No. 1 bore 200 glands and re- 
ceived 4,^00 of a grain of the salt. Subtracting the seventeen ten- 
tacles which were not inflected, each gland could have absorbed 
only the ^ T glooo of a grain (.00000738 nig.). This amount caused 
the tentacle bearing each gland to be greatly inflected. The blade 
was also inflected. 

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

( 1 ) After 2 hrs. 30 m. all the tentacles but twenty-two inflected 
but some only sub-inflected; the blade much inflected; after 6 hrs. 
30 m. all but thirteen inflected, with the blade immensely inflected; 
and remained so for 48 hrs. 

(2) No change for the first 12 hrs., but after 24 hrs. all the 
tentacles inflected, excepting those of the outermost row, of which 
only eleven were inflected. The inflection continued to increase, 
and after 48 hrs. all the tentacles except three were infleote<l, 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 30 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. 1.5 m. a most unusual circumstance occurred, namely, the 
whole blade became slightly bowed towards the footstalk, and so 
remained for 48 hrs. The exterior tentacles, excepting those of the 
three or four outermost rows, were now also inflected to an unusual 
degree. 



Chap. VII.] PHOSPHATE OF AMMONIA. 135 

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

When the two lots of eight leaves in the solution and in the 
water were compared after the lapse of 24 hrs., they undoubtedly 
differed much in apjiearance. The few tentacles on the leaves in 
water which were inflected had after this interval re-expanded, with 
the exception of one leaf; and this presented the very unusual case 
of the blade being somewhat inflected, though in a degree hardly 
approaching that of the two leaves in the solution. Of these latter 
leaves, No. 1 had almost all its tentacles, together with its blade, 
inflected after an immersion of 2 hrs. 30 m. Leaves No. 2 and 3 
were affected at a much slower rate; but after from 24 hrs. to 48 
hrs. almost all their tentacles were closely inflected, and the blade 
of one quite doubled up. We must therefore admit, incredible as 
the fact may at first appear, that this extremely weak solution 
acted on the most sensitive leaves ; each of which received only the 
go^flj of a grain (.00081 mg.) of the phosphate. Now, leaf No. 3 
bore 178 tentacles, and, subtracting the three which were not in- 
flected, each gland could have absorbed only the uoi ^ oooo o^ * 
grain, or .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 ^^^-^t!VJ^s 
of a grain, or .00000328 mg. ; and this excessively minute amount 
sufficed to cause all the tentacles bearing these glands to be greatly 
inflected. The blade was also inflected. 

Summary of the Results with Phosphate of Ammonia. 
The glands of the disc, -when excited by a half-minim drop 
(.0296 c.c), containing v^rs of a grain (.0169 mg.) of this 
salt, transmit a motor impulse to the exterior tentacles, caus- 
ing them to bend inwards. A minute drop, containing 
nJgaa 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 h t 8^0 jo t of a grain 
(.00000328 mg.^, this is enough to excite the tentacle into 
movement, so that it becomes closely inflected, as does some- 
times the glade. 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. 

F!iilphate of Ammonia. The few trials made with this and the 
following five salts of ammonia were undertaken merely to ascer- 



136 DROSERA ROTUNDIFOLIA. [Chap. VII. 

tain whether they induced inflection, Hnlf-mininis of a solution 
of one part of the sulphate of ammonia to 437 of water were 
placed on the tiiscs of seven leaves, so that each received ^n 
of a grain, or .OUTo mg. After 1 hr. the tentacles of live of them, 
as well as the blade of one, were strongly inflected. The leaves 
were not afterwards observed. 

Citrate of Ammonia. Half-minims of a solution of one part to 
437 of water were placed on the discs of six leaves. In 1 hr. the 
short outer tentacles round the discs were a little inflected, wit> 
the glands on the discs blackened. After 3 hrs. 25 m. one leaf had 
its blade inflected, but none of the exterior tentacles. All six 
loaves remained in nearly the .name state during the day, the sub- 
ninrginal tentacles, however, becoming more and more inflected. 
After 23 hrs. three of the leaves had their blades somewhat in- 
flected, 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 decoc- 
tion of grass. The glands on the discs of the above leaves, instead 
of being almost black, as after the first hour, were now, after 23 
hrs., very pale. I next tried on four leaves half-minims of a 
weaker solution, of one part to 1312 of water (1 grain to 3 oz.) ; so 
that each received -j-^j^ of a grain (.0225 mg.). After 2 hrs, 18 m. 
the glands on the disc were very dark-coloured; after 24 hrs. two 
of the leaves were slightly afTccted; the other two not at all. 

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

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

Tartrate of Ammonia. Half-minims of a solution of one part 
to 437 of water were placed on the discs of five leaves. In 31 m. 
there was a trace of inflection in the exterior tentacles of some of 
the leaves, and this became more decided after 1 hr. with all the 
leaves; but the tentacles were never closely 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 in- 
flei'ted. 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 per- 
ceptible in 25 m.; and this increased during the next three or four 
hours, but never became strongly marked. After only 8 hrs, 30 m. 
the tentacles began to re-expand, and by the next morning, after 
24 hrs., were fully re-expanded on four of the leaves, but still 
slightly inflected on two. 



Chap. VII.] OTHER SALTS OF AMMONIA. 



137 



General Summary and Concluding Remarks on the Salts 
of Ammonia. We have now seen that the nine salts of am- 
monia which were tried all cause the inflection of the tenta- 
cles, and often of the blade of the leaf. As far as can be as- 
certained 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 effi- 
ciency of the carbonate, nitrate, and phosphate, .is shown in 
the following table by the smallest amount which suffices to 
cause the inflection of the tentacles. 



Solutions, how applied. 



Carbonate of 
Ammonia. 



Nitrate of 
Ammonia. 



Phosphate of 
Ammonia. 



Placed on the glands of the ' 
disc, so as to act indirectly 
ou the outer tentacles . j 

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 gland 
which suffices to cause tiie 
aggregation of the proto- 
plasm in the adjoining 
cells of the tentacles . . 



sio of a 
grain, or 
.0675 mg. 

wlinrof a 
grain, or 
.00145 mg. 

n^mv of a 
grain, or 
.00024 mg. 



TsAvs of a 
gniin, or 
.00048 mg. 



tAb of a 
grain, or 
.027 mg. 

nisvof a 
grain, or 
.0025 mg. 

191100 01 a 

grain, or 

.0000937 mg. 



sAb of a 
grain, or 
.0169 mg. 

TT;fcwof a 

grain, or 

.000423 mg. 

lOTniooo 01 a 

gniin. or 

.00000328 rag. 



From the experiments tried in these three different ways, 
we see that the carbonate, which contains 23.7 per cent, of 
nitrogen, is less efficient than the nitrate, which contains 35 
per cent. The phosphate contains less nitrogen than either 
of these salts, namely, only 21.2 per cent., and yet is far 
more efficient; its power, no doubt, depending quite as much 
on the phosphorus as on the nitrogen which it contains. We 
may infer that this is the case, from the energetic manner in 
which bits of bone and phosphate of lime affect the leaves. 
The inflection excited by the other salts of ammonia is prob-' 
ably due solely to their nitrogen, on the same principle 
that nitrogenous organic fluids act powerfully, whilst non- 



138 DROSERA ROTUNDIFOLIA. [Chap. VII. 

nitrogenous organic fluids are powerless. As such minute 
doses of the salts of ammonia affect the leaves, we may feel 
almost sure that Drosera absorbs and profits by the amount, 
though small, which is present in rain-water, in the same 
manner as other plants absorb these same salts by their roots. 

The smallness of the doses of the nitrate, and more espe- 
cially 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 yVrir of a 
grain placed on the disc is only just able to cause the outer 
tentacles of a highly sensitive leaf to bend. It is certainly 
a most surprising fact that the tttVothjv of a grain, or in 
round numbers the one-twenty-millionth of a grain (.0000033 
mg.), of the phosphate should affect any plant or indeed any 
animal ; and as this salt contains 35.33 per cent, of water of 
crj'stallisation, the efficient elements are reduced to tvtj'httt 
of a grain, or in round numbers to one-thirty-millionth of a 
grain (.00000216 mg.). The solution, moreover, in these ex- 
periments 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 suf- 
ficed to cause the inflection of almost every tentacle, and 
often of the blade of the leaf. 

I am well aware that this statement will at first appear 
incredible to almost every one. Drosera is far from rivalling 

* It Is Bcarcely noBslble to In lonjrth, and Btretch It along 

realise what a nillllon means. the wnll of a Inrse hall; then 

The best llliistrnllon which I mark off at one eml the tenth of 

have met with In that jrlven by an Inch. This tenth will reprc- 

Mr. Croll, who snys, Take a sent a hundred, and the entire 

narmw strip of paper 83 ft. 4 In. strip a million. 



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

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 incredi- 
ble 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 meas- 
ured many times with care. The observations were repeated 
during several years. Two of my sons, who were as incredu- 
lous as myself, compared several lots of leaves simultane- 
ously immersed in the weaker solutions and in water, and 
declared that there could be no doubt about the difference in 
their appearance. I hope that some one may hereafter be in- 
duced to repeat my experiments ; in this case he should select 
young and vigorous leaves, with the glands surrounded by 
abundant secretion. The leaves should be carefully cut off 
and laid gently in watch-glasses, and a measured quantity of 
the solution and of water poured over each. The water used 
must be as absolutely pure as it can be made. It is to be 
especially observed that the experiments with the weaker 
solutions ought to be tried after several days of very warm 
weather. Those with the weakest solutions should be made 
on plants which have been kept for a considerable time in a 
warm greenhouse, or cool hothouse; but this is by no means 
necessary for trials with solutions of moderate strength. 

I beg the reader to observe that the sensitiveness or irri- 
tability of the tentacles was ascertained by three different 
methods indirectly by drops placed on the disc, directly by 
drops applied to the glands of the outer tentacles, and by the 
immersion of whole leaves; and it was found by these three 
methods that the nitrate was more powerful than the car- 
bonate, and the phosphate much more powerful than the 
nitrate; this result being intelligible from the difference in 

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

were made on the nitrate of am- edit. 1871, p. 228). With respect 

monin, fourteen years ago, the to ordinary chemical tests, I 

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

not been discovered; and I felt work on ' Poisons ' that about 

all the greater interest in the ^Ja <>f fi K^aln ot nmonic, jjm nt a 

then unrivalled powers of Dro- gruinof prussicacid, ,^'oo of iodine, 

sera. Now the spectroscope has and ko* of tartarised antimony, 

altogether beaten Drosera: for, can be detected: but the power 

according to Bunsen and Kirch- of detection depends much on 

hofr, probably less than one the solutions under trial not be- 

in'Of a grain of sodium can ing extremely weak, 
be thus detected (ee Balfour 



140 DROSERA ROTUNDIFOLIA. fOiup. VII. 

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

There is nothing remarkable in the mere fact of the one- 
twenty-millionth of a grain of the phosphate, dissolved in 
about two-million times its weight of water, being absorbed 
by a gland. All physiologists admit that the roots of plants 
absorb the salts of ammonia brought to them by the rain; 
and fourteen gallons of rain-water contain * a grain of am- 
monia, therefore only a little more than twice as much as in 
the weakest solution employed by me. The fact which ap- 
pears truly wonderful is, that the one-twenty-millionth of a 
grain of the phosphate of ammonia (including loss than the 
one-thirty-millionth of efiicient 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 Ruyter, he inferred that less than the one-mil- 
lionth of a grain of sulphate of atropine, in an extremely 
diluted state, if applied directly to the iris of a dog, paraly- 
ses 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 dr other animal, and perceives 

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



Chap. VII.] SUMMARY, SALTS OF AMMONIA. 141 

its presence, the odorous particles produce some change in 
the olfactory nerves; yet these particles must be infinitely 
smaller^ than those of the phosphate of ammonia weighing 
the one-twenty-millionth of a grain. These nerves then 
transmit some influence to the brain of the dog, which leads 
to action on its part. With Drosera, the really marvellous 
fact is, that a plant without any specialised nervous system 
should be affected by such minute particles; but we have 
no grounds for assuming that other tissues could not be ren- 
dered as exquisitely susceptible to impressions from without, 
if this were beneficial to the organism, as is the nervous sys- 
tem of the higher animals. 

* My son, George Darwin, has millimeter that is, from nht to 

calculated for me the diameter utooo of an inch in diameter, 

of a sphere of phosphate of am- Therefore, an object between ^ 

monia (specific gravity 1.C78), and ^ of the size of a sphere of 

weighing the one-twenty-mil- the phosphate of ammonia of the 

lionth of a grain, and finds it to above weight can be seen under 

be T^ of an inch. Now, Dr. a high power; and no one sup- 

Klefu informs me that the small- poses that odorous particles, such 

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

tinctly discernible under a power in the above illustration, could 

of 800 diameters, are estimated be seen under any power of the 

to be from .0002 to .0005 of a microscope. 



142 



DROSERA ROTUNDIFOLIA. [Chap. VIIL 



CHAPTER Vin. 

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 iTfFLitCTiox. 



Salts not cAxrsnro Iwtlection. 



lArranged in Groups according to tfu Chemical Clasti/leatton in Wattt^ 
' Dictionary of Chemistry.') 



Sodinm carbonate, rapid inflec- 
tion. 
Sodium nitrate, rapid inflection. 

Sodium sulphate, moderately 
rapid inflection. 

Sodium phosphate, very rapid In- 
flection. 

Sodium citrate, rapid Inflection. 

Sodium oxalate, rapid Inflection. 

Sodium chloride, moderutelf 
rapid Inflection. 

Sodium iodide, rather slow Inflec- 
tion. 

Sodium bromide, moderately 
rapid Inflection. 

Potanxlum oxninte, slow and 
doubtful Inflection. 



Potassium carbonate: slowly poi- 
sonous. 

Potassium nitrate: somewhat poi- 
sonous. 

Potassium sulphate. 

Potassium phosphate. 

Potassium citrate. 

Potassium chloride. 

Potnsxlum Iodide, a sllirht nnd 

doubtful amount of Inflection. 
Potassium bromide. 



Chap. VIIL] EFFECTS OF VARIOUS SALTS. 



143 



Salts causing Inflection. 



Salts not causing Inflection. 



(.Arranged in Groups according to the Chemical Clauification in Wattt' 
' Dictionary of C/iernvitrt/.') 



Lithium nitrate, moderately rapid 
inflection. 

Csesium chloride, rather slow In- 
flection. 

Silver nitrate, rapid inflection: 
quick poison. 

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



Aluminium chloride, slow and 

doubtful inflection. 
Gold chloride, rapid inflection: 

quick poison. 

Tin chloride, slow inflection: poi- 
sonous. 



Lithium acetate. 
Rubidium 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 sul- 
phate. 

Lead chloride. 



Antimony tartrate, slow Inflec- 
tion: probably poisonous. 

Arsenious acid, quick inflection: 
poisonous. 

Iron chloride, slow Inflection: Manganese chloride, 
probably poisonous. 

Chromic acid, quick inflection: 
highly poisonous. 

Copper chloride, rather slow In- Cobalt chloride, 
flection: poisonous. 

Nickel chloride, rapid Inflection: 
probably poisonous. 

Platinum chloride, rapid inflec- 
tion: poisonous. 

Sodium, Carbonate of (pure, given me by Prof. Hoffmann). 
Half-minims (.0296 c.c.) of a solution of one part to 218 of water 
(2 prs. 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 unaf- 
fected. But the dose, though only the j^^ of a grain (.135 mg.), 
was evidently too strong, for three of the seven well-inflected leaves 



144 DROSEUA BOTUNDIPOLIA. [Cuap. Vlll. 

were killed. On the other hand, one of the seven, which had only 
a few tentacles inflected, re-expanded and seemed quite healthy 
after 48 hrs. By employing a weaker solution (viz. one part to 4H7 
of water, or 1 gr. to 1 oz.), doses of y^jj of a grain (.(Mi75 mg.) were 
given to six leaves. Some of these were affccteil in 37 m. ; and in 
8 hrs. the outer tentacles of all, as Avell as the blades of two, were 
considerably inflected. After 23 hrs. 15 ra. the tentacles had al- 
most re-expanded, but the blades of the two were still just percep- 
tibly cur>'ed inwards. After 48 hrs. all six leaves were fully re- 
expanded, and appeared perfectly healthy. 

Three leaves were immersed, each in thirty minims of a solu- 
tion of one part to 875 of water (1 gr. to 2 oz.), so that each re- 
ceived ^ of a grain (2.02 mg.) ; after 40 ni. the three were much 
affected and after 6 hrs. 45 m. the tentacles of all and the blade of 
one closely inflected. 

Sodium, Nitrate of (pure). Half-minims of a solution of one 
part to 437 of water, containing ^^^j of a grain (.0675 mg.), were 
placed on the discs of five leaves. After 1 hr. 25 ra. the tentacles 
of nearly all, and the blade of one, were somewhat inflected. The 
inflection continued to increa.se, 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 begin- 
ning to expand. Four days after the solution had been applied, 
two of the leaves had quite, and one had partially, re-expandetl; 
whilst the remaining two remained closely inflected and appeared 
injured. 

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

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

Sodium, I'lioHphate of. Half-minims of a solution of one part 
to 437 of water were placed on the discs of six leavesj. The solu- 
tion acted with extraordinary rapidity, for in 8 m. the outer ten- 
tacles on several of the leaves were much incur>'ed. After 6 hrs. 
the tentacles of all leaves, and the blades of two, were closely in- 
flected. This state of things ctmtinued for 24 hrs., excepting that 
the blade of a third leaf became incun'ed. After 48 hrs. all the 
leaves re-expanded. It is clear that vln of a grain of phosphate 
of soda has great power in causing inflection. 



Chap. VIII.] SALTS OF SODIUM. 145 

Sodiuvi, Xitrate of. Half-minims of a solution of one part to 
437 of water were placed on the discs of six leaves, but these were 
not observed until 22 hrs. had elapsed. The submarginal tenta- 
cles of five of them, and the blades of four, were then found in- 
flected; but the outer rows of tentacles were not affected. One 
leaf, wliich appeared older than the others, was very little affected 
in any way. After 46 hrs. four of the leaves were almost re- 
expanded, including their blades. Three leaves were also im- 
mersed, 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, were 
much affected. In 22 hrs., besides the inflection of the tentacles, 
the blades of all seven leaves were so much doubled over that 
their tips and bases almost touched. On no other occasion have I 
seen the blades so strongly affected. Three leaves were also im- 
mersed, each in thirty minims of a solution of one part to 875 of 
water; after 30 m. there was much inflection, and after 6 In-s. 
35 m. the blades of two and the tentacles of all were closely in- 
flected. 

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 tentacles inflected in 24 hrs., and these did not begin 
to re-expand until the fourth day, and were not perfectly expanded 
on the seventh day. I presume that this leaf was injured by the 
salt. Half-minims of a weaker solution, of one part to 437 of 
water, were then dropped on the discs of six leaves, so that each 
received y^-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 consider- 
ably, but not closely, inflected. After 23 hrs. 15 m. all had com- 
pletely re-expande<l, and did not appear in the least injured. 

Three leaves were immersed, each in thirty minims of a solu- 
tion of one part to 875 of water, so that each received ^ of a grain, 
or 2.02 mg. After 1 hr. there was much inflection; after 8 hrs. 
30 m. all the tentacles and the blades of all three Avere closely in- 
flected. Four other leaves wer^also immersed in the solution, each 
receiving the same amoimt of salt as before, viz. ^'y of a grain. 
They all soon became inflected ; after 48 hrs. they began to re-ex- 
pand, and appeared quite uninjured, though the solution was sufK- 
ciently 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 hr. 
four of them had their blades and many tentacles inflected. The 
other two had only their submarginal tentacles inflected; the outer 
one in most of the leaves being but little affected. After 4fi hrs. 
the leaves had nearly re-expanded. Three leaves were also im- 



14G DROSERA ROTUNDIPOLIA. [Cuap. VIII. 

mersed, each in thirty minimB of a sodium of one part to 875 of 
>vater. After U hrs. :iU in. ulinost all the tentacles, and the blade 
of one leaf, were closely inflected. 

ISodium, Bromide of. lialf-minims of a solution of one part to 
437 of water were placed on six leaves. After 7 hrs. there was 
some inflection; after 22 hrs. three of the leaves had their blades 
and most of their tentacles inflected; the fourth leaf was very 
slightly, and the fifth and sixth hardly at all, affected. Three 
leaves were also immersed, each in thirty minims of a solution of 
one part to 875 of water; after 40 m. there was some 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, how- 
ever, seemed the result of their being injured; for, on the third day 
after the solution was given, three of the leaves were dead, and one 
was very unhealthy; the other two were recovering, but with 
several of their tentacles apparently injured, and these remained 
permanently inflected. It is evident that the tj^^ of a grain of 
this salt acts as a poison. Three leaves were also immersed, each 
in thirty minims of a solution of one part to 875 of water, though 
only for 9 hrs.; and, very difTerently 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. 
Kight leaves were treated in the same manner, with drops of a 
weaker solution, of one part to 218 of water. After 50 hrs. there 
was no inflection, but two of the leaves seemed injured. Five of 
these leaves were subsequentlj' teste<l with drops of milk and a 
solution of gelatine on their discs, and only one became inflected; 
so that the solution of the nitrate of the above strength, acting for 
50 hrs., apparently had injured or paralysed the leaves. Six leaves 
were then treated in the same manner with a still weaker solution, 
of one part to 437 of water, and these, after 48 hrs., were in no 
way aflTected, with the exception of perhaps a single leaf. Three 
leaves were next immersed for 25 hrs., each in thirty minims of a 
solution of one part to 875 of water, and this produced no ap- 
parent effect. They were then put into a solution of one part of 
carbonate of ammonia to 218 of water; the glands were immediate- 
ly 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. 

Potassium, Sulphate of. Half-minims of a solution of one part 
to 437 of water were placed on the discs of six leaves. After 20 
hrs. 30 m. no effect was produced; after an additional 24 hrs. three 



Chap. VIII.] SALTS OP POTASSIUM. 147 

remained quite unaffected; two seemed injured, and the sixth 
seemed almost dead, with its tentacles inflected. Nevertheless, 
after two additional days, all six leaves recovered. The immersion 
of three leaves for 24 hi-s., each in thirty minims of a solution of 
one part to 875 of water, produced no apparent eflFect. They were 
then treated with the same solution of carbonate of ammonia, 
with the same result as in the case of the nitrate of potash. 

Potassium, Phosphate of. Half-minims of a solution of one 
part to 437 of water were placed on the discs of six leaves, which 
were observed during three days; but no effect was produced. 
The partial drying up of the fluid on the disc slightly drew to- 
gether 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 immersion of three leaves for 9 hrs., each in 30 minims of a 
solution of one part to 875 of water, did not produce the least 
effect. 

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

Potassium, Bromide of. Ilalf-niinims of a solution of one part 
to 437 of water were placed on the discs of six leaves; after 22 hrs. 
one had its blade and many tentacles inflected ; but I suspect that 
11 



148 DROSERA ROTUNDIFOLIA. [Chap. VIII. 

an inwot might have alighted on it and then escaped; the five 
other leaves wore in no way affected. I tested three of thcae 
leaves with bits of meat, and after 24 hra. they became splendidly 
inflected. Three leaves were also immersed for 21 hrs. in 30 min- 
ims of a solution of one part to 875 of water; but they wtre 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, y^ of a 
grain. After 24 hrs. there was no inflection. I then added, for the 
sake of testing the leaves, some strong solution (viz. 1 gr. to 20 oz., 
or one part to 8750 of water) of phosphate of ammonia, and all 
four became in 30 m. closely inflected. 

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

Ccrsium, 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 darkene<l; after 4 hrs. 20 m. there was a 
trace of inflection; after hrs. 40 m. two leaves were greatly, but 
not closely, and the other two considerably inflected. After 22 hrs. 
the inflection was extremely gieat, and two had their blades in- 
flected. I then transferred the leaves into water, and in 46 hrs. 
from their first immersion they were almost re-expanded. 

Rubidium, Chloride of. Four leaves which were immersed, as 
above, in 120 minims of a solution of one part to 437 of water, were 
not acted on in 22 hrs. I then addeil 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 re- 
ceived, as before, i^g- of a grain. After 5 m. slight inflection, and 
after 11m. very strong inflection, the glands becoming excessively 
black; after 40 m. all the tentacles were clo.sely 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 minima 
of a solution of one part to 437 of water; after 24 hrs. none of the 
tentacles were inflet^ted, 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 rcndere<l the leaves torpid. 

Calcium, Nitrate of. Four leaves were immerseil in 120 minims 
of a solution of one part to 437 of water, but were not affected in 
24 hrs. I then addeil some of the solution of phosphate of am- 
monia (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 



Chjlp.VIIL] effects OF VARIOUS SALTS. 149 

the above strengths of the nitrate of calcium and phosphate of am- 
monia, and it tecame closely inflected in between 5 m. and 10 m. 
Ualf-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 pro- 
duced 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 inflec- 
tion; 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 pronounmi after 24 hrs. Those in 
the mixed nitrate were decidedly inflected in 4 hrs. 30 m., but the 
degree of inflection did not afterwards much increase; whereas 
the four leaves in the mixed chloride were greatly inflected in 
a few minutes, and after 4 hrs, had almost every tentacle 
closely inflected. We thus see that the acetate and nitrate of 
magnesium injure the leaves, or at least prevent the subsequent 
action of phosphate of ammonia; whereas the chloride has no such 
tendency. 

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

Barium, Acetate of. Four leaves were immersed in 120 minims 
of a solution of one part to 437 of water, and after 22 hrs. there 
was no inflection, but the glands were blackened. The leaves were 
then placed in a solution (1 gr. to 20 oz.) of phosphate of ammonia, 
which caused after 26 hrs. only a little inflection in two of the 
leaves. 

Barium, Nitrate of. Four leaves were immersed in 120 minima 
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 fol- 
lows from an immersion of this length in pure water. I then added 
some of the same solution of phosphate of ammonia, and after 
30 m. one leaf was greatly inflected, two others moderately, and the 
fourth not at all. The leaves remained in this state for 24 hrs. 

Strontium, Acetate of. Four leaves, immersed in 120 minims 
of a solution of one part to 437 of water, were not aflTected in 22 
hrs. They were then placed in some of the same solution of phos- 
phate of ammonia, and in 25 m. two of them were greatly inflected ; 
after 8 hrs. the third leaf was considerabl}' 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 min- 
ims of a solution of one part to 437 of water; after 22 hrs. there 
was some slight inflection, but not more than sometimes occurs 
with leaves in water. They were then placed in the same solution 
of phosphate of ammonia; after 8 hrs. three of them were moder- 
ately inflected, as were all five after 24 hrs.; but not one was 



150 DROSERA ROTUNDIFOLIA. [Chap. VIII. 

closely inflected. It appears that the nitrate of strontium renders 
the leaves hiilf torpid. 

Cadmiuin, 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 inflei'tion occurred, which increased during the next three 
hours. After 24 hrs. all three leaves had their tentacles well in- 
flected, and remained so for an additional 24 hrs.; glands nut 
discoloured. 

Mercury, Pcrchloride of. Three leaves were immersed in 
ninety minims of a solution of one part to 437 of water; after 
22 m. there was some sliglit 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 dis- 
coloured. The leaves were then removed and left for two days 
in water; but they never re-expanded, being evidently dead. 

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

Aluminium, Chloride of. Four leaves were immersed in 120 
minims of a solution of one part to 437 of water; after 7 hrs. 45 m. 
no inflection; after 24 hrs. one leaf rather closely, the second mod- 
erately, 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. Those leaves wore 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, }k'itrate of. Four leaves were immersed in 120 
minims of a solution of one part to 437 of water; after 7 hrs. 45 m. 
there was only a trace of inflection; after 24 hrs. one leaf was 
moderately inflected. The evidence is here again doubtful, as in 
the case of the chloride of aluminium. The leaves were then 
transferred to the same solution as before, of phosphate of am- 
monia; this produced hardly any effect in 7 hrs. 30 m. ; but after 
25 hrs. one leaf was pretty closely inflected, the three others very 
slightly, perhaps not more so than from water. 

Aluminium and Potassium, Sulphate of (common alum). 
Half-minims of a solution of the iisual strength were placed on the 
discs of nine leaves, but produce<l no effect. 

(Hold, Chloride of. Seven leaves were immer8e<l in so much of a 
solution of one part to 437 of water that each received 30 minims, 
containing A of a grain, or 4.048 mg., of the chloride. There was 
some inflection in 8 m., which IxK-ame extreme in 45 m. In 3 hrs. 
the surrounding fluid was coloured purple, and the glands were 
blackened. After hrs. the leaves were transferroil to water; next 
morning they were found discoloured and evidently killed. The 
secretion decomposes the chloride very readily; the glands them- 
selves becoming coated with the thinnest layer of metallic gold, 
and particles float almut on the surface of the surrounding fluid. 

IjCad, Chloride of. Three loaves were immerswl in ninety min- 
ims of a solution of one part to 437 of water. After 23 hrs. there 



Chap. Vlll.] EFFECTS OF VARIOUS SALTS. 151 

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

Tin, Chloride of, Four leaves were immersed in 120 minims of 
a solution of about one part (all not being dissolved) to 437 of 
water. After 4 hrs. no effect; after 6 hrs. 30 m. all four leaves had 
their submarginal tentacles inflected; after 22 hrs. every single 
tentacle and the blades were closely inflected. The surrounding 
fluid was now coloured pink. The leaves were washed and trans- 
ferred 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 dark- 
ened. The leaves were washed and placed in water, but they re- 
mained 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 in- 
flection; 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 min- 
ims 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. consider- 
able, inflection; after 2 hrs. all the tentacles closely inflected, with 
the glands discoloured. Placed in water, next day leaves quite 
discoloured and evidently killed. 

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

Copper, Chloride of. Three leaves immersed in ninety minima 
of a solution of one part to 437 of water; after 2 hrs. some inflec- 
tion; after 3 hrs. 45 m. tentacles closely inflected, with the glands 
blackened. After 22 hrs. still closely inflected, and the leaves flac- 
cid. Placed in pure water, next day evidently dead. A rapid 
poison. 

Nickel, Chloride of. Three leaves immersed in ninety minima 
of a solution of one part to 437 of water; in 25 m. considerable in* 



152 DEOSERA ROTUNDIPOLIA. [Chap. VIIL 

flection, and in 3 hre. all the tentacles closely inflected. After 22 
hrs. still closely inflected; most of the glandH, but not all, black- 
enal. The leaves were then placed in water; after 24 hr. re- 
mained inflected; were somewhat discoloured, with the glands 
and tentacles dingy red. Probably killed. 

Cobalt, Chloride of. Three leaves immersed in ninety minims 
of a solution of one part to 437 of water; after 23 hrs. there was 
not a trace of inflection, and the glands were not more blackened 
than often occurs after an equally long immersion in water. 

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

Concluding Remarks on the Action of the foregoing 
Salts. Of the fifty-one salts and metallic acids which were 
tried, twenty-five caused the tentacles to be inflected, and 
twenty-six had no such effect, two rather doubtful cases oc- 
curring in each series. In the table at the head of this dis- 
cussion, the salts are arranged according to their chemical 
affinities; but their action on Drosera does not seem to be 
thus governed. The nature of the base is far more impor- 
tant, 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 induce a slight and rather doubtful amount 
of inflection. This difference between the two series is in- 
teresting, as Dr. Burdon Sanderson informs me that sodium 
salts may be introduced in large doses into the circulation of 
mammals without any injurious effects; whilst small doses 
of potassium salts cause death by suddenly arresting the 
movements of the heart. An excellent instance of the differ- 
ent action of the two series is presented by the phosphate of 
soda quickly causing vigorous inflection, whilst phosphate of 
potash is quite inefficient. The great power of the former is 
probably due to the presence of phosphorus, as in the cases of 
phosphate of lime and of ammonia. Hence we may infer 



Chxp. VIII.] CONCLUDING REMARKS, SALTS. 163 

that Drosera cannot obtain phosphorus from the phosphate of 
potash. This is remarkable, as I hear from Dr. Burdon 
Sanderson that phosphate of potash is certainly decomposed 
within the bodies of animals. Most of the salts of soda act 
very rapidly; the iodide acting slowest. The oxalate, ni- 
trate, 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 im- 
pulse 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 acetic 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 caesium causes 
inflection, and rubidium does not; and these two metals are 
aUied to sodium and potassium. Most of the earthy salts are 
inoperative. Two salts of calcium, four of magnesium, two 
of barium, and two of strontium, did not cause any inflection, 
and thus follow the rule of the preponderant power of the 
base. Of three salts of aluminium, one did not act, a second 
showed a trace of action, and the third acted slowly and 
doubtfully, so that their effects are nearly alike. 

Of the salts and acids of ordinary metals, seventeen, were 
tried, and only four, namely those of the zinc, lead, mangan- 
ese, and cobalt, failed to cause inflection. The salts of cad- 
mivma, tin, antimony, and iron act slowly; and the three 
latter seem more or less poisonous. The salts of silver, mer- 
cury, gold, copper, nickel, and platinum, chromic and arseni- 
ous acids, cause ^reat inflection with extreme quickness, and 
are deadly poisons. It is surprising, judging from animals, 
that lead and barium should not be poisonous. Most of the 
poisonous salts make the glands black, but chloride of plati- 
num made them very pale. I shall have occasion, in the 
next chapter, to add a few remarks on the different effects of 
phosphate of ammonia on leaves previously immersed in va- 
rious solutions. 

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



154 



DROSERA ROTUNDIFOLIA. [Chap. VIII. 



AODS. 

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



Acids, much diluted, which 
CAUSE Inflection. 



1. Nitric, strong inflection; poi- 

sonous. 

2. Hydrochloric, moderate and 

slow inflection; not poison- 
ous. 

8. Hydriodic, strong inflection; 
poisonous. 

4. Iodic, strong Inflection; poi- 
sonous. 

6. Sulpliuric, strong Inflection; 
somewliat poisonous. 

6. Pbosplioric, strong Inflection; 

poisonous. 

7. Boraclc, moderate and rather 

slow inflection; not poison- 
ous. 

a Formic, very slight inflection; 
not poisonous. 

0. Acetic, strong and rapid In- 
flection; poisonous. . 

10. rropionlc, strong but not very 

rapid inflection; poisonous. 

11. Oleic, qulclc inflection; very 

poisonous. 

12. Carbolic, very slow Inflection; 

poisonous. 

13. Lactic, slow and moderate In- 

flection; poisonous. 

14. Oxalic, moderately quick In- 

flection; very poisonous. 

15. Malic, very slow but consid- 

erable Inflection; not poison- 
ous. 

16. Bentolc, rapid inflection; rery 

poisonous. 

17. Succinic, moderately quick In- 

flection; moderately poison- 
ous. 

18. nippnric, rather slow Inflec- 

tion; poisonous. 

19. Hydrocyanic, rather rapid In- 

flection; very poisonous. 



Acids, diluted to the sahb 
Degree, which do nut caubb 

Inflection. 

1. Gallic; not poisonous. 

2. Tannic; not poisonous. 

3. Tartaric; not poisonous. 

4. Citric; not poisonous. 
0. Uric; (?) not polaonoas. 



Chap. VIII.] THE EFFECTS OF ACIDS. 155 

Nitric Acid. Four leaves were placed, each in thirty minima 
of one part by weight of the acid to 437 of water, so that each 
received -^ oi & grain, or 4.048 mg. This strength was chosen for 
this and most of the following experiments, as it is the same as 
that of most of the foregoing saline solutions. In 2 hre. 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 b^n injured. They were then left in water for three days; 
but they remained inflected and were evidently killed. Most of the 
glands had become colourless. Two leaves were then immersed, 
each in thirty minims of one part to 1000 of water ; in a few hours 
there was some inflection; and after 24 hrs. both leaves had al- 
most 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 in- 
flected, 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 moderate- 
ly inflected, and the blade of one slightly. The surrounding fluid 
was not coloured at all pink. After 25 hrs. three of these four 
leaves began to re-expand, but their glands were of a pink instead 
of a red colour; after two more days they fully re-expanded; but 
the fourth leaf remained inflected, and seemed much injured or 
killed, with its glands white. Four leaves were then treated, each 
with thirty minims of one part to 875 of water; after 21 hrs. they 
M'ere moderately inflected; and, on being transferre<l to water, 
fully re-expanded in two days, and seemed quite healthy. 

Hydriodic Acid. One to 437 of water; three leaves were im- 
mersed as before, each in thirty minims. After 45 m. the glands 
were discoloured, and the surrounding fluid became pinkish, but 
there was no inflection. After 5 hrs. all the tentacles were closely 
inflected; and an immense amount of mucus was secreted, so that 
the fluid could be drawn out into long ropes. The leaves were 
then placed in water, but never re-expanded, and were 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 hydro- 
chloric, 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 evident- 
ly dead. - 



156 DROSERA ROTUNDIFOLIA. [Chap. VUI. 

Sulphuric Acid. One to 437 of water; four leaves were im- 
mersed each in thirty minims; after 4 hrs. great inllcction; after 
hrs. surrounding liuid just tinged pink; they were then placed 
in water, and after 40 hrs. two of them were still closely inllected, 
two beginning to re-expand; many of the glands colourless. Thia 
acid is not so poisonous as hydriodic or iodic acids. 

Phosphoric Acid. One to 437 of water; three leaves were im- 
mersed together in ninety minims; after 5 hrs. 30 m. some inflec- 
tion, 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. 

Boracic Acid. One to 437 of water; four leaves wei-e immersed 
together in 120 minims; after 6 hrs. very slight inflection; after 8 
hrs. 15 m. two were considerably inflected, the otiier 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-ex- 
panded and looked healthy. This acid agrees closely with hy- 
drochloric acid of the same strength in its power of causing inflec- 
tion, and in not being poisonous. 

Formic Acid. Four leaves were immersed together in 120 min- 
ims of one part to 437 of water ; after 40 m. slight, and after 6 hrs. 
30 m. very moderate inflection; after 22 hrs. only a little more 
inflection than often occurs in water. Two of the leaves were then 
washed and placed in a solution (1 gr. to 20 oz.) of phosphate of 
ammonia; after 24 hrs. they were considerably inflected, with the 
contents of their cells aggregated, showing that the phosphate had 
acted, though not to the full and ordinary degree. 

Acetic Acid. Four leaves were immersed together in 120 min- 
ims of one part to 437 of water. In 1 hr. 20 m. the tentacles of 
all four and the blades of two were greatly inflected. After 8 hrs. 
the leaves had become flaccid, but still remained closely inflected, 
the surrounding fluid being coloured pink. They were then 
washed and placed in water; next morning they were still inflected 
and of a very dark red colour, but with their glands colourless. 
After another day they were dingy-coloured, and evidently dead. 
This acid is far more powerful than formic, and is highly poisonous. 
Half-minim drops of a stronger mixture (viz. one part by measure 
to 320 of water) were placed on the discs of five leaves; none of 
the exterior tentacles, only those on the borders of the disc which 
actunlly absorbed the acid, became inflected. Probably the dose 
was too strong and paralysed the leaves, for drops of a weaker 
mixture caused much inflection; nevertheless, the leaves all died 
after two days. 

Propionic Acid. Three leaves were immersed in ninety minims 
of a mixture of one part to 437 of water; in 1 hr. 50 m. there was 
no inflection; but after 3 hrs. 40 m. one leaf was greatly inflected, 
and the other two slightly. The inflection continued to increase, 
BO that in 8 hrs. all three leaves were closely inflected. Next 
morning, after 20 hrs., most of the glands were very pale, but some 



Chap. VIII.] THE EFFECTS OF ACIDS. 157 

few were almost black. No e&ucus had been secreted, and the 
surrounding lluid was only just perceptibly tinted of a pale pink. 
After 46 hrs. the leaves became slightly flaccid and were evidently 
killed, as was afterwards proved to be the case by keeping them 
in water. The protoplasm in the closely inflected tentacles was not 
in the least aggregated, but towards their base^ it was collected in 
little brownish masses at the bottoms of the cells. This proto- 
plasm was dead, for, on leaving the leaf in a solution of carbonate 
of ammonia, no aggregation ensued. Propionic acid is highly poi- 
sonous to Drosera, like its ally acetic acid, but induces inflection 
at a much slower rate. 

Oleic Acid (given me by Prof. Frankland).^Three leaves were 
immersed in this acid; some inflection was almost immediately 
caused, which increased slightly, but then ceased, and the leaves 
seemed killed. Next morning they were rather shrivelled, and 
many of the glands had fallen olT 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 ease)- 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 secre- 
tion surrounding the glands of the outer tentacles, these were oc- 
casionally, but by no means always, inflected. Two leaves were 
also immersed in this oil, and there was no inflection for about 
12 hrs.; but after 23 hrs. almost all the tentacles were inflected. 
Three leaves were likewise immersed in unboiled linseed oil, and 
soon became somewhat, and in 3 hrs. greatly inflected. After 1 hr. 
the secretion round the glands was coloured pink. I infer from 
this latter fact that the power of linseed oil to cause inflection can- 
not be attributed to the albumin which it is said to contain. 

Carbolic Acid. Two leaves were immersed in sixty minims of 
a solution of 1 gr. to 437 of water; in 7 hrs. one was slightly; and 
in 24 hrs. both were closely, inflected, with a surprising amount 
of mucus secreted. These leaves were washed and left for two 
days in water; they rtmained inflected; most of their glands be- 
came pale, and they seemed dead. This acid is poisonous, but does 
not act nearly so rapidly or powerfully as might have been ex- 
pected from its known destructive power on the lowest organisms. 
Half-minims of the same solution were placed on the discs of three 
leaves; after 24 hrs. no inflection of the outer tentacles ensued, and 
when bits of meat were given them they became fairly well in- 
flected. 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 be- 
fore; one leaf alone became well inflected, the discal glands of the 
other two appearing much injure<i and dry. We thus see that 
the glands of the discs, after absorbing this acid, rarely transmit 

See articles on Glycerine and Oleic Acid in Watts' ' Diet, of Cltcm- 
Istry.' 



158 DROSERA ROTUNDIFOLIA. [Chap. VIIL 

any motor impulse to the outer tentacles; though these, when 
their own glands al)8orb the acid, are strongly actcii on. 

Lactic Acid. Three leaves were iuunersed in ninety minims of 
one part to 437 of water. After 48 m. there was no inlloction, but 
the surrounding fluid was coloured pink; after 8 hrs. 30 m. one 
leaf alone was a little intlooted, and almust all the glands on all 
thi-ce leaves were of a very pale c-olour. The leaves were then 
wa.shed and placed in a solution (I gr. to 20 oz.) of phosphate of 
ammonia; after about IC hrs. there was only a trace of intlectioo. 
They were left in the phosphate for 48 hrs., and remained in the 
same state, with almost all their glands discoloured. The proto- 
plasm within the cells was not aggregated, except in a very few ten- 
tacles, 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 inllcction was caused. 
Four leaves were next immersed in 120 minims of a weaker solu- 
tion, of one part to 875 of water; after 2 hrs. 30 m. the sur- 
rounding lluid 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 ex- 
traordinarily 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. 

Oallic, Tannic, Tartaric, and Citric Acidg. 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 -j'^ of a grain, or 
4.048 mg. No inflection was caused in 24 hrs., and the loaves 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 phos- 
phate of ammonia, but no inflection ensued in 24 hrs. On the 
other hand, the four leaves which had been in the citric acid, when 
treatetl 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 immerse<l in ninety minims of a 
solution of one part to 437 of water; no infle<-tion 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 placed in water, and after two days partially re- 
expande<l. Hence this acid is not poisonotis. 

Oxalic Acid. Three leaves were immersed in ninety minims ol 



C5HAP. VIII.] THE EFFECTS OP ACIDS. 159 

a solution of 1 gr. to 437 of water; after 2 hrs. 10 m, there was 
much inflection; glands pale; the surrounding fluid of a dark pink 
colour; after 8 hrs. successive 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 ad- 
ditional hours, the three leaves were dead and their glands col- 
ourless. 

Benzoic Acid. Five leaves were immersed, each in thirty min- 
ims of a solution of 1 gr. to 437 of water. This solution was so 
weak that it only just tasted acid, yet, as we shall see, was highly 
poisonous to Drosera. After 52 m. the submarginal tentacles were 
somewhat inflected, and all the glands very pale-coloured; the sur- 
rounding fluid was coloured pink. On one occasion the fluid be- 
came pink in the course of only 12 m. and the glands as white as 
if the leaf had been dipped in boiling water. After 4 hrs. much 
inflection; but none of the tentacles were closely inflected, owing, 
as I believe, to their having been paralysed before they had time to 
complete their movement. An extraordinary quantity of mucus 
was secreted. Some of the leaves were left in the solution; others, 
after an immersion of 6 hrs. 30 m., were placed in water. Next 
morning both lots were quite dead; the leaves in the solution be- 
ing flaccid, those in the water (now coloured yellow) of a pale 
brown tint, and their glands white. 

Succinic Acid. Three leaves were immersed in ninety minims 
of a solution of one gr. to 437 of water; after 4 hrs. 15 m. con- 
siderable, 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. 

Ui'ic 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 ^^g of a grain. After 25 m. 
there was some slight inflection; but this never increased; iifter 

hrs. the glands were not discoloured, nor was the solution col- 
oured pink ; nevertlicless, much mucus was secreted. The leaves 
were then placed in water, and by next morning fully re-expanded. 

1 doubt whether this acid really causes inflection, for the slight 
movement which at first occurred may have been due to the pres- 
ence of a trace of albuminous matter. But it produces some effect, 
as shown by the secretion of so much mucus. 

nippvric Acid. Four leaves were immersed in 120 minims of a 
solution of 1 gr. to 437 of water. After 2 hrs. the fluid was col- 
oured pink; glands pale, but no inflection. After 6 hrs. some in- 
flection; after 9 hrs. all four leaves greatly inflected; much mucus 
secreted; all the glands very pale. The leaves were then left in 
water for two days; they remained closely inflected, with their 
glands colourless, and I do not doubt were killed. 

Hydrocyanic Acid. Four leaves were immersed, each in thirty 
minims of one part to 437 of water; in 2 hrs. 45 m. all the tentacles 
were considerably inflected, with many of the glands pale; after 



160 DROSERA ROTUNDIFOLIA. [Chap. VIIL 

3 hrs. 45 m. all strongly inflected, and the surrounding fluid col- 
oureti pink; after 6 hrs. all closely inflected. After an iiiunersion 
of 8 hrs. 20 ni. the leaves were washed and placed in water; next 
morning, after about 10 hrs., they were still inflected and discol- 
oured; 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 ap- 
peared much injured. I likewise touched the secretion round a 
large number of glands with minute drops (about -^ of a minim, or 
.00296 c.c.) of Scheele's mixture (containing 4 per cent, of anhy- 
drous acid) ; the glands first became bright red, and after 3 hrs. 
15 m. about two-thirds of the tentacles bearing these glands were 
inflected, and remained so for the two succeeding days, when they 
appeared dead. 

Concluding Remarks on the Action of Acids. It is evi- 
dent that acids have a strong tendency to cause the inflection 
of the tentacles;* for, out of twenty-four acids tried, nine- 
teen 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 econ- 
omy. Of the five cases in which acids did not cause the 
tentacles to be inflected, one is doubtful; for uric acid did 
act slightly, and caused a copious secretion of mucus. Mere 
sourness to the taste is no criterion of the power of an acid 
on Drosera, as citric and tartaric acids are very sour, yet do 
not excite inflection. It is remarkable how acids differ in 
their power. Thus, hydrochloric acid acts far less power- 
fully than hydriodic and many other acids of the same 
strenf^h, and is not poisonous. This is an interesting fact, 
as hydrochloric acid plays so important a part in the diges- 

Aocordlnjr to M. Fonrnler Berbprls Instnntly to close; 

i' De la FCcondntlon dnns les though drops of water have no 

>han(^roKanie8,' 18(Vi, p. 01) drops such power, which latter state- 

of acetic, hydrocyanic, and sul- ment I can confirm, 
pburic acid cause the stamens of 



N 



Chap. VIII.] CONCLUDING REMARKS, ACIDS. 161 

tive process of animals. Formic acid induces very slight in- 
flection, and is not poisonous; whereas, its ally, acetic acid, 
acts rapidly and powerfully, and is poisonous. Malic acid 
acts slightly, whereas citric and tartaric acids produce no 
effect. Lactic acid is poisonous, and. is remarkable from in- 
ducing inflection only after a considerable interval of time. 
Nothing surprised me more than that a solution of benzoic 
acid, so weak as to be hardly acidulous to the taste, should 
act with great rapidity and be highly poisonous; for I am 
informed that it produces no marked effect on the animal 
economy. It may be seen, by looking down the list at the 
head of this discussion, that most of the acids are poisonous, 
often highly so. Diluted acids are known to induce n^ative 
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 
poisqnous acids, such as hydriodic, benzoic, hippuric, and 
carbolic (but I neglected to record all the cases), caused the 
secretion of an extraordinary amount of mucus, so that long 
ropes of this matter hung from the leaves when they were 
lifted out of the solutions. Other acids, such as hydro- 
chloric and malic, have no such tendency; in these two 
latter cases the surrounding fluid was not coloured pink, and 
the leaves were not poisoned. On the other hand, propionic 
acid, which is poisonous, does not cause much mucus to be 
secreted, yet the surrounding fluid became slightly pink. 
Lastly, as in the case of saline solutions, leaves, after being 
immersed in certain acids, were soon acted on by phosphate 
of ammonia ; on the other hand, they were not thus affected 
after immersion in certain other acids. To this subject, 
however, I shall have to recur. 

* Miller's ' Elements of Chemistry,' part 1. 1867, p. 87. 



162 DROSERA ROTUNDIFOLIA. [Chap. IX 



CHAPTER IX. 

THE EFFECTS OF CEBTAIfir ALKALOID POISONS, OTHEB SUBSTANCES 
AND VAPOURS. 

Strychnine, salts of Quinine, sulphate of, does not soon arrest the move- 
ment of the protoplasm Other salts of quinine Digitaline Nicotine 
Atropine Veratrine Colchicine Theine Curare Morphia 
Hyoscyamus Poison of the cobra, apparently accelerates the move- 
mente of the protoplasm Camphor, a powerful stimulant, its va]K>ur 
narcotic Certiiin essential oils excite movement (ilycerine Water 
and certain solutions rotiird or prevent the subsHiuont action of phos- 
phate of ammonia Alcohol innocuous, it8 vapour narcotic and poison- 
ous Chloroform, sulphuric and nitric ether, their stimulant, poison- 
ous, and narcotic power Carbonic acid narcotic, not quickly poisonous 
Concluding remarks. 

As in the last chapter, I will first give my experiments 
and then a brief summary of the results with some con- 
cluding 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 ^^ of a grain, or .()C75 nig. In 2 hrs. 30 m. the outer 
tentacles on some of them were inflected, but in an irregular man- 
ner, sometimes only on one side of the leaf. The next morning, 
after 22 hrs. 30 m., the inflection had not increased. The glands 
on the central disc were blackened, and had ceased secreting. 
After an additional 24 hrs. all the central glands seemed dead, but 
the inflected tentacles had re-expanded and appeared quite healthy. 
Hence the poisonous action of strychnine seems confined to the 
glands which have absorbed it; nevertheless, these glands transmit 
a motor impulse to the exterior tentacles. Minute drops (about ^ 
of a minim) of the same solution applied to the glands of the 
outer tentacles occasionally caused them to bend. The poison does 
not seem to act quickly, for having applied to several glands sim- 
ilar drops of a rather stronger solution, of one part to 292 of 
water, this did not prevent the tentacles bending, when their 
glands were excitetl, 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 
blackene<l the glands; some few tentacles thus treated moved, 
whilst others did not. The latter, however, on being subsequently 
moistened with saliva or given bits of meat, became incurve<l, 
though with extreme slowness; and this shows that they had been 



Chap. IX.] ALKALOID POISONS. 168 

injured. Stronger solutions (but the strength was not ascer- 
tained) 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 pro- 
duce nearly so plain an effect as the drops of a much weaker solu- 
tion 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 ^ oi 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 proto- 
plasm in the cells of the tentacles was well aggregated. By this 
time two of the leaves were greatly inflected, but the three others 
not much more inflected than they were before. Nevertheless two 
fresh leaves, after an immersion respectively for 2 hrs. and 4 hrs. 
in the solution, were not killed ; for on being left for 1 hr. 30 m. in 
a solution of one part of carbonate of ammonia to 218 of water, 
their tentacles became more inflected, and there was much aggre- 
gation. 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 -n^ part of its weight. Five leaves were 
immersed, each in thirty minims of this solution, which tasted bitter. 
In less than 1 hr. some of them had a few tentacles inflected. In 
3 hrs. most of the glands became whitish, others dark-coloured, 
and many oddly mottled. After 6 hrs. two of the leaves had a 
good ma^y tentacles inflected, but this very moderate degree of 
12 



1G4 DROSERA ROTUNDIPOLIA. [Chap. IX. 

inflection never increased. One of the leaves was taken out of 
the solution after 4 hrs., and placed in water; by the next morn- 
ing some few of the inflected tentacles had re-expanded, showing 
that they were not dead, but the glands were still much discol- 
oured. Another leaf not included in the above lot, after an immer- 
sion of 3 hrs. 15 m., was carefully examined; the protoplasm in 
the cells of the outer tentacles,, and of the short green ones on the 
disc, had become strongly aggregated down to their bases; and I 
distinctly saw that the Httle masses changed their positions and 
shapes rather rapidly; some coalescing and again separating. I 
was surprised at this fact, because quinine is said to arrest all 
movement in the white corpuscles of the blood; but as, according 
to liinz,' this is due to their being no longer sup])lied with o.xygen 
by the red corpuscles, any such arrestment of movement could not 
be expected in Drosera. That the glands had absorbed some of 
the salt was evident from their change of colour; but I at first 
thought that the solution might not have travelled down the cells 
of the tentacles, where the protoplasm was seen in active move- 
ment. This view, however, 1 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 am- 
monia to 218 of water; and in 30 m. the glands and the upper- 
cells of the tentacles became intensely black, with the protoplasm 
presenting a very unusual appearance; for it had become aggre- 
gated 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 nnist 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 so- 
lution, became somewhat flaccid, and the protoplasm in all the 
cells was aggregated. Many of the aggregated masses were dis- 
coloured, and presente<l a granular appearance; they were spher- 
ical, 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 soluticm were placed on the discs of six 
leaves; after 23 hrs. one had all its tentacles, two had a few, and 
the others none inflected; so that the discal glands, when irritated 
by this salt, do not transmit any strong motor impulse to the 
outer tentacles. After 48 hrs. the glands on the discs of all six 
leaves were evidently much injured or quite killed. It is clear that 
this salt is highly poisonous.' 

' Quarterly Journal of Micro- onorpotlc poison to low vojretable 

scoplcnl Bclence,' April, 1874, p. ami nnlinal orjrMnlsins. Kven one 

IW. part nddod to 4tHX pnrfs of blood 

' Bins found several years ago arn'sta the niovcnuMits nt the 

(as stated In ' The Journal of white corpuscli's, wlilch become 

Anntoniy nnd Phys.,' November, " rounded and jinuiulnr." In the 

1872, p. li>5) that quluia Is au tentacles of Drusera the aggre- 



Chap. IX.] ALKALOID POISONS. 165 

Acetate of Quinine. Four 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 G hrs. immensely, inflected. 
They were then left in water for GO hrs., but never re-expanded; 
the glands were white, and the leaves evidently dead. This salt 
is far more eliicient than the sulphate in causing inflection, and, 
like that salt, is highly poisonous. 

Nitrate of Quinine. Four leaves were immersed, each in thirty 
minims of a solution of one part to 437 of water. After 6 hrs. 
there was hardly a trace of inflection; after 22 hrs. three of the 
leaves were moderately, and the fourth slightly inflected; so 
that this salt induces, though rather slowly, well-marked inflec- 
tion. These leaves, on being left in water for 48 hrs., almost com- 
pletely re-expanded, but the glands were much discoloured. Hence 
this salt is not poisonous in any high degree. The diflferent action 
of the three foregoing salts of quinine is singular. 

Digitaline. Half-minims of a solution of one part to 437 of 
water were placed on the discs of five leaves. In 3 hrs. 45 m. some 
of them had their tentacles, and one had its blade, moderately in- 
flected. 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 be- 
came inflected. A minute drop (about ^ of a minim) of the solu- 
tion was applied to three glands, and after 6 hrs. all three ten- 
tacles were inflected, but next day had nearly re-expanded ; so that 
this very small dose of ttJctj of a grain (.00225 mg.) acts on a 
tentacle, but is not poisonous. It appears from these several facts 
that digitaline causes inflection, and poisons the glands which ab- 
sorb a moderately large amount. 

Nicotine. The secretion round several glands was touched" with 
a minute drop of the pure fluid, and the glands were instantly 
blackened; the tentacles becoming inflected in a few minutes. 
Two leaves were immersed in a weak solution of two drops to 1 oz., 
or 437 grains, of water. When examined after 3 hrs. 20 m., only 
twenty-one tentacles on one leaf were closely inflected, and six on 
the other slightly so; but all the glands were blackened, or very 
dark coloured, with the protoplasm in all the cells of all the ten- 
tacles 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 A oz. of water) 
were placed on the discs of six leaves, and in 30 m. all those 
tentacles became inflected; the glands of which had actually 

gated masses of protoplasm, granular apnenranco. A similar 
which api)oai-pd killed by the appearance is caused by very hot 
quiuine, likewise presented a water. 



166 DROSERA ROTUNDIPOLIA. [Chap. IX 

touched the Bolution, as Bhown by their blackness; but hardly any 
motor influence was transmitted to the outer tentacles. After 22 
hrs. most of the glands on the discs npi)eared dead; but this could 
not have been the case, as, wlien 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 protoplasm, but, except when pure, has 
very moderate power of inducing inflection, and still less power of 
causing a motor influence to be transmitted from the discal glands 
to the outer tentacles. It is moderately poisonous. 

Atropine. A grain was added to 437 grains of water, but waa 
not all dissolved ; another grain was added to 437 grains of a mix- 
ture 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 pro- 
duced, excepting that the glands on the discs to which the valeri- 
anate was given were slightly discoloured. The six leaves on 
which drops of the solution of atropine in diluted alcohol had 
been left for 21 hrs. were given bits of meat, and all became in 
24 hrs. fairly well inflected; so that atropine does not excite 
movement, and is not poisonous. I also tried in the same man- 
ner the alkaloid sold as daturine, which is believed not to differ 
from atropine, and it produced no effect. Three of the leaves on 
which drops of this latter solution had been left for 24 hrs. were 
likewise given bits of meat, and they had in the course of 24 hrs. 
a good many of their submarginal tentacles inflected. 

Veratrine, Colchicine, Thcine. Solutions were made of these 
three alkaloids by adding one part to 437 of water. Half-minims 
were placed, in each case, on the discs of at least six leaves, but no 
inflection was caused, except perhaps a very slight amount by the 
theine. Half-minims of a strong infusion of tea likewise produced, 
as formerly stated, no effect. I also tried similar drops of an in- 
fusion 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 vera- 
trine had been left for 26 hrs. were given bits of meat, and after 
21 hrs. were well inflected. These three alkaloids are therefore 
quite innocuous. 

Curare. One part of this famous poison was added to 218 of 
water, and three leaves were immersed in ninety minims of the 
filtered solution. In 3 hrs. 30 m. some of the tentacles were a little 
inflecte<l; as was the blade of one, after 4 hrs. After 7 hrs. the 
glands were wonderfully blackened, showing that matter of some 
kind had been absorbed. In hrs. two of the loaves had most 
of their tentacles sub-inflected, but the inflection did not increase 
in the course of 24 hrs. One of these leaves, after being immersed 
for 9 hrs. in the solution, was placed in water, and by next 
morning had largely re-expanded; the other two, after their im- 
mersion for 24 hrs., were likewise plare<l in water, and in 24 hrs. 
were considerably re-expanded, though their glands were as black 



Chap. IX.] ALKALOID TOISONS. 1G7 

as ever. Half-minims were placed on the discs of six leaves, and no 
inflection ensued; but after three days the glands on the discs 
appeared rather dry, yet to my surprise were not blackened. On 
another occasion drops were placed on the discs of six leaves, and 
a considerable amount of inflection was soon caused; but as I had 
not filtered the solution, floating particles may have acted on the 
glands. After 24 hrs. bits of meat were placed on the discs of three 
of these leaves, and next day they became strongly inflected. As 
I at first thought that the poison might not have been dissolved in 
pure water, one grain was added to 437 grains of a mixture of one 
part of alcohol to seven of water, and half-minims were placed on 
the discs of six leaves. These were not at all affected, and when 
after a day bits of meat were given them, they were slightly in- 
flected in 5 hrs., and closely after 24 hrs. It follows from these 
several facta 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 inflected, 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 numbe* 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 
w^ell aggregated. If, however, whilst the leaves were immersed in 
the morphia, phosphate 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 G m., bits of meat, a little 
saliva, or particles of glass, were placed on them, the movement 
of the tentacles was grea'tly retarded. But on other occasions no 
such retardation occurred. Drops of water similarly applied never 
have any retarding power. Minute drops of a solution of sugar 
of the same strength (one part to 218 of water) sometimes 
retarded the subsequent action of meat and of particles of glass, 
and sometimes did not do so. At one time I felt convinced that 
morphia acted as a narcotic on Drosera, but after having found in 
what a singular manner immersion in certain non-poisonous salts 
and acids prevents the subsequent action of phosphate of ammonia, 
whereas other solutions have no such power, my first conviction 
seems very doubtful. 

Extract of Jluoseyamvu. Several leaves were place<1, each in 
thirty minims of an infusion of 3 grs. of the extract sold by drug- 
gists to 1 oz. of water. One of them, after being immerseil for 5 
hrs. 15 m., was not inflected, and was then put into a solution (1 gr. 
to 1 oz.) of carbonate of ammonia; after 2 hrs. 40 m. it was found 
considei^bly inflected, and the glands much blackened. Four of 



168 DROSERA ROTUNDIFOLIA. [Chap. IX. 

the leaves, ofter being immersed for 2 hrs. 14 m., were placed in 
120 minims of a solution (1 gr. to 20 oz.) of phosphate of ammonia; 
they had already become slightly inflected from the hyoscyamus, 
probably owing to the presence of some albuminous matter, as 
formerly explained, but the inflection immediately increased, and 
after 1 hr. was strongly pronounced; so that hyoscyamus does not 
act as a narcotic or poison. 

Poison from the Fang of a Living Adder. Minute drops were 
placed on the glands of many tentacles; these were quickly in- 
flected, 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 in- 
vestigations 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 jiiy of a minim) of a solution of one part to 437 of water was 
applieil to the secretion round four glands; so that each received 
only about ^riinr of a grain (.0016 mg.). The operation was re- 
peated on four other glands ; and in 15 m. several of the eight ten- 
tacles became well inflected, and all of them in 2 hrs. Next morn- 
ing, 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. 

Ilalf-minims of the same solution were placed on the discs of 
three leaves, so that each received ^^ of a grain (.0G75 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 alTected. The 
leaves remained in the same state during the next day, but after 
48 hrs. re-expanded. 

Three leaves were now immersed, each in thirty minims of the 
solution, so that each received ^ of a grain, or 4.048 mg. In 6 m. 
there was some inflection, which steadily increasetl. so that after 
2 hrs. 30 m. all three leaves were closely inflected; tlie glunds 
were at first somewliat darkened, then rendere<l pale; and the pro- 
toplasm within the cells of the tentacles was partially aggregated. 
The little masses of protoplasm were examined after 3 hi-s., and 
again after 7 hrs., and on no other occasion have I seen them under- 
going such rapid changes of form. After 8 hrs. 30 m. the glands had 
become quite white; they had not secreted any great quantity of 
mucus. The leaves were now place<l in water, and after 40 hrs. re- 
expanded, showing that they were not much or at all injured. 
During their immersion in water the protoplasm within the cells 
of the tentacles was occasionally examined, and always found in 
strong movement. 

Two leaves were next immerse<l, each in thirty minims of a 
much stronger solution, of one part to 100 of water; so that each 
received ^ of a grain, or 16.2 mg. After 1 hr. 45 m. the sub- 

Dr. Fayrer, 'The Thanatopbldia of Inaia,' 1872, p. 130. 



Chap. IX.] POISON OF THE COBRA. 169 

marginal tentacles were strongly inflected, with the glands some- 
what pale; after 3 hrs. 30 m. both leaves had all their tentacles 
closely inflected and the glands white. Hence the weaker solu- 
tion, as in so many other cases, induced more rapid inflection than 
the stronger one; but the glands were sooner rendered white by 
the latter. After an immersion of 24 hrs. some of the tentacles 
were examined, and the protoplasm, still of a fine purple colour, 
was found aggregated into chains of small globular masses. These 
changed their shapes with remarkable quickness. After an im- 
mersion of 48 hrs. they were again examined, and their movements 
were so plain that they could easily be seen under a weak power. 
The leaves were now placed in water, and after 24 hrs. (i. e. 72 
hrs. from their first immersion) the little masses of protoplasm, 
which had become of a dingy purple, were still in strong move- 
ment, 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 exception 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 an- 
other leaf, which had been immersed for 48 hrs. in the poison and 
afterwards for 24 hrs. in water, in a little solution of one part of 
carbonate of ammonia to 218 of water; in 30 m. the protoplasm 
in the cells beneath the glands became darker, and in the course of 
24 hrs. the tentacles were filled down to their bases with dark- 
coloured spherical masses. Hence the glands had not lost their 
power of absorption, as far as the carbonate of ammonia is con- 
cerned. 

From these facts it is manifest that the poison of the cobra, 
though so deadly to animals, is not at all poisonous to Drosera; 
yet it causes strong and rapid inflection of the tentacles, and soon 
discharges all colour from the glands. It seems even to act as a 
stimulant to the protoplasm, for after considerable experience in 
observing the movements of this substance in Drosera, I have never 
seen it on any other occasion in so active a state. I was therefore 
anxious to l^am how this poison affected animal protoplasm ; and 
Dr. Fayrer w^is so kind as to make some observations for me, which 
he has since published.* Ciliated epithelium from the mouth of 
a frog was placed in a solution of .03 gramm to 4.6 cubic cm. of 
water ; others being placed at the same time in pure water for com- 
parison. The movements of the cilia in the solution seemed at 

' Proceeding of Royal Society,* Feb. 18, 1875. 



170 DROSERA ROTUNDIFOLIA. [Chap. IX. 

fii-st increased, but soon languished, and after between 15 and 20 
minutes ccascti ; whilst those in the water were still acting vigor- 
ously. The white corpuscles of the blood of a frog, and the cilia 
on two infusorial animals, a Param&ecium and Volvox, were simi- 
larly affected by the poison. Dr. Fayrer also found that the muscle 
of a frog lost its irritability after an immersion of 20 m. in the 
solution, not then responding to a strong electrical current. On 
the other hand, the movements of the cilia on the mantle of an 
Unio were not always arrested, even when left for a considerable 
time in a very strong solution. On the whole, it seems that the 
poison of the cobra acts far more injuriously on the protoplasm of 
the higher animals than on that of Drosera. 

There is one other point which may be noticed. I have occasionally 
observed that the drops of secretion round the glands were ren- 
dered somewhat turbid by certain solutions, and more especially 
by some acids, a film being formetl on the surfaces of the drops; 
but I never saw this effect produced in so conspicuous a manner 
as by the cobra poison. When the stronger solution was employed, 
the drops appeared in 10 m. like little white rounded clouds. After 
48 hrs. the secretion was changed into threads and sheets of a 
membranous substance, including minute granules of various 
sizes. 

Camphor. Some scraped camphor was left for a day in a bottle 
with distilled water, and then filtered. A solution thus made is 
said to contain yi^ 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 in- 
flected in 17 m. and quite closed in 24 m.; the seventh began to 
move in 17 m., and was completely shut in 26 m. The eighth, 
ninth, and tenth leaves were old and of a very dark red colour, 
and tiiese 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 secrete<l much 
mucus; although their tentacles were closely inflected, the pro- 
toplasm within the cells was not at all aggregate<l. On another 
occasion, however, after a longer immersion of 24 hrs., there was 
well-marked aggregation. A solution made by adding two drops 
of camphorate<l spirits to an ounce of water did not act on one 
leaf; whereas thirty minims added to an ounce of water acted on 
two leaves immersed together. 

M. Vogel has shown ' that the flowers of various plants do not 
wither so soon when their stems are placed in a solution of cam- 
phor as when in water; and that if already slightly withered, tbey 
recover more quickly. The gennination of certain seeds is also ac- 
celerated by the solution. So that camphor acts as a stimulant, 
and it is the only known stimulant for plants. I wished, there- 

Onnlfner'B rhronlcle,* 1874, tlons were made in 1798 by B. 8. 
p. G71. Nearly similar observa- Barton. 



Chap. IX,] 



CAMPHOR. 



171 



fore, to ascertain whether camphor would render the leaves of 
Drosera more sensitive to mechanical irritation than they natu- 
rally are. Six leaves were left in distilled water for 5 m. or 6 rn., 
and then gently brushed twice or thrice, whilst still under water, 
with a soft camel-hair brush; but no movement ensued. Nine 



Length of 
Immersion 

in the 
Solution of 
Camphor. 



5 m. 
5 m. 
5 m. 

4 m. 30 s. 

4 m. 

4 m. 

4 m. 

3 m. 

3 m. 



Length of Time between the Act of Bmshing 
and the Inflection of the Tentacles. 



f 3 m. considerable inflection ; 4 m. all I 
1 the tentacles except 3 or 4 inflected, j 
6 m. first sign of inflection. 

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

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

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

2 m. 30 s. decided inflection ; 3 m. 30 s. 
strongly marked. 

2 m. 30 s. slight inflection ; 3 m. plain ; 
4 m. well marked. 

2 m. trace of inflection ; 3 m. consider- 
able, 6 m. strong inflection. 

2 m. trace of inflection ; 3 m. consider- 
able, 6 m. strong inflection. 



Length of 
Time between 
the Immer- 
sion of the 
Leaves in the 
Solution and 
the Kirsl Sign 
of the Inflec- 
tion of the 
Tentacles. 



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

7 m. 

6 m. 30 s. 

6 m. 30 s. 

6 m. 30 s. 

5 m. 

5 m. 



leaves, which had been immersed in the above solution of cam- 
phor for the times stated in the above table, were next brushed only 
once with the same brush and in the same manner as before; the 
results are given in the table. My first trials were made by 
brushing the leaves whilst still immersed in the solution; but it 
occurred to me that the viscid secretion round the glands would 
thus be removed, and the camphor might act more effectually on 
them. In all the 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 dif- 
ference 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 1.5 m. had elapse<l, and 
two not until a few minutes later. On the other hand, it will be 
seen in the right-hand column of the table thnt most of t':o leaves 
subjected to the solution, and which were brushct!, became in- 



172 DROSEUA ROTITNDIFOLIA. [Chap. IX. 

fleeted in a much shorter time. The movement of the tentacles of 
some of these leaves was so rapid that it could be plainly seen 
through a very weak lens. 

Two or three other experiments are worth giving. A large old 
leaf, after being immersed for 10 m. in the solution, did not appear 
likely to be soon inllected; so I brushed it, and in 2 ni. it began 
to move, and in 3 m. was completely shut. Another leaf, after an- 
immersion of 15 m., showed no signs of inflection, so was brushed, 
and in 4 m. was grandly inflected. A third leaf, after an immersion 
of 17 m., likewise showed no signs of 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 in- 
flected; the failure therefore was not complete. 

We may conclude that a small dose of camphor in solution is a 
powerful stimulant to Drosera. It not only soon excites the ten- 
tacles to bend, but apparently renders the glands sensitive to a 
touch, which by itself does not cause any movement. Or it may 
be that a slight mechanical irritation not enough to cause any in- 
flection yet gives some tendency to movement, and thus reinforces 
the action of the camphor. This latter view would have appeared 
to me the more probable one, had it not been shown by M. Vogel 
that camphor is a stimulant in other ways to various plants and 
seeds. 

Two plants bearing four or five leaves, and with their roots in 
a little cup of water, were exposed to the vapour of some bits of 
camphor (about as large as a filbert nut), under a vessel holding 
ten fluid ounces. After 10 hrs. no inflection ensued; but the 
glands appeared to be secreting more copiously. The leaves were 
in a narcotised condition, for on bits of meat being placed on two 
of them, there was no inflection in 3 hi-s. 15 m., and even after 13 
l)rs. 15 m. only a few of the outer tentacles were slightly in- 
flected; but this degree of movement shows that the leaves had 
not been killed by an exposure during 10 hrs. to the vapour of 
camphor. 

Oil of Caraway. Water is said to dissolve about a thousandth 
part of its weight of this oil. A drop was added to an ounce of 
water and the bottle occasionally shaken during a day; but many 
minute globules remained undissolved. Five leaves were immersed 
in this mixture; in from 4 m. to 5 m. there was 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 showe<l a trace of inflection. After 5 
hrs. 20 m. the cover was taken ofl" and the leaves examined; one 
had all its tentacles closely inflectefl. the second about half in the 
same state; and the third all sub-inflected. The plant Mas left in 



Chap. IX.] ESSENTIAL OILS, ETC. 173 

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 poison- 
ous to Drosera, 

Oil of Cloves. A mixture was made in the same manner as in 
the last case, and three leaves were immersed in it. After 30 m. 
there was only a trace of inflection which never increased. After 
1 hr. 30 m. the glands were pale, and after 6 hrs. white. No doubt 
the leaves were much injured or killed. 

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

Glycerine. Half-minims were placed on the discs of three 
leaves; in 2 hrs. some of the outer tentacles were irregularly in- 
flected; and in 19 hrs. the leaves were flaccid and apparently dead; 
the glands which had touched the glycerine were colourless. Mi- 
nute drops (about sV of a minim) were applied to the glands of sev- 
eral tentacles, and in a few minutes these moved and soon reached 
the centre. Similar drops of a mixture of four dropped drops to 
1 oz. of water were likewise applied to several glands; but only a 
few of the tentacles moved, and these very slowly and slightly. 
Half minims of this same mixture placed on the discs of some 
leaves caused, to my surprise, no inflection in the course of 48 hrs. 
Bits of meat were then given them, and next day they were well 
inflected; notwithstanding that some of the discal glands had been 
rendered almost colourless. Two leaves were immersed in the 
same mixture, but only for 4 hrs. ; they were not inflected, and on 
being afterwards left for 2 hrs. 30 m. in a solution (1 gr. to 1 oz.) 
of carbonate of ammonia, their glands were blackened, their ten- 
tacles inflected and the protoplasm within their cells aggregated. 
It appears from these facts that a mixture of four drops of glycer- 
ine to an ounce of water is not poisonous, and excites very, little 
inflection; but that pure glycerine is poisonous, and if applied in 
very minute quantities to the glands of the outer tentacles causes 
their inflection. 

The Effects of Immersion in Water and in various Solutions on 
the Subsequent Action of Phosphate and Carbonate of Ammotiia. 
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 tem- 
perature. 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 



174 DROSEBA ROTUNDIFOLIA. [Cuap. IX. 

day in the solution, still remained quite unaffected. When, how- 
ever, 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 subse- 
quent 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 delaye<l; 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 ni. 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 subse- 
quently increased, though slowly. Hence diluted alcohol, which, 
as we shall see, is hardly at all poisonous, plainly retards the sub- 
sequent action of the phosphate. 

It was shown in the last chapter that leaves which did not be- 
come inflected by nearly a day's immereion in solutions of various 
salts and acids behaved very differently from one another when 
subsequently placed in the phosphate solution. I give on the op- 
posite page a table summing up the results. 

In a large majority of these twenty cases, a varying degree of 
inflection was slowly caused by the phosphate. In four cases, how- 
ever, 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 l)een previously immersed in these three solutions. The 
majority of the other solutions behaved to a certain extent like 
water, for the phosphate pro<luced. after a considerable interval of 
time, only a slight effect. On the other hand, the leaves which 
had been immersetl 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 



Chap. IX.] EFFECTS OF PREVIOUS IMMERSION. 



175 



Name of the Salts and 
Acids iu Solution. 



Period of 

IniDic-niiun of 

the Leaves 

in Soliitious 

of one part to 

437 of water. 



Effects produced on the Leaves by their 
siibst queut luiuierbion for stated pcTiods 
in a Solution of one part of phocpiiate of 
auiuiouia to 8750 of water, or 1 gr. to 

aooz. 



Babidiam chloride 

Potassium carbonate 

Calcium acetate 
Calcium nitrate . 
Magnesium acetate 

Magnesium nitrate 

Magnesium chloride 

Barium acetate . . 
Barium nitrate . . 

Strontium acetate . 



Strontium nitrate 



Alominium chloride 



22 his. 

20 m. 

24hr8. 
24 hrs. 
22 his. 

22hr8. 

22hrs. 

22hr8. 
22hr8. 

22hr8. 



22hr8. 



24 his. 



Aluminium nitrate . 


24hr8. 


Lead chloride . . . 


23hr8. 


Manganese chloride . 


22hrs. 


Lactic acid . . t . 


48hr8. 


Tannic acid .... 
Tartaric acid . . . 
Citric acid .... 


24hr8. 
24hrs. 
24br8. 


Formic acid .... 


22hr8. 



After 30 m. strong inflection of the 
tentacles. 

Scarcely any inflection until 5 his. 
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 in- 
flected. 

After 24 hrs. two leaves out of four 
slightly inflected. 

After 30 m. one leaf greatly, and two 
others moderately, inflected ; they 
remained thus for 24 hrs. 

After 25 m. two leaves greatly in- 
flected; after 8 hrs. a third leaf 
moderately, and the fourth very 
slightly, inflected. All four thus 
remained for 24 hrs. 

After 8 hours three leaves out of five 
moderately inflected ; after 24 his. 
all five in this state; but not one 
closely inflected. 

Three leaves which had either been 
slightly or not at all aflectt^d by the 
chloride became after 7 hrs.. 30 m. 
rather closely inflected. 

After 25 hrs. slight and doubtful 
eflTect. 

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

After 48 his. not the least inflec- 
tion. 

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

After 24 hrs. no inflection. 
Do. do. 

After 50 m. tentacles decidedly inflect- 
ed, and after 5 hrs. strongly inflt'<t- 
ed ; so remained for the next :M 
hrs. 

Not observed until 24 hrs. had clap8'd ; 
tentacles considerably inflected, and 
protoplasm aggregated. 



176 DROSERA ROTUNDIPOLIA. [Chap. IX. 

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 phos- 
phate would not afterwards have produced any eflcct? It further 
appears that the molecules of the carbonate of ammonia can quick- 
ly 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, how- 
ever they may have been treated, seem easily to permit the subse- 
quent entrance of the molecules of carbonate of ammonia. Thus 
leaves which had been immersed in a solution (of one part to 437 of 
water) of nitrate of potassium for 48 hrs. of sulphate of potas- 
sium for 24 hrs. and of the chloride of potassium for 25 hrs. on 
being placeil in a solution of one part of carbonate of ammonia to 
218 of water, had their glands imme<liately blackened, and after 
1 hr. their tentacles somewhat inflected, and the protoplasm aggre- 
gated. 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 tliis strength placed on the discs of 
leaves do not cause any inflection; and that when two days after- 
wards the leaves were given bits of meat, they became strongly in- 
flected. Four leaves were immersed in this mixture, and two of 
them after 30 m. were brushed with a camel-hair brush, like leaves 
in a solution of camphor, but this produced no eflTect. Nor did 
these four leaves, on being left for 24 hrs. in the diluted alcohol, 
undergo any inflection. They were then removed ; one being placed 
in an infusion of raw meat, and bits of meat on the discs of the 
other three, with their stalks in water. Next_,day one 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 

fire Dr. M. Tmubo's curious By allowing; a precipitation of 

experlinoiits on the production sulphate of barium to take place 

of artllU'lal cells, and on their at the same tlnu>, the mi'mbranc 

porin':iblIlty to various salts, de- boronies " Infiltrated " with this 

8Tlb'd In his papers: " Rxjierl- salt; and In con8i'iuonce of the 

nicnte zur Theorle der Zfllonbll- Intercalation of niotccules of sul- 

dtini; und Kndosmose," Hreslau, phato of l)arliim ariouK those of 

IKIVI; and"Kxpprlm<nte zur physl- the K^latlne precipitate, the niolec- 

callsrhen KrklilnmK dor KlldunR ular Interstices In the membrane 

tier Zfllhaiit, Ihres Wachnthums are made smaller. In this altered 

durch IntusHUsreptlon." Itrcsluu, condition, the membrane no 

1H74. These researches perhaps lonijer allows the passace through 

explain my results. Dr. Tranne It of either sulphate of ammonia 

commonly employed as a mem- or nitrate of barium, thouKh It 

bmne the precipitate formed retains Its permeabliltv for water 

whaa tannic aeld eomes Into con- and chloride of auimonla. 
taeC wHU BolaUon of gelatine. 



Chap. IX.] VAPOUR OF CHLOROFORM. 177 

good leaves was left for 25 m. under a receiver holding 19 oz. with 
sixty minims of alcohol in a watch-glass. Xo 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 am- 
monia. Immediately on the removal of the receiver particles of 
raw meat were placed on many of the glands, those which re- 
tained their proper colour being chiefly selected. But not a single 
tentacle was inflected during the next 4 hrs. After the first 2 hi-s. 
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 in- 
flected. 

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 tiie glands of several tentacles. After 10 m. some of 
them began to curve inwards, and after 55 m. nearly all were con- 
siderably inflected; but a few did not move. Some anaesthetic 
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. Parti- 
cles 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 Drosei-a 
is very variable, depending, I suppose, on the constitution or age of 
the plant, or on some unknown condition. It sometimes causes 
the tentacles to move with extraordinary rapidity, and sometimes 
produces no such effect. The glands are sometimes 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 
email 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 in- 
curved 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 
employe<l, 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 extraordi- 
nary quickness by little starts, and therefore in an unnatural man- 



178 DROSERA ROTUNDIPOLIA. [Chap. IX. 

ner; but they never reached the centre. After 22 hrs. they fully 
re-expanded, and on meat being placed on their glands, or wlien 
roughly touched by a needle, they promptly became inflected; so 
that these leaves had not been in the least injured. 

Another plant was placed under the same small bell-glass with 
three drops of chloroform, and before two minutes had elapsed, the 
tentacles began to curl inwards with rapid little jerks. The glass 
was then removed, and in the course of two or three additional 
minutes almost every tentacle reached the centre. On several 
other occasions the vapour did not excite any movemnt of this 
kind. 

There seems also to be great variability in the degree and man- 
ner in which chloroform renders the glands insensible to the subse- 
quent action of meat. In the plant last referred to, which had 
been exposed for 2 m. to three drops of chloroform, some few ten- 
tacles curved up only to a perpendicular position, and particles 
of meat were placed on their glands; this caused them in 5 m. 
to begin moving, but they moved so slowly that they did not reach 
the centre until 1 hr. 30 m. had elapsed. Another plant was simi- 
larly 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 cur\-ed 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 slight anajs- 
thetic effect apparently had been produced. On the following day 
the plant had perfectly recovered. 

Another plant bearing two leaves was exposed for 2 m. under 
the 19-oz. vessel to two drops of chloroform; it was then taken 
out and examined; again exposed for 2 m. to two drops; taken 
out, and re-exposed for 3 m. to three drops; so that altogether it 
was exposed alternately to the air and during 7 m. to the vapour 
of seven drops of chlorofonn. Bits of meat were now plaoetl 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 
anipsthctic influence on the leaves. 

On the other hand, another plant was exposc<l under the same 
vessel for a much longer time, viz. 20 m., to twice as much chloro- 
form. Bits of meat were then placed on the glands of many tenta- 
cles, and all of them, with a single exception, reachefl the centre in 
from 13 m. to 14 m. In this case, little or no anaesthetic effect had 
been produced; and how to reconcile these discordant results I 
know not. 

Vapour of Sulphuric Ether. A plant was exposed for 30 m. to 
thirty minims of this ether in a vessel holding 19 oz. ; and bits of 
raw meat were afterwards placed on many glands which had be- 



Chap. IX.] VAPOUR OF ETHER. 179 

come pale-coloured; but none of the tentacles moved. After 6 hrs. 
30 ni. 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 mat- 
ter had been absorl)ed from the meat which had increased the evil 
elFects of the vapour. After four days the plant itself died. An- 
other plant was expose<l 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 be- 
came 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 un- 
injured, but the whole plant after three days became verj' sickly. 

In the two foregoing experiments the doses were evidently too 
large and poisonous. With weaker doses, the anaesthetic effect 
was variable, as in the case of chloroform. A plant was exposed 
for 5 m. to ten drops under a 12-oz. vessel, and bits of meat were 
then placed on many glands. None of the tentacles thus treated 
began to move in a decided manner until 40 m. had elapsetl; 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 with and 
without meat, were closely inflected; so that the ether apparently 
had stimulated these leaves, causing all the tentacles to bend. 

Vapour of Xitric Ether. This vapour seems more injurious 
than that of sulphuric ether. A plant was exposed for 5 m. in a 
12-oz. vessel to eight drops in a watch-glass, and I distinctly saw 
a few tentacles curling inwards before the glass was removed. Im- 
mediately 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. vessal 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 inflecte<l, though they seemed much injure*!. In 
this and .the previous experiment, it is doubtful, owing to the in- 
13 



180 DROSERA ROTUNDIFOLIA. [CniP. IX. 

i'ury which the leaves had suffered, whether any anesthetic effect 
lad been produced. 

A third plant, having two good leaves, was exposed for only 4 
ni. in the Jl)-oz. vessel to the vapour from six drops. Bits of meat 
were then phiced on the glands of seven tentacles on the same leaf. 
A single tentacle moved after 1 hr. 23 m. ; after 2 hrs. 3 m. several 
were inflected; and after 3 hrs. 3 m. all the seven tentacles with 
meat were well inflected. From the slowness of these movements 
it is clear that this leaf had been rendered insensible for a time 
to the action of the meat. A second leaf was rather difTerently 
affected; bits of meat were placed on the glands of five tentacles, 
three of which were slightly inflected in 28 m.; after 1 hr. 21 m. 
one reached the centre, but the other two were still only slightly 
inflected; after 3 hrs. they were much more inflected; but even 
after 5 hrs. 16 m. all five had not reached the centre. Although 
some of the tentacles began to move moderately soon, they after- 
wards 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 in- 
jured, though the tentacles were still inflected; after 72 hrs. one 
was almost dead, whilst the other was re-expanding and recov- 
ering. 

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 
Buflicient allowance for the absorption of the gas by the water, so 
that towards the latter part of the experiment some air was 
drawn in. After an exposure of 2 hrs. the plant was removed, and 
bits of raw meat placed on the glands of three leaves. One of 
these leaves hung a little down, and was at first partly and soon 
afterwards completely covered by the water, which rose within 
the vessel as the gas was absorbed. On this latter leaf the ten- 
tacles, 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 remem- 
bered that the leaf had been protected from the gas, and might 
perhaps have absorbed oxygen from the water which was con- 
tinually 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 placeil 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 inter^'al 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 4.5 m., and bits of 
meat were then placed on four glands. But the tentacles did not 
move for 1 hr. 40 ni.; after 2 hrs. 30 m. all four were well inflected, 
and after 3 hrs. reached the centre. 



Chap. IX.] CARBONIC ACID. 181 

The following singular phenomenon sometimes, but by no 
means always, occurred. A plant was immersed for 2 hrs., and 
bits of meat were then placed on several glands. In the course of 
13 m. all the submarginal tentacles on one leaf became considerably 
inflected ; those with the 'meat not in the least degree more than 
the othera 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 pre- 
sume, may be attributed to excitement from the absorption of oxy 
gen. 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 extremely irregular manner; some only on one side of the 
leaf and some on the other. They remained in this position for 
some time; the tentacles with the bits of meat not having at first 
moved more quickly or farther inwards than the others without 
meat. But after 2 hrs. 20 m. the former began to move, and stead- 
ily went on bending until they reached the centre. Next morning, 
after 22 hrs., all the tentacles on these leaves were closely clasped 
over the meat which had been carried to their centres; whilst the 
vertical and sub-vertical tentacles on the other leaves to which no 
meat had been given had fully re-expanded. Judging, however, 
from the subsequent action of a weak solution of carbonate of am- 
monia on 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 recovered, judging 
from the manner in which it clasped a fly placed in 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 undergoing any inflection, with the exception of two ten- 
tacles. This leaf had been almost completely .paralysed, and was 
not able to recover its sensibility whilst still in the solution, which 
from having been made with distilled water probably contained 
little oxygen. 

Concluding Remarks on the Effects of the foregoing 
Agents. As the glands, when excited, transmit some in- 
fluence to the surrounding tentacles, causing them to bend 



182 DROSERA ROTUNDIPOLIA. [Chap. IX. 

and thoir glands to pour forth an increased amount of modi- 
fied 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 trans- 
mission. 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 Dro- 
sera, and caused a certain amount of inflection. Hydrocy- 
anic acid, again, which is so deadly a poison to animals, 
caused rapid movement of the tentacles. But as several in- 
nocuous acids, though much diluted, such as benzoic, acetic, 
&c., as well as some essential oils, are extremely poisonous 
to Drosera, and quickly cause strong inflection, it seems prob- 
able that strychnine, nicotine, digitaline, and hydrocyanic 
acid, excite inflection by acting on elements in no way an- 
alogous to the nerve-cells of animals. If elements of this 
latter nature had been present in the leaves, it might have 
been expected that morphia, hyoscyamus, atropine, veratrine, 
colchicine, curare, and diluted alcohol would have produced 
some marked effect ; whereas these substances are not poison- 
ous and have no power, or only a very slight one, of in- 
ducing inflection. It should, however, be observed that cu- 
rare, colchicine, and veratrine are muscle-poisons that is, 
act on nerves having some special relation with the muscles, 
and, therefore, could not be expected to act on Drosera, The 
poison of the cobra is most deadly to animals, by paralysing 
their nerve-centres,' yet is not in the least so to Drosera, 
though quickly causing strong inflection. 

Notwithstanding the foregoing facts, which show how 
widely different is the effect of certain substances on the 
health or life of animals and of Drosera, yet there exists a 
certain degree of parallelism in the action of certain other 
substances. We have seen that this holds good in a striking 
manner with the salts of sodium and potassium. Again, 
various metallic salts and acids, namely those of silver, mer- 
cury, gold, tin, arsenic, chromium, copper, and platina, most 
or all of which are highly poisonous to animals, are equally 
8o to Drosera. But it is a singular fact that the chloride of 

* Dr. Payrer. ' The Tbanatopbldia of India,' 1872, p. 4. 



Chap, IX.] SUMMARY OP THE CilAPTER. 183 

lead and two salts of barium were not poisonous to this 
plant. It is an equally strange fact, that, though acetic and 
propionic acids are highly poisonous, their ally, formic acid, 
is not so; and that, whilst certain vegetable acids, namely, 
oxalic, benzoic, &c., are poisonous in a high degree, gallic, 
tannic, tartaric, and malic (all diluted to an equal degree) 
are not so. Malic acid induces inflection, whilst the three 
other just named vegetable acids have no such power. But a 
pharmacopoeia woidd be requisite to describe the diversified 
effects of various substances on Drosera.' 

Of the alkaloids and their salts which were tried, several 
had not the least power of inducing inflection ; others, which 
were certainly absorbed, as shown by the changed colour of 
the glands, had but a very moderate power of this kind; 
others, again, such as the acetate of quinine and digitaline, 
caused strong inflection. 

The several substances mentioned in this chapter affect 
the colour of the glands very differently. These often be- 
come dark at first, and then very pale or white, as was con- 
spicuously the case with glands subjected to the poison of the 
cobra and citrate of strychnine. In other cases they are 
from the first rendered white, as with leaves placed in hot 
water and several acids ; and this, I presume, is the result of 
the coagulation of the albumen. On the same leaf some 
glands become white and others dark-coloured, as occurred 
with leaves in a solution of the sulphate of quinine, and in 
the vapour of alcohol. Prolonged immersion in nicotine, 
curare, and even water, blackens the glands; and this, I be- 
lieve, 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 qui- 
nine 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 

Seeing that acetic, hydro- materially Influenced by any of 

cyanic, and chromic acids, ace- the poisons used, which did not 

tate of strychnine, and vapour of act chemically, with the exccn- 

ether, are poisonous to Drosera, tlon of chloroform and cnrbonlc 

It Is remarkable that Dr. Kansom acid." I find It stated by several 

(' Pbllosoph. Transact." 18<57, p. writers that curare has no Influ- 

480), who used much stronger ence on sareode or protoplasm, 

solutions of these substances and we have seen that, tbouKb 

than I did, states " that the curare excites some degree of In- 

rhytbmic contractility of the yolk flection. It causes very little ag- 

(of the ova of the pike) Is not gregatiou of the protoplasm. 



184 DROSERA ROTUNDIFOLIA. [Chap. IX 

exhibited incessant 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 vi- 
bratile cilia and white corpuscles of the blood seem to be 
quickly paral^'sed 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 strych- 
nine, for the acetate of quinine causes much more inflection 
than the sulphate, and both are poisonous, whereas the 
nitrate of quinine is not poisonous, and induces inflection at 
a much slower rate than the acetate. The action of the 
citrate of strychnine is also somewhat different from that of 
the sulphate. 

Leaves which have been immersed for 24 hrs. in water, 
and for only 20 m. in diluted alcohol, or in a weak solution 
of sugar, are afterwards acted on very slowly, or not at all, 
by the phosphate of ammonia, though they are quickly acted 
on by the carbonate. Immersion for 20 m. in a solution of 
gum arable has no such inhibitory power. The solutions of 
certain salts and acids affect the leaves, with respect to the 
subsequent action of the phosphate, exactly like water, whilst 
others allow the phosphate afterwards to act quickly and 
energetically. In this latter case, the interstices of the cell- 
walls may have been blocked up by the molecules of the 
salts first given in solution, so that water could not after- 
wards enter, though the molecules of the phosphate could do 
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 the other hand, serves as a narcotic. 

Some essential oils, both in solution and in vapour, cause 



Chap. IX.] SUMMARY OP THE CHAPTER. 185 

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 anajsthetic, and long exposure to it kills the 
leaves. 

The vapours of chloroform, sulphuric and nitric ether, 
act in a singularly variable manner on different leaves, and 
on the several tentacles of the same leaf. This, I suppose, is 
owing to differences in the age or constitution of the leaves, 
and to whether certain tentacles have lately been in action. 
That, these vapours are absorbed by the glands is shown by 
their changed colour; but as other plants not furnished 
with glands are affected by these vapours, it is probable that 
they are likewise absorbed by the stomata of Drosera. They 
sometimes excite extraordinarily rapid inflection, but this is 
not an invariable result. If allowed to act for even a moder- 
ately long time, they kill the leaves; whilst a small dose act- 
ing for only a short time serves as a narcotic or anaesthetic. 
In this case the tentacles, whether or not they have become 
inflected, are not excited to further movement by bits of 
meat placed on the glands, until some considerable time has 
elapsed. It is generally believed that with animals and 
plants these vapours act by arresting oxidation. 

Exposure to carbonic acid for 2 hrs,, and in one case for 
only 45 m., likewise rendered the glands insensible for a 
time to the powerful stimulus of raw meat. The leaves, 
however, recovered their full powers, and did not seem in 
the least injured, on being left in the air for 24 or 48 hrs. 
We have seen in the third chapter that the process of 
aggregation in leaves 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 



186 DROSERA ROTUNDIFOLIA. [Chap. IX. 

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 carbolic acid, or to the 
exclusion of oxygen, I know not. 

Sachs. ' Tralte de Bot.' 1874, pp. 846, 1037. 



Chap, X.] SENSITIVENESS OP THE LEAVES. 187 



CHAPTER X. 

ON THE SENSITIVENESS OF THE LEAVES, AND ON THE LINES OP 
TRANSMISSION OF THE MOTOR IMPULSE. 

Glands and summits pf 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 dis- 
charge of the motor impulse sudden Direction of the movements of 
the tentacles Motor impulse transmitted through the cellular tissue 
Mechanism of the movements Nature of the motor impulse Ee- 
expansion of the tentacles. 

We have seen in the previous chapters that many widely 
different stimulants, mechanical and chemical, excite the 
movement of the tentacles, as well as of the blade of the leaf ; 
and we must now consider, firstly, what are the points which 
are irritable or sensitive, and secondly how the motor impulse 
is transmitted from one point to another. The glands are 
almost exclusively the seat of irritability, yet this irritability 
must extend for a very short distance below them; for when 
they were cut off with a sharp pair of scissors without being 
themselves touched, the tentacles often became inflected. 
These headless tentacles frequently re-expanded; and when 
afterwards drops of the two most powerful known stimulants 
were placed on the cut-off ends, no effect was produced. 
Nevertheless these headless tentacles are capable of sub- 
sequent inflection if excited by an impulse sent from the disc. 
I succeeded on several occasions in crushing glands between 
fine pincers, but this did not excite any movement ; nor did 
raw meat and salts of ammonia, when placed on such crushed 
glands. It is probable that they were killed so instantly 
that they were not able to transmit any motor impulse; for 
in six observed cases (in two of which, however, the gland 
was quite pinched off) the protoplasm within the cells of the 
tentacles did not become aggregated; whereas in some ad- 
joining tentacles, which were inflected from having been 
roughly touched by the pincers, it was well aggregated. In 



188 DROSERA ROTUNDIFOLIA. [Chap. X. 

like manner the protoplasm does not become aggregated when 
a leaf is instantly killed by being dipped into boiling water. 
On the other hand, in several cases in which tentacles became 
inflected after their glands had been cut off with sharp scis- 
sors, a distinct though moderate degree of aggregation super- 
vened. 

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 ob- 
served. 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 papillee, 
which do not secrete, but have the power of absorption. 
These papillte 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 secre- 
tion had been excited. Ilence I moistened them with saliva, 
solutions of ammonia, weak hydrochloric acid, and frequent- 
ly 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 

> ' Dot. Zvltuug,' 18G0, p. 234. 



Chap. X.] SENSITIVENESS OF THE LEAVES. 189 

I never saw any true movement. I was led to make so many 
trials because, contrary to my previous experience, Nitschke 
states' that, after affixing objects to the backs of leaves by 
the aid of the viscid secretion, he repeatedly saw the tentacles 
(and in one instance the blade) become reflexed. This move- 
ment, 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 up- 
wards. Even on the fifth day the leaves did not appear dead. 
Now, as sugar does not in the least excite Drosera, we may 
safely attribute the reflexion of the blades and tentacles of 
the above leaves to exosmose from the cells which were in 
contact with the syrup, and their consequent contraction. 
When drops of syrup are placed on the leaves of plants with 
their roots still in damp earth, no inflection ensues, for the 
roots, no doubt, pump up water as quickly as it is lost by 
exosmose. But if cut-off leaves are immersed in syrup, or in 
any dense fluid, the tentacles are greatly, though irr^ularly, 
inflected, some of them assimiing the shape of corkscrews; 

Bot. Zeltung,' 18C0, p. 377. 



190 DROSERA ROTUNDIPOLIA. [Chip. X. 

and the leaves soon become flaccid. If they are now im- 
mersed 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 
that they cause reflection by inducing exosmose. Dr. Nitsch- 
ke used the secretion for sticking insects to the backs of 
the leaves; and I suppose that he used a large quantity, 
which from being dense probably caused exosmose. Per- 
haps 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 ex- 
cited 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 ten- 
tacles bend. Touch a gland once or twice, and no movement 
follows; touch it three or four times, and the tentacle be- 
comes 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 move- 
ment 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 tenta- 
cles are inflected; place it on several glands, and many more 
are acted on; place it on thirty or forty, and all the ten- 
tacles, 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. 



Chap. X.] TRANSMISSION OP MOTOR IMPULSE. 191 

Transmission of the Motor Impulse. In every case the 
impulse from a gland has to travel for at least a short dis- 
tance 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 inflected, the impulse is transmitted across half the 
diameter of the disc, and when the glands on one side of the 
disc are stimulated, the impulse is transmitted across nearly 
the whole width of the disc. A gland transmits its motor 
impulse far more easily and quickly down its own tentacle 
to the bending place than across the disc to neighbouring 
tentacles. Thus a minute dose of a very weak solution of 
ammonia, if given to one of the glands of the exterior ten- 
tacles, causes it to bend and reach the centre; whereas a 
large drop of the same solution, given to a score of glands 
on the disc, will not cause through their combined influence 
the least inflection of the exterior tentacles. Again, when a 
bit of meat is placed on the gland of an exterior tentacle, 
I have seen movement in ten seconds, and repeatedly within 
a minute; but a much larger bit placed on several glands on 
the disc does not cause the exterior tentacles to bend until 
half an hour or even several hours have elapsed. 

The motor impulse spreads gradually on all sides from 
one or more excited glands, so that the tentacles which stand 
nearest are always first affected. Hence, when the glands 
in the centre of the disc are excited, the extreme marginal 
tentacles are the last inflected. But the glands on different 
parts of the leaf transmit their motor power in a somewhat 
different manner. If a bit of meat be placed on the long- 
headed gland of a marginal tentacle, it quickly transmits 
an impulse to its own bending portion ; but never, as far as 
I have observed, to the adjoining tentacles ; for these are not 
affected until the meat has been carried to the central glands, 
which then radiate forth their conjoint impulse on all sides. 
On four occasions leaves were prepared by removing some 
days previously all the glands from the centre, so that these 
could not be excited by the bits of meat brought to them by 
the inflection of the marginal tentacles ; and now these mar- 
ginal tentacles re-expand after a time without any other 



193 DROSERA ROTUNDIFOLIA. [Chap. X. 

tentacle being aflFceted. Other leaves were similarly pre- 
pared, 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 ten- 
tacles. In one of these cases only a single tentacle on each 
side of the one with meat was affected. In the three other 
cases, from half a dozen to a dozen tentacles, both laterally 
and towards the centre, were well inflected, or sub-inflected. 
Lastly, in ten other experiments, minute bits of meat were 
placed on a single gland or on two glands in the centre of 
the disc. In order that no other glands should touch the 
meat, through the inflection of the closely adjoining short 
tentacles, about half a dozen glands had been previously re- 
moved round the selected ones. On eight of these leaves 
from sixteen to twenty-five of the short surrounding ten- 
tacles 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 
aflFected. 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 moist- 
ened with saliva, I have seen the inflection spread still far- 
ther from a single gland thus treated; but even in this case 
the three or four outer rows of tentacles were not affected. 
From these exiwjriraents 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 ten- 
tacles; and this probably follows, at least in part, from the 
impulse having to travel a very short distance down the pedi- 
cels of the central tentacles, so that it is able to spread to a 
considerable distance all round. 

Whilst examining these leaves, I was struck with the fact 
that in six, perhaps seven, of them the tentacles were much 
more inflected at the distal and proximal ends of the leaf 
(t. e. towards the apex and base) than on either side; and yet 
the tentacles on the sides stood as near to the gland where 



Chap. X.] TRANSMISSION OP MOTOR IMPULSE. 193 

the bit of meat lay as did those at the two ends. It thus ap- 
peared 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 in- 
teresting fact in the physiology of plants, thirty-five fresh 
exi)eriments were made to test its truth. Minute bits of 
meat were placed on a single gland or on a few glands, on 
the right or left side of the discs of eighteen leaves; other 
bits of the same size being placed on the distal or proximal 
ends of seventeen other leaves. Now if the motor impulse 
were transmitted with equal force or at an equal rate 
through the blade in all directions, a bit of meat placed at 
one side or at one end of the disc ought to affect equally all 
the tentacles situated at an equal distance from it; but this 
certainly is not the case. Before giving the general results, 
it may be well to describe three or four rather unvisual cases, 

(1) A minute fragment of a fly was placed on one side of the 
disc, and after 32 m. seven of the outer tentacles near the fragment 
were inflected: after 10 hrs. several more became so, and after 23 
hrs. a still greater number; and now the blade of the leaf on this 
side was bent inwards so as to stand up at right angles to the 
other side. Neither the blade of the leaf nor a single tentacle on 
the opposite side was aflTected; the line of separation between the 
two hands extending from the footstalk to the apex. The leaf 
remained in this state for three days, and on the fourth day be- 
gan to re-expand; not a single tentacle havii^ 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 1.5 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 foot- 
stalk; after 2 hrs. 30 m. some neighbouring tentacles were in- 
flected ; after 6 hrs. the tentacles on Iwth 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. 



194 DROSERA ROTUNDIFOUA. [Cdap. X. 

(5) A minute bit of meat was piaced on one side of the disc; 
next day tiie noifjhlM)uring short tentacles were iiitlectcd, a well aa 
in a sli^lit degree three or four on the opposite side near the ftjot- 
stalk. On the second day these latter tentacles showed signs of re- 
expanding, so I added a fresh bit of meat at nearly the same spot, 
and after two days some of the short tentacles on the opposite 
side of the disc were inflected. As soon as these began to re- 
expand, I added another bit of meat, and next day all the tentacles 
on the opposite side of the disc were inflected towards the meat; 
whereas we have seen that those on the same side were affected 
by the first bit of meat which was given. 

Now for the general results. Of the 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 in- 
flected side was active, and the other paralysed. In the re- 
maining 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 af- 
fected, 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 



Chap.X.] transmission OP MOTOR IMPULSE. 195 

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 op- 
posite 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 experiments, not to mention the six or seven 
previous ones, that the motor impulse is transmitted from 
any single gland or small group of glands through the blade 
to the other tentacles more readily and effectually in a longi- 
tudinal 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 im- 
pulse to the basal and bending parts of their own pedicels, 
for otherwise they would re-expand. The great difference in 
the length of time during which tentacles remain inflected 
over inorganic objects, and over objects of the same size con- 
taining 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 op- 
posite 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 ten- 
tacles on the same side, for these never became inflected. 
If, however, meat had been placed on the glands of these 
same tentacles before they had begun to secrete copiously 
and to absorb, they undoubtedly would have affected the ex- 
terior rows. Nevertheless, when I gave some phosphate of 
lime, which is a most powerful stimulant, to several sub- 
marginal tentacles already considerably inflected, but not 
14 



196 DROSKRA ROTUNDIPOLIA. [Chap. X. 

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 op- 
posite tentacles to be temporarily inflected, but the glands 
which remained in contact with the insect, though they con- 
tinued for several days to send an impulse down their own 
pedicels to the bending place, did not prevent the tentacles 
on the opposite side from quickly re-expanding; so that the 
motor discharge must at first have been more powerful than 
afterwards. 

When an object of any kind is placed on the disc, and the 
surrounding tentacles are inflected, their glands secrete more 
copiously and the secretion remains 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 cen- 
tral 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 scis- 
sors often become inflected and again re-expand, still ap- 
pearing 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 those seventeen leaves, and when observed next day, seven 
of the headless tentacles were inflected over the meat as close- 



Chap.X.] transmission OP MOTOR IMPULSK 197 

ly as the uninjured ones on the same leaves; and an eighth 
headless tentacle became inflected after three additional 
days. The meat was removed from one of these leaves, and 
the surface washed with a little stream of water, and after 
three days the headless tentacle re-expanded for the second 
time. These tentacles without glands were, however, in a dif- 
ferent 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 aggr^ation, 
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 previ- 
ous bending of the tentacles, as we clearly see when leaves 
are immersed in certain strong solutions. Nor does it de- 
pend 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 carbon- 
ate of ammonia or an infusion of raw meat. When a gland 
is directly stimulated in any way, as by the pressure of a 
minute particle of glass, the protoplasm within the cells of 
the gland first becomes aggregated, then that in the cells 
immediately beneath the gland, and so lower and lower down 
the tentacles to their bases; that is, if the stimulus has 
been sufficient and not injurious. Now, when the glands of 
the disc are excited, the exterior tentacles are affected in 
exactly the same manner: the aggr^ation always com- 
mences 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 af- 
fected, 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 



198 DROSERA ROTUNDIPOLIA. [Chap. X. 

protoplasm in a tentacle has been aggregated, its redissolu- 
tion always begins in the lower part, and slowly travels up 
the pedicel to the gland, so that the protoplasm last aggre- 
gated 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 
fiuid. 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 
a large object is placed on their glands, or when an insect is 
caught by them. In this latter case we can see that the 
inflection of the short central tentacles would be useless, as 
their glands are already in contact with their prey. 

The result is very different when a single gland on one 
side of the disc is excited, or a few in a group. These send 
an impulse to the surrounding tentacles, which do not now 
bond towards the centre of the leaf, but to the point of ex- 
citement. We owe this capital observation to Nitschke,* 
and since reading his paper a few years ago, I have re- 
peatedly 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 to- 
gether, halfway between the centre and the circumference of 
the disc, the directed movement of the surrounding tentacles 
is well exhibited. An accurate drawing of a leaf with meat 
in this position is here reproduced (Fig. 10), and we see the 
tentacles, including some of the exterior ones, accurately di- 
rected 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 op- 
posite side. In four such trials the excitement was not suf- 

Dot. Zettung,' 1800, p. 240. 



Chap. X.] DmECTION OP INFLECTED TENTACLES. 199 



ficient to affect the outer tentacles, but all those near the two 
points were directed to them, so that two wheels were formed 
on the disc of the same leaf; the pedicels of the tentacles 
forming the spokes, and the glands united in a mass over 
the phosphate representing the axles. The precision with 
which each tentacle pointed to the particle was wonderful; 
80 that in some cases I could detect no deviation from per- 
fect accuracy. Thus, although 
the short tentacles in the mid- 
dle of the disc do not bend 
when their glands are excited 
in a direct manner; yet if 
they receive a motor impulse 
from a point on one side, they 
direct themselves to the point 
equally well vCith the ten- 
tacles 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 ex- 
citing fluid, were now inflected 
in an exactly opposite direc- 
tion, viz. towards the circmn- 
ference. These tentacles, there- 
fore, 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 con- 
sidered as the normal one. Between this, the greatest possi- 
ble and no deviation from the normal direction, every degree 
could be observed in the tentacles on these several leaves. 
Notwithstanding the precision with which the tentacles gen- 
erally were directed, those near the circumference of one leaf 
were not accurately directed towards some phosphate of lime 
at a rather distant point on the opposite side of the disc. It 
appeared as if the motor impulse in passing transversely 
across nearly the whole width of the disc had departed 
somewhat from a true course. This accords with what we 




Fig. 10. 
(Drosera rotundifolia.) 
Leaf (enlarged) with the tenta- 
cles inflected over a bit of meat 
placed on one side of the disc. 



200 DROSERA ROTUNDIFOLIA. [Chap. X. 

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 cen- 
tral ones. 

Nothing could be more striking than the appearance 
of the above four leaves, each with their tentacles pointing 
truly to the two little masses of the phosphate on their discs. 
We might imagine that we were looking at a lowly organised 
animal seizing prey with its arms. In the case of Drosera 
the explanation of this accurate power of movement, no 
doubt, lies in the motor impulse radiating in all directions, 
and whichever side of a tentacle it first strikes, that side 
contracts, and the tentacle consequently bends towards the 
point of excitement. The pedicels of the tentacles are flat- 
tened, or elliptic in section. Near the bases of the short 
central tentacles, the flattened or broad face is formed of 
about five longitudinal rows of cells; in the outer tentacles 
of the disc, it consists of about six or seven rows; and in 
the extreme marginal tentacles of above a dozen rows. As 
the flattened bases are thus formed of only a few rows of 
cells, the precision of the movements of the tentacles is the 
more 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; never- 
theless, 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 de- 
scribe briefly the course of the main fibro-vascular bundles. 

[In n letter (IWS) to Sir III. p. .121. the writer Bpenks of 
Joneph Hooker. In the ' Life nnd the exUtence In DroHem of " dlf- 
LetterH of Charles Darwin,' vol. fused nervous mutter," In some 



Chap. X.] 



CONDUCTING TISSUES. 



201 



These are shown in the accompanying sketch (Fig. 11) of a 
small leaf. Little vessels from the neighboring bundles 
enter all the many tentacles with which the surface is stud- 
ded; 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. Bifur- 
cation 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 in- 
osculates with a branch from 
the lateral bundle, and that 
there is a smaller inoscula- 
tion between the two chief 
branches of the lateral bun- 
dle. The course of the ves- 
sels 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 ves- 
sels, but whether these points open into each other by 
their attached, surfaces, I do not know. By means of the 
two inosculations all the vessels on the same side of the 
leaf are brought into some sort of connection. Near the 
circumference of the larger leaves the bifurcating branches 
also come into close union, and then separate again, forming 




Fig. 11. 
(Drosera rotundifolia.) 
Diagram showiDg the distribution 
of the vascular tissue iu a small 
leaf. 



decree nnnlojfons In constitution 
and function to the nervous mat- 
ter of nnlmnls. Now. that 
through the researches of Gar- 
diner ( Phil. Trans.' 18S.3) and 
others the connection between 



plant-cells by Inter-cellular nroto- 
ptasm has been establlsheu, we 
can understand the trnnsmlKslon 
of the motor Impulse as a molec- 
ular change in the protoplasm 
from cell to cell. F. D.] 



203 DROSERA ROTUNDIPOLIA. [Chap. X 

a continuous zigzag line of vessels round the whole circum- 
ference. But the union of the vessels in this zigzag line 
seems to be much less intimate than at the main inoscula- 
tion. It should be added that the course of the vessels dif- 
fers somewhat in different leaves, and even on opposite sides 
of the same leaf, but the main inosculation is always present. 

Now in my first experiments with bits of meat placed on 
one side of the disc, it so happened that not a single tentacle 
was inflected on the opposite side ; and when I saw that the 
vessels on the same side were all connected together by the 
two inosculations, whilst not a vessel passed over to the op- 
posite side, it seemed probable 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 be- 
neath 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: 

(1) This leaf proved rather torpid: after 4 hrs. 40 m. (in all 
cases reckoning from the time when the meat was given) the ten- 
tacles 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 hre. 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 afTected. On the third day, however, some of the short 
tentacles on the disc near the base were very slightly inflected. 
The incision was found on dissection to extend across the leaf as 
in the last case. 

(3) After 4 hrs. 30 m. strong inflection of the tentacles at the 
distal end, which during the next two days never extended in the 
least to the basal end. The incision as before. 

(4) This leaf was not observed until 1.5 hrs. had elapsed, and 
then all the tentacles, except the extreme marginal ones, were 
found equally well inflected all round the leaf. On careful ex- 
amination 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.* 

M. Zlegler made similar ox- (' Comptes rondtis.* 1874, p. 1417), 
perlmonts hy cnttlnjt the spiral Imt nrrlvcnl at conrluslooa widely 
vessels of Droacra intermedia clillcreDt from nilne. 



Chap.X.] conducting TISSUES. 203 

The appearance presented by the leaves (2) and (3) was 
very curious, and might be aptly compared with that of a 
man with his backbone broken and lower extremities par- 
alysed. 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 sufiiced for complete trans- 
mission. 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 impjerfectly, in a transverse direction across the whole 
breadth of the leaf. Nor can this latter fact be accounted 
for by supposing that the transmission is affected through 
the two inosculations, or through the circumferential zigzag 
line of union, for had this been the case, the exterior ten- 
tacles on the opposite side of the disc would have been af- 
fected before the more central ones, which never occurred. 
We have also seen that the extreme marginal tentacles ap- 
pear to have no power to transmit an impulse to the adjoin- 
ing tentacles ; yet the little bundle of vessels which .enters 
each marginal tentacle sends off a minute branch to those 
on both sides, and this I have not observed in any other ten- 
tacles; so that the marginal ones are more closely connected 
together by spiral vessels than are the others, and yet have 
much less power of communicating 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 



204 DROSERA ROTUNDIFOLIA. [Chap. X. 

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 cir- 
cuitous 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 communi- 
cated, so that all the surrounding tentacles should bend 
precisely to the point of excitement. The impulse no doubt 
is transmitted in straight radiating lines from the excited 
gland to the surrounding 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 here- 
after see, when we treat of Dionsea^ that this same conclu- 
sion, namely that the motor impulse is not transmitted by 
the fibro-vascular bundles, is plainly confirmed; and Pro- 
fessor Cohn has come to the same conclusion with respect to 
Aldrovanda both members of the Droseracese.* 

As the motor impulse is not transmitted along the ves- 
sels, 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, 

[Bntnlln (' Flora,' 1877) ex- siipKostod that In the case of 

perlniented on the transmission MasdrraUia muscona the Impulse 

of the motor Impnise, and con- travels In a sheath of thin walled 

firms the observations of Zlejjler pareiK'hyma afOonipanylnK the 

('<'ompto8 rendus,' 1874), from xyleni. If we make a similar as- 

whleh that nattirallst concluded sumption for Drosera, we should 

that the vascular bundles form pet rUI of a difflculty, for whcth- 

the path for the transmission of er the Impulse travels In the 

the Impulse. Katalln concludes course of the vascular bundles or 

that Impulse travels with far transversely across the leaf. It 

jrreater ease aloni; the vessels would In either case be travel- 

than across the parenchyma, and llnj? In parenchymatous tissue; 

that the course of the stlmtilus the only difference between the 

Is normally almost exclusively two cases bclnic that the paren- 

alunK the vessels. ohyma aceompanyInK the vessels 

If wo believe that the motor would be specially adapte<l for 

Impulse travels ns n molecular rapid transmission In a definite 

chanKe In the protoplasm, we direction, whereas the ordinary 

cannot suppose that it travels In narencbyma has to transmit the 

the trachelds. Now Oliver (* An- impulse In a variety of dlrec- 

nals of Botany,' Feb. 1888) has tiuus. F. D.] 



Chap. X.] CONDUCTING TISSUES. 205 

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. 

The greater celerity with which the impulse is trans- 
mitted 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 thq 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- 
municating 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 either case it is remarkable that the 
impulse is able to pass through so many partitions down 
nearly the whole length of the pedicel, and to act on the 
bending place, in ten seconds. Why the impulse, after hav- 

* ' Vldennkahellge Mwldelelser hnjjne/ Nos. 10-12, 1872, wood- 
de la Soc. d'lllst. nat. de Copen- cuts ir. and t. 



206 DROSERA ROTUNDIFOLIA. [Chap. X. 

ing passed so quickly down one of the extreme marginal 
tentacles (about iV of an inch in length), should never, as 
far as I have seen, aflfect the adjoining tentacles, I do not 
understand. It may be in part accounted for by much 
energy being expended in the rapidity of the transmission. 

Most of the cells of the disc, both the superficial ones and 
the larger cells which form the five or six underlying layers, 
are about four times as long as broad. They are arranged 
almost longitudinally, radiating from the footstalk. The 
motor impulse, therefore, when transmitted across the disc, 
has to cross nearly four times as many cell- walls as when 
transmitted in a longitudinal direction, and would conse- 
quently 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 tentacles tends to travel laterally and towards the 
centre of the leaf, but not centrifugally, is by no means 
clear. 

Mechanism of the Movements, and Nature of the Motor 
Impulse. Whatever may be the means of movement, the 
exterior tentacles, considering their delicacy, are inflected 
with much force. A bristle, held so that a length of 1 inch 
projected from a handle, yielded when I tried to lift with it 
an 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 
reflected, as often occurs, the angle is considerably greater. 
It is probably the superficial cells at the bending place which 
chiefly or exclusively contract; for the interior cells have 
very delicate walls, and are so few in number that they could 
hardly cause a tentacle to bend with precision to a definite 
point. Though I carefully looked, I could never detect any 
wrinkling of the surface at the bending place, even in the 
case of a tentacle abnormally curved into a complete circle, 
under circumstances hereafter to be mentioned. 

All the cells are not acted on, though the motor impulse 



CniP. X.] MEANS OP MOVEMENT. 207 

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 bend- 
ing, 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 
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 vigor- 
ous shoot if slowly bent into a semi-circle.* In the case of 
Drosera there is certainly much movement of the fluid 
throughout the tentacles whilst they are undergoing inflec- 
tion. Many leaves can be found in which the purple fluid 
within the cells is of an equally dark tint on the upper and 
lower sides of the tentacles, extending also downwards on 
both sides to equally near their bases. If the tentacles of such 
a leaf are excited into movement, it will generally be found 
after some hours that the cells on the concave side are much 
paler than they were before, or are quite colourless, those 
on the convex side having become much darker. In two in- 
stances, after particles of hair had been placed on glands, 
and when in the course of 1 hr. 10 m. the tentacles were in- 
curved half-way towards the centre of the leaf, this change 
of colour in the two sides was conspicuously plain. In an- 
other 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 

"SachB. 'Trnlt<' dp Bot.* .'Idortlt. Sachs, Traits de Dot.' 3d 

1874. p. 1038. This vlow was. I he- edit. 1874, p. Oia. 
lieve, first suggested by Lamarck. 



208 DROSERA ROTUNDIFOLIA. [Chap. X. 

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 com- 
pared with the contortions which many vegetable tissues 
undergo when subjected to exosmose. It is there- 
fore doubtful whether they throw any light on the natural 
movements. 

If we admit that the outward passage of fluid is the cause 
of the bending of the tentacles, we must suppose that the 
cells, before the act of inflection, are in a high state of 
tension, and that they are elastic to an extraordinary degree; 
for otherwise their contraction could not cause the tentacles 
often to sweep through an angle of above 180. Professqr 
Cohn, in his interesting paper" on the movements of the 
stamens of certain Compositaj, states that these organs, 
when dead, are as elastic as threads of India-rubber, and are 
then only half as long as they were when alive. He believes 
that the living protoplasm within their cells is ordinarily in 
a state of expansion, but is paralysed by irritation, or may 
be said to suffer temporary death; the elasticity of the cell- 
walls then coming into play, and causing the contraction of 
the stamens. Now the cells on the upper or concave side of 
the bonding 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 move- 
ments cannot be accounted for by the inherent elasticity of 

' Abhnnrt. <lcr Schlos. Oenell. nnper Ih iflven In the ' Annals and 
fflr rati>rl. Cultnr.' IHGl, Heft I. Mnjc. of Nnt. Illst.' .'ird series. 
Ad excellent abstract of this 18U3, vol. Ix. pp. 188-11)7. 



Chap.X.] nature op the MOTOR IMPULSE. 209 

certain cells, opposed as long as they are alive and not irri- 
tated by the expanded state of their contents. 

A somewhat different view has been advanced by other 
physiologists namely that the protoplasm, when irritated, 
contracts like the soft sarcode of the muscles of animals. 
In Drosera the fluid within the cells of the tentacles at the 
bending place appears \inder the microscope thin and homo- 
geneous, and after aggregation consists of small, soft masses 
of matter, undergoing incessant changes of form and float- 
ing 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 exi)ected 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 the 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 
rejected by most others, is that the whole cell, including the 
walls, actively contracts. If the walls are composed solely 
of non-nitrogenous cellulose, this view is highly improbable; 
but it can hardly be doubted that they must be permeated 
by proteid matter, at least whilst they are growing. . Nor 
does there seem any inherent improbability in the cell-walls 
of Drosera contracting, considering their high state of or- 
ganisation; as shown in the case of the glands by their 
power of absorption and secretion, and by being exquisitely 
sensitive so as to be affected by the pressure of the most 
minute particles. The cell-walls of the pedicels also allow 
various impulses to pass through them, inducing movement, 
increased secretion and aggregation. On the whole the be- 
lief that the walls of certain cells contract, some of their 
contained fluid being at the same time forced outwards, per- 
haps accords best with the observed facts. If this view is 
rejected, the next most probable one is that the fluid contents 
of the cells shrink, owing to a change in their molecular 
state, with the consequent closing in of the walls. Anyhow, 



SIO DROSERA ROTUNDIFOLIA. [Chap. X. 

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, 
showing that the exciting cause of the aggregating process 
has then quite ceased. Exposure to carbonic acid causes 
both the latter process and the motor impulse to travel very 
slowly down the tentacles. We know that the aggregating 
process is delayed in passing through the cell-walls, and we 
have good reason to believe that this holds good with the 
motor impulse; for we can thus understand the different 
rates of its transmission in a longitudinal and transverse 
line across the disc. Under a high power the first sign of 
aggregation is the appearance of a cloud, and soon after- 
wards 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 ap- 
proach each other, and the cell-wall would contract. 

To this view it may with truth be objected that when 
leaves are immersed in various strong solutions, or are sub- 

" [Bee Gnnllnor's Intorostlnj? mnde innrkR on the lower Burface 

rmpor " On the ('ontrnctlllty of and fonnd that when tlie curva- 

he ProtopInBin of Plant Cells " Hire take.s place, the distance be- 

(' I'roo. R. Soc.' Nov. 24, 1887, tween the iKarks on what J)e- 

vol. xllll.). In which he frlves evi- comes the convex surface of the 

dence tendhiK to show that the leaf or tentacle Increases. When 

cnrvature of the tentacles of the leaf opens, or the tentacle 

DroMorn Is brought about by con- BtralRhtens. the distance between 

traction of the protoplnflin. the marks does not return to 

liatalln (' Flora.' 1877) experl- what It was at first, and this 

mented on the curvature of the pornianent Increase shows that 

tentacles as well as on the bend- the oirvntnre Is connected with 

log of the blade of the leaf. Ue actual growth. F. D.] 



Chap.x.] re-expansion of the tentacles. 211 

jected to a heat of above 130" Fahr. (54.4 Cent.), aggre- 
gation ensues, but there is no movement. Again, various 
acids and some fluids cause rapid movement, but no aggre- 
gation, 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 an- 
other 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 Re-expansion of the Tentacles. This movement is 
always slow and gradual. When the centre of the leaf is ex- 
cited, or a leaf is immersed in a proper solution, all the ten- 
tacles bend directly towards the centre, and afterwards di- 
rectly 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 direc- 
tion; when they afterwards re-expand, they bend obliquely 
back, so as to recover their original positions. The tentacles 
farthest from an excited point, wherever they may be, are 
the last and the least affected, and probably in consequence 
of this they are the first to re-expand. The bent portion of 
a closely inflected tentacle is in a state of active contraction, 
as shown by the following experiment. Meat was placed on 
a leaf, and after the tentacles were closely inflected and had 
quite ceased to move, narrow strips of the disc, with a few of 
the outer tentacles attached to it, were cut off and laid on 
one side under the microscope. After several failures, I suc- 
ceeded 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 sur- 
face must therefore have previously been in a state of ten- 
sion, suflScient to counterbalance that of the concave surface, 
which, when free, curled into a complete ring. 

The tentacles of an expanded and unexcited leaf are 
15 



212 DROSERA ROTUNDIFOLIA. [Chap. X. 

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 bal- 
ancing 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 indi- 
cates that the tension of the outer surface is mechanical, 
whilst that of the inner surface is vital, and is instantly de- 
stroyed by the boiling water. We can thus also understand 
why the tentacles as they grow old and feeble slowly become 
much reflexed. If a leaf with its tentacles closely inflected 
is dipped into boiling water, these rise up a little, but by no 
means fully re-expand. This may be owing to the heat 
quickly destroying the tension and elasticity of the cells of 
the convex surface; but I can hardly believe that their ten- 
sion, at any one time, would suflace to carry back the ten- 
tacles 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 this 
chapter will be given at the close of the next chapter. 



Chap. XL] GENERAL SUMMARY. 213 



CHAPTER XI. 

RECAPITULATION OF THE CHIEF OBSERVATIONS ON 
DROSERA ROTUNDIFOLIA.' 

As summaries have been given to most of the chapters, it 
will be sufficient here to recapitulate, as briefly as I can, the 
chief points. In the first chapter a preliminary sketch was 
given of the structure of the leaves, and of the manner in 
which they capture insects. This is effected by drops of 
extremely viscid fluid surrounding the glands and by the 
inward movement of the tentacles. As the plants gain most 
of their nutriment by this means, their roots are very poorly 
developed; and they often grow in places where hardly any 
other plant except mosses can exist. The glands have the 
power of absorption, besides that of secretion. They are ex- 
tremely sensitive to various stimulants, namely repeated 
touches, the pressure of minute particles, the absorption of 
animal matter and of various fluids, heat, and galvanic ac- 
tion. 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 sum- 
mit of the same tentacle, and from one or more glands of the 
neighbouring tentacles. Tentacles, when inflected, re-ex- 
pand after a time, and during this process the glands secrete 
less copiously or become dry. As soon as they begin to se- 
crete again, the tentacles are ready to re-act; and this may 
be repeated at least three, probably many more times. 

> [The reader consulting this the list of additions In the pres- 
chapter. without hnvlns road the ent e<)ltion given at the beginning 
foregoing pages should look at of the book. B\ D.] 



214 DROSERA ROTUNDIFOLIA. [Cuap. XI. 

It was shown in the second chapter that animal sub- 
stances placed on the discs cause much more prompt and en- 
ergetic inflection than do inorganic bodies of the same size, 
or mere mechanical irritation; but there is 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 tAt5 of 
an inch (.203 mm.) in length, and weighing only rF7T5 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 
surrounding 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 in- 
sensible to the weight and repeated blows of drops of heavy 
rain, and the plants are thus likewise saved from much iise- 
Icss 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 



Chap. XI.] GENERAL SUMMARY. 215 

in the cells of the glands, the contents of which first become 
cloudy; and this has been observed within 10 s. after a 
gland has been excited. Granules just resolvable under a 
very high power soon appear, sometimes within a minute, in 
the cells beneath the glands; and these then aggregate into 
minute spheres. The process afterwards travels down the 
tentacles, being arrested for a short time at each transverse 
partition. The small spheres coalesce into larger spheres, or 
into oval, club-headed, thread- 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 
three times, the pressure of minute inorganic particles, the 
absorption of various fluids, even long immersion in distilled 
water, exosmose, and heat. Of the many stimulants tried, 
carbonate of ammonia is the most energetic and acts the 
quickest; a dose of ttAutt of a grain (.00048 mg.) given to 
a single gland suffices to cause in one hour well-marked 
aggregation in the upper cells of the tentacle. The process 
goes on only as long as the protoplasm is in a living, vigor- 
ous, 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 trans- 



216 DROSERA ROTUNDIFOLIA. [Chap. XI. 

mit centrifugally an influence up the pedicels of the ex- 
terior tentacles to their glands; but the actual process of 
aggregation travels centripetally, from the glands of the 
exterior tentacles down their pedicels. The exciting in- 
fluence,' therefore, which is transmitted from one part of 
the leaf to another must be different from that which actu- 
ally induces aggregation. The process does not depend on 
the glands secreting more copiously than they did before; 
and is independent of the inflection of the tentacles. It 
continues as long as the tentacles remain inflected, and as 
soon as these are fully re-expanded, the little masses of pro- 
toplasm 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 evi- 
dently 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 rrhnr of a grain 
and largely supported by the dense secretion, for this ex- 
cessively 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 appear* 
ance, distinguishable even by the naked eye. 

In the fourth chapter it was shown that leaves placed for 
a short time in water at a temperature of 110 Fahr. (43'*.3 
Cent.) become somewhat inflected; they are thus also ren- 
dered more sensitive to the action of meat than they were 
before. If exposed to a temperature of between 115** and 
125* (46**.l Sl^.e Cent.), they are quickly inflected, and 
their protoplasm undergoes aggregation; when afterwards 
placed in cold water, they re-expand. Exposed to 130* 



Chap. XI.] GENERAL SUMMARY. 217 

(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 pro- 
toplasm in movement. In other leaves treated in the same 
manner, and then immersed in a solution of carbonate of 
ammonia, strong aggregation ensued. Leaves placed in 
cold water, after an exposure to so high a temperature as 
145 (62.7 Cent.), sometimes become slightly, though 
slowly inflected; and afterwards have the contents of their 
cells strongly aggregated by carbonate of ammonia. But 
the duration of the immersion is an important element, for 
if left in water at 145 (62.7 Cent.), or only at 140 (60 
Cent.), until it becomes cool, thej' are killed, and the con- 
tents of the glands are rendered white and opaque. This 
latter result seems to be due to the coagulation of the albu- 
men, and was almost always caused by even a short exposure 
to 150 (65.5 Cent.) ; but different leaves, and even the 
separate cells in the same tentacle, differ considerably in 
their power of resisting heat. Unless the heat has been suf- 
ficient to coagulate the albumen, carbonate of ammonia sub- 
sequently induces aggregation. 

In the fifth chapter the results of placing drops of vari- 
ous nitrogenous and non-nitrogenous organic fluids on the 
discs of leaves were given, and it was shown that they detect 
with almost unerring certainty the presence of nitrogen. A 
decoction of green peas or of fresh cabbage-leaves acts al- 
most 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 cab- 
bage-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 diges- 
tion, and that the glands absorb the digested matter, are 
given in detail in the sixth chapter. These are, perhaps, the 
most interesting of all my observations on Drosera, as no 
such power was before distinctly known to exist in the vege- 
table kingdom. It is likewise an interesting fact that the 
glands of the disc, when irritated, should transmit some in- 



218 DROSERA ROTUNDIFOLIA. [Chap. XI. 

fluence to the glands of the exterior tentacles, causing them 
to secrete 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 indis- 
pensable for digestion, and so it is with the secretion of 
Drosera. When the ptomach of an animal is mechanically 
irritated, it secretes an acid, and when particles of glass or 
other such objects were placed on the glands of Drosera, the 
secretion, and that of the surrounding and untouched 
glands, was increased in quantity and became acid. But ac- 
cording to Schiff, the stomach of an animal does not secrete 
its proper ferment, pepsin, until certain substances, which 
he calls peptogenes, are absorbed; and it appears from my 
experiments that some matter must be absorbed by the 
glands of Drosera before they secrete their proper ferment. 
That the secretion does contain a ferment which acts only 
in the presence of an acid on solid animal matter, was clearly 
proved by adding minute doses of an alkali, which entirely 
arrested the process of digestion, this immediately recom- 
mencing as soon as the alkali was neutralised by a little weak 
hydrochloric acid. From trials made with a large number 
of substances, it was found that those which the secretion of 
Drosera dissolves completely, or partially, or not at all, are 
acted on in exactly the same manner by gastric juice. We 
may therefore conclude that the ferment of Drosera is close- 
ly 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 se- 
cretion of Drosera, and subsequent absorption, is, perhaps, 
one of the most striking cases. But it is not really more 
remarkable than the digestion of meat, which is dissolved by 
this secretion in the same manner and by the same stages as 
by gastric juice. The secretion dissolves bone, and even the 



Chap. XL] GENERAL SUMMARY. 219 

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 de- 
composed and free acid is present, and then the fibrous basis 
is quickly dissolved. Lastly, the secretion attacks and dis- 
solves 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 
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 efiiciency of only three 
salts of ammonia was carefully determined, namely the car- 
bonate, nitrate, and phosphate. The experiments were made 
by placing half-minims (.0296 c.c.) of the solutions of differ- 
ent strengths on the discs of the leaves, by applying a min- 
ute drop (about the yV 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 
exx)eriments 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 d^ree. 

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 tiv of a grain (.0675 mg.) is the least quantity 
which, when placed on the glands of the disc, excites the 
exterior tentacles to bend inwards. But a minute drop, con- 
taining irirnr of a grain (.00445 mg.), if applied for a few 
seconds to the secretion surrounding a gland, causes the 
inflection of the same tentacle. When a highly sensitive 
leaf is immersed in a solution, and there is ample time for 
absorption, the yrsSniir of a grain (.00024 mg.) is sufficient 
to excite a single tentacle into movement. 



220 DROSERA ROTUNDIFOLIA. [Chap. XL 

The nitrate of ammonia induces aggr^ation of the pro- 
toplasm much less quickly than the carbonate, but is more 
potent in causing inflection. A drop containing Yitv 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 yVffv of a grain caused 
only a few of these tentacles to bend, but affected rather 
more plainly the blade. A minute drop applied as before, 
and containing ^shsv of a grain (.0025 mg.), caused the 
tentacle bearing this gland to bend. By the immersion of 
whole leaves, it was proved that the absorption by a single 
gland of ^T^sjtv of a grain (.0000937 mg.) was sufficient to 
set the same tentacle into movement. 

The phosphate of ammonia is much more powerful than 
the nitrate. A Srop containing Wijs of a grain (.0169 mg.) 
placed on the disc of a sensitive leaf causes most of the ex- 
terior tentacles to be inflected, as well as the blade of the 
leaf. A minute drop containing jzi^Tsv of a grain (.000423 
mg.), applied for a few seconds to a gland, acts, as shown by 
the movement of the tentacle. When a leaf is immersed in 
thirty minims (1.7748 c.c.) of a solution of one part by 
weight of the salt to 21,875,000 of water, the absorption by 
a gland of only the Trr^vjnns of a 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 the 
one-thirty-millionth of a grain of the efficient elements 
could have been absorbed. There is nothing remarkable in 
such minute quantities being absorbed by the glands, for all 
physiologists admit that the salts of ammonia, which must 
be brought in still smaller quantity by a single shower of 
rain to the roots, are absorbed by them. Nor is it surprising 
that Drosera should be enabled to profit by the absorption of 
these salts, for yeast and other low fungoid forms flourish in 
solutions of ammonia, if the other necessary elements are 
present. But it is an astonishing fact, on which I will not 
here again enlarge, that so inconceivably minute a quantity 
as the one-twenty-millionth of a grain of phosphate of am- 
monia should induce some change in a gland of Drosera, 
sufficient to cause a motor impulse to be sent down the 



Chap. XL] GENERAL SUMMARY. 221 

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 pres- 
sure of a minute bit of hair, supported by the dense secre- 
tion, should quickly cause conspicuous movement. More- 
over, this extreme sensitiveness, exceeding that of the most 
delicate part of the human body, as well as the power of 
transmitting various impulses from one part of the leaf to 
another, have been acquired without the intervention of any 
nervous system. 

As few plants are at present known to possess glands 
specially adapted for absorption, it seemed worth while to 
try the effects on Drosera of various other salts, besides 
those of ammonia, and of various acids. Their action, as 
described in the eighth chapter, does not correspond at all 
strictly with their chemical affinities, as inferred from the 
classification commonly followed. The nature of the base is 
far more influential than that of the acid ; and this is known 
to hold good with animals. For instance, nine salts of so- 
dium 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 poi- 
sonous. 

Most of the acids which were tried, though much diluted 
(one part to 437 of water), and given in small doses, acted 
powerfully on Drosera; nineteen, out of the twenty-four, 
causing the tentacles to be more or less inflected. Most of 
them, even the organic acids, are poisonous, often highly so; 
and this is remarkable, as the juices of so many plants con- 
tain 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 



222 DROSERA ROTUNDIFOLIA. [Chap. XI. 

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 with- 
in 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; where- 
as acetic acid of the same strength acts most powerfully and 
is poisonous. Lactic acid is also poisonous, but causes in- 
flection 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 ani- 
mals, produce no effect on Drosera, we may infer that the 
extreme sensibility of the glands, and their power of trans- 
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 im- 
mersion in the poison of the cobra-snake does not in the 
least check, but rather stimulates, the spontaneous move- 
ment of the protoplasm in the cells of the tentacles. Solu- 
tions 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 essen- 
tial oils, for they cause rapid and strong inflection. Alcohol 
is not a stimulant. The vapours of camphor, alcohol, chloro- 
form, sulphuric and nitric ether, are poisonous in moder- 
ately large doses, but in small doses serve as narcotics or 
anaesthetics, greatly delaying the subsequent action of 
meat. But some of these vapours also act as stimulants, ex- 
citing rapid, almost spasmodic movements in the tentacles. 
Carbonic acid is likewise a narcotic, and retards the aggre- 
gation of the protoplasm when carbonate of ammonia is sub- 
sequently given. The first access of air to plants which 
have been immersed in this gas sometimes acts as a stimu- 
lant and induces movement. But, as before remarked, a 



Chap. XL] GENERAL SUMMARY. 223 

special pharmacopoeia would be necessary to describe the di- 
versified 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 innuences, pro- 
ceeding 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 trans- 
verse line across the disc. The impulse proceeding from the 
glands of the extreme marginal tentacles does not seem to 
have force enough to affect the adjoining tentacles; and this 
may be in part due to their length. The impulse from the 
glands of the next few inner rows spreads chiefly to the 
tentacles on each side and towards the centre of the leaf ; but 
that proceeding from the glands of the shorter tentacles on 
the disc radiates almost equally on all sides. 

When a gland is strongly excited by the quantity or 
quality of the substance placed on it, the motor impulse 
travels farther than from one slightly excited; and if sev- 
eral glands are simultaneously excited, the impulses from all 
unite and spread still farther. As soon as a gland is excited, 
it discharges an impulse which extends to a considerable dis- 
tance; but afterwards, whilst the gland is secreting and ab- 
sorbing, 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 ex- 



224 DROSERA ROTUNDIFOLU. [Cu ap. \ I. 

cepted, 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 i}oint of excitement, wherever this may be 
seated. Thj^ 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 
diflFerent sides of the surrounding tentacles must be acted on, 
in order that all should bend with precision to the point of 
excitement. 

The motor impulse, as it spreads from one or more glands 
across the disc, enters the bases of the surrounding tentacles, 
and immediately acts on the bending place. It does not in 
the first place proceed up the tentacles to the glands, exciting 
them to reflect back an impulse to their bases. Nevertheless, 
some influence is sent up to the glands, as their secretion is 
soon increased and rendered acid ; and then the glands, be- 
ing thus excited, send back some other influence (not de- 
pendent on increased secretion, nor on the inflection of the 
tentacles), causing the protoplasm to aggregate in cell be- 
neath cell. This may be called a reflex action, though prob- 
ably very diflFerent 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 na- 
ture to the aggregating process; and that this causes the 
molecules 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-ex- 
pansion of the tentacles is largely due to the elasticity of 
their outer cells, which comes into play as soon as those 
on the inner side cease contracting with prepotent force ; but 



Chap. XI.] GENERAL SUMMARY. 225 

we have reason to suspect that fluid is continually and slow- 
ly attracted into the outer cells during the act of re-expan- 
sion, thus increasing their tension.' 

I have now given a brief recapitulation of the chief 
I)oints observed by me, with respect to the structure, move- 
ments, constitution, and habits of Drosera rotundifolia; and 
we see how little has been made out in comparison with what 
remains unexplained and imknown. 

* [Increase of fluid In the ex- to prevent re-expansion, not to 
ternal (convex) cells would tend facilitate it. F. D.] 



226 DROSERA ANGLICA. [Chap. XII. 



CHAPTER XII. 

ON THE STRUCTURE AND MOVEMENTS OP SOME OTHER SPECIES 
OF DROSERA. 

Drosera anglica Dronera intermedia Drosera capensia Drosera gpathtdata 
Drosera Jilifurmin Drosera binata Cuucluding remarks. 

I EXAMINED six Other species of Drosera, some of them in- 
habitants of distant countries, chiefly for the sake of ascer- 
taining whether they caught insects. This seemed the more 
necessary as the leaves of some of the species differ to an 
extraordinary degree in shape from the rounded ones of 
Drosera rotundifolia. In functional powers, however, they 
differ very little. 

Drosera anglica (Hudson).' The leaves of this species, which 
was sent to me from Ireland, are much elongated, and gradually 
widen from the footstalk to the bluntly pointed apex. They stand 
almost erect, and their blades sometimes exceed 1 inch in length, 
whilst their breadth is only the | of an inch. The glands of all 
the tentacles have the same structure, so that the extreme mar- 
ginal ones do not differ from the others, as in the case of Drosera 
rotundifolia. When they are irritated by being roughly touched, 
or by the pressure of minute inorganic particles, or by contact with 
animal matter, or by the absorption of carbonate of ammonia, the 
tentacles become inflected; the basal portion being the chief seat 
of movement. Cutting or pricking the blade of the leaf did not ex- 
cite any movement. They frequently captured 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 fire, were placed, by the aid of an 
instrument which had been immersed in boiling water, on five 
glands; these superfluous precautions hnving been taken on ac- 
count of M. Ziegler's statements. One of the particles of cinder 
caused some inflection in 8 hrs. 45 m., as did after 23 hrs. the other 
particle of cinder, the bit of thread, and both bits of cork. Three 

' Mrw. Treat has given nn ex- Ih n synonym In pnrt of Dronrra 

cellent account In ' The Anioricnn anglicn). of Droacra rotundifolia 

NntumllHt,' DecembPf. 1873. p. uud fiUformit. 
706, of Drotcra longifoUa (which 



Chap. XII.] DROSERA CAPENSIS. 227 

glands were touched half a dozen times with a needle; one of the 
tentacles became well inflected in 17 m., and re-expanded after 24 
hrs.; the two others never moved. The homogeneous fluid within 
the cells of the tentacles undergoes aggregation after these have 
become inflected ; especially if given a solution of carbonate of am- 
monia; and I observed the usual movements in the masses of pro- 
toplasm. In one case, aggr^ation 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 rot undi folia. 

If an insect is placed on the central glands, or has been natu- 
rally caught there, the apex of the leaf curls inwards. For in- 
stance, dead flies were placed on three leaves near their bases, 
and after 24 hrs. the previously straight apices were curled com- 
pletely 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 difl"er- 
ence between this species and Drosera rot undi folia. 

Drosera intermedia (Hayne). This species is quite as com- 
mon in some parts of England as Drosera rotundifoUa. It difl"er3 
from Drosera anylica, as far as the leaves are concerned, only in 
their smaller size, and in their tips being generally a little reflexed. 
They capture a large number of insects. The tentacles are excited 
into movement by all the causes above specified; and aggregation 
ensues, 'with movement of the protoplasmic masses. I have seen, 
through a lens, a tentacle beginning to bend in less than a minute 
after a particle of raw meat had been placed on the gland. The 
apex of the leaf curls over an exciting object as in the case of 
Drosera anylica. Acid secretion is copiously poured over captured 
insects. A leaf which had embraced a fly with all its tentacles re- 
expanded after nearly three days. 

Drosera capensis. This species, a native of the Cape of Good 
Hope, was sent to me by Dr. Hooker. The leaves are elongated, 
slightly concave along the middle and taper towards the apex, 
which is bluntly pointed and reflexed. They rise from an almost 
woody axis, and their greatest peculiarity consists in their folia- 
ceous 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 in- 
sects, than the other 8f>ecies of the genus. Nevertheless, the ten- 
tacles are crowded together on the disc, and are extremely numer- 
ous; those on the margins being much longer than the central 
ones. All the glands have the same form; their secretion is ex- 
tremely viscid and acid. 

The specimen which I examined had only just recovered from a 
weak state of health. This may account for the tentacles moving 
very slowly when particles of meat were placed on the glands, and 
perhaps for my never succeeding in causing any movement by 
repeatedly touching them with a needle. But with all the species 
16 



DROSERA FILIFORMIS. [Chap. XIL 

of the genus this latter stimulus is the least effective of any. Par- 
ticles of gla.s8, cork, and coal-c-inders, were placed on the glands of 
six tentacles; and one alone moved after an interval of 2 hrs. 3U 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 Trhjsv o' 
a grain (.000502 mg.) of the salt. Fragments of Hies 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. Uy 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 wa 
placed on the foliaceous footstalk, but produced no elTect. 

Drosera spathtilata (sent to me by Dr. Hooker). I made only 
a few observations on this Australian species, which has long, nar- 
row leaves, gradually widening towards their tips. The glands of 
the extreme marginal tentacles are elongated and difl'er from the 
others, as in the case of Drosera rotundifolia. A fly was placed on 
a leaf, and in 18 hrs. it was embraced by the adjoining tentacles. 
Gum-water dropped on several leaves produced no effect. A frag- 
ment of a leaf was immersed in a few drops of a solution of one 
part of carbonate of ammonia to 140 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 hrs. some marginal ten- 
tacles 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. j^ 
of a grain or .202 mg.) was too powerful, for in the course oif 23 hrs. 
the leaf died. 

Drosera filiformis. This North American species grows in 
such abundance in parts of New Jersey as almost to cover the 
ground. It catches, according to Mrs. Treat,* an extraordinary 
number of small and large insects, even great flies of the genus 
Asilus, moths, and butterflies. The specimen which I examined, 
sent me by Dr. Hooker, had thread-like leaves, from to 12 inches 
in length, with the upper surface convex and the lower flat and 
slightly channelled. The whole convex surface, down to the roots 
for there is no distinct footstalk is covered with short gland- 
bearing tentacles, those on the margins being the longest and re- 
flexed. Bits of meat placed on the ^ands of some tentacles caused 
them to be slightly inflected in 20 m. ; but the plant was not in a 
vigorous state. After 6 hrs. they moved through an angle of 90, 
and in 24 hrs. reached the centre. The surrounding tentacles by 

* ' American Natarallst/ Dec. 1878, p. 700i. 



Chap. XII.] DROSERA BINATA. 229 

this time began to curve inwards. Ultimately a large drop of 
extremely viscid, slightly acid secretion was poured over the meat 
from the united glands. Several other glands were touched with a 
little saliva, and the tentacles became incurved in under 1 hr., 
and re-expanded after 18 hrs. Particles of glass, cork, cinders, 
thread, and gold-leaf, were placed on numerous glands on two 
leaves; in about 1 hr. four tentacles became curved, and four 
others after an additional interval of 2 hrs. 30 m. I never once 
succeeded in causing any movement by repeatedly touching the 
glands with a needle; and Mrs. Treat made similar trials for me 
with no success. Small flies were placed on several leaves near 
their tips, but the thread-like blade became only on one occasion 
very slightly bent, directly beneath the insect. Perhaps this indi- 
cates 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 Mre. Treat. 

Drosera binata (or dichotoma).* I am much indebted to Lady 
Dorothy Nevill for a fine plant of this almost gigantic Australian 
species, which difTers in some interesting points from those previ- 
ously described. In this specimen the rush-like footstalks of the 
leaves were 20 inches in length. The blade bifurcates at its junc- 
tion 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 7i inches long, so that the entire 
leaf, including the footstalk, was above 27 inches in length. Both 
surfaces are slightly hollowed out. The upper surface is covered 
with tentacles arranged in alternate rows; those in the middle 
being short and crowded together, those towards the margins 
longer, even twice or thrice as long as the blade is broad. The 
glands of the exterior tentacles are of a much darker red than those 
of the central ones. The pedicels of all are green. The apex of the 
blade is attenuated, and bears very long tentacles. Mr. Copland 
informs me that the leaves of a plant which he kept for some years 
were generally covered with captured insects before they withered. 

The leaves do not differ in essential points of structure or of 
function from those of the previously described species. Bits of 
meat or a little saliva placed on the glands of the exterior tentacles 
caused well-marked movement in 3 m., and particles of glass acted 
in 4 m. The tentacles ^vith the latter particles re-expanded after 
22 hrs. A piece of leaf immersed in a few drops of a solution of 
one part of carbonate of ammonia to 437 of water had all the 
glands blackened and all the tentacles inflected in 5 m. A bit of 
raw meat, placed on several glands in the medial furrow, was well 
clasped in 2 hrs. 10 m. by the 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 

* [8e B. Morren, ' Bull, de pinnt Is fli^nred. and some expert- 
I'Acad. Royale de Belgique,' 2 meuts described. F. D.J 
sCrle, .torn. 40, 1875, where the 



230 DROSERA BINATA. [Chap. XII. 

Bome 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 
sufficiently for any motor impulse to be sent to the outer tentacles. 
In no case was the blade of the leaf, even the attenuated apex, at 
all inflected. 

On both the upper and lower surface of the blade there are 
numerous minute, almost se.sile 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 footstalks, 
but they are smaller and often in a shrivelled condition. The mi- 
nute glands on the blade can absorb rapidly: thus, a piece of leaf 
was immersed in a solution of one part of carbonate of ammonia 
to 218 of water (2 gr. to 1 oz.), and in 5 m. they were all so much 
darkened as to be almost black, with their contents aggregated. 
They do not, as far as I could observe, secrete spontaneously; but 
in between 2 and 3 hrs. after a leaf had been rubbed with a bit of 
raw meat moistened with saliva, they seemed to be secreting 
freely; and this conclusion was afterwards supported by other 
appearances. They are, therefore, homologous with the sessile 
glands hereafter to be described on the leaves of Dioneea and Droso- 
phyllum. In this latter genus they are associated, as in the present 
case, with glands which secrete spontaneously, that is, without be- 
ing excited. 

Drosera binata presents another and more remarkable peculiar- 
ity, 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 aggregated, when a leaf was placed in a little 
solution of one part of carbonate of ammonia to 437 of water. 
These dorsal tentacles are short, not being nearly so long as the 
marginal ones on the upper surface; some of them are so short 
as almost to graduate into the minute sessile glands. Their pres- 
ence, number, and size, vary on different leaves, and they are ar- 
ranged rather irregularly. On the back of one leaf I counted as 
many as twenty-one along one side. 

These dorsal tentacles differ in one important respect from those 
on the upper surface, namely, in not possessing any power of 
movement, in whatever manner they may be stimulated. Thus, 
portions of four leaves were placed at different times in solutions 
of carbonate of ammonia (one part to 437 or 218 of water), and all 
the tentacles on the upper surface soon became closely inflected; 
but the dorsal ones did not move, though the leaves were left in 
the solution for many hours, and though their glands from their 
blackened colour had obviously absorlMMl some of the salt. Rather 
young leaves should be selected for such trials, for the dorsal ten- 
tacles, 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 



Chap. XII.] CONCLUDING REMARKS. 231 

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 in- 
sects can be caught. Although they have no power of movement, 
they are probably of some use by absorbing animal matter from 
any minute insect which may be caught by them, and by absorbing 
ammonia from the rain-water. But their varying presence and 
size, and their irregular position, indicate that they are not of 
much service, and that they are tending towards abortion. In a 
future chapter we shall see that Drosophyllum, with its elongated 
leaves, probably represents the condition of an early progenitor of 
the genus Drosera; and none of the tentacles of Drosophyllum, 
neither those on the upper nor lower surface of the leaves, are 
capable of movement when excited, though they capture numer- 
ous insects, which serve as nutriment. Therefore it seems that 
Drosera binata has retained remnants of certain ancestral charac- 
ters namely, a few motionless tentacles on the backs of the leaves, 
and fairly well developed sessile glands which have been lost by 
most or all of the other species of the genus. 

Concluding Remarks. From what we have now seen, 
there can be little doubt that most or probably all the species 
of Drosera are adapted for catching insects by nearly the 
same means. Besides the two Australian species above de- 
scribed, 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 phe- 
nomenon is manifested by an Indian species, D. lunaia, and 
by several of those of the Cape of Good Hope, especially by 
D. trinervis." Another Australian species, Drosera hetero- 
phylla (made by Lindlcy into a distinct genus, Sondera) is 
remarkable from its peculiarly shaped leaves, but I know 
nothing of its i>ower 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 surface and the edges of the cups are 
studded with tentacles, which include fibro-vascular bundles, 
rather different from those seen by me in any other species: 
for some of the vessels are barred and punctured, instead of 
being spiral. The glands secrete copiously, judging from 
the quantity of dried secretion adhering to them. 

* Gardener's Chronicle,' 1874, p. 209. 



232 DIONiEA MUSCIPULA. [Chap. XIII. 



CHAPTER Xin. 

DIONi{:A MUSCTPULA. 

Structure of the leaves Sensitiveness of the filaments Rapid movement 
of the lobes caused by irritation of the filameutB 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 cap- 
tured Use of the marginal spikes Kinds of insects captured ^Tho 
transmission of the motor impulse and mechanism of the movements 
Ke-czpansion of the lobes. 

This plant, commonly called Venus' fly-trap, from the 
rapidity and force of its movements, is one of the most won- 
derful in the world.' It is a member of the small family of 
the Droseraceffi, 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 gar- 
dener, 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.* The form of the bilobcd leaf, with its 
foliaceous footstalk, is shown in the accompanying drawing 
(Fig. 12). The two lobes stand at rather less than a right 
angle to each other. Three minute pointed processes or fila- 
ments, placed triangularly, project from the upper surfaces 
of both; but I have seen two leaves with four filaments on 
each side, and another with only two. These filaments are 
remarkable from their extreme sensitiveness to a touch, as 
shown not by their own movement, but by that of the lobes. 

* Dr. Hooker, In hlft addroBii to pnrt to ropont them. [A good ac- 

the British Assoclntlon at Bel- count of the onrly Ilt)>riitiire is 

fast, 1874, has given ho full an given l>y Kiirts in Relchert and 

blntorionl account of the obsorvn- l)u Bols-Reymond's * Archlv.' 

tlons which have been publlshi^d 1876. F. I>. ) 

on the habits of this plant, that ' ' Gardener's Chronicle,' 1874, 

it would l>e superfluous on my p. 464. 



Chap. XIII.] SENSITIVENESS OF FILAMENTS. 233 

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 strong- 
ly developed and prominent. 

The upper surface * of the leaf is thickly covered, except- 
ing towards the margins, with minute glands of a reddish or 
purplish colour, the rest of the leaf being green. There are 
no glands on the spikes, or on the foliaceous footstalk. The 
glands are formed of from twenty to thirty polygonal cells, 




Fro. 12. 

(Dioniea mnscipula.) 

Leaf viewed laterally in its expanded state. 

filled with purple fluid. Their upper surface is convex. 
They stand on very short pedicels, into which spiral vessels 
do not enter, in which respect they differ from the tentacles 
of Drosera. They secrete, but only when excited by the 
absorption of certain matters; and they have the power of 
absorption. Minute projections, formed of eight divergent 
arms of a reddish-brown or orange colour, and appearing 
under the microscope like elegant little flowers, are scattered 

[A. Fraustaclt, In his Rreslau tlons the same fact. It Is easy to 
dissertation on Dlonaea (Mar. see that the lower surface of the 
1876) states that the upper sur- leaf is a better one for the de- 
face of the leaf is devoid of velopment of stoinata than the 
stomata. C. De Cnndolle, upper surface, which Is liable to 
' Archives des Sciences IMiys. et l)e constantly bathed In secre- 
Nat.' Geneva, April, 1876, men- tlon. F. D.] 



234 DION-ffiA MUSCIPULA. [Chip. XIII. 

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 papillae on the leaves of Drosera rotundifolia. 
There are also a few very minute, simple, pointed hairs,* 
about TT^ of an inch (.0148 mm.) in length on the backs 
of the leaves. 

The sensitive filaments' are formed of several rows of 
elongated cells, filled with purplish fluid. They are a little 
above the jV 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. Toward the base there is constriction, formed of 
broader cells, beneath which there is an articulation, sup- 
ported on an enlarged base, consisting of diflferently shaped 
polygonal cells. As the filaments project at right angles to 
the surface of the leaf, they would have been liable to be 
broken whenever the lobes closed together, had it not been 
for the articulation which allows them to bend flat down. 

These filaments, from their tips to their bases,* are ex- 
quisitely sensitive to a momentary touch. It is scarcely 
possible to touch them ever so lightly or quickly with any 
hard object without causing the lobes to close. A piece of 
very delicate human hair, 2i inches in length, held dangling 
over a filament, and swayed to and fro so as to touch it, did 
not excite any movement. But when a rather thick cotton 
thread of the same length was similarly swayed, the lobes 
closed. Pinches of fine wheaten flour, dropped from a 
height, produced no effect. The above-mentioned hair was 
then fixed into a handle, and cut off so that 1 inch projected ; 
this length being sufficiently rigid to support itself in a 
nearly horizontal line. The extremity was then brought by a 
slow movement laterally into contact with the tip of a fila- 

* [ThoRc hairs worn nbRont In [Ratnlln (' Flora.' 1877) auotes 
the p'rliii'nH 'xninlnMl by Knrtz Oiidomnns (U. Academy of Sol- 
(Relchert ami I)u Hols-Keymond's enooa of Anisterdam. IS.'iO). to the 
Archlv.' 17C>. F. D.] effect that the tllanicnta are 

(Both FrauBtadt and De Can- much more senKltlve at the base 
dolle describe the structure of than elsewhere. Bntallu confirms 
these filaments, and have shown the fact fmm his own observa- 
thnt their morphological rank Is tlons. F. D.] 

that of " emergencies." F. D.] 



Chap. XIII.] SENSITIVENESS OF FILAMENTS. 235 

ment, 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 
considerable force, and no movement ensues. This singular 
difference 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 the two plants. If a minute insect 
alights with its delicate feet on the glands of Drosera, it is 
caught by the viscid secretion, and the slight, though pro- 
longed 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 Dionjea are not viscid, 
and the capture of insects can be assured only by their sen- 
sitiveness 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 am- 
monia (one part to 146 of water), placed on two filaments, 
not producing any effect on the contents of their cells, nor 
causing the lobes to close. When, however, a small portion 
of a leaf with an attached filament was cut off and immersed 
in the same solution, the fluid within the basal cells became 

^ [Munk(Relchert and Du Bol8- removed. It l8 remarkable that 

Reymond's ' Archlv.' 187(5, p. 10.">) the ebanee from a damp to a dry 

states that the leaves of his atmosphere should produce this 

plants frequently closeil when eflfect. F. D.] 
the bell-Jar covering them was 



236 DION-ffiA MUSCIPULA. [Cdap. XIII. 

almost instantly aggregated into purplish or colourless, ir- 
regularly shaped masses of matter. The process of aggrega- 
tion gradually travelled up the filaments from cell to cell to 
their extremities, that is in a reverse course to what occurs 
in the tentacles of Drosera when their glands have been ex- 
cited. Several other filaments were cut off close to their 
bases, and left for 1 hr. 30 m. in a weak 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 like- 
wise causes aggregation. Nor is it rare to find the contents 
of a few of the terminal cells in a spontaneously aggr^ated 
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 travel- 
ling 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 Dioncea behave exactly like the tentacles of Drosera. 

Notwithstanding this similarity there is one remarkable 
difference. The tentacles of Drosera, after their glands have 
been repeatedly touched, or a particle of any kind has been 
placed on them, become inflected and strongly aggregated. 
No such effect is produced by touching the filaments of 
Dionffia; 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 con- 
tents 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 (' Archlre* Ipiifcth do not stlmulntp the leaf, 

de 8c. I'hys. et Nat.* Geneva. but that It may bo mndo to cloae 

April. 187rt HtatoB that drops of by a current of water directed at 

water which Infringe on the flla- right angles to the filament. F. 

meota In the direction of their D.] 



Chap. XIII.] SENSITIVENESS OP FILAMENTS. 237 

sensitive. No doubt, as in the case of Drosera, the plant is 
indiflFerent to the heaviest shower of rain. Drops of a solu- 
tion of half an ounce of sugar to a fluid ounce of water were 
repeatedly allowed to fall from a height on the filaments, but 
produced no effect, unless they adhered to them. Again, I 
blew many times through a fine pointed tube with my utmost 
force against the filaments without any effect; such blowing 
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 59 and 65 (15 to 18. 3 Cent.) 
without any effect. One, however, of these four leaves, on 
being gently withdrawn from the water, closed rather quick- 
ly. The three other leaves were proved to be in good condi- 
tion, as they closed when their filaments were touched. 
Nevertheless 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 fila- 
ments one of them closed. This latter leaf after an addi- 
tional 24 hrs. again re-expanded, and now, on the filaments of 
both leaves being touched, both closed. We thus see that a 
short immersion in water does not at all injure the leaves, 
but sometimes excites the lobes to close. The movements 
in the above cases was evidently not caused by the tempera- 
ture of the water. It has been shown that long immersion 
causes the purple fluid within the cells of the sensitive fila- 
ments 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 prob- 
ably due to a slight degree of exosmose. 

I am confirmed in this belief by the effects of immersing 
a leaf of Dionsea in a moderately strong solution of sugar; 



238 DION^A MUSCIPULA. [Chap. XIII. 

the leaf having been previously left for 1 hr. 10 m. in water 
without any eflfect; for now the lobes closed rather quickly, 
the tips of the marginal spikes crossing in 2 m. 30 s., and 
the leaf being completely shut in 3 m. Three leaves were 
then immersed in a solution of half an ounce of sugar to a 
fluid ounce of water, and all three leaves closed quickly. 
As I was doubtful whether this was due to the cells on the 
upper surface of the lobes, or to the sensitive filaments being 
acted on by exosmose, one leaf was first tried by pouring a 
little of the same solution in the furrow between the lobes 
over the midrib, which is the chief seat of movement. It 
was left there for some time, but no movement ensued. 
The whole upper surface of leaf was then painted (except 
close round the bases of the sensitive filaments, which I 
could not do without risk of touching them) with the same 
solution, but no eflfect was produced. So that the cells on 
the upper sui^uce are not thus aflFected. But when, after 
many trials, I succeeded in getting a drop of the solution to 
c''Ag 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 con- 
tents, analogous to that which must be produced by a touch. 

The immersion of leaves in a solution of sugar aflfects 
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 discol- 
oured, 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 



Chap. XIII.] SENSITIVENESS OF FILAMENTS. 239 

injured, being touched. After a day these three leaves 
opened, and were fairly sensitive when the uninjured fila- 
ments were touched. The sudden immersion of a leaf into 
boiling water does not cause it to close. Judging from the 
analogy of Drosera, the heat in these several cases was too 
great and too suddenly applied. The surface of the blade is 
very slightly sensitive; it may be freely and roughly 
handled, without any movement being caused. A leaf was 
scratched rather hard with a needle, but did not close; but 
when the triangular space between the three filaments on 
another leaf was similarly scratched, the lobes closed. They 
always closed when the blade or midrib was deeply pricked 
or cut. Inorganic bodies, even of large size, such as bits of 
stone, glass, &c. or organic bodies not containing soluble 
nitrogenous matter, such as bits of wood, cork, moss, or 
bodies containing soluble nitrogenous matter, if perfectly 
dry, such as bits of meat, albumen, gelatine, &c., may be 
long left (and many were tried) on the lobes, and no move- 
ment 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 foot- 
stalk 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 

[Gardiner has described these a central position; the protoplasm 

f lands In the ' Proceedings of the is much less granular than be- 

:. Society,' Tol. xxxvl. p. 180. fore, and contains a number of 

When at rest the gland-cells small vacuoles, so that the nu- 

show a grannlar protoplasm, con- cleus appears suspenf^'vl bv radl- 

talning In most cases a single atlng strands of protoplasu. in 

large vacuole; the nucleus Is situ- the centre of the cell, 

ated at the base of the cell. At Another change produced by 

the end of the secreting period the feeding the leaf is the ap- 

the following changes have oc- penrance, m the parenchyma, of 

curred. The nucleus seems to tufts of greenish yellow crystals 

diminish in size, It has assumed of unknown nature. F. D.] 



2-1:0 DION^A MUSCIPULA. [Chap. XIII. 

remains quite dry. Nor does it make any difference if the 
lobes close over such objects. For instance, some little balls 
of blotting-paper were placed on a leaf, and a filament was 
touched; and when after 24 hrs. the lobes began to re-open, 
the balls were removed by the aid of thin pincers, and were 
found pKjrfectly dry. On the other hand, if a bit of damp 
meat or a crushed fly is placed on the surface of an expanded 
leaf, the glands after a time secrete freely. In one such 
case there was a little secretion directly beneath the meat in 
4 hrs.; and after an additional 3 hrs. there was a 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 ani- 
mal 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, con- 
taining dissolved animal matter, spreads by capillary at- 
traction, causing fresh glands on both sides to begin se- 
creting in a continually widening circle. The secretion is 
almost colourless, slightly mucilaginous, and, judging by the 
manner in which it coloured litmus paper, more strongly 
acid than that of Drosera. It is so copious that on one 
occasion, when a leaf was cut open, on which a small cube 
of albumen had been' placed 45 hrs. before, drops rolled off 
the leaf. On another occasion, in which a leaf with an 
enclosed bit of roast meat spontaneously opened after eight 
days, there was so much secretion in the furrow over the 
midrib that it trickled down. A large crushed fly (Tipula) 
was placed on a leaf from which a small portion at the base 
of one lobe had previously been cut away, so that an open- 
ing wf.: 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. 



Chap. XIII.] SECRETION AND ABSORPTION. 241 

We have seen that inorganic and non-nitrogenous objects 
placed on the leaves do not excite any movement ; but nitrog- 
enous bodies, if in the least degree damp, cause after several 
hours the lobes to close slowly. Thus bits of quite dry meat 
and gelatine were placed at opposite ends of the same leaf," 
and in the course of 24 hrs. excited neither secretion nor 
movement. They were then dipped in water, their surfaces 
dried on blotting-paper, and replaced on the same leaf, the 
plant being now covered with a bell-glass. After 24 hrs. the 
damp meat had excited some acid secretion, and the lobes 
at this end of the leaf were almost shut. At the other end, 
where the damp gelatine lay, the leaf was still quite open, 
nor had any secretion been excited ; so that, as with Drosera, 
gelatine is not nearly so exciting a substance 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 se- 
cretion, 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 bit 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 sur- 
rounded by much secretion, was gently removed, and al- 
though 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 



242 DION^A MUSCIPULA. [Chap. XIII. 

end of the leaf ^vhere 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 
should have observed the leaves for a longer time, and they 
would probably have been found closed, though the solution 
(judging from Drosera) was, perhaps, too strong. 

From the foregoing cases it is certain that bits of meat 
and albumen, if at all damp, excite not only the glands to 
secrete, but the lobes to close. This movement is widely 
different from the rapid closure caused by one of the fila- 
ments 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 Diontea in the eflfects 
produced by mechanical irritation on the one hand, and the 
absorption of animal matter on the other. Particles of 
glass placed on the glands of the exterior tentacles of Dro- 
sera excite movement within nearly the same time, as do 
particles of meat, the latter being rather the most eflScient; 
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 Diontea, touching the filaments excites in- 
comparably 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 in- 
sects 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-nitroge- 
nous bodies, and between these latter in a dry and damp con- 
dition. 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 quan- 



Chap. XIIT.] SECRETION AND ABSORPTION. 243 

tity of animal matter, when absorbed, suffices to produce 
these two effects. It seems hardly credible, and yet it is 
certainly a fact, that a bit of hard-boiled white of egg, first 
thoroughly dried, then soaked for some minutes in water 
and rolled on blotting-paper, should yield in a few hours 
enough animal matter to the glands to cause them to secrete, 
and afterwards the lobes to close. That the glands have the 
power of absorption is likewise shown by the very different 
lengths of time (as we shall presently see) during which the 
lobes remain closed over insects and other bodies yielding 
soluble nitrogenous matter, and over such as do not yield 
any. But there is direct evidence of absorption in the con- 
dition 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 beau- 
tiful 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. Boil- 
ing 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 func- 
tions of the minute octofid processes with which the leaves 
17 



244 



DION-a:A MUSCIPULA. 



[Chap. XIII. 



are studded. From facts hereafter to be given in the chap- 
ters on Aldrovanda and Utricularia, it seemed probable that 
they served to absorb decayed matter left by the captured in- 
sects; but their position on the backs of the leaves and on 
the footstalks rendered this almost impossible. Neverthe- 
less, leaves were immersed in a solution of one part of urea 
to 437 of water, and after 24 hrs. the orange layer of proto- 
plasm 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 
infusion of raw meat, to see whether they absorbed the va- 
pour, 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 tempo- 
rary stomach; and if the object yields ever so little animal 



'Dr. W. M. Cnnby, of Wll- 
mln^oD, to whom I nin much in- 
dobtpd for Information rppirding 
I)lonn>n In Its native home, has 

aiibUHhed In the ' Gardener's 
[onthly.' Philadelphia, August, 
18(W, 8ome Interesting observa- 
tions. He ascertained that the 
secretion digests animal matter, 
such as the contents of Insects, 
bits of meat, &c.; and that the 
secretion Is reabsorbed. He was 
also well aware that the lobes 
remain closed for a much longer 
time when In contact with animal 
matter than when made to shut 
by a mere touch, or over objects 
not yielding soluble nutriment; 
and that In thewe latter cases the 

f lands do not secrete. The Kev. 
>r. f'urtis first observed (' Bos- 
ton Journal Nat. Hist.' vol. i. p. 
12.1) the secretion from the 
glands. I may here add that a 
gardener. Mr. Knight, Is said 
{KIrby and Spenoe's ' Introduc- 
tion to Entomology,' 1818, vol. I. 
p. 205) to have found that a 

ftlant of the I)lona?a, on the 
eaves of which " he laid fine fila- 
ments of raw beef, was much 
more luxuriant in its growth 
than others not so treated." 

[The earlier history of the 
siil)Je<'t is given in Sir Josnh 
Hooljer's " Address to the De- 
partment of Hot any and Zoolo- 
gy." Hrltlsh AKSoolatlon Ue- 
port,' 1874, p. lf2, whence the 
following facts are taken. 

Aliout 1708 Ellis, a well known 
Rncllsh naturalist, sent to Iiln- 
lupus a drawing and specimens of 



Dlonsea with the following re- 
marks ("A Itotnnlcal DeHcrtptioii 
of the Dion<rn muMcipula .... In 
a letter to Sir Charles Linnseus," 
p. 37):- 

" The plant, of which I now 
enclose you an exact figure .... 
shows that Nature may have 
8om views towards its nourish- 
ment. In forming the upper Joint 
of its leaf like a machine to catch 
food." 

Llnnneus was unable to believe 
that the plant could profit by the 
captured Insects; he only saw in 
the phenomena " an extreme case 
of sensitiveness in the leaves 
which causes them to fold up 
where Irritated, Just as the sensi- 
tive plant does; and he conse- 
quentlv reganled the capture of 
the disturbing insect as some- 
thing merely accidental and of 
no importance to the plant. . . . 
LJnnHMis's authority overbore 
criticism If any was offered; and 
his statement alMxit the behav- 
iour of the leaves was copied 
from book to book. . . . Dr. 
[Erasmus] Darwin (1791) was 
contented to suppose that Dlomea 
surrounded Itself with Insect- 
traps to prevent depredations 
upon its flowers. Dr. Curtis, 
whose ct)ntrlbutl(>n to the subject 
has been alreaiiy mentioned, de- 
scribes the capturefl Insects na 
envelopefl In a fluid of a mucilag- 
inous consistence which seems to 
act as a solvent, the Insects be- 
ing more or less consumed by it." 
-F. D.] 



Chap. XIIL] DIGESTION. 245 

matter, this serves, to use SchifFs expression, as a pepto- 
gene," and the glands on the surface pour forth their acid 
secretion, which acts like the gastric juice of animals. As 
80 many experiments were tried on the digestive power of 
Drosera, only a few were made with Dionsea, but they were 
amply sufficient to prove that it digests. This plant, more- 
over, is not so well fitted as Drosera for observation, as the 
process goes on within the closed lobes. Insects, even beetles, 
after being subjected to the secretion for several days, are 
surprisingly softened, though their chitinous coats are not 
corroded. 

Experiment 1. A cube of albumen of -^ of an inch (2.540 mm.) 
was placed at one end of a leaf, and at the other end an oblong 
piece of gelatine, ^ of an inch (5.08 ram.) 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 Drosera, 
and this agrees with the length of time during which the leaves 
remain closed over digestible objects. 

Experiment 2. A bit of albumen -^ of an inch square, but only 
^ in thickness, and a piece of gelatine of the same size as before, 
were placed on a leaf, which eight days afterwards was cut open. 
The surface was bathed with slightly adhesive, very acid secretion, 
and the glands were all in an aggregated condition. Not a vestige 
of the albumen or gelatine was left. Similarly sized pieces were 
placed at the same time on wet moss on the same pot, so that they 
were subjected to nearly similar conditions; after eight days these 
were brown, decayed, and matted with fibres of mould, biit had 
not disappeared. 

Experiment S. A piece of albumen ^ of an inch (3.81 mm.) 
long, and t^ 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 spon- 
taneously 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 con- 
tained nothing except a vestige of brown matter where the albu- 
men had lain. 

" [flee footnote, p. 10G.-F. D.] 



;3^ DION^A MU8CIPULA. [Chap. XI il. 

Experiment 6. A cube of albumen of -^ of an inch and a piece 
of gelatine of the same size as before were placed on a leaf, which 
opened spontaneously after thirteen days. The albumen, which 
was twice as thick as in the latter experiments, was too large; for 
the glands in contact with it were injured and were dropping off; 
a film also of albumen of a brown colour, matted with mould, was 
left. All the gelatine was absorbed, and there was only a little 
acid secretion left on the midrib. 

Experiment 7. A "bit of half roasted meat (not measured) and 
a bit of gelatine were placed on the two ends of a leaf, which 
opened spontaneously after eleven days; a vestige of the meat was 
left, and the surface of the leaf was here blackened; the gelatine 
had all disappeared. 

Experiment 8. A bit of half roaste<l meat (not measured) was 
placed on a leaf which was forcibly kept open by a clip, so that 
it was moistened with the secretion (very acid) only on its lower 
surface. Nevertheless, after only 22* hrs. it was surprisingly soft- 
ened, when compared with another bit of the same meat which 
had been kept damp. 

Experiment 9. A cube of ^ of an inch of very compact roasted 
beef was placed on a leaf, which opened spontaneously after twelve 
days; so much feebly acid secretion was left on the leaf that it 
trickled off. The meat was completely disintegrated, but not at 
all dissolved; there was no mould. The little mass was placed 
under the microscope; some of the fibrillce in the middle still ex- 
hibited transverse striae; others showed not a vestige of stria:; 
and every gradation could be traced between these two states. 
Globules, apparently of fat, and some undigested fibro-elastic tissue 
remained. The meat was thus in the same state as that formerly 
described, which was half digested by Drosera. Here, again, as in 
the case of albumen, the digestive process seems slower than in 
Drosera. At the opposite end of the same leaf, a firmly compressed 

fellet of bread had been placed; this was completely disintegrated, 
suppose, owing to the digestion of the gluten, but seemed very 
little re<luced in bulk. 

Experiment 10. A cube of ^ of an inch of cheese and another 
of albumen were placed at opposite ends of the same leaf. After 
nine days the lobes opened spontaneously a little at the end en- 
closing the cheese, but hardly any or none was dissolved, though 
it was softened and surrounded by secretion. Two days subse- 
quently the end with the albumen also opened spontaneously (i. e. 
eleven days after it was put on), a mere trace in the blackened 
and dry condition being left. 

Experiment tl. The same experiment with cheese and albumen 
repeate<l 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 culje 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 



Chap. XIII.] EFFECTS OF VAPOUKS. 247 

again the leaf at the end enclosing the cheese opened before the 
opposite end with the albumen; but no further observations were 
made. 

Experiment IS. A globule of chemically prepared casein, about 
i\f of an inch in diameter, was placed on a leaf, which spontaneous- 
ly 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 secre- 
tion from the glands of Diona3a dissolves albumen, gelatine, 
and meat, if too large pieces are not given. Globules of fat 
and fibro-elastic tissue are not digested. The secretion, with 
its dissolved matter, if not in excess, is subsequently ab- 
sorbed. On the other hand, although chemically prepared 
casein and cheese (as in the case of Drosera) excite much 
acid secretion, owing, I presume, to the absorption of some 
included albuminous matter, these substances are not di- 
gested, and are not appreciably, if at all, reduced in bulk. 

Effects of the Vapours of Chloroform, Sulphuric Ether, and 
Uydrocyunic Acid. A plant bearing one leaf was introduced into 
a large bottle with a drachm (3.549 c.c.) of chloroform, the mouth 
being imperfectly closed with cotton-wool. The vaf)our 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 after a time, as did the other whilst being removed from 
the vessel without being touched. Both leaves were greatly in- 
jured. 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 iila- 
raents were repeatedly touched, but closed when the end of the 
open leaf was cut off. This shows either that the internal parts 
had not been rendered insensible, or that an incision is a more pow- 
erful stimulus than repeated touches on the filaments. Whether 
the larger doses of chloroform and ether, which caused the loaves to 
close slowly, acted on the sensitive filaments or on the leaf itself, I 
do not know. 



248 DIONuEA MUSCIPULA. [Ceap. XIII. 

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

On the Manner in which Insects are caught. We will 
now consider the action of the leaves when insects happen to 
touch one of the sensitive filaments. This often occurred in 
my greenhouse, but I do not know whether insects are at- 
tracted in any special way by the leaves. They are caught 
in large numbers by the plant in its native country'. As 
soon as a filament is touched, both close with astonishing 
quickness; and as they stand at less than a right angle to 
each other, they have a good chance of catching any intruder. 
The angle between the blade and footstalk does not change 
when the lobes close. The chief seat of movement is near 
the midrib, but it 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 com- 
pletely over, passing through an angle of from 120 to 130, 
80 as to occupy a position almost at right angles to that 
which it would have held had the opposite lobe been present. 

From the curving inwards of the two lobes, as they move 
towards each other, the straight marginal spikes intercross 
by their tips at first, and ultimately by their bases. The 
leaf is then completely shut and encloses a shallow cavity. 
If it has been made to shut merely by one of the sensitive 

" [Munk (Rolchert nnd Du ment occnrs nt the c<lKe of the 
Bolii-UpymoiHl'H ' Arrhlv.' 187(1, lonf. by which the teeth are car- 
p. 108) states that a special move- rled Inwards. F. D.J 



Chap. XIII.] MANNER OP CAPTURING INSECTS. 24:9 

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 or- 
ganic matter is enclosed was observed in ten cases. In all 
of these, the leaves re-expanded to about two-thirds of the 
full extent in 24 hrs. from the time of closure. Even the 
leaf from which a portion of one lobe had been cut off opened 
to a slight degree within this same time. In one case a leaf 
re-expanded to about two-thirds of the full extent in 7 hrs., 
and completely in 32 hrs.; but one of its filaments had been 
touched merely with a hair just enough to cause the leaf 
to close. Of these ten leaves only a few re-expanded com- 
pletely in less than two days, and two or three required even 
a little longer time. Before, however, they fully re-expand, 
they are ready to close instantly if their sensitive filaments 
are touched. How many times a leaf is capable of shutting 
and opening if no animal matter is left enclosed, 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 nitrog- 
enous matter, the lobes, instead of remaining concave, thus 
including a concavity, slowly press closely together through- 
out their whole breadth. As this takes place, the margins 
gradually become a little everted, so that the spikes, which 
at first intercrossed, at last project in two parallel rows. 
The lobes press against each other with such force that I have 
seen a cube of albumen much flattened, with distinct impres- 
sions of the little prominent glands; but this latter circum- 
stance may have been partly caused by the corroding action 

>* According to Dr. Curtis, in ' Boston Journal of Nat. Hist.' roi. 
I. 1837, p. 123. 



250 DION-fiA MUSCIPULA. [Chap. XIIL 

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 dis- 
tinctly 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 gen- 
erally ruptured rather than yield. If not ruptured, they 
close again, as Dr. Canby informs me in a letter, " with quite 
a loud flap." But if the end of a leaf is held firmly between 
the thumb and finger, or by a clip, so that the lobes cannot 
begin to close, they exert, whilst in this position, very little 
force. 

I thought at first that the gradual pressing together of 
the lobes was caused exclusively by captured insects crawling 
over and repeatedly irritating the sensitive filaments; and 
this view seemed the more probable when I learnt from Dr. 
Burdon Sanderson that whenever the filaments of a closed 
leaf are irritated, the normal electric current is disturbed. 
Nevertheless, such irritation is by no means necessary, for a 
dead insect, or bit of meat, or of albumen, all act equally 
well; proving that in these cases it is the absorption of 
animal matter which excites the lobes slowly to press close 
together. We have seen that the absorption of an extremely 
small quantity of such matter also causes a fully expanded 
leaf to close slowly, and this movement is clearly analogous to 
the slow pressing together of the concave lobes. This latter 
action is of high functional importance to the plant, for the 
glands on both sides are thus brought into contact with a 
captured insect, and consequently secrete. The secretion 
with animal matter in solution is then drawn by capillary 
attraction over the whole surface of the leaf, causing all the 
glands to secrete and allowing them to absorb the diffused 
animal matter. The movement, excited by the absorption of 
such matter, though slow, sufiices 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 wide- 
ly diflFerent means, are thus both well adapted, like all the 
other functions of the plant, for the purposes which they 
subserve. 

There is another wide difference in the action of leaves 



Chap. XIII.] MANNER OF CAPTURING INSECTS. 251 

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 ni- 
trogenous 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 close- 
ly 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, for twenty-four 
days, though the fly was small; in a third for twenty-four 
days over a woodlouse; and in a fourth, for thirty-five days 
over a large Tipula. In two other cases leaves remained 
closed for at least nine days over flies, and for how many 
more I do not know. It should, however, be added that in 
two instances in which very small insects had been naturally 
caught the leaf opened as quickly as if nothing had been 
caught; and I suppose that this was due to such small in- 
sects not having been crushed or not having excreted any 
animal matter, so that the glands were not excited. Small 
angular bits of albumen and gelatine were placed at both 
ends of three leaves, two of which remained closed for 
thirteen and the other for twelve days. Two other leaves 
remained closed over bits of meat for eleven days, a third 
leaf for eight days, and a fourth (but this had been cracked 
and injured) for only six days. Bits of cheese, or casein, 
were placed at one end and albumen at the other end of three 
leaves ; and the ends with the former opened after six, eight, 
and nine days, whilst the opposite ends opened a little later. 
None of the above bits of meat, albumen, &c., exceeded a 
cube of -^ of an inch (2.54 mm.) in size, and were some- 
times smaller; yet these small portions sufficed to keep the 
leaves closed for many days. Dr. Canby informs me that 
leaves remain shut for a longer time over insects than over 
meat; and from what I have seen, I can well believe that 
this is the case, especially if the insects are large. 

In all the above cases, and in many others in which leaves 
remained closed for a long but unknown period over insects 
naturally caught, they were more or less torpid when they 



252 DION^A MUSCIPULA. [Chap. XII L 

re-opened. Generally they were so torpid during many 
succeeding days that no excitement of the filaments caused 
the least movement. In one instance, however, on the day 
after a leaf opened which had clasped a fly, it closed with 
extreme slowness when one of its filaments was touched ; and 
although no object was left enclosed, it was so torpid that it 
did not re-open for the second time until 44 hrs. had elapsed. 
In a second case, a leaf which had expanded after remaining 
closed for at least nine days over a fly, when greatly irritated, 
moved one alone of its two lobes, and retained this unusual 
position for the next two days. A third case offers the 
strongest exception which I have observed; a leaf, after 
remaining clasped for an unknown time over a fly, opened, 
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 un- 
serviceable." Mrs. Treat, who cultivated many plants in 
New Jersey, also informs me that several leaves caught suc- 
cessively 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 Dionaja differs from 
Drosera, which catches and digests many insects after 
shorter intervals of time. 

We are now prepared to understand the use of the mar- 
ginal spikes, which form so conspicuous a feature in the 
appearance of the plant (Fig. 12, p. 233), 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 



Chap. XIII.] MANNER OP CAPTURING INSECTS. 253 

from the iV to the iV of an inch (1.693 to 2.540 mm.) in 
breadth, according to the size of the leaf, are left open. 
Thus an insect, if its body is not thicker than these measure- 
ments, can easily escape between the crossed spikes, when 
disturbed by the closing lobes and increasing darkness; and 
one of my sons actually saw a small insect thus escaping. 
A moderately large insect, on the other hand, if it tries to 
escape between the bars will surely be pushed back again 
into its horrid prison with closing walls, for the spikes con- 
tinue to cross more and more until the edges of the lobes- 
come into contact. A very strong insect, however, would be 
able to free itself, and Mrs. Treat saw this effected by a 
rose-chafer (Macrodactylus subspinosus) in the United 
States. Now it would manifestly be a great disadvantage to 
the plant to waste many days in remaining clasped over a 
minute insect, and several additional days or weeks in after- 
wards recovering its sensibility; inasmuch as a minute in- 
sect would afford but little nutriment. It would be far bet- 
ter for the plant to wait for a time until a moderately 
large insect was captured, and to allow all the little ones 
to escape; and this advantage is secured by the slowly 
intercrossing marginal spikes, which act like the large 
meshes of a fishing-net, allowing the small and useless fry 
to escape. 

As I was anxious to know whether this view was correct 
and as it seems a good illustration of how cautious we 
ought to be in assuming, as I had done with respect "to the 
marginal spikes, that any fully developed structure is useless 
I applied to Dr. Canby. He visited the native site of the 
plant, early in the season, before the leaves had grown to 
their full size, and sent me fourteen leaves, containing natu- 
rally captured insects. Four of these had caught rather 
small insects, viz. three of them ants, and the fourth a rather 
small fly, but the other ten had all caught large insects, 
namely, five elaters, two chrysomelas, a curculio, a thick and 
broad spider, and a scolopendra. Out of these ten insects, 
no less than eight were beetles," and out of the whole four- 

" Dr. Canby remarks (' (Jar- after a short time are rejected." 

dener'8 Monthly,' Aug. 1808). I am surprised at this statement. 

" as a general thing beetles and at least with respect to such 

insects .o/ that kind, though ai- beetles as elaters, for the Ave 

ways killed, seemed to be too which I examined were in an 

hard-shelled to serve as food, and extremely fragile and empty con- 



254 DION^A MUSCIPULA. [Chap. XII L 

teen there was only one, viz. a dipterous insect, which could 
readily take flight. Drosera, on the other hand, Uvea chiefly 
on insects which are good flyers, especially Diptera, caught 
by the aid of its viscid secretion. But what most concerns 
us is the size of the ten larger insects. Their average length 
from head to tail was .256 of an inch, the lobes of the leaves 
being on an average .53 of an inch in length, so that the in- 
sects were very nearly half as long as the leaves within which 
they were enclosed. Only a few of these leaves, therefore, 
had wasted their powers by capturing small prey, though it 
is probable that many small insects had crawled over them 
and been caught, but had then escaped through the bars. 

The Transmission of the Motor Impulse, and means of 
Movement. It is sufficient to touch any one of the six fila- 
ments to cause both lobes to close, these becoming at the 
same time incurved throughout their whole breadth. The 
stimulus must therefore radiate in all directions from any 
one filament. It must also be transmitted with much rapid- 
ity across the leaf, for in all ordinary cases both lobes close 
simultaneously, as far as the eye can judge. Most physiolo- 
gists believe that in irritable plants the excitement is trans- 
mitted along, or in close connection with, the fibro-vascular 
bundles. In Dionsea, the course of tliese 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 to- 
wards the margin, and close to the margin small branches 
from adjoining small 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 con- 
tinuous zigzag line of vessels thus runs round the whole cir- 
cumference of the leaf, and in the midrib all the vessels are 
in close contact; so that all parts of the leaf seem to bo 
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 iv of an inch 
in length), into which no vessels enter; and these could not 

(Htlon. nB !f all tholr Intornnl nInntR which Rho cnltlvnted !n 
pnrts had been partially digested. New Jersey chiefly caught Dip- 
Mrs. Treat Informs me that the tcra. 



Chap. XIII.] TRANSMISSION OF MOTOR IMPULSE. 255 

have been overlooked, as I made thin vertical sections of the 
leaf at the bases of the filaments. 

On several occasions, slits about the iV 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 side of the fila- 
ments; and after several days, when the leaves had re- 
opened, these filaments were touched roughly (for they were 
always rendered in some degree torpid by the operation), and 
the lobes then closed in the ordinary manner, though slowly, 
and sometimes not until after a considerable interval of 
time. These cases show that the motor impulse is not trans- 
mitted along the vessels, and they further show that there 
is not necessity for a direct line of communication from the 
filament which is touched towards the midrib and opposite 
lobe, or towards the outer parts of the same lobe. 

Two slits near each other, both parallel to the midrib, 
were next made in the same manner as before, one on each 
side of the base of a filament, on five distinct leaves, so that 
a little slip bearing a filament was connected with the rest 
of the leaf only at its two ends. These slips were nearly of 
the same size; one was carefully measured; it was .12 of an 
inch (3.048 mm.) in length, and .08 of an inch (2.032 mm.) 
in breadth; and in the middle stood the filament. Only one 
of these slips withered and perished. After the leaf had 
recovered from the operation, though the slits were still open, 
the filaments thus circumstanced were roughly touched, and 
both lobes, or one alone, slowly closed. In two instances 
touching the filament produced no effect; but when the 
point of a needle was driven into the slip at the base of the 
filament, the lobes slowly closed. Now in these cases the 
impulse must have proceeded along the slip in a line par- 
allel 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 



256 DION^A MUSCIPULA. [Chap. XIII. 

distance in a line at right angles to the midrib, and then 
have radiated forth on all sides over both lobes. These sev- 
eral cases prove that the motor impulse travels, in all direc- 
tions 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 largely governed by the 
length of the cells and the direction of their longer axes. 
Thin sections of a leaf of Dionaea were made by my son, 
and the cells, both these of the central and of the more super- 
ficial layers, were found much elongated, with their longer 
axes directed towards the midrib; and it is in this direction 
that the motor impulse must be sent with great rapidity 
from one lobe to the other, as both close simultaneously. 
The central parenchymatous cells are larger, more closely aV 
tached together, and have more delicate walls than the more 
superficial cells. A thick mass of cellular tissue forms the 
upper surface of the midrib over the great central bundle of 
vessels. 

When the filaments were roughly touched, at the bases of 
which slits had been made, either on both sides or on one 
side, parallel to the midrib or at right angles to it, the two 
lobes, or only one, moved. In one of these cases, the lobe 
on the side which bore the filament that was touched moved, 
but in three other cases the opposite lobe alone moved: so 
that an injury which was sufficient to prevent a lobe moving 
did not prevent the transmission from it of a stimulus which 
excited the opposite lobe to move. We thus learn that, al- 
though normally both lobes move together, each has the 
power of independent movement. A case, indeed, has al- 
ready been given of a torpid leaf that had lately re-opened 
after catching an insect, of which one lobe alone moved when 
irritated. Moreover, one end of the same lobe can close 
and re-expand, independently of the other end, as was seen 
in some of the foregoing experiments. 

When the lobes, which are rather thick, close, no trace of 
wrinkling can be seen on any part of their upper surfaces. 
It appears therefore that the cells must contract. The chief 
seat of the movement is evidently in the thick mass of cells 
which overlies the central bundle of vessels in the midrib. 



Chap. XIII.] TRANSMISSION OF MOTOR IMPULSE. 257 

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 rHrr of an inch apart. One of the filaments was then 
touched and the lobes closed; but as they were prevented 
from meeting, I could still see the two dots, which now were 
iHv of an inch apart, so that a small portion of the upper 
surface of the midrib had contracted in a transverse line 
tAtt 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 
rJ^ of an inch, so that the two extreme dots were tWs- of 
an inch apart. One of the filaments was now touched and 
the leaf closed. On again measuring the distances between 
the dots, the two next to the midrib were nearer together 
by TiHi^ of an inch, and the two further dots by f wJ of an 
inch, than they were before; so that the two extreme dots 
now stood about tAt of an inch (.127 mm.) nearer together 
than before. If we suppose the whole surface of the lobe, 
which was tV^ of an inch in breadth, to have contracted in 
the same proportion, the total contraction will have amount- 
ed to about -jihi 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." 

" [Rntnlln hns discussed the are made on the lower or ex- 

mcchanlRin of closure In Dlonaea ternal snrfnce of the leaf, and 

In his InterpstlnB essay In 'Flora,' the distance between them is 

1877. He n^rees In general with found to Increase when the leaf 

the statements above given, but closes. When the loaf opens the 

as in the case of Drosera, so distance does not perfectly re- 

here he believes that the move- turn to its former dimensions, 

ments are associated with a suinll and thus shows n certain aniount 

amount of actual growth. Marks of permanent growth has taken 



258 



DION^A MUSCIPULA. 



[Chap. XIII. 



Finally, with respect to the movement of the leaves the 
wonderful discovery made by Dr. Burdon Sanderson " is now 
universally known; namely that there exists a normal elec- 
trical current in the blade and footstalk; and that when the 
leaves are irritated, the current is disturbed in the same 
manner as takes place during the contraction of the muscle 
of an animal." 



place. It will be seen that Bata- 
lln's observations do not support 
the Idea (see p. 259) that the re- 
opening of the loaf 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 removed. 
Munk (loc. cit.) and Pfoffer (' Os- 
motlsche UntersuchunKon,' 1877, 
p. IIMJ) have with Justice called 
attention to the unsatisfactory 
nature of the discussion In the 
text on the mechanlsni of the 
movement. Batalln shows fur- 
ther that the ultimate closure? of 
the leaf by which the two valves 
are closely pressed together Is 
effected by the shortening or 
contraction of the outer surface 
of the leaf. He records a curious 
fact which has not elsewhere 
been noted, namely, that the mid- 
rib becomes more curved after 
the closure of the leaf. Munk 
(Uelchert and Du Bols-Ucyinoud's 
' Archlv.' 1870, p. 121). on the 
other hand, Is Inclined to believe 
that the curvature .of the midrib 
diminishes when the leaf closes. 
-F. I).] 

u ' proc. Royal Soc.' vol. xxl. 

f. 41>r>; and lecture at the Royal 
nstltutlon. June .'>, 1874, given In 

Nature,' 1874. pp. 105 and 127. 

" [Professor Simflerson's work 
has been crltlclHod by Professor 
Munk In Relchert and Du Bots- 
Reymond's ' Ar<-hlv.' 1870, and 
by Professor Kunkel In Sachs' 

Arbelten a. d. Iwt. Instltut In 
Wllntburg,' Bd. II. p. 1. 

Professor Sanderson has con- 
tinued to work at the subject, 
and has given his results In an 
elaborate paper In ' Phil. Trans- 
actions,' 1882. It will be suffi- 
cient 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 Mtmk's 
method of explaining the state 
of the leaf by a mechanical 
trhrmnnn arrangement of cop- 
per and sine cylluderB. He does 



BO, not only because he accepts 
" as fundamental the doctrine 
that whatever physiological prop- 
erties the leaf poHscHscs, It pos- 
sesses 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 th(>oretlcal deductions. 
He Inclines to admit that the 
electrical differences observtHl be- 
tween different parts of the nn- 
exclted leaf may be partly ex- 
plained by the migration of 
water. "For on the one hand 
we know that In conse<iuence of 
the surface evaporation, migra- 
tion of water certainly exists, 
while on the other we have proof 
In the experiments of Dr. Kunkel 
that such migration cannot occur 
without protludng electrical dif- 
ferences. In a similar way he Is 
Inclined to believe that the grad- 
ual electrical change resulting 
from repeated excitation, as well 
as the after effect of a alngU^ ex- 
citation, 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 excita- 
tion cannot be due to water-mi- 
gration, but that It Is the ex- 
pression of molecular changes In 
the protoplasm of the leaf. Pro- 
fessor Sanderson takes occasion 
to correct the Impression pro- 
duced by certain expressions In 
his lecture at the Royal Institu- 
tion in 1874. Professor Munk, 
among others, seems to have be- 
lievea that Pmfessor Sanderson 
claimed absolute Identity l>e- 
tween muscular action and the 
movement of the leaf of Dloniva. 
It nee<l hardiv be stated that no 
such implication was intended by 
Professor Sanderson: the view 
which he hold In 1874 he still ad- 
heres to. namely, that the rapid- 
ly propagated molecular change 
In an excited Dloni^a loaf can 
only be identified with the corre- 



Chap. XIII.] RE-EXPANSION. 269 

The Re-expansion of the Leaves. This is effected at an 
insensibly slow rate, whether or not any object is enclosed.'* 
One lobe can re-expand by itself, as occurred with the 
torpid leaf of which one lobe alone had closed. We have also 
seen in the experiments with cheese and albumen that the 
two ends of the same lobe can re-expand to a certain extent 
independently of each other. But in all ordinary cases both 
lobes open at the same time. The re-expansion is not de- 
termined by the sensitive filaments; all three filaments on 
one lobe are 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 

snonding process In the excitable during the first tenth. If we as- 

tlssues of animals. sume that the distance travelled 

Certain unpublished re- by the disturbance Is one ceutl- 

searches made during the last meter, this gives 100 miUimctera 

two years have led Professor prr second as the rate of propaga- 

Sanderson to extend his views In tion. This, as Professor Sander- 

the direction above Indicated, son has pointed out, happens to 

and to conclude that the " leaf- be just about the rate of propaga- 

current," *. e. the electrical dif- tlon of the excitatory electrical 

ference between the upper and disturbance In the muscular tls- 

lower surfaces of the leaf, Is In- sue of the heart of the frog. 

tlraately connected with the P. D.] 

physiological conditions of that " Nuttall, In his ' Gen. Amerl- 
part of the upper surface from can Plants,' p. 277 (note), says 
which spring the sensitive flla- that, whilst collecting this plant 
ments: thus It will probably be In Its native home, "1 had oc- 
establlshed that the " leaf-cur- caslon to observe that a detached 
rent " and the excitatory disturb- leaf would make repeated efforts 
ance are dlflTerent manifestations towards disclosing Itself to the 
of the same property. F'rom Influence of the sun; these at- 
nieasurements made with his tempts consisted In an undula- 
Rheotome, of six carefully chosen tory motion of the marginal clllse, 
leaves, taken from vigorous accompanied by a partial open- 
plants (Aug. 188"), Professor Ing and succeeding collapse of 
Sanderson found that the elec- the lamina, which at length ter- 
trlcal disturbance produced In minnted In a complete expansion 
one lobe by stimulation of the and In the destruction of sensi- 
other by an Induction current, be- blllty." I am Indebted to Pro- 
gins In the course of the itecond fessor Oliver for this reference; 
tenth of a tecond following the but I do not understaud what 
excitation. . In five out of the six took place, 
leaves no effect was perceptible 
18 



260 DION^A MUSCIPULA. [Chap. XI i I. 

their having been strongly aflFected through exosmose, so that 
they continue for some time to transmit a motor impulse to 
the upper surface of the leaf. 

The following facts make me believe that the several 
layers of cells forming the lower surface of the leaf are 
always in a state of tension; and that it is owing to this 
mechanical state, aided probably by fresh fluid being at- 
tracted into the cells, that the lobes begin to separate or 
expand as soon as the contraction of the upper surface di- 
minishes. A leaf was cut oflF and suddenly plunged perpen- 
dicularly into boiling water: I expected that the lobes would 
have closed, but instead of doing so, they diverged a little. I 
then took another fine leaf, with the lobes standing at an 
angle of nearly 80 to each other; and on immersing it as 
before, the angle suddenly increased to 90. A third leaf 
was torpid from having recently re-expanded after having 
caught a fly, so that repeated touches of the filaments caused 
not the least movement; nevertheless when similarly im- 
mersed, the lobes separated a little. As these leaves were in- 
serted 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 ten- 
sion, 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 Dionsea. 

In some concluding remarks in the fifteenth chapter on 
the Droseraceffi, the different kinds of irritability possessed 
by the several genera, and the different manner in which 
they capture insects, will be compared. 



Chap. XIV.] ALDROVANDA VESICULOSA. 261 



CHAPTER XIV. 

ALDROVANDA VESICULOSA. 

Captnres crustaceans Structure of the leaves in comparison with those of 
DioDsea Absorption by the glands, by the quadrifid processes, and 
points on the infolded margins Ahlrovanda vesiculosa, var. australis 
Captures prey Absorption of animal matter Aldrovanda vesiculosa, 
var. vertukllata Concluding remarlis. 

This plant may be called a miniature aquatic Dionsea. 
Stein discovered in 1873 that the bilobed leaves, which are 
generally found closed in Europe, open under a suflBciently 
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 con- 
tain bubbles of air, and were formerly supposed to be blad- 
ders; 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 grow- 
ing plants many kinds of crustaceans and larvae.' Plants 
which have been kept in filtered water were placed by him 
in a vessel containing numerous crustaceans of the genua 
Cypris, and next morning many were found imprisoned and 
alive, still swimming about within the closed leaves, but 
doomed to certain death. 

Directly after reading Prof. Cohn's memoir, I received 
through the kindness of Dr. Hooker living plants from 

Since his original pubiicatlon, [The late Professor Caspary 

Stein has found out that the Ir- published in the ' Bot. Zeituug,' 

rltability of the leaves was ob- 1859, p. 117, an elaborate paper 

served by De Snssus, as recorded on Aldrovanda, dealing chiefly 

In ' Bull. Bot. Soc. de France,' in with its morphology, anatomy, 

1W51. Dolpino states in a paper systematic position and geo- 

published In 1871 (' Nuovo Glor- graphical distribution. The early 

nale Bot. Ital.' vol. III. p. 174) literature of the species Is also 

that "una quantity dl chiocoioline fully given. F. D.] 

e dl altrt nnlmalcoll aoqnatioi " ' I am greatly Indebted to this 

are caught and suflfocated l)y the distinguished naturalist for hav- 

leaves. I presume that chiocrio- Ing sent m> a copy of his memoir 

line are fresh-water molluscs. on Aldrovanda. before it.s piildi- 

It would be interesting to know cation in his ' Beitrilge sur Hlolo- 

whether their shells are at all gie dor I'flanzeu,' drittea Ileft. 

corr<Mled' by the acid of the dl- 1875, p. 71. 
gestlve secretion. 



26i ALDROVANDA VESICULOSA. [Chap. XIV. 

Germany. Ab I can add nothing to Prof. Cohn's excellent 
description, I will give only two illustrations, one of a 
whorl of leaves copied from his work, and the other of a leaf 
pressed flat open, drawn by my son Francis. I will, however, 
append a few remarks on the differences between this plant 
and Dionffia. 

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 pro- 
jections,* 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 Dionrea; and this must make the 
capture of aquatic animals more easy. The outside of the 
leaves and the petioles are covered with minute two-armed 
papillae, evidently answering to the eight-rayed papillae of 
Diona>a. 

Each lobe rather exceeds a semi-circle in convexity, and 
consists of two very different concentric portions; the inner 
and lesser portion, or that next to the midrib, is slightly 
concave, and is formed, according to Cohn, of three layers of 
cells. Its upper surface is studded with colourless glands 
like, but more simple than, those of Dioncea; they are sup- 
ported on distinct footstalks, consisting of two rows of cells. 
The outer and broader portion of the lobe is flat and very 
thin, being formed of only two layers of cells.* Its upper 
surface does not bear any glands, but, in their place, small 
quadrifid processes, each consisting of four tapering pro- 
jections, which rise from a common prominence. These pro- 
cesses arc formed of very delicate membrane lined with a 
layer of protoplasm ; and they sometimes contain aggregated 

There ban been much discus- 1850) and Caspary ( Bot. Zel- 
lon by botanlHtM on the homo- tiing,' 1850). the two layers of 
logical nature of these nrojee- cells ore so comtiiiied ns to pro- 
tlons. Dr. Nltscbke (' Bot Zel- diiee the effect of a HliiRle layer, 
tang,' 1801, p. 140) believes that The three layers of which the 
they correspond with the flmbri- centnil part Is made up consist 
ated scale-like bodies found at of external and Internal eplder- 
the bases of the petioles of Dro- nilc layers, and a single layer of 
erm. parenchyma. P. D.] 

* According to Cohn (* Flora,' 



Chap. XIV.] ALDROVANDA VESICULOSA. 



263 



globules of hyaline matter. Two of the slightly diverging 
arms are directed towards the circumference, and two to- 
wards the midrib, forming together a sort of Greek cross. 
Occasionally two of the arms are replaced by one, and then 
the projection is trifid. We shall see in a future chapter 
that these projections curiously resemble those found within 
the bladders of Utricularia, more especially of Utricularia 
montana, although this genus is not related to Aldrovanda. 





Fig. 18. 
(Aldrovanda veaicnUna.) 
Upper fiKnr, whorl of leaves (from Prof. Cohn). 
Lower figare, leaf pressed flat open and greatly enlarged. 

A narrow rim of the broad flat exterior part of each lobe 
is turned inwards, so that, when the lobes are closed, the 
exterior surfaces of the infolded portions come into contact. 
The edge itself bears a row of conical, flattened, transparent 



264 ALDROVANDA VESICULOSA. [Chap. XIV. 

points with broad bases, like the prickles on the stem of a 
bramble or Kubus. As the rim is infolded, these points are 
directed towards the midrib, and they appear at first as if 
they were adapted to prevent the escape of prey; but this 
can hardly be their chief function, for they are composed of 
very delicate and highly flexible membrane, which can be 
easily bent or quite doubled back without being cracked. 
Nevertheless, the infolded rims, together with the points, 
must somewhat interfere with the retrograde movement of 
any small creature, as soon as the lobes begin to close. The 
circumferential part of the leaf of Aldrovanda thus differs 
greatly from that of Dionaja; nor can the points on t^e 
rim be considered as homologous with the spikes round the 
leaves of Dionaja, as these latter are prolongations of the 
blade, and not mere epidermic productions. They appear 
also to serve for a widely different purpose. 

On the concave gland-bearing portion of the lobes, and 
especially on the midrib, there are numerous long, finely 
pointed hairs, which, as Prof. Cohn remarks, there can be 
little doubt are sensitive to a touch," and, when touched, 
cause the leaf to close. They are formed of two rows of cells, 
or, according to Cohn, sometimes of four, and do not include 
any vasctdar tissue. They differ also from the six sensitive 
filaments of Dionaa in being colourless, and in having a me- 
dial 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 struc- 
ture of some of them, I experimented on only two, as I hoped 
that the plants would grow; and I now regret that I did not 
sacrifice a greater number. 

A leaf was cut open along the midrib, and the glands 
examined under a high power. It was then placed in a few 
drops of an infusion of raw meat. After 3 hrs. 20 m. there 
was no change, but when next examined after 23 hrs. 20 m., 
the outer cells of the glands contained, instead of limpid 

[In a paper In the * Nnovo irritability rcaldes exclnslvely In 

Olornnle Rotnnico Itnllano,' vol. the contml jrlaudular region of 

vlll. 1S70. p. Ki, Mori KtatoH thnt the leaf. F. D.] 
this la the caae, namely that the 



Chap. XIV.] ALDROVANDA VESICULOSA. 265 

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 mat- 
ter out of the bodies of the creatures which the leaves cap- 
ture, is also highly probable from the analogy of Diontea. 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 in- 
folded 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 from a curious little fact men- 
tioned by Prof. Cohn, namely, that when rather large crus- 
taceans 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 excrement itious 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 Dioneea. 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 



266 ALDROVANDA VESICULOSA. [Chap. XIV. 

of the quadrifids included a few spherical granules, but 
several were transparent and empty, and their positions 
were marked. This leaf was now immersed in a little solu- 
tion of one part of urea to 146 of water, or three grains to 
the ounce. After 3 hrs. 40 m. there was no change either 
in the glands or quadrifids ; nor was there ' any certain 
change in the glands after 24 hrs.; so that, as far as one 
trial goes, urea does not act on them in the same manner as 
an infusion of raw meat. It was different with the quadri- 
fids; 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 quad- 
rifids of Utricularia when treated with this same solution. 
Moreover, 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 similar- 
ly 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 ab- 
sorbed matter from the solution in the course of 24 hrs.; 
but to this subject I shall recur. In another rather old 
leaf, to which nothing had been given, but which had been 
kept in foul water, some of the quadrifids contained aggre- 
gated translucent globules. These were not acted on by a 
solution of one part of carbonate of ammonia to 218 of 
water: and this negative result agrees with what I have 
observed under similar circumstances with Utricularia. 

Aldrovanda vesiculosa, var. australis. Dried leaves of 
this plant from Queensland in Australia were sent me by 
Prof. Oliver from the herbarium at Kew. Whether it ought 
to be considered as a distinct species or a variety, cannot be 
told until the flowers are examined by a botanist. The pro- 
jections at the upF)er end of the petiole (from four to six in 
number) are considerably longer relatively to the blade, and 
much more attenuated than those of the European form. 
They are thickly covered for a considerable space near their 



Chap. XIV.] ALDROVANDA VESICULOSA. 267 

extremities with the upcurved prickles, which are quite 
absent in the latter form; and they generally bear on their 
tips two or three straight prickles instead of one. The bi- 
lobed leaf appears also to be rather larger and somewhat 
broader, with the pedicel by which it is attached to the 
upper end of the petiole a little longer. The points on the 
infolded margins likewise differ; they have narrower bases, 
and are more pointed; long and short points also alternate 
with much more regularity than in the European form. 
The glands and sensitive hairs are similar in the two forms. 
No quadrifid processes could be seen on several of the leaves, 
but I do not doubt that they were present, though indistin- 
guishable 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 
tibiae I suppose was an aquatic species, but was not allied to 
Colymbetes. All the softer tissues of this beetle were com- 
pletely dissolved, and its chitinous integuments were as 
clean as if they had been boiled in caustic potash ; so that it 
must have been enclosed for a considerable time. The glands 
were browner and more, opaque than those on other leaves 
which had caught nothing ; and the quadrifid processes, from 
being partly filled with brown granular matter, could be 
plainly distinguished, which was not the case, as already 
stated, on the other leaves. Some of the points on the in- 
folded margins likewise contained brownish granular matter. 
We thus gain additional evidence that the glands, the 
quadrifid processes, and the marginal points, all have the 
power of absorbing matter, though probably of a different 
nature. 

Within another leaf disintegrated remnants of a rather 
small animal, not a crustacean, which had simple, strong, 
opaque mandibles, and a large unarticulated chitinous coat, 
were present. Lumps of black organic matter, possibly of 
a vegetable nature, were enclosed in two other leaves; but 
in one of these there was also a small worm much decayed. 
But the nature of partially digested and decayed bodies, 
which have been pressed flat, long dried, and then soaked in 
water, cannot be recognised easily. All the leaves contained 



^68 ALDROVANDA VESICULOSA. [Cuap. XIV. 

unicellular and other Algse, still of a greenish colour, which 
had evidently lived as intruders, in the same manner as oc- 
curs, according to Cohn, within the leaves of this plant in 
Germany. 

Aldrovanida vesiculosa, var. verlicillata. Dr. King, Su- 
perintendent of the Botanic Gardens, kindly sent me dried 
specimens collected near Calcutta. This form was, I believe, 
considered by Wallich as a distinct species, under the name 
of verticillata. It resembles the Australian form much 
more nearly than the 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, 1 believe, 
larger and certainly broader even than those of the Austral- 
ian form; so that the greater convexity of their margins 
was conspicuous. The length of an open leaf being taken 
at 100, the breadth of the Bengal form is nearly 173, of the 
Australian form 147, and of the German 134. The points 
on the infolded margins are like those in the Australian 
form. Of the few leaves which were examined, three con- 
tained entomostracan crustaceans. 

Concluding Remarks. The leaves of the three foregoing 
closely allied species or varieties are manifestly adapted for 
catching living creatures. With respect to the functions of 
the several parts, there can be little doubt that the long 
jointed hairs are sensitive, like those of Diontea, and that, 
when touched, they cause the lobes to close. That the glands 
secrete a true digestive fluid and afterwards absorb the di- 
gested matter, is highly probable from the analogy of Di- 
ontea, from the limpid fluid within their cells being aggre- 
gated into spherical masses, after they had absorbed an 
infusion of raw meat, from their opaque and granular con- 
dition in the leaf, which had enclosed a beetle for a long 
time, and from the clean condition of the integuments of 
this insect, as well as of crustaceans (as described by Cohn), 
which have been long captured. Again, from the effect pro- 
duced on the quadrifld processes by an immersion for 24 hrs. 
in a solution of urea, from the presence of brown granular 
matter within the quadrifids of the leaf in which the beetle 
had been caught, and from the analogy of Utricularia, it 
is probable that these processes absorb excremcntitious and 



Chap. XIV.] CONCLUDING REMARKS. 

decaying animal matter. It is a more curious face that the 
points on the infolded margins apparently serve to absorb 
decayed animal matter in the same manner as the quadrifids. 
We can thus understand the meaning of the infolded mar- 
gins of the lobes furnished with delicate points directed 
inwards, and of the broad, flat, outer portions, bearing quad- 
rifid processes; for these surfaces must be liable to be irri- 
gated by foul water flowing from the concavity of the leaf 
when it contains dead animals." This would follow from vari- 
ous causes, from the gradual contraction of the concavity, 
from fluid in excess being secreted, and from the genera- 
tion of bubbles of air. More observations are requisite on 
this head; but if this view is correct, we have the remark- 
able case of different parts of the same leaf serving for very 
different purposes one part for true digestion, and another 
for the absorption of decayed animal matter. We can thus 
also understand how, by the gradual loss of either power, a 
plant might be gradually adapted for the one function to the 
exclusion of the other: and it will hereafter be shown that 
two genera, namely Pinguicula and Utricularia, belonging 
to the same family, have been adapted for these two dif- 
ferent functions. 

[Duval-Jouve's obaorvatlons Similar structures are described 
throw some doubt on this point. by Duval-Jouve as occurring ou 
He has shown (' Bull. Soc. Bot. the leaves of Callltrlche, Nuphar 
de France,' t. xxlll. p. 1.30) that httcum and N]/mph<Fa alba, and 
In the uHnter buds of Aldrovanda similar observations were made 
the leaves are reduced to a petl- by the late E. Ray Lanljester 
Die, the lamina being absent. C Brit. Assoc. Report,' 1850, pub- 
Now the lamina bears both the llshed 1851. 2nd part of volume, 
glands for which a peptic func- p. 11.3). This being so we must 
tlon Is suggested In the text, and suspend judgment as to the func- 
also the quadrlfld processes which tlon of the quadrlfld processes on 
are believed to absorb the prod- the outer region of the lamina of 
ucts of deca;y. Since the leaves the leaves of Aldrovanda. Charles 
of the winter buds have no Darwin appears to have been Im- 
lamlnse, and cannot therefore pressed with the Importance of 
capture prey, we . must believe these facts, as I Infer from a 
that the glands on the petioles note pencilled In Professor Mar- 
have merely general absorptive tin's translation of ' Insectlvo- 
functlon, and are not specialised rous Plants,' where Duval-Jouve's 
In relation to the products of the paper Is discussed In a note by 
decaying victims of the plant. the translator. F. D.] 



970 DROSOPUYLLUM LUSITANICUM. L^uap. XV. 



CHAPTER XV. 

DROSOPUYLLUM RORIDULA BYBLIS GLANDULAR HAIRS OF OTHER 
PLANTS CONCLUDING REMARKS ON TUE DROSERACE^ 

Drofiophyllum Structure of leaves Nature of the secretion Manner of 
catching insects Power of absorption Digestion of aninial sub- 
stiinccs Summary on Drosopliylluni lioridula Byblis Ctlandular 
hairs of other plants, their power of abs(>ri)tion Saxifraga l*rimula 
Pelargonium Erica Mirabilis Nicotiana Summary on glandular 
hairs Concluding remarks on the Droseracese. 

Drosophyllum 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 plenti- 
fully on the sides of dry hills near Oporto, and that vast 
numbers of flies adhere to the leaves. This latter fact is 
well known to the villagers, who call the plant the " fly- 
catcher," and hang it up in their cottages for this purpose. 
A plant in my hothouse caught so many insects during the 
early part of April, although the weather was cold and in- 
sects 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 IG minute insects, chiefly Diptera, were 
found in the autumn adhering to them. I neglected to ex- 
amine the roots, but I hear from Dr. Hooker that they are 
very small, as in the case of the previously mentioned mem- 
bers of the same family of the Droseracero. 

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 sur- 
faces, 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 



Chap. XV.] SECRETION. 271 

much in lenpth. The glands also differ in size, and are of 
a bright pink or of a purple colour; their upper surfaces are 
convex, and the lower flat or even concave, so that they re- 
semble 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 ,r^ Y^' ' , . 
the glands on pedicels were secreting tan'icum.) 

copiously. Nevertheless, if little bits of Part of leaf, enlarged 
damp albumen or fibrin are placed on seven times, show- 
^, Mill , . , ing lower surface, 

these sessile glands, they, begin after a 

time to secrete, in the same manner as do the glands of 
Dionaea 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 remark- 
able manner from that of Drosera, in being acid before the 
glands have been in any way excited;' and judging from the 




272 DROSOPIIYLLUM LUSITANICITM. [Chap. XV. 

changed colour of litmus paper, more strongly acid than that 
of Drosera. This fact was observed repeatedly; on one oc- 
casion I chose a young leaf, which was not secreting freely, 
and had never caught an insect, yet the secretion on all the 
glands coloured litmus paper of a bright red. From the 
quickness with which the glands are able to obtain animal 
matter from such substances as well-washed fibrin and car- 
tilage, I suspect that a small quantity of the proper fer- 
ment must be present in the secretion before the glands 
are excited, so that a little animal matter is quickly dis- 
solved. 

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 diflficult, by the aid of a finely 
pointed polished needle, slightly damped with water, to place 
a minute particle of any kind on one of the drops; for on 
withdrawing the needle, the drop is generally withdrawn; 
whereas with Drosera there is no such difficulty, though the 
drops are occasionally withdrawn. From this p)eculiarity, 
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 crawl- 
ing of the insect, as from its wings being clogged by the se* 
cretion it .cannot fly away. 

There is another difference in function between the 
glands of these two plants : we know that the glands of Dro- 
sera 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 Drosophyllum, the amount of secretion never ap- 
peared to be in the least increased. As insects do not com- 
monly adhere to the tnllcr glands, but withdraw the secre- 
tion, we can see that there would be little use in their having 



Chap. XV.] SECRETION. 278 

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, with- 
out being stimulated, continually secrete, so as to replace 
the loss by evaporation. Thus when a plant was placed 
under a small bell-glass with its inner surface and support 
thoroughly wetted, there was no loss by evaporation, and so 
much 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 sub- 
stances and liquids were given did not, as just stated, se- 
crete more copiously; on the contrary, they absorbed their 
own drops of secretion with surprising quickness. Bits of 
damp fibrin were placed on five glands, and when they were 
looked at after an interval of 1 hr. 12 m., the fibrin was 
almost dry, the secretion having been all absorbed. So it 
was with three cubes of albumen after 1 hr. 19 m., and with 
four other cubes, though these latter were not looked at 
until 2 hrs. 15 m. had elapsed. The same result followed 
in between 1 hr. 15 m. and 1 hr. 30 m. when particles both of 
cartilage and meat were placed on several glands. Lastly, a 
minute drop (about ^ of a minim) of a solution of one part 
of nitrate of ammonia to 146 of water was distributed be- 
tween the secretion surrounding three glands, so that the 
amount of fluid surrounding each was slightly increased; 
yet when looked at after 2 hrs., all three were dry. On the 
other hand, seven particles of glass and three of coal-cinders, 
of nearly the same size as those of the above-named organic 
substances, were placed on ten glands; some of them being 
observed for 18 hrs., and others for two or three days; but 
there was not the least sign of the secretion being absorbed. 
Hence, in the former cases, the absorption of the secretion 
must have been due to the presence of some nitrogenous 
matter, which was either already soluble or was rendered so 
by the secretion. As the fibrin was pure, and had been well 
washed in distilled water after being kept in glycerine, and 
as the cartilage had been soaked in water, I suspect that 
these substances must have been slightly acted on and ren- 
dered soluble within the above stated short periods. 

The glands have not only the power of rapid absorption. 



874 DROSOPHYLLUM LUSITANICUM. [Chap. XV. 

but likewise of secreting again quickly; and this latter habit 
has perhaps been gained, inasmuch as insects, if they touch 
the glands, generally withdraw the drops of secretion, which 
have to be restored. The exact period of re-secretion was 
recorded in only a few cases. The glands on which bits of 
meat were placed, and which were nearly dry after about 1 
hr. 30 m., when looked at after 22 additional hours, were 
found secreting; so it was after 24 hrs. with one gland on 
which a bit of albumen had been placetl. 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 be- 
ginning to re-secrete after only 12 additional hours. 

Tentacles Incapable of Movement. Many of the tall 
tentacles, 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 repeated- 
ly irritated the glands with a needle, and scratched and 
pricked the blades, but neither the blade nor the tentacles 
became at all inflected. We may therefore conclude that 
they are incapable of movement. 

On the Power of Absorption possessed hy the Olands. ^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 sub- 
stances 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 stimulated, the 
exterior cells commonly contain only limpid purple fluid; 
the more central ones including mulberry-like masses of 
purple granular matter. A leaf was placed in a little solu- 
tion 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 strong- 
ly marked aggregation of their contents, more especially of 
the inner cells. Another leaf was placed in a solution of 
the same strength of nitrate of ammonia, and the glands 
were slightly darkened in 25 m., more so in 50 m., and after 
1 hr. 30 m. were of so dark a red as to appear almost black. 



Cdap. XV.] ABSORPTION. 275 

Other leaves were placed in a weak infusion of raw meat and 
in human saliva, and the glands were much darkened in 25 
m., and after 40 m. were so dark as almost to deserve to be 
called black. Even immersion for a whole day in distilled 
water occasionally induces some aggregation within the 
glands, so that they become of a darker tint. In all these 
cases the glands are affected in exactly the same manner 
as those of Drosera. Milk, however, which acts so ener- 
getically on Drosera, seems rather less effective on Drosophyl- 
lum, for the glands were only slightly darkened by an im- 
mersion of 1 hr. 20 m., but became decidedly darker after 
3 hrs. Leaves which had been left for 7 hrs. in an infusion 
of raw meat or in saliva were placed in the solution of car- 
bonate of ammonia, and the glands now became greenish; 
whereas, if they had been first placed in the carbonate, they 
would have become black. In this latter case, the ammonia 
probably combines with the acid of the secretion, and there- 
fore 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 undecomposed carbon- 
ate 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 
19 



276 DROSOPHYLLUM LUSITANICUM. [Chap. XV. 

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 cir- 
cumstance for which I cannot account. 

Digestion of Solid Animal Matter. Whilst I was trying 
to place on two of the taller glands little cubes of albumen, 
these slipped down, and, besmeared with secretion, were left 
resting on some of the small sessile glands. After 24 hrs. 
one of these cubes was found completely liquefied, but with 
a few white streaks still visible; the other was much round- 
ed, but not quite dissolved. Two other cubes were left on 
tall glands for 2 hrs. 45 m., by which time all the secretion 
was absorbed ; but they were not perceptibly acted on, though 
no doubt some slight amount of animal matter had been 
absorbed from them. They were then placed on the small 
sessile glands, which being thus stimulated secreted copious- 
ly in the course of 7 hrs. One of these cubes was much 
liquefied within this short time; and both were completely 
liquefied after 21 hrs. 15 m. ; the little liquid masses, how- 
ever, still showing some white streaks. These streaks disap- 
peared after an additional period of 6 hrs. 30 m. ; and by 
next morning (t. 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 con- 
clude, 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 insufiicient to 
dissolve a particle of albumen which within the same time 
would have been dissolved by the secretion from several of 
the small sessile glands. Owing to the death of my last 
plant, I was unable to ascertain which of these alternatives 
is the true one. 

Four minute shreds of pure fibrin were placed, each rest- 
ing on one, two, or three of the taller glands. In the course 
of 2 hrs. 30 m. the secretion was all absorbed, and the shreds 
wore left almost dry. They were then pushed on to the ses- 
sile glands. One shred, after 2 hrs. 30 m., seemed quite dis- 



Chap. XV.] CONCLUDING REMARKS. 277 

solved, 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 gran- 
ules of fibrin. The other two shreds were completely lique- 
fied after 21 hrs. 30 m. ; but in one of the drops a few 
granules could still be detected. These, however, were dis- 
solved 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 di- 
gests albumen and fibrin rather more quickly than Drosera 
can; and this may perhaps be attributed to the acid, to- 
gether probably with some small amount of the ferment, be- 
ing present in the secretion, before the glands have been 
stimulated; so that digestion begins at once. 

Concluding Remarks. The linear leaves of Drosophyl- 
lum 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 
nitrogenous matter. But glands of this kind are present on 
the leaves of Drosera hinata, and appear to be represented by 
the papilla3 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 tend- 
ing towards abortion, are retained on the backs of the leaves 
of Drosera hinata. 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 se- 
cretion 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, smoth- 
ered 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 nitroge- 
nous matter; on the contrary, they then absorb their own se- 
cretion with extraordinary quickness. In a short time they 
begin to secrete again. All these circumstances are prob- 



2T8 RORIDULA. [Chap. XV. 

ably connected with the fact that insects do not commonly 
adhere to the glands with which they first come into con- 
tact, though this does sometimes occur; and that it is chiefly 
the secretion from the sessile glands which dissolves animal 
matter out of their bodies. 

RORIDULA. 

Roridula dentata. This plant, a native of the western 
parts of the Cape of Good Hope, was sent to me in a dried 
state from Kew. It has an almost woody stem and branches, 
and apparently grows to a height of some feet. The leaves 
are linear, with their summits much attenuated. Their 
upper and lower surfaces are concave, with a ridge in the 
middle, and both are covered with tentacles, which differ 
greatly in length; some being very long, especially those 
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 projecting at right 
angles to the main linear blade. These lateral divisions are 
often very short and bear only a single terminal tentacle, 
with one or two short ones on the sides. No distinct line of 
demarcation can be drawn between the pedicels of the long 
terminal tentacles and the much attenuated summits of the 
leaves. We may, indeed, arbitrarily fix on the point to 
which the spiral vessels proceeding from the blade extend; 
but there is no other distinction. 

It was evident from the many particles of dirt 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 



Chap. XV.] BYBLIS. 279 

possessed the power of movement. Hence, in this negative 
character, Koridula resembles its northern representative, 
Drosophyllum. 

BYBLIS. 

Byhlis gigantea (Western Australia). A dried speci- 
men, 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 
intersecting spiral lines. Whether these lines are the result 
of contraction from the drying of the walls, I do not know, 
but the whole pedicel was often spirally rolled up. These 
glandular hairs are far more simple in structure than the so- 
called tentacles of the preceding genera, and they do not dif- 
fer essentially from those borne by innumerable other plants. 
The flower-peduncles bear similar glands. The most singu- 
lar 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 be- 
smeared with the secretion and rest on the small sessile 
glands, which, if we may judge by the analogy of Drosophyl- 
lum, then pour forth their secretion and afterwards ab- 
sorb the digested matter. 

Supplementary Observations on the Power of Absorption 
by the Glandular Hairs of other Plants. A few observations 
on this subject may be here conveniently introduced. As the 
glands of many, probably of all, the species of Droseraccaj 

Snohs, ' Tralt6 de Bot..' 8rrt edit. 1874. p. 1026. 



280 GLANDULAR HAIRS. [Chap. XV. 

absorb various fliiida or at least allow them readily to enter/ 
it seems 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 Droseracec^. 
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 Droseracese 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 
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 ani- 
mal substances, but such experiments would have been diffi- 
cult 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 cer- 
tainly dissolves animal matter. 

Saxifraga vmbrosa. The flower-peduncles and petioles of the 
leaves are clothed with short hairs, bearing pink-coloured glandn, 
formed of several polygonal cells, with their pedicels divided by 
partitions into distinct cells, which are generally colourless, but 
sometimes pink. The glands secrete a yellowish viscid fluid, by 
which minute Diptera are sometimes, though not often, caught.* 
The cells of the glands contain bright pink fluid, charged with 
granules or with globular masses of pinkisli pulpy matter. This 
nuitter must be protoplasm, for it is seen to undergo slow but in- 
esaant changes of form if a gland be plaee<l in a dmp 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 glnmls retainel llioir bright pink roloiir; and the 
protoplasm within their cells did not appear to have become more 

' The distinction between tnie mncentlcnl .Toiirnnl,' May 1875> 

absorption and mero permeation, that he examined some dozens of 

or Imbibition, Is by no means plants, and In almost every In- 

clearly understood: see MUller's stance remnants of Insects ad- 

' I'hysloloKy.' Kng. translat. 18.38, herod to the leaves. So It Is, as 

vol. I. p. 280. I hear from a friend, with this 

* In the case of Saxifraga tri- plant In Ireland.' 
Oaettflitet, Mr. Druce says (' Pbar- 



Chap. XV.] THEIR POWER OF ABSORPTION. 281 

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 i)lant, 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 purj)le 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 wrter; 
so that the cells had a ditterent appearance every four or five min- 
utes. Elongated masses became in the course of one or tw3 
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 Urosera. The 
cells of the pedicels were not allected by the infusion; nor were 
they in the following experiment. 

Another flower-stem was placed in the same manner and for the 
same length of time in a solution of one part of nitrate of ammonia 
to 146 of water (or 3 grs. to 1 oz.), and the glands were discol- 
oured in exactly the same manner as by the infusion of raw meat. 

Another flower-stem was immersed, as before, in a solution of 
one part carbonate of ammonia to 109 of water. The glands, after 
1 hr. 30 m., were not discoloured, but after 3 hrs. 45 m. most of them 
had become dull purple, some of them blackish-green, a few being 
still unaffected. The little masses of protoplasm within the cells 
were seen in movement. The cells of the pedicels were unaltered. 
The experiment was repeated, and a fresh flower-stem was left for 
23 hrs. in the solution, and now a great effect was produced ; all 
the glands were much blackened, and the previously transparent 
fluid in the cells of the pedicels, even down to their bases, contained 
spherical masses of granular matter. By comparing many diflfer- 
ent hairs, it was evident Ihat the glands first absorb the carbon- 
ate, and that the eflTect 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, in the 
darkening of the glands, and in the process of aggregation travel- 
ling down the cells of the pedicels, there is the closest resemblance 
to what takes place when a tentacle of Drosera is immersed in n 
weak solution of the same salt. The glands, however, absorb very 
much more slowjy than those of Drosera. Besides the glandular 
hairs, there are star-shaped organs which do not appear to secrete, 
and which were not in the least affected by the above solutions. 

Although in the case of uninjured flower-stems and leaves the 
carbonate seems to be absorbed only by the glands, yet it enters a 
cut surface much more quickly than a gland. Strips of the rind of 
a flower-stem were torn off, and the cells of the pedicels were seen 
to contain only colourless transparent fluid; those of the glands 



282 GLANDULAR HAIRS. [Chap. XV. 

including na usual some granular matter. These stripes were 
then immersed in the same solution as before (one part of the car- 
bonate to 109 of water), and in a few minutes granular matter ap- 
peared in the lower cells of all the pedicels. The action invariably 
commenced (for I tried the experiment repeatedly) in the lowest 
cells, and therefore close to the torn surface, and then gradually 
travelled up the hairs until it reached the glands, in a reversed di- 
rection 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 to 218 of water; and in both specimens the 
pedicels of the hairs near the cut ends now contained much granu- 
lar matter; and the glands were completely discoloured. 

Lastly, bits of meat were placed on some glands; these were 
examined after 23 hrs., as were others, which had apparently not 
long before caught minute flies; but they did not present any 
difference from the glands of other hairs. Perhaps there may not 
have been time enough for absorption. I think so, as some glands, 
on which dead flies had evidently long lain, were of a pale dirty 
purple colour or even almost colourless, and the granular matter 
within them presented an unusual and somewhat peculiar appear- 
ance. That these glands had absorbed animal matter from the 
flies, probably by exosmose into the viscid secretion, we may infer, 
not only from their changed colour, but because, when placed in a 
solution of carbonate of ammonia, some of the cells in their pe<licels 
become filled with granular matter; whereas the cells of other 
liairs, which had not caught flies, after being treated with the 
same solution for the same length of time, contained only a small 
quantity of granular matter. 15ut more evidence is necessary be- 
fore we fully admit that the glands of this saxifrage can absorb, 
even with ample time allowed, animal matter from the minute in- 
sects which they occasionally and accidentally capture. 

SoTifraga rotund i folia (?). The hairs on the flower-stems of 
this species are longer than those just described, and bear pale 
brown glands. Many were examined, and the cells of the pedicels 
were quite transparent. A bent stem was immersed for 30 m. in 
a solution of one part of carbonate of ammonia to 100 of water, 
and two or three of the uppermost cells in the pedicels now con- 
tained granular or aggregated matter; the glands having become 
of a bright yellowish-green. The glands of this species therefore 
absorb the oarbtjnate much more quickly than do those of 8axi- 
fraffd vtubrom, and the upper cells of the pedicels are likewise af- 
fected 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 afTecte<l. 

Primula sinensis. The flower-stems, the upper and lower sur- 
faces of the leaves and their footstalks, are all clothed with a mul- 
titude of longer and shorter hairs. The pedicels of the longer hairs 
are divided by transverse partitions into eight or nine cells. The 



Chap. XV.] THEIR POWER OP ABSORPTION. 283 

enlarged terminal cell is globular, forming a gland which secretes 
a variable amount of thick, slightly viscid, not acid, brownish- 
yellow matter. 

A piece of a young flower-stem was first immersed in distilled 
water for 2 hrs. 30 m., and the glandular hairs were not at all 
affected. Another piece, bearing twenty-five short and nine long 
hairs, was carefully examined. The glands of the latter contained 
no solid or semi-solid matter ; and those of only two of the twenty- 
five short hairs contained some globules. This piece was then im- 
mersed 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 serai-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 imme- 
diately beneath the glands. Looking to all thirty-four hairs, there 
could be no doubt that the glands had absorbed some of the car- 
bonate. Another piece was left for only 1 hr. in the same solu- 
tion, and aggregated matter appeared in all the glands. My son 
Francis examined some glands of the longer hairs, which con- 
tained 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 haira 
for 1 hr. 15 m., whilst under the microscope, with a solution of 
one part of the carbonate to 218 of water; the glands were not 
perceptibly affected, nor could this have been expected, as their 
contents were already aggregated. But in the cells of the pedicels 
numerous, almost colourless, spheres of matter appeared, which 
changed their forms and slowly coalesced ; the appearance of the 
cells being thus totally changed at successive intervals of time. 

The glands on a young Hower-stem, after having been left for 
2 hrs. t5 m. in a strong solution of one part of the carbonate to 109 
of water, contained an abundance of aggregated masses, but 
whether generated by the action of the salt, I do not know. This 
piece was again placed in the solution, so that it was immersed 
altogether for 6 hrs. 15 m., and now there was a great change; for 
almost all the spherical masses within the gland-cells had disap- 
peared, 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 
brown granular matter, a few still remained. If the spherical 
masses of aggregated matter had been originally produced merely 
by some chemical or physical action, it seems strange that a some- 
what longer immersion in the same solution should so completely 
alter their character. But as the masses which slowly and spon- 
taneously changed their forms must have consisted of living pro- 
toplasm, there is nothing surprising at its being injured or killed, 
and its appearance wholly changed by long immersion in so strong 
a solution of the carbonate as that employed. A solution of this 
strength paralyses all movement in Drosera, but does not kill the 



284 GLANDULAR HAIRa [Chap. XV. 

protoplasm; a still stronijer 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 im- 
perfect kind ot aggregation in the cells of Drosera; the little 
masses afterwards breaking up into granular or pulpy brown mat- 
ter. 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 carbonate. After 10 m. the glands showed a con- 
siderable degree of aggregation, and the protoplasm lining the cells 
of the pedicels was a little separated from the walls. Another leaf 
was left for 50 m. with the same result, excepting that the hairs 
became throughout their whole length of a brownish colour. In 
a third leaf, which was exposed for 1 hr. 50 m., there was much 
aggregated matter in the glands; and some of the masses showed 
signs of breaking up into brown granular matter. This leaf was 
again placed in the vapour, so that it was exposed altogether for 5 
hrs. 30 m. ; and now, though I examined a large number of glands, 
aggregated masses were found in only two or three; in all the 
others, the masses, which before had been globular, were con- 
verted into brown, opaque, granular matter. We thus see that 
exposure to the vapour for a considerable time produces the same 
eflfects as long immersion in a strong solution. In both cases there 
could hardly be a doubt that the salt had been absorbed chiefly or 
exclusively by the glands. 

On another occasion bits of damp fibrin, drops of a weak in- 
fusion of raw meat and water, were left for 24 hrs. on some leaves; 
the hairs were then examined, but to my surprise differed in no re- 
spect from others which had not been touched by these fluids, 
^lost of the cells, however, inelude<l hyaline, motionless little 
spheres, which did not seem to consist of protoplasm, but, I suppose, 
of some balsam or essential oil. 

Pelnrffonium zoiialc (var. edged with white). The leaves are 
clothed with numerous multicellular hairs; some simply pointetl; 
others bearing glandular heads, and differing much in length. The 
glands on a piece of leaf were examined and found to contain only 
a limpid fluid; most of the water was removed from beneath the 
covering glass and a minute drop of one part of carbonate of 
ammonia to 146 of water was added ; so that an extremely small 
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 



Chap. XV.] THEIR POWER OF ABSORPTION. 285 

of the longer hairs. After the specimen had been left for 1 hr. in 
the solution, many of the smaller globules had changed their posi- 
tions; 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 
of darker brown granular matter. Hence from what we have seen 
with Primula sinensis, there can be little doubt that these masses 
originally consisted of living protoplasm. 

A drop of a weak infusion of raw meat was placed on a leaf, 
and after 2 hrs. 30 m. many spheres could be seen within the 
glands. These spheres, when looked at again after 30 m., had 
slightly changed their positions and forms, and one had separated 
into two; but the changes were not quite like those which the 
protoplasm of Drosera undergoes. These hairs, moreover, had not 
been examined before immersion, and there were similar spheres in 
some glands which had not been touched by the infusion. 

Erica 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 occa- 
sionally though rarely, caught. Some leaves were left for 23 hrs. 
in a weak infusion of raw meat and in water, and the hairs were 
then compared, but they differed very little or not at all. In both 
cases the contents of the cells seemed rather more granular than 
they were before; but the granules did not exhibit any movement. 
Other leaves were left for 23 hrs. in a solution of one part of car- 
bonate of ammonia to 218 of water, and here again the granular 
matter appeared to have increased in amount; but one such mass 
retained exactly the same form as before after an interval of 5 hrs., 
so that it could hardly have consisted of living protoplasm. These 
glands seem to have very little or no power of absorption, certainly 
much less than those of the foregoing plants. 

Mirabilis longiftora. The stems and both surfaces of the leaves 
bare viscid hairs. Young plants, from 12 to 18 inches in height in 
my greenhouse, caught so many minute Diptera, Colcoptera, and 
larve, that they were quite du.sted with them. The hairs are 
short, of unequal .lengths, formed of a single row of cells, sur- 
mounted by an enlarged cell which secretes viscid matter. These 
terminal cells or glands contain granules and often globules of 
granular matter. Within a gland which had caught a small in- 
sect, one such mass was observed to undergo incess;int changes 
of fom, with the occasional appearance of vacuoles. Hut I do not 
believe that this protoplasm had been generatetl by matter ab- 
sorbed 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 granu- 
lar matter. A piece of leaf was immersed for 24 hrs. in a solution 



286 GLANDULAR HAIRS. [Chap. XV. 

of one part of mrlwnnte of ammonia to 218 of water, but the hairs 
seenjed very little atreeteti by it, excepting that |)erhap8 the glands 
were rendered rather more opaque. In the leaf itself, however, the 
grains of chlorophyll near the cut surfaces had run together, or 
become aggregated. Nor were the glands on another leaf, after 
an immersion for 24 hrs. in an infusion of raw meat, in the least 
affected; but the protoplasm lining the cells of the pedicels had 
shrunk greatly from the walls. This latter effect may have been 
due to exosmose, as the infusion was strong. We may therefore 
conclude that the glands of this plant either have no power of ab- 
sorption or that the protoplasm which they contain is not acted on 
by a solution of carbonate of ammonia (and this seems scarcely 
credible) or by an infusion of meat. 

Nicotiana tabacum. This plant is covered with innumerable 
hairs of unequal lengths, which catch many minute insects. The 
pedicels of the hairs are divided by transverse partitions, and the 
secreting glands are formed of many cells, containing greenish mat- 
ter with little globules of some substance. Leaves were left in an 
infusion of raw meat and in water for 20 hrs., but presented no 
difference. Some of tliese same leaves were then left for above 2 
hrs. in a solution of carbonate of ammonia, but no effect was pro- 
duced. I regret that other experiments were not tried with more 
care, as M. Schloesing has shown * that tobacco plants supplied 
with the vapour of carbonate of ammonia yield on analysis a 
greater amount of nitrogen than other plants not thus treated; 
and, from what we have seen, it is probable that some of the 
vapour may be absorbed by the glandular hairs. 

Summary of the Observations on Glandular Hairs. 
From the foregoing observations, few as they are, we see that 
the glands of two species of Saxifraga, of a Primula and Pe- 
largonium, have the power of rapid absorption; whereas the 
glands of an Erica, Mirabilis, and Nicotiana, either have no 
such power, or the contents of the cells are not affected by 
the fluids employed, namely a solution of carbonate of am- 
monia and an infusion of raw meat. As the glands of 
the Mirabilis contain protoplasm, which did not become 
aggregated from exposure to the fluids just named, though 
the contents of the cells in the blade of the leaf were greatly 
affected by carbonate of ammonia, we may infer that they 
cannot absorb. We may further infer that the innumerable 
insects caught by this plant are of no more service to iti 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 

* Compte* rcndns.' June 15. paper In given in the ' Gardener's 
1874. A good abstract of this Chronicle,' July 11, 1874. 



Chap. XV.] THEIR POWER OP ABSORPTION. 287 

of Saxifraga, as this genus is distantly allied to Drosera. 
Their glands absorb matter from an infusion of raw meat, 
from solutions of the nitrate and carbonate of ammonia, and 
apparently from decayed insects. This was shown by the 
changed dull purple colour of the protoplasm within the cells 
of the glands, by its state of aggregation, and apparently by 
its more rapid spontaneous movements. The aggregating 
process spreads from the glands down the pedicels of the 
hairs; and we may assume that any matter which is ab- 
sorbed ultimately reaches the tissues of the plant. On the 
other hand, the process travels up the hairs whenever a sur- 
face is cut and exposed to a solution of the carbonate of am- 
monia. 

The glands on the flower-stalks and leaves of Primula 
sinensis quickly absorb a solution of the carbonate of am- 
monia, and the protoplasm which they contain becomes ag- 
gregated. 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 solu- 
tion, 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 tlie 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 disintegration 
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 
percent^e of ammonia, and the atmosphere a minute quan- 
tity of the carbonate, this power can hardly fail to be 



288 GLANDULAR HAIRS. [Chap. XV. 

beneficial. Nor can the benefit be quite so insi(?nificant as 
it mifirlit at first be thought, for a moderately tine plant of 
Primula sinensis bears the astonishiufi: number of above two 
millions and a half of glandular hairs," all of which are able 
to absorb ammonia brought to them by the rain. It is more- 
over probable that the glands of some of the above-named 
plants obtain animal matter from the insects which are oc- 
casionally entangled by the viscid secretion. 

CONCLUDING REMARKS 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 affected by Drosophyllum, Roridula, and Byblis, solely by 
the viscid fluid secreted from their glands; by Drosera, 
through the same means, together with the movements of 
the tentacles; by Diona?a 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 con- 
tract and carry with them the broad, thin margins of the 
lobes. In Dionaa 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. 

My son Frnncls connted the eluded) wns found by a plnnim- 
baira on a spaee measured by eter to be .3!i.28r Honnre inclieH: 
means of a mierouieter, and so that the area of both surfaees 
found that there were :C),336 on was 78.57 K(iuare Inches. Thus 
a square Inch of the upper sur- the phmt (excluding the flower- 
face of the leaf, and 30,035 on stems) must have lioriie the as- 
the lower surface; that Is. in tonlslilujj number of 2.5U8,()9U 
about the prrjportlon of 100 on Kliindular hairs. The hairs were 
the upper to 8.) on the lower sur- counted late In the autumn, and 
face. On a sipiare Inch of both by the following spring (May) the 
surfaces there were (!5,;i71 hairs. leaves of some other plants of 
A moderately fine plant bearing the same lot were found to be 
twelve leaves (the larger ones be- from one-tliird to one-fourth 
Ing a little more than two Inches broader and longer than they 
in diameter) was now selected, were before: so that no doubt 
and the area of all the leaves, the Klandular hairs had Increased 
together with their footstalks In number, and probably now 
(the flower-stems not being in- much exceeded tliree millions. 



Chap. XV.] DROSERACE^. 289 

There can hardly be a doubt that all the plants belonging 
to these six genera have the power of dissolving animal mat- 
ter 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, Dro- 
sophyllum, and Dionaja; almost certainly with Aldrovanda; 
and, from analogy, very probable with Roridula and Byblis. 
We can thus understand how it is that the three first-named 
genera are provided with such small roots," and that Aldro- 
vanda is quite rootless; about the roots of the two other 
genera nothing is known. It is, no doubt, a surprising fact 
that a whole group of plants (and, as we shall presently see, 
some other plants not allied to the Droseracese) should sub- 
sist partly by digesting animal matter, and partly by de- 
composing carbonic acid, instead of exclusively by this latter 
means, together with the absorption of matter froni the soil 
by the aid of roots. We have, however, an equally anomalous 
case in the animal kingdom; the rhizocephalous crustace- 
ans do not feed like other animals by their mouths, for they 
are destitute of an alimentary canal; but they live by ab- 
sorbing through root-like processes the juices of the animals 
on which they are parasitic' 

Of the six genera, Drosera has been incomparably the 
most successful in the battle for life; and a large part of its 

[Fraustndt (Dissertation, by absorption through branching 
Breslau, 1876) shows that the root-like processes. If one rare 
roots of DIousea are by no means clrrlpede, the Anelasma aqualicola, 
small. In another Breslau DIs- had become extinct, it would 
sertatlon (1887) Otto Peuzig have been very ditficult to conjee- 
shows that the roots of Droxo- ture how so enormous a change 
phyllum luHitanictim are also well could have been gradually ef- 
developed. Pfeffer ('Landwirth. fected. But, as Fritz MilUer re- 
Jahrbucher,' 1877) points out that marks, we have In Anelasma an 
the argument from the small de- animal In an almost exactly In- 
velopment of roots In some car- termedlate condition, for it has 
nlvorous plants Is. valueless, be- root-like processes embedded In 
cause the same state of things is the skin of the shark on which It 
found In many marsh and aquatic Is parasitic, and Its prehensile 

Slants which neither catch nor cirri and mouth (as described In 
Igest Insects. F. I).] my monograph on the Lepadlda^, 
' Fritz MUUer. ' Facts for Dar- ' Ray Soc.' 1851, p. 1(59) are In a 
win,' Eng. trans. 18(!9, p. i:{0. most feeble an<i almost rudl- 
The rhizocephalous crustaceans nientary condition. Dr. K. Koss- 
are allied to the clrrlpe<les. It Is mann has given a very Interest- 
hardly possible to Imagine a Ing discussion on this subject In 
greater difference than between his ' Suctoria and Lepadidie," 
an animal with prehensile limbs, 187.3. See. also. Dr. Dohrn, ' Der 
a well-constructed mouth and all- Urspruug der Wirbelthlere,' 1875, 
mentary canal, and one destitute p. 77. 
of all these organs and feeding 



290 CONCLUDING REMARKS [Chap. XV. 

success may be attributed to its manner of catching insects. 
It is a dominant form, for it is believed to include about 100 
species,* which range in the Old World from the Arctic 
regions to Southern India, to the Cape of Good Hope, Mada- 
gascar, and Australia ; and in the New World from Canada 
to Tierra del Fuego. In this respect it presents a marked 
contrast with the five other genera, which appear to be fail- 
ing groups. Dionsea includes only a single species, which is 
confined to one district in Carolina. The three varieties or 
closely allied species of Aldrovanda, like so many water- 
plants, have a wide range from Central Europe to Bengal 
and Australia. Drosophyllum includes only one species, 
limited to Portugal and Morocco. Roridula and Byblis each 
have (as I hear from Prof. Oliver) two species; the former 
confined to the westei-n parts of the Cape of Good Hope, and 
the latter to Australia. It is a strange fact that Dioncea, 
which is one of the most beautifully adapted plants in the 
vegetable kingdom, should apparently be on the high road 
to extinction. This is all the more strange as the organs of 
Dionaea are more highly differentiated than those of Dros- 
era; its filaments serve exclusively as organs of touch, 
the lobes for capturing insects, and the glands, when excited, 
for secretion as well as for absorption ; whereas with Drosera 
the glands serve all these purposes, and secrete without being 
excited. 

By comparing the structure of the leaves, their d^ree of 
complication, and their rudimentary parts in the six genera, 
we are led to infer that their common parent form partook 
of the characters of Drosophyllum, Roridula, and Byblis. 
The leaves of this ancient form were almost certainly linear, 
perhaps divided, and bore on their upper and lower surfaces 
glands which had the power of secreting and absorbing. 
Some of these glands were mounted on pedicels, and others 
were almost sessile; the latter secreting only when stimu- 
lated by the absorption of nitrogenous matter. In Byblis 
the glands consist of a single layer of cells, supported on a 
unicellular pedicel; in Koridula they have a more complex 
structure, and are supported on pedicels formed of several 
rows of cells; in Drosophyllum they further include spiral 

Bfnthnm nnd Hooker, ' (Jon- one Bpeeles having been de- 
era I'lantanim.' Anstralln Ir the Borlbed from this country, as Pro- 
metropolis of the genus, forty- fessor Oliver Informs me. 



Chap. XV.] ON THE DROSERACE^. 291 

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 
thus led to inquire how the so-called tentacles of Drosera, 
which are manifestly of the same general nature as the glan- 
dular 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 tentacles 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. Roridula, perhaps, shows us 
how we may reconcile these diflSculties with respect to the 
homological nature of the tentacles. The lateral divisions 
of the leaves of this plant terminate in long tentacles; 
and these include spiral vessels which extend for only a 
short distance up them, with no line of demarcation between 
what is plainly the prolongation of the leaf and the pedicel 
of a glandular hair. Therefore there would be nothing anom- 
alous or unusual in the basal parts of these tentacles, 
which correspond with the marginal ones of Drosera, acquir- 
ing the power of movement ; and we know that in Drosera it 
is only the lower part which becomes inflected. But in order 
to understand how in this latter genus not only the marginal 
but all the inner tentacles have become capable of movement, 
we must further assume, either that through the principle of 
correlated development this power was transferred to the 
basal parts of the hairs, or that the surface of the leaf has 
been prolonged upwards at numerous points, so as to unite 
with the hairs, thus forming the bases of the inner tentacles. 
The above-named three genera, namely Drosophyllum, 

Snchs, Tralte de Botanique,' penhajrno. 1873, p. 0. ' Extrnit 

3rd edit. 1874, p. 1026. des Vldensknbellge Moddolelser 

' Dr. Warming. ' Sur la Dlf- de la Sop. d'HIst. nnt. de Copen- 

Wrence entre les Trichomes,' Co- hague,' Nos. 10-12, 1872. 
20 



292 CONCLUDING REMARKS [Chap. XV. 

Roridula, and Byblis, which appear to have retained a 
primordial condition, still bear glandular hairs on both 
surfaces of their leaves; but those on the lower surface have 
since disappeared in the more highly developed genera, with 
the partial exception of one species, Drosera binata. The 
small sessile glands have also disappeared in some of the 
genera, being replaced in Koridula by hairs, and in most 
species of Drosera by absorbent papillae. Drosera binata, 
with its linear and bifurcating leaves, is in an intermediate 
condition. It still bears some sessile glands on both surfaces 
of the leaves, and on the lower surface a few irr^rularly 
placed tentacles, which are incapable of movement. A 
further slight change would convert the linear leaves of this 
latter species into the oblong leaves of Drosera anglica, and 
these might easily pass into orbicular ones with footstalks 
like those of Drosera rotundifolia. The footstalks of this 
latter species bear multicellular hairs, which we have good 
reason to believe represent aborted tentacles. 

The parent form of Dionaja 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 Dionaja apparently represent the ex- 
treme marginal tentacles of Drosera, the six (sometimes 
eight) sensitive filaments on the upper surface, as well aa 
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- 
sereral members of the Droseracete consist in the leaves of 
some having the p)ower 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 



Chap. XV.] ON THE DROSERACEL^. 293 

surprising that they should readily allow fluids to pass in- 
wards; aud this inward passage would deserve to be called 
an act of absorption, if the fluids combined with the con- 
tents of the glands. Judging from the evidence above given, 
the secreting glands of many other plants can absorb salts 
of anunouia, of which they must receive small quantities from 
the rain. This is the case with two species of Saxifraga, 
and the glands of one of them apparently absorb matter from 
captured insects, and certainly from an infusion of raw 
meat. There is, therefore, nothing anomalous in the Drose- 
raceae having acquired the power of absorption in a much 
more highly developed d^ree. 

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 Droseracese 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 Droseraceae. But the difllculty 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 sub- 
stances 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 albumi- 
nous or proteid substances, such as protoplasm, chlorophyll, 
gluten, aleurone, and of carrying them from one part to 
other parts of their tissues. This must be effected by a 
solvent, probably consisting of a ferment together with an 
acid." Now, in the case of plants which are able to absorb 
already soluble matter from captured insects, though not 

" ' Traits do Botnnlquo.' Srd tho aid of Dr. H. Will, has aotu- 

wllt. 1S74, p. S44. See also for ally made the discovery that the 

following facts pp. 64, 70, 81i8, stn-ds of the vetch contain a fer- 

831. nient, which, when extracted hy 

" Since this sentence was glycerine, dissolves albuminous 

written, I have received a paper substances, such as fibrin, and 

by Gorup-Besanez (' Berlchte der converts them Into true peptones. 

Deutscheri Chem. (Jesellschaft.' [See, however, Vines' ' Plivslology 

Berlin, 1S74, p. 1478), who, with of Plants,' p. 190.-F. D.] 



294 CONCLUDING REMARKS [Chap. XV. 

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, in- 
asmuch as endosmose is accompanied by exosmose. If such 
exudation did ever occur, the solvent would act on the ani- 
mal matter contained within the captured insects, and this 
would be an act of true digestion. As it cannot be doubted 
that this process would be of high service to plants growing 
in very poor soil, it would tend to be perfected through natu- 
ral selection. Therefore, 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 diges- 
tive 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 Droseracece, 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 (. e. plants 
with their leaves, petioles and flower-peduncles, Ac, modi- 
fied for prehension) belonging to a large number of the most 
widely distinct orders, in the leaves of the many plants 



Chap. XV.] ON THE DROSERACE^. 295 

which go to sleep at night, or move when shaken, and in 
irritable stamens and pistils of not a few species. We may 
therefore infer that the power of movement can be by some 
means readily acquired. Such movements imply irritability 
or sensitiveness, but, as Cohn has remarked," the tissues of 
the plants thus endowed do not differ in any uniform man- 
ner from those of ordinary plants; it is therefore probable 
that all leaves are to a slight degree irritable. Even if an 
insect alights on a leaf, a slight molecular change is probably 
transmitted to some distance across its tissue, with the sole 
difference that no perceptible effect is produced. We have 
some evidence in favour of this belief, for we know that a 
single touch on the glands of Drosera does not excite in- 
flection; yet it must produce some effect, for if the glands 
have been immersed in a solution of camphor, inflection fol- 
lows within a shorter time than would have followed from 
the effects of camphor alone. So again with Dionaea, the 
blades in their ordinary state may be roughly touched with- 
out their closing; yet some effect must be thus caused and 
transmitted across the whole leaf, for if the glands have re- 
cently absorbed animal matter, even a delicate touch causes 
them to close instantly. On the whole we may conclude that 
the acquirement of a high degree of sensitiveness and of the 
power of movement by certain genera of the Droseraceae 
presents no greater diflficulty 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 Dionaa, and by certain other plants, well de- 
serves 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 par- 
ticle excites movement. On the other hand, a particle many 
times heavier may be gently laid on one of the filaments of 
Dionsea with no effect ; but if touched only once by the slow 
movement of a delicate hair, the lobes close; and this 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 

"See. the nbstrnct of his me- of \nt. Hist.' 3rd series, vol. xl. 
molr on the contrnctlle tissues of p. 188. 
plants, In the ' Annals and Mag. 



296 CONCLUDING REMARKS [Chap. XV. 

impulse to the exterior tentacles much more quickly than 
when they are mechanically irritated; whilst with Dionsca 
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 ob- 
served, 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 
Dionffia are also specialised, so as not to be uselessly affected 
by the weight or impact of drops of rain, or by blasts of air. 
This may be accounted for by 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 perfec- 
tion 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 
I>owerfully on the nervous system of animals, it does not 
appear that they include any diffused matter analogous to 
nerve-tissue. 

Although the cells of Drosera and Dionsea are quite as 
sensitive to certain stimulants as are the tissues which sur- 
round 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 ener- 
getic movement. When a gland of Drosera, or one of the 
filaments of Dioniea, is excited, the motor impulse radiates 
in all directions, and is not, as in the case of animals, di- 
rected 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 



Chap. XV.] ON THE DROSERACE^. 297 

two points. The rate at which the motor impulse is trans- 
mitted, though rapid in Diona;a, 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 prefigurement of the formation of nerves in 
animals in the transmission of the motor impulse being so 
much more rapid down the confined space within the ten- 
tacles of Drosera than elsewhere, and somewhat more rapid 
in a longitudinal than in a transverse direction across the 
disc. These plants exhibit still more plainly their inferior- 
ity to animals in the absence of any reflex action, except in 
so far as the glands of Drosera, when excited from a dis- 
tance, 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. 



298 PINGUICULA VULGARIS. [Chap. XVL 



CHAPTER XVI. 

PINGUICULA. 

Pinguicula vnlgarM Rtructnre of leaves Number of insects and other 
objects ciiuglit Movement of the margins of the leaves Uses of this 
movement Secretion, digestion, and absorption Action of the secre- 
tion on various animal and vegetable subsfcinces The ettects of sub- 
stances not contjiining soluble nitrogenous matter on the glands 
PingiiicHia grandiflora Pinguicula lusitanica, catches insects Move- 
ment of the leaves, secretion and digestion. 

Pinguicula vulgaris. This plant grows in moist places, 
generally on mountains. It bears on an average eight, 
rather thick, oblong, light green ' leaves, having scarcely 
any footstalk. A full-sized leaf is about li inch in length 
and i inch in breadth. The young central leaves are deeply 
concave, and project upwards; the older ones towards the 
outside are flat or convex, and lie close to the ground; form- 
ing a rosette from 3 to 4 inches in diameter. The margins 
of the leaves are incurved. Their upper surfaces are thickly 
covered with two sets of glandular hairs, differing in the 
size of the glands and in the length of their pedicels. The 
larger glands have a circular outline as seen from above, and 
are of moderate thickness; they are divided by radiating 
partitions into sixteen cells, containing light-green, homo- 
geneous fluid. They are supported on elongated, unicellular 
pHxliccls (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 Bntnlin plants grown In shndy places. It 

(* Flora,' 18(7) the yellowish- Is due to a yellow homogencons 

green colour Is peculiar to plants substance found In the epTdorraal 

grown In strong light, being re- cells aud In the glands. F. D.] 
placed by a more lively green in 



Chap. XVI.] PINGUICULA VULGARIS. 299 

of 18 inches; but the fluid in this case was secreted by a 
gland which had been excited. The edge of the leaf is trans- 
lucent, 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 Septem- 
ber 28; these had a greater number of roots, namely eight 
and eighteen, all under 1 inch in length, and very little 
branched. 

I was led to investigate the habits of this plant by being 
told by Mr. W. Marshall that on the mountains of Cumber- 
land many insects adhere to the leaves. 

A friend sent me on June 23 thirty-nine leaves from North Wales, 
which were selected owing to objects of some kind adhering to 
them. Of these leaves, thirty-two had caught 142 insects, or on an 
average 4.4 per leaf, minute fragments of insects not being in- 
cluded. Besides the insects, small leaves belonging to four diflfer- 
ent kinds of plants, those of Erica tetralix being much the com- 
monest, and three minute seedling plants, blown by the wind, 
adhered to nineteen of the leaves. One had caught as many as ten 
leaves of the Erica. Seeds or fruits, commonly of Carex and one 
of Juncus, besides bits of moss and other rubbish, likewise adhered 
to six of the thirty-nine leaves. The same friend, on June 27, 
collected nine plants bearing seventy-four leaves, and all of. these, 
with the exception of three young leaves, had caught insects; 
thirty insects were counted on one leaf, eighteen on a second, and 
sixteen on a third. Another friend examined on August 22 some 
plants in Donegal, Ireland, and found insects on 70 out of 157 
leaves; fifteen of these leaves were sent me, each having caught 
on an average 2.4 insects. To nine of them, leaves (mostly of 
Erica tetralix) adhered; 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 Care.x on the leaves of 
a Pinguicula in Switzerland, probably Pinguicula alpina : some in- 
sects, 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 num- 
ber; 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 some 



300 PINGUICULA VULGARIS. [Chap. XVI. 

plant. The sixteen seeds belonged to nine difTorent kinds, which 
could not be recognised, excepting one of Ranunculus, and several 
belonging to three or four distinct species of Carex. It apjK'ars 
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, larvae, 
spiders, and even small moths. 

We thus see that numerous insects and other objects are 
caught by the viscid leaves; but we have no right to infer 
from this fact that the habit is beneficial to the plant, any 
more than in the before-given case of the Mirabilis, or of 
the horse-chestnut. But it will 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 
capturing many insects; as old leaves, at least those grow- 
ing 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. 

ETperiment 1. A young and almost upright leaf was selected, 
with its two lateral edges equally and very slightly incurved. A 
row of small flies was placed along one margin. When looked at 



Chap. XVI.] MOVEMENTS OF THE LEAVES. 



301 



next day, after 15 hrs., this margin, but not the other, was found 
folded inwards, like the helix of the human ear, to the breadth 
of -^ of an inch, so as to lie partly over the row of flies (Fig. 15). 
The glands on which the flieS rested, as well as those on the over- 
lapping margin which had been brought into contact with the flies, 
were all secreting copiously. 

Experiment 2. A row of flies was placed on one margin of a 
rather old leaf, which lay flat on the ground; and in this case 
the margin, after the same interval as 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 reckon- 
ing from the time when the flies were placed 
on the leaf) the margin had everywhere be- 
gun 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 af- 
fected) 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 incurved 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 
between the apex and base of a leaf and halfway between the mid- 
rib and one margin. A short space of this margin, opposite the 




Fig. 15. 

(Pinguicula vulgaris.) 

Outline of leaf with 

left margin inflected 

over a row of small 

flies. 



309 



PINQUICULA VULGARIS. 



[Chap. XVL 



fly, showed a trace of incurvation after 3 hrs., and this became 
strongly pronounced in 7 hrs. After 24 hrs. the infolded edge waa 
only .10 of an inch (4.0G4 nun.) from the midrib. The margin now 
began to unfold, though the lly was left on the leaf; so. that by the 
next morning (/. e. 48 hrs. from the time when the fly was first 
put on) the infolded edge had almost recovered its original posi- 
tion, being now .3 of an inch (7.02 mm.), instead of .16 of an inch, 
from the midrib. A trace of ile.xure was, however, still visible. 

Uxiicrimcnt 6. A young and concave leaf was selected with its 
margins slightly and naturally incurved. Two rather large, ob- 
long, rectangular pieces of roast meat were placed with their ends 
touching the infolded edge, and .40 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 af- 
fected over a greater length between the two 
bits, owing to their conjoint action, than be- 
yond 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 al- 
most unfolded, and the bits had sunk down. 
When again examined after two days, the 
margin was quite unfolded, with the excep- 
tion 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 
.3.5 of an inch (8.89 mm.); so that the bit 
had been pushed inwards and across nearly one-third of its semi- 
diameter. 

Experiment 8. Cubes of sponge, soaked in a strong infusion of 
raw meat, were placed in close contact with the incurved edges of 
two leaves, an older and younger one. The distance from the 
o<lge8 to the midribs was carefully measured. After 1 hr. 17 m. 
there appeared to ho a trace of incurvation. After 2 hrs. 17 m. 
both leaves were plainly inflected ; the distance between the edges 
and midribs iM'ing now only half what it was at first. The in- 
curvation increased slightly during the next 4J hrs., but remained 
nearly the same for the next 17 hrs. 30 m. In ^~y hrs. from the 
time when the sponges were placed on the leaves, the margins 




Fio. 16. 

(PinguictUa vulgaris.) 
Outline of leaf, with 
right murKin in- 
flected against two 
square bite of meat. 



Chap. XVL] MOVEMENTS OF THE LEAVES. 303 

were a little unfolded to a greater degree in the younger than in 
the older leaf. Tlie latter was not quite unfolded until the third 
day, and now both bits of sponge were left at the distance of .1 of 
an inch (2.54 mm.) from the edges; or about a quarter of the dis- 
tance between the edge and the midrib. A third bit of sponge ad- 
hered to the edge, and, as the margin unfolded, was dragged back- 
wards, into its original position. 

Experiment 9. A chain of fibres of roast meat, as thin as 
bristles and moistened with saliva, were placed down one whole 
side, close to the narrow, naturally incurved edge of a leaf. In 3 
hrs. this side was greatly incurved along its whole length, and after 
8 hrs. formed a cylinder, about ^ijj of an inch (1.27 mm.) in di- 
ameter, 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 breatlth, 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 com- 
pletely, re-expanded. As the seeds were no longer held by the in- 
flected margin, and as the secretion was beginning to fail, they 
rolled some way down the marginal channel. 

Experiment 11. Fragments of glass were placed on the mar- 
gins of two fine young leaves. After 2 hrs. 30 m. the margin of one 
certainly became slightly incurved; but the inflection never in- 
creased, and disappeared in 16 hrs. 30 m. from the time when the 
fragments were first applied. With the second leaf there was a 
trace of incurvation in 2 hrs. 15 m., which became decided in 4 hrs. 
30 m., and still more strongly pronounced in 7 hrs., but after 19 
hrs. 30 m. had plainly decreased. The fragments excited at most 
a slight ana doubtful increase of the secretion; and in two other 
trials, no increase could be perceived. Bits of coal-cinders, placed 
on a leaf, produced no eflect, 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 infu.sion 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 percep- 
tible; certainly none in the degree of incurvation; but the incur- 
vation round the bits of sponge lasted rather longer, as might per- 



804 PINGUKJULA VULGARIS. IChap. XVI. 

haps have l)oen expected from the sponge remaining damp and 
supplying nitrogenous matter for a longer time. Tlie margins, with 
the drops, became plainly incurved in 2 hrs. 17 m. The incurvation 
subsequently increased somewhat, but after 24 hrs. had greatly 
decreased. 

KxiH'riment 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 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 exi)eri- 
ment we learn that the motor impulse can be transmitted to a 
distance of .22 of an inch (5.590 mm.) in a transverse direction 
from the midrib to both margins; but it would be safer to say .2 
of an inch (.5.08 mm.), as the drops spread a little beyond the mid- 
rib. The incurvation thus caused lasted for an unusually short 
time. 

Experiment H. ^Three drops of a solution of one part of car- 
bonate 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 in- 
cur\'ation, I scratche<l the margins of two leaves for some minutes 
with a blunt needle, but no effect was produced. The surface of a 
leaf beneath a drop of a strong infusion of raw meat was also 
rubbe<l 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. 



Chap. XVI.] MOVEMENTS OP THE LEAVES. 305 

We learn from the foregoing experiments that the mar- 
gins of the leaves curl inwards when excited by the mere 
pressure of objects not yielding any soluble matter, by ob- 
jects yielding 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, paraly- 
ses 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 pedi- 
cels of the glandular hairs have no power of movement. I 
observed on several occasions that the surface of the leaf be- 
came slightly concave where bits of meat or large flies had 
long lain, but this may have been due to injury from over- 
stimulation.* 

The shortest time in which plainly marked movement was 
observed was 2 hrs. 17 m., and this occurred when either 
nitrogenous substances or fluids were "placed on the leaves; 
but I believe that in some cases there was a trace of move- 
ment in 1 hr. or 1 hr. 30 m. The pressure from fragments 
of glass excites movement almost as quickly as the absorp- 
tion of nitrogenous matter, but the degree of incurvation 
thus caused is much less. After a leaf has become well in- 
curved and has again expanded, it will not soon answer to a 
fresh stimulus. The margin was affected longitudinally, up- 
wards 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 dis- 
tance 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- 

* [Bfltnlln (' Flora.' 1887) be- by nctnnl growth, and thiiR a 

lleves that the depresHiona are permanent alteration In the form 

due to the fact that the curva- of the leaf is effected. F. D.J 
ture of the leaf Is accompanied 



306 PINGUICULA VULGARIS. [Chap. XVL 

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. 

One of the most curious facts with respect to the move- 
ment of the leaves is the short time during which they 
remain incurved, although the exciting object is left on 
them. In the majority of cases there was well-marked re- 
expansion within 24 hrs. from the time when even large 
pieces of meat, &c., were placed on the leaves, and in all cases 
within 48 hrs. In one instance the margin of a leaf re- 
mained for 32 hrs. closely inflected round thin fibres of meat; 
in another instance, when a bit of sponge, soaked in a strong 
infusion of raw meat, had been applied to a leaf, the margin 
began to unfold in 35 hrs. Fragments of glass keep the 
margin incurved for a shorter time than do nitrogenous 
botlies; for in the former case there was complete re-expan- 
sion in 16 hrs. 30 m. Nitrogenous fluids act for a shorter 
time than nitrogenous substances; thus, when drops of an 
infusion of raw meat were placed on the midrib of a leaf, 
the incurved margins began to unfold in only 10 hrs. 37 m., 
and this was the quickest act of re-expansion observed by 
me ; but it may have" been partly due to the distance of the 
margins from the midrib where the drops lay. 

We are naturally led to inquire what is the use of this 
movement which lasts for so short 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 in- 
curvation lasts for so short a time, any such benefit can be of 
only slight importance, yet perhaps greater than at first ap- 
pears. 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 inter- 
val) found some of them quite washed away, and many oth- 
ers safely tucked under the now closely inflected margins, the 



Chap. XVL] MOVEMENTS OP THE LEAVES. 307 

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 
exciting object, must be serviceable in another and probably 
more important way. We have seen that when large bits of 
meat, or of sponge soaked in the juice of meat, were placed 
on a leaf, the margin was not able to embrace them, but, as 
it became incurved, pushed them very slowly towards the 
middle of the leaf, to a distance from the outside of fully .1 
of an inch (2.54 mm.), that is, across between one- third and 
one-fourth of the space between the edge and the midrib. 
Any object, such as a moderately sized insect, would thus be 
brought slowly into contact with a far larger number of 
glands, including 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 Di- 
onsea has caught an insect, the slow pressing together of 
the two lobes serves merely to bring the glands on both sides 
into contact ^th 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 
movements of the leaves: otherwise, we must look at 
these movements as a remnant of a more highly devel- 
oped power formerly 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 in- 
curved. This incurvation serves, as already shown, to pre- 
21 



308 PINGUICULA VULGARIS. [Chap. XVI. 

vent 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. More- 
over, the secretion often collects in little pools within the 
channel, or in the spoon-like tips of the leaves; and I ascer- 
tained that bits of albumen, fibrin, and gluten are here dis- 
solved 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 protect- 
ed from the rain; and with exposed plants there would be 
still greater need of some provision to prevent, as far as pos- 
sible, 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 accited 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 r^ret 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 im- 
mediately curl downwards so as to almost conceal the roots, 
a fact which has been noticed by many persons. I sup- 
pose 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 irrita- 
ble, for Dr. Johnson states that they " bend backwards if 
rudely handled."* 

* ' Kntrllth notnnv,' by Sir J. turgeBCPnt Btom. This wonld be 

E. Smith; with coloured flRnros likely to occur In the course of 

by J. Sowerhy; edit, of IKtt. tub. the " roujfh handling." and we 

24. 2r. 'M. (It Ir well known that may porhnps thus account for Dr. 

permanent curvatures may be Johnson's curvatures. P. D.] 
produced by bending or shaking a 



Chap. XVI.] SECRETION, ABSORPTION, DIGESTION. 309 

Secretion, Absorption, and Digestion. I will first give 
my observations and experiments, and then a summary of 
the results. 

The Effects of Obfects containing Soluble Nitrogenous Matter. 

( 1 ) Flies were placed on many leaves, and excited the glands to 
secrete copiously; the secretion always becoming acid, though not 
so before. After a time these insects were rendered so tender that 
their limbs and bodies could be separated by a mere touch, owing 
no doubt to the digestion and disintegration of their muscles. The 
glands in contact with a small fly 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 pre- 
sented a wonderful contrast. Those which had been in contact 
were filled with brownish granular matter, the others with homo- 
geneous fluid. There could therefore be no doubt that the former 
had absorbed matter from the fly. 

(2) Small bits of roast meat, placed on a leaf, always caused 
much acid secretion in the course of a few hours in one case 
within 40 m. When thin fibres of meat were laid along the margin 
of a leaf which stood almost upright, the secretion ran down to the 
ground. Angular bits of meat, placed in little pools of the secre- 
tion 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 miich 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 ab- 
sorbed in from 24 hrs, to 48 hrs.; the glands being left dry. But 
when the supply of secretion was copious, round either a single 
rather large bit of meat, or round several small bits, the glands 
did not become dry until six or seven days had elapsed. The most 
rapid case of absorption observed by me was when a small drop 
of an infusion of raw meat was placed on a leaf, for the glands 
here became almost dry in 3 hrs. 20 m. Glands excited by small 
particles of meat, and which have quickly absorbed their own se- 
cretion, begin to sex-rete again in the course of seven or eight days 
from the time when the meat was given them. 

(3) Three minute cubes of tough cartilnije from the leg-bone of 
a sheep were laid on a leaf. After 10 hrs. 30 ra. some acid secretion 
was excited, but the cartilage appeared little or not at all aflTected. 
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 com- 
pletely liquefied, but all the secretion was absorbed and the glands 
left dry. 



310 PINQUICULA VULGARIS. [Ciup. XVI. 

(4) Small cubes of albumen were placed on a leaf; in R hns. 
feebly acid secretion extended to a distance of nearly -^ 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 ren- 
dere<l throughout very tender; after 30 hrs. the secretion began to 
decrease, and after 48 hrs. the glands were left dry; but very 
minute bits of albumen were still left undissolved. 

(5) Smaller cubes of albuimn (about -^ or -^ ol an inch, .508 
or .423 nmi.) were placed on four glands; after 18 hrs. one cube 
was completely dissolved, the others being much reduced in size, 
softened and transparent. After 24 hrs. two of the cubes were 
completely dissolved, and already the secretion on these glands was 
almost wholly absorbed. After 42 hrs. the two other cubes were 
completely dissolved. These four glands began to secrete again 
after eight or nine days. 

(0) 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 hrs. there was much secretion, which after 48 hrs. 
accumulated in a little pool round the cube near the margin. This 
cube was much more dissolved than that on the blade of the leaf; 
so that after three days it was greatly reduced in size, with all the 
angles rounded, but it was too large to be wholly dissolved. The 
secretion was pailially absorbed after four days. The cube on the 
blade was much less retluced, 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 threads were placed on some glands, and in 3 hrs. 45 m. 
their secretion was plainly increased. The smaller shred of the 
two was completely liquefled in 6 hrs. 15 m., and the other in 24 
hrs.; but even after 48 hrs. a few granules of fibrin could still be 
seen through a lens floating in both drops of secretion. After 56 
hrs. 30 m. these granules were completely dissolved. A third 
shred was placed in a little pool of secretion, within the margin 
of a leaf where a seed had been lying, and this was completely 
dissolved in the course of 15 hrs. 30 m. 

(8) Five very small bits of gluten were placed on a leaf, and 
they excited so much secretion that one of the bits glide<l down 
into the marginal furrow. After a day all five bits seemed much 
reduce<l 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 l>e detectwl, the other two having quite disap- 
peare<l; but I am doubtful whether they had reolly l)een i-omplete- 
ly dissolved. Two fresh bits were now place<l, one near the mid- 
dle and the other near the margin of another leaf; l)oth excited 
an extraordinary amount of secretion; that near the margin had 
a little pool formed round it, and was much more re<luce<l in size than 
that on the blade, but after four days was not completely dis- 
solved. Gluten, therefore, excites the glands greati}', but is dis- 
solved with much diiliculty, exactly as in the caxe of Drosera. I 



Chap. XVI.] SECRETION, ABSORPTION, DIGESTION. 311 

r^ret that I did not try this substance after having been im- 
mersed in weak hydrochloric acid, as it would then probably have 
been quickly dissolved. 

(9) A siiiail square thin piece of pure gelatine, moistened with 
water, was placed on a leaf, and excited very little secretion in 5 
hrs. 30 ni., 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 then began to dry. Nor could their complete dissolution 
nave been expected from what we have seen with Drosera. 

(11) Minute drops of skimmed milk were placed on a leaf, and 
these caused the glands to secrete freely. After 3 hrs. the milk 
was found curdled, and after 23 hrs. the curds were dissolved. On 
placing the now clear drops under the microscope, nothing could 
be detected except some oil-globules. The secretion, therefore, 
dissolves fresh casein. 

(12) Two fragments of a leaf were immersed for 17 hrs., each 
in a drachm of a solution of carbonate of ammonia, of two 
strengths, namely of one part to 347 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 re- 
peated with the same result; and on this occasion I observed that 
the protoplasm had shrunk a little from the walls of the single 
elongated cells forming the pedicels. In order to observe the pro- 
cess of aggregation, a narrow strip of leaf was laid edgewaj's 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 be- 
came 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 appearc<l within the upper ends of 
the piedicels, and the protoplasm lining their walls had shrunk a 
little. It is thus evident that the glands of Pinguicula absorb 
carbonate of ammonia; but they do not absorb it, or are not 
acted on by it, nearly so quickly as those of Drosera. 

(13) Little masses of the orange-coloured pollen of the common 
pea, placed on several le.nves, excitetl the glands to secrete freely. 
Even a verj' few grains whit-h accidentally fell on a single gland 
caused the drop surrounding it to increase so much in size, in 23 
hrs., as to be manifestly larger than the drops on the adjoining 
glands. Grains subjected to the secretion for 48 hrs. did not emit 
their tubes^ they were quite discoloured, and seeme<l to contain 
less matter than before; that which was left being of a dirty col- 



813 PINGUICULA VULGARIS. [Chap. XVL 

our, including globules of oil. They thus tlifTered 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 bils of the leaves of spinach, cabbage, and a saxi- 
frage, and the entire leaves of Erica tetralix, all excited the glands 
to increased secretioq. The spinach was the most effective, for it 
caused the secretion evidently to increase in 1 hr. 40 m., and ul- 
timately to run some way down the leaf; but the glands soon be- 
gan to dry, viz. after 35 hrs. The leaves of Erica tetralix began 
to act in 7 hrs. 30 m., but never caused much secretion; nor did 
the bits of leaf of the saxifrage, though in this case the glands 
continued to secrete for seven days. Some leaves of Pinguicula 
were sent me from North Wales, to which leaves of Erica tetralix 
and of an unknown plant adhered; and the glands in contact 
with them had their contents plainly aggregated, as if they had 
been in contact with insects; whilst the other glands on the same 
leaves contained only clear homogeneous fluid. 

(15) Seeds. A considerable number of seeds or fruits selected 
by hazard, some fresh and some a year old, some soaketl for a 
short time in water and some not soaked, were tried. The ten 
following kinds, namely, cabbage, radish, Anemone nemorosa, Ru- 
mcx acetosa, Carex sylvatica, mustard, turnip, cress, RanunculM 
acris, and Arena pubcscens, all excited much secretion, which waa 
in several cases tested and always found acid. The five first- 
named seeds excited the glands more than the others. The secre- 
tion was seldom copious until about 24 hrs. had elapsed, no doubt 
owing to the coats of the seeds not being easily permeable. Never- 
theless, cabbage seeds excited some secretion in 4 hrs. 30 m. ; and 
this increased so much in 18 hrs. as to run down the leaves. The 
seeds, or properly the fruits, of Carex are much oftener found 
adhering to leaves in a state of nature than those of any other 
genus; and the fruits of Carex sylvatica excited so much secre- 
tion that in 15 hrs. it ran into the incurved edges; but the glands 
ceasecl to secrete after 40 hrs. On the other hand, the glands on 
which the seeds of the Ilumex and Avcna rested continued to se- 
crete for nine days. 

The nine following kinds of seeds excited only a slight amount 
of secretion, namely, celery, parsnip, caraway, Linum grandi- 
flortim, Cassia, Trifoliiim pannonicvm, Plantago, onion, and Hro- 
mus. Most of these seeds did not excite any secretion until 48 hrs. 
had elapsed, and in the case of the Trifolium only one seed acted, 
and this not until the third day. Although the seeds of the 
PlanUigo excite<l very little secretion, the glands continued to se- 
crete for six tiays. Lastly, the five following kinds excite<l no 
secretion, though left on the leaves for two or three days, namely, 
lettuce. Erica tetralix, Atriplrx hortensia, Phalarls cnnariensis, 
and wheat. Nevertheless, when the soels of the lettuce, wheat, 
and Atriplex were split open and applied to leaves, secretion wa 
excited in considerable (quantity in 10 hrs., and I believe that 



Chap. XVI.] SECRETION, ABSORPTION, DIGESTION, 313 

some were excited in six hours. In the case of the Atriplex the se- 
cretion 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 secre- 
tion, and only after a long interval of time. A slice of the com- 
mon 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 secre- 
tion, is chiefly or wholly due to the different permeability of their 
coats. 

Some thin slices of the common pea, which had been previously 
soaked for 1 hr. in water, were placed on a leaf, and quickly ex- 
cited much acid secretion. After 24 hrs. these slices were com- 
pared 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 was much cleaner and more trans- 
parent, 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 injuretl. Fourteen 
cabbage seeds were left for three days on leaves and excited nwich 
secretion; they were then placed on damp sand under conditions 
known to be favourable for germination. Three never germinated, 
and this was a &ir larger proportion of deaths than occurred with 
seeds of the same lot, which had not been subjected to the secre- 
tion, 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 cotyle<lons were marked with brown patches and their radi- 
cles 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 dietl 
and the other germinated ; but its radicle was brown and soon 
withered. Both seeds of the Avena germinate<l, one grew well, 
the other had its radicle brown and withered. Of six seeds of the 
Erica none germinated, and when cut open after having been left 
for five months on damp sand, one alone seemed alive. Twenty- 
two seeds of various kinds were found adhering to the leaves of 



314 PINGUICULA VULGARIS. [Chap. XVL 

plants growing in a state of nature; and of these, though kept 
for five iiiuntha on damp sand, none germinated, some being then 
evidently dead. 

The Effects of Objects not containing Soluble Nitrogenous Matter. 

(10) It has already been shown that bits of glass, placed on 
leavel, 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 tixe coats are not permeable to the secretion, and which, 
therefore, acted like inorganic bodies. Cubes of fat, left for two 
days on a leaf, produced no effect. 

(17) A particle of white sugar, placed on a leaf, formed in 1 
hr. 10 m. a large drop of fluid, which in the course of 2 additional 
hours ran down into the naturally inflected margin. This fluid 
was not in the least acid, and began to dry up, or more probably 
was absorbed, in 5 hrs. 30 m. The exijerinient was repeated; par- 
ticles being placed on a leaf, and others of the same size on a 
slip of glass in a moistened state; both being coverel by a bell- 
glass. This was done to see whether the increased amount of 
fluid on the leaves could be due to mere deliciuescence; but this 
was proved not to be the case. The particle on the leaf caused so 
much secretion that in the course of 4 hrs. it ran down across two- 
thirds of the leaf. After 8 hrs. the leaf, which was concave, was 
actually filled with very viscid fluid; and it particularly deserves 
notice that this, as on the former occasion, was not in the least 
acid. This great amount of secretion may be attributed to exos- 
mose. The glands which had been covered for 24 hrs. by this fluid 
did not differ, when examined under the microscope, from others 
on the same leaf, which had not come into contact with it. This 
is an interesting fact in contrast with the invariably aggregated 
condition of glands which have l)een 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 6 hrs., that is for as long 
a time as the leaf was observed. 

(19) Six small particles of dry starch of commerce were placed 
on a leaf, and one of these caused some secretion in 1 hr. 15 m., 
and the others in from 8 hrs. to 9 hrs. The glands which had thus 
been excited to secrete soon became dry, and did not l)egin to se- 
crete 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 J of 
an inch. This secretion, though so abundant, was not in the 
least acid. As it was so copiously excited, and as seeds not mrely 
adhere to the leaves of naturally growing plants, it occurred to 
me that the glands might j)erhap have the |)ower of secreting a 
ferment, like ptyaline, capable of dissolving starch; so I carefully 



Chap. XVI]. SECRETION, ABSORPTION, DIGESTION. 315 

obser\-ed the above six small particles during several days, but 
they did not seem in the least reduced in bulk. A particle was 
also left for two days in a little pool of secretion, which had run 
down from a piece of spinach leaf; but although the particle was 
so minute no diminution was perceptible. We may therefore con- 
clude that the secretion cannot dissolve starch. The increase 
caused by this substance may, I presume, be attributed to exos- 
mose. But I am surprised that starch acted so quickly and power- 
fully 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 dif- 
fused starch, those in the starch became flaccid, but to a less de- 
gree and at a much slower rate than the leaves in the syrup; 
those in water remaining all the time crisp. 

From the foregoing experiments and observations we see 
that objects not containing soluble matter have little or no 
power of exciting the glands to secrete. Non-nitrogenous 
fluids, if dense, cause the glands to pour forth a large supply 
of viscid fluid, but this is not in the least acid. On the 
other hand, the secretion from glands excited by contact 
with nitrogenous solids or liquids is invariably acid, and is 
80 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 

[Pfeffer (' Ueber flelschfes- to the nm use In the Italian 

sende PflnnBen,' In the ' Land- Alps. The property of the plant 

wIrthBchaft. Jahrbficher.' 1877) seems to be widely known amon;; 

quotes Linnaeus (' Flora Lappon- primitive people, for. within the 

lea,' 1737, p. 10 to the effect last 30 years. It wan used as ren- 

that certain Lapland tribes use net by mountain farmers In Nor'h 

the leaves- of rinnnlcnla to coajf- Wales. I have myself succejnleU 

ulate milk. I'ft'fTer learnt from In cunllInK milk with this vegf- 

an old shepherd that they are put table rennet. F. D.] 



816 PINQUICULA VULGARIS. [Chap. XVL 

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, etc., 
growing where Pinguicula lives, on to the leaves thickly 
covered with viscid glands and forming large rosettes. Even 
a few grains of pollen on a single gland causes it to secrete 
copiously. We have also seen how frequently the small 
leaves of Erica tetralix and of other plants, as well as various 
kinds of seeds and fruits, especially of Carex, adhere to the 
leaves. One leaf of the Pinguicula had caught ten of the 
little leaves of the Erica; and three leaves on the same 
plant had each caught a seed. Seeds subjected to the action 
of the secretion are sometimes killed, or the seedlings injured. 
We may therefore 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 orandiflora. 

This species is so closely allied to the last that it is ranked 
by Dr. Hooker as a sub-species. It differs chiefly in the 
larger size of its leaves, and in the glandular hairs near the 
basal part of the midrib being longer. But it likewise 
differs in constitution; I hear from Mr. Ralfs, who was so 
kind as to send me plants from Cornwall, that it grows in 
rather different sites; and Dr. Moore, of the Glasnevin 
Botanic Gardens, informs me that it is much more manage- 
able under culture, growing freely and flowering annually; 
while Pinguicula vulgaris has to be renewed every year. 
Mr. Ralfs found numerous insects and fragments of insects 
adhering to almost all tbo leaves. These consisted chiefly 



Chap. XVI.] PINGUICULA LUSITANICA. 317 

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, adher- 
ing to the leaves. I tried only two experiments with this spe- 
cies; firstly, a fly was placed near the margin of a leaf, and 
after 16 hrs. this was found well inflected. Secondly, several 
small flies were placed in a row along one margin of another 
leaf, and by the next morning this whole margin was curled 
inwards, exactly as in the case of Pinguicula vulgaris. 

Pinguicula lusitanica. 

This 8i)ecies, of which living specimens were sent me by 
Mr. Ralfs from Cornwall, is very distinct from the two fore- 
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 
glandvdar 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 the margin is des- 
titute of glands; these being replaced by long, rather stiff, 
multicellular hairs, which intercross over the midrib. These 
hairs perhaps serve to prevent insects from settling on this 
part of the leaf, where there are no viscid glands by which 
they could be caught ; but it is hardly probable that they were 
developed for this purpose. The spiral vessels 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 pet- 
als, are studded with glandular hairs, like those on the leaves. 

The leaves catch many small insects, which are found 
chiefly beneath the involuted margins, probably washed there 
by the rain. The colour of the glands on which insects have 
long lain is changed, being either brownish or pale purple, 
with their contents coarsely granular so that they evidently 
absorb matter from their prey. Leaves of the Erica ietralix. 



318 PINGUICULA LUSITANICA. [Chap. XVI. 

flowera 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 Pinyuicula 
lusitanica, and these will now be given. 

(1) A moderately sized and angular bit of albumen was placed 
on one side of a leaf, lialfway between the midrib and the natu- 
rally involuted margin. In 2 hrs. 15 m. the glands poured forth 
much secretion, and this side became more infolded than the op- 
posite 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 t<j within the -i^ of an inch of the niidril). After 48 
hrs. it began to unfold, and in 72 hrs. was completely unfolded. 
The cube was rounded and greatly reduced in size; the remainder 
being in a semi-liquefied state. 

(2) A moderately sized bit of albumen was placed near the 
apex of a leaf, under the naturally incurved margin. In 2 hrs. 30 
m. much secretion was excited, and next morning the margin on 
this side was more incurved than the opposite one, but not to so 
great a degree as in the last case. The margin unfolded at the 
same rate as before. A large proportion of the albumen was dis- 
solved, a remnant being still left. 

(3) Large bits of albumen were laid in a row on the midribs 
of two leaves, but produced in the course of 24 hrs. no elFect: 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 jjushed 
close to one margin, and in 3 hrs. 30 m. this became so greatly in- 
flected that the outer surface touched the blade; the opposite mar- 
gin not being in the least alFected. After three days the mnrgina 
of both leaves with the albumen were still as nnuh intlectcnl aa 
ever, and the glands were still secreting copiously. With I'imjui- 
cula vuUjaris I have never seen inflection lasting so long. 

(4) Two cabbage seeds, after being soakeil 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 fre<dy. 
These l)egan to dry in 48 hrs., and after 72 hrs. were almost dry. 
Ihe 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 
secretion; and after 3 hrs. 20 m. plain incurvation of the margin. 
The margin was well inflected after 9 hrs. 15 m., but after 24 hrs. 
was almost fully re-cxpande<l. The glands in contact with the 
spinach l)eeame dry in 72 hrs. Hits of albumen had l)een placed 
the day licfore on the opposite margin of this same leaf, as well as 
on that of a leaf with cabbage seeils, and these nuirgins remained 



Chap. XVI.] PINGUICULA LITSITANICA. 310 

closely inflected for 72 hrs., showing how much more enduring is 
the eliect 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 efl'ect 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 G hrs. The glands 
in contact with the fragments now secreted more freely than be- 
fore; so that they appear to be more easily excited by tlie pressure 
of inorganic objects than are the glands of Pinguicula vulgaris. 
The above slight inflection of the margin had not increased after 
24 hrs., and the glands were now beginning to dry. The surface 
of a leaf, near the midrib and towards the base, was rubbed and 
scratched for some time, but no movement ensued. The long hairs 
which are situated here were treated in the same manner, with no 
eflFect. This latter trial was made because I thought that the hairs 
might perhaps be sensitive to a touch, like the filaments of Dionsea. 

(7) The flower-peduncles, sepals and petals bear glands in gen- 
eral appearance like those on the leaves. A piece of a flower- 
peduncle was therefore left for 1 hr. in a solution of one part of 
carbonate of ammonia to 437 of water, and this caused the glands 
to change from bright pink to a dull purple colour; but their 
contents exhibited no distinct aggregation. After 8 hrs. 30 m. 
they became colourless. Two minute cubes of albumen were placed 
on the glands of a flower-peduncle, and another cube on the glands 
of a sepal; but they were not excited to increased secretion, and 
the albumen after two days was not in the least softened. Hence 
these glands apparently differ greatly in function from those on 
the leaves. 

From the foregoing observations on Pinguicula lusitanica 
we see that the naturally much incurved margins of the 
leaves are excited to curve still farther inwards by coA.tact 
with organic and inorganic bodies; that albumen, cabbage 
seeds, bits of spinach leaves, and fragments of glass, cause 
the glands to secrete more freely; that albumen is dissolved 
by the secretion, and cabbage seeds killed by it; and lastly 
that matter is absorbed by the glands from the insects which 
are caught in large numbers by the viscid secretion. The 
glands on the flower-peduncles seem to have no such power. 
This species differs from Pinguicula vulgaris and grandiflora 
in the margins of the leaves, when excited by organic bodies, 
being inflected to a greater degree, and in the inflection 
lasting for a longer time. The glands, also, seem to be more 
easily excited to increased secretion by bodies not yielding 
soluble nitrogenous matter. In other respects, as far as my 
observatiqns serve, all three species agree in their functional 
powers. 



320 UTRICULARIA NEQLECTA. [Chap. XVII. 



CHAPTER XVn. 

UTRICULARIA. 

VtrietUaria nepfecta 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 Exi>eriments on the absorption of certain fluid^ by the quad- 
rifid processes Absorption by the glands Summary of the observa- 
tions on absorption Development of the bladders Utricularia vul- 
garis Utrictdaria minor Utricularia clandestvia. 

I WAS led to investigate the habits and structure of the 
species of this genus partly from their belonging to the same 
natural family as Pinguicula, but more especially by Mr. 
Holland's statement, that " water insects are often found 
imprisoned in the bladders," which he suspects " are destined 
for the plant to feed on." ' The plants which I first received 
as Utricularia vulgaris from the New Forest in Hampshire 
and from Cornwall, and which I have chiefly worked on, 
have been determined by Dr. Hooker to be a very rare 
British species, the Utricularia neglecta of Lehm.' I subse- 
quently received the true Utricularia vulgaris from York- 
shire. Since drawing up the following description from my 
own observations and those of my son, Francis Darwin, an 
important memoir by Prof. Cohn on Utricularia vulgaris has 
appeared ; * and it has been no small satisfaction to me to 
find that my account agrees almost completely with that of 
this distinguished observer. I will publish my description 
as it stood before reading that by Prof. Cohn, adding occa- 
sionally some statements on his authority. 

Utricularia neglecta. The general appearance of a 

> The ' Quart. Mag. of the Rev. H. M. Wilkinson, of Blstem, 

High Wycombe Nnt. Hist. 8oc.' for having sent me sevoml tine 

July, iSBS, p. 5. Delpino (' Ult. lots of thlw speolos from the New 

Osservas. nulla DIeogamla.' &c. Forest. Mr. Kalfs was also ho 

IWW 18(N), p. in) alHO quotes kind as to send me living plants 

Crouan as having found (1W>H) of the same hpm-I'k from near 

cruHtaoeanH within the bladders I'ensanre in Cornwiill. 
of l/'lriculaHa vulmrUt. Heitrllge ssnr Itlologle der 

* I am much indebted to the Pflanzen,' drittes Heft, 1^5. 



Chap. XVII.] STRUCTURE OP THE BLADDER. 



321 



branch (about twice enlarged), with the pinnatifid leaves 
bearing bladders, is represented in the following sketch (Fig. 
17). The leaves continually bifurcate, so that a full-grown 
one terminates in from twenty to thirty points. Each point 
is tipped by a short, straight bristle; and slight notches on 
the sides of the leaves bear similar bristles. On both surfaces 
there are many small papilla), crowned with two hemi- 




Fio. 17. 

( Vtrictdaria negleda. ) 

Branch with the divided leaves bearing bladders ; about twice enlarged. 

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 in- 
habit, as more than one observer has remarked to me, re- 
markably foul ditches. 



* I Infer that this Is the ease 
from a drnwin;; of n st^edlinc 
given by Dr. Wnrmlug In his 
paper, " Rldrne til Kundsknlton 
om Lentlbularlaeete," from the 



' Vldenskabellge Meddelelser.' 

Copenhagen. 1874. Nos. a-7, pp. 
3.-i-58. fCf. KamlenskI, ' But. 
Zelt.' 1877, p. 765.] 



322 UTRICULARIA NEGLECTA. [Chap. XVI L 

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 -^ of an inch (2.54 mm.) in length. 
They are translucent, of a green colour, and the walls are 
formed of two layers of cells. The exterior cells are polyg- 
onal and rather large; but at many of the points where the 
angles meet, there are smaller rounded cells. These latter 
support short conical projections, surmounted by two hemi- 
spherical cells in such close apposition that they appear 
united; but they often separate a little when immersed in 
certain fluids. The papillte thus formed are exactly like 
those on the surfaces of the leaves. Those on the same 




Fio. 18. 

(UtriaUaria neglecta.) 

Bladder ; ranch enlarged, c, collar indistinctly seen throngh the walls. 

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 
in thickness, but are always somewhat compressed. At an 
early stage of growth, the flat or ventral surface faces the 



CHAP.XVn.] STRUCTURE OF THE BLADDER. 323 

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 
downward. The Rev. H. M. Wilkinson examined plants for 
me in a state of nature, and found this commonly to be the 
case, but the younger bladders often had their valves turned 
upwards. 

The general appearance of a bladder viewed laterally, with 
the appendages on the near side alone represented, is shown 
on the opposite page (Fig. 18). The lower side, where 
the footstalk arises, is nearly straight, and I have called it 
the ventral surface. The outer or dorsal surface is convex, 
and terminates in two long prolongations, formed of several 
rows of cells, containing chlorophyll, and bearing, chiefly on 




Fig. 19. 

(Utrieularia negleeia.) 

Valve of bladder ; greatly enlarged. 

the outside, six or seven long, pointed, multicellular bristles. 
These prolongations of the bladder may be conveniently 
called the antennce, 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 antennte the end of the 
bladder is slightly truncated, and here is situated the most 
imjwrtant part of the whole structure, namely the entrance 
and valve. On each side of the entrance from three to rarely 
seven long, multicellular bristles project outwards ; but only 
those (four in number) on the near side are shown in the 
22 



834 UTRICULARIA NEGLECTA. [Chap. XVII. 

drawing. These bristles, together with those borne by the 
antennse, form a sort of hollow cone surrounding the en- 
trance. 

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. 




Fio. 20. 
( Utrieularia negleda.) 
LongitDdinal vertical section througli the ventral portion of a bladder; 
showing valve and collar, v, valve ; the whole pnyection above e 
fonuB the collar ; 6, 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 antennaj. There 



Chap. XVII.] STRUCTURE OF THE BLADDER. 325 

are also on the surface of the valve niunerous glands, as I 
will call them; for they have the power of absorption, 
though I doubt whether they ever secrete. They consist of 
three kinds, which to a certain extent graduate into one 
another. Those situated round the anterior margin of the 
valve (upper margin in Fig. 19) are very numerous and 
crowded together; they consist of an oblong head on a long 
pedicel. The pedicel itself is formed of an elongated cell, 
surmounted by a short one. The glands towards the free 
posterior margin are much larger, few in number, and almost 
spherical, having short footstalks; the head is formed by the 
confluence of two cells, the lower one answering to the short 
upper cell of the pedicel of the oblong glands. The glands of 
the third kind have transversely elongated heads, and are 
seated on very short footstalks; so that they stand parallel 
and close to the surface of the valve; they may be. called 
the two-armed glands. The cells forming all these glands 
contain a nucleus, and are lined by a thin layer of more or 
less granular protoplasm, the primordial utricle of Mohl. 
They are filled with fluid, which must hold much matter in 
solution, judging from the quantity coagulated after they 
have been long immersed in alcohol or ether. The depression 
in which the valve lies is also lined with innumerable glands ; 
those at the sides having oblong heads and elongated 
pedicels, 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 



826 



UTRICULARIA NEGLECTA. [Chap. XVII. 



thin and flexible valve would be liable to be distorted, and 
in this case would not act properly. 

Altogether the entrance into the bladder, formed by the 
transparent valve, with its four obliquely 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 antenna;, pre- 
sents an extraordinary complex appearance when viewed 
under the microscope. 

We will now consider the internal structure of the blad- 
der. The whole inner surface, with the exception of the 





Fio. 21. Fig. 22. 

( inHcularia negUda.) ( Ulrieularia negleela. ) 

Rmnll portion of inside-of bladder, One of tho qiia<lrifid proMflBM 
much ciilarRed, showing quad- greatly enlarged, 

rifld processes. 

valve, is seen under a moderately high power to be covered 
with a serried mass of processes (Fig. 21). Each of these 
consists of four divergent arms; whence their name of 
quadrifld 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 to- 
wards the posterior end of the bladder. The two others are 



Chap. XVII.] STRUCTURE OF THE BLADDER. 327 

much shorter, and project at a smaller angle, that is, are 
more nearly horizontal, and are directed towards the an- 
terior end of the bladder. These arms are only moderately 
sharp; they are composed of extremely thin transparent 
membrane, so that they can be bent or doubled in any di- 
rection without being broken. They are lined with a deli- 
cate layer of protoplasm, as is likewise the short conical pro- 
jection from which they arise. Each arm generally (but not 
invariably) contains a minute, faintly brown particle, either 
rounded or more conmionly elongated, which exhibits inces- 
sant 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 condi- 
tion, for when absent, I could occasionally just distinguish 
in their places a delicate halo of matter, including a darker 
spot. Moreover, the quadrifids of Utricularia montana con- 
tain rather larger and much more regularly spherical, but 
otherwise similar, particles, which closely resemble the nu- 
clei in the cells forming the walls of the bladders. In the 
present case there were sometimes two, three, or even more, 
nearly similar particles within a single arm; but, as we shall 
hereafter see, the presence of more than one seemed always 
to be connected with the absorption of decayed matter. 

The inner side of the collar (see the previous Fig, 20) is 
covered with several crowded rows of processes, differing in 
no important respect from the quadrifids, except in bearing 
only two arms instead of four; they are, however, rather nar- 
rower and more delicate. I shall call them the bifids. They 
project into the bladder, and are directed towards its poste- 
rior end. The quadrifid and bifid processes no doubt are 
homologous with the papillse on the outside of the bladder 
and of the leaves; and we shall see that they are developed 
from closely similar papillte. 

The Uses of the several Parts. After the above long but 
necfessary 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 



828 UTRICULARIA NEGLECTA. [Chap. XVIL 

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 
bladders; and some old bladders with much decaying matter 
had no bubbles. 

The real use of the bladders is to capture small aquatic 
animals, and this they do on a large scale. In the first lot of 
plants, which I received from the New Forest early in July, 
a large proportion of the fully grown bladders contained 
prey; in a second lot, received in the beginning of August, 
most of the bladders were empty, but plants had been select- 
ed 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 crus- 
taceans, three larva; 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 re- 
mains, but not appearing very full, there were one, two, four, 
two, and five crustaceans. A plant of Utricularia vulgariSf 
which had been kept in almost pure water, was placed by 
Cohn one evening into water swarming with crustaceans, 
and by the next morning most of the bladders contained 
these animals entrapped and swimming round and round 
their prisons. They remained alive for several days; but at 
last perished, asphyxiated, as I suppose, by the oxygen in 
the water having been all consumed. Freshwater worms 
were also found by Cohn in some bladders. In all cases the 
bladders with decayed remains swarmed with living Algte of 
many kinds, Infusoria, and other low organisms, which evi- 
dently lived as intruders. 

Animals enter the bladders by bending inwards the pos- 
terior free edge of the valve, which from being highly elastic 
shuts again instantly. As the e<lge 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 



Chap. XVII,] MANNER OP CAPTURING PREY. 329 

the edge fits, I may mention that my son found a Daphnia 
which had inserted one of its antennas into the slit, and it 
was thus held fast during a whole day. On three or four 
occasions I have seen long narrow larvae, both dead and alive, 
wedged between the comer of the valve and collar, with half 
their bodies within the bladder and half out. 

As I felt much diflSculty in understanding how such mi- 
nute 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 
80 as to project barely i of an inch, entered with some diffi- 
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 dis- 
appeared so suddenly that, not seeing what had happened, I 
thought that I had flirted them off; but on examining the 
bladders, they were found safely enclosed. The same thing 
occurred to my son, who placed little cubes of green box-wood 
(about 1^ of an inch, .423 mm.) on some valves; and thrice 
in the act of placing them on, or whilst gently moving them 
to another spot, the valve suddenly 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 oblique- 
ly 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 larvte, 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 t** of an 
inch, .391 mm.) of green box-wood, which were just heavy 
enough to sink in water, on three valves. These were exam- 
ined after 19 hrs. 30 m., and were still lying on the valves; 



830 UTIilCULARIA NEGLECTA. [Chap. XVII. 

but after 22 hre. 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 blade three grains; 
these must have fallen by some accident on the valves, and 
then entered like the particles of glass. 

The slow bending of the valve from the weight of parti- 
cles of glass and even of box-wood, though largely supported 
by the water, is, I suppose, analogous to the slow bending of 
colloid substances. For instance, particles of glass were 
placed on various points of narrow strips of moistened gela- 
tine, and these yielded and became bent with extreme slow- 
ness. It is much more diflScult to understand how gently 
moving a particle from one part of a valve to another causes 
it suddenly to open. To ascertain whether the valves were 
endowed with irritability, the surfaces of several were 
scratched with a needle or brushed with a fine camel-hair 
brush, so as to imitate the crawling movement of small crus- 
taceans, but the valve did not open. Some bladders, before 
being brushed, were left for a time in water at temperatures 
between 80 and 130 F. (26.6 54''.4 Cent.), as, judging 
from a widespread analogy, this would have rendered them 
more sensitive to irritation, or would by itself have excited 
movement; but no effect was produced. We may therefore 
conclude that animals enter merely by forcing their way 
through the slit-like orifice; their heads serving as a wedge. 
But I am surj^rised that such small and weak creatures as 
are often captured (for instance, the nauplius of a crusta- 
cean, 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 i of an inch in length. Nevertheless, it is 
certain that weak and small creatures do enter, and Mrs. 
Treat, of New Jerey, has been more successful than any 
other observer, and has often witnessed in the case of Utricu- 
laria clandestina the whole process.* She saw a tardigrade 
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 vari- 
ous minute crustaceans. Cypris "was quite wary, but 
nevertheless, was often caught. Coming to the entrance of 

' Now York Tribune,* reprinted In the ' Gardener's Chronicle,' 
187S, p. 303. 



Chap. XVII.] MANNER OF CAPTURING PREY. 331 

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." Larvaj, 
apparently of gnats, when " feeding near the entrance, are 
pretty certain to run their heads into the net, whence there 
is no retreat. A large larva is sometimes three or four hours 
in being swallowed, the process bringing to mind what I 
have witnessed when a small snake makes a large frog its 
victim." But as the valve does not appear to be in the least 
irritable,' the slow swallowing process must be the effect of 
the onward movement of the larva. 

It is difficult to conjecture what can attract so many 
creatures, animal- and vegetable-feeding crustaceans, worms, 
tardigrades, and various larvae, to enter the bladders. Mrs. 
Treat says that the larvae just referred to are vegetable feed- 
ers, and seem to have a special liking for the long bristles 
round the valve, but this taste will not account for the en- 
trance of animal-feeding crustaceans. Perhaps small aquat- 
ic animals habitually try to enter every small crevice, like 
that between the valve and collar, in search of food or pro- 
tection. It is not probable that the remarkable transparency 
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 em- 
bedded either in entangled vegetation or in mud, have no 
bristles round the entrance, and these under such conditions 
would be of no service as a guide. Nevertheless, with these 
epiphytic and marsh species, two pairs of bristles project from 
the surface of the valve, as in the aquatic species; and their 
use 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- 

[Gnlded by her observations conohideg that the valve Is Ir- 
(' Harper's Magazine.' Feb. 1870) rltable. F. D.] 
00 the act of capture, Mrs. Treat 



332 UTRICULARIA NEGLECTA. [Chap. XVII. 

ccans; as the valve is so well fitted to allow animals to 
enter and to prevent their eseai)e; 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, i'rom the analogy of Pinguicula, belonging to the 
same family, I naturally expected that the bladders would 
have digested their prey; but this is not the case, and there 
are no glands fitted for secreting the proper fluid. Neverthe- 
less, in order to test their power of digestion, minute frag- 
ments of roast meat, three small cubes of albumen, and three 
of cartilage were pushed through the orifice into the bladders 
of vigorous plants. They were left from one day to three 
days and a half within, and the bladders were then cut open : 
but none of the above substances exhibited the least signs 
of digestion or dissolution; the angles of the cubes being as 
sharp as ever. These observations were made subsequently 
to those on Drosera, Dionica, Drosophyllum, and Pinguicula ; 
so that I was familiar with the apjxjarance of these sub- 
stances when undergoing the early and final stages of diges- 
tion. We may therefore conclude that Utricularia cannot 
digest the animals which it habitually captures. 

In mQst 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 pre- 
served better than anything else. Limbs, jaws, fec., 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 impris- 
oned animals in a fresh state compared with those utterly 
decayed.' Mrs. Treat states with respect to the larva? 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 bwame 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 in- 
herent improbability in this supposition, considering that 

' [Sohlmper (' BotanlBcho ZpI- the snine fact In the cose of 
tang,' IbtSi, p. 245) was struck by U. comuta.F. O.] 



CuAP. XVII,] MilNNER OP CAPTURING PREY. 333 

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 Ja- 
maica,' into a state of putridity. 

Whether or not the decay of the imprisoned animals is in 
any way hastened, it is certain that matter is absorbed from 
them by the quadrifid and bifid processes. The extremely 
delicate nature of the membrane of which these processes 
are formed, and the large surface which they expose, owing 
to their number crowded over the whole interior of the blad- 
der, are circumstances all favouring the process of absorp- 
tion. Many perfectly clean bladders which had never caught 
any prey were opened, and nothing could be distinguished 
with a No. 8 object-glass of Hartnack within the delicate, 
structureless protoplasmic lining of the arms, excepting in 
each a single yellowish particle or modified nucleus. Some- 
times two or even three such particles were present; but in 
this case traces of decaying matter could generally be de- 
tected. On the other hand, in bladders containing either 
one large or several small decayed animals, the processes pre- 
sented a widely different appearance. Six such bladders 
were carefully examined; one contained an elongated, coiled- 
up larva; another a single large entomostracan, and the 
others from two to five smaller ones, all in a decayed state. 
In these six bladders, a large number of the quadrifid pro- 
cesses contained transparent, often yellowish, more or less 
confluent, spherical or irregularly shaped, masses of matter. 
Some of the processes, however, contained only fine granular 
matter, the particles of which were so small that they could 
not be defined clearly with No. 8 of Hartnack. The delicate 
layer of protoplasm lining their walls was in some cases a 
little shrunk.* On three occasions the above small masses of 
matter were observed and sketched at short intervals of time; 
and they certainly changed their positions relatively to each 
other and to the walls of the arms. Separate masses some- 
times became confluent, and then again divided. A single 

[Schimper (loc. eit. p. 247) ob- the commonest chanjre is a col- 
served n marked dlfferonoe In the leotlon of the protoplasm In the 
appearance of the hairs In those axis of the cell where It Is sus- 
bladders of V. comuta which con- pended by radiating strands to 
tain captured prey. The proto- the delicate layer of protoplasm 
plasm Is- Kometlnies more granu- lining the walls. F. D.J 
far than In empty bladders, but 



334 UTRICULAEIA NEGLECTA. [Chap. XVII. 

little mass would send out a projection, which after a time 
separated itself. Hence there could be no doubt that these 
masses consisted of protoplasm. Bearing in mind that 
many clean bladders were examined with equal care, and 
that these presented no such appearance, we may confidently 
believe that the protoplasm in the above cases had been gen- 
erated by the absorption of nitrogenous matter from the de- 
caying animals. In two or three other bladders, which at 
first appeared quite clean, on careful search a few processes 
were found, with their outsides clogged with a little brown 
matter, showing that some minute animal had been captured 
and had decayed, and the arms here included a very few 
more or less spherical and aggregated masses; the processes 
in other parts of the bladders being empty and transparent. 
On the other hand, it must be stated that in three bladders 
containing dead crustaceans, the processes were likewise 
empty. This fact may be accounted for by the animals not 
having been sufficiently decayed, or by time enough not hav- 
ing 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 Qtiadrifid 
and Bifid Processes. These experiments were tried to ascer- 
tain 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 sev- 
eral 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, except- 
ing 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 dc- 



Chap. XVTL] ABSORPTION BY THE QUADRIPIDS. 335 

cay. Therefore most of my experiments were made by cut- 
ting bladders longitudinally into two; the quadrifids were 
examined with No. 8 of Hartnack, then irrigated, whilst 
under the covering glass, with a few drops of the fluid under 
trial, kept in a damp chamber, and re-examined after stated 
intervals of time with the same power as before. 

Four bladders were first tried as a control experiment, in the 
manner 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 bifids after 21 hrs. Four bladders were then 
treated in the same manner with a solution of one part of nitrate 
of ammonia to 437 of water, and re-examined after 21 hrs. In two 
of these the quadrifids now appeared full of very finely granular 
matter, and their protoplasmic lining or primordial utricle was a 
little shrunk. In the third bladder, the quadrifids included dis- 
tinctly 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 solu- 
tion for 17 hrs.; and their quadrifids now contained very fine 
granular matter. 

A bladder was bisected, examined, and irrigated with a solu- 
tion of one part of carbonate of ammonia to 437 of water. After 
8 hrs. 30 m. the quadrifids contained a good many granules, and 
the primordial utricle was somewhat shrunk; after 23 hrs. the 
quadrifids and bifids contained many spheres of hyaline -matter, 
and in one arm twenty-four such spheres of moderate size were 
counted. Two bisected bladders, which had been previously left 
for 21 hrs. in the solution of gum (one part to 218 of water) with- 
out 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 examine<l 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 am- 
monia. Several uninjured bladders were left in the same solution, 
as well as in a weaker solution of one part to 1750 of water, or 1 
gr. to 4 oz. ; and after two days the quadrifids were more or less 
opaque, with their contents finely granular; but whether the solu- 
tion had entered by the orifice, or had been absorbed from the out- 
side, I know not. 



336 UTRICULARIA NEGLECTA. [Chap. XVIL 

Two bisected bladders were irrigated with a solution of one 
part of urea to 218 of water; but when this solution wa.s em- 
ployed, I forgot that it had been kept for some days in a warm 
room, and had therefore probably generated ammonia; anyhow, 
the quadrifids Avere affected after 21 hrs. as if a solution of car- 
bonate of ammonia had been used; for the primordial utricle was 
thickened in specks, which seemed to graduate into separate gran- 
ules. Three bisected bladders were also irrigated with a fresh 
solution of urea of the same strength; their quadritids after 21 hrs. 
were much less affected than in the former case; nevertheletw, the 
primonlial utricle in some of the arms was a little shrunk, and 
m others was divided into two almost symmetrical sacks. 

Three bisected bladders, after being examined, were irrigated 
with a j)utrid and very offensive infusion of raw meat. After 23 
hrs. the quadrilids and bifids in all three specimens abounded with 
minute, hyaline, spherical masses; and some of their primordial 
utricles were a little shrunk. Three bisected bladders were also 
irrigated with a fresh infusion of raw meat; and to my surprise 
the quadrifids in one of them appeared, after 23 hrs., finely granu- 
lar, with their primordial utricles somewhat shrunk and marked 
jvith thickened yellowish specks; so that they had been acted 
on in the same manner as by the putrid infusion or by the salts 
of ammonia. In the second bladder some of the quadrifids were 
similarly acted on, though to a very slight degree; whilst the 
third bladder was not at all affected. 

From these experiments it is clear that the quadrifid and 
bifid processes have the power of absorbing carbonate and 
nitrate of ammonia, and matter of some kind from a putrid 
infusion of meat. Salts of ammonia were selected for trial, 
as they are known to be rapidly generated by the decay of 
animal matter in the presence of air and water, and would 
therefore be generated within the bladders containing cap- 
tured prey. The effect produced on the processes by these 
salts and by a putrid infusion of raw meat differs from that 
produced by the decay of the naturally captured animals 
only in the aggregated masses of protoplasm being in the 
latter case of lasgor 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 aggregate 
into larger, more or less rounded, ma.<ses; and that the gran- 
ules in the layer of protoplasm which flows round the walls 
ultimately coalesce with these masses. Changes of this nature 



Chap. XVII.] ABSORPTION BY THE GLANDS. 337 

are, however, far more rapid in Drosera than in Utricularia. 
Since the bladders have no power of digesting albumen, car- 
tilage, or roast meat, I was surprised that matter was ab- 
sorbed, at least in one case, from a fresh infusion of raw 
meat, I was also surprised, from what we shall presently 
see with respect to the glands round the orifice, that a fresh 
solution of urea produced only a moderate effect on the 
quadrifids. 

As the quadrifids are developed from papillae which at 
first closely resemble those on the outside of the bladders and 
on the surfaces of the leaves, I may here state that the two 
hemispherical cells with which these latter papillse are 
crowned, and which in their natural state are perfectly trans- 
parent, likewise absorb carbonate and nitrate of ammonia; 
for, after an immersion of 23 hrs. in solutions of one part of 
both these salts to 437 of water, their primordial utricles 
were a little shrunk and of a pale brown tint, and sometimes 
finely granular. The same result followed from the immer- 
sion of a whole branch for nearly three days in a solution of 
one part of the carbonate to 1750 of water. The grains 
of chlorophyll, also, in the cells of the leaves on this branch 
became in many places aggregated into little green 
masses, which were often connected together by the finest 
threads. 

On the Absorption of certain Fluids hy the Glands on the 
Valve and Collar. The glands round the orifices of bladders 
which are still young, or which have been long kept in 
moderately pure water, are colourless; and their primordial 
utricles are only slightly or hardly at all granular. But in 
the greater number of plants in a state of nature and we 
must remember that they generally grow in very foul water, 
and with plants kept in an aquarium in foul water, most 
of the glands were of a pale brownish tint; their primordial 
utricles were more or less shrunk, sometimes ruptured, with 
their contents often coarsely granular or aggregated into 
little masses. That this state of the glands is due to their 
having absorbed matter from the surrounding water, I can- 
not 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- 



338 UTRICULARIA NEGLECTA. [Chap. XVII. 

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 
fluid habitually passes outwards. But we must remember 
that a bladder generally captures several animals; and that 
each time a fresh animal enters, a puff of foul water must 
pass out and bathe the glands. Moreover, I have repeatedly 
found that, by gently pressing bladders which contained air, 
minute bubbles were driven out through the orifice; and if a 
bladder is laid on blotting paper and gently pressed, water 
oozes out. In this latter case, as soon as the pressure is re- 
laxed, 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 ori- 
fice. Hence I can hardly doubt that the numerous glands 
crowded round the orifice are adapted to absorb matter from 
the putrid water, which will occasionally escape from blad- 
ders including decayed animals. 

In order to test this conclusion, I experimented with vnriotia 
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, inchiding the valve, collar, 
and antenna;, were sliced ofT, and the condition of the plands ob- 
8erve<l ; they were then irrigated, whilst beneath a covorincj glass, 
>ith the solutions, and after a time re-examined with the same 
power as before, namely No. 8 of Hartnack. The following ex- 
]>crinient8 were thus made. 



Chap. XVIL] ABSORPTION BY THE GLANDS. 339 

As a control experiment solutions of one part of white sugar and 
of one part of gum to 218 of water were first used, to see whether 
these produced any change in the glands. It was also necessary to 
observe whether the glands were alFected by the summits of the 
bladdere having been cut oflf. The summits of four were thus 
tried; one being examined after 2 hrs. 30 m., and the other three 
after 23 hrs.; but there was no marked change in the glands of 
any of them. 

Two summits bearing quite colourless glands were irrigated 
with a solution of carbonate of ammonia of the same strength 
(viz. one part to 218 of water), and in 5 m. the primordial utricles 
of most of the glands were somewhat contracted ; they were also 
thickened in specks or patches, and had assumed a pale brown tint. 
When looked at again after 1 hr. 30., most of them presented a 
somewhat different appearance. A third specimen was treated with 
a weaker solution of one part of the carbonate to 437 of water, 
and after 1 hr. the glands were pale brown and contained numerous 
granules. 

Four summits were irrigated with a solution of one part of 
nitrate of ammonia to 437 of water. One was examined after 
15 m., and the glands seemed affected; after 1 hr. 10 m. there was 
a greater change, and the primordial utricles in most of them were 
somewhat shrunk, and included many granules. In the second 
specimen, the primordial utricles were considerably shrunk and 
brownish after 2 hrs. Similar effects were observed in the two 
other specimens, but these were not examined until 21 hrs. had 
elapsed. The nuclei of many of the glands apparently had in- 
creased 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 re- 
mainder 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 phosphate of ammonia, each of one 
part to 437 of water. After 2 hrs. some few of the glands were 
brownish. After 8 hrs. almost all the oblong glands were brown 
and much more opaque than they were before; their primordial 
utricles were somewhat shrunk and contained a little aggregated 
granular matter. The spherical glands were still white, but their 
utricles were broken up into three or four small hyaline spheres, 
with an irregularly contracted mass in the middle of the basal 
part. These smaller spheres changed their forms in the course ot 
a few hours, and some of them disappeared. By the next morn- 
ing, 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 
23 



340 UTRICULARIA NEGLECTA. [Chap. XVII. 

hrs. with a solution of one part of sugar to 218 of water without 
being alFected, was trcuted with the above mixed solution; and 
after 8 hrs. .'iO m. all the glands became brown, with their primor- 
dial 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 opacjue 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 was not affected was then irrigated with the 
mixed solution of the nitrate and phosphate of ammonia, and after 
only 25 m. the glands contained from four or five to a dozen 
granules. After six additional hours their primordial utricles were 
greatly shrunk. 

The summit of a bladder was examined, and all the glands 
found colourless, with their primordial utricles not at all shrunk; 
yet many of the oblong glands contained granules just resolvable 
with No. 8 of Hartnack. It was then irrigated with a few drops 
of a solution of one part of urea to 218 of water. After 2 hrs. 

25 m. the spherical glands were still colourless; whilst the oblong 
and two-armed ones were of a brownish tint, and their primordial 
utricles much shrunk, some containing distinctly visible granules. 
After 9 hrs. some of the spherical glands were brownish, and the 
oblong glands were still more changed, but they contained fewer 
separate granules; their nuclei, on the other hand, appeared larger, 
as if they had absorbed the granules. After 23 hrs. all the glands 
were brown, their primordial utricles greatly shrunk, and in many 
cases ruptured. 

A bladder was now experimented on, which was already some- 
what affected by the surrounding water; for the spherical glands, 
though colourless, had their primordial utricles slightly shrunk; 
and the oblong glands were brownish, with their utricles much, 
but irregularly, shrunk. The summit was treated with the solu- 
tion of urea, but was little affected by it in 9 hrs.; nevertheless, 
after 23 hrs. the spherical glands were brown, with their utricles 
more shrunk; several of the other glands were still browner, with 
their utricles contracted into irregular little masses. 

Two other summits, with their glands colourless and their 
utricles not shnmk, were treated with the same solution of urea. 
After 5 hrs. many of the glands presented a shade of brown, with 
their utricles slightly shrunk. After 20 hrs. 40 m. some few of 
them were quite brown, and contained irregularly aggregated 
masses; others were still colourless, though their utricles were 
shrunk ; but the greater number were not much affected. This was 
a good instance of how unequally the glands on the same bladder 
are sometimes affected, as likewise often occurs with plants grow- 
ing in foul water. Two other summits were treated with a solu- 



CuAP. XVII.] SUMMARY ON ABSORPTION". 341 

tion which had been kept during several days in a warm room, 
and their glands were not at all affected wlien 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 ob- 
long glands, those which were before colourless, became brown in 
3 hrs. 12 m. after irrigation, with their utricles slightly shrunk. 
The spherical glands did not become brown, but their contents 
seemed changed in appearance, and after 23 hrs. still more changed 
and granular. Most of the oblong glands were now dark brown, 
but their utricles were not greatly shrunk. The four other speci- 
mens were examined after 3 hrs. 30 m., after 4 hrs. and 9 hrs.; 
a brief account of their condition will be sufficient. The spherical 
glands were not brown, but some of them were finely granular. 
Many of the oblong glands were brown; and these, as well as 
others which still remained colourless, had their utricles more or less 
shrunk, some of them including small aggregated masses of matter. 

Summary of the Observations on Absorption. From the 
facts now given there can be no doubt that the variously 
shaped glands on the valve and round the collar have the 
power of absorbing matter from weak solutions of certain 
salts of ammonia and urea, and from a putrid infusion of 
raw meat. Prof. Cohn believes that they secrete slimy mat- 
ter; but I was not able to perceive any trace of such aclion, 
excepting that, after immersion in alcohol, extremely fine 
lines could sometimes be seen radiating from their surfaces. 
The glands are variously alBFected by absorption: they often 
become of a brown colour; sometimes they contain very fine 
granules, or moderately sized grains, or irregularly aggre- 
gated little masses; sometimes the nuclei appear to have in- 
creased 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 gener- 
ally affected rather differently from the oblong and two- 
armed ones. The former do not so commonly become brown, 
and are acted on more slowly. We may therefore infer that 
they differ somewhat in their natural functions. 



r 



842 UTRICULARIA NEQLECTA. [Cbap. XVII. 

It is remarkable how unequally the glands on the blad- 
ders on the same branch, and even the glands of the same 
kind on the bladder, are affected by the foul water in which 
the plants have grown, and by the solutions which were em- 
ployed. 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 pre- 
viously absorbed a small amount of matter from the water. 
However this may be, we have seen that the glands on the 
same leaf of Drosera are sometimes very unequally affected, 
more especially when exposed to certain vapours. 

If glands which have already become brown, with their 
primordial utricles shrunk, are irrigated with one of the 
effective solutions, they are not acted on, or only slightly and 
slowly. If, however, a gland contains merely a few coarse 
granules, this does not prevent a solution from acting. I 
have never seen any appearance making it probable that 
glands which have been strongly affected by absorbing mat- 
ter of any kind are capable of recovering their pristine, col- 
ourless, 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 con- 
tents of the oblong glands were never seen by me or by my 
son to undergo those spontaneous changes of form charac- 
teristic of protoplasm. On the other hand, the contents of 
the larger spherical glands often separated into small hy- 
aline globules or irregularly shaped masses, which changed 
their forms very slowly and ultimately coalesced, forming a 
central shrunken mass. Whatever may be the nature of the 
contents of the several kinds of glands, after they have been 
acted on by foul water or by one of the nitrogenous solutions, 
it is probable that the matter thus generated is of service 
to the plant, and is ultimately transferred to other parts. 

The glands apparently absorb more quickly than do the 
quadrifid and bifid processes; and on the view above main- 
tained, namely that they absorb matter from putrid water 
occasionally emitted from the bladders, they ought to act 



Chap. XVII.] DEVELOrMENT OP THE BLADDERS. 343 

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 blad- 
ders, 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 particular- 
ly interesting, because we have seen that it produces no 
effect on Drosera, the leaves of which are adapted to digest 
fresh animal matter. But the most important fact of all is, 
that in the present and following species the quadrifid and 
bifid processes of bladders containing decayed animals gen- 
erally include little masses of spontaneously moving proto- 
plasm; whilst such masses are never seen in perfectly clean 
bladders. 

Development of the Bladders. My son and I spent much 
time over this subject with small success. Our observations 
apply to the present species and to Utricularia vulgaris, but 
were made chiefly on the latter, as the bladders are twice as 
large as those of Utricularia neglecta. In the early part of 
autumn the stems terminate in large buds, which fall off and 
lie dormant during the winter at the bottom. The young 
leaves forming these buds bear bladders in various stages of 
early development. When the bladders of Utricularia vul- 
garis are about ihs inch (.254 mm.) in diameter (or rhs in 
the case of Utricularia neglecta), they are circular in out- 
line, with a narrow, almost closed, transverse orifice, leading 
into a hollow filled with water; but the bladders are hollow 
when much under rm of an inch in diameter. The orifices 
face inwards or towards the axis of the plant. At this early 
age the bladders are flattened in the plane in which the 
orifice lies, and therefore at right angles to that of the ma- 
ture bladders. They are covered exteriorly with papillae 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. 



344 



UTRICULARIA NEGLECTA. [Chap. XVII. 



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 comers of the valve unite with the collar; but these 
branches could not be seen in very young bladders. 

The accompanying figure (Fig. 23) shows a section, which 
happened to be strictly medial, through the footstalk and 
between the nascent antennse of a bladder of Utricularia vul- 
garis, T^T inch in diameter. The specimen was soft, and the 
young valve became separated from the collar to a greater de- 
gree than is natural, and is thus repre- 
sented. We here clearly see that the 
valve and collar are infolded pro- 
longations of the wall of the bladder. 
Even at this early age, glands could 
be detected on the valve. The state 
of the quadrifid processes will pres- 
ently be described. The antenna? at 
this period consist of minute cellular 
projections (not shown in the accom- 
panying figure, as they do not lie in 
the medial plane), which soon bear 
incipient bristles. In five instances 
the young antennae were not of quite 
equal length; and this fact is intelli- 
gible if I am right in believing that 
they represent two divisions of the 
leaf, rising from the end of the blad- 
der; for, with the true leaves, whilst very young, the divi- 
sions 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 antenna?. 

At a much earlier age, when the half-formed bladders are 
only rhr inch (.0846 mm.) in diameter or a little more, they 
present a totally different appearance. One is represented on 
the left side of the drawing on the opposite page (Fig. 24). 
The young leaves at this age have broad flattened segments, 
with 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 blad- 




FlG. 23. 
( Utriadaria mdgaris.) 
Longitudinal section 
through a young blad- 
der, TOO of an inch in 
length, with the orifice 
too widely open. 



Chap. XVII.] DEVELOPMENT OF THE BLADDERS. 345 

ders appeared as if formed by the oblique folding over of the 
apex and of one margin with a prominence, against the op- 
posite 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 op- 
posed margins of the rest of the leaf. But strong objections 
may be urged against this view, for we must in this case sup- 
pose 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 




Fig. 24. 

( Utricularia vulgarvt.) 

Toang leaf from a winter bud, showing on the left side a bladder in its 

earliest stage of development. 

irrespective of the original form of the leaf. Until grada- 
tions can be shown to exist between this the earliest state 
and a young yet perfect bladder, the case must be left doubt- 
ful. 

As the quadrifid and bifid processes offer one of the 
greatest peculiarities in the genus, I carefully observed their 
development in Utricularia neglecta. In bladders about ^iv 
of an inch in diameter, the inner surface is studded with 
papillse, rising from small cells at the junctions of the larger 
ones. These papillaj consist of a delicate conical protuber- 
ance, which narrows into a very short footstalk, surmounted 



846 UTRICULARIA NEGLECTA. [Chap. XVII. 

by two minute cells. They thus occupy the same relative 
position, and closely resemble, except in being smaller and 
rather more prominent, the papilla; on the outside of the 
bladders, and on the surfaces of the leaves. The two termi- 
nal cells of the papillae first become much elongated in a line 
parallel to the inner surface of the bladder. Next, each is 
divided by a longitudinal partition. Soon the two half-cells 
thus formed 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, in- 
stead of their apices, continue to grow. The two lower cells, 
which have slid partly beneath the two upper ones, form the 
longer and more upright pair of processes: whilst the two 
upper cells form the shorter and more horizontal pair; the 
four together forming a perfect quadrifid. A trace of the 
primary division between the two cells on the summits of 
the papillae can still be seen between the bases of the longer 
processes. The development of the quadrifids is very liable 
to be arrested. I have seen a bladder -sz of an inch in length 
including only primordial papilla;; and another bladder, 
about half its full size, with the quadrifids in an early stage 
of development. 

As far as I could make out, the bifid processes are de- 
veloped in the same manner as the quadrifids, excepting that 
the two primary terminal cells never become divided, and 
only increase in length. The glands on the valve and collar 
appear at so early an age that I could not trace their devel- 
opment; but we may reasonably suspect that they are de- 
veloped from papilla; like those on the outside of the bladder, 
but with their terminal cells not divided into two. The two 
s^ments 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 papilla; like those on the out- 
side of the bladders, from the fact that in Utricularia ame- 
thystina the glands extend along the whole ventral surface 
of the bladder close to the footstalk. 



Chap. XVIL] 



UTRICULARIA MINOR. 



34T 



UTRICULARU VULGARIS. 

Living plants from Yorkshire were sent me by Dr. Hooker. 
This species differs from the last in the stems and leaves being 
thicker or coarser; their divisions form a more acute angle with 
one another; the notches on the leaves bear three or four short 
bristles instead of one; and the bladders are twice as large, or 
about ^ of an inch (5.08 mm.) in diameter. In all essential re- 
spects the bladders resemble those of Utricularia neylccta, but the 
sides of the peristome are perhaps a little more prominent, and 
always bear, as far as I have seen, seven or eight long multicellular 
bristles. There, are eleven long bristles on each antenna, the ter- 
minal pair being included. Five bladders, containing prey of some 
kind, were examined. The first included five Cypris, a large cope- 
pod 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 there- 
fore consisted of protoplasm. 



UTRICULARIA MINOR. 

This rare species was sent me in a living state from Cheshire, 
through the kindness of Mr. John Price. The leaves and bladders 
are much smaller than those of Utricularia neglecta. The leaves 
bear fewer and shorter bristles, and the bladders are more globular. 
The antennae, instead of projecting in front of the bladders, are 
curled under the valve, and are armed with twelve or fourteen 
extremely long multicellular bristles, generally arranged in pairs. 
These, with seven or eight long bristles on 
both sides of the peristome, form a sort of 
net over the valve, which would tend to 
prevent all 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 pre- 
vent 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 




Fro. 25. 

( Utricularia minor.) 

Quadrifid process; 

greatly enlarged. 



848 UTRICULARIA CLANDESTINA. [Chap. XVII. 

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 con- 
tents of five bladders, which from their opacity seemed full of 
prey, were examined. The first contained no less than twenty-four 
minute fresh-water crustaceans, most of them consisting of empty 
shells, or including only a few drops of red oily matter; the second 
contained twenty; the third, fifteen; the fourth, ten, some of them 
being rather larger than usual; and the fifth, which seemed stuffed 
quite full, contained only seven, but five of these were of unusu- 
ally large size. The prey, therefore, judging from these five blad- 
ders, 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 mat- 
ter, which slowly changed their forms and positions. 

UTRICULARIA CLANDESTINA. 

This North American species, which is aquatic like the three 
foregoing ones, has been described by Mrs. Treat, of New Jersey, 
whose excellent observations have already been largely quoted. 
1 have not as yet seen any full description by her of the structure 
of the bladder, but it appears to be lined with quadrifid processes. 
A vast number of captured animals were found within the blad- 
ders; some being crustaceans, but the greater number delicate, 
elongated larva;, I suppose of Culicidee. On some stems, " fully 
nine out of every ten bladders contained these larvae or their re- 
mains." The larvae " showed signs of life from twenty-four to 
thirty-six hours after being imprisoned," and then perished. 



Chap. XVIII.] UTRICULARIA MONTANA. 349 



CHAPTER XVin. 
UTRICULARIA (continued). 

UtriaUaria 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 Polyiwmpholyx Genlisea, different nature of the 
trap for capturing prey [Sarracenia] Diversified methods by which 
plants are nourished. 

Utricularia Montana. This species inhabits the tropical 
parts of South America, and is said to be epiphytic; but, 
judging from the state of the roots (rhizomes) of some dried 
specimens from the herbarium at Kew, it likewise lives in 
earth, probably in crevices of rocks. In English hot-houses 
it is grown in peaty soil. Lady Dorothy Nevill was so kind 
as to give me a fine plant, and I received another from Dr. 
Hooker. The leaves are entire instead of being much divid- 
ed, as in the foregoing aquatic species. They are elongated, 
about li 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 occasion- 
ally swell into tubers, as will hereafter be described. These 
rhizomes appear exactly like roots, but occasionally throw up 
green shoots. They penetrate the earth sometimes to the 
depth of more than 2 inches: but when the plant grows as 

> Hovelacque. In the ' Comptes by him in the mountains of 

Rendus,' vols. cv. p. C92, and cvl. Dominica. UtriettUiria corntita, 

p. 310, has discussed the nature described by Schlmper In the 

of the underground runners; he ' Bot. Zeltung,' 18S2, p. 241, has 

considers them to be morphologl- similar underground runners, as 

cally leaves. In opposition to well as aerial organs usually de- 

Scbenk (Pringshelm's ' Jahr- scribed as leaves. He discusses 

bilcher,' vol. xvlli. p. 218), who the possibility of a morphological 

regards them as rhizomes. Schlm- Identity between the runners and 

per. In his paper on the West In- the "leaves" from a point of view 

dian Epiphytes (' Bot. Central- opposite to that of Hovelacnue's 

blatt,' vol. xvll, p. 257), takes a namely, that the " leaves '' as 

view similar to Schenk's as to well as the stolons mav be mor- 

stolons or .runners In the new phologlcally stems. F. D.] 
species, U. Schimperi, discovered 



350 



UTRICULARIA MONTANA. [Chap. XVIII. 



an epiphyte, they must creep amidst the mosses, roots, de- 
cayed bark, tc., with which the trees of these countries are 
thickly covered. 

As the bladders are attached to the rhizomes, they are 
necessarily subterranean. They are produced in extraordi- 
nary numbers. One of my plants, though young, must have 
borne several hundreds; for a sin- 
gle branch out of an entangled mass 
had thirty-two, and another branch, 
about 2 inches in length (but with 
its end and one side branch broken 
off), had seventy - three bladders.* 
The bladders are compressed and 
rounded, with the ventral surface, or 
that between the summit of the long 
delicate footstalk and valve, 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 be- 
ing under the sV of an inch (1.27 
mm.) in its longer diameter. They 
Ehizome swollen into a are formed of rather large angular 
tnber; the branches pells, at the junctions of which ob- 
bcanng minute blad- , -n 

ders ; of natural size. long papiUsB project, corresponding 

with those on the surfaces of the blad- 
ders of the previous species. Similar papilla; abound on the 
rhizomes, and even on the entire leaves, but they are rather 
broader on the latter. Vessels, marked with parallel bars 
instead of by a spiral line, run up the footstalks, and just 
enter the bases of the bladders; but they do not bifurcate 
and extend up the dorsal and ventral surfaces, as in the 
previous species. 

The antenna; are of moderate length, and taper to a fine 
point; they differ conspicuously from those before described, 




Fig. 26. 
(Utriailaria montana.) 



* ProfoBHor Ollvor hns flpurod a 
plant of I'Irirularin Jammoninnn 
( Proc. Linn. Soc' vol. Iv. i). Hn 
having entire leaves an<l rhi- 
zomes, like those of onr present 
species: but the margins of the 
terminal halves of some of the 
lenves are converted Into blad- 
ders. This fact clearly indicates 



that the bladders on the rhi- 
zomes of the present and follow- 
ing 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 tbe aquatic 
species. 



Chap. XVIIL] STRUCTURE OF THE BLADDERS. 351 

in not being armed with bristles. Their bases are so ab- 
ruptly 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 in the draw- 
ing, as well as a narrow passage between the bases of the 
two antennse. As the bladders are subterranean, had it not 
been for the roof, the cavity in which the valve lies would 




Fig. 27. 

( Utrieularia moniana.) 

Bladder; about 27 times enlarged. 

have been liable to be blocked up with earth and rubbish ; so 
that the curvature of the antennse is a serviceable character. 
There are no bristles on the outside of the collar or peristome, 
as in the foregoing species. 

The valve is small and steeply inclined, with its free pos- 
terior edge abutting against a semicircular, deeply depend- 
ing collar. It is moderately transparent, and bears two pairs 
of short stiff bristles, in the same position as in the other 
species. The presence of these four bristles, in contrast with 
the absence of those on the antennae and collar, indicates 
that they are of functional importance, namely, as I believe, 



862 UTRICULARIA MONTANA. [Chap. XVIII. 

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 i^sn of an inch (.019 
mm.) in length; though so small, they act as absorbents. 
The collar is thick, stiflF, 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 
rows. The two pairs of arms of which they are formed dif- 
fer only a little in length, and stand in a peculiar position 



Fig. 28. 

( Utrictilaria montano.) 

One of the quadrifid processes ; much enlarged. 

(Fig. 28) ; the two longer ones forming one line, and the 
two shorter ones another parallel line. Each arm includes a 
small spherical mass of brownish matter, which, when 
crushed, breaks into angular pieces. I have no doubt that 
these spheres are nuclei, for closely similar ones are present 
in the cells forming the walls of the bladders. Bifid pro- 
cesses, having rather short oval arms, arise in the usual po- 
sition on the inner side of the collar. 

These bladders, therefore, resemble in all essential re- 
spects 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 antenna? and on the 
outside of the collar. The presence of these bristles in the 
previously mentioned species probably relates to the capture 
of aquatic animals. 



Chap. XVIII.] CAPTURED ANIMALS. 353 

It seemed to me an interesting question whether the 
minute bladders of Utricularia montana served, as in the 
previous species, to capture animals living in the earth, or 
in the dense vegetation covering the trees on which this 
species is epiphytic; for in this case we should have a new 
sub-class of carnivorous plants, namely, subterranean feed- 
ers. Many bladders, therefore, were examined, with the fol- 
lowing results: 



(1) A small bladder, less than ^ of an inch (.847 mm.) in 
diameter contained a minute mass of brown, much decayed matter; 
and in this, a tarsus with four or five joints, terminating in a 
double hook, was clearly distinguished under the microscope. I 
suspect that it was a remnant of one of the Thysanoura. The 
quadrifids in contact with this decayed remnant contained either 
small masses of translucent, yellowish matter, generally more or 
less globular, or fine granules. In distant parts of the same blad- 
der, 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; some- 
times 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 aggravated 
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, ex- 
cepting that the nuclei in the several arms differed much in size; 
some of them containing two masses having a similar appearance. 

(4) A fourth bladder contained an articulate organism, for I 
distinctly saw the remnant of a limb, terminating in a hook. The 
quadrifids were not examined. 

(5) A fifth included much decayed matter apparently of some 
animal, but with no recognisable features. The quadrifids in con- 
tact contained numerous spheres of protoplasm. 

(6) Some few bladders on the plant which I received from Kew 
were examined; and in one, there was a worm-shaped animal very 
little decayed, with a distinct remnant of a similar one greatly 
decayed. Several of the arms of the processes in contact with these 
remains contained two spherical masses, like the single solid nucleus 
which is properly found in each arm. In another bladder there was 
a minute grain of quartz, reminding me of two similar cases with 
Utricularia neglecta. 

As it appeared probable that this plant would capture a greater 
munber of animals in its native country than under culture, I 



854 UTRICULARIA MONTANA. [Chap. XVIII. 

obtained permission to remove small portions of the rhizomes from 
dried specimens in the herbarium at Kew. I did not at first find 
out that it was advisable to soak the rhizomes for two or three 
days, and that it was necessary to open the bladders and spread 
out their contents on glass: as from their state of decay and 
from having been dried and pressed, their nature could not other- 
wise be well distinguished. Several bladders on a plant which had 
gi'own 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 oesophagus was suspended, but I 
could see no mandibles; also the double hook of the tarsus of 
some animal ; also an elongated greatly decayed animal ; and lastly, 
a curious fiask-shaped organism, having the walls formed of 
rounded cells. Professor Claus has looked at this latter organism, 
and thinks that it is the shell of a rhizopod, probably one of the 
Arcellidae. In this bladder, as well as in several others, there were 
some unicellular Algae, and one multicellular Alga, which no doubt 
had lived as intruders. 

A second bladder contained an Acarus much less decayed than 
the former one, with its eight legs preserved ; as well as remnants of 
several other articulate animals. A third bladder contained the 
end of the abdomen with the two hinder limbs of an Acarus, as 
I believe. A fourth contained remnants of a distinctly articulated 
bristly animal, and of several other 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 qiiadrifids 
in two were brownish, with their contents granular; and it was 
evident that they had absorbed matter. In a fifth bladder there 
was a fiask-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 the quadrifid processes 
and glands with reference to their power of absorption. A 
bladder was punctured and left for 24 hrs. in a solution of 
one part of urea to 437 of water, and the quadrifid and bifid 
processes were found much affected. In some arms there 
was only a single symmetrical globular mass, larger than 
the proper nucleus, and consisting of yellowish matter, gen- 
erally translucent but sometimes granular; in others there 



Chap. XVIII.] ABSORPTION. 355 

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 be- 
come aggregated sometimes round the nucleus, and some- 
times into separate masses; and that these then tended to 
coalesce. The primordial utricle or protoplasm lining the 
processes was also thickened here and there into irregular 
and variously shaped specks of yellowish translucent matter, 
as occurred in the case of Utricularia neglecta under similar 
treatment. These specks apparently did not change their 
forms. 

The minute two-armed glands on the valve were also 
affected by the solution; for they now contained several, 
sometimes as many as six or eight, almost spherical masses 
of translucent matter, tinged with yellow, which slowly 
changed their forms and positions. Such masses were never 
observed in these glands in their ordinary state. We may 
therefore infer that they serve for absorption. Whenever a 
little water is expelled from a bladder containing animal 
remains (by the means formerly specified, more especially 
by the generation of bubbles of air), it will fill the cavity 
in which the valve lies; and thus the glands will be able 
to utilise decayed matter which otherwise would have been 
wasted. 

Finally, as numerous minute animals are captured by 
this plant in its native country and when cultivated, there 
can be no doubt that the bladders, though so small, are far 
from being in a rudimentary condition; on the contrary, 
they are highly efficient traps. Nor can there be any doubt 
that matter is absorbed from the decayed prey by the quad- 
rifid and bifid processes, and that protoplasm is thus gener- 
ated. What tempts animals of such diverse kinds to enter 
the cavity beneath the bowed antennae, and then force their 
way through the little slit-like orifice between the valve and 
collar into the bladders filled with water, I cannot con- 
jecture. 

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 

S4 



356 UTRICULARIA MONTANA. [Chap. XV 111. 

twenty, there were all possible gradations between a short 
length of a rhizome just perceptibly swollen and one so much 
swollen that it might be doubtfully called a tuber. When 
well developed, they are oval and symmetrical, more so than 
appears in the figure. The largest which I saw was 1 inch 
(25.4 mm.) in length and .45 inch (11.43 mm.) in breadth. 
They commonly lie near the surface, but some are buried at 
the depth of 2 inches. The buried ones are dirty white, but 
those partly exposed to the light become greenish from the 
development of chlorophyll in their superficial cells. Th^y 
terminate in a rhizome, but this sometimes decays and drops 
off. They do not contain any air, and they sink in water; 
their surfaces are covered with the usual papilla?. The bun- 
dle of vessels which runs up each rhizome, as soon as it enters 
the tuber, separates into three distinct bundles, which re- 
unite 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, grow- 
ing in light peaty earth in a pot (only 4i by 4J inches out- 
side measure) was copiously watered, and then kept without 
a drop of water in the hothouse. Two of the upper tubers 
were beforehand uncovered and measured, and then loosely 
covered up again. In a fortnight's time the earth in the pot 
appeared extremely dry; but not until the thirty-fifth day 
were the leaves in the least affected; they then became 
slightly reflexed, though still soft and green. This plant, 
which bore only ten tubers, would no doubt have resisted 
the drought for even a longer time, had I not previously re- 
moved 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 



Chap. XVIII.] RESERVOIRS FOR WATER. 357 

the tubers had their surfaces much wrinkled, instead of be- 
ing smooth and tense. They had all shrunk, but I cannot 
say accurately how much; for as they were at first symmet- 
rically oval, I measured only their length and thickness ; but 
they contracted in a transverse line much more in one direc- 
tion 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 thick- 
ness. The other tuber was one-fourth shorter, one-eighth 
less thick in the direction in which it had been measured, 
and only half as thick in another direction. 

A slice was cut from one of these shrivelled tubers and 
examined. The cells still contained much water and no air, 
but they were more rounded or less angular than before, and 
their walls not nearly so straight; it was therefore clear 
that the cells had contracted. The tubers, as long as 
they remain alive, have a strong attraction for water; the 
shrivelled one, from which a slice had been cut, was left 
in water for 22 hrs. 30 m., and its surface became as smooth 
and tense as it originally was. On the other hand, a shriv- 
elled tuber, which by some accident had been separated from 
its rhizome, and which appeared dead, did not swell in the 
least, though left for several days in water. 

With many kinds of plants, tubers, bulbs, &c., no doubt 
serve in part as reservoirs for water, but I know of no case, 
besides the present one, of such organs having been developed 
solely for this purpose. Prof. Oliver informs me that two or 
three other species of Utricularia are provided with these ap- 
pendages; and the group containing them has in consequence 
received the name of orchidioides. All the other species of 
Utricularia, as wejl as of certain closely related genera, are 
either aquatic or marsh plants; therefore, on the principle 
of nearly allied plants generally having a similar constitu- 
tion, a never-failing supply of water would probably be of 
great importance to our present species. We can thus under- 
stand the meaning of the development of its tubers, and of 
their number on the same plant, amounting in one instance 
to at least twenty. 



868 UTRICULARIA NELUMBIFOLIA. [Chap. XVIIL 



UTRICULARIA NELUMBIFOLIA, AMETIIYSTINA, GRIFFITHII, 
C.RULEA, ORBICULATA, MULTICAULI8 [cX)RNUTa]. 

As I wished to ascertain whether the bladders on the 
rhizomes of other species of Utricularia, and of the species 
of certain closely allied genera, had the same essential struc- 
ture as those of Utricularia montana, and whether they cap- 
tured 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 observa- 
tions; but it should be borne in mind that it is extremely 
difficult to make out the structure of such minute and deli- 
cate objects after they have been dried and pressed.* 

Utricularia nelumbifolia (Organ Mountains, Brazil). 
The habitat of this species is remark^ible. According to its 
discoverer, Mr. Gardner,* it is aquatic, but " is only to be 
found growing in the water which collects in the bottom 
of the leaves of a large Tillandsia, that inhabits abundantly 
an arid rocky part of the mountain, at an elevation of about 
5000 feet above the level of the sea. Besides the ordinary 
method by seed, it propagates itself by runners, which it 
throws out from the base of the flower-stem; this runner is 
always found directing itself towards the nearest Tillandsia, 
when it inserts its point into the water and gives origin to 
a new plant, which in its turn sends out another shoot. In 
this manner I have seen not less than six plants united." 
The bladders resemble those of Utricularia montana in all 
essential respects, even to the presence of a few minute two- 
armed glands on the valve. Within one bladder there was 
the remnant of the abdomen of some larva or crustacean of 
large size, having a brush of long sharp bristles at the apex. 
Other bladders included fragments of articulate animals, 
and many of them contained broken pieces of a curious or- 
ganism, the nature of which was not recognised by any one 
to whom it was shown. 

ProfeiMwr Oliver has g\\en tata ; but he does not appear to 

(' Proc. Linn. Soc' vol. Iv. p. 160) have paid particular attention to 

flKureH of the bladders of two these orRans. 

Bouth American species, namely, * Travels In the Interior of 

Vtricularia Jamcsonlana and pel- Brazil, 183C-41,' p. 527. 



Chap. XVIII.] UTRICULARIA ORBICULATA. 369 

Utricularia amelhystina (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 mon- 
tana, and are covered outside with the usual papillse; but 
they differ remarkably in the antennae being reduced to two 
short points, united by a membrane hollowed out in the mid- 
dle. 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 and decaying prey. 

Utricularia griffithii (Malay and Borneo). The bladders 
are transparent and minute; one which was measured being 
only tUtt of an inch (.711 mm.) in diameter. The anten- 
nae are of moderate length, and project straight forward; 
they are united for a short space at their bases by a mem- 
brane; 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 ccerulea (India). The bladders resemble 
those of the last species, both in the general character of the 
antennae and in the processes within being exclusively bifid. 
They contained remnants of entomostracan crustaceans. 

Utricularia orhiculata (India). The orbicular leaves 
and the fitems bearing the bladders apparently float in water. 



860 POLYPOMPHOLYX. [Chap. XVIII. 

The bladders do not differ much from those of the two last 
species. The antenna;, which are united for a short dis- 
tance at their bases, bear on their outer surfaces and sum- 
mits numerous, long, multicellular hairs, surmounted by 
glands. The processes within the bladders are quadrifid, with 
the four diverging arms of equal length. The prey which 
they had captured consisted of entomostracan crustaceans. 

Utricularia muUicaulis (Sikkim, India, 7000 to 11,000 
feet). The bladders, attached to rhizomes, are remarkable 
from the structure of the antenna;. These are broad, flat- 
tened, and of large size; they bear on their margins multi- 
cellular 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 blad- 
der. Internally the quadrifid processes have divergent arms 
of equal length. The bladders contained remnants of arti- 
culate animals. 

[Utricularia cornuta, Michx. (United States). This 
species has been studied by A. Schimper in America, and is 
the subject of a short paper in the * Botanische Zeitung.' ' 
It grows in swampy ground, and presents a remarkable ap- 
pearance; 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. cor- 
nuta 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 gener- 
ally 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 

[" Notlzen liber InBectfressende Pflnnzen," 1882, p. 241.] 



Chap. XVIIL] GENLISEA ORNATA. 361 

respects, as Prof. Oliver remarks,* " it is quite a Utricu- 
laria." 

Polypompholyx multifida. The bladders are attached in 
whorls round the summits of stiff stalks. The two antennse 
are represented by a minute membranous fork, the basal part 
of which forms a sort of hood over the orifice. This hood 
expands into two wings on each side of the bladder. A third 
wing or crest appears to be formed by the extension of the 
dorsal surface of the petiole; but the structure of these 
three wings could not be clearly made out, owing to the state 
of the 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 de- 
scribed 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 col- 
lar round the valve there are in the place of glands numer- 
ous one-celled papillae, having very short footstalks. The 
quadrifid processes have divergent arms of equal length. 
Remains of entomostracan crustaceans were found within 
the bladders. 

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 
TJtricularia, as I hear from Prof. Oliver, by having a five- 
partite caljTC. Species are found in several parts of the 
world, and are said to be " herbae annua paludosae." 

Genlisea ornata (Brazil). This species has been de- 
scribed and figured by Dr. Warming,' who states that it 
bears two kinds of leaves, called by him spathulate and utricu- 
liferous. 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 

' Proc. Linn. Soc' vol. Iv. p. Lentlbulariacese," Copenhagen. 
171. 1874. 

' " Bidrag til Kundskaben om 



GENLISEA ORNATA. 



fCnAP. XVIII. 




thrice enlarged, 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 en- 
largement of the narrow blade of the leaf. A hollow neck 
(n), no less than fifteen times as long as the utricle itself, 
forms a passage from the transverse 
slit-like orifice (o) into the cavity of 
the utricle. A utricle which measured 
A of an inch (.705 mm.) in its longer 
diameter had a neck if of an inch 
(10.583 mm.) in length, and tIv of an 
inch (.254 mm.) in breadth. On each 
side of the orifice there is a long 
spiral arm or tube (a) ; the structrue 
of which will be best understood by 
the following illustration. Take a nar- 
row ribbon and wind it spirally round 
a thin cylinder, so that the edges 
come into contact along its whole 
length; then pinch up the two edges 
so as to form a little crest, which will 
of course wind spirally round the 
cylinder like a thread round a screw. 
If the cylinder is now removed, we 
shall have a tube like one of the spiral 
arms. The two projecting edges are 
not actually united, and a needle can 
be pushed in easily between them. 
They are indeed in many places a 
little separated, forming narrow en- 
trances into the tube; but this may 



-tu 



Fig. 29. 
(Genlisea omata.) 
Utriculiferous leaf: en- 
larRod about til recti iTies. be the result of the drying of the 

specimens. The lamina of which the 
tube is formed seem? to be a lateral 
prolongation of the lip of the orifice; 
and the spiral line between the two 



I Upper part of lamina 

of leaf. 
b Utricle or bladder, 
n Neck of utricle. 
o Orifice. 
a Spirally wound nnns, 



with tlieir ends projecting edges is continuous with 

the corner of the orifice. If a fine 

bristle is pushed down one of the arms, it passes into the top 

of the hollow neck. Whether the arms are open or closed at 

their extremities could not be determined, as all the speci- 



Chap. XVIII.] STRUCTURE OP THE LEAVES. 



363 



mens were broken; nor does it appear that Dr. Wanning 
ascertained this point. 

So much for the external structure. Internally the lower 
part of the utricle is covered with spherical papillae, formed 
of four cells (sometimes eight ac- 
cording to Dr. Warming), which evi- 
dently answer to the quadrifid pro- 
cesses within the bladders of Utri- 
cularia. These papillae extend a 
little way up the dorsal and ventral 
surfaces of the utricle; and a few, 
according to Warming, may be found 
in the upper part. This upper region 
is covered by many transverse rows, 
one above the other, of short, closely 
approximating hairs, pointing down- 
wards. These hairs have broad bases, 
and their tips are formed by a sepa- 
rate cell. They are absent in the 
lower part of the utricle where the 
papillae abound. The neck is like- 
wise lined throughout its whole length 
with transverse rows of long, thin, 
transparent hairs, having broad bulb- 
ous (Fig. 30) bases, with similarly con- 
structed 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 Portion of inside of neck 
below; so that if the neck is split open leading into the utricle, 
and laid flat, the inner surface resem- 
bles a paper of pins, the hairs repre- 
senting the pins, and the little trans- 
verse ridges representing the folds of 
paper through which the pins are thrust. These rows of 
hairs are indicated in the previous figure (29) by numerous 
transverse lines crossing the neck. The inside of the neck 
is also studded with papillae; those in the lower part are 
spherical and formed of four cells, as in the lower part of the 
utricle ; thoee in the upper part a|p formed of two cells. 




Fig. 30. 
(Genlisea omata.) 



greatly enlarged, show- 
ing the downward 
pointed bristles, and 
small quadrifid cells or 
processes. 



364 GENLISEA ORNATA. [Cuap. XVIII. 

which are much elongated downwards beneath their points 
of attachment. These two-celled papillae apparently cor- 
respond with the bifid process in the upper part of the blad- 
ders of Utricularia. The narrow transverse orifice (o, Fig. 
29) is situated between the bases of the two spiral arms. No 
valve could be detected here, nor was any such structure seen 
by Dr. Warming. The lips of the orifice are armed with 
many short, thick, sharply pointed, somewhat incurved hairs 
or teeth. 

The two projecting edges of the spirally wound lamina, 
forming the arms, are provided with short incurved hairs or 
teeth, exactly like those on the lips. These project inwards 
at right angles to the spiral line of junction between the 
two edges. The inner surface of the lamina supports two- 
celled, elongated papillae, 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 papilla} within 
the neck rest on small cells sunk amidst the larger ones. 
These spiral arms form a conspicuous difference between the 
present genus and Utricularia. 

Lastly, there is a bundle of spiral vessels which, running 
up the lower part of the linear leaf, divides close beneath 
the utricle. One branch extends up the dorsal and the 
other up the ventral side of both the utricle and neck. Of 
these two branches, one enters one spiral arm, and the other 
branch the other arm. 

The utricles contained much debris or dirty matter, 
which seemed organic, though no distinct organisms could be 
recognised. It is, indeed, scarcely possible that any object 
could enter the small orifice and pass down the long narrow 
nock, except a living creature. Within the necks, however, 
of some specimens, a worm with retracted homy jaws, the 
abdomen of some articulate animal, and specks of dirt, prob- 
ably the remnants of other minute creatures, were found. 
Many of the papillce within both the utricles and necks were 
discoloured, as if they had absorbed matter. 

From this description it is sufficiently obvious how Gen- 
lisea secures its prey. Small animals entering the narrow 
orifice but what induces them to enter is not known any 
more than in the case af Utricularia would find their ^ress 



Chap. XVIII.] CAPTURED PREY. 365 

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 or bifid papillae would absorb 
matter from their decayed remains. The transverse rows of 
hairs are so numerous that they seem superfluous merely for 
the sake of preventing the escape of prey, and as they are 
thin and delicate, they probably serve as additional ab- 
sorbents, 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 re- 
mains would be absorbed and utilised by the bifid papillse. 
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 com- 
plex. 

Genlisea africana (South Africa). Fragments of the 
utriculiferous leaves of this species exhibited the same struc- 
ture 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 papillae, 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 



866 GENLISEA FILIFORMIS. [Chap. XVIII. 

rhizomes of Utricularia. These bladders are transparent, 
and very small, viz, only rhv of an inch (2.54 mm.) in length. 
The antennte are not united at their bases, and apparently 
bear some long hairs. On the outside of the bladders there 
are only a few papilla, and internally very few quadrifid pro- 
cesses. 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 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 Utri- 
cularia, aboriginally possess bladders on their rhizomes, 
which they afterwards lost, acquiring in their place utricu- 
liferous leaves? In support of this view it may be urged 
that the bladders of Genlisea filiformis appear from their 
small size and from the fewness of their quadrifid processes 
to be tending towards abortion ; but why has not this species 
acquired utriculiferous leaves, like its congeners? 

Conclusion. It has now been shown that many si)ecie8 
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 req- 
uisite 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 
l)revious part of this work that there is a class of plants 
which digest and afterwards absorb animal matter, namely, 
all the Droscracea?, 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 iK)llen, seeds, 
and bits of leaves. No doubt their glands likewise absorb 
the salts of ammonia brought to them by the rain. It has 
also been shown that some other plants can absorb ammonia 



Chap. XVIII.] CONCLUSION. 867 

by their glandular hairs; and those will profit by that 
brought to them by the rain. There is a second class of 
plants which, as we have just seen, cannot digest, but absorb 
the products of the decay of the animals which they capture, 
namely, Utricularia * and its close allies; and from the ex- 
cellent observations of Dr. Mellichamp and Dr. Canby, there 
can scarcely be a doubt that Sarracenia and Darlingtonia 
may be added to this class, though the fact can hardly be 
considered as yet fully proved. 

[A. Schimper, in an interesting paper,' gives evidence 
that the products of decay are absorbed by the pitchers of 
Sarracenia 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. F. D.] 

There is a third class of plants which feed, as is now 
generally admitted, on the products of the decay of vegetable 

[The late Professor de Bary 21)0, Burnett (as Mr. Thiselton 
showed me at Strasburg two Dyer points out to me) wrote as 
dried specimens of Vtriculnria follows: " Sarracenlse, If kept 
(vulgariat) which clearly demon- from the access of flies, are said 
strated the advantage which tnis to be less flourishing In their 
plant derives from captured In- growth than when each pouch Is 
sects. One had been grown In truly a sarcophagus. According 
water swarming with minute to F'ulvre (* Comptes rendus,' vol. 
crustaceans, the other in clean Ixxxill. 1870, p. lirt't) both Nepen- 
water; the difference In size be- thes and Sarracenia flourish oet- 
tween the " fed " and the ter when their pitchers are sup- 
** starved " plants was most piled with water, and Wiesner 
striking. F. I).] states that Sarracenia can be kept 

[" Notlzen Uber Insectfres- fresh for months without water- 
sende Pflnnzen," ' Bot. Zeltung,' Ing the roots if the pitchers are 
1882. p. 22.5.1 well supplied. (' Klemente der 

' [In the 'Quarterly Journal of Anat. iind Fhys. <ler Pflanzen,' 
Sdence ajii Art,' 1829, vol. 11, p. 2nd Edit. 1885, p. 226). F. D.] 



368 



CONCLUSION. 



[Chap. XVIII. 



matter, such as the bird's-nest orchis (Neottia), &c." Last- 
ly, there is the well-known fourth class of parasites (such as 
the mistletoe), which are nourished by the juices of living 
plants. Most, however, of the plants belonging to these four 
classes obtain part of their carbon like ordinary species, from 
the atmosphere. Such are the diversified means, as far as at 
present known, by which higher plants gain their subsist- 
ence. 



" [Dischidia Raffleaiana, Wall., 
Is sumetiiues doubtfully uieu- 
tioned as an Insectivorous plant. 
The researches of Trenb ('An- 
naU>s du Jardin botanique de 
Buitenzorg,' vol. 111. 1883. p. 13) 
show that this Is not the case. 
Dischidia grows as a cllml>lng 
epiphyte on trees, and bears clus- 
ters of modified leaves or pitch- 
ers. They are of Interest mor- 
phologically because it Is the in- 
side of the pitcher which corre- 
sponds to the lower surface of 
the leaf, so that the pitchers are 
involutions or pouchtngs of the 
leaf from the lower instead of 
from the upper surface as in 
Nepenthes, Sarracenla and Cepha- 
lotus (see Diclison, ' Journal of 
Botany,' 1881. p. 133). The 

Citchers of Dischidia are covered, 
oth inside and out. with a waxy 
coating which is heaped up in a 
curious manner round the stom- 
ata, forming a tower-lilce struc- 
ture round each of these open- 
ings. There are no giuuds on 



the surface of the pitchers, and 
the fluid with which they are 
often partially filled Is simply 
collected rain-water. Adventi- 
tious roots are numerous and 
commonly 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 
tlie roots. Treub on the other 
hand l)elleves that the drowning 
of ants within the pitchers Is ac- 
cidental rather than wilful on the 
part of the plant. He points out 
that no arrangement for retain- 
ing the ants exists, and that the 
adventitious roots supply ladders 
by which they may escape; more- 
over the ants are as often as not 
found alive and well within the 
pitchers. Treub is inclined to 
consider that the pitchers' func- 
tion is as stores or cisterns of 
water: but their use in the 
economy of the i>lnnt cannot be 
considered as denultely settled. 
F. D.l 



INDEX. 



ABSORPTION. 



A. 



Absorption by Dionsea, 239. 

by Drosera, 1, 14. 

by Drosophylluui, 274. 

by Piuguleula, 3<)8. 

by glandular hairs, 279. 

by glands of Utrlcularia, 338, 

341. 

by quadriflds of Utrlcularia, 

334 341. 

by Utrlcularia montana, 354. 

Acid, nature of, In digestive se- 
cretion of Drosera, 73. 

present In digestive fluid of 

various species of Drosera, Dl- 
onsea, Drosophyllum, and Pln- 
gulcula. 226, 244, 275. 309. 

Acids, various, action of, on 
Drosera, 154. 

of the acetic series replac- 
ing hydrochloric In digestion, 

^*^ 

, arsenlous and chromic, ac- 
tion on Drosera. 151. 

, diluted. Inducing negative 

osmose, 161. 

Adder's poison, action on Dros- 
era, 168. 

Aggregation of protoplasm In 
Drosera, Xi. 

In Drosera Induced by salts 

of ammonia, 38. 

caused by small doses of 

carbonate of ammonia, 119. 

of protoplasm in Drosera, a 

reflex action, 197. 

in various species of 

Drosera, 226. 

In Dlonnea, 236. 244. 

In Drosophyllum, 274, 

275. 

In Plngulcuia. 300, 315. 

in Utrlcularia, 333, 336, 

346. 347, 353. 
Albumen, digested by Drosera, 

77. 
, liquid, action on Droseru, 

67. 



ATROPINE. 

Alcohol, diluted, action of, on 

Drosera, 65, 176. 
Aldrovanda vesiculosa, 261. 
, absorption and digestion by, 

265. 

, varieties of, 266. 

Algse, aggregation In fronds of, 

55. 
Alkalies, arrest digestive process 

in Drosera, 78. 
Aluminium, salts of, action on 

Drosera, 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, 

115. 
, , 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, 12.5, 137. 

, , size of particles affect- 
ing Dxosera, 141. 

, nitrate, smallness of doses 

causing Inflection in Drosera, 

120, 137. 

, salts of, action on Dros- 
era, 11. 

. , their action affected b.v 

previous immersion in water 
and various solutions, 173. 

, , induce aggregation In 

Drosera, 38. 

, various salts of, causing In- 
flection In Drosera, 135. 

Antimony, tartrate, action on 
Drosera, 15. 

Areolar tissue, its digestion by 
Drosera, 85. 

Arsenlous add, action on Dros- 
era. 151. 

Atropine, action on Drosera, 166. 

SG9 



870 



INDEX. 



B. 



Barium, salts of, action on Dros- 

era, 149. 
Bases of salts, preponderant ac- 
tion of, on Drosoru, 1')'2. 

Basis, flbrous, of boue, its diges- 
tion by Drosera, DO. 

Batallu, on motor impulse In 
Drosera, 204. 

, on bending of tentacles of 

Drosera, 210. 

, on Dlouaea, 234. 

, on mecbauism of closure In 

Dionasa, 257. 

, on colour of Plnguicula 

leaves, 208. 

, on movement in Plnguicula, 

305. 

Belladonna, extract of, action on 
Drosera, 70. 

Bennett, Mr. A. W., on Drosera, 
1, 2, 7. 

, coats of pollen grains not 

digested by insects, 97. 

Binz, on action of quinine on 
white blood-corpuscles, 104. 

, on poisonous a<'tion of qui- 
nine on low organisms, l(t4. 

Bone, Its digestion by Drosera, 
88. 

Brunton, Lander, on digestion of 
gelatine. 02. 

.on the composition of casein, 

95. 

. on the digestion of urea, 

102. 

, of chlorophyll, 103. 

, of pepsin. 102. 

Btisgen. Dr. M.. on nutrition of 
Drosera. 16. 

Burnett, on Sarracenla, 307. 

Bybils, 279. 



C. 



Cabbaice, decoction of. action on 
Drosera, 69. 

Cadmium chloride, action on 
Drosera, LV). 

Cff>Hlum. chloride of, action on 
Drosera, 148. 

Calcium, salts of, action on Dros- 
era. 148. 

Camphor, action of Drosera. 170. 

Canby, Dr., on DIonsea, 244, 251, 
253. 

, on Drosera flliformls. 229. 

Caraway, oil of. action on Dros- 
era. 1Y2. 

Corhonlc acid, action on Drosera, 
180. 



DE BABT. 

Carbonic acid, delays aggregation 
In Drosera. 51. 

Cartilage, Its digestion by Dros- 
era, 80. 

Casein, Its digestion by Drosera, 
95. 

Cuspary, on Aldrovanda, 261. 202. 

Cellulose, not digested by Dros- 
era. 103. 

Chalk, precipitated, causing In- 
Uectlon of I>rosera, 28. 

Cheese, its digestion by Drosera, 
96. 

Chitine, not digested by Drosera, 
102. 

Chloroform, effects of, on Dros- 
era, 177. 

, , on Dloniea, 247. 

Chlorophyll, grains of. In living 
plants, digested by Droseru, 
103. 

, pure, not digested by Dros- 
era, 103. 

Choudrln, Its digestion by Dros- 
era, 03. 

Chromic acid, action on Drosera, 
151. 

Cloves, oil of, action on Drosera, 
173. 

Cobalt chloride, action on Dros- 
era, 152. 

Cobni poison, action on Drosera, 
168. 

Cohn, Prof., on Aldrovanda, 261. 

, on contractile tissues in 

plants, 295. 

, on movements of stamens of 

Composlta?. 208. 

, on Utrlcularia, 320. 

Colchicine, action on Drosera, 
160. 

Copper chloride, action on Dros- 
era, 151. 

Crystallln, its digestion by Dros- 
era. 99. 

Curare, action on Drosera, 188. 

Curtis, Dr., on Dionsea, 244. 



D. 

Darwin. C. papers on action of 

ammonia on roots, 55. 

, Krasmus, on Dloniea, 244. 

, Francis, on the effect of an 

Induced galvanic current on 

Drosera. Xi. 
. on aggregation In Drosera, 

33. 40. 

, on nutrition of Drosera. 15. 

. on the digestion of grains of 

chlorophyll. 103. 
De Bnry. effect of animal food 

on Utrlcularia, 367. 



INDEX. 



371 



DB CANDOIXB. 

De Candolle, on Dlonsea, 233, 234, 

236. 
Delpino, on Aldrovanrta, 2C1. 

, on Utrlculnrla, 320. 

, on Dlschiilia, 3t>8. 

Dentine, its digestion by Dros- 

era, 8. 
Digestion of various substances 

by Dlonsta, 244. 

bj' Drosera, 71. 

by Drosophyllum, 270. 

by Pinguicula, 309. 

, origin of power of, 292. 

Digitaliue, action on Drosera, 

105. 
Dlonae, early literature of, 232. 
Dionsea, muscipula, small size of 

roots, 232. 

, structure of leaves, 2SS. 

, sensitiveness of filaments, 

235. 

, absorption by, 239. 

, secretion by, 239. 

, digestion by, 244. 

, effects on, of chloroform, 

247. 
, manner of capturing Insects, 

24a 
, transmission of motor im- 
pulse, 254. 

, re-expansion of lobes, 259. 

Direction of Inflected tentacles of 

Drosera, 198. 
Dlschidia's Rafflesiana, 368. 
Dohrn. Dr., on rhizocephalous 

crustaceans, 289. 
Douders, Prof., small amount of 

atropine affecting the iris of 

the dog, 140. 
Dragonfly caught by Drosera, 2. 
Drosera, absorption by, 1, 14. 

angllca, 226. 

binata, vel dichotoma, 229. 

capensis, 227. 

dichotoma, 5. 

flllformls, 228. 

heterophylla, 231. 

intermelia, 227. 

, sensitiveness of, 22. 

Drosera rotundifolia, structure 

of leaves. 3. 

, artificial feeding of, 15. 

, effects on, of nitrogenous 

fluids. 64. 

, effects of heat on. 56. 

, its power of digestion, 71. 

, backs of leaves not sensi- 
tive. 188. 

. transmission of motor im- 
pulse, 191. 

, general summary, 213. 

spathulata, 228. 

DroseracesD, concluding remarks 

on, 288. . 

25 



GALVANISM. 

Droseracen>, their sensitiveness 
compared with that of animals, 

Drosophyllum, structure of leaves, 
270. 

, secretion by, 271. 

, absorption by, 274. 

, digestion by, 270. 

Duval-Jouve, on Aidrovanda, 209, 



Ellis, on Dloneea, 244. 

Enamel, its digestion by Drosera, 
88. 

Erica, tetralix, glandular hairs 
of, 285. 

Ether, effects of, on Drosera, 178. 

, , on Dlonaja, 247. 

Euphorbia, process of aggrega- 
tion In roots of, 54. 

Ewald, on peptogenes, 106. 

Exosmose from backs of leaves 
of Drosera, 189. 



Falvre, on Nepenthes and Sarra- 

cenla, 367. 
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, 182. 
Ferment, nature of. In secretion 

of Dronera, 78. 81. 
Fibrin, its digestion by Drosera, 

84. 
Fibro-cartllage, Its digestion by 

Drosera, 87. 
Fibi-o-eiastic tissue, not digested 

by Drosera, 100. 
Fibrous basis of bone, its diges- 
tion by Drosera, 90. 
Fluids, nitrogenous, effects of, on 

Drosera, 64. 
Foiirnler, on acids causing move- 
ments in stamens of Berberis, 

160. 
Frankland, Prof., on nature of 

acid In secretion of Drosera, 73. 
Fraustadt, A., on Dlonsea, 233, 

234. 
, on roots of Diontea, 280. 

0. 

Galvanism, current of. causing 
inflection of Drosera, 32. 



372 



INDEX. 



OALVANI8M. 

GalTaDlsiu, effects of, on Dlonsea, 
258. 

Gardiner, W., on Drosera dlchot- 
oiua, 5. 

, on the KhnlKlold, 33. 

, on UKKregatlon, 35. 

, on process of secretion in 

Drosera, 72. 

. on Intercellular protoplasm, 

201. 

, on contractility of plant- 
cells. 210. 

. on gland-cells of Dlonsea, 

239. 

Gardner, Mr., on Utrlcularla ne- 
Uunblfolla, 358. 

Gelatine. Impure, action on Dros- 
era, 07. 

, pure. Its digestion by Dros- 
era. irj. 

Genllsea afrleana, 305. 

Ollfornils, 3(55. 

ornata, structure of, 301. 

, manner of capturing prey, 

304. 

Glandular balrs, absorption by, 
279. 

, summary on, 286. 

Glauer, on aggregation, 40. 

Globulin, its digestion by Dros- 
era, 99. 

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 a solvent in seeds of the 
vet<-h, 293. 

Grass, decoction of, action on 
Drosera, 7(. 

Gray, Asa, on the Droseraceaj, 2. 

Gro'iilaiid, on Drosera, 1, 4. 

Gum, a<'tlon of, on Drosera, 05. 

Gun-cotton, not digested by Dros- 
era, loa 



nrematln. Its digestion by Dros- 
era, {>. 

Iluiilonhain, on peptogenes, 100. 

Hairs, glandular, absorption by, 
279. 

, , summary on, 280. 

Heat, Inducing aggregation In 
Drosera, 40. 

, effect of, on Drosera, .''(O. 

, , on Dloiuea, 2.T8. ). 

Heckel, on state of stamens of 
Berl>eris after excitement, 38. 



Hofmeister, on pressure arresting 
movements of protoplasm, 52. 

Holland, Mr., on Utrlcularla, 
320. 

Hooker, Dr., on carnivorous 
plants, 2. 

, on power of digestion by Ne- 
penthes, 81. 

, history of observations on 

DlonH>a, 232, 244. 

Hovelacgue, on Utrlcularla, 349. 

Hydrocyanic acid, effects of, on 
Dloniea, 247. 

Uyoscyamus, action on Drosera, 
70, 107. 



Iron chloride, action on Drosera. 

151. 
Isinglass, solution of, action on 

Drosera, 07. 



J. 

Johnson, Dr., on movement of 
flower-stems of Pingulcuia, 308. 



K. 

Kellermann and Von Ranmer, on 
nutrition of Drosera, 15. 

Klein, Dr., on microscopic char- 
acter of half dlgestwl l)one, 89. 

, on state of half digested 

flbro-cartllage, 87. 

. on size of micrococci, 141. 

Knight, Mr., on feeding Dlonica, 
244. 

Kossman, Dr., on rhizocephalous 
crustaceans, 28J. 

Kunkcl, on electric phenomena 
in DIouwa. 258. 

Kurtz, on Dioutea, 232, 234. 



L. 

Lankester, E. Ray, on glands of 

water plants, 2ra). 
Lead chloride, action on Drosera, 

150. 
Leaves of I>ro8era, backs of, not 

sensitive, 1K8. 
Legumin, its digestion by Dros- 
era, 941. 
Lcinna, aggregation in leaves of, 

.55. 
Lime, carb>nate of, precipitated, 

causing inflection of Drosera, 

28. . 



INDEX. 



373 



LIME. 

Lime, phosphate of. Its action on 
Drosera, yl. 

Liniiieiis, on DIonsea, 244. 

Litliium, salts of, action on Dros- 
era, 148. 



Magnesinm, salts of, action on 

Drosera, 149. 
Manganese chloride, action on 

Drosera, 151. 
Marshall, Mr. W., on Pinguicula, 

299. 
Means of movement in Dionaea, 

^54. 

in Drosera, 20G. 

Meat, Infusion of, causing aggre- 
gation in Drosera, 44. 

, , action on Drosera, 67. 

, its digestion by Drosera, 82. 

Mercury perchlorlde, action on 
Drosera. 1.50. 

Milk, inducing aggregation in 
Drosera, 45. 

, action on Drosera, 66. 

, its digestion by Drosera, 94. 

Mirabilis lougitlora, glandular 
hairs of, 285. 

Moggrldge, Traherne, on acids in- 
juring seeds, 105. 

Moore, Dr., on Pinguicula, 316. 

Mori, on Aldrovanda. 264. 

Morphia acetate, action on Dros- 
era, 167. 

Morren, E., on Drosera binata, 
2*29. 

Motor impulse in Drosera, 191, 
210. 

In DIoniea. 2.54. 

Movement, origin of power of, 

294. 
Movements of leaves of I'inguic- 
ula, SOO. 

of tentacles of Drosera, 

means of, 206. 

of Dionaea, means of, 254. 

Mncin, not digested by Drosera, 

101. 
Mucus, action on. Drosera, 67. 
MOller, Fritz, on rhlzocephalous 

crustaceans. 289. 
Munlc. on Dionwa, 2.^5. 248. 
, on electric phenomena In 

Dionaea, 258. 



Nepenthes, Its power of diges- 
tion. 81. 

Nickel chloride, action on Dros- 
era, 151. 



PINOUICCLA. 

Nicotlana tabacum, glandular 

hairs of, 286. 
Nicotine, action on Drosera, 165. 
Nitric ether, action on Drosera, 

179. 
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, 262. 

Nourishment, various means of, 

by plants, 366. 
Nuttall, Dr., on re-expansion of 

Dionaea, 259. 



0. 



Odour of pepsin, emitted from 

leaves of Drosera, 74. 
Oels, W., on comp. anatomy of 

Droseraceae, 2. 
Oil, olive, action of, on Drosera, 

66, 104. 
Oliver, F., on motor impulse, 204. 
, Prof., on Utrlcularia, 350, 

357-360. 
Oudemansv on Dionsea, 234. 



Papaw, Juice of, hastening putre- 
faction, 333. 

Particles, minute size of. causing 
Inflection in Drosera, 24. 28. 

Peas, decoction of, action on 
Drosera, >9. 

Pelargonium zonale, glandular 
hairs of. 284. 

Penzljr, Otto, on roots of Droso- 
pbyllum, 289. 

Pepsin, odour of, emitted from 
Drosera leaves, 74. 

, not digested by Drosera, 

101. 

, its secretion by animals ex- 
cited only after absorption, 
107. 

Peptogenes, 106. 

Pfeflfer, on sensitiveness of Dros- 
era to contact. 22. 31. 

, on nucleus In Drosera, 33. 

, on airgregatlon, 35. 

, on Dionapa, 258. 

, on roots of carnivorous 

plants, 289. 

. >n Plngulciiln. 31.5. 

Pinguicula graiidlflora, 316. 

lusitnnlca. 317. 

vulgaris, structure of leave* 

and roots, 298. 



374 



INDEX. 



PIMOUICULA. 

PInRuIcula. number of Insects 

caiiKht l)y, 2!t. 

, power of movement, 300. 

, secretion and absorption by, 

308. 

, digestion by, 309. 

, leaves of, used to curdle 

milk, 315. 
, effects of secretion on living 

seeds, 316. 
Platinum chloride, action on 

Drosera, 152. 
Poison of cobra and adder, their 

action on Drosera, KW. 
Pollen, its digestion by Drosera, 

96. 
Polypompholyx, structure of, 

360. 
Potassium, salts of. Inducing ag- 
gregation In Drosera, 43. 

, , action on Drosera, 146. 

phosphate, not decomposed 

by Drosera, 147, 153. 
Price, Mr. John, on Utricularia, 

347. 
Primula sinensis, glandular hairs 

of, 282. 
, number of glandular hairs 

of, 288. 
Protoplasm, aggregated, re-dis- 
solution of, 46. 
, aggregation of. In Drosera, 

33, 35, 36. 

, , in Drosera, a reflex ac- 

, , in Drosera, caused by 

small doses of carbonate of am- 
monia, 119. 
, , in Drosera, a reflex 

action, 197. 
, , In various species of 

Drosera, 226. 

, in Dlona?a, 2.36, 243. 

, , In Drosophyllum. 275. 

, , in I'Ingulcula, 300, 31.'). 

, , in L'trlcularia, 333, 

336, 347, 353. 



Qninlne. salts, of, action on Dros- 
era, UKi 



B. 

Rnln-water, amount of ammonia 
In. 141. 

Kalfs, Mr., on I'lngulculn. 'Ml. 

Ransom. I)r., action of poisons 
on the yolk of eggs. 18.'{. 

Roes and Will, on digestive ac- 
tion In Drosera. 73. 81. 

Re-ex|insl(>n of headless ten- 
tacles of Drosera, 187. 



8BCBBTION. 

Re-expanslon of tentacles of 
Drosera. 211. 

of Dlono'a, 259. 

Roots of Drosera, 17. 

, process of aggregation 

in, 54. 

, absorb carbonate of am- 
monia, 115. 

of DIonnea, 2.'12. 

of Drosophyllum, 270. 

of Pingulcula, 290. 

Rorldula, 278. 

Rubidium chloride, action on 
Drosera, 148. 



8. 



Sachs, Prof., effects of heat on 
protoplasm, 56, 59. 

, on the dissolution of proteid 

compounds in the tissues of 
plants, 25(3. 

Saliva, action on Drosera, 67. 

Salts and adds, various, effects 
of, on subsequent action of 
ammonia, 175. 

Sanderson, Hurdon, on coagula- 
tion 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, 1.52. 

, on electric currents In Di- 

onspa, 258. 

Sarraconla, 366. .*57. 

Saxlfraga umbrosa, glandular 
hairs of. 280. 

Schenk, on I'trlcnlnrla, 349. 

Schlff, on hydrochloric add dis- 
solving coagulated albumen, 71. 

, on maimer of digestion of 

albumen, 77. 

, on changes in meat during 

digestion. 8;{. 

, on the coagulation of nitlk.iM. 

Schlff, on the digestion of casein, 
96. 

, on the digestion of mucus, 

101. 

, on peptogenes, 106. 

Schimper. on aggregation. 35. 

, on ITtrlcularla, :2, .^33. 

, on Sarracenla puri)nrea, 367. 

Schloesing, on absorption of ni- 
trogen by NIcollana. 286. 

Scott, Mr., on Drosera, 1. 

Secretion of Drosera, general ac- 
count of, 11. 



INDEX. 



375 



SECRETION. 

Secretion of Drosera, Its antisep- 
tic power, 12. 

, becomes acid from ex- 
citement, 72. 

, nature of Its ferment, 

78, 81. 

by Dlonsea, 239. 

by Drosophvllum, 272. 

by Pinguicula, 309. 

Seeds, living, acted on by Dros- 
era, 104. 
, , acted on by Pinguicula, 

312, 316. 
Sensitiveness, localisation of. In 

Drosera, 187. 

of Dlonsea, 234. 

of Pinguicula, 300. 

Sliver nitrate, action on Drosera, 
148. 

Sodium, salts of, action on Dros- 
era, 143. 

, , inducing aggregation in 

Drosera, 44. 

Sondera heterophylla, 231. 

Sorby, Mr., on colouring matter 
of Drosera, 4. 

Spectroscope, its power com- 
pared with that of Drosera, 139. 

Stnrch, action of, on Drosera, 65, 
104. 

Stein, on Aldrovanda, 261. 

Strontium, salts of, action on 
Drosera, 149. 

Strychnine, salts of, action on 
Drosera, 162. 

Suprar, solution of, action of, on 
Drosera, 65. 

, . Inducing aggregation In 

Drosera, 4r>. 

Sulphuric ether, action on Dros- 
era, 178. 

Sulphuric ether, action on Dl- 
onsea, 247. 

Syntonin, Its action on Drosera, 
85. 



Talt, Mr., on Drosophyllum, 270. 

Taylor, Alfred, on the detection 
of minute doses of poisons, 139. 

Tea, infusion of, action on Dros- 
era, m. 

Tentacles of Drosera, move when 
glands cut of.". 31, 187. 

, Inflection, direction of, 198. 

, means of uiovenient, 206. 

. re-expnnslon of, 211. 

Thelne, action on Drosera, 166. 

Tin chloride, action on Drosera, 
l.'il. 

Tissue, areolar, Its digestion by 
Droseru, S5. 



VOGEL. 

Tissue, flbro-elastlc, not digested 

by Drosera, 100. 
Tissues through which impulse is 

transmitted In Drosera, 200. 

In Dlonsea, 254. 

Touches repeated, causing Inflec- 
tion In Drosera, 29. 
Transmission of motor Impulse In 

Drosera, 191. 

in Dlonsea, 234. 

Traube, Dr., on artificial cells, 

176. 
Treat, Mrs., on Drosera fill- 

formls, 228. 

, on Dlonsea, 252. 

, on valve in Utricularla, 330, 

331, 348. 
Tr^cul, on Drosera, 1, 4. 
Treub, on Dischidia, 368. 
Tubers of Utricularla montana, 

353. 
Turpentine, action on Drosera, 

173. 



TJ. 

Urea, not digested by Drosera, 
102. 

Urine, action on Drosera, 66. 

Utricularla clandestlna, 348. 

minor, 347. 

montana, structure of blad- 
ders, 349. 

Utricularla montana, animals 
caught by, 353. 

, absorption by, 274. 

, tubers of, serving as reser- 
voirs, 355. 

Utricularla neglecta, structure of 
bladders, 322. 

, animals caught by, 328. 

, absorption by, 334. 

, summary on absorption, 341. 

, development of bladders, 

343. 

Utricularla, various species of, 
358. 

Utricularla vulgaris, 347. 



Veratrlne, action on Drosera, 166. 

Vessels In leaves of Drosera, 201. 

Vessels of Dlonsea, 254. 

Vines, on digestive fluid of Ne- 
penthes, 81. 

. on the ferment of the Vetch, 

293. 

VoKol. on effects of camphor on 
plants, 170. 



376 



INDEX. 



VON aORUP. 

Von Gorup and Will, on digestive 
notion In Drosera, 73, 81. 

Vrles, U. de, on aggregation, 35, 
40. 



W. 

Wanning, Dr., on Drosera, 1, 5. 

, on roots of Utrleularla, 321. 

, on trlc'hoiues, 291. 

, on Genlisea, 3G1. 

, on pareuchymatons cells In 

tentacles of Drosera, 205. 

Water, drops of, not causing In- 
flection In Drosera, 31. 

, Its power In causing aggre- 
gation In Drosera, 45. 



Water, Its power In causing in- 
flection In Drosera, 113. 

and various solutions, effects 

of, on subsequent action of am- 
monia, 173. 

Wiesner, on Sarrncenla, 307. 

Wilkinson, Uev. H. M.,ou Utrleu- 
larla, 323. 



Zlegler, his statements with re- 
spect to Drosera, 21, 204. 

, experliuonts by cutting ves- 
sels of Drosera, 202. 

Zinc chloride, action on Drosera, 
150. 



THE END. 




UJ. 



o 
o 



QK Darwin, Charles 

917 Insectivorous plants 

D24 

1899 
c.l 



2nd ed, 



ESCI 






>to- 



itv^P