CHAPTER IX.
THE EFFECTS OF CERTAIN ALKALOID POISONS, OTHER SUBSTANCES AND VAPOURS.
Strychnine, salts of—Quinine, sulphate of, does not soon arrest the
movement of the protoplasm—Other salts of
quinine—Digitaline—Nicotine—Atropine—Veratrine— Colchicine—
Theine—Curare—Morphia—Hyoscyamus—Poison of the cobra, apparently
accelerates the movements of the protoplasm—Camphor, a powerful
stimulant, its vapour narcotic—Certain essential oils excite
movement—Glycerine—Water and certain solutions retard or prevent the
subsequent action of phosphate of ammonia—Alcohol innocuous, its vapour
narcotic and poisonous—Chloroform, sulphuric and nitric ether, their
stimulant, poisonous, and narcotic power—Carbonic acid narcotic, not
quickly poisonous—Concluding remarks.
As in the last chapter, I will first give my experiments, and then a
brief summary of the results with some concluding remarks.
[Acetate of Strychnine.—Half-minims of a solution of one part to 437 of
water were placed on the discs of six leaves; so that each received
1/960 of a grain, or .0675 mg. In 2 hrs. 30 m. the outer tentacles on
some of them were inflected, but in an irregular manner, sometimes only
on one side of the leaf. The next morning, after 22 hrs. 30 m. the
inflection had not increased. The glands on the central disc were
blackened, and had ceased secreting. After an additional 24 hrs. all
the central glands seemed dead, but the inflected tentacles had
re-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 1/20 of a minim) of the same solution
applied to the glands of the outer tentacles occasionally caused them
to bend. The poison does not seem to act quickly, for having applied to
several glands similar drops of a rather stronger solution, of one part
to 292 of water, this did not prevent the tentacles bending, when their
glands [page 200] were excited, after an interval of a quarter to three
quarters of an hour, by being rubbed or given bits of meat. Similar
drops of a solution of one part to 218 of water (2 grs. to 1 oz.)
quickly blackened the glands; some few tentacles thus treated moved,
whilst others did not. The latter, however, on being subsequently
moistened with saliva or given bits of meat, became incurved, though
with extreme slowness; and this shows that they had been injured.
Stronger solutions (but the strength was not ascertained) sometimes
arrested all power of movement very quickly; thus bits of meat were
placed on the glands of several exterior tentacles, and as soon as they
began to move, minute drops of the strong solution were added. They
continued for a short time to go on bending, and then suddenly stood
still; other tentacles on the same leaves, with meat on their glands,
but not wetted with the strychnine, continued to bend and soon reached
the centre of the leaf.
Citrate of Strychnine.—Half-minims of a solution of one part to 437 of
water were placed on the discs of six leaves; after 24 hrs. the outer
tentacles showed only a trace of inflection. Bits of meat were then
placed on three of these leaves, but in 24 hrs. only slight and
irregular inflection occurred, proving that the leaves had been greatly
injured. Two of the leaves to which meat had not been given had their
discal glands dry and much injured. Minute drops of a strong solution
of one part to 109 of water (4 grs. to 1 oz.) were added to the
secretion round several glands, but did not produce nearly so plain an
effect as the drops of a much weaker solution of the acetate. Particles
of the dry citrate were placed on six glands; two of these moved some
way towards the centre, and then stood still, being no doubt killed;
three others curved much farther inwards, and were then fixed; one
alone reached the centre. Five leaves were immersed, each in thirty
minims of a solution of one part to 437 of water; so that each received
1/16 of a grain; after about 1 hr. some of the outer tentacles became
inflected, and the glands were oddly mottled with black and white.
These glands, in from 4 hrs. to 5 hrs., became whitish and opaque, and
the protoplasm in the cells of the tentacles was well aggregated. By
this time two of the leaves were greatly inflected, but the three
others not much more inflected than they were before. Nevertheless two
fresh leaves, after an immersion respectively for 2 hrs. and 4 hrs. in
the solution, were not killed; for on being left for 1 hr. 30 m. in a
solution of one part of carbonate of ammonia to 218 of water, their
tentacles became more inflected, and there was much aggregation. The
glands [page 201] of two other leaves, after an immersion for 2 hrs. in
a stronger solution, of one part of the citrate to 218 of water, became
of an opaque, pale pink colour, which before long disappeared, leaving
them white. One of these two leaves had its blade and tentacles greatly
inflected; the other hardly at all; but the protoplasm in the cells of
both was aggregated down to the bases of the tentacles, with the
spherical masses in the cells close beneath the glands blackened. After
24 hrs. one of these leaves was colourless, and evidently dead.
Sulphate of Quinine.—Some of this salt was added to water, which is
said to dissolve 1/1000 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 many tentacles
inflected, but this very moderate degree of inflection never increased.
One of the leaves was taken out of the solution after 4 hrs., and
placed in water; by the next morning some few of the inflected
tentacles had re-expanded, showing that they were not dead; but the
glands were still much discoloured. Another leaf not included in the
above lot, after an immersion of 3 hrs. 15 m., was carefully examined;
the protoplasm in the cells of the outer tentacles, and of the short
green ones on the disc, had become strongly aggregated down to their
bases; and I distinctly saw that the little masses changed their
positions and shapes rather rapidly; some coalescing and again
separating. I was surprised at this fact, because quinine is said to
arrest all movement in the white corpuscles of the blood; but as,
according to Binz,* this is due to their being no longer supplied with
oxygen by the red corpuscles, any such arrestment of movement could not
be expected in Drosera. That the glands had absorbed some of the salt
was evident from their change of colour; but I at first thought that
the solution might not have travelled down the cells of the tentacles,
where the protoplasm was seen in active movement. This view, however, I
have no doubt, is erroneous, for a leaf which had been immersed for 3
hrs. in the quinine solution was then placed in a little solution of
one part of carbonate of ammonia to 218 of water; and in 30 m. the
glands and the upper cells of the tentacles became intensely black,
with the protoplasm presenting a very unusual appearance; for it
* ‘Quarterly Journal of Microscopical Science,’ April 1874, p. 185.
[page 202]
had become aggregated into reticulated dingy-coloured masses, having
rounded and angular interspaces. As I have never seen this effect
produced by the carbonate of ammonia alone, it must be attributed to
the previous action of the quinine. These reticulated masses were
watched for some time, but did not change their forms; so that the
protoplasm no doubt had been killed by the combined action of the two
salts, though exposed to them for only a short time.
Another leaf, after an immersion for 24 hrs. in the quinine solution,
became somewhat flaccid, and the protoplasm in all the cells was
aggregated. Many of the aggregated masses were discoloured, and
presented a granular appearance; they were spherical, or elongated, or
still more commonly consisted of little curved chains of small
globules. None of these masses exhibited the least movement, and no
doubt were all dead.
Half-minims of the solution were placed on the discs of six leaves;
after 23 hrs. one had all its tentacles, two had a few, and the others
none inflected; so that the discal glands, when irritated by this salt,
do not transmit any strong motor impulse to the outer tentacles. After
48 hrs. the glands on the discs of all six leaves were evidently much
injured or quite killed. It is clear that this salt is highly
poisonous.*
Acetate of Quinine.—Four leaves were immersed, each in thirty minims of
a solution of one part to 437 of water. The solution was tested with
litmus paper, and was not acid. After only 10 m. all four leaves were
greatly, and after 6 hrs. immensely, inflected. They were then left in
water for 60 hrs., but never re-expanded; the glands were white, and
the leaves evidently dead. This salt is far more efficient than the
sulphate in causing inflection, and, like that salt, is highly
poisonous.
Nitrate of Quinine.—Four leaves were immersed, each in thirty minims of
a solution of one part to 437 of water. After 6 hrs. there was hardly a
trace of inflection; after 22 hrs. three of the leaves were moderately,
and the fourth slightly inflected; so that this salt induces, though
rather slowly, well-marked inflection. These leaves, on being left in
water for 48 hrs., almost
*Binz found several years ago (as stated in ‘The Journal of Anatomy and
Phys.’ November 1872, p. 195) that quinia is an energetic poison to low
vegetable and animal organisms. Even one part added to 4000 parts of
blood arrests the movements of the white corpuscles, which become
“rounded and granular.” In the tentacles of Drosera the aggregated
masses of protoplasm, which appeared killed by the quinine, likewise
presented a granular appearance. A similar appearance is caused by very
hot water. [page 203]
completely re-expanded, but the glands were much discoloured. Hence
this salt is not poisonous in any high degree. The different action of
the three foregoing salts of quinine is singular.
Digitaline.—Half-minims of a solution of one part to 437 of water were
placed on the discs of five leaves. In 3 hrs. 45 m. Some of them had
their tentacles, and one had its blade, moderately inflected. After 8
hrs. three of them were well inflected; the fourth had only a few
tentacles inflected, and the fifth (an old leaf) was not at all
affected. They remained in nearly the same state for two days, but the
glands on their discs became pale. On the third day the leaves appeared
much injured. Nevertheless, when bits of meat were placed on two of
them, the outer tentacles became inflected. A minute drop (about 1/20
of a minim) of the solution was applied to three glands, and after 6
hrs. all three tentacles were inflected, but next day had nearly
re-expanded; so that this very small dose of 1/28800 of a grain (.00225
mg.) acts on a tentacle, but is not poisonous. It appears from these
several facts that digitaline causes inflection, and poisons the glands
which absorb a moderately large amount.
Nicotine.—The secretion round several glands was touched with a minute
drop of the pure fluid, and the glands were instantly blackened; the
tentacles becoming inflected in a few minutes. Two leaves were immersed
in a weak solution of two drops to 1 oz., or 437 grains, of water. When
examined after 3 hrs. 20 m., only twenty-one tentacles on one leaf were
closely inflected, and six on the other slightly so; but all the glands
were blackened, or very dark-coloured, with the protoplasm in all the
cells of all the tentacles much aggregated and dark-coloured. The
leaves were not quite killed, for on being placed in a little solution
of carbonate of ammonia (2 grs. to 1 oz.) a few more tentacles became
inflected, the remainder not being acted on during the next 24 hrs.
Half-minims of a stronger solution (two drops to 1/2 oz. of water) were
placed on the discs of six leaves, and in 30 m. all those tentacles
became inflected; the glands of which had actually touched the
solution, as shown by their blackness; but hardly any motor influence
was transmitted to the outer tentacles. After 22 hrs. most of the
glands on the discs appeared dead; but this could not have been the
case, as when bits of meat were placed on three of them, some few of
the outer tentacles were inflected in 24 hrs. Hence nicotine has a
great tendency to blacken the glands and to induce aggregation [page
204] 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 was not all
dissolved; another grain was added to 437 grains of a mixture of one
part of alcohol to seven parts of water; and a third solution was made
by adding one part of valerianate of atropine to 437 of water.
Half-minims of these three solutions were placed, in each case, on the
discs of six leaves; but no effect whatever was produced, excepting
that the glands on the discs to which the valerianate was given were
slightly discoloured. The six leaves on which drops of the solution of
atropine in diluted alcohol had been left for 21 hrs. were given bits
of meat, and all became in 24 hrs. fairly well inflected; so that
atropine does not excite movement, and is not poisonous. I also tried
in the same manner the alkaloid sold as daturine, which is believed not
to differ from atropine, and it produced no effect. Three of the leaves
on which drops of this latter solution had been left for 24 hrs. were
likewise given bits of meat, and they had in the course of 24 hrs. a
good many of their submarginal tentacles inflected.
Veratrine, Colchicine, Theine.—Solutions were made of these three
alkaloids by adding one part to 437 of water. Half-minims were placed,
in each case; on the discs of at least six leaves, but no inflection
was caused, except perhaps a very slight amount by the theine.
Half-minims of a strong infusion of tea likewise produced, as formerly
stated, no effect. I also tried similar drops of an infusion of one
part of the extract of colchicum, sold by druggists, to 218 of water;
and the leaves were observed for 48 hrs., without any effect being
produced. The seven leaves on which drops of veratrine had been left
for 26 hrs. were given bits of meat, and after 21 hrs. were well
inflected. These three alkaloids are therefore quite innocuous.
Curare.—One part of this famous poison was added to 218 of water, and
three leaves were immersed in ninety minims of the filtered solution.
In 3 hrs. 30 m. some of the tentacles were a little inflected; as was
the blade of one; after 4 hrs. After 7 hrs. the glands were wonderfully
blackened, showing that matter of some kind had been absorbed. In 9
hrs. two of the leaves had most of their tentacles sub-inflected, but
the inflection did not increase in the course of 24 hrs. One of these
leaves, after being immersed for 9 hrs. in the solution, was placed in
water, and by next morning had largely re-expanded; [page 205] the
other two, after their immersion for 24 hrs., were likewise placed in
water, and in 24 hrs. were considerably re-expanded, though their
glands were as black as ever. Half-minims were placed on the discs of
six leaves, and no inflection ensued; but after three days the glands
on the discs appeared rather dry, yet to my surprise were not
blackened. On another occasion drops were placed on the discs of six
leaves, and a considerable amount of inflection was soon caused; but as
I had not filtered the solution, floating particles may have acted on
the glands. After 24 hrs. bits of meat were placed on the discs of
three of these leaves, and next day they became strongly inflected. As
I at first thought that the poison might not have been dissolved in
pure water, one grain was added to 437 grains of a mixture of one part
of alcohol to seven of water, and half-minims were placed on the discs
of six leaves. These were not at all affected, and when after a day
bits of meat were given them, they were slightly inflected in 5 hrs.,
and closely after 24 hrs. It follows from these several facts that a
solution of curare induces a very moderate degree of inflection, and
this may perhaps be due to the presence of a minute quantity of
albumen. It certainly is not poisonous. The protoplasm in one of the
leaves, which had been immersed for 24 hrs., and which had become
slightly 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 number of experiments with this
substance, but with no certain result. A considerable number of leaves
were immersed from between 2 hrs. and 6 hrs. in a solution of one part
to 218 of water, and did not become inflected. Nor were they poisoned;
for when they were washed and placed in weak solutions of phosphate and
carbonate of ammonia, they soon became strongly inflected, with the
protoplasm in the cells well aggregated. If, however, whilst the leaves
were immersed in the morphia, 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 6 m:, bits of meat, a
little saliva, or particles of glass, were placed on them, the movement
of the tentacles was greatly retarded. But on other occasions no such
retardation occurred. Drops of water similarly applied never have any
retarding power. Minute drops of a solution of sugar of the same
strength (one part to 218 of water) sometimes retarded the subsequent
action of meat and of particles of glass, and [page 206] sometimes did
not do so. At one time I felt convinced that morphia acted as a
narcotic on Drosera, but after having found in what a singular manner
immersion in certain non-poisonous salts and acids prevents the
subsequent action of phosphate of ammonia, whereas other solutions have
no such power, my first conviction seems very doubtful.
Extract of Hyoscyamus.—Several leaves were placed, each in thirty
minims of an infusion of 3 grs. of the extract sold by druggists to 1
oz. of water. One of them, after being immersed for 5 hrs. 15 m., was
not inflected, and was then put into a solution (1 gr. to 1 oz.) of
carbonate of ammonia; after 2 hrs. 40 m. it was found considerably
inflected, and the glands much blackened. Four of the leaves, after
being immersed for 2 hrs. 14 m., were placed in 120 minims of a
solution (1 gr. to 20 oz.) of phosphate of ammonia; they had already
become slightly inflected from the hyoscyamus, probably owing to the
presence of some albuminous matter, as formerly explained, but the
inflection immediately increased, and after 1 hr. was strongly
pronounced; so that hyoscyamus does not act as a narcotic or poison.
Poison from the Fang of a Living Adder.—Minute drops were placed on the
glands of many tentacles; these were quickly inflected, just as if
saliva had been given them, Next morning, after 17 hrs. 30 m., all were
beginning to re-expand, and they appeared uninjured.
Poison from the Cobra.—Dr. Fayrer, well known from his investigations
on the poison of this deadly snake, was so kind as to give me some in a
dried state. It is an albuminous substance, and is believed to replace
the ptyaline of saliva.* A minute drop (about 1/20 of a minim) of a
solution of one part to 437 of water was applied to the secretion round
four glands; so that each received only about 1/38400 of a grain (.0016
mg.). The operation was repeated on four other glands; and in 15 m.
several of the eight tentacles became well inflected, and all of them
in 2 hrs. Next morning, after 24 hrs., they were still inflected, and
the glands of a very pale pink colour. After an additional 24 hrs. they
were nearly re-expanded, and completely so on the succeeding day; but
most of the glands remained almost white.
Half-minims of the same solution were placed on the discs of three
leaves, so that each received 1/960 of a grain (.0675 mg.); in
*Dr. Fayrer, ‘The Thanatophidia of India,’ 1872, p. 150. [page 207]
4 hrs. 15 m. the outer tentacles were much inflected; and after 6 hrs.
30 m. those on two of the leaves were closely inflected and the blade
of one; the third leaf was only moderately affected. The leaves
remained in the same state during the next day, but after 48 hrs.
re-expanded.
Three leaves were now immersed, each in thirty minims of the solution,
so that each received 1/16 of a grain, or 4.048 mg. In 6 m. there was
some inflection, which steadily increased, so that after 2 hrs. 30 m.
all three leaves were closely inflected; the glands were at first
somewhat darkened, then rendered pale; and the protoplasm within the
cells of the tentacles was partially aggregated. The little masses of
protoplasm were examined after 3 hrs., and again after 7 hrs., and on
no other occasion have I seen them undergoing such rapid changes of
form. After 8 hrs. 30 m. the glands had become quite white; they had
not secreted any great quantity of mucus. The leaves were now placed in
water, and after 40 hrs. re-expanded, showing that they were not much
or at all injured. During their immersion in water the protoplasm
within the cells of the tentacles was occasionally examined, and always
found in strong movement.
Two leaves were next immersed, each in thirty minims of a much stronger
solution, of one part to 109 of water; so that each received 1/4 of a
grain, or 16.2 mg; After 1 hr. 45 m. the sub-marginal tentacles were
strongly inflected, with the glands somewhat pale; after 3 hrs. 30 m.
both leaves had all their tentacles closely inflected and the glands
white. Hence the weaker solution, as in so many other cases, induced
more rapid inflection than the stronger one; but the glands were sooner
rendered white by the latter. After an immersion of 24 hrs. some of the
tentacles were examined, and the protoplasm, still of a fine purple
colour, was found aggregated into chains of small globular masses.
These changed their shapes with remarkable quickness. After an
immersion of 48 hrs. they were again examined, and their movements were
so plain that they could easily be seen under a weak power. The leaves
were now placed in water, and after 24 hrs. (i.e. 72 hrs. from their
first immersion) the little masses of protoplasm, which had become of a
dingy purple, were still in strong movement, changing their shapes,
coalescing, and again separating.
In 8 hrs. after these two leaves had been placed in water (i.e. in 56
hrs. after their immersion in the solution) they began to re-expand,
and by the next morning were more expanded. After an additional day
(i.e. on the fourth day after their immersion in the solution) they
were largely, but not quite fully [page 208] expanded. The tentacles
were now examined, and the aggregated masses were almost wholly
redissolved; the cells being filled with homogeneous purple fluid, with
the exception here and there of a single globular mass. We thus see how
completely the protoplasm had escaped all injury from the poison. As
the glands were soon rendered quite white, it occurred to me that their
texture might have been modified in such a manner as to prevent the
poison passing into the cells beneath, and consequently that the
protoplasm within these cells had not been at all affected. Accordingly
I placed another leaf, which had been immersed for 48 hrs. in the
poison and afterwards for 24 hrs. in water, in a little solution of one
part of carbonate of ammonia to 218 of water; in 30 m. the protoplasm
in the cells beneath the glands became darker, and in the course of 24
hrs. the tentacles were filled down to their bases with dark-coloured
spherical masses. Hence the glands had not lost their power of
absorption, as far as the carbonate of ammonia is concerned.
From these facts it is manifest that the poison of the cobra, though so
deadly to animals, is not at all poisonous to Drosera; yet it causes
strong and rapid inflection of the tentacles, and soon discharges all
colour from the glands. It seems even to act as a stimulant to the
protoplasm, for after considerable 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 learn
how this poison affected animal protoplasm; and Dr. Fayrer was so kind
as to make some observations for me, which he has since published.*
Ciliated epithelium from the mouth of a frog was placed in a solution
of .03 gramme to 4.6 cubic cm. of water; others being placed at the
same time in pure water for comparison. The movements of the cilia in
the solution seemed at first increased, but soon languished, and after
between 15 and 20 minutes ceased; whilst those in the water were still
acting vigorously. The white corpuscles of the blood of a frog, and the
cilia on two infusorial animals, a Paramaecium and Volvox, were
similarly affected by the poison. Dr. Fayrer also found that the muscle
of a frog lost its irritability after an immersion of 20 m. in the
solution, not then responding to a strong electrical current. On the
other hand, the movements of the cilia on the mantle of an Unio were
not always arrested, even when left for a consider-
* ‘Proceedings of Royal Society,’ Feb. 18, 1875. [page 209]
able time in a very strong solution. On the whole, it seems that the
poison of the cobra acts far more injuriously on the protoplasm of the
higher animals than on that of Drosera.
There is one other point which may be noticed. I have occasionally
observed that the drops of secretion round the glands were rendered
somewhat turbid by certain solutions, and more especially by some
acids, a film being formed on the surfaces of the drops; but I never
saw this effect produced in so conspicuous a manner as by the cobra
poison. When the stronger solution was employed, the drops appeared in
10 m. like little white rounded clouds. After 48 hrs. the secretion was
changed into threads and sheets of a membranous substance, including
minute granules of various sizes.
Camphor.—Some scraped camphor was left for a day in a bottle with
distilled water, and then filtered. A solution thus made is said to
contain 1/1000 of its weight of camphor; it smelt and tasted of this
substance. Ten leaves were immersed in this solution; after 15 m. five
of them were well inflected, two showing a first trace of movement in
11 m. and 12 m.; the sixth leaf did not begin to move until 15 m. had
elapsed, but was fairly well inflected in 17 m. and quite closed in 24
m.; the seventh began to move in 17 m., and was completely shut in 26
m. The eighth, ninth, and tenth leaves were old and of a very dark red
colour, and these were not inflected after an immersion of 24 hrs.; so
that in making experiments with camphor it is necessary to avoid such
leaves. Some of these leaves, on being left in the solution for 4 hrs.,
became of a rather dingy pink colour, and secreted much mucus; although
their tentacles were closely inflected, the protoplasm within the cells
was not at all aggregated. On another occasion, however, after a longer
immersion of 24 hrs., there was well marked aggregation. A solution
made by adding two drops of camphorated 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 camphor as when in
water; and that if already slightly withered, they recover more
quickly. The germination of certain seeds is also accelerated by the
solution. So that camphor acts as a stimulant, and it is the only known
stimulant for plants. I
* ‘Gardener’s Chronicle,’ 1874, p. 671. Nearly similar observations
were made in 1798 by B. S. Barton. [page 210]
wished, therefore, to ascertain whether camphor would render the leaves
of Drosera more sensitive to mechanical irritation than they naturally
are. Six leaves were left in distilled water for 5 m. or 6 m., and then
gently brushed twice or thrice, whilst still under water, with a soft
camel-hair brush; but no movement ensued. Nine leaves, which had been
immersed in the above solution of camphor for the times stated in the
following table, were next brushed only once with the same brush and in
the same manner as before; the results are given in the table. My first
trials were made by brushing the leaves whilst still immersed in the
solution; but it occurred to me that the viscid secretion round the
glands would thus be removed, and the camphor might act more
effectually on them. In all the following trials, therefore, each leaf
was taken out of the solution, waved for about 15 s. in water, then
placed in fresh water and brushed, so that the brushing would not allow
the freer access of the camphor; but this treatment made no difference
in the results.
Column 1 : Number of Leaves. Column 2 : Length of Immersion in the
Solution of Camphor. Column 3 : Length of Time between the Act of
Brushing and the Inflection of the Tentacles. Column 4 : Length of Time
between the Immersion of the Leaves in the Solution and the First Sign
of the Inflection of the Tentacles.
1 : 5 m. : 3 m. considerable inflection; 4 m. all the tentacles except
3 or 4 inflected. : 8 m.
2 : 5 m. : 6 m. first sign of inflection. : 11 m.
3 : 5 m. : 6 m. 30 s. slight inflection; 7 m. 30 s. plain inflection. :
11 m. 30 s.
4 : 4 m. 30 s. : 2 m. 30 s. a trace of inflection; 3 m. plain; 4 m.
strongly marked. : 7 m.
5 : 4 m. : 2 m. 30 s. a trace of inflection; 3 m. plain inflection. : 6
m. 30 s.
6 : 4 m. : 2 m. 30 s. decided inflection; 3 m. 30 s. strongly marked. :
6 m. 30 s.
7 : 4 m. : 2 m. 30 s. slight inflection; 3 m. plain; 4 m. well marked.
: 6 m. 30 s.
8 : 3 m. : 2 m. trace of inflection; 3 m. considerable, 6 m. strong
inflection. : 5 m.
9 : 3 m. : 2 m. trace of inflection; 3 m. considerable, 6 m. strong
inflection. : 5 m.
Other leaves were left in the solution without being brushed; one of
these first showed a trace of inflection after 11 m.; a second after 12
m.; five were not inflected until 15 m. had [page 211] elapsed, and two
not until a few minutes later. On the other hand, it will be seen in
the right-hand column of the table that most of the leaves subjected to
the solution, and which were brushed, became inflected in a much
shorter time. The movement of the tentacles of some of these leaves was
so rapid that it could be plainly seen through a very weak lens.
Two or three other experiments are worth giving. A large old leaf,
after being immersed for 10 m. in the solution, did not appear likely
to be soon inflected; so I brushed it, and in 2 m. it began to move,
and in 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 inflected; the failure therefore was not
complete.
We may conclude that a small dose of camphor in solution is a powerful
stimulant to Drosera. It not only soon excites the tentacles to bend,
but apparently renders the glands sensitive to a touch, which by itself
does not cause any movement. Or it may be that a slight mechanical
irritation not enough to cause any inflection yet gives some tendency
to movement, and thus reinforces the action of the camphor. This latter
view would have appeared to me the more probable one, had it not been
shown by M. Vogel that camphor is a stimulant in other ways to various
plants and seeds.
Two plants bearing four or five leaves, and with their roots in a
little cup of water, were exposed to the vapour of some bits of camphor
(about as large as a filbert-nut), under a vessel holding ten fluid oz.
After 10 hrs. no inflection ensued; but the glands appeared to be
secreting more copiously. The leaves were in a narcotised condition,
for on bits of meat being placed on two of them, there was no
inflection in 3 hrs. 15 m., and even after 13 hrs. 15 m. only a few of
the outer tentacles were slightly inflected; but this degree of
movement shows that the leaves had not been killed by an exposure
during 10 hrs. to the vapour of camphor.
Oil of Caraway.—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 [page 212] three additional minutes. After 14 m.
all five leaves were well, and some of them closely, inflected. After 6
hrs. the glands were white, and much mucus had been secreted. The
leaves were now flaccid, of a peculiar dull-red colour, and evidently
dead. One of the leaves, after an immersion of 4 m., was brushed, like
the leaves in the camphor, but this produced no effect. A plant with
its roots in water was exposed under a 10-oz. vessel to the vapour of
this oil, and in 1 hr. 20 m. one leaf showed a trace of inflection.
After 5 hrs. 20 m. the cover was taken off and the leaves examined; one
had all its tentacles closely inflected, the second about half in the
same state; and the third all sub-inflected. The plant was left in the
open air for 42 hrs., but not a single tentacle expanded; all the
glands appeared dead, except here and there one, which was still
secreting. It is evident that this oil is highly exciting and poisonous
to Drosera.
Oil of Cloves.—A mixture was made in the same manner as in the last
case, and three leaves were immersed in it. After 30 m. there was only
a trace of inflection which never increased. After 1 hr. 30 m. the
glands were pale, and after 6 hrs. white. No doubt the leaves were much
injured or killed.
Turpentine.—Small drops placed on the discs of some leaves killed them,
as did likewise drops of creosote. A plant was left for 15 m. under a
12-oz. vessel, with its inner surface wetted with twelve drops of
turpentine; but no movement of the tentacles ensued. After 24 hrs. the
plant was dead.
Glycerine.—Half-minims were placed on the discs of three leaves: in 2
hrs. some of the outer tentacles were irregularly inflected; and in 19
hrs. the leaves were flaccid and apparently dead; the glands which had
touched the glycerine were colourless. Minute drops (about 1/20 of a
minim) were applied to the glands of several tentacles, and in a few
minutes these moved and soon reached the centre. Similar drops of a
mixture of four dropped drops to 1 oz. of water were likewise applied
to several glands; but only a few of the tentacles moved, and these
very slowly and slightly. Half-minims of this same mixture placed on
the discs of some leaves caused, to my surprise, no inflection in the
course of 48 hrs. Bits of meat were then given them, and next day they
were well inflected; notwithstanding that some of the discal glands had
been rendered almost colourless. Two leaves were immersed in the same
mixture, but only for 4 hrs.; they were not inflected, and on being
afterwards left for 2 hrs. 30 m. in a solution (1 gr. to 1 oz.) of
carbonate of ammonia, their glands were blackened, their tentacles
inflected, and the protoplasm within their cells aggregated. It appears
[page 213] from these facts that a mixture of four drops of glycerine
to an ounce of water is not poisonous, and excites very little
inflection; but that pure glycerine is poisonous, and if applied in
very minute quantities to the glands of the outer tentacles causes
their inflection.
The Effects of Immersion in Water and in various Solutions on the
subsequent Action of Phosphate and Carbonate of Ammonia.—We have seen
in the third and seventh chapters that immersion in distilled water
causes after a time some degree of aggregation of the protoplasm, and a
moderate amount of inflection, especially in the case of plants which
have been kept at a rather high temperature. Water does not excite a
copious secretion of mucus. We have here to consider the effects of
immersion in various fluids on the subsequent action of salts of
ammonia and other stimulants. Four leaves which had been left for 24
hrs. in water were given bits of meat, but did not clasp them. Ten
leaves, after a similar immersion, were left for 24 hrs. in a powerful
solution (1 gr. to 20 oz.) of phosphate of ammonia, and only one showed
even a trace of inflection. Three of these leaves, on being left for an
additional day in the solution, still remained quite unaffected. When,
however, some of these leaves, which had been first immersed in water
for 24 hrs., and then in the phosphate for 24 hrs. were placed in a
solution of carbonate of ammonia (one part to 218 of water), the
protoplasm in the cells of the tentacles became in a few hours strongly
aggregated, showing that this salt had been absorbed and taken effect.
A short immersion in water for 20 m. did not retard the subsequent
action of the phosphate, or of splinters of glass placed on the glands;
but in two instances an immersion for 50 m. prevented any effect from a
solution of camphor. Several leaves which had been left for 20 m. in a
solution of one part of white sugar to 218 of water were placed in the
phosphate solution, the action of which was delayed; whereas a mixed
solution of sugar and the phosphate did not in the least interfere with
the effects of the latter. Three leaves, after being immersed for 20 m.
in the sugar solution, were placed in a solution of carbonate of
ammonia (one part to 218 of water); in 2 m. or 3 m. the glands were
blackened, and after 7 m. the tentacles were considerably inflected, so
that the solution of sugar, though it delayed the action of the
phosphate, did not delay that of the carbonate. Immersion in a similar
solution of gum arabic for 20 m. had no retarding action on the
phosphate. Three leaves were left for 20 m. in a mixture of one part of
alcohol to seven parts of water, [page 214] and then placed in the
phosphate solution: in 2 hrs. 15 m. there was a trace of inflection in
one leaf, and in 5 hrs. 30 m. a second was slightly affected; the
inflection subsequently increased, though slowly. Hence diluted
alcohol, which, as we shall see, is hardly at all poisonous, plainly
retards the subsequent action of the phosphate.
It was shown in the last chapter that leaves which did not become
inflected by nearly a day’s immersion in solutions of various salts and
acids behaved very differently from one another when subsequently
placed in the phosphate solution. I here give a table summing up the
results.
Column 1 : Name of the Salts and Acids in Solution. Column 2 : Period
of Immersion of the Leaves in Solutions of one part to 437 of water.
Column 3 : Effects produced on the Leaves by their subsequent Immersion
for stated periods in a Solution of one part of phosphate of ammonia to
8750 of water, or 1 gr. to 20 oz.
Rubidium chloride. : 22 hrs. : After 30 m. strong inflection of the
tentacles.
Potassium carbonate : 20 m. : Scarcely any inflection until 5 hrs. had
elapsed.
Calcium acetate. : 24 hrs. : After 24 hrs. very slight inflection.
Calcium nitrate. : 24 hrs. : Do. do.
Magnesium acetate. : 22 hrs. : Some slight inflection, which became
well pronounced in 24 hrs.
Magnesium nitrate. : 22 hrs. : After 4 hrs. 30 m. a fair amount of
inflection, which never increased.
Magnesium chloride : 22 hrs. : After a few minutes great inflection;
after 4 hrs. all four leaves with almost every tentacle closely
inflected.
Barium acetate. : 22 hrs. : After 24 hrs. two leaves out of four
slightly inflected.
Barium nitrate. : 22 hrs. : After 30 m. one leaf greatly, and two
others moderately, inflected; they remained thus for 24 hrs.
Strontium acetate. : 22 hrs. : After 25 m. two leaves greatly
inflected; after 8 hrs. a third leaf moderately, and the fourth very
slightly, inflected. All four thus remained for 24 hrs.
Strontium nitrate. : 22 hrs. : After 8 hrs. three leaves out of five
moderately inflected; after 24 hrs. all five in this state; but not one
closely inflected.
Aluminium chloride : 24 hrs. : Three leaves which had either been
slightly or not at all affected by the chloride became after 7 hrs. 30
m. rather closely inflected. [page 215]
Column 1 : Name of the Salts and Acids in Solution. Column 2 : Period
of Immersion of the Leaves in Solutions of one part to 437 of water.
Column 3 : Effects produced on the Leaves by their subsequent Immersion
for stated periods in a Solution of one part of phosphate of ammonia to
8750 of water, or 1 gr. to 20 oz.
Aluminium nitrate. : 24 hrs. : After 25 hrs. slight and doubtful
effect.
Lead chloride. : 23 hrs. : After 24 hrs. two leaves somewhat inflected,
the third very little; and thus remained.
Manganese chloride : 22 hrs. : After 48 hrs. not the least inflection.
Lactic acid. : 48 hrs. : After 24 hrs. a trace of inflection in a few
tentacles, the glands of which had not been killed by the acid.
Tannic acid. : 24 hrs. : After 24 hrs. no inflection.
Tartaric acid. : 24 hrs. : Do. do.
Citric acid. : 24 hrs. : After 50 m. tentacles decidedly inflected, and
after 5 hrs. strongly inflected; so remained for the next 24 hrs.
Formic acid. : 22 hrs. : Not observed until 24 hrs. had elapsed;
tentacles considerably inflected, and protoplasm aggregated.
In a large majority of these twenty cases, a varying degree of
inflection was slowly caused by the phosphate. In four cases, however,
the inflection was rapid, occurring in less than half an hour or at
most in 50 m. In three cases the phosphate did not produce the least
effect. Now what are we to infer from these facts? We know from ten
trials that immersion in distilled water for 24 hrs. prevents the
subsequent action of the phosphate solution. It would, therefore,
appear as if the solutions of chloride of manganese, tannic and
tartaric acids, which are not poisonous, acted exactly like water, for
the phosphate produced no effect on the leaves which had been
previously immersed in these three solutions. The majority of the other
solutions behaved to a certain extent like water, for the phosphate
produced, after a considerable interval of time, only a slight effect.
On the other hand, the leaves which had been immersed in the solutions
of the chloride of rubidium and magnesium, of acetate of strontium,
nitrate of barium, and citric acid, were quickly acted on by the
phosphate. Now was water absorbed from these five weak solutions, and
yet, owing to the presence of the salts, did not prevent the subsequent
action of the phosphate? Or [page 216] may we not suppose* that the
interstices of the walls of the glands were blocked up with the
molecules of these five substances, so that they were rendered
impermeable to water; for had water entered, we know from the ten
trials that the phosphate would not afterwards have produced any
effect? It further appears that the molecules of the carbonate of
ammonia can quickly pass into glands which, from having been immersed
for 20 m. in a weak solution of sugar, either absorb the phosphate very
slowly or are acted on by it very slowly. On the other hand, glands,
however they may have been treated, seem easily to permit the
subsequent entrance of the molecules of carbonate of ammonia. Thus
leaves which had been immersed in a solution (of one part to 437 of
water) of nitrate of potassium for 48 hrs.—of sulphate of potassium for
24 hrs.—and of the chloride of potassium for 25 hrs.—on being placed in
a solution of one part of carbonate of ammonia to 218 of water, had
their glands immediately blackened, and after 1 hr. their tentacles
somewhat inflected, and the protoplasm aggregated. But it would be an
endless task to endeavour to ascertain the wonderfully diversified
effects of various solutions on Drosera.
Alcohol (one part to seven of water).—It has already been shown that
half-minims of this strength placed on the discs of leaves do not cause
any inflection; and that when two days afterwards the leaves were given
bits of meat, they became strongly inflected. Four leaves were immersed
in this mixture, and two of them after 30 m. were brushed with a
camel-hair brush, like the leaves in the solution of camphor, but this
produced no effect.
* See Dr. M. Traube’s curious experiments on the production of
artificial cells, and on their permeability to various salts, described
in his papers: “Experimente zur Theorie der Zellenbildung und
Endosmose,” Breslau, 1866; and “Experimente zur physicalischen Erklrung
der Bildung der Zellhaut, ihres Wachsthums durch Intussusception,”
Breslau, 1874. These researches perhaps explain my results. Dr. Traube
commonly employed as a membrane the precipitate formed when tannic acid
comes into contact with a solution of gelatine. By allowing a
precipitation of sulphate of barium to take place at the same time, the
membrane becomes “infiltrated” with this salt; and in consequence of
the intercalation of molecules of sulphate of barium among those of the
gelatine precipitate, the molecular interstices in the membrane are
made smaller. In this altered condition, the membrane no longer allows
the passage through it of either sulphate of ammonia or nitrate of
barium, though it retains its permeability for water and chloride of
ammonia. [page 217]
Nor did these four leaves, on being left for 24 hrs. in the diluted
alcohol, undergo any inflection. They were then removed; one being
placed in an infusion of raw meat, and bits of meat on the discs of the
other three, with their stalks in water. Next day one seemed a little
injured, whilst two others showed merely a trace of inflection. We
must, however, bear in mind that immersion for 24 hrs. in water
prevents leaves from clasping meat. Hence alcohol of the above strength
is not poisonous, nor does it stimulate the leaves like camphor does.
The vapour of alcohol acts differently. A plant having three good
leaves was left for 25 m. under a receiver holding 19 oz. with sixty
minims of alcohol in a watch-glass. No movement ensued, but some few of
the glands were blackened and shrivelled, whilst many became quite
pale. These were scattered over all the leaves in the most irregular
manner, reminding me of the manner in which the glands were affected by
the vapour of carbonate of ammonia. Immediately on the removal of the
receiver particles of raw meat were placed on many of the glands, those
which retained their proper colour being chiefly selected. But not a
single tentacle was inflected during the next 4 hrs. After the first 2
hrs. the glands on all the tentacles began to dry; and next morning,
after 22 hrs., all three leaves appeared almost dead, with their glands
dry; the tentacles on one leaf alone being partially inflected.
A second plant was left for only 5 m. with some alcohol in a
watch-glass, under a 12-oz. receiver, and particles of meat were then
placed on the glands of several tentacles. After 10 m. some of them
began to curve inwards, and after 55 m. nearly all were considerably
inflected; but a few did not move. Some 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. Particles of meat were now placed on
the glands of several tentacles, some of which first began to move in
25 m.; after 40 m. most of them were somewhat inflected, and after 1
hr. 10 m. almost all were considerably inflected. From their slow rate
of movement there can be no doubt that the glands of these tentacles
had been rendered insensible for a time by exposure during 5 m. to the
vapour of alcohol.
Vapour of Chloroform.—The action of this vapour on Drosera is 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 [page 218] rendered for a time
insensible to the action of raw meat, but sometimes are not thus
affected, or in a very slight degree. A plant recovers from a small
dose, but is easily killed by a larger one.
A plant was left for 30 m. under a bell-glass holding 19 fluid oz.
(539.6 ml.) with eight drops of chloroform, and before the cover was
removed, most of the tentacles became much inflected, though they did
not reach the centre. After the cover was removed, bits of meat were
placed on the glands of several of the somewhat incurved tentacles;
these glands were found much blackened after 6 hrs. 30 m., but no
further movement ensued. After 24 hrs. the leaves appeared almost dead.
A smaller bell-glass, holding 12 fluid oz. (340.8 ml.), was now
employed, and a plant was left for 90 s. under it, with only two drops
of chloroform. Immediately on the removal of the glass all the
tentacles curved inwards so as to stand perpendicularly up; and some of
them could actually be seen moving with extraordinary quickness by
little starts, and therefore in an unnatural manner; but they never
reached the centre. After 22 hrs. they fully re-expanded, and on meat
being placed on their glands, or when roughly touched by a needle, they
promptly became inflected; so that these leaves had not been in the
least injured.
Another plant was placed under the same small bell-glass with three
drops of chloroform, and before two minutes had elapsed, the tentacles
began to curl inwards with rapid little jerks. The glass was then
removed, and in the course of two or three additional minutes almost
every tentacle reached the centre. On several other occasions the
vapour did not excite any movement of this kind.
There seems also to be great variability in the degree and manner in
which chloroform renders the glands insensible to the subsequent action
of meat. In the plant last referred to, which had been exposed for 2 m.
to three drops of chloroform, some few tentacles curved up only to a
perpendicular position, and particles of meat were placed on their
glands; this caused them in 5 m. to begin moving, but they moved so
slowly that they did not reach the centre until 1 hr. 30 m. had
elapsed. Another plant was similarly exposed, that is, for 2 m. to
three drops of chloroform, and on particles of meat being placed on the
glands of several tentacles, which had curved up into a perpendicular
position, one of these began to bend in 8 m., but afterwards moved very
slowly; whilst none of the other tentacles [page 219] moved for the
next 40 m. Nevertheless, in 1 hr. 45 m. from the time when the bits of
meat had been given, all the tentacles reached the centre. In this case
some slight anaesthetic effect apparently had been produced. On the
following day the plant had perfectly recovered.
Another plant bearing two leaves was exposed for 2 m. under the 19-oz.
vessel to two drops of chloroform; it was then taken out and examined;
again exposed for 2 m. to two drops; taken out, and re-exposed for 3 m.
to three drops; so that altogether it was exposed alternately to the
air and during 7 m. to the vapour of seven drops of chloroform. Bits of
meat were now placed on thirteen glands on the two leaves. On one of
these leaves, a single tentacle first began moving in 40 m., and two
others in 54 m. On the second leaf some tentacles first moved in 1 hr.
11 m. After 2 hrs. many tentacles on both leaves were inflected; but
none had reached the centre within this time. In this case there could
not be the least doubt that the chloroform had exerted an anaesthetic
influence on the leaves.
On the other hand, another plant was exposed under the same vessel for
a much longer time, viz. 20 m., to twice as much chloroform. Bits of
meat were then placed on the glands of many tentacles, and all of them,
with a single exception, reached the centre in from 13 m. to 14 m. In
this case, little or no 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 become pale-coloured;
but none of the tentacles moved. After 6 hrs. 30 m. the leaves appeared
sickly, and the discal glands were almost dry. By the next morning many
of the tentacles were dead, as were all those on which meat had been
placed; showing that matter had been absorbed from the meat which had
increased the evil effects of the vapour. After four days the plant
itself died. Another plant was exposed in the same vessel for 15 m. to
forty minims. One young, small, and tender leaf had all its tentacles
inflected, and seemed much injured. Bits of raw meat were placed on
several glands on two other and older leaves. These glands became dry
after 6 hrs.; and seemed injured; the tentacles never moved, excepting
one which was ultimately a little inflected. The glands of the other
tentacles continued to secrete, and appeared uninjured, but the whole
plant after three days became very sickly. [page 220]
In the two foregoing experiments the doses were evidently too large and
poisonous. With weaker doses, the anaesthetic effect was variable, as
in the case of chloroform. A plant was exposed for 5 m. to ten drops
under a 12-oz. vessel, and bits of meat were then placed on many
glands. None of the tentacles thus treated began to move in a decided
manner until 40 m. had elapsed; but then some of them moved very
quickly, so that two reached the centre after an additional interval of
only 10 m. In 2 hrs. 12 m. from the time when the meat was given, all
the tentacles reached the centre. Another plant, with two leaves, was
exposed in the same vessel for 5 m. to a rather larger dose of ether,
and bits of meat were placed on several glands. In this case one
tentacle on each leaf began to bend in 5 m.; and after 12 m. two
tentacles on one leaf, and one on the second leaf, reached the centre.
In 30 m. after the meat had been given, all the tentacles, both those
with and without meat, were closely inflected; so that the ether
apparently had stimulated these leaves, causing all the tentacles to
bend.
Vapour of Nitric Ether.—This vapour seems more injurious than that of
sulphuric ether. A plant was exposed for 5 m. in a 12-oz. vessel to
eight drops in a watch-glass, and I distinctly saw a few tentacles
curling inwards before the glass was removed. Immediately afterwards
bits of meat were placed on three glands, but no movement ensued in the
course of 18 m. The same plant was placed again under the same vessel
for 16 m. with ten drops of the ether. None of the tentacles moved, and
next morning those with the meat were still in the same position. After
48 hrs. one leaf seemed healthy, but the others were much injured.
Another plant, having two good leaves, was exposed for 6 m. under a
19-oz. vessel to the vapour from ten minims of the ether, and bits of
meat were then placed on the glands of many tentacles on both leaves.
After 36 m. several of them on one leaf became inflected, and after 1
hr. almost all the tentacles, those with and without meat, nearly
reached the centre. On the other leaf the glands began to dry in 1 hr.
40 m., and after several hours not a single tentacle was inflected; but
by the next morning, after 21 hrs., many were inflected, though they
seemed much injured. In this and the previous experiment, it is
doubtful, owing to the injury which the leaves had suffered, whether
any anaesthetic effect had been produced.
A third plant, having two good leaves, was exposed for only 4 m. in the
19-oz. vessel to the vapour from six drops. Bits of meat were then
placed on the glands of seven tentacles on the [page 221] same leaf. A
single tentacle moved after 1 hr. 23 m.; after 2 hrs. 3 m. several were
inflected; and after 3 hrs. 3 m. all the seven tentacles with meat were
well inflected. From the slowness of these movements it is clear that
this leaf had been rendered insensible for a time to the action of the
meat. A second leaf was rather differently affected; bits of meat were
placed on the glands of five tentacles, three of which were slightly
inflected in 28 m.; after 1 hr. 21 m. one reached the centre, but the
other two were still only slightly inflected; after 3 hrs. they were
much more inflected; but even after 5 hrs. 16 m. all five had not
reached the centre. Although some of the tentacles began to move
moderately soon, they afterwards moved with extreme slowness. By next
morning, after 20 hrs., most of the tentacles on both leaves were
closely inflected, but not quite regularly. After 48 hrs. neither leaf
appeared injured, though the tentacles were still inflected; after 72
hrs. one was almost dead, whilst the other was re-expanding and
recovering.
Carbonic Acid.—A plant was placed under a 122-oz. bell-glass filled
with this gas and standing over water; but I did not make sufficient
allowance for the absorption of the gas by the water, so that towards
the latter part of the experiment some air was drawn in. After an
exposure of 2 hrs. the plant was removed, and bits of raw meat placed
on the glands of three leaves. One of these leaves hung a little down,
and was at first partly and soon afterwards completely covered by the
water, which rose within the vessel as the gas was absorbed. On this
latter leaf the tentacles, to which meat had been given, became well
inflected in 2 m. 30 s., that is, at about the normal rate; so that
until I remembered that the leaf had been protected from the gas, and
might perhaps have absorbed oxygen from the water which was continually
drawn inwards, I falsely concluded that the carbonic acid had produced
no effect. On the other two leaves, the tentacles with meat behaved
very differently from those on the first leaf; two of them first began
to move slightly in 1 hr. 50 m., always reckoning from the time when
the meat was placed on the glands—were plainly inflected in 2 hrs. 22
m.—and in 3 hrs 22 m. reached the centre. Three other tentacles did not
begin to move until 2 hrs. 20 m. had elapsed, but reached the centre at
about the same time with the others, viz. in 3 hrs. 22 m.
This experiment was repeated several times with nearly the same
results, excepting that the interval before the tentacles began to move
varied a little. I will give only one other case. [page 222] A plant
was exposed in the same vessel to the gas for 45 m., and bits of meat
were then placed on four glands. But the tentacles did not move for 1
hr. 40 m.; after 2 hrs. 30 m. all four were well inflected, and after 3
hrs. reached the centre.
The following singular phenomenon sometimes, but by no means always,
occurred. A plant was immersed for 2 hrs., and bits of meat were then
placed on several glands. In the course of 13 m. all the submarginal
tentacles on one leaf became considerably inflected; those with the
meat not in the least degree more than the others. On a second leaf,
which was rather old, the tentacles with meat, as well as a few others,
were moderately inflected. On a third leaf all the tentacles were
closely inflected, though meat had not been placed on any of the
glands. This movement, I presume, may be attributed to excitement from
the absorption of oxygen. The last-mentioned leaf, to which no meat had
been given, was fully re-expanded after 24 hrs.; whereas the two other
leaves had all their tentacles closely inflected over the bits of meat
which by this time had been carried to their centres. Thus these three
leaves had perfectly recovered from the effects of the gas in the
course of 24 hrs.
On another occasion some fine plants, after having been left for 2 hrs.
in the gas, were immediately given bits of meat in the usual manner,
and on their exposure to the air most of their tentacles became in 12
m. curved into a vertical or sub-vertical position, but in an extremely
irregular manner; some only on one side of the leaf and some on the
other. They remained in this position for some time; the tentacles with
the bits of meat not having at first moved more quickly or farther
inwards than the others without meat. But after 2 hrs. 20 m. the former
began to move, and steadily went on bending until they reached the
centre. Next morning, after 22 hrs., all the tentacles on these leaves
were closely clasped over the meat which had been carried to their
centres; whilst the vertical and sub-vertical tentacles on the other
leaves to which no meat had been given had fully re-expanded. Judging,
however, from the subsequent action of a weak solution of carbonate of
ammonia on one of these latter leaves, it had not perfectly recovered
its excitability and 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 on its disc.
I will give only one other experiment. After the exposure of a plant
for 2 hrs. to the gas, one of its leaves was immersed in a rather
strong solution of carbonate of ammonia, together with [page 223] a
fresh leaf from another plant. The latter had most of its tentacles
strongly inflected within 30 m.; whereas the leaf which had been
exposed to the carbonic acid remained for 24 hrs. in the solution
without undergoing any inflection, with the exception of two tentacles.
This leaf had been almost completely paralysed, and was not able to
recover its sensibility whilst still in the solution, which from having
been made with distilled water probably contained little oxygen.]
Concluding Remarks on the Effects of the foregoing Agents.—As the
glands, when excited, transmit some influence to the surrounding
tentacles, causing them to bend and their glands to pour forth an
increased amount of modified secretion, I was anxious to ascertain
whether the leaves included any element having the nature of
nerve-tissue, which, though not continuous, served as the channel of
transmission. This led me to try the several alkaloids and other
substances which are known to exert a powerful influence on the nervous
system of animals; I was at first encouraged in my trials by finding
that strychnine, digitaline, and nicotine, which all act on the nervous
system, were poisonous to Drosera, and caused a certain amount of
inflection. Hydrocyanic acid, again, which is so deadly a poison to
animals, caused rapid movement of the tentacles. But as several
innocuous acids, though much diluted, such as benzoic, acetic, &c., as
well as some essential oils, are extremely poisonous to Drosera, and
quickly cause strong inflection, it seems probable that strychnine,
nicotine, digitaline, and hydrocyanic acid, excite inflection by acting
on elements in no way analogous to the nerve-cells of animals. If
elements of this latter nature had been present in the leaves, it might
have been expected that morphia, hyoscyamus, atropine, veratrine,
colchicine, curare, and diluted alcohol would have produced some marked
effect; whereas [page 224] these substances are not poisonous and have
no power, or only a very slight one, of inducing inflection. It should,
however, be observed that curare, colchicine, and veratrine are
muscle-poisons—that is, act on nerves having some special relation with
the muscles, and, therefore, could not be expected to act on Drosera.
The poison of the cobra is most deadly to animals, by paralysing their
nerve-centres,* yet is not in the least so to Drosera, though quickly
causing strong inflection.
Notwithstanding the foregoing facts, which show how widely different is
the effect of certain substances on the health or life of animals and
of Drosera, yet there exists a certain degree of parallelism in the
action of certain other substances. We have seen that this holds good
in a striking manner with the salts of sodium and potassium. Again,
various metallic salts and acids, namely those of silver, mercury,
gold, tin, arsenic, chromium, copper, and platina, most or all of which
are highly poisonous to animals, are equally so to Drosera. But it is a
singular fact that the chloride of lead and two salts of barium were
not poisonous to this plant. It is an equally strange fact, that,
though acetic and propionic acids are highly poisonous, their ally,
formic acid, is not so; and that, whilst certain vegetable acids,
namely oxalic, benzoic, &c., are poisonous in a high degree, gallic,
tannic, tartaric, and malic (all diluted to an equal degree) are not
so. Malic acid induces inflection, whilst the three other just named
vegetable acids have no such power. But a pharmacopoeia would be
requisite to describe the diversified effects of various substances on
Drosera.**
* Dr. Fayrer, ‘The Thanatophidia of India,’ 1872, p. 4.
** Seeing that acetic, hydrocyanic, and chromic acids, acetate of
strychnine, and vapour of ether, are poisonous to Drosera, [[page 225]]
it is remarkable that Dr. Ransom (‘Philosoph. Transact.’ 1867, p. 480),
who used much stronger solutions of these substances than I did, states
“that the rhythmic contractility of the yolk (of the ova of the pike)
is not materially influenced by any of the poisons used, which did not
act chemically, with the exception of chloroform and carbonic acid.” I
find it stated by several writers that curare has no influence on
sarcode or protoplasm, and we have seen that, though curare excites
some degree of inflection, it causes very little aggregation of the
protoplasm.) [page 226]
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 become dark at first, and then
very pale or white, as was conspicuously the case with glands subjected
to the poison of the cobra and citrate of strychnine. In other cases
they are from the first rendered white, as with leaves placed in hot
water and several acids; and this, I presume, is the result of the
coagulation of the albumen. On the same leaf some glands become white
and others dark-coloured, as occurred with leaves in a solution of the
sulphate of quinine, and in the vapour of alcohol. Prolonged immersion
in nicotine, curare, and even water, blackens the glands; and this, I
believe, is due to the aggregation of the protoplasm within their
cells. Yet curare caused very little aggregation in the cells of the
tentacles, whereas nicotine and sulphate of quinine induced strongly
marked aggregation down their bases. The aggregated masses in leaves
which had been immersed for 3 hrs. 15 m. in a saturated solution of
sulphate of quinine exhibited incessant [page 226] changes of form, but
after 24 hrs. were motionless; the leaf being flaccid and apparently
dead. On the other hand, with leaves subjected for 48 hrs. to a strong
solution of the poison of the cobra, the protoplasmic masses were
unusually active, whilst with the higher animals the vibratile cilia
and white corpuscles of the blood seem to be quickly paralysed by this
substance.
With the salts of alkalies and earths, the nature of the base, and not
that of the acid, determines their physiological action on Drosera, as
is likewise the case with animals; but this rule hardly applies to the
salts of quinine and strychnine, for the acetate of quinine causes much
more inflection than the sulphate, and both are poisonous, whereas the
nitrate of quinine is not poisonous, and induces inflection at a much
slower rate than the acetate. The action of the citrate of strychnine
is also somewhat different from that of the sulphate.
Leaves which have been immersed for 24 hrs. in water, and for only 20
m. in diluted alcohol, or in a weak solution of sugar, are afterwards
acted on very slowly, or not at all, by the phosphate of ammonia,
though they are quickly acted on by the carbonate. Immersion for 20 m.
in a solution of gum arabic has no such inhibitory power. The solutions
of certain salts and acids affect the leaves, with respect to the
subsequent action of the phosphate, exactly like water, whilst others
allow the phosphate afterwards to act quickly and energetically. In
this latter case, the interstices of the cell-walls may have been
blocked up by the molecules of the salts first given in solution, so
that water could not afterwards enter, though the molecules of the
phosphate could do so, and those of the carbonate still more easily.
[page 227]
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 rapid
inflection, others have no such power; those which I tried were all
poisonous.
Diluted alcohol (one part to seven of water) is not poisonous, does not
induce inflection, nor increase the sensitiveness of the glands to
mechanical irritation. The vapour acts as a narcotic or anaesthetic,
and long exposure to it kills the leaves.
The vapours of chloroform, sulphuric and nitric ether, act in a
singularly variable manner on different leaves, and on the several
tentacles of the same leaf. This, I suppose, is owing to differences in
the age or constitution of the leaves, and to whether certain tentacles
have lately been in action. That these vapours are absorbed by the
glands is shown by their changed colour; but as other plants not
furnished with glands are affected by these vapours, it is probable
that they are likewise absorbed by the stomata of Drosera. They
sometimes excite extraordinarily rapid inflection, but this is not an
invariable result. If allowed to act for even a moderately long time,
they kill the leaves; whilst a small dose acting for only a short time
serves as a narcotic or anaesthetic. In this case the tentacles,
whether or not they have [page 228] 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 aggregated. In some cases, soon after
the leaves were removed from the gas and brought into the air, the
tentacles moved spontaneously; this being due, I presume, to the
excitement from the access of oxygen. These inflected tentacles,
however, could not be excited for some time afterwards to any further
movement by their glands being stimulated. With other irritable plants
it is known* that the exclusion of oxygen prevents their moving, and
arrests the movements of the protoplasm within their cells, but this
arrest is a different phenomenon from the retardation of the process of
aggregation just alluded to. Whether this latter fact ought to be
attributed to the direct action of the carbonic acid, or to the
exclusion of oxygen, I know not.
* Sachs, ‘Traité de Bot.’ 1874, pp. 846, 1037. [page 229]