Insectivorous Plants

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

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

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

I have only just seen quoted iu touch and have moved; for he the ' Gardener's Chronicle ' (Oct. says, " the contents of each indi- 10, 1874), he appears to have vidnal cell are collected together observed a similar phenomenon in in the centre of the cavity." darken in 10 s. (seconds); and in 13 s. were conspicuously darker. In 1 m. extremely small spherical masses of protoplasm could be seen arising in the cells of the pedicels close beneath the glands, as well as in the cushions on which the long- headed marginal glands rest. In several cases the process travelled down the pedicels for a length twice or thrice as great as that of the glands, in about 10 m. It was interesting to observe the process momentarily arrested at each transverse partition between two cells, and then to see the transparent contents of the cell next below almost flashing into a cloudy mass. In the lower part of the pedicels, the action proceeded slower, so that it took about 20 m. before the cells halfway down the long marginal and submarginal tentacles became aggregated.

We may infer that the carbonate of ammonia is absorbed by the glands, not only from its action being so rapid, but from its effect being somewhat different from that of other salts. As the glands, when excited, secrete an acid belonging to the acetic series, the carbonate is probably at once converted into a salt of this series ; and we shall presently see that the acetate of ammonia causes aggregation almost or quite as energetically as does the carbonate. If a few drops of a solution of one part of the carbonate to 437 of water (or 1 gr. to 1 oz.) be added to the purple fluid which exudes from crushed tentacles, or to paper stained by being rubbed with them, the fluid and the paper are changed into a pale dirty green. Nevertheless, some purple colour could still be detected after 1 hr. 30 m. within the glands of a leaf left in a solution of twice the above strength (viz. 2 grs. to 1 oz.) ; and after 24 hi's. the cells of the pedicels close beneath the glands still contained spheres of protoplasm of a fine purple tint. These facts show that the ammonia had not entered as a carbonate, for otherwise the colour would have been discharged. I have, however, sometimes observed, espe- cially with the long-headed tentacles on the margins of very pale leaves immersed in a solution, that the glands as well as the upper cells of the pedicels were discoloured ; and in these cases I presume that the unchanged carbonate had been absorbed. The appearance above described, of the aggregating process 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 pos- sibly be in the case of the carbonate of ammonia. As, how- ever, the aggregation caused by this salt travels down the tentacles at a quicker rate than when insoluble particles are placed on the glands, it is probable that ammonia in some form is absorbed not only by the glands, but passes down the tentacles. Having examined a leaf in water, and found the contents of the cells homogeneous, I placed it in a few drops of a solution of one part of the carbonate to 437 of water, and attended to the cells immediately beneath the glands, but did not use a very high power. No aggregation was visible in 3 m. ; but after 15 m. small spheres of protoplasm were formed, more especially beneath tne long-headed marginal glands; the process, how- ever, in this case took place with unusual slowness. In 25 m. conspicuous spherical masses were present in the cells of the pedicels for a length about equal to that of the glands ; and in 3 hrs. to that of a third or half of the whole tentacle.

If tentacles with cells containing only very pale pink fluid, and apparently but little protoplasm, are placed in a few drops of a weak solution of one part of the carbonate to 4375 of water (1 gr. to 10 oz.), and the highly transparent cells beneath the glands are carefully observed under a high power, these may be seen first to become slightly cloudy from the formation of numberless, only just perceptible, granules, which rapidly grow larger either from coalescence or from attracting more protoplasm from the surrounding fluid. On one occasion I chose a singularly pale leaf, and gave it, whilst under the microscope, a single drop of a stronger solution of one part to 437 of water; in this case the contents of the cells did not become cloudy, but after 10 m. minute irregular granules of protoplasm could be detected, which soon increased into irregular masses and globules of a greenish or very pale purple tint ; but these never formed perfect spheres, though incessantly changing their shapes and positions.

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

it nearly equalled the cell in diameter; and a second sphere about half as large as the first, together with a few other minute ones, were formed. After 6 hrs. the fluid in which these spheres floated was almost colourless. After 8 hrs. 35 m. (always reckoning from the time when the solution was first added) four new minute spheres had appeared. Next morning, after 22 hrs., there were, besides the two large spheres, seven smaller ones, floating in absolutely colourless fluid, in which some flocculent greenish matter was suspended.

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

After leaves have been left for several hours in a solution of the carbonate, and complete aggregation has been effected, the * With other plants I have caused by a solution of carbonate often seen what appears to be a of ammonia, as likewise follow § true shrinking of the primordial from mechanical injuries, atricle from the walk of the cells, stream of protoplasm on the walls of the cells coases to be visible ; I observed this fact repeatedly, but will give only one instance. A pale purple leaf was placed in a few drops of a solution of one part to 292 of water, and in 2 hrs. some fine purple spheres were formed in the upper cells of the pedicels, the stream of protoplasm round their walls being still quite distinct ; but after an additional 4 hrs., during which time many more spheres were formed, the stream was no longer distinguishable on the most careful examination ; and this no doubt was due to the contained granules having become united with the spheres, so that nothing was left by which the move- ment of the limpid protoplasm could be perceived. But minute free spheres still travelled up and down the cells, showing that there was still a current. So it was next morning, after 22 hrs., by which time some new minute spheres had been formed ; these oscillated from side to side and changed their positions, proving that the current had not ceased, though no stream of protoplasm was visible. On another occasion, however, a stream was seen flowing round the cell-walls of a vigorous, dark- coloured leaf, after it had been left for 21 hrs. in a rather stronger solution, namely, of one part of the carbonate to 218 of water. This leaf, therefore, was not much or at all injured by an immersion for this length of time in the above solution of two grains to the ounce ; and on being afterwards left for 24 hrs. in water, the aggregated masses in many of the cells were re- dissolved, in the same manner as occurs with leaves in a state of nature when they re-expand after having caught insects.

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

From these several facts we may conclude that when vigorous dark-coloured leaves are subjected to the action of carbonate of ammonia, the fluid within the cells of the tentacles often 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 repeatedly coalesce and redivide. After a longer or shorter time the granules in the colourless layer of protoplasm, which flows round the walls, are drawn to and unite with the larger spheres, or form small independent spheres ; these latter being of a much paler colour, and more brittle than the first aggregated masses. After the granules of protoplasm have been thus attracted, the layer of flowing protoplasm can no longer be dis- tinguished, though a current of limpid fluid still flows round the walls.

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

All the foregoing observations relate to the exterior tentacles, which are of a purple colour; but the green pedicels of the short central tentacles are acted on by the carbonate, and by an infusion of raw meat, in exactly the same manner, with the sole difference that the aggregated masses are of a greenish colour ; so that the process is in no way dependent on the colour of the fluid within the cells. Finally, the most remarkable fact with respect to this salt is the extraordinary small amount which suffices to cause aggre- gation. Full details will be given in the seventh chapter, and here it will be enough to say that with a sensitive leaf the absorption by a gland of y^Voo^ of a grain ( • 000482 mgr.) is enough to cause in the course of one hour well-marked aggrega- tion in the cells immediately beneath the gland.

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

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

lowed from an immersion of from 5 m. to 10 m. in an equally strong solution of the carbonate. Lastly, a leaf was placed in thirty minims of a solution of one part of phosphate of ammonia to 4.3,750 of water (1 gr. to 100 oz.), so that it received j-gVo °f a grain ('04079 mgr.); this soon caused the tentacles to be strongly inflected ; and after 24 hrs. the contents of the cells were aggregated into oval and irregularly globular masses, with a conspicuous current of protoplasm flowing round the walls. But after so long an interval aggregation would have ensued, whatever had caused inflection.

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

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

which by the next morning, after 24 hrs., had almost dis- appeared, the leaf being evidently dead. Nor was there any true aggregation in leaves immersed in propionic acid of the same strength; but in this case the protoplasm was collected in irregular masses towards the bases of the lower cells of the tentacles. A filtered infusion of raw meat induces strong aggregation, but not very quickly. In one leaf thus immersed there was n little aggregation after 1 hr. 20 m., and in another after 1 hr. 50 m. With other leaves a considerably longer time was re- quired : for instance, one immersed for 5 hrs. showed no aggre- gation, but was plainly acted on in 5 m., when placed in a few drops of a solution of one part of carbonate of ammonia to 146 of water. Some leaves were left in the infusion for 24 hrs., and these became aggregated to a wonderful degree, so that the inflected tentacles presented to the naked eye a plainly mottled appearance. The little masses of purple protoplasm were generally oval or beaded, and not nearly so often spherical as in the case of leaves subjected to carbonate of ammonia. They underwent incessant changes of form ; and the current of colourless protoplasm round the walls was conspicuously plain after an immersion of 25 hrs. Eaw meat is too powerful a stimulant, and even small bits generally injure, and sometimes kill, the leaves to which they are given : the aggregated masses of protoplasm become dingy or almost colourless, and present in unusual granular appearance, as is likewise the case with leaves which have been immersed in a very strong solution of carbonate of ammonia. A leaf placed in milk had the contents of its cells somewhat aggregated in 1 hr. Two other leaves, one immersed in human saliva for 2 hrs. 30 m., and another in unboiled white of egg for 1 hr. 30 m., were not acted on in this manner; though they undoubtedly would have been so, had more time been allowed. These same two leaves, on being afterwards placed in a solution of carbonate of ammonia (3 grs. to 1 oz.), had their cells aggregated, the one in 10 m. and the other in 5 m.

Several leaves were left for 4 hrs. 30 m. in a solution of one part of white sugar to 146 of water, and no aggregation ensued on being placed in a solution of this same strength of carbonate of ammonia, they were acted on in 5 m. ; as was likewise a leaf which had been left for 1 hr. 45 m. in a moderately thick solu- tion of gum arabic. Several other leaves were immersed for some hours in denser solutions of sugar, gum, and starch, and they had the contents of their cells greatly aggregated. This

effect may be attributed to exosiuose ; for the leaves in the syrup became quite flaccid, and those in the gum and starch somewhat flaccid, with their tentacles twisted about in the most irregular manner, the longer ones like corkscrews. We shall hereafter see that solutions of these substances, when placed on the discs of leaves, do not incite inflection. Particles of soft sugar were added to the secretion round several glands and were soon dissolved, causing a great increase of the secre- tion, no doubt by exosmose ; and after 24 hrs. the cells showed a certain amount of aggregation, though the tentacles wero not inflected. Glycerine causes in a few minutes well-pro- nounced aggregation, commencing as usual within the glands and then travelling down the tentacles ; and this I presume may be attributed to the strong attraction of this substanco for water. Immersion for several hours in water causes some degree of aggregation. Twenty leaves were first carefully examined, and re-examined after having been left immersed in distilled water for various periods, with the following resiilts. It is rare to find even a trace of aggregation until 4 or 5 and generally not until several more hours have elapsed. When however a leaf becomes quickly inflected in water, as sometimes happens, especially during very warm weather, aggregation may occur in little over 1 hr. In all cases leaves left in water for more than 24 hrs. have their glands blackened, which shows that their contents are aggregated ; and in the specimens which were carefully examined, there was fairly well-marked aggregation in the upper cells of the pedicels. These trials were made with cut-off leaves, and it occurred to me that this circumstance might influence the result, as the footstalks would not perhaps absorb water quickly enough to supply the glands as they continued to secrete.

But this view was proved erroneous, for a plant with uninjured roots, bearing four leaves, was submerged in distilled water for 4.7 hrs., and the glands were blackened, though the tentacles were very little inflected. In one of these leaves there was only a slight degree of aggregation in the tentacles; in the second rather more, the purple contents of the cells being a little separated from the walls ; in the third and fourth, which were pale leaves, the aggregation in the upper parts of the pedicels was well marked. In these leaves the little masses of proto- plasm, many of which were oval, slowly changed their forms and positions so that a submergence for 47 hrs. had not killed the protoplasm. In a previous trial with a submerged plant^ the tentacles were not in the least indected.

Heat induces aggregation. A leaf, with the cells of the tentacles containing only homogeneous fluid, was waved about for 1 m. in water at 130° Fahr. (54°'4 Cent.), and was then examined under the microscope as quickly as possible, that is in 2 m. or 3 m. ; and by this time the contents of the cells had undergone some degree of aggregation. A second leaf was waved for 2 m. in water at 125° (510>6 Cent.) and quickly examined as before ; the tentacles were well inflected ; the purple fluid in all the cells had shrunk a little from the walls, and contained many oval and elongated masses of protoplasm, with a few minute spheres. A third leaf was left in water at 125°, until it cooled, and when examined after 1 hr. 45 m., the inflected tentacles showed some aggregation, which became after 3 hrs. more strongly marked, but did not subsequently increase. Lastly, a leaf was waved for 1 m. in water at 12CP (48°'8 Cent.) and then left for 1 hr. 26 m. in cold water ; the tentacles were but little inflected, and there was only here and there a trace of aggregation. In all these and other trials with warm water the protoplasm showed much less tendency to aggregate into spherical masses than when excited by car- bonate of ammonia.

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

could be seen filled with purple fluid, without a vestige of aggregated protoplasm ; the whole having been redissolved. A leaf with aggregated masses, caused by its having been waved for 2 m. in water at the temperature of 125° 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 wras still somewhat aggre- gated. Another leaf, with the contents of all the cells strongly aggregated from the action of a weak solution of phosphate of ammonia, was left for between three and four days in a mixture (known to be innocuous) of one drachm of alcohol to eight drachms of water, and when re-examined every trace of aggre- gation had disappeared, the cells being now filled with homo- geneous fluid.

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

As most of the stimulants which cause the inflection of the tentacles likewise induce aggregation in the contents of their cells, this latter process might be thought to be the direct result of inflection ; but this is not the case. If leaves are placed in rather strong solutions of carbonate of ammonia, for instance of three or four, and even sometimes of only two grains to the ounce of water (i.e. one part to 109, or 146, 01 218, of water), the tentacles are paralysed, and do not become inflected, yet they soon exhibit strongly marked aggregation. Moreover, the short central tentacles of a leaf which has been immersed in a weak solution of any salt of ammonia, or in any nitrogenous organic fluid, do not become in the least inflected; nevertheless they exhibit all the pheno- mena of aggregation. On the other hand, several acids cause strongly pronounced inflection, but no aggregation.

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