Insectivorous Plants

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

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

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

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

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

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

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

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

(10) After 38 m. twenty-one tentacles inflected; after 3 hrs. 12 m. forty-six tentacles inflected or sub-inflected; after 6 hrs. 40 m. all but seventeen inflected, though none closely; after 24 hrs. every tentacle slightly curved inwards; after 27 hrs. 40 m. blade strongly inflected, and so continued for two days, and then the tentacles and blade very slowly re-expanded.

(11) This fine dark red and rather old leaf, though not very large, bore an extraordinary number of tentacles (viz. 252), and behaved in an anomalous manner. After 6 hrs. 40 m. only the short tentacles round the outer part of the disc were inflected, forming a ring, as so often occurs in from 8 to 24 hrs. With leaves both in water and the weaker solutions. But after 9 hrs. 40 m. all the outer tentacles except twenty-five were inflected; as was the blade in a strongly marked manner. After 24 hrs. every tentacle except one was closely inflected, and the blade was completely doubled over. Thus the leaf remained for two days, when it began to re-expand. I may add that the three latter leaves (Nos. 9, 10, and 11) were still somewhat inflected after three days. The tentacles in but few of these eleven leaves became closelyinflected within so short a time as in the previous experiments with stronger solutions.

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

Of the leaves in the solution, the glands on leaf No. 1, which in 2 hrs. had all its tentacles except eight inflected, were counted and found to be 202. Subtracting the eight, each gland could have received only the 1/1552000 grain (.0000411 mg.) of the phosphate. Leaf No. 9 had 213 tentacles, all of which, with the exception of four, were inflected after 24 hrs., but none of them closely; the blade was also inflected; each gland could have received only the 1/1672000 of a grain, or .0000387 mg. Lastly, leaf No. 11, which had after 24 hrs. all its tentacles, except one, closely inflected, as well as the blade, bore the unusually large number of 252 tentacles; and on the same principle as before, each gland could have absorbed only the 1/2008000 of a grain, or .0000322 mg.

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

Four leaves were immersed as before, each in thirty minims of a solution of one part to 328,125 of water (1 gr. to 750 oz.). Each leaf thus received 1/12000 of a grain (.0054 mg.) of the salt; and all four were greatly inflected.

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

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

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

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

Of the four corresponding leaves in water: —

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

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

(3) and (4) Not affected, except that, as usual, after 11 hrs. the short tentacles on the borders of the disc formed a ring.

There can, therefore, be no doubt about the efficiency of the above solution; and it follows as before that each gland of No. 1 could have absorbed only 1/2412000 of a grain (.0000268 mg.) and of No. 2 only 1/2460000 of a grain (.0000263 mg.) of the phosphate.

Seven leaves were immersed, each in thirty minims of a solution of one part to 437,500 of water (1 gr. to 1000 oz.). Each leaf thus received 1/16000 of a grain (.00405 mg.). The day was warm, and the leaves were very fine, so that all circumstances were favourable.

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

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

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

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

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

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

(7) After 4 hrs. 30 m. only thirty-five tentacles inflected or sub-inflected, and this small amount of inflection never increased.

Now for the seven corresponding leaves in water: —

(1) After 4 hrs. thirty-eight tentacles inflected; but after 7 hrs. these, with the exception of six, re-expanded.

(2) After 4 hrs. 20 m. twenty inflected; these after 9 hrs. partially re-expanded.

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

(4) After 24 hrs. one inflected.

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

A comparison of the leaves in the solution, especially of the first five or even six on the list, with those in the water, after 1 hr. or after 4 hrs., and in a still more marked degree after 7 hrs. or 8 hrs., could not leave the least doubt that the solution had produced a great effect. This was shown not only by the vastly greater number of inflected tentacles, but by the degree or closeness of their inflection, and by that of their blades. Yet each gland on leaf No. 1 (which bore 255 glands, all of which, excepting five, were inflected in 30 m.) could not have received more than one-four-millionth of a grain (.0000162 mg.) of the salt. Again, each gland on leaf No. 3 (which bore 233 glands, all of which, except nine, were inflected in 2 hrs. 30 m.) could have received at most only the 1/3584000 of a grain, or .0000181 mg.

Four leaves were immersed as before in a solution of one part to 656,250 of water (1 gr. to 1500 oz.); but on this occasion I happened to select leaves which were very little sensitive, as on other occasions I chanced to select unusually sensitive leaves. The leaves were not more affected after 12 hrs. than the four corresponding ones in water; but after 24 hrs. they were slightly more inflected. Such evidence, however, is not at all trustworthy.

Twelve leaves were immersed, each in thirty minims of a solution of one part to 1,312,500 of water (1 gr. to 3000 oz.); so that each leaf received 1/48000 of a grain (.00135 mg.). The leaves were not in very good condition; four of them were too old and of a dark red colour; four were too pale, yet one of these latter acted well; the four others, as far as could be told by the eye, seemed in excellent condition. The result was as follows: —

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

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

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

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

(5) to (12) These were not more inflected than leaves often are in water, having respectively 16, 8, 10, 8, 4, 9, 14, and 0 tentacles inflected. Two of these leaves, however, were remarkable from having their blades slightly inflected after 6 hrs.

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

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

Of the leaves in the solution, No. 1 bore 200 glands and received 1/48000 of a grain of the salt. Subtracting the seventeen tentacles which were not inflected, each gland could have absorbed only the 1/8784000 of a grain (.00000738 mg.). This amount caused the tentacle bearing each gland to be greatly inflected. The blade was also inflected.

Lastly, eight leaves were immersed, each in thirty minims of a solution of one part of the phosphate to 21,875,000 of water (1 gr. to 5000 oz.). Each leaf thus received 1/80000 of a grain of the salt, or .00081 mg. I took especial pains in selecting the finest leaves from the hot-house for immersion, both in the solution and the water, and almost all proved extremely sensitive. Beginning as before with those in the solution: —

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