91 the capture, but a true digestive fluid | found in the contraction of muscle; and poured out, like our own gastric juice such a manifestation we possibly have after the ingestion of food. Dionæa. also in the contraction of the leaf of known to be accompanied by certain The contraction of muscle is well electrical phenomena. When we place a fragment of muscle in connection with a delicate galvanometer, we find that between the outside surface and a cut what is called the electro-motive force of surface there is a definite current, due to the muscle. Now, when the muscle is made to contract, this electro-motive force the galvanometer, deflected before, swings back towards the point of rest; there is what is called a negative variation. All students of the vegetable side of organized nature were astonished to hear from Dr. Sanderson that certain experiments which, at the instigation of Mr. Darwin, he had made, proved to demonstration that when a leaf of Dionæa contracts, the effects produced are precisely similar to those which occur when muscle contracts. For another generation the history of this wonderful plant stood still; but in 1868 an American botanist, Mr. Canby, who is happily still engaged in botanical research while staying in the Dionæa district,, studied the habits of the plant pretty carefully, especially the points which Dr. Curtis had made out. first idea was that "the leaf had the powHis er of dissolving animal matter, which was then allowed to flow along the somewhat trough-like petiole to the root, thus fur-momentarily disappears. The needle of nishing the plant with highly nitrogenous food." By feeding the leaves with small pieces of beef, he found, however, that these were completely dissolved and absorbed; the leaf opening again with a dry surface, and ready for another meal, though with an appetite somewhat jaded. He found that cheese disagreed horribly with the leaves, turning them black, and finally killing them. Finally, he details the useless struggles of a curculio to escape, as thoroughly establishing the fact that the fluid already mentioned is actually secreted, and is not the result of the decomposition of the substance which the leaf has seized. The curculio, being of a resolute nature, attempted to eat his way out -"when discovered he was still alive, and had made a small hole through the side of the leaf, but was evidently becoming very weak. On opening the leaf, the fluid was found in considerable quantity around him, and was without doubt gradually overcoming him. The leaf being again allowed to close upon him, he soon died." of digestion in this wonderful plant like Not merely, then, are the phenomena those of animals, but the phenomena of contractility agree with those of animals also. district in the New World, but distributDrosera.- Not confined to ed over the temperate parts of both hema single ispheres, in sandy and marshy places, are the curious plants called Sundews the species of the genus Drosera. They are now known to be near congeners of Dionæa, a fact which was little more than I am about to describe were first disguessed at when the curious habits which covered. At the meeting of this Association last year, Dr. Burdon-Sanderson made a communication, which, from its remarkable character, was well worthy of the singu- sons - one an Englishman, the other a Within a year of each other, two perlar history of this plant; one by no German means closed yet, but in which his ob-hairs which every one notices on the leaf observed that the curious servations will head a most interesting of Drosera were sensitive. chapter. It is a generalization - now almost a a Derbyshire botanist, gives of what his This is the account which Mr. Gardom, household word— that all living things friend Mr. Whateley, "an eminent Lonhave a common bond of union in a sub- don surgeon," made out in 1785 : — “On stance always present where life man-inspecting some of the contracted leaves ifests itself which underlies all their we observed a small insect or fly very details of structure. This is called closely imprisoned therein, which occaprotoplasm. One of its most distinctive sioned some astonishment as to how it properties is its aptitude to contract; and happened to get into so confined a situawhen in any given organism the particles tion. of protoplasm are so arranged that they centrically pressing with a pin other Afterwards, on Mr. Whateley's act as it were in concert, they produce a leaves yet in their natural and expanded cumulative effect which is very manifest form, we observed a remarkably sudden in its results. Such a manifestation island elastic spring of the leaves, so as to become inverted upwards, and, as it were, encircling the pin, which evidently showed the method by which the fly came into its embarrassing situation." This must have been an account given from memory, and represents the movement of the hairs as much more rapid than it really is. In July of the preceding year (though the account was not published till two years afterwards), Roth, in Germany, had remarked in Drosera rotundifolia and longifolia, "that many leaves were folded together from the point towards the base, and that all the hairs were bent like a bow, but that there was no apparent change on the leaf-stalk." Upon opening these leaves, he says, "I found in each a dead insect; hence I imagined that this plant, which has some resemblance to the Dionea muscipula might also have a similar moving power. Mr. Darwin found that the hairs on the leaf of Drosera responded to a piece of muscle or other animal substance, while to any particle of inorganic matter they were nearly indifferent. To minute fragments of carbonate of ammonia they were more responsive. Own I will now give the results of Mrs. Treat's experiments, in her words: : "Fifteen minutes past ten I placed bits of raw beef on some of the most vigorous leaves of Drosera longifolia. Ten minutes past twelve two of the leaves had folded around the beef, hiding it from sight. Half-past eleven on the same day, I placed living flies on the leaves of D. longifolia. At twelve o'clock and forty-eight minutes, one of the leaves had folded entirely round its victim, and the other leaves had partially folded, and the flies had ceased to struggle. By "With a pair of pliers I placed an ant half-past two, four leaves had each folded upon the middle of the leaf of D. rotun-around a fly. The leaf folds from the difolia, but not so as to disturb the plant. The ant endeavoured to escape, but was held fast by the clammy juice at the points of the hairs, which was drawn out by its feet into fine threads. In some minutes the short hairs on the disc of the leaf began to bend, then the long hairs, and laid themselves upon the insect. After a while the leaf began to bend, and in some hours the end of the leaf was so bent inwards as to touch the base. The ant died in fifteen minutes, which was before all the hairs had bent themselves." These facts, established nearly a century ago by the testimony of independent observers, have up to the present time been almost ignored; and Trecul, writing in 1855, boldly asserted that the facts were not true. More recently, however, they have been repeatedly verified in Germany by Nilschke, in 1855; in America by a lady, Mrs. Treat, of New Jersey, in 1871; in this country by Mr. Darwin, and also by Mr. A. W. Bennett. To Mr. Darwin, who for some years past has had the subject under investigation, we are indebted, not merely for the complete confirmation of the facts attested by the earliest observers, but also for some additions to those facts which are extremely important. The whole investigation still awaits publication at his hands, but some of the points which were established have been announced by Professor Asa Gray in America, to whom Mr. Darwin had communicated them. apex to the petiole, after the manner of its vernation. I tried mineral substances, bits of dried chalk, magnesia, and pebbles. In twenty-four hours neither the leaves nor the bristles had made any move in clasping these articles. I wetted a piece of chalk in water, and in less than an hour the bristles were curving about it, but soon unfolded again, leaving the chalk free on the blade of the leaf." Time will not allow me to enter into further details with respect to Dionæa and Drosera. The repeated testimony of various observers spreads over a century, and though at no time warmly received, must, I think, satisfy you that in this small family of the Droseracea we have plants which in the first place capture animals for purposes of food, and in the second, digest and dissolve them by means of a fluid which is poured out for the purpose; and thirdly, absorb the solution of animal matter which is so produced. Before the investigations of Mr. Darwin had led other persons to work at the subject, the meaning of these phenomena was very little appreciated. Only a few years ago, Duchartre, a French physiological botanist, after mentioning the views of Ellis and Curtis with respect to Dionæa, expressed his opinion that the idea that its leaves absorbed dissolved animal substances was too evidently in d sagreement with our knowledge of the function of leaves and the whole course of vegetable nutrition to deserve being seriously discussed. Perhaps if the Droseracea were an isolated case of a group of plants exhibiting propensities of this kind, there might be some reason for such a criticism. But I think I shall be able to show you that this is by no means the case. We have now reason to believe that there are many instances of these carnivorous habits in different parts of the vegetable kingdom, and among plants which have nothing else in common but this. As another illustration I shall take the very curious group of Pitcher-plants which is peculiar to the New World. And here also I think we shall find it most convenient to follow the historical order in the facts. has been commemorated in the name of the genus, by Tournefort. The first fact which was observed about the pitchers was, that when they grew they contained water. But the next fact which was recorded about them was curiously mythical. Perhaps Morrison, who is responsible for it, had no favourable opportunities of studying them, for he declares them to be, what is by no means really the case, intolerant of cultivation (respuere culturam videntur). He speaks of the lid, which in all the species is tolerably rigidly fixed, as being furnished, by a special act of providence, with a hinge. This idea was adopted by Linnæus, and somewhat amplified by succeeding writers, who declared that in dry Sarracenia. The genus Sarracenia weather the lid closed over the mouth, consists of eight species, all similar in and checked the loss of water by evapo. habit, and all natives of the Eastern ration. Catesby, in his fine work on the States of North America, where they are Natural History of Carolina, supposed found more especially in bogs, and even that these water-receptacles might "serve in places covered with shallow water. as an asylum or secure retreat for numerTheir leaves, which give them a charac-ous insects, from frogs and other animals ter entirely their own, are pitcher-shaped or trumpet-like, and are collected in tufts springing immediately from the ground; and they send up at the flowering season one or more slender stems bearing each a solitary flower. This has a singular aspect, due to a great extent to the umbrella-like expansion in which the style terminates; the shape of this, or perhaps of the whole flower, caused the first English settlers to give to the plant the name of Side-saddle Flower. which feed on them;" and others followed Linnæus in regarding the pitchers as reservoirs for birds and other animals, more especially in times of drought; "præbet aquam sitientibus aviculis.” The superficial teleology of the last century was easily satisfied without looking far for explanations, but it is just worth while pausing for a moment to observe that, although Linnæus had no materials for making any real investigation as to the purpose of the pitchers of Sarracenias, he very sagaciously anticipated the modern views as to their affinities. They are now regarded as very near allies of water-lilies - precisely the position which Linnæus assigned to them in his fragmentary attempt at natural classification. And besides this, he also suggested the analogy, which, improbable as it may seem at first sight, has been worked out in detail by Baillon (in apparent ignorance of Linnæus's writings) between the leaves of Sarracenia and water-lilies. a true Sarracenia purpurea is the best known species. About ten years ago it enjoyed an evanescent notoriety from the fact that its rootstock was proposed as a remedy for small-pox. It is found from Newfoundland southward to Florida, and is fairly hardy under open-air cultivation in the British Isles. At the commencement of the seventeenth century, Clusius published a figure of it, from a sketch which found its way to Lisbon and thence to Paris. Thirty years later Johnson copied this in his edition of Gerard's Herbal, hoping "that some or other that travel Linnæus seems to have supposed that into foreign parts may find this elegant Sarracenia was originally aquatic in its plant, and know it by this small expres- habits, that it had Nymphæa-like leaves, sion, and bring it home with them, so and that when it took to a terrestrial life that we may come to perfecter knowl-its leaves became hollowed out, to conedge thereof." A few years afterwards tain the water in which they could no this wish was gratified. John Tradescant longer float-in fact, he showed himself the younger found the plant in Virginia, to be an evolutionist of the true Darwinand succeeded in bringing it home alive to ian type. England. It was also sent to Paris from Catesby's suggestion was a very infe Quebec by Dr. Sarrazin, whose memory | licitous one. The insects which visit these plants may find in them a retreat, but it is one from which they never return. Linnæus's correspondent Collinson remarked in one of his letters that "many poor insects lose their lives by being drowned in these cisterns of water; " but William Bartram, the son of the botanist, seems to have been the first to put on record, at the end of the last century, the fact that Sarracenias catch insects and put them to death in the wholesale way that they do. Before stopping to consider how this is actually achieved, I will carry the history a little further. In the two species in which the mouth is unprotected by the lid it could not be doubted that a part, at any rate, of the contained fluid was supplied by rain. But in Sarracenia variolaris, in which the lid closes over the mouth, so that rain cannot readily enter it, there is no doubt that a fluid is secreted at the bottom of the pitchers, which probably has a digestive function. William Bartram, in the preface to his travels in 1791, described this fluid, but he was mistaken in supposing that it acted as a lure. There is a sugary secretion which attracts insects, but this is only found at the upper part of the tube. Bartram must be credited with the suggestion, which he, however, only put forward doubtfully, that the insects were dissolved in the fluid, and then became available for the alimentation of the plants. Sir J. E. Smith, who published a figure and description of Sarracenia variolaris, noticed that it secreted fluid, but was content to suppose that it was merely the gaseous products of the decomposition cf insects that subserved the processes of vegetation. In 1829, however, thirty years after Bartram's book, Burnett wrote a paper containing a good many original ideas expressed in a somewhat quaint fashion, in which he very strongly insisted on the existence of a true digestive process in the case of Sarracenia, analogous to that which takes place in the stomach of an animal. Our knowledge of the habits of Sarracenia variolaris is now pretty complete, owing to the observations of two South Carolina physicians. One, Dr. M'Bride, made his observations half a century ago, but they had, till quite recently, completely fallen into oblivion. He devoted himself to the task of ascertaining why it was that Sarracenia variolaris was visited by flies, and how it was that it captured them. This is what he ascertained. "The cause which attracts flies is evidently a viscid substance resembling honey, secreted by or exuding from the internal surface of the tube. From the margin, where it commences, it does not extend lower than one-fourth of an inch. The falling of the insect as soon as it enters the tube is wholly attributable to the downward or inverted position of the hairs of the internal surface of the leaf. At the bottom of a tube split open, the hairs are plainly discernible, pointing downwards; as the eye ranges upward they gradually become shorter and attenuated, til at or just below the surface covered by the bait they are no longer perceptible to the naked eye, nor to the most delicate touch. It is here that the fly cannot take a hold sufficiently strong to support itself, but falls.” Dr. Mellichamp, who is now resident in the district in which Dr. M'Bride made his observations, has added a good many particulars to our knowledge. He first investigated the fluid which is secreted at the bottom of the tubes. He satisfied himself that it was really secreted, and describes it as mucilaginous, but leaving in the mouth a peculiar astringency. He compared the action of this fluid with that of distilled water on pieces of fresh venison, and found that after fifteen hours the fluid had produced most change, and also most smell; he therefore concluded that as the leaves when stuffed with insects become most disgusting in odour, we have to do, not with a true digestion, but with an accelerated decomposition. Although he did not attribute any true digestive power to the fluid secreted by the pitchers, he found that it had a remarkable anæsthetic effect upon flies immersed in it. He remarked that "a fly when thrown into water is very apt to escape, as the fluid seems to run from its wings," but it never escaped from the Sarracenia secretion. About half a minute after being thrown in, the fly became to all appearance dead, though, if removed, it gradually recovered in from half an hour to an hour. According to Dr. Mellichamp, the sugary lure discovered by Dr. M'Bride, at the mouth of the pitchers, is not found on either the young ones of one season or the older ones of the previous year. He found, however, that about May it could be detected without difficulty, and more wonderful still, that there is a honeybaited pathway leading directly from the ground to the mouth, along the broad wing of the pitcher, up which insects are led to their destruction. From these! 4. A detentive surface, which occupies narratives it is evident that there are two the lower part of the pitcher, in some very different types of pitcher in Sarra- cases for nearly its whole length. It cenia, and an examination of the species possesses no cuticle, and is studded with shows that there may probably be three. deflexed, rigid, glass-like, needle-formed, These may be primarily classified into striated hairs, which further converge those with the mouth open and lid erect, towards the axis of the diminishing cavand which consequently receive the rain-ity; so that an insect, if once amongst water in more or less abundance; and them, is effectually detained, and its those with the mouth closed by the lid, struggles have no other result than to into which rain can hardly, if at all, find wedge it lower and more firmly in the ingress. pitcher. To the first of these belongs the wellknown S. purpurea, with inclined pitchers, and a lid so disposed as to direct all the rain that falls upon it also into the pitcher; also S. flava, rubra, and Drummondii, all with erect pitchers and vertical lids; of these three, the lid in a young state arches over the mouth, and in an old state stands nearly erect, and has the sides so reflected that the rain which falls on its upper surface is guided down the outside of the back of the pitcher, as if to prevent the flooding of the latter. To the second group belong S. psittacina and S. variolaris. Now, it is a very curious thing that in S. purpurea, which has an open pitcher, so formed as to receive and retain a maximum of rain, no honey-secretion has hitherto been found, nor has any water been seen to be secreted in the pitcher; it is, further, the only species in which (as stated above) I have found a special glandular surface, and in which no glands occur on the detentive surface. This concurrence of circumstances suggests the possibility of this plant either having no proper secretion of its own, or only giving it off after the pitcher has been filled with rain-water. In S. flava, which has open-mouthed The tissues of the internal surfaces of pitchers and no special glandular surface, the pitchers are singularly beautiful. I find glands in the upper portion of the They have been described in one species detentive surface, among the hairs, but only, the S. purpurea, by August Vogl; not in the middle or lower part of the but from this all the other species which same surface. It is proved that S. flava I have examined differ materially. Be- secretes fluid, but under what precise ginning from the upper part of the pitch-conditions I am not aware. I have found er, there are four surfaces, characterized by different tissues, which I shall name and define as follows: 1. An attractive surface, occupying the inner surface of the lid, which is covered with an epidermis, stomata, and (in common with the mouth of the pitcher) with minute honey-secreting glands; it is further often more highly coloured than any other part of the pitcher, in order to attract insects to the honey. none but what may have been accidentally introduced in the few cultivated specimens which I have examined, either in the full-grown state, or in the half-grown when the lid arches over the pitcher. I find the honey in these as described by the American observers, and honey-secreting glands on the edge of the wing of the pitcher, together with similar glands on the outer surface of the pitcher, as seen by Vogl in S. purpurea. 2. A conducting surface, which is Of the pitchers with closed mouths, I opaque, formed of glassy cells, which have examined those of S. variolaris are produced into deflexed, short, coni-only, whose tissues closely resemble cal, spinous processes. These processes, those of S. flava. That it secretes a overlapping like the tiles of a house, fluid noxious to insects there is no doubt, form a surface down which an insect though in the specimens I examined I slips, and affords no foothold to an insect found none. attempting to crawl up again. There is thus obviously much still to 3. A glandular surface (seen in S. pur-be learned with regard to Sarracenia, purea), which occupies a considerable and I hope that American botanists will portion of the cavity of the pitcher be- apply themselves to this task. It is not low the conducting surface. It is formed probable that three pitchers, so differof a layer of epidermis with sinuous ently constructed as those of S. flava, cells, and is studded with glands; and purpurea, and variolaris, and presenting being smooth and polished, this too af- such differences in their tissues, should fords no foothold for escaping insects. act similarly. The fact that insects nor |