A. Christin Bag, Gult beigagade Kjwbenhave. e a INSECTIVOROUS PLANTS. WORKS BY THE SAME AUTHOR. A NATURALIST’S JOURNAL OF RESEARCHES INTO THE NATURAL HISTORY AND GEOLOGY oF COUNTRIES VISITED during a VOYAGE Rouxd THE WorLD. Eighteenth Thousand. Woodcuts. MURRAY. THE ORIGIN OF SPECIES BY MEANS OF NATURAL SELECTION; or, THE PRESERVATION OF FAVOURED RACES IN THE STRUGGLE For Lire. Thirty-third Thousand. Woodcuts. Large Type Edition. 2 vols, Crown 8vo., 12s. Cheap Edition, 6s. MURRAY. THE VARIOUS CONTRIVANCES BY WHICH ORCHIDS ARE FERTILIZED BY INSECTS. Fourth Thousand. bere 7s. 6d. Murray. THE VARIATION OF ANIMALS AND PLANTS UNDER DOMESTICATION. Sixth Thousand. Illustrations. 15s. MURRAY. THE DESCENT OF MAN, AND SELECTION IN RELA- TION TO SEX. Twenty-first Thousand, Illustrations. Large Type Edition. 2 vols. Crown 8vo., 15s. Cheap Edition, 7s. 6d. Murray. THE EXPRESSION OF THE EMOTIONS IN MAN AND ANIMALS. Ninth Thousand, Illustrations. Murray. INSECTIVOROUS PLANTS. Fifth Thousand. 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A MONOGRAPH OF THE FOSSIL LEPADIDÆ, OR PEDUNCULATED CIRRIPEDS OF GREAT BRITAIN. PALÆONTOGRAPHICAL SOCIETY. A MONOGRAPH OF THE FOSSIL BALANIDÆ AND VERRUCIDE OF GREAT BRITAIN. PALÆONTOGRAPHICAL SOCIETY. FACTS AND ARGUMENTS FOR DARWIN. By Frirz MÜLLER, From the German, with Additions by the Author. Translated by W, S. Darras, F.L.S, Illustrations. 6s, MUBRAY. INSECTIVOROUS PLANTS. By CHARLES DARWIN, M.A. F.R.S, ETC. SECOND EDITION REVISED BY FRANCIS DARWIN. WITH ILLUSTRATIONS. Mo. Bot, Garden, 1893 LONDON: JOHN MURRAY, ALBEMARLE STREET. 1888. The right of Translation is reser ved, LONDON: PRINTED BY WILLIAM CLOWES AND SONS, Limirep, STAMFORD STREET AND CHARING CROSS. PREFACE TO THE SECOND EDITION. Ix the present Edition I have not attempted to give a complete account of the progress of the subject since 1875. Nor have I called attention to those passages occurring occasionally throughout the book wherein the Author makes use of explanations, illustrations, or reference to authorities which seem to me not perfectly satisfactory. I have merely wished to indicate the more important points brought to light by recent research. The additions are In some cases placed in the text, but they are more commonly given as footnotes. They are, in all cases, indicated by means of square brackets. Misprints, errors in numbers, &c., have been set right, and a few verbal corrections have been taken from Charles Darwin’s copy of the First Edition. Otherwise the text remains unchanged. Francis DARWIN. CAMBRIDGE, July, 1888. CONTENTS. CHAPTER I. DROSERA ROTUNDIFOLIA, OR THE COMMON SuN-DEW. Number of insects captured—Description of the leaves and their appendages or tentacles—Preliminary sketch of the action of the various parts, and of the manner in which insects are captured— Duration of the inflection of the tentacles—Nature of the secretion —Manner in which insects are carried to the centre of the leaf— Evidence that the glands have the power of absorption—Small size Of the roots 12 4. 5s te eek Pages 1-17 CHAPTER II. Tue MOVEMENTS oF THE TENTACLES FROM THE CONTACT oF SOLID Bovigs. Inflection of the exterior tentacles owing to the glands of the disc being excited by repeated touches, or by objects left in contact with them—Difference in the action of bodies yielding and not yielding soluble nitrogenous matter— Inflection of the exterior tentacles directly caused by objects left in contact with their glands —Periods of commencing inflection and of subsequent re-expansion Extreme minuteness of the particles causing inflection —Action under water—Inflection of the exterior tentacles when their glands are excited by repeated touches—Falling drops of water do not cause inflection be ps a ee a 18-31 CHAPTER III. AGGREGATION OF THE PROTOPLASM WITHIN THE CELLS OF THE TENTACLES. Nature of the contents of the cells before aggregation—Various causes oo” 7O which excite aggregation—The process commences within the vili CONTENTS. glands and travels down the tentacles—Description of the aggregated masses and of their spontaneous movements—Currents of protoplasm along the walls of the cells—Action of carbonate of ammonia—The granules in the protoplasm which flows along the walls coalesce with the central ‘masses—Minuteness of the quantity of carbonate of ammonia causing aggregation—Action of other salts of ammonia —Of other substances, organic fluids, &e.—Of water—Of heat— Redissolution of the aggregated masses—Proximate causes of the aggregation of the protoplaam—Summary and concluding remarks —Supplementary observations on aggregation in the roots of pante. o we ve Oe ee i, ee CHAPTER IV. THe EFFECTS oF HEAT oN THE LEAVES. Nature of the experiments—Effects of boiling water—Warm water causes rapid inflection—Water at a higher temperature does not cause immediate inflection, but does not kill the leaves, as shown by their subsequent re-expansion and by the aggregation of the protoplasm—A still higher temperature kills the leaves and coagu- lates the albuminous contents of the glands Bias 56-63 CHAPTER V. Tue EFFECTS or NoN-NITROGENOUS AND NITROGENOUS ORGANIC FLUIDS oN THE LEAVES. Non-nitrogenous fluids—Solutions of gum arabic—Sugar—Starch— Diluted alcohoi—Olive oil—Infusion and decoction of tea—Nitro- genous fluids—Milk—Urine—Liquid albumen—lInfusion of raw meat—Impure mucus—Saliva—Solution of isinglass—Difference in the action of these two sets of fluids—Decoction of green peas— Decoction and infusion of cabbage—Decoction of grass leaves 64-70 CHAPTER VI. THE DIGESTIVE POWER OF THE SECRETION OF Drosera. The secretion rendered acid by the direct and indirect excitement of the glands—Nature of the acid—Digestible substances—Albumen, its digestion arrested by alkalies, recommences by the addition of an acid—Meat—Fibrin—Syntonin—Areolar _ tissue—Cartilage— Fibro-cartilage—Bone—Enamel and dentine—Phosphate of lime— Fibrous basis of bone—Gelatine—Chondrin—Milk, casein and cheese — Gluten — Legumin — Pollen — Globulin — Hematin — CONTENTS. ix Indigestible substances — Epidermic productions — Fibro-elastic tissue—M ucin—Pepsin— Urea—Chitine—Cellulose—Gun-cotton — Chlorophyll—Fat and oil—Starch—Action of the secretion on living seeds—Summary and concluding remarks Pages 71-110 CHAPEBReViIE Tne EFFECTS oF SALTS oF AMMONIA. Manner. of performing the experiments—Action of distilled water in comparison with the solutions—Carbonate of ammonia, absorbed by the roots—The vapour absorbed by the glands—Drops on the disc—Minute drops applied to separate glands—Leaves immersed i ; in weak solutions—Minuteness of the doses which induce aggrega- l tion of the protoplasm—Nitrate of ammonia, analogous experiments with—Phosphate of ammonia, analogous experiments with—Other salts of ammonia—Summary and concluding remarks on the action bate CF MORIA o n a ae e ee ee CHAPTER VIII. y THE EFFECTS OF VARIOUS OTHER SALTS, AND ACIDS, ON THE LEAVES. Salts of sodium, potassium, and other alkaline, earthy, and metallic salts—Summary on the action of these salts—Various acids— unitary on their action .: e : > : - - 100 194:4 Total calculated weight of seed . . . 100 319:7 Total calculated number of seeds . : 100 241:5 These results show clearly enough that insectivorous plants derive great advantage from animal food. It is of interest to note that the most striking difference between the two sets of plants is seen in what relates to reproduction— i.e. in the flower-stems, the capsules, and the seeds. After cutting off the flower-stems, three sets of plants were allowed to rest throughout the winter, in order to test (by a comparison of spring-growth) the amounts of reserve material accumulated during the summer. Both starved and fed plants were kept without food until April 3rd, when it was found that the average weights per plant were 100 for the starved, 213:0 for the fed. This proves that the fed plants had laid by a far greater store of reserve material in spite of having produced nearly four times as much seed. In Kellermann and Von Raumer’s experiments (loc. cit.) aphides were used as food instead of meat—a method which adds greatly to the value of their results. Their conclusions are similar to my own, and they show that not only is the seed production of the fed plants greater, but they also form much heavier winter-buds than the starved plants. Dr. M. Büsgen has more recently published an interesting paper* on the same subject. His experiments have the * “ Die Bedeutung des Insectfanges für Drosera rotundifolia (L.),” ‘Bot. Zeitung, 1883. Cuar. I] ACTION OF THE PARTS. yi advantage of having been made on young Droseras grown from seed, The unfed plants are thus much more effectually starved than in experiments on full-grown plants possessing already a store of reserve matter. It is therefore not to be wondered at that Biisgen’s results are more striking than Kellermann’s and Von Raumer’s or my own—thus, for instance, he found that the “fed” plants, as compared with the starved ones, produced more than five times as many capsules, while my figures are 100: 194. Büsgen gives a good résumé of the whole subject, and sums up by saying that the demonstrable superiority of fed over unfed plants is great enough to render comprehensible the organisation of the plants with reference to the capture of insects.—F. D.] 18 DROSERA ROTUNDIFOLIA. [Cuap. II. CHAPTER IL. THE MOVEMENTS OF THE TENTACLES FROM THE CONTACT OF SOLID BODIES. Inflection of the exterior tentacles owing to the glands of the disc being excited by repeated touches, or by objects left in contact with them— Difference in the action of bodies yielding and not yielding soluble nitrogenous matter—Inflection of the exterior tentacles directly caused by objects left in contact with their glands—Periods of commencing inflection and of subsequent re-expansion—Extreme minuteness of the particles causing inflection—Action under water—Inflection of the ex- terior tentacles when their glands are excited by repeated touches— Falling drops of water do not cause inflection. I wit. give in this and the following chapters some of the many experiments made, which best illustrate the manner and rate of movement of the tentacles, when excited in various ways. The glands alone in all ordinary cases are susceptible to excitement. When excited they do not them- selves move or change form, but transmit a motor impulse to the bending part of their own and adjoining tentacles, and are thus carried towards the centre of the leaf. Strictly speaking, the glands ought to be called irritable, as the term sensitive generally implies consciousness; but no one supposes that the Sensitive-plant is conscious, and, as I have found the term convenient, I shall use it without scruple. I will commence with the movements of the exterior tentacles, when indirectly excited by stimulants applied to the glands of the short tentacles on the disc. The exterior tentacles may be said in this case to be indirectly excited, because their own glands are not directly acted on. The stimulus proceeding from the glands of the disc acts on the bending part of the exterior tentacles, near their bases, and does not (as will hereafter be proved) first travel up the pedicels to the glands, to be then reflected back to the bending place. Nevertheless, some influence does travel up to the glands, causing them to secrete more copiously, and the secretion to become acid. This latter fact is, I believe, quite new in the physiology of plants; it has indeed only recently been esta- blished that in the animal kingdom an influence can be trans- Cuar. IL] INFLECTION INDIRECTLY CAUSED. 19 mitted along the nerves to glands, modifying their power _ of secretion, independently of the state of the blood-vessels. The Inflection of the Exterior Tentacles from the Glands of the Disc being excited by Repeated Touches, or by Objects left in Contact with them. The central glands of a Jeaf were irritated with a small stiff camel-hair brush, and in 70 m. (minutes) several of the outer tentacles were inflected ; in 5 hrs. (hours) all the sub- marginal tentacles were inflected; next morning after an interval of about 22 hrs. they were fully re-expanded. In all the following cases the period is reckoned from the time of first irritation. Another leaf treated in the same manner had a few tentacles inflected in 20 m.; in 4 hrs. all the sub- marginal and some of the extreme marginal tentacles, as well as the edge of the leaf itself, were inflected; in 17 hrs. they had recovered their proper, expanded position. I then put a dead fly in the centre of the last-mentioned leaf, and next morning it was closely clasped; five days afterwards the leaf re-expanded, and the tentacles, with their glands surrounded by secretion, were ready to act again. Particles of meat, dead flies, bits of paper, wood, dried moss, sponge, cinders, glass, &c., were repeatedly placed on leaves, and these objects were well embraced in various periods from 1 hr. to as long as 24 hrs., and set free again, with the leaf fully re-expanded, in from one or two, to seven or even ten days, according to the nature of the object. On a leaf which had naturally caught two flies, and therefore had already closed and reopened either once, or more pro- bably twice, I put a fresh fly: in 7 hrs. it was moderately, and in 21 hrs. thoroughly well, clasped, with the edges of the leaf inflected. In two days and a half the leaf had nearly re-expanded; as the exciting object was an insect, this unusually short period of inflection was, no doubt, due to the leaf having recently been in action. Allowing this same leaf to rest for only a single day, I put on another fly, and it again closed, but now very slowly ; nevertheless, in less than two days it succeeded in thoroughly clasping the fly. When a small object is placed on the glands of the dise, on one side of a leaf, as near as possible to its circumference, the tentacles on this side are first affected, those on the opposite side much later, or, as often occurred, not at all. This was c 2 20 DROSERA ROTUNDIFOLIA. (Cuar. IL. repeatedly proved by trials with bits of meat ; but Iwill here give only the case of a minute fly, naturally caught and still alive, which I found adhering by its delicate feet to the glands on the extreme left side of the central disc. The marginal tentacles on this side closed inwards and killed the fly, and after a time the edge of the leaf on this side also became inflected, and thus remained for several days, whilst neither the tentacles nor the edge on the opposite side were in the least affected. If young and active leaves are selected, inorganic particles not larger than the head of a small pin, placed on the central glands, sometimes cause the outer tentacles to bend inwards. But this follows much more surely and quickly, if the object contains nitrogenous matter which can be dissolved by the secretion. On one occasion I observed the following unusual circumstance. Small bits of raw meat (which acts more energetically than any other substance), of paper, dried moss, and of the quill of a pen were placed on several leaves, and they were all embraced equally well in about 2 hrs. On other occasions the above-named substances, or more commonly particles of glass, coal-cinder (taken from the fire), stone, gold-leaf, dried grass, cork, blotting-paper, cotton-wool, and hair rolled up into little balls, were used, and these substances, though they were sometimes well embraced, often caused no movement whatever in the outer tentacles, or an extremely slight and slow movement. Yet these same leaves were proved to be in an active condition, as they were excited to move by substances yielding soluble nitrogenous matter, such as bits of raw or roast meat, the yolk or white of boiled eggs, fragments of insects of all orders, spiders, &c. I will give only two instances. Minute flies were placed on the discs of several leaves, and on others balls of paper, bits of moss and quill of about the same size as the flies, and the latter were well embraced in a few hours; whereas after 25 hrs. only a very few tentacles were inflected over the other objects. The bits of paper, moss, and quill were then removed from these leaves, and bits of raw meat placed on them; and now all the tentacles were soon energetically inflected. Again, particles of coal cinder (weighing rather more than the flies used in the last experiment) were placed on the centres of three leaves: after an interval of 19 hrs. one of the particles was tolerably well embraced; a second by a very tew tentacles; and a third by none. I then removed the aiiai te tia ital Nini ong Cuar. II] INFLECTION INDIRECTLY CAUSED. 21 particles from the two latter leaves, and put them on recently killed flies. These were fairly well embraced in 74 hrs. and thoroughly after 203 hrs.; the tentacles remaining inflected for many subsequent days. On the other hand, the one leaf which had in the course of 19 hrs. embraced the bit of cinder moderately well, and to which no fly was given, after an addi- tional 33 hrs. (i.e. in 52 hrs. from the time when the cinder was put on) was completely re-expanded and ready to act again. From these and numerous other experiments not worth giving, it is certain that inorganic substances, or such organic substances as are not attacked by the secretion, act much less quickly and efficiently than organic substances yielding soluble matter which is absorbed. Moreover, I have met with very few exceptions to the rule, and these exceptions apparently depended on the leaf having been too recently in action, that the tentacles remain clasped for a much longer time over organic bodies of the nature just specified than over those which are not acted on by the secretion, or over inorganic objects.* * Owing to the extraordinary be- lief held by M. Ziegler (‘Comptes rendus? May 1872, p. 122), that albuminous substances, if held for a moment between the fingers, acquire the property of making the tentacles of Drosera contract, whereas, if not thus held, they have no such power, I tried some experiments with great care, but the results did not confirm this belief. Red-hot cinders were taken out of the fire, and bits of ‘glass, cotton-thread, blotting paper and thin slices of cork were immersed in boiling water; and particles were then placed (every instrument with which they were touched having been previously immersed in boiling water) on the glands of several leaves, and they acted in exactly the same manner as other particles, which had been purposely handled for some time. Bits of a boiled egg, cut with a knife which had been washed in boiling water, also acted like any other animal substance. I breathed on some leaves for above a minute, and repeated the act two or three times, with my mouth close to them, but this produced no effect. I may here add, as showing that the leaves are not acted on by the odour of nitrogenous substances, that pieces of raw meat stuck on needles were fixed as close as possible, without actual contact, to several leaves, but pro- duced no effect whatever. On the other hand, as we shall hereafter see, the vapours of certain volatile sub- stances and fluids, such as of carbonate of ammonia, chloroform, certain es- sential oils, &c., cause inflection. M. Ziegler makes still more extra- ordinary statements with respect to the power of animal substances, which have been left close to, but not in contact with, sulphate of quinine. The action of salts of quinine will be described in a future chapter. Since the appearance of the paper above referred to, M. Ziegler has published a book on the same subject, entitled, ‘Atonicité et Zoicité,’ 1874. 29 DROSERA ROTUNDIFOLIA. [Cuar. II. The Inflection of the Exterior Tentacles as directly caused by Objects left in Contact with their Glands.* I made a vast number of trials by placing, by means of a fine needle moistened with distilled water, and with the aid of a lens, particles of various substances on the viscid secretion surrounding the glands of the outer tentacles. I experi- mented on both the oval and long-headed glands. When a particle is thus placed on a single gland, the movement of the tentacle is particularly well seen in contrast with the stationary condition of the surrounding tentacles. (See pre- vious fig. 6.) In four cases small particles of raw meat caused the tentacles to be greatly inflected in between 5 and 6 m. Another tentacle similarly treated, and observed with special care, distinctly, though slightly, changed its position in 10 s. (seconds); and this is the quickest movement seen by me. In 2 m. 30 s. it had moved through an angle of about 45°. * [The researches of Pfefer ( Unters. aus d. Bot. Institut zu Tiibingen,’ vol. i., 1885, p. 483) on the sensitiveness of various organs to contact show that the conclusions as to the sensitiveness of Drosera cannot be maintained in their present form (see p. 24). Pfeffer shows, both in the case of the tendrils of climbing plants, and also in ‘that of the tentacles of Drosera, that uniform pressure has no stimulating action: the effect which is ascribed simply to contact is in reality due to unequal compres- sion of closely neighbouring points. Tendrils which move after having been rubbed with a light stick fail to be stimulated when they are rubbed with a glass rod coated with gelatine. The gelatine has the same uniformity of action as drops of water falling on the tendril, which are known to produce no effect. If the gelatine is sprinkled with fine particles of sand, or if the water holds particles of clay in suspension, stimulation results. Analogous ex- periments were made on Drosera (p-511). It was found impossible to produce movement of the tentacles by rubbing the glands with a surface of mercury, whereas by rubbing or repeated touches with solid bodies movement is called forth. Other experiments of Pfeffer’s show con- clusively that continuous uniform pressure has no stimulating effect. He placed small globules of glass om the glands, and convinced himself that, by examination with a lens, that contact was affected. Some of the tentacles moved, but the majority showed no movement, as long as the plants were so placed that no vibration from the table or floor could reach then. When they were exposed to vibration, and when, therefore, the glass globules must have rubbed against or jarred the gland, the tentacles moved. The results de- tailed above in the text must pre- sumably be set down to the same cause, namely, the vibration of the table and floor. The sensitiveness of Drosera, therefore, by no means ceases to be astonishing, Instead of believ- ing in movements caused by the steady pressure of very small weights, we set down the results as being due to the jarring of the gland by these same minute bodies.—F, D.J is an Cuar. IL.) INFLECTION INDIRECTLY CAUSED. 20 The movement as seen through a lens resembled that of the hand of a large clock. In 5m. it had moved through 90°, and when I looked again after 10 m., the particle had reached the centre of the leaf; so that the whole movement was completed in less than 17 m. 30s. In the course of some hours this minute bit of meat, from having been brought into contact with some of the glands of the central disc, acted centrifugally on the outer tentacles, which all became closely inflected. Fragments of flies were placed on the glands of four of the outer tentacles, extended in the same plane with that of the blade, and three of these fragments were carried in 35 m. through an angle of 180° to the centre. The fragment on the fourth tentacle was very minute, and it was not carried to the centre until 3 hrs. had elapsed. In three other cases minute flies or portions of larger ones were carried to the centre in 1 hr. 30 s. In these seven cases, the fragments or small flies, which had been carried. by a single tentacle to the central glands, were well em- braced by the other tentacles after an interval of from 4 to 10 hrs. I also placed in the manner just described six small balls of writing paper (rolled up by the aid of pincers, so that they were not touched by my fingers) on the glands of six exterior tentacles on distinct leaves; three of these were carried to the centre in about 1 hr., and the other three in rather more than 4 hrs.; but after 24 hrs. only two of the six balls were well embraced by the other tentacles. It is possible that the secretion may have dissolved a trace of glue or animalised matter from the balls of paper. Four particles of coal-cinder were then placed on the glands of tour exterior tentacles; one of these reached the centre in 3 hrs. 40 m.; the second in 9 hrs.; the third within 24 hrs., but had moved only part of the way in 9 hrs.; whilst the fourth moved only a very short distance in 24 hrs., and never moved any farther. Of the above three bits of cinder which were ultimately carried to the centre, one alone was well embraced by many of the other tentacles. We here see clearly that such bodies as particles of cinder or little balls of paper, after being carried by the tentacles to the central glands, act very differently from fragments of flies, in causing the movement of the surrounding tentacles. I made, without carefully recording the times of move- ment, many similar trials with other substances, such as 24 DROSERA ROTUNDIFOLIA. (Cuar. I. splinters of white and blue glass, particles of cork, minute bits of gold-leaf, &c.; and the proportional number of cases varied much in which the tentacles reached the centre, or moved only slightly, or not at all. One evening, particles of glass and cork, rather larger than those usually employed, were placed on about a dozen glands, and next morning, after 13 hrs., every single tentacle had carried its little load to the centre; but the unusually large size of the particles will account for this result. Im another case £ of the particles of cinder, glass, and thread, placed on separate glands, were carried towards, or actually to, the centre ; in another case 7, in another >, and in the last case only sẹ were thus carried inwards, the small proportion being here due, at least in part, to the leaves being rather old and inactive. Occasionally a gland, with its light load, could be seen through a strong lens to move an extremely short distance and then stop; this was especially apt to occur when excessively minute particles, much less than those of which the measurements will be immediately given, were placed on glands; so that we here have nearly the limit of any action. I was so much surprised at the smallness of the particles which caused the tentacles to become greatly inflected that it seemed worth while carefully to ascertain how minute a particle would plainly act. Accordingly, measured lengths of a narrow strip of blotting-paper, of fine cotton-thread, and of a woman’s hair, were carefully weighed for me by Mr. Trenham Reeks, in an excellent balance, in the laboratory in Jermyn Street. Short bits of the paper, thread, and hair were then cut off and measured by a micrometer, so that their weights could be easily calculated. The bits were placed on the viscid secretion surrounding the glands of the exterior tentacles, with the precautions already stated, and I am certain that the gland itself was never touched; nor indeed would a single touch have produced any effect. A bit of the blotting-paper, weighing l5 of a grain, was placed so as to rest on three glands together, and all three tentacles slowly curved inwards; each gland, therefore, supposing the weight to be distributed equally, could have been pressed on by only qyz of a grain, or -0464 of a milli- gram. Five nearly equal bits of cotton-thread were tried, and all acted. The shortest of these was =), of an inch in length, and weighed ,,'5; of a grain. The tentacle in this | PRAA in Cuar. II] INFLECTION INDIRECTLY CAUSED. 25 case was considerably inflected in 1 hr. 30 m., and the bit of thread was carried to the centre of the leaf in 1 hr. 40 m. Again, two particles of the thinner end of a woman’s hair, one of these being +385 of an inch in length, and weighing 35714 Of a grain, the other ,}?,5 of an inch in length, and weighing of course a little more, were placed on two glands on opposite sides of the same leaf, and these two tentacles were inflected halfway towards the centre in 1 hr. 10 m.; all the many other tentacles round the same leaf remaining motionless. The appearance of this one leaf showed in an unequivocal manner that these minute particles sufficed to cause the tentacles to bend. Altogether, ten such particles of hair were placed on ten glands on several leaves, and seven of them caused the tentacles to move in a conspicuous manner. The smallest particle which was tried, and which acted plainly, was only +o‘ of an inch (+203 millimeter) in length, and weighed the ş}4y of a grain, or *000822 milligram. In these several cases, not only was the inflection of the tentacles conspicuous, but the purple fluid within their cells became aggregated into little masses of protoplasm, in the manner to be described in the next chapter ; and the aggregation was so plain that I could, by this clue alone, have readily picked out under the microscope ‘all the tentacles which had carried their light loads towards the centre, from the hundreds of other tentacles on the same leaves which had not thus acted. My surprise was greatly excited, not only by the minute- ness of the particles which caused movement, but how they could possibly act on the glands; for it must be remembered that they were laid with the greatest care on the convex surface of the secretion. At first I thought—but, as I now know, erroneously—that particles of such low specific gravity as those of cork, thread, and paper, would never come into contact with the surfaces of the glands. The particles cannot act simply by their weight being added to that of the secretion, for small drops of water, many times heavier than the particles, were repeatedly added, and never produced any effect. Nor does the disturbance of the secre- tion produce any effect, for long threads were drawn out by a needle, and affixed to some adjoining object, and thus left for hours; but the tentacles remained motionless. I also carefully removed the secretion from four glands with a sharply pointed piece of blotting-paper, so that they 26 DROSERA ROTUNDIFOLIA. [CHar. II. were exposed for a time naked to the air, but this caused no movement; yet these glands were in an efficient state, for, after 24 hrs. had elapsed, they were tried with bits of meat, and all became quickly inflected. It then occurred to me that particles floating on the secretion would cast shadows on the glands which might be sensitive to the interception of the light. Although this seemed highly improbable, as minute and thin splinters of colourless glass acted power- fully, nevertheless, after it was dark, I put on, by the aid of a single tallow candle, as quickly as possible, particles of cork and glass on the glands of a dozen tentacles, as well as some of meat on other glands, and covered them up so that not a ray of light could enter; but by the next morning, after an interval of 13 hrs., all the particles were carried to the centres of the leaves. These negative results led me to try many more experi- ments, by placing particles on the surface of the drops of secretion, observing, as carefully as I could, whether they penetrated it and touched the surface of the glands. The secretion, from its weight, generally forms a thicker layer on the under than on the upper sides of the glands, whatever may be the position of the tentacles. Minute bits of dry cork, thread, blotting-paper, and coal-cinders were tried, such as those previously employed ; and I now observed that they absorbed much more of the secretion, in the course of a few minutes, than I should have thought possible; and as they had been laid on the upper surface of the secretion, where it is thinnest, they were often drawn down, after a time, into contact with at least some one point of the gland. With respect to the minute splinters of glass and particles of hair, I observed that the secretion slowly spread itself a little over their surfaces, by which means they were likewise drawn downwards or sideways, and thus one end, or some minute prominence, often came to touch, sooner or later, the gland. In the foregoing and following cases, it is probable that the vibrations, to which the furniture in every room is continually liable, aids in bringing the particles into contact with the glands. But as it was sometimes difficult, owing to the refractich of the secretion, to feel sure whether the particles were in contact, I tried the following experiment. Unusually minute particles of glass, hair, and cork were gently placed on the drops round several glands, and very Cuar. II] INFLECTION INDIRECTLY CAUSED. a few of the tentacles moved. ‘Those which were not affected were left for about half an hour, and the particles were then disturbed or tilted up several times with a fine needle under the microscope, the glands not being touched. And now in the course of a few minutes almost all the hitherto motion- less tentacles began to move; and this, no doubt, was caused by one end or some prominence of the particles having come into contact with the surface of the glands. But, as the particles were unusually minute, the movement was small. Lastly, some dark blue glass pounded into fine splinters was used, in order that the points of the particles might be better distinguished when immersed in the secretion; and thirteen such particles were placed in contact with the depending and therefore thicker part of the drops round so many glands. Five of the tentacles began moving after an interval of a few minutes, and in these cases I clearly saw that the particles touched the lower surface of the gland. A sixth tentacle moved after 1 hr. 45 m., and the particle was now in contact with the gland, which was not the case at first. So it was with the seventh tentacle, but its movement did not begin until 3 hrs. 45 m. had elapsed. The remaining six tentacles never moved as long as they were observed ; and the particles apparently never came into contact with the surfaces of the glands. From these experiments we learn that particles not con- taining soluble matter, when placed on glands, often cause the tentacles to begin bending in the course of from one to five minutes ; and that in such cases the particles have been from the first in contact with the surfaces of the glands. When the tentacles do not begin moving for a much longer time, namely, from half an hour to three or four hours, the particles have been slowly brought into contact with the glands either by the secretion being absorbed by the particles or by its gradual spreading over them, together with its consequent quicker evaporation. When the tentacles do not move at all, the particles have never come into contact with the glands, or in some cases the tentacles may not have been in an active condition. In order to excite movement, 1t 1s indispensable that the particles should actually rest on the glands; for a touch once, twice, or even thrice repeated by any hard body, is not sufficient to excite movement. Another experiment, showing that extremely minute par- ticles act on the glands when immersed in water, may here 28 DROSERA ROTUNDIFOLIA. [Cuar II be given. A grain of sulphate of quinine was added to an ounce of water, which was not afterwards filtered; and, on placing three leaves in ninety minims of this fluid, I was much surprised to find that all three leaves were greatly inflected in 15 m. : for I knew from previous trials that the solution does not act so quickly as this. It immediately occurred to me that the particles of the undissolved salt, which were so light as to float about, might have come into contact with the glands, and caused this rapid movement. Accord- ingly I added to some distilled water a pinch of a quite inno- cent substance, namely, precipitated carbonate of lime, which consists of an impalpable powder; I shook the mixture, and thus got a fluid like thin milk. Two leaves were immersed in it, and in 6 m. almost every tentacle was much inflected. I placed one of these leaves under the microscope, and saw innumerable atoms of lime adhering to the external surface of the secretion. Some, however, had penetrated it, and were lying on the surfaces of the glands; and no doubt it was these particles which caused the tentacles to bend. When a leaf is immersed in water, the secretion instantly swells much; and I presume that it is ruptured here and there, so that little eddies of water rush in. If so, we can understand how the atoms of chalk, which rested on the surfaces of the glands, had penetrated the secretion. Any one who has rubbed precipitated chalk between his fingers will have perceived how excessively fine the powder is. No doubt there must be a limit, beyond which a particle would be too small to act on a gland; but what this limit is I know not. I have often seen fibres and dust, which had fallen from the air, on the glands of plants kept in my room, and these never induced any movement; but then such particles lay on the surface of the secretion and never reached the gland itself. Finally, it is an extraordinary fact that a little bit of soft thread, 5 of an inch in length and weighing yyy of a grain, or of a human hair, oog of an inch in length and weighing only ys+şy Of a grain (-000822 milligram), or particles of precipitated chalk, after resting for a short time on a gland, should induce some change in its cells, exciting them to transmit a motor impulse throughout the whole length of the pedicel, consisting of about twenty cells, to near its base, causing this part to bend, and the tentacle to sweep through an angle of above 180°. That the contents of the cells of the Cuar. Il.] THE EFFECTS OF REPEATED TOUCHES. 29 glands, and afterwards those of the pedicels, are affected in a plainly visible manner by the pressure of minute particles, we shall have abundant evidence when we treat of the aggregation of the protoplasm. But the case is much more remarkable than as yet stated; for the particles are supported by the viscid and dense secretion; nevertheless, even smaller ones than those of which the measurements have been given, when brought by an insensibly slow movement, through the means above specified, into contact with the surface of a gland, act on it, and the tentacle bends. The pressure exerted by the particle of hair, weighing only +ş}yy ofa grain and supported by a dense fluid, must have been inconceivably slight. We may conjecture that it could hardly have equalled the millionth of a grain; and we shall hereafter see that far less than the millionth of a grain of phosphate of ammonia in solution, when absorbed by a gland, acts on it and induces movement. A bit of hair, -ly of an inch in length, and there- fore much larger than those used in the above experiments, was not perceived when placed on my tongue; and it is extremely doubtful whether any nerve in the human body, even if in an inflamed condition, would be in any way affected by such a particle supported in a dense fluid, and slowly brought into contact with the nerve. Yet the cells of the glands of Drosera are thus excited to transmit a motor impulse to a distant point, inducing movement. It appears to me that hardly any more remarkable fact than this has been observed in the vegetable kingdom. The Inflection of the Exterior Tentacles, when their Glands are excited by Repeated Touches. We have already seen that, if the central glands are excited by being gently brushed, they transmit a motor impulse to the exterior tentacles, causing them to bend; and we have now to consider the effects which follow from the glands of the exterior tentacles being themselves touched. On several occasions, a large number of glands were touched only once with a needle or fine brush, hard enough to bend the whole flexible tentacle; and, though this must have caused a thousand-fold greater pressure than the weight of the above-described particles, not a tentacle moved. On another occasion forty-five glands on eleven leaves were touched once, twice, or even thrice, with a needle or stifti 30 DROSERA ROTUNDIFOLIA. (Cuar. ID. bristle. This was done as quickly as possible, but with force sufficient to bend the tentacles ; yet only six of them became inflected,—three plainly, and three in a slight degree. In order to ascertain whether these tentacles which were not affected were in an efficient state, bits of meat were placed on ten of them, and they all soon became greatly incurved. On the other hand, when a large number of glands were struck four, five, or six times with the same force as before, a needle or sharp splinter of glass being used, a much larger proportion of tentacles became inflected; but the result was so uncertain as to seem capricious. For instance, I struck in the above manner three glands, which happened to be extremely sensitive, and all three were inflected almost as quickly as if bits of meat had been placed upon them. On another occasion I gave a single forcible touch to a consider- able number of glands, and not one moved; but these same glands, after an interval of some hours, being touched four or five times with a needle, several of the tentacles soon became inflected. The fact of a single touch or even of two or three touches not causing inflection must be of some service to the plant; as, during stormy weather, the glands cannot fail to be occasionally touched by the tall blades of grass, or by other plants growing near; and it would be a great evil if the tentacles were thus brought into action, for the act of re- expansion takes a considerable time, and until the tentacles are re-expanded they cannot catch prey. On the other hand, extreme sensitiveness to slight pressure is of the highest service to the plant; for, as we have seen, if the delicate feet of a minute struggling insect press ever so lightly on the surfaces of two or three glands, the tentacles bearing these glands soon curl inwards and carry the insect with them to the centre, causing, after a time, all the circum- ferential tentacles to embrace it. Nevertheless, the move- ments of the plant are not perfectly adapted to its require- ments; for if a bit of dry moss, peat, or other rubbish, is blown on to the disc, as often happens, the tentacles clasp it in a useless manner. They soon, however, discover their mistake and release such innutritious objects. It is also a remarkable fact, that drops of water falling from a height, whether under the form of natural or artificial rain, do not cause the tentacles to move; yet the drops must strike the glands with considerable force, more especially IRAE Cbs, eria Cuar. I.] THE EFFECTS OF REPEATED TOUCHES. Əl after the secretion has been all washed away by heavy rain; and this often occurs, though the secretion is so viscid that it can be removed with difficulty merely by waving the leaves in water. If the falling drops of water are small, they adhere to the secretion, the weight of which must be increased in a much greater degree, as before remarked, than by the. addition of minute particles of solid matter; yet the drops never cause the tentacles to become inflected. It would obviously have been a great evil to the plant (as in the case of occasional touches) if the tentacles were excited to bend by every shower of rain; but this evil has been avoided by the glands either having become through habit insensible to the blows and prolonged pressure of drops of water, or to their having been originally rendered sensitive solely to the contact of solid bodies.* We shall hereafter see that the filaments on the leaves of Dionza are likewise insensible to the impact of fluids, though exquisitely sensitive to momen- tary touches from any solid body. When the pedicel of a tentacle is cut off by a sharp pair of scissors quite close beneath the gland, the tentacle generally becomes inflected. I tried this experiment repeatedly, as I was much surprised at the fact, for all other parts of the pedicels are insensible to any stimulus. These headless tentacles after a time re-expand; but I shall return to this subject. On the other hand, I occasionally succeeded in crushing a gland between a pair of pincers, but this caused no inflection. In this latter case the tentacles seem paralysed, as likewise follows from the action of too strong solutions of certain salts, and of too great heat, whilst weaker solutions of the same salts and a more gentle heat cause movement. We shall also see in future chapters that various other fluids, some vapours, and oxygen (after the plant has been for some time excluded from its action), all induce inflection, and this likewise results from an induced galvanic current.f * [Pfeffer’s experiments, given move; but that, if similar needles in above (p. 22), explain the failure of connection with the secondary coil of a Du Bois induction apparatus are inserted, the tentacles curve inwards in the course of a few minutes. My son hopes soon to publish an account of his observations. rain to cause movement.—F. D.] + My son Francis, guided by the observations of Dr. Burdon Sanderson on Dionæa, finds that, if two needles are inserted into the blade of a leaf of Drosera, the tentacles do not DROSERA ROTUNDIFOLIA. [Cuar. II. CHAPTER III. AGGREGATION OF THE PROTOPLASM WITHIN THE CELLS OF THE TENTACLES. Nature of the contents of the cells before aggregation—Various causes which excite aggregation—The process commences within the glands and travels down the tentacles—Description of the aggregated masses and of their spontaneous movements—Currents of protoplasm along the walls of the cells—Action of carbonate of ammonia—The granules in the protoplasm which flows along the walls coalesce with the central masses—Minuteness of the quantity of carbonate of ammonia causing aggregation— pe i pee E eE Cuap. V] EFFECTS OF ORGANIC FLUIDS. 67 was converted into a cup. The power of urine does not lie in the urea, which, as we shall hereafter see, is inoperative. Albumen (fresh from a hen’s egg), placed on seven leaves, caused the tentacles of six of them to be well inflected. In one case the edge of the leaf itself became much curled in after 20 hrs, The one leaf which was unaffected remained so for 26 hrs., and was then treated We a drop of milk, and this caused the tentacles to bend inwards in 12 hrs. Cold Filtered Infusion of Raw Meat.—This was tried only ona single leaf, which had most of its outer tentacles and the blade inflected in 19 hrs, During subsequent years I repeatedly used this infusion to test leaves which had been experimented on with other substances, and it was found to act most energetically, but as no exact account of these trials was kept, they are not here introduced. Mucus.—Thick and thin mucus from the bronchial tubes, placed on three leaves, caused inflection. A leaf with thin mucus had its marginal tentacles and blade somewhat curved inwards in 5 hrs. 80 m. and greatly so in 20 hrs. The action of, this fluid no doubt is due either to the saliva or to some albuminous matter* mingled with it, and not, as we shall see in the next chapter, to mucin or the chemical principle of mucus. Saliva.—Human saliva, when evaporated, yieldst from 1°14 te 1°19 per cent. of residue; and this yields 0°25 per cent. of ashes, so that the proportion of nitrogenous matter which saliva contains must be small. Nevertheless, drops placed on the discs of eight leaves acted on them all. In one case all the exterior tentacles, excepting nine, were inflected in 19 hrs. 30 m.; in another case a few became so in 2 hrs., and after 7 hrs. 80 m. all those situated near where the drop lay, as well as the blade, were acted on, Since making these trials, I have many scores of times just touched the glands with the handle of my scalpel wetted with saliva, to ascertain whether a leaf was in an active condition ; for this was shown in the course of a few minutes by the bending inwards of the tentacies. The edible nest of the Chinese swallow is formed of matter secreted by the salivary glands; two grains were added to one ourice of distilled water (one part to 218), which was boiled for several minutes, but did not dissolve the whole. The usual-sized drops were placed on three leaves, and these in 1 hr. 30 m. were well, and in 2 hrs. 15 m. closely, inflected. Isinglass.—Drops of a solution about as thick as milk, and of a still thicker solution, were placed on eight leaves, and the tentacles of all became inflected. In one case the exterior tentacles were well curved in after 6 hrs. 30 m., and the blade of the leaf to a partial extent after 24 hrs. As saliva acted so efficiently, and yet contains so small a proportion of nitrogenous matter, I tried how small a quantity cf * Mucus from the air-passages is some albumen. said in Marshall, ‘Outlines of Physi- t Miiller’s ‘ Elements of Physiology,’ ology,’ vol. ii. 1867, p. 364, to contain Eng. Trans. vcl. i. p. 514. F 2 68 DROSERA ROTUNDIFOLIA. [Cuar. V. isinglass would act. One part was dissolved in 218 parts of distilled water, and drops were placed on four leaves. After 5 hrs. two of these were considerably and two moderately inflected; after 22 hrs. the former were greatly and the latter much more inflected. In the course of 48 hrs. from the time when the drops were placed on the leaves, atl four had almost re-expanded. They were then given little bits of meat, and these acted more powerfully than the solution. One part of isinglass was next dissolved in 437 of water; the fluid thus formes was so thin that it could not be distinguished from pure water. The usual-sized drops were placed on seven leaves, each of which thus received 51, of a grain (*0295 mg.). Three of them were observed for 41 hrs., but were in no way affected; the fourth and fifth had two or three of their exterior tentacles inflected after 18 hrs.; the sixth had a few more; and the seventh had in addition the edge of the leaf just perceptibly curved inwards. The tertacles of the four latter leaves began to re-expand after an additional interval of only 8 hrs. Hence the 515 of a grain of isinglass is sufficient to affect very slightly the more sensitive or active leaves. On one of the leaves, which had not been acted on by the weak solution, and on another, which had only two of its tentacles inflected, drops of the solution as thick as milk were placed ; and next morning, after an interval of 16 hrs., both were found with all their tentacles strongly inflected. Altogether I experimented on sixty-four leaves with the above nitrogenous fluids, the five leaves tried only with the extremely weak solution of isinglass not being included, nor the numerous trials subsequently made, of which no exact account was kept. Of these sixty-four leaves, sixty- three had their tentacles and often their blades well inflected. The one which failed was probably too old and torpid. But to obtain so large a proportion of successful cases, care must be taken to select young and active leaves. Leaves in this condition were chosen with equal care for the sixty-one trials with non-nitrogenous fluids (water not included) ; and we have seen that not one of these was in the least affected. We may therefore safely conclude that in the sixty-four experiments with nitrogenous fluids the inflection of the exterior tentacles was due to the absorption of nitro- genous matter by the glands of the tentacles on the disc. Some of the leaves which were not affected by the non- nitrogenous fluids were, as above stated, immediately after- wards tested with bits of meat, and were thus proved to be in an active condition. But in addition to these trials, twenty-three of the leaves, with drops of gum, syrup, or starch, still lying on their discs, which had produced no effect — es Cuar. V.] EFFECTS OF ORGANIC FLUIDS. 69 in the course of between 24 hrs. and 48 hrs., were then tested with drops of milk, urine, or albumen. Of the twenty- three leaves thus treated, seventeen had their tentacles, and in some cases their blades, well inflected ; but their powers were ;somewhat impaired, for the'rate of movement was decidedly slower than when fresh leaves were treated with these same nitrogenous fluids. This impairment, as well as the insensibility of six of the leaves, may be attributed to injury from exosmose, caused by the density of the fluids placed on their discs. The results of a few other experiments with nitrogenous fluids may be here conveniently given. Decoctions of some vegetables known to be rich in nitrogen, were made, and these acted like animal fluids. Thus, a few green peas were boiled for some time in distilled water, and the moderately thick decoction thus made was allowed to settle. Drops of the superincumbent fluid were placed on four leaves, and when these were looked at after 16 hrs., the tentacles and blades of all were found strongly inflected. I infer from a remark by Gerhardt* that legumin is present in peas “in combination with an alkali, forming an incoagulable solution,” and this would mingle with boiling water. I may mention, in relation to the above and following experiments, that according to Schifff certain forms of albumen exist which are not coagulated by boiling water, but are converted into soluble peptones. On three occasions chopped cabbage leaves f were boiled in distilled water for 1 hr. or for 1} hr. ; and by decanting the decoction after it had been allowed to rest, a pale dirty green fluid was obtained. The usual- sized drops were placed on thirteen leaves. Their tentacles and blades were inflected after 4 hrs. to a quite extraordinary degree. Next day the protoplasm within the cells of the tentacles was found aggregated in the most strongly-marked manner, 1 also touched the viscid secretion round the glands of several tentacles with minute drops of the decoction on the head of a small pin, and they became well inflected in a few minutes. The fluid proving so powerful, one part was diluted with three of water, and drops were placed on the discs of five leaves; and these next morning were so much acted on that their blades were completely doubled over. We thus see that a decoction of cabbage leaves is nearly or quite as potent as an infusion of raw meat. * Watts’ ‘Dict. of Chemistry,’ before the heart is formed, such as vol. iii. p. 568, were used by me, contain 2'1 per t ‘Leçons sur la Phys. de la Di- cent. of albuminous matter, and the gestion,’ tom. i. p. 379; tom. ii. pp. outer leaves of mature plants 1°6 154, 166, on legumin, per cent. Watts’ ‘ Dict. of Chemistry, + The leaves of young plants, vol. i. p. 653. 70 DROSERA ROTUNDIFOLIA. (Cuar. V About the same quantity of chopped cabbage leaves and of distilled water as in the last experiment, were kept in a vessel for 20 hrs. in a hot closet, but not heated to near the boiling point. Drops of this infusion were placed on four leaves. One of these, after 23 hrs., was much inflected; a second slightly; a third had only the submarginal tentacles inflected ; and the fourth was not at all affected. The power of this infusion is therefore very much less than that of the decoction ; and it is clear that the immersion of cabbage leaves for an hour in water at the boiling temperature is much more efficient in extracting matter which excites Drosera than immersion during many hours in warm water. Perhaps the contents of the cells are protected (as Schiff remarks with respect to legumin) by the walls being formed of cellulose, and that until these are ruptured by boiling-water, but little of the contained albuminous matter is dissolved. We know from the strong odour of cooked cabbage leaves that boiling-water produces some chemical change in them, and that they are thus rendered far more digestible and nutritious to man. It is therefore an interesting fact that water at this temperature extracts matter from them which excites Drosera to an extraordinary degree. Grasses contain far less nitrogenous matter than do peas or cabbages. The leaves and stalks of three common kinds were chopped and boiled for some time in distilled water. Drops of this decoction (after having stood for 24 hrs.) were placed on six leaves, and acted in a rather peculiar manner, of which other instances will be given in the seventh chapter on the salts of ammonia. After 2 hrs. 30 m. four of the leaves had their blades greatly inflected, but not their exterior tentacle ; and so it was with all six leaves after 24 hrs. Two days afterwards the blades, as well as the few submarginal tentacles which had been inflected, all re-expanded; and much of the fluid on their discs was by this time absorbed. It appears that the decoction strongly excites the glands on the disc, causing the blade to be quickly and greatly inflected ; but that the stimulus, differently from what occurs in ordinary cases, does not spread, or only in a feeble degree, to the exterior tentacles. I may here add that one part of the extract of belladonna (procured from a druggist) was dissolved in 437 of water, and drops were placed on six leaves. Next day all six were somewhat inflected, and after 48 hrs. were completely re-expanded. It was not the included atropine which produced this effect, for I subsequently ascertained that it is quite powerless. I also procured some extract of hyoscyamus from three shops, and made infusions of the same strength as before. Of these three infusions, only one acted on some of the leaves, which were tried. Though druggists believe that all the albumen is precipi- tated in the preparation of these drugs, I cannot doubt that some is occasionally retained ; and a trace would be sufficient to excite the more sensitive leaves of Drosera. erate TAA Cuar. VL] DIGESTION. 71 CHAPTER VI. THE DIGESTIVE POWER OF THE SECRETION OF DROSERA. The secretion rendered acid by the direct and indirect excitement of the glands—Nature of the acid—Digestible substances—Albumen, its diges- tion arrested by alkalies, recommences by the addition of an acid—Meat —Fibrin—Syntonin—Areolar tissue—Cartilage — Fibro-cartilage — Bone —Enamel and dentine—Phosphate of lime—Fibrous basis of bone— Gelatine—Chondrin —Milk, casein and cheese—Gluten—Legumin-—Pollen —Globulin—Hematin—lIndigestible substances — Epidermic productions —Fibro-elastic tissue—Mucin—Pepsin—Urea—Chitine—Cellulose—Gun- cotton—Chlorophyll—Fat and oil—Starch—Action of the secretion on living seeds—Summary and concluding remarks. As we have seen that nitrogenous fluids act very differ- ently on the leaves of Drosera from non-nitrogenous fluids, and as the leaves remain clasped for a much longer time over various organic bodies than over inorganic bodies, such as bits of glass, cinder, wood, &c., it becomes an interesting inquiry, whether they can only absorb matter already in solution, or render it soluble,—that is, have the power of digestion. We shall immediately see that they certainly have this power, and that they act on albuminous compounds in exactly the same manner as does the gastric juice of mam- mals; the digested matter being afterwards absorbed. This fact, which will be clearly proved, is a wonderful one in the physiology of plants. I must here state that I have been aided throughout all my later experiments by many valuable suggestions and assistance given me with the greatest kind- ness by Dr. Burdon Sanderson. It may be well to premise for the sake of any reader who knows nothing about the digestion of albuminous compounds by animals that this is effected by means ofa ferment, pepsin, together with weak hydrochloric acid, though almost any acid will serve. Yet neither pepsin nor an acid by itself has any such power.* We have seen that when the * It appears, however, according a very minute quantity of coagulated to Schiff, and contrary to the opinion albumen. Schiff, ‘Phys. de la Di- of some physiologists, that weak hy- gestion, 1867, tom. ii. p. 25. drochloric dissolves, though slowly, 72 DROSERA ROTUNDIFOLIA. [Cuar. VI. glands of the disc are excited by the contact of any object, especially of one’ containing nitrogenous matter, the outer tentacles and often the blade become inflected; the leaf being thus converted into a temporary cup or stomach. At the same time the discal glands secrete * more copiously, and the secretion becomes acid. Moreover, they transmit some influence to the glands of the exterior tentacles, causing them to pour forth a more copious secretion, which also becomes acid or more acid than it was before. As this result is an important one, I will give the evidence. The secretion of many glands on thirty leaves, which had not been in any way excited, was tested with litmus paper ; and the secretion of twenty-two of these leaves did not in the least affect the colour, whereas that of eight caused an exceedingly feeble and sometimes doubtful tinge of red. Two other old leaves, however, which appeared to have been inflected several times, acted much more decidedly on the paper. Particles of clean glass were then placed on five of the leaves, cubes of albumen on six, and bits of raw meat on three, on none of which was the secretion at this time in the least acid. After an interval of 24 hrs., when almost all the tentacles on these fourteen leaves had become more or less inflected, T again tested the secretion, selecting glands which had not as yet reached the centre or touched any object, and it was now plainly acid. The degree of acidity of the secretion varied somewhat on the glands of the same leaf. On some leaves, a few tentacles did not, from some unknown cause, become inflected as often happens; and in five in- stances their secretion was found not to be in the least acid ; whilst the secretion of the adjoining and inflected tentacles on the same leaf was decidedly acid. With leaves excited by particles of glass placed on the central glands, the secretion which collects on the disc beneath them was much more strongly acid than that poured forth from the exterior tentacles, which were as yet only moderately inflected. When bits of albumen (and this is naturally alkaline), or bits of meat were placed on the disc, the secretion collected beneath them was likewise strongly acid. As raw meat * [In the ‘ Proceedings of the Royal ing secretion, and gives evidence that Society,’ 1886, No. 240, Gardiner has the secretion results from the break described the changes which go on in ing downof the protoplasmic reti- the glands of Drosera dichotoma dur- culum of the gland-cell.—F. D.] egg gt ne eaman ncn Cuar. VI] DIGESTION, 73 moistened with water is slightly acid, I compared its action on litmus paper before it was placed on the leaves, and afterwards when bathed in the secretion; and there could not be the least doubt that the latter was very much more acid. I have indeed tried hundreds of times the state of the secretion on the discs of leaves which were inflected over various objects, and never failed to find it acid. We may, therefore, conclude that the secretion from unexcited leaves, though extremely viscid, is not acid or only slightly so, but that it becomes acid, or much more strongly so, after the tentacles have begun to bend over any inorganic or organic object; and still more strongly acid after the tentacles have remained for some time closely clasped over any object. I may here remind the reader that the secretion appears to be to a certain extent antiseptic, as it checks the appearance of mould and infusoria, thus preventing for a time the discoloration and decay of such substances as the white of an egg, cheese, &c. It therefore acts like the gastric juice of the higher animals, which is known to arrest putrefaction by destroying the microzymes. As I was anxious to learn what acid* the secretion contained, 445 leaves were washed in distilled water, given me by Prof. Frankland ; but the secretion is so viscid that it is scarcely possible to scrape or wash off the whole. The conditions were also unfavourable, as it was late in the year and the leaves were small. Prof. Frankland with great kindness undertook to test the fluid thus collected. The leaves were excited by clean particles of glass placed on them 24 hrs. previously. No doubt much more acid would have been secreted had the leaves been excited by animal matter, but this would have rendered the analysis more difficult. Prof. Frankland informs me that the fluid contained no trace of hydrochloric, sulphuric, tartaric, oxalic, or formic acids. This having been ascertained, the remainder of the fluid was evaporated nearly to dryness, and acidified with sulphuric acid; it then evolved volatile acid vapour, which was condensed and Gorup * [Messrs Rees and Will (‘ Bot. Zeitung,’ 1875, p. 716) stimulated the glands of some thousand Drosera plants with glass-dust and analysed the secretion thus produced. They found a variety of fatty acids present, among which Formic acid was recog- nised with certainty, and Propionic and Butyric acids were suspected from the eyidence of the smell. and Will have shown that the neutral secretion of Nepenthes becomes power- fully digestive when acidulated with formic acid (see ‘ Bot. Zeitung,’ 1876, p- 476). It is therefore interesting to find this acid naturally present in the secretion of Drosera.—F.D.] T4 DROSERA ROTUNDIFOLIA. [Cuap. VI. digested with carbonate of silver. ‘The weight of the silver salt thus produced was only °37 gr., much too small a quantity for the accurate determination of the molecular weight of the acid. The number obtained, however, corresponded nearly with that of propionic acid ; and I believe that this, or a mixture of acetic and butyric acids, were present in the liquid. The acid doubtless belongs to the acetic or fatty series.” Prof. Frankland, as well as his assistant, observed (and this is an important fact) that the fluid, “when acidified with sulphuric acid, emitted a powerful odour like that of pepsin.” The leaves from which the secretion had been washed were also sent to Prof. Frankland; they were macerated for some hours, then acidified with sulphuric acid and distilled, but no acid passed over. Therefore the acid which fresh leaves contain, as shown by their discolouring litmus paper when crushed, must be of a different nature from that present in the secretion. Nor was any odour of pepsin emitted by them. Although it has long been known that pepsin with acetic acid has the power of digesting albuminous compounds, it appeared advisable to ascertain whether acetic acid could be replaced, without the loss of digestive power, by the allied acids which are believed to occur in the secretion of Drosera, namely, propionic, butyric, or valerianic. Dr. Burdon Sanderson was so kind as to make for me the following ex- periments, the results of which are valuable, independently of the present inquiry. Prof. Frankland supplied the acids. “1. The purpose of the following experiments was to determine the digestive activity of liquids containing pepsin, when acidulated with certain volatile acids belonging to the acetic series, in comparison with liquids acidulated with hydrochloric acid, in proportion similar to that in which it exists in gastric juice. “2. It has been determined empirically that the best results are obtained in artificial digestion when a liquid containing two per thousand of hydrochloric acid gas by weight is used. This corre- sponds to about 6°25 cubic centimetres per litre of ordinary strong hydrochloric acid. The quantities of propionic, butyric, and valerianic acids respectively which are required to neutralise as much base as 6°25 cubic centimetres of HCl, are in grammes 4°04 of propionic acid, 4°82 of butyric acid, and 5°68 of valerianic acid. It was therefore judged expedient, in comparing the digestive powers of these acids with that of hydrochloric acid, to use them in these proportions. “3. Five hundred cub. cent. of a liquid containing about 8 cub. cent. of a glycerine extract of the mucous membrane of the stomach of a dog killed during digestion having been prepared, 10 cub. cent. of it were evaporated and dried at 110°. This quantity yielded 0°0031 of residue. “4, Of this liquid four quantities were taken which were severally acidulated with hydrochloric, propionic, butyric, and valerianic acids, in the proportions above indicated. Each liquid was then placed in a tube, which was allowed to float in a water bath, containing a ther- einen apn RR ts pstncn Cuar. VL] DIGESTION. is mometer which indicated a temperature of 38° to 40° Cent. Into each, a quantity of unboiled fibrin was introduced, and the whole allowed to stand for four hours, the temperature being maintained during the whole time, and care being taken that each contained throughout an excess of fibrin. At the end of the period each liquid was filtered. Of the filtrate, which of course contained as much of the fibrin as had been digested during the four hours, 10 cub. cent. were measured out and evaporated, and dried at 110° as before. The residues were respectively— “ In the liquid containing hydrochloric acid 0°4079 propionic acid 0°0601 293 » 4 butyric acid 0°1468 > h valerianic acid 0:1254 “ Hence, deducting from each of these the above-mentioned residue, left when the digestive liquid itself was evaporated, viz. 0°0031, we have, “For propionic acid .. es 0:0570 sy Putyric add .. :: b ae 0:1437 „ Valerianic acid .. i ae ue 0°1223 as compared with 0°4048 for hydrochloric acid; these several numbers expressing the quantities of fibrin by weight digested in presence of equivalent quantities of the respective acids under identical conditions. “ The results of the experiment may be stated thus :—If 100 repre- sent the digestive power of a liquid containing pepsin with the usual proportion of hydrochloric acid, 14°0, 35°4, and 30:2, will represent respectively the digestive powers of the three acids under investigation. “5. Ina second experiment in which the procedure was in every respect the same, excepting that all the tubes were plunged into the same water-bath, and the residues dried at 115° C., the results were as follows :— “ Quantity of fibrin dissolved in four hours by 10 cub. cent. of the liquid— “Propionic acid .. 5 — 0:0563 Butyric acid = Ss 2 0:0835 Valerianic acid .. z 0:0615 “ The quantity digested by a similar liquid containing hydrochloric acid was 0:3376. Hence, taking this as 100, the following numbers represent the relative quantities digested by the other acids : “Propionic acid .. s> ef 16°5 Butyric acid. Ki F 24°7 Valerianic acid .. z$ A 16'1 “6, A third experiment of the same kind gave: 76 DROSERA ROTUNDIFOLIA. [Cuar. VI. “Quantity of fibrin digested in four hours by 10 cub. cent. of the liquid : “ Hydrochloric acid = me 0° 2915 Propionic acid .. ae 0:1490 Butyric acid -i z 0:1044 Valerianic acid .. oC oc 0:0520 “Comparing, as before, the three last numbers with the first taken as 100, the digestive power of propionic acid is represented by 16°8; that of butyric acid by 85°8; and that of valerianic by 17°8. “The mean of these three sets of observations (hydrochloric acid being taken as 100) gives for “Propionic acid... es z 15°8 Butyric acid - PS = 32°0 Valerianic acid .. es - 21°4 «7. A further experiment was made to ascertain whether the digestive activity of butyric acid (which was selected as being apparently the most efficacious) was relatively greater at ordinary temperatures than at the temperature of the body. It was found that whereas 10 cub. cent. of a liquid containing the ordinary proportion of hydrochloric acid digested 0°1311 gramme, a similar liquid prepared with butyric acid digested 0°0455 gramme of fibrin. “Hence, taking the quantities digested with hydrochloric acid at the temperature of the body as 100, we have the digestive power of hydrochloric acid at the temperature of 16° to 18° Cent. represented by 44°95 that of butyric acid at the same temperature being 15:6.” We here see that at the lower of these two temperatures, hydro- chloric acid with pepsin digests, within the same time, rather less than half the quantity of fibrin compared with what it digests at the higher temperature: and the power of butyric acid is reduced in the same proportion under similar conditions and temperatures. We have also seen that butyric acid, which is much more efficacious than propionic or valerianic acids, digests with pepsin at the higher tem- perature less than a third of the fibrin which is digested at the same temperature by hydrochloric acid. I will now give in detail my experiments on the digestive power of the secretion of Drosera, dividing the substances tried into two series, namely those which are digested more or less completely, and those which are not digested. We shall presently see that all these substances are acted on by the gastric juice of the higher animals in the same manner. I beg leave to call attention to the experiments under the air fag: Cuar. VLJ DIGESTION. 77 head albumen, showing that the secretion loses its power when neutralised by an alkali, and recovers it when an acid is added. Substances which are completely or partially Digested by the Secretion of Drosera. Albumen.—After having tried various substances, Dr. Burdon Sanderson suggested to me the use of cubes of coagulated albumen or hard-boiled egg. I may premise that five cubes of the same size as those used in the following experiments were placed for the sake of comparison at the same time on wet moss close to the plants of Drosera. The weather was hot, and after four days some of the cubes were discoloured and mouldy, with their angles a little rounded; but they were not surrounded by a zone of transparent fluid as in the case of those undergoing digestion. Other cubes retained their angles and white colour. After eight days all were somewhat reduced in size, discoloured, with their angles much rounded. Nevertheless in four out of the five speci- mens, the central parts were still white and opaque. So that their state differed widely, as we shall see, from that of the cubes subjected to the action of the secretion. Experiment 1.—Rather large cubes of albumen were first tried; the tentacles were well inflected in 24 hrs; after an additional day the angles of the cubes were dissolved and rounded ;* but the cubes were too large, so that the leaves were injured, and after seven days one died and the others were dying. Albumen which has been kept for four or five days, and which, it may be presumed, has begun to decay slightly, seems to act more quickly than freshly boiled eggs. As the latter were generally used, I often moistened them with a little saliva, to make the tentacles close more quickly. Experiment 2.—A cube of 3 of an inch (i.e. with each side +1, of an inch, or 2°54 mm., in length) was placed on a leaf, and after 50 hrs. it was converted into a sphere about -$ of an inch (1:905 mm.) in diameter, surrounded by perfectly transparent fluid. After ten days * In all my numerous experi- ments on the digestion of cubes of albumen, the angles and edges were invariably first rounded. Now, Schiff states (‘ Leçons Phys, de la Digestion,’ 1867, tom. ii. p. 149) that this is characteristic of the digestion of albumen by the gastric juice of animals, On the other hand, he remarks, ‘ les dissolutions, en chimie, ont lieu sur toute la surface des corps en contact avec l'agent dissolvant.” 78 DROSERA ROTUNDIFOLIA. [Cuar. VI. the leaf re-expanded, but there was still left on the disc a minute bit of albumen now rendered transparent. More albumen had been given to this leaf than could be dissolved or digested. Experiment 3.—Two cubes of albumen of ṣẹ of an inch (1°27 mm.) were placed on two leaves, After 46 hrs. every atom of one was dis- solved, and most of the liquefied matter was absorbed, the fluid which remained being in this, as in all other cases, very acid and viscid. ‘Lhe other cube was acted on at a rather slower rate. Experiment 4.—Two cubes of albumen of the same size as the last were placed on two leaves, and were converted in 50 hrs. into two large drops of transparent fluid; but when these were removed from beneath the inflected tentacles, and viewed by reflected light under the microscope, fine streaks of white opaque matter could be seen in the one, and traces of similar streaks in the other. The drops were replaced on the leaves, which re-expanded after 10 days; and now nothing was left except a very little transparent acid fluid. Experiment 5—This experiment was slightly varied, so that the albumen might be more quickly exposed to the action of the secretion. Two cubes, each of about =j; of an inch (*635 mm.) were placed on the same leaf, and two similar cubes on another leaf. These were examined after 21 hrs. 30 m., and all four were found rounded. After 46 hrs. the two cubes on the one leaf were completely liquefied, the fluid being perfectly transparent ; on the other leaf some opaque white streaks could still be seen in the midst of the fluid. After 72 hrs. these streaks disappeared, but there was still a little viscid fluid left on the disc; whereas it was almost all absorbed on the first leaf. Both leaves were now beginning to re-expand. The best and almost sole test of the presence of some ferment analogous to pepsin in the secretion appeared to be to neutralise the acid of the secretion with an alkali, and to observe whether the process of digestion ceased ; and then to add a little acid and observe whether the process recom- menced. This was done, and, as we shall see, with success, but it was necessary first to try two control experiments ; namely, whether the addition of minute drops of water of the same size as those of the dissolved alkalies to be used would stop the process of digestion ; and, secondly, whether minute drops of weak hydrochloric acid, of the same strength and size as those to be used, would injure the leaves, The two following experiments were therefore tried :— Experiment 6.—Small cubes of albumen were put on three leaves, and minute drops of distilled water on the head of a pin were added two or three times daily. These did not in the least delay the process ; Cuar. VI] DIGESTION. 79 for, after 48 hrs., the cubes were completely dissolved on all three leaves. On the third day the leaves began to re-expand, and on the fourth day all the fluid was absorbed. Experiment T.—Small cubes of albumen were put on two leaves, and minute drops of hydrochloric acid, of the strength of one part to 437 of water, were added two or three times. This did not in the least delay, but seemed rather to hasten, the process of digestion ; for every trace of the albumen disappeared in 24 hrs. 30 m. After three days the leaves partially re-expanded, and by this time almost all the viscid fluid on their discs was absorbed. It is almost super- fluous to state that cubes of albumen of the same size as those above used, left for seven days in a little hydrochloric acid of the above strength, retained all their angles as perfect as ever. Experiment 8.—Cubes of albumen (of 35 of an inch, or 1°27 mm.) were placed on five leaves, and minute drops of a solution of one part of carbonate of soda to 437 of water were added at intervals to three of them, and drops of carbonate of potash, of the same strength to the other two. The drops were given on the head of a rather large pin, and I ascertained that each was equal to about 4, of a minim (-0059 c.c.), so that each contained only ṣọ of a grain (‘0135 mg.) of the alkali. ‘This was not sufficient, for after 46 hrs. all five cubes were dissolved. Experiment 9.—The last experiment was repeated on four leaves, with this difference, that drops of the same solution of carbonate of soda were added rather oftener, as often as the secretion became acid, so that it was much more effectually neutralised. And now after 24 hrs. the angles of three of the cubes were not in the least rounded, those of the fourth being so in a very slight degree. Drops of extremely weak hydrochloric acid (viz. one part to 847 of water) were then added, just enough to neutralise the alkali which was still present ; and now digestion immediately recommenced, so that after 23 hrs. 30 m. three of the cubes were completely dissolved, whilst the fourth was converted into a minute sphere, surrounded by transparent fluid; and this sphere next day disappeared. Experiment 10.—Stronger solutions of carbonate of soda and of potash were next used, viz. one part to 109 of water; and as the same- sized drops were given as before, each drop contained 5,55 of a grain (°0539 mg.) of either salt. Two cubes of albumen (each about 75 of an inch, or *635 mm.) were placed on the same leaf, and two on another. Each leaf received, as soon as the secretion became slightly acid (and this occurred four times within 24 hrs.), drops either of the soda or potash, and the acid was thus effectually neutralised. ‘The experiment now succeeded perfectly, for after 22 hrs. the angles of the cubes were as sharp as they were at first, and we know from experiment 5 that such small cubes would have been completely rounded within this time by the secretion in its natural state. Some of the fluid was now removed with blotting-paper from the discs of the leaves, and minute drops of hydrochloric acid of the strength of one part to 200 of water 80 DROSERA ROTUNDIFOLIA. [Cmar. VI. was added. Acid of this greater strength was used as the solutions of the alkalies were stronger. The process of digestion now com- menced, so that within 48 hrs. from the time when the acid was given the four cubes were not only completely dissolved, but much of the liquefied albumen was absorbed. Experiment 11.—T wo cubes of albumen (5 ofan inch, or *635 mm.) were placed on two leaves, and were treated with alkalies as in the last experiment, and with the same result; for after 22 hrs. they had their angles perfectly sharp, showing that the digestive process had been completely arrested. I then wished to ascertain what would be the effect of using stronger hydrochloric acid; so I added minute drops of the strength of 1 per cent. This proved rather too strong, for after 48 hrs. from the time when the acid was added one cube was still almost perfect, and the other only very slightly rounded, and both were stained slightly pink. This latter fact shows that the leaves were injured,* for during the normal process of digestion the albumen is not thus coloured, and we can thus understand why the cubes were not dissolved, From these experiments we clearly see that the secretion has the power of dissolving albumen, and we further see that if an alkali is added, the process of digestion is stopped, but immediately recommences as soon as the alkali is neutralised by weak hydrochloric acid. Even if I had tried no other experiments than these, they would have almost sufficed to prove that the glands of Drosera secrete some ferment analogous to pepsin, which in presence of an acid gives to the secretion its power of dissolving albuminous compounds. Splinters of clean glass were scattered on a large number of leaves, and these became moderately inflected. They were cut off and divided into three lots; two of them, after being left for some time in a little distilled water, were strained, and some discoloured, viscid, slightly acid fluid was thus obtained. The third lot was well soaked in a few drops of glycerine, which is well known to dissolve pepsin. Cubes of albumen (>ç of an inch) were now placed in the three fluids in watch-glasses, some of which were kept for several days at about 90° Fahr. (82°-2 Cent.), and others at the temperature of my room; but none of the cubes were * Sachs remarks (‘Traité de Bot.’ 1874, p. 774), that cells which are killed by freezing, by too great heat, or by chemical agents, allow all their colouring matter to escape into the surrounding water. — ae paete Cuar. VI] DIGESTION. 81 dissolved, the angles remaining as sharp as ever. This fact probably indicates that the ferment is not secreted until the glands are excited by the absorption of a minute quantity of already soluble animal matter,—a conclusion which is sup- ported by what we shall hereafter see with respect to Dionæa. Dr. Hooker likewise found that, although the fluid within the pitchers of Nepenthes possesses extraordinary power of digestion, yet when removed from the pitchers before they have been excited and placed in a vessel, it has no such power, although it is already acid; and we can account for this fact only on the supposition that the proper ferment is not secreted until some exciting matter is absorbed.* * [With regard to Drosera Messrs. Rees and Will Ç Bot. Zeitung,’ 1875, p- 715) state that a glycerine extract of Drosera leaves in a state of unex- cited secretion, and fairly free from insects, had no digestive action. But that the same extract, artificially acid- ulated, digested fibrin thoroughly well. The authors believe that the natu- ral acid of the glands was possibly destroyed in the process of preparing the extract. No conclusion can there- fore be drawn from their results as to the acidity of unexcited leaves. It is probable, however, judging from Von Gorup’s work on Nepenthes, that Drosera does not secrete the requisite amount of acid until it has been stimulated by the capture of insects. tees and Will’s experiments are not quite conclusive on this point, but they tend to show that what is want- ing in the secretion of unexcited leaves is the acid, not the ferment. The ex- periments of Von Gorup and Will on Nepenthes, as given in the ‘ Bot. Zei- tung,’ 1876, p. 473, do not confirm Hooker’s results on Nepenthes. The authors state that the secretion col- lected from pitchers which are free from insects is neutral, while the fluid of pitchers which contain the remains of insects is distinctly acid. The neutral secretion of the unexcited pitchers has no digestive power until it is acidulated, when it rapidly dis- solves fibrin. It seems, therefore, that the analogy with animal digestion pointed out at p. 106 does not altogether hold good. For Schiff states that in the gastric juice produced by mechanical irrita- tion, the element absent is the fer- ment, not the acid. On the other hand an interesting point of resemblance of a different kind has been made out by Vines in his paper on the digestive ferment of Nepenthes (‘Journal of the Linn. Soc.’ vol. xv. p. 427 ; also ‘ Journal of Anatomy and Physiology,’ series ii. vol. xi. p. 124). The work was undertaken inde- pendently of Von Gorup and carried out by a different method, namely the preparation ofa glycerine extract. Vines having found that the extract was far less active than the natural secretion used by Von Gorup, was led to an interesting explanation of this fact by Ebstein and Griitzner’s work on animal digestion. These writers show that the glycerine ex- tract gains in digestive activity if it is prepared from mucous membrane previously treated with acid. Vines accordingly treated Nepenthes witi one per cent acetic acid for 24 hrs. previously to the preparation of the extract, and thus obtained glycerine of much greater peptic activity. This 82 DROSERA ROTUNDIFOLIA. [Cuap. VI. On three other occasions eight leaves were strongly ex- cited with albumen moistened with saliva; they were then cut off, and allowed to soak for several hours or for a whole day in a few drops of glycerine. Some of this extract was added to a little hydrochloric acid of various strengths (generally one to 400 of water), and minute cubes of albumen were placed in the mixture.* In two of these trials the cubes were not in the least acted on; but in the third the experiment was successful. For in a vessel containing two cubes, both were reduced in size in 3 hrs; and after 24 hrs. mere streaks of undissolved albumen were left. In a second vessel, containing two minute ragged bits of albumen, both were likewise reduced in size in 3 hrs. and after 24 hrs. com- pletely disappeared. I then added a little weak hydro- chloric acid to both vessels, and placed fresh cubes of albumen in them; but these were not acted on. This latter fact is intelligible according to the high authority of Schiff,t who has demonstrated, as he believes, in opposition to the view held by some physiologists, that a certain small amount of pepsin is destroyed during the act of digestion. So that if my solution contained, as is probable, an extremely small amount of the ferment, this would have been consumed by the dissolution of the cubes of albumen first given: none being left when the hydrochloric acid was added. The destruction of the ferment during the process of digestion, or its absorption after the albumen had been converted into a peptone, will also account for only one out of the three latter sets of experiments having been successful. Digestion of Roast Meat.—Cubes of about -y of an inch (1:27 mm.) of moderately roasted meat were placed on five leaves which became in 12 hrs. closely inflected. After 48 hrs. I gently opened one leaf, and the meat now consisted of a minute central sphere, partially digested and surrounded by a thick envelope of transparent viscid fluid. The whole, fact would lead us to believe that the act of secretion in Nepenthes is pre- ceded by the production of a mother substance, or pepsinogen, from which the peptic ferment is formed by ac- tion of acid—just as the pancreatic ferment may, according to Heidenhain, be produced by the action of acid on zymogen—F, D.] * As a control experiment bits of albumen were placed in the same glycerine with hydrochloric acid of the same strength ; and the albumen, as might have been expected, was not in the least affected after two days. t ‘Leçons phys. de la Digestion,’ 1867, tom. ii, pp. 114-126. Cmar. VL] DIGESTION. 83 without being much disturbed, was removed and placed under the microscope. In the central part the transverse striz on the muscular fibres were quite distinct; and it was interesting to observe how gradually they disappeared, when the same fibre was traced into the surrounding fluid. They disappeared by the striæ being replaced by transverse lines formed of excessively minute dark points, which towards the exterior could be seen only under a very high power; and ultimately these points were lost. When I made these observations, I had not read Schiff’s account* of the digestion of meat by gastric juice, and I did not understand the meaning of the dark points. But this is explained in the following statement, and we further see how closely similar is the process of digestion by gastric juice and by the secretion of Drosera. “On a dit que le suc gastrique faisait perdre à la fibre musculaire ses stries transversales. Ainsi énoncée, cette proposition pourrait donner lieu à une équivoque, car ce qui se perd, ce west que Paspect extérieur de la striature et non les éléments anatomiques qui la com- posent. Onsait que les stries qui donnent un aspect si caractéristique à la fibre musculaire, sont le résultat de la juxtaposition et du parallélisme des corpuscules élémentaires, placés, à distances égales, dans Vintérieur des fibrilles contiguës. Or, dès que le tissu connectif qui relie entre elles les fibrilles élémentaires vient à se gonfler et à se dissoudre, et que les fibrilles elles-mêmes se dissocient, ce parallélisme est détruit et avec lui laspect, le phénomène optique des stries. Si, après la désagrégation des fibres, on examine au microscope les fibrilles élémentaires, on distingue encore très-nettement à leur intérieur les corpuscules, et on continue à les voir, de plus en plus pâles, jusqu’au moment où les fibrilles elles-mêmes se liquéfient et disparaissent dans le suc gastrique. Ce qui constitue la striature, à proprement parler, n’est done pas détruit, avant la liquéfaction de la fibre charnue elle- méme.” In the viscid fluid surrounding the central sphere of undigested meat there were globules of fat and little bits of fibro-elastic tissue; neither of which were in the least digested. There were also little free parallelograms of yellowish, highly translucent matter. Schiff, in speaking of the digestion of meat by gastric juice, alludes to such parallelograms, and says :— * t Leçons phys. de Ja Digestion,’ 1867, tom. ii. p. 145. i G 84 DROSERA ROTUNDIFOLIA. [Cuap. VI. “Le gonflement par lequel commence la digestion ‘de la viande, résulte de laction du suc gastrique acide sur le tissu connectif qui se dissout d’abord, et qui, par sa liquéfaction, désagrége les fibrilles. Celles-ci’se dissolvent ensuite en grande partie, mais, avant de passer à létat liquide, elles tendent à se briser en petits fragments transver- saux. Les ‘ sarcous elements’ de Bowman, qui ne sont autre chose que les produits de cette division transversale des fibrilles élémentaires, peuvent étre préparés et isolés à laide du suc gastrique, pourvu qu’on n’attend pas jusqu’à la liquéfaction complète du muscle.” After an interval of 72 hrs., from the time when the five cubes were placed on the leaves, I opened the four remaining ones. On two nothing could be seen but little masses of transparent viscid fluid; but when these were examined under a high power, fat-globules, bits of fibro-elastic tissue, and some few parallelograms of sarcous matter, could be distinguished, but not a vestige of transverse strie. On the other two leaves there were minute spheres of only partially digested meat in the centre of much transparent fluid. Fibrin.—Bits of fibrin were left in water during four days, whilst the following experiments were tried, but they were not in the least acted on. The fibrin which I first used was not pure, and included dark particles: it had either not been well prepared or had subsequently undergone some change. Thin portions, about „y of an inch square, were placed on several leaves, and though the fibrin was soon liquefied, the whole was never dissolved. Smaller particles were then placed on four leaves, and minute drops of hydrochloric acid (one part to 437 of water) were added ; this seemed to hasten the process of digestion, for on one leaf all was liquefied and absorbed after 20 hrs.; but on the three other leaves some undissolved residue was left after 48 hrs. It is remarkable that in all the above and following experiments, as well as when much larger bits of fibrin were used, the leaves were very little excited; and it was sometimes necessary to add a little saliva to induce complete inflection. The leaves, moreover, began to re-expand after only 48 hrs., whereas they would have remained inflected for a much longer time had insects, meat, cartilage, albumen, &c., been placed on them. I then tried some pure white fibrin, sent me by Dr. jurdon Sanderson. vipe PET Cuar. VI] DIGESTION. 85 Experiment 1.—Two particles, barely 35 of an inch (1°27 mm.) square, were placed on opposite sides of the same leaf. One of these did not excite the surrounding tentacles, and the gland on which it rested soon dried. The other particle caused a few of the short adjoin- ing tentacles to be inflected, the more distant ones not being affected. After 24 hrs. both were almost, and after 72 hrs. completely, dis- solved. Experiment 2.—The same experiment with the same result, only one of the two bits of fibrin exciting the short surrounding tentacles. This bit was so slowly acted on that after a day I pushed it on to some fresh glands. In three days from the time when it was first placed on the leaf it was completely dissolved. Experiment 3.—Bits of fibrin of about the same size as before were placed on the discs of two leaves; these caused very little inflection in 23 hrs., but after 48 hrs. both were well clasped by the surrounding short tentacles, and after an additional 24 hrs. were completely dis- solved. On the disc of one of these leaves much clear acid fluid was left. Experiment 4.—Similar bits of fibrin were placed on the discs of two leaves; as after 2 hrs. the glands seemed rather dry, they were freely moistened with saliva; this soon caused strong inflection both of the tentacles and blades, with copious secretion from the glands. In 18 hrs. the fibrin was completely liquefied, but undigested atoms still floated in the liquid; these, however, disappeared in under two additional days. From these experiments it is clear that the secretion completely dissolves pure fibrin. ‘lhe rate of dissolution is rather slow; but this depends merely on this substance not exciting the leaves sufficiently, so that only the immediately adjoining tentacles are inflected, and the supply of secretion is small. Syntonin.—This substance, extracted from muscle, was kindly prepared for me by Dr. Moore.* Very differently from fibrin, it acts quickly and energetically. Small portions placed on the discs of three leaves caused their tentacles and blades to be strongly inflected within 8 hrs.; but no further observations were made. It is probably due to the presence of this substance that raw meat is too powerful a stimulant, often injuring or even killing the leaves. Areolar Tissue-—Small portions of this tissue from a sheep were placed on the discs of three leaves; these became * [These results cannot be considered trustworthy; it appears that the syntonin prepared by the late Dr. Moore was far from pure.—F. D. 86 DROSERA ROTUNDIFOLIA. [Cuar. VI. moderately well inflected in 24 hrs., but began to re-expand after 48 hrs., and were fully re-expanded in 72 hrs., always reckoning from the time when the bits were first given. This substance, therefore, like fibrin, excites the leaves for only a short time. The residue left on the leaves, after they were fully re-expanded, was examined under a high power and found much altered, but, owing to the presence of a quantity of elastic tissue, which is never acted on, could hardly be said to be in a liquefied condition. Some areolar tissue free from elastic tissue was next procured from the visceral cavity of a toad, and moderately sized, as well as very small, bits were placed on five leaves. After 24 hrs. two of the bits were completely liquefied ; two others were rendered transparent, but not quite liquefied ; whilst the fifth was but little affected. Several glands on the three latter leaves were now moistened with a little saliva, which soon caused much inflection and secretion, with the result that in the course of 12 additional hrs. one leaf alone showed a remnant of undigested tissue. On the discs of the four other leaves (to one of which a rather large bit had been given) nothing was left except some transparent viscid fluid. I may add that some of this tissue included points of black pigment, and these were not at all affected. As a control experiment, small portions of this tissue were left in water and on wet moss for the same length of time, and remained white and opaque. From these facts it is clear that areolar tissue is easily and quickly digested by the secretion ; but that it does not greatly excite the leaves. Cartilage—Three cubes (>p of an inch or 1°27 mm.) of white, translucent, extremely tough cartilage were cut from the end of a slightly roasted leg-bone of a sheep. These were placed on three leaves, borne by poor, small plants in my greenhouse during November; and it seemed in the highest degree improbable that so hard a substance would be digested under such unfavourable circumstances. Neverthe- less, after 48 hrs., the cubes were largely dissolved and converted into minute spheres, surrounded by transparent, very acid fluid. Two of these spheres were completely softened to their centres; whilst the third still contained a very small irregularly shaped core of solid cartilage. Their surfaces were seen under the microscope to be curiously marked by prominent ridges, showing that the cartilage had been unequally corroded by the secretion. I need hardly say Cuar. VI] DIGESTION. 87 that cubes of the same cartilage, kept in water for the same length of time, were not in the least affected. During a more favourable season, moderately sized bits of the skinned ear of a cat, which includes cartilage, areolar and elastic tissue, were placed on three leaves. Some of the glands were touched with saliva, which caused prompt in- flection. Two of the leaves began to re-expand after three days, and the third on the fifth day. The fluid residue left on their discs was now examined, and consisted in one case of perfectly transparent, viscid matter; in the other two cases, it contained some elastic tissue and apparently remnants of half digested areolar tissue. Fibro-Cartilage (from between the vertebre of the tail of a sheep). Moderately sized and small bits (the latter about sly of an inch) were placed on nine leaves. Some of these were well and some very little inflected. In the latter case the bits were dragged over the discs, so that they were well bedaubed with the secretion, and many glands thus irritated. All the leaves re-expanded after only two days; so that they were but little excited by this substance. The bits were not liquefied, but were certainly in an altered condition, being swollen, much more transparent, and so tender as to disin- tegrate very easily. Myson Francis prepared some artificial gastric juice, which was proved efficient by quickly dis- solving fibrin, and suspended portions of the fibro-cartilage in it. These swelled and became hyaline, exactly like those exposed to the secretion of Drosera, but were not dissolved. This result surprised me much, as two physiologists were of opinion that fibro-cartilage would be easily digested by gastric juice. I therefore asked Dr. Klein to examine the specimens; and he reports that the two which had been subjected to artificial gastric juice were “in that state of digestion in which we find connective tissue when treated with an acid, viz. swollen, more or less hyaline, the fibrillar bundles having become homogeneous and lost their fibrillar structure.” In the specimens which had been left on the leaves of Drosera, until they re-expanded, “parts were altered, though only slightly so, in the same manner as those subjected to the gastric juice, as they had become more transparent, almost hyaline, with the fibrillation of the bundles indistinct.” Fibro-cartilage is therefore acted on in nearly the same manner by gastric juice and by the secretion of Drosera. 88 DROSERA ROTUNDIFOLIA. [Cuar. VI. Bone.—Small smooth bits of the dried hyoidal bone of a fowl moistened with saliva were placed on two leaves, and a similarly moistened splinter of an extremely hard, broiled mutton-chop bone on a third leaf. These leaves soon became strongly inflected, and remained so for an unusual length of time; namely, one leaf for ten and the other two for nine days. The bits of bone were surrounded all the time by acid secretion. When examined under a weak power, they were found quite softened, so that they were readily penetrated by a blunt needle, torn into fibres, or compressed. Dr. Klein was so kind as to make sections of both bones and examine them. He informs me that both presented the normal appearance of decalcified bone, with traces of the earthy salts occasionally left. The corpuscles with their processes were very distinct in most parts; but in some parts, especially near the periphery of the hyoidal bone, none could be seen. Other parts again appeared amorphous, with even the longitudinal striation of bone not distinguishable. This amorphous structure, as Dr. Klein thinks, may be the result either of the incipient digestion of the fibrous basis or of all the earthy matter having been removed, the corpuscles being thus rendered invisible. A hard, brittle, yellowish substance occupied the position of the medulla in the fragments of the hyoidal bone. As the angles and little projections of the fibrous basis were not in the least rounded or corroded, two of the bits. were placed on fresh leaves. These by the next morning were closely inflected, and remained so,—the one for six and the other for seven days,—therefore for not so long a time as on the first occasion, but for a much longer time than ever occurs with leaves inflected over inorganic or even over many organic bodies. The secretion during the whole time coloured litmus paper of a bright red; but this may have been due to the presence of the acid superphosphate of lime. When the leaves re-expanded, the angles and projections of the fibrous basis were as sharp as ever. I therefore con- cluded, falsely, as we shall presently see, that the secretion cannot touch the fibrous basis of bone. The more probable- explanation is that the acid was all consumed in decomposing the phosphate of lime which still remained ; so that none was left in a free state to act in conjunction with the ferment on the fibrous basis. Enamel and Dentine.—As the secretion decalcified ordinary PNE E indice SE I EET Cuar. VL] DIGESTION. 89- bone, I determined to try whether it would act on enamel and dentine, but did not expect that it would succeed with so hard a substance as enamel. Dr. Klein gave me some thin transverse slices of the canine tooth of a dog; small angular fragments of which were placed on four leaves; and these were examined each succeeding day at the same hour. The results are, I think, worth giving in detail. Experiment 1.—May Ist, fragment placed on leaf; 3rd, tentacles but little inflected, so a little saliva was added; 6th, as the tentacles were not strongly inflected, the fragment was transferred to another leaf, which acted at first slowly, but by the 9th closely embraced it. On the 11th this second leaf began to re-expand; the fragment was manifestly softened, and Dr. Klein reports, “a great deal of enamel and the greater part of the dentine decalcified.” Experiment 2.—May 1st, fragment placed on leaf; 2nd, tentacles fairly well inflected, with much secretion on the disc, and remained so until the 7th, when the leaf re-expanded. The fragment was now transferred to a fresh leaf, which next day (8th) was inflected in the strongest manner, and thus remained until the llth, when it re- expanded. Dr. Klein reports, “a great deal of enamel and the greater part of the dentine decalcified.” Experiment 3.—May 1st, fragment moistened with saliva and placed on a leaf, which remained well inflected until 5th, when it re-expanded. The enamel was not at all, and the dentine only slightly, softened. The fragment was now transferred to a fresh leaf, which next morning (6th) was strongly inflected, and remained so until the 11th. The enamel and dentine both now somewhat softened; and Dr. Klein reports, “less than half the enamel, but the greater part of the dentine decalcified.” Experiment 4.—May 1st, a minute and thin bit of dentine, mois- tened with saliva, was placed on a leaf, which was soon inflected, and re-expanded on the 5th. The dentine had become as flexible as thin paper. It was then transferred to a fresh leaf, which next morning (6th) was strongly inflected, and reopened on the 10th. The decalci- tied dentine was now so tender that it was torn into shreds merely by the force of the re-expanding tentacles. From these experiments it appears that enamel is attacked by the secretion with more difficulty than dentine, as might have been expected from its extreme hardness; and both with more difficulty than ordinary bone. After the process of dissolution has once commenced, it is carried on with greater ease; this may be inferred from the leaves, to which the fragments were transferred, becoming in all four cases strongly inflected in the course of a single day; whereas the 90 DROSERA ROTUNDIFOLIA. [Cuar. VI. first set of leaves acted much less quickly and energetically. The angles or projections of the fibrous basis of the enamel and dentine (except, perhaps, in No. 4, which could not be well observed) were not in the least rounded; and Dr. Klein remarks that their microscopical structure was not altered. But this could not have been expected, as the decalcification was not complete in the three specimens which were carefully examined. Fibrous Basis of Bone.—I at first concluded, as already stated, that the secretion could not digest this substance. I therefore asked Dr. Burdon Sanderson to try bone, enamel, and dentine, in artificial gastric juice, and he found that they were after a considerable time completely dissolved. Dr. Klein examined some of the small lamelle, into which part of the skull of a cat became broken up after about a week’s im- mersion in the fluid, and he found that towards the edges the “ matrix appeared rarified, thus producing the appearance as if the canaliculi of the bone-corpuscles had become larger. Otherwise the corpuscles and their canaliculi were very distinct.” So that with bone subjected to artificial gastric juice complete decalcification precedes the dissolution of the fibrous basis. Dr. Burdon Sanderson suggested to me that the failure of Drosera to digest the fibrous basis of bone, enamel, and dentine, might be due to the acid being con- sumed in the decomposition of the earthy salts, so that there was none left for the work of digestion. Accordingly, my son thoroughly decalcified the bone of a sheep with weak hydrochloric acid; and seven minute fragments of the fibrous basis were placed on so many leaves, four of the fragments being first damped with saliva to aid prompt inflection. All seven leaves became inflected, but only very moderately, in the course of a day. They quickly began to re-expand; five of them on the second day, and the other two on the third day. On all seven leaves the fibrous tissue was converted into perfectly transparent, viscid, more or less liquefied little masses. In the middle, however, of one, my son saw under a high power a few corpuscles, with traces of fibrillation in the surrounding transparent matter. From these facts it is clear that the leaves are very little excited by the fibrous basis of bone, but that the secretion easily and quickly liquefies it, if thoroughly decalcified. The glands which had remained in contact for two or three days with the viscid masses were not discoloured, and apparently had I ee a A EA Cuar. VL] DIGESTION. 91 absorbed little of the liquefied tissue, or had been little affected by it. Phosphate of Lime.—As we have seen that the tentacles of the first set of leaves remained clasped for nine or ten days over minute fragments of bone, and the tentacles of the second set for six or seven days over the same fragments, I was led to suppose that it was the phosphate of lime, and not any included animal matter, which caused such long- continued inflection. It is at least certain from what has just been shown that this cannot have been due to the presence of the fibrous basis. With enamel and dentine (the former of which contains only 4 per cent. of organic matter) the tentacles of two successive sets of leaves remained inflected altogether for eleven days. In order to test my belief in the potency of phosphate of lime, I procured some from Prof. Frankland absolutely free of animal matter and of any acid. A small quantity moistened with water was placed on the discs of two leaves. One of these was only slightly affected; the other remained closely inflected for ten days, when a few of the tentacles began to re-expand, the rest being much injured or killed. I repeated the experiment, but moistened the phosphate with saliva to insure prompt inflection ; one leaf remained inflected for six days (the little saliva used would not have acted for nearly so long a time) and then died; the other leaf tried to re-expand on the sixth day, but after nine days failed to do so, and likewise died. Although the quantity of phosphate given to the above four leaves was extremely small, much was left in every case undissolved. A larger quantity wetted with water was next placed on the disc of three leaves; and these became most strongly inflected in the course of 24 hrs. They never re- expanded ; on the fourth day they looked sickly, and on the sixth were almost dead. Large drops of not very viscid fluid hung from their edges during the six days. This fluid was tested each day with litmus paper, but never coloured it; and this circumstance I do not understand, as the super- phosphate of lime is acid. I suppose that some superphos- phate must have been formed by the acid of the secre- tion acting on the phosphate, but that it was all absorbed and injured the leaves; the large drops which hung from their edges being an abnormal and dropsical secretion. Anyhow, it is manifest that the phosphate of lime is a most powerful stimulant. Even small doses are more or less 92 DROSERA ROTUNDIFOLIA. [Cuar. VI. poisonous, probably on the same principle that raw meat and other nutritious substances, given in excess, kill the leaves. Hence the conclusion, that the long-continued inflection of the tentacles over fragments of bone, enamel and dentine, is caused by the presence of phosphate of lime, and not of any included animal matter, is no doubt correct. Gelatine.—I used pure gelatine in thin sheets given me by Prof. Hoffmann. For comparison, squares of the same size as those placed on the leaves were left close by on wet moss. These soon swelled, but retained their angles for three days ; after five days they formed rounded, softened masses, but even on the eighth day a trace of gelatine could still be detected. Other squares were immersed in water, and these, though much swollen, retained their angles for six days. Squares of ,!, of an inch (2°54 mm.), just moistened with water, were placed on two leaves; and after two or three days nothing was left on them but some acid viscid fluid, which in this and other cases never showed any tendency to regelatinise; so that the secretion must act on the gelatine differently to what water does, and apparently in the same manner as gastric juice.* Four squares of the same size as before were then soaked for three days in water, and placed on large leaves; the gelatine was liquefied and rendered acid in two days, but did not excite much inflection. The leaves began to re-expand after four or five days, much viscid fluid being left on their discs, as if but little had been absorbed. One of these leaves as soon as it re-expanded, caught a small fly, and after 24 hrs. was closely inflected, showing how much more potent than gelatine is the animal matter ab- sorbed from an insect. Some larger pieces of gelatine, soaked for five days in water, were next placed on three leaves, but these did not become much inflected until the third day, nor was the gelatine completely liquefied until the fourth day. On this day one leaf began to re-expand; the second on the fifth; and third on the sixth. These several facts prove that gelatine is far from acting energetically on Drosera. In the last chapter it was shown that a solution of isin- glass of commerce, as thick as milk or cream, induces strong inflection, I therefore wished to compare its action with that of pure gelatine. Solutions of one part of both substances * Dr. Lauder Brunton, ‘Handbook for the Phys. Laboratory,’ 1873, pp- 477, 487; Schiff, ‘ Leçons phys. de la Digestion,’ 1867, tom. ii. p. 249. Cuar. VI] DIGESTION. 93 to 218 of water were made ; and half-minim drops (0296 c.c.) were placed on the discs of eight leaves, so that each received ip Of a grain, or ‘135 mg. The four with the isinglass were much more strongly inflected than the other four. 1 conclude, therefore, that isinglass contains some, though per- haps very little, soluble albuminous matter. As soon as these eight leaves re-expanded, they were given bits of roast meat, and in some hours all became greatly inflected ; again showing how much more meat excites Drosera than does gelatine or isinglass. This is an interesting fact, as it is well known that gelatine by itself has little power of nourishing animals. Chondrin.—This was sent me by Dr. Moore in a gelatinous state. Some was slowly dried, and a small chip was placed on a leaf, and a much larger chip on a second leaf. The first was liquefied in a day; the larger piece was much swollen and softened, but was not completely liquefied until the third day. The undried jelly was next tried, and as a control experiment small cubes were left in water for four days and retained their angles. Cubes of the same size were placed on two leaves, and larger cubes on two other leaves. The tentacles and lamine of the latter were closely inflected after 22 hrs. but those of the two leaves with the smaller cubes only to a moderate degree. The jelly on all four was by this time liquefied, and rendered very acid. ‘The glands were blackened from the aggregation of their protoplasmic contents. In 46 hrs. from the time when the jelly was given, the leaves had almost re-expanded, and completely so after 70 hrs.; and now only a little slightly adhesive fluid was left unabsorbed on their discs. One part of chondrin jelly was dissolved in 218 parts of boiling water, and half-minim drops were given to four leaves; so that each received about z1, of a grain (°135 mg.) of the jelly; and, of course, much less of dry chondrin. This acted most powerfully, for after only 3 hrs. 30 m. all four leaves were strongly inflected. Three of them began to re-expand after 24 hrs., and in 48 hrs. were completely open ; but the fourth had only partially re-expanded. All the liquefied chondrin was by this time absorbed. Hence a solution of chondrin seems to act far more quickly and ener- * Dr. Lauder Brunton gives inthe indirect part which gelatine plays in ‘Medical Record,’ January 1873, p. nutrition. j 36, an account of Viot’s view of the 94 DROSERA ROTUNDIFOLIA. [Cuap. VI. getically than pure gelatine or isinglass; but I am assured by good authorities that it is most difficult, or impossible, to know whether chondrin is pure, and if it contained any albu- minous compound, this would have produced the above effects. Nevertheless, I have thought these facts worth giving, as there is so much doubt on the nutritious value of gelatine; and Dr. Lauder Brunton does not know of any experiments with re- spect to animals on the relative value of gelatine and chrondrin. Milk.—We have seen in the last chapter that milk acts most powerfully on the leaves; but whether this is due to the contained casein or albumen, I know not. Rather large drops of milk excite so much secretion (which is very acid) that it sometimes trickles down from the leaves, and this is likewise characteristic of chemically prepared casein. Minute drops of milk, placed on Jeaves, were coagulated in about ten minutes. Schiff denies* that the coagulation of milk by gastric juice is exclusively due to the acid which is present, but attributes it in part to the pepsin; and it seems doubtful whether with Drosera the coagulation can be wholly due to the acid, as the secretion does not commonly colour litmus paper until the tentacles have become well inflected ; whereas the coagulation commences, as we have seen, in about ten minutes. Minute drops of skimmed milk were placed on the discs of five leaves ; and a large proportion of the coagulated matter or curd was dissolved in 6 hrs. and still more com- pletely in 8 hrs. These leaves re-expanded after two days, and the viscid fluid left on their discs was then carefully scraped off and examined. It seemed at first sight as if all the casein had not been dissolved, for a little matter was left which appeared of a whitish colour by reflected light. But this matter, when examined under a high power, and when compared with a minute drop of skimmed milk coagulated by acetic acid, was seen to consist exclusively of oil-globules, more or less aggregated together, with no trace of casein. As I was not familiar with the microscopical appearance of milk, I asked Dr. Lauder Brunton to examine the slides, and he tested the globules with ether, and found that they were dissolved. We may therefore conclude that the secretion quickly dissolves casein, in the state in which it exists in milk.t * 6 Leçons, &c. tom. ii. p. 151. of cow’s milk contains a small pro- + (Professor Sanderson has called portion of nuclein, which is entirely my attention to the fact that the casein indigestible by gastric juice—F. D.]} ae sete state Oy aR Cuar. VL] DIGESTION. 95 Chemically Prepared Casein.—This substance, which is in- soluble in water, is supposed by many chemists to differ from the casein of fresh milk. I procured some, consisting of hard globules, from Messrs. Hopkins and Williams, and tried many experiments with it. Small particles and the powder, both in a dry state and moistened with water, caused the leaves on which they were placed to be inflected very slowly, generally not until two days had elapsed. Other particles, wetted with weak hydrochloric acid (one part to 437 of water) acted in a single day, as did some casein freshly prepared for me by Dr. Moore. ‘The tentacles commonly remained inflected for from seven to nine days; and during the whole of this time the secretion was strongly acid. Even on the eleventh day some secretion left on the discs of a fully re-expanded leaf was strongly acid. ‘The acid seems to be secreted quickly, for in one case the secretion from the discal glands, on which a little powdered casein had been strewed, coloured litmus paper, before any of the exterior tentacles were inflected. Some cubes of hard casein, moistened with water, were placed on two leaves; after three days one cube had its angles a little rounded, and after seven days both consisted of rounded softened masses, in the midst of much viscid and acid secretion; but it must not beinferred from this fact that the angles were dissolved, for cubes immersed in water were similarly acted on. After nine days these leaves began to re-expand, but in this and other cases the casein did not appear, as far as could be judged by the eye, much, if at all, reduced in bulk. According to Hoppe-Seyler and Lubavin* casein consists of an albuminous, with a non-albuminous, substance ; and the absorption of a very small quantity of the former would excite the leaves, and yet not decrease the casein to a perceptible degree. Schiff assertst—and this is an important fact for us—that “la caséine purifiée des chimistes est un corps presque complétement inattaquable par le suc gastrique.” Sothat here we have another point of accordance between the secretion of Drosera and gastric juice, as both act so differently on the fresh casein of milk, and on that prepared by chemists.t * Dr. Lauder Brunton, ‘Handbook that this difference is no doubt due for Phys. Lab.’ p. 529. to the action of the alcohol used + ‘Leçons; &c. tom, ii. p. 153. in making ‘chemically prepared t [Professor Sanderson | tells me _ casein.’’—F. D. 96 DROSERA ROTUNDIFOLIA. [Cuar. VI. A few trials were made with cheese; cubes of 55 of an inch (1-27 mm.) were placed on four leaves, and these after one or two days became well inflected, their glands pouring forth much acid secretion. After five days they began to re- expand, but one died, and some of the glands on the other leaves were injured. Judging by the eye, the softened and subsided masses of cheese, left on the discs, were very little or not at all reduced in bulk. We may, however, infer from the time during which the tentacles remained inflected,— from the changed colour of some of the glands,—and from the injury done to others, that matter had been absorbed from the cheese. Legumin.—I did not procure this substance in a separate state; but there can hardly be a doubt that it would be easily digested, judging from the powerful effect produced by drops of a decoction of green peas, as described in the last chapter. Thin slices of a dried pea, after being soaked in water, were placed on two leaves; these became somewhat inflected in the course of a single hour, and most strongly so in 21 hrs. They re-expanded after three or four days. The slices were not liquefied, for the walls of the cells, composed of cellulose, are not in the least acted on by the secretion. Pollen.—A little fresh pollen from the common pea was placed on the dises of five leaves, which soon became closely inflected, and remained so for two or three days. The grains being then removed, and examined under the microscope, were found discoloured, with the oil-globules remarkably aggregated. Many had their contents much shrunk, and some were almost empty. In only a few cases were the pollen-tubes emitted. There could be no doubt that the secretion had penetrated the outer coats of the grains, and had partially digested their contents. So it must be with the gastric juice of the insects which feed on pollen, without masticating it.* Drosera in a state of nature cannot fail to profit to a certain extent by this power of digesting pollen, as innumerable grains from the carices, grasses, rumices, fir-trees, and other wind-fertilised plants, which commonly grow in the same neighbourhood, will be * Mr. A. W. Bennett found the tera; see ‘Journal of Hort. Soc. of undigested coats of the grains in the London, vol. iv. 1874, p. 158. intestinal canal of pollen-eating Dip- Te SA a OR IND se Cuar. VI.] DIGESTION. 97 inevitably caught by the viscid secretion surrounding the many glands. Gluten.—This substance is composed of two albuminoids, one soluble, the other insoluble in alcohol.* Some was prepared by merely washing wheaten flour in water. A provisional trial was made with rather large pieces placed on two leaves; these, after 21 hrs., were closely inflected, and remained so for four days,when one was killed and the other had its glands extremely blackened, but was not afterwards cbserved. Smaller bits were placed on two leaves ; these were only slightly inflected in two days, but afterwards became much more so. Their secretion was not so strongly acid as that of leaves excited by casein. The bits of gluten, after lying for three days on the leaves, were more transparent than other bits left for the same time in water. After seven days both leaves re-expanded, but the gluten seemed hardly at all reduced in bulk. The glands which had been in contact with it were extremely black. Still smaller bits of half putrid gluten were now tried on two leaves ; these were well inflected in 24 hrs., and thoroughly in four days, the glands in contact being much blackened. After five days one leaf began to re-expand, and after eight days both were fully re-expanded, some gluten being still left on their discs. Four little chips of dried gluten, just dipped in water, were next tried, and these acted rather differently from fresh gluten. One leaf was almost fully re-expanded in three days, and the other three leaves in four days. The chips were greatly softened, almost liquefied, but not nearly all dissolved. The glands which had been in contact with them, instead of being much blackened, were of avery pale colour, and many of them were evidently killed. In not one of these ten cases was the whole of the gluten dissolved, even when very small bits were given. I there- fore asked Dr. Burdon Sanderson to try gluten in artificial digestive fluid of pepsin with hydrochloric acid; and this di-solved the whole. The gluten, however, was acted on much more slowly than fibrin; the proportion dissolved within four hours being as 40°8 of gluten to 100 of fibrin. Gluten was also tried in two other digestive fluids, in which hydrochloric acid was replaced by propionic and butyric acids, and it was completely dissolved by these fluids at the * Watts’ ‘Dict. of Chemistry,’ vol. ii. 1872, p. 875. H 98 DROSERA ROTUNDIFOLIA. [Cuar. VI. ordinary temperature of a room. Here, then, at last, we have a case in which it appears that there exists an essential difference in digestive power between the secretion of Drosera and gastric juice; the difference being confined to the ferment, for, as we have just seen, pepsin in combination with acids of the acetic series acts perfectly on gluten. I believe that the explanation lies simply in the fact that gluten is too powerful a stimulant (like raw meat, or phosphate of lime, or even too large a piece of albumen), and that it injures or kills the glands before they have had time to pour forth a sufficient supply of the proper secretion. That some matter is absorbed from the gluten, we have clear evidence in the length of time during which the tentacles remain inflected, and in the greatly changed colour of the glands. At the suggestion of Dr. Sanderson, some gluten was left for 15 hrs. in weak hydrochloric acid (+02 per cent.) in order toremove thestarch. It became colourless, more transparent, and swollen. Small portions were washed and placed on five leaves, which were soon closely inflected, but to my surprise re-expanded completely in 48 hrs, A mere vestige of gluten was left on two of the leaves, and not a vestige on the other three. The viscid and acid secretion, which remained on the discs of the three latter leaves, was scraped off and examined by my son under a high power; but nothing could be seen except a little dirt, and a good many starch grains which had not been dissolved by the hydrochloric acid. Some of the glands were rather pale. We thus learn that gluten, treated with weak hydrochloric acid, is not so powerful or so enduring a stimulant as fresh gluten, and does not much injure the glands; and we further learn that it can be digested quickly and completely by the secretion. Globulin or Crystallin.—This substance was kindly prepared for me from the lens of the eye by Dr. Moore, and consisted of hard, colourless, transparent fragments. It is said * that globulin ought to “swell up in water and dissolve, for the most part forming a gummy liquid;” but this did not occur with the above fragments, though kept in water for four days. Particles, some moistened with water, others with weak hydrochloric acid, others soaked in water for one or two days, were placed on nineteen leaves. Most of these leaves, * Watts’ ‘ Dict. of Chemistry,’ vol. ii. p. 874. E Cee a By Se Cumar. VI] DIGESTION, 99 especially those with the long soaked particles, became strongly inflected in a few hours. The greater number re-expanded after three or four days; but three of the leaves remained inflected during one, two, or three additional days. Hence some exciting matter must have been absorbed; but the fragments, though perhaps softened in a greater degree than those kept for the same time in water, retained all their angles as sharp as ever. As globulin is an albuminous sub- stance, I was astonished at this result;* and my object being to compare the action of the secretion with that of gastric juice, I asked Dr. Burdon Sanderson to try some of the globulin used by me. He reports that “it was subjected to a liquid containing 0'2 per cent. of hydrochloric acid, and about 1 per cent. of glycerine extract of the stomach of a dog. It was then ascertained that this liquid was capable of digesting 1°31 of its weight of unboiled fibrin in 1 hr.; whereas, during the hour, only 0°141 of the above globulin was dissolved. In both cases an excess of the substance to be digested was subjected to the liquid.” t We thus see that within the same time less than one- ninth by weight of globulin than of fibrin was dissolved: and bearing in mind that pepsin with acids of the acetic series has only about one- third of the digestive power of pepsin with hydrochloric acid, it is not surprising that the fragments of globulin were not corroded or rounded by the secretion of Drosera, though some soluble matter was certainly extracted from them and absorbed by the glands. Hematin.—Some dark red granules, prepared from bullock’s blood, were given me; these were found by Dr. Sanderson to be insoluble in water, acids, and alcohol, so that they were probably hamatin, to- gether with other bodies derived from the blood. Particles with little drops of water were placed on four leaves, three of which were pretty closely inflected in two days; the fourth only moderately so. On the third day the glands in contact with the hematin were blackened, and some of the tentacles seemed injured. After five days two leaves died, and the third was dying; the fourth was beginning to re-expand, but many of its glands were blackened and injured. It is therefore clear that matter had been absorbed which was either actually poisonous or of too stimulating a nature. The particles were much more softened than those kept for the same time in water, but, judging by the eye, very little reduced in bulk. Dr. Sanderson tried this substance with artificial digestive fluid, in the manner described under globulin, and found that whilst 1°31 of fibrin, only 0°456 of the hematin was * [The result was no doubt due was dissolved within the same time, (as I learn from Professor Sanderson) to the fact that the globulin had been treated with alcohol in the course of its preparation—F, D.] t I may add that Dr. Sanderson prepared some fresh globulin by Schmidt’s method, and of this 0°865 namely, one hour; so that it was far more soluble than that which I used, though less soluble than fibrin, of which, as we have seen, 1°31 was dissolved. I wish that I had tried on Drosera globulin prepared by this method. H 2 100 DROSERA ROTUNDIFOLIA. [Cuar. VI. dissolved in an hour; but the dissolution by the secretion of even a less amount would account for its action on Drosera. The residue left by the artificial digestive fluid at first yielded nothing more to it during several succeeding days. Substances which are not Digested by the Secretion. All the substances hitherto mentioned cause prolonged inflection of the tentacles, and are either completely or at least partially dissolved by the secretion. But there are many other substances, some of them containing nitrogen, which are not in the least acted on by the secretion, and do not induce inflection for a longer time than do inorganic and insoluble objects. These unexciting and indigestible sub- stances are, as far as I have observed, epidermic productions {such as bits of human nails, balls of hair, the quills of feathers), fibro-elastic tissue, mucin, pepsin. urea, chitine, chlorophyll, cellulose, gun-cotton, fat, oil, and starch. To these may be added dissolved sugar and gum, diluted alcohol, and vegetable infusions not containing albumen, for none of these, as shown in the last chapter, excite inflection. Now, it is 2 remarkable fact, which affords additional and important evidence, that the ferment of Drosera is closely similar to or identical with pepsin, that none of these same substances are, as far as it is known, digested by the gastric juice of animals, though some of them are acted on by the ther secretions of the alimentary canal. Nothing more need be said about some of the above enumerated substances, excepting that they were repeatedly tried on the leaves of Drosera, and were not in the least affected by the secretion. About the others it will be advisable to give my experi- ments. 7 Fibro-elastic Tissue—We have already seen that when little cubes of meat, &c., were placed on leaves, the muscles, areclar tissue, and cartilage was completely dissolved, but the fibro-elastic tissue, even the most delicate threads, were left without the least signs of having been attacked. And it is well known that this tissue cannot be digested by the gastric juice of animals.* Mucin.—As this substance contains about 7 per cent. of nitrogen, I expected that it would have excited the leaves greatly and been digested by the secretion, but in this I was mistaken. From what is .* See, for instance, Schiff, ‘ Phys. de la Digestion,’ 1867, tom. ii. p. 38. Cuar. VL] DIGESTION. 101 stated in chemical works, it appears extremely doubtful whether mucin can be prepared as a pure principle. ‘That which I used (prepared by Dr. Moore) was dry and hard. Particles moistened with water were placed on four leaves, but after two days there was only a trace of inflection in the immediately adjoining tentacles. These leaves were then tried with bits of meat, and all four soon became strongly inflected. Some of the dried mucin was then soaked in water for two days, and little cubes of the proper size were placed on three leaves. After four days the tentacles round the margins of the discs were a little inflected, and the secretion collected on the disc was acid, but the exterior tentacles were not affected. One leaf began to re-expand on the fourth day, and all were fully re-expanded on the sixth. The glands which had been in contact with the mucin were a little darkened. We may therefore conclude that a small amount of some impurity of a moderately exciting nature had been absorbed. That the mucin employed by me did contain some soluble matter was proved by Dr. Sanderson, who on subjecting it to artificial gastric juice found that in 1 hr. some was dissolved, but only in the proportion of 23 to 100 of fibrin during the same time. The cubes, though perhaps rather softer than those left in water for the same time, retained their angles as sharp as ever. We may therefore infer that the mucin itself was not dissolved or digested. Nor is it digested by the gastric juice of living animals, and according to Schiff* it isa layer of this substance which protects the coats of the stomach from being corroded during digestion. Pepsin.—My experiments are hardly worth giving, as it is scarcely possible to prepare pepsin free from other albuminoids; but I was curious to ascertain, as far as that was possible, whether the ferment of the secretion of Drosera would act on the ferment of the gastric juice of animals. I first used the common pepsin sold for medicinal pur- poses, and afterwards some which was much purer, prepared for me by Dr. Moore. Five leaves to which a considerable quantity of the former was given remained inflected for five days; four of them then died, apparently from too great stimulation. I then tried Dr. Moore’s pepsin, making it into a paste with water, and placing such small particles on the discs of five leaves that all would have been quickly dissolved had it been meat or albumen. The leaves were soon in- tlected ; two of them began to re-expand after only 20 hrs., and the other three were almost completely re-expanded after 44 hrs. Some of the glands which had been in contact with the particles of pepsin, or with the acid secretion surrounding them, were singularly pale, whereas others were singularly dark-coloured. Some of the secretion was scraped off and examined under a high power; and it abounded with granules undistinguishable from those of pepsin left in water for the same length of time. We may therefore infer, as highly probable * < Leçons phys. de la Digestion,’ 1867, tom. ii. p. 304. 102 DROSERA ROTUNDIFOLIA. [CHAE VI. (remembering what small quantities were given), that the ferment of Drosera does not act on or digest pepsin, but absorbs from it some albuminous impurity which induces inflection, and which in large quantity is highly injurious. Dr. Lauder Brunton at my request endeavoured to ascertain whether pepsin with hydrochloric acid would digest pepsin, and as far as he could judge, it had no such power. Gastric juice, therefore, apparently agrees in this respect with the secretion of Drosera. Urea.—It seemed to me an interesting inquiry whether this refuse of the living body, which contains much nitrogen, would, like so many other animal fiuids and substances, be absorbed by the glands of Drosera and cause mflection. Half-minim drops of a solution of one part to 437 of water were placed on the discs of four leaves, each drop containing the quantity usually employed by me, namely 53, ofa grain, or ‘0674 mg.; but the leaves were hardly at all affected. They were then tested with bits of meat, and soon became closely inflected. I repeated the same experiment on four leaves with some fresh urea prepared by Dr. Moore; after two days there was no inflection; I then gave them another dose, but still there was no inflection. These leaves were afterwards tested with similarly sized drops of an infusion of raw meat, and in 6 hrs. there was considerable inflection, which became excessive in 24 hrs. But the urea apparently was not quite pure, for when four leaves were immersed in 2 dr. (7°1 c.c.) of the sotution, so that all the glands, instead of merely those on the disc, were enabled to absorb any small amount of impurity in solution, there was considerable inflection after 24 hrs., certainly more than would have followed from a similar immersion in pure water. ‘lhat the urea, which was not perfectly white, should have contained a sufficient quantity of albuminous matter, or of some salt of ammonia, to have caused the above effect, is far from surprising, for, as we shall see in the next chapter, astonishingly small doses of ammonia are highly efficient. We may therefore conclude that the urea itself is not exciting or nutritious to Drosera; nor is it modified by the secretion, so as to be rendered nutritious, for, had this been the case, all the leaves with drops on their discs assuredly would have been well inflected. Dr. Lauder Brunton informs me that from experiments made at my request at St. Bartholomew’s Hospital it appears that urea is not acted on by artificial gastric juice, that is by pepsin with hydrochloric acid. Chitine.—The chitinous coats of insects naturally captured by the leaves do not appear in the least corroded. Small square pieces of the delicate wing and of the elytron of a Staphylinus were placed on some leaves, and after these had re-expanded, the pieces were carefully examined. ‘Their angles were as sharp as ever, and they did not differ in appearance from the other wing and elytron of the same insect which had been left in water. The elytron, however, had evidently yielded some nutritious matter, for the leaf remained clasped over it for four days; whereas the leaves with bits of the true wing re-expanded on SP ernie, ENN NCE eg nee lpi naa ENE PEPE OEA Cuar. VL] DIGESTION. 103 the second day. Any one who will examine the excrement of insect- eating animals will see how powerless their gastric-juice is on chitine. Cellulose.—I did not obtain this substance in a separate state, but tried angular bits of dry wood, cork, sphagnum moss, linen, and cotton thread. None of these bodies were in the least attacked by the secretion, and they caused only that moderate amount of inflection which is common to all inorganic objects. Gun-cotton, which consists of cellulose, with the hydrogen replaced by nitrogen, was tried with the same result. We have seen that a decoction of cabbage leaves excites the most powerful inflection. I therefore placed two little square bits of the blade of a cabbage leaf, and four little cubes cut from the midrib, on six leaves of Drosera. These became well inflected in 12 hrs., and remained so for between two and four days; the bits of cabbage being bathed all the time by acid secretion. ‘This shows that some exciting matter, to which I shall presently refer, had been absorbed; but the angles of the squares and cubes remained as sharp as ever, proving that the framework of cellulose had not been attacked. Small square bits of spinach leaves were tried with the same result; the glands pouring forth a moderate supply of acid secretion, and the tentacles remaining inflected for three days. We have also seen that the delicate coats of pollen grains are not dissolved by the secretion. It is well known that the gastric juice of animals does not attack cellulose. Chlorophyll_—This substance was tried, as it contains nitrogen. Dr. Moore sent me some preserved in alcohol; it was dried, but soon deliquesced. Particles were placed on four leaves; after 3 hrs. the secretion was acid; after 8 hrs. there was a good deal of inflection, which in 24 hrs. became fairly well marked. After four days two of the leaves began to open, and the other two were then almost fully re- expanded, It is therefore clear that this chlorophyll contained matter which excited the leaves to a moderate degree; but judging by the eye, little or none was dissolved; so that in a pure state it would not probably have been attacked by the seeretion. Dr. Sanderson tried that which I used, as well as some freshly prepared, with artificial digestive liquid, and found that it was not digested. Dr. Lauder Brunton likewise tried some prepared by the process given in the British Phar- macopeia, and exposed it for five days at the temperature of 37° Cent. to digestive liquid, but it was not diminished in bulk, though the fluid acquired a slightly brown colour. It was also tried with the glycerine extract of pancreas with a negative result. Nor does chlorophyll seem affected by the intestinal secretions of various animals, judging by the colour of their excrement. . It must not be supposed from these facts that the grains of chllorophyll, as they exist in living plants, cannot be attacked by the secretion; for these grains consist of protoplasm merely coloured by chlorophyll. My son Francis placed a thin slice of spinach leaf, moistened with saliva, on a leaf of Drosera, and other slices on damp cotton-wool, all exposed to the same temperature. After 19 hrs. the 104 DROSERA ROTUNDIFOLIA. [CHAE VI. slice on the leaf of the Drosera was bathed in much secretion from the inflected tentacles, and was now examined under the microscope. No perfect grains of chlorophyll could be distinguished; some were shrunken, of a yellowish-green colour, and collected in the middle of the cells; others were disintegrated and formed a yellowish mass, likewise in the middle of the cells. On the other hand, in the slices surrounded by damp cotton-wool, the grains of chlorophyll were green and as perfect as ever. My son also placed some slices in artificial gastric juice, and these were acted on in nearly the same manner as by the secretion. We have seen that bits of fresh cabbage and spinach leaves cause the tentacles to be inflected and the glands to pour forth much acid secretion; and there can be little doubt that it is the protoplasm forming the grains of chlorophyll, as well as that lining the walls of the cells, which excites the leaves. Fat and Oil—Cubes of almost pure uncooked fat, placed on several leaves, did not have their angles in the least rounded. We have also seen that the oil-globules in milk are not digested. Nor does olive oil dropped on the discs of leaves cause any inflection; but when they are immersed in olive oil they become strongly inflected; but to this subject I shall have to recur. Oily substances are not digested by the gastric juice of animals. Starch.—Rather large bits of dry starch caused well-marked in- flection, and the leaves did not re-expand until the fourth day; but I have no doubt that this was due to the prolonged irritation of the glands, as the starch continued to absorb the secretion. The particles were not in the least reduced in size; and we know that leaves immersed in an emulsion of starch are not at all affected. I need hardly say that starch is not digested by the gastric juice of animals. Action of the Secretion on Living Seeds. The results of some experiments on living seeds, selected by hazard, may here be given, though they bear only indirectly on our present subject of digestion. Seven cabbage seeds of the previous year were placed on the same number of leaves. Some of these leaves were moderately, but the greater number only slightly inflected, and most of them re-expanded on the third day. One, however, remained clasped till the fourth, and another till the fifth day. ‘These leaves therefore were excited some- what more by the seeds than by inorganic objects of the same size. After they re-expanded, the seeds were placed under favourable con- ditions on damp sand; other seeds of the same lot being tried at the same time in the same manner, and found to germinate well. Of the seven seeds which had been exposed to the secretion, only three ger- minated; and one of the three seedlings soon perished, the tip of its radicle being from the first decayed, and the edges of its cotyledons of a dark brown colour; so that altogether five out of the seven seeds ultimately perished, , Cuar. VI] DIGESTION. 105 Radish seeds (Raphanus sativus) of the previous year were placed on three leaves, which became moderately inflected, and re-expanded on the third or fourth day. Two of these seeds were transferred to damp sand; only one germinated, and that very slowly. This seedling had an extremely short, crooked, diseased, radicle, with no absorbent hairs; and the cotyledons were oddly mottled with purple, with the edges blackened and partly withered. Cress seeds (Lepidium sativum) of the previous year were placed on four leaves; two of these inext morning were moderately and two strongly inflected, and remained so for four, five, and even six days. Soon after these sceds were placed on the leaves and had become damp, they secreted in the usual manner a layer of tenacious mucus; and to ascertain whether it was the absorption of this substance by the glands. which caused so much inflection, two seeds were put into water, and as much of the mucus as possible scraped off. They were then placed on leaves, which became very strongly inflected in the course of 3 hrs., and were still closely inflected on the third day; so that it evidently was not the mucus which excited so much inflection; on the contrary, this served to a certain extent as a protection to the sees. Two of the six seeds germinated whilst still lying on the leaves, but the seedlings, when transferred to damp sand, soon died; of the other four seeds, only one germinated. Two seeds of mustard (Sinapis nigra), two of celery (Apium grave- olens)—both of the previous year, two seeds well soaked of caraway (Carum carui), and two of wheat, did not excite the leaves more than inorganic objects often do. Five seeds, hardly ripe, of a buttercup (Ranunculus), and two fresh seeds of Anemone nemorosd, induced only a little more effect. On the other hand, four seeds, perhaps not quite ripe, of Carex sylvatica caused the leaves on which they weie placed to be very strongly inflected; and these only began to re-expand on the third day, one remaining inflected for seven days. It follows from these few facts that different kinas of seeds excite the leaves in very different degrees; whether this is solely due to the nature of their coats is not clear. ln the case of the cress seeds, the partial removal of the layer of mucus hastened the inflection of the tentacles. Whenever the leaves remain inflected during several days over seeds, it is clear that they absorb some matter from them. That the secretion penetrates their coats is also evident from the large pro- portion of cabbage, raddish, and cress seeds which were killed, ande from several of the seedlings being greatly injured. This injury to the seeds and seedlings may, however, be due solely to the acid of the secretion, and not to any process of digestion; for Mr. Traherne Moggridge has shown that very weak acids of the acetic series are highly injurious to seeds. It never occurred to me to observe whether seeds are often blown on to the viscid leaves of plants growing 1n @ state of nature; but this can hardly fail sometimes to occur, as we shall hereafter see in the case of Pinguicula. If so, Drosera will profit to a slight degree by absorbing matter from such seeds, 106 DROSERA ROTUNDIFOLIA. [Cuap. VI. Summary and Concluding Remarks on the Digestive Power of Drosera. When the glands on the disc are excited either by the absorption of nitrogenous matter or by mechanical irritation, their secretion increases in quantity and becomes acid. They likewise transmit some influence to the glands of the exterior tentacles, causing them to secrete more copiously ; and their secretion likewise becomes acid. With animals, according to Schiff,* mechanical irritation excites the glands of the stomach to secrete an acid, but not pepsin. Now, I have every reason to believe (though the fact is not fully established), that although the glands of Drosera are con- tinually secreting viscid fluid to replace that lost by evaporation, yet they do not secrete the ferment proper for digestion when mechanically irritated, but only after ab- sorbing certain matter, probably of a nitrogenous nature. I infer that this is the case, as the secretion from a large number of leaves which had been irritated by particles of glass placed on their discs did not digest albumen; and more especially from the analogy of Dionza and Nepenthes. In like manner, the glands of the stomach of animals secrete pepsin, as Schiff asserts, only after they have absorbed certain soluble substances, which he designates as peptogenes. There is, therefore, a remarkable parallelism between the glands of Drosera and those of the stomach in the secretion of their proper acid and ferment.t * ‘Phys. de la Digestion,’ 1867, acid and pepsin make their appearance tom. ii. pp. 188, 245. + [it will be seen from the facts given in a footnote at p. 81, that even if we accept Schiff’s peptogen theory, the evidence on the bo- tanical side is against the existence of the above suggested parallelism. Moreover, Schiffs peptogen theory is not generally accepted by physio- logists. Professor Sanderson has called my attention to Ewald’s views on this question as given in his “Klinik der Verdauungs krankheiten, (i) Die Lehre von der Verdauung, 1886, p. 91. Ewald does not believe in any special action of the so-called peptogens. He writes, “I find that almost immediately after the intro- duction of a starch solution into the stomach. The same thing naturally follows on the introduction of Schiff’s peptogens, so that no inconsiderable quantity of acid and pepsin is in readiness for a subsequent act of digestion, which is, in consequence, rendered far more energetic.” Haidenhain, in Hermann’s ‘ Hand- buch der Physiologie,’ vol. v. part i. p- 153, also criticises Schiff’s theory, and shows that the observations on which this theory is founded are to some extent untrustworthy, owing to a fault inthe method employed—F, D.] Cuar. VL] DIGESTION. 107 The secretion, as we have seen, completely dissolves albumen, muscle, fibrin, areolar tissue, cartilage, the fibrous basis of bone, gelatine, chondrin, casein in the state in which it exists in milk, and gluten which has been subjected to weak hydrochloric acid. Syntonin and legumin excite the leaves so powerfully and quickly that there can hardly be a doubt that both would be dissolved by the secretion. T'he secretion failed to digest fresh gluten, apparently from its injuring the glands, though some was absorbed. Raw meat, unless in very small bits, and large pieces of albumen, &c., likewise injure the leaves, which seem to suffer, like animals, from a surfeit. I know not whether the analogy is a real one, but it is worth notice that a decoction of cabbage leaves is fur more exciting and probably nutritious to Drosera than an infusion made with tepid water ; and boiled cabbages are far more nutritious, at least to man, than the uncooked leaves. The most striking of all the cases, though not really more remarkable than many others, is the digestion of so hard and tough a substance as cartilage. The dissolution of pure phosphate of lime, of bone, dentine, and especially enamel, seems wonderful; but it depends merely on the jong-continued secretion of an acid; and this is secreted for a longer time under these circumstances than under any other. It was interesting to observe that as long as the acid was consumed in dissolving the phosphate of lime, no true di- gestion occurred; but that as soon as the bone was completely decalcified, the fibrous basis was attacked and liquefied with the greatest ease. The twelve substances above enumerated, which are completely dissolved by the secretion, are likewise dissolved by the gastric juice of the higher animals; and they are acted on in the same manner, as shown by the rounding of the angles of albumen, and more especially by the manner in which the transverse striæ of the fibres of muscle disappear. The secretion of Drosera and gastric juice were both able to dissolve some element or impurity out of the globulin and hematin employed by me. The secretion also dissolved something out of chemically prepared casein which is said to consist of two substances; and although Schiff asserts that casein in this state is not attacked by gastric juice, he might easily have overlooked a minute quantity of some albu- minous matter, which Drosera would detect and absorb. Again, fibro-cartilage, though not properly dissolved, is 108 DROSERA ROTUNDIFOLIA. [Cuap. VI. acted on in the same manner, both by the secretion of Drosera and gastric juice. But this substance, as well as the so- called hematin used by me, ought perhaps to have been classed with indigestible substances. : That gastric juice acts by means of its ferment, pepsin, solely in the presence of an acid, is well established ; and we have excellent evidence that a ferment is present in the secretion of Drosera, which likewise acts only in the presence of an acid; for we have seen that when the secretion is neutralised by minute drops of the solution of an alkali, the digestion of albumen is completely stopped, and that on the addition of a minute dose of hydrochloric acid it imme- diately recommences. The nine following substances, or classes of substances, namely epidermic productions, fibro-elastic tissue, mucin, pepsin, urea, chitine, cellulose, gun-cotton, chlorophyll, starch, fat and oil, are not acted on by the secretion of Drosera ; nor are they, as far as is known, by the gastric juice of animals. Some soluble matter, however, was extracted from the mucin, pepsin, and chlorophyll, used by me, both by the secretion and by artificial gastric juice. The several substances, which are completely dissolved by the secretion, and which are afterwards absorbed by the glands, affect the leaves rather differently. They induce inflection at very different rates, and in very different degrees ; and the tentacles remain inflected for very different periods of time. Quick inflection depends partly on the quantity of the substance given, so that many glands are simultaneously affected, partly on the facility with which it is penetrated, and liquefied by the secretion, and partly on its nature, but chiefly on the presence of exciting matter already in solution. ‘Thus saliva, or a weak solution of raw meat, acts much more quickly than even a strong solution of gelatine. So again leaves which have re-expanded, after absorbing drops of a solution of pure gelatine or isinglass (the latter being the more powerful of the two), if given bits of meat, are inflected much more energetically and quickly than they were before, notwithstanding that some rest is gener- ally requisite between two acts of inflection. We probably see the influence of texture in gelatine and globulin when softened by having been soaked in water acting more quickly than when merely wetted. It may be partly due to changed texture, and partly tochanged chemical nature, that albumen, Ne notes JR. aaneen. pe sii T a E AS popen Eea S aaa Cuar. VI] DIGESTION. 109 which has been kept for some time, and gluten which has been subjected to weak hydrochloric acid, act more quickly than these substances in their fresh state. The length of time during which the tentacles remain inflected largely depends on the quantity of the substance given, partly on the facility with which it is penetrated or acted on by the secretion, and partly on its essential nature. The tentacles always remain inflected much longer over large bits or large drops than over small bits or drops. ‘Texture probably plays a part in determining the extra- ordinary length of time during which the tentacles remain inflected over the hard grains of chemically prepared casein. But the tentacles remain inflected for an equally long time over finely powdered, precipitated phosphate of lime; phos- phorus in this latter case evidently being the attraction, and animal matter in the case of casein. The leaves remain long inflected over insects, but it is doubtful how far this is due to the protection afforded by their chitinous integu- ments; for animal matter is soon extracted from insects (probably by exosmose from their bodies into the dense sur- rounding secretion), as shown by the prompt inflection of the leaves. We see the influence of the nature of different substances in bits of meat, albumen, and flesh gluten acting very differently from equal-sized bits of gelatine, areolar tissue, and the fibrous basis of bone. The former cause not only far more prompt and energetic, but more prolonged, inflection than do the latter. Hence we are, I think, justi- fied in believing that gelatine, areolar tissue, and the fibrous basis of bone, would be far less nutritious to Drosera than such substances as insects, meat, albumen, &c. This is an interesting conclusion, as it is known that gelatine affords but little nutriment to animals; and so, probably would areolar tissue and the fibrous basis of bone. ‘The chondrin which I used acted more powerfully than gelatine, but then I do not know that it was pure. It is a more remarkable fact that fibrin, which belongs to the great class of Proteids,* including albumen in one of its sub-groups, does not excite the tentacles in a greater degree, or keep them inflected for a longer time, than does gelatine, or areolar tissue, or the fibrous basis of bone. It is not known how long an animal * See the classification adopted by Dr. Michael Foster in Watts’ ‘Dict. of Chemistry,’ Supplement 1872, p. 969. 110 DROSERA ROTUNDIFOLIA. [CHAP VI. would survive if fed on fibrin alone, but Dr. Sanderson has no doubt longer than on gelatine, and it would be hardly rash to predict, judging from the effects on Drosera, that albumen would be found more nutritious than fibrin. Globulin likewise belongs to the Proteids, forming another sub-group, and this substance, though containing some matter which excited Drosera rather strongly, was hardly attacked by the secretion, and was very little or very slowly attacked by gastric juice. How far globulin would be nutritious to animals is not known. We thus see how differently the above specified several digestible substances act on Drosera; and we may infer, as highly probable, that they would in like manner be nutritious in very different degrees both to Drosera and to animals. The glands of Drosera absorb matter from living seeds, which are injured or killed by the secretion. They likewise absorb matter from pollen, and from fresh leaves; and this is notoriously the case with the stomachs of vegetable- feeding animals. Drosera is properly an insectivorous plant; but as pollen cannot fail to be often blown on to the glands, as will occasionally the seeds and leaves of sur- rounding plants, Drosera is, to a certain extent, a vegetable- feeder. Finally the experiments recorded in this chapter show us that there is a remarkable accordance in the power of digestion between the gastric juice of animals with its pepsin and hydrochloric acid and the secretion of Drosera with its ferment and acid belonging to the acetic series. We can therefore hardly doubt that the ferment in both cases is closely similar, if not identically the same. That a plant and an animal should pour forth the same, or nearly the same, complex secretion, adapted for the same purpose of digestion, is a new and wonderful fact in physiology. But I shall have to recur to this subject in the fifteenth chapter, in my concluding remarks on the Droseracew, Cuar. VIL] SALTS OF AMMONIA. 111 CHAPTER VII. THE EFFECTS OF SALTS OF AMMONIA. Manner of performing the experiments—Action of distilled water in com- parison with the solutions—Carbonate of ammonia, absorbed by the roots —The vapour absorbed by the glands—Drops on the disc—Minute drops applied to separate glands—Leayes immersed in weak solutions—Minute- ness of the doses which induce aggregation of the protoplasm—Nitrate of ammonia, analogous experiments with—Phosphate of ammonia, analogous experiments with—Other saits of ammonia—Summary and concluding remarks on the action of the salts of ammonia, TuE chief object in this chapter is to show how powerfully the salts of ammonia act on the leaves of Drosera, and more especially to show what an extraordinarily small quantity suffices to excite inflection. I shall therefore be compelled to enter into full details. Doubly distilled water was always used; and for the more delicate experiments, water which had been prepared with the utmost possible care was given me by Professor Frankland. The graduated measures were tested, and found as accurate as such measures can be. The salts were carefully weighed, and in all the more delicate experiments, by Borda’s double method. But extreme accuracy would have been superfluous, as the leaves differ greatly in irritability, according to age, condition, and constitution. Even the tentacles on the same leaf differ in irritability to a marked degree. My experiments were tried in the following several ways. Firstly.—Drops which were ascertained by repeated trials to be on an average about half a minim, or the 51, of a fluid ounce (*0296 c.c.), were placed by the same pointed instrument on the dises of the leaves, and the inflection of the exterior rows of tentacles observed at succes- sive intervals of time. It was first ascertained, from between thirty and forty trials, that distilled water dropped in this manner produces no effect, except that sometimes, though rarely, two or three tentacles become inflected. In fact all the many trials with solutions which were so weak as to produce no effect lead to the same result that water is inefficient. : ; Secondly.—The head of a small pin, fixed into a handle, was dipped 112 DROSERA ROTUNDIFOLIA. (Cuar. VII. into the solution under trial. The small drop which adhered to it, and which was much too small to fall off, was cautiously placed, by the aid of a lens, in contact with the secretion surrounding the glands of one, two, three, or four of the exterior tentacles of the same leaf. Great care was taken that the glands themselves should not be touched. I had supposed that the drops were of nearly the same size; Dut on trial this proved a great mistake. I first measured some water, and removed 300 drops, touching the pin’s head each time on blotting- paper; and on again measuring the water, a drop was found to equal on an average about the ṣẹ of a minim. Some water in a small vessel Was weighed (and this is a more accurate method), and 300 drops re- moved as before; and on again weighing the water, a drop was found to equal on an average only the 3; ofa minim. I repeated the opera- tion, but endeavoured this time, by taking the pin’s head out of the water obliquely and rather quickly, to remove as large drops as possible; and the result showed that I had succeeded, for each drop on an average equalled qz ofa minim. I repeated the operation in 19-4 exactly the same manner, and now the drops averaged 5235 of a Ə minim. Bearing in mind that on these two latter occasions special pains were taken to remove as large drops as possible, we may safely conclude that the drops used in my experiments were at least equal to the J, of a minim, or *0029 c.c. One of these drops could be applied to three or even four glands, andif the tentacles became inflected, some of the solution must have been absorbed by all; for drops of pure water, applied in the same manner, never produced any effect. I was able to hold the drop in steady contact with the secretion only for ten to tifteen seconds; and this was not time enough for the diffusion of all the salt in solution, as was evident, from three or four tentacles treated successively with the same drop, often becoming inflected. All the matter in solution was even then probably not exhausted. Thirdly.—Leaves were cut off and immersed in a measured quantity of the solution under trial; the same number of leaves being im- mersed at the same time, in the same quantity of the distilled water which had been used in making the solution. ‘The leaves in the two lots were compared at short intervals of time, up to 24 hrs., and some- times to 48 hrs. They were immersed by being laid as gently as possible in numbered watchglasses, and thirty minims (1:775 c.c.) of the solution or of water was poured over each. Some solutions, for instance that of carbonate of ammonia, quickly discolour the glands; and as all on the same leaf were discoloured simultaneously, they must all have absorbed some of the salt within the same short period of time. This was likewise shown by the simultaneous inflection of the several exterior rows of tentacles. If we had no such evidence as this, it might have been supposed that only the glands of the exterior and inflected tentacles had absorbed the salt; or that only those on the disc had absorbed it, and had ther transmitted a motor impulse to the exterior tentacles; but in this latter case the exterior tentacles would not have become inflected aiaa patie ee ye — Cumar. VIL] EFFECTS OF WATER. 113 until some time had elapsed, instead of within half an hour, or even within a few minutes, as usually occurred. All the glands on tke same leaf are of nearly the same size, as may best be seen by cutting off a narrow transverse strip, and laying it on its side; hence their absorbing surfaces are nearly equal. The iong-headed glands on the extreme margin must be excepted, as they are much longer than the others; but only the upper surface is capable of absorption. Besides the glands, both surfaces of the leaves and the pedicels of the tentacles bear numerous minute papillæ, which absorb carbonate of ammonia, an infusion of raw meat, metallic salts, and probably many other substances, but the absorption of matter by these papillæ never induces inflection. We must remember that the movement of each separate tentacle depends on its gland being excited, except when a motor impulse is transmitted from the glands of the disc, and then the movement, as just stated, does not take place until some little time has elapsed. I have made these remarks because they show us that when a leaf is immersed in a solution, and the tentacles are inflected, we can judge with some accuracy how much of the salt each gland has absorbed. For instance, if a leaf bearing 212 glands, be immersed in a measured quantity of a solution, containing , of a grain of a salt, and all the exterior tentacles, except twelve, are inflected, we may feel sure that each of the 200 glands can on an average have absorbed at most sg, of a grain of the salt. I say at most, for the papilla will have absorbed some small amount, and so will perhaps the glands of the twelve excluded tentacles which did not become intlected. ‘The application of this principle leads to remarkable conclusions with respect to the minuteness of the doses causing inflection. On the Action of Distilled Water in causing Inflection. Although in all the more important experiments the difference between the leaves simultaneously immersed in water and in the several solutions will be described, nevertheless it may be well here to give a summary of the effects of water. ‘lhe fact, moreover, of pure water acting on the glands deserves in itself some notice. Leaves to the number of 141 were immersed in water at the same time with those in the solutions, and their state recorded at short intervals of time. Thirty-two other leaves were separately observed in water, making altogether 173 experiments. Many scores of leaves were also immersed in water at other times, but no exact record of the effects produced was kept; yet these cursory observations support the con- clusions arrived at in thischapter. A few of the long-headed tentacles, namely from one to about six, were commonly inflected within half an hour after immersion; as were occasionally a few, and rarely a considerable number of the exterior round-headed tentacles. After an immersion of from 5 to 8 hrs. the short tentacles surrounding the outer parts of the disc generally become inflected, so that their glands form a small dark ring on the disc; the exterior tentacles not par- I 114 DROSERA ROTUNDIFOLIA. [Cuar. VIL taking of this movement. Hence, excepting iu a few cases hereafter to be specified, we can judge whether a solution produces any efiect only by observing the exterior tentacles within the first 3 or 4 hrs. after immersion. Now for a summary of the state of the 173 leaves after an immersion of 3 or 4 hrs. in pure water. One leaf had almost all its tentacles inflected ; three leaves had most of them sub-inflected ; and thirteen had on an average 36°5 tentacles inflected. Thus seventeen leaves out of the 173 were acted on in a marked manner. Eighteen leaves bad from seven to nineteen tentacles inflected, the average being 9°3 ten- tacles for each leaf. Forty-four leaves had from one to six tentacles inflected, generally the long-headed ones. So that altogether of the 173 leaves carefully observed, seventy-nine were aflected by the water in some degree, though commonly toa very slight degree ; and ninety-four were not affected in the least degree. This amount of inflection is utterly insignifi- cant, as we shall hereafter see, compared with that caused by very weak solutions of several salts of ammonia. Plants which have lived for some time in a rather high tem- perature are far more sensitive to the action of water than those grown out of doors, or recently brought inte a warm greenhouse. ee Thus in the above seventeen cases, (Drosera rotundifolia.) in which the immersed leaves had dest (enlarked) with ail the tentacles a considerable number of tentacles closely inflected, from immersion in a inflected, the plants had been kept solution of phosphate of ammonia (one during the winter in a very warm part to 87,500 of water). ~ c greenhouse; and they bore in the early spring remarkably fineleaves, of a light red colour. Had I then known that the sensitiveness of plants was thus increased, perhaps I should not have used the leaves for my experiments with the very weak solutions of phosphate of ammonia; but my experiments are not thus vitiated, as I invariably used leaves from the same plants for simultaneous immersion in water. It often happened that some leaves on the same plant, and some ten- tacles on the same leaf, were more sensitive than others; but why this should be so, I do not know. Besides the differences just indicated between the leaves immersed in water and in weak solutions of ammonia, the tentacles of the latter are in most cases much more closely inflected. The appearance of a set seietieee ad en aR ae TOE, zep rey We eee ee er Cuar. VIL] CARBONATE OF AMMONIA. 115 leaf after immersion in a few drops of a solution of one grain of phosphate of ammonia to 200 oz. of water (ùe. one part to 87,500) is here reproduced: such energetic inflection is never caused by water alone. With leaves in the weak solutions, the blade or lamina otten becomes inflected; and this is so rare a circumstance with leaves in water that I have seen only two instances; and in both of these the inflection was very feeble. Again, with leaves in the weak solutions the inflection of the tentacles and blade often goes on steadily, though slowly, increasing during many hours; and this again is so rare a cir- cumstance with leaves in water that I have seen only three instances of any such increase after the first 8 to 12 hrs.; and in these three instances the two outer rows of tentacles were not at all affected. Hence there is sometimes a much greater difference between the leaves in water and in the weak solutions, after from 8 hrs. to 24 hrs., than there was within the first 3 hrs.; though as a general rule it is best to trust to the difference observed within the shorter time. With respect to the period of the re-expansion of the leaves, when left immersed either in water or in the weak solutions, nothing could be more variable. In both cases the exterior tentacles not rarely begin to re-expand, after an interval of only from 6 to 8 hrs.; that is just about the time when the short tentacles round the borders of the disc become inflected. On the other hand the tentacles sometimes remain inflected for a whole day or even two days; but as a general rule they remain inflected for a longer period in very weak solutions than in water. In solutions which are not extremely weak, they never re-expand within nearly so short a period as six or eight hours. From these statements it might be thought difficult to distinguish between the effects of water and the weaker solutions; but in truth there is not the slightest difficulty until excessively weak solutions are tried ; and then the distinction, as might be expected, becomes very doubtful, and at last disappears. But as in all, except the simplest, cases the state of the leaves simultaneously immersed for an equal length of time water and in the solutions will be described, the reader can judge for himself. CARBONATE OF AMMONIA. This salt, when absorbed by the roots, does not cause the tentacles to be inflected. A plant was so placed in a solution of one part of the carbonate to 146 of water that the young uninjured roots could be observed. The terminal cells, which were of a pink colour, instantly became colourless, and their limpid contents cloudy, like a mezzo-tinto engraving, SO that some degree of aggregation was almost instantly caused , but no further change ensued, and the absorbent hairs were not visibly affected. The tentacles did not bend. Two 12 116 DROSERA ROTUNDIFOLIA. [Cuap. VII. other plants were placed with their roots surrounded by damp moss, in half an ounce (14:198 c.c.) of a solution of one part of the carbonate to 218 of water, and were observed for 24 hrs.; but not a single tentacle was inflected. In order to produce this effect, the carbonate must be absorbed by the glands. The vapour produces a powerful effect on the glands, and induces inflection. Three plants with their roots in bottles, so that the surrounding air could not have become very humid, were placed under a bell-glass (holding 122 fluid ounces), together with 4 grains of carbonate of ammonia in a watch-glass. After an interval of 6 hrs. 15 m. the leaves appeared unaffected ; but next morning, after 20 hrs., the blackened glands were secreting copiously, and most of the tentacles were strongly inflected. These plants soon died. Two other plants were placed under the same _ bell-glass together with half a grain of the carbonate, the air being rendered as damp as possible; and in 2 hrs. most of the leaves were affected, many of the glands being blackened and the tentacles inflected. But it isa curious fact that some of the closely adjoining tentacles on the same leaf, both on the disc and round the margins, were much, and some, apparently, not in the least affected. The plants were kept under the bell-glass for 24 hrs., but no further change ensued. One healthy leaf was hardly at all affected, though other leaves on the same plant were much affected. On some leaves all the tentacles on one side, but not those on the opposite side, were inflected. I doubt whether this extremely unequal action can be explained by supposing that the more active. glands absorb all the vapour as quickly as it is generated, so that none is left for the others; for we shall meet with analogous cases with air thoroughly permeated with the vapours of chloroform and ether. Minute particles of the carbonate were added to the secre- tion surrounding several glands. These instantly became black and secreted copiously; but, except in two instances, when extremely minute particles were given, there was no inflection. This result is analogous to that which follows from the immersion of leaves in a strong solution of one part of the carbonate to 109, or 146, or even 218 of water, for the leaves are then paralysed and no inflection ensues, though the glands are blackened, and the protoplasm in the cells of the tentacles undergoes strong aggregation, Cuar. VIL] CARBONATE OF AMMONIA. 117 We will now turn to the effects of solutions of the carbonate. Half- minims of a solution of one part to 437 of water were placed on the discs of twelve leaves ; so that each received 545 ofa grain or ‘0675 mg. Ten of these had their exterior tentacles well inflected; the blades of some being also much curved inwards. In two cases several of the exterior tentacles were inflected in 35 m.; but themovement was generally slower. ‘These ten leaves re-expanded in periods varying between 21 hrs. and 45 hrs., but in one case not until 67 hrs. had elapsed; so that they re-expanded much more quickly than leaves which have caught insects. The same-sized drops of a solution of one part to 875 of water were placed on the discs of eleven leaves; six remained quite unaffected, whilst five had from three to six or eight of their exterior tentacles intlected; but this degree of movement can hardly be considered as trustworthy. Each of these leaves received sp of a grain (*0337 mg.), distributed between the glands of the disc, but this was too small an amount to produce any decided effect on the exterior tentacles, the glands of which had not themselves received any of the salt. Minute drops on the head of a small pin, of a solution of one part of the carbonate to 218 of water, were next tried in the manner above described. A drop of this kind equals on an average ;45 of a minim, and therefore contains gsp of a grain (°0135 mg.) of the carbonate. 1 touched with it the viscid secretion round three glands, so that each gland received only ;;19,5 of a grain (*00445 mg.). Nevertheless, in two trials all the glands were plainly blackened ; in one case all three tentacles were well inflected after an interval of 2 hrs. 40 m.; and in another case two of the three tentacles were inflected. I then tried drops of a weaker solution of one part to 292 of water on twenty-four glands, always touching the viscid secretion round three glands with the same little drop. Each gland thus received only the z5455 of a grain (°00337 mg.), yet some of them were a little darkened; but in no one instance were any of the tentacles inflected, though they were watched for 12 hrs. When a still weaker solution (viz. one part to 437 of water) was tried on six glands, no effect whatever was perceptible. We thus learn that the z;15, of a grain (*00445 mg.) of carbonate of ammonia, if absorbed by a gland, suffices to induce inflection in the basal part of the same tentacle; but as already stated, I was able to hold with a steady hand the minute drops in contact with the secretion only for a few seconds; and if more time had been allowed ior diffusion and absorption, a much weaker solution would certainly have acted. Some experiments were made by immersing cut-off leaves in solutions of different strengths. Thus four leaves were left for about 3 hrs. each in a drachm (3°549 c.c.) of a solution of one part of the carbonate to 5250 of water; two of these had almost every tentacle intlected, the third had about half the tentacles and the fourth about one-third inflected; and all the glands were blackened. Another leaf was placed in the same quantity of a solution of one part to 7000 of water, and in 1 hr. 16 m. every single tentacle was well infected, and 118 DROSERA ROTUNDIFOLIA. [Cuar. VII. all the glands blackened. Six leaves were immersed, each in thirty minims (1°774. c.c.) of a solution of one part toj4375 of water, and the glands were all blackened in 31 m. All six leaves exhibited some slight inflection, and one was strongly inflected. Four leaves were then immersed in thirty minims of a solution of one part to 8750 of water, so that each leaf received the 53; of a grain (*2025 mg.). Only one became strongly inflected; but all the glands on all the leaves were of so dark a red after one hour as almost to deserve to be called black, whereas this did not occur with the leaves which were at the same time immersed in water; nor did water produce this effect on any other occasion in nearly so short a time as an hour. These cases of the simultaneous darkening or blackening of the glands from the action of weak solutions are important, as they show that all the glands absorbed the carbonate within the same time, which fact indeed there was not the least reason to doubt. So again, whenever all the tentacles become inflected within the same time, we have evidence, as before remarked, of simultaneous absorption. I did not count the number of glands on these four leaves; but as they were fine ones, and as we know that the average number of glands on thirty-one leaves was 192, we may safely assume that each bore on an average at least 170; and if so, each blackened gland could have absorbed only z147 Of a grain (*00119 mg.) of the carbonate. A large number of trials had been previously made with solutions of one part of the nitrate and phosphate of ammonia to 43750 of water (i. e. one grain to 100 ounces), and these were found highly efficient. Fourteen leaves were therefore placed, each in thirty minims of a solution of one part of the carbonate to the above quantity of water ; so that each leaf received -gpp of a grain (°0405 mg.). The glands were not much darkened. ‘Ten of the leaves were not affected, cr only very slightly so. Four, however, were strongly affected; the first having all the tentacles, except forty, inflected in 47 m. ; in 6 hrs. 80m. all except eight; and after 4 hrs. the blade itself. The second leaf after 9 m. had all its tentacles except nine inflected; after 6 hrs. 30 m. these nine were sub-inflected ; the blade having become much inflected in4hrs. The third leaf after 1 hr. 6 m. had all but forty tentacles inflected. The fourth, after 2 hrs. 5 m., had about half its tentacles and after 4 hrs. all but forty-five inflected. Leaves which were immersed in water at the same time were not at all affected, with the exception of one; and this not until 8 hrs. had elapsed. Hence there can be no doubt that a highly sensitive leaf, if immersed in a solution, so that all the glands are able to absorb, is acted on by 105p Of a grain of the carbonate. Assuming that the leaf, which was a large one, and which had all its tentacles excepting eight inflected, bore 170 glands, each gland could have absorbed only 33555 of a grain (-00024 mg.) ; yet this sufficed to act on each of the 162 tentacles which were inflected. But as only four out of the above fourteen leaves were plainly affected, this is nearly the minimum dose which is efficient. Aggregation of the Protoplasm from the Action of Carbonate of remoting Niles Cuar. VIL] CARBONATE OF AMMONIA. 119 Ammonia.—I have fully described in the third chapter the remarkable effects of moderately strong doses of this salt in causing the aggre- gation of the protoplasm within the cells of the glands and tentacles ; and here my object is merely to show what small doses suffice. A leaf was immersed in twenty minims (1°183 c.c.) of a solution of one part to 1750 of water, and another leaf in the same quantity of a solution of one part to 3062; in the former case aggregation occurred in 4 m., in the latter in 11m. A leaf was then immersed in twenty minims of a solution of one part to 4375 of water, so that it received gis of a grain (*27 mg.); in 5 m. there was a slight change of colour in the glands, and in 15 m. small spheres of protoplasm were formed in the cells beneath the glands of all the tentacles. In these cases there could not be a shadow of a doubt about the action of the solution. A solution was then made of one part to 5250 of water, and F experimented on fourteen leaves, but will give only a few of the cases. Hight young leaves were selected and examined with care, and they showed no trace of aggregation. Four of these were placed in a drachm (3:549 c.c.) of distilled water; and four in a similar vessel, with a drachm of the solution. After a time the leaves were examined under a high power, being taken alternately from the solution and the water. ‘The first leaf was taken out of the solution after an immersion of 2 hrs. 40 m., and the last leaf out of the water after 3 hrs. 50 m.; the examination lasting for 1 hr. 40 m. In the four leaves out of the water there was no trace of aggregation except in one specimen, in which a very few extremely minute spheres of protoplasm were present beneath some of the round glands. All the glands were translucent and red. The four leaves which had been immersed in the solution, besides being inflected, presented a widely different appearance; for the contents of the cells of every single tentacle on all four leaves were conspicucusly aggregated; the spheres and elongated masses of proto- plasm in many cases extending halfway down the tentacles. All the glands, both those of the central and exterior tentacles, were opaque and blackened; and this shows that all had absorbed some of the carbonate. These four leaves were of very nearly the same size, and the glands were counted on one and found to be 167. This being the case, and the four leaves having been immersed in a drachm of the solution, each gland could have received on an average only g;455 of a grain (001009 mg.) of the salt : and this quantity sufficed to induce within a short time conspicuous aggregation in the cells beneath all the glands. A vigorous but rather small red leaf was placed in six minims of the same solution (viz. one part to 5250 of water), so that it received 5}5 of a grain (0675 mg). In 40 m. the glands appeared rather darker ; and in 1 hr. from four to six spheres of protoplasm were formed in the cells beneath the glands of all. the tentacles. I did not count the tentacles ; but we may safely assume that there were at least 140; and if so, each gland could have received only the z3dyo5 Of @ grain, or -00048 mg. A weaker solution was then made of one part to 7000 of water, and 120 DROSERA ROTUNDIFOLIA. [Cuar. VII. four leaves were immersed in it; but I will give only one case. A leaf was placed in ten minims of this solution; after 1 hr. 37 m. the glands became somewhat darker, and the cells beneath all of them now contained many spheres of aggregated protoplasm. This leaf received aig of a grain, and bore 166 glands. ach gland could, therefore, have received only y37¢s¢ of a grain (*000507 mg.) of the carbonate. ‘wo other experiments are worth giving. A leaf was immersed for 4 hrs. 15 m. in distilled water, and there was no aggregation ; it was then placed for 1 hr. 15 m. in a little solution of one part to 5250 of water; and this excited welf-marked aggregation and inflection. Another leaf, after having been immersed for 21 hrs. 15 m. in distilled water, had its glands blackened, but there was no aggregation in the cells beneath them ; it was then left in six minims of the same solution, and in 1 hr. there was much aggregation in many of the tentacles; in 2 hrs. all the tentacles (146 in number) were affected—the aggregation extending down for a len:th equal to half or the whole of the glands. lt is extremely improbable that these two leaves would have undergone aggregation if they had been left for a little longer in the water, namely for 1 hr. and 1 hr. 15 m., during which time they were immersed in the solution; for the process of aggregation seems in- variably to snpervene slowly and very gradually in water. Summary of the Results with Carbonate of Ammonia.—The roots absorb the solution, as shown by their changed colour, aud by the aggregation of the contents of their cells. The vapour is absorbed by the glands; these are blackened, and the tentacles are intiected. The glands of the disc, when excited by a half-minim drop (‘0296 c.c.), containing 51, of a grain (‘0675 mg.), transmit a motor impulse to the exterior tentacles, causing them to bend inwards. A minute drop, containing yz}, Of a grain (-00445 mg.), if held for a few seconds in contact with a gland, soon causes the tentacle bearing it to be inflected. If a leaf is left immersed for a few hours in a solution, and a gland absorbs the +y+ryy of a grain (00048 mg.), its colour becomes darker, though not actually black; and the contents of the cells beneath the gland are plainly aggregated. Lastly, under the same circumstances, the absorption by a gland of the s¢soy of a grain (-00024 mg.) suffices to excite the tentacle bearing this gland into movement. NITRATE OF AMMONIA. With this salt I attended only to the inflection of the leaves, for it is far less efficient than the carbonate in causing aggregation, although considerably more potent in causing inflection. I experimented with Se... Cuar. VIL] NITRATE OF AMMONIA. 121 half-minims (+0296 c.c.) on the discs of fifty-two leaves, but will give only a few cases. A solution of one part to 109 of water was too strong, causing little inflection, and after 24 hrs. killing, or nearly killing, four out of six leaves which were thus tried; each of which received the zły of a grain (or *27 mg.). A solution of one part to 218 of water acted most energetically, causing not only the tentacles of all the leaves, but the blades of some to be strongly inflected. Fourteen leaves were tried with drops of a solution of one part to 875 of water, so that the diss of each received the +4, of a grain (‘0337 mg,). Of these leaves, seven were very strongly acted on, the edges being generally inflected ; two were moderately acted on; and five notatail. I subsequently tried three of these latter five leaves with urine, saliva, and mucus, but they were only slightly affected; and this proves that they were not in an active condition. I mention this fact to show how necessary it is to experiment on several leaves. Two of the leaves, which were well intiected, re-expanded after 51 hrs. In the following experiment I happened to select very sensitive leaves. Half-minims of a solution of one part to 1094 of water (i.e. 1 gr. to 23 oz.) were placed on the discs of nine leaves, so that each received the 5345 of a grain (*027 mg.). ‘Three of them had their tentacles strongly inflected and their blades curled inwards; five were slightly and somewhat doubtfully affected, having from three to eight of their exterior tentacles inflected; one leaf was not at all affected, yet was afterwards acted on by saliva. In six of these cases, a trace of action was perceptible in 7 hrs., but the full effect was not produced until from 24 hrs, tu 80 hrs. had elapsed. Two of the leaves, which were only slightly inflected, re-expanded after an additional interval of 19 hrs. Half-minims of a rather weaker solution, viz. of one part to 1312 of water (1 gr. to 3 oz.) were tried on fourteen leaves; so that each received 5,4, of a grain (*0225 mg.), instead of, as in the last experi- ment, 5,455 of a grain. ‘lhe blade of one was plainly inflected, as were 3 six of the exterior tentacles; the blade of a second was slightly, and two of the exterior tentacles well inflected, all the other tentacles being curled in at right angles to the disc ; three other leaves had trom tive to eight tentacles inflected ; five others only two or three, and occasionally, though very rarely, drops of pure water cause this much action; the four remaining leaves were in no way affected, yet three of them, when subsequently tried with urine, became greatly inflected. In most of these cases a slight effect was perceptible in from 6 hrs. to 7 hrs., but the full effect was not produced until from 24 hrs. to 30 hrs. had elapsed. It is obvious that we have reached very nearly the minimum amount, which, distributed between the glands of the disc, acts on the exterior tentacles; these having themselves not received any of the solution. : In the next place, the viscid secretion round three of the exterior glands was touched with the same little drop (54; of a minim) of a solution of one part to 437 of water; and after an interval of 2 hrs. 50 m. all three tentacles were well inflected. Each of these glands a DROSERA ROTUNDIFOLIA. [Cuar. VIE. could have received only the si55 of a grain, or 00225 mg. A little drop of the same size and strength was also applied to four other of this strength produced no effect. I tried minute drops of a still weaker solution of the nitrate, viz. one part to 875 of water, on twenty-one glands, but no effect whatever was produced, except perhaps in one instance. Sixty-three leaves were immersed in solutions of various strengths ; other leaves being immersed at the same time in the same pure water used in making the solutions. The results are so remarkable, though less so than with phosphate of ammonia, that I must describe the experiments in detail, but I will give only a few. In speaking of the successive periods when inflection occurred, I always reckon from the time of first immersion. Having made some preliminary trials as a guide, five leaves were placed in the same little vessel in thirty minims of a solution of one part of the nitrate to 7875 of water (1 gr. to 18 oz.); and this amount of fluid just sufticed to cover them. After 2 hrs. 10 m. three of the leaves were considerably inflected, and the other two moderately. The glands of all became of so dark a red as a’most to deserve to be called black. After 8 hrs. four of the leaves had all their tentacles more or less inflected ; whilst the fifth, which I then perceived to be an old leaf, had only thirty tentacles inflected. Next morning, after 23 hrs. 40 m., all the leaves were in the same state, excepting that the old leaf had a few more tentacles inflected. Five leaves which had been placed at the same time in water were observed at the same intervals of time; after 2 hrs. 10 m. two of them had four, one had seven, one had ten, of the long-headed marginal tentacles, and the fifth had four round-headed tentacles, inflected. After 8 hrs. there was no change in these leaves, and alter 24 hrs. all the marginal tentacles had re- expanded ; but in one leaf, a dozen, and in a second leaf, half a dozen, submarginal tentacles had become inflected. As the glands of the five leaves in the solution were simultaneously darkened, no doubt they had all absorbed a nearly equal amount of the salt: and as si; of a grain was given to the five leaves together, each got -44y of a grain (°045 mg.). 1 did not count the tentacles on these leaves, which were moderately fine ones, but as the average number on thirty-one leaves was 192, it would be safe to assume that each bore on an average at least 160. If so, each of the darkened glands could have received only ssa4ao Of a grain of the nitrate ; and this caused the inflection of a great majority of the tentacles. This plan of immersing several leaves in the same vessel is a bad cne, as it is impossible to feel sure that the more vigorous leaves do not rob the weaker ones of their share of the salt. The glands, more- over, must often touch one another or the sides of the vessel, and Cmar. VIL] NITRATE OF AMMONIA. 128 movement may have been thus excited; but the corresponding leaves in water, which were little inflected, though rather more so than commonly occurs, were exposed in an almost equal degree to these same sources of error. I wiil, therefore, give only one other experiment made in this manner, though many were tried and all confirmed the foregoing and following results. Four leaves were placed in forty minims of a solution of one part to 10,500 of water; and assuming that they absorbed equally, each leaf received ;)55 of a grain (*0562 mg.). After 1 hr. 20 m. many of the tentacles on all four leaves were somewhat inflected. After 5 hrs. 30 m. two leaves had all their tentacles inflected; a third leaf all except the extreme marginals, which seemed old and torpid; and the fourth a large number. After 21 hrs. every single tentacle, on all four leaves, was closely inflected. Of the four leaves placed at the same time in water, one had, after 5 hrs. 45 m., five marginal tentacles inflected; a second, ten; a third, nine marginals and submarginals; and the fourth, twelve, chiefly sub- marginals, inflected. After 21 hrs. all these marginal tentacles re- expanded, but a few of the submarginals on two of the leaves remained slightly curved inwards. The contrast was wonderfully great between these four leaves in water and those in the solution, the latter having every one of their tentacles closely inflected. Making the moderate assumption that each of these leaves bore 160 tentacles, each gland could have absorbed only , 7355 of a grain (*000351 mg.). This ex- periment was repeated on three leaves with the same relative amount of the solution ; and after 6 hrs. 15 m. all the tentacles except nine, on all three leaves taken together, were closely intlected. In this case the tentacles on each leaf were counted, and gave an average of 162 er leaf. The following experiments were tried during the summer of 1873, by placing the leaves, each in a separate watch-glass and pouring over it thirty minims (1°775 c.c.) of the solution; other leaves being treated in exactly the same manner with the doubly distilled water used in making the solutions. The trials above given were made several years before, and when I read over my notes, I could not believe in the results; so I resolved to begin again with moderately strong solutions. Six leaves were first immersed, each in thirty minims of a solution of one part of the nitrate to 8750 of water (1 gr. to 20 0z.), so that each received 1, of a grain (*2025 mg.). Before 30 m. had elapsed, four of these leaves were immensely, and two of them moder- ately, inflected. The glands were rendered of a dark red. The four corresponding leaves in water were not at all affected until 6 hrs. had elapsed, and then only the short tentacles on the borders of the disc; and their inflection, as previously explained, is never of any significance. : Four leaves were immersed, each in thirty minims of a solution of one part to 17,500 of water (1 gr. to 40 oz.), so that each received 5}, of a grain (‘101 mg.); and in less than 45 m. three of them had all their tentacles, except from four to ten, inflected ; the blade of one 124 DROSERA ROTUNDIFOLIA. [Ckar. VIL. being inflected after 6 hrs., and the blade of a second after 21 hrs. The fourth leaf was not at all affected. The glands of none were darkened. Of the corresponding leaves in water, only one had any of its exterior tentacles, namely five, inflected; after 6 hrs. in one case, and after 21 hrs. in two other cases, the short tentacles on the borders of the disc formed a ring, in the usual manner. ~ Four leaves were immersed, each in thirty minims of a solution of one part to 43,750 of water (1 gr. to 100 0z.), so that each leaf got seo Of a grain (°0405 mg.). Of these, one was much inflected in 8 m., and after 2 hrs. 7m. had all the tentacles, except thirteen, inflected. ‘The second leaf, alter 10 m., had all except three inflected. The third and fourth were hardly at ail affected, scarcely more than the cor- responding leaves in water. Of the latter, only one was affected, this having two tentacles inflected, with those on the outer parts of the disc forming a ring in the usual manner. In the leaf which had all its tentacles except three inflected in 10 m., each gland (assuming that the leaf bore 160 tentacles) could have absorbed only 33~;o9 of a grain, or *Q00258 mg. four leaves were separately immersed as before in a sclution of one part to 131,250 of water (1 gr. to 300 0z.), so that each received z355 of a grain, or 0135 mg. After 50 m. one leaf had all its tentacles except sixteen, and after 8 hrs. 20 m. all but fourteen, inflected. The second leaf, after 40 m, had all but twenty inflected; and after 8 hrs. 10 m. began to re-expand. The third, in 3 hrs. had about half its tentacles inflected, which began to re-expand after 8 hrs. 15 m. The fourth leaf, after 3 hrs. 7 m., had only twenty-nine tentacles more or less inflected. Thus three out of the four leaves were strongly acted on. Itis clear that very sensitive leaves had been accidentally selected. The day moreover was hot. The four corresponding leaves in water were likewise acted on rather more than is usual; for after 3 hrs, one had nine tentacles, another four, and another two, and the fourth none, inflected. With respect to the leaf of which all the tentacles, except sixteen, were inflected after 50 m., each gland (as- suming that the leaf bore 160 tentacles) could have absorbed only Sorzo0 Of a grain (*0000937 mg.), and this appears to be about the least quantity of the nitrate which suffices to induce the inflection of a single tentacle. As negative results are important in confirming the foregoing positive ones, eight leaves were immersed as before, each in thirty minims of a solution of one part to 175,000 of water (1 gr. to 400 0z.), so that each received only a5 of a grain (*0101 mg.). This minute quantity produced a slight effect on only four of the cight leaves. One had titty-six tentacles inflected after 2 hrs. 13 m.; a second, twenty-six intlected, or sub-inflected, after 38 m.; a third, eighteen inflected, after lhr.; and a fourth, ten inflected, after 35 m. The four other leaves were not in the least affected. Of the eight corresponding leaves in water, one had, after 2 hrs. 10 m., nine tentacles, and four others from one to four long-headed tentacles, inflected; the remaining three being Cuar, VII.) PHOSPHATE OF AMMONIA. 125 unaffected. Hence, the 3yo of a grain given to a sensitive leaf during warm weather perhaps produces a slight effect; but we must bear in mind that occasionally water causes as great an amount of inflection as occurred in this last experiment. Summary of the Results with Nitrate of Ammonia—The glands of the disc, when excited by a half-minim drop oer c.c.), containing zy, of a grain of the nitrate ‘027 mg. ), transmit a motor impulse to the exterior tentacles, causing them to bend inwards. A minute drop, containing avon Of a grain (-00225 mg.), if held for a few seconds in contact with a gland, causes the tentacle bearing this gland to be inflected. If a leaf is left immersed for a few hours, and sometimes for only a few minutes, in a solution of such strength that each gland can absorb only the gyy'yg5 of a grain (-0000937 mg.), this small amount is enough to excite each tentacle into movement, and it becomes closely in- flected. PHOSPHATE OF AMMONIA. This salt is more powerful than the nitrate, even in a greater degree than the nitrate is more powerful than the car- bonate. This is shown by weaker solutions of the phosphate acting when dropped on the discs, or applied to the glands of the exterior tentacles, or when leaves are immersed. The difference in the power of these three salts, as tried in three different ways, supports the results presently to be given, which are so surprising that their credibility requires every kind of support. In 1872 I experimented on twelve immersed leaves, giving each only ten minims of a solution: but this was a bad method, for so small a quantity hardly covered them. None of these experiments will, therefore, be given, though they indicate that excessively minute doses are efficient. When I read over my notes, in 1873, I entirely disbelieved them, and determined to make another set of experiments with scrupulous care, on the same plan as those made with the nitrate; namely by placing leaves in watch glasses, and pouring over each thirty minims of the solution under trial, treating at the same time and in the samo ianuer other leaves with the distilled water used in making the solutions. During 1873, seventy-one leaves were thus tried in solutions of various strengths, and the same number 126 DROSERA ROTUNDIFOLIA, (Car. VIL in water. Notwithstanding the care taken and the number of the trials made, when in the following year I looked merely at the results, without reading over my observations, I again thought that there must have been some error, and thirty-five fresh trials were made with the weakest solution; but the results were as plainly marked as before. Altogether, 106 carefully selected leaves were tried, both in water and in solutions of the phosphate. Hence, after the most anxious consideration, I can entertain no doubt of the substantial accuracy of my results. Before giving my experiments, it may be well to premise that crystallised phosphate of ammonia, such as I used, contains 35°33 per cent. of water of crystallisation; so that in all the following trials the efficient elements formed only 64°67 per cent. of the salt used. Extremely minute particles of the dry phosphate were placed with the point of a needle on the secretion surrounding several glands. These poured forth much secretion, were blackened, and ultimately died; but the tentacles moved only slightly. The dose, small as it was, evidently was too great, and the result was the same as with particles of the carbonate of ammonia. Half-minims of a solution of one part to 437 of water were placed on the discs of three leaves and acted most energetically, causing the tentacles of one to be inflected in 15 m., and the blades of all three to be much curved inwards in 2 hrs. 15 m. Similar drops of a solution of one part to 1312 of water (1 gr. to 3 oz.) were then placed on the discs of five leaves, so that each received the zy, of a grain (*0225 mg.). After 8 hrs. the tentacles of four of them were considerably inflected, and after 24 hrs. the blades of three. After 48 hrs. all five were almost iully re-expanded. I may mention with respect to one of these leaves, that a drop of water had been left during the previous 24 hrs. on its disc, but produced no effect ; and that this was hardly dry when the solution was added. Similar drops of a solution of one part to 1750 of water (1 gr. to 4 oz.) were next placed on the discs of six leaves; so that each received geio Of a grain (°0169 mg.); after 8 hrs. three of them had many tentacles and their blades inflected ; two others had only a few tentacles slightly inflected, and the sixth was not at all affected. After 24 hrs. most of the leaves had a few more tentacles inflected, but one had begun to re-expand. We thus see that with the more sensitive leaves the zg of a grain, absorbed by the central glands, is enough to make many of the exterior tentacles and the blades bend, whereas the +355 of a grain of the carbonate similarly given produced no effect ; and esp Of a grain of the nitrate was only just sufficient to produce a well- marked effect. A minute drop, about equal to ṣẹ of a minim, of a solution of one Cuar. VIL] PHOSPHATE OF AMMONIA. 127 part of the phosphate to 875 of water, was applied to the secretion on three glands, each of which thus received only 57155 of a grain (00112 mg.), and all three tentacles became inflected. Similar drops of a solution of one part to 1312 of water (1 gr. to 3 oz.) were now tried on three leaves; a drop being applied to four glands on the same leaf. On the first leaf three of the tentacles became slightly inflected in 6 m., and re-expanded after 8 hrs. 45 m. On the second, two tentacles became sub-inflected in 12 m. And on the third all four tentacles were decidedly inflected in 12 m.; they remained so for 8 hrs, 30 m., but by the next morning were fully re-expanded. In this latter case each gland could have received only the +750 (or *000563 mg.) of a grain. Lastly, similar drops of a solution of one part to 1750 of water (1 gr. to 4 0z.) were tried on five leaves; a drop being applied to four glands on the same leaf. The tentacles on three of these leaves were not’in the least affected; on the fourth leaf two became inflected ; whilst on the fifth, which happened to be a very sensitive one, all four tentacles were plainly inflected in 6 hrs. 15 m.; but only one remained inflected after 24 hrs. I should, however, state that in this case an unusually large drop adhered to the head of the pin. Each of these glands could have received very little more than 753500 of a grain (or *000423); but this small quantity sufficed to cause inflection. We must bear in mind that these drops were applied to the viscid secretion for only from 10 to 15 seconds, and we have good reason to believe that all the phosphate in the solution would not be diffused and absorbed in this time. We have seen under the same circumstances that the absorption by a gland of 5455 of a grain of the carbonate, and of 5715y of a grain of the nitrate, did not cause the tentacle bearing the gland in question to be inflected; so that here again the phosphate is much more powerful than the other two salts. We will now turn to the 106 experiments with immersed leaves. Having ascertained by repeated trials that moderately strong solutions were highly efficient, I commenced with sixteen leaves, each placed in thirty minims of a solution of one part to 43,750 of water (1 gr. to 109 02.); so that each received z,55 of a grain, or *04058 mg. Of these leaves, eleven had nearly ali or a great number of their tentacles inflected in 1 hr., and the twelfth leaf in 3 hrs. One of the eleven had every single tentacle closely inflected in 50 m. Two leaves out of the sixteen were only moderately affected, yet more so than any of those simultaneously immersed in water; and the remaining two, which were pale leaves, were hardly at all affected. Of the sixteen corre- sponding leaves in water, one had nine tentacles, another six, and two others two tentacles inflected, in the course of 5 hrs. So that the contrast in appearance between the two lots was extremely great. Eighteen leaves were immersed, each in thirty minims of a solution of one part to 87,500 of water (1 gr. to 200 oz.), so that each received gio Of a grain ('0202 mg.). Fourteen of these were strongly inflected within 2 hrs., and some of them within 15 m.; three out of 128 DROSERA ROTUNDIFOLIA. [Cuar. VII: the eighteen were only slightly affected, having twenty-one, nineteen, and twelve tentacles inflected; and one was not at all acted on. By an accident only fifteen, instead of eighteen leaves were immersed at the same time in water; these were observed for 24 hrs.; one had six, another four, and a third two, of their outer tentacles inflected; the remainder being quite unaffected. The next experiment was tried under very favourable circumstances, for the day (July 8) was very warm, and I happened to have unusually tine leaves, Five were immersed as before in a solution of one part to 131,250 of water (1 gr. to 300 oz.), so that each received adua fa grain, or *0135 mg. Afteranimmersion of 25 m. all five leaves were much inflected. After 1 hr. 25 m. one leaf had all but eight tentacles inflected ; the second, all but three; the third, all but five; the fourth, all but twenty-three; the fifth, on the other hand, never had more than twenty-four inflected. Of the corresponding five leaves in water, one had seven, a second two, a third ten, a fourth one, and a fifth none inflected. Let it be observed what a contrast is presented between these latter leaves and those in the solution. I counted the glands on the second leaf in the solution, and the number was 217; assuming that the three tentacles which did not become inflected absorbed nothing, we find that each of the 214 remaining giands could have absorbed only yga7uqo Of a grain, or *0000631 mg. The third leaf bore 236 glands, and subtracting the five which did not become inflected, each of the remaining 231 glands could have absorbed only sioisoo Of a grain (or *0000584 mg.), and this amount sufficed to cause the tentacles to bend. Twelve leaves were tried as before in a solution of one part to 175,000 of water (1 gr. to 400 0z.), so that each leaf received 535, of 2 grain (0101 mg.). My plants were not at the time in a good state, and many of the leaves were young and pale. Nevertheless, two of them had all their tentacles, except three or four, closely inflected in under 1 hr. Seven were considerably affected, some within 1 hr., and others not until 3 hrs., 4 hrs. 30 m., and 8 hrs. had elapsed; and this slow action may be attributed to the leaves being young and pale. Of these nine leaves, four had their blades well inflected, and a fifth slightly so. The three remaining leaves were not affected. With respect to the twelve corresponding leaves in water, not one had its blade inflected; after from 1 to 2 hrs. one had thirteen of its outer tentacles inflected; a second six, and four others either one or two inflected. After 8 hrs. the outer tentacles did not become more inflected; whereas this occurred with the leaves in the solution. record in my notes that after the 8 hrs. it was impossible to compare the two lots, and doubt for an instant the power of the solution. Two of the above leaves in the solution had all their tentacles, except three and four, inflected within an hour. I counted their glands, and, on the same principle as before, each gland on one leaf could have absorbed only zzg¢so, and on the other leaf only 1474000 of a grain of the phosphate. Cuar.. VIL] PHOSPHATE OF AMMONIA. 129- Twenty leaves were immersed in the usual manner, each in thirty minims of a solution of one part to 218,750 of water (1 gr. to 500 oz.). So many leaves were tried because I was then under the false im- pression that it was incredible that any weaker solution could produce an effect. Each leaf received oyy of a grain, or 0081 mg. ‘The first eight leaves which I tried both in the solution and water were either young and pale or too old; and the weather was not hot. They were hardly at all affected; nevertheless, it would be unfair to exclude them. I then waited until I had got eight pairs of fine leaves, and the weather was favourable, the temperature of the room where the leaves were immersed varyiug from 75° to 81° (23°°8 to 27°2 Cent.). In another trial with four pairs (included in the above twenty pairs), the temperature in my room was rather low, about 60° (15°°5 Cent.); but the plants had been kept for several days in a very warm greenhouse and thus rendered extremely sensitive. Special precautions were taken for this set of experiments; a chemist weighed for me a grain in an excellent balance; and fresh water, given me by Professor Frank- land, was carefully measured. The leaves were selected from a large number of plants in the following manuer: the four finest were immersed in water, and the next four finest in the solution, and so on till the twenty pairs were complete. The water specimens were thus a little favoured, but they did not undergo more inflection than in the previous cases, comparatively with those in the solution. Of the twenty leaves in the solution, eleven became inflected within 40 m.; eight of them plainly aud three rather doubtfully ; but the latter had at least twenty of their outer tentacles inflected. Owing to the weakness of the solution, inflection occurred, except in No. 1, much more slowly than in the previous trials. ‘The condition of the eleven leaves which were considerably inflected will now be given at stated intervals, always reckoning from the time of immersion :— L) After only 8 m. a large number of tentacles inflected, and after 17 m. all but fifteen; after 2 hrs. all but eight inflected, or plainly sub-inflected. After 4 hrs. the tentacles began to re-expand, and such prompt re-expansion is unusual; after 7 hrs, 30 m. they were almost fully re-expanded. (2) After 39 m. a large number of tentacles inflected; after 2 hrs, 18 m. all but twenty-five inflected; after 4 hrs. 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. K 130 DROSERA ROTUNDIFOLIA. [Cuar. VII. (T) 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; alter 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 5 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. l (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; aiter 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. 'l'hus the leaf remained for two days, when it began to re-expand. | may add that the three latter leaves (Nos. 9, 10, and 11) were still somewhat inflected after three days. The tentacles in but few of these eleven leaves became closely inflected within so short a time as in the previous experiments with stronger solutions, ove 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 ygs4o00 Of a 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 setivas of a grain, weit. | Cuar. VIL] PHOSPHATE OF AMMONIA. 131 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 s55}o55 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 z5455 Of a grain (*0054 mg.) of the salt; and all four were greatly intlected. (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 lirs, 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 dise 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 3574559 Of a grain (*0000268 mg.) and of No. 2 only szadoos 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 +;355 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 K 2 132 DROSERA ROTUNDIFOLIA. [Cuar VII. 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. 80 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 fitty-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. (T) After 4 hrs. 80 m. only thirty-five tentacles inflected or sub- inflected, and this small amount of intlection 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 leat No. 3 (which bore 233 glands, all of which, except nine, were inflected in 2 hrs. 80 m.) could have received at most only the sgstoo5 Of a grain, or *0000181 mz. 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 1 happened to select leaves which were very little sensitive, as on other occasions I chanced to select unusually sensitive leaves. The leaves were not ooo eee iite i Cuar. VIL] PHOSPHATE OF AMMONIA. igo 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 1,812,500 of water (1 er. to 3000 oz.) ; so that each leaf received = 7355 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; atter 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-ex pand, (5) to (12) These were not more inflected than leaves often are in water, having respectively 16, 8, 10, 8, 4, 9, 14, and O 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, tor 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 24 hrs. Comparing the states of the twelve leaves in water with those in the solution, there could be no doubt that in the latter a larger number of tentacles were inflected, and these to a greater degree; but the evidence was by no means so clear as in the former experiments with stronger solutions. It deserves attention that the inflection of four of the leaves 134 DROSERA ROTUNDIFOLIA. (Cuar. VII. 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 re- markable 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 astoo Of a grain of the salt. Subtracting the seventeen tentacles which were not inflected, each gland could have absorbed only the 5754000 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 21,875,000 of water 1 gr. to 5000 oz.). Each leaf thus received .545, 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. (2) No change for the first 12 hrs., but after 24 hrs. all the ten- tacles inflected, excepting those of the outermost row, of which only eleven were inflected. The inflection continued to increase, and after 48 hrs. all the tentacles except three were inflected, and most of them rather closely, four or five being only sub-inflected. (8) No change for the first 12 hrs.; but after 24 hrs. all the tentacles excepting those of the outermost row were sub-inflected, with the blade inflected. After 36 hrs. blade strongly inflected, with all the tentacles, except three, inflected or sub-inflected. After 48 hrs. in the same state. (4) to (8) These leaves, after 2 hrs. 30 m., had respectively 32, 17, T, 4, and O, tentacles inflected, most of which, after a few hours, re- expanded, with the exception of No. 4, which retained its thirty-two tentacles inflected for 48 hrs. Now for the eight corresponding leaves in water :— (1) After 2 hrs. 40 m. this had twenty of its outer tentacles inflected, five of which re-expanded alter 6 hrs. 30m. After 10 hrs. 15 m. a most unusual circumstance occurred, namely, the whole Cuap. VIL] PHOSPHATE OF AMMONIA. 135 blade became slightly bowed towards the footstalk, and so remained for 48 hrs. ‘The exterior tentacles, excepting those of the three or four outermost rows, were now also inflected to an unusual degree. (2) to (8) These leaves, after 2 hrs. 40 m., had respectively 42, 12, 9, 8, 2,1, and 0 tentacles inflected, which all re-expanded within 24 hrs., and most of them within a much shorter time. When the two lots of eight leaves in the solution and in the water were compared after the lapse of 24 hrs., they undoubtedly differed much in appearance. The few tentacles on the leaves in water which were inflected had after this interval re-expanded, with the exception of one leaf; and this presented the very unusual case of the blade being somewhat inflected, though in a degree hardly approaching that of the two leaves in the solution. Of these latter leaves, No. 1 had almost all its tentacles, together with its blade, inflected after an immersion of 2 hrs. 30 m. Leaves No. 2 and 3 were affected at a much slower rate; but after from 24 hrs. to 48 hrs. almost all their tentacles were closely inflected, and the blade of one quite doubled up. We must therefore admit, incredible as the fact may at first appear, that this extremly weak solution acted on the more sensitive leaves ; each of which received only the oboy Of a grain (*00081 mg.) of the phosphate. Now, leaf No. 3 bore 178 tentacles, and, subtracting the three which were not inflected, each gland could have absorbed only the -1005007 Of a grain, or *00000463 mg. Leaf No. 1, which was strongly acted on within 2 hrs. 30 m., and had all its outer tentacles, except thirteen, inflected within 6 hrs. 30 m., bore 260 tentacles ; and, on the same principle as before, each gland could have absorbed only ze7eooon Of a grain, or (00000328 mg.; and this excessively minute amount sufficed to cause all the tentacles bearing these glands to be greatly inflected. The blade was also inflected. Summary of the Results with Phosphate of Ammonia.—The glands of the disc, when excited by a half-minim drop (‘0296 c.c.), containing 545 of a grain (:0169 mg.) of this salt, transmit a motor impulse to the exterior tentacles, causing them to bend inwards. A minute drop, containing x53000 of a grain (-000423 mg.), if held for a few seconds in contact with a gland, causes the tentacle bearing this gland to be inflected. Ifa leaf is left immersed for a few hours, and sometimes for a shorter time, in a solution so weak that each gland can absorb only the y57¢yo00 Of a grain (00000328 ing.), this is enough to excite the tentacle into movement, so that it becomes closely inflected, as does sometimes the blade. In the general summary to this chapter a few remarks will be added, showing that the efficiency of such extremely minute doses is not so incredible as it must at first appear. 136 DROSERA ROTUNDIFOLIA. [Cuar, VII. Sulphate of Ammonia.—The few trials made with this and the following five salts of ammonia were undertaken merely to ascertain whether they induced inflection. Half-minims of a solution of one part of the sulphate of ammonia to 437 of water were placed on the discs of seven leaves, so that each received 54, of a grain, or *0675 mg. After 1 hr. the tentacles of five of them, as well as the blade of one, were strongly inflected. The leaves were not afterwards observed. Citrate of Ammonia.—Half-minims of a solution of one part to 437 of water were placed on the discs of six leaves. In 1 hr. the short outer tentacles round the discs were a little inflected, with the glands on the discs blackened. Aliter 3 hrs. 25 m. one leaf had its blade inflected, but none of the exterior tentacles. All six leaves remained in nearly the same state during the day, the submarginal tentacles, however, becoming more and more inflected. After 23 hrs. three of the leaves had their blades somewhat inflected, and the submarginal tentacles of all considerably inflected, but in none were the two, three, or four outer rows affected. I have rarely seen cases like this, except from the action of a decoction of grass, ‘the glands on the discs of the above leaves, instead of being almost black, as after the first hour, were now, after 23 hrs., very pale. I next tried on four leaves half- minims of a weaker solution, of one part to 1312 of water (1 grain to 3 0z.); so that each received z850 of a grain (°0225 mg.). After 2 hrs. 18 m. the glands on the disc were very dark-coloured; after 24 hrs. two of the leaves were slightly affected; the other two not at all. Acetate of Ammonia.—Half-minims of a solution of about one part to 109 of water were placed on the discs of two leaves, both of which were acted on in 5 hrs. 30 m., and after 23 hrs. had every single tentacle closely inflected. Oxalate of Ammonia—Half-minims of a solution of one part to 218 of water were placed on two leaves, which, after 7 hrs., became moderately, and after 23 hrs. strongly, inflected. ‘lwo other leaves were tried with a weaker solution of one part to 437 of water; one was strongly inflected in 7 hrs.; the other not until 30 hrs. had capsed. Tartrate of Ammonia.—Half-minims of a solution of one part to 437 of water were placed on the discs of five leaves. In 31 m. there was a trace of inflection in the exterior tentacles of some of the leaves, and this became more decided after 1 hr. with all the leaves; but the tentacles were never closely inflected. After 8 hrs. 30 m. they began to re-expand. Next morning, after 23 hrs., all were fully re- expanded, excepting one which was still slightly inflected. ‘The shortness of the period of inflection in this and the following case is remarkable. Chloride of Ammonia.—Hal{-minims of a solution of one part to 437 of water were placed on the discs of six leaves. A decided degree of inflection in the outer and submarginal tentacles was perceptible in 25 m.; and this increased during the next three or four hours, but never Cm VIL] OTHER SALTS OF AMMONIA. — 137 became strongly marked. After only 8 hrs. 30 m. the tentacles began to re-expand, and by the next morning, after 24 hrs., were fully re-expanded on four of the leaves, but still slightly inflected on two. General Summary and Concluding Remarks on the Salts of Ammonia.—We have now seen that the nine salts of ammonia which were tried all cause the inflection of the tentacles, and often of the blade of the leaf. As far as can be ascer- tained from the superficial trials with the last six salts, the citrate is the least powerful, and the phosphate certainly by far the most. The tartrate and chloride are remarkable from the short duration of their action. The relative efficiency of the carbonate, nitrate, and phosphate, is shown in the fol- lowing table by the smallest amount which suffices to cause the inflection of the tentacles. | P v . io F ; Carbonate of | Nitrate of Phosphate of Solutions, how applied. Ammonia. | Ammonia. Ammonia. Placed on the glands of thej! as of a | 700 of a mw Ofa disc, so as to act indirectly grain, or | grain, or grain, or on the outer tentacles .) +0675 mg. -027 mg. *0169 mg. . ji | . Applied for a few seconds); yy\y5 0f 8 | aofa | asw of a directly to the gland of an> grain, or | grain, or | grain, or outer tentacle, . . .) 00445 mg.| °0025 mg. *000423 mg. | | Leaf immersed, with time]) sgg of a 301200 of a 10180000 of a allowed for each gland tobi grain, or grain, or grain, or absorb all that it can. .}) -00024mg.} *0000937 mg. | °00000328 mg. | | Amount absorbed by a gland)! which suffices to cause thef| yyy455 of a aggregation of the proto->| grain, or plasm in the my saa d Mosc mg. cells of the tentacles . . | | From the experiments tried in these three different ways, we see that the carbonate, which contains 23-7 per cent. of nitrogen, is less efficient than the nitrate, which contains 35 per cent. The phosphate contains less nitrogen than either of these salts, namely, only 21-2 per cent., and yet is far more efficient ; its power, no doubt, depending quite as much on the phosphorus as on the nitrogen which it contains. We may infer that this is the case, from the energetic manner in 138 DROSERA ROTUNDIFOLIA. (Cuar. VII. which bits of bone and phosphate of lime affect the leaves. Theinflection excited by the other salts of ammonia is pro- bably due solely to their nitrogen, —on the same principle that nitrogenous organic fluids act powerfully, whilst non-nitro- genous organic fluids are powerless. As such minute doses of the salts of ammonia affect the leaves, we may feel almost sure that Drosera absorbs and profits by the amount, though small, which is present in rain-water, in the same manner as other plants absorb these same salts by their roots. The smallness of the doses of the nitrate, and more especially of the phosphate of ammonia, which cause the ten- tacles of immersed leaves to be inflected, is perhaps the most remarkable fact recorded in this volume. When we see that much less than the millionth* of a grain of the phosphate, absorbed by a gland of one of the exterior tentacles, causes it to bend, it may be thought that the effects of the solution on the glands of the disc have been overlooked ; namely, the transmission of a motor impulse from them to the exterior tentacles. No doubt the movements of the latter are thus aided; but the aid thus rendered must be insignificant; for we know that a drop containing as much as the 3 J;, of a grain placed on the disc is only just able to cause the outer tentacles of a highly sensitive leaf to bend. It is certainly a most surprising fact that the y57¢po09 Of a grain, or in round numbers the one-twenty-millionth of a grain (0000033 mg.), of the phosphate should affect any plant or indeed any animal; and as this salt contains 35°33 per cent. of water of crystallisation, the efficient elements are reduced to BUSS 5130 of a grain, or in round numbers to one-thirty-millionth of a grain (‘00000216 mg.). The solution, moreover, in these experiments was diluted in the proportion of one part of the salt to 2,187,500 of water, or one grain to 5000 oz. The reader will perhaps best realise this. degree of dilution by remembering that 5000 oz. would more than fill a 31-gallon cask; and that to this large body of water one grain of the salt was added ; only half a drachm, or thirty minims, of the solution being poured over the leaf. Yet this amount * It is scarcely possible to realise what a million means. The best illustration which I have met with is that given by Mr. Croll, who says, —Take a narrow strip of paper 85 ft. 4 in. in length, and stretch it along the wall of a large hall; then mark off at one end the tenth of an inch. This tenth will represent a hundred, and the entire strip a million. i i - E E E NE E Cuar. VII.] SUMMARY, SALTS OF AMMONIA. 139 sufficed to cause the inflection of almost every tentacle, and often of the blade of the leaf. Iam well aware that this statement will at first appear incredible to almost every one. Drosera is far from rivalling the power of the spectroscope, but it can detect, as shown by the movements of its leaves, a very much smaller quantity of the phosphate of ammonia than the most skilful chemist can of any substance.* My results were for a long time incredible even to myself, and I anxiously sought for every source of error. The salt was in some cases weighed for me by a chemist in an excellent balance ; and fresh water was measured many times with care. The observations were repeated during several years. Two of my sons, who were as incre- dulous as myself, compared several lots of leaves simultane- ously immersed in the weaker solutions and in water, and declared that there could be no doubt about the difference in their appearance. I hope that some one may hereafter be in- duced to repeat my experiments; in this case he should select young and vigorous leaves, with the glands surrounded by abundant secretion. The leaves should be carefully cut off and laid gently in watch-glasses, and a measured quantity of the solution and of water poured over each. The water used must be as absolutely pure as it can be made. It is to be especially observed that the experiments with the weaker solutions ought to be tried after several days of very warm weather. Those with the weakest solutions should be made on plants which have been kept for a considerable time in a warm greenhouse, or cool hothouse; but this is by no means necessary for trials with solutions of moderate strength. I beg the reader to observe that the sensitiveness or irri- tability of the tentacles was ascertained by three different methods—indirectly by drops placed on the disc, directly by * When my first observations were (see Balfour Stewart, ‘Treatise on made on the nitrate of ammonia, Heat, 2nd edit. 1871, p. 228). With fourteen years ago, the powers of respect to ordinary chemical tests, I the spectroscope had not been dis- gather from Dr. Alfred Tay lor’s covered ; and I felt all the greater work on ‘ Poisons’ that about 1055 Of interest in the then unrivalled powers a grain of arsenic, 3/55 of a grain of of Drosera. Now the spectroscope prussic acid, phy of iodine, and B05 has altogether beaten Drosera; for, of tartarised antimony, can be de- according to Bunsen and Kirchhoff, tected; but the power of detection probably less than one skg of a depends much on the solutions under grain of sodium can be thus detected trial not being extremely weak. 140 DROSERA ROTUNDIFOLIA. (Cuar. VIL. drops applied to the glands of the outer tentacles, and by the immersion of whole leaves; and it was found by these three methods that the nitrate was more powerful than the car- bonate, and the phosphate much more powerful than the nitrate; this result being intelligible from the difference in the amount of nitrogen in the first two salts, and from the presence of phosphorus in the third. It may aid the reader’s faith to turn to the experiments with a solution of one grain of the phosphate to 1000 oz. of water, and he will there find decisive evidence that the one-four-millionth of a grain is sufficient to cause the inflection of a single tentacle. There is, therefore, nothing very improbable in the fifth of this weight, or the one-twenty-millionth of a grain, acting on the tentacle of a highly sensitive leaf. Again, two of the leaves in the solution of one grain to 3000 oz., and three of the leaves in the solution of one grain to 5000 oz., were affected, not only far more than the leaves tried at the same time in water, but incomparably more than any five leaves which can be picked out of the 173 observed by me at different times in water. There is nothing remarkable in the mere fact of the one- twenty-millionth of a grain of the phosphate, dissolved in about two million times its weight of water, being absorbed by a gland. All physiologists admit that the roots of plants absorb the salts of ammonia brought to them by the rain; and fourteen gallons of rain-water contain* a grain of ammonia, therefore only a little more than twice as much as in the weakest solution employed by me. The fact which appears truly wonderful is, that the one-twenty-millionth of a grain of the phosphate of ammonia (including less than the one-thirty-millionth of efficient matter), when absorbed by a gland, should induce some change in it, which leads to a motor impulse being transmitted down the whole length of the tentacle, causing the basal part to bend, often through an angle of above 180 degrees. Astonishing as is this result, there is no sound reason why we should reject it as incredible. Prof. Donders, of Utrecht, informs me that, from experiments formerly made by him and Dr. De Ruyter, he inferred that less than the one-millionth ofa grain of sulphate of atropine, in an extremely diluted * Miller’s ‘Elements of Chemistry,’ part ii. p. 107, 3rd edit. 1864. iiie Cuar. VIL] SUMMARY, SALTS OF AMMONIA. 141 state, if applied directly to the iris of a dog, paralyses. the muscles of this organ. But, in fact, every time that we perceive an odour, we have evidence that infinitely smaller particles act on our nerves. When a dog stands a quarter of a mile to leeward of a deer or other animal, and perceives its presence, the odorous particles produce some change in the olfactory nerves; yet these particles must be infinitely smaller* than those of the phosphate of ammonia weighing the one-twenty-millionth of a grain. These nerves then transmit some influence to the brain of the dog, which leads to action on its part. With Drosera, the really marvellous fact is, that a plant without any specialised nervous system should be affected by such minute particles; but we have no grounds for assuming that other tissues could not be ren- dered as exquisitely susceptible to impressions from without, if this were beneficial to the organism, as is the nervous system of the higher animals. * My son, George Darwin, has —that is, from 5155 to taby of an calculated for me the diameter of |inch—in diameter. Therefore, an a sphere of phosphate of ammonia object between 3; and J, of the size (specific gravity 1:678), weighing of a sphere of the phosphate of the one-twenty-millionth of a grain, | ammonia of the above weight can be and finds it to be rdg Of an inch. seen under a high power; and no one Now, Dr. Klein informs me that the smallest Micrococci, which are dis- tinctly discernible under a power of 800 diameters, are estimated to be from +0002 to 0005 of a millimeter supposes that odorous particles, such as those emitted from the deer in the above illustration, could be seen under any power of the microscope. 142 DROSERA ROTUNDIFOLIA. (Cuar. VII. CHAPTER VIII. THE EFFECTS OF VARIOUS SALTS AND ACIDS ON THE LEAVES. Salts of sodium, potassium, and other alkaline, earthy, and metallic salts— Summary on the action of these salts—Various acids—Summary on their action. Havine found that the salts of ammonia were so powerful, I was led to investigate the action of some other salts. It will be convenient, first, to give a list of the substances tried (including forty-nine salts and two metallic acids), divided into two columns, showing those which cause inflection, and those which do not do so, or only doubtfully. My experi- ments were made by placing half-minim drops on the discs of leaves, or, more commonly, by immersing them in the solutions; and sometimes by both methods. A summary of the results, with some concluding remarks, will then be given. The action of various acids will afterwards be de- scribed. SALTS CAUSING INFLECTION. SALTS NOT CAUSING INFLECTION. (Arranged in Groups according to the Chemical Classification in Watts’ < Dictionary of Chemistry.) Sodium carbonate, rapid inflection. Potassium carbonate: slowly poison- ous. Sodium nitrate, rapid inflection. Potassium nitrate: somewhat poison- ous. Sodium sulphate, moderately rapid Potassium sulphate. inflection. Sodium phosphate, very rapid in- Potassium phosphate. flection. Sodium citrate, rapid inflection. Potassium citrate. Sodium oxalate, rapid inflection. Sodium chloride, moderately rapid Potassium chloride. inflection. Sodium iodide, rather slow inflection, Potassium iodide, a slight and doubt- ful amount of inflection. Sodium bromide, moderately rapid Potassium bromide. inflection. Potassium oxalate, slow and doubtful inflection. Cuar. VIIL] SALTS CAUSING INFLECTION, (Arranged in Groups according to the Chemical Classification in Watts EFFECTS OF VARIOUS SALTS. 143 SALTS NOT CAUSING INFLECTION. > ‘ Dictionary of Chemistry.’) Lithium nitrate, moderately rapid inflection. Cæsium chloride, rather slow inflec- tion. 5 Silver nitrate, rapid inflection: quick poison, Cadmium chloride, slow inflection. Mercury perchloride, rapid inflection : quick poison. Aluminium chloride, slow and doubt- ful inflection. Gold chloride, rapid inflection : quick poison. Tin chloride, slow inflection: poison- ous. My Antimony tartrate, slow inflection : probably poisonous. Arsenious acid, quick inflection : poi- sonous. Iron chloride, slow inflection: pro- bably poisonous. Chromic acid, quick inflection : highly poisonous. Copper chloride, rather slow inflec- tion: poisonous, Nickel chloride, rapid probably poisonous. Platinum chloride, rapid inflection : poisonous. inflection : Lithium acetate. Rubidium chloride. Calcium acetate. Calcium nitrate. Magnesium acetate. Magnesium nitrate. Magnesium chloride. Magnesium sulphate, Barium acetate. Barium nitrate. Strontium acetate, Strontium nitrate. Zine chloride. Aluminium nitrate, a trace of in- flection. Aluminium and potassium sulphate. Lead chloride. Manganese chloride Cobalt chloride Sodium, Carbonate of (pure, given me by Prof. Hoffmann).—Half- minims (*0296 c.c.) of a solution of one part to 218 of water (2 grs. to 1 oz.) were placed on the discs of twelve leaves. Seven of these becaine well inflected; three had only two or three of their outer tentacles inflectec, and the remaining two were quite unaffected. But 144 DROSERA ROTUNDIFOLIA. [Cuar. VIII. the dose, though only the ;1; of a grain (-185 mg.), was evidently too strong, for three of the seven well-inflected leaves were killed. On the other hand, one of the seven, which had only a few tentacles inflected, re-expanded and seemed quite healthy after 48 hrs. By employing a weaker solution (viz. one part to 457 of water, or 1 gr. to 1 0z.), doses of 545 of a grain (0675 mg.) were given to six leaves. Some of these were affected in 37 m.; and in 8 hrs. the outer tentacles of all, as well as the blades of two, were considerably inflected. After 23 hrs. 15 m. the tentacles had almost re-expanded, but the blades of the two were still just perceptibly curved inwards. After 48 hrs. all six leaves were fully re-expanded, and appeared perfectly healthy. Three leaves were immersed, each in thirty minims of a solution of one part to 875 of water (1 gr. to 2 0z.), so that each received 3} of a grain (2°02 mg.); after 40 nı. the three were much affected, and after 6 hrs. 45 m. the tentacles of alland the blade of one closely inflected. Sodium, Nitrate of (pure).—Half-minims of a solution of one part to 437 of water, containing 515 of a grain (+0675 mg.), were placed on the discs of five leaves. After 1 hr. 25 m. the tentacles of nearly all, and the blade of one, were somewhat inflected. The inflection continued to increase, and in 21 hrs. 15 m. the tentacles and the blades of four of them were greatly affected, and the blade of the fifth to a slight extent. After an additional 24 hrs. the four leaves still remained closely inflected, whilst the fifth was beginning to expand. Four days after the solution had been applied, two of the leaves had quite, and one had partially, re-expanded ; whilst the remaining two remained closely inflected and appeared injured. Three leaves were immersed, each in thirty minims of a solution of one part to 875 of water; in 1 hr. there was great inflection, and after 8 hrs. 15 m. every tentacle and the blades of all three were most strongly inflected. Sodium, Sulphate of.—Nalf-ninims of a solution of one part to 437 of water were placed on the discs of six leaves. After 5 hrs. 30 m. the tentacles of three of them (with the blade of one) were considerably, and those of the other three slightly, inflected. After 21 hrs. the inflection had a little decreased, and in 45 hrs. the leaves were fully expanded, appearing quite healthy. : Three leaves were immersed, each in thirty minims of a solution of one part of the sulphate to 875 of water; after 1 hr. 30 m. there was some inflection, which increased so much that in 8 hrs. 10 m. all the tentacles and the blades of all three leaves were closely inflected. Sodium, Phosphate of.—Half-minims of a solution of one part to 437 of water were placed on the discs of six leaves. The solution acted with extraordinary rapidity, for in 8 m. the outer tentacles on several of the leaves were much incurved. After 6 hrs. the tentacles of all six leaves, and the blades of two, were closely inflected. This state of things continued for 24 hrs., excepting that the blade of a third leas became incurved. After 48 hrs. all the leaves re-expanded. It is Cmar.. VIII] SALTS OF SODIUM. 145 clear that 535 of a grain of phosphate of soda has great power in causing inflection. Sodium, Citrate of.—Half-minims of a solution of one part to 437 of water were placed on the discs of six leaves, but these were not observed until 22 hrs. had elapsed. The submarginal tentacles of five of them, and the blades of four, were then found inflected; but the outer rows of tentacles were not affected. One leaf, which appeared older than the others, was very little affected in any way. After 46 hrs. four of the leaves were almost re-expanded, including their blades. ‘Three leaves were also immersed, each in thirty mivims of a solution of one part of the citrate to 875 of water; they were much acted on in 25 m.; and after 6 hrs. 35 m. almost all the tentacles, including those of the outer rows, were inflected, but not the blades. Sodium, Oxalate of.—Half-minims of a solution of one part to 487 of water were placed on the disc of seven leaves; after 5 hrs. 30 m. the tentacles of all, and the blades of most of them, were much affected. In 22 hrs., besides the inflection of the tentacles, the blades of all seven leaves were so much doubled over that their tips and bases almost touched. On no other occasion have I seen the blades so strongly affected. Three leaves were also immersed, each in thirty minims of a solution of one part to 875 of water; after 30 m. there was much inflection, and after 6 brs. 35 m. the blades of two and the tentacles or all were closely inflected. Sodium, Chloride of (best culinary salt).—Half-minims of a solution of one part to 218 of water were placed on the discs of four leaves. Two, apparently, were not at all affected in 48 hrs.; the third had its tentacles slightly inflected; whilst the fourth had almost all its ten- tacles inflected in 24 hrs., and these did not begin to re-expand until the fourth day, and were not perfectly expanded on the seventh day. I presume that this leaf was injured by the salt. Half-minims of a weaker solution, of one part to 437 of water, were then dropped on the discs of six leaves, so that each received 51, ofa grain. In 1 hr. 33m. there was slight inflection; and after 5 hrs. 30 m. the tentacles of all six leaves were considerably, but not closely, inflected. After 23 hrs. 15 m. all had completely re-expanded, and did not appear in the least injured. Three leaves were immersed, each in thirty minims of a solution of one part to 875 of water, so that each received J, of a grain, or 2°02 mg. After 1 hr. there was much inflection; after 8 hrs. 30 m. all the tentacles and the blades of all three were closely inflected. Four other leaves were also immersed in the solution, each receiving the same amount of salt as before, viz. 3y of a grain. They all soor became inflected; after 48 hrs. they began to re-expand, aud appeared quite uninjured, though the solution was sufficiently strong to taste saline. Sodium, Jodide of.—Half-minims of a solution of one part to 437 of water were placed on the discs of six leaves. After 24 hrs. four of them had their blades and many tentacles inflected. The other two had only their submarginal tentacles inflected ; the outer ones in most of L 146 DROSERA ROTUNDIFOLIA. (Cuar. VIE the leaves being but little affected. After 46 hrs. the leaves had nearly re-expanded. Three leaves were also immersed, each in thirty minims of a solution of one part to 875 of water. After 6 hrs. 30 m.. almost all the tentacles, and the blade of one leaf, were closely in- flected. Sodium, Bromide of.—Half-minims of a solution of one part to 437 of water were placed on six leaves. After 7 hrs. there was some in- flection; after 22 hrs. three of the leaves had their blades and most of their tentacles inflected; the fourth leaf was very slightly, and the fifth and sixth hardly at all, affected. Three leaves were also im- mersed, each in thirty minims of a solution of one part to 875 of water; after 40 m, there was some inflection; after 4 hrs. the tentacles of all three leaves and the blades of two were inflected. These leaves. were then placed in water, and after 17 hrs. 50 m. two of them were almost completely, and the third partially, re-expanded; so that apparently they were not injured. Potassium, Carbonate of (pure).—Half-minims of a solution of one part to 437 of water were placed on six leaves. No effect was produced: in 24 hrs.; but after 48 hrs. some of the leaves had their tentacles, and one the blade, considerably inflected. ‘This, however, seemed the result of their being injured; for, on the third day after the solutiom was given, three of the leaves were dead, and one was very unhealthy ; the other two were recovering, but with several of their tentacles apparently injured, and these remained permanently inflected. It is: evident that the 51, ofa grain ef this salt acts as a poison. Three leaves were also immersed, each in thirty minims of a solution of one part to 875 of water, though only for 9 hrs.; and, very differently from what occurs with the salts of soda, no inflection ensued. Potassium, Nitrate of—Half-minims of a strong solution, of one part to 109 of water (4 grs. to 1 oz. ), were placed on the discs. of four leaves ; two were much injured, but no inflection ensued. Eight leaves were treated in the same manner, with drops of a weaker solu-- tion, of one part to 218 of water. After 50 hrs. there was no inflection, but two of the leaves seemed injured. Five of these leaves were subsequently tested with drops of milk and a solution of gelatine on their discs, and only one became inflected ; so that the solution of the: nitrate of the above strength, acting for 50 hrs., apparently had injured or paralysed the leaves. Six leaves were then treated in the same manner with a still weaker solution, of one part to 437 of water, and these, after 48 hrs., were in no way affected, with the exception of perhaps a single leaf. Three leaves were next immersed for 25 hrs., each in thirty minims of a solution of one part to 875 of water, and this produced no apparent effect. They were then put into a solution of one part of carbonate of ammonia to 218 of water; the glands were immediately blackened, and after 1 hr. there was some inflection, and the protoplasmic contents of the cells became plainly aggregated. This shows that the leaves had not been much injured. by their immer- sion for 25 hrs. in the nitrate. PO ere ec eats Ra Cuar. VIL] SALTS OF POTASSIUM. 147 Potassium, Sulphate of.—Balf-minims of a solution of one part to 437 of water were placed on the discs of six leaves. After 20 hrs. 80 m. no effect was produced; after an additional 24 hrs. three remained quite unaffected; two seemed injured, and the sixth seemed almost dead, with its tentacles inflected. Nevertheless, after two additional days, all six leaves recovered. The immersion of three leaves for 24 hrs., each in thirty minims of a solution of one part to 875 of water, produced no apparent effect. They were then treated with the same solution of carbonate of ammonia, with the same result as in the case of the nitrate of potash. Potassium, Phosphate of.—Half-minims of a solution of one part to 437 of water were placed on the discs of six leaves, which were observed during three days; but no effect was produced. The partial drying up of the fluid on the disc slightly drew together the tentacles on it, as often occurs in experiments of this kind. ‘he leaves on the third day appeared quite healthy. Potassium, Citrate of —Half-ninims of a solution of one part to 437 of water, left on the discs of six leaves for three days, and the immer- sion of three leaves for 9 hrs., each in 80 minims of a solution of one part to 875 of water, did not produce the least etfect. Potassium, Oxalate of.—Half-minims were placed on different occ2- sions on the discs of seventeen leaves; and the results perplexed me much, as they still do. Inflection supervened very slowly. After 24 hrs. four leaves out of the seventeen were well inflected, together with the blades of two; six were slightly affected, and seven not at all. Three leaves of one lot were observed for five days, and all died; but in another lot of six all excepting one looked healthy after four days. Three leaves were immersed during 9 hrs., each in 30 minims of a solution of one part to 875 of water, and were not in the least affected ; but they ought to have been observed jor a longer time. Potassium, Chloride of.—Neither half-minims of a solution of one part to 437 of water, left on the discs of six leaves for three days, nor the immersion of three leaves during 25 hrs., in 80 minims of a solution of one part to 875 of water, produced the least effect. The immersed leaves were then treated with carbonate of ammonia, as described under nitrate of potash, and with the same result. Potassium, Iodide of.—Halt-minims of a solution of one part to 437 of water were placed on the discs of seven leaves. In 30 m. one leaf had the blade inflected; after some hours three leaves had most of their submarginal tentacles moderately inflected ; the remaining three being very slightly affected. Hardly any of these leaves had their outer tentactes inflected. After 21 hrs, all re-expanded, excepting two which still had a few submarginal tentacles inflected. Three leaves were next immersed for 8 hrs. 40 m., each in 30 minims of a solution of one part to 875 of water, and were not in the least affected. I do not know what to conclude from this conflicting evidence; but it is clear that the iodide of potassium does not generally produce any marked effect. L 2 148 DROSERA ROTUNDIFOLLA. [Cuar. VIL. Potassium, Bromide of.—Half-minims of a solution of one part to 437 of water were placed on the discs of six leaves; after 22 hrs. one had its blade and many tentacles inflected, but I suspect that an insect might have alighted on it and then escaped; the five other leaves were in no way affected. I tested three of these leaves with bits of meat, and alter 24 hrs. they became splendidly inflected. Three leaves were also immersed for 21 hrs. in 30 minims of a solution of one part to 875 of water; but they were not at all affected, excepting that the glands looked rather pale. Lithium, Acetate of.—Four leaves were immersed together in a vessel containing 120 minims of a solution of one part to 437 of water; so that each received, if the leaves absorbed equally, 34; of a grain. After 24 hrs. there was no inflection. I then added, for the sake of testing the leaves, some strong solution (viz. 1 gr. to 20 oz., or one part to 8750 of water) of phosphate of ammonia, and all four became in 30 m. closely inflected. Lithium, Nitrate of.—Four leaves were immersed, as in the last case, in 120 minims of a solution of one part to 437 of water; after 1 hr. 80 m. all four were a little, and after 24 hrs. greatly, inflected, I then diluted the solution with some water, but they still remained somewhat inflected on the third day. Cesium, Chloride of —Your leaves were immersed, as above, in 120 minims of a solution of one part to 487 of water. After 1 hr. 5 m. the glands were darkened; after + hrs. 20 m. there was a trace of inflection; after 6 hrs. 40 m. two leaves were greatly, but not closely, and the other two considerably inflected. After 22 hrs. the inflection was extremely great, and two had their blades inflected. I then transferred the leaves into water, and in 46 hrs. from their first immersion they were almost re-expanded. Rubidium, Chloride of.—¥our leaves which were immersed, as above, in 120 minims of a solution of one part to 437 of water, were not acted on in 22 hrs. I then added some of the strong solution (1 gr. to 20 oz.) of phosphate of ammonia, and in 30 m. all were immensely inflected. Silver, Nitrate of—Three leaves were immersed in ninety minims of a solution of one part to 437 of water; so that each received, as before, =}; of a grain. After 5 m. slight inflection, and after 11 m. very strong inflection, the glands becoming excessively black; after 40 m. all the tentacles were closely inflected. After 6 hrs. the leaves were taken out of the solution, washed, and placed in water; but next morning they were evidently dead. Yalcium, Acetate of.—Four leaves were immersed in 120 minims of a solution of one part to 437 of water; after 24 hrs. none of the tentacles were inflected, excepting a few where the blade joined the petiole; and this may have been caused by the absorption of the salt by the cut-oft end of the petiole. I then added some of the solution (1 gr. to 20 oz.) of phosphate of ammonia, but this to my surprise excited only slight inflection, even after 24 hrs. Hence it would appear that the acetate had rendered the leaves torpid. Cuar. VIIL] EFFECTS OF VARIOUS SALTS. 149 Calcium, Nitrate of —Four leaves were immersed in 120 minims of a solution of one part to 437 of water, but were not affected in 24 hrs. I then added some of the solution of phosphate of ammonia (1 gr. to 20 0z.), but this caused only very slight inflection after 24 hrs. A fresh leaf was next put into a mixed solution of the above strengths of the nitrate of calcium and phosphate of ammonia, and it became closely inflected in between 5 m. and 10m. Half-minims of a solution of one part of the nitrate of calcium to 218 of water were dropped on the discs of three leaves, but produced no effect. Magnesium, Acetate, Nitrate, and Chloride of —Four leaves were immersed in 120 minims of solutions, of one part to 437 of water, of each of these three salts; after 6 hrs. there was no inflection; but after 22 hrs. one of the leaves in the acetate was rather more inflected than generally occurs from an immersion for this length of time in water. Some of the solution (1 gr. to 20 0z.) of phosphate of ammonia was then added to the three solutions. The leaves in the acetate mixed with the phosphate underwent some inflection; and this was well pronounced after 24 hrs. Those in the mixed nitrate were decidedly inflected in 4 hrs. 30 m., but the degree of inflection did not afterwards much increase; whereas the four leaves in the mixed chloride were greatly inflected in a few minutes, and after 4 hrs. had almost every tentacle closely inflected. We thus see that the acetate and nitrate of magnesium injure the leaves, or at least prevent the subsequent action of phosphate of ammonia; whereas the chloride has no such tendency. Magnesium, Sulphate of.—Half-minims of a solution of one part to 218 of water were placed on the discs of ten leaves, and produced no effect. Barium, Acetate of.—Four leaves were immersed in 120 minims of a solution of one part to 437 of water, and after 22 hrs. there was no inflection, but the glands were blackened. ‘The leaves were then placed in a solution (1 gr. to 20 0z.) of phosphate of ammonia, which caused after 26 hrs. only a little inflection in two of the leaves. Barium, Nitrate of.—F¥our leaves were immersed in 120 minims of a solution of one part to 437 of water; and after 22 hrs. there was no more than that slight degree of inflection which often follows from an immersion of this length in pure water. I then added some of the same solution of phosphate of ammonia, and after 30 m. one leaf was greatly inflected, two others moderately, and the fourth not at all. ‘The leaves remained in this state for 24 hrs. Strontium, Acetate of—Four leaves, immersed in 120 minims of a solution of one part to 437 of water, were not affected in 22 hrs. They were then placed in some of the same solution of phosphate of ammonia, and in 25 m. two of them were greatly inflected ; after g hrs. the third leaf was considerably inflected, and the fourth exhibited a trace of inflection. They were in the same state next morning, — Strontium, Nitrate of.—Five leaves were immersed in 120 minims of a solution of one part to 487 of water; after 22 hrs. there was some 150 DROSERA ROTUNDIFOLIA. (Cuar. VII. slight inflection, but not more than sometimes occurs with leaves in water. "They were then placed in the same solution of phosphate of ammonia; after 8 hrs. three of them were moderately inflected, as were all five after 24 hrs.; but not one was closely inflected. It appears that the nitrate of strontium renders the leaves half torpid. Cadmium, Chloride of—Three leaves were immersed in ninety minims of a solution of one part to 437 of water; after 5 hrs. 20 m. slight inflection occurred, which increased during the next three hours. After 24 hrs. all three leaves had their tentacles well inflected, and remained so for an additional 24 hrs.; glands not discoloured. Mercury, Perchloride of —Vhree leaves were immersed in ninety minims of a solution of one part to 437 of water; after 22 m. there was some slight inflection, which in 48 m. became well pronounced ; the giands were now blackened. After 5 hrs. 35 m. all the tentacles closely inflected; after 24 hrs. still inflected and discoloured. The leaves were then removed and left for two days in water; but they never re-expanded, being evidently dead. Zinc, Chloride of —Three leaves immersed in ninety minims of a solution of one part to 437 of water were not affected in 25 hrs. 30 m. Aluminium, Chloride of—Four leaves were immersed in 120 minims of a solution of one part to 437 of water; after 7 hrs. 45 m. no inflection; after 24 hrs. one leaf rather closely, the second moderately, the third and fourth hardly at all, inflected. ‘The evidence is doubtful, but I think some power in slowly causing inflection must be attributed to this salt. These leaves were then placed in the solution (1 gr. to 20 oz.) of phosphate of ammonia, and after 7 hrs. 30 m. the three, which had been but little affected by the chloride, became rather closely inflected. Aluminium, Nitrate of —Four leaves were immersed in 120 minims of a solution of one part to 437 of water; after 7 hrs. 45 m. there was only a trace of inflection; after 24 hrs. one leaf was moderately inflected. The evidence is here again doubtful, as in the case of the chloride of aluminium. ‘The leaves were then transferred to the same solution as before, of phosphate of ammonia; this produced hardly any effect in 7 hrs. 30 m.; but after 25 hrs. one leaf was pretty closely inflected, the three others very slightly, perhaps not more so than from water. Aluminium and Potassium, Sulphate of (common alum),—Half- minims of a solution of the usual strength were placed on the discs of nine leaves, but produced no effect. Gold, Chloride of.—Seven leaves were immersed in so much of a solution of one part to 437 of water that each received 30 minims, containing 5}; of a grain, or 4°048 mg., of the chloride. There was some inflection in 8 m., which became extreme in 45 m. In 8 hrs. the surrounding fluid was coloured purple, and the glands were blackened. After 6 hrs. the leaves were transferred to water; next morning they were found discoloured and evidently killed. The secretion decomposes the chloride very readily ; the glands themselves becoming coated with za Otar, VIIL] EFFECTS OF VARIOUS SALTS. 151 the thinnest layer of metallic gold, and particles float about on the surface of the surrounding fluid. Lead, Chloride of.-—Yhree leaves were immersed in ninety minims of a solution of one part to 437 of water. After 23 hrs. there was not a trace of inflection; the glands were not blackened, and the leaves did not appear injured. They were then transferred to the solution (1 gr. to 20 oz.) of phosphate of ammonia, and after 24 hrs. two of them were somewhat, the third very little, inflected; and they thus remained for another 24 hrs. Tin, Chloride of.—Four leaves were immersed in 120 minims of a solution of about one part (all not being dissolved) to 437 of water. After 4 hrs. no effect; after 6 hrs. 30 m. all four leaves had their sub- marginal tentacles inflected; after 22 hrs. every single tentacle and the blades were closely inflected. The surrounding fluid was now coloured pink. The leaves were washed and transferred to water, but next morning were evidently dead. ‘his chloride is a deadly poison, but acts slowly. Antimony, Tartrate of.—Three leaves were immersed in ninety minims ofa solution of one part to 437 of water. After 8 hrs. 30 m. there was slight inflection; after 24 hrs. two of the leaves were closely, and the third moderately, inflected; glands not much darkened. The leaves were washed and placed in water, but they remained in the same state for 48 additional hours. This salt is probably poisonous, but acts slowly. Arsenious Acid.—A solution of one part to 437 of water; three leaves were immersed in ninety minims; in 25 m. considerable inflec- tion; in 1 hr. great inflection; glands not discoloured. After 6 hrs. the leaves were transferred to water; next morning they looked fresh, but after four days were pale-coloured, had not re-expanded, and were evidently dead. Iron, Chloride of.—Three leaves were immersed in ninety minims of a solution of one part to 437 of water; in 8 hrs. no inflection; but after 24 hrs. considerable inflection; glands blackened; fluid coloured yellow, with floating flocculent particles of oxide of iron. The leaves were then placed in water; after 48 hrs. they had re-expanded a very little, but I think were killed; glands excessively black. Chromic Acid.—One part to 437 of water; three leaves were immersed in ninety minims; in 30 m. some, and in 1 hr. considerable, inflection; after 2 hrs. all the tentacles closely inflected, with the glands discoloured. Placed in water, next day leaves quite discoloured and evidently killed. = Manganese, Chloride of.—Three leaves immersed in ninety minims of a solution of one part to 437 of water; after 22 hrs. no more inflection than often occurs in water; glands not blackened, The leaves were then placed in the usual solution of phosphate of ammonia, but no inflection was caused even after 48 hrs. ee Copper, Chloride of.—Three leaves immersed in ninety minims of a solution of one part to 437 of water; after 2 hrs. some inflection ; after 152 DROSERA ROTUNDIFOLIA. [Cuar. VII. 3 hrs. 45 m. tentacles closely inflected, with the glands blackened. After 22 hrs. still closely inflected, and the leaves flaccid. Placed im pure water, next day evidently dead. A rapid poison. Nickel, Chloride of.—Three leaves immersed in ninety minims of à solution of one part to 437 of water; in 25 m. considerable inflection, and in 3 hrs. all the tentacles closely inflected. After 22 hrs. still closely inflected; most of the glands, but not all, blackened. The leaves were then placed in water; after 24 hrs. remained inflected ; were somewhat discoloured, with the glands and tentacles dingy red.. Probably killed. . Cobalt, Chloride ọf.—Three leaves immersed in ninety minims of a. solution of one part to 437 of water; after 23 hrs. there was not a trace of inflection, and the glands were not more blackened than often occurs after an equally long immersion in water. Platinum, Chloride of.—Three leaves immersed in ninety minims of a solution of one part, to 437 of water; in 6 m. some inflection, which became immense after 48 m. After 3 hrs. the glands were rather pale. After 24 hrs. all the tentacles still closely inflected; glands colourless ; remained in same state for four days; leaves evidently killed. Concluding Remarks on the Action of the foregoing Salts ——Of the fifty-one salts and metallic acids which were tried, twenty-five caused the tentacles to be inflected, and twenty- six had no such effect, two rather doubtful cases occurring in each series. In the table at the head of this discussion, the salts are arranged according to their chemical affinities; but their action on Drosera does not seem to be thus governed. The nature of the base is far more important, as far as can be judged from the few experiments here given, than that of the acid; and this is the conclusion at which physiologists have arrived with respect to animals. We see this fact illustrated in all the nine salts of soda causing inflection, and in not being poisonous except when given in large doses; whereas seven of the corresponding salts of potash do not cause inflection, and some of them are poisonous. Two of them, however, viz. the oxalate and iodide of potash, slowly in- duced a slight and rather doubtful amount of inflection. This difference between the two series is interesting, as Dr. 3urdon Sanderson informs me that sodium salts may be introduced in large doses into the circulation of mammals without any injurious effects; whilst small doses of potas- sium salts cause death by suddenly arresting the movements of the heart. An excellent instance of the different action of the two series is presented by the phosphate of soda quickly causing vigorous inflection, whilst phosphate of potash is Car. VHI] CONCLUDING REMARKS, SALTS. 153 quite inefficient. The great power of the former is probably due to the presence of phosphorus, as in the cases of phos- phate of lime and of ammonia. Hence we may infer that Drosera cannot obtain phosphorus from the phosphate of potash. This is remarkable, as I hear from Dr. Burdon Sanderson that phosphate of potash is certainly decomposed within the bodies of animals. Most of the salts of soda act very rapidly ; the iodide acting slowest. The oxalate, nitrate, and citrate seem to have a special tendency to cause the blade of the leaf to be inflected. The glands of the disc, after absorbing the citrate, transmit hardly any motor impulse to the outer tentacles; and in this character the citrate of soda resembles the citrate of ammonia, or a decoction of grass-leaves; these three fluids all acting chiefly on the blade. It seems opposed to the rule of the preponderant influence of the base that the nitrate of lithium causes moderately rapid inflection, whereas the acetate causes none; but this metal is closely allied to sodium and potassium,* which act so differently; therefore we might expect that its action would be intermediate. We see, also, that cæsium causes inflection, and rubidium does not; and these two metals are allied to sodium and potassium. Most of the earthy salts are inoperative. Two salts of calcium, four of magnesium, two of barium, and two of strontium, did not cause any inflection, and thus follow the rule of the preponderant power of the base. Of three salts of aluminium, one did not act, a second showed a trace of action, and the third acted slowly and doubtfully, so that their effects are nearly alike. Of the salts and acids of ordinary metals, seventeen were tried, and only four, namely those of zinc, lead, manganese, and cobalt, failed to cause inflection. The salts of cad- mium, tin, antimony, and iron act slowly; and the three latter seem more or less poisonous. The salts of silver, mercury, gold, copper, nickel, and platinum, chromic and arsenious acids, cause great inflection with extreme quick- ness, and are deadly poisons. It is surprising, judging from animals, that lead and barium should not be poisonous. Most of the poisonous salts make the glands black, but chloride of platinum made them very pale. I shall have occasion, in the next chapter, to add a few remarks on the * Miller’s ‘ Elements of Chemistry,’ 3rd edit. pp. 337, 448. 154 DROSERA ROTUNDIFOLIA. [CHAF VIII. different effects of phosphate of ammonia on leaves previously immersed in various solutions. ACIDS. I will first give, as in the case of the salts, a list of the twenty-four acids which were tried, divided into two series, according as they cause or do not cause inflection. After describing the experiments, a few concluding remarks will be added. ACIDS, MUCH DILUTED, WHICH CAUSE ACIDS, DILUTED TO THE SAME INFLECTION. DEGREE, WHICH DO NOT CAUSE INFLECTION. . Gallic; not poisonous. . Tannic; not poisonous. . Tartaric ; not poisonous. . Citric ; not poisonous. . Uric; (2) not poisonous. 1. Nitric, strong inflection; poi- sonous. 2. Hydrochloric, moderate and slow inflection ; not poisonous. 3. Hydriodic, strong inflection ; poisonous. 4. lodic, strong inflection ; poisonous. 5. Sulphuric, strong inflection; somewhat poisonous. 6. Phosphoric, strong inflection ; poisonous, 7. Boracic, moderate and rather slow inflection; not poisonous. 8. Formic, very slight inflection; not poisonous. 9, Acetic, strong and rapid inflec- tion ; poisonous. 10, Propionic, strong but not very rapid inflection ; poisonous. 11. Oleic, quick inflection; very poisonous. 12, Carbolic, very slow inflection; poisonous, 13. Lactic, slow and moderate inflec- tion ; poisonous. 14. Oxalic, moderately quick inflec- tion; very poisonous. 15. Malic, very slow but considerable inflection; not poisonous. 16. Benzoic,* rapid inflection; very poisonous. 17. Succinic, moderately quick in- flection ; moderately poisonous. 18. Hippuric, rather slow inflection ; poisonous. 19. Hydrocyanic, rather rapid in- flection ; very poisonous. Cue Oboe Car. VILL] THE EFFECTS OF ACIDS. 159 Nitric Acid.—Four leaves were placed, each in thirty minims of one part by weight of the acid to 437 of water, so that each reccived >}, of a grain, or 4°048 mg. This strength was chosen for this and most of the following experiments, as it is the same as that of most of the foregoing saline solutions. In 2 hrs. 30 m. some of the leaves were considerably, and in 6 hrs. 30 m. all were immensely, inflected, as were their blades. ‘The surrounding fluid was slightly coloured pink, which always shows that the leaves have been injured. ‘They were then left in water for three days; but they remained inflected and were evidently killed. Most of the glands had become colourless. Two leaves were then immersed, each in thirty minims of one part to 1000 of water; in a few hours there was some inflection; and after 24 hrs. both leaves had almost all their tentacles and blades inflected; they were left in water for three days, and one partially re-expanded and recovered. Two leaves were next immersed, each in thirty minims of one part to ‘2000 of water; this produced very little effect, except that most of the tentacles close to the summit of the petiole were inflected, as if the acid had been absorbed by the cut-off end. Hydrochloric Acid.—One part to 437 of water; four leaves were immersed as before, each in thirty minims. After 6 hrs. only one leaf was considerably inflected. After 8 hrs. 15 m. one had its tentacles and blade well inflected; the other three were moderately inflected, and the blade of one slightly. The surrounding fluid was not coloured at all pink. After 25 hrs. three of these four leaves began to re- expand, but their glands were of a pink instead of a red colour; after two more days they fully re-expanded; but the fourth leaf remained inflected, and seemed much injured or killed, with its glands white. Four leaves were then treated, each with thirty minims of one part to 875 of water; after 21 hrs. they were moderately inflected; and, on being transferred to water, fully re-expanded in two days, and seemed quite healthy. Hydriodic Acid.—One to 437 of water; three leaves were immersed as before, each in thirty minims. After 45 m. the glands were dis- coloured, and the surrounding fluid became pinkish, but there was no inflection. After 5 hrs. all the tentacles were closely inflected ; and an immense amount of mucus was secreted, so that the fluid could be ‘drawn out into long ropes. The leaves were then placed in water, but never re-expanded, and were evidently killed. Four leaves were next immersed in one part to 875 of water; the action was now slower, but after 22 hrs. all four leaves were closely inflected, and were affected in other respects as above described. These leaves did not re-expand, though left for four days in water. This acid acts far more powerfully than hydrochloric, and is poisonous. lodic Acid.—One to 437 of water; three leaves were immersed, each in thirty minims; after 3 hrs. strong inflection; after 4 hrs. glands dark brown; after 8 hrs. 30 m. close inflection, and the leaves had become flaccid; surrounding fluid not coloured pink. These leaves were then placed in water, and next day were evidently dead. 156 DROSERA ROTUNDIFOLIA. [Cuap. VIIE Sulphuric Acid.—One to 487 of water; four leaves were immersed each in thirty minims; after 4 hrs. great inflection; after 6 hrs. surrounding fluid just tinged pink; they were then placed in water, and after 46 hrs. two of them were still closely inflected, two begin- ning to re-expand; many of the glands colourless, This acid is not so poisonous as hydriodic or iodic acids. Phosphoric Acid.—One to 437 of water ; three leaves were immersed together in ninety minims; after 5 hrs. 30 m. some inflection, and some glands colourless; after 8 brs. all the tentacles closely inflected, and many glands colourless : surrounding fluid pink. Left in water for two days and a half, remained in the same state and appeared dead. Boracic Acid.—One to 437 cf water; four leaves were immersed. together in 120 minims; after 6 hrs. very slight inflection; after 8 hrs. 15 m. two were considerably inflected, the other two slightly. After 24 hrs. one leaf was rather closely inflected, the second less closely, the third and fourth moderately. The leaves were washed and put into water; after 24 hrs. they were almost fully re-expanded and looked healthy. ‘This acid agrees closely with hydrochloric acid of the same strength in its power of causing inflection, and in not being poisonous. Formic Acid.—Four leaves were immersed together in 120 minims of one part to 437 of water; after 40 m. slight, and after 6 hrs, 30 m- very moderate inflection; after 22 hrs, only a little more inflection than often occurs in water. Two of the leaves were then washed and placed in a solution (1 gr. to 20 oz.) of phosphate of ammonia; after 24 hrs. they were considerably inflected, with the contents of their cells aggregated, showing that the phosphate had acted, though not to the full and ordinary degree. Acetic Acid—Four leaves were immersed together in 120 minims of one part to 437 of water. In 1 hr. 20 m. the tentacles of all four and the blades of two were greatly inflected. After 8 hrs. the leaves had become flaccid, but still remained closely inflected, the surrounding fluid being coloured pink. They were then washed and placed in water ; next morning they were still inflected and of a very dark red colour, but with their glands colourless. After another day they were dingy- coloured, and evidently dead. This acid is far more powerful than formic, and is highly poisonous. Half-minim drops of a stronger mixture (viz. one part by measure to 320 of water) were placed on the discs of five leaves; none of the exterior tentacles, only those on the borders of the disc which actually absorbed the acid, became inflected. Probably the dose was too strong and paralysed the leaves, for drops of a weaker mixture caused much inflection; nevertheless, the leaves all died after two days. Propionic Acid.—Three leaves were immersed in ninety minims of a mixture of one part to 437 of water; in 1 hr. 50 m. there was no inflection; but after 3 hrs, 40 m. one leaf was greatly inflected, and the other two slightly. The inflection continued to increase, so that iu 8 hrs. all three leaves were closely inflected. Next morning, alter ETIE Cuar. VIIL] THE EFFECTS OF ACIDS. 157 20 hrs., most of the glands were very pale, but some few were almost black. No mucus had been secreted, and the surrounding fluid was only just perceptibly tinted of a pale pink. After 46 hrs. the leaves became slightly flaccid and were evidently killed, as was alterwards proved to be the case by keeping them in water. The protoplasm in the closely inflected tentacles was not in the least aggregated, but towards their bases it was collected in little brownish masses at the bottoms of the cells. This protoplasm was dead, for, on leaving the leaf in a solution of carbonate of ammonia, no aggregation ensued. Propionic acid is highly poisonous to Drosera, like its ally acetic acid, but induces inflection at a much slower rate. Oleic Acid (given me by Prof. Frankland).—Three leaves were immersed in this acid; some inflection was almost immediately caused, which increased slightly, but then ceased, and the leaves seemed killed. Next morning they were rather shrivelled, and many of the glands had fallen off the tentacles. Drops of this acid were placed on the discs of four leaves; in 40 m. all the tentacles were greatly inflected, excepting the extreme marginal ones; and many of these after 3 hrs. became inflected. I was led to try this acid from supposing that it was present (which does not seem to be the case)* in olive oil, the action of which is anomalous. Thus drops of this oil placed on the disc do not cause the outer tentacles to be inflected ; yet, when minute drops were added to the secretion surrounding the glands of the outer tentacles, these were occasionally, but by no means always, inflected. Two leaves were also immersed in this oil, and there was no inflection for about 12 hrs.; but after 23 hrs. almost all the tentacles were inflected. Three leaves were likewise immersed in unboiled linseed oil, and soon became somewhat, and in 3 hrs. greatly inflected. After 1 hr. the secretion round the glands was coloured pink. I infer from this latter fact that the power of linseed oil to cause inflection cannot be attributed to the albumin which it is said to contain. Carbolic Acid.—\wo leaves were immersed in sixty minims of a solution of 1 gr. to 437 of water; in 7 hrs. one was slightly, and in 24 hrs. both were closely, inflected, with a surprising amount of mucus secreted. These leaves were washed and left for two days in water; they remained inflected; most of their glands became pale, and they seemed dead. This acid is poisonous, but does not act nearly so apidly or powerfully as might have been expected from its known de- structive power on the lowest organisms. Half-minims of the same solution were placed on the discs of three leaves; after 24 hrs. no inflection of the outer tentacles ensued, and when bits of meat were given them they became fairly well inflected. Again half-minims of a stronger solution, of one part to 218 of water, were placed on the discs of three leaves; no inflection of the outer tentacles ensued; bits of meat were then given as before; one leaf alone became well inflected, * See articles on Glycerine and Oleic Acid in Watts’ ‘ Dict. of Chemistry.’ 158 DROSERA ROTUNDIFOLIA. [Cuap. VIII. the discal glands of the other two appearing much injured and dry. We thus see that the glands of the discs, after absorbing this. acid, rarely transmit any motor impulse to the outer tentacles ; thongh these, when their own glands absorb the acid, are strongly acted on. Lactic Acid.—Three leaves were immersed in ninety minims of one part to 437 of water. After 48 m. there was no inflection, but the surrounding fluid was coloured pink ; after 8 hrs. 30 m. one leaf alone was a little inflected, and almost all the glands on all three leaves were of a very pale colour. The leaves were then washed and placed in a solution (1 gr. to 20 oz.) of phosphate of ammonia; after about 16 hrs. there was only a trace of inflection. They were left inthe phosphate for 48 hrs., and remained in the same state, with almest all their glands disccloured. The protoplasm within the cells was not ag- gregated, except in a very few tentacles, the glands of which were not much discoloured. I believe, therefore, that almost all the glands and tentacles had been killed by the acid so suddenly that hardly any inflection was caused. Four leaves were next immersed in 120 minims of a weaker solution, of one part to 875 of water; after 2 hrs. 80 m. the surrounding fluid was quite pink ; the glands were pale, but there was no inflection; after 7 hrs. 80 m. two of the leaves showed some inflection, and the glands were almost white; after 21 hrs. two of the leaves were considerably inflected, and a third slightly; most of the glands were white, the others dark red. After 45 hrs. one leaf had almost every tentacle inflected ; a second a large number; the third and fourth very few; almost all the glands were white, excepting those on the discs of two of the leaves, and many of these were very dark red. The leaves appeared dead. Hence lactic acid acts in a very peculiar manner, causing inflection at an extraordinarily slow rate, and being highly poisonous. Immersion in even weaker solutions, viz. of one part to 1312 and 1750 of water, apparently killed the leaves (the tentacles after a time being bowed backwards), and rendered the glands white, but caused no inflection. Gallic, Tannic, Tartaric, and Citrie Acids.—One part to 437 of water. Three or four leaves were immersed, each in 30 minims of these four solutions, so that each leaf received jj; of a grain, or 4°048 mg. No inflection was caused in 24 hrs., and the leaves did not appear at all injured. Those which had been in the tannic and tartaric acids were placed in a solution (1 gr. to 20 oz.) of phosphate of ammonia, but no inflection ensued in 24 hrs. On the other hand, the four leaves which had been in the citric acid, when treated with the phosphate, became decidedly inflected in 50 m., and strongly inflected after 5 hrs., and so remained for the next 24 hrs. Malic acid.—Three leaves were immersed in ninety minims of a solution of one part to 437 of water; no inflection was caused in 8 hrs. 20 m., but after 24 hrs. two of them were considerably, and the third slightly, inflected—more so than could be accounted fer by the action of water. No great amount of mucus was secreted. They were then ce ee O E ee Te ee aT a ee T Cuar. VIII.) THE EFFECTS OF ACIDS. 159 placed in water, and after two days partially re-expanded. Hence this acid is not poisonous. Oxalic Acid.—Three leaves were immersed in ninety minims of a solution of 1 gr. to 487 of water; after 2 hrs. 10 m. there was much inflection ; glands pale; the surrounding fluid of a dark pink colour ; after 8 hrs. excessive inflection. The leaves were then placed in water ; after about 16 hrs. the tentacles were of a very dark red colour, like those of the leaves in acetic acid. After 24 additional hours, the three leaves were dead and their glands colourless, Benzoic Acid.—Five leaves were immersed, each in thirty minims. of a solution of 1 gr. to 437 of water. This solution was so weak that it only just tasted acid, yet, as we shall see, was highly poisonous to Drosera. After 52 m. the submarginal tentacles were somewhat inflected, and all the glands very pale-coloured; the surrounding fluid was coloured pink. On one occasion the fluid became pink in the course of only 12 m. and the glands as white as if the leaf had been dipped in boiling water. After 4 hrs, much inflection; but none of the tentacles were closely inflected, owing, as I believe, to their having been paralysed before they had time to complete their movement. An extraordinary quantity of mucus was secreted. Some of the leaves were left in the solution; others, after an immersion of 6 hrs. 30 m., were placed in water. Next morning both lots were quite dead; the leaves in the solution being flaccid, those in the water (now coloured yellow) of a pale brown tint, and their glands white. Succinic Acid.—Three leaves were immersed in ninety minims of a solution of one gr. to 437 of water; after 4 hrs. 15 m. considerable, and after 23 hrs. great, inflection; many of the glands pale; fluid coloured pink. The leaves were then washed and placed in water; after two days there was some re-expansion, but many of the glands were still white. This acid is not nearly so poisonous as oxalic or benzoic. Uric Acid.—Three leaves were immersed in 180 minims of a solution of 1 gr. to 875 of warm water, but all the acid was not dissolved; so that each received nearly 4; of a grain. After 25 m. there was some slight inflection; but this never increased; after 9 hrs. the glands were not discoloured, nor was the solution coloured pink ; nevertheless, much mucus was secreted. ‘The leaves were then placed in water, and by next morning fully re-expanded. I doubt whether this acid really causes inflection, for the slight movement which at first occurred may have been due to the presence of a trace of albuminous matter. But it produces some effect, as shown by the secretion of so much mucus. Hippuric Acid.—Four leaves were immersed in 120 minims of a solution of 1 gr. to 437 of water. After 2 hrs. the fluid was coloured pink; glands pale, but no inflection. After 6 hrs. some inflection ; after 9 hrs. all four leaves greatly inflected; much mucus secreted; all the glands very pale. The leaves were then left in water for two days; they remained closely inflected, with their glands colourless, and I do not doubt were killed. 160 DROSERA ROTUNDIFOLIA. [Cuar. VII. Hydrocyanic Acid.—Four leaves were immersed, each in thirty minims of one part to 437 of water; in 2 hrs. 45 m. all the tentacles were considerably inflected, with many of the glands pale; after 3 hrs. 45 m. all strongly inflected, and the surrounding fluid coloured pink ; alter 6 hrs. ail closely inflected. After an immersion of 8 hrs. 20 m. the leaves were washed and placed in water; next morning, after about 16 hrs., they were still inflected and discoloured; on the succeeding day they were evidently dead. Two leaves were immersed in & stronger mixture, of one part to fifty of water; in 1 hr. 15 m. the glands became as white as porcelain, as if they had been dipped in boiling water; very few of the tentacles were inflected; but after 4 hrs. almost all were inflected. ‘These leaves were then placed in water and next morning were evidently dead. Half-nsinim drops of the same strength (viz. one part to fifty of water) were next placed on the discs of five leaves; after 21 hrs, all the outer tentacles were inflected, and the leaves appeared much injured. I likewise touched the secretion round a large number of glands with minute drops (about zp of a minim, or *00296 c.c.) of Scheele’s mixture (containing 4 per cent. of anhydrous acid); the glands first became bright red, and after 3 hrs. 15 m. about two-thirds of the tentacles bearing these glands were inflected, and remained so for the two succeeding days, when they appeared dead, Concluding Remarks on the Action of Acids.—It is evident that acids have a strong tendency to cause the inflection of the tentacles ; * for, out of twenty-four acids tried, nineteen thus acted, either rapidly and energetically, or slowly and slightly. This fact is remarkable, as the juices of many plants contain more acid, judging by the taste, than the solutions employed in my experiments. From the powerful effects of so many acids on Drosera, we are led to infer that those naturally contained in the tissues of this plant, as well as of others, must play some important part in their economy. Of the five cases in which acids did not cause the tentacles to be inflected, one is doubtful; for uric acid did act slightly, and caused a copious secretion of mucus. Mere sourness to the taste is no criterion of the power of an acid on Drosera, as citric and tartaric acids are very sour, yet do not excite inflection. It is remarkable how acids differ in their power. Thus, hydrochloric acid acts far less powerfully than hydriodic * According to M. Fournier (‘De cause the stamens of Berberis in- la Fécondation dans les Phanéro- stantly to close; though drops of games,’ 1863, p. 61) drops of acetic, water have no such power, which hydrocyanic, and sulphuric acid latter statement I can confirm. Pa so eam ei Dis $ f $ H Cuar. VIEL] CONCLUDING REMARKS, ACIDS. 161 and many other acids of the same strength, and is not poisonous. This is an interesting fact, as hydrochloric acid plays so important a part in the digestive process of animals. Formic acid induces very slight inflection, and is not poison- ous; whereas its ally, acetic acid, acts rapidly and powerfully, and is poisonous. Malic acid acts slightly, whereas citric and tartaric acids produce no effect. Lactic acid is poisonous, and is remarkable from inducing inflection only after a considerable interval of time. Nothing surprised me more than that a solution of benzoic acid, so weak as to be hardly acidulous to the taste, should act with great rapidity and be highly poisonous; for I am informed that it produces no marked effect on the animal economy. It may be seen, by looking down the list at the head of this discussion, that most of the acids are poisonous, often highly so. Diluted acids are known to induce negative osmose,* and the poisonous action of so many acids on Drosera is, perhaps, connected with this power, for we have seen that the fluid in which they were immersed often became pink, and the glands pale-colonred or white. Many of the poisonous acids, such as hydriodic, benzoic, hippuric, and carbolic (but I neglected to record all the cases), caused the secretion of an extraordinary amount of mucus, so that long ropes of this matter hung from the leaves when they were lifted out of the solutions, Other acids, such as hydrochloric and malic, have no such tendency; in these two latter cases the sur- rounding fluid was not coloured pink, and the leaves were not poisoned. On the other hand, propionic acid, which is poisonous, does not cause much mucus to be secreted, yet the surrounding fluid became slightly pink. Lastly, as in the case of saline solutions, leaves, after being immersed in cer- tain acids, were soon acted on by phosphate of ammonia; on the other hand, they were not thus affected after immersion in certain other acids. To this subject, however, I shall have to recur. * Miller’s ‘Elements of Chemistry,’ part i. 1867, p. 87, 162 . DROSERA ROTUNDIFOLIA. (Cuar. IX. CHAPTER IX. THE EFFECTS OF CERTAIN ALKALOID POISONS, OTHER SUBSTANCES AND VAPOURS. Strychnine, salts of—Quinine, sulphate of, does not soon arrest the move- ment of the protoplasm—Other salts of quinine—Digitaline—Nicotine— Atropine — Veratrine — Colchicine — Theine — Curare—Morphia—Hyos- eyamus—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—Aleohol innocuous, its vapour narcotic and poisonous—Chloro- form, 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 ghz of a grain, or °0675 mg. In 2 hrs. 80 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-ex- panded and appeared quite healthy. Hence the poisonous action of strychnine seems confined to the glands which have absorbed it; never- theless, these glands transmit a motor impulse to the exterior tentacles. Minute drops (about 34 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 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 TARY rn RIGA NAD aan asa reac emt ee Cmar. IX] ALKALOID POISONS. 163 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 0z.) 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 487 of water; so that each received Jj; 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 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 24,5 part of its weight. Five leaves were immersed, each in thirty minims of this solution, which tasted bitter. In less M 2 164 DROSERA ROTUNDIFOLIA. [Cuar. IX: 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, afier an immersion of 3 hrs. 15 m., was carefully examined; the pro- toplasm 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 pro- toplasm presenting a very unusual appearance; for it 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 * ‘Quarterly Journal of Microscopical Science,’ April 1874, p. 185. Cmar. IX.) <. ALKALOID POISONS. 165 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 487 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 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 3% 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 sslo5 of a grain (*00225 mg.) acts on a tentacle, but is not poisonous. lt 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 * Binz found several years ago corpuscles, which become * rounded (as stated in ‘The Journal of and granular.” In the tentacles of Anatomy and Phys.) November Drosera the aggregated masses of 1872, p. 195) that quinia is an protoplasm, which appeared killed energetic poison to low vegetable by the quinine, likewise presented a and animal organisms. Even one granular appearance. A similar part added to 4000 parts of blood appearance is caused by very hot arrests the movements of the white water. 166 DROSERA ROTUNDIFOLIA. (Cne. IX. 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 pro- toplasm in all the cells of all the tentacles much aggregated and dark coloured. The leaves were not quite killed, for on being placed ina 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 4 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 solu- tion, 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 glandsard to induce aggregation of the protoplasm, but, except when pure, has very moderate power of inducing inflection, and still less power of causing a motor influence to be transmitted from the discal glands to the outer tentacles. It is moderately poisonous. Atropine.—A grain was added to 487 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 atiopine 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 difier 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 like- wise 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 solu- Cuap. IX.] ALKALOID POISONS. 167 tion, 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; 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 in- flected, 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, phos- phate 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 sometimes did not do so. At one time I felt convinced that morphia acted as a narcotic on Drosera, but after having found in 168 DROSERA ROTUNDIFOLIA. (Cua. IX. 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 car- bonate 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 pro- nounced; 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. vO m., all were beginning to re-expand, and they appeared uninjured. Poison from the Cobra.a—Dr. Fayrer, well known from his investi- gations 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 34 of a minim) of a soluticn of one part to 437 of water was applied to the secretion round four glands ; so-that each received only about ṣ5157y 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 piak 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 54, ofa grain (°0675 mg.); in 4 hrs. 15 m. the outer tentacles were much inflected; and after 6 hrs. 30 m. those on two of the leaves were closely inflected and the blade of one; the third leaf was only moderately atfected. 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 y% of a grain, or 4°048 mg. In 6 m. there was some inflection, which steadily increased, so that after 2 hrs. 230 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 * Dr. Fayrer, ‘The Thanatophidia of India,’ 1872, p. 150. Cuap. IX] -POISON OF THE COBRA. 169 of protoplasm were examined after 3 hrs., and again after 7 hrs., and on ne other occasion have | seen them undergoing such rapid changes of form. After 8 hrs. 30 m. the glands had becume quite white; they had not secreted any great quantity of mucus. The leaves were now placed in water, and after 40 hre. 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 4 of a grain, or 16°2 mg. After 1 hr. 45 m. the submarginal tentacles were strongly inflected, with the glands somewhat pale; after 3 hrs. 50 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 pro- toplasm, 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, expanded. The tentacles were now examined, and the aggregated masses were almost wholly re-dissolved ; the cells being filled with homogeneous purple fluid, with the ex- ception here and there of a single globular mass. We thus see how completely the protoplasm bad 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 170 DROSERA ROTUNDIFOLIA. [Omar IX. colour from the glands. It seems even to act as a stimulant to the protoplasm, for after considerable experience in observing the move- ments 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 gramm 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 tne 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 Paramecium 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 considerable time in a very strong solution. On the whole, it seems that the poison of the cobra acts far more injuriously on the protoplasm of the higher animals than on that of Drosera. There is one other point which may be noticed. I have occasionally observed that the drops of secretion round the glands were 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 5y of its weight of camphor; it smelt and tasted of this substance. ‘l’en 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 26m. 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 * «Proceedings of Royal Society,’ Feb. 18, 1875. ee Cuar. IX.] CAMPHOR. 171 occasion, however, after a longer immersion of 24 hrs., there was well- marked aggregation. A solution made by adding two drops of campho- rated 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. - S j | Length of Z | Length of | | Time between ~ | ae the Immersion s Immersion A Length of Time between the Act of Brushing | of the Leaves 8 | the Solution | and the Inflection of the Tentacles. peg EE £ | of Camphor. | Sign of the is | | Inflection of the : | | Tentacles. 1 i 3m. considerable inflection; 4 m. all e Pin t the tentacles except 3 or 4 inflected. : 2 5m. | 6 m. first sign of inflection. | 11 m. 6 m. 30 s. slight inflection; 7 m. 398.) 41 m. 30s. a k Co ico Tis Pee | . } { plain inflection. | x 2 m. 30 s.a trace of inflection; 3 m. A 4 4m.30s. i 7m, plain ; 4 m. strongly marked. (9 2 ý Ps tan: R 2 m. 30 s. a trace of inflection m. : ? 5 4m. Heir z - F | 6m. 30s. plain inflection. j 2 m. 30 s. decided inflection; 3 m. 50 s. ; 30 ¢ 6 4m . é 6 m. 30 s. strongly marked. . 2 m. 30 s. slight inflection; 3 m. plain;) ș& aN a 7 4m. f eee >m. 30 s. 4 m. well marked. Í 8 2 (2 m. trace of inflection; 3 m. consider-) 5m 3 m. : : 5 5m. , \ able, 6 m. strong inflection. 2m. trace of inflection; 3 m. consider-) - 9 3 m. ; : ae om. able, 6 m. strong inflection. 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 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 above table, * edly verified it. If a minute bit of meat be placed by the a aid of a needle on a single gland, or on three or four T together, halfway between the centre and the circum- i ference of the disc, the di- 5 rected movement of the sur- rounding tentacles is well exhibited. An accurate draw- ing of a leaf with meat in this position is here repro- duced (fig. 10), and we see the tentacles, including some of the exterior ones, accu- rately directed to the point where the meat lay. But a Leaf (enlarged) with the tentacles inflected much better plan as +0 place over a bit of meat placed on one side of & particle of the phosphate the disc. of lime moistened with saliva on a single gland on one side of the disc of a large leaf, and another particle on a single gland on the opposite side. In four such trials the excitement was not sufficient to affect the outer tentacles, but all those near the two points were directed to them, so that two wheels were formed on the disc of the same leaf; the pedicels of the tentacles forming the spokes, and the glands united in a mass over the phosphate representing the axles. The precision with which each tentacle pointed to the particle Fic. 10. (Drosera rotundifolia.) * ‘Bot. Zeitung,’ 1860, p. 240. Cuar. X.) DIRECTION OF INFLECTED TENTACLES. 199 was wonderful; so that in some cases I could detect no deviation from perfect accuracy. Thus, although the short tentacles in the middle of the dise do not bend when their glands are excited in a direct manner, yet if they receive a motor impulse from a point on one side, they direct them- selves to the point equally well with the tentacles on the borders of the disc. In these experiments, some of the short tentacles on the disc, which would have been directed to the centre, had the leaf been immersed in an exciting fluid, were now inflected in an exactly opposite direction, viz. towards the circumference. These tentacles, therefore, had deviated as much as 180° from the direction which they would have assumed if their . own glands had been stimulated, and which may be considered as the normal one. Between this, the greatest possible and no deviation from the normal direction, every degree could be observed in the tentacles on these several leaves. Notwithstanding the precision with which the ten- tacles generally were directed, those near the circumference of one leaf were not accurately directed towards some phos- hate of lime at a rather distant point on the opposite side of the disc. It appeared as if the motor impulse in passing transversely across nearly the whole width of the disc had departed somewhat from a true course, This accords with what we have already seen of the impulse travelling less readily in a transverse than in a longitudinal direction. In some other cases, the exterior tentacles did not seem capable of such accurate movement as the shorter and more central ones. Nothing could be more striking than the appearance of the above four leaves, each with their tentacles pointing truly to the two little masses of the phosphate on their discs. We might imagine that we were looking at a lowly organised animal seizing prey with its arms. In the case of Drosera the explanation of this accurate power of movement, no doubt, lies in the motor impulse radiating in all directions, and whichever side of a tentacle it first strikes, that side contracts, and the tentacle consequently bends towards the oint of excitement. The pedicels of the tentacles are flattened, or elliptic in section. Near the bases of the short central tentacles, the flattened or broad face is formed of about five longitudinal rows of cells; in the outer tentacles of the disc, it consists of about six or seven rows; and in 200 DROSERA ROTUNDIFOLIA. [Cnar. X. the extreme marginal tentacles of above a dozen rows. As the flattened bases are thus formed of only a few rows of cells, the precision of the movements of the tentacles is the more remarkable; for when the motor impulse strikes the base of a tentacle in a very oblique direction relatively to its broad face, scarcely more than one or two cells towards one end can be affected at first, and the contraction of these cells must draw the whole tentacle into the proper direction. It is, perhaps, owing to the exterior pedicels being much flattened that they do not bend quite so accurately to the point of excitement as the more central ones. The properly directed movement of the tentacles is not an unique case in the vegetable kingdom, for the tendrils of many plants curve towards the side which is touched; but the case of Drosera is far more interesting, as here the tentacles are not directly excited, but receive an impulse from a distant point ; nevertheless, they bend accurately towards this point. On the Nature of the Tissues through which the Motor Impulse* is Transmitted.—It will be necessary first to describe briefly the course of the main fibro-vascular bundles. These are shown in the accompanying sketch (fig. 11) of a small leaf. Little vessels from the neighbouring bundles enter all the many tentacles with which the surface is studded ; but these are not here represented. The central trunk, which runs up the footstalk, bifurcates near the centre of the leaf, each branch bifurcating again and again according to the size of the leaf. This central trunk sends off, low down on each side, a delicate branch, which may be called the sublateral branch. There is also, on each side, a main lateral branch or bundle, which bifurcates in the same manner as the others. Bifurcation does not imply that any single vessel divides, but that a bundle divides into two. By looking to either side of the leaf, it will be seen that a branch from the great central bifurcation inosculates with a branch from the lateral bundle, and that there is a smaller inosculation between the * [In a letter (1862) to Sir Joseph Hooker, in the ‘Life and Letters of Charles Darwin,’ vol. iii. p. 321, the writer speaks of the existence in Drosera of “ diffused nervous matter,” in some degree analogous in constitu- tion and function to the nervous matter of animals. Now, that through the researches of Gardiner (‘Phil. Trans.’ 1883) and others the connection between plant-cells by inter-cellular protoplasm has been established, we can understand the transmission of the motor impulse as a molecular change in the protoplasm from cell to cel]l.—F. D.] nat Cuar. X.] CONDUCTING TISSUES. 201 two chief branches of the lateral bundle. The course of the vessels is very complex at the larger inosculation ; and here vessels, retaining the same diameter, are often formed by the union of the bluntly pointed ends of two vessels, but whether these points open into each other by their attached surfaces, I do not know. By means of the two inosculations all the vessels on the same side of the leaf are brought into some sort of connection. Near the circumference of the larger leaves the bifurcating branches also come into close union, and then separate again, forming a continuous zigzag line of vessels round the whole circumfer- ence. But the union of the vessels in this zigzag line seems to be much less inti- mate than at the main in- osculation. It should be added that the course of the vessels differs somewhat in different leaves, and even on opposite sides of the same leaf, but the main inoscula- tion is always present. Now in my first experi- ments with bits of meat placed on one side of the disc, it so happened that not a single tentacle was inflected on the opposite side; and when I saw that the vessels on the same side were all connected together by the two inosculations, whilst not Diagram showing the distribution of the vascular tissue in a small leaf, a vessel passed over to the opposite side, it seemed pro- - bable that the motor impulse was conducted exclusively along them. In order to test this view, I divided transversely with the point of a lancet the central trunks of four leaves, just beneath the main bifurcation; and two days afterwards placed rather large bits of raw meat (a most powerful stimulant) near the centre of the discs above the incision— that is, a little towards the apex—with the following results :— Fic. 11, (Drosera rotundifolia.) 202 DROSERA ROTUNDIFOLIA. [Cuar. X. (1) This leaf proved rather torpid : after 4 hrs. 40 m. (in all cases reckoning from the time when the meat was given) the tentacles at the distal end were a little inflected, but nowhere else; they remained so for three days, and re-expanded on the fourth day. The leaf was then dissected, and the trunk, as well as the two sublateral branches, were found divided. (2) After 4 hrs. 30 m. many of the tentacles at the distal end were well inflected. Next day the blade and all the tentacles at this end were strongly inflected, and were separated by a distinct transverse line from the basal half of the leaf, which was not in the least affected. On the third day, however, some of the short tentacles on the disc near the base were very slightly inflected. The incision was found on dissection to extend across the leaf as in the last case. (3) After 4 hrs. 30 m. strong inflection of the tentacles at the distal end, which during the next two days never extended in the least to the basal end. The incision as before. (4) This leaf was not observed until 15 hrs. had elapsed, and then all the tentacles, except the extreme marginal ones, were found equally well inflected all round the leaf. On careful examination the spiral vessels of the central trunk were certainly divided; but the incision on one side had not passed through the fibrous tissue surrounding these vessels, though it had passed through the tissue on the other side.* The appearance presented by the leaves (2) and (3) was very curious, and might be aptly compared with that of a man with his backbone broken and lower extremities paralysed. Excepting that the line between the two halves was here transverse instead of longitudinal, these leaves were in the same state as some of those in the former experiments, with bits of meat placed on one side of the disc. The case of leaf (4) proves that the spiral vessels of the central trunk may be divided, and yet the motor impulse be transmitted from the distal to the basal end; and this led me at first to suppose that the motor force was sent through the closely surrounding fibrous tissue; and that if one half of this tissue was left undivided, it sufficed for complete transmission. 3ut opposed to this conclusion is the fact that no vessels pass directly from one side of the leaf to the other, and yet, as we have seen, if a rather large bit of meat is placed on one side, the motor impulse is sent, though slowly and imperfectly, in * M. Ziegler made similar ex- rendus, 1874, p. 1417), but arrived periments by cutting the spiral ves- at conclusions widely different from sels of Drosera intermedia («Comptes mine. Cuar. X.] CONDUCTING TISSUES, 203 a transverse direction across the whole breadth of the leaf. Nor can this latter fact be accounted for by supposing that the transmission is affected through the two inosculations, or through the circumferential zigzag line of union, for had this been the case, the exterior tentacles on the opposite side of the disc would have been affected before the more central ones, which never occurred. We have also seen that the extreme marginal tentacles appear to have no power to transmit an impulse to the adjoining tentacles; yet the little bundle of vessels which enters each marginal tentacle sends off a minute branch to those on both sides, and this I have not observed in any other tentacles; so that the marginal ones are more closely connected together by spiral vessels than are the others, and yet have much less power of com- municating a motor impulse to one another. But besides these several facts and arguments we have conclusive evidence that the motor impulse is not seni, at least exclusively, through the spiral vessels, or through the tissue immediately surrounding them. We know that if a bit of meat is placed on a gland (the immediately adjoining ones having been removed) on any part of the disc, all the short surrounding tentacles bend almost simultaneously with great precision towards it. Now there are tentacles on the disc, for instance near the extremities of the sublateral bundles (fig. 11), which are supplied with vessels that do not come into contact with the branches that enter the sur- rounding tentacles, except by a very long and extremely circuitous course. Nevertheless, if a bit of meat is placed on the gland of a tentacle of this kind, all the surrounding ones are inflected towards it with great precision. Itis, of course, possible that an impulse might be sent through a long and circuitous course, but it is obviously impossible that the direction of the movement could be thus communicated, so that all the surrounding tentacles should bend precisely to the point of excitement. The impulse no doubt is trans- mitted in straight radiating lines from the excited gland to the surrounding tentacles; it cannot, therefore, be sent along the fibro-vascular bundles. The effect of cutting the central vessels, in the above cases, in preventing the transmission of the motor impulse from the distal to the basal end of a leaf, may be attributed to a considerable space of the cellular tissue having been divided. We shall hereafter see, when we treat of Dionæa, that this same conclusion, namely that 204 DROSERA ROTUNDIFOLIA. (Cuar. X. the motor impulse is not transmitted by the fibro-vascular bundles, is plainly confirmed; and Professor Cohn has come to the same conclusion with respect to Aldrovanda—both members of the Droseraceæ.* As the motor impulse is not transmitted along the vessels, there remains for its passage only the cellular tissue; and the structure of this tissue explains to a certain extent how it travels so quickly down the long exterior tentacles, and much more slowly across the blade of the leaf. We shall also see why it crosses the blade more quickly in a longi- tudinal than in a transverse direction; though with time it can pass in any direction. We know that the same stimulus causes movement of the tentacles and aggregation of the protoplasm, and that both influences originate in and proceed from the glands within the same brief space of time. It seems therefore probable that the motor impulse consists of the first commencement of a molecular change in the pro- toplasm, which, when well developed, is plainly visible, and has been designated aggregation ; but to this subject I shall return. We further know that in the transmission of the aggregating process the chief delay is caused by the passage of the transverse cell-walls; for as the aggregation travels down the tentacles, the contents of each successive cell seem almost to flash into a cloudy mass. We may therefore infer that the motor impulse is in like manner delayed chiefly by passing through the cell-walls. * [Batalin (‘ Flora, 1877) experi- mented on the transmission of the of Masdevallia muscosa the impulse travels in a sheath of thin walled motor impulse, and confirms the ob- servations of Ziegler (‘Comptes ren- dus,’ 1874), from which that natu- ralist concluded that the vascular bundles form the path for the trans- mission of the impulse. Batalin concludes that impulse travels with far greater ease along the vessels than across the parenchyma, and that the course of the stimulus is normally almost exclusively along the vessels. If we believe that the motor im- pulse travels as a molecular change in the protoplasm, we cannot suppose that it travels in the tracheids. Now Oliver (‘Annals of Botany,’ Feb. 1888) has suggested that in the case parenchyma accompanying the xylem. If we make a similar assumption for Drosera, we should get rid of a difti- culty, for whether the impulse travels in the course of the vascular bundles or transversely across the leaf, it would in either case. be travelling in parenchymatous tissue ; the only difference between the two cases being that the parenchyma accompanying the vessels would be specially adapted for rapid transmis- sion in a definite direction, whereas the ordinary parenchyma has to transmit the impulse in a variety of directions.—F. D.] CHAP. X] CONDUCTING TISSUES. 205 The greater celerity with which the impulse is transmitted down the long exterior tentacles than across the dise may be largely attributed to its being closely confined within the narrow pedicel, instead of radiating forth on all sides as on the dise. But besides this confinement, the exterior cells of the tentacles are fully twice as long as those of the disc; so that only half the number of transverse partitions have to be traversed in a given length of a tentacle, compared with an equal space on the disc; and there would be in the same proportion less retardation of the impulse. Moreover, in sections of the exterior tentacles given by Dr. Warming,* the parenchymatous cells are shown to be still more elon- gated; and these would form the most direct line of com- munication from the gland to the bending place of the tentacle. Ifthe impulse travels down the exterior cells, it would have to cross from between twenty to thirty trans- verse partitions: but rather fewer if down the inner paren- chymatous tissue. In either case it is remarkable that the impulse is able to pass through so many partitions down nearly the whole length of the pedicel, and to act on the bending place, in ten seconds. Why the impulse, after having passed so quickly down one of the extreme marginal tentacles (about >} of an inch in length), should never, as far as I have seen, affect the adjoining tentacles, I do not understand. It may be in part accounted for by much energy being expended in the rapidity of the transmission. Most of the cells of the disc, both the superficial ones and’ the larger cells which form the five or six underlying layers, are about four times as long as broad. They are arranged almost longitudinally, radiating from the footstalk. The motor impulse, therefore, when transmitted across the disc, has to cross nearly four times as many cell-walls as when trans- mitted in a longitudinal direction, and would consequently be much delayed in the former case. The cells of the disc converge towards the bases of the tentacles, and are thus fitted to convey the motor impulse to them from all sides. On the whole, the arrangement and shape of the cells, both those of the disc and tentacles, throw much light on the rate and manner of diffusion of the motor impulse. But why the impulse proceeding from the glands of the exterior rows of * ¢Videnskabelige Meddelelser de la Soc, d’Hist. nat. de Copenhazue,” Nos, 10-12, 1872, woodcuts iv. and v. 206 DROSERA ROTUNDIFOLIA. [Cuar. X. tentacles tends to travel laterally and towards the centre of the leaf, but not centrifugally, is by no means clear. Mechanism of the Movements, and Nature of the Motor Impulse.—W hatever may be the means of movement, the exterior tentacles, considering their delicacy, are inflected with much force. p of a minim, or -00296 c.c.) for a few seconds to three or four glands,—and by the immersion of whole leaves in a measured quantity. In relation to these experiments it was necessary first to ascertain the effects of distilled water, and it was found, as described in detail, that the more sensitive leaves are affected by it, but only ina slight degree. A solution of the carbonate is absorbed by the roots and induces aggregation in their cells, but does not affect the leaves. The vapour is absorbed by the glands, and causes inflection as well as aggregation. A drop of a solution con- taining „ły of a grain (°0675 mg.) is the least quantity which, when placed on the glands of the disc, excites the exterior tentacles to bend inwards. Buta minute drop, con- taining yy455 of a grain (00445 mg.), if applied for a few seconds to the secretion surrounding a gland, causes the inflection of the same tentacle. When a highly sensitive leaf is immersed in a solution, and there is ample time for absorption, the s¢Jsj5 of a grain (°00024 mg.) is sufficient to excite a single tentacle into movement. The nitrate of ammonia induces aggregation of the protoplasm much less quickly than the carbonate, but is more potent in causing inflection. A drop containing 5755 of a grain (+027 mg.) placed on the disc acts powerfully on all the exterior tentacles, which have not themselves received any of the solution ; whereas a drop with ,.,5 of a grain caused only a few of these tentacles to bend, but affected rather more plainly the blade. A minute drop ap- plied as before, and containing 5,1), of a grain (+0025 mg.), caused the tentacle bearing this gland to bend. By the immersion of whole leaves, it was proved that the absorp- tion by a single gland of syrsyo of a grain (0000937 mg.) was sufficient to set the same tentacle into movement. Cuar. XI.] GENERAL SUMMARY. 219 The phosphate of ammonia is much more powerful than the nitrate. A drop containing 55 of a grain (+0169 mg.) placed on the disc of a sensitive leaf causes most of the ex- terior tentacles to be inflected, as well as the blade of the leaf. A minute drop containing y53\59y of a grain (-000423 mg.), applied for a few seconds to a gland, acts, as shown by the movement of the tentacle. When a leaf is immersed in thirty minims (1°7748 c.c.) of a solution of one part by weight of the salt to 21,875,000 of water, the absorption by a gland of only the tørevovy Of a grain (-00000328 mg.), that is, a little more than the one-twenty-millionth of a grain, is suflicient to cause the tentacle bearing this gland to bend to the centre of the leaf. In this experiment, owing to the presence of the water of crystallisation, less than the one-thirty-millionth of a grain of the efficient elements could have been absorbed. There is nothing remarkable in such minute quantities being absorbed by the glands, for all physiologists admit that the salts of ammonia, which must be brought in still smaller quantity by a single shower of rain to the roots, are absorbed by them. Nor is it surprising that Drosera should be enabled to profit by the absorption of these salts, for yeast and other low fungoid forms flourish in solutions of ammonia, if the other necessary elements are present. But it is an astonishing fact, on which I will not here again enlarge, that so inconceivably minute a quantity as the one-twenty-millionth of a grain of phosphate of ammonia should induce some change in a gland of Drosera, sufficient to cause a motor impulse to be sent down the whole length of the tentacle; this impulse exciting move- ment often through an angle of above 180°. I know not whether to be most astonished at this fact, or that the pressure of a minute bit of hair, supported by the dense secretion, should quickly cause conspicuous movement. Moreover, this extreme sensitiveness, exceeding that of the most delicate part of the human body, as well as the power of transmitting various impulses from one part of the leaf to another, have been acquired without the intervention of any nervous system. As few plants are at present known to possess glands specially adapted for absorption, it seemed worth while to try the effects on Drosera of various other salts, besides those of ammonia, and of various acids. Their action, as described in the eighth chapter, does not correspond at all 220 DROSERA ROTUNDIFOLIA. [Omir XI. strictly with their chemical affinities, as inferred from the classification commonly followed. The nature of the base is far more influential than that of the acid; and this is known to hold good with animals. For instance, nine salts of sodium all caused well-marked inflection, and none of them were poisonous in small doses; whereas seven of the nine corresponding salts of potassium produced no effect, two causing slight inflection. Small doses, moreover, of some of the latter salts were poisonous. The salts of sodium and potassium, when injected into the veins of animals, likewise differ widely in their action. The so-called earthy salts produce hardly any effect on Drosera. On the other hand, most of the metallic salts cause rapid and strong inflection, and are highly poisonous; but there are some odd exceptions to this rule; thus chloride of lead and zinc, as well as two salts of barium, did not cause inflection, and were not poisonous. Most of the acids which were tried, though much diluted (one part to 437 of water), and given in small doses, acted powerfully on Drosera; nineteen, out of the twenty-four, causing the tentacles to be more or less inflected. Most of them, even the organic acids, are poisonous, often highly so ; and this is remarkable, as the juices of so many plants contain acids. Benzoic acid, which is innocuous to animals, seems to be as poisonous to Drosera as hydrocyanic. On the other hand, hydrochloric acid is not poisonous either to animals or to Drosera, and induces only a moderate amount of inflection. Many acids excite the glands to secrete an extraordinary quantity of mucus; and the protoplasm within their cells seems to be often killed, as may be inferred . from the surrounding fluid soon becoming pink. It is strange that allied acids act very differently: formic acid induces very slight inflection, and is not poisonous; whereas acetic acid of the same strength acts most powerfully and is poisonous. Lactic acid is also poisonous, but causes inflection only after a considerable lapse of time. Malic acid acts slightly, whereas citric and tartaric acids produce no effect. In the ninth chapter the effects of the absorption of various alkaloids and certain other substances were de- scribed. Although some of these are poisonous, yet as several, which act powerfully on the nervous system of animals, produce no effect on Drosera, we may infer that the extreme sensibility of the glands, and their power of trans- ‘Sah ainiaan ananasai AA CHAP. XL) GENERAL SUMMARY. 221 mitting an influence to other parts of the leaf, causing movement, or modified secretion, or aggregation, does not depend on the presence of a diffused element, allied to nerve- tissue. One of the most remarkable facts is that long immersion in the poison of the cobra-snake does not in the least check, but rather stimulates, the spontaneous move- ment of the protoplasm in the cells of the tentacles. Solutions of various salts and acids behave very differently in delaying or in quite arresting the subsequent action of a solution of phosphate of ammonia. Camphor dissolved in water acts as a stimulant, as do small doses of certain essential oils, for they cause rapid and strong inflection. Alcohol is not a stimulant. The vapours of camphor, alcohol, chloroform, sulphuric and nitric ether, are poisonous in moderately large doses, but in small doses serve as narcotics or anæsthetics, greatly delaying the subsequent action of meat. But some of these vapours also act as stimulants, exciting rapid, almost spasmodic movements in the tentacles. Carbonic acid is likewise a narcotic, and retards the aggregation of the protoplasm when carbonate of ammonia is subsequently given. The first access of air to plants which have been immersed in this gas sometimes acts as a stimulant and induces movement. But, as before remarked, a special pharmacopceia would be necessary to describe the diversified effects of various substances on the leaves of Drosera. In the tenth chapter it was shown that the sensitiveness of the leaves appears to be wholly confined to the glands and to the immediately underlying cells. It was further shown that the motor impulse and other forces or influences, proceeding from the glands when excited, pass through the cellular tissue, and not along the fibro-vascular bundles. A gland sends its motor impulse with great rapidity down the pedicel of the same tentacle to the basal part which alone bends. The impulse, then passing onwards, spreads on all sides to the surrounding tentacles, first affecting those which stand nearest and then those farther off. But by being thus spread out, and from the cells of the disc not being so much elongated as those of the tentacles, it loses force, and here travels much more slowly than down the pedicels. Owing also to the direction and form of the cells, it passes with greater ease and celerity in a longitudinal than in a transverse line across the disc. The impulse proceeding 222 DROSERA ROTUNDIFOLIA. [Cuar. XI. from the glands of the extreme marginal tentacles does not seem to have force enough to affect the adjoining tentacles ; and this may be in part due to their length. The impulse from the glands of the next few inner rows spreads chiefly to the tentacles on each side and towards the centre of the leaf; but that proceeding from the glands of the shorter tentacles on the disc radiates almost equally on all sides. When a gland is strongly excited by the quantity or quality of the substance placed on it, the motor impulse travels farther than from one slightly excited; and if several glands are simultaneously excited, the impulses from all unite and spread still farther. As soon as a gland is excited, it discharges an impulse which extends to a con- siderable distance; but afterwards, whilst the gland is secreting and absorbing, the impulse suffices only to keep the same tentacle inflected; though the inflection may last for many days. If the bending place of a tentacle receives an impulse from its own gland, the movement is always towards the centre of the leaf; and so it is with all the tentacles, when their glands are excited by immersion in a proper fluid. The short ones in the middle part of the disc must be excepted, as these do not bend at all when thus excited. On the other hand, when the motor impulse comes from one side of the disc, the surrounding tentacles, including the short ones in the middle of the disc, all bend with precision towards the point of excitement, wherever this may be seated. This is in every way a remarkable phenomenon ; for the leaf falsely appears as if endowed with the senses of an animal. It is all the more remarkable, as when the motor impulse strikes the base of a tentacle obliquely with respect to its flattened surface, the contraction of the cells must be confined to one, two, or a very few rows at one end. And different sides of the surrounding tentacles must be acted on, in order that all should bend with precision to the point of excitement. The motor impulse, as it spreads from one or more glands across the disc, enters the bases of the surrounding tentacles, and immediately acts on the bending place. It does not in the first place proceed up the tentacles to the glands, exciting them to reflect back an impulse to their bases. Nevertheless, some influence is sent up to the glands, as their secretion is soon increased and rendered acid; and a a E ON Cair. XI] GENERAL SUMMARY. 225 then the glands, being thus excited, send back some other influence (not dependent on increased secretion, nor on the inflection of the tentacles), causing the protoplasm to aggregato in cell beneath cell. This may be called a reflex action, though probably very different from that proceeding from the nerve-ganglion of an animal; and it is the only known case of reflex action in the vegetable kingdom. : About the mechanism of the movements and the nature of the motor impulse we know very little. During the act of inflection fluid certainly travels from one part to another of the tentacles. But the hypothesis which agrees best with the observed facts is that the motor impulse is allied in nature to the aggregating process; and that this causes the mole- cules of the cell-walls to approach each other, in the same manner as do the molecules of the protoplasm within the cells; so that the cell-walls contract, But some strong objections may be urged against this view. The re-expansion of the tentacles is largely due to the elasticity of their outer cells, which comes into play as soon as those on the inner side cease contracting with prepotent force; but we have reason to suspect that fluid is continually and slowly attracted into the outer cells during the act of re-expansion, thus increasing their tension.* I have now given a brief recapitulation of the chief points observed by me, with respect to the structure, movements, constitution, and habits of Drosera rotundifolia ; and we see how little has been made out in comparison with what remains unexplained and unknown. * [Increase of fluid iv the external (convex) cells would tend to prevent re-expansion, not to facilitate it—F. D.] 224. DROSERA ANGLICA. . [Cuar. XIE CHAPTER XII. ON THE STRUCTURE AND MOVEMENTS OF SOME OTHER SPECIES OF DROSERA, Drosera anglica—Drosera intermedia—Drosera capensis—Drosera spathulata— Drosera filiformis—Drosera binata—Concluding remarks. J EXAMINED six other species of Drosera, some of them in- habitants of distant countries, chiefly for the sake of ascer- taining whether they caught insects. This seemed the more necessary as the leaves of some of the species differ to an extraordinary degree in shape from the rounded ones of Drosera rotundifolia. In functional powers, however, they differ very little. Drosera anglica (Hudson).*—The leaves of this species, which was sent to me from Ireland, are much elongated, and gradually widen from the footstalk to the bluntly pointed apex. They stand almost erect, and their blades sometimes exceed 1 inch in length, whilst their breadth is only the t of an inch. The glands of all the tentacles have the same structure, so that the extreme marginal ones do not differ from the others, as in the case of Drosera rotundifolia. When they are irritated by being roughly touched, or by the pressure of minute inorganic particles, or by contact with animal matter, or by the absorption of carbonate of ammonia, the tentacles become inflected; the basal portion being the chief seat of movement. Cutting or pricking the blade of the leaf did not excite any movement. They frequently capture insects, and the glands of the inflected tentacles pour forth much acid secretion. Bits of roast meat were placed on some glands, and the tentacles began to move in 1 m. or 1 m. 308.3 and in 1 hr. 10 m. reached the centre. "Two bits of boiled cork, one of boiled thread, and two of coal-cinders taken from the fire, were placed, by the aid of an instrument which had been immersed in boiling water, on five glands ; these superfluous precautions having been taken on account of M. Ziegler’s statements. One of the particles of cinder * Mrs. Treat has given an ex- of Drosera longifolia (which is a syn- cellent account in ‘The American onym in part of Drosera anglica), of Naturalist,’ December 1873, p. 705, Drosera rotundifolia and filiformis, Cuar. XIL] DROSERA CAPENSIS. 225 caused some inflection in 8 hrs. 45 m., as did after 23 hrs. the other particle of cinder, the bit of thread, and both bits of cork. Three glands were touched half a dozen times with a needle; one of the tentacles became well inflected in 17 m., and re-expanded after 24 hrs.; the two others never moved. The homogeneous fluid within the cells of the tentacles undergoes aggregation after these have become inflected ; especially if given a solution of carbonate of ammonia; and I observed the usual movements in the masses of protoplasm. In one case, aggregation ensued in 1 hr. 10 m. after a tentacle had carried a bit of meat to the centre. From these facts it is clear that the tentacles of Drosera anglica behave like those of Drosera rotundi- folia. If an insect is placed on the central glands, or has been naturally caught there, the apex of the leaf curls inwards. For instance, dead flies were placed on three leaves near their bases, and after 24 hrs. the previously straight apices were curled completely over, so as to embrace and conceal the flies; they had therefore moved through an angle of 180°. After three days the apex of one leaf, together with the tentacles, began to re-expand. But as far as I have seen—and I made many trials—the sides of the leaf are never inflected, and this is the one functional ditference between this species and Drosera rotundifolia. Drosera intermedia (Hayne). ‘This species. is quite as common in some parts of England as Drosera rotundifolia. It differs from Drosera anglica, as far as the leaves are concerned, only in their smaller size, and in their tips being generally a little reflexed. They capture a large number of insects. ‘he tentacles are excited into movement by all the causes above specified; and aggregation ensues, vith movement of the protoplasmic masses. I have seen, through a lens, a tentacle beginning to bend in less than a minute after a particle of raw meat had been placed on the gland. The apex of the leaf curls over an exciting object as in the case of Drosera anglica. Acid secretion is copiously poured over captured insects. A leaf which had embraced a fly with all its tentacles re-expanded after nearly three days. Drosera capensis.—This species, a native of the Cape of Good Hope, was sent to me by Dr. Hooker. The leaves are elongated, slighty concave along the middle and taper towards the apex, which is bluntly pointed and reflexed. ‘They rise from an almost woody axis, and their greatest peculiarity consists in their foliaceous green footstalks, which are almost as broad and even longer than the gland-bearing blade. This species, therefore, probably draws more nourishment from the air, and less from captured insects, than the other species of the genus. Nevertheless, the tentacles are crowded together on the disc, and are extremely numerous; those on the margins being much longer than the central ones. All the glands have the same form ; their secretion is extremely,viscid and acid. The specimen which I examined had only just recovered from a weak state of health, This may account for the téntacles moving Q 226 DROSERA FILIFORMIS. (Cmar. XII. very slowly when particles of meat were placed on the glands, and perhaps for my never succeeding in causing any movement by repeatedly touching them with a needle. But with all the species of the genus this latter stimulus is the least effective of any. articles of glass, cork, and coal-cinders, were placed on the glands of six tentacles; and one alone moved after an interval of 2 hrs. 30 m. Nevertheless, two glands were extremely sensitive to very small doses of the nitrate ofammonia, namely to about 54; of a minim of a solution (one part to 5250 of water), containing only y;3555 Of a grain (-000562 mg.) of the salt. Fragments of flies were placed on two leaves near their tips, which became incurved in 15 hrs. A fly was also placed in the middle of the leaf; in a few hours the tentacles on each side embraced it, and in 8 hrs. the whole leaf directly beneath the fly was a little bent transversely. By the next morning, after 23 hrs., the leaf was curled so completely over that the apex rested on the upper end of the footstalk. In no case did the sides of the leaves become inflected. A crushed fly was placed on the foliaceous footstalk, but produced no effect. Drosera spathulata (sent to me by Dr. Hooker),—I made only a few observations on this Australian species, which has long, narrow leaves, gradually widening towards their tips. The glands of the extreme marginal tentacles are elongated and differ from the others, as in the case of Drosera rotundifolia. A fly was placed on a leaf, and in 18 hrs. it was embraced by the adjoining tentacles. Gum-water dropped on several leaves produced no effect. A fragment of a leaf was immersed in a few drops of a solution of one part of carbonate of ammonia to 146 of water; all the glands were instantly blackened ; the process of aggregation could be seen travelling rapidly down the cells of the tentacles; and the granules of protoplasm soon united into spheres and variously shaped masses, which displayed the usual movements. Half a minim of a solution of one part of nitrate of ammonia to 146 of water was next placed on the centre of a leaf; after 6 hrs. some marginal tentacles on both sides were inflected, and after 9 hrs. they met in the centre. The lateral edges of the leaf also became incurved, so that it formed a half-cylinder; but the apex of the leaf in none of my few trials was inflected. The above dose of the nitrate (viz. ył of a grain or *202 mg.) was too powerful, for in the course of 23 hrs. the leaf died. Drosera filiformis.—This North American species grows in such abundance in parts of New Jersey as almost to cover the ground. It catches, according to Mrs, Treat,* an extraordinary number of small and large insects,—even great flies of the genus Asilus, moths, and butter- flies. The specimen which I examined, sent me by Dr. Hooker, had thread-like leaves, from 6 to 12 inches in length, with the upper surface convex and the lower fiat and slightly channelled. The whole convex * ¢ American Naturalist,’ Dec. 1873, p. 705. Cuar. XIIL] DROSERA BINATA. wae surface, down to the roots—for there is no distinct footstalk—is covered with short gland-bearing tentacles, those on the margins being the longest and reflexed. Bits of meat placed on the glands of some tentacles caused them to be slightly inflected in 20 m.; but the plant was not in a vigorous state. After 6 hrs. they moved through an angle of 90°, and in 24 hrs. reached the centre. The surrounding tentacles by this time began to curve inwards. Ultimately a large drop of extremely viscid, slightly acid secretion was poured over the meat from the united glands. Several other glands were touched with a little saliva, and the tentacles became incurved in under 1 hr., and re-expanded after 18 hrs. Particles of glass, cork, cinders, thread, and gold-leaf, were placed on numerous glands on two leaves; in about 1 hr. four tentacles became curved, and four others after an additional interval of 2 hrs. 30 m. I never once succeeded in causing any movement by repeatedly touching the glands with a needle; and Mrs. Treat made similar trials for me with no success. Small tlies were placed on several leaves near their tips, but the thread-like blade became only on one occasion very slightly bent, directly beneath the insect. Perhaps this indicates that the blades of vigorous plants would bend over captured insects, and Dr. Canby informs me that this is the case; but the movement cannot be strongly pronounced, as it was not observed by Mrs. Treat. Drosera binata (or dichotoma).*—I am much indebted to Lady Dorothy Nevill for a fine plant of this almost gigantic Australian species, which differs in some interesting points from those previously described. In this specimen the rush-like footstalks of the leaves were 20 inches in length. The blade bifurcates at its junction with the footstalk, and twice or thrice afterwards, curling about in an irregular manner. It is narrow, being only 4, of an inch in breadth. One blade was 73 inches long, so that the entire leaf, including the footstalk, was above 27 ‘inches in length. Both surfaces are slightly hollowed out. The upper surface is covered with tentacles arranged in alternate rows; those in the middle being short and crowded together, those towards the margins longer, even twice or thrice as long as the blade is broad. The glands of the exterior tentacles are of a much darker red than those of the central ones. The pedicels of all are green. The apex of the blade is attenuated, and bears very long tentacles. Mr. Copland informs me that the leaves of a plant which he kept for some years were generally covered with captured insects before they withered. The leaves do not differ in essential points of structure or of function from those of the previously described species. Bits of meat or a little saliva placed on the glands of the exterior tentacles caused well-marked movement in 3 m., and particles of glass acted in 4m. The tentacles with the latter particles re-expanded after 22 hrs. A piece of leaf immersed in a few drops of a solution of one part of carbonate of * [See E. Morren, ‘Bull. de Acad. Royale de Belgique,’ 2™° série, tom 40, 1875, where the plant is figured, and some experiments described.— F. D,} Q 2 228 DROSERA BINATA. [Cuar. XIL ammonia to 437 of water had all the glands blackened and all the tentacles inflected in 5 m. A bit of raw meat, placed on several glands in the medial furrow, was well clasped in 2 hrs. 10 m. by the marginal tentacles on both sides. Bits of roast meat and small flies did not act quite so quickly; and albumen and fibrin still less quickly. One of the bits of meat excited so much secretion (which is always acid) that it flowed some way down the medial furrow, causing the inflection of the tentacles on both sides as far as it extended. Particles of glass placed on the glands in the medial furrow did not stimulate them sufliciently for any motor impulse to be sent to the outer tentacles. In no case was the blade of the leaf, even the attenuated apex, at all inflected. On both the upper and lower surface of the blade there are numerous minute, almost sessile glands, consisting of four, eight, or twelve cells. On the lower surface they are pale purple, on the upper, greenish. Nearly similar organs occur on the foot-stalks, but they are smaller and often in a shrivelled condition. The minute glands on the blade can absorb rapidly: thus, a piece of leaf was immersed in a solution of one part of carbonate of ammonia to 218 of water (2 gr. to 1 oz.), and in 5 m. they were all so much darkened as to be almost black, with their contents aggregated. They do not, as far as I could observe, secrete spontaneously ; but in between 2 and 3 hrs. after a leaf had been rubbed with a bit of raw meat moistened with saliva, they seemed to be secreting freely ; and this conclusion was afterwards supported by other appearances. ‘They are, therefore, homologous with the sessile glands hereafter to be described on the leaves of Dionwa and Droso- phyllum. In this latter genus they are associated, as in the present case, with glands which secrete. spontaneously, that is, without being excited. Drosera binata presents another and more remarkable peculiarity, namely, the presence of a few tentacles on the backs of the leaves, near their margins. ‘These are perfect in structure; spiral vessels run up their pedicels; their glands are surrounded by drops of viscid secretion, and they have the power of absorbing. This latter fact was shown by the glands immediately becoming black, and the protoplasm aggregateu, when a leaf was placed in a little solution of one part of carbonate of ammonia to 437 of water. These dorsal tentacles are short, not being. nearly so long as the marginal ones on the upper surface; some of them are so short as almost to graduate into the minute sessile glands. Their presence, number, and size, vary on different leaves, and they are arranged rather irregularly. On the back of one leaf I counted as many as twenty-one along one side. These dorsal tentacles differ in one important respect from those on the upper surface, namely, in not possessing any power of movement,. in whatever manner they may be stimulated. Thus, portions of four leaves were placed at different times in solutions of carbonate of ammonia (one part to 437 or 218 of water), and all the tentacles on the: upper surface soon became closely inflected; but the dorsal ones did Cumar. XII] CONCLUDING REMARKS. 229 not move, though the leaves were left in the solution for many hours, and though their glands from their blackened colour had obviously absorbed some of the salt. Rather young leaves should be selected for such trials, for the dorsal tentacles, as they grow old and begin to Wither, often spontaneously incline towards the middle of the leaf. If these tentacles had possessed the power of movement, they would not have been thus rendered more serviceable to the plant ; for they are not long enough to bend round the margin of the leaf so as to reach an insect caught on the upper surface. Nor would it have been of any use if these tentacles could have moved towards the middle of the lower surface, for there are no viscid glands there by which insects can be caught. Although they have no power of movement, they are probably of some use by absorbing animal matter from any minute insect which may be caught by them, and by absorbing ammonia from the rain-water. But their varying presence and size, and their irregular position, indicate that they are not of much service, and that they are tending towards abortion. In a future chapter we shall see that Drosophyllum, with its elongated leaves, probably represents the condition of an early progenitor of the genus Drosera; and none of the tentacles of Drosophyllum, neither those on the upper nor lower surface of the leaves, are capable of movement when excited, though they capture numerous insects, which serve as nutriment. Therefore it seems that Drosera binata has retained remnants of certain ancestral characters—namely, a few motionless tentacles on the backs of the leaves, and fairly well developed sessile glands—which have been lost by most or all of the other species of the genus. Concluding Remarks.—F rom what we have now seen, there can be little doubt that most or probably all the species of Drosera are adapted for catching insects by nearly the same means. Besides the two Australian species above described, it is said* that two other species from this country, namely Drosera pallida and Drosera sulphurea, “close their leaves upon insects with great rapidity: and the same phenomenon is manifested by an Indian species, D. lunata, and by several of those of the Cape of Good Hope, especially by D. trinervis.” Another Australian species, Drosera heterophylla (made by Lindley into a distinct genus, Sondera) is remarkable from its peculiarly shaped leaves, but I know nothing of its power of catching insects, for I have seen only dried specimens. The leaves form minute flattened cups, with the footstalks attached not to one margin, but to the bottom. The inner * ¢Gardener’s Chronicle,’ 1874, p. 209. 230 CONCLUDING REMARKS. (Cuar. XI. surface and the edges of the cups are studded with tentacles, which include fibro-vascular bundles, rather different from those seen by me in any other species: for some of the vessels. are barred and punctured, instead of being spiral. The glands secrete copiously, judging from the quantity of dried secretion adhering to them. j Cuar. XIII] DIONÆA MUSCIPULA. 2P CHAPTER XIII. DION A MUSCIPULA. Structure of the leaves—Sensitiveness of the filaments—Rapid movement of the lobes caused by irritation of the filaments—Glands, their power of secretion—Slow movement caused by the absorption of animal matter— Evidence of absorption from the aggregated condition of the glands— Digestive power of the secretion—Action of chloroform, ether, and hydro- cyanic acid—The manner in which insects are captured—Use of the marginal spikes—Kinds of insects captured—The transmission of the motor impulse and mechanism of the movements—Re-expansion of the lobes. Tus plant, commonly called Venus’ fly-trap, from the rapidity and force of its movements, is one of the most wonderful in the world.* It is a member of the small family of the Droseracex, and is found only in the eastern part of North Carolina, growing in damp situations. The roots are small ; those of a moderately fine plant which I examined consisted of two branches about 1 inch in length, springing from a bulbous enlargement. They probably serve, as in the case of Drosera, solely for the absorption of water ; fora gardener, who has been very successful in the cultivation of this plant, grows it, like an epiphytic orchid, in well-drained damp moss without any soil.t The form of the bilobed leaf, with its foliaceous footstalk, is shown in the accompanying drawing (fig. 12). The two lobes stand at rather less than a right angle to each other. Three minute pointed processes or fila- ments, placed triangularly, project from the upper surfaces of both ; but I have seen two leaves with four filaments on each side, and another with only two. These filaments are * Dr. Hooker, in his address to [A good account of the early the British Association at Belfast, literature is given by Kurtz in Reich- 1874, has given so full an historical ert and Du Bois-Reymond’s ‘ Archiv.’ account of the observations which 1876.—F. D.] have been published on the habits of + ‘Gardener’s Chronicle,’ 1874, p. this plant, that it would be super- 464, fluous on my part to repeat them. 232 DIONÆA MUSCIPULA. [Cuar. XII. remarkable from their extreme sensitiveness to a touch, as shown not by their own movement, but by that of the lobes. The margins of the leaf are prolonged into sharp rigid pro- jections which I will call spikes, into each of which a bundle of spiral vessels enters. The spikes stand in such a position that, when the lobes close, they interlock like the teeth of arat-trap. The midrib of the leaf, on the lower side, is strongly developed and prominent. The upper surface* of the leafis thickly covered, excepting towards the margins, with minute glands of a reddish or Fic. 12. (Dionza muscipula.) Leaf viewed laterally in its expanded state. purplish colour, the rest of the leaf being green. There are no glands on the spikes, or on the foliaceous footstalk. The glands are formed of from twenty to thirty polygonal cells, filled with purple fluid. Their upper surface is convex. They stand on very short pedicels, into which spiral vessels do not enter, in which respect they differ from the tentacles of Drosera. They secrete, but only when excited by the absorption of certain matters; and they have the power of * (A. Fraustadt, in his Breslau dis- fact. It is easy to see that the lower sertationon Dionza (Mar. 1876) states that the upper surface of the leaf is devoid of stomata. C. De Candolle, ‘Archives des Sciences Phys. et Nat.’ Geneva, April 1876, mentions the same surface of the leaf is a better one for the development of stomata than the upper surfaee, which is liable to be constantly bathed in secretion.— FE; D) LE ETE I TT a TEL EY a Cuar. XII.] SENSITIVENESS OF FILAMENTS. ase absorption. Minute projections, formed of eight divergent arms of a reddish-brown or orange colour, and appearing under the microscope like elegant little flowers, are scattered in considerable numbers over the footstalk, the backs of the leaves, and the spikes, with a few on the upper surface of the lobes. These octofid projections are no doubt homologous with the papille on the leaves of Drosera rotundifolia. There are also a iew very minute, simple, pointed hairs,* about 17407 Of an inch (+0148 mm.) in lengih on the backs of the eaves, The sensitive filamentst are formed of several rows of elongated cells, filled with purplish fluid. They are a little above the >} of an inch in length; are thin and delicate, and taper toa point. I examined the bases of several, making sections of them, but no trace of the entrance of any vessel could be seen. The apex is sometimes bifid or even trifid, owing to a slight separation between the terminal pointed cells. Towards the base there is constriction, formed of broader cells, beneath which there is an articulation, supported on an enlarged base, consisting of differently shaped poly- gonal cells. As the filaments project at right angles to the surface of the leaf, they would have been lable to be broken whenever the lobes closed together, had it not been for the articulation which allows them to bend flat down. These filaments, from their tips to their bases,f are ex- quisitely sensitive to a momentary touch. It is scarcely possible to touch them ever so lightly or quickly with any hard object without causing the lobes to close. A piece of very delicate human hair, 24 inches in length, held dangling over a filament, and swayed to and fro so as to touch it, did not excite any movement. But when a rather thick cotton thread of the same length was similarly swayed, the lobes closed. Pinches of fine wheaten flour, dropped from a height, produced no effect. The above-mentioned hair was then fixed into a handle, and cut off so that 1 inch projected; this * [These hairs were absent in the specimens examined by Kurtz (Reich- ert and Du Bois-Reymond’s ‘ Archiv.’ 1876).—F. D.] + [Both Fraustadt and De Candolle have described the structure of these tilaments, and have shown that their morphological rank is that of “ emer- gencies.””—F. D.] t [Batalin (‘ Flora,’ 1877) quotes Oudemans (R. Academy of Sciences of Amsterdam, 1859), to the effect that the filaments are much more sensitive at the base than elsewhere. Batalin confirms the fact from his own obser- vations.—F, D.] 234 DIONEA MUSCIPULA. [Cuap. XII. length being sufficiently rigid to support itself in a nearly horizontal line. The extremity was then brought by a slow movement laterally into contact with the tip of a filament, and the leaf instantly closed. On another occasion two or three touches of the same kind were necessary before any movement ensued. When we consider how flexible a fine hair is, we may form some idea how slight must be the touch given by the extremity of a piece, 1 inch in length, moved slowly. Although these filaments are so sensitive to a momentary and delicate touch, they are far less sensitive than the glands of Drosera to prolonged pressure. Several times I succeeded in placing on the tip of a filament, by the aid of a needle moved with extreme slowness, bits ot rather thick human hair, and these did not excite movement, although they were more than ten times as long as those which caused the ten- tacles of Drosera to bend; and although in this latter case they were largely supported by the dense secretion. On the other hand, the glands of Drosera may be struck with a needle or any hard object, once, twice, or even thrice, with consider- able force, and no movement ensues. This singular differenc in the nature of the sensitiveness of the filaments of Dionxa and of the glands of Drosera evidently stands in relation to the habits of the two plants. Ifa minute insect alights with its delicate feet on the glands of Drosera, it is caught by the viscid secretion, and the slight, though prolonged pressure, gives notice of the presence of prey, which is secured by the slow bending of the tentacles. On the other hand, the sensitive filaments of Dionæa are not viscid, and the capture of insects can be assured only by their sensitiveness to a momentary touch, followed by the rapid closure of the lobes.* As just stated, the filaments are not glandular, and do not secrete. Nor have they the power of absorption, as may be inferred from drops of a solution of carbonate of ammonia (one part to 146 of water), placed on two filaments, not pro- ducing any effect on the contents of their cells, nor causing the lobes to close. When, however, a small portion of a leaf with an attached filament was cut off and immersed in the * [Munk (Reichert and du Bois- covering them was removed. It is Reymond’s ‘Archiv.’ 1876, p. 105) remarkable that the change from a states that the leaves of his plants damp to a dry atmosphere should frequently closed when the bell-jar produce this effect.—F. D.] Cuar, XIUI.] SENSITIVENESS OF FILAMENTS. 235 same solution, the fluid within the basal cells became almost. instantly aggregated into purplish or colourless, irregularly shaped masses of matter. The process of aggregation grad- ually travelled up the filaments from cell to cell to their ex- tremities, thatis in a reverse course to what occurs in the ten- tacles of Drosera when their glands have been excited. Several other filaments were cut off close to their bases, and left for 1hr. 30 m.in a weaker solution of one part of the carbonate to 218 of water, and this caused aggregation in all the cells, commencing as before at the bases of the filaments. Long immersion of the filaments in distilled water likewise causes aggregation. Nor is it rare to find the contents of a few of the terminal cells in a spontaneously aggregated condition. The aggregated masses undergo incessant slow changes of form, uniting and again separating; and some of them apparently revolve round their own axes. A current of colourless granular protoplasm could also be seen travelling round the walls of the cells. This current ceases to be visible as soon as the contents are well aggregated; but it probably still continues, though no longer visible, owing to all the granules in the flowing layer having become united with the central masses. In all these respects the filaments of Dionza behave exactly like the tentacles of Drosera. Notwithstanding this similarity there is one remarkable difference. The tentacles of Drosera, after their glands have been repeatedly touched, or a particle of any kind has been placed on them, become inflected and strongly aggregated. No such effect is produced by touching the filaments of Dionæa ; I compared, after an hour or two, some which had been touched and some which had not, and others after twenty-five hours, and there was no difference in the contents of the cells. The leaves were kept open all the time by clips; so that the filaments were not pressed against the opposite lobe. Drops of water,* or a thin broken stream, falling from a height on the filaments, did not cause the blades to close; though these filaments were afterwards proved to be highly * [C. De Candolle (‘Archives des late the leaf, but that it may be made Sc. Phys. et Nat.’ Geneva, April 1876) to close by a current of water directed states that drops of water which in- at right angles to the filament.— fringe on the filaments in the direc- F, D.J tion of their length do not stimu- 236 DIONEA MUSCIPULA. (Car. XIII. sensitive. No doubt, as in the case of Drosera, the plant is indifferent to the heaviest shower of rain. Drops ofa solution of half an ounce of sugar to a fluid ounce of water were repeatedly allowed to fall from a height on the filaments, but produced no effect, unless they adhered to them. Again, I blew many times through a fine pointed tube with my utmost force against the filaments without any effect; such blowing heing received with as much indifference as no doubt is a heavy gale of wind. We thus see that the sensitiveness of the filaments is of a specialised nature, being related to a momentary touch rather than to prolonged pressure ; and the touch must not be from fluids, such as air or water, but from some solid object. Although drops of water and of a moderately strong solu- tion of sugar, falling on the filaments, does not excite them, yet the immersion of a leaf in pure water sometimes caused the lobes to close. One leaf was left immersed for 1 hr. 10m. and three other leaves for some minutes, in water at tem- peratures varying between 59° and 65° (15° to 18°°3 Cent.) without any effect. One, however, of these four leaves, on being gently withdrawn from the water, closed rather quickly. The three other leaves were proved to he in good condition, as they closed when their filaments were touched. Never- theless two fresh leaves on being dipped into water at 75° and 625° (23°°8 and 16°-9 Cent.) instantly closed. These were then placed with their footstalks in water, and after 23 hrs. partially re-expanded ; on touching their filaments one of them closed. This latter leaf after an additional 24 hrs. again re-expanded, and now, on the filaments of both leaves being touched, both closed. We thus see that a short immer- sion in water does not at all injure the leaves, but sometimes excites the lobes to close. The movement in the above cases was evidently not caused by the temperature of the water. It has been shown that long immersion causes the purple fluid within the cells of the sensitive filaments to become aggregated; and the tentacles of Drosera are acted on in the same manner by long immersion, often being somewhat inflected. In both cases the result is probably due to a slight degree of exosmose. I am confirmed in this belief by the effects of immersing a leaf of Dionæa in a moderately strong solution of sugar; the leaf having been previously left for 1 hr. 10 m. in water without any effect; for now the lobes closed rather quickly, PAO ie E es Cuar. XIII.] SENSITIVENESS OF FILAMENTS. O51 the tips of the marginal spikes crossing in 2 m. 30 s., and the leaf being completely shut in 3 m. Three leaves were then immersed in a solution of half an ounce of sugar to a fluid ounce of water, and all three leaves closed quickly. As I was doubtful whether this was due to the cells on the upper surface of the lobes, or to the sensitive filaments, being acted on by exosmose, one leaf was first tried by pouring a little of the same solution in the furrow between the lobes over the midrib, which is the chief seat of movement. It was left there for some time, but no movement ensued. The whole upper surface of leaf was then painted (except close round the bases of the sensitive filaments, which I could not do without risk of touching them) with the same solution, but no effect was produced. So that the cells on the upper surface are not thus affected. But when, after many trials, I succeeded in getting a drop of the solution to cling to one of the filaments, the leaf quickly closed. Hence we may, I think, conclude that the solution causes fluid to pass out of the delicate cell of the filaments by exosmose; and that this sets up some molecular change in their contents, analogous to that which must be produced by a touch. The immersion of leaves .in a solution of sugar affects them for a much longer time than does an immersion in water, or a touch on the filaments; for in these latter cases the lobes begin to re-expand in less than a day. On the other hand, of the three leaves which were immersed for a short time in the solution, and were then washed by means of a syringe inserted between the lobes, one re-expanded after two days; a second after seven days; and the third after nine days. The leaf which closed, owing to a drop of the solution having adhered to one of the filaments, opened after two days. I was surprised to find on two occasions that the heat from the rays of the sun, concentrated by a lens on the bases of several filaments, so that they were scorched and discoloured, did not cause any movement; though the leaves were active, as they closed, though rather slowly, when a filament on the opposite side was touched. On a third trial, a fresh leaf closed after a time, though very slowly; the rate not being increased by one of the filaments, which had not been injured, being touched. After a day these three leaves opened, and were fairly sensitive when the uninjured fila- ments were touched. The sudden immersion of a leaf into boiling water does not cause it to close. Judging from the 238 DIONÆA MUSCIPULA. (Cap. XIII. analogy of Drosera, the heat in these several cases was too great and too suddenly applied. The surface of the blade is very slightly sensitive; it may be freely and roughly handled, without any movement being caused. A leaf was scratched rather hard with a needle, but did not close; but when the triangular space between the three filaments on another leaf was similarly scratched, the lobes closed. They always closed when the blade or midrib was deeply pricked or cut. Inorganic bodies, even of large size, such as bits of stone, glass, &c.—or organic bodies not containing soluble nitro- genous matter, such as bits of wood, cork, moss, or bodies containing soluble nitrogenous matter, if perfectly dry, such as bits of meat, albumen, gelatine, &c., may be long left (and many were tried) on the lobes, and no movement is excited. The result, however, is widely different, as we shall presently see, if nitrogenous organic bodies which are at all damp, are left on the lobes; for these then close by a slow and gradual movement, very different from that caused by touching one of the sensitive filaments. The footstalk is not in the least sensitive; a pin may be driven through it, or it may be cut off, and no movement follows. ‘The upper surface of the lobes, as already stated, is thickly covered with small purplish, almost sessile glands.* These have the power both of secretion and absorption ; but, unlike those of Drosera, they do not secrete until excited by the absorption of nitrogenous matter. No other excite- ment, as far as I have seen, produces this effect. Objects, such as bits of wood, cork, moss, paper, stone, or glass, may be left for a length of time on the surface of a leaf, and it remains quite dry. Nor does it make any difference if the lobes close over such objects. For instance, some little balls of blotting-paper were placed on a leaf, and a filament was touched; and when after 24 hrs. the lobes began to re-open, * [Gardiner has described these protoplasm is much less granular glands in the ‘ Proceedings of the R. Society,’ vol xxxvi. p.180. When at rest the gland-cells show a granular protoplasm, containing in most cases a single large vacuole; the nucleus is situated at the base of the cell. At the end of the secreting period the following changes have occurred, The nucleus seems to diminish in size, it has assumed a central position; the than before, and contains a number of small vacuoles, so that the nucleus appears suspended by radiating strands of protoplasm in the centre of the cell. Another change produced by the feeding the leaf is the appearance, in the parenchyma, of tufts of greenish yellow crystals of unknown nature.— F, D] Car. XIIL] SECRETION AND ABSORPTION. 239 the balls were removed by the aid of thin pincers, and were found perfectly dry. On the other hand, if a bit of damp meat or a crushed tly is placed on the surface of an expanded leaf, the glands after a time secrete freely. In one such case there was a little secretion directly beneath the meat in 4 hrs. ; and atier an additional 3 hrs. there was a consider- able quantity both under and close round it. In another case, after 3 hrs. 40 m., the bit of meat was quite wet. But none of the glands secreted, excepting those which actually touched the meat or the secretion containing dissolved animal matter. If, however, the lobes are made to close over a bit of meat or an insect, the result is different, for the glands over the whole surface of the leaf now secrete copiously. As in this case the glands on both sides are pressed against the meat or insect, the secretion from the first is twice as great as when a bit of meat is laid on the surface of one lobe; and as the two lobes come into almost close contact, the secretion, containing dissolved animal matter, spreads by capillary attraction, causing fresh glands on both sides to begin secreting in a continually widening circle. The secretion is almost colourless, slightly mucilaginous, and, judging by the manner in which it coloured litmus paper, more strongly acid than that of Drosera. It is so copious that on one occasion, when a leaf was cut open, on which a small cube of albumen had been placed 45 hrs. before, drops rolled off the leaf. On another occasion, in which a leaf with an enclosed bit of roast meat spontaneously opened after eight days, there was so much secretion in the furrow over the midrib that it trickled down. A large crushed fly (Tipula) was placed on a leaf from which a small portion at the base of one lobe had previously been cut away, so that an opening was left; and through this, the secretion continued to run down the footstalk during nine days,—that is, for as long a time as it was observed. By forcing up one of the lobes, I was able to see some distance between them, and all the glands within sight were secreting freely. We have seen that inorganic and non-nitrogenous objects placed on the leaves do not excite any movement; but nitrogenous bodies, if in the least degree damp, cause after several hours the lobes to close slowly. Thus bits of quite dry meat and gelatine were placed at opposite ends of the same leaf, and in the course of 24 hrs. excited neither 240 DIONEA MUSCIPULA, (Cuap. XIII. secretion nor movement. They were then dipped in water, their surfaces dried on blotting-paper, and replaced on the same leaf, the plant being now covered with a bell-glass. After 24 hrs. the damp meat had excited some acid secretion, and the lobes at this end of the leaf were almost shut. At the other end, where the damp gelatine lay, the leaf was still quite open, nor had any secretion been excited ; so that, as with Drosera, gelatine is not nearly so exciting a sub- stance as meat. The secretion beneath the meat was tested by pushing a strip of litmus paper under it (the filaments not being touched), and this slight stimulus caused the leaf to shut. On the eleventh day it reopened; but the end where the gelatine lay, expanded several hours before the opposite end with the meat. A second bit of roast meat, which appeared dry, though it had not been purposely dried, was left for 24 hrs. on a leaf, caused neither movement nor secretion. The plant in its pot was now covered with a bell-glass, and the meat absorbed some moisture from the air; this sufficed to excite acid secretion, and by the next morning the leaf was closely shut. A third bit of meat, dried so as to be quite brittle, was placed on a leaf under a bell-glass, and this also became in 24 hrs. slightly damp, and excited some acid secretion, but no movement. A rather large piece of perfectly dry albumen was left at one end of a leaf for 24 hrs. without any effect. It was then soaked for a few minutes in water, rolled about on blotting- paper, and replaced on the leaf; in 9 hrs. some slightly acid secretion was excited, and in 24 hrs. this end of the leaf was partially closed. The bit of albumen, which was now surrounded by much secretion, was gently removed, and although no filament was touched, the lobes closed. In this and the previous case, it appears that the absorption of animal matter by the glands renders the surface of the leaf much more sensitive to a touch than it is in its ordinary state; and this is a curious fact. Two days afterwards the end of the leaf where nothing had been placed began to open, and on the third day was much more open than the opposite end where the albumen had lain. Lastly, large drops of a solution of one pari of carbonate of ammonia to 146 of water were placed on some leaves, but no immediate movement ensued. I did not then know of the slow movement caused by animal matter, otherwise £ 4 Te Cuar. XIII] SECRETION AND ABSORPTION. 241 should have observed the leaves for a longer time, and they would probably have been found closed, though the solution (judging from Drosera) was, perhaps, too strong. From the foregoing cases it is certain that bits of meat and albumen, if at all damp, excite not only the glands to secrete, but the lobes to close. This movement is widely different from the rapid closure caused by one of the filaments being touched. We shall see its importance when we treat of the manner in which insects are captured. There is a great contrast between Drosera and Dionza in the effects produced by mechanical irritation on the one hand, and the absorption of animal matter on the other. Particles of glass placed on the glands of the exterior tentacles of Drosera excite movement within nearly the same time, as do particles of meat, the latter being rather the most efficient ; but when the glands of the disc have bits of meat given them, they transmit a motor impulse to the exterior tentacles much more quickly than do these glands when bearing inorganic particles, or when irritated by repeated touches. On the other hand, with Dionea, touching the filaments excites incomparably quicker movement than the absorption of animal matter by the glands. Nevertheless, in certain cases, this latter stimulus is the more powerful of the two. On three occasions leaves were found which from some cause were torpid, so that their lobes closed only slightly, however much their filaments were irritated ; but on inserting crushed insects between the lobes, they became in a day closely shut. The facts just given plainly show that the glands have the power of absorption, for otherwise it is impossible that the leaves should be so differently affected by non-nitro- genous and nitrogenous bodies, and between these latter in a dry and damp condition. It is surprising how slightly damp a bit of meat or albumen need be in order to excite secretion and afterwards slow movement, and equally surprising how minute a quantity of animal matter, when absorbed, suffices to produce these two effects. It seems hardly credible, and yet it is certainly a fact, that a bit of hard-boiled white of egg, first thoroughly dried, then soaked for some minutes in water and rolled on blotting-paper, should yield in a few hours enough animal matter to the glands to cause them to secret>, and afterwards the lobes to close. That the glands have the power of absorption is R 242 DIONÆA MUSCIPULA. [Cuap. XIII. likewise shown by the very different lengths of time (as we shall presently see) during which the lobes remain closed over insects and other bodies yielding soluble nitrogenous matter, and over such as do not yield any. But there is direct evidence of absorption in the condition of the glands which have remained for some time in contact with animal matter. Thus bits of meat and crushed insects were several times placed on glands, and these were compared after some hours with other glands from distant parts of the same leaf. The latter showed not a trace of aggregation, whereas those which had been in contact with the animal matter were well ageregated. Aggregation may be seen to occur very quickly if a piece ofa leaf is immersed in a weak solution of carbonate of ammonia. Again, small cubes of albumen and gelatine were left for eight days on a leaf, which was then cut open. The whole surface was bathed with acid secretion, and every cell in the many glands which were examined had its contents aggregated in a beautiful manner into dark or pale purple, or colourless globular masses of protoplasm. These underwent incessant slow changes of forms; sometimes separating from one another and then reuniting, exactly as in the cells of Drosera, Boiling water makes the contents of the gland-cells white and opaque, but not so purely white and porcelain-like as in the case of Drosera. How living insects, when naturally caught, excite the glands to secrete so quickly as they do, I know not; but I suppose that the great pressure to which they are subjected forces a little excretion from either extremity of their bodies, and we have seen that an extremely small amount of nitrogenous matter is sufficient to excite the glands. Before passing on to the subject of digestion, I may state that I endeavoured to discover, with no success, the functions of the minute octofid processes with which the leaves are studded. From facts hereafter to be given in the chapters on Aldrovanda and Utricularia, it seemed probable that they served to absorb decayed matter left by the captured insects ;. but their position on the backs of the leaves and on the footstalks rendered this almost impossible. Nevertheless, leaves were immersed in a solution of one part of urea to 437 of water, and after 24 hrs. the orange layer of protoplasm within the arms of these processes did not appear more aggregated than in other specimens kept in water. I then tried suspending a leaf in a bottle over an excessively putrid Pe SSN Straten eneon, Cuar. XIU] DIGESTION, 243 infusion of raw meat, to see whether they absorbed the vapour, but their contents were not affected. Digestive Power of the Secretion.*—When a leaf closes over any object, it may be said to form itself into a temporary stomach; and if the object yields ever so little animal matter, this serves, to use Schiff’s expression, as a peptogene, t and the glands on the surface pour forth their acid secretion, which acts like the gastric juice of animals. As so many ex- periments were tried on the digestive power of Drosera, only a few were made with Dionæa, but they were amply sufficient to prove that it digests. This plant, moreover, is not so * Dr. W. M. Canby, of Wilmington, to whom I am much indebted for information regarding Dionza in its native home, has published in the ‘Gardener’s Monthly,’ Philadelphia, August 1868, some interesting ob- servations. He ascertained that the secretion digests animal matter, such as the contents of insects, bits of meat, &c.; and that the secretion is reabsorbed. He was also well aware that the lobes remain closed for a much longer time when in contact with animal matter than when made to shut by a mere touch, or over objects not yielding soluble nutri- ment; and that in these latter cases the glands do not secrete. The Rey. Dr. Curtis first observed (¢ Boston Journal Nat. Hist.’ vol. i. p. 123) the secretion from the glands. I may here add that a gardener, Mr. Knight, is said (Kirby and Spence’s ‘Introduction to Entomology,’ 1818, vol. i. p. 295) to have found that a plant of the Dionza, on the leaves of which “ he laid fine filaments of raw beef, was much more luxuriant in its growth than others not so treated.” [The earlier history of the subject is given in Sir Joseph Hooker’s “ Ad- dress to the Department of Botany and Zoology,” ‘British Association Report,’ 1874, p. 102, whence the following facts are taken. About 1768 Ellis, a well-known English naturalist, sent to Linnzus a drawing and specimens of Dionea with the following remarks (“ A Bo- tanical Description of the Ponza muscipula.... in a letter to Sir Charles Linnzeus,” p. 37) :— “The plant, of which I now enclose you an exact figure. . . . shows that Nature may have some views towards its nourishment, in forming the upper joint of its leaf like a machine to catch food.” Linnzus was unable to believe that the plant could profit by the captured insects ; he only saw in the phenomena “an extreme case of sensitiveness in the leaves which causes them to fold up where irritated, just as the sensi- tive plant does; and he consequently regarded the capture of the disturb- ing insect as something merely accidental and of no importance to the piant. . . . Linnzus’s authority overbore criticism if any was offered ; and his statement about the behaviour of the leaves was copied from book to book. ... Dr. [Erasmus] Darwin (1791) was contented to suppose that Dionæa surrounded itself with insect- traps to prevent depredations upon its flowers. Dr. Curtis, whose con- tribution to the subject has been already mentioned, describes the captured insects as enveloped in a fluid of a mucilaginous consistence which seems to act as a solvent, the insects being more or less consumed by it.”—F. D.] t [See footnote, p. 106.—F. D.] E2 244 DIONZA MUSCIPULA. [Cuar. XIII. well fitted as Drosera for observation, as the process goes on within the closed lobes. Insects, even beetles, after being subjected to the secretion for several days, are surprisingly softened, though their chitinous coats are not corroded. Experiment 1.—A cube of albumen of 54, of an inch (2:540 mm.) was placed at one end of a leaf, and at the other end an oblong piece of gelatine, 4 of an inch (5°08 mm.) long, and ṣẹ broad; the leaf was then made to close. It was cut open after 45 hrs. The albumen was hard and compressed, with its angles only a little rounded; the gelatine was corroded into an oval form; and both were bathed in so much acid secretion that it drepped off the leaf. ‘The digestive process apparently is rather slower than in Drosera, and this agrees with the length of time during which the leaves remain closed over digestible objects. Experiment 2.—A bit of albumen + of an inch square, but only zy in thickness, and a piece of gelatine of the same size as before, were placed on a leaf, which eight days afterwards was cut open. The sur- face was bathed with slightly adhesive, very acid secretion, and the glands were all in an aggregated condition. Not a vestige of the albumen or gelatine was left. Similarly sized pieces were placed at the same time on wet moss on the same pot, so that they were sub- jected to nearly similar conditions ; after eight days these were brown, decayed, and matted with fibres of mould, but had not disappeared. Experiment 3.—A piece of albumen ;3, of an inch (3°81 mm.) long, and 55 broad and thick, and a piece of gelatine of the same size as before, were placed on another leaf, which was cut open after seven days; not a vestige of either substance was left, and only a moderate amount of secretion on the surface. Experiment 4.—Pieces of albumen and gelatine, of the same size as in the last experiment, were placed on a leaf, which spontaneously opened after twelve days, and here again not a vestige of either was left, and only a little secretion at one end of the midrib. Experiment 5.—Pieces of albumen and gelatine of the same size were placed on another leaf, which after twelve days was still firmly closed, but had begun to wither; it was cut open, and contained nothing except a vestige of brown matter where the albumen had lain. Experiment 6.—A cube of albumen of zo Of an inch and a piece of gelatine of the same size as before were placed on a leaf, which opened spontaneously after thirteen days. The albumen, which was twice as thick as in the latter experiments, was too large; for the glands in contact with it were injured and were dropping off; a film also of albumen of a brown colour, matted with mould, was left. All the gelatine was absorbed, and there was only a little acid secretion left on the midrib. Experiment 7.—A bit of half roasted meat (not measured) and a Lit of gelatine were placed on the two ends of a leaf, which opened eae — itamo, asii ARRIE Cuap. XIILJ DIGESTION. 245 spontaneously after eleven days; a vestige of the meat was left, and the surface of the leaf was here blackened ; the gelatine had all dis- appeared. Experiment 8.—A bit of half roasted meat (not measured) was placed on a leaf which was forcibly kept open by a clip, so that it was moistened with the secretion (very acid) only on its lower surface. Nevertheless, after -only 224 hrs. it was surprisingly softened, when Suet age with another bit of the same meat which had been kept amp. Experiment 9.—A cube of 54, of an inch of very compact roasted beef was placed on a leaf, whicn opened spontaneously after twelve days; so much feebly acid secretion was left on the leaf that it trickled off. The meat was completely disintegrated, but not all dissolved ; there wasno mould, The little mass was placed under the microscope ; some of the fibrillea in the middie still exhibited transverse striæ ; others showed not a vestige of striae; and every gradation could -be traced between these two states. Globules, apparently of fat, and some undigested fibro-elastic tissue remained. The meat was thus in the same state as that formerly described, which was half digested by Drosera. Here, again, as in the case of albumen, the digestive process seems slower than in Drosera. At the opposite end of the same leaf, a firmly compressed pellet of bread had been placed; this was completely disintegrated, I suppose, owing to the digestion of the gluten, but seemed very little reduced in bulk. Experiment 10.—A cube of 3 of an inch of checse and another of albumen were placed at opposite ends of the same leaf. After nine days the lobes opened spontaneously a little at the end enclosing the cheese, but hardly any or none was dissolved, though it was softened and surrounded by secretion. Two days subsequently the end with the albumen also opened spontaneously (i.e. eleven days after it was put on), a mere trace in the blackened and dry condition being left. Experiment 11.—The same experiment with cheese and albumen repeated on another and rather torpid leaf. ‘The lobes at the end with the cheese, after an interval of six days, opened spontaneously a little ; the cube of cheese was much softened, but not dissolved, and but little, if at all reduced in size. Twelve hours afterwards the end with the albumen opened, which now consisted of a large drop of transparent, not acid, viscid fluid. Experiment 12.—Same experiment as the two last, and here again the leaf at the end enclosing the cheese opened before the oppo- site end with the albumen; but no further observations were made, Experiment 13.—A globule of chemically prepared casein, about 75 of an inch in diameter, was placed on a leaf, which spontaneously opened after eight days. The casein now consisted of a soft sticky mass, very little, if at all, reduced in size, but bathed in acid secretion. These experiments are sufficient to show that the secretion from the glands of Dionæa dissolves albumen, gelatine, and 246 DION. ZA MUSCIPULA. (Cuap. XIII. meat, if too large pieces are not given. Globules of fat and fibro-elastic tissue are not digested. The secretion, with its dissolved matter, if not in excess, is subsequently absorbed. On the other hand, although chemically prepared casein and cheese (as in the case of Drosera) excite much acid secretion, owing, I presume, to the absorption of some included albuminous matter, these substances are not digested, and are not appreciably, if at all, reduced in bulk. Effects of the Vapours of Chloroform, Sulphuric Ether, and Hydro- cyanic Acid.—A plant bearing one leaf was introduced into a large bottle with a drachm (3°549 c.c.) of chloroform, the mouth being im- perfectly closed with cotton-wool. The vapour caused in 1 m. the lobes to begin moving at an imperceptibly slow rate; but in 3 m. the spikes crossed, and the leaf was soon completely shut. The dose, however, was much too large, for in between 2 and 3 hrs. the leaf appeared as if burnt, and soon died. Two leaves were exposed for 30 m. in a 2-oz. vessel to the vapour of 30 minims (1:774 c.c.) of sulphuric ether. One leaf closed alter a time, as did the other whilst being removed from the vessel without being touched. Both leaves were greatly injured. Another leaf, exposed for 20 m. to 15 minims of ether, closed its lobes to a certain extent, and the sensitive filaments were now quite insensible. After 24 hrs. this leaf recovered its sensibility, but was still rather torpid. A leaf exposed in a large bottle for only 3 m. to ten drops was rendered insensible. After 52 m. it recovered its sensibility, and when one of the filaments was touched, the lobes closed. It began to reopen after 20 hrs. Lastly another leaf was exposed for 4 m. to only four drops of the ether; it was rendered insensible, and did not close when its filaments were repeatedly touched, but closed when the end of the open leaf was cut off. This shows either that the internal parts had not been rendered insensible, or that an incision is a more powerful stimulus than repeated touches on the filaments. Whether the larger doses of chloroform and ether, which caused the leaves to close slowly, acted on the sensitive filaments or on the leaf itself, I do not know. Cyanide of potassium, when left in a bottle, generates prussic or hydrocyanic acid. A leaf was exposed for 1 hr. 35 m. to the vapour thus formed ; and the glands became within this time so colourless and shrunken as to be scarcely visible, and I at first thought that they had all dropped off. The leaf was not rendered insensible ; for as soon as one of the filaments was touched it closed. It had, however, suffered, for it did not reopen until nearly two days had passed, and was not even then in the least sensitive. After an additional day it recovered its powers, and closed on being touched and subsequently re-opened. Another leaf behaved in nearly the same manner after a shorter exposure to this vapour. Cuar. XIII] MANNER OF CAPTURING INSECTS. 247 On the Manner in which Insects are caught.—We will now consider the action of the leaves when insects happen to touch one of the sensitive filaments. This often occurred in my greenhouse, but I do not know whether insects are attracted in any special way by the leaves. They are caught in large numbers by the plant in its native country. As soon as a filament is touched, both close with astonishing quickness ; and as they stand at less than a right angle to each other, they have a good chance of catching any intruder. The angle between the blade and footstalk does not change when the lobes close. The chief seat of movement is near the midrib, but is not confined to this part; for, as the lobes come together, each curves inwards across its whole breadth ; the marginal spikes, however, not becoming curved.* This movement of the whole lobe was well seen in a leaf to which a Jarge fly had been given, and from which a large portion had been cut off the end of one lobe; so that the opposite lobe, meeting with no resistance in this part, went on curving inwards much beyond the medial line. The whole of the lobe, from which a portion had been cut, was afterwards removed, and the opposite lobe now curled completely over, passing through an angle of from 120° to 130°, so as to occupy a position almost at right angles to that which it would have held had the opposite lobe been present. From the curving inwards of the two lobes, as they move towards each other, the straight marginal spikes inter- cross by their tips at first, and ultimately by their bases. The leaf is then completely shut and encloses a shallow cavity. Ifit has been made to shut merely by one of the sensitive filaments having been touched, or if it includes an object not yielding soluble nitrogenous matter, the two lobes retain their inwardly concave form until they re-expand. The re-expansion under these circumstances—that is when no organic matter is enclosed—was observed in ten cases. In all of these, the leaves re-expanded to about two-thirds of the full extent in 24 hrs. from the time of closure. Even the leaf from which a portion of one lobe had been cut off opened to a slight degree within this same time. In one * (Munk (Reichert and Du Bois’- at the edge of the leaf, by which the _Reymond’s ‘ Archiv.’ 1876, p. 108) teeth are carried inwards.—F. D.J states that a special movement occurs 248 DIONÆA MUSCIPULA. (Omir. XMI case a leaf re-expanded to about two-thirds of the full extent in 7 hrs., and completely in 32 lrs.; but one of its filaments had been touched merely with a hair just enough to cause the leaf to close. Of these ten leaves only a few re-expanded completely in less than two days, and two or three required even a little longer time. Before, however, they fully re-expand, they are ready to close instantly if their sensitive filaments are touched. How many times a leaf is capable of shutting and opening if no animal matter is left enclosed, Ido not know; but one leaf was made to close four times, reopening afterwards, within six days. On the last occasion it caught a fly, and then remained closed for many days. This power of reopening quickly after the filaments have been accidentally touched by blades of grass, or by objects blown on the leaf by the wind, as occasionally happens in its native place,* must be of some importance to the plant; for as long as a leaf remains closed, it cannot of course capture an insect. When the filaments are irritated and a leaf is made to shut over an insect, a bit of meat, albumen, gelatine, casein, and, no doubt, any other substance containing soluble nitrogenous matter, the lobes, instead of remaining concave, thus including a concavity, slowly press closely together throughout their whole breadth. As this takes place, the margins gradually become a little everted, so that the spikes, which at first intercrossed, at last project in two parallel rows. The lobes press against each other with such force that I have seen a cube of albumen much flattened, with distinct impressions of the little prominent glands; but this latter circumstance may have been partly caused by the corroding action of the secretion. So firmly do they become pressed together that, if any large insect or other object has been caught, a corresponding projection on the outside of the leaf is distinctly visible. When the two lobes are thus completely shnt, they resist being opened, as by a thin wedge being driven between them, with astonishing force, and are generally ruptured rather than yield. If not ruptured, they close again, as Dr. Canby informs me in a letter, “ with quite a loud flap.” But if the end ofa leaf is held firmly between the thumb and finger, or by a clip, so * According to Dr. Curtis, in ‘ Boston Journal of Nat. Hist.’ vol. i. 1837, p: 123. a scent Cuar. XIII] MANNER OF CAPTURING INSECTS. 249 that the lobes cannot begin to close, they exert, whilst in this position, very little force. I thought at first that the gradual pressing together of the lobes was caused exclusively by captured insects crawling over and repeatedly irritating the sensitive filaments; and this view seemed the more probable when I learnt from Dr. Burdon Sanderson that whenever the filaments of a closed leaf are irritated, the normal electric current is disturbed. Nevertheless, such irritation is by no means necessary, for a dead insect, or a bit of meat, or of albumen, all act equally well; proving that in these cases it is the absorption of animal matter which excites the lobes slowly to press close together. We have seen that the absorption of an extremely small quantity of such matter also causes a fully expanded leaf to close slowly ; and this movement is clearly analogous to the slow pressing together of the concave lobes. This latter action is of high functional importance to the plant, for the glands on both sides are thus brought into contact with a captured insect, and consequently secrete. ‘The secretion with animal matter in solution is then drawn by capillary attraction over the whole surface of the leaf, causing all the glands to secrete and allowing them to absorb the diffused animal matter. The movement, excited by the absorption of such matter, though slow, suffices for its final purpose, whilst the movement excited by one of the sensitive tilaments being touched is rapid, and this is indispensable for the capturing of insects. These two movements, excited by two such widely different means, are thus both well adapted, like all the other functions of the plant, for the purposes which they subserve. There is another wide difference in the action of leaves which enclose objects, such as bits of wood, cork, balls of paper, or which have had their filaments merely touched, and those which enclose organic bodies yielding soluble nitrogenous matter. In the former case the leaves, as we have seen, open in under 24 hrs. and are then ready, even before being fully expanded, to shut again. But if they have closed over nitrogen-yielding bodies, they remain closely shut for many days; and after re-expanding are torpid, and never act again, or only after a considerable interval of time. In four instances, leaves after catching insects never re-opened, but began to wither, remaining closed—in one case for fifteen days over a fly; in a second, 250 DIONÆA MUSCIPULA. (Car. XIII. for twenty-four days, though the fly was small; in a third for twenty-four days over a woodiouse; and in a fourth, for thirty-five days over a large Tipula. In two other cases leaves remained closed for at least nine days over flies, and for how many more I do not know. It should, however, be added that in two instances in which very small insects had been naturally caught the leaf opened as quickly as if nothing had been caught ; and I suppose that this was due to such small insects not having been crushed or not having excreted any animal matter, so that the glands were not excited. Small angular bits of albumen and gelatine were placed at both ends of three leaves, two of which remained closed for thirteen and the other for twelve days. Two other leaves remained closed over bits of meat for eleven days, a third leaf for eight days, and a fourth (but this had been cracked and injured) for only six days. Bits of cheese, or casein, were placed at one end and albumen at the other end of three leaves; and the ends with the former opened after six, eight, and nine days, whilst the opposite ends opened a little later. None of the above bits of meat, albumen, &c., exceeded a cube of -y of an inch (2°54 mm.) in size, and were sometimes smaller ; yet these small portions sufficed to keep the leaves closed for many days. Dr. Canby informs me that leaves remain shut for a longer time over insects than over meat; and from what I have seen, I can well believe that this is the case, especially if the insects are large. In all the above cases, and in many others in which leaves remained closed for a long but unknown period over insects naturally caught, they were more or less torpid when they re-opened, Generally they were so torpid during many succeeding days that no excitement of the filaments caused the least movement. In one instance, however, on the day after a leaf opened which had clasped a fly, it closed with extreme slowness when one of its filaments was touched ; and although no object was left enclosed, it was so torpid that it did not re-open for the second time until 44 hrs. had elapsed. In a second case, a leaf which had expanded after remaining closed for at least nine days over a fly, when greatly irritated, moved one alone of its two lobes, and retained this unusual position for the next two days. A third case offers the strongest exception which I have observed; a leaf, after 1emaining clasped for an unknown time over a fly, opened, Cuar. XIII.] MANNER OF CAPTURING INSECTS. 205 and when one of its filaments was touched, closed, though rather slowly. Dr. Canby, who observed in the United States a large number of plants which, although not in their native site, were probably more vigorous than my plants, informs me that he has “several times known vigorous leaves to devour their prey several times; but ordinarily twice, or quite often, once was enough to render them unserviceable.” Mrs. Treat, who cultivated many plants in New Jersey, also informs me that “ several leaves caught successively three insects each, but most of them were not able to digest the third fly, but died in the attempt. Five leaves, however, digested each three flies, and closed over the fourth, but died soon after the fourth capture. Many leaves did not digest even one large insect,” 1t thus appears that the power of digestion is somewhat limited, and it is certain that leaves always remain clasped for many days over an insect, and do not recover their power of closing again for many subsequent days. In this respect Dionæa differs from Drosera, which catches and digests many insects after shorter intervals of time. We are now prepared to understand the use of the mar- ginal spikes, which form so conspicuous a feature in the appearance of the plant (fig. 12, p. 232), and which at first seemed to me in my ignorance useless appendages. From the inward curvature of the lobes as they approach each other, the tips of the marginal spikes first intercross, and ultimately their bases. Until the edges of the lobes come into contact, elongated spaces between the spikes, varying from the ;!; to the ;, of an inch (1:693 to 2:540 mm.) in breadth, according to the size of the leaf, are left open. Thus an insect, if its body is not thicker than these measure- ments, can easily escape between the crossed spikes, when disturbed by the closing lobes and increasing darkness; and one of my sons actually saw a small insect thus escaping. A moderately large insect, on the other hand, if it tries to escape between the bars will surely be pushed back again into its horrid prison with closing walls, for the spikes continue to cross more and more until the edges of the lobes ` come into contact. A very strong insect, however, would be able to free itself, and Mrs. Treat saw this effected by a rose-chafer (Macrodactylus subspinosus) in the United States. Now it would manifestly be a great disadvantage to the plant to waste many days in remaining clasped over a 252 DIONZA MUSCIPULA. [Ome XIII. minute insect, and several additional days or weeks in afterwards recovering its sensibility; inasmuch as a minute insect would afford but little nutriment. It would be far better for the plant to wait for a time until a moderately large insect was captured, and to allow all the little ones to escape ; and this advantage is secured by the slowly inter- crossing marginal spikes, which act like the large meshes of a fishing-net, allowing the small and useless fry to escape. As I was anxious to know whether this view was correct— and as it seems a good illustration of how cautious we ought to be in assuming, as I had done with respect to the marginal spikes, that any fully developed structure is useless—I applied to Dr. Canby. He visited the native site of the plant, early in the season, before the leaves had grown to their full size, and sent me fourteen leaves, containing naturally captured insects. Four of these had caught rather small insects, viz. three of them ants, and the fourth a rather small fly, but the other ten had all caught large insects, namely, five elaters, two chrysomelas, a curculio, a thick and broad spider, and a scolopendra. Out of these ten insects, no less than eight were bevtles,* and out of the whole four- teen there was only one, viz. a dipterous insect, which could readily take flight. Drosera, on the other hand, lives chiefly on insects which are good flyers, especially Diptera, caught by the aid of its viscid secretion. But what most concerns us is the size of the ten larger insects. Their average length from head to tail was +256 of an inch, the lobes of the leaves being on an average *53 of an inch in length, so that the insects were very nearly half as long as the leaves within which they were enclosed. Only a few of these leaves, therefore, had wasted their powers by capturing small prey, though it is probable that many small insects had crawled over them and been caught, but had then escaped through the bars. The Transmission of the Motor Impulse, and means of Move- * Dr. Canby remarks (‘Gardener’s elaters, for the five which I examined Monthly,’ Aug. 1868), “as a general were in an extremely fragile and thing beetles and insectsof that kind, empty condition, as if all their in- though always killed, seem to be ternal parts had been partially di- too hard-shelled to serve as food, gested. Mrs. Treat informs me that and after a short time are rejected.” the plants which she cultivated in I am surprised at this statement, at New Jersey chiefly caught Diptera. least with respect to such beetles as Cuar. XIIL] TRANSMISSION OF MOTOR IMPULSE. 253 ment.—It is sufficient to touch any one of the six filaments to cause both lobes to close, these becoming at the same time incurved throughout their whole breadth. The stimulus must therefore radiate in all directions from any one filament. It must also be transmitted with much rapidity across the leaf, for in all ordinary cases both lobes close simultaneously, as far us the eye can judge. Most physiologists believe that in irritable plants the excitement is transmitted along, or in close connection with, the fibro-vascular bundles. In Dionzxa, the course of these vessels (composed of spiral and ordinary vascular tissue) seems at first sight to favour this belief; for they run up the midrib in a great bundle, sending off small bundles almost at right angles on eachside. These bifurcate occasionally as they extend towards the margin, and close to the margin small branches from adjoining vessels unite and enter the marginal spikes. At some of these points of union the vessels form curious loops, like those described under Drosera. A continuous zigzag line of vessels thus runs round the whole circumference of the leaf, and in the midrib all the vessels are in close contact; so that all parts of the leaf seem to be brought into some degree of communication. Nevertheless, the presence of vessels is not necessary for the transmission of the motor impulse, for it is transmitted from the tips of the sensitive filaments (these being about the 5\, of an inch in length), into which no vessels enter; and these could not have been overlooked, as I made thin vertical sections of the leaf at the bases of the filaments. On several occasions, slits about the 4‘; ofan inch in length were made with a lancet, close to the bases of the filaments, parallel to the midrib, and, therefore, directly across the course of the vessels. These were made sometimes on the inner and sometimes on the outer side of the filaments; and after several days, when the leaves had reopened, these filaments were touched roughly (for they were always ren- dered in some degree torpid by the operation), and the lobes then closed in the ordinary,manner, though slowly, and some- times not until after a considerable interval of time. These cases show that the motor impulse is not transmitted along the vessels, and they further show that there is no necessity for a direct line of communication from the filament which is touched towards the midrib and opposite lobe, or towards the outer parts of the same lobe. Two slits near each other, both parallel to the midrib, 254 DIONÆA MUSCIPULA. (Cuap. XIII. were next made in the same manner as before, one on each side of the base of a filament, on five distinct leaves, so that a little slip bearing a filament was connected with the rest of the leaf only at its two ends. These slips were nearly of the same size; one was carefully measured ; it was *12 of an inch (3:048 mm.) in length, and +08 of an inch (2-032 mm.) in breadth ; and in the middle stood the filament. Only one of these slips withered and perished. After the leaf had recovered from the operation, though the slits were still open, the filaments thus circumstanced were roughly touched, and both lobes, or one alone, slowly closed. In two instances touching the filament produced no effect; but when the point of a needle was driven into the slip at the base of the filament, the lobes slowly closed. Now in these cases the impuise must have proceeded along the slip in a line parallel to the midrib, and then have radiated forth, either from both ends or from one end alone of the slip, over the whole surface of the two lobes. Again, two parallel slits, like the former ones, were made, one on each side of the base of a filament, at right angles to the midrib. After the leaves (two in number) had recovered, the filaments were roughly touched, and the lobes slowly closed; and here the impulse must have travelled for a short distance in a line at right angles to the midrib, and then have radiated forth on all sides over both lobes. These several cases prove that the motor impulse travels, in all directions through the cellular tissue, independently of the course of the vessels. With Drosera we have seen that the motor impulse is transmitted in like manner in all directions through the cellular tissue; but that its rate is largly governed by the length of the cells and the direction of their longer axes. Thin sections of a leaf of Dionæa were made by my son, and the cells, both these of the central and of the more superficial layers, were found much elongated, with their longer axes directed towards the midrib; and it is in this direction that the motor impulse must be sent with great rapidity from one lobe to the other, as both close simultaneously. ‘I'he central parenchymatous cells are larger, more loosely attached together, and have more delicate walls than the more super- ficial cells. A thick mass of cellular tissue forms the upper surface of the midrib over the great central bundle of vessels. i cuneate Cuar. XIII] TRANSMISSION OF MOTOR IMPULSE. 255 When the filaments were roughly touched, at the bases of which slits had been made, either on both sides or on one side, parallel to the midrib or at right angles to it, the two lobes, or only one, moved. In one of these cases, the lobe on the side which bore the filament that was touched moved, but in three other cases the opposite lobe alone moved: so that an injury which was sufficient to prevent a lobe moving did not prevent the transmission from it of a stimulus which excited the opposite lobe to move. We thus also learn that, although normally both lobes move together, each has the power of independent movement. A case, indeed, has already been given of a torpid leaf that had lately re-opened after catching an insect, of which one lobe alone moved when irritated. Moreover, one end of the same lobe can close and re-expand, independently of the other end, as was seen in some of the foregoing experiments. When the lobes, which are rather thick, close, no trace of wrinkling can be seen on any part of their upper surfaces. It appears therefore that the cells must contract. The chief seat of the movement is evidentiy in the thick mass of cells which overlies the central bundle of vessels in the midrib. To ascertain whether this part contracts, a leaf was fastened on the stage of the microscope in such a manner that the two lobes could not become quite shut, and having made two minute black dots on the midrib, in a transverse line and a little towards one side, they were found by the micrometer to be -44y of an inch apart. One of the filaments was then touched and the lobes closed; but as they were prevented from meeting, I could still see the two dots, which now were +i3, of an inch apart, so that a small portion of the upper surface of the midrib had contracted in a transverse line +7755 of an inch (*0508 mm.). We know that the lobes, whilst closing, become slightly incurved throughout their whole breadth. This movement. appears to be due to the contraction of the superficial layers of cells over the whole upper surface. In order to observe their contraction, a narrow strip was cut out of one lobe at right angles to the midrib, so that the surface of the opposite lobe could be seen in this part when the leaf was shut. After the leaf had recovered from the operation and had re- expanded, three minute black dots were made on the surface opposite to the slit or window, in a line at right angles tu the midrib. The distance between the dots was found to be 256 DIONÆA MUSCIPULA. (Cuar, XII. 142v of an inch, so that the two extreme dots were 75} of an inch apart. One of the filaments was now touched and the leaf closed. On again measuring the distances between the dots, the two next to the midrib were nearer together by 14y% of an inch, and the two further dots by ?j3% of an 5 now stood about y¢%;5 of an inch (*127 mm.) nearer together than before. If we suppose the whole upper surface of the lobe, which was 429% of an inch in breadth, to have con- tracted in the same proportion, the total contraction will have amounted to about +235 or 4p of an inch (°635 mm.): but whether this is sufficient to account for the slight inward curvature of the whole lobe, I am unable to say.* Finally, with respect to the movement of the leaves the wonderful discovery made by Dr. Burdon Sanderson} is now universally known ; namely that there exists a normal elec- trical current in the blade and footstalk; and that when the leaves are irritated, the current is disturbed in the same manner as takes place during the contraction of the muscle of an animal.t * [Batalin has discussed the me- chanism of closure in Dionza in his interesting essay in ‘Flora,’ 1877. He agrees in general with the state- ments above given, but as in the case of Drosera, so here he believes that the movements are associated with a small amount of actual growth. Marks are made on the lower or external surface of the leaf, and the distance between them is found to increase when the leaf closes. When the leaf opens the distance does not perfectly return to its former dimen- sions, and thus shows a certain amount of permanent growth has taken place. It will be seen that Batalin’s observations do not support the idea (see p. 258) that the re-open- ing of the leaf is due to the return of the outer cells to their natural size when the tension put on them by the contraction of the inner surface is re- moved. Munk (loc. cit.) and Pfeffer (‘Osmotische Untersuchungen,’ 1877, p- 196) have with justice called at- tention to the unsatisfactory nature of the discussion in the text on the mechanism of the movement. Batalin shows further that the ultimate closure of the leaf by which the two valves are closely pressed together is effected by the shortening or con- traction of the outer surface of the leaf. He records a curious fact which has not elsewhere been noted, namely, that the midrib becomes more curved after the closure of the leaf. Munk (Reichert and Du Bois-Reymond, ‘Archiv.’ 1876, p. 121), on the other hand, is inclined to believe that the curvature of the midrib diminishes when the leaf closes.—F, D.] t ‘Proc. Royal Soc.’ vol. xxi. p. 495; and lecture at the Royal In- stitution, June 5, 1874, given in ‘Nature,’ 1874, pp. 105 and 127. t [Professor Sanderson’s work has been criticised by Professor Munk in Reichert and Du _ Bois-Reymond’s ‘Archiv.’ 1876, and by Professor Kunkel in Sachs’ ‘Arbeiten a. d. bot. Institut in Wiizburg,’ Bd. ii. p. 1. Professor Sanderson. has continued RETEST ena antag AR ~ Cuar. XIIL] RE-EXPANSION. ZFT The Re-expansion of the Leaves.-—This is effected at an in- sensibly slow rate, whether or not any object is enclosed.* to work at the subject, and has given his results in an elaborate paper in ‘Phil. Transactions,’ 1882. It will be sufficient to note his conclusions with regard to the two points men- tioned in the text.. First, for the electrical condition of the leaf at rest. Sanderson rejects Munk’s method of cxplaining the state of the leaf by a mechanical schema—an arrangement of copper and zine cylinders. He does so, not only because he accepts “as fundamental the doctrine that what- ever physiological properties the leaf possesses, it possesses by virtue of its being a system of living cells;” but also because the facts of the case are not in accordance with Professor Munk’s theoretical deductions. He in- clines to admit that the electrical differences observed between different parts of the unexcited leaf may be partly explained by the migration of water. “ For on the one hand we know that in consequence of the surface evaporation, migration of water cer- tainly exists, while on the other we have proof in the experiments of Dr. Kunkel that such migration cannot occur without producing electrical differences.” In a similar way he is in- clined to believe that the gradual elec- trical change resulting from repeated excitation, as well as the after effect-of a single excitation, are to be explained by migration of water accompanying the motion of the leaf. On the other hand he believes that the primary, and rapidly propagated electrical disturbance which is the immediate effect of excitation cannot be due to water-migration, but that it is the expression of molecular changes in the protoplasm of the leaf. Prof. Sanderson takes occasion to correct the impression produced by certain expressions in his lecture at the Royal Institution in 1874. Prof. Munk, among others, seems to have believed that Professor Sanderson claimed absolute identity between muscular action and the movement of the leaf of Dionza. It need hardly be stated that no such implication was intended by Prof. Sanderson; the view which he held in 1874 he still adheres to, namely, that the rapidly propagated molecular change in an excited Dionga © leaf can only be identified with the corresponding process in the excitable tissues of animals. Certain unpublished researches made during the last two years have led Professor Sanderson to extend his views in the direction above indicated, and to conclude that the “ leaf- current,” i.e. the electrical difference between the upper and lower surfaces of the leaf, is intimately} connected with the physiological conditions of that part of the upper surface from which spring the sensitive filaments : thus it will probably be established that the “leaf-current ” and the ex- citatory disturbance are different manifestations of the same property. From measurements made with his Rheotome, of six carefully chosen leaves, taken from vigorous plants (Aug. 1887), Professor Sanderson found that the electrical disturbance produced in one lobe by stimulation of the other by an induction current, begins in the course of the second tenth of a second following the ex- citation. In five out of the six leaves no effect was perceptible during the first tenth. If we assume that the distance travelled by the disturbance is one centimeter, this gives 100 millimeters per second as the rate of propagation. This, as Professor San- derson has pointed out, happens to be just about the rate of propagation of the excitatory electrical disturbance in the muscular tissue of the heart of the frog.—F. D.] * Nuttall, in his ‘Gen. American S 258 DION A MUSCIPULA. One lobe can re-expand by itself, as occurred with the torpid leaf of which one lobe alone had closed. We havealso seen in the experiments with cheese and albumen that the two ends of the same lobe can re-expand to a certain extent independently of each other. But in all ordinary cases both lobes open at the same time. The re-expansion is not determined by the sensitive filaments; all three filaments on one lobe were cut off close to their bases; and the three leaves thus treated re-expanded,—one to a partial extent in 24 hrs.,—a second to the same extent in 48 hrs.,—and the third, which had been previously injured, not until the sixth day. These leaves after their re-expansion closed quickly when the filaments on the other lube were irritated. These were then cut off one of the leaves, so that none were left. This mutilated leaf, notwithstanding the loss of all its filaments, re-expanded in two days in the usual manner. When the filaments have been excited by immersion in a solution of sugar, the lobes do not expand so soon as when the filaments have been merely touched ; and this, I presume, is due to their having been strongly affected through exosmose, so that they con- tinue for some time to transmit a motor impulse to the upper surface of the leaf. The following facts make me believe that the several layers of cells forming the lower surface of the leaf are always in a state of tension; and that it is owing to this mechanical state, aided probably by fresh fiuid being attracted into the cells, that the lobes begin to separate or expand as soon as the contraction of the upper surface diminishes. A leaf was cut off and suddenly plunged perpendicularly into boiling water: I expected that the lobes would have closed, but instead of doing so, they diverged a little. I then took another fine leaf, with the lobes standing at an angle of nearly 80° to each other; and on immersing it as before, the angle suddenly increased to 90°. A third leaf was torpid from having recently re- Plants,’ p. 277 (note), says that, cilia, accompanied by a partial open- [Cuar. XIII. whilst collecting this plant in its native home, “1 had occasion to ob- serve that a detached leaf would make repeated efforts towards dis- closing itself to the influence of the sun ; these attempts consisted in an undulatory motion ef the marginal ing and succeeding collapse of the lamina, which at length terminated in a complete expansion and in the destruction of sensibility.” I am indebted to Prof. Oliver for this reference; but I do not understand what took place. fo ESE: a Se Car. XIIL] RE-EXPANSION. 259 expanded after having caught a fly, so that repeated touches of the filaments caused not the least movement ; nevertheless when similarly immersed, the lobes separated a little. As these leaves were inserted perpendicularly into the boiling water, both surfaces and the filaments must have been equally affected; and I can understand the divergence of the lobes only by supposing that the cells on the lower side, owing to their state of tension, acted mechanically and thus suddenly drew the lobes a little apart, as soon as the cells on the upper surface were killed and lost their contractile power. We have seen that boiling water in like manner causes the tentacles of Drosera to curve backwards; and this is an analogous movement to the divergence of the lobes of Dionzea. Tn some concluding remarks in the fifteenth chapter on the Droseraceæ, the different kinds of irritability possessed by the several genera, and the different manner in which they capture insects, will be compared. 260 ALDROVANDA VESICULOSA. (CHar. XIV. CHAPTER XIV. ALDROVANDA VESICULOSA. Captures erustaceans—Structure of the leaves in comparison with those of Dionza—Absorption by the glands, by the quadrifid processes, and points on the infolded margins—Aldrovanda vesiculosa, var. australis—Captures prey—Absorption of animal matter—A/drovanda vesiculosa, var. verticillata —Concluding remarks. Tuts plant may be called a miniature aquatic Dionæa. Stein discovered in 1873 that the bilobed leaves, which are generally found closed in Europe, open under a sufficiently high temperature, and, when touched, suddenly close.* They re-expand in from 24 to 36 hrs., but only, as it appears, when inorganic objects are enclosed. The leaves sometimes contain bubbles of air, and were formerly supposed to be bladders; hence the specific name of vesiculosa. Stein observed that water-insects were sometimes caught, and Prof. Cohn has recently found within the leaves of naturally growing plants many kinds of crustaceans and larvæ.f Plants which have been kept in filtered water were placed by him in a vessel containing numerous crustaceans of the genus Cypris, and next morning many were found imprisoned and alive, still swimming about within the closed leaves, but doomed to certain death. * Since his original publication, alec nan Stein has found out that the irrita- bility of the leaves was observed by De Sassus, as recorded in * Bull. Bot. Soc. de France,’ in 1861. Delpino states in a paper published in 1871 (‘Nuovo Giornale Bot. Ital.’ vol. iii. p- 174) that “una quantita di chioc- cioline e di altri animalcoli acquatici ” are caught and suffocated by the leaves. I presume that chioccioline are fresh-water molluscs. It would be interesting to know whether their shells are at all corroded by the acid of the digestive secretion. | [The late Professor Caspary pub- lished in the ‘Bot. Zeitung,’ 1859, p. 117, an elaborate paper on Aldro- vanda, dealing chiefly with its morpho- logy, anatomy, systematic position and geographical distribution. The early literature of the species is also fully given.—F. D. t+ I am greatly indebted to this distinguished naturalist for having sent me a copy of his memoir on Aldrovanda, before its publication in his ‘ Beiträge zur Biologie der Pflan- zen,’ drittes Heft, 1875, p. 71. ee Cuar. XIV.] ALDROVANDA VESICULOSA. 261 Directly after reading Prof. Cohn’s memoir, I received through the kindness of Dr. Hooker living plants from Germany. As I can add nothing to Prof. Cohn’s excellent description, I will give only two illustrations, one of a whorl of leaves copied from his work, and the other of a leaf pressed flat open, drawn by my son Francis. I will, how- ever, append a few remarks on the differences between this plant and Dionza. Aldrovanda is destitute of roots and floats freely in the water. The leaves are arranged in whorls round the stem. Their broad petioles terminate in from four to six rigid projections,* each tipped with a stiff, short bristle. ‘lhe bilobed leaf, with the midrib likewise tipped with a bristle, stands in the midst of these projections, and is evidently defended by them. The lobes are formed of very delicate tissue, so as to be translucent ; they open, according to Cohn, about as much as the two valves of a living mussel-shell, therefore even less than the lobes of Dionæə ; and this must make the capture of aquatic animals more easy. The outside of the leaves and the petioles are covered with minute two-armed papillæ, evidently answering to the eight-rayed papille of Dionza. Each lobe rather exceeds a semi-circle in convexity, and consists of two very different concentric portions ; the inner and lesser portion, or that next to the midrib, is slightly concave, and is formed, according to Cohn, of three layers of cells. Its upper surface is studded with colourless glands like, but more simple than, those of Dionxa; they are supported on distinct footstalks, consisting of two rows of cells. The outer and broader portion of the lobe is flat and very thin, being formed of only two layers of cells.{ Its upper surface does not bear any glands, but, in their place, smail quadrifid processes, each consisting of four tapering projections, which rise from a common prominence. These * There has been much discussion 1850) and Caspary (‘Bot. Zei- by botanists on the homological nature of these projections. Dr. Nitschke (‘ Bot. Zeitung,’ 1861, p. 146) believes that they correspond with the ftim- briated scale-like bodies found at the bases of the petioles ot Drosera, t [According to Cohn (¢Fiora,’ tung,’ 1859), the two layers of cells are so combined as to produce the effect of a single layer. The three layers of which the central part is made up consist of external and internal epidermic layers, and a single layer of parenchyma.—F. D.] 262 ALDROVANDA VESICULOSA. (Cuapr. XIV. processes are formed of very delicate membrane lined with a layer of protoplasm ; and they sometimes contain aggregated globules of hyaline matter. Two of the slightly diverging arms are directed towards the circumference, and two towards the midrib, forming together a sort of Greek cross. Occasionally two of the arms are replaced by one, and then Fic. 13. (Aldrovanda vesicutosa.y' Upper figure, whorl of leaves (from Prof, Cohn.) Lower figure, leaf pressed flat open and greatly enlarged. the projection is trifid. We shall see in a future chapter that these projections curiously resemble those found within the bladders of Utricularia, more especially of Utricularia montana, although this genus is not related to Aldrovanda. A narrow rim of the broad flat exterior part of each lobe is Cuar, XIV] ALDROVANDA VESICULOSA. 263 turned inwards, so that, when the lobes are closed, the exterior surfaces of the infolded portions come into contact. The edge itself bears a row of conical, flattened, transparent points with broad bases, like the prickles on the stem ofa bramble or Rubus. As the rim is infolded, these points are directed towards the midrib, and they appear at first as if they were adapted to prevent the escape of prey; but this can hardly be their chief function, for they are composed of very delicate and highly flexible membrane, which can be easily bent or quite doubled back without being cracked. Nevertheless, the infolded rims, together with the points, must somewhat interfere with the retrograde movement of any small creature, as soon as the lobes begin to close. The circumferential part of the leaf of Aldrovanda thus differs greatly from that of Dionza; nor can the points on the rim be considered as homologous with the spikes round the leaves of Dionæa, as these latter are prolongations of the blade, and not mere epidermic productions. They appear also to serve for a widely different purpose. On the concave gland-bearing portion of the lobes, and especially on the midrib, there are numerous long, finely pointed hairs, which, as Prof. Cohn remarks, there can be little doubt are sensitive to a touch,* and, when touched, cause the leaf toclose. They are formed of two rows of cells, or, according to Cohn, sometimes of four, and do not include any vascular tissue. They differ also from the six sensitive filaments of Dionwa in being colourless, and in having a medial as well as a basal articulation. No doubt it is owing to these two articulations that, notwithstanding their length, they escape being broken when the lobes close. The plants which I received during the early part of October from Kew never opened their leaves, though sub- jected toa high temperature. After examining the structure of some of them, I experimented on only two, as I hoped that the plants would grow; and I now regret that I did not sacrifice a greater number. A leaf was cut open along the midrib, and the glands examined under a high power. It was then placed in a few drops of an infusion of raw meat. After 3 hrs. 20 m. there * [In a paper in the ‘Nuovo Gior- case, namely that the irritability nale Botanico Italiano,’ vol. viii. 1876, resides exclusively in the central p. 62, Mori states that this is the glandular region of the leafi—F, D.] 264 ALDROVANDA VESICULOSA. [Cuar. XIV. was no change, but when next examined after 23 hrs. 20 mM the outer cells of the glands contained, instead of limpid fluid, spherical masses of a granular substance, showing that matter had been absorbed from the infusion. That these glands secrete a fluid which dissolves or digests animal matter out of the bodies of the creatures which the leaves capture, is also highly probable from the analogy of Dionzea. If we may trust to the same analogy, the concave and inner portions of the two lobes probably close together by a slow movement, as soon as the glands have absorbed a slight amount of already soluble animal matter. The included water would thus be pressed out, and the secretion conse- quently not be too much diluted to act. With respect to the quadrifid processes on the outer parts of the lobes, I was not able to decide whether they had been acted on by the infusion ; for the lining of protoplasm was somewhat shrunk before they were immersed. Many of the points on the infolded rims also had their lining of protoplasm similarly shrunk, and contained spherical granules of hyaline matter. A solution of urea was next employed. This substance was chosen partly because it is absorbed by the quadrifid processes and more especially by the glands of Utricularia— a plant which, as we shall hereafter see, feeds. on decayed animal matter. As urea is one of the last products of the chemical changes going on in the living body, it seems fitted to represent the early stages of the decay of the dead body. IL was also led to try urea irom a curious little fact mentioned by Prof. Cohn, namely that when rather large crustaceans are caught between the closing lobes, they are pressed so hard whilst making their escape that they often void their sausage-shaped masses of excrement, which were found within most of the leaves. These masses, no doubt, contain urea. They would be left either on the broad outer surfaces of the lobes where the quadrifids are situated, or within the closed concavity. In the latter case, water charged with excrementitious and decaying matter would be slowly forced outwards, and would bathe the quadrifids, if I am right in believing that the concave lobes contract after a time like those of Dionza. Foul water would also be apt to ooze out at all times, especially when bubbles of air were generated within the concavity. A leaf was cut open and examined, and the outer cells of the glands were found to contain only limpid fluid. Some : Cuar. XIV.] ALDROVANDA VESICULOSA. 265 of the quadrifids included a few spherical granules, but several were transparent and empty, and their positions were marked. This leaf was now immersed in a little solution of one part of urea to 146 of water, or three grains to the ounce. After 3 hrs. 40 m. there was no change either in the glands or quadrifids; nor was there any certain change in the glands after 24 hrs.; so that, as far as one trial goes, urea does not act on them in the same manner as an infusion of raw meat. It was different with the quadrifids ; for the lining of protoplasm, instead of presenting a uniform texture, was now slightly shrunk, and exhibited in many places minute, thickened, irregular, yellowish specks and ridges, exactly like those which appear within the quadrifids of Utricularia when treated with this same solution. More- over, several of the quadrifids, which were before empty, now contained moderately sized or very small, more or less aggregated, globules of yellowish matter, as likewise occurs under the same circumstances with Utricularia. Some of the points on the infolded margins of the lobes were similarly affected; for their lining of protoplasm was a little shrunk and included yellowish specks; and those which were before empty now contained small spheres and irregular masses of hyaline matter, more or less aggregated ; so that both the points on the margins and the quadrifids had absorbed matter from the solution in the course of 24 hrs.; but to this subject I shall recur. In another rather old leaf, to which nothing had been given, but which had been kept in foul water, some of the quadrifids contained aggregated translucent globules. These were not acted on by a solution of one part of carbonate of ammonia to 218 of water: and this negative result agrees with what I have observed under similar circumstances with Utricularia. Aldrovanda vesiculosa, var. australis—Dried leaves of this plant from Queensland in Australia were sent me by Prof. Oliver from the herbarium at Kew. Whether it ought to be considered as a distinct species or a variety, cannot be told until the flowers are examined by a botanist. The pro- jections at the upper end of the petiole ape four to six in number) are considerably longer relatively to the blade, and much more attenuated than those of the European form. They are thickly covered for a considerable space near their extremities with the upcurved prickles, which are quite absent in the latter form; and they generally bear on their 266 ALDROVANDA VESICULOSA. (Cuar. XIV. tips two or three straight prickles instead of one. The bilobed leaf appears also to be rather larger and somewhat broader, with the pedicel by which it is attached to the upper end of the petiole a little longer. The points on the infolded margins likewise differ; they have narrower bases, and are more pointed; long and short points also alternate with much more regularity than in the European form. The glands and sensitive hairs are similar in the two forms. No quadrifid processes could be seen on several of the leaves, but I do not doubt that they were present, though indistinguishable from their delicacy and from having shrivelled; for they were quite distinct on one leaf under circumstances presently to be mentioned. Some of the closed leaves contained no prey, but in one there was rather a large beetle, which from its flattened tibiz I suppose was an aquatic species, but was not allied to Colymbetes. All the softer tissues of this beetle were com- pletely dissolved, and its chitinous integuments were as clean as if they had been boiled in caustic potash ; so that it must have been enclosed for a considerable time. The glands were browner and more opaque than those on other leaves which had caught nothing; and the quadrifid processes, from being partly filled with brown granular matter, could be plainly distinguished, which was not the case, as already stated, on the other leaves. Some of the points on the infolded margins likewise contained brownish granular matter. We thus gain additional evidence that the glands, the quadrifid processes, and the marginal points, all have the power of absorbing matter, though probably of a different nature. Within another leaf disintegrated remnants of a rather small animal, not a crustacean, which had simple, strong, opaque mandibles, and a large unarticulated chitinous coat, were present. Lumps of black organic matter, possibly of a vegetable nature, were enclosed in two other leaves; but in one of these there was also a small worm much decayed. But the nature of partially digested and decayed bodies, which have been pressed flat, long dried, and then soaked in water, cannot be recognised easily. All the leaves contained unicellular and other Alga, still of a greenish colour, which had evidently lived as intruders, in the same manner as occurs, according to Cohn, within the leaves of this plant in Germany. Cmar. XIV.) CONCLUDING REMARKS. 267 Aldrovanda vesiculosa, var. verticillata.—Dyr, King, Superin- tendent of the Botanic Gardens, kindly sent me dried specimens collected near Calcutta. This form was, 1 believe, considered by Wallich as a distinct species, under the name of verticillata. It resembles the Australian form much more nearly than the European; namely in the projections at the upper end of the petiole being much attenuated and covered with upcurved prickles; they terminate also in two straight little prickles. The bilobed leaves are, I believe, larger and certainly broader even than those of the Australian form; so that the greater convexity of their margins was conspicuous. The length of an open leaf being taken at 100, the breadth of the Bengal form is nearly 173, of the Australian form 147, and of the German 134. The points on the infolded margins are like those in the Australian form. Of the few leaves which were examined, three contained entomostracan crus- taceans, . Concluding Remarks.—The leaves of the three foregoing closely allied species or varieties are manifestly adapted for catching living creatures. With respect to the functions of the several parts, there can be little doubt that the long jointed hairs are sensitive, like those of Dionæa, and that, when touched, they cause the lobes to close. That the glands secrete a true digestive fluid and afterwards absorb the digested matter, is highly probable from the analogy of Dionza,—from the limpid fluid within their cells being aggregated into spherical masses, after they had absorbed an infusion of raw meat,—from their opaque and granular condition in the leaf, which had enclosed a beetle for a long time,—and from the clean condition of the integuments of this insect, as well as of crustaceans (as described by Cohn), which have been long captured. Again, from the effect produced on the quadrifid processes by an immersion for 24 hrs. in a solution of urea,—from the presence of brown granular matter within the quadrifids of the leaf in which the beetle had been caught,—and from the analogy of Utricularia,—it is probable that these processes absorb excrementitious and decaying animal matter. It is a more curious fact that the points on the infolded margins ap- parently serve to absorb decayed animal matter in the same manner as the quadrifids. We can thus understand the meaning of the infulded margins of the lobes furnished with delicate points directed inwards, and of the broad, flat, outer 268 CONCLUDING REMARKS. [Cuar. XIV. portions, bearing quadrifid processes; for these surfaces must be liable to be irrigated by foul water flowing from the concavity of the leaf when it contains dead animals.* This would follow from various causes,—from the gradual con- traction of the concavity,—from fluid in excess being secreted, —and from the generation of bubbles of air. More observa- tions are requisite on this head; but if this view is correct, we have the remarkable case of different parts of the same leaf serving for very different purposes—one part for true digestion, and another for the absorption of decayed animal matter. We can thus also understand how, by the gradual loss of either power, a plant might be gradually adapted for the one function to the exclusion of the other: and it will hereafter be shown that two genera, namely Pinguicula and Utricularia, belonging to the same family, have been adapted for these two different functions. * [Duval-Jouve’s observations throw some doubt on this point. He has shown (‘Bull. Soc. Bot. de France,’ t. xxiii. p. 130) that in the lar structures are described by Duval- Jouve as occurring on the leaves of Callitriche, Nuphar luteum and Nym- phea alba, and similar observations winter buds of Aldrovanda the leaves are reduced to a petiole, the lamina being absent. Now the lamina bears both the glands for which a peptic function is suggested in the text, and also the quadrifid processes which are believed to absorb the products of decay. Since the leaves of the winter buds have no lamina, and cannot therefore capture prey, we must believe that the glands on the petioles have merely general absorp- tive function, and are not specialised in relation to the products of the decaying victims of the plant. Ximi- were made by the late E. Ray Lan- kester (‘ Brit. Assoc, Report,’ 1850, published 1851, 2nd part of volume, p. 113). This being so we must sus- pend judgment as to the function of the quadrifid processes on the outer region of the lamina of the leaves of Aldrovanda. Charles Darwin appears to have been impressed with the im- portance of these facts, as I infer from a note pencilled in Prof. Mar- tin’s tranlation of ‘ Insectivorous Plants,’ where Duval-Jouve’s paper is discussed in a note by the trans- lator.—F, D.] Cuar. XV.] DROSOPHYLLUM LUSITANICUM. 269 CHAPTER XV. DROSOPHYLLUM—RORIDULA—-BYBLIS—GLANDULAR HAIRS OF OTHER PLANTS—CONCLUDING REMARKS ON THE DROSERACEÆ. Drosophyllum—Structure of leaves—Nature of the secretion—Manner of catching insects—Power of absorption—Digestion of animal substances— Summary on Drosophyllum—Roridula—Byblis—Glandular hairs of other plants, their power of absorption—Saxifraga—Primula— Pelargonium — Erica—Mirabilis—Nicotiana—Summary on glandular hairs—Concludine remarks on the Droseracez. DrosopHYLLUM LusiTaNnicuM.—This rare plant has been found! only in Portugal, and, as I hear from Dr. Hooker, in Morocco. I obtained living specimens through the great kindness of Mr. W. C. Tait, and afterwards from Mr. G. Maw and Dr. Moore. Mr. Tait informs me that it grows plentifully on the sides of dry hills near Oporto, and that vast numbers of flies adhere to the leaves. This latter fact is well known to the villagers, who call the plant the “ fly-catcher,” and hang it up in their cottages for this purpose. A plant in my hot- house caught so many insects during the early part of April, although the weather was cold and insects scarce, that it must have been in some manner strongly attractive to them. On four leaves of a young and small plant, 8, 10, 14, and 16 minute insects, chiefly Diptera, were found in the autumn adhering to them. I neglected to examine the roots, but I hear from Dr. Hooker that they are very small, as in the case of the previously mentioned members of the same family of the Droseraceie. The leaves arise from an almost woody axis; they are linear, much attenuated towards their tips, and several inches in length. The upper surface is concave, the lower convex, with a narrow channel down the middle. Both surfaces, with the exception of the channel, are covered with glands, supported on pedicels and arranged in irregular longitudinal rows. These organs I shall call tentacles, from their close resemblance to those of Drosera, though they have no power of movement, Those on the same leaf differ much in length. 270 DROSOPHYLLUM LUSITANICUM. [Cmar. XV. The glands also differ in size, and are of a bright pink or of a purple colour; their upper surfaces are convex, and the lower flat or even concave, so that they resemble miniature mushrooms in appearance. They are formed of two (as I believe) layers of delicate angular cells, enclosing eight or ten larger cells with thicker zigzag walls. Within these larger cells there are others marked by spiral lines, and apparently connected with the spiral vessels which run up the green multicellular pedicels. The glands secrete large drops of viscid secretion. Other glands, having the same general appearance, are found on the flower-peduncles and calyx. Besides the glands which are borne on longer or shorter pedicels, there are numerous ones, both on the upper and lower surfaces of the leaves, so small as to be scarcely visible to the naked eye. They are colourless and almost sessile, either circular or oval in outline; the latter occurring chiefly on the backs of the leaves (fig. 14). Internally they have exactly the same structure as the larger glands which are supported on pedicels; and indeed the two sets almost graduate into one another. But the sessile glands differ in one important respect, for they never secrete spontaneously, as far as I _ have seen, though I have examined them ee lusi- under a high power on a hot day, whilst Part of leaf, enlargea the glands on pedicels were secreting co- seven times, show- piously. Nevertheless, if little bits of damp ing lower surface. ™ albumen or fibrin are placed on these sessile glands, they begin after a time to secrete, in the same manner as do the glands of Dionæa when similarly treated. When they were merely rubbed with a bit of raw meat, I believe that they likewise secreted. Both the sessile glands and the taller ones on pedicels have the power of rapidly absorbing nitrogenous matter. The secretion from the taller glands differs in a remarkable manner from that of Drosera, in being acid before the glands have been in any way excited; and judging from the changed colour of litmus paper, more strongly acid than that of Drosera. This fact was observed repeatedly; on one oceasion I chose a young leaf, which was not secreting freely, Ciar. XV.] SECRETION. 271 and had never caught an insect, yet the secretion on all the glands coloured litmus paper of a bright red. From the quickness with which the glands are able to obtain animal matter from such substances as well-washed fibrin and cartilage, I suspect that a small quantity of the proper ferment must be present in the secretion before the glands are excited, so that a little animal matter is quickly dissolved. Owing to the nature of the secretion or to the shape of the glands, the drops are removed from them with singular facility. It is even somewhat difficult, by the aid of a finely pointed polished needle, slightly damped with water, to place a minute particle of any kind on one of the drops; for on withdrawing the needle, the drop is ‘generally withdrawn; whereas with Drosera there is no such difficulty, though the drops are occasionally withdrawn. From this peculiarity, when a small insect alights on a leaf of Drosophyllum, the drops adhere to its wings, feet, or body, and are drawn from the gland ; the insect then crawls onward and other drops adhere to it; so that at last, bathed by the viscid secretion, it sinks down and dies, resting on the small sessile glands with which the surface of the leaf is thickly covered. In the case of Drosera, an insect sticking to one or more of the exterior glands is carried by their movement to the centre of the leaf; with Drosophyllum, this is effected by the crawling of the insect, as from its wings being clogged by the secretion it cannot fly away. There is another difference in function between the glands of ‘these two plants: we know that the glands of Drosera secrete more copiously when properly excited. But when minute particles of carbonate of ammonia, drops of a solution of this salt or of the nitrate of ammonia, saliva, small insects, bits of raw or roast meat, albumen, fibrin or cartilage, as well as inorganic particles, were placed on the glands of Droso- phyllum, the amount of secretion never appeared to be in the least increased. As insects do not commonly adhere to the taller glands, but withdraw the secretion, we can see that there would be little use in their having acquired the habit of secreting copiously when stimulated; whereas with Drosera this is of use, and the habit has been acquired. Nevertheless, the glands of Drosophyllum, without being stimulated, continually secrete, so as to replace the loss by evaporation. Thus when a plant was placed under a small 272 DROSOPHYLLUM LUSITANICUM. [Cmar. XV. bell-glass with its inner surface and support thoroughly wetted, there was no loss by evaporation, and so much secretion was accumulated in the course of a day that it ran down the tentacies and covered large spaces of the leaves. The glands to which the above named nitrogenous substances and liquids were given did not, as just stated, secrete more copiously ; on the contrary, they absorbed their own drops of secretion with surprising quickness. Bits of damp fibrin were placed on five glands, and when they were looked at after an interval of 1 hr. 12 m., the fibrin was almost dry, the secretion having been all absorbed. So it was with three cubes of albumen after 1 hr. 19 m., and with four other cubes, though these latter were not looked at until 2 hrs. 15 m. had elapsed. The same result followed in between 1 hr. 15 m. and 1 hr. 30 m. when particles both of cartilage and meat were placed on several glands. Lastly, a minute drop (about „y of a minim) of a solution of one part of nitrate of ammonia to»146 of water was distributed between the secretion surrounding three glands, so that the amount of fluid surrounding each was slightly increased ; yet when looked at after 2 hrs., all three were dry. On the other hand, seven particles of glass and three of coal-cinders, of nearly the same size as those of the above-named organic substances, were placed on ten glands; some of them being observed for 18 hrs., and others for two or three days; but there was not the least sign of the secretion being absorbed. Hence, in the former cases, the absorption of the secretion must have been due to the presence of some nitrogenous matter, which was either already soluble or was rendered so by the secretion. As the fibrin was pure, and had been well washed in distilled water after being kept in glycerine, and as the cartilage had been soaked in water, I suspect that these substances must have been slightly acted on and rendered soluble within the above stated short periods. The glands have not only the power of rapid absorption, but likewise of secreting again quickly; and this latter habit has perhaps been gained, inasmuch as insects, if they touch the glands, generally withdraw the drops of secretion, which have to be restored. The exact period of re-secretion was recorded in only a few cases. The glands on which bits of meat were placed, and which were nearly dry after about 1 hr. 30 m., when looked at after 22 additional hours, were found secreting ; so it was after 24 hrs. with one gland Cuar. XV.] ABSORPTION. 273 on which a bit of albumen had been placed. The three glands to which a minute drop of a solution of nitrate of ammonia was distributed, and which became dry after 2 hrs., were beginning to re-secrete after only 12 additional hours. Tentacles Incapable of Movement.—Many of the tall ten- tacles, with insects adhering to them, were carefully ob- served ; and fragments of insects, bits of raw meat, albumen, &c., drops of a solution of two salts of ammonia and of saliva, were placed on the glands of many tentacles; but not a trace of movement could ever be detected. I also repeatedly irritated the glands with a needle, and scratched and pricked the blades, but neither the blade nor the tentacles became at all inflected. We may therefore con- clude that they are incapable of movement. On the Power of Absorption possessed by the Glands.—It has already been indirectly shown that the glands on pedicels absorb animal matter; and this is further shown by their changed colour, and by the aggregation of their contents, after they have been left in contact with nitrogenous substances or liquids. The following observations apply both to the glands supported on pedicels and to the minute sessile ones. Before a gland has been in any way stimu- lated, the exterior cells commonly contain only limpid purple fluid; the more central ones including mulberry-like masses of purple granular matter. A leaf was placed in a little solution of one part of carbonate of ammonia to 146 of water (3 grs. to 1 oz.), and the glands were instantly darkened and very soon became black; this change being due to the strongly marked aggregation of their contents, more especially of the inner cells. Another leaf was placed in a solution of the same strength of nitrate of ammonia, and the glands were slightly darkened in 25 m., more so in 50 m., and after 1 hr. 30 m. were of so dark a red as to appear almost black. Other leaves were placed in a weak infusion of raw meat and in human saliva, and the glands were much darkened in 25 m., and after 40 m. were so dark as almost to deserve to be called black. Even immersion for a whole day in distilled water occasionally induces some aggregation within the glands, so that they become of a darker tint. In all these cases the glands are affected in exactly the same manner as those of Drosera. Milk, however, which acts so energetically on Drosera, seems rather less effective on Drosophyllum, for the glands were only slightly T 274 DROSOPHYLLUM LUSITANICUM. ([Cuar. XV darkened by an immersion ¢f 1 hr. 20 m., but became decidedly darker after 3 hrs. Leaves which had been left for 7 hrs. in an infusion of raw meat or in saliva were placed in the solution of carbonate of ammonia, and the glands now be- came greenish ; whereas, if they had been first placed in the carbonate, they would have become black. In this latter case, the ammonia probably combines with the acid of the secretion, and therefore does not act on the colouring matter ; but when the glands are first subjected to an organic fluid, either the acid is consumed in the work of digestion or the cell-walls are rendered more permeable, so that the undecom- posed carbonate enters and acts on the colouring matter. If a particle of the dry carbonate is placed on a gland, the purple colour is quickly discharged, owing probably to an excess of the salt. The gland, moreover, is killed. Turning now to the action of organic substances, the glands on which bits of raw meat were placed became dark- coloured; and in 18 hrs. their contents were conspicuously aggregated. Several glands with bits of albumen and fibrin were darkened in between 2 hrs. and 3 brs. ; but in one case the purple colour was completely discharged. Some glands which had caught flies were compared with others close by ; and though they did not differ much in colour, there was a marked difference in their state of aggregation. In some few instances, however, there was no such difference, and this appeared to be due to the insects having been caught long ago, so that the glands had recovered their pristine state. In one case, a group of the sessile colourless glands, to which a small fly adhered, presented a peculiar appear- ance; for they had become purple, owing to purple granular matter coating the cell-walls. I may here mention as a caution that, soon after some of my plants arrived in the spring from Portugal, the glands were not plainly acted on by bits of meat, or insects, or a solution of ammonia—a circumstance for which I cannot account. Digestion of Solid Animal Matter.—Whilst I was trying to place on two of the taller glands little cubes of albumen, these slipped down, and, besmeared with secretion, were left resting on some of the small sessile glands. After 24 hrs. one of these cubes was found completely liquefied, but with a few white streaks still visible; the other was much rounded, but not quite dissolved. Two other cubes were left on tall glands for 2 hrs. 45 m., by which time all the Cuar. XV.J DIGESTION. 275 secretion was absorbed ; but they were not perceptibly acted on, though no doubt some slight amount of animal matter had been absorbed from them. They were then placed on the small sessile glands, which being thus stimulated secreted copiously in the course of 7 hrs. One of these cubes was much liquefied within this short time; and both were completely liquefied after 21 hrs. 15 m.; the little liquid masses, how- ever, still showing some white streaks. These streaks disappeared after an additional period of 6 hrs. 30 m.; and by next morning (i.e. 48 hrs. from the time when the cubes were first placed on the glands) the liquefied matter was wholly absorbed. A cube of albumen was left on another tall gland, which first absorbed the secretion and after 24 hrs. poured forth a fresh supply. This cube, now surrounded by secretion, was left on the gland for an additional 24 hrs., but was very little, if at all, acted on. We may therefore conclude, either that the secretion from the tall glands has little power of digestion, though strongly acid, or that the amount poured forth froma single gland is insufficient to dis- solve a particle of albumen which within the same time would have been dissolved by the secretion from several of the small sessile glands. Owing to the death of my last plant, I was unable to ascertain which of these alternatives is the true one. Four minute shreds of pure fibrin were placed, each resting on one, two, or three of the taller glands. In the course of 2 hrs. 30 m. the secretion was all absorbed, and the shreds were left almost dry. They were then pushed on to the sessile glands. One shred, after 2 hrs. 30 m., seemed quite dissolved, but this may have been a mistake. A second, when examined after 17 hrs. 25 m., was liquefied, but the liquid as seen under the microscope still contained floating granules of fibrin. The other two shreds were com- pletely liquefied after 21 hrs. 30 m.; but in one of the drops a very few granules could still be detected. These, however, were dissolved after an additional interval of 6 hrs. 30 m.; and the surface of the leaf for some distance all round was covered with limpid fluid. It thus appears that Drosophyllum digests albumen and fibrin rather more quickly than Drosera can ; and this may perhaps be attributed to the acid, together probably with some small amount of the ferment, being present in the secretion, before the glands have been stimulated ; so that digestion begins at once. T 2 276 RORIDULA. [Cmar. XV. Concluding Remarks—The linear leaves of Drosophyllum differ but slightly from those of certain species of Drosera ; the chief differences being, firstly, the presence of minute, almost sessile, glands, which, like those of Dionea, do not secrete until they are excited by the absorption of nitro- genous matter. But glands of this kind are present on the leaves of Drosera binata, and appear to be represented by the papille on the leaves of Drosera rotundifolia. Secondly, the presence of tentacles on the backs of the leaves; but we have seen that a few tentacles, irregularly placed and tending towards abortion, are retained on the backs of the leaves of Drosera binata. There are greater differences in function between the two genera. The most important one is that the tentacles of Drosophyllum have no power of movement ; this loss being partially replaced by the drops of viscid secretion being readily withdrawn from the glands ; so that, when an insect comes into contact with a drop, it is able to crawl away, but soon touches other drops, and then, smothered by the secretion, sinks down on the sessile glands and dies. Another difference is, that the secretion from the tall glands, before they have been in any way excited, is strongly acid, and perhaps contains a small quantity of the proper ferment. Again, these glands do not secrete more copiously from being excited by the absorption of nitro- genous matter; on the contrary, they then absorb their own secretion with extraordinary quickness. In a short time they begin to secrete again. All these circumstances are probably connected with the fact that insects do not commonly adhere to the glands with which they first come into contact, though this does sometimes occur; and that it is chiefly the secretion from the sessile glands which dissolves animal matter out of their bodies. RORIDULA. Roridula dentata.—This plant, a native of the western parts of the Cape of Good Hope, was sent to me in a dried state from Kew. It has an almost woody stem and branches, and apparently grows to a height of some feet. The leaves are linear, with their summits much attenuated. Their upper and lower surfaces are concave, with a ridge in the middle, and both are covered with tentacles, which differ greatly in length; some being very long, especially those Cuar. XV.] BYBLIS. ya af on the tips of the leaves, and some very short. The glands also differ much in size and are somewhat elongated. They are supported on multicellular pedicels. This plant, therefore, agrees in several respects with Drosophyllum, but differs in the following points. I could detect no sessile glands; nor would these have been of any use, as the upper surface of the leaves is thickly clothed with pointed, unicellular hairs directed upwards. The pedicels of the tentacles do not include spiral vessels; nor are there any spiral cells within the glands. The leaves often arise in tufts and are pinnatifid, the divisions pro- jecting at right angles to the main linear blade. These lateral divisions are often very short and bear only a single terminal tentacle, with one or two short ones on the sides. No distinct line of demarcation can be drawn between the pedicels of the long terminal tentacles and the much attenu- ated summits of the leaves. We may, indeed, arbitrarily fix on the point to which the spiral vessels proceeding from the blade extend; but there is no other distinction. It was evident from the many particles of dirt sticking to the glands that they secrete much viscid matter. A large number of insects of many kinds also adhered to the leaves. I could nowhere discover any signs of the tentacles having been inflected over the captured insects; and this probably would have been seen even in the dried specimens, had they possessed the power of movement. Hence, in this negative character, Roridula resembles its northern representative, Drosophyllum. BYBLIS. Byblis gigantea (Western Australia)—A dried specimen, about 18 inches in height, with a strong stem, was sent me from Kew. The leaves are some inches in length, linear, slightly flattened, with a small projecting rib on the lower surface. They are covered on all sides by glands of two kinds—sessile ones arranged in rows, and others supported on moderately long pedicels. Towards the narrow summits of the leaves the pedicels are longer than elsewhere, and here equal the diameter of the leaf. The glands are purplish, much flattened, and formed of a single layer of radiating cells, which in the larger glands are from forty to fifty in number. The pedicels consist of single elongated cells, with colourless, extremely delicate walls, marked with the finest 278 GLANDULAR HAIRS: [Cuar. XV. intersecting spiral lines. Whether these lines are the result of contraction from the drying of the walls, I do not know, but the whole pedicel was often spirally rolled up. ‘These glandular hairs are far more simple in structure than the so- called tentacles of the preceding genera, and they do not differ essentially from those borne by innumerable other plants. The flower-peduncles bear similar glands. The most singular character about the leaves is that the apex is enlarged into a little knob, covered with glands, and about a third broader than the adjoining part of the attenuated leaf. In two places dead flies adhered to the glands. As no instance is known of unicellular structures having any power of movement,* Byblis, no doubt, catches insects solely by the aid of its viscid secretion. These probably sink down besmeared with the secretion and rest on the small sessile glands, which, if we may judge by the analogy of Droso- phyllum, then pour forth their secretion and afterwards absorb the digested matter. Supplementary Observations on the Power of Absorption by the Glandular Hairs of other Plants—A few observations on this subject may be here conveniently introduced. As the glands of many, probably of all, the species of Droseraceze absorb various fluids or at least allow them readily to enter,f it seemed desirable to ascertain how far the glands of other plants which are not specially adapted for capturing insects, had the same power. Plants were chosen for trial at hazard, with the exception of two species of saxifrage, which were selected from belonging to a family allied to the Droseracez. Most of the experiments were made by immersing the glands either in an infusion of raw meat or more commonly in a solution of carbonate of ammonia, as this latter substance acts so powerfully and rapidly on protoplasm. It seemed also particularly desirable to ascertain whether ammonia was absorbed, as a small amount is contained in rain-water. With the Droseraceæ the secretion of a viscid fluid by the glands does not prevent their absorbing; so that the glands of other plants might excrete superfluous matter, or secrete an odoriferous fluid as a protection against the attacks of * Sachs, ‘Traité de Bot.’ 3rd edit. imbibition, is by no means clearly 1874, p. 1026. understood: see Miiller’s ‘ Physio- ł The distinction between true logy; Eng. translat. 1838, vol. i. p. absorption and mere permeation, or 280. paa Cuar. XV.] THEIR POWER OF ABSORPTION. 279 insects, or for any other purpose, and yet have the power of absorbing. I regret that in the following cases I did not try whether the secretion could digest or render soluble animal substances, but such experiments would have been difficult on account of the small size of the glands and the small amount of secretion. We shall see in the next chapter that the secretion from the glandular hairs of Pinguicula certainly dissolves animal matter. Saxifraga umbrosa.—The flower-peduncles and petioles of the leaves are clothed with short hairs, bearing pink-coloured glands, formed of several polygonal cells, with their pedicels divided by partitions into distinct cells, which are generally colourless, but sometimes pink. The glands secrete a yellowish viscid fluid, by which minute Diptera are sometimes, though not often, caught.* The cells of the glands contain bright pink fluid, charged with granules or with globular masses of pinkish pulpy matter. This matter must be protoplasm, for it is seen to undergo slow but incessant changes of form if a gland be placed in a drop of water and examined. Similar movements were observed after glands had been immersed in water for 1, 3, 5, 18, and 27 hrs. Even after this latter period the glands retained their bright pink colour; and the protoplasm within their cells did not appear to have become more aggregated. The continually changing forms of the little masses of protoplasm are not due to the absorption of water, as they were seen in glands kept dry. A flower-stem, still attached to a plant, was bent (May 29) so as to remain immersed for 23 hrs. 30 m. in a strong infusion of raw meat. The colour of the contents of the glands was slightly changed, being now of a duller and more purple tint than before. ‘The contents also appeared more aggregated, for the spaces between the little masses of protoplasm were wider; but this latter result did not follow in some other and similar experiments. ‘The masses seemed to change their forms more rapidly than did those in water; so that the cells had a different appearance every four or five minutes. Elongated masses became in the course of one or two minutes spherical; and spherical ones drew themselves out and united with others. Minute masses rapidly increased in size, and three distinct ones were seen to unite. The movements were, in short, exactly like those described in the case of Drosera. The cells of the pedicels were not affected by the infusion ; nor were they in the following experiment. Another flower-stem was placed in the same manner and for the same length of time in a solution of one part of nitrate of ammonia to * In the case of Sarifraga tri- and in almost every instance remnants dactylites, Mr. Druce says (‘Phar- of insects adhered to the leaves. So maceutical Journal,’ May 1875) that it is, as I hear from a friend, with he examined some dozens of plants, this plant in Ireland, 280 GLANDULAR HAIRS: [Cuar. XV. 146 of water (or 3 grs. to 1 oz.), and the glands were discoloured in exactly the same manner as by the infusion of raw meat. Another flower-stem was immersed, as before, in a solution of one part carbonate of ammonia to 109 of water. The glands, after 1 hr. 30 m., were not discoloured, but after 3 hrs. 45 m. most of them had become dull purple, some of them blackish-green, a few being still unaffected. The little masses of protoplasm within the cells were seen in movement. The cells of the pedicels were unaltered. ‘The experiment was repeated, and a fresh flower-stem was left for 23 hrs. in the solution, and now a great effect was produced; all the glands were much blackened, and the previously transparent fluid in the cells of the pedicels, even down to their bases, contained spherical masses of granular matter. By comparing many different hairs, it was evident that the glands first absorb the carbonate, and that the effect thus produced travels down the hairs from cell to cell, The first change which could be observed is a cloudy appearance in the fluid, due to the formation of very fine granules, which afterwards aggregate into larger masses. Altogether, m the darkening of the glands, and in the process of aggregation travelling down the cells of the pedicels, there is the closest resemblance to what takes place when a tentacle of Drosera is immersed in a weak solution of the same salt. ‘The glands, however, absorb very much more slowly than those of Drosera. Besides the glandular hairs, there are star-shaped organs which do not appear to secrete, and which were not in the least affected by the above solutions. Although in the case of uninjured flower-stems and leaves the carbonate seems to be absorbed only by the glands, yet it enters a cut surface much more quickly than a gland. Strips of the rind of a flower-stem were torn off, and the cells of the pedicels were seen to contain only colourless transparent fluid ; those of the glands including as usual some granular matter. These strips were then immersed in the same solution as before (one part of the carbonate to 109 of water), and in a few minutes granular matter appeared in the lower cells of all the pedicels. The action invariably commenced (for I tried the ex- periment repeatedly) in the lowest cells, and therefore close to the torn surface, and then gradually travelled up the hairs until it reached the glands, in a reversed direction to what occurs in uninjured specimens. The glands then became discoloured, and the previously contained granular matter was aggregated into larger masses. Two short bits of a flower-stem were also left for 2 hrs. 40 m. ina weaker solution of one part of the carbonate of 218 of water; and in both specimens the pedicels of the hairs near the cut ends now contained much granular matter; and the glands were completely discoloured. Lastly, bits of meat were placed on some glands; these were examined after 23 hrs., as were others, which had apparently not long before caught minute flies; but they did not present any difference from the glands of other hairs. Perhaps there may not have been time enough for absorption. I think so, as some glands, on which W oF Cuar. XV.] THEIR POWER OF ABSORPTION. 281 dead flies had evidently long lain, were of a pale dirty purple colour or even almost colourless, and the granular matter within them presented. an unusual and somewhat peculiar appearance. That these glands. had absorbed animal matter from the flies, probably by exosmose into the viscid secretion, we may infer, not only from their changed colour, but because, when placed in a solution of carbonate of ammonia, some of the cells in their pedicels become filled with granular matter ; whereas the cells of other hairs, which had not caught flies, after being treated with the same solution for the same length of time, contained only a small quantity of granular matter. But more evidence is neces-ary before we fully admit that the glands of this saxifrage can absorb, even with ample time allowed, animal matter from the minute insects which they occasionally and accidentally capture. Saxifraga rotundifolia (?).—The hairs on the flower-stems of this species are longer than those just described, and bear pale brown glands. Many were examined, and the cells of the pedicels were quite trans- parent. A bent stem was immersed for 30 m. in a solution of one part of carbonate of ammonia to 109 of water, and two or three of the uppermost cells in the pedicels now contained granular or aggregated matter; the glands having become of a bright yellowish-green. ‘The glands of this species therefore absorb the carbonate much more quickly than do those of Saxifraga umbrosa, and the upper cells of the pedicels are likewise atiected much more quickly. Pieces of the stem were cut off and immersed in the same solution; and now the process of aggregation travelled up the hairs in a reversed direction ; the cells close to the cut surfaces being first affected. Primula sinensis.—Vhe flower-stems, the upper and lower surfaces of the leaves and their footstalks, are all clothed with a multitude of longer and shorter hairs. The pedicels of the longer hairs are divided by transverse partitions into eight or nine cells. The enlarged ter- minal cell is globular, forming a gland which secretes a variable amount of thick, slightly viscid, not acid, brownish-yellow matter. A piece of a young flower-stem was first immersed in distilled water for 2 hrs. 30 m., and the glandular hairs were not at all affected. Another piece, bearing twenty-five short and nine long hairs, was carefully examined. ‘lhe glands of the latter contained no solid or semi-solid matter; and those of only two of the twenty-five short hairs contained some globules. This piece was then immersed for 2 hrs. in a solution of one part of carbonate of ammonia to 109 of water, and now the glands of the twenty-five shorter hairs, with two or three exceptions, contained either one large or from two to five smaller spherical masses of semi-solid matter. Three of the glands of the nine long hairs likewise included similar masses. In a few hairs there were also globules in the cells immediately beneath the glands. Looking to all thirty-fonr hairs, there could be no doubt that the glands had absorbed some of the carbonate. Another piece was left for only 1 hr. in the same solution, and aggregated matter appeared in all the glands. Myson Francis examined some glands of the longer 282 GLANDULAR HAIRS: [Cuar. XV. hairs, which contained little masses of matter, before they were immersed in any solution; and these masses slowly changed their forms, so that no doubt they consisted of protoplasm. He then irrigated these hairs for 1 hr. 15 m., whilst under the microscope, with a solution of one part of the carbonate to 218 of water; the glands were not perceptibly affected, nor could this have been expected, as their contents were already aggregated. But in the cells of the pedicels numerous, almost colourless, spheres of matter appeared, which changed their forms and slowly coalesced; the appearance of the cells being thus totally changed at successive intervals of time. The glands on a young flower-stem, after having been left for 2 hrs. 45 m. in a strong solution of one part of the carbonate to 109 of water, contained an abundance of aggregated masses, but whether generated by the action of the salt, Ido not know. This piece was again placed in the solution, so that it was immersed altogether for 6 hrs. 15 m., and now there was a great change; for almost all the spherical masses within the gland-cells had disappeared, being replaced by granular matter of a darker brown. The experiment was thrice repeated with nearly the same result. On one occasion the piece was left immersed for 8 hrs. 80 m., and though almost all the spherical masses were changed into the brown granular matter, a few still remained. If the spherical masses of aggregated matter had been originally produced merely by some chemical or physical action, it seems strange that a somewhat longer immersion in the same solution should so completely alter their character. But as the masses which slowly and sponta- neously changed their forms must have consisted of living protoplasm, there is nothing surprising in its being injured or killed, and its appearance wholly changed by long immersion in so strong a solution of the carbonate as that employed. A solution of this strength paralyses all movement in Drosera, but does not kill the protoplasm ; a still stronger solution prevents the protoplasm from aggregating into the ordinary full-sized globular masses, and these, though they do not disintegrate, become granular and opaque. In nearly the same manner, too, hot water and certain solutions (for instance, of the salts of soda and potash) canse at first an imperfect kind of aggregation in the cells of Drosera ; the little masses afterwards breaking ‘up into granular or pulpy brown matter. All the foregoing experiments were made on tlower-stems, but a piece of a leaf was immersed for 30 m. in a strong solution of the carbonate (one part to 109 of water), and little globular masses of matter appeared in all the glands, which before contained only limpid fluid. I made also several experiments on the action of the vapour of the carbonate on the glands; but will give only a few cases. The cut end of the footstalk of a young leaf was protected with sealing-wax, and was then placed under a small bell-glass, with a large pinch of the carbon- ate. After 10 m. the glands showed a considerable degree of aggrega- tion, and the protoplasm lining the cells of the pedicels was a little separated from the walls. Another leaf was left for 50 m. with the Cuar. XV. THEIR POWER OF ABSORPTION. 283 same result, excepting that the hairs became throughout their whole length of a brownish colour. In a third leaf, which was exposed for 1 hr. 50 m., there was much aggregated matter in the glands; and some of the masses showed signs of breaking up into brown granular matter. This leaf was again placed in the vapour, so that it was exposed altogether for 5 hrs. 80 m.; and now, though I examined a large number of glands, aggregated masses were found in only two or three; in all the others, the masses, which before had been globular, were converted into brown, opaque, granular matter. We thus see that exposure to the vapour for a considerable time produces the same effects as long immersion in a strong solution. In both cases there could hardly be a doubt that the salt had been absorbed chiefly or exclusively by the glands. On another occasion bits of damp fibrin, drops of a weak infusion of raw meat and of water, were left fur 24 hrs. on some leaves ; the hairs were then examined, but to my surprise differed in no respect from others which had not been touched by these fluids. Most of the cells, however, included hyaline, motionless little spheres, which did not seem to consist of protoplasm, but, 1 suppose, of some balsam or essential oil. Pelargonium zonale (var. edged with white),—The leaves are clothed with numerous multicellular hairs; some simply pointed; others bearing glandular heads, and differing much in length. The glands on a piece of leaf were examined and found to contain only a limpid fluid; most of the water was removed from beneath the covering glass, and a minute drop of one part of carbonate of ammonia to 146 of water was added; so that an extremely small cose was given. After an interval of only 3 m. there were signs of aggregation within the glands of the shorter hairs; and after 5 m. many small globules of a pale brown tint appeared in all of them; similar giobules, but larger, being found in the large glands of the longer hairs. After the specimen had been left for 1 hr. in the solution, many of the smaller globules had changed their positions; and two or three vacuoles or small spheres (for 1 know not which they were) of a rather darker tint appeared within some of the larger globules. Little globules could now be seen in some of the uppermost cells of the pedicels, and the protoplasmic lining was slightly separated from the walls of the lower cells. After 2 hrs. 30 m. from the time of first immersion, the large globules within the glands of the longer hairs were converted into masses of darker brown granular matter. Hence from what we have seen with Primula sinensis, there can be little doubt that these masses originally consisted of living protoplasm, A drop of a weak infusion of raw meat was placed on a leaf, and after 2 hrs, 30 m. many spheres could be seen within the glands. These spheres, when looked at again after 30 m., had slightly changed their positions and forms, and one had separated into two; but the changes were not quite like those which the protoplasm of Drosera undergves. These hairs, moreover, had not been examined before 284 GLANDULAR HAIRS: [Cuar. XV. immersion, and there were similar spheres in some glands which had not been touched by the infusion. Erica tretraliv.—A few long glandular hairs project from the margins of the upper surfaces of the leaves. The pedicels are formed of several rows of cells, and support rather large globular heads, secreting viscid matter, by which minute insects are occasionally though rarely, caught. Some leaves were left for 23 hrs. in a weak infusion of raw meat and in water, and the hairs were then com- pared, but they differed very little or not at all. In both cases the contents of the cells seemed rather more granular than they were before; but the granules did not exhibit any movement. Other leaves were left for 23 hrs. in a solution of one part of carbonate of ammonia to 218 of water, and here again the granular matter appeared to have increased in amount; but one such mass retained exactly the same form as before after an interval of 5 hrs., so that it could hardly have consisted of living protoplasm. These glands seem to have very little or no power of absorption, certainly much less than those of the foregoing plants. Mirabilis longiflora.—The stems and both surfaces of the leaves bare viscid hairs. Young plants, from 12 to 18 inches in height in my greenhouse, caught so many minute Diptera, Coleoptera, and larva, that they were quite dusted with them. ‘lhe hairs are short, of unequal lengths, formed of a single row of cells, surmounted by an enlarged cell which secretes viscid matter. These terminal cells or glands contain granules and often globules of granular matter. Within a gland which had caught a small insect, one such mass was observed to undergo incessant changes of form, with the occa- sional appearance of vacuoles. But 1 do not believe that this protoplasm had been generated by matter absorbed from the dead insect; for, on comparing several glands which had and had not caught insects, not a shade of difference could be perceived between them, and they all contained fine granular matter. A piece of leaf was immersed for 24 hrs. in a solution of one part of carbonate of ammonia to 218 of water, but the hairs seemed very little affected by it, excepting that perhaps the glands were rendered rather more opaque. In the leaf itself, however, the grains of chlorophyll near the cut surfaces had run together, or become aggregated. Nor were the glands on another leaf, after an immersion ‘for 24 hrs. in an in- fusion of raw meat, in the least affected; but the protoplasm luing the cells of the pedicels had shrunk greatly from the walls. This latter effect may have been due to exosmose, as the infusion was strong. We may therefore conclude that the glands of this plant either have no power of absorption or that the protoplasm which they contain is not acted on by a solution of carbonate of ammonia (and this seems scarcely credible) or by an infusion of meat. Nicotiana tabacum.—This plant is covered with innumerable hairs of unequal lengths, which catch many minute insects. ‘The pedicels of the hairs are divided by transverse partitions, and the secreting Cuar. XV.] THEIR POWER OF ABSORPTION. 285 glands are formed of many cells, containing greenish matter with little globules of some substance. Leaves were left in an infusion of raw meat and in water for 26 hrs., but presented no difference. Some of these same leaves were then left tor above 2 hrs. in a solution of carbonate of ammonia, but no effect was produced. I regret that other experiments were not tried with more care, as M. Schloesing has shown* that tobacco plants supplied with the vapour of carbonate of ammonia yield on analysis a greater amount of nitrogen than other plants not thus treated ; and, from what we have seen, it is probable that some of the vapour may be absorbed by the glandular hairs. Summary of the Observations on Glandular Hairs—From the foregoing observations, few as they are, we see that the glands of two species of Saxifraga, of a Primula and Pelar- gonium, have the power of rapid absorption; whereas the glands of an Erica, Mirabilis, and Nicotiana, either have no such power, or the contents of the cells are not affected by the fluids employed, namely a solution of carbonate of ammonia and an infusion of raw meat. As the glands of the Mirabilis contain protoplasm, which did not become aggregated from exposure to the fluids just named, though the contents of the cells in the blade of the leaf were greatly affected by carbonate of ammonia, we may infer that they cannot absorb. We may further infer that the innumerable insects caught by this plant are of no more service to it than are those which adhere to the deciduous and sticky scales of the leaf-buds of the horse-chestnut. The most interesting case for us is that of the two species of Saxifraga, as this genus is distantly allied to Drosera. Their glands absorb matter from an infusion of raw meat, from solutions of the nitrate and carbonate of ammonia, and apparently from decayed insects. This was shown by the changed dull purple colour of the protoplasm within the cells of the glands, by its state of aggregation, and apparently by its more rapid spontaneous movements. ‘The aggregating process spreads from the glands down the pedicels of the hairs; and we may assume that any matter which is absorbed ultimately reaches the tissues of the plant. On the other hand, the process travels up the hairs whenever a surface is cut and exposed to a solution of the carbonate of ammonia. * «Comptes rendus, June 15, 1874. A good abstract of this paper is given in the ‘Gardener’s Chronicle,’ July 11, 1874, 286 GLANDULAR HAIRS. (Cuar, XV. The glands on the flower-stalks and leaves of Primula sinensis quickly absorb a solution of the carbonate of ammonia, and the protoplasm which they contain becomes aggregated. The process was seen in some cases to travel from the glands into the upper cells of the pedicels. Exposure for 10 m. to the vapour of this salt likewise induced aggregation. When leaves were left from 6 hrs. to 7 hrs. in a strong solution, or were long exposed to the vapour, the little masses of protoplasm became disintegrated, brown, and granular, and were apparently killed. An infusion of raw meat produced no effect on the glands. The limpid contents of the glands of Pelargonium zonale became cloudy and granular in from 3 m. to 5 m. when they were immersed in a weak solution of the carbonate of am- monia ; and in the course of 1 hr. granules appeared in the upper cells of the pedicels. As the aggregated masses slowly changed their forms, and as they sutfered disintegra- tion when left for a considerable time in a strong solntion, there can be little doubt that they consisted of protoplasm. It is doubtful whether an infusion of raw meat produced any effect. The glandular hairs of ordinary plants have generally been considered by physiologists to serve only as secreting or excreting organs, but we now know that they have the power, at least in some cases, of absorbing both a solution and the vapour of ammonia. As rain-water contains a small percentage of ammonia, and the atmosphere a minute quantity of the carbonate, this power can hardly fail to be beneficial. Nor can the benefit be quite so insignificant as it might at first be thought, for a moderately fine plant of Primula sinensis bears the astonishing number of above two millions and a half of glandular hairs,* all of which are able to absorb * My son Francis counted the (the larger ones being a little more hairs on a space measured by means than 2 inches in diameter) was now of a micrometer, and found that selected, and the area of all the there were 35,336 on a square inch leaves, together with their footstalks of the upper surface of a leaf, and (the flower-stems not being included) 30,035 on the lower surface; that is, was found by a planimeter to be in about the proportion of 100 on the 39°285 square inches; so that the upper to 85 on the lower surface. area of both surfaces was 78°57 On a square inch of both surfaces square inches. Thus the plant (ex- there were 65,371 hairs. A moder- cluding the flower-stems) must have ately fine plant bearing twelve leaves borne the astonishing number of Cuar. XV.] DROSERACE®. 287 ammonia brought to them by the rain. It is moreover probable that the glands of some of the above-named plants obtain animal matter from the insects which are occasionally entangled by the viscid secretion. ConcLuDING REMARKS ON THE DROSERACEÆ. The six known genera composing this family have now been described in relation to our present subject, as far as my means have permitted. They all capture insects. This is effected by Drosophyllum, Roridula, and Byblis, solely by the viscid fluid secreted from their glands; by Drosera, through the same means, together with the movements of the tentacles; by Dionæa and Aldrovanda, through the closing of the blades of the leaf. In these two last genera rapid movement makes up for the loss of viscid secretion. In every case it is some part of the leaf which moves. In Aldrovanda it appears to be the basal parts alone which contract and carry with them the broad, thin margins of the lobes. In Dionza the whole lobe, with the exception of the marginal prolongations or spikes, curves inwards, though the chief seat of movement is near the midrib. In Drosera the chief seat is in the lower part of the tentacles, which, homologically, may be considered as prolongations of the leaf; but the whole blade often curls inwards, converting the leaf into a temporary stomach. There can hardly be a doubt that all the plants belonging to these six genera have the power of dissolving animal matter by the aid of their secretion, which contains an acid, together with a ferment almost identical in nature with pepsin; and that they afterwards absorb the matter thus digested. This is certainly the case with Drosera, Droso- phyllum, and Dionea; almost certainly with Aldrovanda ; and, from analogy, very probable with Roridula and Byblis. We can thus understand how it is that the three first-named 2,568,099 glandular hairs. The hairs were counted late in the autumn, and by the following spring (May) the leaves of some other plants of the same lot were found to be from one- third to one-fourth broader and longer than they were before; so that no doubt the glandular hairs had increased in number, and }ro- bably now much exceeded three millions. 288 CONCLUDING REMARKS [Cuar, XV. genera are provided with such small roots,* and that Aldro- vanda is quite rootless; about the roots of the two other genera nothing is known. It is, no doubt, a surprising fact that a whole group of plants (and, as we shall presently see, some other plants not allied to the Droseraceæ) should subsist partly by digesting animal matter, and partly by decomposing carbonic acid, instead of exclusively by this latter means, together with the absorption of matter from the soil by the aid of roots. We have, however, an equally anomalous case in the animal kingdom ; the rhizocephalous crustaceans do not feed like other animals by their mouths, for they are destitute of an alimentary canal; but they live by absorbing through root-like processes the juices of the animals on which they are parasitic.t Of the six genera, Drosera has been incomparably the most successful in the battle for life; and a large part of its success may be attributed to its manner of catching insects. It is a dominant form, for it is believed to include about 100 species,t which range in the Old World from the Arctic regions to Southern India, to the Cape of Good Hope, *(Fraustadt (Dissertation, Breslau, cirripede, the Anelasma squalicola, 1876) shows that the roots of Dionwa had become extinct, it would have are by no means small. In another been very difficult to conjecture how Breslau Dissertation (1887) Otto so enormous a change could have Penzig shows that the roots of been gradually effected. But, as Drosophyllum lusitanicum are also Fritz Müller remarks, we have in well developed. Pfeffer (‘Landwirth. Anelasma an animal in an almost Jahrbucher, 1877) points out thatthe exactly intermediate condition, for it argument from the small develop- has root-like processes embedded in ment of roots in some carnivorous the skin of the shark on which it is plants is valueless, because the same parasitic, and its prehensile cirri and state of things is found in many mouth (as described in my monograph marsh and aquatic plants which on the Lepadide, ‘Ray Soc.’ 1851, neither catch nor digest insects— p. 169) are in a most feeble and F. DJ almost rudimentary condition. Dr. + Fritz Müller, ‘Facts for Darwin, R. Kossmann has given a very in- Eng. trans. 1869, p. 139. The rhizo- teresting discussion on this subject cephalous crustaceans are allied to in his ‘Suctoria and Lepadidæ, 1873. the cirripedes. It is hardly possible See also, Dr. Dohrn, ‘ Der Ursprung to imagine a greater difference than der Wirbelthiere,’ 1875, p. 77. that between an animal with pre- } Bentham and Hooker, ‘Genera hensile limbs, a well-constructed Plantarum.’ mouth and alimentary canal, and one tropolis of the genus, forty-one destitute of all these organs and species having been described from feeding by absorption through branch- this country, as Prof. Oliver informs ing root-like processes. If one rare me. Australia is the me- Cuar, XYV.] ON THE DROSERACE®. 289 Madagascar, and Australia; and in the New World from Canada to Tierra del Fuego. In this respect it presents a marked contrast with the five other genera, which appear to be failing groups. Dionæa includes only a single species, which is confined to one district in Carolina. The three varieties or closely allied species of Aldrovanda, like so many water-plants, have a wide range from Central Europe to Bengal and Australia. Drosophyllum includes only one species, limited to Portugal and Morocco, Roridula and Byblis each have (as I hear from Prof. Oliver) two species ; the former confined to the western parts of the Cape of Good Hope, and the latter to Australia. It is a strange fact that Dionza, which is one of the most beautifully adapted plants in the vegetable kingdom, should apparently be on the high road to extinction. This is all the more strange as the organs of Dionza are more highly differentiated than those of Drosera; its filaments serve exclusively as organs of touch, the lobes for capturing insects, and the glands, when excited, for secretion as well as for absorption ; whereas with Drosera the glands serve all these purposes, and secrete without being excited. By comparing the structure of the leaves, their degree of complication, and their rudimentary parts in the six genera, we are led to infer that their common parent form partook of the characters of Drosophyllum, Roridula, and Byblis. The leaves of this ancient form were almost certainly linear, perhaps divided, and bore on their upper and lower surfaces glands which had the power of secreting and absorbing. Some of these glands were mounted on pedicels, and others were almost sessile; the latter secreting only when stimu- lated by the absorption of nitrogenous matter. In Byblis the glands consist of a single layer of cells, supported on a unicellular pedicel; in Roridula they have a more complex structure, and are supported on pedicels formed of several rows of cells; in Drosophyllum they further include spiral cells, and the pedicels include a bundle of spiral vessels. But in these three genera these organs do not possess any power of movement, and there is no reason to doubt that they are of the nature of hairs or trichomes. Although in innumerable instances foliar organs move when excited, no case is known of a trichome having such power.* We are * Sachs, ‘Traité de Botanique, 3rd edit. 1874, p. 1026. U 290 CONCLUDING REMARKS [Cuar. XV. thus led to inquire how the so-called tentacles of Drosera, which are manifestly of the same general nature as the glandular hairs of the above three genera, could have acquired the power of moving. Many botanists maintain that these tentacles consist of prolongations of the leaf, because they include vascular tissue, but this can no longer be considered as a trustworthy distinction.* The possession of the power of movement on excitement would have been safer evidence. But when we consider the vast number of the tenacles on both surfaces of the leaves of Drosophyllum, and on the upper surface of the leaves of Drosera, it seems searcely possible that each tentacle could have aboriginally existed as a prolongation of the leaf. Roridula, perhaps, shows us how we may reconcile these difficulties with respect to the homological nature of the tentacles. The lateral divisions of the leaves of this plant terminate in long ten- tacles; and these include spiral vessels which extend for only a short distance up them, with no line of demarcation between what is plainly the prolongation of the leaf and the pedicel of a glandular hair. Therefore there would be nothing anomalous or unusual in the basal parts of these tentacles, which correspond with the marginal ones of Drosera, acquiring the power of movement; and we know that in Drosera it is only the lower part which becomes inflected. But in order to understand how in this latter genus not only the marginal but all the inner tentacles have become capable of movement, we must further assume, either that through the principle of correlated development this power was transferred to the basal parts of the hairs, or that the surface of the leaf has been prolonged upwards at numer- ous points, so as to unite with the hairs, thus forming the bases of the inner tentacles, The above-named three genera, namely Drosophyllum, Roridula, and Byblis, which appear to have retained a primordial condition, still bear glandular hairs on both surfaces of their leaves; but those on the lower surface have since disappeared in the more highly developed genera, with the partial exception of one species, Drosera binata. The small sessile glands have also disappeared in some of * Dr. Warming, ‘Sur la Différence belige Meddelelser de la Soc. d’Hist. entre les Trichomes,’ Copenhague, nat. de Copenhague, Nos. 10-12, 1873, p. 6. ‘Extrait des Videnska- 1872. CHAF. XV.) ON THE DROSERACE. 291 the gerera, being replaced in Roridula by hairs, and in most species of Drosera by absorbent papillae. Drosera binata, with its linear and bifurcating leaves, is in an inter- mediate condition. It still bears some sessile glands on both surfaces of the leaves, and on the lower surface a few irregularly placed tentacles, which are incapable of move- ment. A further slight change would convert the linear leaves of this latter species into the oblong leaves of Drosera anglica, and these might easily pass into orbicular ones with footstalks like those of Drosera rotundifolia. The footstalks of this latter species bear multicellular hairs, which we have good reason to believe represent aborted tentacles. The parent form of Dionæa and Aldrovanda seems to have been closely allied to Drosera, and to have had rounded leaves, supported on distinct footstalks, and furnished with tentacles all round the circumference, with other tentacles and sessile glands on the upper surface. I think so because the marginal spikes of Dionza apparently represent the extreme marginal tentacles of Drosera, the six (sometimes eight) sensitive filaments on the upper surface, as well as the more numerous ones in Aldrovanda, representing the central tentacles of Drosera, with their glands aborted, but their sensitiveness retained. Under this point of view we should bear in mind that the summits of the tentacles of Drosera, close beneath the glands, are sensitive. The three most remarkable characters possessed by the several members of the Droseracez consist in the leaves of some having the power of movement when excited, in their glands secreting a fluid which digests animal matter, and in their absorption of the digested matter. Can any light be thrown on the steps by which these remarkable powers were gradually acquired ? As the walls of the cells are necessarily permeable to fluids, in order to allow the glands to secrete, it is not surprising that they should readily allow fluids to pass in- wards; and this inward passage would deserve to be called an act of absorption, if the fluids combined with the contents of the glands. Judging from the evidence above given, the secreting glands of many other plants can absorb salts of ammonia, of which they must receive small quantities from the rain. This is the case with two species of Saxifraga. U2 292 CONCLUDING REMARKS. [CHAP. XV. and the glands of one of them apparently absorb matter from captured insects, and certainly from an infusion of raw meat. There is, therefore, nothing anomalous in the Droseraceæ having acquired the power of absorption in a much more highly developed degree. It is a far more remarkable problem how the members of this family, and Pinguicula, and, as Dr. Hooker has recently shown, Nepenthes, could all have acquired the power of secreting a fluid which dissolves or digests animal matter. The six genera of the Droseracew have probably inherited this power from a common progenitor, but this cannot apply to Pinguicula or Nepenthes, for these plants are not at all closely related to the Droseracexw. But the difficulty is not nearly so great as it at first appears. Firstly, the juices of many plants contain an acid, and, apparently, any acid serves for digestion. Secondly, as Dr. Hooker has remarked in relation to the present subject in his address at Belfast (1874), and as Sachs repeatedly insists,* the embryos of some plants secrete a fluid which dissolves albuminous substances out of the endosperm ; although the endosperm is not actually united with, only in contact with, the embryo. All plants, moreover, have the power of dissolving albuminous or proteid substances, such as protoplasm, chlorophyll, gluten, aleurone, and of carrying them from one part to other parts of their tissues. This must be effected by a solvent, probably con- sisting of a ferment together with an acid.t Now, in the case of plants which are able to absorb already soluble matter from captured insects, though not capable of true digestion, the solvent just referred to, which must be occasionally present in the glands, would be apt to exude from the glands together with the viscid secretion, inasmuch as endosmose is accompanied by exosmose. If such exudation did ever occur, the solvent would act on the animal matter contained within the captured insects, and this would be an act of true digestion. As it cannot be doubted that this process would * ¢Traité de Botanique, 3rd edit. 1874, p. 844. See also for following facts pp. 64, 76, 828, 831. + Since this sentence was written, I have received a paper by Gorup- Besanez (‘Berichte der Deutschen Chem. Gesellschaft,’ Berlin, 1874, p. 1478), who, with the aid of Dr. H. Will, has actually made the discovery that the seeds of the vetch contain a ferment, which, when extracted by glycerine, dissolves albuminous sub- stances, such as fibrin, and converts them into true peptones. [See, how- ever, Vines’ ‘Physiology of Plants,” p. 190.—F. D) Cuar. XV] ON THE DROSERACE:. 293 be of high service to plants growing in very poor soil, it would tend to be perfected through natural selection. There- fore, any ordinary plant having viscid glands, which occasionally caught insects, might thus be converted under favourable circumstances into a species capable of true digestion. It ceases, therefore, to be any great mystery how several genera of plants, in no way closely related together, have independently acquired this same power. As there exist several plants the glands of which cannot, as far as is known, digest animal matter, yet can absorb salts of ammonia and animal fluids, it is probable that this latter power forms the first stage towards that of digestion. It might, however, happen, under certain conditions, that a plant, after having acquired the power of digestion, should degenerate into one capable only of absorbing animal matter in solution, or in a state of decay, or the final products of decay, namely the salts of ammonia. It would appear that this has actually occurred to a partial extent with the leaves of Aldrovanda; the outer parts of which possess absorbent organs, but no glands fitted for the secretion of any digestive fluid, these being confined to the inner parts. Little light can be thrown on the gradual acquirement of the third remarkable character possessed by the more highly developed genera of the Droseraceæ, namely the power of movement when excited. It should, however, be borne in mind that leaves and their homologues as well as flower- peduncles, have gained this power, in innumerable instances, independently of inheritance from any common parent form ; for instance, in tendril-bearers and leaf-climbers (i.e. plants with their leaves, petioles and flower-peduncles, &c., modified for prehension) belonging to a large number of the most widely distinct orders,—in the leaves of the many plants which go to sleep at night, or move when shaken,—and in irritable stamens and pistils of not a few species. We may therefore infer that the power of movement can be by some means readily acquired. Such movements imply irritability or sensitiveness, but, as Cohn has remarked,* the tissues of the plants thus endowed do not differ in any uniform manner * See the abstract of his memoir on the contractile tissues of plants, in the * Annals and Mag. of Nat, Hist.’ 3rd series, vol. xi. p. 188. 294 CONCLUDING REMARKS (Cmar. XV. from those of ordinary plants; it is therefore probable that all leaves are to a slight degree irritable. Even if an insect alights on a leaf, a slight molecular change is probably trans- mitted to some distance across its tissue, with the sole difference that no perceptible effect is produced. We have some evidence in favour of this belief, for we know that a single touch on the glands of Drosera does not excite inflec- tion; yet it must produce some effect, for if the glands have been immersed in a solution of camphor, inflection follows within a shorter time than would have followed from the effects of camphor alone. So again with Dionwa, the blades in their ordinary state may be roughly touched without their closing; yet some effect must be thus caused and trans- mitted across the whole leaf, for if the glands have recently absorbed animal matter, even a delicate touch causes them to close instantly. On the whole we may conclude that the acquirement of a high degree of sensitiveness and of the power of movement by certain genera of the Drose- race presents no greater difficulty than that presented by the similar but feebler powers of a multitude of other plants. The specialised nature of the sensitiveness possessed by Drosera and Dionwa, and by certain other plants, well deserves attention. A gland of Drosera may be forcibly hit once, twice, or even thrice, without any effect being produced, whilst the continued pressure of an extremely minute particle excites movement. On the other hand, a particle many times heavier may be gently laid on one of the filaments of Dionea with no effect ; but if touched only once by the slow movement of a delicate hair, the lobes close; and this differ- ence in the nature of the sensitiveness of these two plants stands in manifest adaptation to their manner of capturing insects. So does the fact, that when the central glands of Drosera absorb nitrogenous matter, they transmit a motor impulse to the exterior tentacles much more quickly than when they are mechanically irritated; whilst with Dionza the absorption of nitrogenous matter causes the lobes to press together with' extreme slowness, whilst a touch excites rapid movement. Somewhat analogous cases may be observed, as I have shown in another work, with the tendrils of various plants ; some being most excited by contact with fine fibres, others by contact with bristles, others with a flat or a creviced surface. The sensitive organs of Drosera and Dionæa are also specialised, so as not to be uselessly affected by the Car. XV.] ON THE DROSERACE. 295 weight or impact of drops of rain, or by blasts of air. This may be accounted for by supposing that these plants and their progenitors have grown accustomed to the repeated action of rain and wind, so that no molecular change is thus induced; whilst they have been rendered more sensitive by means of natural selection to the rarer impact or pressure of solid bodies. Although the absorption by the glands of Drosera of various fluids excites movement, there is a great difference in the action of allied fluids; for instance, between certain vegetable acids, and between citrate and phosphate of ammonia. The specialised nature and per- fection of the sensitiveness in these two plants is all the more astonishing as no one supposes that they possess nerves; and by testing Drosera with several substances which act powerfully on the nervous system of animals, it does not appear that they include any diffused matter analogous to nerve-tissue. Although the cells of Drosera and Dionza are quite as sensitive to certain stimulants as are the tissues which surround the terminations of the nerves in the higher animals, yet these plants are inferior even to animals low down in the scale, in not being affected except by stimulants in contact with their sensitive parts. They would, however, probably be affected by radiant heat; for warm water excites energetic movement. When a gland of Drosera, or one of the filaments of Dionza, is excited, the motor impulse radiates in all direc- tions, and is not, as in the case of animals, directed towards special points or organs. This holds good even in the case of Drosera when some exciting substance has been placed at two points on the disc, and when the tentacles all round are inflected with marvellous precision towards the two points. The rate at which the motor impulse is transmitted, though rapid in Dionæa, is much slower than in most or all animals. This fact, as well as that of the motor impulse not being specially directed to certain points, are both no doubt due to the absence of nerves. Nevertheless we perhaps see the pre- figurement of the formation of nerves in animals in the trans- mission of the motor impulse being so much more rapid down the confined space within the tentacles of Drosera than else- where, and somewhat more rapid in a longitudinal than ina transverse direction across the disc. These plants exhibit still more plainly their inferiority to animals in the absence of any reflex action, except in so far as the glands of Drosera, 296 CONCLUDING REMARKS. [Cuar. XV. when excited from a distance, send back some influence which causes the contents of the cells to become aggregated down to the bases of the tentacles. But the greatest inferiority of all is the absence of a central organ, able to receive impressions from all points, to transmit their effects in any definite direction, to store them up and reproduce them. Cuar. XVI] PINGUICULA VULGARIS. | 297 CHAPTER XVI. PINGUICULA. Pinguicula vulgaris—Structure of leaves—Number of insects and other objects caught—Movement of the margins of the leaves—Uses of this movement —Secretion, digestion, and absorption—Action of the secretion on various animal and vegetable substances—The effects of substances not containing soluble nitrogenous matter on the glands—Pinguicula grandiflora—Pin- guicula lusitanica, catches insects—Movement of the leaves, secretion and digestion, r PINGUICULA VULGARIS.— This plant grows in moist places, generally on mountains. It bears on an average eight, rather thick, oblong, light green * leaves, having scarcely any footstalk. A full-sized leaf is about 1} inch in length and } inch in breadth. The young central leaves are deeply concave, and project upwards; the older ones towards the outside are flat or convex, and lie close to the ground, form- ing a rosette from 3 to 4 inches in diameter. The margins of the leaves are incurved. Their upper surfaces are thickly covered with two sets of glandular hairs, differing in the size of the glands and in the length of their pedicels. The larger glands have a circular outline as seen from above, and are of moderate thickness; they are divided by radiating partitions into sixteen cells, containing light-green, homo- geneous fluid. They are supported on elongated, unicellular pedicels (containing a nucleus with a nucleolus) which rest on slight prominences. The small glands differ only in being formed of about half the number of cells, containing much paler fluid, and supported on much shorter pedicels. Near the midrib, towards the base of the leaf, the pedicels are multicellular, are longer than elsewhere, and bear smaller glands. All the glands secrete a colourless fluid, which is so viscid that I have seen a fine thread drawn out toa length * (According to Batalin (¢ Flora,’ green in plants grown in shady places. 1877) the yellowish-green colour is It is due to a yellow homogeneous peculiar to plants grown in strong substance found in the epidermal light, being replaced bya more lively cells andin the glands.—F. D.J] 298 PINGUICULA VULGARIS. (Cuar. XVI. of 18 inches; but the fluid in this case was secreted by a gland which had been excited. The edge of the leaf is translucent, and does not bear any glands; and here the spiral vessels, proceeding from the midrib, terminate in cells marked by a spiral line, somewhat like those within the glands of Drosera. The roots are short. Three plants were dug up in North Wales on June 20, and carefully washed ; each bore five or six unbranched roots, the longest of which was only 1+2 of an inch. ‘Two rather young plants were examined on September 28; these had a greater number of roots, namely eight and eighteen, all under 1 inch in length, and very little branched. I was led to investigate the habits of this plant by being told by Mr. W. Marshall that on the mountains of Cumber- land many insects adhere to the leaves. A friend sent me on June 23 thirty-nine leaves from North Wales, which were selected owing to objects of some kind adhering to them. Of these leaves, thirty-two had caught 142 insects, or on an average 4'4 per leaf, minute fragments of insects not being included. Besides the insects, small leaves belonging to four different kinds of plants, those of Erica tetralix being much the commonest, and three minute seedling plants, blown by the wind, adhered to nineteen of the leaves. One had caught as many as ten leaves of the Erica. Seeds or fruits, commonly of Carex and one of Juncus, besides bits of moss and other rubbish, likewise adhered to six of the thirty-nine leaves. The same friend, on June 27, collected nine plants bearing seventy-four leaves, and all of these, with the exception of three young leaves, had caught insects; thirty insects were counted on one leaf, eighteen on a second, and sixteen on a third. Another friend examined on August 22 some plants in Donegal, Ireland, and found insects on 70 out of 157 leaves; fifteen of these leaves were sent me, each having caught on an average 2°4 insects. To nine of them, leaves (mostly of Erica tetralix) ad- hered ; but they had been specially selected on this latter account. I may add that early in August my son found leaves of this same Erica and the fruits of a Carex on the leaves of a Pinguicula in Switzerland, probably Pinguicula alpina; some insects, but no great number, also adhered to the leaves of this plant, which had much better developed roots than those of Pinguicula vulgaris. In Cumberland, Mr. Marshall, on September 3, carefully examined for me ten plants bearing eighty leaves; and on sixty-three of these (i.e. on 79 per cent.) he found insects, 143 in number; so that each leaf had on an average 2°27 insects. A few days later he sent me some plants with sixteen seeds or fruits adhering to fourteen leaves. There was a seed on three leaves on the same plant. The sixteen seeds belonged to Cuar. XVI.] MOVEMENTS OF THE LEAVES. 299 nine different kinds, which could not be recognised, excepting one of Ranunculus, and several belonging to three or four distinct species of Carex. It appears that fewer insects are caught late in the year than earlier; thus in Cumberland from twenty to twenty-four insects were observed in the middle of July on several leaves, whereas in the beginning of September the average number was only 2°27. Most of the insects, in all the foregoing cases, were Diptera, but with many minute Hymenoptera, including some ants, a few small Coleoptera, larvee, spiders, and even small moths. We thus see that numerous insects and other objects are caught by the viscid leaves ; but we have no right to infer from this fact that the habit is beneficial to the plant, any more than in the before-given case of the Mirabilis, or of the horse-chestnut. But it will presently be seen that dead insects and other nitrogenous bodies excite the glands to increased secretion; and that the secretion then becomes acid and has the power of digesting animal substances, such as albumen, fibrin, &c. Moreover, the dissolved nitrogenous matter is absorbed by the glands, as shown by their limpid contents being aggregated into slowly moving granular masses of protoplasm. The same results follow when insects are naturally captured, and as the plant lives in poor soil and has small roots, there can be no doubt that it profits by its power of digesting and absorbing matter from the prey which it habitually captures in such large numbers. It will, however, be convenient first to describe the movements of the leaves. Movements of the Leaves.—That such thick, large leaves as those of Pinguicula vulgaris should have the power of curving inwards when excited has never even been suspected. It is necessary to select for experiment leaves with their glands secreting freely, and which have been prevented from cap- turing many insects; as old leaves, at least those growing in a state of nature, have their margins already curled so much inwards that they exhibit little power of movement, or move very slowly. I will first give in detail the more important experiments which were tried, and then make some concluding remarks, Experiment 1.—A young and almost upright leaf was selected, with its two lateral edges equally and very slightly incurved. A row of small flies was placed along one margin. When looked at next day, after 15 hrs., this margin, but not the other, was found folded inwards, 300 PINGUICULA VULGARIS. (Cuar. XVI. like the helix of the human ear, to the breadth of 345 of an inch, so as to lie partly over the row of flies (fig. 15). The glands on which the flies rested, as well as those on the over-lapping margin which had been brought into contact with the flies, were all secreting copiously. Experiment 2.—A row of flies was placed on one margin of a rather old leaf, which lay flat on the ground; and in this case the margin, after the same interval as before, namely 15 hrs., had only just begun to curl inwards; but so much secretion had been poured forth that the spoon-shaped tip of the leaf was filled with it. Experiment 3,—Fragments of a large fly were placed close to the apex of a vigorous leaf, as well as along half one margin. After 4 hrs. 20 m. there was decided incurvation, which increased a little during the afternoon, but was in the same state on the following morning. Near the apex both margins were inwardly curved. I have never seen a case of the apex itself being in the least curved towards the base of the leaf. After 48 hrs. (always reckoning from the time when the flies were placed on the leaf) the margin had everywhere begun to unfold. Experiment 4.—A large fragment of a fly was placed on a leaf, in a medial line, alittle beneath the apex. Both lateral margins were perceptibly incurved in 3 hrs., and after 4 hrs. 20 m. to such a degree that the fragment was clasped by both margins. After 24 hrs. the two infolded edges near the apex (for the lower part of the leaf was not at all affected) were measured and found to be *11 of an inch (2°795 mm.) apart. The fly was now removed, and a stream of water poured over the leaf so as to wash the surface; and after Fig. 15. 24 hrs. the margins were *25 of an‘inch (6°349 (Pinguicula vulgaris.) mm.) apart, so that they were largely unfolded. Outline of leaf with left After an additional 24 hrs. they were completely margin inflected over a ynfolded. Another fly was now put on the same Aa a e spot to see whether this leaf, on which the first fly had been left 24 hrs., would move again; after 10 hrs. there was a trace of incurvation, but this did not increase during the next 24 hrs. 1 of an inch (2°54 mm.), that is, across between one-third and one-fourth of the space between the edge and midrib. Any object, such as a moderately sized insect, would thus be brought slowly into contact with a far larger number of glands, inducing much more secretion and absorption, than would otherwise have been the case. That this would be highly serviceable to the plant, we may infer from the fact that Drosera has acquired highly developed powers of move- ment, merely for the sake of bringing all its glands Into contact with captured insects. So again, after a leaf of Dionæa has caught an insect, the slow pressing together of the two lobes serves merely to bring the glands on both sides into contact with it, causing also the secretion charged with animal matter to spread by capillary attraction over the whole surface. In the case of Pinguicula, as soon as an insect has been pushed for some little distance towards the midrib, immediate re-expansion would be beneficial, as the margins could not capture fresh prey until they were un- folded. The service rendered by this pushing action, as well as that from the marginal glands being brought into contact for a short time with the upper surfaces of minute captured insects, may perhaps account for the peculiar move- ments of the leaves: otherwise, we must look at these move- ments as a remnant of a more highly developed power for- merly possessed by the progenitors of the genus. In the four British species, and, as I hear from Prof. Dyer, in most or all the species of the genus, the edges of the leaves are in some degree naturally and permanently incurved. This incurvation serves, as already shown, to prevent insects from being washed away by the rain; but it likewise serves for another end. When a number of glands have been powerfully excited by bits of meat, insects, or any other stimulus, the secretion often trickles down the leaf, and is caught by the incurved edges, instead of rolling off and being lost. As it runs down the channel, fresh glands are able to absorb the animal matter held in solution. Moreover, the secretion often collects in little pools within the channel, Cuar. XVI] SECRETION, ABSORPTION, DIGESTION. 307 or in the spoon-like tips of the leaves; and I ascertained that bits of albumen, fibrin, and gluten are here dissolved more quickly and completely than on the surface of the leaf, where the secretion cannot accumulate; and so it would be with naturally caught insects. The secretion was repeatedly seen thus to collect on the leaves of plants protected from the rain; and with exposed plants there would be still greater need of some provision to prevent, as far as possible, the secretion, with its dissolved animal matter, being wholly lost. It has already been remarked that plants growing in a state of nature have the margins of their leaves much more strongly incurved than those grown in pots and prevented from catching many insects. We have seen that insects washed down by the rain from all parts of the leaf often lodge within the margins; which are thus excited to curl farther inwards ; and we may suspect that this action, many times repeated during the life of the plant, leads to their permanent and well-marked incurvation. I regret that this view did not occur to me in time to test its truth. It may here be added, though not immediately bearing on our subject, that when a plant is pulled up, the leaves immediately curl downwards so as to almost conceal the roots,—a fact which has been noticed by many persons. I suppose that this is due to the same tendency which causes the outer and older leaves to lie flat on the ground. It further appears that the flower-stalks are to a certain extent irritable, for Dr. Johnson states that they “bend backwards if rudely handled.” * Secretion, Absorption, and Digestion —I will first give my observations and experiments, and then a summary of the results. The Effects of Objects containing Soluble Nitrogenous Matter. (1) Flies were placed on many leaves, and excited the glands to secrete copiously; the secretion always becoming acid, though not so vefore. After a time these insects were rendered so tender that their imbs and bodies could be separated by a mere touch, owing no doubt * ‘English Botany,’ by Sir J. E. bending or shaking a turgescent stem. Smith; with coloured figures by J. This would be likely to occur in the Sowerby ; edit. of 1832, tab. 24, 25, course of the “rough handling,” and 26. [It is well known that perma- we may perhaps thus account for nent curvatures may be produced by Dr, Johnson’s curvatures.—F, D,] I2 308 PINGUICULA VULGARIS. [Cuar. XVI. to the digestion and disintegration of their muscles. The glands in contact with a small fly continued to secrete for four days, and then became almost dry. A narrow strip of this leaf was cut off, and the glands of the longer and shorter hairs, which had lain in contact for the four days with the fly, and those which had not touched it, were compared under the microscope, and presented a wonderful contrast. Those which had been in contact were filled with brownish granular matter, the others with homogeneous fluid. There could therefore be no doubt that the former had absorbed matter from the fly. (2) Small bits of roast meat, placed on a leaf, always caused much acid secretion in the course of a few hours—in one case within 40 m. When thin fibres of meat were laid along the margin of a leaf which stood almost upright, the secretion ran down to the ground. Angular bits of meat, placed in little pools of the secretion near the margin, were in the course of two or three days much reduced in size, rounded, rendered more or less colourless and transparent, and so much softened that they fell to pieces on the slightest touch. In only one instance was a very minute particle completely dissolved, and this occurred within 48 hrs. When only a small amount of secretion was excited, this was generally absorbed in from 24 hrs. to 48 hrs.; the glands being left dry. But when the supply of secretion was copious, round either a single rather large bit of meat, or round several small bits, the glands did not become dry until six or seven days had elapsed. The most rapid case of absorption observed by me was when a small drop of an infusion of raw meat was placed on a leaf, for the glands here became almost dry in3 hrs. 20 m. Glands excited by small articles of meat, and which have quickly absorbed their own secretion, gin to secrete again in the course of seven or eight days from the time when the meat was given them. (8) Three minute cubes of tough cartilage from the leg-bone of a sheep were laid on a leaf. After 10 hrs, 30 m. some acid secretion was excited, but the cartilage appeared little or not at all affected. After 24 hrs. the cubes were rounded and much reduced in size; after 32 hrs. they were softened to the centre, and one was quite liquefied; after 35 hrs. mere traces of solid cartilage were left; and after 48 hrs. a trace could still be seen through a lens in only one of the three. After 82 hrs. not only were all three cubes completely liquefied, but all the secretion was absorbed and the glands left dry. (4) Small cubes of albumen were placed on a leaf; in 8 hrs. feebly acid secretion extended to a distance of nearly 3, of an inch round them, and the angles of one cube were rounded. After 24 hrs. the angles of all the cubes were rounded, and they were rendered through- out very tender; after 30 hrs. the secretion began to decrease, and after 48 hrs. the glands were left dry; but very minute bits of albumen were still left undissolved. (5) Smaller cubes of albumen (about sy or a of an inch, -508 or +423 mm.) were placed on four glands; after 18 hrs. one cube was completely dissolved, the others being much reduced in size, softened Cuar. XVI.] SECRETION, ABSORPTION, DIGESTION. 309 and transparent. After 24 hrs. two of the cubes were completely dissolved, and already the secretion on these glands was almost wholly absorbed. After 42 hrs, the two other cubes were completely dissolved. These four glands began to secrete again after eight or nine days. (6) Two large cubes of albumen (fully 5 of an inch, 1°27 mm.) were placed, one near the midrib and the other near the margin of a leaf; in 6 hrs. there was much secretion, which after 48 hrs. accumulated in a little pool round the cube near the margin. This cube was much more dissolved than that on the blade of the leaf; so that after three days it was greatly reduced in size, with all the angles rounded, but it was too large to be wholly dissolved. ‘The secretion was partially absorbed after four days. The cube on the blade was much less reduced, and the glands on which it rested began to dry after only two days. (7) Fibrin excites less secretion than does meat or albumen. Several trials were made, but I will give only three of them. Two minute shreds were placed on some glands, and in 3 hrs. 45 m. their secretion was plainly increased. The smaller shred of the two was completely liquefied in 6 hrs. 15 m., and the other in 24 hrs.; but even after 48 hrs. a few granules of fibrin could still be seen through a lens floating in both drops of secretion. After 56 hrs. 30 m. these granules were completely dissolved. A third shred was placed ina little pool of secretion, within the margin of a leaf where a seed had been lying, and this was completely dissolved in the course of 15 hrs. 80 m. (8) Five very small bits of gluten were placed on a leaf, and they excited so much secretion that one of the bits glided down into the marginal furrow. After a day all five bits seemed much reduced in size, but none were wholly dissolved. On the third day | pushed two of. them which had begun to dry, on to fresh glands. On the fourth day undissolved traces of three out of the five bits could still be detected, the other two having quite disappeared ; but I am doubtful whether they had really been completely dissolved. Two fresh bits were now placed, one near the middle and the other near the margin of another leaf; both excited an extraordinary amount of secretion; that near the margin had a little pool formed round it, and was much more reduced in size than that on the blade, but after four days was not completely dissolved. Gluten, therefore, excites the glands greatly, but is dissolved with much difficulty, exactly as in the case of Drosera. I regret that I did not try this substance after having been immersed in weak hydrochloric acid, as it would then probably have been quickly dissolved. (9) A small square thin piece of pure gelatine, moistened with water, was placed on a leaf, and excited very little secretion in 5 hrs. 30 m., but later in the day a greater amount. After 24 hrs. the whole square was completely liquefied; and this would not have occurred had it been left in water. The liquid was acid. (10) Small particles of chemically prepared casein excited acid secretion, but were not quite dissolved after two days; and the glands 310 PINGUICULA VULGARIS. [Cuar. XVI. then began to dry. Nor could their complete dissolution have been expected from what we have seen with Drosera. (11) Minute drops of skimmed milk were placed on a leaf, and these caused the glands to secrete freely. After 3 hrs. the milk was found curdled, and after 23 hrs. the curds were dissolved. On placing the now clear drops under the microscope, nothing could be detected except some oil-globules. The secretion, therefore, dissolves fresh casein. (12) Two fragments of a leaf were immersed for 17 hrs., each in a drachm of a solution of carbonate of ammonia, of two strengths, namely of one part to 437 and 218 of water. The glands of the longer and shorter hairs were then examined, and their contents found aggregated into granular matter of a brownish-green colour. These granular masses were seen by my son slowly to change their forms, and no doubt consisted of protoplasm. The aggregation was more strongly pronounced, and the movements of the protoplasm more rapid, within the glands subjected to the stronger solution than in the others. The experiment was repeated with the same result; and on this occasion I observed that the protoplasm had shrunk a little from the walls of the single elongated cells forming the pedicels. In order to observe the process of aggregation, a narrow strip of leaf was laid edgeways under the microscope, and the glands were seen to be quite transparent; a little of the stronger solution (viz. one part to 218 of water) was now added under the covering glass; after an hour or two the glands contained very fine granular matter, which slowly became coarsely granular and slightly opaque; but even after 5 hrs. not as yet of a brownish tint. By this time a few rather large, transparent, globular masses appeared within the upper ends of the pedicels, and the protoplasm lining their walls had shrunk a little. It is thus evident that the glands of Pinguicula absorb carbonate of ammonia; but they do not absorb it, or are not acted on by it, nearly so quickly as those of Drosera. (13) Little masses of the orange-coloured pollen of the common pea, placed on several leaves, excited the glands to secrete freely. Even a very few grains which accidentally fell on a single gland caused the drop surrounding it to increase so much in size, in 23 hrs., as to be manifestly larger than the drops on the adjoining glands. Grains subjected to the secretion for 48 hrs, did not emit their tubes; they were quite discoloured, and seemed to contain less matter than before; that which was left being of a dirty colour, including globules of oil. ‘They thus differed in appearance from other grains kept in water for the same length of time. The glands in contact with the pollen-grains had evidently absorbed matter from them; for they had lost their natural pale-green tint, and contained aggregated globular masses of protoplasm. (14) Square bits of the leaves of spinach, cabbage, and a saxifrage, and the entire leaves of Erica tetralix, all excited the glands to increased secretion. The spinach was the most effective, for it caused the secretion evidently to increase in 1 hr. 40 m., and ultimately to run Cuar. XVI.] SECRETION, ABSORPTION, DIGESTION. 311 some way down the leaf; but the glands soon began to dry, viz. after 35 hrs. The leaves of Erica tetralix began to act in 7 hrs. 30 m., but never caused much secretion; nor did the bits of leaf of the saxifrage, though in this case the glands continued to secrete for seven days. Some leaves of Pinguicula were sent me from North Wales, to which leaves of Erica tetralix and of an unknown plant adhered; and the glands in contact with them had their contents plainly aggregated, as if they had been in contact with insects; whilst the other glands on the same leaves contained only clear homogeneous fluid. (15) Seeds.—A considerable number of seeds or fruits selected by hazard, some fresh and some a year old, some soaked for a short time in water and some not soaked, were tried. ‘The ten following kinds, namely, cabbage, radish, Anemone nemorosa, Rumex acetosa, Carex sylvatica, mustard, turnip, cress, Ranunculus acris, and Avena pubescens, all excited much secretion, which was in several cases tested and found always acid. The five first-named seeds excited the glands more than the others. The secretion was seldom copious until about 24 hrs. had elapsed, no doubt owing to the coats of the seeds not being easily permeable. Nevertheless, cabbage seeds excited some secretion in 4 hrs. 30 m.; and this increased so much in 18 hrs. as to run down the leaves. The seeds, or properly the fruits, of Carex are much oftener found adhering to leaves in a state of nature than those of any other genus ; and the fruits of Carex sylvatica excited so much secretion that in 15 hrs. it ran into the incurved edges; but the glands ceased to secrete after 40 hrs. On the other hand, the glands on which the seeds of the Rumex and Avena rested continued to secrete for nine days. The nine following kinds of seeds excited only a slight amount of secretion, namely, celery, parsnip, caraway, Linum grandiflorum, Cassia, Trifolium pannonicum, Plantago, onion, and Bromus. Most of these seeds did not excite any secretion until 48 hrs. had elapsed, and in the case of the Trifolium only one seed acted, and this not until the third day. Although the seeds of the Plantago excited very little secretion, the glands continued to secrete for six days. Lastly, the five following kinds excited no secretion, though left on the leaves for two or three days, namely, lettuce, Erica tetralix, Atriplex hortensis, Phalaris canariensis, and wheat.. Nevertheless, when the seeds of the lettuce, wheat, and Atriplex were split open and applied to leaves, secretion was excited in considerable quantity in 10 hrs., and I believe that some was excited in six hours. In the case of the Atriplex the secretion ran down to the margin, and after 24 hrs. I speak of it in my notes “as immense in quantity, and acid.” The split seeds also of the Trifolium and celery acted powerfully and quickly, though the whole seeds caused, as we have scen, very little secretion, and only after a long interval of time. A slice of the common pea, which however was not tried whole, caused secretion in 2 hrs, From these facts we may conclude that the great difference in the degree and rate at which various kinds of seeds excite secretion, is chiefly or wholly due to the different permeability of their coats. 312 PINGUICULA VULGARIS. [Cuar. XVI. Some thin slices of the common pea, which had been previously soaked for 1 hr. in water, were placed on a leaf, and quickly excited much acid secretion. After 24 hrs. these slices were compared under a high power with others left in water for the same time; the latter contained so many fine granules of legumin that the slide was rendered muddy; whereas the slices which had been subjected to the secretion were much cleaner and more transparent, the granules of legumin apparently having been dissolved. A cabbage seed which had lain for two days on a leaf and had excited much acid secretion, was cut into slices, and these were compared with those of a seed which had been left for the same time in water. Those subjected to the secretion were of a paler colour; their coats presenting the greatest differences, for they were of a pale dirty tint instead of chestnut-brown. The glands on which the cabbage seeds had rested, as well as those bathed by the surrounding secretion, differed greatly in appearance from the other glands on the same leaf, for they all contained brownish granular matter, proving that they had absorbed matter from the seeds. That the secretion acts on the seeds was also shown by some of them being killed, or by the seedlings being injured. Fourteen cabbage seeds were left for three days on leaves and excited much secretion ; they were then placed on damp sand under conditions known to be favourable for germination. ‘Three never germinated, and this was a far larger proportion of deaths than occurred with seeds of the same lot, which had not been subjected to the secretion, but were otherwise treated in the same manner. Of the eleven seedlings raised, three had the edges of their cotyledons slightly browned, as if scorched; and the cotyledons of one grew into a curious indented shape. Two mustard seeds germinated; but their cotyledons were marked with brown patches and their radicles deformed. Of two radish seeds, neither germinated; whereas of many seeds of the same lot not subjected to the secretion, all, excepting one, germinated. Of the two Rumex seeds, one died and the other germinated ; but its radicle was brown and soon withered. Both seeds of the Avena germinated, one grew well, the other had its radicle brown and withered. Of six seeds of the Erica none germinated, and when cut open after having been left for five months on damp sand, one alone seemed alive. ‘Twenty-two seeds of various kinds were found adhering to the leaves of plants growing in a state of nature; and of these, though kept for five months on damp sand, none germinated, some being then evidently dead. The Effects of Objects not containing Soluble Nitrogenous Matter. (16) It has already been shown that bits of glass, placed on leaves, excite little or no secretion. The small amount which lay beneath the fragments was tested and found not acid. A bit of wood excited no secretion; nor did the several kinds of seeds of which the coats are not permeable to the secretion, and which, therefore, acted like inorganic bodies. Cubes of fat, left for two days on a leaf, produced no effect. Cnar, XVI] SECRETION, ABSORPTION, DIGESTION. 313 (17) A particle of white sugar, placed on a leaf, formed in 1 hr. 10 m. a large drop of fluid, which in the course of 2 additional hours ran down into the naturally inflected margin. This fluid was not in the least acid, and began to dry up, or more probably was absorbed, in 5 hrs. 830m. The experiment was repeated; particles being placed on a leaf, and others of the same size on a slip of glass in a moistened state; both being covered by a bell-glass. This was done to see whether the increased amount of fluid on the leaves could be due to mere deliquescence; but this was proved not to be the case. The particle on the leaf caused so much secretion that in the course of 4 hrs. it ran down across two-thirds of the leaf. After 8 hrs. the leaf, which was concaye, was actually filled with very viscid fluid; and it particu- larly deserves notice that this, as on the former occasion, was not in the least acid. This great amount of secretion may be attributed to exosmose. The glands which had been covered for 24 hrs, by this fluid did not differ, when examined under the microscope, from others on the same leaf, which had not come into contact with it. This is an interesting fact in contrast with the invariably aggregated condition of glands which have been bathed by the secretion, when holding animal matter in solution. (18) Two particles of gum arabic were placed on a leaf, and they certainly caused in 1 hr. 20 m, a slight increase of secretion. This continued to increase for the next 5 hrs., that is for as long a time as the leaf was observed. (19) Six small particles of dry starch of commerce were placed on a leaf, and one of these caused some secretion in 1 hr. 15 m., and the others in from 8 hrs. to 9 hrs. The glands which had thus been excited to secrete soon became dry, and did not begin to secrete again until the sixth day. A larger bit of starch was then placed on a leaf, and no secretion was excited in 5 hrs. 30 m.; but after 8 hrs. there was a considerable supply, which increased so much in 24 hrs. as to run down the leaf to the distance of ? of an inch. This secretion, though so abundant, was not in the least acid. As it was so copiously excited, and as seeds not rarely adhere to the leaves of naturally growing plants, it occurred to me that the glands might perhaps have the power of secreting a ferment, like ptyaline, capable of dissolving starch; so I carefully observed the above six small particles during several days, but they did not seem in the least reduced in bulk. A particle was also left for two days in a little pool of secretion, which had run down from a piece of spinach leaf; but although the particle was so minute no diminution was perceptible. We may therefore conclude that the secretion cannot dissolve starch. The increase caused by this substance may, I presume, be attributed to exosmose. But lam surprised that starch acted so quickly and powerfully as it did, though in a less degree than sugar. Colloids are known to possess some slight power of dialysis; and on placing the leaves of a Primula in water, and others in syrup and diffused starch, those in the starch became flaccid, but to a less degree and at a much slower rate than the leaves in the syrup ; those in water remaining all the time crisp. 9 314 PINGUICULA VULGARIS. (Cuar. XVI. From the foregoing experiments and observations we see that objects not containing soluble matter have little or no power of exciting the glands to secrete. Non-nitrogenous fluids, if dense, cause the glands to pour forth a large supply of viscid fluid, but this is not in the least acid. On the other hand, the secretion from glands excited by contact with nitrogenous solids or liquids is invariably acid, and is so copious that it often runs down the leaves and collects within the naturally incurved margins. The secretion in this state has the power of quickly dissolving, that is of digesting, the muscles of insects, meat, cartilage, albumen, fibrin, gelatine, and casein as it exists in the curds of milk.* The glands are strongly excited by chemically prepared casein and gluten; but these substances (the latter not having been soaked in weak hydrochloric acid) are only partially dissolved, as was likewise the case with Drosera. The secretion, when containing animal matter in solution, whether derived from solids or from liquids, such as an infusion of raw meat, milk, or a weak solution of carbonate of ammonia, is quickly absorbed; and the glands, which were before limpid and of a greenish colour, become brownish and contain masses of aggregated granular matter. This matter, from its spontaneous movements, no doubt consists of protoplasm. No such effect is produced by the action of non- nitrogenous fluids. After the glands have been excited to secrete freely, they cease for a time to secrete, but begin again in the course of a few days. Glands in contact with pollen, the leaves of other plants, and various kinds of seeds, pour forth much acid secretion, and afterwards absorb matter probably of an albuminous nature from them. Nor can the benefit thus derived be insignificant, for a considerable amount of pollen must be blown from the many wind-fertilised carices, grasses, &c., growing where Pinguicula lives, on to the leaves thickly covered with viscid glands and forming large rosettes. Even * [Pfeffer (‘Ueber fleischfessende same use in the Italian Alps. The Pflanzen,’ in the ‘Landwirthschaft. property of the plant seems to be Jahrbücher, 1877) quotes Linneus widely known among primitive (‘ Flora Lapponica,’ 1737, p.10) tothe people, for, within the last 30 years, effect that certain Lapland tribes use it was used as rennet by mountain the leaves of Pinguicula to coagulate farmers in North Wales. I have milk. Pfeffer learnt from an old myself succeeded in curdling milk shepherd that they are put to the with this vegetable rennet.—F. D.] Cuar. XVL] PINGUICULA LUSITANICA. 315 a few grains of pollen on a single gland causes it to secrete copiously. We have also seen how frequently the small leaves of Erica tetralix and of other plants, as well as various kinds of seeds and fruits, epecially of Carex, adhere to the leaves. One leaf of the Pinguicula had caught ten of the little leaves of the Erica; and three leaves on the same plant had each caught a seed. Seeds subjected to the action of the secretion are sometimes killed, or the seedlings injured. We may therefore conclude that Pinguicula vulgaris, with its small roots, is not only supported to a large extent by the extraordinary number of insects which it habitually captures, but likewise draws some nourishment from the pollen, leaves, and seeds of other plants which often adhere to its leaves. It is therefore partly a vegetable as well as an animal feeder. PINGUICULA GRANDIFLORA. This species is so closely allied to the last that it is ranked by Dr. Hooker as a sub-species. It differs chiefly in the larger size of its leaves, and in the glandular hairs near the basal part of the mid-rib being longer. But it likewise differs in constitution; I hear from Mr. Ralfs, who was so kind as to send me plants from Cornwall, that it grows in rather different sites; and Dr. Moore, of the Glasnevin Botanic Gardens, informs me that it is much more manage- able under culture, growing freely and flowering annually ; whilst Pinguicula vulgaris has to be renewed every year. Mr. Ralfs found numerous insects and fragments of insects adhering to almost all the leaves. These consisted chiefly of Diptera, with some Hymenoptera, Homoptera, Coleoptera, and a moth; on one leaf there were nine dead insects, besides a few still alive. He also observed a few fruits of Carex pulicaris, as wellas the seeds of this same Pinguicula, adhering to the leaves. I tried only two experiments with this species ; firstly, a fly was placed near the margin of a leaf, and after 16 hrs. this was found well inflected. Secondly, several small flies were placed in a row along one margin of another leaf, and by the next morning this whole margin was curled inwards, exactly as in the case of Pinguicula vulgaris. PINGUICULA LUSITANICA. This species, of which living specimens were sent me by Mr. Ralfs from Cornwall, is very distinct from the two fore- 316 PINGUICULA LUSITANICA. [Cuar. XVI. going ones. The leaves are rather smaller, much more transparent, and are marked with purple branching veins. The margins of the leaves are much more involuted ; those of the older ones extending over a third of the space between the midrib and the outside. As in the two other species, the glandular hairs consist of longer and shorter ones, and have the same structure; but the glands differ in being purple, and in often containing granular matter before they have been excited. In the lower part of the leaf, almost half the space on each side between the midrib and margin is destitute of glands; these being replaced by long, rather stiff, multi- cellular hairs, which intercross over the midrib. These hairs perhaps serve to prevent insects from settling on this part of the leaf, where there are no viscid glands by which they could be caught; but it is hardly probable that they were developed for this purpose. The spiral vessels proceeding from the midrib terminate at the extreme margin of the leaf in spiral cells; but these are not so well developed as in the two preceding species. The flower-peduncles, sepals, and petals, are studded with glandular hairs, like those on the leaves. The leaves catch many small insects, which are found chiefly beneath the involuted margins, probably washed there by the rain, The colour of the glands on which insects have long lain is changed, being either brownish or pale purple, with their contents coarsely granular ; so that they evidently absorb matter from their prey. Leaves of the Erica tetralix, flowers of a Galium, scales of grasses, &c., likewise adhered to some of the leaves. Several of the experiments which were tried on Pinguicula vulgaris were repeated on Pinguicula lusitanica, and these will now be given. (1) A moderately sized and angular bit of albumen was placed on one side of a leaf, halfway between the midrib and the naturally involuted margin. In 2 hrs. 15 m. the glands poured forth much secretion, and this side became more infolded than the opposite one. The inflection increased, and in 3 hrs. 30 m. extended up almost to the apex. After 24 hrs. the margin was rolled into a cylinder, the outer surface of which touched the blade of the leaf and reached to within the 5 of an inch of the midrib. After 48 hrs. it began to unfold, and in 72 hrs. was completely unfolded. The cube was rounded and greatly reduced in size; the remainder being in a semi-liquefied state. (2) A moderately sized bit of albwmen was placed near the apex of Cuar. XVL] PINGUICULA LUSITANICA. 317 a leaf, under the naturally incurved margin. In 2 hrs. 30 m. much secretion was excited, and next morning the margin on this side was more incurved than the opposite one, but not to so great a degree as in the last case. The margin unfolded at the same rate as before. aF proportion of the albumen was dissolved, a remnant being stil! eit. (3) Large bits of albumen were laid in a row on the midribs of two leaves, but produced in the course of 24 hrs. no effect; nor could this have been expected, for even had glands existed here, the long bristles would have prevented the albumen from coming in contact with them. On both leaves the bits were now pushed close to one margin, and in 3 hrs. 30 m. this became so greatly inflected that the outer surface touched the blade; the opposite margin not being in the least affected. After three days the margins of both leaves with the albumen were still as much inflected as ever, and the glands were still secreting copiously. With Pinguicula vulgaris I have never seen inflection lasting so long. (4) Two cabbage seeds, after being soaked for an hour in water, were placed near the margin of a leaf, and caused in 3 hrs. 20 m. increased secretion and incurvation. After 24 hrs. the leaf was partially unfolded, but the glands were still secreting freely. These began to dry in 48 hrs., and after 72 hrs. were almost dry. The two seeds were then placed on damp sand under favourable conditions for growth ; but they never germinated, and after a time were found rotten. They had no doubt been killed by the secretion. (5) Small bits of a spinach leaf caused in 1 hr. 20 m. increased se- cretion; and after 3 hrs. 20 m. plain incurvation of the margin. The margin was well inflected after 9 hrs. 15 m., but after 24 hrs. was almost fully re-expanded. The glands in contact with the spinach became dry in 72 hrs. Bits of albumen had been placed the day before on the opposite margin of this same leaf, as well as on that of a leaf with cabbage seeds, and these margins remained closely inflected for 72 hrs., showing how much more enduring is the effect of albumen than of spinach leaves or cabbage seeds. (6) A row of small fragments of glass was laid along one margin of a leaf; no effect was produced in 2 hrs. 10 m., but after 3 hrs. 25 m. there seemed to be a trace of inflection, and this was distinct, though not strongly marked, after 6 hrs. The glands in contact with the fragments now secreted more freely than before; so that they appear to be more easily excited by the pressure of inorganic objects than are the glands of Pinguicula vulgaris. The above slight inflection of the margin had not increased after 24 hrs., and the glands were now beginning to dry. The surface of a leaf, near the midrib and towards the base, was rubbed and scratched for some time, but nomovement ensued. The long hairs which are situated here were treated in the same manner, with no effect. This latter trial was made because I thought that the hairs might perhaps be sensitive to a touch, like the filaments of Dionza, 318 PINGUICULA LUSITANICA. [Cuar. XVI. (7) The flower-peduncles, sepals and petals bear glands in general appearance like those on the leaves. A piece of a flower-peduncle was therefore left for 1 hr. in a solution of one part of carbonate of ammonia to 437 of water, and this caused the glands to change from bright pink to a dull purple colour; but their contents exhibited no distinct aggregation. After 8 hrs. 30 m. they became colourless. Two minute cubes of albumen were placed on the glands of a flower- peduncle, and another cube on the glands of a sepal; but they were not excited to increased secretion, and the albumen after two days was not in the least softened. Hence these glands apparently differ greatly in function from those on the leaves. From the foregoing observations on Pinguicula lusitanica we see that the naturally much incurved margins of the leaves are excited to curve still farther inwards by contact with organic and inorganic bodies; that albumen, cabbage seeds, bits of spinach leaves, and fragments of glass, cause the glands to secrete more freely ; that albumen is dissolved by the secretion, and cabbage seeds killed by it; and lastly that matter is absorbed by the glands from the insects which are caught in large numbers by the viscid secretion. The glands on the flower-peduncles seem to have no such power. ‘This species differs from Pinguicula vulgaris and grandiflora in the margins of the leaves, when excited by organic bodies, being inflected to a greater degree, and in the inflection lasting for a longer time. ‘The glands, also, seem to be more easily excited to increased secretion by bodies not yielding soluble nitrogenous matter. In other respects, as far as my observa- tions serve, all three species agree in their functional powers. Cuar. XVIL] UTRICULARIA NEGLECTA. 319 CHAPTER XVII. UTRICULARIA. Utricularia neglecta— Structure of the bladder—The uses of the several parts— Number of imprisoned animals—Manner of capture—The bladders cannot digest animal matter, but absorb the products of its decay—Experiments on the absorption of certain fluids by the quadrifid processes—Absorption by the glands—Summary of the observations on absorption—Development of the bladders— Utricularia vulgaris — Utricularia minor — Utricularia clandestina, I was led to investigate the habits and structure of the species of this genus partly from their belonging to the same natural family as Pinguicula, but more especially by Mr. Holland’s statement, that “water insects are often found imprisoned in the bladders,” which he suspects “are destined for the plant to feed on.” * The plants which I first received as Utricularia vulgaris from the New Forest in Hampshire and from Cornwall, and which I have chiefly worked on, have been determined by Dr. Hooker to be a very rare British species, the Utricularia neglecta of Lehm.t I subse- quently received the true Utricularia vulgaris from Yorkshire. Since drawing up the following description from my own observations and those of my son, Francis Darwin, an important memoir by Prof. Cohn on Utricularia vulgaris has appeared ;{ and it has been no small satisfaction to me to find that my account agrees almost completely with that of this distinguished observer. I will publish my description as it stood before reading that by Prof. Cohn, adding occasionally some statements on his authority. * The ‘Quart. Mag. of the High Wycombe Nat. Hist. Soc.’ July 1868, p. 5. Delpino (‘ Ult. Osservaz. sulla Dicogamia,’ &c. 1868-1869, p. 16) also quotes Crouan as having found (1858) crustaceans within the blad- ders of Utricularia vulgaris. t+ Iam much indebted to the Rey. H. M. Wilkinson, of Bistern, for having sent me several fine lots of this species from the New Forest. Mr. Ralfs was also so kind as to send me living plants of the same species from near Penzance in Cornwall. + ‘ Beiträge zur Biologie der Pflan- zen,’ drittes Heft, 1875. D 320 UTRICULARIA NEGLECTA. [Cmar. XVII. Utricularia neglecta.—The general appearance of a branch (about twice enlarged), with the pinnatifid leaves bearing bladders, is represented in the following sketch (fig. 17). The leaves continually bifurcate, so that a full-grown one terminates in from twenty to thirty points. Each point is tipped by a short, straight bristle ; and slight notches on the Fic. 17. (Utricularia neglecta.) Branch with the divided leaves bearing bladders; about twice enlarged. sides of the leaves bear similar bristles. On both surfaces there are many small papille, crowned with two hemi- spherical cells in close contact. The plants float near the surface of the water, and are quite destitute of roots, even during the earliest period of growth.* They commonly * Linfer that this is the case from from the ‘ Videnskabelige Meddelel- a drawing of a seedling given by Dr. ser; Copenhagen, 1874, Nos. 3-7, pp. Warming in his paper, “ Bidrag til 33-58. [Cf. Kamienski, ‘ Bot. Zeit.’ Kundskaben om Lentibulariacee,” 1877, p. 765.] Cair. XVII.] STRUCTURE OF THE BLADDER. 821 inhabit, as more than one observer has remarked to me, remarkably foul ditches. The bladders offer the chief point of interest. There are often two or three on the same divided leaf, generally near the base ; though I have seen a single one growing from the stem. ‘They are supported on short footstalks. When fully grown, they are nearly 75 of an inch (2°54 mm.) in length. They are translucent, of a green colour, and the walls are formed of two layers of cells. The exterior cells are poly- gonal and rather large; but at many of the points where the angles meet, there are smaller rounded cells. These latter support short conical projections, surmounted by two hemi- spherical cells in such close apposition that they appear Fig. 18. (Utricularia neglecta.) Bladder; much enlarged. c, collar indistinctly seen through the walls. united ; but they often separate a little when immersed in certain fluids. The papille thus formed are exactly like those on the surfaces of the leaves. Those on the same bladder vary much in size; and there are a few, especially on very young bladders, which have an elliptical instead of a circular outline. The two terminal cells are transparent, but must hold much matter in solution, judging from the area coagulated by prolonged immersion in alcohol or ether. The bladders are filled with water. They generally, but by no means always, contain bubbles of air. According to the quantity of the contained water and air, they vary much f è 822 UTRICULARIA NEGLECTA. (Cuar. XVII. in thickness, but are always somewhat compressed. At an early stage of growth, the flat or ventral surface faces the axis or stem; but the footstalks must have some power of movement; for in plants kept in my greenhouse the ventral surface was generally turned either straight or obliquely downwards. The Rev. H. M. Wilkinson examined plants for me in a state of nature, and found this commonly to be the case, but the younger bladders often had their valves turned upwards. The general appearance of a bladder viewed laterally, with the appendages on the near side alone represented, is shown on the preceding page (fig. 18). The lower side, where the footstalk arises, is nearly straight, and I have called it Mn DDN Qe an Ala (nf SERRA SN PSR AINIS WARS OLN TIA (NAMES ENTS ZL, Aa ee Fia. 19. (Utricularia neglecta.) Valve of bladder; greatly enlarged. the ventral surface. The other or dorsal surface is convex, and terminates in two long prolongations, formed of several rows of cells, containing chlorophyll, and bearing, chiefly on the outside, six or seven long, pointed, multicellular bristles. These prolongations of the bladder may be conveniently called the antenne, for the whole bladder (sce fig. 17) curiously resembles an entomostracan crustacean, the short footstalk representing the tail. In fig. 18, the near antenna alone is shown. Beneath the two antenne the end of the bladder is slightly truncated, and here is situated the most important part of the whole structure, namely the entrance and valve. On each side of the entrance from three to rarely seven long, multicellular bristles project outwards; but only oe Czar. XVII.] STRUCTURE OF THE BLADDER. 323 those (four in number) on the near side are shown in the drawing. These bristles, together with those borne by the antenne, form a sort of hollow cone surrounding the entrance. The valve slopes into the cavity of the bladder, or upwards in fig. 18. It is attached on all sides to the bladder, excepting by its posterior margin, or the lower one in fig. 19, which is free, and forms one side of the slit-like orifice leading into the bladder. This margin is sharp, thin, and smooth, and rests on the edge of a rim or collar, which dips deeply into the bladder, as shown in the longitudinal section (fig. 20) of the collar and valve; it is also shown at c, in fig. 18. The edge of the valve can thus open only inwards. Fic. 20. (Utricularia neglecta.) Longitudinai vertical section through the ventral portion of a bladder; sbowing valve and collar. v, valve; the whole projection above c forms the collar; b, bifid processes; $, ventral surface of bladder, As both the valve and collar dip into the bladder, a hollow or depression is here formed, at the base of which lies the slit-like orifice. The valve is colourless, highly transparent, flexible and elastic. It is convex in a transverse direction, but has been drawn (fig. 19) in a flattened state, by which its apparent breadth is increased. It is formed, according to Cohn, of two layers of small cells, which are continuous with the two layers of larger cells forming the walls of the bladder, of which it is evidently a prolongation. Two pairs of trans- parent pointed bristles, about as long as the valve itself, arise from near the free posterior margin (fig. 19), and point obliquely outwards in the direction of the antennæ. There Y2 324 UTRICULARIA NEGLECTA. (Gaar. XVII. are also on the surface of the valve numerous glands, as I will call them; for they have the power of absorption, though I doubt whether they ever secrete. They consist of three kinds, which to a certain extent graduate into one another. Those situated round the anterior margin of the valve (upper margin in fig. 19) are very numerous and crowded together; they consist of an oblong head on a long pedicel. The pedicel itself is formed of an elongated cell, surmounted by a short one. The glands towards the free posterior margin are much larger, few in number, and almost spherical, having short footstalks ; the head is formed by the confluence of two cells, the lower one answering to the short upper cell of the pedicel of the oblong glands. The glands of the third kind have transversely elongated heads, and are seated on very short footstalks; so that they stand parallel and close to the surface of the valve; they may be called the two-armed glands. The cells forming all these glands contain a nucleus, and are lined by a thin layer of more or less granular protoplasm, the primordial utricle of Mohl. They are filled with fluid, which must hold much matter in solution, judging from the quantity coagulated after they have been long immersed in alcohol or ether. The depression in which the valve lies is also lined with innumerable glands; those at the sides having oblong heads and elongated pe- oe exactly like the glands on the adjoining parts of the valve. The collar (called the peristome by Cohn) is evidently formed, like the valve, by an inward projection of the walls of the bladder. The cells composing the outer surface, or that facing the valve, have rather thick walls, are of a brownish colour, minute, very numerous, and elongated; the ‘ower ones being divided into two by vertical partitions. The whole presents a complex and elegant appearance. The cells forming the inner surface are continuous with those over the whole inner surface of the bladder. The space be- tween the inner and outer surface consists of coarse cellular tissue (fig. 20). The inner side is thickly covered with delicate bifid processes, hereafter to be described. The collar is thus made thick; and it is rigid, so that it retains the same outline whether the bladder contains little or much air and water. This is of great importance, as otherwise the thin and flexible valve would be liable to be distorted, and in this case would not act properly. Cuar. XVII.] STRUCTURE OF THE BLADDER. 325 Altogether the entrance into the bladder, formed by the transparent valve, with its four obliquely projecting bristles, its numerous diversely shaped glands, surrounded by the collar, bearing glands on the inside and bristles on the out- side, together with the bristles borne by the antennæ, presents an extraordinary complex appearance when viewed under the microscope. We wiil now consider the internal structure of the bladder. The whole inner surface, with the exception of the valve, is seen under a moderately high power to be covered with a serried mass of processes (fig. 21). Each of these consists of jFic. 21, Fic, 22 (Utricularia neglecta.) ue lecta.) ` En riculart cla. Small portion of inside of bladder, oe sh z much enlarged, showing quadrifid One of the quadrifid processes processes, greatly enlarged, four divergent arms; whence their name of quadrifid processes. They arise from small angular cells, at the Junctions of the angles of the larger cells which form the interior of the bladder. The middle part of the upper surface of these small cells projects a little, and then con- tracts into a very short and narrow footstalk which bears the four arms (fig. 22). Of these, two are long, but often of not quite equal length, and project obliquely inwards and towards the posterior end of the bladder. The two others are much shorter, and project at a smaller angle, that is, are more nearly horizontal, and are directed towards the anterior 326 UTRICULARIA NEGLECTA. [Cuar. XVII. end of the bladder. These arms are only moderately sharp ; they are composed of extremely thin transparent membrane, so that they can be bent or doubled in any direction without being broken. They are lined with a delicate layer of protoplasm, as is likewise the short conical projection from which they arise. Each arm generally (but not invariably) contains a minute, faintly brown particle, either rounded or more commonly elongated, which exhibits incessant 3rownian movements. These particles slowly change their positions, and travel from one end to the other of the arms, but are commonly found near their bases. They are present in the quadrifids of young bladders, when only about a third of their full size. They do not resemble ordinary nuclei, but I believe that they are nuclei in a modified condition, for when absent, I could occasionally just distinguish in their places a delicate halo of matter, including a darker spot. Moreover, the quadrifids of Utricularia montana contain rather larger and much more regularly spherical, but otherwise similar, particles, which closely resemble the nuclei in the cells forming the walls of the bladders. In the present case there were sometimes two, three, or even more, nearly similar particles within a single arm; but, as we shall hereafter see, the presence of more than one seemed always to be connected with the absorption of decayed matter. The inner side of the collar (see the previous fig. 20) is covered with several crowded rows of processes, differing in no important respect from the quadrifids, except in bearing only two arms instead of four; they are, however, rather narrower and more delicate. I shall call them the bifids. They project into the bladder, and are directed towards its posterior end. The quadrifid and bifid processes no doubt are homologous with the papillee on the outside of the bladder and of the leaves; and we shall see that they are developed from closely similar papille. The Uses of the several Parts— After the above long but necessary description of the parts, we will turn to their uses. The bladders have been supposed by some authors to serve as floats; but branches which bore no bladders, and others from which they had been removed, floated perfectly, owing to the air in the intercellular spaces. Bladders containing dead and captured animals usually include bubbles of air, but these cannot have been generated solely by the process of decay, as I have often seen air in young, clean, and empty Cmar. XVII.] MANNER OF CAPTURING PREY. oat bladders; and some old bladders with much decaying matter had no bubbles. The real use of the bladders is to capture small aquatic animals, and this they do on a large scale. In the first lot of plants, which I received from the New Forest early in July, a large proportion of the fully grown bladders contained prey ; in a second lot, received in the beginning of August, most of the bladders were empty, but plants had been selected which had grown in unusually pure water. In the first lot, my son examined seventeen bladders, including prey of some kind, and eight of these contained entomostracan crustaceans, three larvæ of insects, one being still alive, and six remnants of animals so much decayed that their nature could not be distinguished, I picked out five bladders which seemed very full, and found in them four, five, eight, and ten crustaceans, and in the fifth a single much elongated larva. In five other bladders, selected from containing remains, but not appearing very full, there were one, two, four, two, and five crustaceans. A plant of Utricularia vulgaris, which had been kept in almost pure water, was placed by Cohn one evening into water swarming with crustaceans, and by the next morning most of the bladders contained these animals entrapped and swimming round and round their prisons. They remained alive for several days; but at last perished, asphyxiated, as I suppose, by the oxygen in the water having been all con- sumed, Freshwater worms were also found by Cohn in some bladders. In all cases the bladders with decayed remains swarmed with living Alge of many kinds, Infusoria, and other low organisms, which evidently lived as intruders. Animals enter the bladders by bending inwards the pos- terior free edge of the valve, which from being highly elastic shuts again instantly. As the edge is extremely thin, and fits closely against the edge of the collar, both projecting into the bladder (see section, fig. 20), it would evidently be very difficult for any animal to get out when once imprisoned, and apparently they never do escape. To show how closely the edge fits, I may mention that my son found a Daphnia which had inserted one of its antennæ into the slit, and it was thus held fast during a whole day. On three or four occasions I have seen long narrow larve, both dead and alive, wedged between the corner of the valve and collar, with half their bodies within the bladder and half out. As I felt much difficulty in understanding how such 328 UTRICULARIA NEGLECTA. (Cuar. XVII. minute and weak animals, as are often captured, could force their way into the bladders, I tried many experiments to ascertain how this was affected. The free margin of the valve bends so easily that no resistance is felt when a needle or thin bristle is inserted. A thin human hair, fixed to a handle, and cut off so as to project barely } of an inch, en- tered with some difficulty ; a longer piece yielded instead of entering. On three occasions minute particles of blue glass (so as to be easily distinguished) were placed on valves whilst under water; and on trying gently to move them with a needle, they disappeared so suddenly that, not see- ing what had happened, I thought that I had flirted them off; but on examining the bladders, they were found safely enclosed. ‘The same thing occurred to my son, who placed little cubes of green box-wood (about z} of an inch, 423 mm.) on some valves; and thrice in the act of placing them on, or whilst gently moving them to another spot, the valve sud- denly opened and they were engulfed. He then placed similar bits of wood on other valves, and moved them about for some time, but they did not enter. Again, particles of blue glass were placed by me on three valves, and extremely minute shavings of lead on two other valves ; after 1 or 2 brs. none had entered, but in from 2 to 5 hrs. all five were enclosed. One of the particles of glass was a long splinter, of which one end rested obliquely on the valve, and after a few hours it was found fixed, half within the bladder and half projecting out, with the edge of the valve fitting closely all round, except at one angle, where a small open space was left. It was so firmly fixed, like the above-mentioned larve, that the bladder was torn from the branch and shaken, and yet the splinter did not fall out. My son also placed little cubes (about s of an inch, +391 mm.) of green box-wood, which were just heavy enough to sink in water, on three valves. ‘These were examined after 19 hrs. 30 m., and were still lying on the valves; but after 22 hrs. 30 m. one was found enclosed. I may here mention that I found in a bladder on a naturally growing plant a grain of sand, and in another bladder three grains; these must have fallen by some accident on the valves, and then entered like the par- ticles of glass. The slow bending of the valve from the weight of particles of glass and even of box-wood, though largely supported by the water, is, I suppese, analogous to the slow bending of Cuir. XVII] MANNER OF CAPTURING PREY. 329 colloid substances. For instance, particles of glass were placed en various points of narrow strips of moistened gela- tine, and these yielded and hecame bent with extreme slow- ness. It is much more difficult to understand how gently moving a particle from one part of a valve to another causes it suddenly to open. To ascertain whether the valves were endowed with irritability, the surfaces of several were scratched with a needle or brushed with a fine camel-hair brush, so as to imitate the crawling movement of small crustaceans, but the valve did not open. Some bladders, before being brushed, were left for a time in water at tem- peratures between 80° and 130° F. (26°-6—54°°4 Cent.), as, judging from a wide-spread analogy, this would have ren- dered them more sensitive to irritation, or would by itself have excited movement; but no effect was produced. We may therefore conclude that animals enter merely by forcing their way through the slit-like orifice; their heads serving as a wedge. But I am surprised that such small and weak creatures as are often captured (for instance, the nauplius ot a crustacean, and a tardigrade) should be strong enough to act in this manner, seeing that it was difficult to push in one end of a bit of hair 4 of an inch in length. Nevertheless, it is certain that weak and small creatures do enter, and Mrs. Treat, of New Jersey, has been more successful than any other observer, and has often witnessed in the case of Utriculria clandestina the whole process.* She saw a tardi- grade slowly walking round a bladder, as if reconnoitring ; at last it crawled into the depression where the valve lies, and then easily entered. She also witnessed the entrapment of various minute crustaceans. Cypris “was quite wary, “ but nevertheless was often caught. Coming tothe entrance “of a bladder, it would sometimes pause a moment, and then “dash away ; at other times it would come close up, and even “venture part of the way into the entrance and back out as “if afraid. Another, more heedless, would open the door “and walk in; but it was no sooner in than it manifested “alarm, drew in its feet and antenne, and closed its shell.” Larve, apparently of gnats, when “feeding near the en- “trance, are pretty certain to run their heads into the net, “ whence there is no retreat. A large larva is sometimes * «New York Tribune,’ reprinted in the ‘Gard. Chron.’ 1875, p. 303. 390 UTRICULARIA NEGLECTA. (Cuar. XVII. “three or four hours in being swallowed, the process bring- “ing to mind what I have witnessed when a small snake “makes a large frog its victim.” But as the valve does not appear to be in the least irritable,* the slow swallowing process must be the effect of the onward movement of the larva. It is*difficult to conjecture what can attract so many creatures, animal- and vegetable-feeding crustaceans, worms, tardigrades, and various larve, to enter the bladders. Mrs. Treat says that the larve just referred to are vegetable feeders, and seem to have a special liking for the long bristles round the valve, but this taste will not account for the entrance of animal-feeding crustaceans. Perhaps small aquatic animals habitually try to enter every small crevice, like that between the valve and collar, in search of food or protection. Itis not probable that the remarkable trans- parency of the valve is an accidental circumstance, and the spot of light thus formed may serve as a guide. The long bristles round the entrance apparently serve for the same purpose. I believe that this is the case, because the bladders of some epiphytic and marsh species of Utricularia which live embedded either in entangled vegetation or in mud, have no bristles round the entrance, and these under such condi- tions would be of no service as a guide. Nevertheless, with these epiphytic and marsh species, two pairs of bristles pro- ject from the surface of the valve, as in the aquatic species ; and their use probably is to prevent too large animals from trying to force an entrance into the bladder, thus rupturing the orifice. As under favourable circumstances most of the bladders succeed in securing prey, in one case as many as ten crusta- ceans ;—as the valve is so well fitted to allow animals to enter and to prevent their escape ;—and as the inside of the bladder presents so singular a structure, clothed with innu- merable quadrifid and bifid processes, it is impossible to doubt that the plant has been specially adapted for securing prey. From the analogy of Pinguicula, belonging to the saine family, I naturally expected that the bladders would * [Guided by her observations (‘ Harper’s Magazine,’ Feb. 1876) on the act of capture, Mrs, Treat concludes that the valve is irritable.—F. D.] Car. XVII] MANNER OF CAPTURING PREY. 831 have digested their prey; but this is not the case, and there are no glands fitted for secreting the proper fluid. Never- theless, in order to test their power of digestion, minute fragments of roast meat, three small cubes of albumen, and three of cartilage, were pushed through the orifice into the bladders of vigorous plants. They were left from one day to three days and a half within, and the bladders were then cut open: but none of the above substances exhibited the least signs of digestion or dissolution; the angles of the cubes being as sharp as ever. These observations were made subsequently to those on Drosera, Dionza, Drosophyllum, and Pinguicula; so that I was familar with the appearance of these substances when undergoing the early and final stages of digestion. We may therefore conclude : that Utricularia cannot digest the animals which it habitually captures. In most of the bladders the captured animals are so much decayed that they form a pale brown, pulpy mass, with their chitinous coats so tender that they fall to pieces with the greatest ease. The black pigment of the eye-spots is preserved better than anything else. Limbs, jaws, &c. are often found quite detached ; and this I suppose is the result of the vain struggles of the later captured animals. I have sometimes felt surprised at the small proportion of im- prisoned animals in a fresh state compared with those utterly decayed.* Mrs. Treat states with respect to the larvae above referred to, that “ usually in less than two days after a large “one was captured the fluid contents of the bladders began “ to assume a cloudy or muddy appearance, and often became “so dense that the outline of the animal was lost to view.” This statement raises the suspicion that the bladders secrete some ferment hastening the process of decay. There is no inherent improbability in this supposition, considering that meat soaked for ten minutes in water mingled with the milky juice of the papaw becomes quite tender and soon passes, as Browne remarks in his ‘Natural History of Jamaica,’ into a state of putridity. Whether or not the decay of the imprisoned animals is in any way hastened, it is certain that matter is absorbed from * [Schimper (‘ Botanische Zeitung,’ 1882, p. 245) was struck by the same fact in the case of U. cornuta.—F. D.] 332 UTRICULARIA NEGLECTA. (Cuar. XVI. them by the quadrifid and bifid processes. The extremely delicate nature of the membrane of which these processes are formed, and the large surface which they expose, owing to their number crowded over the whole interior of the bladder, are circumstances all favouring the process of absorption. Many perfectly clean bladders which had never caught any prey were opened, and nothing could be distin- guished with a No. 8 object-glass of Hartnack within the delicate, structureless protoplasmic lining of the arms, ex- cepting in each a single yellowish particle or modified nucleus. Sometimes two or even three such particles were present; but in this case traces of decaying matter could generally be detected. On the other hand, in bladders con- taining either one large or several small decayed animals, the processes presented a widely different appearance. Six such bladders were carefully examined; one contained an elongated, coiled-up larva; another a single large entomo- stracan crustacean, and the others from two to five smaller ones, all in a decayed state. In these six bladders, a large number of the quadrifid processes contained transparent, often yellowish, more or less confluent, spherical or irregu- larly shaped, masses of matter. Some of the processes, however, contained only fine granular matter, the particles of which were so small that they could not be defined clearly with No. 8 of Hartnack. The delicate layer of protoplasm lining their walls was in some cases a little shrunk.* On three occasions the above small masses of matter were observed and sketched at short intervals of time; and they certainly changed their positions relatively to each other and to the walls of the arms. Separate masses sometimes became con- fluent, and then again divided. A single little mass would send out a projection, which after a time separated itself. Hence there could be no doubt that these masses consisted of protoplasm. Bearing in mind that many clean bladders were examined with equal care, and that these presented no such appearance, we may confidently believe that the pro- * [Schimper (loc. cit. p. 247) ob- empty bladders, but the commonest served a marked difference in the change is a collection of the pro- appearance of the hairs in those bladders of U. cornuta which contain captured prey. ‘The protoplasm is sometimes more granular than in toplasm in the axis of the cell where it is suspended by radiating strands to the delicate layer of protoplasm lining the walls.—F. D.] Osmar. XVII] ABSORPTION BY THE QUADRIFIDS. 333 toplasm in the above cases had been generated by the absorption of nitrogenous matter from the decaying animals. In two or three other bladders, which at first appeared quite clean, on careful search a few processes were found, with their outsides clogged with a little brown matter, showing that some minute animal had been captured and had de- cayed, and the arms here included a very few more or less spherical and aggregated masses; the processes in other parts of the bladders being empty and transparent. On the other hand, it must be stated that in three bladders con- taining dead crustaceans, the processes were likewise empty. This fact may be accounted for by the animals not having been sufficiently decayed, or by time enough not having been allowed for the generation of protoplasm, or by its subsequent absorption and transference to other parts of the plant. It will hereafter be seen that in three or four other species of Utricularia the quadrifid processes in contact with decaying animals likewise contained aggregated masses of protoplasm. On the Absorption of certain Fluids by the Quadrifid and Bifid Processes—These experiments were tried to ascertain whether certain fluids, which seemed adapted for the purpose would produce the same effects on the processes as the absorption of decayed animal matter. Such experiments are, however, troublesome ; for it is not sufficient merely to place a branch in the fluid, as the valve shuts so closely that the fluid apparently does not enter soon, if at all. Even when bristles were pushed into the orifices, they were in several cases wrapped so closely round by the thin flexible edge of the valve that the fluid was apparently excluded ; so that the experiments tried in this manner are doubtful and not worth giving. The best plan would have been to puncture the bladders, but I did not think of this till too late, excepting in a few cases. In all such trials, however, it cannot be ascertained positively that the bladder, though translucent, does not contain some minute animal in the last stage of decay. Therefore most of my experiments were made by cutting bladders longitudinally into two; the quadrifids were examined with No. 8 of Hartnack, then irrigated, whilst under the covering glass, with a few drops of the fluid under trial, kept in a damp chamber, and re- examined after stated intervals of time with the same power as before. 334 UTRICULARIA NEGLECTA. [Cuar. XVII. Four bladders were first tried as a control experiment, in the manner just described, in a solution of one part of gum arabic to 218 of water, and two bladders in a solution of one part of sugar to 437 of water ; and in neither case was any change perceptible in the quadrifids or bifids after 21 hrs. Four bladders were then treated in the same manner with a solution of one part of nitrate of ammonia to 487 of water, and re-examined after 21 hrs. In two cf these the quadrifids now appeared full of very finely granular matter, and their protoplasmic lining or primordial utricle was a little shrunk. In the third bladder, the quadrifids included distinctly visible granules, and the primordial utricle was a little shrunk after only 8 hrs. In the fourth bladder the primordial utricle in most of the processes was here and there thickened into little irregular yellowish specks ; and from the gradations which could be traced in this and other cases, these specks appear to give rise to the larger free granules contained within some of the processes. Other bladders, which, as far as could be judged, had never caught, any prey, were punctured and left in the same solution for 17 hrs.; and their quadrifids now contained very fine granular matter. A bladder was bisected, examined, and irrigated with a solution of one part of carbonate of ammonia to 437 of water. After 8 hrs. 30 m. the quadrifids contained a good many granules, and the primordial utricle was somewhat shrunk; after 23 hrs. the quadrifids and bifids contained many spheres of hyaline matter, and in one arm twenty-four such spheres of moderate size were counted. Two bisected bladders, which had been previously left for 21 hrs. in the solution of gum (one part to 218 of water) without being affected, were irrigated with the solution of carbonate of ammonia; and both had their quadrifids modified in nearly the same manner as just described,—one after only 9 hrs. and the other after 24 hrs. Two bladders which appeared never to have caught any prey were punctured and placed in the solution ; the quadrifids of one were examined after 17 hrs., and found slightly opaque ; the quadrifids of the other, examined after 45 hrs., had their primordial utricles more or less shrunk with thickened yellowish specks like those due to the action of nitrate of ammonia. Several un- injured bladders were left in the same solution, as well as in a weaker solution of one part to 1750 of water, or 1 gr. to 4 oz. ; and after two days the quadrifids were more or less opaque, with their contents finely granular; but whether the solution had entered by the orifice, or had been absorbed from the outside, I know not. Two bisected bladders were irrigated with a solution of one part of urea to 218 of water; but when this solution was employed, I forgot that it had been kept for some days in a warm room, and had there- fore probably generated ammonia; anyhow, the quadrifids were affected after 21 hrs. as if a solution of carbonate of ammonia had been used; for the primordial utricle was thickened in specks, which seemed to graduate into separate granules. Three bisected bladders were also irrigated with a fresh solution of urea of the same strength; their quadrifids after 21 hrs. were much less affected than in the former Cmar. XVII.] ABSORPTION BY THE QUADRIFIDS. 300 case; nevertheless, the primordial utricle in some of the arms was a little shrunk, and in others was divided into two almost symmetrical sacks. Three bisected bladders, after being examined, were irrigated with a putrid and very offensive infusion of raw meat. After 23 hrs. the quadrifids and bifids in all three specimens abounded with minute, hyaline, spherical masses; and some of their primordial utricles were a little shrunk. Three bisected bladders were also irrigated with a fresh infusion of raw meat; and to my surprise the quadrifids in one of them appeared, after 23 hrs., finely granular, with their primordial utricles somewhat shrunk and marked with thickened yellow- ish specks; so that they had been acted on in the same manner as by the putrid infusion or by the salts of ammonia. In the second bladder some of the quadrifids were similarly acted on, though to a very slight degree ; whilst the third bladder was not at all affected. From these experiments it is clear that the quadrifid and bifid processes have the power of absorbing carbonate and nitrate of ammonia, and matter of some kind from a putrid infusion of meat. Salts of ammonia were selected for trial, as they are known to be rapidly generated by the decay of animal matter in the presence of air and water, and would therefore be generated within the bladders containing cap- tured prey. The effect produced on the processes by these salts and by a putrid infusion of raw meat differs from that produced by the decay of the naturally captured animals only in the aggregated masses of protoplasm being in the latter case of larger size; but it is probable that the fine granules and small hyaline spheres produced by the solutions would coalesce into larger masses, with time enough allowed. We have seen with Drosera that the first effect of a weak solution of carbonate of ammonia on the cell-contents is the production of the finest granules, which afterwards aggre- gate into larger, more or less rounded, masses; and that the granules in the layer of protoplasm which flows round the walls ultimately coalesce with these masses. Changes of this nature are, however, far more rapid in Drosera than in Utricularia. Since the bladders have no power of digesting albumen, cartilage, or roast meat, I was surprised that matter was absorbed, at least in one case, from a fresh infusion of raw meat. I was also surprised, from what we shall presently see with respect to the glands round the orifice, that a fresh solution of urea produced only a moderate effect on the quadrifids. 336 UTRICULARIA NEGLECTA. LCnar. XVII. As the quadrifids are developed from papille which at first closely resemble those on the outside of the bladders and on the surfaces of the leaves, I may here state that the two hemispherical cells with which these latter papille are crowned, and which in their natural state are perfectly transparent, likewise absorb carbonate and nitrate of am- monia; for, after an immersion of 23 hrs. in solutions of one part of both these salts to 437 of water, their primordial utricles were a little shrunk and of a pale brown tint, and sometimes finely granular. The same result followed from the immersion of a whole branch for nearly three days in a solution of one part of the carbonate to 1750 of water. The grains of chlorophyll, also, in the cells of the leaves on this branch became in many places aggregated into little green masses, which were often connected together by the finest threads. On the Absorption of certain Fluids by the Glands on the Valve and Collar.—The glands round the orifices of bladders which are still young, or which have been long kept in moderately pure water, are colourless ; and their primordial utricles are only slightly or hardly at all granular. But in the greater number of plants in a state of nature—and we must remember that they generally grow in very foul water, —and with plants kept in an aquarium in foul water, most of the glands were of a pale brownish tint; their primordial utricles were more or less shrunk, sometimes ruptured, with their contents often coarsely granular or aggregated into little masses. That this state of the glands is due to their having absorbed matter from the surrounding water, I cannot doubt; for, as we shall immediately see, nearly the same results follow from their immersion for a few hours in various solutions. Nor is it probable that this absorption is useless, seeing that it is almost universal with plants grow- ing in a state of nature, excepting when the water is remark- ably pure. The pedicels of the glands which are situated close to the slit-like orifice, both those on the valve and on the collar, are short; whereas the pedicels of the more distant glands are much elongated and project inwards. The glands are thus well placed so as to be washed by any fluid coming out of the bladder through the orifice. The valve fits so closely, judging from the result of immersing uninjured bladders in various solutions, that it is doubtful whether any putrid Cuar. XVIIL] ABSORPTION BY THE GLANDS. oor fluid habitually passes outwards. But we must remember that a bladder generally captures several animals; and that each time a fresh animal enters, a puff of foul water must pass out and bathe the glands. Moreover, I have repeatedly found that, by gently pressing bladders which contained air, minute bubbles were driven out through the orifice; and if a bladder is laid on blotting paper and gently pressed, water oozes out. In this latter case, as soon as the pressure is relaxed, air is drawn in, and the bladder recovers its proper form. If it is now placed under water and again gently pressed, minute bubbles issue from the orifice and nowhere else, showing that the walls of the bladder have not been ruptured. I mention this because Cohn quotes a statement by Treviranus, that air cannot be forced out of a bladder without rupturing it. We may therefore conclude that whenever air is secreted within a bladder already full of water, some water will be slowly driven out through the orifice. Hence I can hardly doubt that the numerous glands crowded round the orifice are adapted to absorb matter from the putrid water, which will occasionally escape from bladders including decayed animals. In order to test this conclusion, I experimented with various solutions on the glands. As in the case of the quadrifids, salts of ammonia were tried, since these are generated by the final decay of animal matter under water. Unfortunately the glands cannot be carefully examined whilst attached to the bladders in their entire state. Their summits, therefore, including the valve, collar, and antenny, were sliced off, and the condition of the glands observed ; they were then irrigated, whilst beneath a covering glass, with the solutions, and after a time re-examined with the same power as before, aed No. 8 of Hartnack. The following experiments were thus made. As a control experiment solutions of one part of white sugar and of one part of gum to 218 of water were first used, to see whether these produced any change in the glands. It was also necessary to observe whether the glands were affected by the summits of the bladders having been cut off. The summits of four were thus tried; one being exam- ined after 2 hrs. 30 m., and the other three after 23 hrs.; but there was no marked change in the glands of any of them. — : Two summits bearing quite colourless glands were irrigated with a solution of carbonate of ammonia of the same strength (viz. one part to 218 of water), and in 5 m. the primordial utricles of most of the glands were somewhat contracted; they were also thickened in specks or patches, and had assumed a pale brown tint. When looked at Z 338 UTRICULARIA NEGLECTA. [Cuar. XVII. again after 1 hr. 30 m., most of them presented a somewhat different appearance. A third specimen was treated with a weaker solution of one part of the carbonate to 437 of water, and after 1 hr. the glands were pale brown and contained numerous granules. Four summits were irrigated with a solution of one part of nitrate of ammonia to 437 of water. One was examined after 15 m., and the glands seemed affected ; after 1 hr. 10 m. there was a greater change, and the primordial utricles in most of them were somewhat shrunk, and included many granules. In the second specimen, the primordial utricles were considerably shrunk and brownish after 2 hrs. Similar effects were observed in the two other specimens, but these were not examined until 21 hrs. had elapsed. The nuclei of many of the glands apparently had increased in size. Five bladders on a branch, which had been kept for a long time in moderately pure water, were cut off and examined, and their glands found very little modified. The remainder of this branch was placed in the solution of the nitrate, and after 21 hrs. two bladders were examined, and all their glands were brownish, with their primordial utricles somewhat shrunk and finely granular. The summit of another bladder, the glands of which were in a beautifully clear condition, was irrigated with a few drops of a mixed solution of nitrate and phospate of ammonia, each of one part to 437 of water. After 2 hrs. some few of the glands were brownish. After 8 hrs. almost all the oblong glands were brown and much more opaque than they were before ; their primordial utricles were somewhat shrunk and contained a little aggregated granular matter. The spherical glands were still white, but their utricles were broken up into three or four small hyaline spheres, with an irregularly contracted mass in the middle of the basal part. These smaller spheres changed their forms in the course of a few hours, and some of them disappeared. By the next morning, after 23 hrs. 80 m., they had all disappeared, and the glands were ‘brown; their utricles now formed a globular shrunken mass in the middle. The utricles of the oblong glands had shrunk very little, but their contents were somewhat aggregated. Lastly, the summit of a bladder which had been previously irrigated for 21 hrs. with a solution of one part of sugar to 218 of water without being affected, was treated with the above mixed solution; and after 8 hrs. 30 m. all the glands became brown, with their primordial utricles slightly shrunk. Four summits were irrigated with a putrid infusion of raw meat. No change in the glands was observable for some hours, but after 24 hrs. most of them had become brownish, and more opaque and granular than they were before. In these specimens, as in those irrigated with the salts of ammonia, the nuclei seemed to have increased both in size and solidity, but they were not measured. Five summits were also irrigated with a fresh infusion of raw meat; three of these were not at all affected in 24 hrs., but the glands of the other two had perhaps become more granular, One of the specimens which Cmar. XVII.] ABSORPTION BY THE GLANDS. 339 was not affected was then irrigated with the mixed solution of the nitrate and phosphate of ammonia, and after only 25 m. the glands contained from four or five toa dozen granules, After six additional hours their primordial utricles were greatly shrunk. The summit of a bladder was examined, and all the glands found colourless, with their primordial utricles not at all shrunk ; yet many of the oblong glands contained granules just resolvable with No. 8 of Hartnack. It was then irrigated with a few drops of a solution of one part of urea to 218 of water.’ After 2 hrs. 25 m. the spherical glands were still colourless; whilst the oblong and two-armed ones were of a brownish tint, and their primordial utricles much shrunk, some containing distinctly visible granules. After 9 hrs. some of the spherical glands were brownish, and the oblong glands were still more changed, but they contained fewer separate granules ; their nuclei, on the other hand, appeared larger, as if they had absorbed the granules. After 23 hrs. all the glands were brown, their pri- mordial utricles greatly shrunk, and in many cases ruptured. A bladder was now experimented on, which was already somewhat affected by the surrounding water; for the spherical glands, though colourless, had their primordial utricles slightly shrunk; and the oblong glands were brownish, with their utricles much, but irregularly, shrunk. ‘The summit was treated with the solution of urea, but was little affected by it in 9 hrs.; nevertheless, after 23 hrs. the spherical glands were brown, with their utricles more shrunk; several of the other glands were still browner, with their utricles contracted into irregular little masses. Two other summits, with their glands colourless and their utricles not shrunk, were treated with the same solution of urea. After 5 hrs. many of the glands presented a shade of brown, with their utricles slightly shrunk. After 20 hrs. 40 m. some few of them were quite brown, and contained irregularly aggregated masses; others were still colourless, though their utricles were shrunk; but the greater number were not much affected. This was a good instance of how unequally the glands on the same bladder are sometimes affected, as likewise often occurs with plants growing in foul water. Two other summits were treated with a solution which had been kept during several days in a warm room, and their glands were not at all affected when examined after 21 hours. ; A weaker solution of one part of urea to 437 of water was next tried on six summits, all carefully examined before being irrigated. The first was re-examined after 8 hrs. 30 m., and the glands, including the spherical ones, were brown; many of the oblong glands having their primordial utricles much shrunk and including granules. The second summit, before being irrigated, had been somewhat affected by the Surrounding water, for the spherical glands were not quite uniform in appearance; and a few of the oblong ones were brown, with their utricles shrunk. Of the oblong glands, those which were before colour- less, became brown in 3 hrs, 12 m. after irrigation, with their utricles Z 2 340 UTRICULARIA NEGLECTA. [Cuar. XVII. slightly shrunk. The spherical glands did not become brown, but their contents seemed changed in appearance, and after 23 hrs. still more changed and granular. Most of the oblong glands were now dark brown, but their utricles were not greatly shrunk. The four other specimens were examined after 3 hrs. 80 m., after 4 hrs. and 9 hrs. ; a brief account of their condition will be sufficient. The spherical glands were not brown, but some of them were finely granular. Many of the oblong glands were brown; and these, as well as others which still remained colourless, had their utricles more or less shrunk, some of them including small aggregated masses of matter. Summary of the Observations on Absorption.—-From the facts now given there can be no doubt that the variously shaped glands on the valve and round the collar have the power of absorbing matter from weak solutions of certain salts of ammonia and urea, and from a putrid infusion of raw meat. Prof. Cohn believes that they secrete slimy matter; but I was not able to perceive any trace of such action, excepting that, after immersion in alcohol, extremely fine lines could sometimes be seen radiating from their surfaces. The glands are variously affected by absorption: they often become of a brown colour; sometimes they contain very fine granules, or moderately sized grains, or irregularly aggregated little masses; sometimes the nuclei appear to have increased in size; the primordial utricles are generally more or less shrunk and sometimes ruptured. Exactly the same changes may be observed in the glands of plants growing and flourishing in foul water. The spherical glands are generally affected rather differently from the oblong and two-armed ones. The former do not so commonly become brown, and are acted on more slowly. We may therefore infer that they differ somewhat in their natural functions. It is remarkable how unequally the glands on the bladders on the same branch, and even the glands of the same kind on the same bladder, are affected by the foul water in which the plants have grown, and by the solutions which were employed. In the former case I presume that this is due either to little currents bringing matter to some glands and not to others, or to unknown differences in their constitution. When the glands on the same bladder are differently affected ‘by a solution, we may suspect that some of them had previously absorbed a small amount of matter from the water. However this may be, we have seen that the glands ey eee Cuar. XVII.] SUMMARY ON ABSORPTION. 341 on the same leaf of Drosera are sometimes very unequally affected, more especially when exposed to certain vapours. If glands which have already become brown, with their primordial utricles shrunk, are irrigated with one of the effective solutions, they are not acted on, or only slightly and slowly. If, however, a gland contains merely a few coarse granules, this does not prevent a solution from acting. I have never seen any appearance making it probable that glands which have been strongly affected by absorbing matter of any kind are capable of recovering their pristine, colour- less, and homogeneous condition, and of regaining the power of absorbing. From the nature of the solutions which were tried, I presume that nitrogen is absorbed by the glands; but the modified, brownish, more or less shrunk, and aggregated contents of the oblong glands were never seen by me or by my son to undergo those spontaneous changes of form characteristic of protoplasm. On the other hand, the contents of the larger spherical glands often separated into small hyaline globules or irregularly shaped masses, which changed their forms very slowly and ultimately coalesced, forming a central shrunken mass. Whatever may be the nature of the contents of the several kinds of glands, after they have been acted on by foul water or by one of the nitrogenous solutions, it is probable that the matter thus generated is of service to the plant, and is ultimately transferred to other parts. The glands apparently absorb more quickly than do the quadrifid and bifid processes; and on the view above main- tained, namely that they absorb matter from putrid water occasionally emitted from the bladders, they ought to act more quickly than the processes; as these latter remain in permanent contact with captured and decaying animals. Finally, the conclusion to which we are led by the fore- going experiments and observations is that the bladders have no power of digesting animal matter, though it appears that the quadrifids are somewhat affected by a fresh infusion of raw meat. It is certain that the processes within the bladders, and the glands outside, absorb matter from salts of ammonia, from a putrid infusion of raw meat, and from urea, Lhe glands apparently are acted on more strongly by a solution of urea, and less strongly by an infusion of raw meat, than are the processes. The case of urea is particularly interesting, because we have seen that it produces no effect 342 UTRICULARIA NEGLECTA. (Cuap. XVII. on Drosera, the leaves of which are adapted to digest fresh animal matter. But the most important fact of all is, that in the present and following species the quadrifid and bifid processes of bladders containing decayed animals generally include little masses of spontaneously moving protoplasm ; whilst such masses are never seen in perfectly clean bladders. Development of the Bladders.—My son and I spent much time over this subject with small success. Our observations apply to the present species and to Utricularia vulgaris, but were made chiefly on the latter, as the bladders are twice as large as those of Utricularia neglecta. In the early part of autumn the stems terminate in large buds, which fall off and lie dormant during the winter at the bottom. The young leaves forming these buds bear bladders in various stages of early development. When the bladders of Utricularia vul- garis are about +1, inch (+254 mm.) in diameter (or 5), in the case of Utricularia neglecta), they are circular in outline, with a narrow, almost closed, transverse orifice, leading into a hollow filled with water; but the bladders are hollow when much under 14y of an inch in diameter. The orifices face inwards or towards the Fic, 23. axis of the plant. At this early age (Utricularia vulgaris.) the bladders are flattened in the plane Longitudinal section through in Which the orifice lies, and therefore in length, With te oie we at right angles to that of the mature widely open, bladders. They are covered exteriorly with papillz of different sizes, many of which have an elliptical outline. A bundle of vessels, formed of simple elongated cells, runs up the short footstalk, and divides at the base of the bladder. One branch extends up the middle of the dorsal surface, and the other up the middle of the ventral surface. In full-grown bladders the ventral bundle divides close beneath the collar, and the two branches run on each side to near where the corners of the valve unite with the collar; but these branches could not be seen in very young bladders. The accompanying figure (fig. 23) shows a section, which happened to be strictly medial, through the footstalk and between ihe nascent antenne of a bladder of Utricularia Cuar. XVII.] DEVELOPMENT OF THE BLADDERS. 343 vulgaris, +1, inch in diameter. The specimen was soft, and the young valve became separated from the collar toa greater degree than is natural, and is thus represented. We here clearly see that the valve and collar are infolded prolon- gations of the wall of the bladder. Even at this early age, glands could be detected on the valve. The state of the quadrifid processes will presently be described. The antenne at this period consist of minute cellular projections (not shown in the above figure, as they do not lie in the medial plane), which soon bear incipient bristles. In five instances the young antennæ were not of quite equal length; and this Fic. 24. (Utricularia vulgaris.) Young leaf from a winter bud, showing on the left side a bladder in its earliest stage of development. fact is intelligible if I am right in believing that they represent two divisions of the leaf, rising from the end of the bladder ; for, with the true leaves, whilst very young, the divisions are never, as far as I have seen, strictly opposite; they must therefore be developed one after the other, and so 1t would be with the two antenne. At a much earlier age, when the half formed bladders are only ly inch (+0846 mm.) in diameter or a little more, they present a totally different appearance. One is represented on the left side of the accompanying drawing (fig. 24). The young leaves at this age have broad flattened segments, with 344 UTRICULARIA NEGLECTA. ([Cuar, XVII. their future divisions represented by prominences, one of which is shown on the right side. Now, in a large number of specimens examined by my son, the young bladders appeared as if formed by the oblique folding over of the apex and of one margin with a prominence, against the opposite margin. The circular hollow between the infolded apex and infolded prominence apparently contracts into the narrow orifice, wherein the valve and collar will be developed; the bladder itself being formed by the confluence of the opposed margins of the rest of the leaf. But strong objections may be urged against this view, for we must in this case suppose that the valve and collar are developed as symmetrically from the sides of the apex and prominence. Moreover, the bundles of vascular tissue have to be formed in lines quite irre- spective of the original form of the leaf. Until gradations can be shown to exist between this the earliest state and a young yet perfect bladder, the case must be left doubtful. As the quadrifid and bifid processes offer one of the greatest peculiarities in the genus, I carefully observed their development in Utricularia neglecta. In bladders about 44> of an inch in diameter, the inner surface is studded with papillx, rising from small cells at the junctions of the larger ones. ‘These papille consist of a delicate conical protuber- ance, which narrows into a very short footstaik, surmounted by two minute cells. They thus occupy the same relative position, and closely resemble, except in being smaller and rather more prominent, the papille on the cutside of the bladders, and on the surfaces of the leaves. The two terminal cells of the papillx first become much elongated in a line parallel to the inner surface of the bladder. Next, each is divided by a longitudinal partition. Soon the two half-cells thus formed separate from one another; and we now have four cells or an incipient quadrifid process. As there is not space for the two new cells to increase in breadth in their original plane, the one slides partly under the other. Their manner of growth now changes, and their outer sides, instead of their apices, continue to grow. The two lower cells, which have slid partly beneath the two upper ones, form the longer and more upright pair of processes: whilst the two upper cells form the shorter and more horizontal pair; the four together forming a perfect quadrifid. A trace of the primary division between the two cells on the summits of the papille can still be seen between the bases Cmar. XVIL] UTRICULARIA MINOR. 845 of the longer processes. The development of the quadrifids is very liable to be arrested. I have seen a bladder y of an inch in length including only primordial papillae; and another bladder, about half its full size, with the quadrifids in an early stage of development. As far as I could make out, the bifid processes are de- veloped in the same manner as the quadrifids, excepting that the two primary terminal cells never become divided, and only increase in length. The glands on the valve and collar appear at so early an age that I could not trace their develop- ment; but we may reasonably suspect that they are developed from papille like those on the outside of the bladder, but with their terminal cells not divided into two. The two segments forming the pedicels of the glands probably answer to the conical protuberance and short footstalk of the quadri- fid and bifid processes. I am strengthened in the belief that the glands are developed from papille like those on the outside of the bladders, from the fact that in Utricularia amethystina the glands extend along the whole ventral surface of the bladder close to the footstalk. UTRICULARIA VULGARIS. Living plants from Yorkshire were sent me by Dr. Hooker. This Species differs from the last in the stems and leaves being thicker or coarser; their divisions form a more acute angle with one another; the notches on the leaves bear three or four short bristles instead of one ; aud the bladders are twice as large, or about 4 of an inch (5°08 mm.) in diameter. In all essential respects the bladders resemble those of Utricularia neglecta, but the sides of the peristome are perhaps a little more prominent, and always bear, as far as I have seen, seven or eight long multicellular bristles. There are eleven long bristles on each antenna, the terminal pair being included. Five bladders, con- taining prey of some kind, were examined. ‘The first included five Cypris, a large copepod and a Diaptomus; the second, four Cypris; the third, a single rather large crustacean; the fourth, six crustaceans ; and the fifth, ten. My son examined the quadrifid processes in a bladder containing the remains of two crustaceans, and found some of them full of spherical or irregularly shaped masses of matter, which were observed to move and to coalesce. These masses therefore con- sisted of protoplasm. UTRICULARIA MINOR. This rare species was sent me in a living state from Cheshire, through the kindness of Mr. John Price. The leaves and bladders are much 346 UTRICULARIA CLANDESTINA. [OmiP. XVII. smaller than those of Utricularia neglecta. The leaves bear fewer and shorter bristles, and the bladders are more globular. ‘The antenna, instead of projecting in front of the bladders, are curled under the valve, and are armed with twelve or fourteen extremely long multi- cellular bristles, generally arranged in pairs. These, with seven or eight long bristles on both sides of the peristome, form a sort of net over the valve, which would tend to prevent all animals, excepting very small ones, entering the bladder. ‘The valve and collar have the same essential structure as in the two previous species; but the glands are not quite so numerous; the oblong ones are rather more elongated, whilst the two-armed ones are rather less elongated. The four bristles which project obliquely from the lower edge of the valve are short. Their shortness, compared with those on the valves of the foregoing species, is intelligible if my view is correct that they serve to prevent too large animals forcing an entrance through the valve, thus injuring it; for the valve is already protected to a certain extent by the incurved antenne, together with the lateral bristles. ‘The bifid processes are like those in the previous species; but the quadrifids differ in the four arms (fig. 25) being ig 6s directed to the same side; the two ee longer ones being central, and the two shorter ones on the outside. The plants were collected in the middle of July; and the contents of five bladders, which from their opacity seemed full of prey were examined. ‘lhe first contained no less than twenty-four minute fresh- water crustaceans, most of them consisting of empty shells, or includ- ing only a few drops of red oily matter; the second contained twenty ; the third, fifteen; the fourth, ten, some of them being rather larger than usual; and the fifth, which seemed stuffed quite full, contained only seven, but five of these were of unusually large size. The prey, therefore, judging from these five bladders, consists exclusively of fresh-water crustaceans, most of which appeared to be distinct species from those found in the bladders of the two former species. In one bladder the quadrifids in contact with a decaying mass contained numerous spheres of granular matter, which slowly changed their forms and positions. (Uiricularia minor.) Quadrifid process; greatly enlarged. UTRICULARIA CLANDESTINA. This North American species, which is aquatic like the three fore- going ones, has been described by Mrs. Treat, of New Jersey, whose excellent observations have already been largely quoted. I have not as yet seen any full description by her of the structure of the bladder, Cuar. XVII] UTRICULARIA CLANDESTINA. 347 but it appears to be lined with quadrifid processes. A vast number of captured animals were found within the bladders; some being crustaceans, but the greater number delicate, elongated larvae, I sup- pose of Culicide. On some stems, “ fully nine out of every ten bladders contained these larve or their remains.” The larve “ showed signs of life from twenty-four to thirty-six hours after being imprisoned,” and then perished. 348 UTRICULARIA MONTANA. [Cuar. XVIII. CHAPTER XVIII. UTRICULARIA (continued). Utricularia montana—Description of the bladders on the subterranean rhizomes—Prey captured by the bladders of plants under culture and in a state of nature—Absorption by the quadrifid processes and glands— Tubers serving as reservoirs for water—Various other species of Utricu- laria—Poly pompholyx—Genlisea, different nature of the trap for capturing prey—{Sarracenia]—Diversified methods by which plants are nourished. UTRICULARIA MoNTANA.—This species inhabits the tropical parts of South America, and is said to be epiphytic; but, judging from the state of the roots (rhizomes) of some dried specimens from the herbarium at Kew, it likewise lives in earth, probably in crevices of rocks. In English hot-houses it is grown in peaty soil. Lady Dorothy Nevill was so kind as to give me a fine plant, and I received another from Dr. Hooker. The leaves are entire, instead of being much divided, as in the foregoing aquatic species. They are elongated, about 14 inch in breadth, and furnished with a distinct foot- stalk, The plant produces numerous colourless rhizomes,* as thin as threads, which bear minute bladders, and occasionally swell into tubers, as will hereafter be described. These rhizomes appear exactly like roots, but occasionally throw up * [Hovelacque, in the ‘Comptes mountains of Dominica. Utricularia Rendus, vols. cv. p. 692, and cvi. p. 310, has discussed the nature of the underground runners; he considers them to be morphologically leaves, in opposition to Schenk (Pringsheim’s ‘Jahrbiicher,’ vol. xviii. p. 218), who rgards them as rhizomes. Schimper, in his paper on the West Indian Epiphytes (‘ Bot. Central- blatt,’ vol. xvii. p. 257), takes a view similar to Schenk’s as to stolons or runners in the new species, U. Schimperi, discovered by him in the cornuta, described by Schimper in the ‘Bot. Zeitung,’ 1882, p. 241, has similar underground runners, as well as aerial organs usually described as leaves. He discusses the possibility of a morphological identity between the runners and the “leaves” from a point of view opposite to that of Hovelacque’s— namely, that the “leaves” as well as the stolons may be morphologically stems,—F. D,] Onar: XVIII] STRUCTURE OF THE BLADDERS. 549 green shoots. They penetrate the earth sometimes to the depth of more than 2 inches: but when the plant grows as an epiphyte, they must creep amidst the mosses. roots, decayed bark, &c., with which the trees of these countries are thickly covered. As the bladders are attached to the rhizomes, they are neces- sarily subterranean. They are produced in extraordinary num- bers. One of my plants, though young, must have borne several hundreds; for a single branch out of an entangled mass had thirty-two, and another branch, about 2 inches in length (but, with its end and one side branch broken off), had seventy- three bladders.* The bladders are compressed and rounded, with the ventral surface, or that be- tween the summit of the long delicate footstalk and valve, ex- tremely short (fig. 27). They are colourless and almost as transparent as glass, so that they appear smaller than they really are, the largest being under the s> of an inch (1°27 mm.) in its longer diameter. They are formed of rather large angular cells, at the junctions of which oblong papille project, corresponding with those on the surfaces of the bladders of the previous species. Similar papille abound on the rhizomes, and even on the entire leaves, but they are rather broader on the latter. Vessels, marked with parallel bars instead of by a spiral line, run up the footstalks, and just enter the bases of the bladders; but they Frc. 26. (Utricularia montana.) Rhizome swollen into a tuber; the branches bearing minute bladders; of natural size. * Prof. Oliver has figured a plant that the bladders on the rhizomes of of Utricularia Jamesoniana (‘ Proc. Linn. Soc.’ vol. iv. p- 169) having entire leaves and rhizomes, like those of our present species; but the mar- gins of the terminal halves of some of the leaves are converted into bladders, This fact clearly indicates the present and following species are modified segments of the leaf; and they are thus brought into accordance with the bladders attached to the divided and floating leaves of the aquatic species. 350 UTRICULARIA MONTANA. [Cmar. XVIII. do not bifurcate and extend up the dorsal and ventral surfaces, as in the previous species. The antennæ are of moderate length, and taper to a fine point; they differ conspicuously from those before described, in not being armed with bristles. Their bases are so abruptly curved that their tips generally rest one on each side of the middle of the bladder, but sometimes near the margin. Their curved bases thus form a roof over the cavity in which the valve lies; but there is always left on each side a little circular passage into the cavity, as may be seen Fig. 27. (Utricularia montana.) Bladder; about 27 times enlarged. in the drawing, as well as a narrow passage between the bases of the two antennz. As the bladders are subterranean, had it not been for the roof, the cavity in which the valve lies would have been liable to be blocked up with earth and rubbish; so that the curvature of the antenns is a service- able character. There are no bristles on the outside of the collar or peristome, as in the foregoing species. The valve is small and steeply inclined, with its free pos- terior edge abutting against a semicircular, deeply depending Cuap. XVIII.] CAPTURED ANIMALS. 351 collar. Itis moderately transparent, and bears two pairs of short stiff bristles, in the same position as in the other species. The presence of these four bristles, in contrast with the absence of those on the antennæ and collar, indicates that they are of functional importance, namely, as I believe, to prevent too large animals forcing an entrance through the valve. The many glands of diverse shapes attached to the valve and round the collar in the previous species are here absent, with the exception of about a dozen of the two-armed or transversely elongated kind, which are seated near the borders of the valve, and are mounted on very short foot- stalks. These glands are only the şov of an inch (019 mm.,) in length; though so small, they act as absorbents. The collar is thick, stiff, and almost semicircular ; it is formed of the same peculiar brownish tissue as in the former species. The bladders are filled with water, and sometimes include bubbles of air. They bear internally rather short, thick, quadrifid processes arranged in approximately concentric Fig. 28. (Utricularia montana.) One of the quadrifid processes; much enlarged. rows. The two pairs of arms of which they are formed differ only a little in length, and stand in a peculiar position (fig. 28); the two longer ones forming one line, and the two shorter ones another parallel line. Each arm includes a small spherical mass of brownish matter, which, when crushed, breaks into angular pieces. I have no doubt that these spheres are nuclei, for closely similar ones are present in the cells forming the walls of the bladders. Bifid processes, having rather short oval arms, arise in the usual position on the inner side of the collar. These bladders, therefore, resemble in all essential respects the larger ones of the foregoing species. They differ chiefly in the absence of the numerous glands on the valve and round the collar, a few minute ones of one kind alone being present on the valve. They differ more conspicuously in the absence of the long bristles on the antennæ and on the outside of the collar. ‘The presence of these bristles in the 352 UTRICULARIA MONTANA. [Cuar. XVIII. previously mentioned species probably relates to the capture of aquatic animals. It seemed to me an interesting question whether the minute bladders of Utricularia montana served, as in the previous species, to capture animals living in the earth, or in the dense vegetation covering the trees on which this species is epiphytic; for in this case we should have a new sub-class of carnivorous plants, namely, subterranean feeders. Many bladders, therefore, were examined, with the following results :— (1) A small bladder, less than {1 of an inch (*847 mm.) in diameter contained a minute mass of brown, much decayed matter; and in this, a tarsus with four or five joints, terminating in a double hook, was clearly distinguished under the microscope. I suspect that it was a remnant of one of the Thysanoura. The quadrifids in contact with this decayed remnant contained either small masses of translucent, yellowish matter, generally more or less globular, or fine granules. In distant parts of the same bladder, the processes were transparent and quite empty, with the exception of their solid nuclei. My son made at short intervals of time sketches of one of the above aggregated masses, and found that they continually and completely changed their forms; sometimes separating from one another and again coalescing. Evidently protoplasm had been generated by the absorption of some element from the decaying animal matter. (2) Another bladder included a still smaller speck of decayed brown matter, and the adjoining quadrifids contained aggregated matter, exactly as in the last case. (3) A third bladder included a larger organism, which was so much decayed that I could only make out that it was spinose or hairy. The quadrifids in this case were not much affected, excepting that the nuclei in the several arms differed much in size ; some of them contain- ing two masses having a similar appearance. (4) A fourth bladder contained an articulate organism, for I distinctly saw the remnant of a limb, terminating in a hook. The quadrifids were not examined. (5) A fifth included much decayed matter apparently of some animal, but with no recognisable features. The quadrifids in contact contained numerous spheres of protoplasm. (6) Some few bladders on the plant which I received from Kew were examined; and in one, there was a worm-shaped animal very little decayed, with a distinct remnant of a similar one greatly decayed. Several of the arms of the processes in contact with these remains contained two spherical masses, like the single solid nucleus which is properly found in each arm. In another bladder there was a minute grain of quartz, reminding me of two similar cases with Utricularia neglecta, ameman 3 CHAP. XVIL] ABSORPTION. Soe © As it appeared probable that this plant would capture a greater number of animals in its native country than under culture, I obtained permission to remove small portions of the rhizomes from dried speci- mens in the herbarium at Kew. I did not at first find out that it was advisable to soak the rhizomes for two or three days, and that it was necessary to open the bladders and spread out their contents on glass: as from their state of decay and from having been dried and pressed, their nature could not otherwise be well distinguished. Several bladders on a plant which had grown in black earth in New Granada were first examined; and four of these included remnants of animals. The first contained a hairy Acarus, so much decayed that nothing was left except its transparent coat; also a yellow chitinous head of some animal with an internal fork, to which the cesophagus was suspended, but I could see no mandibles; also the double hook of the tarsus of some animal; also an elongated greatly decayed animal; and lastly, a curious flask-shaped organism, having the walls formed of rounded cells. Professor Claus has looked at this latter organism, and thinks that it is the shell of a rhizopod, probably one of the Arcellidæ. In this bladder, as well as in several others, there were some unicellular Alge, and one multicellular Alga, which no doubt had lived as intruders. A second bladder contained an Acarus much less decayed than the former one, with its eight legs preserved; as well as remnants ot several other articulate animals. A third bladder contained the end of the abdomen with the two hinder limbs of an Acarus, as I believe. A fourth contained remnants of a distinctly articulated bristly animal, and of several other organisms, as well as much dark brown organic inatter, the nature of which could not be made out. : ; Some bladders from a plant, which had lived as an epiphyte in Trinidad, in the West Indies, were next examined, but not so carefully as the others; nor had they been soaked long enough. Four of them contained much brown, translucent granular matter, apparently organic, with no distinguishable parts. The quadrifids in two were brownish, with their contents granular; and it was evident that they had absorbed matter. In a fifth bladder there was a flask-shaped organism, like that above mentioned. A sixth contained a very long, much decayed, worm-shaped animal. Lastly, a seventh bladder contained an organism, but vf what nature could not be distinguished. Only one experiment was tried on the quadrifid processes and glands with reference to their power of absorption. A bladder was punctured and left for 24 hrs. in a solution of one part of urea to 437 of water, and the quadrifid and bifid processes were found much affected. In some arms there was only a single symmetrical globular mass, larger than the proper nucleus, and consisting of yellowish matter, generally translucent but sometimes granular ; Pa others k 354 UTRICULARIA MONTANA. [Cuar. XVIII. there were two masses of different sizes, one large and the other small; and in others there were irregularly shaped globules; so that it appeared as if the limpid contents of the processes, owing to the absorption of matter from the solution, had become aggregated sometimes round the nucleus, and sometimes into separate masses; and that these then tended to coalesce. The primordial utricle or protoplasm lining the processes was also thickened here and there into irregular and variously shaped specks of yellowish translucent matter, as occurred in the case of Utricularia neglecta under similar treatment. These specks apparently did not change their forms. The minute two-armed glands on the valve were also affected by the solution; for they now contained several, sometimes as many as six or eight, almost spherical masses of translucent matter, tinged with yellow, which slowly changed their forms and positions. Such masses were never observed in these glands in their ordinary state. We may therefore infer that they serve for absorption. Whenever a little water is expelled from a bladder containing animal remains (by the means formerly specified, more especially by the generation of bubbles of air), it will fill the cavity in which the valve lies; and thus the glands will be able to utilise decayed matter which otherwise would have been wasted. Finally, as numerous minute animals are captured by this plant in its native country and when cultivated, there can be no doubt that the bladders, though so small, are far from being in a rudimentary condition; on the contrary, they are highly efficient traps. Nor can there be any doubt that matter is absorbed from the decayed prey by the quadrifid and bifid processes, and that protoplasm is thus generated. What tempts animals of such diverse kinds to enter the cavity beneath the bowed antenne, and then force their way through the little slit-like orifice between the valve and collar into the bladders filled with water, I cannot conjecture. Tubers.—These organs, one of which is represented in 4 previous figure (fig. 26) of the natural size, deserve a few remarks. Twenty were found on the rhizomes of a single plant, but they cannot be strictly counted ; for, besides the twenty, there were all possible gradations between a short length of a rhizome just perceptibly swollen and one 80 Cuar. XVIIL] RESERVOIRS FOR WATER. 899 much swollen that it might be doubtfully called a tuber. When well developed, they are oval and symmetrical, more so than appears in the figure. The largest which I saw was 1 inch (25-4 mm.) in length and +45 inch (11°43 mm.) in breadth. They commonly lie near the surface, but some are buried at the depth of 2 inches. The buried ones are dirty white, but those partly exposed to the light become greenish from the development of chlorophyll in their superficial cells. They terminate in a rhizome, but this sometimes decays and drops off. They do not contain any air, and they sink in water; their surfaces are covered with the usual papillæ. The bundle of vessels which runs up each rhizome, as soon as it enters the tuber, separates into three distinct bundles, which reunite at the opposite end. A rather thick slice of a tuber is almost as transparent as glass, and is seen to consist of large angular cells, full of water and not containing starch or any other solid matter. Some slices were left in alcohol for several days, but only a few extremely minute granules of matter were precipitated on the walls of the cells; and these were much smaller and fewer than those precipitated on the cell-walls of the rhizomes and bladders. We may therefore conclude that the tubers do not serve as reservoirs for food, but for water during the dry season to which the plant is probably exposed. The many little bladders filled with water would aid towards the same end. To test the correctness of this view, a small plant, growing in light peaty earth in a pot (only 45 by 44 inches outside measure) was copiously watered, and then kept without a drop of water in the hothouse. Two of the upper tubers were beforehand uncovered and measured, and then loosely covered up again. In a fortnight’s time the earth in the pot appeared extremely dry ; but not until the thirty-fifth day were the leaves in the least affected; they then became slightly reflexed, though still soft and green. This plant, which bore only ten tubers, would no doubt have resisted the drought for even a longer time, had I not previously removed three of the tubers and cut off several long rhizomes. When, on the thirty-fifth day, the earth in the pot was turned out, it appeared as dry as the dust on the road. All the tubers had their surfaces much wrinkled, instead of being smooth and tense. They had all shrunk, but I cannot say accurately ow much ; for as they were at first EE ed lem I aA 356 UTRICULARIA MONTANA. (Cuar. XVIIL measured only their length and thickness; but they con- tracted in a transverse line much more in one direction than in another, so as to become greatly flattened. One of the two tubers which had been measured was now three-fourths of its original length, and two-thirds of its original thickness in the direction in which it had been measured, but in another direction only one-third of its former thickness. The other tuber was one-fourth shorter, one-eighth less thick in the direction in which it had been measured, and only half as thick in another direction. A slice was cut from one of these shrivelled tubers and examined. The cells still contained much water and no air, but they were more rounded or less angular than before, and their walls not nearly so straight; it was therefore clear that the cells had contracted. The tubers, as long as they remain alive, have a strong attraction for water ; the shrivelled one, from which a slice had been cut, was left in water for 22 hrs. 30 m., and its surface became as smooth and tense as it originally was. On the other hand, a shrivelled tuber, which by some accident had been separated from its rhizome, and which appeared dead, did not swell in the least, though left for several days in water. With many kinds of plants, tubers, bulbs, &c., no doubt serve in part as reservoirs for water, but I know of no case, besides the present one, of such organs having been developed solely for this purpose. Prof. Oliver informs me that two or three other species of Utricularia are provided with these appendages; and the group containing them has in conse- quence received the name of orchidioides. All the other species of Utricularia, as well as of certain closely related genera, are either aquatic or marsh plants; therefore, on the principle of nearly allied plants generally having a similar constitution, a never-failing supply of water would probably be of great importance to our present species. We can thus understand the meaning of the development of its tubers, and of their number on the same plant, amounting in one instance to at least twenty. UTRICULARIA NELUMBIFOLIA, AMETHYSTINA, GRIFFITHH, CERULEA, ORBICULATA, MULTICAULIS [CORNUTA]. As I wished to ascertain whether the bladders on ithe rhizomes of other species of Utricularia, and of the species Cuar. XVIII.) UTRICULARIA AMETHYSTINA. 3857 of certain closely allied genera, had the same essential structure as those of Utricularia montana, and whether they captured prey, I asked Prof. Oliver to send me fragments from the herbarium at Kew. He kindly selected some of the most distinct forms, having entire leaves, and believed to inhabit marshy ground or water. My son, Francis Darwin, examined them, and has given me the following observations; but it should be borne in mind that it is extremely difficult to make out the structure of such minute and delicate objects after they have been dried and pressed.* Utricularia nelumbifolia (Organ Mountains, Brazil).—The habitat of this species is remarkable. According to its discoverer, Mr. Gardner,f it is aquatic, but “is only to be found growing in the water which collects in the bottom of the leaves of a large Tillandsia, that inhabits abundantly an arid rocky part of the mountain, at an elevation of about 5000 feet above the level of the sea. Besides the ordinary method by seed, it propagates itself by runners, which it throws out from the base of the flower-stem; this runner is always found directing itself towards the nearest Tillandsia, when it inserts its point into the water and gives origin to a new plant, which in its turn sends out another shoot. In this manner I have seen not less than six plants united.” The bladders resemble those of Utricularia montana in all essential respects, even to the presence of a few minute two- armed glands on the valve. Within one bladder there was the remnant of the abdomen of some larva or crustacean of large size, having a brush of long sharp bristles at the apex. Other bladders included fragments of articulate animals, and many of them contained broken pieces of a curious organism, the nature of which was not recognised by any one to whom it was shown. : Utricularia amethystina (Guiana).—This species has small entire leaves, and is apparently a marsh plant ; but it must grow in places where crustaceans exist, for there were two small species within one of the bladders. The bladders are nearly of the same shape as those of Utricularia montana, and * Prof. Oliver has given (‘ Proc. appear to have paid particular atten- Linn. Soc.’ vol. iv. p. 169) figures of tion to these organs. Í a the bladders of two South American t ‘Travels in the Interior of Brazil, species, namely, Utricularia Jameso- 1836-41; p. 527. niana and peltata; but he does not 358 UTRICULARIA ORLICULATA. ([Cuar. XVIII. are covered outside with the usual papille ; but they differ remarkably in the antenne being reduced to two short points, united by a membrane hollowed out in the middle. This membrane is covered with innumerable oblong glands supported on long footstalks ; most of which are arranged in two rows converging towards the valve. Some, however, are seated on the margins of the membrane; and the short ventral surface of the bladder, between the petiole and valve, is thickly covered with glands. Most of the heads had failen off, and the footstalks alone remained; so that the ventral surface and the orifice, when viewed under a weak power, appeared as if clothed with fine bristles. The valve is narrow, and bears a few almost sessile glands. The collar against which the edge shuts is yellowish, and presents the usual structure. From the large number of glands on the ventral surface and round the orifice, it is probable that this species lives in very foul water, from which it absorbs matter, as well as from its captured and decaying prey. Utricularia grifithii (Malay and Borneo).—The bladders are transparent and minute; one which was measured being only ;25, of an inch (+711 mm.) in diameter. The antenne are of moderate length, and project straight forward; they are united fur a short space at their bases by a membrane ; and they bear a moderate number of bristles or hairs, not simple as heretofore, but surmounted by glands. ‘he bladders also differ remarkably from those of the previous species, as within there are no quadrifid, only bifid processes. In one bladder there was a minute aquatic larva; in another the remains of some articulate animal; and in most of them grains of sand. Utricularia cærulea (India).—The bladders resemble those of the last species, both in the general character of the antenne and in the processes within being exclusively bifid. They contained remnants of entomostracan crustaceans. Utricularia orbiculata (India).—The orbicular leaves and the stems bearing the bladders apparently float in water. The bladders do not differ much from those of the two last species. The antenne, which are united for a short distance at their bases, bear on their outer surfaces and summits numerous, long, multicellular hairs, surmounted by glands. The processes within the bladders are quadrifid, with the four diverging arms of equal length. The prey which they had captured consisted of entomostracan crustaceans. — Cuar. XVIIL] POLYPOMPHOLYX. 359 Utricularia multicaulis (Sikkim, India, 7000 to 11,000 feet). —The bladders, attached to rhizomes, are remarkable from the structure of the antennæ. These are broad, flattened, and of large size; they bear on their margins multicellular hairs, surmounted by glands. Their bases are united into a single, rather narrow pedicel, and they thus appear like a great digitate expansion at one end of the bladder. Inter- nally the quadrifid processes have divergent arms of equal length. The bladders contained remnants of articulate animals. | Utricularia cornuta, Michx. (United States).—This species has been studied by A. Schimper in America, and is the sub- ject of a short paper in the ‘ Botanische Zeitung.’ * It grows in swampy ground, and presents a remarkable appearance ; the aerial part of the plant seems at first sight to consist of nothing but almost naked flower-stems a foot in height, bearing from two to five large yellow flowers. U. cornuta has no roots, its underground stem or rhizome is much branched and bears numerous minute bladders. The branches of the rhizome throw up here and there grass-like leaves which cover the ground without having any apparent connection with the flower-stem. The structure of the blad- ders is not in any way remarkable, resembling in its general features that of the European species. The bladders generally contain organic remains; out of 114 only 11 contained no débris. The contents include diatoms and small animals,— worms, rotifers, small crustaceans; and the hairs lining the inside of the bladders give evidence of having absorbed matter from the decaying mass.—F. D. | PoLYPOMPHOLYX. This genus, which is confined to Western Australia, is characterised by having a “quadripartite calyx.” In other respects, as Prof. Oliver remarks,t “it is quite a Utricularia.” i Polypompholyx multifida.—The bladders are attached in whorls round the summits of stiff stalks. The two antennæ are represented by a minute membranous fork, the basal part of which forms a sort of hood over the orifice. This [* “ Notizen über Insectfressende Pflanzen,” 1882, p. 241.] t ‘Proc. Linn. Soe.’ vol. iv. p. 171. 360 GENLISEA ORNATA. [Cuar. XVIII. hood expands into two wings on each side of the bladder. A third wing or crest appears to be formed by the extension of the dorsal surface of the petiole; but the structure of these three wings could not be clearly made out, owing to the state of the specimens. The inner surface of the hood is lined with long simple hairs, containing aggregated matter, like that within the quadrifid processes or the previously described species when in contact with decayed animals. These hairs appear therefore to serve as absorbents. A valve was seen, but its structure could not be determined. On the collar round the valve there are in the place of glands numerous one-celled papillw, having very short footstalks. The quadrifid processes have divergent arms of equal length. Remains of entomostracan crustraceans were found within the bladders. Polypompholyx tenella—The bladders are smaller than those of the last species, but have the same general structure. They were full of débris, apparently organic, but no remains of articulate animals could be distinguished. GENLISEA. This remarkable genus is technically distinguished from Utricularia, as I hear from Prof. Oliver, by having a five- partite calyx. Species are found in several parts of the world, and are said to be “ herbee annuz paludose.” Genlisea ornata (Brazil).—This species has been described and figured by Dr. Warming,* who states that it bears two kinds of leaves, called by him spathulate and utriculiferous. The latter include cavities; and as these differ much from the bladders of the foregoing species, it will be convenient to speak of them as utricles. The accompanying figure (fig. 29) of one of the utriculiferous leaves, about thrice en- larged, will illustrate the following description by my son, which agrees in all essential points with that given by Dr. Warming. The utricle (b) is formed by a slight enlarge- ment of the narrow blade of the leaf. A hollow neck (n), no less than fifteen times as long as the utricle itself, forms a passage from the transverse slit-like orifice (o) into the cavity of the utricle. A utricle which measured 3}; of an * “Bidrag til Kundskaben om Lentibulariacee,” Copenhagen, 1874. Cuar. XVIII] STRUCTURE OF THE LEAVES. 361 inch (+705 mm.) in its longer diameter had a neck 14 of an inch (10:583 mm.) in length, and +}, of an inch (+254 mm.) in breadth. On each side of the orifice there is a long spiral arm or tube (a); the structure of which will be best under- stood by the following illustration. Take a narrow ribbon and wind it spirally round a thin cylinder, so that the edges come into contact along its whole length; then pinch up the two edges so as to form a little crest, which will of course wind spirally round the cylinder like a thread round a screw. If the cylinder is now removed, we shall have a tube like one of the spiral arms. The two projecting edges are not actually united, and a needle can be pushed in easily between them. They are indeed in many places a little separated, forming narrow entrances into the tube ; but this may be the result of the drying of the specimens. The lamina of which the tube is 4 LTR n sad formed seems to be a lateral pro- longation of the lip of the orifice ; and the spiral line between the two projecting edges is contin- vous with the corner of the orifice. If a fine bristle is pushed down i one of the arms, it passes into Fio. 2. the top of the hollow neck. (Genlisea ornata.) Whether the arms are open Or Utriculiferous leaf; enlarged about closed at their extremities could : ee not be determined, as all the T Upper part of lamina of leaf. Specimens were broken; nor does n Neck of utricle. it appear that Dr. Warming 5 Spirally wound arms, with their ascertained this point. ends broken off. So much for the external struc- : ture. Internally the lower part of the utricle is covered with spherical papille, formed of four cells (sometimes eight according to Dr. Warming), which evidently answer to the quadrifid processes within the bladders of Utricularia. These 362 GENLISEA ORNATA. [Ciir X VILL papille extend a little way up the dorsal and ventral surfaces of the utricle; and a few, according to Warming, may be found in the upper part. This upper region is covered by many transverse rows, one above the other, of short, closely approximate hairs, pointing downwards. These hairs have broad bases, and their tips are formed by a separate cell. They are absent in the lower part of the utricle where the papille abound. The neck is likewise lined throughout its whole length with transverse rows of long, thin, transparent hairs, having broad bulbous (fig. 30) bases, with similarly constructed sharp points. They arise from little projecting ridges, formed of rectangular epidermic cells. The hairs vary a little in length, but their points generally extend down to the row next below; so that if the neck is split open and laid flat, the inner surface re- sembles a paper of pins,—the hairs representing the pins, and the little transverse ridges re- presenting the folds of paper through which the pins are thrust. These rows of hairs are indicated in the previous figure (29) by numerous transverse Fic. 30. lines crossing the neck. The (Genlisea ornata.) inside of the neck is also studded Portion of inside of neck leading With papille; those in the lower into the utricle, greatly enlarged, show- : ing the downward pointed bristles, and part are spherical and formed small quadrifid cells or processes. of four cells, as in the lower part of the utricle ; those in the upper part are formed of two cells, which are much elongated downwards beneath their points of attachment. These two- celled papille apparently correspond with the bifid process in the upper part of the bladders of Utricularia. The narrow transverse orifice (0, fig. 29) is situated between the bases of the two spiral arms. No valve could be detected here, nor Cuar. XVIIL] CAPTURED PREY. 363 was any such structure seen by Dr. Warming. The lips of the oritice are armed with many short, thick, sharply pointed, somewhat incurved hairs or teeth. The two projecting edges of the spirally wound lamina, forming the arms, are provided with short incurved hairs or teeth, exactly like those on the lips. These project inwards at right angles to the spiral line of junction between the two edges. The inner surface of the lamina supports two- celled, elongated papille, resembling those in the upper part of the neck, but differing slightly from them, according to Warming, in their footstalks being formed by prolonga- tions of large epidermic cells; whereas the papillae within the neck rest on small cells sunk amidst the larger ones. These spiral arms form a conspicuous difference between the present genus and Utricularia. Lastly, there is a bundle of spiral vessels which, running up the lower part of the linear leaf, divides close beneath the utricle. One branch extends up the dorsal and the other up the ventral side of both the utricle and neck. Of these two branches, one enters one spiral arm, and the other branch the other arm. e The utricles contained much débris or dirty matter, which seemed organic, though no distinct organisms could þe recognised. It is, indeed, scarcely possible that any object could enter the small orifice and pass down the long narrow neck, except a living creature. Within the necks, however, of some specimens, a worm with retracted horny jaws, the abdomen of some articulate animal, and specks of dirt, pro- bably the remnants of other minute creatures, were found. Many of the papillæ within both the utricles and necks were discoloured, as if they had absorbed matter. From this description it is sufficiently obvious how Genlisea secures its prey. Small animals entering the narrow orifice —but what induces them to enter is not known any more than in the case of Utricularia—would find their egress rendered. difficult by the sharp incurved hairs on the lips, and as soon as they passed some way down the neck, it would be scarcely possible for them to return, owing to the many transverse rows of long, straight, downward pointing airs, together with the ridges from which these project. Such creatures would, therefore, perish either within the neck or utricle; and the quadrifid and bifid papilla would absorb matter from their decayed remains. The transverse 364 GENLISEA FILIFORMIS. [Cuar. XVIII. rows of hairs are so numerous that they seem superfluous merely for the sake of preventing the escape of prey, and as they are thin and delicate, they probably serve as additional absorbents, in the same manner as the flexible bristles on the infolded margins of the leaves of Aldrovanda. The spiral arms no doubt act as accessory traps. Until fresh leaves are examined, it cannot be told whether the line ot junction of the spirally wound lamina is a little open along its whole course, or only in parts, but a small creature which forced its way into the tube at any point, would be prevented from escaping by the incurved hairs, and would find an open path down tue tube into the neck, and so into the utricle. If the creature perished within the spiral arms, its decaying remains would be absorbed and utilised by the bifid papille. We thus see that animals are captured by Genlisea, not by means of an elastic valve, as with the foregoing species, but by a contrivance resembling an eel-trap, though more complex. : i Genlisea africana (South Africa).—Fragments of the utri- culiferous leaves of this species exhibited the same structure as those of Genlisea ornata. A nearly perfect Acarus was found within the utricle or neck of one leaf, but in which of the two was not recorded. Genlisea aurea (Brazil).—A fragment of the neck of a utricle was lined with transverse rows of hairs, and was fur- nished with elongated papillæ, exactly like those within the neck of Genlisea ornata. It is probable, therefore, that the whole utricle is similarly constructed. Genlisea filiformis (Bahia, Brazil)—Many leaves were examined and none were found provided with utricles, whereas such leaves were found without difficulty in the three previous species. On the other hand, the rhizomes bear bladders resembling in essential character those on the rhizomes of Utricularia. These bladders are transparent, and very small, viz. only +}, of an inch (+254 mm.) in length. The antenne are not united at their bases, and apparently bear some long hairs. On the outside of the bladders there are only a few papille, and internally very few quadrifid processes. These latter, however, are of unusually large size, relatively to the bladder, with the four divergent arms of equal length. No prey couid be seen within these = bladders. As the rhizomes of this species were furnishe with bladders, those of Genlisea africana, ornata, and aurea Cuar. XVIIL] CONCLUSION. 365 were carefully examined, but none could be found. What are we to infer from these facts? Did the three species just named, like their close allies, the several species of Utricu- laria, aboriginally possess bladders on their rhizomes, which they afterwards lost, acquiring in their place utriculiferous leaves? In support of this view it may be urged that the bladders of Genlisea filiformis appear from their small size and from the fewness of their quadrifid processes to be tending towards abortion; but why has not this species acquired utriculiferous leaves, like its congeners ? ConcLuston.—It has now been shown that many species of Utricularia and of two closely allied genera, inhabiting the most distant parts of the world—Kurope, Africa, India, the Malay Archipelago, Australia, North and South America— are admirably adapted for capturing by two methods small aquatic or terrestrial animals, and that they absorb the pro- ducts of their decay. = Ordinary plants of the higher classes procure the requisite inorganic elements from the soil by means of their roots, and absorb carbonic acid from the atmosphere by means of their leaves and stems. But we have seen in a previous part of this work that there is a class of plants which digest and afterwards absorb animal matter, namely, all the Droseracewx, Pinguicula, and, as discovered by Dr. Hooker, Nepenthes, and to this class other species will almost certainly soon be added. These plants can dissolve matter out of certain vegetable substances, such as pollen, seeds, and bits of leaves. No doubt their glands likewise absorb the salts of ammonia brought to them by the rain. It has also been shown that some other plants can absorb ammonia by their glandular hairs ; and these will profit by that brought to them by the rain. There is a second class of plants which, as we have just seen, cannot digest, but absorb the products of the decay of the animals which they capture, namely, Utricularia* and its close allies; and from the excellent observations of [* The late Professor de Bary grown in water swarming with showed me at Strasburg two dried specimens of Utricularia (vulgaris ?) which clearly demonstrated the ad- vantage which this plant derives from captured insects. One had been minute crustaceans, the other in clean water ; the difference in size between the “fed” and the “starved” plants was most striking.—F. D.] 366 : CONCLUSION. (Cuar. XVIII. Dr. Mellichamp and Dr. Canby, there can scarcely be a doubt that Sarracenia and Darlingtonia may be added to this class, though the fact can hardly be considered as yet fully proved. [A. Schimper, in an interesting paper,* gives evidence that the products of decay are absorbed by the pitchers of Sarra- cenia purpurea.t In the epidermic cells at the base of the pitcher the changes produced by the presence of decaying animal matter are strikingly evident, and bear a strong resemblance to the process of aggregation as seen in Drosera. The cell-sap is rich in tannin (as in Drosera), and when aggregation takes place the single vacuole containing the cell-sap is replaced by several highly refractive drops. The process resembles in fact the division and concentration of the vacuole as described by De Vries (see footnote, p. 35). Schimper supposes that the cell-sap gives up to the proto- plasm part of its water, and he describes the concentrated, tannin-containing drops which are thus formed, as lying in the swollen watery protoplasm which now takes up more space than in the unstimulated condition. Schimper’s paper also contains a good general description of the pitchers of Sarracenia.—F’. D. | There is a third class of plants which feed, as is now . generally admitted, on the products of the decay of vegetable matter, such as the bird’s-nest orchis (Neottia), &c.t Lastly, * [“ Notizen über Insectfressende Pflanzen,” ‘Bot. Zeitung, 1882, p. 225. + [In the ‘Quarterly Journal of Science and Art,’ 1829, vol. ii. p. 290, Burnett (as Mr. Thiselton Dyer points out to me) wrote as follows: “Sarracenia, if kept from the access of flies, are said to be less flourishing in their growth than when each pouch is truly a sarcophagus.” According to Faivre (‘Comptes ren- dus,’ vol. Ixxxiii. 1876, p. 1155) both Nepenthes and Sarracenia flourish better when their pitchers are sup- plied with water, and Wiesner states that Sarracenia can be kept fresh for months without watering the roots if the pitchers are well supplied. (‘Elemente der Anat. und Phys. der Pflanzen, 2nd Edit. 1885, p. 226).— F. D.] . t [Dischidia Rafflesiana, Wall., is sometimes doubtfully mentioned as an insectivorous plant. The re- searches of Treub (¢ Annales du Jardin botanique de Buitenzorg, vol. iii.1885, p. 13) show that this is not the case. Dischidia grows as a climbing epi- phyte on trees, and bears clusters of modified leaves or pitchers. They are of interest morphologically be- cause it is the inside of the pitcher which corresponds to the lower sur- face of the leaf, so that, the pitchers are involutions or pouchings of the leaf from the lower instead of from the upper surface as in Nepenthes, Sarracenia and Cephalotus (see Dick- son, ‘Journal of Botany,’ 1881, p. 133). The pitchers of Dischidia are covered, both inside and out, with a waxy coating which is heaped up in a curious manner round the stomata, Cuar. XVIIL] CONCLUSION. 367 there is the well-known fourth class of parasites (such as the mistletoe), which are nourished by the juices of living plants. Most, however, of the plants belonging to these four classes obtain part of their carbon like ordinary species, from the atmosphere. Such are the diversified means, as far as at present known, by which higher plants gain their subsis- tence. forming a tower-like structure round each of these openings. There are no glands on the surface of the pitchers, and the fluid with which they are often partially filled is simply collected rain-water. Adven- titious roots are numerous and com- monly enter the cavities of the pitchers. Delpino (quoted by Treub) believes that the pitchers serve to collect ants, &c., whose dead bodies may supply food tothe roots. Treub on the other hand believes that the drowning of ants within the pitchers is accidental rather than wilful on the part of the plant. He points out that no arrangement for retaining the ants exists, and that the adven- titious roots supply ladders by which they may escape; moreover the ants are as often as not found alive and well within the pitchers. Treub is inclined to consider that the pitchers’ function is as stores or cisterns of water; but their use in the economy of the plant cannot be considered as definitely settled.—F. D.] ( 369 ) INDEX. ABSORPTION. A. ABSORPTION by Dionza, 238 —— by Drosera, 1, 14 —— by Drosophyllum, 273 —— by Pinguicula, 307 —— by glandular hairs, 278 —— by glands of Utricularia, 336, 340 —— by quadrifids of Utricularia, 333, 340 —— by Utricularia montana, 353 Acid, nature of, in digestive secretion of Drosera, 73 —— present in digestive fluid of various species of Drosera, Dionza, Drosophyllum, and Pinguicula, 224, 243, 274, 307 Acids, various, action of, on Drosera, 154 of the acetic series replacing hydrochloric in digestion, 74 —, arsenious and chromic, action on Drosera, 151 , diluted, osmose, 161 Adder’s poison, action on Drosera, 168 Aggregation of protoplasm in Dro- sera, 32 inducing negative — in Drosera induced by salts of | ammonia, 37 caused by small doses of carbonate of ammonia, 119 — of protoplasm in Drosera, a reflex action, 196 in various species of Dro- — me sera, 224 AMMONIA. Aggregation of protoplasm in Dionæa, 235, 243 in Drosophyllum, 273, 274 —— —— in Pinguicula, 299, 314 in Utricularia, 332, 335, 345, 346, 352 Albumen, digested by Drosera, 77 , liquid, action on Drosera, 67 Alcohol, diluted, action of, on Dro- sera, 65, 177 Aldrovanda vesiculosa, 260 , absorption and digestion by, 264 , varieties of, 265 Algæ, aggregation in fronds of, 54 Alkalies, arrest digestive process in Drosera, 78 Aluminium, salts of, action on Dro- sera, 150 Ammonia, amount of, in rain water, 140 , carbonate, action on heated leaves of Drosera, 58 i , smallness of doses causing aggregation in Drosera, 119 s „its action on Drosera, 115 ; , vapour of, absorbed by glands of Drosera, 116 y , smallness of doses causing inflection in Drosera, 119, 137 , phosphate, smallness of doses causing inflection in Drosera, 125, 137 —, , size of particles affecting Drosera, 141 , nitrate, smallness of doses causing inflection in Drosera, 120, 137 —__ 2 B INDEX. AMMONIA. Ammonia, salts of, action on Drosera, 13 x , their action affected by previous immersion in water and various solutions, 174 ’ , induce aggregation in Drosera, 37 » various salts of, inflection in Drosera, 135 Antimony, tartrate, action on Dro- sera, 15 Areolar tissue, its digestion by Dro- sera, 85 Arsenious acid, action on Drosera, 151 Atropine, action on Drosera, 166 causing B. Barium, salts of, action on Drosera, 149 Bases of salts, preponderant action of, on Drosera, 152 Basis, fibrous, of bone, its digestion by Drosera, 90 Batalin, on motor impulse in Drosera, 204 , on bending of tentacles of Drosera, 209 , on Dionxa, 233 , on mechanism of closure in Dionæa, 256 , on colour of Pinguicula leaves, 297 , on movement in Pinguicula, 304 Belladonna, extract of, action on Drosera, 70 Bennett, Mr. A. W., on Drosera, 1, 2,7 , coats of pollen grains not digested by insects, 96 Binz, on action of quinine on white blood-corpuscles, 164 , On poisonous action of quinine on low organisms, 165 Bone, its digestion by Drosera, 88 Brunton, Lauder, on digestion of gelatine, 92 —, on the composition of casein, 95 CHROMIC. Brunton, Lauder, on the digestion of urea, 102 id of chlorophyll, 103 of pepsin, 102 nutrition of ? Biisgen, Dr. M., on Drosera, 16 Burnett, on Sarracenia, 366 Byblis, 277 C. Cabbage, decoction Drosera, 70 Cadmium chloride, action on Drosera, 150 Cæsium, chloride of, action on Dro- sera, 148 Calcium, salts of, action on Drosera, 148 Camphor, action of Drosera, 170 _ Canby, Dr., on Dionæa, 243, 250, 252 , on Drosera filiformis, 227 Caraway, oil of, action on Drosera, 172 Carbonic acid, action on Drosera, 180 delays aggregation in Drosera, of, action on 50 Cartilage, its digestion by Drosera, 86 Casein, its digestion by Drosera, 95 Caspary, on Aldrovanda, 260, 261 Cellulose, not digested by Drosera, 103 Chalk, precipitated, causing inflec- tion of Drosera, 28 Cheese, its digestion by Drosera, 96 Chitine, not digested by Drosera, 102 Chloroform, effects of, on Drosera 1? . , on Dionæa, 246 i Chlorophyll, grains of, in living plants, digested by Drosera, 103 , pure, not digested by Drosera, Chondrin, its digestion by Drosera, 93 Chromic acid, action on Drosera, 151 INDEX. CLOVES. Cloves, oil of, action on Drosera, 173 Cobalt chloride, action on Drosera, 152 Cobra poison, action on Drosera, 168 Cohn, Prof., on Aldrovanda, 260 , on contractile tissues in plants, 293 , on movements of stamens of Composite, 208 , on Utricularia, 319 Colchicine, action on Drosera, 166 Copper chloride, action on Drosera, 151 Crystallin, its digestion by Drosera, 98 Co, Curare, action on Drosera, 166 Curtis, Dr., on Dionza, 243 p. Darwin, C., papers on action of ammonia on roots, 55 , Erasmus, on Diongæa, 243 , Francis, on the effect of an induced galvanic current on Dro- sera, 31 , on aggregation in Drosera, 32, 39 , on nutrition of Drosera, 15 „on the digestion of grains of chlorophyll, 103 De Bary, effect of animal food on Utricularia, 365 De Candolle, on Dionæa, 232, 233, 235 Delpino, on Aldrovanda, 260 , on Utricularia, 319, 366 , on Dischidia, 367 Dentine, its digestion by Drosera, 88 Digestion of various substances by Dionæa, 243 by Drosera, 71 —— —— by Drosophyllum, 274 by Pinguicula, 307 , origin of power of, 291 Digitaline, action on Drosera, 165 Dionza, early literature of, 231 —_—, _—— DROSOPHYLLUM. Dionza, muscipula, small size of roots, 231 - » structure of leaves, 232 , Sensitiveness of filaments, 254 , absorption by, 238 , secretion by, 238 —, digestion by, 243 , effects on, of chloroform, 246 » manner of capturing insects, 247 , transmission of motor impulse, 253 , re-expansion of lobes, 257 Direction of inflected tentacles of Drosera, 197 Dischidia. Rafflesiana, 366 Dohrn, Dr., on rhizocephalous crus- taceans, 288 Donders, Prof, small amount of atropine affecting the iris of the dog, 140 Dragonfly caught by Drosera, 2 Drosera, absorption by, 1, 14 anglica, 224 binata, vel dichotoma, 227 capensis, 225 dichotoma, 5 —— filiformis, 226 heterophylla, 229 —— intermedia, 225 , sensitiveness of, 22 Drosera rotundifolia, structure of leaves, 3 , artificial feeding of, 15 , effects on, of nitrogenous fluids, 64 , effects of heat on, 56 , its power of digestion, 71 ——, backs of leaves not sensitive, 188 ——, transmission of motor impulse, 190. ——, general summary, 212 spathulata, 226 Droseraceez concluding remarks on, 287 ——, their sensitiveness compared with that of animals, 295 Drosophyllum, structure of leaves, 269 , secretion by, 270 INDEX. DROSOPHYLLUM. Drosophyllum, absorption by, 273 , digestion by, 274 Duval-Jouve, on Aldrovanda, 268 E. Ellis, on Dionga, 245 Enamel, its digestion by Drosera, 88 Erica, tetralix, glandular hairs of, 284 Ether, effects of, on Drosera, 179 $ , on Dionæa, 246 Euphorbia, process of aggregation in roots of, 53 Ewald, on peptogenes, 106 Exosmose from backs of leaves of Dro- | sera, 188 F. Faivre, on Nepenthes and Sarra- cenia, 366 Fat not digested by Drosera, 104 Fayrer, Dr., on the nature of cobra poison, 168 yon the action of cobra poison on animal protoplasm, 170 » on cobra poison paralysing nerve centres, 185 Ferment, nature of, in secretion of Drosera, 78, 81 Fibrin, its digestion by Drosera, 84 Fibro-cartilage, its digestion by Drosera, 87 Fibro-elastic tissue, not digested by Drosera, 100 Fibrous basis of bone, its digestion by Drosera, 90 Fluids, nitrogenous, effects of, on Drosera, 64 Fournier, on acids causing movements in stamens of Berberis, 160, Frankland, Prof., on nature of acid in secretion of Drosera, 73 Fraustadt, A., on Dionæa, 232, 233 ——, on roots of Dionæa, 288 HAIDENHAIN, G. Galyanism, current of, causing in- flection of Drosera, 31 , effects of, on Dionza, 256 Gardiner, W., on Drosera dichotoma, 5 , on the Rhabdoid, 32 , on aggregation, 34 : » on process of secretion in Drosera, 72 » on intercellular protoplasm, 200 „on contractility of plant-cells, 209 , on gland-cells of Dionæa, 238 Gardner, Mr., on Utricularia nelum- bifolia, 357 Gelatine, impure, action on Drosera, 67 —, pure, its digestion by Drosera, 92 ~ Genlisea africana, 364 filiformis, 364 ornata, structure of, 360 : , manner of capturing prey, 369 Glandular hairs, absorpion by, 278 , Summary on, 285 Glauer, on aggregation, 39 Globulin, its digestion by Drosera, 98 Gluten, its digestion by Drosera, 97 Glycerine, inducing aggregation m Drosera, 45 » action on Drosera, 173 : Gold chloride, action on Drosera, 150 Gorup-Besanez, on the presence of & solvent in seeds of the vetch, 292 Grass, decoction of, action on Dro- sera, 70 Gray, Asa, on the Droseracez, 2 Greenland, on Drosera, 1, 5 Gum, action of, on Drosera, 65 Gun-cotton, not digested by Drosera, 103 H. Hæmatin, its digestion by Drosera, 9 Haidenhain, on peptogenes, 106 INDEX. 373 HAIRS, Hairs, glandular, absorption by, 278 —, , Summary on, 285 - Heat, inducing aggregation in Dro- sera, 45 ——, effect of, on Drosera, 56 —, , on Dionæa, 237, 258 Heckel, on state of stamens of Ber- beris after excitement, 37 Hofmeister, on pressure arresting movements of protoplasm, 52 Holland, Mr., on Utricularia, 319 Hooker, Dr., on carnivorous plants, 2 ———, on power of digestion by Ne- penthes, 81 —, history of observations on Dionza, 231, 243 Hovelacque, on Utricularia, 348 Hydrocyanic acid, effects of, on Dionæa, 246 apa action on Drosera, 70, it Iron chloride, action on Drosera, 151 Isinglass, solution of, action on Dro- sera, 67 J. Johnson, Dr., on movement of flower- stems of Pinguicula, 307 K. Kellermann and Von Raumer, on _ nutrition of Drosera, 15 Klein, Dr., on microscopic character of half digested bone, 88 ——,, on state of half digested fibro- cartilage, 87 —, on size of micrococci, 141 Knight, Mr., on feeding Dionxa, 243 Kossman, Dr., on rhizocephalous crustaceans, 288 MORI. Kunkel, on electric phenomena in Dionea, 256 Kurtz, on Dionæa, 231, 253 L. Lankester, E. Ray, on glands of water plants, 268 Lead chloride, action on Drosera, 151 Leaves of Drosera, backs of, not sensitive, 188 Legumin, its digestion by Drosera, 96 Lemna, aggregation in leaves of, 54 Lime, carbonate of, precipitated, causing inflection of Drosera, 28 , phosphate of, its action on Drosera, 91 Linnæus, on Dionæa, 243 Lithium, salts of, action on Drosera, 148 M. Magnesium, salts of, action on Dro- sera, 149 Manganese chloride, action on Dro- sera, 151 Marshall, Mr. W., on Pinguicula, 298 Means of movement in Dionæa, 253 in Drosera, 206 Meat, infusion of, causing aggrega- tion in Drosera, 44 , action on Drosera, 67 , its digestion by Drosera, 82 Mercury perchloride, action on Dro- sera, 150 Milk, inducing aggregation in Dro- sera, 44 , action on Drosera, 66 , its digestion by Drosera, 94 Mirabilis longiflora, glandular hairs of, 284 Moggridge, Traherne, on acids in- juring seeds, 105 Moore, Dr., on Pinguicula, 315 Mori, on Aldrovanda, 263 ? 374 INDEX. MORPHIA. Morphia acetate, action on Drosera, 167 Morren, E., on Drosera binata, 227 Motor impulse in Drosera, 190, 209 in Dionæa, 252 Movement, origin of power of, 293 Movements of leaves of Pinguicula, 299 of tentacles of Drosera, means of, 206 of Dionæa, means of, 252 Mucin, not digested by Drosera, 100 Mucus, action on Drosera, 67 Müller, Fritz, on rhizocephalous crustaceans, 288 Munk, on Dionæa, 234, 247 , onelectric phenomena in Dionæa, ose 256 N. Nepenthes, its power of digestion, 81 Nickel chloride, action on Drosera, 152 Nicotiana tabacum, glandular hairs of, 284 Nicotine, action on Drosera, 165 Nitric ether, action on Drosera, 180 Nitschke, Dr., references to his papers on Drosera, 1 : , On sensitiveness of backs of leaves of Drosera, 188 , on direction of inflected ten- tacles in Drosera, 198 , on Aldrovanda, 261 Nourishment, various means of, by plants, 365 Nuttall, Dr., on re-expansion of Dionza, 257 0. Odour of pepsin, emitted from leaves of Drosera, 74 Oels, W., on comp, anatomy of Dro- seraceæ, 2 Oil, olive, action of, on Drosera, 66, 104 POISON. Oliver, F., on motor impulse, 204 , Prof, on Utricularia, 349, 356-360 a Oudemans, on Dionæa, 233 P. Papaw, juice of, hastening putrefac- tion, 331 Particles, minute size of, causing inflection in Drosera, 24, 28 Peas, decoction of, action on Drosera, 69 Pelargonium zonale, glandular hairs of, 283 Penzig, Otto, on roots of Droso- phyllum, 288 Pepsin, odour of, emitted from Dro- sera leaves, 74 , not digested by Drosera, 101 , its secretion by animals excited only after absorption, 107 Peptogenes, 106 Pfeffer, on sensitiveness of Drosera to contact, 22, 31 , on nucleus in Drosera, 32 , on aggregation, 34 , on Dionzea, 256 , on roots of carnivorous plants, 288 , on Pinguicula, 314 Pinguicula grandiflora, 315 lusitanica, 315 vulgaris, structure of leaves and roots, 297 , number of insects caught by, 298 < , power of movement, 299 : , Secretion and absorption by, 307 ——-, digestion by, 307 ‘ , leaves of, used to curdle milk, 314 , effects of secretion on living seeds, 315 Platinum chloride, action on Drosera, 152 Poison of cobra and adder, their action on Drosera, 168 INDEX. (Jt) -~ Or POLLEN. Pollen, its digestion by Drosera, 96 Polypompholyx, structure of, 359 Potassium, salts of, inducing aggre- gation in Drosera, 43 ’ , action on Drosera, 146 phosphate, not decomposed by Drosera, 147, 153 Price, Mr. John, on Utricularia, 345 Primula sinensis, glandular hairs of, 281 , number of glandular hairs of, 286 Protoplasm, aggregated, re-dissolu- tion of, 46 ——, aggregation of, in Drosera, 32, 34, 35 —, „in Drosera, caused by small doses of carbonate of am- monia, 119 3 , in Drosera, a reflex action, 196 —, , in various species of Dro- sera, 224 , in Dionæa, 235, 242 ——, ——, in Drosophyllum, 273, 274 ——, —, in Pinguicula, 299, 314 , in Utricularia, 352, 335, _ —_—, ? 346, 352 Q. Quinine, salts of, action on Drosera, 163 R. Rain-water, amount of ammonia in, 140 Ralts, Mr., on Pinguicula, 315 Ransom, Dr., action of poisons on the yolk of eggs, 183 Rees and Will, on digestive action in Drosera, 73, 81 Re-expansion of headless tentacles of Drosera, 187 — of tentacles of Drosera, 210 —— of Dionæa, 257 SCHIFF. Roots of Drosera, 17 » process of aggregation x in, 53 — , absorb carbonate of am- monia, 115 of Dionga, 231 of Drosophyllum, 269 of Pinguicula, 298 Roridula, 276 Rubidium chloride, action on Drosera, 148 Sachs, Prof., effects of heat on pro- toplasm, 56, 59 , on the dissolution of proteid compounds in the tissues of plants, 292 Saliva, action on Drosera, 67 Salts and acids, various, effects of, on subsequent action of ammonia, 175 Sanderson, Burdon, on coagulation of albumen from heat, 62 » on acids replacing chloric in digestion, 74 , on the digestion of fibrous basis of bone, 90 of gluten, 97 of globulin, 99 of chlorophyll, 103 „on different effect of sodium and potassium on animals, 152 , on electric currents in Dionza, 256 Sarracenia, 365, 366 Saxifraga umbrosa, glandular hairs of, 279 Schenk, on Utricularia, 348 Schiff, on hydrochloric acid dis- solying coagulated albumen, 71 „on manner of digestion of albumen, 77 , on changes in meat during digestion, 83 on the coagulation of milk, hydro- ? , ? —— , 94 INDEX. SCHIFF. Schiff, on the digestion of casein, 95 , on the digestion of mucus, 101 , on peptogenes, 106 Schimper, on aggregation, 34 , on Utricularia, 331, 332 , on Sarracenia purpurea, 365 Schloesing, on absorption of nitro- gen by Nicotiana, 285 Scott, Mr., on Drosera, 1 Secretion of Drosera, general account of, 11 , its antiseptic power, 13 , becomes acid from excite- ment, 72 ——, nature of its ferment, 78, 81 — by Dionza, 238 —— by Drosophyllum, 271 — by Pinguicula, 307 Seeds, living, acted on by Drosera, 104 —, , acted on by Pinguicula, | 311, 314 Sensitiveness, localisation of, in Dro- sera, 187 of Dionæa, 233 of Pinguicula, 299 Silver nitrate, action on Drosera, 148 Sodium, salts of, action on Drosera, 143 —, , inducing aggregation in Drosera, 43 Sondera heterophylla, 229 Sorby, Mr., on colouring matter of Drosera, 4 Spectroscope, its power compared with that of Drosera, 139 Starch, action of, on Drosera, 65, 104 Stein, on Aldrovanda, 260 Strontium, salts of, action on Dro- sera, 149 Strychnine, salts of, action on Dro- sera, 162 Sugar, solution of, action of, on Dro- sera, 65 s , inducing aggregation in Drosera, 44 Sulphuric ether, action on Drosera, 179 } UTRICULARIA. Sulphuric ether, action on Dionæa, 246 Syntonin, its action on Drosera, 85 T. Tait, Mr., on Drosophyllum, 269 Taylor, Alfred, on the detection of minute doses of poisons, 139 Tea, infusion of, action on Drosera, 65 Tentacles of Drosera, move when glands cut off, 31, 187 , inflection, direction of, 197 ——, means of movement, 206 , Te-expansion of, 210 Theine, action on Drosera, 166 Tin chloride, action on Drosera, 151 Tissue, areolar, its digestion by Drosera, 85 , fibro-elastic, not digested by Drosera, 100 | Tissues through which impulse is transmitted in Drosera, 200 in Dionæa, 252 : Touches repeated, causing inflection in Drosera, 29 : Transmission of motor impulse in Drosera, 190 in Dionæa, 252 Traube, Dr., on artificial cells, 176 Treat, Mrs., on Drosera filiformis, 226 , on Dionæa, 251 „on valve in Utricularia, 329, 330, 346 | Trécul, on Drosera, 1, 5 Treub, on Dischidia, 366, 367 __ Tubers of Utricularia montana, 354 Turpentine, action on Drosera, 173 v. Urea, not digested by Drosera, 102 Urine, action on Drosera, 66 Utricularia clandestina, 346 minor, 345 -— montana, structure of bladders, 348 INDEX. 377 UTRICULARIA, Utricularia, montana animals caught by, 352 , absorption by, 353 , tubers of, serving as reservoirs, 354 Utricularia neglecta, structure of bladders, 321 , animals caught by, 327 , absorption by, 333 ——, summary on absorption, 340 , development of bladders, 342 Utricularia, various species of, 356 Utricularia vulgaris, 345 V. Veratrine, action on Drosera, 166 Vessels in leaves of Drosera, 200 Vessels of Dionæa, 253 Vines, on digestive fluid of Nepen- thes, 81 ——, on the ferment of the Vetch, 292 Vogel, on effects of camphor on plants, 171 Von Gorup and Will, on digestive action in Drosera, 73, 81 Vries, H. de, on aggregation, 35, 39 ZINC. W. 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