their proper vertical position. Some curious facts have been given under this head, showing that horizontally extended leaves suffered more at night, when the air, which is not cooled by radiation, was prevented from freely circulating beneath their lower surfaces; and so it was, when the leaves were allowed to go to sleep on branches which had been rendered motionless. In some species the petioles rise up greatly at night, and the pinnae close together. The whole plant is thus rendered more compact, and a much smaller surface is exposed to radiation.
That the various nyctitropic movements of leaves result from modified circumnutation has, we think, been clearly shown. In the simplest cases a leaf describes a single large ellipse during the 24 h.; and the movement is so arranged that the blade stands vertically during the night, and reassumes its former position on the following morning. The course pursued differs from ordinary circumnutation only in its greater amplitude, and in its greater rapidity late in the evening and early on the following morning. Unless this movement is admitted to be one of circumnutation, such leaves do not circumnutate at all, and this would be a monstrous anomaly. In other cases, leaves and cotyledons describe several vertical ellipses during the 24 h.; and in the evening one of them is increased greatly in amplitude until the blade stands vertically either upwards or downwards. In this position it continues to circumnutate until the following morning, when it reassumes its former position. These movements, when a pulvinus is present, are often complicated by the rotation of the leaf or leaflet; and such rotation on a small scale occurs during ordinary circumnutation. The many diagrams showing the movements of sleeping and non-sleeping leaves and cotyledons should be compared, and it will be seen that they are essentially alike. Ordinary circumnutation is converted into a nyctitropic movement, firstly by an increase in its amplitude, but not to so great a degree as in the case of climbing plants, and secondly by its being rendered periodic in relation to the alternations of day and night. But there is frequently a distinct trace of periodicity in the circumnutating movements of non-sleeping leaves and cotyledons. The fact that nyctitropic movements occur in species distributed in many families throughout the whole vascular series, is intelligible, if they result from the modification of the universally present movement of circumnutation; otherwise the fact is inexplicable.
In the seventh chapter we have given the case of a Porlieria, the leaflets of which remained closed all day, as if asleep, when the plant was kept dry, apparently for the sake of checking evaporation.
Something of the same kind occurs with certain Gramineæ. At the close of this same chapter, a few observations were appended on what may be called the embryology of leaves. The leaves produced by young shoots on cut-down plants of Melilotus Taurica slept like those of a Trifolium, whilst the leaves on the older branches on the same plants slept in a very different manner, proper to the genus; and from the reasons assigned we are tempted to look at this case as one of reversion to a former nyctitropic habit. So again with Desmodium gyrans, the absence of small lateral leaflets on very young plants, makes us suspect that the immediate progenitor of this species did not possess lateral leaflets, and that their appearance in an almost rudimentary condition at a somewhat more advanced age is the result of reversion to a trifoliate predecessor. However this may be, the rapid circumnutating or gyrating movements of the little lateral leaflets, seem to be due proximately to the pulvinus, or organ of movement, not having been reduced nearly so much as the blade, during the successive modifications through which the species has passed.
We now come to the highly important class of movements due to the action of a lateral light. When stems, leaves, or other organs are placed, so that one side is illuminated more brightly than the other, they bend towards the light. This heliotropic movement manifestly results from the modification of ordinary circumnutation; and every gradation between the two movements could be followed. When the light was dim, and only a very little brighter on one side than on the other, the movement consisted of a succession of ellipses, directed towards the light, each of which approached nearer to its source than the previous one. When the difference in the light on the two sides was somewhat greater, the ellipses were drawn out into a strongly-marked zigzag line, and when much greater the course became rectilinear. We have reason to believe that changes in the turgescence of the cells is the proximate cause of the movement of circumnutation; and it appears that when a plant is unequally illuminated on the two sides, the always changing turgescence is augmented along one side, and is weakened or quite arrested along the other sides. Increased turgescence is commonly followed by increased growth, so that a plant which has bent itself towards the light during the day would be fixed in this position were it not for apogeotropism acting during the night. But parts provided with pulvini bend, as Pfeffer has shown, towards the light; and here growth does not come into play any more than in the ordinary circumnutating movements of pulvini.
Heliotropism prevails widely throughout the vegetable kingdom, but whenever, from the changed habits of life of any plant, such movements become injurious or useless, the tendency is easily eliminated, as we see with climbing and insectivorous plants.
Apheliotropic movements are comparatively rare in a well-marked degree, excepting with sub-aërial roots. In the two cases investigated by us, the movement certainly consisted of modified circumnutation.
The position which leaves and cotyledons occupy during the day, namely, more or less transversely to the direction of the light, is due, according to Frank, to what we call diaheliotropism. As all leaves and cotyledons are continually circumnutating, there can hardly be a doubt that diaheliotropism results from modified circumnutation. From the fact of leaves and cotyledons frequently rising a little in the evening, it appears as if diaheliotropism had to conquer during the middle of the day a widely prevalent tendency to apogeotropism.
Lastly, the leaflets and cotyledons of some plants are known to be injured by too much light; and when the sun shines brightly on them, they move upwards or downwards, or twist laterally, so that they direct their edges towards the light, and thus they escape being injured.
These paraheliotropic movements certainly consisted in one case of modified circumnutation; and so it probably is in all cases, for the leaves of all the species described circumnutate in a conspicuous manner. This movement has hitherto been observed only with leaflets provided with pulvini, in which the increased turgescence on opposite sides is not followed by growth; and we can understand why this should be so, as the movement is required only for a temporary purpose. It would manifestly be disadvantageous for the leaf to be fixed by growth in its inclined position. For it has to assume its former horizontal position, as soon as possible after the sun has ceased shining too brightly on it.
The extreme sensitiveness of certain seedlings to light, as shown in our ninth chapter, is highly remarkable. The cotyledons of Phalaris became curved towards a distant lamp, which emitted so little light, that a pencil held vertically close to the plants, did not cast any shadow which the eye could perceive on a white card. These cotyledons, therefore, were affected by a difference in the amount of light on their two sides, which the eye could not distinguish. The degree of their curvature within a given time towards a lateral light did not correspond at all strictly with the amount of light which they received; the light not being at any time in excess. They continued for nearly half an hour to bend towards a lateral light, after it had been extinguished. They bend with remarkable precision towards it, and this depends on the illumination of one whole side, or on the obscuration of the whole opposite side. The difference in the amount of light which plants at any time receive in comparison with what they have shortly before received, seems in all cases to be the chief exciting cause of those movements which are influenced by light. Thus seedlings brought out of darkness bend towards a dim lateral light, sooner than others which had previously been exposed to daylight. We have seen several analogous cases with the nyctitropic movements of leaves. A striking instance was observed in the case of the periodic movements of the cotyledons of a Cassia; in the morning a pot was placed in an obscure part of a room, and all the cotyledons rose up closed; another pot had stood in the sunlight, and the cotyledons of course remained expanded; both pots were now placed close together in the middle of the room, and the cotyledons which had been exposed to the sun, immediately began to close, while the others opened; so that the cotyledons in the two pots moved in exactly opposite directions whilst exposed to the same degree of light.
We found that if seedlings, kept in a dark place, were laterally illuminated by a small wax taper for only two or three minutes at intervals of about three-quarters of an hour, they all became bowed to the point where the taper had been held. We felt much surprised at this fact, and until we had read Wiesner’s observations, we attributed it to the after-effects of the light; but he has shown that the same degree of curvature in a plant may be induced in the course of an hour by several interrupted illuminations lasting altogether for 20 m., as by a continuous illumination of 60 m. We believe that this case, as well as our own, may be explained by the excitement from light being due not so much to its actual amount, as to the difference in amount from that previously received; and in our case there were repeated alternations from complete darkness to light. In this, and in several of the above specified respects, light seems to act on the tissues of plants, almost in the same manner as it does on the nervous system of animals. There is a much more striking analogy of the same kind, in the sensitiveness to light being localised in the tips of the cotyledons of Phalaris and Avena, and in the upper part of the hypocotyls of Brassica and Beta; and in the transmission of some influence from these upper to the lower parts, causing the latter to bend towards the light. This influence is also transmitted beneath the soil to a depth where no light enters. It follows from this localisation, that the lower parts of the cotyledons of Phalaris, etc., which normally become more bent towards a lateral light than the upper parts, may be brightly illuminated during many hours, and will not bend in the least, if all light be excluded from the tip. It is an interesting experiment to place caps over the tips of the cotyledons of Phalaris, and to allow a very little light to enter through minute orifices on one side of the caps, for the lower part of the cotyledons will then bend to this side, and not to the side which has been brightly illuminated during the whole time. In the case of the radicles of Sinapis alba, sensitiveness to light also resides in the tip, which, when laterally illuminated, causes the adjoining part of the root to bend apheliotropically.
Gravitation excites plants to bend away from the centre of the earth, or towards it, or to place themselves in a transverse position with respect to it. Although it is impossible to modify in any direct manner the attraction of gravity, yet its influence could be moderated indirectly, in the several ways described in the tenth chapter; and under such circumstances the same kind of evidence as that given in the chapter on Heliotropism, showed in the plainest manner that apogeotropic and geotropic, and probably diageotropic movements, are all modified forms of circumnutation.
Different parts of the same plant and different species are affected by gravitation in widely different degrees and manners. Some plants and organs exhibit hardly a trace of its action. Young seedlings which, as we know, circumnutate rapidly, are eminently sensitive; and we have seen the hypocotyl of Beta bending upwards through 109° in 3 h. 8 m. The after-effects of apogeotropism last for above half an hour; and horizontally-laid hypocotyls are sometimes thus carried temporarily beyond an upright position. The benefits derived from geotropism, apogeotropism, and diageotropism, are generally so manifest that they need not be specified. With the flower-peduncles of Oxalis, epinasty causes them to bend down, so that the ripening pods may be protected by the calyx from the rain.
Afterwards they are carried upwards by apogeotropism in combination with hyponasty, and are thus enabled to scatter their seeds over a wider space. The capsules and flower-heads of some plants are bowed downwards through geotropism, and they then bury themselves in the earth for the protection and slow maturation of the seeds. This burying process is much facilitated by the rocking movement due to circumnutation.
In the case of the radicles of several, probably of all seedling plants, sensitiveness to gravitation is confined to the tip, which transmits an influence to the adjoining upper part, causing it to bend towards the centre of the earth. That there is transmission of this kind was proved in an interesting manner when horizontally extended radicles of the bean were exposed to the attraction of gravity for 1 or 1½ h., and their tips were then amputated. Within this time no trace of curvature was exhibited, and the radicles were now placed pointing vertically downwards; but an influence had already been transmitted from the tip to the adjoining part, for it soon became bent to one side, in the same manner as would have occurred had the radicle remained horizontal and been still acted on by geotropism. Radicles thus treated continued to grow out horizontally for two or three days, until a new tip was re-formed; and this was then acted on by geotropism, and the radicle became curved perpendicularly downwards.
It has now been shown that the following important classes of movement all arise from modified circumnutation, which is omnipresent whilst growth lasts, and after growth has ceased, whenever pulvini are present. These classes of movement consist of those due to epinasty and hyponasty,—those proper to climbing plants, commonly called revolving nutation,—the nyctitropic or sleep movements of leaves and cotyledons,—and the two immense classes of movement excited by light and gravitation. When we speak of modified circumnutation we mean that light, or the alternations of light and darkness, gravitation, slight pressure or other irritants, and certain innate or constitutional states of the plant, do not directly cause the movement; they merely lead to a temporary increase or diminution of those spontaneous changes in the turgescence of the cells which are already in progress. In what manner, light, gravitation, etc., act on the cells is not known; and we will here only remark that, if any stimulus affected the cells in such a manner as to cause some slight tendency in the affected part to bend in a beneficial manner, this tendency might easily be increased through the preservation of the more sensitive individuals. But if such bending were injurious, the tendency would be eliminated unless it was overpoweringly strong; for we know how commonly all characters in all organisms vary. Nor can we see any reason to doubt, that after the complete elimination of a tendency to bend in some one direction under a certain stimulus, the power to bend in a directly opposite direction might gradually be acquired through natural selection.[2] [2] See the remarks in Frank’s ‘Die wagerechte Richtung von Pflanzentheilen’ (1870, pp. 90, 91, etc.), on natural selection in connection with geotropism, heliotropism, etc.
Although so many movements have arisen through modified circumnutation, there are others which appear to have had a quite independent origin; but they do not form such large and important classes. When a leaf of a Mimosa is touched it suddenly assumes the same position as when asleep, but Brucke has shown that this movement results from a different state of turgescence in the cells from that which occurs during sleep; and as sleep-movements are certainly due to modified circumnutation, those from a touch can hardly be thus due. The back of a leaf of Drosera rotundifolia was cemented to the summit of a stick driven into the ground, so that it could not move in the least, and a tentacle was observed during many hours under the microscope; but it exhibited no circumnutating movement, yet after being momentarily touched with a bit of raw meat, its basal part began to curve in 23 seconds. This curving movement therefore could not have resulted from modified circumnutation. But when a small object, such as a fragment of a bristle, was placed on one side of the tip of a radicle, which we know is continually circumnutating, the induced curvature was so similar to the movement caused by geotropism, that we can hardly doubt that it is due to modified circumnutation. A flower of a Mahonia was cemented to a stick, and the stamens exhibited no signs of circumnutation under the microscope, yet when they were lightly touched they suddenly moved towards the pistil. Lastly, the curling of the extremity of a tendril when touched seems to be independent of its revolving or circumnutating movement. This is best shown by the part which is the most sensitive to contact, circumnutating much less than the lower parts, or apparently not at all.[3] [3] For the evidence on this head, see the ‘Movements and Habits of Although in these cases we have no reason to believe that the movement depends on modified circumnutation, as with the several classes of movement described in this volume, yet the difference between the two sets of cases may not be so great as it at first appears. In the one set, an irritant causes an increase or diminution in the turgescence of the cells, which are already in a state of change; whilst in the other set, the irritant first starts a similar change in their state of turgescence. Why a touch, slight pressure or any other irritant, such as electricity, heat, or the absorption of animal matter, should modify the turgescence of the affected cells in such a manner as to cause movement, we do not know. But a touch acts in this manner so often, and on such widely distinct plants, that the tendency seems to be a very general one; and if beneficial, it might be increased to any extent. In other cases, a touch produces a very different effect, as with Nitella, in which the protoplasm may be seen to recede from the walls of the cell; in Lactuca, in which a milky fluid exudes; and in the tendrils of certain Vitaceae, Cucurbitaceæ, and Bignoniaceae, in which slight pressure causes a cellular outgrowth.
Finally it is impossible not to be struck with the resemblance between the foregoing movements of plants and many of the actions performed unconsciously by the lower animals.[4] With plants an astonishingly small stimulus suffices; and even with allied plants one may be highly sensitive to the slightest continued pressure, and another highly sensitive to a slight momentary touch. The habit of moving at certain periods is inherited both by plants and animals; and several other points of similitude have been specified. But the most striking resemblance is the localisation of their sensitiveness, and the transmission of an influence from the excited part to another which consequently moves. Yet plants do not of course possess nerves or a central nervous system; and we may infer that with animals such structures serve only for the more perfect transmission of impressions, and for the more complete intercommunication of the several parts.
[4] Sachs remarks to nearly the same effect: “Dass sich die lebende Pflanzensubstanz derart innerlich differenzirt, dass einzelne Theile mit specifischen Energien ausgerüstet sind, ähnlich, wie die verschiedenen Sinnesnerven des Thiere” (‘Arbeiten des Bot. Inst. in We believe that there is no structure in plants more wonderful, as far as its functions are concerned, than the tip of the radicle. If the tip be lightly pressed or burnt or cut, it transmits an influence to the upper adjoining part, causing it to bend away from the affected side; and, what is more surprising, the tip can distinguish between a slightly harder and softer object, by which it is simultaneously pressed on opposite sides. If, however, the radicle is pressed by a similar object a little above the tip, the pressed part does not transmit any influence to the more distant parts, but bends abruptly towards the object. If the tip perceives the air to be moister on one side than on the other, it likewise transmits an influence to the upper adjoining part, which bends towards the source of moisture. When the tip is excited by light (though in the case of radicles this was ascertained in only a single instance) the adjoining part bends from the light; but when excited by gravitation the same part bends towards the centre of gravity. In almost every case we can clearly perceive the final purpose or advantage of the several movements. Two, or perhaps more, of the exciting causes often act simultaneously on the tip, and one conquers the other, no doubt in accordance with its importance for the life of the plant. The course pursued by the radicle in penetrating the ground must be determined by the tip; hence it has acquired such diverse kinds of sensitiveness. It is hardly an exaggeration to say that the tip of the radicle thus endowed, and having the power of directing the movements of the adjoining parts, acts like the brain of one of the lower animals; the brain being seated within the anterior end of the body, receiving impressions from the sense-organs, and directing the several movements.
INDEX.
A.
Abies communis, effect of killing or injuring the leading shoot, 187 — pectinata, effect of killing or injuring the leading shoot, 187 —, affected by Æcidium elatinum, 188 Abronia umbellata, its single, developed cotyledon, 78 —, rudimentary cotyledon, 95 —, rupture of the seed coats, 105 Abutilon Darwinii, sleep of leaves and not of cotyledons, 314 —, nocturnal movement of leaves, 323 Acacia Farnesiana, state of plant when awake and asleep, 381, 382 —, appearance at night, 395 —, nyctitropic movements of pinnae, 402 —, the axes of the ellipses, 404 — lophantha, character of first leaf, 415 — retinoides, circumnutation of young phyllode, 236 Acanthosicyos horrida, nocturnal movement of cotyledon 304 Acanthus candelabrum, inequality in the two first leaves, 79 —, petioles not arched, 553 — latifolius, variability in first leaves 79 — mollis, seedling, manner of breaking through the ground, 78, 79 —, circumnutation of young leaf, 249, 269 — spinosus, 79 —, movement of leaves, 249 Adenanthera pavonia, nyctitropic movements of leaflets, 374 Æcidium elatinum, effect on the lateral branches of the silver fir, 188 Æsculus hippocastanum, movements of radicle, 28, 29 —, sensitiveness of apex of radicle, 172–174 Albizzia lophantha, nyctitropic movements of leaflets, 383 —, of pinnae, 402 Allium cepa, conical protuberance on arched cotyledon, 59 —, circumnutation of basal half of arched cotyledon, 60 —, mode of breaking through ground, 87 —, straightening process, 101 — porrum, movements of flower-stems, 226 Alopecurus pratensis, joints affected by apogeotropism, 503 Aloysia citriodora, circumnutation of stem, 210 Amaranthus, sleep of leaves, 387 — caudatus, nocturnal movement of cotyledons, 307 Amorpha fruticosa, sleep of leaflets, 354 Ampelopsis tricuspidata, hyponastic movement of hooked tips, 272–275 Amphicarpoea monoica, circumnutation and nyctitropic movements of leaves, 365 —, effect of sunshine on leaflets, 445 —, geotropic movements of, 520 Anoda Wrightii, sleep of cotyledons, 302, 312 —, of leaves, 324 —, downward movement of cotyledons, 444 Apheliotropism, or negative heliotropism, 5, 419, 432 Apios graveolens, heliotropic movements of hypocotyl, 422–424 — tuberosa, vertical sinking of leaflets at night, 368 Apium graveolens, sleep of cotyledons, 305 —, petroselinum, sleep of cotyledons, 304 Apogeotropic movements effected by joints or pulvini, 502 Apogeotropism, 5, 494; retarded by heliotropism, 501; concluding remarks on, 507 Arachis hypogoea, circumnutation of gynophore, 225 —, effects of radiation on leaves, 289, 296 —, movements of leaves, 357 — rate of movement, 404 —, circumnutation of vertically dependent young gynophores, 519 —, downward movement of the same, 519 Arching of various organs, importance of, to seedling plants, 87, 88; emergence of hypocotyls or epicotyls in the form of an, 553 Asparagus officinalis, circumnutation of plumules, 60–62.
—, effect of lateral light, 484 Asplenium trichomanes, movement in the fruiting fronds, 257, n.
Astragalus uliginosus, movement of leaflets, 355 Avena sativa, movement of cotyledons, 65, 66.
—, sensitiveness of tip of radicle to moist air, 183 —, heliotropic movement and circumnutation of cotyledon, 421, 422 —, sensitiveness of cotyledon to a lateral light, 477 —, young sheath-like cotyledons strongly apogeotropic, 499 Avena sativa, movements of oldish cotyledons, 499, 500 Averrhoa bilimbi, leaf asleep, 330 —, angular movements when going to sleep, 331–335 —, leaflets exposed to bright sunshine, 447 Azalea Indica, circumnutation of stem, 208 B.
Bary, de, on the effect of the Æcidium on the silver fir, 188 Batalin, Prof., on the nyctitropic movements of leaves, 283; on the sleep of leaves of Sida napoea, 322; on Polygonum aviculare, 387; on the effect of sunshine on leaflets of Oxalis acetosella, 447 Bauhinia, nyctitropic movements, 373 —, movements of petioles of young seedlings, 401 —, appearance of young plants at night, 402 Beta vulgaris, circumnutation of hypocotyl of seedlings, 52 —, movements of cotyledons, 52, 53 —, effect of light, 124 —, nocturnal movement of cotyledons, 307 —, heliotropic movements of, 420 —, transmitted effect of light on hypocotyl, 482 —, apogeotropic movement of hypocotyl, 496 Bignonia capreolata, apheliotropic movement of tendrils, 432, 450 Bouché on Melaleuca ericaefolia, 383 Brassica napus, circumnutation of flower-stems, 226 Brassica oleracea, circumnutation of seedling, 10 —, of radicle, 11 —, geotropic movement of radicle, 11 —, movement of buried and arched hypocotyl, 13, 14, 15 —, conjoint circumnutation of hypocotyl and cotyledons, 16, 17, 18 —, of hypocotyl in darkness, 19 —, of a cotyledon with hypocotyl secured to a stick, 19, 20 —, rate of movement, 20 —, ellipses described by hypocotyls when erect, 105 —, movements of cotyledons, 115 —, — of stem, 202 —, — of leaves at night, 229, 230 —, sleep of cotyledons, 301 —, circumnutation of hypocotyl of seedling plant, 425 —, heliotropic movement and circumnutation of hypocotyls, 426 —, effect of lateral light on hypocotyls, 479–482 —, apogeotropic movement of hypocotyls, 500, 501 Brassica rapa, movements of leaves, 230 Brongniart, A., on the sleep of Strephium floribundum, 391 Bruce, Dr., on the sleep of leaves in Averrhoa, 330 Bryophyllum (vel Calanchoe) calycinum, movement of leaves, 237 C.
Camellia Japonica, circumnutation of leaf, 231, 232 Candolle, A. de, on Trapa natans, 95; on sensitiveness of cotyledons, 127 Canna Warscewiczii, circumnutation of plumules, 58, 59 —, of leaf, 252 Cannabis sativa, movements of leaves, 250 —, nocturnal movements of cotyledons, 307 Cannabis sativa, sinking of the young leaves at night, 444 Cassia, nyctitropic movement of leaves, 369 Cassia Barclayana, nocturnal movement of leaves, 372 —, slight movement of leaflets, 401 — calliantha, uninjured by exposure at night, 289, n.
—, nyctitropic movement of leaves, 371 — circumnutating movement of leaves, 372 — corymbosa, cotyledons sensitive to contact, 126 —, nyctitropic movement of leaves, 369 — floribunda, use of sleep movements, 289 —, effect of radiation on the leaves at night, 294 —, circumnutating and nyctitropic movement of a terminal leaflet, 372, 373 —, movements of young and older leaves, 400 — florida, cotyledons sensitive to contact, 126 —, sleep of cotyledons, 308 — glauca, cotyledons sensitive to contact, 126 —, sleep of cotyledons, 308 — laevigata, effect of radiation on leaves, 289, n.
— mimosoides, movement of cotyledons. 116 —, sensitiveness of, 126 —, sleep of, 308 —, nyctitropic movement of leaves, 372 —, effect of bright sunshine on cotyledons, 446 — neglecta, movements of, 117 —, effect of light, 124 —, sensitiveness of cotyledons, 126 —, do not rise at night, 308 Cassia pubescens, uninjured by exposure at night, 293 —, sleep of cotyledons, 308 —, nyctitropic movement of leaves, 371 —, circumnutating movement of leaves, 372 —, nyctitropic movement of petioles, 400 —, diameter of plant at night, 402 — sp. (?) movement of cotyledons, 116 — tora, circumnutation of cotyledons and hypocotyls, 34, 35, 109, 308 —, effect of light, 124, 125 —, sensitiveness to contact, 125 —, heliotropic movement and circumnutation of hypocotyl, 431 —, hypocotyl of seedling slightly heliotropic, 454 —, apogeotropic movement of old hypocotyl, 497 —, movement of hypocotyl of young seedling, 510 Caustic (nitrate of silver), effect of, on radicle of bean, 150, 156; on the common pea, 160.
Cells, table of the measurement of, in the pulvini of Oxalis corniculata, 120; changes in, 547 Centrosema, 365 Ceratophyllum demersum, movements of stem, 211 Cereus Landbeckii, its rudimentary cotyledons, 97 — speciossimus, circumnutation of stem, 206, 207 Cerinthe major, circumnutation of hypocotyl, 49 —, of cotyledons, 49 —, ellipses described by hypocotyls when erect, 107 — effect of darkness, 124 Chatin, M., on Pinus Nordmanniana, 389 Chenopodium album, sleep of leaves but not of cotyledons, 314, 319 Chenopodium album, movement of leaves, 387 Chlorophyll injured by bright light, 446 Ciesielski, on the sensitiveness of the tip of the radicles, 4, 523 Circumnutation, meaning explained, 1; modified, 263–279; and heliotropism, relation between, 435; of paramount importance to every plant, 547 Cissus discolor, circumnutation of leaf, 233 Citrus aurantium, circumnutation of epicotyl, 28 —, unequal cotyledons, 95 Clianthus Dampieri, nocturnal movement of leaves, 297 Cobœa scandens, circumnutation of, 270 Cohn, on the water secreted by Lathraea squamaria, 86, n.; on the movement of leaflets of Oxalis, 447 Colutea arborea, nocturnal movement of leaflets, 355 Coniferæ, circumnutation of, 211 Coronilla rosea, leaflets asleep, 355 Corylus avellana, circumnutation of young shoot, emitted from the epicotyl, 55, 56 —, arched epicotyl, 77 Cotyledon umbilicus, circumnutation of stolons, 219, 220 Cotyledons, rudimentary, 94–98; circumnutation of, 109–112; nocturnal movements, 111, 112; pulvini or joints of, 112–122; disturbed periodic movements by light, 123; sensitiveness of, to contact, 125; nyctitropic movements of, 283, 297; list of cotyledons which rise or sink at night, 300; concluding remarks on their movements, 311 Crambe maritima, circumnutation of leaves, 228, 229 Crinum Capense, shape of leaves, 253 —, circumnutation of, 254 Crotolaria (sp.?), sleep of leaves, 340 Cryptogams, circumnutation of, 257–259 Cucumis dudaim, movement of cotyledons, 43, 44 —, sleep of cotyledons, 304 Cucurbita aurantia, movement of hypocotyl, 42 —, cotyledons vertical at night, 304 —, ovifera, geotropic movement of radicle, 38, 39 —, circumnutation of arched hypocotyl, 39 —, of straight and vertical hypocotyl, 40 —, position of radicle, 89 —, rupture of the seed-coats, 102 —, circumnutation of hypocotyl when erect, 107, 108 —, sensitiveness of apex of radicle, 169–171 —, cotyledons vertical at night, 304 —, not affected by apogeotropism, 509 —, tips cauterised transversely, 537 Curvature of the radicle, 193 Cycas pectinata, circumnutation of young leaf, whilst emerging from the ground, 58 —, first leaf arched, 78 —, circumnutation of terminal leaflets, 252 Cyclamen Persicum, movement of cotyledon, 46 —, circumnutation of peduncle, 225 —, downward apheliotropic movement of a flower-peduncle, 433–435 Cyclamen Persicum, burying of the pods, 433 Cyperus alternifolius, circumnutation of stem, 212 —, movement of stem, 509 Cytisus fragrans, circumnutation of hypocotyl, 37 —, sleep of leaves, 344, 397 —, apogeotropic movement of stem, 494–496 + D.
Dahlia, circumnutation of young leaves, 244–246 Dalea alopecuroides, leaflets depressed at night, 354 Darkness, effect of, on the movement of leaves, 407 Darlingtonia Californica, its leaves or pitchers apheliotropic, 450, n.
Darwin, Charles, on Maurandia semperflorens, 225; on the Swedish turnip, 230, n.; movements of climbing plants, 266, 271; the heliotropic movement of the tendrils of Bignonia capreolata, 433; revolution of climbing plants, 451; on the curling of a tendril, 570 —, Erasmus, on the peduncles of Cyclamens, 433 —, Francis, on the radicle of Sinapis alba, 486; on Hygroscopic seeds, 489, n.
Datura stramonium, nocturnal movement of cotyledons, 298 Delpino, on cotyledons of Chaerophyllum and Corydalis, 96, n.
Delphinium nudicaule, mode of breaking through the ground, 80 —, confluent petioles of two cotyledons, 553