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Nutritive Properties of Elm Leaves.- In the Number for March of the same year, 1839, p. 125., a notice is given by M. Poiteau of the nutritive properties of the leaves of the elm, as forage for horned cattle. This is also an idea contemporary with Cato the censor. In proof of it, let us look at chap. 30. De Re Rustica : “Feed the cows on elm, poplar, oak, and fig leaves, as long as they last.” And also in this neighbourhood, perhaps from tradition, but more certainly from experience, the leaves of the elm are so esteemed for fattening horned cattle, that the trees are stripped of their leaves twice a year; and, in fact, there is here no forage nor hay which fattens cattle more quickly than the foliage of the elm. We may presume that these nutritive properties depend on the mucilage contained in the parenchymal tissue, and thence we may conclude that the U'Imus fúlva, from what has been said in the Gardener's Magazine for April 1840, p. 231., is the most abundant in mucilage, and will furnish, in its twigs and leaves, the most nutritive fodder for cattle.

If in these and many other things modern discoveries coincide with more ancient practices, there are also other subjects in which the ancient practice is entirely discordant to the modern doctrine. Thus, for example, Cato sowed the seeds of cupressus in soil well manured with sheep or goat dung. In opposition to this, Prof. Lindley, in his excellent Theory of Horticulture, p. 354., observes, “coniferous plants can scarcely bear any manure.”—Giuseppe Manetti. Monza, April 27. 1843.

Yellow Glass suggested for Plant-houses. — A hundred other comparisons could be made, but let the shades of the ancient Romans repose for the present, and let us turn our attention to an argument of the day. From the excellent observations of the celebrated T. A. Knight, the necessity is evident of letting the plants repose or grow torpid, to induce them to produce flowers and fruit in season. Prof. Lindley says that “ very low temperature, under the influence of much light, by retarding and diminishing the expenditure of sap of the growth of plants comparatively with its creation, produces nearly similar effects, and causes an early appearance of fruit." This being granted, and the observations of Mr. Horner of Hull and Mr. Hunt, mentioned in Gard. Mag., 1841, p. 629. and 630., being borne in mind, will it not be useful, in furnishing the elaborated matter destined for resting plants, to have the glass of a yellow colour ? — Idem.

Art. V. Queries and Answers. LARCH Plantations at Linley.— I propose visiting the extensive larch plantations of the late Mr. More, of Linley in Shropshire, who, I have been informed, first introduced this tree into our country. This gentleman, upon a fortune of about 1000l. per annum, clothed a 'naked country with noble woods, erected a spacious mansion-house, employed a considerable number of labourers in various improvements, travelled over most countries in Europe, collected a valuable library, employed artists in making drawings in natural history, introduced new species of forest trees and exotics

, was an independent member of the senate in several parliaments, and left his fortune unencumbered. You will credit me that he was not a man of unnecessary show and parade. (E. Harries, Esq., of Hanwood, in Young's Arnals of Agriculture, vol. xiii. p. 100.)

Can any of our readers oblige us with an account of the present state of the larch plantations at Linley, and of the exotic trees introduced there by Mr. More ? Cond.

Art. VI. Obituary. Died, on the 4th of April, at Sedbury Park, Yorkshire, William Sawrey Gilpin, Esq., Landscape-Gardener, late of Painesfield, East Sheen, aged 81. (Times, April 7. 1843.)

THE

GARDENER'S MAGAZINE,

JULY, 1843.

ORIGINAL COMMUNICATIONS.

Art. I. Comparative Physiology. By R. LYMBURN.

(Continued from p. 215.) In Chap. II. On Vital Stimuli, Dr. Carpenter says: “It has been shown in the last chapter, that the actions of living beings depend on an organised structure possessing vital properties, and certain agents necessary to call the operation of these properties into existence. In the higher classes especially, of living beings, the influence of the stimuli supplied by alimentary materials, heat, light, electricity, &c., is directed towards the preparation of a nutrient fluid, which contains the elements of all the solid tissues of the body, and which not only supplies the materials of growth, but stimulates the organs to the performance of their actions. Light, heat, &c., serve as external stimuli, and their immediate action is upon the simplest of the organic processes. The nutrient fluid is the chief internal stimulus to the nutritive actions of the system, assisted by the continued influence of external agents. The motion of the blood through the lungs is as dependent upon the influence of the air in the cells, as sneezing is upon a stimulant applied to the nostrils; and, if the circulation be suspended, the nerves and muscles lose their power, from the want of the stimulant action of the blood. Both the external and internal stimuli must thus be regarded as vital, as they not only give rise to vital actions, but these actions conduce to the maintenance of life. The action of the internal stimuli will be best considered under the functions of absorption, nutrition, respiration, &c. The dependence of life on the external stimuli, heat, light, electricity, &c., is greater in proportion to the perfection of the structure, and the variety of its organs, and vice versâ. Beings of a simple organisation are capable of enduring a deprivation of these stimuli, which would be fatal to those higher in the scale ; as the more developed the parts of the system are, the more closely are the parts connected with one another.

3d Ser. - 1843. VII.

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“ The simpler the condition of any organism, the more susceptible is it of being modified in form and structure by external causes. In the more simple embryonic state also, changes are inore easily effected: the germ is hybridised by being furnished with different nutrient matter from another female parent than usual; the bee is changed from a working neuter to a queen by peculiarities in the cell and food; and, among the lowest

groups of plants, there seems reason to believe that the same germ may assume very different forms, according to the circumstances under which it is developed.”

Some have denied the existence of any such thing as stimuli at all, especially as applied to the alimentary materials. It is, they say, the production of the aliment in a proper form, and under the requisite circumstances, that produces activity in the vital functions. When the circulating fluid contains the proper elements, in the requisite condition for absorption, nutrition, &c., these functions will become active, which would cease to be the case, if the necessary changes were not produced by reaction, &c. The presence of nitrogen in the form of ammonia, and alkaline substances, in the young shoots and leaves of plants, producing the well-known dark-green colour so characteristic of vigour, has been thought to produce a stimulating action on the organs, increasing their activity. It has been sometimes known to take place without vigour of growth following; and it may be doubtful whether it denotes the proper state of the food for growth merely, or produces a stimulating action. From the excitability prevalent, however, through all organised tissues, their capability of being stimulated to action has been generally inferred. Müller defines stimulus as a reaction following a disturbing cause, something similar to elasticity, in which a power of attraction causes the disturbed particles to communicate the attempt to displace a portion to the whole, and bring into activity a power of restitution, accompanied by elasticity. The power of reaction or restitution, he says, in organised beings, is, however, more uniform than the elasticity, &c., of inorganic, and arises from that fundamental property resident in them, of counterbalancing disturbances in their composition by a force which, in the healthy state of the body, is much stronger than the disturbing cause. Dutrochet calls excitability a state of susceptibility of excitation. The power of resisting excitation has by others been termed a vital property, antagonist of that of the chemical or exciting, which tends to destroy; and the capability of stimulus would, from the above definition, appear to be a capability of displaying vital actions, or a susceptibility thereto. The quiescent state of the vital principle he terms “a capability of living;” the simplest organised beings retaining this state longest, and seeming least

dependent on stimuli. He distinguishes between mechanical stimuli, as pressure, &c., which exhaust, and vital, which renovate. “ Nutriment is not merely a stimulus of the organic body; it is itself susceptible of life; it is a stimulus which vivifies, and can itself receive vitality. The constant reanimation of the tissues by the general vital stimuli ordinarily renders them capable of a proportionate exercise of their functions ; but, if their action is increased and accelerated, subsequent rest is necessary to restore as much power for new action as has been thus consumed. Rest alone, however, induces weakness; the power of an organ is increased by exercise, not carried too far, and alternating with rest.” The affinity of the tissues for the vital stimuli seems to be greater where the developement is less complete, or in the young state. That the power of vitality is increased by its exercise, I have often before noticed; it is from this cause that a lazy slow-growing plant is converted, by cutting in the shoots, into a more vigorous growth; the activity given by the start made after cutting continues. Sets from vigorous-grown potatoes, and cuttings and seeds from vigorousgrown plants, always thrive best. The bad consequences, however, of too much and too long continued excitement in plants, without a due proportion of rest, have been often pointed out, and have been most conspicuous in the forcing of the vine. Much of the bad consequences attributed to excitement are probably also due to a want of balance in the effects of stimuli. Were it possible to follow up the great expansion by heat with a corresponding degree of light, the weakness produced by the former might not be so apparent; and great part of what is ascribed to over-stimulus may be rather due to a deficiency of other stimuli, to a want of light, as well as too much heat.

That the embryo is susceptible of changes at the time of formation, of which it is not susceptible afterwards, is clearly to be seen in the many hybrids produced ; and those hybrids being more frequent among plants, shows that the lower grades of beings are more susceptible of these changes. Whether any or what portion of the change is due to stimuli, we are, however, perhaps unable to decide. Whether the germ is produced by the male or female, or the joint influence of both, in seeds, can hardly be said to be decided. There may also be much owing to certain kinds and states of food being required for the developement of parts, without which they cannot be produced. Of this kind seems the transformation from a leaf bud to a flower; the greater degree of elaboration of the sap seeming all that is requisite to produce from a bud, the germ of a branch, 80 apparently different an organ as a flower. That it is a real transformation seems evident from the many changes observed, from petal to leaf, from stamen to petal, and from a stigma to a branch. The difference however is, perhaps, as much produced from the different quality of the food enabling a different form to be developed and vice versa, as from a stimulus given by the food. The production, or capability of production, of a new being from the bud seems only a lower grade of the function of reproduction, than the more perfect form of it in producing a seed. The changes produced by the different nature of the food in the lowest grades of plants, producing sometimes a lichen, sometimes a conferva, from the same germ, according to the absence or presence of water, seem apparently to countenance the idea of there being something equivocal in their developement, perhaps more than in their generation. The changes produced on higher grades of plants, by the different nature of their food, have frequently been found to alter them so much as to cause them to be reckoned distinct species; yet it has been found that the seedlings from these plants resume the ordinary habit of the species, when again under ordinary circumstances. There may be much of this in the changes of plants so nearly resembling each other as confervæ and lichens; and a fixed character in the germ is more indicative of purpose and wisdom, till the equivocal has been more certainly determined.

On Heat as a Vital Stimulus, he remarks that “all vital action requires a certain amount of caloric for its due performance, and can only continue within a certain range of temperature. The greater the amount and variety of vital action, the more immediate is the dependence of the individual on the maintenance of its usual temperature. Plants are almost entirely dependent on the medium they inhabit for the necessary supply of caloric; and their vital actions are so adjusted as to be carried on within very wide extremes of heat and cold. In the Chinese embassy, a species of Marchántia was found at the Island of Amsterdam, growing in mud hotter than boiling water, at a hot spring; and the beautiful Protococcus nivalis, or red snow, reddens extensive tracts in the arctic regions, where the perpetual frost of the surface scarcely yields to the influence of the solar rays at midsummer. The stimulating action of heat is very obvious on plants; it increases evaporation by the leaves, and consequently absorption by the roots, supplying the water which prevents its tissue from being dried up, and, by its conversion into vapour, moderating the temperature, which would otherwise be excessive. If the supply of water is deficient, the tissues get dense and contracted; the shrubs in sandy Eastern deserts assuming a stunted and prickly appearance. Cold depresses vital action, and, if very severe, congeals the juices, and bursts the vessels ; the viscidity of the fluids, and the slow conducting power of the wood, tend to resist this

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