Agriculture is the art of cultivating the ground, more especially with the plough and in large areas or fields, in order to raise grain and other crops for man and beast; including the art of preparing the soil, sowing and planting seeds, removing the crops, and also the raising and feeding of cattle or other live stock. This art is the basis of all other arts, and in all countries coeval with the first dawn of civilization. At how remote a period it must have been successfully practised in Egypt, Mesopotamia, and China we have no means of knowing, but archaeologists have found evidence of agriculture being practised around 7000 BC. Egypt was renowned as a corn country in the time of the Jewish patriarchs, who themselves were keepers of flocks and herds rather than tillers of the soil. Naturally very little is known of the methods and details of agriculture in early times, though field archaeologists at Butser Ancient Farm in Hampshire have been conducting experiments for some years.
Among the ancient Greeks the implements of agriculture were very few and simple. Hesiod, who wrote a poem on agriculture as early as the eighth century BC, mentions a plough consisting of three parts, the share-beam, the draught-pole, and the plough-tail, but antiquarians are not agreed as to its exact form. The ground received three ploughings, one in autumn, another in spring, and a third immediately before sowing the seed. Manures were applied, and the advantage of mixing soils, as sand with clay or clay with sand, was understood. Seed was sown by hand, and covered with a rake. Grain was reaped with a sickle, bound in sheaves, thrashed, then winnowed by wind, laid in chests, bins, or granaries, and taken out as wanted by the family, to be ground.
Agriculture was highly esteemed among the ancient Romans. Cato, the censor, who was celebrated as a statesman, orator, and general, derived his highest honours from having written a voluminous work on agriculture. In his Georgics Virgil has thought the subject of agriculture worthy of being treated in the most graceful and harmoniousverse. The Romans used a great many different implements of agriculture. The plough is represented by Cato as of two kinds, one for strong, the other for light soils. Yarro mentions one with two mould-boards, with which, he says, 'when they plough, after sowing the seed, they are said to ridge'. Pliny mentions a plough with one mould-board, and others with a coulter, of which he says there were many kinds. Fallowing was a practice rarely deviated from by the Romans. In most cases a fallow and a year's crop succeeded each other. Manure was collected from nearly or quite as many sources as have been resorted to by the moderns. Irrigation on a large scale was applied both to arable and grasslands.
The Romans introduced their agricultural knowledge among the Britons, though it is known that the Britons were already practising agriculture, and during the most flourishing period of the Roman occupation large quantities of corn were exported from Britain to the Continent. During the time that the Angles and Saxons were extending their conquests over the country agriculture may have been neglected; but afterwards it was practised with some success among the Anglo-Saxon population, especially, as was generally the case during the middle ages, on lands belonging to the church. Swine formed at this time a most important portion of the live stock, finding plenty of oak and beech mast to eat.
The feudal system introduced by the Normans, though beneficial in some respects as tending to ensure the personal security of individuals, operated powerfully against progress in agricultural improvements. War and the chase, the two ancient and deadliest foes of husbandry, formed the most prominent occupations of the Norman princes and nobles. Thriving villages and smiling fields were converted into deer forests, vexatious imposts were laid on the farmers, and the serfs had no interest in the cultivation of the soil. But the monks of every monastery retained such of their lands as they could most conveniently take charge of, and these they cultivated with great care, under their own inspection, and frequently with their own hands. The various operations of husbandry, such as manuring, ploughing, sowing, harrowing, reaping, thrashing, winnowing, etc, are incidentally mentioned by the writers of those days; but it is impossible to collect from them a definite account of the manner in which those operations were performed.
The first English treatise on husbandry and the best of the early works on the subject was published in the reign of Henry VIII in 1534, by Sir A Fitzherbert, judge of the Common Pleas. It is entitled the Book of Husbandry, and contains directions for draining, clearing, and inclosing a farm, for enriching the soil, and rendering it fit for tillage. Lime, marl, and fallowing are strongly recommended. The subject of agriculture attained some prominence during the reign of Elizabeth I. The principal writers of that period were Tusser, Googe, and Sir Hugh Platt. Tusser's Five Hundredth Points of Good Husbandry (first complete edition published in 1580) conveys much useful instruction in metre, but few works of this time contain much that is original or valuable.
The first half of the seventeenth century produced no systematic work on agriculture, though several on different branches of the subject. About 1645 the field cultivation of red clover was introduced into England, the merit of this improvement being due to Sir Richard Weston, author of a Discourse on the Husbandry of Brabant and Flanders. The Dutch had devoted much attention to the improvement of winter roots, and also to the cultivation of clover and other artificial grasses, and the farmers and proprietors of England soon saw the advantages to be derived from their introduction. The cultivation of clover soon spread, and Sir Richard Weston seems also to have introduced turnips. Potatoes had been introduced during the latter part of the sixteenth century, but were not for long in general cultivation. A number of writers on agriculture appeared in England during the Commonwealth, the most important works on the subject being Blythe's Improver Improved and Hartlib's Legacy. The former writer speaks of a rotation, or rather alternation of crops, and well knew the use of lime, as also of other manures. In the eighteenth century the first name of importance in British agriculture is that of Jethro Tull, a gentleman of Berkshire, who began to drillwheat and other crops about the year 1701, and whose Horse-hoeing Husbandry was published in 1731.
Jethro Tull was a great advocate of the system of sowing crops in rows or drills with an interval between every two or three rows wide enough to allow of ploughing or hoeing to be carried on. After the time of Jethro Tull's publication no great alteration in British agriculture took place, until Robert Bakewell and others effected some important improvements in the breeds of cattle, sheep, and swine, in the latter half of the eighteenth century. The raising and maintenance of live stock, especially of sheep, was a characteristic of English farming from a very early time, and for several centuries the country had almost a monopoly in the supply of wool. To Bakewell we owe the breed of Leicestersheep. By the end of the nineteenth century it was a common practice to alternate green crops with grain crops, instead of exhausting the land with a number of successive crops of corn. A well-known writer on agriculture at this period, and one who did a great deal of good in diffusing a knowledge of the subject, was Arthur Young.
Scotland was for a long time behind England in agricultural progress. Great progress was made during the eighteenth century, however, especially in the latter half of it, turnips being introduced as a field-crop, and new implements such as the swing-plough and the thrashing-machine coming into general use. The construction of good roads through the country also gave agriculture a great impulse. During the wars caused by the French revolution of 1795 to 1814 the high price of agricultural produce led to an extraordinary improvement in agriculture all over Britain. The establishment of the institution called the National Board of Agriculture was also of very great service to British husbandry at this period. Though a private association it was assisted by an annual parliamentary grant, and prizes were given by it for the encouragement of experiments and improvements in agriculture. It existed from 1793 to 1816.
Among other societies which have greatly furthered the progress of agriculture in Britain, the chief are the Royal Agricultural Society of England, established in 1838; the Highland and Agricultural Society of Scotland, founded in 1783; and the Royal Agricultural Society of Ireland, instituted in 1841. The objects of these and similar societies were such as the following: to encourage the introduction of improvements in agriculture; to encourage the improvement of agricultural implements and farm buildings; the application of chemistry to agriculture; the destruction of insects injurious to vegetation; to promote the discovery and adoption of new varieties of grain, or other useful vegetables; to collect information regarding the management of woods, plantations, and fences; to improve the education of those supported by the cultivation of the soil; to improve the veterinary art; to improve the breeds of live stock, etc. Shows are held, at which prizes are distributed for live stock, implements, and farm produce.
Through the efforts of the above-mentioned and other societies, the investigations of scientific men, the general diffusion of knowledge among all classes, and the necessity of competing with producers in foreign countries, agriculture made vast strides in Britain during the nineteenth century. Among the chief improvements were deep ploughing and thoroughdraining By the introduction of new or improved implements the labour necessary to the carrying out of agricultural operations was greatly diminished, as by the steam thrashing-machine, the steam-plough, and the reaping-machine. The nineteenth century saw also the introduction of chemistry into agriculture in Britain. The organization of plants, the primary elements of which they are composed, the food on which they live, and the constituents of soils, were all investigated, and most important results obtained particularly with regard to manures and rotations. Artificial manures, in great variety to supply the elements wanted for plant growth, came into common use at the end of the nineteenth century, not only increasing the produce of lands previously cultivated, but extending the limits of cultivation itself. An improvement in all kinds of stock became more and more general, feeding was conducted on more scientific principles, and improved varieties of plants used as field crops were introduced at the same time. At the end of the nineteenth century was introduced the system of ensilage for preserving fodder in a green state. However, by the start of the 20th century writers were proclaiming that, chiefly owing to foreign competition, agriculture had become a very unprofitable industry in Britain.
It is only since the nineteenth century that much progress was made in perfecting implements and machinery for cultivating the soil, sowing seed, drilling, rolling, hoeing, reaping, digging, etc. The first application of steam to ploughing dates from 1770, when Richard Edgeworth took out a patent for a steam ploughing machine, but it was 1852 before such application proved of any economic value. As early as 1829 a reaping-machine was invented by the Reverend Mr. Bell of Carmylie, Forfarshire, which, in an improved form, was still in use at the start of the twentieth century when numerous mowing and reaping-machines of ingenious construction were also introduced, many of which not only cut down the grain, but also bind it up into sheaves. At the start of the twentieth century steam was extensively used as a motive power in thrashing, in chaff-cutting, turnip-slicing, and even in churning. Only to be replaced after the invention of the combustion engine with petrol-power. Mechanisation led to the enlargement of fields, with small fields being amalgamated by the destruction of separating hedgerows to enable mechanical tractors and other farm vehicles to operate efficiently. The effect upon wildlife in Britain was devastating, and public concern started to grow.
The Second World War revolutionized agriculture in Britain, and led to the development of intensive farming techniques known as 'factory farming' and new anonymous breeds of livestock being developed which mature very quickly. During the later half of the twentieth century the public in Britain rebelled against the inhumanity of intensive animal husbandry, typified by 'battery hens' in which thousands of hens are kept in individual tiny cages within massive warehouses, unable to stretch let alone move around, and free-range or more traditional animal husbandry started to reappear in commercial agriculture.
The twentieth century also saw the wide scale introduction of chemical fertilizers and insecticides, many of which were harmful to the consumers and from a public backlash emerged a return to traditional farming, known as organic farming. Research Agriculture
Bone manure was formerly one of the most important fertilizers in agriculture. The value of bones as manure arises chiefly from the phosphates and nitrogenous organic matters they contain; and where the soil is already rich in phosphatesbone is of little use as manure. It is of most service therefore where the soil is deficient in this respect, or in the case of crops whose rapid growth or small roots do not enable them to extract a sufficient supply of phosphate from the earth, turnips, for instance, or late-sown oats and barley. There are several methods for increasing the value of bones as manure, by boiling out the fat and gelatine, for instance, the removal of which makes the bones more readily acted on by the weather and hastens the decay and distribution of their parts, or by grinding them to dust or dissolving them in sulphuric acid, by which latter course the phosphates are rendered soluble in water.
Bones have long been used as manure in some parts of England, but only in a rude, unscientific way. It was in 1814 or 1815 that machinery was first used for crushing them in Yorkshire and Lincolnshire, and bone-dust and dissolved bones were then largely employed as manures, great quantities of bones being imported into Great Britain for this purpose. Before being utilized in agriculture they were often boiled for the oil or fat they contain, which was used in the manufacture of soap and lubricants. Research Bone Manure
Dyeing is the art of giving colour to textile and other articles in such a way that the colours are more or less permanent, and not readily affected by the action of light, washing, etc. Like spinning and weaving it was originally a home industry, as it still is in many places. Until about 1850 natural dye-stuffs alone were employed, but the discovery of dyes of all colours that can be obtained from coal-tar products revolutionized dyeing as an industry, and the vegetable dye-stuffs were gradually superseded by the newer colours.
Before dyeing, the materials have generally to be cleansed or bleached to get rid of undesirable colouring matters or impurities; and frequently a textile material is subjected to some subsidiary treatment in order to obtain special effects. For example, cottonyarn may be subjected to the action of strong causticsoda ('mercerizing' process) while in a state of great tension, in order to give it a permanent silky lustre.
Dyeing is not only an art, it is also a branch of applied chemistry. One fundamental principle is, that the colouring matter and other necessary substances must be applied in a state of solution, and while in direct contact with the fibre they must be rendered insoluble, so that they are precipitated within or upon the fibre and thus permanently fixed. The method of effecting this varies greatly according to the fibre and the colouring matter employed. As a rule the vegetable and the animal fibres are dyed by very different methods. The affinity of the animal fibres for certain colouring matters is often so great that they are readily dyed by simple immersion in hot colour solutions;
but this simple process is not generally sufficient. According to the method of their application in dyeing the following groups: of dye-stuffs may be distinguished: Avid Colours, Basic Colours, Direct Colours, Developed Colours, Mordant Colours, Miscellaneous Colours, Reactive Colours.
The acid colours are so called because they are of an acid character and are applied in an acid dye-bath. As a rule, they are only suitable for dyeing the animal fibres, e.g. wool and silk, also leather, horn, feathers, etc. Only a few vegetable dye-stuffs belong to this class, for example, the purple colour orchil and the blue colour indigo extract. On the other hand, the acid colours derived from coal-tar - and increasingly petroleum - are very numerous and yield a great variety of hues - red, orange, yellow, green, blue, violet, brown, and black, each with its particular name.
The basic colours are so called because their essential constituents, to which they owe their dyeing power, are organicbases. The bases themselves are colourless and too insoluble in water to be of use, hence they are employed in the form of their soluble coloured salts, usually the hydrochlorides of the colour-bases. Their solutions are precipitated by tannic acid, because it combines with the colour-bases to form insoluble tannates. Wool, silk, and animal substances generally have a direct attraction for colour-bases, and hence these fibres are readily dyed by simple immersion in hot aqueous solutions of the basic colours. Cotton and linen, on the other hand, are not dyed so readily; they need first to be prepared or impregnated with tannic acid, and thus prepared are said to be mordanted, the tannic acid in this connection being styled the mordant. Most of the colours of this class are fugitive to light, and all but one, barberryroot, are derived from coal-tar products.
The direct colours are so called because they dyecotton direct, that is, without the aid of any mordanting process. The first of this class derived from coal-tar was congo red, discovered in 1884; this group includes a very great variety of fast colours, and forms, indeed, one of the most important and valuable series of dye-stuffs employed. Cotton, linen, and the vegetable fibres generally are dyed in the simplest possible manner by merely boiling them in a solution of the dye-stuff, with or without the addition of a little soap, carbonate or sulphate of soda, etc. Wool and silk are frequently dyed in the same manner as cotton. Very few vegetable dye-stuffs belong to the direct colours, e.g. Safflower, Turmeric, Saffron, Annatto. They are all fugitive, and have been of little or no importance to the dyer since the end of the 19th century. The coal-tar colours of this class, on the other hand, are extremely numerous.
The developed colours include a variety of colours which are formed in situ upon the fibre by the successive application of two or more substances. These colours are all of coal-tar origin. A number of them belong to the so-called azo colours, derived from compounds containing nitrogen.
The mordant colours form one of the most important classes of colouring matters, for they include not only most of the vegetable dye-stuffs, e.g. madder, logwood, fustic, etc, but also many valuable fast coal-tar colours, commonly known as the alizarin colours, after their typical representative, alizarin. These mordant colours have by themselves very little colouring power, as a rule, and if employed alone in dyeing give little or no result. If applied, however, in conjunction with metallic salts, notably those of chromium, aluminium, iron, tin, and copper, they each yield a variety of colours, according to the metallic salt employed. In employing them usually two distinct operations are involved: first, that of applying the metallic salt or mordant, called the mordanting process ; and second, that of dyeing proper, in which the mordanted material is boiled in a solution or decoction of the dye-stuff. During the dyeing operation the colouring principle of the dye-stuff combines with the metallic salt already upon the material, and the colour is thus produced and fixed upon the fibre. The method of mordanting varies with the fibre and the metallic salt employed. The vegetable dye-stuffs of this class include Madder, Sapanwood, Camwood, Barwood, Old Fustic, Young Fustic, Quercitron Bark, Persian Berries, Weld, Logwood. Madder was formerly the most important and highly valued of the dye-stuffs of this class, being especially employed to produce the fine 'Turkey-red' dye; but was entirely superseded by the coal-tar colour alizarin towards the end of the 19th century.
Reactive colours combine directly with the fibre being dyed through a chemical reaction and result in a fast colour. The first ranges of reactive dyes for cellulose fibres were introduced in the mid-1950s.
Similarly, the employment of cochineal (an insect dye) has also greatly diminished through the introduction of the cheaper colours. Camwood and barwood are almost entirely used in wool-dyeing, either in conjunction with the indigo-vat or for the purpose of dyeing various shades of brown. Old fustic is the most important of the yellow mordant dye-stuffs, and the colours are fast although not very brilliant. Young fustic yields fugitive colours, and has been little used since 1900. Quercitron bark is an excellent dye-stuff employed by wool-dyers for the production of bright orange and yellow colours. Persian berries and weld, a species of wild mignonette, are both excellent dye-stuffs, but their employment is now limited. Logwood is largely employed by wool, silk, and cotton dyers for dyeing black and dark-blues, which, although fast to washing, are only moderately so towards light. During the 20th century dyewoods were gradually replaced by coal-tar colours.
Among miscellaneous colours are several dye-stuffs applied in a distinct manner. Indigo is a dark-blue powder quite insoluble in water, but can be rendered soluble for dyeing purposes by two methods. The first method converts the indigo into so-called indigo extract, which is sold as a blue paste and applied as an acid colour in dyeing wool and silk. In the second method the indigo-blue is converted into indigo-white, which readily dissolves in the alkalipresent, the solution thus obtained being called an indigo-vat. If cotton, wool, or silk is steeped for some time in the clear yellow solution of such a vat, and then exposed to the oxidizing influence of the air, they are dyed a permanent blue. The indigo-white absorbed by the fibre loses its acquired hydrogen, and thus insoluble indigo-blue is regenerated within and upon the fibre. Aniline black is a valuable colour, produced direct upon the fibre by the oxidation of aniline, and remarkable for its extreme permanency.
Catechu is a vegetable dye-stuff used in dyeing cotton and woollen brown. On wool, catechu yields khaki browns in single bath by using copper sulphate as the mordant. On silk it is largely employed for weighting purposes in the process of dyeing black. Chrome Yellow, Iron Buff, Prussian Blue, and Manganese Brown, employed in cotton dyeing, are frequently classed as mineral colours. Chrome yellow is obtained by immersing cotton successively in solutions of acetate of lead and bichromate of potash, whereby the yellow precipitate of chromate of lead is fixed upon the fibre. Iron buff is obtained in a similar manner by the successive application of iron sulphate and carbonate of soda, and finally developing the full colour by washing with water and exposure to air. The buff colour is really due to the precipitation of oxide of iron on the cotton. Prussian blue is at once developed by passing the buff-dyed cotton through an acidified solution of potassium ferrocyanide. The production of manganese brown on cotton is similar to that of iron buff. The brown colour ultimately produced upon the fibre is an oxide of manganese. The mineral colours are very useful for certain purposes, and are to be regarded as very fast to light. Research Dyeing
History (from the Greek historia, from historeo, meaning I inquire into) is a term first used by Herodotus in the sense which it has since retained, of a narrative of events and circumstances relating to man in his social or civic condition. A. record of bare facts by themselves does not constitute history. Such a record (forming a chronicle or annals) is chronologically valuable; but to attain the dignity of history we must have social events and evolution detailed with considerable fulness, and the growth and movements of society, from one phase to another, distinctly traced and recorded.
The modern school of historians devote much attention to the social life of the people; their method being further characterized by the utmost accuracy of research, the extreme importance assigned to contemporary documentary evidence, and careful weighing of data. The field of history proper is so far restricted as to its subject, that only the doings of a community possessing something of an independent organic life can constitute it.
History may be conveniently divided into ancient, mediaeval, and modern; but these divisions have little scientific value. The first includes the Jewish history and that of the nations of antiquity, reaching down to the destruction of the Roman Empire in 476 AD; the second begins with 476 and comes down to the discovery of America in 1492, or to the Reformation; the third section extends from either of these eras to our own times. The earliest written history is found graven on the monuments of Egypt, Assyria, etc. These, though of the barest description, have the value of contemporary chronicles. Next come the histories found in the canonical books of the Old Testament; but the real inventors of the artistic form of history were the Greeks. Research History
Red is a colour ranging from pink (purple-red) to orange (yellow-red). Red is traditionally associated with danger, stop, blood, warnings, prohibition. Red can evoke images of blood, and hence of murder, of ghoulishness and of horror. Red is associated with energy, activity, anger, fertility and is associated with the planetMars and with war.
Apple - Almost any shade of red you wish. A purely poetic term, though more usually applied to a pale green.
Auburn - A reddish-brown colour, the colour of an orang-utan's hair. Auburn is usually used to describe the colour of hair.
Burgundy - A dark, purplish-red colour of Burgundywine.
Crimson - A deep rich-red inclining towards purple.
Ruddle - A deep orange-red ochre-based pigment used for marking sheep.
Ruddy - Tinged with red. Reddish. Implying a colour of blood.
Rusty - Reddish-brown or brownish-orange colour of iron oxide (rust). Rusty implies decay, age, weathering.
Rufous - Rust-coloured. Rufous implies more organic than mineral, an animal may be described as being rufous in colour, while a weathered piece of iron is more likely rusty.
Russet - Reddish-brown. Russet is more usually applied to flora, such as apples or potatoes, while rufous may describe an animal and rusty a mineral or metal item.
Rubicund - Tinged with red. Rubicund is used to describe a person's complexion, and implies the appearance that occurs as a result of excessive good living. The ruddy complexion one might achieve from plenty of alcoholconsumption, for example.
Sanguine - A rather archaic term for the red colour of blood, implying blood.
Soil erosion is the wearing away and redistribution of the Earth's soil layer. It is caused by the action of water, wind, and ice, and also by improper methods of agriculture. If unchecked, soil erosion results in the formation of deserts (a process known as desertification). It has been estimated that 20% of the world's cultivated topsoil was lost between 1950 and 1990. If the rate of erosion exceeds the rate of soilformation (from rock and decomposing organic matter), then the land will become infertile.
The removal of forests (the process of deforestation) or other vegetation often leads to serious soil erosion, because plant roots bindsoil, and without them the soil is free to wash or blow away, as in the American dust bowl. The effect is worse on hillsides, and there has been devastating loss of soil where forests have been cleared from mountainsides, as in Madagascar. Improved agricultural practices such as contour ploughing are needed to combat soil erosion. Windbreaks, such as hedges or strips planted with coarse grass, are valuable, and organic farming can reduce soil erosion by as much as 75%. Soil degradation and erosion are becoming as serious as the loss of the rainforest. Research Soil Erosion
In its narrow, everyday use, vegetable is a word indicating any herb that is cultivated specially for table use in whole or part, such as the turnip (root), cabbage (leaves), broccoli (flowers), peas and beans (fruit). In its widest sense it includes all living things that are not animals - trees, shrubs, herbs, ferns, mosses, seaweeds, fungi, and the microscopic diatoms.
The unit of structure, the cell, is essentially the same in both animals and plants, but the combination of the cells into tissues and organs shows marked differences.
All animals depend for their food upon material originally elaborated by plants. The green plants alone have the power to construct this basic food material from elemental substances, and physiological processes different from those of animal assimilation are rendered necessary. The fungi approach the animals in this respect: they must feed upon material that has already done service as part of the structure of other plants or of animals.
The fine divisions of roots explore the soil in search of water in which are dissolved the salts of sodium, iron, potassium, phosphorus, calcium, sulphur, etc. The hairs with which the rootlets are clothed absorb this fluid by osmosis, and it is passed upward through the long vessels of the wood bundles until it reaches the cells of the leaf. These cells contain green bodies (chloroplasts) in their protoplasm, and it is these that impart the green colour to leaves and soft shoots. In the leaf-skin (epidermis) there are innumerable pores or stomata through which surplus water from the roots is evaporated and through which atmospheric air is admitted to the spaces between the leaf-cells.
The chloroplasts in these cells have the power to utilise solar energy in decomposing the carbon dioxide of the air, and the cells retain the carbon, setting free the oxygen. Water from the roots is broken up also into its elements, hydrogen and oxygen, and with these plus carbonstarch is formed. This, converted into grape sugar, is passed from cell to cell to parts of the plant whore it is needed for the production of new cells, wood, bark, leaves, or fruit. Starch is the material from which are made all the organic substances produced by the plant.
The surplus over present requirements is stored up as reserves in seeds, enlarged roots or stems, bulbs, or tubers for renewed growth or floral display at a later season. Waste products are converted into resins, oils/wax, or alkaloids - many of these being of considerable economic value to man. Part of the water stream from the roots passes by osmosis from cell to cell, where it is necessary in order to keep the protoplasm in an active condition; any insufficiency is followed by a flagging of the tissues, the drooping of leaves and young shoots. In addition to the absorption of carbon by the protoplasts for building purposes, the leaf-cells also take up oxygen from the atmosphere and give off carbon much as animals do.
As the plant respires without lungs and assimilates without digestive organs, so also it can effect movements without a muscular system and react to external stimuli without a nervous system. It is sensitive to light and heat; many plants have distinct night and day positions for their leaves. It responds positively and negatively to the force of gravity, the root going down into the earth and the stem rising into the air. The growing tip of a stem or shoot commonly nutates, i.e. moves from side to side or in a circle or ellipse. The plant can orientate itself, i.e. take up a definite position in regard to the incidence of light or other external stimulus. These movements appear to be controlled largely by alterations in the position of the mobile chloroplasts.
The reproductive process is, in essentials, similar to that of animals, the ovules or seed-eggs in the ovary requiring to be fertilised by male sperms represented by the pollen grains produced in the anthers. The result of such fertilisation is to cause the ovule to develop into an embryo capable of further development under suitable conditions into a plant resembling the parent. Research Vegetable
An animal is an organized and sentient living being. Life in the earlier periods of natural history was attributed almost exclusively to animals. With the progress of science, however, it was extended to plants. In the case of the higher animals and plants there is no difficulty in assigning the individual to one of the two great kingdoms of organic nature, but in their lowest manifestations, the vegetable and animal kingdoms are brought into such immediate contact that it becomes almost impossible to assign them precise limits, and to say with certainty where the one begins and the other ends. From form no absolute distinction can be fixed between animals and plants. Many animals, such as the sea-shrubs, sea-mats, etc, so resemble plants in external appearance that they were looked upon as such. With regard to internal structure no line of demarcation can be laid down, all plants and animals being, in this respect, fundamentally similar; that is, alike composed of molecular, cellular, and fibrous tissues. Neither are the chemical characters of animal and vegetable substances more distinct. Animals contain in their tissues and fluids a larger proportion of nitrogen than plants, whilst plants are richer in carbonaceous compounds than the former. In some animals, moreover, substances almost exclusively confined to plants are found. Thus the outer wall of Sea-squirts contains cellulose, a substance largely found in plant-tissues; whilst chlorophyll, the colouring-matter of plants, occurs in Hydra and many other lower animals.
Power of motion, again, though broadly distinctive of animals, cannot be said to be absolutely characteristic of them. Thus many animals, as oysters, sponges, corals, etc, in their mature condition are rooted or fixed, while the embryos of many plants, together with numerous fully developed forms, are endowed with locomotive power by means of vibratile, hair-like processes called cilia. The distinctive points between animals and plants which are most to be relied on are those derived from the nature and mode of assimilation of the food. Plants feed on inorganic matters, consisting of water, ammonia, carbonic acid, and mineral matters. They can only take in food which is presented to them in a liquid or gaseous state. The exceptions to these rules are found chiefly in the case of plants which live parasitically on other plants or on animals, in which cases the plant may be said to feed on organic matters, represented by the juices of their hosts. Animals, on the contrary, require organized matters for food. They feed either upon plants or upon other animals. But even carnivorous animals can be shown to be dependent upon plants for subsistence; since the animals upon which Carnivora prey are in their turn supported by plants. Animals, further, can subsist on solid food in addition to liquids and gases; but many animals (such as the Tapeworms) live by the mere imbibition of fluids which are absorbed by their tissues, such forms possessing no distinct digestive system.
Animals require a due supply of oxygen gas for their sustenance, this gas being used in respiration. Plants, on the contrary, require carbon dioxide. The animal exhales or gives out carbon dioxide as the part result of its tissue-waste, whilst the plant taking in this gas is enabled to decompose it into its constituent carbon and oxygen. The plant retains the former for the uses of its economy, and liberates the oxygen, which is thus restored to the atmosphere for the use of the animal. Animals receive their food into the interior of their bodies, and assimilation takes place in their internal surfaces. Plants, on the other hand, receive their food into their external surfaces, and assimilation is effected in the external parts, as are exemplified in the leaf-surfaces under the influence of sunlight. All animals possess a certain amount of heat or temperature which is necessary for the performance of vital action. The only classes of animals in which a constantly-elevated temperature is kept up are birds and mammals. The bodily heat of the former varies from 100 degrees Fahrenheit to 112 degrees Fahrenheit and of the latter from 96 degrees to 104 degrees. The mean or average heat of the human body is about 99 degrees Fahrenheit, and it never falls much below this in health. Below birds animals are named cold-blooded, this term meaning in its strictly physiological sense that their temperature is usually that of the medium in which they live, and that it varies with that of the surrounding medium, Warm-blooded animals, on the contrary, do not exhibit such variations, but mostly retain their normal temperature in any atmosphere. The cause of the evolution of heat in the animal body is referred to the union (by a process resembling ordinary combustion) of the carbon and hydrogen of the system with the oxygen taken in from the air in the process of respiration. Research Animal
Autotrophism is a type of nutrition in which organisms synthesize the organic materials they require from inorganic sources. Chief sources of carbon and nitrogen are carbon dioxide and nitrates, respectively. All green plants are autotrophic and use light as a source of energy for the synthesis, i.e. they are photoautotrophic. Some bacteria are also photoautotrophic; others are chemoautotrophic, using energy derived from chemical processes. Research Autotrophism
The Probert Encyclopaedia was designed, edited and programed by
Matt and Leela Probert
Abbreviations
Research Agriculture
