The Complete Works of Aristotle

by Barnes, Jonathan, Aristotle

  Plants ought not to grow in salt water, on account of its low temperature and dryness. This is because a plant needs two things—its proper material and a position suitable to its nature; when these two conditions are present a plant will grow. Now [40] we find that snow is the substance furthest removed from an equable temperature, and its most striking characteristic is the impossibility of its existing in a temperate [825a1] region. We do not, therefore, find plants growing in snow; yet we often find plants appearing in the snow, and animals of all kinds, especially worms (for they are bred in the snow), and mullein and all bitter herbs. But it is not the snow which causes [5] this to be so; but a certain characteristic of snow is active. The reason is that snow falls like smoke, and the wind congeals it and the air binds it together. There is therefore rarity amongst its parts, and air will be retained in it and will grow hot, [10] and foul water flows from it, which had before enclosed the air; and when the air is present in considerable quantities and the sun shines upon it, the air which is enclosed in the snow will burst its way out, and a foul moisture will appear and will [15] be solidified by the heat of the sun. But if the place is covered up, plants will grow in it, but without leaves, because it is cut off from the equable temperature of the earth which is congenial to it. This is the reason why there are numerous flowers and leaves on small plants in places where the air and water are temperate, and few [20] flowers and leaves on a plant which occurs in the snow. So too in very salty and dry places plants do not usually appear, because these places are far from being temperate; and the ground is impoverished, because heat and moisture, which are [25] the characteristics of fresh water, are absent. So the soil that is fresh is the mountain soil, and there plants grow quickly.

  But in warm places, because there the water is fresh and the heat plentiful, the process of concoction proceeds for two reasons, partly as a result of the position and [30] the air which is found there, and partly because there is a concoction of the air owing to the heat of the sun there. On mountains, because they attract moisture and the clearness of the air assists the process, concoction proceeds apace; and therefore plants are generally found on mountains. In deserts the saltness gains the upper hand, as we have already shown, and rarities resembling one another are left [35] between the particles of sand; the sun has therefore no power to produce or perpetuate any continuous plant life; and so in deserts separate species of plants will not occur, but species similar to one another.

  4 · Plants which grow on the surface of the water will only do so when there is density in the water; the reason of this is that, when heat touches water which has [825b1] no current to move it, something of the nature of a cloud comes over it and retains a little of the air, and the moisture putrefies and the heat draws it up, and it spreads over the face of the water. Such a plant has no root, because roots will only attach [5] themselves to the hard particles of the earth, and the particles of water are loose and scattered. The heat then comes forth with the putrefaction which takes place on the surface of the water. Such a plant has no leaves because it is produced under [10] conditions which are far from temperate, and its parts are not compact, because the parts of water are not compact. It is for this reason too that such plants grow like threads.13 It is because the parts of earth are compact that the plants too which grow in the earth are compact. Sometimes putrefactions are set up in damp, smoky ground, and hold the air—the sun causing them to appear when rain and winds are [15] frequent—and the dryness of the earth will make their roots dry up and solidify, and thus fungi and mushrooms and the like will be produced. In places that are exceedingly warm, because the heat concocts the water in the interior of the earth [20] and the sun holds the heat, a vapour is formed and a plant is thus produced. This process takes place in all warm places, and the formation of the plant is thus completed. A cold locality causes a similar but contrary process; the cold air forces [25] the heat downwards and its particles collect together, and the ground undergoes concoction with the moisture present in it; the ground is then cleft open and a plant emerges from it. Where the ground is fresh, water is generally not far away. When, [30] therefore, the air which is enclosed in the earth is stirred into motion, the moisture of the water will remain behind, and the air will solidify inside the water and a plant is produced, such as the water-lily and various kinds of small plants; these plants grow straight up and do not expand, because their roots are above the earth. In [35] places too where there is warm water running, plants often grow, because the heat of the water attracts the vapours which are retained in the earth, and draws the cold moisture upwards, and air is solidified from the moisture, which it concocts owing to the heat of the water, and a plant appears, but only after a long lapse of time. Small [826a1] plants too appear in sulphurous places: and when the wind blows violently upon the brimstone, it will recoil back again, and the air which is in it will be stirred up, and the place will become hot, and fire will be produced from it, and will continue to be [5] produced from it, because it exists deep down in the brimstone, which is due to impurities deposited by the air; the fire attracts the air when the sulphur putrefies, and a plant will be produced from it. Such a plant, as we have shown before, will not generally have many leaves, because it is produced under conditions which are far [10] from equable.

  Edible products will grow from plants in positions which are warm even, and elevated, especially in the third and fourth zones; and products almost edible grow [15] in cold and high districts. Many species are produced in cold, high positions owing to the attraction of the moisture and the temperate conditions which prevail in the warmth of the sun on spring days. Similarly natural soil readily produces plants which are full of oil; such soil, as we have already seen, is found where there is fresh water.

  [20] 5 · A plant which grows upon solid rock takes a long time to grow; for the air which is enclosed in the stone strives to rise, and when it cannot find a way, owing to the resistance of the stone, it retreats back again and becomes heated, and attracts the residuum of the moisture in the stone upwards, and with this moisture a vapour [25] comes forth accompanied by a resolution of small particles of the stone; and because the sun often acts upon the stone, it assists the moisture in the process of concoction, and as a result a plant is produced. Such plants do not generally grow to any height, [30] unless they are near some soil or moisture. The rest of the plant requires soil, water, and air. If you look at the matter, you will see that if a plant faces the east, it will grow quickly, and slowly if it faces the west. A plant, when water is the predominant element in it, will retain the air and will not allow it to rise, and thus the plant is not [35] nourished. Similarly, when dryness predominates, the natural heat will be diverted into the extremities of the plant and will block up the ducts through which the flow of water passed, and the plant does not receive nourishment.

  6 · Every plant needs four things (just as an animal needs four things), namely, a definite seed, a suitable position, and a suitable supply of water and air. [826b1] When these four conditions are fulfilled, a plant will grow and increase; but if they are lacking, the plant will be correspondingly weakened. A plant which is used for medicinal purposes will be more serviceable and suitable for such purposes if it grows on high mountains; its fruit, however, will be harder to concoct and will [5] contain less nourishment. Places which are secluded from the sun’s rays will not produce much plant life (just as they will not produce much animal life), because the sun makes the day long according to the duration of its absence, and it is the sun which draws out the moisture; and so plants which grow in sunless places will not [10] have the strength to produce leaves and fruit. As for plants which grow in watery places, when the water is still, a foulness is formed, and there will be no power in the air to rarefy the particles of water, and the air will be imprisoned inside the earth, [15] and this will prevent the thick matter in the water from rising; then the wind will invade14 the spot and the earth will be cleft open, and the air which is enclosed will re
treat into the earth, and the wind will solidify the moisture, and from this condition of moisture marsh plants will spring. Usually such plants do not differ from one another in form on account of the constant presence of water and its thick [20] consistency and the heat of the sun overhead. The plants which grow in damp places will appear like patches of verdure on the surface of the earth. In such a place there is, in my opinion, little rarity, and when the sun falls upon it, it will stir up the moisture and the spot will grow warm through the resulting motion and the heat [25] which is enclosed within the earth; and so there is nothing to cause the upward growth of the plant, while the moisture helps its expansion; and so it spreads over the earth in a sheet of verdure and produces no leaves. A kind of plant also grows which appears above the surface of the water and is smaller in quantity than that [30] just mentioned, because it is like the nature of earth, and it neither grows upwards nor expands. Often, too, one plant grows out of another plant of a different form from itself, without any root, and spreads all over the plant. For when a plant which [35] has numerous thorns and contains an oily juice moves, its parts will open and the sun will cause its putrefactions to turn into vapour, and the putrefied place of its own accord will produce a plant, and the wind and a moderate heat assist, and the plant grows in the form of threads and extends over the original plant. This is a peculiarity of very thorny plants, dodder and the like. [827a1]

  There is also a class of plant which has neither root nor leaves, and another which has a stalk, but no fruit or leaves, the tamarisk, for example.15

  All herbs and all things that grow above or in earth have their origin in one of five ways, namely, either from seed, or from putrefaction, or from the moisture of [5] water, or from being planted, or from growing as parasites on other plants. These are the five causes of plants.

  7 · Trees have three different methods of production; they produce their fruit either before their leaves, or at the same time as their leaves, or else after their leaves have grown. We have already described these three methods. A plant which [10] produces its fruit before its leaves contains a considerable amount of oily juice, and when the heat which is natural to the plant has concocted the juice, its maturity will quickly follow, and the juice will acquire force and boil up within the branches of [15] the plant and will prevent the moisture from rising; the result is that the fruit appears before the leaves. But in plants which produce their leaves more quickly than their fruits, the effects of the moisture are various. When the heat of the sun [20] begins to disperse the particles of water, the sun attracts the particles of this moisture upwards, and the process of ripening will be delayed, because the concoction of the fruit will only take place through coagulation, and so the leaves come before the fruit. A plant which produces its leaves and fruit simultaneously has much moisture, and frequently also contains an oily juice. When the heat has concocted the moisture, it will, as a result, rise upward, carrying the juice with it, [25] and the air and sun will draw it out, and the oily juice which forms the fruit will come out, while the moisture will produce the leaves, leaves and fruit coming forth together. The wise men of old used to assert that all leaves were really fruits, but so much moisture was present, because the fruit did not mature or solidify owing to the [30] presence of heat above and the sudden attraction exerted by the sun, and consequently the moisture on which the process of concoction had had no effect changed into leaves; the leaves, they said, are simply intended to attract the [35] moisture and serve as a protection to the fruit from the violence of the sun. The leaves ought therefore, they said, to be equally regarded as fruit. But the truth is that the moisture rises above them and the leaves are converted into real fruits, as we have already said. The same theory applies to olives, which often fail to produce [827b1] fruit; for when nature brings about concoction of moisture, some of the thin moisture, which has not matured, will rise first, and this will produce leaves and its concoction will produce flowers, and when in the second year the process of concoction is completed, the fruit will grow and will eventually use up all the [5] available material according to the space which it has in it.

  Thorns are not characteristic of plants or natural to them. My opinion is that there is rarity present in a plant, and concoction will take place at the beginning of its existence, and moisture and cold rise upwards, and they are accompanied by a [10] slight concoction; this circulates where there is rarity, and the sun causes it to solidify, and thus the thorns will be produced. Their form is pyramidal; for they begin by being thin at the point and gradually grow thicker, because when the air is withdrawn from the plant its parts increase, and the material expands. The same is [15] true of any plant or tree which is pyramidal at the top.

  8 · Greenness must be the most common characteristic of plant life; for we see that trees are white internally and green externally. The reason is that the [20] material which supplies their nutriment is more readily accessible: it follows therefore that there is greenness in all plants, because their material is absorbed and rarefies the wood of the tree, and the heat causes a slight concoction, and the moisture remains in the tree and appears externally: consequently there will be greenness. This is also the case with the leaves, unless the concoction in them is [25] unusually powerful; and leaves are in respect of strength midway between bark and wood. But greenness does not persist, nor indeed come into existence without the presence of moisture, and is of the element of earth, and is the intermediate colour between that of earth and water. This is indicated by the fact that when the bark of [30] trees dries up it turns black, and the wood inside the tree becomes white, and the green, which comes between these two colours, is the colour presented by the outward appearance of the plant.

  The shapes of plants fall under three classes. Some spread upwards, others downwards, while others are intermediate. The upward extension is due to the fact [35] that the nutritive material makes its appearance in the marrow of the plant, and the heat draws it up, and the air, which is present in the rarities of the plant, compresses it, and it assumes a pyramidal form, just as fire assumes a pyramidal form in bodies in which it is present and rises upwards. Downward extension is due to the blocking of ducts in the plant, and, when the material is concocted, the water, which contains [828a1] the marrow of the plant, will thicken, and the rarefied portion proceeds on its upward course, while the water returns to its former position in the lower portion of the plant, and by its weight presses the plant downwards. In the plants which are intermediate between the two classes already mentioned, the moisture is rarefied and the natural state of the plant is very nearly a temperate condition during the process of concoction, and the ducts are open through the middle of the plant, and [5] the nutritive material spreads upwards and downwards. There is a double process of concoction; the first takes place below the plant, while the second takes place in the marrow which comes out of the earth and is in the middle of the plant; afterwards the nutritive materials make their appearance fully matured and are distributed [10] through the plant, and do not undergo a third concoction. In animals there is a third process of concoction; this is due simply to the diversity of their limbs and to the distinctness of their parts from one another. Plants, on the other hand, are more [15] homogeneous and repeat the same members over and over again, and the nutritive material generally has a downward tendency. The shapes of plants will depend on the quantity of the seed, while the flower and fruit is dependent on the water and nutritive material. In all animals the first process of maturation and concoction [20] takes place within the animal; there is no exception to this rule. But in plants the first concoction and maturation takes place in the nutritive material. Every tree continues to grow up, until its growth is completed and it dies. The reason is that, while in any animal its height is much the same as its width, in a plant it is far from [25] being so, because water and fire, the elements which compose it, rise quickly, and therefore the plant grows. Variety in the branches of a plant is due to excessive rarity, and, when
the moisture is intercepted there, the process of nature will cause it to grow hot and will hasten the concoction, and thus boughs will form and leaves [30] will appear, as we have already said.

  9 · The shedding of leaves from trees will be due to the tendency to fall, induced by quickly formed rarity. When the moisture is concocted with the nutritive material, it will assume a pyramidal form, and therefore the ducts within [35] will be wide and will afterwards become narrow and pyramidal; when the nutritive material makes its appearance already concocted and formed, it will close up the extremities of the ducts above, and the leaves will have no nutritive material, and therefore dry up. When the contrary process to the one we have described takes place, the leaves do not fall from the trees. When coldness dominates in the plant, it [40] will affect its colour owing to the secretion of heat in the middle of the plant and the presence of cold outside in its extremities; the result is that the leaves are blue-grey [828b1] and do not fall, as in the olive, and myrtle, and similar trees. When trees or plants exercise a violent force of attraction, fruit will be produced once a year; when they [5] do not exercise such a force, nature will employ the process of concoction on successive occasions and at each concoction they produce fruit, and so some plants bear fruit several times in the year. Plants which are of the nature of water bear fruit with difficulty on account of the predominance of moisture in them, and the [10] wideness of their ducts and the tendency of their roots to fall off; when the heat is intense, the concoction will be quick and will be rarefied owing to the water and will not solidify; this we find to be the case in all small herbs and in some vegetables. [15]