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Book I, Tract I
Chapter 1 [Objective of Book]
... We must begin with the bodies of plants. Concerning this, we intend to present in this book the usual things appropriate to plants according to the whole and its parts, since particulars are infinite and no science can be made of them, as Plato put it very well. Now, since the first common principle appropriate to all plants and their parts is life [itself], which is found in plants, we shall first inquire about the life of plants.
Chapter 6 Concerning the Reasons of Aristotle by Which He Proves That Plants Do Not Sense or Sleep
Now, according to our intent, we must investigate a problem about which we made mention in our preceding discussion, namely whether plants have desire, animal motion, and a soul, and concerning what was said about plants being relaxed by sleep and wakefulness, just as sleep in an animal is caused by what is released by evaporation from the place of digestion. That plants do not have such a spirit, which is drawn by inhaling and exhaling, as Anaxagoras said, we can prove in this way: because we find that there are many animals that do not inhale and exhale; however, such a spirit is more appropriate to animals than plants, because animals are, by their natures, hotter and participate in [that is, contain more of] the higher elements than plants, which are earthy and cold. For this reason animals require animal spirits more than plants.
Similarly, we find that plants do not sleep or wake, since in them evaporation does not occur from the place of digestion to any cool place located ill their bodies. Therefore, the evaporation which is released in them descends and immobilizes the exterior parts of the plant, which by nature always exist immobile and insensible. This is especially so since, as was made clear in On Sleep and Waking, to be awake is a certain faculty and force and effect of the senses; sleep, on the contrary, is a certain weakness and loss of the senses. But since plants wholly lack sense they cannot participate in accidents of the senses which involve a force or power [of the senses] and a lack of the senses.
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Chapter 4 On the Diversity of the Essential and Principal Parts of a Plant
... There are parts of all plants ... which grow and increase ... and these are the essential parts of plants: These are roots, branches of roots, stems, and branches. For these parts in plants are like the parts of animals ... .
Barks, wood, and pith, and all such essential parts of this kind arise from the seminal humor [or sap] and from the food of the plant. Some call the pith the mother of the tree because in it the seed seems to be conceived and formed ... . Nodes, veins, and the woody or herbaceous tissues of plants, which fill what is between the veins and nodes, are all constituted of the four elements. Indeed, in these things the powers of the elements are found more than in the parts of animals, because plants are more material and nearer to the elements and in them the elements are altered less than in the bodies of animals.
Chapter 5 In Which the Genus of Plants Is Divided into Species and the Reason for This
If we now consider the plant according to the community and range of its predication, parts of it are designated univocally by name and structure. Of these, some are trees; some lie between trees and herbs and their name shows their intermediate being, for in Greek they are called ambragyonand in Latin are called by the common name arbusta, bushes. Moreover, some are bushy herbs. Almost every plant falls under these names. I say almost because the arborescent shrub lies between shrub and tree, inclining, however, more toward the tree. And according to this, the highest of the plants is the tree, the lowest the herb. But since nature does not pass instantaneously from extreme to extreme, but passes through all means that have been fitted between them, thus it [nature] has made many means, of which only one is equidistant and middle; and there are others which are closer to the extremes. This will be obvious in the example and definitions of the names introduced.
A tree is that which has a strong stem from its root, and on this stem arise many branches, and on the branches many slender branches, and on the latter arise what are called ultimate branchlets, as in the olive, cypress, and fig trees. Plants that are mean between trees and herbs are called ambragyon in Greek and arbusta (bush) in Latin. From their roots they send forth many branches in the manner of long branches ... .
There is another mean plant with much the property of an herb which is called bushy herb by authors. This plant projects many stems from one root and different branches on the stems, but it has little or nothing woody, although, in later age, some of them grow hard like wood. Among this kind are rue, cabbage, and many others. Herbs seem to retain the lowest place among plants; they have one root, from which nothing is produced but leaves, as a clump of scallions, and some others.
In this division of plants there are no fungi, truffles, or mushrooms of any kind, because they seem to possess the least of the life and powers of a plant, so that they lack the force to form leaves but are said to be certain plant-like things that have been exhaled and evaporated from other plants. For this reason they are rarely found except between other plants and they endure for a short time.
Book II, Tract II In Which These Things Are Investigated: What Happens Naturally to Plants Which Contributes to Their Production of Fruit or Generation
Chapter 1 In Which We Discuss What Will Be Said in This Tractate and also about the Nature of Leaves
We shall now examine the common things that happen essentially and naturally to plants with respect to their generation, according as nature intends to save each of their species. We shall not inquire here about the place or mode of generation, but we only desire to know the nature of those parts which remain on them when they are in generation. Now, these parts are the leaves, which have the function of covering the fruits, the flowers, which are the signs of fruits, and the fruits and seeds. It is indeed necessary to know the natures which these have in common and their differences, so that after these things have been considered, the causes of the same parts of the body are assigned more carefully and in an orderly manner. For a cause is sought in vain if the reason for which the cause is sought is not known before. Indeed, to philosophize is to investigate the certain, manifest, and true cause of a known effect and to show how it is the cause of it and that it is impossible that it be related otherwise.
Therefore, we say of the leaf in general that the matter of a leaf in all plants is a watery humor mixed somewhat with, and not well separated from, dried earth—not purged from the dregs of earthy matter. The sign of this is that the leaves of large plants having broad and thin leaves suck up moisture quickly and thus almost all leaves are produced full of holes. But where the humor is viscous and more watery, being agitated from the heat that has been retained within its viscosity, the leaves are thicker and cling more. to those plants. But the reason why leaves are frequently thick in herbs and bushes is that the humor is abundantly distributed and multiplied in them because of their nearness to, and continuity with, their roots.
Now, a final purpose [or goal] of leaves is to cover the fruit; [moreover,] nature requires a purging from an excess of watery humidity. Now, since nature is wise and ingenious, it uses the same purging for the protection of the fruits. Thus in many plants nature produces the leaves under the fruit, so that the spread leaf is extended beyond the fruit. However, the production and location of leaves is more general, because the leaf sprouts at the base of the peduncle of the fruit. This is more fitting for the matter and purpose of the leaf. There are two kinds of material vapors in the flesh of the plant and in all other vapors, namely a humid vapor and a dry, windy vapor.
The humid vapor is the matter of the leaf and the dry, windy vapor is the matter of the fruit. For this reason the fruit is judged to be windy by virtue of its nature. The dry vapor is sharper and distributed in the flesh of the tree; the humid vapor is duller [or weaker]. With its sharpness it cuts the body of the plant so that each of these vapors bursts forth. The vapor of the fruits ascends higher and the vapor of the leaves emerges under it. Nevertheless, since these vapors are mixed together in the flesh of the plant, it is necessary that the humid vapor should have a motion by virtue of the windy vapor mixed with it. And so it happens that because the leaf is generated by a humid vapor it comes forth near the fruit, close to the base of the fruit as in many [plants].
The location of a leaf is varied in three ways. Sometimes it is under the fruit at the base of the peduncle of the fruit, as in pear, apple, bullace, and plum trees, and in many others; sometimes it is opposite the fruit, as in vines; and sometimes it is above the fruit, as in the violet and many other herbs. The cause of the leaf being at the base of [or below] the fruit has been assigned above in terms of the fitness [or suitability] of the matter. This location is also appropriate to its goal [or end], because the leaf that comes forth underneath is extended toward the flower and covers it more usefully and protects the flower.
When the leaf is opposite the fruit, it comes forth in plants, drawing much humor, and especially does the fruit of these plants fill very much with a subtle vaporous and windy humor. From this vapor the watery vapor, which is less distributable and less subtle—just as if it were a contrary—is expelled to the opposite side by a formative power. It is for this reason that the leaf comes forth in an opposite place. This is also appropriate for the purpose of the leaf, since the fruit of such a plant requires a great boiling [action] on the part of the sun because of the abundance of humor. But if the leaf was spread over the fruit it would hinder [the necessary boiling action of the sun on the fruit] ... .
Leaves that emerge above the fruit especially cover the fruit, so that it is almost always in the shade. And the cause of this is matter, because the fruits have much of earthiness and therefore, when the windiness has been closed off [or hindered], the water humor in them rises higher, and the vapor, from which the fruit is generated, comes forth in the lower parts of it as if drawn with violence. The utility of this effort of nature can be judged by its end [or goal], since such fruits are cold and humid, so that frequently the shade of the leaves helps preserve these two things [namely the coldness and humidity of the fruit]. These, then, are the three general locations of leaves, and from their causes the variation of the location of the leaves is easily known. Nevertheless, perhaps sometimes ways other than those declared here may be found in certain plants.
Chapter 4 On the Nature and Generation of Flowers
The flower, which is the sign of fruit, is found in plants. As in several things, the generation of flowers is of the same substance with fruit. For this reason, also, the flower very frequently adheres to the upper part of the fruit, as in trees; or the fruit is formed in the middle of a flower, as in bushes and herbs. And what we have said about trees to whose fruit the flower adheres when first formed is especially apparent in the flowers of the pomegranate and in pears and apples. But it is not generally suitable, because in almost all fruits having “stones” inside, the flower is formed around the fruit and the fruit is formed in the middle of the flower, as in all plums and acacias. And this is proper for all bushes, as the poppy, and in almost all herbs whose seed vessels where seeds are formed, come forth from the middle of the flower.
From all this one may easily infer [things about flowers], since the flower is produced from the nature of a subtle watery humor well mixed with earth. In substance, then, a flower is of a very solid and smooth substance. Therefore, when it is immersed in water their solidity and compactness prevent the entrance of air and prevent their rise above the water.
That flowers are changed to another color than green happens because of the moist transparency in them and because of the earth that is well distributed and mixed with it. For all the differences of colors are caused by different floatations of earth expanded as vapor in the moistness, or in fiery or clear smoke, or in burned earth, as we said in our discussion of the generation of sensible things.
Generally, the substance of flowers is made from very subtle moisture which appears first from heat and, because of the abundance of water in it, is extended like a leaf. Therefore, since the moisture has a great distribution, the flower is almost universally of good odor. But this would not happen unless the moisture were very well distributed and very subtle [or rare] and the earth in it were very rare and very well mixed with the moisture. For since the creation of fruits is from windy earthy vapor, there is in this vapor something rarer and wetter and of a lesser earthiness which does not easily show, and it is thickened by a distributive heat. And since this is more vaporizable than the rest of what is in the substance of the plant where the bud is located and where the fruit emerges, it comes forth immediately with the first heat and is formed into a flower.
For this reason, the dew, which produces honey and wax clings to the flower. And these are found deep in the interiors of the flowers, for when nature forms a subtle moisture which has been effected by a rare and very well mixed dryness, there flows from it this rare and well-boiled watery moisture—in the manner of a sweet phlegm in the creation of humors in animals—and this [substance], gathered and warmed by the effort of bees, is converted into the nature of honey ... .
Wax, which is in the lowest parts, is like a purge of yellow bile that trickles from the ears of animals in the purging of the brain of animals. While the flower is formed, what it has of earth is rejected with the easily inflammable fat and like a powder is sprinkled over the insides of the flower, because what is inflammable cannot endure, by natural or alchemical means, the action of natural heat determining and forming the being of things. Indeed, before it can be formed it burns and is converted to the yellowness of yellow bile. It appears to be a formal yellow, especially in the flowers of the poppy, the linden tree, and the white birch. But it is in all flowers more or less, and it clings to the rear legs of bees when they gather honey. Indeed, they build their hives from it for the preservation of the honey ... .
Book IV, Tract III On the Principles of Generation and the Fecundity of Plants
Chapter 1 On the Five Principles of Generation and Growth of Plants and the Doubts Emerging about Them
Herbs and whatever is planted and grows from a root fixed in the earth require one or more of five things. These are a seed, putridity [rottenness], humor [or sap], water, and planting. Of these five, the first has the formative power of the plant in itself and matter and the power to effect is in it at the same time, as we said in the second book of the Physics. The second thing (putridity) receives a formative power from the power of the stars. The humor, which is mixed from the elements, is the food and matter both of generation and of the plant that has been generated; indeed the plant draws this [material] purified from the earth with its first digestion. As in all nutriments, water plays no role except that it is the vehicle of the food. Nor does food flow to the parts of the plant except by means of the motion of water.
Translated by Edward Grant
Reading and Discussion Questions
1.What properties and/or powers of plants does Albertus Magnus take to differentiate them from animals? What are some key characteristics he thinks we should use in the classification of plants?
2.What does his discussion of leaves and fruits suggest to you about the level of detail at which Albertus Magnus is observing? To what extent is he pursuing a causal as well as descriptive project in his account of plant life?