6th. The peduncles and petioles sometimes change into tendris, as in the vine; this plant at first throws out many large leaves and clusters of flowers; but the food not being sufficient to support such a profuse vegetation, the new leaves and clusters of flowers appear smaller; the nourishment becoming still more scanty, at length neither flower nor leaf is developed, and the peduncle and petiole become tendrils, which, by attaching themselves to some firm bodies, serve to sustain the rich fruit which is perfected on the lower parts of the branch.

7th. The last change we shall notice is the transformation of buds into thorns. When a plant forms more buds than it can nourish, some of them do not develop branches and leaves, but becoming hardened by the accumulation of sap, which is insufficient for their full perfection, they then exhibit the short, indurated process, called a thorn. It is said that wild plants, by rich cultivation, do, in time, become divested of their thorns, which change into what they seemed originally destined for, viz., leaves and branches.

Prickles, such as may be seen upon the rose, gooseberry, and other plants, do not change by cultivation, for these are a natural appenlage, originating from the bark; while the thorn may be found connected with the wood, of which it seems to make a part.

Diseases of Plants.*

The diseases of plants (for these organized beings are, like animals, subject to disease and death) may, in many cases, arise from causes within the knowledge of the attentive naturalist.

1st. We notice constitutional diseases. Of this class are the varied colours of some leaves, such as the box and holly; this is supposed to be owing to certain juices which, by changing their elements, vary the colour of the leaf.

2d. Plants become diseased by being subjected to too great or too scanty a supply of food, as light, heat, water, air, and soil. Excess of light causes an escape of oxygen, and a too rapid deposite of carbon; the sap, incapable of sustaining so great a degree of action, becomes exhausted, the plant withers, and the leaves fall off. In this situation the food should be either increased by watering, or the vegetation retarded, by diminishing the light. Excess of heat absorbs the juices of the plant; deficiency of heat produces dropsy, and the plant losing its leaves, ultimately decomposes. More water is evaporated by a plant than is retained for its nourishment; therefore the absorption by the roots should be in proportion to the evaporation by the leaves.

3d. External injuries often affect the health of plants. Rains injure the wood by penetrating through apertures in the bark; the bark itself seems from its nature better fitted to bear the action of the weather. Winds, when violent, are mechanically destructive to vegetables; when moderate, the agitation which they produce is thought to be advantageous, by favouring the descent of the cambi um, and promoting a more free circulation of the other juices.

Smoke is injurious to plants, it being composed of particles which, though invisible to our sight, are yet too gross to be absorbed by the minute pores of the leaves; it serves, therefore, to obstruct these

*This constitutes a department of Botany called pathology; a term derived from two Greek words, pathos, disease, and logos, account of.

6th, peduncles and petioles become vines-7th, buds, how transformed-PricklesDiseases of plants-1st, Constitutional-2d, Light and heat-3d, External injuriesRains-Wind-Smoke.

pores, and prevent their exhaling the oxygen gas which is necessary for the decomposition of the carbonic acid and the consequent deposition of carbon.

4th. Plants sustain injuries from animals, which produce diseases. Insects in particular make their way into the bark and external coats of the plant and deposite their eggs; these eggs when hatched produce larvæ, which, by their peculiar juices, often rot the wood. These insects are called cynips. One kind produces the hard protuberances on trees of different kinds, which are called gall-nuts, or nut-galls; others, which are softer and more spongy, are called applegalls or berry-galls. Another kind of insect, caled cochineal, attaches itself to the bark of trees, and preys upon the juices. One species of the cochineal is of a brilliant scarlet co.our and much valued for its use in dying; this species feeds on the Cactus cochinillifer, a Mexican plant.

5th. Diseases are produced by plants preying upon each other, either by fastening themselves upon their surfaces, or by so`near a location as to deprive others of their necessary food. Parasites fasten themselves upon the surfaces of other plants; they are distinguished into two kinds, the false and true parasites; the former adhere to the plant without feeding on its juices, as mosses and lichens. These derive their nourishment from the atmosphere; but they injure the tree by harbouring insects, and attracting moisture which often rots the part of the stem on which they grow. The mistletoe is a true parasite, whose root, piercing the bark of trees, plants itself in the alburnum, and absorbs food from it, in the same manner as if it were fixed in the soil. The Pterospora is a very curious parasite which is sometimes found upon the leaves of shrubs, but more frequently upon the branches and leaves of trees. Mushrooms are of the class of false parasites. Smut is a black fungus, which fastens itself upon the ears of oats and other grain. The rot is a fungus excrescence which preys upon the seed; if seeds which have this dis ease fastened upon them are sown, the rot will be propagated also. Ergot is a disease mostly confined to rye. Rust is chiefly confined to the grasses; both are of the fungi family.

6th. Diseases resulting from age. Plants differ from animals in one important circumstance; the latter develop their organs at once; these organs in process of time become indurated and ob structed, until they at length decay from old age. Plants, on the contrary, renew themselves every year; that is, they form new vessels to convey the juices, new leaves to elaborate them, and new buds to produce flowers and fruits. Plants do not, then, like animals, seem destined to die with old age; or there does not seem to be in perennial plants any prescribed term of existence. The producing of fruit appears to exhaust the vital energy of the plant, in annuals in one year, in biennials in two, in perennials in a longer or shorter period, according to their natural constitution, and the quantity of fruit which they produce. Apple-trees, which bear heavy loads of fruit, are very short-lived in comparison with the oak, which perfects from each flower but one of six seeds, and this fruit is but a sinall acorn.

There are some trees now known to exist, which are supposed to be of great age; in the Island of Teneriffe is the DRACENA draco, which, according to many circumstances, appears to have some thousand years of age. In England, at Blenheim Park, it is said,

4th, Animals-5th, Parasites-6th, Diseases resulting from age-Aged trees

may be seen trunks of trees which shaded the bower of fair Rosa mond, and which it is supposed are not less than a thousand years old. At Hartford, in Connecticut, is the Charter-oak, which was a hollow tree in the days of James II., nearly two hundred years ago. In the hollow of this tree was concealed the charter of the state, when the King of England, through his agents, attempted to deprive the colonists of that guarantee of their civil rights. This oak must, ever, at that period, have been an aged tree.

Economical uses of various Plants.

We perceive among the various species of vegetable beings, some which seem destined only to beautify and enliven the earth; others, with little or no beauty, are valuable only for their utility; and in some instances we find utility and beauty united; roses, lilies, tulips carnations, and most of the green-house and garden plants, belong to the first mentioned class. Trees are not only beautiful, but many of them are highly useful, affording fuel, shelter, and shade, nuts, berries, and other fruits; their bark is used in tanning, for medicine, and spices, and ther sap and secretions furnish sugar and various medicinal ex'racts.

Trees, with respect to their wood, may be divided, 1st, into such as have hard wɩ ›d, as the oak, elm, apple, &c.; 2d, such as have soft wood, as the pop r and willow; 3d, such as have resinous wood, as the pine and fir, t such as are evergreens, but not resinous, as the evergreen oak hesh of Europe.

Hard wood is consir best for fuel; as it contains the greatest quantity of carbon, it is a more intense and permanent heat; resinous wood convinine hydrogen, burns with a more briliiant flame.

The fermented juis of th A produces wine. Grain of different kinds produce gin whiske, & Apples, by their fermentation, produce cider; this quor, conated by distillation, produces brandy and alcohol. The vineyards of Italy and France, and of some of the Atlantic is). 's, are the most celebrated for their wine. not flourish 1. the same luxuriance as

t.

In America, the vine do upon the eastern contine Grasses are the palms fold climates; they are of the class of monocotyledons, and have endogenous stems. Some are perennial, some annual; the meadow grasses are of the former kind. The grains, Indian corn, and rice are annual. There are certain grasses which are called artificial, because they do not spring up without cultivation; of this kind is clover. Gramineous plants, although very important, as furnishing from their leaves food for cattle, are yet more especially useful for their seeds, which furnish food for man. Some plants furnish oils, which are of important uses in various ways. Of the fixed and volatile oils we have already spoken. The fixed oils are extracted from plants called oleaginous; they may be considered under three heads: 1st, olive-oil, produced from the olive in warm countries; 2d, nut-oil, of temperate climates, as obtained from walnus &c.; 3d, oil obtained from the seed of oleaginous, or oily plants, as the flax.

Tuberous rots, as the turnip potato, carrot, beet, parsnip, &c., furnish important rticles of food.

Asparagus, wh n young, is esteemed a luxury; the rhubarb plant is used in making pies; celery, o ions, and even garlic, are esteem

Charter-oak-Plant. wch are chiefly vt trees with respect to Liquors proa plants-Tuberous roots-s, ragus, &c.

able for beauty-For utility-Division of ed from plants-Grasses-Oleaginous

ed valuable for food and seasoning. Many of the labiate plants, as thyme, sage, &c., are used in cookery. The Cruciform family af ford the cabbage, cauliflower, turnips, &c.; the Leguminous family, beans, peas, &c.

The Cucurbitaceæ furnish us with melons, squashes, and cucumbers; umbelliferous plants, with the aromatics, caraway, coriander, &c., which are useful in medicine and confectionary.

The plants chiefly used in domestic economy differ in different climates and countries; some, as many kinds of grain and grasses, are in common use in all countries; while others, as the bread-fruit and plantain, are only used in the few countries which produce them. The bread-corn of the temperate climates, is chiefly wheat, rice, and maize; rice is a substitute for these in warm countries, and barley in cold countries.

The esculent roots of the old world, are chiefly the yam, carrot, and turnip; of the new, the potato.

The pot-herbs, such as the cabbage, sea-kale, and others of the cruciform family, are used in temperate climates; in hot climates they are little used. Legumes furnish an important article of food in most parts of the old world, and in North America.

LECTURE LII.

HISTORY OF BOTANY, FROM THE CREATION OF THE WORLD, TO THE REVIVAL OF LETTERS IN THe reign of CHARLEMAGNE, A. D. 770.

We now propose to give a brief sketch of the progress of botanical knowledge; and as this is closely connected with other branches of natural science, a history of the advancement of the one will necessarily be, in some degree, a record of the march of the others. Natural Philosophy, Chemistry, and Botany, were all nursed in the same cradle, and thus grew and gained strength side by side; though Botany (at first rude and imperfect) may be considered the elder sister.

After becoming familiar with a science, the mind naturally seeks for information respecting its origin, and the progress by which it advanced from the first rude conceptions which might have been formed, to its gradual development and comparative perfection. The history of the progress of a science makes a part of the science itself; we are interested in the various efforts of philosophers, their experience and observations, and the trains of reasoning by which they arrived at those conclusions which constitute the basis of the science.

In Botany, as in the other sciences, physical wants were the firs guides; man at first sought to find in vegetables, food, then renes for diseases, and lastly, amusement and instruction.

The first account of plants may be traced to the history of the C ation by Moses. It was on the third day of this great work! God said, "Let the earth bring forth grass, the herb yielding se and the fruit-tree yielding fruit after his kind, whose seed is in itseɩ upon the earth and it was so; and the earth brought forth grass, and the herb yielding seed after his kind, and the tree yielding fruit,

Melons-Umbelliferous plants-Bread-corn-Pot-herbs-Legumes-History of botanical science- -Why do we wish to learn the progress of science-First account of plants traced to the history of the creation.

whose seed was in itself, after his kind; and God saw that it was good." After this, it is recorded that God gave to Adam every herb and every tree bearing fruit; the latter was for him exclusively, but to the beasts of the earth, and the fowls of the air, and to every thing wherein there is life, he also gave the green herb for meat.

It is recorded that Adam gave names to all the beasts of the field, and the fowls of the air; and Milton imagines, that to Eve was assigned the pleasant task of giving names to flowers, and numbering the tribes of plants. When our first parents, as a punishment for their disobedience, are about to leave their delightful Eden, Eve, in the language of the poet, with bitter regret, exclaims:

The Bible, and the poems of Homer, afford us the only vestiges of the botanical knowledge of the earliest ages of the world. Great advantages were afforded to the Jews for obtaining a knowledge of plants, in their long wanderings over the face of the earth, before they settled in Judea. When in possession of this fertile country they extended their intercourse with foreign nations; the vessels of Solomon frequented the shores of the Red Sea, the Persian Gulf, and the East Indian islands. In the Book of Kings it is said, "God gave Solomon wisdom and understanding_above all the children of the East country, and all the wisdom of Egypt, for he was wiser than all men. He spake proverbs and songs; he also spake of trees, from the cedar-tree that is in Lebanon, even unto the hyssop, that springeth out of the wall; and people from all countries came to hear his wisdom."

The Magi, or "wise men of the East," cultivated the sciences to a great extent; but they kept their discoveries in mysterious concealment, in order the better to tyrannize over the minds of the people. Their researches were in a great measure lost to the world. Greece, however, received from Asia and Egypt the first elements of knowledge.

The philosophers of Greece, too eager to learn nature at one glance, were not satisfied with the slow process of observation and experiment, and to ascend from particular facts to general principles; but they believed themselves able, by the force of their own genius, to build up systems which would explain a phenomena; supposing that man had in his mind preconceived ideas of what nature ought to be. This error in the philosophy of the ancients for a long time obstructed the progress of all science; and it was not until laying aside this false notion, and admitting that the only sure method of learning nature is to study her works, that the la bours of philosophers began to be followed by important discoveries The greater part of the ancient Greek philosophers asserted, that plants were organized like animals, that they possessed sensible and rational souls capable of desires and fears, pleasure and pain. Pythagoras of Samos, who travelled in Egypt, and was there instructed by the priests of the goddess Isis, is said by Pliny to have been

Milton imagines that Eve gave names to the plants, and numbered their tribesWhat is known of the progress of botany during the earliest ages of the world-Solomon is said to have spoken of trees and other plants-The Magi-Philosophers & Greece Pythagoras.