of the filaments and antheræ, namely, Monadelphia and Syngenesia. The last Order of both classes is called Gynandria; not because in the plants which belong to it the stamina stand upon the style, but because in the male flowers there is a production resembling a style, to which the stamina are attached. This production Linnæus considers as an imperfect pistulum.

In the 23d class the Orders are called Monacia, Diacia. The last class has the following Orders, Filices, Musci, Alga, and Fungi. From the foregoing analysis it will be seen that the Linnæan system consists of an artificial and sexual arrangement, and that it does not answer the idea, we have given above, of a perfect system. But till such a one is found out, a system partly natural, partly artificial, is the best; we must, however, as we cannot deny the usefulness of Linnæus's system, point out its defects.

Linnæus endeavoured, from the number of the stamina, their various lengths, and different modes of connexion, to unite a natural elassification with an artificial one. Hence arose some faults, which would not have happened had he at the same time made use of the corola as a character. For instance, in the fourteenth class are contained the labiated and ringent flowers; but because Linnæus characterised it from the four stamens, two of which are shorter, there are some of these plants which must stand in the second class, and others in the fourth, though they properly belong to this class. In the same manner, all the papilionaceous flowers are referred to the seventeenth class; but the assumed character, viz. that the filaments are united into two sets, is not to be found in all these plants. Many have the filaments united in one cylinder; and in the tenth class stand many plants with papilionaceous flowers. These two faults are not the greatest which may be attributed to this system: it is a more important objection that Linnæus has numbered the stamens in the first classes without attending to their insertion, while in the twelfth he remarks that they are inserted in the calyx, and in the twentieth, that they stand on the pistillum. In the nineteenth class are comprehended all the compound flowers, and yet he drags into the last order of this class other plants whose antheræ are only sometimes united. It is also to be regretted, that in the 21st, 22d, and 23d classes, Linnæus has taken notice of different sexes in the same plant, which he had not done before; there being many plants in the former classes that properly belong to these.

These defects and some others, from which no system can easily be exempted, have suggested to several botanists the possibility of correcting them and making the system more useful. Among all the improvements of the Linnæan system, those by Thunberg seem to be the chief. He has reduced the number of classes to twenty, by referring the plants of the 20th, 21st, 22d, and 23d classes to others, according to the number or connexion of the stamens. All the plants which stand in the 20th class ought to have the stamens placed upon the style; but the most of the plants arranged by Linnæus in this class want these characters, the genus of Orchis alone excepted. The three following classes are not always constant with regard to sex; a difference of climate will sometimes remove a plant from the class Monacia to that of Polygamia.

Liljebad has made the following changes on the Linnæan system. He joins the 7th, 8th, and 9th classes to the 10th. His Decandria thus contains the Heptandria, Octandria, Ennæandria and Decandria of Linnæus. The eleventh class he joins to the 13th. 18th, 21st, 22d, and 23d, he includes in one.

tains only sixteen classes, viz.

1. Monandria,

2. Diandria,

3. Triandria,

4. Tetrandia,
5. Pentandria,
6. Hexandria,

7. Decandria,

8. Icosandria,

The

Thus his system con

9. Polyandria,

10. Gynandria,

11. Didynamia,
12. Tetradynamia,
13. Monadelphia,
14. Diadelphia,
15. Syngenesia,

16. Cryptogamia.

Some other botanists have changed the orders of the 19th class, by leaving out the word Polygamia, and removing the plants of the order Monogamia to other classes.

But this order of the 19th class ought to be altogether suppresed; because the genera belonging to it have nothing in common with the other syngenesious flowers but the united anthers, which other genera, for instance the Solanum, possesses likewise. If this order be taken away the class becomes perfectly natural.

Schreber, in the last edition of the Genera Plantarum, has changed the Orders of the 24th class, as follows:

It would be superfluous here to take notice of other alterations which do not tend to the improvenent of the science.

CHAP. III.

NATURAL HISTORY OF PLANTS.

[Wildenow.

By the Natural History of Plants, we mean a comprehensive view

of the effects of Climate on Vegetation; the changes which it is probable plants undergo from the revolutions of our globe; their dispersion over its surface; their migration; and, lastly, the means pursued by Nature for their preservation.

Geographers have imagined the globe to be surrounded by certain Zones, and they have divided these into degrees and circles. They suppose the hottest climate to be under the line, or at the equator; a hot climate under the tropics; between these and the polar circles, two different climates, a temperate and a cold; and, lastly, they consider, under the polar circle, a very cold climate to prevail.

Upon the whole, these divisions sufficiently coincide; but great differences are produced by mountains, vallies, rivers, marshes, woods, seas, and inequalities of surface; so that there are places which, according to the above divisions, ought to be hot, which are however temperate, or even cold, and vice versa. We must therefore distinguish between a physical and geographical climate. America and Asia are much colder in the same northern geogra phical latitude than our part of the world. Plants which in America grow under the 42d degree of northern latitude, bear in our climate the cold of 52°. The reason of this great difference seems to be the enormous swamps and woods of America, and the immense elevation of the land in Asia. Africa, under the tropics, is incomparably warmer than Asia or America. The chains of mountains in these last countries, and the humidity of the vallies, moderate the great heats, while the burning sands, of which almost the

whole of the African surface consists, increases the heat. The regions about the North Pole are much more temperate than those at the South Pole. Tierra del Fuego lies under the 55th degree of southern latitude, and has a much more inclement sky than prevails in Europe under the 60th. Mountains that raise themselves high above the clouds, have, in all latitudes, perennial snow upon their extreme summits. Cook found such a mountain in the Sandwich islands; and in America, the celebrated Andes have their tops covered with perpetual ice under the tropics and the line, while a constant summer is felt in the vallies.

Situation, heat and cold, wet and dry soils, have great influence on the whole of vegetation. It is not therefore surprising to find in every region of the globe, plants adapted to each particular situation. Accordingly, when we meet on the tops of high mountains the plants of Polar regions, we infer that these plants were destined for cold climates: nor ought we to wonder that, under the same latitudes in Asia, Africa, and America, we find, on similar soils, plants which are natives in all these quarters of the globe.

In one geographical latitude, if no mountains or other circumstances change the temperature, the same plants are found to grow; but places in the same longitude, must always exhibit various productions of the vegetable kingdom. The Mark of Brandenburgh, the coasts of Labrador and Kamtschatka, lie nearly under the same latitude, and produce therefore many plants in common. Berlin, Venice, Tripoli, and Angola, are nearly in the same longitude; but their plants are very different.

It is well known that warmth is necessary to vegetation: hence it naturally follows, that in the warmer climates the number of native plants will be most considerable. The Floras, made by botanists in different countries, shew, that vegetation increases according to the degree of heat. In Southern Georgia *, by the best accounts, there are only two native plants: in Spitzbergen, there are 30 in Lapland, 534: in Iceland, 553: in Sweden, 1299: in the Mark of Brandenburgh, 2000: in Piedmont, 2800: on the

An island of considerable extent, discovered by La Roche in 1674, and explored by Captain Cook in 1775, who named it Georgia. It is a land of ice and snow, with few vegetables but lichens.-EDITOR.

coast of Coromandel, nearly 4000: as many in the island of Jamaica in Madagascar, above 5000. In every region there are plants, except in the regions round the pole covered with perpetual snow, on the icy tops of the highest mountains, and in the dry and sandy wastes of Africa. On the bare and barren places where volcanic fires predominate, there are to be found few plants, and those miserably stunted; as in the island of Ascension and Kerguelen's land.

Climate influences the growth, as well as the form, of every vegetable product. The plants of the polar regions, and of high mountains, are low, with very small and close-set leaves, but with flowers proportionally large. The plants of Europe have no very showy flowers, and many of them are catkins: the Asiatic climates are particularly rich in splendid flowers: the African plants have, for the most part, very succulent leaves and variegated flowers. American plants are remarkable for long smooth leaves, and the singular structure of their flowers and fruits. The plants of New Holland are distinguished by thin dry leaves, and a more compressed form. Those of the Archipelago in the Mediterranean Sea, are in general shrubby and prickly. The plants of Arabia are of a low and stunted growth. In the Canary islands, the most of the plants and even genera that in other climates are herbaceous, become either shrubs or trees.

The resemblance between the trees and shrubs of northern Asia and America is remarkable, though the herbaceous and perennial plants of both these parts of the world have almost nothing in common, with respect to form. The following comparative list will make this apparent :