the smallest of all the orders. The black, felty cellar-fungus and the gray mucor or mould on preserves are familiar illustrations of this order. The sixth and last order is that of the Ascomycetes, or asci-bearing fungi, whose spores, generally eight in number, are produced in the interior of groups of elongated sacs or thecæ contained in fleshy, leathery, or wart-like fructification. These fungi, of which the morel, truffle, and vine disease are well-known examples, resemble lichens in every respect except that they are produced on decaying substances, and are possessed of a mycelium or spawn destitute of the green cellular matter of lichens. Although fungi are in an especial manner capable of universal dissemination, yet we find that in their geographical distribution they are as much restricted as other plants. Some representatives of the class are found in every part of the world, and some particular species have the power of indefinite extension and localization, but, as a whole, like the higher cryptogams, they can only spread within certain limited areas. In tropical forests, where the exuberance of the vegetation excludes the rays of the sun, and creates the dim light and the still, moist air which they love, and where there is always an immense quantity of decaying organic matter, we might expect to find them in the greatest quantity and luxuriance. But, strange to say, fungi, as a class, are comparatively rare in tropical woods. Their headquarters seem to be in northern latitudes, where the temperature is mild and genial, and where there is a constant supply of moisture. Professor Fries of Upsal, the presiding genius of these plants, gathered in Sweden, within a space of ground not exceeding a square furlong, more than two thousand distinct species. “This country,” says Mr. Berkeley, “with its various soils, large mixed forests, and warm summer temperature, seems to produce more species than any part of the known world; and next in order, perhaps, are the United States as far south as South Carolina, where they absolutely swarm. A moist autumn after a genial summer is most conducive to their growth, but cold, wet summers are seldom productive. The portion of the Himalayas which lies immediately north of Calcutta is, perhaps, almost as prolific in point of individuals as the countries named above, but the number of species on examination proves far less than might at first have been suspected. It is probably not a fifth of what occurs in Sweden. Great Britain, though possessing a considerable list of species, is not abundant in individuals, except as regards a limited number of species. The exuberance, even in the most favorable autumn, is not to be compared with that of Sweden or many parts of Germany.” They are found in Arctic and Antarctic regions, almost as far as the limits of vegetation. They penetrate to the dreary regions of Greenland and Lapland, supplying the natives with their tinder, and with an