DIVISION OF MICROSCOPY. The exhibit of the Microscopist, Dr. Thomas Taylor, consists of about 500 water-color drawings, a large proportion of which represents the leading types of the genera of microscopic fungi; another section of the exhibit presents the results of original investigations upon chemical tests for flax, cotton, ramie, silk, wool, hair, and both animal and vegetable cellulose; and still another series, illustrating the principal vegetable starches to the number of about 100 varieties. These drawings present highly magnified views of all these microscopic objects, including those most important in economic mycology, especially the fungi commonly known as molds, so destructive to vegetation. The edible and poisonous mushrooms are distinguished in one class of these drawings. The importance of the mushroom as an article of diet has never been properly understood in the United States, nor is it generally known how abundant our supply of edible mushrooms is. Many of those popularly supposed to be poisonous are not merely innocuous but highly nutritious, containing, as they do, many of the elements of animal food. In France, Germany, and Italy the mushroom forms so important a part of the food of the people that one distinguished writer has spoken of it as the "manna of the poor." In Transylvania the oyster mushroom is so abundant, and is so largely used, that tons of it may often be seen in the markets; and in some parts of Germany the Morel mushroom is so popular that the people, finding it to grow best on a soil treated with wood ashes, were accustomed to burn down portions of the forests in order to secure favorable spots for its cultivation—a practice which the Government ultimately found it necessary to interdict. It is hoped that the collection of drawings, which has been made with so much care by Mr. Taylor, will serve to call public attention to the value of the mushroom as an article of food, and at the same time furnish means of discriminating between the poisonous and the edible varieties of the plant. Particular pains have been taken to represent the last-named class of plants as fully as possible, a number of collectors having been employed for the purpose in various parts of the United States. Among these may be mentioned Professor Peck, of New York, who, in that State alone, gathered specimens of no less than 80 species of mushrooms, including several which are new to science. The specimens furnished by Professor Peck are admirably copied and colored to nature; and there are also a number of excellent photographs, made from specimens furnished by various collectors, representing different genera and species of the same class of plants. Another series of drawings illustrates the action of pear-tree blight, showing the effects of the chemical changes which take place in the interior structure of the tree under the attacks of the fungus to which this disease is due. The disease of plum and cherry trees, known as "black-knot," is illustrated in a similar manner, some of the drawings exhibiting it as it appears to the naked eye, while others show in detail its distorted, woody structure. The fungus which produces it is also shown at various stages of its growth. The fungus Peronospora infestans, which causes potato-rot, is illus trated in the various stages of its growth. There is also a series of drawings of its "resting-spores," recently discovered by Professor Worthington Smith, and so named from the fact that they remain for months in a stationary condition, or, in other words, rest for that time without germinating. There is an interesting series of drawings representing, as seen through the microscope, the mold of bread, cheese, jellies, &c., and illustrating their habits of growth, a knowledge of which may often be useful in preventing beer or milk from souring, and wine or bread from becoming "ropy." One of the most curious of the cryptogamic plants is the Protococcus nivalis, which we believe was first found by Captain Parry during his northern exploration, and to which was given the name of "red snow," from the fact that it gives its own red color to the surface of the snow on which it grows. This singular little plant is represented by several drawings of exquisite finish and color. The fibers of hemp, flax, jute, ramie, esparto grass, and Australian flax, as well as wool, silk, calf's hair, and the hair of the Cashmere and Angora goats, are exhibited as seen through the microscope, both in their natural condition and under various forms of chemical action. In the course of his investigations on this subject, Dr. Taylor has discovered a number of new chemical tests by which the presence or absence of certain of these fibers, in every fabric, may be determined. This series of drawings will, therefore, be of considerable interest to manufacturers of textile fabrics, to dealers in that class of goods, and to the Government, which, besides being an extensive purchaser of clothing for the Army and Navy, is largely interested in determining correctly the materials composing the fabrics which pass through the customhouses. The investigations to which these drawings relate are still in progress; but the great majority of the drawings relate to the leading families, orders, and genera of cryptogamic plants or fungi, of which by far the greater number are microscopic in size. The latter are often visible to the naked eye when massed together in large numbers, presenting in some cases the appearance of a pigment on the surfaces of the plants upon which they fasten. In such cases the microscope sometimes reveals millions of spores to the square inch. The ravages of these minute vegetable organisms are incredible in their extent. The potato has, at times, been threatened almost with extinction. Grasses have been affected by them, and the cereals throughout large districts have at times suffered blights so serious and often repeated that the farmer has been almost ready to abandon their cultivation in despair. Fields of hops, vineyards and orchards have withered under their blighting touch, and in lower latitudes they have assailed coffee plantations, and groves of orange, lemon, and olive trees, with equally fatal results. Even the lordly forest trees have not in all cases escaped their devastating influence, and at the present moment many of the stately maples in the public grounds of our cities are withering under the insidious attacks of these minute destroyers. In short, there is hardly any department of agriculture, horticulture, or forestry that can claim exemption from their ravages; and the importance of a correct knowledge of their characteristics, modes of propagation and development, and the conditions under which they tend to flourish or decay, can hardly be overestimated. As a contribution toward the dissemination of such knowledge, the collection just described must be regarded as possessing a high practical value. No large collection of well-executed drawings of cryptogamic plants has heretofore existed in this country; but by the assistance of Dr. M. C. Cooke, of London, and others, Dr. Taylor has supplied the defect in an admirable manner, and has formed a collection which will be of permanent value to mycological science. The drawings, nearly all of which were made from nature for the special purpose to which they are now destined, exhibit a high degree of delicacy and finish. Mushrooms, in their composition, more nearly resemble flesh than any other vegetable. Dr. Marcet proves that, like animals, they absorb a large quantity of oxygen, and give out in return carbonic acid, hydrogen, or azotic gas. Chemical analysis demonstrates the presence in their structure of the several components of which animal matter is formed, many containing sugar, gum, resin, fungic acid, various salts, albumen, adipocere, and ozmazone, "which last is that principle that gives flavor to meat gravy," according to Dr. Badham. Fungi are applicable to other than culinary uses, though their most important use is the gastronomic one. To obviate the difficulty arising from the prejudice against the wholesomeness of any mushroom, Mr. Berkeley recommends a good quantity of bread to be eaten with them. He is of opinion that mushrooms are only indigestible when eaten alone or in imprudent quantity. Of course this remark applies equally to any sort of mushroom, though it is made with reference to the one in familiar use. As an indirect but very important article of diet, the tiny fungus known as yeast stands pre-eminent. It is composed of globular cells |