been entirely abandoned since the discovery and demonstration of their organic structure, and a verility similar to that of plants of higher order could no longer be denied. Micheli suggested that they were propagated by seeds, and immediately these were supposed to be floating in the air. Hedwig described the seeds which he pretended to have found, and also the impregnating male organs, though he failed to describe the female organs. Hedwig's seeds have been called germ grains, but propagation by them has not succeeded.

From known facts we deduce the following, in order to give an explanation of the process applied in raising mushrooms. The mushroom appears to be the product of two elements of vegetation-the brood and the mushroom; the latter without power to propagate itself by itself; the former producing-probably by elongation-a necessrry foundation for the formation of the mushroom, and producing it only under very favorable circumstances. The growth of the brood depends upon an increased degree of heat and moisture, which increase is not yet determined by measurement; +9° R. are known to be proper and sufficient, so far as heat is concerned, but moisture and heat should be in a given relative proportion, not yet determined. At +9° R. a degree of moisture may be injurious, which at +12° R. would be proper and even necessary. The hydrogen. exhaled by mushrooms suggests a decomposition of water and a consumption of oxygen, and thus the necessity of an increased moisture for the production of mushrooms from the dry brood is explained. The exhalation of hydrogen furnishes an indirect explanation why mushrooms are grown better on stable manure from grain fodder than from that of any other kind of fodder. The principal elements of the mushroom are saccharine matter and parenchyma. The starch of the grains, barely decomposed by the action of digestion, is by fermentation. with nitrogen and water, again changed to parenchyma, which, perhaps, becomes the first foundation of the mushroom, and which, as is the case with all vegetables, derives all other necessary elements from its surroundings. This parenchyma is changed into saccharine substance by oxydation, and thus we find the oxygen from the decomposed water entering into combination, while the hydrogen is evolved free or in connection with carbon. Fermentation of manure produces ammonia, and if produced to a very considerable extent vegetable life is destroyed. For this reason, we have directed that the beds should be so managed as to prevent fermentation. And it is plain that the plants will thrive best when the elements which they require are in the proper proportion-an excess of one element will operate to disadvantage with the other, and a want, whether arising from the elements being appropriated or changed by heat, air, moisture or mold, will of course cause only a partial and incomplete development of the plants. The brood appears to be an organic texture of fibres, for whose growth the same elements are necessary as in fungi, and which apparently stand in the same relation to the mushroom as the plant to the flower, or the root to the stem.

THE INTERNAL STRUCTURE OF THE EDIBLE MUSHROOM.—Agaricus Campestris, L. BY W. F. LINK.

It is necessary to speak of the internal structure of the mushroom, because every thing s id of its cultivation is unintelligible without a knowledge of this. The mushroom grows from a substance which very much resembles mold. It consists of small branching fibres or tubes, which are divided into cells by partitions or cross walls, distinctly visible under the microscope. The botanists call this portion the mushroom "thallus," and compare it to the base of the lichens. Linne said, that in these vegetables, root, stem and leaves are blended together; and the more this imperfect vegetation is observed, the more apparent becomes the truth of this observation. They are greatly in error who consider the so-called mushroom to be the whole plant. The organized parenchyma is an essential part, and a mushroom cannot exist except it is formed from this. What is generally called the mushroom is nothing but the fruit-bearing portion, which is provided with a stem, and grows to an extraordinary size in proportion to the whole plant. This thallus is called brood in the preceding essays. There can be no doubt but that the mushroom is reproduced as many other plants are produced-by division, so long as there is life in the divided parts; and at the same time, there can be no doubt but that they are produced by the regular method by means of seeds.

On this thallus of the mushroom, small grains are found, plainly visible with the microscope. As the mushroom has real seeds besides, as we shall see soon, it is probable that these grains are eyes or buds, from which other mushrooms are produced. Upon the thallus of lichens just such buds or grains have been found, and have produced perfect plants; on which account, some botanists have termed them "germ powder." Besides these, we have plants of higher orderLilium bulbifirum, L. Tigrium, and Trerinana pulchello-which are reproduced by eyes and bus which fall from the perfect plant. These eyes preserve their vitality even longer than the branches, and it seems probable that these germ grains preserve their power for a long time although they are very small; for the exceedingly small spores of the fern preserve their vitality for a long time. Instances have been known when fern spores, after having lain in the herbarium for thirty years, have germinated.

The propagation of mushrooms by brood is doubtless accomplished in two ways by torn-off pieces of the thallus itself, or by the germ grains adhering to the same. The foregoing essays gave practical instruction, as regards raising the plants from the brood, but now the question arises, Is it absolutely necessary, in raising mushrooms, that portions of thallus, or germ grains, exist beforehand, or can mushrooms be raised without them? In other words, can there be a spontaneous generation of mushrooms? The answer is not to be implied from the above essays. To settle this question, a bed should be made from stable manure which has never been exposed to brood, in an isolated situation, where it

would be impossible for the grain germs to have access. On account of the minuteness of the germs, this will be a difficult thing to accomplish, and we cannot venture an opinon as to the result, except by reverting to laws which are already known to govern in other cases.

Mushrooms are propagated not only by brood and grain germs, but by seeds. The mushroom consists in the greater part, as above said, of the stem and pilens, or hat; on the under side of this latter are found the leaves. If a portion of one of these leaflets be examined through a powerful microscope, a stratum of small tubes or fibres will be seen, which are separated from each other by cellular tissue. This stratum may be seen with the naked eye, or with a glass of low magnifying power; but thus viewed, it appears so dense as to resemble a naked membrane. Porsoon described it as such under the name of hymenium. There lies in every tube a row of grains which form granules on the surface of the leaflet, and often cover it entirely. In different species of the "leaf fungi," these seeds assume different colors when matured. In the edible mushroom they are reddish brown. The fungi which are found growing on manure heaps have a remarkable structure. Every seed-tube contains four rows of seed, and when expelled from the tube, they lie in squares on the surface of the leaflet. I believe myself to have been the first to describe and demonstrate the structure of the leaf fungi, in my essay which appeared in the magazine of the Association of the Friends of Physiology, in 1807. I am convinced, by my own experiments, that mushrooms grow from leaflets or from the seed which is abundantly contained in them.

In regard to the chemical composition of mushrooms and fungi, we cannot place much reliance on analyses made during the last century. We have recent analyses of many species, especially the poisonous kinds. The most recent and reliable analysis of the edible mushroom (Agaricus campestris) was made by Vanquelin, which is quoted by Berzelius in his Compend. Vanquelin found no parenchyma, but some coagulated albumen, together with a nitrogenous compound, which he considers analogous to as mazone, or the organic principle of meat. This dissolves in water and alcohol, and belongs to the division of extractive matters. Besides this, he found another nitrogenous compound, which dissolves in water or diluted alcohol, and is precipitated by a decoction of nut-galls. The sugar frequently contained in mushrooms is grape sugar, which is not so sweet, dissolves more freely, and is more readily crystallized than cane sugar.

Various experiments have been made of late with a view to discover the best method of improving and increasing the crop of mushrooms, which have been very successful. The method described by Mr. Edward Callow, is highly recommended in the Gardeners' Magazine. In the same periodical, Mr. Collier describes his method, which was crowned with extraordinary success as regards the abundance of the crop, and especially the size of the mushrooms. One specimen was exhibited whose pilens or hat measured 8 feet 7 inches in circumference, and weighed 2 pounds and 1 ounce. The French reporter justly remarks that an improved culture has for its aim not the size but a superior flavor; but

he praises the whole process as being well planned and executed, and as being entirely new. The following is the method used:

The bed is made 3 feet deep, with coarse and fine stable manure.

The bed is not completed at once, but in order to prevent fermentation and too great a degree of heat, it is made at two different times, at an interval of five or six days, each time 14 feet deep, and well pressed down.

A heavy layer of manure, from 3 to 9 inches in depth, is then added.

The bed is never covered closely with boards, but a space of 3 inches at least is left between the cover and the beds.

The deep bed is said to secure a permanent and uniform warmth, the more abundant formation of thallus, and the abundant and continued yield.

The last layer of manure is put on for the purpose of growing melons on the bed previous to its use for mushrooms; it is also said to secure uniformity of moisture and a better development of mushrooms.

The greater elevation of cover prevents the attacks of insects by removing their protection, while it allows greater development to the mushrooms.

Mr. Ellis describes a method of raising mushrooms in open fields. He prepares his beds in the usual way, spreading on the top a layer of manure from an old mushroom bed. The beds are then planted with carrots, cauliflowers and radishes, which grow luxuriantly, and protect, by their leaves, the bed from drying out. He gathers several crops during the year, and thinks the expense not greater than that of gathering wild mushrooms, aside from the inconvenience of wet feet, &c., are avoided.

THE GRAIN APHIS.

BY J. KIRKPATRICK, CLEVELAND, OHIO.

Until the year 1861 the grain aphis was generally unknown in the United States, and no writer in this country had given an account of it from actua observation. Its sudden and simultaneous appearance in that year over a large portion of New York and most of the Eastern States was therefore the more unexpected and surprising. In Europe, where it had been long known, it had never been observed in such numbers, and at no time was there any alarm felt in regard to the amount of injury resultant from its habits. Kirby and Spence, those accurate observers of insect life, devote but five words to this insect, and these in relation to oats only. Kollar does not mention it in his work as existing in Austria. Wilson, in "Our Farm Crops," has but a short notice of, and seems never to have seen it; and this is the less surprising, as it rarely occurs in Scotland. Curtis gives a full and accurate description, with plates, in "Farm Insects." From this work I learn that it was seen by Mr. Markwick and also Mr. Kirby on wheat, oats and barley, in some of the English counties, in 1797. In the "Wheat Plant," published at Cincinnati in 1860, Mr. Klippart gives the annexed figure and description of this aphis, although it had not as yet, to my knowledge, been observed in this

country. "Aphis Granaria. Wheat Plant Louse. Inhabits corn crops, having been observed upon barley and oats as well as upon wheat. In July and August it is sometimes abundant in the ears of wheat, sucking the stem and impoverishing the grain. The male is green; figure No. 3 natural dimension; horns very long and black; eyes and three ocelli black; disk of trunk dark; tubes slender, longish and black; nervures of wings pale brown; terminal cell semi-heart-shaped; stigma long and green; hinder legs very long; thighs, excepting the base, tips of shanks and feet, black. Females often apterous (wingless), No. 1; dull orange; horns (excepting the base), eyes and abdominal tubes (which are stouter than in the winged specimens) black; legs blackish; anterior thighs and base of tibiæ more or less ochreous." About the 1st of September, 1861, Prof. J. P. Kirtland received specimens of this insect from a friend who was then on a visit to Schuyler Falls, Clinton county, N. Y., and kindly placed them in my hands,