lifted out of their beds by the growth of large toadstools beneath them. One of these stones measured twenty-two inches by twentyone, and weighed 83 lbs; and the resistance offered by the mortar which held it in its place would probably be even a greater obstacle than the weight. It became necessary to re-pave the whole town, in consequence of this remarkable disturbance.

61. But though in these and many other ways Fungi are injurious to man, the benefits they confer upon him far outweigh their occasional devastations; and it is only through the constancy of the former that they are overlooked and unappreciated. It is not only to man that they are of the most essential service, but to the whole animal kingdom. To Fungi may be justly applied the designation which has been conferred upon Insects, that of the "scavengers of nature;" for, like insects, they labour with the most astonishing effect in the removal of refuse and decaying substances, which, were they left upon the surface of the earth, would prove not merely useless tenants but injurious incumbrances. Their vapour-like germs float about in the atmosphere in countless myriads, only waiting for the presence of a fitter soil on which to alight and grow. As long as there is no refuse decomposing matter to be removed, these spores remain inactive and undeveloped, ("the scavengers are unemployed"); but as soon as any quantity, large or small, of decaying animal or vegetable matter, is left exposed, it is soon covered with a deposition of spores, which rapidly develope themselves into fungi of various kinds.

- 62. Their astonishing fertility, and the rapidity with which they arrive at maturity, are among the most remarkable characters of this tribe of plants. Of the former, some account has already been given. Of the latter many instances are recorded. Thus one species has been known to attain the weight of 34lbs in six weeks; and on the continent, Fungi of this tribe have grown to upwards of 100lbs., having begun from a point not perceptible to the naked eye. A large fungus of the Puff-ball tribe has been seen to grow in one night from a minute speck to the size of a large gourd. No other living beings have powers of growth at all

52

IMPORTANT USES OF FUNGI.

to be compared to this. The more rapid the decomposition, and the greater the quantity of noxious exhalations which would thus be spread through the atmosphere, the greater is the tendency to multiplication and luxuriant growth in these humble plants, to which such exhalations serve as the most appropriate food.

63. Hence what has been said by Naturalists of Insects, applies with equal truth and force to these humbler tribes; and we may adopt with slight modification an interesting statement which has been given of the agency of Insects, as a striking delineation of the operations of the Fungi.

64. "The peculiarity of their agency consists in their power of suddenly multiplying their numbers, to a degree which could only be accomplished in a considerable lapse of time by any larger beings; and then as instantaneously relapsing, without the intervention of any violent disturbing cause, to their former insignificance. If, for the sake of employing on different but rare occasions a power of many hundreds or thousands of horses, we were under the necessity of feeding all these animals at a great cost in the intervals, when their services were not required, we should greatly admire the invention of a machine, such as the steam engine, which should be capable at any moment of exerting the same degree of strength, without any consumption of food during the periods of inaction; and the same kind of admiration is strongly excited when we contemplate the powers of Insect and Fungous life, in the creation of which Nature has been so prodigal. A scanty number of minute individuals, only to be detected by careful research, and often not detectable at all, are ready, in a few days or weeks, to give birth to myriads, which may repress or remove the nuisances referred to. But no sooner has the commission been executed, than the gigantic power becomes dormant ; each of the mighty host soon reaches the term of its transient existence; and when the fitting food lessens in quantity, when the offal to be removed diminishes, then fewer of the spores find soil on which to germinate; and when the whole has been consumed, the legions before so active all return to their latent unnoticed state,-ready, however, at a moment's warning again to be

developed, and, when labour is to be done again, again to commence their work either in the same districts, or to migrate in clouds like locusts to other lands. In almost every season there are some species, but especially in autumn there are many, which in this manner put forth their strength; and then, like the spirits of the poet, which thronged the spacious hall, 'reduce to smallest forms their shapes immense.'

65. Among the uses of Fungi to man, their service as food must not be forgotten. In chemical composition they more nearly resemble animal flesh than do any other vegetable substances; and, accordingly, those of them which are free from injurious properties furnish a highly nutritious article of diet, and some of the rarer species are greatly valued as dainties by the epicure. There is much difficulty, however, in distinguishing the innocent from the noxious species of Mushroom; and many fatal accidents have occurred from the employment of the poisonous kinds. Amongst the Fungi remarkable for their peculiar properties may be mentioned one which is of great service, from its astringent properties, as a styptic, to check the flow of blood; and another which has the power, even when dry, of producing a curious kind of intoxication, and is used for that purpose by the Tartars.

CHAPTER III.

OF THE ELEMENTARY STRUCTURE OF PLANTS.

66. When we examine yet more closely into the conformation of the different parts of which an organized structure is composed, we find that, though the several organs are variously constructed, and are adapted for different offices or functions, they are built up, as it were, of the same materials. With the same bricks, stones, mortar, and timbers, a church, a palace, or a prison may be reared. Just so is it in organized structures. We do not find that each organ is entirely different from the rest, though it has usually something peculiar to it; but we are enabled to separate it into many distinct portions, something similar to which, if not exactly correspondent, may be recognized in other parts. Thus, for example, it was formerly stated that the leaf consists of a midrib and veins proceeding from it, a fleshy substance filling up the interstices, and a cuticle or skin covering the whole. Now the midrib and vei s, as well as the footstalk of which these are a prolongation, consist of three kinds of structure;-woody fibre, to which they owe their toughness, and by which they are adapted to give support to the softer structures;-ducts or canals for the transmission of fluid;-and spiral vessels which are designed to convey air. On tracing these to the stem, it will be found that they all exist in it under the same form, and that these portions of the leaves are in reality but continuations of it. Again, if we examine the fleshy substance which lies amongst them, we shall find that it corresponds very closely in character with the pulp of soft fruits, or the pith of the stem. And if we strip off the cuticle and investigate its structure, we shall perceive that it is but

PRIMARY TISSUES OF PLANTS.

55

another form of the same kind of substance, and that it corresponds with the skin which covers all the newly-formed parts of the stem and branches, as well as the various parts of the flower, and even the roots.

67. These several kinds of structure are termed the primary tissues, being the elements, as it were, of which the edifice is built up; and they are to the vegetable fabric what the bones, muscles, fat, blood-vessels, nerves, skin, &c. are to the animal.

68. Even these primary tissues may be regarded as consisting of other parts still more simple,-namely, membrane and fibre. The fleshy portion of the leaf, for example, or the pulp of fruits, consists of a number of little bags adhering together: each bag or vesicle consisting of a delicate membrane, without any perceptible orifice, and containing fluid. The membrane which encloses an egg after the shell is removed, will afford a good illustration on a large scale of the nature of these vesicles; they may, however, be readily distinguished and separated in an over-ripe orange, where they are of considerable size. Now the membrane which composes their walls may be regarded as one of the very simplest forms of vegetable tissue. Again, if the stalk of a strawberry or geranium leaf be carefully cut round but not through, and the two parts be then pulled asunder for a short space, a number of glistening fibres of extreme delicacy will be seen running from one portion to the other. If these be put under the microscope, it will be evident that they had lain in spiral coils, which are partially straightened when they are thus drawn out, just as when a spiral spring is strained. These were coiled within the membranous tubes that constitute the external sheath of the spiral vessels, which have been mentioned as existing in the leaf-stalk; and thus we are able to separate these vessels into the two other elements, membrane and fibre. These very minute delicate spiral fibres must not be confounded with the woody fibre, of which mention has been made, and the nature of which will be presently explained.

69. The delicate Membrane, of which, in combination with fibre, all the tissues of plants may be regarded as consisting, when they are newly formed, is of variable thickness and transparency.