growing-places appear to be the grapes, whose succulent saccharine juices supply it with abundant nutriment. It shows itself principally upon the young grape when about the size of a pea. The slightest injury from a touch or an insect, affords it a basis of propagation, and once established, it increases with amazing rapidity, frequently blasting the hopes of the grape-harvest over many districts. Its effect upon the grape is to absorb the juices of the superficial cells of the cuticle, which consequently cease to expand with the pulp of the fruit; it then bursts, dries up, and is finally destroyed. To the naked eye the plant appears a mere effused, indefinite, white patch; under the microscope it resolves itself into a collection of little, downy heaps, with egg-like sporidia arising from the necklace joints of the threads.

The following report of its devastating effects may be interesting "In 1847, the spores of this oidium reached France, and were found in the forcing-houses of Versailles, and other places near Paris. The disease soon reached the trellised vines, and destroyed the grapes out of doors in the neighbourhood, and continued to extend from place to place; but, until 1850, it was chiefly observed in vineries, which lost from this cause, season after season, the whole of their crops. Unhappily in 1851, it was found to have extended to the south and southwest of France and Italy, and the grapes were so affected that they either decayed, or the wine made from them was detestable. In 1852, the Oidium Tuckeri re-appeared in France with increased and fatal energy; it crossed the Mediterranean to Algeria, has shown itself in Syria and Asia Minor, attacked the muscat grapes at Malaga,

injured the vines in the Balearic Islands, utterly destroyed the vintage in Madeira, greatly injured it in the Greek Islands, and destroyed the currants in Zante and Cephalonia, rendering them almost unfit for use, and so diminished the supply that 500 gatherers did the ordinary work of 8000! But it is in France that its frightful ravages are chiefly to be regarded as a national calamity, where the produce of the soil in wine is said. to exceed 500 millions of hectolitres; two-fifths of the usual quantity of wine made there has been destroyed, and what has been made is bad. The vineyards of the Médoc, in 1851, were untouched, and the cultivators laughed at the existence of the oidium; but last year the disease showed itself everywhere in the Gironde, even to the borders of the Médoc, with serious injury. The eastern Pyrenees were all deplorably affected, and at Frontignan and Lunel the vineyards were abandoned in despair. Thousands of labourers were thrown out of employ, and the distress was awful. Wine, in France, is the common drink of the peasant; upon this, his bread, and some legumes, he labours; but the wine, bad as it is, has risen to double, and, in the countries most injured, treble its ordinary price." Strange to say, "the vine mildew does not occur in the United States on native vines, but only on those which are imported; and the American varieties cultivated in Switzerland and elsewhere are uniformly exempt."

A very familiar example of an oidium occurs on decaying oranges, commencing at first in minute, distinct, pulverulent spots, which speedily become confluent, and of a deep greenish-grey tinge. This genus of fungi is

very destructive to fruits of all kinds; and one species commits great ravages on peach-trees, peas, and cabbages. The blanc de rosier, which infests rose-bushes, is also an ally of this destructive corps. The year 1854 proved most disastrous to the hop-growers in many districts, owing to the ravages of an oidium. The lover of fruit may have often noticed thin concentric, cream-coloured, or fawn-coloured patches on the skin of apples, pears, and plums, producing very rapid decay. These patches are caused by Oidium fructigenum, which, when it has once obtained possession of a tree, spreads with fatal rapidity, destroying the fruit while still hanging on the branches.

All the mildews and blights hitherto described are light-coloured; but there is another class of fungi equally destructive, called black mildews. They are caused principally by species of Antennaria and allied genera, which form thick, black, felt-like patches on leaves, disfiguring trees, and injuring them fatally, by closing up their pores, and preventing the free admission of the air; as also by depriving them of the full, direct light of the sun. They are principally developed on those leaves which had previously been covered with the honey-dew of the aphides or plant-lice; and as these little creatures cluster together and impair the vitality of whole trees and forests, it may easily be seen how extensive are the ravages of the fungi which are thus developed. In the Azores the orange-groves have suffered dreadfully from this cause; while in Ceylon the coffee-plantations, and in the south of Europe the olive-trees, have sustained of late years immense damage from an unusual development

of black mildews. Few objects, it may be remarked, are more beautiful under the microscope than the wheelshaped, ray-like processes which radiate from the seedbearing organs.

These sporiferous bodies sometimes contain a perfect miniature plant or embryo, similar to that of flowering plants, which waits only circumstances favourable for its expansion. Another allied species, called Fusarium mori, is produced in such abundance on the leaves of the mulberry, in Syria and China, as materially to diminish the supply of food provided for the silk-worm.

But it is not only in food and luxuries that man

suffers from the ravages of fungi; he also suffers in his property. Builders have painful knowledge of one or two species, known under the common name of dry-rot. This most destructive plague is usually caused in this country by the Merulius lachrymans (Fig. 41). It occurs on the inside of wainscoting, in the hollow trunks of trees, in the timber of ships, and in the floors and

beams of buildings in moist, warm situations, where there is not a free circulation of air. It appears at first in round, white, cottony patches, from one to eight inches broad, which afterwards develop over their whole surface a number of fine, yellow, orange, or reddishbrown irregular folds, most frequently so arranged as to have the appearance of pores, and distilling drops of moisture when perfect; whence its specific name. In the mature state it produces an immense number of minute, rusty sporules, which alight and speedily vegetate in the circumjacent timber, however sound and dry it may appear, destroying its elasticity and toughness, and rendering it incapable of resisting any pressure, until gradually it crumbles into dry, brown dust. This insidious disease, once established, spreads with amazing rapidity, destroying some of the best and most solid-looking houses in a few years. The ships in the Crimea suffered more from this cause than from the ravages of fire, or the shot and shells of the enemy. So virulent is its nature, that it

extends from the woodwork of a house even to the walls themselves, and by penetrating their interstices, crumbles them into pieces. "I knew," says Professor Burnett,

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a house into which the rot gained admittance, and which, during the four years we rented it, had the parlours twice wainscoted, and a new flight of stairs, the dry-rot having rendered it unsafe to go from the ground floor to the bed-rooms. Every precaution was taken to remove the decaying timbers when the new work was done; yet the dry-rot so rapidly gained strength that the house was ultimately pulled down. Some of my books which suffered least, and which I still retain, bear