and, 3. Those which only attack the roots. All are extremely simple in their organisation, and very minute in their forms; they seldom appear but in autumn, except in forcinghouses.

The first class, or mildew composed of those fungi that live on the surface of leaves, injure a plant by preventing its respiration, but do not appear to draw any nourishment from it. One of the most common of the fungi which attack the common cabbage (fig. 85.) is Cylindrosporium concéntricum

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Grev. These very destructive fungi have the appearance of small white patches, or specks, of frosty incrustation, which, when magnified, are found to consist of a number of small cylinders, lying end to end, or across each other. These cylinders are all filled with seed, and

burst when it is ripe, scattering it in every direction: wherever it falls upon the leaf it takes root, and thus the fungus spreads rapidly. The superficial mildew which attacks rose trees and many other flowering shrubs is a kind of Urèdo. This

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name, derived from uro, Lat., to burn or scorch, is applied to those occasional discolorations of the surfaces of plants which were formerly attributed to blights, or injuries from the atmosphere, and which have the appearance of a brown powder. Urèdo effùsa Grev. (fig. 86.) generally shows itself on the under sides of the leaves of the Rosacea, and spreads rapidly. Urèdo Rosæ Pers. is another kind, which also attacks rose trees. The fungus called Acrosporium moniliöìdes (fig. 87.) consists of a number of globules, attached to each other, which, when magnified, appear like the beads of a necklace, and in many cases are found standing upright. When ripe, these globules fall,

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and, taking root, form fresh strings, or necklaces, like the first. Sometimes little tufts of these globules appear fixed to stalks; and, from some fancied resemblance to the brushes used for sprinkling holy water, are called Aspergillus. (fig. 88.) The superficial mildew which infects the onion, and is very fatal to that plant, is

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called Botrytis. Its name signifies a bunch of grapes; and it is thus called from a fancied resemblance between that fruit and its clusters of little globular seeds and seed-vessels. The bean and pea have a superficial mildew, Urèdo Fabæ Pers. (fig. 89.), which spreads along their leaves, like white roots curiously interlaced. From these roots spring a number of branch-like shoots, each bearing a ball-like head, or brown berry, which, when ripe, bursts, and discharges seed.

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The second class of fungi, viz. those which spring from the interior of leaves and stems, are by far the most fatal. These fungi generally appear in a sort of bag supposed to be formed of the cuticle of The oak is attacked by a species of different varieties of which are found on many kinds of forest trees. The Ecídium Pìni (fig. 90.),

or case, which is the affected leaf. fungus, Ecídium,

found on pine trees, has, when magnified, the appearance of a number of nine-pins. When ripe, the cuticle which covers the fungus bursts, and emits a powder of a bright orange colour, which is the seed. A mildew of this kind, which infects corn, is highly injurious to the farmer. It is vulgarly called the pepper brand; and, when corn is attacked by it, it gradually consumes the substance of the grain, leaving in its stead only a dark powder, which has a very offensive smell. This fungus is found only on barley, and in this respect differs from the Urèdo Ségetum,

or smut, which is destructive not only of barley, but also of wheat and oats. The Urèdo Ségetum, or smut, has been the subject of many interesting experiments by Mr. Bauer of Kew, whose discoveries will no doubt throw very considerable light upon the subject. It not only destroys the grain, which it converts into a kind of jelly, but it attacks the leaves and stems, always forming in the interior of the plant, and burst

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ing forth when ripe. Corn is also attacked by a species of Puccinia, a very fatal kind of fungus, which always appears divided into cells. Puccínia Gráminis (fig. 9.5.), which attacks corn, forms in the interior of the stalk, and, when ripe, bursts forth in clusters, like bunches of grapes, of a dark brown colour. Puccinia Rose Grev. (fig. 96.) appears on the leaves of rose trees, in little brown tufts, which, when opened and magnified, are found divided into extremely minute cells. A correspondent of this Magazine (Vol. IV. p. 320.) mentions that his celery was infected with ferruginous spots, occasioned, no

doubt, by the Puccínia Heraclei Grev.; and another cor

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respondent, Mr. Robert Errington (Vol. V. p. 107.), gives a detailed account of the manner in which his celery was attacked by the same disease, and of the means which he adopted for its cure. He describes

his celery as having the appearance of having been scorched by fire. He says he dug up the infected plants, and buried them, but this only seemed to increase the evil; and he tried several other remedies, but without any permanent success.

It is a vulgar error to suppose that a berberry tree (Bérberis vulgaris L.), if planted in a corn field, will, if infected with mildew, communicate the disease to the corn. This cannot be the case, as the mildew which attacks the berberry (cídium Berbéridis Pers., fig. 92.) is quite different from any of the fungi which are found on corn. The berberry mildew, when magnified, is found to consist of a number of small orange cups with white films over each. When ripe, these lids burst, and the top of the cup assumes a ragged uneven appearance, like white fungi. Each cup has within it a number of little boxes containing seeds. The mildew on the pear tree is called Æcídium cancellàtum (fig. 97.) [See

a, A leaf with the Ecidium becoming developed. b, A leaf bearing the Ecídium fully developed. c, Portion of a leaf with the Ecidium farther developed. d, Section of a leaf, to show the fleshy thickening that accompanies the developement of the Ecídium. ee, Seeds of the Ecídium: a seed is called a sporidium; in the plural, sporidia. ff, Plants of the Ecidium: each is called a peridium; in the plural, peridia.

Vol. VIII. p. 738., and p. 332. of the present volume]: it first appears like mucus, but consists of a number of hairy substances. These hairs, when magnified, appear like a collection of granules of a bulbous shape, each containing a number of balls connected by strings. These balls, though so minute as to be scarcely perceptible by the eye, are yet only receptacles for seed. This is a most destructive fungus: it always seizes on the veins of the leaves, which afterwards turn yellow, and fall off; the branches next wither, and in two or three years a whole orchard is destroyed. Mr. Knight, in 1832, suffered severely from this fungus, and

has tried many experiments respecting its cure. Hawthorn trees are attacked by a fungus, which at first appears merely a point made by an insect, but afterwards looks like fungi (Æcídium laceràtum Dec.). [See Vol. VIII. p. 179. and 739.] The sycamore fungus is a black spot consisting of oblong purplish bodies, yellow inside, and containing tubes filled with seeds. Ecidium Grossulària Dec. (fig. 91.) attacks gooseberry bushes, and Ecídium cornùtum (fig. 94.) the mountain ash: both spread rapidly, and are very difficult to cure. The ergot on the rye is a well-known and very destructive species of mildew. It partakes of the nature of the truffle, and grows out of a spike of corn like a prolonged kernel. It is long, horny, and cartilaginous; and it consists of fibres closely interlaced. This disease evidently originates in the centre of the stem. It affects maize, various species of grass, and is often found in plants of yellow gentian, &c.

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The principal fungi of the third class, or those which attack the roots of plants, are two; and both closely resemble truffles. One of these (Rhizoctònia Crocòrum) (fig. 98.), which is of a brownish yellow, attacks crocuses; and, in those countries where the crocus is cultivated for its saffron as an article of commerce, it makes great ravages. It is called by the French la mort du safran, and soon destroys a whole crop. The other fungus, Periòla tomentosa, is found on the potato, lucern, &c. It turns the roots, which are naturally white, of a purplish hue. Its ravages are often attributed to grubs. Both these fungi appear to be propagated by spawn, or fibres which spread through the earth, and cling round the roots which they find in their way.

Having given a rapid sketch of some of the principal kinds of fungi which produce mildew, Dr. Lindley proceeded to speak of the causes which produce them, and of their cure. All are very easily propagated, from the rapidity with which they arrive at maturity, and the immense number of seeds which they produce. Most of the mildew fungi require only twentyfour hours from the first springing of the plant to the ripening of its seed; and the number produced by each may be guessed from the circumstance of one mushroom being sufficient to propagate 250,000,000. The extreme minuteness of the mildew fungi renders them still more numerous. The first class, or the superficial mildew, appears to be communicated by the air, the seeds when ripe being carried by it from one plant to another, and establishing themselves wher