SHORT ACCOUNT

OF THE

CAUSE OF THE DISEASE IN CORN,

CALLED BY FARMERS

The Blight, the Mildew, and the Rust.

BY

SIR JOSEPH BANKS, BART.

THIRD EDITION, WITH ADDITIONS:

AND

A LETTER TO SIR J. BANKS,

ON THE ORIGIN OF THE BLIGHT,

AND ON THE MEANS OF

RAISING LATE CROPS OF GARDEN PEASE.

BY T. A. KNIGHT, ESQ.

ON THE

BLIGHT IN CORN, &c.

BOTANISTS have long known that the Blight in Corn is occasioned by the growth of a minute parasitic fungus or mushroom on the leaves, stems, and glumes of the living plant. Felice Fontana published, in the year 1767, an elaborate account of this mischievous weed,' with microscopic figures, which give a tolerable idea of its form: more modern botanists have given figures both of corn and of grass affected by it, but have not used high magnifying powers in their researches.

2

Agriculturists do not appear to have paid, on this head, sufficient attention to the discoveries of their fellow-laborers in the field of nature; for though scarce any English writer of note on the subject of rural economy has failed to state his opinion of the origin of this evil, no one of them has yet attributed it to the real cause, unless Mr. Kirby's excellent papers on some diseases of corn, published in the Tranasctions of the Linnæan Society, are considered as agricultural essays.

'Observazioni sopra la Ruggine del Grano. Lucca, 1767, 8vo. 2 Sowerby's English Fungi, Vol. II. Tab. 140, Wheat, Tab. 139. Poa aquatica.

On this account it has been deemed expedient to offer to the consideration of farmers, engravings of this destructive plant, made from the drawings of the accurate and ingenious Mr. Bauer, Botanical Painter to his Majesty, accompanied with his explanation, from whence it is presumed an attentive reader will be able to form a correct idea of the facts intended to be represented, and a just opinion whether or not they are, as is presumed to be the case, correct and satisfactory.

In order, however, to render Mr. Bauer's explanation more easy to be understood, it is necessary to premise, that the striped appearance of the surface of a straw which may be seen with a common magnifying glass, is caused by alternate longitudinal partitions of the bark, the one imperforate, and the other furnished with one or two rows of pores or mouths, shut in dry, open in wet weather, and well calculated to imbibe fluid whenever the straw is damp.'

By these pores, which exist also on the leaves and glumes, it is presumed that the seeds of the fungus gain admission, and at the bottom of the hollows to which they lead, they germinate and push their minute roots, no doubt (though these have not yet been traced) into the cellular texture beyond the bark, where they draw their nourishment, by intercepting the sap that was intended by nature for the nutri

1 Pores or mouths similar to these, are placed by nature on the surface of the leaves, branches, and stems, of all perfect plants; a provision intended no doubt to compensate, in some measure, the want of loco-motion in vegetables. A plant cannot when thirsty go to the. brook and drink, but it can open innumerable orifices for the reception of every degree of moisture, which either falls in the shape of rain and of dew, or is separated from the mass of water always held in solution by the atmosphere; it seldom happens in the driest season, that the night does not afford some refreshment of this kind, to restore the mois ture that has been exhausted by the heats of the preceding day.

ment of the grain; the corn of course becomes shrivelled in proportion as the fungi are more or less numerous on the plant; and as the kernel only is abstracted from the grain, while the cortical part remains undiminished, the proportion of flour to bran in blighted corn, is always reduced in the same degree as the corn is made light. Some corn of this year's crop will not yield a stone of flour from a sack of wheat; and it is not impossible that in some cases the corn has been so completely robbed of its flour by the fungus, that if the proprietor should choose to incur the expense of thrashing and grinding it, bran would be the produce, with scarce an atom of flour for each grain.

Every species of corn, properly so called, is subject to the Blight; but it is observable that spring corn is less damaged by it than winter, and rye less than wheat, probably because it is ripe and cut down before the fungus has had time to increase in any great degree.-Tull says that "white cone or bearded wheat, which hath its straw like a rush, full of pith, is less subject to Blight than Lanimas wheat, which ripens a week later." See page 74. The spring wheat of Lincolnshire was not in the least shrivelled this year, though the straw was in some degree infected: the millers allowed that it was the best sample brought to market. Barley was in some places considerably spotted, but as the whole of the stem of that grain is naturally enveloped in the hose or basis of the leaf, the fungus can in no case gain admittance to the straw; it is however to be observed that barley rises from the flail lighter this year, than was expected from the appearance of the crop when gathered in.

Though diligent inquiry was made during the last autumn, no information of importance relative to the origin This was written, January 1805.

or the progress of the blight could be obtained: this is not to be wondered at; for as no one of the persons applied to had any knowledge of the real cause of the malady, none of them could direct their curiosity in a proper channel. Now that its nature and cause have been explained, we may reasonably expect that a few years will produce an interesting collection of facts and observations, and we may hope that some progress will be made towards the very desirable attainment of either a preventive or a cure.

It seems probable that the leaf is first infected in the spring, or early in the summer, before the corn shoots up into straw, and that the fungus is then of an orange color;' after the straw is become yellow, the fungus assumes a deep chocolate brown; each individual is so small that every pore on a straw will produce from 20 to 40 fungi, as may be seen in the plate, and every one of these will no doubt produce at least 100 seeds; if then one of these seeds tillows out into the number of plants that appear at the bottom of a pore, how incalculably large must the increase be! A few diseased plants scattered over a field must very speedily infect a whole neighbourhood, for the seeds of fungi are not much heavier than air, as every one who has trod upon a ripe puff-ball must have observed, by seeing the dust, among which is its seed, rise up and float on before him.

How long it is before this fungus arrives at puberty, and scatters its seeds in the wind, can only be guessed at by the analogy of others; probably the period of a generation

The Abbé Tessier in his Traité des Maladies des Grains, tells us, that in France this disease first shows itself in minute spots of a dirty white color on the leaves and stems, which spots extend themselves by degrees, and in time change to a yellow color, and throw off a dry orange colored powder. pp. 201, 340.