THE

QUARTERLY

JOURNAL OF AGRICULTURE.

ON SMUT, CANKER, AND RUST OR MILDEW IN CORN, WITH THE ALLEGED AND ASCERTAINED CAUSES, AND MODEs of preVENTION.

IT has recently been said, that the numerous conflicting opinions as to the cause of smut, render it impossible to recommend any certain mode of investigation to clear up this perplexing subject, and, after all that has been written upon it, the cause of the disease in corn may be regarded as one of those secrets of Nature with which the human mind will probably never be intrusted. Not one single opinion has been advanced on this subject, it is farther said, that has not been refuted; so that it would appear, the more we inquire into the mysteries of the works of Nature, the more they are presented to the human mind in a perplexing form.

Now, it is to be feared that remarks of this kind are very apt to damp and deaden the spirit of inquiry, and to prevent the investigation of points which have hitherto baffled research. This, however, ought not to be, so long as the field of discovery is so amply and daily rewarding those who endeavour to extend its boundaries. It is to be lamented, not only that the labourers are few, but also that the inquiries of scientific men are so rarely directed towards subjects of the highest interest to practical cultivators. A striking instance was recently given, in this jour

VOL. VIII.-NO. XXXV

A

nal, of the hop-fty (Aphis Humuli), never yet figured, nor its history minutely written, while other insects of no particular interest to farmers are carefully traced from the moment they are hatched till they die. It sets the apathy of scientific men to subjects bearing a practical tendency in a strong light, that some imaginative remarks, and a few loose and inaccurate experiments, by an unknown anonymous periodical writer who signs Rusticus, respecting the turnip-fly, or rather beetle (Haltica Nemorum), should have been copied as important in almost every journal, both in this country and the continent, yet when these were taken up by a man of science,-J. O. Westwood, Esq., Secretarty to the Entomological Society,-and shewn not only to be erroneous, but impossible: the anonymous writer tardily and reluctantly gives in. Similar fancies, given as actual observations, from the same quarter, have been extensively propagated in a similar way respecting the apple weevil and the burrowing beetle.

In the same way, the greatest errors have obtained respecting the rust and the smut in corn,-the investigations having been chiefly conducted by practical men not acquainted with science, or by scientific men ignorant of practical matters. By passing in review the chief points connected with the interesting subjects of smut and rust, it is not to be expected that errors can be avoided, though it is of high interest to know that several recent discoveries, bearing on the point, tend greatly to lessen the chance of error, from opening new, unexpected, and simple views of the economy of nature in the production of these destructive agents. It is to be hoped that these more correct views will soon take their place in practical works, instead of the prejudices, to call them by no other name, propagated from one writer to another for successive ages. It will be requisite, before proceeding farther, to determine the obvious external characters by which these affections of corn may be distinguished, as there can be little doubt that some confusion prevails both among botanists and agriculturists in this respect. There seems, then, to be three affections of corn apparently very distinct in character, though often confounded (see Rees' Cyclopædia, Art. SmutPlenck, infra), namely, Smut, Canker, and Rust or mildew.

1. Smut.

What is termed smut, smut-brand, burnt corn, soot dustbrand, and black corn in England; and la bosse, nielle, nielle volante, or charbon, by the French, meaning, by these terms, "crimpled, blasted, or charred corn," occurs most commonly among oats, but is also found affecting barley and wheat. Mr Kirby (Linn. Trans. v. 113.), Dr Greville (Flor. Edin. 443.), add rye; but M. Tillet says, he never met with a smutty ear of rye (Dissert. p. 133.); and Plenck says, if it occur at all, it is exceedingly rare in rye (Patholog. Plantar. 153.). M. Decandolle says, that, besides oats, barley, and wheat (he does not mention rye), it attacks millet, maize, and several sorts of grasses; such as Agrostis pumila, Triticum repens, Avena pratensis, and Paspalum dactylis, (Encycl. Meth. Bot. viii. 227). Kirby adds Festuca fluitans and some other grasses. M. Tessier found, by repeated experiment, that bearded wheat was less subject to smut than smooth wheat,* a fact which, if ascertained, would be highly important to farmers, in districts where smut is prevalent.

So early as March or April, M. Duhamel, upon carefully opening the envelopes, and examining the embryo seed, then not one sixth part of an inch in length, found it already black, though he is of opinion it may not always affect the plants at so early a stage. The Rev. Henry Bryant (Causes of Brand, p. 42-4) gives a more minute account of the early stages of the affection, though somewhat vitiated by a mistaken theory. When the corn is what the farmers term "in the milk," if it be squeezed, a sweetish liquor oozes out,-the basis of the future farina, which, becoming diseased instead of hardening into ripe grain, grows oily and rancid, ferments, turns sour, and curdles. These changes commence soon after the corn is in bloom, and may be recognised by the embryo grain bulging out more than it ought to do, pushing out the chaffy envelope by its swelling, so as to cause the valves to stand more widely apart than they ought to do. This difference in the figure of the ear, will enable the observer to recognise ears affected with smut at an early stage, before any blackness is apparent.

We believe that bearded and woolly-eared wheat are less liable to be attacked by the wheat-fly than the smooth kinds.-EDITOR.

As the ear continues to grow, or, as Mr Bryant says, "when this fermentation is over, but not before," the embryo grain assumes a darker colour, which grows deeper and deeper every day, till it is quite black-constituting the brand. "I opened," says Mr Bryant, "some of these seed-buds when they were most swelled, greenest, and consequently less forward in their progressive advancement to this sooty state, and found that the curdled milk had not gained everywhere the same degree of consistence in them. Those parts nearer the surface were driest and blackest, those near the centre clammy, dirty, tinged with yellow and green, and which, by the microscope, appeared of no certain and determinate figure. The particles stuck together, were easily separable into others, and those again separable ad infinitum. To the palate, they were not gritty, but soft like the finest flour, melting away without leaving any particular taste behind them, except a little bitterness."—(Inquiry, p. 45.) When the distempered ear bursts through the leafy sheath, it appears lank and meagre, and the chaff immediately covering the grain is so thin and translucent, that the black-smut within is easily perceived. If one of the upper leaves on a stem appears streaked or clouded with yellow and green, or dry and withered at the tip, it is highly probable that the ear will be smutty. M. Tessier says that this character never deceived him.(Maladies des Grains, p. 296.) When the chaff bursts, as it speedily does, the spikes or heads look as if they had been charred by fire-hence the terms brand and charbon. When more advanced, there remains of the chaff only the formless fragments of a whitish colour, intermingled with the black dust. Sometimes, though rarely, the ears are enveloped in a membrane similar to the sheath (spatha) of lilies. The black dust insensibly becomes dry, and is scattered by the winds or washed away by the rain, nothing being left for the farmer to house but the barren skeletons of the spikes.-(Tessier, p. 296.)

The upper part of the stalk of corn infected with smut is usually less straight than a healthy one, the deviation beginning about half an inch beneath the spike; but, as Mr Bryant remarks, the infected plants, taken as a whole, are more upright than the healthy ones; for the milky juice which should have been consolidated into heavy grain is wanting, and the quantity

of matter being much less in the smutty ears than in the healthy ones, will keep them in the upright posture, while the others are bending beneath their own weight.-(Disease in Wheat, p. 47.) When a stalk of this description is squeezed there, it scarcely yields in the least to pressure; and, if cut asunder at about a sixth part or a quarter of an inch below the spike, it will be found to be entirely filled with pith, so that only a very small tube can be perceived in the centre, instead of the large one always present in healthy plants.--(Tillet, Cause qui corrompe les Grains, p. 73.) The stem of smutty corn, when strongly pulled, separates at the first upper joint, and the lower end of this joint is distinctly sweet to the taste, similar to what is observed in healthy plants, a fact which M. Tessier thinks is good proof that the sap is not altered on entering the plant, nor till it has passed higher up than this joint.

Sometimes only a part of the ear is infected with smut. "I have seen," says Kirby, “ more than once, half an ear of corn affected, when the other half was good and sound;" and Tessier says, it is in such cases only those grains nearest the spike-stalk which are smutty; while Mr Bryant has observed even the embryo or germen itself in branded ears as green and well shaped as in those not infected. Sometimes the half of the sheath, or hose, is affected with smut and converted into black dust, in which case the sound part encloses blossoms that are developed and bear grain capable of arriving at maturity, though smaller in size than healthy grain; for, in such cases, the stalk grows more or less after the ear has appeared, while at this period vegetation is quite finished in plants entirely smutty.-(Tessier.) The whole ear, according to Bauer, is often found entirely destroyed, many weeks before even the individual florets are entirely developed, or the sound ears emerge from the hose. Sometimes, but rarely, the infection takes place after the blooming, and its progress is then more easily traced. The embryo or germen is generally the first attacked and found partially or half filled with smut; then the pistils, the stigmas, and the anthers. Oats are often later in being affected than barley or wheat, the whole head frequently issuing from the sheath, or hose, to all appearance in a perfectly sound state, or perhaps with only a few black spots on the spikelets at the base; but these spread