Page:Popular Science Monthly Volume 2.djvu/265

Rh extension of the disease, and decay of the leaves and stalks, often ensue. Botrytis infestans is the name applied to the fungus, and it is on the under surface of the leaf that it is generally found; it abounds also in the diseased tubers, which, when cut, produce an abundant crop from the fresh surface, and it sometimes vegetates even from the natural skins. The resting spores of the fungus may lie dormant through the winter, germinating the next season; and hence, though the eyes of a diseased tuber appear healthy, to plant them would be the certain means of spreading the disease. The same fungus has been found in the berries of the tomato when diseased, and on the leaves of other plants of the natural order Solanaceæ, but never on any plant not of that order.

The influences which favor the development of Botrytis are not well understood. It is most prevalent, however, in cloudy, moist summers, and all authorities agree that it makes its first decided appearance during thundery weather. The exceptional amount of electrical disturbance which extended over almost the whole of England, during July last, appears to have been most unfavorable to the potato-crop, but in a portion of the county of Devon, where thunder-storms are remarkably rare, the potatoes are said to be comparatively free from the disease. The most destructive out-breaks of the blight have been observed to recur at intervals of about twelve years. In 1846, as before mentioned, the disease was general in Europe, and in some places, as in Ireland, it swept away the entire crop. From 1859 to 1861 it again did a great amount of damage; and now, in 1872, it is more destructive than at anytime since 1846. The London Times states that the loss to the country from the destruction of the present crop will exceed twenty millions sterling, and very pertinently asks: "What are we doing, or what have we done, to obviate the recurrence of a disease which is always impending? Probably all we can remember is, that there is always a talk of the potato-rot, and that some years it has been worse than others. We can only say that this is a disgraceful confession. There is no matter in which science could interfere with more advantage; and we seem to have all the conditions of the subject under control." Nature, in an article upon the subject, admits the force of these remarks, and, pointing out the reasons why neither individuals nor societies should be expected to undertake the work, urges that the government appoint a commission to investigate the origin, course and remedies for the potato-disease.

"Little objection can be anticipated to the course we advocate, on the ground of the money value at stake in the question. We are at the present time spending a large sum of money and employing the highest talent in the country in the settlement of a claim for a few millions; to save the country several times as much per annum cannot be objected to as a matter unworthy the attention of our rulers. And yet, because the one infliction will fall upon us in the form of an additional twopence to our income-tax for a single year, the other in the form of a much heavier addition to our butchers' and greengrocers' bills for many years in succession, we are content in the latter case to grumble and bear it, without making any serious efforts to relieve ourselves from it. Science is often charged with being 'un-practical;' indeed, in the minds of perhaps the majority of people, there is a kind of hazy feeling of a necessary antagonism between what is scientific and what is practical. It is time for science to redeem herself from this imputation, and no better opportunity could be found than in discovering a remedy for the potato-disease."

Action of Plaster on Soils.—Though generally employed by farmers as a fertilizer, the action of plaster (gypsum) on the soil is not well understood. It has been shown, however, by actual experiment, that plaster is capable of absorbing ammonia from the air, and also from decomposing animal and vegetable matter, holding it in the form of sulphide of ammonium. This, again, may be changed into carbonate of ammonia, by absorption of carbonic acid from the air. These changes occur when gypsum is brought in contact with moisture and vegetable matter. Whatever other purpose it may serve, this must be regarded as the most important, as by it plants are supplied with food of the highest value.

From this fact it may be inferred that