Page:The Pamphleteer (Volume 8).djvu/117

Rh bright, very abundant, and heavy; some wheat which had been set on a newly-inclosed common where the land had not become firm, but was spongy and full of springs, was so much injured by the mildew that it seemed scarcely worth the trouble of reaping. This devoted field of wheat was only divided by a hedge from another, which was entirely exempt from it, although most of the neighbouring fields were partially affected. On enquiry I found that this fortunate field was not drilled until Christmas time. We rarely hear of oats or barley being mildewed. Now it is obvious that spring corn is free from the frosts of winter, and much more so from those of spring than the corn which is sown in autumn. Wheat is a very hardy plant, but it suffers probably more severely from the vernal than the winter frosts. If the season is mild the vessels of the young wheat begin to fill with fluids as early as the latter end of February or beginning of March; a severity of frost at this time, which in the winter would be perfectly harmless, is very likely to burst its tumid and tender vessels, and so materially injure the plant as to render it an unresisting prey to the ravages of this fungus. Thus we frequently see the young shoots of trees blighted, particularly the ash, the weeping willow, and the almond, while those of the preceding season, which are more hardy, remain uninjured: the juices of these succulent and delicate shoots are expanded by the frost until the vessels which contain them are ruptured, the organization is destroyed, and decomposition follows.

Sir Joseph says, "that the leaf is probably first infected in the spring, or early in the summer, before the corn shoots up into straw:" this is accounted for on the supposition now suggested, that the first injury arises from the severity of vernal frosts; but according to the hypothesis of Sir Joseph, it ought not to be the case, for, as was just now observed, the quantity of the fungus seed must be much greater in summer than in spring, and the size of the orifices into which it finds admission must also increase with the increased size of the straw, and thus afford a larger surface for attachment.

Again—the mildew is partial in its ravages—so is frost. Per-