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Rh decayed trees, &c. fungi are always to be found. Would Sir Joseph hazard the assertion, that the tree became diseased and decayed because a fungus was attached to it? Would he not rather suspect that because the tree was decayed, therefore it became the recipient of the fungus? There may be difficulties on both sides; but the hypothesis of Sir Joseph Banks has some very serious objections to encounter. How comes it to pass that the mildew, blight, call it what you will, should be so partially distributed that of two adjoining fields, nay that of two adjoining ridges in the same field, one may be entirely exempt from the disease, and the other severely suffer by it? But every farmer knows that this is no imaginary or even uncommon case: the track of the mildew is oftentimes remarkably distinct, which it would hardly be if the air were impregnated with this poisonous and prolific dust. Go into a hay-field when the anthers are shedding their pollen; see the cloud of virility which is diffused over the whole surface of the field by every undulation of the air. Were the disease, which we call the mildew, occasioned by such a cloud of contagious dust as this, we should as rarely see the precise extent and boundaries of the evil as we do of a shower of rain or a fall of snow.

Sir Joseph thinks it probable that the leaf is first infected in the spring, or early in the summer, before the corn shoots up into straw; but this cannot be accounted for consistently with his hypothesis. The increase of these fungi is allowed to be incalculably great, and the period of their pubescence and maturity is short. As the summer advances, therefore, the air must be more and more heavily laden with these seeds, and as the size of the cuticular orifices of the straw increases with its growth, the seeds of the fungus would find more room as the summer advances, and the mischief extend with an immeasurable rapidity over the whole country. We should never be free from it: many thousand acres would annually be destroyed in the summer, which were uninfected in the spring. The fact, however, is as Sir Joseph states it, namely that the leaf is first infected in the spring, or early in the summer. No one fears what is called a mildew on his wheat crop after the blossom is set. The season of flowering is indeed a very critical one: heavy rains and blustering winds may wash away or so disperse the pollen as to frustrate and render abortive the necessary process of fecundation. For the same reason it is injudicious to hoe corn during the time of blossoming; the clothes of those employed are very likely to brush away the farina and injure the impregnation. When this is the case, from whatever circumstance it arises, the farmer will find at harvest that much of his wheat is blind (that is to say), many of the coshes or seed vessels are destitute of kernels, while the straw is perfectly bright and free from any appearance of disease.