Wet lands are peculiarly subject to mildew, and if in any field one spot is wetter than the rest, that spot will be most frequently and earliest affected. Again, newly inclosed commons, which are often light and spongy, approaching to elastic, very much expose the wheat which grows upon them to mildew. How are these facts to be accounted for on the hypothesis of Sir Joseph Banks? If the atmosphere is charged with the seeds of these fungi, floating there like the dust of a puff-ball, they would be indiscriminately scattered, and no one particular spot be more affected than another; the first shower of rain, or the first fog that fell, must precipitate the seed with an equal and an even vengeance, attaching it to every straw in the field. I cannot but suspect, therefore, that the plant is diseased before the fungus seizes on it, and that those stems which are in sound health resist its advances, or counteract its activity.
Fungi find an appropriate nidus in diseased and decayed vegetable matter, and particularly if it remains in a state of moisture; the wood-work of vaults, as was before observed, and indeed their walls are always covered with them, rotten timber and the hollow trunks of trees are rarely free from them. Nature suffers no fit recipient for animal or vegetable life to remain void; microscopic beings of both kingdoms are always ready to seize on and make their prey of every thing which can furnish them with subsistence, and the decomposition of all animal and vegetable matter affords food for myriads. If the branch of a tree is rent by the wind, or blasted by the lightning, that branch will frequently become a prey to fungi and musci, while the sound healthy parts of the same tree resist the encroachments of the parasites. But if mildew is not caused by these parasitic fungi, to what is it to be attributed? I am inclined to believe that the disease so called, that is to say the dark and striped appearance of the straw and shrivelled kernel, is produced by the immediate operation of these fungi, and that they act precisely as Sir Joseph Banks has suggested. At the same time, I suspect that the remote cause is some disease in the plant, probably arising from an interrupted circulation of its sap, and totally unconnected with mildew. Is it inquired what this disease may be? I cannot answer the enquiry with any confidence, but the notice of a few facts may possibly suggest an answer.
Spring corn, Sir Joseph truly remarks, is less damaged by it than winter corn: the spring wheat of Lincolnshire was not in the least shrivelled in the harvest of 1804, although the straw was in some degree affected. About a fortnight ago I passed a few days in the country and examined the corn in the neighbourhood of the gentleman's house where I was staying. The barleys were very
