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126 are insufficiently drained, and indeed they scarcely ever can be sufficiently drained, are of all others the least capable of resisting the ravages of mildew. These plants become unhealthy from superabundant moisture, rather than from excessive cold, or sudden variations in temperature, and in consequence of that unhealthiness are attacked by parasitic fungi which they are incapable of repelling. Where there is a substratum of clay through which no water can filter, the land is soaked and saturated with it, and can only be relieved by the tardy process of exhalation. On such soils beans are perhaps the best preparative for wheat: for in the first place their leaves are shed on the ground and contribute to manure it, and in the second place, their strong tubular roots are left in the soil and contribute in a most essential manner to keep it loose and open.

After all that can be said concerning the mildew, as to its nature, character, or cause; even supposing it may occasionally be prevented by an intention to those circumstances of shelter, drainage, and general culture which contribute to the healthy vigor of the growing crops, since we are not possessed of such a command over the elements as the Philosopher Imlac enjoyed, the mischief will occasionally spread itself over our fields, as it has done in the present year, far and fatally. When this is the case, a question arises of some consequence, about which farmers differ, namely, should the infected crop be cut early or late? The general practice is to cut it early, before the corn is fully ripe. This practice is founded, so far as I have been able to learn from enquiry of those who have taken the trouble to reason upon it at all, on a supposition, that "as the mildew feeds upon the living straw, the sooner you destroy the life of the straw the sooner you check the progress of the mildew." This is very unsatisfactory: Sir Joseph Banks and Mr. Bauer have traced the action of the parasitic fungi in a manner described in the early part of this paper: their minute roots passing under the bark and into the cellular substance of the straw intercept a part of the nourishment which was destined for the kernel. But it is clear that they intercept only a part of that nourishment: if they intercepted the whole, there could be no flour in the kernel, which would then be an empty husk, nothing but bran. So long as there is a living principle in the straw sufficient to convey nourishment from the earth to the ear, it must be injurious to cut off the communication between them. The mildew intercepts a part of the nourishment, the sickle intercepts the whole.