The simplest peasant has sense enough to see, and all agriculturists agree with him, that clover, turnips, hay, &c., cannot be sold off from a farm without most materially damaging the cultivation of the corn. Every one willingly admits that the sale and exportation of clover, turnips, &c., exercise a detrimental influence on the growing of corn. “Above all, let us take care to have plenty of fodder; the corn crop will then take care of itself.” But that the _exportation of corn_ may possibly exercise an injurious influence on the cultivation of clover or turnips; that it is, above all, indispensable to restore to the soil the mineral constituents of the corn, to enable the clover or turnip crop to “take care of itself;” in other words, that in order to grow clover, turnip, &c., we must manure the land—this is a notion utterly incomprehensible, nay absolutely impossible, for most agriculturists. For, is not the clover grown for the sake of manure? What advantage, then, would there be if it were necessary to manure again to produce the clover? _This clover the farmer expects to grow for nothing._ The mutual relations existing in the order of nature between the two classes of plants are, however, as clear as daylight. The mineral constituents of the clover, turnips, &c., and of the corn, form the conditions for the production of the clover, turnips, &c., and of the corn, and they are in their elements quite identical. The clovers, &c., require for their growth a certain amount of phosphoric acid, potash, lime, magnesia,—so does the corn. The mineral constituents contained in the clover are the same as those in the corn, _plus_ a certain excess of potash, lime, and sulphuric acid. The clover draws these constituents from the soil; the cereal plant receives them,—we may so represent it from the clover. In selling his clover, therefore, the farmer removes from his land the conditions for the production of corn. If, on the other hand, he sells his corn, there will be no clover crop in the following year; _for in his corn he has sold some of the most essential conditions for the production of a clover crop_.—pp. 183-5. This discussion, then, upon the so-called clover-sickness leads us to adopt the following propositions:— First. That the larger induced plant of our cultivated clovers has not, as a rule, that perennial constitution of the smaller wild species. Second. Even its induced habit is much deteriorated by transportation under adverse climatal circumstances. Third. The seed itself is often full of weeds, which, by gaining the mastery, kill out the young clover plant. Fourth. This effect is enhanced by growing clover with barley, in which, if not smothered, it must become weakened.