PHYSICAL CONDITION OF THE SOIL.

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flourishes and produces abundance of fruit on the graniticgravels of New England, which would certainly he too poorfor cotton, even though the climate there were as favourableas in Mississippi State. It is probable that the barrennature of the subsoil, arising from its being so compact, can-not maintain the magnolia and peach in healthy growth, bothof which must have their roots where there is a sufficientsupply of moisture during the torrid heat of summer. I wasinformed that neither the peach nor any other fruit treewould thrive on the exhausted soils, however well they weremanured, unless the ground was cultivated by the plough orthe spade. If the cultivation be neglected, many of the leavesdrop off during dry weather; and when the rains again setin, the fruit becomes dropsical, and falls off also. The samekinds of fruit trees do well on unexhausted ground withoutany cultivation or manure. These facts all point to theview I have already expressed—that in these instances it isthe physical condition of the soils which determines the par-ticular kinds of trees that flourish on exhausted and unex-hausted soils. The pine, it is probable, evaporates less thanthe broad-leaved trees, and can therefore thrive in drysandy soils, where other trees cannot live. Sir HumphryDavy says, in some of his lectures on agricultural chemistry,that plants with glossy leaves do not evaporate so much asothers. Perhaps this will explain the reason why we findthe live oak, with its thick glossy leaves, the only hard-woodtree growing beside the long-leaved pine on the dry sands ofthe pine barrens.