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Rh power to accumulate in the roots; thus as they have no season for strengthening themselves, they have no strength to impart in their turn, and hence it is that the foliage of the tropical trees is usually pensile, because there is not vigour of vegetation enough for the branches to shoot upward."

A more philosophical hypothesis to account for the manner in which the American trees spread their roots horizontally is given by Volney.

"I must not omit, he says, a singular fact in natural history, which is well established in Kentucky, that many of the streams have become more abundant, since the woods in their neighbourhood have been cut down.

"I have discussed the causes of this phenomenon on the spot with witnesses deserving of credit; and it appeared to us that in times past the leaves of the forest trees, accumulating on the ground, formed there a thick compact bed, retaining