Were our eyes sharp enough we might discern a certain strangeness in the nocturnal expression of every plant and tree. But in no tree is this expression so remarkably emphasized as in the locust, a member of the same leguminous order of plants with the clover. These trees are especially noted for the pronounced irritability of their leaves, and odd nocturnal capers, whose seeming vital consciousness has induced some authorities to place them at the extremity of their system, in contact with the limits of the animal kingdom. How strange the pigweeds look at night! Their upper leaves, which during the day had extended wide on their long stems, now incline upward against the stalk, enclosing the tops of the younger branches, but still older plants are seen with leaves extended much as at mid-day, but nearly all turned edgewise by a twist in the stem. Circling in a close curve, the creeping-mallow blossom now ignores her proud array of cheeses, and the oxalis flower has forgotten her shooting pods to keep the vigil, closed and nodding upon her stem, while her leaves masquerade in one of the oddest disguises, their three heart-shaped leaflets being seen reflexed and adjusting themselves back to back around the stem with many contortions. Whatever the function of this strange nocturnal movement may be, and it is still a matter of dispute with botanists, one thing we are certain about, that is, its essential condition to the life of the plant, careful experiment having demonstrated, according to one authority, that “if the leaves are prevented from so regulating their surface, they lose their color and die in a few days”--a fact which Darwin has just as conclusively shown to be the case with other plants.