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After contraction has endured for a greater or less time, dependent upon circumstances which we do not well understand, re-expansion of the leaves is effected at an insensibly slow rate, whether or not any object is enclosed, both lobes opening in all ordinary cases at the same time, although each lobe may act to a certain extent independently of the other. The re-expansion is not determined by the sensitive filaments, for these may be cut off close to their bases, or be entirely removed, and re-expansion occur in the usual manner. It is believed that the several layers of cells forming the lower surface of the leaf are always in a state of tension, and that it is owing to this mechanical state, aided probably by fresh fluid being drawn into the cells, that the lobes begin to separate as soon as the contraction of the upper surface diminishes.

Six known genera, Drosophyllum, Roridula, Byblis, Drosera, Dionæa and Aldrovanda comprise the Droseraceæ, all of which capture insects. The first three genera effect this purpose solely by the viscid fluid secreted from their glands, and the last, like Dionæa, which has already been described, through the closing of the blades of the leaf. In these last two genera rapid movement makes up for the loss of viscid secretion. But of all the genera none is more interesting than the typical Sundews.