We see at least in the Maurandia a plant which might, by a little augmentation of qualities which it already possesses, come first to grasp a support by its flower-peduncles (as with Vitis or Cardiospermum) and then, by the abortion of some of its flowers, acquire perfect tendrils. There is one interesting point which deserves notice. We have seen that some tendrils have originated from modified leaves, and others from modified flower-peduncles; so that some are foliar and some axial in their homological nature. Hence it might have been expected that they would have presented some difference in function. This is not the case. On the contrary, they present the most perfect identity in their several remarkable characteristics. Tendrils of both kinds spontaneously revolve at about the same rate. Both, when touched, bend quickly to the touched side, and afterward recover themselves and are able to act again. In both the sensitiveness is either confined to one side or extends all round the tendril. They are either attracted or repelled by the light. The tips of the tendrils in these two plants become, after contact, enlarged into disks, which are at first adhesive by the secretion of some cement. Tendrils of both kinds, soon after grasping a support, contract spirally; they then increase greatly in thickness and strength. When we add to these several points of identity the fact of the petiole of the Solanum jaspinoides assuming the most characteristic feature of the axis, namely, a closed ring of woody vessels, we can hardly avoid asking whether the difference between foliar and axial organs can be of so fundamental a nature as is generally supposed to be the case. We have attempted to trace some of the stages in the genesis of climbing plants. But, during the endless fluctuations in the conditions of life to which all organic beings have been exposed, it might have been expected that some climbing plants would have lost the habit of climbing. In the cases of certain South African plants belonging to great twining families, which in certain districts of their native country never twine, but resume this habit when cultivated in England, we have a case in point. In the leaf-climbing Clematis flammula, and in the tendril-bearing vine, we see no loss in the power of climbing, but only a remnant of that revolving power which is indispensable to all twiners, and is so common, as well as so advantageous, to most climbers. In Tecoma radicans, one of the Bignoniaceæ, we see a last and doubtful trace of the revolving power.