BY tendrils I mean filamentary organs, sensitive to contact and used exclusively for climbing. By this definition, spines, hooks and rootlets, all of which are used for climbing, are excluded. True tendrils are formed by the modification of leaves with their petioles, of flower-peduncles, branches, {84} and perhaps stipules. Mohl, who includes under the name of tendrils various organs having a similar external appearance, classes them according to their homological nature, as being modified leaves, flower-peduncles, &c. This would be an excellent scheme; but I observe that botanists are by no means unanimous on the homological nature of certain tendrils. Consequently I will describe tendril-bearing plants by natural families, following Lindley’s classification; and this will in most cases keep those of the same nature together. The species to be described belong to ten families, and will be given in the following order:—_Bignoniaceæ_, _Polemoniaceæ_, _Leguminosæ_, _Compositæ_, _Smilaceæ_, _Fumariaceæ_, _Cucurbitaceæ_, _Vitaceæ_, _Sapindaceæ_, _Passifloraceæ_. {85} BIGNONIACEÆ.—This family contains many tendril-bearers, some twiners, and some root-climbers. The tendrils always consist of modified leaves. Nine species of _Bignonia_, selected by hazard, are here described, in order to show what diversity of structure and action there may be within the same genus, and to show what remarkable powers some tendrils possess. The species, taken together, afford connecting links between twiners, leaf-climbers, tendril-bearers, and root-climbers. [Picture: Fig. 5. Bignonia. Unnamed species from Kew] _Bignonia_ (an unnamed species from Kew, closely allied to _B. unguis_, but with smaller and rather broader leaves).—A young shoot from a cut-down plant made three revolutions against the sun, at an average rate of 2 hrs. 6 m. The stem is thin and flexible; it twined round a slender vertical stick, ascending from left to right, as perfectly and as regularly as any true twining-plant. When thus ascending, it makes no use of its tendrils or petioles; but when it twined round a rather thick stick, and its petioles were brought into contact with it, these curved round the stick, showing that they have some degree of irritability. The petioles also exhibit a slight degree of spontaneous movement; for in one case they certainly described minute, irregular, vertical ellipses. The tendrils apparently curve themselves spontaneously to the same side with the petioles; but from various causes, it was difficult to observe the movement of either the tendrils or petioles, in this and the two following species. The tendrils are so closely similar in all respects to those of _B. unguis_, that one description will suffice.