logical nature together; but I shall treat of each family, one after the other, according to convenience[1]. 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.
Bignoniaceæ.—This family contains many tendril-bearers, some twiners, and some root-climbers. The tendrils are always 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 in species of the same genus, and to show how remarkable the action of the tendrils may be in some cases. The species, taken together, afford connecting links between twiners, leaf-climbers, tendril-bearers, and root-climbers.
Bignonia (an unnamed species from Kew, closely allied to B. unguis, but with smaller and rather broader 
Bignonia, unnamed species from Kew[2].leaves).—A young shoot from a cut-down plant made three revolutions against the sun, at an average rate of 2 h. 6 m. The stem is thin and flexible and twined, ascending, from left to right, round a slender vertical stick as perfectly and as regularly as any true twining-plant. When thus ascending, it makes no use of its tendrils or its 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
- ↑ As far as I can make out, the history of our knowledge on tendrils is as follows:—We have seen that Palm and Von Mohl observed about the same time the singular phenomenon of the spontaneous revolving movement of twining-plants. Palm (S. 58), I presume, observed likewise the revolving movement of tendrils; but I do not feel sure of this, for he says very little on the subject. Dutrochet fully described this movement of the tendril in the common Pea. Mohl first discovered that tendrils were sensitive to contact; but from some cause, probably from observing too old tendrils, he was not aware how sensitive they were, and thought that prolonged pressure was necessary to excite movement. Professor Asa Gray, in a paper already quoted, first noticed the extreme sensitiveness and rapidity of movements in the tendrils of certain Cucurbitaceous plants.
- ↑ This and the following drawings, from which the woodcuts have been engraved, were carefully made from me from living plants by my son Mr. George H. Darwin.
