The Movements and Habits of Climbing Plants [30]
remaining suspended. Petioles which have clasped an object for some little time cannot recover their original position. After remaining clasped for two or three days, they generally increase much in thickness either throughout their whole diameter or on one side alone; they subsequently become stronger and more woody, sometimes to a wonderful degree; and in some cases they acquire an internal structure like that of the stem or axis.
The young internodes of the Lophospermum as well as the petioles are sensitive to a touch, and by their combined movement seize an object. The flower-peduncles of the Maurandia semperflorens revolve spontaneously and are sensitive to a touch, yet are not used for climbing. The leaves of at least two, and probably of most, of the species of Clematis, of Fumaria and Adlumia, spontaneously curve from side to side, like the internodes, and are thus better adapted to seize distant objects. The petioles of the perfect leaves of Tropaeolum tricolorum, as well as the tendril-like filaments of the plants whilst young, ultimately move towards the stem or the supporting stick, which they then clasp. These petioles and filaments also show some tendency to contract spirally. The tips of the uncaught leaves of the Gloriosa, as they grow old, contract into a flat spire or helix. These several facts are interesting in relation to true tendrils.
With leaf climbers, as with twining plants, the first internodes which rise from the ground do not, at least in the cases observed by me, spontaneously revolve; nor are the petioles or tips of the first- formed leaves sensitive. In certain species of Clematis, the large size of the leaves, together with their habit of revolving, and the extreme sensitiveness of their petioles, appear to render the revolving movement of the internodes superfluous; and this latter power has consequently become much enfeebled. In certain species of Tropaeolum, both the spontaneous movements of the internodes and the sensitiveness of the petioles have become much enfeebled, and in one species have been completely lost.
CHAPTER III.--TENDRIL-BEARERS.
Nature of tendrils--BIGNONIACEAE, various species of, and their different modes of climbing--Tendrils which avoid the light and creep into crevices--Development of adhesive discs--Excellent adaptations for seizing different kinds of supports.--POLEMONIACEAE--Cobaea scandens much branched and hooked tendrils, their manner of action-- LEGUMINOSAE--COMPOSITAE--SMILACEAE--Smilax aspera, its inefficient tendrils--FUMARIACEAE--Corydalis claviculata, its state intermediate between that of a leaf-climber and a tendril-bearer.
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, {24} 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: --Bignoniaceae, Polemoniaceae, Leguminosae, Compositae, Smilaceae, Fumariaceae, Cucurbitaceae, Vitaceae, Sapindaceae, Passifloraceae. {25}
BIGNONIACEAE.--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
The young internodes of the Lophospermum as well as the petioles are sensitive to a touch, and by their combined movement seize an object. The flower-peduncles of the Maurandia semperflorens revolve spontaneously and are sensitive to a touch, yet are not used for climbing. The leaves of at least two, and probably of most, of the species of Clematis, of Fumaria and Adlumia, spontaneously curve from side to side, like the internodes, and are thus better adapted to seize distant objects. The petioles of the perfect leaves of Tropaeolum tricolorum, as well as the tendril-like filaments of the plants whilst young, ultimately move towards the stem or the supporting stick, which they then clasp. These petioles and filaments also show some tendency to contract spirally. The tips of the uncaught leaves of the Gloriosa, as they grow old, contract into a flat spire or helix. These several facts are interesting in relation to true tendrils.
With leaf climbers, as with twining plants, the first internodes which rise from the ground do not, at least in the cases observed by me, spontaneously revolve; nor are the petioles or tips of the first- formed leaves sensitive. In certain species of Clematis, the large size of the leaves, together with their habit of revolving, and the extreme sensitiveness of their petioles, appear to render the revolving movement of the internodes superfluous; and this latter power has consequently become much enfeebled. In certain species of Tropaeolum, both the spontaneous movements of the internodes and the sensitiveness of the petioles have become much enfeebled, and in one species have been completely lost.
CHAPTER III.--TENDRIL-BEARERS.
Nature of tendrils--BIGNONIACEAE, various species of, and their different modes of climbing--Tendrils which avoid the light and creep into crevices--Development of adhesive discs--Excellent adaptations for seizing different kinds of supports.--POLEMONIACEAE--Cobaea scandens much branched and hooked tendrils, their manner of action-- LEGUMINOSAE--COMPOSITAE--SMILACEAE--Smilax aspera, its inefficient tendrils--FUMARIACEAE--Corydalis claviculata, its state intermediate between that of a leaf-climber and a tendril-bearer.
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, {24} 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: --Bignoniaceae, Polemoniaceae, Leguminosae, Compositae, Smilaceae, Fumariaceae, Cucurbitaceae, Vitaceae, Sapindaceae, Passifloraceae. {25}
BIGNONIACEAE.--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