692 CLIMBING PLANTS. 



formed of tendril -bearing stems, is borne by two adjacent trees or thickets as 

 though by two gigantic piers. Another advantage which tendril-bearing stems 

 have over twiners consists in the fact that they can reach the same height above 

 the ground with less expenditure of material. The twining stem of the Scarlet- 

 runner, which has climbed a metre above the ground, shows, when unrolled, a 

 length of 1^ metres. The pea, which climbs with tendrils to the same height, is 

 little more than a metre long. Of course in the production of tendrils building 

 material is expended, but this bears but a small proportion to that which is required 

 for the extra half-metre of stem. 



Now as to the nature of tendrils, are they leaf, stem, or root? They may be 

 each of these according to the species in question. A tendril may even be formed 

 by metamorphosis from each of the different sections of a leaf independently, and 

 the leaf-blade, the mid-rib, the leaf-stalk, even the stipules themselves may become 

 tendrils. From the standpoint of development and with regard to the origin and 

 mutual relation of individual plant - members, the exceedingly manifold tendril- 

 structures have been classed generally in the following groups. First of all the 

 stipule-tendrils (cirrhus stipularis), of which species of smilax (Smilax) afford an 

 excellent example. As may be seen in Smilax aspera (see fig. 162), so common in 

 the region of the Mediterranean flora, the leaves ai-e divided into lamina, leaf -stalk, 

 sheath, and stipules, and the two stipules arising from the sheath are transformed 

 into rather long tendrils which surround the branches of other plants, and even 

 their own branches. 



More common than this ratlier rare form is iheleaf-stalk tendril{cirrhus petiolaris), 

 which itself again shows numerous modifications according as to whether the whole 

 leaf-stalk of an undivided leaf, or the stalks of single leaf-segments play the part of 

 tendrils. The former is seen very beautifully in the numerous species of Nasturtium 

 {Tropceolum) and in the tendril-bearing snap-dragon (Antirrhinum cirrhosum); 

 the latter in many species of fumitory (Fumai'ia), in the Traveller's Joy {Clematis), 

 and in the only liane of the European Alps, the Atragene alpina, illustrated on 

 the last page (fig. 163). In pitcher-plants {Nepenthes) a portion of the leaf- 

 rachis is transformed into a tendril, and by it the pitchers are suspended on the 

 branches of supporting plants {cf. fig. 24, p. 133). When the midrib of a foliage- 

 leaf projects far beyond the green tissue of the blade, as a filament which grasps 

 and surrounds firm supports and attaches the whole plant to tliem, this structure 

 is known as a midrib-tendril {cirrhus costalis). To this class belong the strange 

 South American mutisias {e.g. Mutisia ilicifolia, hastata, subsinnosa, decitrrens), 

 the Indian Flagellaria Indica and Gloriosa superba, and several fritillaries 

 {Fritillaria cirrhosa, verticillata, and Ruthenica), attaching themselves to stiff 

 culms and leaves of neighbouring grasses. The leaf-tendril {drrhtts foliaris) is 

 also interpreted as the midrib of a leaf-blade or of a leaf-segment, but here none of 

 the green tissue of the blade is developed, and only the midribs are seen to form 

 filaments which curve and fasten as soon .as they come into contact with a prop. 

 This form of tendril is the connnonest of all, and is found particularly in Papilion- 



