206 HOW PLANTS CLIMB. 



chiefly on the concave side at the end. It does not revolve, but 

 the young internodes do so, carrying the tendrils with them. 



2. — Te7idrils which are modified leaves. 



Several orders contain examples of this type of tendril. A 

 familiar one is Fisuin sativum, the common Garden Pea. Here 

 the leaf has a few pairs of leaflets, one or two pairs of tendrils, and 

 a terminal one, often branched— /.<?., some lateral leaflets and the 

 terminal ones are changed into tendrils. The young internodes 

 and the tendrils revolve in eflipses. The motion in this case is 

 independent of light, the latter neither retarding nor quickening it. 

 When young the tendrils are sensitive to so small an irritant as a 

 loop of thread one seventh of a grain in weight — i.e., on their 

 concave surface only. 



Many other examples could be quoted. The Bignojiiacece, 

 or Trumpet-flower Order, furnish perhaps the best. Darwin made 

 extensive researches on many species of Bigiionia, which I can- 

 not stay to quote now. Some species have tendrils with claws 

 like those of a bird, highly sensitive, and capable of such firm 

 grasping that Darwin says these species could probably ascend a 

 highly polished stem, even when tossed by storms. The claws 

 end in hooks, which, of course, increase the power of the grip. 

 Bignonia Tweediana can twine, has clasping petioles as well as 

 hooked tendrils, and moreover presently emits aerial roots from 

 the bases of its leaves, which curl round the support. It thus 

 very curiously unites four difterent movements of climbing plants, 

 viz., twining, leaf-climbing, .tendril-climbing, and root-climbing. 



" One species climbs by spirally twining and then by grasping 

 the stick with opposite tendrils alternately, like a sailor climbing a 

 rope, hand over hand. Another pulls itself up like a sailor 

 seizing with both hands together a rope above his head." Others 

 develop an instinct for inserting the sharp ends of their tendrils 

 into chinks and crevices of wood, or any other support which may 

 possess these, sometimes prying into one hole, and, finding it not 

 to its liking, seeking another ! In Bignonia cap7xolata, after the 

 tips had crawled into the crevices, or the hooked ends had seized 

 on a projecting point, the tips began to swell for two or three 

 days, and then to form whitish balls or discs, one twentieth of an 

 inch in diameter. These secreted a viscid matter, which would 



