644 THE POPULAR SCIENCE MONTHLY. 



by the Virginia creeper, as its only method of support, and it forms 

 the fifth means of climbing to be met with among the JBignonias. 

 "We see now the meaning of the power possessed by the tendrils of 

 moving toward the dark, for in this way they are enabled to find out 

 and reach the trunks of trees to which they then become attached. It 

 seems, moreover, that the tendrils are especially adapted to the rnoss- 

 or lichen-covered trees, for the tendrils are much excited by wool, 

 flax, or moss, the fibers of which they can seize in little bundles. The 

 swelling process is so delicate that, when two or three fine fibers rest 

 on the end of a tendril, the swelling occurs in crests, thinner than a 

 hair, which insert themselves between and finally envelop the fibers. 

 This goes on so that the ball at the end of a tendril may have as many 

 as fifty or sixty fibers imbedded in it, crossing each other in different 



directions. 



The tendrils of the Virginia creeper may here be worth noticing. 

 This plant can climb up a flat wall, and is not adapted to seize sticks 

 or twigs ; its tendrils do occasionally curl round a stick, but they often 

 let go again. They, like bignonia-tendrils, are sensitive to the light, 

 and grow away from it, and thus easily find out where the wall lies 

 up which they have to climb. A tendril which has come against the 

 wall is often seen to rise and come down afresh, as if not satisfied 

 with its first position. In a few days after a tendril has touched a 

 wall the tip swells up, becomes red, and forms one of the little feet or 

 sticky cushions by which the tendrils adhere, and which are shown in 

 Fig. 5. The adherence is caused by a resinous cement secreted by the 

 cushions, and which forms a strong bond of union between the wall 

 and the tendril. After the tendril has become attached it becomes 

 woody, and is in this state remarkably durable, and may remain firm- 

 ly attached and quite strong, for as many as fifteen years. 



Besides this sense of touch, by which a bignonia-tendril distin- 

 guishes between the objects which it touches, there are other instances 

 of much more perfect and incomprehensible sensibility. Thus some 

 tendrils, which are so sensitive that they curl up when a- weight of 

 one-thirtieth or even one-fiftieth of a grain is placed on them, do not 

 take the least notice of a shower of rain whose falling drops must cause 

 a much greater shock to the tendrils. 



Again, some tendrils seem to have the power of distinguishing be- 

 tween objects which they wish to seize and their brother tendrils 

 which they do not wish to catch. A tendril may be drawn repeatedly 

 over another without causing the latter to contract. 



The tendrils of another excellent climber ( Co bcea scandens) possess 

 some curious properties. The tendrils are much divided, and end in 

 delicate branchlets, as thin as bristles, and very flexible, each bearing 

 a minute double hook at its tip. These are formed of a hard, woody 

 substance, and are as sharp as needles ; a single tendril may bear be- 

 tween ninety and a hundred of these beautiful little grappling-hooks. 



