40 MR- BABWIN ON CLIMBING PLANTS. 



duced no effect ; but loops of string weighing '82 and 1*64 grain 

 acted capriciously, sometimes causing a slight curvature ; but they 

 were never clasped, like the far lighter loops of thread by the 

 petioles. 



In the nine vigorous plants which I observed, it is certain that 

 neither the slight spontaneous movements nor the slight sensitive- 

 ness of the flower-peduncles were of any service to the plants in 

 climbing. If any member of the Scrophulariacese had been known 

 to have flower-peduncles used for climbiag, or had tendrils pro- 

 duced by their modification, I should have thought that this 

 Maurandia still retained a useless or rudimentary vestige of a 

 former habit; but this view cannot be maintained. We are 

 almost compelled to believe that by some correlation of growth 

 the power of movement has been transferred from the young 

 internodes to the young peduncles, and in the same manner sen- 

 sitiveness from the young petioles to the young peduncles ; but 

 this latter supposition is the more improbable, as I could detect 

 no sensitiveness in the young internodes of the Maurandia^ 

 "though in a closely allied genus, Lopliospe^^mmn^ the young inter- 

 nodes, as we shall see, are sensitive. By whatever means the 

 peduncles of this Maurandia have acquired their power of spon- 

 taneous movement and their sensitiveness, the case is interesting 

 for us ; for we can see that if these now useless capacities were a 

 little perfected, the flower-peduncles could be made as useful for 

 climbing as are the flower-peduncles of Vitis and Cardiospermmtj 

 as will hereafter be described. 



Wiodochiton volubile. — Along flexible shoot swept a large circle, 

 following the sun, in 5 h. 30 m. ; and, as the day became warmer, a 

 second circle in 4 h. 10 m. The shoots sometimes make a whole or 

 half spire round a vertical stick, then run up for a space straight, 

 and afterwards make spiral turns in an opposite direction. The 

 petioles of very young leaves, about one-tenth of their full size^ 

 are highly sensitive, apd bend towards any side which has been 

 touched ; but they do not move quickly : one, after being lightly 

 rubbed, was perceptibly curved in 1 h. 10 m., and became consider- 

 ably arched in 5h. 40m. after the rubbing; some other petioles, 

 after being rubbed, were scarcely curved in 5h. 30 m., but in 6h. 

 30 m. were distinctly curved. A curvature was perceptible in a 

 petiole in between 4h. 30m, and 5h., after the suspension of a little 

 loop of string. A loop of fine cotton thread, weighing one-sixteenth 

 of a grain, not only slowly caused a petiole to bend, but was ulti- 

 mately firmly clasped by it, so that it could be withdraAvn only by 



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