410 



the distance through which the tendril might pull the plant in the 

 progress of coiling. In a few minutes after placing the first stake 

 the end of the tendril was seen to have moved perceptibly tow- 

 ards the stake, but in this case no note was taken of its rate of 

 bending. 



Auff. 21. The tendril had made two turns around the stake, 

 and had besides formed two close spires next to it, and two large 

 open ones towards the stem. The plant had been drawn away 

 from the second stake nearly one inch. 



Aug. 22. Six close coils had been formed next the first stake, 

 and the same number of open ones towards the stem. The plant 

 had been moved two inches. 



Aug. 23. There w^ere eight coils next the stake, wound so 

 tightly as to touch, and eight larger and opener towards the stem. 

 The plant had been pulled away from its first position between 

 two and a half and three inches. 



Compared with other like observations, this is an average ex- 

 ample of the rate of formation of the coils, and of the force 

 which they exert in moving or bracing the stem. 



The form assumed by the tendril is that which would be pro- 

 duced by a coiling force applied in a uniform direction midway 

 on a flexible line with fixed ends ; that is, the number of turns is the 

 same for the outer and the inner half of the tendril, but the direction 

 is opposite, making the one a dextral and the other a sinistral spi- 

 ral, and leaving between the two a comparatively straight space or 

 a loop at which the transition occurs. Where two or three such 

 pairs of coils are formed in the same tendril, as sometimes hap- 

 pens, the aggregate of the right hand turns is still always the 

 same as that of the sinistral. 



2. One extremity of a short thread was tied around the curv- 

 ing end of a young tendril, and the other fastened to a stake. 

 On the following day the tendril was found to have made one 

 close turn around the thread, and after this it formed itself into a 

 coil of several turns, all in one direction, the thread being twisted 

 to correspond with the opposite spiral. 



3. As in the preceding cases the whole length of the tendril 

 shared in the coiling movement, it became interesting to deter- 

 mine if any one section of it when fixed at the ends would act in 

 the same way. 



