118 CLIMBING PLANTS. 



" A tendril which was straight, except a slight 

 hook on the tip, on being gently touched once or 

 twice with a piece of wood on the upper side, 

 coiled at the end into 2 -3 turns within a minute 

 and a half. The motion began after an interval 

 of several seconds, and fully half of the coiling 

 was quick enough to be very distinctly seen. After 

 a little more than an hour had elapsed, it was 

 found to be straight again. The contact was re- 

 peated, timing the result by the second-hand of a 

 watch. The coiling began within four seconds, 

 and made one circle and a quarter in about four 

 seconds. 



" It had straightened itself again in an hour 

 and five minutes (perhaps sooner, but it was then 

 observed) ; and it coiled the third time on being 

 touched rather firmly, but not so quickly as before ; 

 viz., li turns in half a minute. 



"I have indications of the same movement in 

 the tendrils of the Grape-vine ; but a favorable 

 day has not occurred for the experiment since my 

 attention was first directed to the subject." 



This paper set Darwin also to studying climbers. 

 In 1863 he writes to Sir Joseph Hooker : * 



1 "Life and Letters of Charles Darwin/' By Francis Darwin. 

 Vol. II. p. 484. 



