162 TENDIUL-BEAEEES. Ohap. IV. 



two days after clasping a stick, and in two more 

 days formed several spires. It appears, therefore, that 

 the contraction does not begin until the tendril is 

 grown to nearly its full length. Another yotmg 

 tendril of about the same age and length as the last 

 did not catch any object ; it acquired its full length 

 in four days ; in six additional days it first became 

 flexuous, and in two more days formed one com- 

 plete spire. This first spire was formed towards the 

 basal end, and the contraction steadily but slowly 

 progressed towards the apex ; but the whole was not 

 closely wound up into a spire until 21 days had 

 elapsed from the first observation, that is, until 17 

 days after the tendril had grown to its full length. 



The spiral contraction of tendrils is quite indepen- 

 dent of their power of spontaneously revolving, for it 

 occurs in tendrils, such as those of Lathyrus grainM- 

 fixyrus and Ampelopsis Jiederacea, which do not revolve. 

 It is not necessarily related to the curling of the tips 

 round a support, as we see with the Ampelopsis and 

 Bignonia capreolata, in which the development of 

 adherent discs sufiSces to cause spiral contraction. 

 Yet in some cases this contraction seems connected 

 with the curling or clasping movement, due to contact 

 with a support ; for not only does it soon follow this 

 act, but the contraction generally begins close to the 

 curled extremity, and travels downwards to the base. 

 If, however, a tendril be very slack, the whole length 

 almost simultaneously becomes at first flexuous and 

 then spiral. Again, the tendrils of some few plants 



