124 CLIMBING PLANTS. 



more strictly speaking, of the continuous bowing 

 movement, directed successively to all points of 

 the compass, is, as Mohl has remarked, to favor 

 the shoot finding a support. This is admirably 

 effected by the revolutions carried on night and 

 day, a wider and wider circle being swept as the 

 shoot increases in length. This movement like- 

 wise explains how the plants twine, for when a 

 revolving shoot meets with a support, its motion 

 is necessarily arrested at the point of contact, but 

 the free projecting part goes on revolving. As this 

 continues, higher and higher points are brought 

 into contact with the support and are arrested, 

 and so onwards to the extremity ; and thus the 

 shoot winds round its support. When the shoot 

 follows the sun in its revolving course, it winds 

 round the support from right to left, the support 

 being supposed to stand in front of the beholder ; 

 when the shoot revolves in an opposite direction, 

 the line of winding is reversed. As each internode 

 loses from age its power of revolving, it likewise 

 loses its power of spirally twining." 



Darwin tried experiments with many twiners. 

 In the case of one plant (Ceropegia Gardnerii} the 



1 "The Movements and Habits of Climbing Plants." By Charles 

 Darwin. D. Appleton & Co. 1888. p. 14. 



