Chap. V. CONCLUDING EEMAEKS. 203 



first rises vertically up, Avitli its branclies divergent 

 and with the terminal hooks turned outwards; the 

 young shoot at the extremity of the stem is at the 

 same time bent to one side, so as to be out of the way. 

 The young leaves of Clematis, on the other hand, 

 prepare for action by temporarily curving themselves 

 downwards, so as to serve as grapnels. 



Secondly, if a twining plant or a tendril gets by 

 any accident into an inclined position, it soon bends 

 upwards, though secluded from the light. The guid- 

 ing stimulus no doubt is the attraction of gravity, as 

 Andrew Knight showed to be the case with germinat- 

 ing plants. If a shoot of any ordinary plant be placed 

 in an inclined position in a glass of water in the dark, 

 the extremity will, in a few hours, bend upwards ; and 

 if the position of the shoot be then reversed, the 

 downward-bent shoot reverses its curvature; but if 

 the stolon of a strawberry, which has no tendency to 

 grow upwards, be thus treated, it will curve downwards 

 in the direction of, instead of in opposition to, the 

 force of gravity. As with the strawberry, so it is 

 generally with the twining shoots of the Sibbertia 

 demtata, which climbs laterally from bush to bush ; for 

 these shoots, if placed in a position inclined downwards, 

 show little and sometimes no tendency to curve up- 

 wards. 



Thirdly, climbing plants, like other plantSj bend 

 towards the light by a movement closely analogous to 

 the incurvation which causes them to revolve, so that 

 their revolving movement is often accelerated or retarded 



