40 TWINING PLANTS. Chap. I. 



Shoots of the Kidney-bean, cut off and placed in 

 water, were similarly retarded, but in a less degree. 

 I have repeatedly observed that carrying a plant from 

 the greenhouse to my room, or from one part to 

 another of the greenhouse, always stopped the move- 

 ment for a time ; hence I conclude that plants in a 

 state of nature and growing in exposed situations, 

 would not make their revolutions during very stormy 

 weather. A decrease in temperature always caused a 

 considerable retardation in the rate of revolution ; but 

 Dutrochet (torn. xvii. pp. 994, 996) has given such 

 precise observations on this head with respect to the 

 common pea that I need say nothing more. When 

 twining plants are placed near a window in a room, 

 the light in some cases has a remarkable power 

 (as was likewise observed by Dutrochet, p. 998, with 

 the pea) on the revolving movement, but this differs 

 in degree with different plants ; thus Ipomcea juewnda 

 made a complete circle in 5 hrs. 30 m. ; the semi- 

 circle from the light taking 4 hrs. 30 m., and that 

 towards the light only 1 hr. Lomcera Irachypoda 

 revolved, in a reversed direction to the Ipomoea, in 

 8 hrs. ; the semicircle from the light taking 5 hrs. 23 m., 

 and that to the light only 2 hrs. 37 m. From the 

 rate of revolution in all the plants observed by me, 

 being nearly the same during the night and the 

 day, I infer that the action of the light is confined to 

 retarding one semicircle and accelerating the other, 

 so as not to modify greatly the rate of the whole 

 revolution. This action of the ligiit is remarkable. 



