40 “TWINING PLANTS. Cuar. 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 (tom. 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 Ipomea jucunda 
made a complete circle in 5 hrs. 30m.; the semi- 
circle from the light taking 4 hrs. 80 m., and that 
towards the light only 1 hr. Lonicera brachypoda 
revolved, in a reversed direction to the Ipomea, in 
8 hrs. ; the semicircle from the light taking 5 hrs, 23 m., 
and that to the ight 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 light is remarkable, 
