CH. Vl] 



TEMPERATURE. 



147 



will greatly increase in vertical height, — the flame is 

 extinguished so that the fall in rate of growth may be 



Fig. 28. Exp. 186. 



recorded. Fig. 28 gives a copy of a tracing taken as here 

 described: the numbers give the temperatures (C) to 

 which the plant was exposed. 



(187) Ught 



Fit up a Narcissus as above described in the dark 

 room, and after 2 or 3 hrs. take down the shutter so that 

 the plant is illuminated ; no sunshine must be admitted, 

 . otherwise the ' temperatxire of the room will be affected. 

 The period of illumination should last 3 hours, when the 

 shutters should be once more closed. In this experiment 

 it is important to take readings of the wet and dry bulb 

 thermometers occasionally, both during the dark and the 

 light period. 



10—2 



