158 



GROWTH. 



[CH. VI 



(185) Respiration: roots. 



Proceed as in exp. 183, and when the growth is fairly 

 uniform fill up the vessel so as to cover the cotyledons. 

 Note the rapid fall in the rate of growth, and the recovery 

 when the cotyledons are again exposed to air. 



(186) Temperature: stems. 



The effect of warmth on growth can be well shown 

 with the recording auxanometer. In fitting up the appa- 

 ratus the following points must be noted. Let the paper 



Fig. 29. Exp. 186. 



be smooth and tight on the drum, to insure which the 

 unglazed side of the paper should be wetted with a 

 sponge before it is attached. Do not smoke the paper too 

 heavily : a paraffin stove-lamp, with the long wick turned 

 up so as to flare, may be used for the smoking. The 

 drum should be accurately vertical, which may be tested 



