20 



Esther Pearl Hensel 



Open dandelions when put into the cold chamber do not ordi- 

 narily close at night in the manner of those under normal condi- 

 tions. They look perfectly natural and do not wither on removal, 

 but seem to be in a rigid condition. The change from normal 

 temperature to that of the cold chamber (19° or 21° to 2° or 

 5° C.) is probably so extreme that the flower is unable to react 

 to the stimulus of the variation in temperature, for, when a plant 

 with open flowers is put out of doors or in another room where 

 the temperature difference is not so great, closing occurs very 

 readily at any time of day. When the temperature in the cold 

 chamber was not too low, closing occurred in certain instances 

 at about the normal time. 



Follqv.'ing are two instances of this sort with figures showing 

 normal closing: 



210 



