On the M ovements of Petals 



31 



In the following instance opening v;as not complete at any 

 time during the day : 



This late closing is always associated with a late opening in 

 the morning accompanied by a low temperature. 



Experiments zvith Oxalis stricta. The flowers of Oxalis stricta 

 open from 9:30 a.m. to 11:00 a.m., and close for the first and 

 only time between i 130 and 3 :oo p.m. The same phenomena 

 are to be observed as in the other ephemeral day blooming spe- 

 cies studied, i. e., a low temperature hinders opening and also 

 prolongs it when there has been a temperature high enough to 

 induce opening. Opening can be made to occur earlier than nor- 

 mal also, as in the case of the other flowers studied, by increasing 

 the amount of heat to a few degrees above the normal. As evi- 

 dences of the eft'ect of low temperatures on the time of opening, 

 the following figures are conclusive. Table I shows the normal 

 condition of the flowers under normal temperatures; table II, 

 the effect of a lower temperature continuing more or less through- 

 out the dav : 



