Behavior of Stigma Lips. 263 



them. Under such treatment, one can easily be assured that the 

 closure is due to withering.. 



Without knowing of Burck's work, at the time, I was led to 

 identical conclusions with regard to Diplacus. An examination 

 of the naturally pollinated flowers shows that, especially in the 

 earlier part of the day, there are many stigmas which, in spite of 

 the presence of pollen, are not closed. Towards the close of the 

 day many will be found closed and in practically all cases in which 

 pollen is present the lips will be more or less curved. Further, 

 pollinated stigmas display a withered aspect, and are character- 

 ized by an opacity absent from unpollinated stigmas. It is im- 

 portant to remark here that the closure due to the presence of 

 pollen is not such as to closely approximate the stigma lips, and 

 the vigorous curvature seen after mechanical response is absent. 

 These observations led me to investigate the matter experimental- 

 ly. It was found that, unpollinated, the stigma persists (in the 

 laboratory in the climate of Carmel, Cal.) for ten or twelve days, 

 retaining its ability to respond to mechanical stimuli during that 

 period. Pollinated stigmas, however, do not close at once, unless 

 pollination is accompanied by mechanical stimulus, in which 

 event they reopen in a short time. In the absence of mechanical 

 stimulus the stigma-lips either approach each other or each may 

 display bendings in various directions, but only after the lapse of 

 several hows, the same occuring, of course, when the pollinated 

 stigmas reopen after mechanical stimulus. They wither com- 

 pletely in three or four days after pollination. The following 

 experiments are typical. Four fresh stigmas were pollinated by 

 placing a mass of pollen across the throat (Figure 6, a). They 

 were stimulated mechanically, but the lips reopened. All four 

 closed later. In two cases some curvature was noted in two 

 hours and twenty minutes, in an upper lip, with which there was 

 more pollen in contact than with the lower, it being difficult to 

 place it in precisely the desired position. In another hour the 

 change in position was still more marked, and was visible in all 

 four cases. On the following morning, 24 hours after pollination, 

 the lips were closed together at their bases, while the apices v ere 

 curled away from each other., in which position (Figure 7) sub- 

 stantially, they remained until withering ensued three days later. 



