NOTES OX THE IRRlTABltlTY OF THE STIGMA. 207 



possible toucli as, for example, witli the tip of a l)ri.st]e or hair. On 

 the other hand, plaeing a small drop of water on the stiginatie lobes 

 or blowino- upon them does not iiidiiee the motion. Again, mere rub- 

 bing on the style or on the (joter surface of the hjlies does not show 

 even the least sign of motion, though a slight touch on the inner sur- 

 face is very effective. Moreover, this curious property is not contined 

 to the lower lobe only, as may at first sight appear, but it is possessed 

 by the upper lobe as w^ell. Since the lower lobe is widely reflexed, the 

 motion there is very manifest ; but the upper one being nearly in the 

 same line with the style shows no decided motion other than a 

 slight bending down. 



I made these experiments on the natural position of the flowers, 

 and measured the time required for the closing and reopening of the 

 lobes. The results varied not only in the flowers of different stocks, 

 but in diff'erent flowers of the same stock, even in the same flower in 

 different stages of development, in different hours of the day, and 

 also in different states of temperature and weather. Generally speak- 

 ing, the closing and reopening in a given flower are more rapid at 

 the middle of a clear warm day than at other times and in other 

 states of weather. Complete closing is performed usually in 

 3-6 seconds, but may sometimes take 7, even 10, seconds. Com- 

 plete reopening takes place usually after 7-12 minutes, but some- 

 times sooner, sometimes later. Some flowers which I examined on a 

 very warm day, reopened only after 5 minutes. I also found that in 

 young flowers, the closing is more rapid, while the reopening is much 

 slower, requiring about 13-15 minutes. But in mature flowers, 

 chasing takes place in the usual interval of time, while reopening is 

 quicker (7-10 minutes). In all cases the movement of closing may 

 easily be observed, but that of reopening is so gradual that we cannot 

 recognise it without careful observation. The experiments may be 



