igS 



JOHN H. WILSON 



[march 1899 



and takes their place. If the action of an insect attempting to enter 

 the flower be imitated, and the lightest touch given in the throat, the 

 protruding organ swings with startling rapidity through an angle of 

 270°, and comes to lie over the flower with its apex pointing down- 

 wards. After a short interval the gynostemium slowly rises and 

 resumes its former position, there to gather energy for another stroke. 

 It is easy to demonstrate that it is most sensitive where it is bent at 

 the throat of the flower. The sudden movement is ostensibly associated 

 with the visits of insects. From the visitor's point of view the recep- 

 tion can hardly be characterised as anything else than violent. One 

 almost feels inclined to think that Stylidium has become more annoyed 



10 " / <f 



Flowers and floral parts of Stylidium. 



Fig. 6. — Flower undisturbed. Fig. 7. — Touched. Figs. 8, 9. — Sticky shield. 



Figs. 10, 11. — Earlier and later conditions of the apex of the gynostemium. (All enlarged.) 



than the barberry at the slow pace of the insects, and has acquired 

 means of suddenly stimulating them to greater activity. 



It may be mentioned that the nettle, and its allies pellitory and 

 the " Artillery Plant " (Pilea) spontaneously and violently fling the 

 pollen out of the anthers, once for all, by the sudden release of the 

 tense filaments at maturity. 



A movement analogous to that of the leaves of the Sensitive Plant 

 is seen in the closing of the stigmatic lobes of Musk, Torenia, Bignonia, 

 Butterwort, and certain other plants, when they are touched. 



All motility in flowers, whether spontaneous or induced, has 

 reference to fertilisation processes. 



"We have confined our attention to examples of plants which per- 

 form induced movements quick enough to be seen by the unaided eye. 

 We are greatly tempted to regard the phenomena as sentient, and 

 unwittingly fall into the habit of speaking of them as such. An 

 effort is made, by using the rather ambiguous words " irritable," 

 " contractile," and the like, to avoid giving wrong impressions. 



St. Andrews. 



