PLANT IRRITABILITY 177 



Method. Study the various plants selected. Observe 

 the direction in which they coil about a support. Do all 

 twist in the same direction? if not, which turn from right 

 to left, and which from left to right ? 



Uncoil a stem several turns and try to make it twine in 

 the opposite direction. Result? See if you can make a 

 stem which has not yet begun to twist, coil opposite to the 

 way in which the other branches of the same plant tend to 

 coil. 



Conclusion. State in general what this experiment has 

 taught you. 



161. RESPONSE TO CONTACT 



Object. To learn something of the irritability of sta- 

 mens of some flowers- 



Apparatus. Flowers of barberry, mountain laurel, and almost 

 any mint. 



Method. 1. Examine the position of the stamens and 

 pistil in a cluster of barberry flowers. Now thrust a pin 

 into the pistil and observe the result. Repeat the experi- 

 ment with the same flowers and with other flowers. 



2. Examine a freshly opened flower of laurel. Note the 

 position of the stamens. Examine an older flower. What 

 is the position of the stamens? Touch the stamens of the 

 young flower. What happens? What would occur if 

 a bee should enter such a flower ? If possible, watch for a 

 bee to visit the laurel flowers. What happens ? 



3. Study a mint flower in the same way. What move- 

 ments are to be witnessed here ? 



Conclusion. What may be inferred from these observa- 

 tions ? 



EXP. BOT. 12 



