EXERCISE 66 

 RESPONSE OF TENDRILS 



Materials. Pea plants with tendrils, or other tendril-bearing 

 plants. 



Directions for work. Select vigorous plants in apparent good 

 condition. Stroke a tendril gently with a pencil, being careful 

 that it shall be touched only on one side. Repeat with several 

 other tendrils. Make careful note of the position and curvature 

 of the tendril and observe it repeatedly for several minutes, 

 making memorandum of the time and the curvature of the 

 tendril at each observation. Does the stimulus of contact pro- 

 duce any curvature ? If so, to which side does the tendril 

 curve, and is this curvature permanent ? 



Thrust a wire or other slender object into the soil and bend 

 it so that it is in contact with one of the tendrils near its tip. 

 Allow the wire to remain in this position, so that in this case 

 the contact with the tendril is permanent, instead of temporary 

 as in the previous trial. Repeat with several other tendrils. 

 Does the tendril curve ? Is the curvature permanent ? Does 

 the curvature become greater in amount than in the previous 

 trial ? Does the tendril finally take hold of the object as you 

 are used to seeing tendrils attached ? 



In writing your notes discuss both parts of the exercise and 

 write a clear account of how a tendril takes hold of a support. 



References 



BERGEN and CALDWELL. Practical Botany, pp. 62-01. 

 BERGEN and CALDWELL. Introduction to Botany, pp. 71, 75. 



[82] 



