Stimulation and Correlation. 



127 



with a pencil, noting the resulting movements. What advan- 

 tage to the plant would movements of the stamens give ? 

 (Fig. 98.) 



139. Movements of tendrils in response to con- 

 tact of solid objects. Secure vigorous specimens of a pas- 



Fig-. ioi. A, surface view of sensory cell of tendril of squash; .5, profile of 

 external wall of same. After Detmer. 



sion flower, bryony, or squash, and observe the form of the 

 slender tendrils at various stages in their development. Note 

 behavior of these organs as exhibited by their attachment to 

 various objects or supports. Select an extended and nearly 

 mature tendril, and touch 

 the concave surface near the 

 tip with a pencil or some 

 hard object. Before doing 

 this, place a sheet of paper 

 back of the tendril in such 

 manner as to mark the posi- 

 tion and outline of the ten- 

 dril. Now follow the change 

 in form exhibited. Estimate 



the length of time necessary to carry out the full movement, 

 and also the period over which the resumption of the original 

 form extends. Fasten a small stick or cord in a position 

 where it will be in contact with the concave surface of a ten- 



Fig. 102. Transverse section through 

 sensory (epidermal) cells of tendrils of 

 Entada scandens (West Indian filbert). 



