272 EXPERIMENTS WITH PLANTS 



blade, either in whole or in part, becomes transformed 

 into a tendril, as in the Pea family ; in still other 

 eases it is a branch which becomes a tendril (as shown 

 by its position and development, or by the fact that 

 it may occasionally bear leaves), as in the Squash, 

 Pumpkin, Grrape-vine and Passion Flower. The last- 

 mentioned plants have tendrils which are especially 

 suitable for study. Find out all you can about the 

 development of the tendrils and their behavior. 

 Does the tendril always grow out straight at first ? 

 How large must it be before it becomes sensitive to 

 contact ? Does the tendril tend to swing around in a 

 circle, as if seeking a support? How long does it take 

 to make a complete circle? Does this depend some- 

 what on the temperature? Does this movement seem 

 to be performed by the tendril or by the stem on 

 which it is borne ? How soon does the tendril coil 

 after finding a support? Sticks of w^ood about the 

 thickness of a lead - pencil fastened to upright pieces 

 by a single nail so that they may be set at any angle 

 are very convenient for experiments of this kind. 

 The upright piece (a lath or portion of one) should 

 be sharpened so as to be easily set in the ground. 

 Is the tendril everywhere equally sensitive ? Can the 

 tendril coil equally well regardless of the angle at 

 which the support is set I How does it behave when 

 the support is too large for it to coil around ? Do 

 rain - drops falling on the tendril cause it to coil I 



