274 EXPERIMENTS WITB PLANTS 



Study also the tendrils of the Virginia Creeper or 

 of the Boston Ivy (sometimes called Japanese Ivy). 

 Why do they grow toward the wall ? Bend back the 

 tip of the vine so that the tendrils are directed away 

 from the wall, and fasten it in this position. How 

 do the tendrils (especially the newly formed ones) 

 behave f Is this due to the light ? Conduct some of 

 the growing tips into boxes fastened on or near the 

 wall, so that you can control the direction of the light 

 as you please or exclude it altogether (if the plants 

 are growing on a brick or stone wall the boxes may 

 be simply wired to nails driven into the mortar be- 

 tween the bricks or stones). How do the tips of the 

 tendrils behave on touching the wall ? If the little 

 cushions by which the tendril attaches itself be in- 

 jured or removed, can the tendril replace them? 

 How long does it take a branch of the tendril to 

 attach itself firmly ? How much weight does it take 

 to tear it loose when it has firmly attached itself? 

 Attach a small box to it and pour shot into it until 

 the tendril breaks loose from the suppoi't. 



In what direction do the main stem and the 

 branches of these plants grow ? Is this direction due 

 to gravity? Bend back and fasten some of the tips 

 (of both main stems and branches) in a horizontal 

 position and also pointing downward. Is the growth 

 of the stem affected by light? Experiment on the 

 stems by changing the direction of the light and by 



