PLANT IRRITABILITY 179 



Count the number of coils. Carefully remove the pencil 

 and insert a small wire in its place. What change takes 

 place in the number of turns in the coil? What does this 

 show? 



Note. To observe automatic movement in a plant place it 

 under a bell jar or inverted battery jar, or support a plate of glass 

 above it just so that it does not touch the plant. With a wax 

 pencil used for marking on glass, and with the eye exactly above 

 the plant, sketch the position of the uppermost pair of leaves. The 

 sketch will thus become the orthographic projection of the leaves 

 drawn. 



After an hour make another observation, and if any change of 

 position has occurred, sketch again as before. Continue observa- 

 tions and sketches until the fact has been established or disproved. 



