20 LABORATORY AND FIELD EXERCISES 



observe changes in the form of the pulvini cor- 

 responding to the positions assumed by the leaves ? 

 How does the pulvinus effect the movement of 

 the leaf blade ? 

 (2) Draw a leaf with pulvini greatly magnified. Label 



all parts of your drawing. 



d. Naming of stimulus and response. Label the parts of 

 the largest seedling drawn in such a manner as to 

 indicate the tropism and response of each organ in 

 accordance with the nomenclature given on page 30 

 in the text. 

 3. Experiments. Observe the following experiments on the 



tropisms of the bean seedling : 



a. Place one growing seedling of a bean in a horizontal 

 position, and another in an erect position, in a place 

 where the lighting will be uniform on all sides. 

 Observe at successive laboratory periods until both 

 plants are adjusted in their positions. Write up the 

 experiment after the following plan, indicating actual 

 results by drawings properly labeled to indicate the 

 kinds of stimuli and the nature of the response in 

 each instance. 



(1) Object in view in performing the experiment. What 



do you expect to prove ? 



(2) The method and conditions under which the experi- 



ment is performed. Make outline drawings of the 

 two plants to indicate the position of leaves and 

 stems at the beginning of the experiment. 



(3) Actual results observed on each plant after several 



hours. State the changes observed in each plant. 

 Indicate these changes by outline drawings. Ex- 

 plain the mechanism of the response in the case 

 of each organ. Label each organ, indicating the 



