BIOLOGY OF HIGHER SEED PLANTS 21 



nature of the stimulus and response ; for exam- 

 ple, apogeotropic. Consult the text discussion 

 (pp. 28-31) concerning the mechanism of response 

 in plants and the naming of stimulus and response. 

 (4) Conclusions. State briefly your conclusions from 

 the above experiment as to the relations existing 

 between the bean plant and some of the forces 

 of the environment. 



b. Place two plants before a window. Rotate one on a 



clinostat. Observe and record as indicated above 

 after several hours, when the plants have become 

 adjusted to the new environmental conditions. 



c. TJie gravity sense. Observe germinating seeds of corn 



or beans with protruding roots which are rotated on 

 a clinostat, as in Fig. 18, a-d, of the text. Compare the 

 position assumed by the rotated roots and hypocotyls 

 with positions taken by these organs in seeds pinned 

 to a stationary disk, Record the object, method, 

 results, and conclusions as in experiment a, above. 



SUPPLEMENTARY STUDIES 



Adjustments of common plants to the environment. Observe 

 common plants in the field and in the laboratory, and record the 

 positions assumed by the various organs. Eecord the results of 

 your observations and your conclusions in a manner similar to 

 tluit indicated above for writing up experiments on movements. 

 The dandelion (Taraxacum\ white sweet clover (Melilotiis), 

 cultivated geranium, and some climber, such as the ivy, are 

 good species for observation. At least one such plant should 

 be assigned to each student to work up independently and hand in 

 with appropriate drawings and notes. 



