ABSORPTION OF WATER BY PLANTS 33 



Experiment 12. Demonstration of the Osmoscope 

 (by the instructor).* 



18. Make a drawing showing clearly all essential parts 

 as seen in longitudinal section, and describe the 

 apparatus as set up and explained by the instructor. 



19. Record observations on the height of the column 

 of water in the tube of the osmoscope: 



(a) At the beginning of the experiment. 



(b) On successive half-hours. 



(c) On successive days. 



20. Explain the results observed. 



Experiment 13. Demonstration of "exudation-pres- 

 sure" (by the instructor). 



21. Describe and make a drawing of the experiment at 

 its beginning, as set up by the instructor. 



22. Complete your observations and record as directed 

 under Experiment 12, naming the species of plant 

 used. 



23. Compare the conditions and results in this experi- 

 ment with those in Experiment 12. 



* It is here taken for granted that the instructor will be able to make 

 this demonstration (as well as that under Experiment 13) without further 

 suggestions, using any one of the various types of osmoscope commonly 

 found in botanical laboratories. 



