176 



EXCHANGES AND MOVEMENTS OF FLUIDS 



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w 



Fig. 84. 



245. Increase in Walls by Imbibition. Cut 



longitudinal and transverse sections from 

 stalks of Laminaria which have been pre- 

 served dry, or in alcohol, and mount in al- 

 cohol. Measure the thickness of the walls 

 by means of a micrometer eyepiece. Meas- 

 ure changes in length of a strip 2 cm. long. 

 Now put a strip of blotting paper in contact 

 with the edge of the cover-glass on one side 

 and run a large drop of water in at the other 

 as the alcohol is withdrawn. Compare the 

 increase in the thicknesses of the wall in the 

 three axes of the stalk. 



246. Energy of Imbibition. Secure a screw- 

 topped jar, at least 6 cm. in diameter and 10 

 cm. in width, or use a Mason fruit jar. Make 

 a manometer by sealing one end of a glass tube 

 with an internal diameter of 2 mm., and then 

 bending it twice at right angles to form a U the 

 arms of which are at least 1 5 cm. long, with 

 the free open arm twice this length. Thrust 

 the free arm through a hole of sufficient size 

 cut through the metal cover of the jar. Run 

 in enough mercury so that it will stand at about 

 8 cm. in both arms at normal pressure and run 

 water into the free arm by means of a minute 

 glass or metal tube until it is full. Care must 

 be taken to have it rising to the same height in , 

 the arms. Now fill a rubber bulb of a capac- 

 ity of about 100 cc. with water and fasten to 

 the open end of the manometer, and after it is 

 in place run a wire along the tube into the bulb 

 to relieve any compression set up. Withdraw 

 the wire and use it to bind the mouth of the 

 bulb tightly to the manometer arm. The wire 



