VIII. MECHANICAL USES OF WATER IN THE PLANT 



A . Rigidity and Maintenance of Form: 



Experiment 15. To ascertain the cause of rigidity in 

 beet tissue: 



1. From a beet cut four slices about 5 mm. thick, 

 10 mm. wide, and 75 mm. long. 



2. Place the slices as follows: 



(a) In tap-water.. 



(b) In a 10 per cent, salt solution. 



(c) and (d) In boiling water for two or three min- 

 utes. 



Then place 



(c) In tap-water, and 



(d) In the 10 per cent, salt solution. 



3. At the end of fifteen minutes observe and record 

 the relative rigidity of the various slices, ascer- 

 tained by carefully bending them. 



4. Thoroughly rinse the slices, b and d, and then 

 transfer them to tap-water. At the end of an 

 hour (or sooner) observe them again and describe 

 the result. 



5. Explain your observations on the basis of your 

 previous experiments. 



6. What is one mechanical use of water in a plant- 

 tissue, and how is this accomplished? 



Experiment 16. To demonstrate longitudinal tissue- 

 tension. 



7. Obtain a petiole of rhubarb, or burdock, or a 

 stalk of celery. With a scalpel make a lengthwise 

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