EXERCISE 36 



Problem. How does gravity influence the direction of growing roots ? 



What to use. Two small glass plates (those made by cleaning negatives will serve very well) ; filter 

 or blotting paper ; radish or lettuce seeds ; water. 



What to do. Thoroughly moisten two or three sheets 

 of blotting paper and cover one plate with it. Place several 

 soaked seeds on blotter in different positions, and gently 

 place glass plate over the seeds. It may be necessary to put 

 bits of match sticks in the corners to prevent the glass from 

 crushing the seeds. 



Record. When the seeds have sprouted, observe and 

 sketch direction of growth of roots ; after twenty-four hours 

 observe and sketch again and turn plate one fourth of the 

 way around, as indicated. Repeat every twenty-four hours 

 for several days. 



What do you conclude concerning the relation of gravity to the direction of growth of roots ? 



Jf-^S Match-stick sup forts 



for glass 



Moistened filter or 

 blotting faper 



Radish or flax or 

 any small seeds 



Glass 



Questions. 1. In what way do the stems seem to be affected ? 



2. How is the reaction of the root to gravity related to the life of the plant ? 



3. How is the reaction of the stem to gravity related to the life of the plant? 



4. How can you distinguish between growing down and simply falling ? 



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