PROBLEM 53 73 



ondary roots. Notice the direction taken by the main root ; by 

 the secondary roots; by the rootlets. 



Conclusion. Remembering that a tall stem is sent into the 

 air: 



1. What is one reason for the wide spreading of roots? 



2. What might be one other use of roots to a plant? 



Problem, 52: To determine the influence of gravity on the 

 direction of growth of roots. 



Materials. Radish or mustard seeds, pocket garden. 1 Dia- 

 gram page 72, Civic Biology. 



Method. Grow radish or mustard seeds in a pocket garden 

 placed on edge until the roots are a half inch long ; then turn it 

 on another edge and examine again after 24 hours. Repeat after 

 another 24 hours. 



Observations. Which part of the root grows down each time 

 the garden is turned ? 



NOTE. The force which pulls objects toward the center of the earth is known 

 as gravity. 



Conclusion. 1. What causes roots to turn downward? 

 2. What part of a root is most influenced by this force? 



Problem 53 : To find the effect of water on the growth of 

 roots. 



Materials. Radish or mustard seeds, sponge. 



Method. Plant soaked mustard or radish seeds on the outer 

 side of a moist sponge. Suspend the sponge under a bell jar in 

 moderate temperature. 



Observations. What happens to the roots? 



Conclusion. 1. What effect does water have on the direc- 

 tion of growth of roots? 



2. Which influence is more powerful, moisture or gravity? 



1 A pocket garden may be made as follows : Get a couple of 4 X 5 negative 

 plates, clean them, and cut five pieces of blotting paper about \ inch smaller than 

 the glasses. Lay the blotters on one of the plates, and cut four j-inch strips of 

 wood so as just to fit on the glass outside the blotters. Moisten the blotters, 

 place some well-soaked seeds of mustard, barley, or radish on them, cover the 

 seeds with the other glass, and bind the glasses together with bicycle tape. 



