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 i-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. 



