82 PHYSIOLOGICAL PROCESSES IN PLANTS 



seedlings in the jars so that their roots extend down into the 

 liquids. Or better, put cuttings of tradescantia in the liquids. 

 Observe the growths for two or three weeks. 



Observation. Which jar shows the most vigorous growth? 



Conclusions. 1. What else do plants need besides water, 

 air, moderate temperature, and organic matter (humus) in 

 order to live ? 



2. Write a paragraph summing up the factors that make 

 soil fertile. 



1. ANOTHER USE OF ROOT HAIRS (OPTIONAL) 



Method. Grow a number of radish seeds in a pocket garden. Place 

 a sheet of blue litmus paper so that the growing roots will he against it. 



Observation. Observe them from time to time. Does any change 

 of color take place ? If so, what ? 



Note. Blue litmus paper will turn red whenever an acid comes in 

 contact with it, while red litmus paper will turn blue whenever an alka- 

 line substance comes in contact with it. (The instructor should here 

 demonstrate these changes.) 



Conclusions. 1. Do root hairs give off an acid or alkaline substance ? 

 Explain. 



Note. Many mineral substances are dissolved by the action of an 

 acid, as carbonic acid in the soil, from roots. The minerals mentioned 

 in the formula for making nutrient solution are some of them, such as 

 calcium, iron, sodium, etc. 



2. Try dissolving some calcium phosphate in distilled water. Result ? 

 Now add a few drops of hydrochloric acid or sulphuric acid. Is there any 

 difference in result ? What ? 



3. See if you can now tell another indirect use of root hairs. 



f. Root Tubercles 



Method. Carefully remove the roots from a clover plant, or 

 alfalfa, or vetch. If these cannot well be obtained, use a well- 

 developed bean seedling. Wash the roots carefully. When 

 they are dry, look for nodules, or small wartlike growths on 

 them. 



Observation. Describe the appearance of the nodules. 

 Where are they located? 



