PROBLEM 62 79 



Observations. — In which does the most vigorous growth take 

 place ? 



Conclusion. — 1. What materials do plants take in with 

 water ? 



2. What is the source of these materials ? 



Problem 61 : How are root hairs able to take mineral matter 

 out of the soil? 



Materials. — Vigorous bean or corn seedling, test tubes on base, 

 phenolphthalein solution. 



Method. — To a solution of phenolphthalein add drop by drop 

 a little strong nitric acid. Notice what happens. 



Place in another tube containing a phenolphthalein solution 

 (which should be almost neutral) a growing seedling. Leave 

 overnight and then observe. Compare with a control tube con- 

 taining phenolphthalein. 



Observations. — Compare the color in the control tube with the 

 color in the tube containing the seedling. 



Compare the tube to which acid was added with that containing 

 the seedling. 



Conclusion. — 1. What substance is given off by roots? 



2. What effect might this have upon certain minerals in the 

 soil? (Try the effect on a bit of limestone.) 



Problem, 62 : What are root tubercles and what is their use ? 



Materials. — Clover or bean plants. Diagram page 81, Civic 

 Biology. 



Method. — Remove and wash carefully the roots of a clover or 

 bean plant. Place in a test tube with a base for laboratory 

 study. 



Observations. — Do you find little lumps or tubercles on the 

 roots? Locate exactly. 



NOTE. — Root tubercles are small knoblike structures which develop on the 

 roots of leguminous plants (clover, alfalfa, peas, beans, cowpeas, etc.). In these 

 tubercles develop millions of little plants called nitrifying bacteria. These plants 

 alone of all others are able to take nitrogen from the air and to combine it with 

 certain mineral substances in the soil to form nitrates. In this form it is taken 

 up by plants. 



