368 



LIFE ON THE EARTH 



gram of potassium nitrate, \ gram iron phosphate, ^ gram cal- 

 cium sulphate, and -fo gram magnesium sulphate. Add to the 

 water in the second jar the same ingredients with the exception 

 of the potassium nitrate. Replace this by 

 potassium chloride. Add nothing to the 

 water of the third jar. Put the three jars 

 where they will receive plenty of sunlight 

 and warmth and place in each a slip of 

 Wandering Jew about 10 inches long. Note 

 which slip grows the most thriftily. In the 

 third jar there is no mineral food, in the 

 first all of this food which is necessary, and 

 in the second all the necessary food except 

 nitrogen. 



In Experiment 108, it was found that 

 in the distilled water the plant made 

 but little growth. Water and air 

 alone are not sufficient. It did not 

 thrive when the nitrogen was lacking, 

 but grew very well when all the neces- 

 sary elements were present. All plant 

 foods, however, must be in dilute solu- 

 tion before plants can appropriate 

 them. 



Experiment 109. In another fruit jar 

 make a very strong solution of potassium 

 nitrate or, as it is commonly called, salt- 

 peter. Place in this a slip of Wandering 

 Jew as was done in the previous experiment. 

 Does the slip grow well? It has a great 



abundance of nitrogen, which was found so important. Place in a 

 similar strong solution a growing beet or radish freshly removed 

 from the ground. Notice how it shrivels up. Place a similar 

 beet or radish in water. It is not similarly affected. What is the 

 effect of strong solutions on plants? 



A TYPICAL PLANT 



Showing root, stem, leaf, 

 and flower. 



