EXERCISE 3. TO SHOW THAT PLANTS GET FOOD 

 MATERIAL FROM THE SOIL 



Equipment: Two quarts of clean sand; two flower pots 

 or quart cans; a few beans. 



Method : Heat the sand to redness on a shovel or in an 

 iron pan until all the organic matter is burned out. Fill the 

 two pots with this ignited sand. Select ten large, plump 

 beans and, after soaking them over night, plant five in each 

 pot. Water both pots with rain- or distilled water and set 

 them in a warm place until the beans begin to grow. After 

 this, treat both pots aUke, except that one is watered with 

 rain-water and the other is supplied with a soil solution.* 

 As soon as the beans are about two inches high, thin out, 

 leaving three uniform plants in each pot. 



Continue the watering until the plants are four of five 

 weeks old, by which time the beans that have received the 

 soil solution should be much larger and stronger than those 

 that have received only rain-water. To what is this differ- 

 ence in growth rate due? Why not use spring-water instead 

 of rain-water? 



Discussion : Plant food in the soil is dissolved by water 

 and by weak acids given off by the root hairs much in the 



* To make this soil solution fill a large pail half full with rich soil 

 from beneath or near the edge of a manure heap and add enough rain- 

 water to fill the pail. Stir and set aside to settle, then strain off some of 

 the liquid through a piece of cheesecloth. 



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