EXERCISE 7. TO SHOW THAT HEAT IS NECESSARY 

 FOR PLANT GROWTH 



Equipment: Two flower pots or tin cans and a few 

 grains of corn or wheat. 



Method: Fill the pots with soil and plant the same 

 number of seeds in each. The pots should be watered 

 and treated exactly alike except that one is kept at room 

 temperature (65° to 85° F.), while the other pot is kept 

 in a cool place at a temperature of 40° to 50° F. Note 

 the time necessary for the plants to appear above the sur- 

 face of the soil and the rate at which growth takes place. 



Discussion: Some seeds will germinate at a tempera- 

 ture only slightly above freezing, while others require a 

 much higher temperature. Oats, clover and other crops 

 that are seeded early in the spring have seeds that germinate 

 at a comparatively low temperature, while corn and melons 

 must not be planted until the soil has attained a much 

 higher temperature. 



14 



