EXERCISE 5. TO SHOW THAT SUNLIGHT IS NECES- 

 SARY FOR PLANT GROWTH 



Equipment: Two flower pots; some grains of wheat 

 and corn. 



Method: Fill the two pots with moist soil and plant 

 to wheat or corn. Place one of the pots in the window and 

 cover the other with a black paper cone or a box through 

 which the light cannot penetrate. Give both pots the same 

 temperature and the same moisture supply. Observe the 

 contrast in the appearance of the two sets of plants. After 

 the plants under the cone or box have reached a height of 

 three or four inches, remove the covering and note what 

 takes place. 



Discussion : The leaves are the workshop of the plant. 

 It is here, under the influence of sunshine, that the plant 

 takes the food materials from the air and combines them 

 with the nutrients gathered from the soil by the roots. 

 The process which goes on in the leaf results in the pro- 

 duction of the starches, sugars, fats and proteid substances 

 which are stored in the body and seeds of the plant. The 

 details of the process are not understood, but we know that 

 sunlight is a necessary factor. 



The work of the green leaves of the plant is, therefore, 

 to manufacture sugar and starches, which are sometimes 

 called carbohydrates. This is an extremely important proc- 

 ess, for all life on the earth is dependent upon it for support. 



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