42 AGRICULTURE FOR BEGINNERS 



A single factory in Germany is estimated to give back to 

 the air daily about 5,280,000 pounds of carbon. You see 

 that the air is thus being replenished to make up for the 

 carbon taken by the growing plants. 



The carbon of the air can be used by none but green 

 plants, and by them only in the sunlight. We may com- 

 pare the green coloring matter of the leaf to a machine, 

 and the sunlight to the power, or energy, which keeps the 

 machine in motion. By means, then, of sunlight and the 

 green coloring matter of the leaves, the plant secures carbon. 

 The carbon passes into the plant and is there made into two 

 foods very necessary to the plant, namely, starch and sugar. 



Sometimes the plant uses the starch and sugar immedi- 

 ately. At other times it stores both away, as in the Irish 

 and the sweet potato, beets, cabbage, peas, and beans. 

 These plants are used as food by man because they contain 

 so much nourishment, that is, starch and sugar that was 

 stored away by the plant for its own future use. 



EXERCISE 



Examine some charcoal. Can you see the rings of growth? 

 Slightly char paper, cloth, meat, sugar, starch, etc. What does the 

 turning black prove? What per cent of these substances do you 

 think is pure carbon? 



SECTION XIII THE SAP CURRENT 



The root hairs take nourishment from the soil. The 

 leaves manufacture starch and sugar. These manufactured 

 foods must be carried to all parts of the plant. There are 

 two currents to carry them. One passes from the roots 



