Our Plants. 21 



that certain plants can feed upon the nitrogen in 

 the atmosphere and store it up in their tissues. As 

 they grow they take their phosphoric acid and pot- 

 ash from the soil. It is believed that plants are en- 

 abled to get this nitrogen through the activity of the 

 lower forms of life, bacteria or microbes. They 

 produce or cause to be produced little nodules or 

 tubercles on the roots. Through these tubercles 

 the plants get their atmospheric nitrogen. 



" These discoveries throw a new light on green 

 manuring and on plants best adapted for that pur- 

 pose. They recommend it more highly than ever 

 before as a soil renovator and a cheap means of 

 maintaining the fertility. 



" It will thus be seen that it is possible to manure 

 the soil with nitrogen of the air, which is free and 

 inexhaustible, and thus save buying this most ex- 

 pensive element, which as stated above, costs from 

 15 to 20 cents per pound, while potash and phos- 

 phoric acid cost only 5 to 7 cents and even less." 



Speaking of the cow pea as a fertilizer, the same 

 author says : " It responds readily to the application 

 of potash and phosphates. An acre of cow peas at 

 the Louisiana Station yielded 3,970.38 pounds of 

 organic matter, containing 64.95 pounds of nitrogen, 

 20.39 pounds of phosphoric acid, and 110.56 pounds 

 of potash. " 



