58 GARDENS AND THEIR MEANING 



A recent writer gives such a person no quarter. He says : 

 " The individual who deliberately fails to return to the soil its 

 fair share of the product abuses nature, cheats and degrades 

 himself, robs his children, defrauds the future, and is not an 

 intelligent, patriotic citizen." 



It is a blessing that new and more economical means of 

 fertilizing have supplanted the old. The three most valuable 

 chemical elements supplied by fertilizers are potash, phos- 

 phoric acid, and nitrogen. Nitrogen, the most important ele- 

 ment in manure, happens to be the most costly of the three. 



Until recently it was believed that green plants could 

 under no circumstances feed on free nitrogen, but that they 

 must use it in some one of its chemical combinations. This 

 is doubtless true of most green plants. It has, however, been 

 found that one class of plants is able to collect free nitro- 

 gen from the air mixed in with the soil, and stores this in 

 its roots. 



These legumes, or pod-bearing plants, including the clover, 

 vetch, and pea, as well as alfalfa and soy bean, bear little 

 nodules, like warts, upon their roots. The nodules are made 

 up of a lot of microscopic plants, or bacteria, ten thousand 

 or so to the square inch. The free nitrogen in the air supplies 

 these bacteria with food. Besides using the free nitrogen as 

 food, these bacteria store it, or " fix " it, as the term is, so that 

 later the whole plant may get the benefit of it. Moreover, 

 through the plowing under of nitrogen-fixing plants the earth 

 becomes enriched by just so much new nitrogen. To-day 

 these tiny organisms alone are saving farmers millions of dol- 

 lars in fertilizers. In some cases, however, it happens that 

 these leguminous plants do not develop nodules. But if 

 nodules are lacking, they can be supplied, so scientists have 

 learned, by inoculation. The formula for inoculation is simple, 

 so that the process has frequently been carried on even by 



