WHAT IS PHYSICAL LIFE 



supply of available nitrogen to feed the 

 nations. The store of Chili saltpetre, 

 which was originally a vast deposit of 

 guano, is being reduced at a disquieting 

 rate, and the plan of fixing air nitrogen by 

 electricity, though promising, is still ex- 

 pensive. It is therefore welcome news to 

 hear that these benevolent hordes of bac- 

 teria have been discovered in the very act 

 of " fixing " nitrogen, and moreover just 

 where it is most wanted, viz., on the root- 

 lets of plants. Professor Hilgard of the 

 University of California, in his treatise on 

 Soils, p. 155, says that seeds sown after 

 they have been inoculated with the pur- 

 chased bacteria at the cost of two dollars 

 an acre, can add thirty to forty dollars' 

 worth of nitrogen more and better than the 

 nitrogen in two tons of a chemical fertilizer 

 such as the Chili saltpetre. 



Professor Whitney of the United States 

 Department of Agriculture goes so far 

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