THE NITRIC A^;ID OF THE SOIL. 



271 



Mtric Acid as Food to Plants. — Experiments demon- 

 strating thaf nitric acid is capable of perfectly supplying 



vegetation with 

 nitrogen were 

 first made by 

 Bouss i n g a u 1 1 

 ( Agroiiomie ^ 

 Chimie A(jri- 

 cole, etc., 1,210). 

 We give an ac- 

 count of some 

 of tliese. 



Two seeds of 

 a dwarf Sunflow- 

 er {Ilellanthus 

 argophyllxis), 

 Avere planted in 

 each of three 

 pots, the soil of 

 which, consist- 

 ing of a mixture 

 of brick - dust 

 and sand, as well 

 as the pots them- 

 selves, liad been 

 thoroughly 

 freed from all ni- 

 trogenous com- 

 pounds by igni- 

 tion and wash- 

 ing with dis tili- 

 ng. 0. ed Avater. To 

 the soil of the pot A, fig. 9, nothing was added save the 

 two seeds, and distilled water, Avith which all the plants 

 were watered from time to time. With the soil of pot 

 C, w^ere incorporated small quantities of phosphate of lime, 



