INFLUENCE OF NITRATES. 101 



indispensable to the constitution of plants exert no appre- 

 ciable action upon vegetation, except when accompanied by 

 matters capable of furnishing assimilable nitrogen. Two 

 plants of the same kind, grown under the same conditions as 

 above, but with the perfectly sterile soil adequately supplied 

 with phosphate of lime, alkali in the form of bicarbonate of 

 potash, and silex from the ashes of grasses, resulted in only 

 0.498 grams of dried vegetable matter, from seeds weighing 

 0.107 grams ; and had acquired only 0.0027 grams of nitrogen 

 beyond what was in the seeds. 



(3) But nitrate of potash furnishing assimilable nitrogen, 

 associated with phosphate of lime and silicate of potash, 

 forms a complete manure, and suffices for the full develop- 

 ment of vegetation. Parallel experiments with nitrate in 

 place of bicarbonate of potash resulted in the vigorous growth 

 of the Sunflower plants, and the formation of 21.248 grams of 

 organic matter, from seeds weighing as before only 0.107. 

 This 21.111 grams of new vegetable matter, produced in three 

 months of vegetation, contained 8.444 of carbon derived from 

 the carbonic acid of the air and 0.1666 grams of nitrogen. 

 The 1.4 grams of nitrate of potash supplied to the soil con- 

 tained 0.1969 grams of nitrogen, leaving a balance of 0.0303, 

 nearly all of which was found unappropriated in the soil. 



Finally Boussingault made a neat series of comparative 

 experiments, introducing into calcined sand the same amount 

 of phosphate of lime and carbonate of potash, but different 

 proportions of nitrate of soda, or in other words of assimi- 

 lable nitrogen, and watering with water free from ammonia 

 but containing a quarter of its volume of carbonic acid. The 

 soil was divided among four pots, each having two seeds of 

 Sunflower (^H. argophyllus was the species used in all the ex- 

 periments) ; the pot 



No. 1 received of nitrate of soda 0.00 grams. 



No. 2 " " " 0.02 " 



No. 3 " « " 0.04 " 



No. 4 " " " 0.16 " 



The results of fifty days' vegetation are given in the rate 



