VALUE OF AMMONIA AND NITRIC ACID. 303 



by Kiilin, that so soon as ammonia was taken up by the 

 plant, the acid with which it was combined, becoming free, 

 acted as a poison. 



In 1866, Ilampe ( Vs. St., IX., 165), using i^hosphate 

 of ammonia as the single source of nitrogen, and taking 

 care to keep the solution but fjxiutly acid, obtained a 

 maize-plant which had a dry Aveight of 18 grams, includ- 

 ing 36 perfect seeds ; no nitrates were formed in the 

 solution. 



The same summer Kiihn ( Vs. St., IX,, 167) produced 

 two small maize-plants, one with phosphate, the other 

 with sulphate of ammonia as the source of nitrogen, but 

 his experiments were interrupted by excessive heat in the 

 glass-house. 



In 1866, Beyer ( T^. St., IX., 480) also made trials on 

 the growth of the oat-plant in a solution containing bi- 

 carbonate of ammonia. The j^lants vegetated, though 

 poorly, and several blossomed and even produced a few 

 seeds. Quite at the close of tlie experiments the plants 

 suddenly began to grow, with formation of new shoots. 

 Examination of the liquid showed that the ammonia had 

 been almost completely converted into nitric acid, and the 

 increased growth was obviously connected with this nitrifi- 

 cation. 



In 1867, Hampe ( Vs. St., X., 176) made new experi- 

 ments with ammonia-salts, and obtained one maize-plant 

 2' I, ft. high, bearing 40 handsome seeds, and weighing, 

 dry, 25' \^ grams. In these trials the seedlings, at the 

 time of unfolding the sixth or seventh leaf, after consum- 

 ing the nutriment of the seeds, manifested remarkable 

 symptoms of disturbed nutrition, growth being sup- 

 pressed, and the foliage becoming yellow. After a week 

 or two the plants recovered their green color, began to 

 grow again, and preserved a healthy appearance until 

 mature. Experiment demonstrated that this diseased 

 state was not affected by the concentration of the nour- 



