H. B. rilTTCIIINSON AND N. IF. J. Mll.LKR 183 



duced. It was found that ainmoniuin salts are rapidly converted into 

 asparagine, whilst nitrates tended to accumulate, and, during the short 

 time the experiment lasted, generally failed to increase the amount of 

 asparagine. The production of asparagine is promoted by the presence 

 of suear, and in absence of sufjar, or other suitable material, it was 

 found that ammonia may accumulate in the plants and eventually 

 cause injury. 



In 1898, Maze (32) grew maize in sterilised water-cultures con- 

 taining ammonium sulphate and sodium nitrate respectively ; calcium 

 carbonate 0'2 per cent, was added. Two months afterwards the plants 

 were taken up, and it was found that the ammonium sulphate solutions 

 still contained ammonia, and that no nitrate was produced. The plants 

 grew about equally well in the two solutions. In later experiments (33), 

 culture solutions were employed containing both forms of nitrogen in 

 different proportions. The results showed that when the relations of 

 ammonium sulphate to sodium nitrate were 1:2 or 1:4 the whole of 

 the ammonia was utilised whilst some nitrate remained in the solutions. 



Kossowitsch (35) experimented with peas in sterili.'^cd sand-cultures. 

 Calcium carbonate was present in addition to the usual minerals, and 

 the ammonium salt was added gradually during growth. The results 

 showed that ammonium sulpha,te and sodium nitrate were equally 

 suitable as sources of nitrogen. The solutions and sand to which 

 ammonium sulphate had been added were found at the end of the 

 experiment to be free from nitrates and nitrifying organisms ; in some 

 cases, however, it was discovered that other micro-organisms were 

 present, and in some moulds. 



Gerlach and Vogel (37) found that maize plants, grown in sterilised 

 soil manured with ammonium sulphate, contained more nitrogen 

 (0'418 gram.) than similar plants grown in the same soil without 

 nitrogen ; the soils were found to be free from nitrates at the con- 

 clusion of the experiment. 



Kriiger (38) made a large number of experiments with various 

 plants grown in a sterilised mixture of soil and sand. Sterilisation 

 was effected by heating the pots in steam for one hour on 6 days; 

 the seeds were sterilised with mercuric chloride. At the conclusion of 

 the experiment, the soils were examined and those containing nitrate 

 excluded. The conclusion is drawn that ammonium salts and nitrates 

 are equally suitable for mustard, oats and barley ; that ammonia is, if 

 anything, better than nitrates for potatoes, whilst for mangolds nitrates 

 are decidedly better than ammonium salts. 



