182 Direct Assiitillatlon of Ammonmm Salts hij Plants 



were not sterilised, and the only precaution to avoid nitrification was 

 to add calcium in the form of chloride instead of as carbonate. The 

 solutions were found, however, to be free from nitrates and to contain 

 ammonia at the end of the experiment. The beans grew fairly well 

 when supplied with an ammonium salt, and the stems were found to 

 be free from nitrates. 



Miintz, in 1889 (24) experimented with beans, kidney beans, maize, 

 barley and hemp which were grown in soil which was first extracted 

 and then heated at 100 '. The seeds were sterilised by dipping for a 

 moment into boiling water, and the pots were kept in cases ("veritables 

 cages de Tyndall") provided with openings, covered with cloth, to render 

 the air passing in free from germs. At the conclusion of the experi- 

 ment the soils were found to be free from nitrates. The different plants 

 assimilated 49 to 915 m.g. of nitrogen, probably in the form of ammonia. 

 There is, however, no proof that nitrification had been entirely absent. 

 If the ammonium salts had been only slowly, and perhaps locally, nitrified 

 all traces of nitrates might have been removed by the plants. In Pitsch's 

 experiments as already mentioned, the soils were left for some time after 

 the plants were taken out before being examined for nitrates, so as to 

 allow time for further nitrification in the event of nitrifying organisms 

 being present. 



Griffiths (25), almost at the same time as Miintz, grew beans in 

 sterilised water-cultures, with ammonium sulphate as source of nitrogen. 

 The seeds were sterilised by remaining half-an-hour in copper sulphate 

 solution, and the jars containing the solutions were placed under large 

 bell-jars the openings of which were closed with cotton wool. The 

 plants grew remarkably well for four weeks, and reduced the amount 

 of nitrogen in the solution from 005 to 0"027 per cent. ; no nitrate 

 could be detected. 



The next experiments, by Breal (28), were made with Poa annua. 

 Tufts of the grass growing in soil were dug up, and the roots washed 

 until free from soil and then placed in water. New roots were soon 

 produced, whilst the original roots left off growing. After cutting off the 

 old roots the plants were supplied with dilute solutions of ammonium 

 sulphate. It was found that after 24< hours all the ammonia had been 

 taken up. In these experiments sterilisation was unnecessary as the 

 time was too short for nitrification to occur. 



Kiuoshita (29), and, subsequently Suzuki (30), grew seedlings of 

 various plants for short periods in solutions of ammonium salts and 

 sodium nitrate, in order to compare the amounts of asparagine pro- 



