190 Direct Assimilation of Ammonium Salts by Plants 



The solutions were sterilised by heating for an hour at 100° on four 

 successive days. Calcium carbonate (2 grams) was sterilised, and added 

 to each bottle at the same time that the seedlings were put in. The 

 bottles were arranged in sets of three, each set being connected with 

 a Pasteur flask filled with sterilised distilled water. One set received 

 sodium nitrate, and one ammonium sulphate, and there were two similar 

 sets which received 2 grams of dextrose in addition, so that there were 

 altogether twelve bottles as follows : — 



I. Nos. 1, 2, 3 Sodium nitrate 



II, ,, 4, 5, 6 „ „ -I- dextrose 



III. ,, 7, 8, 9 Ammonium sulphate 



IV. „ 10, 11, 12 „ „ -f- dextrose 



The seedlings were put in on June 1, and the plants taken up on 

 July 20, 1908. With the exception of No. 8, which failed at an early 

 date,, all the plants grew normally and showed no appreciable dififerences 

 under the different conditions. Towards the end of the experiment 

 No. 6 suddenly lost its green colour owing to the development of a 

 mould which quickly appropriated all the available nitrogen. All the 

 other plants remained perfectly healthy to the end. 



On taking up the plants it was found that the solutions of Nos. 3, 

 4, 5 and 12 were infected. The remaining ammonium solutions were 

 free from nitrites and nitrates as well as from nitrifying organisms. In 

 the following table are set out the amounts of dry produce, the nitrogen 

 in the produce and in the solutions of Nos, 1, 2, 7, 9, 10 and 11. 



Table III. Peas growing in Water Cultures. 



* Including any nitrogenous matter in suspension. 



The small amount of growth in No. 9 is due to the ftiiliire of the 

 original seedling ; the new plant was consequently a few days behind 



