10 GROWTH OF WHEAT SEEDLINGS. 



of 82 parts per million of sulphate in solution. This solution showed 

 on analysis 29.4 parts per million of sulphuric acid, an amount more 

 than twice as large as that originally present in solution 11, thus 

 again showing the extent to which the selective action of roots for 

 one radical of a salt may be carried. Leclerc du Sablon 1 put forth 

 the theory that such useful ions as potassium (K) , phosphorus (PO 4 ) , 

 nitrogen (NO 3 ), and iodin (I) combine with the organic substance of 

 the plant, thus relieving the osmotic pressure within the plant and 

 permitting a still larger quantity of these ions to be absorbed. On 

 the other hand, such ions as chlorin (Cl) and sodium (Na) do not 

 form this organic combination, the result being that the pressure 

 inside the plant soon equals that outside, and the plant is, therefore, 

 satisfied with a relatively small amount of then}. 



Of the 10 parts per million of sulphuric acid present in solution 

 11, all but 4.9 parts per million disappeared. The appearance of 

 the plant roots in the potassium sulphate solution was even worse 

 than that of those grown in potassium chlorid. Maze 2 obtained 

 results which may be similarly interpreted in his experiments in 

 growing corn in water cultures. He found that when ammonium 

 sulphate was used the crop was not so well developed as when am- 

 monium chlorid was applied. Calcium carbonate overcame the in- 

 jurious effects in these as in the preceding cultures, thus again show- 

 ing how beneficial it is to the crop to maintain the alkalinity of the 

 culture medium. 



The effect of sodium nitrate and potassium sulphate separately and 

 in combination. In Plate II, figure >, are shown the cultures of sodium 

 nitrate (alkaline reacting), potassium sulphate (acid reacting), and a 

 mixture of the two. The mixture was prepared so as to become alka- 

 line and produce good plants, and it did so. In this case the nitrate of 

 the sodium nitrate and the potassium of the potassium sulphate were 

 drawn up into the plant, while the sodium left in solution from the 

 sodium nitrate combined with the sulphate from the potassium sul- 

 phate to form sodium sulphate, with a sufficient excess of sodium to 

 make the solution alkaline. 



Discussion of data obtained on the first crop. All of the culture 

 solutions to which no sulphate was added ; that is, the sodium nitrate, 

 the hydrochloric acid, and the distilled water cultures, contained a 

 small amount of SO 4 , due probably to its excretion from the seed. 

 In solutions 7 and 8, however, containing 150 parts per million of 

 potassium sulphate, the amounts of SO 4 were noticeably large, 57 out 

 of the 87 parts per million being found in the solution. This was 

 about 6 times more than was found in the sulphate-free solutions 

 and would seem to indicate that the plant at this stage does not 



1 Engagement d'eau par les plantes, Rev. gen. Bot., 1909, 21: 295. 

 2 Compt. rend., 1911, 152:783. 



