316 The Wohum Pot- Culture Experiments, 1910-11-12. 



In 1909 the experiments were continued on wheat with the 

 same salts but in lesser quantity, they supplying lithium at the 

 rate of '0018 per cent. only. Now for the first time the lithium 

 salts appeared to lose their toxic effect and to exercise in all 

 cases a slightly stimulating effect. This, indeed, reached, in 

 the case of the nitrate, a very high figure. Reference to tlie 

 published details (Journal R.A.S.E., 1910, pp. 344-5) will show 

 that the yields of corn were, with the chloride 119, the sulphate 

 115, the carbonate 115, and with the nitrate as much as 198, as 

 compared with 100 for the untreated crop, and those of straw 

 101*6, 101*1, 101, and 163, respectively, against 100 for the 

 untreated. Up to this point, accordingly, the general conclusion 

 was reached that lithium salts, if used to an extent not supplying 

 more than "002 parts of the metal lithium in 100 parts of the 

 soil, would exert a stimulating influence upon the wheat plant, 

 but that if the quantity of lithium went up to "003 per cent, 

 a toxic effect was produced. 



The striking increase recorded in 1909 from the use of 

 lithium nitrate pointed to the desirability of repeating this 

 experiment, and, as lithium phosphate had not been yet tried, 

 it was decided to employ it also in future work. 



From this date began an interesting series of experiments 

 which, commencing with the use of lithium salts in 1910, 

 gradually' extended to that of zinc salt and of lead salts, and 

 was continued throughout the three seasons 1910, 1911, 1912. 



To enable the reader to follow better the course of the 

 enquiry, it has been thought well to abandon the usual plan 

 of giving each season's work in detail, and to deal consecutively 

 with the story of experiment with each of the metals forming 

 the subject of enquiry. Accordingly, a summary having been 

 already given of the work with lithium salts up to 1909 

 (inclusive), the account is now continued for the years 1910, 

 1911 and 1912. 



1. Lithium phosphate. 1910. 



In 1910 a start was made with lithiuui phosphate on the 

 wheat plant, the first question calling for answer being whether 

 the metal lithium in this form would show the same toxic 

 influence as it did in other salts. The proportions of the salts 

 used were such as to provide respectively {a) '002 per cent., 

 (6) "005 per cent., (c) "01 per cent, of metallic lithium in the 

 soil. The lithium phosphate was intimately mixed with the 

 whole of the soil (40 lb.) filling a pot, and each experiment was 

 in duplicate. The salts were mixed with the soil on Decem- 

 ber 1, 1909, and the seed was sown on December 3. As com- 

 pared with the control experiment, there was no apparent 

 injury to germination, but the retardation in appearance of the 

 shoots amounted to three or four days where the heavier 



