The Woburn Pot- Culture Experiments, 1910-11-12. 315 



which has been collected concerning these being now in a 

 condition to set forth consecutively, it is the aim of the present 

 note io do this. 



The first experiment was made in 18'.*8 with lithium 

 chloride ; this was repeated in 1900 ; in 1901 the oxide, 

 carbonate and siilphate were also tried ; in 1903 the oxide 

 and the iodide. In tlie first three of these cases the salts were 

 dissolved and pour.^d on the surface of the soil ; in 1903 they 

 were mixed with the top layer of soil. The quantities, beginning 

 at the rate of 5 cwt. per acre of the salts, were reduced in the 

 successive experiments to 2 cwt., 1 cwt., and h cwt. per acre ; 

 they were tried principally on wheat and barley, but also on 

 mustard, peas, and clover. Further work was done in water- 

 culture and in seed-soaking experiments. The general result 

 of these trials (for the details of which see Journals R.A.S.E., 

 1900, 1901, 1902, 1904) was to show that all lithium salts 

 applied in the above quantities either killed the crops outright, 

 or else prolonged the period of incubation and ultimately 

 produced a decreased crop. 



In 1906 more systematic experiments v\ere begun, and were 

 confined to wheat and barley, the lithium salts being no longer 

 given in solution, or mixed merely with the surface soil, but 

 they were given so as to supply to the soil definite amounts of 

 the metal lithium. For this pm-pose the salts were incorpor- 

 ated, by intimate mixing, with the whole of the soil used, so 

 that the soil could be fairly represented as one containing a 

 definite proportion of the metal. This method has, l)y experi- 

 ence, been found to be much more satisfactory than that of 

 dissolving the salts and pouring them on the surface, or even 

 that of mixing them with the top soil, inasmuch as there can 

 be no doubt that the germinating seed or the young plant 

 comes at times into contact with the salts in stronger concen- 

 tration than intended, whereas when the salts are intimately 

 m.ixed with the soil their distribution is more equal throughout. 

 It is unnecessary to deal in detail with the earlier work of this 

 new series. Suffice it to say that the endeavour was made to 

 reach the point at which the metal, as represented by its 

 different salts, might cease to produce a toxic effect. In 1906, 

 lithium salts (chloride, sulphate, carbonate, and nitrate) were 

 used supplying "Oo per cent, of the metal to the soil used ; in 

 1907, -007.5 per cent., and in 1908, -00375 per cent, only (see 

 Journal R.A.S.E., 1909, page 388). In all these cases lithium 

 showed a marked prolonging of the period of incubation, the 

 plants as they grew became more or less sickly, and ultimately 

 a lessened crop was produced. Up to this point one could 

 therefore say that lithium when present in the soil to the 

 extent of -00375 per cent, exercised a distinctly toxic effect. 



