326 The Wohurii Pot-Culture Expei'iments^ 1910-11-12. 



magnesia in soils, and the beai-ing of one on the other. There 

 has, however, been no detailed account published as yet in this 

 Journal, though the work has been made familiar to visitors at 

 the country Shows of the Society. It was at Lincoln in 1907 

 that the first exhil)it on this subject was made, this comprising 

 the produce of wheat grown in 190G, with illustrations of the 

 growing crop and the roots of the several wheat plants. 



As, however, these have not as yet been published, they are 

 now set out in Plates 9 and 10. The soil used in these experi- 

 ments was the ordinary Wol)urn soil containing lime '-lO per 

 cent., magnesia "20 per cent. 



In 1906, while the amount of lime was kept at the same 

 figure (40 per cent.), magnesia was gradually added so as to 

 give respectively (J) •2(S per cent. ; {c) "SS per cent. : {d) '50 

 per cent. 



The harvest results were : — 



These figures show that there was an increase of yield as 

 magnesia was added, so long as the magnesia did not exceed 

 the lime present, but that as soon as the ratio 1 : 1 (lime to 

 magnesia) was exceeded, a falling oft" took place. 



In Plate 10 are given the appearances of the roots of plants 

 taken from the respective sets. The diff"erences in these, as 

 well as the increase of nitrogen in the grain, as more magnesia 

 was added, will be referred to later. 



In 1907 the experiment was repeated with some modifi- 

 cation, for, while one " untreated " set was kept to, in the other 

 cases the quantity of lime was doubled, with the object of 

 seeing whether similar conclusions to those of 1906 could be 

 drawn when lime was present in greater amount. Accordingly, 

 while (a) remained the natural or " untreated " soil with lime 

 in excess of magnesia (ratio 2 : 1), in the other sets lime was 

 added to bring the amount of lime up to '80 per cent. Mag- 

 nesia was then added so as to bring up the amounts of magnesia 



