344 SALT, NITRATE OF SODA, SALTS OF AMMONIA, ETC. 



enormous increase in the weight of the stems, and a not 

 inconsiderable one in the weight of the leaves, we find no 

 increase of flowers, and consequently also none of seed 

 (Pincus). These most carefully conducted experiments 

 confirm the general rule, that wherever external causes 

 favoirr the developement of some organs, it can only be 

 effected under hke conditions of the soil, at the expense 

 of other organs, and that in the case of clover, as in that 

 of the cereals, increase of straw is attended with decrease 

 of seed. (For further details of these experiments, see 

 Appendix J.) 



As the substitution of magnesia for lime, in the experi- 

 ments now described, led to an increase of the clover crop, 

 it may be safely assumed that in cases where gypsum is 

 found to be favourable to the growth of clover, the cause 

 must not be sought for in the hme, although it is very 

 often found that many fields ^\all grow clover only after a 

 copious dressing with hydrate of lime. For we know 

 also that gy[3sum promotes the growth of clover on many 

 fields naturally abundant in hme ; and since arable soil 

 has the property of absorbing ammonia from the air and 

 rain-water, and fixing it in the same or even a higher 

 degree than salts of hme, there is only the sulphuric acid 

 left to look to for an explanation of the favouivable action 

 of gypsum upon the growth of clover. 



But the experiments of Pincus clearly demonstrate that 

 the crops obtained by manuring with the sulphates bear 

 no proportion whatever to the quantity of sulphuric acid 

 supplied in them to the field. 



The quantities of sulphuric acid severally contained in 

 the two sulphates used were 30T2 lbs. in the sulphate of 

 magnesia, and 44T8 lbs. in the sulphate of hme, which is 

 as 6 : 8-8. The quantities of sulphuric acid in the two 

 crops obtamed severally by sulphate of lime and sulphate 



