MANURE, YIELD AND SOLUBLK SALTS IN SOILS. 57 



be recovered by the treatment with water, relatively less of both 

 lime and magnesia than did those growing upon the unmanured 

 ground and which produced the smallest final yields. 



If reference is made to the general table it will be seen that, 

 for the corn, there are no exceptions to this statement among 

 the individual data ; that there is but one exception among the 

 potatoes with magnesia ; but that there are three exceptions 

 with lime, one of which is percentagely large. 



The observed relations of the three bases determined in the 

 studies and here referred to, cannot be ascribed to a differential 

 effect of the soils upon them, the manure holding these salts 

 back, for it has been shown that more of all three bases existed 

 in the manured soils in a form which could be recovered by 

 washing in distilled water. The relations of limel and mag- 

 nesia are, however, such as might be expected if the views of 

 Loew* regarding the functions and movements of limei and 

 magnesia in living tissues are correct. We refer specially to 

 the statement, p. 56, that, "as a matter of fact, it is found that 

 magnesia always increases where rapid development is taking 

 place," and that "the calcium content increases with the mass 

 of nuclear substance and chlorophyll bodies." If these state- 

 ments are correct, and if the lime and magnesia thus accumu- 

 lated become insoluble, or are otherwise held back from the solu- 

 tion, then there should be observed a greater reduction of the 

 soluble lime and magnesia in the plant sap where the most vig- 

 orous growth is taking place. It is, of course, recognized that 

 observations of this character are suggestive rather than demon- 

 strative. Attention should also be called to the fact that the 

 amounts in the table are relative to the dry matter and not 

 absolute. 



*United States Department of Agriculture, Bureau of Plant Industry, Bulletin 

 No. 45. 



