No. 129.] 314 



liquid, and all that it contains, without selection'. The substances 

 thus conveyed to plants are retained in greater or less quantity, 

 or are entirely separated when not suited for assimilation." 



Decandolle supposes that the roots of plants imbibe soluble 

 matter of every kind from the soil, and thus necessarily absorb 

 a number of substances v/hich are not adapted to the purpose of 

 nutrition, and must be subsequently expelled by the roots, and 

 returned to the soil as excrements. Now, as excrements cannot 

 be assimilated by the plants which eject them, the more of these 

 matters the soil contains, the more unfertile must it be for the 

 plants of the same species. These excrementitious matters may, 

 however, still be capable of assimilation by other kinds of plants, 

 which would thus remove them from the soil, and render it again 

 fertile for the first. And if the plants last grown also expel sub- 

 stances from their roots which can be appropriated as good by 

 the farmer, they will improve the soil in two ways. 



The tobacco administration in France have used chemical 

 analysis as a test of the value of tobacco. They burn a portion, 

 and the relative quantity of potash found in the ashes decides the 

 relative value ; the greater the amount of potash, the better the 

 tobacco. 



[From the London Farmers' Magazine, June, ISaO.] 



How far it is possible to recover exhausted lands without manure. 

 By M. M. M. — There is not a better understood fact in agricul- 

 tural science than this ; that if we take off from a soil its ferti- 

 lizing qualities, and none are returned, it must by and by become 

 barren ; and not only is this true in its widest and most extreme 

 sense, but it is also equally true, that the more you take away 

 from a soil the elements of the growth of plants, the greater will 

 be the difficulty of obtaining the crop, and the smaller will be 

 the produce of that crop year after year. 



It is true, some soils will bear much more severe cropping than 

 others. Either there has been a greater per centage of the ele- 

 ments calculated to produce crops present in the soil at the com- 

 mencement, or there has been a much greater depth of soil with 

 the ordinary percentage, which Is in fact the same thieg ; and it 



