VARIATION IN THE CHARACTER OF PLANTS. 151 



to cover these risks; and on the whole he will not feel safe 

 until he supplies to his fields at least as much as, and if 

 possible more than the crops draw from them, and not 

 only retain the original stock of fertility and accumulate 

 each year the contributions of the atmosphere/ but keep 

 adding to these, either by direct additions in the shape of 

 manures, or of green crops or other vegetable matter 

 plowed in, or procure some additional matter from the soil 

 through the agency of tillage. 



It is a frequent supposition that crops of different kinds 

 are constant and unchangeable in regard to their constitu- 

 ents and the quantities of the various elements they draw 

 from the soil. And while it has been stated as a rule, that 

 these drafts made upon the soil are in so great a measure 

 constant and regular that they are typical of the various 

 crops grown, yet within narrow limits; a certain variation 

 is found to exist which is the result of distinct differences 

 in soils. Every farmer has known in his own personal ex- 

 perience, or through the experience of others, that any par- 

 ticular crop, as wheat, varies in character according to the 

 nature of the soil. That upon soils of a silicious or sandy 

 character with an abundance of lime in it, the wheat has a 

 bright clean thin husk and a stiff bright clean straw, while 

 upon other soils containing a large quantity of organic 

 matter and being deficient in silica and lime, the grain has 

 a soft thick husk, a very weak chaff, and straw that is not 

 able to bear the weight of the ear and lodges very easily. 

 Similar differences have been experienced in regard to 

 other crops; oats; barley and potatoes; and even with for- 

 est trees and many other plants and their fruits. Wheat 

 straw has been known to vary so much in this respect that 

 various samples of 100 Ibs. of it grown upon different soils, 

 have contained 3i Ibs. ; 4i Ibs. 6 Ibs. 15i Ibs. and 16* Ibs. 

 of ash, varying with each particular soil. Where the ash 

 was the heaviest the soil consisted of a limestone gravel; 

 while the straw with the' lightest ash was on reclaimed 

 swamp land. 



The same variations are well known, to occur on the same 



