HEVIBW AN1> CONCLUSION. 375 



hythe soil converted into, and retained In, a condition not 

 of absolute, bxt <>f relative insolubility, and are kept avail- 

 able to the plant by the continual circulation in the soil 

 of the more abundunt saline matters. 



" Tlie soil (spt'uking in the widest sense) is then not only 

 tlie ultimate exhaustless source of mineral (fixed) food, 

 to vegetation, hut it is the storehouse and conservatory 

 of this food, protecting its own resources from waste and 

 from too rapid use, and converting the highly soluble 

 matters of animal exuviae as well as of artificial refuse 

 (manures) into permanent supplies."* 



By absorption as well as by nitrification the soil acts 

 therefore to prepare the food of the plant, and to present 

 it in due kind and quantity. 



* The author quotes here the concluding paragraphs of an article by him " On 

 Some points of Agricultural Science," from the A?nerican Journal of Science and 

 Arts, May. IRj-:). (p. 85). which have historic interest in being, so far as he is 

 aware, the earliest, broad and accurate generalization on record, of the facts of 

 soil-absorption. 



NOTICE TO TEACHERS. 



At the Author's request, Mr. Louis Stadtmuller, of New Haven, 

 Conn., will undertake to furnish collections of the minerals and rocks 

 which chiefly compose soils (see pp. 108-122), suitable for study and 

 illustration, as also the apparatus and materials needful for the chemieal 

 experiments described iu "How Crops Grow.^' 



TOOPERTY OF 



X'&M.C0llE6EUBIWRY. 



