ORIGIN AND COMPOSITION OF SOILS 29 



be properly carried to every part of the animal 

 body. 



Titanium is apparently of no importance in 

 plant nutrition, but its occurrence in many soils 

 requires notice. It has been found to be one of 

 the most widely distributed elements. 



Manganese, next to iron, is the most abundant 

 of the heavy metals. It occurs in nature in com- 

 bination with oxygen, in which form it is associ- 

 ated in minute quantities with iron in igneous 

 rocks or in the forms known mineralogically as 

 pyrolusite, psilomelane and wad. As the peroxide 

 of manganese it occurs in concretionary forms 

 scattered abundantly over the bottom of the deep 

 sea. It is found in the ash of some plants, but is 

 not believed to be essential to plant growth. 



Chromium in so far as known takes no part in 

 plant nutrition and its occurrence in the soil is 

 only of importance from an analytical and color 

 standpoint. 



Barium occurs in nature combined with sul- 

 phuric acid, forming the mineral barite, or heavy 

 spar, or with carbon dioxide forming the mineral 

 witherite. It is of small importance from an 

 agricultural standpoint. 



