106 Agricultural Chemistry. 



Considerable knowledge has accumulated as to the status of 

 these ash constituents in the plant. Their functions, however, 

 are in many cases not clearly understood. 



Calcium has already been referred to as a constituent of salts 

 of organic acids. It occurs widely distributed in this form. Al- 

 though essential to the plant and apparently playing an impor- 

 tant part in the chemical changes of living cells, its specific func- 

 tion is unknown. In some cases it appears to be of advantage in 

 forming insoluble salts of organic acids, such as calcium oxalate. 

 thus preventing harmful accumulations of free acids in the plant 

 Loew is of the opinion that calcium-protein compounds exist in 

 the organized parts of plant cells, from which the nucleus and 

 the chlorophyll bodies are built up. He attributes the charac- 

 teristic poisonous action of soluble oxalates to their power of de- 

 priving these compounds of their calcium, converting it into the 

 insoluble oxalate. According to this view, calcium is partic- 

 ularly essential to the metabolic processes in plants. 



Magnesium exceeds calcium in the amount present in seeds 

 and, according to Loew, it is attended by phosphorus and favors 

 the assimilation of the latter body by retaining it in the form of 

 soluble compounds. In the same manner, its abundant supply 

 in the seed favors easy assimilation of the reserve phosphorus of 

 this organ by the seedling. 



Potassium is of common occurrence as a constituent of the salts 

 of organic acids. It has also been known for a long time that" 

 potassium is intimately connected with the formation of starch 

 and sugar by plants. It is uniformly abundant in the ash of 

 plants rich in these carbohydrates. The lodging of cereal grain 

 plants has been attributed to lack of potassium. This theory is 

 probably based upon the known stimulating effect of potassium 

 on the formation of cellulose and the simpler carbohydrates in 

 plant growth, since it has been shown that lodging is due in some 

 cases to lack of cellulose compounds in the cell walls of the plant. 

 Stoklasa has recently shown that potassium is a constituent of the 

 chlorophyll of grasses. This investigator states that it is more 



