22 



The injuries characteristic of an excess of each fertilizer are recorded 

 from observations made in the greenhouse. 



Determinations of dry weight and ash made upon the foHage of the 

 plants, showed an increase in both values with increased applications of 

 the fertilizers. 



A sufficient number of determinations of the mineral constituents of 

 the foliage was made to show the increased content of the fertilizing salts 

 in the plants after large applications of them to the soil. 



Total nitrogen determinations made upon plants in different stages of 

 injury showed an increased intake of nitrogen when ammonium sulfate 

 was applied but an acquired tolerance by the plant when successive small 

 applications were made. Injury from ammonium sulfate is not propor- 

 tional to the total nitrogen content. 



The sap was expressed from the stems of the plants after freezing to 

 render the plasma membrane permeable to the contents of the cells. 

 Osmotic pressure determinations made upon this sap proved that with each 

 fertilizer used the degree of injury varied with the osmotic pressure, 

 but that not the same degree of injury was caused by different fertilizers 

 at the same osmotic pressure. Injury is not a result of increased osmotic 

 pressure exclusively. 



The increase in the osmotic pressure in a series of plants on soil receiv- 

 ing increasing applications of commercial fertilizers was accompanied by an 

 increase in the total solids and ash of the sap and in the amount of the 

 fertilizer taken up by the plant. 



Determinations of total acidity showed an increase in the total acidity 

 of the sap of plants fed with ammonium sulfate, disodium phosphate and 

 monocalcium phosphate, when phenolphthalein was used as the indica- 

 tor. 



The relation between the increase in total acidity and in the phosphorus 

 content of the sap when the plants were fed with disodium phosphate 

 proved that the phosphorus was taken in the form of dihydrogen phos- 

 phate, due, as was shown, not entirely at least to absorption of the base 

 by the soil but to the selective action of the plant. Applications of potas- 

 sium sulfate had no effect upon the acidity of the sap. 



The sap from the stems of plants grown on soil to which large applica- 

 tions of potassium sulfate had been made showed a higher total sugar 

 content, the same results being obtained with extracts of foliage. The 

 starch content of the foliage of such plants was lower. These data indi- 

 cate a more rapid hydrolysis of the starch in the foliage in the presence of 

 an excess of potassium sulfate. The increased exudation of nectar in the 

 flowers of these plants probably resulted from this increase in sugar con- 

 tent. 



