lO 



sulfuric acid (0.01550) being titrated back with potassium hydroxide 

 0.02130 with sodium ahzarin sulfonate as the indicator. Results are 

 given in Table VI. 



Table VI. — Free Ammonia in Plant Saps.* 



The white spots on the leaves of plants treated with ammonium sulfate, 

 and of crystals imbedded beneath the epidermis of the sepals were studied 

 by microchemical methods.* 



1. January 21, 19 14. Plant Number 4, Section 281, White Enchantress. 

 Plant apparently normal. A drop of. sap from the stem of a shoot was 

 treated with a drop of ammonia-free hydrochloric acid and chloroplatinic 

 acid, and evaporated at room temperature under a loosely covering watch- 

 glass. A few crystal masses, tetrahedral and often aggregated in shape 

 of a cross, appeared. They were yellow in color. Sap from Number 8, 

 somewhat injured, and Number 12, badly affected, gave these characteristic 

 crystals, also. 



2. A section of the leaf showing white blotches was immersed in chloro- 

 platinic acid after removal of the epidermis and allowed to remain over- 

 night. Large and perfect crystals appeared, arranged usually around 

 the injured spot, never in it. They were insoluble in 95% alcohol which 

 removed the excess of chloroplatinic acid. 



3. A drop of sap from plant Number 4, Section 281 was distilled with a 

 pinch of sodium carbonate over a micro-burner and the distillate caught 

 in a hanging drop of hydrochloric acid in a cover glass placed on a glass 

 ring above it. Treatment as above gave small, yellow tetrahedra in- 

 soluble in 95% alcohol. 



Ammonium salts were evidently present and apparently caused plas-' 

 molysis of certain of the chlorophyll bearing cells. Why injury of this 

 type is caused by ammonium sulfate in contrast to the even lightening 

 of the color of the whole leaf by the other soluble salts, sodium nitrate 

 and sodium chloride, is not known. 



Nitrate determinations according to the phenolsulfonic method of 

 Mason^^ were made upon the sap of a "check" and an ammonium sulfate 

 fed plant from the set of March 9, 19 15. The values of o.oi and 0.40 

 mg. N as nitrate per cc. of sap, respectively, showed that nitrification was 

 proceeding in the soil although it was quite strongly acid."^^ 



* In earlier stages of feeding with ammonium sulfate, samples have been taken in 

 which no NHj was detected by this method. 



