16 BULLETIN" 454, IT. S. DEPARTMENT OF AGRICULTURE. 



The percentage of esters in the oils increases as the plants approach 

 maturity. The menthol content of the oil bears a close relationship 

 to the ester content. The free acidity and ester content of the oil 

 distilled from dry plants is considerably higher than in the oil from 

 fresh plants. The drying of the plants causes changes favorable to 

 esterification, while the percentage of free and total menthol in oils 

 distilled from dried plants is also uniformly high. 



The formation of esters and menthol takes place most readily in 

 the leaves and tops of the plant, the metabolic processes showing 

 increased activity as the plant matures. 



The effect of shade upon the peppermint plant is to decrease 

 esterification and the formation of menthol, and is due possibly to 

 the lessened activity of the elimination of water by the plant. 



The action of frost noticeably increases esterification and the 

 formation of menthol. 



ADDITIONAL COPIES 



OF THIS PUBLICATION MAT BE PEOCXTEED FROM 



THE SUPERINTENDENT OF DOCUMENTS 



GOVERNMENT PRINTING OFFICE 



WASHINGTON, D. C. 



AT 



5 CENTS PER COPY 



w 



WASHINGTON : GOVERNMENT FEINTING OFFICEi : 1916 



