EFFECT OF CULTUKE AND CLIMATE ON PEPPERMINT OIL. 13 



these factors upon the process of synthesis in the plant are usually 

 confined to the least stable constituents. 



The process of esterification is common to most aromatic plants 

 and is more or less affected by the conditions of temperature, light, 

 and moisture under which the plant grows. Among these factors 

 the effect of frost action upon the formation of aromatic compounds 

 in plants has perhaps received least attention, and whether it pro- 

 motes or retards the development of the odorous compounds in the 

 oil is not yet definitely known. Charabot, 1 in an investigation on 

 the' relation of esters to the chlorophyl in plants, states that the 

 effect of reduced temperature on the formation of esters is opposite 

 to that of either intense light or a dry atmosphere. Schimmel & 

 Co., 2 in a report on the oil distilled from frozen leaves of the 

 bergamot mint {Mentha citrata Ehrh.) grown in Florida, state that 

 the yield of oil did not differ materially from that of the unfrozen 

 plant, but that the physical and chemical properties disclosed marked 

 variations. The most striking difference was the large increase in 

 ester content (linalyl acetate) of the oil from the frozen leaves, the 

 oil from the unfrozen plants containing only one-third as much ester. 



In the course of some studies on the peppermint plant made at 

 Arlington Farm during the seasons of 1910 and 1911, advantage was 

 taken of the second crop, which came on late in the autumn, to col- 

 lect some data regarding the effect of frost action upon the new 

 growth of plants. These plants were from 12 to 18 inches tall, in an 

 early although fairly vigorous stage of growth, and bore an abundance 

 of leaves. After having been exposed to several heavy frosts the 

 plants were distilled and the oils subjected to a thorough examina- 

 tion. As a basis for comparison, plants unaffected by frost were 

 distilled each year. In 1910, plants from the first crop in an early 

 stage of growth, and consisting mainly of leaves with no buds, were 

 distilled on July 25. In 1911, plants from the second crop, which had 

 made a short growth after the harvesting of the first crop, were dis- 

 tilled on October 30. These plants consisted of leaves with a few 

 buds. Table VII gives the results of the examinations. 



An inspection of Table VII shows that the yield of oil from both 

 the frozen and unfrozen plants is practically the same, although it 

 is considerably lower than that from fully grown plants, the yield 

 from which is approximately double that here recorded. The oil 

 from the frozen plants had the more agreeable and flowery odor, 

 which may be attributed to the very high content of esters of menthol. 

 The cooling sensation resulting when the oil from the frozen plants 

 was applied to the tongue was noticeably greater than from that of 



1 Charabot, Eugene. Sur le role de la fonction chlorophyllienne dans Involution des composes terpS- 

 niques. In Compt. Rend. Aead. Sci. [Paris], t. 132, no. 3, p. 159-161. 1901. 



a Schimmel & Co. (Fritzsche Brothers). Semiannual Report, p. 14. Miltitz, London, New York, 

 Nov., 1908. 



