32 THE PKODUCTION OF VOLATILE OILS AND PERFUMEEY PLANTS. 



To picture more clearly the results of the experiments and the 

 changes observed in the oils, tabulations were made as follows : 



Table I. — Yield of oil and changes observed in plants at different stages of 



groicth. 



PErPERMINT (MENTHA PIPERITA). 



Stage of growth. 



Before flowering (July 22) 



At flowering time (August 21) . . 

 After flowering (September 25). 



Ester con- 

 tent as 



menthyl 

 acetate. 



I'er cent. I Per cent. 

 0. 23 9. .5 



.20 

 .10 



14. .5 

 24.0 



Alcohol 

 content as 

 free men- 

 thol. 



Per cent. 

 31.0 

 23.6 

 34.0 



BERGAMOT MINT (MENTHA CITRATA). 



Stage of growth. 



Before flowering (July 20) 



At flowering time (September22i 

 After flowering (October 14) 



Yield of 

 oil. 



Per cent. 

 0.32 

 .37 

 .22 



Ester con- 

 tent as 

 linalyl 

 acetate. 



Alcohol 



content as 



linalool, 



free. 



Percent. Psr cnt. 

 47.6 7.3 



5.5.0 7.3 



52.0 5.5 



WORMWOOD (ARTEMISIA ABSINTHIUM). 



Stage of growth. 



Before flowering (July 2) . . 

 At flowering time (July 14) 

 After flowering (August 4) 



Alcohol 



content as 



thujyl 



alcohol, 



free. 



Per cent. 

 14.7 

 n.7 

 12.0 



It is obvious from these results that in two cases, with peppermint 

 and with wormwood, the aromatic quality of the oil, if measured by 

 the percentage of esters, is increased gradually during each stage of 

 growth, the percentage of free alcohol remaining fairly constant. In 

 the peppermint the oil from the "after-flowering" stage was notice- 

 ably more fragrant than the oils from the two earlier stages. The 

 yield of oil remains fairh' constant up to the last stage, when there 

 is a marked diminution. The plant in the first two stages is very 

 much the same as regards moisture content, while the low percentage 

 of oil from the plant after flowering, when it possesses much less 

 succulency, may be attributed to the consumption of other constitu- 

 ents than the esters and alcohol. This applies to all of the plants 

 which seem to follow the same general course in this respect. 



The oils from the l:>ergamot mint disclose a verv slight decrease 

 in ester content and alcohol content in the " after-flowering " stage. 



195 



