12 



From this and other evidence of like purport it seems unquestion- 

 able that injury to the seed was due to local circumstances; and as oil 

 of lemon is known to be of varying quality and in this case was ob- 

 tained from different sources, it was at first surmised that differences 

 in the quality of the oil caused these differences in the result of its 

 application. In this connection the following statement in a letter 

 dated July 10, 1907, from J. M. Francis, of the well-known firm of 

 Parke, Davis & Co., druggists, of Detroit, Mich., will be of interest. 



"I have consulted all of the authorities available and have also 

 looked up the data which we have accumulated in our own laboratory 

 as the result of examining quite a large number of samples of this 

 [lemon] oil. and it appears that the substance generally used for the 

 adulteration of oil of lemon is the terpene oil which results from the 

 manufacture of the terpeneless oil of lemon. 



"You understand, of course, that the oils of orange and lemon, 

 and in fact all of the similar oils, contain greater or less quantities of 

 terpenes which are very similar to ordinary oil of turpentine, and 

 which give to these oils a peculiar disagreeable turpentine odor when 

 they undergo an oxidizing process through age. In order to avoid this 

 objectionable change in odor, and also to render the oils more freely 

 soluble in water, many firms extract the desired flavoring principle from 

 the oil of lemon or orange, leaving these terpenes behind as a by- 

 product. It is very natural that oil dealers should desire to cheapen 

 their oil of lemon by using these terpenes, as they are normal constitu- 

 ents of the oil. It appears that ordinary turpentine is sometimes used 

 as a diluent." 



From these statements T was disposed to surmise that an excess 

 of terpenes in the Bloomington sample might have been the cause of 

 the injury to seed-corn in the McLean county field of the canning com- 

 pany, and this supposition was tested Ijy several series of experiments 

 made by one of my assistants, John J. Davis. 



TESTS OF LEMON OILS AND TERPENES 



These experiments were in three series of pot-plantings, each 

 made with fifty kernels of corn, and handled as nearly as practicable in 

 an identical manner. Each variation of the treatment included two 

 hundred kernels planted in four pots ; but as the results in the dift'erent 

 sets dift'er from each other, generally speaking, less than the results 

 from the different pots of the same set, it is unnecessary to give de- 

 tails by sets of four, and the product of the experiments may be re- 

 ported in much more general terms. 



