512 Journal of Agricultural Research voi. x, no. io 



with lye solution seems to destroy the insecticidal value of the extract 

 obtained, lye probably causing decomposition of the quassiin. There 

 seems to be no difference in effectiveness between the unboiled soap- 

 solution and the lye-solution extracts; but the soap-solution extract 

 obtained by boiling the powder for two hours appears to be the most 

 effective of the extracts obtained from this powder. It is thus seen 

 that the addition of lye and soap to the water materially increases the 

 effectiveness of the extracts obtained, while the addition of sodium 

 carbonate to the water only slightly increases the effectiveness of the 

 extract obtained. These results agree with those of the quantitative 

 determinations recorded in Table V, with the exception that the effec- 

 tiveness of the extract obtained by the sodium-carbonate solution does 

 not correspond to the quantity of extract removed by this solvent. 



(b) Experiments with Quassia Chips 



According to the results of the quantitative determinations (Table III), 

 it was found that the greater the comminution of the quassia material the 

 larger is the quantity of extract capable of being removed. Hence, ex- 

 tracts obtained from quassia powder should be more efficient than those 

 from quassia chips. In the preliminary experiments with aphids, it was 

 ascertained that the former extracts were little, if any, more eflficient than 

 the latter extracts. This may be due to two reasons : (i) Since these ex- 

 periments were performed with such a small number of aphids, the differ- 

 ence in efficiency was not noticeable; and (2) the powder and chips were 

 not from the same identical tree, and probably not from trees of the same 

 species. Since quassia powder will in all probability never be used to 

 any great extent in practical spraying, owing to the expense involved in 

 pulverizing the chips, it will be omitted from the following discussions, 

 and only those results pertaining to the extracts from quassia chips will 

 be briefly described. In all of the following experiments only tulip-tree 

 aphids were used, and for the sake of brevity only the first experiment is 

 briefly stated, and all of them are then summarized in Table VII. 



(l) WATER AS A SOLVENT 



Experiment 13. — Twenty-five gm. of chips were macerated in 350 c. c. of water 

 for one-half hour; this process was repeated four times in i, 3, 10, and 48 hour periods. 

 With the extracts thus obtained the length of time required to kill the aphids tested 

 varied from four to eight hours (see Table VII). 



Reference to Table VII shows that the summary of the results of these 

 experiments agrees closely with that of the results of the experiments 

 recorded in Table VI, which deals with quassiin. Briefly stated, the 

 similarity of these two summaries is as follows : The addition of lye and 

 soap to the water greatly increases the effectiveness of the extracts ob- 

 tained, while the effectiveness of the extract dissolved by the sodium- 

 carbonate solution is only slightly better than that of the water extract. 



