520 Journal of Agricultural Research voi.x. No. lo 



buried in the powder; after a few moments they invariably came to the 

 surface and crawled away from the powder without apparently being 

 affected. 



This powder is made from quassia chips finely ground. It has a very 

 faint odor, but while handling it a person does not experience a bitter 

 taste as he does while working with quassiin powder. The minutest 

 particles of the powder are no larger than those of the quassiin powder, 

 but the largest particles are considerably larger than those of the 

 quassiin powder. While the particles of the quassiin powder adhere 

 to one another considerably, those of the quassia powder do not. 



(c) Effects of Water Extract of Quassiin Powder 



A strong extract was secured by boiling for two hours 200 c. c. of 

 water containing i gm. of the quassiin powder. When the mixture was 

 filtered, the filtrate was not quite as clear as water; it emitted a very 

 faint odor and had a bitter taste. When applied with an atomizer it 

 seems that some of the fine spray carried by the air must have passed 

 into the operator's mouth, because a bitter taste was always experienced 

 whenever this solution was used as a spray. 



To determine whether the exhalations or vapor from the preceding 

 solution is alone sufficient to kill aphids, a 75-c. c. beaker was filled with 

 this spray mixture. A wire screen was then laid over the liquid and a 

 nasturtium leaf bearing many aphids was placed upon the wire screen so 

 that the insects were near the liquid, but not in contact with it. Not 

 one of the aphids apparently was affected. 



To ascertain whether the quassiin contained in the preceding solution 

 is volatile when heated, 50 c. c. of the solution were poured into a loo-c. c. 

 retort and heated. It was found that the steam produced by heating 

 the solution had no apparent effect upon the aphids (Aphis rumicis and 

 Macrosiphum liriodendri) tested. The steam was odorless, and, when 

 condensed, the resultant liquid was as clear as water. It was tasteless 

 and lead acetate did not precipitate it, while the same compound slightly 

 precipitated the quassiin solution. It is thus seen that the quassiin 

 contained in the solution is nonvolatile, and therefore such solutions 

 can not be used for fumigating purposes. Furthermore, it follows that 

 the vapors arising from quassia extract solutions do not carry quassiin. 



At 9 a. m. 508 aphids upon tulip-tree leaves were sprayed with quassiin 

 solution. At 12 noon only a few of the aphids were dead, at 4 p. m. 90 

 per cent were dead, and the following morning all were dead. It was 

 noted that a faint odor was emitted by the spray solution upon the 

 leaves, and even when the leaves became dry a very faint odor resembling 

 that of the quassiin solution was still given off. 



On account of the long time required for the quassiin to kill the aphids, 

 it is probable that this insecticide acted as a stomach poison. The spray 

 solution might have passed through the stomata and epidermis of the 



