Materials and Formulas. 165 



diluted a little. (2) Dissolve about 4 ounces of powder in 1 

 gill of alcohol, and add 12 gallons of water. 



" 6. Decoction. Whole flower-heads are treated to boiling 

 water, and the liquid is covered to prevent evaporation. Boiling 

 the liquid destroys its value. 



" 7. Water extract. Pour 2 quarts hot water through about 

 a half-pound of pyrethrum, held in a coarse bag, and then add 

 cold water enough to make 2 gallons, and it is well to stir in 

 the powder itself. For aphis and cabbage w r orms. It will keep 

 but a few days. Or the extract can be made as follows : Make 

 a paste of 2 tablespoon fuls of pyrethrum by adding water. 

 Stir this into 2 gallons of water, and apply with a tine nozzle. 

 This is recommended for the rose-chafer. 



"8. PyretJiro-kerosene emulsion. See under KEROSENE-PY- 

 RETHKUM EMULSION." 



The cost of pyrethrum varies from twenty to nearly seventy- 

 five cents per pound. 



QUASSIA. The wood of Plcnena (or Picrasma) excelsa con- 

 tains a principle which is fatal to many insects when brought in 

 contact with them. The wood has an extremely bitter taste, 

 and for this reason it has been supposed that seeds placed in 

 water in which the wood had been soaked would be protected 

 from birds and vermin. Its value for this purpose is, however, 

 doubtful. Quassia wood is generally sold after having been 

 cut into " chips," and it is commonly used as follows : 



Quassia chips 1 pound. 



Water 8 gallons. 



Boil until reduced to 6 gallons. 



Another formula has been recommended which is probably 

 more effective than the preceding : 



Quassia chips \ pound. 



Water 1 gallon. 



The chips are boiled in the water for about fifteen minutes ; 

 the liquid should then be strained, and to the solution is added 



Soft soap \ pound. 



When thoroughly mixed, the liquid is ready for use. This 

 insecticide is not very energetic, but possesses a certain value in 



