12 The Horticidturis? s Rule- Book. 



Oil and alkali wash, continued. 



and purity. Whichever one is chosen, add to each amount 

 named ^ pound of commercial potash and dissolve in 6 

 gallons of water. 



Both washes are for scale insects on deciduous trees in 

 winter. (Californian.) 



Paraffine oil. When plants are infested with lice, water 

 them at intervals of three or four days for about three 

 weeks with diluted paraffine in the proportion of a wine- 

 glassful to watering can of water. 



Paris green. See Arsenites. 



Plaster and kerosene. 2 quarts of plaster or wood ashes, 

 i tablespoonful of kerosene. Mix and rub with the hands 

 until the oil is well incorporated. Bone-flour may be sub- 

 stituted for the plaster. 



Promoting growth. Any course that tends to promote 

 vigor will be helpful in enabling plants to withstand the 

 attacks of plant lice and other insects. 



Pyrethrum. A very fine and light brown powder made 

 from the flower heads of species of pyrethrum. It is 

 scarcely injurious to man. Three brands are upon the 

 market : 



PERSIAN INSECT POWDER, made from the heads of Pyrethrum 

 roseum, a species now cultivated as an ornamental plant. 

 The plant is native to the Caucasus region. 

 DALMATIAN INSECT POWDER, made from Pyrethrum cinera- 

 ria; folium. 



BUHACH, made in California from cultivated plants of P. 

 cineraria folium. 



When fresh and pure, all these brands appear to be 

 equally valuable, but the home-grown product is usually 

 considered most reliable. Pyrethrum soon loses its value 

 when exposed to the air. It is used in various ways : 



1. In solution in water, i ounce to 3 gallons. 



2. Dry, without dilution. 



