INSECTICIDES. 355 



If the extract is to be extensively used, it will pay 

 to put in a specially arranged tank and piping for the 

 purpose. This consists of a galvanized iron tank, in 

 which a quart of the extract is placed for 8,000 feet of 

 glass. The steam supply pipe enters at the top and 

 extends iiearly to the bottom. Prom this tank, the 

 vapor is carried in pipes to the various houses, where 

 there should be a vent every twenty-five feet. The size 

 of the pipes should vary from one inch to one and one- 

 half inches or larger, according to the amount to be 

 treated. The pipes leading from the tank should have 

 a downward slope, so that any condensed liquid will not 

 collect. To prevent injury to the plants, the pipes 

 should be carried in the walks or under the benches, and 

 at each outlet there should be an ell and a valve, the 

 former to turn the steam horizontally so that it will not 

 reach the plants, and ithe valve to regulate and control 

 the escape of the vapor. The piping and tank should 

 be provided with drip cocks wherever necessary, and 

 such valves as will be required to control the steam, and 

 to permit the washing out of the tank and pipes. 



As compared with tobacco stems, dust or tea, the 

 concentrated extract, the one most commonly used being 

 the "Eose leaf," is clean, easily and quickly applied 

 and it has but little odor. For a house 200 by twenty 

 feet, the cost is about twenty cents. 



Aside from throwing the tobacco dust over the 

 plants, it may be placed over an oil stove. The fumes 

 should be slowly driven off, but the flame should be so 

 regulated that it does not take fire. The burning of a 

 pound of tobacco upon stoves, thirty feet apart in a 

 bonse, will be effectual. 



HOT WATER, 



Especially for house plants, hot water forms a sim- 

 ple and effectual remedy, as nearly all insects are killed 



