ECONOMIC IMPORTANCE OF PUNGI 311 



portant and effective. The most effective prophylactic 

 measures are the following : 



1. Personal hygiene, involving bodily cleanliness, tem- 

 perate habits, and careful diet. With plant diseases 

 hygienic measures include such practices as sterilizing 

 seeds before planting, by rinsing them in solutions of 

 some germ-killing substance, like formaldehyde; spray- 

 ing diseased trees vn'th fungicides (fungus-killing solu- 

 tions) ; washing the branches and foliage with various solu- 

 tions, such as whale-oil soap (good for scale insects) ; and 

 painting the cut surfaces of trees, after trimming, to 

 prevent the mycelium of germinating fungus spores from 

 entering the woody tissue. 



2. Public hygiene, or sanitation, which means maintain- 

 ing healthful surroundings. In the case of animal dis- 

 eases this includes preserving a pure public water supply, 

 proper sewage systems, clean streets, a pure milk supply 

 (especially a healthful condition of the cows and their 

 surroundings), and a careful inspection of meat and all 

 other foods shipped and sold in pubHc. 



In the case of plants, sanitation includes preserving 

 a proper drainage and aeration of the soil; maintaining a 

 pure atmosphere, and especially one free from smoke and 

 the poisonous gases that accompany it; fumigating in 

 plant houses with potassium cyanide fumes, or with to- 

 bacco smoke to kill scale insects, and other insects, the 

 burning up of trees or other plants infected with a trans- 

 missible disease, such for example, as the chestnut bark 

 disease, or barberry bushes carrying wheat rust, and 

 eradication of injurious furigi from the soil of cultivated 

 fields by crop-rotation, as indicated in Chapter VII. 



3. Quarantine. This is a method of sanitation by which 



