NUTRITION IN THE LOWER PLANTS 79 



of disease, and second, its prevention. The preventive measures 

 may all be summed up under the term prophylaxis and are similar 

 in their methods whether one is a physician, a veterinarian, or a 

 plant pathologist. Seven methods of preventing disease are in 

 common practice and may be briefly described: 



1. Personal hygiene. By this is meant cleanliness and the or- 

 dinary methods employed to keep the organisms of disease from 

 multiplying or finding refuge on the person. With plants the 

 common method of washing is spraying, in which the plants are 

 covered with a solution of chemicals which prohibits the growth 

 of microorganisms and at the same time does not hinder the 

 development of the plant sprayed. Various sprays are applied 

 differing with the disease to be warded off, the species of plant, as 

 well as with the condition of the plant at the spraying season. A 

 plant in full blossom will require different treatment from one 

 bearing leaves or one with only the bare stems exposed. 



2. Public hygiene or sanitation. In the combat against human 

 diseases, the maintenance of a pure water supply, of proper 

 drainage, of pure air, etc., are included under sanitation. Similarly 

 with plants, pure air must be maintained and not air full of smelter 

 smoke with its contained toxins. Pure air for a plant is air with 

 a plentiful supply of carbon dioxide but free from carbon monoxide, 

 sulphur fumes, and other poisonous gases. It is the business of the 

 sanitation or public health official to see that infected areas are 

 disinfected as soon as the disease has been checked. Similarly 

 the plant pathologist attends to the burning of diseased plants 

 and takes all measures possible to stop the further spread of the 

 disease. The maintenance of a good water supply, of proper drain- 

 age, etc., are all included in the work of the plant sanitary engineer. 



3. Quarantine. Just as a man who is infected with a dangerous 

 communicable disease is isolated by measures of quarantine, so are 

 quarantine stations provided by the U. S. Department of Agricul- 

 ture and by the State governments to prohibit the entrance and 

 spread of plants with communicable diseases. The " influenza/ ' 

 which caused more deaths throughout the world in a given length 

 of time than any disease in recent times, was imported from Europe 

 in the summer of 1918. In like manner many of our worst plant 

 diseases have been imported from foreign lands because of an 

 ineffective quarantine. The rice smut came to South Carolina 

 from Japan in 1898. The chrysanthemum rust came from Japan to 



