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STRUCTURE AND LIFE HISTORIES 



diseased individuals are prevented by isolation from com- 

 ing into contact with those who are well. When one 

 member of the family is sick with a contagious disease he 



Fig. 227. — Map, illustrating the inter-continental migration of plant 

 diseases. No. i, potato blight: Chili-Colorado-Europe. No. 2, asparagus 

 rust: Europe, 1805; New Jersey, 1896; South Carolina, 1897; Michigan, 

 1898; Illinois, 1899; Dakota, Nebraska and Texas, 1900; California, 1901. 

 No. 3, potato cercosporose: Europe, 1854; United States, 1903. No. 4, 

 rice smut: Japan-South Carolina, 1898. No. 5, sorghum smut: Japan- 

 United States, 1884. No. 6, grape anthracnose: Europe- America, 1880, 

 or earlier, now widespread. No. 7, cucumber downy mildew: Cuba, 1868; 

 United States, 1889. No. 8, grape black rot: N)rth America, early; 

 France, 1885; Italy and the Caucasus, 1898. No. 9, potato vvart: Hun- 

 gary, 1896; England, 1900; Newfoundland, 1909; Boston and New York, 

 1910. No. 10, grape downy mildew: America early; France, 1873; the 

 Rhineland, Savoy and Italy, 1879; The Tyrol and Algiers, 1880; Portugal 

 and Greece, 1881; Alsace, 1882; the Caucasus, 1887; Brazil, 1890. Now 

 known in all countries except Australia. No. 11, grape powdery mildew: 

 United States, early; England, 1845; Belgium and France, 1848; all Europe 

 1849; Madeira, 1852. Known everywhere now. No. 12, chrysanthemum 

 rust: Japan-England, 1895; America, 1896. (After F. L. Stevens.) 



should be confined to one part of the house, apart from 

 the others, and not allowed to mingle with them until well. 

 Hospitals have *' isolation wards" where persons with 

 communicable diseases are kept apart from other patients. 



