3 I2 



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: North America, early; 

 France, 1885; Italy and the Caucasus, 1898. No. 9, potato wart: 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. n, 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. 



