312 
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; tne 
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. 
