400 GEOGRAPHICAL DISTRIBUTION OF FUNGI 



Endemic species, artificially dispersed. The existence of 

 endemism among pathogenic Phvcomycetes can be shown by 

 numerous examples. Among them is Physodcnua zeae-maydis } 

 which is known to have existed for about 40 years in the south- 

 eastern United States, throughout the area south of the Ohio River 

 and east of the Mississippi River. It is, however, found sparingly 

 in the Corn Belt north and west of this range, but here it occurs 

 sporadically. It produces serious losses within its normal range, 

 especially in low, poorly drained lands during seasons of abun- 

 dant and frequent rains. This fungus has been dispersed widely 

 outside the United States, as is shown by records of collections in 

 India, China, Japan, Rhodesia, Sierra Leone, Guatemala, and Mex- 

 ico. It would be expected to occur wherever corn has been in- 

 troduced, provided that moisture and temperature are favorable. 



Another example of this kind is the organism that causes potato 

 wart, Synchytrium endobioticum, first described from Hungary 

 in 1896. Soon thereafter it was encountered in other portions of 

 central Europe, where it is presumably indigenous, for example, in 

 Czechoslovakia, Poland, Silesia, Austria, and Germany. In 1902 

 it was reported in the British Isles, in 1912 in Canada, in 1918 in 

 the United States, in 1922 in South Africa, and in 1929 in Peru 

 and Russia. Meantime stringent quarantines were established in 

 many countries to prevent the introduction and spread of this 

 organism. 



Among the classic examples of a pathogenic species that has 

 been artificially dispersed is Fhytophthora infestans. This fungus, 

 native of the northern Andes, home of the potato, was introduced 

 into Europe and North America between 1830 and 1840. In 1845 

 and 1846 an cpiphvtotic so severe as to cause failure of the potato 

 crop occurred throughout northern Europe, especially in Ireland, 

 where famine resulted. This pathogen was introduced into India 

 between 1870 and 1880 and into Australia and South Africa be- 

 tween 1900 and 1910. 



North America has contributed an organism, Plasmopara viti- 

 colii, which becomes notoriously destructive when introduced 

 into new areas. This downy mildew was first described in 1834 

 and was transplanted into France with grape nursery stock early 

 in the I870's. There it produced an epiphvtotic in 1879 and 

 rapidly spread throughout the vineyards of France and Italy. Ef- 

 forts to check this grape disease led to the discovery and use of 



