158 TORREYA 



1. Life history and classification of the fungous pathogens. Following 

 the demonstration of heteroecism in the stem rust of wheat by de Bary (1865), 

 the life histories of many rusts were determined. De Bary ( 1866) demonstrated 

 heteroecism in the crown rust of oats caused by Puccinia coronata, the aecial 

 stage occurring on species of Rhainnus. Oersted (1865) established the hereroe- 

 cism of Gyinnosporangiiun sabinae. Almost every year one or more connec- 

 tions were established, largely by w^orkers in Europe. Halsted (1886) and 

 Thaxter (1887) showed that the life cycle of Gymnosporangium juniperi-vir- 

 ginianae required the red cedar and the apple for its completion. Klebahn 

 (1888) demonstrated the connection between the white pine and species of 

 Ribes in the blister rust, Cronartimn ribicola, and for a period of years he 

 devoted himself to a study of heteroecious types, by 1904 listing 178 species be- 

 longing to 11 rust genera. Dietel (1918) listed a total of 264 heteroecious rusts. 

 Arthur (1900-1921) was an active worker in growing cultures of various rusts 

 on different hosts in order to determine their life history, and demonstrated 

 that approximately 50 different Xorth American rusts were heteroecious, in 

 1934 listing 153 species belonging to 14 genera in his Manual of the Rust Flora 

 of the United States and Canada. 



Along other lines, great advances in our knowledge of the rusts have been 

 made. Eriksson (1894) discovered racial specialization. Blackman (1904) and 

 Christman ( 1905) described what they interpreted as a method of sexual repro- 

 duction at the base of the young aecial cups. It remained for Craigie (1927- 

 1933), in a series of papers, to demonstrate the relation of the pycnia and the 

 young aecia in the life cycle, thus completing the main outlines of the life his- 

 tory of this pathogen. There was an immediate application of these studies in 

 connection with the possible origination of new races of rusts. 



The main facts in the life history of the bunt of wheat were established by 

 Tillet (1755), Prevost (1807) and Kiihn (1858). A further point in the 

 method of distribution was brought out by Woolman and Humphrey (1924) 

 in which they showed that soil contamination was an important factor in our 

 Xorthwestern States. 



The life history of the other smuts of cereals has also been worked out. 

 L. R. and C. Tulasne (1847) diiTerentiated some of the main types. Jensen 

 (1888) devised the hot water treatment for the oat and barley smuts and 

 distinguished two species on the latter host and Kellerman and Swingle (1890) 

 separated the covered smut of oats from the loose smut. Brefeld (1870-1912) 

 published 15 volumes recording the results of his labors on the smuts and other 

 fungi. Of special significance was the demonstration of the flower infection 

 method in the loose smut of barley and wheat by Brefeld and Falck (1905). 

 Zade (1924) added to our knowledge of the method of distribution of the loose 

 smut of oats, suggesting that to a large extent the wind-blown spores germ- 



