THE AECIDIAL STAGE OF PUCCINIA GBAMINIS PERS. 279 



Life History of the Rust. 

 In the 18th century farmers in Europe associated the 

 presence of the common barberry (Berberis vulgaris L.) 

 with the spread of rust on wheat. But it remained for 

 De Bary (3) to prove in classic fashion that the relation 

 between the two was causal. He worked out the complete 

 life history of the rust. Teleutospores on wheat straw 

 that lias been exposed to winter conditions germinate in 

 the following spring and produce sporidia. If these sporidia 

 fall upon the young growth of the barberry or several 

 allied plants, they bring about infection and the production 

 of the spermagonial and the aecidial or "cluster-cup" stage 

 of the parasite. Aecidiospores from the barberry will 

 infect wheat and lead to the production of the iiredospore 

 or "red-rust" stage. Later in the summer the same uredo 

 mycelium in wheat may give rise to the teleutospore stage, 

 thus completing the life history. 



The proof of this connection of the barberry with cereal 

 rust led to the eradication of the plant in parts of Europe. 

 In U.S.A., a vigorous Barberry Eradication Campaign has 

 been in progress since 1918. A sum of $200,000 annually 

 is being spent on this work. In these countries the absence 

 of the barberry has been found to decrease the amount of 

 rust on wheat. For example, in Denmark (4) a gradual dis- 

 appearance of the stem rust has been contemporaneous 

 with the destruction of the barberry. But it does not 

 always follow that the elimination of the barberry will 

 necessarily get rid of the rust. The uredo-spore stage is 

 capable, under some conditions, of keeping the fungus alive 

 on stray wheat plants and certain grasses until the next 

 season's wheat crop is grown. 



Previous Work in Australia. 



In Australia no native species of Berberis are known. 

 But several introduced species are present in the cooler 



