Cereals 311 



upon the stems and leaf sheaths, more rare upon the leaf 

 blade. Following this stage the black telia appear upon the 

 stems and leaf sheaths, constituting the most conspicuous 

 and predominating symptom. 



The damage by this disease is due to the inroads of the 

 fungus upon the green leaf tissue, destroying the starch- 

 producing power, diminishing the vigor of the plant, and 

 showing its effects finally in the shrunken, shriveled grain. 



Since this rust usually appears late in the season, the 

 varieties of wheat that mature early are likely to escape its 

 attack to a greater extent than those varieties which are 

 late in maturing. For a similar reason climatic or agronomic 

 conditions which conduce to slow growth and late maturing 

 of the crop favor the rust. 



Since the common barberry (Berberis vulgaris) and its 

 varieties, or Mahonia is necessary to the functioning of the 

 teliospores, these plants should not be tolerated. ^^^ In Den- 

 mark in 1903 laws enforced eradication of this barberry. 

 Eleven years after we read "'^- 



" That black rust has disappeared gradually, contemporary 

 with the barberry bush. 



"That the violent, destructive black rust attacks, which 

 affected the whole or most of the country, with two or three 

 years interval, have now ceased. 



"That the weaker attacks which affected the grain and 

 grasses and especially the oats in Jutland are now practically 

 unheard of, or at least come late in the fall." 



Influenced by such evidence, in 1918 and 1919 the Federal 

 authorities and those of many states, particularly in the 

 Middle States and Northwest, took energetic measures to 

 eliminate the barberry and Mahonia. Anti-barberry laws 

 were passed in Saskatchewan, Manitoba, Canada, and many 

 states, notably in North Dakota, Iowa, Colorado, Minnesota, 

 Montana, Nebraska, South Dakota, Wisconsin, Michigan, 

 Illinois. It is clear from experimental evidence that the rust 

 does not commonly pass to the next crop on the seed, nor 

 does it commonly overwinter in the living host plants, except 



