290 



Minnesota Plant Diseases. 



In the production of rust-proof varieties the selection of seed 

 becomes of great importance. Many farmers instinctively believe 

 that seed from rusted fields will necessarily produce a rusted 

 crop. Such is not the case as can easily be seen by a perusal of 

 the above life-history of the rust. The rust does not live over 

 in the seed and seed from rusted fields have no more chance of 

 becoming rusted than that from fields that have had no rust, 

 provided, of course, that it is not shriveled or in other way dam- 



Fic. 145.— Cluster-cups of the black or stem rust of wheat (Puccinia graminis), on stems 

 and leaves of Barberry. Photograph by Arthur and Holway. 



aged. In fact good seeds from rusted fields should be highly 

 prized for seeding purposes since they indicate that the plants 

 which bore them were probably rust-resistant. It would there- 

 fore be advisable to select seed from rusted fields, but such seed 

 must be carefully cleaned and graded so that only strong and 

 healthy berries are used. Of seed from regions free from rust 

 nothing definite can be predicted. The absence may be due to 

 rust-resistance or it may be due to an absence of the fungus in 



