Methods in Rust Investigations 257 



Stakman, E. C, and Levine, M. N. The Determination of Biologic 

 Forms of Piicciyiia graminis on Triticum sp. Minn. Agr. Exp. Sta. Tech. 

 Bui. 8, 10 p. 1922. 



, Piemeisel, F. I., and Levine, M. N. Plasticity 



of Biologic Forms of Puccinia gramiyiis. Jour. Agr. Research. 15: 221- 

 250. 1918. 



Theil, A. F., and Weis, Freeman. The Effect of Citric Acid on 

 the Germination of the Teliospores of Puccinia graminis tritici. Phyto- 

 path. 10: 448-452. 1920. 



Vavilov, N. I. Beitrage zur Frage iiber die Verschiedene Wider- 

 standsfahigkeit der Getreide gegen Parasitische Pilze. Trudy Selek. 

 Stan. Moskov. Selskokhoz Inst. 1: 1-108. 1913. 



17—27933 



