1. Eriksson, J., Ber. deut. botan. Ges. 12: 292 (1894).
2. Levine, M. N., J. Agr. Research 13: 651 (1918).
3. Stakman, E. C., Phytopathology 7: 73 (1917).
4. Minn. Univ. Agr. Expt. Sta. Tech. Bull. 1922 8
5. Stakman, E. C., J. Agr. Research. 16: 103 (1919).