1. Robbins, W. J., and Kavanagh, F., Proc. U.S. Nat. Acad. Sci., 28 4 and 65 (1942).
2. Fries, N., Svensk Bot. Tidskr., 44, 379 (1950).
3. Fries, N., Symb. Bot. Upsal., 3, No. 2 (1938).
4. Fries, N., Svensk Bot. Tidskr., 43, 316 (1949).
5. cf. Cushing, J. E., Schwartz, M., and Bennett, R., J. Bact., 58, 433 (1949).