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aNew York State Agricultural Experiment Station, Geneva, New York
2
The author wishes to acknowledge the many helpful criticisms and suggestions made by Drs. E. B. Fred and W. H. Peterson of the University of Wisconsin, Dr. J. M. Sherman, New York State College of Agriculture, and Dr. R. S, Breed, New York Agricultural Experiment Station.
1
Approved by the Director, New York State Agricultural Experiment Station for publication as Journal Paper No. 109.