The relationship of the hay fever excitants in the pollens of Bermuda grass and timothy grass is of clinical importance and to the best of our knowledge has not been studied. When in 1923 Dr. A. Vander Veer, Jr., examined this question in several cases of timothy hay fever, he observed a similarity of the skin reactions and of the eye reactions produced by the two extracts, but he came to no definite conclusions because of some uncertainty as to the quality of the pollen extracts that he was using, and because the method of passive transfer was not employed. Dr. Vander Veer did not publish these experiments, and it was at his suggestion that the present investigation was begun. For this study ten hay fever subjects sensitive to timothy pollen were selected whose constitutional sensitivity ranged from class A to class C, (classification of R. A. Cooke).