In the middle of September, 1886, Prof W. G. Farlow sent to me several specimens of the heads of Achillea (probably A. millefolium L.) collected on Mt. Washington. They correspond well with the deformity described by Dr. Fr. Thomas in Giebel's Zeitschr., 1872, vol. 39, p. 464, on A. moschata Wulf. The flowers are to a large part changed in white hairy sacs or galls, containing a number of living Phytoptas. As far as known to me, this gall is not yet described from the U. S., and is very similar to those of A. millefolium described by Mr. Fr. Loew, Verhdl. Wien. Z. B. Ges., 1878, vol. 28, p. 130, which is to be found in Baron Thuemen Herbar. mycolog. oeconom. Suppl., I., No. 60. Our collection possesses a specimen by Prof. Thomas with the indication of Tylenchus (Anguillula) millefolii Loew.