In the present edition the Flora has been extensively revised, and numerous changes have been made, in accordance with recent discoveries and the general progress of the science of Phytology. These changes consist especially of the addition of species hitherto unknown to our Flora, of new and corrected names for the old species, of new localities of species and corrected dates of flowering. In these improvements we have received valuable aid from Mr. E. L. Hankenson, of Newark, Wayne Co., N. Y., Messrs. W. R. Gerard, and G. M. Wilbur, of Poughkeepsie, N. Y., Mr. J. Wolf, Canton, Fulton Co., Ill., and others whose names appear in the proper place.