Populus Nigra, L. European, was not recognized by the Michaux in this country, but trees found near Albany, N. Y., on the Hudson, and in New York city, were described by them as T. Hudsonica, and by Pursh as the betulifolia. There is little doubt about its having been introduced from Europe, where it grows to a large size, and with P. alba is much used along the Danube in reclaiming low overflowed lands, whose thickets arrest the drift of floods and furnish abundant material for the fascines used in the wing dams and levees, and for improving navigation.