v i P R E F A C E .
which had long ago been described by Kaulfuss, and others were made
known to botanists by Sir William Jackson Hooker in the early volumes
of his SJicms F'dir.un. Most of these species are enumerated in the
Report on the United States and Mexican Boundary Survey.
Increased activity among investigators of the Flora of the Northern
States has now detected within the limits of the Republic all but one
of the European species of Kerns which Drummond long ago discovered
in the Rocky Mountains of British America. Of Ferns not previously
known in North America, or entirely new to science, New England
and the Northern States have yielded three species, and the Middle
States (including Northern Alabama), four or five more; while the zeal
of several collectors in Florida lias brought up the number of Tropical
Ferns known in that peninsula from four or five in 18 18 to eighteen
in 1877, and to twenty-three by April, 1879, At the same time, the explorers
of California have made several discoveries of great interest;
and the army of botanists everyivherc have found many new stations
for rare Ferns, and have greatly extended the known geographical range
of commoner species.
The Ferns de.scribed in the fifth edition of Gray’s Manual (1867)
comprise fifty-seven species. Were a sixth edition to be prepared now,
at least seven more sy,e.d\st% — Adiantum Capilhis-Veneris, Cheilanthes
Alabamensis. Asplénium parvulum, A . viride. A. Bradleyi. Trichomanes
radicans and Boiryddum inairicaricefoliuin — would each claim a place;
and possibly some of the reputed varieties would have to be recognized
as distinct species. Horace Mann’s Catalogue o f the Vascular Crypio-
gainia o f North. America, published in 1868, enumerates one hundred
and twenty-four species of Ferns; Robinson's Check-list, of 1876, names
one hundred and thirty-seven : and the species now attributed, by good
authority, to that portion of our continent which is north of the Mexican
boundary, are at least one hundred and forty-three, and will probably
exceed that number before the present work is completed.
The plan adopted for this work is essentially that of Hooker's
Filices Exotica:. In order to extend the usefulness of the book, the
definitions of species are written in English rather than in I.atin, and
they are often made to include some points of generic importance,
thereby making the recognition of the species easier to the student.
All the definitions are newly drawn up from actual specimens before
the eyes of the author, living plants being used whenever obtainable.
Ample references and synonymy are given, so that those who use the
work may know where to look for the history of each species. I he
Habitat is generally given from specimens in my own collection, though
sometimes taken from those preserved in the great herbaria at Kcw
and at Cambridge, or from facts kindly communicated by helpful correspondents,
Under the Description, besides a more particular account