Bulletin - United States National Museum - Smithsonian Institution

14 FLORA OF WASHINGTON AND VICINITY.
The botanist familiar with this flora will be able to form a judgment
more or less correct as to what the plants probably were to which these
last names were assigned.
With regard to the 146 species above enumerated, it must not be
hastily concluded that they represent the disappearance from our flora
of that number of plants. While they doubtless indicate such a move-
ment to a certain extent, there are ample e\idences that many of them
can be accounted for in other ways. After careful consideration I have
been able to divide them into four principal classes as arising out of
1st. Errors on the part of those early botanists in assigning to them
the wrong names.
2d. The introduction into the catalogue of adventitious and even of
mere cultivated species never belonging to the flora of the place.
3d. The undue extension by those collectors of the range of the local
flora, so as to make it embrace a portion of the maritime vegetation of
the Lower Potomac or the Chesapeake Bay, and also the mountain flora
of the Blue Eidge.
4th. The actual extermination and disappearance of indigenous plants
during the fifty years that have intervened since they made their re-
searches.
The figure placed in parenthesis before each name in the list denotes
the class in the order above indicated to which I would assign each one
of these species. This assignment is of course in great part conjectural,
and may be incorrect in many cases, while another botanist might have
diftered considerably in regard to special plants ; yet it is not based
upon a general judgment drawn from my acquaintance with the present
flora, but upon several kinds of special evidence, which in numerous in-
stances has reversed mj prima facie decision. In the first place I have
carefully 'Compared the range of each species as given in the text-books
to determine the probabilities for or against its being found here, and
in the second place I have prepared a corresponding list of plants now
found but not enumerated in the Prodromus and compared the two lists.
I have also endeavored to make due allowance on the one hand for the
tendency above referred to, to swell the catalogue as fully as possible,
and on the other, for the well known fact that every flora is at all times
undergoing changes. It must not be forgotten either that half a century
ago the surface of the entire country here must have presented a very
different appearance from that which it presents now. The population
of the District of Columbia in 1830, when it included a portion of Vir-
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