FERNS OF THE DisTRICT OF COLUMBIA — 39 
and are well known to support characteristic floras. 
The interlocking of these zones along the fall line in 
the vicinity of Washington and the various factors 
controlling to a great extent the local distribution 
of plant and animal life are interestingly discussed 
by W. L. McAtee in a recent volume entitled “A Sketch 
of the Natural History of the District of Columbia 
and Vicinity.’’? Similar data are presented also in the 
forthcoming ‘‘Flora of the District of Columbia and 
Vicinity,’’* by A. 8. Hitchcock and Paul C. Standley, 
with the assistance of the botanists of Washington. 
In both works the more important collecting localities 
and their characteristic vegetation are described, and 
to these the reader is referred for fuller information. 
The list of species given below is deemed of sufficient 
interest to fern students to justify its publication separ- 
ately, and it may besides serve a useful purpose to 
members of the Fern Society visiting Washington. 
The local Piedmont area lies chiefly northwestward 
and includes most of Rock Creek Park and the upper 
Potomac region, extending from the Aqueduct Bridge 
at Georgetown to Little Falls, High Island, Cabin J ohn, 
and the Great Falls of the Potomac, the last mentioned 
locality lying at the edge of the 15-mile circle. The 
soils of this region are derived by the disintegration 
of metamorphic rocks and are mostly neutral or but 
weakly acid. It is mostly broken country, character- 
ized by sharp declivities and by frequent streams run- 
ning rapidly between steep banks, and, especially in 
the near vicinity of the river, is beautiful and often 
picturesque. The abrupt wooded blufis of the Vir- 
ginia shore from Great Falls to a point opposite Cabin 
John are of especial interest as sheltering several of 
the rarer local ferns. Camptosorus occurs sparingly on 
3 Bulletin No. 1, Biological Society of Washington. Pp. 142. 1918. 
‘Contr. U. S. Nat. Herb., Vol. 21. (In press.) 
