Bulletin - United States National Museum - Smithsonian Institution

24 FLORA OF WASHINGTON AND VICINITY.
On tlie opposite side of the river the site of the ancient canal around
the falls has proved very fertile in botanical trophies. Polygala amhigua
is found near the boat-landiug, while by climbing the cliffs below this
jjoint the native of more northern climes may gaze once more upon his
familiar hemlock sj^ruce {Tstiga Canadensis). Difficult Run, a mile
farther down, though indeed difficult of approach, repays the effort
with Podostemon ceratophyllns, SmUacina stellata, Fotamogeton Claytoniiy
and numerous other herbal treasures.
3. The Lower Potomac Region.
Passing next to the Lower Potomac, the localities of special interest
are : 1. Custis Spring, opposite the Arlington estate, with the extensive
marsh below, where Sagittaria pusilla, Discopleura capillacea, Gyperus
erythrorhizos, and other rare species are alone known to grow. 2. The
point and bay below Jackson City, known as Roach's Run, where are found,
among other good things, Scrophularia nodosa, Tripsacum dactyloides,
and Pycnanthemum lanceolatum. 3. Four Mile Run, halfway to Alexan-
dria, not yet sufficiently explored, including the vicinity of Fort Scott, to
the northwest, where Clematis ochroleuca and Asclepias quadrifolia may
be collected ; and, 4. Hunting Creek, a large estuary below Alexandria,
including Cameron Run, the stream which debouches into it with its
tributaries, Back Lick Run and Holmes Run, which unite to form it.
Here have been found at various points Clematis ochroleuca, Gonolohus
hirsutus, Itea Virginica, Geranium columhinum, Micranthemum Nuttalliij
Habenaria virescens, Quercus macrocarpa, Carex gracillima, Geum stric-
tum, Galium asprellum, and very many other rare plants.
On the left bank of the Lower Potomac the chief locality of interest
is a large wooded area below the Government Hospital for the Insane.
This has proved a rich hunting ground I'or the botanist, and has yielded
Carex pallescens, C. ietanica, var. Woodii, GonoloMts hirsutus, Silene Ar-
meria, Parietaria Pennsylvanica, Myosotis arvensis, Scutellaria nervosa,
&c, Asplenium angustifolium is known only at Marshall Hall, where it
has been collected by Mr. O. M. Bryan, while opposite Fort Foote Mr.
Zumbrock has found Myriophyllum spicatum, and opposite Alexandria
Professor J. H. Comstock and MissH. B. Willets have discovered Plan-
tago cordata.
4. The Terra Cotta Region.
This embraces some low grounds and undulating barrens near the
terra cotta works at Terra Cotta Station, on the Metroj)olitan Branch
of the Baltimore and Ohio Railroad, three miles iiom the city, and also