Bulletin - United States National Museum - Smithsonian Institution

22 FLORA OF WASHINGTON AND VICINITY.
practically an island, and is well known to all as High Island. These
river flats are in most places covered with large bowlders of the char-
acteristic gneiss rock of the country. In some parts the surface is very
rough, and numerous pools or small ponds of water occur. Overflows
and leakages from the canal cause large sloughs and quagmires, while
annual ice-gorges crush down the aspiring fruticose vegetation. All
these circumstances lend variety to the locality, and, as might be ex-
pected, the flora partakes largely of this characteristic. It would iiro-
iong this sketch unduly to enumerate aU the rare and interesting
plants which this region has contributed to our vegetable treasures, but
conspicuous among them are Polygonum amjfhibimn, var. terrestre, Isan-
thus cwruleus, Herpestis 7iigrescens, Brasenia peltata, Cyperus virenSy
and Nescea verticillata, all of which occur below Eads' Mill ; Ammannia
humilis, a remarkable variety of Salix nigra {S. nigra, var. Wardi., Bebb.
q. V. infra), Salix cordata, and S.longifolia, as also Spiranthes latifoUa and
JSamolus Valerandi, var. Americanus, which may be found between this
point and the bridge ; while at the Little Falls we are favored with
Paronychia dichotoma, CEnothera fruticosa, var. linearis (very distinct
from the type), and Ceanothus ovatus, also Ranunculus pusillus and Utri-
cularia gibba. But rich and varied as are these lower flats, they are ex-
celled by High Island, the flora of which is by far the most exuberant
of all within the knowledge of botanists. Here we find Jeffersonia
diphylla, Caulophyllum thalictraides, Erigenia bulbosa, Silene nivea, Vale-
riana pancijiora, Urythroniuni albidum, Iris cristata, and great numbers
of others of our most highly-prized plants, many of which are found
here only.
Above the feeder is a series of islands in the river, lying for the most
part near the Maryland shore, and to which the maps, so far as I can
learn, assign no names. The first of these lies well out in the river,
and has been made to form a part of the feeder-dam. It is low and
frequently overflowed, and has not as yet furnished many rare plants,
though here Arabis dentata and some others have been found. It has
I)een designated Feeder-dam Island. The second is half or three quar-
ters of a mile above, lies higher, and is covered with a very dense and
luxuriant herbaceous vegetation and fine trees, chiefly of box-elder
{Negundo aceroides), from which circumstance and the peculiar impres-
sion which the long, gracefully-pendant, staminate flowers of these trees
produced on the occasion of its first discovery by a botanical party, it
received the name of Box-Elder Island. The third island is a short