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 thalictr aides, 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 



