PHILOSOPHICAL SOCIETY OF WASHINGTON. 75 



October and November, 1875 ; Botanical Gazette, October, 1880, 

 p. 123.] Here also grows very sparingly Microstylis ophioglossoides, 

 and quite abundantly Pyrola elliptica and P. secunda. It is also a 

 rich locality for many other species rare elsewhere. 



2. The Upper Potomac Region. — The flora of the left bank of 

 the Potomac is, in many respects, very unlike that of any other 

 locality within our limits. A mile above Georgetown, and com- 

 mencing from the recently constructed outlet lock of the Chesa- 

 peake and Ohio canal, there exists a broad and low strip of coun- 

 try formerly known by the name of Car berry Meadows, lying be- 

 tween the canal and the river, and extending to the feeder of the 

 canal, a distance of about three and a half miles. This interval is 

 relieved by two convenient landmarks, viz., one mile above the 

 outlet lock, a grist-mill and guano factory, popularly known as 

 Eads! mill ; and a mile further, the celebrated Chain Bridge. Little 

 Falls, proper, begin a hundred yards above the bridge, and extend 

 half a mile or more. The region above the bridge will, therefore, 

 be designated as Little Falls. The flats terminate in a remarkable 

 knoll or small hillock of very regular outline and abrupt sides, 

 which, from the combined effects of the feeder on one side, and large 

 •overflows from it below, becomes practically an island, and is well 

 known to all as High Island. These river flats are, in most places, 

 covered with large boulders of the characteristic 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 

 prolong this sketch unduly to enumerate all the rare and interest- 

 ing plants which this region has contributed to our vegetable treas- 

 ures, but conspicuous among them are Polygonum amphibium, var. 

 terrestre, Isanthus cceruleus, Herpestis nigrescens, Brasenia peltata, 

 Cyperus virens, and Nesoza verticillata, all of which recur below 

 Ead's mill ; Ammannia humilis, a remarkable variety of Salix 

 nigra, (S. nigra var. Wardi, Bebb.) Salix cordata, and S. longifolia; 

 as also Spiranthes latifolia, and Samolus valerandi var. Americanus, 

 Vitis vulpina and Panicum pauciflorum, which may be found be- 

 tween this point and the bridge, while at the Little Falls we are 

 favored with Paronychia dichotoma, Oenothera fruticosa, var. lineare 



