10 F1>0EA OF WASHINGTON AND VICINITY. 



Dr. E. Foreman lias also furnished the names of a few of the Chara- 

 cece collected here by himself, and named by Professor Farlow of Cam- 

 bridge, which, in the present unsettled state of the classification of the 

 CryiJtogams, have for convenience been placed at the foot of the series. 



In undertaking this compilation I have endeavored to resist the usual 

 temptation of catalogue-makers to expand their lists beyond the propor- 

 tions which are strictly warranted by the concrete facts as revealed by 

 specimens actually collected or species authentically observed, but have 

 been content to set down only such as I can either personally vouch for 

 or as are vouched for by others who have something more substantial 

 than memory to rely uj)on, preferring that a few species actually occur- 

 ring, but not yet seen, should be omitted and afterwards sui)plied, 

 rather than that others supposed to exist, but which cannot be found, 

 should stand in our flora to be apologized for to those who would be 

 glad to obtain them. A few species, however, which are positively 

 known to have once occurred within our limits, but which have been 

 obliterated in the course of the constant changes taking place, have 

 been retained, as well as several of which only a single specimen has 

 been found ; but in all such cases the facts are fully stated in the notes 

 accompanying each plant. 



II. RANGE OF THE LOCAL FLORA. 



The extent of territory which has of late years been tacitly recog- 

 nized by botanists here as constituting the area of what has been 

 called the " Flora Columbiana " is limited on the north by the Great Falls 

 of the Potomac, and on the south by the Mount Vernon Estate, in Vir- 

 ginia, and Marshall Hall, just opjiosite this on the Maryland side of the 

 river, while it may reach back from the river as far as the divide to the 

 east, where the waters fall into the Chesapeake Bay, and as far west- 

 ward as the foot of the Blue Ridge, so as uot to embrace any of the 

 peculiarly mountain forms. Practically, however, the east and west 

 range is much less than this, and only extends a few miles in either 

 direction. The only three cases in which these limits are overstepped in 

 this catalogue are in including : 1. Drciba ramosissinia, not yet collected 

 this side of Hariier's Ferry, but which may be confidently looked for 5 

 2. Filago Germanica, collected at Occoquan Falls, and liable to be found 

 farther north ; and 3. Poterium Sangimorha, obtained from Odenton, 

 Md., an introduced species which may yet be found nearer home. 



