FLORA OF WASHINGTON AND VICINITY. 11 



III. COMPARISON OF THE FLORA OF 1830 "WITH THAT OF 1880. 



Washington and its vicinity has long been a field of botanical re- 

 search. The year 1825 ^ritnessed the dissolution of the " Washington 

 Botanical Society," which had for many years cultivated the science, 

 and the same year also saw the formation of the "Botanic Club," which 

 continued the work, and in one respect at least excelled the former in 

 usefulness, since it handed down to us of the present generation, a valu- 

 able record in the form of a catalogue of the plants then known to exist 

 in this locality. This catalogue, which was fittingly entitled Florae 

 Columbiance Prodromus, and claimed to exhibit " a list of all the plants 

 which have as yet been collected," though now rare and long out of 

 print, is still to be found in a few botanical libraries. I have succeeded 

 in securing a cojjy of this work, and have been deeply interested in 

 comparing the results then reached with those which we are now able 

 to present. A few of these comparisons are well worth reproducing. 

 It should be premised that the Frodromns is arranged on the artificial 

 system of Linnseus, so that before the plants could be placed in juxta- 

 position with those in modern works they required to be rearranged. 

 This, however, was not the principal difficulty. Such extensive changes 

 have taken place in the names of i^lants during the fifty years which 

 have elapsed since that work appeared (1830), that it is only with the 

 greatest difficulty that they can be identified. I have succeeded in 

 identifying the greater part of them, and in thus ascertaining about to 

 what extent the two lists are in unison. This also reveals the extent 

 to which each overlaps the other, and thus affords a sort of rude index 

 to the changes which our flora has undergone in half a century. There 

 are, however, as will be seen, many qualifying considerations which 

 greatly influence these conclusions and diminish the value of the data 

 comj)ared. 



The whole number of distinct names (species and varieties) enumer- 

 ated in the Frodromus is 919. Of these, 59 are mere synonyms or du- 

 plicate names for the same plant, leaving 860 distinct plants. I have 

 succeeded in identifying 708 of these with certainty as among those now 

 found, and these are marked in the general catalogue by the sign (t). 

 Six others, not yet clearly identified, should probably be placed in this 

 class. This leaves 146 enumerated in the old catalogue which have not 

 been found in recent investigations. The importance of these 146 

 plants as pointing out the direction of future search, and also as indi- 

 cating the disappearance of former species, justifies their enumeration 



