PHILOSOPHICAL SOCIETY OF WASHINGTON. 69 



2d. That 12 of these plants, or 8 per cent., belong to the second 

 class, or were simply cultivated species, and never belonged to this 

 flora. 



3d. That 10 of them, or 7 per cent., belong to the third class and 

 were collected beyond the reasonable limits of our local flora. 



4th. The remaining 81, or 56 per cent., belong to the fourth class, 

 and represent bona fide discoveries in 1830 of species which either 

 do not now occur or are so rare as to have escaped the investigations 

 of the present generation of botanists. 



With regard to the first of these classes, the large number of errors 

 in naming cannot be considered any derogation from the ability or 

 fidelity of the compilers of the Prodromus or their immediate pre- 

 decessors, when we remember the very unsettled state that American 

 botany was in at that time. Both names and authorities were badly 

 confused, and errors were committed even by the most experienced 

 botanists. For example, their Corydalis glauca as probably also 

 their C. aurea, meant C. flavula which is now abundant, but omitted 

 by them. Their Arabis stricta might have been A. hirsuta or A. 

 patens, which are both now rare, though it was more probably a 

 form of A. laevigata, as they seemed to be specially fond of drawing 

 nice distinctions and expressing them by synonyms. Varieties, 

 however, were scarcely recognized by them, the trinomial theory 

 being then in its infancy. I might thus proceed to discuss all their 

 supposed errors, but this is not necessary. 



The second and third classes, amounting together to 16 per cent, 

 of the alleged excess over the present flora, consist also of errors, 

 but errors which it is much less easy to palliate. It is natural to 

 wish to make as large a showing as possible, and the temptation to 

 insert into a catalogue everything which by any construction can 

 be claimed to belong there is rarely resisted. To show that this 

 propensity still exists, it may be remarked that of the 1054 species 

 enumerated in the preliminary catalogue of plants of this vicinity, 

 published by the Potomac Side Naturalist's Club in 1876, 89, or 

 about 82 per cent, are now admitted by all not to have been seen 

 here at that time, and have never been found by any one since, al- 

 though nearly three hundred other species have since been added 

 to the flora. This is certainly not a scientific method to proceed 

 upon, and as already remarked, the present effort aims to eliminate 

 to a great extent this source of error. 



The 81 species constituting the fourth class remain, therefore, the 



