212 Statistics of the Flora of the Northern States, 



floras are to be compared. This is not the place to discuss the 

 principles involved in the general question, nor to explain or 

 defend any conclusions to which I may have arrived ; — except to 

 say that my determination of species in each particular case has 

 been based on the evidence before me as irrespective of all theo- 

 retical considerations as possibly could be. It is necessary to 

 state, however, that, so far as I can judge, the authors of the 

 principal and most esteemed recent European Floras, if in my 

 place, would be likely to increase the present number of our 

 Phaenogamous plants and Ferns about five per cent. One school, 

 indeed, would doubtless add at least ten or twelve per cent, to 

 the species here received, and give results quite incommeasurable 

 with my own. I can only say, on my own part, that an en- 

 larged experience certainly inclines one to take broader views 

 of species than those which prevail among the generality of 

 European botanists. 



The numerical comparison of our Phaenogamous with our 

 Cryptogamous species, however interesting it might become in 

 a complete flora, is here of little moment ; only the higher Cryp- 

 togamia being included. Moreover, it should be noted that the 

 Musci and Hepaticoe enumerated in the above table are those of 

 a geographical area about twice that of the higher or Acrogen- 

 ous Cryptogamia and the Phaenogamia. For the distinguished 

 American muscologist who elaborated these two orders for our 

 'Botany of the Northern States,' anxious to afford facilities for 

 the study of our mosses throughout the country, has included all 

 known to him within the whole United States east of the Mis- 

 sissippi, and even some as yet found only to the north and west 

 of these limits. It is evident, also, that the number of forms 

 admitted as species is proportionally larger in these two orders 

 than in the rest of the work. On the other hand it is to be con- 

 sidered how little our mosses have as yet been collected and 

 studied, and how likely it is, in view of their general wide range, 

 that most of these outlying species may yet be detected within 

 the Northern States, including Virginia and Kentucky. 



We naturally restrict our attention mainly to the Phaenoga- 

 mous vegetation, asr best known in all countries and affording 

 the most precise data for comparison. And we exclude at once 

 the 260 introduced species, most if not all of which have become 

 denizens of our country since its settlement by Europeans, and 

 in consequence of that settlement; — leaving the question of their 

 origin, introduction, &c, for future consideration. Their admis- 

 sion into the account in the comparing our flora with that of 

 Europe, as has been done, seriously vitiates our conclusions.* 



* Thus Mr. Watson, as cited by Alph. DeCandolle (Geogr. Bot. p. 511) enumer- 

 ates 602, out of 1428 phaenogamous British plants, as common to Great Britain and 

 America. I count only 321 out of 2091 phasnogamous species indigenous to the 

 Northern United States as indigenous also to Europe. . 



