Statistics of the Flora of the Northern States. 225 



• 



S Belong also to Western temperate Asia, viz., Menispermum, 

 Planer a, and Zizania ; two of these being peculiar to that 

 district and to ours. 



73 Extend southward beyond the limits of the United States 

 and into tropical regions, or recur in the southern hemis- 

 phere. 



120 Are characteristic Eastern United States genera. 



As already stated, only three genera are actually restricted to 

 the geographical area comprised in our ' Botany of the Northern 

 United States'. If, however, we allow our area to embrace Can- 

 ada, which naturally belongs to it, and also include those plants 

 which extend southward much beyond lat. 36° 30' only in the 

 Alleghanies or cool upper country of the Southern States, we 

 may enumerate 37 genera peculiar to this flora ; viz. — 



Zanthorhiza. 



Echinocystis. 



Pyxidanthera. 



Hydrastis. 



Sullivantia. 



Dirca. 



Caulophyllum. 



Zizia. 



Hamiltonia. 



Diphylleia. 



Erigenia. 



Comptonia. 



Jeffersonia. 



BrachycliEeta. 



Arethusa. 



Adlumia. 



Chiogenes. 



Tipularia. 



Solea. 



Oxydendrum. 



Aplectrum. 



Huds § ia. 

 Napsea. 



Rhodora. 



Medeola. 



Leiophyllum. 



Helonias. 



Cladrastis. 



Schweinitzia. 



Chamseliriura. 



Gymnocladus. 



Galax. 



Amphicarpum. 



Gillenia. 



Nemopanthes. 



Dalibarda. 



Hemianthus. 





To show, however, how slight an influence, after all, these 37 

 characteristic genera exert upon our flora, we have only to re- 

 mark that they comprise altogether only 39 of our species: — that 

 is, they have only one species apiece, except Hudsouia and Gille- 

 nia, which have two each. The characteristics of our flora of 

 the Northern States merge in those of the flora of Eastern North 

 America, and these again into those of the North American flora 

 generally ; and no idea can be formed of the real features of a 

 flora like ours from such a dissection, and piecemeal presentation, 

 or from an exhibition of what is strictly peculiar to each part, 

 rather than what is predominant, — at least as respects generic 

 forms. 



Keturning now to the species, — the real exponents of vegeta- 

 tion; — these have already been considered as regards their nu- 

 merical proportions in the several classes and orders of the flora 

 of the Northern States : it remains to note some facts respecting 

 their geographical distribution. 



SECOND SERIES, VOL. XXII, NO. 66. — SEPT., 1856. 



29 



