216 Statistics of the Flora of the Northern States. 



Thus it appears, 1, that, of our 19 extra-European orders not 

 peculiarly American, only 3 or 4 are represented on the western 

 or Pacific side of the United States, while all but one are repre- 

 sented in the corresponding parts of Eastern Asia ; — indicating a 

 curious analogy in the vegetation of the eastern sides of the two 

 great continental masses in the northern hemisphere, which is 

 also borne out, though not so strikingly, in a comparison of the 

 genera. 



2. That the flora of the Northern United States is remarkably 

 rich in ordinal types, as compared with Europe, which, (exclu- 

 sive of the Mediterranean region, furnished with two or three), 

 has only seven orders that we have not, while we have 26 that 

 are wholly unknown to the European flora. 



3. And it is worth noticing that our additional or character- 

 istic orders are all of warm-temperature or sub-tropical general 

 character (which is the more remarkable when the lower mean 

 temperature of the year as compared with that of Western Eu- 

 rope is considered) : all of these 26 orders have their principal 

 development in the tropical regions, excepting six of the smaller 

 ones; and three of these have tropical or sub-tropical repre- 

 sentatives. 



4. But the peculiar and extra-European families do not pre- 

 dominate, nor overcome the general European aspect of^ our 

 vegetation, on account of the fewness of their species. Of the 

 largest in our flora (Hydrophyllacece) we count only 11 species; 

 and the whole 26 orders give us only 64, or barely three per 

 cent of our phasnogamous species. 



Our Phsenogamous genera, 681 in number, average three spe- 

 cies apiece. Far the largest genus is Carex, with 132 species. 

 On the other hand one half of our genera are represented by 

 single species; and about 92 of these are monotypic, having only 

 a single known species. 



The genera which are strictly confined within the geographical 

 limits of this work are only three, namely, Napcea, Sullivantia, 

 and Hemianthus (the last a dubious genus) ; and all three are 

 monotypic. 



The number of our genera which have no indigenous repre- 

 sentatives in Europe appears to be 353, or twelve more than half 

 of our whole number, (the naturalized plants being of course 

 excluded), belonging to 95 families. In the following table 

 (which is hastily prepared, and likely to contain not a few errors), 

 our extra-European Phsenogamous genera are enumerated, under 

 their respective families, and their distribution in longitude is 

 attempted to be given in the two parallel columns. 



