268 ESSAYS. 
the allied American type, Gaylussacia) will attract attention. 
It is interesting to note the rapid falling away of Hricacew 
westward in the valley of the Mississippi as the forest thins 
out. 
3. The wealth of this flora in Composite is a most obvious 
feature; one especially prominent at this season of the year, 
when the open grounds are becoming golden with Solidago, 
and the earlier of the autumnal Asters are beginning to blos- 
som. The Composite form the largest order of Phenogamous 
plants in all temperate floras of the northern hemisphere, are 
well up to the average in Europe, but are nowhere so numer- 
ous as in North America, where they form an eighth part of 
the whole. But the contrast between the Composite of 
Europe and Atlantic North America is striking. Europe 
runs to Thistles, to Inuloidew, to Anthemidew, and to Cicho- 
riacee. It has very few Asters, and only two Solidagoes, no 
Sunflowers, and hardly anything of that tribe. Our Atlantic 
flora surpasses all the world in Asters and Solidagoes, as also 
in Sunflowers and their various allies, is rich in Hupatoriacee, 
of which Europe has extremely few, and is well supplied with 
Vernoniacee and Helenioidece, of which she has none; but is 
scanty in all the groups that predominate in Europe. I may 
remark that if our larger and most troublesome genera, such 
as Solidago and Aster, were treated in our systematic works 
even in the way that Nyman has treated Hieracium in Europe, 
the species of these two genera (now numbering seventy-eight 
and one hundred and twenty-four respectively) would be at 
least doubled. 
4. Perhaps the most interesting contrast between the flora 
of Europe and that of the eastern border of North America 
is in the number of generic and even ordinal types here met 
with which are wholly absent from Europe. Possibly we may 
distinguish these into two sets of differing history. One will 
represent a tropical element, more or less transformed, which 
has probably acquired or been able to hold its position so far 
north in virtue of our high summer temperature. (In this 
whole survey the peninsula of Florida is left out of view, re- 
garding its botany as essentially Bahaman and Cuban, with a 
