NORTH AMERICAN FLORA. 269 
certain admixture of northern elements.) To the first type I 
refer such trees and shrubs as Asimina, sole representative of 
the Anonacee out of the tropics, and reaching even to lat. 42° ; 
Chrysobalanus, representing a tropical suborder; Pinckneya, 
representing as far north as Georgia the Cinchoneous tribe ; 
the Baccharis of our coast, reaching even to New England ; 
Cyrilla and Cliftonia, the former actually West Indian ; 
Bumelia, representing the tropical order Sapotacee; Big- 
nonia and Tecoma of the Bignoniacee ; Forestiera in Ole- 
acee ; Persea of the Laurinew ; and finally the Cactacee. 
Among the herbaceous plants of this set I will allude only to 
some of peculiar orders. Among them I reckon Sarracenia, 
of which the only extra-North American representative is 
tropical-American, the J/elastomacee, represented by Rhexia ; 
Passiflora (our species being herbaceous), a few representa- 
tives of Loasacee and Turneracee, also of Hydrophyllacee ; 
our two genera of Burmanniacee ; three genera of Hamo- 
doracee ; Tillandsia in Bromeliacee ; two genera of Ponte- 
deriacee ; two of Commelynacee ; the outlying Mayaca and 
Xyris, and three genera of Hriocaulonacee. I do not forget 
that one of our species of Eriocaulon occurs on the west coast 
of Ireland and in Skye, wonderfully out of place, though on 
this side of the Atlantic it reaches Newfoundland. It may be 
a survival in the Old World; but it is more prababis of 
chance introduction. 
The other set of extra-European types, characteristic of the 
Atlantic North American flora, is very notable. According to 
a view which I have much and for a long while insisted on, it 
may be said to represent a certain portion of the once rather 
uniform flora of the arctic and less boreal zone, from the late 
Tertiary down to the incoming of the Glacial period, and 
which, brought down to our lower latitudes by the gradual 
refrigeration, has been preserved here in eastern North 
America and in the corresponding parts of Asia, but was lost 
to Europe. I need not recapitulate the evidence upon which 
this now generally accepted doctrine was founded; and to 
enumerate the plants which testify in its favor would amount 
to an enumeration of the greater part of the genera or sub- 
