GEOGRAPHIC AFFINITIES 
225 
scribed from the Antilles; while others, like Eleocharis interstincta 
(fig. 5) or Erigeron pusillus, are widely dispersed in tropical and sub- 
tropical America, occurring in the Bermudas and tropical Mexico, 
and by way of the Antilles or of Central America extending to South 
America. 
Swinging northward from the Gulf of Mexico along the Mississippi 
basin, we come into a flora which is famihar to the New Englander, 
though rarely known to the botanist of the South Atlantic States. 
This flora common to the Mississippi basin and southern New England 
is well illustrated by Ludvigia polycarpa (fig. 6) , which occurs in sloughs 
and wet depressions from southwestern Ontario and Ohio to Nebraska, 
southern Missouri and Tennessee,^ and east of the Appalachians 
occurs in three isolated areas: Cumberland Co., Maine; Middlesex 
Co., Massachusetts; and Hartford Co., Connecticut. This group of 
species is further illustrated by Cyperus Engelmanni, a plant of less 
general occurrence in the Great Lake-Mississippi region — from south- 
ern Ontario to Minnesota and Missouri — and eastward found only in 
Seneca Co., New York, and in Middlesex Co., Massachusetts, where 
it has long been known as a characteristic plant of lake-alluvium. 
The plants of the drier prairies and plains of the interior are not 
so definitely restricted to the interior of the continent as might be 
supposed. In fact, many lists of characteristic plants of dry prairies 
have a very familiar appearance to the New Englander — Sporoholus 
heterolepis, Sorghastrum nutans, Andropogon furcatus, Muhlenbergia 
mexicana, Aster novae-angliae, Heliopsis scabra, etc. These plants, 
typical of the drier prairies and plains of the interior, are well illus- 
trated by Solidago rigida, which is widely dispersed from the Missis- 
sippi Valley westward, in one or another of its variations, to the Rocky 
Mountains and northward to Peace River, and eastward into Ohio and 
western New York. East of the Alleghenies the plant is localized, 
from the District of Columbia to Massachusetts. 
Another characteristic element in the western flora which has a 
greater representation in the extreme East than is generally realized 
is the flora of subsaline or brackish habitats of the Great Plains and 
the foothills of the Rocky Mountains; such plants, for instance, as 
Erigeron loncophyllus , a species of saline meadows from the Black 
^ In the maps the northeastern range may be taken as fairly representing the 
facts in detail, but the ranges west and south of New England are only approximate, 
and, owing to lack of detailed reports, cannot be considered final. 
