572 METASPERMAE OF THE MINNESOTA VALLEY. 
area of drainage, then, the valley of the Minnesota is one of 
central location. Its continental position is no less central. If 
the 50th meridian west of Greenwich be taken for the eastern 
boundary of the solid portion of the North American continent 
and the 140th meridian, passing near Mount St. Elias and cut- 
ting off the great Alaskan peninsula, for the western, the inter- 
mediate meridian will be the 95th west of Greenwich, and this 
meridian passes squarely through the valley of the Minnesota, 
cutting-the counties of Jackson, Cottonwood, Brown, Redwood, 
Renville and Kandiyohi. Or if the meridian of 20° west be 
be taken for the eastern boundary of the North American con- 
tinent, thus including the whole of Greenland, and the merid- 
ian of 170° west be taken for the western boundary, thus in- 
cluding the Alaskan peninsula and passing through Berings 
straits, the intermediate meridian as before is the 95th west. 
In like manner, if the parallel of 70° north latitude, passing 
near the mouth of the Mackenzie river, and the parallel of 20° 
north latitude passing near the city of Mexico be adopted as 
the northern and southern boundaries, respectively, of the 
solid portion of the North American continent. the intermedi- 
ate parallel will be the 45th of north latitude and this passes 
through Hennepin, Kandiyohi, Chippewa and Lac Qui Parle 
counties of the valley in Minnesota, and through Grant and 
Codington counties in South Dakota. The same 45th parallel 
becomes the intermediate one if 80° north latitude be selected 
for the northern boundary and 10° north latitude for the south- 
ern. The 95th meridian and the 45th parallel intersect in Kan- 
diyohi county just at the north edge of the valley. 
The continental and hydrographic position of the Minnesota 
basin is seen to be peculiarly central and this adds much to the 
interest of determining the character of its plant inhabitants. 
General topographical features. Big Stone lake which is 
the head lake of the main stream lies at an altitude of 962 feet 
above the sea. Into the northwestern part of this lake, near 
the town of Brown’s Valley, the head stream enters after 
running for about twenty-two miles in a southeastern direction 
from the Coteau des Prairies of South Dakota. This head 
stream drains land that lies at an elevation of 2,000 feet above 
the sea level. The two principal tributaries from the north 
are the Pomme de Terre and the Chippewa rivers, both of 
which arise in the high morainic hills of southern Otter Tail 
county. Some of these hills reach an altitude of 1,750 feet 
above the level of the sea. Lake Stalker which is the head 
