654 METASPERMAE OF THE MINNESOTA VALLEY. 
peculiar to it. Sometimes this area will be almost coéxtensive 
with that of the continent; again it will be comparatively re- 
stricted. Of the first condition Typha latifolia is a good ex- 
ample; of the second Synthyris houghtoniana may be cited. In 
most cases, however, if theareaof the species should be drawn 
on a map, such area would always be cut by one or both of the 
two median lines which have been established as dividing the 
continent into northern and southern, eastern and western 
portions. If, now, the two lines of 95° W. long. and 45° N. 
lat. chance to cut any specific area into four approximately 
equal areas, such a species may be entered in the tabulation as 
of north, east, south and west distribution. But if one of the 
areas is very distinctly less than the other three, or if two are 
much less than the opposite two, the species may be entered 
in three of the four, or in two of the four divisions. 
As in the case of the genera, when similarly tabulated, no 
very rigid circumscribing line has been drawn for any species, 
for in almost every case the absolute east, west, north or south 
limit of a species is only approximately determined, Where any 
doubt about preponderant range has been felt the species has 
been entered in both of the groups. The evident result is that 
D. Table Illustrating General Continental Range 
NORTHERN. SOUTHERN. 
Typh'aceac. 
Typha latifolia................ Typha latifolia.............. 
Sparga|niaceae. 
Sparganium simplex 
Sparganium androcladum 
Sparganium eurycarpum...... 
Potamog 
Sparganium androcladum .... 
Sparganium eurycarpum 
etonaceae, 
Potamogeton natans 
Potamogeton fluitans.......... 
Potamogeton amplifolius 
Potamogeton perfoliatus 
Potamogeton heterophyllos... 
Potamogeton gramineus var. 
Zizii 
Caer ie ee ee ee 
oe? 
Potamogeton pectinatus....... 
Potamogeton pusillus 
Potamogeton lucens 
ey 
Potamogeton natans 
Potamogeton fluitans......... 
Potamogeton amplifolius 
Potamogeton perfoliatus 
PE OR, wg mL RE OL ACO Ot wae Wee BL eet ele arte Sat 
ZAZAL 
ee a ay 
Ce 
-Potamogeton illinoensis 
Potamogeton pectinatus 
Potamogeton pusillus 
Potamogeton lucens 
serene 
