654 



METASPERMAE OF THE MINNESOTA VALLEY. 



peculiar to it. Sometimes this area will be almost coextensive 

 with that of the continent; again it will be comparatively re- 

 stricted. Of the first condition Tijpha latifolia is a good ex- 

 ample; of the second Synthyris houglitoniana may be cited. In 

 most cases, however, if the area of 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 iAto 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. Tal)le Illustrating General Continental Range 



NORTHERN, 



SOUTHERN. 



Typha latifolia. 



TypJi 

 Sparga 



Sparganium simplex 

 Sparganium androcladum 

 Sparganium eurycarpum . 



Potamog 



Potamogeton natans 



Potamogeton fluitans 



Potamogeton amplifolius 



Potamogeton perfoliatus 



Potamogeton heterophyllos . . . 

 Potamogeton gratnineus var. 



zizii 



Potamogeton rutilus 



Potamogeton pectinatus , 

 Potamogeton pusillus . . 

 Potamogeton lucens. ... 



aceac. 

 Typha latifolia. 

 niaceac. 



Sparganium androcladum 

 Sparganium eurycarpum . 

 etonaceae. 



Potamogeton natans 



Potamogeton fluitans 



Potamogeton amplifolius. 

 Potamogeton perfoliatus. 



Potamogeton gramineus var. 

 zizii 



Potamogeton illinoensis. 

 Potamogeton pectinatus. 

 Potamogeton pusillus. . . 

 Potamogeton lucens 



