8 



annotinum var. pungens, Mertensia paniculata, Betula glandu- 

 losa, Yaccinium vitis-idsea and Carex vaginata. Even of these, 

 Betnla glandnlosa and Yaccinium vitis-idrea were found on the 

 St. Louis river nearly thirty miles south of Vermilion lake and 

 more directly within the influence of lake Superior; and Alnus 

 viridis was not observed south of Long lake, some miles north- 

 ward, if we except its occurrence on the cliffs of lake Superior 

 at Agate bay. 



One of the most striking features of this flora is its monotony. 

 Although the expedition has good reason to .believe that it col- 

 lected four-fifths of the flowering plants and vascular crypto- 

 gams common to the region, the collection from lake Superior 

 to the International Boundary, did not much exceed 100 species. 

 The flora of a similar area six degrees southwards would com- 

 prise from 1,000 to 1,200 species. Here is an illustration of the 

 law that species decrease with the increase of latitude. I took 

 pains to count the number of species growing upon given areas. 

 Upon an area similar to that which would give from thirty to 

 fifty species at Lansing, Mich., I counted from a dozen to twenty 

 species. One of these areas, some four or more square rods, 

 comprised the following : 



Aspen — Populus tremuloides. 



Birch — Betula papyrifera. 



Willow — Salix rostrata. 



Bush honeysuckle — Diervilla trifida. 



Dogwood — Cornus stolonifera. 



Bird cherry — Primus pennsylvanica. 



Epilobium — E. spicatum. 



Plantain — Plantago major. 



Strawberry — Fragaria virginiana, var. illinoensis. 



Anten naria — A. plantaginifolia. 



White clover — Tri folium repens. 



Kush — Juncus tenuis. 



Vetches — Lathy rus venosus and L. paluster. 



Aster — A. paniculatus. 



Carex — C. stipata. 



Red -top — Agrostis vulgaris. 



Brake — Pteris aquilina. 

 Moreover, most of these plants existed only as single speci- 

 mens, and the character of the flora was determined by a half 

 dozen species. 

 A few very rare or local plants were found, as follows: 



Sparganium simplex, var. fluitans, abundant. 



