STATE GEOLOGIST. 15 



A group of species, most notably represented in the pine and 

 heath families, including our three pines, black spruce, balsam fir, 

 tamarack and arbor-vitee, huckleberry, blueberry, cranberry, snow- 

 berry, aromatic wintergreen or checkerberry, Labrador tea, and the 

 clintonia and dwarf cornel, extends through the northeast part of 

 the state to limits approximately coinciding with the Mississippi 

 river, Red lake and the lake of the Woods. 



The northern limits of yellow birch, bur oak, sugar maple and 

 basswood here coincide nearly with the international boundary. 

 The red cedar, cottonwood, hornbeam, white, black and red oaks, 

 butternut, bitter-nut or swamp hickory, hackberry, box-elder, frost 

 grape and prickly ash reach their general northern limits in the 

 north half of this state; but several of them, like many herbaceous 

 species of similar range, continue somewhat farther northwestward 

 into Manitoba. The shell-bark hickory, black walnut, red mul- 

 berry and Kentucky coffee-tree attain their most northern range 

 in the south half of the state. 



The accompanying map shows the portions of Minnesota re- 

 spectively occupied by forest and prairie, and the approximate limits 

 of many of our trees.* 



Introduced Plants. 



About eight per cent, of the plants growing without cultivation 

 in this state are introduced species, distinguished in the catalogue 

 by being printed in Italics. Most of them are such as follow 

 civilized man, and grow in his cultivated fields and gardens, in 

 spite of all efforts to banish them. Among the most notable in- 

 troduced weeds in this state may be mentioned mustard, cow-herb 

 and cockle, specially troublesome in wheat-fields; shepherd's purse, 

 purslane, mallow, May-weed, burdock, mullein, pigweeds, tumble- 

 weed, black bindweed, curled or yellow dock, sheep sorrel, hemp, 

 barnyard-grass, and foxtail or pigeon-grass, frequently too plenti- 

 ful in cultivated ground, about dwellings, by the road-side, or on 

 pasture-land. The ox-eye daisy or white-weed, Canada thistle and 

 cheat or chess are sparingly established, and may become very com- 

 mon bad weeds here, as farther east. It shculd be added that, be- 

 sides these immigrants, a considerable number of weeds native to 

 this country ai-e also common, including species of Lepidium, Iva, 

 Ambrosia, Helianthus and Stachys. Up to the present time, only 



*Its method of delineation is similar to tliat of Dr. Robert Bell's map, recently 

 published by the Geological Survey of Canada, showing the general northern limits of 

 the principal forest trees of Canada. 



