STATE GEOLOGTST. 11 



attention to the study of the fresh-water algse, determining a large 

 number of species. 



A.nother successful student of fresh-water algae, especially of the 

 Desmids, is Miss Eloise Butler, of Minneapolis. An article respect- 

 ing these microscopic plants, by Mr. Francis Wolle, in the Bulletin 

 of the Torrey Botanical Club for February, 1883 (vol. x, pages 13 to 

 21), enumerates eighteen species new to the United States, collected 

 by Miss Butler in the viciniti' of Minneapolis, including eight 

 forms (three species and five varieties) new to science. 



CONDITIOIfS DETERMINING THE CHARACTER OF THE FlORA. 



In considering the botany of any district, its geographic position, 

 elevation and contour, the climate, and the diverse rocks and soils 

 v/hich it presents, need to be briefly stated, since these circumstan- 

 ces control the development of the flora. 



Minnesota lies in the middle of the North American continent, 

 almost midway between the Atlantic and Pacific oceans and between 

 the gulf of Mexico and the Arctic ocean, being distant a thousand 

 miles or more from each of these grand bodies of water. The extent 

 of the state from south to north is 380 miles, and its average width 

 about 220 miles. It lies between 43° 30' and 49° north latitude, 

 and between 90° and 97° west longitude. Its area is 84,286 square 

 miles. 



The topographic features of Minnesota may be briefly summed 

 up for its western three-quarters, as being a moderately undulating, 

 sometimes nearly flat, but occasionally hilly expanse, gradually 

 descending from the Coteau des Prairies and from the Leaf hills, 

 respectively about 2000 and 1700 feet above the sea, to half that 

 hight, or from 1000 to 800 feet, in the long flat basin of the Red 

 river valley, and to the same hight along the valley of the Missis- 

 sippi from Saint Cloud to Minneapolis. The only exceptions to 

 this moderately undulating or rolling and rarely hilly contour, are 

 the southeast part of the state where the Mississippi river and its 

 tributaries are enclosed by blufls from 200 to 600 feet high, and the 

 northwest shore of lake Superior and the part of the state lying 

 north of this lake and east of Vermilion lake. A very bold rocky 

 highland rises 400 to 800 feet above lake Superior, within from 

 one to five miles back from its shore-line, all along the distance of 

 150 miles from Duluth to Pigeon point, the most eastern extremity 

 of Minnesota; while farther north are many hill-ranges, 200 to 500 

 feet higher, mostly trending from northeast to southwest or from 

 east to west. 



