Minnesota Plant Life. 15 



the plant's point of view, Minnesota is not a province, for, to 

 the plant, political boundaries as established by man, have slight 

 significance. Nor does the prairie, which occupies the south- 

 ern part of the state, exist as a special Minnesota prairie. 

 Rather is it the northeastern extension of the great plains which 

 occupy the whole central area of the continent from the foothills 

 of the Rockies back to the forests of Kentucky, Tennessee, Indi- 

 ana and Wisconsin. The question then arises how did the for- 

 ests come to consist of the plants which dominate them, and 

 how did the prairie come to have its particular inhabitants 

 rather than others? 



If a census be taken of all the kinds of plants in the forests 

 of North America and be compared with a similar census taken 

 in the forests of Europe and Siberia there will be perceived a 

 great similarity between the plants of the two regions. But if 

 in like manner the plants of the prairies of the United States 

 be compared with those growing upon the steppes of Russia 

 and Siberia it will be discovered that the similarity is not by any 

 means so great. A very much larger number of plants are 

 common to the forest districts of Europe, Asia and North 

 America than are common to the steppes and prairies of the two 

 hemispheres. Yet, in this latter instance, there are many 

 groups which are similar and not a few identical species. Sup- 

 pose, further, that the forests of the northern hemsiphere, of 

 which the Minnesota forest is but a portion, be compared with 

 the deciduous forests of the southern hemisphere, including 

 those of the Transvaal Republic, Chili and the Argentine, New 

 Zealand and Tasmania, it would be noticed that almost no com- 

 mon species, and but few common groups of species can be 

 found. Or if the pampas of the Argentine be compared with 

 the prairies of the United States, again would it be discovered 

 that the common species are exceedingly scarce. 



It would seem, then, that the greatest differences which exist 

 between plant populations of the world are between those of 

 the north temperate and the south temperate regions. The 

 occasion of this will be understood if it be remembered for a 

 moment what are the opportunities for the expansion of plant- 

 life in the tropics and under the equator. There for countless 

 thousands of years plants have been developing and competing 



