Minnesota Plant Life. 23 



Where the story of plant migration is recorded. It is im- 

 possible to mention except in a more extended account the 

 many and various ways in which plants influence the distribu- 

 tion of each other or receive influence from outside sources, but 

 enough has been said to indicate the general laws under which 

 the State of Minnesota has received the plants which now 

 inhabit its territory. They have come from all points of the 

 compass, from all parts of the world, bringing with them habits 

 acquired through countless generations of struggle and adapta- 

 tion. To the enlightened eye, the form of a plant tells a story 

 of its life and of the experiences it must have undergone to 

 develop one type of structure rather than another. Just as in 

 the formidable defensive armor of an extinct armadillo may 

 be read somewhat of the story of its struggle with its enemies, 

 so in the three hundred feet of solid trunk and in the massive 

 girth of a living Big-tree in the Sierras one may read the story 

 of its struggle in the ancient forests when its allies and com- 

 petitors were perhaps more numerous and more vigorous in 

 their aspiration for light than are the neighbors of to-day. 



In the Minnesota valley, not far from New Ulm, there are 

 found upon rocks exposed in the river-bed by the erosion of the 

 waters, some specimens of the little prickly-pear cactus, a desert 

 plant which has found its way from the plains of Arizona and 

 New Mexico. By all its characters it indicates how it must 

 have been trained in a school of life different from that in which 

 the plants around it receive their education. Its solid, leafless, 

 flattened stem with a resistent rind is fitted to withstand the 

 evaporation of moisture a character much needed in the des- 

 ert, but less necessary in the valley of the Minnesota. Its 

 strong root system extending out a yard or more on every side 

 was indispensible to collect what little moisture there might 

 have been in the arid soil of the southwestern desert; with a 

 smaller root system it could do very well in its northern home. 

 The sharp thorns and spines with which it is covered were a 

 necessary protective armor where vegetation was sparse and 

 grazing animals hungry ; without this armor it could live very 

 well on the hills of New Ulm, for there dwell other plants, with- 

 out armor nor do the herds destroy them. Such a plant, evi- 

 dently a wanderer from another land, is like a man of mediaeval 



