30 METASPERMAE OF THE MINNESOTA VALLEY. 



Many other titles might be added to this list, but those cited 

 will put any student into contact with the general literature. 

 Most of these works do not devote themselves solely to the 

 subject in the caption, but all serve to illuminate it more or 

 less. Works of purely historical value, such as those of Brong- 

 niart, Amici, R. Brown, Schacht, Radlkofer, Karsten, et al., 

 have not been cited, for it is not my intention to give in this 

 place a complete bibliography of the subject, but only to cite 

 enough works to enable readers to come in contact with the 

 original sources. 



Statistical discussions. The chapters following the list 

 take up in order certain statistical investigations based 

 upon facts collated in the list itself. No complete sta- 

 tistical investigation can be made of even this limited area, the 

 Minnesota valley, in the present advancement of our know- 

 ledge. There are, however, data enough at hand to determine 

 certain characters of our flora. It is believed that the points 

 of view from which the statistics are gathered, and the prin- 

 ciples underlying their tabulation, enable one to present some 

 facts less barren and meaningless than those commonly put 

 forward in such chapters. By keeping steadily in view the 

 facts discussed above, in relation to the difference between 

 natural and artificial districts, and with a constant compre- 

 hension of the indubitable fact that one can not consider even 

 a natural district apart from surrounding districts, the writer 

 has attempted to penetrate to some of the inner facts which 

 become accessible in such a labor as has been undertaken. 'It 

 is believed that the characters of the Minnesota valley flora thus 

 determined throw some unexpected light upon the general con- 

 ditions of plant distribution in this central region of the conti- 

 nent. And while some of the conclusions may seem simple to 

 trained geographical botanists, it must be recalled by them 

 that this work is not primarily addressed to any coterie of 

 savants in some special line of science, but to the general pub- 

 lic of Minnesota, under whose ultimate sanction, and by whose 

 open-minded comprehension of the value of scientific knowledge 

 in all departments of human activity, this Geological and Na- 

 tural History Survey has been established, developed and 

 directed. 



