STATISTICS OF METASPEEMIC PLANTS OE THE 

 MINNESOTA VALLEY. 



Value of statistics. In the following pages such numerical 

 data as have seemed most necessary for an understanding of 

 the distributional characters and physiognomic features of the 

 Minnesota valley Metaspermae have been compiled. lb is pro- 

 per first of all to call attention to what has well been stated by 

 De Candolle — that somewhat too great an air of mathematical 

 exactness is conveyed even to professional botanists, by sta- 

 tistics of such a nature. The apparent rigidity of the calcula- 

 tions inspires a mistaken notion of rigidity in the distribution. 

 On the contrary, however, the statistics are not truly indicative 

 of such mathematical exactness of distribution as their appear- 

 ance would imply; they are to a certain extent of the nature 

 of averages or estimates. There are in their compilation, too, 

 certain sources of error; for example, in the table which gives 

 the north, south, east and west preponderance of species in the 

 North American continent, the entry of any species is a matter 

 of judgment from published geographical lists, and either the 

 data of the lists may be incomplete or erroneous, or the judg- 

 ment may be faulty. In order to correct such error it tias 

 been my effort to compile the statistics from several points of 

 view. Under such method it is presumed that they will mutu- 

 all correct each other and the general results will thus come to 

 be of definite reliability. 



Again, there is the danger that the personal equation of 

 error, indicated in mistakes of counting or calculation, will per- 

 mit a degree of vitiation that were better avoided. Although 

 each group of statistics has been carefully compiled and the 

 results checked in such a way as to guard the general results 

 to what extent may be possible, it will readily be seen that a 

 single small error would propagate itself unlimitedly, if by 

 accident it should creep into the preliminary count. 



