STATISTICS OF METASPERMAE. 653 



younger element, may be expected to mass themselves more dis- 

 tinctly in lines parallel with the general continental tension-line. 

 The Monocotyledones, being peculiarly the older and more gen- 

 erally distributed element, may be expected to manifest dissipa- 

 tion over the different degrees of latitude. This they are found 

 to manifest, so the relative development of the two groups is 

 admirably exhibited by these data of comparative latitudinal 

 and longitudinal distribution. 



The total per cents, are of importance, too, as determining in 

 a preliminary way the character of the Minnesota valley 

 flora, so far as regards its North American distribution. We 

 find that the relations are as follows: 



So far then as may be indicated by the genera of metaspermic 

 plants, the valley of the Minnesota is much more eastern and 

 southern in its character than northern or western. Although 

 generally regarded as a northern district, it is seen to be least 

 characterised by this range-element. While continental ly cen- 

 tral it is by no means botanically central, but is peculiarly an 

 Atlantic coast and a southern region. The explanation of this 

 may be deferred until the examination of the species-distribu- 

 tion has been completed. 



III. EXAMINATION OF SPECIES REPRESENTED IN THE 

 MINNESOTA VALLEY. 



Since 73.0 per cent, of the species in the Minnesota valley 

 native metaspermic flora are limited to the North American 

 continent it will hardly be worth while to attempt any ex- 

 tended examination of them along the lines of Table A or 

 Table B. The extra continental element may be isolated for 

 study and the remainder which will consist of the endemic 

 species may be classified as were the genera in Table C. The 

 area occupied by a species is, as De CandoUe has shown, in 

 general either circular or elliptical. The species which are 

 found in the Minnesota metaspermic flora are without excep- 

 tion to be found also outside of the basin. Each species or 

 variety occupies such an elliptical or circular area as may be 



