76 The Vegetation of the 



All the other genera are either cosmopolitan or predominate in the 

 northern temperate zone of both hemispheres, though some are chiefly 

 North American as: Aster, Erigeron, Solidago, Polemonium, Fraxiuus 

 and Comandra. 



When the entire upper Mississippi valley to the 38° N. L. emerged 

 the last time, after the drift period, then it is obvious that the whole con- 

 cern of our flora must have immigrated. The relationship and the present 

 center of preservation of each species will point to the direction of the 

 probable immigration. 



There are only a few species, that so far are observed only in the up- 

 per Mississippi district: Desmodium lUinoensc A.Gr. Aster anomalus 

 Engelm., Phlox bifida Beck., Asclepias Meadii Torr., Trillium recurvatum 

 Beck., Eleocharis Wolfii Gr. These may elsewhere been overlooked or 

 taken for other species; they may have been formed by variation or 

 hybridation in the present period, but not spread over a wider territory or 

 they may have covered a wider area and be restricted now to their present 

 habitat; all that is possible but not proved. 



The majority of the species no doubt came from the AUeghanies; for 

 not less than 715 extend to that mountain range and 642 of them surpass 

 the same. A good many of such species, that America has in common 

 with the eastern continent, (114 of our flora) may have immigrated from 

 the north. 



All the species that in the same latitude do not reach the Alleghannies 

 but have their eastern limits in Ohio, Indiana, or Illinois may be either 

 western or southern. The southern species (excepted those that keep 

 along the coast) go generally farther northward in the west than in the 

 east of the Alleghannies. 



Besides the above mentioned 6 species 48 others do not extend to 

 Ohio, and of those came probably from the south 13: 



Nasturtium sessilifolium. Coreopsis lanceolata. 



Callirhoe triangulare. Lobelia leptostachys. 



Cornus asperifolia. Amsonia tabernseraontana. 



Eupatorium serotinum. Carya olivseformis. 



Liatris cylindracea. Leersia lenticularis. 



liudbeckia subtomentosa. Panicum autumnale. 

 Coreopsis palmata. 



From southwest 10: 



Desmantus brachylobus. Dysodia chrysanthemoides. 



Liatris pyenostachya. Hieracium longipilum. 



Erigeron divaricatum. Euphorbia heterophylla. 



Ambrosia bidentata. • Echinodorus rostratus. 



Ambrosia psilostachya. Cyperus acuminatus. 



