34 The Ohio Naturalist. [Vol. VII, No. 2, 



character. Other varieties appear to be localized either in the 

 center of the distributional area or at one side of it although still 

 within the limits occupied by the type. Geographical botany in 

 America is still in its infancy, and it is a question whether much 

 weight is to be attached to present statements in regard to dis- 

 tribution ; but there is no more certainty as to the data concern- 

 ing subspecies localized in geographically distinct areas, whether 

 isolated by physiographic or climatic barriers. In the Verbena 

 mutant we have not only a distinct type which originated by a 

 saltation in a definite direction but a type which spread side by 

 side in the same habitat with the parent and kept itself distinct 

 without the aid of external selection or isolation of any kind. 

 The isolation in this case is resident in the internal nature of the 

 plant and had its origin in the same ph> siological and hereditary 

 processes which gave rise to the original mutant. 



It is assumed by many that, in case a new species arises with 

 a character or quality more advantageous than the old, the new 

 will finally displace the old through the struggle for existence. 

 This is a hypothetical assumption which often appears to be 

 without foundation in fact. If conditions of habitat were 

 uniform and if each species lived in only one type of habitat and 

 could endure only one narrow set of conditions there would be 

 grounds for the general assumption. But most species can live 

 in quite diverse habitats and under quite diverse and varying 

 degrees of favorable and unfavorable conditions. There is a 

 great difference in the character of plants adapted to similar 

 habitats and still on a natural prairie conditions settle down to a 

 sort of equilibrium with a complex flora where one species or at 

 most a few ought to hold complete sway. The physiography, 

 the habitat, the soil, and the plants are always shifting, always 

 changing; and in this constant shifting and changing room is 

 made not only for the stronger but also for the weaker. Burrow- 

 ing animals, rain, wind, and gravity, are ever at work. It is not 

 always necessary for the new type to migrate to a separate geo- 

 graphical area in order to survive unless its nature has been 

 changed to such a degree as to put it out of all harmony with its 

 surroundings. The two forms may divide the diverse and varying 

 habitats of the region between themselves and exist side by side 

 for an indefinite period just as the parent stock before division 

 shared the habitat with others. Or one might say that the wild 

 species may continue to exist in a continually changing physiog- 

 raphy for much the same reason as cultivated plants continue to 

 exist in man's cultivated field. And finally, is it not immaterial 

 whether a species, to be a good species, cover a square mile or a 

 continent, whether it continue for ten generations with a few 

 thousand individuals or for a geological period with countless 

 millions ? 



