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 outrff 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 ? 
