The close relationship between railroad expansion and the genera development and prosperity of the country is nowhere brought more distinctly into relief than in connection with the construction of the Pacific railroads.
I accept extinction as best explaining disjoined species. I see that the same cause must have reduced many species of great range to small, and that it may have reduced large genera to so small, and of families.
Every paleontologist knows that most new species, genera, and families, and that nearly all categories above the level of family appear in the record suddenly and are not led up to by known, gradual, completely continuous transitional sequences.
Is it philosophical, is it quite allowable, to assume without evidence from fossil plants that the family or any of the genera was once larger and wide spread? and occupied a continuous area?
People began to understand that with the acquisition of California the nation had obtained practically half a continent, of which the future possibilities were almost unlimited, so far as the development of natural resources and the genera production of wealth were concerned.
Splitting and gradual divergence of genera is exemplified very well and in a large variety of organisms.