LOO Evolution and Adaptation 
than in the following statement: “If it has taken centuries or 
thousands of years to improve or modify most of our plants 
up to their present standard of usefulness to man, we can 
understand how it is that neither Australia, the Cape of 
Good Hope, nor any other region inhabited by quite uncivil- 
ized man has afforded us a single plant worth culture. It is 
not that these countries, so rich in species, do not by a 
strange chance possess the aboriginal stocks of any useful 
plants, but that the native plants have not been improved by 
continued selection up to a standard of perfection comparable 
with that acquired by the plants in countries anciently 
civilized.” 
In reply to this, it may be said that if the selection of 
fluctuating variations leads to an accumulation in the given 
direction, it is not apparent why it should take thousands of 
years to produce a new race, or require such a high degree 
of skill as Darwin supposes the breeder to possess. 
The conditions favorable to artificial selection are, accord- 
ing to Darwin: 1. The possession of a large number of in- 
dividuals, for in this way the chance of the desired variation 
appearing is increased. 2. Prevention of intercrossing, such 
as results when the land is enclosed, so that new forms may 
be kept apart. 3. Changed conditions, as introducing varia- 
bility. 4. The intercrossing of aboriginally distinct species. 
5. The intercrossing of new breeds, “but the importance 
of intercrossing has been much exaggerated.” 6. In plants 
propagation of bud variations by means of cuttings. The 
chapter concludes with the statement, “Over all these 
causes of Change, the accumulative action of Selection, 
whether applied methodically and quickly, or unconsciously 
and slowly, but more efficiently, seems to have been the pre- 
dominant Power.” 
Variability, Darwin says, is governed by many unknown 
laws, and the final result is “infinitely complex.” If this is 
so, we may at least hesitate before we accept the statement 
