as did subsequently Dr. Hooker, even in stronger terms. I shall reserve
for my future work the discussion of these difficulties, and the tables
themselves of the proportional numbers of the varying species. Dr.
Hooker permits me to add, that after having carefully read my
manuscript, and examined the tables, he thinks that the following
statements are fairly well established. The whole subject, however,
treated as it necessarily here is with much brevity, is rather
perplexing, and allusions cannot be avoided to the struggle for
existence, divergence of character, and other questions, hereafter
to be discussed.
Alph. De Candolle and others have shown that plants which have very
wide ranges generally present varieties; and this might have been
expected, as they become exposed to diverse physical conditions, and as
they come into competition (which, as we shall hereafter see, is a far
more important circumstance) with different sets of organic beings. But
my tables further show that, in any limited country, the species which
are most common, that is abound most in individuals, and the species
which are most widely diffused within their own country (and this is a
different consideration from wide range, and to a certain extent from
commonness), often give rise to varieties sufficiently well-marked to
have been recorded in botanical works. Hence it is the most
flourishing, or, as they may be called, the dominant species, those
which range widely over the world, are the most diffused in their own
country, and are the most numerous in individuals, which oftenest
produce well-marked varieties, or, as I consider them, incipient
species. And this, perhaps, might have been anticipated; for, as
varieties, in order to become in any degree permanent, necessarily have
to struggle with the other inhabitants of the country, the species
which are already dominant will be the most likely to yield offspring
which, though in some slight degree modified, will still inherit those
advantages that enabled their parents to become dominant over their
compatriots.
If the plants inhabiting a country and described in any Flora be
divided into two equal masses, all those in the larger genera being
placed on one side, and all those in the smaller genera on the other
side, a somewhat larger number of the very common and much diffused or
dominant species will be found on the side of the larger genera. This,
again, might have been anticipated; for the mere fact of many species
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