That they owed
their origin to insects flying from flower to flower, whilst collecting pollen,
there can be no doubt. Although insects thus rob the flowers of a most precious
substance, yet they do great good; for, as I have elsewhere shown, the seedlings
of V. thapsus raised from flowers fertilised with pollen from another plant, are
more vigorous than those raised from self-fertilised flowers. (2/26. 'The
Effects of Cross and Self-fertilisation' 1876 page 89.) But in this particular
instance the insects did great harm, as they led to the production of utterly
barren plants. Secondly, these hybrids are remarkable from differing much from
one another in many of their characters; for hybrids of the first generation, if
raised from uncultivated plants, are generally uniform in character. That these
hybrids belonged to the first generation we may safely conclude, from the
absolute sterility of all those observed by me in a state of nature and of the
one plant in my garden, excepting when artificially and repeatedly fertilised
with pure pollen, and then the number of seeds produced was extremely small. As
these hybrids varied so much, an almost perfectly graduated series of forms,
connecting together the two widely distinct parent-species, could easily have
been selected. This case, like that of the common oxlip, shows that botanists
ought to be cautious in inferring the specific identity of two forms from the
presence of intermediate gradations; nor would it be easy in the many cases in
which hybrids are moderately fertile to detect a slight degree of sterility in
such plants growing in a state of nature and liable to be fertilised by either
parent-species.
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