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Darwin, Charles, 1809-1882

"Effects of Cross and Self Fertilisation in the Vegetable Kingdom"

The
inferiority of the crossed plants of this first generation cannot be
attributed to the immaturity of the seeds, for I carefully examined
them; nor to the seeds being diseased or in any way injured in some one
capsule, for the contents of the ten crossed capsules were mingled
together and a few taken by chance for sowing. In the second generation
the crossed and self-fertilised plants were nearly equal in height. In
the third generation, crossed and self-fertilised seeds were obtained
from two plants of the previous generation, and the seedlings raised
from them differed remarkably in constitution; the crossed in the one
case exceeded the self-fertilised in height in the ratio of 100 to 83,
and in the other case were almost equal. This difference between the two
lots, raised at the same time from two plants growing in the same pot,
and treated in every respect alike, as well as the extraordinary
superiority of the self-fertilised over the crossed plants in the first
generation, considered together, make me believe that some individuals
of the present species differ to a certain extent from others in their
sexual affinities (to use the term employed by Gartner), like closely
allied species of the same genus. Consequently if two plants which thus
differ are crossed, the seedlings suffer and are beaten by those from
the self-fertilised flowers, in which the sexual elements are of the
same nature.


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