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Darwin, Charles, 1809-1882

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

The
longest leaves on the three crossed plants, when turned out, exceeded
those on the self-fertilised plants by a mere trifle, namely, on an
average by .17 of an inch. When fully grown the three crossed plants
produced twenty-six flower-stems; the two tallest of which on each plant
were on an average 54.04 inches in height. The three self-fertilised
plants produced twenty-three flower-stems, the two tallest of which on
each plant had an average height of 46.18 inches. So that the difference
between these two lots, which hardly competed together, is much less
than in the last case when there was moderately severe competition,
namely, as 100 to 85, instead of as 100 to 70.
THE EFFECTS ON THE OFFSPRING OF INTERCROSSING DIFFERENT FLOWERS ON THE
SAME PLANT, INSTEAD OF CROSSING DISTINCT INDIVIDUALS.
A fine plant growing in my garden (one of the foregoing seedlings) was
covered with a net, and six flowers were crossed with pollen from
another flower on the same plant, and six others were fertilised with
their own pollen. All produced good capsules. The seeds from each were
placed in separate watch-glasses, and no difference could be perceived
by the eye between the two lots of seeds; and when they were weighed
there was no difference of any significance, as the seeds from the
self-fertilised capsules weighed 7.65 grains, whilst those from the
crossed capsules weighed 7.


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