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Darwin, Charles, 1809-1882

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

--Sir W. MacArthur informed me that in
New South Wales the flowers do not set, unless the petals are moved in
the same manner as is done by insects.
Lathyrus grandiflorus (Leguminosae).--Is in this country more or less
sterile. It never sets pods unless the flowers are visited by
humble-bees (and this happens only rarely), or unless they are
artificially fertilised: see my article in 'Gardeners' Chronicle' 1858
page 828.
Sarothamnus scoparius (Leguminosae).--Extremely sterile when the flowers
are neither visited by bees, nor disturbed by being beaten by the wind
against the surrounding net.
Melilotus officinalis (Leguminosae).--An unprotected plant visited by
bees produced at least thirty times more seeds than a protected one. On
this latter plant many scores of racemes did not produce a single pod;
several racemes produced each one or two pods; five produced three; six
produced four; and one produced six pods. On the unprotected plant each
of several racemes produced fifteen pods; nine produced between sixteen
and twenty-two pods, and one produced thirty pods.
Lotus corniculatus (Leguminosae).--Several covered-up plants produced
only two empty pods, and not a single good seed.
Trifolium repens (Leguminosae).--Several plants were protected from
insects, and the seeds from ten flowers-heads on these plants, and from
ten heads on other plants growing outside the net (which I saw visited
by bees), were counted; and the seeds from the latter plants were very
nearly ten times as numerous as those from the protected plants.


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