As insects, and especially honeybees, usually visit all recently
opened flowers on a raceme, experiments C and D were conducted to
determine whether more seed would be produced when pollen from other
flowers on the same raceme was placed on the stigmas of the flowers
than when only the pollen produced by each flower was placed on its
own stigma. The effect of pollination when only the pollen produced by
an individual flower was placed on its own stigmas was also obtained
in experiment F, as by this method of pollination no pollen was
transferred from one flower to another. It can not be stated definitely
that the seed produced by the cross-pollinated flowers was the result
of fertilization with foreign pollen, as the anthers were not removed
from the flowers pollinated because it would be necessary to remove
the anthers when the flowers were not more than two-thirds mature, and
in doing this the flowers would be so mutilated that only occasionally
would pollination at this time or at a later date be effective. The
flowers listed in experiment E were pollinated a short time before they
opened, and in each case pollen taken from flowers of other plants
was placed on the stigmas. The petals of the cross-pollinated flowers
were not mutilated, and in each case they returned to their original
positions soon after pollination. The results obtained in experiment B,
where the racemes were simply labeled and left open to the action of
insects at all times, serve for comparison with other experiments where
the flowers were protected from insect visitation and were artificially
manipulated.
Martin (25) found the setting of alfalfa seed and Westgate (40)
found the setting of red-clover seed to be affected by an excessive
quantity of moisture in the soil or atmosphere. In order to overcome
the possible effect of this or of other detrimental factors, in each
experiment only the flowers on a certain number of racemes were
pollinated at one time. All of the experiments were repeated a number
of times during the months of July and August, 1916, and the results
given in Table III show the total number of flowers pollinated and the
number of pods that formed during the two months.
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