I should, however, state that some of the
above flowers of the primrose were fertilised with pollen from the polyanthus,
which is certainly a variety of the cowslip, as may be inferred from the perfect
fertility inter se of the crossed offspring from these two plants. (2/6. Mr.
Scott has discussed the nature of the polyanthus ('Proceedings of the Linnean
Society' 8 Botany 1864 page 103), and arrives at a different conclusion; but I
do not think that his experiments were sufficiently numerous. The degree of
infertility of a cross is liable to much fluctuation. Pollen from the cowslip at
first appears rather more efficient on the primrose than that of the polyanthus;
for 12 flowers of both forms of the primrose, fertilised legitimately and
illegitimately with pollen of the cowslip gave five capsules, containing on an
average 32.4 seeds; whilst 18 flowers similarly fertilised by polyanthus-pollen
yielded only five capsules, containing only 22.6 seeds. On the other hand, the
seeds produced by the polyanthus-pollen were much the finest of the whole lot,
and were the only ones which germinated.) To show how sterile these hybrid
unions were I may remind the reader that 90 per cent of the flowers of the
primrose fertilised legitimately with primrose-pollen yielded capsules,
containing on an average 66 seeds; and that 54 per cent of the flowers
fertilised illegitimately yielded capsules containing on an average 35.
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