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 35.5 seeds
per capsule. The primrose, especially the short-styled form, when fertilised by
the cowslip, is less sterile, as Gartner likewise observed, than is the cowslip
when fertilised by the primrose. The above experiments also show that a cross
between the same forms of the primrose and cowslip is much more sterile than
that between different forms of these two species.

The seeds from the several foregoing crosses were sown, but none germinated
except those from the short-styled primrose fertilised with pollen of the
polyanthus; and these seeds were the finest of the whole lot. I thus raised six
plants, and compared them with a group of wild oxlips which I had transplanted
into my garden. One of these wild oxlips produced slightly larger flowers than
the others, and this one was identical in every character (in foliage, flower-