When insects were excluded
the flower-heads seemed to produce as many and as fine seeds as the
exposed heads.
Trifolium procumbens.--On one occasion covered-up plants seemed to yield
as many seeds as the uncovered. On a second occasion sixty uncovered
flower-heads yielded 9.1 grains weight of seeds, whilst sixty heads on
protected plants yielded no less than 17.7 grains; so that these latter
plants were much more productive; but this result I suppose was
accidental. I have often watched this plant, and have never seen the
flowers visited by insects; but I suspect that the flowers of this
species, and more especially of Trifolium minus, are frequented by small
nocturnal moths which, as I hear from Mr. Bond, haunt the smaller
clovers.
Medicago lupulina (Leguminosae).--On account of the danger of losing the
seeds, I was forced to gather the pods before they were quite ripe; 150
flower-heads on plants visited by bees yielded pods weighing 101 grains;
whilst 150 heads on protected plants yielded pods weighing 77 grains.
The inequality would probably have been greater if the mature seeds
could have been all safely collected and compared. Ig. Urban (Keimung,
Bluthen, etc., bei Medicago 1873) has described the means of
fertilisation in this genus, as has the Reverend G. Henslow in the
'Journal of the Linnean Society Botany' volume 9 1866 pages 327 and 355.
Nicotiana tabacum (Solanaceae).
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