62 seeds; but we have no means of judging how
near an approach this average makes to that from flowers legitimately
fertilised. He also fertilised 45 flowers with pollen from the shortest stamens,
and these yielded only 17 capsules, or 31 per cent, containing on an average
only 2.65 seeds. We thus see that about thrice as many flowers, when fertilised
with pollen from the mid-length stamens, produced capsules, and these contained
twice as many seeds, as did the flowers fertilised with pollen from the shortest
stamens. It thus appears (and we find some evidence of the same fact with O.
speciosa), that the same rule holds good with Oxalis as with Lythrum salicaria;
namely, that in any two unions, the greater the inequality in length between the
pistils and stamens, or, which is the same thing, the greater the distance of
the stigma from the anthers, the pollen of which is used for fertilisation, the
less fertile is the union,--whether judged by the proportion of flowers which
set capsules, or by the average number of seeds per capsule. The rule cannot be
explained in this case any more than in that of Lythrum, by supposing that
wherever there is greater liability to self-fertilisation, this is checked by
the union being rendered more sterile; for exactly the reverse occurs, the
liability to self-fertilisation being greatest in the unions between the pistils
and stamens which approach each other the nearest, and these are the more
fertile.
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