a little before, and more profusely than
the self-fertilised plants. On opposite sides of another _small_ pot a
large number of crossed and self-fertilised seeds were sown, so that
they had to struggle for bare existence; a single rod was given to each
lot: here again the crossed plants showed from the first their
advantage; they never quite reached the summit of the seven-foot rod,
but relatively to the self-fertilised plants their average height was
as seven feet to five feet two inches. The experiment was repeated in
the two following generations with plants raised from the
self-fertilised and crossed plants, treated in exactly the same manner,
and with nearly the same result. In the second generation, the crossed
plants, which were again crossed, produced 121 seed-capsules, whilst
the self-fertilised plants, again self-fertilised, produced only 84
capsules.

Some flowers of the _Mimulus luteus_ were fertilised with their own
pollen, and others were crossed with pollen from distinct plants
growing in the same pot. The seeds after germinating were thickly
planted on opposite sides of a pot. The seedlings were at first equal
in height; but when the young crossed plants were exactly half an inch,
the {129} self-fertilised plants were only a quarter of an inch high.
But this inequality did not continue, for, when the crossed plants were
four and a half inches high, the self-fertilised were three inches; and
they retained the same relative difference till their growth was
complete. The crossed plants looked far more vigorous than the
uncrossed, and flowered before them; they produced also a far greater
number of flowers, which yielded capsules (judging, however, from only
a few) containing more seeds. As in the former case, the experiment was
repeated in the same manner during the next two generations, and with
exactly the same result. Had I not watched these plants of the Mimulus
and Ipomoea during their whole growth, I could not have believed it
possible, that a difference apparently so slight, as that of the pollen
being taken from the same flower, and from a distinct plant growing in
the same small pot, could have made so wonderful a difference in the
growth and vigour of the plants thus produced. This, under a
physiological point of view, is a most remarkable phenomenon.

*