but not all, of these experiments, the crossed plants yielded much more
seed than the self-fertilised plants; and I have never seen the {128}
reversed case. The self-fertilised and crossed seeds thus obtained were
allowed to germinate in the same glass vessel on damp sand; and as the
seeds successively germinated, they were planted in pairs on opposite
sides of the same pot, with a superficial partition between them, and
were placed so as to be equally exposed to the light. In other cases
the self-fertilised and crossed seeds were simply sown on opposite
sides of the same small pot. I have, in short, followed different
plans, but in every case have taken all the precautions which I could
think of, so that the two lots should be equally favoured. Now, I have
carefully observed the growth of plants raised from crossed and
self-fertilised seed, from their germination to maturity, in species of
the following genera, namely, Brassica, Lathyrus, Lupinus, Lobelia,
Lactuca, Dianthus, Myosotis, Petunia, Linaria, Calceolaria, Mimulus,
and Ipomoea, and the difference in their powers of growth, and of
withstanding in certain cases unfavourable conditions, was most
manifest and strongly marked. It is of importance that the two lots of
seed should be sown or planted on opposite sides of the same pot, so
that the seedlings may struggle against each other; for if sown
separately in ample and good soil, there is often but little difference
in their growth.

I will briefly describe the two most striking cases as yet observed by
me. Six crossed and six self-fertilised seeds of _Ipomoea purpurea_,
from plants treated in the manner above described, were planted as soon
as they had germinated, in pairs on opposite sides of two pots, and
rods of equal thickness were given them to twine up. Five of the
crossed plants grew from the first more quickly than the opposed
self-fertilised plants; the sixth, however, was weakly and was for a
time beaten, but at last its sounder constitution prevailed and it shot
ahead of its antagonist. As soon as each crossed plant reached the top
of its seven-foot rod its fellow was measured, and the result was that,
when the crossed plants were seven feet high, the self-fertilised had
attained the average height of only five feet four and a half inches.
The crossed plants flowered