As a large number of seeds were placed on the sand to germinate, many
remained after the pairs had been selected, some of which were in a
state of germination and others not so; and these were sown crowded
together on the opposite sides of one or two rather larger pots, or
sometimes in two long rows out of doors. In these cases there was the
most severe struggle for life among the crossed seedlings on one side of
the pot, and the self-fertilised seedlings on the other side, and
between the two lots which grew in competition in the same pot. A vast
number soon perished, and the tallest of the survivors on both sides
when fully grown were measured. Plants treated in this manner, were
subjected to nearly the same conditions as those growing in a state of
nature, which have to struggle to maturity in the midst of a host of
competitors.
On other occasions, from the want of time, the seeds, instead of being
allowed to germinate on damp sand, were sown on the opposite sides of
pots, and the fully grown plants measured. But this plan is less
accurate, as the seeds sometimes germinated more quickly on one side
than on the other. It was however necessary to act in this manner with
some few species, as certain kinds of seeds would not germinate well
when exposed to the light; though the glasses containing them were kept
on the chimney-piece on one side of a room, and some way from the two
windows which faced the north-east.
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