its children and grandchildren. A cross between the children of Hero did
not give to the grandchildren any advantage over the self-fertilised
grandchildren raised from the self-fertilised children. And as far as my
observations can be trusted, which were made on very unhealthy plants,
the great-grandchildren raised from intercrossing the grandchildren had
no advantage over the seedlings from the grandchildren the product of
continued self-fertilisation; and what is far more remarkable, the
great-grandchildren raised by crossing the grandchildren with a fresh
stock, had no advantage over either the intercrossed or self-fertilised
great-grandchildren. It thus appears that Hero and its descendants
differed in constitution in an extraordinary manner from ordinary plants
of the present species.

Although the plants raised during ten successive generations from
crosses between distinct yet inter-related plants almost invariably
exceeded in height, constitutional vigour, and fertility their
self-fertilised opponents, it has been proved that seedlings raised by
intercrossing flowers on the same plant are by no means superior, on the
contrary are somewhat inferior in height and weight, to seedlings raised
from flowers fertilised with their own pollen. This is a remarkable
fact, which seems to indicate that self-fertilisation is in some manner
more advantageous than crossing, unless the cross brings with it, as is
generally the case, some decided and preponderant advantage; but to this
subject I shall recur in a future chapter.

The benefits which so generally follow from a cross between two plants
apparently depend on the two differing somewhat in constitution or
character. This is shown by the seedlings from the intercrossed plants
of the ninth generation, when crossed with pollen from a fresh stock,
being as superior in height and almost as superior in fertility to the