Immeasurable variability seems here to be the result of
crossing. But on a closer inspection the range of characters is not so
very much wider in these hybrid races than in the groups of parent
species which have contributed to the origin of the hybrids. Our
tuberous begonias owe their variability to at least seven original
parent species, [273] and to the almost incredible number of
combinations which are possible between their characters. The first of
these crosses was made in the nursery of Veitch and Sons near London by
Seden, and the first hybrid is accordingly known as _Begonia sedeni_ and
is still to be met with. It has been superseded by subsequent crosses
between the _sedeni_ itself and the _Veitchi_ and _rosiflora_, the
_davisii_, the _clarkii_ and others. Each of them contributed its
advantageous qualities, such as round flowers, rosy color, erect flower
stalks, elevation of the flowers above the foliage and others. New
crosses are being made continuously, partly between the already existing
hybrids and partly with newly introduced wild species. Only rarely is it
possible to get pure seeds, and I have not yet been able to ascertain
whether the hybrids would come true from seed. Specific and varietal
characters may occur together in many of the several forms, but nothing
is as yet accurately known as to their behavior in pure fertilizations.
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