ven a single white eye, but a whole white tuber, which has since been
propagated and keeps true.[883] Several cases have been recorded of
large portions of whole rows of potatoes slightly changing their
character.[884]

Dahlias propagated by tubers under the hot climate of St. Domingo vary
much; Sir R. Schomburgk gives the case of the "Butterfly variety,"
which the second year produced on the same plant "double and single
flowers; here white petals edged with maroon; there of a uniform deep
maroon."[885] Mr. Bree also mentions a plant "which bore two different
kinds of self-coloured flowers, as well as a third kind which partook
of both colours beautifully intermixed."[886] Another case is described
of a dahlia with purple flowers which bore a white flower streaked with
purple.[887]

Considering how long and extensively many Bulbous plants have been
cultivated, and how numerous are the varieties produced from seed,
these plants have not varied so much by offsets,--that is, by the
production of new bulbs,--as might have been expected. With the
Hyacinth a case has been recorded of a blue variety which for three
successive years gave offsets which produced white flowers with a red
centre.[888] Another hyacinth has been described[889] as bearing on the
same truss a perfectly pink and a perfectly blue flower.

Mr. John Scott informs me that in 1862 _Imatophyllum miniatum_, in the
Botanic Gardens of Edinburgh, threw up a sucker which differed from the
normal form, in the leaves being two-ranked instead of four-ranked. The
leaves were also smaller, with the upper surface raised instead of
being channelled.

In the propagation of _Tulips_, seedlings are raised, called _selfs_ or
_breeders_, which "consist of one plain colour on a white or yellow
bottom. These, being cultivated on a dry and rather poor soil, become
broken or variegated and produce new varieties. The time that elapses
before they break varies from one to twenty years or more, and
sometimes this change never takes place."[890] The various broken or
variegated colours which give value to all tulips are due to
bud-variation; for although the {386} Bybloemens and some other kinds
have been raised from several distinct breeders, yet all the Baguets
are said to have come from a single breeder or seedling. This
bud-variation,