* * *

_Bud-variation by Suckers, Tubers, and Bulbs._--All the cases hitherto
given of bud-variation in fruits, flowers, leaves, and shoots, have
been confined to buds on the stems or branches, with the exception of a
few cases incidentally noticed of varying suckers in the rose,
pelargonium, and chrysanthemum. I will now give a few instances of
variation in subterranean buds, that is, by suckers, tubers, and bulbs;
not that there is any essential difference between buds above and
beneath the ground. Mr. Salter informs me that two variegated varieties
of Phlox originated as suckers; but I should not have thought these
worth mentioning, had not Mr. Salter found, after repeated trials, that
he could not propagate them by "root-joints," whereas, the variegated
_Tussilago farfara_ can thus be safely propagated;[879] but this latter
plant may have originated as a variegated seedling, which would account
for its greater fixedness of character. The Barberry (_Berberis
vulgaris_) offers an analogous case; there is a well-known variety with
seedless fruit, which can be propagated by cuttings or layers; but
suckers always revert to the common form, which produces fruit
containing seeds.[880] My father repeatedly tried this experiment, and
always with the same result.

Turning now to tubers: in the common Potato (_Solanum tuberosum_) a
single bud or eye sometimes varies and produces a new variety; or,
occasionally, and this is a much more remarkable circumstance, all the
eyes in a tuber vary in the same manner and at the same time, so that
the whole tuber assumes a new character. For instance, a single eye in
a tuber of the {385} old _Forty-fold potato_, which is a purple
variety, was observed[881] to become white; this eye was cut out and
planted separately, and the kind has since been largely propagated.
_Kemp's Potato_ is properly white, but a plant in Lancashire produced
two tubers which were red, and two which were white; the red kind was
propagated in the usual manner by eyes, and kept true to its new
colour, and, being found a more productive variety, soon became widely
known under the name of _Taylor's Forty-fold_.[882] The _Old
Forty-fold_ potato, as already stated, is a purple variety; but a plant
long cultivated on the same ground produced, not as in the case above
gi