e variety as between the different varieties. The flowers vary in
size, and in colour between white and purple, but in no other respect,
except that in one kind the sepals were somewhat elongated. One strange
variety has been described which always produces two sorts of flowers,
the first double and sterile, the second single and fertile.[610] The
fruit or berries also differ, but only in a slight degree.[611]

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The tubers, on the other hand, present a wonderful amount of diversity.
This fact accords with the principle that the valuable and selected
parts of all cultivated productions present the greatest amount of
modification. They differ much in size and shape, being globular, oval,
flattened, kidney-like, or cylindrical. One variety from Peru is
described[612] as being quite straight, and at least six inches in
length, though no thicker than a man's finger. The eyes or buds differ
in form, position, and colour. The manner in which the tubers are
arranged on the so-called roots is different; thus in the
_gurken-kartoffeln_ they form a pyramid with the apex downwards, and in
another variety they bury themselves deep in the ground. The roots
themselves run either near the surface or deep in the ground. The
tubers also differ in smoothness and colour, being externally white,
red, purple, or almost black, and internally white, yellow, or almost
black. They differ in flavour and quality, being either waxy or mealy;
in their period of maturity, and in their capacity for long
preservation.

As with many other plants which have been long propagated by bulbs,
tubers, cuttings, &c., by which means the same individual is exposed
during a length of time to diversified conditions, seedling potatoes
generally display innumerable slight differences. Several varieties,
even when propagated by tubers, are far from constant, as will be seen
in the chapter on Bud-variation. Dr. Anderson[613] procured seed from
an Irish purple potato, which grew far from any other kind, so that it
could not at least in this generation have been crossed, yet the many
seedlings varied in almost every possible respect, so that "scarcely
two plants were exactly alike." Some of the plants which closely
resembled each other above ground, produced extremely dissimilar
tubers; and some tubers which externally could h