me flower,[525] says he remembers when young being delighted with
the portraits in Sweet's work; "but what are they in point of beauty
compared with the Pelargoniums of this day? Here again nature did not
advance by leaps; the improvement was gradual, and, if we had neglected
those very gradual advances, we must have foregone the present grand
results." How well this practical horticulturist appreciates and
illustrates the gradual and accumulative force of selection! The Dahlia has
advanced in beauty in a like manner; the line of improvement being guided
by fashion, and by the successive modifications which the flower slowly
underwent.[526] A steady and gradual change has been noticed in many other
flowers: thus an old florist,[527] after describing the leading varieties
of the Pink which were grown in 1813, adds, "the pinks of those days would
now be scarcely grown as border-flowers." The improvement of {217} so many
flowers and the number of the varieties which have been raised is all the
more striking when we hear that the earliest known flower-garden in Europe,
namely at Padua, dates only from the year 1545.[528]

* * * * *

_Effects of Selection, as shown by the parts most valued by man presenting
the greatest amount of Difference._--The power of long-continued selection,
whether methodical or unconscious, or both combined, is well shown in a
general way, namely, by the comparison of the differences between the
varieties of distinct species, which are valued for different parts, such
as for the leaves, or stems, or tubers, the seed, or fruit, or flowers.
Whatever part man values most, that part will be found to present the
greatest amount of difference. With trees cultivated for their fruit,
Sageret remarks that the fruit is larger than in the parent-species, whilst
with those cultivated for the seed, as with nuts, walnuts, almonds,
chesnuts, &c., it is the seed itself which is larger; and he accounts for
this fact by the fruit in the one case, and by the seed in the other,
having been carefully attended to and selected during many ages. Gallesio
has made the same observation. Godron insists on the diversity of the tuber
in the potato, of the bulb in the onion, and of the fruit in the melon; and
on the close similarity in these same plants of the other parts.[529]

In order to judge how far my own impression on this subject was correct, I
cultivated numerous varieties of the same spec