Flora’s Secret Gardens j 491491 491
In another section of Origin of Species titled “Utilitarian Doctrine, How Far True: Beauty,
How Acquired,” Darwin commented that “some naturalists” still objected to “the utilitar-
ian doctrine that every detail of structure has been produced for the good of the possessor.”
Instead, they believe that the most attractive structures were “created for the sake of beauty,
to delight man or the Creator.” Darwin’s argument against this idea is based on a compari-
son of the corollas of wind- pollinated versus insect- pollinated flowers:Flowers rank amongst the most beautiful productions of nature; but they have been
rendered conspicuous in contrast with the green leaves, and in consequence at the
same time beautiful, so that they can be easily observed by insects. I have come to this
conclusion from finding it an invariable rule that when a flower is fertilized by the
wind it never has a gaily colored corolla. ... Hence we may conclude that, if insects
had not been developed on the face of the earth, our plants would not have been
decked with beautiful flowers, but would have produced only such poor flowers as we
see on our fir, oak, nut and ash trees, on grasses, spinach, docks, and nettles, which are
all fertilized through the agency of wind.^19One aspect of plant reproduction that Darwin was unable to explain, however, was the
cause of variability among hybrid progeny. According to essentialist doctrine, the heredi-
tary material was a uniform essence. It followed that during hybrid formation the two dif-
ferent essences mixed with one another like two miscible fluids. If such were the case, one
would expect that all the progeny of a cross would be identical to each other and intermediate
between the two parents. Furthermore, if the progeny of the hybrid cross (F 1 generation) were
crossed with each other, the progeny of the second cross (F 2 generation) would be expected
to be identical to the F 1 generation. Instead, the F 2 generation was far more variable than the
F 1 generation. During the classical era, this phenomenon was referred to as “degeneration”—
which, from the point of view of farmers wishing to perpetuate the desirable characteristics
of cultivated fruits, it certainly was. Olive trees are, of course, the classic example.
Koelreuter, Gaertner, and others were puzzled by the fact that F 1 hybrids of different crosses
sometimes exhibited slightly different phenotypes: some appeared to be intermediate between
the two parents in all respects, some were mixtures of the features of both parents, whereas
others tended to resemble one or the other of the parents. Koelreuter had tried to attribute
these anomalies to incomplete mixing of the two parental essences during fertilization.
As for the extreme variability of the F 2 generation, Koelreuter was completely baffled.
Darwin tried, but failed, to come up with an explanation. In the 1861 edition of Origin, he
argued that the variability of the F 2 generation was caused by the physiological condition
of the flower:For it bears on and corroborates the view which I have taken on the cause of ordinary
variability; namely, that it is due to the reproductive system being eminently sensitive
to any change in the conditions of life, being thus often rendered either impotent or at
least incapable of its proper function of producing offspring identical with the parent-
form. Now hybrids in the first generation are descended from species (excluding those
long cultivated) which have not had their reproductive systems in any way affected,
and they are not variable; but hybrids themselves have their reproductive systems seri-
ously affected, and their descendants are highly variable.^20