Belgian savant finds to
prove his rule, inasmuch as although there is a co-existence of
variegated foliage and double flowers in these illustrations, yet the
plants are weakly, the flowers ill formed, or fall off before expansion.
Admitting all this, there still remain cases in which double flowers and
variegated foliage do exist in conjunction, and where the plants are
vigorous and the flowers well developed. Instances of this are known to
cultivators in species of _Dianthus_, _Hemerocallis_, _Althaea_,
_Paeonia_, _Rosa_, _Ranunculus_, _Serissa_, _Saponaria_, etc., and
probably the art of the cultivator would speedily be successful in
raising other examples, were it a matter of importance or interest to
them to do so. At any rate, the existence of a few unimpeachable
illustrations is sufficient to support the opinion of the present
writer, and objected to so strongly by M. Morren that, in the present
state of our knowledge, "no safe inferences can be drawn" from the facts
alluded to by the Belgian professor.[572]

Mr. Darwin[573] has thrown out the suggestion that the cause for the
appearance of double flowers may be sought for in some previous state of
things, bringing about sterility or imperfect formation, or functional
activity of the genitalia of the flower, and consequent compensatory
increase of the petaline element, either in the form of an increased
number of bracts, petals, &c., or in the substitution of petals for
stamens and pistils, &c.

In considering these points the question arises whether they can be
reconciled one with another. And there is little doubt but that they may
be. The production of a flower is preceded by an arrest of vegetation;
this is obvious: the current of the plant's life becomes changed, the
growth of the leaves is checked, the lengthening of the branches is
arrested as the flower-bud forms; moreover, there is a close
relationship in a large majority of flowers between the outer envelopes
of the flower and the scales of a leaf-bud; this is especially so in
regard to the venation, and is admitted by all morphologists. So far,
then, it may be said that the production of a flower, like that of a
bud, is due to a diminution of vegetative action; and as in double
flowers we have, for the most part, merely a repetition and exuberant
formation of floral envelopes, so we may attribute their formation to a
continuance of the same feeble vegetative action as that which produced
the first or