y be
placed a short distance within it, as in the case of some open carpels
of _Ranunculus Ficaria_,[417] and in which two ovules were borne in
shallow depressions on the upper or inner surface of the open carpel and
supplied with vascular cords from the central bundle or midrib. The
outer coating of the ovule here contained barred or spiral fusiform
vessels derived from the source just indicated.

In the very common cases where the pistil of _Trifolium repens_ becomes
foliaceous (see Frondescence), the outer ovules are generally two or
more instead of being solitary. So, also, in the Rose with polliniferous
ovules (see p. 274). Among _Umbelliferae_ affected with frondescence of
the pistil a similar increase in the number of ovules takes place. It
will be borne in mind that in most, if not all, these cases the
structure of the ovule is itself imperfect.[418]

What are called in popular parlance double almonds or double nuts
(_Corylus_) are cases where two seeds are developed in place of one.

In the 'Revue Horticole,' 1867, p. 382, mention is made of a bush which
produces these double nuts each year--in fact, it never produces any
single-seeded fruit. The plant was a chance seedling, perhaps itself the
offspring of a double-seeded parent. It would be interesting to observe
if the character be retained by the original plant, and whether it can
be perpetuated by seed or by grafting.

It is necessary to distinguish in the case of the nut between additional
seeds or ovules, as just described, and the double, triple, or fourfold
nuts that are occasionally met with, and which are the result either of
actual multiplication of the carpels or of the continued development of
some of the carpels which, under ordinary circumstances cease to grow
(see _ante_, p. 364). In the case of a ripe nut with two seeds it might
be impossible to tell whether the adventitious seed were the product of
multiplication, or whether it belonged, in the first instance, to the
same carpel as that producing the fellow-seed, or to a different and now
obliterated ovary. In all probability, however, the second seed would be
accounted for by the development of two seeds in one carpellary cavity.

There is still another condition occasionally met with in the almond,
and which must be discriminated from the more common multiplication of
the seed, and which is the multiplication of the embryos within the
seed, and which furnishes the subject of the succeedi