bryony results from an adventitious production
of embryos from the cells of the nucellus around the top of the
embryo-sac. In a species of _Allium_, embryos have been found
developing in the same individual from the egg-cell, synergids,
antipodal cells and cells of the nucellus. In two Malayan species of
_Balanophora_, the embryo is developed from a cell of the endosperm,
which is formed from the upper polar nucleus only, the egg apparatus
becoming disorganized. The last-mentioned case has been regarded
as representing an apogamous development of the sporophyte from the
gametophyte comparable to the cases of apogamy described in Ferns. But
the great diversity of these abnormal cases as shown in the examples
cited above suggests the use of great caution in formulating definite
morphological theories upon them.

_Fruit and seed._

As the development of embryo and endosperm proceeds within the
embryo-sac, its wall enlarges and commonly absorbs the substance of
the nucellus (which is likewise enlarging) to near its outer limit,
and combines with it and the integument to form the _seed-coat_; or
the whole nucellus and even the integument may be absorbed. In some
plants the nucellus is not thus absorbed, but itself becomes a seat of
deposit of reserve-food constituting the _perisperm_ which may coexist
with endosperm, as in the water-lily order, or may alone form a
food-reserve for the embryo, as in _Canna_. Endospermic food-reserve
has evident advantages over perispermic, and the latter is
comparatively rarely found and only in non-progressive series. Seeds
in which endosperm or perisperm or both exist are commonly called
_albuminous_ or _endospermic_, those in which neither is found are
termed _exalbuminous_ or _exendospermic_. These terms, extensively
used by systematists, only refer, however, to the grosser features
of the seed, and indicate the more or less evident occurrence of a
food-reserve; many so-called exalbuminous seeds show to microscopic
examination a distinct endosperm which may have other than a nutritive
function. The presence or absence of endosperm, its relative amount
when present, and the position of the embryo within it, are valuable
characters for the distinction of orders and groups of orders.
Meanwhile the ovary wall has developed to form the fruit or pericarp,
the structure of which is closely associated with the manner of
distribution of the seed. Frequently the influence of fertilization is
f