species of _Thalictrum_, _Antennaria_ and _Alchemilla_. Polyembryony
is generally associated with the development of cells other than the
egg-cell. Thus in _Erythronium_ and _Limnocharis_ the fertilized
egg may form a mass of tissue on which several embryos are produced.
Isolated cases show that any of the cells within the embryo-sac may
exceptionally form an embryo, _e.g._ the synergidae in species of
_Mimosa_, _Iris_ and _Allium_, and in the last-mentioned the
antipodal cells also. In _Coelebogyne_ (Euphorbiaceae) and in _Funkia_
(Liliaceae) polyembryony 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