Some Problems of Reproduction: a Comparative Study of ...

SOME PROBLEMS OF BEPBODUOTION. 39
there is no question of giving a mystical significance to this
"excretion process."
(4) The Lower Subbasal and the two Basal Cells
lie huddled and inert at the base of the embryo-sac, as
"Antipodal cells/ 5 and finally disappear in the growing
endosperm.
The homologies of these structures are somewhat obscure,
but the following explanation may be tendered as a fair
one:
(1) The four cells of the form N z correspond to prothallial
cells of a Cryptogam or Gymnosperm; cells which we
know form the common initials of both archegonium-wall (or
neck at least) and oogonium.
(2) The Apical cell (N 2 a) divides to form an archegonium
of two neck-cells only, without any oogonium (such an archegonial
neck of two cells is found in Cycads).
(3) The Subapical cell (N 3 sa) divides into a superposed
pair of which the Upper is the oosphere, of whose significance
as a gamete there can be "no possible doubt whatever."
(4) The Lower Subapical cell (N 3 lsa) is that which conjugates
with the Upper Subbasal (N 3 usb) ; as a consequence
the cell produced by their fusion rejuvenesces, and by its
repeated bipartition forms the endosperm. This structure is
comparable to a thallogenous plant of low organisation and
limited life; the endosperm-cell that produces it must be
regarded as a zygote, and the two cells that unite to form this
zygote are necessarily gametes, whose close kinship, though
the most distant possible under the circumstances, may influence
the low organisation and limited life of their zygote. 1
Thus the subapical cell producing by bipartition two gametes
is a gametogonium; or we may go further and identify it with
an initial cell, producing an archegoninm without a neck, and
reduced to the oogonium. Of the two gametes formed by the
1 This important identification of the endosperm-cell as a zygote was first
made out by Professor Le Monnier, of Nancy, in an unpretentious little note
in ' Morot's Journal de Botanique,' vol. i, p. 140 (June, 1887).