180 EVOLUTION OF PLANTS 
(Fig. 44, B, pn) coalesce. About the three nuclei at 
the upper or micropylar end of the embryo-sac there is 
formed an aggregation of protoplasm resulting in three 
naked cells, which constitute the so-called “ egg-appa- 
ratus.”” The three nuclei at the other end become also 
surrounded by protoplasm, which usually is bounded 
by a definite cell-wall. These three cells are called the 
antipodal cells (Fig. 44, B, ant). 
In some of the simpler Monocotyledons, eg. the 
grasses, the number of antipodal cells is more numer- 
ous, and a few cases are known where there seems to 
be a multiplication of the other cells within the embryo- 
sac; but these are not yet sufficiently understood to 
throw much light upon the homologies existing between 
the female gametophyte of the Angiosperms and that 
of the Gymnosperms and heterosporous Pteridophytes. 
Whether the egg-apparatus is to be considered as a 
single archegonium, or whether each of its cells is to 
be so regarded, cannot be positively decided at present. 
The other cells, z.e. the antipodals and the endosperm 
cells formed later, represent probably the vegetative 
part of the gametophyte. 
The microsporangia are much less modified, and the 
development of the microspores (pollen) corresponds 
exactly with that of the Gymnosperms and’the Arche- 
goniates from the mosses up, even to the final division 
of the mother-cell into four spores. The ripe pollen- 
spore shows exactly the same structure as the spores 
of the Archegoniates. On germination two cells are 
formed, a large vegetative one and a small antheridial 
cell (Fig. 44, C). The former, when the spore falls 
upon the pistil, develops into the pollen-tube, and the 
