THE OVULE 
81 
three at the micropylar end form the egg-apparatus , three at 
the other end the antipodal cells (a). The egg-apparatus is 
composed of three cells, an ovum (o) and two infertile 
synergidae ; the antipodal cells appear to be usually function- 
less. The pollen tube (/) passes from the stigma down the 
style, carrying the male cell-nuclei. It may enter the ovary 
and pass into the micropyle ( micropylar , porogamic , or 
acrogamic fertilisation) or burrow in the carpel wall and 
through the funicle and chalaza to the embryo-sac ( chalazo - 
gamic fertilisation, see Chalazogamae). 
Fig. 9. Diagrammatic longitudinal Section of an anatro- 
pous Ovule. //, the placenta,/; funicle, united to side of ovule forming 
the raphe, (r); v.b ., vascular bundle, ch, chalaza of ovule, ii and oi 9 inner 
and outer integuments, m y micropyle ; nu, nucellus, containing e , 
embryo-sac, in which are o, the ovum with the two synergidae, n y the 
central nucleus, and a , the antipodal cells. A pollen-tube, t , is 
approaching the micropyle. 
One of the male nuclei fertilises the ovum, forming the 
zygote; the other in many cases (and perhaps usually) unites 
with the central nucleus, which then divides rapidly to form 
a mass of endosperm cells tilling up the embryo-sac. This 
endosperm is thus not homologous with that of the 
Gymnospermae. The zygote grows into the embryo, and 
feeds upon the stores made by the parent plant in the 
endosperm ; the ovule ripens to a seed. 
w. 6 
