LIFE HISTORY OF AN ANGIOSPERM 
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the gynoecium or female system of organs. This, upon dissection, 
will be found to consist of three fused carpellary leaves termed mega- 
sporophylls (carpels) forming a somewhat flask-shaped structure 
called a pistil. The swollen basal portion of the pistil is called the 
ovary; the stalk which arises from it is called the style and the knob- 
like viscid summit of the style is termed the stigma. 
Development of the Female Gamelophyte Through the Maturation of 
the Embryo Sac. — In its immature condition the embryo sac ( mega- 
spore ) contains a mass of protoplasm surrounding a nucleus. This 
nucleus undergoes three divisions forming as a result eight nuclei 
which ultimately arrange themselves within the protoplasm of the 
embryo sac as follows: three of them occupy a position at the apex, 
the lower nucleus of the group being that of the egg or ovum , the 
other two nuclei being the synergids or assisting nuclei; at the oppo- 
site end of the sac three nuclei known as antipodals take their posi- 
tion; the two remaining nuclei called polar nuclei take up a position 
near the center of the embryo sac. In this condition the contents 
of the embryo sac constitutes the female gamelophyte. 
POLLINATION AND FERTILIZATION 
The mature pollen grains are discharged from the ripened anther 
through the splitting open of its wall. They are transferred to the 
stigma of the pistil of another Erythronium flower through the 
agency of insects. Here they germinate, each putting forth a tube 
(pollen tube). The pollen tubes, carrying within it two sperm 
nuclei and a tube nucleus embedded in protoplasm, penetrate 
through the style canal until they reach the micropyles of various 
ovules. Each enters and passes through a micropyle, then piercing 
the nucellus, grows toward the embryo sac. The tip of the tube 
fuses with the end of the embryo sac and the two sperm nuclei are 
discharged into the sac. One of these sperm nuclei passes between 
the synergids and fuses with the nucleus of the egg to form an 
oospore. By this time the tube nucleus has disintegrated. The 
oospore by repeated divisions develops into as many as four embryos 
or young sporophyte plants. Only one of these, however, persists, 
The polar nuclei fuse to form the endosperm nucleus which soon 
undergoes rapid division into a large number of nuclei scattered 
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