242 BOTANICAL GAZETTE [OCTOBER 
only by the epidermal layer. The archesporial cell without dividing 
functions as a megaspore mother cell, which divides to two daughter 
cells, which in turn divide to form four megaspores. The last division 
may be simultaneous in both daughter cells, but usually it is delayed 
in the one nearest the micropyle (/ig. 2). 
Soon after the formation of the megaspores the chalazal one begins 
to enlarge at the expense of the other three, which soon degenerate. 
Before this degeneration has proceeded far the nucleus of the function- 
ing megaspore divides (jig. 3) and the two daughter nuclei remain 
t.—Fic. 5. Bight 
—Fre. 6. ash 
a, degenerating 
Fic. 4. Nuclei of four-nucleate embryo sac dividing to eigh 
nucleate embryo sac: s, synergids; e, egg; a, antipodals; , polar nuclei 
bryo sac with fusing polar nuclei; 9, polar nuclei; s, synergids; e, egg; 
antipodals.—Fic. 7, Young embryo and degenerating endosperm nucleus. 
in the polar positions in the enlarging sac. Each of these two nucle! 
by two successive divisions gives rise to four, so that the mature sac 
contains eight nuclei (fig. 5). As the sac continues to enlarge, the 
nucellar cells which surrounded the four megaspores degenerate, so 
that at about the four-nucleate stage the sac comes to lie against - 
inner integument. At the last division of the embryo sac nucle! a 
two spindles in each end are arranged approximately at right ang ci 
to one another (fig. 4). As is usual, the transverse spindle in the micro 
pylar end gives rise to two synergids, while the longitudinal on¢ ger 
the egg and the micropylar polar nucleus. In the chalazal oe 
longitudinal spindle gives rise to the antipodal polar nucleus and 
