170 ANGIOSPERMS. 
the cell. The first nuclear division is heterotypic, corresponding in 
detail with the first karyokinesis in the microspore mother-cell of the 
same plant. The two resulting cells soon divide again, thus giving 
rise to the axial row of four cells, the four potential macrospores. 
The second nuclear division is the same as the second division in the 
pollen mother-cell. A phenomenon which sometimes occurs in Hedle- 
éorus (and it is probable that 
it may take place in other plants 
also) furnishes additional evi- 
dence in support of our hy- 
pothesis, namely, that the two 
divisions in this hypodermal 
cell, or embryo-sac mother-cell, 
are homologous with the two 
divisions in the pollen mother- 
cell, Cell division may not 
take place until after the second 
nuclear division, when the four 
granddaughter nuclei will lie in 
the upper end of the cell, and 
the cell-plates are laid down 
simultaneously (Fig. 7o, B). 
It has been observed also that 
the four nuclei, instead of lying 
in one plane as in Fig. 70, B, 
are sometimes arranged in a 
tetrad and connected with each 
other by a system of kinoplas- 
mic connecting fibers, asin the 
Fic. 70.—Embryo-sac mother-cell of Helleborus 
Setidus, ‘ 
A, Upper portion of mother-cell showing nucleus in the corresponding stage of the pol- 
prophase of the first mitosis. len mother-cell. 
B, same less highly magnified, showing the four poten- ‘ 
tial macrospores; in this case cell-division did not The lower cell of the axial 
ke pa ‘ ; ‘ 
follow first mitosis, and the plasma membranes mark- row becomes ,asart ule, the 
ing out the four cells were formed simultaneously, % ql 
functional macrospore. It in- 
creases rapidly in size at the expense of the other three cells and the 
adjacent tissue of the nucellus, and develops in the usual way into the 
embryo-sac. 
The unmistakable homology of the macrospore mother-cell of the 
Angiosperms with that of the Gymnosperms has been very clearly 
shown by Juel (1900). This author finds in Zarzx that the first and 
second nuclear divisions in the macrospore mother-cell, which give 
