386 Cooke and Schively on Observations on the 
about, so that they lie one above the other, just as does the 
lower pair. The sac elongates steadily, and the connecting 
thread of protoplasm between the two poles becomes con- 
siderably longer. There seems to be no increase in the total 
amount of cytoplasm present. 
Next, division occurs in these four cells. Similar pointed 
spindles form, on which lie many small stout rod-like chro- 
mosomes. ‘The two spindles at the upper end show exactly 
the same relation to each other as did the two spindles of the 
preceding stage. Division of the two lower cells was not 
observed, but it is supposed the spindles lie in the same rela- 
tions as in the upper region, since the relative positions of 
the nuclei after division indicate it. 
In the mature embryo sac, the cytoplasm is aggregated in 
three distinct masses. It narrows toward the lower free 
end of the ovule, and is broadest just below the micropylar 
end. The eight typical nuclei are now present. The two 
synergidal nuclei lie side by side just below the micropyle. 
A little farther down is the egg nucleus, larger and more 
deeply stained than the synergids. Below is a sharp trans- 
verse break in the cytoplasm. Right under this lie the two 
fusion nuclei. They are seen to be approaching each other, 
though lying some distance apart. Later they lie side by side 
(Fig. 10), closely appressed and flattened against each other. 
They are the largest, densest nuclei in the entire embryo sac. 
They have a large amount of deeply stained chromatin, and 
a very large, dense spherical nucleolus. At a considerably 
later stage they are seen to have fused to form the single 
large endosperm nucleus. 
Below, in the same mass of cytoplasm that contains the 
endosperm nucleus, extends the long central vacuole before 
noted ; it is surrounded by narrow protoplasmic walls. An- 
other complete transverse split in the cytoplasm occurs 
(Figs. 10, 11). In the lower cytoplasmic mass lie the three 
antipodal cells, the lower two lying side by side, and having 
the appearance of being separated by a faint cell wall. They 
