18 ARISAEMA TRIPHYLLUM 
endosperm nuclei, indicates that the division of the primary 
nucleus and the migration of the daughter nuclei take place very 
quickly. 
At the time of the division of the primary endosperm nucleus, 
the protoplasm in the embryo-sac becomes highly vacuolated or 
frothy, many small vacuoles taking the place of the few large ones 
usually found (PLATE I, FIG. 6). Some preparations seem to show 
a delicate cross wall formed after the first division of the endosperm 
nucleus. Most of the preparations seem to indicate that nothing 
more than a slight condensation of the protoplasm occurs. It 
seems certain that one daughter of the endosperm nucleus moves 
toward the egg and by two or three consecutive divisions produces 
four to eight free nuclei in the upper portion of the embryo-sac, 
PLATE I, FIG: 6. Contrary to the report of Gow (13, p. 42) these 
nuclei do not retire to the periphery of the cavity but remain 
scattered promiscuously through its upper portion. There is a 
slight tendency for all to move toward the micropylar end of the 
sac, so that the mass of large irregular endosperm cells, produced 
by the formation of walls in all directions about the nuclei, is 
crowded into that portion of the cavity (PLATE I, FIGS. 7, 9, I2). 
Congregation in the upper end is further produced by the rapid 
increase of liquid contents in the lower or residual cavity. The 
embryo-sac enlarges rapidly at the time of fertilization and the 
remnant of the lateral nucellar tissue is quickly disorganized. As 
a result, not infrequently the nuclei of this tissue are seen in 
contact with the thin walls of the new endosperm cells or even 
buried in the protoplasm of the cavity before walls are formed, so 
as to seem to belong to the endosperm. At this early stage, 
however, the active endosperm nuclei are quite large and well 
organized, frequently showing two or more nucleoli. In older 
cells the nuclei are smaller and resemble those of the nucellar tissue 
closely enough to be confused with them. 
The formation of the endosperm as just described leaves the 
egg cell (and the synergids if not destroyed) closely invested by 
the upper end of a large endosperm cell (PLATE 1, FIG. 9) or by two 
or three such cells (PLATE 1, FIGS. 7,11, 14). Fora time further 
growth of the endosperm is accomplished by the division of the 
cells bordering the first wall formed across the embryo-sac cavity. 
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