The Embryosac. 
The inner megaspore which from the very first moment shows 
itself the functioning one, is regularly filled up with cytoplasm. 
Its nucleus is to be tound at the top end, where it divides 
(Plate I, Fig. 10, 11). Soon after this first division one of the 
daughter nuclei commences to move to the lower end of the 
sac. This migration is accompanied by an ever increasing polari- 
sation, the result being the typical and well know figure of the 
polisared two-nucleate stage of the embryosac: two nuclei separa- 
ted by a large central vacuole (Plate I, Fig. 12, Plate II, Fig. 13, 14), 
and both embedded in a comparatively small mass of cytoplasm. 
By a second division the four-nucleate stage is reached. 
(Plate I, Fig. 18, 19). The primary micropylar nucleus however 
seems to be in advance (Plate II, Fig. 15), sometimes even as 
much as having finished its division when the primary chalazal 
nucleus is still at rest (Plate II, Fig. 16, 17). Embryosacs are 
then three-nucleate. 
The four-nucleate stage is followed by a division of one of 
the nuclei only, both chalazal and one micropylar nucleus 
remaining undivided. So at the top end never more than three 
and at the chalazal end never more than two nuclei are seen. 
(Plate III, Fig. 20, 21, 22). The egg apparatus is formed in the 
usual way, the three nuclei get separated by cell walls (Plate III, 
Fig. 23) and finally the two well shaped synergids partly cover 
the egg (Plate III, Fig. 24). In the mature sac cytoplasm in the 
cells of the egg apparatus shows the normal distribution. As 
usual the synergids are characterized by a large vacuole at 
the lower end, cytoplasm and nuclei being gathered at the topend. 
During the formation of the egg apparatus the two chalazal 
nuclei are seen in close connection and steadily moving upwards 
(Plate III, Fig. 21, 22, 23), Finally a position is reached at the 
very topend of the embryosac quite close to egg and synergids 
(Plate III, Fig. 24). There has never been seen any sign of fur- 
ther division or of fusion. 
Thus the mature embryosac is five-nucleate, three of the 
nuclei being of micropylar and two of chalazal origin. The 
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