408 The Botanical Gazette. [December, 
ly polyhedral in outline, but later more oval in contour, 
elongates and containsa nucleus with nucleolus imbedded in 
a rich mass of protoplasm. In some sections the nucleus ap- 
peared to be elongated in the same direction as that of the 
embryo-sac. During the subsequent growth of the integu- 
ment and nucellus the embryonal sac enlarges (figs. 13 and 
14), and the nucleus of the mother-cell undergoes subdivis- 
ion. In fig. 15 the nucleus has divided, and the mother-cell 
is now separated into two equal parts by a transverse wall, 
each part containing a nucleated-cell. Presently, the two nu- 
clei divide, a transverse wall is formed in each half, and thus 
we have, at the end of the second and last subdivision of the 
mother-cell of the embryo-sac, four equal nueleated-cells 
(fig. 16). At this stage of the embryo-sac there is a very 
close analogy to the division of the mother-cell into four cells, 
worked out by Strasburger in Polygonum and Senecio. The 
cross walls formed between the cells are very strongly re- 
fractive and much swollen; the middle transverse wall is re- 
markably distended and persists much longer than the other 
two partitions; in several sections the middle wall was found 
intact when the coutents of the cells were completely ab- 
sorbed. 
Of the four cells into which the primitive mother-cell of the 
embryonal sac is now divided, only the lower one is charac- 
terized by further growth;® this cell, therefore, becomes the 
true mother-cell of the embryo-sac (fig. 17,@). Subsequently, 
the protoplasm of the upper three cells becomes viscid, the 
nuclei show disintegration, and the upper wall of the lower, 
club-shaped cell (mother-cell) indicates a rigid turgescence- 
When the upper three cells begin to disorganize (in centrifugal 
order), they become crescent-shaped; their nuclei disappeat, 
their walls are displaced, and the cell contents are absorbed 
by the encroachment of the lower, mother-cell. After the 
cells are completely disorganized and absorbed, the mother- 
cell assumes a central position in the embryo-sac (fig. 19): 
Simultaneously with the obliteration of the upper cells of the 
embryo-sac, the one-cell-layer of the nucellus undergoes 4 
similar process of disintegration. The first mark of displace- 
ment is shown by the reduction of the cell contents to 4 
granular protoplasmic mass; then follows the disappearance 
is 
. 
® The micropylar end is known as the upper extremity of the ovule, while its 
opposite is the lower end, 
