412 BOTANICAL GAZETTE [JUNE 
expended in the important changes which follow in rapid suc- 
cession. 
EMBRYO-SAC, 
At length certain cells centrally located in this archesporial 
mass indicate by a thickening of the linin network, enlargement 
of the granules, and a coarser appearance of the nucleus, that they 
are entering the prophase of mitosis. The nucleoli of such cells 
contrast with those of neighboring cells in size and staining 
qualities. 
Before the spirem is formed the race is usually yielded to 
a single vigorous cell, apparently the fourth or fifth below the 
surface. This cell; improving the advantage thus accorded, crowds 
upon its sister cells, and they in turn may soon show evidence 
of collapse. figs. 27 and 22 show a condition not uncommon, 
in which some of the adjacent cells are in advanced stage of 
deterioration, while in other instances the neighboring cells show 
little evidence of breaking down when the spirem is formed in 
the fertile megaspore ( figs. 24, 25). It is not unusual to find the © 
condition represented in fig. 23, in which the nuclei of cells in the 
apical region of the nucellus, previous to the spirem stage of the 
fertile megaspore, contain numerous small nucleoli, presumably 
the fragments of a single large nucleolus common to all healthy 
cells, and whose fragmentation may be regarded as an early evi- 
dence of the deterioration of the cell. 
Inasmuch as these more marked cells usually bear a lineal 
relation to each other, it might suggest the usual type of tapetal 
cells, potential and fertile megaspores recorded for angiosperms. 
The events leading to this condition, and those that follow, pre- 
clude this hypothesis; and in addition it may be said that the 
axial position does not always obtain. Such cells may lie side 
by side, or they may be separated by one or more intervening 
Celis. 
As stated above, it is usual that but a single archesporial 
cell proceeds so far as to form the spirem. It is, however, not 
always the case. Fig. 29 shows a well-defined exception. It 
shows two well-formed spindles with the chromosomes arranged 
ws is 
