106 BOTANICAL GAZETTE [FEBRUARY 
division is certainly to be regarded as a valuable factor. Consider- 
ing it, for the moment, as of primary importance, the cell in which 
it occurs in the ovule is a megaspore mother cell, producing by 
two successive divisions four megaspores, the innermost of which 
germinates. The presence of a tapetal cell would be determined, 
not by its size or shape, but by its being cut off before the 
reduction division occurs. 
Many botanists, however, look upon the linear arrangement 
of the four cells, and the entire absence of any internal cell divi- 
sion in their formation, as serious objections to this view, and 
prefer to call each of the four a spore mother-cell, of which the 
fertile one develops directly into the megaspore. This would 
make each of the four cells in a form like Silphium the homo- 
logue of the single fertile cell of Lilium. But to the writer, the 
linear arrangement of the four cells finds a parallel in the 
“zonate” method of division in the tetraspores of some Rhodo- 
phycee; and it seems but natural that a process of ‘‘rejuvenes- 
cence’’ should be abandoned in the development of a spore 
which is not to be shed, but germinates zm situ. The condition 
found in Lilium would then be but the extreme abbreviation of 
the story, the archesporial cell itself developing into the mega 
spore. 
The successive stages in the development of the megaspore, 
accompanied by the destruction of the potential megaspores; 
are shown in figs. 31-37, and present no essential deviations 
from the process as ordinarily described. The megaspore 
encroaches but slightly upon the cells of the chalazal region, 
apparently finding less resistance to growth in the opposite 
direction. This results in a stretching of the cells of the nucel- 
lus, which consists of but a single layer of cells, the epidermis, 
surrounding the row of megaspores; and finally the rupture of 
the nucellus ( fig. 36), part of which may be carried downward 
on the tip of the growing sac (jig. 37). The greater part of the 
sac, from this time on, lies free in the space between the funic- 
ulus and the integument. At its base may usually be seen the 
remnants of the broken nucellus. 
