50 COMPARATIVE EMBRYOLOGY OF THE RUBIACEAE 
there any further growth of nucellar tissue above the archesporium. 
The conditions then, are precisely as in the Galzeae in which the 
archesporium is surmounted only by a group of epidermal capping 
cells. In the form, here being described, the archesporium, how- 
ever, contains only one functional megaspore mother-cell ( £g. 3) 
surrounded by a number—about a half dozen—of cells of similar 
character, but reduced in size, and as their later history shows, 
possessing usually no ability to divide or to act as embryo-sac 
fundaments. No instance has been found in which two embryo- 
sacs have been present in a single ovule, a witness to the reduced 
ability of these cells as compared with their homologues in the 
Gaheae. 
The functional megaspore, however, grows apace and is easily 
to be recognized by its size and appearance. Its cytoplasm, 
especially at its outer end, is of a loose reticular structure 
which, in this form in particular, is very marked. Whether by 
division this cell divides to form megaspores or not, I can not at 
present say. In the figure shown (fig. 3) the synapsis stage 
there represented indicates that such divisions do occur since the 
first division of the embryo-sac nucleus takes place, in a closely 
related plant, at a later stage. To say that a direct development 
of the megaspore mother-cell into the embryo-sac takes place would, 
however, in the absence of positive evidence, be gratuitous. We 
therefore assume that such is not the case until a more favorable 
opportunity is presented for more careful investigation of the 
point, 
The embryo-sac cell, when the integument is well grown, is 
ready to commence its development. It is to be noticed that in 
the case before us the subsidiary archesporial cells do not suffer 
disintegration during the enlargement of the functional embryo-sac 
cell. The latter when fully developed pushes forward, causing dis- 
integration of the epidermal capping cells and enters the micro- 
pylar canal. Down this it moves, dividing meanwhile so as to 
give rise to the usual complement of embryo-sac cells. The re- 
maining undivided megaspore mother-cells follow the moving 
embryo-sac cell, and arrange themselves lengthwise in the arche- 
sporial cavity and the adjacent portion of the micropylar canal in 
such a manner as to form a continuous strand of elongated cells 
