58 COMPARATIVE EMBRYOLOGY OF THE RUBIACEAE 
embryo-sac destroys the surrounding nucellar tissue ( £g. 8), but 
more rapidly in the direction of the egg pole, and leaving the tis- 
sue about the archesporium intact. The suppressed megaspores, 
which are represented on either side the functional one in Sig. 5; 
meanwhile enlarge somewhat, and a vacuole appears in the cyto- 
plasm. In this condition they may be seen, when the embryo-sac 
is mature, occupying the space previously mapped out as the 
archesporium, behind the antipodal cells, to which they are very 
similar in cytological characters, differing only in size. The anti- 
podals are all of a size, densely filled with finely granular cyto- 
plasm, and having a large vacuole in the end adjacent to the en- 
dosperm cells. Soon after fertilization both the megaspores, which 
persist up till this time, and the antipodal cells degenerate, and are 
seen as irregular, deeply staining masses. 
Before the endosperm nucleus commences to divide it is seen 
lying against the young embryo. The growth of the endosperm 
is at first parietal, remaining so until two or three irregular layers 
of cells have been formed. As the result of the rapid increase in 
amount of vacuolation, however, the endosperm cells increase in 
size so as to obliterate the enclosed cavity, thus passing from the 
parietal condition to that found in the Galieae, but by a different 
mode of development (figs. ro, II, and 12). 
The development of the embryo is exceedingly slow. From 
the condition, in which it has a rather characteristic cylindrical 
form, it becomes multicellular by transverse divisions which occur 
slowly. No haustoria are produced, nor is there any point of par- 
ticular interest in the later development. 
When mature the seed consists of a seed coat of a few layers 
of very much compressed cells derived from the outer zone of the 
integument, enveloping the endosperm, which, in turn, surrounds 
the embryo. 
The cells of the endosperm are rich in proteids with a few 
scattered starch grains. The cell walls are moderately thick, 
while those of the outer layer of cells are considerably thickened. 
The separation of the seed from the placenta takes place at 
the plane of the insertion of the funicle in the seed, along the plane, 
therefore, in which the growth of the funicular cells by division 
takes place (ff, fig. 10). 
