16 THE COMPARATIVE EMBRYOLOGY OF THE RUBIACEAE 
and relatively inconspicuous; the third and basal, is very long, 
being on the average about two thirds the length of the whole em- 
bryo-sac, though it may, in exceptional cases which I have noted, 
attain a considerably greater length. At its expanded upper end it 
is separated from the upper region ofthe embryo-sac by a very thin 
transverse wall. Its lower end is somewhat knobbed, and is em- 
bedded in a mass of degenerating megaspores. The position of 
the nucleus of this antipodal is always lateral and about one fourth 
to one half the cell’s length from the upper end (Pl. 2, Figs. 7-11). 
It is large and prominent, and evidently active. Its function has 
already been discussed. The fate of the antipodals will be discussed 
somewhat later. 
DEVELOPMENT OF THE EMBRYO 
After the egg is fertilized, its vacuole enlarges considerably, 
pushing the cytoplasmic end rather more deeply into the endo- 
sperm stuff. Immediately the endosperm nucleus commences to 
divide so that before the’ first division of the fertilized egg takes 
place 20 to 30 endosperm nuclei are present (Pl. 2, Fig. 10). The 
proembryo now grows rapidly by the successive occurrence of 
approximately transverse divisions. When about five cells have 
been formed, the proembryo becomes bent to one side and the 
other. This is due to the lateral enlargement of certain of the sus- 
pensor cells, as a result of which they bulge out into the endo- 
sperm which is now of some bulk. In these enlarging suspensor 
cells, the cytoplasm becomes vacuolated to a considerable degree. 
These facts and later developments indicate that these cells are 
concerned in the absorption of foods in solution from the endo- 
sperm, which, however, is not broken down by the enlarging sus- 
pensor cells, The cells of the end of the embryo away from the 
micropyle are always smaller during the earlier development of 
the proembryo, while they get successively larger toward the 
micropylar end where the basal cell tapers off acutely, giving the 
young proembryo something of a spindle shape (Pl. 4, Figs. 1, 2)- 
When the proembryo attains the number of about six cells, 
longitudinal divisions occur in some of the suspensor cells. The 
divisions sometimes occur in two planes, and the resulting elements 
continue to grow and bulge out further into the endosperm and 
in a een 
