1915] BURLINGAME—ARAUCARIA BRASILIENSIS It 
After or just about the time of the cessation of free nuclear 
division the nuclei arrange themselves as shown in fig. 30, which 
is a median vertical section. It will be seen that there is a central 
group of nuclei arranged more or less regularly in two tiers, sur- 
rounded by a complete jacket of peripheral nuclei. These pe- 
ripheral nuclei are usually more numerous on the lower side than 
on the upper. Even before walls are formed the lower nuclei 
sometimes begin to elongate, foreshadowing the formation of the 
cap. Fig. 32 shows a proembryo in which walls are forming about 
the lower nuclei, which are already set off in definite cells. The 
walls appear to form first in that part of the embryo which first 
begins elongating. In fig. 32 the lower cells formed first and began 
elongating while there is yet no indication of the future cells in 
the upper portion of the proembryo. Precisely the opposite state 
of affairs is shown in fig. 31, where the upper cells are elongating 
and forming walls while the lower cells are just forming but have 
not begun elongation and have only faint traces of walls around 
some of them. 
After the complete establishment of walled cells the elongation 
which had already begun continues simultaneously in both the 
upper and lower cells. It is only after this elongation that one may 
properly speak of tiers, for, as already pointed out, the cells are 
arranged concentrically rather than in layers. Few or no divisions 
occur in the terminal group of cells, destined to form the cap, 
during this preliminary elongation, and none at all subsequently. 
There is a considerable increase in the upper group. They divide 
longitudinally, so that there are ordinarily about twice as many 
cells in the young suspensors as there were in the group of cells 
from which they were developed. The number shown in cross- 
section varies somewhat, but is usually not far from 20. As the 
suspensor cells elongate, their upper ends are thrust backward and 
upward (that is, in the direction of least resistance) until they 
encounter the firm top of the archegonium. Their upper ends 
ordinarily become swollen during elongation, so as to stretch 
the upper part of the archegonium (fig. 33). Incidentally this 
figure also shows that the neck is not ruptured by the entrance 
of the male cells and is not torn away from its mooring to the 
