14 E antes . — The Morphology of A gat his australis. 
further change occurs until the descending embryo attains its final position. 
It is this rather insignificant portion of the proembryo which forms the 
embryo proper. The terminal groups are concerned only in the transfer 
of this central section to the centre of the endosperm. Growth in the 
embryo proper goes on rapidly after that. 
The upper group, which is to form suspensors, elongates distally, 
reaching out in long tube-like processes through the upper section of the 
archegonium (Fig. 31), at times even out through the ruptured top. 
The lower group becomes more specialized, forming a cap that fits 
over and protects in a remarkable way the initials of the true embryo 
above. This cap consists of a terminal, conical cluster of firm-walled, 
tightly fitted cells elongated backward from the apex, somewhat like the 
neck-cell complex. The cap form is secured by smoothly ‘ stepping ’ the 
cells one upon the other. A circular rim of cells is placed upon the edge 
of the cap, extending upward and sheathing the embryonic tier (which is 
partially sunken in the hollow of the cap) and the base of the suspensors. 
Fig- 31, a proembryo nearly mature, exhibits all these features. The cap 
and embryo proper may be better seen in Fig. 32, which illustrates a later 
stage. 
Among Gymnosperms there are two other instances known where the 
terminal cells of the proembryo do not become embryo proper but form a 
cap — Cephalotaxus ( 7 ) and some species of Podocarpus ( 11 ). But in these 
genera the cap is very simple — a large terminal cell, and one to several 
smaller ones placed irregularly between it and the young embryo behind. 
When the cap is perfected and distal elongation ceases in the suspensor 
tier, the proembryo has acquired a shuttlecock-like form (Fig. 31). It has 
now attained maturity. 
There are three distinct tiers, as in the proembryos of other Conifers, 
but their functions are very different. In this case the central tier is fertile, 
whereas generally this becomes suspensors. The lower tier, which usually 
is fertile, becomes a sterile tip, and the suspensors in this case correspond 
to the rosette tier of many others. The tier of naked nuclei above the 
rosette layer finds no homologous portion in the araucarian proembryo. 
The total number of cells at this stage is found to vary from thirty to 
seventy. The greatest variation is among the suspensors ; a range of eleven 
to thirty-eight was found, fourteen and twenty-six being most common. 
From eight to fifteen cells compose the embryo proper. The cells of the 
protective cap number from ten to twenty. 
In that region of the gametophyte into which the descending embryos 
are to penetrate a marked change takes place at an early stage. This is in 
the form of preparation to supply greater nourishment for their develop- 
ment, and also for the suspensors during the descent. The cells so situated 
as to be likely of absorption become richer in content. The change can 
