562 Saxton.—Contributions to the Life-History of Callitris. 
and those of Wehvitschia. The origin of the latter has now been definitely 
ascertained (Pearson ( 11 )), and is so radically different from that of the same 
cells in the former genera that any comparison between them must be 
abandoned. 
It is certain that at least three separate embryos are derived from 
a single proembryo. From the material examined it has not been possible 
to determine precisely how this takes place, but it seems likely that the 
whole proembryo is inclined to partially separate into groups of two or three 
cells, of which the smallest becomes the embryo initial and a larger one the 
single suspensor cell. Indications of such a state of affairs are seen in the 
upper proembryo of Fig. 18, and especially in Fig. 22, which shows part of 
a proembryo in longitudinal section, in which two such groups, of three cells 
each, seem clearly indicated. It is merely suggested that this is what 
happens. The evidence is by no means conclusive. The next stage seen 
shows a tortuous mass of thick-walled suspensors below the crushed remains 
of the archegonia, the free ends of which protrude in all directions from this 
mass (except immediately above, and especially below). About a dozen of 
these embryos may be found in a single ovule. Since more than two pollen- 
tubes never reach maturity (usually only one) it is only possible for four 
archegonia to be fertilized. In confirmation of this inference (if any were 
required) four is the maximum number of proembryos found in an ovule. 
Hence the presence of a dozen or so embryos in an ovule proves conclusively 
that at least three must be formed from a single proembryo, as stated 
above. 
The free tip of one of these conspicuous suspensors, bearing a four- 
celled embryo, is drawn in Fig. 23. The first two divisions of the embryo 
cell are constantly vertical, giving rise to a single tier of four cells. This is 
exactly the opposite to what occurs in Pinus , where the first division is 
always (?), and the second nearly always, transverse, but it agrees with 
Sequoia , as described by Arnoldi (1). 
The next division in each cell is transverse, giving two tiers of four cells 
each. In its further development, which has been followed fairly closely, 
the embryo agrees essentially with that of Pinus , as recently described by 
the writer ( 14 ). The meristem which gives rise to embryonal tubes, root- 
cap, and periblem, appears perhaps a little earlier than in Pinus. The 
region traversed by the suspensors is also relatively shorter than in other 
conifers, this being probably a necessary consequence of the position of the 
archegonia. The part of the prothallus above the archegonia develops no 
further, and in advanced stages of the embryo, very little can be seen 
of it. 
Fig. 1, PI. XLVI shows an embryo shortly after the differentiation of the 
cotyledons. The region in which starch is present is clearly shown. Fig. 24 
is a drawing of a few cells just on the boundary line of the starch-containing 
