134 
Sargant . — The Reconstruction of a Race of 
c Moreover, if the polar nucleus is regarded as the homologue of the 
jacket-initial nucleus, it is possible to trace among the eight nuclei of the 
Angiosperm embryo-sac representatives of the four classes of cells which 
we find in the sac of Ephedra and other Gymnosperms. 
‘ 1. The egg-nucleus in Angiosperms is homologous with the initial 
nucleus of the archegonium, which, as in Gnetum , matures without the for- 
mation of that organ ; it therefore represents the latter. 
‘ 2. The synergidae probably represent the cells in the upper part of 
the prothallium, whose only function appears to be the nutritive one common 
to the whole, but which, as Strasburger suggests, have assumed in Angio- 
sperms a new one in relation to the pollen-tube. 
‘ 3. The antipodal nuclei represent the nutritive and haustorial cells 
which compose the lower part of the prothallium. 
‘4. The upper polar nucleus represents the jacket-cells, which, though 
not as a rule capable of fertilization, yet, after union with another nucleus, 
appear to be in a condition to receive stimulus from the contents of the 
pollen-tube and to proceed to the formation of proembryos. Since in the 
Angiosperm embryo-sac there is reduction to one solitary nucleus, the 
stimulus from the pollen-tube naturally takes the form of fusion with the 
second male gamete ’ (11, pp. 283-4). 
Certain details in the above scheme are perhaps open to criticism. 
The synergidae might well be considered to represent two initial cells, 
comparable with the archegonium initial represented by the ovum, and 
the jacket-cell initial represented by the upper polar nucleus. The lower 
polar nucleus is presumably of prothallial nature, like the antipodals, 
though this is not definitely stated. But these are mere details. Miss 
Berridge’s comparison of the apogamous proembryos of Ephedra with 
the endosperm of Angiosperms throws a completely new light on this 
obscure subject, and suggests definite lines of research. Our knowledge 
of embryo-sac structure and of the details of fertilization in other 
species of Ephedra is so far very fragmentary. More complete infor- 
mation on these points, and on the corresponding features in Welzvit - 
schia, may possibly settle the vexed question of the homology of the endo- 
sperm, and at the same time determine the true position of the Gnetaceae 
in the Natural System. 
Comparison with the embryo-sac of Gnetum is of the utmost interest, 
though at present it can be only tentative. We may suppose that the 
common ancestor of all branches of the Gnetaceae possessed an embryo-sac 
in which a group of archegonium initials occupied the apex, and true 
prothallial tissue the base. Some of these initials may have produced 
jacket-cells in the mature sac. Whether this were so or not, all the initials 
might be reduced alike to naked nuclei. Thus in G11. Gnemon each of the 
equivalent nuclei in the apex of the sac, supposed by Dr. Lotsy to be all 
