The Origin of Triple Fusion. 283 
pollen-tube seems imminent. This, the first jacket-nucleus to 
escape into the egg-cell, is apparently attracted hy the proximity of 
the contents of the pollen-tube 1 ; the ventral canal-nucleus, though 
still quite recognizable, appears to be in a dying and inactive 
condition. 
Fig. 17. Jacket-nucleus entering apex of archegonium containing four 
nuclei from the pollen-tube, j.n., jacket-nucleus ; p.t., pollen-tube ; />.«., nuclei 
from the pollen-tube ; v.c., ventral canal-nucleus. 
Here therefore vve have a process occurring in the embryo-sac 
of a Gymnospermic genus, which shows a remarkable likeness to 
the development of the Angiospermic endosperm after triple fusion, 
that is to say, we have cell-formation resulting from the fusion of 
nuclei, one of which at least is allied to the egg-nucleus, and taking 
place under the stimulus due to the entry of the pollen-tube. 
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 formation 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 he the- 
J I have not been able to trace the origin of these pollen-tube 
nuclei, several of which in this case have the appearance of 
gametes, but there are indications, even when the tube is still 
within the pollen-chamber, that more than the four nuclei seen 
by Dr. Land in his artificial cultures are formed. 
