40 MARCUS M. HARTOG. 
divisions of the oogonium both are functional though in dif- 
ferent ways.' 
(5) The Upper Subbasal cell (N*usb) is one of the gametes 
of the endosperm ; its sister-cell, the Lower Subbasal cell, 
is, therefore, an arrested gamete; and the Subbasal cell 
(N2sb) is a gametogonium like the subapical (N’sa). 
(6) From the symmetry of the embryo-sac we may regard 
the basal cell (N*) as equivalent to the apical, and their 
divisions as homologous; or we may regard the basal pair 
of cells as the remains of the prothalliar tissue of the Gymno- 
sperms. 
The above identifications we may summarise thus: four 
prothalliar cells (N?) are formed ; of these the two in the mean 
position (N*sa, N’sb) are gametogonia, which by a mitotic 
division form four gametes, three functional, one arrested. 
The apical cell (N’a) forms an archegonium reduced to a two- 
cellular neck; the basal cell (N*b) forms two cells consti- 
tuting a barren archegonium or mere prothalliar cells. I 
assume that the sister-cell of a gamete is necessarily a 
gamete, functional, arrested, or degraded; but the same rule 
does not apply to a gametogonium, which in all but the lowest 
Protophytes must have tissue-cells, not gametogonia, for its 
sisters.” 
From the above explanation one thing is certain, that the 
endosperm of Gymnosperms is not homologous with that of 
Angiosperms, though its final function of nourishing the seed 
be the same. 
1 The relations of position would indeed identify the oosphere with the 
Gymnosperm canal-cell, and the lower subapical cell with the Gymnosperm 
oosphore. 
2 From a consideration of Guignard’s researches I am now compelled to 
regard the embryo-sac as morphologically equivalent to a spore mother-cell, 
and the four nuclei, N2, as megaspores, which differentiate as in the above 
statement; for it shows the same nuclear reduction in the prophases of its 
first mitosis that occurs in the primary pollen mother-cell, which has certainly 
this value. 
