EMBRYO-SAC OF GYMNADENIA CONOPSEA. 
3 
around it. The cells are thin-walled, and full of slightly 
granular protoplasm, without any vacuoles, and each has a 
large spherical nucleus with a bright nucleolus in the 
centre. 
At an early stage the terminal cell of the central series 
increases considerably in size, its protoplasm becomes very 
granular, and its nucleus remarkably bright. About the 
same time certain cells in a zone above the middle of the 
whole ovule divide by walls parallel to the periphery of the 
ovule and form the rudiment of the inner integument. At this 
period the ovule is represented in fig. 1, where, however, the 
protoplasm has been mostly removed by amnionic hydrate. 
It will be useful to name the central series of cells the 
axial row,” and the large terminal cell of this row has 
been called the embryo’sac mother-cell,” since the em- 
byro-sac apparently arises as a daughter-cell by division of 
this, as pointed out by Strasburger.^ Reasons will be given 
later for considering the embryo-sac as possibly less simple 
than here stated. 
As the ovule lengthens its curvature increases, the integu- 
ment grows upwards, and the embryo-sac mother-cell becomes 
longer (fig. 2) ; this latter cell now divides by a transverse 
wall appearing at about one third its length from the top, 
and the smaller cell thus cut off appears like a cap sitting on 
the larger one below. The lower and larger cell is mean- 
while growing, and tends to compress this cap-cell against 
the epidermal cells above. When it has reached a size about 
equal to that with which it started, the larger cell repeats 
the above division exactly as before, and so a second cap-cell 
is thrown off, soon to be forced up against the other by 
growth of its sister-cell below. 
The specimen represented in fig. S shows this second 
division in progress, the characteristic “ barrel figure” having 
been fixed by absolute alcohol. A similar stage is figured 
by Strasburger (‘ Angiosp. u. Gyrnnosp.,’ Taf. vi, fig. 90), 
where, however, the division appears to follow more rapidly 
upon the first one. The division walls thus established are 
remarkably thick and bright, as if mucilaginous and swollen, 
and the appearance they present is not easily indicated in a 
drawing, especially at stages a little later, when the whole 
becomes more homogeneous as the lower cell compresses the 
uj)])er ones. 
Meanwhile the ovule has become decidedly anatropous, 
and the inner integument is already slowly closing in above ; 
the outer integument has also appeared, by similar divisions 
^ Loc. cit. 
