1895.] Embryology of the Ranunculacee. 243 
row of four cells now becomes a mother-cell of the embryo- 
sac. It increases in size, gradually absorbing the three cells 
above and also the adjacent cells of the nucellus, a process 
that almost invariably obtains in all angiosperms. In fig. 8 
the mother-cell may be seen separated from the disorganized 
remains of the three superposed cells by an arched wall which 
is somewhat swollen. 
The nucellus here has elongated, so that at this stage of de- 
velopment the three disorganized cells do not appear as flat- 
tened caps above the encroaching mother-cell, but seem to 
form only a narrow cavity containing a structureless substance 
which stains deeply. I have not been able to show this ac- 
Curately in the pen drawing. This cavity is made narrow 
both by the increase in length of the nucellus and by the 
turgor of the cells immediately surrounding it. The walls of 
the turgid cells here in question, which border upon the 
Cavity, are usually much swollen. The mother-cell now de- 
velops into the embryo-sac in the normal manner. The ma- 
ture embryo-sac is covered by the nucellar cap varying from 
two to four cells in thickness. The antipodal cells attain an 
extraordinary size compared with that of the egg-apparatus, 
as a glance at figs. 10@ and 100 will plainly show. This con- 
dition of affairs exists in the embryo-sac at the time of 
anthesis or shortly before. The three cells almost always lie 
side by side in the same horizontal plane, consequently only 
two are shown in the figure, the other being in the next suc- 
cessive section. They gradually increase in volume with the 
Subsequent growth of the embryo-sac, and persist for a time 
after fertilization, when they are finally absorbed. About 
the time of fertilization they may be seen upon a projection 
of the chalaza at that end of the sac which has now become 
cess is that given by Strasburger® for Myosurus minimus. In 
ee ee a . 
“Strasburger, Ueber. Befruchtung und Zelltheilung 38. 1878. 
*Strasburger, Die Angiospermen und Gymuospermen 13. 1879. 
