1895.] Embryology of the Ranunculaceae. 247 
neighboring cells of the nucellus. Fig. 18 presents a sac 
with two nuclei in each end. The outer integument has now 
put in an appearance on the side turned from the funiculus 
(on the right in the figure), and the epidermis of the apex of 
the nucellus has given rise by periclinal divisions to a layer of 
three or four cells in thickness. This layer may be formed 
earlier in the development of the ovule (fig. 17). The 
embryo-sac is not infrequently mature when the inner integu- 
ment has reached the apex of the nucellus. In regard to this 
point there is considerable variation, for both integuments 
may exceed the nucellus before the maturity of the embryo- 
sac 
The embryo-sac presents nothing abnormal. In the antip- 
odal cells, which become quite large, the nuclei undergo 
fragmentation, so that each cell at the time of anthesis, con- 
tains three or four nuclei. 
On account of insufficient material only a limited study of 
the mature sac was made. In all cases examined only one 
embryo-sac was found in each ovule, yet the probability is 
not excluded that more than one may reach maturity as in 
Delphinium. 
Seems to be a tapetal cell (fig. 20). The lower and larger 
cell now divides transversely (fig. 21), each of the resulting 
cells dividing in a similar way (fig. 22). More frequently, 
however, no such tapetal cell is formed, the initial producing 
a series of four cells in the manner described for Delphinium 
