44 BOTANICAL GAZETTE [july 
Only the heterotypic division is followed by a cell-wall, and | 
thus an axial row of two cells is formed each containing two 
nuclei. 
Shortly after anthesis the transverse wall disappears and the 
four nuclei all divide simultaneously, producing four daughter 
nuclei at each end of the embryo-sac. The endosperm nucleus — 
is formed by the fusion of one nucleus from each group. After — 
the transverse wall is destroyed, therefore, the process is the — 
same as in Lilium. i 
The number of chromosomes in the vegetative nucleus — 
is about thirty-six. During the heterotypic and so-called — 
“reducing” divisions eighteen may be counted. The apparent 
reduction therefore takes place prior to the first division of the — 
archesporium, + 
Potamogeton.—The first division of the archesporial nucleus 
is followed by a cell-wall, but the second is not; so that an axial } 
row of two cells, each containing two nuclei, is produced as in 
Convallaria, i 
The lower cell forms the embryo-sac, while the upper diss 
integrates. . 
Four nuclei are formed in the lower cell; the two at the 
upper end are at once enclosed by a cell membrane, and from | 
them develop the two evanescent synergids and the egg. 4 
The lower remain free. From one of these all three of th 
small chromatic antipodals are probably formed. The other 
divides, forming the fourth antipodal cell and the polar nucleus 
with a cross-wall between the two. The polar nucleus become 
the endosperm nucleus without fusion. 
The mature embryo-sac contains two small synergids and 
large egg nucleus enclosed by a wall near the micropyle; @ very 
thin parietal layer of endosperm; and four antipodal cells 
enclosed by a transverse wall at the lower end of the embry 
sac, of which three are very small and one is very large. 
The nuclei of Potamogeton are peculiar in having most 
of the chromatin aggregated in a ball at the center of 
cavity. 
