THE EMBRYO-SAC OF AGLAONEMA 105 



show sections of embryo-sacs with four nuclei from A. com- 

 mutatuiH. In figs. 15 and 16 only one nucleus appears in the 

 section, but a second one was present. Fig. 17 shows the 

 upper end of the sac with the two micropylar nuclei. 



In his first paper the writer describes and figures a peculiar 

 embryo-sac from the Jamaican species (Campbell, 4; figs. 

 22-24). This stage of the embryo-sac was not found in A. 

 comniutatuni, although it may perhaps occur in this species, 

 but it was repeatedly met with and appears to be typical for 

 both A. simplex and A. niodestiiin. The embryo-sac at this 

 time shows what is apparently a typical ^^'g apparatus con- 

 sisting of the usual three cells, an ^gg and two synergidae. 

 In the first specimen found this Q,gq^ apparatus occupied the 

 usual position at the apex in the embryo-sac, and this is not 

 infrequently the case also in A. simplex (figs. 12, 13) ; quite 

 as often, however, the &gg apparatus is lateral in position, 

 but may even be developed at the chalazal end of the sac 

 (PI. IV. figs. 30, 36). In addition to the ^gg apparatus there 

 is seen at the chalazal end of the sac (fig. 12) two large free 

 nuclei surrounded by a more or less distinct aggregation of 

 cytoplasm, suggesting two large antipodal cells. This was 

 especially conspicuous in the Jamaican species. Stages 

 between the four-nucleate condition and that in which the 

 sgg apparatus was completely developed were not found, 

 but it is practically certain that one only of the upper pair of 

 nuclei divides, giving rise to the synergidee, while the other 

 remains undivided and becomes the nucleus of the ^%g, there 

 being no polar nucleus present. Thus at the time when the 

 ^gg apparatus seems to be fully developed there are only five 

 nuclei in the embryo-sac, instead of the eight usually found 

 in angiosperms. 



In the brief account published of A. pictum (Campbell, 5 ; 

 p. djj^ the statement was made that the embryo-sac was 

 of the usual angiospermous type ; but a further examination 

 of the few preparations that were made showed that in this 

 species also it is probable that the same type as that of A. 

 simplex may occur. One embryo-sac showed what appeared 

 to be a typical group of three antipodal cells. However, as 

 the adjacent cells of the nucellus are quite like the antipodal 

 cells in appearance, it may be that these " antipodal" cells 



VOL. I. 8 



