780 Campbell.-—The Embryo-sac of Pandamis . 
elongated form. A somewhat younger stage, with eight chalazal nuclei, is 
shown in Fig. 19, PI. LX. 
Fig. 20 shows the base of an embryo-sac, differing somewhat from the 
usual type. It was apparently somewhat older than that figured in 21, 
being decidedly larger. There were two micropylar nuclei and ten large 
nuclei in the antipodal region. There were also present two or three small 
nuclei, but it was a question whether these properly belonged to the embryo- 
sac. The most remarkable feature of this embryo-sac was a very large free 
nucleus, closely resembling the primary endosperm nucleus formed in the 
older embryo-sac as the result of the fusion of the * polar* nuclei. This 
nucleus (Fig. 20, b) was embedded in a mass of cytoplasm, and contained 
two very conspicuous nucleoli, which gave it very much the appearance of 
having resulted from the fusion of two of the twelve original antipodal 
nuclei. As a rule no such fusion nuclei were found until a much later stage 
of development. 
In the next stages met with, the two micropylar nuclei had divided, so 
that there were four nuclei at the upper end of the sac, and the eight or 
twelve chalazal nuclei had increased in number to 32-6. Although many 
preparations were made, none of them showed the division stages, and it is 
impossible to say whether the divisions of all the chalazal nuclei take place 
simultaneously, or whether the nuclei divide at the same time as the two 
micropylar nuclei. 
In all these later stages the nuclei, which in the earlier condition were 
free, are separated by evident cell-walls, so that the base of the embryo-sac 
is occupied by a broad mass of antipodal cells very much like those that 
occur in Sparganinm after fertilization has taken place. 1 There is, how¬ 
ever, a marked difference to be noted. In Sparganium, at the time of 
fertilization, the embryo-sac has the usual form with three distinct antipodal 
cells. The very greatly increased number of antipodals found later results 
from a subsequent division of these three original antipodal cells. In 
Pandanus , however, up to the time that twelve or sometimes fourteen 
nuclei are present in the antipodal region, there is no trace of cell-division. 
The formation of this mass of antipodal cells in Pandamis resembles, there¬ 
fore, very closely the formation of the endosperm after fertilization has 
taken place, and it is quite likely, although this is not easy to demonstrate, 
that more than one nucleus may sometimes be enclosed within the irregular 
cells composing the antipodal tissue.. 
In the micropylar region three of the four nuclei form a fairly typical 
egg apparatus (Figs. 22-4). Two of these, probably sister nuclei, give rise 
to the synergidae. The latter are separated by what seems to be a definite 
cell-wall, and are rounded off below, not presenting any peculiar character- 
1 See Campbell, Studies on the Flower and Embryo of Sparganium. Proc. Calif. Acad, of 
Sciences, 3rd Ser., Bot., vol. i, No. 9, 1899. 
