786 Campbell —The Embryo-sac of Pandanus . 
upper one, the latter dividing again by an anticlinal wall. The lower cell 
is the young embryo-sac. 
3. The early divisions of the embryo-sac follow the usual course up to 
the stage with four nuclei, two being at each pole of the embryo-sac. 
4. The next divisions are confined to the antipodal region where the 
two original nuclei, by subsequent divisions, give rise to a group of large 
free nuclei, usually twelve in number. 
5. The two micropylar nuclei divide once, and there is formed a typical 
egg apparatus and an upper polar nucleus. 
6. The antipodal nuclei divide further, the later divisions being ac¬ 
companied by the formation of cell-walls much as in the formation of the 
endosperm. The number of antipodal cells may finally exceed sixty-four. 
7. A varying number of the antipodal nuclei become free and assume 
the role of polar nuclei, fusing with the upper polar nucleus into a single 
large endosperm nucleus. Sometimes the fusion results in two primary 
endosperm nuclei. 
8. The secondary endosperm nuclei diminish in size as division pro¬ 
ceeds, and this diminution in size is accompanied by a corresponding 
reduction in the number of chromosomes. 
9. The endosperm formation is of the usual type. After a large 
number of free nuclei have been formed, cell-walls arise between them, and 
cell-formation proceeds centripetally until the whole embryo-sac is filled 
with solid endosperm. 
10. The embryo is very small and shows no external differentiation. 
Conclusions. 
In Pandanus the embryo-sac reaches the highest development before 
fertilization that has yet been recorded for the Angiosperms. Instead of 
the eight nuclei of the ordinary embryo-sac there are at least thirty-six, 
and sometimes twice that number, at the time fertilization occurs. 
The early history of the embryo-sac follows closely the usual course 
up to the time that four nuclei have been formed, and then a difference is 
to be noted. The condition with two micropylar nuclei and eight to 
fourteen free nuclei at the base of the embryo-sac may be compared to 
that described by Johnson for Peperomia hispidula} where there is a 
similar arrangement of the nuclei. The eight-nucleate stage found in 
Gunner a macrophylla 2 also resembles this stage of Pandanus , but the final 
nuclear division in Gunner a , resulting in sixteen nuclei, is accompanied by 
1 Johnson, D. S. : A New Type of Embryo-sac in Peperomia . Johns Hopkins University 
Circular, 1907, No. 3, pp. 19-21. 
2 Ernst, A.: Zur Phylogenie des Embryosackes der Angiospermen. Ber. der deutsch. bot. 
Gesellsch., xxvi, 1908, pp. 419-38. 
