46 BOTANICAL GAZETTE | JuLy 
Fic. 4. Nuclear-plate stage of the first or heterotypic division of the 
archesporial nucleus; the chromosomes appear + -shaped, as in the pollen 
mother-cell. 
Fic. 5. Anaphase of the same division; the V-shaped segments have . 
reached the poles, and the cell-plate is forming. 
Fic. 6. The nuclear plate stage of the second or so-called “reducing” 
division ; the chromosomes are arranged very differently ; between the two 
spindles is the wall formed during the previous division. 
1G, 7. Anaphase of the same division. 
Fic. 8, A later stage showing the four nuclei thus formed. 
FG. 9. Each of these nuclei now divides forming four at each end of the — 
embryo-sac ; the cross-wall has disappeared. ; 
Fic. 10. The mature embryo-sac ready for fertilization ; over the apex is 
the epidermis and the remains of the other wall-cells; the egg-apparatus 
consists of the large egg nucleus and two striated synergids ; at the base are 
the disorganized antipodal cells enclosed by a cell wall, and above is the 
endosperm nucleus. 
Fic. 11. A spindle from the vegetative tissue, nuclear-plate stage ; the : 
chromosomes extend in all directions. a 
Figures 12-27, Potamogeton foliosus Rat. 
Fig. 12. A cross section of the apex of the nucellus, showing at the cenlet 
the two wall-cells lying above the archesporium. 
IG. 13. Same in the four-celled stage. 
Fie. 14. Vertical section of the nucellus, showing the archesporial cell 
with resting nucleus, and one wall-cell above. 
Fig. 15. The axial row of two cells ; the cross-wall was formed after the : 
first or heterotypic division of the archesporium. 
Fic. 16. Same, later Stage; the “reducing” division is not followed b! el 
cell-wall, 
ie nt See ata 
Fic. 17. The lower cell developing into the embryo-sac ; the upper © : 
forms a crushed mass above. 
1G. 18. Same, but each nucleus has divided again. : 
FiG. 19. Same, with a wall forming just below the two upper nucléh 
Separating them from the Cavity below. 
1G. 20. The young embryo-sac with the large egg and two small syne : 
gids enclosed by a cell-wall, three small antipodal cells at the base and a ve : 
large nucleus above. : 
Fic. 21, Same, slightly older; the large nucleus has divided into 4 polar 
nucleus above and a large antipodal nucleus below separated by a cell-wall 
the former becomes immediately t 
Fig. 22. Egg a 
nuclei lie ne 
tion, 
ee 
he definitive nucleus. <a 
Pparatus showing a stage in fertilization ; the two SP 
ar the egg, and one synergid above is in the process of disinteg™ 
