152 MINNESOTA BOTANICAL STUDIES. 



Plate X. 



12. Embryo sac of Rumex salicifolius showing the two nuclei as 

 above and the lower one also slightly larger. 



13. Embryo sac of Rumex salicifolius showing the four nuclei de- 

 rived from division of two corresponding to those figured in n and 12, 

 and also showing the persistent spindle in the anterior end of the sac. 



14. Embryo sac of Rtimex salicifolius showing the corresponding 

 four nuclei in a somewhat older sac. 



15. Embryo sac of Rzimex salicifolius showing eight nuclei derived 

 from four corresponding to those figured in 13 and 14. The polar 

 nuclei are approaching each other. The three anterior nuclei are of 

 about equal size and not enclosed in walls. Only the nucleoli of the 

 antipodal s could be seen. 



1 6. Embryo sac of Polygonum erectum showing the earlier forma- 

 tion of cell walls about the anterior nuclei, one of which was lying be- 

 low the other two. The polar nuclei are approaching each other, and 

 the cellular structure in the antipodal area is distinct, one cell here also 

 lying below the other two. 



17. Embryo sac of Rumex salicifolitts showing the egg yet free, 

 cell walls forming about the synergidae, the polar nuclei fusing and 

 three distinct nucleated antipodal cells. 



18. Embryo sac showing the sister nuclei which form the synergidae 

 yet free and the wall forming about the egg after the definitive nucleus 

 is formed. 



19. Anterior end of a mature embryo sac showing the synergidaa 

 and the egg. 



20. Embryo sac of Rumex salicifolius showing all of the nuclei of 

 the mature sac, except the antipodals and at about the same stage as 

 the corresponding nuclei in 17. 



21. Posterior end of a mature embryo sac showing three antipodal 

 cells. 



22. Anterior end of the embryo sac of Rumex salicifolius showing 

 walls forming about the egg after the definitive nucleus is formed. 



23. Mature embryo sac showing more than three nuclei in the anti- 

 podal end. 



24. Mature embryo sac of Rumex salicifolius, with the antipodal 

 region perhaps not distinctly seen. 



Plate XL 



25. Anterior end of embryo sac showing one synergid degenerated, 

 the pollen tube entering and showing two nuclei very indistinctly. 

 The egg and definitive nucleus are also shown. 



26. Anterior end of embryo sac showing a pollen tube discharged 

 and containing an undischarged sperm-nucleus. The two synergidae 



