Text-fig. III. i. Two embryo sac mother-cells in synapsis. 2. Double axial rows of tetrads; the left one is disintegrating. 3. Micropylar and chalazal 
megaspores developing. 4. Two binucleate megaspores, one of which is partly attached on the curved side of the other. 5. Upper megaspore contains two mitotic 
gures the lower one is binucleate. 6. Two megaspores equally in binucleate condition; one of the nuclei is left in the adjoining section. 7. Binucleate 
megaspore and the uninucleate sister one; the latter survives lying on ;the si«!e of the former. 8. Upper megaspore in binucleate condition; the middle one still 
survives. 9. two excess sister megaspores surviving. 10. Upper megaspore contains four nuclei in telophase; the lower one binucleate, though the nuclei are not 
snown m the figure. 11 Mature embryo sac with binucleate sister megaspore, whose nuclei show a sign of disintegration. 12. Ripe embryo sac with three surviving 
megasports, two of which are going to disintegrate. 13. Two embryo sacs lying one upon the other; the upper one is fertilized. 14. Two sacs lying side 
y siae. 15. iwo sacs in axial row; the lower one is pressing the upper one. 16. Two sacs lying collaterally; portions of synergids are left in the next section. 
17. Une embryo sac is partly encircled by the lower half of the other; part of egg apparatus is in another section. All figs, x 980. 
3-12, 17, Oenothera pycnocarpa. 1, a, Hybrid *pycnella '. 13-16, Oe. nutans. 
Ishikawa.Studies on the Embryo Sac and Fertilization in Oenothera. April , 1918. 
