360 CALIFORNIA ACADEMY OF SCIENCES. [Proc. 3D Ser. 



EXPLANATION OF PLATE LL 



(Reduced about one-fourth). 



Fig. 16. Four sister cells in which cell-wall formation accompanied nuclear 



division: X 320. 

 Fig. 17. Sister cells of which the outermost, which shows in the adjacent 



figure (17a), has been absorbed: X 320. 

 Fig. 18. Sister cells of which the outermost has been consumed: X 320. 

 Fig. 19. Longitudinal section of an ovule in which the macrospore has 



nearly absorbed the two middle sister cells: X 320. 

 Fig. 20. A four-celled embryo-sac: X 320. 

 Fig. 20a. Nucleus belonging to embryo-sac figured above. 

 Fig. 21, i\a. An eight-celled embryo-sac in which the polar nuclei are 

 approaching each other: X 320; ant, antipodal cells; e^ egg; 

 syn, synergidce; p, polar nuclei. 



