360 



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



EXPLANATION OF PLATE LI. 



Fig. 



16. 



Fig. 



17- 



Fig. 



18. 



Fig. 



19- 



Fig. 



20. 



Fig. 



20a 



Fig. 



21, 



(Reduced about one-fourth). 



Four sister cells in which cell-wall formation accompanied nuclear 



division: X 320. 

 Sister cells of which the outermost, which shows in the adjacent 



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

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

 Longitudinal section of an ovule in which the macrospore has 



nearly absorbed the two middle sister cells: X 320. 

 A four-celled embryo-sac: X 320. 

 , Nucleus belonging to embryo-sac figured above. 

 2 iff. An eight-celled embryo-sac in which the polar nuclei are 

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

 syn, synergidas; p, polar nuclei. 



