324 



INTRODUCTION TO EMBRYOLOGY OF ANGIOSPERMS 



is a triploid (2n = 21), is an apomict (Fig. 185). During the divi- 

 sion of the megaspore mother cell there is no evidence of any pairing 

 of the chromosomes. Even at anaphase the chromosomes are 



Fig. 185. Development of unreduced embryo sac in Ixeris dentata. A, prophase 

 of first division of megaspore mother cell. B, later stage, showing 21 univalent 

 chromosomes. C, restitution nucleus. D, metaphase. E, telophase. F,G, two- 

 nucleate embryo sacs. H, four-nucleate embryo sac. /, mature embryo sac. 

 J, later stage, showing two-celled proembryo. {After Okabe, 1932.) 



irregularly scattered on the spindle, and instead of forming two 

 separate groups they become enclosed in a common nuclear mem- 

 brane, forming a restitution nucleus which contains the unreduced 

 chromosome number. Further divisions are entirely mitotic and 



