320 INTRODUCTION TO EMBRYOLOGY OF ANGIOSPERMS 



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Fig. 182. Diagrams illustrating formation of restitution nucleus (A-G); pseudo- 

 homotypic division (H-L) ; and somatic division (M-R) in megaspore mother cells 

 of apomictic angiosperms. A, nucleus of megaspore mother cell in prophase; note 

 absence of pairing. B, diakinesis. C, semiheterotypic metaphase. D,E, forma- 

 tion of nuclear membrane enclosing all the chromosomes. F, fully formed restitu- 

 tion nucleus. G, homotypic metaphase. H, nucleus of megaspore mother cell in 

 prophase. I-L, stages in formation of daughter nuclei by pseudohomotypic 

 division. M-R, somatic division of nucleus of megaspore mother cell. (After 

 Gustafsson, 1985.) 



rounded and the following divisions are entirely mitotic. In the 

 pseudohomotypic division the chromosomes are short, thick, and 

 contracted, as in meiosis, but do not show any pairing. In the 

 beginning of the metaphase the univalents are scattered over the 

 spindle, but gradually they arrange themselves in an equatorial 



