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INTRODUCTION TO EMBRYOLOGY OF ANGIOSPERMS 



The second table summarizes the time relations of the divisions 

 in the embryo and endosperm of Taraxacum kok-saghys (Poddub- 

 naja-Arnoldi and Dianowa, 1934), where at least for the first few 

 days both develop more or less concurrently and neither has any 

 appreciable advantage over the other. 



In all cases the first division of the zygote is followed by wall 

 formation. This is in sharp contrast with the condition in the 



gymnosperms, where the first few divisions are almost always free 

 nuclear. The only reported instance of a free nuclear embryo in 



the 64-nucleate stage the embryo becomes more aggressive and mitoses occur more 

 slowly in the endosperm. 



Pope (1943) suggests that the extra number of chromosomes and genes in the 

 primary endosperm nucleus may be a factor contributing to the more rapid growth 

 of the endosperm as compared with that of the embryo. This is an interesting 

 suggestion, but even in the Onagraceae, where the zygote and the primary endo- 

 sperm nucleus have the same genetic constitution, the development of the endo- 

 sperm proceeds at a much quicker rate. 



