101 



The greatest difficulty in the estimation of the morphological 

 value to be attributed to the diiferent parts of the Angio- 

 spermic embryosac was to my mind , our total ignorance as 

 to the possible morphological value of the polar nuclei. 



It needs only be remembered that the embryosac-nucleus 

 among the Angiosperms divides into two, the one daughter- 

 nucleus moving towards the micropyle the other towards the 

 chalaza. Each of these nuclei gives rise to four new ones, in 

 the micropylar part one becomes the oval nucleus , two become 

 synergidal nuclei while the fourth remains free and is called 

 a polar nucleus. 



Of the four chalazal nuclei three become nuclei of antipodal 

 cells while the last one remains free as a polar nucleus also. 

 These two polar nuclei subsequently fuse together to the en- 

 dospermnucleus from which all later endospermnuclei are des- 

 cendants. 



The meaning of this process is of the most obscure, the 

 morphological value of each of these nuclei only more so. 

 Mann in his work on the embryosac of Myosurus ^) has tried 

 to explain this as a fusion of sexual nuclei but after carefuU 

 perusal of his memoir the only conclusion I can come to is 

 that — even if one accepts Mann's view — this would be a 

 fusion of two female nuclei — an extraordinary proceeding — 

 which proves nothing. 



Against this view of the sexuality of the polar nuclei 

 Treub's masterly investigation of the female organ of Balano- 

 phora elongata Bl. speaks loudly and this work gives us — 

 for the first time — a clue at least, as to the morphological 

 value of the polar nucleus. 



Treub observes that the first occurrences in the embryosac of 

 Balanophora are normal. In the usual way the division of the 

 nuclei takes place , in the usual way at the one end an ovum , 

 tw^o synergidae and a polar nucleus are formed, in the usual 



1) GusTAV Mann. The embryosac of Myosurus minimus L., a cell study. Trans- 

 actions and Proceedings of the Botanical Society of Edinburgh 1892. 



