370 TRAXSACTIOXS AND PROCEEDINGS OF [Sess. lvi. 



Very rarely do we meet with a condition as shown in 

 tig. 28, due to the diaster {ant., fig. 24) being placed in the 

 long axis of the sac instead of being placed, as usual, at right 

 angles to it ; in this ovule the third antipode (sister-cell to 

 the antipodal primordial cell) was placed alongside the two 

 shown. 



At first the antipodes bulge into the cavity of the embryo- 

 sac (fig. 25'') and may continue to do so up to a compara- 

 tively late stage (figs. 27, 28, 29^ 30), but as a rule they 

 become concave on that surface next the interior of the sac, 

 from two causes, namely, pressure of the central cell (the 

 result of the fusion of the two primordial cells), and by being 

 pulled outwards and stretched by the enlarging embryo-sac 

 (figs. 2o^ 26, 31). 



We shall have to consider next the difficult problem : — 

 "What is the nature of tlie eight cells within the embryo- 

 sac. 



Strasburger's researches have undoubtedly thrown the 

 most light on the phenomena taking place within the em- 

 bryo-sac, for he demonstrated how the " primary nucleus" 

 of the embryo-sac divides into two nuclei, how these again 

 divide and redivide, thus giving rise to eight nuclei, how, 

 further, two of these develop into the two synergida3, while 

 one forms the ovum, three others form the antipodes, and 

 the remaining two nuclei fuse and give rise to the "secondary 

 nucleus " of the embryo-sac, a " nucleus " concerned in the 

 formation of endosperm. 



That these changes take place in the embryo-sac has 

 been confirmed again and again, and their very confirmation 

 has led botanists to accept the interpretation given to the 

 embryo-sac by Strasburger after Hofmeister. Strasburger 

 believes the embryo-sac to correspond to a macrospore, and 

 considers the cells within the sac as the cells of a female 

 prothallus. Yet facts have been discovered since Stras- 

 burger's researches were published, which show that the 

 embryo-sac-cell can not be a macrospore, wliatever else it 

 may represent. 



It has been pointed out in my previous papers, and also 

 above, that the walls of the embryo-sac in Myosurus show a 

 gelatinisation identical with that occurring in the sporocytes 

 of all other sporangia, and that Ouignard has established the 



