A NGIOSPERMS. 387 



the upper and lower group of cells there is still an unemployed nucleus {polar 

 nucleus). These two nuclei move towards the middle of the embryo-sac and ihc-rc 

 coalesce and form a larger nucleus (Fig. 319 VIII, sck), which is now the nucleus of 



7^0 



Fig. 319. Polygonum divaricatuni. Ovules and development of the embryo-sac. /a longitudinal section through a 

 young ovary ; the ovule terminates the floral axis. lb longitudinal section through a rudimentary ovule before the for- 

 mation of the integument ; evt mother-cell of the embryo-sac (archesporium), t primary tapetal cell, //older stage, the 

 mother-cell of the embryo-sac has divided into two cells, in both of which the nucleus is in the act of dividing. /// mother- 

 cell of the embryo-sac divided into four (sporogenous mass of cells) ; the lowest of these cells e displaces the rest and 

 becomes the embryo-sac in IV\ peh is the primary nucleus of the embryo-sac and has divided in y into two daughter- 

 nuclei, which in VI and VII form the egg-apparatus and the antipodal cells ; o the oosphere, J synergidae, g antipodal 

 cells. VIII is a longitudinal section through a mature ovule with the inner integument jVand the outer at, the nucellus 

 n and the vascular bundle £/" entering the funiculus^; sek secondary nucleus in the embryo-sac. After Strasburger. 



the embryo-sac [secondary nucleus). The perfected embryo-sac therefore contains 

 the egg-apparatus consisting of the two synergidae and the oosphere, the nucleus of 

 the embryo-sac and the antipodal cells, and these elements are found with slight 

 variations in all embryo-sacs. 



A comparison of Angiosperms with Gymnospcrms shows that there is an almost 

 perfect agreement between them in the matter of the formation of the embryo-sac 

 (macrospore). The mother-cell of the embryo-sac in both Angiosperms and 



