182 STRUCTURAL BOTANY 



itself becomes the embryo- sac, usually witbout any 

 further divisions. It grows to a comparatively large 

 size, so much so that there are no plants more favour- 

 able for the study of the embryo-sac than the Lilies. 

 The divisions of the nucleus follow the same general 

 course as that described above (see p. 119). We find as 

 the final result three nuclei at the end of the sac towards 

 the micropyle, three at the 

 opposite end and two near the 

 middle. The three nuclei next 

 the micropyle have cells round 

 them, though without any cell- 

 wall ; these three cells are the 

 egg-apparatus, the ovum being the 

 deepest seated of the three, while 

 the two others are the helpers 

 or synergidae (see Fig. 84, s). 

 In like manner the three nuclei 

 at the other end become the 



Fl of a L^ ^? 1 - centres of the antipodal cells, 

 sty, style ; stig, stigma.' which, unlike their opposite 

 (After neighbours, have cell-walls. The 

 two polar nuclei are of exception- 

 ally large size, especially the one from the antipodal 

 end (see Fig. 84, p 2 ). A more interesting fact is, 

 that these two nuclei do not fuse till very late in 

 fact, not till after fertilisation. On the whole, how- 

 ever, the processes inside the embryo-sac are closely 

 similar to those in the dicotyledonous type, the 

 description of which should be carefully compared 

 (pp. 119-122). 



