THE CARPEL AND OVULE 263 



group ; those at the micropylar end form the egg-apparatus. The 

 latter consists of the two synergidae which occupy the extreme apex, 

 and the ovum attached rather lower. The odd nuclei from either 

 end approach one another, and finally coalesce (vii.) to form the central 

 fusion-nucleus. The embryo -sac is then ready for fertilisation. 



All the nuclei resulting from this development of the contents. of 

 the embryo-sac are haploid. Reduction has already taken place in 

 the divisions of the mother-cell. The embryo-sac, or megaspore, 

 being one of the products of that division, its nucleus is already 

 reduced. The whole group of nuclei, together with the cytoplasm 

 that surrounds them, may be recognised as the sexual phase or gameto- 

 phyte. It is characterised by differing in the constitution of its 

 nuclei from the ordinary vegetative cells of the plant. The ovum is 

 that cell of the gametophyte which will be fertilised. It is the female 

 gamete, or sexual cell, which is to take part in sexual reproduction. 



