8'20 RECORD OF CURRENT RESEARCHES RELATING TO 



The three nuclei in the chalazal end of the embryo-sac around 

 which the antipodals are subsequently formed, are termed by Fischer 

 the antipodal nuclei; the fourth nucleus is called the loicer polar 

 nucleus; the two sister nuclei in the upper end of the embryo-sac 

 which are taken up into the synergidse, are denominated synerg- 

 nuclei ; the two others, the germinal nucleus and the lower polar 

 nucleus, according as they subsequently form the embryo or unite 

 with the lower polar nucleus ; the product of this union may be called 

 the central nucleus of the embryo-sac. 



In monocotyledons a very great uniformity was observed in the 

 development of the groups of cells in the end of the embryo-sac, and in 

 the origin of the central nucleus. The cells of the germinal apparatus 

 are always formed in threes, and never multiply. Two synergidse are 

 always produced, the nuclei of which stand to one another as sister- 

 cells, in the same relation as the germinal nucleus to the upper polar 

 nucleus. The two synergida3 are usually inserted at the apex, with 

 exceptions in the cases of Sesleria and Allium fistulosum. The mode 

 of attachment of the germinal nucleus is subject to greater variations. 

 Thus we find it inserted into the wall of the embryo-sac beneath the 

 synergidfe, apparently attached to them, in Luzula, TriglocJiin, Carex, 

 Alisma, Elodea, and Nothoscordum. In Alopecurus, Melica, Orchis, 

 Gymnadenia, Ornithogalum, Gladiolus, Crocus vermis, and FunJcia, the 

 germinal nucleus is attached to the apex of the embryo-sac in the 

 same way as the synergidfe, so that it appears to be covered by them, 

 or to lie upon them, according to the side from which the observation 

 is made. Si^ecial interest is attached to the arrangements in Sesleria 

 and Allium fistulosum, with which Ehrharta agrees in some respects. 



The antipodals always originate in threes. They have but a 

 transitory existence in Alisma, TriglocJiin, Orcliis, and a majority of 

 the monocotyledons examined. Those of the Graminefe are dis- 

 tinguished by the extent to which they divide, and by their 

 comparatively late resorption. 



The union of the two polar nuclei takes place in two ways. In 

 one case the two nuclei approach one another, and the coalescence 

 takes place in the centre of the embryo-sac ; in the other case the 

 uj)per of the two remains stationary, and the lower one passes com- 

 pletely across the embryo-sac. The former occurs in Luzula, Alisma, 

 Carex, TriglocJiin, OrcJiis, OrnitJiogalum, and Nothoscordum ; the latter 

 in Elodea, Graminefe, and Allium fistulosum. The coalescence usually 

 takes place before impregnation ; but in Alisma and Allium fistulosum 

 only during the contact of the pollen-tube, or even after impregnation 

 has been completely effected. 



The formation of " tapeten-cells " was observed only in Luzula 

 and TriglocJiin. The mother-cell springs from the subepidermal 

 layer in Elodea, Alisma, TriglocJiin, Luzula, and Graminea3 ; in Carex 

 from a deeper layer of the nucellus. In Alisma and Allium fistulosum 

 the activity of the mother-cell is exhausted in the formation of 

 primary daughter-cells. In Gymnadenia, OrcJiis, and AntJiericum 

 three cells are formed by further division of the lower of these 

 daughter-cells ; while four secondary daughter-cells are developed 



