806 SUMMAEY OF CURRENT RESEARCHES RELATING TO 



always from the increase in size of one only. While this cell is 

 usually the lower daughter-cell among those which arise from the 

 mother- cell, it may he any one of the others, thus establishing a 

 certain equivalence among them. In the latter case only are there one 

 or more anticlinals. Sometimes the axile hypodermal cell of the 

 nucellus divides, giving rise immediately, in contact with the epider- 

 mis, to an apical cell, or initial cell of the calotte, and below to a 

 subapical cell or mother-cell of the embryo-sac ; sometimes it is itself 

 the mother-cell of the embryo-sac. Both these forms occur among 

 monocotyledons and apopetalous dicotyledons, but among gamopeta- 

 lous dicotyledons the former only has been met with. 



Among monocotyledons the mother-cell either remains undivided, 

 or divides into a variable number of daughter-cells ; in the former 

 case it developes directly into the embryo-sac. Among apopetalous 

 dicotyledons several mother-cells may develope, and in some cases this 

 phenomenon seems to be constant ; but ultimately there is never more 

 than one embryo- sac. The mother-eell gives birth either to three 

 daughter-cells in basipetal order, or to four secondary ones formed by 

 bipartition of the primary daughter-cells, or even to a large number. 

 Among gamopetalous dicotyledons the formation of four secondary 

 daughter-cells seems to be normal. 



In the greater part of angiosperms the mother-cell of the 

 embryo-sac is the lower daughter-cell; but there are exceptions to 

 this rule. The tendency of the other daughter-cells to develope 

 into the embryo-sac is manifested by the frequent development of 

 two adjacent cells, the nuclei of which divide like that of the 

 mother-cell of the embryo-sac. The walls of the daughter-cells are 

 often thick, refringent, and present some analogy to those of the 

 anther. 



The number of cells of the female apparatus and of antipodal cells 

 is remarkably constant, apart from well-known exceptions, as Santa- 

 lum, Gomphrena, and Loranthus ; but their form and disposition are 

 very variable. Among monocotyledons the synergidsB occupy the 

 summit of the embryo-sac ; they are usually ovoid, and provided with 

 a vacuole. The oosphere is inserted either at the same level at the 

 summit, or lower down laterally. The antipodals often remain very 

 small, or sometimes become almost as large as the sexual cells ; 

 occasionally they even divide. The fusion of the polar nuclei often 

 takes place towards the centre of the embryo-sac, rarely in its upper 

 part. Among apopetalse the synergidse are situated at the summit, 

 and are rarely without a vacuole when mature. The oosphere is dis- 

 tinguished by its nucleus, situated at the base ; it is inserted laterally, 

 and generally descends much lower than the two synergidse. The 

 antipodals are sometimes small, sometimes large. The fusion of the 

 polar nuclei takes place towards the centre or towards the apex. 

 Among gamopetalas the synergidas, placed on each side of the plane 

 of symmetry, have a characteristic form; in the majority of cases 

 they are elongated, and contract to a point at the summit ; they have 

 a large vacuole. The oosphere is always inserted laterally, and its 

 nucleus is larger than that of the synergidse. The antipodals are rarely 



