THE MALE GAMETOPHYTE. 



175 



which case only one of these cells is at once disorganized, the other 

 retaining its normal structure for some time, or it may enter between 

 the two synergidae, when both cells are destroyed almost immediately. 



ant 



FIG. 73. Formation of egg-apparatus and mature embryo-sac in Lilium martafott. 



A, telophase of third mitosis; the four nuclei, three only shown, form a tetrad; the lower nucleus to 



the right is the egg-nucleus, the one to left the upper polar nucleus ; plasma membranes delimiting 

 the three cells of egg-apparatus are just formed. 



B, same stage, perhaps a little later, showing all four nuclei in a plane ; the lower nucleus on left is the 



upper polar nucleus. 



C, mature embryo-sac into which the male nuclei have been discharged, e.tt., egg-nucleus ; m.n., male 



nucleus applied to that of the egg; irt.n.*, second male nucleus approaching upper polar nucleus ; 

 sy*., disorganized synergid ; /.*., polar nuclei ; t.t., trophoplasmic body ; ant., antipodal cells. 



As soon as the end of the pollen tube enters the embryo-sac it 

 opens, discharging the two male gametes and other contents. One 

 of the male nuclei enters the egg-cell and applies itself to the nucleus 

 of the egg, while the other passes on into the cavity of the sac (Fig. 

 73, C). As soon as the male nuclei have been discharged into the 



