[JANUARY 



BOTANICAL GAZETTE 62 



Figs. 43 and 44 show stages of fusion of the male and female 

 nuclei. In fig. 43 one of the male nuclei is in contact with the egg 

 and the other with the embryo sac nucleus, and in fig. 44 one of 

 the male nuclei has fused with the egg nucleus. 



In connection with the fertilization process it should be reported 

 that at this time a proteid-like substance makes its appearance in 

 the cavity between the carpels and ovules (figs. 26, 27). This 

 material forms a network, probably as the result of coagulation 

 by the fixing agent, and stains deeply with cytoplasmic dyes. The 

 only suggestion which can be offered as to the function of this sub- 

 stance is that it may be related to the nutrition of the pollen tube, 

 since it appears just before fertilization and disappears shortly 

 after that process is completed. 



Formation of endosperm 



After fertilization the primary endosperm nucleus moves toward 

 the center of the embryo sac, and its first division takes place there. 

 This division is followed by the formation of a wall which divides 

 the sac into two approximately equal chambers, the micropylar 

 and the antipodal chambers (figs. 45, 46). Such a formation of a 

 two-chambered embryo sac has been observed in many plants, 

 both monocotyledons and dicotyledons, by Hofmeister (10), 



SCHAFFNER (17), CAMPBELL (2), GuiGNARD (6), HALL (8), MUR- 



beck (15) , Cook (3) , and others. Several other cases are mentioned 

 by Coulter and Chamberlain (4) . 



The nucleus of the micropylar chamber gradually changes its 

 position, moving toward the middle of the chamber, and soon after- 

 ward produces a great many free nuclei (figs. 46, 47), around 

 which walls are subsequently formed, beginning at the micropylar 

 end. This mode of development of the endosperm corresponds to 

 the third type in Hegelmaier's (9) classification. Twelve chromo- 

 somes, that is, the 3X number, were often counted in these nuclear 

 divisions. The nucleus of the antipodal chamber also moves toward 

 the center of that chamber, and increases in size, but does not 

 undergo division for a long time (figs. 46, 47) . The antipodal cham- 

 ber elongates like a haustorial tube, extending to the chalazal 

 extremity of the ovule, sometimes becoming exceedingly curved. 



