172 



ANGIOSPERMS. 



by beautiful systems of kinoplasmic connecting fibers. Cell-plates, or 

 plasma membranes, are next formed by the connecting fibers, in a man- 

 ner common to the higher plants, by which the three cells of the egg- 

 apparatus are differentiated, while a fourth nucleus, the upper polar 

 nucleus and a sister of the egg-nucleus, remains free in the cytoplasm 

 (Fig. 73, B). In A, Fig. 73, three nuclei of the tetrad are shown. 

 The cell-plates are nearly formed, and it is clear that the lower cell to 

 the right will become the egg-cell, while the nucleus to the left is 



FIG. 72. Later stages in development of embryo-sac of Lilium martn^on. 



A, the nucleus hat divided ; the daughter-nuclei are connected by connecting fibers 

 which have shown a tendency to form a cell-plate. 



B, close of second nuclear division ; the four nuclei are connected with each other 



and with plasma membrane by kinoplasmic fibers. 



unquestionably the upper polar nucleus. The cytoplasm immediately 

 surrounding this nucleus is not delimited by a plasma membrane as in 

 the case of the other three cells. In B, Fig. 73, the relation of all 

 four nuclei is evident. 



The antipodal cells in Lilium martagon are formed in the same 

 way as those of the egg-apparatus when the process is normal, although 

 the development of these cells is not infrequently variable in this 

 species (Mottier, '97). Among the Angiosperms in general the anti- 

 podal cells represent a very variable group both as to number and 



