June, 1904.] The Embryo- sac and Embryo of Nelumbo. 169 



approaching each other, the lower polar nucleus travels much 

 farther than the upper one and the fusion usually occurs near 

 the Qgg or even in contact with it (Fig. 13). Quite a number of 

 examples of a triple fusion were found. In many of the prep- 

 arations in which the pollen tube had appeared, two of the nuclei 

 were about the same size while the third one was smaller (Fig. 

 14). Several other examples were found where there were three 

 conjugating nuclei, almost equal in size and similar in appearance 

 even before the pollen tube had appeared. It seems that in the 

 first instance where fertilization had occurred, the small nucleus 

 of the three conjugating nuclei represents the second male cell 

 and that there is here a true case of what has been called double 

 fertilization ; while in the second instance the conjugating nuclei 

 were embr5'0-sac nuclei, since the pollen tube had not yet entered 

 the sac. 



Soon after the eight-celled sac is formed it begins to grow very 

 rapidly in the direction of the longitudinal axis of the ovule. 

 The c^lls of the tissue below the antipodal region of the sac 

 become greatly enlarged and between them are large intercellular 

 spaces. Usually there is a single row of cells very rich in cyto- 

 plasm, which becomes very prominent in the preparations because 

 of its deep stain. This row extends downward from the base of 

 the sac toward the lower end of the ovule (Fig. 14). The cells 

 surrounding this axial row become much larger in sizi and then 

 disintegrate, leaving a large space filled with thin cytoplasm 

 (Fig. 18). The cytoplasm of the embrj'o-sac extends down to 

 the axial row of cells ( Fig. 14). These central cells are present 

 some time after the adjacent cells have disappeared, and since 

 they are rich in cytoplasm, it seems that they serve as a conduct- 

 ing passage for food from the lower ovular tissue to the cytoplasm 

 above, which in turn carries the food to the egg apparatus. 

 After fertilization the axial row begins to degenerate and then 

 disappears entirely, leaving a cavity reaching far back into the 

 tissue of the ovule (Fig. 21 ) Sometimes the nuclei of the axial 

 row of cells become active and divide (Fig. 20), and are after- 

 wards found massed together in the lower part of the cavity after 

 their walls have disappeared (Fig. 21). The cavity formed by 

 the disintegration of the cells below the antipodal region enlarges 

 greatly while the embryo is developing and into it the two basal 

 lobes of the embryo are rapidly extended, their outer surface 

 lying in contact with the walls of the cavity. 



The first division of the definitive nucleus occurs about the time 

 of the formation of the two-celled embryo and a very delicate 

 wall is formed between the two daughter nuclei which divides 

 the embr3'o-sac into two chambers. A division of one of the two 

 endosperm nuclei thus formed takes place and a second wall is 

 formed across the sac so that there are then three superposed 



