No. 504] NOTES AND LITERATURE 



819 



The second experiment (B) consisted in fertilizing the egg- 

 cells of Bryonia dioica (using flowers from the same plant as 

 used in Experiment A) with pollen from the same species. Of 

 67 seedlings in the first year 41 came to flower, 21 being male and 

 20 female, all pure B. dioica. Combining the results of this 

 experiment with those of experiment A it becomes positive that 

 the egg-cell possessed a definite sex-tendency, and that the sex 

 was not, however, unalterably determined in it; otherwise in 

 experiment B all the offspring would have become female as in 

 experiment A. The sperm-cells also must have played a role 

 in the sex-determination, since until the time of impregnation 

 of the eggs by the male gametes the conditions of both experi- 

 ments were the same. As far as this experiment discloses, all 

 the pollen-grains might have carried the male tendency. After 

 union with the egg-cells of female sex-tendency a struggle may 

 be conceived to have proceeded, the victory coming now to the 

 female tendency, and now to the male, so that the final outcome 

 resulted in 50 per cent, individuals with definite male characters 

 and 50 per cent individuals with female characters. That this 

 was not the case, the third experiment (C) makes clear. 



In experiment C, female flowers of Bryonia alba were polli- 

 nated by male flowers of B. dioica. In other words, B. alba fur- 

 nished the egg-cells and B. dioica the sperm-cells. The fruit of 

 the cross was black, and of 87 seedlings, 76 came to bloom the 

 first year, 38 of which were female and 38 male. All the plants 

 showed hybrid characters and were completely sterile. The 

 decision in regard to the sex of the hybrid must have been 

 brought about through the influence of the male gamete (pollen) 

 as in experiment B, since B. alba self -pollinated gives rise only 

 to monoecious plants. There is here a second point in evidence, 

 unconnected with the first, against the unalterable "progame" 

 determination of the egg-cells, and in favor of ascribing definite 

 influence to the sperm-cells and to fertilization. The pollen- 

 grains of B. dioica can not all have been alike in regard to sex- 

 tendency, else the offspring would all have been of the same sex, 

 since the egg cells of B. alba were all alike in their tendency to 

 give origin to monoecious forms. Again, not all the pollen- 

 grains of B. dioica can have had the same sex-tendency, else all 

 hybrids, due to the dominance of diceciousness, would have had 

 the same sex. Nor can they have been endowed merely with 

 the tendency of diceciousness, but without a tendency for a 



