20 



INTRODUCTION TO EMBRYOLOGY OF ANGIOSPERMS 



a monstrous and highly abnormal shape because of the intrusion 

 of the lower polar nucleus. Strasburger (1900) suggested that only 

 the fusion of the male gamete with the egg was to be regarded as 

 true or "generative" fertilization, while the fusion of the polar nuclei 



I J K L M N 



Fig. 19. Double fertilization in Lilium martagon. A, mature embryo sac. B, 

 same, showing discharge of pollen tube. One male nucleus has entered the egg 

 and the other is in contact with the upper polar nucleus; the nucleus of one of the 

 synergids is in process of degeneration. C, one male nucleus in contact with the 

 egg nucleus and the other in contact with the two polar nuclei. D, same, slightly 

 more advanced stage. E-H , stages in fusion of egg nucleus and one male nucleus. 

 I-N, stages in triple fusion. {After Guignard, 1899.) 



