16 



INTRODUCTION TO EMBRYOLOGY OF ANGIOSPERMS 



of the male gametophyte. He now confessed that, owing to its 

 similarity both in position and origin with the prothallial cells of 

 gymnosperms, the small lenticular cell in the angiosperm pollen 

 grain had been formerly misinterpreted by him as being the "vegeta- 

 tive" cell. Also, in the earlier studies in his laboratory (which had 

 been based on whole mounts stained with iodine green) the nuclei 

 in the pollen grains were often quite indistinguishable and had there- 

 fore been supposed to have degenerated. His improved technique 

 (such as staining with picrocarmine and the cutting of the larger 

 pollen grains into thin sections), devised after 1877, had shown that 



B C 



E F H 



Fig. 14. Fertilization in Monotropa hypopitys. A, pollen grain stained in iodine 

 green and acetic acid to show vegetative and generative nucleus. B,C, tips of 

 pollen tubes showing the two male nuclei; in B the vegetative nucleus is also visible. 

 D, upper part of embryo sac, showing egg apparatus. E-G, stages in union of male 

 and female nuclei. H, syngamy completed; primary endosperm nucleus dividing. 

 (After Strasburger, 1884-.) 



this was really not the case. It was now clear that the 'first division 

 of the microspore gives rise to two cells, the smaller being the genera- 

 tive cell and the larger the vegetative. Further, the generative 

 cell loosens itself from the wall of the pollen grain and divides either 

 before or after the germination of the pollen grain, while the vegeta- 



