— 161 — 



mature a long time before the final destruction. It appears as if 

 they had long awaited the pollen tube, which however I have 

 never been able to discover. 



A B C 



Fig. XI. H. flagellare, embryo- and endosperm-formation in the aposporic 



embryo sac. 



The Embryo-formation. 



In H. excellens there are only a few ovules, where the typical 

 ES is fully developed, and where consequently the egg cell has the 

 reduced number of chromosomes. A fertilization act is necessary for 

 a further development of this egg cell, but as this species appears 

 only as female plants, such ES must always be fertilized by the 

 pollen from another species. Naturally enough this seems to take 

 place rather seldom, as one always finds sterile fruits in the heads 

 of H. excellens. 



