382 BOTANICAL GAZETTE [November 



herdii the development is very irregular, but in fully mature sacs 

 eight nuclei are present. 



5. In Phajus grandifolius, Corallorhiza maculata, and Brough- 

 tonia sanguinea the primary antipodal nucleus divides only once, 

 so that the embryo sac contains but six nuclei: four micropylar 

 and two chalazal. 



6. Polar fusion occurs in all of the forms studied. In the 

 8-nucleate sacs the fusion is between two equivalent polar nuclei. 

 In the 6-nucleate sacs the micropylar polar migrates to the chalazal 

 end and there fuses with the two nuclei which have resulted from 

 the division of the primary antipodal nucleus. 



7. In all of the species in which fertilization was observed it is 

 of the usual type; one of the two male nuclei fuses with the egg 

 nucleus, while the other fuses with the two polars. 



coram 



Epidendrum a filament 



many as 20 cells may be formed. In the mature seed the 

 regions have not yet been marked out in the proembryo. 



9. In all of the species examined the endosperm nuclei 

 organizes without dividing. 



10. The ordinary 8-nucleate embryo sac produced by a 

 megaspore is the prevailing condition among orchids. The causes 



comparative 



to be 



sought largely in the conditions surrounding the developing nuclei. 



1 1 . The orchids show very commonly a marked variation within 



the species. This variability, seen chiefly in connection with 



megaspore formation, is resulting in making an embryo sac in 



which the egg is removed from the megaspore by a single division 

 a conspicuous feature in the group. 



12. Although endosperm has been eliminated and the seed 



ery sim 



female gametophytes very 



monoco 



1 



dijoli 



Shepherdii show that in these species the stimulus necessary to 

 development of ovules with embryo sacs may be furnished 

 foreign pollen incapable of effecting fertilization. 



