The embryo-sac of Pandanus 



Douglas Houghton Campbell 



(with plates 1 6 AND I7) 



A 



tention of botanists at the present time is the study of certain 

 anomalies in the structure of the embryo-sac of the angiosperms, 

 to which, of late, attention has been called. The stereotyped char- 

 acter of the embryo-sac structures was long taken for granted ; 

 but it is becoming more and more evident that the departures from 

 the type are more numerous and more marked than has generally 

 been supposed. Further discoveries in this direction are therefore 

 naturally of interest. 



As -the Pandanaceae are considered to be among the lowest of 

 the Monocotyledons, it was thought that they might show some 

 deviations from the ordinary type of embryo-sac and a special ef- 

 fort was made to obtain material during a visit to the East Indies 

 made in 1906. While in Java in the spring of 1906, I had an 

 opportunity of collecting material of several species of Pandamts^ 

 and an examination of this made it evident that the embryo-sac in 

 this genus differs very markedly from that known in any other 

 plant. A preliminary note * was published ^wm^ the most im- 

 portant facts. The present paper treats in detail the development 

 of the embryo-sac up to what is probably the stage of fertilization, 

 but unfortunately none of the material was old enough to show 

 the fertilization and the early stages of endosperm formation or the 

 development of the embryo. The results, however, seemed im- 

 portant enough to warrant publication and are set forth at length 



m the following pages. 



The most marked departure from the typical embryo-sac that 



has yet been 



Pep 



first demonstrated that there were normally sixteen nuclei instead 

 of the eight characteristic of the typical embryo-sac.t Through 



* Campbell, D. H. The embryo-sac of Pandanm. Preliminary note. Ann. 



Bot. 22 : 330. 1908, 



t Campbell, D. H. The embryo-sac of Peperomia, Ami. Bot. 15; 103-I18. 



//, b, IQOI. 



205 



