DupLER: AIR CHAMBERS OF REBOULIA 249. 
ture as due to the occurrence of such splitting. Projecting into 
the primary chambers are cell plates, beginning while the chambers 
are yet quite small (Fic. 21) and becoming quite pronounced by 
the time of maturity. 
A surface view of the young receptacles (Fic. 17) shows that 
young air chambers arise at most of the intersection points of the 
cells dorsal to the archegonia, the young pores being bounded 
originally by four or five cells which in vertical section appear 
papillate (Fic. 13). The primary bounding cells then divide by 
walls extending from pore to pore, forming a circle of wedge-shaped 
Fic. 12. ‘Section through a young female receptacle, showing the apical cell 
and archegonium initial. At this stage there is no indication of air chamber forma- 
tion, x 433. Fic. 13. Young receptacle showing oldest air chambers at the crest. 
The tissue near the archegonium is yet compact, x 433. Fic. 14. Air chamber: 
more advanced than in Fic. 13, x 433. Fic. 15. Young air chamber immediately 
dorsal to the archegonium, x 433. Fic. 16. Air chambers nearer the crest of same 
Surface view of young receptacle, showing 
receptacle as F1G. 15, x 433- iG. 17. 
beginning of air chambers, same stage as Fic. 13, x 433- Fic. 18. Surface view of 
Fic. 20. Beginning of the barrel-pore of the female receptacle, x 433. 
