DupLER: AIR CHAMBERS OF REBOULIA 245 
account of the development of the chambers of the receptacle is 
given by either Evans or Haupt for the two forms which. they 
studied. 
AIR CHAMBERS OF THE THALLUS 
Mature features—In such forms as Marchantia and Cono- 
cephalum surface markings indicate the internal chambers, but 
Reboulia and its allies have no such external markings, the upper 
Fic. 1. Transverse section of a mature thallus, in the midrib region, x 40. 
et 2. _ Teapeyere wegen: of a oe seneitec resiaied cages — hen 1G. 
showing 
the pits series of chambers, overlapping shingle-like and seid from the 
surface to the compact tissue, x 40. FIG. 4 Transverse section through the dorsal 
portion of the air-chamber tissue, x 82. Fic. 5. Section through a small air chamber 
cut parallel with the surface, x 82. 
surface being uniform in color and smooth except for the very slight 
conical projections with air-pores in the center. Whole mounts 
of the thallus, stained in toto, show that the very elongated air 
chambers extend lengthwise along the midrib and from this 
