494 BOTANICAL GAZETTE [JUNE 
often are so long that they grow snugly up against the roof, thus 
giving the impression, in section, as though there were filaments 
depending from the roof of the chamber, as well as standing up from 
the floor. Directly beneath the pore 
the filaments are slightly modified, 
the distal cell being hyaline and con- 
taining no chloroplasts except one or 
two lying along the bottom wall. 
There is no modification in the form of 
Fic. 5 Fic. 6 
Fics. 4-6.—Fig. 4, young air chamber before appearance of the chlorophyllose 
filaments; fig. 5, air chamber with two chlorophyllose filaments and primordium of a 
third; fig. 6, later stage of air chamber, showing distortion due to unequal elongation 
of cells of the thallus. 
these hyaline cells, as there is in Conocephalus; they retain the same 
ovoid shape found in the other cells of the filament (figs. 7 and 8). 
The cells surrounding the air pore are arranged in a series of 
concentric rings, raised crater-like a little above the dorsal surface 
of the thallus. The innermost ring is composed of dead cells, 
collapsed and highly cutinized; and is not, as stated by CAVERS, a 
hardened membranous ring which has been put forth by the inner- 
most layer of cells surrounding the pore (fig. 9). 
The ventral scales are placed in two rows on either side of the 
midrib and are of an intense dark purple or red-brown color. They 
are inserted on the posterior margin, and arranged on the ventral 
surface in a wonderfully exact and regular fashion. On the anterior 
margin of the scale is borne a curious little appendage (fig. 10) 
