» 248 Dup_LeR: AIR CHAMBERS OF REBOULIA 
chambers as to give the appearance in section (FIG. 10) of narrow 
passage ways between “‘dorsal’’ and ‘‘more deeply situated”’ 
chambers, though in fact but lateral outgrowths of the primary 
chambers. They arise at different levels and contribute to the 
complex network of the mature thallus. I find no indication of 
secondary splitting in the compact tissue. Chambers appearing 
as such are easily found, but when traced always show connections 
with the surface chambers. A section of Fic. 10 along the line 
aa would show a few large chambers. One at the level bb would 
show smaller but more numerous spaces between the cells, an 
appearance similar to that shown by Evans (7, f. zz, 12) for 
Grimaldia. His f. 13 of a longitudinal section of the same stage 
is essentially like that of Fic. 10 and would lend itself to the same 
interpretation as is here made for Reboulia. 
The single superficial cell of the partition (F1G. 7) soon divides 
into segments, and a circle of triangular cells around the young 
pore is thus formed. These divide by oblique tangential walls 
(Fic. 9), forming the first circle of the actual air-pore cells. Con- 
tinued divisions (Fics. 10, 11) build up the series of concentric 
circles surrounding the simple pore. 
THE FEMALE RECEPTACLE 
At first the young female receptacle consists of a very compact 
tissue, air chambers not appearing until after the archegonia have 
started their development (Fics. 12,13). The first air chanibers 
are formed at the crest of the young receptacle (Fic. 13) but with 
the growth of the latter appear nearer the archegonia (FIGs. 14, 
15). The young chambers arise by internal splitting, but super- 
ficial splitting also begins very soon and the two proceed simul- 
taneously just as in the thallus (Fics. 13, 14). The internal split 
extends to a depth of but a few layers of cells (F1G. 16), increase in 
depth and diameter being due to intercalary growth of the parti- 
tions, which remain but one cell layer thick. The chambers 
become obliquely pyramidal (Fics. 19, 21), with the apex pointing 
toward the center of the receptacle, and overlap one another at 
maturity, as in the case of the thallus only to a less extent. I 
found no indication of secondary deep splitting on the young 
receptacle and see no necessity for interpreting the mature struc- 
